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Zhang H, Zhou J, Yang L, Zhang X, Shi W, Yang H, Zhang G, She J, Li H. Sex differences in ocular biometric measurements: A twin study. Front Med (Lausanne) 2022; 9:936738. [DOI: 10.3389/fmed.2022.936738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 10/31/2022] [Indexed: 11/18/2022] Open
Abstract
ObjectiveGender differences in ocular biometric measurements of opposite-sex and same-sex twin pairs are still unclear. We aimed to investigate the difference between ocular biometric measurements in adolescent twin pairs.Materials and methodsThis retrospective study included a total of 64 eyes of 64 adolescents from 32 twins. The ocular biometric measurements and refractive prediction error (RE) were acquired from four groups of dizygotic (DZ) twins: boys from same-sex twin-pairs (SSM, n = 20), boys from opposite-sex twin-pairs (OSM, n = 8), girls from opposite-sex twin-pairs (OSF, n = 8), and girls from same-sex twin-pairs (SSF, n = 29).ResultsThe mean age of the patient was 9.92 ± 2.84 (range: 6–18) years. Overall, boys had higher height, AL, WTW, but lower Ks, and Kf than girls (p < 0.05). Specifically, SSF was found to have the lowest lens thickness (LT), anterior chamber depth (ACD), central corneal thickness (CCT), white to white (WTW), and axial length (AL) levels, while the highest keratometry readings in the flat (Kf) and steep (Ks) levels compared with OSM, OSF, and SSM adolescents (p < 0.05). Compared with the OSF adolescents, ACD levels of the SSF adolescents were significantly lower [(2.99 ± 0.35) and (3.26 ± 0.15) mm, p = 0.033)], but Kf indicator was significantly larger [(43.93 ± 1.64) and (42.91 ± 1.75), p = 0.016)].ConclusionOur study indicates that there was a significant difference in ocular biometric measurements between twin pairs, and sharing the uterus with a DZ twin SSF has smaller ocular indicator measurements. Our findings provide information on the eyeball and refractive development in adolescents.
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García‐Campos C, Modesto‐Mata M, Martinón‐Torres M, Martín‐Francés L, Martínez de Pinillos M, Arsuaga JL, Bermúdez de Castro JM. Similarities and differences in the dental tissue proportions of the deciduous and permanent canines of Early and Middle Pleistocene human populations. J Anat 2022; 240:339-356. [PMID: 34611899 PMCID: PMC8742968 DOI: 10.1111/joa.13558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 09/14/2021] [Accepted: 09/15/2021] [Indexed: 11/28/2022] Open
Abstract
The two- and three-dimensional assessment of dental tissues has become routine in human taxonomic studies throughout the years. Nonetheless, most of our knowledge of the variability of the enamel and dentine dimensions of the human evolutionary lineage comes from the study of permanent dentition, and particularly from molars. This leads to a biased view of the variability of these features. Due to their early formation and rapid development, the deciduous teeth allow more simplified inferences regarding the processes involved in the dental tissue development of each group. Therefore, their study could be very valuable in dental palaeohistology. In this research, we have explored the dental tissue proportions of the deciduous canines belonging to some human samples of the Early and Middle Pleistocene. The purpose of this was to discuss the meaning of the similarities and differences observed in their histological pattern, as well as to evaluate the degree of covariance with that observed in the permanent dentition of these populations. Our results show that, although there are some similarities in the dental tissue proportions between the deciduous and permanent canines of the study samples, the two dental classes do not provide a similar or comparable pictures of the dental tissue pattern present in the dentition of fossil hominins. Future works on the dental tissue patterns of the anterior and posterior dentition, including deciduous teeth, of fossil samples, may help to shed light on this hypothesis.
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Affiliation(s)
| | | | - María Martinón‐Torres
- Centro Nacional de Investigación sobre la Evolución HumanaBurgosSpain
- Anthropology DepartmentUniversity College LondonLondonUK
| | - Laura Martín‐Francés
- Centro Nacional de Investigación sobre la Evolución HumanaBurgosSpain
- Anthropology DepartmentUniversity College LondonLondonUK
- Institut Català de Paleoecologia Humana i Evolució Social (IPHES)TarragonaSpain
| | | | - Juan Luis Arsuaga
- Centro MixtoUCM‐ISCIII de Evolución y Comportamiento HumanosMadridSpain
| | - José María Bermúdez de Castro
- Centro Nacional de Investigación sobre la Evolución HumanaBurgosSpain
- Anthropology DepartmentUniversity College LondonLondonUK
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Tabakcilar D, Bundak R, Gencay K. Dental Age in Precocious and Delayed Puberty Periods. Eur J Dent 2021; 15:539-545. [PMID: 34041730 PMCID: PMC8475244 DOI: 10.1055/s-0041-1726156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVES Precocious puberty indicates quick growth inception and delayed puberty indicates retardation in growth. This study aimed to investigate whether dental development is synchronous with somatic development. MATERIALS AND METHODS In this study, 62 girls and 34 boys with precocious puberty aged 5 to 9, 29 girls with delayed puberty aged 13 to 16, and 43 boys with delayed puberty aged 14 to 17; 169 children (91 girls and 78 boys) with normal development were compared about their dental ages through their panoramic radiographs by using the Demirjian method and skeletal ages from hand-wrist radiographs by using Greulich-Pyle atlas. RESULTS The findings showed that, in all cases, the dental age values were higher than chronologic and skeletal age values to a statistically significant degree. In the precocious puberty group, the dental age values were higher than chronologic age values to a statistically significant degree. In the delayed puberty group, the difference determined between the chronological age and the dental age was not found to be statistically significant. CONCLUSION Given that the Demirjian method is inclined to make calculations that are higher than the chronological age, our findings suggest that the dental development was faster in the precocious puberty group and retarded in the delayed puberty group.
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Affiliation(s)
- Derya Tabakcilar
- Department of Pediatric Dentistry, Faculty of Dentistry, Yeditepe University, Istanbul, Turkey
| | - Ruveyde Bundak
- Department of Pediatric Endocrinology, Faculty of Medicine, Kyrenia University, Kyrenia, Cyprus
| | - Koray Gencay
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
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Fernée C, Zakrzewski S, Robson Brown K. Dimorphism in dental tissues: Sex differences in archaeological individuals for multiple tooth types. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 175:106-127. [PMID: 33247477 DOI: 10.1002/ajpa.24174] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/29/2020] [Accepted: 11/04/2020] [Indexed: 12/29/2022]
Abstract
OBJECTIVES Dimorphism in the dentition has been observed in human populations worldwide. However, research has largely focused on traditional linear crown measurements. As imaging systems, such as micro-computed tomography (micro-CT), become increasingly more accessible, new dental measurements such as dental tissue size and proportions can be obtained. This research investigates the variation of dental tissues and proportions by sex in archaeological samples. MATERIALS AND METHODS Upper and lower first incisor to second premolar tooth rows were obtained from 30 individuals (n = 300), from 3 archaeological samples. The teeth were micro-CT scanned and surface area and volumetric measurements were obtained from the surface meshes extracted. Dental wear was also recorded and differences between sexes determined. RESULTS Enamel and crown measurements were found to be larger in females. Conversely, dentine and root measurements were larger in males. DISCUSSION The findings support the potential use of dental tissues to estimate sex of individuals from archaeological samples, while also indicating that individuals aged using current dental aging methods may be underaged or overaged due to sex differences in enamel thickness.
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Affiliation(s)
- Christianne Fernée
- Department of Anthropology and Archaeology, University of Bristol, Bristol, UK.,Department of Archaeology, University of Southampton, Southampton, UK
| | - Sonia Zakrzewski
- Department of Archaeology, University of Southampton, Southampton, UK
| | - Kate Robson Brown
- Department of Anthropology and Archaeology, University of Bristol, Bristol, UK
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Mahoney P, McFarlane G, Pitfield R, O'Hara MC, Miszkiewicz JJ, Deter C, Seal H, Guatelli-Steinberg D. A structural biorhythm related to human sexual dimorphism. J Struct Biol 2020; 211:107550. [DOI: 10.1016/j.jsb.2020.107550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 06/09/2020] [Accepted: 06/11/2020] [Indexed: 01/26/2023]
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Azcorra H. The association of sex of co-twin and birth size in twins born in Yucatan, Mexico between 2008 and 2017. Ann Hum Biol 2020; 47:250-255. [PMID: 32321309 DOI: 10.1080/03014460.2020.1749301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Background: Birth measures of twins are potentially influenced by sex of co-twin.Aim: To analyse the association between sex of co-twin and birth weight, length and ponderal index in twin infants from Yucatan, Mexico.Subjects and methods: A total of 2057 twin pairs born during 2008-2017 were analysed. Female-female (F-F), male-male (M-M) and male-female (M-F) twin pair types were defined. Multiple linear regression models were used to analyse the association of (1) being female from M-F pairs and birth measures among overall female infants (M-F and F-F), and (2) being male from M-F pairs and birth measures among overall male infants (M-F and M-M). The length of gestation and mothers' age and level of education were used as covariates.Results: Models showed that being male from M-F pairs was associated with increases of 81 g in birth weight and 0.61 cm in length, compared to males from M-M pairs, and being female from opposite-sex pairs was associated with increases of 0.36 cm in length, compared to females from same-sex pairs.Conclusions: Males from M-F pairs show greater birth size than males from same-sex pairs, which supports the hypothesis that birth measures of twins are influenced by sex of the co-twin.
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Affiliation(s)
- Hugo Azcorra
- Centro de Investigaciones Silvio Zavala, Universidad Modelo, Mérida, México
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7
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Opposite-sex and same-sex twin studies of physiological, cognitive and behavioral traits. Neurosci Biobehav Rev 2019; 108:322-340. [PMID: 31711815 DOI: 10.1016/j.neubiorev.2019.11.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/30/2019] [Accepted: 11/07/2019] [Indexed: 01/12/2023]
Abstract
A scientific interest in opposite-sex (OS) twins comes from animal studies showing hormone transfer between fetuses in utero. A parallel effect in humans may occur, especially for OS females who may be exposed to androgens, in particular testosterone, from the male co-twin. Conversely, OS males may be exposed to lower levels of prenatal testosterone than do same-sex (SS) males. In this special issue, we reviewed published studies investigating potential differences between OS and SS twins in physiological, cognitive and behavioral traits focusing on the Twin Testosterone Transfer (TTT) hypothesis. Sixty articles fulfilled the eligibility criteria including 23 studies published since the review by Tapp et al. (2011). In general, studies of cognition are conflicting, but it is the phenotype for which most support for the TTT hypothesis is found. Less consistent evidence has been found regarding physiological and behavioral traits. We hope that this special issue will stimulate a discussion about how an investigation of the TTT hypothesis should continue in future research.
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Machado V, Botelho J, Pereira D, Vasques M, Fernandes-Retto P, Proença L, Mendes JJ, Delgado A. Bolton ratios in Portuguese subjects among different malocclusion groups. J Clin Exp Dent 2018; 10:e864-e868. [PMID: 30386518 PMCID: PMC6203920 DOI: 10.4317/jced.54977] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 06/08/2018] [Indexed: 11/22/2022] Open
Abstract
Background Several methods have been described to estimate inter-arch tooth size relationship, such as Bolton’s ratios. The aims of this study were to verify the validity of Bolton indexes in a sample of untreated Portuguese subjects based on Angle classification and to evaluate the gender difference. Material and Methods 168 pre-treatment dental casts of orthodontics Portuguese subjects (59 males and 109 females) with different occlusions were used, which were selected randomly from 541 consecutively treated orthodontic patients. The mesiodistal widths from first molar to first molar were measured on each pre-treatment cast to the nearest 0.01 mm using digital caliper, and Bolton’s anterior and overall ratios were calculated. Descriptive statistics as mean, standard deviation and range were calculated. Moreover, the results were compared to Bolton’s ratios and differences based on gender and occlusion groups were evaluated by statistical inference methods. Results The results reveal that the mean values, standard deviation and range were larger than Bolton’s in normal occlusion group (78.3±3.5% in anterior ratio and 92.1±2.2% in overall ratio) and there were no differences between genders (p >0.05). Class I (anterior and overall ratios, p=0.001 and p<0.001, respectively), Class II/2 (anterior ratio, p=0.032) and Class III (overall ratio, p=0.041) were significantly different from Bolton’s reference data. Conclusions The results showed no differences between gender and no difference between normal occlusion and malocclusion groups. Moreover, in normal occlusion group, the anterior and overall tooth size ratios was equivalent to the original Bolton’s ratios, although the mean and standard deviation were large. Key words:Bolton anterior and overall ratios, normal occlusion, malocclusion, portuguese population.
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Affiliation(s)
- Vanessa Machado
- Clinical Research Unit (CRU), Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal.,Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - João Botelho
- Clinical Research Unit (CRU), Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal.,Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - Dinis Pereira
- Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - Mariana Vasques
- Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - Paulo Fernandes-Retto
- Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - Luís Proença
- Clinical Research Unit (CRU), Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal.,Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - José-João Mendes
- Clinical Research Unit (CRU), Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal.,Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
| | - Ana Delgado
- Clinical Research Unit (CRU), Centro de Investigação Interdisciplinar Egas Moniz (CiiEM), Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal.,Egas Moniz Cooperativa de Ensino Superior, C.R.L., Monte de Caparica, Almada, Portugal
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9
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O'Hanlan KA, Gordon JC, Sullivan MW. Biological origins of sexual orientation and gender identity: Impact on health. Gynecol Oncol 2018; 149:33-42. [PMID: 29605047 DOI: 10.1016/j.ygyno.2017.11.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 10/30/2017] [Accepted: 11/07/2017] [Indexed: 01/19/2023]
Abstract
Gynecologic Oncologists are sometimes consulted to care for patients who present with diverse gender identities or sexual orientations. Clinicians can create more helpful relationships with their patients if they understand the etiologies of these diverse expressions of sexual humanity. Multidisciplinary evidence reveals that a sexually dimorphic spectrum of somatic and neurologic anatomy, traits and abilities, including sexual orientation and gender identity, are conferred together during the first half of pregnancy due to genetics, epigenetics and the diversity of timing and function of sex chromosomes, sex-determining protein secretion, gonadal hormone secretion, receptor levels, adrenal function, maternally ingested dietary hormones, fetal health, and many other factors. Multiple layers of evidence confirm that sexual orientation and gender identity are as biological, innate and immutable as the other traits conferred during that critical time in gestation. Negative social responses to diverse orientations or gender identities have caused marginalization of these individuals with resultant alienation from medical care, reduced self-care and reduced access to medical care. The increased risks for many diseases, including gynecologic cancers are reviewed. Gynecologic Oncologists can potentially create more effective healthcare relationships with their patients if they have this information.
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Affiliation(s)
- Katherine A O'Hanlan
- Laparoscopic Institute for Gynecology and Oncology (LIGO), 4370 Alpine Rd. Suite 104, Portola Valley, CA 94028, United States.
| | - Jennifer C Gordon
- University of Tennessee Health Sciences Center, Memphis, TN, United States.
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10
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de Paula Júnior DF, Mendonça EF, da Costa PSS, Leles CR. Malocclusion and maxillofacial characteristics of young girls having precocious puberty. Int J Paediatr Dent 2018; 28:540-546. [PMID: 29926997 DOI: 10.1111/ipd.12374] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
AIM This study aimed to evaluate the dentofacial characteristics and need for orthodontic treatment in young girls having precocious puberty (PP). DESIGN It was a cross-sectional study that included 39 girls, age ranging from 6 to 11 years old, with confirmed diagnosis of PP. The Dental Aesthetic Index (DAI) and the Index of Orthodontic Treatment Need (IOTN) were used to assess malocclusion and the need for orthodontic treatment, and cephalometric analysis was used for the diagnosis of facial growth abnormalities. Data analysis included descriptive statistics and one-sample t-test. RESULTS Findings revealed high prevalence (64.1%) of severe and very severe malocclusion (DAI grades 3-4), and 82.1% of cases were classified as having moderate to high treatment need (IOTN grades 3-4). All linear cephalometric measures and most of the angular parameters differed significantly from the reference values, indicating a tendency for Class II molar relationship. There was a high proportion of the sample outside the reference value limits, ranging from 79.5% of cases below the reference limits for facial height to 59.0% of cases above the limits for incisor-mandibular plane angle. CONCLUSIONS Results suggest that dental and craniofacial development may be associated with PP in young girls, which may be considered in the diagnosis and treatment decisions for orthopaedic/orthodontic intervention.
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Affiliation(s)
| | | | | | - Cláudio Rodrigues Leles
- Department of Oral Rehabilitation, School of Dentistry, Federal University of Goiás, Goiânia, GO, Brazil
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11
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García‐Campos C, Martinón‐Torres M, Martín‐Francés L, Martínez de Pinillos M, Modesto‐Mata M, Perea‐Pérez B, Zanolli C, Labajo González E, Sánchez Sánchez JA, Ruiz Mediavilla E, Tuniz C, Bermúdez de Castro JM. Contribution of dental tissues to sex determination in modern human populations. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2018; 166:459-472. [DOI: 10.1002/ajpa.23447] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 02/05/2018] [Accepted: 02/06/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Cecilia García‐Campos
- Departamento de Paleobiología de Homínidos, Centro Nacional de Investigación sobre la Evolución HumanaPaseo de la Sierra de Atapuerca 3, Burgos09002 Spain
- Anthropology DepartmentUniversity College LondonLondonWC1H 0BW United Kingdom
| | - María Martinón‐Torres
- Departamento de Paleobiología de Homínidos, Centro Nacional de Investigación sobre la Evolución HumanaPaseo de la Sierra de Atapuerca 3, Burgos09002 Spain
- Anthropology DepartmentUniversity College LondonLondonWC1H 0BW United Kingdom
| | - Laura Martín‐Francés
- Departamento de Paleobiología de Homínidos, Centro Nacional de Investigación sobre la Evolución HumanaPaseo de la Sierra de Atapuerca 3, Burgos09002 Spain
- De la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie, University of Bordeaux, CNRS, MCC, PACEA, UMR 5199 F_33615Pessac Cedex France
| | - Marina Martínez de Pinillos
- Departamento de Paleobiología de Homínidos, Centro Nacional de Investigación sobre la Evolución HumanaPaseo de la Sierra de Atapuerca 3, Burgos09002 Spain
- Anthropology DepartmentUniversity College LondonLondonWC1H 0BW United Kingdom
| | - Mario Modesto‐Mata
- Departamento de Paleobiología de Homínidos, Centro Nacional de Investigación sobre la Evolución HumanaPaseo de la Sierra de Atapuerca 3, Burgos09002 Spain
- Anthropology DepartmentUniversity College LondonLondonWC1H 0BW United Kingdom
- Equipo Primeros Pobladores de Extremadura, Casa de la Cultura Rodríguez MoñinoCáceres Spain
| | - Bernardo Perea‐Pérez
- Laboratorio de Antropología Forense, Escuela de Medicina Legal y ForenseUniversidad Complutense de Madrid Spain
| | - Clément Zanolli
- Laboratoire d'Anthropobiologie Moléculaire et d'Imagerie de Synthèse, UMR 5288 CNRS, University Toulouse III—Paul Sabatier France
| | - Elena Labajo González
- Laboratorio de Antropología Forense, Escuela de Medicina Legal y ForenseUniversidad Complutense de Madrid Spain
| | | | - Elena Ruiz Mediavilla
- Laboratorio de Antropología Forense, Escuela de Medicina Legal y ForenseUniversidad Complutense de Madrid Spain
| | - Claudio Tuniz
- Multidisciplinary Laboratory, International Centre for Theoretical Physics (ICTP) of TriesteTrieste Italy
| | - José María Bermúdez de Castro
- Departamento de Paleobiología de Homínidos, Centro Nacional de Investigación sobre la Evolución HumanaPaseo de la Sierra de Atapuerca 3, Burgos09002 Spain
- Anthropology DepartmentUniversity College LondonLondonWC1H 0BW United Kingdom
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Ahrenfeldt LJ, Larsen LA, Lindahl-Jacobsen R, Skytthe A, Hjelmborg JVB, Möller S, Christensen K. Early-life mortality risks in opposite-sex and same-sex twins: a Danish cohort study of the twin testosterone transfer hypothesis. Ann Epidemiol 2016; 27:115-120.e2. [PMID: 28024904 DOI: 10.1016/j.annepidem.2016.11.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 09/28/2016] [Accepted: 11/30/2016] [Indexed: 12/21/2022]
Abstract
PURPOSE To investigate the twin testosterone transfer (TTT) hypothesis by comparing early-life mortality risks of opposite-sex (OS) and same-sex (SS) twins during the first 15 years of life. METHODS We performed a population-based cohort study to compare mortality in OS and SS twins. We included 68,629 live-born Danish twins from 1973 to 2009 identified through the Danish Twin Registry and performed piecewise stratified Cox regression and log-binomial regression. RESULTS Among 1933 deaths, we found significantly higher mortality for twin boys than for twin girls. For both sexes, OS twins had lower mortality than SS twins; the difference persisted for the first year of life for boys and for the first week of life for girls. CONCLUSIONS Although the mortality risk for OS boys was in the expected direction according to the TTT hypothesis, the results for OS girls pointed in the opposite direction, providing no clear evidence for the TTT hypothesis.
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Affiliation(s)
- Linda Juel Ahrenfeldt
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark; Department of Public Health, Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense C, Denmark.
| | - Lisbeth Aagaard Larsen
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Rune Lindahl-Jacobsen
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark; Department of Public Health, Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense C, Denmark
| | - Axel Skytthe
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Jacob V B Hjelmborg
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Sören Möller
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark
| | - Kaare Christensen
- Department of Public Health, The Danish Twin Registry, Unit of Epidemiology, Biostatistics and Biodemography, University of Southern Denmark, Odense C, Denmark; Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense C, Denmark; Department of Clinical Genetics, Odense University Hospital, Odense C, Denmark
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13
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Heikkinen T, Harila V, Ollikkala A, Alvesalo L. Primary tooth size asymmetry in twins and singletons. Orthod Craniofac Res 2016; 19:145-53. [PMID: 26898820 DOI: 10.1111/ocr.12122] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2016] [Indexed: 12/01/2022]
Abstract
OBJECTIVES To explore asymmetry values of antimeric deciduous tooth crown dimensions in three types of twins: monozygotic (MZ), dizygotic same-sex (DZ) and opposite-sex (OS) vs. single-born controls. SETTING AND SAMPLE POPULATION Mesiodistal and labio-lingual crown dimensions of second deciduous molars and mesiodistal canine and first molar crown dimensions of 2159 children at 6-12 years of age were evaluated, originating from the US cross-sectional Collaborative Perinatal Study from the 1970s, including altogether MZ (n = 28), DZ same-sex (n = 33) and OS (n = 39) pairs. Single born (n = 1959) were used as controls. MATERIAL AND METHODS Dental casts were measured for comparison of variance relationships calculated from antimeric teeth, exhibiting fluctuating (FA), and directional (DA) asymmetry using anova. RESULTS Significant differences appeared in MZ and OS girls in DA of deciduous canines, which gain size in the first and second trimester, and deciduous second molars, which finally stop crown growth during the early post-natal period. Significantly, increased FA values appeared for lower deciduous canines and second molars, indicating greatest environmental stress in OS girls, MZ girls and DZ boys. Twin girls had more fluctuating and directional crown asymmetry than twin boys, but in some dimensions, the twins were more symmetric than controls. CONCLUSIONS Transmembrane hormonal influence between opposite-sex twins, and late gestational stress factors, caused by placental malfunction and/or monochorionicity, may be involved in asymmetric growth of antimers, during critical periods of crown size gain.
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Affiliation(s)
- T Heikkinen
- Oral Development and Orthodontics, Unit of Oral Health Sciences, University of Oulu, Oulu, Finland.,Medical Research Center, Oulu, Oulu, Finland.,Oulu University Hospital, Oulu, Finland
| | - V Harila
- Oral Development and Orthodontics, Unit of Oral Health Sciences, University of Oulu, Oulu, Finland.,Medical Research Center, Oulu, Oulu, Finland.,Oulu University Hospital, Oulu, Finland
| | - A Ollikkala
- Oral Development and Orthodontics, Unit of Oral Health Sciences, University of Oulu, Oulu, Finland.,Medical Research Center, Oulu, Oulu, Finland.,Oulu University Hospital, Oulu, Finland
| | - L Alvesalo
- Oral Development and Orthodontics, Unit of Oral Health Sciences, University of Oulu, Oulu, Finland.,Medical Research Center, Oulu, Oulu, Finland.,Oulu University Hospital, Oulu, Finland
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Eriksson JM, Lundström S, Lichtenstein P, Bejerot S, Eriksson E. Effect of co-twin gender on neurodevelopmental symptoms: a twin register study. Mol Autism 2016; 7:8. [PMID: 26793297 PMCID: PMC4719693 DOI: 10.1186/s13229-016-0074-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 01/12/2016] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are neurodevelopmental disorders thought to have both genetic and environmental causes. It has been hypothesized that exposure to elevated levels of prenatal testosterone is associated with elevated traits of ASD and ADHD. Assuming that testosterone levels from a dizygotic male twin fetus may lead to enhanced testosterone exposure of its co-twins, we aimed to test the prenatal testosterone hypothesis by comparing same-sex with opposite-sex dizygotic twins with respect to neurodevelopmental symptoms. METHODS Neuropsychiatric traits were assessed in a population-based twin cohort from the Child and Adolescent Twin Study in Sweden (CATSS). Parental interviews were conducted for 16,312 dizygotic twins, 9 and 12 years old, with the Autism-Tics, ADHD, and other Comorbidities inventory (A-TAC). RESULTS Girls with a female co-twin had an increased risk of reaching the cut-off score for ADHD compared with girls with a male co-twin. Both boys and girls with a female co-twin displayed a larger number of traits related to attention deficit and repetitive and stereotyped behaviors than those with a male twin. In girls, this also extended to social interaction and the combined measures for ASD and ADHD, however, with small effect sizes. CONCLUSIONS Our results are reverse to what would have been expected from the prenatal testosterone hypothesis but consistent with a previous study of ASD and ADHD traits in dizygotic twins. The seemingly protective effect for girls of having a twin brother may be an effect of parent report bias, but may also be an unexpected effect of sharing the intrauterine environment with a male co-twin.
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Affiliation(s)
- Jonna Maria Eriksson
- Department of Clinical Neuroscience, Karolinska Institutet, KIND, Gävleg 22, SE-113 30, Stockholm, Sweden
| | - Sebastian Lundström
- Centre for Ethics, Law and Mental Health (CELAM), University of Gothenburg, Gothenburg, Sweden ; Gillberg Neuropsychiatry Centre, University of Gothenburg, Gothenburg, Sweden
| | - Paul Lichtenstein
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Susanne Bejerot
- Department of Clinical Neuroscience, Karolinska Institutet, KIND, Gävleg 22, SE-113 30, Stockholm, Sweden ; School of Medical Sciences, Örebro University, Örebro, Sweden
| | - Elias Eriksson
- Department of Pharmacology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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15
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Wang Q, Kessler MJ, Kensler TB, Dechow PC. The mandibles of castrated male rhesus macaques (Macaca mulatta): The effects of orchidectomy on bone and teeth. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 159:31-51. [DOI: 10.1002/ajpa.22833] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 08/06/2015] [Accepted: 08/06/2015] [Indexed: 10/23/2022]
Affiliation(s)
- Qian Wang
- Department of Biomedical Sciences; Texas A&M University Baylor College of Dentistry; Dallas TX
| | - Matthew J. Kessler
- Office of Laboratory Animal Resources; Robert C. Byrd Health Sciences Center West Virginia University; Morgantown WV
| | - Terry B. Kensler
- Caribbean Primate Research Center; University of Puerto Rico Medical Sciences Campus; San Juan Puerto Rico
| | - Paul C. Dechow
- Department of Biomedical Sciences; Texas A&M University Baylor College of Dentistry; Dallas TX
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Ahrenfeldt L, Petersen I, Johnson W, Christensen K. Academic performance of opposite-sex and same-sex twins in adolescence: A Danish national cohort study. Horm Behav 2015; 69:123-31. [PMID: 25655669 PMCID: PMC4444512 DOI: 10.1016/j.yhbeh.2015.01.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 01/07/2015] [Accepted: 01/12/2015] [Indexed: 10/24/2022]
Abstract
Testosterone is an important hormone in the sexual differentiation of the brain, contributing to differences in cognitive abilities between males and females. For instance, studies in clinical populations such as females with congenital adrenal hyperplasia (CAH) who are exposed to high levels of androgens in utero support arguments for prenatal testosterone effects on characteristics such as visuospatial cognition and behaviour. The comparison of opposite-sex (OS) and same-sex (SS) twin pairs can be used to help establish the role of prenatal testosterone. However, although some twin studies confirm a masculinizing effect of a male co-twin regarding for instance perception and cognition it remains unclear whether intra-uterine hormone transfer exists in humans. Our aim was to test the potential influences of testosterone on academic performance in OS twins. We compared ninth-grade test scores and teacher ratings of OS (n=1812) and SS (n=4054) twins as well as of twins and singletons (n=13,900) in mathematics, physics/chemistry, Danish, and English. We found that males had significantly higher test scores in mathematics than females (.06-.15 SD), whereas females performed better in Danish (.33-.49 SD), English (.20 SD), and neatness (.45-.64 SD). However, we did not find that OS females performed better in mathematics than SS and singleton females, nor did they perform worse either in Danish or English. Scores for OS and SS males were similar in all topics. In conclusion, this study did not provide evidence for a masculinization of female twins with male co-twins with regard to academic performance in adolescence.
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Affiliation(s)
- Linda Ahrenfeldt
- The Danish Twin Registry, Epidemiology, Biostatistics and Biodemography, The University of Southern Denmark, 5000 Odense, Denmark.
| | - Inge Petersen
- The Danish Twin Registry, Epidemiology, Biostatistics and Biodemography, The University of Southern Denmark, 5000 Odense, Denmark.
| | - Wendy Johnson
- Department of Psychology, The University of Edinburgh, Edinburgh, Scotland, UK.
| | - Kaare Christensen
- The Danish Twin Registry, Epidemiology, Biostatistics and Biodemography, The University of Southern Denmark, 5000 Odense, Denmark; Department of Clinical Biochemistry and Pharmacology and Department of Clinical Genetics, Odense University Hospital, 5000 Odense, Denmark.
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17
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Identifying craniofacial features associated with prenatal exposure to androgens and testing their relationship with brain development. Brain Struct Funct 2014; 220:3233-44. [PMID: 25074752 DOI: 10.1007/s00429-014-0852-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 07/15/2014] [Indexed: 02/07/2023]
Abstract
We used magnetic resonance (MR) images obtained in same-sex and opposite-sex dizygotic twins (n = 119, 8 years of age) to study possible effects of prenatal androgens on craniofacial features. Using a principal component analysis of 19 craniofacial landmarks placed on the MR images, we identified a principal component capturing craniofacial features that distinguished females with a presumed differential exposure to prenatal androgens by virtue of having a male (vs. a female) co-twin (Cohen's d = 0.76). Subsequently, we tested the possibility that this craniofacial "signature" of prenatal exposure to androgens predicts brain size, a known sexually dimorphic trait. In an independent sample of female adolescents (singletons; n = 462), we found that the facial signature predicts up to 8% of variance in brain size. These findings are consistent with the organizational effects of androgens on brain development and suggest that the facial signature derived in this study could complement other indirect measures of prenatal exposure to androgens.
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18
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Korsoff P, Bogl LH, Korhonen P, Kangas AJ, Soininen P, Ala-Korpela M, Rose RJ, Kaaja R, Kaprio J. A comparison of anthropometric, metabolic, and reproductive characteristics of young adult women from opposite-sex and same-sex twin pairs. Front Endocrinol (Lausanne) 2014; 5:28. [PMID: 24639667 PMCID: PMC3945783 DOI: 10.3389/fendo.2014.00028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Accepted: 02/19/2014] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Prenatal exposure to androgens has been linked to masculinization of several traits. We aimed to determine whether putative female intra-uterine exposure to androgens influences anthropometric, metabolic, and reproductive parameters using a twin design. METHODS Two cohorts of Finnish twins born in 1975-1979 and 1983-1987 formed the basis for the longitudinal FinnTwin16 (FT16) and FinnTwin12 (FT12) studies. Self-reported anthropometric characteristics, disease status, and reproductive history were compared between 679 same-sex (SS) and 789 opposite-sex (OS) female twins (mean age ± SD: 34 ± 1.1) from the wave 5 of data collection in FT16. Serum lipid and lipoprotein subclass concentrations measured by nuclear magnetic resonance spectroscopy were compared in 226 SS and 169 OS female twins (mean age ± SD: 24 ± 2.1) from the wave 4 of data collection in FT12 and FT16. RESULTS Anthropometric measures, the prevalence of hypertension and diabetes mellitus type 2 did not differ significantly between females from SS and OS twin pairs at age 34. Similarly, the prevalence of infertility, age at first pregnancy and number of induced and spontaneous abortions did not differ significantly between these two groups of women. The serum lipid and lipoprotein profile did not differ between females from SS and OS twins at age 24. CONCLUSION We found no evidence that androgen overexposure of the female fetus affects obesity, metabolic profile, or reproductive health in young adult females. However, these results do not exclude the possibility that prenatal androgen exposure in females could be adversely associated with these phenotypes later in life.
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Affiliation(s)
| | - Leonie H. Bogl
- Department of Public Health, University of Helsinki, Helsinki, Finland
| | - Päivi Korhonen
- Satakunta Central Hospital, Pori and University of Turku, Turku, Finland
| | - Antti J. Kangas
- Computational Medicine, Institute of Health Sciences, Faculty of Medicine, University of Oulu, Oulu, Finland
| | - Pasi Soininen
- Computational Medicine, Institute of Health Sciences, Faculty of Medicine, University of Oulu, Oulu, Finland
- NMR Metabolomics Laboratory, School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Mika Ala-Korpela
- Computational Medicine, Institute of Health Sciences, Faculty of Medicine, University of Oulu, Oulu, Finland
- NMR Metabolomics Laboratory, School of Pharmacy, University of Eastern Finland, Kuopio, Finland
- Oulu University Hospital, Oulu, Finland
- Computational Medicine, Medical Research Council Integrative Epidemiology Unit, School of Social and Community Medicine, University of Bristol, Bristol, UK
| | - Richard J. Rose
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - Risto Kaaja
- Satakunta Central Hospital, Pori and University of Turku, Turku, Finland
| | - Jaakko Kaprio
- Department of Public Health, University of Helsinki, Helsinki, Finland
- Department of Mental Health and Substance Abuse Services, National Institute for Health and Welfare, Helsinki, Finland
- Institute for Molecular Medicine FIMM, Helsinki, Finland
- *Correspondence: Jaakko Kaprio, Department of Public Health, University of Helsinki, PO Box 41, Helsinki, Finland e-mail:
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19
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Odontometric sex variation in Malaysians with application to sex prediction. Forensic Sci Int 2014; 234:183.e1-7. [DOI: 10.1016/j.forsciint.2013.09.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 07/17/2013] [Accepted: 09/16/2013] [Indexed: 11/20/2022]
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20
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Hughes TE, Townsend GC, Pinkerton SK, Bockmann MR, Seow WK, Brook AH, Richards LC, Mihailidis S, Ranjitkar S, Lekkas D. The teeth and faces of twins: providing insights into dentofacial development and oral health for practising oral health professionals. Aust Dent J 2013; 59 Suppl 1:101-16. [DOI: 10.1111/adj.12101] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- TE Hughes
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - GC Townsend
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - SK Pinkerton
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - MR Bockmann
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - WK Seow
- School of Dentistry; The University of Queensland; Brisbane Australia
| | - AH Brook
- School of Dentistry; The University of Adelaide; South Australia Australia
- Institute of Dentistry; Queen Mary University of London; United Kingdom
| | - LC Richards
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - S Mihailidis
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - S Ranjitkar
- School of Dentistry; The University of Adelaide; South Australia Australia
| | - D Lekkas
- School of Dentistry; The University of Adelaide; South Australia Australia
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Heikkinen T, Harila V, Tapanainen JS, Alvesalo L. Masculinization of the eruption pattern of permanent mandibular canines in opposite sex twin girls. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2013; 151:566-72. [PMID: 23754587 DOI: 10.1002/ajpa.22298] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 04/24/2013] [Indexed: 11/06/2022]
Abstract
The aim of this study is to explore the effect of prenatal androgenization on the clinical eruption of permanent teeth expressing dimorphism and bimaturism. The eruption curves of permanent teeth (except third molars), including those that make up the canine complex (permanent canines, lower first premolars), are compared among opposite sex twins (OS twins) relative to single-born boys and girls. The comparisons are made with regard to three phases of eruption (pierced mucosa, half- erupted, and completely erupted) from a cross-sectional sample of dental casts, using Kaplan-Meier survival and Cox regression analyzes. The casts were collected from 2159 school children from the US Collaborative Perinatal Project, including 39 pairs of OS-twins, of which 12 pairs (30.8%) were Euro-Americans and 27 pairs (69.2%) were of African-American ancestry. The eruption patterns of the incisors, upper first molars, and lower canines were found to be significantly masculinized (delayed) among OS twin girls. The differences in most other teeth were either not significant, or the number of observations of active eruption phases were too few, such as in the upper first molars and incisors, to yield strong evidence and meaningful results. The masculinization of the tooth eruption pattern in OS twin girls is intriguing because of the lower canine responses during puberty, as well as canine primordial formation during early fetal androgenization of their co-twin during the 8th to 14th gestational weeks. The present results offer a challenge for future research exploring tooth eruption mechanisms, and may also highlight some cases of delayed or ectopic canines, which are biased toward females.
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Affiliation(s)
- Tuomo Heikkinen
- Oral Development and Orthodontics, Institute of Dentistry, University of Oulu, Oulu, Finland.
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22
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23
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Ribeiro DC, Brook AH, Hughes TE, Sampson WJ, Townsend GC. Intrauterine hormone effects on tooth dimensions. J Dent Res 2013; 92:425-31. [PMID: 23549090 DOI: 10.1177/0022034513484934] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The human dentition is a complex adaptive system that is influenced by genetic, epigenetic, and environmental factors. Within this system, is sexual dimorphism related to the growth promotion of the Y chromosome, or to hormonal influences, or both? This study is the first to investigate both primary and permanent tooth sizes in females from opposite-sex dizygotic (DZOS) twin pairs compared with females from dizygotic same-sex (DZSS) and monozygotic (MZ) twin pairs to indicate the influence of intrauterine male hormone, including the initial testosterone surge, on dental development. Serial dental models of the primary, mixed, and permanent dentitions of 134 females from DZOS, DZSS, and MZ twins were examined. Mesiodistal, buccolingual, crown height, and intercuspal dimensions of all primary teeth and selected permanent teeth were determined by image analysis. Univariate and multivariate analyses showed statistically significantly larger crown size in DZOS females in both dentitions, with the crown height dimensions displaying the greatest increase in size. These findings strongly support the Twin Testosterone Transfer (TTT) hypothesis. We propose that the growth-promoting effects of the Y chromosome and intrauterine male hormone levels influence different tooth dimensions and contribute differentially to the sexual dimorphism of human teeth.
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Affiliation(s)
- D C Ribeiro
- School of Dentistry, The University of Adelaide, Adelaide, Australia, 5005
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24
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Cohen-Bendahan CCC, van Goozen SHM, Buitelaar JK, Cohen-Kettenis PT. Maternal Serum Steroid Levels Are Unrelated to Fetal Sex: A Study in Twin Pregnancies. Twin Res Hum Genet 2012. [DOI: 10.1375/twin.8.2.173] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractIncreased prenatal exposure to testosterone (T) in females of an opposite-sex (OS) twin pair may have an effect on the development of sex-typical cognitive and behavioral patterns. The prenatal exposure to T due to hormone transfer in OS twin females may occur in two ways, one directly via the feto–fetal transfer route within the uterus, the other indirectly through maternal–fetal transfer and based in the maternal–fetal compartment. Although some studies in singletons indeed found that women pregnant with a male fetus have higher T levels during gestation than women pregnant with a female fetus, many other studies could not find any relation between the sex of the fetus and maternal serum steroid levels. Therefore at present it is unclear whether a pregnant woman bearing a male has higher levels of T than a woman bearing a female. Up to this point, no-one has investigated this issue in twin pregnancies. We examined the relationship between maternal serum steroid levels and sex of fetus in 17 female–female, 9 male–male and 29 OS twin pregnancies. No differences were observed between the maternal serum steroid levels of women expecting single-sex and mixed-sex offspring. It is concluded that the source of prenatal T exposure in females probably comes from the fetal unit, which is the direct route of fetal hormone transfer.
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Townsend G, Richards L, Messer LB, Hughes T, Pinkerton S, Seow K, Gotjamanos T, Gully N, Bockmann M. Genetic and Environmental Influences on Dentofacial Structures and Oral Health: Studies of Australian Twins and Their Families. Twin Res Hum Genet 2012. [DOI: 10.1375/twin.9.6.727] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractOur studies of the teeth and faces of Australian twins commenced at the School of Dentistry, The University of Adelaide in the early 1980s. There are now over 900 pairs of twins enrolled in our continuing investigations, together with 1200 relatives. There are 3 main cohorts of participants. The first cohort comprises around 300 pairs of teenage twins for whom various records have been collected, including dental casts, facial photographs, finger and palm prints and information on laterality, including handedness. The second cohort comprises around 300 pairs of twins who have been examined at 3 stages of dental development from approximately 4 years of age to about 14 years: at primary, mixed, and permanent dentition (excluding 3rd molars) stages. The most recent study of tooth emergence and oral health, for which we are currently recruiting twins, will provide a third cohort of around 500 twin pairs aged from around birth to 3 to 4 years of age. Our broad aim in these studies has been to improve our understanding of how genetic and environmental factors contribute to variation in dental and facial features, and to oral health. We have also used our data to investigate aspects of the determination of laterality, particularly the fascinating phenomenon of mirror imaging. We plan to maximize the use of the longitudinal data and DNA we have collected, and continue to collect, by performing genome-wide scans for putative genetic linkage peaks for a range of dental features, and then to test for association between a series of likely candidate genes and our phenotypes.
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Phillips DI, Davies MJ, Robinson JS. Fetal Growth and the Fetal Origins Hypothesis in Twins — Problems and Perspectives. ACTA ACUST UNITED AC 2012. [DOI: 10.1375/twin.4.5.327] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractAlthough there is substantial evidence from studies of singletons that small size at birth is linked with long-term adverse health effects, until recently little was known as to whether these associations extend to twins. A review of published studies suggests that at present there is little consistent evidence that birthsize in twins is associated with increased morbidity or morality. While, these findings may reflect methodological limitations, it is also argued that they arise as a consequence of the substantially different biology of fetal growth in twins.
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Tapp AL, Maybery MT, Whitehouse AJO. Evaluating the twin testosterone transfer hypothesis: a review of the empirical evidence. Horm Behav 2011; 60:713-22. [PMID: 21893061 DOI: 10.1016/j.yhbeh.2011.08.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2010] [Revised: 08/17/2011] [Accepted: 08/19/2011] [Indexed: 11/26/2022]
Abstract
In this paper we review the evidence that fetuses gestated with a male co-twin are masculinized in development, perhaps due to the influence of prenatal androgens: the so-called twin testosterone transfer (TTT) hypothesis. Evidence from studies of behavioral, perceptual, cognitive, morphological and physiological traits in same- and opposite-sex human twins is considered. Apart from two studies reporting increases in aspects of sensation-seeking for females with a male rather than a female co-twin, there is sparse evidence supporting the TTT hypothesis in behavioral studies. Outcomes from studies of perception (in particular otoacoustic emissions) and cognition (in particular vocabulary acquisition and visuo-spatial ability) provide more consistent evidence in support of masculinized performance in twins with a male co-twin compared to twins with a female co-twin. The outcomes favorable to the TTT hypothesis for otoacoustic emissions and visuo-spatial ability are restricted to females. Studies of physiology and morphology (e.g., brain volume, tooth size and 2D:4D ratio) also show some influence of co-twin sex, but again these effects are often restricted to female twins. Because females produce little endogenous testosterone, the effects of gestation with a male co-twin may be more pronounced in females than males. Thus, while uneven, the evidence for the TTT hypothesis is sufficient to warrant further investigation, ideally using large samples of same- and opposite-sex twins, along with control groups of same- and opposite-sex siblings when the characteristics assessed are potentially open to social influences.
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Affiliation(s)
- Aimee L Tapp
- Neurocognitive Development Unit, School of Psychology, University of Western Australia, Australia
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Chou ST, Tseng YC, Pan CY, Chang JZC, Chang HP. Craniofacial skeletal dysplasia of opposite-sex dizygotic twins. J Formos Med Assoc 2011; 110:342-6. [PMID: 21621156 DOI: 10.1016/s0929-6646(11)60051-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 02/25/2009] [Accepted: 04/08/2009] [Indexed: 11/16/2022] Open
Abstract
Craniofacial skeletal dysplasia can lead to different skeletal malocclusions. Both environmental factors and heredity contribute to the formation of malocclusions. There are strong familial tendencies in the development of Angle's Class II and III malocclusions. Cases such as opposite-typed (Class II and III) malocclusions with skeletal and dentoalveolar discordance in siblings or dizygotic (DZ) twins have seldom been reported. We describe the rare case of a pair of opposite-sex DZ twins with completely different skeletal malocclusions, and discuss the clinical considerations for treatment. The patients were twins aged 13 years and 4 months. The girl had mandibular prognathism and a Class III dentoskeletal relationship, whereas the boy had skeletal Class II with mandibular retrusion. Several morphological traits have been implicated with hormonal effect. However, there was no evidence of whether the masculinization effect had any impact on jaw size in the female fetus or whether this effect lasted into adolescence. We suggest that, although DZ twins share the same growth environment, genetic or other unknown extrinsic factors can result in discordance of characteristics of the craniofacial skeleton, dentition, and occlusion.
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Affiliation(s)
- Szu-Ting Chou
- Department of Orthodontics, Kaohsiung Medical University Hospital, and Faculty of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
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29
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McFadden D. Sexual orientation and the auditory system. Front Neuroendocrinol 2011; 32:201-13. [PMID: 21310172 PMCID: PMC3085661 DOI: 10.1016/j.yfrne.2011.02.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Revised: 01/31/2011] [Accepted: 02/02/2011] [Indexed: 10/18/2022]
Abstract
The auditory system exhibits differences by sex and by sexual orientation, and the implication is that relevant auditory structures are altered during prenatal development, possibly by exposure to androgens. The otoacoustic emissions (OAEs) of newborn male infants are weaker than those of newborn females, and these sex differences persist through the lifespan. The OAEs of nonheterosexual females also are weaker than those of heterosexual females, suggesting an atypically strong exposure to androgens some time early in development. Auditory evoked potentials (AEPs) also exhibit sex differences beginning early in life. Some AEPs are different for heterosexual and nonheterosexual females, and other AEPs are different for heterosexual and nonheterosexual males. Research on non-humans treated with androgenic or anti-androgenic agents also suggests that OAEs are masculinized by prenatal exposure to androgens late in gestation. Collectively, the evidence suggests that prenatal androgens, acting globally or locally, affect both nonheterosexuality and the auditory system.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, 1 University Station A8000, University of Texas, Austin, TX 78712-0187, USA.
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Influence of having a male twin on body mass index and risk for dyslipidemia in middle-aged and old women. Int J Obes (Lond) 2011; 35:1466-9. [PMID: 21386807 DOI: 10.1038/ijo.2011.18] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND Animal experiments suggest that exposure to elevated levels of androgens during development by means of so-called hormonal programming causes metabolic aberrations at adulthood. An indirect strategy to address the possible importance of such an influence also in humans would be to study female dizygotic twins, presuming that those with a twin brother--due to diffusion of testosterone--have been exposed to higher androgen levels prenatally. DESIGN We have compared 8409 women with a male twin with 9166 women with a dizygotic female twin with respect to self-reported indices of anthropometry and metabolic aberrations at age 42 or older. RESULTS Body mass index (BMI), body weight and rate of dyslipidemia were moderately, but significantly, higher in women from opposite-sexed (OS) twin pairs; splitting for age revealed this difference to be present in those ≥ 60 years of age only. CONCLUSION The results (i) support the notion that comparisons of women with a twin brother with women from same-sexed twin pairs may be used to shed light on possible long-term effects of interindividual variations in early androgen exposure, and (ii) suggest that the effects of early androgen exposure on metabolism previously observed in animal experiments are of relevance also for humans.
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Heil M, Kavšek M, Rolke B, Beste C, Jansen P. Mental rotation in female fraternal twins: Evidence for intra-uterine hormone transfer? Biol Psychol 2011; 86:90-3. [DOI: 10.1016/j.biopsycho.2010.11.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 11/04/2010] [Accepted: 11/09/2010] [Indexed: 10/18/2022]
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Cederroth CR, Nef S. Fetal programming of adult glucose homeostasis in mice. PLoS One 2009; 4:e7281. [PMID: 19789640 PMCID: PMC2748646 DOI: 10.1371/journal.pone.0007281] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Accepted: 09/08/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Emerging evidence suggests that dietary soy and phytoestrogens can have beneficial effects on lipid and glucose metabolism. We have previously shown that male mice fed from conception to adulthood with a high soy-containing diet had reduced body weight, adiposity and a decrease in glucose intolerance, an early marker of insulin resistance and diabetes. OBJECTIVES The purpose of this study was to identify the precise periods of exposure during which phytoestrogens and dietary soy improve lipid and glucose metabolism. Since intrauterine position (IUP) has been shown to alter sensitivity to endocrine disruptors, we also investigated whether the combination of IUP and fetal exposure to dietary phytoestrogens could potentially affect adult metabolic parameters. METHODS Male outbred mice (CD-1) were allowed ad libitum access to either a high soy-containing diet or a soy-free diet either during gestation, lactation or after weaning. Adiposity and bone mass density was assessed by dual x-ray absorptiometry. Glucose tolerance was assessed by a glucose tolerance test. Blood pressure was examined by the tail-cuff system. RESULTS Here we show that metabolic improvements are dependent on precise windows of exposure during life. The beneficial effects of dietary soy and phytoestrogens on adiposity were apparent only in animals fed post-natally, while the improvements in glucose tolerance are restricted to animals with fetal exposure to soy. Interestingly, we observed that IUP influenced adult glucose tolerance, but not adiposity. Similar IUP trends were observed for other estrogen-related metabolic parameters such as blood pressure and bone mass density. CONCLUSION Our results suggest that IUP and fetal exposure to estrogenic environmental disrupting compounds, such as dietary phytoestrogens, could alter metabolic and cardiovascular parameters in adult individuals independently of adipose gain.
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Affiliation(s)
- Christopher R. Cederroth
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Serge Nef
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
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McFadden D. Masculinization of the mammalian cochlea. Hear Res 2009; 252:37-48. [PMID: 19272340 DOI: 10.1016/j.heares.2009.01.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 01/08/2009] [Accepted: 01/12/2009] [Indexed: 11/30/2022]
Abstract
Otoacoustic emissions (OAEs) differ between the sexes in humans, rhesus and marmoset monkeys, and sheep. OAEs also are different in a number of special populations of humans. Those basic findings are reviewed and discussed in the context of possible prenatal-androgen effects on the auditory system. A parsimonious explanation for several outcomes is that prenatal exposure to high levels of androgens can weaken the cochlear amplifiers and thereby weaken otoacoustic emissions (OAEs). Prenatal androgen exposure apparently also can alter auditory evoked potentials (AEPs). Some non-hormonal factors possibly capable of producing sex and group differences are discussed, and some speculations are offered about specific cochlear structures that might differ between the two sexes.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, University of Texas at Austin, Seay Building, 1 University Station, A8000, Austin, TX 78712-0187, USA.
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34
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Wasmer C, Pohl Y, Filippi A. Traumatic dental injuries in twins: Is there a genetic risk for dental injuries? Dent Traumatol 2008; 24:619-24. [DOI: 10.1111/j.1600-9657.2008.00681.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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35
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Guatelli-Steinberg D, Sciulli PW, Betsinger TK. Dental crown size and sex hormone concentrations: Another look at the development of sexual dimorphism. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2008; 137:324-33. [DOI: 10.1002/ajpa.20878] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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36
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Townsend G, Alvesalo L, Brook A. Variation in the human dentition: some past advances and future opportunities. J Dent Res 2008; 87:802-5. [PMID: 18719205 DOI: 10.1177/154405910808700919] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- G Townsend
- School of Dentistry, The University of Adelaide, Adelaide, South Australia.
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Genetic and environmental influences on human dental variation: a critical evaluation of studies involving twins. Arch Oral Biol 2008; 54 Suppl 1:S45-51. [PMID: 18715551 PMCID: PMC2981882 DOI: 10.1016/j.archoralbio.2008.06.009] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 06/25/2008] [Accepted: 06/25/2008] [Indexed: 11/21/2022]
Abstract
Utilising data derived from twins and their families, different approaches can be applied to study genetic and environmental influences on human dental variation. The different methods have advantages and limitations and special features of the twinning process are important to consider. Model-fitting approaches have shown that different combinations of additive genetic variance (A), non-additive genetic variance (D), common environmental variance (C), and unique environmental variance (E) contribute to phenotypic variation within the dentition, reflecting different ontogenetic and phylogenetic influences. Epigenetic factors are also proposed as important in explaining differences in the dentitions of monozygotic co-twins. Heritability estimates are high for most tooth size variables, for Carabelli trait and for dental arch dimensions, moderate for intercuspal distances, and low for some occlusal traits. In addition to estimating the contributions of unmeasured genetic and environmental influences to phenotypic variation, structural equation models can also be used to test the effects of measured genetic and environmental factors. Whole-genome linkage analysis, association analysis of putative candidate genes, and whole genome association approaches, now offer exciting opportunities to locate key genes involved in human dental development.
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38
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Bakhireva LN, Schatz M, Jones KL, Tucker CM, Slymen DJ, Klonoff-Cohen HS, Gresham L, Johnson D, Chambers CD. Fetal sex and maternal asthma control in pregnancy. J Asthma 2008; 45:403-7. [PMID: 18569234 DOI: 10.1080/02770900801971826] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Asthma is a prevalent chronic disorder that might substantially complicate pregnancy. Some recent reports suggest that the presence of a female fetus might be associated with worse maternal asthma symptoms during pregnancy. We tested this hypothesis using the sample of 719 pregnant women with asthma prospectively enrolled in the OTIS study. The presence of a female fetus was associated with a higher incidence of hospitalizations for asthma during pregnancy (OR = 1.84; 95% CI: 1.05; 3.21) independent of maternal age, BMI, ethnicity, smoking, and socioeconomic status. The current study suggests that pregnant asthmatic women carrying a girl might be more susceptible to asthma exacerbations.
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Affiliation(s)
- Ludmila N Bakhireva
- Division of Pharmacy Practice and Department of Family/Community Medicine, University of New Mexico, Albuquerque, New Mexico, USA
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McFadden D. What Do Sex, Twins, Spotted Hyenas, ADHD, and Sexual Orientation Have in Common? PERSPECTIVES ON PSYCHOLOGICAL SCIENCE 2008; 3:309-23. [DOI: 10.1111/j.1745-6924.2008.00082.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The otoacoustic emissions (OAEs) measured in a collection of special populations of humans and certain nonhuman species suggest that OAEs may provide a window into some processes of human prenatal development and sexual differentiation. For reasons that are unclear, OAEs appear to be highly sensitive to events occurring during prenatal development that seem to be related to the degree of exposure to androgens a fetus receives. The (largely circumstantial) evidence for a relationship between androgen exposure and OAE strength comes from a series of studies of twins, children with attention-deficit/hyperactivity disorder, people of differing sexual orientations, and spotted hyenas, among others. Some conclusions are bolstered by parallel studies using auditory evoked potentials (AEPs). OAEs and AEPs are simple, objective, noninvasive measures that appear to have potential as tools of value to researchers working on a wide variety of basic and applied topics beyond audition.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, University of Texas
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40
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Culbert KM, Breedlove SM, Burt SA, Klump KL. Prenatal hormone exposure and risk for eating disorders: a comparison of opposite-sex and same-sex twins. ACTA ACUST UNITED AC 2008; 65:329-36. [PMID: 18316679 DOI: 10.1001/archgenpsychiatry.2007.47] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT Although the sex difference in eating disorder prevalence has typically been attributed to psychosocial factors, biological factors may also play a role. Prenatal testosterone exposure is a promising candidate, since it masculinizes behavior in animals and humans via its permanent effects on the central nervous system. OBJECTIVE To examine whether in utero testosterone exposure has masculinizing effects on disordered eating (DE) by comparing opposite-sex (OS) and same-sex (SS) twins. Twin type (SS vs OS) is considered a proxy measure of prenatal hormone exposure, since females from OS pairs are exposed to more testosterone in utero than females from SS pairs. A linear trend in mean levels of DE was predicted based on expected prenatal testosterone exposure, with SS female twins exhibiting the highest levels of DE followed by OS female twins, OS male twins, and SS male twins. DESIGN A twin study comparison of OS vs SS twins. SETTING Michigan State University Twin Registry. PARTICIPANTS Participants included 304 SS female twins, 59 OS female twins, 54 OS male twins, and 165 SS male twins. MAIN OUTCOME MEASURE Overall levels of DE were assessed with the Minnesota Eating Behavior Survey. RESULTS Confirming hypotheses, DE exhibited significant linear trends, with SS female twins exhibiting the highest levels of DE followed by OS female twins, OS male twins, and SS male twins. This linear trend could not be accounted for by levels of anxiety or socialization effects. Indeed, OS female twins exhibited lower levels of DE compared with an independent sample of undergraduate women (n = 69) who were raised with 1 or more brothers. CONCLUSIONS The masculinization of DE in OS female twins is unlikely to be due to socialization effects alone. Biological factors, such as the masculinization of the central nervous system by prenatal testosterone exposure, may also contribute to sex differences in DE prevalence.
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Affiliation(s)
- Kristen M Culbert
- Department of Psychology, Michigan State University, East Lansing, MI 48824-1116, USA
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41
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Shinwell ES, Reichman B, Lerner-Geva L, Boyko V, Blickstein I. "Masculinizing" effect on respiratory morbidity in girls from unlike-sex preterm twins: a possible transchorionic paracrine effect. Pediatrics 2007; 120:e447-53. [PMID: 17766488 DOI: 10.1542/peds.2006-3574] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVES Preterm male infants are at a disadvantage when compared with female infants regarding the incidence of respiratory and neurologic morbidity and mortality. At term, female infants from unlike-sex twin pairs have birth weights that are closer to their male co-twins than to girls from like-sex twin pairs. We hypothesized that if the male disadvantage is mediated via factors that affect fetal lung development, there may be a potential effect on the incidence of respiratory distress syndrome and its complications in female infants from unlike-sex pairs. PATIENTS AND METHODS In this population-based study we used data from the Israel Neonatal Network, which included data from 8858 very low birth weight (500-1500 g) infants of 24 to 34 weeks' gestation. The incidence of morbidity and mortality was compared in male and female infants from singletons and like-sex and unlike-sex twin pairs. Multivariable analyses were used, accounting for relevant confounding variables. RESULTS Male singletons and like-sex twins were at increased risk for mortality, respiratory distress syndrome, pneumothorax, bronchopulmonary dysplasia, periventricular-intraventricular hemorrhage, and periventricular leukomalacia. However, in unlike-sex twin pairs, no difference was seen in the incidence of respiratory morbidity between male and female twins. The male disadvantage was maintained for mortality and periventricular-intraventricular hemorrhage. CONCLUSIONS These findings suggest that the difference in morbidity and mortality between male and female premature infants represents a male disadvantage as opposed to a female advantage and that this disadvantage may be transferred from boys to girls in unlike-sex twin pairs, perhaps via an intrauterine paracrine effect.
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Affiliation(s)
- Eric S Shinwell
- Department of Neonatology, Kaplan Medical Center, PO Box 1, Rehovot 76100, Israel.
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42
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Lummaa V, Pettay JE, Russell AF. Male twins reduce fitness of female co-twins in humans. Proc Natl Acad Sci U S A 2007; 104:10915-20. [PMID: 17576931 PMCID: PMC1904168 DOI: 10.1073/pnas.0605875104] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In mammals, including humans, female fetuses that are exposed to testosterone from adjacent male fetuses in utero can have masculinized anatomy and behavior. However, the reproductive consequences of such prebirth sex-ratio effects for offspring and their implications for maternal fitness remain unexplored. Here we investigate the effects of being gestated with a male co-twin for daughter lifetime reproductive success, and the fitness consequences for mothers of producing mixed-sex twins in preindustrial (1734-1888) Finns. We show that daughters born with a male co-twin have reduced lifetime reproductive success compared to those born with a female co-twin. This reduction arises because such daughters have decreased probabilities of marrying as well as reduced fecundity. Mothers who produce opposite-sex twins consequently have fewer grandchildren (and hence lower fitness) than mothers who produce same-sex twins. Our results are unlikely to be a consequence of females born with male co-twins receiving less nutrition because such females do not have reduced survival and increases in food availability fail to improve their reproductive success. Nor are our results explained by after-birth social factors (females growing up with similarly aged brothers) because females born with a male co-twin have reduced success even when their co-twin dies shortly after birth and are raised as singletons after birth. Our findings suggest that hormonal interactions between opposite-sex fetuses known to influence female morphology and behavior can also have negative effects on daughter fecundity and, hence, maternal fitness, and bear significant implications for adaptive sex allocation in mammals.
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Affiliation(s)
- Virpi Lummaa
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom.
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43
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Boskey AL, Young MF, Kilts T, Verdelis K. Variation in mineral properties in normal and mutant bones and teeth. Cells Tissues Organs 2006; 181:144-53. [PMID: 16612080 DOI: 10.1159/000091376] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Hydroxyapatite mineral is deposited in an organized fashion in the matrices of bones and teeth. The amount of mineral present, the composition of the mineral, and the size of the mineral crystals varies with both tissue and animal age, diet, health status, and the tissue being examined. Here, we review methods for measuring these differences in mineral properties and provide some illustrations from bones and teeth of animals in which the small leucine-rich proteoglycans (biglycan and decorin) were ablated. Differences in mineral properties between biglycan-deficient bones and teeth are related to the functions of this small proteoglycan in these tissues.
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Affiliation(s)
- Adele L Boskey
- Mineralized Tissue Research Laboratory, Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY 10021, USA.
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44
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van Anders SM, Vernon PA, Wilbur CJ. Finger-length ratios show evidence of prenatal hormone-transfer between opposite-sex twins. Horm Behav 2006; 49:315-9. [PMID: 16143332 DOI: 10.1016/j.yhbeh.2005.08.003] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 08/08/2005] [Accepted: 08/09/2005] [Indexed: 11/22/2022]
Abstract
Finger-length ratio (second to fourth finger; 2D:4D) has been associated with various measures thought to be related to prenatal androgens. In addition, hormone-transfer theory posits that hormones can transfer between twins. We examined 2D:4D in same-sex (SS) and opposite-sex (OS) dizygotic twins to test both propositions. Results show that 2D:4D is masculinized in OS females compared to SS females. This provides strong evidence that 2D:4D is laid down prenatally, and that hormones (likely androgens) can transfer from male to female fetuses. Implications for developmental timeframes for both hormone-transfer and 2D:4D are discussed.
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Affiliation(s)
- Sari M van Anders
- Department of Psychology, Simon Fraser University, Burnaby BC, Canada.
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45
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Cohen-Bendahan CCC, van de Beek C, Berenbaum SA. Prenatal sex hormone effects on child and adult sex-typed behavior: methods and findings. Neurosci Biobehav Rev 2005; 29:353-84. [PMID: 15811504 DOI: 10.1016/j.neubiorev.2004.11.004] [Citation(s) in RCA: 346] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Revised: 10/21/2004] [Accepted: 11/05/2004] [Indexed: 11/27/2022]
Abstract
There is now good evidence that human sex-typed behavior is influenced by sex hormones that are present during prenatal development, confirming studies in other mammalian species. Most of the evidence comes from clinical populations, in which prenatal hormone exposure is atypical for a person's sex, but there is increasing evidence from the normal population for the importance of prenatal hormones. In this paper, we briefly review the evidence, focusing attention on the methods used to study behavioral effects of prenatal hormones. We discuss the promises and pitfalls of various types of studies, including those using clinical populations (concentrating on those most commonly studied, congenital adrenal hyperplasia, androgen insensitivity syndrome, ablatio penis, and cloacal exstrophy), direct measures of hormones in the general population (assayed through umbilical cord blood, amniotic fluid, and maternal serum during pregnancy), and indirect measures of hormones in the general population (inferred from intrauterine position and biomarkers such as otoacoustic emissions, finger length ratios, and dermatoglyphic asymmetries). We conclude with suggestions for interpreting and conducting studies of the behavioral effects of prenatal hormones.
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Affiliation(s)
- Celina C C Cohen-Bendahan
- Department of Child and Adolescent Psychiatry, and Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, The Netherlands
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46
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Cohen-Bendahan CCC, Buitelaar JK, van Goozen SHM, Orlebeke JF, Cohen-Kettenis PT. Is there an effect of prenatal testosterone on aggression and other behavioral traits? A study comparing same-sex and opposite-sex twin girls. Horm Behav 2005; 47:230-7. [PMID: 15664027 DOI: 10.1016/j.yhbeh.2004.10.006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Accepted: 10/15/2004] [Indexed: 11/23/2022]
Abstract
Men and women differ in temperament and personality traits, such as aggression and sensation seeking. The sex hormone testosterone could play a role in the origin of these differences, but it remains unclear how and when testosterone could have these effects. One way to investigate the prenatal exposure effect of testosterone is to compare opposite-sex (OS) and same-sex (SS) female twins. It has been suggested that OS twin girls are exposed prenatally to elevated testosterone levels and that this may result in some masculinization of their personality and behavior. We measured sexually dimorphic traits and circulating testosterone levels in 13-year-old OS (n = 74) and SS (n = 55) twins. Testosterone levels showed a clear circadian rhythm, with higher levels in the morning than in the afternoon. Testosterone was higher in boys than girls, but similar in OS and SS twin girls. Testosterone was not in any way systematically related to the different personality traits. However, a sex difference in aggression proneness was observed, and OS girls showed a more masculine pattern of aggression proneness than the SS girls. It is argued that it is unlikely that this difference is due to social factors, such as a gender-specific upbringing.
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Affiliation(s)
- Celina C C Cohen-Bendahan
- Department of Child and Adolescent Psychiatry, A01.468, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
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Abstract
A number of recent studies have used data from twins to shed light on the causal pathways underlying the observed association between birthweight and cardiovascular risk factors or coronary heart disease. The issue of whether findings from twin studies are generally informative, or whether factors associated with twinning preclude generalisation, is considered here. It is concluded that the association between birthweight and later health may differ quantitatively between twins and singletons, but evidence regarding blood pressure suggests it may not differ qualitatively. However, more information is needed on a number of gestational and maternal factors, and on measures of health other than blood pressure. Placentation and issues relating to infertility and its treatment need to be recorded and, together with gestation length, may need to be taken into account in analyses.
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Affiliation(s)
- Ruth Morley
- Clinical Epidemiology and Biostatistics Unit, University of Melbourne Department of Paediatrics, and Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Australia.
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48
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Abstract
Due to recent advances in molecular genetics, studies of twins will continue to provide important insights into how genetic and environmental factors contribute to variation in human physical and behavioural traits and disorders. This review emphasizes that biometrical genetic studies of twins are particularly valuable in complementing and directing molecular approaches to facilitate the detection of quantitative trait loci. It also describes several other research models involving twins, apart from the traditional comparison of similarities in monozygotic (identical) and dizygotic (non-identical) pairs, that have the potential to provide new information in the future. Current knowledge about the genetic bases of common dental problems is summarized and future directions in dental research involving twins are outlined.
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Affiliation(s)
- G C Townsend
- Dental School, The University of Adelaide, Adelaide, South Australia.
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49
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Kaijser M, Lichtenstein P, Granath F, Erlandsson G, Cnattingius S, Ekbom A. In utero exposures and breast cancer: a study of opposite-sexed twins. J Natl Cancer Inst 2001; 93:60-2. [PMID: 11136844 DOI: 10.1093/jnci/93.1.60] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- M Kaijser
- Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden.
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