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DeSesso JM, Scialli AR. Bone development in laboratory mammals used in developmental toxicity studies. Birth Defects Res 2018; 110:1157-1187. [PMID: 29921029 DOI: 10.1002/bdr2.1350] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 04/19/2018] [Accepted: 04/25/2018] [Indexed: 01/12/2023]
Abstract
Evaluation of the skeleton in laboratory animals is a standard component of developmental toxicology testing. Standard methods of performing the evaluation have been established, and modification of the evaluation using imaging technologies is under development. The embryology of the rodent, rabbit, and primate skeleton has been characterized in detail and summarized herein. The rich literature on variations and malformations in skeletal development that can occur in the offspring of normal animals and animals exposed to test articles in toxicology studies is reviewed. These perturbations of skeletal development include ossification delays, alterations in number, shape, and size of ossification centers, and alterations in numbers of ribs and vertebrae. Because the skeleton is undergoing developmental changes at the time fetuses are evaluated in most study designs, transient delays in development can produce apparent findings of abnormal skeletal structure. The determination of whether a finding represents a permanent change in embryo development with adverse consequences for the organism is important in study interpretation. Knowledge of embryological processes and schedules can assist in interpretation of skeletal findings.
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Aly I, Chapman JR, Oskouian RJ, Loukas M, Tubbs RS. Lumbar ribs: a comprehensive review. Childs Nerv Syst 2016; 32:781-5. [PMID: 26350805 DOI: 10.1007/s00381-015-2904-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 09/01/2015] [Indexed: 11/26/2022]
Abstract
BACKGROUND To date, no single comprehensive review has been published regarding lumbar ribs. Therefore, the present review was conducted to better elucidate these variant anatomical structures, which can be confused with transverse process fractures or result in miscounting of spine segments for surgical procedures. METHODS Using standard search engines, a review of lumbar ribs was performed. CONCLUSIONS Lumbar ribs are uncommon but can be misinterpreted on imaging or cause confusion during surgery. Mutations of the FGD1 or Hox10 gene may be involved in the development of lumbar ribs. Knowledge of these structures can decrease misdiagnosis when they are present.
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Affiliation(s)
- Islam Aly
- Seattle Science Foundation, Seattle, WA, USA
| | | | | | - Marios Loukas
- Department of Anatomical Sciences, St. George's University, True Blue, Grenada
| | - R Shane Tubbs
- Seattle Science Foundation, Seattle, WA, USA.
- , 1600 7th Ave South, Birmingham, AL, USA.
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Bailey JM, Oliveri AN, Karbhari N, Brooks RAJ, De La Rocha AJ, Janardhan S, Levin ED. Persistent behavioral effects following early life exposure to retinoic acid or valproic acid in zebrafish. Neurotoxicology 2015; 52:23-33. [PMID: 26439099 DOI: 10.1016/j.neuro.2015.10.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 09/30/2015] [Accepted: 10/01/2015] [Indexed: 10/22/2022]
Abstract
BACKGROUND Moderate to severe dysregulation in retinoid signaling during early development is associated with a constellation of physical malformations and/or neural tube defects, including spina bifida. It is thought that more subtle dysregulation of this system, which might be achievable via dietary (i.e. hypervitaminosis A) or pharmacological (i.e. valproic acid) exposure in humans, will manifest on behavioral domains including sociability, without overt physical abnormalities. METHODS During early life, zebrafish were exposed to low doses of two chemicals that disrupt retinoid signaling. From 0 to 5dpf, larvae were reared in aqueous solutions containing retinoic acid (0, 0.02, 0.2 or 2nM) or valproic acid (0, 0.5, 5.0 or 50μM). One cohort of zebrafish was assessed using a locomotor activity screen at 6-dpf; another was reared to adulthood and assessed using a neurobehavioral test battery (startle habituation, novel tank exploration, shoaling, and predator escape/avoidance). RESULTS There was no significant increase in the incidence of physical malformation among exposed fish compared to controls. Both retinoic acid and valproic acid exposures during development disrupted larval activity with persisting behavioral alterations later in life, primarily manifesting as decreased social affiliation. CONCLUSIONS Social behavior and some aspects of motor function were altered in exposed fish; the importance of examining emotional or psychological consequences of early life exposure to retinoid acting chemicals is discussed.
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Affiliation(s)
- Jordan M Bailey
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27710, USA
| | - Anthony N Oliveri
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
| | - Nishika Karbhari
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27710, USA
| | - Roy A J Brooks
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27710, USA
| | - Amberlene J De La Rocha
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27710, USA
| | - Sheila Janardhan
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27710, USA
| | - Edward D Levin
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC 27710, USA; Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA.
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Rengasamy P. Critical Periods of Development in Teratology. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2015. [DOI: 10.1007/7653_2015_55] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Ten Broek CMA, Bakker AJ, Varela-Lasheras I, Bugiani M, Van Dongen S, Galis F. Evo-Devo of the Human Vertebral Column: On Homeotic Transformations, Pathologies and Prenatal Selection. Evol Biol 2012; 39:456-471. [PMID: 23226903 PMCID: PMC3514701 DOI: 10.1007/s11692-012-9196-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 07/11/2012] [Indexed: 12/21/2022]
Abstract
Homeotic transformations of vertebrae are particularly common in humans and tend to come associated with malformations in a wide variety of organ systems. In a dataset of 1,389 deceased human foetuses and infants a majority had cervical ribs and approximately half of these individuals also had missing twelfth ribs or lumbar ribs. In ~10 % of all cases there was an additional shift of the lumbo-sacral boundary and, hence, homeotic transformations resulted in shifts of at least three vertebral boundaries. We found a strong coupling between the abnormality of the vertebral patterns and the amount and strength of associated malformations, i.e., the longer the disturbance of the vertebral patterning has lasted, the more associated malformations have developed and the more organ systems are affected. The germ layer of origin of the malformations was not significantly associated with the frequency of vertebral patterns. In contrast, we find significant associations with the different developmental mechanisms that are involved in the causation of the malformations, that is, segmentation, neural crest development, left-right patterning, etc. Our results, thus, suggest that locally perceived developmental signals are more important for the developmental outcome than the origin of the cells. The low robustness of vertebral A-P patterning apparent from the large number of homeotic transformations is probably caused by the strong interactivity of developmental processes and the low redundancy of involved morphogens during early organogenesis. Additionally, the early irreversibility of the specification of the A-P identity of vertebrae probably adds to the vulnerability of the process by limiting the possibility for recovery from developmental disturbances. The low developmental robustness of vertebral A-P patterning contrasts with a high robustness of the A-P patterning of the vertebral regions. Not only the order is invariable, also the variation in the number of vertebrae per region is small. This robustness is in agreement with the evolutionary stability of vertebral regions in tetrapods. Finally, we propose a new hypothesis regarding the constancy of the presacral number of vertebrae in mammals.
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Affiliation(s)
- Clara M A Ten Broek
- Group of Evolutionary Ecology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium ; Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, The Netherlands
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Campion SN, Davenport SJ, Nowland WS, Cappon GD, Bowman CJ, Hurtt ME. Sensitive windows of skeletal development in rabbits determined by hydroxyurea exposure at different times throughout gestation. ACTA ACUST UNITED AC 2012; 95:238-49. [PMID: 22495808 DOI: 10.1002/bdrb.21013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 02/27/2012] [Indexed: 11/07/2022]
Abstract
The critical periods of axial skeletal development in rats and mice have been well characterized, however the timing of skeletal development in rabbits is not as well known. It is important to have a more precise understanding of this timing of axial skeletal development in rabbits due to the common use of this species in standard nonclinical studies to assess embryo-fetal developmental toxicity. Hydroxyurea, a teratogen known to induce a variety of fetal skeletal malformations, was administered to New Zealand White rabbits as a single dose (500 mg/kg) on individual days during gestation (gestation day, GD 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 19) and fetal external, visceral, and skeletal morphology was examined following cesarean sections on GD 29. A wide range of fetal skeletal effects was observed following hydroxyurea treatment, with a progression of malformations from anterior to posterior structures over time, as well as from proximal to distal structures over time. The sensitive window of axial skeletal development was determined to be GD 8 to 13, while disruption of appendicular and cranio-facial skeletal development occurred primarily from GD 11 to 16 and GD 11 to 12, respectively. The results of this study provide a better understanding of the critical developmental window for different segments of the rabbit skeleton, which will aid in the design of window studies to investigate teratogenicity in rabbits.
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Affiliation(s)
- Sarah N Campion
- Drug Safety Research and Development, Pfizer Worldwide Research & Development, Groton, CT 06340, USA.
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Cadot S, Frenz D, Maconochie M. A novel method for retinoic acid administration reveals differential and dose-dependent downregulation of Fgf3 in the developing inner ear and anterior CNS. Dev Dyn 2012; 241:741-58. [DOI: 10.1002/dvdy.23748] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2012] [Indexed: 12/23/2022] Open
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Alexander PG, Tuan RS. Role of environmental factors in axial skeletal dysmorphogenesis. ACTA ACUST UNITED AC 2010; 90:118-32. [DOI: 10.1002/bdrc.20179] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Quemelo PRV, Lourenço CM, Peres LC. Teratogenic effect of retinoic acid in swiss mice. Acta Cir Bras 2009; 22:451-6. [PMID: 18235933 DOI: 10.1590/s0102-86502007000600007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Accepted: 07/17/2007] [Indexed: 11/22/2022] Open
Abstract
PURPOSE To identify the types of malformations resulting from the administration of retinoic acid (RA) to Swiss mice on different days of pregnancy. METHODS Twenty-four pregnant Swiss mice were divided into 4 groups of 6 animals each. The experimental groups received a single intraperitoneal injection of RA (70 mg/kg) on gestational days 7, 8 and 9 (D7, D8 and D9), while control animals (C) received only saline solution. RESULTS Were obtained: exencephaly (C:0; D7:16.1%; D8:25.4%; D9:0), myelomeningocele (C:0; D7:25.8%, D8:30.9%, D9:0), spina bifida occulta (C:0, D7:29%, D8:41.8%, D90), gastroschisis (C:0, D7:6.4% D8:5.4%, D9:0), omphalocele (C:0, D7:6.4%, D8:14.5%, D9:0), lower limb alterations (C:0, D7:74.1%, D8:80%, D9:0), imperforated anus (C:0, D7:100%, D8:100%, D9:100%), and tail agenesis/alteration (C: D7:100%, D8:100%, D9:100%). CONCLUSION The experimental model using Swiss mice proved to be efficient in the induction of the different types of defects, with the eighth gestational day being the one that most favored the induction of neural tube defect, omphalocele, gastroschisis, lower limb defects, imperforated anus and tail agenesis/alteration. On this basis, this is a useful model for future investigation of neural development and of the formation of the appendicular skeleton.
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Daston GP, Seed J. Skeletal malformations and variations in developmental toxicity studies: interpretation issues for human risk assessment. ACTA ACUST UNITED AC 2008; 80:421-4. [PMID: 18157902 DOI: 10.1002/bdrb.20135] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- George P Daston
- Miami Valley Innovation Center, Procter & Gamble, Cincinnati, Ohio 45253, USA.
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Yerby MS. Chapter 10 Teratogenicity and Antiepileptic Drugs. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2008; 83:181-204. [DOI: 10.1016/s0074-7742(08)00010-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Menegola E, Di Renzo F, Broccia ML, Giavini E. Inhibition of histone deacetylase as a new mechanism of teratogenesis. ACTA ACUST UNITED AC 2007; 78:345-53. [PMID: 17315247 DOI: 10.1002/bdrc.20082] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Histone deacetylases (HDACs) are nuclear and cytoplasmic enzymes that deacetylate a number of substrates, of which histones are the best known and described in the literature. HDACs are present in eukaryotic and bacteria cells, and are fundamental for a number of cellular functions, including correct gene expression. Surprisingly, only up to 20% of the whole genome is controlled by HDACs, but key processes for survival, proliferation, and differentiation have been strictly linked to HDAC enzyme functioning. The use of HDAC inhibitors (HDACi) has been proposed for the treatment of neoplastic diseases. Their effectiveness has been suggested for a number of liquid and solid tumors, particularly acute promyelocytic leukemia (APL). The role of HDACs in embryo development is currently under investigation. Published data indicate knockout phenotype analysis to be of particular interest, in which a number of HDACs play a key role during development. Little data have been published on the effects of HDACi on embryonic development, although for valproic acid (VPA), literature from the 1980s described its teratogenic effects in experimental animals and humans. To date, all tested HDACi have shown teratogenic effects similar to those described for VPA when tested in zebrafish, Xenopus laevis, and mice. HDACs were also able to alter embryo development in invertebrates and plants. A model, similar to that proposed in APL, involving retinoic acid receptors (RAR) and tissue specific Hox gene expression, is suggested to explain the HDAC effects on embryo development.
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Affiliation(s)
- Elena Menegola
- Department of Biology, University of Milan, Milan, Italy.
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Di Renzo F, Broccia ML, Giavini E, Menegola E. Antifungal triazole derivative triadimefon induces ectopic maxillary cartilage by altering the morphogenesis of the first branchial arch. ACTA ACUST UNITED AC 2007; 80:2-11. [PMID: 17187389 DOI: 10.1002/bdrb.20097] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The triazole derivative, triadimefon (FON), induces branchial arch abnormalities in post-implantation rat embryos cultured in vitro, and cranio-facial malformations in mouse fetuses. Ectopic maxillary cartilage has been also described as a typical FON-related malformation. This work studies the morphogenesis of the ectopic cartilage in rat embryos and fetuses exposed in vivo to FON during the early postimplantation period. METHODS Pregnant rats were treated with 0, 250, and 500 mg/kg FON on Day 9.5 of pregnancy (D9.5) and sacrificed at term (D20), during the early fetal period (D17) or at different embryogenetic periods (D10, D11, D12). The skeleton was examined after stain of bone and cartilage or of cartilage alone respectively at term or at D17. The neural crest cell (NCC) migration and compaction was investigated at D10 and D11 and the cranial nerve organization described at D12. RESULTS Triadimefon is teratogenic in rats under the chosen experimental conditions. The malformations were at the level of the cranio-facial and axial skeleton at term and of the hindbrain nerves in embryos. A NCC abnormal migration and compaction was observed at the level of the first branchial arch: in FON-exposed embryos NCC were detected at the level of both maxillary and mandibular processes, whereas control embryos showed the immunostained tissue only at the level of the mandibular bud. CONCLUSIONS The pathogenic pathway, proposed to explain the ectopic cartilage, is the displacement of part of the NCC-derived tissues at the maxillary region of the first branchial arch.
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Induction of the homeotic gene Hoxa1 through valproic acid's teratogenic mechanism of action. Neurotoxicol Teratol 2006; 28:617-24. [DOI: 10.1016/j.ntt.2006.08.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Revised: 07/20/2006] [Accepted: 08/10/2006] [Indexed: 11/21/2022]
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Massa V, Cabrera RM, Menegola E, Giavini E, Finnell RH. Valproic acid-induced skeletal malformations: associated gene expression cascades. Pharmacogenet Genomics 2006; 15:787-800. [PMID: 16220111 DOI: 10.1097/01.fpc.0000170914.11898.3a] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVES Valproic acid (VPA) is a widely used anticonvulsant medication with well-known teratogenic effects in both humans and in experimental animal model systems. The most commonly observed malformations induced by VPA in experimental animals include neural and skeletal defects. In this study the potential alterations in somitic tissue gene expression relative to the development of observed axial skeletal defects were examined. METHODS SWV mice were treated at 8.5 days post coitum (d.p.c.) with 1.36 mmol/kg or 2.72 mmol/kg VPA by i.p. injection. At 18.5 d.p.c., animals were killed and stained for morphological and skeletal examination. Cervical malformations consisting of vertebral fusions and cervical ribs were consistently observed. Phenotypic analysis confirmed the presence of dose-dependent axial skeletal malformations induced by in-utero VPA-exposure. Using antisense RNA amplification and cDNA microarrays, we examined the expression of approximately 5700 genes in the first six postotic somites of control and treated embryos at 6, 12, 18 and 24 h after the 8.5 d.p.c. VPA treatment. RESULTS Analysis indicated that several ontological groups (e.g. histone deacetylase complex, guanosine triphosphatases, cell proliferation and cytoskeletal) have significantly enriched gene expression changes in response to the teratogenic insult. The RNA from 6 h post-treatment was also subjected to a microarray cross-platform validation, and genes identified on both platforms are presented. CONCLUSION These data were then used to deduce candidate cellular pathways that may be responsible for the VPA-induced teratogenic skeletal phenotypes.
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Okada A, Aoki Y, Kushima K, Kurihara H, Bialer M, Fujiwara M. Polycomb homologs are involved in teratogenicity of valproic acid in mice. ACTA ACUST UNITED AC 2005; 70:870-9. [PMID: 15523661 DOI: 10.1002/bdra.20085] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Valproic acid (VPA) is widely used to treat epilepsy and bipolar disorder and is also a potent teratogen, but its teratogenic mechanisms are unknown. We have attempted to describe a fundamental role of the Polycomb group (Pc-G) in VPA-induced transformations of the axial skeleton. METHODS Pregnant NMRI mice were given a single subcutaneous injection of vehicle or VPA (800 mg/kg) on gestation day (GD) 8. The expression of genes encoding Polycomb and trithorax groups was measured by quantitative real-time RT-PCR using total RNA isolated from the embryos exposed to vehicle or VPA for 1, 3, and 6 hr. In addition, the use of two less teratogenic antiepileptic chemicals valpromide (VPD) and valnoctamide (VCD) provide reliable evidence to support the relationship between VPA teratogenicity and the Polycomb group. RESULTS At a teratogenic level, VPA inhibits the expression of the Polycomb group genes, including Eed, Ezh2, Zfp144, Bmi1, Cbx2, Rnf2, and YY1 in the mouse embryos. In contrast, neither VPD nor VCD have significant effects on the expression of those genes affected by VPA. The trithorax group (trx-G) gene MLL, which is known to be required to maintain homeobox gene expression such as the Polycomb gene, is not affected by a teratogenic dose of VPA. CONCLUSIONS We propose that, during embryonic development, VPA may affect the gene silencing pathway mediated by the Polycomb group complex. The epigenetic mechanism of VPA teratogenicity on anteroposterior patterning is suspected.
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Affiliation(s)
- Akinobu Okada
- Safety Research Laboratories, Yamanouchi Pharmaceutical Co., Ltd., Tokyo, Japan
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Merks JHM, Smets AM, Van Rijn RR, Kobes J, Caron HN, Maas M, Hennekam RCM. Prevalence of rib anomalies in normal Caucasian children and childhood cancer patients. Eur J Med Genet 2005; 48:113-29. [PMID: 16053903 DOI: 10.1016/j.ejmg.2005.01.029] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Indexed: 10/25/2022]
Abstract
PURPOSE To evaluate the prevalence of abnormalities of rib development in normal Caucasian children and patients with childhood cancer. MATERIALS AND METHODS Chest radiographs of 881 Caucasian pediatric controls and 906 childhood cancer patients were reviewed, and independently scored by four blinded observers, using strict definitions. Prevalences of 6 major rib anomaly categories in controls were compared to their prevalence in the total group of childhood cancer patients, and the 12 individual larger tumor groups using Chi-square tests. RESULTS Values in the control population were generated for the occurrence of six major rib anomaly categories; cervical rib anomalies were present in 6.1% of controls, aplasia of 12th ribs in 6.6%, lumbar ribs in 0.9%, bifurcations in 0.7%, synostosis-bridging in 0.3%, and segmentations were not found. The overall prevalence of total rib anomalies in cases and controls was equal (14.9% and 14.2%, respectively). Cervical rib anomalies were found significantly more often in cases (8.6%) compared to controls (p-value=0.047), three groups accounting for this higher prevalence: 12.1% of acute lymphoblastic leukemia patients (p=0.011), 18.2% of astrocytoma patients (p=0.023), and 14.7% of germ cell tumor patients (p=0.046) had a cervical rib anomaly. CONCLUSION Prevalence figures for the presence and type of rib anomalies in a large group of normal Caucasian children were generated. In childhood cancer patients a significantly higher prevalence of cervical rib anomalies was demonstrated in patients with acute lymphoblastic leukemia, astrocytoma, and germ cell tumors.
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Affiliation(s)
- Johannes H M Merks
- Department of Pediatric Oncology, Emma Children's Hospital, Academic Medical Center, Amsterdam, The Netherlands.
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Chernoff N, Rogers JM. Supernumerary ribs in developmental toxicity bioassays and in human populations: incidence and biological significance. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2004; 7:437-449. [PMID: 15586878 DOI: 10.1080/10937400490512447] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Supernumerary or accessory ribs (SNR), either lumbar (LR) or cervical (CR), are a common finding in standard developmental toxicology bioassays. The biological significance of these anomalies within the regulatory arena has been problematic and the subject of some debate. In rodents, the spontaneous incidence of SNR is species and strain related and ranges from <1% to >30%. Compound-induced LR are induced by a wide variety of chemical and physical agents when pregnant animals are exposed during specific gestational periods. A significant portion of the agent-induced LR may be due to maternal factors, as it has been shown that stress alone will induce LR in rodents. SNR are not isolated phenomena and signify basic alterations in the architecture of the axial skeleton. LR are associated with longer ribs, increased numbers of vertebrosternal ribs, and the presence of extra presacral vertebrae ("anteriorization"). CR are associated with reduced numbers of vertebrosternal ribs (posteriorization). It is evident that SNR are not a single anomaly, but consist of two unrelated structures: an extra rib that has a cartilaginous segment at the distal end, and an ossification site that lacks cartilage. These have a bimodal size distribution, with the population of extra ribs being significantly longer than the ossification sites, and 0.6 mm can be used as an approximate length for distinguishing the two populations in mice. Extra ribs are permanent structures in contrast to ossification sites that disappear postnatally, probably becoming part of the lateral transverse vertebral processes. SNR are also found in humans although, in contrast to laboratory species, CR are more commonly noted. SNR are associated with adverse heath effects, and CR with inducing thoracic outlet disease characterized by diminished blood flow and altered position of the ganglia and nerve roots in the area of the C7-T1 vertebrae. LR are associated with lower back pain and L4-5 degeneration. The incidence of CR is greatly reduced in adult humans as compared to fetuses, and it has been hypothesized that fetal "SNR" may be largely composed of ossification sites that disappear postnatally. The mechanisms involved in the formation of extra ribs are not understood at this time, although the fact that the early sensitive periods for their initiation during embryogenesis is coupled with the associated changes in the axial skeleton argues for their induction being due to fundamental changes in gene expression. The sum of the experimental evidence supports the idea of SNR being composed of two different structures: extra ribs that are permanent dysmorphological structures that may be induced by xenobiotics and/or maternal stress, and ossification sites that may be transient variations in the formation of the lateral processes of the vertebrae.
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Affiliation(s)
- Neil Chernoff
- US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Reproductive Toxicology Division, Research Triangle Park, North Carolina 27711, USA.
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