Month of birth and offspring count of women: data from the Southern hemisphere

BACKGROUND

Several studies indicate that the month of birth affects later reproductive output of women in the Northern hemisphere.

METHODS

To investigate whether a comparable but time-shifted effect is also present in the Southern hemisphere where the seasonal variation of the environment is reversed, we analysed the association between birth month and offspring count in post-reproductive New Zealand women. We further examined whether this association differed with the hemisphere of birth as well as the socio-economic background.

RESULTS

We find that the association between birth month and offspring count of New Zealand women born in the Southern, albeit not Northern, hemisphere is a mirror image of the pattern reported from Austrian women: on average, women born during the Southern hemisphere summer months have fewer children than women born in winter. This association is highly significant within the lowest family income category but insignificant within higher family income categories.

CONCLUSIONS

This study provides evidence for a causal link between the seasonality of the environment during the pre- and perinatal period and offspring count of women. It further indicates that the main contribution of the birth month effect found in the present study comes from the lowest family income category.

Host immune responses to coxsackievirus B3

Group B coxsackieviruses are members of the picornavirus family of small nonenveloped RNA viruses and have been associated with diseases of multiple organs including the heart, acinar and islet pancreas, liver, skeletal muscle, central nervous system, and testes. Damage to tissues occurs not only from the direct virus replication and infection of cells, but also from the host response to infection. However, without host immunity and response, the viruses are not appropriately cleared and chronic infection occurs. The host response to coxsackieviruses is diverse and complex. Also, the host response both benefits and is detrimental to the virus. This review discusses the major aspects of the host response to coxsackieviruses and attempts to demonstrate the interplay between the virus and the cell, which ultimately determines both the type and strength of the adaptive immune response as well as whether autoimmunity will follow the infection.

The effects of early environmental conditions on the reproductive and somatic development of juvenile guinea pigs (Cavia aperea f. porcellus)

Little is known about the effects of the early environment on the development of non-seasonally reproducing species like the domestic guinea pig (Cavia aperea f. porcellus). Although guinea pigs reproduce throughout the year, there is evidence for environmental sensitivity of their reproductive physiology. To investigate the sensitivity of juvenile body weight and puberty to differences in the prenatal and early postnatal environment, subjects were exposed to either of two experimental conditions mimicking seasonal variation: a long photoperiod with 25 degrees C ambient temperature ("LD/25 degrees C"), or a short photoperiod with 15 degrees C ("SD/15 degrees C"). Mean body weight of F1-males from LD/25 degrees C-conditions was higher than that of SD/15 degrees C-males during the whole pubertal period, although the difference was significant only during the early growth phase. Testosterone concentrations also differed significantly between the two treatment groups, pointing to an earlier pubertal onset in LD/25 degrees C- than SD/15 degrees C-males. In F1-females, treatment effects on body weight or age at first estrus were absent. This indicates that the somatic and reproductive development is more sensitive to early photoperiod and temperature conditions in male than female guinea pigs, and that other environmental factors may also play a crucial role for reproductive maturation in this species.

Parental age difference and offspring count in humans

Preferences for certain age characteristics of partners are reported across cultures: men prefer mates who are younger and women prefer mates older than themselves. To examine whether these age preferences entail fitness effects for men and women, we investigated the association among age differences between partners and offspring count. On the basis of a sample of approximately 10,000 post-reproductive Swedish men and women who did not change their partner between the birth of their first and last child, we find maximum offspring count in men if their partner is approximately 6 years younger, and in women if their partner is approximately 4 years older. We further find that after separation, on average, both men and women shift to a partner younger than the first, albeit in women the new partner is still older than the female herself. We conclude that the age preference for the partner yields fitness benefits for both men and women and may thus be an evolutionarily acquired trait.

Sirolimus-associated infertility: case report and literature review of possible mechanisms

The mammalian-target-of-rapamycin/mTOR-inhibitor sirolimus as a component of the immunosuppressive strategy after solid organ transplantation is effective at preventing allograft rejection. However, recent reports indicate that sirolimus is associated with altered sex hormone levels and impaired sperm quality parameters. Herein, we report on a case of sirolimus-associated infertility in a young male heart-lung transplant recipient and provide a detailed synopsis of potential mechanisms by which sirolimus may negatively influence spermatogenesis. Testicular immunohistochemistry, the course of sex hormone and sperm quality parameters of our patient support the hypothesis that mTOR might act as an important key regulator in the reproductive system. Fortunately, due to withdrawal of sirolimus as part of the maintenance, immunosuppression improved sperm quality and sex hormone parameters could be observed. Recently, these improvements even resulted in a spontaneous pregnancy of the patient's wife more than 1 year after the drug was withdrawn. In our view, oligospermia as a possible and at least partly reversible side-effect of mTOR inhibitors has to be taken into consideration, particularly, when administrated to young male patients.

Inhibition of the mammalian target of rapamycin impedes lymphangiogenesis

Lymphatic complications are common side effects of mammalian target of rapamycin (mTOR) inhibitor-based immunosuppression in kidney transplantation. Therefore, we investigated whether the mTOR inhibitor rapamycin, besides its known antihemangiogenic effect, also impedes regenerative lymphangiogenesis. In a murine skin flap model, rapamycin impaired recovery of lymphatic flow across surgical incisions resulting in prolonged wound edema in these animals. Importantly, the antilymphangiogenic effect of rapamycin was not related to a general inhibition of wound healing as demonstrated an in vivo Matrigeltrade mark lymphangiogenesis assay and a model of lymphangioma. Rapamycin concentrations as low as 1 ng/ml potently inhibited vascular endothelial growth factor (VEGF)-C driven proliferation and migration, respectively, of isolated human lymphatic endothelial cells (LECs) in vitro. Mechanistically, mTOR inhibition impairs downstream signaling of VEGF-A as well as VEGF-C via mTOR to the p70S6 kinase in LECs. In conclusion, we provide extensive experimental evidence for an antilymphangiogenic activity of mTOR inhibition suggesting that the early use of mTOR inhibitor following tissue injury should be avoided. Conversely, the antilymphangiogenic properties of rapamycin and its derivates may provide therapeutic value for the prevention and treatment of malignancies, respectively.

Season of birth contributes to variation in university examination outcomes

Epidemiological studies show that birth season influences a wide range of biological parameters such as growth, reproduction, mental illnesses, dyslexia, personality, and success in school. The present study is aimed at examining birth season's relationship to examination marks achieved at a university in a very large contemporary sample of male and female undergraduate students. We find that female university students born in spring and summer achieve better marks than those born in autumn and winter. Male students born in spring receive worse marks than those born in other seasons of the year. Furthermore, we find a birth-week periodicity in examination results of female students, with highest examination results for those born in May. We suppose that biological mechanisms might explain part of the observed effects.

Controlling reaching movements with predictable and unpredictable target motion in 10-year-old children and adults

We investigated interception behavior in adults and 10-year-old children. Participants had to intercept virtual targets moving on either a predictable (linear) or unpredictable (non-linear) path (with random direction changes). Targets moved at two different velocities, which varied randomly from trial to trial. Participants reached for the targets via a force-feedback device. Reaching movements for linearly moving targets in a block of linearly moving targets were compared with reaching movements for linearly moving targets in the context of non-linearly moving targets. Movement direction and maximum speed of the first sub-movement were analyzed as well as frequency of target hits and number of sub-movements. Unpredictable target motion caused faster movement speeds than predictable target motion for both children and adults. Additionally, unpredictable target motion caused children and adults to gear their initial movement direction further towards the current position of the target, while with predictable target motion, they geared their initial movement direction further ahead of the target towards an anticipated interception position. Together, these results suggest differential processing of predictable and unpredictable object behavior in an interception task, and that this differential processing is already in place in 10-year-olds.

Gaze behaviour in hereditary prosopagnosia

Prosopagnosia is the inability to recognize someone by the face alone in the absence of sensory or intellectual impairment. In contrast to the acquired form of prosopagnosia we studied the congenital form. Since we could recently show that this form is inherited as a simple monogenic trait we called it hereditary form. To determine whether not only face recognition and neuronal processing but also the perceptual acquisition of facial information is specific to prosopagnosia, we studied the gaze behaviour of four hereditary prosopagnosics in comparison to matched control subjects. This rarely studied form of prosopagnosia ensures that deficits are limited to face recognition. Whereas the control participants focused their gaze on the central facial features, the hereditary prosopagnosics showed a significantly different gaze behaviour. They had a more dispersed gaze and also fixated external facial features. Thus, the face recognition impairment of the hereditary prosopagnosics is reflected in their gaze behaviour.

[The clinical significance of cosmic radiation in aviation]

The possible adverse health effects of cosmic radiation remains an important topic in the consultation of aviators and frequent flyers. A good number of articles, dealing with this questions have been published recently but produced controversial results.

METHODS

We performed a Medline database search and identified 20 relevant articles that were published between 1990 and 2003. There were one retro-/prospective, 13 retrospective, 3 prospective cohort studies and 3 metaanalysis reviewed. Sixteen studies were set in the civil aviation environment, two studies in the military aviation environment and two studies were set in both environments.

RESULTS

Seven out of nine studies found an identical or decreased over-all-risk for aviators to develop cancer of any kind compared to the general population. In re- gards to skin cancer, seven out of eight studies found an increased risk for aviators to develop malignant melanoma, basalioma or other kinds of skin cancer. Three studies found an increased risk for the development of prostate cancer and two studies were able to demonstrate a higher risk for the appearance of leukaemia.

CONCLUSIONS

Although our review found some studies, that identified higher risks for pilots to develop cancer of the skin, prostate cancer or leukaemia, there is not enough scientific evidence to support the hypothesis, that cosmic radiation is the cause for these findings. It shows to be important to include other factors in the interpretation of the results, since some of the findings may be well explained by life-style factors of the aviation community.

Academic mothers have a pronounced seasonal variation in their offspring sex ratio

OBJECTIVES

Environmental and socio-demographic factors can influence the variation of the human sex ratio at birth (SRB = the ratio of males to males plus females). In particular, findings of seasonal, parental education, birth order, and maternal age effects on the SRB are not always in agreement, and a number of works report minimal variation.

SETTING

Here, we investigated the seasonality of SRB in academic and non-academic mothers employed at the University of Vienna, and who gave birth between 1963 and 2000 (n = 1932 births).

METHODS

All data were available from an anonymous employee database.

RESULTS

Both groups, academic and non-academic mothers do not differ between their overall SRB. In academic mothers the SRB is significantly (P = 0.004) increased during the springtime and decreased during the summertime. Although in non-academic mothers the trend is comparable, it is far less pronounced and not significant (P = 0.345). When a multiple logistic model was applied to the data of academic mothers the only significant influencing factor on the SRB is the season, while birth order of children and mothers' age at childbirth has no effect. None of the three independent variables influence the SRB in non-academic mothers.

MAIN FINDINGS

These findings suggest a more flexible SRB rate in academic mothers than in non-academics within the seasons.

CONCLUSION

We conclude that the significant seasonal variation of the SRB in academic women cannot be merely interpreted as an effect of socio-economic status but more likely as the interaction between socio-economic and environmental working conditions.