Neville W. Bruce

Placental Growth in Rats Exposed to Carbon Monoxide at Selected Stages of Pregnancy

Maternal hypoxemia has been associated with fetal-growth retardation and placental hypertrophy. Here, rats were exposed to carbon monoxide (CO), 100 ppm, at different stages of gestation to determine when during pregnancy placental hypertrophy can be elicited, whether hypertrophy is sustained when the stimulus is removed, and whether placental hypertrophy correlates with maintenance of normal fetal growth. Groups of rats (11-17 per group) were exposed to CO, throughout gestation, or over days 1-16, 4-12, 10-22 and 18-22, to cover significant periods of placental growth. Maternal carboxyhemoglobin levels were estimated to be in the order of 10-14%, but there was no effect on fetal survival. Fetal weights were significantly reduced by 8 and 6% in groups treated over days 1-22 and 10-22 of pregnancy, but not in those where treatment ceased before term, and surprisingly not in the group treated over days 18-22, the stage of maximal fetal growth. Placental weights were significantly increased by 11-13% in all groups in which carbon monoxide exposure was continued to term, but were unaffected in cases where treatment ceased before term. These results show that near term the placenta, when it is thought to normally reach the limit of its functional capacity, can hypertrophy in response to CO, and suggest that this response benefits the fetus presumably by improving oxygen transport.

Psychosocial stress and the menstrual cycle.

The relationship between mood states, urinary stress hormone output (adrenaline, noradrenaline and cortisol) and adequacy of the menstrual cycle was examined in 120 recorded non-conception cycles from 34 women. It was hypothesized that women with higher stress levels would be more likely to experience abnormal cycles and that within women higher stress levels would positively relate to follicular phase length and inversely relate to luteal phase length. There was a non-significant trend for women to report higher stress levels during oligomenorrhoeic and unclear cycles compared with normal cycles. Analysis of covariance indicated that there was no consistent relationship between the measures of stress used here and follicular or luteal phase length within women. There was also no consistent pattern of relationship between reported mood states and stress hormone excretion within women. Further research is warranted to understand the role of stress and subtle menstrual cycle abnormalities in female fertility.

Incidence and duration of romantic attraction in students progressing from secondary to tertiary education

There is increasing interest in the nature and biological significance of romantic love but few quantitative data are available for testing specific hypotheses. This paper describes the use of a survey instrument to assess incidence and duration of romantic attractions over a 2-year period amongst students (121 male; 162 female) progressing from school to university education. The results for males and females were similar and schooling single-sex or co-educational--had little effect. Students averaged 1.45 romantic episodes per year and 93% of students reported at least one episode over the survey period. Duration of attraction was around 9 weeks if never reciprocated and around 12 weeks if reciprocated. There was seasonal variation of onset of episodes with peak incidence over the summer or early autumn seasons. Collectively the results accord with the view that frequent, short-duration romantic episodes could have a role in selection of appropriate long-term reproductive partnerships.

Effect of dichotomous thinking on the association of depression with BMI and weight change among obese females.

This study tested whether a dichotomous thinking style moderates the association of depression with body mass, and investigated the effect of dichotomous thinking and depression on weight loss during a cognitive behavioural therapy (CBT) intervention. Overweight and obese females (n=76) participated in CBT for weight management for 12 weeks. Before treatment, dichotomous thinking moderated the association of depression with BMI, such that depression was positively associated with BMI among those with low dichotomous thinking, but was not associated among those with high dichotomous thinking. Weight loss was negatively associated with pre-treatment depression and frequency of treatment attendance, but not with dichotomous thinking. Females who regard their weight as unacceptably high and who think dichotomously may experience high levels of depression irrespective of their actual weight, while depression may be proportionate to the degree of obesity among those who do not think dichotomously. Depression, but not dichotomous thinking, is likely to interfere with the ability to adhere to short-term weight loss strategies.

Resistance of the rat embryo to elevated maternal epinephrine concentrations

This study examined the effects of a chronic maternal infusion of epinephrine on development of the rat embryo. Epinephrine was infused during days 1 to 8, 8 to 15, or 15 to 22 of pregnancy to cover periods of implantation, embryogenesis, and rapid fetal growth, respectively. Infusions were accomplished with osmotic minipumps to avoid repeated handling stress. The infusion rate of 0.125 micrograms/min elevated resting plasma concentrations of epinephrine in nonpregnant rats by about sevenfold (from 0.28 to 1.98 ng/ml). Under these conditions, epinephrine did not affect the number of rats maintaining pregnancy, their litter size, or the numbers of resorptions, fetal deaths, and malformations. Fetal and placental weights were unaffected except for a slight trend for fetal weight to be depressed in larger litters of rats treated during days 15 to 22. It seems that the rat embryo is resistant to elevations of epinephrine concentrations equivalent to those observed under mild to severe stress conditions.

A study of handling cytotoxic drugs and risk of birth defects in offspring of female veterinarians

We examined the association of occupational exposure to handling cytotoxic drugs at work with risk of birth defects among a cohort of female veterinarians. This study is a follow up survey of 321 female participants (633 pregnancies) who participated in the Health Risks of Australian Veterinarian project. Data on pregnancies and exposure during each pregnancy was obtained by self-administered mailed questionnaire. Female veterinarians handling cytotoxic drugs during their pregnancy had a two-fold increased risk of birth defects in their offspring (RR = 2.08, 95% CI (1.05–4.15)). Results were consistent in subgroup analysis of those who graduated during the period of 1961 to 1980 (RR = 5.04, 95% CI (1.81, 14.03) and in those working specifically in small and large animal practice. There was no increased risk in the subgroup that graduated after 1980. Women with unplanned pregnancies were more likely to handle cytotoxic drugs on a daily basis (RR = 1.86, 95% CI, 1.00–3.48) and had a higher increased risk of birth defects than those who planned their pregnancies in recent graduates and in those who worked specifically in small animal practice (RR = 2.53, 95% CI, 1.18–5.42). This study suggests that the adverse effects of handling cytotoxic drugs in pregnant women may include an increased risk of birth defects. Pregnancy intention status is an important health behavior and should be considered in prenatal programs.