16 resultados para Environnement foetal défavorable

em Deakin Research Online - Australia


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Background: Recent developments have made screening tests for foetal abnormalities available earlier in pregnancy and women have a range of testing options accessible to them. It is now recommended that all women, regardless of their age, are provided with information on prenatal screening tests. General Practitioners (GPs) are often the first health professionals a woman consults in pregnancy. As such, GPs are well positioned to inform women of the increasing range of prenatal screening tests available. The aim of this study was to explore GPs experience of informing women of prenatal genetic screening tests for foetal abnormality.
Methods: A qualitative study consisting of four focus groups was conducted in metropolitan and rural Victoria, Australia. A discussion guide was used and the audio-taped transcripts were independently coded
by two researchers using thematic analysis. Multiple coders and analysts and informant feedback were employed to reduce the potential for researcher bias and increase the validity of the findings.
Results: Six themes were identified and classified as 'intrinsic' if they occurred within the context of the consultation or 'extrinsic' if they consisted of elements that impacted on the GP beyond the scope of the
consultation. The three intrinsic themes were the way GPs explained the limitations of screening, the extent to which GPs provided information selectively and the time pressures at play. The three extrinsic
factors were GPs' attitudes and values towards screening, the conflict they experienced in offering screening information and the sense of powerlessness within the screening test process and the health
care system generally. Extrinsic themes reveal GPs' attitudes and values to screening and to disability, as well as raising questions about the fundamental premise of testing.
Conclusion: The increasing availability and utilisation of screening tests, in particular first trimester tests,has expanded GPs' role in facilitating women's informed decision-making. Recognition of the importance
of providing this complex information warrants longer consultations to respond to the time pressures that GPs experience. Understanding the intrinsic and extrinsic factors that impact on GPs may serve to shape
educational resources to be more appropriate, relevant and supportive.

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1.Sex allocation theory has received considerable attention, yet the mechanism(s) by which mothers skew offspring sex ratios remain unknown. In birds, females are the heterogametic sex, which potentially gives them control of whether gametes will be male or female. How females might control the sex of the gamete is unclear, but one possibility is that variation in steroid hormones may mediate this process. 2.We experimentally altered circulating levels of corticosterone in female Gouldian finches (Erythrura gouldiae), a species that demonstrates both extreme stress responses and extreme offspring sex ratio biases when breeding with a low-quality (genetically incompatible) partner. 3.During egg production, individual females received both corticosterone and metyrapone (a corticosterone-synthesis inhibitor) implants, in random order, to induce both high and low levels of circulating stress hormones (within physiological limits). 4.We found that females with elevated corticosterone levels produced male-biased sex ratios, but when the same females were treated with metyrapone they produced female-biased offspring sex ratios. 5.These stress responses are adaptive because females constrained to breeding with low-quality males can substantially increase their fitness by overproducing sons. Changes in maternal corticosterone levels during stressful situations, such as the quality of a breeding partner, may provide an endocrine mechanism that can be exploited for strategic sex allocation.

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Development of the foetal autonomic nervous system can be indirectly understood by looking at the changes in beat to beat variability in foetal heart rates. This study presents Tone-Entropy (T-E) analysis of foetal heart rate variability (HRV) at multiple lags (1–8) to understand the influence of gestational ages (early and late) on the development of the foetal autonomic nervous system (ANS). The analysis was based on foetal electrocardiograms (FECGs) of 46 healthy foetuses of 20–32 weeks (early group) and 22 foetuses of 35–41 weeks (late group). Tone represents sympatho-vagal balance and entropy the total autonomic activities. Results show that tone increases and entropy decreases at all lags for the late foetus group. On the other hand, tone decreases and entropy increases at lags 1–4 in the early foetus group. Increasing tone in late foetuses might represent significant maturation of sympathetic nervous systems because foetuses approaching to delivery period need increased sympathetic activity. T-E could be quantitative clinical index to determine the early foetuses from late ones on the basis of maturation of autonomic nervous system.

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The heart is the first organ to form and undergoes adaptive remodelling with age. Ventricular hypertrophy is one such adaptation, which allows the heart to cope with an increase in cardiac demand. This adaptation is necessary as part of natural growth from foetal life to adulthood. It may also occur in response to resistance in blood flow due to various insults on the heart and vessels that accumulate with age. The heart can only compensate to this increase in workload to a certain extent without losing its functional architecture, ultimately resulting in heart failure. Many genes have been implicated in cardiac hypertrophy, however none have been shown conclusively to be responsible for pathological cardiac hypertrophy. MicroRNAs offer an alternative mechanism for cellular regulation by altering gene expression. Since 1993 when the function of a non-coding DNA sequence was first discovered in the model organism Caenorhabditis elegans, many microRNAs have been implicated in having a central role in numerous physiological and pathological cellular processes. The level of control these antisense oligonucleotides offer can often be exploited to manipulate the expression of target genes. Moreover, altered levels of microRNAs can serve as diagnostic biomarkers, with the prospect of diagnosing a disease process as early as during foetal life. Therefore, it is vital to ascertain and investigate the function of microRNAs that are involved in heart development and subsequent ventricular remodelling. Here we present an overview of the complicated network of microRNAs and their target genes that have previously been implicated in cardiogenesis and hypertrophy. It is interesting to note that microRNAs in both of these growth processes can be of possible remedial value to counter a similar disease pathophysiology.

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Copper deficiency during pregnancy results in early embryonic death and foetal structural abnormalities including skeletal, pulmonary and cardiovascular defects. During pregnancy, copper is transported from the maternal circulation to the foetus by mechanisms which have not been clearly elucidated. Two coppertransporting ATPases, Menkes (ATP7A; MNK) and Wilson (ATP7B; WND), are expressed in the placenta and both are involved in placental copper transport, as copper accumulates in the placenta in both Menkes and Wilson disease. The regulatory mechanisms of MNKand WNDand their exact role in the placenta are unknown. Using a differentiated polarized Jeg-3 cell culture model of placental trophoblasts, MNK and WND were shown to be expressed within these cells. Distinct roles forMNKandWND are suggested on the basis of their opposing responses to insulin. Insulin and oestrogen increased both MNK mRNA and protein levels, altered the localization of MNK towards the basolateral membrane in a copper-independent manner, and increased the transport of copper across this membrane. In contrast, levels of WND were decreased in response to insulin, and the protein was located in a tight perinuclear region, with a corresponding decrease in copper efflux across the apical membrane. These results are consistent with a model of copper transport in the placenta in which MNK delivers copper to the foetus and WND returns excess copper to the maternal circulation. Insulin and oestrogen stimulate copper transport to the foetus by increasing the expression of MNK and reducing the expression of WND. These data show for the first time that MNK and WND are differentially regulated by the hormones insulin and oestrogen in human placental cells.

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The publication of a Preliminary Final Assessment Report on 4 April 2007 heralded another step towards the introduction of a new Health Claims Standard to be inserted into the Australia New Zealand Food Standards Code. This Health Claims Standard, once approved by the Board of Food Standards Australia New Zealand and by the Australia New Zealand Food Regulation Ministerial Council, will permit the making of certain substantiated health claims. Prior to the introduction of the new Standard, health claims have not been permitted on food labels, with the exception of claims in relation to maternal folate consumption and its positive effect in reducing the risk of foetal neural tube defects. The new Health Claims Standard as outlined in the Preliminary Final Assessment Report is likely to have a significant impact on the dairy industry. This paper seeks to analyse that impact, including threats, opportunities and challenges that the Standard poses to the dairy industry and other food suppliers.

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Information on the status of long-chain polyunsaturated fatty acids (LCPUFAs) in pregnancy and breast milk in very high fish-eating populations is limited. The aim of this study was to examine dietary intake and changes in fatty acid status in a population of pregnant women in the Republic of Seychelles. Serum docosahexaenoic acid (DHA) decreased significantly between 28-week gestation and delivery (n=196). DHA status did not correlate significantly with length of gestation and was not associated with self-reported fish intake, which was high at 527 g/week. In breast milk, the ratio of DHA to arachidonic acid (AA) was consistent with those observed in other high fish-eating populations. Overall the data suggest that high exposure to LCPUFAs from habitual fish consumption does not prevent the documented decrease in LCPUFA status in pregnancy that occurs as a result of foetal accretion in the third trimester of pregnancy.

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To investigate the mechanisms for the previously reported development of adult cardiac hypertrophy in male rats following growth restriction, the levels of oxidative stress and activation of signaling kinases were measured in the left ventricle (LV) of adult rat offspring. In experiment one, bilateral uterine vessel ligation to induce uteroplacental insufficiency and growth restriction in the offspring (Restricted) or sham surgery was performed during pregnancy. Litters from sham mothers had litter size either reduced (Reduced Litter), which also restricted postnatal growth, or were left unaltered (Control). In males, Reduced Litter offspring had increased LV phosphorylation of AMPKa, p38 MAPK and Akt compared with Restricted and Controls (P,0.05). In females, both Restricted and Reduced Litter adult offspring had increased LV phosphorylation of p38 MAPK and Akt, however, only Restricted offspring had increased phosphorylation of AMPKa (P,0.05). In addition, only Restricted male offspring displayed LV oxidative stress (P,0.05). Experiment two investigated in mothers exposed to uteroplacental insufficiency or sham surgery the effects of cross-fostering offspring at birth, and therefore the effects of the postnatal lactational environment. Surprisingly, the cross-fostering itself resulted in increased LV phosphorylation of AMPKa and Akt in females and increased phosphorylation of Akt in males compared with Control non-cross-fostered offspring (P,0.05). In conclusion, kinase signaling in the adult LV can be programmed by uteroplacental insufficiency induced growth restriction in a gender-specific manner. In addition, the heart of adult rats is also sensitive to programming following the postnatal intervention of cross-fostering alone as well as by postnatal growth restriction.

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Foetal growth restriction impairs skeletal muscle development and adult muscle mitochondrial biogenesis. We hypothesized that key genes involved in muscle development and mitochondrial biogenesis would be altered following uteroplacental insufficiency in rat pups, and improving postnatal nutrition by cross-fostering would ameliorate these deficits. Bilateral uterine vessel ligation (Restricted) or sham (Control) surgery was performed on day 18 of gestation. Males and females were investigated at day 20 of gestation (E20), 1 (PN1), 7 (PN7) and 35 (PN35) days postnatally. A separate cohort of Control and Restricted pups were cross-fostered onto a different Control or Restricted mother and examined at PN7. In both sexes, peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α (PGC-1α), cytochrome c oxidase subunits 3 and 4 (COX III and IV) and myogenic regulatory factor 4 expression increased from late gestation to postnatal life, whereas mitochondrial transcription factor A, myogenic differentiation 1 (MyoD), myogenin and insulin-like growth factor I (IGF-I) decreased. Foetal growth restriction increased MyoD mRNA in females at PN7, whereas in males IGF-I mRNA was higher at E20 and PN1. Cross-fostering Restricted pups onto a Control mother significantly increased COX III mRNA in males and COX IV mRNA in both sexes above controls with little effect on other genes. Developmental age appears to be a major factor regulating skeletal muscle mitochondrial and developmental genes, with growth restriction and cross-fostering having only subtle effects. It therefore appears that reductions in adult mitochondrial biogenesis markers likely develop after weaning.

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Pregnancy is now considered to be an important risk factor for new or persistent obesity among women during the childbearing years. High gestational weight gain is the strongest predictor of maternal overweight or obesity following pregnancy. A growing body of evidence also suggests that both high and low gestational weight gains are independently associated with an increased risk of childhood obesity, suggesting that influences occurring very early in life are contributing to obesity onset. In response to these data, the US Institute of Medicine (IOM) revised gestational weight gain guidelines in 2009 for the first time in nearly two decades. However, less than one third of pregnant women achieve guideline-recommended gains, with the majority gaining above IOM recommended levels. To date, interventions to optimize pregnancy weight gains have had mixed success. In this paper, we summarize the evidence from human and animal studies linking over-nutrition and under-nutrition in pregnancy to maternal and child obesity. In addition, we discuss published trials and ongoing interventions to achieve appropriate gestational weight gain as a strategy for obesity prevention in women and their children.

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Long chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) particularly, eicosapentaenoic acid (EPA, 22: 5n-3) and docosahexaenoic acid (DHA, 22: 6n-3) have been reported to reduce the risks of cardiovascular disease (CVD) including myocardial infarction, stroke, coronary artery disease and sudden cardiac death. In addition, these fatty acids play an important role in reduction of cancer risks, Alzheimer's disease, depression and schizophrenia. Furthermore, studies also showed that EPA and DHA are important for foetal development, particularly neuronal and retinal functions. Several recent human trials have strengthened the evidence that EPA and DHA can reduce the risks of various chronic diseases although this has not been a uniform finding. In general, the high prevalence of mortality caused by chronic disease can be prevented by consumption of LC n-3 PUFA, which has been proven to have considerable health benefits. The aim of this paper was to review main scientific evidence regarding the health impact of LC n-3 PUFA, especially EPA and DHA on chronic disease including CVD, cancer, mental health, arthritis and infant development.

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Postpartum weight retention can predict future weight gain and long-term obesity. Moreover, failure to lose weight gained during pregnancy can lead to increased body mass index for subsequent pregnancies, increasing the risk of adverse maternal and foetal pregnancy outcomes. This systematic review evaluates the effectiveness of lifestyle interventions aimed at reducing postpartum weight retention. Seven electronic databases were searched for intervention studies and trials enrolling women with singleton pregnancies and published in English from January 1990 to October 2012. Studies were included when postpartum weight was a main outcome and when diet and/or exercise and/or weight monitoring were intervention components. No limitations were placed on age, body mass index or parity. Eleven studies were identified as eligible for inclusion in this review, of which 10 were randomized controlled trials. Seven studies were successful in decreasing postpartum weight retention, six of which included both dietary and physical activity components, incorporated via a range of methods and delivered by a variety of health practitioners. Few studies utilized modern technologies as alternatives to traditional face-to-face support and cost-effectiveness was not assessed in any of the studies. These results suggest that postpartum weight loss is achievable, which may form an important component of obesity prevention in mothers; however, the optimal setting, delivery, intervention length and recruitment approach remains unclear.

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The contribution of mitochondrial dysfunction to insulin resistance is a contentious issue in metabolic research. Recent evidence implicates mitochondrial dysfunction as contributing to multiple forms of insulin resistance. However, some models of mitochondrial dysfunction fail to induce insulin resistance, suggesting greater complexity describes mitochondrial regulation of insulin action. We report that mitochondrial dysfunction is not necessary for cellular models of insulin resistance. However, impairment of mitochondrial function is sufficient for insulin resistance in a cell type-dependent manner, with impaired mitochondrial function inducing insulin resistance in adipocytes, but having no effect, or insulin sensitising effects in hepatocytes. The mechanism of mitochondrial impairment was important in determining the impact on insulin action, but was independent of mitochondrial ROS production. These data can account for opposing findings on this issue and highlight the complexity of mitochondrial regulation of cell type-specific insulin action, which is not described by current reductionist paradigms.