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Suppression of luteinizing hormone pulses by restriction of glucose availability is mediated by sensors in the brain stem.

The availability of metabolic fuels such as glucose is known to influence reproductive function. Peripheral administration of 2-deoxyglucose (2DG), a competitive inhibitor of glycolysis, inhibits pulsatile LH secretion in the rat and growth-retarded lamb. We hypothesized that such glucoprivic suppression of LH secretion is mediated by the lower brain stem, because studies of both ingestive and reproductive behavior implicate lower brain stem structures, such as the area postrema, as a site that is sensitive to glucose availability. In the present study, the effect of a 2DG infusion, targeted to the fourth ventricle, on pulsatile LH secretion was examined in male rats. The males were castrated or castrated and immediately implanted with testosterone. Blood samples were collected through an indwelling atrial cannula every 6 min for 4 h for LH determination. After the first hour of blood sampling, 2DG (4 or 40 mg/kg) was infused into the fourth ventricle at a flow rate of 0.2 microliter/min through a cannula that had been stereotaxically implanted 1 week before sampling. The high dose of 2DG (40 mg/kg), but not the low dose (4 mg/kg), suppressed pulsatile LH secretion and increased food intake in both castrated and testosterone-treated castrated rats. LH secretion and food intake were not affected by the infusion of xylose (40 mg/kg) as an isoosmotic control. The site specificity of the 2DG treatment was confirmed by histological examination after an isovolumetric infusion of dye (0.2 microliter/min). These results suggest that glucose availability could influence LH secretion as well as feeding through a central sensor in the lower brain stem and are consistent with the idea that the area postrema might be an important glucosensor involved in the modulation of LH secretion.

Animals↗

Estrogen increases proenkephalin messenger ribonucleic acid levels in the ventromedial hypothalamus of the rat.

The effects of estrogen on proenkephalin (PE) gene expression were measured in neurons of the ventromedial hypothalamus. Slot blot hybridization analysis indicates that the levels of PE mRNA in the ventromedial hypothalamus of ovariectomized rats increase 3.1-fold after 2 weeks of estrogen replacement. In situ hybridization reveals that the estrogen-inducible enkephalinergic neurons are located in the ventrolateral aspect of the ventromedial nucleus, a subnucleus known to contain many estrogen-concentrating neurons. The increase in PE mRNA levels is due to both a 63% increase in the number of detectable PE mRNA-containing neurons and a 2.0-fold increase in the levels of PE mRNA per enkephalinergic neuron (1.63 x 2.0 = 3.3-fold overall induction). This estrogen-regulated enkephalinergic cell group may represent part of the neural network mediating estrogen's effects on reproductive behavior and/or other neuroendocrine processes.

Animals↗

Introduction to menstrual disturbances in athletes.

The first symposium on this topic at an annual meeting of ACSM was presented 22 yr ago when the high prevalence of menstrual disorders in athletes was becoming increasingly apparent. The clinical consequences and need for treatment for menstrual disturbances in athletes have been recognized by ACSM through the publication of its 1997 Position Stand on the Female Athlete Triad. This mini-symposium presents an update on recent scientific advances on this topic. The first review in this symposium concentrates on a menstrual disturbance in which the length of the luteal phase is abbreviated and luteal function is suppressed. Such luteal suppression occurs in a large proportion of even the most regularly menstruating athletes. The next two papers summarize what has been learned about the mechanism of these disturbances from prospective experiments that have employed diet, exercise, cold exposure, and pharmacological blockers of metabolic pathways to disrupt menstrual cycles in monkeys and humans as well as estrous cycles and reproductive behavior in hamsters.

Adolescent↗

Limb malformations and abnormal sex hormone concentrations in frogs.

Declines in amphibian populations, and amphibians with gross malformations, have prompted concern regarding the biological status of many anuran species. A survey of bullfrogs, Rana catesbeiana, and green frogs, Rana clamitans, conducted in central and southern New Hampshire showed malformed frogs at 81% of the sites sampled (13 of 16 sites). Brain gonadotropin-releasing hormone (GnRH) and the synthesis of androgens and estradiol, hormones essential to reproductive processes, were measured from limb-malformed and normal (no limb malformation) frogs. Normal frogs had significantly higher concentrations (nearly 3-fold) of in vitro produced androgens and of brain GnRH than malformed frogs. Because most malformations are thought to occur during development, we propose that environmental factors or endocrine-disrupting chemicals that may cause developmental abnormalities also act during early development to ultimately cause abnormally reduced GnRH and androgen production in adult frogs. The consequences of reduced GnRH and androgens on anuran reproductive behavior and population dynamics are unknown but certainly may be profound and warrant further research.

Androgens↗

Aromatase activity in the ovary and brain of the eastern mosquitofish (Gambusia holbrooki) exposed to paper mill effluent.

Studies have shown that female mosquitofish living downstream of a paper mill located on the Fenholloway River, Florida, have masculinized secondary sex characteristics, including altered anal fin development and reproductive behavior. Masculinization can be caused by exposure to androgens in the water or from an alteration in aromatase activity in the fish. We hypothesized that aromatase activity would be inhibited by a component(s) of the paper mill effluent. Aromatase inhibition could masculinize the hormonal profile and, subsequently, secondary sex characteristics of the exposed females. Therefore, we predicted that ovarian and brain aromatase activity would be lower in the female mosquitofish from the Fenholloway River compared with the reference site, the Econfina River. Adult females were collected and standard length, body mass, anal fin length, and segment number were measured. Ovarian and brain aromatase activity were determined using a tritiated water assay. Fenholloway females had masculinized anal fin development as indicated by an increase in the number of segments in the longest anal fin ray (p < 0.0001), yet the length of the ray did not differ between sites (p = 0.95). Fenholloway females exhibited higher ovarian (p = 0.0039) and brain (p = 0.0003) aromatase activity compared with reference site fish. These data do not support aromatase inhibition as the mechanism for masculinization, suggesting that the masculinization of the Fenholloway female mosquitofish is due to androgenic contaminants. Future studies should examine the relationship between aromatase enzyme activity and exposure to environmental androgens.

Animals↗

Tinkering with the tinkerer: pollution versus evolution.

Pollutants can act as powerful selective forces by altering genetic variability, its intergenerational transfer, and the size, functional viability, adaptability, and survival of future generations. It is at the level of the cell and the individual that meiosis occurs, that genetic diversity is maintained, and behavior, reproduction, growth, and survival occur and are regulated. It is at this level that evolutionary processes occur and most pollutants exert their toxic effects. Chronic exposure to chemicals contributes to the cumulative stress on individuals and disrupts physiological processes and chemically mediated communication thereby threatening the diversity and long-term survival of sexually reproducing biota. Regional or global effects of pollution on the atmosphere, hydrosphere, and lithosphere have indirectly altered Earth's life-support systems, thereby modifying trace metal balance, reproduction, and incidence of UV-B-induced DNA damage in biota. By altering the competitive ability and survival of species, chemical pollutants potentially threaten evolutionary processes and the biodiversity and function of intercepting ecosystems.

Animals↗

Effects of organochlorine contaminants on thyroid hormone levels in Arctic breeding glaucous gulls, Larus hyperboreus.

Studies on glaucous gulls (Larus hyperboreus) breeding in the Barents Sea have reported that high blood levels of halogenated organic contaminants in this species might cause reproductive, behavioral, and developmental stress. However, potential endocrine system modulation caused by contaminant exposure has yet not been reported in this Arctic apical predator. In this present study we aimed to investigate whether the current levels of a selection of organochlorines (OCs) were associated with altered circulating levels of thyroid hormones (THs) in free-ranging adult glaucous gulls breeding at Bear Island in the Barents Sea. Blood concentrations of 14 polychlorinated biphenyls, hexachlorobenzene (HCB), oxychlordane, and p,p' -dichlorodiphenyldichloroethylene (p,p' -DDE) were quantified, in addition to free and total thyroxine (T4) and triiodothyronine (T3), in plasma of 66 glaucous gulls in the spring of 2001. Negative correlations were found between plasma levels of T4 and T4:T3 ratio, and blood levels of OCs in male glaucous gulls. Despite their relatively low contribution to the total OC fraction, HCB and oxychlordane were the most prominent compounds in terms of their negative effect on the variation of the T4:T3 ratio. Moreover, lower T4 levels and T4:T3 ratios were measured in glaucous gulls breeding in a colony exposed to high levels of OCs, compared with a less exposed colony. Levels of T3 were elevated in the high-OC-exposed colony. This may indicate that the glaucous gull is susceptible to changes to TH homeostasis mediated by exposure to halogenated organic contaminants.

Animals↗

Ecological aspects of mercury--selenium interactions in the marine environment.

In the marine environment, mercury is accompanied by selenium in all investigated species of mammals, birds, and fish--possibly due to a normal homeostatic regulation. It therefore seems likely that selenium will exert its protective action against mercury toxicity in the marine environment, decreasing its detrimental effects on reproduction, behavior, growth, etc. of the organisms and thus protect the population and ecosystem. On the other hand, the increased retention of mercury caused by selenium may lead to a higher level of biomagnification in the food chain and a higher burden in the individual. This might counteract the positive effect of decreased intoxication.

Animals↗

Mechanisms of spontaneous human cancers.

The causes of much of human cancer remain obscure. The fraction that is spontaneous is unknown and cannot be calculated until all known external causes have been accounted for. This is not a feasible proposition. However, there is substantial evidence that about 80% of human cancer could be avoided by eliminating tobacco consumption; by dietary changes; by reducing infection with certain viruses, bacteria, and parasitic worms; and, in white populations, by avoiding sunburn. Alcohol, occupational and medical carcinogens, and certain patterns of reproductive behavior also contribute to the cancer burden. Cancers that cannot be attributed to these causes, and for which no other causes can be found, could be considered spontaneous and to arise from endogenous processes. Epidemiological evidence suggests that spontaneous and induced cancers share the same mechanism. Cancer is a genetic disorder of somatic cells. An accumulation of mutant genes that control the cell cycle, maintain genomic stability, and mediate apoptosis is central to carcinogenesis. Spontaneous mutation may cause spontaneous cancer. Endogenous causes of mutation include depurination and depyrimidation of DNA; proofreading and mismatch errors during DNA replication; deamination of 5-methylcytosine to produce C to T base pair substitutions; and damage to DNA and its replication imposed by products of metabolism (notably oxidative damage caused by oxygen free radicals). Deficiencies in cellular defense mechanisms may also provoke spontaneous mutation. These include defective DNA excision-repair; low levels of antioxidants, antioxidant enzymes, and nucleophiles that trap DNA-reactive electrophiles; and enzymes that conjugate nucleophiles with DNA-damaging electrophiles. Mechanisms underlying many of those cellular defenses are under genetic control. Thus, germ line mutations or polymorphisms of genes that govern them may also contribute to spontaneous cancer.

5-Methylcytosine↗

Three-dimensional image analysis of a head of the giant panda by the cone-beam type CT.

The cone-beam type CT (Computed Tomography) enabled us to collect the three-dimensional (3D) digitalized data directly from the animal carcass. In this study, we applied the techniques of the cone-beam type CT for a carcass head of the giant panda (Ailuropoda melanoleuca) to obtain the 3D images easily without reconstruction process, and could morphologically examine the sections from the 3D data by means of non-destructive observations. The important results of the study represent the two following points. 1) We could show the morphological relationships between the muscles of mastication and the mandible in non-destructive status from the 3D data. The exact position of the coronoid process could be recognized in the rostro-lateral space of the temporal fossa. 2) By the serial sections from the 3D data sets, the morphological characteristics in the nasal cavity were detailed with high resolution in this rare species. The nasal concha was well-developed in the nasal cavity. The ethmoidal labyrinth was encountered immediately caudal to the nasal cavity and close to the region of the olfactory bulb. The ethmoidal labyrinth consisted of the complicated osseous structure in this area. The data will be useful to discuss the olfactory function in the reproduction behavior of this species.

Animals↗

Breast cancer: a psychogenic disease?

Over the centuries, the breast cancer literature has contained numerous references to the role of psychological factors in the etiology of the disease. Theories and research findings pertaining to this work are reviewed, with a focus on twentieth century work. The specific hypotheses examined in each historic period can be seen in the context of views held about women in society. Epidemiologic features of breast cancer, particularly certain reproductive behaviors, are associated with specific lifestyles, and these features lend themselves to the investigation of the role of personality in the etiology of the disease. In the eighteenth and 19th centuries, clinicians wrote of the role of depression, grief and anxiety in the etiology of breast cancer. Hard work, which women were not supposed to engage in, resulted in breast tumors. The rise of interest in psychodynamic theories in the twentieth century resulted in a proliferation of investigations demonstrating the association between sexual repression or ambivalence about the female role and breast cancer. The language of psychoanalysis was used throughout society. Single women, at increased risk of breast cancer, were seen as suffering from unconscious rejection of their femininity. Although the study designs used to investigate this association were inadequate and the findings equivocal, belief in this association has continued. More recent work in this field has focussed on the role of repressed anger, reflecting a societal preoccupation with constraints on self-expression. Hypotheses regarding the psychological etiology of breast cancer can be examined in the social context in which they evolve and tend to reflect views of women rather than truths derived from research data.

Anger↗

Women's choice between indigenous and Western contraception in urban Mozambique.

Research on women's reproductive behavior and family planning in developing countries is usually focused on western contraceptive methods and rarely addresses indigenous contraception, such as herbs, amulets, and charms that are believed to prevent pregnancy. However, the available data demonstrate that indigenous contraception is widely known, and its prevalence often rivals that of western methods. Based on qualitative data collected in Greater Maputo, Mozambique, in 1993, this study explores and analyzes women's choice between western methods-mainly oral contraceptives, intra-uterine devices and injectables-available from state-run family planning clinics, and indigenous contraception, a combination of herbal and magical medicine, provided by traditional healers. The study demonstrates that women's choice between the two types of methods is determined by their sociodemographic characteristics and cultural background, access to these methods, perceptions of the effectiveness and undesirable side-effects of these methods, and by restrictions imposed by the providers. Although indigenous methods may not compete with western contraception in the long run, their present-day persistence warrants the attention of scholars and policymakers who intend to integrate women's concerns and constraints in the design of family planning systems.

Choice Behavior↗

Ethnic variations in observance and rationale for postpartum sexual abstinence in Malawi.

Using quantitative and qualitative data from three culturally heterogeneous ethnic groups in Malawi, I show that differences in postpartum sexual abstinence are closely associated with community-specific rationales for the practice, particularly differences in the definition and timing of child-strengthening rituals that couples are required to perform before resuming intercourse. Contrary to conventional wisdom, the primary rationale for abstinence in the study areas is not linked to child spacing. Among Tumbukas in the north, most women perform the ritual immediately after resuming menstruation. Among the other ethnic groups, the rituals can be performed at any time after the end of postpartum bleeding. The study underscores the utility of the complementary micro-level approach in understanding reproductive behavior in sub-Saharan Africa.

Amenorrhea↗

Has the Chinese family planning policy been successful in changing fertility preferences?

Has China's strict one-child policy been successful in changing fertility preferences? Using linked data from surveys conducted in four counties of northern China in 1991 and 1994, we compare reproductive behavior against prior fertility preferences and show when and where women change from wanting to not wanting more children. The acceptance of policy-sanctioned family size follows a development gradient and reflects the degree of enforcement. High acceptance occurs in the most urban, industrialized county and in the county with the most rigid family planning policy. Acceptance is weaker among women living in the poorest county and in the county where enforcement is most lenient.

Birth Rate↗

Estradiol and progesterone modulate the nitric oxide/cyclic gmp pathway in the hypothalamus of female rats and in GT1-1 cells.

Considerable evidence suggests that the nitric oxide (NO)/cGMP signaling pathway plays an important role in the expression of reproductive behavior and in gonadotropin-releasing hormone (GnRH) release from the hypothalamus The effects of the NO/cGMP pathway on GnRH release and gene expression have also been examined in GT1 cells. However, it is still controversial whether NO/cGMP signaling facilitates or inhibits GnRH release in these cells. The current study examined the effects of estradiol and progesterone on neuronal NO synthase (nNOS), soluble guanylyl cyclase (sGC), and NO-dependent cGMP production in the preoptic area (POA) and hypothalamus (HYP) as well as in GT1-1 cells. Ovariectomized female rats received vehicle, estradiol benzoate (48 h) and/or progesterone (3-4 h) before preparation of brain slices. GT1-1 cells were incubated with vehicle, estradiol (48 h), progesterone (3-4 h), or with both hormones. The combination of estradiol and progesterone increased the expression of nNOS protein in the POA and HYP. Hormones had little effect on the abundance of sGC. Estradiol and progesterone together greatly enhanced NO-stimulated sGC activity in HYP-POA slices. In GT1-1 cells, NO-stimulated sGC activity was significantly increased by estradiol and progesterone, alone or in combination, but sGC expression was not altered by hormones.

Animals↗

Genetic counseling and neonatal screening for cystic fibrosis: an assessment of the communication process.

OBJECTIVE: To assess the effectiveness of communication between health care providers (physicians, nurses, genetic counselors) in Wisconsin and parents of children identified as heterozygote carriers for cystic fibrosis (CF) in the routine Wisconsin Newborn Screening Program that was implemented using trypsinogen/DNA testing. METHODS: Routine CF neonatal screening, implemented in July 1994, involved a statewide system that recommended but did not mandate follow-up sweat tests at 1 of the Wisconsin's 2 certified CF centers. The Wisconsin Division of Health sent requests to participate to the parents of 483 infants identified as CF carriers between July 1994 and December 1997. Of the 483 parents, 183 agreed to participate and were asked to complete a questionnaire assessing their CF newborn screening experiences and their knowledge of CF genetics and any changes they made in their reproductive behavior as a result of this knowledge. Follow-up telephone interviews by a genetic counselor were attempted within 1 year for those completing the questionnaire. RESULTS: Within 4 months after the mailing, 138 of 183 (75%) parents completed the questionnaire. Subsequently, 123 of the 138 responders (89%) were contacted and interviewed by telephone. We learned that 67.6% of parents recalled receiving genetic counseling, but 32.4% of parents apparently did not participate in a risk communication session. When asked, "Who performed the genetic counseling?" parents indicated that their communication was with physicians in 8% of cases, nurses in 12.4%, and certified genetic counselors in 32.8% of cases; 17.5% of parents did not recall who performed the genetic counseling and 29.2% of parents indicated they did not receive genetic counseling. Based on the 138 responses, it was found that 88.3% of parents understood that their child was a carrier for CF, but 15.4% of parents were unsure whether being a carrier could cause illness. In addition, 12.4% of parents were unsure whether at least 1 of them (parents) was a carrier of the CF gene. Only 57% of parents knew there was a 1 in 4 chance that their child could have a child with CF if he or she reproduced with another carrier of the CF gene. Statistically significant differences were noted when comparing the frequency of correct responses between parents who received genetic counseling and parents who had not. The frequency of accurate responses did not depend on which health care professional provided the genetic counseling. Comparing responses of parents who were seen at a certified CF center with parents seen at other community hospitals and clinics revealed significant differences in the frequency of correct responses, with the former group showing a higher percentage of correct responses. Telephone interviews revealed that 11.4% of parents were unaware that their child was a carrier for CF and that 54.5% wished they had more information made available to them at the time of the initial positive newborn screen result, before the definitive sweat test. Also, 13.8% of parents recommended that community physicians be better informed of the details and implications of positive screening results for CF. CONCLUSION: Genetic counseling is imperative for the success of newborn screening for CF and other congenital diseases. With the completion of the Human Genome Project, more molecular screening for childhood disease is bound to enter the clinical arena. Based on our findings, efforts must be made to ensure that newborn screening programs have the means and the methods to communicate newborn screening results effectively to families. In addition, both the general public and community health providers must be better informed of the implications of all newborn screening results. Additional research is needed to determine whether there are communication styles and approaches that are better suited to counseling parents regarding newborn screening results.

Adult↗

Maternal mode of living and child health.

In this article, maternal mode of living is investigated, examining both socioeconomic conditions and lifestyle factors, in order to identify to what extent health policies are tangibly meeting the needs of low income Brazilian mothers and children. Data are derived from unstructured interviews with 17 mothers with children under age 6, residing in the Federal District, Brazil. Their stories reveal a life marked by economic difficulties and inadequate living conditions, aggravated by early reproductive behavior, confinement to the home and no leisure. Although they have access to primary health care, the quality is inadequate. Increased awareness to the mother's situation is necessary in order to improve the health of young children.

Adult↗

[Correlation between maternal age, social class and smoking, and birth weight].

An epidemiological survey was carried out in Ribeirão Preto, Brazil, from June 1978 to May 1979. Interviews were held with mother of singleton live borne children, delivered in hospitals, which accounted for 98% of all births in the area. The higher percentages of low birthweight children related to the offspring of smokers, young mother and women belonging to the working class. The majority of young women were found in the working class and the prevalence of smoking was higher in the group of women below 20 years of age. There was no statistical difference in the smoking habit as between different social classes. A larger number of low birthweight children were observed in nonsmoking women of the working class than among women smokers of the middle class. A log model was adjusted to the data in order to study the possible multiple association of smoking, maternal age and social class with birthweight. The results indicated that maternal smoking, maternal age and social class had independent effects on birthweight. The was no interaction between them. These findings suggest that the higher prevalence of low birthweight in nonsmoking mothers of the working class in relation to smoking mothers of the middle class probably reflects clustering of other risk factors-such as poor education inadequate prenatal care, high parity and differences in reproductive behavior in women of the working class.

Adult↗