Search results for "SEX RATIO"
showing 10 items of 121 documents
Association between the polymorphism of CCR5 and Alzheimer's disease: results of a study performed on male and female patients from Northern Italy.
2007
Alzheimer's disease (AD) is the most common cause of dementia in Western society. The prevalence of AD is greater in women than in men, largely due to longevity and survival differences favoring women. However, some studies suggest that incidence rates may really be increased in women. One possible factor influencing AD incidence in women is the loss of ovarian estrogens production after menopause, which might be involved in AD pathogenesis. Estrogens seem to influence some neuronal functions. Many of these actions appear beneficial (i.e., neuroprotective action against a variety of insults, as oxidative stress, and reduction of beta-amyloid plaques formation). Furthermore, several studies …
Sex hormones and risk of liver tumor.
2007
The liver is morphologically and functionally modulated by sex hormones. Long-term use of oral contraceptives (OCs) and anabolic androgenic steroids (AASs) can induce both benign (hemangioma, adenoma, and focal nodular hyperplasia [FNH]) and malignant (hepatocellular carcinoma [HCC]) hepatocellular tumors. Hepatic adenomas (HAs) are rare, benign neoplasms usually occurring in young women, the development and the complications of which have been related to the strength of OCs and the duration of their use. HA incidence has fallen since the introduction of pills containing smaller amounts of estrogens. FNH is a benign lesion, most commonly seen in young women, which is thought to represent a …
The impact of sexual selection on Corynosoma magdaleni (Acanthocephala) infrapopulations in Saimaa ringed seals (Phoca hispida saimensis)
2004
In free-living animals sexual selection is a central force shaping the spatial distribution of individuals in a population as well as sexual size dimorphism. We studied the influence of sexual selection on spatial distribution, female-to-male body size ratio, and female mating success of acanthocephalans in a natural host population of Saimaa ringed seal (Phoca hispida saimensis) harbouring a single intestinal helminth species, Corynosoma magdaleni. The acanthocephalans were always found along the full length of the small intestine; however, the site selection varied among the individual seals according to the age of the infection. The distribution of male acanthocephalans was not random wi…
A set of female pheromones affects reproduction before, during and after mating in Drosophila
2004
0022-0949 (Print) Comparative Study Journal Article Research Support, Non-U.S. Gov't; Sex pheromones are chemical signals used for mate attraction and discrimination in many invertebrate species. These compounds are often complex mixtures with different components having different effects. We tested live Drosophila melanogaster mutant female flies genetically depleted for unsaturated cuticular hydrocarbons, which were then perfumed with these substances to measure their influence on various aspects of reproduction. Female pheromones of the control Cs strain enhanced female attractivity, copulation duration and tended to decrease the number of female progeny of mutant females mated with Cs m…
A cost of Wolbachia-induced sex reversal and female-biased sex ratios: decrease in female fertility after sperm depletion in a terrestrial isopod.
2004
A number of parasites are vertically transmitted to new host generations via female eggs. In such cases, host reproduction is an intimate component of parasite fitness and no cost of the infection on host reproduction is expected to evolve. A number of these parasites distort host sex ratios towards females, thereby increasing either parasite fitness or the proportion of the host that transmit the parasite. In terrestrial isopods (woodlice), Wolbachia bacteria are responsible for sex reversion and female-biased sex ratios, changing genetic males into functional neo-females. Although sex ratio distortion is a powerful means for parasites to increase in frequency in host populations, it also …
A multi-generational study on low-dose BPA exposure in Wistar rats: Effects on maternal behavior, flavor intake and development
2012
Bisphenol A (BPA) is a common endocrine disruptor found as an environmental and food contaminant. It exerts both developmental and behavioral effects, mainly when exposure occurs in early life. The aim of this study was to determine the multi-generational effects of chronic, human-relevant low-dose exposure to BPA on development, maternal behavior and flavor preference in Wistar rats. BPA was orally administered at a daily dose of 5 mu g/kg body weight to FO pregnant dams from the first day of gestation (GD 1) until the last day of lactation (LD 21), and then to Fl offspring from weaning (PND 21) to adulthood (PND 100). F2 offspring were not exposed. Development and clinical signs of toxici…
Infection by a vertically-transmitted microsporidian parasite is associated with a female-biased sex ratio and survival advantage in the amphipod Gam…
2007
SUMMARYVertically transmitted parasites may have positive, neutral or negative effects on host fitness, and are also predicted to exhibit sex-specific virulence to increase the proportion or fitness of the transmitting sex. We investigated these predictions in a study on the survival and sex ratio of offspring of the amphipod Gammarus roeseli from females infected by the vertically transmitted microsporidia Nosema granulosis. We found, to our knowledge, the first evidence for a positive relationship between N. granulosis infection and host survival. Infection was associated with sex ratio distortion, not by male-killing, but probably by parasite-induced feminization of putative G. roeseli m…
Direct costs of glaucoma and severity of the disease: a multinational long term study of resource utilisation in Europe
2005
International audience; Background: Resource utilisation and direct costs associated with glaucoma progression in Europe are unknown. As population progressively ages, the economic impact of the disease will increase. Methods: From a total of 1655 consecutive cases, the records of 194 patients were selected and stratified by disease severity. Record selection was based on diagnoses of primary open angle glaucoma, glaucoma suspect, ocular hypertension, or normal tension glaucoma; 5 years minimum follow up were required. Glaucoma severity was assessed using a six stage glaucoma staging system based on static threshold visual field parameters. Resource utilisation data were abstracted from the…
A mathematical model for the phase of sexual reproduction in monogonont rotifers
2000
Recently, the optimal sex allocation in monogonont rotifers is studied in [1], and, as a closely related question, the relative frequencies of the relevant types of mictic females. The authors focus on the evolution of the age at which young mictic females lose their fertilization susceptibility and they address the threshold age of fertilization that maximizes resting egg production. Assuming that a stationary population is achieved, with stable age distribution, they obtain their results, without knowing the stationary population. Our aim is to study this problem in the framework of the theory of nonlinear age-dependent population dynamics developed by G. F. Webb in [13], which is more ap…
Ant Societies Buffer Individual-Level Effects of Parasite Infections
2012
Parasites decrease host fitness and can induce changes in host behavior, morphology, and physiology. When parasites exploit social insects, they influence not only infected individuals but also the society as a whole. Workers of the ant Temnothorax nylanderi are an intermediate host for the cestode Anomotaenia brevis. We studied a heavily parasitized population and found that, although parasite infection had strong and diverse consequences for individual workers, colony fitness remained unchanged. At the individual level, we uncovered differences among the three worker types, infected and healthy workers from parasitized colonies and healthy workers from nonparasitized colonies. Infected wo…