Assessing seasonal demographic covariation to understand environmental‐change impacts on a hibernating mammal

Natural populations are exposed to seasonal variation in environmental factors that simultaneously affect several demographic rates (survival, development and reproduction). The resulting covariation in these rates determines population dynamics, but accounting for its numerous biotic and abiotic drivers is a significant challenge. Here, we use a factor‐analytic approach to capture partially unobserved drivers of seasonal population dynamics. We use 40 years of individual‐based demography from yellow‐bellied marmots (Marmota flaviventer) to fit and project population models that account for seasonal demographic covariation using a latent variable. We show that this latent variable, by producing positive covariation among winter demographic rates, depicts a measure of environmental quality. Simultaneously, negative responses of winter survival and reproductive‐status change to declining environmental quality result in a higher risk of population quasi‐extinction, regardless of summer demography where recruitment takes place. We demonstrate how complex environmental processes can be summarized to understand population persistence in seasonal environments.     

Assessment of peripheral DNA damage by alkaline comet assay in maintenance hemodialysis subjects with hepatitis C infection

Despite the high prevalence of hepatitis C infection among hemodialysis subjects, there is no information concerning the DNA damage of hepatitis C (+) hemodialysis subjects. We aimed to find out if there is any additional effect of hepatitis C infection on peripheral DNA damage in maintenance hemodialysis subjects. Fifteen hepatitis C (+) and 22 hepatitis C (-) hemodialysis subjects, 21 hepatitis C subjects without renal disease, and 22 healthy controls were enrolled. Peripheral DNA damage was assayed using alkaline comet assay. Median DNA damage levels of the study groups were as follows: hepatitis C (+) maintenance hemodialysis subjects, 88 (0-232); hepatitis C (-) maintenance hemodialysis subjects, 58 (0-228); hepatitis C (+) subjects without renal disease, 112 (44-252); controls, 26 (0-72). DNA damage level was significantly higher among hepatitis C (+) subjects without renal disease than hepatitis C (-) maintenance hemodialysis subjects and healthy controls (both p<0.05/6). Both maintenance hemodialysis subjects with and without HCV infection had significantly higher DNA damage level than healthy controls (both p<0.05/6). DNA damage level was comparable between hepatitis C (+) subjects without renal disease and HCV (+) hemodialysis subjects, and between hemodialysis subjects with and without hepatitis C infection (all p>0.05/6). Linear regression analysis revealed that hepatitis C infection was the only independent factor in predicting the peripheral DNA damage (p<0.05, beta=0.395). Each one of end-stage renal disease and hepatitis C infection significantly increases DNA damage level. However, in hemodialysis subjects, hepatitis C infection does not cause significant additional increase in DNA damage level, and it may be partly due to protective effect of hemodialysis on hepatitis C infection.     

Antibiotic resistance patterns of coagulase-negative staphylococcus strains isolated from blood cultures of septicemic patients in Turkey

The aim of this study is to determine antibiotic resistance patterns and slime production characteristics of coagulase-negative Staphylococci (CoNS) caused nosocomial bacteremia. A total of 200 CoNS strains were isolated from blood samples of patients with true bacteremia who were hospitalized in intensive care units and in other departments of Istanbul University Cerrahpasa Medical Hospital between 1999 and 2006. Among 200 CoNS isolates, Staphylococcus epidermidis was the most prevalent species (87) followed by Staphylococcus haemolyticus (23), Staphylococcus hominis (19), Staphylococcus lugdunensis (18), Staphylococcus capitis (15), Staphylococcus xylosus (10), Staphylococcus warneri (8), Staphylococcus saprophyticus (5), Staphylococcus lentus (5), Staphylococcus simulans (4), Staphylococcus chromogenes (3), Staphylococcus cohnii (1), Staphylococcus schleiferi (1), and Staphylococcus auricularis (1). Resistance to methicillin was detected in 67.5% of CoNS isolates. Methicillin-resistant CoNS strains were determined to be more resistant to antibiotics than methicillin-susceptible CoNS strains. Resistance rates of methicillin-resistant and methicillin-susceptible CoNS strains to the antibacterial agents, respectively, were as follows: gentamicin 90% and 17%, erythromycin 80% and 37%, clindamycin 72% and 18%, trimethoprim-sulfamethoxazole 68% and 38%, ciprofloxacin 67% and 23%, tetracycline 60% and 45%, chloramphenicol 56% and 13% and fusidic acid 25% and 15%. None of the strains were resistant to vancomycin and teicoplanin. Slime production was detected in 86 of 200 CoNS strains. Resistance to methicillin was found in 81% of slime-positive and in 57% of slime-negative strains. Our results indicated that there is a high level of resistance to widely used agents in causative methicillin-resistant CoNS strains. However fusidic acid has the smallest resistance ratio, with the exception of glycopeptides. Additionally, most S. epidermidis strains were slime-positive, with statistically significant (p<0.001) association between methicillin resistance and slime production.     

Vitamin D receptor gene polymorphism and osteoporosis in the Turkish population

Osteoporosis is one of the most important medical problems facing the aging population. It is defined as a decrease in the bone mass leading to an unacceptably high risk of fractures. Osteoporosis is a multifactorial disease. It is well established that genetic factors are involved in the pathogenesis of osteoporosis. Polymorphism of the vitamin D receptor (VDR) gene has been reported to play a major role in variations for genetic regulation of bone mass. Its role within various ethnic populations is not clear. The purpose of this project was to determine the frequencies of VDR genotypes in Turkey. Three polymorphisms of the VDR gene were analyzed using the polymerase chain reaction-restriction fragment length polymorphism technique. The sample for our study was comprised of postmenopausal women in Turkey, 100 of whom were diagnosed with osteoporosis. They were compared with 146 healthy controls. BsmI genotype frequencies in Turks resemble Caucasians rather than Asians, and Taq genotype frequencies in Turks neither resemble Caucasians nor Asians. The genotype frequencies of VDR were not statistically different between patients with osteoporosis and the control group. Among VDR haplotypes, bbAATT and bbTtAa are more frequent in the osteoporosis group than the control group.     

Sperm fatty acid composition in subfertile men

INTRODUCTION: The lipid composition of spermatozoa plays an important role for successful fertilization. PATIENTS AND METHODS: In the present study, we analyzed the fatty acid (FA) composition of spermatozoa of normozoospermic, asthenozoospermic, oligozoospermic and oligoasthenozoospermic men. RESULTS: Spermatozoa from asthenozoospermic (P<0.01), oligozoospermic (P<0.05) and oligoasthenozoospermic men (P<0.05) had lower levels of docosahexaenoic acid (22:6w3, DHA) than those from normozoospermic men. In oligozoospermic and asthenozoospermic men, spermatozoa 18:0 content was higher than that of normozoospermics (P<0.01 and P<0.001, respectively). 18:1w9 was higher in oligoasthenozoospermic and oligozoospermic samples when compared with normozoospermic samples (P<0.05 for both). While from the point of view of total w6 FAs there was no significant difference among the groups, the w6/w3 ratio was significantly higher in asthenozoospermic samples than in normozoospermic samples (P<0.05). Monounsaturated fatty acids (MFA) were higher in oligozoospermic samples (P<0.05) than in normozoospermic samples, polyunsaturated fatty acids (PUFA) were lower in asthenozoospermic (P<0.01), oligoasthenozoospermic (P<0.05) and oligozoospermic samples (P<0.05) than in normozoospermic samples. Saturated fatty acids (SFA) were significantly higher in asthenozoospermic (P<0.01) and oligozoospermic samples (P<0.05) compared with normozoospermic samples. In correlation analysis, there were significant positive correlations between DHA with sperm motility (r=0.53), sperm concentration (r=0.36) and normal sperm morphology (r=0.30). In addition, there were significant correlations between PUFA with sperm motility (r=0.50), sperm concentration (r=0.35), and normal sperm morphology (r=0.28), and between w6/w3 with sperm motility (r=-0.47), sperm concentration (r=-0.27), and normal sperm morphology(r=-0.24). DISCUSSION: These suggest that decreased DHA and PUFA, and increased w6/w3 in spermatozoa may be related to infertility in oligo- and/or asthenozoospermic men.     

Cytotoxic and Antimigratory Activity of Retrochalcones from Glycyrrhiza echinata L. on Human Cancer Cells

Cytotoxic activity-guided fractionation studies on Glycyrrhiza echinata roots led to the isolation of eight compounds ( 1 – 8 ). Chemical structures of the isolates were identified by NMR and MS analysis. Among the tested molecules, retrochalcones namely echinatin ( 3 ) (IC₅₀=23.45–41.83 μM), licochalcone B ( 4 ) (IC₅₀=36.04–39.53 μM) and tetrahydroxylmethoxychalcone ( 5 ) (IC₅₀=7.09–80.81 μM) were the most active ones against PC3, MCF7 and HepG2 cells. Moreover, 5 exhibited selectivity on prostate cancer cells (SI: 5.19). Hoechst staining and Annexin V/PI binding assays as well as cell cycle analysis on the compounds 3 (23 μM) and 5 (5 and 7 μM) demonstrated that these retrochalcones induced apoptosis and significantly suppressed cell cycle in G₁ and G₂/M phases. Furthermore, 3 and 5 showed antimigratory effects on PC3 cells by wound healing assay. The results indicated that tested retrochalcones most particularly 5 could be potential anticancer drug candidates that prevent proliferation and migration of cancer cells.     

Patterns of activity and body temperature of Aldabra giant tortoises in relation to environmental temperature

We studied the temperature relations of wild and zoo Aldabra giant tortoises (Aldabrachelys gigantea) focusing on (1) the relationship between environmental temperature and tortoise activity patterns (n = 8 wild individuals) and (2) on tortoise body temperature fluctuations, including how their core and external body temperatures vary in relation to different environmental temperature ranges (seasons; n = 4 wild and n = 5 zoo individuals). In addition, we surveyed the literature to review the effect of body mass on core body temperature range in relation to environmental temperature in the Testudinidae. Diurnal activity of tortoises was bimodally distributed and influenced by environmental temperature and season. The mean air temperature at which activity is maximized was 27.9°C, with a range of 25.8–31.7°C. Furthermore, air temperature explained changes in the core body temperature better than did mass, and only during the coldest trial, did tortoises with higher mass show more stable temperatures. Our results, together with the overall Testudinidae overview, suggest that, once variation in environmental temperature has been taken into account, there is little effect of mass on the temperature stability of tortoises. Moreover, the presence of thermal inertia in an individual tortoise depends on the environmental temperatures, and we found no evidence for inertial homeothermy. Finally, patterns of core and external body temperatures in comparison with environmental temperatures suggest that Aldabra giant tortoises act as mixed conformer–regulators. Our study provides a baseline to manage the thermal environment of wild and rewilded populations of an important island ecosystem engineer species in an era of climate change.     

Direct negative density‐dependence in a pond‐breeding frog population

Understanding population dynamics is critical for the management of animal populations. Comparatively little is known about the relative importance of endogenous (i.e. density‐dependent) and exogenous (i.e. density‐independent) factors on the population dynamics of amphibians with complex life cycles. We examined the potential effects of density‐dependent and ‐independent (i.e. climatic) factors on population dynamics by analyzing a 15‐yr time series data of the agile frog Rana dalmatina population from Târnava Mare Valley, Romania. We used two statistical models: 1) the partial rate correlation function to identify the feedback structure and the potential time lags in the time series data and 2) a Gompertz state‐space model to simultaneously investigate direct and delayed density dependence as well as climatic effects on population growth rate. We found evidence for direct negative density dependence, whereas delayed density dependence and climate did not show a strong influence on population growth rate. Here we demonstrated that direct density dependence rather than delayed density dependence or climate determined the dynamics of our study population. Our results confirm the findings of many experimental studies and suggest that density dependence may buffer amphibian populations against environmental stress. Consequently, it may not be easy to scale up from individual‐level effects to population‐level effects.     

Interactive life‐history traits predict sensitivity of plants and animals to temporal autocorrelation

Temporal autocorrelation in demographic processes is an important aspect of population dynamics, but a comprehensive examination of its effects on different life‐history strategies is lacking. We use matrix population models from 454 plant and animal populations to simulate stochastic population growth rates (log λ_s) under different temporal autocorrelations in demographic rates , using simulated and observed covariation among rates. We then test for differences in sensitivities, or changes of log λ_s to changes in autocorrelation among two major axes of life‐history strategies, obtained from phylogenetically informed principal component analysis: the fast‐slow and reproductive‐strategy continua. Fast life histories exhibit highest sensitivities to simulated autocorrelation in demographic rates across reproductive strategies. Slow life histories are less sensitive to temporal autocorrelation, but their sensitivities increase among highly iteroparous species. We provide cross‐taxonomic evidence that changes in the autocorrelation of environmental variation may affect a wide range of species, depending on complex interactions of life‐history strategies.