Adverse effects of environmental antiandrogens and androgens on reproductive development in mammals

Within the last decade, several classes of chemicals have been shown in laboratory studies to disrupt reproductive development by acting as androgen receptor (AR) antagonists and/or inhibitors of fetal Leydig cell testosterone production. Some phthalate esters alter gubernacular differentiation by reducing insulin-like 3 (insl3) mRNA levels. We have found that AR antagonists and inhibitors of fetal testis hormone production generally induce cumulative, apparently dose-additive adverse effects when administered in mixtures. New research has also revealed the presence of androgens in the environment. Effluents from pulp and paper mills display androgenic activity of sufficient potency to masculinize and/or sex-reverse female fish. Effluent from beef cattle concentrated animal feedlot operations from the United States also displays androgenic activity in vitro, due, in part, to the presence of a steroid used to promote growth in beef cattle. In summary, we are only beginning to identify the classes of chemicals that have the potential to alter the androgen signalling pathway in utero. This review will (i) present information on the classes of environmental chemicals that display antiandrogenic and androgenic activities in vitro and in vivo, and (ii) provide an insight into how exposure to mixtures these chemicals might behave in utero.     

Evaluation of stimulus-induced acrosome reaction by two-colour flow cytometric analysis

Acrosome status in human spermatozoa from 20 normozoospermic men was evaluated by flow cytometry following the induction of the acrosome reaction with the ionophore A23187. Dual fluorescence staining of methanol fixed spermatozoa incubated with and without (control) the ionophore A23187 was performed with probes which targeted the outer acrosomal membrane (OAM) (rhodamine-labelled Arachis hypogaea agglutinin) or constituents of the acrosomal vesicle (fluorescein- labelled Pisum sativum agglutinin). Flow cytometry analysis revealed two major subpopulations of cells: acrosome-intact and acrosome-reacted spermatozoa after induction of the acrosome reaction. The intensity of green and red fluorescence in acrosome-reacted spermatozoa was significantly lower than that of the acrosome-intact control spermatozoa (P < 0.0001). The intensity of green fluorescence in the acrosome-intact subpopulation of spermatozoa was significantly higher than that of the control population (P < 0.002). Exposure of spermatozoa to the ionophore A23187 resulted in reliable enhancement of the number of spermatozoa with very high intensity of green and/or red fluorescence compared with the control (P < 0.03). An inverse correlation between the number of acrosome-reacted spermatozoa and spermatozoa with a very high intensity of green and/or red fluorescence was demonstrated (r = -0.631, P < 0.01). This method provides an objective and efficient procedure for quantitative estimation of the acrosomal status of human spermatozoa.      

Early referral to the nephrologist and timely initiation of renal replacement therapy: a paradigm shift in the management of patients with chronic renal failure

The high mortality rate among dialysis patients has spawned investigation into potentially correctable factors that are associated with an increased risk of death. Several studies have demonstrated a strong association between an increased risk of death in dialysis patients and suboptimal delivered dose of dialysis, malnutrition, and non-renal comorbidity. In addition, the use of unsubstituted cellulose dialyzers and reprocessed dialyzers also has been associated with an increased risk of death. Increased attention to these factors has resulted in a significant improvement in patient survival. Nonetheless, the mortality of dialysis patients remains unacceptably high and indicates that other factors may be operative. One of the factors that has thus far received scant attention, but could significantly affect morbidity and mortality in dialysis patients, is the timing and quality of care before initiation of dialysis. Optimal pre-end-stage renal disease care involves early interventions aimed at delaying progression of chronic renal failure, judicious management of uremic complications, timely placement of vascular access, timely initiation of renal replacement therapy, and implementation of educational programs targeted at maximum rehabilitation. Given the fact that early referral to the nephrologist is likely to result in optimal pre-dialysis care, the 1993 National Institutes of Health Consensus Statement on Morbidity and Mortality of Dialysis recommended that referral of a patient to a renal team should occur at a serum creatinine of 1.5 mg/dL in women and 2.0 mg/dL in men. Several investigators also have argued that patients with chronic renal failure who begin dialysis at a relatively "high level of residual renal function" (early start) may have lower morbidity and mortality compared with patients who begin dialysis at a more traditional "low level of renal function" (late start). This hypothesis is based on evidence that declining renal function is associated with malnutrition and that malnutrition at the start of dialysis is associated with poor clinical outcomes. Furthermore, patients are started on dialysis at an endogenous solute clearance that is lower than that accepted as optimum for patients on dialysis. Finally, limited clinical studies have demonstrated the benefit of early initiation of dialysis. Consequently, the Peritoneal Dialysis Adequacy Work Group of the National Kidney Foundation-Dialysis Outcomes Quality Initiative recommends that dialysis be initiated when the weekly renal Kt/Vurea decreases to below 2.0 unless all three of the following criteria are fulfilled: (1) stable or increased edema-free body weight, (2) normalized protein equivalent of total nitrogen appearance greater than 0.8, and (3) absence of clinical symptoms and signs attributable to uremia.     

Effects of a short-term exposure to the fungicide prochloraz on endocrine function and gene expression in female fathead minnows (Pimephales promelas)

Prochloraz is a fungicide known to cause endocrine disruption through effects on the hypothalamic-pituitary-gonadal (HPG) axis. To determine the short-term impacts of prochloraz on gene expression and steroid production, adult female fathead minnows (Pimephales promelas) were exposed to the chemical (0 or 300 μg/L) for a time-course of 6, 12 and 24 h. Consistent with inhibition of cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17) and aromatase (CYP19), known molecular targets of prochloraz, plasma 17β-estradiol (E2) was reduced within 6 h. Ex vivo E2 production was significantly reduced at all time-points, while ex vivo testosterone (T) production remained unchanged. Consistent with the decrease in E2 levels, plasma concentrations of the estrogen-responsive protein vitellogenin were significantly reduced at 24 h. Genes coding for CYP19, CYP17, and steroidogenic acute regulatory protein were up-regulated in a compensatory manner in ovaries of the prochloraz-treated fish. In addition to targeted quantitative real-time polymerase chain reaction analyses, a 15k feature fathead minnow microarray was used to determine gene expression profiles in ovaries. From time-point to time-point, the microarray results showed a relatively rapid change in the differentially expressed gene (DEG) profiles associated with the chemical exposure. Functional analysis of the DEGs indicated changes in expression of genes associated with cofactor and coenzyme binding (GO:0048037 and 0050662), fatty acid binding (GO:0005504) and organelle organization and biogenesis (GO:0006996). Overall, the results from this study are consistent with compensation of the fish HPG axis to inhibition of steroidogenesis by prochloraz, and provide further insights into relatively rapid, system-wide, effects of a model chemical stressor on fish.