Influence of age on the relative sensitivity of Hyalella azteca to diazinon,alkylphenol ethoxylates,copper, cadmium,and zinc

Laboratories testing Hyalella azteca use a wide range of ages (or sizes) of the amphipod in their studies. The objective of this study was to investigate age-specific differences in sensitivity of the amphipod to contaminants with varying toxic modes of action. Hyalella azteca, ranging in age from <1 to 26 d, were tested in 96-h water-only exposures with the organophosphate pesticide diazinon, a mixture of alkylphenol ethoxylates (nonionic surfactants), copper sulfate, cadmium chloride, and zinc sulfate. Overall age-specific differences in sensitivity to the five test chemicals were relatively small; 96-h LC50 values typically varied by 50% or less among the various age classes of H. azteca. When differences in sensitivity were observed, trends were apparently related to the contaminant tested rather than to the age of the amphipods, i.e., no particular age class consistently was the most sensitive to the toxicants.     

Measures of reproductive success and polychlorinated biphenyl residues in eggs and chicks of Forster's terns on Green Bay,Lake Michigan,Wisconsin—1988

Data on reproductive success of Forster's tern (Sterna forsteri) from Green Bay, Lake Michigan in 1983 are compared with data collected in 1988. In 1988 measures of reproductive performance (hatching success, number of young fledged, and length of incubation) were improved. Concentrations of total polychlorinated biphenyls (PCBs) and planar PCB congeners in the eggs were compared between years. Median total PCB residue was 67% lower in 1988 ( =7.3 μg/g). This corresponds to a 42% reduction in tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ) from 1983 to 1988. We suggest that contaminant reduction and improved reproductive performance were due to low river flows in 1988 and associated reduced PBC loading into Green Bay. Forty-two percent of the matured chicks died before fledgling, and their body weight growth curves were much lower than normal. Young accumulate total PCBs at a rate of 17.6 μg/day. A no-observable-adverse-effects level (NOAEL) of 40–84 μg/kg/day was estimated from the two year results using the least observable adverse effects level (LOAEL)/NOAEL rating values.     

Piperonyl butoxide as a tool in aquatic toxicological research with organophosphate insecticides

Experiments were conducted to determine the effects of piperonyl butoxide, a synthetic methylenedioxyphenyl inhibitor of cytochrome(s) P450, on the toxicity of organophosphate insecticides to three cladoceran test species: Ceriodaphnia dubia. Daphnia magna, and Daphnia pulex. Coadministration of piperonyl butoxide effectively reduced the acute toxicity of four metabolically activated organophosphates (parathion, methyl parathion, diazinon, and malathion) and did not affect the toxicity of three organophosphates not requiring metabolic activation (dichlorvos, chlorfenvinphos, and mevinphos). These results indicate that piperonyl butoxide may be an effective tool in toxicological research focused upon identifying specific compounds responsible for toxicity in complex aqueous mixtures.     

Staphylococcus aureus versus Staphylococcus epidermidis in periprosthetic joint infection—Outcome analysis of methicillin-resistant versus methicillin-susceptible strains

Periprosthetic joint infections (PJIs) are a major complication in total joint arthroplasty. Staphylococcus aureus and coagulase-negative staphylococci are known to cause the majority of all PJIs. This study aimed to analyze the eradication rates of S. aureus and S. epidermidis with methicillin susceptibility and methicillin resistance in a 2-stage therapy algorithm. Seventy-four patients with PJI caused by methicillin-resistant S. aureus (MRSA), methicillin-resistant coagulase-negative staphylococci (MRSE), methicillin-susceptible S. aureus (MSSA), and methicillin-susceptible coagulase-negative staphylococci (MSSE) were included, and the outcome was analyzed retrospectively. After a minimal follow-up of 2?years, n?=?56 patients (75.7%) were definitively free of infection. The analysis revealed significant differences between the groups, with eradication rates as follows: MSSA (92.6%), MSSE (95.2%), MRSA (80%), and MRSE (54.2%). MRSE showed a significantly lower rate of patients graded as “definitively free of infection” as compared to patients with infections caused by MSSA, MSSE, and MRSA.     

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.