Tributyltin disrupts fin development in Fundulus heteroclitus from both PCB-sensitive and resistant populations: Investigations of potential interactions between AHR and PPARγ.

Tributyltin (TBT) and dioxin-like polychlorinated biphenyls (PCBs) are environmental contaminants that are highly toxic to fish and co-occur in New Bedford Harbor (NBH), an estuarine Superfund site located in Massachusetts, USA. Atlantic killifish (Fundulus heteroclitus) that reside in NBH (and other highly contaminated sites along the east coast of the United States) have developed resistance to activation of the aryl hydrocarbon receptor (AHR) pathway and the toxicity of dioxin-like chemicals, such as 3,3',4,4',5-pentachlorobiphenyl, PCB126. In many biological systems, TBT disregulates adipose and bone development via the PPARγ-RXR pathway; AHR activation also disrupts adipose and bone homeostasis, potentially through molecular crosstalk between AHR and PPARγ. However, little is known about how co-exposure and the interaction of these pathways modulate the toxicological effects of these contaminants. Here, we tested the hypotheses that TBT would induce teratogenesis in killifish via activation of PPARγ and that PCB126 co-exposure would suppress PPARγ pathway activation in PCB-sensitive killifish from a reference site (Scorton Creek, SC, PCB-sensitive) but not in PCB-tolerant NBH killifish. Killifish embryos from both populations exposed to TBT (50 and 100 nM) displayed caudal fin deformities. TBT did not change the expression of pparg or its target genes related to adipogenesis (fabp11a and fabp1b) in either population. However, expression of osx/sp7, an osteoblast marker gene, and col2a1b, a chondroblast marker gene, was significantly suppressed by TBT only in SC killifish. An RXR-specific agonist, but not a PPARγ-specific agonist, induced caudal fin deformities like those observed in TBT-treated embryos. PCB126 did not induce caudal fin deformities and did not exacerbate TBT-induced fin deformities. Further, PCB126 increased expression of pparg in SC embryos and not NBH embryos, but did not change the expression of fabp1b. Taken together, these results suggest that in killifish embryos the PPARγ pathway is regulated in part by AHR, but is minimally active at least in this early life stage. In killifish, RXR activation, rather than PPARγ activation, appears to be the mechanism by which TBT induces caudal fin teratogenicity, which is not modulated by AHR responsiveness.

Identification and cloning of a locus of serine repeat antigen (sera)-related genes from Plasmodium vivax.

Polymerase chain reaction (PCR) primers based on the cysteine proteinase-like active site regions of the Plasmodium falciparum serine repeat antigen (SERA) were used to identify related sequences within the genome of P. vivax. Molecular cloning and sequence analysis of approximately 25 kb of P. vivax genomic DNA revealed a cluster of five repeated SERA-like genes (V-SERA-1-5), each encoding a cysteine proteinase-related protein. In addition to DNA sequence homology, significant similarities in deduced intron/exon organizations were also observed. The characteristic polyserine sequence found in SERA was not present in any of the deduced V-SERA sequences. Instead, in this region of the five genes, considerable sequence differences were found, suggesting the potential for antigenic variation in the V-SERA molecules. In common with SERA, however, the codon at the position corresponding to the active site cysteine residue of active mammalian and plant cysteinyl proteinases was found to be that of a serine residue in each of the V-SERA genes. Furthermore, in four of the five genes, including the expressed V-SERA-5 gene, the codon for the active site histidine residue was changed to that of a leucine residue. These critical differences reinforce the concept that a biological activity other than proteolysis is likely to be the primary function of the proteins encoded by this family of genes.

Correlation of age-associated increases in follicle stimulating hormone secretion with decreases in antral follicles: failure of progesterone-induced acyclicity to prevent these changes.

It is well known that the number of follicles in the mammalian ovary decreases with age. In light of previous data from this laboratory showing age-related alterations in the secretion and production of follicle-stimulating hormone (FSH) in rats by 5-6 months of age, one objective of the present study was to determine if alterations in FSH secretion were accompanied by changes in the number of antral follicles. A second objective of this study was to determine whether or not interruption of cyclic activity by continuous progesterone (P) treatment could decelerate age-associated changes in FSH secretion possibly by retarding the depletion of follicles through ovulation. For this study, one group of 4-day cycling, 7-week-old rats received one empty Silastic implant while another group received 3-40 mm implants containing 30 mm crystalline P. Implants were replaced every 2 weeks until the animals were 5 months old. Progesterone-implanted rats were acyclic during treatment exhibiting predominantly leukocytic vaginal smears. Regular 4-day cycles resumed when P implants were withdrawn (rats approximately 5-6-months-old). A group of 2-3-month-old untreated rats were used for comparison. As expected from our previous results, serum FSH levels at 1600 h on estrus were significantly higher in 5-6-month-old rats receiving empty capsules than in younger rats. Serum FSH concentrations measured in P-treated rats at this time also were significantly higher than levels of this gonadotropin measured in younger rats. Ovaries of older control and P-treated rats contained significantly fewer medium and large antral follicles (greater than 250 microns) than the ovaries of younger rats despite the curtailment of estrous cyclicity and ovulation by continuous P treatment. Interestingly, P treatment prevented the age-associated decrease in thymus weight. Taken together, the present observations suggest that a decrease in the number of growing follicles may be a factor contributing to early age-related alterations in FSH secretion. Furthermore, the prevention (at least temporarily) of age-related thymic involution by P treatment may be indicative of an interrelationship between thymic and reproductive aging.

Evidence for immune selection of hepatitis C virus (HCV) putative envelope glycoprotein variants: potential role in chronic HCV infections.

E2/nonstructural protein 1, the putative envelope glycoprotein (gp72) of HCV, possesses an N-terminal hypervariable (E2 HV) domain from amino acids 384 to 414 of unknown significance. The high degree of amino acid sequence variation in the E2 HV domain appears to be comparable to that observed in the human immunodeficiency virus type 1 gp120 V3 domain. This observation and the observation that the HCV E2 HV domain lacks conserved secondary structure imply that, like the V3 loop of human immunodeficiency virus 1 gp120, the N-terminal E2 region may encode protective epitopes that are subject to immune selection. Antibody-epitope binding studies revealed five isolate-specific linear epitopes located in the E2 HV region. These results suggest that the E2 HV domain is a target for the human immune response and that, in addition to the three major groups of HCV, defined by nucleotide and amino acid sequence identity among HCV isolates, E2 HV-specific subgroups also exist. Analysis of the partial or complete E2 sequences of two individuals indicated that E2 HV variants can either coexist simultaneously in a single individual or that a particular variant may predominate during different episodes of disease. In the latter situation, we found one individual who developed antibodies to a subregion of the E2 HV domain (amino acids 396-407) specific to a variant that was predominant during one major episode of hepatitis but who lacked detectable antibodies to the corresponding region of a second variant that was predominant during a later episode of disease. The data suggest that the variability in the E2 HV domain may result from immune selection. The findings of this report could impact vaccine strategies and drug therapy programs designed to control and eliminate HCV.

Attention in discrimination learning in relation to certain teacher-rated behavior anomalies.

Teacher ratings of the anomalous classroom behaviors hyperactivity, inattention, perceptual-motor impairment, perserveration, and stereotypy were examined as predictors of performance on a visual discrimination task. Weak but statistically reliable correlations were obtained.

Efficacy of amoscanate against experimental schistosomal infections in monkeys.

The antischistosomal activity of oral doses of amoscanate (4-isothiocyanato-4'-nitrodiphenylamine) was determined in infected Cebus apella (capuchin monkeys) and Macaca mulatta (rhesus monkeys). In C. apella infected with Schistosoma japonicum or S. mansoni an initial dose of 10 mg/kg body weight did not alter fecal egg counts, but a subsequent dose of 25 mg/kg markedly reduced both egg counts and worm burdens; in animals infected with S. haematobium, a single dose of 25 mg/kg of amoscanate was similarly effective. Comparable schistosomicidal effects were also produced in S. japonicum- and S. mansoni-infected M. mulatta by single oral doses of 20 and 35 mg/kg, respectively. In both C. apella and M. mulatta the coadministration of single oral doses of 50 or 75 mg/kg of erythromycin attenuated the appearance of mutagenic metabolites of amoscanate in the urine but did not interfere with the antischistosomal action of amoscanate. In non-infected monkeys single oral doses of 75 mg/kg of amoscanate with or without erythromycin (50 mg/kg in C. apella or 75 mg/kg in M. mulatta) did not cause any major organ toxicity as revealed by gross and histopathologic examination, hematology, blood chemistry, electrocardiograms and urinalysis. The data indicate that in C. apella and M. mulatta, amoscanate is a relatively non-toxic antischistosomal agent effective orally against a broad spectrum of schistosome species.

Two-year follow-up study of discrimination learning by mentally retarded children.

Mentally retarded children were taught to discriminate the dimensions of a visual display using a matching-to-sample procedure that provided full verbal feedback of the reasons for successes and failures. A control group attempted the matching procedure but received no feedback. The trained subjects exhibited marked superiority in intradimensional transfer. Two years later, the trained subjects continued their advantage but to a lesser degree.

Dopamine metabolism and receptor sensitivity in rat brain after REM sleep deprivation.

Different dopaminergic mechanisms that could explain behavioral supersensitivity to amphetamine or apomorphine in REM-deprived rats were examined. Four days of REM sleep deprivation induced a highly significant elevation in striatal DOPAC relative to normal controls, but not to stress controls. DOPAC levels in frontal cortex were not affected in any of the groups. Post synaptic D2 receptor number (Bmax) and affinity (Kd) were unchanged in both terminal regions. Similarly, no changes in pre-synaptic receptor sensitivity (apomorphine-induced inhibition of tyrosine hydroxylase) occurred in striatum. A stress control group exhibited no changes in any of the biochemical measures in comparison with either the REM deprived group or unstressed controls. Thus, the enhanced response to dopamine agonists reported previously is not due to altered dopamine receptor sensitivity. Alternative hypotheses to explain enhanced responses to direct and indirect acting dopamine agonists are discussed.

Improving the visual discrimination of mentally retarded children: a training strategy.

Mentally retarded children were asked to judge whether a series of visual stimuli matched a standard. With each judgment the investigator verbalized "right" or "wrong" and then provided full feedback of particulars, indicating with gesture and words the cue similarities and differences that supported each correct and each incorrect judgment. Control subjects were either given no training (test--retest only) or were asked to make the judgments but given no feedback. Attesting to the efficacy of the training procedure, the trained subjects exhibited total intradimensional transfer; the control subjects, none. The results were related to the attention-retention theory of discrimination learning developed by Fisher and Zeaman and to the "differentiation" methodology and theory presented by Gibson and Gibson.