Novel phosphoserine phosphatase inhibitors

Phosphoserine phosphatase (EC 3.1.1.3) catalyzes the final step in the major pathway of L-serine biosynthesis in brain. This enzyme may also regulate the levels of glycine and D-serine, the known and putative co-agonists for the glycine site of the N-methyl-D-aspartate receptor in caudal and rostral brain regions, respectively. Using L-phosphoserine as substrate, the rank order potency for inhibition of phosphoserine phosphatase was p-chloromercuriphenylsulfonic acid (CMPSA) > glycerophosphorylcholine > hexadecylphosphocholine > or = phosphorylcholine > N-ethylmaleimide > or = L-serine > fluoride > D-2-amino-3-phosphonopropionic acid (D-AP3). Glycerylphosphorylcholine (IC50 18 microM) was found to be an uncompetitive inhibitor of phosphoserine phosphatase. Glycerylphosphorylcholine probably binds a novel site on the enzyme since the known allosteric inhibitor L-serine is highly selective for its feedback regulatory site, indicated by the inactivity of 25 L-serine analogs. Fluoride ion (IC50 770 microM) may bind the active site as has been shown for other Mg2+-dependent enzymes. The sulfhydryl reagent CMPSA is a potent, noncompetitive inhibitor of the enzyme using L-phosphoserine as substrate (IC50 9 microM) but is > 300-fold less potent using D-phosphoserine as substrate. Substrate-dependent differences are also observed with the sulfhydryl alkylator N-ethylmaleimide, which inhibits L-phosphoserine, but stimulates D-phosphoserine hydrolysis. These sulfhydryl reagents may dissociate multimeric forms of the enzyme to form monomers; the multimeric forms and monomers may preferentially cleave L- and D-phosphoserine, respectively. Phosphorylcholine esters and sulfhydryl reagents may prove useful in determining the contribution of phosphoserine phosphatase to the biosynthesis of glycine and D-serine in neuronal tissue in vitro.     

Prostate specific antigen in the expressed prostatic fluid of men with benign prostatic hyperplasia and prostate carcinoma

PURPOSE: We tested the hypothesis that the histochemically demonstrated prostate specific antigen (PSA) content of prostate carcinoma cells does not necessarily reflect PSA production and secretion by evaluating expressed prostatic fluid. MATERIALS AND METHODS: Expressed prostatic fluid and serum from 152 men with clinical benign prostatic hypertrophy (BPH), 132 with histologically proved BPH and 46 with prostate carcinoma were analyzed with the Hybritech PSA assay. RESULTS: Expressed prostatic fluid PSA levels from carcinoma patients (median 1.70 mg./ml., mean 2.25) were significantly higher than in the histologically proved BPH group (median 1.28 mg./ml., mean 1.42, p < 0.05). CONCLUSIONS: PSA concentration is increased in the expressed prostatic fluid of prostates of men with carcinoma compared to those with histological BPH. This finding may be a functional manifestation of a field change or paracrine effects within the prostate.     

Truncated human endothelin receptor A produced by alternative splicing and its expression in melanoma

PURPOSE: Traumatic sphincter disruption frequently is associated with a rectovaginal fistula, but the effect of a persistent sphincter defect on the outcome of rectovaginal fistula repair is poorly documented. We analyzed the outcome of rectovaginal fistula repairs based on preoperative sphincter status. PATIENTS AND METHODS: We identified 52 women who underwent 62 repairs of simple obstetrical rectovaginal fistulas between 1992 and 1995. Fourteen patients (27 percent) had preoperative endoanal ultrasound studies and 25 (48 percent) had anal manometry studies. Follow-up was by mailed questionnaire in 36 patients (69 percent) and by telephone interview in 12 (23 percent), for a total response rate of 92 percent. Median age was 30.5 (range, 18-70) years, and median follow-up was 15 (range, 0.5-123) months. Twenty-five patients (48 percent) complained of varying degrees of fecal incontinence before surgery. There were 27 endorectal advancement flaps and 35 sphincteroplasties (28 with and 8 without levatoroplasty). RESULTS: Success rates were 41 percent with endorectal advancement flaps and 80 percent with sphincteroplasties (96 percent success with and 33 percent without levatoroplasty; P = 0.0001). Endorectal advancement flap was successful in 50 percent of patients with normal sphincter function but in only 33 percent of patients with abnormal sphincter function (P = not significant). For sphincteroplasties, success rates were 73 vs. 84 percent for normal and abnormal sphincter function, respectively (P = not significant). Results were better after sphincteroplasties vs. endorectal advancement flaps in patients with sphincter defects identified by endoanal ultrasound (88 vs. 33 percent; P = not significant) and by manometry (86 vs. 33 percent; P = not significant). Poor results correlated with prior surgery in patients undergoing endorectal advancement flaps (45 percent vs. 25 percent; P = not significant) but not sphincteroplasties (80 vs. 75 percent; P = not significant). CONCLUSIONS: All patients with rectovaginal fistula should undergo preoperative evaluation for occult sphincter defects by endoanal ultrasound or anal manometry or both procedures. Local tissues are inadequate for endorectal advancement flap repairs in patients with sphincter defects and a history of previous repairs. Patients with clinical or anatomic sphincter defects should be treated by sphincteroplasty with levatoroplasty.     

Fate of wheat bound malathion residues in rats during gestation

Malathion [S-1,2-di(ethoxycarbonyl) ethyl 0,0-dimethyl phosphorodithioate], treated wheat when stored for 28 months at 20 degrees C with or without food grade white mineral oil on grains contained about 62 and 79% of the applied insecticide as bound residues, respectively. These bound residues were present mainly in the form of the parent compound. The stored wheat containing bound malathion residues, as well as wheat material freshly spiked with malathion were fed to rats during gestation. No residues of malathion and/or metabolites were detected in urine, feces and body tissues. Further no significant effect on body weight, serum chemistry and cytochrome P450 levels were observed in the mothers. There was no evidence for the histopathological alteration or teratogenic anomalies in the fetuses. However, placental transfer of malathion was indicated by the presence of the insecticide residues in fetuses from rats fed wheat material containing bound residues.     

Gastric microbleeding following single and repeated dosing with naproxen

Our previous study provided evidence that higher serum levels of the active form of vitamin D, 1,25-dihydroxyvitamin D (1, 25-D), might possibly slow the progression of subclinical to clinically significant prostate cancer in both black and white men, especially after age 57. This paper extends the prior study by contrasting seasonal variation in 1,25-D and its precursor, 25-hydroxyvitamin D (25-D), in case and control subjects. In addition, the risk of prostate cancer is related to serum levels of vitamin D-binding protein (VDBP) and total dehydroepiandrosterone and to polymorphic variation in VDBP. The expected elevated summer levels of 25-D were seen in case and control subjects and, as expected, 1,25-D did not vary throughout the year in the control subjects. Unexpectedly, lower case levels of 1,25-D were limited largely to the summer months (P = 0.01) in both black and white cases and to cases greater than or equal to the median age of 57 years. Levels of VDBP and dehydroepiandrosterone and the frequencies of VDBP polymorphisms were similar in case and control subjects, although striking differences were seen in allelic frequencies in black and white men. These observations provide additional evidence that vitamin D metabolism may impact the risk of prostate cancer.     

Atypical mycobacterial pulmonary disease and bronchial obstruction in HIV-negative children

Atypical mycobacterial infection in HIV-negative children usually presents with cervical lymphadenopathy. We report on 10 children who are HIV-negative and who presented with pulmonary disease, in whom either culture-proven atypical mycobacterium infection (four), positive avian Mantoux test (five), or lack of response to human tuberculosis treatment (one) had been observed. One case was subsequently diagnosed as chronic granulomatous disease and illustrates that children with atypical mycobacterial pulmonary infection should have their immune status fully investigated. Bronchial obstruction was observed in eight cases, and of these, endobronchial disease was found in six children. The diagnosis of atypical mycobacterial disease is difficult, and a negative avian Mantoux test does not exclude the diagnosis. The availability of clarithromycin and rifabutin has offered new therapeutic options in treating atypical mycobacterial pulmonary infection, but management of these cases can be prolonged and difficult.     

Biochemistry, cell biology and molecular biology of lipids of Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae is a powerful experimental system to study biochemical, cell biological and molecular biological aspects of lipid synthesis. Most but not all genes encoding enzymes involved in fatty acid, phospholipid, sterol or sphingolipid biosynthesis of this unicellular eukaryote have been cloned, and many gene products have been functionally characterized. Less information is available about genes and gene products governing the transport of lipids between organelles and within membranes, turnover and degradation of complex lipids, regulation of lipid biosynthesis, and linkage of lipid metabolism to other cellular processes. Here we summarize current knowledge about lipid biosynthetic pathways in S. cerevisiae and describe the characteristic features of the gene products involved. We focus on recent discoveries in these fields and address questions on the regulation of lipid synthesis, subcellular localization of lipid biosynthetic steps, cross-talk between organelles during lipid synthesis and subcellular distribution of lipids. Finally, we discuss distinct functions of certain key lipids and their possible roles in cellular processes.