Uptake characteristics of loracarbef and cephalexin in the Caco-2 cell culture model: effects of the proton gradient and possible presence of a distinctive second component

The mechanisms of apical (AP) uptake of cephalexin (CEPH) and loracarbef (LOR) in the absence or presence of an (extemally imposed) proton gradient were determined using well-stirred diffusion chambers that minimize the effects of the unstirred water layer. The results indicated that, compared to AP uptake in the presence of an imposed proton gradient, AP uptake in the absence of an imposed proton gradient had higher K(m) values and lower Jmax values. Furthermore, when inhibition studies were performed in the absence of a proton gradient, only natural peptides were effective, whereas the peptide analogs (e.g., enalapril) were not. In addition to the effects of concentration and competitive inhibitors, the results also indicated that (1) the AP uptake of both drugs was decreased more than 60% by FCCP, regardless of whether the proton gradient was present or absent; (2) effects of protein kinase C promoter were dependent upon the presence of a proton gradient; and (3) AP uptake in the presence of an imposed proton gradient was not affected by feeding restriction, whereas AP uptake in the absence of an imposed proton gradient was. These results showed for the first time that two substrates with similar AP uptake characteristics in the presence of an imposed proton gradient may not share those characteristics in the absence of an imposed proton gradient. Taken together, these results suggest that the AP uptake component that functions in the absence of an imposed proton gradient is distinctly different from the one that functions in the presence of an imposed proton gradient. Data generated from the present study and those in the literature lend support to the hypothesis that this distinctive component represents the second binding site on the AP peptide transporter. However, an alternative hypothesis that there are two AP peptide transporters remains to be disapproved.     

Circadian rhythm of lymphocytes and their glucocorticoid receptors in HIV-infected homosexual men

Glucocorticoids (Gc) are known to modulate protein synthesis by immune cells through binding to a specific receptor (GcR). We outlined the circadian rhythm of plasma cortisol, ACTH, of the peripheral blood mononuclear cells (PBMC isolated by Ficoll-Hypaque technique), and of their subsets CD4, CD8 in 14 asymptomatic HIV+ homosexual men and in nine controls. We also estimated the GcR of the PBMC at 0700 and at 2300 hours, near the peak and nadir of the cortisol rhythm. In the HIV+ subjects, the PBMC circadian rhythm is abolished, an observation that confirms previous reports; in more than half of these patients, the GcR dissociation constant is larger than that of the controls. The circadian rhythms of plasma cortisol and ACTH levels do not differ from those of the controls. These changes may impair the function of the hypothalamic pituitary-adrenal axis in the HIV-infected subject.     

A high proportion of novel mutations in BRCA1 with strong founder effects among Dutch and Belgian hereditary breast and ovarian cancer families

We have identified 79 mutations in BRCA1 in a set of 643 Dutch and 23 Belgian hereditary breast and ovarian cancer families collected either for research or for clinical diagnostic purposes. Twenty-eight distinct mutations have been observed, 18 of them not previously reported and 12 of them occurring more than once. Most conspicuously, a 2804delAA mutation has been found 19 times and has never been reported outside the Netherlands. A common haplotype spanning > or = 375 kb could be identified for each of the nine examined recurrent mutations, indicating the presence of multiple BRCA1 founder mutations in the Dutch population. The 2804delAA mutation has been estimated to have originated approximately 32 generations ago. No specific breast or ovarian cancer phenotype could be assigned to any of the common mutations, and the ovarian cancer incidence among 18 families with the 2804delAA mutation was heterogeneous.     

Effects of a quick-release form of bromocriptine (Ergoset) on fasting and postprandial plasma glucose, insulin, lipid, and lipoprotein concentrations in obese nondiabetic hyperinsulinemic women

OBJECTIVE: To assess the effect on various aspects of carbohydrate and lipid metabolism of administering a quick-release formulation of bromocriptine (Ergoset) to obese, nondiabetic, hyperinsulinemic women. RESEARCH DESIGN AND METHODS: Hourly concentrations of prolactin, glucose, insulin, free fatty acid (FFA), and triglyceride were measured for 24 h before and after approximately 8 weeks of treatment with Ergoset. In addition, fasting lipid and lipoprotein concentrations and the steady-state plasma glucose (SSPG) concentration in response to a continuous infusion of somatostatin, insulin, and glucose were determined before and after Ergoset administration. RESULTS: Circulating prolactin concentrations were dramatically decreased (P < 0.001) following treatment, associated with a significant fall (P < 0.05) in 24-h-long plasma glucose, FFA, and triglyceride concentrations. Neither circulating plasma insulin concentrations nor the ability of insulin to mediate glucose disposal changed with treatment. Finally, fasting total cholesterol fell (P < 0.05) and the ratio of total to HDL cholesterol decreased (P = 0.06) in association with Ergoset treatment. CONCLUSIONS: The fact that significant metabolic improvement was seen in the obese nondiabetic hyperinsulinemic women studied suggests that Ergoset could be of therapeutic benefit in clinical conditions of hyperglycemia and/or dyslipidemia.     

Polymerase chain reaction in the diagnosis of tuberculosis. Comparison of two target sequences for amplification

Amplification of a 340 bp sequence of the 38 kDa protein gene of Mycobacterium tuberculosis by the polymerase chain reaction has been developed. The sensitivity of this PCR was shown to be 10 fg both by agarose gel electrophoresis and Southern blot hybridisation being equivalent to 2-3 organisms and highly specific to M. tuberculosis and excluding even M. tuberculosis H37Ra and Mycobacterium bovis BCG. Sputum samples from patients with pulmonary tuberculosis gave a positivity rate of 45%. PCR was also performed using pt8 and pt9 primers which amplified a 541 bp sequence of IS6110. 41% of the above samples gave positive amplification. Three samples that were positive for 38 kDa sequence were negative for IS6110.     

Neutral endopeptidase inhibition increases the potency of ANP in isolated rat pulmonary resistance vessels and isolated blood perfused lungs

We have investigated the effects of the neutral endopeptidase inhibitor, SCH 42354, on the vasoreactivity of atrial natriuretic peptide (ANP) in rat isolated pulmonary resistance vessels (PRV) and isolated perfused lungs (IPL). PRV (n = 37) were mounted onto the jaws of a myograph and precontracted with PGF2alpha (100 mu M). Concentration-responses to ANP (0.17 to 340 nM) were determined before and after the addition of SCH 42354 (10, 30 and 100 nM). Each concentration of SCH 42354 caused a significant increase in potency (- log EC50) of ANP in isolated PRV. Lungs from normoxic rats (n = 13) were isolated and perfused with whole blood. An increase in pulmonary artery pressure was achieved by ventilating with an hypoxic gas mixture and concentration-responses obtained by incremental additions of ANP (40 nM to 12 mu M), before and after the addition of SCH 42354 (100 nM). SCH 42354 significantly increased the potency (- log EC50) of ANP in the rat IPL. ANP is partly metabolized by NEP. That an inhibitor of NEP increased the potency of ANP in isolated pulmonary vessels, and in isolated perfused whole lungs, suggested that SCH 42354 may be having a local action within the pulmonary vasculature.