Pharmacokinetics,Safety, and Tolerability of GS-9851, a Nucleotide Analog Polymerase Inhibitor for Hepatitis C Virus,following Single Ascending Doses in Healthy Subjects

To investigate the pharmacokinetics, safety, and tolerability of GS-9851 (formerly PSI-7851), a new nucleotide analog inhibitor of hepatitis C virus (HCV), we conducted a double-blind, parallel, placebo-controlled, randomized, single-ascending-dose study. Healthy subjects received oral doses of 25 to 800 mg GS-9851. Peak concentrations of GS-9851 in plasma were achieved more rapidly than those of the metabolites GS-566500 (formerly PSI-352707) and GS-331007 (formerly PSI-6206), with time to maximum concentration of drug in plasma (t_max) values of 1.0 to 1.8 h, 1.5 to 3.0 h, and 3.0 to 6.0 h, respectively. The majority of systemic drug exposure was from the nucleoside GS-331007, with maximum concentration of drug in plasma (C_max) and area under the concentration-time curve to the last measurable concentration (AUC_0–t) values at least 7- and 41-fold higher, respectively, than those obtained for GS-9851 after adjusting for differences in molecular weight. The terminal elimination half-life (t_1/2) of GS-331007 increased with the dose, achieving a t_1/2 of 25.7 h at 800 mg GS-9851. Dose proportionality was not observed for GS-331007. The majority of drug recovered in urine was in the form of GS-331007, with the percentage of this metabolite in urine samples ranging from 57% to 27% with increasing dose. GS-9851 was generally well tolerated, with no maximum tolerated dose identified. In conclusion, GS-9851 and its metabolites demonstrated a favorable pharmacokinetic profile consistent with once-daily dosing, and therefore, further clinical studies evaluating GS-9851 in HCV-infected patients are warranted.     

Comparative Pharmacokinetics of Oral Ceftibuten,Cefixime, Cefaclor,and Cefuroxime Axetil in Healthy Volunteers

Study Objective . To compare the pharmacokinetics of ceftibuten, cefixime, cefuroxime axetil, and cefaclor after oral administration. Design . Randomized, four-period, crossover study. Setting . Hospital-based clinical research center. Subjects . Healthy adult men and women volunteers. Interventions . Single 400-mg doses of cefixime and ceftibuten, and 500-mg doses of cefuroxime axetil and cefaclor. Measurements and Main Results . Serum concentrations were determined by high-performance liquid chromatography methods. The mean oral clearances of cefixime, cefuroxime axetil, and cefaclor were similar, ranging from 20.4–27.0 L/hour; clearance of ceftibuten was approximately 4-fold less, 5.45 L/hour. The serum half-lives of ceftibuten (2.35 hrs) and cefixime (2.38 hrs) were prolonged compared with those of cefuroxime axetil (1.30 hrs) and cefaclor (0.693 hr). These agents also differed in terms of time to maximum concentration, time to peak plasma level, area under the curve, and apparent volume of distribution, the last reflecting differences in bioavailability. Conclusion . Ceftibuten had a relatively high time to maximum concentration and long half-life, resulting in a 3.5-fold higher area under the curve than cefixime, cefuroxime axetil, and cefaclor. These pharmacokinetic data can be used as a basis to compare the four oral cephalosporins; however, comparative susceptibility data must also be considered.     

The effect of human calcitonin on the cytoplasmic spreading of rat osteoclasts

We previously found that calcitonin (CT), which inhibits osteoclastic bone resorption, abolished the cytoplasmic motility of isolated osteoclasts. The transition from motility to immotility was accompanied by a characteristic change in cell shape which coincided with the loss of pseudopodial ruffling activity and gradual cytoplasmic retraction. In this report we used computer-assisted morphometry to quantify the reduction in cytoplasmic spreading induced by human CT (hCT). Osteoclasts, isolated from neonatal rat long bones, were allowed to spread on a plastic surface for 120 min. The outlines of six osteoclasts were recorded on a time-lapse video recorder. hCT, other hormones, or plasma samples were then added. The outlines of the same six osteoclasts were recorded after incubation, and the area covered by the cells after incubation was calculated as a percentage of the area covered by the same cells before hormone addition. Osteoclastic spreading was reduced by hCT in a dose-dependent manner and was significantly decreased by concentrations of 2 pg/ml and above. High concentrations of PTH and 1,25-dihydroxyvitamin D3 had no effect on osteoclasts. This technique is a sensitive and quantitative assay of hCT concentration which is unaffected by the presence of other calcium-regulating hormones likely to be present in plasma.     

Long-term effects of nutritional programming of the embryo and fetus: mechanisms and critical windows

The maternal nutritional and metabolic environment is critical in determining not only reproduction, but also long-term health and viability. In the present review, the effects of maternal nutritional manipulation at defined stages of gestation coinciding with embryogenesis, maximal placental or fetal growth will be discussed. Long-term outcomes from these three developmental windows appear to be very different, with brain and cardiovascular function being most sensitive to influences in the embryonic period, the kidney during placental development and adipose tissue in the fetal phase. In view of the similarities in fetal development, number and maturity at birth, there are close similarities in these outcomes between findings from epidemiological studies in historical human cohorts and nutritional manipulation of large animals, such as sheep. One key nutrient that may modulate the long-term metabolic effects is the supply of glucose from the mother to the fetus, because this is sensitive to both global changes in food intake, maternal glucocorticoid status and an increase in the carbohydrate content of the diet. The extent to which these dietary-induced changes may reflect epigenetic changes remains to be established, especially when considering the very artificial diets used to induce these types of effects. In summary, the maintenance of a balanced and appropriate supply of glucose from the mother to the fetus may be pivotal in ensuring optimal embryonic, placental and fetal growth. Increased or decreased maternal plasma glucose alone, or in conjunction with other macro- or micronutrients, may result in offspring at increased risk of adult diseases.     

Severe perinatal thrombosis in double and triple heterozygous offspring of a family segregating two independent protein S mutations and a protein C mutation

Molecular genetic and phenotypic analyses were performed in a highly unusual case of combined protein S and protein C deficiency manifesting in a family in which a child had died perinatally from renal vein thrombosis. Antenatal diagnosis in a second pregnancy was initially performed by indirect restriction fragment length polymorphism (RFLP) tracking using a neutral dimorphism within the PROS gene and served to exclude severe protein S deficiency. Am umbilical vein blood sample at 22 weeks gestation showed isolated protein C deficiency. This pregnancy proceeded to a full-term delivery without thrombotic complications. Molecular genetic analysis of the PROC and PROS gene segregating in the family then yielded one PROC gene lesion in the father and two PROS gene lesions, one in each parent. These lesions were shown to segregate with the respective deficiency states through the family pedigree. Analysis of DNA from paraffin-embedded liver tissue taken from the deceased child showed the presence of both PROS mutations, as well as the PROC mutation. Genotypic analysis of the second child showed a PROC mutation, but neither PROS mutation consistent with its possession of normal protein S levels and a low/borderline protein C level. Antenatal diagnosis was then performed in a third pregnancy by direct mutation detection. However, although the fetus carried only the paternal PROS and PROC gene lesions, the child developed renal thrombosis in utero. It may be that a further genetic lesion at a third locus still remains to be defined. Alternatively, the intrauterine development of thrombosis in this infant could have been caused, at least in part by a transplacental thrombotic stimulus arising in the protein S-deficient maternal circulation. This analysis may, therefore, serve as a warning against extrapolating too readily from genotype to phenotype in families with a complex thrombotic disorder.     

Detection of cervical intraepithelial neoplasia in developing countries

The reduction of cervical cancer mortality in developing countries is only one of many priorities competing for scarce funds. Incidence of cervical cancer may be up to six times higher in these countries than in developed countries due to lack of screening programs. The current WHO recommendation is to evaluate visual inspection as a way of identifying early curable cancer, as screening by cytology is too complex and expensive. Hence, an assessment of visual inspection aided by acetic acid (VIA) has been conducted in Zimbabwe. The study aimed to find out the true sensitivity, specificity, and positive predictive value (PPV) for high-grade CIN. The subject group was composed of 10,934 women screened by VIA and by exfoliative cervical cytology. The main findings of the study were that VIA was abnormal in about 20% of women; moreover, the test had a PPV of 25.9%, meaning that 3 out of 4 women would potentially be overtreated. VIA, however, represents a proven, simple means of identifying women in undeveloped health facilities, though level of training is probably critical to its success. Screening should go hand in hand with health education, which has proven valuable in reducing the rate of deaths from cervical cancer.     

A quantitative PCR (TaqMan) assay for pathogenic Leptospira spp

Background  

Leptospirosis is an emerging infectious disease. The differential diagnosis of leptospirosis is difficult due to the varied and often "flu like" symptoms which may result in a missed or delayed diagnosis. There are over 230 known serovars in the genus Leptospira. Confirmatory serological diagnosis of leptospirosis is usually made using the microscopic agglutination test (MAT) which relies on the use of live cultures as the source of antigen, often performed using a panel of antigens representative of local serovars. Other techniques, such as the enzyme linked immunosorbent assay (ELISA) and slide agglutination test (SAT), can detect different classes of antibody but may be subject to false positive reactions and require confirmation of these results by the MAT.