Characterization of the activation pathway of phosphoramidate triester prodrugs of stavudine and zidovudine.

The phosphoramidate triester prodrugs of anti-human HIV 2', 3'-dideoxynucleoside analogs (ddN) represent a convenient approach to bypass the first phosphorylation to ddN 5'-monophosphate (ddNMP), resulting in an improved formation of ddN 5'-triphosphate and, hence, higher antiviral efficacy. Although phosphoramidate derivatization markedly increases the anti-HIV activity of 2',3'-didehydro-2', 3'-dideoxythymidine (d4T) in both wild-type and thymidine kinase-deficient CEM cells, the concept is far less successful for the 3'-azido-2',3'-dideoxythymidine (AZT) triesters. We now investigated the metabolism of triester prodrugs of d4T and AZT using pure enzymes or different biological media. The efficiency of the first activation step, mediated by carboxylesterases, consists of the formation of the amino acyl ddNMP metabolite. The efficiency of this step was shown to be dependent on the amino acid, alkyl ester, and ddN moiety. Triesters that showed no conversion to the amino acyl ddNMP accumulated as the phenyl-containing intermediate and had poor, if any, anti-HIV activity. In contrast to the relative stability of the triesters in human serum, carboxylesterase-mediated cleavage of the prodrugs was found to be remarkably high in mouse serum. The subsequent conversion of the amino acyl ddNMP metabolite to ddNMP or ddN was highest in rat liver cytosolic enzyme preparations. Although L-alaninyl-d4TMP was efficiently converted to d4TMP, the main metabolite formed from L-alaninyl-AZTMP was the free nucleoside (AZT), thus explaining why d4T prodrugs, but not AZT prodrugs, retain anti-HIV activity in HIV-infected thymidine kinase-deficient cell cultures. The rat liver phosphoramidase responsible for the formation of ddNMP was shown to be distinct from creatine kinase, alkaline phosphatase, and phosphodiesterase.     

Aristolochic acids in Aristolochia chilensis

The major components of the acid fraction of the leaves and tender stems of Aristolochia chilensis Miers are aristolochic acids I and Ia. Aristolochic acid Ia has been isolated from plant material for the f?rst time, and its PMR spectrum is discussed.     

Respiratory syncytial virus genotypes and disease severity among children in hospital

OBJECTIVES: To determine the spectrum of N and G genotypes of respiratory syncytial virus (RSV) causing respiratory tract infection and whether particular genotypes are associated with severity of infection. PATIENTS AND METHODS: Nasopharyngeal aspirates (NPAs) were obtained from 114 infants with acute respiratory tract infection due to RSV over two seasons. Viral mRNA was extracted from NPAs or cultured virus, reverse transcribed, and the cDNA amplified by the polymerase chain reaction using primers directed to parts of the N and G gene respectively. Amplicons were separately digested with four different restriction endonucleases for each gene. The fragments were separated by agarose gel, electrophoresis, and the electrophoretic patterns used to assign the various genotypes. Disease severity was assessed as very mild (upper respiratory tract signs only), mild (coryza and signs of lower respiratory tract infection), moderate (requiring nasogastric or intravenous fluids), and severe (requiring oxygen or ventilation). RESULTS: Five of the six known N genotypes were detected, but NP4 and NP2 were found most frequently. There was no association between N genotype and disease severity. Six G (SHL) genotypes were detected. Significantly (p = 0.04) more of the infants infected with the SHL2 genotype had severe or moderate disease. CONCLUSIONS: During the seasonal peaks of RSV respiratory tract infection at least 10 different RSV genotypes cocirculated. While there is no association between N genotypes and disease severity, infection with the SHL2 G genotype appears to result in moderate to severe disease.     

Non beating heart donors as a possible source for liver transplantation

Organ shortage for liver transplantation continues to be a major problem. Non heart beating donors (NHBD) are gaining increasing importance as a potential source of transplantable organs for clinical use, mainly in kidney transplantation. Up to now, the experience in liver transplantation with this type of donors has been limited and has only been considered in donors in whom cardiac arrest (CA) has occurred at a known given time. This is due to the high risk of primary non-function and late complications related to intrahepatic biliary lesions when warm ischemia time (WIT) is not controlled. The method of retrieval of these organs should offer the possibility to stop liver injury, revert histologic lesions appeared after WIT, and to assess the quality of the potential donor liver. Based on the experience of kidney transplantation, total body cooling achieved by extracorporal cardiopulmonary bypass seems to be the best method. Moreover it allows the inclusion of a time for tissue oxygenation at 37 degrees C (Normothermic Recirculation, NR) prior to body cooling which has been shown to improve graft viability, and also allows a time to measure organ quality before transplantation. In our experience, we demonstrated that liver transplantation from NHBD is feasible; NR has beneficial effect on liver viability improving endothelial cell damage, hepatocyte energy charge and histological changes at 5 days. We also showed that time of cardiac arrest is determinant of graft viability; even if hepatocellular function is preserved after 40 minutes of CA using NR, irreversible intrahepatic biliary lesions are always present and burden long-term survival. Moreover, bypass pump and blood flows are directly related to WIT and the achievement of better pump flows may predict survival during NR. In animals with 40 minutes of CA, we also reported the possibility to manipulate the potential graft during NR with L-Arginine, Glycine and S-Adenosyl-Methyonine, which minimize endothelial and hepatocellular damage as well as lesions at 5 days. Further research needs to be done in order to confirm our experimental data.     

Hérida Regina Nunes SALGADO,et al:Microbiological assay for the determination of azithromycin in ophthalmic solutionsMicrobiological assay for the determination of azithromycin in ophthalmic solutions

IntroductionAzithromyciniscommercializedbypharmaciesinBrazilinophthalmicsolutionform. Despitetheproveneffectivenessandsafetyinitstreatment, thisdrug,untilthen, doesnotpossessamethodologyofstandar dizedanalysisforophthalmicsolutionsinofficialcom pendiumsan…     

国内真菌性角膜溃疡治疗进展

真菌性角膜角膜溃疡发病率逐年上升,目前主要采用抗真菌药物治疗、手术治疗、抗真菌药物联合手术治疗以及中西结合治疗,尚无特效的治疗方法。本文就治疗该病的最新进展进行了综述。     

60家医院创建无烟医院对医生控烟知识态度行为的影响

目的：通过创建无烟医院活动,了解医生的吸烟状况和控烟知识、态度与行为,并对干预效果进行评价。方法：在北京、上海、广州选择60家医院创建无烟医院,对全院医生开展控烟干预,在干预前对19580名医生、干预后对20772名医生进行问卷调查,了解医生的吸烟状况和控烟知识、态度与行为的变化。结果：通过一年的控烟干预,医生吸烟率由...