Statistical evaluation of inter- and intra-laboratory variations of the Ames test, as related to the genetic stability of Salmonella tester strains

A statistical analysis was performed on the data resulting from an international collaborative study of the Ames test according to a standardized experimental protocol, which involved the comparative testing of 4NQO (4 doses), in 3 separate experiments for each of the 38 participating laboratories, by using a common reference (R) culture and in-house laboratory (L) cultures of 5 strains of S. typhimurium. Despite some toxicity phenomena recorded at the highest dose of 4NQO, the majority of the dose-response curves in individual laboratories were linear on a bi-log scale and their mean values fitted a linear regression framework. Scattering of data around mean values of laboratories was Gaussian-like even at the highest dose of 4NQO, toxic effects being expressed as a dose-related increase of variance. A weighted least-square analysis could therefore take into account toxic effects without resorting to a sophisticated non-linear model incompatible with log transformation. Various analytical approaches--e.g. the weighted estimates of linear regression parameters, a multifactor (laboratory, experiment, dose, culture of each strain) analysis of variance with all the possible interactions, the assessment of correlations in individual laboratories and of coefficients of variation for induced and spontaneous mutability--could detect some statistically significant differences between L and R cultures. However, at a critical evaluation on an individual basis, only few of these differences, without any peculiar involvement of given strains, were convincing in view of the existence of real phenomena of genetic drift. Therefore, on the whole, the genetic drift of Salmonella tester strains appears to lend a negligible contribution to the considerable inter- and intra-laboratory variability detected in this study. With a background variability between replications averaging 26%, a dose-related variability was evident both between experiments (28-54%) and between laboratories (44-127%).     

Effect of glucose on protein phosphorylation in rat pancreatic islets

Isolated rat pancreatic islets, incubated in the presence of extracellular ³²Pi to steady state ³²P incorporation into cellular phosphopeptides, were exposed to glucose for 10 min. Glucose (16.7 mM) significantly stimulated the phosphorylation of six phosphoproteins with molecular weights of 15,000, 35,000, 49,000, 64,000, 93,000 and 138,000. Mannoheptulose (16.7 mM) markedly inhibited glucose-stimulated phosphorylation of these six phosphoproteins. This protein phosphorylation might be important in mediating glucose-stimulated insulin release.     

Following the recovery of naso-pharyngeal cancer patients by trace elements in hair using statistical pattern recognition methods

This article describes a study where the recovery of nasopharyngeal cancer (NPC) patients was traced by trace elements (TEs) in hair of these patients. These patients whose concentrations of TEs in hair were studied are volunteers who were divided into three groups B, C, and D. Group B was made up of volunteers who had just been diagnosed as having NPC, group C and group D were made up of volunteers who had been diagnosed as having NPC after 3 and 6 mo, respectively, of treatment. For comparison, a control group, namely group A, which was made up of volunteers from healthy persons was added to this study. By implementation of statistic pattern recognition methods, it has been found that the concentrations of TEs in hair can remarkably reflect different recovery phases of NPC patients.     

人热休克蛋白gp96基因的克隆及其在大肠杆菌中的表达与纯化

热休克蛋白gp96是热休克蛋白90家族成员,能够引起非特异性和特异性免疫反应。得到大量高纯度的蛋白质是研究开发gp96的关键。然而重组的gp96容易在E．coli中降解,并在一定条件下形成多聚体。实验先将人gp96基因克隆到pET-30a载体上并在E．coli Blstar中表达,再经过亲和层析、阴离子交换、分子筛分别纯化gp96。最终去掉了大部分的降解片段和多聚体,得到一定量的可溶性gp96,为进一步研究其结构和功能打下一定的基础。     

Microbial analysis of clinical material taken from patients at the Oncology Center, Maria Skłodowkda-Curie Institute in Warsaw in 1997

An analysis was carried out of the microbiological investigations of clinical material samples obtained from the patients of two oncology centres belonging to the Warsaw Oncology Centre. Microorganisms cultured from urine, blood, catheters, smears of wounds and other materials were analysed. From 4839 clinical material samples from the Ursynów centre 1755 bacterial strains were isolated. From 423 samples from the centre in Wawelska Street 171 strains were obtained. In infections of patients from the centres the number of Gram-positive cocci was twice that of Gram-negative rods. In the investigated clinical material S. aureus was the most frequently isolated Gram-positive coccus, while E. coli was the most frequent species among Gram-negative bacteria. In the infections of oncological patients a considerable frequency was noted of yeast-like fungi, especially C. albicans. Particularly disquieting was the increasing number of isolates of C. glabrata and C. krusei strains resistant to fluconazole.     

分子内二硫键对HERV囊膜蛋白融合核心结构的影响

合胞素(Syncytin)是一类由人俘获的逆转录病毒囊膜蛋白,与胎盘的形态发生中细胞滋养层到合胞滋养层的分化过程十分相关。Syncytin与人免疫缺陷病毒I型(HIV-1)囊膜蛋白(Env)在结构上具有相似的特点,二者可能具有相似的膜融合机制。本文通过PCR对融合核心部位七肽重复区HR1和HR2之间linker中自然存在的一对保守的分子内二硫键进行定点突变,表达纯化该突变蛋白,并进行了相应的结构及稳定性探讨,通过与未突变蛋白的性质比较确证该分子内二硫键在蛋白结构的正确形成及稳定性上起着一定的作用。