Activation and injury of Clostridium perfringens spores by alcohols

The activation properties of Clostridium perfringens NCTC 8679 spores were demonstrated by increases in CFU after heating in water or aqueous alcohols. The temperature range for maximum activation, which was 70 to 80 degrees C in water, was lowered by the addition of alcohols. The response at a given temperature was dependent on the time of exposure and the alcohol concentration. The monohydric alcohols and some, but not all, of the polyhydric alcohols could activate spores at 37 degrees C. The concentration of a monohydric alcohol that produced optimal spore activation was inversely related to its lipophilic character. Spore injury, which was manifested as a dependence on lysozyme for germination and colony formation, occurred under some conditions of alcohol treatment that exceeded those for optimal spore activation. Treatment with aqueous solutions of monohydric alcohols effectively activated C. perfringens spores and suggests a hydrophobic site for spore activation.     

A rapid and preparative method for the separation of yeast ribosomal proteins by using high-performance liquid chromatography.

Ribosomal proteins from the yeast Saccharomyces cerevisiae were separated, on a preparative scale, by ion-exchange h.p.l.c. Proteins from the small and large ribosomal subunits were resolved, respectively, into 33 and 23 peaks, and most of the proteins present in these peaks were identified by using one- and two-dimensional gel electrophoresis. Several of the peaks appeared to contain a single protein uncontaminated by other species. Ribosomal proteins were also separated by using reverse-phase h.p.l.c. Analysis of the peaks resolved indicated that the order of elution for the proteins of both ribosomal subunits is, in certain cases, different for each of the two h.p.l.c. techniques used. Thus a combination of the two chromatographic methods employed here has the potential to facilitate the rapid and preparative separation of each of the proteins present in yeast ribosomes.     

Analysis of all protein amino acids as their tert.-butyldimethylsilyl derivatives by gas-liquid chromatography

A gas chromatographic method for the separation and quantitation of the 20 protein amino acids is described using N-methyl-N(tert.-butyldimethylsilyl)trifluoroacetamide, with 1% tert.-butyldimethylchlorosilane as catalyst, to prepare the tert.-butyldimethylsilyl amino acid derivatives. Alkylsilylation of amino acids proceeds at 140 degrees C in 20 min. The derivatives formed in the one-step reaction are used directly for gas-liquid chromatographic analysis, using a flame-ionization detector, without prior isolation or purification. Complete separation and quantitation of all protein amino acids are readily achieved using a 15-m DB-5 capillary column. Strict linearity extends from less than 15 to about 100 ng for all amino acids except Arg, which has a linear range from 50 to 300 ng. The limits of detection, however, range from one to several hundred nanograms. The method was used to analyze the free amino acid pool in carnation petals.     

A cyanogen bromide fragment of S4 that specifically rebinds 16S RNA.

Escherichia coli ribosomal protein S4 was subjected to cyanogen bromide cleavage and was found to generate a complete cleavage product capable of rebinding 16S rRNA. This fragment, consisting of residues 1-103, was found to bind with an apparent association constant of 11 microM-1. This fragment was used in place of S4 in an in vitro reconstitution experiment. Although the particles formed had a protein composition not significantly different from reconstituted 30S ribosomal subunits, their sedimentation behavior was more like that of particles reconstituted without S4. These results indicate to us that, although residues 104-203 of S4 are involved in the assembly of the 30S ribosome, they are not necessary for the binding of S4 to 16S RNA. Taken with previous results, the domain of S4 involved in specific binding of 16S RNA can be confined to residues 47-103.     

A prospective study of maternal and fetal outcome in acute Lassa fever infection during pregnancy.

Several viral infections have been reported to result in more severe disease in pregnant than non-pregnant women, but the relative risks have not been well characterised. This has now been done for Lassa fever in a prospective study of 68 pregnant and 79 non-pregnant women who were admitted to hospital in Sierra Leone with confirmed Lassa fever. Lassa fever was the main cause of maternal mortality in the hospital, accounting for 25% of maternal deaths. Twelve of 40 patients in the third trimester died, compared with two of 28 in the first two trimesters and 10 of 79 non-pregnant women. The odds ratio for death in the third trimester compared with the first two trimesters was 5.57 (95% confidence intervals 1.02 to 30.26). The condition of the mother improved rapidly after evacuation of the uterus, whether by spontaneous abortion, evacuation of retained products of conception, or normal delivery; 10 of 26 women without uterine evacuation died, but only four of 39 women with evacuation died (p = 0.0016). The odds ratio for death with pregnancy intact was 5.47 (95% confidence interval 1.35 to 22.16). Fetal and neonatal loss was 87%. The risk of death from Lassa fever in the third trimester is significantly higher than that in the first two trimesters and higher than that for non-pregnant women, but evacuation of the uterus can significantly improve the mother''s chance of survival.     

Modeling problems in conservation genetics using captive Drosophila populations: Consequences of equalizing founder representation

Equalizing founder representation is a recommended practice for maintaining captive populations. However, this procedure has not been subject to controlled experimental evaluation. The effects on inbreeding, genetic variation, and reproductive fitness of maintaining small captive populations by equalizing founder representation (EFR) versus randomly choosing parents (RC) were compared. Ten replicate lines were created with unequal founder representations, split into EFR and RC lines, and maintained for a further eight generations. Founder representations computed from pedigrees were closer to equality in the EFR lines than in the RC lines or the base population, most of the changes being evident after one generation. Significant benefits of EFR were found in lowered inbreeding (mean inbreeding coefficients of 0.35 and 0.41, respectively, for EFR and RC lines) and average heterozygosity (0.141 for EFR, 0.084 for RC, compared with 0.216 in the base population). However, EFR was not significantly better than RC in moving allele frequencies towards equalized founder representation. No significant difference was found in reproductive fitness between EFR and RC (relative fitnesses compared to the base population were 0.179 for EFR and 0.182 for RC). The use of equalization of founder representation for a few generations can be recommended in the genetic management of captive populations derived from a small number of founders that contribute unequally. © 1992 Wiley-Liss, Inc.     

Growth of Clostridium perfringens in cooked chili during cooling.

U.S. Department of Agriculture regulations require that brick chili be cooled from 48.9 degrees C to 4.4 degrees C within 2 h of cooking, but processors may not always be able to comply. Studies were conducted to evaluate the extent of bacterial multiplication resulting from outgrowth of germinated Clostridium perfringens spores experimentally inoculated into chili and incubated at various temperatures. Inoculated samples were heated (75 degrees C for 20 min) to activate spores, quickly equilibrated, and held at one of five desired temperatures for 6 h. No growth was observed for C. perfringens in samples held at 26.7 degrees C and below for 6 h, but growth was observed by 6 h in samples held at 32.2 degrees C and after 2 h in samples held at temperatures between 37.8 degrees C and 48.9 degrees C. Using isothermal growth data, we developed a simple model for predicting the growth of bacteria with time under exponential cooling conditions. The model predicts both the lag phase and the numbers of bacteria at specific times during the growth phase. It was developed by using isothermal growth data and tested by using temperature-varying growth data from experiments with spores of C. perfringens in chili. Actual data agreed closely with predicted results. The results should be useful for evaluating the hazard potential for growth of C. perfringens in chili.     

Gonadal development and gonadotrophin secretion in the male vole (Microtus agrestis) after an abrupt change in photoperiod

Male voles were reared from birth to age 28 days in 6L:18D. Pairs of animals showing similar sexual development were assigned at random to 16L:8D or 6L:18D. Treatments continued for a further 56 days. Increase in the activity of the hypothalamo-hypophysial system occurred within 4 days of exposure to 16L:8D, as shown by significant elevation of plasma LH and FSH. Pituitary LH did not increase until Day 7, and pituitary FSH did not increase until Day 21. After exposure to 16L:8D for 4 days, pituitary FSH was lower than in corresponding animals in 6L:18D. These discrepancies between pituitary and plasma values of gonadotrophins indicate that increase in hormone release occurs before synthesis is fully stimulated. Enhanced output of testicular hormones probably began between Day 7 and Day 14, as indicated by an increase in seminal vesicle weight, yet plasma and pituitary concentrations of LH and FSH remained elevated. This suggests that long photoperiods may cause direct stimulation of the hypothalamo-hypophysial system which increasing values of testicular hormones are initially unable to inhibit. The response of this system in voles to an abrupt change from a non-stimulating to a stimulating photoperiod has a time course resembling that for the Soay ram but appreciably slower than for the Japanese quail.