Cloning ofCandida boidinii DNA fragments promoting autonomous replication of plasmids inSaccharomyces cerevisiae

Fragments of Candida boidinii chromosomal DNA were inserted into the integrative vector YIp-kanr and examined for the presence of sequences promoting autonomous replication of plasmids in Saccharomyces cerevisiae. Restriction maps of two plasmids, designated S6/4 and S6/5, originating from the same S. cerevisiae transformant, were constructed. Southern hybridization data confirmed that the plasmids carry sequences from the C. boidinii chromosome. Both plasmids transform S. cerevisiae strains at 4-5-fold higher frequency than cloning vectors based on the replication origin of the 2 microns plasmid. Mitotic stability of the constructed plasmids is similar to that of the 2 mu-based vector pNF2 in S. cerevisiae.     

Patterns of energy metabolism and growth kinetics of Kluyveromyces marxianus in whey chemostat culture

The influence of physiological parameters such as carbon substrate flux and O₂ uptake rates on energy metabolism are reported with reference to biomass productivity in whey chemostat culture. The combined results show that oxidoreductive energy metabolism may be attained independently of the yeast reaching its maximum respiratory capacity. A novel metabolic interpretation is presented proposing that a relative imbalance between glycolysis and subsequent oxidative steps alone is sufficient to account for the observed results. By means of a mathematical model the results could be reproduced under all experimental conditions. The new interpretation provides an insight into the manner in which energy mettbolism is regulated and influences growth-related process Kluyveromyces marxianus, as well as other yeasts with similar physiological characteristics. Correspondence to: J. I. Castrillo     

Decarboxylation of branched-chain alpha-ketoacids in hepatocytes from alloxan-diabetic rats. The effect of insulin

The flux through branched-chain alpha-ketoacid dehydrogenase and the activity of the branched-chain alpha-ketoacid dehydrogenase complex were measured in hepatocytes isolated from fed, starved and alloxan diabetic rats. The highest rate of branched-chain alpha-ketoacid oxidation was found in hepatocytes isolated from starved rats, slightly lower in those from fed rats, and significantly lower in diabetic hepatocytes. The amount of the active form of branched-chain alpha-ketoacid dehydrogenase was only slightly diminished in diabetic hepatocytes, whereas the flux through the dehydrogenase was inversely correlated with the rate of endogenous ketogenesis. The same was observed in hepatocytes isolated from starved rats when branched-chain alpha-ketoacid oxidation was measured in the presence of added oleate. In both cases the diminished flux through the dehydrogenase, restored by a short preincubation of hepatocytes with insulin, was paralleled by a decrease of fatty acid-derived ketogenesis. The significance of these findings is discussed in relation to the role of insulin in branched-chain alpha-ketoacid oxidation in liver of diabetic rats.     

Individual variability of pathological parameters in chemically induced rat colon tumors.

The development of tumorigenic conditions in the carcinogen-exposed rat colon was studied using selected morphological, histochemical, immunohistochemical and biochemical methods of analysis. Rats were treated with two carcinogens: 1,2-dimethylhydrazine and N-methyl-N'-nitro-N-nitrosoguanidine alone or with deoxycholic acid as a tumor promoter. It was found that 3 months after treatment of animals with the carcinogens the following changes were developed in colonic tissue: infiltration of lymphocytes in the mucous membrane, high increase in mitotic index among epithelial cells, negative reactions of colonic cells for neutral mucopolysaccharides and sulfomucins and positive reactions to carboxyl groups, nonsulfated acid mucosubstances and tissue polypeptide antigens. An increase in the activity of ornithine decarboxylase in colonic tissue was developed within the same time period and has been seen only in those tissues which were characterized by the development of precancerous conditions. Individual variations were observed in the manifestation of the studied parameters in rat neoplastic colonic tissues. It is suggested that these differences reflect an individual sensitivity of animals to carcinogens and the magnitude of the dysplastic processes induced in the colon.     

Unaltered metabolism of taurolithocholic acid with changes in composition of rat intestinal microflora

Changes in composition of both total aerobes and anaerobes of rat intestinal microflora do not appear to affect the metabolism of taurolithocholic acid.     

Characteristics of patients aged over 75 not seen during one year in general practice.

A study was carried out in two large urban practices to determine the number of patients aged over 75 years who had had no contact with the primary care team during one year and to examine their medical and social characteristics. Although their general health was considered to be good, over half needed treatment or other action and half had no identifiable career.     

Isolation and characteristics of the biological and genetic properties of neamin-resistant mutants of Salmonella typhimurium and Salmonella dublin candidates for vaccine creation

Mutants, resistant to neamine and spectinomycin, have been isolated from S. typhimurium and S. dublin highly virulent strains. The neamine-resistant mutants can be divided into 3 classes in accordance with their sensitivity to streptomycin: sensitive, resistant to low and high concentrations of this antibiotic. The transduction analysis with the use of bacteriophage P 22 has revealed that the spectinomycin-resistant mutations under study are spc A mutations, while the mutations leading to resistance to neamine in class Near Strr 500 are nea B mutations. The mutation leading to resistance to spectinomycin (spc A) has been found to produce no changes in the virulence of salmonellae in the intraperitoneal infection of mice. The mutations leading to resistance to neamine and streptomycin (nea B and str A) have been found to decrease virulence.