Enzyme kinetics of a highly purified mitochondrial creatine kinase in comparison with cytosolic forms

Summary Mitochondrial creatine kinase (CK) purified from canine myocardium showed a single protein band on SDS-PAGE and was free of MMCK. Its amino acid composition was different than MMCK or BBCK and did not react to antiserum to MMCK or BBCK. Using purified mitochondrial, MM and BBCK, the velocity of reaction (V) was estimated for creatine phosphate (CP), creatine (C), adenosine triphosphate (ATP) and adenosine diphosphate (ADP) over a wide range of concentrations including those at V_max. The values for K_m (mM/L) derived from Lineweaver-Burke plots are shown: The affinity of mitochondrial CK for C is much greater than MMCK which is compatible with the energy shuttle hypothesis, namely ATP is converted by mitochondrial CK to CP, and then diffuses to the myofibril for conversion to ATP for utilization.     

The Fertility of Melanesian Girls, Laboratory Mice, and Prostitutes: A Comment on the "Bruce Effect"

Greenfield has recently proposed that low fertility in both prostitutes and unmarried Trobriand girls may be explained by the "Bruce effect": the inhibition of pregnancy in female mice that have had intercourse with different males within a short period. An examination of Malinowski's data indicates that a Trobriand girl usually had intercourse with only one man over a fairly long period and her sex life was not at all comparable to that of a prostitute or one of Bruce's mice. Low fertility in unmarried girls has been well documented for several Melanesian societies that differ notably in the behavior permitted to girls. The existence of so-called adolescent sterility still seems to be the best explanation to cover all of these cases. [fertility, sexual behavior, Melanesia]     

A Survey of Infantile Gastroenteritis

In 1967 we admitted 339 cases of infantile gastroenteritis; one-third of these were dehydrated, and in this group the commonest biochemical abnormality found was hypernatraemia, sometimes with metabolic acidosis. A higher incidence of dehydration was found in the patients who had received oral glucose fluids before admission. Enteropathic Escherichia coli were isolated from the faeces of 16% of the cases. Associated infections, especially of the respiratory tract, were common. Treatment was aimed at the restoration of fluid and electrolyte balance. Usually this was achieved with oral fluids, though intravenous fluids were used in the most severely dehydrated cases. Recovery was complete in 320 cases and a further 14 cases were discharged as carriers of enteropathic E. coli. There were five deaths (1·5%) in the series; three occurred immediately after admission.     

The ribosomal binding site for peptidyl-transfer-ribonucleic acid

The properties of a site, on Escherichia coli ribosomes, which binds peptidyl-s-RNA (where s-RNA refers to ;soluble' or transfer RNA) have been investigated. The binding is stable both in low Mg(2+) concentration (0.1mm), and in high Mg(2+) concentration (10mm) in the absence or presence of potassium chloride (86mm). Puromycin has been used to break the bond between the s-RNA and the polypeptide, and in the absence of further protein synthesis this technique exposes free s-RNA molecules on the ribosomes. The s-RNA exposed remains bound in high Mg(2+) concentration, but the binding is unstable in high Mg(2+) concentration with potassium chloride and the s-RNA can be freed completely from the ribosomes by lowering the Mg(2+) concentration. It can also be displaced by s-RNA in the medium. It is suggested that this ribosomal binding site for peptidyl-s-RNA is the site for peptide bond formation. Further, it is proposed that it is the same site that can be demonstrated on ribosomes not engaged in protein synthesis and that, in high Mg(2+) concentration, will bind s-RNA molecules charged or uncharged with amino acids.     

Electron Microscope Study of Lens Fibers

Comparative electron microscope investigations on sections of the lens cortex of the normal, mature rat, rabbit, monkey, and the normal calf reveal similar patterns of intracellular organization. The superficial lens fiber contains a nucleus, mitochondria, endoplasmic reticulum, dense granules, Golgi complex, and a quantity of small structures of low opacity which appear as filamentous and spherical configurations. Variations in number, distribution, and spatial arrangement of cytoplasmic elements in lens fibers are described. These changes in the pattern of cytoplasmic organization are concomitant with development of fibers and their displacement towards the center of the lens. Structural details of the various zones of the lens epithelium and the lens fibers are compared.     

BC,Ontario taking different routes in trying to lower drug costs

Changes to pharmacare programs in British Columbia and Ontario were compared during a recent Toronto conference on the business aspects of Canadian health care. The brunt of the changes in BC are being borne by pharmaceutical companies and prescribers, while in Ontario the new program affects those who receive free drugs from the province and People and groups that rely on private health insurance.     

The Saccharomyces cerevisiae SGE1 gene product: a novel drug-resistance protein within the major facilitator superfamily

Several pleiotropic drug sensitivities have been described in yeast. Some involve the loss of putative drug efflux pumps analogous to mammalian P-glycoproteins, others are caused by defects in sterol synthesis resulting in higher plasma membrane permeability. We have constructed a Saccharomyces cerevisiae strain that exhibits a strong crystal violet-sensitive phenotype. By selecting cells of the supersensitive strain for normal sensitivity after transformation with a wild-type yeast genomic library, a complementing 10-kb DNA fragment was isolated, a 3.4-kb subfragment of which was sufficient for complementation. DNA sequence analysis revealed that the complementing fragment comprised the recently sequenced SGE1 gene, a partial multicopy suppressor of gal11 mutations. The supersensitive strain was found to be a sge1 null mutant. Overexpression of SGE1 on a high-copy-number plasmid increased the resistance of the supersensitive strain. Disruption of SGE1 in a wild-type strain increased the sensitivity of the strain. These features of the SGE1 phenotype, as well as sequence homologies of SGE1 at the amino acid level, confirm that the Sge1 protein is a member of the drug-resistance protein family within the major facilitator superfamily (MFS).     

The mosquito dihydrofolate reductase gene functions as a dominant selectable marker in transfected cells

An Aedes albopictus dihydrofolate reductase gene was used to construct two chimeric DNA vectors that functioned as dominant selectable markers in transfected, wild type mosquito cells. Stably transformed clones were recovered after 10–15 days in the presence of selective medium containing 1 μM methotrexate. The transformed clones contained an estimated 100–500 copies of transfected DNA per nucleus. Combined data from Southern blots and in situ hybridization to metaphase chromosomes indicated that transfected DNA was likely integrated into chromosomes both as repeated structures and as randomly integrated single copy molecules, with minimal rearrangement of coding sequences. Transfected DNA was stably maintained under selective conditions, but in some cases was lost when cells were maintained for prolonged periods in the absence of methotrexate. These observations provide a general framework for further development of stable gene transfer systems for mosquito cells in culture.