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Biomedical subjects

M B Kennedy

Publications and source records attributed to M B Kennedy.

61 records · Page 4Linked to original sources
PubMed1981

Two calcium/calmodulin-dependent protein kinases, which are highly concentrated in brain, phosphorylate protein I at distinct sites.

Two calcium-stimulated protein kinase activities (ATP:protein phosphotransferase, EC 2.7.1.37) that phosphorylate protein I, a specific synaptic protein, have been identified in homogenates of rat brain. One of these is found in both the particulate and cytosolic fractions and phosphorylates a region of protein I that is phosphorylated in intact synaptosomes in response to calcium but not to cyclic AMP. The stimulation by calcium of the particulate enzyme and of the partially purified cytosolic enzyme requires the addition of calmodulin. It is not yet known whether the particulate and cytosolic enzymes are related. A second calcium-stimulated protein I kinase is found only in the cytosol and phosphorylates a region of protein I that is phosphorylated in intact synaptosomes in response to either calcium or cyclic AMP. The calcium stimulation of this latter kinase is probably mediated by calmodulin, judging from its inhibition by low concentrations of trifluoperazine. Both of the calcium-stimulated protein I kinases are more highly concentrated in brain than in other tissues. The two cytosolic kinases are distinguishable from each other and from myosin light chain kinase and phosphorylase b kinase by their substrate specificities and their chromatographic behavior on DEAE-cellulose.

Animals↗
PubMed1980

Lysophosphatidyl choline facilitates labeling of CNS projections with horseradish peroxidase.

Previously, it has been difficult to label sensory terminations in the CNS by back-filling peripheral sensory nerves with horseradish peroxidase (HRP), apparently because the amount of HRP transported along the axons is insufficient. Labeling of central sensory projections in axolotls and frogs can be improved by agents known to disrupt membranes. Of those tested, L-alpha-lysophosphatidyl choline is the most effective. The addition of this detergent ot the HRP solution dramatically increases both the number of axons labeled and the density of label within single axons.

Ambystoma↗
PubMed1979

Characterization of the extracellular lipase of Bacillus subtilis and its relationship to a membrane-bound lipase found in a mutant strain.

Bacillus subtilis CMK33 is a mutant that is more osmotically fragile than the wild type when it is converted to the protoplast form. The protoplasts of this mutant contain a membrane-bound lipase, which is not found in protoplasts of the wild type. Hydrolysis of the membrane lipid of mutant protoplasts by the lipase is the cause of their fragility. A protein found in the wild type organism specifically inhibits the lipase (Kent, C., and Lennarz, W. J. (1972) Proc. Natl. Acad. Sci. U. S. A. 69, 2793-2797). This paper reports that cultures of both mutant and wild type cells contain an extracellular lipase which accumulates during the logarithmic phase of growth. The extracellular activity appears to be induced by a component of the growth medium. The membrane-bound lipase of the mutant has been partially purified and its properties have been compared to those of the extracellular lipase of the wild type. Their properties and sensitivity to the wild type inhibitor are similar, which suggests that the two molecules are closely related. The subcellular location of the lipase in the mutant has been investigated and compared to the location of the membrane-bound portion of the lipase inhibitor in the wild type. The lipase is located almost exclusively in the cytoplasmic membrane and not in mesosomal vesicles. In contrast, the lipase inhibitor is located in both types of membranes and is more concentrated in mesosomal vesicles. Under appropriate conditions, the appearance of new extracellular lipase activity in mutant cultures is paralleled by the loss of an equivalent amount of lipase activity from protoplasts prepared from the cells. This suggests that the membrane-bound lipase may be an intermediate in the secretion of the extracellular lipase. Because of the mutation in B. subtilis CMK33, which results in the absence of the lipase inhibitor, this intermediate can be found in protoplasts of the mutant, although it is not detectable in the wild type. Consequently, the mutant may be useful in studies of the mechanism of secretion of exoenzymes by Bacilli.

Bacillus subtilis↗
PubMedDate not supplied

Assessing HIV risk among women who have sex with women: scientific and communication issues.

Data on human immunodeficiency virus (HIV) risk faced by women who have sex with women (WSW) are scarce. The biologic risk of female-to-female transmission is not known. Several surveys have reported that certain groups of WSW engage in behaviors that put them at risk for HIV infection, such as unprotected sex with men, unprotected sex or sharing of sex toys with women, and injection drug use. WSW may also be at risk for HIV through use of unscreened semen from sources other than sperm banks. An evaluation of HIV risk behaviors among WSW has been hampered by methodological issues, such as lack of data about the extent of the population, the use of standard definitions in research, and the design of data collection instruments. HIV prevention efforts have been hampered by communication issues, such as what "safer sex" means to this population and difficulties in interactions with health care providers. Prevention interventions for this population must address behaviors that put WSW at risk for HIV infection, including injection drug use and unprotected penile sex. At the same time, the possibility of sexual transmission of HIV via female-to-female sex should not be discounted. Health providers should understand that sexual identity does not necessarily predict sexual behavior and should not make any assumptions regarding HIV risk based on self-reported or presumed sexual identity.

Epidemiologic Methods↗