Kinetics of beta-glucuronidase induction by androgen. Genetic variation in the first order rate constant

Measurements of enzyme activity, rates of protein synthesis, and mRNA activity suggest that the induction of beta-glucuronidase in mouse kidney in response to androgen is regulated at a pretranslational level. Following an initial lag period, the rate and extent of induction follow the rules of simple turnover kinetics and can be described in terms of a zero order rate constant for acquisition of mRNA activity (ka) and a first order rate constant for loss of activity (kb). Genetic variation in kb, described here for the first time, alters the half-time and extent of induction. Variation in kb is independent of previously described variation in ka and, unlike changes in ka, is not associated with change in the lag time. The DNA sequences determining kb, like those determining ka, are genetically linked to the structural gene for beta-glucuronidase. Following the removal of androgen, beta-glucuronidase activity, rate of synthesis, and mRNA activity all decline rapidly with half-lives of 1-2 days. Even in the most rapidly inducing strains, this is significantly faster than the half-time for induction determined by kb. Furthermore, genetic variation in kb does not affect the rate of de-induction. These facts suggest that kb may not describe the turnover of beta-glucuronidase mRNA, but rather the turnover of another step in the induction process.     

The Effect of Decreasing the External Salinity on the Primary Processes of Photosynthesis in Dunaliella tertiolecta

The euryhaline unicellular green alga Dunaliella tertiolectalost intracellular glycerol when subjected to a decrease inexternal salinity. After the salinity was decreased, photosynthesiswas inhibited for at least the first 100 min, but dark oxygenuptake was transiently stimulated. The extent of the 519 nmfield-indicating absorption change induced by photosystem Ialone was inhibited by decreasing the salinity, but other photosyntheticparameters were largely unaffected. A comparison of these resultswith hypertonic stress indicated that although both stressesinhibit the overall process of photosynthesis, they do so bydifferent mechanisms. Resuspending the algal cells in distilledwater resulted in an inhibition of all the photosynthetic parametersmeasured. Key words: Dunaliella, Photosynthesis, Hypotonicity     

Manifestations of angina morbidity as a reflection of the self-regulation of the epidemic process in streptococcal infection

The data on the application of the principles of the self regulation of the epidemic process for understanding the annual dynamics of angina morbidity in organized groups of adults are presented. In this case the reservation of group A streptococci occurs in chronic (resident) carriers, whose proportion was found to be 15.8 +/- 2.6%. The epidemic manifestations of morbidity are regulated mainly by the concentration of newly arrived members in the groups, i. e. by the size of the stratum providing the optimum conditions for the parasitization of the streptococcal population. The annual morbidity levels depend essentially not only on the heterogeneity of the group members with respect to their susceptibility to streptococcal infection, but also on the conditions of their accommodation, affecting the transmission of droplet infection. The role of individual risk factors in the variation of the quantitative characteristics of the angina morbidity manifestations under study is calculated.     

The physical mechanism of calcium pump regulation in the heart.

The Ca-ATPase in the cardiac sarcoplasmic reticulum membrane is regulated by an amphipathic transmembrane protein, phospholamban. We have used time-resolved phosphorescence anisotropy to detect the microsecond rotational dynamics, and thereby the self-association, of the Ca-ATPase as a function of phospholamban phosphorylation and physiologically relevant calcium levels. The phosphorylation of phospholamban increases the rotational mobility of the Ca-ATPase in the sarcoplasmic reticulum bilayer, due to a decrease in large-scale protein association, with a [Ca2+] dependence parallel to that of enzyme activation. These results support a model in which phospholamban phosphorylation or calcium free the enzyme from a kinetically unfavorable associated state.     

Specific silver staining of experimentally undercondensed chromosome regions

Treatment of human and mouse cell cultures with DNA binding AT-specific compounds and with some base analogues induced distinct undercondensations in several heterochromatic chromosome regions. All those heterochromatic regions undercondensed by AT-specific DNA ligands (distamycin A, DAPI, Hoechst 33258) could be heavily labeled with the silver(Ag)-staining technique; but the heterochromatic regions undercondensed with the cytidine analogue 5-azacytidine were Ag-negative. In metaphase chromosomes from BrdU-treated human cell cultures, the bifilarly substituted chromatids, which show a slight undercondensation, were also Ag-negative. Cytochemical analyses of the Ag-stained undercondensed heterochromatic regions showed that the Ag-stainable material consisted of nonhistone proteins. The mechanism of Ag staining in the undercondensed heterochromatic regions was compared with Ag staining of the nucleolus organizer regions.     

Electrophoretic analysis of the estrogen receptor. Molybdate stabilization and identification of the classical estrogen receptor

Conditions are defined which permit analysis of estrogen receptors from the mammalian uterus by polyacrylamide gel electrophoresis, thereby solving a longstanding problem encountered in previous attempts at such analysis, namely the failure of a large portion of the receptor population to enter such gels. A paramount requirement for entry of the estrogen-receptor complex into polyacrylamide gels is its maintenance in an untransformed state which does not form aggregates that are excluded from these gels. Of the multiple estrogen-binding proteins separated, only one (relative mobility of 0.5-0.6) possessed the definitive characteristics of the classical estrogen receptor. The inclusion of molybdate in extraction buffers selectively enhanced receptor recovery and facilitated its separation. Moreover, the estrogen-receptor complex so resolved is separated from other types of estrogen-binding proteins present in the uterine cytosol. These findings show that the molybdate-stabilized estrogen receptor exists in a single discrete form, but otherwise exhibits multiple forms that are probably artifactual. Electrophoresis in discontinuous buffers, but not in a continuous buffer system, promoted aggregate formation. This finding has implications concerning the subunit structure of the untransformed receptor.     

Interaction of hydrophobic bis (D-mannose) derivatives with adipocyte and erythrocyte sugar transport systems

The inhibition of sugar uptake by a series of hydrophobic bis(D-mannose) derivatives has been measured in rat adipocytes. When the D-mannose moieties of the bis compounds are separated by a hexane bridge the transport inhibition constant (Ki) is greater than for a decane-bridged molecule. This is probably due to the increased hydrophobicity of the bridge of the decane-bridged compound. The enhancement in affinity due to the second sugar in the bis(D-mannose) derivatives is probably only 2-fold, since half reduction of the bis(D-mannosyloxy)hexane increases Ki approx. 2-3-fold. N'-DNP-1,3-bis(D-mannos-4'-yloxy)propyl-2-amine has very high affinity in insulin-treated cells. The affinity is approx. 1000-fold higher than for D-mannose. This enhancement is probably due to the hydrophobicity of the DNP group. The distance from the sugar to the hydrophobic group is important because an increase in Ki occurs if an aminocaproyl spacer is introduced between the DNP group and 1,3-bis(D-mannos-4'-yloxy)propyl-2-amine. Aminocaproyl and glycyl spacers also increase the Ki for NAP derivatives of 1,3-bis(D-mannos-4'-yloxy)propyl-2-amine. Each of the hydrophobic bis(D-mannose) derivatives has a lower Ki in insulin-treated cells. This may be due to an insulin responsive hydrophobic interaction between the hydrophobic portion of the sugar and a hydrophobic domain in the transport system. The inhibition constants for the hydrophobic bis(D-mannose) compounds have also been measured in human erythrocytes.     

Comparative effects of various classes of mouse interferons on macrophage activation for tumor cell killing

The effects of mouse interferon-alpha (MuIFN-alpha), -beta (MuIFN-beta), and -gamma (MuIFN-gamma) on macrophage activation for tumor cell killing were determined by using proteose peptone-elicited peritoneal macrophages from C3H/HeN and C3H/HeJ mice under conditions that either included or were free of detectable endotoxin. Alone, under the conditions used, none of the interferons was able to activate macrophages directly for tumor cell killing. However, with a second signal provided to responsive macrophages by contaminating endotoxin, added bacterial lipopolysaccharide (LPS), or heat-killed Listeria monocytogenes (HKLM), all three types of interferon induced cytolytic activity, with MuIFN-gamma approximately 500 to 1000-fold more active than either MuIFN-alpha or -beta. Thus, all three interferons were able to prime macrophages for killing but required a second signal before cytolytic activity could be expressed. When MuIFN-gamma was mixed with either MuIFN-alpha or -beta and placed on macrophages, little or no killing developed. Mixtures of MuIFN-gamma with either MuIFN-alpha or -beta did increase the sensitivity of macrophages to triggering by LPS, however, compared with macrophages treated with MuIFN-gamma alone. The results are collectively important because they i) confirm that significant quantitative differences exist between the various interferons with regard to their capacity to prime macrophages for tumor cell killing; ii) indicate that to be an efficient activator each type of interferon must be combined with a second stimulus, such as LPS or HKLM; iii) show that neither MuIFN-alpha nor -beta can provide an efficient second triggering signal for macrophages that are primed by MuIFN-gamma; and iv) document that mixtures of MuIFN-gamma with either MuIFN-alpha or -beta are most efficient at inducing priming, compared with any one of the interferons used alone.