Effects of ethanol on protein kinase C activity induced by filamentous actin.

Protein kinase C (PKC) can be activated by interaction with filamentous actin (F-actin) in the absence of membrane lipids (S.J. Slater, S.K. Milano, B.A. Stagliano, K.J. Gergich, J.P. Curry, F.J. Taddeo and C.D. Stubbs, Biochemistry 39 (2000) 271-280). Here, the effects of ethanol on the F-actin-induced activities of a panel of PKC isoforms consisting of 'conventional' (cPKC) alpha, betaI, gamma, 'novel' (nPKC) delta, epsilon and 'atypical' (aPKC) zeta were investigated using purified PKC and F-actin. Ethanol was found to inhibit the Ca2+- and phorbol ester-dependent activities of cPKCalpha and betaI, and the Ca2+- and phorbol ester-independent activity of cPKCgamma, whereas the activities of nPKCdelta, epsilon and aPKCzeta were unaffected. Although the activities of cPKCalpha and betaI induced by saturating levels of phorbol ester were inhibited by ethanol, the binding of these isozymes to F-actin was unaffected within the same phorbol ester concentration range. Conversely, within submaximal levels of phorbol ester, cPKCalpha and betaI activities were unaffected by ethanol whereas binding to F-actin was inhibited. The potency of the inhibition of F-actin-induced cPKCbetaI activity increased with n-alkanol chain length up to n-hexanol, after which it declined. The results indicate that PKC activities associated with F-actin, and therefore cellular processes involving the actin cytoskeleton, are potential targets for ethanol action. The effects of ethanol on these processes may differ according to the particular regulating PKC isoform, its intracellular localization and the presence of activators and cofactors.

Interaction of protein kinase C with filamentous actin: isozyme specificity resulting from divergent phorbol ester and calcium dependencies.

The mechanism of activation of protein kinase C isoforms by filamentous actin (F-actin) was investigated with respect to isozyme specificity and phorbol ester and Ca(2+) dependencies. It was found that the "conventional" (cPKC), alpha, betaI, betaII, and gamma, "novel" (nPKC) delta and epsilon, and "atypical" (aPKC) zeta isoforms were each activated by F-actin with varying potencies. The level of activity along with the affinity for binding to F-actin was further potentiated by the phorbol ester 4beta-12-O-tetradecanoylphorbol 13-acetate (TPA), the potency of which again varied for each isoform. By contrast to the other cPKC isoforms, the level of cPKC-gamma activity was unaffected by TPA, as was also the case for aPKC-zeta. It was found that whereas in the absence of F-actin the soluble form of cPKC-betaI contained two phorbol ester binding sites of low and high affinity, respectively, as previously reported for cPKC-alpha [Slater et al. (1998) J. Biol. Chem. 273, 23160-23168], the F-actin-bound form of the isozyme contained only a single site of relatively low affinity. The level of TPA required to induce cPKC-alpha, -betaI, and -betaII activity and the binding of these isozymes to F-actin was reduced in the presence of Ca(2+). By contrast, the activity of cPKC-gamma was unaffected by Ca(2+), as were the activities of nPKC-delta and -epsilon and aPKC-zeta, as expected. Thus, the interaction with F-actin appears to be a general property of each of the seven PKC isozymes tested. However, isoform specificity may, in part, be directed by differences in the phorbol ester and Ca(2+) dependences, which, with the notable exception of cPKC-gamma, appear to resemble those observed for the activation of each isoform by membrane association. The observation that cPKC isoforms may translocate to F-actin as well as the membrane as a response to an elevation of Ca(2+) levels may allow for the functional coupling of fluctuations of intracellular Ca(2+) levels through cPKC to F-actin cytoskeleton-mediated processes.

Carbon and nitrogen stable isotope ratios in body tissue and mucus of feeding and fasting earthworms (Lumbricus festivus).

We used natural abundance stable isotope techniques to estimate carbon and nitrogen turnover rates in body tissue and mucus of earthworms. Isotope ratios of carbon (delta(13)C) and nitrogen (delta(15)N) were monitored simultaneously in body tissue and mucus for up to 101 days in feeding or fasting Lumbricus festivus kept in an artificial substrate. When the diet of the earthworms was switched from clover (C(3) plant, legume) to maize (C(4), non-legume), the new dietary delta(13)C signature manifested itself much more rapidly in the mucus than in the body tissue of the animals, causing a delta(13)C shift of about 4 per thousand in mucus and 1 per thousand in tissue after 13.5 days. Turnover of earthworm body tissue carbon, unlike that of mucus carbon, was described adequately by an exponential, single-pool model. Nitrogen turnover could not be assessed because the delta(15)N difference between sources was too small. Fasting for 56 days did not result in the expected whole-body (15)N or (13)C enrichment, but it caused a significant decrease in mucus and tissue C:N ratios and in the ratio (mucus C:N ratio):(tissue C:N ratio). We conclude that the separate analysis of body tissue and mucus has great potential for studying the ecophysiology, feeding ecology and role in elemental cycling of earthworms and other invertebrates.

Rural-urban differences in access to Iowa child health services.

Indicators of access, utilization, and quality of available child health services as well as health status were obtained through a telephone survey of Iowa households with children under age six. These indicators were compared for rural-urban subsamples within an AFDC sample drawn from Iowa Department of Human Service files (N = 637), and within poverty (N = 129) and nonpoverty groups (N = 631) drawn from the population of all households in the state with children under age six. About 55 percent of all households studied were rural. Rural households were generally larger than urban households, more likely to be intact maritally, white, and earning a living from farming. The findings support the hypothesis that place of residence has an impact on access, utilization, and quality of child health services over and above family income, although not always to the disadvantage of rural children. Typical problems for rural children, irrespective of income, were access to pediatric care, greater travel time to providers, and discontinuity of well care and sick care. Rural children in all income groups had lower seat belt use than urban children; they were also less likely to have well visits and their providers showed less attentiveness to behavioral and developmental issues at these visits. Rural residency exacerbated problems in access to care for low income children, who were less likely to be eligible for AFDC/Medicaid than their urban counterparts. Medicaid coverage, however, did not eliminate rural-urban differences in receiving desired medical care.

The determinants of small-area variation in hospital utilization. The evidence from hospital discharge abstracts.

Small-area differences in hospital use were examined using hospital discharge abstract data for the populations of seven small service areas in Iowa that exhibited substantial variation in admission rates during 1980. The results indicate a marked difference in the age composition of the patient populations with older patients being more common among residents of high-use areas, higher age- and sex-adjusted discharge rates per 1000 in the high-use areas across many diagnostic categories, frequently higher average lengths of stay in high-use areas, a lack of conformity between discharge patterns for selected surgical procedures and diagnoses, and more readmissions to the same hospital during a 12-month period for residents of high-use areas. This data set comprises one part of a study of small-area differences that also employed household surveys, physician surveys, and other existing data sets. The findings illustrate the potential and limitations of hospital discharge abstracts as a data base for evaluating hospital discharge abstracts as a data base for evaluating hospital utilization differentials.

Determinants of turnover among nursing department employees.

A causal model of turnover, or quitting, among hospital nursing department employees was evaluated. This model includes job satisfaction, organizational commitment, and intent to leave as intervening variables that mediate 13 determinants of turnover. The sample consisted of 841 female nursing department employees selected from five hospitals in a western state. Attitudinal and background data were obtained through a mail questionnaire survey, and turnover was monitored for 18 months following the survey. Intent to leave had a strong direct effect on turnover while kinship responsibility, job satisfaction, and organizational commitment had indirect effects on turnover through intent to leave. Task repetitiveness, autonomy, promotional opportunities, and fairness of rewards were important determinants of jobs satisfaction and thus provide a mechanism whereby hospital management may enhance commitment to the organization while reducing turnover.

The relationship between apartment living and fertility for blacks, Mexican-Americans, and other Americans in Racine, Wisconsin.

Recently published data from a sample of Bogotá, Colombia public housing residents show that apartment dwellers, but not house dwellers, reduced their fertility in a tight housing market. We propose that the utility-cost theory of fertility accounts for this finding, and, using this theory, we predict that (a) apartment residents will not decrease their fertility in an open housing market and (b) higher fertility will be associated with larger dwellings. Longitudinal data from a sample of Midwest urban blacks, Mexican-Americans, and other Americans support both predictions. The substantive implications are discussed.