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Biomedical subjects

R M Bell

Publications and source records attributed to R M Bell.

At least 73 records · Page 4Linked to original sources
PubMed1994

A phorbol ester binding domain of protein kinase C gamma. Deletion analysis of the Cys2 domain defines a minimal 43-amino acid peptide.

Cysteine-rich regions of protein kinase C (PKC) are critical for the lipid-dependent regulation of activity and are implicated in the coordination of zinc. A glutathione S-transferase fusion protein containing the second cysteine-rich region, Cys2, of PKC gamma with bound zinc with a stoichiometry of 1.8 +/- 0.1 mol of zinc/mol of protein. Deletion analysis within this cysteine-rich region defined amino acids essential for zinc coordination. An NH2-terminal histidine (His102) and a COOH-terminal cysteine (Cys151) were both critical for the coordination of distinct zinc atoms. Both represent the ultimate residues of a 50-amino acid consensus motif with six conserved cysteines and two conserved histidines present in the cysteine-rich regions of all PKC isoforms. Removal of histidine His102 abolished phorbol ester binding, while deletion of cysteine Cys151 did not. Deletion of valine (Val147) greatly diminished phorbol ester binding, which was completely lost only when valine (Val144) was also deleted. No significant further reduction in zinc stoichiometry below one resulted even when three COOH-terminal conserved cysteines (Cys151, Cys143, and Cys135) and a conserved histidine (His140) were deleted. These results are consistent with a model in which two zinc atoms are tetracoordinated per cysteine-rich region in two independent coordination spheres that are not functionally equivalent. These analyses determine a minimal peptide (residues 102-144) of 43 amino acids capable of [3H]PDBu binding.

Amino Acid Sequence↗
PubMed1994

The 1966 enactment of Medicare: its effect on discharges from Los Angeles County-operated hospitals.

The effect of Medicare on two public hospitals in Los Angeles County was analyzed by examining the percentage of patients 65 years of age and older among all discharges from 1958 through 1971. At Harbor General Hospital, discharges of elderly patients had dropped from 21.7% to 7.9% by late 1966; at Los Angeles County General Hospital, discharges decreased from 15.3% to 10.7% between 1966 and 1967. Monitoring public hospitals' demographic changes after enacting a national health plan may provide information on patients' and providers' acceptance of insurance and on resources needed by public hospitals to care for those left without coverage.

Age Factors↗
PubMed1994

Do response options influence self-reports of alcohol use?

The influence of response options on self-reported frequency of alcohol use was evaluated in an experimental study of 350 students at a west coast university. Respondents were asked about their frequency of alcohol use in the last 7 days, 30 days, 90 days, and 180 days with three methodological factors randomized: 1) how quantitative the response options were; 2) order of presentation of close-ended response options; and 3) relative placement of alcohol use items in the questionnaire. Results indicate that the quantitativeness of response options and the location of items within the questionnaire have minimal effects on the average frequency of alcohol use and number of inconsistent responses over a wide range of time frames. However, presenting higher frequency response options prior to lower frequency response options increased self-reported frequency of having consumed 2 or more drinks in the last 30 days and frequency of alcohol use over the last 180 days.

Adolescent↗
PubMed1994

The urge to merge: linking vital statistics records and Medicaid claims.

This paper describes a procedure used to link Medicaid claims data to California vital statistics records for very low birthweight infants. The linkage involved about 53,000 infants born from 1980 to 1987 and 1.46 million claims for delivery/birth-related hospital admissions during the same period. Because the two data files did not share a unique identifier, record linkage required combining evidence across several linking variables: delivery hospital, delivery/birth date or hospitalization period, names, mother's age, and zip code. To combine the various pieces of evidence, we used record linkage theory to compute scores that measure the likelihood of a match, i.e., that two records correspond to the same delivery. These scores appropriately weight the various pieces of evidence for or against a match. Implementation required dealing with large amounts of missing data in one of the files, errors and variations in reported names, and the need to minimize the number of incorrect links. The approach applies to a wide range of linkage problems. The ability to combine existing datasets to form new datasets containing analysis variables from each facilitates analyses that would otherwise be impossible, or prohibitively expensive.

Bias↗
PubMed1994

The impact of response options and location in a microcomputer interview on drinking drivers' alcohol use self-reports.

The influence of response options for and location of frequency of alcohol use items in a self-administered microcomputer interview were evaluated in a randomized, experimental study of 296 clients at a west coast treatment site for drinking drivers. Respondents were asked about their frequency of alcohol use in the last 7 days, 30 days, 90 days, and 180 days with three methodological factors randomized: (1) how quantitative the response options were; (2) order of presentation of close-ended response options; and (3) relative placement of alcohol use items in the questionnaire. Results indicate that these methodological factors had minimal influence on self-reports of the frequency of alcohol use. Only two statistically significant effects out of 44 possible were observed. The findings of this study suggest that frequency of alcohol use reports by drinking drivers yield similar information for a range of different response formats and location of the items in a microcomputer interview.

Adult↗
PubMed1993

Do drug prevention effects persist into high school? How project ALERT did with ninth graders.

BACKGROUND: This article reports follow-up results during grade 9 for a multisite drug prevention program that curbed both marijuana and cigarette use during junior high. Based on the social influence model of prevention, the curriculum sought to motivate young people against drug use and to teach them skills for resisting pro-drug pressures. METHODS: Thirty schools drawn from eight urban, rural, and suburban communities in California and Oregon were randomly assigned to three experimental conditions, two treatment groups and one control. Students in 20 schools received 11 lessons, 8 during grade 7 and 3 in grade 8; in 10 of the treatment schools, older teens assisted an adult teacher in program delivery. Students were pretested prior to the program (grade 7) and post-tested 24 months later (grade 9). RESULTS: Earlier effects on cognitive risk factors (perceived consequences of drug use, normative beliefs, resistance self-efficacy, and expectations of future use) persisted through grade 9 in the teen leader schools; in the condition under which adults taught the lessons without teens, the prior beneficial effects on beliefs largely eroded. All of the earlier effects on actual use disappeared by grade 9, regardless of who taught the lesions. CONCLUSION: Continued reinforcement of earlier lessons may be required to sustain prevention gains through the transition to high school.

Adolescent↗
PubMed1993

Changing adolescent propensities to use drugs: results from Project ALERT.

Do successful drug prevention programs suppress the risk factors they were intended to modify? This paper addresses that issue for Project ALERT, a school-based program for seventh and eighth graders that has been shown to curb both cigarette and marijuana use. Evaluated with over 4,000 students in an experimental test that included 30 diverse California and Oregon schools, the curriculum seeks to help young people develop both the motivation to avoid drugs and the skills they need to resist pro-drug pressures. Using regression analyses, we examine the program's impact on the intervening (cognitive) variables hypothesized to affect actual use: adolescent beliefs in their ability to resist, perceived consequences of use, normative perceptions about peer use and tolerance of drugs, and expectations of future use. The analysis depicts program effects for perceptions linked to each target substance (alcohol, cigarettes, and marijuana), across all students and for those at different levels of risk for future use. Results show that the curriculum successfully dampened cognitive risk factors from each of the above categories for both cigarettes and marijuana, indicating that social influence programs can mitigate a broad range of beliefs associated with the propensity to use drugs. However, it had a limited impact on beliefs about alcohol, the most widely used and socially accepted of the three drugs. Implications for drug prevention programs and practitioners are discussed.

Adolescent↗
PubMed1993

Preventing adolescent drug use: long-term results of a junior high program.

OBJECTIVES: Although several studies have reported short-term gains for drug-use prevention programs targeted at young adolescents, few have assessed the long-term effects of such programs. Such information is essential for judging how long prevention benefits last. This paper reports results over a 6-year period for a multisite randomized trial that achieved reductions in drug use during the junior high school years. METHODS: The 11-lesson curriculum, which was tested in 30 schools in eight highly diverse West Coast communities, focused on helping 7th and 8th grade students develop the motivation and skills to resist drugs. Schools were randomly assigned to treatment and control conditions. About 4000 students were assessed in grade 7 and six times thereafter through grade 12. Program effects were adjusted for pretest covariates and school effects. RESULTS: Once the lessons stopped, the program's effects on drug use stopped. Effects on cognitive risk factors persisted for a longer time (many through grade 10), but were not sufficient to produce corresponding reductions in use. CONCLUSIONS: It is unlikely that early prevention gains can be maintained without additional prevention efforts during high school. Future research is needed to develop and test such efforts.

Adolescent↗
PubMed1993

Bilateral neck exploration for primary hyperparathyroidism.

Controversy about the operative approach for primary hyperparathyroidism has prompted a review of our operative experience since 1980. We treated 73 patients with primary hyperparathyroidism during this 10-year period, all of whom underwent bilateral neck exploration in which the surgeons attempted to locate all parathyroid tissue. Thirty-eight patients (52%) were found to have a solitary adenoma, while 35 (48%) patients had multiple gland pathology. There were two cases of persistent hypercalcemia because of a synchronous parathyroid hormone-secreting malignancy in one patient and aberrant fifth gland adenoma in the other patient. Without bilateral neck exploration, about one-half of the patients in our series would not have been cured of primary hyperparathyroidism. Because of the high incidence of multiple parathyroid gland involvement, we conclude that thorough bilateral neck exploration must be considered the goal for surgical treatment of primary hyperparathyroidism.

Adenoma↗
PubMed1992

Changes in bioactive lipids, alkylacylglycerol and ceramide, occur in HIV-infected cells.

The mass levels of bioactive lipids known to modulate signal transduction or to possess other biological activities were measured in HIV-infected CEM cells. The levels of diacylglycerol, an activator of protein kinase C, as well as of alkylacylglycerol were elevated. A more drastic increase was observed in the ceramide levels after HIV-infection, whereas sphingosine levels were hardly influenced. Interestingly, the magnitude of the changes was related to the infection time, being higher at 8 days after infection then at 4 days. The possible role of these lipids in the cytopathic effects of HIV-infection is discussed. In addition, an improved methodology to quantitate simultaneously diacylglycerol and alkylacylglycerol in crude lipid extracts, based upon their phosphorylation by E. coli diacylglycerol kinase, is presented.

Cell Line↗
PubMed1992

Supplementation of the phosphatidyl-L-serine requirement of protein kinase C with nonactivating phospholipids.

The mechanism of protein kinase C (PKC) activation by phosphatidyl-L-serine (PS) is highly specific and occurs with high cooperativity [Lee, M.-H., & Bell, R. M. (1989) J. Biol. Chem. 264, 14797-14805]. To further investigate the multiplicity and specificity of PS cofactor requirement, some of the PS molecules present in Triton X-100 mixed micelles were substituted with nonactivating phospholipids devoid of required amino or carboxyl functional groups. The ability of these phospholipids to spare or reduce the mole percent of PS required was determined. Addition of phosphatidyl-(3-hydroxypropionate) (PP) or phosphatidate (PA) reduced the mole percent of PS required for maximal activity from 10 to 4 mol %, and also reduced the cooperativity of activation with PS. In contrast, phosphatidylethanolamine did not alter the dependence on PS. Phosphatidylethanol (P-Et) reduced the PS requirement to 2-4 mol % and cooperatively less efficiently than PP or PA. Phosphatidylglycerol and phosphatidylinositol resemble P-Et in their ability to reduce PS requirements and cooperativity. Therefore, it appears that the ability of phospholipids to substitute for PS in PKC activation depends on the negative charge in the phospholipid head group and the efficiency of substitution appears to be directly related to the negative charge density. The presence of two acyl groups within the phospholipid cofactor proved important since lyso-PS and lyso-PA replaced a portion of PS molecules required less efficiently than P-Et. Sodium oleate and sodium dodecyl sulfate behaved like lyso-PS. When other anionic lipids are present, approximately four molecules of PS per micelle are required for maximal PKC activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The regulatory domain of protein kinase C coordinates four atoms of zinc.

Protein kinase C (PKC) was found to be a zinc metallo-enzyme. Atomic absorption measurements on the intact enzyme indicated that four zinc atoms (4.2 +/- 0.5) were bound per PKC alpha molecule. Similar stoichiometric ratios were determined for PKC beta II and PKC gamma, other PKC isoforms individually expressed in the baculovirus-insect cell expression system, as well as for purified rat brain PKC. By trypsin treatment of PKC alpha, a 32-kDa lipid binding regulatory and a 50-kDa catalytic domain were generated that were subsequently completely separated by gel filtration in the presence of Triton X-100/phosphatidylserine mixed micelles. Zinc was present at levels significantly above background in fractions that contained the 32-kDa fragment and displayed phorbol ester binding activity. Lipid association and phorbol ester binding did not lead to displacement of zinc from the protein. The stoichiometry determined for this fragment (4.7 +/- 0.9) suggested that zinc was bound exclusively within the lipid binding regulatory domain of intact PKC. Furthermore, this stoichiometry is consistent with zinc being coordinated between 6 cysteine residues in a structural motif related to the Zn(II)2Cys6 binuclear cluster identified in the GAL4 transcriptional factor (Pan, T., and Coleman, J.E. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 2077-2081).

Amino Acid Sequence↗
PubMed1992

Elevated ceramide levels in GH4C1 cells treated with retinoic acid.

Ceramide is produced in HL 60 cells in response to 1 alpha,25-dihydroxy vitamin D3 (vitamin D3) (Okazaki et al. (1989) J. Biol. Chem. 264, 19076-19080). HL 60 cell differentiation can be mimicked by cell permeable ceramides (Okazaki et al. (1990) J. Biol. Chem. 265, 15823-15831). Vitamin D3 like other thyroid-steroid hormones binds to a member of the steroid hormone family. We sought to investigate whether agonists other than vitamin D3 which exert their effects through members of the steroid receptor family affect cellular ceramide levels. Treatment of GH4C1 cells with 10 microM all-trans retinoic acid for 8 h caused a 230% increase in cellular ceramide content. This concentration of retinoic acid also inhibited cell proliferation as measured by [3H]thymidine incorporation. Under these conditions, a 35% decrease in sn-1,2-diacylglycerol mass occurred, but no change in sphingomyelin, sphingosine or phosphatidylcholine mass was observed. To determine the mechanism of increased ceramide production by 10 microM retinoic acid, cells were labeled with [3H]palmitic acid. After a 2 h period, a 4-fold increase in the incorporation of palmitate into ceramide was observed. Hydrolysis of the labeled ceramide to sphingosine and free fatty acid demonstrated that only 6% of the label was recovered in the sphingosine backbone of cells treated with retinoic acid, whereas 20% of the label was recovered in the sphingosine backbone of cells treated with vehicle alone. The data are consistent with retinoic acid causing an increase in cellular ceramide levels in GH4C1 cells through an increase in sphingosine N-acylation.

Animals↗
PubMed1992

Inhibition of sphingosine kinase in vitro and in platelets. Implications for signal transduction pathways.

Sphingosine kinase was partially purified and characterized from rat brain microsomes. A new assay, utilizing octyl-beta-D-glucopyranoside and sphingosine mixed micelles, was developed to quantitate formation of the sphingosine-1-phosphate product. The assay was proportional with respect to time and protein, displayed Michaelis-Menten kinetics, and was subject to surface dilution in regard to the sphingosine substrate. Investigations into substrate specificity showed that the enzyme is specific for the erythro-enantiomers of sphingosine and dihydrosphingosine. Neither of the threo-enantiomers were phosphorylated in this system, but both were found to be potent competitive inhibitors of sphingosine kinase activity. Human platelet sphingosine kinase activity displayed substrate and inhibitor specificities similar to the rat brain enzyme. A mixture of DL-threo-dihydrosphingosine competitively inhibited sphingosine kinase activity in a dose dependent manner in isolated platelets. DL-Threo-dihydrosphingosine caused a prolongation of the inhibition of thrombin-induced protein kinase C-dependent 40 (47)-kDa protein phosphorylation in platelets. D-, L-, or DL-Threo-dihydrosphingosine may be useful as a tool to investigate D-Erythrosphingosine metabolism and the function of sphingosine-1-phosphate in signal transduction processes.

Animals↗