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Biomedical subjects

J Weiner

Publications and source records attributed to J Weiner.

At least 55 records · Page 3Linked to original sources
PubMed1995

Clinical staffing in staff- and group-model HMOs.

Analysts frequently have used health maintenance organization (HMO) staffing patterns as a yardstick for estimating national clinical workforce requirements. Based on a nationwide survey of fifty-four staff- and group-model HMOs, the largest sample yet used in an analysis of this type, this DataWatch examines physician-to-member ratios, the use of nonphysician providers, and HMOs' methods of estimating clinical staffing needs. Overall physician staffing ratios and primary care physician staffing ratios closely resemble those reported in previous studies, but they exhibit wide variability and are strongly correlated with HMO size. Although caution should be exercised when using HMO staffing ratios in projections of physician workforce requirements, the ratios described here support projections of a specialty physician surplus.

Data Collection↗
PubMed1994

Cloning and functional expression of a cyclic-nucleotide-gated channel from mammalian sperm.

Cyclic nucleotide-gated (CNG) channels serve as downstream targets of signalling pathways in vertebrate photoreceptor cells and olfactory sensory neurons (see ref. 1 for review). Ca2+ ions that enter through CNG channels intimately control these signalling pathways by regulating synthesis or hydrolysis of cyclic nucleotides, and by decreasing ligand sensitivity of CNG channels. Several lines of evidence suggest that cyclic nucleotides and Ca2+ play important roles in chemotaxis of invertebrate sperm and fertilization (see ref. 9 for review), whereas their mechanisms of action in vertebrate sperm are largely unknown. Here we report the cloning and functional expression of a novel CNG channel from bovine testis. The channel polypeptide was functionally localized in sperm, but is also specifically expressed in cone photoreceptor cells. These channels might be involved in chemotaxis of sperm by controlling Ca2+ entry through a cyclic-nucleotide signalling pathway.

Amino Acid Sequence↗
PubMed1994

Development of the Leeds Dependence Questionnaire (LDQ): a questionnaire to measure alcohol and opiate dependence in the context of a treatment evaluation package.

The Leeds Dependence Questionnaire (LDQ) has been developed as part of a treatment evaluation package. The LDQ is a 10-item, self completion questionnaire designed to measure dependence upon a variety of substances; it has been shown to be understood by users of alcohol and opiates. The questionnaire was designed to be sensitive to change over time and to be sensitive through the range from mild to severe dependence; the follow-up data are insufficient to demonstrate change over time, but are encouraging. It is expected that both clinicians and researchers will find it useful to have a single measure relating to substance use, but not limited by specific substances. All items are scored 0-1-2-3; there are no normative data. The procedure for establishing content validity is described and estimates of concurrent, discriminant and convergent validities are reported; these validities are thought to be satisfactory. A principal components analysis produced a single factor accounting for 64% of the variance. Cronbach's alpha was 0.94. Test-retest reliability was found to be 0.95.

Adult↗
PubMed1993

Reversible electrochemistry of fumarate reductase immobilized on an electrode surface. Direct voltammetric observations of redox centers and their participation in rapid catalytic electron transport.

Fumarate reductase (Escherichia coli) can be immobilized in an extremely electroactive state at an electrode, with retention of native catalytic properties. The membrane-extrinsic FrdAB component adsorbs to monolayer coverage at edge-oriented pyrolytic graphite and catalyzes reduction of fumarate or oxidation of succinate, depending upon the electrode potential. In the absence of substrates, reversible redox transformations of centers in the enzyme are observed by cyclic voltammetry. The major component of the voltammograms is a pair of narrow reduction and oxidation signals corresponding to a pH-sensitive couple with formal reduction potential E degree' = -48 mV vs SHE at pH 7.0 (25 degrees C). This is assigned to two-electron reduction and oxidation of the active-site FAD. A redox couple with E degree' = -311 mV at pH 7 is assigned to center 2 ([4Fe-4S]2+/1+). Voltammograms for fumarate reduction at 25 degrees C, measured with a rotating-disk electrode, show high catalytic activity without the low-potential switch-off that is observed for the related enzyme succinate dehydrogenase. The catalytic electrochemistry is interpreted in terms of a basic model incorporating mass transport of substrate, interfacial electron transfer, and intrinsic kinetic properties of the enzyme, each of these becoming a rate-determining factor under certain conditions. Electrochemical reversibility is approached under conditions of low turnover rate, for example, as the supply of substrate to the active site is limited. In this situation, electrocatalytic half-wave potentials, E1/2, are similar for oxidation of bulk succinate and reduction of bulk fumarate and coincide closely with the E degree' value assigned to the FAD. At 25 degrees C and pH 7, the apparent KM for fumarate reduction is 0.16 mM, and kcat is 840 s-1. Accordingly the second-order rate constant, kcat/KM, is 5.3 x 10(6) M-1 s-1. Under the same conditions, oxidation of succinate is much slower. As the supply of fumarate to the enzyme is raised to increase turnover, the electrochemical reaction eventually becomes limited by the rate of electron transfer from the electrode. Under these conditions a second catalytic wave becomes evident, the E1/2 value of which corresponds to the reduction potential of the redox couple suggested to be center 2. This small boost to the catalytic current indicates that the low-potential [4Fe-4S] cluster can function as a second center for relaying electrons to the FAD.

Adsorption↗
PubMed1993

Effect of NMDA receptor antagonists on rapid tolerance to ethanol.

Hypothermia and motor impairment (tilt-plane test) were used to assess whether N-methyl-D-aspartate (NMDA) receptors play a role in the development of rapid tolerance to ethanol, i.e., tolerance to a second dose of ethanol given 24 h after the effect of the first dose of ethanol had disappeared. Results showed that (+)-MK-801 and ketamine blocked the development of rapid tolerance to ethanol on both tests. Since these drugs did not modify blood or brain alcohol levels in any of the groups, the blockade of ethanol rapid tolerance cannot be attributed to changes in pharmacokinetics of ethanol. These data suggest that the role of NMDA receptors in ethanol tolerance may be similar to their role in memory and learning, involving a facilitation of transmission in certain synapses.

Animals↗
PubMed1993

Intern candidates who withdraw from contracts: incidence and internal medicine program directors' attitudes.

OBJECTIVE: To study the prevalence of intern candidates accepted through the National Resident Matching Program (NRMP) or after the match who subsequently withdraw and the attitudes of program directors regarding this issue. DESIGN: Mailed survey. SETTING: Four hundred fifty-four internal medicine program directors. MEASUREMENTS: Questionnaires assessing program directors' attitudes toward interns who contract for positions after having verbal or written agreements elsewhere (and the program directors who accept them), the importance of this problem, and the incidence of this problem. MAIN RESULTS: Fifty-five programs (of the 221 responding) experienced intern withdrawals. Programs with larger numbers of open positions after the match had more intern withdrawals (p = 0.03). Eleven of the program directors knew of the prior commitment of the intern, and in all cases the other program director was called for permission to accept the intern. Program directors had negative feelings about both the interns who withdrew and the program directors who accepted them. Community, municipal, and Veterans Affairs hospital program directors were significantly less negative than those in university and university-affiliated hospitals toward interns who withdrew from written commitments (p = 0.001) and the program directors who accepted them (p < 0.05). CONCLUSION: Problems with intern candidate withdrawals from offered/matched programs affect a significant proportion of programs, especially those with larger numbers of unmatched positions. Program directors are generally disapproving.

Analysis of Variance↗