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Biomedical subjects

N Bennett

Publications and source records attributed to N Bennett.

At least 37 records · Page 2Linked to original sources
PubMed1996

Improved rapid method for the isolation, purification and identification of collagen glycosides.

An updated method for obtaining purified glucosylgalactosyl hydroxylysine (Glc-Gal-Hyl) is presented. Marine sponge is subjected to alkaline hydrolysis followed by ion-exchange chromatography and gel filtration. Identification is confirmed by consecutive mild acid hydrolysis of the extract to produce galactosyl hydroxylysine (Gal-Hyl) and hydroxylysine (Hyl). High-performance liquid chromatography (HPCL) with a sodium acetate-acetonitrile buffer and dabsyl chloride as the derivatizing agent demonstrated the purity of the extract and its hydrolyzates. Glc-Gal-Hyl is not commercially available but this easy and efficient method can provide large amounts of it for collagen metabolism studies.

Animals↗
PubMed1996

The interconnectedness of nurses' lives. Implications for nursing management.

OBJECTIVE: This study extends knowledge of how nurses' careers interact with their personal lives and professional development. BACKGROUND: Extant research suggests that nurses' career patterns are unstable or unplanned. However, these images may be a reflection of the models that are applied. Such models are overwhelmingly normative and do not reflect the actual life experience of nurses. METHODS: A series of interviews explored how nurses make changes in their lives. Questions focused on the stimulus for change and the resources used, problems associated with changes, and the effects of changes on the nurses themselves and others. RESULTS: The results show that nurses' careers, professional development, and personal lives are interconnected. CONCLUSIONS: The concept of interconnectedness reflects the confluence of events or people and their contemplation and integration by the nurses into their lives and relationships. The results contradict normative admonitions about career planning and have implications for the development of theories on nursing careers and for nurse managers.

Adaptation, Psychological↗
PubMed1996

Pulmonary aspiration in a long-term care setting: clinical and laboratory observations and an analysis of risk factors.

OBJECTIVE: To determine the incidence and risk factors associated with aspiration in a high risk group in a long-term care setting. DESIGN: A prospective study of demographic, nutritional, clinical, dental, and survival characteristics in 69 patients who suffered 98 aspirations events from May 1, 1990, to December 31, 1990. Demographic and nutritional data from 192 patients who did not aspirate were collected from September 1991 to December 1991. SETTING: A long-term care VA facility. PATIENTS: Long-term care residents, most of whom were neurologically debilitated. MEASUREMENTS: The incidence of aspiration was measured and the clinical and microbiological characteristics of aspiration-associated nosocomial pneumonia described. Mortality and demographic, clinical, and nutritional characteristics were compared between patients who aspirated and those who did not. MAIN RESULTS: Twenty-five percent of the study group aspirated during the 8-month observational period, and 56% of the aspiration events progressed to roentgenographically proven cases of nosocomial pneumonia. Six bacteremic episodes were documented, and results of sputum cultures were consistent with mixed Gram-positive and Gram-negative infections. During the study period, patients who aspirated were at three times the risk of dying compared with patients who did not aspirate. Three years later, only 17% of the original group of patients who aspirated were still alive compared with 60% of the patients who had not aspirated. Multivariate analysis identified tube feeding, presence of a hyperextended neck or contractions, malnutrition, and the use of benzodiazepines and anticholinergics as risk factors. CONCLUSIONS: Pulmonary aspiration is a common and serious event in neurologically impaired long-term care patients. Some risk factors are amenable to change.

Aged↗
PubMed1995

Effects of cysteine modification on the activity of the cGMP-gated channel from retinal rods.

The effect of sulfhydryl reagents on the activity of the cGMP-gated channel from bovine retinal rods was studied by measurements of 8-Br-cGMP-(cGMP)-induced calcium efflux from rod membrane vesicles and records of 8-Br-cGMP-dependent sodium currents through channels incorporated into planar lipid bilayers. N-ethylmaleimide and mersalyl (thiol blockers) as well as diamide (dithiol-disulfide conversion agent) have a dual effect on the channels activity: at low concentration, they increase the apparent affinity for cyclic nucleotide ("activation") at the same time inducing a loss of cooperativity for nucleotide binding; at higher concentration, N-ethylmaleimide and diamide produce a reduction of the amplitude and initial rate of the calcium release at saturating nucleotide concentration, while mersalyl is shown to reduce the activity of the channels in bilayer experiments ("inhibition"). Nitric oxide precursors have no effect. The results suggest that blocking at least 1 of the 3 cytoplasmic cysteine residues situated close to the cGMP-binding site in each channel subunit by N-ethylmaleimide, mersalyl, or diamide (forming a dimer between 2 subunits) increases the affinity for the nucleotide. Inhibition is produced by blocking at least one of the 2 other cytoplasmic sulfhydryl groups (N-ethylmaleimide, mersalyl, oxidized glutathione) or the 2 others (diamide, intrasubunit bridge), and may concern a process of channel inactivation. The 3 cytoplasmic sulfhydryl groups are accessible when the channels are in the open state, but not (or much less) accessible when the channels are in the closed state.

Animals↗
PubMed1995

Reasoning and the art of therapy for spinal cord injury.

In this pilot study, qualitative methodology was used to examine the clinical reasoning of four experienced occupational therapists as they presented and modified therapeutic activities to treat patients with spinal cord injuries. The therapists demonstrated the multi-layered thinking discovered in previous research, but hierarchical structuring of knowledge emerged as an unexpectedly dominant theme in their reasoning. Examples of hierarchical thinking about therapeutic activity included creating mental files of therapy tasks and materials sequenced from elementary to advanced and determining the level of difficulty at which to present an activity in order to build the patient's skills in a stepwise manner. The therapists reported that they learned to make decisions about the use of activities in treatment by observing skilled clinicians and by treating patients.

Activities of Daily Living↗
PubMed1993

Patient, family, and staff perceptions of coercion in mental hospital admission: an exploratory study.

Little is known about the coercive pressures brought to bear on psychiatric patients in the hospitalization process. Significant methodological hurdles stand in the way of this research. Most notably, reliable and valid methods of ascertaining and quantifying perceptions of coercion have not been developed. This report summarizes the findings of an exploratory study designed to gather data needed to refine the conceptualization and measurement of coercion. Multiple perspectives on admission incidents for forty-three patients (26% of whom were involuntarily hospitalized) were obtained. Patients were administered research interviews and completed a self-administered inventory shortly after the admission decision. The admitting clinician and a family member involved in the admission were administered parallel interviews. In addition, focus groups comprised of outpatients, former patients, family members, and clinical staff were conducted to uncover the terminology and description of coercion commonly used. The implications of these preliminary quantitative and qualitative findings for future research are discussed.

Adult↗
PubMed1993

Two scales for measuring patients' perceptions for coercion during mental hospital admission.

Legal and extra-legal coercion are pervasive in mental hospital admission and there are sharp disputes about its appropriate role. This article presents two scales for measuring psychiatric patients' perceptions of coercion during hospital admission and reports data on these scales' internal consistency. We measure patients' perceptions of coercion by asking questions, in either an interview or questionnaire format, about their experience of lack of control, choice, influence, and freedom in hospital admission. Patients' responses to questions about their perceptions of coercion were highly internally consistent. The internal consistency of the scale was robust with respect to variation in site, instrument format, patient population, and interview procedure. Correspondence analysis was used to construct two numerical scales of perceived coercion.

Adolescent↗
PubMed1993

Healthcare foodservice report 1993. Getting ready for reform. Interview by Mitchell Schechter.

Hospital foodservice directors & dietitians are facing the greatest challenge of their careers -- to prepare, along with their institutions, for the most thoroughgoing reform of America's healthcare system ever proposed. Healthcare institutions across the country are seeking the means to offer enhanced patient services & gain competitive advantages by forming new alliances, new patient-centered care systems & cost-reduction programs. To aid in these efforts, their foodservices are developing comprehensive cross-training schemes, inter-departmental teams with other service groups & new ways to cut operating subsidies. Here's how five hospital foodservice departments are using cost controls, revenue building, quality management processes & enhanced efficiencies to help their institutions prepare for the changes ahead.

Cost Control↗
PubMed1992

Interaction between cGMP-phosphodiesterase and transducin alpha-subunit in retinal rods. A cross-linking study.

Cross-linking of the different subunits of the retinal cGMP-phosphodiesterase (PDE) with its activator G alpha GTP gamma S (alpha subunit of the retinal G-protein transducin with GTP gamma S (guanosine 5'-O-(3-thiotriphosphate) bound) has been investigated using purified proteins, with a N-hydroxysuccinimide homobifunctional cross-linker, bis(sulfosuccinimidyl)suberate (BS3) and its cleavable analog 3,3'-dithiobis(sulfosuccinimidylpropionate) (DTSSP). Interaction of purified G-protein and PDE is achieved in the presence of lecithin vesicles, at protein concentrations sufficient for full PDE activation. Protein subunits linked with DTSSP are separated by cleavage of the disulfide bridge and identified by electrophoresis. Complexes of PDE alpha (PDE beta) with 1 and 2 molecules of activator G alpha GTP gamma S are observed, providing direct evidence for an interaction or at least a close proximity between 2 molecules of activator G alpha and each of the catalytic PDE subunits in the activated state of PDE. The results also reveal symmetrical roles of PDE alpha and PDE beta, with the existence of one site for PDE gamma and one site for G alpha on each catalytic subunit.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

Activated cGMP phosphodiesterase of retinal rods. A complex with transducin alpha subunit.

Purified G-protein (transducin) activated with the nonhydrolyzable analog guanosine 5'-O-(thiotriphosphate) (GTP gamma S) and cGMP phosphodiesterase (PDE) from retinal rods are added to protein-stripped disc membranes. Specific binding of the mainly soluble alpha subunit of G-protein with GTP gamma S bound (G alpha GTP gamma S, activator of the PDE) to the disc membrane in the presence of PDE is measured from gel scans or experiments with labeled G-protein alpha subunit (G alpha). Its variation as a function of G concentration matches the theoretical variation of G alpha involved in the activation of PDE calculated with previously estimated dissociation constants (Bennett, N., and Clerc, A. (1989) Biochemistry 28, 7418-7424), and the G alpha bound/PDE ratio at saturation is close to 2. No increase of G alpha binding to the membrane is observed when purified inhibitory subunit of PDE (PDE gamma) is added together with or instead of total PDE, and excess PDE gamma remains soluble. These results suggest that activated PDE is a complex with the activator G alpha GTP rather than PDE from which the inhibitory subunits have been removed. A method for purifying PDE gamma with a high yield of recovery and activity is described.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

cGMP phosphodiesterase dependent light-induced scattering changes in suspensions of retinal disc membranes.

Light-induced GTP-dependent scattering changes are studied in suspensions of retinal disc membranes to which one or both of the purified proteins involved in the phototransduction mechanism (G-protein and cGMP phosphodiesterase) are reassociated; a scattering change which depends on the presence of both G-protein (G) and inhibited cGMP phosphodiesterase (PDE) and on an ATPase-dependent process, previously described in Bennett [(1986) Eur. J. Biochem. 157, 487-495] is compared to the signal observed in the absence of PDE or of ATP and to PDE activity. The same signal can also be induced either in the dark or in the light by addition of preactivated G in the presence of inhibited PDE. This PDE-dependent scattering change is composed of two components (fast and slow); the variation of the amplitude and kinetics of both components with PDE or G concentration is similar to the variation of the active PDE state with two activator GGTP molecules (G with GTP bound), calculated with dissociation constants previously reported for the interaction between GGTP and PDE [Bennett, N., & Clerc, A. (1989) Biochemistry 28, 7418-7424]. The two components are therefore proposed to be associated with processes which depend on the formation of the active PDE state with two activators.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

Gating of retinal rod cation channel by different nucleotides: comparative study of unitary currents.

Single channels are observed after incorporation of native vesicles from bovine rod outer segment membranes into planar lipid bilayers. The activity of a single channel in the presence of cGMP is compared to that induced by the analog 8-bromo-cGMP and by cAMP. At +80 mV, K0.5 is about 3 microM for 8Br-cGMP, 18 microM for cGMP and 740 microM for cAMP. In cAMP, the amplitude of the current is smaller than in cGMP or 8Br-cGMP and depends on the filter cut-off frequency. The open/closed transition rates of the channel are slightly slower with 8Br-cGMP than with cGMP while they are 5 to 10 times faster with cAMP. Addition of Ni2+ ions to either cGMP or cAMP increases the open probability: the open/closed transition rates and amplitude of the current in cAMP are then comparable to those in cGMP. A dual effect of the addition of cAMP on the cGMP- or 8Br-cGMP-dependent activity previously reported (Furman, R.E., Tanaka, J.C. 1989. Biochemistry 28:2785-2788) is observed with a single channel: addition of subthreshold cAMP concentrations to cGMP (or to 8Br-cGMP) markedly increases Po; addition of cAMP concentrations higher than about 70 microM progressively accelerates the kinetics and reduces the amplitude to values observed in cAMP alone. The results are discussed in relation with the model previously proposed to account for the existence of four current levels (Ildefonse, M., Bennett, N. 1991. J. Membrane Biol. 123:133-147).

Animals↗
PubMed1991

An interleukin 1 beta point mutant demonstrates that jun/fos expression is not sufficient for fibroblast metalloproteinase expression.

Substitution of glycine for arginine at position 127 of the mature human interleukin 1 beta protein generates a mutant IL-1 beta protein (IL-1 beta R----G) which binds cellular IL-1 receptors with high affinity but fails to elicit significant proliferation of T-helper cells (Gehrke, L., Jobling, S. A., Paik, L. S. K., McDonald, B., Rosenwasser, L. J., and Auron, P. E. (1990) J. Biol. Chem. 265, 5922-5925). Although both IL-1 beta and the IL-1 beta R----G mutein stimulate transcription of fibroblast immediate early (fos and jun) and early (IL-1 beta and IL-6) genes, the IL-1 beta R----G mutein, in contrast to the wild-type IL-1 beta protein, induces minimal or no transcription of late genes such as procollagenase and prostromelysin. The effect of the naturally occurring IL-1 receptor antagonist protein (IL-1ra) on fibroblast transcription is distinct from that of the IL-1 beta R----G mutein, for the IL-1ra fails to stimulate not only late (procollagenase and prostromelysin) but also immediate early (fos and jun) gene expression. These data suggest that the IL-I beta R----G mutein triggers an incomplete or defective signal transduction cascade and demonstrate that fibroblast fos and jun expression is not necessarily accompanied by increased transcription of genes containing the AP-1 binding site. These data also suggest that at least two events are required for IL-1-mediated late gene induction in fibroblasts.

Blotting, Northern↗