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Biomedical subjects

N Owens

Publications and source records attributed to N Owens.

14 recordsLinked to original sources
PubMed2001

Predictors of compliance with neuroleptic medication among inpatients with schizophrenia: a discriminant function analysis.

OBJECTIVE: To identify clinically useful predictors of adherence to medication among persons with schizophrenia. METHOD: We evaluated levels of compliance with neuroleptic medication among 32 consecutive admissions with DSM-III-R schizophrenia from a geographically defined catchment area using a compliance interview. We also assessed symptomatology, insight, neurological status and memory. RESULTS: Less than 25% of consecutive admissions reported being fully compliant. Drug attitudes were the best predictor of regular compliance, symptomatology the best predictor of noncompliance, and memory the best predictor of partial compliance with neuroleptic medication. CONCLUSIONS: These data emphasise the complexity of factors that influence whether a person adheres to his medication regimen. Furthermore, they suggest that these factors may vary within the same person over time.

Adolescent↗
PubMed1997

Clinical nutrition in pancreatitis.

In patients with acute pancreatitis or an acute flare of chronic pancreatitis, a discrepancy exists between increased protein/calorie requirements induced by a hypermetabolic stress state and reduced ingestion/assimilation of exogenous nutrients, which promotes progressive nutritional deterioration. Patients with severe pancreatitis (defined by > or =3 Ranson criteria, an APACHE II score of > or =10, development of major organ failure, and/or presence of pancreatic necrosis) are more likely to require aggressive nutritional support than patients with mild disease. The type of formula and level of the gastrointestinal tract into which nutrients are infused determine the degree to which pancreatic exocrine secretion is stimulated. Animal studies and early prospective randomized controlled trials in humans suggest that total enteral nutrition via jejunal feeding may be the preferred route to parenteral alimentation in this disease setting.

Acute Disease↗
PubMed1995

Functional effects of mutations in the putative agonist binding region of recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors.

Structural correlates of ligand binding to alpha-amino-3-hydroxy-5-methyl- 4-isoxazolepropionic acid (AMPA) receptors were examined by altering conserved lysine residues to either glutamate or glutamate at position 445 of the GluR-A subunit and position 449 of the GluR-B subunit. Receptors were expressed in human embryonic kidney 293 cells and in Xenopus oocytes as homomeric GluR-A or heteromeric combinations of GluR-A/B. The functional properties of the resulting receptors were measured with patch-clamp and voltage-clamp electrophysiology. These mutations, which reduced the total positive charge at the lysine 445 position, selectively altered the affinity of some ligands and had no obvious effect on receptor desensitization properties. The L-glutamate EC50 was 10.2 microM when wild-type GluR-A was coexpressed with GluR-B (GluR-A/B) and 38.9 microM when GluR-A445Q/B449Q receptors were tested. The AMPA EC50 was similarly reduced (wild-type, 3.71 microM; GluR-A445Q/B449Q, 21.4 microM). Receptors containing a glutamate residue at this position were even less sensitive to L-glutamate and AMPA. Whereas the apparent potency of L-glutamate varied inversely with the total positive charge regardless of the subunit, the affinity of AMPA was more sensitive to mutations in GluR-A than to those in GluR-B. Interestingly, the EC50 of kainate was unaffected by most of these mutations and actually increased slightly with GluR-A445E/B449E receptors. The affinity of 6-cyano-2,3-dihydroxy-7- nitroquinoxaline (CNQX) was slightly reduced with GluR-A445E/B449E receptors, whereas the apparent affinity of GYKI52466 was unchanged. These data confirm that structural correlates of binding to AMPA receptors vary among different ligands.

Animals↗
PubMed1994

Inhibition of platelet spreading from plasma onto glass by an adsorbed layer of a novel fluorescent-labeled poly(ethylene oxide)/poly(butylene oxide) block copolymer: characteristics of the exclusion zone probed by means of polystyrene beads and macromolecules.

We have investigated the anti-adhesive properties of a newly synthesized fluorescent triblock copolymer containing poly(ethylene oxide). This adsorbs from aqueous solution onto glass that has been rendered hydrophobic. When the polymer-treated surface was exposed to human platelet-rich plasma (PRP) or whole blood at 37 degrees C, platelet adhesion and spreading were prevented. Avid adhesion and rapid platelet spreading occurred along tracks scraped in the adsorbed polymer coating, as seen by video-enhanced interference reflection microscopy. Leukocytes from whole blood are eventually able to adhere to the polymer-treated surface and were seen to remove labeled polymer from their vicinity and accumulate it at the cell body. Interferometry using polystyrene spheres showed that they do not adhere to polymer-coated glass and are unable to approach closer than 70-95 nm. On scraped tracks, beads make molecular contacts with the glass. Because the fully extended solvated (EO)400 arms may extend up to 100 nm from the glass, this suggests that the polymer forms a monolayer with the hydrophilic arms projecting into the water, whereas the hydrophobic (BO)55 segment binds the molecule to the hydrophobic surface. Another tri-bloc copolymer with shorter hydrophilic arms allows particles to approach more closely.

Adsorption↗
PubMed1994

Adsorption of a novel fluorescent derivative of a poly(ethylene oxide)/poly(butylene oxide) block copolymer on octadecyl glass studied by total internal reflection fluorescence and interferometry.

We have used total internal reflection fluorescence (TIRF) to measure the adsorption kinetics of a newly synthesized fluorescent derivative of a triblock copolymer comprising two poly(ethylene oxide) arms connected by a poly(butylene oxide) segment. The composition is (EO)400 (BO)55 (EO)400, in which EO represents ethylene oxide, BO represents butylene oxide, and one or both of the terminal OH groups of the two (EO)400 arms are labeled with tetramethylrhodamine. The poly(butylene oxide) segment binds to hydrophobic octadecyl glass, used as a substratum. The TIRF signal is shown to be derived almost entirely from surface-adsorbed polymer. This facilitates calculation of adsorption isotherms from 0.1-0.005% bulk polymer solution by means of diffusion kinetics. Information about the effective thickness of the adsorbed polymer, determined by optical interference microscopy, corresponds with what is known about the conformation of similar molecules at interfaces and indicates monolayer adsorption on the glass.

Adsorption↗
PubMed1990

The Senior Care Study. A controlled trial of a consultative/unit-based geriatric assessment program in acute care.

Successful models of inpatient geriatric assessment have often involved long hospital stays, specialized interdisciplinary care, and prolonged follow-up, which are difficult to achieve within a prospective payment system. A randomized clinical trial was undertaken to evaluate the efficacy (maintenance or improvement in mental, emotional, and physical function) of using a geriatric assessment process in acute hospital care without increasing hospital charges or lengths of stay. Four hundred thirty-six patients greater than or equal to 75 years of age were randomly allocated to treatment (n = 221) or control (n = 215) conditions. Patients in the treatment group were admitted to a special unit and evaluated on admission by an interdisciplinary team, which developed a care plan. Although primary care was provided by the patient's own physician, the team followed the patients as consultants on the unit in the hospital, and by telephone for 2 months after discharge. The control group was placed on other units and received usual hospital care. The treatment and control groups were similar at study entry. At follow-up, there were no significant differences between the groups with respect to lengths of stay, hospital charges, mortality, change in physical function, or change in mental function. The treatment group changed more often in measured emotional function (chi 2 = 6.213, P = .045). This study indicates that it is feasible to implement consultative interdisciplinary team care in the acute-care hospital, but that its efficacy may be limited when applied to an unselected group of older patients.

Activities of Daily Living↗
PubMed1984

Serological and biochemical identification of a plasma membrane antigen specific to Leydig cells.

Purified mouse Leydig cells have been prepared from interstitial cell suspensions using a Percoll gradient procedure. The isolated cells are 88-95% pure as determined by light microscopy. Staining for 3-beta-hydroxysteroid dehydrogenase indicates that over 85% of the Leydig cells recognized by differential interference microscopy are also positive for this enzyme. After separation, the Leydig cells are viable by dye exclusion assays and exhibit normal in situ morphology when examined at the ultrastructural level. Leydig cell suspensions have been used to raise a polyclonal antiserum in rabbits. This antiserum, prior to absorption, reacts in indirect immunofluorescent studies with the surfaces of isolated Leydig cells, with testicular germ cells, with spermatozoa and with somatic cells such as splenocytes. Following absorption with lymphocytes and spermatogenic cells, the antiserum binds only to Leydig cell plasma membranes. Quantitative measurements with 125I-protein A confirm the specific labeling of Leydig cells by the absorbed antiserum. Biochemical identification of the Leydig cell plasma membrane antigen has been accomplished by immunoblotting polyacrylamide gel nitrocellulose transfers. A single major band of Mr approximately 40,000 is detected on one-dimensional transfers; two weakly reactive spots of Mr 43,000 and 45,000 are detected using two-dimensional immunoblots. Blotting experiments conducted using concanavalin A have identified the major Leydig cell constituents reactive with this lectin. The Leydig cell plasma membrane antigen(s) does not bind concanavalin A.

3-Hydroxysteroid Dehydrogenases↗
PubMed1982

Interaction between intracellular vacuoles and the cell surface analysed by finite aperture theory interference reflection microscopy.

Using finite aperture theory we have shown that localized very dark areas in the interference reflection images of Dictyostelium discoideum amoebae are due to the close intracellular approach of vesicles and tubular elements of the contractile vacuole system to the plasma membrane adjacent to the substratum. Vesicles interacting in this way become locally deformed to the planar contour of the substratum and are separated from the cell surface membrane by a constant approximately less than 0.1 micron of cytoplasm. Lamellar processes formed by these cells on very adhesive surfaces have identical dimensions. This minimal thickness may be a mechanical consequence of a contractile mechanism which pulls membranes together.

Animals↗
PubMed1981

Hypertonic cryohemolysis and the cytoskeletal system.

Hypertonic cryohemolysis is defined as the lysis of erythrocytes in a hypertonic environment when the temperature is lowered from above 15-18 degrees C below that temperature. This has been found to be a general phenomenon (that is, whether the solute is charged or not), to exhibit interesting temperature characteristics and to be preventable by agents such as valinomycin which tend to dissipate the concentration gradient across the cell membrane. As yet, no clear information is available to translate this phenomenon to the molecular level and to relate it to current structure/function concepts in the erythrocyte membrane. In this study, data are presented which would indicate on the basis of two entirely separate methodologies that the spectrin-actin cytoskeletal framework is involved in this phenomenon. The first of these methodologies is based on radiation-induced ablation of cryohemolysis and indicates that an intact macromolecular complex of an order of 16000 000 daltons is required for cryohemolysis with hypertonic NaCl. The second methodology is based on selective cross-linking of spectrin and actin in the agent diamide, which resulted in concentration-dependent suppression of cryohemolysis. Polyacrylamide gel electrophoresis of the erythrocyte from diamide-treated cells showed intense protein aggregation with loss of spectrin-actin and bands 4.1, 4.2. We conclude that the spectrin-actin cytoskeletal system possibly including its interaction with phospholipids is the key to the phenomenon of hypertonic cryohemolysis.

Cold Temperature↗