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Biomedical subjects

P Davis

Publications and source records attributed to P Davis.

At least 109 records · Page 6Linked to original sources
PubMed1999

Postprandial lipid, glucose, insulin, and cholecystokinin responses in men fed barley pasta enriched with beta-glucan.

BACKGROUND: Fiber regulates the rate and site of lipid and carbohydrate digestion and absorption and thus can modify the alimentary responses to a meal. When fiber sources containing viscous polysaccharides are included in a meal, a slower rate of carbohydrate and lipid absorption will modify the alimentary hormone and lipid responses. OBJECTIVE: We investigated in 11 healthy men the response of insulin, glucose, cholecystokinin, and lipid to 2 test meals containing beta-glucan. DESIGN: One of the meals was high in fiber (15.7 g) and the other meal was low in fiber (5.0 g). The low-fiber meal contained pasta made with wheat flour. The high-fiber meals contained pasta prepared by replacing 40% of the wheat with 2 types of barley flour: barley naturally high in beta-glucan and the other a flour enriched in beta-glucan during processing. RESULTS: Plasma glucose and insulin concentrations increased significantly after all meals but the insulin response was more blunted after the barley-containing meals. The test meals were low in fat (25% of energy) but elicited an increase in plasma triacylglycerol and cholecystokinin. Cholecystokinin remained elevated for a longer time after the barley-containing meals. After the low-fiber meal, plasma cholesterol concentrations did not change significantly; however, 4 h after the barley-containing meals, the cholesterol concentration dropped below the fasting concentration and was significantly lower than that after the low-fiber meal. CONCLUSIONS: Carbohydrate was more slowly absorbed from the 2 high-fiber meals. Consumption of the barley-containing meals appeared to stimulate reverse cholesterol transport, which may contribute to the cholesterol-lowering ability of barley.

Adult↗
PubMed1999

Recovery process of low-frequency fluctuations in laser diodes with external optical feedback.

The recovery process of low-frequency fluctuations is experimentally investigated in a semiconductor laser with external optical feedback. Monotonic stepwise increase of the light output intensity is observed for various external cavity lengths. The time interval of each step corresponds to the round-trip time of the external cavity. Transitions between steps and dynamics within each step are analyzed. Experimental results are discussed with reference to the scenario of chaotic mode itinerancy. Statistical properties of time intervals between power dropout events are also discussed.

Journal Article↗
PubMed1999

The New Zealand Socioeconomic Index: developing and validating an occupationally-derived indicator of socio-economic status.

OBJECTIVE: Following revision of the international standard classification (ISCO88), to update and validate on health data an occupationally derived indicator of socio-economic status (SES) adapted to changing occupational and demographic conditions. METHOD: The development of the New Zealand Socioeconomic Index (NZSEI) is based on a 'returns to human capital' model of the stratification process and uses data from the 1991 New Zealand Census (n = 1,051, 926) to generate scores for 97 occupational groups. The construct validation of the scale is carried out on data from the 1992-93 nationwide Household Health Survey (n = 3,000) using three health indicators (self-assessed health, cigarette smoking, general practitioner visits). RESULTS: In general, the results are consistent with expected socio-economic patterns drawn from the literature for the three indicators. CONCLUSIONS: While further work is required on a number of methodological and conceptual issues, the NZSEI provides a robust, standardised and internationally comparable occupational scale of SES for both males and females in either full- or part-time employment. IMPLICATIONS: The NZSEI can be used on routinely collected occupational data. It has a clear conceptual rationale, updates existing SES scales, and provides a link to international standards in SES and occupational classification.

Adult↗
PubMed1999

Health expectancy in New Zealand, 1981-1991: social variations and trends in a period of rapid social and economic change.

STUDY OBJECTIVE: To assess social variations and trends in health expectancy over a period of rapid social and economic change. DESIGN: Cross sectional survey data on the association between social status--gender, socioeconomic class and ethnic group--and measures of health status at two points in time approximately a decade apart. The Sullivan method of calculating health expectancy was used. SETTING: The adult population of New Zealand in the periods 1980-81 and 1992-93. PARTICIPANTS: Representative samples of the adult civilian non-institutionalised population of 6,891 (1980-81) and 5,873 (1992-93) respectively. MAIN RESULTS: In comparison with life expectancy, adjusting for health status narrowed the gender gap but widened socioeconomic and ethnic differentials. These results were replicated for three measures--self reported health, mobility, and handicap--suggesting a robustness of outcome to specific indicators. Comparable data over the period of study were only available for the mobility measure. Increases in longevity appeared to be fully absorbed by minor disability. Ethnic and socioeconomic disadvantages remained static or widened for the 15-64 age group, suggesting a potential social polarisation in the disability transition. CONCLUSIONS: The operationalization of health expectancy appears to be rather robust to specific indicators. Health expectancy may provide a sensitive health impact assessment of social and economic policy. Existing theories of the disability transition may need to be modified to take account of social variation, at least in the special case of disability free health expectancy over the 15-64 age range.

Adolescent↗
PubMed1999

Effect of upper airway negative pressure on proprioceptive afferents from the tongue.

We examined whether receptors in the tongue muscle respond to negative upper airway pressure (NUAP). In six cats, one hypoglossal nerve was cut and its distal end was prepared for single-fiber recording. Twelve afferent fibers were selected for study on the basis of their sensitivity to passive stretch (PS) of the tongue. Fiber discharge frequency was measured during PS of the tongue and after the rapid onset of constant NUAP. During PS of 1-3 cm, firing frequency increased from 17 +/- 7 to 40 +/- 11 (SE) Hz (P < 0.01). In addition, 8 of the 12 fibers responded to NUAP (-10 to -30 cmH2O), with firing frequency increasing from 23 +/- 9 to 41 +/- 9 Hz (P < 0.001). In two fibers tested, the increase in firing frequency in response to NUAP was not altered by topical anesthesia (10% lignocaine) applied liberally to the entire upper airway mucosa. Our results demonstrate that afferent discharges from the hypoglossal nerve are elicited by 1) stretching of the tongue and 2) NUAP before and after upper airway anesthesia. We speculate that activation of proprioceptive mechanoreceptors in the cat's tongue provides an additional pathway for the reflex activation of upper airway dilator muscles in response to NUAP, independent of superficially located mucosal mechanoreceptors.

Afferent Pathways↗
PubMed1999

Proteins bound to polyethylene components in patients who have aseptic loosening after total joint arthroplasty. A preliminary report.

BACKGROUND: Immunological responses to proteins that adhere to ultra-high molecular weight polyethylene have not, to our knowledge, been examined previously in patients who have aseptic loosening. In the current study, polyethylene components from forty-nine failed prostheses recovered during revision procedures were examined for the presence of antibodies that were bound to the polyethylene surface or that were reactive with other proteins that were bound to the polyethylene surface. METHODS: The polyethylene components consisted of thirty acetabular cups recovered during revision total hip arthroplasties and nineteen tibial components recovered during revision total knee arthroplasties. After extensive washing, bound proteins were extracted from the polyethylene components with use of 0.1-molar glycine-hydrogen chloride solution followed by four-molar guanidine hydrochloride solution. RESULTS: Sufficient protein for analysis was recovered from forty-two polyethylene components. Polyacrylamide gel electrophoresis demonstrated a minimum of one and a maximum of twelve protein bands, with molecular weights ranging from thirteen to 231 kilodaltons. Immunoblotting revealed the presence of type-I collagen in most (thirty-four) of the forty-two explants, whereas aggrecan proteoglycans were detected in eight samples. Immunoglobulin also was detected in most (thirty-three) extracts, whereas type-II collagen was consistently absent. The presence of autologous antibodies directed against polyethylene-bound proteins in sera drawn at the time of the revision was investigated. Antibodies that were reactive against the ultra-high molecular weight polyethylene-bound proteins were detected in twenty-six of the forty-two patients with use of the Western blot technique. The number of reactive bands ranged from one to six, and the strongest binding was directed against a 103-kilodalton protein. Assays for specificity revealed that these sera autologous antibodies were reactive against the type-I collagen that was present in the explant solutions. CONCLUSIONS: We hypothesize that immunoglobulin complexed with polyethylene may fix complement and that the complement cascade may in turn attract inflammatory cells to the polyethylene surface. Our data support the hypothesis that an immunological response to antigens bound to the polyethylene surface may contribute to aseptic loosening. CLINICAL RELEVANCE: Despite improvements in materials and designs of prostheses, aseptic loosening is the most common complication of total joint replacement, frequently leading to revision operations. We examined the immunological response to proteins that bind to ultra-high molecular weight polyethylene in patients who had aseptic loosening and discovered a high prevalence of antibodies to polyethylene-bound proteins. This immunological response may contribute to an inflammatory reaction in the periprosthetic tissue, ultimately leading to increased bone resorption around the prosthesis.

Antigen-Antibody Complex↗
PubMed1999

Transverse cerebellar diameter on cranial ultrasound scan in preterm neonates in an Australian population.

OBJECTIVE: Fetal measurement of transverse cerebellar diameter (TCD) has been shown to correlate well with gestational age (GA), even in the presence of growth retardation. The aim of this study was to define the normal range of TCD in preterm neonates in an Australian population between 23 and 32 weeks GA. METHODOLOGY: Infants admitted to the Royal Women's Hospital, Melbourne, having routine cranial ultrasound scans (< 1500 g and/or of gestational age </= 32 weeks at birth) had their TCD measured on a cranial scan performed during the first 3 days of life. The posterior fossa was examined through the asterion using a General Electric LOGIQ 500 scanner (GE Medical Systems, Waukesha, USA) and TCD measurement was taken in the coronal plane. RESULTS: 106 infants < 1500 g and/or of GA </= 32 weeks at birth had their TCD measured between 1 January 1997 and 30 November 1997. Transverse cerebellar diameter and associated 95% confidence intervals are described for infants between 23 and 32 weeks GA. The linear regression equation relating TCD and GA was: TCD (mm) = -12.9 + 1.61 x GA (weeks). R2 = 0.80, P < 0.001. CONCLUSION: This is the only study of TCD measurement using cranial ultrasound in a group of preterm newborns, and forms the basis for nomograms of TCD which can be used as a tool to assist in the assessment of GA, even in growth-retarded preterm newborns, and in the diagnosis of cerebellar hypoplasia.

Cephalometry↗
PubMed1999

Post-extubation prophylactic nasal continuous positive airway pressure in preterm infants: systematic review and meta-analysis.

OBJECTIVES: To determine whether management with nasal continuous positive airway pressure (NCPAP) in preterm infants having their endotracheal tube removed following a period of intermittent positive pressure ventilation (IPPV), leads to an increased proportion remaining free of additional ventilatory support, compared to extubation directly to headbox oxygen. METHODOLOGY: Search Strategy - Searches were made of the Oxford Database of Perinatal Trials, Medline, abstracts of conferences and symposia proceedings, expert informants, journal hand searching mainly in the English language and expert informant searches in the Japanese language. Selection criteria - All trials utilising random or quasi-random patient allocation, in which NCPAP (delivered by any method) was compared with headbox oxygen for postextubation care were included. Methodological quality was assessed independently by the two authors. Data collection and analysis - Data were extracted independently by the two authors. Meta-analysis using event rate ratios (ERRs) and event rate differences (ERDs) was performed using Revman 3.0 statistical software. Prespecified subgroup analysis to determine the impact of different levels of NCPAP and use of aminophylline were also performed using the same package. Similar analysis to investigate the effect of postnatal age on outcomes of interest was also undertaken. RESULTS: Nasal CPAP, when applied to preterm infants being extubated following IPPV, reduces the incidence of adverse clinical events (apnoea, respiratory acidosis and increased oxygen requirements) indicating the need for additional ventilatory support. This result is both statistically significant and clinically important; ERR, 0.62 (0.49, 0.79) and ERD, - 0.175 (- 0.256, - 0.095). A trend towards reduction in the incidence of oxygen dependency at 28 days of age is also seen in the group extubated to NCPAP; ERR, 0.86 (0.67, 1.10) and ERD, - 0.069 (- 0.177, 0.039). CONCLUSION: Nasal CPAP is effective in preventing failure of extubation in preterm infants following a period of endotracheal intubation and IPPV. Further definition of the patient gestational age and weight groups to whom these results apply is required. Optimal levels of NCPAP as well as methods of administration remain to be determined.

Aminophylline↗
PubMed1999

Case studies in osteoporosis: a problem based learning intervention for family physicians.

OBJECTIVE: To develop and evaluate a practice based small group (PBSG) learning intervention on osteoporosis for primary care physicians. METHODS: A needs assessment on osteoporosis was performed and objectives for a continuing medical education (CME) program developed by an interdisciplinary advisory committee. Nine clinical cases were developed for evaluation by CME participants with a trained facilitator and content expert using the PBSG format. The effect of the CME intervention was evaluated using a pre and post-test consisting of objective structured clinical examination stations and standardized patients. RESULTS: Fifty-four family physicians participated in 4 pilot PBSG learning sessions. The program format, content, and participant satisfaction was highly rated (> 3.35:4.0). Participants expected the program to have a significant effect on the practices (3:40:4.0). Ninety-eight percent of participants improved their pretest scores, with a mean increase of 13% (range 1-36%). CONCLUSION: Based on our experience, we advocate the use of PBSG learning interventions as an effective and acceptable method of providing CME by rheumatologists for their family physician colleagues. This format appears to be associated with a significant effect on knowledge, skills, and behavior as assessed by our study.

Aged↗
PubMed1998

De novo design, synthesis, and biological activities of high-affinity and selective non-peptide agonists of the delta-opioid receptor.

On the basis of the structure-activity relationships of delta-opioid-selective peptide ligands and on a model of the proposed bioactive conformation for a potent and selective, conformationally constrained delta-opioid peptide ligand [(2S, 3R)-TMT1]DPDPE, a series of small organic peptide mimetic compounds targeted for the delta-opioid receptor have been designed, synthesized, and evaluated in radiolabeled ligand binding assays and in vitro bioassays. The new non-peptide ligands use piperazine as a template to present the most important pharmacophore groups, including phenol and phenyl groups and a hydrophobic moiety. This hydrophobic group was designed to mimic the hydrophobic character of the D-Pen residues in DPDPE, which has been found to be extremely important for increasing the binding affinity and selectivity of these non-peptide ligands for the delta-opioid receptor over the mu-opioid receptor. Compound 6f (SL-3111) showed 8 nM binding affinity and over 2000-fold selectivity for the delta-opioid receptor over the mu-opioid receptor. Both enantiomers of SL-3111 were separated, and the (-)-isomer was shown to be the compound with the highest affinity for the delta-opioid receptor found in our study (IC50 = 4.1 nM), with a selectivity very similar to that observed for the racemic compound. The phenol hydroxyl group of SL-3111 turned out to be essential to maintain high affinity for the delta-opioid receptor, which also was observed in the case of the delta-opioid-selective peptide ligand DPDPE. Binding studies of SL-3111 and [p-ClPhe4]DPDPE on the cloned wild-type and mutated human delta-opioid receptors suggested that the new non-peptide ligand has a binding profile similar to that of DPDPE but different from that of (+)-4-[((alphaR)-alpha(2S,5R)-4-allyl-2, 5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC-80), another delta-opioid-selective non-peptide ligand.

Animals↗
PubMed1998

Trends in general practice in the Waikato, 1979-80/1991-92, II: Social variations in service use and clinical activity.

AIMS: To document trends in ethnic group and occupational class differences in the use of general practitioner services and in patterns of clinical activity for the Hamilton Health District of the Waikato over the period 1979-80 to 1991-92. METHODS: The data are drawn from a baseline and a follow-up survey of general practice in the Waikato region representing a one per cent sample of all in-surgery, in-hours, week-day encounters at two points in time. The data were recorded by participating general practitioners in four collection weeks spaced over the period of a year. In total, 9468 and 10,235 patient encounter forms were completed respectively. RESULTS: Over a period in which service availability and rates of medical contact grew, there was a relatively greater increase in utilisation among Maori and lower socioeconomic groups: between the two surveys the ratio of Maori to non-Maori rates increased from 0.8 to 1.0 and the ratio of visits for lower to higher socioeconomic groups grew from a differential of 2.5 to one of 3.1. More serious conditions apart, these changes seemed to occur uniformly regardless of the severity, amenability or susceptibility of the condition presented to the general practitioner. Changes in ethnic group and occupational class patterns of service activity almost exactly mirrored these trends. CONCLUSIONS: A notable relative increase in rates of contact for primary medical care among Maori and lower socioeconomic groups seems to have accompanied the growth in the 1980s of the availability of general practitioner services in this region of New Zealand.

Data Collection↗
PubMed1998

Effect of nebulized ipratropium on the hospitalization rates of children with asthma.

BACKGROUND: Anticholinergic medications such as ipratropium improve the pulmonary function of patients with acute exacerbations of asthma, but their effect on hospitalization rates is uncertain. METHODS: We conducted a randomized, double-blind, placebo-controlled study of 434 children (2 to 18 years old) who had acute exacerbations of moderate or severe asthma treated in the emergency department. All the children received a nebulized solution of albuterol (2.5 or 5 mg per dose, depending on body weight) every 20 minutes for three doses and then as needed. A corticosteroid (2 mg of prednisone or prednisolone per kilogram of body weight) was given orally with the second dose of albuterol. Children in the treatment group received 500 microg (2.5 ml) of ipratropium bromide with the second and third doses of albuterol; children in the control group received 2.5 ml of normal saline at these times. RESULTS: Overall, the rate of hospitalization was lower in the ipratropium group (59 of 215 children [27.4 percent]) than in the control group (80 of 219 [36.5 percent], P=0.05). For patients with moderate asthma (indicated by a peak expiratory flow rate of 50 to 70 percent of the predicted value or an asthma score of 8 to 11 on a 15-point scale), hospitalization rates were similar in the two groups (ipratropium: 8 of 79 children [10.1 percent]; control: 9 of 84 [10.7 percent]). For patients with severe asthma (defined as a peak expiratory flow rate of <50 percent of the predicted value or an asthma score of 12 to 15), the addition of ipratropium significantly reduced the need for hospitalization (51 of 136 children [37.5 percent], as compared with 71 of 135 [52.6 percent] in the control group; P=0.02). CONCLUSIONS: Among children with a severe exacerbation of asthma, the addition of ipratropium bromide to albuterol and corticosteroid therapy significantly decreases the hospitalization rate.

Adolescent↗
PubMed1998

Synthesis, opioid receptor binding, and bioassay of naltrindole analogues substituted in the indolic benzene moiety.

A series of analogues of the delta opioid receptor antagonist naltrindole (1) possessing a phenyl, phenoxy, or benzyloxy group at the 4'-, 5'-, 6'-, or - 7'-positions (4-15) and a 2-(2-pyridinyl)ethenyl group at the 5'-position (16) on the indolic benzene ring were synthesized through Fischer indolization of naltrexone. Compounds 4-16 were evaluated for their affinities in opioid receptor binding assays in rat or guinea pig brain membranes and for their opioid antagonist and agonist activities in vitro on the guinea pig ileum (GPI) and mouse vas deferens (MVD) preparations. All of the compounds displayed delta selectivity in binding to the delta, mu, and kappa opioid receptors. The binding potencies of most of the compounds at the delta, mu, and kappa sites, however, were lower than that of 1. Among positional isomers, the 7'-substituted compounds in general had higher affinities than 6'-, 5'-, or 4'-substituted analogues, indicating that bulky groups are tolerated better at the 7'-position than at other positions. The affinity of the compounds were also determined at putative subtypes of the delta and kappa receptors: deltacx-1 (mu-like), deltacx-2 (delta-like), and the kappa2b site in an attempt to identify subtype selective agents. Although none were identified, the data revealed a different rank-order of potency beteween mu vs deltacx-1, deltacx-2 vs delta, and the kappa2b vs mu, delta, and kappa1. The antagonist potencies of the compounds in the MVD were in agreement with their binding affinities at the delta site in rat brain membrane. The most potent member of the series, the 7'-phenoxy compound 14, binds to the delta site with a Ki of 0.71 nM, shows >40-fold delta over mu and delta over kappa binding selectivity, and exhibits delta receptor antagonist potency in the MVD with a Ke of 0.25 nM, properties which are comparable to the delta receptor affinity and antagonist potency of naltrindole (Ki = 0.29 nM, Ke = 0. 49 nM). Interestingly, many members of the series were found to possess significant partial to full agonist activities in the MVD (6, 9, 10, 13, 16) or GPI (6, 11, 14, 15). Among the compounds studied, the highest agonist activity in the MVD was displayed by 16 (IC50 = 220 nM), and the highest agonist activity in the GPI was displayed by 14 (IC50 = 450 nM). The overall affinity and activity profile of compound 14 is, therefore, that of a nonpeptide ligand possessing mixed mu agonist/delta antagonist properties. Recently there has been considerable interest in such compounds possessing mu agonist/delta antagonist activities because of their potential therapeutic usefulness as analgesics with low propensity to produce tolerance and dependence side effects. The results of the present study suggest that morphinan derivatives related to 16 and 14 may provide useful leads for the development of potent nonpeptide ligands possessing delta agonist or mixed delta antagonist/mu agonist activities.

Animals↗
PubMed1998

Trends in general practice in the Waikato, 1979-80/1991-92, I: Practitioner availability, service use and clinical activity.

AIMS: To document trends in availability and use of general practitioner services and in patterns of clinical activity for the Waikato over the period 1979-80 to 1991-92. METHODS: The data are drawn from a baseline and a follow-up survey of general practice in the Waikato region representing a 1% sample of all in-surgery, in-hours, week-day encounters at two points in time. The data were recorded by participating general practitioners in four collection weeks spaced over the period of a year. In total, 9468 and 10,235 patient encounter forms were completed. RESULTS: While the number of general practitioners increased by a half over the period, average workload declined by a fifth, the inflation-adjusted value of the usual adult fee increased by nearly 50% and visits went up by an average of a half a visit a year. Clinical activity declined for prescribing but increased for referral and follow-up. CONCLUSIONS: The increase in availability of general practitioners over the last decade has been associated with significant changes in patterns of practice organisation, service utilisation and clinical activity. Further research is required into the potential impact of greater service availability on patient demand and resource use.

Adult↗