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Biomedical subjects

J A Lewis

Publications and source records attributed to J A Lewis.

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

The feasibility of collecting in-flight EEG data from helicopter pilots.

An assessment of whether valid EEG data could be collected on helicopter pilots in flight was conducted. Each subject provided eyes-open/eyes-closed EEG in the laboratory and in a helicopter. During flights, EEG's were monitored on the ground in real-time via radio telemetry. Analyses were conducted on the data recorded from Fz, Cz, Pz, P3, P4, O1, and O2 from eight subjects. Delta activity at one recording site (Fz) was higher in the aircraft than in the laboratory probably because of increased eye movements. Both theta and alpha activity at several sites also were increased in the aircraft, and alpha activity at all electrodes showed the expected augmentation from eyes-opened to eyes-closed; however, there were no interactions indicative of problems detecting normal alpha changes due to eye closure in the aircraft. Beta activity recorded from Cz and O1 was elevated during flight testing, but it was concluded that at least the O1 effect was due to muscle artifact in the more active environment. While there were more recording artifacts in the helicopter than in the laboratory, the overall results show it is possible to telemeter EEG from helicopter pilots in flight. Follow-on studies are needed to assess whether recordings can be obtained while pilots are performing flight-related tasks.

Adult↗
PubMed1994

Social competence deficits in adolescents at risk for schizophrenia.

Social competence in subjects at risk for schizophrenia and affective disorder and in normal-comparison subjects was examined in childhood and adolescence. Based on interviews with the parents of the subjects and with the children and adolescents themselves, subjects at risk for schizophrenia had poorer overall social competence than subjects at risk for affective disorder and comparison subjects in early adolescence and adolescence but not in childhood. In analyses of specific aspects of social competence, the adolescents at risk for schizophrenia had significantly poorer peer relationships and decreased hobbies/interests than the adolescents at risk for affective disorder and the normal-comparison adolescents. With respect to school adjustment, however, the two groups of adolescent offspring of parents with psychiatric disorders had significantly poorer adjustment than the comparison adolescents but did not differ from each other on this measure. These results suggest that various aspects of poor social competence may precede the onset of schizophrenia and play an important role in its development.

Adolescent↗
PubMed1994

Role of areca nut in the causation of oral submucous fibrosis: a case-control study in Pakistan.

A case-control study on chewing and smoking habits and oral submucous fibrosis (OSF) was undertaken in Karachi in 1989/90. Cases were patients detected with fibrous bands and leathery mucosa and hospital-based controls were matched by age and sex. Information on habits was collected by personal interview of 157 cases and 157 controls. Despite overall female preponderance, a substantial number of young men were enlisted. The male/female risks were found to be similar. Immigrants from India to Pakistan (Mohajir) had a similar risk status to local Punjabis. No differences between risks were found when comparing the three age categories, 21, 21-40, 41-60 yr. Among the cases, an increased risk was observed for areca nut chewing. This habit when practised alone appeared to have the highest risk (RR 154), followed by pan with or without tobacco (RR 64, 32 respectively). Logistic regression and discriminant analysis showed that daily consumption rates appeared to be more important with respect to risk than lifetime duration of habit. Tobacco habits were more prevalent amongst those 15 cases who presented with concurrent carcinoma and OSF: We conclude that areca nut chewing has a causal relationship with OSF: additional tobacco insult may be necessary for subsequent carcinoma development.

Adult↗
PubMed1994

Alternative nurse rostering: an evaluation.

An evaluative research study was conducted to determine the principles underlying the implementation of alternative nurse rostering. The results of three research studies conducted in the Western Australian health care system over a period of three years were reviewed. It was clearly demonstrated that alternative rosters are a valid management tool that will improve nursing productivity and the quality of care. A subject's age and hospital category influenced the acceptance of alternative rostering systems.

Age Factors↗
PubMed1994

Mortality trials in cardiovascular medicine.

Over the past 20 years, large mortality trials have become an increasingly prominent feature of cardiovascular research. The numbers of patients enrolled in the trials has increased, and the quality of research has improved in line with recent methodological advances. This paper reviews important aspects of the design and analysis of key clinical studies and assesses the impact of the results of clinical trials on clinical practice.

Cardiology↗
PubMed1993

Phylogenetic relationships of dengue-2 viruses.

RNA oligonucleotide fingerprinting studies on a large number of virus isolates previously demonstrated considerable genetic variation in isolates of dengue (DEN)-2 serotype. We report the entire envelope (E) glycoprotein gene and deduced amino acid sequences of 16 DEN-2 viruses and the phylogenetic relationships of these, plus 17 additional published DEN E gene sequences. Comparison of DEN-2 E glycoprotein gene sequences revealed base substitutions scattered throughout the entire gene with as much as 22% sequence divergence. Aligned E glycoprotein amino acid sequences revealed the viruses differed by as much as 10%. There appeared to be constraints on the overall structure of the E protein to maintain biological function. Clusters of amino acid substitutions were present in the hydrophobic membrane anchor region at the carboxyl terminal end of the protein. Maximum parsimony analysis of the E gene sequences allowed construction of a phylogram indicating evolutionary relationships of the virus isolates within the DEN-2 serotype. Five genetic subtypes were identified. Phylogenetic relationships of the DEN-2 serotype and other flaviviruses based on E protein sequences reflected traditional antigenic and serologic classifications.

Adult↗
PubMed1993

Acetylcholine receptor molecules of the nematode Caenorhabditis elegans.

Receptors for acetylcholine are present in nematodes. Studies using physiological and biochemical methods have revealed the existence of nicotinic acetylcholine receptors with a novel pharmacology. Caenorhabditis elegans provides a particularly suitable organism with which to investigate such receptors using molecular genetic approaches. Mutants resistant to the cholinergic agonist (and anthelmintic drug) levamisole have permitted the isolation of a number of genes, including structural subunits of the nicotinic acetylcholine receptor. The only known viable mutants of nicotinic receptors are those of Caenorhabditis elegans. This organism offers the prospect of studying the developmental and regulatory effects of the loss of a single component of the receptor. Using Caenorhabditis elegans it is possible to select interesting phenotypic mutations by in vivo mutagenesis before determining the causative lesion. Resistance genes other than those encoding structural subunits are of particular interest, as they will encode additional polypeptides closely associated with nicotinic receptor function. Such proteins are often difficult or impossible to identify using conventional biochemical approaches, whereas genetic selection should permit their identification.

Amino Acid Sequence↗
PubMed1993

Single and booster dose responses to an inactivated hepatitis A virus vaccine: comparison with immune serum globulin prophylaxis.

Pre- and postexposure prophylaxis against hepatitis A virus (HAV) infection with immune serum globulin (Ig) is only effective for 4-6 months. We compared the safety, tolerability and immunogenicity of a single i.m. injection of Ig with a single and booster dose of an inactivated hepatitis A virus vaccine (iHAV) in adults. Healthy volunteers (18-50 years) received a single Ig i.m. injection (n = 30), or iHAV i.m. (n = 15) at 0 and 24 weeks, or placebo (n = 4) at the same intervals. Anti-HAV seroconversion was measured by radioimmunoassay (RIA) and neutralizing antibodies by an antigen reduction assay. After Ig injection (0.06 ml/kg), anti-HAV seroconversion occurred in 100% of recipients at week 1, declining to 10% at week 12 and 0% by week 20. In contrast, after a single 25 ng dose, RIA seropositivity in iHAV vaccinees was 80% by week 2, reaching 100% by week 5 and persisted up to week 24, at which time anti-HAV geometric mean titres (GMT) were two fold higher than those seen at week 1 after Ig. Postbooster anti-HAV titres in iHAV recipients rose within 4 weeks to 73-fold greater than the peak GMT seen one week after Ig, and 400-fold higher than GMT at 12 weeks after Ig. Neutralizing antibody titres after iHAV followed a similar pattern, as observed for anti-HAV. iHAV was well tolerated; placebo and vaccine tolerability were indistinguishable, with no serious adverse experiences observed. In conclusion, active vaccination with a single iHAV dose may eventually replace Ig for pre-exposure prophylaxis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Development of the formalin-inactivated hepatitis A vaccine, VAQTA from the live attenuated virus strain CR326F.

The development of the formalin-inactivated hepatitis A vaccine, VAQTA, culminates nearly two decades of the basic science studies of VAQTA in hepatitis A virology at the MRL. The master seed virus for production of VAQTA is derived from the F'(P18) variant of the strain CR326F which has been studied in human clinical trials and shown to the highly attenuated. The antigen is highly purified to make possible the consistency and thoroughness of its inactivation by formalin. Phase I clinical studies of VAQTA were initiated in 1989 and have progressed since that time to the recent Phase III clinical trials which demonstrated efficacy of a single dose of the vaccine in preventing clinical hepatitis A disease in pediatric populations in Monroe, NY.

Animals↗
PubMed1993

Safety, tolerability, and immunogenicity of an inactivated hepatitis A vaccine: effects of single and booster injections, and comparison to administration of immune globulin.

Hepatitis A virus (HAV) infection in adults is often symptomatic and disabling. The present article summarizes our experience with phase 2 studies of an inactivated hepatitis A virus vaccine. Pre- and post-exposure prophylaxis with immune globulin (IG) is only effective for 4-6 months. We compared the safety, tolerability, and immunogenicity of a single i.m. injection of IG with single and booster doses of an inactivated hepatitis A virus vaccine (iHAV) in adults. A total of 75 healthy volunteers (aged 18-50 years) were evaluated in two separate studies. The first included 15 volunteers who received 25 units iHAV i.m. at 0 and 24 weeks. The second, a randomly controlled study, consisted of three groups receiving 25 units iHAV i.m. at 0, 1, and 6 months, or at 0, 2, and 6 months, or 0.06 ml/kg IG i.m. given once. Anti-HAV seroconversion was measured by radioimmunoassay (RIA). After IG injection, anti-HAV seroconversion occurred in 100% of recipients at week 1, declining to 10% at week 12, and 0% by week 20. In contrast, after a single 25-unit dose, RIA seropositivity in iHAV vaccines was 73% by week 2, reaching 100% by week 5, and persisted in all up to week 24, at which time anti-HAV geometric mean titers (GMT) were 2-fold higher than those seen at week 1 after IG. Administration of a booster dose given 1 or 2 months after primary immunization did not significantly improve the quantitative anti-HAV response at 6 months as compared to the effect of the primary dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Mycobacterium avium antigenuria in patients with AIDS and disseminated M. avium disease.

A 22,500-Da antigen apparently specific to Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum has been identified by Western immunoblotting. By use of a dot immunoassay, this antigen was found in the urine of 64% of patients with AIDS and disseminated M. avium disease. It was not found in the urine of healthy control subjects. Detection of antigenuria might provide the basis for rapid diagnosis of M. avium disease in patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Childhood precursors of affective vs. social deficits in adolescents at risk for schizophrenia.

Childhood attentional and neuromotor precursors of social competence and affective deficits in adolescents at risk for schizophrenia, adolescents at risk for affective disorder, and matched comparison adolescents were examined. The subjects were offspring of parents with schizophrenia or affective disorder and of normal parents matched on age, sex, and socioeconomic status from the New York High-Risk Project (Sample B). On the basis of interviews conducted when the subjects were children and adolescents, social competence was rated from child reports and parent reports, affective deficits were assessed by affective flattening ratings, and smiling was assessed by counting broad smiles. Adolescents at risk for schizophrenia had significantly greater social and affective deficits than adolescents at risk for affective disorder and comparison adolescents. In subjects at risk for schizophrenia, childhood neuromotor dysfunction predicted adolescent affective flattening, and childhood attentional dysfunction predicted adolescent social deficits. The results suggest that affective and social deficits in schizophrenia have different childhood precursors.

Adolescent↗
PubMed1992

Computer simulation for the prediction of separation as a function of pH for reversed-phase high-performance liquid chromatography. I. Accuracy of a theory-based model.

Computer simulation software (DryLab I/mp) is described for predicting high-performance liquid chromatographic separation as a function of changes in mobile phase pH. Three experimental runs with pH (only) varied are used to derive values of pKa plus capacity factors (k') for the ionized and non-ionized form of each ionizable solute. Various tests of the experimental data then allow classification of each solute as acidic, basic, neutral (including strong or weak acids or bases) and amphoteric. Experimental data are reported for the separation of several substituted anilines as a function of pH and solvent composition (%B). Experimental requirements for the accurate prediction of separation (ca. +/- 2-4% in alpha) as a function of pH are discussed. The reliability of the software is demonstrated for three different samples: mixtures of (a) substituted benzoic acids, (b) substituted anilines and (c) catecholamine-related compounds.

Aniline Compounds↗