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Biomedical subjects

R A Knight

Publications and source records attributed to R A Knight.

At least 127 records · Page 7Linked to original sources
PubMed1991

Temporal evolution of ischemic damage in rat brain measured by proton nuclear magnetic resonance imaging.

We studied the effect of focal cerebral ischemia on the "state" of brain water using proton nuclear magnetic resonance imaging. Focal cerebral ischemia was induced in five halothane-anesthetized rats via tandem occlusion of the left common carotid artery and the left middle cerebral artery. The proton transverse relaxation time, the proton density, and the water diffusion coefficient were measured at various times from the same region of brain tissue from 1.5 to 168 hours after occlusion. Early measurements indicated significant changes in the transverse relaxation time (p = 0.004) and water diffusion coefficient (p = 0.002) of ischemic brain tissue compared with a homologous region from the contralateral hemisphere. However, the transverse relaxation time, proton density, and water diffusion coefficient in ischemic brain tissue showed different temporal evolutions over the study period. Diffusion coefficient weighting was superior to relaxation time and proton density weighting for the visualization of early cerebral ischemia. Our data suggest that nuclear magnetic resonance imaging is sensitive in detecting changes in proton-associated parameters during early cerebral ischemia and confirm significant changes (p less than or equal to 0.01) in the temporal evolution of transverse relaxation times, proton densities, and diffusion coefficients following middle cerebral artery occlusion.

Animals↗
PubMed1991

Child molesters who abduct.

This study examined the differences between 97 abducting and 60 nonabducting child molesters on selected typological and antisocial/criminal variables. Although the results supported one a priori hypothesis, they disconfirmed two others and yielded an unpredicted but theoretically interesting abductor covariate. Our hypothesis that child abductors would more likely be classified as "low" in their contact with children (i.e., have little or no contact with children outside of their offenses) than the nonabductors was supported. In contrast, our hypotheses that the abductors were more likely to be characterized by a history of antisocial and criminal behavior as well as a greater degree of aggression were not supported. Abductors were found to be lower in social competence than the child molesters who never abducted their victims. The results were discussed in terms of abduction as in victim control strategy that is more likely employed by offenders with poor social and interpersonal skills. The complex interrelation among social competence, weapons, and sadism for abductors and nonabductors was explored.

Child↗
PubMed1991

Production of a growth hormone-releasing hormone-like peptide and its mRNA by human lymphocytes.

Human peripheral blood lymphocytes (PBL) contain immunoreactive growth hormone-releasing hormone (irGRH). Both the intracellular content and the release of irGRH from PBL are increased following lymphocyte activation. Although binding of lymphocyte-derived irGRH to a GRH1-44 antibody dilutes in parallel with standard GRH1-44, irGRH elutes earlier on gel chromatography with an apparent molecular weight of approximately 50 kD. On reverse-phase high performance liquid chromatography, irGRH elutes later than GRH1-44. Northern blot analysis also detected the presence of two GRH mRNA transcripts in PBL, one similar in size to the hypothalamic species of 0.75 kb and another larger transcript of approximately 10 kb. Despite these differences in physicochemical behaviour, both the lymphocyte-derived irGRH GRH1-44 were biologically active as demonstrated by enhancing the transcription of growth hormone mRNA both in dispersed rat pituitary cells and in PBL.

Animals↗
PubMed1991

Expression of pre-opiomelanocortin (POMC) mRNA in undifferentiated and in vitro differentiated human neuroblastoma cell lines.

Several human neuroblastoma cell lines express transcripts of the proopiomelanocortin (POMC) gene of 0.8 kb and 9.5 kb, thus different from the characteristic pituitary 1.2 kb POMC mRNA. The expression of POMC mRNA decreases when the cell lines are differentiated with retinoic acid or alpha-difluoromethylornithine. Since both POMC and MYCN genes are present on the same chromosome segment (2p23), it is possible that the 2 genes are coamplified and coexpressed. Alternatively the expression of opiate peptides by neuroblastoma cells might act as an autocrine factor or it may modulate the action of tumour infiltrating lymphocytes.

Cell Differentiation↗
PubMed1990

Independent genetic determinants of pancreatic and pulmonary status in cystic fibrosis.

The concordance of pancreatic and pulmonary status among siblings with cystic fibrosis, the cystic fibrosis genotype, and non-genetic factors were analysed in adult patients with cystic fibrosis. Genetic factors were more important than non-genetic factors in affecting the severity of pancreatic and lung disease. The genetic factors were independent of each other and did not invariably cosegregate with specific mutations at the cystic fibrosis locus.

Adult↗
PubMed1990

Linked marker haplotypes and the delta F508 mutation in adults with mild pulmonary disease and cystic fibrosis.

The frequencies of the delta F508 mutation and haplotypes at the loci linked to the cystic fibrosis (CF) gene have been compared in adult CF patients with very mild and with severe lung disease. In patients who are compound heterozygotes for the delta F508 mutation, or who lack the mutation on both chromosomes, the as yet undefined mutations may influence the severity of lung involvement. In patients homozygous for the delta F508 mutation, non-genetic factors cannot fully account for variation in the severity of lung disease. Genes outside the CF locus may influence clinical expression of the disease.

Adolescent↗
PubMed1990

Corticotrophin-releasing factor-like immunoreactivity and mRNA in human leukocytes.

Unstimulated normal leukocytes were studied for their expression of corticotrophin-releasing factor (CRF)-like mRNA and peptide. In situ hybridization demonstrated CRF mRNA in T and B lymphocytes and in neutrophils. Northern blot analysis also detected the presence of a CRF mRNA species of approximately 1.7 Kb from lymphocytes and a peptide that reacted with anti-CRF antiserum was also detected by radioimmunoassay. This lymphocyte-derived peptide eluted earlier than standard CRF on high performance liquid chromatography. These findings suggest that regulatory mechanisms within the hypothalamus and the immune system may utilize closely related peptides.

B-Lymphocytes↗
PubMed1989

The relevance of the health belief model to Australian smokers.

The Health Belief Model is one of the few models predicting health behavior which explicitly evaluates the role of cues to action from the doctor or others. Rarely have such cues to action been examined formally by the comparison of groups receiving different interventions. Initial and follow-up data covering a wide range of sociopsychological variables were gathered from typical smokers among family-practice patients participating in an Australian quit-smoking program. Patients were randomly assigned either to a control or experimental group, the latter receiving the Give-Up Smoking (GUS) kit, and quit-smoking advice from their doctor. Factor analysis of the initial data largely confirmed the clusters of the Health Belief Model. At follow-up, after the experimental and control group treatment, a totally different factor structure emerged, comprising some very specific sociopsychological variables and cues to action. Implications are discussed for the Health Belief Model relative to other health behavior models.

Attitude to Health↗
PubMed1988

Evaluation of two commercially available test methods to determine the feasibility of testing for respiratory syncytial virus in a community hospital laboratory.

The feasibility of performing respiratory syncytial virus (RSV) testing in a community hospital laboratory was assessed. The Abbott RSV EIA Kit, an enzyme immunoassay (EIA), and the Ortho Respiratory Syncytial Virus Identification Reagent, a direct fluorescent antibody (DFA) technique, were evaluated in terms of technologist time, result time, cost, and agreement of results. There was little difference in the amount of technologist time required for either method. The DFA technique was shown to be much less expensive than the EIA method and also required at least 50% less time to generate a final result. When compared with an indirect fluorescent antibody technique, the EIA technique was more sensitive (87%) than the DFA method (81%). Both methods showed 100% specificity. Based on the findings of this study, the DFA technique was determined to be the more feasible method for a community hospital laboratory to use for the rapid detection of RSV.

Child↗
PubMed1988

Effects of beta endorphin on specific immune responses in man.

Synthetic human beta endorphin shows a biphasic effect on the production of specific anti-herpes viral antibodies in vitro. At higher concentrations antibody production is reduced, at lower concentrations it is enhanced. In a proportion of donors whose cells do not produce specific antibody when cultured with antigen alone, the lower concentrations of beta endorphin allow antigen-driven specific antibody production to occur. Specific anti-herpes viral antibodies are also made by natural killer (NK) cell-depleted populations from the same non-producer donors. beta endorphin also exerts biphasic effects on NK, although the direction of the modulation is a mirror image of the effects on antibody production. This suggests that the immunomodulatory actions of beta endorphin on specific immune responses are mediated in part by effects on NK suppressor-inducer cells.

Antibodies, Viral↗
PubMed1988

Validating the components of a taxonomic system for rapists: a path analytic approach.

This study was part of a series designed to validate a classification system for rapists developed at the Massachusetts Treatment Center. This system (MTC:R2) determines subtypes according to three major dimensions: the meaning of the aggression in the rapist's offenses (expressive versus instrumental), the meaning of the sexual behavior (compensatory, exploitative, displaced anger, or sadistic), and the degree of general lifestyle impulsivity (low or high). A total of 201 rapists were subtyped using this system. A path analytic approach was used to relate family, juvenile, and adult histories to the main decisions of subtype assignment. The classification of an offender on each of the three dimensions was informed by a developmental perspective. Results provided support for the use of the discriminators used and highlighted the deficiencies in our current knowledge regarding developmental precursors. These results were integrated with the findings from other studies using MTC:R2 and suggestions for revisions to the current classification system were discussed.

Aggression↗
PubMed1987

Therapy vs no therapy for bacteriuria in elderly ambulatory nonhospitalized women.

This prospective randomized study was undertaken to determine the efficacy of antimicrobial therapy compared with no therapy for bacteriuria in elderly ambulatory nonhospitalized women. Sixty-one women (mean age, 85.8 years) with bacteriuria were in the no therapy control group and 63 women (mean age, 85.8 years) with bacteriuria were in the therapy group; none had symptoms of urinary tract infection. One short course of antimicrobial therapy achieved a cure rate of 68.3% (43 of 63 women cured) two weeks after treatment. During the six-month follow-up period, ten (16.4%) of 61 women in the no therapy group and five (7.9%) of 63 women in the therapy group developed symptomatic urinary tract infection. At the time of six-month follow-up, 19 (34.5%) of 55 women in the no therapy group and 35 (63.6%) of 55 women in the therapy group did not have bacteriuria. We conclude that for asymptomatic bacteriuria in elderly ambulatory nonhospitalized women, short-course antimicrobial therapy is effective at two-week follow-up and that antimicrobial therapy can eliminate bacteriuria in most of these women for at least a six-month period.

Aged↗
PubMed1987

Differential effects of beta-endorphin fragments on human natural killing.

The endogenous opiate peptide, beta-endorphin, has two effects on human natural killing (NK). Preincubation of effector lymphocytes with between 10(-7) and 10(-11) M beta-endorphin increases NK. Preincubation with lower concentrations results in a reduction in NK. Endorphin peptides containing an unmodified N-terminal sequence, and which are known to bind only to opiate receptors, increase NK. Sequences reported to bind only to nonopiate receptors reduce NK.

Cytotoxicity, Immunologic↗
PubMed1987

In vitro response to mitogens and antigens in elderly and post-cytotoxic patients can be modified by a new hypoxanthine derivative (PCF-39).

The in vitro immunomodulatory properties of the hypoxanthine derivative N alpha-5(1.6-dihidro-6-oxo-9-purinyl)pentyloxy/carbonyl -L-arginine (PCF-39) are described. Data obtained with PHA in vitro indicate that PCF-39 exhibits immunopharmacologic activity in elderly and post-cytotoxic patients, while showing no significant activity in normal donors. Antigen induced proliferation was unaffected by PCF-39, while PMN induced chemiluminescence was significantly enhanced. PCF-39 can be considered a new drug in the family of the hypoxanthine derivatives endowed with immunomdulatory properties.

Aged↗
PubMed1986

Epidemiology of bacteriuria in an elderly ambulatory population.

This study of bacteriuria in elderly (mean age 85 years, range 68 to 103) Jewish subjects of mostly middle and upper class attempted to determine disease prevalence, define the turnover in infected subjects, and assess the relation between functional status and infection. The prevalence of bacteriuria (midstream clean-catch method) was assessed in 373 women and 150 men. It was higher in women (18.2 percent) than in men (6.0 percent) (p less than 0.001) and was more common in functionally impaired nursing home residents (23.5 percent) than in apartment house dwellers (12.1 percent) (p less than 0.01). In longitudinal studies, 260 subjects (184 women and 76 men) had three urine culture surveys at six-month intervals. The cumulative percent infected on at least one survey was high (women 30.4 percent, men 10.5 percent). However, persistence of the same organism on all three surveys was surprisingly infrequent (women 6.0 percent, men 1.3 percent), and the turnover of infected and noninfected subjects was considerable. Persistence of bacteriuria on all three surveys was significantly more common in nursing home residents (13.9 percent) than in apartment house dwellers (3.1 percent) (p less than 0.01). Thus, bacteriuria is common in the elderly and appears related to functional status. However, the turnover of infected and noninfected subjects was high, and surprisingly, persistence was not found in most. The transient nature of bacteriuria in most provides support against the treatment of asymptomatic bacteriuria in the elderly.

Activities of Daily Living↗