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Biomedical subjects

P L Horn

Publications and source records attributed to P L Horn.

At least 19 recordsLinked to original sources
PubMed2004

CD94 expression and natural killer cell activity after acute exercise.

This study examined the effects of acute exercise on natural killer (NK) cell numbers, their expression of CD94 and cytotoxic capacity in triathletes over a 10-week training period. Nine highly trained male triathletes (age 25.9+/-4.1 yrs, VO2max 5.14+/-0.33 L.min(-1)) attended the laboratory on weeks 0, 2, 5 and 10 for incremental submaximal and maximal cycle ergometry. Peripheral blood was analysed for white blood cell counts, lymphocyte phenotype and cytolytic activity (51Cr release from K562 cells). Maximum oxygen consumption increased from week 2 (5.14+/-0.33 L.min(-1)) to week 10 (5.28+/-0.32 L.min(-1)). Resting NK cell numbers and their expression of CD94 were not altered over the 10-week study period. Natural killer cells expressing CD94+ were not differentially recruited into the circulation and cytolytic activity of exercise-recruited NKs did not differ from those present at rest. There was longitudinal stability (over the 10 weeks of the study) in CD94 expression on NK cells, exercise recruitment of CD94+ NK cells and cytolytic capacity of NK cells. The distribution and functional activity of NK cells are not markedly influenced by 10 weeks of training in competitive triathletes. Natural killer cytotoxic activity after exercise reflects numbers of NK cells and not a changed activation state of these cells per se.

Adaptation, Physiological↗
PubMed2002

Expression of CD94 and 56(bright) on natural killer lymphocytes - the influence of exercise.

This study was undertaken to determine the effects of acute intense exercise on the cell membrane-bound glycoprotein designated cluster of differentiation (CD) 94. This marker on natural killer (NK) lymphocytes contributes to control of cell function. CD94 was measured on natural killer lymphocytes from 11 adult (average 25 yrs), well-trained male subjects, (Vdot;O 2 peak mean, 5.01 L x min -1) before and immediately after a final, 4 min all-out, cycle ergometry test. Using flow cytometry, lymphocyte populations were distinguished as either having (CD94 +) or lacking (CD94 -) the cell marker. The absolute number of CD94 + and CD94 - natural killer cells increased with exercise but the mean fluorescence intensity (MFI) for CD94 decreased from pre 131, to post 117 (p = 0.01). The percentage of NK cells that were CD94 + did not change, but exercise did mobilise natural killer cells of greater MFI for the surface markers designated CD16/CD56 (pre 750 to post 1 050, p < 0.001). The latter suggests that some exercise-mobilised natural killer cells may have originated from the liver as CD56 +bright cells.

Adult↗
PubMed1999

Exercise-induced stimulation of K(+) transport in human erythrocytes.

The hypothesis was tested that exercise-induced changes in plasma composition stimulate unidirectional K(+) transport (J(in)K) in human red blood cells (RBCs). Ten men performed two 30-s high-intensity leg-cycling tests separated by 4 min of rest. Antecubital venous blood was sampled before exercise and at the end of the second exercise bout. RBCs were separated from true exercise plasma, (42)K was added to plasma, and RBC K(+) transport was studied in vitro at 37 degrees C. In the second part of the study, blood from nine healthy men studied in vitro at 37 degrees C was used to test the hypothesis that exercise-simulated (ES) plasma stimulates net K(+) transport and J(in)K (measured using (86)Rb) in human RBCs. The J(in)K of resting RBCs added to true exercise plasma was 1,574 +/- 200 (SE) micromol. h(-1). l(-1) vs. 1,236 +/- 256 micromol. h(-1). l(-1) in true resting plasma at 2 min (controls). In true exercise and ES plasma, J(in)K was increased through activation of the ouabain-sensitive Na(+)-K(+) pump and the bumetanide-sensitive Na(+)-K(+)-2Cl(-) cotransporter. Increases in plasma osmolality and K(+), H(+), and epinephrine concentrations independently and in combination stimulated K(+) transport into human RBCs. In a third series of experiments, in which ES plasma K(+) concentration was continuously measured during the first 5 min of incubation of RBCs, a 1.6 +/- 0.3 mmol/l decrease in plasma K(+) concentration occurred during the first 2 min. It is concluded that RBCs transport K(+) at elevated rates in response to exercise-induced changes in plasma composition.

Adult↗
PubMed1996

Pneumococcal antibody responses in elite swimmers.

The ability of elite swimmers to mount an antibody response to the pneumococcal vaccine, Pneumovax 23, was assessed at the end of an intensive 12-week training programme. Antibody titres to six pneumococcal polysaccharide types were measured in 20 elite swimmers (10 male, 10 female) aged 17-23 years and 19 sedentary age- and sex-matched students (eight male, 11 female) aged 18-23 years. Blood samples were tested 14 days apart to assess the magnitude of the antibody response and changes in serum immunoglobulin isotypes and IgG subclasses. There were no significant differences in any of the pneumococcal antibody responses to the Pneumovax between swimmers and controls, and no gender effect, either before or after vaccination. The clinically adequate response to the vaccine was greatest for the pneumococcal serotype 4, which was 97% for the total study population. There were no significant correlations between the magnitude of any of the pneumococcal antibody responses and (i) changes in the scores for the swimmers' international performance; (ii) infection rates in either swimmers or controls; (iii) any psychological variables, assessed by the Profile of Mood States (POMS) questionnaire for either swimmers or controls. Swimmers had significantly lower concentrations of serum IgG2 (P = 0.04) and IgG3 (P = 0.002) before pneumococcal vaccination. The swimmers had an increase in all immunoglobulin isotypes and IgG subclasses post-vaccination, suggesting a polyclonal response to the vaccine that was not observed in control subjects. The magnitude of the subclass responses after vaccination was significantly greater in swimmers compared with controls for IgG1 (P = 0.04), IgG3 (P = 0.04) and IgG4 (P = 0.01). The data indicated that elite swimmers undertaking an intensive training programme were capable of mounting an antibody response to pneumococcal antigens equivalent to that of age- and sex-matched sedentary control subjects, despite the swimmers having lower prevaccination levels of serum immunoglobulins.

Adolescent↗
PubMed1988

Risk of contralateral breast cancer. Associations with histologic, clinical, and therapeutic factors.

A case-control study was conducted to assess the risk factors associated with the development of a contralateral primary breast cancer among women who had had a first primary breast cancer. Hospital records were reviewed for 292 women with an incident contralateral breast cancer, diagnosed in one of eight hospitals between July 1, 1975 and December 31, 1983, and for a comparison group of 264 surviving unilateral breast cancer patients, previously diagnosed in the same hospitals. All subjects were identified through the records of the Connecticut Tumor Registry. Having an initial tumor containing lobular carcinoma was associated with an almost twofold increased risk of developing a contralateral cancer (aOR = 1.8; 95% CI: 1.0-3.5). Among those for whom a progesterone receptor assay was available, a positive assay was associated with an increased risk of a contralateral primary (aOR = 3.2; 95% CI: 1.0-9.5). AB blood type was also associated with an elevated risk, but this elevation was not statistically significant (aOR = 2.3; 95% CI: 0.7-7.7). Having received radiation treatment was not significantly associated with the risk of a contralateral primary (aOR = 0.9; 95% CI: 0.6-1.4), whereas chemotherapy treatment was associated with a significantly lowered risk (aOR = 0.3; 95% CI: 0.1-0.7). The association with chemotherapy appeared to be modified by body build (ROR = 1.5; 95% CI: 1.0-2.3 for a 2.5-unit differential in Quetelet's index).

Adult↗
PubMed1988

Dysplastic nevi in association with multiple primary melanoma.

Risk factors for multiple primary cutaneous melanoma were evaluated in a case-control study. Eight cases of multiple primary melanoma were matched on sex, age, and education to 24 first primary melanoma controls. Risk factors examined in the analysis included pigmentary characteristics, history of sun exposure, and nevi. The importance of histologically dysplastic nevi (DN) and clinically atypical nevi was of particular interest. Single-factor conditional logistic regression analysis showed that first primary melanoma patients with histological DN are at increased risk for a second primary (odds ratio, 6.2; 95% confidence interval, 1.2-33.4). Patients with two or more clinically atypical nevi also have elevated risk for a second primary (odds ratio, 8.8; 95% confidence interval, 1.0-80.7). Two-factor logistic models were used to evaluate the effect of histological DN while controlling singly for all other variables as potential confounders. Odds ratios for the association of histological DN varied from 6.1 to 10.4 when adjusting singly for pigmentary and sun exposure variables. In the two-factor model that included histological and clinical DN, both variables retained marginally significant statistical association with multiple primary melanoma. These results suggest that DN is a marker of increased risk for multiple primary melanoma and suggest that melanoma patients with evidence of DN should be followed closely for the development of additional primaries.

Dysplastic Nevus Syndrome↗
PubMed1988

Risk of contralateral breast cancer: associations with factors related to initial breast cancer.

A case-control study was conducted to assess the risk factors associated with the development of a contralateral primary breast cancer among women who had had a first primary breast cancer. Hospital records were reviewed for 292 women who had an incident contralateral breast cancer, diagnosed in one of eight Connecticut hospitals between July 1, 1975 and December 31, 1983, and for a comparison group of 264 surviving unilateral breast cancer patients previously diagnosed in the same hospitals. All subjects were identified through the records of the Connecticut Tumor Registry. A family history of breast cancer in any first- or second-degree relative was associated with an almost threefold increased risk of developing a contralateral cancer (adjusted odds ratio (OR) = 2.8, 95% confidence interval (CI) = 1.6-4.9). Further, this relation was modified by the time elapsed since the initial cancer diagnosis (ratio of OR = 1.9, 95% CI = 1.2-3.0 for a five-year differential in time since initial diagnosis). A delay of 10 years in first full-term pregnancy was associated with a 36% decrease in risk (adjusted OR = 0.6, 95% CI = 0.3-1.2); this estimate excluded the magnitude of increased risk usually observed in studies of initial breast cancer. A conceptual framework is presented for assessing the study findings in the context of previous studies that have examined the corresponding associations for initial primary breast cancers.

Adult↗
PubMed1987

Factors associated with the risk of second primary breast cancer: an analysis of data from the Connecticut Tumor Registry.

To examine further the epidemiology of contralateral primary breast cancer, a case-control analysis, utilizing information available from the Connecticut Tumor Registry, was conducted. Recent cases of second primary breast cancer were compared to control women who had survived a first breast cancer but had not developed a second. Three hundred and thirty eight incident cases of contralateral breast cancer diagnosed between 1979 and 1982 were identified and compared with an equal number of randomly selected controls and 336 controls frequency matched to the cases on the basis of age at initial cancer diagnosis and the calendar time elapsing since that diagnosis. Risk of second primary breast cancer was found to be significantly elevated among women whose initial cancer was lobular carcinoma and during the first year following diagnosis of the initial primary. Additionally, for women initially treated with radiotherapy, risk of a contralateral primary increased for 10-14 years following treatment, after which it declined. Among young women, having never married was protective whereas the opposite was found among older women. These findings and the methods used are discussed in the context of the epidemiology of both contralateral and initial breast primaries.

Adult↗
PubMed1987

Haemocytes secrete basement membrane components in embryonic locusts.

Several monoclonal antibodies raised against a glycoprotein-enriched fraction of adult muscle membranes of Locusta migratoria selectively stain particles within haemocytes and basement membrane in developing locust embryos. Haemocytes containing immunoreactive particles are found associated with areas where basement membrane is being laid down. The underlying ectoderm does not show immunoreactivity. We conclude that haemocytes contribute to basement membrane formation in embryonic locusts.

Animals↗
PubMed1984

A cloning assay for 6-thioguanine resistance provides evidence against certain somatic mutational theories of aging.

The frequencies of 6-thioguanine-resistant primary clones from the kidneys and skeletal muscles of aging male cohorts of two F1 hybrid strains of Mus musculus varied from 0.59 to 10.96 X 10(-5) and did not increase as a function of donor age (up to 40 months). Resistant clones were shown to be severely deficient in the activity of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8). These deficiencies presumably resulted from molecular alterations at this X-linked locus, including point mutations. No alterations of the X-chromosome were observed at the level of the light microscope. These results are inconsistent with predictions of the intrinsic mutagenesis and protein synthesis error catastrophe theories of aging. They do not rule out, however, somatic mutational theories that invoke comparatively large-scale chromosomal lesions, many of which would be likely to be lethal at the cellular level.

Adenine↗
PubMed1983

Intelligence and achievement of adult illiterates in a tutorial project: a preliminary analysis.

Reports the results of preliminary analyses of intelligence and achievement in an adult tutorial project. Incarcerated adult illiterates volunteered to participate in a peer tutoring program wherein they received 27 hours of structured tutoring. Significant achievement was demonstrated in all areas. Achievement and gains in achievement were analyzed in relation to Verbal, Performance, and Full Scale IQ scores using four sets of analyses. Significant correlations were noted between IQ scores and achievement, but not gains in achievement. Gains in achievement were not significantly different among Ss at different Verbal, Performance and Full Scale IQ levels, nor were gains in achievement different between Ss who had a significant Verbal-Performance discrepancy and those who did not. Gains in achievement were not significantly different across subgroups categorized according to both IQ level and Verbal-Performance discrepancy.

Achievement↗
PubMed1982

Achievement in reading, verbal language, listening comprehension and locus of control of adult illiterates in a volunteer tutorial project.

This study examined the effectiveness of specific psychoeducational tutoring methods on achievement in reading, verbal language, listening comprehension, and locus of control. Subjects were 76 youths and adults reading below fifth grade who volunteered to participate in an adult tutorial project. After the assessment of entry level achievement, subjects were tutored for 34 hr. by trained volunteers. Comparison of pretest and posttest scores with a control group that received no tutoring indicated that subjects made significant improvement in both general reading and discrete reading subskills. As gains in verbal language, listening comprehension, and locus of control were nonsignificant, further research is needed over a longer period of time or employing other standardized measures. Results support the use of well-trained volunteers in ameliorating problems of adult illiteracy.

Achievement↗
PubMed1981

Changes of aging parameters among rats on diets differing in fat quantity and quality.

Portion rats in a life span study were fed three diets which differed in the quantity and quality of total fats but were supplied in calorically equal amounts. In an attempt to comparing aging rates, we used a combination of tests involving different organ systems. This holistic approach to measuring aging included the assessment of changes in multifactorially regulated systems of glucose homeostasis and oxygen consumption; changes in tension responses of the extracellular protein collagen and accumulation of lipofuscin pigment in adrenal glands were also measured. Glucose tolerance and oxygen consumption changed in age largely as expected and there were no consistent differences between the aging rates for the three different diets. Accumulation of the intracellular aging pigment lipofuscin and the breaking time of tail tendons also showed the expected increases with increasing age. Dietary differences were noted with the 2-year-old rats consuming the low fat stock diet showing the greatest accumulation of lipofuscin and the longest tail tendon breaking times.

Adrenal Glands↗
PubMed1979

Effects of life span feeding of ruminant-derived human diets to rats.

A freeze-dried human diet, based on linoleic acid-enriched food stuffs derived from ruminants, was evaluated and compared with a similarly-prepared diet based on conventional ruminant-derived foodstuffs, using Porton rats in a whole-of-life study. A cereal-based stock diet was used for comparison. Serum biochemical and histopathological examinations were carried out at 0.25, 1.1 and 2.1 years of age and other rats were left until they died of natural causes. Although some diet-specific biochemical differences were noted, triglyceride and cholesterol levels showed changes which were more age-specific than diet-specific. Longevity did not seem to be influenced by quantity or quality of dietary fat. The most common cause of death was a bronchopneumonia at about 2 years of age. Dietary fat also did not affect incidence of tumors. The most common tumor was a pituitary adenoma which occurred most often in females. Only minor causes of death were specific to diet with waxy intra-cardial plaques occurring in less than 5% of rats fed both of the high-fat diets and severe systemic hypertension occurring in rats fed the low-fat stock diet at the same frequency. No deleterious changes were noted that were unique to the linoleic acid-enriched diet.

Animals↗