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Biomedical subjects

G A Harrison

Publications and source records attributed to G A Harrison.

At least 73 records · Page 4Linked to original sources
PubMed1991

Geographic distributions of within-population variability in blood pressure.

Data on mean blood pressure with standard deviation were extracted from the medical and anthropologic literature for as many populations as possible. The populations were classified as traditional, transitional, or modern. Both mean and within-population variability were found to be higher in more modern populations, confirming the prediction that variability of a character of low heritability is higher in an adverse environment, where it is more difficult to maintain homeostasis. In addition, variability increases with age, indicating a breakdown in homeostasis with aging. On average, males had higher diastolic blood pressure than females, and on average, females had greater variability in systolic blood pressure than males. There was a highly significant negative relationship between latitude and within-population variability in blood pressure.

Adult↗
PubMed1990

Pseudomonas aeruginosa orbital cellulitis in four neutropenic patients.

Four neutropenic patients on a haematology ward developed orbital cellulitis due to different strains of Pseudomonas aeruginosa over a 7-month period. Investigation of patients and the ward environment revealed two P. aeruginosa isolates indistinguishable from the infecting strains in a plastic washing bowl and a sink in a single cubicle respectively. These items were unlikely to have been the sources of the infecting strains but were a potential cross infection hazard. Treatment of orbital cellulitis is discussed briefly.

Adolescent↗
PubMed1990

Components of growth variation in human stature.

Traditional methods of estimating the heritability of a trait such as height utilize a single observation of the variance. This, however, provides little insight into the way in which the variance is generated. In this paper, we propose that repeat measurements of height over a period of childhood growth can be used to estimate different components of the variation in height increment. By height increment we mean the successively longer increments computed relative to a common initial height. Models are developed which indicate that the genetic component of the variance accumulates as a quadratic function of the mean, while the environmental component accumulates until it reaches a constant. This 'homeostatic constant' represents an equilibrium between the input of environmentally induced variation and its removal through homeostasis. Large constants are indicative of poor environments and poor homeostatic responses. The constant therefore provides a measure of the adaptive status of the children at the level of the population. The models are here applied to growth data collected on Hong Kong infants. The resulting estimate of the genetic component of the variance is 0.0044 cm2 per cm2 of mean height increment. This is somewhat higher than expectation but easily accounted for through the effects of environmental stratification on the variance. The homeostatic constant is estimated to be approximately 1.2 cm2. This is the first such estimate of its kind.

Analysis of Variance↗
PubMed1990

Baseline activated coagulation time should be measured after surgical incision.

The activated coagulation time (ACT) is widely used to guide heparin and protamine dosing during cardiac surgery. A common protocol involves establishing a baseline ACT before administering heparin, then using this ACT as a target value for assessing the adequacy of heparin neutralization after cardiopulmonary bypass. Results vary in previous comparisons of baseline ACT to postprotamine ACT, with some showing postprotamine ACT significantly below baseline values. The present study examined ACTs at three possible baseline intervals in 68 patients at two institutions: (a) before anesthetic induction; (b) after anesthetic induction; and (c) after sternotomy. Baseline ACT decreased significantly with anesthesia and surgery. The poststernotomy baseline ACT best matched the postprotamine ACT. It appears likely that surgery induces a thromboplastic response that decreases ACT. Establishing baseline ACT before anesthetic induction would predispose to false diagnoses of adequate protamine neutralization after cardiopulmonary bypass, because ACT is relatively insensitive to low concentrations of unneutralized heparin. Baseline ACTs should therefore be measured after surgical incision.

Aged↗
PubMed1990

Cross-infection and diversity of Candida albicans strain carriage in patients and nursing staff on an intensive care unit.

Colonization of patients and nursing staff on an intensive care unit by Candida albicans was studied over a 4-month period. Multiple swabs and samples were taken from patients and their nurses on 12 occasions during the study period. During this study there were no obvious clinically relevant candidal infections. Patients yielded C. albicans from at least one body site on 68%, and nurses on 57% of occasions. All isolates of C. albicans were further characterized by both morphotyping and resistotyping. All patients but one were colonized by a single strain throughout their stay on the unit, whereas nurses were often colonized by more than one strain type. Strains isolated from nurses' hands were all indistinguishable from strains colonizing the patient under their care, whilst strains isolated from nurses' mouths were usually distinct from their patients'. The probability that a C. albicans culture positive nurse carried an indistinguishable strain from that of her positive patient was p = 0.632, compared with p = 0.325 that a randomly chosen positive nurse would carry a strain indistinguishable from that of a randomly chosen positive patient. Diversity in patients' strains was low (D = 0.667) compared with nurses' strains (D = 0.778). These results suggest that cross-infection by C. albicans is a common occurrence on intensive care units. The reason outbreaks of candidal disease are not more common may be related to differences in virulence of the strains.

Candida albicans↗
PubMed1989

Open cardiac compression in the postoperative cardiac intensive care unit.

Thirty-nine patients required heroic resuscitative measures for sudden hypotension and cardiac arrest in the first 72 hours following cardiac surgery between January 1, 1984 and May 31, 1988. Emergency sternotomy with open cardiac compression was performed in twenty-four of these patients when external cardiac compression failed. These were categorised as Group A. Group B comprised the fifteen patients in whom resuscitation was entirely by means of external compression and adjuvant measures. Survival with NYHA Functional Class I and II status was noted in 75% of patients in Group A, compared with 20% in Group B (P less than 0.002). Emergency sternotomy with open cardiac compression is an effective way of resuscitating patients in the intensive care unit in the first few days following open heart surgery.

Cardiac Surgical Procedures↗
PubMed1988

Genetic and morphometric variances in three human populations.

Data from three human populations were used to investigate the putative relationship between genetic and morphological variances. There was no evidence to support the hypothesis that individuals heterozygous at a small number of marker loci are more often near the mean for anthropometric characters than are homozygotes. In one population (Otmoor), apparent support for the hypothesis was due to the confounding factors of correlations between anthropometric traits and population subdivision. It is unlikely that such relationships can be detected by intrapopulation comparisons because of the low association between measured and total heterozygosity.

Adult↗
PubMed1988

Influence of dietary cation-anion balance on milk, blood, urine, and rumen fluid in lactating dairy cattle.

Twelve lactating Holstein cows were blocked according to age and milk production into groups of three cows and assigned to three 4 x 4 Latin squares in a split-plot design with subtreatments. Treatments on each square were four diets formulated to provide -10, 0, +10, or +20 meq/Na + K) -Cl/100 g diet DM. The four balances were achieved on squares 1, 2, and 3 by manipulating Na, K, and Cl, respectively. Actual milk yield was 8.6% higher on +20 than -10 averaged across the three squares. Blood pH and bicarbonate increased linearly with dietary cation-anion balance. Rumen pH increased linearly with dietary cation-anion balance, but fermentation patterns were largely unaffected. Urine pH increased linearly and quadratically with increasing dietary cation-anion balance. Square times balance response differences proved nonsignificant for all parameters except blood bicarbonate and rumen isovalerate, indicating responses could be attributed to the dietary cation-anion balance itself rather than to the effects of a single ion. Regulation of dietary cation-anion balance may become a useful tool for improving the performance of lactating dairy cattle.

Animals↗
PubMed1988

Efficacy of simulated, slow release sodium bicarbonate in stabilizing ruminal milieu and acid-base status in lactating dairy cattle.

Four primiparous, ruminally fistulated, lactating Holstein cows were assigned to a 4 X 4 Latin square to study the effects of NaHCO3 infusion time on ruminal milieu and systemic acid-base balance. Sodium bicarbonate, approximating .8% of diet DM, was mixed with water and infused into the rumen for 1, 2, 4, or 6 h postfeeding to simulate different timed-release rates of NaHCO3. All cows received a corn silage and concentrate diet mixed at a 40:60 ratio on a DM basis and fed in amounts that were consumed within 1 h. Ruminal fluid, blood, and urine samples were collected at 0, 1, 2, 3, 4, 5, 6, 8, and 10 h postfeeding. Length of infusion time did not alter ruminal, blood, or urine pH, but all three variables were affected by sampling time, with the 5, 1, and 3-h sampling intervals yielding the lowest values for the three measurements, respectively. Ruminal VFA molar percentages of acetate, propionate, butyrate, isovalerate, and valerate were not influenced by infusion interval but were all different due to time of sampling. Blood pCO2 and HCO3 were affected by sampling time but not by infusion interval. With the exception of blood HCO3, all treatment X sampling time interactions were nonsignificant. It appears that timed release of NaHCO3 does not alter ruminal function or acid-base balance.

Acid-Base Equilibrium↗
PubMed1988

Influence of addition of yeast culture supplement to diets of lactating cows on ruminal fermentation and microbial populations.

Six ruminally fistulated Holstein cows were utilized in a randomized block design to examine effects of yeast culture supplement on ruminal metabolism and apparent digestibility. Cows were fed a diet of 40% corn silage and 60% concentrate (DM basis). Treatments were control (supplement without yeast cells) and yeast culture supplement. Treatment periods were 6 wk. Ruminal pH, ammonia, molar proportions of acetate and isovalerate, and acetate: propionate ratio were lower and molar proportions of propionate and valerate higher in cows receiving yeast. The concentration of anaerobic bacteria tended to be higher and cellulolytic bacteria concentrations were greater in cows fed yeast than in cows receiving control diet. Supplemental yeast did not affect molar proportions of isobutyrate or butyrate, total VFA, or viable yeast concentrations in ruminal fluid. Ruminal liquid dilution rate and total tract apparent digestibilities were not different between treatments. Rate of disappearance of cellulose in vitro was lower in cows receiving yeast. Less variation in ammonia concentrations and microbial numbers suggest that ruminal fermentation was more stable in cows receiving yeast culture supplement.

Animals↗
PubMed1987

24-h catecholamine excretion: relationships with age and weight.

24-hour urines were obtained from groups of volunteer subjects recruited from populations in the UK, USA, Nigeria and the South Pacific. Urines were collected during the course of normal daily activities. HPLC/electrochemical detection was used to measure concentrations of adrenaline and noradrenaline in each urine. Calculated 24-h output of catecholamines was tested for significant linear regression relationships with age, weight and 24-h urine volume in each population. Noradrenaline excretion tended to be positively related to age and to body wt. Adrenaline excretion tended to show little or no relationship with either age or body wt. Relationships based on catecholamine excretion/U creatinine were notably different to those based on absolute catecholamine excretion. Differences were observed in the nature and strength of the relationships in the different populations, indicating the likely importance of interactions with other factors.

Adult↗
PubMed1987

Variation in lifestyle characteristics and catecholamine excretion rates among young Western Samoan men.

Comparisons of 13 lifestyle characteristics and the rates of urinary catecholamine excretion during typical morning activity are examined among four groups of young Samoan men in Western Samoa. The groups include 28 manual laborers, 33 sedentary workers, and 31 college students from the urban area of Apia, and 31 rural agriculturalists. Associations between the lifestyle variables and catecholamine excretion rates are also investigated in the total sample (N = 123) using correlations and multiple stepwise regression techniques. Results of the lifestyle characteristic comparisons show that the villagers have greater life satisfaction, emotional stability, agreement with Samoan customs, and familial responsibility (P less than 0.05). The catecholamine comparisons show that the villagers have lower rates of epinephrine and norepinephrine excretion than any of the Apia groups (P less than 0.05 and P less than 0.005 respectively). The regressions indicate that diet, activity, day of specimen collection and the overall lifestyle and ecological differences between the village and Apia are associated with 25 and 31% of the variation in the rates of epinephrine and norepinephrine excretion respectively. These results suggest that both psychological and habitual behavioral differences contribute to the catecholamine variation of the men in this study, and that these differences are related to the degree of participation in Western lifestyles.

Adult↗