Search PubMed⌕ Search

Biomedical subjects

G L Robertson

Publications and source records attributed to G L Robertson.

121 records · Page 7Linked to original sources
PubMed1973

The role of blood osmolality and volume in regulating vasopressin secretion in the rat.

A sensitive and specific radioimmunoassay for plasma arginine vasopressin (AVP) has been used to study the effects of blood osmolality and volume in regulating AVP secretion in unanesthetized rats. Under basal conditions, plasma AVP and osmolality were relatively constant, averaging 2.3+/-0.9 (SD) pg/ml and 294+/-1.4 mosmol/kg, respectively. Fluid restriction, which increased osmolality and decreased volume, resulted in a progressive rise in plasma AVP to about 10 times basal levels after 96 h. A 2-3-fold increase in plasma AVP occurred as early as 12 h, when osmolality and volume had each changed by less than 2%. Intraperitoneal injections of hypertonic saline, which had no effect on blood volume, also produced a rise in plasma AVP that was linearly correlated with the rise in osmolality (r > 0.9) and quantitatively similar to that found during fluid restriction (plasma AVP increased 2-4-fold with each 1% increase in osmolality). Intraperitoneal injection of polyethylene glycol, which decreased blood volume without altering osmolality, also increased plasma AVP but this response followed an exponential pattern and did not become significant until volume had decreased by 8% or more. At these levels of hypovolemia, the osmoregulatory system continued to function but showed a lower threshold and increase sensitivity to osmotic stimulation. We conclude that AVP secretion is regulated principally by blood osmolality but that the responsiveness of this mechanism may be significantly altered by modest changes in blood volume.

Animals↗
PubMed1970

Immunoassay of plasma vasopressin in man.

A radioimmunoassay for arginine vasopressin has been developed that is sensitive to the hormone at 1 pg/ml. When plasma was filtered on G-25 Sephadex, immunoreactivity was detected in three regions. Endogenous arginine vasopressin was the third and smallest of the peaks and was recovered just after the salt. By combining gel filtration with immunoassay, we have made precise measurements of arginine vasopressin in a few milliliters of plasma.

Adult↗
PubMed1967

The influence of morphology on prognosis in acute leukemia.

The presence of definite cytoplasmic granulation in at least some of the malignant cells was used as the sole criterion to separate 156 patients with acute leukemia into two groups: 110 with myeloblastic (AML), and 46 with lymphoblastic or stem cell leukemia (ALL). The median survival from the onset of symptoms in patients with AML was 20 weeks, and those with ALL 37 weeks. The difference in survival in these two groups is much greater for patients under the age of 25 than for those over the age of 25.

Adolescent↗
PubMed1966

Ocular manifestations of hemoglobin S-C disease.

Three patients with hemoglobin S-C disease, all with ocular lesions, were studied and contrasted with four other patients who had predominantly either hemoglobin S or C but no ocular lesions. Attention is drawn to the diagnostic value of hemoglobin electrophoresis in such cases. With this technique a diagnosis of hemoglobin S-C disease was made in a patient previously thought to the "Eales' disease"; one sister was found to have asymptomatic hemoglobin S-C disease and unsuspected early ocular lesions. The number of persons in Canada with hemoglobinopathies is increasing. Awareness of an association between abnormal hemoglobins and ocular disease may lead to the recognition of an unsuspected blood disorder or of an unsuspected retinopathy.

Adrenal Cortex Hormones↗
PubMedDate not supplied

A new Met-enkephalin analogue suppresses plasma vasopressin in man.

Metkephamid acetate, a newly synthetized analogue of methionine enkephalin, suppressed plasma vasopressin levels from 2.4 pg/ml to 0.8 pg/ml after intramuscular administration to 4 normal human volunteers. This suppression occurred in the absence of significant changes in either plasma osmolality or blood pressure. Thus, metkephamid acetate, like many other opiates which bind to the mu subtype of opiate receptors, has a direct suppressive effect on plasma vasopressin levels.

Blood Glucose↗
PubMedDate not supplied

Diurnal variation in water homeostasis among schizophrenic patients subject to water intoxication.

Among seven schizophrenic patients subject to water intoxication (six men and one woman, mean age 39.1 +/- 6.9 years), we measured serum sodium, plasma arginine vasopressin, and urine osmolality at 7 a.m. and 4 p.m. on eight consecutive Thursdays. On the days of greatest diurnal change in serum sodium, the 7 a.m. serum sodium was 141.1 +/- 1.8 mEq/l and the 4 p.m. value was 129.9 +/- 3.2 mEq/l. Plasma vasopressin also tended to be lower at 4 p.m. but, in many cases, was inadequately suppressed for the level of hyponatremia. The urine was dilute at both 7 a.m. and 4 p.m. and mean urine osmolality did not differ at the two times. In three patients, urine osmolality was consistently subnormal relative to plasma vasopressin at both 7 a.m. and 4 p.m. This abnormality was consistent with nephrogenic diabetes insipidus secondary to lithium and, possibly, phenytoin which the patients received to protect them against hyponatremia. We conclude that the combination of polydipsia and abnormal osmoregulation of vasopressin secretion contributes importantly to the afternoon hyponatremia found in schizophrenic patients subject to water intoxication.

Adult↗
PubMedDate not supplied

Spatial distributions of arsenic exposure and mining communities from NHEXAS Arizona. National Human Exposure Assessment Survey.

Within the context of the National Human Exposure Assessment Survey (NHEXAS), metals were evaluated in the air, soil, dust, water, food, beverages, and urine of a single respondent. Potential doses were calculated for five metals including arsenic. In this paper, we seek to validate the potential dose calculations through spatial analysis of the data. Others report elevated arsenic concentrations in biological and environmental samples from residents of mining towns, particularly Ajo, Arizona. These reports led us to expect potential arsenic doses above the 90th percentile of the NHEXAS exposure distribution to be from residents of mining communities. Arsenic dose was calculated using media concentrations, time activity patterns, and published exposure factors. Of the 179 homes evaluated, 54 were in mining communities; 11 of these were considered separately for reasons of population bias. Of the 17 homes with the greatest potential arsenic doses, almost half (47%) were in mining communities. We evaluated the potential doses by media from nonmining and mining areas using the nonparametric Mann-Whitney U test. Statistically significant (p = 0.05) differences were found between mining (n = 43) and nonmining sites (n = 122) for total exposure and for each of the following media: house dust, yard soil, outdoor air, beverage consumed, and water consumed. No differences were found in either food or indoor air of mining and nonmining areas. We eliminated outliers and repeated the test for all media; significance increased. Dietary, organic arsenic from fish consumption contributed to elevated arsenic exposure among people from nonmining communities and acted as an initial confounder. When controlling for fish consumption, we were able to validate our potential dose model using arsenic, particularly in Ajo. Further, we identified three mining communities lacking elevated arsenic exposure. Additional work is needed speciating the arsenic and evaluating health risks. The utilization of Geographic Information System facilitated spatial this project and paves the way for more sophisticated future spatial analyses.

Adult↗
PubMedDate not supplied

The National Human Exposure Assessment Survey (NHEXAS) study in Arizona--introduction and preliminary results.

The objective of the National Human Exposure Assessment Survey (NHEXAS) in Arizona is to determine the multimedia distribution of total human exposure to environmental pollutants in the classes of metals, pesticides, and volatile organic compounds (VOCs) for the population of Arizona. This was accomplished by studying a probability-based sample of the total population in Arizona with a nested design for the different stages of sampling (954 Stage I, 505 Stage II, and 179 Stage III participants). This report compares the study population demographics with those from the U.S. Census and provides preliminary data on the distributions of the example pollutant for each class, lead for metals, chlorpyrifos for pesticides, and benzene for metals. The probability-based sample age and gender demographics compare reasonably well with the Census data (1990 Census and 1996 Census Estimate). The race/ethnicity compared less well with 21% Hispanics in the 1996 Census Estimate and 42% Hispanics in the entire NHEXAS-Arizona sample and 30% Hispanics as Stage III participants for this study. The chemical analyses of the various media (yard soil, foundation soil, house dust, indoor air, outdoor air, drinking water, food, and beverage) show generally low levels of the representative pollutants. The 50th percentiles of the distributions are generally near or below the analytical detection limits, and applicable Federal action limits were rarely exceeded.

Adolescent↗