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Biomedical subjects

H D Johnson

Publications and source records attributed to H D Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1980

A trial of meptazinol for the relief of pain after abdominal surgery.

Meptazinol is an opioid drug having mixed agonist-antagonist properties. Chemically it is a hexahydroazepine derivative. It has been used to provide postoperative analgesia for patients undergoing abdominal surgery but only in single dose studies. The drug is of particular interest in that the clinical impression of minimal ventilatory depression has been confirmed, 60 mg meptazinol showing less ventilatory depression than 10 mg of morphine. To test its efficacy in patients undergoing abdominal surgery and to assess the incidence of side effects, an open study was undertaken in 43 patients.

Abdomen↗
PubMed1980

High perfusion pressure damages the sieving ability of sinusoidal endothelium in rat livers.

Fenestrated endothelium lining liver sinusoids forms an ultrastructural sieve between blood and hepatocytes which at physiological perfusion pressures has previously been shown to shield hepatocytes from large triglyceride-rich chylomicrons. In the study reported in this paper, enlargement of endothelial fenestrae at high perfusion pressures has been confirmed and a concurrent increase in trapping of large chylomicrons by the liver noted. These findings suggest the importance of employing physiological perfusion pressures in studies designed to examine hepatic lipoprotein metabolism and also suggest a possible mechanism in the pathogenesis of fatty change seen in the "nutmeg" liver of chronic venous congestion.

Animals↗
PubMed1979

High-performance liquid chromatographic analysis of biogenic amines in biological materials as o-phthalaldehyde derivatives.

A remarkably sensitive, simple and selective reversed-phase high-performance liquid chromatographic (HPLC) method has been developed, allowing, for the first time, the direct measurement of histamine, norepinephrine, octopamine, normetanephrine, dopamine, serotonin and tyramine in a single sample of plasma (2 ml), tissue (0.2 g), or urine. The biogenic amines were modified by pre-column derivatization with o-phthalaldehyde which stabilizes the molecules, aids in extraction, and improves HPLC detection at the nanogram level. To minimize losses during the sampling procedure a careful collection procedure was designed. We developed a simple sample cleanup in which the samples were thawed, neutralized with KOH, immediately derivatized, extracted into ethyl acetate (EtOAc) and then chromatographed by HPLC. The derivatives were stable in EtOAc for more then 24 h. Interfering amino acids were removed from the EtOAc by partitioning twice with Na2HPO4 buffer (pH 10.0). Complete separation was achieved in ca. 60--90 min on a muBondapak phenyl column using a stepwise gradient of acetonitrile and/or methanol-phosphate buffer (pH 5.1). A variable wavelength fluorometer with a 5-microliter flow-cell was used (excitation 340 nm; emission 480 nm). Linearity ranged from 200 pg to 50 ng onto the column. Precision (R.S.D.) for retention times was 1% and for derivatization and injection 2.5%. Recoveries of the seven biogenic amines from plasma spiked with 25 ng/ml averaged 70%, with a relative standard deviation of 6%. Separation studies were also done using a muBondapak C18 column. The effects of various eluents are presented. Gas-liquid chromatography was also investigated but lacked the sensitivity achieved by HPLC. The HPLC method is used routinely for the determination of biogenic amines in plasma from pigs with malignant hyperthemia and thermally stressed bovine. Significant differences in levels of biogenic amines were noted between stressed and non-stressed animals. Data on rat brain tissue samples were compared with the trihydroxyindole method and canine heart tissue was analyzed for ventricular norepinephrine and dopamine. Application of the method to urine from normal persons and a patient with a brain tumor has been demonstrated.

Animals↗
PubMed1978

Effect of adrenocorticotropic hormone on plasma glucocorticoids and antidiuretic hormone of cattle exposed to 20 and 33 C.

Four open, dry Holstein cows in the University of Missouri Climatic Laboratory were used to study the effect of adrenocorticotropic hormone administration on glucocorticoids and antidiuretic hormone of plasma in two reversal trials at thermoneutral (20 C, 50% relative humidity) and heat (33 C, 50% relative humidity) conditions. Average glucocorticoids (saline versus adrenocorticotropic hormone) at thermoneutral were 8.3 and 41.2 ng/ml while values for heat were 6.2 and 40.4 ng/ml. The effect of heat on glucocorticoids of plasma was not significant. Injection of adrenocorticotropic hormone under thermoneutrality and heat caused a marked increase in antidiuretic hormone within 5 min which lasted to 120 min. At thermoneutral average antidiuretic hormone levels (saline versus adrenocorticotropic hormone) were .5 and 1.9 pg/ml while values for heat were 1.8 and 3.6 pg/ml. Antidiuretic hormone concentrations under heat were higher than thermoneutral in cows injected with saline and andrenocorticotropic hormone. The fast response of antidiuretic hormone of plasma to exogenous adrenocorticotropic hormone suggests that adrenocorticotropic hormone might act directly at higher levels of the central nervous system causing release of antidiuretic hormone.

Adrenocorticotropic Hormone↗
PubMed1978

Determination of corticosterone concentration in plasma of turkeys using raioimmunoassay.

A method of determining corticosterone concentration in turkey plasma was developed using radioimmunoassay. Compared to fluorometric analysis and competitive protein-binding radioassay, this method had the following advantages: 1) results were consistent, 2) the method was simple and rapid to perform, 3) only 20 lambda of plasma was required, 4) all procedures were performed using the same tube except for counting, and 5) unknown and standard samples were treated identically. The coefficient of variation with the 5 ng/ml standard sample between 14 sets of assays was 12.6% and the average coefficient of variation within duplicate assays of unknown samples randomly selected from each of the 14 series was 4%. Using this method, there was an increase in the average plasma corticosterone concentration in all groups of inoculated turkeys one day after inoculation of Pasteurella multocida which was significantly (P less than .05) greater than that of the noninoculated groups.

Animals↗
PubMed1978

High-performance liquid-chromatographic separation and fluorescence measurement of biogenic amines in plasma, urine, and tissue.

We describe a high-performance liquid-chromatographic method for measuring histamine, norepinephrine, octopamine, normetanephrine, dopamine, serotonin, and tyramine in plasma (2 ml), brain (0.2 g), or urine. These amines are modifed by pre-column derivatization with o-phthalaldehyde, which stabilizes the molecules, facilitates extraction, and improves detection of nanogram amounts. Before separation, samples were neutralized with KOH and immediately derivatized and extracted into ethyl acetate, in which derivatives were stable for longer than 24 h. Interfering amino acids were removed from ethyl acetate by partitioning twice with Na2HPO4 buffer (pH 10.0). Separation was complete in about 90 min on a ""mu Bondapak/phenyl" column, with which a stepwise gradient of methanol/phosphate buffer (pH 5.1) was used. A variable-wavelength fluorometer was used (exciting wavelength, 340 nm; emission wavelength, 480 nm). Amount and response were linearly related from 1 to 200 pmol. Precision (CV) for retention times was 1%, for derivatization and injection 2.5%. Analytical recoveries of the seven amines from 2 ml of plasma fortified with 200 pmol averaged 65% (CV approximately 8%). Data on rat-brain tissue samples are compared with results by the trihydroxyindole method. Application of the method to urine from normal persons and a patient with a brain tumor is demonstrated.

Biogenic Amines↗
PubMed1976

Effect of horn flies on vanilmandelic acid excretion of dairy cattle.

This study measured a physiological effect of known horn fly (Haematoba irritans L.) population densities on dairy cattle. Urinary excretion of the catecholamine metabolite, 3-methoxy-4-hydroxy mandelic acid, was an indicator of physiological response to the parasites. Six lactating Holstein cows were acclimated to the test room prior to a 3-wk control at 21 C. Animals were then exposed to approximately 500 horn flies per cow per day for 4 wk. On days 1 and 21 of exposure, two urine samples were obtained from each cow. Mean urinary values for cows were 13.3 +/- 3.1 mug/100 ml in the control period and 18.9 +/- 3.4 mug/100 ml during fly exposure. We believe that increased vanilmandelic acid reflects an increase in standing time and nervous activity associated with the physical disturbance due to the biting of the flies.

Animals↗
PubMed1976

Effects of environmental and other stressors on blood hormone patterns in lactating animals.

Recent data on various environmental stressors and blood hormone patterns are presented for lactating cattle. Known stressor effects of such factors as environmental temperature, air pollution, and noise on the plasma thyroxine, growth hormone, cortisol, prolactin, progesterone, luteinzing hormone, epinephrine, and norepinephrine of lactating cattle are discussed. Information on stressor effects is lacking on glucagon, insulin, vasopressin, calcitonin, oxytocin, thyrotrophic hormone, follicle stimulating hormone, melatonin, parathyroid hormone, and estrogens in the lactating cow. The importance of evaluating both the effect of environmental stressor and of production or lactation intensity is emphasized in the overall interpretation of changes in hormone of plasma. The short and long term environmental heat effects on thyroxine, cortisol, and growth hormone are clear with initial increased due to acute stressors and a decline of amounts in plasma after prolonged exposure to stressors. The relationship of amounts in plasma of these hormones to milk production appears to be related directly for cortisol, growth hormone, and prolactin with an inverse relationship with thyroxine. Epinephrine and norepinephrine seem to be elevated with prolonged environmental heat stress. However, the influence of intensity of lactation has not been measured. Hormones in plasma as they relate to stressor effects and milk production are important as potential indicators of the physiological state of a cow and reflect the physiological compensations a cow undergoes at various lactation intensities and/or stress exposure.

Adrenal Cortex Hormones↗
PubMed1975

Thyroid activity in desert rodents: a mechanism for lowered metabolic rate.

Desert rodents are known to exhibit three different levels of metabolic rate (MR) when related to the mouse-elephant equation. Several species have an MR that is either higher, lower, or similar to that predicted from the equation. The role of thyroid function as a possible mechanism associated with these different MR was examined in 12 species of desert rodents, representing 3 families and 3 different biotic communities. Thyroidal 131I uptake, ratio of neck-to-thigh 131I counts per minute (N/T ratio), thyroxine secretion rate (TSR), and plasma protein binding sites were used as indices of thyroid function. When relating thyroid function to MR, TSR was found to be low in species exhibiting low MR and vice versa. Other thyroid indices did not show a consistent relationship to MR. Also, TSR seems to be related to ecologic distribution: low TSR in desert areas and high TSR in arid woodland and montane forest areas. TSR was found to be correlated to body weight. The low TSR associated with reduced MR represents a useful adaptive mechanism for survival of desert rodents under their natural stressful environment.

Animals↗
PubMed1975

Effects of moderate heat and milk yield on plasma thyroxine in cattle.

The effects of milk yield (lactational intensity) and short (18 h) moderate heat exposure (30 C) on plasma thyroxine were studies in spring (March) and fall (October) in the University of Missouri dairy herd. Spring and fall thyroxine did not differ at thermoneutral temperature of 15 C. The relatively short moderate heat exposure had no effect within production groups either in the spring or fall sampling. As stage of lactation progressed, thyroxine also increased. The effect of stage of gestation was an elevation in the first trimester (compared to nonbred) that progressed into the second and third trimesters. In both spring and fall (15 C), the high production group (adjusted and unadjusted) had lower plasma thyroxine compared with middle and low production groups, while no difference in adjusted means was significant between middle and low production groups. Correlations were --.51 between plasma thyroxine and lactational intensity in both spring and fall. The short exposure to moderately high environmental temperature intensified the relationship of lowered plasma thyroxine in hibh producing cows, and thyroxine was negatively correlated (--.63 and --.64) with lactational intensity. Because total plasma thyroxine is inversely related to lactational intensity, studies are warranted to quantitate free hormonal concentrations and utilization by dairy cattle with varying productivity.

Animals↗