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Biomedical subjects

D G Butler

Publications and source records attributed to D G Butler.

At least 55 records · Page 3Linked to original sources
PubMed1983

Adrenalectomy inhibits noradrenergic, adrenergic, and vasopressor responses to angiotensin II in the Pekin duck (Anas platyrhynchos).

The iv injection of Asp1, Val5-angiotensin II(AII) was followed by increases in arterial plasma norepinephrine (NE) and epinephrine (E) concentrations and elevation of arterial blood pressure in the anesthetized Pekin duck. AII injection did not affect the concentration of unconjugated dopamine in arterial plasma. Adrenalectomy inhibited the increases in plasma NE and E concentrations elicited by AII. Pressor responses to AII also were diminished after adrenalectomy, whereas pressor responses to exogenous NE and tyramine were not measurably affected. The alpha-adrenergic blocking drug phenoxybenzamine diminished the pressor effect of AII in both shamoperated and adrenalectomized ducks. The blockade of alpha-adrenergic receptors by phenoxybenzamine was incomplete, since pressor responses to exogenous NE were lessened by not abolished. We conclude from these experiments that AII increases arterial blood pressure in the Pekin duck by mobilizing NE and E from both adrenal and extraadrenal stores. It remains unknown whether the residual pressor response to AII in phenoxybenzamine-treated, adrenalectomized ducks involves an alpha-adrenergic mechanism.

Adrenalectomy↗
PubMed1983

6-Hydroxydopamine treatment diminishes noradrenergic and pressor responses to angiotensin II in adrenalectomized ducks.

The extent to which the vasopressor action of angiotensin II (AII) in birds depends upon the sympathetic nervous system in not known. Therefore, we have tested whether the sympathetic neurotransmitter norepinephrine (NE) mediates the residual vasopressor response to AII in adrenalectomized ducks (Anas platyrhynchos). Treatment with 6-hydroxydopamine (6-OHDA) inhibited by up to 100% the pressor effect of exogenous AII in anesthetized adrenalectomized ducks. After high doses of AII, a transient drop in blood pressure (BP) often preceded or supplanted the pressor response. Systolic BP responses to injections of tyramine also were decreased by 6-OHDA, but responses to NE were increased (diastolic BP) or not affected significantly (systolic BP). Inhibition with SQ20881 of converting enzyme, to decrease endogenous production of AII, reduced pressor responses to AI, but did not affect either baseline BP or responses to AII. Thus, the diminished responsiveness to AII in these catecholamine-depleted ducks was not due to competition from endogeneous AII. Furthermore, the increases in plasma NE and E concentrations that normally follow AII injection were abolished by adrenalectomy and 6-OHDA treatment. The coincident extinction of both cathecholamine and vasopressor responses comprises new evidence that AII raises BP in the Pekin duck by stimulating the sympathetic nervous system. The vasopressor response is mediated by extraadrenal as well as adrenal sources of NE.

Adrenalectomy↗
PubMed1983

A bovine virus diarrhea calfhood vaccination trial in a persistently infected herd: effects on titres, health and growth.

A controlled calfhood vaccination trial to prevent bovine virus diarrhea was conducted in a 100 head cow-calf operation with a three year history of annual calf losses due to enteric bovine virus diarrhea (persistently infected herd). Approximately 50% of the calves were vaccinated at six, 12 and 24 weeks of age. Paired serum samples and growth data were collected on three occasions for comparison between vaccinates and controls. Three vaccinated calves died of enteric bovine virus diarrhea in the first year of the trial and one nonvaccinated calf died in the second year. Two of the three vaccinated calves had developed bovine virus diarrhea virus neutralization antibody titres of 2048 or greater before developing clinical signs. The control and third vaccinated calf failed to seroconvert before dying of enteric bovine virus diarrhea. Approximately 90% of the vaccinated calves seroconverted compared to approximately 40% of the controls. Paired serum samples collected from 75% of the cows in the spring, summer and fall of each year of the trial, showed persistent high bovine virus diarrhea virus neutralization titres in all samples. Calf vaccination before 12 weeks of age had little effect on seroconversion due to high levels of passive antibody to bovine virus diarrhea. Growth data showed that there was no improvement in weight gain or rate of growth in the vaccinated calves.

Age Factors↗
PubMed1983

Enterotoxemia in the goat: the humoral response and local tissue reaction following vaccination with two different bacterin-toxoids.

A vaccination trial involving 72 goats was designed to compare the epsilon antitoxin titres and local reactions at the injection sites, of two commercial enterotoxemia vaccines. Three dosage regimens were used for each vaccine (12 goats per group). Although no significant differences were noted in humoral immune response between the two vaccines (P = 0.05), one vaccine regime resulted in low titres (P = 0.05) on two occasions. Local tissue reactions at injection sites persisted for six months in 53% of the goats regardless of vaccine used or dosage administered. No immunological basis for the reported differences in vaccine efficacy between sheep and goats was observed in this trial.

Animals↗
PubMed1983

Magnesium oxide induced metabolic alkalosis in cattle.

A study was designed to compare the metabolic alkalosis produced in cattle from the use of an antacid (magnesium oxide) and a saline cathartic (magnesium sulphate). Six, mature, normal cattle were treated orally with a magnesium oxide (MgO) product and one week later given a comparable cathartic dose of magnesium sulphate (MgSO(4)). The mean percent dry matter content of the cattle feces changed significantly (P<0.001) following administration of both MgO (15.6-8.1) and MgSO(4) (17.0-8.7) but there was no significant difference between treatments. The mean rumen pH values changed significantly (P<0.001) following administration of both MgO (7.-8.7) and MgSO(4) (7.3-8.3) but there was no significant difference between treatments. However, use of the MgO product caused a more severe (P<0.001) metabolic alkalosis as determined by base excess values. The base excess values remained elevated for 24 hours in the MgO treated group compared to only 12 hours after MgSO(4) administration. Following MgO administration, mean hydrogen ion concentration (pH), bicarbonate ion concentration ([HCO(3)-]) and base excess were 7.44, 33.3 mmol/L and +8.0 respectively compared to 7.38, 27 mmol/L and +3.0 after MgSO(4). Since the oral use of MgO in normal cattle causes a greater and more prolonged metabolic alkalosis compared to MgSO(4), MgO is contraindicated as a cathartic in normal cattle or in cattle with abomasal abnormalities characterized by pyloric obstruction and metabolic alkalosis.

Alkalosis↗
PubMed1981

Distribution and structure of the adrenocortical homologue in the garpike.

The microanatomy of the yellow corpuscles (adrenocortical homologue, AH) in the holostean fish, Lepisosteus spp. was studied by serial sectioning, steroid histochemistry, and electron microscopy. The modification of this tissue to short-term ACTH treatment was also observed. The distribution of the AH within the renal tissue of the garpike phylogenetically represents a more advanced condition than that seen in its closest holostean relative, the bowfin, and appears to approximate that in teleosts. The homology of this tissue of vertebrate adrenocortical tissue was established by the positive identification of the enzyme, gamma 5-3 beta-hydroxysteroid dehydrogenase, and by the ultrastructural features of the cells before and after ACTH administration. The AH cells possess fine structural features characteristic of steroidogenic cells, namely, polymorphic mitochondria with tubular cristae, abundant tubules of smooth endoplasmic reticulum, a prominent Golgi complex, and lipid droplets. Other interesting features include the presence of annulate lamellae and a variety of dense bodies. Digitonin perfusion results in the deposition of presumed, cholesterol-digitonide crystalline spicules on the surface microplicae of the cells and as dense accumulations in association with smooth endoplasmic reticulum. ACTH administration results in swelling of mitochondria, a loss of their cristae, and a smooth decrease in electron density of their matrices. Alterations also occur in the smooth and rough endoplasmic reticulum, and large osmiophilic inclusions of irregular profile appear. Some of the ACTH-induced modifications are similar to those observed in the adrenocortical cells of other vertebrate groups following comparable stimulation.

3-Hydroxysteroid Dehydrogenases↗
PubMed1981

Intestinal glucose transport in acute viral enteritis in piglets.

1. We studied intestinal glucose transport in pigs during the acute and convalescent phases of an invasive viral enteritis, transmissible gastroenteritis. 2. When diarhoea was severe 40 h after experimental infection, net absorption of glucose, Na+ and water, measured by marker perfusion in the jejunum, was reduced; the enhancement of Na+ and water absorption in response to increasing perfusate glucose concentrations up to 120 mmol/l was diminished compared with the response observed in control and convalescent pigs. 3. Measured in vitro, 40 h after infection, unidirectional fluxes of 3-O-methyl-D-glucose across the jejunal epithelium were reduced and net absorption of the sugar was obliterated. Phlorizin (0.05 mmol/l), which completely inhibited net 3-O-methyl-D-glucose absorption in control tissue, had no significant effect on transmissible gastroenteritis jejunum. 4. Our data suggest that in this invasive viral enteritis, which closely resembles human rotavirus enteritis, glucose absorption is impaired as a result of defects in both active and passive glucose flux. 5. Differences between the mechanisms of viral diarrhoea, demonstrated by our study and those of the enterotoxigenic diarrhoeas, should be taken into consideration in formulating active therapeutic measures for children with acute viral diarrhoea.

3-O-Methylglucose↗
PubMed1980

Metabolic alkalosis with paradoxic aciduria in cattle.

In 4 cases of metabolic alkalosis with paradoxic aciduria in cattle, generalized muscle weakness was the predominant feature. In 3 of the 4 cases, prolonged anorexia preceded development of muscle weakness and aciduria. Plasma electrolyte concentrations varied but, in 3 of 4 cases, a transient decrease in plasma potassium concentration was detected. In the 3 cases in which prolonged therapy with sodium chloride, potassium chloride, and dextrose was offered, resolution of aciduria was rapid, followed by correction of metabolic alkalosis and return of muscle strength.

Acid-Base Imbalance↗
PubMed1980

Escherichia coli heat-stable enterotoxin in feces and intestines of calves with diarrhea.

Two experiments were conducted to evaluate detection of Escherichia coli heat-stable enterotoxin (ST) in the feces of calves as a method for implicating E coli in neonatal calf diarrhea. The first experiment evaluated the use of the infant mouse test for detection of ST in the feces of calves with naturally occurring diarrhea. Simultaneous identification of bovine enteropathogenic strains of E coli (EEC) and of other infective agents implicated in neonatal calf diarrhea was attempted in these samples. The ST was detected with certainty in only 7 of 41 samples from calves less than or equal to 3 weeks old. Enteropathogenic E coli, however, was detected in 27 samples. In 23 of these 27 samples, EEC was the only recognizable diarrheagenic agent. In a small percentage of the samples, Salmonella, rotavirus, coronavirus, and cryptosporidium were recognized alone, in combination with each other, or with EEC. In the second experiment, 6 calves were fed colostrum from cows inoculated with the bovine EEC strain B44; 6 were given colostrum from cows vaccinated with non-EEC strain 28F, and 4 were given milk from nonvaccinated heifers. Two of the calves that were given colostrum from cows inoculated with strain B44 were challenge exposed with the non-EEC strain 28F. The remaining calves were challenge exposed with the EEc strain B44. Fecal samples were taken from these calves at intervals and were examined for the presence of ST and of the challenge-exposure organism. The ST was detected in approximately one half of the fecal samples obtained, and it was most often detected in the early stages of the induced diarrhea. Calves were observed to shed the challenge-exposure EEC strain for long periods in the absence of diarrhea or detectable amounts of ST in the feces. The ST was detectable in fecal samples when the diarrhea was severe and when the dry matter content of the fecal samples was low.

Animals↗
PubMed1980

Ultrastructure of the adrenocortical homologue in dexamethasone-treated eels.

The ultrastructural modifications of the adrenocortical homologue (AH) in the North American eel (Anguilla rostrata) were studied following a 10 day treatment with dexamethasone (20 mg/day). The principal changes were: disorganization of smooth endoplasmic reticlum, regression and fragmentation of the Golgi apparatus, and a lowering of matrix density in the mitochondria. Steroid treatment also induced the appearance of numerous cytoplasmic inclusions: (a) lamellated bodies with electron-lucent cores; (b) membranous whorls isolating cytoplasmic regions containing smooth endoplasmic reticulum and mitochondria and (c) complex aggregates showing whorls of membranes, residues of cytoplasmic organelles, and dense matrix. The non-accumulation of lipid droplets in repressed AH cells was noteworthy. These subcellular changes indicate endogenous cellular autophagy in the AH as a result of steroid-induced suppression of ACTH production by the pituitary.

Adrenal Cortex↗
PubMed1979

The effect of increased metabolic rate on renal function in the rainbow trout, Salmo Gairdneri.

1. A highly significant linear correlation was found between glomerular filtration rate and urine flow rate in both freshwater and seawater trout. The percentage tubular reabsorption of water was approximately 33% greater in seawater trout than in freshwater trout. 2. As oxygen consumption increased, the urine flow rate increased in freshwater and seawater rainbow trout. The proportional increase in urine flow with incremental changes in oxygen consumption was approximately the same in fresh water and sea water. 3. A significant positive linear relationship between oxygen consumption and glomerular filtration rate was found in both salinities. The proportional increase in GFR with incremental changes in the oxygen consumption rate was higher in the seawater trout than in the freshwater trout. 4. As oxygen consumption increased, the percentage tubular reabsorption of water decreased in the freshwater trout. No significant relationship between these two factors was found in the seawater trout.

Animals↗
PubMed1979

Determinants of diarrhea in viral enteritis. The role of ion transport and epithelial changes in the ileum in transmissible gastroenteritis in piglets.

To understand mechanisms of viral diarrhea further, we studied ileal ion transport in vitro in relation to mucosal changes and epithelial differentiation in transmissible gastroenteritis in piglets, an invasive viral enteritis thought to involve mainly proximal intestine. In infected pigs, at the height of diarrhea, short-circuited ileal epithelium failed actively to transport Na+ and Cl-, and there was a defect of glucose-mediated Na+ transport. The Cl- secretory response to theophylline remained intact. Conductance measurements indicate that paracellular permeability may be reduced and transcellular transport may be altered. A mucosal lesion was observed at the time of the transport changes, characterized by villus blunting, crypt hyperplasia, and immature crypt-type enterocytes on the villus epithelium, deficient in disaccharidase and (Na+, K+)ATPase activity but rich in thymidine kinase. Consideration of the major determinants of diarrhea in this invasive enteritis must take into account not only altered mucosal function and differentiation but also the extent of intestinal involvement, including the ileum, a major site of fluid absorption in the intestine.

Animals↗
PubMed1978

Chronic enteritis associated with the malabsorption and protein-losing enteropathy in the horse.

Chronic granulomatous enteritis associated with weight loss and hypoproteinemia was identified in 2 horses. Both horses continued to have normally formed feces. Malabsorption of carbohydrate and lipid, with concomitant gastrointestinal protein loss was demonstrated in 1 case. One horse was treated symptomatically and gained 108 kg. In both cases, principal gastrointestinal lesions were partial to total villus atrophy and transmural mononuclear leukocytosis, with lymphocytes and histiocytes predominating. The cause of the condition was not identified in either case.

Animals↗