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Biomedical subjects

M F Tansy

Publications and source records attributed to M F Tansy.

At least 37 records · Page 2Linked to original sources
PubMed1979

Hypophysectomy-induced inhibition of augmented acetylcholine responses of the rat bowel following adrenalectomy and/or whole body irradiation.

Functional changes in the intestinal responsiveness to a fixed dose of acetylcholine were studied in muscle strips removed from young adult male rats previously exposed to whole body gamma radiation. In the irradiated rat the responsiveness to a fixed dose of acetylcholine was found to be augmented in the small intestine but not in the colon. Similar motor patterns for the small intestine were found when muscle strips from adrenalectomized rats were studied. Preradiation adrenalectomy further exaggerated the post-radiation sensitivity of the rat small intestine to acetylcholine. Hypophysectomy prior to either adrenalectomy and/or whole body radiation was associated with an absence of augmented small intestinal motor activity following administration of acetylcholine. The response of the large bowel to acetylcholine, however, was not modified by adrenalectomy and/or hypophysectomy. These observations suggest an endocrine component to the acute 3--5 day intestinal radiation syndrome.

Acetylcholine↗
PubMed1979

Metabolic performance and GI function in magnesium-deficient rats.

A quantitative evaluation of the mass balance and GI motor effects of dietary magnesium deficiency in the adult male Sprague-Dawley rat is described. Seventy-seven animals were used. Both sham control and experimental groups were maintained on a commercial stock laboratory diet ad libitum for 30 days, after which the experimental rats were switched for 30 days to magnesium-deficient diet ad libitum, containing a magnesium concentration of 16.2 ppm. Ten rats were used to determine the acetylcholine responsiveness of duodenal muscle segments in vitro. In all cases, the segments from the deficient rats were hyperresponsive to a fixed acetylcholine dose. Forty-six rats were used to determine the average intestinal transit rate, which increased significantly in 30-day magnesium-deficient rats. A final series employed 21 rats who were housed in individual metabolic cages. After 5 days on the deficient diet, the average daily fecal pellet counts and fecal weights were significantly reduced. It is concluded that chronic magnesium deficiency is associated with altered GI motor function in the adult male rat.

Animals↗
PubMed1979

Species difference in GI motor response to somatostatin.

Acute experiments were performed on overnight fasted chloralose-urethan anesthetized dogs, cats, rabbits, and rats. Under these conditions, somatostatin practically abolished gastric contractions and decreased GI tonus in all species examined. The canine duodenum, jejunum, and ileum exhibited only a contractile response to somatostatin, whereas motor activities of the small intestines of the cat, rabbit, and rat were inhibited. In all instances and at all dosages, both the inhibitory and excitatory effects showed suggestions of tachyphylaxis. The data also indicate that excitatory or inhibitory effects were not dependent on the presence of long arc pathways. It is concluded that somatostatin exerts a direct stimulatory effect on the canine small intestine that is mediated by the muscularis mucosa.

Animals↗
PubMed1979

Update on the toxicity of inhaled methyl methacrylate vapor.

The current threshold limit value (TLV) of 100 ppm for methyl methacrylate vapor was originally set because it was considered to be a value sufficiently low to preclude either systemic toxicological effects or discomfort from irritation in workers chronically exposed to the vapor. Shortly after this limit was proposed we became interested in evaluating the toxicological properties of methyl methacrylate vapor and, subsequently, of providing experimental data which would be useful in evaluating the adequacy of this TLV. The purpose of this article is to review some of the more relevant literature prior to 1976 which pertains to inhalation exposure and to summarize our more recent data which resulted from statistically designed studies employing acute and subchronic exposures to known concentrations of the vapor including the near-TLV value of 116 ppm.

Animals↗
PubMed1979

Evidence of reflexive beta adrenergic motor stimulation in the canine stomach and small intestine.

Studies in our laboratory have confirmed the previous observations that adequate electrical stimulation of either the left or right central vagus nerves in the dog after bilateral vagectomy produces relaxation of the stomach and small intestine. On the other hand, central vagal stimuli delivered to dogs that were either chronically reserpinized or were premedicated with the alpha adrenolytic phenoxybenzamine resulted in increased segmenting activity of these two organs. These excitatory responses were abolished by bilateral section of the sympathetic chains and could be reproduced by electrically stimulating the chains. The excitatory effects of either central vagal stimulation, peripheral sympathetic stimulation or intravenous isoproterenol administration could be abolished by dichloroisoproterenol. It was also determined that isoproterenol produced a tonic contraction of the separated muscularis mucosa which was distinguishable from a relaxation of the muscularis externa. It is suggested that a sympathetic pathway exists which is excitatory to the stomach and small intestine and that these excitatory effects are mediated by beta adrenergic neurotransmitters. The results further suggests that the beta excitatory reflex response is mediated by the muscularis mucosa as the target effector system.

Animals↗
PubMed1977

GI motor inhibition associated with acute exposure to methyl methacrylate vapor.

A mixture of monomeric methyl methacrylate vapor in air was delivered into the breathing air of chloralose-urethan anesthetized dogs. Fixed length exposures to 2000-ppm doses of the vapor resulted in a transient drop in arterial blood pressure and a marked inhibition of ongoing GI motor activities. Motor inhibition always continued for a variable time (approximately 10-15 min) subsequent to the cessation of methyl methacrylate vapor administration. This inhibitory response was not blocked by bilateral vagotomy, spinal transection, splanchnectomy, or the intravenous administration of tetraethylammonium chloride. Another series of experiments determined that the administration of blood from a dog receiving methyl methacrylate vapor produced GI motor inhibition in another dog not connected to the experimental gas mixture. Therefore, it is concluded that, aside from any reflex effects produced, methyl methacrylate vapor in sufficient concentration probably exerts a direct inhibitory effect upon GI smooth muscle that is mediated by the cardiopulmonary systems.

Aerosols↗
PubMed1977

GI pharmacology of polyethyleneimine I: effects on gastric emptying in rats.

Experiments were conducted to determine the effect of ingested polyethyleneimine upon gastric emptying of the fasted rat. Emptying was evaluated by the phenolsulfonphthalein and resin bead methods. The two techniques gave comparable results; both showed that this agent inhibited gastric emptying. A delay in gastric emptying could be detected within 15 min of intubation. The effect was dose related, quite long lasting (approximately 4 hr), and reversible. Commercially available, branched polyethyleneimines were highly active, but the linear polyethyleneimine was without observable effect. A branched polyethyleneimine derivative with all primary amine sites selectively acetylated also was inactive.

Animals↗
PubMed1977

GI pharmacology of polyethyleneimine II: motor activity in anesthetized dogs.

The effects of orally and intravenously administered doses of polyethyleneimine were observed in 18 chloralose-urethan-anesthetized dogs. Polyethyleneimine produced an initial augmentation of rhythmic segmenting gastric antral contractions, a copious flow of gastric mucus, increased segmenting and propulsive activities of the small and large intestines, and occasional micturition and defecation. The gastric corpus and fundic regions became relaxed and enlarged. These events were associated with the prompt appearance of retching. The retching response to oral administration could only be abolished by bilateral vagotomy or bilateral sympathectomy. The skeletal muscle component of retching was blocked by tubocurarine. Intravenous administration of chlorpromazine blocked the retching response and gastric corporal atonia to either intravenous or oral doses of polyethyleneimine. Either oral or intravenous administration of polyethyleneimine produced no detectable changes in the lead II ECG but was associated with marked transient reductions in both mean and pulsatile arterial blood pressures. These depressor effects showed clear tachyphylaxis. In all cases where GI effects were noted, respiration was augmented and erratic in a manner associated with the retching responses.

Animals↗
PubMed1977

Thermal stimulation of the oral mucosa and nasal airway resistance.

A procedure for measuring nasal airway resistance using posterior rhinorheometry is described. Baseline nasal airway resistances +/- 1 S.D. at an airflow of 0.5 L/sec were found to be 1.077 +/- 0.683 cm H2O for inhalation and 1.359 +/- 0.792 cm H2O for exhalation. Application of either cold water (4 to 6 C) or warm water (44 to 52 C) to the oral mucosa significantly increased nasal airway resistance. Application of tepid water (26 to 28 C) did not alter nasal airway resistance significantly.

Airway Resistance↗
PubMed1977

The occlusive competence of the duodenal orifice of the canine pancreatic duct.

Observations by scanning electron microscopy indicate that the mucosa of the terminal part of the major pancreatic duct of the dog is organized into numerous, highly convoluted folds. The individual mucosal cells are tall, columnar and studded with numerous microvilli. These folds are highly vascularized. The intraluminal administration of bethanechol and norepinephrine is associated with subsequent increases and decreases of mean opening pressures. Mean opening pressures were not observed to be associated with autonomic nervous activity that was unaccompanied by changes in systemic arterial pressure. It is concluded that the terminal portion of the canine major pancreatic duct probably acts as a passive valve, the occlusive competence of which is influenced by the status of the vasculature of the lining mucosa in this region.

Animals↗
PubMed1977

A cilia-bearing cell system in the intrahepatic bile ductules of the rat.

A scanning electron microscopic investigation of the luminal surface of the intrahepatic bile ducts of the rat has been performed using tissue prepared by critical point drying. Results of these studies have demonstrated that intrahepatic bile ducts of the rat are composed of cells, the luminal surface of which contains either microvilli or numerous long cilia. It was suggested that these cilia play an important role in tissue function, particularly in the propulsion of hepatic bile.

Animals↗