Martin F. Tansy

Gastric mucosal ulceration associated with electrochemical stimulation of the limbic brain

Electrochemical stimulation of the medial amygdaloid nucleus of chloralose-urethan anesthetized rats of either sex leads uniformly to the appearance of gastric ulcers within four hours. The effect is not present with sodium pentobarbital anesthesia, vagotomy, or following pretreatment with atropine sulfate or tetraethylammonium chloride (TEA). The effect is reduced by chlorpromazine and is not blocked by cimetidine in dosages as high as 160 mg/kg. It is concluded that the vagus nerve is a necessary component of the response and that the response appears to be cholinergic.

Pigeons: a new role in air pollution

A pilot study was conducted to determine the lead content of the various tissues and organs of two groups of wild pigeons. One group was obtained in the City of Philadelphia. The other group was ca...

Acute and subchronic toxicity studies of rats exposed to vapors of methyl mercaptan and other reduced‐sulfur compounds

Acute inhalation experiments were conducted to determine 24-h LC50 values for adult Sprague-Dawley rats of both sexes exposed to vapors of methyl mercaptan and other reduced-S compounds for 4 h periods. Using calculated gas concentrations, the following LC50 value for each gas and combination was determined: metyhl mercaptan, 675 ppm; dimethyl sulfide, 40,250 ppm; dimethyl disulfide, 805 ppm; hydrogen sulfide, 444 ppm; and an equimolar mixture of methyl mercaptan, dimethyl sulfide, and dimethyl disulfide, 550 ppm. The effects of body and tissue weights, gross metabolic performance, O2 consumption, systolic blood pressure, various blood parameters, and intestinal transit time associated with 3-mo exposures of young adult male rats to chemically verified concentrations of 2, 17, and 57 ppm methyl mercaptan vapor are summarized in this report. No mortality was experienced by any group. Histopathological findings were essentially nil except for microscopic suggestions of liver damage. The most readily apparent phenomenon was the decrease in body weight. Average values of terminal body weights for all exposed groups were lower than that for the sham control group. This difference was significant in the 57 ppm group and followed a statistically significant dose-related trend.

An evaluation of neural influences on the sphincter of Oddi in the dog

Opening pressures of the choledochoduodenal junction were measured in anesthetized dogs before and after vagotomy. Measurements were also made in anesthetized, vagotomized dogs prior to and during appropriate electrical stimulation of the severed ends of the peripheral and central vagi and of the peripheral splanchnic nerves. Vagotomy itself was not associated with significant changes in mean ductal opening pressures. Central and peripheral vagal stimulation and peripheral splanchnic nerve stimulation did not yield significant effects on the mean opening pressure parameter. However, changes in circulating fluid volume were shown to significantly influence mean ductal opening pressures. Reductions in systemic arterial pressure were associated with a reduction in mean opening pressures, whereas increases in cardiovascular fluid volume were associated with a marked elevation of opening pressures. It is concluded that ductal opening pressures can be significantly changed by hydraulic factors but are apparently unresponsive to direct neural influences.

Experimental and clinical aspects of gastrocolic reflexes

It is doubtful whether any hypothesis which has so far been advanced to explain the relation between the ingestion of food and defecation in normal man and in lower animals is adequate. The literature pertaining to this subject matter has, in recent years, become so voluminous that all of the experimental evidence in favor of the various views cannot be reviewed here but rather an attempt has been made to point out certain lines of evidence which, to the authors, appear to be the most outstanding. The earliest description of a mass emptying response of the large bowel was that which was radiographically observed by Walter Cannon (1) in 1902. His observations were made in cats which had been fed test meals subsequent to the administration of opaque enemas. MacEwen (2) in 1904 supplied the first published human data on mass colonic emptying after ingestion of a meal in patients with cecal fistulas. In 1909, Holzknecht (3) provided radiographic evidence of mass peristalsis as he observed a wave of contraction passing down the colon subsequent to the disappearance of interhaustral folds. A year earlier, Hertz (4) similarly observed that colonic contents tended to travel further during the dinner hour than in any other defined period during the day. Hertz also deserves the credit for designating this propulsive response as a gastrocolic reflex. In later experiments, Hertz and Newton (5) noted again in humans that when the propulsive movement occurred, the colonic contents of a distended section near the hepatic flexure

Chronic biological effects of methyl methacrylate vapor: I. Body and tissue weights, blood chemistries, and intestinal transit in the rat☆

Abstract The effects upon body and tissue weights, various blood parameters, and intestinal transit time associated with chronic exposures of rats to monomeric methyl methacrylate (MMA) vapor concentrations are summarized in this report. The most remarkable and readily apparent phenomenon was the obvious lack of body fat in the group which had been exposed for 3 months to an MMA vapor concentration of 116 ppm in air. It was determined that rats which have received a daily 8-hour exposure to 116 ppm of MMA vapor for 6 months have significantly lower adiposity, as measured by the popliteal fat pad, than those of a similar group which have received sham exposures. It was also determined that protracted exposures to MMA vapor in this concentration were associated with a significant decrease in intestinal transit performance.

LC50 values for rats acutely exposed to vapors of acrylic and methacrylic acid esters

Acute exposure studies were conducted using adult male Sprague-Dawley rats to obtain LC50/24 concentrations for the common esters of acrylic and methacrylic acids. The order of acute toxicity was determined to be methyl acrylate greater than ethyl acrylate greater than butyl acrylate greater than butyl methacrylate greater than methyl methacrylate greater than ethyl methacrylate. Four-hour daily exposures (excluding weekends) of young adult male rats to 110 ppm methyl acrylate in air over a period of 32 d failed to produce significant differences in body or tissue weights, blood chemistries, gross metabolic performance, and spontaneous small-intestinal motor activities when compared with a sham-exposed group.

Particulate inhalation during the removal of amalgam restorations

An aerosol that contains amalgam particles is created when a high-speed hand-piece is used to remove an existing amalgam restoration. Those particles smaller than 10 microns are considered to be fully respirable. This means that a significant percentage of the particles have the potential to travel to the terminal alveoli, where they may become lodged. Long-term exposure to fully respirable particles may compromise a persons respiratory function. Amalgam restorations were placed in the typodont teeth of a mannequin designed to simulate the head and the respiratory tract of a patient. The amalgam restorations were removed under three experimental conditions: dry cut (control), wet cut (water spray) with high-velocity evacuation, and wet cut with high-velocity evacuation and a rubber dam. Particulate exposure was evaluated in the simulated respiratory tracts of the patient and the dentist that were equipped with ambient particle sizing samplers. Use of water spray and high-velocity evacuation significantly reduced patient exposure to particles. The use of a rubber dam, together with water spray and high-velocity evacuation, was responsible for a further significant reduction of exposure to particles when compared with water spray and high-velocity evacuation alone. The dentist, however, was exposed to moderate levels of fully respirable particles for all conditions tested. It is therefore recommended that all dental personnel wear face masks while removing existing amalgam restorations.

Mechanisms of the secretory and motor responses of the Brunner's gland region of the intestines to duodenal acidification

The secretory and motor responses of the Brunners gland region of the duodenum to luminal acidification were examined in rabbits anesthetized with urethan. Isomotic solutions of sodium chloride (pH 7.2) were perfused continuously through adjacent in situ segments. The pH of the perfusate of the proximal segment was changed to 2.0 for 30 min. Perfusion pressure (motor response) and volume and hexosamine concentration (secretory response) of the effluent were recorded for 3h. The motor and secretory responses to luminal acidification were examined after intravenous (atropine) or intraluminal (lidocaine) pretreatment. Responses to intravenous infusions of serotonin or secretin were determined, also. Both atropine and lidocaine eliminated the initial motor and secretory responses of the proximal segment. Lidocaine eliminated the delayed secretory response of the distal segment. Serotonin caused initial motor and secretory responses, but secretin caused a delayed secretory response only.These results suggest that duodenal acidification elicits a two-phase increase in Brunners gland secretion, the first being motor-dependent and the second motor-independent. The initial motor response was mediated by a local reflex composed of cholinergic and perhaps tryptaminergic receptors. the delayed secretory response was mediated by local and nonlocal, possibly hormonal, factors. Increased duodenal motility may provide a vehicle for the rapid expulsion of mucus, and thereby serve an important role in the function of the Brunners glands.

Chronic biological effects of methyl methacrylate vapor: III. Histopathology, blood chemistries, and hepatic and ciliary function in the rat☆

Abstract Inhalation experiments were conducted by exposing rats, mice, and frogs to methyl methacrylate (MMA) monomer vapor in air. Rats were exposed for periods of up to 6 months to near threshold limit value (TLV) concentrations and for a shorter period to approximately ten times the TLV. Blood chemistries were unremarkable. Histopathological findings were essentially nil except for microscopic indications of damage to the tracheal mucosa, supported by scanning electron microscopy (SEM) observations that the cilia and microvilli characteristic of these epithelial cells were absent. A reduction in oropharyngeal transport efficiency was shown when frogs were exposed to 400 ppm of MMA vapor. The sodium pentobarbital detoxification function of mouse liver may be altered consequent to exposures to 160 hr to both 100 and 400 ppm of MMA vapor. It is concluded that, at the TLV, cellular responses may be manifested regardless of whether gross systemic effects are seen.