Biomedical subjects
Publications and source records attributed to A R Moossa.
The lower esophageal high pressure zone of eight Rhesus monkeys was characterized by manometry and reflux testing. It was found to respond characteristically to pentagastrin infusions. After excision of the lower esophageal segment and tis replacement by a stomach tube, an apparently normal, functional high pressure zone was demonstrable within the substitute.
The clinical, surgical, and pathologic findings in a five year prospective study of 192 patients referred with a high probability of pancreatic cancer are reported. We have defined the requirements of any pancreatic imaging procedure as its ability to distinguish a normal pancreas from pancreatic cancer or chronic pancreatitis and the capability of detecting tumors less than 5 cm in diameter. There was a 47 percent incidence of pancreatic disease (27 percent pancreatic cancer and 20 percent chronic pancreatitis). Prospective radionuclide imaging as routinely performed was found to be of little clinical value in this patient population; it was neither specific nor sensitive to pancreatic cancer or chronic pancreatitis. Preliminary data with longitudinal multiplane emission tomography show an improved diagnostic accuracy and the ability to detect resectable tumors, but its efficacy needs to be prospectively compared with other screening tests on a carefully defined patient population.
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The effect of bowel resection, sufficient to cause gastric secretory changes, on gastric emptying is unknown. Gastric evacuation was characterized in 8 Rhesus monkeys by a modification of George's double sampling test meal. Fifty per cent distal small bowel resection was then performed. Gastric emptying was again studied at 6 weeks and 6 months. The rate constant fell from -0.00289 +/- 0.000467 (+/-1 SEM) to -0.00232 +/- 0.00106 during the early phase, but role to -0.00308 +/- 0.00186 by 6 months, neither value being statistically different from the preoperative values. T1/2 rose from 125.2 +/- 19.2 mins to 367 +/- 173.4 mins by 6 weeks and to 380.9 +/- 161.6 mins by the end of the experiments. Corresponding values for T were: control period 425.8 +/- 63.2 mins, early phase 1223 +/- 589 mins and late phase 1245.9 +/- 529.6 mins. None of these changes were statistically significant. Alterations in emptying time within each animal were consistent at the two postoperative phases. Although the two animals showing acceleration of evacuation were those with least change in secretion, compensation for the observed increase in output of gastric juice did not materially alter the results.
An unchaired monkey model for the repeated long-term study of biliary secretory physiology is reported. Postoperative management with cholre recorded. Evaluation was performed by repeated measurement, over a period of months, of bile flow and 14C erythritol clearance at three rates of taurocholate infusion given intravenously in a random order. Response to secretin was tested at the final infusion rate of taurocholate for each experiment. The outcomes of 9 monkeys were described of which 5 were repeatedly studied. They demonstrated an increase in bile flow and 14C erythritol clearance with increasing bile salt output. A dramatic choleresis over a wide range of bile salt excretion was noted with secretin and a linear relationship between bile bicarbonate output and bile salt secretion rate was observed. The new model has several major advantages and gives higher bile flows than previously recorded in the chaired model.
Seven male Rhesus monkeys, with demonstrated gastric hypersecretory response to 50% distal small bowel resection, were studied. This increase in gastric acid output had persisted for more than 6 months. Precise, anatomical antrectomy without vagotomy was performed and intestinal continuity restored by gastroduodenostomy. Complete abolition of basal acid secretion and of the secretory response to histamine occurred. These effects could not be reversed by continuous (5 hour) infusions of pentagastrin at 0.2 microgram/kg hr-1 or 2 microgram/kg hr-1. The dose response curve to gastrin pentapeptide was altered; maximum secretion was greatly reduced and occurred at 10 microgram/kg hr-1. Neither basal serum gastrin or basal serum GIP was significantly reduced by antrectomy. These findings indicate that in this animal model the antrum is essential in the genesis of the hypersecretory state. If these findings are relevant to man precise antrectomy may be the procedure of choice for symptomatic acid hypersecretion after small bowel resection or disease.
Total plasma immunoreactive pancreatic glucagon (IRG) was measured in samples taken simultaneously from the proximal portal vein and superior vena cava of 26 healthy rats. The portal-peripheral ratio of IRG was 2.80+/-0.25, the portal-peripheral difference (Delta) 124+/-15 pg/ml, and percentage extraction 58+/-3. Gel filtration of paired portal and peripheral vein samples showed that reduction in the 3,500-dalton IRG component (glucagon) in peripheral samples accounted for almost all the differences, there being minimal and inconsistent changes in the high molecular weight (>40,000) fraction. The portal-peripheral ratio of the 3,500-dalton glucagon was 5.24+/-1.10, the portal-peripheral difference 130+/-33 pg/ml, and the percentage extraction 81+/-5. To study the transhepatic differences in the 9,000-dalton "proglucagon-like" material, the experiment was repeated in nine rats 24 h after bilateral nephrectomy, a procedure which increases plasma levels of this fraction. The portal-peripheral ratio for plasma IRG in these rats was 1.48+/-0.12, the portal-peripheral difference 140+/-29 pg/ml, and percentage extraction 28+/-5. Gel filtration revealed no consistent differences between portal and peripheral concentrations of the 9,000- and >40,000-dalton components, which comprised 40 and 13%, respectively, of the mean IRG level of 492+/-35 pg/ml. In contrast, there were marked differences between portal and peripheral levels of the 3,500-dalton component the ratio being 3.42+/-0.63, the portal-peripheral difference 182+/-32 pg/ml, and percentage extraction 64+/-5. Similar studies in a healthy dog, in which species there are significant circulating levels of the 9,000-dalton IRG component, confirmed the selective hepatic extraction of the 3,500-dalton fraction. We conclude that the various IRG fractions are metabolized differently by the liver, and that portal-peripheral ratios based on direct assay of plasma IRG will vary depending on the percentage glucagon immunoreactivity in each fraction; the greater the combined contribution of fractions other than the 3,500-dalton component to total plasma IRG, the lower will be the ratio. Because of the heterogeneity of circulating IRG and significant differences in the metabolism of its various components, gel filtration of plasma samples is necessary for precise quantitation of the hepatic uptake of each particular fraction.
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Fifteen pediatric patients have been presented who required operative treatment for Crohn's disease. This disease is associated with severe side-effects in children, especially maturation and growth arrest. There are clear indications for surgical treatment: fistula, chronic obstruction, hemorrhage and perforation. Failure to grow, when associated with obstruction of the small intestine, is an urgent indication for operation. From our observations, we conclude that growth arrest in these patients occurs because of malnutrition. In a majority of patients, chronic obstruction of the small intestine contributes significantly to this malnutrition. Operative treatment is one of conservative resection, and the operative mortality is nil. The majority of patients with growth arrest will grow postoperatively. Operative treatment of Crohn's disease is carried out for its complications, and treatment is quite effective in relieving these complications, although the disease itself may persist.
Thirty-one anesthetized dogs were surface cooled at 5 C and rewarmed after a variable period. Respiration was controlled with a volume respirator. When cardiac arrest occurred, circulation was provided with the mechanical ventricular assistance (MVA) device in 23 dogs. Of the animals maintained for four hours below 10 C on the MVA, 83% were successfully resuscitated. None of the dogs maintained for two hours below 10 C without circulation could be resuscitated. Eleven dogs were studied for a long-term survival after chest closure. Only four of them survived longer than three days. Death after rewarming was due to severe pulmonary insufficiency. Results of this study suggest that provision of oxygenation and a pulsatile circulation during hypothermia improve tissue viability of nonhibernators. The model shows potential for in situ preservation of multiple organs in the cadaver.
Thirty-eight patients with incidental thyroid carcinoma were reviewed. Thyroid lobectomy was adequate therapy in 15 to 17 patients. Both patients in whom lobectomy alone was inadequate had received prior irradiation. Five patients had antecedent head and neck irradiation, and in three of them, multicentric foci of tumor developed. Lobectomy alone was inadequate in three of these patients; they required thyroidectomy. A clinical recurrence developed in only two of 38 patients, and both of them had received previous irradiation. Reoperation in previously dissected areas was associated with an increased rate of complications. Lobectomy in nonirradiated and total thyroidectomy in irradiated patients cured the majority of patients suffering from incidental carcinoma of the thyroid.
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From 1970 to mid-1975, we have operated on 25 consecutive patients with toxic dilatation of the colon with no mortality. This report deals with the principles of management which we follow; primary emphasis is given to aggressive diagnosis and resuscitation, followed by early operative intervention. We prefer total abdominal colectomy with ileostomy and sigmoid mucous fistula for cases of toxic megacolon not complicated by hemorrhage.
Five Rhesus monkeys and four human adults with colonic reconstruction of the esophagus have been studied by manometric, fluoroscopic and reflux tests. Transit through the graft is mainly under the influence of gravity. Infrequent colon contractions can be propulsive, and sequential haustral contractions give the appearance of peristalsis. The diaphragmatic hiatus and esophagocolic anastomosis are the sites of weak barriers to reflux which are readily overcome by abdominal compression and gastric distension. Esophageal peristalsis is necessary to return refluxed material and cricopharyngeus muscle is the final barrier to regurgitation.