Biomedical subjects
Publications and source records attributed to D C Robinson.
Cerebral vascular accidents of uncertain origin in any patient pose a burden on the family physician to uncover the underlying cause by means of a thorough and concise workup. Even though cardiac tumors are rare, missing the diagnosis may lead to devastating results. The case reported here is of a 40-year-old man with a left atrial myxoma as the cause of his embolic cerebral infarct.
Peptide YY is an ileocolonic peptide known to inhibit postprandial and cholecystokinin-induced pancreatic exocrine secretion. It has also been shown to increase intestinal water and electrolyte absorption. These findings implicate PYY as being potentially useful for controlling watery diarrhea. Although its inhibitory effect on stimulated pancreatic secretion has been well established, PYY effects on interdigestive, unstimulated pancreatic secretion is not known. This study was designed to evaluate the effect of PYY on basal pancreatic exocrine secretion in a conscious rat. Male Sprague-Dawley rats were prepared with catheters for internal biliary bypass, pancreatic juice collection, and intraduodenal reinfusion of pancreatic juice. Jugular and carotid catheters were inserted for drug infusions and blood sampling. After overnight recovery, fasting rats were infused over 6 hours with saline or PYY (400 or 800 pmol/kg/hr). Pancreatic juice was measured and sampled at 60-minute intervals for volume and its protein and bicarbonate content. The remainder was reinfused into the duodenum. Before and after the experiment, pancreatic juice was automatically reinfused by a photocell-controlled peristaltic pump system. Intraductal pancreatic secretion was not affected by PYY at a dose of 400 pmol/kg/hr. PYY at a dose of 800 pmol/kg/hr significantly reduced the volume of pancreatic secretion and its protein and bicarbonate content. Pancreatic secretory response normalized within 24 hours. In conclusion, unstimulated pancreatic exocrine secretion can be inhibited by exogenous PYY in the rat.
OBJECTIVE: To examine the effect of energy restriction and wrestling on muscle glycogen content in highly-trained male wrestlers. DESIGN: Randomized, unblinded intervention trial. SETTING: McMaster University Nutrition and Metabolism Research Laboratory. PARTICIPANTS: Twelve highly trained male wrestlers volunteered as subjects and were randomly assigned to one of two groups (Group A, n = 6; Group B, n = 6) as defined below. ASSESSMENT OF RISK FACTORS: All subjects were free of medical conditions that would preclude participation in the study and all had performed rapid weight loss at least three times/year with no medical complications. INTERVENTIONS: Group A: simulated wrestling tournament, four 5-min wrestling bouts ( > 7 h) following a 5% body weight loss and 17 h repletion period; Group B: 5% weight loss through energy restriction (1,141 kcal/day), exercise, fluid restriction, and dehydration methods (sauna) > 72 h. MAIN OUTCOME MEASURES: Group A: muscle glycogen content before and after wrestling tournament and plasma lactate after each bout; Group B: muscle glycogen before and after weight loss. RESULTS: Group A: no significant effect on muscle glycogen concentration, yet large increases were observed in blood lactate concentrations (up to 14.7 mmol/L); Group B: weight loss resulted in a 54% (p < 0.018) reduction in muscle glycogen concentration. CONCLUSIONS: The weight loss methods commonly performed by wrestlers resulted in large decreases in muscle glycogen concentration that were largely reversed during the 17-h repletion period between weigh-in and the start of the competition; participation in a wrestling tournament did not have a significant impact upon biceps brachii glycogen concentration when ad libitum feeding is allowed between matches.
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OBJECTIVE: To assess the relationship between low-dose tamoxifen, usage and endometrial cancer in breast cancer patients. METHODS: In this case-control study, the records of the 1017 patients treated at Wilford Hall Medical Center for primary breast cancer between 1978 and 1989 were reviewed. Dose and duration of tamoxifen therapy were recorded as well as the presence of a uterus. Potential confounding variables including diabetes mellitus, hypertension, age, weight, tobacco use, and family history of breast or gynecologic cancer were recorded. RESULTS: Of the 1017 patients in the study, 56 had inadequate records and 375 had undergone a prior hysterectomy and these patients were excluded from the study, leaving 586 eligible patients. Of these 586 women with primary breast cancer and no previous hysterectomy, 108 patients had received tamoxifen, 10 mg twice a day for greater than 1 year. Four of the 108 patients subsequently developed endometrial adenocarcinoma. Four hundred seventy-eight breast cancer patients did not receive tamoxifen and 4 later developed endometrial adenocarcinoma. The odds ratio for the development of endometrial cancer when exposed to tamoxifen was 15.2 with a 95% confidence interval of 2.8-84.4. The patients exposed and not exposed to tamoxifen were compared for potential confounding variables and after controlling for the potential confounders, tamoxifen was found to be an independent risk factor for the development of endometrial cancer. CONCLUSIONS: Low-dose tamoxifen when given for greater than 1 year is associated with secondary endometrial cancer in patients with primary breast cancer.
STUDY OBJECTIVE: To compare the features of available drug interaction software programs in terms of general applicability to an emergency department setting. DESIGN: Prospective evaluation of drug interaction software programs based on presence or absence of a variety of performance features. SETTING: University and community hospital EDs. PARTICIPANTS: Eight commercially available drug interaction software programs. RESULTS: Programs were evaluated according to designated performance and data base features. Tabulated results were compiled for purposes of comparison. CONCLUSION: Although no computer program tested completely met the specific needs of a busy ED, many programs have features with at least some general applicability.
Intravenous ondansetron was administered at doses from 0.01 to 0.48 mg/kg every 4 h for three doses to patients receiving cisplatin 60-120 mg/m2 for the first time. Plasma samples were collected from 28 patients at baseline and at suitable times post-dose for pharmacokinetic analysis, and were assayed for ondansetron by high-pressure liquid chromatography. Plasma trough level was defined as the level before the third dose and 4 h area-under-the-curve (AUC4) was calculated with the linear trapezoidal method. Despite wide inter-patient variation, a correlation was seen between both trough level (r = 0.737, P less than 0.0001) and AUC4 (r = 0.903, P less than 0.001) related to dose. Trough level was also predictive of AUC4 (r = 0.824, P less than 0.0001). Frequency of complete protection (no emetic episodes) was equivalent throughout the AUC4 range, suggesting anti-emetic activity even at low AUC4. However, a trend toward better protection against failure (5 or more episodes) was seen when higher values of AUC4 were achieved, suggesting more consistent anti-emetic activity at moderate to high AUC4.
Two hundred ninety-five endocervical swab specimens were obtained from patients presenting to a gynecology clinic in order to compare a nonradioactive chemiluminescent DNA probe with cell culture for detection of Chlamydia trachomatis. Discrepancies between cell culture and DNA probe were resolved by retesting and reculturing samples. In a population with a 10.8% prevalence, the corrected sensitivity, specificity, positive predictive value, and negative predictive value for the DNA probe were 80.6, 95.8, 71.4, and 97.3%, respectively. These results compare favorably to other non-culture methods such as direct fluorescent antibody and enzyme immunoassay tests for the detection of C trachomatis in populations with similar prevalence rates.
The histopathological features of 20 tropical ulcers with the electron microscopic findings on seven biopsy specimens are reported. The main findings were loss of epidermis associated with extensive dermal oedema, infiltration by polymorphonuclear leucocytes, and disruption of collagen bundles. The presence of micro-organisms at the site of tissue damage was shown and compared with the morphology of the organisms grown in culture. The most commonly identified bacteria were pleomorphic rods whose electron microscopic appearances accorded most closely with Fusobacteria grown in vitro. Spirochaetes, identified ultrastructurally as Treponema sp, were also present. There was no evidence of vasculitis to explain the rapid onset of ulceration, but necrotic changes seen in the dermis and the inflammatory cell infiltrate suggest that, associated with cell necrosis, bacteria previously shown in vitro have an important role in the pathogenesis of tropical ulcers.
A guideline for the preparation of peripherally administered antibiotics in fluid-restricted patients was developed. A maximum osmolality of 560 mOsmol/kg was selected since this corresponds to the theoretical osmolality of dextrose 5% in NaCl 0.9%, a solution commonly administered peripherally without significant incidence of phlebitis. Percentage concentrations corresponding to 560 mOsmol/kg of 26 intravenous antibiotics were calculated using sodium chloride equivalents. The antibiotics were reconstituted using sterile water, dextrose 5%, and NaCl 0.9% to provide an osmolality of 560 mOsmol/kg. The resulting solutions were measured for osmolality using a freezing-point depression osmometer. A total of 78 solutions were prepared and measured in triplicate. Of the 78 measured osmolalities, 67 (86 percent) were within 20 percent of the desired 560 mOsmol/kg. Only two osmolalities were more than 10 percent above the projected value. The percentage concentrations of 26 antibiotics in three solutions corresponding to 560 mOsmol/kg are presented. A method is also provided for tailoring concentrations to achieve desired osmolalities other than 560 mOsmol/kg.
We have previously described hemolytic activity in extracts of lyophilized Schistosoma mansoni adult worms. In contrast, freshly homogenized live worms have little hemolytic activity. However, preincubation of the homogenate at 38 C, pH 5.1 for 22 hr resulted in an 18 fold increase in specific activity (Hb released/mg protein) due to dramatic increases in hemolytic activity and decreases in protein concentration. No activation occurred when the homogenate was boiled prior to preincubation or when preincubation was performed at 4 C. In addition, a thermostable inhibitor of hemolytic activity is present in freshly homogenized live adult S. mansoni. Hydrolysis of the inhibitor and activation of the hemolytic agent appear to be due in part to hydrolytic activity of one or more cysteinyl proteinases.
The clinical features of 86 tropical ulcers in 64 subjects seen in hospitals and rural clinics in Zambia are described. Pre-ulcerative lesions were identified. 85% of the patients came from subsistence farming families. Few wore shoes but more than a quarter wore clothes below the knee at some time. No association with dental caries or gingivitis was observed. Ulcers were seen in some clinically well-nourished individuals of appropriate weight for height and occurred in areas where animal protein was plentiful. Family studies showed that concurrent cases within households were uncommon.
The successful isolation of anaerobes largely depends on adequate transportation of the specimens after collection. We are investigating the role of anaerobes in the pathogenesis of tropical ulcer and have used Hungate tubes with pre-reduced peptone yeast broth and agar as a transportation system. The medium included 0.05% cysteine and 0.03% sodium formaldehyde sulphoxylate as an Eh buffer. Resazurin 1 microgram/ml seved as an Eh indicator. We found the tubes convenient to use and very reliable at maintaining anaerobiasis.
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We examined the relationship between ventricular isomyosin composition and plasma thyroxine (T4) 5 wk after partial constriction of the abdominal aorta in weanling (21 day) and adult (8 wk) rats. Cardiac enlargement in weanling aorta-constricted animals was associated with a significant (P less than 0.001) decrease in %V1 isomyosin in both left (32%) and right ventricles (25%) with a corresponding increase in the %V3 isomyosin and a reduction in plasma T4 levels. However, the ratio of V1/T4 was similar in weanling control (17.8 +/- 0.8) and aorta-constricted (18.0 +/- 1.4) rats. In adult aorta-constricted animals, there was a significant (P less than 0.001) reduction in the %V1 (16%) isomyosin in the left ventricle and a smaller decrease in the right ventricular V1 (8%) with no change in plasma T4 levels. There was also a significant difference in V1/T4 between control (16.1 +/- 0.4) and aorta-constricted (13.9 +/- 0.7) adult rats in contrast to the maintenance of the V1/T4 in weanling aorta-constricted animals. Thus both increased workload and changes in thyroxine levels contribute to the isomyosin redistribution seen in weanling rats subjected to a pressure overload, whereas, in adult hypertrophied hearts, alterations of the ventricular isomyosin composition appear to be due solely to the increased pressure overload.
To reduce the high maternal and fetal mortality in pheochromocytoma of pregnancy, therapy is advocated with phenoxybenzamine and propranolol to obtain adequate alpha- and beta-adrenergic receptor blockade. In early pregnancy control of symptoms may be difficult, but the patient may be carried to term with such medical therapy. Delivery should be by cesarean section before the onset of labour, with, if possible, simultaneous removal of the tumour. Additional preoperative preparation with phenoxybenzamine and propranolol and careful intraoperative management are essential. During her third pregnancy a 29-year-old woman was found to have a pheochromocytoma of the left adrenal gland. After the medical therapy and preparation described, the infant was delivered by cesarean section and the mother's left adrenal gland excised. Eight-year follow-up, including during a fourth pregnancy, showed no recurrence of tumour in the mother and only mild hypertension. The infant developed normally.
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