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Biomedical subjects

A Simard

Publications and source records attributed to A Simard.

At least 19 recordsLinked to original sources
PubMed2000

Uptake of lactate by the liver: effect of red blood cell carriage.

Multiple-indicator dilution experiments with labeled lactate were performed in the livers of anesthetized dogs. A mixture of (51)Cr-labeled erythrocytes, [(3)H]sucrose, and L-[1-(14)C]lactate or a mixture of (51)Cr-labeled erythrocytes, [(14)C]sucrose, and L-[2-(3)H]lactate was injected into the portal vein, and samples were obtained from the hepatic vein. Data were evaluated using a model comprising flow along sinusoids, exchange of lactate between plasma and erythrocytes and between plasma and hepatocytes, and, in the case of L-[1-(14)C]lactate, metabolism to H[(14)C]O(-)(3) within hepatocytes. The coefficient for lactate efflux from erythrocytes was 0.62 +/- 0.24 s(-1), and those for influx into and efflux from hepatocytes were 0.44 +/- 0.13 and 0.14 +/- 0.07 s(-1), respectively. The influx permeability-surface area product of the hepatocyte membrane for lactate (P(in)S, in ml x s(-1) x g(-1)) varied with total flow rate (F, in ml s(-1) x g(-1)) according to P(in)S = (3.1 +/- 0.5)F + (0.021 +/- 0.014). Lactate in plasma, erythrocytes, and hepatocytes was close to equilibrium, whereas lactate metabolism was rate limiting.

Acetates↗
PubMed1999

Kinetics of endothelin-1 binding in the dog liver microcirculation in vivo.

Endothelin-1 (ET-1) is a 21-amino acid peptide produced by vascular endothelial cells that acts as a potent constrictor of hepatic sinusoids. Hepatic binding of tracer (125)I-labeled ET-1 was investigated in anesthetized dogs with the multiple-indicator dilution technique with simultaneous measurements of unlabeled immunoreactive ET-1 plasma levels. Despite 80% binding to albumin, tracer (125)I-ET-1 was avidly extracted by the liver, with only 15 +/- 6% of the peptide surviving passage through the organ. Exchange of ET-1 between plasma and binding sites, probably located on the surface of liver cells, was quantitatively described by a barrier-limited, space-distributed variable transit time model. Reversible and irreversible parallel binding sites were found. Reversible and irreversible plasma clearances of unbound (125)I-ET-1 were 0.084 +/- 0.033 ml. s(-1). g liver(-1) and 0.17 +/- 0.09 ml. s(-1). g liver(-1), respectively, and the dissociation rate constant for reversible binding was 0.24 +/- 0.12 s(-1). The specific ET(A) receptor antagonist BMS-182874 did not modify binding to either site. The nonspecific ET(A)/ET(B) antagonist LU-224332 dose-dependently reduced irreversible binding only. ET-1 levels in the hepatic vein were significantly lower than in the portal vein but were not different from those in the hepatic artery. The ratio between hepatic vein and portal vein levels (0.64 +/- 0.31) was considerably higher than survival fractions, suggesting a substantial simultaneous release of newly synthesized or stored ET-1 by the liver. These results demonstrate both substantial clearance and production of ET-1 by the intact liver. Hepatic ET-1 clearance is mediated by the ET(B) receptor, with the presence of reversible, nonspecific ET-1 binding at the liver surface

Animals↗
PubMed1997

Epidemiologic aspects of gallbladder cancer: a case-control study of the SEARCH Program of the International Agency for Research on Cancer.

BACKGROUND: There are few previous epidemiologic studies of gallbladder cancer, a rare but nearly always lethal gastrointestinal cancer with a demonstrated greater frequency in adult women and older subjects of both sexes, and also in the members of populations throughout central and eastern Europe and certain racial groups such as native American Indians. Unfortunately, the prospects for the prevention of this form of cancer are poor. PURPOSE: Our purpose in conducting this study was to investigate possible new risk factors for gallbladder cancer and to strengthen our understanding of established causal agents that may be involved in this disease. METHODS: A large, collaborative, multicenter, case-control study of cancer of the gallbladder was conducted in five centers located in Australia (Adelaide), Canada (Montreal and Toronto), The Netherlands (Utrecht), and Poland (Opole) from January 1983 through July 1988. Case subjects with gallbladder cancer were accrued by the centers from hospital pathology records and from reports to regional cancer registries. Cancer diagnosis was confirmed by either biopsy, cholecystectomy, or at the time of autopsy. Control subjects were randomly assigned at each center from the population. The pooled analysis included 196 case subjects and 1515 control subjects (who did not report previous cholecystectomy). Ninety-eight percent of the subjects were white. Personal interviews of case subjects, control subjects, and surrogates (spouse or next of kin) were conducted by trained personnel. RESULTS: After adjusting for potential confounding factors (age, sex, center, type of interview, years of schooling, alcohol intake, and lifetime cigarette smoking), a history of gallbladder symptoms requiring medical attention (e.g., reduced bile secretion from the gallbladder into the small intestine due to obstructions of the common bile or cystic ducts) was the major risk factor associated with this form of cancer (odds ratio [OR] = 4.4; 95% confidence interval [CI] = 2.6-7.5). This association was present even in subjects who had their first gallbladder examination because of symptoms present more than 20 years earlier (OR = 6.2; 95% CI = 2.8-13.4). Other variables associated with gallbladder cancer risk included an elevated body mass index, high total energy intake, high carbohydrate intake (after adjustment for total energy intake), and chronic diarrhea. All of these risk factors have been previously associated with gallstone disease. CONCLUSIONS: These findings are consistent with a major role of gallstones, or risk factors for gallstones, in the cause of gallbladder cancer. Additional information on whether or not screening high-risk subjects for gallstones or gallbladder cancer is needed.

Adult↗
PubMed1997

Endothelin-1 myocardial clearance, production, and effect on capillary permeability in vivo.

Myocardial metabolism of endothelin-1 (ET-1) and its effect on coronary microcirculatory exchanges were obtained in anesthetized dogs by combining the indicator-dilution technique with immunoreactive ET-1 measurements. The myocardium extracted 17.7 +/- 4.6% of tracer ET-1 (n = 12). Simultaneously measured ET-1 levels in the aorta (0.97 +/- 0.46 pg/ml) and coronary sinus (0.96 +/- 0.53 pg/ml) were not different, supporting a production of ET-1 by the heart that balances the amount extracted. Intracoronary infusion of ET-1 (5 ng.kg-1.min-1) increased coronary sinus ET-1 levels approximately 50-fold, decreased coronary blood flow per unit of interstitial space by approximately 30% (P = 0.006), and increased myocardial microcirculatory transit times (n = 6). Permeability to albumin was unaffected by ET-1, whereas the permeability-surface area product for sucrose decreased following derecruitment of myocardial capillaries. We conclude that there is a normal myocardial metabolic balance of ET-1 and that the heart marginally contributes to circulating ET-1. Pharmacological doses of ET-1 may adversely affect myocardial metabolism by reducing blood flow and the permeability-surface area product for small circulating substances.

Animals↗
PubMed1997

Increased hepatocyte permeability surface area product for 86Rb with increase in blood flow.

Liver cell recruitment (the equivalent of capillary recruitment in other organs) was explored by carrying out multiple indicator dilution experiments with labeled rubidium across the liver of the anesthetized dog under basal conditions and after bleeding with saline replacement infusion, which increases liver blood flow. A mixture of 51Cr-labeled red blood cells (a vascular reference), 22Na (which immediately equilibrates in the extracellular space, the sum of the sinusoidal plasma and Disse or interstitial spaces, the expected distribution space for labeled rubidium in the absence of cellular entry), and 86Rb was injected into the portal vein, and normalized outflow patterns, expressed as outflowing fractions of each injected tracer per milliliter versus time, were obtained. In relation to the labeled red blood cell curve, the labeled sodium curve is displaced by flow-limited distribution into the Disse or interstitial space; it is lower on the upslope, reaches a lower and delayed peak, and decays more slowly. The early part of the labeled rubidium curve lies within the labeled sodium curve; it reaches a much reduced peak, and the later return of tracer entering cells is so slow that it is obscured by recirculation. Modeling of the concentrative cellular uptake of rubidium from the Disse space provided an influx permeability surface area product for labeled rubidium. This increases with flow over the observed flow range, demonstrating that sinusoidal recruitment occurs with increase in hepatic blood flow.

Animals↗
PubMed1996

Cigarette smoking and pancreas cancer: a case control study of the search programme of the IARC.

A multi-centre case-control study of pancreas cancer, designed to be population-based, to use a random sample of local populations as controls and to use a common protocol and core questionnaire, was conducted as the first study of the SEARCH programme of the International Agency for Research on Cancer. "Ever-smokers" were found to be at increased risk for pancreas cancer compared with "never-smokers" consistently in all strata of gender, response status and centre. Risk of pancreas cancer was found to increase with increasing lifetime consumption of cigarettes, the relative risk rising to 2.70 (95% C.I. 1.95 to 3.74) in the highest intake category. The overall trend in risk was highly significant and the association was found consistently in each stratum of gender, response status and centre. Fifteen years had to pass from quitting cigarette smoking until the risk fell to a level compatible with that in never-smokers among the heaviest group of smokers; among the 2 lowest tertiles this happened within 5 years. Further, reported smoking habits more than 15 years before diagnosis appeared to have no influence on pancreas-cancer risk, irrespective of amount smoked. The results are consistent with a causal role for cigarette smoking in the aetiology of pancreas cancer and illustrate that ceasing to smoke cigarettes can lead to reductions in the elevated risk of pancreas cancer produced by this habit.

Case-Control Studies↗
PubMed1996

Oleate uptake by isolated hepatocytes and the perfused rat liver is competitively inhibited by palmitate.

Competition for uptake between long-chain free fatty acids has been difficult to document, because there has been no algorithm for computing unbound concentrations of two fatty acids simultaneously in solution with albumin. We modified an iterative procedure to permit this computation and studied initial [3H]oleate uptake by isolated hepatocytes and steady-state uptake by the single-pass perfused rat liver from 600 microM bovine serum albumin solutions containing various concentrations of oleate in the presence and absence of palmitate. In both systems, the Michaelis-Menten constant was significantly higher in the presence of palmitate than in its absence, whereas the maximal reaction velocity was unaltered, indicating competitive inhibition. In additional experiments employing the multiple transhepatic indicator-dilution technique, the influx rate constant and permeability-surface area product for oleate influx were significantly reduced by palmitate, confirming that the competition observed in the conventional perfused liver studies was at the influx step. Long-chain fatty acid uptake has now been shown to exhibit all the kinetic properties of facilitated transport and cannot be attributed solely to passive diffusion.

Animals↗
PubMed1996

Kinetics of pulmonary uptake of serotonin during exercise in dogs.

The multiple indicator-dilution technique was employed in the exercising dog to evaluate the effect of increasing activity on the pulmonary extraction and kinetics of removal of tracer 3H-labeled serotonin (5-HT) and on the measured central blood volume and tracer-accessible extravascular lung water. 51Cr-labeled red blood cells, 125I-labeled albumin, and 14C-labeled 1,8-octanediol were injected with labeled 5-HT at rest and at two increasing levels of exercise (lower and higher in 9 dogs). Blood flow approximately tripled at the highest level of exercise, and the central blood volume increased linearly with increasing blood flow. The tracer-accessible extravascular lung water increased in the transition from rest to low-level exercise and stabilized at an average proportion of 0.85 of the gravimetric extravascular lung water at the higher values of blood flow. The average labeled 5-HT extraction at rest was 42 +/- 11%, and this slowly decreased with increase in flow. The calculated permeability-surface area product for 5-HT increased approximately directly with increasing blood flow. We conclude that exercise results in an increase in the central blood volume that is accompanied by an increase in the tracer-accessible extravascular lung water (lung tissue recruitment) over low exercise levels, with no change at higher levels of exercise, and that the pulmonary capillary surface area subserving 5-HT uptake increases almost linearly with flow over the range of flows attained.

Animals↗
PubMed1995

Effects of flow, perfusion pressure, and oxygen consumption on cardiac capillary exchange.

The roles of blood flow, local oxygen consumption, and perfusion pressure on cardiac transcapillary exchange were characterized in closed-chest anesthetized dogs by use of the multiple-indicator dilution technique. Occlusion of the carotid arteries or injection of dipyridamole increased coronary flow to significantly higher values compared with a group of animals in a basal state obtained in a previous study. Carotid occlusion resulted in a significant increase in perfusion pressure and myocardial oxygen consumption, whereas these two variables were significantly reduced after dipyridamole. For the whole group of animals, the capillary permeability-surface area product for sucrose increased with coronary flow, which appeared to be the important controller for this microcirculatory exchange parameter. Perfusion pressure and myocardial oxygen consumption also regulated permeability-surface area product values, although to a lesser extent than flow. The heterogeneity of transit times in the capillaries was reduced at high coronary flow values, despite large differences in the cardiac utilization of oxygen. The data suggest that cardiac capillary exchange responds mostly to hemodynamic changes originating at the precapillary level.

Animals↗
PubMed1995

Tracer oxygen distribution is barrier-limited in the cerebral microcirculation.

The kinetics of tracer oxygen distribution in the brain microcirculation of the awake dog were investigated with the multiple indicator dilution technique. A bolus containing 51Cr-labeled red blood cells, previously totally desaturated and then resaturated with [18O]2 (oxygen), 125I-albumin, 22Na, and [3H]water, was injected into the carotid artery, and serial anaerobic blood samples were collected from the sagittal sinus over the next 30 seconds. The outflow recovery curves were analyzed with a distributed-in-space two-barrier model for water and a one-barrier model for oxygen. The analysis provided an estimate of flow per gram brain weight as well as estimates for the tracer water and oxygen rate constants for blood-to-brain exchange and tracer oxygen parenchymal sequestration. Flow to tissue was found to vary between different animals, in concert with parallel changes in oxygen consumption. The 18O2 outflow curves showed an early peak, coincident with and more than half the magnitude of its vascular reference curve (labeled red blood cells), whereas the [3H]water curve increased abruptly to a low-in-magnitude curve at low flow values and to a small early peak at high flow values. Analysis indicates that the transfers of both 18O2 and [3H]water indicators from blood to brain are barrier-limited, with the former highly so because of the large red blood cell capacity for oxygen, and that the proportion of the tracer oxygen returning to the circulation from tissue is a small fraction of the total tracer emerging at the outflow.

Animals↗
PubMed1995

Sulfation of acetaminophen by the perfused rat liver: the effect of red blood cell carriage.

Acetaminophen uptake and conversion in the perfused rat liver to acetaminophen sulfate was studied with the multiple indicator dilution technique (MID). Because acetaminophen is avidly bound to red blood cells and not albumin, a pre-equilibrated MID dose containing the noneliminated references (51Cr-labeled red blood cells [RBC, a vascular reference], [58Co]EDTA [a small molecular weight interstitial reference that does not enter cells], and D2O [a cellular reference]) and [3H]-acetaminophen was introduced into the portal vein of the single-pass perfused rat liver (1 mg/L acetaminophen) under varying conditions of hematocrit, with observation of timed outflow profiles in the hepatic venous blood. The [3H]acetaminophen curve exhibited an early high peak, paralleling that for red cells and varying with hematocrit, followed by a prolonged decline, with the late appearance of acetaminophen sulfate product; the early peak disappeared when red cells were absent from the dose and perfusate. Analysis demonstrated a slow release of acetaminophen from the red blood cells and rapid liver cell entry, so that red cell binding was displayed as a red cell carriage effect that reduced the rate of liver cell entry and hence of sulfation of [3H]-acetaminophen. The liver cells exhibited a concomitant very low permeability to product acetaminophen sulfate, leading to protracted product outflow curves. An inferred slow efflux-mediated storage phenomenon for product was found to evolve as a result.

Acetaminophen↗
PubMed1995

Food habits and pancreatic cancer: a case-control study of the Francophone community in Montreal, Canada.

In a population-based case-control study of pancreatic cancer and nutrition among the Francophone population of Montreal (Quebec, Canada), a total of 179 cases and 239 controls matched for age, sex, and language (French) were interviewed between 1984 and 1988. Data on food habits, methods of food preparation and preservation, and related information were obtained through a questionnaire. The study found an increased risk of pancreatic cancer associated with a high consumption of salt [relative risk (RR) = 4.28; 95% confidence interval (CI) = 2.20-8.36], smoked meat (RR = 4.68; CI = 2.05-10.69), dehydrated food (RR = 3.10; 95% CI = 1.55-6.22), fried food (RR= 3.84; 95% CI = 1.74-8.48), and refined sugar (RR = 2.81; 95% CI = 0.94-8.45). An inverse association was found with the consumption of food with no preservatives or additives (RR = 0.08; 95% CI = 0.01-0.59), raw food (RR = 0.28; 95% CI = 0.10-0.75), and food prepared by presto or high-pressure cooking (RR = 0.35% 95% CI = 0.15-0.81), electricity (RR = 0.30; 95% CI = 0.90), or microwave oven (RR = 0.56; 95% CI = 0.34-0.92). Cooking with firewood was associated with a significantly higher risk for pancreatic cancer (RR = 4.63; 95% CI = 1.15-16.52). The results of this study suggest that food habits may play an important role in the etiology of cancer of the pancreas among French Canadians in Montreal, whereas other food habits may reduce the risk of this disease.

Adult↗
PubMed1993

Nutritional profile of women with fibrocystic breast disease.

The relationship between nutritional factors including eating habits and the presence or absence of fibrocystic breast disease (FBD) with regard to other known risk factors has been investigated in women participating in the National Breast Screening Study (NBSS) in Montreal, Canada. Included in this case-control study were 334 patients with FBD aged 40-59 years at entry to NBSS and 340 controls. Personal and family history was collected from medical records and by interview conducted by a research nurse. Nutritional assessment was done by 24-hour dietary recall, by a food frequency questionnaire and by identification of changes in eating habits 5 years prior to diagnosis. Women > or = 50 years with FBD had higher intake of energy, carbohydrate, fibre, vitamin D, free folacin, calcium, sodium, potassium and magnesium but lower intake of cholesterol than controls. In women < 50 years body mass index and lower protein, niacin and zinc intake, were associated with FBD. In logistic regression analysis, breast pain and education > 12 years were among the most important predictive variables for FBD. The use of oral contraceptives, cholesterol intake > or = 300 mg/day, the proportion of energy provided by fat and saturated fatty acid intake above 10% of energy had a protective effect. The comparison of FBD patients diagnosed by biopsy and those by clinical examination indicated that increasing age had a significant association with the risk of biopsy and a rather weak association with the percentage of energy supplied by fat.

Adult↗
PubMed1993

Case-control study of fibrocystic breast disease.

An epidemiological case-control study of FBD has been conducted to evaluate the differences observed between cases and controls in relation to the presence or absence of clinical findings and risk factors for fibrocystic breast disease (FBD). A total of 334 patients with FBD were identified among 6,232 women aged 40-59 who had participated in the National Breast Screening Study in Montréal while 340 age-matched controls were selected at random from the same cohort. All women were interviewed by a well trained nurse. Controls were significantly heavier and had a higher body mass index (BMI) than cases; however, cases had longer school attendance than controls. The menstrual cycle was shorter in cases and the number of pregnancies was greater in controls. Significant odds ratios were observed for BMI (O.R. = 0.72, 95% CI = 0.51 - 1.02) suggesting that a higher value of BMI had a rather protective effect; a similar pattern was observed in women using oral contraceptives. Since nodularity was strongly associated with FBD, it was excluded from a model of logistic regression; in this instance, longer school attendance (> 12 years), older age at menopause (> 45 years) and breast pain were significantly associated with an increased risk of FBD.

Adult↗
PubMed1993

A population-based case-control study of cancer of the bile ducts and gallbladder in Quebec, Canada.

In a population-based case-control study of pancreatic cancer in Greater Montreal between 1984 and 1988, a total of 24 patients with cancer of the bile ducts and 33 patients suffering from cancer of the gallbladder were compared to 239 population-based controls. This study was part of the SEARCH program of the International Agency for Research on Cancer. In cases of cancer of the bile ducts, smoking nonfiltered cigarettes produced a relative risk of 2.82 and a 95% confidence interval of 1.01-7.86 after adjustment for age, sex, other smoking habits, alcohol consumption, schooling, and respondent status. Laxative intake was associated with a risk of 2.87 (1.00-8.22). Coffee drinkers were collectively at lower risk than non-drinkers: OR = 0.26 (0.07-0.95). In patients with cancer of the gallbladder, constipation was related to a risk of 3.19 (1.02-9.95) after adjustment for the same factors. In cases with previous gallbladder problems, the risk was found to be significant [OR = 7.96 (2.03-31.2)], 8 times greater in cases than in controls.

Adult↗