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Biomedical subjects

M B Patel

Publications and source records attributed to M B Patel.

At least 37 records · Page 2Linked to original sources
PubMed1990

Atriopeptin 24 regulates myocardial function via Frank-Starling mechanism in conscious dogs.

Recent studies have shown that the infusion of atriopeptins decreases blood volume because of the diuresis and also because of changes in vascular volume. In dogs chronically instrumented for the measurement of left ventricular pressure and internal left ventricular diameter, infusion of atriopeptin 24 (500 ng.kg-1.min-1 for 1 h), steady-state plasma levels of 6,000 pg/ml resulted in 5.9 +/- 1.7% decrease in left ventricular (LV) end-diastolic diameter (EDD) from 34.7 +/- 2.3 mm (P less than 0.05) and no significant change in LV first derivative of pressure with time (dP/dt), LV first derivative of dimension with time, LV dP/dt divided by internal diastolic circumference or percent shortening. Hematocrit increased from 42 to 46% (P less than 0.05). During pacing, infusion of atriopeptin 24 still reduced LV EDD by 7.5 +/- 1.8% from 32 +/- 2.8 mm (P less than 0.05), although there were no changes in the indexes of inotropic state. These results were unaffected by combined autonomic receptor blockade or by ganglionic blockade. Inflation of a hydraulic occluder around the aorta during the infusion of atriopeptin 24 to return LV EDD to preinfusion levels did not cause any index of myocardial contractility to increase significantly. At lower infusion rates that resulted in plasma atriopeptin levels of 2,000 pg/ml, atriopeptin 24 still reduced LV EDD without effect on inotropic state. Thus in the conscious dog, atriopeptins reduce preload independent of neuronal influences and without affecting inotropic state.

Animals↗
PubMed1990

Regulation of plasma ANF after increases in afterload in conscious dogs.

Although atrial stretch is the primary stimulus for atrial natriuretic factor (ANF) secretion, hormones may directly affect ANF secretion or may indirectly influence ANF by changing left ventricular afterload, thereby altering atrial stretch. To determine whether direct effects are important for the release of ANF in vivo, we measured changes in plasma ANF and in atrial wall function in the conscious dog after the administration of vasopressin, angiotensin II, and phenylephrine and by mechanically increasing left ventricular afterload by partial aortic occlusion. Injections of phenylephrine, angiotensin II, and arginine vasopressin (AVP) that were chosen to cause similar changes in systemic arterial pressure resulted in similar changes in atrial pressure and diameter. Maximum V wave atrial wall stress increased to 283 +/- 12, 311 +/- 41, 327 +/- 24, and 277 +/- 22 g/cm2 for AVP, angiotensin, phenylephrine, and occlusion, respectively, and plasma ANF increased to 242 +/- 81, 248 +/- 62, 299 +/- 95, and 190 +/- 53 pg/ml. There were significant linear correlations between left ventricular afterload and left atrial pressure, and each method for increasing left ventricular afterload shifted the position to the left on an atrial pressure-diameter, compliance curve, by a similar degree. Thus changes in left ventricular afterload result in changes in atrial wall function and similar changes in plasma ANF. No hormonal-specific increase in plasma ANF was found in conscious dogs after increases in afterload.

Angiotensin II↗
PubMed1989

Global myocardial hypertrophy in conscious dogs with chronic elevation of plasma norepinephrine levels.

Chronically elevated plasma norepinephrine is associated with many disease states in which myocardial hypertrophy is also found, yet whether the hypertrophy results from the hemodynamic actions of catecholamines or a trophic effect is still unknown. The goal of our study was to determine the extent of hypertrophy following 28 days of norepinephrine infusion and the role of altered hemodynamics as the stimulus for the hypertrophy in conscious dogs. In a retrospective study gross cardiac weights were examined in 25 control instrumented dogs (controls) and in 41 instrumented dogs with elevated norepinephrine (NE). In the NE dogs LV (94 +/- 2.8 g), septum (33 +/- 1.5 g) and total heart weights (172 +/- 4.5 g) were greater than in controls (85 +/- 5.0, 31 +/- 1.9, and 158 +/- 9.0 g, respectively). The LV (3.95 +/- 0.10 g/kg), RV (1.91 +/- 0.06), septum (1.38 +/- 0.06) and total weight (7.23 +/- 0.15) to body weight ratios were also significantly greater (3.32 +/- 0.12, 1.73 +/- 0.08, 1.24 +/- 0.06, and 6.28 +/- 0.23 g/kg). The dry/wet weight ratios were not different in the two groups. After cutting the hearts into 1 cm rings, the planimetered area of each ring showed that the wall thickness increased at all levels, e.g. at the base by 25 +/- 3.2%. The chamber internal diameter was significantly increased only near the apex in the NE dogs making the heart more cylindrical in shape. There was no obvious sign of fibrosis in any layer of the myocardium. In physiologic studies, no index of contractility was altered including: LV dP/dt, LV dD/dt, shortening, LV dWT/dt and there was also no change in preload. Heart rate was significantly reduced throughout the 28 days of study. Cardiac output was reduced and there were no significant changes in cardiac work. Thus in these dogs NE caused a 19% and 10% increase in LV and RV to body weight ratios, respectively, without any obvious hemodynamic stimulus.

Animals↗
PubMed1989

Atrial wall function and plasma atriopeptin during volume expansion in conscious dogs.

Mean left atrial pressure is believed to be an accurate estimate of atrial stretch in vivo and is used to assess the stimulus for atriopeptin release in both animals and humans. However, for a number of years it has been known that atrial stretch receptor discharge occurs during specific phases of the atrial cycle and that B-receptor discharge correlates with the passive filling of the atrium, which occurs during the V wave. The purpose of this study was to develop the concept that phase-specific changes in atrial wall stress are responsible for atriopeptin secretion. In chronically instrumented conscious dogs, volume expansion (1,000 ml of saline in 5 min) increased left atrial pressure and dimensions and caused a 663 +/- 189% increase in plasma immunoreactive atriopeptin from 44 pg/ml. At this time, mean left atrial pressure increased only 202 +/- 36% (mean +/- SE), whereas A wave pressure increased 146 +/- 19% and V wave pressure increased 290 +/- 67%. A and V wave dimensions increased only a few percent. After developing atrial wall thickness constants for diastole (KCl fixation) and systole (BaCl2 fixation), calculated atrial A wave wall stress increased 163 +/- 25%, and V wave wall stress increased 346 +/- 85%. Minute wall stress (wall stress times heart rate) gave an even better correlation with changes in plasma atriopeptin. V wave minute wall stress increased 690 +/- 168%, whereas A wave wall stress increased 366 +/- 56%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The effect of autoclaving and enzyme supplementation of guar meal on the performance of chicks and laying hens.

Four experiments with broilers and one with laying hens were conducted to study the effects of processing and hemicellulase supplementation of guar meal (37.0% protein) on growth, feed efficiency, and egg production. Guar meal at 0, 10, and 15%, either in raw form or autoclaved at 100, 102, or 132 C for 3, 15, or 30 min, was fed alone or in the presence of 0 to 250 ppm hemicellulase. In an experiment utilizing full-term broilers, 10 and 15% autoclaved guar meal was fed in the presence of lincomycin (3.3 ppm) or in combination with lincomycin and hemicellulase (25 ppm). The laying hen experiment was conducted with 36-week-old hens for 8 weeks. They were fed the raw or autoclaved meal (102 C, 15 min) alone and in combination with 30 ppm hemicellulase. The raw guar meal depressed growth and the depression was dose-related. Autoclaving at 102 C for 15 min increased growth and feed efficiency. A higher temperature or a longer time of autoclaving failed to give any further increase in growth or feed efficiency. The lowest (16.5 ppm) hemicellulase was as effective as the highest (250 ppm) in increasing growth and feed efficiency of chicks when added to guar meal diets. Penicillin had no effect on growth or feed efficiency when added to the diet containing autoclaved guar meal in the presence of hemicellulase. Dry heating at 150 C for 6 hr or water treatment of guar meal was not effective in stimulating growth or feed efficiency. Guar meal also increased stickiness of droppings; autoclaving enhanced the effect, whereas hemicellulase prevented the sticky droppings.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Effect of dietary cereal grain, citrus pectin, and guar gum on liver fat in laying hens and young chicks.

One laying hen and three chick experiments were conducted to study the effect of cereal grains, citrus pectin, and guar gum on liver fat of chicks and hens and on serum cholesterol of chicks. Feeding of wheat, rye, or 2% pectin in place of corn reduced liver fat content. The decrease in liver fat of hens fed wheat or rye was larger than that of those fed 2% pectin (P less than .05). The smallest amount of liver fat was found in livers of hens fed the rye diet. Wheat or pectin did not affect egg production of egg weight, but rye caused a significant decline in egg production in comparison with other treatments. Addition of 4% pectin or 2% guar gum to the corn control diet lowered liver fat, serum cholesterol (P less than .05), and body weight in chicks (P less than .05). Penicillin added to the diets containing 2% guar gum gave an increase in body weight (P less than .05) but had no effect on body weight of chicks fed diets containing 4% pectin. In contrast, pectinase prevented growth depression by pectin and guar gum. Pectinase also increased liver fat and serum cholesterol of birds fed the diet containing pectin or guar gum. When the corn control diet was pair-fed to the pectin diet, growth of the pair-fed chicks was better than that of the pectin-fed birds but was lower than that of birds fed the control diet ad libitium. Pectin-fed birds again had lower liver fat the serum cholesterol than the control birds. The reduced feed intake of chicks pair-fed the corn control diet had no effect on liver fat content.

Adipose Tissue↗
PubMed1980

Effect of gamma irradiation, penicillin, and/or pectic enzyme on chick growth depression and fecal stickiness caused by rye, citrus pectin, and guar gum.

The effects of gamma irradiation of rye, corn, pectin, and guar gum and supplementation of procaine penicillin and/or pectic enzyme (Irgazyme-100) were studied. Addition of 62.5% rye, 4% pectin, or 2% guar gum in place of corn significantly reduced chick growth (P < .05). Exposure to gamma irradiation, procaine penicillin, or pectic enzyme supplementation improved the growth of chicks fed rye. Growth response on the rye diet to one or more combinations of gamma irradiation, procaine penicillin, and pectic enzyme was greater than that of gamma irradiation, procaine penicillin, or pectic enzyme alone. Gamma irradiation or pectic enzyme supplementatin of pectin or guar gum improved chick growth and almost eliminated their growth depressing properties. A combination of gamma irradiation and pectic enzyme failed to give a further significant increase in growth over that of either alone. Addition of procaine penicillin to diets containing rye, irradiated pectin, or guar gum elicited a significant growth response, but the response was greatly reduced when diets contained irradiated guar gum or irradiated pectin. Feces of chicks fed diets containing rye, pectin, or guar gum adhered to screen floors in much greater amounts than for corn-fed chicks. Gamma irradiation, procaine penicillin, or pectic enzyme had no significant effect on fecal condition of birds fed diets containing rye or guar gum. In contrast, fecal condition of birds fed guar gum was significantly improved by a combination of gamma irradiation and pectic enzyme supplement. Gamma irradiation almost eliminated and pectic enzyme supplementation completely eliminated properties of pectin causing sticky feces. Results indicate that the component of rye that causes sticky feces was not changed by gamma irradiation and/or pectic enzyme, and, therefore, is different from the growth depressing factor and from citrus pectin.

Animals↗
PubMed1980

The effect of vitamin B12 on the tolerance of chicks for high levels of dietary fat and carbohydrate.

Three experiments were conducted with White Leghorn chicks hatched from hens fed diets varying in levels of protein, fat, and vitamin B12. Adding animal fat at a level of 10% in the chick diet caused growth depression of vitamin B12 deficient chicks, regardless of protein or energy level of hen or chick diet. Increasing the level of fat to 20% in the chick diet caused further growth depression and increased mortality. Feed efficiency of vitamin B12 deficient chicks was severely depressed by each additional increment in the fat level. Increasing protein content from 20 to 30% in the chick diet resulted in severe growth depression and poor feed efficiency. Although the added fat in the 30% protein chick diet depressed growth of chicks hatched from hens fed the 16 and 32% protein with added fat, it improved growth of those hatched from hens fed the similar diets with no added fat. Added fat in the 30% protein chick diet also improved feed efficiency of all chicks regardless of breeder diet treatments. Chicks hatched with an adequate carry-over of vitamin B12 from hens or chicks fed a diet with 10 micrograms of added vitamin B12/kg of feed did not show the growth depression caused by the high level of fat in the 20 and 30% protein chick diets. Feed efficiency was greatly improved by the addition of vitamin B12 to all chick diets. In a 22% protein vitamin B12 deficient diet, isocaloric substitution of glucose for fat depressed chick growth significantly and this growth depression was counteracted by supplementing the diet with 10 or 100 micrograms of vitamin B12/kg of feed. The vitamin B12 requirement was not increased by such substitution in the 22% protein diet. In contrast, isocaloric substitution of fat for glucose in the 32% protein chick diet increased the vitamin B12 need for optimum growth.

Animals↗
PubMed1976

Effects of different cereal grains in diets for laying hens on production parameters and liver fat content.

Two experiments were conducted with White Leghorn laying hens to study the effects of different cereal grains on production criteria and liver fat content. The results of Experiment 1, in which pullets 21 weeks of age were used for a period of 22 weeks indicated that Gaines wheat or triticale (Trailblazer) were equal to corn in supporting egg production, egg weight and body weight, with comparable feed consumption. Henry wheat(a hard red winter class) was slightly, yet significantly (P less than 0.05) inferior to corn for the above criteria. No significant differences were observed among four treatments in wet liver weight and liver fat content. Hens fed the corn diet had significantly (P less than 0.05) lower carcass fat followed by the hens fed triticale in comparison with those fed Gaines or Henyry wheat. Mortality was very low and not related to dietary treatments. Neither dietary fat nor energy content was related to fat content of liver and carcass of the hens. Body weight and liver fat content were not closely related to each other. Wet liver weight was the only significantly (P less than 0.05) related factor to liver fat content. In the second experiment, in which hens 33 weeks of age were used for an experimental period of 20 weeks, opaque-2 corn was slightly superior to normal corn and triticale was comparable to normal corn in supporting egg production and egg weight. Supplementation of the diets containing the two corns and triticale with lysine failed to improve egg production and egg weight. Hens fed the diets containing either normal corn or opaque-2 corn as the only grain in the diet had significantly (P less than 0.05) higher liver fat content in comparison with hens fed the diet containing triticale as the only grain. Mortality, however, was much higher among hens fed triticale-containing diets in comparison with groups fed corn-containing diets in spite of the fact that they had significantly lower liver fat content. Regardless of dietary treatments or grains used, the hens that died were diagnosed to have fatty liver hemorrhagic syndrome. Dietary fat content was postively and significantly (P less than 0.05) related to liver fat content. Dietary energy or body weight was not closely related to liver content. Liver fat content and mortality were negatively related to each other. The higher for content did not adversely affect laying performance.

Animal Feed↗