The American journal of physiology
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Sequential glucose flux studies were carried out in five normal and six epileptic children and ten adult volunteers using [6,6-2H2]glucose to determine the effect of ketosis on carbohydrate homeostasis in children and adults. All subjects were studied after 14 and 30-38 h of fasting while consuming a normal diet and the epileptic children under 14 h of fasting while consuming an isocaloric ketogenic diet (75% fat wt/wt). ⋯ When glucose flux was corrected for estimated brain weight, the relationship between glucose flux and ketonemia was linearly related in children (P less than 0.001), in adults (P less than 0.02), and when all subjects were considered together (P less than 0.001). The inverse relationship between ketonemia and glucose flux corrected for estimated brain mass is consistent with a partial replacement of glucose by ketone bodies for cerebral metabolism and may provide a more rational means of expressing glucose flux data to take into account the higher brain-to-body ratio in children.
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The concentration of ketone bodies and their rate of transport (estimated with an infusion of beta-[14C]-hydroxybutyrate) were determined before, during, and after exercise in overnight-fasted and 3- to 5-day-fasted subjects who walked on a treadmill for 2 h at approximately 50% of their VO2max. In overnight-fasted subjects, exercise increased the rate of turnover (+125% after 2 h) and the metabolic clearance rate of ketone bodies whose concentration rose from 0.20 to 0.39 mM. ⋯ In sharp contrast with overnight-fasted subjects, starved subjects (with a resting ketone level averaging 5.7 mM) responded to work by a decrease in the turnover rate and in the concentration of ketones, their metabolic clearance rate remaining unchanged. Thus, the response of ketogenesis and muscular ketone uptake to exercise are both markedly influenced by the initial degree of fasting ketosis.
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In vitro studies indicated that one ventricle can influence diastolic distensibility and systolic function of the opposite ventricle. Based on these in vitro observations, ventricular interdependence was examined in 12 anesthetized dogs. Right (RV) and left (LV) ventricular volumes and pressures and esophageal pressure (EP) were simultaneously measured during intermittent positive-pressure ventilation (IPPV) at zero end-expiratory pressure. ⋯ As for systolic function, a comparison of end-expiration and peak inspiration data shows that RV ejection fraction increased (0.48 +/- 0.03 to 0.55 +/- 0.03 P less than 0.05) and RV stroke volume increased 5.6 +/- 1.0 ml, whereas LV ejection fraction decreased (0.54 +/- 0.03 to 0.52 +/- 0.03, P less than 0.05) and LV stroke volume decreased 0.8 +/- 0.6 ml. The decreased LV ejection fraction and stroke volume may suggest systolic interaction between the ventricles. The data indicate that the cardiovascular response to IPPV is complex, with ventricular interdependence being an important element.
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Rats consuming Coca-Cola and Purina chow ad libitum increased their total energy intake by 50% without excess weight gain. Their resistance to cold was markedly improved. These phenomena were characterized by significant increases in interscapular brown adipose tissue weight (IBAT) (91%), cellularity (59%), triglyceride content (52%), protein content (94%), and cytochrome oxidase activity (167%). ⋯ Physiol. 239 (Endocrinol. Metab. 2): E422-E429, 1980). It is concluded a) that sucrose and Coca-Cola consumption improve the resistance of rats to cold, most probably by increasing brown adipose tissue cellularity, and b) that moderate caffeine intake might be useful for inhibiting proliferative activity in white adipose tissue, thereby preventing obesity.
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Carotid sinus baroreceptor (CBR) sensitivity may be increased by electrical stimulation of sympathetic nerves passing to the carotid sinus region. It remains unknown if reflexly induced changes in efferent sympathetic discharge affect CBR function. In 17 anesthetized dogs, we reflexly induced alterations in sympathetic discharge and recorded CBR activity originating from a vascularly isolated carotid sinus. ⋯ Raising pressure (to 200 mmHg) in the contralateral carotid sinus (n = 7) resulted in a reflex decrease in arterial pressure (169 +/- 16 to 129 +/- 13 mmHg) and a reduction (82 +/- 3% of control) in baroreceptor activity (P less than 0.05). The changes in baroreceptor discharge were abolished by ipsilateral cervical sympathectomy or ganglionic blockade (n = 4). Our findings demonstrate that reflexly induced alterations in the activity of sympathetic fibers innervating the carotid sinuses can modulate baroreceptor discharge.