ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We studied the influence of altered rates of intrarenal prostaglandin synthesis on known renin control mechanisms in single, filtering and nonfiltering, denervated kidneys of chloralose, anesthetized dogs. Infusion of indomethacin directly into the renal artery resulted in 50% reductions in both renin and prostaglandins effluxing from the renal vein. The increased plasma renin resulting from suprarenal aortic constriction was unaffected by indomethacin despite suppressed renal vein prostaglandin efflux. However, the renin response to furosemide was blunted by prior renal arterial indomethacin administration even though furosemide had no influence on prostaglandin efflux. Renin secretion also was suppressed by intrarenal indomethacin administration in nonfiltering kidneys. Intrarenal arachidonic acid infusion resulted in parallel increases in renin and prostaglandin in both papaverine-treated and untreated, nonfiltering, denervated kidneys. Imposition of intrarenal indomethacin during arachidonic acid infusion in nonfiltering kidneys suppressed prostaglandin efflux from both papaverinize-treated and untreated kidneys; however, renin secretion was suppressed by indomethacin in only the control kidney. Since renin was stimulated by arachidonic acid in nonfiltering, denervated, papaverine-treated kidneys, it is concluded that the in vivo intrarenal cyclooxygenase-dependent conversion of arachidonic acid to prostaglandins exerts its influence on renin secretion by a direct influence on juxtaglomerular cells and is independent of other presently recognized renin control mechanisms. Ore Res 45:13-25, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

After cervical aortic nerve section, mean arterial pressure in the unanesthetized dog increased by an average of 7.4 mm Hg. Following a more extensive denervation of aortic arch receptors by section of intrathoracic vagal branches, arterial pressure increased by 16.7 mm Hg. The above changes were seen in the stable state after the effects of surgery had disappeared. In both cases carotid baroreceptors were functional. After administration of nitroglycerin and phenylephrine subsequent to either denervation procedure, blood pressure changes were larger and heart rate responses were smaller than in the control state. The unanesthetized dog regulates mean arterial pressure at a higher-than-normal pressure after aortic baroreceptor denervation. Reflexes from the aortic baroreceptors continuously participate in the normal control of mean arterial pressure. Section of the cervical aortic nerves only partially denervates aortic baroreceptors. Our findings may be relevant to human essential hypertension. Ore Res 45: 26-34, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We studied the kinetics of very low density lipoprotein (VLDL) B-apoprotein by compartmental analysis in 28 human subjects, 20 of whom were hyperlipoproteinemic. Three parameters were derived: the size of the major pool (MA)> the flux of B-apoprotein through pool A (PRA), and the fractional removal rate from the pool (KAA). Highly significant correlations were found between MAand PRA(positive) and between MAand KAA(negative). The findings indicated that expansion of pool size was brought about in part by an increased input. Although the strong negative correlation between MAand KAAwould also imply an important role for removal rates, this conclusion remains tentative without knowledge of whether removal rate is independent of pool size. Body weight was also highly significantly correlated with KAA(negatively) but not with PRA, suggesting that overweight contributes to expanded VLDL pools by decreasing removal, and also that removal rate may therefore determine pool size independently of production. The mean fluxes were similar in 10 subjects with hypertriglyceridemia alone and in eight subjects with combined hyperlipoproteinemia. In normolipidemic subjects, pool A appeared capable of accommodating a relatively greater input without as large an expansion in size as was observed in hyperlipidemic subjects. Ore Res 45: 35-41, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The femoral and popliteal arteries are least affected by atherosclerosis where they cross the hip and knee joint. We evaluated possible reasons for this by studying the changes in arterial length and diameter, and the patterns of blood flow in these arteries. The changes of length due to bending of human and canine popliteal arteries were determined radiographically and changes in arterial resistance and diameter were deduced from simultaneous measurements of pressure and flow in the artery above and below the canine knee joint in different degrees of flexion. Flow patterns were assessed in the canine popliteal artery during bending by radiographic screening of a streamline. Equivalent observations were made in a mechanical model. During flexion of the knee joint, the adjacent artery shortens by as much as 20%, but the arterial diameter remains effectively unchanged. The results of the flow pattern experiments suggest that turbulent flow is generated in the distal position of an artery crossing a bending joint. We suggest that these changes may be responsible for the lack of atherosclerosis in the segments of arteries that cross joints. Circ Res 46: 41-47, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The cerebral ischemic response was elicited in anesthetized rabbits by briefly clamping both common carotid arteries after previously occluding the vertebral arteries. The primary cerebral ischemic response, elicited after elimination of baroreceptors, consisted of arterial hypertension, bradycardia, and apnea. The hypertension resulted from a sterotyped and differentiated pattern of vasoconstriction in renal, mesenteric, and femoral arteries. Total peripheral conductance and cardiac output were decreased. Vagotomy usually changed the bradycardia to a tachycardia unaffected by adrenalectomy. With baroreceptors intact the magnitude of the bradycardia increased and its latency decreased. The ischemic response persisted after transection of brainstem at the pontomedullary junction and/or of lower cranial nerves (except for the bradycardia which was abolished by transection of vagal rootlets). Transection of the spinal cord at Cl abolished the reflex hypertension and apnea, but not the bradycardia. Hypertension and changes of regional blood flow, comparable qualitatively and quantitatively to those elicited by ischemia, were produced by electrical stimulation of areas of the medullary reticular formation encompassing portions of the gigantocellular and parvocellular reticular nuclei. We conclude: (1) the primary cerebral ischemic response i« associated with a neurally mediated and differentiated pattern of vasoconstriction and with coactivation of the cardiac vagal and sympathetic nerves; (2) the reflex cardiac, but not vasomotor, components are secondarily modified by baroreceptor reflexes; (3) the ischemic response results from direct stimulation of neurons in the medulla oblongata; (4) the parvocellular and gigantocellular nuclei mediate the vasomotor but not the cardiac and respiratory components of the response. Ore Res 44: 48-62, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We studied the effect of bilateral electrolytic lesions in the medulla oblongata on the cerebral ischemic reflex in 24 anesthetized rabbits. In IS animals lesions were placed in areas from which the differentiated vasomotor component of the response was elicited by electrical stimulation. In four rabbits (group A) the lesions entirely abolished the vasomotor, but not cardiac responses to cerebral ischemia, and resulted in an irreversible fall, to 30-40 mm Hg, of the arterial pressure (AP). These lesions destroyed large portions of the nucleus reticularis parvocellularis, the dorsal part of the nucleus reticularis gigantocellularis, and the ventromedial portion of the medial vestibular nuclei at the level of the inferior olive (3 mm rostral to the obex). In four other rabbits (group B) the pressor response was reduced to 25-87% of control with a fall of AP not as marked as that in group A. These lesions were within the same areas or very close to those of group A but smaller. In the remaining seven rabbits (group C) the lesions did not alter the ischemic response or AP; they were either restricted to the nucleus reticularis gigantocellularis alone, were smaller than in group B, or if large, were located several millimeters more rostral to those of group A. In nine control rabbits lesions placed elsewhere in the medulla failed to alter the ischemic response or resting AP. We conclude that the vasomotor, but not the cardiac or respiratory, components of the cerebral ischemic response depend upon a restricted portion of the bulbar reticular formation. Moreover, the integrity of this region is essential for maintenance of normal resting levels of AP and, hence, appears to function as the so-called tonic vasomotor center of the brainstem. Ore Res 44: 63-70, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Previous studies from this laboratory have demonstrated that the central hypervolemia induced by water immersion to the neck (NI) constitutes a suitable model for assessing the hormonal response to volume expansion without concomitant alterations in plasma composition. The NI model was used to assess in a kinetic fashion the relationship between renal prostaglandin E (PGE) and renal sodium handling. Nine normal subjects were studied twice in the sodium-replete state during NI: with indomethacin (Ind) pretreatment (50 mg q6h x 6)(NI + Ind) and without indomethacin (NI). Urinary sodium, potassium, and PGE excretion (UPGEV) were measured hourly. NI was associated with marked increases in UN.V [from 87 ± 20 (SE) to 219 ± 25 μEq/min (P < 0.06)] and UpGKV[from 6.4 ± 1.4 to 12.9 ± 2.5 ng/min (P < 0.05)]. Although indomethacin administration lowered the basal rate of UPGBV prior to immersion, it neither prevented the subsequent augmentation of UPGEV during NI + Ind nor affected the magnitude of the natriuresis during NI + Ind. Subsequently, six of the subjects were restudied following dietary sodium restriction (10 mEq/day). The changes in UPGBV during NI and NI + Ind were qualitatively similar to those observed in the sodium-replete state. In contrast to the sodium-replete studies, however, the natriuresis of immersion was attenuated markedly by indomethacin pretreatment. In summary, the data demonstrate that immersion-induced central volume expansion is associated with a striking increase in renal PGE excretion which is attenuated but not prevented by indomethacin. In addition, indomethacin administration attenuates markedly the natriuretic response of immersion in sodium-depleted, but not in sodium-replete, normal subjects. These observations are consistent with the suggestion that renal PGE may constitute a determinant of the renal response to volume expansion in sodium-depleted man. Circ Res 45: 71-80, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Chronic pressure overload leads to hypertrophy, depressed mechanical function, and reduced myosin ATPase activity. However, it is not known whether the lowered myosin ATPase activity results from the hypertrophic process per se or whether the elevated afterload is required for the depressed myosin ATPase activity. Further, a causal relationship between lowered myosin ATPase and weakened mechanical function in pressure overload has not been established. Chronic volume overload on the myocardium, leading to hypertrophy equivalent to that in pressure overload, allows the effects of pressure overload to be separated from the effects of hypertrophy and provides insight into the association between myosin ATPase and mechanical function. We produced large atrial septal defects (ASD) with a transvenous biopsy catheter in six adult cats. This resulted in 63% right ventricular hypertrophy, normal (P > 0.05) papillary muscle mechanical function (velocity at 0.5-g/mm2load: control-1.01 ± 0.05 muscle lengths per second; ASD-1.02 + 0.26 muscle lengths per second), and normal (P > 0.05) myosin ATPase activity in three activating mediums (actin: C-0.20 ± 0.02, ASD «· 0.21 ± 0.03; Ca1+: C - 0.41 ± 0.03, ASD - 0.38 ± 0.02; K-EDTA: C - 1.67 ± 0.05, ASD - 1.69 ± 0.07 pmol Pi/min · ing). We concluded that pressure overload is required for depression of myosin ATPase activity. Our study supports the concept that depression of myosin ATPase is causally related to depressed mechanical function in chronic pressure overload. Circ Res 46: 81-87, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

This study was designed to quantify and compare transmural myocardial blood flow in the right and left ventricles of awake dogs during systole and diastole, and during total coronary artery occlusion. Studies were performed in six awake dogs chronically prepared with electromagnetic flowmeters and pneumatic occluders on the left circumflex and right coronary arteries. Intermittent coronary perfusion, confined to the interval of cardiac systole or an equivalent period during diastole, was effected by an R wave-triggered pneumatic valve connected to the occluders. To measure regional myocardial blood flow, radionuclide-la'oeled microspheres, 7-10 jim in diameter, were injected into the left atrium. We found that when arterial inflow was confined to systole, blood flow was normal in the left ventricular subepicardium, whereas flow to deeper myocardial layers was decreased as a linear function of tissue depth. When coronary arterial inflow was limited to an equivalent period in diastole, left ventricular transmural flow was uniform. In contrast to this, right ventricular transmural myocar-dial blood flow was unchanged from control values when coronary inflow was confined to systole or to an equivalent interval in diastole. During total coronary artery occlusion, absolute blood flow decreased similarly in myocardial areas perfused by the left circumflex and right coronary arteries. However, the transmural distribution of collateral blood flow was markedly different in the two ventricles. Left ventricular collateral flow was preferentially directed to the subepicardial layers, but right ventricular collateral flow was distributed uniformly across the ventricular wall. The transmural gradients observed in the left ventricle during total coronary artery occlusion and when arterial inflow was confined to systole can be explained by the functioning of a vascular waterfall during left ventricular contraction. Ore Res 45: 88-94, 1979

ISSN:0009-7330    

出版商:OVID    

年代:1979

数据来源: OVID