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Biomedical subjects

R D Murray

Publications and source records attributed to R D Murray.

At least 163 records · Page 9Linked to original sources
PubMed1982

Contralateral renal function following unilateral renal artery constriction.

The acute (0.5-3.0 h) response of the contralateral kidney to unilateral renal artery constriction was studied in 7 pentobarbital-anesthetized dogs. Within 30 min after unilateral renal artery constriction to a pressure of about 60 mm Hg, contralateral vascular resistance, sodium excretion and filtration fraction increased significantly while glomerular filtration rate, blood flow and plasma flow did not change. Renin secretion decreased dramatically within 30 min, demonstrating a negative venous minus arterial plasma renin activity in some dogs. Unilateral renal artery constriction did not change the rate of angiotensin II extraction across the contralateral kidney or the urinary renin activity (measured in 4 dogs). These results indicate that the acute response of the contralateral kidney to unilateral renal artery constriction is somewhat different from that seen in the chronic state.

Angiotensin II↗
PubMed1981

Use of cloprostenol with dexamethasone in the termination of advanced pregnancy in heifers.

The difficulty of devising a standard treatment regime for cattle which would predictably terminate pregnancies in the 200 to 250 day range is described. Eight 15-month-old heifers which had been accidentally mated when approximately eight months old were examined by rectal palpation and condition scored. To induce abortion an intramuscular injection of 20 mg dexamethasone phenylpropionate was given followed 11 days later by an intramuscular injection of 500 microgram cloprostenol. A record was made of the time of calving along with calving and post calving details. Two of the heifers aborted before the injection of cloprostenol. The other six aborted within 48 hours of receiving this injection. The practical problems associated with aborting immature cattle are discussed as well as the financial aspects.

Abortion, Induced↗
PubMed1980

Significance of sodium, sympathetic innervation, and central adrenergic structures on renal vascular responsiveness in DOCA-treated rats.

The effects of sodium, sympathetic innervation, and central adrenergic structures on the development of changes in renal vascular reactivity were studied in unilaterally nephrectomized rats treated with a single implant of deoxycorticosterone acetate (DOCA; 100 mg/kg). Vascular reactivity to norepinephrine (NE) and vasopressin (ADH) was assessed in isolated kidneys perfused with a synthetic medium. Influence of sodium was determined by placing DOCA-treated rats on high, normal, and low sodium intakes. Neural influence was studied by means of local denervation of the renal artery and by intravenous (iv) and intraventricular (ivt) administration of 6-hydroxydopamine (6-OHDA). Marked changes in renal vascular reactivity in DOCA-treated rats were already apparent prior to the rise in blood pressure. Dose-response curves for NE and ADH showed parallel leftward shifts and decreased threshold doses. Normal sodium intake, local denervation, and peripheral sympathectomy had no effect on the development of these vascular changes in DOCA-treated rats. However, sodium deficiency and ivt administration of 6-OHDA totally prevented development of enhanced vascular reactivity. These results imply that increased vascular reactivity is a major factor in the development of DOCA-hypertension.

Adrenergic Fibers↗
PubMed1979

Intrarenal renin and autoregulation of renal plasma flow and glomerular filtration rate.

Autoregulatory responses of renal plasma flow (RPF) and glomerular filtration rate (GFR) to reductions in renal artery pressure (RAP) were studied in both kidneys of two-kidney, one-clamp dogs and in dogs treated with deoxycorticosterone acetate (DOCA; 25 mg/kg) plus high sodium diets with and without renal arterial clamping. In non-DOCA-treated animals, unilateral renal artery constriction resulted in a significant difference (P = 0.004) in renal renin activity (RRA) between the clamped (171 +/- 37 ng AI.mg-1.h-1) and the contralateral (57 +/- 23 mg AI.mg-1.h-1) kidneys with no change in their relative autoregulatory ability. In dogs treated with DOCA/high sodium there were no differences in RRA between the clamped and contralateral kidneys. The dogs treated with DOCA/high sodium were able to autoregulate both RPF and GFR even though their RRA was only 5.4 ng AI.mg-1.h-1. DOCA/high sodium treatment, however, reduced basal RPF (22%) and GFR (23%) below those in non-DOCA-treated animals. Analysis of the autoregulatory ability of individual kidneys showed no relationship to either RRA or renin secretory rates. These results support the conclusion that the renin-angiotensin system is not necessary component in the autoregulation of RPF or GFR.

Animals↗
PubMed1978

Renin secretion as a function of renal renin content in dogs.

The in vivo and in vitro rates of renin secretion were measured in kidneys from five groups of dogs in which renal perfusion pressure, salt diet, and neural input were varied to cause large changes in renin secretion rates and renal renin content. It was found that both the in vivo and in vitro secretory rates were proportional to the renal renin content. However, in vitro secretion rates were dependent on content up to 100 ng angiotensin I/mg tissue per h. At higher renin contents no increment in in vitro secretion rate was seen. In vivo secretion rate did not appear to reach a maximum until renal renin content was above 250 ng AI/mg tissue per h. The data are interpreted to support the hypothesis that there exist at least two pools of renin. One releases renin at a fractional rate of about 1.5% of the total content per hour. The other releases renin at a rate dependent on the magnitude of the stimuli acting on the kidneys. It is also suggested that the rate of renin synthesis may be a determinant of the basla rate of renin secretion.

Angiotensin I↗
PubMed1977

Shallow habitat air dives I and II: human hematologic responses to compressed air saturation diving.

Two subjects each were exposed to pressure equivalents of 50 (SHAD I) and 60 (SHAD II) feet of sea water gauge (FSWG) for 30 and 28 d, respectively. Red blood cell (RBC) count, hemoglobin (Hb) content, and reticulocyte count of venous blood from divers were measured before, during, and after these exposures. RBC count of the divers decreased a maximum of 7.1% in the 50-ft dive and 10.7% in the 60-ft dive compared to surface control values. Hb content fell 7.7% and 11.1% in the 50- and 60-ft dives, respectively, when compared to nondiving subjects. Reticulocyte counts tended to increase late in the pressurization phase and during the recovery. The total month-long responses of Hgb in SHAD I, and RBC, Hgb, and reticulocyte count in SHAD II were significantly altered when compared to those of the surface control subjects. The changes in these factors were directly attributable to the month-long exposure to the total hyperbaric environment. The threshold for hematological effects of chronic exposure to compressed air would seem to lie between 50 and 60 FSWG.

Air↗
PubMedDate not supplied

Absorption of valproic acid from the gastrointestinal tract of the piglet.

Valproic acid is a commonly used drug for the treatment of epilepsy. Since valproic acid can only be given orally, its absorption from the gastrointestinal (GI) tract especially in patients with short bowel syndrome (SBS) and in neonates is important. The specific sites of absorption for valproic acid in the small intestine and colon have not been investigated. It is currently unknown whether these patients are able to absorb oral valproic acid sufficiently to maintain a therapeutic serum concentration. The primary objectives of the study were to: (a) determine the relative absorption of valproic acid from specific sites in the GI tract; and (b) investigate the influence of intestinal development on valproic acid absorption using the newborn piglet as a model. Two groups were studied: Group I included 5 piglets 18-21 days of age, and Group II included 5 piglets 1-3 days of age. A valproic acid solution was simultaneously perfused through 5 partitioned segments of the gastrointestinal tract: the duodenum, jejunum, ileum, right colon and left colon. Tritiated [3H] polyethylene glycol was co-administered to monitor water movement across the GI mucosa. Following steady state, samples were collected from each segment, and analyzed by a specific enzyme-mediated immunoassay. The absorption rates (micrograms/min/cm) of valproic acid in Group I were as follows: 9.96 +/- 2.8 duodenum; 11.28 +/- 2.79, jejunum; 9.42 +/- 3.34, ileum; 10.88 +/- 3.35, right colon; 10.96 +/- 2.92, left colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Absorption of theophylline from the small and large intestine of the neonatal piglet.

In this study, the newborn piglet model was used to assess theophylline absorption from various areas of the GI tract. 13 piglets, ages 9-14 days, had their intestines surgically exposed. Four segments of equal length (jejunum, ileum, right colon and left colon) were simultaneously perfused with a saline solution containing [3H]-polyethylene glycol 4000 to measure water shifts and theophylline at a total dose of 5 mg/kg, a typical neonatal dose. Absorption of theophylline, appearance in serum, and the effects of the drug on water and electrolyte movement in the intestinal segments were monitored. Serum concentrations of theophylline after an intravenous and oral dose were also studied in 2 piglets. The data showed excellent absorption of the drug from all intestinal segments studied (jejunum 0.97 +/- 0.16, ileum 0.7 +/- 0.13, right colon 0.7 +/- 0.13, and left colon 0.88 +/- 0.19 micrograms/cm/min), despite a concomitant secretion of sodium chloride and water. No statistical differences in absorptive capacity were seen among segments. The results suggest that as little as 100 cm of residual intestine could, theoretically, absorb a 5 mg dose of theophylline if presented slowly. These findings have ramifications for neonates who may receive theophylline orally or rectally.

Animals↗
PubMedDate not supplied

An angiographic evaluation of vascular changes in sole lesions in the hooves of cattle.

In an angiographic study of vascular changes in sole lesions in cattle hooves, it was shown that hooves with sole haemorrhage at the ulcer site in the outer hind claw had constriction of the lumen of the terminal part of the proper digital artery. Severe constriction or occlusion of the lumen of the terminal part of the proper digital artery was seen in hooves with a developing sole ulcer. An avascular area at the ulcer site was seen in hooves with an early or a fully developed sole ulcer. It is concluded that vascular changes caused by hoof pathology may have an important role in the development of sole ulcers and white line lesions in cattle.

Angiography↗
PubMedDate not supplied

The effect of technical factors on the quality of pulmonary venous flow from the transverse and longitudinal imaging planes with transesophageal echocardiography.

Right and left upper pulmonary venous flow is usually assessed with monoplane transesophageal echocardiography (TEE) in the transverse imaging plane. Pulmonary venous flow in the transverse imaging plane may be relatively difficult to record because of the larger angle between the pulmonary vein and the transducer beam. To compare the quality of echocardiographically derived Doppler flows of the right and left upper pulmonary veins between the longitudinal and transverse imaging planes with TEE, we performed pulsed-wave Doppler TEE of both upper pulmonary veins in transverse and longitudinal imaging planes in 36 patients with various diseases. We also recorded a quality index for each flow profile and the angle between the transducer beam and the pulmonary vein. The quality index of the left pulmonary venous flow assessed with the longitudinal and transverse imaging planes was similar in 35 (95%) of 36 patients, whereas the longitudinal imaging plane was superior to the transverse plane in one patient (3%). In contrast, the quality index of the right pulmonary venous flow assessed with the longitudinal and transverse imaging planes was similar in only 19 (53%) of 36 patients, whereas in 17 patients (47%) the longitudinal imaging plane was superior to the transverse imaging plane. The quality index had a significant effect on the Doppler flow recordings; suboptimal-quality flow recordings significantly underestimated the pulmonary venous diastolic flow integrals. The left atrium was larger in those patients with unobtainable flows than in those patients with exclusively obtainable flows (p < 0.001). The angle between the sample volume and the right pulmonary vein was larger in the transverse imaging plane than in the longitudinal plane (p < 0.001). In conclusion, the longitudinal imaging plane is generally superior to the transverse imaging plane for assessing right pulmonary venous flow and is recommended for performing a comprehensive assessment of pulmonary venous flow. The ability to obtain quality images and accurate assessment of flow may be related to the size of the left atrium and angle of the pulmonary vein.

Adult↗
PubMedDate not supplied

Left and right atrial transport function after the Maze procedure for atrial fibrillation: an echocardiographic Doppler follow-up study.

OBJECTIVES: We evaluated atrial transport function after the Maze procedure in long-term follow-up and compared left and right atrial function in Maze patients with that of healthy age-matched controls using echo Doppler techniques. BACKGROUND: The Maze procedure is designed to eliminate atrial fibrillation, restore normal sinus rhythm, and preserve atrial contraction. Initial data indicate that atrial transport function is restored in most patients undergoing the Maze procedure. The long-term echo Doppler evaluation of patients after the Maze procedure has not been well described. METHODS: We performed pulsed-wave Doppler and two-dimensional echocardiographic studies on 31 patients (24 men, mean age 53.8 years) who underwent the Maze procedure and who had a follow-up study greater than 3 months (mean 16.5 months) after the procedure. Measurements included peak left ventricular and right ventricular inflow A-wave velocity, maximum and minimum left atrial and right atrial areas, and fractional area change of the left and right atria. Results were compared with those obtained from 15 age-matched control subjects (11 men, mean age 53.8 years). RESULTS: Twenty-two patients (71%) had left atrial function shown by the presence of left ventricular inflow A-wave, and 25 patients (81%) had right atrial function shown by the presence of right ventricular inflow A-wave on Doppler echocardiography. The left ventricular inflow A-wave velocity was significantly lower than that of age-matched controls (37.5 +/- 15.5 versus 61.0 +/- 13.9 cm/sec; p < 0.001), whereas the right ventricular inflow A-wave velocity did not significantly differ between patients and control subjects (35.4 +/- 9.9 versus 35.3 +/- 4.9 cm/sec; p = Not significant). Although left and right atrial areas decreased significantly after the procedure, there was no significant change in the fractional area change which was smaller in Maze patients than control individuals. CONCLUSIONS: (1) In long-term follow-up of 16.5 months after the Maze procedure, left atrial systolic function was preserved in 71% of our patients and right atrial systolic function was preserved in 81%; (2) the left ventricular inflow peak A-wave velocity after Maze is considerably less than that in age-matched controls; and (3) left and right atrial sizes decreased after the procedure with no change in the fractional area change. These findings suggest that the Maze procedure is effective in restoring atrial function in the majority of patients; however, restored function is less than in control individuals.

Adult↗
PubMedDate not supplied

Experimental and numerically modeled effects of altered loading conditions on pulmonary venous flow and left atrial pressure in patients with mitral regurgitation.

Pulmonary venous flow measured by pulsed-wave Doppler transesophageal echocardiography reflects the effects of mitral regurgitation on left atrial pressure contour. To assess the relationship between pulmonary venous flow and left atrial pressure in patients with mitral regurgitation under altered loading conditions, we studied 25 patients with 3+ or 4+ mitral regurgitation and a control group by measuring pulmonary venous flow with transesophageal echocardiography and left atrial pressures after administering saline solution (n = 6), nitroglycerin (n = 6), phenylephrine (n = 6), or nitroprusside (n = 7). After administration, the left atrial pressure v wave increased in the group given phenylephrine, concomitant with an increased diastolic flow. In contrast, the left atrial pressure v wave decreased in the group given nitroglycerin, concomitant with a decreased diastolic flow. Changes in diastolic flow were closely related to changes in the left atrial pressure v wave under all loading conditions (r = 0.91; p < 0.0001). Numeric modeling of left atrial pressure and pulmonary venous diastolic flow corroborated the experimental findings. We conclude that changes in pulmonary venous diastolic flow are closely related to changes in the left atrial pressure v wave in mitral regurgitation, under altered loading conditions.

Adult↗
PubMedDate not supplied

Vasopressin and vascular reactivity in the development of DOCA hypertension in rats with hereditary diabetes insipidus.

To examine the role of vasopressin (VP) in DOCA-salt hypertension, arterial pressure and renal vascular reactivity were studied in control Long-Evans (LE) rats and in Brattleboro rats homozygous for diabetes insipidus (DI rats). Vascular reactivity to norepinephrine, VP and angiotensin II was assessed in isolated kidneys perfused at constant flow. LE rats showed an increase in arterial pressure (AP) which was significant at 2 weeks post DOCA and averaged 180 mm Hg at 4 weeks. DI rats lacking VP showed no rise in AP after DOCA; however, DI rats given VP and DOCA developed hypertension with a course and magnitude similar to that observed in LE rats. At 6 to 10 weeks post DOCA, renal vascular reactivity to all agents was increased in LE rats and DI rats replaced with VP. Normotensive DI rats lacking VP showed depressed reactivity. Assessment of changes in reactivity at 3 days post DOCA showed that changes preceded the rise in AP. These data suggest that VP may play a primary role in the pathogenesis of DOCA hypertension and that its mechanism may involve an induction of increased vascular reactivity.

Animals↗
PubMedDate not supplied

Rectal myopathy in chronically constipated children.

We examined full-thickness rectal biopsies from 30 children who had chronic constipation, including 5 children with constipation associated with clinical symptoms of intestinal pseudo-obstruction. Biopsies from 9 patients who required colonic interposition and from 7 with Hirschsprung's disease were used as controls. Tissues were evaluated for muscularis mucosae thickness (in mm), for absolute circular and longitudinal muscle layer thicknesses and their ratio, and for the intensity of neural vasoactive intestinal peptide (VIP) immunohistochemical staining. Atrophy of the rectal musculature with focal muscle fiber vacuolation or muscle fiber disappearance was found in all children with chronic constipation. Muscularis mucosae thickness was increased (P < .01) and the circular-to-longitudinal muscle ratio was decreased in the constipation group, with the greatest degree of atrophy being demonstrated in the circular layer. Two of the patients had additional biopsies up to 9 years after the first that illustrate progressive myopathic changes over time. This study demonstrates muscular atrophy in the rectum of children with chronic constipation. Besides primary idiopathic disease, potential etiologies include chronic distention, denervation, functional obstruction from obstipation, alteration in gut hormones, and toxic, ischemic, or neural injury.

Adolescent↗