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Biomedical subjects

R Osgood

Publications and source records attributed to R Osgood.

7 recordsLinked to original sources
PubMed1996

The use of a novel monitoring apparatus and modified Belzer hydroxyethyl starch perfusate for analysis of glomerular filtration during hypothermic perfusion preservation.

The present study describes an experimental model for measurement of glomerular filtration during hypothermic perfusion preservation (HPP). To facilitate glomerular filtration during HPP, perfusate oncotic pressure was reduced by lowering the concentration of hydroxyethyl starch. Lewis rats underwent HPP at a mean perfusion pressure of 40-46 mmHg. An isograft model was used to demonstrate that retrieval and preparation for HPP did not impact adversely on renal function. Total cold ischemic time (CIT) consisted of the time from retrieval and preparation for perfusion (2 hr) added to the time of HPP. Tubular function studies demonstrated identical concentrations of Na+ and iohexol in ureteral effluent (UE) compared with circulating perfusate and, as such, established that UE flow represented a direct measure of glomerular filtration. Glomerular filtration rate (GFR) was then monitored during HPP by collecting UE in a beaker housed within a computerized Mettler balance system. GFR evolved in a characteristic, biphasic pattern during HPP, increasing from baseline values to reach a peak level at 4.8+/-0.3 hr of CIT and declining progressively thereafter. At 2.5 hr, time of peak values, 10 hr, 19.5 hr, and 24 hr of CIT, GFR values were 29+/-6 microl/min, 39+/-7 microl/min, 20+/-4 microl/min (n=15; P<0.01), 7+/-2 microl/min (n=14; P<0.001), and 14+/-6 microl/min (n=5), respectively. Intrarenal perfusate flows at the same time intervals were 4180+/-292 microl/min, 4083+/-290 microl/min, 3577+/-294 microl/min (P=NS), 1948+/-393 microl/min (P<0.001), and 2175+/-743 microl/min, respectively. Filtration fraction (FF) initially changed in parallel to glomerular filtration. Thereafter, FF either declined at a disproportionately slow rate compared with GFR (n=8) or increased rapidly (n=7). The data suggest that (1) primary change(s) in glomerular dynamics occur during HPP and (2) declining perfusate flow during the later stages of HPP reflects increasing renal vascular resistance localized at a postglomerular level. The data provide an experimental basis for investigating the clinical utility of monitoring glomerular filtration during HPP.

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PubMed1989

Effect of exogenous ANP on initial renal function following 24-hour cold preservation.

The impact of synthetic atrial natriuretic peptide (sANP) on renal function following cold ischemic injury was studied in a canine autotransplant model. Following a prenephrectomy inulin clearance determination (CIn), the left kidney was excised, flushed with Eurocollins solution, and cold-stored for 24 hours. Immediately following reperfusion and a 10 minute equilibration period, baseline CIn was measured over a 20-minute time interval (Collection Period I). Experimental animals (N = 11) then received 1 mcg/kg sANP by intravenous bolus followed by a continuous infusion at 0.3 mcg/kg/min for 30 minutes. CIn was measured throughout the infusion (Collection Period II). Normal saline was substituted for sANP in control animals (N = 11). CIn was also measured 24 hours following reimplantation in seven control and seven sANP-treated animals. Autograft inulin clearance increased from 0.32 +/- 0.11 ml/min during Period I to 2.5 +/- 0.6 ml/min during sANP infusion (P less than 0.01). This increase in CIn associated with ANP infusion was accompanied by increases in urine flow rate (V) (0.15 +/- 0.05 ml/min to 0.98 +/- 0.21 ml/min, P less than 0.01) and renal blood flow (RBF) measured by electromagnetic flow probe (85 +/- 17 ml/min to 171 +/- 13 ml/min, P less than 0.05). No significant changes in CIn, V, or RBF occurred in control animals between periods I and II. Although systemic blood pressure declined during sANP infusion, it did not decrease to an extent that compromised peripheral perfusion. CIn determined 24 hours after autograft reimplantation in the ANP-treated animals approximated or exceeded values determined during ANP infusion (Period II).(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1984

Delineation of the site of action of guanabenz in the renal tubule.

Guanabenz, a centrally acting alpha 2-agonist, has been shown to lower blood pressure (BP) while maintaining glomerular filtration rate and increasing water and solute excretion. The site and mechanism of the increased solute excretion are still unclear. To evaluate the effect of guanabenz on water and solute reabsorption in the collecting duct, Munich Wistar rats were utilized in micropuncture experiments. Micropuncture samples were obtained from the most proximal portion (base) of the collecting duct and the most distal part (tip). In an initial group of hydropenic rats, collecting duct water and chloride (Cl) reabsorption were evaluated during a control and experimental period during which guanabenz was infused at 20-40 micrograms/kg/min. Although the mean drop in BP was 18 mm Hg after guanabenz infusion, at any given rate of Cl delivery, the reabsorption was less than that for the control period. Another group of studies utilizing the plasma repletion method to increase Cl excretion was used to evaluate collecting duct reabsorption. BP was lowered in rats by an aortic snare to approximately 95 mm Hg and papillary collecting duct (PCD) samples were obtained. The snare was then released and 100-400 micrograms/kg/min of guanabenz was infused and the rate adjusted to produce a drop in BP similar to that of the initial period. During the control period, PCD fluid to plasma inulin ratios were 23.1 +/- 4.3 and 37.3 +/- 4.6 at the base and tip, respectively. This ratio was decreased to 10.9 +/- 3.1 and 15.7 +/- 4.6 at the base and tip puncture sites, respectively, during guanabenz infusion. PCD chloride reabsorption during the initial period was 40.3% +/- 7.0% of the load delivered. During the guanabenz infusion, however, only 12.8% +/- 3.4% of the delivered load was reabsorbed (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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