Biomedical subjects

C D Brown

Publications and source records attributed to C D Brown.

At least 55 records · Page 3Linked to original sources

PubMed1995

Reduction of lipoprotein(a) following treatment with lovastatin in patients with unremitting nephrotic syndrome.

Pharmocologic treatment of the hyperlipidemia associated with the nephrotic syndrome with lovastatin has been previously shown to be safe and effective. However, there is no information on the effect of lovastatin treatment on plasma lipoprotein(a) [Lp(a)] levels in patients with the nephrotic syndrome. We administered lovastatin (40 to 80 mg/day) to 20 adult patients with unremitting nephrotic syndrome for 8 weeks to assess its effect on plasma Lp(a) and other plasma lipid concentrations. Apoprotein(a) (apo(a)) phenotype was determined in all patients. Patients were grouped according to their plasma Lp(a) levels. Those with elevated plasma Lp(a) (> or = 30 mg/dL) were placed in group I and those with normal Lp(a) levels (< 30 mg/dL) were placed in group II. Mean total cholesterol and LDL cholesterol were similarly and significantly reduced in groups I and II (-35.9% and -43.3%, P < 0.0005, P < 0.0005 group I, and -31.0% and -42.0%, P < 0.02, P < 0.03 group II, respectively). The median reduction in plasma Lp(a) was -32% (P < 0.003) in nephrotic patients in group I, whereas the median decline in plasma Lp(a) levels in nephrotic patients in group II was only -8.0% (P = 0.052). The overall frequency of the high molecular weight (M(r)) apo(a) phenotype S4 was 70% in nephrotic patients. There was no correlation between plasma Lp(a) and apo(a) phenotype. Treatment with lovastatin results in a favorable response in terms of total and low-density lipoprotein cholesterol lowering in patients with the nephrotic syndrome; however, plasma Lp(a) levels are uniformly and significantly reduced only in nephrotic patients with elevated baseline plasma Lp(a) concentrations. There was no correlation between plasma Lp(a) concentration and other lipid and biochemical parameters.

Adult↗

PubMed1995

Erythropoietin in diabetic macular edema and renal insufficiency.

Erythropoietin was administered to five anemic azotemic diabetic subjects for 1 year to assess the effect of increasing red cell mass on clinical well-being and the course of renal functional decline. None of the subjects manifested worsened hypertension or cerebrovascular or cardiovascular complications despite an increase in mean hematocrit from a baseline mean of 29.6% to a mean of 39.5%. The serum creatinine concentration after 1 year of treatment with erythropoietin was 3.7 mg/dL, which was unchanged from the baseline value of 3.5 mg/dL. Plasma viscosity remained constant as red cell mass increased. Although the viscosity of whole blood rose as the hematocrit increased, it was within the range of normal blood viscosity for an equivalent hematocrit. The favorable impact of erythropoietin treatment on three diabetic subjects who had macular edema and anemia is described. One hypothesis to explain the benefit of a raised hematocrit on both diabetic nephropathy and retinopathy is that the metabolic, hormonal, and hemodynamic components of the diabetic syndrome, in concert, produce tissue and cellular hypoxia that is ameliorated in part by the greater oxygen-transporting capacity of a raised red cell mass. The pseudohypoxia of diabetes may be implicated in the pathogenesis of diabetic neuropathy, retinopathy, muscular dysfunction, and nephropathy.

Blood Viscosity↗

PubMed1995

pH-dependent transport of procainamide in cultured renal epithelial monolayers of OK cells: consistent with nonionic diffusion.

1. Previous studies suggest that procainamide is a substrate for organic cation/proton antiport. In order to study the coupling between procainamide flux and proton flux in greater detail we investigated the effects of extracellular procainamide addition upon intracellular pH in cultured monolayers of renal OK cells. Intracellular pH was monitored by use of BCECF as a probe. 2. Apical addition of procainamide (10 mM) caused a significant alkalinisation of intracellular pH. Basolateral addition of procainamide was equally effective in raising intracellular pH. A similar alkalinisation was found in two other renal cell lines: MDCK strain 1 and LLCPK1. 3. In contrast, both tetraethylammonium and N-methylnicotinamide, archetypal substrates for organic cation/proton antiport were without effect upon intracellular pH. 4. At physiological pH values, procainamide exists as a neutral weak base (B) and its conjugate weak acid (BH+). To test which species of procainamide was responsible for the alkalinisation, experiments in which [B] was kept constant whilst [BH+] was varied from 1.15 mM to 7.25 mM were performed. The results suggested that the neutral weak base (B) was the permeant species. 5. Procainamide efflux from procainamide-loaded cell monolayers resulted in a significant acidification of intracellular pH. As with procainamide uptake, this result could be ascribed to the movement of neutral weak base. 6. These effects of procainamide upon intracellular pH are consistent with nonionic diffusion of procainamide rather than an interaction of procainamide with the organic cation/proton antiporter. In addition, the results suggest that organic cation/proton antiport is not highly expressed in OK cells.

Animals↗

PubMed1995

The prognosis and treatment of true local cutaneous recurrent malignant melanoma.

BACKGROUND: The prognosis and treatment of true local cutaneous recurrent malignant melanoma is presently unknown. We define this entity as melanoma bearing an in situ component that recurs contiguous with the scar of the primary excision. Although previously uncommon, the incidence of true local recurrent melanoma may rise due to the recent use of more narrow margins for excision of thin primary melanoma. OBJECTIVE: We hypothesized that there is a difference in prognosis between true local cutaneous recurrent melanoma versus local recurrence from satellite or in-transit metastases. Also, we defined guidelines for the surgical management of true local cutaneous recurrent melanoma. METHODS: We calculated the surgical margin necessary to reach a tumor-free plane using Mohs surgery in 50 patients with true local recurrent melanoma. Patient survival was determined by the Kaplan-Meier method. RESULTS: Seventy-six percent of the tumors were completely excised using a margin of less than 1 cm. However, a margin of up to 2 cm was required to successfully treat all 50 patients. Thicker tumors did require significantly larger margins. The Kaplan-Meier 5-year overall and melanoma survival rates were 89% and 98%, respectively. The 5-year disease-free survival rate was 66%. CONCLUSION: The prognosis of true local recurrent melanoma is related to tumor thickness. We recommend full-thickness excision of the entire old scar including a 2-cm margin or Mohs surgery if a narrower margin of resection is desired.

Adult↗

PubMed1995

Choice of wound dressings and ointments.

Over the last several decades, methods for wound dressing have dramatically changed. This article reviews the effects of wound dressing, antiseptics, and antimicrobials on the process of wound healing and on the incidence of wound infection. A set of guidelines is provided to help the surgeon decide what to apply topically to wounds and which dressing to select to achieve the best possible outcome in wound healing.

Anti-Infective Agents, Local↗

PubMed1994

Metabolism and testicular toxicity of 1,3-dinitrobenzene in rats of different ages.

Susceptibility to 1,3-dinitrobenzene (1,3-DNB)-induced testicular damage is known to increase with age. The present study investigated the possibility that age-dependent differences in metabolism and disposition could account for differences in toxicity. [14C]1,3-DNB (25 mg/kg, ip) was administered to Sprague-Dawley rats which were 31, 75, or 120 days of age. Levels of 1,3-DNB and 1,3-DNB metabolites were determined in blood and urine. As animal age increased, peak blood concentrations of 1,3-DNB were lower and declined more slowly indicating an age-dependent decrease in rate of metabolism and a possible increase in volume of distribution. In younger animals, faster elimination rates were associated with higher blood levels of metabolites. Urinary metabolites were generally similar for all age groups with the exception of the diacetamidobenzene metabolite which was significantly lower in the urine of 31 days old rats. There were clear differences in the toxicokinetic profile for 1,3-DNB between the 31 day old rats and the other two age groups. However, differences between the 75 and 120 day old animals were less marked. Testicular damage induced by 1,3-DNB (25 mg/kg, ip) was hardly detectable in the youngest animals, while the intermediate age group showed a moderate lesion particularly in later stages of spermatogenesis. For the oldest animals, testicular damage was more severe, particularly in the earlier stages of spermatogenesis. Overall, the rapid elimination rate could account for the lack of 1,3-DNB toxicity in very young animals. However, simple metabolic differences were less likely to adequately explain the increase in testicular damage found as animal age increased from 75 to 120 days.

Age Factors↗

PubMed1994

L-alanine absorption in human intestinal Caco-2 cells driven by the proton electrochemical gradient.

In human Caco-2 intestinal epithelial layers, L-alanine absorption can be energized by a proton gradient across the brush-border membrane. Acidification of the apical medium, even in Na(+)-free media, is associated with a saturable net transepithelial absorption of L-alanine. L-Alanine transport causes cytosolic acidification consistent with proton/amino acid symport. L-Alanine transport in Na(+)-free media is rheogenic, stimulating an inward short-circuit current in voltage-clamped epithelial monolayers. By measurement of rapid L-alanine influx across the apical membrane, L-alanine-stimulated inward short-circuit current and intracellular acidification in the same cell batch, we estimate L-alanine/proton stoichiometry to be 1:0.62 +/- 0.25 (SD) (short-circuit current) or 1:0.73 +/- 0.19 (intracellular acidification). From competition studies, it is likely that L-proline, alpha-aminoisobutyric acid, and beta-alanine, but not L-valine and L-serine, are substrates for proton-linked, substrate transport in the brush border of Caco-2 cells.

Alanine↗

PubMed1994

Na-K-Cl cotransport in villus and crypt cells from rat duodenum.

The aim of the present study was to examine the possibility that Cl- uptake into both villus and crypt epithelial cells of rat duodenum occurs via an electroneutral Na-K-Cl coupled-transport mechanism. Sheets of villus cells and whole crypts were isolated using a Ca2+ chelation technique combined with continuous vibration at low temperatures. Structurally intact, viable epithelia from defined regions along the villus-crypt axis were produced. Uptake of 86Rb+ (as a proxy for K+) into both villus and crypt cells appeared to depend on a coupled process, as evidenced by the inhibition of 86Rb+ uptake by bumetanide and by the removal of either Na+ or Cl- from the bathing media. We report an improved method of isolation of viable enterocytes from defined regions along the villus-crypt axis. We demonstrate the presence of Na-K-Cl cotransport in both villus and crypt duodenal enterocytes.

Animals↗

PubMed1994

Cyclosporin A has divergent effects on plasma LDL cholesterol (LDL-C) and lipoprotein(a) [Lp(a)] levels in renal transplant recipients. Evidence for renal involvement in the maintenance of LDL-C and the elevation of Lp(a) concentrations in hemodialysis patients.

Cardiovascular disease is the major cause of mortality in renal transplant recipients. Plasma levels of low-density lipoprotein cholesterol (LDL-C) are often elevated following renal transplantation, and the immunosuppressant cyclosporin A has been implicated as a predisposing factor for posttransplantation hyperlipidemia. Lipoprotein(a) [Lp(a)] is an LDL-like lipoprotein particle; elevated levels of Lp(a) provide an independent and significant risk factor for cardiovascular disease. Plasma concentrations of Lp(a) vary greatly among individuals, and the mechanisms that govern changes in their levels in transplant patients are unknown. The effect(s) of cyclosporin A on Lp(a) was studied in two groups of renal transplantation patients. In group I plasma lipoproteins including Lp(a) were measured before and after successful renal transplantation; this group received both prednisone and cyclosporin A for immunosuppression. Group II patients were studied after renal transplantation and received prednisone alone for immunosuppression. Following surgery, group I patients demonstrated increased plasma concentrations of LDL-C (mean +/- SEM range, 111 +/- 6 to 142 +/- 17 mg/dL; P < .005). In contrast, plasma Lp(a) levels for this group were markedly decreased after renal transplantation (median, 34.3 to 19.7 mg/dL). Patients not treated with cyclosporin A (group II) exhibited mean LDL-C and median Lp(a) levels (118 +/- 42 and 33.1 mg/dL, respectively) that were remarkably similar to those observed before renal transplantation (group I). These data confirm that hyperlipidemia following renal transplantation is associated with cyclosporin A therapy and show that this drug has opposing effects on plasma Lp(a) and LDL-C accumulations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

H(+)-coupled dipeptide (glycylsarcosine) transport across apical and basal borders of human intestinal Caco-2 cell monolayers display distinctive characteristics.

Transepithelial transport and intracellular accumulation of the dipeptide glycylsarcosine (Gly-Sar) were studied using intact monolayers of the human intestinal epithelial cell line, Caco-2. Gly-Sar transport was demonstrated in both absorptive (apical-to-basal) and secretory (basal-to-apical) directions. In both directions, transport and accumulation were enhanced in the presence of a pH gradient (pHo < pHi). Under conditions similar to those found at the intestinal membrane in vivo (apical pH 6.0, basolateral pH 7.4), net absorption (145.2 pmol/cm2 per h) was observed, although experimental conditions could also be manipulated (apical pH 7.4, basolateral pH 6.0) so that net secretion was observed. Transport and accumulation (in both directions) were inhibited in the presence of either 20 mM (unlabelled) Gly-Sar or 20 mM cephalexin (an aminocephalosporin antibiotic). When added to either the apical or basolateral surface of BCECF (2',7',-bis(2-carboxyethyl)-5(6)-carboxyfluorescein)-loaded Caco-2 cell monolayers Gly-Sar (20 mM), at pH 6.0, caused a marked intracellular acidification, demonstrating that dipeptide absorption is accompanied by H(+)-flow into the cells. Cephalexin (20 mM) had similar effects (as Gly-Sar) when presented at the apical surface but also caused a marked intracellular acidification when perfused into the basolateral chamber at pH 7.4. In contrast, addition of Gly-Sar (20 mM) to the basolateral chamber (at pH 7.4) had no effect. Transepithelial absorption of dipeptides (Gly-Sar) and beta-lactam antibiotics (cephalexin) at low concentrations is predominately via a transcellular route mediated by carrier mechanisms located at both apical and basolateral membranes. Interestingly, Gly-Sar and cephalexin transport across the basolateral membrane (and, therefore, exit from the cell) display both common and distinct characteristics suggesting that more than one mechanism may be responsible for exit into the basolateral space.

Biological Transport↗

PubMed1993

Na(+)-independent, H(+)-coupled transepithelial beta-alanine absorption by human intestinal Caco-2 cell monolayers.

beta-Alanine transport across intact human intestinal epithelial (Caco-2) cell layers has been investigated. In Na(+)-containing solutions, net absorptive flux of beta-alanine from apical-to-basal surfaces is small or absent, despite Na(+)-dependent intracellular beta-alanine accumulation across both apical and basal surfaces. Upon apical acidification (apical pH 6.0, basal pH 7.5), beta-alanine absorptive flux and accumulation across the apical surface are increased. In Na(+)-free conditions, a significant absorptive flux of beta-alanine is observed, which is markedly stimulated upon apical acidification (pH 6.0). Cellular accumulation of beta-alanine across the apical but not basal surface is observed in Na(+)-free conditions, and this is increased by acidic (pH 6.0) solutions. Absorptive beta-alanine flux in Na(+)-free conditions with acidic apical solutions displays saturation kinetics and competitive inhibition by alanine and glycine, but not valine or serine. Addition of 20 mM beta-alanine to the apical solution of epithelial monolayers loaded with the pH indicator 2',7'-bis(2-carboxyethyl-5(6)-carboxyfluorescein) causes a marked decrement in intracellular pH. beta-Alanine transport is also electrogenic, a concentration-dependent increase in an inward short circuit current being observed in voltage-clamped epithelial monolayers. We conclude that a proton-dependent, but Na(+)-independent, amino acid transporter is expressed at the apical membrane of human intestinal Caco-2 cells, and we provide direct evidence for amino acid-stimulated proton influx across the apical membrane in this intact epithelial cell system.

Biological Transport↗

PubMed1993

Prevalence of high blood cholesterol among US adults. An update based on guidelines from the second report of the National Cholesterol Education Program Adult Treatment Panel.

OBJECTIVE: To estimate the current levels and trends in the proportion of US adults with high blood cholesterol based on guidelines from the second report of the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP II). DESIGN: Nationally representative cross-sectional surveys. SETTING/PARTICIPANTS: Data for 7775 participants 20 years of age and older from phase 1 of the third National Health and Nutrition Examination Survey (NHANES III) (data collected from 1988 through 1991) and for 9797 participants 20 through 74 years of age from NHANES II (data collected from 1976 through 1980) were used. RESULTS: From the data collection period in NHANES II (1976 through 1980) to the period in NHANES III (1988 through 1991), the proportion of adults with high blood cholesterol levels (> or = 240 mg/dL [6.21 mmol bd) fell from 26% to 20%, while the proportion with desirable levels (< 200 mg/dL [5.17 mmol/L]) rose from 44% to 49%. Currently, using the ATP II guidelines and NHANES III data, 40% of all adults 20 years of age and older would require fasting lipoprotein analysis; and 29% of all adults would be candidates for dietary therapy (as compared with 36%, using NHANES II data). Based on 1990 population data, it is estimated that approximately 52 million Americans 20 years of age and older would be candidates for dietary therapy. Assuming that dietary intervention would reduce low-density lipoprotein (LDL) cholesterol levels by 10%, as many as 7% of all adult Americans (approximately 12.7 million) might be candidates for cholesterol-lowering drugs. This estimate reflects approximately 4 million adults with established coronary heart disease, of whom half are aged 65 years and older, and up to 8.7 million adults without established coronary heart disease, of whom up to 3.1 million are aged 65 years and older. CONCLUSIONS: Substantial progress has been made in reducing the prevalence of high blood cholesterol; yet a large proportion of all adults, approximately 29%, require dietary intervention for high blood cholesterol.

Adult↗

PubMed1993

Declining serum total cholesterol levels among US adults. The National Health and Nutrition Examination Surveys.

OBJECTIVE: To examine the secular trend in serum total cholesterol levels of the US adult population. DESIGN: Nationally representative cross-sectional surveys with both an in person interview and a medical examination that included the measurement of blood lipid levels. SETTING/PARTICIPANTS: Between 6000 and 13,000 adults aged 20 through 74 years examined in each of four separate national surveys during 1960 through 1962, 1971 through 1974, 1976 through 1980, and 1988 through 1991. RESULTS: Mean serum total cholesterol levels in US adults aged 20 through 74 years have consistently declined over the time period 1960 through 1991. More than half of the decline occurred during the time period 1976 through 1991. This decline occurred across the entire distribution of serum cholesterol levels and in all age-sex groups. High-density lipoprotein cholesterol and very low-density lipoprotein cholesterol levels have not changed, suggesting that the decline in total cholesterol levels is due to a decline in low-density lipoprotein cholesterol levels. CONCLUSIONS: These results document a continuing and substantial decline in serum cholesterol levels among US adults. They suggest that public health programs, designed to reduce cholesterol levels, are proving successful. The observed downward trend in serum cholesterol levels has coincided with a continuing decline in coronary heart disease mortality. These observations suggest that the Healthy People 2000 goal of reducing the mean serum cholesterol level of US adults to no more than 200 mg/dL (5.17 mmol/L) is attainable.

Adult↗

PubMed1993

Transepithelial glycylsarcosine transport in intestinal Caco-2 cells mediated by expression of H(+)-coupled carriers at both apical and basal membranes.

Glycylsarcosine (Gly-Sar) transport in human intestinal epithelial (Caco-2) cells has been investigated. Gly-Sar transport, from apical to basal surfaces (Ja-b), and intracellular accumulation are greatest when the apical medium is acidified (apical pH 6.0, basal pH 7.4). Both transport and accumulation are susceptible to saturation and competition. Similarly, Gly-Sar transport, from basal to apical surfaces (Jb-a), is increased with acidification of the basal medium (basal pH 6.0, apical pH 7.4). Apical addition of 20 mM Gly-Sar (pH 6.0) to Caco-2 cell monolayers loaded with the pH indicator BCECF (2',7'-bis(2-carboxyethyl)-5-(6)-carboxyfluorescein) caused a marked cytosolic acidification. Basolateral application of 20 mM Gly-Sar (pH 6.0) also caused a fall in intracellular pH. These observations are consistent with the expression of H(+)-coupled dipeptide transporters at both membrane faces of the human intestinal epithelial Caco-2 cell line. We also provide direct evidence for dipeptide-stimulated H(+)-influx, across both apical and basolateral membranes, in this intact epithelial cell system.

Adenocarcinoma↗

PubMed1993

Characterisation of volume-activated ion transport across epithelial monolayers of human intestinal T84 cells.

The effects of hypo-osmolarity upon transepithelial ion transport in human intestinal cell layers have been investigated. Exposure of the basal-lateral surfaces to hypo-osmotic media resulted in a transient stimulation of inward short-circuit current (Isc). This transient stimulation of inward current by hypo-osmotic media was abolished by 100 mumol/l 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS). After prestimulation of inward Isc by vasoactive intestinal peptide (VIP) or by combinations of carbachol and prostaglandin E1, hypo-osmotic exposure of the basal-lateral surfaces resulted in a further transient stimulation of Isc. The stimulation of Isc in these conditions was largely insensitive to DIDS inhibition. Exposure of the basal-lateral surfaces to hypo-osmotic media resulted in a stimulation of loop-diuretic-insensitive 86Rb efflux across the basal-lateral surfaces. In addition, hypo-osmotic exposure of T84 cells is also associated with an increase in cytosolic Ca2+. It is concluded that the effects of hypo-osmotic exposure of T84 cells on secretory Isc are consistent with the activation of a DIDS-sensitive apical Cl- conductance and a basal-lateral K+ conductance. With prior activation of inward Isc by VIP via a cAMP-activated DIDS-insensitive apical Cl- conductance, augmentation of the secretory current by hypo-osmotic exposure is likely to result primarily from increased basal-lateral K+ current and loop-diuretic-sensitive Cl- uptake.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1993

Co-expression of an anion conductance pathway with Na(+)-glucose cotransport in rat renal brush-border membrane vesicles.

Brush-border membrane vesicles were prepared from superficial rat renal cortex by a Mg(2+)-precipitation technique. The initial (20 s) [14C]glucose uptake rate from solutions containing 100 mmol/l Na (salt) was found to be dependent upon the anion composition of the medium; in comparison to gluconate-containing medium (0.46 +/- 0.05 nmol/mg protein), Cl- accelerated the initial rate to 1.47 +/- 0.21 nmol/mg protein (n = 4 preparations, +/- SEM). This enhancement was reduced by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 0.5 mmol/l), but was unaffected by 4,4'-diisothiocyanatostilbene 2,2'-disulphonate (DIDS, 0.5 mmol/l). When membrane vesicles were pre-equilibrated with 100 mmol/l K (salt) and 100 mmol/l mannitol and glucose uptake was measured from a solution containing 100 mmol/l Na gluconate and 100 mmol/l mannitol in the presence of 80 mumol/l valinomycin (to generate an outward K+ diffusion electrical p. d.), it was found that intravesicular KCl depressed the initial glucose uptake compared to K gluconate. NPPB (0.5 mmol/l) increased the initial glucose uptake with intravesicular KCl towards values seen in K gluconate vesicles. In conditions where the only driving force for glucose uptake was established by an inward anion gradient (Nao = Nai) it was found that inward Cl- gradients could drive uphill glucose transport and that this was sensitive to NPPB (0.5 mmol/l), but insensitive to DIDS. We conclude that a Cl- conductance co-exists with Na-cotransport in rat renal brush-border membrane vesicles prepared from superficial renal cortex and this may function to regulate the activity of electrogenic transport systems at this membrane.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1993

A review of topical agents for wounds and methods of wounding. Guidelines for wound management.

This article reviews the effects of antiseptics, antimicrobials, hemostatic agents and surgical methods on the incidence of wound infection and the process of wound healing. A set of guidelines is provided to help decide what to apply topically to wounds and which method of wounding to select in order to achieve the best possible outcome in wound healing.

Administration, Cutaneous↗

PubMed1993

Left ventricular unloading decreases rate of isovolumic right ventricular pressure decline.

To determine whether direct ventricular interaction affects right ventricular (RV) relaxation, we compared the minimum rate of change of RV pressure (dP/dtmin) and the time constant, tau, of isovolumic RV pressure decline in open-chest, anesthetized pigs following a normal left ventricular (LV) contraction and an acutely unloaded LV contraction. Rapid removal of blood via the LV apex into a prosthetic ventricle during a single systole decreased the LV pressure-time integral 68.3% and peak systolic pressure 49.9% without changing RV end-diastolic conditions. Micromanometers measured ventricular chamber pressures during single RV isovolumic beats, which were produced by transient pulmonary artery occlusion in both the control and the LV-unloaded states. When the LV was unloaded, RV tau rose significantly from 41.7 +/- (SD) 7.1 to 49.8 +/- 9.4 ms, P < 0.005 (pericardium intact) and 42.9 +/- 10.8 to 51.8 +/- 13.9 ms, P < 0.005 (pericardium opened). Simultaneously, RV dP/dtmin decreased from -400.5 +/- 136.6 to -288.3 +/- 46.8 mmHg/s, P = 0.14 (pericardium intact), and -342.4 +/- 104.2 to -241.2 +/- 118.9 mmHg/s, P < 0.01 (pericardium opened). These data indicate that LV systolic unloading decreases the rate of RV relaxation. We conclude that RV relaxation is influenced by direct anatomic ventricular interaction.

Animals↗