Genotypic and Phenotypic Variables Affect Meiotic Cell Cycle Progression, Tumor Ploidy, and Cancer-Associated Mortality in a brca2-Mutant Zebrafish Model.

Successful cell replication requires both cell cycle completion and accurate chromosomal segregation. The tumor suppressor BRCA2 is positioned to influence both of these outcomes, and thereby influence genomic integrity, during meiotic and mitotic cell cycles. Accordingly, mutations in BRCA2 induce chromosomal abnormalities and disrupt cell cycle progression in both germ cells and somatic cells. Despite these findings, aneuploidy is not more prevalent in BRCA2-associated versus non-BRCA2-associated human cancers. More puzzlingly, diploidy in BRCA2-associated cancers is a negative prognostic factor, unlike non-BRCA2-associated cancers and many other human cancers. We used a brca2-mutant/tp53-mutant cancer-prone zebrafish model to explore the impact of BRCA2 mutation on cell cycle progression, ploidy, and cancer-associated mortality by performing DNA content/cell cycle analysis on zebrafish germ cells, somatic cells, and cancer cells. First, we determined that combined brca2/tp53 mutations uniquely disrupt meiotic progression. Second, we determined that sex significantly influences ploidy outcome in zebrafish cancers. Third, we determined that brca2 mutation and female sex each significantly reduce survival time in cancer-bearing zebrafish. Finally, we provide evidence to support a link between BRCA2 mutation, tumor diploidy, and poor survival outcome. These outcomes underscore the utility of this model for studying BRCA2-associated genomic aberrations in normal and cancer cells.

Characteristics of aggregation in aqueous solutions of dialkylpyrrolidinium bromides.

Three pyrrolidinium-based ionic liquids-N-dodecyl-N-methylpyrrolidinium bromide, N-butyl-N-octylpyrrolidinium bromide, and N-butyl-N-dodecylpyrrolodinium bromide-were synthesized and characterized by their decomposition temperatures (T(d)) measured by thermogravimetric analysis, and by their melting point (T(m)), glass transition (T(g)) and crystallization temperatures (T(cryst)) determined by differential scanning calorimetry. Their self-aggregation properties in aqueous solution were studied and their behavior is compared with that of analogous conventional cationic surfactants, namely tetra-alkylammonium bromide salts. The critical micellar concentration, cmcs were obtained by isothermal titration calorimetry (ITC); which were further validated by measurements of interfacial tension, fluorescence and NMR spectroscopy. Enthalpies of micellization were measured at three different temperatures using ITC. The Taylor dispersion method and DOSY NMR were used to determine diffusion coefficients of the ionic liquid surfactants in aqueous solution at 298.15K. Several correlations between structural features of the surfactant species, such as the number and size of their alkyl chains, and the thermodynamic quantities of micellization-expressed by experimental values of cmc, counter-ion binding fraction, Δ(mic)G°, Δ(mic)°, and Δ(mic)S°-are established. We could interpret the different contributions of the two alkyl side chains to the aggregation properties in terms of the balance of interactions in homogeneous and micellar phases, contributing to understanding the aggregation behavior of ionic liquids in water and the parallel between these systems and traditional ionic surfactants.

Late relapse of metastatic non-seminomatous testicular germ cell tumours.

Although the majority of men presenting with non-seminomatous germ cell tumours (NSGCT) are cured, late relapse (occurring more than 2 years after obtaining a complete response to treatment) is increasingly recognized. The typical patterns of disease spread have been well-documented, but the findings at late relapse are more variable and less well-described. We discuss the phenomenon of late relapse, the characteristics of teratoma differentiated (TD), and the issue of long-term imaging surveillance of patients with NSGCT. The potential sites of late relapse of NSGCT and the associated spectrum of imaging appearances are illustrated.

Myocardial infarction redefined: the new ACC/ESC definition, based on cardiac troponin, increases the apparent incidence of infarction.

OBJECTIVES: To investigate the impact of the redefinition of the diagnostic criteria for myocardial infarction on its apparent incidence in a non-selected and representative series of patients admitted with acute chest pain. DESIGN: Single centre prospective study. SETTING: Medical assessment unit and cardiology wards of an inner city university hospital. PATIENTS: 80 consecutive patients aged over 25 years admitted with suspected ischaemic acute chest pain (excluding those where the ECG indicated definite myocardial infarction). INTERVENTIONS: Measurement of concentrations of conventional cardiac biomarkers (creatine kinase and its MB isoenzyme, CK-MB) and concentrations of the highly specific diagnostic indicator of myocardial damage, cardiac troponin I (cTnI) 12-24 hours after the onset of acute chest pain. MAIN OUTCOME MEASURES: Frequency of myocardial infarction as assessed by conventional diagnostic criteria (creatine kinase and CK-MB) plus clinical symptoms of infarction, versus frequency of infarction based on high sensitivity troponin assays. RESULTS: Among patients with acute coronary syndromes but non-diagnostic ECG changes, 40% (32/80) fulfilled the new criteria for myocardial infarction using high sensitivity cTnI measurement, compared with 29% (23/80) using the conventional diagnostic criteria for myocardial infarction. CONCLUSIONS: The implications of the redefinition of myocardial infarction on patients, their care, and the use of health care resources are substantial.

Central versus peripheral mediation of naloxone's perfusion effects in endotoxic rats.

Opioid receptor antagonists can act centrally and peripherally. It is unclear if these 2 pathways differentially mediate the perfusion-associated effects of opioid antagonism during endotoxemia. Male, Sprague-Dawley rats (340-390 g) were surgically prepared with left ventricular, tail artery, and jugular vein catheters 24 h before experiments were begun. Conscious, unrestrained rats were challenged with Escherichia coli lipopolysaccharide (LPS; 2 mg/kg/hr over 30 min) infusion. Measurements of regional blood flows were made using radioactive microspheres prior to (baseline), and at 60 and 120 min after LPS infusion. Saline (1 mL/kg bolus + 0.5 mL/kg/h infusion), naloxone (Nlx; 4 mg/kg bolus + 2 mg/kg/h infusion), or naloxone methyl bromide (Nlx-mb; 4.64 mg/kg, bolus + 2.32 mg/kg/h infusion) were administered 40 min after LPS infusion was begun. Nlx-mb does not cross the blood-brain barrier, and was thus used to differentiate central from peripherally mediated responses. At the end of each experiment, blood samples were collected for determination of ET-1 and nitric oxide metabolites (NOx = NO3 + NO2) using enzyme-linked immunosorbent assay (ELISA) and Griess reaction methods, respectively. Endotoxemia produced a significant decrease in cardiac output and an increase in systemic vascular resistance. Treatment with Nlx or Nlx-mb significantly attenuated the endotoxin-induced elevation in systemic vascular resistance and the decrease in cardiac output at 60 min after induction of endotoxemia compared with their respective baseline values. Nlx and Nlx-mb also attenuated the endotoxin-induced increases in hepatic portal and skeletal vascular resistances. These observations suggested that the ameliorative effect of Nlx on endotoxemia-induced regional vascular resistance alterations was mediated via peripheral opioid receptor mechanisms. However, although Nlx attenuated the endotoxin-induced decreases in the blood flow to the stomach and pancreas, Nlx-mb attenuated the endotoxin-induced decreases in the blood flow to the small intestine and cecum, in addition to the pancreas and, to some extent, the stomach. As such, separate central and peripherally mediated actions of opioid receptor antagonism were indicated. Nlx also resulted in an increase in the plasma levels of ET-1 only, whereas Nlx-mb increased the plasma levels of ET-1 and NOx. These observations suggest that separate central and peripheral effects of opioids during endotoxemia play a role in the associated circulatory alterations, and may differentially affect the release and/or synthesis of vasoactive mediators that might be related to their varied hepatosplanchnic vascular response during endotoxemia.

Interdependence of adenosine and nitric oxide in hepato-splanchnic circulation during sepsis.

BACKGROUND: We tested the hypothesis that some of the maintenance of resting, regional hepato-splanchnic perfusion that is mediated by endogenous adenosine (ADO) during sepsis is interdependent with nitric oxide (NO). MATERIALS AND METHODS: Twenty-four hours after sepsis/sham induction, rats were divided into two groups. Group 1 received a 10-min infusion of the ADO antagonist 8-sulfophenyltheophylline (8-SPT; 0.9 mg/kg x min), followed by 10 min of 8-SPT plus L-NAME (0.5 mg/kg x min). Group 2 received L-NAME first followed by 8-SPT in the presence of L-NAME (all groups: n = 6-10). Hemodynamic and regional hepato-splanchnic blood flow measurements were made prior to infusions, 10 min after initiation of each single agent infusion, and again after double agent infusion. RESULTS: Twenty-four hours after sepsis hepato-splanchnic blood flow was significantly elevated, compared to nonseptic rats. Both ADO receptor blockade alone and NOS inhibition alone decreased total hepato-splanchnic blood flow to nonseptic values. Decreases in small intestinal and cecal blood flow accounted for the majority of this decrease, but decreased hepatic arterial perfusion contributed as well. No further alterations were seen when 8-SPT was infused in the presence of L-NAME, nor when L-NAME was infused in the presence of 8-SPT. CONCLUSIONS: These data indicate that there is significant interdependence of endogenous NO and ADO in maintaining resting small bowel, cecal, and hepatic arterial perfusion during sepsis. The lack of responses in other regions of the hepato-splanchnic circulation demonstrate regional specificity of this ADO-NO interdependence.

Adenosine and nitric oxide regulate regional vascular resistance via interdependent and independent mechanisms during sepsis.

OBJECTIVE: Adenosine receptor blockade increases regional resting vascular resistance during sepsis. In healthy subjects, part of adenosine's actions are mediated via stimulation of nitric oxide synthase. Because nitric oxide synthase activity is thought to be a major contributor to altered vascular tone in sepsis, we tested the hypothesis that some of the nitric oxide-mediated resting regional resistance during sepsis is secondary to endogenous adenosine stimulation of nitric oxide synthase. DESIGN: Prospective, randomized, controlled experiment. SETTING: Shock-trauma and basic science laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Twenty-four hours after sepsis or sham induction, rats were separated into two groups (n = 6 to 10 in each group). Group 1 received a 10-min infusion of the adenosine antagonist 8-sulfophenyltheophylline (0.9 mg/kg x min) followed by a 10-min infusion of L-nitro-arginine-methyl ester (0.5 mg/kg x min). Group 2 similarly received L-nitro-arginine-methyl ester followed by 8-sulfophenyltheophylline in the presence of L-nitro-arginine-methyl ester. MEASUREMENTS AND MAIN RESULTS: Hemodynamic and blood flow measurements (microspheres) were made before infusions, 10 mins after the administration of each single-agent infusion, and 10 mins after combined-agent infusions were administered. No significant resistance alterations were observed in nonseptic rats. In septic rats, adenosine receptor blockade alone increased hepatosplanchnic and skeletal muscle vascular resistance, but no further increases were seen when L-nitro-arginine-methyl ester was added. Nitric oxide synthase inhibition alone increased hepatosplanchnic and skeletal muscle vascular resistances. When 8-sulfophenyltheophylline was added to the infusion, skeletal muscle vascular resistance increased significantly more than with L-nitro-arginine-methyl ester alone, but there were no further increases in hepatosplanchnic resistance. Renal and adipose vascular resistances increased with L-nitro-arginine-methyl ester infusions, and 8-sulfophenyltheophylline produced no effect. CONCLUSIONS: During sepsis, nitric oxide caused resting vasodilation independent of adenosine in the renal and adipose vasculature. In the hepatosplanchnic circulation, there is reciprocal adenosine-nitric oxide interaction in maintaining resting regional resistance. Skeletal muscle displayed a dual adenosine-mediated (nitric oxide-independent) and nitric oxide-mediated (adenosine receptors required) interaction to regulate resting resistance during sepsis. These data indicate that in the hepatosplanchnic and skeletal muscle vasculature, all of the resting nitric oxide-mediated vasodilation is secondary to endogenous adenosine action, but in adipose and renal vasculature, resting nitric oxide mediated vasodilation is independent of adenosine. Endogenous adenosine also appears to play a significant role in determining resting skeletal muscle resistance that is independent of nitric oxide synthase during sepsis.

Elevated coronary endothelin-1 but not nitric oxide in diabetics during CABG.

BACKGROUND: After coronary artery bypass grafting procedures, a higher incidence of morbidity and mortality has been reported in diabetic patients. We tested whether coronary artery bypass grafting in diabetics affects the endothelin-1 and nitric oxide coronary effluent profile during reperfusion. METHODS: Twenty-one consecutive patients (9 with type II diabetes mellitus, 12 non-diabetics) underwent coronary artery bypass grafting by one surgeon. The two groups did not differ in preoperative ejection fraction, Parsonnet score, number of vessels bypassed, or cross-clamp time. Each patient was treated in the same intraoperative manner with single atrial, aortic, and antegrade and retrograde cardioplegia (CPL) cannulas. Cold CPL arrest was by antegrade and retrograde infusion of modified Buckberg CPL solution. Warm CPL solution was infused before reperfusion. Coronary sinus blood samples were obtained for estimation of endothelin-1 and nitrite plus nitrate before CPL arrest and at 1 and 15 minutes after each of 2 reperfusion periods. RESULTS: In diabetics, endothelin-1 was significantly increased at all reperfusion times as compared with non-diabetics. Nitrite plus nitrate levels were significantly higher in patients with diabetes than in those without, but did not change with time in either of the groups. CONCLUSIONS: Reperfusion after CPL during coronary artery bypass grafting procedure can trigger the release of endothelin-1 in patients with diabetes mellitus. This may favor increased vascular tone or positive inotropic responses after coronary artery bypass grafting and may contribute to significant cardiovascular consequences in diabetic patients.

Cardiopulmonary bypass increases coronary IL-8 in diabetic patients without evidence of reperfusion injury.

BACKGROUND: Endothelin-1 (ET-1) has been shown to be a potent agonist for monocyte production of the neutrophil chemotactic cytokine interleukin-8 (IL-8). We have shown that diabetic patients demonstrate elevated coronary ET-1 after coronary artery bypass grafting (CABG). We hypothesized that these same diabetic patients would manifest elevated coronary IL-8 and conjugated diene concentrations (an index of reperfusion injury). METHODS: Sixteen patients [9 nondiabetics and 7 type II diabetics] underwent nonemergent CABG. The two groups did not differ significantly in preoperative ejection fraction, number of vessels bypassed, or cross-clamp time. Coronary sinus samples were obtained prior to cardioplegic arrest (baseline) and at 1 and 15 min after reperfusion periods A and B (A, reperfusion of native coronaries + LIMA; B, reperfusion of saphenous vein grafts in addition to native coronary system + LIMA). Plasma samples were analyzed for IL-8 (ELISA) and conjugated dienes (spectrophotometry). RESULTS: Initially after reperfusion, IL-8 in both groups was significantly lower than precardioplegia values. In reperfusion B, only the diabetic group demonstrated a significant increase in IL-8 concentrations at 1 and 15 min compared to nondiabetics. Conjugated diene levels were significantly higher in diabetics at each time point than nondiabetics. CONCLUSIONS: This study demonstrates an early decrease in IL-8 in both groups, most likely related to depressed production secondary to hypothermia. The subsequent elevation in IL-8 only in the diabetic group was seen without concomitant conjugated diene elevation. While no evidence of reperfusion injury was demonstrated in this time frame, the elevation of IL-8 in diabetics after CABG may contribute to later infiltration and associated oxidative damage.

Sepsis produces depression of testosterone and steroidogenic acute regulatory (StAR) protein.

The hypothesis that induction of chronic peritoneal sepsis would produce depression of serum testosterone due to a decrease in Leydig cell steroidogenic acute regulatory (StAR) protein or P450c17 steroidogenic enzyme was tested. Male Sprague-Dawley rats (350-400 g) were randomized to septic and nonseptic groups. Sepsis was induced with a cecal slurry (200 mg/kg in 5 mL of 5% dextrose in water (D5W); intraperitoneal) while nonseptic rats received only sterile D5W. Animals (n = 6, in each group) were killed by CO2 asphyxiation and blood samples were collected by direct cardiac puncture at 24 h after induction of sepsis/sham sepsis. The serum concentration of corticosterone, progesterone, estradiol, and testosterone was determined using radioimmunoassay. Western blot analysis was utilized to quantify Leydig cell StAR protein and P450c17 enzyme. Sepsis produced a significant decrease in the serum concentration of testosterone, a down-regulation of StAR protein, and an increase in serum estradiol 24 h after induction of sepsis (as compared with the nonseptic group). Protein levels of P450c17 in Leydig cells and serum concentrations of progesterone and corticosterone 24 h after induction of sham sepsis or sepsis were not different. It is concluded that the decreases in serum testosterone after 24 h of chronic peritoneal sepsis correlated with reductions in StAR protein.

A differential response of diffuse brain injury on the concentrations of endothelin and nitric oxide in the plasma and brain regions in rats.

In the present study, we hypothesized that acute diffuse brain injury (DBI) in rats would produce an increase in endothelin-1 (ET-1), a potent vasoconstrictor, and/or nitric oxide (NO), a potent vasodilator, in plasma and brain areas in rats. DBI was induced in anesthetized male Sprague-Dawley rats (350-400 g) using a 350 g weight dropped from 1 meter height impact through a device designed by Marmarou et al., 1994. Blood plasma and brain tissue (cerebral cortex, diencephalon and brain stem) samples were collected for estimation of ET-1 and NO at zero or 6 h from rats (n = 6) subjected to DBI as well as control rats (n = 6), i.e., not subjected to DBI. In a separate group of animals, cerebral blood flow (CBF) was recorded at 0, 5, 10, 15, 30, 60, 120, 240 and 360 min after induction of DBI or sham-DBI. Acute DBI produced a significant decrease in CBF at 120 min after induction of DBI. Plasma levels of ET-1 was found to be significantly increased (from 0.89 +/- 0.09 to 2.09 +/- 0.29 pg ml-1), at 6 h following DBI. DBI produced a significant decrease in the levels of ET-1 in diencephalon (from 70.97 +/- 9.47 to 57.64 +/- 2.65 pg g-1). In contrast to ET-1, DBI produced a significant increase in the concentrations of NO in the diencephalon, cerebral cortex and brain stem at 6 h post DBI. It appears that DBI-induced increase in the levels of NO in brain regions which might be down regulating the synthesis of ET-1 in diencephalon. It is concluded that ET and NO homeostatic mechanisms may play a role in the regional and vascular responses associated with acute DBI.

Diabetic patients produce an increase in coronary sinus endothelin 1 after coronary artery bypass grafting.

Diabetes is associated with altered vascular responses, and diabetic patients demonstrate increased morbidity and mortality after coronary artery bypass grafting (CABG). We tested whether endothelin (ET)-1 levels in this patient population differed from those in nondiabetic subjects after CABG. Of 14 consecutive patients who underwent CABG by the same surgeon, 7 had type 2 diabetes and 7 were nondiabetic. The two groups did not differ significantly in preoperative ejection fraction, number of vessels bypassed, cross-clamp time, or Parsonnet's score. Coronary sinus blood samples were obtained before cardioplegic arrest and then obtained at 1 and 15 min after each of two reperfusion periods: reperfusion A (native coronary perfusion plus the left internal mammary artery), reperfusion B (saphenous vein graft perfusion). ET-1 was significantly increased at all reperfusion time points in diabetic patients compared with nondiabetic patients. In diabetic patients, reperfusion after CABG can trigger the release of ET-1, which may be a contributing factor in the increased cardiac morbidity seen in this patient population.

Effect of aminoguanidine on plasma nitric oxide by-products and blood flow during chronic peritoneal sepsis.

We hypothesized that plasma nitric oxide (NO), generated via inducible NO synthase (iNOS) or endothelial constitutive NO synthase and measured via its by-products NO2- and NO3- (NO2- + NO3- = NOx) would increase and remain elevated during chronic peritoneal sepsis. We further hypothesized that treatment with aminoguanidine (AG; 50 mg/kg), a selective iNOS inhibitor, would decrease NO production and alter blood flow. Sprague Dawley rats were randomized to septic and nonseptic groups. Septic rats received an intraperitoneal cecal slurry (200 mg of cecal material/5 mL 5% dextrose-H2O/kg); control rats received sterile 5% dextrose-H2O (5 mL/kg) only. Plasma NOx and hemodynamics were measured 0, 4, 12, 24, and 48 h after sepsis or sham induction. We also examined the effect of AG, an iNOS inhibitor, on plasma NOx levels and tissue blood flow at 24 h. Septic rats uniformly displayed signs of sepsis, including lethargy, piloerection, and diarrhea. NOx levels were significantly elevated compared with controls at 4, 12, 24, and 48 h (p < or = .05). Septic rats also demonstrated hypotension (t = 12, 24, and 48 h) and tachycardia (t = 4, 12, 24, and 48 h). The infusion of AG (50 mg/kg intravenously for 30 min) at 24 h significantly decreased plasma NOx in septic animals. Plasma NOx concentrations returned to basal levels by 90 min after infusion of AG. In addition, blood flow studies demonstrated that AG treatment in nonseptic rats resulted in a significant decrease in blood flow to the stomach, skin, and adipose tissue, whereas AG infusion did not significantly alter the regional perfusion profile in septic animals. Furthermore, treatment with AG did not significantly alter mean arterial pressure in either group; however, nonseptic animals exhibited a decrease in stroke volume, and septic animals demonstrated an increase in heart rate. In contrast to the rise and fall of NOx levels in endotoxemia, this study demonstrates that the initial rise is sustained during 48 h of peritoneal sepsis. This sustained increase in NOx levels in this model correlated with the observable signs of systemic infection and may relate to enhanced iNOS activity. AG infusion demonstrated variable effects on regional tissue blood flow profiles in septic and nonseptic animals and attenuated the increase in plasma NOx levels in septic animals, an index of iNOS activity.

Effect of NG-nitro-L-arginine methyl ester on testicular blood flow and serum steroid hormones during sepsis.

Production of nitric oxide (NO) via NO synthase (NOS) has been implicated in the regulation of steroidogenesis in normal physiology and septic pathophysiology. The hypothesis that blockade of NOS by NG-nitro-L-arginine methyl ester (L-NAME) would affect testicular blood flow and circulating levels of steroid reproductive hormones was tested. Male Sprague-Dawley rats (350-450 g) were randomized to septic and nonseptic groups. Sepsis was induced with an intraperitoneal (i.p.) injection of a cecal slurry (200 mg/kg in 5 mL 5% dextrose in water (D5W)) in rats, while nonseptic rats received only sterile D5W. The rats (n = 6 per group) were catheterized in the jugular vein, left ventricle (via right carotid artery), and tail artery to determine blood flow and systemic hemodynamics and to collect blood at 24 h after induction of sepsis/sham sepsis. After baseline (24 h post-cecal slurry challenge) measurement, L-NAME (.50 mg/ kg x min) was infused through the jugular vein for 10 min, blood flow was determined using a radioactive microsphere technique, and blood samples were collected. The serum concentrations of corticosterone, progesterone, and testosterone were determined using radioimmunoassay. Plasma concentrations of NO byproducts (NOx) were determined using the Greiss reaction. After 24 h, heart rate, testicular blood flow, and NOx levels were significantly increased, whereas the serum concentration of testosterone was significantly decreased in the septic group as compared with the nonseptic group. However, serum concentrations of progesterone and corticosterone at 24 h after induction of sham-sepsis or sepsis were not statistically different. Infusion of L-NAME significantly reduced the testicular blood flow and serum NOx levels in septic rats as compared with their baseline values. The administration of L-NAME significantly increased the concentration of testosterone in nonseptic and septic rats as compared with their respective basal values. However, testosterone levels in septic rats were still significantly lower than in nonseptic rats. The results of this study indicate that the synthesis of NO through NO synthase may play a role in the regulation of testicular blood flow and the serum levels of testosterone, associated with chronic peritoneal sepsis in the rat.

Adenosine receptor antagonism affects regional resting vascular resistance during rat peritoneal sepsis.

BACKGROUND: To identify vascular beds where endogenous adenosine plays a significant role as a mediator of resting perfusion alterations associated with sepsis, we tested the hypothesis that adenosine receptor blockade would cause differential regional increases in vascular resistance during intraperitoneal (ip) sepsis in the rat. MATERIALS AND METHODS: Rats (250-350 g) were catheterized and randomized to septic or nonseptic groups. Sepsis was induced with an ip injection of cecal slurry (150 mg/kg in D5W; 5 ml/kg), and baseline hemodynamics, cardiac output (CO), and blood flows (microspheres) were measured 24 h later. Animals then received the adenosine receptor antagonist 8-phenyltheophylline (8-PTH; 10 mM, 1.5 ml/kg), its vehicle (1.5 ml/kg), or normal saline (1.5 ml/kg), iv, and measurements were repeated. RESULTS: Septic animals treated with 8-PTH had a significant increase in skeletal muscle, hepatic portal, and cerebral vascular resistance with concomitant decreases in CO when compared with vehicle at 1 min. No significant resistance changes were observed in the renal, adipose, or coronary vasculatures. Adenosine receptor blockade caused a significant increase in +dP/dt and -dP/dt during sepsis, indicating that the reduced CO was not secondary to myocardial depression. CONCLUSIONS: These data suggest that adenosine receptor-mediated actions during sepsis affect vascular beds selectively and indicate a significant role for adenosine in resting perfusion redistribution in sepsis.

Splanchnic vascular control during sepsis and endotoxemia.

Endotoxemia and sepsis often result in circulatory derangements which manifest as perfusion maldistributions. It has been widely accepted that the splanchnic circulation decreases in perfusion during advanced septic or endotoxemic states. Impaired perfusion of splanchnic organs may result not only in organ dysfunction but also exacerbations of polymicrobial bacteremia due to intestinal mucosal leakage. Consequently, evaluation of the splanchnic mechanisms of vasoregulation and how perfusion is maintained is vital to any topic concerning the management of the septic patient.

Evidence that adenosine contributes to maintenance of hepatosplanchnic blood flow during peritoneal sepsis in rats.

Sepsis induced derangements in hepatosplanchnic perfusion can contribute to organ damage and death. Adenosine, a common and potent metabolic vasodilator, has not been evaluated as a mechanism for maintenance of blood flow during sepsis. We tested the hypothesis that adenosine receptor blockade would cause a decrease in hepatosplanchnic blood flow during intraperitoneal (i.p.) sepsis in the rat. Rats (250-350 g) were catheterized for hemodynamic and blood flow measurements with tracer microspheres. Sepsis was induced with an i.p. injection of cecal material (150 mg/kg in D5W; 5 mL/kg), and baseline measurements were taken 24 h later. Animals then received either the adenosine receptor antagonist 8-PTH (10 mM, 1.5 mL/kg), its vehicle (1.5 mL/kg) or normal saline (1.5 mL/kg), intravenously, and measurements were repeated 1 and 10 min later. There was a significant increase in hepatosplanchnic portal resistance in septic animals given 8-PTH, with no change in mean arterial blood pressure (MAP) or heart rate. Regionally, there was a significant decrease in gastric, small intestinal, cecal, and pancreatic blood flow when compared with vehicle. Adenosine receptor blockade caused a significant reduction in hepatosplanchnic blood flow during sepsis, suggesting that maintenance of splanchnic blood flow during sepsis involves receptor mediated adenosine actions.

Sepsis alters myocardial and plasma concentrations of endothelin and nitric oxide in rats.

Cardiovascular derangements during sepsis may arise from a mismatch between endothelin (ET) and nitric oxide (NO). We hypothesized that progression of chronic peritoneal sepsis would affect cardiac performance and would modulate the concentrations of NO and ET in the heart and plasma. Male Sprague-Dawley rats (340-390 g) were catheterized and made septic with a cecal slurry (200 mg/kg: i.p.). Heart rate, mean arterial pressure, and plasma ET and nitrite/nitrate (NOX) were determined at 0, 4, 8, 12, 24, and 48 h after induction of sepsis. Septic rats were found to have tachycardia at 48 h following induction of sepsis. Mean arterial pressure and pulse pressure were not altered in septic and non-septic rats. In a separate series of experiments, the function of isolated hearts from septic and non-septic rats was assessed at preload pressures of 2, 5, and 10 mmHg. Sepsis produced a significant decrease in rates of pressure development and relaxation (+/-dP/dt) at 24 and 48 h as compared to the hearts of non-septic rats. In septic rats, plasma concentrations of ET were significantly increased at t = 4, 8, 12 h as compared to basal values, and at 12 h as compared to non-septic rats, and returned to basal levels at 24 and 48 h. In contrast, circulating NO levels did not become elevated until t = 8 h and remained elevated throughout the remaining times. In the left ventricle, the concentration of ET was found to be significantly increased both in septic and non-septic rats at 4 and 8 h as compared to t = 0 h. In the left ventricles of non-septic rats, ET levels returned to baseline values at 12 h, while in septic rats, the concentration of ET remained significantly elevated until 12 h. In septic rats, left ventricular NO levels were found to be significantly increased at t = 12 h. It appeared that induction of sepsis contributed to an imbalance in the plasma concentration of ET and NO 12 h after the induction of sepsis. However, a similar imbalance was not observed in the left ventricle. It is concluded from these observations that peritoneal sepsis in a chronic rat model produced a divergence of plasma NO and ET levels. This suggests a homeostatic imbalance between vasoactive mediators, i.e. ET and NO, could contribute to the cardiovascular derangements that occur during sepsis.

Effects of phentolamine or yohimbine on naloxone's actions during endotoxin shock in rats.

Endogenous opioids are known to mediate some of the cardiovascular sequelae of sepsis. Inhibition of adrenergic action has been implicated as a physiological path by which endogenous opioids cause deleterious changes in cardiovascular function during endotoxin shock, but where and to what extent this accounts for changes in regional vascular resistance remains unclear. In this study, we addressed this question by examining the role of alpha-adrenergic actions in cardiovascular performance and the regional perfusion changes caused by naloxone during endotoxin shock. Rats had catheters inserted into the tail artery, left cardiac ventricle, and jugular vein. Twenty-four hours later, rats received saline or endotoxin (2 mg/kg) challenge intravenously over 30 min, followed at 40 min by intravenous naloxone (or saline) treatment (4 mg/kg + 2 mg/kg x h) in the presence or absence of phentolamine (100 micrograms/kg + 600 micrograms/kg x h) or yohimbine (40 micrograms/kg + 4 micrograms/kg x h). Radiolabeled microspheres were used to determine cardiac outputs and blood flows at 0, 30, 60, and 120 min after beginning endotoxin infusion. Naloxone attenuated the endotoxin-induced decline in mean arterial pressure (MAP) and cardiac output (CO), but had no effect on increased systemic vascular resistance (SVR). Phentolamine blocked naloxone's ability to increase MAP and CO, but permitted an increase in SVR by naloxone. In the presence of yohimbine, naloxone still increased MAP, but not CO nor SVR. Regional vascular responses varied, with naloxone demonstrating a vasoconstrictive effect despite alpha-adrenergic receptor blockade in some beds, and no effect in others. The response of individual organs in the hepatosplanchnic circulation was heterogenous as well. These data suggest that some effects of endogenous opioids during endotoxin shock are mediated via inhibition of alpha-adrenergic effects, but that some cardiovascular effects of endogenous opioids are independent of adrenergic control during endotoxin shock.