Rocket Sled Based High Speed Rail Track Test Facilities

The present study introduces and compares several high-speed track based ground test facilities available all over the world to simulate high-speed dynamic events for selected portions of flight trajectories. The scope of performing high speed flight-testing is addressed, which is followed by the requirements of these track based test facilities. The facilities deliver flight test articles under controlled conditions to achieve high velocity impact, acceleration, aerodynamic and other related testing for small and large test articles depending upon the requirements. Sled is designed in such a way so that it can carry the test articles like aircrafts, payloads, warheads, missiles and many other ballistic systems to achieve high velocities ranging from subsonic to hypersonic by accelerating these sleds using solid rocket motors over the rail track. Such facilities provide instrumentation for large set of trial data acquisition and offline analysis for both recovery and non- recovery (impact) trials, which makes such facilities important for test, research and evaluation purposes. Here, the detailed description of test facilities, which are available in many countries such as India, United States (US), Japan, United Kingdom (UK), France, and others countries based on their technical characteristics is presented. Additionally, a brief history and introduction into basic rocket sled test facility aspects, essential technical characteristics and major features to support high speed testing at these facilities as an accurate testing technique based on quality of construction and engineering design are also covered in this paper. Compilation of available or under development facilities is done in one place which provides the information about facilities’ technological gaps. The paper concludes with an explanation of the role, major capabilities and limitations of these test facilities in the present global scenario.

Evaluation of the association between a single-nucleotide polymorphism of bone morphogenetic proteins 5 gene and risk of knee osteoarthritis

Background:

Osteoarthritis (OA) is a chronic degenerative disorder probably affected by both genetic and environmental causes. Bone morphogenetic proteins (BMPs) are bone-derived factors that can induce new bone formation. Single-nucleotide polymorphisms (SNPs) of BMP5 gene alters the transcriptional activity of the BMP5 promoter that has been involved in OA susceptibility. This case–control study investigated the association of rs1470527 and rs9382564 SNP of BMP5 gene with susceptibility to knee OA (KOA).

Materials and Methods:

A total of 499 cases with radiographic KOA and 458 age- and sex-matched healthy controls were enrolled. Venous blood samples were obtained from all the cases as well as controls for polymerase chain reaction-restriction fragment length polymorphism.

Results:

The genotype distribution for rs1470527 and rs9382564 SNP was significantly different in cases and controls (P < 0.0001). Within both the SNPs of BMP5 gene, genotype CT and TT were significantly (P < 0.0001) associated with KOA as compared to the CC genotype. T allele of both the studied SNP was significantly associated with KOA (P < 0.0001). The allele frequencies of rs1470527 were 0.56(T) and 0.44(C) in cases and 0.33(T) and 0.67(C) in controls and in rs9382564 were 0.57(C) and 0.43(T) in cases and 0.71(C) and 0.29(T) in controls. Further in relation with clinical severity of OA, we observed signification association of TT genotype with both visual analog scale (P < 0.0001) and Western Ontario and McMaster Universities score (P < 0.05).

Conclusion:

Our results indicate significant association of rs1470527 and rs9382564 polymorphism of BMP5 gene with KOA.

Electron-phonon relaxation in disordered two-dimensional electron gas with dynamically screened deformation potential

We study the effect of a dynamically screened deformation potential on the electron longitudinal phonon relaxation in a disordered two-dimensional electron gas. On consideration of the dynamic dielectric function and polarization operator, and the frequency ω dependence, we find a significant change in the temperature exponent as well as the pre-factor α from the earlier reported approximate temperature power law dependence αT(4) obtained under static strong screening and impurity limit. More strikingly, a reversal in the character of the dependence of scattering rate on the mean free path takes place on the incorporation of dynamic screening, where the behaviour changes from the static 1/l to the dynamic l(2) at T = 1.0 K and l = 10 nm.

Near-Field High-Energy Spectroscopic Gamma Imaging Using a Rotation Modulation Collimator

Certain trace elements are vital to the body and elemental imbalances can be indicators of certain diseases including cancer and liver diseases. Neutron Stimulated Emission Computed Tomography (NSECT) is being developed as spectroscopic imaging technique to non-invasively and non-destructively measure and image elemental concentrations within the body. A region of interest is illuminated via a high-energy beam of neutrons that scatter inelastically with elemental nuclei within the body. The excited nuclei then relax by emitting characteristic gamma rays. Acquiring the gamma spectrum in a tomographic manner allows not only the identification of elements, but also the formation of images representing spatial distributions of specific elements. We are developing a high-energy position-sensitive gamma camera that allows full illumination of the entire region of interest. Because current scintillation crystal based position-sensitive gamma cameras operate in too low of an energy range, we are adapting high-energy gamma imaging techniques used in space-based imaging. A High Purity Germanium (HPGe) detector provides high-resolution energy spectra while a rotating modulation collimator (RMC) placed in front of the detector modulates the incoming signal to provide spatial information. The purpose of this manuscript is to describe the near-field RMC geometry, which varies greatly from the infinite-focus space-based applications, and how it modulates the incident gamma flux. A simple geometric model is presented and then used to reconstruct two-dimensional planar images of both simulated point sources and extended sources.

Experimental detection of iron overload in liver through neutron stimulated emission spectroscopy

Iron overload disorders have been the focus of several quantification studies involving non-invasive imaging modalities. Neutron spectroscopic techniques have demonstrated great potential in detecting iron concentrations within biological tissue. We are developing a neutron spectroscopic technique called neutron stimulated emission computed tomography (NSECT), which has the potential to diagnose iron overload in the liver at clinically acceptable patient dose levels through a non-invasive scan. The technique uses inelastic scatter interactions between atomic nuclei in the sample and incoming fast neutrons to non-invasively determine the concentration of elements in the sample. This paper discusses a non-tomographic application of NSECT investigating the feasibility of detecting elevated iron concentrations in the liver. A model of iron overload in the human body was created using bovine liver tissue housed inside a human torso phantom and was scanned with a 5 MeV pulsed beam using single-position spectroscopy. Spectra were reconstructed and analyzed with algorithms designed specifically for NSECT. Results from spectroscopic quantification indicate that NSECT can currently detect liver iron concentrations of 6 mg g(-1) or higher and has the potential to detect lower concentrations by optimizing the acquisition geometry to scan a larger volume of tissue. The experiment described in this paper has two important outcomes: (i) it demonstrates that NSECT has the potential to detect clinically relevant concentrations of iron in the human body through a non-invasive scan and (ii) it provides a comparative standard to guide the design of iron overload phantoms for future NSECT liver iron quantification studies.

Breast cancer detection using neutron stimulated emission computed tomography: prominent elements and dose requirements

Neutron stimulated emission computed tomography (NSECT) is being developed to noninvasively determine concentrations of trace elements in biological tissue. Studies have shown prominent differences in the trace element concentration of normal and malignant breast tissue. NSECT has the potential to detect these differences and diagnose malignancy with high accuracy with dose comparable to that of a single mammogram. In this study, NSECT imaging was simulated for normal and malignant human breast tissue samples to determine the significance of individual elements in determining malignancy. The normal and malignant models were designed with different elemental compositions, and each was scanned spectroscopically using a simulated 2.5 MeV neutron beam. The number of incident neutrons was varied from 0.5 million to 10 million neutrons. The resulting gamma spectra were evaluated through receiver operating characteristic (ROC) analysis to determine which trace elements were prominent enough to be considered markers for breast cancer detection. Four elemental isotopes (133Cs, 81Br, 79Br, and 87Rb) at five energy levels were shown to be promising features for breast cancer detection with an area under the ROC curve (A(Z)) above 0.85. One of these elements--87Rb at 1338 keV--achieved perfect classification at 10 million incident neutrons and could be detected with as low as 3 million incident neutrons. Patient dose was calculated for each gamma spectrum obtained and was found to range from between 0.05 and 0.112 mSv depending on the number of neutrons. This simulation demonstrates that NSECT has the potential to noninvasively detect breast cancer through five prominent trace element energy levels, at dose levels comparable to other breast cancer screening techniques.

Introduction to neutron stimulated emission computed tomography

Neutron stimulated emission computed tomography (NSECT) is presented as a new technique for in vivo tomographic spectroscopic imaging. A full implementation of NSECT is intended to provide an elemental spectrum of the body or part of the body being interrogated at each voxel of a three-dimensional computed tomographic image. An external neutron beam illuminates the sample and some of these neutrons scatter inelastically, producing characteristic gamma emission from the scattering nuclei. These characteristic gamma rays are acquired by a gamma spectrometer and the emitting nucleus is identified by the emitted gamma energy. The neutron beam is scanned over the body in a geometry that allows for tomographic reconstruction. Tomographic images of each element in the spectrum can be reconstructed to represent the spatial distribution of elements within the sample. Here we offer proof of concept for the NSECT method, present the first single projection spectra acquired from multi-element phantoms, and discuss potential biomedical applications.

A finite-element method model of soft tissue response to impulsive acoustic radiation force

Several groups are studying acoustic radiation force and its ability to image the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) imaging is one modality using standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation forces in tissue. The dynamic response of tissue is measured via conventional ultrasonic speckle-tracking methods and provides information about the mechanical properties of tissue. A finite-element method (FEM) model has been developed that simulates the dynamic response of tissues, with and without spherical inclusions, to an impulsive acoustic radiation force excitation from a linear array transducer. These FEM models were validated with calibrated phantoms. Shear wave speed, and therefore elasticity, dictates tissue relaxation following ARFI excitation, but Poisson's ratio and density do not significantly alter tissue relaxation rates. Increased acoustic attenuation in tissue increases the relative amount of tissue displacement in the near field compared with the focal depth, but relaxation rates are not altered. Applications of this model include improving image quality, and distilling material and structural information from tissue's dynamic response to ARFI excitation. Future work on these models includes incorporation of viscous material properties and modeling the ultrasonic tracking of displaced scatterers.

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.

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.

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.

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.

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 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.

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.

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.

Role of ET and NO in resuscitative effect of diaspirin cross-linked hemoglobin after hemorrhage in rat

Diaspirin cross-linked hemoglobin (DCLHb) is a hemoglobin-based therapeutic agent that produces significant cardiovascular effects, possibly due to its actions on vasoactive substances, such as endothelin (ET) and nitric oxide (NO). We have studied the modulation of cardiovascular effects of DCLHb by an NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), and an ETA-receptor antagonist, FR-139317, in hemorrhaged rats. Control rats resuscitated with vehicle [Ringer lactate (RL), 4 ml/kg iv] did not show any improvement in O2 consumption, base deficit, systemic hemodynamics, or regional blood flow after hemorrhage, and the rats survived for < 70 min. Administration of DCLHb (400 mg/kg iv) significantly improved O2 consumption, base deficit, systemic hemodynamics, and regional blood circulation after resuscitation, and the rats survived for > 120 min after hemorrhage. Plasma ET-1 and guanosine 3',5'-cyclic monophosphate (cGMP) concentrations increased after hemorrhage. DCLHb produced an increase in ET-1 and decreased cGMP concentrations in plasma. Pretreatment with L-NAME (10 mg/kg iv) or FR-139317 (4 mg/kg iv) attenuated the DCLHb-induced improvement in survival time, base deficit, systemic hemodynamics, and regional blood circulation. L-NAME (10 mg/kg iv) per se did not produce any resuscitative effect; therefore the NO mechanism may not be contributing toward the efficacy of DCLHb in hemorrhaged rats. However, FR-139317 attenuated the efficacy of DCLHb; therefore an increase in plasma ET-1 concentration by DCLHb may be contributing toward the efficacy of DCLHb in hemorrhage. Hemorrhage-induced increase in cGMP levels could be attenuated by L-NAME, but L-NAME was not effective in resuscitation of hemorrhaged rats, indicating a lack of role of NO in resuscitation. It is concluded that the ET mechanism is more important in the beneficial effect of DCLHb than the NO mechanism in hemorrhage.

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.

Interleukin-1 beta increases airway epithelial cell mitogenesis partly by stimulating endothelin-1 production

To investigate the influence of interleukin-1 beta (IL-1 beta) on airway epithelial cell growth, we measured [3H]thymidine incorporation and cell numbers of cultured porcine tracheal epithelial cells in the presence or absence of human recombinant IL-1 beta with or without the following: goat antiporcine polyclonal antibody to platelet-derived growth factor (PDGF); IL-1 receptor antagonist; indomethacin; PD-145065, a combined endothelin-A and -B receptor antagonist; BQ-123, an antagonist selective for endothelin-A receptors; or phosphoramidon, an inhibitor, in part, of endothelin-converting enzymes, including neutral endopeptidase. We found that IL-1 beta stimulated the proliferation of airway epithelial cells, and this response was inhibited by the IL-1 receptor antagonist and by PD-145065 or BQ-123. However, neither indomethacin nor PDGF antibody was influential. The endothelin receptor antagonists also decreased basal thymidine incorporation by these cells as did phosphormidon, although to a lesser degree. Data from radioimmunoassays indicated that phosphormidon reduced the endogenous production of endothelin-1 from the cells, and IL-1 beta clearly increased it over time. We conclude that IL-1 beta is a stimulant of airway epithelial cell growth, and its mitogenic effects are mediated, in part, by endogenous endothelin-1 production.

Steroid hormone alterations following induction of chronic intraperitoneal sepsis in male rats

The influence of sepsis on male reproductive function in chronic animal models has not been extensively investigated. On the basis of earlier clinical studies, it was hypothesized that chronic intraperitoneal (i.p.) sepsis in rats would modulate the circulating levels of steroid reproductive hormones. Male Sprague-Dawley rats (300-375 g) were randomized to septic and nonseptic groups. Sepsis was induced with cecal slurry (200 mg/kg/5 mL 5% dextrose in water (D5W); i.p.) in septic rats, while nonseptic rats received only sterile D5W. The rats (n = 8-12) were catheterized to measure systemic hemodynamics and to collect blood at 0, 12, 24, and 48 h after induction of sepsis/sham sepsis. A separate group of normal rats was included to serve as an unoperated control group. The plasma concentration of corticosterone, progesterone, and testosterone in serum was determined using radioimmunoassay. The heart rate was significantly increased at t = 12, 24, and 48 h following induction of sepsis. However, septic rats did not display any significant alterations in the mean arterial pressure and pulse pressure. Basal circulating concentrations of serum corticosterone, progesterone, and testosterone were 356 +/- 124 ng/mL, 2.37 +/- 1.03 ng/mL, and 1.88 +/- .29 ng/mL, respectively, in the unoperated rats. At t = 0 h there was a significant increase in the levels of corticosterone in septic rats and in the levels of progesterone in both septic and nonseptic rats. The elevations in the concentrations of corticosterone and progesterone returned to basal values after 24 and 48 h. The septic animals had significantly decreased levels of testosterone at t = 24 and 48 h as compared with basal values and nonseptic groups. Our model of sepsis produced a time-dependent decrease in levels of testosterone, an end product of male steroidogenesis. This, along with unchanged levels of corticosterone and progesterone at 24 and 48 h following sepsis, indicates that separate mechanisms for steroidogenesis regulating synthesis of these steroid hormones (progesterone and testosterone) occur with sepsis. It is concluded that in our chronic septic rat model, induction of i.p. sepsis produced dysfunction in steroidogenesis, which selectively affected the synthesis of testosterone.

Role of endothelin in the cardiovascular effects of diaspirin crosslinked and stroma reduced hemoglobin

OBJECTIVES

Diaspirin crosslinked hemoglobin is a resuscitative solution with excellent oxygen-carrying capacity. Diaspirin crosslinked hemoglobin produces an immediate increase in blood pressure and marked regional circulatory changes in rats and pigs. Our objective was to determine the role of endothelin in the cardiovascular actions of diaspirin crosslinked hemoglobin (modified) and (unmodified) stroma reduced hemoglobin solutions.

DESIGN

Prospective, randomized comparison of cardiovascular effects of diaspirin crosslinked and stroma reduced hemoglobin in control rats and in rats pretreated with cyclo(D-Asp-Pro-D-Val-Leu-D-Trp) (BQ-123), an endothelin-A receptor antagonist.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Modified, highly purified, and heat pasteurized (diaspirin crosslinked) and unmodified (stroma reduced) hemoglobin in control (untreated) and BQ-123 (5 mg/kg/hr iv)-treated rats.

MEASUREMENTS AND MAIN RESULTS

Infusion of stroma reduced hemoglobin (400 mg/kg iv) in control rats produced an increase in blood pressure (43%) and total peripheral resistance (65%) without any change in heart rate, cardiac output, and stroke volume. Stroma reduced hemoglobin decreased blood flow to the kidneys and liver, increased blood flow to the heart, and had no effect on blood flow to the brain, gastrointestinal tract, spleen, musculoskeletal system, skin, and mesentery and pancreas. Infusion of stroma reduced hemoglobin in rats treated with BQ-123 (5 mg/kg/hr iv) increased the blood pressure to a similar degree when compared with control rats, but the increase in total peripheral resistance was significantly attenuated. The stroma reduced hemoglobin-induced decrease in blood flow to the kidneys and liver was significantly attenuated in BQ-123-treated rats as compared with control rats. However, the stroma reduced hemoglobin-induced increase in blood flow to the heart of BQ-123-treated rats was similar to the increase in control rats. Infusion of diaspirin crosslinked hemoglobin (400 mg/kg iv) produced increases in blood pressure (81%), cardiac output (36%), stroke volume (30%), and total peripheral vascular resistance (45%), along with increases in blood flow to the heart, spleen, gastrointestinal tract, and skin of control rats. The blood flows to the brain, kidneys, liver, musculoskeletal system, and mesentery and pancreas were not altered by diaspirin crosslinked hemoglobin in control rats. The increases in blood pressure, cardiac output, stroke volume, and total peripheral vascular resistance by diaspirin crosslinked hemoglobin were significantly blocked in BQ-123-treated rats as compared with control rats. The increases in blood flow to the heart, spleen, and skin by diaspirin crosslinked hemoglobin were significantly blocked in BQ-123-treated rats as compared with control rats. Diaspirin crosslinked hemoglobin produced an increase in the blood flow to the brain and a decrease in blood flow to the kidney and musculoskeletal system of BQ-123-treated rats as compared with control rats. Blood plasma endothelin-1-like immunoreactivity was found to be significantly increased after treatment with diaspirin crosslinked hemoglobin or stroma reduced hemoglobin.

CONCLUSIONS

The endothelin-A receptor antagonist, BQ-123, could attenuate the systemic hemodynamic and regional circulatory effects of diaspirin crosslinked hemoglobin and stroma reduced hemoglobin. However, the increase in blood flow to the heart induced by stroma reduced hemoglobin could not be attenuated by BQ-123.

Role of NO mechanism in cardiovascular effects of diaspirin cross-linked hemoglobin in anesthetized rats

The role of nitric oxide (NO) in the cardiovascular actions of diaspirin cross-linked hemoglobin (DCLHb) was studied in anesthetized rats. The regional circulatory and systemic hemodynamic effects of DCLHb (400 mg/kg iv) were studied using a radioactive microsphere technique in control (untreated) and L-arginine (a NO precursor) pretreated rats. DCLHb produced a significant increase in blood pressure (75%), cardiac output (42%), stroke volume (36%), and total peripheral resistance (45%), without affecting heart rate, when administered to control rats. L-Arginine pretreatment significantly attenuated DCLHb-induced systemic hemodynamic effects. DCLHb-induced increase in blood flow to the skin and spleen was completely blocked, and that to the heart was partially blocked, by L-arginine pretreatment, suggesting that cardiovascular actions induced by DCLHb could be antagonized by the NO precursor L-arginine. The NO synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) produced significant increases in regional vascular resistance, leading to a decrease in blood flow to all the organs except the heart, where an increase in blood flow and a decrease in vascular resistance was observed. DCLHb, when administered in L-NAME-pretreated rats, accentuated the decrease in blood flow to the gastrointestinal system, spleen, mesentery and pancreas, skin, and musculoskeletal system. These studies provide evidence that the NO precursor L-arginine can attenuate the effects of DCLHb and that DCLHb can potentiate the effect of the NOS inhibitor L-NAME. The role of NO in the mechanism of action of DCLHb was further studied by estimating plasma guanosine 3',5'-cyclic monophosphate (cGMP) in control, DCLHb-treated, L-NAME-treated, and L-NAME followed by DCLHb-treated rats. DCLHb and L-NAME significantly decreased the concentration of circulating cGMP in blood plasma. L-NAME pretreatment potentiated DCLHb-induced decrease in cGMP levels. Because the formation of cGMP is stimulated by NO, these studies provide additional evidence for the involvement of NO in the mechanism of action of DCLHb. It is concluded that NO plays an important role in the cardiovascular effects of DCLHb.

Yohimbine modulates diaspirin crosslinked hemoglobin-induced systemic hemodynamics and regional circulatory effects

OBJECTIVE

Diaspirin crosslinked hemoglobin, a hemoglobin-based blood substitute, is proposed to be an effective resuscitative solution. It produces an immediate, but limited increase in blood pressure when administered to conscious or anesthetized rats. This vasoactivity is associated with an increase in blood flow to several major organs. It has been shown that alpha-adrenergic receptors in the peripheral vascular system are sensitized by diaspirin crosslinked hemoglobin in rats. The present study was conducted to determine the effect of yohimbine, an alpha 2-adrenergic receptor antagonist on systemic hemodynamics and regional circulatory effects of diaspirin crosslinked hemoglobin.

DESIGN

Prospective, randomized comparison of cardiovascular effects of diaspirin crosslinked hemoglobin in control and yohimbine-pretreated rats.

SETTING

Laboratory of experimental medicine.

SUBJECTS

Male Sprague-Dawley rats weighing 300 to 350 g.

INTERVENTIONS

Modified, highly purified, and heat-pasteurized hemoglobin (diaspirin crosslinked hemoglobin) in control and yohimbine-treated (2 mg/kg i.v.) rats.

MEASUREMENTS AND MAIN RESULTS

The systemic hemodynamics and regional circulation were measured using a radioactive microsphere technique. Diaspirin crosslinked hemoglobin (400 mg/kg i.v.) produced an increase in blood pressure and total peripheral resistance, while heart rate, cardiac output, and stroke volume were not significantly altered in control rats. In yohimbine-pretreated (2 mg/kg i.v.) animals, diaspirin crosslinked hemoglobin did not produce any change in heart rate, stroke volume, cardiac output, and total peripheral resistance, but a slight increase in blood pressure was observed compared with baseline values obtained after the administration of yohimbine. The increase in blood pressure induced by diaspirin crosslinked hemoglobin was significantly blocked by pretreatment with yohimbine. Yohimbine (2 mg/kg i.v.) per se decreased blood pressure, while other systemic hemodynamic parameters were not affected. Diaspirin crosslinked hemoglobin increased blood flow to the heart, gastrointestinal tract (stomach, small intestine, cecum, and large intestine), portal (spleen, mesentery, and pancreas) and skin, while blood flow to the brain (cerebral hemispheres, diencephalon, cerebellum, and brain stem), liver, kidneys, and musculoskeletal system was not affected in control rats. In yohimbine-pretreated animals, diaspirin crosslinked hemoglobin produced an increase in blood flow to the heart, brain (cerebellum and brain stem), liver, small intestine, cecum, spleen, mesentery and pancreas, kidneys, skin and musculoskeletal system, while blood flow to the stomach and large intestine was not affected. Yohimbine pretreatment significantly attenuated the diaspirin crosslinked hemoglobin-induced increase in blood flow to the large intestine, mesentery, and pancreas.

CONCLUSIONS

The cardiovascular actions of diaspirin crosslinked hemoglobin are partially mediated through alpha 2-adrenergic receptors. Adrenergic receptor antagonists may be useful in attenuating the pressor effect of diaspirin crosslinked hemoglobin while maintaining the regional perfusion.

Effect of diaspirin crosslinked and stroma-reduced hemoglobin on mean arterial pressure and endothelin-1 concentration in rats

The effect of unmodified stroma reduced (SRHb) and modified diaspirin crosslinked (DCLHb) hemoglobin solutions on the mean arterial pressure and endothelin-1 (ET-1) concentration in blood plasma and various tissues was studied. Infusion of DCLHb or SRHb increased mean arterial blood pressure by 96% and 39%, respectively. Heart rate was not significantly affected by DCLHb or SRHb. A significant increase (P < 0.003) in the ET-1 levels in blood plasma after DCLHb and SRHb infusion was observed. The increase in plasma ET-1 concentration was significantly more marked with SRHb (141%) as compared to DCLHb (78%) treated rats. The concentration of ET-1 in the heart and brain regions was not altered in DCLHb or SRHb treated rats as compared to control. However, ET-1 concentration was significantly increased in the thoracic aorta (151%) and renal medulla (272%) of DCLHb treated rats. SRHb treated rats also showed a significant increase in ET-1 concentration in the thoracic aorta (141%) and renal medulla (429%). The effect of SRHb on the renal medulla was found to be significantly greater than that of DCLHb. ET may be one of the factors responsible for the cardiovascular effects of hemoglobin solutions.

Endothelin ETA receptor antagonist, BQ-123, blocks the vasoconstriction induced by sarafotoxin 6b in the heart but not in other vascular beds

1. The cardiovascular effects of SRT6b in control and BQ-123, a specific ETA receptor antagonist, pretreated rats were determined in anesthetized rats using a radioactive microsphere technique. 2. Infusion of SRT6b produced an increase in blood pressure and total peripheral resistance, decrease in cardiac output and stroke volume, and no change in heart rate of control or BQ-123 treated rats. 3. SRT6b induced a decrease in blood flow to the heart which was completely blocked by BQ-123 pretreatment. The decrease in blood flow to other organs by SRT6b was not affected by BQ-123 pretreatment. 4. This study indicates that ET receptors in the coronary blood vessels are of a different type (neither ETA nor ETB) to those in other vascular beds.

Effect of diaspirin cross-linked hemoglobin and norepinephrine on systemic hemodynamics and regional circulation in rats

Diaspirin cross-linked hemoglobin (DCLHb) (400 mg/kg, i.v.) produced a pressor effect that was equal to that produced by norepinephrine (NE) (25 micrograms/kg/min i.v. infusion). Total peripheral resistance was increased by DCLHb and more significantly by NE. Heart rate was not affected by DCLHb but was significantly increased by NE. The cardiac output and stroke volume were insignificantly increased by DCLHb but were significantly decreased by NE. DCLHb and NE produced a significant increase in blood flow to the heart. The vascular resistance in the heart was not affected by DCLHb but was decreased by NE. DCLHb did not affect the renal and brain circulation, but NE in kidneys decreased the blood flow and increased the vascular resistance, whereas in the brain it increased the blood flow and decreased the vascular resistance. DCLHb increased the blood flow to the stomach and small intestine. The vascular resistance was not affected by DCLHb in the gastrointestinal tract. NE did not affect the blood circulation in the gastrointestinal tract. Blood flow to the spleen was increased by DCLHb, and there was no change in the vascular resistance. NE insignificantly decreased the blood flow to the spleen and significantly increased the vascular resistance. The blood circulation to the mesentery and pancreas was not affected by DCLHb, whereas NE increased the blood flow without affecting the vascular resistance. DCLHb produced a significant increase in the blood flow to the skin without affecting the vascular resistance, whereas NE did not affect the blood flow but increased the vascular resistance. DCLHb did not affect the blood flow to the musculo-skeletal system but increased the vascular resistance, whereas NE decreased the blood flow and increased the vascular resistance. In summary, although the pressor effect of DCLHb and NE at the doses studied is equal, DCLHb did not decrease the blood flow to any organ, whereas NE produced significant decreases in blood flow to several organs. It is concluded that the blood flow to most of the organs is either increased or not affected by DCLHb.

Prazosin blocks the pressor but not the regional circulatory effects of diaspirin crosslinked hemoglobin

Diaspirin crosslinked hemoglobin (DCLHb) (400 mg/kg, i.v.) produces an increase in blood pressure and blood flow to the heart, spleen, stomach, small intestine, skin, mesentery and pancreas when administered to rats. The present study was conducted to determine (1) whether prazosin, an alpha 1-adrenergic antagonist, can block the pressor effect of DCLHb and (2) the effect of prazosin pretreatment on regional circulatory changes induced by DCLHb in rats. DCLHb (400 mg/kg, i.v.) produced an increase in blood pressure (64%), cardiac output (20%) and total peripheral resistance (65%) when administered to control rats. Infusion of DCLHb in prazosin (1 mg/kg, i.v.) treated rats did not show any significant pressor effect, but reversed the hypotensive effect of prazosin. Cardiac output and stroke volume were significantly increased and total peripheral resistance decreased in prazosin treated rats as compared to control (untreated) rats. DCLHb significantly increased blood flow to the heart, gastrointestinal tract, portal system (spleen), and skin of control rats. Blood flow to the brain, kidneys, and musculo-skeletal system was not altered following the infusion of DCLHb in controls rats. Infusion of DCLHb in prazosin treated rats produced a significant increase in blood flow to the brain, heart, kidneys, gastrointestinal tract, portal system, skin and musculoskeletal system. In summary, prazosin pretreatment blocked the pressor effect of DCLHb, however, blood flow to the heart, brain, gastrointestinal tract, portal system, kidneys, skin and musculoskeletal system was increased by DCLHb. It is concluded that blood flow to most of the organs is increased by DCLHb but the pressor effect of DCLHb is blocked by prazosin pretreatment.

Regional circulatory and systemic hemodynamic effects of diaspirin cross-linked hemoglobin in the rat

Diaspirin cross-linked hemoglobin (DCLHb) (Baxter Healthcare Corporation) is a promising resuscitative fluid. The effect of DCLHb (400 mg/kg, i.v.), on regional circulation and systemic hemodynamics was studied in male Sprague-Dawley rats using a radioactive microsphere technique. Systemic hemodynamics, distribution of cardiac output, regional blood flow and vascular resistance were determined before (baseline) and 15, 30 and 60 min after the administration of DCLHb. Infusion of an equal volume of saline did not produce any significant change in systemic hemodynamics or regional circulation. DCLHb produced an increase (79%) in the mean blood pressure which lasted for more than 60 min. Heart rate, cardiac output and stroke volume were not significantly affected, while total peripheral resistance was increased after the administration of DCLHb. DCLHb produced significant increases in blood flow to the heart, gastrointestinal tract (GIT), portal system and skin. The blood flow to the kidney, brain and musculoskeletal system was not significantly affected by DCLHb. The vascular resistance was not altered in the heart, brain, GIT, portal system, kidney or skin, but there was a marked increase in the vascular resistance in the musculoskeletal system. There was a significant increase in the percentage of cardiac output to visceral organs like heart, GIT and portal system, while a marked decrease in the percent cardiac output to musculoskeletal system was observed with DCLHb. It is concluded that the blood flow to most of the organs is either increased or is not affected by DCLHb.

Renal endothelin mechanism in altered thyroid states

Endothelin (ET) mechanisms were studied in hyper- and hypo-thyroid states in rats. Hyperthyroidism was induced by daily administration of thyroxine (0.1 mg/kg, i.p.) for 8 weeks, while hypothyroidism was induced by daily administration of methimazole (10 mg/kg, i.p.) for 8 weeks. The concentration of endogenous ET-1 was determined in the kidneys using radioimmunoassay. Systemic hemodynamics and renal blood circulation was measured using a radioactive microsphere technique. A significant increase in systolic and diastolic blood pressure, heart rate and cardiac output was observed in hyperthyroid rats as compared to eu- and hypo-thyroid rats. Total peripheral resistance was found to be similar in eu-, hyper- and hypo-thyroid rats. The endogenous concentration of ET-1 in the kidneys was significantly lower in hyper- as compared to eu- and hypo-thyroid rats. The blood flow to the kidneys was significantly increased in hyper- as compared to eu- and hypo-thyroid rats. Infusion of ET-1 (100 ng/kg/min i.v. for 45 min) produced a significant decrease in blood flow to the kidneys of eu-, hyper- and hypo-thyroid rats. The decrease in blood flow was similar in eu-, hyper- and hypo-thyroid rats, indicating that the response of renal blood vessels to exogenous ET-1 is not altered during thyroid dysfunction. Since endogenous ET-1 is involved in the regulation of vascular tone, it may be concluded that in hyper-thyroid rats decrease in concentration of the renal ET-1 could be contributing to an increase in blood flow to the kidney.

Effect of stroma-free hemoglobin and diaspirin cross-linked hemoglobin on the regional circulation and systemic hemodynamics

The effects of unmodified stroma-free hemoglobin (SFHb) and diaspirin cross-linked hemoglobin (DCLHb) on the regional blood circulation and systemic hemodynamics were studied in rats using a radioactive microsphere technique. SFHb and DCLHb increased mean arterial blood pressure without affecting heart rate. SFHb produced a 24.9% decrease in the cardiac output while DCLHb produced an 44.8% increase in the cardiac output. Stroke volume was decreased (-27.3%) by SFHb and increased (+36.4%) by DCLHb. Total peripheral resistance increased with both SFHb and DCLHb. DCLHb increased blood flow to the heart, spleen, stomach, small intestine and skin, and had no effect on blood flow to the brain, kidneys, liver, mesentery, pancreas, caecum, large intestine and musculo-skeletal system. In contrast, in animals infused with SFHb, blood flow decreased to the kidneys, liver and spleen, increased to the heart, small intestine and skin, and had no effect to the brain, caecum, large intestine and musculo-skeletal system. DCLHb had no effect on vascular resistance in any organ except for an increase in the musculo-skeletal system. In contrast, SFHb increased vascular resistance in the kidneys, liver, spleen, skin, mesentery and pancreas, and had no effect on vascular resistance in the musculo-skeletal system, brain, heart, stomach, small intestine, caecum and large intestine. SFHb had no effect on distribution of cardiac output to the brain, gastrointestinal tract (GIT), kidneys, skin, musculo-skeletal and portal system, while DCLHb significantly decreased the percent cardiac output to the musculo-skeletal system. DCLHb did not affect the distribution of cardiac output to the brain, GIT, kidneys, skin and portal system. SFHb and DCLHb increased the percent cardiac output to the heart. It is concluded that similar concentrations and doses of DCLHb and SFHb produce different effects on the regional blood circulation and systemic hemodynamics.

(+/-)Baclofen sensitive scopolamine-induced short-term memory deficits in mice

Possible involvement of GABA receptor systems in scopolamine-induced short-term memory deficits was investigated using latency of mice to reach shock-free zone (SFZ) and number of mistakes (descents) the animal made in 15 min as parameters for acquisition and retention of memory in passive avoidance paradigm. Atropine (1-5 mg/kg), scopolamine (0.1-0.5 mg/kg) but not pirenzepine (5-20 mg/kg) caused disruption of memory. GABA (50, 75 and 100 mg/kg) showed retention enhancing effects in scopolamine-treated and untreated animals but GABA agonist progabide (5-20 mg/kg) did not affect any of the parameter significantly. GABAA agonist, muscimol (0.05 and 0.1 mg/kg) and GABAB agonist, (+/-)baclofen (0.25, 0.5 and 1 mg/kg) and (-)baclofen (0.25 and 0.5 mg/kg) also displayed memory enhancing action. Whereas, GABAA antagonist, bicuculline produced hind limb rigidity, GABAB antagonist, CGP 35348 did not show any effect per se, but reversed the (+/-)baclofen-induced delay in latency, without affecting retention enhancing action of (+/-)baclofen. Combined administration of subeffective dose of GABA (50 mg/kg) and (+/-)baclofen (0.25 mg/kg), showed a significant improvement in acquisition and retention. However, the effect of GABA (100 mg/kg) on acquisition was reversed by bicuculline (2 mg/kg) and by CGP 35348 (100 mg/kg) while improving retention. The present study extends support to the cholinergic concept in cognitive performance and provide an evidence for the influence of GABAergic (particularly GABAB) modulation in scopolamine-induced learning and memory deficits in mice.

Evidence for benzodiazepine receptor interaction with MK 801 in anxiety related behaviour in rats

Antianxiety effect of noncompetitive NMDA receptor antagonist MK 801 was investigated on elevated plus-maze paradigm in rats. Interactional effects of MK 801 with the specific anxiolytic agent, diazepam; the anxiogenic beta-carboline agent, FG-7142 and the central BZ receptor antagonist Ro 15-1788 were explored. MK 801 (0.025-0.1 mg/kg) produced anxiolytic effect at all the doses in rats. Effect was potentiated by diazepam in rats. Both, FG-7142 and Ro 15-1788 reversed the effects of MK 801 and diazepam, when these agents were concomitantly administered. The study revealed anxiolytic profile of MK 801 and indicates that NMDA receptors can modulate the benzodiazepine receptor activity in rodents in elevated plus-maze apparatus.

Evaluation of learning and memory mechanisms employing elevated plus-maze in rats and mice

1. The effect of drugs affecting learning and memory was investigated using transfer latency (TL) as parameter for acquisition and retention of memory process on elevated plus-maze both in rats and mice. Further the validity of the procedure was envisaged. 2. The results provide an evidence for utility of shortened TL on 2nd day trial in old rats and mice as a parameter for retention or consolidation of memory, while treatment of drugs 30 min prior to 1st day may also be utilised for acquisition related action of drugs. 3. The drugs producing acquisition deficits namely scopolamine (0.1-0.5 mg/kg) and MK 801 (0.05-0.1 mg/kg) did not affect the shortened TL on elevated plus-maze in rats while nootropics, like piracetam (150 mg/kg) and captopril (30 mg/kg) reduced the shortened TL. The memory enhancing effect of these agent was reversed by scopolamine (0.3 mg/kg) and MK 801 (0.1 mg/kg) both in rats and mice. The results suggested the acquisition affecting drugs, however, did not show any effect on retention parameter (shortened TL) but can reverse the retention facilitatory action of nootropics. The results also provide indirect evidence for participation of cholinergic and NMDA-receptor blockade in the mechanism of these drugs. 4. Scopolamine and MK 801 produced acquisition deficits in mice, as they increased the TL on 1st and 2nd day trial while physostigmine (0.05 mg/kg) decreased the 2nd day TL. Physostigmine (0.1 mg/kg) reversed scopolamine and MK 801 induced acquisition deficits suggested participation of cholinergic and NMDA- receptor in learning process. 5. The results validate the utility of the elevated plus-maze for evaluation of possible nootropic action of drugs.

Effect of NMDA-receptor ligands on neocortical and hippocampal EEG activity of rat brain

Neocortex and hippocampus play important role in motor activity, neuronal plasticity and learning and memory mechanisms. Electroencephalographic (EEG) activity of neocortex and hippocampus of rat following NMDA-receptor agonist, N-methyl-D-aspartate (NMDA), 0.25-2 nmol in 10 microliters, ICV and noncompetitive NMDA-receptor antagonists, MK 801 (0.025-0.1 mg/kg, ip) and ketamine (10-50 mg/kg, ip) at OH, 1/2H, 4H, 8H and 24H was recorded. The electrodes were implanted stereotaxically in hippocampus and neocortex respectively. NMDA (0.25 and 1 nmol) showed longer lasting decrease in amplitude in hippocampus and in frequency in cortical neurons while 2 nmol produced epileptogenic neurotoxicity. Opposite effect i.e. increase in amplitude in both, hippocampus and neocortex was observed with MK 801 and ketamine and these agents also showed longer lasting influence. Administration of MK 801 (0.05 mg/kg) and ketamine (50 mg/kg) prior to NMDA 2 nmol protected 40% animals from NMDA-induced neurotoxicity and blockade of NMDA-induced long term influence. The EEG effect of NMDA agonist and NMDA-induced neurotoxicity at higher dose and its modification by NMDA-antagonist, MK 801 and ketamine suggest that beside NMDA agonists (NMDA), its antagonists may, also affect long lasting changes in hippocampus and cortex. These antagonists reverse NMDA-mediated long term influence in these brain areas.

Effects of MK-801 and ketamine on short-term memory deficits in passive avoidance step-down task paradigm in mice

The phenomenon of long-term potentiation (LTP) formation in hippocampal and neocortical brain areas has been suggested as a mechanism for learning and memory where NMDA-receptors play a significant role. Various agonists have been proposed to facilitate LTP and thereby learning and memory. Competitive and non-competitive antagonists of NMDA-receptors block LTP formation and produce attentional or acquisition deficit in animals. A series of experiments were carried out with noncompetitive NMDA antagonists, MK-801 (10-100 micrograms/kg) and ketamine (1-10 mg/kg), in passive avoidance step-down task paradigm in mice. MK-801 showed complete disruption of acquisition at higher doses, while very low doses showed improvement in retention. MK-801 showed additive or potentiating influence on scopolamine-induced deficits. The results of the interaction of NMDA antagonists with scopolamine provide a basis for the speculation that cholinergic- and NMDA-antagonism may play a hand in hand role in short-term memory disturbances in passive avoidance step-down task paradigm in mice.

Dizocilpine, ketamine and ethanol reverse NMDA-induced EEG changes and convulsions in rats and mice

Electroencephalographic (EEG) activity in neocortex of rats following intracerebroventricular (icv) administration of NMDA (0.25-2 nmol/10 microliters) and its modification by noncompetitive NMDA-receptor antagonists, dizocilpine (MK-801) (0.025-0.1 mg/kg, ip) and ketamine (10-50 mg/kg, ip) was recorded at 0, 0.5, 4, 8 and 24 hr with chronically implanted electrodes. NMDA (0.25 and 1 nmol) showed longer lasting decrease in frequency in cortical neurons while 2 nmol produced convulsions and death. Administration of MK 801 (0.05 mg/kg) and ketamine (50 mg/kg) prior to NMDA offered protection in 40% of animals against NMDA-induced convulsions and blocked NMDA-induced long term influence. However, ketamine and MK 801 showed an increase in percent amplitude and also had long lasting effects per se. In conscious mice, NMDA (0.5-10 nmol/microliters icv) induced dose dependent convulsions. Both MK 801 and ketamine showed potent anticonvulsant effect. Ethanol (0.5-2 g/kg, ip) also offered significant protection against NMDA-induced convulsions. MK 801 (0.1 mg/kg) when administered concurrently with ethanol (0.5 g/kg) exhibited synergistic anticonvulsant effect. The EEG study in rats and effect of NMDA in conscious mice provide a direct evidence for the role of NMDA-receptor system in convulsions and in anticonvulsant action of ethanol.

Evidence for GABA-BZ receptor modulation in short-term memory passive avoidance task paradigm in mice

The possible involvement of gamma-aminobutyric acid/benzodiazepine (GABA-BZ) receptor modulation in scopolamine-induced short-term memory deficit was investigated in mice. Passive avoidance step-down task behavior was observed. Latency of mice to reach shock-free zone (SFZ) and number of mistakes the animal made in 15 min were used as separate parameters for acquisition and memory retention, respectively. Scopolamine (0.3 mg/kg) caused a delay in reaching SFZ and an increased number of mistakes. Physostigmine reversed the scopolamine-induced increase in number of mistakes; however, it caused a delay in the time to reach SFZ. Subeffective dose of GABA, when combined with physostigmine, further delayed the latency to reach SFZ, but reduced the number of mistakes very significantly. GABA (50, 75 and 100 mg/kg, i.p.) and GABA agonists sodium valproate (30 and 60 mg/kg, i.p.), fengabine (5 and 10 mg/kg, i.p.), (+/-)baclofen (0.25, 0.5 and 1.0 mg/kg, i.p.) and (-)baclofen (0.25 and 0.5 mg/kg i.p.) reversed the scopolamine-induced effect; however, sodium valproate at higher dose delayed time to reach SFZ. Combined administration of lower dose (+/-)baclofen and subeffective dose of GABA showed significant decrease in latency and number of mistakes in scopolamine-treated animals. The specific benzodiazepine antagonist flumazenil (Ro-15-1788) (5 and 10 mg/kg, i.p.) and inverse agonist FG-7142 (10 mg/kg, i.p.) very significantly reversed scopolamine-induced increase in number of mistakes, but Ro-15-1788 failed to show any effect on latency per se and in scopolamine-treated experiments, as well.(ABSTRACT TRUNCATED AT 250 WORDS)