Harold D. Battarbee

Role of Glutaraldehyde in Calcification of Porcine Aortic Valve Fibroblasts

Glutaraldehyde-treated porcine aortic valve xenografts frequently fail due to calcification. Calcification in the prostheses begins intracellularly. In a previous study, various types of cell injury to canine valvular fibroblasts, including glutaraldehyde treatment, led to calcification. An influx of extracellular Ca2+ into the phosphate-rich cytosol was theorized to be the mechanism of calcification. To test the Ca2+ influx theory, cytosolic Ca2+ and Pi concentrations were assessed in glutaraldehyde-treated porcine aortic valve fibroblasts, and their relationship to a subsequent calcification was studied. Glutaraldehyde caused an immediate and sustained massive cytosolic Ca2+ increase that was dose dependent and a several-fold increase in Pi. Calcification of cells followed within a week. The earliest calcification was observed in blebs formed on glutaraldehyde-treated cells. Live control cells or cells fixed with glutaraldehyde in Ca2+-free solution did not calcify under the same conditions. Concomitant increases in Ca2+ and Pi in glutaraldehyde-treated cells appear to underlie the mechanism of calcification, and the presence of extracellular Ca2+ during glutaraldehyde fixation promotes calcification.

The Effect of Dietary Sodium and Potassium Upon Blood Pressure and Catecholamine Excretion in the Rat

Summary Male Sprague-Dawley derived rats fed a moderately high sodium diet became hypertensive by the 6th dietary month. After the 12th dietary month, the urinary excretion of epinephrine and norepinephrine was moderately increased in this group. The inclusion of a small dietary supplement of potassium in the diet had an ameliorating effect upon the development of hypertension and resulted in lower excretion rate for catecholamines.

Enzyme activities in the central nervous system of the epilepsy-prone rat

Abstract Tyrosine hydroxylase and monoamine oxidase activities were measured in 6 areas of the central nervous system of genetically determined epilepsy-prone rats (GEPR). Monoamine oxidase activity did not differ from control. Tyrosine hydroxylase activity was 173% of control in the midbrain of the GEPR group. Kinetic analysis revealed similar Km values for control and GEPR. These findings confirm and extend earlier studies relating seizures in the GEPR to abnormalities in central nervous system monoaminergic function.

A vasopressor potentiator for norepinephrine in hypertensive rats.

Recently, attention has been given to a hyperresponsiveness to vasopressor agents in various forms of hypertension. Hypertrophy and/or “water-logging” of blood vessels associated with prolonged hypertension has been found to narrow vessel lu-mina and lead to such hyperresponsiveness (1). In addition, subnormal mono-amine oxidase activity accompanied by increased tissue norepinephrine concentration has been reported in genetically hypertensive turkeys, which also exhibited a greater vasopressor response to exoge-nously administered norepinephrine (2). Lately there has been a renewed interest in a “sensitizing factor” to catechol-amines in hypertension, but because of the diverse nature of some studies and the frequent utilization of inadequate controls, reports have been conflicting. Several investigators have found evidence for a vasopressor agent potentiating factor among hypertensive subjects (3-6), and a transmittable humoral factor has been suggested by a study that utilized the par-abiotic union of a strain of rats that was genetically susceptible to the development of hypertension (7). In addition, a blood-borne factor in hypertensive humans that sensitized normal assay animals to the vasopressor effects of norepinephrine and an-giotensin II has been reported (8). The present study was conducted to determine if a factor exists in the serum of salt-induced hypertensive rats that would enhance the vasopressor activity of exoge-nously administered norepinephrine in normotensive bioassay animals. Materials and methods. Development of experimental hypertension. Sixty-eight male rats, initially weighing 166 ± 29 g (SD), were quartered in a climate controlled room (25° ± 2± and 50-60% relative humidity) with 12 hr of light each day (6 am to 6 pm). Animals were divided into three groups of 20-24 animals and placed on diets consisting of Purina Lab Chow with NaCl added to make up 1.3, 5.6, and 8.4% of the ration by weight. 1

The Role of Lipophilic Bile Acids in the Development of Cirrhotic Cardiomyopathy

Marked hemodynamic changes occur in humans and experimental animals with cirrhotic liver disease. In the heart, basal contractility, responsiveness to β-adrenoceptor activation, and excitation–contraction coupling (ECC) are negatively affected in models of cirrhosis and portal hypertension with portosystemic shunting (PVS), and comprise what has been called cirrhotic cardiomyopathy. These effects are accompanied by elevated circulating levels of bile acids. We investigated whether elevated bile acids act as a myocardial toxicant by exposing cardiac muscle in vitro to bile acids and compared these results with two models of cirrhotic cardiomyopathy with elevated bile acids: CCl4-induced cirrhosis and PVS. Cholic acid, a lipophilic bile acid, produced a decrease in basal cardiac contractility and responsiveness to β-adrenoceptor activation, both of which appeared to result from altered ECC. β-Adrenoceptor density and signaling were unaffected. Acutely, ursodeoxycholic acid, a more hydrophilic bile acid, had no effect. Cirrhosis produced a decrease in basal force, depressed β-adrenoceptor responsiveness, and altered ECC similar to cholic acid. However, cirrhosis also altered β-adrenoceptor signaling including decreases in cyclic AMP formation, expression of the stimulatory G protein, GS, and β-adrenoceptor density. Displacement of lipophilic bile acids by chronic administration of ursodeoxycholic acid to rats during the development of cirrhotic cardiomyopathy produced by PVS produced attenuation of the effect on ECC. These results suggest a possible role for lipophilic bile acids in some, but not all of the myocardial consequences of chronic portal vein stenosis and CCl4-induced cirrhosis.

A Humoral Sensitizing Factor for Norepinephrine in the Spontaneously Hypertensive Rat

Abstract The vasopressor effect of exogenous norepinephrine was compared before and after iv injection of sera from Aoki-Okamoto spontaneously hypertensive rats into bioassay animals. Changes in the pressor responses were compared to those produced by the sera of normotensive Sprague-Dawley-derived rats. The systolic blood pressures of serum donor animals were periodically taken via a cuff over the caudal artery. The animals were decapitated and trunk blood was collected. The mean systolic blood pressure of the spontaneously hypertensive group was 184 ± 4 mm Hg just prior to killing. A separate group of normotensive rats was bilaterally nephrectonized and after 24 hr was ganglionically blocked with hexamethonium and used as bioassay animals. Bioassay animals were given standardized doses of norepinephrine iv at 6-min intervals both before and after iv injection of 15-25 μl of either normotensive or spontaneously hypertensive rat serum. Spontaneously hypertensive rat serum increased the average pressor response to norepinephrine 22 ± 7% (P < 0.02). Normotensive serum did not increase the pressor response to norepinephrine. These data suggest there is a humoral factor in spontaneously hypertensive rat serum that potentiates the pressor effect of norepinephrine when injected into bioassay animals.

The effects of thyroid state on rat liver glucose-6-phosphatase activity and glycogen content.

Summary Treatment of animals with 100 μxg of L-thyroxine resulted in great increases in liver G-6-Pase activity and depleted glycogen stores. Comparable animals rendered hypothyroid by radiothyroidectomy exhibited a decrease in G-6-Pase activity and considerable deposition of glycogen when compared to thyrotoxic animals. No differences in glycogen content were noted between euthyroid and hypothyroid animals. Possible physiological consequences of these changes were discussed.

The quantitative estimation of microvessels in microvascular networks

A novel method is presented that greatly facilitates the determination of vessel segment number and density in both simple and complex microvascular networks. This approach was applied to microvascular networks represented by the Bra-Ket operator technique and accurately predicted the number of vessel segments in both tree-branched and loop-branched (arcade) networks. The method was then applied to the complex hexagonal array network described by Engelson et al. for gastrointestinal mucosa and accurately yielded an average vessel segment number of three around each hexagonal loop. This new method may be used for conveniently estimating tissue microvascular densities, such as vessel rarefaction or proliferation, and for the modelling of microvascular networks.

Implementation of near-infrared spectroscopy in a rat model of cardiac arrest and resuscitation

Transient global cerebral ischemia accompanying cardiac arrest (CA) often leads to permanent brain damage with poor neurological outcome. The precise chain of events underlying the cerebral damage after CA is still not fully understood. Progress in this area may profit from the development of new non-invasive tools that provide real-time information on the vascular and cellular processes preceding the damage. One way to assess these processes is through near-IR spectroscopy, which has demonstrated the ability to quantify changes in blood volume, hemoglobin oxygenation, cytochrome oxidase redox state, and tissue water content. Here we report on the successful implementation of this form of spectroscopy in a rat model of asphyxial CA and resuscitation, under hypothermic and normothermic conditions. Preliminary results are shown that provide a new temporal insight into the cerebral circulation during CA and post-resuscitation.

Feasibility of using diffuse reflectance spectroscopy for the quantification of brain edema

Many diseased states of the brain can result in the displacement of brain tissues and restrict cerebral blood flow, disrupting function in a life-threatening manner. Clinical examples where displacements are observed include venous thromboses, hematomas, strokes, tumors, abscesses, and, particularly, brain edema. For the latter, the brain tissue swells, displacing the cerebral spinal fluid (CSF) layer that surrounds it, eventually pressing itself against the skull. Under such conditions, catheters are often inserted into the brains ventricles or the subarachnoid space to monitor increased pressure. These are invasive procedures that incur increased risk of infection and consequently are used reluctantly by clinicians. Recent studies in the field of biomedical optics have suggested that the presence or absence of the CSF layer can lead to dramatic changes in NIR signals obtained from diffuse reflectance measurements around the head. In this study, we consider how this sensitivity of NIR signals to CSF might be exploited to non-invasively monitor the onset and resolution of brain edema.