Pathology and diseases of great apes at the National Zoological Park

Knowledge of the diseases of great apes in captivity is essential for captive management of self-sustaining populations. This survey of medical and pathology records of orangutans, gorillas, and one chimpanzee at the National Zoological Park was conducted to provide a data base for improving health care of captive apes. Strongyloidiasis, balantidiasis, and entamoebiasis were recurrent problems in adult and juvenile apes of all species. Cardiac fibrosis also was prevalent in middle-aged apes and was a major cause of mortality. Bacterial infections were prevalent in perinatal orangutans and resulted in the death of two. For gorillas, rheumatoid arthritis associated with mycoplasma infections, and infertility were major problems. Because the pathogenesis of many of these lesions is unknown, survival of great ape populations in captivity may depend on future research on these problems.     

The role of protein kinases and protein phosphatases in the regulation of cardiac sarcoplasmic reticulum function

Summary Canine cardiac sarcoplasmic reticulum is phosphorylated by adenosine 3,5-monophosphate (cAMP)-dependent and by calcium · calmodulin-dependent protein kinases on a 27 000 proteolipid, called phospholamban. Both types of phosphorylation are associated with an increase in the initial rates of Ca²⁺ transport by SR vesicles which reflects an increased turnover of elementary steps of the calcium ATPase reaction sequence. The stimulatory effects of the protein kinases on the calcium pump may be reversed by an endogenous protein phosphatase, which can dephosphorylate both the CAMP-dependent and the calcium · calmodulin-dependent sites on phospholamban. Thus, the calcium pump in cardiac sarcoplasmic reticulum appears to be under reversible regulation mediated by protein kinases and protein phosphatases.     

Post-receptor modulation of the effects of cyclic AMP in isolated cardiac myocytes

Summary The actions of cyclic AMP are subject to several levels of post-receptor modulation in cardiac tissue. Isoproterenol and prostaglandin E₁ both stimulate cAMP accumulation, but only isoproterenol causes activation of particulate cAMP-dependent protein kinase, leading to activation of phosphorylase kinase and glycogen phosphorylase, and inhibition of glycogen synthase. Through the use of isolated, adult ventricular myocytes, we have determined that the hormone-specific activation of glycogen phosphorylase is due to subcellular compartmentation of cAMP. There is some evidence that cyclic nucleotide phosphodiesterases, whose activity is stimulated by alpha₁-adrenergic agonists in isolated myocytes, may have a role in compartmentation. Phosphoinositide hydrolysis is stimulated by alpha, and muscarinic agonists, presumably leading to activation of protein kinase C, which in turn has multiple effects on hormone-sensitive adenylate cyclase.Abbreviations cAMP Adenosine-3,5-Cyclic Monophosphate - cGMP Guanosine-3,5-Cyclic Monophosphate - G_i, G_S Guanine nucleotide-binding proteins linked to inhibition and stimulation, respectively, of adenylate cyclase - GTP Guanosine-5-triphosphate - PDE Cyclic Nucleotide Phosphodiesterase - PGE₁ Prostaglandin E₁     

Acute Uteroplacental Ischemic Embryo: Lactic Acid Accumulation and Prostaglandin Production in the Fetal Rat Brain

A new experimental model for studying the effects of acute ischemia on brain development in the near-term fetal rat has been devised. Ischemic conditions are achieved by complete clamping of blood vessels branching from the uterine vasculature into each individual fetus for designated times followed by removal of the clamps to permit reperfusion. Accumulation of lactic acid in the fetal brain depends on the length of the restriction period, reaching a plateau level of 29 mumol/g tissue at about 30 min. It also depends on the reperfusion time. Thus after a period of 15 min of restriction lactate levels show an increase over the next 30-min reperfusion to a value of 25.5 mumol/g followed by a rapid decrease to normal values by 3 h of reperfusion. Restriction of 15 min followed by reperfusion of 45 min causes an elevation of prostaglandin E2 (PGE2) level from 12.4 +/- 0.86 ng/g to 21.1 +/- 0.6 ng/g (p less than 0.001). This elevation in PGE2 level is less apparent after 20 min of restriction. No effects are seen on the level of PGF2 alpha. Both PGE2 and PGF2 alpha accumulate in vitro in a time-dependent manner by brain particulate fraction. In vitro synthesis of both PGE2 and PGF2 alpha is inhibited by indomethacin (100% and 68%, respectively) and AA861 (94% and 76%, respectively). BW755c and nordihydroguaiaretic acid do not affect PGE2 formation but enhance PGF2 alpha production by 112% and 152%, respectively. Particulate fractions from restricted brain produce less PGF2 alpha than control brains (6.38 +/- 1.62 versus 11.43 +/- 2.2, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Beta-adrenergic receptor characteristics of postnatal rat myocardial cell preparations

Summary Primary mycolardial cell cultures and freshly isolated cardiac cells in suspension resprensent two isolated, whole cell models for investigating cellular transsarcolemmal⁴⁵Ca⁺⁺ exchange in response to a receptor-coupled stimulus. Studies were performed to characterize beta-adrenergic receptor binding, beta-adrenergic receptor mediated cellular calcium (⁴⁵Ca⁺⁺) exchange, and viability in purified primary myocardial cell cultures and freshly isolated cardiac cells in suspension obtained from 3-to 3-d-old Sprague-Dawley rats. In addition, beta-adrenergic receptor binding was characterized in whole-heart crude membrane preparations. All three preparations had saturable beta-adrenergic binding sites with the antagonist [¹²⁵I]iodopindolol ([¹²⁵I]IPIN). The suspensions had a significantly lower B _max (42±6 fmol/mg protein) than the membranes and cultures (77±8 and 95±10 fmol/mg protein, respectively). The K _D of the cultures (218±2.0 pM) was significantly higher than that for the suspensions (107 ±1.3 pM) and membranes (93±1.3 pM). Viability was significantly lower in the suspensions (57%) when compared to 94% viability in myocardial cell cultures after 3 h of incubation in Kreb's Henseleit buffer. Incubation of the cultures with 5.0×10⁻⁷ M isoproterenol resulted in a significant increase in⁴⁵Ca⁺⁺ exchange as early as 15 s. In contrast,⁴⁵Ca⁺⁺ exchange into the suspensions was not increased. Although both primary cell cultures and cardiac cells in suspension possess saturable beta-adrenergic receptors, only the monolayer cultures exhibited functional beta-adrenergic receptor-mediated⁴⁵Ca⁺⁺ exchange. Of the two intact cell models investigated, these data suggest that primary myocardial cell cultures are more suitable than cell suspensions for investigating beta-adrenergic receptor binding and functions in the postnatal rat heart. This research was supported by The University of Texas Research Institute, a grant from the Texas Advanced Research Technology Program awarded to S. W. Leslie and R. E. Wilcox, and contract 223-86-2109 from the Food and Drug Administration.     

Heart sarcolemmal Ca2+ transport in endotoxin shock: I. Impairment of ATP-dependent Ca2+ transport

Effects of endotoxin administration on the ATP-dependent Ca²⁺ transport in canine cardiac sarcolemma were investigated. The results show that the sidedness of the sarcolemmal vesicles was not affected but the ATP-dependent Ca²⁺ transport in cardiac sarcolemma was decreased by 22 to 46% (p < 0.05) at 4 h following endotoxin administration. The kinetic analysis indicates that the V_max for ATP and for Ca²⁺ were decreased by 50% (p < 0.01) and 32% (p < 0.01), respectively, while the Km values for ATP and Ca²⁺ were not significantly affected after endotoxin administration. Magnesium (1–5 mM) stimulated while vanadate (0.25–3.0 M) inhibited the ATP-dependent Ca²⁺ transport, but the Mg²⁺-stimulated and the vanadate-inhibitable activities remained significantly lower in the endotoxin-treated animals. These data demonstrate that endotoxin administration impairs the ATP-dependent Ca²⁺ transport in canine cardiac sarcolemma and that the impairment is associated with a mechanism not affecting the affinity towards ATP and Ca²⁺. Additional experiments show that the Ca²⁺ sensitivity of the Ca²⁺-ATPase activity was indifferent between the control and endotoxic groups suggesting that endotoxic injury impairs Ca²⁺ pumping without affecting Ca²⁺-ATPase activity. Since sarcolemmal ATP-dependent Ca²⁺ transport plays an important role in the regulation of cytosolic Ca²⁺ homeostasis, an impairment in the sarcolemmal ATP-dependent Ca²⁺ transport induced by endotoxin administration may have a pathophysiological significance in contributing to the development of myocardial dysfunction in endotoxin shock.     

Long term incubation of cardiac myocytes with oleic acid and very-low density lipoprotein reduces heparin-releasable lipoprotein lipase activity

An exogenous [³H]triolein emulsion was hydrolyzed by intact cardiac myocytes with functional LPL located on the cell surface. This surface-bound LPL could be released into the medium when cardiac myocytes were incubated with heparin. Incubation of cardiac myocytes with VLDL, or the products of TG breakdown, oleic acid or 2-monoolein, did not increase LPL activity in the medium. However, incubation of cardiac myocytes with either VLDL or oleic acid for > 60 min did reduce heparin-releasable LPL activity. In the heart, this inhibitory effect of FFA could regulate the translocation of LPL from its site of synthesis in the cardiac myocyte to its functional site at the capillary endothelium.Abbreviations LPL lipoprotein lipase - TG triacylglycerol - FFA free fatty acids - VLDL very-low density lipoprotein     

Oxygen free radicals in volume overload heart failure

It has been suggested that oxygen free radicals (OFR) depress the excitation-contraction coupling in cardiac muscle. It is possible that a decrease in the cardiac contractility in the failing heart may be due to an increased OFR producing activity of polymorphonuclear (PMN) leukocytes. We studied the OFR producing activity (chemiluminescence) of PMN leukocytes from blood in dogs with heart failure due to chronic volume overload. The animals were divided into two groups: I) normal, (n = 10): II) dogs with mitral insufficiency (MI) of 6 to 9 months duration, (n = 10). Hemodynamic studies were done to establish the presence of heart failure. Blood samples were collected to measure PMN leukocyte chemiluminescence. There was a decrease in the cardiac index and index of myocardial contractility (dp/dt/IIP) and an increase in the left ventricular end-diastolic pressure in dogs with MI indicating left ventricular failure. The peak chemiluminescent activity of the PMN leukocytes in blood of dogs with failure was about four folds greater than that in the blood from normal dogs. These results suggest that there may be an increased OFR generation in dogs with volume overload heart failure. The decrease in the myocardial contractility in the failing heart might be due to an increase in the OFR produced by the PMN leukocytes.     

Non-coordinate expression of collagen mRNAs during carbon monoxide-induced cardiac hypertrophy

Collagen gene expression during volume overload-induced cardiac hypertrophy was investigated in adult male rats. Hypertrophy of the left ventricle (22%) and right ventricle (37%) occurred following 27 days continuous exposure to 700 ppm carbon monoxide; hematocrit increased nearly 47%. To examine potential cellular and molecular control of restructuring in the heart, we investigated the expression of two specific procollagen mRNAs for collagen types which have different structural-functional roles [Type I (alpha-1) & Type IV]. Type I (interstitial) mRNA levels increased at least 100% relative to controls within 3 days of initial exposure to 700ppm CO, then declined afterwards; type IV(basement membrane) mRNA levels increased more modestly at first, and increased further afterwards. The ratio of type I/type IV RNA's also increased initially, then later declined, with the greatest differences in the relative responses of type I and IV mRNAs seen in the right ventricle. These data suggest that types I and IV collagen mRNA expression is not coordinately expressed during this type of volume overload-induced hypertrophy in rat heart.     

Singlet oxygen: a potential culprit in myocardial injury?

The purpose of this study was to explore the role of singlet oxygen in cardiovascular injury. To accomplish this objective, we investigated the effect of singlet oxygen [generated from photoactivation of rose-bengal] on the calcium transport and Ca²⁺-ATPase activity of cardiac sarcoplasmic reticulum and compared these results with those obtained by superoxide radical, hydrogen peroxide and hydroxyl radical. Isolated cardiac SR exposed to rose bengal (10 nM) irradiated at (560 nm) produced a significant inhibition of Ca ²⁺ uptake; from 2.27 ± 0.05 to 0.62 ± 0.05 µmol Ca⁺/mg.min (mean ± SE) (P < 0.01) and Ca²⁺-ATPase activity from 2.08 ± 0.05 µmol Pi/min. mg to 0.28 ± 0.04 µmol Pi/min. mg (mean ± SE) (P < 0.01). The inhibition of calcium uptake and Ca²⁺-ATPase activity by rose bengal derived activatedoxygen (singlet oxygen) was dependent on the duration of exposure and intensity of light. The singlet oxygen scavengers ascorbic acid and histidine significantly protected SR Ca²⁺-ATPase against rose bengal derived activated oxygen species but superoxide dismutase and catalase did not attenuate the inhibition. SDS-polyacrylamide gel electrophoresis of SR exposed to photoactivated rose bengal up to 14 min, demonstrated complete loss of Ca²⁺-ATPase monomer band which was significantly protected by histidine. Irradiation of rose bengal also caused an 18% loss of total sulfhydryl groups of SR. On the other hand, superoxide (generated from xanthine oxidase action on xanthine) and hydroxyl radical (0.5 mM H₂O₂ + Fe²⁺ -EDTA) as well as H₂O₂ (12 mM) were without any effect on the 97,000 dalton Ca²⁺-ATPase band ofsarcoplasmic reticulum. The results suggest that oxidative damage of cardiac sarcoplasmic reticulum may be mediated by singlet oxygen. This may represent an important mechanism by which the oxidative injury to the myocardium induces both a loss of tension development and arrhythmogenesis.