Hormonally sensitive cyclic AMP phosphodiesterase in liver cells. An ecto-enzyme

Ecto-cyclic AMP phosphodiesterase activity was determined from freshly isolated and cultured liver cells. The cells were capable of hydrolyzing cyclic AMP in the medium. The ecto-phosphodiesterase represents a low Km phosphodiesterase which was activated by physiological concentrations of insulin. The product, 5'-AMP, was recovered in the medium and not with the cells. The enzyme was inhibited with aminophylline and trypsin. The ecto-phosphodiesterase activity was proportional to cell number, and total phosphodiesterase activity increased 5- to 10-fold when the cells were ruptured. About one-third of the ecto-phosphodiesterase activity from freshly isolated liver was due to phosphodiesterase in the medium. No phosphodiesterase was in the medium of cultured liver cells.     

Comparative particle recoveries by the retracting rotorod,rotoslide and Burkard spore trap sampling in a compact array

An array comprising 4 intermittent (retracting) rotorods, 3 (swingshield) rotoslides and one Burkard (Hirst) automatic volumetric spore trap was operated on an urban rooftop during 70 periods of 9, 15 or 24 hours in late summer. Standard sampling procedures were utilized and recoveries of pollens as well as spores ofAlternaria, Epicoccum, Pithomyces andGanoderma species compared. Differences between paired counts from each sampler type showed variances increasing with levels of particle prevalence (and deposition). In addition, minimal, non-random, side-to-side and intersampler differences were noted for both impactor types. Exclusion of particles between operating intervals by rotoslides and rotorods was virtually complete. Spore trap recoveries for all particle categories, per m³, exceeded those by both impactors. The greatest (7-fold) difference was noted for the smallest type examined (Ganoderma). For ragweed pollen, an overall spore trap/impactor ratio approached 1.5. Rain effects were difficult to discern but seemed to influence rotoslides least. Overall differences between impactors were quite small but generally favored the rotoslide in this comparison. Our data confirm the relative advantages of suction traps for small particles. Both impactors and spore traps are suited to pollen and large spore collection, and, with some qualification, data from both may be compared.     

SEQUENTIAL ELECTROCARDIOGRAPHIC ANALYSIS OF STONE HEART SYNDROME IN A PATIENT SUPPORTED SIX DAYS WITH AN ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD)

A 21-year-old male patient underwent aortic and mitral valve replacement for progressive cardiac failure due to acute bacterial endocarditis. Ischemic myocardial contracture developed during attempts to restore cardiac activity following hypothermic, ischemic, cardioplegic arrest. An abdominal left ventricular assist device (ALVAD) was implanted and supported the circulation for nearly six days prior to cardiac transplantation. The preoperative EKG showed sinus tachycardia with left anterior hemiblock. Postoperatively, there was complete electromechanical dissociation. The postoperative EKG showed a superior and leftward shift of the axis. There was a marked loss of QRS voltage and variable degrees of atrioventricular block. At times, only P waves were present. On the fourth postoperative day, there was an axis shift to the extreme right. Prior to transplantation, sinus rhythm returned, and the axis shifted leftward once again. The common denominator of all the abnormal postoperative electrocardiograms was the conspicuous low voltage that probably signified early and extensive myocardial damage. To our knowledge, this is the first instance wherein a sequential electrocardiographic analysis of stone heart syndrome has been undertaken.     

L-histidine induced changes in adenosine 3':5'-monophosphate levels in rat brain and amounts of apo-, holo-a and holo-b fatty acid synthetases in rat liver.

When fasted rats were fed a chow or fat-free diet supplemented 5% with L-histidine for three days, the brain adenosine 3′:5′-monophosphate (cAMP) level increased. A 50% increase occurred in rats fed a chow diet and 20% increase in rats fed a fat-free diet. Purification of liver fatty acid synthetase and the isolation of liver apo-, holo-$\text{a}$ and holo-$\text{b}$ fatty acid synthetases demonstrated that L-histidine feeding caused changes in the relative amounts of these enzymes. Apo- and holo-$\text{b}$ fatty acid synthetases increased while the holo-$\text{a}$ form simultaneously decreased. This effect was observed in rats fed either chow or fat-free diets supplemented with L-histidine.     

L-histidine-induced suppression of lipogenic enzymes.

Diets supplemented 5% with L-histidine produce hypercholesterolemia and increase cholesterol biosynthesis in rat liver. We now report an $\text{inhibitory}$ effect of L-histidine on lipogenic enzymes in the liver. In this study, L-histidine was added to chow and fat-free diets and fed to rats for 18 days. After two days of fasting, the rats were refed the same diet for three days prior to sacrifice. L-histidine decreased fatty acid synthetase activity by 51% when it was added to the chow diet and by 26% when it was added to the fat-free diet. Isocitrate dehydrogenase activity was not altered significantly in rats fed diets supplemented with L-histidine.     

Independent variation of β-adrenergic receptor binding and catecholamine-stimulated adenylate cyclase activity in rat erythrocytes

Isoproterenol-stimulated adenylate cyclase activity in membrane preparations of reticulocyte-rich (90%) erythrocytes from phenylhydrazine-treated rats is 9 times greater than in untreated animals (1% reticulocytes); basal and fluoride-stimulated activities are also enhanced 2 and 4-fold respectively. In contrast, the number of β-adrenergic receptor sites detected by the binding of ¹²⁵I-hydroxybenzylpindolol (¹²⁵I-HYP) is increased only 40% in these same preparations. The dissociation constant (K_D) of ¹²⁵I-HYP and the IC₅₀ of (-)-isoproterenol for receptor binding sites are unchanged, as is the EC₅₀ of (-)-isoproterenol for activation of adenylate cyclase. The disproportionately large increase in the activity of the isoproterenol-sensitive adenylate cyclase, compared with the small increase in the number of ¹²⁵I-HYP binding sites indicates that the functions of catecholamine recognition and consequent adenylate cyclase response can vary independently and suggest that the receptor and the cyclase may be autonomous molecular entities.     

On the synthesis of viral ribonucleic acids and ribonucleoproteins in the submitochondrial system completely free of interfering cytoplasmic contaminations

Summary The synthesis of virus-specific macromolecules was studied in the reconstituted system containing inner membrane-matrix fraction from rat liver mitochondria and infectious RNA of Venezuelian equine encephalomyelitis (VEE) virus. In a series of preliminary experiments it was shown that isolated submitochondrial fraction was completely free of interfering cytoplasmic contaminations and particularly, of cytoplasmic 80S ribosomes. VEE RNA when added to submitochondrial system caused significant stimulation of RNA and protein synthesis. These processes were resistant to actinomycin D which inhibited profoundly the synthesis of proper mitochondrial macromolecules. The stimulating effect of VEE RNA in experiments with submitochondrial system was about three times higher than that with intact mitochondria. The stimulation of¹⁴C-amino acid incorporation increased as a function of incubation time; a certain lag-period being observed. The newly formed virus-specific RNA's and ribonucleoproteins were identified with the aid of sedimentation analysis. In particular, radioactive RNA's with sedimentation coefficients 40S and 26-18S were isolated from the incubated system. These RNA's are similar respectively to VEE genome RNA and doublestranded VEE replicative RNA. In double labelling experiments with³H-uridine and¹⁴Camino acids it was shown that VEE RNA induced synthesis of ribonucleoproteins containing newly formed RNA and protein. These RNP possessed sedimentation coefficients 60-80S, 140S and 300S in sucrose gradient and buoyant densities 1.32 and 1.50 g/cm³ in cesium chloride gradients. These properties of ribonucleoproteins synthesized de novo in submitochondrial system are close to those of RNP intermediates of VEE virus reproduction in the infected cells. We concluded that viral RNA could program virus-specific synthesis in the submitochondrial system under conditions that eliminated the contribution of cytoplasmic ribosomes.     

Temperature dependence of the magnetic susceptibility of cobalt (II) stellacyanin.

Magnetic susceptibility measurements on cobalt(II) stellacyanin ($\text{Rhus vernicifera}$) have been performed between 2.2 and 50 K. The effective magnetic moment of Co(II) in the protein is 3.91 ± 0.12 (μ_B). Nonlinear behavior below 3 K evidences the presence of zero-field splitting attributable to a low-symmetry component of the ligand field. The results are consistent with a structural model based on a distorted tetrahedral Co(II) site involving one or more extremely covalent metal-ligand bonds.