The activity of neutral ribonucleases in nuclei of rat sympathetic ganglia and effects of nerve injury

Nuclei were isolated from homogenates of rat superior cervical ganglion by a conventional differential centrifugation technique with approximately 60% recovery. Ribonuclease activity at pH 7.1 (neutral ribonuclease) was associated with the nuclei fraction and represented 19% of the overall activity in normal ganglia. Ribonuclease in the nuclei fraction was stimulated variably by the sulfhydryl blocker N-ethylmaleimide indicating that a proportion was bound to the endogenous ribonuclease inhibitor present in these ganglia. The total activity of nuclear ribonuclease was increased 2–6 days after postaganglionic nerve injury, such that the inhibitor-bound form of the enzyme increased maximally by 600% at day 4. The percentage of the total ganglionic activity in the nuclei fraction decreased in injured ganglia as a result of a rise in the activity of non-nuclear components. The changes in nuclear ribonuclease activity were distinct from those in the 850g supernatant indicating that specific nuclear enzymes are being affected during regeneration.Special Issue dedicated to Dr. O. H. Lowry.     

Fixation of Vervet Monkey Oral Mucosa for Ultrastructural Investigation-Tem

This study was undertaken to determine optimal fixation procedure for vervet monkey (Cercopithecui pygerythrta) oral mucosa. Perfusion and immersion fixation were investigated using glutaraldehyde and glutaraldehyde-paraformaldehyde fixatives with either a phosphate or sodium cacodylate buffer as vehicle and with osmolalities varying from 2010 to 320 mosm. Good fixation could not be obtained uniformly or consistently by perfusion. Vervet monkey oral mucosa is best fixed by first perfusing the head and neck of the animal with 250-500 ml 0.9% saline containing Procaine-HCl and heparin, followed by decapitation and immersion of the head in a 2.5% glutaraldehyde: 2% paraformaldehyde: 0.02 M sodium cacodylate buffered fixative (900 mosm) at 4 C for 24 hr.     

DEVELOPMENT OF A BIMODAL HEART RATE PATTERN IN UNDISTURBED FETAL HARBOR SEALS

Fetal and maternal heart rates were studied in unrestrained, pregnant harbor seals during the last third of gestation. Heart rates were recorded while the mothers were resting on land or performing trained simulated dives of up to 2.25 min. Data from resting mothers showed the development of a bimodal or two-speed fetal heart rate pattern during late gestation. The mean faster and slower fetal heart rates at term were 125 ± 3.7 and 79 ± 3.1 (mean + SEM) respectively. The amount of fetal bradycardia observed increased steadily towards term, and fetal heart rate changes were not correlated with changes in maternal heart rate or maternal respiration. The bimodal fetal heart rate was also seen during the simulated dives, and no decrease in either the faster or slower heart rate was found. Heart rates from resting, unrestrained harbor seal pups were also studied. The pups displayed a bimodal heart rate similar to the fetuses' with the slower rate occurring during breath-holds. The bradycardia in the pups was equivalent to the slower fetal heart rate. These findings suggest that the regulatory mechanism that determines the apneic bradycardia in young harbor seals during non-stressful conditions develops in the last quarter of gestation.     

Convolvulus grandiflorus Jacq. (Convolvulaceae) re-examined

Convolvulus grandiflorus Jacq. has been treated as a synonym ofOperculina ventricosa andStictocardia tiliifolia. It is here accepted as identifiable withIpomoea (sect.Calonyction)macrantha which is the correct name for Jacquin’s taxon. Full synonymies ofIpomoea macrantha andOperculina ventricosa are given, along with a comment about a variant occurring in Micronesia.     

Formation of glutamine from [13n]ammonia, [13n]dinitrogen, and [14C]glutamate by heterocysts isolated from Anabaena cylindrica.

A method is described for the isolation of metabolically active heterocysts from Anabaena cylindrica. These isolated heterocysts accounted for up to 34% of the acetylene-reducing activity of whole filaments and had a specific activity of up to 1,560 nmol of C2H4 formed per mg of heterocyst chlorphyll per min. Activity of glutamine synthetase was coupled to activity of nitrogenase in isolated heterocysts as shown by acetylene-inhibitable formation of [13N]NH3 and of amidelabeled [13N]glutamine form [13N]N2. A method is also described for the production of 6-mCi amounts of [13N]NH3. Isolated heterocysts formed [13N]glutamine from [13N]NH3 and glutamate, and [14C]glutamine from NH3 and [14C]glutamate, in the presence of magnesium adenosine 5'-triphosphate. Methionine sulfoximine strongly inhibited these syntheses. Glutamate synthase is, after nitrogenase and glutamine synthetase, the third sequential enzyme involved in the assimilation of N2 by intact filaments. However, the kinetics of solubilization of the activity of glutamate synthase during cavitation of suspensions of A. cylindrica indicated that very little, if any, of the activity of that enzyme was located in heterocysts. Concordantly, isolated heterocysts failed to form substantial amounts of radioactive glutamate from either [13N]glutamine or alph-[14C]ketoglutarate in the presence of other substrates and cofactors of the glutamate synthase reaction. However, they formed [14C]glutamate rapidly from alpha-[14C]ketoglutarate by aminotransferase reactions, with various amino acids as the nitrogen donor. The implication of these findings with regard to the identities of the substances moving between heterocysts and vegetative cells are discussed.     

IN VIVO SYNTHESIS OF STABLE RNA WITHIN THE RAT NODOSE GANGLIA FOLLOWING VAGOTOMY

Abstract— We have investigated the in vivo synthesis of stable RNA in the rat nodose ganglia following unilateral vagotomy. Incorporation of precursor into rRNA, and possibly tRNA, in the injured ganglion increases rapidly after vagotomy, reaching twice the normal value at 2 days post-crush. In contrast to this, incorporation within the uninjured colateral ganglion decreases to about 65% of normal values after 4 days. But, by 7 days, both ganglia appear to be returning to their normal levels. One phase of DNA synthesis is detected in the injured ganglion, at days 1 and 2. while two phases are found in the contralateral ganglion, at days 2 and 34.     

Somatostatin Receptor Subtype-4 Regulates mRNA Expression of Amyloid-Beta Degrading Enzymes and Microglia Mediators of Phagocytosis in Brains of 3xTg-AD Mice

Neurochemical Research - Alzheimer’s disease (AD) is a progressive neurodegenerative disorder resulting in memory and cognitive impairment. The use of somatostatin receptor subtype-4 (SSTR4)...