The primary structure of pancreatic ribonuclease from mole rat superspecies Spalax leucodon

The primary structure of pancreatic ribonuclease of the superspecies Spalax leucodon has been determined. Only one difference with the previously determined sequence of the superspecies Spalax ehrenbergi was detected; the proline residue at position 42 has been replaced by alanine. Proline-42 is a well-conserved residue in mammalian pancreatic ribonucleases; the only other species with alanine at this position is the three-toed sloth. As the Muridae and the Spalacidae diverged 20-40 million years ago and the superspecies S. leucodon and S. ehrenbergi about 1-2 million years ago, and as pancreatic ribonuclease exhibits 24 substitutions in the line from the Muridae/Spalacidae ancestor to Spalax, a difference of one amino residue between the sequences of the two Spalax superspecies is what may be expected.

Gap junctions modulate tissue contractility and alpha 1 adrenergic agonist efficacy in isolated rat aorta

Immunocytochemical analysis, using antibodies directed against connexin43, revealed abundant gap junctions between smooth muscle cells in intact aorta from Fischer 344 rats. Therefore, the authors evaluated the potential contribution of these intercellular junctions to contractile responses elicited by alpha 1 adrenergic receptor activation in rat aortic rings. Preincubation with the selective junctional uncoupling agent heptanol (200 microM) diminished the magnitude of contractions induced by the low-efficacy partial agonist oxymetazoline (1-3 microM) by 50.6 +/- 4.5% (P < .01; n = 16 rings from 16 rats) but had no effect on equivalent contractions induced by the high-efficacy agonist phenylephrine (0.1 microM; n = 16 rings from 16 animals). Reduced phenylephrine contractility was observed at higher heptanol concentrations (500 microM). However, neither 200 nor 500 microM heptanol altered the magnitude of contractions elicited by 60 mM KCl, indicating that tissue contractility per se was unaffected by heptanol. In calcium-free solution, the magnitude of the phasic contraction induced by phenylephrine was three-fold greater than the magnitude of the oxymetazoline-induced phasic contraction (P < .001) but the phasic responses to both agonists were unaffected by the same heptanol concentrations that significantly diminished their steady-state responses. Because heptanol, at the concentrations used, has selective pharmacological actions on gap junctions, these studies provide additional support for a role of gap junctions in the maintenance and modulation of vasomotor tone. In rat aorta, junctional transfer of alpha 1 adrenergic-receptor activated second-messenger molecules appears to be an important modulator of tissue contractility and agonist efficacy.

Nitric oxide mediates IL-1 beta-induced islet dysfunction and destruction: prevention by dexamethasone

Nitric oxide has recently been implicated as a cellular molecule that mediates interleukin-1 beta (IL-1 beta)-induced inhibition of glucose-stimulated insulin secretion by islets of Langerhans. In this study evidence is presented which demonstrates that islets contain both the cytokine inducible and the constitutive isoforms of nitric oxide synthase as determined by NADPH diaphorase staining and immunohistochemical localization. Untreated islets contain NADPH diaphorase activity, and the intensity of NADPH diaphorase staining is dramatically increased after culture for 18 hrs with IL-1 beta. Both control and IL-1 beta-induced NADPH diaphorase staining of islets is inhibited by the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (NMMA). Importantly, approximately 60-70% of islet cells stained positive for NADPH diaphorase (under both IL-1 beta treated and control conditions), suggesting that a subset of islet cells contain nitric oxide synthase. The beta-cell appears to be the endocrine cell type which contains constitutive nitric oxide synthase as demonstrated by immunohistochemical co-localization of constitutive nitric oxide synthase and insulin. IL-1 beta is believed to stimulate the expression of cytokine inducible nitric oxide synthase because the synthetic glucocorticoid, dexamethasone, prevents IL-1 beta induced inhibition of glucose stimulated insulin secretion and cGMP accumulation by islets. Both dexamethasone, and the nitric oxide synthase inhibitors NMMA and aminoguanidine also prevent IL-1 beta induced islet degeneration. These results indicate that nitric oxide produced by the inducible isoform of nitric oxide synthase mediates cytokine induced islet dysfunction and destruction, and that the beta-cell is the islet endocrine cellular source of constitutive nitric oxide synthase.

Registration and three-dimensional reconstruction of autoradiographic images by the disparity analysis method

Quantitative autoradiography is a powerful radioisotopic-imaging method for neuroscientists to study local cerebral blood flow and glucose-metabolic rate at rest, in response to physiologic activation of the visual, auditory, somatosensory, and motor systems, and in pathologic conditions. Most autoradiographic studies analyze glucose utilization and blood flow in two-dimensional (2D) coronal sections. With modern digital computer and image-processing techniques, a large number of closely spaced coronal sections can be stacked appropriately to form a three-dimensional (3D) image. 3D autoradiography allows investigators to observe cerebral sections and surfaces from any viewing angle. A fundamental problem in 3D reconstruction is the alignment (registration) of the coronal sections. A new alignment method based on disparity analysis is presented, which can overcome many of the difficulties encountered by previous methods. The disparity analysis method can deal with asymmetric, damaged, or tilted coronal sections under the same general framework, and it can be used to match coronal sections of different sizes and shapes. Experimental results on alignment and 3D reconstruction are presented.

Varieties of inhibition in the processing and control of processing in the mammalian cochlear nucleus

Seven-barrel micropipettes were used to apply drugs microiontophoretically to single units in the dorsal cochlear nucleus (DCN) in chloralose-anaesthetised guinea-pigs. While both agonists and antagonists of putative neurotransmitters in the cochlear nucleus have been investigated in these experiments, the main thrust has been to explore the influence of specific antagonists on cells' spectral and temporal properties, thus elucidating the effects of naturally occurring inhibitory transmitters. At least five types of inhibition appear to be pharmacologically/physiologically separable: (1) Stimulus-evoked tonic "lateral/sideband" inhibition: glycinergic; (blocked by strychnine); responsible for the lateral inhibition of dorsal cochlear nucleus (DCN) type III and IV cells. Strychnine has its predominant effect on sustained (lateral) inhibition compared with the more transient forms of inhibition. Subtraction of receptive field maps enables us to visualise the extent of the inhibitory receptive field. It extends virtually throughout the unit's response field for both these classes but is generally, especially in type IV cells, maximal at the characteristic frequency (CF). This type of inhibition will primarily be responsible for enhancing spectral contrasts in the way that, in the visual system, surround inhibition enhances visual contrast. Furthermore, lateral inhibitory sidebands can "bias" the "working point" of a cell's response so that the dynamic range of effective stimuli and response can be extended. (2) "Background" tonic inhibition: GABAAergic; (blocked by bicuculline). Blocking this inhibition generally results in an increase in the background (i.e., spontaneous) activity. This inhibition is probably responsible for adjusting excitatory-inhibitory contrasts in both spectral and temporal domains. (3) Stimulus-related off-inhibition appears to be neither glycinergic nor GABAAergic. Blocking these receptors actually enhances off-inhibition. Nicotinic cholinergic blockers may have a small effect on off-inhibition, but so far we have not been able to block it entirely. This off-inhibition is important for enhancing temporal contrast. This inhibition must, therefore, be mediated by other transmitters, yet undetermined, or by a local feedback circuit or, less likely, be a membrane-based after-effect of stimulation. (4) Pre-synaptic inhibition, mediated by GABAB receptors presumed to act on primary afferent terminals, thus controlling afferent input to DCN principal cells. (5) Short-latency contralateral inhibition, mediated by glycine.

[Image-analysis of salivary tumors]

The image analysis of 49 cases of salivary tumors showed that the cellular DNA content of most tumors (42/49) was diploidy and near diploidy. The heteroploidy rate was only 14.29% (7/49), which may be related to such clinical behaviors of salivary tumors as slow growth, relative low invasivity and metastatic ability. Among these morphologic parameters, nuclear perim and form PE were closely correlated with the malignancy of salivary tumors, the former was positive and the latter was negative. The insignificant nuclear heteromorphous appearance of adenoid cystic carcinoma and its relatively high cellular DNA content may be related to strong invasivity and metastatic ability. In conclusion, these parameters of DNA content and nuclear morphology supplied by image analysis are of value in the diagnosis of salivary tumors.

Preparation and evaluation of oral dosage form using acylglycerols. II. Effect of food ingestion on dissolution and absorption of aspirin from the granules prepared by acylglycerols in human subjects

The dissolution behavior of the aspirin enteric granule prepared using acylglycerols, glyceryl monostearate (GMS) and glyceryl trilaurate (GTL), was investigated in vitro and in human subjects in a fasting or non-fasting state. Aspirin was slowly released from the granule in vitro at pH 1.2. No acceleration of the aspirin dissolution rate in the medium without lipase and cholic acid was observed when the pH level of the medium increased to a neutral region (pH 6.4). However, the dissolution of aspirin was significantly increased by increasing the concentrations of lipase and cholic acid in the medium. Lipase appears to play an essential role in the dissolution process of aspirin granules. In human subjects, the average levels of the cumulative amount of total salicylate excreted in a urine-time curve, and the mean residence time (MRT) obtained after oral administration of a granule in the fasting state were markedly delayed in comparison with the results observed using an aqueous solution and a crystalline form of aspirin. In comparing the fasting condition with the non-fasting condition (after food ingestion), no significant difference was recognized in the total amount of salicylate excreted in urine to an infinite time (Ae(infinity)), whether the MRT was obtained by granule, crystalline form or aqueous solution. It can be concluded that aspirin granule prepared by GMS and GTL has a property of pancreatic lipase-sensitive dissolution, and its bioavailability is unaffected by food intake.

Development of Diapiric Structures in the Upper Mantle Due to Phase Transitions

Solid-state phase transitions in time-dependent mantle convection can induce diapiric flows in the upper mantle. When a deep mantle plume rises toward phase boundaries in the upper mantle, the changes in the local thermal buoyancy, local heat capacity, and latent heat associated with the phase change at a depth of 670 kilometers tend to pinch off the plume head from the feeding stem and form a diapir. This mechanism may explain episodic hot spot volcanism. The nature of the multiple phase boundaries at the boundary between the upper and lower mantle may control the fate of deep mantle plumes, allowing hot plumes to go through and retarding the tepid ones.

[A study of the regulatory role of GABA on the LHRH release in the median eminence of rats]

The present study was undertaken to observe the effect of GABA and NA on LHRH neuronal terminals in the median eminence (ME). The results showed that GABA (10(-6) mol/L) significantly increased LHRH and NA release from ME, i.e., respectively from 27.3 +/- 2.5 pg/100 microliters to 150.4 +/- 27.9 pg/100 microliters and from 50.9 +/- 4.2 pg/100 microliters to 105.5 +/- 19.1 pg/100 microliters (both P less than 0.01 vs control group). These effects of GABA could be blocked by bicuculline. When bicuculline and GABA (10(-6) mol/L) were added into the ME, the secretion of LHRH decreased to 18.2 +/- 1.9 pg/100 microliters and that of NA to 43.9 +/- 3.4 pg/100 microliters. The effect of GABA on LHRH release may be mediated by NA. When endogenous NA was depleted by reserpine, GABA increased LHRH secretion only by 26.5% instead of 451.9% as in the normal animal.

Molecular mechanisms of memory formation

Studies with neonate chicks, trained on a passive avoidance task, suggest that at least two shorter-term memory stages precede long-term, protein synthesis-dependent memory consolidation. Posttetanic neuronal hyperpolarization arising from two distinct mechanisms is postulated to underlie formation of these two early memory stages. Maintenance of the second of these stages may involve a prolonged period of hyperpolarization brought about by phosphorylation of particular proteins. A triggering mechanism for long-term consolidation is postulated to occur at a specific time during the second stage, and may involve reinforcement-contingent release of neuronal noradrenaline stimulating cAMP-dependent intracellular processes. The possibility that astroglia may have a critical role to play in these early stages of memory processing is raised.

Analgesia produced by pituitary ACTH and dopaminergic transmission in the arcuate

Analgesia (NAA) caused by nonacupuncture point (abdominal muscle) stimulation after lesioning the analgesia inhibitory system (AIS) or treating the subject with proglumide was abolished by hypophysectomy or adrenalectomy. The final sector of the NAA afferent pathway from the nonacupuncture point to the pituitary gland and the initial sector of the descending pain inhibitory system were found in the anterior and posterior arcuate nucleus (A-HARN and P-HARN), respectively. Analgesia caused by ACTH microinjected into the P-HARN disappeared after denervation of the A-HARN, but that caused by dopamine did not. Firing rates of P-HARN neurons were increased by nonacupuncture point simulation (NAPS) after lesion of the AIS or treatment with proglumide. The NAPS responsive neurons also responded to ultramicroinjected dopamine, but not to ultramicroinjected ACTH. Both NAA and NAPS responsive neuron activity that were abolished by hypophysectomy were restored by concurrent application of NAPS and intraperitoneal ACTH. Reduction of sodium ions due to adrenalectomy was found to abolish NAA. It was concluded that NAA production involves dopaminergic transmission in the HARN and ACTH acting presynaptically on this transmission.

[Deleterious effects of calcium on the pathogenesis of ischemic brain damage]

Using atomic absorption spectroscopy, we measured the regional distribution of tissue Ca++ contents of 24 rabbit brains sampled at 2,4,24 and 48 hours after the occlusion of Middle Cerebral Artery (MCAo) with accompanying histopathological examinations with 10 controls. At 2 hours after MCAo, brain tissue Ca++ concentration increased significantly (P less than 0.005) in the ischemic territory and increased further with times, far preceding the detectable pathological findings termed necrosis, which appeared at 12 hours after MCAo. It seems most probable that the deleterious effects of calcium play an important role in the pathogenesis of ischemic brain damage.