Adrenergic innervation of the salivary glands in the rat

Summary The adrenergic innervation of the major salivary glands in the rat has been studied by a specific histochemical method for the visualization of the adrenergic transmitter. Adrenergic varicose nerve fibres were found, located in a typical adrenergic ground plexus closely surrounding the serous acini of the submaxillary and parotid glands, but not the acini of the mainly mucous sublingual gland. The ducts were found to be completely devoid of adrenergic innervation. Arterioles and venules in the stroma of all three glands and certain very small vessels, possibly the sphincters of arterio-venous anastomoses, were also richly innervated by adrenergic vasomotor fibres. The relationship of the adrenergic nerve fibres to the different functional units of the gland parenchyma is discussed.The investigation has been supported by a research grant (B 66–257) from the Swedish Medical Research Council and by a Public Health Service Research Grant (NB 05236-01) from the National Institute of Neurological Diseases and Blindness.     

Topographic control of vegetation in a mountain big sagebrush steppe

Mountain big sagebrush steppes in Wyoming have strong spatial patterning associated with topography. We describe the spatial variability of vegetation in a sagebrush steppe, and test the relationship between topography and vegetation using canonical correlation. Results of the analysis suggest that the main control over vegetation distribution in this system is wind exposure. Exposed sites are characterized by cushion plant communities and Artemisia nova, and less exposed sites by the taller sagebrush species Artemisia tridentata ssp. vaseyana. Topographic depressions and leeward slopes are characterized by aspen stands and nivation hollows. Measurements of soil microclimate suggest that a major influence of topographic position on vegetation is snow redistribution and its effect on soil moisture and temperature.Abbreviations ARNO Artemisia nova - ARTRW Artemisia tridentata ssp. wyomingensis - ARTRV Artemisia tridentata ssp. vaseyana - PUTR Purshia tridentata - RIP riparian community - POTR Populus tremuloides - NIV nivation hollow community     

Surface area-independent assessment of lung microvascular permeability with an amphipathic tracer

A combination of an amphipathic-indicator-dilution (ID) diffusing tracer 1,4[14C]butanediol (B) and a hydrophilic tracer ([14C]urea) (U) was hypothesized to provide a capillary surface area- (S) independent assessment of lung microvascular permeability (P). We performed ID studies on isolated perfused dog lungs and administered randomly two interventions, increasing P by alloxan infusion and reduction in S by lobar ligation. The ratio of PS product of U (PSU) to that for butanediol (PSB) was sensitive to changes in P yet insensitive to changes in S. We performed ID studies in which the dependence of PSU and PSB on flow, hematocrit, and plasma protein binding were examined. Measurements of PSU and PSB after flow and hematocrit were changed suggested that these factors have no significant independent effects. From ID and in vitro studies we also found that no significant binding of B to plasma proteins (albumin) occurred. We concluded that ID techniques using B and U provide a consistent measure of P, despite changes in S, hematocrit, plasma protein concentration, and recruitment.     

The effects of lipid composition on the rate and extent of heme binding to membranes

The effects of membrane composition on heme binding to large unilamellar vesicles were examined using 30 separate phospholipid mixtures. Although there was some variation, most lecithins with Tm values less than or equal to 20 degrees C showed overall equilibrium partition constants equal to approximately 5 x 10(5) and association and dissociation partition rate constants equal to approximately 3 x 10(6) s-1 and 7 s-1, respectively, for CO-heme binding at 30 degrees C. A sharp decrease in the association rate for CO-heme uptake was observed as the lipid vesicles changed from liquid-crystalline to the gel phase. The addition of dicetyl phosphate or dimyristoylphosphatidylglycerol, which are negatively charged at neutral pH, decreased the affinity of the vesicles for CO-heme. The association rate and equilibrium partition constants for CO-heme uptake in unsaturated lecithins were unaffected by cholesterol content at levels up to 40%/mol. The affinity of saturated dimyristoylphosphatidylcholine (DMPC) vesicles for CO-heme decreased with increasing cholesterol content at 30 degrees C. This effect appears to be related to the influence of cholesterol on the DMPC phase transition temperature (Tm) since at low temperatures (less than or equal to 20 degrees C) little CO-heme binds to vesicles composed of DMPC even in the absence of cholesterol.     

Plant-Derived Neurotoxic Amino Acids (β-N-Oxalylamino-l-Alanine and β-N-Methylamino-l-Alanine): Effects on Central Monoamine Neurons

In the present study the subacute effects of beta-N-oxalylamino-L-alanine (BOAA) and beta-N-methylamino-L-alanine (BMAA) on CNS monoamine neurons in rats were investigated following intracisternal injections or local intracerebral administration into substantia nigra. In vitro effects of BOAA and BMAA on high-affinity synaptosomal uptake of dopamine (DA), noradrenaline (NA), and serotonin (5-HT) were also examined. Intracisternal administration of BMAA decreased NA levels in hypothalamus, whereas no effects were seen on DA or 5-HT levels. Following intranigral injections of BOAA, NA levels tended to decrease in several regions, whereas the DA levels and the levels of DA metabolites were unaffected in all regions analyzed. Loss of tyrosine hydroxylase (TH) immunoreactivity in the intranigral injection sites and the presence of TH-immunoreactive pyknotic neurons near the borders of the injection sites were observed following both BOAA and BMAA treatments. Furthermore, substance P-immunoreactive terminals in substantia nigra pars reticulata were also found to have disappeared within the lesioned area following either BOAA or BMAA injections. Incubations with both BOAA and BMAA (10(-5) M) reduced high-affinity [3H]NA uptake in cortical synaptosomes to 69% and 41% of controls, respectively, whereas the striatal high-affinity [3H]DA uptake and the cortical high-affinity [3H]5-HT uptake were unaffected by BOAA or BMAA. The results demonstrate that both BOAA and BMAA can affect central monoamine neurons, although the potency and specificity of these substances on monoamine neurons when administered acutely into cerebral tissue or liquor cerebri seem to be low. However, the in vitro studies indicate selective effects of both compounds on NA neurons in synaptosomal preparations.     

Amonabactin, a novel tryptophan- or phenylalanine-containing phenolate siderophore in Aeromonas hydrophila.

Aeromonas hydrophila 495A2 excreted two forms of amonabactin, a new phenolate siderophore composed of 2,3-dihydroxybenzoic acid, lysine, glycine, and either tryptophan (amonabactin T) or phenylalanine (amonabactin P). Supplementing cultures with L-tryptophan (0.3 mM) caused exclusive synthesis of amonabactin T, whereas supplements of L-phenylalanine (0.3 to 30 mM) gave predominant production of amonabactin P. The two forms of amonabactin were separately purified by a combination of production and polyamide column chromatographic methods. Both forms were biologically active, stimulating growth in iron-deficient medium of an amonabactin-negative mutant. Of 43 additional siderophore-producing isolates of the Aeromonas species that were tested, 76% (19 of 25) of the A. hydrophila isolates were amonabactin positive, whereas only 19% (3 of 16) of the A. sobria isolates and all (3 of 3) of the A. caviae isolates produced amonabactin, suggesting a predominant synthesis of amonabactin in certain Aeromonas species.     

Increase in Gs and cyclic AMP generation in HIT cells. Evidence that the 45-kDa alpha-subunit of Gs has greater functional activity than the 52-kDa alpha-subunit

Cyclic AMP accumulation in response to forskolin, cholera toxin, or isoproterenol is dramatically increased in HIT T-15 cells, a clonal cell line of Syrian hamster pancreatic islet beta cells, as a function of passage number. Forskolin and cholera toxin elevate cyclic AMP levels 5- to 10-fold higher in later passages (87-100) than in earlier passages (70-80). A similar phenomenon is observed with isoproterenol (10 microM) which increases cyclic AMP levels 56-fold in older HIT cells (passage 94), whereas only marginally stimulating cyclic AMP production in younger cells (passage 70-82). To determine whether a change in the stimulatory or inhibitory guanine nucleotide regulatory proteins, Gs or Gi, was responsible for these observations, ADP-ribosylation of HIT cell membranes with cholera toxin and pertussis toxin was examined. All passages contained two cholera toxin substrates at 52 and 45 kDa. The amount of 52 kDa did not appear to change with passage number, but the amount of 45 kDa increased in the later passages (89 and 94). The ratio of 45 to 52 kDa cholera toxin substrate, as determined by densitometric analysis, increased from 0.1 in passages 70, 75, and 82 to 0.45 at passage 89. No passage related changes in a 40-kDa pertussis toxin substrate were observed. An increase in the amount of the 45-kDa alpha-subunit of Gs was confirmed on immunoblots using antisera specific for the alpha-subunits of Gs. The amount of functional Gs present in various HIT cell passages was examined by determining the extent to which extracts from HIT cell membranes reconstituted guanine nucleotide-sensitive adenylyl cyclase in S49 cyc- membranes. Extracts derived from passage 94 reconstituted three to four times more adenylyl cyclase activity in cyc- membranes than extracts from passages 70, 75, and 82. These data indicate that an increase in functional Gs in later passages may be the underlying cause for the increased responsiveness to isoproterenol and forskolin in later passages. These data also suggest that functional differences exist between the Gs alpha-subunits, with the smaller 45-kDa subunit being more efficacious in coupling to cyclic AMP synthesis than the larger 52-kDa subunit. This is a departure from the commonly held view that the two subunits have similar efficacies in stimulating adenylyl cyclase.     

Regulation of proacrosin conversion in isolated guinea pig sperm acrosomal apical segments

Following sodium dodecyl sulfate-polyacrylamide gel electrophoresis, proacrosin has been identified in extracts of intact guinea spermatozoa as a major silver staining band which reacted immunologically with antibodies made against purified proacrosin from guinea pig testis. Proacrosin exhibited an approximate Mr of 50,000 and was rapidly converted to an Mr 45,000 protein following induction of the acrosome reaction with 2.0 mM CaCl2 and 1 micrograms/ml A23187. Apical segments isolated at pH 6.0 from guinea pig spermatozoa also contained a major silver staining band of Mr 50,000 which cross-reacted with antibodies to guinea pig testis proacrosin. Subcellular fractionation of spermatozoa indicated that proacrosin remained in the particulate fraction of homogenized spermatozoa and was enriched within the isolated acrosomal apical segment. When apical segments isolated at pH 6.0 were incubated at pH 7.5, proacrosin was rapidly converted to the Mr 45,000 form observed in spermatozoa undergoing the acrosome reaction. The conversion process in isolated apical segments was inhibited by leupeptin and was accelerated in the presence of calcium, magnesium, and manganese. Zinc completely inhibited the conversion of proacrosin to the Mr 45,000 protein. Neither proacrosin nor the Mr 45,000 protein were released into the supernatant fluid during the incubation of apical segments at pH 7.5. Furthermore, the proteins were resistant to solubilization by 150 mM NaCl and 1% Triton X-100 but were solubilized by treatment of apical segments with 1 M NaCl. These results provide evidence as to the identity and subcellular distribution of proacrosin in intact guinea pig sperm prior to zymogen conversion and suggest that isolated apical segments exhibit a subset of the exocytotic reactions leading to completion of the acrosome reaction.     

Computed tomographic measurement of cortical bone geometry

In this study digital images of bone cross-sections obtained by computed tomography were analyzed with an automated outlining method. It was shown that unbiased cross-sectional geometric measurements of cortical bone could be obtained if the periosteal and endosteal surfaces were defined at separate thresholds. Use of different threshold levels for these two surfaces resulted in errors of 2.6% for periosteal diameters, 7.4% for endosteal diameters and 7.3% for cortical area. If incorrect thresholds were used, cortical thickness measurements can have errors as high as 30%. In addition, simulated variation in medullary fat content did not affect measurement of medullary dimensions.