ATP-induced Secretion in PC12 Cells and Photoaffinity Labeling of Receptors

Abstract— Secretion of catecholamines by rat PC12 cells is strongly stimulated by extracellular ATP via a P₂-type pur-inergic receptor. ATP-induced norepinephrine release was inhibited 80% when extracellular Ca²⁺ was absent. Only four nucleotides, ATP, ATPγS, benzoylbenzoyl ATP (BzATP), and 2-methylthio-ATP, gave substantial stimulation of norepinephrine release from PC12 cells. ATP-induced secretion was inhibited by Mg²⁺, and this inhibition was overcome by the addition of excess ATP suggesting that ATP^4-was the active ligand. ATP-induced secretion of catecholamine release was enhanced by treatment of cells with pertussis toxin or 12- O -tetradecanoylphorbol 13-acetate. The stimulatory effects of 12- O -tetradecanoyl-phorbol 13-acetate and pertussis toxin on norepinephrine release were additive. After brief exposure of intact cells to the photoaffinity analog, [α-³²P]BzATP, two major proteins of 44 and 50 kDa and a minor protein of 97 kDa were labeled. An excess of ATP-γS and BzATP but not GTP blocked labeling of the proteins by [³²P]BzATP. Labeling of the 50-kDa protein was more sensitive to competition by 2-methylthio-ATP than the other labeled proteins, suggesting that the 50-kDa protein represents the P₂ receptor responsible for ATP-stimulated secretion in these cells.     

Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.     

Changes in carbonic anhydrase may be the initial step of altered metabolism in hypertension

Carbonic anhydrase (CA) is a well characterized pH regulatory enzyme in most of the tissues in the body. Changes in activities of CA have been associated with altered metabolism, especially in diabetes mellitus. Insulin resistance and hyperinsulinemia are common in hypertension. To investigate the possible role of CA, we measured the CA activity spectrophotometrically using p-nitrophenyl acetate as a substrate and acetazolamide, the specific inhibitor, in erythrocytes from normotensive and essential hypertensive subjects. Further, to evaluate the insulin action on CA, we used two different hemolysates; (i) insulin applied into hemolysate and (ii) hemolysate from insulin treated erythrocytes in vitro before the determination of CA activity. Two different levels of CA activities were obtained in these patients. CA activities were much lower (mean +/- SD, 0.88 +/- 0.19 U/min/mL) and higher (mean +/- SD, 1.77 +/- 0.23 U/min/mL) in patients than the normotensive controls (mean +/- 1 SD, 1.41 +/- 0.1 U/min/mL). These differences in both the groups were statistically significant (p less than 0.001). Similarly, total esterase activities in patients were (1.41 +/- 0.27 U/min/mL) that was 30% less in low activity group and (2.47 +/- 0.25 U/min/mL) that was 22% more in higher activity group in comparison with those from normotensives (2.02 +/- 0.17 U/min/mL). The relative percent of CA activities of insulin treated erythrocytes from normotensives and hypertensives were 11% and 18% higher than without insulin (p less than 0.05). No difference was observed when insulin was applied in the hemolysate. We conclude that essential hypertensive patients are associated with altered CA activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Radiation of the Tnt1 retrotransposon superfamily in three Solanaceae genera

Background  

Tnt1 was the first active plant retrotransposon identified in tobacco after nitrate reductase gene disruption. The Tnt1 superfamily comprises elements from Nicotiana (Tnt1 and Tto1) and Lycopersicon (Retrolyc1 and Tlc1) species. The study presented here was conducted to characterise Tnt1-related sequences in 20 wild species of Solanum and five cultivars of Solanum tuberosum.     

Taxonomy of Soldier Flies (Diptera: Stratiomyidae) of Sunderban Biosphere Reserve,India

The present communication deals with recording of nine species of soldier flies (Insecta: Diptera: Stratiomyidae) from Sunderban Biosphere Reserve of India, of which, Tinda indica (Walker, 1851), Hermetia illucens (Linnaeus, 1758), Odontomyia kashmirensis Brunetti, 1920, Odontomyia viridana (Wiedemann, 1824), Prosopochrysa vitripennis (Doleschall, 1856) are being reported for the first time from this unique and globally acclaimed mangrove ecosystem. Odontomyia kashmirensis Brunetti, 1920 is reported for the first time from the state of West Bengal. A key to identify these species is provided with taxonomic notes.     

Biochemical analysis of four species ofCassia L. pollen

The present paper describes the comparative biochemical studies in terms of quantitative analyses of carbohydrates, lipids, proteins, free amino acids, nucleic acids, minerals, ash and moisture as well as the identification of free amino acids of pollen of four species ofCassia L. (C. alata L,C. fistula L,C. occidentalis L andC. siamea Lam.). A significant variation in the chemical constituents was observed among the four species.C. occidentalis showed the highest levels of carbohydrate (15.15%) and protein (22.45%), andC. siamea had the lowest levels of carbohydrate (7.15%), lipid (6.2%) and protein (13.85%).C. alata andC. fistula showed intermediate results. However,C. alata showed the highest amount of free amino acids (3.8%) and the least of 1.42% was found inC. fistula. Thin layer chromatography (TLC) of free amino acids of the four species showed some homology in their amino acid content, of which proline, glutamic acid, methionine and phenyl-alanine were the most dominant. The level of nucleic acids and minerals was found to be comparatively low.C. siamea andC. alata showed an exceptionally high level of ash content (8.6 and 8.8%, respectively) while moisture content varied from 8 to 11%.     

Expression,localization and possible functions of aquaporins 3 and 8 in rat digestive system

Although aquaporins (AQPs) play important roles in transcellular water movement, their precise quantification and localization remains controversial. We investigated expression levels and localizations of AQP3 and AQP8 and their possible functions in the rat digestive system using real-time polymerase chain reactions, western blot analysis and immunohistochemistry. We investigated the expression levels and localizations of AQP3 and AQP8 in esophagus, forestomach, glandular stomach, duodenum, jejunum, ileum, proximal and distal colon, and liver. AQP3 was expressed in the basolateral membranes of stratified epithelia (esophagus and forestomach) and simple columnar epithelia (glandular stomach, ileum, and proximal and distal colon). Expression was particularly abundant in the esophagus, and proximal and distal colon. AQP8 was found in the subapical compartment of columnar epithelial cells of the jejunum, ileum, proximal colon and liver; the most intense staining occurred in the jejunum. Our results suggest that AQP3 and AQP8 play significant roles in intestinal function and/or fluid homeostasis and may be an important subject for future investigation of disorders that involve disruption of intestinal fluid homeostasis, such as inflammatory bowel disease and irritable bowel syndrome.