Immunohistochemistry of adenosine deaminase: implications for adenosine neurotransmission

Immunohistochemical analysis of adenosine deaminase in rat brain revealed an extensive plexus of adenosine deaminase-containing neurons in the basal hypothalamus. These neurons converged on and were most numerous in three major centers, namely, the tuberal, caudal, and postmammillary caudal magnocellular nuclei. Most other brain regions were devoid of cells containing adenosine deaminase. Some adenosine deaminase-containing neurons were retrogradely labeled with the fluorescent dye fast blue when the dye was injected into the frontal cortex and striatum. Specific populations of neurons having high levels of adenosine deaminase may release adenosine as a neurotransmitter.     

不同剂量腺苷对肺炎大鼠肺动脉高压的调节作用

目的观察金黄色葡菌球菌（金葡菌）感染大鼠肺炎对肺动脉压力的影响,以及不同剂量腺苷对其调节作用。方法50只SD大鼠被随机分为对照组、肺炎组和腺苷处理A、B、C组。金葡菌经气管插管注入复制肺炎大鼠模型,实验第5天各腺苷处理组于心内肺动脉测压管内持续注射不同剂量的腺苷（50、100、150μg.kg-1.min-1）,各腺苷处理组动态测定心率（HR）和平均肺动脉压（mPAP）。对照组、肺炎组同法注射等量的生理盐水,测定指标同前。处死大鼠取心肌组织作病理检测。结果（1）心肌病理组织检查示肺炎组病变明显,与对照组比较P＜0.01;（2）肺炎组肺动脉压力较对照组增高[（2.67±0.38）vs（2.03±0.41）,P＜0.01）];（3）腺苷处理B、C组用药后平均肺动脉压均低于肺炎组（均P＜0.05）,而与对照组比较差异无统计学意义（P＞0.05）。结论金葡菌感染大鼠肺炎可致肺动脉压力增高以及心肌损害,由肺动脉给以外源性腺苷可降低肺动脉压力。     

Adenosine triphosphate synthesis coupled to K+ influx in mitochondria

The influx of K+ into swollen mitochondria in the presence of valinomycin results in the synthesis of adenosine triphosphate in which approximately one H+ disappears per adenosine triphosphate synthesized. The synthesis is blocked by atractyloside but is insensitive to oligomycin and relatively insensitive to uncouplers.     

Adenosine 3',5'-monophosphate phosphodiesterase in the growth medium of Physarum polycephalum

The acellular slime mold Physarum polycephalum releases a soluble adenosine 3', 5'-monophosphate phosphodiesterase into the growth medium. Although this enzyme resembles the particulate diesterase of the same organism in kinetic properties and in inhibition by methyl purines, its greater stability, its insensitivity to stimulation by imidazole and to inhibition by adenosine triphosphate,- and its selective release into the medium indicate a specific function, perhaps protection against exogenous cyclic nucleotide, for the soluble enzyme.     

Mercurial-induced transformation of myosin prevented by adenosine triphosphate and pyrophosphate

Adenosine triphosphate and pyrophosphate prevent the loss of Ca(//)-activated adenosine triphosphatase activity caused by high concentrations of mercurial sulfhydryl reagent. They concomitantly prevent the transformation of myosin into faster-sedimenting products. This is adduced as support for the hypothesis that the strategic sulfhydryl group is not binding adenosine triphosphate at the active site, but is initiating a conformational change upon its reaction with the mercurial reagent.     

Calcium-Activated Adenosine Triphosphatase Localization in Cultured Beating Heart Cells

The calcium-activated adenosine triphosphatase activity of cultured single beating heart cells of the rat was localized and visualized by incubating the cells, after extraction in a mixture of glycerol and water, with adenosine triphosphate and calcium. The calcium phosphate, precipitated at the site of the enzyme reaction, was converted into a visible precipitate. The enzyme activity appeared in bands perpendicular to the myofibrils.     

Renal concentrating mechanism: possible role for sodium-potassium activated adenosine triphosphatase

Sodium-potassium activated adenosine triphosphatase activity was found to be almost twice as high in renal medulla as in cortex. Infusion of digoxin, a specific inhibitor of the enzyme, into one renal artery of the dog resulted in unilateral natriuresis, impaired concentrating capacity, and reduction of the enzyme activity in both cortex and medulla. It is suggested that the sodium-potassium adenosine triphosphatase plays an important role in urine concentration mechanisms.     

Adenosine 3',5'-monophosphate modulates thyrotropin receptor clustering and thyrotropin activity in culture

A biologically active rhodamine conjugate of thyrotropin binds at 4 degrees C to diffusely distributed membrane thyrotropin receptors which patch and become endocytosed into thyroid cells in a temperature-sensitive process. When the cells are first incubated with 8-bromo-cyclic adenosine monophosphate at 37 degrees C, the conjugate also binds to clustered receptors at 4 degrees C. Furthermore, 8-bromo-cyclic adenosine monophosphate reduces the amount of adenosine 3',5'-monophosphate (cyclic AMP) induced by thyrotropin. Hence, increased intracellular cyclic AMP induces receptor patching and reduces the concentration of cyclic AMP normally induced by thyrotropin. This suggests that cyclic AMP acts both as the second messenger of thyrotropin and also as the regulator of the level of thyrotropin receptors.     

Immunocyte Ca2+ influx system mediated by LTRPC2

We characterized an activation mechanism of the human LTRPC2 protein, a member of the transient receptor potential family of ion channels, and demonstrated that LTRPC2 mediates Ca2+ influx into immunocytes. Intracellular pyrimidine nucleotides, adenosine 5'-diphosphoribose (ADPR), and nicotinamide adenine dinucleotide (NAD), directly activated LTRPC2, which functioned as a Ca2+-permeable nonselective cation channel and enabled Ca2+ influx into cells. This activation was suppressed by intracellular adenosine triphosphate. These results reveal that ADPR and NAD act as intracellular messengers and may have an important role in Ca2+ influx by activating LTRPC2 in immunocytes.     

蜜蜂(Apis mellifera)毒的柱层析分离及其主要组份Melittin的抗凝作用

 蜜蜂(Apis mellifera)毒通过葡聚糖凝胶G50分离为七个组份,并进行了酶活力测定和毒性测定,酶测定作了磷酯酶A₂,水解蛋白酶,三磷酸腺甙酶,一磷酸腺甙酶等。对直接溶血组份在血液凝固系统上的作用进行了体内外实验,实验表明:抗血凝固作用是由于抑制了凝血活酶的生成和凝血酶原激活物的生成。     

3H]adenosine triphosphate: release during stimulation of enteric nerves

The isolated taenia coli of the guinea pig takes up tritiated adenosine, adenosine monophosphate, adenosine diphosphate, and adenosine triphosphate, in preference to tritiated inosine and adenine. After uptake, [(3)H]adenosine is converted and retained primarily as [(3)H]adenosine triphosphate. Tritium is released from taenia coli treated with [(3)H]adenosine upon activation of the nonadrenergic inhibitory nerves. These results are consistent with the previous evidence that adenosine triphosphate may be the transmitter from the nerves.     

Cyclic adenosine monphosphate, metabolites, and phosphorylase in neural tissue: a comparison a methods of fixation

Fixation of rat brain tissue by freeze-blowing, microwave irradiation, immersion of whole rats in liquid nitrogen, and decapitation into liquid nitrogen indicates that postmortem changes in metabolites and enzyme forms are minimal in freeze-blown brains. Cyclic adenosine monophosphate levels are lowest in microwave-irradiated brains, which has been interpreted by some investigators to indicate rapid fixation and minimal anoxia. However, the changes in phosphocreatine, adenosine triphosphate, lactate, and phosphorylase clearly demonstrate that fixation by freeze-blowing or immersion in liquid nitrogen more closely approximate the state in vivo.     

Cell growth with trans fatty acids is affected by adenosine 3',5'-monophosphate and membrane fluidity

Two positional isomers (9 and 11) of trans octadecenoates did not support growth on glucose of an Escherichia coli mutant that requires unsaturated fatty acids. However, the trans fatty acids provided sufficient fluidity to produce much higher cell yields when the concentration of adenosine 3',5'-monophosphate was raised. The effectiveness of the trans acids rose from 0 to 1 cell per femtomole to 15 to 20 cells per femtomole as the concentration of adenosine 3',5'-monophosphate was increased. The corresponding cis positional isomers supported high yields (35 to 40 cells per femtomole) independent of supplementation. The enhanced growth with adenosine 3',5'-monophosphate supplementation is not due to an increased uptake and incorporation of the trans isomers relative to the cis isomers, since the 9-trans isomer was incorporated more rapidly than the 9-cis isomer into the membrane phospholipids under all growth conditions and represented 21 +/- 2 mole percent of the acids. The finding that cells growing with trans fatty acid isomers have a higher requirement for adenosine 3',5'-monophosphate may indicate that some fatty acids can alter the metabolic regulation normally exerted by the cyclic nucleotide.     

Structure and allostery of the PKA RIIβ tetrameric holoenzyme

In its physiological state, cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is a tetramer that contains a regulatory (R) subunit dimer and two catalytic (C) subunits. We describe here the 2.3 angstrom structure of full-length tetrameric RIIβ(2):C(2) holoenzyme. This structure showing a dimer of dimers provides a mechanistic understanding of allosteric activation by cAMP. The heterodimers are anchored together by an interface created by the β4-β5 loop in the RIIβ subunit, which docks onto the carboxyl-terminal tail of the adjacent C subunit, thereby forcing the C subunit into a fully closed conformation in the absence of nucleotide. Diffusion of magnesium adenosine triphosphate (ATP) into these crystals trapped not ATP, but the reaction products, adenosine diphosphate and the phosphorylated RIIβ subunit. This complex has implications for the dissociation-reassociation cycling of PKA. The quaternary structure of the RIIβ tetramer differs appreciably from our model of the RIα tetramer, confirming the small-angle x-ray scattering prediction that the structures of each PKA tetramer are different.     

Ethanol oxidation: effect on the redox state of brain in mouse

Administration of a single large dose of ethanol to mice results in increases, for concentrations in the brain, of ratios of lactate to pyruvate, of aglycerophosphate to dihydroxyacetone phosphate, of malate to oxaloacetate, and of glutamate to the product of alpha-ketoglutarate and ammonium ion. These changes are noticed as early as 5 minutes after the single dose is given. Ethanol administration for 30 days also produces these changes in metabolite concentrations in the brain. However, in contrast to the single alcohol dose, long-term alcohol administration results in a marked decrease in the concentration of adenosine triphosphate in brain and increases in those of adenosine diphosphate and adenosine monophosphate. Pyrazole, an inhibitor of alcohol dehydrogenase, prevents the effects of ethanol on the concentration of brain metabolites. These results may provide new insight into the biochemical and pharmacological effects of alcohol on brain metabolism and the importance of alcohol dehydrogenase activity in the brain.     

Adenosine triphosphate usage by flagella

Comparison of beat frequencies with rates of dephosphorylation of adenosine triphosphate by glycerinated sea urchin spermatozoa as functions of adenosine triphosphate concentration suggests that each molecule of the flagellar adenosine triphosphatase, dynein, dephosphorylates one adenosine triphosphate molecule during each beat cycle.     

农杆菌介导的淀粉合成关键酶基因导入超级粳稻的研究

利用农杆菌介导法,将编码腺二磷葡萄糖焦磷酸化酶(adenosine diphosphate glucose pyrophosphorylase,AGP)基因导入粳型水稻中,获得了86株疑似转基因植株,经分子标记检测验证了78株为转化植株。     

Ribonucleic acid biosynthesis in adult and infant rat brain in vitro

The rate of biosynthesis of ribonucleic acid (as judged by the rate of incorporation of uridine into ribonucleic acid) in infant and adullt rat brain cortex slices, incubated (aerobically in tile presenice of various substrates, is directly proportionial to the adenosine triphosphate concentration. This suggests that the adenosine triphosphate concentration is one of the factors involved in the control of ribonucleic acid biosynthesis in infant and adult rat brain. Acetoacetate or beta-hydroxybutyrate is about 70 percent as effective as glucose, with both infant and adult brain, for the promotion of ribonucleic acid biosynthesis. but they are considerably mnore effective than succinate in infant brain than in adult brain.     

Osteoclastic bone resorption by a polarized vacuolar proton pump

Bone resorption depends on the formation, by osteoclasts, of an acidic extracellular compartment wherein matrix is degraded. The mechanism by which osteoclasts transport protons into that resorptive microenvironment was identified by means of adenosine triphosphate-dependent weak base accumulation in isolated osteoclast membrane vesicles, which exhibited substrate and inhibition properties characteristic of the vacuolar, electrogenic H+-transporting adenosine triphosphatase (H+-ATPase). Identify of the proton pump was confirmed by immunoblot of osteoclast membrane proteins probed with antibody to vacuolar H+-ATPase isolated from bovine kidney. The osteoclast's H+-ATPase was immunocytochemically localized to the cell-bone attachment site. Immunoelectron microscopy showed that the H+-ATPase was present in the ruffled membrane, the resorptive organ of the cell.