Proton-pumping adenosine triphosphatase in membrane vesicles of tobacco callus: Sensitivity to vanadate and K+

H⁺-pumping adenosinetriphosphatases (ATPases, EC 3.6.1.3) were demonstrated in sealed microsomal vesicles of tobacco callus. Quinacrine fluorescence quenching was induced specifically by MgATP and stimulated by EGTA and Cl^?. Fluorescence quenching reflected a relative measure of pH gradient formation (inside acid), as it could be reversed by gramicidin (an H⁺/cation conductor) or 10 mM NH₄Cl (an uncoupler). H⁺ pumping was inhibited by tributyltin (an ATPase inhibitor) and sodium vanadate, but it was insensitive to oligomycin or fusicoccin. The vanadate concentration required to inhibit pH gradient formation was similar to that needed to inhibit KCl-stimulated Mg²⁺-ATPase activity and generation of a membrane potential (measured by ATP-dependent ³⁵SCN^? uptake). About 45% of all three activities (ATPase, pH gradient, membrane potential generation) were vanadate-insensitive, supporting the idea that non-mitochondrial membranes of plants have at least two types of electrogenic H⁺ pump.A vanadate-insensitive, H⁺-pumping ATPase previously shown by methylamine accumulation was characterized to be anion-sensitive and possibly enriched in vacuolar membranes (Churchill, K.A. and Sze, H. (1983) Plant Physiol. 71, 610–617). Yet, pH gradient formation determined by quinacrine fluorescence quenching was decreased by monovalent cations with a sequence K⁺, Rb⁺, Na⁺ > Cs⁺,Li⁺> choline, bisTris-propane. Since K⁺ stimulated ATPase activity more than Bistris-propane, K⁺ appeared to collapse formation of the pH gradient by an H⁺/K⁺ countertransport. The sensitivity to vanadate and K⁺ provides evidence that the plasma-membrane ATPase is an electrogenic H⁺ pump.     

Steroid binding to synaptic plasma membrane: differential binding of glucocorticoids and gonadal steroids

The specific binding of [3H]-corticosterone, [3H]-17 beta-estradiol, [3H]-testosterone, and [3H]-progesterone to synaptic plasma membrane (SPM) prepared from rat brain has been characterized. The dissociation constant is estimated as on the order of 1 x 10(-7) M for corticosterone and 1 x 10(-8) M for the other three steroids. In a competition experiment, none of the 3H-steroids was displaced by the other steroids at 500-fold excess, indicating the presence of specific binding sites on the membrane for each type of steroid. Moreover, pre-incubation of the SPM with phospholipase A2 or phospholipase C totally destroys the membrane binding of corticosterone and testosterone, but the binding of estradiol and progesterone remains intact. Since the SPM prepared from brain tissue is derived from many different neuronal cell types, it is possible that the membrane binding sites for glucocorticoids and for gonadal steroids are present in different neurons.     

Inactivation by Na+,K+-ATPase of cytosol glucocorticoid receptors from rat brain and liver

Summary We have examined the effect of Na⁺,K⁺-ATPase on ³H-triamcinolone acetonide binding capacity of cytosol glucocorticoid receptors from rat brain and liver. Preincubation of the brain or liver cytosol with Na⁺,K⁺-ATPase (10 units/ml) at 30 °C resulted in a rapid loss of specific ³H-triamcinolone acetonide binding, with a half-life of approximately 7 min. The ATPase effect could be prevented by the addition of 10^–5 M ouabain, or substantially reduced by the omission of Na⁺,K⁺ or Mg⁺². The cytosol receptor bound with ³H-triamcinolone acetonide was totally resistant to the inactivation by the ATPase. Since there is some evidence that ATP may bind to glucocorticoid receptor, our findings indicate that an ATP-receptor complex may be essential for steroid binding. The effects of the ATPase in the inactivation of the receptor are very similar to those of alkaline phosphatase reported by others. This raises doubts about the proposal based on the phosphatase inactivation that the cytosol glucocorticoid receptor may be phosphorylated.     

Dipeptidase development in cotyledons of Cucurbita maxima during germination

The dipeptidase activity of an unpurified soluble extract of the cotyledons of Cucurbita maxima Duch. var. Hubbard remained unchanged during the first 2 days of germination and then increased at a rapid rate during the next 3 days. The dipeptidase activity of two of three lots of seeds required the presence of the embryo axis for maximal dipeptidase activity, whereas the third lot was uninfluenced by the embryo axis. This discrepancy was possibly due to genetic differences. In those seeds which required the presence of the embryo axis for maximal dipeptidase activity, the cytokinin benzyladenine could replace the embryonic axis. When the protein synthesis inhibitor cycloheximide was added to the seeds at the beginning of germination, it inhibited dipeptidase activity of the cotyledons from 26 to 55 per cent, depending of the basis of calculation, at 5 days. When the cycloheximide was added to 3-day-old seedling the inhibition of dipeptidase activity in the cotyledons was almost immediate. The relative hydrolysis of -leucylglycine and glycylglycine were compared after temperature inactivation and purification; the results showed that more than one enzyme was responsible for the dipeptidase activity. The presence of a dialysable dipeptidase inhibitor(s) was demonstrated. Relatively high dipeptidase activity was also found in the roots and shoots.     

Typing of Nontypable Staphylococci by Lysogeny

Strains of coagulase-positive staphylococci which were nontypable with the routine typing set of phages could be typed by lysogeny with phage-propagating strains as indicators and with ultraviolet induction. About 10% of the strains could be typed without induction. About 36% of them could be typed by this method when ultraviolet irradiation was used as an inducing agent. The phage groups from which the majority of the nontypable staphylococci originated were easily identified by this method of typing.     

Islet-cell Carcinoma (Zollinger—Ellison Syndrome) with Fulminating Adrenocortical Hyperfunction and Hypokalemia

The production of ACTH-like material by tumours arising in non-endocrine tissue may initiate severe adrenocortical hyperfunction. The pathogenesis and clinical and laboratory features of Cushing''s syndrome associated with such tumours are characteristic. The autonomous production by the tumour of ACTH-like material cannot be suppressed by exogenous corticoids. The onset of clinical symptoms is rapid; muscle wasting, general weakness, thirst and peripheral edema predominate, and the classical signs of Cushing''s syndrome may be absent. High levels of plasma 17-hydroxycorticosteroids and urinary 17-hydroxycorticosteroids and 17-ketosteroids, usually with normal levels of urinary aldosterone, commonly occur. Hypokalemic alkalosis unresponsive to replacement therapy may cause death. In the case reported herein, the intriguing possibility exists that two hormone-like substances were produced by the primary growth and its metastases: one, ACTH-like, to account for the adrenal hyperplasia and Cushing''s syndrome; and another, gastrin-like, giving rise to the ulcerogenic diathesis.     

甘蔗幼叶切段培养中的体细胞胚胎发生

本文从形态学和组织学方面研究了甘蔗幼叶胚性愈伤组织发生及体细胞胚胎的形成过程。甘蔗幼叶片切段培养于含2.4—D1.5mg/1的MS培养基上,4—6天后切段开始形成愈伤组织,约10天后愈伤组织表面出现白色颗粒状结构。将含有白色颗粒状结构的愈伤组织转移至不含激素的培养基中,7—10天后可见有小植株长出。组织学和形态学观察表明,甘蔗离体再生植株是通过体细胞胚胎发生途径。     

Genetic Interactions between Reg1/Hex2 and Glc7, the Gene Encoding the Protein Phosphatase Type 1 Catalytic Subunit in Saccharomyces Cerevisiae

Mutations in GLC7, the gene encoding the type 1 protein phosphatase catalytic subunit, cause a variety of abberrant phenotypes in yeast, such as impaired glycogen synthesis and relief of glucose repression of the expression of some genes. Loss of function of the REG1/HEX2 gene, necessary for glucose repression of several genes, was found to suppress the glycogen-deficient phenotype of the glc7-1 allele. Deletion of REG1 in a wild-type background led to overaccumulation of glycogen as well as slow growth and an enlarged cell size. However, loss of REG1 did not suppress other phenotypes associated with GLC7 mutations, such as inability to sporulate or, in cells bearing the glc7(Y-170) allele, lack of growth at 14°. The effect of REG1 deletion on glycogen accumulation is not simply due to derepression of glucose-repressed genes, although it does require the presence of SNF1, which encodes a protein kinase essential for expression of glucose-repressed genes and for glycogen accumulation. We propose that REG1 has a role in controlling glycogen accumulation.     

小麦×玉米杂交后代的蛋白质及酯酶同工酶分析

以８ 个普通小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）品种为母本,２ 个栽培玉米（Ｚｅａ ｍ ａｙｓ Ｌ．）品种为父本杂交所获得的Ｆ２ 代在形态上出现了明显变异。对其籽粒进行蛋白质电泳分析,得到了如下主要结果：杂交后代的蛋白质谱带较母本有了很大的变异,主要集中在高分子量麦谷蛋白（ＨＭＷ－Ｇｌｕ）区域。杂交后代的蛋白质谱带由５ 种类型构成：１．母本型,占全部测试籽粒的２２．６％ ;２．附加型,占１４．３％ ;３．互补型,占１５．５％ ;４．杂种型,占３０．９％ ;５．缺失型,占１６．７％ 。对“矮杆早”ד紫粘”的Ｆ２ 代籽粒进行酯酶同工酶电泳分析发现,变异主要发生在ＥＳＴ－１ 区。由此看来,小麦×玉米的杂合子中玉米染色体在被排除前后,可以诱发小麦染色体组发生遗传变异     

Characterization of a Kinesin-Related Gene ATSV, within the Tuberous Sclerosis Locus (TSC1) Candidate Region on Chromosome 9Q34

In the search for candidate genes for the tuberous sclerosis (TSC1) disease locus on chromosome 9q34, we have isolated an overlapping series of 22 plasmid and phage cDNA clones covering nearly 7 kb and with an open reading frame of 5070 bp encoding a protein of 1690 amino acids. The putative protein product is a member of the kinesin superfamily and is homologous to the mouse KIF1A and theCaenorhabditas elegansunc-104 genes. Both KIF1A and unc-104 function in the anterograde axonal transport of synaptic vesicles. The human homolog is therefore termed H-ATSV (axonal transporter of synaptic vesicles, HGMW-approved nomenclature ATSV) Screening of DNA from 107 tuberous sclerosis patients and 80 unaffected individuals with H-ATSV cDNA probes by pulsed-field gel electrophoresis/Southern blotting following digestion by rare-cutting methylation-sensitive restriction enzymes showed variant banding patterns in three patients with tuberous sclerosis. However, further analysis indicated that these variant fragments represent a rare polymorphism probably associated with methylation of clustered restriction sites. There is no evidence to support H-ATSV as a candidate gene for TSC1.