Enzymes of agmatine degradation and the control of their synthesis in Klebsiella aerogenes.

The degradation of agmatine to succinate by Klebsiella aerogenes occurs in five steps. The enzyme catalyzing the first step, agmatinase, is induced by agmatine. The enzymes catalyzing the second and third steps, putrescine aminotransferase and 4-aminobutyraldehyde dehydrogenase, are induced by putrescine and also by their product, 4-aminobutyrate. The enzymes catalyzing the fourth and fifth steps, 4-aminobutyrate aminotransferase and succinate semialdehyde dehydrogenase, are induced by 4-aminobutyrate. This compound also serves as gratuitous inducer of the catabolic acetylornithine aminotransferase. The formation of the enzymes responsible for agmatine degradation is regulated not only by induction, but also by catabolite repression and activation by glutamine synthetase.     

The Effect of Some Inhibitory Sugars upon the Content of Adenosine Triphosphate in Wheat Roots

The content of adenosine triphosphate (ATP) in roots of -wheat (Triticum aestivum L.) was determined with the fire-fly-luciferase method. The content is decreased by D-mannose, which inhibits root growth, respiration and chloride uptake. In intact seedlings the inhibition of root growth is relieved by other sugars and also by the flavanone naringenin and by 2,4-dinitrophenol. This reversal is combined with an increased content of ATP. The inhibition of chloride uptake by mannose in excised roots is reversed by some other sugars (including D-galactose which is in itself inhibitory to root growth), and also in this case the ATP content is increased. Naringenin and dinitrophenol do not relieve the inhibition of chloride uptake caused by mannose. Nor do they increase the content of ATP in this case. The primary effect of mannose seems to be inhibition of glycolysis whereas the effect upon root growth is secondary. Galactose, which also inhibits root growth, does not inhibit respiration or reduce the ATP content and the primary effect of galactose (and also of 2-deoxy-D-glucose and 2-deoxy-D-galactose) seems to be on the synthesis of cell wall substances.     

Effect of tropane on the cholinoreceptors of the cerebral cortex

Spontaneous electric activity of single neurons of the sensorimotor cortex was recorded extracellularly in experiments on unanesthetized rabbits. During microiontophoretic application of tropane and acetylcholine to the neurons, the response to both the agents was the same. The cells excitable by acetylcholine are also excitable by tropane, while those inhibited by acetylcholine are also inhibited by tropane. The cells that do not respond to acetylcholine are also irresponsive to tropane. The excitatory response pattern to tropane is similar to that of acetylcholine. Under the same conditions of microiontophoretic application, tropane causes less excitation as compared with acetylcholine. Tropane preliminarily applied to the neuron reduces the excitatory effect of acetylcholine. The possible role of agonist-antagonist relations between tropane and acetylcholine in the mechanism of the pharmacological effects of tropane and its derivatives is discussed.     

The occurrence of erythropoiesis in the thymus of the bank vole (Clethrionomys glareolus)

Summary The thymus of wild young and adult bank voles (Clethrionomys glareolus) was examined by histological methods for the presence of developing erythroid cells. Nucleated erythroid cells were observed in 26% of the glands examined by light microscopy and in 69% of the glands examined by electron microscopy.The largest number of developing erythroid cells was observed in the thymus of pregnant females, also showing raised reticulocyte counts (3.1–10.2%). However, erythropoiesis could also be found in breeding and non-breeding, first year and older animals.Erythroid cells were mainly located in the cortex, sometimes in small groups interspersed between lymphoid cells, and also randomly scattered in the cortex. Occasionally, macrocytic erythroid cells were also present. Pyknotic cells were commonly present, and granulopoiesis was frequently observed.     

Study of the damaging effects of acetazolamide on gastric mucosa in rats

The present study demonstrated that acetazolamide (100 and 200 mg/kg, s.c.) induced severe gastric hemorrhagic ulceration in rats. The ulceration was aggravated by oral administration of HCl, but was inhibited by NaHCO3. Furthermore, the severity of ulceration was also decreased by pretreatment with methysergide, chlorpheniramine, or cimetidine. These protective effects were accompanied by an increase in serotonin and histamine released from the stomach. Acetazolamide injection also increased the protein level but reduced the sialic acid content in the gastric secretion, indicating that the gastric mucosal barrier may have been damaged. Prostaglandin E2 content of the gastric mucosa was not affected by the drug; however, carbonic anhydrase activity was markedly reduced in a dose-dependent manner. Thus, it is suggested that the ulceration induced by acetazolamide is mainly due to the inhibition of carbonic anhydrase activity and mucus secretion. The increase in serotonin and histamine release also may have been the contributing factors for gastric ulcer formation.     

The mechanism of the insulin-like effects of ionic zinc

The insulin-like effects of ionic zinc (Zn2+) were studied in isolated rat adipocytes. Concentrations of Zn2+ between 250 and 1000 microM stimulated 3-O-methylglucose transport and glucose metabolism to CO2, glyceride-fatty acid, and glyceride-glycerol. Selective stimulation of the pentose phosphate cycle was observed since a Zn2+-induced increase in glucose carbon 1 oxidation persisted even when glucose transport was blocked with 50 microM cytochalasin B or when transport was no longer rate-limiting for metabolism at high concentrations of glucose. Enhanced pentose phosphate cycle activity may have been due to a selective inhibition of glutathione reductase by the ion, which was also accompanied by a fall in cellular glutathione content. Zn2+ also inhibited lipolysis stimulated by the beta-adrenergic agent ritodrine in the absence of glucose. The effects of Zn2+ on glucose oxidation and stimulated rates of lipolysis were inhibited by extracellular catalase, indicating that they were largely a result of H2O2 generation. The H2O2 production appeared for the most part to be caused by zinc-catalyzed autoxidation of sulfhydryl groups present on external cell membranes, although involvement of sulfhydryl groups on bovine serum albumin in the buffer could also have contributed. The insulin-like effects of Zn2+ in adipocytes are therefore caused not only by direct effects of the ion on intracellular metabolism but also by indirect effects related to H2O2 generation.     

Platelet responses promoted by the activation of protein kinase C or the increase of cytosolic Ca2+ are potentiated by adrenaline. Effects of cAMP and staurosporine.

We studied the action of the alpha 2 adrenergic agonist adrenaline on the platelet responses evoked by the activation of protein kinase C or by the ionophore induced increase of cytosolic Ca2+. Both the phorbol ester and ionomycin-induced aggregation are strongly potentiated by adrenaline which per se does not behave as an activating agonist. The potentiation by adrenaline is observed both when added before and after the aggregating agent; in the latter case the effect increases on increasing the delay of adrenaline addition. Adrenaline also reverses the inhibition by cAMP of the PMA (or ionomycin) induced aggregation. It also has a strong potentiating effect (over 100%) on the phorbol ester induced ATP secretion and a weaker effect on the secretion induced by ionomycin. The effect on secretion is visible only when adrenaline is added prior to the stimulus. The inhibition by cAMP of the PMA or ionomycin induced secretion is also counteracted by adrenaline. In no case adrenaline modifies the pattern of platelet phosphoproteins. Ionomycin induces some platelet aggregation also in the presence of the protein kinase inhibitor staurosporine; also this phosphoprotein independent aggregation is strongly stimulated by adrenaline.     

The regulation of rat liver tryptophan pyrrolase activity by reduced nicotinamide-adenine dinucleotide (phosphate). Experiments with glucose and nicotinamide.

1. Chronic administration of glucose or nicotinamide in drinking water inhibits the activity of rat liver tryptophan pyrrolase, and subsequent withdrawal causes an enhancement. The enzyme activity is also inhibited by administration in drinking water of sucrose, but not fructose, which is capable of preventing the glucose effect. 2. The inhibition by glucose or nictinamide is not due to a defective apoenzyme synthesis nor a decreased cofactor availability. 3. The inhibition by nicotinamide is reversed by regeneration of liver NAD+ and NADP+ in vivo by administration of fructose, pyruvate or phenazine methosulphate. Inhibition by glucose is also reversed by the above agents and by NH4Cl. Reversal of inhibition by glucose or nicotinamide is also achieved in vitro by addition of NAD+ or NADP+. 4. Glucose or nicotinamide increases liver [NADPH]. [NADP+] is also increased by nicotinamide. [NADPH] is also increased by sucrose, but not by fructose, which prevents the glucose effect. Phenazine methosulphate prevents the increase in [NADPH] caused by both glucose and nicotinamide. 5. It is suggested that the inhibition of tryptophan pyrrolase activity by glucose or nicotinamide is mediated by both NADPH and NADH.     

Synthesis of site-specifically modified oligoribonucleotides for studies of the recognition of TAR RNA by HIV-1 tat protein and studies of hammerhead ribozymes.

Synthetic oligoribonucleotides having single uracil residues replaced by dU, dT, 2'-O-methylU or 5-bromodU have been prepared and used in the study of the interaction of HIV-1 tat protein with an RNA stem-loop. The preparation of phosphoramidites of 5-bromouridine and purine riboside suitable for use in solid-phase oligoribonucleotide synthesis is also described. The effect of adenine replacement by purine in a hammerhead ribozyme has also been determined.     

Biotransformation of geraniol, nerol and citral by sporulated surface cultures of Aspergillus niger and Penicillium sp

The biotransformation of geraniol, nerol and citral by Aspergillus niger was studied. A comparison was made between submerged liquid, sporulated surface cultures and spore suspensions. This bioconversion was also carried out with surface cultures of Penicillium sp. The main bioconversion products obtained from geraniol and nerol by liquid cultures of A. niger were linalool and alpha-terpineol. Linalool, alpha-terpineol and limonene were the main products obtained from nerol and citral by sporulated surface cultures, whereas geraniol was converted predominantly to linalool, also resulting in higher yields. Bioconversion of nerol with Penicillium chrysogenum yielded mainly alpha-terpineol and some unidentified compounds. With P. rugulosum the major bioconversion product from nerol and citral was linalool. The bioconversion of nerol to alpha-terpineol and linalool by spore suspensions of A. niger was also investigated. Finally the biotransformation with sporulated surface cultures was also monitored by solid phase microextraction (SPME). It was found that SPME is a very fast and efficient screening technique for biotransformation experiments.     

The role of antibiotics in the decomposition of sawdust; inhibition of the growth of cellulose decomposing fungi

The action of the antibiotics present in deal sawdust on the growth on Czapek-Dox agar of cellulose-decomposing fungi has been examined. Stachybotrys atra and Chaetomium indicum were strongly inhibited by substances in cold-water extracts, but C. globosum only slightly so. The extracts also contained material which stimulated the growth of C. globosum but not that of the other two fungi. The formation of perithecia by C. indicum and C. globosum was also stimulated by the extract. There was no marked inhibition or stimulation of the growth of Aspergillus terreus, A. fumigatus , or three species of Penicillium by the extracts.     

Inhibitory effect of tetrabutylammonium ions on endothelium/nitric oxide-mediated vasorelaxation

Apart from the well-described K+ channel blocking effects in vascular smooth muscle cells, monovalent quaternary ammonium ions may also interact with endothelial cells in the endothelium-intact mammalian arteries. The present study was aimed to examine the effect of tetrabutylammonium ions on endothelium-dependent and -independent relaxation in the rat isolated aortic rings. Pretreatment with tetrabutylammonium concentration dependently reduced the endothelium-dependent relaxation induced by acetylcholine, cyclopiazonic acid and ionomycin. Tetrabutylammonium also inhibited endothelium-independent relaxation induced by hydroxylamine or nitroprusside. Pretreatment of endothelium-denuded rings with tetrabutylammonium did not affect relaxation induced by NS1619 or by diltiazem. In contrast, tetrabutylammonium significantly reduced the pinacidil- or cromakalim-induced relaxation. Tetrabutylammonium also inhibited the acetylcholine- but not nitroprusside-induced increase of tissue content of cyclic GMP in the aortic rings. The present study indicates that tetrabutylammonium ions could inhibit endothelial and exogenous nitric oxide-mediated aortic relaxation while it had no effect on relaxation induced by activation of Ca2+-activated K+ channels (by NS1619) or by inhibition of voltage-gated Ca2+ channels (by diltiazem). The inhibitory effect on pinacidil- and cromakalim-induced relaxation suggests that tetrabutylammonium ions also inhibit ATP-sensitive K+ channels in aortic smooth muscle cells.     

遮荫条件下草莓的光合特性变化

对宝交早生和硕丰两个草莓品种遮荫处理后测定其光合特性变化结果表明,遮荫处理使两个草莓品种叶片光合速率显著降低,分别下降了20%和47%,而表观量子效率分别提高了13%和8%.叶片中叶绿素含量升高而可溶性蛋白含量显著降低.光系统Ⅱ电子传递活性(PSⅡ活性)分别下降了22.5%和53.7%.1,5二磷酸核酮糖羧化酶(Rubisco)活性分别降低了19.6%和35.3%.进一步讨论了草莓光饱和速率下降的生理基础.     

Synergistic antitumor effect of TRAIL and IL-24 with complete eradication of hepatoma in the CTGVT-DG strategy

The ZD55-tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and ZD55-interleukin (IL)-24 were constructed by inserting TRAIL or IL-24 gene separately into the oncolytic adenovirus named ZD55 (with adenovirus E1B-55kD deletion). The resulting ZD55-TRAIL and ZD55-IL-24 were used in combination to treat xenograft tumors in nude mice model. The results showed that it can not only completely eliminate BEL7404 hepatoma xenograft but also have excellent antitumor effect against gaster, lung, prostate, and breast carcinomas. It was also found that ZD55-TRAIL could not only suppress the tumor growth promoting effect by ZD55-IL-24 at lower dosage, but also substantially reduce the cancer cell viability in their combined use. This is because ZD55-IL-24 and ZD55-TRAIL could mutually enhance each other's antitumor effect greatly. All these findings conspicuously showed the synergistic antitumor effect of TRAIL and IL-24, which is also the reason for the antitumor effect by the combined use of TRAIL and IL-24 in vitro and also in vivo.     

遮荫条件下草莓的光合持性变化

对宝交早生和硕丰两个草莓品种遮荫处理后测定其光合特性变化结果表明,遮荫处理使两个草莓品种叶片光合速率显著降低,分别下降了20％和47％,而表观量子效率分别提高了13％和8％,叶片中叶绿素含量升高而可溶性蛋白含量显著降低,光系统II电子传递活笥（PSII活性）分别下降了22．5％和53．7％,1,5二磷酸核酮糖羧化酶（Rubisco)活性分别低了19．6％和35．3％,进一步讨论了草莓光饱和速率下降的生理基础。     

Isolation of tissue collagenase from homogenates of embryonic chick bones

An enzyme capable of digesting undenatured collagen in solution and in the solid state as reconstituted collagen fibrils at neutral pH was extracted from demineralized embryonic chick bone homogenates in 1.0M NaCl at neutral pH. The enzyme could be dissociated from the small amount of collagen which was also solubilized in 1.0M NaCl by the serial use of Diaflo XM-300 and PM-10 membranes, which procedures also concentrated the enzyme. The enzymatic activity was inhibited by EDTA, cysteine and horse serum, and was enhanced by the addition of heparin.     

The inhibition of catalase by glutathione

Reduced glutathione (GSH) inhibited catalase activity in a dose-dependent manner. DL-dithiothreitol (DL-DTT) and dithioerythritol (DTE) also inhibited catalase activity. The inhibition of catalase by GSH and DL-DTT could be reduced by NADPH. Polyacrilamide gel electrophoresis demonstrated the inhibition was partially reversible. The inhibition of catalase by GSH appeared to be partly due to superoxide radicals, since it was inhibited by active manganese superoxide dismutase, but not by heat-inactivated enzyme. Other chemical species also appear to take part in the inhibition, but they could not be identified.     

大鼠卵母细胞体外发育过程中的微管组装研究

大鼠卵母细胞的发育具有许多与其他哺乳动物不同的特点,用激光共聚焦显微术研究了大鼠卵母细胞发育过程中微管的组装过程,以及一些因素对微管组装过程的影响.结果表明,在大鼠卵母细胞减数分裂的细胞周期进程中,细胞微管系统发生广泛而剧烈的重组,紫杉醇、星形孢菌素和冈田酸等药物能显著改变卵母细胞内的微管组织状态.大鼠卵母细胞可以在体外发生自发的孤雌活化,也可以被细胞松弛素诱导发生胞质假分裂.因此,研究了在这些过程中微管结构的特殊构象,以期更加深入认识这些特殊细胞事件的生化机理.     

On the effect of oxygen or copper(II) in radiation-induced degradation of DNA in the presence of thiols

Degradation of DNA when gamma-irradiated in aqueous solutions containing cysteine can be efficiently enhanced not only with oxygen, but to the same extent also with Cu2+ ions under hypoxic conditions. The result can be explained by 'self-repair' in this system due to recombination of DNA. with RSS.-R intermediates, and repair inhibition by oxygen or copper involving RSS.-R scavenging. It is emphasized that oxygen enhancement in DNA-thiol systems may occur not only by peroxidation, via defect fixation (DNA-O2.) or thiol activation (RS-O2.), but also by the well-established inactivation of RSS.-R by oxygen. There is evidence also from literature data for a correlation between oxygen enhancement and RSS.-R stability, which varies with thiol concentration, pH and thiol structure.     

大鼠卵母细胞体外发育过程中的微管组装研究(英)

大鼠卵母细胞的发育具有许多与其他哺乳动物不同的特点,用激光共聚焦显微术研究了大鼠卵母细胞发育过程中微管的组装过程,以及一些因素对微管组装过程的影响.结果表明,在大鼠卵母细胞减数分裂的细胞周期进程中,细胞微管系统发生广泛而剧烈的重组,紫杉醇、星形孢菌素和冈田酸等药物能显著改变卵母细胞内的微管组织状态.大鼠卵母细胞可以在体外发生自发的孤雌活化,也可以被细胞松弛素诱导发生胞质假分裂.因此,研究了在这些过程中微管结构的特殊构象,以期更加深入认识这些特殊细胞事件的生化机理.