Three-dimensional crystal structures of Escherichia coli met repressor with and without corepressor

The three-dimensional crystal structure of met repressor, in the presence or absence of bound corepressor (S-adenosylmethionine), shows a dimer of intertwined monomers, which do not have the helix-turn-helix motif characteristic of other bacterial repressor and activator structures. We propose that the interaction of met repressor with DNA occurs through either a pair of symmetry-related alpha-helices or a pair of beta-strands, and suggest a model for binding of several dimers to met operator regions.     

Baclofen prevents rapid amygdala kindling in adult rats

This study investigates the effect of the gamma-aminobutyric acid (GABA_B) agonist, baclofen, on amygdala kindling in adult rats. Baclofen has been reported to be anticonvulsant in a variety of seizure models and prevents kindling in immature rats. These experiments describe the effects of baclofen (2, 5 and 10 mg/kg, i.p.) on the afterdischarge threshold and kindling rate. Baclofen, 10 mg/kg, significantly increased the afterdischarge threshold in the amygdala. Baclofen at 5 and 10 mg/kg, retarded the rate of kindling as measured by the number of stimuli required to advance to subsequent seizure stages. These results suggest that baclofen may decrease the local excitability of the amygdala and retard the rate of seizure spread (or generalization) throughout the brain. Baclofen, acting at GABA_B receptors exerts an anticonvulsant effect on amygdala kindling in these experiments.     

Gene inactivation triggered by recognition between DNA repeats

This chapter focuses on phenomena of gene inactivation resulting from the presence of repeated gene copies within the genome of plants and fungi, and on their possible relationships to homologous DNA-DNA interactions. Emphasis is given to two related premeiotic processes: Methylation Induced Premeiotically (MIP) and Repeat-Induced Point mutation (RIP) which take place in the fungiAscobolus immersus andNeurospora crassa, respectively. The relationships between these processes and genetic recombination are discussed.     

Dissociated cell suspensions ofCarcinus maenas Y-organs as a tool to study ecdysteroid production and its regulation

In vitro ecdysteroid production by dissociated Y-organ cells of the shore crabCarcinus maenas was characterized during short-term incubations. Under optimized conditions (M199 adjusted to crab osmolality and with the addition of 10% foetal calf serum), ecdysteroid production by dispersed cells increased linearly during 4-hour incubations, with little intra-assay variation. 25-deoxyecdysone was mainly produced. PurifiedCarcinus molt inhbiting hormone (CamMIH) produced a dose-dependent inhibition of ecdysteroid production by dispersed cells. The cells were about 50 times more sensitive than whole glands to MIH. Other structurally-related peptides were tested.     

Protective effect of Shigyaku-to,a traditional Chinese herbal medicine,on the infection of herpes simplex virus type 1 (HSV-1) in mice

The antiviral activity of Shigyaku-to (TJS-109), a traditional Chinese herbal medicine, was investigated in mice infected with herpes simplex virus type 1 (HSV-1). TJS-109 is a combination of the medicinal plant extracts fromZingiberis siccatum rhizoma,Aconiti tuber andGlycyrrhizae radix in a specific proportion. Mice infected with a 10 LD₅₀ dose of HSV-1 were treated with TJS-109 orally at doses of 1.25 to 20 mg/kg 2 days before, and 1 and 4 days after the infection. The treated groups had 80% (1.25 mg/kg), 40% (5 mg/kg) and 23% (20 mg/kg) mortality rates 25 days after the infection as compared with a 100% mortality rate in control mice treated with saline. When HSV-1 infected mice (recipients) received CD8⁺T cell fractions derived from spleens of mice treated with TJS-109 (donors), 70% of recipients survived, as compared with 0% survivors in the groups of mice treated with saline, B cell fractions, CD4⁺ T cell fractions or macrophage-enriched fractions prepared from the same donors. TJS-109 did not show any virucidal activities against HSV-1 or any virostatic activities on the growth of HSV-1 in Vero cells. These results suggest that TJS-109 protected mice exposed to lethal amounts of HSV-1 through the activation of CD8⁺ T cells.     

Role of hsp70 in cytokine production

Interleukin-1 and tumor necrosis factor-alpha are potent, multifunctional cytokine mediators of inflammation and immune responses that are produced primarily by activated monocytes and macrophages. Three published papers by different groups have shown that heat shock and chemical stress with heavy metal salts or sulfhydryl reagents, all of which induce the expression of heat shock protein 70 (hsp70), concomitantly inhibit the production of these cytokines in human monocytes and mouse macrophages activated by lipopolysaccharide. These papers are reviewed and discussed in some detail. Other studies suggest that various anti-inflammatory drugs, including acetylsalicyclic acid, auranofin and dexamethasone, can also facilitate HSP expression in macrophages. However, while these studies are interesting, it is clear that not a great deal of work has been done and/or published in this area. Since many pharmaceutical companies are developing cytokine synthesis inhibitors as potential anti-inflammatory drugs, one aim of this article is to emphasize that understanding the molecular mechanism(s) that lead to increased HSP expression and decreased cytokine biosynthesis may assist in achieving this goal.     

Nb对Li／MgO甲烷氧化偶联催化剂的助催化作用

Ｌｉ／ＭｇＯ甲烷氧化偶联催化剂引入铌的氧化物可降低活性温度，７５０℃以下便达到最高Ｃ２烃产率。铌与锂、镁有多种结合方式，引入方法对活性测试结果有重要影响。铌不与镁紧密结合且分布于锂、镁之间时作用最好。     

胺钨盐的性质及其在制取亚微米级钨粉方面的应用

本文着重研究了自还原性胺钨盐的性质及其氢还原,发现,将自还原与一般氢还原适当结合,可以高效率地制备比表面积大于20m~2/g的极细、超细钨粉。对自还原的本性及该类钨盐在制取极细、超细钨粉方面的应用前景进行了讨论。     

Calcium/calmodulin-dependent protein kinase II increases glutamate and noradrenaline release from synaptosomes

A variety of evidence indicates that calcium-dependent protein phosphorylation modulates the release of neurotransmitter from nerve terminals. For instance, the injection of rat calcium/calmodulin-dependent protein kinase II (Ca2+/CaM-dependent PK II) into the preterminal digit of the squid giant synapse leads to an increase in the release of a so-far unidentified neurotransmitter induced by presynaptic depolarization. But until now, it has not been demonstrated that Ca2+/CaM-dependent PK II can also regulate neurotransmitter release in the vertebrate nervous system. Here we report that the introduction of Ca2+/CaM-dependent PK II, autoactivated by thiophosphorylation, into rat brain synaptosomes (isolated nerve terminals) increases the initial rate of induced release of two neurotransmitters, glutamate and noradrenaline. We also show that introduction of a selective peptidergic inhibitor of Ca2+/CaM-dependent PK II inhibits the initial rate of induced glutamate release. These results support the hypothesis that activation of Ca2+/CaM-dependent PK II in the nerve terminal removes a constraint on neurotransmitter release.