Dynamic interaction between functional groups in the active site of glycogen phosphorylase b

The quenching of coenzyme fluorescence in glycogen phosphorylase b is reinvestigated. Data with anionic quenchers show deviations from the original Stern-Volmer kinetics. A kinetic analysis based on measured lifetime data indicates a collisional quenching process, which is, however, not diffusion-controlled. It is proposed, that the quenching takes place primarily by enzyme-bound quencher species. The observed inhibition of the enzyme reaction by I- and IO-3 is consistent with this hypothesis. The inhibition pattern and spectral investigation refer to a true competition with the substrate, glucose-1-phosphate. So, this dynamic quenching can be regarded as an indicator of rapid conformational fluctuations which bring the two important active-site groups in contact. Effect of ligand binding on the quenching of coenzyme fluorescence should also be revaluated according to these results.     

Oxidative and reductive cleavage of folates--a critical appraisal.

A critical analysis has been made of the oxidative and reductive techniques employedfor cleavage of the C⁹-N¹⁰ bond of folic acid and its derivaatives. The assumption has previously been made that these cleavage reactions reduce folates to a common family of p-aminobenzoylglutamate derivatives varying only in the lengths of γ-polyglutamyl peptide side chains which are readily subjected to quantitative and qualitative analysis. This assumption is incorrect. Oxidation by potassium permanganate effectively cleaved folic acid, dihydrofolic acid, tetrahydrofolic acid, and 5-formyltetrahydrofolic acid to yield p-aminobenzoylglutamate. 5-Methyltetrahydrofolic acid was merely oxidized to 5-methyldihydrofolic acid while 5,10-methenyltetrahydrofolic acid and 10-formyltetrahydrofolic acid were oxidized to 10-formylfolate which was stable to further attack. Of all the folate derivatives tested only folic acid and dihydrofolic acid were cleaved to p-aminobenzoylglutamate by the zinc-hydrochloric acid reduction method. Both tetrahydrofolic acid and 5-methyltetrahydrofolic acid were stable under fully reducing conditions. 5,10-Methenyl-,10-formyl-, and 5-formyltetrahydrofolic acid yielded N-methyl-p-aminobenzoylglutamate. It is evident, therefore, that not only is the dominant mammalian tissue folate derivative, 5-methyltetrahydrofolate, resistant to cleavage by either method, but that a common family of p-aminobenzoylglutamate derivatives is not the end product of those folate compounds that are susceptible. While this may not invalidate the reports of the relative polyglutamate chain lengths of tissue folates such data should be regarded with some caution.     

Different isometric force - [Ca2+] relationships in slow and fast twitch skinned muscle fibres of the rat

Skinned muscle fibres prepared from fast and slow twitch muscles of rat have been activated in Ca²⁺-buffered solutions using a new activation procedure (Moisescu, D.G. and Thieleczek, R. (1978) J. Physiol. 275, 241–262). The results indicate that (i) the Ca²⁺ activation curve is less steep for slow fibres, (ii) physiologically relevant force levels are attained considerably faster at constant [Ca²⁺] in fast fibres, and (iii) active force becomes noticeable at lower [Ca²⁺], but reaches saturation at higher [Ca²⁺] for slow fibres.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

杆状病毒出芽病毒粒子膜融合蛋白的研究进展

杆状病毒是一类感染节肢动物的病原微生物,其基因组为双链环状DNA,大小为80～180kb.     

Inception of the Modern Public Health System in China and Perspectives for Effective Control of Emerging Infectious Diseases: In Commemoration of the 140th Anniversary of the Birth of the Plague Fighter Dr. Wu Lien-Teh

In this article, we systematically review Dr. Wu Lien-Teh's academic achievements and outstanding contributions in the prevention and control of the plague epidemic in northeast China and introduce the development of the earliest public health epidemic prevention system in China in order to commemorate the 140th anniversary of Dr. Wu Lien-Teh's birth. We hope that this article will provide insights into the effective prevention and control of emerging infectious diseases as well as the current worldwide pandemic of COVID-19, facilitating the improvement and development of public health systems in China and around the globe.