Development of glutamic acid decarboxylase-immunoreactive elements in the cerebellar cortex of normal and lurcher mutant mice.

The development of glutamic acid decarboxylase-immunoreactivity (GAD-IR) in cells, fibers, and varicosities of the cerebellar cortex has been examined by light microscopy in normal and lurcher mutant mice between postnatal day 3 and 30 (P3-P30). Purkinje cell morphology was demonstrated in adjacent sections by using an antiserum to the 28Kd vitamin D-dependent calcium binding protein (CaBP). In early postnatal lurcher mice, but not in normal littermates, GAD-IR fibers, presumably Purkinje cell pseudopodia, invade the external granular layer. The plexus of CaBP-IR axons in the internal granular layer is much less complex in lurcher mice than in normal littermates, even before the onset of lurcher Purkinje cell degeneration at P8. In normal mice, GAD-IR fibers encapsulate Purkinje cell somata by P15. Lurcher Purkinje cells, in contrast, receive scattered contacts by GAD-IR puncta and possess a "cap" of such elements surrounding the primary dendrite and apical soma. Pinceau formations, visible as a knot of GAD-IR puncta hanging from the base of Purkinje cells in normal P15 mice, are not present in lurcher littermates. "Empty baskets" or collapsed pinceau formations in regions devoid of Purkinje cells are not revealed by anti-GAD immunohistochemistry in the P17-P30 lurcher cerebellar cortex.     

Biosynthetic and regulatory role of lys9 mutants of Saccharomyces cerevisiae

Summary Derepression of lysine biosynthetic enzymes of Saccharomyces cerevisiae was investigated in lys9 auxotrophs which lack saccharopine reductase activity. Five enzymes (homocitrate synthase, homoisocitrate dehydrogenase, -aminoadipate aminotransferase, -aminoadipate reductase and saccharopine dehydrogenase) were constitutively derepressed in all lys9 mutants with up to eight-fold higher enzyme levels than in isogenic wild-type cells. Levels of these enzymes in lys2, lys14, and lys15 S mutants were the same or lower than those in wild-type cells. The regulatory property of lys9 mutants exhibited recessiveness to the wild-type gene in heterozygous diploids. Unlike the mating type effect, homozygous diploids resulting from crosses between lys9 auxotrophs exhibited even higher levels of derepressed enzymes than the haploid mutants. Addition of a higher concentration of lysine to the growth medium resulted in reduction of enzyme levels although they were still derepressed. These results suggest that lys9 mutants represent a lesion for the saccharopine reductase and may represent a repressor mutation which in the wild-type cells simultaneously represses unlinked structural genes that encode for five of the lysine biosynthetic enzymes.     

Analysis of wild-type and e antigen-defective hepatitis B viruses during the course of a short-term corticosteroid therapy in chronic hepatitis B

Hepatitis B virus (HBV), with a G-to-A point mutation at nucleotide 83 in the precore region (mutant HBV83), accounts for most cases of hepatitis B e antigen (HBeAg)-defective HBV. However, it is still not clear how mutant HBV83 is associated with HBe seroconversion. Twenty-six HBeAgpositive patients with chronic hepatitis B who received oral prednisolone (30 mg/day) for 3 weeks were studied to clarify the prevalence of mutant HBV83 during the treatment using polymerase chain reaction with a restriction fragment length polymorphism assay. Twelve (46%) patients seroconverted to anti-HBe 1 year after treatment, whereas 14 (54%) did not. The proportion of mutant HBV83 to whole HBV remained unchanged in both groups during an acute exacerbation induced by withdrawal of corticosteroids. Among 12 anti-HBe-0seroconverted patients, five (56%) of nine patients with only wild-type HBV at baseline developed detectable levels of mutant HBV83 while all three patients with a mixed viral population of wild-type HBV and mu tant HBV83 at baseline developed a higher pro portion of mutant HBV83 one year after treat ment. In contrast, these changes were observed in only one (14%) of seven who failed to seroconvert. The results indicate that a flare-up of hepa titis precedes emergence or selection of mutant HBV83, followed by HBe seroconversion in patients with chronic hepatitis B. © 1995 WiIey-Liss, Inc.     

A mating deficient and temperature-sensitive lethal mutant of Schizosaccharomyces pombe defines a new fertility locus

Summary A recessive mutant allele, mef1-84, of a novel locus mapping on the left arm of chromosome I, between ade3 and ura1, 5 cM apart from lys5, confers temperature-sensitive growth and mating deficiency at the nonrestrictive temperatures for growth. Two other mutations suppress the phenotype conferred by mef1-84: sts1-1 suppresses the temperature-sensitive growth only, and smd1-35 suppresses both temperature-sensitive growth and mating deficiency.     

Minicircular DNA having sequence homologies with chloroplast DNA in a bleached mutant of Euglena gracilis

Summary Chloroplast DNA was isolated from total cellular DNA of a bleached mutant of Euglena gracilis (Y₃BUD) by enrichment of the light component (p = 1.686) by repeated CsCl equilibrium centrifugations. Electron microscope visualization of this DNA showed minicircular DNA molecules in addition to large circular molecules (42 pm) identical to wild type chloroplast DNA. They were heterogenous in size and their contour lengths ranged from 0.8 to 8.5 m. Fractionnation by agarose gel electrophoresis gave several discrete bands. Some of them hybridized with pure chloroplast DNA and with several cloned chloroplast DNA fragments, particularly to ribosomal fragments, while others did not show homology with chloroplast DNA being probably of extrachloroplatic origin.     

High-resolution analysis of locomotor activity rhythms indisconnected,a visual-system mutant ofDrosophila melanogaster

Free-running locomotor activity and eclosion rhythms ofDrosophila melanogaster, mutant at thedisconnected (disco) locus, are substantially different from the wild-type phenotype. Initial periodogram analysis revealed little or no rhythmicity (Dushayet al., 1989). We have reanalyzed the locomotor activity data using high-resolution signal analysis (maximum-entropy spectral analysis, or MESA). These analyses, corroborated by autocorrelograms, uncovered significant residual circadian rhythmicity and strong ultradian rhythms in most of the animals tested. In this regard thedisco mutants are much like flies expressing mutant alleles of theperiod gene, as well as wild-type flies reared throughout life in constant darkness. We hypothesize that light normally triggers the coupling of multiple ultradian oscillators into a functional circadian clock and that this process is disrupted indisco flies as a result of the neural lesion.This work was supported in part by NIH Grant FM-33205.     

人CGT52TGT MBL突变体在CHO细胞中的表达及其产物分析

目的: 初步探索MBL基因CGT52TGT点突变引起调理吞噬缺损的机制。方法: 采用PCR技术, 从质粒pMBLm52中获取含CGT52TGT点突变的MBL基因, 将其插入真核表达载体pcDNA4 /HisMaxC中构建重组表达载体。经测序验证后, 电转染入CHO细胞。以800mg/LZeocin筛选转染后的CHO细胞30d; 随后的30d中, 维持Zeocin的浓度在200mg/L, 以获取稳定转染的细胞。以RT PCR分析其mRNA的表达情况。表达产物经Ni NTAagarose纯化后, 以非还原SDS PAGE和Westernblot对表达产物进行初步鉴定。结果:以PCR扩增的MBLm52基因片段长约750bp, 将其插入表达载体构建重组真核表达载体pcDNA4 /HisMaxC MBLm52, 测序验证序列正确后将其电转染入CHO细胞。从细胞培养上清中获得的纯化的表达产物, 主要为相对分子质量(Mr)约60 000的分子, 寡聚化程度明显低于重组人野生型MBL和从人血浆中分离的MBL。结论: MBL基因CGT52TGT点突变可能并不影响其表达产物向胞外分泌的过程, 但突变后产生的Cys可能形成新的二硫键, 影响MBL结构单位和/或寡聚分子的形成, 推测该突变MBL蛋白不能发挥正常的功能。     

Isolation of a Trichoderma reesei cDNA encoding GTP: a-d-mannose-1-phosphate guanyltransferase involved in early steps of protein glycosylation

A cDNA coding for GTP: α-d-mannose-1-phosphate guanyltransferase (MPG1 transferase) (EC 2.7.7.13) was isolated from a cDNA library of the Trichoderma reesei RutC-30 strain by suppression of the yeast Saccharomyces cerevisiae mutation in the DPM1gene encoding mannosylphosphodolichol (MPD) synthase. The nucleotide sequence of the 1.6 kb-long cDNA revealed an ORF which encodes a protein of 364 amino acids. Sequence comparisons demonstrate 70% identity with the S. cerevisiae guanyl transferase gene (MPG1) and 75% identity with the Schizosaccharomyces pombe homologue. No similarity was found with the MPD synthase encoded by the S. cerevisiae DPM1 gene. The possibility that cloned cDNA encodes a product with a MPD synthase activity was also excluded by transforming a heterozygous S. cerevisiae dpm1::LEU2/DPM1 diploid, which did not lead to the restoration of viability of the dpm1 spores. Simultaneously, a significant increase in MPG transferase activity, as compared with the wild-type yeast, was observed in cellular extracts when the mpg1 cDNA from Trichoderma was expressed in the S. cerevisiae dpm1-6 mutant. Received: 21 July 1997 / 24 April 1998     

Characterization of a very Virulent Marek’s Disease Virus Mutant Expressing the pp38 Protein from the Serotype 1 Vaccine Strain CVI988/Rispens

Marek’s disease virus (MDV), a highly cell-associated oncogenic chicken herpesvirus, causes Marek’s disease in domestic chickens. A unique phosphoprotein of MDV, pp38, has previously been associated with the maintenance of transformation in MDV-induced tumor cell lines. However, recently, the biological properties of a deletion mutant virus (rMd5Δpp38) revealed that pp38 is involved in early cytolytic infection in lymphocytes but not in the induction of tumors. Thus, pp38 is important for early cytolytic infection and not for transformation. The pp38 protein of the MDV serotype 1 vaccine strain CVI988/Rispens differs by one amino acid when compared to the pathogenic strains of MDV. Monoclonal antibody, H19, recognizes all serotype 1 MDV strains except CVI988/Rispens. Previous studies have also shown that the unique pp38 epitope in CVI988/Rispens induced high antibody response. In order to study the role of this epitope in the protective properties of CVI988/Rispens, we generated a mutant rMd5 virus in which the wild type pp38 gene has been substituted with that of CVI988/Rispens (rMd5/pp38CVI). The replication properties of rMd5/pp38CVI, both in vitro and in vivo, and tumor induction were examined. We found that the biological properties of rMd5/pp38CVI were similar to the wild type rMd5 virus with regards to in vivo replication, antibody response and tumor induction. This shows that the pp38 derived from CVI988/Rispens is not involved in protective properties as was previously suggested.     

Horizontal optokinetic ocular nystagmus in wildtype (B6CBA+/+) and weaver mutant mice

Summary Horizontal optokinetic nystagmus (OKN) evoked by a random dot pattern moving at a constant speed around the animal was investigated in wild-type mice and Weaver mutants (cerebellar impairment) by means of chronically implanted EOG-electrodes. The shape of OKN in the homozygotic Weaver mouse was clearly different from that in normal mice. The OKN in the mutant showed inconstant velocity during the slow phase. Nystagmus frequency of the mutant was significantly below that of normal controls for velocities of 1.4 to 25 degrees · s^-1. In one group of normals the mean slow-phase gain was relatively constant for stimulus angular velocities between 1.4 and 15 degrees · s^-1 and declined thereafter. In a second group the mean slow-phase gam decreased gradually between stimulus angular velocities from 1.4 to 15 degrees · s^-1 and thereafter with a steeper slope. In mutants gain decreases with increasing stimulus velocity over the entire range tested (1.4 to 42 degrees · s^-1). Normals and mutants with one eye occluded exhibited strong OKN when the pattern was moved in a temporonasal direction; little response was obtained by stimuli moving in a naso-temporal direction.