A missense mutation (Asp250----Asn) in exon 6 of the human lipoprotein lipase gene causes chylomicronemia in patients of different ancestries.

We have previously reported two common lipoprotein lipase (LPL) gene mutations underlying LPL deficiency in the majority of 37 French Canadians (Monsalve et al., 1990. J. Clin. Invest. 86: 728-734; Ma et al., 1991. N. Engl. J. Med. 324: 1761-1766). By examining the 10 coding exons of the LPL gene in another French Canadian patient, we have identified a third missense mutation that is found in two of the three remaining patients for whom mutations are undefined. This is a G to A transition in exon 6 that results in a substitution of asparagine for aspartic acid at residue 250. Using in vitro site-directed mutagenesis, we have confirmed that this mutation causes a catalytically defective LPL protein. In addition, the Asp250----Asn mutation was also found on the same haplotype in an LPL-deficient patient of Dutch ancestry, suggesting a common origin. This mutation alters a TaqI restriction site in exon 6 and will allow for rapid screening in patients with LPL deficiency.     

Recombinational analysis of a natural noncytopathic human immunodeficiency virus type 1 (HIV-1) isolate: role of the vif gene in HIV-1 infection kinetics and cytopathicity.

Two molecularly cloned coisolates of human immunodeficiency virus type 1 (HIV-1) have been found to exhibit different phenotypes of viral expression, either rapid and cytopathic (N1T-A virus) or delayed and noncytopathic (N1T-E virus [X. Ma, K. Sakai, F. Sinangil, E. Golub, and D. J. Volsky, Virology 176:184-194, 1990]). To identify the viral genetic elements responsible for these phenotypes, we prepared reciprocal recombinants in different regions of N1T-A and N1T-E viral genomes. Infectivity experiments with the recombinant viruses revealed that the rapid/cytopathic (N1T-A-like) phenotype assorted cleanly with the V1f-coding region and Vif expression. The smallest HIV-1 DNA region that conferred the complete phenotypic switch was a 284-bp NdeI-StuI fragment within the vif open reading frame. Nucleotide sequence analysis revealed a 35-bp deletion starting at nucleotide 218 in the N1T-E vif gene. A 23-kDa Vif protein was detected by immunoblotting using Vif-specific antiserum in extracts of cells infected with N1T-A but not N1T-E virus. No detectable vif protein was found in association with sedimented particles of either virus. Cotransfection of a eucaryotic vif expression plasmid with N1T-E DNA complemented the N1T-E defect; rapid/cytopathic infection similar to that in N1T-A-transfected cells was observed. We conclude that Vif controls the rate, and consequently the cytopathic outcome, of HIV-1 infection.     

Ethmoidal endocranium in primitive triassic amphibians

Three-dimensionally preserved and chemically prepared skulls and natural casts of representatives of the families Benthosuchidae, Melosauridae, and Capitosauridae yield data on the structure of the ethmoidal endocranium, i. e. of those nasal cranial structures that consisted originally of cartilage. This study demonstrates that the ethmoidal endocranium was principally a dorsoventrally compressed plate, pierced by a broad and oblique canal which communicated anteriorly with the outer dorsal surface by the fenestra endonarina and posteriorly with the mouth cavity by the fenestra endochoanalis(seu foris). The canal was very short, and housed the olfactory organ. The ethmoidal endocranium was connected with the palatoquadrate by the commissura quadratocranialis anterior; there was no lateral ethmoidal commissure, however, in older individuals the anterior section of the palatoquadrate might also contact the postchoanal part of the nasal endocranial skeleton.     

Developmental Regulation of the (1,3)-beta-Glucan (Callose) Synthase from Tomato : Possible Role of Endogenous Phospholipases

Activity levels of UDP-glucose: (1,3)-β-glucan (callose) synthase in microsomal membranes of pericarp tissue from tomato fruit (Lycoperisicon esculentum Mill, cv Rutgers) were determined during development and ripening. Addition of the phospholipase inhibitors O-phosphorylcholine and glycerol-1-phosphate to homogenization buffers was necessary to preserve enzyme activity during homogenization and membrane isolation. Enzyme activity declined 90% from the immature green to the red ripe stage. The polypeptide composition of the membranes did not change significantly during ripening. The enzyme from immature fruit was inactivated by exogenously added phospholipases A₂, C, and D. These results suggest that the decline in callose synthase activity during ontogeny may be a secondary effect of endogenous lipase action.     

Determination of the spatial structure of insectotoxin 15A from Buthus erpeus by (1)H-NMR spectroscopy data]

The solution structure of insectotoxin 15A (35 residues) from scorpion Buthus eupeus was determined on the basis of 386 interproton distance restraints 12 hydrogen-bonding restraints and 113 dihedral angle restraints derived from 1H NMR experiments. A group of 20 structures was calculated with the distance geometry program DIANA followed by the restrained energy minimization with the program CHARMM. The atomic RMS distribution about the mean coordinate position is 0.64 +/- 0.11 A for the backbone atoms and 1.35 +/- 0.20 A for all atoms. The structure contains an alpha-helix (residues 10-20) and a three-stranded antiparallel beta-sheet (residues 2-5, 24-28 and 29-33). A pairing of the eight cysteine residues of insectotoxin 15A was established basing on NMR data. Three disulfide bridges (residues 2-19, 16-31 and 20-33) connect the alpha-helix with the beta-sheet, and the fourth one (5-26) joins beta-strands together. The spatial fold of secondary structure elements (the alpha-helix and the beta-sheet) of the insectotoxin 15A is very similar to those of the other short and long scorpion toxins in spite of a low (about 20%) sequence homology.     

The root-knot nematode resistance gene (Mi) in tomato: construction of a molecular linkage map and identification of dominant cDNA markers in resistant genotypes

A dominant allele at the Mi locus on chromosome 6 of tomato (Lycopersicon esculentum Mill) confers resistance to three species of root-knot nematodes (Meloidogyne). The resistance, which is associated with a localized necrotic response, was originally introduced into tomato from the wild species Lycopersicon peruvianum. As a step towards the molecular cloning of Mi, we have identified closely linked DNA markers from both cDNA and genomic DNA libraries as restriction fragment length polymorphisms (RFLPs). DNA from tomato populations segregating for nematode resistance was analyzed to generate a high-resolution genetic map of this region. Additional information on gene order was obtained by comparing the size of the introgressed L. peruvianum chromosomal segment within a collection of nematode-resistant tomato lines. Among the four cDNA markers that are tightly linked to Mi, three are dominant, i.e. L. peruvianum-specific. One cDNA marker corresponds to a gene family comprising 20-30 members, one of which is diagnostic for all nematode-resistant genotypes tested. The presence of non-homologous sequences around the Mi gene may contribute to the suppression of recombination in this region of the genome in crosses heterozygous for Mi. The potential of 'walking' from closely linked markers to Mi is discussed.     

白暨豚正常心电图的初步探讨

1980年以来,我们测定了白鱀豚(Lipotes vexillifer)“淇淇”和“珍珍”的心电图,并与人和其他海豚的心电图作了比较,从而确定了白鱀豚心电图常规导联的联接方法,并比较完整地描述了白鱀豚正常心电图的特征。研究发现,白鱀豚的心电图各波、段和间期的正常范围基本与人的相近,但T波的特征与人不同,人的T波与同导联的主波方向一致,而白鱀豚的T波却正好相反。P—R间期明显比人的延长。本研究将为白鱀豚心血管疾病的诊断提供重要依据。     

森林土壤氮转化的微生物功能研究

本文研究了不同林型下土壤(A+6层和A_1层)微生物、土壤酶活性在森林土壤氮转化中的作用。结果表明不同林型下土壤具有不同的固氮作用、反硝化作用、氨化作用和硝化作用速率,即阔叶林>针阔混交林>针叶林。已经证明,固氮作用主要存在于森林土壤的A_1层,反硝化作用主要存在于A_0层。森林土壤存在2种硝化作用过程,即由自养微生物所引起的自养硝化作用过程和异养微生物所引起的异养硝化作用过程。它的存在与林型有关,某些森林土壤中这2种硝化作用过程都存在,如针阔混交林下的A_0层和A_1层。有些林型下土壤,则以异养硝化作用过程为主,如针叶林的A_0层。     

Cultural characteristics and zearalenone production by strains of<Emphasis Type="Underline">Fusarium</Emphasis> from wheat

Conidia of the speciesFusarium culmorum /W.G.Sm./ Sacc. andFusarium graminearum Schwabe are characterized by variability in zearalenone production and dimensions depending on the substrate. The sporulation of isolates from some wheat eultivars have been deprived in vivo and in vitro in the first passage, but not their pathogenicity and toxic metabolites production. Nonsporulating strains produced lower quantités of zearalenone than sporulating ones. Liquid filtrates of such nonsporulating strains had a high phytotoxic effect on wheat caryopses. The crystalline toxin DAS /0,25 ug/ml/ had low phytotoxic effect on wheat caryopses.     

中国大鲵视网膜的光镜和扫描电镜研究

用光镜和扫描电镜观察了大鲵视网膜各类细胞的形态及分布, 对视细胞和节细胞进行计数。视网腊中三个核层及两个网状层分布均匀,无中央凹。每张视网膜的视细胞总数约130000,节细胞约8000,视杆与视锥之比为8.5：1。扫描电镜下,视杆外节表面的小叶间沟清晰;视杆视锥外节均有从内节伸出的20-30条萼状突起;核周体表面亦有20-30条细胞质突起。文中还报道了幼体视细胞的形态及密度。讨论了上述结构的机能。