Bioconversion of Xylan to Triglycerides by Oil-Rich Yeasts

A series of lipid-accumulating yeasts was examined for their potential to saccharify xylan and accumulate triglyceride. Of the genera tested, including Candida, Cryptococcus, Lipomyces, Rhodosporidium, Rhodotorula, and Trichosporon, only Cryptococcus and Trichosporon isolates saccharified xylan. All of the strains could assimilate xylose and accumuate triglyceride under nitrogen-limiting conditions. Strains of Cryptococcus albidus were found to be especially useful for a one-step saccharification of xylan coupled to triglyceride synthesis. Cryptococcus terricolus, a strain constitutive for lipid accumulation, lacked extracellular xylanase, but did assimilate xylose and xylobiose and was able to continuously convert xylan to triglyceride if the culture medium was supplemented with xylanase.     

Lipid composition of Escherichia coli in relation to resistance to penicillin.

Clinical isolates of Escherichia coli sensitive and resistant to penicillin were compared in lipid composition and 14C-labelled penicillin uptake, as possible factors in resistance. Except for a slight increase in the triglyceride fraction in sensitive strains there were no qualitative or quantitative differences in the classes of extractable lipids present. Gas-liquid chromatography of the phospholipid and triglyceride fatty acids of the polar and non-polar fatty acids of the bound lipids showed that the same kinds of fatty acids were present. There was an increase of myristate in the chloroform-methanol extractable lipids of highly resistant strains accompanied by a rather general decrease of other fatty acids. Gas-chromatographic analysis of the polar-bound lipids showed an increase of the beta-hydroxydecanoic acid in the resistant strains. By studying the uptake of 14C-labelled benzylpenicillin and the crypticity of the beta-lactamase, evidence has been produced that a decreased permeability of resistant strains to penicillin cooperates with beta-lactamase to induce a high level of resistance. The altered lipid metabolism may reflect the special architectural changes in the cell wall which cause decreased permeability.     

Modulation of Triglyceride and Cholesterol Ester Synthesis Impairs Assembly of Infectious Hepatitis C Virus

In hepatitis C virus infection, replication of the viral genome and virion assembly are linked to cellular metabolic processes. In particular, lipid droplets, which store principally triacylglycerides (TAGs) and cholesterol esters (CEs), have been implicated in production of infectious virus. Here, we examine the effect on productive infection of triacsin C and YIC-C8-434, which inhibit synthesis of TAGs and CEs by targeting long-chain acyl-CoA synthetase and acyl-CoA:cholesterol acyltransferase, respectively. Our results present high resolution data on the acylglycerol and cholesterol ester species that were affected by the compounds. Moreover, triacsin C, which blocks both triglyceride and cholesterol ester synthesis, cleared most of the lipid droplets in cells. By contrast, YIC-C8-434, which only abrogates production of cholesterol esters, induced an increase in size of droplets. Although both compounds slightly reduced viral RNA synthesis, they significantly impaired assembly of infectious virions in infected cells. In the case of triacsin C, reduced stability of the viral core protein, which forms the virion nucleocapsid and is targeted to the surface of lipid droplets, correlated with lower virion assembly. In addition, the virus particles that were released from cells had reduced specific infectivity. YIC-C8-434 did not alter the association of core with lipid droplets but appeared to decrease production of infectious virus particles, suggesting a block in virion assembly. Thus, the compounds have antiviral properties, indicating that targeting synthesis of lipids stored in lipid droplets might be an option for therapeutic intervention in treating chronic hepatitis C virus infection.     

Wild Animal Mycobacterial Isolates

Thirteen strains of mycobacteria isolated from deer and various species of wild birds were analysed by gas chromatography (GG) for cellular fatty acids and by thin-layer chromatography (TLG) for polar lipids. These strains were compared to reference strains of Mycobacterium avium, M. para tuberculosis and M. mal-moense. All the examined strains exhibited a generally similar fatty acid pattern characterized by relatively large amounts of hexadenca-noate (16:0), octadecenoate (18:1), octadecanoate (18:0) and 10-me-thyl-octadecanoate (tuberculostearic acid, 10-Me-18:0). Several additional acids were also generally present but in smaller amounts. By means of small but distinct differences in fatty acid composition, the wild animal isolates could be distinguished from both M. paratuber-culosis and M. malmoense but not from M. avium. The TLG polar lipid patterns on the other hand separated the wild animal isolates into 2 distinct groups of complex and simple polar lipid composition which corresponded to the morphologically smooth and rough types, respectively. The complex patterns of the smooth strains were comparable to those of the M. avium serovars whereas both the rough wild animal isolates and all the M. paratuber-culosis strains showed a simple pattern of polar lipids. Both fatty acid profiles and TLG polar lipid patterns support allocation of the wild animal isolates to the MAIS complex. Moreover, the 2 chemical techniques, particularly the GC procedure, are very useful for a more rapid and precise identification of the slow-growing wild animal mycobacterial isolates which have hitherto been characterized on basis of vague criteria.     

Production of VLDL and vitellogenin(s) in oestrogen-challenged hypothyroid chickens

Compared with normal control birds of the same breed, obese strain (OS) White Leghorn chickens, exhibiting classical symptoms of hypothyroidism, were generally half as responsive to an oestrogen challenge in terms of synthesis of VLDL and vitellogenins, despite having livers which were, on the average, twice as large. Even the few OS birds which were laying eggs and therefore enjoying a degree of thyroid function, failed to exhibit normal responses to hyperdynamic doses of oestrogens. However, simultaneous injections of triiodothyronine (T3), in the physiological range, and hyperdynamic doses of oestrogenic substances (Ayerst Co., mainly oestrone) into OS chickens resulted in serum levels of VLDL and vitellogenins which were more than double those achieved without thyroid hormone treatment. Untreated OS birds were found typically to exhibit a unique hyperlipaemia (i.e. increased synthesis of serum triglyceride and phospholipid without corresponding increases in synthesis of apoprotein B (normally associated with VLDL and LDL) or apoprotein A-1 (normally associated with HDL). This type of hyperlipaemia resulted in formation of large lipid micelles which imparted turbidity to the serum. Injection of oestrogenic substances into two OS chickens especially hyperlipaemic in this unique fashion resulted in rapid liver production of apoprotein B. By 2 days post injection the levels of apoprotein B in the sera were increased fifteen times over original levels. The initially turbid sera were completely cleared by 36 h post oestrogen treatment. Since the VLDL present during the first 2 days floated at faster rates than those present at 6 days following injection of oestrogen, it appears that newly synthesized apoprotein B (very likely as lipoprotein B) can combine with existing lipid micelles in the plasma, thus ultimately dispersing the larger lipid micelles into lipoproteins of a size consistent with the loss of turbidity.     

Nature and distribution of feline sarcoma virus nucleotide sequences.

The genomes of three independent isolates of feline sarcoma virus (FeSV) were compared by molecular hybridization techniques. Using complementary DNAs prepared from two strains, SM- and ST-FeSV, common complementary DNA'S were selected by sequential hybridization to FeSV and feline leukemia virus RNAs. These DNAs were shown to be highly related among the three independent sarcoma virus isolates. FeSV-specific complementary DNAs were prepared by selection for hybridization by the homologous FeSV RNA and against hybridization by fline leukemia virus RNA. Sarcoma virus-specific sequences of SM-FeSV were shown to differ from those of either ST- or GA-FeSV strains, whereas ST-FeSV-specific DNA shared extensive sequence homology with GA-FeSV. By molecular hybridization, each set of FeSV-specific sequences was demonstrated to be present in normal cat cellular DNA in approximately one copy per haploid genome and was conserved throughout Felidae. In contrast, FeSV-common sequences were present in multiple DNA copies and were found only in Mediterranean cats. The present results are consistent with the concept that each FeSV strain has arisen by a mechanism involving recombination between feline leukemia virus and cat cellular DNA sequences, the latter represented within the cat genome in a manner analogous to that of a cellular gene.     

Apolipoprotein A-I synthesis in rat small intestine: regulation by dietary triglyceride and biliary lipid

Techniques were developed to provide direct quantitation of apolipoprotein A-I (apoA-I) synthesis rates in rat small intestine. Following intralumenal administration of a pulse of [3H]leucine, newly synthesized enterocyte apoA-I was quantitated by specific immunoprecipitation and compared to [3H]leucine incorporation into total trichloroacetic acid-precipitable protein. ApoA-I synthesis rates (% total protein) were found to be significantly higher in jejunal enterocytes (1.84 +/- 0.20) compared to ileal enterocytes (0.91 +/- 0.25) from the same, fasting, animals, P less than 0.01. It was found that rats consuming regular (4.5% w/w fat) rodent chow had apoA-I synthesis rates, 30 to 240 min after receiving an intraduodenal bolus of 100 mg of triglyceride, that were indistinguishable from control animals receiving either saline or an isocaloric, but fat-free, enteral preparation. By contrast, animals consuming a fat-free chow for 8 days prior to study had a small but significant response to acute reintroduction of dietary triglyceride. Four hours after 100 mg of triglyceride was administered, jejunal apoA-I synthesis (% total protein) was 1.84 +/- 0.1 compared to 1.37 +/- 0.04 for animals exposed to an isocaloric, fat-free enteral preparation, P less than 0.01. External bile diversion for 48 hr, which effectively removed all lumenal sources of lipid, reduced apoA-I synthesis in jejunal enterocytes but produced no more depression than that found in sham-operated controls infused for 48 hr with dextrosesaline or control animals fasted for 30 hr. By contrast, apoA-I synthesis in ileal enterocytes was reduced significantly by external bile diversion (0.59 +/- 0.20) in comparison to sham-operated controls (1.19 +/- 0.32) P less than 0.01. Continuous infusion of 10 mM Na taurocholate for 48 hr or 10 mM Na taurocholate for 44 hr and 80 mg of micellar lipid for 4 hr produced results similar to those obtained by bile diversion alone (0.56 +/- 0.2 and 0.61 +/- 0.25, respectively) suggesting that bile salt deficiency alone was not responsible for the observed depression in ileal apoA-I synthesis. These results suggest that, under conditions of physiological dietary triglyceride intake, apoA-I synthesis in jejunal enterocytes is not actuely regulated by changes in triglyceride flux. After prolonged dietary triglyceride withdrawal, the reintroduction of fat produces a small, but significant, increase in jejunal apoA-I synthesis. The data further suggest that apoA-I synthesis in jejunal enterocytes is regulated in part by the availability of lumenal lipid, but that the presence of bile does not exert an additional level of control.(ABSTRACT TRUNCATED AT 400 WORDS)     

中国1995～2004年鸡传染性支气管炎病毒地方分离株膜蛋白基因的遗传变异分析

应用RT-PCR方法扩增到了我国1995～2004年20株IBV现地分离株的膜蛋白(Membrane,M)基因片段.序列测定表明,20株IBV分离株M基因开放阅读框由672～681bp组成,编码由223～226个氨基酸残基组成的多肽.与我国分离株LX4相比,M基因推导氨基酸序列的变异主要发生在2～17位、221～223位,其中4～6位存在氨基酸的插入和缺失,导致IBV毒株间M蛋白糖基化位点的差异.与GenBank中34株IBV参考毒株M蛋白基因推导氨基酸序列进行比较和分析,系统进化关系显示54株IBV毒株分属于5个进化群.我国IBV分离株M基因在进化关系上较为独立,主要分布在第Ⅱ群和第Ⅳ群,其中第Ⅱ群分离株和中国台湾毒株进化关系密切.此外,参考IBV国内分离株S1基因及N基因系统发育进化树的研究结果,并与M基因进行比较,表明我国IBV也存在着基因重组现象,尤其是疫苗毒和流行毒之间的重组.     

Characterization of virulent and avirulent A/chicken/Pennsylvania/83 influenza A viruses: potential role of defective interfering RNAs in nature.

In April 1983, an influenza virus of low virulence appeared in chickens in Pennsylvania. Subsequently, in October 1983, the virus became virulent and caused high mortality in poultry. The causative agent has been identified as an influenza virus of the H5N2 serotype. The hemagglutinin is antigenically closely related to tern/South Africa/61 (H5N3) and the neuraminidase is similar to that from human H2N2 strains (e.g., A/Japan/305/57) and from some avian influenza virus strains (e.g., A/turkey/Mass/66 [H6N2]). Comparison of the genome RNAs of chicken/Penn with other influenza virus isolates by RNA-RNA hybridization indicated that all of the genes of this virus were closely related to those of various other influenza virus isolates from wild birds. Chickens infected with the virulent strain shed high concentrations of virus in their feces (10(7) 50% egg infective dose per g), and the virus was isolated from the albumin and yolk of eggs layed just before death. Virus was also isolated from house flies in chicken houses. Serological and virological studies showed that humans are not susceptible to infection with the virus, but can serve as short-term mechanical carriers. Analysis of the RNA of the viruses isolated in April and October by gel migration and RNA-RNA hybridization suggested that these strains were very closely related. Oligonucleotide mapping of the individual genes of virulent and avirulent strains showed a limited number of changes in the genome RNAs, but no consistent differences between the virulent and avirulent strains that could be correlated with pathogenicity were found. Polyacrylamide gel analysis of the early (avirulent) isolates demonstrated the presence of low-molecular-weight RNA bands which is indicative of defective-interfering particles. These RNAs were not present in the virulent isolates. Experimental infection of chickens with mixtures of the avirulent and virulent strains demonstrated that the avirulent virus interferes with the pathogenicity of the virulent virus. The results suggest that the original avirulent virus was probably derived from influenza viruses from wild birds and that the virulent strain was derived from the avirulent strain by selective adaptation rather than by recombination or the introduction of a new virus into the population. This adaptation may have involved the loss of defective RNAs, as well as mutations, and thus provides a possible model for a role of defective-interfering particles in nature.     

Lipogenesis in Fatty Liver by Amino Acid Imbalance

Lipogenesis in the fatty liver of rat which was induced by feeding an amino acid-irnbalanced diet containing 8% casein supplemented with 0.3% dl-methionine has been investigated by measuring the incorporation of acetate-1-¹⁴C into various lipid fractions during in vitro incubation of liver slices.

In the incorporation of acetate-1-¹⁴C into the total lipid per one g of the slices, no significant difference for the imbalance group was observed. However, the total radioactivity of liver lipid per 100 g of the body and the incorporation into triglyceride in the lipids were significantly higher in the imbalance group than in the control group. Conversion of acetate-1-¹⁴C to CO₂ was not impaired in the imbalance group.

It is evident from these results that the induction of this type of fatty liver is due mainly to the synthesis of triglyceride.     

Evolution of alphaviruses in the eastern equine encephalomyelitis complex.

Evolution of viruses in the eastern equine encephalomyelitis (EEE) complex was studied by analyzing RNA sequences and oligonucleotide fingerprints from isolates representing the North and South American antigenic varieties. By using homologous sequences of Venezuelan equine encephalomyelitis virus as an outgroup, phylogenetic trees revealed three main EEE virus monophyletic groups. A North American variety group included all isolates from North America and the Caribbean. One South American variety group included isolates from the Amazon basin in Brazil and Peru, while the other included strains from Argentina, Guyana, Ecuador, Panama, Trinidad, and Venezuela. No evidence of heterologous recombination was obtained when three separate regions of the EEE virus genome were analyzed independently. Estimates of the overall rate of EEE virus evolution (nucleotide substitution) were 1.6 x 10(-4) substitution per nucleotide per year for the North American group and 4.3 x 10(-4) for the Argentina-Panama South American group. Evolutionary rate estimates for the North American group increased over 10-fold (from about 2 x 10(-5) to 4 x 10(-4)) concurrent with divergence of two monophyletic groups during the early 1970s. The North and South American antigenic varieties diverged roughly 1,000 years ago, while the two main South American groups diverged about 450 years ago. Analysis of multiple strains isolated from an upstate New York transmission focus during the same years suggested that, in certain locations, EEE virus may be relatively isolated for short time periods.     

Estimation of Lipid Reserves in Unstained Living and Dead Nematodes by Image Analysis

During storage, non-feeding stages of entomopathogenic nematodes become visibly more transparent due to depletion of energy reserves. Optical density per unit area (OD per area) of infective juveniles of Steinernerna carpocapsae (All) and two Heterorhabditis isolates (UK211 and HF85) was measured with an image analysis system and compared with neutral lipid levels obtained by Oil Red O staining. Optical density (OD) measurements were compared with triglyceride levels of UK211 and HF85. Good correlations between OD per area and neutral lipids (0.90) and between OD and triglycerides (0.87) were found. Thus, OD reflects lipid levels and can be used as an indicator of lipid reserves in these nematodes. Heat-killing of nematodes had no significant effect on OD measurements, but length increased significantly. Storage in a triethanolamine in formaldehyde solution decreased the OD and OD/area by about 5% to 8%. An additional advantage of the image analysis method described is that repeated measurements can be performed on live nematodes. Key words: entomopathogenic nematode, Heterorhabditis, image analysis, neutral lipid, Oil Red O, optical density, Steinernema, triglyceride.     

Evolution of the H3 influenza virus hemagglutinin from human and nonhuman hosts.

The nucleotide and amino acid sequences of 40 influenza virus hemagglutinin genes of the H3 serotype from mammalian and avian species and 9 genes of the H4 serotype were compared, and their evolutionary relationships were evaluated. From these relationships, the differences in the mutational characteristics of the viral hemagglutinin in different hosts were examined and the RNA sequence changes that occurred during the generation of the progenitor of the 1968 human pandemic strain were examined. Three major lineages were defined: one containing only equine virus isolates; one containing only avian virus isolates; and one containing avian, swine, and human virus isolates. The human pandemic strain of 1968 was derived from an avian virus most similar to those isolated from ducks in Asia, and the transfer of this virus to humans probably occurred in 1965. Since then, the human viruses have diverged from this progenitor, with the accumulation of approximately 7.9 nucleotide and 3.4 amino acid substitutions per year. Reconstruction of the sequence of the hypothetical ancestral strain at the avian-human transition indicated that only 6 amino acids in the mature hemagglutinin molecule were changed during the transition between an avian virus strain and a human pandemic strain. All of these changes are located in regions of the molecule known to affect receptor binding and antigenicity. Unlike the human H3 influenza virus strains, the equine virus isolates have no close relatives in other species and appear to have diverged from the avian viruses much earlier than did the human virus strains. Mutations were estimated to have accumulated in the equine virus lineage at approximately 3.1 nucleotides and 0.8 amino acids per year. Four swine virus isolates in the analysis each appeared to have been introduced into pigs independently, with two derived from human viruses and two from avian viruses. A comparison of the coding and noncoding mutations in the mammalian and avian lineages showed a significantly lower ratio of coding to total nucleotide changes in the avian viruses. Additionally, the avian virus lineages of both the H3 and H4 serotypes, but not the mammalian virus lineages, showed significantly greater conservation of amino acid sequence in the internal branches of the phylogenetic tree than in the terminal branches. The small number of amino acid differences between the avian viruses and the progenitor of the 1968 pandemic strain and the great phenotypic stability of the avian viruses suggest that strains similar to the progenitor strain will continue to circulate in birds and will be available for reintroduction into humans.     

The DGA1 gene determines a second triglyceride synthetic pathway in yeast.

Diacylglycerol esterification provides an excellent target for the pharmacological reduction of triglyceride accumulation in several human disease states. We have used Saccharomyces cerevisiae as a model system to study this critical component of triglyceride synthesis. Recent studies of an oleaginous fungus, Mortierella ramanniana, identified a new family of enzymes with in vitro acyl-CoA:diacylglycerol acyltransferase activity. We show here that DGA1, the sole member of this gene family in yeast, has a physiological role in triglyceride synthesis. Metabolic labeling of DGA1 deletion strains with triglyceride precursors detected significant reductions in triglyceride synthesis. Triglyceride synthesis was virtually abolished in four different growth conditions when DGA1 was deleted in concert with LRO1, an enzyme that esterifies diacylglycerol from a phospholipid acyl donor. The relative contributions of the two enzymes depended on growth conditions. The residual synthesis was lost when ARE2, encoding an acyl-CoA:sterol acyltransferase, was deleted. In vitro microsomal assays verified that DGA1 and ARE2 mediate acyl-CoA:diacylglycerol acyltransferase reactions. Three enzymes can thus account for diacylglycerol esterification in yeast. Yeast strains deficient in both diacylglycerol and sterol esterification showed only a slight growth defect indicating that neutral lipid synthesis is dispensable under common laboratory conditions.     

Antigenic and biochemical characterization of poliovirus type 1 isolates

By the introduction of Sabin oral poliovirus vaccine, the circulation of wild type polioviruses has virtually disappeared in Japan. However, an outbreak of poliomyelitis associated with sporadic transmission of type 1 wild strain occurred in Nagano in 1980. Furthermore, we found that some type 1 wild strains were introduced into Japan from abroad in 1981. In recent surveys, the two poliovirus type 1 isolates which have non-vaccine-like antigenic character were detected in Aichi. Then, an investigation to trace the origin of these strains was performed, by using intratypic serodifferentiation and biochemical techniques. Electrophoretic migration patterns of their structural polypeptides were quite different from the vaccine virus. In the oligonucleotide mapping, however, one of them gave patterns very similar to those of the vaccine virus. We could conclude that one originated most probably from wild strains, and the other was an antigenic variant derived from the vaccine virus. It showed that oligonucleotide mapping was a very useful method for identification of antigenic modified Sabin type 1 derivatives.     

Hepatocellular triglyceride synthesis and transfer to lipid droplets and nascent very low density lipoproteins

The transfer of triglyceride from sites of synthesis in the endoplasmic reticulum to cytoplasmic lipid droplets and nascent VLDL (very low density lipoproteins) in rat liver in vivo has been examined with [3H]glycerol, cell fractionation, and electron microscopy. Rates of mass transfer of newly synthesized triglyceride were estimated from the specific radioactivity of triglyceride present in microsomal membranes and the radioactivity observed in recipient triglyceride pools. Fasting decreased the transfer of triglyceride to nascent VLDL without affecting transfer to lipid droplets. Stimulation of triglyceride synthesis with 2-tetradecylglycidic acid (TDGA) increased transfer of triglyceride to nascent VLDL 5-fold, and to lipid droplets 14-fold, 1 hr after TDGA administration. Triglyceride transfer to nascent VLDL was increased 6-fold, and to lipid droplets 37-fold, above control rates 6 hr following TDGA treatment, indicative of saturation of triglyceride assembly into nascent VLDL and storage of excess triglyceride in lipid droplet reservoirs. These liver triglyceride pools were concurrently expanded and electron microscopy demonstrated more abundant VLDL particles in the endoplasmic reticulum together with a proliferation of lipid droplets in hepatocytes. TDGA progressively decreased hepatic sn-glycerol-3-phosphate in fasting rats while triglyceride synthesis increased, indicating that sn-glycerol-3-phosphate does not limit the rate of triglyceride synthesis in this metabolic state. Results implicate triglyceride transfer from endoplasmic reticulum membranes to nascent VLDL as a regulated determinant of hepatic VLDL assembly and VLDL triglyceride secretion in vivo.     

Membrane fluidity and lipid composition in clinical isolates of Candida albicans isolated from AIDS/HIV patients

In this study, we describe the membrane lipid composition of eight clinical isolates (azole resistant and sensitive strains) of Candida albicans isolated from AIDS/ HIV patients. Interestingly, fluorescence polarization measurements of the clinical isolates displayed enhanced membrane fluidity in fluconazole resistant strains as compared to the sensitive ones. The increase in fluidity was reflected in the change of membrane order, which was considerably decreased (decrease in fluorescence polarization "p" value denotes higher membrane fluidity) in the resistant strains. The ergosterol content in azole susceptible isolates was greater, almost twice as compared to the resistant isolates. However, no significant alteration was observed in phospholipid and fatty acid composition of these isolates. Labeling experiments with fluorescamine dye revealed that the percentage of phosphatidylethanolamine exposed to the membrane's outer leaflet was higher in the resistant strains as compared to the sensitive strains, indicating increased floppase activity of the two major ABC drug efflux pumps, CDR1 and CDR2 possibly due to their overexpression in resistant strains. The results of the present study suggest that changes in the status of membrane lipid phase especially the ergosterol content and increased activity of drug efflux pumps by overexpression ofABC transporters, CDR1 and CDR2 might contribute to fluconazole resistance in C. albicans isolated from AIDS/HIV patients.     

Alfalfa mosaic virus isolates from lucerne in South Australia: biological variability and antigenic similarity

Alfalfa mosaic virus (AMV) was isolated from lucerne (Medicago sativa) plants with a variety of disease symptoms in eight of 13 sites in South Australia indicating that the virus is widespread in the state. The host ranges and symptomatology of the virus isolates varied considerably. Twelve selected local lesion isolates were shown to be distinct when mechanically inoculated to a range of plant species and cultivars. However, agar-gel diffusion and enzyme-linked immunoassay tests with polyclonal antisera prepared against glutaraldehyde-fixed virus preparations of the five most readily distinguishable AMV isolates, failed to reveal significant antigenic differences between the 12 virus isolates. This indicates that serological tests with polyclonal antisera can detect a wide range of AMV variants but would be unlikely to differentiate between strains. The wide host range and variability of AMV precluded the grouping of isolates into strains of the virus.     

汉滩病毒西安分离株84FLi的L片段核苷酸序列测定以及分析

采用逆转录 聚合酶链式反应 (RT PCR) ,分节段扩增汉滩病毒 84FLi株的L基因片段cDNA ,纯化的PCR产物片段直接用于序列测定或克隆入 pND18 T载体中进行测序。结果表明 ,84FLi株的L片段cDNA由 6 5 33个核苷酸组成 ,四种核苷酸的比例分别为A33.39% ,C16 .4 3% ,G2 0 .74 % ,T2 9.4 4 %。GC含量为 37.17% ,AT含量为6 2 .83%。推导出的最大开放读码框架为从 38到 6 4 93,共编码 2 15 1个氨基酸。序列同源性分析表明 ,84FLi株核苷酸与HTN型国际标准毒株 76 118的同源性为 83.7% ,差异性为 18.8% ;而与中国株A9的同源性高达 97.6 % ,差异性仅为 2 .4 %。与SEO型代表Seoul80 39的同源性为 75 .2 % ,6 6 .1%～ 6 6 .5 %。L片段的氨基酸比较分析表明 ,L片段与HTN型间的同源性为 97.5 %～ 98.0 % ,而与SEO型的同源性为 83.5 %～ 85 .5 %。与PUC、TUL、SN和AND等其它型汉滩病毒的同源性仅为 6 8.6 %～ 6 9.6 %。结果表明 84FLi株属于HTN型 ,并与分离自国内的HTN型病毒高度同源     

The viscosity and lipid composition of the plasma membrane of multiple drug resistant and sensitive yeast strains.

Four different plasma membrane preparations were isolated from multiple drug resistant and sensitive isolates of two isogenic groups of Saccharomyces cerevisiae strains: zymolyase ghosts, concanavalin A ghosts, pH 4 nonaggregated vesicles, and sucrose-gradient purified vesicles. The viscosities of these preparations were determined by the use of a fluorescence polarization technique with 1,6-diphenyl-1,3,5-hexatriene. The viscosities of all four membrane preparations within an isogenic set were the same for resistant and sensitive strains. A comparison of the viscosity of zymolyase ghost liposomes showed that zymolyase ghost (glyco) proteins of resistant and sensitive strains had the same effect on viscosity. There was no difference between resistant and sensitive isolates in the mole concentration of the following lipid classes extracted from zymolyase ghosts: phospholipid, sterol, sterol ester, triglyceride, diglyceride, and free fatty acid. The fatty acid distribution of esterified and free fatty acids and the distribution of nine phospholipids was the same in zymolyase ghosts from sensitive and resistant strains. It was concluded that multiple drug resistance does not result from an alteration in plasma membrane viscosity or lipid composition.