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J M Weber

Publications and source records attributed to J M Weber.

At least 145 records · Page 8Linked to original sources
PubMed1988

Nonpermissivity of human peripheral blood lymphocytes to adenovirus type 2 infection.

The capacity of freshly explanted human peripheral blood lymphocytes (PBL) to support the replication of human adenovirus type 2 (Ad2) was investigated. Unlike other types of human cells, PBL were found to be highly nonpermissive. Ad2 adsorbed 30 to 40% of both T and non-T cells. Virus uncoating was very slow and inefficient, resulting in a 40-fold reduction compared with HEp-2 cells. On a population basis, viral DNA synthesis was reduced 460-fold and infectious virus production was reduced 10(6)-fold. Only 0.35% of PBL produced infectious centers, yielding 0.8 PFU per infected cell. Phytohemagglutinin stimulation increased DNA synthesis 23-fold, infectious centers 11-fold, and virus yield 14-fold. We conclude that resting human PBL are highly nonpermissive to Ad2 infection and that phytohemagglutinin can only marginally lift this nonpermissiveness.

Adenoviruses, Human↗
PubMed1988

Identification of the gene coding for the precursor of adenovirus core protein X.

Nucleoprotein complexes extracted from infected cells (J. Weber and L. Philipson, Virology 136:321-327, 1984) or ts1 virions grown at 39 degrees C (J. M. Weber, G. Khitto, and A. R. Bhatti, Can. J. Microbiol. 29:235-241, 1983) contain, in addition to known virion proteins, a polypeptide with a molecular weight of 11,000 (11K polypeptide). We identified the gene for this polypeptide by sequence analysis of the radioactively labeled 11K polypeptide isolated from ts1 virions and comparison of this sequence with the nucleotide sequence of the adenovirus type 2 genome. The 11K polypeptide was encoded by an open reading frame of 80 residues located between nucleotides 17,676 and 17,915 in late transcription region 2 of adenovirus type 2; the initiating methionine residue was removed leaving a 79-residue product. The late transcription region 2 that encoded the 79-residue polypeptide (11K) was arginine rich (21%) and had a predicted molecular weight of 8,715. It was cleaved by the viral endoprotease to give two products which comigrated on sodium dodecyl sulfate-polyacrylamide gels as virion polypeptide X. Our data suggest that additional cleavage of the carboxy-terminal 48-residue fragment generates a 19-amino-acid fragment with the amino acid composition of mu (K. Hosokawa and M. T. Sung, J. Virol. 17:924-934, 1976).

Adenoviridae↗
PubMed1988

Metabolic changes in skeletal muscle and blood of greyhounds during 800-m track sprint.

The aim of this study was to examine some metabolic properties and changes that occur in skeletal muscle and blood of greyhounds after an 800-m sprint. Three prime moving fast-twitch muscles were selected: biceps femoris (BF), gastrocnemius (G), and vastus lateralis (VL). The amount of glycogen utilized during the event was 42.57, 43.86, and 42.73 mumol glucosyl units/g wet wt, respectively. Expressed as a function of race time (48.3 +/- 0.7 s, n = 3), the mean rate of glycogen breakdown was 53.48 +/- 0.5 mumol.g wet wt-1.min-1 during the sprint. This is equivalent to an ATP turnover of 160 mumol.g wet wt-1.min-1, assuming 100% anaerobic conversion to lactate. This represents a conservative estimate, since greyhound muscle is heterogeneous and comprised of a large percentage of fast-twitch oxidative fibers (Armstrong et al., Am. J. Anat. 163: 87-98, 1982). The large decrease in muscle glycogen was accompanied by a 6- to 7-fold increase in muscle lactate from 3.48 +/- 0.13 to 25.42 +/- 3.54 (BF), 2.54 +/- 1.05 to 18.96 +/- 2.60 (G), and 4.57 +/- 0.44 to 30.09 +/- 1.94 mumol.g wet wt (VL), and a fall in muscle pH from 6.88 +/- 0.03 to 6.40 +/- 0.02 (BF), 6.92 +/- 0.02 to 6.56 +/- 0.02 (G), and 6.93 +/- 0.02 to 6.47 +/- 0.01 (VL). Cytosolic phosphorylation potential in BF decreased 10-fold from 11,360 +/- 680 to 1,184 +/- 347, and redox potential decreased 5-fold, indicating a marked reduction in the cytosol at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1988

Resistance to retransformation by adenovirus but not by heterologous oncogenes in an E1-positive transformation revertant cell line may be mediated by a cellular function.

Using an indirect selection method based on drug-resistance, we have previously reported the isolation of flat revertants from adenovirus 2 transformed rat cells. Here, we demonstrate that one of these revertants has suffered a mutation in a cellular effector gene specifically required for the adenovirus-mediated expression of the transformed phenotype. Evidence for this conclusion includes the following: (1) the cells contain a 16-times amplified copy of the E1 region, thus reducing the chances of viral mutations, (2) the cells synthesized E1a and E1b proteins indistinguishable from those of the transformed parent, (3) the mutation has been stable for over 2 years, and most importantly (4) the revertant was resistant to re-transformation by E1 but not by c-myc, N-ras or polyoma middle t oncogenes.

3T3 Cells↗
PubMed1987

Isolation and uptake characteristics of adenovirus transformed cell revertants resistant to the antiproliferative effects of methylglyoxal bis(guanylhydrazone).

Four independent variant cell lines resistant to the toxic action of methylglyoxal bis(guanylhydrazone), an anticancer drug and inhibitor of polyamine synthesis, have been isolated by single step selection from an adenovirus type 2-transformed rat brain cell line. Drug-resistance was accompanied by loss of tumorigenic potential in athymic nude mice. MGBG resistance was attributable to decreased drug uptake.

Adenosylmethionine Decarboxylase↗
PubMed1987

Spontaneous reversion of a C/T transition mutation in the adenovirus endoproteinase gene.

A temperature-sensitive mutation (H2ts1) that abolishes the viral endoproteinase activity at the nonpermissive temperature has been mapped by marker rescue between map coordinates 59.8 and 61.9 on the adenovirus type 2 genome. The mutation has been identified by sequencing to be a C/T transition at coordinate 61.1 changing a proline residue to a leucine residue and eliminating a HaeIII restriction enzyme cleavage site (L. Yeh-Kai, G. Akusjarvi, P. Alestrom, U. Pettersson, M. Tremblay, and J. Weber, 1983, J. Mol. Biol. 167, 217-222). This feature of the mutation offered a convenient assay to distinguish between true revertants and suppressor mutations among phenotypic revertants of H2ts1. Seventeen spontaneous revertants were isolated in three independent experiments by picking plaques at 39 degrees after three passages of H2ts1 at 39 degrees in HEp2 cells. All revertants grew like wild-type virus and regained normal endoproteinase activity. The Ncol fragment encompassing the H2ts1 region was terminally labeled and subcleaved with HaeIII to determine the presence or absence of the HaeIII site at 61.1 for each revertant. All revertants had regained the HaeIII site by true reversion. We conclude that the H2ts1 mutation probably lies in a critical domain of the enzyme and is therefore not suppressible, and that the C/T transition at coordinate 61.1 is the sole cause of the H2ts1 phenotype.

Adenoviruses, Human↗
PubMed1987

Sequence of the protease of human subgroup E adenovirus type 4.

A fragment of DNA containing the protease gene and 3' and 5' flanking regions of human adenovirus type 4 (Ad4) has been cloned and sequenced. The gene is located between 59 and 62 map units and codes for a protein of 201 amino acids with a calculated Mr of 22,758. The Ad4 protease has a 72% amino acid homology with the Ad2 protease, the divergence being concentrated in the middle of the molecule. Comparison with other mammalian and bacterial proteases failed to reveal any significant homology and in particular a putative active site. The adenoviral proteases may therefore represent a novel class of enzymes.

Adenoviruses, Human↗
PubMed1987

Cardiac output and oxygen consumption in exercising Thoroughbred horses.

This study characterizes the effects of exercise on the cardiac output (Q) and the metabolic rate (VO2) of trained Thoroughbred racehorses. Heart rate, Q, and arteriovenous (a-v)O2 difference were measured at rest and at three levels of submaximal treadmill exercise (1.6 m/s walk and 3-4 m/s trot at 6% incline, and 6.5 m/s horizontal canter). Heart rate and (a-v)O2 difference were also measured during maximal exercise (12.5 m/s gallop, 5% incline) to obtain an estimate of maximum O2 uptake (VO2max). The walk, trot, and canter represented 25, 45, and 55% VO2max. Mean heart rate went from 48.9 (rest) to 197 beats/min (gallop). Q ranged from 106 (rest) to 571 ml.min-1.kg-1 (canter), and stroke volume went from 1.34 (rest) to a maximum of 1.58 liters (walk). Thoroughbreds were able to bring hematocrit from 38 (rest) to 63% (gallop), and this adjustment allowed them to reach an impressive (a-v)O2 difference of 23 vol%, which represents a fivefold increase over resting values. These outstanding athletes probably support an aerobic scope of 40-fold.

Animals↗
PubMed1987

Lactate kinetics in exercising Thoroughbred horses: regulation of turnover rate in plasma.

Plasma lactate turnover rate of Thoroughbred racehorses was measured by bolus injection of [U-14C]lactate at rest and two levels of submaximal treadmill exercise (3-4 m/s trot, 6% incline, and 6.5 m/s horizontal canter). Our goals were 1) to determine the relative effects of changes in cardiac output and in plasma lactate concentration on turnover rate [using cardiac output data from Weber et al. (28)] and 2) to assess the importance of lactate as a metabolic fuel in a trained animal athlete. Lactate turnover rates were 9.3 mumol.min-1.kg-1 (rest), 75.9 mumol.min-1.kg-1 at the beginning of the trot protocol [45% maximum O2 uptake (VO2max)], 50.3 mumol.min-1.kg-1 later in the same protocol (50% VO2max), and 66.1 mumol.min-1.kg-1 during the canter protocol (55% VO2max). Both changes in cardiac output and in plasma lactate concentration had a significant effect on turnover rate. Variation in plasma lactate fluxes of Thoroughbreds during exercise follows the standard mammalian pattern, but this substrate only plays a minor role as an oxidizable fuel in horses. The oxidation of plasma lactate accounts for less than 5% of metabolic rate (VO2) during submaximal work. Adjustments in cardiac output and in metabolite concentration represent, respectively, the coarse and fine controls for the regulation of plasma metabolite turnover rate.

Animals↗
PubMed1986

Role of the nuclear matrix in adenovirus maturation.

The nuclear matrix has been implicated in several important cellular processes. In this paper, we investigate the role of the nuclear matrix in adenovirus type 2 assembly. Electron microscopic examination of nuclear matrices isolated from adenovirus infected Hep-2 cells clearly reveals that late in the lytic cycle, adenovirus capsids are intimately associated with the nuclear matrix. SDS-PAGE analysis showed that the viral core polypeptides V, PVII and 11 kDa were enriched in the nuclear matrix fraction. After a 3 h chase period a constant high ratio of PVII to VII prevailed in the nuclear matrix suggesting that mostly young virions and viral cores are bound to this structure. Most of the virus maturation endoproteinase activity co-purified with the nuclear matrix and the data suggest that the enzyme may be released from fragile young virions or assembly intermediates. Together these experiments suggest that the nuclear matrix is the site of adenovirus assembly and that mature virions may be released from the matrix by the viral endoproteinase.

Adenoviruses, Human↗
PubMed1986

Mammalian metabolite flux rates in a teleost: lactate and glucose turnover in tuna.

Lactate and glucose turnover rates were measured by bolus injection of [U-14C]lactate and [6-3H]glucose in cannulated lightly anesthetized skipjack tuna, Katsuwonus pelamis. Our goals were to find out whether the high rates of lactate clearance reported during recovery from burst swimming in tuna could be accounted for by high blood lactate fluxes; to extend the observed correlation between lactate turnover and lactate concentration in mammals to a nonmammalian system, and to assess the importance of lactate and glucose as metabolic fuels in tuna and to compare their flux rates with values reported for mammals. Measured lactate turnover rates ranged from 112 to 431 mumol X min-1 X kg-1 and were correlated with blood lactate concentration. Glucose turnover rate averaged 15.3 mumol X min-1 X kg-1. When correcting for body mass and temperature, skipjack tuna has at least as high or even higher lactate turnover rates than those recorded for mammals. Tuna glucose turnover rate is similar to that of mammals but much higher than levels found in other teleosts. Even the highest lactate turnover rate measured in tuna cannot fully account for the rate of blood lactate clearance observed during recovery, suggesting that some of the lactate produced in skeletal muscle must be metabolized in situ. After injection of [U-14C]lactate, less than 5% of the total blood activity was recovered in glucose, suggesting that the Cori cycle is not an important pathway of lactate metabolism in tuna.

Analysis of Variance↗
PubMed1985

Adenovirus DNA synthesis is coupled to virus assembly.

The relationship between viral DNA synthesis and virion assembly was studied in adenovirus type 2 infected HEp2 cells. When cells were infected at the restrictive temperature with ts3, an assembly-negative mutant which permits normal viral DNA and protein synthesis, labeled and shifted to the permissive temperature, only de novo synthesized nonradioactive viral DNA was encapsidated. This suggested that only concurrently synthesized DNA is encapsidated. Blocking protein or DNA synthesis with cycloheximide or hydroxyurea after the temperature shift inhibited virus assembly. Therefore efficient virus assembly requires both concurrent protein and DNA synthesis. When DNA synthesis was arrested by shifting ts125 infected cells to the restrictive temperature, protein synthesis continued but assembly was completely blocked. Sucrose gradient sedimentation analysis of nuclear extracts of wt and ts3 infected cells provided evidence in support of a physical coupling between replication complexes and virus assembly complexes. Further evidence of coupling was also shown by preferential pulse labeling of the molecular right end of the genome isolated from reversibly cross-linked assembly intermediate particles. While DNA replication is not dependent on concurrent virion assembly, at least some significant proportion of replication complexes appear to be coupled to and are prerequisite for virion assembly.

Adenoviruses, Human↗
PubMed1985

The structure of adenovirus chromatin in infected cells.

The structure of adenovirus chromatin in infected cells was studied by micrococcal nuclease digestion and hybridization with virus-specific probes. In the early phase of infection (5 h) a significant proportion of viral molecules was organized like actively transcribed cellular chromatin. As expected for a transcriptionally active population of molecules, even at high multiplicity of infection the nucleosomal repeating pattern was less distinct than in a transformed cell which contained the corresponding but less active genomic region. The observed repeating pattern in infected cells was unlikely to be due to integrated molecules since less than 0.07% of input genomes became associated with cellular DNA. After the onset of viral DNA replication, the pool of viral chromatin organized like cellular chromatin rapidly increased. In addition, newly replicated molecules also maintained the cellular chromatin-like organization as measured by [3H]thymidine incorporation after the cessation of cellular DNA synthesis. These data suggest that newly replicated viral molecules are organized by histones into cell-like chromatin throughout the infection cycle. Coincident with the peak of viral DNA and core protein synthesis, and the decline of histone synthesis, the late, core-like non-repeating viral chromatin became dominant, increasingly obscuring the underlying repeating pattern. Experiments suggest that this late chromatin is destined for encapsidation, that the early chromatin persists and that viral core proteins do not displace histones on viral DNA. A model is proposed suggesting that transcription and type I replication occur on histone-condensed templates, while type II replication products late in infection are condensed by core proteins and are destined for encapsidation.

Adenoviruses, Human↗
PubMed1985

Genetic analysis of erythromycin production in Streptomyces erythreus.

Streptomyces erythreus produces the 14-membered macrolide antibiotic erythromycin A. The properties of erythromycin A nonproducing mutants and their genetic linkage to chromosomal markers were used to establish the rudiments of genetic organization of antibiotic production. Thirty-three Ery- mutants, produced by mutagenesis of S. erythreus NRRL 2338 and affecting the formation of the macrolactone and deoxysugar intermediates of erythromycin A biosynthesis, were classified into four phenotypically different groups based on their cosynthesis behavior, the type of biosynthetic intermediate accumulated, and their ability to biotransform known biochemical intermediates of erythromycin A. Demonstration of the occurrence of natural genetic recombination during conjugal mating in S. erythreus enabled comparison of the genetic linkage relationships of three different ery mutations with seven other markers on a simple chromosome map. This established a chromosomal location for the ery mutations, which appear to be located in at least two positions within one interval of the map.

Chromosome Mapping↗
PubMed1985

Comparison of measles antihemolysin test, enzyme-linked immunosorbent assay, and hemagglutination inhibition test with neutralization test for determination of immune status.

Sera were collected from 238 high-school students in Prince Edward Island for the determination of immune status before an anticipated measles outbreak. In addition, history of vaccination status and measles infection was obtained. In the subsequent outbreak, 28 students did contract measles. Specificity for hemagglutination inhibition (HI), antihemolysin (AH), and enzyme-linked immunosorbent assay (ELISA) was 100%, compared with the neutralization test. Corresponding sensitivity values for the tests were 66.0% (HI), 99.5% (AH), and 99.0% (ELISA). Predictive values for susceptibility were 26.9% (HI), 77.8% (AH), 75.7% (ELISA), 80% (neutralization), and 41.4% as determined by history of infection or vaccination. The predictive value for immunity as determined by history of previous infection or vaccination was 91.8%, compared with 100% for the four serological tests. No false-positive results were seen with any of these tests. Compared with the neutralization test, the HI test had 69 false-negative results, the AH had 1, and the ELISA test had 2. The AH and ELISA tests provided sensitive and specific alternatives to the commonly used HI test for immune status determination.

Adolescent↗