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Biomedical subjects

A Friedmann

Publications and source records attributed to A Friedmann.

At least 91 records · Page 5Linked to original sources
PubMed1982

Extraction of cell-associated varicella-zoster virus DNA with triton X-100-NaCl.

Varicella-zoster virus (VZV) DNA was extracted from infected cells with 0.25% Triton X-100-0.2 M NaCl and purified by isopycnic centrifugation in CsCl. In each of eight experiments, 1.8-9.8 micrograms VZV DNA was obtained from 107 infected cells. The VZV DNA obtained by this procedure had a molecular weight of 88-100 x 106 as determined by sucrose gradient sedimentation and electron microscopy, and cleavage patterns after digestion with four restriction enzymes that corresponded to patterns previously described with six strains of VZV; the pattern of BamHI-cleaved Triton-NaCl-extracted VZV DNA was identical to the pattern seen after DNA extraction from virions. These studies expand the usefulness of Triton X-100-NaCl for extraction of large molecular weight viral DNA from a system where considerable cell-free virus is produced (Pignatti et al., 1979, Virology 93, 260) to a system known for its marked cell association.

Animals↗
PubMed1982

[Acute viral encephalitis with primary psychotic symptoms--diagnosis, course and prognosis].

In 13 cases referred to psychiatric treatment between 1974 and 1980 acute viral encephalitis was diagnosed in the further course of the illness. The majority were female patients. Positive virological or pathological evidence was obtained in 38% of all cases. The most frequent etiology to be found was the herpes-simplex virus. These findings correspond to 36 cases from the literature. 90% of all cases showed neurological symptoms within two weeks of hospital admission. EEG and cerebrospinal fluid examinations proved to yield most in diagnosis, whereas angiography and brain scanning did not have special diagnostic importance. The present diagnostic value of CT is mainly restricted to the detection of herpes-simplex virus encephalitis and acute leukoencephalitis. Initially psychopathological findings varied largely and fluctuations in the level of consciousness were a prominent feature in most cases. In others no difference to schizophrenic psychosis could be noted on admission. Compared to other studies on acute viral encephalitis with initial neurological symptoms, patients with a psychotic onset of the illness tend to have a higher morbidity, while the mortality remains the same.

Acute Disease↗
PubMed1982

The internal organization of the varicella-zoster virus genome.

DNA was extracted from varicella-zoster (VZ) virions prepared in sucrose gradients. Thirty-eight molecules examined by electron microscopy were found to have a mean length of 46.7 micrometers. Examination of self-annealed VZV DNA molecules revealed that the virus genome was composed of a unique linear large sequence with a mol. wt. of 74.4 X 10(6) to 78.4 X 10(6), and a unique short sequence of mol. wt. approx. 9.8 X 10(6) flanked by inverted repeat sequences of 4.7 X 10(6) mol. wt.

Base Sequence↗
PubMed1981

Elevated recombination and pairing structures during meiotic arrest in yeast of the nuclear division mutant cdc5.

A diploid strain of yeast, homozygous for the mutation cdc5-1, undergoes a normal meiosis at 25 degrees C. At the nonpermissive temperature of 34 degrees C, meiosis is arrested at the first meiotic division, after premeiotic DNA replication and recombination commitment have taken place. Haploidisation commitment does not occur at 34 degrees C. Electron microscopy reveals that synaptons (synaptonemal complexes) are formed and the stage of arrest is characterised by a prevalence of "modified synaptons", which consist of paired lateral elements lacking the central elements. Prolonged incubation at this stage of arrest results in unusually high recombination levels, perhaps related to the synaptonal structures observed. Temperature shift-up experiments (transfers of cell from 25 degrees C to 34 degrees C at various times during meiosis) reveal that the CDC5 function is required for both the first and the second divisions of meiosis.

Hot Temperature↗
PubMed1981

Extracellular protein release and its response to pH level in Saccharomyces cerevisiae.

Saccharomyces cerevisiae grown in batch culture at pH 5.5 releases 0.1 to 0.2 pg protein per cell to the external medium over a period of four to five days, final concentration 20-40 micrograms/ml. Cells grown at pH 3.0 release 10-fold this quantity (1-2 pg/cell, final concentration 100-200 micrograms/ml). A kinetic model based on published behavior of periplasmic protein gave a good fit to the observed kinetics of exoprotein yield. The electrophoretic pattern of exoprotein differed from that of cell lysate protein, and exoprotein synthesis was apparently limited to early stages of the life cycle. These results are consistent with the identification of exoprotein as periplasmic protein released to the external medium through the cell wall. Analysis of the observed kinetics of exoprotein yield, utilizing the kinetic model suggests that the greater exoprotein production of cells grown at pH 3.0 was due entirely to greater synthesis of periplasmic proteins while the fraction of periplasmic protein released per unit time was greater for cells grown at pH 5.5. The latter conclusion is supported by thicker cell walls of cells grown at pH 3.0 as observed by electron microscopy. At an applied level the apparent limitation of exoprotein synthesis to the first few hours of cell life, the slow leakage of exoprotein through the cell wall, and the dilute nature of a yeast suspension do not favor the utilization of yeast cells for direct conversion of substrate into protein released to the external medium.

Cell Wall↗
PubMed1981

Theiler's murine encephalomyelitis virus group includes two distinct genetic subgroups that differ pathologically and biologically.

The intracellular development and RNA composition of Theiler's murine encephalomyelitis virus (TMEV) isolates were determined by electron microscopy, sucrose gradient centrifugation, and RNase T1 fingerprinting. Replication of FA virus, a virulent strain of TMEV, was characterized by the appearance of viral crystalline arrays in the cytoplasm of infected cells. In contrast, cells infected with the less virulent isolates (WW, TO4, BeAn 8386, and Yale) showed no crystalline arrays; instead, virions were found to be arranged between two layers of membranes in the cytoplasm of infected cells. Analysis of the RNAs of TMEV isolates showed that the RNAs were single-stranded molecules having sedimentation coefficients of 35S. RNase T1 fingerprinting of TMEV RNA revealed that striking differences between the virulent and less virulent TMEV isolates existed. Moreover, base composition analysis of RNase T1-resistant oligonucleotides of two TMEV isolates which represented the two subgroups indicated that there were no substantial oligonucleotides common to both subgroups. Based on these findings and the known difference in virulence, we suggest that the TMEV group contains two genetically district subgroups of viruses.

Animals↗
PubMed1980

Purification of Theiler's murine encephalomyelitis virus and analysis of the structural virion polypeptides: correlation of the polypeptide profile with virulence.

Theiler's murine encephalomyelitis viruses (TMEV) are separable into two groups based on their biological behavior: those highly virulent isolates which are unable to cause persistent infection and the less virulent isolates which regularly produce persistent central nervous system infection in mice. Two highly virulent and five less virulent TMEV were found to have the same buoyant density (1.34 g/ml) on isopycnic centrifugation and virion structure by electron microscopy. Negatively stained virus particles purified in Cs(2)SO(4) gradients appeared to have icosahedral symmetry and measured 28 nm in diameter. Mature virions were found to possess three major structural polypeptides, VP1, VP2 and VP3, in the range of 25,000 to 35,000 daltons, and a smaller fourth major polypeptide, VP4, of 6,000 daltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The precursor of VP2 and VP4, VP0, which is a minor polypeptide of mature picornavirus particles, was also identified. However, a slight but consistent difference in several of the capsid polypeptides between the highly virulent and less virulent TMEV was found. VP1 was slightly larger (34,000 versus 33,500 daltons) and VP2 was slightly smaller (31,000 versus 32,000 daltons) for the highly virulent strains compared to the same polypeptide species in the less virulent viruses. VP0 was also slightly smaller (35,500 versus 36,000 daltons) for the highly virulent isolates compared to their less virulent counterparts. Finally, trypsin which was used initially in our purification procedure resulted in preferential cleavage of a 2,000-molecular-weight fragment or fragments from VP1 of only the less virulent isolates.

Centrifugation, Density Gradient↗
PubMed1979

Morphogenesis of the synapton during yeast meiosis.

The formation of the synapton (synaptonemal complex) was followed by an electron microscopic examination of large samples of Saccharomyces cerevisiae cells at various stages of meiosis. Three temperature-sensitive mutants were used, cdc4, cdc5 and cdc7, which undergo a slow but normal meiosis at 25 degrees C. At the restrictive temperature of 34 degrees C, cdc4 and cdc5 arrest at an advanced enough stage of meiosis to allow the study of synapton morphogenesis. Based on the frequencies of nuclear structures, we describe the formation of the central region and central elements of the synapton in the dense body, which may be part of the nucleolus. This process occurs during early meiotic stages, concomittantly with recombination commitment and premeiotic DNA replication. Mature synaptons usually appear after premeiotic S, at the pachytene stage, and later disappear. A possible intermediate stage in this disappearance is found in arrested cdc5 cells, which contain paired lateral elements without central elements. Following the frequencies of spindle plaque configurations, we conclude that the plaques in meiosis duplicate once at the beginning of the main DNA replication, as is also observed prior to mitosis. In contrast to mitotic cells, however, meiotic plaques remain duplicated for a long period, until the synaptons disappear, and only then separate from each other to form a spindle. During late stages of the first meiotic division, the outer plates of the spindle plaques thicken, to duplicate later and give the second division spindles. The characteristically thick outer plate may have a role in the formations of the ascopore wall.

Meiosis↗
PubMed1979

Retrovirus-like particles in EBV-negative Burkitt's lymphoma cell line but not in EBV-DNA-positive lines from patients with ataxia telangiectasia and Down's syndrome.

Retrovirus-like particles can be recovered by arginine deprivation from the BJAB-1 Epstein-Barr virus (EBV) negative cell line derived from an African patient with typical Burkitt's lymphoma. These particles resemble retroviruses in their morphology and in their physicochemical properties. Particles with a similar morphology were obtained from derivative cell lines established by infecting BJAB-1 cells with EBV. On the other hand, retrovirus-like particles could not be induced in EBV-DNA-positive lymphoblastoid cell lines derived from non-leukaemic patients with ataxia telangiectasia and Down's syndrome and from a patient with infectious mononucleosis.

Ataxia Telangiectasia↗
PubMed1979

Q beta-defective particles produced in a streptomycin-resistant Escherichia coli mutant.

This paper describes Q beta noninfectious particles produced at 41 degrees C in a streptomycin-resistant Escherichia coli mutant which is temperature sensitive for suppression of a nonsense codon. The noninfectious particles resembled Q beta under the electron microscope and contained coat protein molecules in an amount similar to the amount in Q beta. However, they did not adsorb to F-piliated bacteria, and they were deficient in both minor capsid proteins of Q beta, maturation (IIa) and read-through (IIb). Proteins IIa and IIb were not produced in Qbeta-infected mutant cells at 41 degrees C. In addition, instead of the 30S RNA of Q beta, a shorter RNA, which sedimented mainly at 23 S, was found in the defective particles. The results are discussed in relation to the roles of proteins IIa and IIb of Q beta.

Adsorption↗
PubMed1978

Defective herpes simplex virus DNA: circular and circular-linear molecules resembling rolling circles.

The formation of defective herpes simplex virus (HSV) in BSC-1 cells and the synthesis of defective virus DNA was studied. The fourth consecutive passage of undiluted virus yielded defective DNA that was 0.008 g/ml more dense than wild type (w.t.) virus DNA. The amount of defective DNA increased at passage 6 concomitantly with the decrease in infectious virus progeny. The synthesis of defective DNA was always accompanied by w.t. virus DNA synthesis. Defective DNA from both infected nuclei and defective virions had a mol. wt. of 100 X 10(6) and was linear as determined by electron microscopy. Electron microscopy of defective virus DNA at passage 6 revealed circular molecules varying in size in addition to linear DNA molecules with the length of intact virion DNA. The circular DNA molecules had contour lengths of 10, 5, 2.5 and less than 2.5 micron. The smallest circular DNA molecules had a contour length of 0.3 micron, possibly one virus gene. In addition, circular-linear DNA molecules were observed in which both the circular and the linear components varied in length. Most of these DNA molecules had circular components of either 2.5 or 5.0 micron, and linear components varying in length from less than 1 to 50 micron. Based on the present study, it is proposed that the S component of w.t. virus DNA is fragmented into small circular molecules that serve as templates for DNA synthesis, possibly by the rolling circle mechanism.

Cell Line↗
PubMed1978

Annealing of alkali-resistant HSV DNA strands and isolation of S and L components.

DNA isolated from highly purified virions of herpes simplex virus type-1 (HF strain) was denatured by centrifugation in alkaline sucrose gradients. DNA molecules corresponding to intact single-stranded virion DNA (50 x 10(6) daltons) were isolated and adjusted to neutral pH. The DNA was annealed under conditions permitting reassociation of intact single-stranded molecules and studied by electron microscopy. Three classes of DNA molecules showing double-stranded sequences were observed: (a) fully double-stranded DNA molecules the size of the intact HSV DNA genome, namely 52 micron; (b) DNA hybrids with a region of partial double-strandedness ranging from 5 to 12 micron, plus long single strands; and (c) DNA hybrids with a double-stranded region of 32--40 micron, plus short single strands. (These results suggest that the alkali-resistant single-stranded HSV DNA molecules are composed of several subclasses that permit annealing of either the total genome or the S or L components.) The 5 micron double-stranded region probably constitutes the S component of HSV DNA and the sequences longer than 5 micron and shorter than 12 micron represent annealing of the repeat sequences on either or both sides of the S component. The double-stranded sequences with a length of 32--40 micron may represent the L component. Treatment of the annealed, partially double-stranded hybrid DNA molecules with S1 endonuclease to remove the single-stranded termini and centrifugation in neutral sucrose gradients yielded two distinct peaks. Centrifugation of fractions from the two peaks in caesium chloride density gradients showed that the small DNA component (possibly the S and the repeat sequences) had a higher buoyant density and the longer (possibly the L) DNA component had a lower density than the HSV DNA marker. Annealing of alkali-resistant viral DNA strands therefore provides a means of isolating the L, S and repeat sequence regions of HSV DNA.

Base Sequence↗
PubMed1977

Studies on the biological role of DNA methylation: III Role in excision of one-genome long single-stranded phi X 174 DNA.

Accumulation of replicative intermediates of the bacteriophage phi X174 was observed in E. coli C infected cells when phage DNA methylation has been inhibited by nicotinamide or when cells were infected with a temperature-sensitive mutant in gene A. Analysis of the accumulating replicative intermediates by electron microscopy revealed that these molecules are composed of double-stranded DNA rings with multiple-genome length single-stranded "tails". These results suggest that the single 5-methylcytosine residue present in the phage DNA serves as a recognition site for the gene A protein mediating the excision of one-genome long phage DNA. This excision process is oligatory for the final maturation of the phage.

Coliphages↗
PubMed1977

Electron microscopy of herpes simplex virus DNA molecules isolated from infected cells by centrifugation in CsCl density gradients.

Herpes simplex virus (HSV) DNA molecules were isolated from infected BSC 1 cells and centrifuged in CsCl-ethidium bromide density gradients. Both newly labelled and mature virus DNA molecules were found to have a linear conformation. The morphology of virus DNA molecules at different stages of the virus growth cycle in BSC 1 cells, was studied by electron microscopy after separation of virus DNA from cellular DNA by centrifugation in CsCl gradients. In each sample, about 200 virus DNA molecules were photographed and the different morphological forms were studied. Four classes of virus DNA molecules were observed: (a) mature linear DNA molecules, 52-4 +/- 3-3 micronm in length, (b) DNA intermediates, (c) virus DNA molecules having one or more single-stranded filaments attached to them and (d) molecules with collapsed regions or with branches. A few circular molecules as well as linear DNA molecules longer than unit length were also observed. The virus DNA molecules resembling replicative intermediates gradually increased in number and reached a maximal amount of about 5% of the virus DNA population at 12 h after infection. The other forms of virus DNA were found to persist after the number of replicating DNA molecules decreased.

Cell Line↗
PubMed1977

Circular and circular-linear DNA molecules of herpes simplex virus.

Circular and circular-linear DNA molecules of herpes simplex virus were isolated from infected cells. Two types of circular-linear DNA molecules are described, one with a circular component of about 8 micrometer and a linear component of 45 micrometer and the other with a circular component of 45 micrometer and a linear component of 8 micrometer. The circular DNA molecules were either the size of linear DNA molecules or were shorter and corresponded to the length of the L (long) component of linear virus DNA.

DNA, Circular↗