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Biomedical subjects

M A Morgan

Publications and source records attributed to M A Morgan.

At least 145 records · Page 8Linked to original sources
PubMed1984

Degradation of the gamma-Carboxyl-Containing Diarylpropane Lignin Model Compound 3-(4'-Ethoxy-3'-Methoxyphenyl)-2-(4''-Methoxyphenyl)Propionic Acid by the Basidiomycete Phanerochaete chrysosporium.

The white-rot basidiomycete Phanerochaete chrysosporium metabolized 3-(4'-ethoxy-3'-methoxyphenyl)-2-(4''-methoxyphenyl)propionic acid (V) in low-nitrogen, stationary cultures, conditions under which ligninolytic activity is expressed. The ability of several fungal mutant strains to degrade V reflected their ability to degrade [C]lignin to CO(2). 1-(4'-Ethoxy-3'-methoxyphenyl)-2-(4''-methoxyphenyl)-2- hydroxyethane (VII), anisyl alcohol, and 4-ethoxy-3-methoxybenzyl alcohol were isolated as metabolic products, indicating an initial oxidative decarboxylation of V, followed by alpha, beta cleavage of the intermediate (VII). Exogenously added VII was rapidly converted to anisyl alcohol and 4-ethoxy-3-methoxybenzyl alcohol. When the degradation of V was carried out under O(2), O was incorporated into the beta position of the diarylethane product (VII), indicating that the reaction is oxygenative.

Journal Article↗
PubMed1984

Evaluation of an enzyme-linked immunosorbent assay for the detection of herpes simplex virus antigen.

An enzyme-linked immunosorbent assay (ELISA) kit for herpes simplex virus developed by Ortho Diagnostic Systems, Inc., was evaluated. In phase I experiments, 263 clinical specimens from genital lesions were extracted into serum-free medium and then tested by ELISA for herpes simplex virus antigen. The results were compared with those obtained by conventional viral culture. Of 83 specimens, 65 were positive by ELISA (sensitivity, 78.3%). In phase II experiments, 249 clinical specimens were tested for herpes simplex virus antigen in direct specimen and in cell cultures (MRC-5 and rabbit kidney) incubated for 2, 4, and 7 days. Of 63 specimens, 40 were positive by ELISA in the direct specimen (sensitivity, 63.5%), and by 7 days incubation, 100% of the cultures positive by viral cell culture were also positive by ELISA. The ELISA was reproducible, and when both the direct detection and amplification culture were used, the sensitivity of ELISA paralleled the diagnosis of herpes simplex virus infections by viral cytopathic effect.

Antigens, Viral↗
PubMed1984

Candida pseudotropicalis fungemia and invasive disease in an immunocompromised patient.

A case of Candida pseudotropicalis fungemia and invasive disease in an immunocompromised patient is reported. Multiple blood cultures taken over a 2-week period were positive, and histopathological slides of postmortem spleen and kidney tissue showed tissue invasion by the organism. The source of the yeast infection was determined to be the urinary tract. This is the first report of C. pseudotropicalis fungemia documented by culture.

Candida↗
PubMed1983

Binding of inosine-substituted mRNA to reticulocyte ribosomes and eukaryotic initiation factors 4A and 4B requires ATP.

We examined the hypothesis that initiation of eukaryotic protein synthesis involves ATP-dependent melting of 5'-cap-proximal secondary structure in mRNA by eukaryotic initiation factors 4A and 4B. In reticulocyte lysate depleted of ribonucleoside triphosphates by pretreatment with hexokinase/glucose, initiation complex formation by native reovirus mRNA showed a strict requirement for ATP. The corresponding mRNA synthesized with ITP in place of GTP to minimize secondary structure also required ATP for binding to 40 S ribosomal subunits in complexes characteristic of initiation. In a partial reaction without ribosomes, purified eukaryotic initiation factors 4A and 4B bound and cross-linked to the capped 5'-end of oxidized mRNA. This interaction was ATP-dependent with inosine-substituted or bromouridine-containing reovirus RNAs as observed previously with native mRNA. The results indicate that if initiation involves ATP-dependent denaturation of mRNA, the effect must occur after initiation factor-mediated attachment of mRNA to the 40 S ribosomal subunit.

Adenosine Triphosphate↗
PubMed1983

An extracellular H2O2-requiring enzyme preparation involved in lignin biodegradation by the white rot basidiomycete Phanerochaete chrysosporium.

An H2O2-requiring enzyme system was found in the extracellular medium of ligninolytic cultures of Phanerochaete chrysosporium. The enzyme system generated ethylene from 2-keto-4-thiomethyl butyric acid (KTBA), and oxidized a variety of lignin model compounds including the diarylpropane 1-(4'-ethoxy-3'-methoxyphenyl) 1,3-dihydroxy-2-(4"-methoxyphenyl)propane (I), a beta-ether dimer 1-(4'-ethoxy-3'-methoxyphenyl)glycerol-beta-guaiacyl ether (IV) and an olefin 1-(4'-ethoxy-3'-methoxyphenyl)1,2-propene (VI). The products found were equivalent to the metabolic products previously isolated from intact ligninolytic cultures. In addition, the enzyme system partially degraded 14C-ring labeled lignin. The enzyme was not found in high nitrogen (N) cultures, nor in cultures of a ligninolytic mutant strain which is incapable of metabolizing lignin.

Basidiomycota↗
PubMed1983

Complete amino acid sequence of the nucleic acid-binding protein of bovine leukemia virus.

The complete amino acid sequence of the nucleic acid-binding protein p12 of bovine leukemia virus (BLV) has been determined. Peptides were generated by enzymatic digestion and formic acid cleavage, purified by reversed-phase liquid chromatography and subjected to automated Edman degradation. BLV p12 is a proline-rich linear polypeptide composed of 69 amino acids with Mr 7558. A comparison of the p12 structure to that of the avian and murine type C retroviral nucleic acid-binding proteins shows significant homology only in the putative binding domain. This conserved region is duplicated BLV p12 as in the avian homolog.

Amino Acid Sequence↗
PubMed1983

New initiation factor activity required for globin mRNA translation.

A reconstituted reticulocyte translation system originally designed to be deficient in eukaryotic initiation factor 4B (eIF-4B) was used to identify a new activity required for maximal synthesis of rabbit globin. This new activity purifies as a stable, high molecular weight complex by a variety of chromatographic procedures and is termed eIF-4F. The purified globin stimulatory activity also restores translation of capped mRNAs in extracts of poliovirus-infected HeLa cells. Like restoring activity that was obtained as a protein complex by different procedures (Tahara, S. M., Morgan, M. A. and Shatkin, A. J. (1981) J. Biol. Chem. 256, 791-794), eIF-4F includes the 24,000-dalton cap binding protein and major polypeptides of Mr approximately 200,000 and approximately 46,000. The latter component comigrates with eIF-4A by two-dimensional gel electrophoresis and, like eIF-4A, chemically cross-links to the 5'-end of capped mRNA by an ATP-dependent, m7GDP-sensitive reaction. Unlike eIF-4F, cap binding protein of Mr approximately 24,000 isolated by affinity chromatography on m7GDP-Sepharose does not stimulate globin synthesis in the reconstituted system.

Chromatography, Gel↗
PubMed1983

Modification of macrophage phagocytosis in murine cryptococcosis.

Normal C57BL/6J peritoneal cells exhibited a decreased phagocytosis when cultured with a cell wall antigen of Cryptococcus sp. and lymphocytes from mice infected with C. neoformans. Direct cell-to-cell interaction was not required in that supernatant fluids from cultures of lymphocytes from infected animals could be incubated with normal macrophage monolayers to give comparable suppression. The induction of the suppressor factor required specific cryptococcal antigen; however, suppression at the macrophage level was nonspecific in that the phagocytosis of C. neoformans and Saccharomyces cerevisiae were both decreased. Suppression appeared with lymphocyte supernatants taken from mice infected for 14 days and thereafter. The factor was heat stable, trypsin sensitive, and allospecific.

Animals↗
PubMed1983

Comparison of a radiometric method (BACTEC) and conventional culture media for recovery of mycobacteria from smear-negative specimens.

The BACTEC system and three conventional media (Middlebrook 7H10, selective Middlebrook 7H11 [S7H11], and Lowenstein-Jensen [LJ] were compared for their mean recovery times and recovery rates of mycobacteria from acid-fast, smear-negative clinical specimens. Of the 71 smear-negative, culture-positive specimens recovered from 2,165 submitted smear-negative cultures, the BACTEC system detected 71.8%, compared with 88.7% for the conventional three-medium system. When media were individually compared, BACTEC medium (Middlebrook 7H12) was more successful in recovering mycobacteria (71.8%) than was LJ (62%), Middlebrook medium 7H10 (55.9%), or Middlebrook S7H11 medium (52.1%). Middlebrook 7H11 medium containing sodium selenate was also evaluated and did not increase the recovery rate or decrease the recovery time of mycobacterial species when compared with LJ, Middlebrook 7H10, S7H11, and 7H12 media. The mean detection time for the BACTEC system was less than that by conventional methods for the seven species of mycobacteria recovered. Detection times for Mycobacterium tuberculosis on the BACTEC system and conventional cultural systems were 13.7 and 26.3 days, respectively.

Bacteriological Techniques↗
PubMed1983

Structural and antigenic analysis of the nucleic acid-binding proteins of bovine and feline leukemia viruses.

The nucleic acid-binding proteins of bovine leukemia virus (BLV) and feline leukemia virus (FeLV) were isolated in a high state of purity with chloroform-methanol extraction followed by reversed-phase liquid chromatography. Selective solubilization and purity of BLV p12 and FeLV p10 was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The compositions and molecular weights were determined by amino acid analysis. An abundance of lysine and arginine residues along with their size identifies both BLV p12 and FeLV p10 as small basic proteins similar to well-defined type C viral nucleoproteins. NH2-terminal degradation by the semiautomated Edman method provided the sequence of the first 40 amino acids for both proteins. The putative nucleic acid binding site found in several type C viral nucleoproteins was contained within this sequence, with the most homology centered around an eight-amino acid region involving seven identical residues and one substitution. Antisera were developed in rabbits, and specificity and titers were determined by electroblotting and immunoautoradiography. By this technique, an immunological cross-reaction was found between BLV p12 and FeLV p10. The shared antigenic determinant most likely exists in the highly conserved eight-amino acid region. Although this sequence is also highly conserved in the nucleic acid-binding proteins of murine leukemia viruses, the shared antigenic determinant is not found in these or any other type C viruses tested. It is suggested that substitution of arginine (BLV p12/FeLV p10) to lysine (murine leukemia virus p10) is sufficient to elicit a change in antibody specificity.

Amino Acid Sequence↗
PubMed1982

Characterization of eukaryotic initiation factor 4A, a protein involved in ATP-dependent binding of globin mRNA.

Eukaryotic initiation factor 4A (eIF-4A) has been purified (to apparent homogeneity) from rabbit reticulocyte lysate. It is a single polypeptide accounting for at least 90% of the Coomassie blue staining material when subjected to gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular weight was determined by gel electrophoresis under denaturing conditions at two different bisacrylamide to acrylamide ratios, by gel filtration under native conditions and by sedimentation equilibrium at three different protein concentrations. Additional physical properties of the polypeptide were also determined. In an attempt to characterize the function of eIF-4A, a protein specifically required for mRNA translation, an assay was developed which measures the protein-dependent retention of radiolabeled hemoglobin mRNA on nitrocellulose filters. These studies led to the discovery of an ATP-stimulated binding of mRNA which is dependent on the presence of eIF-4A and eIF-4B that also contains the 24,000-dalton cap binding protein. The reaction apparently requires ATP hydrolysis since a nonhydrolyzable analogue of ATP, adenosine 5'-(beta, gamma-imino)triphosphate, does not stimulate mRNA binding and GTP cannot substitute for ATP. In addition, ATP-stimulated binding of mRNA can be inhibited by an analog of the mRNA 5' terminus, m7GMP, suggesting recognition of the capped 5' end of hemoglobin mRNA. Consistent with this suggestion, ATP also stimulated the covalent cross-linking of eIF-4A and eIF-4B to the cap of oxidized reovirus mRNA, an interaction that was inhibited by m7GDP.

Adenosine Triphosphate↗
PubMed1981

Separation of the plus and minus strands of cytoplasmic polyhedrosis virus and human reovirus double-stranded genome RNAs by gel electrophoresis.

The complementary strands of most of the genome double-stranded RNA segments of insect cytoplasmic polyhedrosis virus (CPV) and human reovirus are separated for the first time by agarose gel electrophoresis in in the presence of 7 M urea. CPV (+) strands and most reovirus (-) strands migrate faster than the corresponding strands of opposite polarity. Glyoxal treatment, which modifies guanine residues and prevents G-C basepairing, results in a loss of strand resolution and concomitantly a significant decrease in electrophoretic mobilities. Reovirus mRNAs synthesized in vitro with ITP substituted for GTP show similar decreased electrophoretic mobilities as the glyoxalated mRNAs. These results clearly indicate that the basis for (+) and (-) strand resolution is the presence of secondary structure formed mainly by G-C(U) base-pairs that are maintained during gel electrophoresis in the presence of 7 M urea. When the plus and minus strands of CPV genomes were separated and compared for protein synthesizing activity, it was found that only the plus strands were able to form stable 80S ribosome-RNA initiation complexes in wheat germ cell-free extracts.

Base Composition↗
PubMed1981

Two forms of purified m7G-cap binding protein with different effects on capped mRNA translation in extracts of uninfected and poliovirus-infected HeLa cells.

Eukaryotic mRNA cap binding proteins were purified from ribosomal salt wash in the presence of protease inhibitors by sucrose gradient sedimentation and m7GDP-Sepharose affinity chromatography. Rabbit reticulocyte and erythrocyte proteins with sedimentation constants of less than 6 S yielded a approximately 24,000-dalton cap binding protein. It stimulated capped mRNA translation in extracts of uninfected HeLa cells but did not restore capped mRNA function in extracts prepared from poliovirus-infected cells. Restoring and stimulatory activities both were associated with a larger, approximately 8-10 S complex that included the approximately 24,000-dalton polypeptide and several higher molecular mass components. The same two translational activities were also obtained in a slightly smaller approximately 5-7 S complex from uninfected HeLa cells but were absent from poliovirus-infected cell preparations.

Animals↗
PubMed1980

Initiation of reovirus transcription by inosine 5'-triphosphate and properties of 7-methylinosine-capped, inosine-substituted messenger ribonucleic acids.

Inosine 5'-triphosphate (ITP) can be utilized in place of guanosine 5'-triphosphate (GTP) for both the initiation and the elongation steps of reovirus transcription, resulting in the synthesis of mRNAs containing 5'-terminal m7IpppIm and internal pI. The apparent molecular weights of the I-substituted products were altered as a consequence of the absence of G-C base pairs and accompanying loss of ordered structure. The migration of I-substituted RNAs in agarose gels and glycerol gradients was similar to glyoxal-treated transcripts; i.e., it decreased 2-fold as compared to the corresponding untreated G-containing mRNAs. 7-Methylinosine-capped (m7I-capped), I-substituted transcripts readily attached to wheat germ 80S ribosomes. Unlike native G-containing mRNAs, they also formed heavier complexes that sedimented faster than 80S complexes even in the presence of the nonhydrolyzable ATP analogue AMPP(NH)P and elongation inhibitor sparsomycin. I-substituted molecules that were capped posttranscriptionally to form m7G-capped 5' ends yielded mostly 80S monosomes, consistent with a strong influence of 5'-terminal structure on initiation of translation. Under limited conditions of initiation, I-substituted RNAs outcompeted G-containing transcripts for ribosome attachment. Although the results are consistent with enhanced binding and freer movement of ribosomes on unstructured templates, synthesis of acid-precipitable polypeptides in wheat germ extract directed by I-substituted RNAs was 15-fold less than with G-containing mRNAs.

Binding Sites↗