Search PubMed⌕ Search

Biomedical subjects

M M Parker

Publications and source records attributed to M M Parker.

7 recordsLinked to original sources
PubMed1992

Repair and mutagenesis of the genome of a deletion mutant of the coronavirus mouse hepatitis virus by targeted RNA recombination.

The genetic characterization of a nucleocapsid (N) protein mutant of the coronavirus mouse hepatitis virus (MHV) is described. The mutant, Albany 4 (Alb4), is both temperature sensitive and thermolabile. Analysis of the progeny of a mixed infection showed that the defective Alb4 allele is recessive to wild type, and its gene product is diffusible. The N protein of Alb4 was found to be smaller than its wild-type counterpart, and sequence analysis of the Alb4 N gene revealed that it contains an internal deletion of 87 nucleotides, producing an in-frame deletion of 29 amino acids. All of these properties of Alb4 made it ideal for use as a recipient in a targeted RNA recombination experiment in which the deletion in Alb4 was repaired by recombination with synthetic RNA7, the smallest MHV subgenomic mRNA. Progeny from a cotransfection of Alb4 genomic RNA and synthetic RNA7 were selected for thermal stability. Polymerase chain reaction analysis of candidate recombinants showed that they had regained the material that is deleted in the Alb4 mutant. They also had acquired a five-nucleotide insertion in the 3' untranslated region, which had been incorporated into the synthetic RNA7 as a molecular tag. The presence of the tag was directly verified, as well, by sequencing the genomic RNA of purified recombinant viruses. This provided a clear genetic proof that the Alb4 phenotype was due to the observed deletion in the N gene. In addition, these results demonstrated that it is possible to obtain stable, independently replicating progeny from recombination between coronavirus genomic RNA and a tailored, synthetic RNA species.

Amino Acid Sequence↗
PubMed1992

Effects of ibuprofen and pentoxifylline on the cardiovascular response of normal humans to endotoxin.

Endotoxin is a major mediator of the life-threatening cardiovascular dysfunction that characterizes Gram-negative sepsis. In animal models of endotoxemia, pretreatment with ibuprofen or pentoxifylline attenuates some of these cardiovascular changes. To evaluate the effects of these agents on the human cardiovascular response to endotoxemia, hemodynamic variables were measured serially in 24 normal subjects who were given intravenous endotoxin. The subjects were randomized to receive oral ibuprofen (n = 9), pentoxifylline (n = 10), or no medication before endotoxin administration (n = 5). The subjects were volume loaded 3-5 h after endotoxin administration, and hemodynamic measurements were reassessed. Core temperature after endotoxin alone or endotoxin-pentoxifylline approached a maximum at 3 h (greater than or equal to 38.6 degrees C), while the endotoxin-ibuprofen group remained afebrile. At 3 and 5 h, all three groups had significant increases in heart rate, cardiac index, oxygen delivery, and oxygen consumption, while systemic vascular resistance index decreased significantly from baseline. The oxygen extraction ratio remained unchanged. After volume loading, the left ventricular ejection fraction and left ventricular end-diastolic and end-systolic volume indexes did not differ among the groups. The hyperdynamic cardiovascular response to endotoxin in humans occurs in the absence of fever and is not significantly ameliorated by oral cyclooxygenase or phosphodiesterase inhibition.

Adult↗
PubMed1990

Sequence comparison of the N genes of five strains of the coronavirus mouse hepatitis virus suggests a three domain structure for the nucleocapsid protein.

To obtain information about the structure and evolution of the nucleocapsid (N) protein of the coronavirus mouse hepatitis virus (MHV), we determined the entire nucleotide sequences of the N genes of MHV-A59, MHV-3, MHV-S, and MHV-1 from cDNA clones. At the nucleotide level, the N gene sequences of these viral strains, and that of MHV-JHM, were more than 92% conserved overall. Even higher nucleotide sequence identity was found in the 3' untranslated regions (3' UTRs) of the five strains, which may reflect the role of the 3' UTR in negative-strand RNA synthesis. All five N genes were found to encode markedly basic proteins of 454 or 455 residues having at least 94% sequence identity in pairwise comparisons. However, amino acid sequence divergences were found to be clustered in two short segments of N, putative spacer regions that, together, constituted only 11% of the molecule. Thus, the data suggest that the MHV N protein is composed of three highly conserved structural domains connected to each other by regions that have much less constraint on their amino acid sequences. The first two conserved domains contain most of the excess of basic amino acid residues; by contrast, the carboxy-terminal domain is acidic. Finally, we noted that four of the five N genes contain an internal open reading frame that potentially encodes a protein of 207 amino acids having a large proportion of basic and hydrophobic residues.

Amino Acid Sequence↗