Search PubMed⌕ Search

Biomedical subjects

P M McGuire

Publications and source records attributed to P M McGuire.

At least 19 recordsLinked to original sources
PubMed2006

Effects of Hydrocotyle sibthorpioides extract on transplanted tumors and immune function in mice.

This paper describes the effects of an ethanolic extract of Hydrocotyle sibthorpioides on transplanted tumors and immunologic function in mice. When the H. sibthorpioides extract was administered orally at a dose of 1.5 or 3.0 g/kg body wt./day for 10 days, the inhibition rates for murine hepatic carcinoma clone (Hep), sarcoma 180 crocker clone (S(180)), and uterine cervical carcinoma clone (U(14)) were significantly enhanced. The antitumor activity of H. sibthorpioides is comparable to that of the common antitumor agent 5-fluorouracil. Also, our results indicate that the H. sibthorpioides extract promoted the thymus and spleen indices, and humoral immunity of mice. These observations demonstrated that H. sibthorpioides exerted a potent inhibitory effect on the growth of tumors, in addition to mediating immunomodulatory effects in mice.

Administration, Oral↗
PubMed1998

Phylogeography of the West Indian manatee (Trichechus manatus): how many populations and how many taxa?

To resolve the population genetic structure and phylogeography of the West Indian manatee (Trichechus manatus), mitochondrial (mt) DNA control region sequences were compared among eight locations across the western Atlantic region. Fifteen haplotypes were identified among 86 individuals from Florida, Puerto Rico, the Dominican Republic, Mexico, Columbia, Venezuela, Guyana and Brazil. Despite the manatee's ability to move thousands of kilometers along continental margins, strong population separations between most locations were demonstrated with significant haplotype frequency shifts. These findings are consistent with tagging studies which indicate that stretches of open water and unsuitable coastal habitats constitute substantial barriers to gene flow and colonization. Low levels of genetic diversity within Florida and Brazilian samples might be explained by recent colonization into high latitudes or bottleneck effects. Three distinctive mtDNA lineages were observed in an intraspecific phylogeny of T. manatus, corresponding approximately to: (i) Florida and the West Indies; (ii) the Gulf of Mexico to the Caribbean rivers of South America; and (iii) the northeast Atlantic coast of South America. These lineages, which are not concordant with previous subspecies designations, are separated by sequence divergence estimates of d = 0.04-0.07, approximately the same level of divergence observed between T. manatus and the Amazonian manatee (T. inunguis, n = 16). Three individuals from Guyana, identified as T. manatus, had mtDNA haplotypes which are affiliated with the endemic Amazon form T. inunguis. The three primary T. manatus lineages and the T. inunguis lineage may represent relatively deep phylogeographic partitions which have been bridged recently due to changes in habitat availability (after the Wisconsin glacial period, 10 000 B P), natural colonization, and human-mediated transplantation.

Animals↗
PubMed1994

Antigens of Vibrio vulnificus.

Rabbit antisera raised against a formalinized culture of Vibrio vulnificus were examined for the development of IgM and IgG antibody by ELISA analysis of serum samples harvested weekly for 5 weeks following the initial injection. V. vulnificus antigens recognized by the sera in three fractions of the culture were identified by immunoblot analysis. The major species recognized in the culture supernatant solution by both IgM and IgG had a molar mass of 58 kD. In fractions derived from the bacterial pellet, IgM recognized a species of 56 kD, while IgG reacted strongly with 29.5, 56, 59, 68, 87, and 186 kD species.

Animals↗
PubMed1990

Site-directed mutagenesis of ricin A chain Trp 211 to Phe.

Oligonucleotide-directed site-specific mutagenesis has been used to make a conservative change in the putative active site of the catalytic subunit of the toxin ricin. The substitution of phenylalanine for tryptophan at position 211 of the A chain reduces but does not abolish catalytic activity, as assayed by inhibition of cell-free protein synthesis.

Amino Acid Sequence↗
PubMed1989

Site-directed mutagenesis at amino terminus of recombinant ricin A chain.

Successful immunotoxin therapy may depend upon reduction of the size of the components in order to decrease antigenicity and rate of clearance. In initial attempts to modify the A chain of ricin by deletion analyses within a prokaryotic expression system, coding sequences were modified by the insertion of unique restriction endonuclease sites and by the removal of 22 codons near the 5' terminus. The work presented here examines the expression, solubility, and activity of these mutant proteins and demonstrates that while amino acid residues may be altered in this region, the deletion of residues 19 through 40 yields an insoluble and inactive toxin molecule.

Amino Acid Sequence↗
PubMed1987

Depurination of yeast 26S ribosomal RNA by recombinant ricin A chain.

The nature of the modification of yeast ribosomes by the recombinant form of the ricin A chain has been examined. Evidence is presented that the 26S rRNA molecule is depurinated at a specific site and that the activity is inhibited by antibody raised to ricin A chain. It thus appears that the recombinant form of this toxin retains the depurination activity of the native molecule. These results are consistent with the model that the site of depurination is in a highly conserved sequence forming a loop on the surface of the ribosome, a domain involved in elongation factor-dependent binding of aminoacyl-tRNA.

Purines↗
PubMed1986

Identification of a nucleoside triphosphate binding site on calf thymus RNA polymerase II.

A nucleoside triphosphate binding site on calf thymus RNA polymerase II was identified by using photoaffinity analogues of adenosine 5'-triphosphate and guanosine 5'-triphosphate. Both radiolabeled 8-azidoadenosine 5'-triphosphate (8-N3ATP) and radiolabeled 8-azidoguanosine 5'-triphosphate (8-N3GTP) bound to a single polypeptide of this enzyme. This polypeptide has a molecular mass of 37 kilodaltons and an isoelectric point of 5.4. Ultraviolet (UV) irradiation was necessary for photolabeling to occur. In addition, no labeling occurred when the probe was prephotolyzed or when the enzyme was inactivated. Furthermore, photolabeling of the enzyme could be decreased by preincubation with natural substrates. To provide evidence that the radiolabeled polypeptide forms a part of the domain of the nucleoside triphosphate binding site, experiments were performed using unlabeled 8-N3ATP. Although this unlabeled analogue was not a substrate for RNA polymerase II, it photoinactivated the enzyme in the presence of UV irradiation, and it inhibited transcription elongation by the enzyme in a competitive manner in the absence of UV irradiation. As in the case with photolabeling, photoinactivation by 8-N3ATP could be decreased by natural substrates; in both cases, purine ribonucleoside triphosphates were more efficient than pyrimidine nucleoside triphosphates. Furthermore, photoinactivation was saturable at about the same concentration as the inhibition constant for 8-N3ATP. Collectively, these results provide evidence that the radiolabeled polypeptide in calf thymus RNA polymerase II is an essential component for activity and suggest that this polypeptide may be part of this enzyme's purine ribonucleoside triphosphate binding site.

Adenosine Triphosphate↗
PubMed1986

Characterization of RNA polymerase type II from human term placenta.

RNA polymerase type II from human term placenta has been isolated and characterized with respect to its template, ammonium sulfate, divalent cation, and buffer preferences. In addition, the apparent Michaelis constants for AMP and UMP incorporation have been determined. The enzyme was also analyzed by native and denaturing polyacrylamide gel electrophoresis, and evidence is presented that a single polypeptide is radiolabeled with azido purine nucleoside triphosphate photoprobes.

Adenosine Triphosphate↗
PubMed1984

Isolation and characterization of a translation inhibitor from human term placenta.

An inhibitor of protein synthesis has been isolated from free cytoplasmic ribonucleoprotein particles of human term placenta. The inhibitor is resistant to phenol, DNase, proteinase K, and heating at 100 degrees C, but is sensitive to alkaline hydrolysis. These data suggest that the inhibitor is RNA. Experiments provide evidence that this preparation contains no RNase contaminant and does not induce an RNase in this assay system. Three lines of evidence suggest that the inhibitor acts at the initiation of protein synthesis in the wheat germ translation system. First, a lag occurs before cessation of translation when the inhibitor is added to translating polyribosomes. This lag is identical to that seen upon the addition of aurintricarboxylic acid, a known inhibitor of initiation. Second, sucrose gradient analyses demonstrate that, when the inhibitor is present at the start of translation, 40 S complexes form, but neither 80 S complexes nor polyribosomes are seen. Third, gradient analyses show that, when the inhibitor is added to translating polyribosomes, 40 S complexes accumulate with a progressive loss of polyribosomes. Finally, the extent of inhibition depends upon the amount of wheat germ extract added to the reaction mixture and not the amount of mRNA present. This suggests an interaction between the inhibitor and a component of the wheat germ extract.

Centrifugation, Density Gradient↗
PubMed1984

Microinjection of RNA polymerase II corrects the temperature-sensitive defect of tsAF8 cells.

tsAF8 cells are a temperature-sensitive (ts) mutant of BHK cells that arrest in the G1 phase of the cell cycle at the non-permissive temperature of 40.6 degrees C. Previous reports had suggested that the temperature-sensitivity of these cells was based on a defect in either the synthesis, assembly or turnover of RNA polymerase II. We now show that the direct microinjection of purified RNA polymerase II into nuclei of tsAF8 cells corrects the ts defect and allows these cells to enter the S phase of the cell cycle.

Animals↗
PubMed1982

Interactive computer programs in sequence data analysis.

We present interactive computer programs for the analysis of nucleic acid sequences. In order to handle these programs, minimum computer experience is sufficient. The nucleotide sequence of the human gamma globin gene complex is used as an example to illustrate the data analysis.

Base Sequence↗
PubMed1982

Mutagenicity of HPLC fractions from extracts of AAtrex-treated corn.

Crude extracts from maize plants treated with varying concentrations of AAtrex, an s-triazine herbicide, were tested for the induction of gene conversion in a diploid strain of Saccharomyces cerevisiae heteroallelic at two loci. These extracts were then subjected to analysis by higher pressure liquid chromatography (HPLC), and the fractions collected in water, 50% methanol, and 100% methanol were similarly tested. Dose-dependent convertogenic activity observed in the 50% methanol fractions suggested that the mutagen(s) is recovered in this fraction.

Atrazine↗
PubMed1977

Histone messenger RNA from HeLa cells: evidence for modified 5' termini.

The distribution of [3H]methyl radioactivity in cytoplasmic histone mRNA, isolated during the DNA synthetic (S) phase of the HeLa S3 cell cycle, has been investigated. Evidence is presented that approximately 30% of the radioactivity is in m7GpppXmpYp oligonucleotides, where Xm represents 2'-O-methylated adenosine and guanosine with a molar ratio of 4:1, respectively. The remainder of the radioactivity is present as m7GpppCmpYmpZp oligonucleotides, where Xm is again 2'-O-methylated adenosine and guanosine (4:1) and where ym represents 2'-O-methylated adenosine, guanosine, cytidine, and uridine with ratios of 2:1:1:1, respectively. While 48.6% of the [3H]methyl radioactivity was present as N6-methyladenosine in poly(adenylic acid)-terminated mRNA from S-phase cells, no evidence for N6-methyladenosine was found in histone mRNA. It thus appears that histone mRNA which lacks 3'-terminal poly(adenylic acid) sequences and functions on cytoplasmic polyribosomes during a limited protion of the cell cycle is capped but lacks internal-modified nucleosides.

Cell Division↗