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Biomedical subjects

P McIntyre

Publications and source records attributed to P McIntyre.

At least 109 records · Page 6Linked to original sources
PubMed1988

A quantitative method for analyzing specific DNA sequences directly from whole cells.

A quick, accurate assay for specific DNA sequences is described in which whole cells are treated with 0.4 M sodium hydroxide at 80 degrees C. DNA is relatively resistant to alkaline hydrolysis, whereas proteins and RNA are degraded rapidly. The DNA in NaOH is then transferred through a slot directly onto a nylon membrane and hybridized with a probe. Since the procedure is so simple, many samples can be analyzed in a short time. A single-copy gene can be detected in as few as 1000 cells and, since the DNA from 10(5) cells can be loaded through a single slot, the sensitivity is sufficient to detect one specific DNA sequence per 100 cells. Accurate quantitative analysis can be achieved by normalizing the amount of DNA available for hybridization in each slot, using a probe derived from total DNA.

Animals↗
PubMed1987

Putative glycophorin-binding protein is secreted from schizonts of Plasmodium falciparum.

A cDNA clone expressing an antigen of Plasmodium falciparum, selected by screening an expression library cloned in Escherichia coli, encodes a portion of the protein identified as a glycophorin-binding protein [Kochan et al. (1986) Cell 44, 689-696]. Human antibodies affinity-purified on extracts from this clone were used to characterize the antigen by immunoblotting. This protein was present in all isolates tested, restricted to mature trophozoites and schizonts. It was abundant in culture supernatants at the time of merozoite release but present in minor amounts if at all in merozoites. The pattern of antigen distribution over schizont-infected cells observed by immunoelectron microscopy differed from that of the precursor of the major merozoite surface antigens in that most of the antigen appeared to be located over the erythrocyte cytoplasm without any obvious association with organelles. It thus appears unlikely that this antigen is present on the merozoite surface prior to schizont rupture.

Amino Acid Sequence↗
PubMed1987

Cutaneous infection with Mycobacterium gordonae.

A case of cutaneous infection with Mycobacterium gordonae and other reports of extrapulmonary infection due to this organism are reviewed. This case confirms the pathogenic potential of M. gordonae which must now be included among the scotochromogens capable of causing cutaneous disease. Isolates of this organism should be tested against a full range of antimicrobial agents since traditional antituberculous therapy may be of limited efficacy. Pending the results of in vitro susceptibility testing, amikacin, ethambutol, rifampicin and co-trimoxazole are suggested as empirical therapy for infections caused by this organism.

Adult↗
PubMed1986

Chemotherapy in giardiasis: clinical responses and in vitro drug sensitivity of human isolates in axenic culture.

To investigate drug sensitivities of human Giardia isolates, we developed a reproducible in vitro 3H-thymidine uptake assay to compare drug potencies. Among 13 Giardia intestinalis stocks obtained from the culture of trophozoites isolated from duodenal juice, considerable variation in susceptibility to a range of currently used drugs was found. The population doubling time of these stocks also varied widely. Clinical features in patients ranged in severity from mild chronic diarrhea to a celiac-like syndrome, with a similar variation in the degree of histologic change in the mucosa. Brush-border enzyme activities were universally reduced in children younger than 5 years of age. The two isolates with the highest ID50 values for furazolidone in vitro were from patients who had persistent symptoms after treatment with this drug; these patients subsequently responded to treatment with a nitroimidazole with greater in vitro potency. These studies suggest that biologic variants of G. intestinalis exist in humans and may in part account for the variable clinical manifestations and for some treatment failures.

Animals↗
PubMed1985

The primary structure of the imported mitochondrial protein, ornithine transcarbamylase from rat liver: mRNA levels during ontogeny.

Ornithine transcarbamylase, one of the enzymes of the urea cycle in ureotelic organisms, is synthesized in the cytoplasm of hepatocytes as a precursor larger than the mature form found in the mitochondrial matrix. We deduced the amino acid sequence of the precursor of ornithine transcarbamylase from rat liver from the nucleotide sequence of overlapping cDNA clones spanning the complete coding region, 3' untranslated region, and most of the 5' untranslated region of the mRNA. The mature enzyme consists of 322 amino acids and is derived from the larger precursor by proteolytic removal of 32 amino acids from the amino-terminus. The amino-terminal extension contains eight basic and no acidic residues. This highly basic character appears to be a feature of presequences on cytoplasmically synthesized mitochondrial proteins. Comparison of the amino acid sequence determined for the enzyme from rat with that from human liver (Horwich et al., 1984) shows that there is a high degree of homology between the sequences of the mature protein (93%) and relatively less homology between the sequences of the amino-terminal extension (72%). The ornithine transcarbamylase from rat liver also shows a considerable degree of amino acid homology (44%) with the enzyme from Escherichia coli (Van Vliet et al., 1984) and leads to suggestions about residues involved in substrate binding and catalysis. An analysis of levels of RNA in fetal and neonatal liver shows that ornithine transcarbamylase mRNA levels increase from about 40% of adult levels at day 14 of gestation to a peak at day 20 of gestation, and, after a drop around the time of birth, rises to adult levels during the second week after birth.

Age Factors↗
PubMed1984

A highly basic N-terminal extension of the mitochondrial matrix enzyme ornithine transcarbamylase from rat liver.

We have deduced the amino acid sequence of the N-terminal leader peptide of the mitochondrial enzyme ornithine transcarbamylase from a cDNA clone obtained from a rat liver cDNA library. The sequence is remarkable in being highly basic, having 4 arginine, 3 lysine and 1 histidine with no acidic residues in a total of 32 residues. The leader sequence has no extensive hydrophobic stretches, has 72% homology with the leader peptide of human ornithine transcarbamylase [1], and in terms of its basic character resembles the N-terminal extensions on a number of fungal mitochondrial [2-5] and pea chloroplast [6] proteins. Thus the basic nature of these leader peptides may constitute the signal for mitochondrial import.

Amino Acid Sequence↗
PubMed1984

Selection of a cDNA clone which contains the complete coding sequence for the mature form of ornithine transcarbamylase from rat liver: expression of the cloned protein in Escherichia coli. Molecular cloning of rat ornithine transcarbamylase.

A cDNA clone corresponding to the mature form of ornithine transcarbamylase (OTCase) was selected from a rat liver cDNA library constructed in bacteriophage lambda gt10. OTCase clones were selected using a synthetic DNA probe of 15 bases corresponding to the 3' end of the OTCase mRNA [Horwich, A. L., Kraus, J.P., Williams, K., Kalousek, F., Königsberg, W. & Rosenberg, L.E. (1983) Proc. Natl Acad. Sci. USA, 80, 4258-4262]. Putative OTCase clones were subcloned into the expression vector, pUC9, and the identity of inserts confirmed by colony immunoassay and by electrophoretic transfer of cloned proteins from sodium dodecyl sulphate/polyacrylamide gels to nitrocellulose filters followed by probing with monospecific anti-OTCase antibodies and 125I-labelled protein A. A clone corresponding to the full-length mature form of rat liver OTCase (plus 15 amino acids from Escherichia coli beta-galactosidase) was obtained and the identity of the clone was confirmed by comparison of the 5' sequence with a limited N-terminal amino acid sequence [Lusty, C., Jilka, R. L. & Nietsch, E. H. (1979) J. Biol. Chem. 254, 10030-10036]. A sequence discrepancy between the published sequence (Lusty et al.) and the sequence predicted from the cDNA structure is noted.

Amino Acid Sequence↗
PubMed1984

A carbamylphosphate synthetase deficiency with no detectable immunoreactive enzyme and no translatable mRNA.

A lethal carbamylphosphate synthetase (CPS: EC 6.3.4.16) deficiency (McKusick 23730) was found in a newborn girl; who presented on the second day of life with acute hyperammonaemia, hypotonia, seizures and who died in a coma 6 days after birth. The activity of the mitochondrial urea cycle enzymes, CPS and ornithine transcarbamylase (OTC: EC 2.1.3.3) were measured on a needle biopsy sample taken from liver and showed that CPS was 1.4% of the normal mean (0.09 nmol/min/mg protein) whereas OTC activity was normal (110 nmol/min/mg protein). Immunological analysis of the liver sample showed no detectable immunoreactive CPS and confirmed the presence of normal levels of OTC. RNA was extracted from postmortem liver and in vitro translation experiments showed that there was no translatable CPS mRNA and confirmed that no CPS protein was synthesized in this child. The absence of translatable mRNA is explicable in terms of a genetic defect which results in a failure to synthesize mRNA for CPS, or synthesis of a defective form of mRNA which is not translated.

Amino Acid Metabolism, Inborn Errors↗
PubMed1983

Occult pneumococcal bacteraemia and febrile convulsions.

Over two years 29 children had bacteraemia due to Streptococcus pneumoniae at this hospital. In 15 previously healthy children the site of infection could not be identified, and in most of them, bacteraemia was not suspected clinically. All 15 had high total white cell (greater than or equal to 17 x 10(9)/1) and neutrophil (greater than or equal to 11 x 10(9)/1) counts. Twelve children were under 4 years of age, and of these, 10 had been admitted because of a simple febrile convulsion and one had a prolonged febrile convulsion. Occult pneumococcal bacteraemia has been reported in the USA for more than 10 years, but no series has been reported from the United Kingdom. Occult pneumococcal bacteraemia may be an important cause of febrile convulsions. Persisting bacteraemia and the development of focal infections, including pneumococcal meningitis, have been reported. Meningitis did not occur after occult bacteraemia in our patients. Studies to date have been retrospective, and thus the true incidence of the complications and the best treatment are not clear. A prospective study of children with febrile convulsions could provide answers.

Age Factors↗
PubMed1983

Changes in carbamyl phosphate synthetase and ornithine transcarbamylase levels during development and in response to changes in diet. Application of the electrophoretic transfer technique.

We have investigated changes in the levels of carbamylphosphate synthetase and ornithine transcarbamylase in response to the protein content of the diet and during development using the electrophoretic transfer technique. Levels of carbamylphosphate synthetase increased from 3.01 +/- 0.21 mg/g liver to 8.80 +/- 0.46 mg/g liver in rats on diet containing 15% and 60% casein. The levels of ornithine transcarbamylase showed a smaller increase from 0.49 +/- 0.06 to 0.82 +/- 0.09 mg/g liver. Developmental patterns for these enzymes were also different: carbamylphosphate synthetase increased sharply from less than 0.01 mg/g liver at 15,16 and 17 days foetal age to 1.6 mg/g liver at birth and 4.9 mg/g liver in adults. Ornithine transcarbamylase increased gradually from 0.04 mg/g liver at 15 days foetal age to 0.23 mg/g liver at birth and 0.59 mg/g liver in adult liver. At no stage during development was the precursor form of either enzyme detected in liver extracts.

Aging↗
PubMed1978

Light propagation in twisted anisotropic media: application to photoreceptors.

The propagation of light through a slowly twisting anisotropic medium is described by a coupled-mode theory; expressions are derived for the electric field for the case of a birefringent dichroic medium with a constant rate of twist. The method provides a simple and intuitive means for determing the effect of twisting on the linear birefringence and dichroic absorption of the medium, particularly when the light is initially linearly polarized. The theory is well suited to the analysis of light absorption in twisting insect photoreceptors, such as found in bees and ants. We provide full expressions and useful approximations for polarization sensitivity and the initial direction of polarization to give maximum absorption for several types of photoreceptors.

Animals↗