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Biomedical subjects

M Rice

Publications and source records attributed to M Rice.

At least 91 records · Page 5Linked to original sources
PubMed1988

ProOmpA spontaneously folds in a membrane assembly competent state which trigger factor stabilizes.

The precursor protein proOmpA can translocate across purified Escherichia coli inner membrane vesicles in the absence of any other soluble proteins. ProOmpA, purified 2000-fold in the presence of 8 M urea, is competent for translocation following rapid renaturation via dilution. ATP, the transmembrane electrochemical potential, and functional secY protein are essential for the translocation of proOmpA renatured by dilution. The kinetics of its translocation and the level of translocation at each concentration of ATP are indistinguishable from that of proOmpA renatured by dialysis with trigger factor. After dilution, the proOmpA rapidly loses its competence for membrane assembly. However, this competence is stabilized by trigger factor. Assembly-competent proOmpA is in a protease-sensitive conformation, whereas proOmpA which has lost this competence is more resistant to degradation. This suggests that the primary role for trigger factor in in vitro protein translocation is to maintain precursor proteins in a translocation-competent conformation. We propose that a properly folded precursor protein and ATP are the only soluble components which are essential for bacterial protein translocation.

Adenosine Triphosphate↗
PubMed1988

Health promotion, education and community participation in the Americas. Reality or myth?

The concepts and understanding of community promotion, education and participation for health have many interpretations and applications in the countries of the Americas. Even though many of the countries have written policies indicating that these are important strategies, very few have developed ways to make them effective and operational. In most cases they are not defined, nor have countries developed concrete objectives and goals. Although the Primary Health Care strategy has been adopted in principle by countries of the Americas, they are encountering serious difficulties in implementing the concept, particularly within large-scale national health programmes. In actuality, the community promotion, education and participation concepts in the health arena are vague and often misunderstood.

Community Health Services↗
PubMed1987

The effect of elevated levels of herpes simplex virus alpha-gene products on the expression of model early and late genes in vivo.

The rate of synthesis in vivo and the steady-state level of mRNA of four "model" herpes simplex virus type 1 (HSV-1) genes were measured as a function of high levels of alpha-gene products. The genes studied were ICP4 (alpha), deoxy-UTPase (beta), VP5 (beta gamma), and glycoprotein C (gC, gamma). Accumulation of high levels of alpha proteins was accomplished either by infection with an HSV-1 mutant, temperature-sensitive in ICP4 (ts606) at the nonpermissive temperature then shift-down to permissive temperature, or by infection with wild-type virus under cycloheximide blockage of protein synthesis followed by release. Compared to RNA expression in normal infections, beta gamma and gamma transcription rates were both transiently stimulated under the experimental conditions employed. The greatest effect was seen with the gamma-gC mRNA transcription rates. In addition, at nonpermissive temperatures with ts 606, the amount of expression of gC mRNA was significantly increased over normal early levels, in contrast to the case with the VP5 transcript. The impact of such results on models of HSV gene expression in vivo are discussed.

Animals↗
PubMed1986

Aminoacyl-tRNA(anticodon): codon adaptation in human and rabbit reticulocytes.

A highly significant correlation was observed between the relative abundances of isoacceptor aminoacyl-tRNAs in human and rabbit reticulocytes and the frequency of their cognate codons in alpha and beta globin mRNAs from the respective tissue. The correlation coefficient (r value) for human reticulocytes was 0.78 and for rabbit reticulocytes was 0.88. These results provide strong evidence that the amounts of most isoacceptors in human and rabbit reticulocytes are adapted to requirements for translating their cognate codons in globin mRNA, i.e., there is an aa-tRNA(anticodon): codon adaptation in these tissues.

Animals↗
PubMed1985

Effects of two sec genes on protein assembly into the plasma membrane of Escherichia coli.

We have examined the effects of thermosensitive mutations in secA and secY (prlA) genes on the export of proteins to the three layers of the Escherichia coli cell surface. After several hours at the nonpermissive temperature, the export of two major outer membrane proteins, lipoprotein and OmpA, is delayed, then essentially blocked, in either a secA or secY strain. These mutations also have a strong effect on the export of several proteins, such as maltose binding protein, to the periplasm, though the export of many periplasmic proteins is not affected. secA and secY block the assembly of leader peptidase, which is made without a leader sequence, into the inner membrane. However, the membrane assembly of M13 coat protein (an inner membrane protein made with an amino-terminal leader sequence) is not affected. Thus, the requirement for sec function for export does not correlate with the presence or absence of leader peptide or with a particular subcellular compartment, but rather is specific to each particular protein.

ATP-Binding Cassette Transporters↗
PubMed1985

Atrioventricular block following overdose of decongestant cold medication.

A 24-year-old man developed high-degree atrioventricular (A-V) block with a pulse rate of 40 beats per minute and hypertension following an overdose of a combination decongestant cold medication that contained phenylpropanolamine, phenylephrine, chlorpheniramine, and phenyltoloxamine. The patient was treated with ipecac, activated charcoal, and cathartics in the emergency department (ED). After his admission to the coronary care unit, the A-V block gradually resolved to sinus rhythm with periods of second-degree block, Mobitz types I and II. No treatment was required. The patient had a normal sinus rhythm and normal blood pressure prior to discharge.

Adult↗
PubMed1985

Binding of glycosaminoglycans to the surface of Treponema pallidum and subsequent effects on complement interactions between antigen and antibody.

Acidified bovine serum albumin (acid BSA) reacts with glycosaminoglycans to form a precipitate. This reaction was adapted to Treponema pallidum to show glycosaminoglycans associated with the surface of the micro-organism. As testicular infection progressed from days 4 to 18, treponemes showed increasing amounts of these surface components. High speed centrifuging effectively removed the glycosaminoglycans, thus indicating that they were loosely bound. The subsequent addition of commercial preparations of hyaluronic acid or chondroitin sulphate resulted in their immediate adherence to the surface of the pathogens T pallidum and T pertenue, but not to the non-pathogens T vincenti, T denticola, or T phagedenis. The amount adhering to the treponemal surface varied depending on the concentration added. Intradermal inoculation showed that the virulence of T pallidum was not altered by the glycosaminoglycans associated with its surface. The coating of treponemes with hyaluronic acid or chondroitin sulphate did not interfere with neutralising antibodies or antibodies found by radioimmunoassay using whole organisms. In contrast, hyaluronic acid or chondroitin sulphate on the treponemal surface did interfere with immobilising antibodies. Results are discussed in terms of the potential role of the treponemal glycosaminoglycans in the infectious process.

Animals↗
PubMed1985

Detection and functional characterization of early appearing antibodies in rabbits with experimental syphilis.

Following testicular infection of rabbits with Treponema pallidum, different antibodies become detectable initially at the time of healing. Experiments were performed to determine a functional role for these antibodies. Rabbits were sacrificed after 4-8 days. Treponemal numbers steadily increased for 10-12 days. Thereafter, host defenses were sufficiently stimulated to begin clearing the organisms. Antibodies in serum and antibodies localized at the site of infection were quantitated using radioimmunoassay and enzyme-linked immunosorbent assay (ELISA) techniques. Anti-treponemal IgG was detected as early as day 4. Quantities of antibody correspondingly increased with time following infection. Treponema pallidum was harvested 7 and 14 days postinfection and tested for surface antibodies. With increasing days postinfection, more antibody was found on the organisms. Two functional properties of these antibodies were shown. Sera from 24 of 45 rabbits infected for 14 days immobilized T. pallidum in the presence of complement and 14-day sera blocked the attachment of T. pallidum to tissue culture cells. We suggest that antibody-mediated, complement-dependent immobilization of T. pallidum and blockage of attachment are at least partially responsible for healing of testicular lesions.

Animals↗
PubMed1985

Immune immobilization of Treponema pallidum: antibody and complement interactions revisited.

The Treponema pallidum immobilization test was designed for serodiagnosis of syphilis and is dependent upon specific antibody and a heat labile component of normal serum. Investigators have shown the component to be dependent upon divalent cations and it is presumed to be complement. Experiments were performed to reevaluate the interactions of antibody and complement and the mechanism of immobilization. The loss of treponemal motility was correlated to the loss of complement activity in the reaction mixture. When motility of treponemes incubated with immune serum IgG and complement had dropped to 50% (3.4 h), 72% of the available complement had been consumed. At the same time, treponemes incubated with normal serum IgG and complement were 82% motile and only 51% of the complement had been consumed. C6 deficient rabbit serum and C4 deficient guinea pig serum were used in conjunction with immune serum IgG to determine which components of the complement cascade were necessary for immobilization. Treponemes were not immobilized by either sera. Results suggest that the heat labile factor in normal sera is complement, that both early and late components of the complement cascade are necessary, and that the reaction proceeds via the classical complement pathway. Although T. pallidum is susceptible to the actions of antibody and complement, the organisms must interact with these components for at least 2 h before immobilization will result.

Animals↗
PubMed1984

O6-Methylguanine-DNA methyltransferase in human cells.

O6-Methylguanine-DNA methyltransferase activity was measured in extracts of human tumor cells and was partially purified from human placenta. Repair of O6-methylguanine in DNA inactivated the methyltransferase, and treatment of cells with MNNG, which produces this alkylated base in DNA, depleted the cells of active methyltransferase. RNA and protein synthesis were required for restoration of methyltransferase activity, which transiently exceeded the original levels by 50% 48 h after treatment. One species of methyltransferase of Mr = 22 kd was present in human tumor cells and human placenta.

Astrocytoma↗
PubMed1983

Hepatosplenic schistosomiasis in a South-East Asian refugee child in South Australia.

This report documents a case of hepatosplenic schistosomiasis in a South-East Asian refugee boy who presented with malaise, abdominal distension, and was found to have massive splenomegaly and esophageal varices. The diagnosis was confirmed by liver biopsy and he was treated with a highly efficacious schistosomicide, Praziquantel. The case highlights the possible occurrence in Australia of non-endemic tropical diseases in immigrants.

Australia↗
PubMed1982

The aminoacyl-tRNA population of human reticulocytes.

The aminoacyl-tRNA population of human reticulocytes has been examined. These studies include: 1) determination of the levels of amino acid acceptance for 20 aminoacyl-tRNAs; 2) comparison of 20 aminoacyl-tRNAs from human reticulocytes to those of rabbit reticulocytes by reverse phase chromatography; 3) comparison of the levels of Ile- and Leu-tRNAs in fetal and adult reticulocytes; and 4) determination of the codon recognition properties of human Ala-, Asn-, His-, Leu-, Thr-, and Val-tRNAs. These studies provide evidence that the aminoacyl-tRNA population of human reticulocytes is adapted to the requirements of protein synthesis.

Adult↗
PubMed1982

Childhood T-cell acute lymphoblastic leukaemia expressing "Ia-like" antigen:" a case report.

A 4-year-old girl presenting with vomiting, abdominal pain, and renal failure was found to have gross hepatosplenomegaly, a renal mass, and bilateral pleural effusions. A diagnosis of acute lymphoblastic leukaemia (ALL) was suggested by a peripheral white cell count (WCC) of 119,000 x 10(6)mm3, 57% blasts, 22% lymphocytes, and confirmed by bone marrow examination. Lymphocyte surface marker studies at diagnosis enabled classification as a T-ALL, with a significant proportion of the T cells also bearing receptors for the third component of complement (C3). Seventy-two percent of the peripheral blood mononuclear cells reacted with anti-Ia monoclonal antibody (FMC44), and a smaller proportion (25%) carried receptors for the Fc portion of IgG. The T-classification of this ALL was verified at central nervous system (CNS) relapse and at a subsequent nodal relapse. Double-marker studies on cells from the infiltrated lymph node prepared in suspension confirmed the presence of Ia-positive T cells. The Ia marker is usually a useful discriminant between T and non-T cells in normal and ALL cell populations. The case described here highlights the need for a panel of markers to be used in classification of childhood ALL and supports the suggestion that there is a distinct subtype of Ia-positive T-ALL.

Antigens, Surface↗
PubMed1982

Aminoacyl-tRNAs from Physarum polycephalum: patterns of codon recognition.

Isoacceptors of Physarum polycephalum Ala-, Arg-, Glu-, Gln-, Gly-, Ile-, Leu-, Lys-, Ser-, Thr-, and Val-tRNAs were resolved by reverse-phase chromatography and isolated, and their codon recognition properties were determined in a ribosomal binding assay. Codon assignments were made to most isoacceptors, and they are summarized along with those determined in other studies from Escherichia coli, yeasts, wheat germ, hymenoptera, Xenopus, and mammals. The patterns of codon recognition by isoacceptors from P. polycephalum are more similar to those of animals than to those of plants or lower fungi.

Animals↗