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Biomedical subjects

C M West

Publications and source records attributed to C M West.

160 records · Page 9Linked to original sources
PubMedDate not supplied

Current ideas on the significance of protein glycosylation.

Carbohydrate has been removed from a number of glycoproteins without major effect on the structure or enzyme activity of the protein. Thus carbohydrate has been suggested to underly a non-primary function for proteins, such as in relatively non-specific interactions with other carbohydrates or macromolecules, stabilization of protein conformation, or protection from proteolysis. This non-specific concept is consistent with both the general similarity in carbohydrate structure on very diverse glycoproteins and the frequent structural microheterogeneity of carbohydrate chains at given sites. The concept is supported in a general sense by the viability of cells whose glycosylation processes have been globally disrupted by mutation or pharmacological inhibitors. In contrast to the above observations, other studies have revealed the existence of specific, selective receptors for discrete oligosaccharide structures on glycoproteins which seem to be important for compartmentalization of the glycoprotein, or the positioning of cells on which the glycoprotein is concentrated. Sometimes multivalency in the carbohydrate-receptor interaction is crucial. There are additional possible roles for carbohydrate in the transduction of information upon binding to a receptor. The possibility of specific roles for carbohydrate is supported by the existence of numerous unique carbohydrate structures, many of which have been detected as glycoantigens by monoclonal antibodies, with unique distributions in developing and differentiated cells. This article attempts to summarize and rationalize the contradictory results. It appears that in general carbohydrate does in fact underlie only roles secondary to a protein's primary function. These secondary roles are simple non-specific ones of protection and stabilization, but often also satisfy the more sophisticated needs of spatial position control and compartmentalization in multicellular eukaryotic organisms. It is suggested that there are advantages, evolutionarily speaking, for the shared use of carbohydrate for non-specific roles and for specific roles primarily as luxury functions to be executed during the processes of cell differentiation and morphogenesis.

Animals↗
PubMedDate not supplied

Glycoantigen expression is regulated both temporally and spatially during development in the cellular slime molds Dictyostelium discoideum and D. mucoroides.

Six monoclonal antibodies were isolated which react with common antigens shared by multiple glycoconjugate species in the cellular slime mold Dictyostelium discoideum. Based on competition of antibody binding by glycopeptides and simple sugars, and inhibition of antibody binding by antigen pretreatment with Na periodate, it is argued that at least five of the six antibodies recognize epitopes which contain carbohydrate. These epitopes are consequently referred to as glycoantigens (GAs). Three of the GAs are expressed during growth and throughout the developmental cycle, but are eventually enriched in prestalk and stalk cells. The remaining three are expressed only during and/or after aggregation and are exclusively expressed or highly enriched in prespore cells and spores. These conclusions are derived from Western blot immunoanalysis of purified cell types, immunofluorescence, and EM immunocytochemistry. The two GAs found only in prespore cells appear to be exclusively enclosed within prespore vesicles. The third GA of this type, which is only enriched in prespore cells compared to prestalk cells, is also found in other vesicle types as well as on the cell surface. Two of the GAs enriched in prestalk cells are initially found in all cells of the slug. They are undetectable in spores and prominent in stalk cells. The third GA, though found in the interiors of both prestalk and prespore cells, is enriched on the cell surface of prestalk cells. The chief characteristics of expression of four of these GAs are conserved in the related species D. mucoroides. This species is characterized by continuous transdifferentiation of prespore cells into prestalk cells. This shows that the prespore cells maintain specific mechanisms for turning over their cell type specific GAs and that prestalk cells express a specific mechanism for inducing at least one of their cell-type specific GAs. These observations identify specific carbohydrate structures (as GAs) whose synthesis, subsequent localization and turnover are developmentally regulated. The exclusive association of two GAs with prespore vesicles identifies these GAs as markers for this organelle and raises questions regarding the functional significance of this association. The restricted cell surface localization of the other four GAs, together with data from cell adhesion studies, suggest the possibility of a potential role for these GAs in intercellular recognition leading to cell sorting.

Antibodies, Monoclonal↗
PubMedDate not supplied

Klebsiella pneumoniae pseudobacteremia due to cross-contamination of a radiometric blood culture analyzer.

Blood isolates from 13 patients in one hospital were positive for Klebsiella pneumoniae over a two-week period. Vials of potassium chloride used in intravenous fluid admixture initially were suspected of being contaminated and thus causing the problem. However, a comparison of patients who had blood cultures positive for K. pneumoniae with control patients who had blood cultures negative for this organism during the same period identified no common features that would explain the increase in K. pneumoniae blood isolates. Careful evaluation of laboratory data suggested that six of the 13 culture-positive patients had probable pseudobacteremia, an explanation that would account for the increase in isolates above the endemic level of true K. pneumoniae bacteremia in the hospital. Epidemiologic data suggested that cross-contamination of adjacent and non-adjacent blood culture vials on the radiometric blood culture analyzer was the cause of pseudobacteremia; K. pneumoniae serotyping data supported this hypothesis. A mock trial using the analyzer demonstrated that cross-contamination of non-adjacent vials by the sampling needles could occur. Changing the sampling needles of the analyzer daily, in accordance with the manufacturer's recommendations, prevented further episodes of pseudobacteremia from the analyzer.

Blood↗
PubMedDate not supplied

Phosphoglucomutase polymorphism detected by isoelectric focusing: gene frequencies, evolution and linkage.

Four alleles at the phosphoglucomutase (PGM1) locus in man have been recently demonstrated by isoelectric focusing, and in this study gene frequencies have been estimated for four populations, and significant differences have been indicated between the results. Pedigree analysis of the PGM1 and rhesus loci confirm a weak linkage in males, but none in females. An examination of PGM1 phenotypes in a range of primates shows that a proportion possess a band focusing at the same isoelectric point as human PGM1+1. We propose that all the human and primate alleles may have evolved from a common ancestral PGM1+1 locus.

Animals↗
PubMedDate not supplied

Engineering, characterization and in vitro efficacy of the major peanut allergens for use in immunotherapy.

BACKGROUND: Numerous strategies have been proposed for the treatment of peanut allergies, but despite the steady advancement in our understanding of atopic immune responses and the increasing number of deaths each year from peanut anaphylaxis, there is still no safe, effective, specific therapy for the peanut-sensitive individual. Immunotherapy would be safer and more effective if the allergens could be altered to reduce their ability to initiate an allergic reaction without altering their ability to desensitize the allergic patient. METHODS: The cDNA clones for three major peanut allergens, Ara h 1, Ara h 2, and Ara h 3, have been cloned and characterized. The IgE-binding epitopes of each of these allergens have been determined and amino acids critical to each epitope identified. Site-directed mutagenesis of the allergen cDNA clones, followed by recombinant production of the modified allergen, provided the reagents necessary to test our hypothesis that hypoallergenic proteins are effective immunotherapeutic reagents for treating peanut-sensitive patients. Modified peanut allergens were subjected to immunoblot analysis using peanut-positive patient sera IgE, T cell proliferation assays, and tested in a murine model of peanut anaphylaxis. RESULTS: In general, the modified allergens were poor competitors for binding of peanut-specific IgE when compared to their wild-type counterpart. The modified allergens demonstrated a greatly reduced IgE-binding capacity when individual patient serum IgE was compared to the binding capacity of the wild-type allergens. In addition, while there was considerable variability between patients, the modified allergens retained the ability to stimulate T cell proliferation. CONCLUSIONS: These modified allergen genes and proteins should provide a safe immunotherapeutic agent for the treatment of peanut allergy.

2S Albumins, Plant↗
PubMedDate not supplied

In vitro effects of recombinant human megakaryocyte growth and development factor on primary human tumour colony growth.

A study was made of the in vitro effects of recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) on breast, prostate, cervix and colon cancers. Tumour growth was assessed using a soft agar clonogenic assay. Stimulation of megakaryocyte numbers was seen in liquid culture following 10 ng/ml PEG-rHuMGDF. The same concentration led to no significant difference in colony-forming efficiencies for 22 of 25 tumour samples. A significant reduction in colony-forming efficiencies was seen for the remaining 3 specimens. These results suggest that PEG-rHuMGDF will not stimulate tumour growth in vivo.

Breast Neoplasms↗
PubMedDate not supplied

Recording of external radiation exposures at Oak Ridge National Laboratory: implications for epidemiological studies.

Accurate measurements of radiation exposure for individuals are critical to assessing radiation-mortality associations. This paper is based on a study of changes in recorded doses and in radiation monitoring programs at Oak Ridge National Laboratory, a U.S. Department of Energy facility where whole body external penetrating radiation exposures have been of primary epidemiological interest. External radiation monitoring data from 1943-1984 are analyzed for a group of white males (N = 8,318). The proportion of workers monitored for external radiation increased from about 50% in 1943 to over 80% in 1944 to above 98% after 1948. Mean radiation doses showed maxima in 1944 and 1957, followed by steady and long-term declines. Numerous changes in monitoring programs occurred during the study period, including changes in the types of dosimeters used, the frequency of reading dosimeters, methods of calculating doses, and practices of recording doses. Temporal patterns of doses in the lower range of the distribution showed some changes suggestive of changes in policies and practices for recording doses, which would influence dose values used in epidemiological studies. Reliable and accurate exposure measurements are especially important in studies of low level exposures due to small differences in outcomes between exposure groups. Evidence of changes in recorded doses due to monitoring and recording practices, rather than to actual changes in exposures in this well-monitored population, suggests the importance of comparable studies of other populations used for epidemiological studies of radiation-mortality associations.

Bias↗
PubMedDate not supplied

p16 overexpression: a potential early indicator of transformation in ovarian carcinoma.

OBJECTIVE: The recently cloned gene p16 (MST1) has been identified as a putative tumor suppressor gene that binds to CDK4 and CDK6 (cyclin-dependent kinases), preventing their interaction with cyclin D1 and thereby preventing cell cycle progression at the G1 stage. In addition, the p16 gene has been shown to have a high frequency of mutation in some tumor cell lines; however, it has also been shown that a much lower frequency of mutation occurs in primary tumors. This study investigated the mRNA expression level and mutation status of the p16 gene in ovarian tumors. METHODS: We performed quantitative polymerase chain reaction and direct cDNA sequencing analysis. To confirm the p16 protein level in ovarian tumors, Western blotting and immunohistochemical staining were performed. Expression levels of mRNA for the p16 gene relative to the beta-tubulin gene were examined in 32 ovarian tumors (24 carcinomas, six low malignant potential tumors, and two benign tumors) and six normal ovaries. RESULTS: The mRNA expression level of p16 was significantly elevated in 28 ovarian tumors (22 carcinomas, five low malignant potential tumors, and one benign tumor) compared with that of normal ovaries. Western blotting analysis and immunohistochemical staining confirmed elevated p16 protein levels in ovarian tumor samples. Among 32 ovarian tumors, cDNA sequencing of the p16 gene showed no p16 mutation resulting in a coding error, although one silent mutation and three polymorphisms were found. CONCLUSIONS: Although p16 is seldom mutated in ovarian tumors, the overexpression of p16 in most ovarian tumor cases indicates a dysfunction in the regulatory complex for G1 arrest. Therefore, overexpression of p16 may be an important early event in the neoplastic transformation of the ovarian epithelium.

Biomarkers, Tumor↗