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Biomedical subjects

M M McCabe

Publications and source records attributed to M M McCabe.

13 recordsLinked to original sources
PubMed1991

Soft tissue and visceral sarcomas in Irish patients. A preliminary report from the Dublin Soft Tissue Tumour Panel.

Sarcomas of the soft tissues and viscera are a diverse group of uncommon neoplasms that often present difficult diagnostic and management problems. The Dublin Soft Tissue Tumour Panel prospectively reviewed pathology material from 137 patients of four Dublin teaching hospitals between January 1989 and August 1990. The prevalence of sarcomas in Irish patients was found to be similar to that estimated for the United States. The most common sarcoma of soft tissues was malignant fibrous histiocytoma (14) and the most common visceral sarcoma was leiomyosarcoma (10). The most problematic diagnoses were 3 peripheral neuroepitheliomas (extraskeletal Ewing's sarcomas) which occurred in patients aged 19-27 years, distinctly younger than the typical adult sarcoma patient. Clinical follow-up is in progress and will be combined with the findings of a linked retrospective study, to facilitate evaluation of all aspects of management.

Abdominal Neoplasms↗
PubMed1991

Identification of transforming growth factor-beta as an immunosuppressive factor in aqueous humor.

The anterior chamber of the eye is an immunologically privileged site. Over the past 15 years, numerous laboratories documented that the privileged status of this unique site is mediated by multifactorial immunoregulatory processes. Among the participating factors is the aqueous humor that circulates in the anterior chamber and is in contact with most of the tissues in the anterior segment of the eye. Recently, it was found that normal aqueous humor is a powerful inhibitor of antigen-driven T lymphocyte activation, but it spares other important functional properties of T cells. The spectrum of immune inhibitory properties resembles some of the activities of transforming growth factor-beta (TGF-beta), a polypeptide cytokine. Because of this similarity, the authors tried to determine if TGF-beta is present in aqueous humor and whether this cytokine could account for the lymphocyte inhibitory activity of this biologic fluid. They found TGF-beta in aqueous humor by dot-blot analysis. Using the CCL-64 mink lung epithelial cell bioassay for this compound, TGF-beta bioactivity was shown in aqueous humor from several different species, including human. In rabbit and human aqueous humor, most of the biologic activity was due to TGF-beta 2 (80-90%). Dose-response curves generated by using purified porcine TGF-beta showed that aqueous humor contained sufficient concentrations of TGF-beta to account for the observed inhibition in several assays for T cell activation and proliferation. Partial purification of the lymphocyte inhibitor in rabbit aqueous humor by size exclusion in high-performance liquid chromatography demonstrated that several lymphocyte inhibitory fractions contained TGF-beta bioactivity. Finally, neutralizing antisera to TGF-beta 2 were able to reverse most of the lymphocyte inhibitory activity of aqueous humor. It was concluded that TGF-beta was present in high concentration in normal aqueous humor and that this cytokine contributed to the immunosuppressive properties of aqueous humor.

Animals↗
PubMed1989

Pulmonary alveolar proteinosis: primary and secondary, a report of three cases.

Three cases of the rare disorder pulmonary alveolar proteinosis (PAP) presented to our unit over the past thirteen years. Two of the patients conformed to the classical description of idiopathic or "primary" PAP. One patient appeared to have co-existing extrinsic allergic alveolitis with "secondary" PAP, an association not previously described. This patient has required continued steroid therapy, a mode of treatment usually contraindicated in PAP.

Adult↗
PubMed1989

High avidity monoclonal antibody to imidazole ring-opened 7-methylguanine.

A hybridoma (K1A8) secreting a high affinity antibody to imidazole ring-opened 7-methylguanine (N5-methyl-N5-formyl-2,5,6-triamino-4-hydroxypyrimidine) was obtained from spleen cells of a mouse immunized with a conjugate of keyhole-limpet hemocyanin and imidazole ring-opened 7-methylguanylic acid (iro-7mGMP). The antibody recognizes the iro-7-methylguanine (iro-7mG) determinant in the BSA-iro-7mGMP conjugate, in chemically methylated, denatured DNA, and in the ring-opened 7-methylguanosine, 7-methyldeoxyguanosine and 7mGMP haptens. In the competitive ELISA of DNA-iro-7mG, 50% inhibition (I50) was observed at 4 fmol determinant per well (8 x 10(-11) M) using BSA-iro-7mGMP as the immobilized antigen. The lower limit of 7-methylguanine (7mG) detection in DNA is determined by the binding of unmodified DNA per se to the antibody. The intrinsic reaction of DNA with antibody is low; in the competitive ELISA I50 was obtained with 330 micrograms calf thymus DNA per 50 microliters well, equivalent to 4 nmol iro-7mG per mol nucleotide. The 7mG content of calf thymus DNA is 7 nmol per mol nucleotide (approximately 20 amol per micrograms DNA). The limit of detection of 7mG by competitive ELISA is quoted provisionally as 7 nmol iro-7mG per mol nucleotide, where 30% inhibition of antibody binding is obtained in the presence of 105 micrograms DNA per 50 microliters well. Nuclear DNAs of tissue culture cells treated with 0, 0.01 and 0.1 mM N-methyl-N'-nitro-N-nitrosoguanidine contained 0.18, 31 and 320 mumol, respectively, of 7-methylguanine adducts per mol of nucleotides. This report indicates that the K1A8 antibody will serve to quantify DNA alkylation in human populations exposed to low levels of methylating carcinogens.

Alkylating Agents↗
PubMed1987

Characterization by affinity electrophoresis of an alpha-1,6-glucan-binding protein from Streptococcus sobrinus.

Glucan-binding protein 1 (GBP1), the most abundant glucan-binding protein isolated from culture supernatants of Streptococcus sobrinus 6715-49, has been purified by affinity chromatography on Sephadex G-50 followed by gel permeation chromatography with Bio-Gel P-10. The specificity and affinity of GBP1 for glucans were assessed by affinity electrophoresis. GBP1 did not detectably bind to glucans lacking linear arrays of alpha-1,6 linkages. The association constant for the linear alpha-1,6-glucan Dextran T2000 was 3 x 10(7) M-1. Providing small isomaltosaccharide ligands to compete with this dextran indicated that the binding site maximally accommodated isomaltosaccharides with a degree of polymerization of 8. When glucans produced by purified S. sobrinus glucosyltransferases were tested, GBP1 displayed the highest affinity for the glucan from the soluble-product, primer-independent glucosyltransferase.

Bacterial Proteins↗
PubMed1978

Multiple forms of dextran-binding proteins from Streptococcus mutans.

We have isolated a series of five proteins which appear to possess characteristic individual capacities for synthesizing dextrans and binding dextrans. Our suggestion that these proteins comprise an isozyme-like distribution of lectin and enzyme activities is, of course, very speculative and remains to be rigourously confirmed. However, the very identification of these several dextran binding proteins provides a biochemical basis to explain numerous observations suggesting that more than one mechanism for dextran binding is possessed by S. mutans (for instance: 24-27), especially the observations with mutants (24). These proteins probably are the molecular determinants of host infection by S. mutans and may prove to be potent immunogens for use in a vaccine. The presence of a dextran-binding lectin in S. mutans implicates this bacterial lectin in the earliest stage of infection: Attachment to host tissues. The multiplicity of proteins possessing characteristic dextran-synthesizing and dextran-binding capacities indicates the complexity of the adherence mechanisms evolved in S. mutans. Experiments with other bacteria (10-12, 28) suggest that bacterial lectins, in concert with host tissue carbohydrates, may be the molecular mediators of host recognition and subsequent initial attachment of bacterial cells to host tissues in non-pathogenic as well as pathogenic bacteria.

Bacterial Proteins↗
PubMed1978

The dextran acceptor reaction of dextransucrase from Streptococcus mutans K1-R.

Soluble dextransucrase activity(ies) was eluted with a solution of clinical dextran from the insoluble dextran--cell complex produced by Streptococcus mutans K1-R grown in the presence of sucrose. Studies of the dextran acceptor-reaction of the soluble enzyme-preparation indicate that it is highly specific for dextran of high molecular weight. Increased dextran synthesis in the presence of dextran acceptor and the apparent inhibition of this stimulation by higher concentrations of dextran result from product modification rather than a direct effect on the level of enzyme activity. The results demonstrate that the potentially water-insoluble structure synthesized by dextransucrase on exogenous, soluble dextran acts as a more-efficient acceptor than the soluble dextran. The role of the acceptor reaction in the biosynthesis of complex dextrans is discussed.

Dextrans↗
PubMed1977

Specific method for the purification of Streptococcus mutans dextransucrase.

A convenient and rapid method for the purification of Streptococcus mutans dextransucrase is described. Affinity chromatography, on a column containing insoluble dextran purified from a culture of S. mutans 6715-49, gave an almost 300-fold purification, with 76% recovery of enzyme. Subsequent hydrophobic chromatography on butyl-agarose increased the overall enzyme purification to more than 1,000-fold, with a 65% recovery of activity. Two components of the dextransucrase activity were separated during hydrophobic chromatography. Both synthesized insoluble glucan as their major product and were capable of synthesizing soluble glucan in the presence of exogenous soluble dextran. However, the major enzyme component, which coeluted with a catalytically inert, dextran-binding protein, was greatly stimulated by exogenous soluble dextran, whereas the second enzyme component was not.

Cell-Free System↗
PubMed1975

Relationship between cell-bound dextransucrase and the agglutination of Streptococcus mutans.

Dextran-induced agglutination of Streptococcus mutans cells is independent of cell-bound dextransucrase activity. Toluene extraction or the presence of Hg2+ or Cu2+ markedly decreased or completely abolished cell-bound dextransucrase activity without adversely affecting dextran-induced cell agglutination. Cells treated by heating at 100 C until cell-bound dextransucrase was completely inactivated continued to agglutinate when induced by dextran-induced cell agglutination resulted from cell treatment with trypsin and several other enzymes, as well as from ethylenediaminetetraacetic acid treatment, without a corresponding loss of cell-bound dextransucrase activity. Cells possessed a greater avidity for branched dextrans of low molecular weight than for linear dextrans of the same weight, indicating that size alone does not determine the efficiency of dextran as an inducer of agglutination. Divalent metal ions were required for both sucrose- and dextran-induced agglutination of S. mutans K1-R cells. Although normal cells of strain 6715-49 did not appear to require divalent cations for agglutination, heat- and ethlyenediaminetetraacetic acid-treated cells specifically required Ca2+. The role of Ca2+ in cell agglutination may be either to activate the cell-surface dextran receptor or to form specific intercellular Ca2+ bridges.

Agglutination↗