Search PubMed⌕ Search

Biomedical subjects

R A Walker

Publications and source records attributed to R A Walker.

At least 181 records · Page 10Linked to original sources
PubMed1985

Lectin binding and steroid receptors in human breast carcinomas.

A series of breast carcinomas of known steroid receptor status have been examined for evidence of binding of the lectins peanut agglutinin, soy bean agglutinin and wheat germ agglutinin. Correlations were found between oestrogen receptor status and reactivity of carcinomas to peanut agglutinin and soy bean agglutinin but these were not absolute. Wheat germ agglutinin binding was unrelated to the presence of oestrogen receptors. No relationship was evident between progestogen receptors and the binding of any lectin. It therefore seems unlikely that lectin histochemistry can replace steroid receptors as markers of hormone dependence in breast carcinomas.

Arachis↗
PubMed1985

Immunological relationships between Salmonella flagella and their potential application for salmonellae detection by immunoassay.

Native flagella of ten Salmonella serotypes were shown to possess serotype-specific antigenic determinants as well as a multiple of common antigenic determinants, which varied in concentration. Each common antigenic determinant was shared by certain, but not all, serotypes. This has been demonstrated from agglutination and radioimmunometric assay (RIMA) results, using ten antisera raised in rabbits against purified polymeric flagellins from ten Salmonella serotypes as immunogens. The minimum detectable populations of salmonellae, as determined by RIMA varied considerably, due to variation in concentrations (and possibly types) of common antigenic determinants. However, the results demonstrated the feasibility of utilizing RIMA for the qualitative detection of salmonellae, using a mixture of only the ten antisera and 125I-labelled protein A as a general tracer. In this way, 77 different salmonellae were detected in less than 8 h after culturing in selective broth. The RIMA developed was specific for salmonellae and showed no cross-reactions with high populations of other members within the family Enterobacteriaceae.

Agglutination↗
PubMed1985

Immunological relationships between Salmonella flagellins and between these and flagellins from other species of Enterobacteriaceae.

Ten antisera raised in rabbits, against polymeric flagellins from ten different Salmonella serotypes were used to determine the relative cross-activities between salmonella flagellins in monomeric form. The results showed a high degree of cross-reactivity between the antisera (IgG antibodies) and all monomeric flagellins investigated. Consequently, it was possible to detect the ten Salmonella serotypes, after heat depolymerization of flagella using radioimmunometric assay with only one antiserum raised against polymeric flagellin from one serotype. The results also showed that native flagella differed antigenically from repolymerized and monomeric flagellins. This is possibly due to changes in the tertiary structure of sub-units of flagella when depolymerized with acid or heat resulting in unfolding and unmasking of common antigenic determinants. The unfolded and unmasked antigenic determinants were not only common to the Salmonella serotypes investigated, but also to other members of Enterobacteriaceae.

Antibody Specificity↗
PubMed1985

Rapid detection of salmonellae by immunoassays with titanous hydroxide as the solid phase.

Radioimmunometric and enzyme-immunometric assays were developed for the detection of salmonellae in pure and mixed cultures as well as in 59 food samples. The performances of titanous hydroxide suspension and microtiter plates as the solid phase for the immobilization of microorganisms were compared in these immunoassays. Detection of populations of salmonella cells in pure culture, diluted with saline, was 4- to 10-fold more sensitive with the microtiter plates. However, with mixed culture of salmonella and other enterobacterial species, the detection sensitivity with titanous hydroxide was 100- to 160-fold more sensitive than with microtiter plates. Good correlation existed between results of a standard cultural method for the detection of salmonellae in foods and those obtained from radioimmunometric and enzyme-immunometric assays utilizing titanous hydroxide. However, a high incidence of false-positive and false-negative results with food samples occurred with the enzyme-immunometric assay utilizing microtiter plates. The results provided strong evidence for the merits of substituting titanous hydroxide for microtiter plates as the solid phase for the immobilization of salmonellae for their detection by immunoassays. The immunoassays were rapid and enabled the analysis of a large number of selective enrichment cultures of food samples for salmonellae within 8 h.

False Negative Reactions↗
PubMed1985

Production of potent Salmonella H antisera by immunization with polymeric flagellins.

Highly purified polymeric flagellin preparations from 10 different Salmonella serotypes were used to produce specific Salmonella H antisera with high titers by the immunization of rabbits. Antigen emulsions in complete Freund adjuvant were administered at the rate of 50 micrograms per rabbit by multiple intradermal injection. Booster injections were given 110 days after the primary immunization. The immune response was monitored regularly over a period of 200 days. The results showed that the H titers, determined with 125I-labeled antigens, averaged 61,000 +/- 39,000, and the H agglutination titers of 83% of the animals were greater than 40,000. The high titers of the immunized animals persisted for approximately 4 months. The O agglutination titers of the antisera were less than 10 for 9 of the flagellin preparations and ranged from 10 to 320 for the remaining preparation. The antisera obtained were serotype specific after appropriate dilution.

Agglutination Tests↗
PubMed1985

Immobilization of microorganisms for detection by solid-phase immunoassays.

Several cultures of gram-negative and gram-positive bacteria were successfully immobilized with titanous hydroxide. The immobilization efficiency for the microorganisms investigated in saline and broth media ranged from 80.2 to 99.9%. The immobilization of salmonellae was effective over a wide pH range. The presence of buffers, particularly phosphate buffer, drastically reduced the immobilization rate. However, buffers may be added to immunoassay systems after immobilization of microorganisms. The immobilization process involved only one step, i.e., shaking 100 microliter of culture with 50 microliter of titanous hydroxide suspension in polystyrene tubes for only 10 min. The immobilized cells were so tenaciously bound that vigorous agitation for 24 h did not result in cell dissociation. The nonspecific binding of 125I-labeled antibody from rabbits and 125I-labeled protein A by titanous hydroxide was inhibited in the presence of 2% gelatin and amounted to only 5.6 and 3.9%, respectively. We conclude that this immobilization procedure is a potentially powerful tool which could be utilized in solid-phase immunoassays concerned with the diagnosis of microorganisms.

Bacteriological Techniques↗
PubMed1985

Method for the isolation of highly purified Salmonella flagellins.

Ten different Salmonella serotypes were grown in a chemically defined medium supplemented with 0.01% yeast extract. After sedimentation of the cells by centrifugation, flagella were detached by exposure to pH 2 for 30 min at room temperature. The flagellaless cells were removed by centrifugation, and the flagellin in the supernatant was further purified by high-speed centrifugation, ammonium sulfate precipitation, and dialysis in 50,000-molecular-weight-cutoff tubing. The 10 flagellin preparations were of a high degree of purity, as demonstrated by electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and measurement of salmonella H and O agglutination titers of antisera raised in rabbits with the flagellin preparations as immunogens.

Antigens, Bacterial↗
PubMed1984

beta 2-microglobulin in non-malignant and malignant human breast: a feature of differentiation.

An indirect immunofluorescent method has been used to study the distribution of the membrane protein beta 2-microglobulin in normal, benign and malignant human breast tissue. A uniform staining of epithelial cell membranes has been found in all normal and benign tissues, with only a minor variation in the intensity of reaction between samples. In contrast the carcinomas have shown a variety of reactions, with some behaving in a manner similar to the normal and benign breast tissue, others being heterogeneous with regard to intensity of staining and the remainder having a weak or a negative reaction. The immunohistochemical behaviour of the carcinomas has paralleled the degree of histological differentiation, with poorly differentiated carcinomas showing little reactivity. A comparable relationship with lymph node status has not been found. Although those carcinomas with a staining pattern akin to non-malignant tissue have a lower incidence of lymph node metastasis it has been the heterogeneous reacting group rather than the weak staining and negative tumours which has shown a higher rate of axillary lymph node metastasis. The prognostic significance of this finding is at present uncertain and can probably only be assessed from information about patient survival.

Breast Diseases↗
PubMed1984

The binding of peroxidase-labelled lectins to human breast epithelium. I--Normal, hyperplastic and lactating breast.

Six peroxidase-labelled lectins have been applied to tissue sections of normal, hyperplastic and lactating human breast. The effect of fixation on binding has been assessed by the comparison of specimens treated with a variety of fixatives with frozen material; the effect of trypsin has also been considered. The other objective has been to establish the consistency of lectin reactivity with this non-malignant breast tissue. Fixation has little effect on the binding of wheat germ agglutinin and peanut lectin, although reactivity with the latter was sometimes increased above that seen in frozen material by the use of Bouin's fluid. Trypsinization of formalin-fixed tissue appears to be a prerequisite for staining with soy bean agglutinin and Ulex europeus. The binding of Lotus tetragonolobus and Dolichos biflorus to fixed tissue has been found to be unreliable in comparison to frozen samples. Soy bean agglutinin and Dolichos biflorus, both specific for N-acetyl-D-galactosamine, have binding patterns which vary between specimens and often between themselves. Of the two fucose-binding lectins Ulex europeus has shown a variability of reaction between specimens, whilst Lotus tetragonolobus consistently reacts with ductal and acinar epithelium but with varying intensities. Consistent binding patterns have been found for wheat germ agglutinin and peanut lectin, the latter after the use of neuraminidase. They therefore form a useful basis for comparison with the reactivity of malignant breast tissue.

Breast↗
PubMed1984

The histochemistry of glycosidases in human benign and malignant breast tissue.

Histochemical methods for the localization of four glycosidases (beta-glucuronidase, beta-N-acetyl glucosaminidase, beta-D-galactosidase and alpha-mannosidase) have been applied to 40 cases of human normal and hyperplastic breast tissue and 100 human breast carcinomas. All tissues have been fixed in formol-calcium at 4 degrees C and washed in gum sucrose. beta-Glucuronidase and beta-N-acetyl glucosaminidase have consistently been detected in essentially all cells of normal and hyperplastic tissue. A similar distribution has been found for better differentiated carcinomas but the number of cells with detectable enzyme decreases in the more poorly differentiated tumour. beta-D-Galactosidase and alpha-mannosidase have only been demonstrated in very occasional cells in normal breast tissue. The incidence increases in hyperplastic tissue, and in approximately half the carcinomas many cells have detectable enzyme. The localization of beta-D-galactosidase has not been related to tumour differentiation but the better differentiated carcinomas tend to have few cells with demonstrable alpha-mannosidase. Although it has been suggested that glycosidases can have an effect on membrane function no differences have been found between those carcinomas having a few or many cells with detectable enzyme and the presence or absence of axillary lymph node metastasis. Total enzyme activity cannot be detected in fixed tissue, nor can an accurate quantitative assessment be made, but under the conditions of this study it is possible to conclude that there are differences between normal and malignant breast tissue in the localization of glycosidases.

Acetylglucosaminidase↗
PubMed1984

The binding of peroxidase-labelled lectins to human breast epithelium. II--The reactivity of breast carcinomas to wheat germ agglutinin.

The binding of peroxidase-labelled wheat germ agglutinin (WGA) to a series of 125 human breast carcinomas has been studied. Routine fixation and processing has been shown to have no deleterious effect on reactivity. In contrast to the homogeneous binding of WGA to normal and hyperplastic human breast previously reported, the binding of WGA to breast carcinomas exhibits heterogeneity. This is of two forms: (1) in relation to cell reactivity, which is significantly correlated to tumour differentiation, with fewer cells reacting in those carcinomas showing loss of histological differentiation; (2) with regard to the interaction between WGA and specific saccharides of cellular glycan-components, binding to sialic acid appearing to be of significance to varying degrees in some carcinomas but not in others nor, as previously reported, in normal breast. The alteration in WGA-saccharide interaction is an indicator of the heterogeneity of the carbohydrate chains of glycoproteins within neoplastic cells of the same tumour and between carcinomas. The other finding of note has been that of the significant association between heterogeneity of cellular reactivity to WGA and the presence of axillary lymph node metastasis, but a lack of correlation between virtual absence of reactivity and nodal metastasis.

Breast↗
PubMed1984

The binding of peroxidase-labelled lectins to human breast epithelium. III--Altered fucose-binding patterns of breast carcinomas and their significance.

Tissue sections from 80 human breast carcinomas have been examined for evidence of binding of the two fucose-specific lectins, Lotus tetragonolobus and Ulex europeus I, with enzymes utilized as an indicator system. Both single-staining and double-staining methods (Lotus tetragonolobus-peroxidase and Ulex europeus I-alkaline phosphatase) have been employed. In contrast to normal breast in which there is consistent reactivity of all epithelium with Lotus tetragonologus a variable loss of binding has been found within carcinomas. Surprisingly, this bears no relationship to tumour differentiation; nor does it correlate with local lymph node metastasis. Ulex europeus I has a variable reactivity with carcinomas, as it does with normal breast epithelium, and this likewise has no correlation with differentiation. However, a relationship has been found between specific patterns of binding and axillary lymph node status. The value of using two lectins with the same major sugar specificity but having different binding affinities is illustrated in this study, in which differences in behavioural characteristics have been identified between fucose-containing glyco-conjugates having minor structural variations.

Breast↗
PubMed1983

The localization of prolactin binding sites in human breast tissue.

An immunohistochemical method involving the application of purified human prolactin and a specific antiserum to human prolactin, followed by the peroxidase-anti-peroxidase immunoperoxidase technique, has been used to detect prolactin binding in benign and malignant human breast tissue. The use of fresh, frozen material has been found to be essential. Prolactin binding has been shown to be a consistent feature of benign breast tissue but a variation within samples has been noted which is irrespective of hyperplastic changes. Fifty six percent of breast carcinomas gave a positive reaction but heterogeneity of binding has been shown to be a significant feature. A relationship between the presence and extent of prolactin binding and good histological differentiation of the tumours has been noted. It is concluded that immunohistochemistry is a suitable method for the demonstration of prolactin binding sites in human breast tissue and can provide useful information with regard to tumour heterogeneity.

Breast↗
PubMed1983

The binding of fluorescent-labelled concanavalin A to human breast tissue--a marker of differentiation.

Fluorescent-labelled Concanavalin A (ConA) has been applied to frozen and fixed, processed sections of normal, hyperplastic and malignant human breast tissue. No loss of binding activity occurs with fixation and the best results are obtained with Bouin's fixed material or trypsinised sections of tissue fixed in 4 per cent. formaldehyde in saline. A difference in reaction has been demonstrated between normal tissue, hyperplastic tissue and carcinomas, which is further accentuated when a lower concentration of ConA-FITC is used. Staining is consistently localised to the cell periphery in all benign tissue, the well differentiated carcinomas and some of the moderately differentiated tumours. A mixed pattern of reaction with staining of the cell periphery and cell cytoplasm is seen in some tumours, whilst many of the poorly differentiated carcinomas show cytoplasmic staining only. There is a significant correlation between the pattern of staining and the histological differentiation of carcinomas, and between the degree of reactivity and differentiation. It is suggested that any relationship ConA reactivity may have to prognosis may be strongly associated with tumour differentiation.

Breast↗
PubMed1982

Biological markers in human breast carcinoma.

An indirect immunoperoxidase method has been used to study a series of breast carcinomas for the presence of five potential biological markers (two appropriate to breast, two placental proteins and one oncofetal protein). One or more markers were detectable in 84 per cent. of tumours, two or more in 60 per cent. and three of more in 32 per cent. Similarity of staining patterns was noted for two placental proteins and for the oncofetal protein and one placental protein. Markers appropriate to breast tissue tended to be detected in separate areas. In certain instances more than one antigen could be detected within the same cell. The relationship of the number of markers present to histological differentiation was found to be complex, but carcinomas with three or more antigens demonstrated showed a tendency to be well or moderately differentiated. Tumours with no markers often had not metastasised to lymph nodes but conversely those with four and five markers had. A striking throughout the study was the heterogenous secretory nature of breast carcinomas.

Antigens↗
PubMed1982

Mucoid carcinomas of the breast: a study using mucin histochemistry and peanut lectin.

The mucin secreted by mucoid carcinomas of the breast has been studied in a series of 20 tumours by histochemical methods and peroxidase labelled peanut lectin. The histochemical techniques showed that the carcinomas could be divided into two groups depending on whether the mucin was composed predominantly of acid or neutral mucopolysaccharides. The specific binding of peanut lectin to beta-galactosyl groups, in combination with neuraminidase treatment, enabled further divisions to be made and so demonstrated the heterogenous nature of the mucin secreted by mucoid carcinomas and also the value of using lectins as specific probes in histological methods.

Adenocarcinoma, Mucinous↗
PubMed1982

Treatment of giardiasis: literature review and recommendations.

Giardia lamblia has emerged as the most common intestinal parasite in the United States. This article presents a brief review of the clinically important aspects of giardiasis and evaluates the currently used therapeutic agents. Three drugs have been advocated for the treatment of giardiasis; furazolidone (Furoxone), metronidazole (Flagyl), and quinacrine (Atabrine). None of them, however, is ideal. Metronidazole and quinacrine are more effective than furazolidone, but furazolidone has the advantage of a liquid formulation that makes administration to children easier. Quinacrine is much less expensive than the other two agents but has a somewhat higher rate of side effects and a bitter taste. There is concern about the carcinogenic potential of furazolidone and metronidazole, but this has not been evaluated for quinacrine. In the balance, we conclude that quinacrine is probably the preferable drug to use in the pediatric age group because of proven effectiveness and lower cost.

Animals↗