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Biomedical subjects

R A Walker

Publications and source records attributed to R A Walker.

At least 145 records · Page 8Linked to original sources
PubMed1989

An evaluation of immunoreactivity for c-erbB-2 protein as a marker of poor short-term prognosis in breast cancer.

Eighty-five breast carcinomas from the same number of patients have been assessed immunohistochemically using the antiserum 21N for the presence of the c-erbB-2 protein. Twenty-two of the patients had evidence of advanced disease (tumour fixation or distant metastases) at presentation. Follow-up was for a median of 24 months. c-erbB-2 protein was detected in the majority of cells in 14 (16.5%) carcinomas, and to a lesser extent in a further six (7%) tumours. There was no relationship between staining and stage, node status or size but more poorly differentiated carcinomas had evidence of staining (36%) than well (17%) or moderately (14%) differentiated carcinomas (P = 0.02). There was a significant association between staining and mortality (P = 0.009) and recurrence (P = 0.0002). The relative risk of death for staining compared to no staining (after adjusting for node status, stage and grade) was 2.97 (95% confidence interval 1.29, 6.84) and the relative risk of recurrence for staining compared to no staining after similar adjustment was 3.85 (95% confidence interval 1.86-7.97). In this particular group of patients immunoreactivity for c-erbB-2 protein is an independent indicator of poor short-term prognosis.

Biomarkers, Tumor↗
PubMed1989

West Midlands Oncology Association trials of adjuvant chemotherapy in operable breast cancer: results after a median follow-up of 7 years. I. Patients with involved axillary lymph nodes.

The aim of this study was to test the effectiveness of a regimen of combination chemotherapy known to be active in advanced breast cancer when given as an adjuvant treatment after mastectomy. A total of 569 patients with cancer of the breast and involvement of axillary lymph nodes were randomised, after simple mastectomy with axillary sampling, to receive either no adjuvant treatment or intravenous adriamycin 50 mg, vincristine 1 mg, cyclophosphamide 250 mg, methotrexate 150 mg and fluorouracil 250 mg (AVCMF) every 21 days for eight cycles. Randomisation was stratified according to menopausal status and tumour size. Treatment was started within 14 days of surgery in 94% of patients. Eighty-eight per cent of patients received at least seven cycles of chemotherapy with no dose reduction. The median relapse-free survival was prolonged by 14 months in patients treated with AVCMF (chi2 1 = 11.7; P = 0.0006). In the premenopausal group this period was 17 months (chi2 1 = 8.8; P = 0.003) compared with 8 months in the post-menopausal group (chi2 1 = 3.3; P = 0.07). Neither overall survival nor survival in these subgroups was significantly influenced by treatment.

Adult↗
PubMed1989

West Midlands Oncology Association trials of adjuvant chemotherapy in operable breast cancer: results after a median follow-up of 7 years. II. Patients without involved axillary lymph nodes.

The aim of this study was to test the effectiveness of a regimen of combination chemotherapy when given as an adjuvant treatment after mastectomy to patients with histologically negative axillary lymph nodes. A total of 574 patients with cancer of the breast and no involvement of axillary lymph nodes were randomised, after simple mastectomy with axillary sampling, to receive either no adjuvant treatment or oral fluorouracil 500 mg, methotrexate 25 mg and chlorambucil 10 mg p.o. on day 1 and fluorouracil 500 mg and chlorambucil 10 mg p.o. on day 2 (LMF) every 21 days for eight cycles. Randomisation was stratified according to menopausal status and tumour size. Treatment was started within 14 days of surgery in 97% of patients. Ninety per cent of patients received eight cycles of chemotherapy with no dose reduction. At a median follow-up of 7 years, there was no evidence that relapse-free or overall survival time were influenced by treatment.

Adult↗
PubMed1989

Asymmetric behavior of severed microtubule ends after ultraviolet-microbeam irradiation of individual microtubules in vitro.

The molecular basis of microtubule dynamic instability is controversial, but is thought to be related to a "GTP cap." A key prediction of the GTP cap model is that the proposed labile GDP-tubulin core will rapidly dissociate if the GTP-tubulin cap is lost. We have tested this prediction by using a UV microbeam to cut the ends from elongating microtubules. Phosphocellulose-purified tubulin was assembled onto the plus and minus ends of sea urchin flagellar axoneme fragments at 21-22 degrees C. The assembly dynamics of individual microtubules were recorded in real time using video microscopy. When the tip of an elongating plus end microtubule was cut off, the severed plus end microtubule always rapidly shortened back to the axoneme at the normal plus end rate. However, when the distal tip of an elongating minus end microtubule was cut off, no rapid shortening occurred. Instead, the severed minus end resumed elongation at the normal minus end rate. Our results show that some form of "stabilizing cap," possibly a GTP cap, governs the transition (catastrophe) from elongation to rapid shortening at the plus end. At the minus end, a simple GTP cap is not sufficient to explain the observed behavior unless UV induces immediate recapping of minus, but not plus, ends. Another possibility is that a second step, perhaps a structural transformation, is required in addition to GTP cap loss for rapid shortening to occur. This transformation would be favored at plus, but not minus ends, to account for the asymmetric behavior of the ends.

Guanosine Diphosphate↗
PubMed1989

Serum levels of pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG) during normal menstrual and combined oral contraceptive cycles and relationship to immunohistological localization.

Serum levels of pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG), the major secretory protein of the endometrium during the late luteal phase of the menstrual cycle and early pregnancy, were measured serially during normal menstrual cycles and in women taking various combined oral contraceptives. Pill users were also sampled on an individual basis. Endometrium from women taking the combined oral contraceptive was examined immunohistochemically using a monoclonal antibody to alpha 2-PEG. Levels of alpha 2-PEG in the menstrual cycle sera showed consistent changes following the luteinizing hormone peak, with a greater than three-fold increase between basal levels at mid-cycle and those in the late luteal phase. Serum levels of alpha 2-PEG in the pill users remained at basal levels throughout the cycle, regardless of the progestagen in the formulation. This finding was noted in serial and individual samples from both monophasic and triphasic preparations. However, there was evidence of induction of alpha 2-PEG production at the local endometrial level when immunohistochemical staining was employed at various stages of the pill cycle. This suggests that serum levels of alpha 2-PEG may not necessarily reflect local endometrial production of the protein. These observations are discussed with reference to the proposed value of serum measurement of this protein in assessing relative progestagenic activity upon the endometrium.

Adult↗
PubMed1989

Oncogene organisation and expression: prediction in breast cancer.

The aim of the present study was to identify genes whose expression and/or organisation are altered in the diseased breast, as compared to the normal breast. Alteration of one or more genes examined has been found to occur in over 60% of breast tumour samples. Changes to three cellular proto-oncogenes are frequent, and amplification of two of these genes correlates with poor short-term prognosis. Deletion of RB-1, a tumour suppressor gene, has been detected and although these deletions do not correlate with poor prognosis, they occur more commonly in advanced tumours. A loss of sequences encoding the progesterone receptors has also been found to be frequent.

Breast Neoplasms↗
PubMed1989

The retinoblastoma gene is frequently altered leading to loss of expression in primary breast tumours.

We have analysed the organisation of the retinoblastoma (RB1) gene in 77 primary breast carcinomas, in metastatic tissue derived from 16 of those primary tumours, and in a variety of benign breast lesions. Expression of RB1 was also assessed in most samples by immunohistochemical detection of the RB1 protein in tissue sections. Structural abnormalities to RB1 were detected in DNA from 15/77 (19%) of primary breast carcinomas examined. Where DNA was available from metastatic tissue derived from such primary tumours, the same aberration could be detected. No alterations were seen in benign breast lesions. 16/56 (29%) of tumours examined for expression by immunohistochemical methods showed a proportion of tumour cells to be completely negative for the RB1 protein. All tumours in which a structural alteration to RB1 was detected had a proportion of negative cells, except for one case where all cells were positive. Several primary tumour samples were identified where there was no detectable structural change to the gene, but there was loss of expression in some tumour cells. The data presented here demonstrate that changes to the RB1 gene leading to loss of expression of both alleles are frequent in primary human breast tumours.

Amino Acid Sequence↗
PubMed1988

HLA class II sublocus expression in benign and malignant breast epithelium.

Using immunohistochemistry and a panel of five monoclonal antibodies, the epithelial expression of HLA class II sublocus products by benign and malignant breast has been studied. The magnitude of the stromal mononuclear inflammatory cell infiltrate was assessed. There was expression of HLA class II by 75 per cent of epithelial cells in the benign tissues, with little variation in intensity and between antibodies. There was coordinate expression of DR and DQW1. Epithelial expression by carcinomas was more complex and variable. Most (61 per cent) carcinomas exhibited variable loss of epithelial expression of class II products, as detected by three antibodies recognizing epitopes on DP, DQ, and DR together. Thirteen (28 per cent) carcinomas were completely negative or had very occasional positive cells. The extent of this loss was unrelated to the magnitude of the inflammatory infiltrate and axillary lymph node status. No well-differentiated carcinomas exhibited complete loss. Furthermore, non-coordinate expression of DR and DQW1 was present in 8 out of 40 carcinomas, with the proportion of DQW1 positive epithelium always being less than that of DR. Carcinomas exhibiting non-coordinate expression were never well differentiated; there was no relationship with the extent of the inflammatory infiltrate. This is the first study to detail HLA class II expression in breast, and our results suggest that alterations in expression of these products may modify or reflect tumour behaviour.

Antibodies, Monoclonal↗
PubMed1988

p21 ras protein expression in benign and malignant human breast.

The ras oncogenes encode for GTP binding and GTPase active proteins of relative molecular mass 21,000 (p21ras) which are involved in the transduction of stimuli for cell proliferation. There have been conflicting reports about the detection and significance of expression of p21ras protein in human breast disease as determined by immunohistochemistry. The antibody Y13-259, which detects a single protein of Mr 21,000, has been applied immunohistochemically to frozen sections of normal, benign proliferative breast, fibroadenomas, and carcinomas. Uniform staining of normal breast epithelium and myoepithelium was found, with occasional stronger staining in areas of epithelial hyperplasia in benign breast disease. Contrary to previous reports, decreased expression, usually heterogeneous, was found in half of the carcinomas examined. Thirty per cent of the carcinomas exhibited heterogeneous staining stronger than that of normal breast, interpreted as increased expression of p21ras protein. This did not relate to tumour grade or node status but showed a significant correlation with proliferation rate as determined by the monoclonal antibody Ki-67. This study confirms previous reports that p21ras protein expression is a feature of normal cells, and has identified increased expression in 30 per cent of tumours associated with higher proliferation rates, which is a lower incidence than previously claimed when a different antibody was employed.

Adenofibroma↗
PubMed1988

Comparison of monoclonal antibody Ki-67 reactivity with grade and DNA flow cytometry of breast carcinomas.

The reactivity of 95 breast carcinomas with the antibody Ki-67, which recognises a nuclear antigen in proliferating cells, has been assessed and compared to their histological grade and, for 47 tumours, DNA index and S-phase content. The effects of freezing and section handling on the stability of the nuclear antigen have been assessed. Evidence of nuclear staining was seen in 56% of carcinomas, with a range of positive cells from less than 1% to 60%. Cytoplasmic rather than nuclear staining was observed in 26% and 18% of carcinomas were negative. A significant correlation was observed between the presence of nuclear staining and poorer histological grade and higher S-phase content, and between the percentage of positive nuclei and S-phase content, but not grade. Three groups of carcinomas were identified: those in which Ki-67 reactivity, grade and S-phase content were similar; ones in which there was prominent nuclear reactivity with Ki-67 but low grade and S-phase content; and a group showing the converse. These patients will be followed to assess which of these three markers of proliferation is of greatest prognostic value.

Antibodies, Monoclonal↗
PubMed1988

Dynamic instability of individual microtubules analyzed by video light microscopy: rate constants and transition frequencies.

We have developed video microscopy methods to visualize the assembly and disassembly of individual microtubules at 33-ms intervals. Porcine brain tubulin, free of microtubule-associated proteins, was assembled onto axoneme fragments at 37 degrees C, and the dynamic behavior of the plus and minus ends of microtubules was analyzed for tubulin concentrations between 7 and 15.5 microM. Elongation and rapid shortening were distinctly different phases. At each end, the elongation phase was characterized by a second order association and a substantial first order dissociation reaction. Association rate constants were 8.9 and 4.3 microM-1 s-1 for the plus and minus ends, respectively; and the corresponding dissociation rate constants were 44 and 23 s-1. For both ends, the rate of tubulin dissociation equaled the rate of tubulin association at 5 microM. The rate of rapid shortening was similar at the two ends (plus = 733 s-1; minus = 915 s-1), and did not vary with tubulin concentration. Transitions between phases were abrupt and stochastic. As the tubulin concentration was increased, catastrophe frequency decreased at both ends, and rescue frequency increased dramatically at the minus end. This resulted in fewer rapid shortening phases at higher tubulin concentrations for both ends and shorter rapid shortening phases at the minus end. At each concentration, the frequency of catastrophe was slightly greater at the plus end, and the frequency of rescue was greater at the minus end. Our data demonstrate that microtubules assembled from pure tubulin undergo dynamic instability over a twofold range of tubulin concentrations, and that the dynamic instability of the plus and minus ends of microtubules can be significantly different. Our analysis indicates that this difference could produce treadmilling, and establishes general limits on the effectiveness of length redistribution as a measure of dynamic instability. Our results are consistent with the existence of a GTP cap during elongation, but are not consistent with existing GTP cap models.

Animals↗
PubMed1988

Immunohistological localization of pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG) in endometrial adenocarcinoma and effect of medroxyprogesterone acetate.

Endometrium from postmenopausal women with endometrial adenocarcinoma was examined immunohistochemically using a monoclonal antibody to pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG), the major secretory protein of the glandular epithelium during the late luteal phase of the menstrual cycle and early pregnancy. Specimens were obtained at initial diagnostic curettage and at hysterectomy after medroxyprogesterone acetate (MPA) therapy. alpha 2-PEG was not detected in any malignant tissue irrespective of histological differentiation. Non-malignant endometrium obtained in association with malignant tissue was negative for alpha 2-PEG before treatment although after MPA therapy all specimens obtained exhibited marked alpha 2-PEG localization in glands. In four specimens endogenous alkaline phosphatase was observed consistently only in the malignant endometrium. Malignant endometrium does not appear to synthesize alpha 2-PEG nor is its synthesis induced by an oral progestogen, so that it does not represent a useful marker for endometrial carcinoma. Non-malignant endometrium in postmenopausal women appears to be fully capable of alpha 2-PEG production after stimulation with an oral progestogen.

Adenocarcinoma↗
PubMed1988

The localization of laminin mRNA and protein in the postimplantation embryo and placenta of the mouse: an in situ hybridization and immunocytochemical study.

In situ hybridization (ISH) and immunocytochemistry were used to localize sites of synthesis and deposition of the basement membrane glycoprotein laminin during development in the postimplantation mouse embryo and extraembryonic membranes. In addition, similar studies were performed on postnatal viscera during the first 20 days after birth. Up to 10 days post coitum, embryonic laminin synthesis was confined to parietal endoderm. In maternal tissue, intense laminin mRNA expression was detected in decidual cells in the mesometrial and antimesometrial endometrium at 5-7 days. At 10 days, uniform expression was still seen within the mesometrial endometrium, with higher levels around migrating trophoblast, but in the antimesometrial aspect expression was restricted to the basal zone. High levels of mRNA expression persisted in parietal endoderm throughout gestation but much lower levels were detected in visceral yolk sac. In the mature placenta, laminin mRNA expression was also found associated with fetal vessels in the labyrinth and giant cells at the fetal/maternal boundary. In the embryo, the external limiting membrane of the cerebral vesicles and spinal cord stained for laminin protein and detectable mRNA was found in the pia mater. Growing peripheral nerves and dorsal and ventral root fibres expressed laminin mRNA and stained for laminin protein. Laminin mRNA expression was found in ureteric buds and nephrogenic vesicles (but not in metanephric blastema) during early prenatal kidney development, and in glomeruli, Bowman's capsule, loops of Henle and collecting duct cells at later stages of development, and after birth. All these structures possessed laminin-rich basement membrane (BM). Laminin mRNA expression fell to below detectable levels in the kidney around weaning. In the gut, laminin expression and protein staining was confined to the muscularis externa and the lamina propria during embryogenesis. After birth, the muscularis externa, muscularis mucosa and lamina propria cells corresponding to fibroblasts had detectable laminin mRNA, but in adult gut no laminin mRNA could be demonstrated in any cell type. In liver, low levels of laminin mRNA were seen in the capsule and in periportal connective tissue. After birth, laminin mRNA was associated with intrahepatic bile channels; no laminin mRNA was detected in the parenchyma and protein deposition was restricted to blood sinus BM. In the adult liver, no laminin mRNA was detected in any cell type. The developing heart showed uniform expression of laminin mRNA from 12 days to before birth. Postnatally, labelling was restricted to connective tissue cells.

Animals↗
PubMed1988

Immunohistological localization of human endometrial secretory protein, 'pregnancy-associated endometrial alpha 2-globulin' (alpha 2-PEG), during the menstrual cycle.

The distribution of alpha 2-PEG, a human analogue of beta-lactoglobulin, in endometrium at different phases of the cycle was determined using immunohistochemistry with monoclonal and polyclonal antibodies. In the epithelial cells of glands in the functional zone of the endometrium, alpha 2-PEG was first detectable from Days 19 to 21 during the mid-luteal phase and maximal immunostaining was observed during the end of the late luteal phase. Intense staining in the glandular secretions and weaker staining in surface luminal epithelial cells during this period were observed. A minor population of basal glands contained alpha 2-PEG during the follicular phase. These results suggest that alpha 2-PEG synthesis by the glandular epithelium of the regenerated endometrium is hormonally regulated. Maximal staining occurring during the late luteal phase suggests that regulation may be related to the hormonal requirement for pre-decidualization rather than that required for histologically defined glandular epithelial secretion.

Endometrium↗