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Biomedical subjects

S Stewart

Publications and source records attributed to S Stewart.

At least 217 records · Page 12Linked to original sources
PubMed1991

Evaluation of the proposed interaction of nucleic acid with Clostridium difficile toxins A and B and the effects of nucleases on cytotoxicity.

Both DNA and RNA were found to co-purify with Clostridium difficile toxin B but not toxin A. DNAase treatment greatly reduced the cytotoxicity of toxin B but not of toxin A. RNAase had no effect on either toxin. The effects on toxin B were shown to be due to a contaminating protease and could be inhibited by the serine protease inhibitor phenylmethylsulphonyl fluoride.

Animals↗
PubMed1991

Beta 1 integrin-mediated lymphocyte adherence to extracellular matrix is enhanced by phorbol ester treatment.

The interaction of the human T cell leukemia, Jurkat, with the extracellular matrix components collagen and fibronectin was examined. These cells displayed constitutive binding to fibronectin and low levels of adherence to collagen which were enhanced following stimulation with phorbol esters. The relevant binding structures were identified as members of the CD29/beta 1 integrin family of adhesion molecules. Adherence to collagen and to fibronectin was mediated by alpha 2 beta 1 and alpha 5 beta 1, respectively. The enhancement of adherence by phorbol esters did not involve up-regulation of receptor expression but appeared to derive from the increased functionality of structures which were expressed on the cell surface.

Cell Adhesion↗
PubMed1991

Antibodies to different members of the beta 1 (CD29) integrins induce homotypic and heterotypic cellular aggregation.

Members of the beta 1 (CD29) integrin family are involved in cellular adhesion to extracellular matrix. However, there have been several reports of CD29 integrin participation in intercellular adhesion. For example, the treatment of the human T cell line Jurkat with antibodies to alpha 4 (CD49d) causes homotypic aggregation. The present report describes the induction of aggregation of Jurkat cells by antibodies to alpha 5 (CD49e) and to a lesser extent by antibodies to the common beta 1/CD29 chain of these integrins. The metabolic requirements for these aggregations are compared with that of the CD49d-induced process. The possible involvement of fibronectin in the cytoadhesion appears to be unlikely as (1) the aggregates form in the absence of plasma fibronectin; (2) antibodies to fibronectin do not inhibit the cell adhesion; and (3) exogenous fibronectin does not influence the process. One of the cognate partners involved in the CD49e-induced aggregation appears to be present on non-antibody-treated Jurkat cells as the cells are coincorporated into aggregates of anti-CD49e-stimulated cells. The adhesion does not appear to involve members of the CD2, CD3, CD4, or CD18 receptor groups. These results indicate that interaction with alpha 4, alpha 5 chain or the beta 1 chain of the CD29 integrins leads to the induction of intercellular adhesion. The possible biological significance of this process is discussed.

Animals↗
PubMed1991

Diamide induces reversible changes in morphology, cytoskeleton and cell-cell coupling in lens epithelial cells.

The isolated frog lens epithelium can be maintained with its cell shape, cytoskeletal organization and membrane electrophysiological characteristics intact for more than 24 hr. Perifusion with the permeant oxidant diamide (1 mM) led to drastic, but reversible, changes in all the above parameters. After a 20 min exposure to diamide, the regular polygonal arrangement of the epithelial cells become increasingly disrupted as the cells reorganized and a 'rosette' pattern formed. The cells at the edges of the rosette pulled apart from one another while those in the centre maintained a relatively normal appearance. Blebs formed on the apical surface of all of the cells on prolonged exposure and the internal structure was also found to be severely disrupted. The cytoplasm became granular, vacuolated and the nucleus had a banded, non-homogeneous appearance. Phalloidin staining of F-actin microfilaments revealed that there was a general disruption of organization, with actin losing its association with the membrane. The microtubule array, organized around the centrosome, was also severely disrupted although microtubules were still discernible in most cells. During exposure to diamide the membrane potential depolarized and both electrical and dye coupling, which are normally extremely efficient in these cells, were disturbed. If the epithelium was exposed to 1 mM diamide for more than 45 min then all of the above changes were irreversible and cell death followed. If exposure was restricted to less than 30 min, then all of the above changes occurred and, in fact, progressed for over 1 hr; but if the epithelium was perifused for a further 20 hr in control medium, then most of the changes were reversible.

Actin Cytoskeleton↗
PubMed1991

Identification and characterization of the IE-1 gene of Orgyia pseudotsugata multicapsid nuclear polyhedrosis virus.

The IE-1 gene of Orgyia pseudotsugata multicapsid nuclear polyhedrosis virus (OpMNPV) was mapped between 95.7 and 97.1 map units on the viral genome. Sequence analysis of the OpMNPV IE-1 gene (OpIE-1) identified an open reading frame that coded for a predicted protein of 560 amino acids with a molecular weight of 64,775. Transcriptional analysis of OpMNPV-infected Lymantria dispar (LD652Y) cells identified two RNAs homologous to the OpIE-1 open reading frame that were 1.7 and 1.9 kb in size. The 1.7-kb transcript could be detected by 0 hr postinfection (hr p.i.) and the steady-state levels increased up to 48 hr p.i. The 1.9-kb message appears to be spliced and has peak expression from 4 to 6 hr p.i. but can still be detected at late times p.i. Comparison of the OpIE-1 and Autographa californica multicapsid nuclear polyhedrosis virus (AcMNPV) IE-1-predicted proteins revealed that the N-terminal region had very low sequence identity (21%) but had maintained an acidic profile, whereas the C-terminal region showed 55% amino acid identity. Transient assay analysis showed that OpIE-1 was able to trans-activate the AcMNPV delayed early reporter gene construct p39CAT in both LD652Y cells and Spodoptera frugiperda (Sf9) cells. The expression of p39CAT trans-activated by OpIE-1 was also found to be enhanced by the AcMNPV hr enhancer sequences. The OpIE-1 promoter was linked to the chloramphenicol acetyl transferase gene and deletion analysis was used to identify regions involved in the regulation of this gene. This analysis revealed that the OpIE-1 promoter contained regions that were responsive to a transcriptional activator that was specific to Sf9 cells. In addition it was shown that OpIE-1 could trans-activate its own promoter and that for maximal expression this required sequences between -420 and -330 relative to the transcriptional start site. These data suggest that OpIE-1 is autoregulated during normal viral infection of insect cells.

Amino Acid Sequence↗
PubMed1991

Neuroendocrine differentiation and clinical behaviour in non-small cell lung tumours.

The present study examines the relationship between neuroendocrine (NE) differentiation and the clinical behaviour of non-small cell lung cancer (NSCLC). Retrospective (n = 315) and prospective (n = 44) cohorts of non-small cell tumours were obtained from surgically treated cases of lung cancer, comprising 218 squamous cell carcinomas, 65 adenocarcinomas, 51 adenosquamous carcinomas, and 25 large cell undifferentiated carcinomas. Paraffin wax embedded and fresh frozen tissue sections were stained for the NE markers neurone specific enolase, creatine kinase-BB, bombesin, neurotensin, chromogranin A, synaptophysin and UJ-13A. The expression of two or more markers was observed in 30% of cases, and was taken to identify NE-NSCLC. A statistically significant correlation between nodal status and NE differentiation (P = 0.05), and disease stage and NE differentiation (P = 0.04) was observed. However, there was no correlation between NE differentiation and survival. These findings suggest that NE-NSCLC, analogous to SCLC is more highly metastatic than non-NE-NSCLC.

Carcinoma, Non-Small-Cell Lung↗
PubMed1991

Cytomegalovirus infection in heart-lung transplant recipients: risk factors, clinical associations, and response to treatment.

The risk factors, clinical associations, and response to treatment of cytomegalovirus (CMV) pneumonia and infection were studied in 65 recipients of heart-lung transplantation. There were 29 episodes of CMV pneumonia in 22 patients. In 80% (20/25) of episodes of CMV pneumonia treated with intravenous ganciclovir, the histologic changes resolved and the patient survived. Among seronegative recipients, a seropositive donor was a significant risk factor for CMV pneumonia and infection in the first 90 days after heart-lung transplantation (P = .004 and .002, respectively). Among seropositive recipients, there was no additional risk associated with a sero-positive donor. Rates of CMV pneumonia and infection were significantly increased when treatment with augmented immunosuppression had been given in the preceding 30 days (P less than .001). A significant association was found between CMV pneumonia or infection and pulmonary bacterial infections occurring 30 days before or after such an episode (P less than .001).

Adolescent↗
PubMed1991

Risk factors for obliterative bronchiolitis in heart-lung transplant recipients.

Obliterative bronchiolitis is the major cause of death of long-term survivors of heart-lung transplantation. Of our first 75 patients who have received heart-lung transplantation, 38 have been followed for a year or longer. Eight patients developed clinical evidence of obliterative bronchiolitis within 15 months of transplantation, of whom four died with postmortem confirmation of extensive obliterative bronchiolitis, interstitial and pleural fibrosis, and vascular sclerosis in the heart and lungs. One further patient died before one year after chronic rejection. All nine patients had evidence on transbronchial biopsy of submucosal fibrosis and vascular sclerosis. Twelve of our remaining patients have shown similar areas of lung fibrosis on transbronchial biopsy, and the other eighteen are well and without fibrosis on transbronchial biopsy. Studies of the 274 biopsies obtained from 38 patients confirmed rejection on 182 occasions with more frequent, more persistent, and more severe rejection in the chronic rejection group than in the without-fibrosis or lung fibrosis groups. Opportunistic infection resulted in pneumonia on 19 occasions, and were most commonly found in lung fibrosis patients. We conclude that obliterative bronchiolitis is the likely outcome in patients with early, poorly controlled, severe rejection.

Adult↗
PubMed1991

B lymphocyte fibronectin receptors: expression and utilization.

Lymphocytes adhere to fibronectin (FN) via multiple receptors of the VLA (beta 1, CD29 integrin) family. The cellular requirement for the variety of FN receptors (FNR) which have been described is unclear, but they may be associated with differential signalling processes, cooperative effects which may stabilize cellular attachment, or cell homing and retention processes. The present study was undertaken to examine the FN adherence properties and receptor utilization patterns of human B cells. Of ten B-cell culture lines which were studied, six demonstrated a significant adherence to FN. Among these, four employed alpha 4 beta 1, (CD49d/29) and two employed alpha 4 beta 1/alpha 5 beta 1, (CD49d/29, CD49e/29). There was no apparent correlation between the differentiation status of the lines and their FNR utilization patterns. Furthermore, expression of FNR alone was not sufficient to confer FN binding potential. Freshly isolated tonsil B cells did not display significant adherence to FN. Following stimulation, a marked increase in VLA antigens was observed, and the capacity to attach to FN-coated surfaces was co-acquired. Analysis of the induced bulk B-cell population demonstrated that both alpha 4 beta 1 and alpha 5 beta 1 were used for adherence. These results clearly indicate that activated B cells, similar to T cells, may express and utilize alpha 5 beta 1 as a FNR.

B-Lymphocytes↗
PubMed1991

Pulmonary fibrosis associated with nabumetone.

A patient is described who developed a rapid onset of pulmonary fibrosis following treatment with a new non-steroidal anti-inflammatory drug, nabumetone. Resolution of symptoms, physical signs and radiographic changes followed drug withdrawal and steroid therapy.

Aged↗
PubMed1990

A study of in vivo immune complex formation and clearance in man.

C and CR1 have been shown to participate in the clearance of injected, preformed, immune complexes in humans and in non-human primates. Their role in the physiologic disposal of immune complexes formed in vivo in humans was investigated in three patients receiving radioimmunotherapy for ovarian carcinoma. On day 0 each patient received, by intraperitoneal injection, 10 mg of 131I-mouse anti-tumor mAb (10 mCi/mg). On days 1 and 2, 18 mg of trace-labeled, 125I-human anti-mouse IgG was administered by i.v. infusion over 15 min, to accelerate the clearance of the 131I-anti-tumor antibody from the circulation and reduce the radiation dose to the marrow. Sequential blood samples were obtained after the injection of the second (anti-mouse) antibody, to monitor clearance. Immune complexes (shown by sucrose gradient centrifugation to be 19 to 40 S in size) formed within 5 min, and were cleared with a half-life of 11 +/- 1.7 min in the liver. Complexes were measured by 4% polyethylene glycol precipitation, and by solid phase C3d- and C1q-binding assays. Between 8 and 11% of the total available complexed material bound to CR1 on E. Peak binding of immune complexes to red cells occurred 10 min after the maximal complex load was detected by precipitation with polyethylene glycol. At that time, immune complexes bound to E constituted one-fifth of the total circulating pool of complexes. Coincident with immune complex formation and clearance, a 47% fall in serum C4, C3, and CH50 was measured, with the deposition of up to 1230 molecules of C4, and 2590 molecules of C3 on the surface of red cells. During 20 min after immune complex formation there was a mean loss of 32% of erythrocyte CR1. The changes in complement and CR1 on E and in serum observed in these patients resembled those seen in patients with SLE: i.e., a reduction in CR1 and an increase in C3 and C4 on E, and reduced serum C.

Adult↗
PubMed1990

Expression of externally-disposed heparin/heparan sulfate binding sites by uterine epithelial cells.

A class of high-affinity binding sites that preferentially bind heparin/heparan sulfate have been identified on the external surfaces of mouse uterine epithelial cells cultured in vitro. [3H]Heparin binding to these surfaces was time-dependent, saturable, and was blocked specifically by the inclusion of unlabeled heparin or endogenous heparan sulfate in the incubation medium. A variety of other glycosaminoglycans did not compete for these binding sites. The presence of sulfate on heparin influenced, but was not essential for, recognition of the polysaccharide by the cell surface binding sites. [3H]-Heparin bound to the cell surface was displaceable by unlabeled heparin, but not chondroitin sulfate. Treatment of intact cells on ice with trypsin markedly reduced [3H]heparin binding, indicating that a large fraction of the surface binding sites were associated with proteins. Scatchard analyses revealed a class of externally disposed binding sites for heparin/heparan sulfate exhibiting an apparent Kd of approximately 50 nM and present at a level of 1.3 x 10(6) sites per cell. Approximately 9-14% of the binding sites were detectable at the apical surface of cells cultured under polarized conditions in vitro. Detachment of cells from the substratum with EDTA stimulated [3H]heparin binding to cell surfaces. These observations suggested that most of the binding sites were basally distributed and were not primarily associated with the extracellular matrix. Collectively, these observations indicate that specific interactions with heparin/heparan sulfate containing molecules can take place at both the apical and basal cell surfaces of uterine epithelial cells. This may have important consequences with regard to embryo-uterine and epithelial-basal lamina interactions.

Animals↗
PubMed1990

The histological changes in transbronchial biopsy after treatment of acute lung rejection in heart-lung transplants.

Transbronchial lung biopsies taken during episodes of acute lung rejection in heart-lung transplant patients were examined histologically. When the diagnosis was confirmed by microscopy, the patients were treated with augmented immunosuppression by high-dose corticosteroids. A second biopsy was obtained an average of 23.5 days after commencement of treatment. These biopsies were examined to determine the histological changes caused by treatment. In most cases, there were both quantitative and morphological differences between the infiltrates in acute rejection and in the remaining perivascular infiltrates after treatment. In acute rejection, 26 of 28 biopsies contained perivascular lymphocytic infiltrates, lymphocytes being large and blast-like. Although 20 of 28 follow-up biopsies still contained perivascular infiltrates, they were smaller and the lymphocytes smaller in size. Half the biopsies in rejection contained neutrophils, but less than half contained eosinophils in the perivascular infiltrates. After treatment, all these cells were less numerous. Another feature of treated rejection was the presence of haemosiderin around vessels suggesting earlier acute vascular injury. However, haemosiderin persists long after the cellular infiltrate has disappeared and cannot be considered a reliable feature of recently treated acute lung rejection. The bronchiolar infiltrates showed a similar pattern of responses to the perivascular infiltrates.

Adult↗
PubMed1990

Powered cutting needle biopsy of the pleura and chest wall.

Over a 24 month period, 35 patients seen consecutively with a pleural or chest wall mass had a percutaneous biopsy using an 18 gauge cutting needle operated by a specially designed, hand held, spring loaded trigger system (Biopty TM, Biopsy instrument, Radiplast A.B. Sweden). Biopsies were performed under local anaesthesia with ultrasound, fluoroscopic, or computed tomography guidance, depending on the site and nature of the lesion. An excellent specimen, consisting of a core of tissue, was consistently obtained and a specific histological diagnosis was possible in 30 patients (28 malignant lesions and two benign lesions). In two patients there was an unequivocal diagnosis of malignancy but the tumour was too necrotic to allow a cell type to be established. In three patients the specimen consisted predominantly of dense fibrous tissue. One of these was a presumed false negative result for malignancy; the other two are presumed true negative results. There were no complications of the procedure.

Biopsy, Needle↗
PubMed1990

Herpes simplex virus infection in heart-lung transplant recipients.

We report our experience of herpes simplex virus infection in a series of 51 recipients of heart lung transplantation (HLT). Nine patients, all of whom were seropositive for the virus preoperatively, developed HSV infection. Seven episodes of culture-proved mucocutaneous HSV infection without evidence of pulmonary involvement occurred in four patients. Six episodes of HSV pneumonia were seen in a further five patients, one of whom died. Diagnosis of HSV pneumonia was by histological appearances on transbronchial biopsy, together with culture of lung tissue or bronchoalveolar lavage. Concomitant cytomegalovirus infection occurred in four patients. All patients who developed HSV pneumonia did so within the first two postoperative months; in four patients following augmented immunosuppression. We now suggest that HLT recipients who are HSV antibody-positive should receive prophylactic acyclovir for the first two months after surgery and at times of augmented immunosuppression.

Acyclovir↗