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Biomedical subjects

T Collins

Publications and source records attributed to T Collins.

At least 163 records · Page 9Linked to original sources
PubMed1989

Aberrant expression of platelet-derived growth factor A-chain cDNAs due to cryptic splicing of RNA transcripts in COS-1 cells.

Platelet-derived growth factor (PDGF) is a cationic dimer composed of two chains, designated A and B. All three dimeric isotypes of PDGF, PDGF-AA, -AB and -BB, are biologically active but may have distinct functional activities. Two A-chain precursors which differ by the presence of a highly basic 15 amino acid C-terminal extension are derived from the A-chain by alternative RNA splicing. To compare the functional properties of these two different forms of the A-chain, expression vectors were generated in which the cDNAs were placed under the transcriptional control of a viral promoter (pSV2). Surprisingly, cryptic RNA splice donor sites were identified in both forms of the PDGF A-chain which modify the A-chain open reading frame and alter the structure of the expressed protein. Recognition of this phenomenon appears to explain the discrepancies between previous results regarding the secretory properties of the PDGF A-chain and may explain difficulties in expression vectors containing splice acceptor sites between the inserted sequence and the polyadenylation site.

Animals↗
PubMed1989

Radiometric studies on the use of selective inhibitors in the identification of Mycobacterium spp.

Radiometric selective inhibition tests were developed and evaluated for the rapid differentiation of Mycobacterium spp. Both a p-nitrobenzoic acid (PNB) test and a commercially-prepared p-nitro-alpha-acetylamino-beta-hydroxypropiophenone (NAP) test successfully differentiated M. tuberculosis and M. bovis from "atypical" mycobacteria or mycobacteria other than tubercle bacilli (MOTT). Thiophene-2-carboxylic acid hydrazide (TCH) readily distinguished human M. tuberculosis strains from M. bovis, irrespective of resistance to isoniazid. Both PNB and TCH tests were utilised in a routine radiometric susceptibility testing scheme over a period of 1 year in which 110 isolates of M. tuberculosis, 10 of M. bovis and one isolate of BCG were correctly differentiated from 10 isolates of MOTT. The rapidity, sensitivity and specificity of these radiometric tests can play a useful role in mycobacterial identification.

Drug Resistance, Microbial↗
PubMed1988

Immortalization of human endothelial cells by murine sarcoma viruses, without morphologic transformation.

Amphotropic murine leukemia virus pseudotypes of murine sarcoma viruses containing the ras or mos oncogenes were constructed to permit efficient introduction of the sarcoma virus genome into early-passage human umbilical vein endothelial cells. The resulting cell lines were morphologically and phenotypically unchanged, retaining properties characteristic of differentiated endothelial cells. For example, the cells in a Kirsten sarcoma virus-modified line were found to biosynthesize and secrete von Willebrand factor in both a constitutive and regulated manner, and they contained ultrastructurally identifiable Weibel-Palade bodies, an endothelial cell-specific organelle. In contrast to the parent cultures, sarcoma virus-modified cells were able to proliferate indefinitely in culture. Examination of both Kirsten sarcoma and Moloney leukemia virus-modified lines indicated that the immortalized cells retained a diploid female karyotype after over 18 months in culture. In addition, the sarcoma virus-modified cells were able to grow independently of added endothelial cell growth factor. This growth factor autonomy does not appear to be due to autocrine production of a biologically cross-reactive growth factor. These immortal, virus-modified endothelial cells express large amounts of sarcoma virus-specific mRNA but no detectable helper virus or transforming virus activity. This technique for immortalization of primary human cells without alteration of the differentiated characteristics of the cell type is readily applied to a variety of human cell types. Moreover, the ability to separate the immortalizing and transforming activities of viral oncogenes should provide further understanding as to mechanisms of oncogene action.

Biomechanical Phenomena↗
PubMed1988

Platelet-derived growth factor A chain: gene structure, chromosomal location, and basis for alternative mRNA splicing.

Genomic clones encoding the A chain of platelet-derived growth factor (PDGF) have been isolated. The gene contains seven exons spanning about 24 kilobases of DNA. The positions of intervening sequences closely match those of the related B-chain (c-sis) gene on chromosome 22. In situ hybridization was used to localize the PDGF A-chain gene to the distal portion of the short arm of chromosome 7 (7p21-p22). Within the (G + C)-rich 5' region, a single transcriptional start site was identified approximately equal to 36 base pairs downstream of a TATAA consensus promoter element. The three size classes of A-chain mRNA probably arise by selection of alternative poly(A) sites in exon 7, but only a single consensus AATAAA signal was identified in this region. Two functionally different A-chain precursors, which differ by the presence or absence of a basic C terminus, are generated as a result of alternative mRNA splicing events, which include or exclude exon 6. This and other structural features of the A-chain gene suggest that PDGF expression may be modulated at transcriptional and post-transcriptional levels.

Base Sequence↗
PubMed1988

Obstructive sleep apnea syndrome: preoperative radiologic evaluation.

The purpose of this study was to determine whether lateral radiographs of the pharynx and fluoroscopy of the lateral pharynx in the sleeping patient could be used as predictors of surgical success in patients undergoing soft-palate surgery for obstructive sleep apnea. A total of 12 patients had surgery after radiologic evaluation. There were six surgical successes and six failures. No successes occurred in patients with a soft-palate length of less than 46 mm, nor were there any successes among patients whose initial point of obstruction on fluoroscopy was inferior to the level of the soft palate. There was one surgical failure among patients in whom fluoroscopy showed upper airway obstruction beginning at the level of the soft palate during sleep. Results suggest that a patient is most likely to benefit from soft-palate resection if the soft palate is long--we conservatively suggest greater than 40 mm--and if sleep fluoroscopy of the lateral pharynx shows airway obstruction beginning at the level of the soft palate.

Fluoroscopy↗
PubMed1987

Sequences of the 5' portion of the human c-sis gene: characterization of the transcriptional promoter and regulation of expression of the protein product by 5' untranslated mRNA sequences.

The c-sis gene encodes the B polypeptide chain of platelet-derived growth factor (PDGF), and is expressed in a number of normal and pathological conditions. In order to study the control of synthesis of the human c-sis product, we have initiated a study of two regions of this genetic locus which regulate transcription and translation. A clone of the 5' portion of the gene was obtained which included 1361 nucleotides upstream of the RNA initiation site. Transcriptional promoter activity of this region was demonstrated in normal and transformed cells using a plasmid with the sequences upstream of the c-sis RNA initiation site fused to an indicator gene, chloramphenicol acetyl transferase. Experiments were also performed to identify other possible regulatory regions of the c-sis gene. These data demonstrated that a portion of the c-sis first exon encoding the 5' untranslated region of the c-sis mRNA inhibited synthesis of the PDGF B product in vitro. These results define regions of the c-sis gene whose activity may be important in the regulation of transcription and translation under normal conditions and in the pathogenesis several human diseases.

Base Sequence↗
PubMed1987

Cultured human endothelial cells express platelet-derived growth factor A chain.

Four principal cell types involved in the pathophysiologic response of the vessel wall--endothelial cells, smooth muscle cells, platelets, and monocyte/macrophages--secrete platelet-derived growth factor-like (PDGF-like) mitogenic activities. Extensive structural data on these activities exist only for the mitogen produced by platelets, which is a 30-kd dimeric protein composed of structurally related A and B polypeptide chains encoded by different genes. It was previously demonstrated that normal cultured endothelial cells transcribe mRNA encoding the B chain of PDGF from the c-sis gene. Here several new structural features of the mitogen produced by cultured vascular endothelial cells are shown. Hybridization analysis of RNA from normal cultured human umbilical vein endothelial (HUVE) cells revealed that they contain three PDGF A chain transcript species. These RNA species comigrated with and appeared to have the same relative abundance as the three RNA species previously identified in RNA from two human tumor cell lines. A chain transcripts were not identified in RNA from a strain of bovine aortic endothelial cells or in human dermal fibroblasts. The A chain transcripts in HUVE had the same relative abundance as the B chain transcripts. Immunoprecipitation of metabolically labeled endothelial conditioned medium with anti-PDGF antiserum revealed a 31-kd species which was split by reduction and alkylation into two species of 16.5 and 17 kd. Thus, endothelial cells secrete a dimeric mitogen antigenically related to PDGF, with a structure identical to previously isolated PDGF A-chain homodimer. These findings are consistent with the possibility that secretion of PDGF by human endothelial cells may be regulated independently of B-chain expression.

Cells, Cultured↗
PubMed1986

Recombinant human tumor necrosis factor increases mRNA levels and surface expression of HLA-A,B antigens in vascular endothelial cells and dermal fibroblasts in vitro.

Recombinant human tumor necrosis factor (TNF), purified to greater than 99% homogeneity, increases surface expression of class I major histocompatibility complex (MHC) antigens to a maximum of 9-fold on cultured human endothelial cells (HEC) and human dermal fibroblasts (HDF). The increase is concentration dependent (peak 20-100 units/ml) and time dependent (nearly maximal by 4 days); expression remains elevated in the continued presence of TNF and requires greater than 7 days to return to basal levels upon TNF withdrawal. The increase in surface expression appears to result from increases in steady-state mRNA levels for the class I antigens, although the increase in mRNA is proportionately greater than for surface expression. No surface expression of or mRNA for class II MHC antigens is detectable in either control or TNF-treated HEC or HDF. These effects are similar to those produced by leukocyte or fibroblast (type I) interferons (IFNs). The protein synthesis inhibitor cycloheximide (CHX), when added coincidentally with type I IFNs, leads to superinduction of mRNA for class I MHC antigens and, unexpectedly, leads to the appearance of mRNA for class II MHC antigens. CHX has no effect by itself upon mRNA levels for class I or class II MHC antigens, nor does it modulate the increases in mRNA produced by immune (type II) IFN. Most interesting, CHX blocks the increase in mRNA for class I MHC antigens induced by TNF. Thus TNF appears to act on MHC gene expression through a newly synthesized protein intermediate. Our results provide direct evidence that TNF can modulate gene expression in normal (untransformed) cell types and contribute to understanding the complex nature of MHC gene regulation. Finally, they suggest that TNF may act in vivo as an immunoregulatory molecule.

Cell Membrane↗
PubMed1986

Immunoglobulin M antibodies present in the acute phase of Kawasaki syndrome lyse cultured vascular endothelial cells stimulated by gamma interferon.

Kawasaki syndrome (KS) is characterized by diffuse vasculitis and marked T cell and B cell activation. In this study, sera from 16 patients with acute KS, 15 patients in the convalescent phase of KS, and 19 age-matched controls were assessed for complement dependent cytotoxic activity against 111In-labeled human umbilical vein endothelial (HUVE) cells, Neither sera from patients with KS nor sera from controls had cytotoxic effects on HUVE cells cultivated under standard conditions. Since activated T cells such as those present in acute KS secrete gamma interferon (gamma-IFN), we also examined the effects of sera from acute KS on HUVE cells preincubated with gamma-IFN. We report here that immunoglobulin M (IgM) antibodies in sera from patients with acute KS cause significant (P less than 0.01) killing of gamma-IFN-treated HUVE cells. Pretreatment with interleukin 2, gamma-IFN, or beta-IFN failed to render HUVE susceptible to lysis with acute KS sera. The observed effects were not mediated via immune complexes. The cytotoxic antibodies in acute KS seem to be directed against inducible monomorphic antigenic determinants present on gamma-IFN-treated HUVE cells but not on control or gamma-IFN treated autologous human dermal fibroblasts (HDF). Similarly, acute KS sera also induced lysis of gamma-IFN-treated human saphenous vein endothelial (HSVE) cells but not gamma-IFN treated human saphenous vein smooth muscle (HSVSM) cells. Since gamma-IFN induces the same level of class I and class II major histocompatibility complex (MHC) antigen expression on HDF, HUVE, HSVE, and HSVSM cells, our results suggest that the anti-endothelial cell antibodies in acute KS are directed to gamma-IFN-inducible molecules other than MHC determinants. These observations are further substantiated by the failure of human B cells or monocytes to absorb the anti-endothelial cell activity. Since most vasculitides, including acute KS, are characterized both by marked immune activation and the secretion of lymphokines, antibodies directed to gamma-IFN-inducible endothelial cell antigens may represent a general mechanism for vascular injury.

Antigen-Antibody Complex↗
PubMed1985

Lesions of spinal cord parelaphostrongylosis in sheep. Sequential changes following intramedullary larval migration.

Spinal cord nematodiasis epidemiologically, clinically, and histologically consistent with Parelaphostrongylus tenuis infection was noted in two flocks of sheep. Spinal cords from two sheep with active infection and one from a partially recovered animal were studied in an effort to determine the sequence of lesions following larval invasion of the central nervous system. In the former two sheep, migration of larvae within the spinal cord induced asymmetrically irregular tracks of disrupted and necrotic tissue, primarily in white matter. Subsequently, macrophages infiltrated these regions and phagocytized the necrotic tissue, which led to cavity formation. Swelling and loss of axons, diminished myelin staining, mononuclear cell infiltration and increase in astrocytic fibers were often seen in adjacent tissue. Only occasional coiled larvae were found in these actively infected animals. Late stage lesions in the white matter in the partially recovered sheep included multiple small astrogliotic regions with diminished myelin and axonal content, and a single large multicavitary, atrophic, gliotic zone.

Animals↗
PubMed1984

Interactions of T lymphocytes with human vascular endothelial cells: role of endothelial cells surface antigens.

We have studied the interactions of peripheral blood T lymphocytes with cultured human vascular endothelial cells, focusing upon endothelial cell surface antigens important for T cell recognition. Under standard culture conditions endothelial cells express class I but not class II major histocompatibility complex (MHC) antigens. However, class II antigens may be induced by activated T cells or T cell products, including the lymphokine immune interferon. Immune interferon concomitantly increases class I antigen expression and causes a change in cell shape. In addition to vascular endothelial cells, we have found that vascular smooth muscle cells and human dermal fibroblasts may also be induced by immune interferon to express class II antigens. All known human class II antigens are induced (i.e. HLA-DR, DC and SB) as is the associated invariant chain. Induced antigen expression in these cells is stable over several days, although mRNA levels decline rapidly upon withdrawal of interferon. Vascular and stromal cell class II antigens are functional, in that they can be recognized by cytolytic and helper T cell clones. Several non-MHC antigens are also involved in the recognition of endothelial and stromal cells by T cells. We propose a model for the role of inducible class II molecules on endothelium and stromal cells in vivo: The induction of class II MHC antigens on endothelial cells, locally mediated by activated T cells, enables endothelium to present an immunogenic cell surface structure, comprised of antigen plus self class II polymorphic determinants, which in turn, serves to recruit additional antigen-specific T cells from the circulation into the site of a developing cell mediated immune response. Class II molecules on stromal cells, also induced locally at the site of a developing response, confers immune accessory function on these cells and may serve to augment and sustain a T cell response.

Antigen-Presenting Cells↗
PubMed1984

Immune interferon activates multiple class II major histocompatibility complex genes and the associated invariant chain gene in human endothelial cells and dermal fibroblasts.

Immune interferon (IFN-gamma) increases the surface expression of HLA-A,B antigens and induces the surface expression of HLA-DR antigens on vascular endothelial cells and dermal fibroblasts. Here we report that IFN-gamma induces parallel expression of two other class II major histocompatibility complex (MHC) antigens, SB and DC. Maximal surface expression of all three antigens is reached in 4-6 days, and HLA-DR and -SB are induced to a higher level of expression than HLA-DC. For all three class II antigens, induction is marked by the de novo appearance of detectable transcripts of class II heavy and light chains and of the non-MHC-encoded invariant chain, suggestive of the transcription of multiple previously silent genes. Class I message levels and antigen expression are also increased by IFN-gamma at similar rates but from initial levels that are 50% of maximal. After removal of IFN-gamma, class II antigen expression persists for at least 4 days, while mRNA levels decrease rapidly. The parallel induction and persistence of the several class II MHC antigens may be important in conferring immune accessory function on vascular and stromal cells.

Endothelium↗
PubMed1984

Acute myocardial infarction in elderly patients.

We conducted a retrospective chart review on 50 patients under age 65 (average age 52.9 years) and 55 patients over 65 (average age 75.6 years). The older patients were much more likely to have atypical pain or no pain (38% vs 4%, P less than .0001). They were less likely to have electrocardiographic QRS changes (47% vs 72%), but more likely to have congestive heart failure (44% vs 16%, P less than .01). In 25% of the older patients, no diagnosis was made in the first 24 hours, as compared to 8% of the younger group. The increased mortality in the older group (16% vs 4%) approached statistical significance (P = .08). We conclude that the manifestations of acute myocardial infarction are more subtle in the elderly, with a higher proportion of atypical chest pain and nondiagnostic electrocardiograms, but the elderly are more likely to have congestive heart failure.

Adult↗
PubMed1984

Human cytolytic T lymphocyte interactions with vascular endothelium and fibroblasts: role of effector and target cell molecules.

Monoclonal antibodies (mAb) against cell surface structures have been used to identify several molecules involved in the interaction of human cytolytic T lymphocytes (CTL) with lymphoid and other bone marrow-derived targets. In allograft rejection or in graft-vs-host disease, however, major cellular targets are vascular and stromal cells, especially endothelium. Yet little is known about whether the same cell surface molecules are involved in the interactions of CTL with these cell types. We assessed the ability of mAb against effector or target cell structures to inhibit cytolysis of susceptible, cultured human vascular endothelium or dermal fibroblasts by a cloned human CTL line. Using mAb reactive with T3, T4, LFA-1, LFA-2, LFA-3, and HLA-DR, we found a qualitatively similar but quantitatively different pattern of inhibition of cytolysis as previously established for lymphoid targets by using the same CTL clone. These results have two implications: 1) the target cell structures recognized by CTL molecules such as T4, LFA-1 and LFA-2 are present on diverse cell types; and 2) the relative importance of such interactions may vary with target cell type. Furthermore, our studies provide several insights into the mechanisms of the interacting molecules. Our model system, and the use of pathophysiologically important target cells, may be useful for further analysis of CTL-mediated immune injury.

Antibodies, Monoclonal↗
PubMed1983

Thrombosis associated with a porcine bioprosthesis and ascending aortic graft in a patient with the Marfan syndrome.

A fatal thrombosis originating at the junction of an aortic bioprosthetic heart valve and a Dacron aortic graft was observed in a patient with the Marfan syndrome, who had had replacement of the ascending aorta with a valved conduit 29 months previously. This unique complication raises the question of whether patients with such prostheses should be on a program of full anticoagulation.

Adult↗