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Biomedical subjects

S Dunlap

Publications and source records attributed to S Dunlap.

18 recordsLinked to original sources
PubMed1997

Alteration of the CD34+ Tf-1 beta cell line profile in response to long-term exposure to IL-15.

Interleukin 15 (IL-15) is a cytokine with many functional characteristics that are similar to IL-2. Most of the functional activities that IL-2 and IL-15 support have been evaluated in short-term assays. It was our intention, then, to determine the long-term effects of IL-15 in comparison to IL-2. These studies were performed using the growth factor-dependent myelomonocytic cell line, Tf-1, which has been well characterized with regard to morphology, CD marker expression, responses to certain growth factors and cytokines (GM-CSF, IL-4, erythropoietin), and can differentiate through the myeloid and erythroid lineages. In order to study IL-2 and IL-15 responses, Tf-1 cells were retrovirally infected with the IL-2R beta chain gene as a means to confer IL-2 responsiveness to this cell type. The results of this study demonstrate that retroviral infection of Tf-1 successfully generated a stable IL-2 responsive cell line, Tf-1 beta, without interfering with the original characteristics of the Tf-1 cell. Tf-1 beta cells respond functionally to both IL-2 and IL-15. When Tf-1 beta cells are grown for 8 weeks in IL-2 (Tf-1 beta 2), rather than GM-CSF, the original morphology, CD marker expression, esterase activity and proliferative response is unaltered in comparison to that of the original Tf-1 beta line maintained in GM-CSF. However, long-term growth of Tf-1 beta in IL-15 (Tf-1 beta 15) results in morphological alterations, downregulation of CD33, CD38, and HLA-DR, and a decreased response to IL-15 in comparison to Tf-1 beta 2. These studies support the concept that retroviral infection, even when it confers new functions upon a cell, does not necessarily alter all other functions, as assessed by evaluation of its phenotypic profile. Furthermore, the production of the Tf-1 beta 2 and Tf-1 beta 15 sublines demonstrates that IL-2 and IL-15 can support long-term cell growth. However, this long-term growth in IL-15 leads to subtle alterations in the cell profile that are not seen with IL-2, suggesting that distinctions in IL-2 and IL-15 function do exist. Further study of the Tf-1 beta 15 cell line will be useful to clarify these functional distinctions between IL-2 and IL-15.

ADP-ribosyl Cyclase↗
PubMed1992

Somatic cell mapping of T-cell receptor CD3 complex and CD8 genes in cattle.

Bovine genes encoding T-cell receptor, CD3, and CD8 molecules have been mapped to syntenic groups using bovine x rodent hybrid somatic cells. T-cell receptor alpha and delta chains were assigned to bovine syntenic group U5, and the beta and gamma genes were syntenic with each other and with markers on U13. CD3E and CD3D genes were syntenic with each other and located to bovine syntenic group U19. CD8 was most concordant with markers of syntenic group U16, although the concordancy was only 85% and the assignment must be regarded as tentative. The comparative gene maps of human chromosome 7, bovine syntenic group U13, and mouse chromosomes 6 and 13 suggest extensive evolutionary conservation.

Animals↗
PubMed1991

A simple and efficient method for purifying and quantifying schizonts from Theileria parva-infected cells.

An improved method for the purification of Theileria parva schizonts from infected bovine cells is described. The technique is simpler and more rapid than previously described methods and gives rise to greater yields of schizonts with negligible contamination by host-cell components. In addition, a fluorescent staining technique was developed whereby live schizonts purified from infected cells can be enumerated and sorted using the flow cytometer. An assessment of the quality of schizonts prepared according to our method as a source of RNA for the construction of parasite cDNA libraries suggests that RNA derived from these preparations is free of host nucleic acids.

Animals↗
PubMed1991

Cell surface phenotype of two cloned populations of bovine lymphocytes displaying non-specific cytotoxic activity.

Monoclonal antibodies specific for T cell differentiation antigens were tested on four cloned populations of lymphocytes derived from the peripheral blood mononuclear cells of an animal immunised with Theileria parva. The clones were defined functionally in terms of cytotoxic activity, MHC restriction and expression of messenger RNA for CD3 and T cell receptor (TCR). Two clones contained RNA transcripts for CD3, TCR-alpha and beta and were positive for CD2, CD5 and CD6; one of these was a typical CD4+ class II MHC-restricted non-cytotoxic clone while the other was a CD8+ class I MHC-restricted cytotoxic clone. By contrast, the remaining two clones had the characteristics of non-specific killer cells in that they exhibited moderate levels of non-MHC-restricted killing; they contained TCR-delta mRNA and a 1.2 kb truncated form of TCR-beta message, but they did not contain CD3 or TCR-alpha mRNA. One of these non-specific killer clones only expressed CD2 whereas the other clone only expressed CD8, but without the CD8 determinant recognised by monoclonal antibodies CC58 and BAT52. All four clones were negative for the WC1 antigen which is expressed on gamma/delta T lymphocytes.

Animals↗
PubMed1991

Influence of calcium administration on the short-term hemodynamic and anti-ischemic effects of nifedipine.

This prospective study investigated whether pretreatment with intravenously administered calcium would influence the effect of nifedipine on rest hemodynamics and treadmill performance in patients with ischemic heart disease. Seventeen patients were studied after undergoing a qualifying treadmill exercise test that revealed ST segment depression indicative of ischemic heart disease. Study subjects performed three additional treadmill tests as part of the protocol. One treadmill test was obtained from each patient to provide baseline measurements without a preceding intravenous infusion and in the absence of all antianginal drugs including nifedipine; two additional exercise tests were preceded by an infusion and 10 mg of bite-and-swallow nifedipine. The infusions, administered in a randomized, double-blind, crossover fashion, consisted of either 10 ml of 10% calcium chloride (13.6 mEq) in 50 ml of 5% dextrose in water or 5% dextrose in water alone. Rest systolic blood pressure (134 +/- 4.6 mm Hg) was unchanged after placebo infusion (135 +/- 4.6 mm Hg) but decreased to 124 +/- 4.1 mm Hg (p less than 0.01) 25 min after nifedipine administration. Rest systolic blood pressure increased after calcium infusion (from 139 +/- 4.3 to 148 +/- 4.8 mm Hg, p less than 0.01) and then decreased significantly 25 min after nifedipine administration to 135 +/- 4.2 mm Hg (p less than 0.01). Despite a decrease at the time of peak nifedipine effect after either infusion, systolic blood pressure was significantly lower after administration of nifedipine alone than after administration of calcium and nifedipine (124 +/- 4.1 vs. 135 +/- 4.2 mm Hg, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1990

Identification of a bovine surface antigen uniquely expressed on CD4-CD8- T cell receptor gamma/delta+ T lymphocytes.

In this study, two monoclonal antibodies, IL-A29 and CC15, are described that identify a novel bovine cell surface marker of 215/300 kDa. The antibodies reacted with a discrete population of resting lymphocytes in peripheral blood which, in young animals, constituted about 25% of the mononuclear cells. Thymus, lymph nodes and spleen contained less than 5% positive cells. These cells were negative for surface Ig, a monocyte/granulocyte marker, and the T lymphocyte antigens CD2, CD6, CD4 and CD8. Immunohistological analyses revealed the presence of IL-A29/CC15-positive lymphocytes in the thymic medulla, in the outer cortex of lymph nodes, in the marginal zones of the spleen, in the dermal and epidermal layers of the skin and in the lamina propria of the gut. The IL-A29/CC15+ cells in unfractionated blood mononuclear cells responded in autologous and allogeneic mixed lymphocyte cultures, and when purified they responded to concanavalin A in the presence of recombinant interleukin 2. These observations suggested this population of cells belonged to the T cell lineage. In order to unambiguously define their lineage, cDNA clones encoding bovine T cell receptor (TcR) and CD3 proteins were isolated. Northern blot analyses of IL-A29/CC15+ cell populations and of established cell lines of various lineages demonstrated that they expressed TcR delta and CD3 gamma, delta and epsilon mRNA: TcR alpha was not expressed, whereas only a truncated form of TcR beta mRNA was present. These results indicate that the IL-A29 and CC15 antibodies define a unique population of CD4-CD8-, gamma/delta T cells.

Animals↗
PubMed1989

An enhancer located in a CpG-island 3' to the TCR/CD3-epsilon gene confers T lymphocyte-specificity to its promoter.

The gene encoding the CD3-epsilon chain of the T cell receptor (TCR/CD3) complex is uniquely transcribed in all T lymphocyte lineage cells. The human CD3-epsilon gene, when introduced into the mouse germ line, was expressed in correct tissue-specific fashion. The gene was then screened for T lymphocyte-specific cis-acting elements in transient chloramphenicol transferase assays. The promoter (-228 to +100) functioned irrespective of cell type. A 1225 bp enhancer with strict T cell-specificity was found in a DNase I hypersensitive site downstream of the last exon, 12 kb from the promoter. This site was present in T cells only. The CD3-epsilon enhancer did not display sequence similarity with the T cell-specific enhancer of CD3-delta, a related gene co-regulated with CD3-epsilon during intrathymic differentiation. The CD3-epsilon enhancer was unusual in that it constituted a CpG island, and was hypomethylated independent of tissue type. Two HTLV I-transformed T cell lines were identified in which the CD3-epsilon gene was not expressed, and in which the enhancer was inactive.

Animals↗
PubMed1988

The transmembrane orientation of the epsilon chain of the TcR/CD3 complex.

The antigen receptor of the T lymphocytes is one of the most complex eukaryotic membrane structures studied to date. The T cell receptor (TcR) consists of two disulfide-linked glycoprotein chains (alpha/beta or gamma/delta) and is noncovalently associated with a group of small and invariable CD 3 proteins. Four CD 3 chains have been recognized: two highly homologous glycoproteins CD 3 gamma and delta, the more distantly related nonglycosylated CD 3 epsilon chain, and the nonglycosylated CD 3 zeta, the latter being present as a homodimer. The unraveling of the architecture of the TcR/CD 3 complex is crucial to our understanding of the processes underlying its assembly, recognition and transmembrane signaling. The transmembrane orientation of the TcR chains and of CD 3 gamma and CD 3 delta can be directly inferred from their primary structure, based on the presence of concensus N-linked glycosylation sites N-terminal of their transmembrane domains. This prediction can not be made, however, for nonglycosylated molecules like the CD 3 epsilon chain. In order to determine the transmembrane orientation of CD 3 epsilon, anti-peptide antisera directed against the N-termini of the human and murine CD 3 epsilon chains were generated in rabbits. Both antisera stained intact T cells, demonstrating that the N-terminus of the CD 3 epsilon chain was located at the outer surface of the plasma membrane. The anti-human CD 3 epsilon peptide antiserum was found to be mitogenic for peripheral blood T cells, a finding previously reported only for monoclonal anti-TcR/CD 3 reagents. Using a novel transient expression system in murine T lymphocytes, the human CD 3 epsilon chain could be expressed on the surface of CD 3+, but not CD 3- murine T cells, as indicated by fluorescence staining with the anti-peptide antiserum. This experiment confirmed the specificity of the anti-peptide antiserum and, perhaps more importantly, indicated that the human CD 3 epsilon chain was correctly assembled in the murine CD 3 complex. Moreover, the anti-human CD 3 monoclonal antibody UCHT1 was found to stain T cells expressing the human CD 3 epsilon chain.

Amino Acid Sequence↗
PubMed1988

Human CD3-epsilon gene contains three miniexons and is transcribed from a non-TATA promoter.

The antigen receptor of the T lymphocyte consists of two variable T-cell receptor chains (either TCR-alpha, TCR-beta or TCR-gamma, TCR-delta) noncovalently linked to four different invariant membrane proteins (CD3-gamma, CD3-delta, CD3-epsilon, and the CD3-zeta homodimer). The CD3 genes are expressed early in thymocyte development, preceding the rearrangement and expression of the T-cell receptor genes. Here we report the isolation and structural analysis of the human CD3-epsilon gene. The gene consisted of nine exons. Three exons, encoding the junction of leader peptide and mature protein, were extremely small (21, 15, and 18 base pairs, respectively). The murine gene contained only two such miniexons, the sequences of which were not homologous to those of the three human miniexons. But from comparisons of intron sequences the regions surrounding the human miniexons III and IV appeared to be closely related to those surrounding the murine miniexons III and IV. The most-3' miniexon in the human gene (IVa) had no murine counterpart and appeared not to duplicate any of the other miniexons. Sequence analysis of CD3-epsilon cDNA clones isolated from four independent libraries gave no evidence for alternative use of these miniexons. Like CD3-delta, the CD3-epsilon gene was transcribed from a weak, nontissue-specific, TATA-less promoter. Pulsed-field electrophoresis showed that the human CD3-epsilon gene was separated from the CD3-gamma, CD3-delta gene pair by at least 30 kilobases, but by no more than 300 kilobases.

Amino Acid Sequence↗
PubMed1988

Characterization and expression of the murine CD3-epsilon gene.

The receptor for antigen on the surface of T lymphocytes consists of a variable disulfide-bridged hetero-dimer (TCR-alpha/beta or -gamma/delta) associated with invariant CD3 proteins (CD3-gamma, -delta, -epsilon, and -zeta). The genes coding for the CD3 proteins are expressed in the earliest recognizable thymocytes, preceding the rearrangement and expression of the TCR genes. The isolation, characterization, and in vitro expression of the murine CD3-epsilon gene, as reported here, represent obligatory steps toward our understanding of the complex rules that govern T-cell-specific gene expression. The CD3-epsilon gene was transcribed from a non-TATA promoter and consisted of eight exons, two of which were unusually small (18 and 15 base pairs). The transmembrane exon was found to be homologous to the transmembrane exons of the CD3-gamma and CD3-delta genes. In transient-transfection experiments, a genomic fragment comprising 4 kilobases of upstream sequence and extending into the second exon sufficient to drive the expression of a reporter gene in murine T cells.

Amino Acid Sequence↗
PubMed1987

Evolutionary relationship between the T3 chains of the T-cell receptor complex and the immunoglobulin supergene family.

Antigen receptors on the surface of the thymus-derived (T) lymphocytes are associated with small integral membrane proteins called the T3 (CD3) gamma, delta, epsilon, and zeta chains. After interaction of the T-cell receptor with antigen, the T3 proteins are believed to transfer an activation signal to the intracellular compartment. In previous studies, the human gamma, epsilon, and delta chains have been cloned along with the mouse delta chain, but a relationship between these sequences and known molecular families has not been established. We now report the molecular cloning and characterization of the murine T3-epsilon protein and a sequence and structural analysis of the relationships between all the T3 chains and the immunoglobulin superfamily. It is established that the T3 chains are immunoglobulin-related and a particular relationship to the neural cell adhesion molecule (N-CAM) is noted. This sequence relationship adds interest to previous findings that the T3 chains are genetically linked to N-CAM and Thy-1 antigen on band q23 of human chromosome 11.

Animals↗
PubMed1980

Echocardiographic practice in a large metropolitan area.

A survey performed concerning echocardiography in a metropolitan area. Of 110 hospitals in the area, 62 reported having echocardiographic facilities. Echocardiographic physicians and/or technicians from 41 of these hospitals responded to questionnaires designed to determine the following: (1) educational background and credentials of technicians, (2) average salaries of technicians, (3) role of the physician and technician in the performance and reporting of echocardiograms, (4) volume, cost, and method of storage of echocardiograms, and (5) number and type of echocardiographic units in use. Our data suggest various trends, including a lack of formal training among technicians, the prevalence of cardiologists-internists as directors of echocardiographic facilities, the performance of echocardiograms by cardiology fellows in only 46% of institutions with cardiology training programs, and the widespread projected availability of cross-sectional echocardiographic capability within the next two years.

Allied Health Personnel↗
PubMed1977

Infective endocarditis: a current review.

Infective endocarditis is a dynamic disease for which various infective organisms may be responsible in different patient populations. Antimicrobial therapy should be directed against the specific organism after it has been identified by blood culture. An agent with a spectrum that includes the enterococci should be given in the meantime. Prophylactic use of a bactericidal agent is necessary for patients with valvular or congenital heart disease. Recent advances in microbiologic and cardiac diagnostic procedures offer the clinician various methods of following the activity of the disease, and immunobiology has provided new insights into its pathogenesis.

Endocarditis, Bacterial↗