Immortalizing genes of Epstein-Barr virus

EBV immortalizes human B lymphocytes efficiently. Ten of its approximately 100 genes are expressed in these proliferating lymphoblasts and are candidates for mediating the changes central to the immortalization of the cell. Enough has been learned now about three of these viral genes to indicate that they are likely to be required for immortalization. As more is learned, additional genes of EBV will probably be found to support the process of immortalization of the host cell. EBNA-2 has been shown genetically to be required for EBV to immortalize an infected B lymphocyte. The biochemical activities of EBNA-2 that constitute this requirement have not been identified. Many experiments indicate that EBNA-2 affects the accumulation of specific viral and cellular RNAs. These effects, however, can be detected only in certain EBV-negative B-lymphoblastoid cells. It is, therefore, not clear that the known effects of EBNA-2 adequately explain its ubiquitous requirement in the immortalization of primary human B lymphocytes. LMP is likely to be required for immortalization because it can affect the growth properties of established human lymphoid and epithelial cells and can transform at least two established rodent cells to proliferate in an anchorage-independent manner. The structure of this viral protein, its position in the plasma membrane, many of its biochemical properties, as well as studies of its mutant derivatives are consistent with its acting as a growth factor receptor or affecting the activity of such a receptor. However, no biochemical activity has been assigned directly to LMP, and both its mechanism of action and its possible contribution to immortalization by EBV remain enigmatic. EBNA-1 presumably is required for EBV to immortalize a B lymphocyte because it is essential for the initiation of plasmid DNA replication by EBV. Circumstantial observations indicate also that EBNA-1 is probably necessary for sustaining viral DNA replication in the proliferating cell population. EBNA-1 may well affect the regulation of transcription of viral genes that themselves are required for immortalization. These roles of EBNA-1 are performed in part by its site-specific binding to the elements of oriP required in cis for the replication of EBV plasmid DNAs. It is probable that EBNA-1 also binds both to a set of cellular proteins that function in transcription and to a nonidentical set of cellular proteins that function in replication. EBV effects a fascinating phenotypic change in B lymphocytes it infects. It does so by using several viral genes that alter the physiology of the cell by different means.(ABSTRACT TRUNCATED AT 400 WORDS)

The relationship between insulin autoantibodies and islet cell histology in the diabetes prone BB rat

The relationship between insulin autoantibodies (IAA) and pancreatic islet cell histology was examined in 71 diabetes prone BB rats from the Toronto colony. Twenty-seven of the 71 became diabetic and of these, 18 (67%) were IAA positive by ELISA. IAA were also detected in 39/44 (89%) which did not develop diabetes, but in none of six control animals at 50-140 days of age. All 27 which became diabetic showed some evidence of lymphocytic infiltration scored + to ++++ histometrically and 26/27 evidence of beta cell degranulation. The frequency of diabetes increased with both intensity of insulitis and degree of beta cell degranulation, but there was no correlation between either and IAA. IAA are a marker for the BB strain of Wistar rat, but do not correlate with islet cell histology and do not predict clinical diabetes.

Effects of supplemental oxygen administration in an infant with pulmonary artery hypertension

In patients with pulmonary disease, pulmonary artery hypertension often occurs as a result of pulmonary artery vasoconstriction, primarily from hypoxia and alveolar hypotension. In this report we describe the hemodynamic effects of breathing supplemental oxygen in a child with bronchopulmonary dysplasia and pulmonary artery hypertension. These hemodynamic effects include an improvement in oxygenation, an increase in systemic vascular resistance, and a decrease in the pulmonary vascular resistance. As a direct result of these changes in vascular resistances, alterations of heart rate, cardiac index, stroke volume, aortic pressure, oxygen consumption, and pulmonary artery pressure have been shown to occur. Oxygen is widely used to treat many physiologic conditions. However, during the administration of supplemental oxygen, rarely do we recognize the hemodynamic changes associated with its use. These hemodynamic effects must be clearly understood and appreciated before oxygen administration in any clinical situation.

Biochemical properties of somatostatin receptors

Somatostatin (SRIF) induces its biological actions by binding to and stimulating membrane-associated receptors. To investigate the molecular mechanisms by which SRIF induces its biological effects, we have characterized the biochemical properties of SRIF receptors. SRIF receptors can be solubilized in an active form with the detergent CHAPS and can be detected with the high-affinity SRIF analog [125I]MK 678. The pharmacological characteristics of solubilized SRIF receptors from brain are similar to the receptors in membranes, suggesting that the solubilized receptors retain their biological activity. Solubilized SRIF receptors appear to be tightly associated with GTP-binding proteins, since analogs of GTP can greatly reduce agonist labeling of the solubilized SRIF receptor. The solubilized SRIF receptor migrates as a mass of approximately 400 kd and is a glycoprotein since it can specifically interact with lectin columns. The solubilization of the SRIF receptor has allowed for its purification by affinity chromatography. The purified SRIF receptor migrates as a mass of 60 kd in denaturing gels. Using affinity chromatography, the receptor can be purified to near homogeneity. Present studies are directed toward sequencing and cloning cDNA encoding the SRIF receptor in order to further characterize its physical properties and expression.

Solubilization of active somatostatin receptors from rat brain

Rat brain somatostatin (SRIF) receptors were solubilized in an active form with the detergent 3-[(cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Solubilized SRIF receptors were detected with the stable SRIF analog 125I-MK 678. CHAPS solubilized approximately 30% of membrane-bound SRIF receptors. 125I-MK 678 binding to the solubilized SRIF receptors reached equilibrium by 90 min and dissociated from the receptor with a t1/2 of 60 min. The binding of 125I-MK 678 to the solubilized SRIF receptor was of high affinity and was selective. The characteristics of 125I-MK 678 binding to the solubilized and membrane-bound SRIF receptors were similar. The solubilized brain SRIF receptor specifically bound to a wheat germ agglutinin-Sepharose column, suggesting that it is a glycoprotein. Analysis of the solubilized SRIF receptor by gel exclusion chromatography on an AcA 34 Ultrogel column revealed that its molecular mass is approximately 400 kDa. This mass is probably representative of the receptor complexed with other proteins or molecules. Further characterization of the fractionated 400-kDa species by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting indicated that Gi and Go may be associated with the solubilized SRIF receptor. This is supported by the finding that guanosine-5'-O-(3-thio)triphosphate abolished 125I-MK 678 binding to the solubilized SRIF receptor. Antibodies directed against a synthetic peptide corresponding to a region of the C-terminal of Gia, which specifically immunoprecipitate Gia, immunoprecipitated over 24% of the solubilized SRIF receptor, suggesting that the receptor, in part, is coupled to Gi. These studies describe for the first time the characterization of the solubilized SRIF receptor in an active form. The ability to solubilize the SRIF receptor should allow for further characterization of its physical properties.

Thrombotic thrombocytopenic purpura causing sudden, unexpected death--a series of eight patients

Eight patients were presented to the medical examiner after dying suddenly and unexpectedly from thrombotic thrombocytopenic purpura. Compared with patients who die after prolonged hospitalization and treatment, these patients showed fewer neurologic symptoms and correspondingly fewer or no microthrombi within the brain. Only four of eight subjects developed fever, which further contributed to misdiagnosis. The differences in clinical presentation between our cases and most published series is striking and may be explained by shorter duration and no treatment. Each case contained the characteristic histology of thrombotic thrombocytopenic purpura. Ischemic injury to the heart and conduction system was the most likely mechanism of sudden death. Included in this series is a patient with acquired immunodeficiency syndrome (AIDS) diagnosed at autopsy, a concurrence that is now appearing more frequently in the medical literature.

Vascularization of corneas of hairless mutant mice

During the course of experiments examining the immunobiology of corneal transplants, the corneas of athymic, nude mice (nu/nu) were found to contain blood vessels that extended through the entire superficial stroma into the centermost portion of the cornea. The presence of corneal vessels was not related to the immunodeficient condition of the nude mouse since corneas from the severe combined immunodeficiency (SCID) mutant mouse strain were avascular and indistinguishable from corneas obtained from immunocompetent BALB/c mice. Furthermore, Langerhans cells were not found to accompany the blood vessels in the corneas of any of the nude mice examined. Corneal vascularization that was similar to that seen in the nude mouse was found in the cuthymic, hairless mutant mouse strain (SKH1; hr/hr). Although vascularization of the corneal stroma was associated with the heritable loss of hair, the genes responsible for hair loss in these two mutant mouse strains reside on different chromosomes. Understanding the processes involved in either promoting or preventing corneal vascularization may have significant impact in preventing corneal allograft rejection and in controlling inflammatory diseases of the corneal surface. The two mutant mouse strains described here may serve as valuable tools for such investigations.

Computer-assisted elaboration of job histories

Three ways are proposed to help the occupational physician in constructing a worker's job history or Curriculum Laboris (CL) with a PC. The quality and, therefore, the usefulness of any job history is greatly conditioned by the method and quality of data collection. The Curriculum Laboris method explained in a previous article has been briefly summarized as a basis of departure. Then, the workers who were submitted to special medical surveillance were considered. After this, the scrolling menu technique was applied in the elaboration of a job history. Finally, the authors show how the representation of company organization by means of a job exposure matrix (JEM) can help to efficiently elaborate job histories.

Characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA)

This study describes the characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA) to quantify murine monoclonal antibodies of all IgG isotypes. Two physical methods (transmission electron microscopy (TEM) and dynamic light scattering (DLS], were used to obtain information about particle size and morphology of the gold sols, but only with DLS antibody labelling could be detected. In addition, electrophoretic methods like agarose electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed also that antibody labelling was successful. The biological activity of the antibody gold conjugates was determined by using them in a SPIA and as an electrondense marker in an immunogold labelling procedure to visualize meningococcal surface exposed outer membrane proteins labelled with monoclonal antibodies. The SPIA was applicable to determine murine monoclonal antibodies of all IgG isotypes with a sensitivity of 20-80 ng/ml and a coëfficiënt of variation of 6.7 +/- 2.2%.

Occupational risks: a follow-up method based on individual work history records including the environmental aspects of the workplace

This article analyzes the Curriculum Laboris or career reconstruction as a means of studying the occupational risks of employees. A type of Curriculum Laboris which makes the established record easier to use has been suggested. The authors point out some advantages to be expected from the proposed computerized method. The usefulness of the proposed Curriculum Laboris is largely conditioned by lack of standards for guiding data collection by physicians. Finally, the Curriculum Laboris has been considered as an element of a larger information system.

Analysis of parathyroid hormone in bovine parathyroid cysts

Parathyroid cysts were found in 2-5% of beef steers and heifers while collecting parathyroids at a local abattoir. The cyst fluid contained parathyroid hormone (PTH), averaging 15 ng/ml of fluid. Reversed-phase high-performance liquid chromatographic (HPLC) analysis of the fluid using an acetonitrile-trifluoroacetic acid solvent system, followed by carboxyl-terminal specific PTH radioimmunoassay of the eluant fractions, revealed two major peaks of PTH immunoreactivity. The first eluted at approximately 25% acetonitrile, a position similar to the commercially available human carboxyl terminal fragment of PTH-(39-84). The second peak, at approximately 37% acetonitrile, corresponded to the elution position for bovine PTH-(1-84). The cyst fluid was tested for enzyme activity by incubation of 125I-labeled bovine PTH with cyst fluid for 30 minutes at 37 degrees C, which resulted in no fragmentation of the labeled peptide. Immunohistochemistry of the cells lining the parathyroid cyst indicated that they contained PTH.

A human melanoma-derived cell line (IGR39) with a very high number of vasoactive-intestinal-peptide (VIP) receptors. 1. Molecular characterization of the binding site

Using mono[125I]iodinated vasoactive intestinal peptide (125I-VIP), a very high number of specific binding sites for VIP were identified at the surface of the human melanoma cell line IGR39. The Scatchard analysis of competitive displacement experiments between native VIP and 125I-VIP was consistent with the existence of two classes of VIP-binding sites. IGR39 cells possess 0.54 x 10(6) high-affinity sites with a dissociation constant (Kd) of 0.66 nM and 1.3 x 10(6) sites of moderate affinity with a Kd of 4.7 nM. Pharmacological studies indicated that the order of potency in inhibiting 125I-VIP binding of the VIP/secretin family peptides was VIP much greater than peptide histidine methioninamide greater than human growth-hormone-releasing factor(1-44) greater than secretin. Glucagon has no effect on the binding of the labelled peptide. By means of photoaffinity labelling a polypeptide of Mr 63,000 was characterized. The labelling of this species was completely abolished by native VIP. The order of potency of VIP-related peptides in inhibiting 125I-VIP cross-linking to its receptor was the same as in the competition experiments. The glycoprotein nature of the VIP-binding sites of IGR39 cells has been investigated by affinity chromatography on wheat-germ-agglutinin-Sepharose.

A human melanoma-derived cell line (IGR39) with a very high number of vasoactive-intestinal-peptide (VIP) receptors. 2. Effect of VIP on cAMP production and on cell-surface VIP-binding sites

Vasoactive intestinal peptide (VIP) stimulated in a dose-dependent manner the accumulation of cAMP in human melanoma-derived cell line IGR39. The maximal effect (about 100 times the basal level) was observed with 10 nM VIP. Half-maximum cAMP production was obtained at 0.78 nM VIP. VIP-related peptides were also potent in stimulating the cAMP production in IGR39 cells. The order of potency was VIP much greater than peptide histidine-methioninamide greater than human growth-hormone-releasing factor(1-44) greater than secretin greater than glucagon. Using the same conditions, IGR37 cells, a metastasic counterpart of IGR39 cells, displayed a weak stimulation of cAMP production. After exposure of IGR39 cells to 10 nM VIP, the cAMP response to a new stimulation by VIP was strongly reduced. This desensitization of IGR39 cells to VIP was rapid (t1/2 less than 2 min) and homologous. Preincubation of IGR39 cells in the presence of native VIP induced disappearance of the VIP-binding sites at the cell surface. This phenomenon was dependent on time and VIP concentration. Maximum effect (loss of 80% of binding capacity) was obtained after exposure of the cells at 37 degrees C with a VIP concentration of 1 microM. The t1/2 of maximum disappearance was less than 2 min and the concentration of VIP giving half-maximum decrease in binding of mono[125I]iodinated VIP (125I-VIP) was 8 nM. This phenomenon was also reversible since 85% of the VIP-binding capacity could be restored in less than 1 h by incubating IGR39 cells in a VIP-free medium. The IGR39 cell line should be a useful model for further study of the structure and function of the human VIP receptor.

Continuous negative pressure and intermittent mandatory ventilation in the management of pulmonary interstitial emphysema: a preliminary study

We reviewed the clinical courses of 12 prematurely born newborns who were placed in continuous negative pressure (CNP) in an Isolette negative pressure ventilator for refractory hypoxemia while receiving intermittent positive pressure mandatory ventilation. All patients had severe lung disease as documented by an increased oxygenation index and bilateral pulmonary interstitial emphysema on x-ray examination. Patients were separated into two groups--survivors and nonsurvivors, with six patients in each group. Initiation of CNP resulted in a significant initial improvement in oxygenation in both groups seen as a 52% decrease in the oxygenation index in survivors and a 57% decrease in the oxygenation index in nonsurvivors (P less than .05). The survivors characterized themselves by showing a further sustained improvement in the oxygenation index--31.4 +/- 9.1 to 6.9 +/- 5.0 (P less than .01)--and a significant decrease in the mean airway pressure--11.6 +/- 4.6 cm H2O to 5.0 +/- 1.9 cm H2O (P less than .05). Four of the six survivors showed radiographic resolution of pulmonary interstitial emphysema. CNP was initiated at a mean age of 68.3 hours in the survivors. Nonsurvivors were initiated in CNP at a mean age of 134.3 hours, but went on to clinically deteriorate owing to irreversible hypoxemia and acidosis. Both oxygenation index and mean airway pressures were virtually unchanged compared with their initial values. The exact mechanisms by which CNP improves pulmonary function in this group of infants is unknown.(ABSTRACT TRUNCATED AT 250 WORDS)

Could bovine serum albumin be the initiating antigen ultimately responsible for the development of insulin dependent diabetes mellitus?

Western blotting of either a cloned rat beta-islet tumour cell extract or isolated BB rat islets with rat anti-bovine serum albumin antiserum revealed a cross-reacting protein (Mr = 69,000). A protein of similar molecular size was observed by fluorography in proteins immunoprecipitated from islet cells labelled with (35S)-methionine using anti-bovine serum albumin antiserum. In comparing the primary structure of the beta subunits of the proteins Ia, DQ and DR a region of homology with bovine serum albumin became evident. Analysis of the amino-acid homology in relation to the DR/DQ allotypes found in the human population gave a strong correlation between the combined DR and DQ homology score with bovine serum albumin and the incidence of insulin dependent diabetes mellitus.

Solubilization of the active vasoactive intestinal peptide receptor from human colonic adenocarcinoma cells

The non-ionic detergent n-octyl-beta-D-glucopyranoside was used to solubilize the VIP (vasoactive intestinal peptide) receptor from human colonic adenocarcinoma cell line HT29-D4. The binding of monoiodinated 125I-VIP to the solubilized receptor was specific, time-dependent, and reversible. Scatchard analysis of data obtained from competitive displacement of monoiodinated 125I-VIP by native VIP suggested the presence of two classes of VIP binding sites with Kd values of 0.32 and 46.7 nM. The binding capacities of these two classes were 1.7 x 10(10) and 30.2 x 10(10) sites/mg of proteins, respectively. The solubilized receptor retained the specificity of the human VIP receptor towards the peptides of the VIP/secretin/glucagon family. The order of potency in inhibiting monoiodinated 125I-VIP binding was VIP (IC50 = 1.0 x 10(-9) M) much greater than peptide histidine methionine amide (IC50 = 10(-7) M) greater than growth hormone-releasing factor (IC50 = 3 x 10(-7) M) greater than secretin (IC50 greater than 10(-6) M); glucagon had no effect on VIP binding. The reducing agent dithiothreitol inhibited in a dose-dependent manner the binding of 125I-VIP. Covalent cross-linking experiments between the solubilized receptor and 125I-VIP showed that after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography two major and one minor polypeptides of Mr 67,000, 72,000, and 83,000 were specifically labeled. When analyzed by gel filtration, the n-octyl-beta-D-glucopyranoside-solubilized 125I-VIP-receptor complex was resolved into two major peaks with molecular mass in the range of 60-70 and 270-300 kDa. Thus, the soluble form of the VIP receptor was probably a multimeric complex in which disulfide bonds may play an important role to hold the receptor in an active configuration.

Hairy cell leukemia and anti-leukocyte common antigen

Thirty-three bone marrow biopsies from 15 patients with hairy cell leukemia (HCL) were evaluated morphologically and immunohistochemically by use of the peroxidase-antiperoxidase technique to demonstrate reactivity for leukocyte common antigen (LCA). Hairy cells in all biopsies showed a distinctive and characteristic pattern for LCA, which decorated the periphery of the cytoplasm but that left most of the cytoplasm and the nucleus unstained. Anti-LCA was particularly helpful in highlighting focal or subtle leukemic infiltrates. Hairy cells in biopsies from three patients had, on routine morphologic examination, a spindled and sarcomatoid appearance, but these too were strongly LCA positive. Treatment regimens were variable: five patients had splenectomy and received chemotherapy; five patients had splenectomy alone; and four patients had chemotherapy alone. Seven patients received interferon, and one patient received no treatment. In those six patients who had multiple biopsies as part of follow-up examinations, hairy cells as identified by anti-LCA were continuously present. Often in significant numbers, and were usually underestimated or not identified by routine examination. In those patients who received chemotherapy, qualitative alterations in the LCA reaction of hairy cells were observed.

The vasoactive intestinal peptide (VIP) receptor: recent data and hypothesis

Vasoactive intestinal peptide (VIP) is a neuropeptide with a broad range of biological activities in various tissues. After interaction with its membrane receptor, VIP generally induces a very large increase in the intracellular cyclic AMP level. Receptors for VIP have been described in numerous tissues and cell lines. The first results on VIP receptor structure have been obtained by covalent cross-linking using bifunctional reagents. The molecular mass of the different components characterized in this way differs greatly according to the species and the tissue used. This heterogeneity may reflect either a difference in the length of the cross-linked polypeptide backbone or differently glycosylated forms of the same polypeptide. The VIP binding site of intact human adenocarcinoma cells (HT29 cells) is an Mr 64,000 glycoprotein with 20kDa of N-linked oligosaccharide side chains containing sialic acid. The structure of the VIP binding site from HT29 cell is compared, first to the structure of the VIP receptor from other tissues, particularly that from rat liver, and second to the structure of the hepatic glucagon binding site. Recently, solubilization of the VIP receptor in an active form has provided a new way of studying this receptor. The HT29 cell line is an appropriate model to study the dynamics of the VIP receptor. After binding to its receptor, VIP is rapidly internalized, probably by receptor-mediated endocytosis. This internalization leads to a decrease in the cell surface receptor number and simultaneously to a homologous desensitization of adenylate cyclase. VIP is then degraded in the lysosomes, while most of the receptors are recycled back to the cell surface. The presence of an intracellular pool of unoccupied VIP receptors has been demonstrated after inactivation of the cell surface receptors by chymotrypsin. The kinetics of the receptor reappearance at the cell surface, after inactivation by chymotrypsin or after receptor-mediated endocytosis, indicate 2 possible intracellular pathways for occupied and unoccupied VIP receptors.