Biomedical subjects

R Ofir

Publications and source records attributed to R Ofir.

26 records · Page 2Linked to original sources

PubMed1990

Negative and positive regulation by transcription factor cAMP response element-binding protein is modulated by phosphorylation.

We have shown that the transcriptional activity of the protooncogene jun (c-jun) promoter is repressed by a transcription factor, the cAMP response element-binding protein (CREB). This repression can be alleviated when CREB is phosphorylated by the catalytic subunit of protein kinase A. Repression cannot be alleviated by a mutant CREB deficient in the protein kinase A phosphorylation site (M1 CREB Ser-133----Ala), suggesting that phosphorylation of CREB at this site is essential for the relief of repression. Repression by CREB requires its binding to the c-jun promoter. In NIH 3T3 cells stably expressing CREB, c-jun is no longer induced by serum, but this repression can be relieved by treatment of the cells with forskolin, an agonist of the adenylate cyclase pathway. Thus, CREB has a dual function, that of a repressor in the absence of phosphorylation and an activator when phosphorylated by protein kinase A.

Animals↗

PubMed1988

Down-regulation of natural killer cell activity in MoLV leukemogenesis: evidence for tumor-cell-mediated suppression.

The role of natural killer (NK) cells in retrovirus-induced leukemogenesis was studied. These cells which do not require prior sensitization are considered as a part of the body's defense system against tumor development and spread. Neonate BALB/c mice infected with Moloney murine leukemia virus (MoLV) develop leukemia within 3-6 months. The MoLV-infected mice showed a progressive loss of endogenous and augmented NK activity, correlated with the development of the leukemic state. Mixing of spleen cells from tumor-bearing mice with NK-augmented splenocytes resulted in suppression of NK activity. In addition, mixing of T cell lines isolated from MoLV-induced tumors with augmented splenocytes also resulted in the down-regulation of NK cell activity. The present study demonstrates that tumor cells from leukemic organs and leukemic T cell lines can actively suppress NK cell function. It is postulated that after MoLV infection the progression of virus-transformed T cells to a fully developed tumor depends on the ability of these cells to down-regulate NK cell activity and thus escape immune surveillance.

Animals↗

PubMed1988

Alterations in lymphokine secretion during leukemogenesis.

The production of interleukin 1 (IL-1), interleukin 2 (IL-2), interleukin 3 (IL-3) and granulocyte/macrophage colony stimulating factor (G/M-CSF) by preleukemic and leukemic spleen cells from Balb/c mice infected with Moloney leukemia virus (MoLV) was examined. During the development of the leukemia, the secretion of IL-1 and IL-2 significantly decreased, while the secretion of IL-3 and G/M CSF was not affected and was even enhanced. In addition, a 10 fold increase in the number of colony forming units in cultures (CFU-C) was found in the leukemic spleen indicating a shift in hematopoiesis from the bone marrow (BM) to the spleen. The low levels of IL-2 found in the conditioned medium of Concanavalin A (Con A) activated leukemic spleen cells could not result from active consumption of IL-2 by the cells, pointing to a genuine defect in IL-2 production. This failure of IL-2 secretion could be partially overcome by the addition of phorbol 12 beta-myristate 13 alpha-acetate (PMA) to the cells but not by the addition of IL-1. The defect in IL-2 production and the enhancement in IL-3 and G/M-CSF production may be of significance in the progression of preleukemic cells to autonomous malignant cells.

Animals↗

PubMed1987

Characterization of mouse thymocyte subpopulations by the enzymatic marker 20-alpha-hydroxysteroid dehydrogenase: differential responses to IL-1 and IL-2.

The responses of thymocytes to Concanavalin A (Con A), and interleukin 1 (IL-1), interleukin 2 (IL-2) and phorbol myristate acetate (PMA) were investigated. The enzyme 20-alpha-hydroxysteroid dehydrogenase (20 alpha SDH) was used as a marker to distinguish between various populations of activated thymocytes. Thymocytes that were selected in Con A + pure or crude IL-2 expressed high 20 alpha SDH activity, while those that were selected in Con A + recombinant IL-1 (rIL-1) or crude IL-1, or Con A + PMA expressed low 20 alpha SDH activity. Both groups proliferate in response to Con A and had IL-2 receptors. After selection, the enzymatic phenotype was stable even if the cells were transferred from Con A + IL-2 to Con A + PMA (or IL-1) or vice versa. A third group was selected from thymocytes that were cultured in PMA + T cell growth factor (TCGF). This group expressed low levels of 20 alpha SDH, had IL-2 receptors, but did not respond to Con A. This paper demonstrates that 20 alpha SDH can be used as an enzymatic marker to distinguish between subpopulations of activated T cells, which have not been previously detected by the conventional surface markers.

Aldehyde-Lyases↗

PubMed1986

Modulation of protein kinase C and Ca2+ lipid-independent protein kinase in lymphoma induced by Moloney murine leukemia virus in BALB/c mice.

We investigated the possible role of protein kinase C (PKC) in the progression of Moloney murine leukemia virus (Mo-MuLV)-induced lymphoma in BALB/c mice. Mice injected with Mo-MuLV on the first day after birth developed lymphoma within 1 1/2-3 months. The development of lymphoma was characterized by a gradual increase in the number of spleen cells. However, no analogous changes could be detected in the thymuses of these mice, although cells of both organs were found to be virus producers as early as 3-4 weeks after inoculation. PKC activity, which was assayed in extracts of spleen and thymus cells, declined gradually during the development of lymphoma. Concomitantly with this decline, a progressive appearance of Ca2+/lipid-independent protein kinase activity was observed. TPA treatment of intact cells from normal mice reduced the level of soluble PKC activity, while inducing Ca2+/lipid-independent phosphorylation. By contrast, TPA had no effect on these enzymatic activities in cells derived from leukemic mice. Spleen enlargement caused by injection of a non-leukemogenic inflammatory agent such as mineral oil was ineffective in this respect, suggesting that the PKC-Ca2+/lipid-independent protein kinase modulation is associated with the virally induced leukemogenesis.

Animals↗

PubMed1985

Development of resistance to MOPC-315 plasmacytoma after intralesional and intraperitoneal melphalan therapy of tumor-bearing BALB/c mice. II. Enhancement of in vitro cell-mediated cytotoxicity by combined chemotherapy-immunotherapy.

As previously reported, tumor-bearing BALB/c mice can be cured by split-course melphalan therapy, with 40-60% of the treated animals developing resistance to subsequent challenge with viable MOPC-315. The present study deals with the identification of effector-cytotoxic cells that may be developed as a result of chemotherapy-induced tumor regression and their possible potentiation by active, specific immunization with melphalan- and glutaraldehyde-treated MOPC-315 plasmacytoma cells. The cytotoxic potential of spleen-derived lymphocytes in treated animals could be demonstrated only after in vitro sensitization against mitomycin-treated MOPC-315 cells. Lymphocyte-mediated cytotoxicity, as measured against syngeneic 51Cr-labeled MOPC-315, could be detected in melphalan-cured animals and was significantly enhanced by active immunization as compared to the cytotoxicity seen in normal and tumor-bearing mice. With the use of M109 syngeneic, unrelated tumor cells as control targets in the assay, no cytotoxicity was detected. Macrophage cytotoxicity was not significantly enhanced in any of the treatment groups described, with these assays performed 6-8 weeks following treatment and cure. When in vitro killing of MOPC-315 targets was tested with the use of peritoneal macrophages harvested shortly following cure of ascitic tumor by ip injected melphalan, the cytotoxic response was significantly enhanced. In conclusion, following chemotherapy-mediated cure of established MOPC-315 tumors, splenic lymphocytes exhibited enhanced antitumor cytotoxicity, which was further augmented by active immunization. Macrophage activation, as measured by direct cytotoxicity against MOPC-315 targets, was found to occur locally and early following the event of melphalan-induced tumor regression.

Animals↗

PubMed1980

Orthoses and ambulation in hemiplegia: a ten year retrospective study.

Of the patients with hemiplegia who had undergone active rehabilitation at the Institute of Rehabilitation Medicine (IRM), New York University Medical Center, from the years 1968 through 1977, 843 were reviewed for functional ambulatory status on admission and at discharge, type of orthotic devices used, time elapsed from onset to admission for rehabilitation, and length of stay at IRM, to determine whether a consistent change had occurred in prescribing lower extremity orthoses for patients with hemiplegia, and if so, to assess the impact of such changes on the ambulation status. Of the 843 patients reviewed, 773 (91%) were partial or nonambulators on admission. Of these, 62% of the nonambulators and 66% of the partial ambulators improved significantly. A consistent decline in the use of metal orthoses, especially of long-leg orthoses, together with an increase in the use of plastic-knee ankle-foot orthoses was demonstrated. A 20% decline in prescription of lower extremity orthoses of all kinds was also observed. The rate of neuromuscular return as mwasured by attainment of functional gait has remained stable, and the proportion of numbers of patients attaining functional gait also was unchanged.

Adolescent↗

PubMed1975

Pneumatic orthosis for paraplegic patients: functional evaluation and prescription considerations.

Fourteen paraplegic patients were studied during ambulation training, 11 with pneumatic orthoses and with conventional metal orthoses, and 3 with pneumatic orthoses only. The purposes of the study were to establish whether pneumatic orthoses could be used by paraplegic patients for effective ambulation, whether these devices presented any advantages or disadvantages over conventional orthoses and how their use would affect the expected level of rehabilitation and independence. As far as application, standing up, sitting down and ambulation within a rehabilitation center are concerned, similar skills and levels of independence were obtained with both types of orthoses. Reduced tendency for orthostatic hypotension, availability, light weight and better endurance make the pneumatic orthosis especially suitable for early ambulation training, but several mechanical problems, mainly its inflation with motorized and heavy compressor units, limit its usefulness for community ambulation.

Adolescent↗