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Biomedical subjects

D Ron

Publications and source records attributed to D Ron.

At least 127 records · Page 7Linked to original sources
PubMed1989

NIH3T3 fibroblasts transformed by the dbl oncogene show altered expression of bradykinin receptors: effect on inositol lipid turnover.

We have examined polyphosphoinositide turnover in mouse fibroblasts (NIH3T3) transformed by the dbl oncogene as compared to normal cells. The dbl-transformed fibroblasts did not show alterations of the basal level of inositol polyphosphates, polyphosphoinositides, diacylglycerol or phosphatidic acid. This indicates that the activity of C-type phospholipases, inositol lipid kinases and diacylglycerol kinase is not altered in dbl-induced transformation. However, dbl-transformed NIH3T3 cells exhibited increased inositol lipid turnover in response to bradykinin. Further analysis revealed significantly higher number of bradykinin receptors in dbl transfectants as compared to control NIH3T3. When several clonally-derived dbl NIH3T3 transfectants were analyzed, we observed a large variation of their bradykinin receptor number. Cell lines exhibiting increased bradykinin binding, however, failed to show augmented mitogenic response to the peptide agonist. Among other oncogenes, only ras showed a similar effect. We conclude that increased bradykinin receptor number is a phenomenon observed with several cell lines transformed by different oncogenes, and it does not correlate with either enhanced mitogenic responsiveness of transformed cells to the peptide, or with the presence of a specific oncogene in the transformant.

Animals↗
PubMed1989

The human dbl-proto-oncogene product is a cytoplasmic phosphoprotein which is associated with the cytoskeletal matrix.

The translational product of the dbl oncogene is a 66 kDa (p66) protein with no apparent sequence similarity to any of the known oncogene products, whereas the human dbl proto-oncogene encodes a translational product of 115 kDa (p115). We compared proto-dbl p115 and dbl p66 with respect to their subcellular localization, biogenesis and post-translational modifications. Like p66, p115 was found to be a cytoplasmic phosphoprotein present in both cytosol and crude membrane preparations. Membrane fractionation studies revealed that p115 as well as p66 were primarily associated with fractions enriched in plasma membranes, suggesting that this subcellular compartment is a likely site of action of dbl proteins. The membrane-associated forms of p115 and p66 were fairly resistant to solubilization by nonionic detergents, suggesting that dbl proteins associate with the cytoskeletal matrix. p115 was also found to be phosphorylated primarily on serine residues. However, p115 was phosphorylated to a lesser extent as compared to the phosphorylated form of p66. The half-life of proto-dbl p115 was significantly shorter (1 hour) than that of dbl p66 (5-6 h). The higher stability of p66 is likely due to the acquisition of unrelated human sequences and/or to the deletion of the N-terminal region of proto-dbl.

Cell Line, Transformed↗
PubMed1989

Expression of the dbl proto-oncogene in Ewing's sarcomas.

We have investigated the expression of the dbl proto-oncogene in childhood tumors of known or suspected neuroectodermal origin. We found that while the dbl gene is consistently found expressed in Ewing's sarcoma as a single mRNA species, of approximately 5.0 kb, it is generally absent in two seemingly related categories of tumors, neuroblastoma and neuroepithelioma. The specificity of expression of the dbl proto-oncogene in Ewing's sarcoma supports the concept that Ewing's sarcoma may be differentiated from two closely related tumors, neuroblastoma and neuroepithelioma, on the basis of the presence of specific molecular markers.

Guanine Nucleotide Exchange Factors↗
PubMed1989

The N-terminal region of proto-dbl down regulates its transforming activity.

The dbl proto-oncogene can transform NIH3T3 cells when overexpressed, but its transforming activity is about 50 to 70 fold lower than that of the dbl oncogene. The dbl oncogene encodes a protein of 478 amino-acids while proto-dbl encodes a protein of 925 amino-acids. The genesis of dbl involved the loss of the first 497 amino-acids of proto-dbl and the acquisition of a new N-terminus from another human locus. The last 428 amino-acids of proto-dbl and dbl product are identical with the exception of a single conservative amino-acid change. Any of these alterations could be responsible for the greater transforming activity of dbl. In order to define the role of these alterations more precisely, we constructed two deletion mutants, one derived from proto-dbl and the second from dbl in which only their last 428 amino-acids were retained. Under the control elements of the same promoter, the transforming activity of each of these mutants was similar to that of the dbl oncogene, i.e. 60-80 fold greater than that of proto-dbl. This finding suggests that the loss of the first 497 amino-acid of proto-dbl, rather than the acquisition of a new N-terminus, is crucial to the enhanced transforming activity of the dbl oncogene. Both mutant proteins were equally distributed between the membrane and cytosolic fractions, a pattern similar to that of their corresponding parental proteins. These results suggest that the subcellular distribution of proto-dbl is determined by its C-terminal 428 amino-acids. Unlike their parental proteins, neither mutant was phosphorylated, indicating that phosphorylation is not required for dbl transforming activity. In addition to the lack of phosphorylation, each mutant protein had a half-life of 5-6 h while the half-life of proto-dbl was about 1 h. Thus, our data suggest that the N-terminal half of proto-dbl can down regulate its transforming activity and that sequences within this region are responsible for rapid turnover of the protein.

Animals↗
PubMed1988

Molecular cloning and characterization of the human dbl proto-oncogene: evidence that its overexpression is sufficient to transform NIH/3T3 cells.

We isolated cDNA clones representing the human dbl proto-oncogene transcript. Nucleotide sequence analysis revealed an open reading frame encoding a predicted protein of 925 amino acids. Using peptide antisera directed against specific proto-dbl peptides, a 115-kd protein was detected in COS cells transfected with an expression vector containing the entire coding region of proto-dbl. This mol. wt is consistent with that predicted from the open reading frame. We have previously shown that the dbl oncogene was generated by substitution of the 5' portion of proto-dbl with an unrelated human sequence. In this study we show that this rearrangement resulted in the loss of the 497 amino-terminal codons of the dbl proto-oncogene. Under the influence of a strong promoter proto-dbl could readily transform NIH/3T3 cells but its transforming activity was less than that of the dbl oncogene driven by the same promoter. Proto-dbl overexpression is, therefore, sufficient to transform NIH/3T3 cells, but specific structural alterations of its coding region significantly enhance its transforming activity. No apparent similarity was detected between the predicted proto-dbl product and other known proto-oncogenes. However, a stretch of 300 amino acids within the N-terminal half of proto-dbl showed structural similarity to the intermediate filament vimentin. This region in proto-dbl contains a heptad repeat motif characteristic of an alpha-helical coiled-coil structure. Taken together, these findings indicate that the human proto-dbl represents a new class of cellular oncogenes that may be related to cytoskeletal elements of the cell.

Amino Acid Sequence↗
PubMed1987

Independently activated dbl oncogenes exhibit similar yet distinct structural alterations.

The dbl oncogene was initially isolated following transfection of NIH3T3 cells with DNA of a human diffuse B cell lymphoma. Its transcribed sequences were shown to be distributed over a 30-kb span within a molecularly cloned 45-kb segment of human DNA which contained the transforming gene. By restriction mapping, its transcribed region corresponded to that of its normal allele, except at the 5' end where a rearrangement involved transcribed dbl oncogene sequences from another locus. An independent isolate of a dbl-related transforming gene was obtained following transfection of NIH3T3 cells with DNA of a human nodular poorly differentiated lymphoma (NPDL). Physical mapping indicated that this transforming gene, designated NPDL-dbl, shared considerable homology with the dbl oncogene, but differed at both 5' and 3' termini. Its point of divergence from the normal allele at the 5' end was at least 10 kb upstream from that of the dbl oncogene. The oncogenes each expressed truncated transcripts compared to the 5.3-kb normal transcript. The dbl and NPDL-dbl oncogene translational products of 66 and 76 kDa, respectively, were consistent with their corresponding major 2.8- and 3.5-kb transcripts. It was not possible to detect evidence of the 5' structural rearrangements associated with these oncogenes in either of the original tumors. Thus, if these rearrangements were critical to their activation, they occurred in the process of gene transfer or in vivo in only a minority of tumor cells.

Animals↗
PubMed1986

Development-dependent replication of minute virus of mice in differentiated mouse testicular cell lines.

The replication of the autonomous parvovirus, minute virus of mice (MVM), requires mitotically active cells and depends on certain factors expressed by cells of particular differentiated phenotype. As an approach to the understanding of these helper functions, we studied the interaction of the fibrotropic [MVM(p)] and the lymphotropic [MVM(i)] strains of MVM with two differentiated cell lines from mouse testicular epithelial origins. The relative support given to viral expression by these cell lines varied extensively. Cells from Sertoli origin (TM4) were permissive to MVM(p) but were mostly restrictive to MVM(i). The other cell line, of Leydig cell origin (TM3), was highly restrictive to both viral strains, but the blocks to their growth in these cells were localized at different stages of their growth cycle, suggesting that the replication of MVM in these cells requires tissue-specific helper functions during at least two stages of viral replication.

Animals↗
PubMed1986

Spontaneous curing of a minute virus of mice carrier state by selection of cells with an intracellular block of viral replication.

We previously described a persistent infection established by the lymphotropic minute virus of mice in mouse L cells at the level of the cell population (D. Ron, P. Tattersall, and J. Tal, J. Virol. 52:63-69, 1984). This carrier state is maintained by a series of consecutive phenotypic changes which take place in both the cells and the virus and is cured spontaneously after 150 to 200 cell generations (D. Ron and J. Tal, J. Virol. 55:424-430, 1985). We show here that the cure was caused by the selection of virus-resistant cells in the culture. The resistance of these survivor cells to virus replication was due to an intracellular block. Infection of a spontaneously cured culture with the fibrotropic parental minute virus of mice resulted in a restrictive infection in which the viral replicative-form DNA was formed and amplified, but the synthesis of single-stranded progeny DNA was markedly reduced. The lymphotropic strain was blocked in these cells at an earlier stage, with little or no amplification of viral replicative-form DNA observed. These data indicate that the replication of minute virus of mice requires host-coded helper functions in at least two stages of its growth cycle.

Animals↗
PubMed1985

Coevolution of cells and virus as a mechanism for the persistence of lymphotropic minute virus of mice in L-cells.

Infection of L-cells with minute virus of mice (i), a lymphotropic strain of minute virus of mice, resulted in the emergence of host range mutant viruses capable of a lytic infection that destroys the initially restrictive parental cells. Despite that, the culture was not lysed completely; instead, a persistent infection resulted which lasted at least 150 days. Throughout the persistent infection, extensive changes occurred in both the tissue tropism of the progeny virus and in the phenotypic properties of the cells. Mutant cells were selected which were increasingly restrictive to the replication of the resident virus, but concomitant changes in the virus enabled it to replicate in a subpopulation of the restrictive cells. The persistent infection could be reconstructed by infection of mutant cells with mutant virus; in contrast, neither infection of parental cells with mutant virus nor infection of mutant cells with parental virus led to persistence. On the basis of these results, we suggest that virus-cell coevolution provides the primary mechanism for the initiation and the maintenance of the persistent infection.

Animals↗
PubMed1984

Formation of a host range mutant of the lymphotropic strain of minute virus of mice during persistent infection in mouse L cells.

Minute virus of mice (i), the lymphotropic strain of minute virus of mice, established a persistent infection in normally restrictive L cells. The carrier state, which lasted 150 days, exhibited three clearly distinguishable stages. During the early stage (days 1 to 10 postinfection), small amounts of virus were formed. A "crisis" then developed that lasted 50 to 60 days and was characterized by massive cell lysis and high titers of virus. This was followed by a 70- to 80-day period in which small but stable quantities of virus were produced. Virus shed by the carrier culture during the latter phase had acquired an altered host range, namely, it had lost its ability to replicate in T-lymphocyte cell lines and had adapted to growth in L cells. Virus isolated at this time from a single plaque in L cells, designated hr301, was shown to possess similar host range properties. No differences, however, could be found between the DNAs of minute virus of mice (i) and of hr301 by restriction enzyme analysis, suggesting that the mutation that affected the viral host range did not involve an extensive region of the viral genome.

Animals↗
PubMed1984

Prevention of acute renal failure in traumatic rhabdomyolysis.

Following the collapse of a building, seven subjects (aged 18 to 41 years) were released from under the rubble within one to 28 hours. All seven suffered from extensive crush injuries with evidence of severe rhabdomyolysis and were treated by the induction of an alkaline solute diuresis immediately on their extrication from the debris. The leakage of muscle constitutents was estimated by quantifying the net total body potassium losses, which averaged 395 mEq (SD, +/- 198) over the first 60 hours of therapy. In the past, injuries of similar severity have been associated with a high incidence of acute renal failure and a high mortality rate, yet none of our patients had azotemia or renal failure. We attribute this success to the unprecedented early institution of appropriate therapy.

Acid-Base Equilibrium↗
PubMed1983

High density lipoprotein in octogenarians.

High density lipoprotein (HDL) cholesterol, total cholesterol, and total triglyceride levels were assayed in the plasma of 42 octogenarians. No differences were found in the levels of HDL cholesterol and total triglycerides when comparing subjects with and without ischemic heart disease. The average lipid profile of males in this age group shows significantly lower levels of triglycerides and total cholesterol when compared with the females. HDL cholesterol levels were 10% higher in the females. The distribution pattern of HDL cholesterol levels in this age group suggests a bimodal distribution with 85% of the population distributed around a low peak of 53 mg% and 15% around a high peak of greater than 70 mg%. This pattern suggests that the hyperalphalipoproteinemia phenotype does exist as a separate entity in a population demonstrating longevity, but its low incidence cannot provide an explanation for longevity in the majority of subjects. Subfractionation of HDL was performed by preparative ultracentrifugation and the subfraction profile of 17 female octogenarians was compared with a group of young controls. The younger individuals had greater fat to protein ratios in the HDL-1 and HDL-2 subfractions. This was only difference in lipoprotein composition. We conclude that neither the total level of HDL particles nor the distribution of lipoprotein components among the subfractions can account for the longevity of the majority of the study population.

Aged↗
PubMed1983

Accumulation of lipoprotein remnants in patients with chronic renal failure.

The composition and concentration of remnant lipoprotein particles accumulating in the plasma of patients with chronic renal failure (CRF) was determined. Ten patients on chronic hemodialysis were compared with 8 controls. The patients' very low density lipoproteins (VLDL) were abnormal and contained more of the dense VLDL subfraction (VLDL3). The concentration of intermediate density lipoproteins (IDL) was increased 3-fold in CRF plasma, whereas the amount of low density lipoprotein (LDL) was decreased by 25%. On electrophoresis of plasma lipoproteins the beta-band from the patients' samples demonstrated increased anodal mobility, indicating an abnormality in composition of the patients' LDL. These abnormalities were present regardless of whether patients were hyperlipidemic or not. These findings suggest defective conversion of VLDL to LDL in CRF, allowing for the accumulation of lipoprotein particles usually absent from plasma. The latter may account for the accelerated atherosclerosis reported in patients with CRF.

Adult↗
PubMed1983

Simultaneous closed dislocation of both interphalangeal joints in one finger.

A rare case of simultaneous dislocation of both interphalangeal joints in one finger in a table-tennis player is presented. The second dislocation took place when the first dislocated joint became the fixed part of the finger as it hit a wall. Treatment was, first, hyperextension to unlock the base of the phalanx, then traction along the phalanx: its base was then pushed into contact with the head of the proximal phalanx. Splinting was applied with the joint in slight flexion.

Adult↗