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S Segal

Publications and source records attributed to S Segal.

At least 217 records · Page 12Linked to original sources
PubMed1992

Regions within the c-Myc protein that are necessary for transformation are also required for inhibition of differentiation of murine erythroleukemia cells.

The c-, L-, and N-Myc nuclear phosphoproteins share several highly conserved regions that partially overlap putative functional domains of the c-Myc protein. All three myc oncogenes can cooperate with an activated ras gene to transform primary rat embryo cells (REC), and deregulated expression of c- and L-myc can block differentiation of murine erythroleukemia (MEL) cells. In the present study, we demonstrate that N-myc also can block MEL cell differentiation, and we identify regions within the c-Myc protein that are necessary for inhibition of MEL differentiation. C19 MEL cells were transfected with six human c-myc genes which were partially deleted in different areas of the coding region. Four of the genes lack sequences that overlap either the putative transcriptional activation domain, the helix-loop-helix motif, or the leucine zipper motif and were previously shown to have lost REC cotransforming activity (J. Stone, T. DeLange, G. Ramsay, E. Jakobovitz, J.M. Bishop, H. Varmus, and W. Lee, Mol. Cell. Biol., 7: 1697-1709, 1987). In this study, we demonstrate that they also fail to inhibit N,N'-hexamethylene-bis-acetamide-induced differentiation of MEL cells. In contrast, two partially deleted c-myc genes, one lacking a short NH2-terminal region and the other lacking 118 amino acids at the center of the coding region, which were fully active in REC cotransformation, also exhibited full activity associated with the former and only partial activity with the latter in blocking MEL differentiation. We conclude that the mutated genes tested in this study behave similarly in inhibition of MEL cell differentiation and in REC cotransformation.

Animals↗
PubMed1991

The influence of pH on cystine and dibasic amino acid transport by rat renal brushborder membrane vesicles.

The uptake of cystine and lysine by rat renal brushborder membrane vesicles was examined at various intravesicular and extravesicular hydrogen ion concentrations to discern whether ionic species are determinants of specificity for the shared transport system and whether hydrogen ion gradients play a role in determining uptake values. When intravesicular and extravesicular pH are identical, the highest uptake of cystine occurred at pH 7.4, with lesser uptake at pH 6.0 and 8.3. Since cystine is electroneutral at pH 6.0 and 90% anionic at pH 8.3, it appears that neither form of the amino acid is a preferred species for transport. A similar relationship between pH and uptake occurs for lysine, which is cationic at pH below 8.5. This suggests that pH affects the functioning of the membrane carrier system independent of ionic species of the substrate. There is no apparent relationship of cystine uptake to hydrogen ion gradients across the membrane. Over the range of extravesicular pH studied, optimal cystine uptake occurred whenever the intravesicular pH was 7.4. Competitive interactions between unlabeled amino acids and labeled cystine were not affected by the extravesicular pH and, therefore, did not seem determined by the ionic species of cystine.

Amino Acids, Diamino↗
PubMed1991

The concentration of red blood cell UDPglucose and UDPgalactose determined by high-performance liquid chromatography.

We have developed a sensitive method that employs high-performance liquid chromatography to separate and quantitate uridine diphosphogalactose (UDPGal) and uridine diphosphoglucose (UDPGlu) in human red blood cells. The trichloracetic acid extracts of red blood cells were chromatographed using a Dionex CarboPac anion-exchange resin and a 20-40% potassium phosphate buffer, pH 4.5, in a gradient-elution program. UDPGal and UDPGlu were detected spectrophotometrically at 254 nm. Recoveries of UDPGal and UDPGlu ranged from 96 to 106%. Under these conditions, there was exceptionally good reproducibility in stored specimens, and the method was sensitive in the low picamole range. The mean values and standard deviations in adults were 2.9 +/- 0.4 and 7.8 +/- 0.8 mumol/100 g Hgb for UDPGal and UDPGlu, respectively. The values in children were 4.5 +/- 1.2 and 10.2 +/- 1.7 mumol/100 g Hgb for UDPGal and UDPGlu, respectively. Values determined by the HPLC method are in excellent agreement with those obtained by enzyme analysis.

Adult↗
PubMed1991

Expression of rat jejunal cystine carrier in Xenopus oocytes.

Functional interactive cystine-lysine carriers have been expressed in Xenopus oocytes following the injection of RNA extracted from rat intestinal mucosa. Lysine-inhibitable cystine uptake was able to be measured 16 h after oocyte injection with RNA. The longer the oocytes were maintained after injection, the more cystine transport capability was induced. Uninjected or water-injected oocytes showed virtually no lysine-inhibitable cystine uptake, and no system developed after the oocytes had been isolated and maintained in vitro. The cystine uptake expressed after RNA injection was selectively inhibited by dibasic amino acids and phenylalanine but not by other amino acids or alpha-methyl-D-glucoside. Expression of the interactive cystine-lysine system was induced only by RNA isolated from intestinal tissue and not by RNA from rat liver. The Km for cystine uptake in RNA-injected oocytes was 0.01 mM and appears identical to the single system found in the RNA source tissue.

Animals↗
PubMed1991

Tumorigenicity, metastasis and suppression of MHC class-I expression in murine fibroblasts transformed by mutant v-ras deficient in GTP binding.

We have introduced point mutations in v-rasH to study their effects on biochemical and biological properties of the ras-encoded protein p21. Several of these mutant proteins do not bind GTP and thus lack GTPase activity, while others were shown to have their GTP binding reduced. We have introduced these ras mutants into NIH 3T3 fibroblastoid cells to study major parameters of clinical importance which are associated with neoplastic transformation, particularly MHC expression in cells, metastasis and tumorigenesis in both nude mice and immune competent mice. Our data show that certain mutations in v-ras differentially affect the expression of the transformed phenotype. Mutant ras molecules deficient in GTP binding fail to generate rapidly progressing tumors in immune competent mice, and not all morphologically transformed cells were capable of experimental metastasis. Cells transformed by certain v-ras mutants form tumors in immunocompetent mice and show reduced expression of MHC class-I antigens. Other cells are morphologically transformed and tumorigenic in athymic nude mice, but fail to form tumors in normal mice and show levels of MHC class-I antigen expression similar to non-transformed 3T3 cells. The inverse relationship between MHC class-I-antigen expression and the degree of transformation in fibroblastoid cells suggests that the ras gene product could be involved in regulating MHC expression.

Animals↗
PubMed1991

Decrease in luteal gonadotropin concentration in conception cycles after in vitro fertilization/gamete intrafallopian transfer.

The concentrations of the gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured in the luteal phase of the cycle in patients undergoing ovarian hyperstimulation. In nonconception cycles, FSH and LH were increased in the late luteal phase compared with conception cycles in which both gonadotropins were suppressed. Estradiol (E2) and progesterone concentrations increased in pregnancy cycles and may be the sole cause for the decreased gonadotropin concentrations as shown by equivalent concentrations of LH and FSH in both pregnancy and nonpregnancy cycles after matching for E2 concentrations. Subjects who subsequently had twin pregnancy or a spontaneous abortion were compared with those with a successful ongoing singleton conception. There were no significant differences relative to LH and FSH between the three groups, although in twin pregnancy FSH tended to be lower at day 16 from oocyte recovery. It is concluded that suppression of LH and FSH in hyperstimulated pregnancy cycles occurs after the time of the rising human chorionic gonadotropin concentrations in plasma.

Abortion, Spontaneous↗
PubMed1991

Intellectual outcome in children with maple syrup urine disease.

We report a controlled study of intellectual outcome in 16 children with maple syrup urine disease (MSUD) that compares the outcome of MSUD diagnosed after symptoms became apparent with that of MSUD diagnosed prospectively and in unaffected siblings and parents. The mean IQ (+/- SD) score in the children with classic MSUD was 78 +/- 24; however, there were two discrete groups: one with normal IQ (greater than 84) whose MSUD had been diagnosed at a mean age of 3.5 days and a second group, with IQ below normal, whose MSUD was diagnosed at a mean of 10 days of age. Affected children treated presymptomatically had higher IQ scores than their affected siblings treated when their disease was symptomatic. Multiple regression analysis indicated that the important influences on IQ were age at the time of diagnosis and long-term metabolic control; control at the time of testing also might have affected performance. The mean score of unaffected siblings was 92 +/- 5 and the mean parental IQ was 83 +/- 9. The mean IQ scores of children with variant MSUD, 97 +/- 4, was similar to that of their parents, 103 +/- 6. This study was not longitudinal and thus could not identify subtle developmental learning problems. We conclude that early and meticulous treatment of MSUD can result in intellectually normal children.

Adult↗
PubMed1991

Amplification of the Moloney murine leukaemia virus genome and its possible role in facilitation of chemical carcinogenesis in normal rat kidney cells.

In a previous study we have shown that a single infectious particle of Moloney murine leukaemia virus per cell is sufficient to facilitate chemical carcinogenesis in normal rat kidney cells. When these cells are exposed to the carcinogen after a low number of passages post-infection (p.i.), cell transformation becomes apparent only after many subsequent passages. On the other hand, when exposure is done after a high number of passages p.i., cell transformation can be detected in the treated culture or at the next passage. It is thus evident that whereas the carcinogenic effect is rapid, the viral effect becomes apparent only after a long period of latency. Here we provide evidence that this viral effect requires multiple proviruses and that the long latent period reflects the time needed for a sufficient accumulation of proviruses in some of the cells. This accumulation may result from multiple rounds of superinfection by virions released into the culture medium, although we cannot exclude other mechanisms of provirus amplification. Our data also suggest that this amplification enhances virus production.

Animals↗
PubMed1991

Misdiagnosed papillary renal adenocarcinoma.

We present 3 patients with papillary renal adenocarcinoma who were initially misdiagnosed owing to unusual clinical presentation. We suggest that if these presentations are borne in mind, pre-operative detection of this uncommon condition should be possible more often than is now the case.

Abdomen, Acute↗
PubMed1991

Differences between OK and LLC-PK1 cells: cystine handling.

Cultured opossum kidney (OK) and porcine kidney (LLC-PK1) cells were compared for biochemical characteristics and cystine transport systems. The cell lines differ in amount of protein per cell, with OK cells having approximately one-half the amount found in LLC-PK1. Both cell lines contain 19 micrograms DNA/10(6) cells. As cells reach confluence, cystine uptake increases in OK and decreases in LLC-PK1 cells. Throughout the growth period, only lysine inhibits cystine uptake in OK, whereas glutamate is the inhibitor in LLC-PK1. The predominant site of cystine transport in OK cells is across the apical membrane, and the basolateral membrane is the corresponding site of transport in LLC-PK1 cells. Although the intracellular reduced glutathione pool is the same, the cysteine pool in OK cells is approximately one-fourth that found in LLC-PK1 cells. The ability of OK cells to reflect the shared cystine-dibasic amino acid transport system and LLC-PK1 to exhibit the cystine-glutamate antiporter system makes available two models for investigation of the development and structure of cystine transport systems.

Animals↗
PubMed1991

Modulation of rat tissue galactose-1-phosphate uridyltransferase by uridine and uridine triphosphate.

Uridine-containing sugar nucleotides, uridine diphosphate (UDP)-glucose and UDPgalactose are important intermediates in galactose metabolism, and tissue UDPgalactose may be a salient factor in the etiology of the long-term clinical manifestations of patients with galactose-1-phosphate uridyltransferase deficient galactosemia. Because uridine and uridine nucleotides such as uridine triphosphate (UTP) are known inhibitors of rat hepatic transferase, we have examined the effects of these compounds on the activity of the enzyme in homogenates of rat brain and ovary which are target organs of galactose toxicity in classical galactosemia. In addition, the concerted effect of uridine and UTP together on hepatic transferase has been assessed. These investigations have been prompted by considerations that uridine administration may have a therapeutic role in the long-term treatment of classical galactosemia. Both uridine and UTP have been found to be potent inhibitors of brain and ovarian transferase activity. Brain enzyme activity is more sensitive to these compounds than is that of the ovary. They are competitive inhibitors of UDPglucose in both newborn and adult brain enzyme preparations with a ki of 0.15 to 0.20 mM. Uridine and UTP at low concentrations were found to have an additive effect on rat hepatic transferase activity, which is especially significant in that uridine administration is known to increase hepatic UTP concentration. These findings suggest judicious caution should be used in giving uridine to patients with genetically limited transferase activity because the possibility exists of inhibiting small amounts of residual enzyme in the tissues of affected subjects.

Animals↗
PubMed1991

Cellular B-2 microglobulin expression as a prognostic indicator in renal cell carcinoma.

The expression of B-2 microglobulin (B-2M) on tumor cells and their normal cell counterparts in 39 patients with renal cell carcinoma was studied and correlated to tumor stage and survival. The median survival time of patients with localized disease (stage I) whose tumors expressed B-2M was 10.2 years while the median survival time for patients whose tumors did not express B-2M was only 3.6 years (p less than 0.001). For patients with more advanced disease (stages II, III, IV) whose tumors expressed B-2M, median survival time was 3.6 years compared to 2.0 years in patients whose tumors did not express B-2M, a non-significant difference. It is suggested that the tumor cell membrane expression of B-2M may serve as an indicator of good prognosis in early renal cell carcinoma.

Adolescent↗
PubMed1991

A comparison of the effects of single- and split-dose methadone administration on the fetus: ultrasound evaluation.

A prospective study was conducted to evaluate the effects of oral methadone on fetal activity (body movements, breathing, longest inactive period) for drug-dependent pregnant women on methadone maintenance. Seven consenting drug-dependent pregnant women between 26 and 37 weeks gestation were enrolled in the study. Pairs of ultrasound observation studies were conducted, before and after single-dose methadone (SDM) treatment and split-dose methadone treatment. There were significant decreases in both body movements (p less than 0.001) and breathing episodes (p less than 0.01), and a significant increase in the longest period of inactivity (p less than 0.001) following SDM. A similar but not significant trend was noted before and after split-dose methadone. The results of the single-dose studies differed significantly from normal controls. However, the results of the split-dose studies were similar to controls. It is recommended that women on methadone maintenance should be offered a split-dose treatment protocol.

Dose-Response Relationship, Drug↗
PubMed1991

Resistance to NK and metastatic potential of fibrosarcoma cells is associated with products encoded by the H-2D region.

We have used the murine 3-methylcholanthrene induced T10 fibrosarcoma tumor cell system originating in (C3II/en x C57BL/6)F1 mice (H-2b x H-2k) to elucidate the possible correlation between metastatic potential, expression of individual H-2 antigens and susceptibility to NK cells. Transfection of the non metastatic and NK sensitive IC9 cells (Db+, Kk, Kb, Kk-) with the H-2Dk gene, altered the metastatic phenotype of the parental cells, yet had no effect on the susceptibility of these tumor cells to lysis by NK and did not elicit a specific CTL response in syngeneic hosts. Variants of the metastatic and NK resistant IE7 clone (Db+, Kk-, Kb-, Kk-), lacking H-2Dk, were selected by treatment with monoclonal anti H-2Dk antibodies and complement. These variants were sensitive to NK and poorly or non metastatic. Transfection of Dk negative variants with the H-2Dk gene, resulted in the isolation of several clones which expressed a wide range of metastatic phenotypes but maintained sensitivity to NK. In addition, by cloning the cDNA of the H-2Dk gene of the metastatic T10-IE7 variant cells and analyzing its nucleotide sequence, we found four single nucleotide changes. Two of them are not expected to alter the encoded amino acids, whereas the others should result in two amino acid substitutions in the alpha-2 domain of the class I H-2Kd protein product. These changes might account, at least partially, for the failure of the transfection of H-2Dk to restore resistance to NK.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Regulatory effects of persistent measles virus infection on tumorigenicity and protooncogene expression in neuroblastoma cells.

MS is among the infectious agents known to persistently infect cells of the CNS. Clones NS20/Y and NS20/MS persistently infected with MS, both originating from the C1300 mouse neuroblastoma, were used. Multiple effects of the MS infection on the neuronal cell communication, expression of protooncogenes tumorigenicity and on the presence of immunoregulatory molecules were studied. Our results demonstrate that the level of the MHC class I and II antigens and beta-2 microglobulin was elevated in the MS infected cells. Furthermore, MS infection results in the significant increase of protein kinase C (PKC) activity concomitantly with the elevation of PKC-I specific m-RNA. The MS infection was found to affect also the expression of the protooncogenes known to associate with the PKC signaling system. Thus, the level of c-fos mRNA was elevated in the MS infected cells, while there were almost no changes in the c-myc gene expression. Ki-ras and Ha-ras appeared to be regulated differently by MS infection. The level of Ki-ras mRNA was unchanged, but the expression of the Ha-ras gene was markedly depressed, correlating well with the low tumorigenicity of the MS infected neuroblastoma cells in nude mice. Our results suggest that viral infection may be beneficial in certain cases of depressing oncogenic genes which may contribute to the development and maintenance of the malignant phenotype.

Animals↗
PubMed1991

Effect of protein kinase C activating tumor promoters on metastases formation by fibrosarcoma cells.

The involvement of protein kinase C (PKC) in regulation of cellular properties related to tumor cell invasiveness was tested in a murine methylcholanthrene-induced fibrosarcoma tumor cell model. A metastatic clone (IE7) derived from the T10 fibrosarcoma was found to possess 30 and 90% more cytosolic and membrane-bound PKC, respectively, compared with the IC9 metastatic clone. Intravenous injection of IE7 but not IC9 cells resulted in lung tumor formation. Long-term (3 months) treatment of IE7 cells with 500 ng/ml phorbol 12,13-dibutyrate (PDB) resulted in a 4-fold reduction in total PKC activity and increase in the tumor cell metastatic ability. Short-term (2h) PDB treatment induced cytosol-to-membrane PKC translocation and decreased the IE7 cells' ability to form hematogenous metastases. Treatment of IC9 cells with PDB did not render them metastatic. To test the possible involvement of distinct PKC isoenzymes in the determination of metastatic properties, we stained the cells with appropriate anti-PKC antibodies followed by FACS analysis. IC9 and IE7 cells exhibited similar levels of fluorescent intensity when stained with either anti-PKC alpha or anti-PKC beta antibodies. The relative proportion of PKC alpha and PKC beta was not changed following short-term PDB treatment of cells, but the intensity of staining was reduced 1.5- to 2-fold following long-term PDB treatment of both cell types. The results indicate that phorbol ester-induced alterations in PKC levels and subcellular distribution affect the metastatic ability of tumor cells and suggest that tumor promoting agents that promote induction of primary tumors may also affect tumor spread by regulating hematogenous metastases formation.

Animals↗
PubMed1990

Changes in the coding sequence of the H-2Dk gene of metastatic cells that might account for immunogenic abnormality of its encoded antigen.

In previous studies we have demonstrated that metastatic cells, derived from T-10 fibrosarcoma, express an immunogenically abnormal H-2Dk glycoprotein which is involved in manifesting their metastatic phenotype. In the present study we show that these cells contain a remarkably high level of H-2Dk specific mRNA. Moreover, by cloning cDNA of this gene and analyzing its nucleotide sequence, we found 4 single nucleotide changes. Two of them did not change the encoded amino acids, whereas the others resulted in two amino acid substitutions in the alpha-2 domain of the protein product that might account for its immunogenic abnormality.

Amino Acid Sequence↗