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S Hirschfeld

Publications and source records attributed to S Hirschfeld.

At least 37 records · Page 2Linked to original sources
PubMed1994

Human osteosarcoma cell lines are dependent on insulin-like growth factor I for in vitro growth.

Osteogenic sarcoma is the most common bone tumor of childhood and typically occurs during the adolescent growth spurt when growth hormone and insulin-like growth factor I (IGF-I) may be at their lifetime highest levels. Since IGF-I is involved in normal bone growth and differentiation, we have evaluated the possible role of IGF-I signaling in the growth of human osteogenic sarcoma cell lines. In this study, we demonstrate that in vitro survival of cells is dependent on exogenously supplied IGF-I. Furthermore, we show that these cells display functional IGF-I receptors on their surface and that in vitro growth is inhibited by blocking these receptors either by monoclonal antibodies or by antisense oligonucleotides. These data demonstrate that human osteogenic sarcoma cell lines are dependent on signaling through the IGF-I receptor for in vitro survival and proliferation. Furthermore, they suggest that modulation of the growth hormone/IGF-I axis may affect the growth of these tumors in vivo.

Cell Division↗
PubMed1993

Inhibition of estrogen-responsive gene activation by the retinoid X receptor beta: evidence for multiple inhibitory pathways.

The retinoid X receptor beta (RXR beta; H-2RIIBP) forms heterodimers with various nuclear hormone receptors and binds multiple hormone response elements, including the estrogen response element (ERE). In this report, we show that endogenous RXR beta contributes to ERE binding activity in nuclear extracts of the human breast cancer cell line MCF-7. To define a possible regulatory role of RXR beta regarding estrogen-responsive transcription in breast cancer cells, RXR beta and a reporter gene driven by the vitellogenin A2 ERE were transfected into estrogen-treated MCF-7 cells. RXR beta inhibited ERE-driven reporter activity in a dose-dependent and element-specific fashion. This inhibition occurred in the absence of the RXR ligand 9-cis retinoic acid. The RXR beta-induced inhibition was specific for estrogen receptor (ER)-mediated ERE activation because inhibition was observed in ER-negative MDA-MB-231 cells only following transfection of the estrogen-activated ER. No inhibition of the basal reporter activity was observed. The inhibition was not caused by simple competition of RXR beta with the ER for ERE binding, since deletion mutants retaining DNA binding activity but lacking the N-terminal or C-terminal domain failed to inhibit reporter activity. In addition, cross-linking studies indicated the presence of an auxiliary nuclear factor present in MCF-7 cells that contributed to RXR beta binding of the ERE. Studies using known heterodimerization partners of RXR beta confirmed that RXR beta/triiodothyronine receptor alpha heterodimers avidly bind the ERE but revealed the existence of another triiodothyronine-independent pathway of ERE inhibition. These results indicate that estrogen-responsive genes may be negatively regulated by RXR beta through two distinct pathways.

Base Sequence↗
PubMed1992

Expression of major histocompatibility complex (MHC) class I genes in astrocytes correlates with the presence of nuclear factors that bind to constitutive and inducible enhancers.

The molecular basis of constitutive and inducible major histocompatibility complex (MHC) class I gene expression was studied in murine astrocytes in primary culture. Astrocytes constitutively expressed MHC class I molecules and treatment of these cells with interferon-gamma (IFN-gamma) further induced expression. The conserved region containing the upstream MHC class I regulatory element (MHC-CRE) and juxtaposed interferon consensus sequence (ICS) enhanced constitutive MHC class I promoter activity. As seen with cell surface expression of MHC molecules, treatment of astrocytes with IFN-gamma increased MHC class I promoter activity. Inducible expression required the presence of the MHC-CRE/ICS enhancer region. Nuclear factors that bind to the MHC-CRE and ICS were constitutively expressed in cultured astrocytes and IFN-gamma treatment further induced binding activity both to the MHC-CRE and ICS and correlated with induction of MHC class I gene expression. This study identifies the MHC-CRE and ICS as the major cis elements in controlling MHC class I promoter activity and suggests that the expression of nuclear factor binding activities to these enhancer elements is a basic transactivating mechanism for the expression of MHC class I genes in astrocytes.

Animals↗
PubMed1992

H-2RIIBP expressed from a baculovirus vector binds to multiple hormone response elements.

H-2RIIBP is a member of the nuclear hormone receptor superfamily that binds to the region II enhancer of major histocompatibility complex class I genes. Based on its homology with Drosophila XR2C/CF1, H-2RIIBP may play a role in development. By using a baculovirus expression system, a large amount of recombinant H-2RIIBP was produced. The recombinant protein accumulated in the nucleus of insect cells. A series of monoclonal antibodies reacting with the recombinant H-2RIIBP was then generated. A DNA-protein immunoprecipitation assay was developed with these antibodies, enabling the DNA-binding specificity of H-2RIIBP to be distinguished from that of an endogenous region II binding factor expressed in uninfected insect cells. We show that H-2RIIBP binds to estrogen response elements with an affinity comparable to that for the region II enhancer. H-2RIIBP also bound to some, but not all, thyroid hormone response elements and retinoic acid response elements, albeit at a lower affinity. Binding to these elements was demonstrated without exogenous addition of a ligand. The H-2RIIBP binding specificity determined by this assay was in agreement with the specificity assessed by Southwestern and gel mobility shift assays. Furthermore, methylation interference assays indicated that H-2RIIBP recognizes the conserved hormone response motif GG(T/A)CA. Taken together, these data demonstrate that H-2RIIBP is capable of binding to hormone response elements of a variety of genes. They suggest that H-2RIIBP may exert a pleiotropic function.

Amino Acid Sequence↗
PubMed1990

A constitutive damage-specific DNA-binding protein is synthesized at higher levels in UV-irradiated primate cells.

Using a DNA band shift assay, we have identified a DNA-binding protein complex in primate cells which is present constitutively and has a high affinity for UV-irradiated, double-stranded DNA. Cells pretreated with UV light, mitomycin C, or aphidicolin have higher levels of this damage-specific DNA-binding protein complex, suggesting that the signal for induction can either be damage to the DNA or interference with cellular DNA replication. Physiochemical modifications of the DNA and competition analysis with defined substrates suggest that the most probable target site for the damage-specific DNA-binding protein complex is a 6-4'-(pyrimidine-2'-one)-pyrimidine dimer: specific binding could not be detected with probes which contain -TT- cyclobutane dimers, and damage-specific DNA binding did not decrease after photoreactivation of UV-irradiated DNA. This damage-specific DNA-binding protein complex is the first such inducible protein complex identified in primate cells. Cells from patients with the sun-sensitive cancer-prone disease, xeroderma pigmentosum (group E), are lacking both the constitutive and the induced damage-specific DNA-binding activities. These findings suggest a possible role for this DNA-binding protein complex in lesion recognition and DNA repair of UV-light-induced photoproducts.

Animals↗
PubMed1989

Developmental and tissue-specific expression of nuclear proteins that bind the regulatory element of the major histocompatibility complex class I gene.

Expression of MHC class I genes varies according to developmental stage and type of tissues. To study the basis of class I gene regulation in tissues in vivo, we examined binding of nuclear proteins to the conserved cis sequence of the murine H-2 gene, class I regulatory element (CRE), which contains two independent factor-binding sites, region I and region II. In gel mobility shift analyses we found that extracts from adult tissues that express class I genes, such as spleen and liver, had binding activity to region I. In contrast, extracts from brain, which does not express class I genes, did not show region I binding activity. In addition, fetal tissues that express class I gene at very low levels, also did not reveal region I binding activity. Binding activity to region I became detectable during the neonatal period when class I gene expression sharply increases. Most of these tissues showed binding activity to region II, irrespective of class I gene expression. Although region II contained a sequence similar to the AP-1 recognition site, AP-1 was not responsible for the region II binding activity detected in this work. These results illustrate a correlation between region I binding activity and developmental and tissue-specific expression of MHC class I genes. The CRE exerts an enhancer-like activity in cultured fibroblasts. We evaluated the significance of each factor binding to CRE. Single 2-bp mutations were introduced into the CRE by site-directed mutagenesis and the ability of each mutant to elicit the enhancer activity was tested in transient CAT assays. A mutation that eliminated region I protein binding greatly impaired enhancer activity. A mutation that eliminated region II binding also caused a lesser but measurable effect. We conclude that region I and region II are both capable of enhancing transcription of the class I gene. These results indicate that in vivo regulation of MHC class I gene expression is mediated by binding of trans-acting factors to the CRE.

Animals↗
PubMed1989

H-2RIIBP, a member of the nuclear hormone receptor superfamily that binds to both the regulatory element of major histocompatibility class I genes and the estrogen response element.

Transcription of major histocompatibility complex (MHC) class I genes is regulated by the conserved MHC class I regulatory element (CRE). The CRE has two factor-binding sites, region I and region II, both of which elicit enhancer function. By screening a mouse lambda gt 11 library with the CRE as a probe, we isolated a cDNA clone that encodes a protein capable of binding to region II of the CRE. This protein, H-2RIIBP (H-2 region II binding protein), bound to the native region II sequence, but not to other MHC cis-acting sequences or to mutant region II sequences, similar to the naturally occurring region II factor in mouse cells. The deduced amino acid sequence of H-2RIIBP revealed two putative zinc fingers homologous to the DNA-binding domain of steroid/thyroid hormone receptors. Although sequence similarity in other regions was minimal, H-2RIIBP has apparent modular domains characteristic of the nuclear hormone receptors. Further analyses showed that both H-2RIIBP and the natural region II factor bind to the estrogen response element (ERE) of the vitellogenin A2 gene. The ERE is composed of a palindrome, and half of this palindrome resembles the region II binding site of the MHC CRE. These results indicate that H-2RIIBP (i) is a member of the superfamily of nuclear hormone receptors and (ii) may regulate not only MHC class I genes but also genes containing the ERE and related sequences. Sequences homologous to the H-2RIIBP gene are widely conserved in the animal kingdom. H-2RIIBP mRNA is expressed in many mouse tissues, in agreement with the distribution of the natural region II factor.

Amino Acid Sequence↗
PubMed1983

Hypertensive encephalopathy. A cause of neonatal seizures.

Hypertensive encephalopathy is rare in newborns. The few reported cases of malignant hypertension in newborns have been secondary to renovascular disease. We studied an infant with hypertensive encephalopathy secondary to isolated coarctation of the aorta. Infants with this condition are generally asymptomatic; to our knowledge, this is the youngest patient to have had neurologic complications secondary to isolated coarctation of the aorta.

Adult↗
PubMed1981

Respiratory variation in Frank vectorcardiography and echocardiography in children.

Forty pediatric patients underwent echocardiographic and Frank vectorcardiographic studies during normal respiration. The right ventricular minor axis (RVEDD) increased significantly with inspiration (p less than 0.005), while the left ventricular minor axis did not significantly change. The distance from the anterior chest wall to the center of the left ventricle did significantly increase with inspiration (p less than 0.005). Some vectorcardiographic parameters changed with inspiration, also. Both the maximal spatial vector to the left (MSVL) and the X to the left (X-L) significantly decreased with inspiration. Although the average magnitude of these changes was small (10-15%), there was wide variation. Five of twenty-one patients with left ventricular hypertrophy during expiration had a clearly normal Frank VCG during inspiration. It is suggested that phases of respiration should be monitored when evaluating the Frank VCG in pediatric patients.

Adolescent↗
PubMed1980

The pediatric spectrum of dynamic left ventricular obstruction.

Twenty-one pediatric patients with echocardiographic and/or hemodynamic evidence of dynamic left ventricular obstruction are presented in order to examine the pathophysiologic mechanisms of this disorder. Neonates commonly had transient hypertrophic cardiomyopathy related to hypertension or to being infants of diabetic mothers. Infants with D-transposition of the great arteries sometimes developed signs of subpulmonic dynamic obstruction. Older children and adolescents had either classic findings of IHSS or concentric left ventricular hypertrophy. The spectrum of hypertrophic cardiomyopathy appears to be broader in pediatric patients than in adults.

Adolescent↗
PubMed1979

Echocardiographic assessment of the adequacy of pulmonary arterial banding.

Thirty-one echocardiograms of 21 patients who had pumonary arterial banding were analyzed to assess the aequacy of surgery. In 5 patients the echocardiograms were obtained before and after banding and in 16 patients only after surgery. Right and left ventricular systolic time intervals were measured echographically. The ratios of the right ventricular preejection period to right ventricular ejection time (RPEP/RVET) were correlated with both diastolic (r = 0.94) and systolic (r = 0.86) pulmonary arterial pressures distal to the band. The analysis of right ventriclar systolic time intervals, especially the RPEP/RVET ratio, clearly differentiated patients with an adequate band (distal pulmonary arterial diastolic pressure less than 15 mm Hg) from patients with an inadequate band (distal pulmonary arterial diastolic pressure equal to or greater than 30 mm Hg). The results indicate that echocardiography is a useful noninvasive tool in evaluating the adequacy of the pulmonary arterial band and facilitates the follow-up of patients after banding.

Blood Pressure↗
PubMed1979

Ventricular septal defect in infancy: a combined vectorgraphic and echocardiographic study.

Echocardiograms (echo) and vectorcardiograms (VCG) from 40 infants with ventricular septal defects (VSD) were compared with cardiac catheterization data to assess noninvasively the hemodynamics of VSD. The specific aim was to use VCG parameters of right ventricular hypertrophy and echo parameters which reflect pulmonary artery pressure to identify all patients with a nonrestrictive VSD. The configuration of the QRS vector in the horizontal plane was more reliable than individual voltages in assessing right ventricular systolic pressure. Among patients older than 2 months with a clockwise or anterior two-main-vector horizontal loop, 73% (eight of 11) had a nonrestrictive VSD. However, a counterclockwise or posterior two-main-vector loop was also frequently found (43%, six of 14) in infants with a nonrestrictive VSD. The most useful echo parameter was the ratio of right ventricular preejection period-to-right ventricular ejection time (RPEP/RVET), which closely (r = 0.74) reflected the pulmonary artery diastolic pressure. An elevated RPEP/RVET to greater than 0.30 was always associated with a nonrestrictive VSD, although many patients (36%, five of 14) with a nonrestrictive VSD had a normal ratio. By combining both echo and VCG parameters, a nonrestrictive VSD was correctly identified in all patients, while a restrictive VSD was correctly identified in 81% (21 of 26).

Cardiac Catheterization↗
PubMed1979

Echocardiographic estimation of ventricular hypoplasia in complete atrioventricular canal.

Echocardiograms from 10 patients with complete atrioventricular canal (CAVC) were compared with autopsy specimens to determine the capabilities of echocardiography in identifying patients with ventricular hypoplasia. On the basis of echographic ventricular size, patients could be divided into three groups: 1) "balanced" CAVC patients had both increased right and left ventricular end-diastolic dimensions (RVED and LVED) and an increased RVED/LVED ratio; 2) "dominant left ventricular" CAVC patients had an increased LVED and small or normal RVED and a diminished RVED/LVED ratio; 3) "dominant right ventricular" CAVC patients had an increased RVED, but small LVED, and increased RVED/LVED. There was complete agreement between echographic ventricular dominance and pathologic findings. This study demonstrates that echocardiography may be valuable in assessing ventricular dominance in the presence of CAVC.

Child, Preschool↗
PubMed1978

Assessment of the pulmonary vascular bed by echocardiographic right ventricular systolic time intervals.

Echocardiography was used to measure right ventricular systolic time intervals (RVSTI) in 85 normal children (group I) and in 229 patients undergoing cardiac catheterization (group II). Corrected right ventricular pre-ejection period (RPEPC) and right ventricular ejection time (RVETc) (based on regression analysis of group I) and RPEP/RVET were each correlated with pulmonary artery (PA) diastolic and mean pressures and pulmonary vascular resistance (PVR). The best correlation (0.83) was between a second degree polynomial of the RPEP/RVET and PA diastolic pressure. The RPEP/RVET allowed prediction of PA diastolic pressure within 10 mm Hg in 85% of the patients. The utility of RPEP/RVET was confirmed in sequential data of 22 patients, in whom alteration in RPEP/RVET accurately reflected the changing PA diastolic pressure. The RPEP/RVET could not be used to assess PA pressure in six patients with congestive cardiomyopathy nor in 18 patients with complete right bundle branch block (CRBBB).

Adolescent↗