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Biomedical subjects

E Schreiber

Publications and source records attributed to E Schreiber.

At least 37 records · Page 2Linked to original sources
PubMed1990

Astrocytes and glioblastoma cells express novel octamer-DNA binding proteins distinct from the ubiquitous Oct-1 and B cell type Oct-2 proteins.

The 'octamer' sequence, ATGCAAAT or its complement ATTTGCAT, is a key element for the transcriptional regulation of immunoglobulin genes in B-lymphocytes as well as a number of housekeeping genes in all cell types. In lymphocytes, the octamer-binding protein Oct-2A and variants thereof are thought to contribute to the B-cell specific gene expression, while the ubiquitous protein Oct-1 seems to control general octamer site-dependent transcription. Various other genes, for example interleukin-1 and MHC class II genes, contain an octamer sequence in the promoter and are expressed in cells of both the immune and nervous systems. This prompted us to analyze the octamer-binding proteins in the latter cells. Using the electrophoretic mobility shift assay, at least six novel octamer binding proteins were detected in nuclear extracts of cultured mouse astrocytes. These proteins are differentially expressed in human glioblastoma and neuroblastoma cell lines. The nervous system-derived (N-Oct) proteins bound to the octamer DNA sequence in a manner which is indistinguishable from the Oct-1 and Oct-2A proteins. The relationship of the N-Oct proteins to Oct-1 and Oct-2A was analyzed by proteolytic clipping bandshift assays and by their reactivity towards antisera raised against recombinant Oct-1 and Oct-2A proteins. On the basis of these assays, all N-Oct-factors were found to be distinct from the ubiquitous Oct-1 and the lymphoid-specific Oct-2A proteins. In melanoma cells that contain the N-Oct-3 factor, a transfected lymphocyte-specific promoter was neither activated nor was it repressed upon contransfection with an Oct-2A expression vector. We therefore speculate that N-Oct-3 and other N-Oct factors have a specific role in gene expression in cells of the nervous system.

Animals↗
PubMed1990

Extinction of an immunoglobulin kappa promoter in cell hybrids is mediated by the octamer motif and correlates with suppression of Oct-2 expression.

When immunoglobulin-expressing B cells are fused with fibroblasts, immunoglobulin expression is rapidly and selectively suppressed. here we demonstrate that the conserved octamer motif of a kappa light chain gene promoter plays a crucial role in mediating this "extinction" phenomenon. Replacement of this octamer site by an Sp1 or NF1 binding site is sufficient to bypass extinction. Furthermore, in early cell hybrids, immunoglobulin suppression is correlated with absence of the cell-specific transcription factor Oct-2 and its transcripts. Such hybrids cannot support transcription of a transiently introduced reporter plasmid, driven by an octamer-containing promoter, unless an expression vector encoding Oct-2 is cotransfected. Transfection of the same Oct-2 expression vector into hybrid cells is also sufficient to "reactivate" an integrated kappa promoter construct. Thus, our data further establish the role of Oct-2 for immunoglobulin transcription and show that in B cell x fibroblast hybrids, the lack of a necessary cell-specific transcription factor is involved in the extinction of immunoglobulin expression.

Animals↗
PubMed1989

The protein CDP, but not CP1, footprints on the CCAAT region of the gamma-globin gene in unfractionated B-cell extracts.

We have identified, by DNase I footprinting, six different factors that interact with the promoter of the human A gamma-globin gene in nuclear extracts of the B-cell line BJA-B. Among them is the vertebrate homologue of the sea-urchin CCAAT displacement protein (CDP) which footprints over the entire duplicated CCAAT region. The CCAAT-binding factor CP1, a potential activator of the gamma-globin promoter, is able to bind to its proximal recognition sequence only once it has been partially enriched and separated from CDP. The factor CDP has an apparent molecular mass of 200 kDa and differs from CP1 by its footprint pattern and competition behavior.

B-Lymphocytes↗
PubMed1989

Octamer transcription factors bind to two different sequence motifs of the immunoglobulin heavy chain promoter.

All promoters of immunoglobulin heavy chain genes contain three conserved sequence motifs: a heptamer motif CTCATGA, an octamer motif ATGCAAAT, and a TATA box. We show that, despite their different sequences, both the heptamer and the octamer motif are bound by the same octamer transcription factors (Oct factors, also referred to as OTFs), namely the lymphoid-specific proteins Oct-2A and Oct-2B, as well as the ubiquitous protein Oct-1. Even though binding to the octamer motif is stronger, a single heptamer motif can bind Oct proteins and mediate transcriptional activity in lymphoid cells. Furthermore, factor binding to the octamer motif facilitates binding to the nearby heptamer motif. We propose that the heptamer element plays a role early in B-cell differentiation to ensure that the heavy chain promoters are transcriptionally activated before the light chain promoters, which do not contain the heptamer motif.

Base Sequence↗
PubMed1989

Long-range activation of transcription by SV40 enhancer is affected by "inhibitory" or "permissive" DNA sequences between enhancer and promoter.

The transcriptional enhancer effect is used in many, if not all, organisms for remote control of gene transcription. An enhancer DNA can dramatically stimulate transcription of a linked gene from positions either 5' or 3' to the gene. Both the proximal promoter and the distal enhancer sequences are binding sites for transcription factors. Interaction between promoter and enhancer is mediated by these factors, presumably via looping out of the intervening DNA. Here we report that the extent of remote activation by an enhancer depends on characteristics of that intervening DNA. Using Beta-globin and SV40 T-antigen test genes, we show that the effect of an SV40 enhancer is transmitted to the responsive promoter, with little or no loss of efficiency, through certain segments of mammalian DNA derived from rabbit beta-globin or mouse alpha-globin gene regions. By contrast, a strong reduction of enhancer activity is observed with certain spacer segments of prokaryotic DNA (from plasmid pBR322 or phage lambda) or sequences of high (G + C) content from eukaryotic genes. We have analyzed more closely sequences that are more or less permissive for transmission of the transcriptional enhancer effect. It appears that these permissive sequences generally have a high (A + T) content and notably a very low abundance of CpG dinucleotides. By contrast, (G + C)-rich DNA segments with high local densities of CpG were the most deleterious for long-range enhancer action. We note that the latter sequence composition is typical for "CpG islands" of many mammalian genes, including housekeeping genes and the human alpha-globin gene. This may be related to the finding that promoters of most cell type-specific genes, whose activity depends on a strong enhancer, do not contain CpG islands. Most likely, the spacer DNAs of typical cell type-specific genes have evolved to allow maximal transmission of the enhancer effect.

Animals↗
PubMed1988

Identification of a novel lymphoid specific octamer binding protein (OTF-2B) by proteolytic clipping bandshift assay (PCBA).

The octamer sequence ATGCAAAT is found in the promoters of immunoglobulin (Ig) heavy and light chain genes and in the heavy chain enhancer and is a major determinant of the cell type specific expression of Ig genes in B cells. An apparent paradox is that the same sequence serves as an upstream promoter or enhancer element in a variety of housekeeping genes such as the histone H2B and U snRNA genes. The differential usage of this regulatory sequence motif is thought to be mediated by different species of octamer binding proteins. One species of 100 kd, designated OTF-1, is present in all cell types and may exert its activating function only when it can interact with additional adjacent transcription factors. The lymphoid cell specific octamer binding protein of 60 kd (OTF-2A) specifically stimulates Ig promoters which consist essentially of a TATA-box and an octamer sequence upstream of it. Here we present evidence for yet another B cell specific octamer binding protein of 75 kd (OTF-2B). From several findings, including the absence of OTF-2B (but not OTF-2A) from a lymphocyte line that cannot respond to the IgH enhancer, we propose a role of the novel octamer factor in the long range activation by the IgH enhancer. We have used the proteolytic clipping bandshift assay (PCBA) technique to distinguish the three different forms found in B cells. This analysis indicates that the 75 kd-species OTF-2B is closely related to the 60 kd species OTF-2A.

Animals↗
PubMed1988

Accuracy of duplex scanning in the detection of stenosis after carotid endarterectomy.

The results of duplex ultrasonography in grading stenosis after carotid endarterectomy (78 sites) were compared with those of contrast angiography in 71 patients studied for recurrent or contralateral occlusive disease of the carotid bifurcation. Duplex and angiographic studies were performed within one month of each other at a mean postoperative interval of 44 months (range 3 to 122 months). Stenosis of the common carotid (CCA) and internal carotid artery (ICA) was classified into five disease categories (normal or less than 15% diameter reduction [DR], 16% to 49% DR, 50% to 75% DR, greater than 75% DR, and occlusion). The overall accuracy of duplex scanning compared with angiography in predicting recurrent carotid bifurcation disease was 83%, a level of agreement similar to classification of disease involving the nonoperated, contralateral bifurcation (overall accuracy 87%). Recurrent stenosis (greater than 50% DR) or occlusion of the CCA or ICA after endarterectomy was identified with an accuracy of 97%. Overestimation of severity of recurrent stenosis accounted for 11 of 13 duplex classification errors (85%). Presence of moderate (30% to 50% DR) recurrent stenosis of the CCA, tortuosity of the ICA, and severe contralateral carotid bifurcation disease were associated with velocity spectra that predicted a more severe recurrent stenosis at the endarterectomy site compared with angiographic grading. The level of agreement between duplex scanning and angiography was comparable to the interobserver variability in angiographic interpretation. The accuracy reported justifies the use of duplex scanning to grade the severity of carotid bifurcation recurrent stenosis and to follow these lesions for disease progression.

Carotid Artery Diseases↗
PubMed1988

[Amniotic fluid embolism].

A case of amniotic fluid embolism during the second stage of labor is reported. Mother and newborn survived. Etiology, symptoms and therapy are discussed.

Adult↗
PubMed1987

A transcriptional enhancer located between adult beta-globin and embryonic epsilon-globin genes in chicken and duck.

We have detected a transcriptional enhancer sequence downstream from the adult beta-globin (beta A-globin) genes of chicken and duck. DNA segments from the beta-globin coding and flanking sequences were cloned into expression vectors containing the SV40 promoter linked to either the T antigen gene or the cat gene. The expression of these genes was measured in a chicken erythroid cell line transfected with the recombinant plasmids. We found that segments located about 400 bp downstream from the poly(A) site of both the chicken and duck beta A-globin genes (and about 1.5 kb upstream from the embryonic epsilon-globin gene) stimulate transcription of the test genes about five-fold. In chicken essentially the same segment was also found by others to act as an erythroid cell-specific enhancer [Hesse et al., Proc. Natl. Acad. Sci. USA 83 (1986) 4312-4316; Choi and Engel, Nature 323 (1986) 731-734]. The sequence containing this enhancer is conserved in evolution. A high degree of homology, reaching 84% in a segment 180 bp in length, was found between chicken and duck despite an evolutionary divergence of 70 myr.

Animals↗
PubMed1986

The effect of sodium warfarin on rabbit monocyte tissue factor expression.

A rabbit model was developed to examine the effect of sodium warfarin on peripheral blood monocyte tissue factor (MTF) activity. After three days of treatment with sodium warfarin, MTF expression was significantly impaired (p less than 0.003). Vitamin K reversed this inhibition despite continued treatment with warfarin. Animals resistant to warfarin did not become anticoagulated and failed to demonstrate inhibition of MTF expression. Cells grown in plasma from warfarin-treated animals expressed reduced amounts of MTF activity, while cells grown in normal rabbit plasma demonstrated procoagulant activity in assays using both normal and factor VII-deficient substrate plasmas. These studies suggest that normal factor VII binds to monocytes during the culture period. Moreover, a plasma component in warfarin-treated animals, possibly abnormal factor VII, may bind to monocytes and block expression of MTF activity. This may represent another mechanism for warfarin-mediated inhibition of cell-mediated coagulation reactions in vivo.

Animals↗
PubMed1985

[Pulmonary edema under tocolytic therapy].

A case of pulmonary edema during tocolytic therapy with beta-mimetic drugs is demonstrated. Isotonic hyperhydration is suspected as the reason favoured by oliguria and hypocalcemia. Diagnostic and therapeutic consequences are discussed.

Adult↗
PubMed1979

Effects of tolmetin, paracetamol, and of two combinations of tolmetin and paracetamol as compared to placebo on experimentally induced pain. A double blind study.

Previous studies in animals suggested that a coadministration of the anti-rheumatic/anti-inflammatory agent tolmetin (Tolectin) and of paracetamol potentiates the effects of these two drugs. The present study was carried out to assess whether or not the dosis of tolmetin necessary to obtain an analgesic effect can be reduced when paracetamol is coadministered in a model with experimentally induced pain in healthy human subjects. The effects of tolmetin 200 mg (T 200), paracetamol 400 mg (P 400), tolmetin 150 mg plus paracetamol 300 mg (T 150 + P 300), and of tolmetin 100 mg plus paracetamol 400 mg (T 100 + P 400) on pain threshold to electrical and thermal stimuli and on pain tolerance to electrical stimuli were compared to the effects of placebo under double blind conditions. Each of 20 healthy volunteers received all of the 5 treatments randomised according to four 5 X 5 Latin squares. The results showed that the combination T 100 + P 400 had better analgesic effects than the double dose of tolmetin, T 200, alone, while the effects of P 400 could not be discrminated from placebo. In a sequential t-test the effects of T 100 + P 400 could be discriminated from placebo already after 14 Ss. The effects of T 200, T 150 + P 300, and T 100 + P 400 respectively could not be differentiated, indicating that the dose of tolmetin can be reduced markedly by simultaneous administration of paracetamol without a loss in analgesic potency. Coadministration of tolmetin and paracetamol permits a marked reduction of the dose of tolmetin without any loss of analgesic potency as measured in a model with experimentally induced pain in healthy subjects.

Acetaminophen↗
PubMed1978

Surgical problems in necrotizing enterocolitis in childhood.

The problem of necrotizing enterocolitis is discussed based on the experience with 24 patients. It has been found that the time factor plays an important role in the decision whether to operate. The indications for operation are intestinal perforation, threatening perforation, and penetration of a covered perforation. Operation is carried out in order to treat the peritonitis caused by perforation. The various operative methods are described and evaluated. Intestinal resection, exclusion enterostomies, and suture of the perforation may all be justified, depending on the findings at operation. The difficulties in the differential diagnosis are discussed. The importance of late complications are stressed, and it is pointed out that every case will require routine controls long after discharge from the hospital. The high mortality is directly related not to the surgical complications, but rather to the septicemia which so often develops.

Diagnosis, Differential↗
PubMed1974

13C nuclear magnetic resonance spectroscopic evidence for hydrophobic lipid-protein interactions in human high density lipoproteins.

Phosphatidylcholines, sphingomyelins, cholesterol, and cholesterol esters were enriched with (13)C by chemical synthesis in specific positions of their hydrophilic groups and aliphatic chains. Their spin-lattice relaxation times were determined in organic solvents. The substances were organized as liposomes and recombined with total human high density apolipoproteins and the two separated main components, apolipoprotein A-I (apoLp-Gln-I) and apolipoprotein A-II (apoLp-Gln-II). These (13)C nuclear magnetic resonance data established that in reassembled high density lipoproteins the phospholipid molecules bind to the apoprotein moieties with their hydrophobic fatty acid chains and not with their hydrophilic zwitterionic groups. Apolipoprotein A-I preferentially binds phosphatidylcholine, although its lipid-binding capacity is smaller than that of apolipoprotein A-II. Apolipoprotein A-II avidly reassembles with sphingomyelin by hydrophobic interactions. A model of the molecular organization of the high density lipoportein particle has been derived.

Apoproteins↗