Search PubMed⌕ Search

Biomedical subjects

S Hahn

Publications and source records attributed to S Hahn.

At least 217 records · Page 12Linked to original sources
PubMed1989

Microsomal induction, alcohol, and lipoprotein metabolism: is there a three-way relationship?

The role of ethanol as a microsomal enzyme-inducing agent and as a modulator of lipid metabolism is reviewed. In an attempt to ascertain the mechanisms underlying the latter effects we examined the changes in hepatic triglyceride lipase (HTGL), hepatic high density lipoprotein (HDL) binding, and apolipoprotein secretion mediated by ethanol in a variety of experimental situations. Chronic administration of ethanol to rats decreased the ability of the liver to secrete HTGL, but primary liver cultures prepared from both ethanol and sucrose-fed rats secreted more HTGL when acutely exposed to ethanol over a 3-day period than when grown in a control medium. Hep G2 cells when grown in ethanol-containing medium for 14-28 days manifested increased HDL-binding capacity; apolipoprotein-A1 secretion was increased by ethanol but apolipoprotein B secretion was not affected. These findings suggest that increased plasma HDL concentrations which follow chronic ethanol ingestion may be due, at least in part, to increased hepatic secretion and reduced intravascular conversion of the lipoprotein despite enhanced reuptake by the liver; they are not consistent with an ethanol-mediated alteration in very low density lipoprotein secretion by the liver.

Animals↗
PubMed1989

Quality assurance for HIV-related care.

Now that models of care for numerous HIV-related conditions have been defined, a knowledge base exists for developing protocols of appropriate, high-quality care for HIV-infected patients. Bronx Municipal Hospital Center in New York City plans to implement a monitoring and evaluation program for HIV-related care that would establish protocols and indicators of quality and appropriateness, monitor compliance with protocols, and generate recommendations for improving care. At present, Bronx Municipal's AIDS consultation service has drafted guidelines for developing indicators of appropriate diagnosis, clinical course, and drug usage for HIV-infected patients, as well as guidelines for reviewing medical records.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Yeast TATA-binding protein TFIID binds to TATA elements with both consensus and nonconsensus DNA sequences.

The DNA binding properties of the yeast TATA element-binding protein TFIID were investigated. The affinity (apparent equilibrium dissociation constant) of TFIID for the adenovirus major late promoter consensus TATA element is 2 x 10(-9) M, a value similar to the affinity of gene-specific regulatory proteins for their binding sites. TFIID binding is highly specific and recognizes nonspecific sites with approximately 10(5)-fold lower affinity. Despite this specificity, TFIID also binds with high affinity to several TATA elements that do not match the consensus TATA sequences (TATAAA and TATATA): the yeast LEU2 TATA (TATTATTTA), the simian virus 40 TATA (CTTATTTAT), and the yeast CYC1 -10 TATA (TTATACATT) all bound TFIID. Furthermore, TFIID was active in promoting transcription in vitro from the nonconsensus TATA elements. Thus, contrary to previous suggestions, the existence of nonconsensus TATA elements does not itself indicate the existence of multiple TATA-binding factors.

Base Sequence↗
PubMed1988

Function of a yeast TATA element-binding protein in a mammalian transcription system.

Saccharomyces cerevisiae contains a protein which is functionally similar to the mammalian TATA element-binding transcription factor, TFIID. The yeast factor substitutes for TFIID in a mammalian RNA polymerase II in vitro transcription system, forms a stable preinitiation complex on the Adenovirus-2 major late promoter, and binds specifically to the TATA boxes of the viral promoter and the yeast CYC1 promoter. Interestingly, the yeast factor promotes initiation at a distance from the TATA element typical of a mammalian system.

DNA-Binding Proteins↗
PubMed1988

Yeast HAP2 and HAP3: transcriptional activators in a heteromeric complex.

Transcription of the yeast C upsilon C1 gene (iso-1-cytochrome c) is regulated in part by the upstream activation site UAS2. Activity of UAS2 requires both the HAP2 and HAP3 activators, which bind to UAS2 in an interdependent manner. To distinguish whether these factors bound to UAS2 cooperatively or formed a complex in the absence of DNA, HAP2 and HAP3 were tagged by gene fusion to LexA and beta-galactosidase, respectively, and purified through four chromatographic steps. The copurification of LexA-HAP2, HAP3 beta-galactosidase, and UAS2 binding activity shows that HAP2 and HAP3 associate in the absence of DNA to form a multisubunit activation complex.

Bacterial Proteins↗
PubMed1988

A yeast and a human CCAAT-binding protein have heterologous subunits that are functionally interchangeable.

The S. cerevisiae HAP2 and HAP3 gene products have been shown to recognize CCAAT-containing transcription elements as a HAP2/HAP3 multisubunit heterologous complex, or heteromer. Recently, we have demonstrated that the human sequence-specific DNA-binding protein, CP1, also recognizes CCAAT-containing transcription elements as a heteromer. Mammalian cells contain at least three distinct CCAAT-binding proteins, all of which appear to be multisubunit complexes composed of heterologous subunits. One of these proteins, CP1, has DNA-binding properties that are virtually identical to the yeast HAP2/HAP3 complex. These two proteins bind to the same target sequences, make the same DNA contacts, and are affected in a similar manner by mutations in the CCAAT element. Most surprisingly, the subunits of CP1 and HAP2/HAP3 are functionally interchangeable. That is, the yeast/human hybrid complexes that are formed retain the ability to specifically recognize CCAAT elements.

Biological Evolution↗
PubMed1988

The HAP3 regulatory locus of Saccharomyces cerevisiae encodes divergent overlapping transcripts.

Activation of the CYC1 upstream activation site, UAS2, and transcription of several other genes encoding respiratory functions requires the product of the regulatory gene HAP2. We report here the isolation and characterization of a second UAS2 regulatory gene, HAP3. Like mutations in HAP2, a mutation in HAP3 abolishes the activity of UAS2 and prevents growth on nonfermentable carbon sources. The HAP3 gene was cloned and, surprisingly, was found to encode two divergently transcribed, overlapping transcripts: a 570-base RNA and a 3-kilobase (kb) RNA. Chromosomal disruption experiments defined the critical region for HAP3 function to a 1.3-kb segment in which the two transcripts overlap. Analysis of the HAP3 DNA sequence showed that the 570-base transcript could encode a protein of 144 amino acids. Synthesis of the 144-amino-acid protein under regulatory control in vivo demonstrated that this protein is essential for activity of UAS2 as well as for growth on nonfermentable carbon sources. The largest open reading frame in the critical region of the 3-kb transcript is only 86 amino acids. Using site-directed mutagenesis, we demonstrated that the 86-amino-acid open reading frame was not involved in UAS2 activity. The possible role of this 3-kb antisense RNA in HAP3 expression or function is discussed.

Amino Acid Sequence↗
PubMed1987

Yeast HAP2 and HAP3 activators both bind to the CYC1 upstream activation site, UAS2, in an interdependent manner.

Transcriptional activation by the yeast CYC1 upstream activation site UAS2UP1 requires the products of both the HAP2 and HAP3 regulatory genes. We show here that both HAP2 and HAP3 in yeast extracts bind to UAS2UP1 and give rise to a single protein-DNA complex, termed C, in nondenaturing polyacrylamide gels. That both products are a part of complex C was shown by altering the mobility of the complex by fusing either HAP2 or HAP3 to beta-galactosidase. Further, methylation interference footprinting showed that sequences in UAS2UP1 contacted in complex C were identical to those contacted in either fusion protein complex. Binding was centered on the sequence TGATTGGT, also found in the UASs of other genes subject to activation by the HAP2-HAP3 system and homologous to the CCAAT box sequence found in higher cells. The binding of either HAP2 or HAP3 was abolished when synthesized in a strain mutant in the complementary HAP gene. Thus the binding of HAP2 and HAP3 to UAS2UP1 is interdependent. The involvement of multiple gene products in binding to a single site is discussed with reference to other systems in yeast and higher cells.

Cytochrome c Group↗
PubMed1987

[Responsibility for patients dependent on outside help, especially elderly citizens].

The present paper will pay attention to tendencies and problems in the care of persons requiring help, particularly of older ones. It is attempted to outline the developmental conditions for the present dealing with old people in our society and from this to derive the growing responsibility of public health and social welfare services for the direct care of these people as well as the organisation of their care within the family and the housing community. The inpatient sector of different specialties in the territory as well as the outpatient sector, in particular the family doctor and the community nurse, must participate in this responsibility. Moreover, the care for older persons, the forming of adequate attitudes to them within the population and the creation of more favourable conditions for a care within the family is a task of the whole society.

Aged↗
PubMed1987

[Dying and death as a theoretical and practical problem in West Germany--attempt at a critical literature reception].

The discrepancy between the theoretical position concerning the care of dying patients already worked out in the GDR and their efficient practising causes to find further ways for a better realisation of such conceptions at the bedside. The reception of the numerous individual scientific, above all sociological and psychological results in the FRG and other highly developed capitalistic countries concerning the care for dying patients might also contribute to reduce this barrier between theory and practice in the care for dying people. At the same time the article shall provide a valuating review on certain basic positions within the great number of literature dealing with the care of dying patients, which is published in the FRG.

Attitude of Health Personnel↗
PubMed1987

A monoclonal anti-human plasma prekallikrein antibody that inhibits activation of prekallikrein by factor XIIa on a surface.

Of five IgGI/k murine monoclonal anti-human prekallikrein antibodies produced (MAbs), MAb 13G11 was selected for studying interaction of prekallikrein with factor XII and high-mol-wt kininogen (HMWK) during activation on a surface. Immunoblots from sodium dodecyl sulfate (SDS) gels showed that this MAb recognizes two variants (88 kd and 85 kd) of prekallikrein and kallikrein both in purified proteins and normal plasma. Under reducing conditions, kallikrein exhibits the epitope on the heavy chain but not on the light chains. Preincubation of MAb 13G11 with prekallikrein (added to prekallikrein-deficient plasma) or with normal plasma inhibited surface activation of prekallikrein 60% to 80%, as judged by amidolytic and coagulant assays. In normal plasma, inhibition by the Fab fragments was 87% of that with the entire MAb. Inhibition was not by competition between the MAb and HMWK, since neither binding of 13G11 to prekallikrein (coated on microtiter plates) was inhibited by an excess of HMWK, nor was hydrolysis of HMWK by kallikrein inhibited by 13G11. Using purified proteins in a system mimicking contact activation, inhibition by 13G11 of prekallikrein activation by factor XIIa, HMWK, and kaolin present was approximately 80%. Decreased inhibition (55% to 25%) occurred without HMWK or when kallikrein was used instead of prekallikrein. Kallikrein activity was not inhibited by 13G11 Fab fragments. These results indicate that the effect of 13G11 in plasma was neither dissociation of prekallikrein-HMWK complex nor a direct effect on kallikrein activity. Similar to the results in plasma, activation of prekallikrein, HMWK present, by factor XIIa bound to kaolin, was inhibited approximately 70% by 13G11. The results suggest a previously unrecognized site on the prekallikrein (heavy chain) required for its interaction with factor XIIa, either shared with the 13G11 epitope or located in very close proximity. The inhibition of kallikrein by intact 13G11 indicates that its binding site on the heavy chain is sterically related to the active site (light chain).

Antibodies, Monoclonal↗
PubMed1986

The region of phage T4 genes 34, 33 and 59: primary structures and organization on the genome.

The product of gene 33 is essential for the regulation of late transcription and gene product 59 is required in recombination, DNA repair and replication. The exact functions of both proteins are not known. Restriction fragments spanning the genomic area of genes 33 and 59 have been cloned into phage M13 and a 4.9 kb nucleotide sequence has been determined. Translation of the DNA sequence predicted that gp33 contains 112 amino acids with a mol.wt. of 12.816 kd while gp59 is composed of 217 amino acids adding up to a mol.wt. of 25.967 kd. The genomic area studied here also contains 3 open reading frames of genes not identified to date and it is thought to include the NH2-terminal part of g34. One of the open reading frames seems to code for the 10 kd protein, probably involved in the regulation of transcription of bacteriophage T4. This protein is predicted to consist of 89 amino acid residues with a mol.wt. of 10.376 kd. Gene 33 and the gene for the 10 kd protein were cloned separately on high expression vectors resulting in over-production of the two proteins.

Amino Acids↗
PubMed1986

Transcription of Escherichia coli ara in vitro. The cyclic AMP receptor protein requirement for PBAD induction that depends on the presence and orientation of the araO2 site.

The mechanism by which the cyclic AMP receptor protein, CRP, stimulates transcription of the Escherichia coli araBAD promoter was studied in vitro. Under one set of conditions, CRP stimulated by eightfold the rate of RNA polymerase open complex formation on supercoiled DNA template containing the normal wild-type araBAD regulatory region. Since previous studies in vivo had identified an upstream site termed araO2 that is involved in both repression and in the CRP requirement for PBAD induction, we performed similar experiments in vitro. Deletion of araO2 or alterations of its orientation with respect to the araI site by half integral numbers of turns greatly reduced the CRP requirement for induction of PBAD. Linearizing the DNA has the same effect as deleting araO2 from the supercoiled DNA template. The similarity of conditions that relieve the classical repression of PBAD in vivo and the conditions that eliminate the requirement for CRP for maximal activity in vitro suggest a close relationship between repression in the ara system and the role of CRP. At lower concentrations of AraC protein and slightly different conditions than those used in the above-mentioned experiments, CRP does stimulate transcription from linear or supercoiled templates lacking araO2. On linear DNA under these conditions, one dimer of AraC protein binds to linear araPBAD DNA, but is incapable of stimulating transcription without the additional binding of CRP. The responses of the ara system under the second set of conditions are unlike its behavior in vivo.

AraC Transcription Factor↗