Search PubMed⌕ Search

Biomedical subjects

E Katz

Publications and source records attributed to E Katz.

At least 199 records · Page 11Linked to original sources
PubMed1985

Changes of H-2 antigen expression on thymocytes during leukemia development by radiation leukemia virus.

The expression of antigens encoded by the K and D region genes of the major histocompatibility complex on thymocytes of BL/6 mice infected with Radiation Leukemia Virus (RadLV) variants, A-RadLV to which they are sensitive or D-RadLV to which they are resistant, was investigated. Reduced thymus cellularity due to the thymolytic effect of both RadLV variants (30-40% cell reduction within 24 h after intrathymic virus injection) was accompanied with elevated H-2 expression on thymocytes. A high density of H-2D and to a lesser degree increased expression of H-2K were observed following infection with both virus variants. This elevated H-2 expression was maintained transiently for 6-7 weeks in the resistant situation and persisted in the sensitive situation until overt leukemia developed. The occurrence of A-RadLV transformed cells in 75% of the tested thymuses within 10 days after infection (vs 16% in D-RadLV treated mice) and their further expansion until overt leukemia developed could explain the continued expression of elevated H-2 expression on thymocytes in the sensitive situation. The majority (85%) of the primary A-RadLV induced leukemias tested expressed more H-2D/H-2K gene products than normal thymocytes. We conclude that leukemia development due to RadLV infection is not associated with the reduction or disappearance of H-2D/H-2K gene products.

Animals↗
PubMed1985

The nucleotide sequence of the tyrosinase gene from Streptomyces antibioticus and characterization of the gene product.

The sequence of a 1.56-kb DNA fragment containing the tyrosinase gene (mel) from Streptomyces antibioticus was determined and the Mr (30612) and amino acid (aa) sequence of the protein were deduced from the nucleotide (nt) sequence. Intracellular and extracellular tyrosinase from S. antibioticus, transformed with pIJ702 (containing mel), were purified to homogeneity; the Mr (29 500), as determined by Sephadex G-75 chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was consistent with the value derived from the nt sequence. Edman degradation established that the N-terminal sequence of both the intracellular and extracellular forms of tyrosinase are identical and correspond to the aa sequence derived from the structural gene. In addition, this sequence exhibits striking homology to the N-terminal region of the intracellular and extracellular enzyme purified from Streptomyces glaucescens (Crameri et al., 1982). An additional open reading frame (ORF438) upstream of the mel gene, was also identified that appears to code for a protein (Mr = 14 754) with a putative signal sequence.

Amino Acid Sequence↗
PubMed1984

Effects of estradiol on myointimal thickenings from catheter injury and on organizing white mural non-occlusive thrombi.

The objective of this present study was to determine the effect of estradiol on the organization of white, mural, nonocclusive thrombus produced with a permanent, indwelling catheter in the abdominal aortae of rabbits and on myointimal thickenings produced by catheter injury but with only transient adhesion of platelets and no thrombosis in the thoracic aorta. Estradiol did not significantly alter the weight of thrombus or myointimal thickenings produced nor did it qualitatively or quantitatively alter Evans Blue uptake by the 7-day myointimal thickenings from injury or alter Evans Blue uptake by the 7-day thrombus. DNA synthesis measured in terms of [3H]thymidine incorporation into biochemical extractable DNA and expressed as dpm/mg DNA was 9 519 for the normal rabbit aortic wall without adventitia; 358 261 for myointimal thickenings including underlying aortic wall without estradiol treatment and 196 336 with estradiol; 55 840 for thrombus without estradiol and 55 250 with estradiol. Expressed as dpm/mg delipidated tissue the values were 62 for the normal rabbit aortic wall; 4 590 for myointimal thickenings without estradiol and 2 037 with estradiol; 1 421 for thrombus without estradiol and 1 403 with estradiol. Estradiol was effective in reducing DNA synthesis in the myointimal thickenings from injury but was not effective in reducing DNA synthesis in the 7-day thrombi. Estradiol significantly increased the influx or retention of [14C]cholesterol found at autopsy in both the organizing thrombi and the myointimal thickenings from injury after an oral dose of 14C-labelled cholesterol was administered 4 days prior to autopsy; however, estradiol did not significantly modify the final cholesterol concentration in the lesions.

Animals↗
PubMed1984

Antiviral activity of SK&F 21681 against herpes simplex virus.

SK&F 21681 (3,10-dimethyl-10-H-s-triazolo[4',3':2,3]-as-triazino-[ 5,6-b]indole) is an inhibitor of the growth of herpes simplex viruses types 1 and 2 at a concentration of 60 micrograms/ml. It inhibits the synthesis of the viral DNA and the formation of virus particles, although the viral polypeptide synthesis is not significantly affected by this compound. Mutants of herpes simplex viruses types 1 and 2 which are able to grow in the presence of SK&F 21681 were isolated. They induced normal levels of thymidine kinase and DNA polymerase activities in the infected cells and did not show resistance to either 9-[2-hydroxyethoxymethyl] guanine or phosphonoacetic acid.

Antiviral Agents↗
PubMed1983

Melittin and a chemically modified trichotoxin form alamethicin-type multi-state pores.

The bee venom constituent, melittin, is structurally and functionally related to alamethicin. By forming solvent-free planar bilayers of small area (approx. 100 microns 2) on the tip of fire-polished glass pipettes we could observe single melittin pores in these membranes. An increase in the applied voltage induced further non-integral conductance levels. This indicates that melittin forms multi-level pores similar to those formed by alamethicin. Trichotoxin A40, an antibiotic analogue of alamethicin, also induces a voltage-dependent bilayer conductivity, but no stable pore states are resolved. However, chemical modification of the C-terminal molecule part by introduction of a dansyl group leads to a steeper voltage-dependence and pore state stabilization. Comparing structure and activity of several natural and synthetic amphiphilic polypeptides, we conclude that a lipophilic, N-terminal alpha-helical part of adequate length (dipole moment) and a large enough hydrophilic, C-terminal region are sufficient prerequisites for voltage-dependent formation of multi-state pores.

Alamethicin↗
PubMed1983

Antiviral compounds. 1. Structure-activity relationship of some antiviral enediones derived from aldehydo sugars.

A series of aldehydo sugars was subjected to condensation reactions with active methylene compounds. Acetylacetone was condensed with 2,4-O-benzylidene-3,5-O-dibenzoyl-D-ribose (1), 2,4:3,5-O-dibenzylidene-D-ribose (6), 2,3,4,5-tetraacetyl-D-ribose (7), and 2,3,4,5,6-pentaacetyl-D-glucose (9) to yield 3-ylidene-2,4-pentanedione derivatives 2, 11, 12, and 13, respectively. Sugar derivatives 1 and 6 were also condensed with benzoylacetone to give 14 and 18, with acetoacetanilide to give 16 and 19, with malononitrile to give 17 and 20, and with alpha-(gamma-butyrolactonylidene)triphenylphosphorane to give 21 and 22, respectively. Condensation of 1 with dibenzoylmethane gave 15. The double bond in compounds 2 and 11 was saturated by hydrogenation to give 23 and 24. All alpha, beta-unsaturated carbonyl compounds obtained exhibited antiviral activity and cytotoxicity. Compound 11 was found to have the most significant and selective antiviral activity against herpes simplex virus.

Alkenes↗
PubMed1983

Cloning and expression of the tyrosinase gene from Streptomyces antibioticus in Streptomyces lividans.

In two separate studies a BclI-generated DNA fragment coding for the enzyme tyrosinase, responsible for melanin synthesis, was cloned from Streptomyces antibioticus DNA into two SLP1.2-based plasmid vectors (pIJ37 and pIJ41) to generate the hybrid plasmids, designated pIJ700 and pIJ701, using S. lividans 66 as the host. The fragment (1.55 kb) was subcloned into the multicopy plasmid pIJ350 (which carries thiostrepton resistance and has two non-essential BclI sites) to generate four new plasmids (pIJ702-pIJ705) with the tyrosinase insert located in either orientation at each site. All six plasmids conferred melanin production (the Mel+ phenotype) on their host. As in the S. antibioticus parent, strains of S. lividans carrying the gene specifying tyrosinase synthesis possessed an enzyme activity which was inducible. Most of the tyrosinase activity was secreted during growth of S. antibioticus; in contrast, the majority remained intracellular in the S. lividans clones. The specific activity of the induced tyrosinase activity (intracellular) was higher (up to 36-fold) when the gene was present on the multicopy vector in comparison with its location on the low copy plasmids, pIJ700 or pIJ701, or in S. antibioticus. Restriction mapping of the tyrosinase fragment in pIJ702 revealed endonuclease cleavage sites for several enzymes, including single sites for BglII, SphI and SstI that are absent from the parent vector (pIJ350). Insertion of DNA fragments at any one of these sites abolished the Mel+ phenotype. The results indicate that pIJ702 is a useful cloning vector with insertional inactivation of the Mel+ character as the basis of clone recognition.

Catechol Oxidase↗
PubMed1983

Cell surface alterations induced by the acycloguanosine (ACG) resistant and sensitive strains of herpes simplex virus type 2 (HSV-2) in the presence of ACG and tunicamycin.

HSV-2-ACG, a mutant of herpes simplex virus type 2, which is resistant to acycloguanosine and also capable of inducing fusion of BSC1 cells, was isolated. The viral-induced surface changes in these cells were studied using scanning electron microscopy. The formation of gigantic fused cells with increased number of microvilli and virus-like particles, extensively covering the infected cell surface, were investigated. Tunicamycin (50 micrograms/ml), an inhibitor of glycosylation of polypeptides, blocks the production of infectious virus, as well as the cell-fusion and efficiently prevents the viral induced alterations occurring on the surface of the cells.

Acyclovir↗
PubMed1982

Characterization of an herpes simplex virus type 2 mutant, which is resistant to acycloguanosine and causes fusion of BSC1 cells.

A mutant of herpes simplex virus type 2, which induces low levels of thymidine-kinase activity in infected BSC1 cells and consequently able to grow in the presence of acycloguanosine, was isolated. This mutant has also been shown to cause fusion of BSC1 cells. In BSC1 cells, co-infected with the wild-type strain and the mutant, the yield of each of the two viruses was normal but the rounding and aggregation of cells observed, resembled that found in wild-type infected cultures. When the mixed infection was performed in the presence of acycloguanosine (100 micrometers), the growth of the two virus strains was inhibited, as well as the cytopathic effect in the cultures. It is suggested that under these conditions, the thymidine-kinase which was induced in the infected cells by the wild-type strain, phosphorylated acycloguanosine and the activated drug formed, inhibited the growth of the two viruses by interference in their DNA syntheses.

Acyclovir↗
PubMed1982

Stability of some bronchodilator solutions during ultrasonic nebulization.

The effect of ultrasonic nebulization on the stability of isoetharine hydrochloride and isoproterenol hydrochloride solutions was studied. Commercially available solutions of isoetharine hydrochloride 1%, isoproterenol hydrochloride 1%, and isoproterenol hydrochloride 0.5% were diluted to 0.25%, 0.125%, and 0.125%, respectively. The solutions were nebulized for 10 or 15 minutes using three ultrasonic nebulizers at 0, 3, 6, 8, and 24 hours. Before and after nebulization, the solutions were assayed for intact drug by chemical assay and by thin-layer chromatography (TLC). The nebulized mist was also collected and assayed. The extent of drug degradation from ultrasonic nebulization was calculated as the apparent percent loss of active drug. Results of the chemical and TLC analyses for samples from two nebulizers showed no substantial chemical degradation of isoetharine hydrochloride or isoproterenol hydrochloride in any solution. Chemical assay was not performed for the third nebulizer, but results of TLC analysis showed no substantial degradation of either drug in any solution. Under the simulated-use conditions of this study, solutions of isoetharine hydrochloride and isoproterenol hydrochloride were stable when nebulized ultrasonically.

Aerosols↗
PubMed1981

H-21-linked control of immunological resistance to viral leukemogenesis as a response to preleukemic cells.

The mechanism of resistance to leukemogenesis by two radiation leukemia virus variants, A-RadLV and D-RadLV, was investigated. Resistance to these viruses is linked to H-21 in both B10.S and C57BL/10 mice. The resistance of virus-infected mice to transplantation of syngeneic. A- or D-RadLV-induced lymphoma cells was similar to their resistance to leukemogenesis by the same viruses. This resistance could be transferred by lymphoid cells from immune donors to normal recipients, and it was specific for RadLV lymphomas. Virus-primed (responder x sensitive)F1 hybrids rejected only resistant-type parental lymphoma cells. Hence, it appears that H-21-linked resistance to RadLV leukemogenesis is regulated by Ir genes. Resistant mice immunized by A- or D-RadLV rejected syngeneic lymphoma cells, irrespective of whether they were sensitive or resistant to the RadLV variant used for the induction of the lymphoma cells. It follows that resistant and sensitive type lymphomas are antigenically similar for the effector mechanism, and that the Ir genes may be expressed in the sensitization phase of the reaction. In virus-infected mice which are resistant to A- or D-RadLV we were able to demonstrate the presence of preleukemic lymphocytes. Normal mice could be immunized by these preleukemic cells against lymphoma challenge. These data are interpreted to suggest that mice having H-21-linked resistance to RadLV infection may be sensitized by their preleukemic cells, and that these preleukemic cells are then arrested in their development as a result of the immune response.

Animals↗
PubMed1981

Inhibition of vaccinia virus maturation by zinc chloride.

Zinc chloride (0.1 mM) inhibited by 96.4% the growth of vaccinia virus in HeLa cells. Approximately 50% inhibition in formation of particles that sedimented in sucrose gradients similarly to vaccinia virions occurred in the presence of zinc ions. Whereas the synthesis of the viral deoxyribonucleic acid was not affected by zinc chloride, a decrease in the overall synthesis of viral polypeptides and inhibition of the cleavage of precursors to the core polypeptides were observed.

Cells, Cultured↗