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Biomedical subjects

M Hirsch-Kauffmann

Publications and source records attributed to M Hirsch-Kauffmann.

At least 55 records · Page 3Linked to original sources
PubMed1982

Intracellular distribution of DNA topoisomerase I in fibroblasts from patients with Fanconi's anaemia.

The activity of DNA topoisomerase I(DNA nicking-closing enzyme) was analysed in cytoplasmic and nuclear extracts of six independently derived Fanconi and four normal fibroblast cell lines. In all experiments the total cellular activity was predominantly found in the nuclear extracts (88-100%). In addition, a minor proportion of the enzyme (up to 12%) was randomly present in some of the cytoplasmic fractions of both Fanconi and normal fibroblasts. These results indicate that Fanconi's anaemia is probably not due to or accompanied by a maldistribution of topoisomerase I between nuclei and cytoplasm.

Anemia, Aplastic↗
PubMed1982

Repair rate in human fibroblasts measured by thymine dimer excorporation.

The UV photoproduct, thymine dimer (-TT), is excorporated with a remarkably low rate from the DNA of human fibroblasts grown in cell culture. An UV dose of 18 J/m2 creates 0.045% -TT (related to thymine). Within the first two days of repair logarithmically growing and quiescent fibroblasts exhibit the same repair rates; thereafter, the proportion of -TT/T is lower in growing cells due to recovery of DNA replication. Only about 50% of the lesions are excised within 24 h. In quiescent cells, 13% of the thymine dimers originally present can be detected as late as a week after UV-irradiation. Two distinct first-order rate constants indicate that approximately half of the dimers are less accessible to repair. Repair measured by the nucleoid decondensation technique corresponds to the faster repair rate, whereas the slow repair rate cannot be detected by this method. Saturation of repair is found beyond 27 J/m2. The remarkably slow rate of excision indicates that thymine dimers are not lethal lesions in human fibroblasts.

Cells, Cultured↗
PubMed1982

UV-repair is impaired in fibroblasts from patients with Fanconi's anemia.

Fanconi's anemia, a hereditary autosomal disease with chromosomal instability, elevated incidence of cancer and clinical symptoms is accompanied by a DNA repair deficiency. Fibroblasts from patients with Fanconi's anemia were found to be impaired in the DNA repair of UV damage. Nucleoid decondensation and recondensation after UV irradiation were less efficient in fibroblasts from patients with Fanconi's anemia than in those from a healthy proband. These data confirm our earlier findings that DNA ligase is deficient in Fanconi's anemia.

Anemia, Aplastic↗
PubMed1982

A sensitive radioimmuno assay for thymine dimers.

A sensitive radioimmuno assay (RIA) method for detection of the UV photoproduct, thymine dimers (TT) has been developed. The limit of detection of this method is 6 X 10(-14) mol or 15 pg thymine dimer. It is highly specific: A structurally similar compound such as uridine dimer (UU) interferes with the detection of thymine dimers only when it is 53,000-fold or more in molar excess. Since this RIA method does not require the use of labeled DNA, it represents a considerable improvement for repair studies with radiation-sensitive cells.

Evaluation Studies as Topic↗
PubMed1981

Characterization of the biochemical basis of a complete deficiency of the adenine phosphoribosyl transferase (APRT).

In order to study the biochemical basis of a complete deficiency of adenine phosphoribosyl transferase (APRT) the enzyme was purified to homogeneity, its properties were characterized, and antibodies raised. The enzyme is indirectly involved in adenine uptake. Apparently, by forming AMP the internal concentration of adenine is kept low allowing it diffusion. The same APRT is present in various tissues as was revealed by antibody inactivations employing anti-erythrocyte APRT as well as by direct enzyme assays in cells from the APRT deficient patient. In vitro cultured fibroblasts derived from this patient had less than 0.02% enzyme activity. No cross-reacting material was found in erythrocytes obtained from an APRT deficient child.

Adenine↗
PubMed1980

Hereditary deficiency of adenine phosphoribosyl transferase.

We describe a 12 year old patient who developed acute renal failure at the age of 18 months due to radiolucent "uric acid" stones. Measurement of APRT activity showed a complete dificiency in this patient (less than 0.02%). In the urine we found instead of uric acid 2.8-dihyroxyadenine as measured by high pressure liquid chromatography. The pedigree indicates an autosomal-recessive inheritance of this disorder.

Acute Kidney Injury↗
PubMed1978

Deficiency of DNA ligase activity in Fanconi's anemia.

A significant decrease in DNA ligase activity was observed in lymphocytes and fibroblasts of a patient with Fanconi's anemia (FA). This decrease is related to the observed DNA repair deficiency indicated by the delayed closing of repair DNA strands following UV irradiation. Other steps of DNA repair were analyzed in the FA fibroblasts, including endonucleolytic incision of DNA, repair DNA synthesis, and exonucleolytic removal of the photoproducts. No differences were found against control cells. The action of DNA ligase is delayed during replication in the FA cells, as seen by an accumulation of replicative intermediates.

Anemia, Aplastic↗
PubMed1978

Nitrofurantoin damages DNA of human cells.

Nitrofurantoin causes damage to DNA of cultured diploid human fibroblasts. As a consequence DNA synthesis is blocked. The damage is removed by the normal enzymatic DNA repair system. Xeroderma pigmentosum fibroblasts which are defective in the excision endonuclease fail to repair nitrofurantoin-caused lesions.

DNA↗
PubMed1977

Gene expression in mitochondria and bacteria.

Mitochondria and bacteria possess protein synthesizing machineries which are similar in many respects; The regulation of gene expression in mitochondria is unknown. We, therefore, tried to use a well-established prokaryotic regulatory system for the exploration of mitochondrial gene regulation. DNA of the bacterial virus can be used as a template for gene expression in a mitochondrial in vitro system. The gene directed enzyme synthesis in the mitochondrial system is the basis for a study of regulation in mitochondrial protein synthesis.

Chloramphenicol↗
PubMed1976

A virus-specified mechanism for the prevention of multiple infection--T7- and T3-mutual and superinfection exclusion.

Co- and superinfection of cells with T3/T7 result in exclusion (mutual or superinfection exclusion). The exclusion mechanism is also directed against homologous (or identical) virus. Exclusion is established after the adsorption but before the genome becomes available for gene expression or replication, that is only one virus per cell develops. The exclusion is triggered by a constituant of the viral particle. An early T7 gene (M gene) (Schweiger et al., 1975) is essential for the formation of exclusion competent virions.

Bacterial Proteins↗
PubMed1975

The sex-factor-dependent exclusion of coli virus T7.

The cause of T7 exclusion by the F episome was investigated. Extracts from neither normal nor infected F+ cells contained an inhibitor of gene expression in vitro. The protein synthesizing systems prepared in vitro from these cells supported T7 early and late protein synthesis with normal efficiency. The content of translational initiation factors in F- and F+ cells, both noninfected and infected, was almost identical. The episome-dependent block of T7 gene expression was observed only in intact cells and detailed kinetics of gene expression in vivo revealed a stop of all transcription and translation at or just before 11 min after T7 infection. The mechanism of F+-dependent T7 exclusion involves both episomal and viral gene products. The data indicate that a T7-induced membrane alteration of the F+ cell membrane leads to cessation of T7 development as well as to the death of the host cell ('suicide').

Cell Survival↗
PubMed1975

Protein kinase of bacteriophage T7. 1. Purification.

A protein kinase, ATP:protein phosphotransferase (EC 2.7.1.37) was detected in Escherichia coli after infection with bacteriophage T7. The enzyme was purified from the ribosomal wash fraction by conventional methods, affinity chromatography on Cibacron blue and on lysozyme coupled to Sepharose, and by cellogel electrophoresis. An approximately 5000-fold purification was achieved.

Chromatography, Affinity↗
PubMed1975

Protein kinase of bacteriophage T7. 2. Properties, enzyme synthesis in vitro and regulation of enzyme synthesis and activity in vivo.

Protein kinase, which was isolated from cells infected with T7, is indeed a viral gene product. This is shown by DNA-dependent synthesis in vitro. The protein kinase transfers phosphate from ATP to seryl or threonyl residues in protein. The enzyme has only a relative requirement for magnesium ions, but is only active at low ionic strength. The best substrate is lysozyme. T7 protein kinase activity is not stimulated by cyclic 3':5'-AMP and/or cyclic 3':5'-GMP. The T7 protein kinase carries -- SH groups essential for activity. There is indication that the enzyme phosphorylates itself and causes self inactivation, which may explain the fast disappearance of enzyme activity in vivo. Bacteriophage T3 also induces a protein kinase which is similar to the T7-induced enzyme in all respects tested.

Ammonium Chloride↗