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Biomedical subjects

K Tempel

Publications and source records attributed to K Tempel.

At least 37 records · Page 2Linked to original sources
PubMed1992

Poly(ADP-ribose)polymerase-activity of chicken embryo cells exposed to nucleotoxic agents.

Poly(ADP-ribose)polymerase (PARP)-activity was assessed in vitro from the incorporation of the adenosine-diphosphate-ribose moiety of 14C-NAD+ in the acid-insoluble cell fraction. When compared to mammalian (rat) cells, chicken embryo cells exhibit an almost three- to fourfold higher constitutive PARP-activity and an about two- to threefold lower chromatin compactness as evidenced by viscometry of alkaline cell lysates and nucleoid sedimentation. X-irradiation, bleomycin and H2O2 activated PARP. Hyperthermia (43 degrees C), doxorubicin, ethidium bromide and novobiocin resulted in an inhibition of the enzyme activity. Even at the highest doses used, UV-light, monofunctionally alkylating agents and the bisbenzimide Hoechst 33258 remained without significant effects. It is suggested that, with respect to DNA-and/or chromatin-interactive agents, the chicken embryo PARP-test may be complementary to the results of morphological and biochemical studies.

Animals↗
PubMed1992

DNA damage and repair in chick embryo cells following X-irradiation in vitro as compared to mammalian cells--biochemical and physico-chemical investigations.

Brain cells (b-cells) and liver cells (l-cells) of the chicken embryo and thymic cells (t-cells) of the rat were X-irradiated in vitro at doses of 1.25-50 Gy. When compared to t-cells, b- and l-cells exhibited 1) a lower stimulation of poly (adenosine diphosphate-ribose) transferase and unscheduled DNA synthesis following X-irradiation, 2) an almost fivefold higher inhibition of semiconservative DNA synthesis, 3) a less condensed chromatin, 4) about fourfold higher threshold doses with regard to significant effects on nucleoid sedimentation and viscometry of alkaline cellular lysates, and 5) an apparently two- to threefold lower DNA repair during a 30 min post-exposure repair period. The results suggest that the lower radiation sensitivity of chicken embryo cells is attributable to an initial mechanism of DNA repair and/or DNA protection which may be closely connected to minor chromatin compactness and higher intrinsic activities of repair enzymes.

Animals↗
PubMed1992

Effect of gyrase inhibitors on some eukaryotic short-term test systems. DNase I in vitro nucleic acid synthesis and DNA repair in primary cultures of chicken embryo and rat cells.

DNase I activity was diminished by ciprofloxacin (CFL), nalidixic acid, norfloxacin, and ofloxacin in a dose-dependent manner, the MIC's (minimal significantly inhibiting concentrations) being 3.2, 2.8, 2.4, and 7.6 micrograms/ml, resp., in phase I-reaction (increase in DNA hyperchromicity) and 21, 20, 55, and 56 micrograms/ml, resp., in phase II-reaction (formation of acid-soluble products). The Line-weaver-Burk plots indicated inhibition by substrate (phase I) and uncompetitive inhibition (phase II). The decrease in scheduled DNA synthesis by CFL showed MIC's of 270, 100, 1000, and 850 micrograms/ml in chicken embryo brain (B) and liver (L) cells and in rat thymic (T) and splenic (S) cells, resp. With regard to ribonucleic acid synthesis, MIC values of 82, 82, 12.5, and 48 micrograms/ml CFL were determined, resp. Within a concentration range of 25-1600 micrograms/ml, no principal differences existed between the 4-quinolones used. In T-cells, DNA repair as induced by X-irradiation or UV-light and determined by nucleoid sedimentation was inhibited by CFL (greater than 100 micrograms/ml). The present results demonstrate biological effects of 4-quinolones on eukaryotic systems at remarkably low concentrations. In this context, the possibility of interactions with DNA catabolizing enzyme systems and synergistic effects with DNA/chromatin-damaging agents should be considered further.

Animals↗
PubMed1991

Inhibition of O6-alkylguanine-DNA alkyltransferase and DNase I activities in vitro by some alkylating substances and antineoplastic agents.

The specificities of the DNA repair enzyme O6-alkylguanine-DNA alkyltransferase from brain and liver cells of the chick embryo and of DNase I were demonstrated in vitro by their response to substrate DNA pretreated with monofunctional alkylating agents of different O6-guanine alkylating ability and some antineoplastic agents. Treatment of DNA with ethidium bromide, Hoechst 33258, doxorubicin, Fe2+/bleomycin, and suramin resulted in a dose-dependent diminution of alkyltransferase activity (DE50 approximately 5 micrograms/ml, 15 micrograms/ml, 5 micrograms/ml, 5 micrograms/ml, 100 micrograms/ml, respectively). Apart from bleomycin, comparable results were obtained with DNase I. Thermal denaturation of the substrate DNA reduced both alkyltransferase and DNase I activity. No effect was seen with X-irradiation. Cisplatin decreased only DNase I activity. Some topoisomerase II and/or gyrase inhibitors remained without significant effects on the alkyltransferase reaction whereas DNA catabolism by DNase I was diminished in a dose-dependent manner (DE50 between 6.5 and 19 micrograms/ml).

Alkylating Agents↗
PubMed1991

Absence of O6-alkylguanine-DNA alkyltransferase induction in chick embryo liver and brain following X-irradiation or treatment with bleomycin.

1. The presence of O6-alkylguanine-DNA alkyltransferase (AT) in liver and brain of chick embryos, chicks and hens was demonstrated. An induction of AT activity has only been found in the liver of chicks and hens 48 hr after X-irradiation (5, 10 or 12 Gy). 2. The administration of methylmethanesulphonate to the chick embryo resulted 3-24 hr later in strong inhibition of AT activity accompanied by DNA alkylation. Under the same conditions, X-irradiation, dimethylnitrosamine and bleomycin exhibited no effect. 3. The results are compared with those obtained in mouse, rat and human foetal tissues.

Animals↗
PubMed1991

Influence of X-irradiation on the motor activity of rat urinary bladder in vitro and in vivo.

Preparations of rat detrusor vesicae urinariae exposed to 50 kV X-irradiation with 10 to 200 Gy (single dose) at dose-rates of 30 and 60 Gy/min reacted immediately with a dose and dose-rate dependent reversible or persistent increase (up to ten hours) of the basal tone and an increase or a decrease of the acetylcholine contractile response. The motor activity was recorded isotonically. For measurements of time changes following treatment in vivo the bladder was locally irradiated from lateral position with single 300 kV X-ray doses of 10, 25 and 50 Gy. The motor reaction of isolated detrusor preparations to acetylcholine had a threshold concentration in control animals of 2.3 X 10(-10) mol/l (n = 33); the sensitivity to acetylcholine was diminished as early as one to two hours after local irradiation with 50 Gy as reflected in a ten times higher threshold concentration, which decreased further with time past treatment up to 40 days. The inhibitory effect after 25 Gy was weaker. The contractile response of acetylcholine at different concentrations (10(-10) to 10(-5) mol/l) was also diminished after irradiation (50 Gy). It is suggested that the pathophysiological reactions of the radiogenic bladder are based on multifactorial mechanisms and X-ray induced tonic contraction as well as inhibition of the acetylcholine contractile response could be essential factors for the clinically observed hypertonia of the irradiated bladder ("radiogene Harnblase") and its functional volume decrease as well as of the diminished pressure during micturition.

Acetylcholine↗
PubMed1990

Changes in nucleoid viscosity following X-irradiation of rat thymic and splenic cells in vitro.

Unscheduled DNA synthesis (UDS) suggested a higher DNA repair capacity of X-irradiated rat thymic (T) cells when compared to splenic (S) cells (Tempel 1980). In the present investigations, damage and repair of DNA supercoiling was measured in T- and S-cells following X-irradiation in vitro by using the nucleoid sedimentation technique and a simplified low-shearing viscometric test. - X-irradiation resulted in a dose (0.6-19.2 Gy) - dependent reduction in sedimentation and viscosity of nucleoids. Within a post-irradiation period of 30-45 min after a challenge dose of 19.2 Gy, DNA repair was accompanied by an increase in nucleoid sedimentation and viscosity in T-cells by about 60 and 300, in S-cells by almost 40 and 100%, resp. The increase in nucleoid viscosity within a 30 min repair period could be reduced in a concentration-dependent manner by DNA polymerase - inhibitors and proteinase K. - The higher DNA repair capacity of T-cells as reflected by UDS is confirmed therefore by the nucleoid characteristics. Apart from this suggestion, measuring nucleoid viscosity may be considered as a sensitive, simple and rapid device to detect radiation-induced DNA supercoiling phenomena.

Animals↗
PubMed1990

Inhibition of ribonucleotide reductase in thymocytes of rats treated by ditiocarb sodium.

The i.p. administration of ditiocarb sodium (diethyldithiocarbamate, DDC) at doses of 500 and 1000 mg/kg body wt. decreased within 1 h and in a competitive manner the ribonucleotide reductase (RNR) activity of rat thymocytes by about 25 and 40%, respectively. Under the same conditions, scheduled DNA synthesis was inhibited by almost 30 and 75%, whereas RNA synthesis remained unchanged. 1000 mg DDC/kg body wt. resulted in a long-lasting diminution in thymus weight; the spleen revealed no significant drug effects. It is suggested that the decrease of RNR activity in thymocytes of DDC-treated rats is a major determinant in the (reversible) inhibition of DNA synthesis which, in turn, may be implicated in the radio- and chemoprotective effects of the drug.

Animals↗
PubMed1989

Scheduled and unscheduled DNA synthesis in chick embryo liver following X-irradiation and treatment with DNA repair inhibitors in vivo.

Three hours following X-irradiation of chick embryos with doses of 4 and 8 Gy the in vitro incorporation of tritiated thymidine [( 3H]dT) into DNA (scheduled DNA synthesis, ss) of hepatocytes was reduced to about one-third. Within 24 h after the exposure, ss returned to control values. The return of ss to a normal rate could be strongly inhibited by 2',3'-dideoxythymidine (ddT), and to a lesser extent by 1-beta-D-arabinofuranosylcytosine (araC). In strong contrast to ss, the hydroxyurea (hu)-resistant [3H]dT incorporation (unscheduled DNA synthesis, us) showed a highly significant increase 24 h after treatment of the embryos with araC and/or X-irradiation. Autoradiographic studies revealed no change of total [3H]dT labelling frequency in the whole chick embryo liver 24 h after treatment with araC and/or X-irradiation, but a persistent depression of ss and a simultaneous increase of us. The histological discrimination between affected and non-affected areas argue for a stimulation of DNA synthesis as an antecedent of subsequent mitosis and reparative proliferation adjacent to cell necrosis. It is suggested that the fast recovery of ss in the 12-15-day-old chick embryo is due to an efficient DNA repair system for which DNA polymerase beta is important. The increase of hu-resistance may be an expression of an aberrant DNA synthesis.

Animals↗
PubMed1989

[The effect of small radiation doses: desoxyribonucleic acid (DNA) synthesis and DNA repair by the thymus, spleen and bone marrow cells of rats following fractionated whole-body X-ray irradiation].

After three to seven days following to fractionated total body X-ray irradiation (TBI) (four exposures with doses of 0.3 to 5.0 cGy per fraction at intervals of 24 hours), a maximum 50 percent stimulation of the semiconservative DNA synthesis (SDS) of spleen cells was measured in vitro. This was not dependent of the fact if an acute high-dose (400 and/or 800 cGy) unique irradiation was applied after the fractionated TBI at the moment of stimulation. A significant increase of 3H-thymidine incorporation into the DNA of bone marrow and thymus cells was only found when doses of 1.25 cGy per fraction had been used. After fractionated TBI with doses of greater than or equal to 5 cGy per fraction, an increase of DNA synthesis resistant to hydroxyurea ("unprogrammed" DNA synthesis, UDS) was demonstrated in spleen cells. The UV-stimulated UDS decreased proportionately. The sedimentation of thymus, spleen, and bone marrow nucleoids in a neutral saccharose gradient gave no evidence of an increased DNA repair capacity after fractionated TBI. Whereas the SDS stimulation by fractionated TBI with small doses can be explained by a modified proliferation behavior of exposed cells, the UDS behavior of spleen cells after considerably higher radiation doses suggests regenerative processes correlated with an increased number of cells resistant to hydroxyurea and cells presenting an UV repair deficiency. These findings can be considered to be a further proof of the assumed immune-stimulating effect of small radiation doses.

Animals↗
PubMed1988

[Deoxyribonucleic acid synthesis by rat thymus and spleen cells in vitro following hyperthermia].

The inhibition of the semiconservative and restorative DNA synthesis caused by hyperthermia (30 to 60 min, 43 degrees C) was significantly higher in spleen cells than in thymus cells. The DNA repair synthesis of thymus cells measured at 37 degrees C was increased by about two times the initial value after a pre-incubation of 30 to 90 min and 30 to 60 min, respectively, with 37 and 43 degrees C, respectively. Under the same conditions, the 3H-thymidine incorporation into the DNA of spleen cells diminished proportionally to the pre-incubation time after a pre-incubation of 30 and 45 min, respectively, with 43 and 37 degrees C, respectively. When hyperthermia and inhibitors of DNA synthesis or DNA repair (hydroxyurea, 1-beta-D-arabinofuranosylcytosine, 3',5'-didesoxythymidine, and 3-aminobenzamide) were combined, overadditive effects--without cell specific particularities--were seen only in the case of 3-aminobenzamide. Only in thymus cells, the inhibitor of DNA topoisomerase II novobiocin caused an overadditive reinforcement of the inhibition induced by hyperthermia of the semiconservative DNA synthesis. The stimulation of DNA repair synthesis in thymus cells caused by novobiocin with the aid of DNA polymerase beta could be compensated by hyperthermia. The sedimentation of thymus and spleen cell nucleoids was increased after hyperthermia. The results suggest a special importance of DNA topology and of the DNA polymerase beta activity for the cellular effect of hyperthermia.

Animals↗
PubMed1987

Stimulation of DNA repair synthesis of rat thymocytes by novobiocin and nalidixic acid in vitro without detectable DNA damage.

Scheduled (SDS) and unscheduled (UDS) DNA synthesis as well as nucleoid sedimentation was investigated in vitro under the influence of novobiocin (NB) and nalidixic acid (NA) using intact thymic (T-cells) and splenic (S-cells) rat cells and cells which were exposed to X-rays, UV irradiation, methyl methanesulfonate (MMS), and DNA polymerase inhibitors. At concentrations of greater than or equal to 56.25 (S-cells) and greater than or equal to 225 micrograms/ml (T-cells), respectively, NB inhibited SDS in a dose-dependent manner. Within a concentration range of greater than or equal to 225-900 micrograms NB/ml, UDS of S-cells decreased to values far below the tracer ([3H-methyl]-thymidine) incorporation of control cells, whereas UDS of T-cells increased by at least 200%. Within a concentration range of 450-1800 micrograms/ml, NA enhanced SDS and UDS by about 30% in S-cells and by 100% in T-cells. The stimulating activity of NB and/or NA could be eliminated specifically by the DNA polymerase beta inhibitor 2',3'-dideoxythymidine. Enhanced nucleoid sedimentation was observed at NB concentrations greater than or equal to 750 micrograms/ml; S-cells revealed a higher sedimentation rate than T-cells. It is suggested that NB (and NA) influence DNA topology in a rather cell specific manner, stimulating UDS of T-cells by a DNA polymerase beta - dependent repair-like mechanism.

Animals↗
PubMed1987

Diethyldithiocarbamate inhibits scheduled and unscheduled DNA synthesis of rat thymocytes in vitro and in vivo--dose-effect relationships and mechanisms of action.

In vitro as well as in animal models, diethyldithiocarbamate (DDC) modifies the tumoricidal activity of some antineoplastic agents. To gain further information about the mechanism of action of DDC, we measured (i) in vitro and (ii) in vivo changes in DNA synthesis of rat thymocytes. (i) In vitro, the scheduled (SDS) and unscheduled (UDS) incorporation of [3H]thymidine ([3H]dT) into DNA of rat thymic cells were biphasically inhibited in a dose range of 1-1000 micrograms DDC/ml. The UV-induced UDS was totally suppressed by 10 and 100 micrograms DDC/ml. (ii) In vivo, 1-4 h following intraperitoneal administration of 250-1000 mg DDC per kg body wt., SDS and UDS were inhibited up to about 80% in a dose-dependent manner. Nucleoid sedimentation, uptake of [3H]dT into the cells, and the pattern of phosphorylation of the intracellular [3H]dT following DDC treatment did not reveal any differences to the controls. A possible effect of DDC treatment on the ribonucleotide reductase and the DNA polymerase alpha is suggested.

Animals↗
PubMed1987

[A new version of the x-ray regulation].

In the Federal Republic of Germany, the medical and veterinary uses of X-rays are governed by legal rules entitled "Röntgenverordnung" which have been enacted in 1973. In the meantime, these directives have undergone an amendment, coming into effect January 1st, 1988. Some new regulations with concern to veterinary medicine are outlined below.

Animals↗
PubMed1985

The cytotoxic action of diethyldithiocarbamate in vitro. Different inhibition of scheduled and unscheduled DNA synthesis of rat thymic and splenic cells.

Within a concentration range of 1-10 micrograms/ml, an addition of diethyldithiocarbamate (DDC) to splenic and thymic rat lymphocytes (2 X 10(6)-4 X 10(6) cells/ml) resulted in a complete inhibition of scheduled (semiconservative) DNA synthesis. Lower and higher concentrations were less effective. Under the same conditions, a strictly dose-dependent inhibition of unscheduled (excision repair) DNA synthesis, a decrease of the sedimentation rate of nucleoids, as well as changes of the thymidine pool were observed. The results suggest that the cytotoxic action of DDC in vitro may be mediated a) by the chelating properties of the drug with inhibitory effects on a variety of cellular functions, including nucleic acid precursor metabolism, b) by an immediate radiomimetic attack of the SH-group of DDC on the DNA.

Animals↗