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J Greger

Publications and source records attributed to J Greger.

88 records · Page 5Linked to original sources
PubMedDate not supplied

Effects of substance P on the growth processes in rat thyroid lobes in vitro.

The effects of substance P (SP) on (1) 3H-thymidine incorporation into the DNA of rat thyroid lobes during a 4-hour incubation, and (2) thymidine kinase (TK, EC 2.7.1.21) activity in homogenates of rat thyroid lobes were investigated. We also examined the influence of the joint action of SP and thyrotropin (TSH) on these processes. It was shown that the effects of SP on these processes were dependent on the concentration of the neuropeptide applied. At the lowest concentration (10(-12) M), SP significantly (p < 0.0025) decreased and at the highest one (10(-6) M) it slightly increased (p < 0.09) the values of the examined growth indices. The activity of TK rose in parallel with the increase in SP concentration. SP and TSH, when used together, exerted similar decreasing effects, both on 3H-thymidine incorporation into DNA and on TK activity.

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PubMedDate not supplied

Different effect of dGTP on 2'-deoxyadenosine metabolism in mitochondria and cytosol.

Two enzymes participating in 2'-deoxyadenosine (dAdo) metabolism: dAdo kinase (dAdoK EC 2.7.1.76) and adenosine deaminase (ADA, EC 3.5.4.4) were partially purified from rat liver mitochondria and cytosol and influence of nucleosides and nucleotides on the activity of these enzymes were investigated. Mitochondrial and cytosol dAdoK are separate proteins, while ADA from both subcellular fractions possesses similar physical properties. dGTP, a competitive inhibitor of mitochondrial dAdoK, inhibits cytosol ADA in a mixed way but activates mitochondrial ADA and cytosol dAdoK. A possible effect of dGTP on dAdo metabolism in mitochondria and cytosol is discussed.

Adenosine Deaminase↗
PubMedDate not supplied

The influence of alkoxymethyl purine and pyrimidine acyclonucleosides on growth inhibition of Kirkman-Robbins hepatoma and possible mechanism of their cytostatic activity.

Newly synthesized allyloxymethyl purine and pyrimidine acyclonucleosides [Fig. 1, comp. 1-6] were tested in Syrian hamster, six days after heterotransplantations of Kirkman-Robbins hepatoma and compared with Th5, Th5P and PMT [Fig. 1, comp. 7-9]. 48 hours after intraperitoneal (i.p.) administration of AMT and Th5 in a dose of 80 mg per kg body weight, these compounds reduced tumor weight by 42%, while AMU (in the same dose) by 30%. The inhibition of tumor weight is accompanied by a decrease in dThd and dGuo kinase activities in tumor cytosol by AMU (36% and 33%, respectively) by AMT (59% and 53%, respectively) and by Th5 (58% and 55%, respectively). AMU, AMT and Th5 are phosphorylated in vivo by kinases present in cytosol of growing hepatoma to mono, di and triphosphates, but allyloxymethyl residue of AMU and AMT is first hydrated to hydroxypropoxymethyl residue, having CH2OH group. The lack of phosphorylation of PMT in vivo (having saturated propoxymethyl residue) and phosphorylation of Th5P (when used as a substrate for dNMP kinase) only to Th5 diphosphate suggested that AMU, AMT and Th5 triphosphates are responsible for the inhibition of dTMP and dGMP synthesis.

Animals↗
PubMedDate not supplied

The activity of thymidine phosphorylase in the uterine myomas and the myometrium in perimenopausal women.

The activity of thymidine phosphorylase (dThdPase) in the myometrium and uterine myomas has been investigated in perimenopausal women. Differences in the activity of dThdPase have been found depending on the myoma type, menopause stage and the phase of the menstrual cycle in which the surgery was performed. The enzyme in the cytoplasmatic soluble fraction obtained at 50,000 x g was the most active in cellular leiomyomas of the follicular phase, the least in adenomyomas of the luteal phase of the menstrual cycle, whereas its activity in myometrium was always unchanged. Greater differences can be observed in the activity of dThdPase after a partial purification of the enzyme from myomas. It seems that the increase in dThdPase activity may point to its correlation with transient, premalignant tumor which may later transform into malignant forms.

Adenomyoma↗
PubMedDate not supplied

Growth inhibition of Kirkman-Robbins hepatoma by 1-(1,3-dihydroxy-2-propoxymethyl)-5,6-tetramethyleneuracil and possible mechanism of its biological activity.

1-(1,3-Dihydroxy-2-propoxymethyl)-5,6-tetramethylene-uracil (DHPTU) is a newly synthesized acyclonucleoside which shows cytostatic properties. It was tested in Syrian hamster 6 days after heterotransplantation of Kirkman-Robbins hepatoma. A reduction of tumour weight by 61% was found 48 h after its intraperitoneal (i.p.) administration in doses of 20 mg per kg of body weight. Inhibition of tumour growth is accompanied by a reduction of dThd, dGuo and dTMP kinase activities in tumour cytosol (by 91% and 74% and 55%, respectively) and decrease in contents of dTTP, dGTP and dATP (by 92%, 77% and 67%, respectively) in dNTP pool. DHPTU is not phosphorylated by any tumour dN kinases, but undergoes cleavage with TU release in reaction catalyzed by the tumour cell enzyme, competitively inhibited by FA. After [14C]DHPTU or [14C]TU had been given i.p. to the animals with the tumour, 90% of the subcellular fraction labelling fell into the nuclear fraction. However, if [14C]DHPTU was administered with FA and DCF, 27% of radioisotope was found in the nuclear fractions and 68% in cytosol. Since DCF which prevented FA deamination to FB (which is not an inhibitor of the mentioned enzyme) reduces DHPTU-induced changes in activity of dN kinases and dTMP kinase in hepatoma cells, the cytostatic activity of DHPTU seems to be connected to an enzyme which releases TU from DHPTU.

Animals↗