Zeitschrift fur Naturforschung. Section C, Biosciences最新文献

This study was aimed at investigating whether cells of CFU-C derived colonies could form secondary colonies. Bone marrow cultures of volumes of agar medium between 25 microliter and 75 microliter contained in glass capillaries were stimulated with mouse lung-conditioned medium (MLCM) containing granulocyte/macrophage colony-stimulating factor (GM-CSF). Agar gels with colonies of up to greater than or equal to 20 were blown out into identical culture medium, completely dispersed on a whirl-mix to single cell suspensions, and used for establishing secondary agar cultures. In these secondary cultures considerable numbers of secondary granulocytic, mixed granulocytic/macrophage and macrophage colonies as well as numerous clusters arose. In contrast, when single colonies were recultured, only few secondary cell aggregates were formed. When primary cultures containing up to greater than or equal to 20 cell aggregates were used for serial reculture at intermittent intervals of 3 and 4 days, a 2-7-fold increase of colony-forming cells was found in tertiary cultures as was monitored by 7 day colony counts. And by use of different kinds of CSF-containing media, an over 4-fold increase of secondary over primary colonies was obtained with bovine lung-conditioned medium (BLCM) in primary and L-cell-conditioned medium (LCCM) in secondary 7 day cultures. Primary capillary cultures were found to be devoid of CFU-S. Also, setting up bone marrow cultures in petri dishes and stimulating with MLCM, growth of primary as well as secondary colonies was obtained. The results indicate some self-renewal potential of CFU-C in vitro.

The calcium free sarcoplasmic reticulum calcium transport ATPase incorporates in the presence of magnesium ions approx. 8 nmol monovanadate per mg protein, indicating the formation of a complex containing one vanadate residue per enzyme molecule. On ligand-removal or dilution, the saturated enzyme complex displays biphasic decay kinetics, while the unsaturated complex slowly dissociates monophasically. -Ligand competition by raising the concentrations of unlabeled vanadate results in a progressive decrease of the dissociation rate of the unsaturated enzyme. The complicated dissociation kinetics indicate a sequential mode of interaction between two ligand binding sites. The one to one stoichiometry of the complex suggests that the two sites are located at adjacent ATPase molecules. -It appears unlikely that the decay of the enzyme, vanadate complex is retarded by the formation of a stable quaternary complex between the enzyme, magnesium, mono- and polyvanadate.

The properties of the sarcoplasmic reticulum membranes isolated from slow-twitch type I soleus and fast-twitch type II psoas muscles of control and thyroxine treated rabbits were comparatively studied. Membrane yield, maximal calcium storing capacity, ATP-supported calcium uptake, calcium-dependent ATPase activity and calcium-dependent phosphoprotein formation were found to be 3-10 fold higher in psoas than in soleus preparations. Membrane yield, calcium-dependent ATPase activity, ATP-supported calcium transport and calcium-dependent phosphoprotein are at least twice enhanced in the membranes from soleus muscles of animals treated for 14-21 days with thyroxine. The corresponding capacities of the membranes from psoas muscles are not further augmented by the same thyroxine treatment. The maximal calcium storing capacity of the psoas membranes is their sole specific property which is significantly increased. The changes in the properties of the soleus muscles' sarcoplasmic reticulum membranes are engendered by an increase from 5 to 30-50% in the number of type II fibres. Since the calcium transporting properties of the sarcoplasmic reticulum membranes from type II fibres qualitatively differ from those of type I fibres, thyroxine does not only affect quantitative but also qualitative parameters of the muscles' sarcoplasmic reticulum membrane system.

The irritant and tumor-promoting constituents of latex of Euphorbia tirucalli L. originating from South Africa were isolated. They were identified as irritant ingenane and tigliane type diterpene esters derived from unsaturated aliphatic acids and acetic acid and the polyfunctional diterpene parent alcohols 4-deoxyphorbol, phorbol and ingenol, respectively. The irritant and tumor-promoting esters of 4-deoxyphorbol are predominant and were fully characterized chemically and biologically. They are positionally isomeric 12,13-acylates, acetates e.g. Euphorbiafactors Ti1-Ti4. As acyl groups they carry homologous, highly unsaturated aliphatic acids of the general structure CH3-(CH2)m-(CH = CH)n-COOH (m = 2,4; n = 1,2, 3,4,5; N = 2n + m + 2). Corresponding diesters of 4-deoxy-4 alpha-phorbol are also present which are biologically inactive. Comparison of structures and biological activities of 12,13-diesters of 4-deoxyphorbol indicates that--for a distinct total number of C-atoms (N) in the acyl moiety--an increasing number of conjugated double bonds (n) may increase the irritant but decrease the tumor-promoting activity. Replacement of the hydroxyl function at C-4 (phorbol-12,13-diesters) by hydrogen (corresponding 4-deoxyphorbol-12,13-diesters) does not essentially alter biological activities. Epimerization of 4-deoxyphorbol-12,13-diesters at C-4 abolishes biological activities. The specific chemical properties demonstrated for the diterpene ester irritants contained in the latex of E. tirucalli and hence in all plant parts may be useful in trials to abolish the potential risk of cancer involved especially in occupational mass production and handling of the plant. Some of the structure activity relations of the Euphorbia factors isolated made them excellent tools in experimental cancer research for the analysis of mechanisms of tumorigenesis.

Under conditions where 2'-deoxycoformycin is enzymatically phosphorylated by wheat shoot phosphotransferase to the 5'-phosphate in 15-20% yield, coformycin is a relatively poor substrate, and is phosphorylated only to the extent of less than or equal to 5%. However, chemical phosphorylation of coformycin by modifications of the Yoshikawa procedure led to isolation of coformycin-5'-phosphate in 20% overall yield. Coformycin-5'-phosphate was characterized by various criteria, including 1H NMR spectroscopy. Comparison of the spectrum with that of the parent nucleoside indicated that the nucleotide is predominantly, although not exclusively, in the conformation anti about the glycosidic bond. Like 2'-deoxycoformycin-5'-phosphate, coformycin-5'-phosphate was a feeble substrate of snake venom 5'-nucleotidase, and is hydrolyzed, quantitatively, at only 2% the rate for 5'-AMP. With 5'-AMP analogues as substrate, the 5'-phosphates of both coformycin and deoxycoformycin were poor inhibitors of the enzyme, with Ki values greater than 0.3 mM. The 5'-phosphates of both coformycin and deoxycoformycin do not significantly inhibit adenosine deaminase (Ki greater than 0.2 mM), but are potent inhibitors of adenylate deaminase (Ki less than or equal to 10(-9) M). Neither coformycin nor deoxycoformycin are inhibitors of mammalian purine nucleoside phosphorylase. The stabilities of coformycin, deoxycoformycin, and their 5'-phosphates, have been examined as a function of pH, and nature of the buffer medium. In particular, all exhibit instability in acid and neutral media, but are relatively stable in the vicinity of pH 9. Some biological aspects of the overall results are presented.

Norfloxacin, a nalidixic acid analogue, inhibited streptolysin S (SLS) production when added to young streptococcal culture. DNA synthesis was mainly affected, but increment of cell mass, RNA and protein was also significantly reduced in streptococci treated with norfloxacin. In stationary phase cells and in the washed resting bacteria, the toxin production was resistant to the drug. Pretreatment with norfloxacin did not abolish the cellular capacity to produce SLS. Although extracellular SLS was detectable at log phase of streptococcal growth, enhanced production of the toxin occurred upon cessation of coccal multiplication. In contrast to norfloxacin, lower concentration of rifampicin inhibited SLS production, even added at late log or early stationary phase. Roles of growth phase, medium and carrier in induction of SLS production were analyzed as well.

The recently developed stereospecific sodium salt glycosylation procedure has been successfully applied to the synthesis of the beta-D-2'-deoxyribofuranosides of benzimidazole, 5,6-dihalogeno benzimidazoles, and some 2-substituted analogues in high yield. The 5,6-dibromo analogue was obtained by bromination of the parent nucleoside. These have all been characterized by spectroscopic methods, including 1H NMR, which permitted analyses of their solution conformations and comparison with those of the corresponding ribofuranosides. Some biological aspects, including preliminary results on cytotoxicity and antiviral activity, are briefly considered.

The potency of L-valine as an inhibitor of Zea mays acetohydroxyacid synthase (AHAS) is increased more than 8000-fold on conversion to its N-phthalyl anilide derivative which is active at 2 microM. The D-valine, alpha-aminobutyric acid, isoleucine and phenylalanine analogs are 11- to 43-fold less potent, and similar N-phthalyl anilide derivatives of other branched-chain amino acids are essentially inactive. Full potency is retained on replacing the phthalimide moiety of the valine anilide with cyclohexane-1,2-dicarboximide or 1-cyclohexene-1,2-dicarboximide groups and partial activity with 4-cyclohexene-1,2-dicarboximide and methyl- or dimethylmaleimide groups. Inhibition of the enzyme and of root growth by the valine derivatives may result from binding at or near the site involved in feedback control of AHAS by L-valine.

The ratios of the scoparone O-demethylation products scopoletin to isoscopoletin were determined for reconstituted complexes of NADPH-P-450 reductase and each of four P-450 isozymes in a 2:1 molar ratio with a 1:1 mixture of [7-O-methyl-14C]- and [6-O-methyl-14C]-scoparone as substrate. The two phenobarbital inducible forms P-450PB-B and P-450PB-D have a 1:0.8 +/- 0.05 scopoletin to isoscopoletin ratio, and the two beta-naphthoflavone inducible forms P-450 beta NF-B and P-450 beta NF/ISF-G have ratios of 1:4.4 +/- 0.1 and 1:3.8 +/- 0.1, respectively. The scoparone-O-demethylation activities of the reconstituted preformed complexes of the four P-450 isozymes are given.

Extracts of S. asoca bark and pure compounds isolated from the bark were tested for properties that might inhibit the conversion of arachidonic acid by the PGH2 synthetase. They were assayed spectrophotometrically with adrenaline as cofactor. Methanol- and ethyl acetate extracts inhibited the conversion. The observed inhibition was confirmed in an oxygraphic assay. Two procyanidin dimers from the ethyl acetate extract showed enzyme catalyzed oxidation in our assay. The ether extract of the bark was also found to contain yet unknown substances which were capable of being oxidised by the PGH2 synthetase. The combined action of the components of the bark may explain the mode of action of the drug Asoka Aristha, the main ingredient of which is the bark of S. asoca. The drug is traditionally used in Sri Lanka to treat menorrhagia.