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1

The RNA formed the first selfreplicating system in prebiological epochs - a hypothesis

100%
Schneider Z.
Bulletin of the Polish Academy of Sciences. Biological Sciences
|
1987
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tom 35
|
nr 7-9
2

Elevation of the adenylate pool in rat cardiomyocytes by S-adenosyl-L-methionine

100%
Smolenski R. T.
Acta Biochimica Polonica
|
2000
|
tom 47
|
nr 4
Rapid resynthesis of the adenylate pool in cardiac myocytes is important for recovery of contractility and normal function of regulatory mechanisms in the heart. Adenosine and adenine are thought to be the most effective substrates for nucleotide synthesis, but the possibility of using other compounds has been studied very little in cardiomyocytes. In the present study, the effect of S-adenosyl-L-methionine (SAM) on the adenylate pool of isolated cardiomyocytes was investigated and compared to the effect of adenine and adenosine. Adult rat cardiomyocytes were isolated using the collagenase perfusion technique. The cells were incubated in the presence of adenine derivatives for 90 min followed by nucleotide determination by HPLC. The concentrations of adenine nucleotides expressed in nmol/mg of cell protein were initially 22.1 ± 1.4, 4.0 ± 0.3 and 0.70 ± 0.08 for ATP, ADP and AMP, respectively (n = 10, ± S.E.M.), and the total adenylate pool was 26.8 ± 1.6. In the presence of 1.25 mM SAM in the medium, the adenylate pool increased by 5.2 ± 0.4 nmol/mg of cell protein, but only if 1 mM ribose was additionally present in the medium. No changes were observed with SAM alone. A similar increase (by 4.9 ± 0.6 nmol/mg protein) was observed after incubation with 1.25 mM adenine plus 1 mM ribose, but no increase was observed if ribose was omitted. Adenosine at 0.1 or 1.25 mM concentrations also caused an increase in the adenylate pool (by 5.2 ± 1.0 and 5.2 ± 0.9 nmol/mg protein, respectively), which in contrast to the SAM or adenine was independent of the additional presence of ribose. Thus, S-adenosyl-L-methionine could be used as a precursor of the adenylate pool in cardiomyocytes, which is as efficient in increasing the adenylate pool after 90 min of incubation as adenosine or adenine. Nucleotide synthesis from SAM involves the formation of adenine as an intermediate with its subsequent incorporation by adenine phosphoribosyltransferase
3

NAD-analogues as potential anticancer agents: Conformational restrictions as basis for selectivity

100%
Pankiewicz K. W., Zatorski A., Watanabe K. A.
Acta Biochimica Polonica
|
1996
|
tom 43
|
nr 1
Cofactor type inhibitors (NAD-analogues) of IMP-dehydrogenase (IMPDH) were synthesized and their application as potential anticancer agents are discussed. C-nucleoside isosteres of NAD, C-NAD and C-PAD, showed an effective competitive inhibition of IMPDH. C-NAD but not C-PAD caused extremely potent inhibition of alcohol dehydrogenase. We also synthesized compounds in which nicotinamide riboside was replaced with tia/.ofurin (TAD-analogues) and the 2' and 3'-positions of adenosine part were fluorinated. The ribose ring of 2'-deoxy-2'-fluoroadenosine is in the Cy-endo conformation whereas 3-deoxy-3'-fluoroadenosine favors the Q2'-endo sugar pucker. These derivatives are good inhibitors of IMPDH type II, the isoenzyme dominant in neoplastic cells. In contrast, all these analogues showed rather week inhibitory activity against alcohol dehydrogenase. Nicotinamide riboside derivatives in which the base and the sugar are linked through an oxygen or a methylene bridge were synthesized. NAD-analogues containing such conformationally restricted nicotinamide nucleoside moiety (syn or anti) are expected to be selective inhibitors of B-specific (IMPDH) or A-specific dehydrogenases, respectively.
4

Advanced glycation end-products prepared in solution under high pressure contain epitopes distinct from those formed in the dry reaction at high temperature

84%
Staniszewska M., Jarosz S., Jon M., Gamian A.
Archivum Immunologiae et Therapiae Experimentalis
|
2005
|
tom 53
|
nr 1
5

Effect of carbohydrates on callus induction and regeneration ability in Brassica napus L.

67%
Bogunia H., Przywara L.
Acta Biologica Cracoviensia. Series Botanica
|
2000
|
tom 42
|
nr 1
The effect of 1%, 3% and 10% fructose, glucose, sucrose and ribose on callus induction and organogenesis was studied in Brassica napus L. cv. Evita. Hypocotyls and cotyledons of 7-day-old seedlings were used as explants. MS (Murashige and Skoog, 1962) was the basal medium. Calluses were produced from both types of explants in the presence of 2,4-D. There were significant differences in the frequency of callus induction between ribose and other sugars tested, as well as between low (1% and 3%) and high (10%) sugar concentrations. Irrespective of sugar type, callus induction was significantly lower on ribose- containing media and at high concentration. On hormone-free media, callus tissue formed very exceptionally and only from cotyledons. The amounts of callus tissue produced were highest on MS with glucose, followed by sucrose and fructose. In the regeneration experiments, explants were cultured on MS with 2,4-D as the sole growth regulator, and with NAA and kinetin. No regeneration occurred on medium with 2,4-D. In the presence of NAA and kinetin, organogenesis was observed only on media with 1% and 3% sugars, but on ribose the number of organs produced was very low. The highest regeneration ability occurred on sucrose-based medium.
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