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Uridine phosphorylase from Hymenolepis diminuta [Cestoda]: Kinetics and ihibition by pyrimidine nucleoside analogs

100%

Drabikowska A. K.

nr 4

A single pyrimidine nucleoside phosphorylase was found in the cytoplasmic extract from Hymenolepis diminuta. This enzyme preferentially cleaves uridine and, to a much lesser extent, thymidine. Its presence directly indicates the existence of pyrimidine nucleoside salvage pathway in this parasite. Detailed kinetic studies in the phosphorolytic and synthetic direction pointed to the sequential mechanism of these reactions. For phosphorolysis, Kurd = 33 ^M and Kp = 806 nM. For synthesis of uridine, KUra = 204 jiM and Ki.p.rib.= 50 pM. Over six times higher Km for uracil than for uridine indicates that phosphorolysis is the favoured reaction in this tapeworm. Well known inhibitors of mammalian uridine phosphorylase: 2,2'-anhydro-5- -ethyluridine and l-(l,3-dihydroxy-2-propoxymethyl)-5-benzyluracil (DHPBU), both with Ki = 0.07 nM were potent competitive inhibitors of the enzyme from H. diminuta. The newly synthesized 2,3'-anhydro-5-ethyluridine (K. Felczak,unpublished) showed only moderate inhibitory activity (Ki = 14 jiM) similarly as l-(l,3-dihydroxy-2- -propoxy-methyl)-5-benzyluracil. The same order of Ki values obtained for the investigated inhibitors vs uridine phosphorylase, irrespective whether the enzyme was isolated from rat intestinal mucosa (Drabikowska etal., 1987,Biochem. Pharmacol. 36,4125-4128) or H. diminuta may point to a great similarity between binding sites on the parasite and the host enzyme.

Usefulness of neutral red uptake method for investigation of the bovine leukocyte viability and lymphocyte proliferation

84%

Fijalkowski K. , Nawrotek P. , Czernomysy-Furowicz D.

nr 1-2

Regional differences in the vulnerability of substantia nigra dopaminergic neurons in weaver mice

84%

Marti J. , Santa-Cruz M. C. , Molina V. , Serra R. , Bayer S. A. , Ghetti B. , Hervas J. P.

nr 2

198-206

Vulnerability of midbrain dopaminergic (DA) neurons in the weaver mouse was studied at postnatal (P) days 8 and 90, in chosen coronal levels throughout the anteroposterior (AP) extent of the substantia nigra pars compacta (SNc). Wild-type (+/+) and homozygous weaver (wv/wv) mice used were the offspring of pregnant dams injected in several cases with tritiated thymidine on embryonic days 11-15. DA neurons were identified for their tyrosine hydroxylase immunoreactivity. Data reveal that at P8, the frequency of both +/+ and wv/wv late-generated DA cells increases from rostral to caudal SNc. No apparent DA-cell loss was observed at P8 in the mutant genotype, irrespective of the AP level considered. However, throughout the AP, there was a significant reduction in the number of these neurons at any level in 90-day-old weavers. Comparison of P8 and P90 +/+ SNc suggests that cell death is not a major aspect in the developmental regulation of normal DA neurons, although numerical cell depletion in the postnatal development of weaver SNc probably results from the amplification of a basal cell-death process, which affected all the coronal levels studied.

Inhibitory effects of herbal decoction Ojeoksan on proliferation and migration in vascular smooth muscle cells

84%

Han B. H. , Yoon J. J. , Kim H. Y. , Ahn Y. M. , Jin S. N. , Wen J. F. , Lee H. S. , Lee Y. J. , Kang D. G.

nr 2

Structure and dynamics of a DNA duplex containing single alpha-anomeric deoxyadenosine residue

84%

Bielecki L. , Adamiak R. W.

nr 1

Structure and dynamics of an undecamer DNA duplex containing a single a-anomeric deoxyadenosine residue placed in opposition to a thymidine unit have been studied using simulation of molecular dynamics in aqueous solution. Despite several noticeable deviations from the B-DNA duplex structure caused by the anomerisation, such as: West type puckering of the a-anomeric sugar, disrupted base stacking pattern and unstable duplex bending, the formation of a non-classical a-dA-T pair was observed. A novel way of visual presentation of trajectory data allowing high throughput screening of the conformational parameters is presented.