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M Sabat

Publications and source records attributed to M Sabat.

36 records · Page 2Linked to original sources
PubMed1996

Experience with pancreas islets separation, immunoisolation and cryopreservation.

Experience of Warsaw Pancreas Laboratory is presented. Some improvement in the methods of rat, human and pig pancreases digestion, and in identification of Langerhans islets by means of intravenous injection of I-DTZ was achieved. For immunoisolation of islets, 2 methods were elaborated: capsules containing alginate/polyethyleneimine/protamine/heparin membrane prepared by modified Sun method, and microcapsules based on Zekorn method. Biocompability of hollow fibers, prepared with polypropylene (PP), surface modified PP (PPS) and polysulphone (PS) was assessed in vitro. Only PS fibers were fully compatible. It was shown, that the mixture of exocrine tissue did not influence in vitro insulin secretion, providing that alginate in which islets are embedded remain gelled. The efficacy of 3 methods of islets cryopreservation was compared: freezing in "semicontrolable" conditions, in programmable Kriomedpol machine, and vitrification. The highest percentage of frozen/thawed living cells, and the most reliable results were obtained with Kriomedpol method.

Alginates↗
PubMed1994

In vitro and in vivo evaluation of protamine-heparin membrane for microencapsulation of rat Langerhans islets.

Rat pancreatic islets were microencapsulated with multilayer protamine-heparin (PH) membrane. Basal and stimulatory insulin secretion of microencapsulated islets was similar to the controlled free islets in vitro. During the long-term culture (up to 2 weeks) mean insulin release of encapsulated islets did not significantly differ from the mean of free ones (the ratio of mentioned means was 54-167%). Empty PH microcapsules transplanted into Wistar rats intraperitoneally and under the kidney capsule were generally harmless up to 4 months. In only a few cases traces of fibrotic tissue around capsules entrapped in the omentum were found. No damage of microcapsules structure was observed. The worst results were obtained in the instance of retroperitoneal transplantation. We conclude, therefore, that PH membrane was proved to be highly biocompatible, nontoxic for islets, and did not impair viability and glucose-dependent insulin secretion of Langerhans islets in in vitro culture.

Animals↗
PubMed1988

Developmental effects of impaired breathing in the face of the growing child.

Craniofacial morphology and occlusal pattern are evaluated in 71 subjects having impaired breathing as diagnosed by an otolaryngologist, and in an equal number of controls. The impaired group demonstrate characteristic combinations of craniofacial deformities and malocclusions, with the younger individuals demonstrating a lesser expression of malocclusion progression and morphologic deformities. This suggests that early recognition of such facial patterns may be utilized to identify those breathing compromised individuals who have a likely tendency to develop certain types of malocclusion.

Adolescent↗
PubMed1985

Crystal structure of the alpha, beta, gamma-tridentate manganese complex of adenosine 5'-triphosphate cocrystallized with 2,2'-dipyridylamine.

The 1:1:1 complex of Mn2+, ATP, and 2,2'-dipyridylamine (DPA) crystallizes as Mn-(HATP)2.Mn(H2O)6.(HDPA)2.12H2O in the orthorhombic space group C222(1) with unit cell dimensions a = 10.234 (3) A, b = 22.699 (3) A, and c = 31.351 (4) A. The structure was solved by the multisolution technique and refined by the least-squares method to a final R index of 0.072 using 3516 intensities. The structure is composed of two ATP molecules sharing a common manganese atom. The metal exhibits alpha, beta, gamma coordination to the triphosphate chains of two dyad-related ATP molecules, resulting in a hexacoordinated Mn2+ ion surrounded by six phosphate groups. The metal to oxygen distances are 2.205 (6), 2.156 (4), and 2.144 (5) A for the alpha-, beta-, and gamma-phosphate groups, respectively. No metal-base interactions are observed. There is a second hexaaqua-coordinated Mn2+ ion that is also located on a dyad axis. The hydrated manganese ions sandwich the phosphate-coordinated manganese ions in the crystal with a metal-metal distance of 5.322 A. The ATP molecule is protonated on the N(1) site of the adenine base and exhibits the anti conformation (chi = 66.0 degrees). The ribofuranose ring is in the 2/3 T conformation with pseudorotation parameters P = 179 (1) degrees and tau m = 34.1 (6) degrees. The adenine bases form hydrogen-bonded self-pairs across a crystallographic dyad axis and stack with both DPA molecules to form a column along the dyad. The structure of the metal-ATP complex provides information about the possible metal coordination, conformation, and environment of the nucleoside triphosphate substrate in the enzyme.

2,2'-Dipyridyl↗
PubMed1983

Similar binding of the carcinostatic drugs cis-[Pt(NH3)2Cl2] and [Ru(NH3)5Cl] Cl2 to tRNAphe and a comparison with the binding of the inactive trans-[Pt(NH3)2Cl2] complex - reluctance in binding to Watson-Crick base pairs within double helix.

A comparative study of the binding of square planar cis- and trans-[Pt(NH3)2Cl2] complexes and the octahedral [Ru(NH3)5(H2O)]3+ complex to tRNAphe from yeast was carried out by X-ray crystallography. Both of the carcinostatic compounds, cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ show similarities in their mode of binding to tRNA. These complexes bind specifically to the N(7) positions of guanines G15 and G18 in the dihydrouridine loop. [Ru(NH3)5(H2O)]3+ has an additional binding site at N(7) of residue G1 after extensive soaking times (58 days). A noncovalent binding site for ruthenium is also observed in the deep groove of the acceptor stem helix with shorter (25 days) soaking time. The major binding site for the inactive trans-[Pt(NH3)Cl2] complex is at the N(1) position of residue A73, with minor trans-Pt binding sites at the N(7) positions of residues Gm34, G18 and G43. The similarities in the binding modes of cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ are expected to be related to their carcinostatic properties.

Base Composition↗
PubMed1983

Interaction of adenosine 5'-triphosphate with metal ions X-ray structure of ternary complexes containing Mg(II), Ca(II), Mn(II), Co(II), ATP and 2,2'-dipyridylamine.

The X-ray structures of the isomorphous Mg2+, Ca2+, Mn2+ and Co2+ complexes of ATP have been determined. The metal ions are wrapped in hexa-coordination by the alpha, beta and gamma phosphate groups of two ATP molecules thus blocking the interaction of the metal ions with the adenine base. A second metal ion which is fully hydrated, M(H2O)2+(6), is engaged in a strong hydrogen bond with the gamma phosphate group of ATP and suggests a possible step in facilitating the cleavage between the beta and gamma phosphates in phosphoryl transfer reactions.

2,2'-Dipyridyl↗
PubMedDate not supplied

Carbamates of (hydroxyphenoxy)methyl heteroaromatic salts as acetylcholinesterase inhibitors and protective agents against organophosphorus compounds.

A series of N,N-dimethylcarbamates of 2-[(2'-, 3'-, and 4'-hydroxyphenoxy)methyl] heteroaromatic salts has been prepared. Pyridine, imidazole, quinoline, benzimidazole, and imidazo-[1,2-alpha]pyridine derivatives were included. Most of the compounds are inhibitors of electric eel acetylcholinesterase and also show prophylactic activity toward a 2LD50 dose of soman in mice.

Animals↗