Integrity of endothelium in cryopreserved human cornea

The aim of the present study was to elaborate an optimal method for cryopreservation of human donor cornea for transplantation and to follow the morphological changes in the structure of the endothelial cell layer using scanning electron microscopy (SEM). Sixteen groups, with four donor cornea each, were cryopreserved at cooling rates of 1 degree C per min and 5 degree C per min. Four cryoprotectants (glycerol, dimethyl sulfoxide, 1,2-propanediol, polyethylene glycol-400) in two concentrations (5% and 10% v/v) were prepared on the bases of medium Optisol GS supplied with 20% v/v human serum albumin. Four additional human cornea were used as controls. Endothelial cell recovery of the cornea after thawing and 24 hours culture, was calculated as a percent of the preserved recovered cells. Sufficient recovery of the endothelial cell layer, making the cornea suitable for transplantation was obtained using the cryoprotectants dimethyl sulfoxide and especially polyethylene glycol-400.     

New chelating sorbents based on pyrazolone containing amines immobilized on styrene-divinylbenzene copolymer-I Synthesis and analytical characterization

A series of new cheating sorbents has been prepared by modification of styrene-divinylbenzene copolymer with different pyrazolone-containing amines. The substances were characterized by elemental analysis and infared spectroscopy. The complexation ability of the sorbents towards alkali, alkaline-earth, transition and precious metals has been studied. The new sorbents may successfully be applied to the simultaneous preconcentration of alkaline-earth and transition elements in neutral medium and to the selective separation of precious metals in acidic medium.     

New boron-oxygen layer in the structure of barium hydrodecaborate Ba5[B20O33(OH)4] ⋅ H2O

The crystal structure of the new synthetic compound Ba₅[B₂₀O₃₃(OH)₄] ? H₂O was established by the methods of X-ray diffraction (a Stoe IPDS diffractometer, λMoK _α?, 1860 independent reflections, anisotropic refinement, R = 1.95%, localization of hydrogen atoms): a = 9.495(2) Å, b = 6.713(1) Å, c = 11.709(2) Å, β = 95.09(1)°, sp. gr. P2, Z = 1. The structure is based on double pseudohexagonal layers consisting of BO₄-tetrahedra and BO₃ triangles linked into three-membered rings in two mutually perpendicular directions. The double layers adjacent along the [100] direction are linked together through the Ba-polyhedra and hydrogen bonds with the participation of the OH-groups occupying the “end” vertices of two B-triangles. The interlayer space is also filled with a sheet of Ba-polyhedra. The structure of the compound is compared to the structures of topologically similar Ba and Ca borates and hydroborates.     

New triclinic modification of lead iodate Pb(IO3)2: Synthesis and crystal structure

A new triclinic modification of lead iodate Pb(IO₃)₂ (space group $C\bar 1$ ) is obtained under hydrothermal conditions. The crystal structure is determined without preliminary knowledge of the chemical formula. [IO₃]^? groups, which are characteristic of pentavalent iodine, have a typical umbrella-like configuration. The new phase has a more complex structure than the known orthorhombic modification. The arrangement of heavy Pb and I atoms follows a’ = a/3 pseudoperiodicity. In the layers of two types that form sheets parallel to the ab plane, Pb and I atoms have different coordinations. A polytypic nature of the new modification is responsible for the one-dimensional disordering along the a axis as well as different variants of layer alternation. It is possible to obtain crystals of acentric and polar derivatives of the centrosymmetric phase that will be promising for application.     

K8Gd3Si12O32Cl · 2H2O,a new member of the family of porous silicates with K and RE elements

Crystals of K₈Gd₃Si₁₂O₃₂Cl · 2H₂O (space group $P\bar 1$ ), a new member of the family of porous silicates containing rare earths, are obtained under hydrothermal conditions. The structure retains the main features of the family in which original one-story layers of Si-tetrahedra formed by 6-membered rings of two types and large-in-diameter 8-membered and 12-membered rings are bound by Gd-octahedra to form a framework. Large pores in the interlayer space of the mixed framework are filled with K⁺ ions. The penetration of Cl^? ions from a concentrated mineralizing solution into the centers of the eight-membered rings of the layer corroborates the ion-exchanging properties of the crystals of this structural type. The filling of rings and pores of different types in different members of the family by K⁺ and Cl^? ions, hydroxyl groups, and water molecules is analyzed.     

Simulation of chemical metabolism for fate and hazard assessment. V. Mammalian hazard assessment

Animals and humans are exposed to a wide array of xenobiotics and have developed complex enzymatic mechanisms to detoxify these chemicals. Detoxification pathways involve a number of biotransformations, such as oxidation, reduction, hydrolysis and conjugation reactions. The intermediate substances created during the detoxification process can be extremely toxic compared with the original toxins, hence metabolism should be accounted for when hazard effects of chemicals are assessed. Alternatively, metabolic transformations could detoxify chemicals that are toxic as parents. The aim of the present paper is to describe specificity of eukaryotic metabolism and its simulation and incorporation in models for predicting skin sensitization, mutagenicity, chromosomal aberration, micronuclei formation and estrogen receptor binding affinity implemented in the TIMES software platform. The current progress in model refinement, data used to parameterize models, logic of simulating metabolism, applicability domain and interpretation of predictions are discussed. Examples illustrating the model predictions are also provided.     

Partial automorphisms and injective partial endomorphisms of a finite undirected path

Semigroup Forum - In this paper, we study partial automorphisms and, more generally, injective partial endomorphisms of a finite undirected path from Semigroup Theory perspective. Our main...     

Novel K/Mn phosphate hydrates,K2Mn3(H2O)2[P2O7]2 and KMn(H2O)2[Al2(PO4)3]: hydrothermal synthesis and crystal chemistry

Two novel K/Mn phosphate hydrates, namely, dipotassium trimanganese dipyrophosphate dihydrate, K₂Mn₃(H₂O)₂[P₂O₇]₂, (I), and potassium manganese dialuminium triphosphate dihydrate, KMn(H₂O)₂[Al₂(PO₄)₃], (II), were obtained in the form of single crystals during a single hydrothermal synthesis experiment. Their crystal structures were studied by X‐ray diffraction. Both new compounds are members of the morphotropic series of phosphates with the following formulae: A₂M₃(H₂O)₂[P₂O₇]₂, where A = K, NH₄, Rb or Na and M = Mn, Fe, Co or Ni, and AM²⁺(H₂O)₂[M³⁺₂(PO₄)₃], where A = Cs, Rb, K, NH₄ or (H₃O); M²⁺ = Mn, Fe, Co or Ni; and M³⁺ = Al, Ga or Fe. A detailed crystal chemical analysis revealed correlations between the unit‐cell parameters of the members of the series, their structural features and the sizes of the cations. It has been shown that a mixed type anionic framework is formed in (II) by aluminophosphate [(AlO₂)₂(PO₄)₂]_∞ layers, with a cationic topology similar to the Si/Al‐topology of the crystal structures of feldspars. A study of the magnetic susceptibility of (II) demonstrates a paramagnetic behaviour of the compound.