Poly(vinyl alcohol)-induced thixotropy of an l-carnosine-based cytocompatible, tripeptidic hydrogel.

The generally poor mechanical stability of hydrogels limits their use as functional materials for many biomedical applications. In this work, a poly(vinyl alcohol) (PVA) embedded hybrid hydrogel of a ß-amino acid-containing Fmoc-protected tripeptide was produced at physiological pH (7.4) and room temperature. The hydrogel system was characterized by a number of techniques, including UV-vis, fluorescence, circular dichroism, FT-IR spectroscopy, electron microscopy, and rheology. While the tripeptide-based pure hydrogel was found to be unstable after ca. half an hour, addition of PVA, a water soluble polymer, increased the temporal and mechanical stability of the hydrogel. A rheological step-strain experiment demonstrates that the peptide-polymer hydrogel is thixotropic. Results from a fluorescence probe study and transmission electron microscopy reveal that addition of PVA increases both the fibre diameter and entanglement. Circular dichroism spectra of the hydrogels confirm the formation of aggregates with supramolecular chirality. The thixotropic nature of the hydrogel has been exploited to entrap and release doxorubicin, an anticancer drug, under physiological conditions. Furthermore, an MTT assay of the Fmoc-tripeptide using AH927 cells confirmed its cytocompatibility, which broadens the utility of the hybrid gel for biomedical applications.

[Biological characteristics of microorganisms for prognosis of trophic ulcers course].

AIM: To substantiate the possibility to use the biological characteristics of microorganism, in particular, factors of its persistence, for assessment of severity of trophic ulcers of lower extremities. MATERIALS AND METHODS: Clinical examinations and bacteriological tests of 48 patients aged from 37 to 80 years with trophic ulcer of lower limbs were performed. Antilysozyme, anticomplement, anticarnosine as well as hemolytic activity of isolated microorganisms were assessed. RESULTS: It was established that microflora of trophic ulcers of lower limbs are diverse and microorganisms were isolated both in monoculture and in associations, with maximal significance of Staphylococcus aureus. Analysis of biological properties of microflora isolated in patients with various courses of trophic ulcers of lower limbs allowed to determine roles of antilysozyme, anticomplement, anticarnosine and hemolytic activities in severity of the illness. CONCLUSION: Performed studies allowed to develop diagnostic models for prediction of severity course of trophic ulcers of lower limbs.

[Diagnostic value of persistent characteristics of staphylococci during their carriage].

Comparative assessment of information value of significant persistent characteristics of staphylococci in state of carriage was made, and the usefulness of these characteristics for creating diagnostic models was defined. One hundred and fifty strains of Staphylococcus aureus and S. epidermidis isolated from healthy persons with subsequent differentiation of carriage types were used in the study. It has been established that strains isolated from resident carriers more often have more markedly expressed factors of persistence. Ranking the factors of persistence of staphylococci according to their information value during carriage allowed to identifythe leading sign among them--anti-carnosine activity. Using factor analysis, obtained signs were united in the single complex defining bacterial carriage, which allows to build a mathematical model permitting to diagnose staphylococcal carriage with 95% probability.

[Anticarnosine activity of staphylococci as a criterion for assessment of their persistence potential].

The analysis on clinical material and the use of experimental models allowed to prove the role of anticarnosine activity of staphylococci in their persistence. Light and electronic microscopy revealed large destruction of ultrastructural eukaryote components and decreased proliferative activity in animals challenged with strains characterized by high anticarnosine activity. Adaptive mechanisms, providing dynamic equilibrium in "eukaryote--prokaryote" system, are described.

[Biological importance of the anti-carnosine activity of bacteria]. / Biologicheskoe znachenie antikarnozinovoi aktivnosti bakterii.

The anticarnosine activity has been found to be widely spread among bacteria, the degree of its manifestation depending on the source of isolation. The fact that anticarnosine activity plays a certain role in the phenomenon of persistence has been proved on the model of experimental staphylococcal infection in rats.

Effect of essential trace metal on bone metabolism in the femoral-metaphyseal tissues of rats with skeletal unloading: comparison with zinc-chelating dipeptide.

The effect of essential trace metals on bone metabolism was investigated in the femoral-metaphyseal tissues obtained from skeletal-unloaded rats. Skeletal unloading was designed by using the model of hindlimb suspension in rats; the animals were fed for 4 days with the unloading. Femoral-metaphyseal tissues were cultured for 24 hours in a medium containing either vehicle (control), nickel, manganese, cobalt, copper, zinc, or zinc-chelating dipeptide (beta-alanyl-L-histidinato zinc; AHZ) in the concentration range of 10(-6) to 10(-4) M. Bone biochemical components (alkaline phosphatase activity, glucose consumption, and DNA content) were significantly decreased by skeletal unloading. The presence of zinc sulfate or AHZ (10(-5) and 10(-4) M) caused a significant increase of alkaline phosphatase activity in the bone tissues from unloaded rats. This effect was not seen by nickel, manganese, cobalt and copper (10(-6) to 10(-4) M). The culture medium glucose was clearly consumed by the bone tissues. This consumption was inhibited by nickel, manganese, or copper (10(-5) and 10(-4) M), while cobalt, zinc, and AHZ had no effect. DNA content in the bone tissues from unloaded rats was significantly increased by all metal compounds (10(-5) M). The effect of AHZ on bone components was greater than zinc sulfate. The AHZ (10(-5) M)-increased alkaline phosphatase activity in the bone tissues from unloaded rats was clearly blocked by the presence of cycloheximide (10(-6) M), staurosporine (10(-7) M), dibucaine (10(-4) M), or okadaic acid (10(-7) M). The present study demonstrates that, of various essential trace metals, zinc compounds have an unique anabolic effect on bone metabolism in the femoral-metaphyseal tissues of rats with skeletal unloading. Zinc-chelating dipeptide may stimulate bone protein synthesis through the mechanism that is involved in protein kinases.