Comparative Structure-Property Characterization of Poly(3-Hydroxybutyrate-Co-3-Hydroxyvalerate)s Films under Hydrolytic and Enzymatic Degradation: Finding a Transition Point in 3-Hydroxyvalerate Content

The hydrolytic and enzymatic degradation of polymer films of poly(3-hydroxybutyrate) (PHB) of different molecular mass and its copolymers with 3-hydroxyvalerate (PHBV) of different 3-hydroxyvalerate (3-HV) content and molecular mass, 3-hydroxy-4-methylvalerate (PHB4MV), and polyethylene glycol (PHBV-PEG) produced by the Azotobacter chroococcum 7B by controlled biosynthesis technique were studied under in vitro model conditions. The changes in the physicochemical properties of the polymers during their in vitro degradation in the pancreatic lipase solution and in phosphate-buffered saline for a long time (183 days) were investigated using different analytical techniques. A mathematical model was used to analyze the kinetics of hydrolytic degradation of poly(3-hydroxyaklannoate)s by not autocatalytic and autocatalytic hydrolysis mechanisms. It was also shown that the degree of crystallinity of some polymers changes differently during degradation in vitro. The total mass of the films decreased slightly up to 8-9% (for the high-molecular weight PHBV with the 3-HV content 17.6% and 9%), in contrast to the copolymer molecular mass, the decrease of which reached 80%. The contact angle for all copolymers after the enzymatic degradation decreased by an average value of 23% compared to 17% after the hydrolytic degradation. Young's modulus increased up to 2-fold. It was shown that the effect of autocatalysis was observed during enzymatic degradation, while autocatalysis was not available during hydrolytic degradation. During hydrolytic and enzymatic degradation in vitro, it was found that PHBV, containing 5.7-5.9 mol.% 3-HV and having about 50% crystallinity degree, presents critical content, beyond which the structural and mechanical properties of the copolymer have essentially changed. The obtained results could be applicable to biomedical polymer systems and food packaging materials.

Dual role of interleukin-10 in the regulation of respiratory syncitial virus (RSV)-induced lung inflammation

RSV lower respiratory tract infections (LRTI) are among the most common diseases necessitating hospital admission in children. In addition to causing acute respiratory failure, RSV infections are associated with sequelae such as secondary bacterial infections and reactive airway disease. One characteristic host response observed in severe RSV-induced LRTI and/or subsequent development of asthma is increased expression of interleukin (IL)-10. However, contradictory results have been reported regarding whether IL-10 inhibits asthmatic responses or intensifies the disease. We aimed to reconcile these discordant observations by elucidating the role of IL-10 in regulating the host response to RSV LRTI. In this study, we used a lung-specific, inducible IL-10 over-expression (OE) transgenic mouse model to address this question. Our results showed that the presence of IL-10 at the time of RSV infection not only attenuated acute inflammatory process (i.e. 24 h post-infection), but also late inflammatory changes [characterized by T helper type 2 (Th2) cytokine and chemokine expression]. While this result appears contradictory to some clinical observations where elevated IL-10 levels are observed in asthmatic patients, we also found that delaying IL-10 OE until the late immune response to RSV infection, additive effects rather than inhibitory effects were observed. Importantly, in non-infected, IL-10 OE mice, IL-10 OE alone induced up-regulation of Th2 cytokine (IL-13 and IL-5) and Th2-related chemokine [monocyte chemoattractant protein 1 (MCP-1), chemokine (C-C motif) ligand 3 (CCL3) and regulated upon activation normal T cell expressed and secreted (RANTES)] expression. We identified a subset of CD11b(+)CD11c(+)CD49b(+)F4/80(-)Gr-1(-) myeloid cells as a prinicipal source of IL-10-induced IL-13 production. Therefore, the augmented pathological responses observed in our 'delayed' IL-10 over-expression model could be attributed to IL-10 OE alone. Taken together, our study indicated dual roles of IL-10 on RSV-induced lung inflammation which appear to depend upon the timing of when elevated IL-10 is expressed in the lung.

Effects of physicochemical forms of phenazepam and Panavir on their action at ultra-low doses

A concept of physicochemical forms of biologically active substances introduced in investigation of the action mechanism of ultra-low doses allows qualitative explanation of the main effects of ultra-low doses, chemical diversity of biologically active substances, and physical boundaries for these effects. Phenazepam was shown to possess activity in ultra-low doses only in disperse state, in the form of nanoparticles with a diameter <100-300 nm; these nanoparticles appear as micelles of surface active substances and solvated. Panavir possesses pharmacological activity in ultra-low doses and appears as nanoparticles with a diameter of 200-300 nm, which have uncompensated negative surface charge and polymer nature.

Inhibition of stem cell factor reduces pulmonary cytokine levels during allergic airway responses

Stem cell factor (SCF) has a significant role in the inflammation and activation of allergic airway responses. When monoclonal anti-SCF was administered intratracheally during allergen challenge there was a significant alteration of eosinophil accumulation and airway hyperreactivity (AHR). Anti-SCF treatment also attenuated pulmonary cytokine and chemokine levels. In particular, there was an antibody dose-dependent decrease in interleukin (IL)-5 and tumour necrosis factor (TNF)-alpha. There was also a significant reduction of CCL2 and CCL5, which correlated with the reduction in AHR. Mice treated with anti-SCF demonstrated a significant decrease in pulmonary gob-5 gene expression, which has been shown to correlate to goblet cell hyperplasia/metaplasia relating to airway mucus production. Blocking SCF-mediated activation within the airway using a monoclonal antibody indicates that this cytokine may represent a viable target for therapeutic intervention that could affect multiple aspects of allergen-induced immunopathology.

Role of interleukin-12 and stat-4 in the regulation of airway inflammation and hyperreactivity in respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a respiratory pathogen that can cause significant morbidity in infants and young children. Interestingly, the majority of children who acquire a RSV infection do not exhibit severe symptoms. Development of a Th1 response has been associated with resolution of symptoms in viral infections and may explain mild RSV illness. The current study investigated the cytokine response observed in mild disease in C57BL/6 mice that had low airway resistance and mucus production with little pulmonary inflammation. RSV infection in these mice was accompanied by a fourfold increase in interleukin-12(IL-12). Treatment of RSV-infected mice with anti-IL-12 resulted in an increase in airway hyperreactivity, mucus production, and airway inflammation (eosinophilia). Since IL-12 activation is dependent on Stat-4-mediated intracellular signal transduction, similar experiments were performed in Stat-4 deficient mice and demonstrated similar results to those obtained from anti-IL-12 treated mice. Again, there was an increase in airway hyperreactivity and mucus production, and goblet cell hypertrophy. These studies support the importance of IL-12 in the immune response to RSV infection resulting in resolution of disease and protection from inappropriate inflammatory responses.

Suspension Flocculation by Polyelectrolytes: Experimental Verification of a Developed Mathematical Model

Using experimental data of AgI sol and poly(2-methyl-5-vinylpyridine) chloride, we show that there is good agreement between the developed mathematical model of suspension flocculation by polyelectrolytes and the experimental data. The rate constants of bridging and nonbridging aggregation of particles and of floc breakup, as well as their ratios, have been determined. It has been shown that the role of the nonbridging mechanism, as compared with that of the bridging one, diminishes when molecular mass of polyelectrolyte increases from 1.4 x 10(5) to 9.3 x 10(5).

[Characteristics of the functional state of the skin of humans in an enclosed environment with limited space]

Changes in man's skin that may influence its protective function were investigated depending on the environmental conditions. Man's exposure to a small sealed environment produced serious changes in the skin. As a result of 90-day enclosure, the desquamation rate and lipid concentration in the skin almost doubled, pH increased by unity, and its biological activity expressed by the redox potential (eH) diminished by nearly 100%. Thus the protective function of man's skin declined significantly after such exposure.

[Protective function of the skin]

This paper reviews published data concerning the protective function of skin and discusses factors that may affect its bactericidal capability, including space flight factors that are known to reduce its protective effect. Various concepts of the mechanisms of the bactericidal function are discussed. It is shown that in an enclosed environment the species composition of the resident autoflora and pH value of the skin of an essentially healthy man may change. The qualitative composition of the water-oil film as a source of nutrition and a skin microflora environment is discussed. Its effect on the autoflora composition and localization in various skin areas and, consequently, on the bactericidal capability of different skin areas is described. The skin bactericidal function results from an interaction of various factors that should be taken into consideration when developing flight-oriented hygienic requirements because space flight induces changes in the skin status.

[Substantiation of the system of sanitary-hygienic procedures]

Various aspects of endogenous contamination of the human skin are discussed. The contamination rate and intensity were measured by analyzing wash water obtained after sanitary-hygienic procedures (SHP) in which no detergents were used. It was found that endogenous contamination of the human skin reached its maximum 3-4 days after the previous SHP and then became stabilized. The wash water composition was shown to be independent of the skin type. The endogenous contamination level did not influence the bactericidal effect of the skin of healthy people. Due to complementary processes such as epidermis desquamation and sebum cutaneum, the role of which is different for different skin types, the amount of indigenous microorganisms is maintained at an optimal level irrespective of the skin type. It is concluded that water SHPs should be performed no more than once every four days. If they are conducted oftener than that, the normal function of the human skin may become deteriorated: epidermis desquamation increases drastically, skin state changes, and the concentration of indigenous microorganisms on the skin surface decreases as compared to the individual norm.

[Hygienic aspects of wash water reclamation systems]

The quality of reclaimed wash water and the composition of used wash water can be best determined by pH, oxygen chemical index, electric conductivity and chlorides that show individual variations but are sex-independent. Wash water contained mostly staphylococci and small amounts of sarcines, diplococci and micrococci. The use of washing and disinfecting agents may significantly modify the microbial characteristics of wash water, reducing noticeably its microbial content and increasing the content of organic substances and chlorides due to chemicals they include and due to more effective removal of sebaceous secretion. It is indicated that chemical components of washing and disinfecting agents that produce organic contaminants should be given special attention when developing a wash water reclamation system.

[Composition of the water obtained after its sanitary and hygienic use by men and women]

The composition of wash water used by men and women was investigated. The results were exposed to multifactorial statistical analysis using the method of principal components. The investigation allowed the following conclusions to be made: 1) wash water used by men and women is comparable in composition; therefore the sex of the crewmembers of space vehicles can be disregarded when designing water reclamation systems; 2) three parameters, viz. oxidizability, electric conductivity and chloride content, can be adequately used to assess the quality of utilized wash water; 3) the composition of wash water is largely dependent on the health status of its users.