Preferential interactions of fluorescent probe Prodan with cholesterol

The fluorescent probe Prodan has been widely used as a probe of model and biological membranes. Its fluorescent maxima in phospholipid bilayers vary as a function of phase state, with maxima at 485 for the liquid crystal Lalpha, 435 nm for the gel L'beta, and 507 nm for the interdigitated gel LbetaI phase, with excitation at 359 nm. These spectral changes have been used for the detection of phase changes among these phases. In the present study, the fluorescent properties and partition coefficients of Prodan in model membranes of phosphatidylcholines and phosphatidylethanols have been studied as a function of lipid phase state and cholesterol content. It is shown that the Prodan spectrum in the presence of cholesterol no longer reflects the known phase state of the lipid; in each phase state, the presence of cholesterol leads to a spectrum with the maximum at 435 nm, characteristic of the noninterdigitated gel phase. The partition coefficient of Prodan into these lipids also varies with the phase state, giving values of 0.35 x 10(4) in the interdigitated gel, 1.8 x 10(4) in the noninterdigitated gel, and 7. 6 x 10(4) in the liquid crystal phase. In the presence of cholesterol these partition coefficients are increased to 13 x 10(4) for the liquid crystal and the gel phase, and 5.1 x 10(4) in the presence of 100 mg/ml ethanol. These results suggest that Prodan has preferential interactions with cholesterol, and is thus not a randomly distributed fluorescent reporter probe in membranes containing cholesterol. These results suggest that Prodan should be used only with great caution in complex lipid mixtures, particularly biological membranes.     

The Cr−Re phase diagram

The phase diagram for the Cr−Re system has been derived from published data in conjunction with measurements on alloys cast and annealed at subsolidus temperatures (XRD, metallography, microprobe analysis, and measurement of the temperature for the onset of melting by the Pirani—Alterthum method). The phase equilibria at solidus temperatures have been determined from studies on alloys annealed at those temperatures. Phase homogeneity regions on the solidus have been identified: for (Cr) up to 43 at.% Re, for the σ phase −50–72 at.%Re, and for (Re) up to 17 at.%Cr; temperatures have also been determined for the invariant equilibria L+σ ⇆ (Cr) at 2150±15°C and L+(Re)⇆σ at 2335±15°C. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 65–71, March–April, 1999.     

Phase equilibria in the nickel corner of the Mo-Ni-B system at temperatures close to melting

The Mo-Ni-B alloys prepared by arc-melting are examined in as-cast and annealed states using x-ray diffraction, scanning electron microscopy with electron probe microanalysis, and differential thermal analysis. The temperatures of invariant equilibria are refined. The projections of liquidus and solidus surfaces are plotted for the Ni-rich region.     

Clinical manifestations and treatment of intestinal dysbacteriosis in patients with Flexner's dysentery

Flexner's dysentery is often accompanied with intestinal dysbacteriosis. Disbiotic changes in the intestine contribute to specific shigella endotoxins entering blood flow thus prolonging clinical symptoms of the underlying disease. Administration of bacterial biological preparations (bifidumbacterin forte, lactobacterin) relieves specific endotoxemia, reduces the duration of the disease and has an immunomodulating action.     

Recommendations for reducing mortality among workers of mining enterprises

The authors elaborated measures aimed to lower mortality and higher life expectancy among workers of able-bodied age. The recommendations involve changes in technology of drift mining, improved electric safety of technologic equipment, annual analysis of mortality parameters among miners, accomplishment of prophylactic recommendations on treatment of functional cardiovascular disorders, provision of workers with pectin as a therapeutic and prophylactic nutrient.     

Activity pulses induce spontaneous flow reversals in viscoelastic environments

Complex interactions between cellular systems and their surrounding extracellular matrices are emerging as important mechanical regulators of cell functions, such as proliferation, motility and cell death, and such cellular systems are often characterized by pulsating actomyosin activities. Here, using an active gel model, we numerically explore spontaneous flow generation by activity pulses in the presence of a viscoelastic medium. The results show that cross-talk between the activity-induced deformations of the viscoelastic surroundings and the time-dependent response of the active medium to these deformations can lead to the reversal of spontaneously generated active flows. We explain the mechanism behind this phenomenon based on the interaction between the active flow and the viscoelastic medium. We show the importance of relaxation time scales of both the polymers and the active particles and provide a phase space over which such spontaneous flow reversals can be observed. Our results suggest new experiments investigating the role of controlled pulses of activity in living systems ensnared in complex mircoenvironments.     

System analysis of the efficiency and competitiveness of chroming technologies

The scientifically based selection of efficient chemical technologies is related to the integrated assessment of indicators of their energy and resource efficiency and environmental safety, as well as indicators of the quality of products. The authors conducted systematic analysis of the efficiency and competitiveness of two electrochemical technologies of chroming from the solutions based on chromium salts of different valences. The strengths and weaknesses of each technology have been defined using the methodology of SWOT analysis, and the defined qualitative indicators of the efficiency of technologies have been determined using the methods of nonparametric statistics.