Photoconversion of 7-dehydrocholesterol to vitamin D3 in synthetic phospholipid bilayers

The incorporation of 7-dehydrocholesterol into synthetic phospholipid bilayers altered the distribution of products after photolysis. In liposomes, the relative amounts of 7-dehydrocholesterol and lumisterol were elevated, and tachysterol was reduced from the levels observed in hexane solution. Z to E isomerization of the previtamin to tachysterol is favored in organic solvents. The inhibition of this process is evidence that an ordered lipid matrix places a new constraint on the conformation of the ring B fission product--one in which the configuration is favorable for a return to a cyclized diene. Further, rate enhancements of up to 15-fold were observed for the thermal isomerization of the previtamin to vitamin D3 in liposomes. The free energies of activation for the reaction at 25 degrees C were reduced by 1.3-1.5 kcal/mol in the bilayer environment compared to that of hexane. As this reaction involves the concerted transfer of a hydrogen via a cyclic intermediate, it provides additional evidence for membrane stabilization of an all-cis conformation of the previtamin. Photoproduct ratios were also studied for 7-dehydrocholesterol adsorbed to a variety of solid supports. That nonspecific interactions of 7-dehydrocholesterol with lipid can influence product formation may have important implications with respect to the mechanism of vitamin D3 biosynthesis.     

Effect of psychotropic substances on the development of alcoholic motivation in noninbred white rats

The experiments have shown the capacity of antidepressant amitriptylin (0.5 mg/kg, i. p.) and tranquilizer phenazepam (0.1 mg/kg i. p.) to normalize the adaptive behaviour and almost completely prevent the development of alcohol motivation in animals with insufficient adaptive behaviour. It was established that in animals initially rejecting alcohol, chronic treatment with these drugs as well as d-amphetamine promoted alcohol motivation. The results obtained have proved our earlier hypothesis that preclinical search for drugs for the prevention and treatment of early stages of alcoholism is possible only in animals pre-selected according to their inclination to experimental alcoholism.     

Demonstration of the presence of G-proteins in hepatic microsomal fraction

The presence of G-proteins in isolated hepatic microsomal vesicles is demonstrated. The G-proteins were identified by their capacity to be ADP-ribosylated by cholera and pertussis toxins. Cholera toxin identified 42 and 45 kDa proteins, corresponding to alpha s-1 and alpha s-2, respectively. Pertussis toxin identified a 40 kDa protein corresponding to alpha i. The microsomal G-proteins are identical to the corresponding G proteins of the plasma membrane, but are present in different proportions; the microsomes have considerably less alpha s proteins than the plasma membrane.     

Cyclic nucleotide alterations in mixed leukocyte reaction: a preliminary report

Endogenous cyclic adenosine and guanosine monophosphate (cAMP, cGMP) levels were studied in human peripheral blood lymphocytes during mixed leukocyte reactions (MLR). cAMP level was consistently elevated in one-way MLR, with good correlation to 3H-thymidine uptake in these reactions. In contrast, cGMP level was practically unchanged. Irradiation of reacting cell populations resulted in inhibition of cyclic nucleotide phosphodiesterase (PDE) activity. These results suggest that metabolic alterations in cAMP may be associated with immune reactions of cellular recognition.     

Serum Agglutination and Immunoglobulin Levels of Mice Infected with Naegleria fowleri1

Agglutinins were not detected in sera from mice given one, two, or three intranasal (i.n.) inoculations or a single intravenous (i.v.) inoculation of trophozoites of Naegleria fowleri. However, agglutinins were produced following second and third i.v. inoculations. Serum immunoglobulin levels increased in both i.n.- and i.v.-inoculated mice. IgG and IgM increased substantially more for i.v.-inoculated mice. IgA levels increased more consistently for i.n.-inoculated mice.     

A comparison of the respiratory chain in particles from Paracoccus denitrificans and bovine heart mitochondria by EPR spectroscopy

A study is presented on the EPR characteristics of the paramagnetic groups in the respiratory chain present in membrane particles of Paracoccus denitrificans, the respiratory system of which is very similar to that in submitochondrial particles from beef heart. All paramagnetic prosthetic groups of the mitochondrial system are also found in the bacterial plasma membrane. Their properties suggest that the respiratory groups are embedded in very similar protein environments in the two systems.