[Effect of hypothyroidism on the structural and functional characteristics of the sarcoplasmic reticulum of rabbit skeletal muscles]. / Vliianie gipotireoza na strukturnye i funktsional'nye kharakteristiki sarkoplazmaticheskogo retikuluma skeletnykh myshts krolika.

Structural and functional characteristics of sarcoplasmic reticulum vesicles (SRV) from skeletal muscle of normal and hypothyroid rabbits were investigated. The rate of Ca2+ absorption was decreased in hypothyroid animals and Ca2-ATPase activity in SRV of these animals was lower than that of control rabbits. The transport ratio (Ca2+/ATP) in hypothyroid rabbits was higher by 20% than in controls. In SRV of hypothyroid animals a decrease in the protein/lipid interaction and higher fluidity of membrane lipids were observed. Administration of L-thyroxine (300 mg/kg of body mass, intraperitoneally) normalized the SR lipids fluidity within about 40 hrs after the injection but did not affect significantly the patterns of protein/lipid interaction. Normal and hypothyroid SRV were similar in their protein spectrum as shown by electrophoresis in polyacrylamide gel. These alterations observed in the SRV structure and function are apparently related to modifications of membrane lipids.

[Changes in spatial organization in sarcoplasmic reticulum membranes in rabbits with experimental thyrotoxicosis]. / Izmenenie prostranstvennoi organizatsii v membranakh sarkoplazmaticheskogo retikuluma pri éksperimental'nom tireotoksikoze krolikov.

The structure of sarcoplasmic reticulum membranes (SR) of skeletal muscles from normal and thyrotoxic rabbits was studied with the use of the fluorescent probe pyrene. It was found that protein globules in SR preparations of thyrotoxic animals were submerged into the lipid bilayer to a greater extent than in the reticulum of normal animals. Electrophoresis in polyacrylamide gel revealed no detectable differences between SR of normal and thyrotoxic rabbits. The ratio protein/lipid in SR membranes remained 2:1 in rabbits with thyrotoxicosis.

[Stoichiometric protein-lipid interactions in liver microsomal membranes measured by the induction-resonance energy transfer method]. / Issledovanie s pomoshch'iu induktivno-rezonansnogo perenosa énergii prostranstvennykh vzaimootnoshenii mezhdu belkami i lipidami v membranakh mikrosom pscheni.

The stoichiometry of proteins and lipids in the microsomal membranes of the liver were studied by the induction-resonance energy transfer method. The energy was transferred between the fluorescent tryptophane residues of membrane proteins and fluorescent probes (pyrene and 4-dimethylaminochalcone) located in the microsomal lipid bilayer. It was assumed that the rate of protein fluorescence is correlated with protein mass. All microsomal proteins were arbitrarily divided into two groups, i.e. proteins located at a distance of more ("peripheral" proteins) and less than 30 A from the lipid bilayer surface. The former proteins made up to 14-24% of total microsomal protein, while microsomal ghosts--less than 10%. In the microsomes the bulk of other proteins is located at an average distance of about 19-26 A from the lipid bilayer surface, while the grosts--at about 4-9 A. Treatment of the ghosts with pronase results in approximation of the protein mass locus with the lipid by about 5 A. In this way the generation of ghosts and their treatment with pronase cause a loss of proteins predominantly from the peripheral parts of the microsomal membrane.

[Use of fluorescent probes for detecting structural reorganizations in the membranes of the hepatic endoplasmic network during the maintenance of rats on an atherogenic diet]. / Ispol'zovanie fliuorestsentnykh zondov dlia vyiavleniia strukturnykh perestroek v membranakh éndoplazmaticheskoi seti pecheni pri soderzhanii krys na aterogennoi diete.

Prolonged feeding of rats with a full-value semi-synthetic diet or diet enriched with cholesterol provoked material changes in the lipid content (the molar ratio of cholesterol/phospholipids) in the liver endoplastic reticulum, in the functional activity (the activity of the membrane-bound glucoso-6-phosphatase) and in the physical structure of the membranes. The changes were detected by means of the fluorescent probes (pyrene, 4-dimethylaminochalcone, 1-anilinonaphthalene-8-sulfonate). All the changes were more pronounced in liver microsomes of rats fed with the atherogenic diet. Fluorescence of the probes in microsomes and in model lipid membranes (liposomes) containing varying amount of cholesterol was compared to find that in vivo changes in the physical properties of microsomal membranes do not completely reduce to the effects consequent on membrane enriching with cholesterol.

[Effect of peroxidation on the physical structure of phospholipid membranes]. / Vliianie perekisnogo okisleniia na fizicheskuiu strukturu fosfolipidnykh membran.

Peroxidation of lipids caused rearrangements in physical structure of biomembranes as it was shown by a method of fluorescent probes. These structural rearrangements were accompanied by an increase in the viscosity on the surface and in the depth of the phospholipid bilayer. The increase in the viscosity was apparently due to oxidation and to elimination from the phospholipid bilayer of the unsaturated fatty acid residues. Presence of the unsaturated fatty acids in biomembranes decreases their viscosity. The fraction of saturated fatty acids after peroxidation was respectively increased in the bilayer.

[Partial fractionation and physico-chemical properties of non-histone chromatin proteins]. / Chastichnoe fraktsionirovanie i fiziko-khimicheskie svoistva negistonovykh belkov khromatina.

The non-histone chromatin proteins (NHP) were isolated by a modified Wang technique. NHP were easily dissoluble in solutions of a physiological ionic strength within a wide pH range. NHP were subdivided into 18 zones by analytical polyacrylamide gel electrophoresis. NHP have molecular weights within the range 15,000 greater than 200,000. A part of NHP showed similar molecular weight but different values of molecular charge. NHP were separated by a gel filtration into 6 fractions. Two fractions were individual proteins. The great bulk of NHP has a molecular weight less than 40,000, and 6-6.5% of NHP-more than 100,000. The fractions different from each other in a specific UV-absorbtion, fluorescence and circular dichroism. The nhp fraction of a smaller molecular weight has a smaller content of alpha-helix (8%) and the greatest polarity of the environment of tryptophan residues; the molecules of this fraction may have a loose tertial structure. Other NHP have 15-24% of alpha-helix and possibly have compact globular sites.

[Isolation of rat liver chromatin non-histone protein]. / Vydelenie negistonovykh belkov khromatina pecheni krys

A chromatin with the protein/DNA ratio of 3.0 was obtained from rat liver cells nuclei. The chromatin was dissolved in 2 M NaCl, pH 7, and reprecipitated by decreasing the ionic strength to 0.4 and increasing pH to 9.0. A fraction of non-histone proteins (NH-1) remained in a supernatant solution, the NH-1/DNA ratio being equal to 1.3 and the ratio of acidic to basic aminoacid residues equal to 1.31. After chromatography on Bio-Rex 70 cation-exchang resin, a fraction (NH-2) with the NH-2/DNA ratio of 1.0 +/- 0.15 and the ratio of acidic to basic aminoacid residues of 1.57 was obtained. According to the data of polyacrylamide gel electrophoresis, the NH-2 fraction contained 2.7% of histone f2 + f3 as an admixture whereas histone f1 was not revealed.

[Application of x-ray analysis for the study of the orientation in DNP films]. / Rentgenograficheskoe izuchenie orientatsii v plenkakh DNP

A planar texture in dried film samples of DNP was found by X-ray study. Axes of DNA macromolecules are located in the film plane and the 77 A reflection is directed along this axis. Periodic structures corresponding to 55 and 34 A are packed parallel to the film plane. The results obtained do not contradict with a supercoil DNP model, however they all allow other possible packing models of DNP molecules, in particular, histone layers alternating with DNA layers in oriented films.