Bound Magnetic Polaron Interactions in Insulating Doped Diluted Magnetic Semiconductors

The magnetic behavior of insulating doped diluted magnetic semiconductors (DMS) is characterized by the interaction of large collective spins known as bound magnetic polarons. Experimental measurements of the susceptibility of these materials have suggested that the polaron-polaron interaction is ferromagnetic, in contrast to the antiferromagnetic carrier-carrier interactions that are characteristic of nonmagnetic semiconductors. To explain this behavior, a model has been developed in which polarons interact via both the standard direct carrier-carrier exchange interaction (due to virtual carrier hopping) and an indirect carrier-ion-carrier exchange interaction (due to the interactions of polarons with magnetic ions in an interstitial region). Using a variational procedure, the optimal values of the model parameters were determined as a function of temperature. At temperatures of interest, the parameters describing polaron-polaron interactions were found to be nearly temperature-independent. For reasonable values of these constant parameters, we find that indirect ferromagnetic interactions can dominate the direct antiferromagnetic interactions and cause the polarons to align. This result supports the experimental evidence for ferromagnetism in insulating doped DMS.Comment: 11 pages, 7 figure

Uptake of cholesterol esters being a part of the different fractions of blood plasma lipoproteins by rats organs and tissues

The paper deals with the functions of the main classes of blood plasma lipoproteins (LP) that are associated with the transport of cholesterol esters included in their composition. The aim of the study was to investigate the features of the uptake of cholesterol esters associated with plasma LP fractions (very low (VLDL), low (LDL), and high density LPs (HDL)) by rat organs and tissues, and to show the participation of various subfractions of HDL (HDL2 and HDL3) as specific cholesterol carriers in the main steroid-producing organs of rats.Material and methods. The in vivo studies with intravenous LP injection of 14C labeled cholesterol oleate (14C-OCh) associated with plasma LP fractions have been carried out.Results. Intravenous injection of a 14C-OCh) in the composition with VLDL led to the maximal mark uptake by the liver. Three times less uptake of labeled cholesterol was observed in the adrenal glands, testes and heart muscle. In other tissues radioactivity gradually decreased in the raw: spleen > lungs > kidneys > thyroid gland and adipose tissue. After the injection of 14C-OCh in the composition of LDL marked predominant uptake of the label by the adrenal glands, testes, and liver. A feature of the use of HDL as a carrier platform for 14C-OCh is the high accumulation of label in steroid-producing organs: the adrenal glands and testis. The dynamics of uptake of 14C-OCh in the composition of HDL by the adrenal glands and testes of rats in different time intervals after injection (30 min, 3, 6 and 12 h) was studied. Adrenal cells actively uptake 14C-OCh from HDL, as a result of which the radioactivity of the tissue increased rapidly and after 30 minutes almost reached its maximum. In contrast to the adrenal glands uptake of the testis was characterized by a gradual increase in radioactivity with a maximum of 6 hours and a rather sharp decrease to 12 hours from the beginning of the experiment. In vitro experiments showed the differences in the effect of HDL2 and HDL3 on the corticosterone production by the adrenal glands of rats.Conclusions. The paper presents the features of uptake of cholesterol esters by organs and tissues of rats depending on the used LP-transporter (VLDL, LDL, HDL). In addition, the results suggest that HDL3 subfraction may be the more preferred source of cholesterol for steroid synthesis in the adrenal cortex of rats compared to HDL2 subfraction

BLOOD LIPOPROTEINS AS A PLATFORM FOR TRANSPORT OF HYDROPHILIC AND HYDROPHOBIC COMPOUNDS

The paper discusses the transport functions of the main classes of blood plasma lipoproteins (LP) that are not associated with the metabolism of lipids that make up their composition. The aim of the study was to study the ability of various plasma LP fractions (very low (VLDL), low (LDL) and high density (HDL)) to interact with certain hydrophilic and hydrophobic compounds and show the role of LP as transport forms of xenobiotics in the organs and tissues of the body. Material and methods. The studies were performed with tritium-labeled cytochalasin B, benzylpenicillin, benzanthracene, benzo(a)pyrene, ultracentrifugation of human plasma LP fractions, column chromatography; in vivo experiments with intravenous injection of LP complexes with tritium-labeled benzanthracene were conducted. Results. The ability of various classes of LP to form complexes with hydrophilic (cytochalasin B, benzylpenicillin) and hydrophobic (benzanthracene, benzo(a)pyrene) compounds is shown by the method of ultracentrifugation. More than 50 % of the radioactivity of hydrophilic compounds in human blood plasma was represented in the composition of the LDL and HDL fractions, and in the composition of the VLDL fractions it was minimal – 6.3 and 5.1 %, respectively. A significant part of cytochalasin and benzylpenicillin was also present in the protein infranatant – 43.6 and 40.9 %, respectively. The distribution in blood plasma for hydrophobic (benzanthracene, benzo(a)pyrene) compounds was different. More than 80 % of the radioactivity was represented in the composition of the LP fractions. The polar protein infranatant contained 16.1 % of the radioactivity of benzantracene and 13.6 % of benzo(a)pyrene. The features of the lipophilic xenobiotics uptake by organs and tissues were shown in vivo experiments with intravenous injection of complexes of LP with tritium-labeled benzanthracene to rats. The highest specific radioactivity was found in the liver and adrenal glands after the intravenous injection of 3H-benzanthracene in the composition of VLDL and LDL. Twice less uptake of the labeled drug was observed in the testis and kidneys. Radioactivity decreased in the series: lungs,adipose tissue, thymus, heart, and spleen. A feature of the use of HDL as a platform for 3H-enzanthracene is the intense accumulation of lipophilic xenobiotics in steroid-producing organs: the adrenal glands and testis. Conclusion. The results obtained allow us to consider the real possibility of using blood plasma PL as transport platforms for hydrophilic and hydrophobic compounds into the cells of organs and tissues

Липопротеины высокой плотности плазмы крови как транспортная форма актиномицина Д

Introduction. The development of new and highly effective antitumor therapy is one of the priorities of pharmacology. The paper presents one of the solutions to the problem related to the development of transport forms of antitumor drugs.The aim of the study was to study the ability of various fractions of plasma lipoproteins (VLDLP, LDL, HDL) to interact with actinomycin D and show the role of HDL as a transport form of actinomycin D in the body cells.Material and methods. The studies were conducted using unlabeled and tritium-labeled actinomycin D, preparative ultracentrifugation of the rat plasma lipoprotein fractions, chromatography, and in vivo experiments with intravenous administration of HDL complexes with labeled actinomycin D.Results. The important role of HDL in the formation of complexes with actinomycin D in comparison with LDL and LPA was shown. The basic physicochemical characteristics of the interaction of HDL and apolipoprotein A-I with actinomycin were obtained. The constants of the association were of the order of 105 M-1, and the number of binding sites for the drug was 26 for HDL and 12 for apolipoprotein A-I. In vivo studies on rats, the highest radioactivity after intravenous injection of HDL complexes with tritium-labelled actinomycin D was observed in the adrenal glands, then in the liver and kidneys. The uptake of tritium-labelled actinomycin D was twice lower in the lungs, adipose tissue, thymus and spleen. The low uptake of the label was observed in the myocardial tissue.Conclusion. The results obtained demonstrate the feasibility of using HDL as a transport form of actinomycin D in body cells.Введение. Разработка новых и высокоэффективных средств противоопухолевой терапии является одной из приоритетных задач фармакологии. В работе представлено одно из решений данной проблемы, связанное с разработкой транспортных форм противоопухолевых препаратов.Цель исследования - изучить способность различных фракций липопротеинов плазмы крови (ЛПОНП, ЛПНП, ЛПВП) взаимодействовать с актиномицином Д и показать роль ЛПВП как транспортной формы актиномицина Д в клетки организма.Материал и методы. Исследования выполнены с использованием немеченого и меченного тритием актиномицина Д, препаративного ультрацентрифугирования фракций липопротеинов плазмы крови крыс, хроматографии, а также в опытах in vivo c внутривенным введением комплексов ЛПВП с меченым актиномицином Д.Результаты. Показана важная роль ЛПВП в образовании комплексов с актиномицином Д по сравнению с ЛПНП и ЛПОН. Получены основные физико-химические характеристики взаимодействия ЛПВП и аполипопротеина А-I с актиномицином Д. Константы ассоциации были порядка 105 М-1, а число центров связывания для препарата составило 26 для ЛПВП и 12 для аполипопротеина А-I. В опытах in vivo с внутривенным введением крысам комплексов ЛПВП с меченным тритием актиномицином Д показано, что через 30 мин после введения наибольшая удельная радиоактивность была обнаружена в надпочечниках, затем в печени и почках. Вдвое меньшее содержание меченого препарата наблюдали в легких, жировой ткани, тимусе и селезенке. Слабое поглощение метки отмечено в ткани миокарда.Заключение. Полученные результаты позволяют считать реальной возможность использования ЛПВП в качестве транспортной формы актиномицина Д в клетки организма

Influence of total low dose fractionated radiation on growth and metastasis of mice Lewis lung carcinoma

Effects of prolonged fractionated ionized radiation in low doses on the growth and metastasis intensity of mice Lewis lung carcinoma (LLC) are studied. On the background of tumor growth, stimulation induced by irradiation in the selected mode of dose fractionation inhibition of spontaneous dissemination of tumor cells into lungs is observed. On the 23-rd day after cell inoculation metastases incidence in irradiated animals was 25 % lower; the number and size of lung metastases decreased by 1.6 and 1.7 times. In the remote terms of tumor growth inhibition of functional activity of macrophages – central effectors of non-specific anti-tumor immunity was revealed

THE INFLUENCE OF ENDOTHELIUM-DEPENDENT MECHANISMS OF VESSEL TONE REGULATION ON THE TISSUE OXYGENATION PARAMETERS IN PATIENTS WITH ISCHEMIC STROKE AT THE BACKGROUND OF ARTERIAL HYPERTENSION SYNDROME

Aim. To study properties of tissue oxygenation and role of nitricoxyde-ergic reactions of circulation in ischemic stroke at the background of arterial hypertension. Material and methods. Totally 62 men and women included with the diagnosis of ischemic stroke. All patients underwent CT and MRI of the brain; cerebral flow was studied by extra- and transcranial ultrasound dopplerography, central hemodynamics was assessed by echocardiography, the basic clinical tests performed, and neurological and neuroophthalmological examination. Study of oxygen transport on the microcirculatory level was performed by polarographic method by transcutaneous measurement of oxygen pressure in tissues. Gases of the blood were measured on the analyzer Easy Stat "Medica Corporation" (USA). For the evaluation of nitric oxide (NO) level, we used the measurements of its stabile metabolites on blood — nitrites and nitrates. Neurological status was examined with the NIHSS score (The Score of the National Health Institute of the US, by T Brot, H.R Adams, 1989). All patients studied were then grouped into 3 groups according to severity of the stroke. Mathematical analysis was performed using software "Statistica 6.0" with non-parametric criteria of Mann-Whitney. Significant were the data with p<0,05.Results. In patients with ischemic stroke, there were disorders of nitricoxide-ergic mechanism of the vessels. Decrease of the level of stable NO metabolites and impairment of tissue oxygenation were linked to the severity of the disease and prominence of neurologic deficiency.Conclusion. In ischemic stroke, there are structural and functional changes in cerebral vessels, which do worsen by the impairment of systemic circulation, increase of systemic pressure, those then lead to tissue hypoxia and neurologic deficiency progression

On the theory of carrier-induced ferromagnetism in diluted magnetic semiconductors

Two different approaches (presented in the literature as alternative approximations) to the problem of carrier-induced ferromagnetism in the system of disordered magnetic ions of a diluted magnetic semiconductor are analyzed. They are based on a self-consistent procedure for the mean exchange fields and the RKKY interaction. Calculations in the framework of exactly solvable model are carried out, and it shows that these approaches stem from two different contributions to the magnetic susceptibility. One stems from the diagonal part of the carrier-ion exchange interaction and corresponds to mean field approximation. The other one stems from the off-diagonal part of the same interaction and describes the indirect interaction between localized spins via free carriers. These two contributions can be responsible for the different magnetic properties. Thus, the aforementioned contributions are complementary but not alternative to each other. A general approach is proposed and compared with different approximations to the problem under consideration