Proliferative and differentiation properties of bone marrow hematopoietic stem cells in CBA mice of various ages

Hemopoietic bone marrow stem cells (CFCs) of young (3-5 months) and old (23-24 months) were studied according to their ability to form colonies in spleens of the lethally irradiated animals. The number, morphology and volume of CFCs were microscopically examined. The content of CFCs remained unchanged during aging. The number of erythroid colonies decreased in old mice, while that of granulocyte-macrophage and mixed colonies did not change. The megakaryocyte colonies showed even an increase with age. Volumes of all the colony types, except megakaryocyte, reduced. The results obtained thus reflect some age-related features of early stages of the stem-cell differentiation.     

Comparative immunological and electron microscopic study of the structure of E-RFC and OKT-3+ lymphocytes from human blood

Methods of immune electrone microscopy have revealed that OKT-3+ cells and E-RFC of human blood have a similar ultrastructure. Definite morphologic spectrum is observed within each of these fractions, that testifies to the heterogeneity of surface markers of circulating T-lymphocytes and their ultrastructure.     

Regulation of purine nucleotide biosynthesis in mutant Saccharomyces cerevisiae yeasts with increased sensitivity of the pathway for de novo synthesis to inhibition by exogenous guanine]

Aza 165 and aza 238 Saccharomyces cerevisiae mutants characterized by a 2.5 times higher sensitivity of the de novo purine synthesis to the inhibitory effect of exogenous guanine, as compared with the wild type strain, have been selected by their sensitivity to 8-azaguanine. The exogenous guanine somewhat inhibits the growth and synthesis of nucleis acids in mutants, this being due in vivo neither to permeability changes of the cell membrane, nor to concentration changes of guanilic derivatives in the acid-soluble pool of yeast cells. Using cell-free extract of the strain aza 165, it has been shown that the synthesis of the first product of metabolic pathway for de novo formation of purines, phosphoribosylamine, is inhibited by GMP by 81% and only by 35% in the 15V-P4 strain of the wild type. The inhibition by other end products, IMP and AMP, is the same in both wild and mutant strains. The enhanced sensitivity of the purine synthesis to guanine in vivo is thus due to changes in regulatory properties of the key enzyme of purine nucleotide formation, phosphoribosylpyrophosphate amido-transferase (EC 2.4.2.14). This change in the regulation of purine synthesis in yeast is likely to be a mechanism to compensate the genetically controlled defect in end steps of the biosynthesis pathway, i.e. the incapability of converting guanilic derivatives to adenilic ones. However, the information concerning the regulation of PRPP-amido-transferase activity responsible for differential sensitivity to adenilic and guanilic nucleotides in yeast is not lost but only strongly repressed.     

The Effects of Radiation and Hindlimb Unloading on Rat Bone Marrow Progenitor Cells

Bone marrow cells of mesenchymal origin play an important role in adaptation of physiological systems to space flight. Hematopoiesis, immunity, and homeostasis of bone tissue depend on their functional activity. An investigation that was carried out in the framework of the Bion and Bion-M programs showed a decrease of the number of rat bone marrow hematopoietic progenitors and the inhibition of lympho- and erythropoiesis when the granulocyte-macrophage linage was activated. A negative influence on nonhematopoietic bone marrow cells was also revealed. The pathogenetic influence of radiation and microgravity on the bone marrow progenitor cells has remained unclear so far. The goal of this research was to study the effect of a 30-day unloading and 6 days of γ-irradiation on rat bone marrow progenitor cells. The study was conducted on male rats of four groups: vivarium control (VC), hindlimb unloading (HU), irradiation (IR), and combined action (HU + IR). The following parameters have been examined: the number of bone marrow mononuclear cells, proliferative activity of marrow mononuclear cells, immunophenotype, number of hematopoietic CFU and CFU-f, and differentiation potency of hematopoietic and stromal bone marrow precursors. It was found that the cellularity and proliferation activity of rat bone marrow cells did not change under simulation of space flight. The number of CFU-f was decreased. Irradiation was accompanied by an increase in the hematopoietic cell share among total bone marrow mononuclear cells, while their activity was attenuated. The osteopotential of the stromal precursors was unchanged. Adipogenic differentiation was stimulated with irradiation. The functional activity of bone marrow progenitor cells was restored after 2 weeks of recovery. Thus, 30-day simulation of space flight factors negatively affected the morphofunctional properties of rat bone marrow progenitor cells. These effects were reversible upon 2 weeks of recovery.     

Atherogenic effect of beta-blocker propranolol revealed in the rabbit denudated aorta

The influence of beta-blocker propranolol onto atherogenic properties of blood serum and to formation of myointimal thickening in rabbit aorta, which was caused by denudation, were investigated. The preparation was introduced per os in the dose 6 mg/kg. Culture of mouse peritoneal macrophages was used to estimate the atherogenic properties of the serum. Serum of propranolol-treated rabbits induced accumulation of cholesterol in cultivated cells. Propranolol also induced an increase of the thickness of aortic intima, lipid accumulation and increasing of cell's number in myointimal thickening. Thus, atherogenic effect of beta-blocker propranolol was found both in vitro and in vivo.     

Synthesis and properties of an affinity sorbent for extraction of atherogenic lipoproteins

A digitonin-containing affinity sorbent was prepared using a hydrophilic polymer carrier. The correlation was found between the polymer structure and crosslink. King degree, on the one hand, and the sorbent capacity to bind cholesterol, protein and lipoproteins--on the other. The sorbent was demonstrated to extract predominantly atherogenic lipoproteins from blood plasma.     

Indirect cues in selecting a hunting site in a sit‐and‐wait predator

Sit‐and‐wait predators use relatively simple rules for their decisions to choose and leave a patch, such as using the direct presence of prey to select a hunting site. However, the direct presence of prey can only be used when there is a highly visited patch in the proximity of the predator. Therefore, it is plausible that sit‐and‐wait predators also exploit indirect cues of prey presence and, consequently, use associative learning to select a hunting site. The present study tests for the role of associative learning in a sit‐and‐wait predator species for which the ecology is well understood: Misumena vatia Clerck crab spiders. An ecologically relevant scenario is used by selecting flower colour as the conditioned stimulus and prey presence as the unconditioned stimulus. The results provide no evidence that M. vatia crab spiders use the association between flower colour and food presence for selecting a hunting site. After a training phase of being exposed to a colourful artificial flower highly visited by bees, spiders select a hunting site independently of its colour during the testing phase. Investigations of similar scope and ecological relevance are required with other sit‐and‐wait predators to identify the conditions promoting the use of associative learning for foraging site selection when animals face an unpredictable food supply.