The neuronal organization of a focus of conditioned excitation in the cat sensory-motor cortex]

The activity of single units in the focus of conditioned excitation was studied during defensive conditioning to direct electrical stimulation of the cat sensorimotor cortex. Reorganizations of spike activity set in during the period of reflex elaboration, were manifest in the increased number of excited neurones and those which respond both to the conditioned and unconditioned stimuli. In the course of elaboration, the inhibitory phase of unit responses to direct electrical stimulation of the sensorimotor cortex was reduced, while the frequency of background unit spike activity was enhanced. Acute extinction of the reflex restored the initial duration of the inhibitory phase and reduced the frequency of the background activity.     

Effect of furfural on the energy metabolism of fodder yeasts]

The effect of furfurol on the rate of oxygen uptake and carbon dioxide production by Candida tropicalis cells was studied. Furfurol was shown to inhibit significantly the yeast respiration, inducing aerobic glycolysis. Enhanced carbon dioxide production in the presence of furfurol was followed by an intensive degradation of trehalose and ethanol accumulation in the medium.     

An ionometric study of Na+ and K+ fluxes across the nystatin-modified human erythrocyte membrane]

The application of ion-selective electrodes is discussed for the kinetic determination of K+ and Na+ concentrations in the system, containing human red blood cells modified by nystatin. A series of mixed solutions was worked out, according to which the Na(+)-glass and the K(+)-thick membrane valinomycin electrodes were calibrated. The human erythrocytes were washed for 3 times with the basic solution (in mol per liter: 0.141 NaCl, 0.004 KCl, 0.002 CaCl2, 0.003 MgCl2, 0.01 glucose), and then were resuspended in it. The suspension was kept in a shaking bath at 37 degrees C. The modification of the cell membranes was performed by the introduction of different amounts of the antibiotic nystatin into the probe. Under these conditions the concentration of Na+ decreased, while K+ concentration increased. The values of concentration were registered ionometrically. In an hour and a half the stationary lines were obtained. Being based on the values of the stationary cation concentrations and the final concentrations, registered after the complete lysis of erythrocytes promoted by saponin, the ratio of cation fluxes across the modified membrane to the flux across the nonmodified membrane was calculated in accordance with the Hodgkin-Katz equation.     

Genetically modified animals as models of the pathological processes in psoriasis

Psoriasis is a chronic recurrent disorder that affects predominantly the skin and is autoimmune in nature. Experimental models help to study the development of psoriasis in controlled conditions and investigate particular aspects of the pathological process. Many mouse models were obtained to reproduce, to a certain extent, the psoriasis signs seen in humans. Genetically modified animals help to reveal the new genes whose mutations potentially underlie the disease and to search for new therapeutic targets. Moreover, the animal models are used to test new drugs and therapies. The review summarizes the published data on the laboratory animal models of the psoriatic process.     

Use of DNA in cytopenia induced by myelosan]

Wistar rats weighing 180-190 g received myleran per os in a single dose of 10 mg/kg, or fractionally (total dose of 25 mg/kg) for 18 days. After myleran administration the animals were injected 4-5 times (every other day) with a homologous DNA in a dose of 2 mg per rat or with a standard salt citrate. The DNA injection reduced the duration of leukopenia. With the least dose of myleran leukocyte count returned to the normal in 6 days in the treated animals and in 25 days in the untreated controls and with the highest dose -- in 15 and in 25 days, respectively, from the beginning of the treatment. The differences in the leukocyte count between the treated and control rats in both experiments were mainly due to the dynamics of neutrophils, the content of which in the treated animals exceeded that in the untreated animals by 54-110% in the course of 6-15 days in the first, and by 23-38% in the course of 10-23 days in the second experiment.     

Interaction of human thrombin I fragment, prethrombin I, and alpha-thrombin with tissue thromboplastin]

The binding of 125I-labeled prothrombin fragment I. prethrombin I and alpha-thrombin to native and papain-treated tissue thromboplastin in the presence of CaCl2 of EDTA was studied. The experimental curves plotted in the Scatchard coordinates testify to the presence in thromboplastin of two types of fragment I binding sites: those with a high (Kd = 7.6 x 10(-6) M) and moderate (Kd = 1.3 x 10(-8) M) binding affinity. The parameters of fragment I binding and their changes reproduced, for the most part, the mode of prothrombin binding observed in previous studies. The experimental results provide indirect evidence in favour of a hydrophobic role of Ca(2+)-dependent binding of prothrombin fragment I to thromboplastin. The binding of prethrombin I was nonspecific and Ca(2+)-independent, whereas alpha-thrombin showed a relatively high level of nonspecific electrostatic binding which was competitively inhibited by Ca2+. Thromboplastin proteins interacted (both directly and in a Ca(2+)-independent fashion) with all the prothrombin derivatives under study.     

Application of competitive immunoenzyme assay for analysis of group B fumonisins]

A varriant of competitive ELISA, making it possible to detect fumonisin B1 (up to 0.4 ng/well) was developed, based on the use of specific polyclonal antibodies obtained by immunization of rabbits with a horseradish peroxidase conjugate of fumonisin B1. The minimum concentration of fumonisin B in water-acetonitrile extracts of corn grain, dry corn products, and feeds, detected by the ELISA version developed is 0.2 mg/kg.