Influence of food motivation on neuronal response of the cat somatic cortex during instrumental reflex

Spike activity in neurons of areas 3 and 4 was investigated in experiments on cats during the conditioned reflex response of placing the paw on a support both before and after feeding ad libitum. Ingestion of a feed consisting of a rapidly absorbed glucose dairy mix did not prevent the reflex taking place if the animals' favorite food was used as reinforcement. Background activity increased in two-thirds of the neurons after the feed; the tonic constituent of neuronal response declined substantially and repeated contraction of the biceps occurring at the same rate as locomotor movements disappeared. Difference in latency of response produced by the conditioned stimulus in the same neurons before and after feeding measured 50–300 msec during the experiment. Measurements of latency of placing motion remained largely unchanged. Changes in the latency of neuronal spike response were thus found to be interrelated with the intensity of the animal's motivational excitation. It is suggested that fluctuations in degree of food motivation lead to changes in cortico-subcortical relationships responsible for initiation and performance of conditioned movements in these animals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 646–653, September–October, 1987.     

L-glutamate activated membrane conductivity in spinal cord neurons during early chick embryogenesis

Transient and steady-state components of L-glutamate-activated membrane currents were investigated using intracellular perfusion, voltage clamp, and concentration clamp techniques in spinal cord neurons of 6–11 day chick embryos. Hill's coefficient was found to equal 1 for transient and 2 for steady-state components. It was shown that the L-glutamate-activated receptors are present, which appear in the membrane of spinal neurons at the early stages of development.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 251–258, March–April, 1987.     

Beta-adrenergic agonists and cyclic AMP decrease intracellular resting free-calcium concentration in ileum smooth muscle

Intracellular free-calcium levels were measured in strips of longitudinal smooth muscle from guinea-pig ileum; fura-2 was used as a calcium monitor. At rest the calcium concentration was about 180 nM, and this rose to 300-400 nM following electrical stimulation and during spontaneous calcium transients (all measurements at 23-25 degrees C). Isoprenaline suppressed the spontaneous calcium transients, and reduced the resting calcium level to about 130 nM. This fall in resting calcium concentration was seen even in muscle strips which did not have spontaneous activity. Elevation of intracellular cyclic AMP levels, produced by forskolin or dibutyryl cyclic AMP, mimicked the actions of isoprenaline. We conclude that the relaxant effects of beta-adrenergic agonists of visceral smooth muscle may be explained partly by a fall in intracellular resting free-calcium level, mediated via an increase in cyclic AMP.     

Human lymphoblastoid cell lines secreting antibodies with restricted HLA specificity

Peripheral B lymphocytes obtained from three healthy individuals who had been immunized against peripheral blood lymphocytes from appropriate HLA-incompatible donors were transformed by the use of Epstein-Barr virus. The transformed blastoid B cells were repeatedly subcultured by means of cluster picking, and the HLA antibody-producing cultures were identified by testing the culture supernatants by means of the cytotoxicity assay, using the corresponding donor cells. Thus far, four cell lines that secrete cytotoxic HLA antibodies (MP1, 3, 4, and 5) have been established. Specific immunoabsorption experiments revealed that the antibody activity is carried by lambda-type IgM for MP1, by kappa-type IgM for MP3 and MP5, and by both for MP4. Specificity analysis of a panel of HLA-pretyped cells indicated that MP1 detects DQw2, whereas MP5 recognizes B7. The specificity of MP3 was similar to a DQ specificity termed DC5 (probably equivalent to TA10) but not the same. In the case of MP4, both of the lambda-type and kappa-type antibodies appeared to be directed toward new HLA class 11 determinants.Abbreviations used in this paper HLA human major histocompatibility - EBV Epstein-Barr virus - B-LCL Blymphoblastoid cell line - NA not absorbed - PBS phosphate-buffered saline - SPA Sepharose protein A - NRS normal rabbit serum     

Structure of a protein catalyzing the formation of 11 cis-retinal in the visual cycle of invertebrate eyes

A pigment made up of a protein able to bind retinal as well as retinol is described. The molecule consists of a dimer with a molecular weight of 50,000 which binds one molecule of retinal. The binding site for retinal is a Schiff base buried in the interior of the protein. Retinol is probably bound to the protein in the same site as for retinal, although not covalently, as suggested by the absorbance spectra. The protein, extracted from honeybee retina, is involved in visual pigment metabolism, and its structure may elucidate the mechanism of the stereospecific photoisomerization of all trans-retinal to 11-cis-retinal.     

The role of the cytosolic fraction and of initiation factor eIF-2 for changes of the rate of protein synthesis during liver regeneration

The protein synthesis-stimulating activity of the cytosolic fraction from regenerating rat liver was tested in a cell-free system using washed polysomes from normal rat liver. This activity undergoes significant changes during liver regeneration after partial hepatectomy (p.h.). An initial decrease until 16 h after p.h. is followed by a significant increase until 24 h after p.h. Beyond 32 h after p.h. the activity begins to decline again. Evidence is presented that these changes of the cytosolic activity may not be due to alterations in the distribution of protein synthesis-stimulating factors between the microsomal and the cytosolic fraction. The Met-tRNAf-binding activity of the cytosolic fraction changes during liver regeneration analogously to the protein synthesis-stimulating activity measured in the polysomal assay. This indicates that initiation factor eIF-2 is involved in the observed changes of the cytosolic activity. This conclusion could be confirmed by addition of purified eIF-2 to the polysomal assay system. Addition of eIF-2 to cytosolic fractions of low endogenous protein synthesis-stimulating activity (16 h after p.h.) enhances amino-acid incorporation to a significantly higher extent than addition to highly active cytosolic fractions (24 h and 32 h after p.h.). From these results it is concluded that changes in eIF-2 plays an essential role in the described alterations of the cytosolic activities during liver regeneration.     

Isolation of antiserum against rat transcortin and characteristics of specific antibodies

Repeated chromatography of rat plasma protein on DEAE-cellulose, hydroxylapatite and subsequent gel-filtration through Sephadex G-200 were used to obtain a pure rat transcortin homogeneous upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The molecular weight of transcortin was about 66 kDa as determined by SDS-polyacrylamide gel electrophoresis. Immunization of a rabbit with the homogeneous preparation of rat plasma transcortin caused development of antibodies to transcortin. It was shown that the antibodies of rabbit antisera in the experiments made in vitro and in vivo neutralized 60 and 65% of 3H-corticosterone-transcortin complexes, respectively. Specific antibodies to the transcortin were isolated from the homogeneous fraction of IgG by affinity chromatography on transcortin-sepharose 4B. 125J-labelled antibodies were adsorbed by protein A-sepharose; IgG can be eluted by IM acetic acid as a sharp peak. The SDS-polyacrylamide gel electrophoresis demonstrated that affinity-eluted material contains 25 and 50 kDa polypeptides.     

Characteristics of the expression of globin genes in blood cells of patients with homozygotic beta-thalassemia from Tadzhikistan

The synthesis of globin protein in blood reticulocytes of patients from Tajikistan suffering from homozygous beta-thalassemia was studied. Beta-thalassemia has been revealed in all cases, with synthesis of beta-globin being retained though essentially reduced. It was shown that, unlike homozygous beta+-thalassemia of other populations, beta +thalassemia with sharp inhibition of the beta-globin protein synthesis is most representative for the region (alpha/beta greater than 10).     

Effect of exogenous DNAses on various stages of DNA replication in microorganisms

Effect of DNAase 1 on DNA synthesis and cell division was studied in microorganisms deficient in some stages of DNA replication initiation. The DNA synthesis induced by exogenous DNAase was found to be a replicative origin since it was registered from the "origin" of chromosomal replication under the conditions of initiation of proteins functioning. Stimulation of DNA synthesis in bacterial cells having mutations in DNA B and DNA G genes by DNAase 1 indicates that exogenous DNAases participate in replicative fork during the DNA synthesis.