Specific binding sites for atrial natriuretic peptide (ANP) in cultured mesenchymal nonmyocardial cells from rat heart

Specific binding sites for atrial natriuretic peptide (ANP) were studied in cultured mesenchymal nonmyocardial cells (NMC) from rat heart. Binding study using 125I-labeled synthetic rat (r) ANP revealed the presence of a single class of high-affinity binding sites for rANP in cultured NMCs derived from both atria and ventricles; the apparent dissociation constant (Kd) was approximately 0.2 - 0.3 nM and the number of maximal binding sites was approximately 190,000 - 300,000 sites/cell. rANP significantly stimulated intracellular cGMP formation of cardiac NMCs in a dose-dependent manner (1.6 X 10(-8) M - 3.2 X 10(-7) M). rANP had no effect on synthesis of prostaglandin I2 by cultured cardiac NMCs. The physiological significance of ANP action on cardiac tissue remains to be determined.     

Purification of a receptor for formaldehyde-treated serum albumin from rat liver

A membrane-associated receptor involved in a specific uptake of formaldehyde-treated serum albumin (f-Alb) was purified from rat livers by Triton X-100 solubilization of a 105,000 X g membrane preparation and affinity chromatography on an f-Alb-Sepharose column. The purified receptor exhibited Mr = 125,000, consisting of two noncovalently linked glycoprotein components with Mr = 53,000 and Mr = 30,000, respectively. Incubation of 125I-receptor with f-Alb, but not with native albumin, resulted in a marked shift of pI value from 5.9 to 5.1, reflecting the presence of a specific ligand-receptor interaction. The receptor incorporated into liposomes displayed a saturable binding to 125I-f-Alb and the binding was effectively replaced by the presence of unlabeled f-Alb, with binding parameters being similar to those obtained from 125I-f-Alb binding to the sinusoidal liver cell membrane (Horiuchi, S., Takata, K., and Morino, Y. (1985) J. Biol. Chem. 260, 475-481). Reaction of anti-f-Alb receptor antibody with extracts of sinusoidal cells resulted in a specific precipitation of two proteins whose molecular weights were identical to those for the purified receptor. The anti-receptor IgG fraction effectively blocked 125I-f-Alb binding to the sinusoidal cell membranes. These results indicate that the purified protein represents the membrane-associated receptor which is presumably involved in a specific uptake of this ligand from the circulation.     

Visual interneurons in the lobula complex of the fleshfly,Boettcherisca peregrina

Summary The physiology and morphology of visual interneurons in the lobula complex of the fleshfly,Boettcherisca peregrina, were studied using intracellular recordings and intracellular cobalt stainings, respectively. Using responses to movements of a spot of light and on-off stimuli at single positions, we classified the interneurons into five physiological groups ON, OFF, ON-OFF, nondirectional motion sensitive (NDM) and directional motion sensitive (DM) neurons. They could be further divided into four morphological types, depending on the location and extent of their dendrites and terminal branches.     

The Lyt phenotype of the T cells responsible for in vivo tumor rejection in syngeneic mice

Summary Spleen cells of BALB/c mice hyperimmunized with a transplantable methylcholanthrene-induced sarcoma Meth A (Meth A-Im-SPL) inhibited the growth of Meth A tumor in vivo in a tumor neutralizing test. Meth A-Im-SPL did not neutralize another antienically distinct sarcoma, Meth 1, indicating that the antitumor activity is tumor specific. Lyt-1⁺2^– cells of Meth A-Im-SPL (Im-Lyt-1⁺2^–) were the effectors since in vitro treatment of Meth A-Im-SPL with anti-Thy 1.2 or anti-Lyt 1.2 antibody plus complement completely abrogated their neutralizing activity, whereas treatment with anti-Lyt 2.2 plus complement did not. To further confirm the effector activity of Im-Lyt-1⁺2^– cells, T cell subpopulations were separated from Meth A-Im-SPL by the panning method. The purified Im-Lyt-1⁺2^–, but not Im-Lyt-1⁺2⁺ cells neutralized the tumor in athymic nu/nu mice as efficiently as in +/+ mice, suggesting that the donor Im-Lyt-1⁺2^– cells but not recipient T cells were primarily responsible for neutralizing the tumor. The present study, however, did not exclude the possible contribution of recipient T cells to the tumor neutralization and this is open to further investigation.Abbreviations Meth A-Im-SPL Meth A-immune mouse spleen cells - Meth 1-Im-SPL Meth 1-immune mouse spleen cells - sIg⁺ cells surface immunoglobulin positive cells - moAb monoclonal antibody     

Transductional Analysis of the leu-thr Region of Chromosome of Serratia marcescens

Transductional analysis of the chromosomal linkage map of Serratia marcescens near leu revealed the following order of loci: ser4-thr3-pyr1-pdx2-leu1-azi8.     

Genetic studies of the ribosomal proteins in Escherichia. coli. II. Altered 30s ribosomal protein component specific to spectinomycin resistant mutants

Summary Spectinomycin resistant (spc ^r) mutants were obtained by treating the cells of E. coli K12, W3637 with nitrosoguanidine. The compositions of ribosomal proteins were analyzed for six out of eleven such spc ^r-mutants with chromatography on a carboxymethyl cellulose (CMC) column. The 30s ribosomal subunit from all of the spc ^r-mutants was found to contain the altered 30-4 protein component, while no difference was detected in 50s ribosomal proteins between spc ^r and spc ^s bacteria.Abbreviations used CMC carboxymethyl cellulose - str streptomycin - spc spectinomycin     

Effect of Ethanol on the Sodium and Potassium Conductances of the Squid Axon Membrane

The effects of ethanol on squid giant axons were studied by means of the sucrose-gap technique. The membrane action potential height is moderately reduced and the duration sometimes shortened by ethanol in sea water. Voltage clamp experiments showed that ethanol in sea water reduced the maximum membrane conductances for sodium (g'_Na) and potassium (g'_K). In experiments with multiple application of ethyl alcohol to the same spot of membrane, a reduction of g'_Na to 82 per cent and of g'_K to 80 per cent of their value in sea water was brought about by 3 per cent ethanol (by volume) while 6 per cent caused a decrease of g'_Na to 59 per cent and of g'_K to 69 per cent. Ethanol has no significant effect on the steady-state inactivation of g_Na (as a function of conditioning membrane potential) or on such kinetic parameters as τ_h or the time course of turning on gi g_Na and g_K. It is concluded that ethanol mainly reduces g_Na and g_K in the Hodgkin-Huxley terminology.     

The Receptor Potential of the Taste Cell of the Rat

The electrical responses of the taste cell of the rat to chemical stimuli were studied by means of microelectrode techniques. Although large positive potential changes in the taste cell were usually elicited by taste stimuli, the response was a small negative potential change with respect to surrounding tissues if the microelectrode was thrust deeply into the taste bud. Both FeCl₃ and cocaine produced a positive change in the steady potential. If this new potential is larger than a certain equilibrium potential, reversal of the polarity of the potential change caused by a taste stimulus is observed. Gamma-aminobutyric acid and acetylcholine had no effect on the receptor steady potential nor on the receptor responses elicited by taste stimuli.     

Mode of antitumor action of recombinant human tumor necrosis factor on the sarcoma Meth A transplanted in the mouse

The mode of antitumor action of rHu-TNF was elucidated in BALB/c mice bearing Meth A fibrosarcoma 7 days after transplantation with respect to time course, dose-response relationships and selectivity of the effects. The maximal cytotoxic effect on tumor cells revealed by inhibition of DNA synthesis and maximal lesional effect on tumor vasculature revealed by change in blood pool-size in the tissue were detected at 30 min and I h after administration of rHu-TNF, respectively. The dose-response relationship between cytotoxic and tumoricidal effects of rHu-TNF was irrespective of administration route. ED₅₀s of these antitumor effects afteri.v. administration of rHu-TNF were about 50 times as high as ED₅₀s afteri.t. administration. ED₅₀ ofi.t. given rHu-TNF for vascular effect was about 20 times as high as that for cytotoxicity while ED₅₀ ofi.v. rHu-TNF for vascular effect was only 2–3 times as high as that for cytotoxicity. The whole body autoradiographies with [¹²⁵I] HSA giveni.v. to see the blood influx into tumor tissue and [¹⁴C]thymidine given i.v. to see DNA synthesis in the whole body after administration of rHu-TNF revealed that the distribution of radioactivity was markedly changed in the tumor alone without any detectable change in other whole body tissues.In conclusion, thein vivo antitumor effect of rHu-TNF giveni.t. ori.v., appears to be exerted through the direct action on Meth A sarcoma rather than indirectly on tumor vasculature. Under present conditions, the effect of rHu-TNF in the whole body tissues seems rather selective on cells and vasculature of the tumor.