Effects of cycloheximide on protein synthesis in human lung tumors, regenerating rat liver and hepatomas

10(-4) M cycloheximide (CHM) inhibits leucine incorporation to about the same degree in slices of human lung tumors, rat hepatomas, regenerating livers and normal tissues. At 10(-6) M, CHM has a more pronounced effect on tumor tissue and regenerating liver than on normal tissues. 10(-8) M CHM stimulates protein synthesis in normal rat liver slices.     

Effect of sodium octanoate on leucine incorporation into protein of rat liver slices and of Yoshida ascites hepatoma cells

Summary 7.38×10^–4 M octanoate does not significantly modify leucine incorporation into protein of rat liver slices, while in hepatoma cells a 19% inhibition has been noted.3.69×10^–3 M octanoate reduces leucine incorporation to about the same extent (71–76%) in both liver slices and hepatoma cells.     

The inhibitory effect of paraquat on histamine and isoproterenol induced changes of cyclic nucleotides in rat lung slices

Summary The incubation of rat lung slices with paraquat ion (10^–4 M) had no effect on cAMP and cGMP levels of the rat lung slices. The preincubation with the same concentration of paraquat inhibited the cAMP elevating effect of histamine (10^–5 M) and isoproterenol (10^–5 M) and reduced the cGMP level to approximately 50% of the level obtained without preincubation with paraquat.This work was supported by the Research Grant No. 5 R01 HL 19720-03 from NHLI Department of Health, Education and Welfare, Washington, D.C.     

The effect of bovine myelin basic protein on uptake and release of H3-labelled 5-hydroxytryptamine,L-noradrenalin and γ-aminobutyric acid in rat cortex slices

Summary At concentrations above 10^–5 M myelin basic protein (MBP) induced a small inhibition of the uptake of H³-5HT and H³-NA into rat cortex slices. Release of 5HT, NA and Gaba was not affected by 10^–5 M MBP.Acknowledgment. The authors wish to thank W. Bucher for the preparation of MBP.     

Somatostatin inhibits in vitro release of luteinizing hormone releasing hormone from rat mediobasal hypothalamic slices

Summary Somatostatin, in concentrations ranging from 10^–10 M to 10^–7 M, induces a dose-dependent inhibition of LHRH release from mediobasal hypothalamic slices incubated in vitro. In contrast, VIP, secretin, glucagon, substance P, neurotensin and arginine-vasotocin do not affect spontaneous release of LHRH.     

Effects of ouabain and furosemide on saliva secretion induced by sympathomimetic agents in isolated,perfused rat submandibular glands

Summary The presence of 10^–3 M ouabain or furosemide in the perfusate inhibited saliva secretion induced by either isoproterenol (10^–5 M) or phenylephrine (10^–5 M) from isolated rat submandibular glands and caused characteristic alterations in the electrolyte composition of saliva.     

Action,in vitro et in vivo,de l'angiotensine II sur le captage cardiaque de la noradrénaline

Summary The action of angiotensin II on cardiac uptake of norepinephrine was investigated in the rat in vivo and in vitro. In contrast to desipramine, neither infusion of subpressive (10 ng/kg/min) or pressive (50–150 ng/kg/min) amounts of angiotensin on intact and/or binephrectomized rats, nor incubation of cardiac slices with angiotensin II (10^–5; 10^–9 M) impair the accumulation of tritiated norepinephrine and the level of metabolites. It is thus concluded that there is no inhibiting action of angiotensin II on the cardiac uptake of norepinephrine.     

Differences in luteinizing hormone release stimulated in rat anterior pituitary cells by leukotriene C4 and by gonadotropin-releasing hormone in vitro

Summary Continuous administration of leukotriene C₄ (LTC₄, 10^–10 M) to superfused rat anterior pituitary cells increased LH release for 40 min only, whereas in a parallel experiment gonadotropin-releasing hormone (GnRH, 10^–9 M) evoked a continuous increase in hormone secretion. In contrast to GnRH, LTC₄ did not desensitize rat anterior pituitary cells. The secretory action resulting from the administration of LTC₄ (10^–10 M) was abolished for 40 min after previous stimulation. The results documented the dual action of LTC₄ on LH exocytosis.     

Induction of the in vitro p-hydroxylation of14C-amphetamine stereoisomers in phenobarbital-treated rats

Summary The rate of p-hydroxylation of¹⁴C-(-)-amphetamine by liver microsomes was higher than that of (+)-isomer in phenobarbital-treated male rats. The apparent K_m values for (-)- and (+)-amphetamine hydroxylation were 4.54×10^–5 M and 2.27×10^–5 M respectively, in both treated and control animals.     

Biological effects of trilostane in vitro on oocyte maturation and fertilization in the hamster

Summary The effects of the inhibition of steroidogenesis by trilostane on oocyte maturation were examined by studying spontaneous maturation and fertilization in vitro. 10^–6 M trilostane had no influence on the meiotic process, whether the oocytes were naked or not. At a concentration of 10^–6 M and 10^–7 M trilostane, low normal pronuclear formation and high polyspermy were found during in vitro fertilization. However, no retarded male pronuclear development could be detected in the trilostane-treated group. Thus, steroid producing activity within ova is apparently necessary to prevent multiple sperm penetration, but it has no effect on meiosis or the action of the so-called male pronucleus growth factor (MPGF).     

Aktivierung der Tyrosinhydroxylase durch Homovanillinsäure

Summary Influence of homovanillic acid on tyrosine hydroxylase activity was investigated in homogenates of rat brain: 10^–3 and 10^–4 M HVA/1 were found to increase enzymatic activity significantly. The probability of physiological concentrations also activating DOPA synthesis is discussed.

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Aktivierung der Tyrosinhydroxylase durch Homovanillinsäure

     

Retinoic acid enhances the proliferation of smooth muscle cells

Summary Retinoic acid (RA, 10^–5–10^–7 M) is shown to enhance the proliferation of cultured rat aortic smooth muscle cells (SMC). This effect is not connected with a synergistic action of RA together with serum mitogens. Moreover, the expression of L1, a surface antigen specific for modulated SMC entering the cell cycle, is amplified by RA treatment.     

Calcium dependence of rat brain tryptophan hydroxylase

Summary The effects of various concentrations of ionized Ca were examined on the activity of rat brain tryptophan hydroxylase previously treated with EGTA. Within the range of ionized Ca-concentrations thought, to be physiologically important (10^–8 to 10^–5 M), no significant activation of the enzyme occurred, although activation was observed at higher concentrations of the metal.     

Selective killing of smooth muscle cells in culture by the ricin A-chain conjugated with monoclonal antibodies to a cell surface antigen via a dextran bridge

Summary Monoclonal antibodies to a surface antigen of the modulated smooth muscle cells originally isolated from the rat aorta media were conjugated with ricin A-chain via an oxidized dextran bridge. The interaction of cultured cells with the conjugates obtained and with control substances was monitored following incorporation of¹⁴C-leucine radioactivity. It was found that¹⁴C-leucine incorporation was suppressed by 80–90% at a conjugate concentration of 10^–6–10^–7 M. Antigen-negative cells (line IAR; rat hepatocytes) were insensitive to the conjugate at any concentration used. Control use of purified ricin A-chain, native or oxidized dextran, specific and nonspecific IgG did not affect normal¹⁴C-leucine incorporation. The data obtained may be useful for designing targeted drug transport systems and for selective screening of modulated smooth cells in vascular pathology models in vivo.     

Phosphoramidon enhances allatostatin-mediated inhibition of juvenile hormone biosynthesis in the corpora allta of the cockroach,Diploptera punctata

Use of the enkephalinase inhibitor phosphoramidon in the in vitro radiochemical assay for juvenile hormone biosynthesis enhanced allatostatin-mediated inhibition of hormone production by corpora allata of the cockroach,Diploptera punctata. Significant increases in inhibition in day 2 virgin female CA by AST 1 (at 10^–7 M) and AST 4 (10^–8–10^–7 M) were observed in the presence of phosphoramidon (10^–5M or greater). No significant increases in inhibition were seen in CA from day 6 mated females with AST 4 (10^–9–10^–7M) and phosphoramidon combined. Phosphoramidon alone had no effect on JH biosynthesis. Analysis of allatostatin content of the CA, as determined by ELISA, revealed that addition of phosphoramidon to the medium increased the endogenous allatostatin conten in CA of virgin and mated females. The similarity in primary structure between allatostatins and enkephalin-like peptides and their similar distribution makes it probable that phosphoramidon acts by preventing breakdown of allatostatins within the CA.     

Activation by S-adenosylhomocysteine of norepinephrine and serotonin in vitro uptake in synaptosomal preparations from rat brain

Summary S-Adenosylhomocysteine (10^–7–10^–5 M) activated norepinephrine (NE) and serotonin (5HT) in vitro uptake in synaptosomal preparations from rat brain, but did not affect dopamine (DA) uptake. When administered to rats (7 mg/kg i.p.), it had the same effect on in vitro NE and 5HT uptake. It did not affect NE and 5HT release.Work achieved within the frame of the research contract institut Mérieux., Institut National des Sciences Appliquées.     

Opposite effect of PGE2 on cAMP levels in human adrenal medulla and pheochromocytoma

Summary PGE₂ (10^–7 M) caused increased cAMP accumulation in 5 pheochromocytomas, while in 3 human adrenal medullae PGE₂ caused a significant decrease of cAMP level on incubating slices in vitro. This finding is discussed in relation to the opposite effect of PGE₂ on catecholamine release from human medulla and pheochromocytoma slices in vitro.Acknowledgment. This paper is part of a Ph. D. thesis of Punya Boonyaviroj.Established Investigator of the Chief Scientist's Bureau, Israeli Ministry of Health.     

Wirkungsverstärkung von Adrenalin und Noradrenalin durch Azetylcholin am isolierten Irisdilatator des Kaninchens

Summary Radial strips of the isolated iris of rabbits were suspended in streaming Tyrode's solution and their contractions were registered isometrically. The contractions produced by adrenaline or noradrenaline were increased after the administration of eserine or neostigmine. Acetylcholine in a concentration 5.10^–7–5.10^–6 M enhanced the effect of adrenaline and noradrenaline on both, the normal and the chronically denervated dilator muscle. Acetylcholine did not enhance the contractions by adrenaline and noradrenaline in the presence of atropine. Choline in a concentration of 5.10^–6 M had no effect whereas concentrations of 5.10^–5 M were slightly effective.     

Differential sensitivity of the two phases of ear artery contraction to intimal and adventitial norepinephrine

Summary The biphasic contraction of the rabbit ear artery to norepinephrine (NE) was investigated in the normal (adventitial stimulation) and the everted (intimal stimulation) segment of ear artery. The 2nd phase response showed an intimal ED₅₀ of 8.2×10^–8 M which was significantly (p<0.05) lower than the adventitial ED₅₀ of 42.6×10^–8 M. This difference was abolished by inhibition of neuronal and extraneuronal uptake for NE. The 1st phase response also showed an ED₅₀ for the intimal stimulation (6.9×10^–8 M) which was significantly (p<0.05) lower than adventitial (65.5×10^–8 M). This difference was reduced but not abolished by NE uptake inhibition. This suggsets that some feature of the adrenergic neuroeffector apparatus is asymmetrically arranged to favor fast responses to blood borne NE.Supported by American Heart Association-Greater Los Angeles Affiliate Grant No. 602. We wish to thank Dr John Bevan and Dr Alasdair MacLean for helpful advice.     

Evidence of a direct action of triiodothyronine (T3) on the cell membrane of GH3 cells: an electrophysiological approach

Summary Electrophysiological experiments demonstrate that triiodothyronine (T₃) exerts a direct effect on the membrane of a strain of cultured rat pituitary tumor cells, GH₃/B₆. These cells respond to pressure application of T₃ (2–5 nl, concentration 1·10^–10 M) with an increase in the membrane resistance (R_m) and a hyperpolarization. Spontaneously firing cells become silent.