Thiaisoleucine and protein synthesis.

Thiaisoleucine is an isoleucine analogue having the gamma-methylene group of the valerianic carbon chain substituted by a sulphur atom. It has been demonstrated that thiaisoleucine is activated and transferred to tRNAIle by rat liver aminoacyl-tRNA synthetase and inhibits isoleucine incorporation into polypeptides in protein synthesizing systems from rat liver or rabbit reticulocytes, whereas it does not affect either leucine incorporation or ribosome run-off or polypeptide chain elongation rate. All tests were performed in comparison with O-methyl-threonine, an isoleucine analogue with the gamma-methylene group substituted by an oxygen atom. In all the reactions studied, both thiaisoleucine and O-methyl-threonine act as competitive inhibitors of isoleucine. With respect to O-methyl-threonine, thiaisoleucine shows higher activity as an isoleucine inhibitor.     

A difference between two strains of rats in their liver non-haem iron content and in their response to the porphyrogenic effect of hexachlorobenzene.

Female Agus rats developed hepatic porphyria at a much faster rate than female Porton-Wistar rats when fed a diet containing 0.01% of hexachlorobenzene (HCB). They also showed a greater inhibition of liver uroporphyrinogen decarboxylase [EC 4.1.1.37] activity and a marked stimulation of 5-aminolaevulinate synthetase [EC 2.3.1.37]. The difference between the two strains could not be correlated with differences in the liver concentrations of HCB. However, control Agus rats were found to possess significantly higher levels of total non-haem iron in their livers than the Porton animals. This was particularly apparent after 24 h of starvation and is further evidence for the involvement of iron in the pathogenesis of HCB-induced porphyria. The posterior lobes of the livers from the Agus rats given HCB became porphyric more slowly than the remainder with less severe inhibition of uroporphyrinogen decarboxylase. In contrast to their increased susceptibility to HCB, the Agus rats were less susceptible to another prophyrogenic agent, 3,5-diethoxycarbonyl-1,4-dihydrocollidine.     

Stimulation of the initiation of DNA synthesis and cell division in several cultured mouse cell types : Effect of growth-promoting hormones and nutrients

The ability of prostaglandin F_2α (PGF_2α) and other prostaglandins to stimulate the initiation of DNA synthesis in quiescent cultures of various mouse fibroblastic cell types has been investigated. PGF_2α was found to be more effective than the other prostaglandins. Most cell types, with the exception of BALB/c 3T3, responded to PGF_2α. Addition of PGF_2α in combination with insulin resulted in a synergistic increase in the proportion of cells synthesizing DNA. The effect of nutrients on the stimulation of the initiation of DNA synthesis has been examined in detail; it was found that Swiss 3T3 cells showed a requirement for hypoxanthine and vitamin B₁₂ whereas Swiss 3T6 cells demonstrated a stringent requirement for vitamin B₁₂ only. The effect of prostaglandin precursors, synthetic analogues of the prostaglandin endoperoxides and inhibitors of prostaglandin synthesis was also examined in two cell types. The effect of PGF_2α was compared with that of two polypeptide growth factors, epidermal growth factor (EGF) and fibroblast growth factor (FGF) in Swiss 3T6 cells grown in 0.0025% (v/v) serum. In combination with insulin each of these three growth factors stimulated the initiation of DNA synthesis in approximately the same number of cells.     

Mutations of Chinese Hamster Somatic Cells from 2-Deoxygalactose Sensitivity to Resistance

In Chinese hamster somatic cells, the spontaneous change of phenotype from 2-deoxygalactose sensitivity to resistance was studied using fluctuation test experiments à la Luria and Delbrück (1943) for four Chinese hamster cell strains derived from V79. The results are consistent with true mutational events. The mutation rates are in the range of 1 to 3.5 X 10(-5) per cell per generation. The relationship between the 2-deoxyglactose resistance and the galactokinase markers is discussed.     

Effect of metabolic control on urinary excretion and plasma levels of catecholamines in diabetics.

Urinary excretion and plasma levels of catecholamines were determined in 20 normal and 39 diabetic subjects to evaluate the sympathetic activity. Diabetic patients were divided into 4 groups according to the metabolic control. Sympathetic activity showed no differences between normal and subjects with chemical diabetes (group I, n = 5). In insulin-treated diabetics in good metabolic control (group II, n = 11) only urinary excretion of free norepinephrine was significantly higher than normals (p less than .05). In insulin-treated diabetics in poor metabolic control (group III, n = 16) urinary excretion and plasma levels of norepinephrine showed a marked increase over groups I and II (p less than .001). In insulin-treated diabetics with ketosis (group IV, n = 7) urinary excretion and plasma levels of both norepinephrine and epinephrine showed the highest values (p less than .001 and less than .1). Finally, in groups III and IV, after achieving improved metabolic control, a significant decrease of urinary excretion and plasma levels of catecholamines was observed. The results confirm that there is an increased rate of catecholamine release in poorly controlled diabeties and suggest a close correlation between sympathetic activity and metabolic derangement in diabetes.     

Synthesis and chromatographic properties of Se-carboxymethyl-selenohomocysteamine (2-carboxymethyl, 3-aminopropyl selenide)

Details are reported for the synthesis of Se-carboxymethylselenohomocysteamine from selenohomocysteamine and monochloroacetic acid. Data on its behaviour on paper and ion-exchange chromatography are also reported, which allow its identification.     

PERFUSION FOR MYOCARDIAL REVASCULARIZATION WITHOUT AN ARTIFICIAL OXYGENATOR (New Method to Reduce Surgical Morbidity)

Thirteen patients were submitted to direct myocardial revascularization (saphenous vein graft) without the use of an artificial oxygenator. The perfusion was done by a left ventricle-to-aorta bypass and autogenous oxygenation. Most patients had three grafts implanted plus endarterectomy of the distal right coronary artery. There was one hospital death that was apparently not related to the method used. Perfusion time ranged from 45 minutes to 4 hours. Body temperature during perfusion was kept between 25 and 30 degrees C. Perfusion flow was maintained between 25 to 50 ml per kg of body weight per minute. Ischemic, hypothermic cardiac arrest was employed. We demonstrated for the first time that perfusion for this kind of heart surgery could be done with no artificial oxygenators and, apparently, is safer for the patients. There were no bleeding problems even in perfusions as long as 4 hours. There was no respiratory dysfunction, and artificial respiration was used for only 6 to 12 hours. The patients awoke at the end of surgery with no signs or symptoms of central nervous system damage, and vasopressor drugs were rarely used after surgery. Although the experience is very small, it suggests that many postoperative problems, especially those related to bleeding and respiratory dysfunction may be reduced or eliminated by this new method.     

Effect of mouse genotype on interferon production

Upon induction with Newcastle disease virus, peritoneal macrophages derived from C57BL/6 mice produced ten times as much interferon as macrophages derived from BALB/c mice. This suggested that the alleles of theIf-1 locus are expressed in vitro by these cells. Further evidence for this was obtained by studying interferon production by peritoneal macrophages derived from seven recombinant inbred and one congenic line: in each case there was complete correlation between in vivo and in vitro phenotype: macrophages fromIf-1^l mice were low producers in vitro, and macrophages fromIf-1 ^h mice were high producers in vitro.     

Role in hemolysis of the interaction of tellurium compounds with glutathione

We have shown that tellurite and tellurate require the interaction with reduced glutathione (GSH) to hemolyze human erythrocytes. The study of the nature of this interaction is the main object of this paper. The degree of hemolysis was determined by the method of Angelone. The addition of extracellular 1 mM GSH or cysteine increased the rate of hemolysis. Concanavalin A (0.3 mg/mL) and/or 4 mg/mL adenosine did not affect the hemolysis by 0.1 mM tellurite. One tenth to 1 mM 4-acetamido-4′-isothiocyanostilbene-2,2′-disulfonate (SITS) inhibited this hemolysis by 60–100%. Millimolar GSH released this inhibition. Incubation of 0.1 mM tellurite with 1 mM GSH for 90 min at 37°C, produced a hemolytic agent when prepared and tested under nitrogen, but one that was not active when prepared in air. The hemolysis byp-hydroxymercuribenzoate orp-hydroxymercuriphenylsulfonate did not involve GSH. Scanning electron micrographs showed a sphero-echinocyte transformation, in the pre-hemolytic stage, with all the agents tested. The rate of penetration of tellurite plays a role in determining the rate of hemolysis, as shown by the effect of SITS. The release by GSH of the inhibition by SITS poses questions concerning the site of action and cell membrane penetration of the hemolytic agent. Telluride or some intermediate in the interaction of GSH with tellurite is the actual hemolytic agent.     

Non-polyadenylated 22 s ribonucleoprotein particle is insensitive to translational inhibitor RNA of cryptobiotic gastrulae of Artemia salina.

A free cytoplasmic 22 S ribonucleoprotein particle exhibiting a major template activity in rabbit reticulocyte system has been identified in the cryptobiotic gastrulae of Artemia salina. This particle contains non-polyadenylated 9 S messenger RNA which codes primarily for a non-histone basic protein with an apparent molecular weight of 26 000 daltons. We have previously demonstrated the presence of a translational inhibitor RNA which is apparently responsible for transforming polyadenylated messenger (Slegers et al., FEBS Letters 80, 390-394, 1977). This inhibitor RNA was found to be completely ineffective on the template activity of non-polyadenylated 22 S messenger ribonucleoprotein, confirming the specificity of this regulatory RNA for polyadenylate sequences.