Relationship between mutagenic potency in Salmonella typhimurium strains and the chemical structure of nitro biphenyls

Most of the positional isomers of mono-, di-, tri- and tetranitrobiphenyls were synthesized and assayed for their mutagenicity in Salmonella typhimurium strains TA98, TA98NR and TA98/1,8DNP6 in the absence of S9 mix. In mono- and dinitrobiphenyls, the structure requirements favoring mutagenic activity are the presence of a nitro group at the 4-position and its absence at the 2-position. TA98 and TA98/1,8DNP6 were reverted by 2-position-free 4-nitro analogues, but TA98NR was not reverted. The results suggest that direct-acting mutagenicity involves the reduction of the nitro group by bacterial nitroreductase but does not involve specific esterification enzymes. Some of the tri- and tetranitrobiphenyls e.g. 3,4,3'-, 3,4,4'-, 3,4,3',4'- and 3,4,2',4'-derivatives reverted not only TA98 and TA98/1,8DNP6 but also TA98NR. Those derivatives commonly have 2 nitro groups at an adjoining position (3,4-dinitro group), whereas 2,4,2',4'-tetranitrobiphenyl, which has strong potency not only in TA98 and TA98/1,8DNP6 but also in TA98NR, possesses 2 nitro groups at the 2-position of each benzene ring.     

General recombination mechanisms in extracts of meiotic cells

RecA-like proteins have been purified from somatic and meiotic cells of mouse and lily. The rec proteins have been designated s-rec and m-rec to indicate their respective tissues of origin. The two proteins differ in molecular weight and in their response to temperature, the latter being consistent with the optimal temperature for physiological function of their tissues of origin. There is a major increase in m-rec protein with the entry of cells into meiosis, the peak of activity being early pachytene. Extracts of the cells and also those of yeast (Saccharomyces cerevisiae) have been prepared that have the capacity to catalyze homologous recombination. These extracts behave similarly to the m-rec proteins upon entry of cells into meiosis. Yeast transferred to sporulation medium displays a 100-fold increase in the recombination activity of the extract at about the time of entry into meiosis. The occurrence of peak levels of m-rec and recombination activity in extracts from cells in early pachytene points strongly to that stage as the time at which the enzymatic phase of recombination occurs.     

Reconstruction of the pharyngoesophagus following pharyngoesophagectomy and irradiation therapy

During the 5-year period between 1978 and 1983, a total of 56 individuals have undergone pharyngoesophageal reconstruction at our hospitals. To restore the continuity of the upper enteric tract, conventional skin flaps with or without the underlying muscle were used in 27 and a segmental free intestinal graft by means of microvascular technique was used in 29. Two-thirds of both groups received irradiation therapy before surgery. Fistula formation was encountered in 8 individuals who received a skin flap. This incidence was found to increase with the use of preoperative irradiation. In contrast, no patient developed a fistula among the 29 patients who received the segmental free intestinal graft.     

Deafferentation pain and stimulation of the thalamic sensory relay nucleus: clinical and experimental study

This report summarizes our clinical experience in which the effects of both thalamic sensory relay nucleus (TSRN) and periaqueductal gray (PAG) stimulation were tested in the same series of patients with various forms of pain. The clinical data indicated that neurogenic pain due to deafferentation at the level of the peripheral nerves or the spinal cord was often controlled by TSRN stimulation but not by PAG stimulation. We also review the results of our experimental investigations in cats which were undertaken in an attempt to clarify the neurophysiologic basis of such differential clinical effects of TSRN and PAG stimulation. It appeared that abnormal hyperactivity within the trigeminal medullary dorsal horn following retrogasserian rhizotomy was far more frequently inhibited by TSRN stimulation than by PAG stimulation.     

Level of translatable messenger RNA coding for argininosuccinate synthetase in the liver of the patients with quantitative-type citrullinemia

Summary The translation activity of mRNA coding for argininosuccinate synthetase in total RNA extracted from the liver of three patients with quantitative-type citrullinemia was determined using a cell-free translation system. In two patients, the hepatic content of the enzyme was about 20% of the control value, whereas translatable mRNA level for the enzyme was similar to or slightly lower than those of control livers. In the third patient, the enzyme content was about 50% of the control value, and mRNA activity for the enzyme was low normal. These results indicate that at least in the first two patients, the decrease in the enzyme protein is due either to increased degradation of the enzyme or to decreased translation in the patient's liver.     

Stereospecific incorporation of hydrogens from NADPH in elongation of very long fatty acyl-CoA by swine cerebral microsomes

The elongation of arachidoyl-CoA by swine cerebral microsomes resulted in the production of behenic acid (22:0) and lignoceric acid (24:0) concomitantly. When 4S-[4-²H₁]NADPH was used for the elongation of arachidoyl-CoA, the incorporation of two deuterium atoms into 22:0 was observed by the technique of mass fragmentography. Furthermore, the incorporation of four deuterium atoms into 24:0 was also detected. On the other hand, when 4R-[4-²H₁]NADPH was used, no deuterium was incorporated into the elongated products.     

Aberrant porphyrin metabolism in hepatocellular carcinoma

In 15 patients with hepatocellular carcinoma (HCC) and 14 patients with liver cirrhosis (LC), urinary excretions of delta-aminolevulinic acid (ALA), porphobilinogen (PBG), uroporphyrin (UP), coproporphyrin (CP), and erythrocyte contents of CP and protoporphyrin (PP) were examined. In patients with HCC, urinary excretions of ALA and PBG and erythrocyte contents of CP and PP were not increased, but urinary excretions of UP and CP were significantly increased more than those of LC patients. Urinary excretions of UP and CP had no correlations with liver function tests and excretion of UP correlated slightly with blood hemoglobin level. After administration of ALA intravenously, urinary excretions of UP and CP were clearly increased in patients with HCC compared to normal controls. A Red fluorescent area was present at the cancerous area but not in the noncancerous cirrhotic area in a patient with HCC. These results suggest that aberrant porphyrin metabolism occurred in patients with HCC compared to other liver diseases.     

CO2 is the first species formed upon CO oxidation by CO dehydrogenase from Pseudomonas carboxydovorans

The active species of CO₂, i.e. CO₂ or HCO ₃ ^- , formed in the CO dehydrogenase reaction was determined using the pure enzyme from the carboxydotrophic bacterium Pseudomonas carboxydovorans. Employing an assay system similar to that used to test for carbonic anhydrase, data were obtained which are quite compatible with those expected if CO₂ is the first species formed. In addition, carbonic anhydrase activity was not detected in P. carboxydovorans.     

Photoreception in pineal organs of larval and adult lampreys,Lampetra japonica

A comparative study of the larval and adult pineal organs, which are sensitive to incident light, was carried out in the river lamprey Lampetra japonica, using intracellular recording from the pineal photoreceptors. The tissue overlying the larval pineal organ is transparent, whereas that over the adult pineal is translucent. The optical density of this oval pineal window in the adult lamprey was 1.2. In order to elucidate the early development of the larval pineal, the ratio r of the diameter (micron) of the pineal to the body-length (cm) was measured. The value of r was 62.5 in a small larva of 2.8 cm, 29.7 in a larger one of 14.3 cm, and 9.3 in an adult of 54 cm body-length. The intracellular response to light of the larval pineal was a hyperpolarization, showing fundamentally the same pattern as that of the adult pineal. It was possible to record a typical response even from the pineal of the smallest larva, 2.8 cm in body length, used in this study. The intensity-amplitude relationship was analysed after Naka-Rushton's hyperbolic equation. The value of sigma of isolated larval pineals was 0.88 log unit higher than that of adults. The value of n was larger in larvae, suggesting a sensitive reaction to changing photic stimulus. The spectral sensitivity was compared. The peak was at 505 nm in the larva, but 525 nm in the adult. A change of visual pigment in the pineal during metamorphosis is suggested.