Enhancement of α-methylglucoside efflux by respiration in respiratory mutants of Escherichia coli K-12

The rate of α-methylglucoside efflux from wild-type cells of Escherichia coli K-12 is enhanced by different substrates, as long as they are readily respired. A similar enhancement takes place in strains with impaired oxidative phosphorylation (unc mutants), regardless of their being able (strains AN120, N₁₄₄, and AN382) or unable (strain NR70) to energize the membrane through respiratory electron flow. The uncouplers carbonylcyanide-m-chlorophenylhydrazone and tetrachlorosalicylanilide do not diminish the efflux acceleration in wild-type strains or unc mutants. However, the stimulation of α-methylglucoside efflux does not occur in the mutant AN59 which cannot perform a normal respiratory electron transport due to a defective synthesis of ubiquinone. The failure to stimulate the efflux is observed with succinate, which is a typical substrate of respiration, as well as with substrates which can yield ATP both at respiratory and substrate levels such as gluconate or glycerol. Moreover, potassium cyanide nullifies the acceleration of α-methylglucoside efflux caused in any type of strain and by any substrate. These results show that neither ATP nor an energized state of the membrane appears to be needed for respiration to accelerate α-methylglucoside release from E. coli cells, and question the existence of any energy-requiring reaction for αMG exit, previously proposed by other authors.     

The effect of S-adenosyl-L-methionine (SAM) on membrane permeability in the perfused rat liver

S-adenosilmethionine is present in most human tissues and is an important factor for transmethylation, transulphuration and aminopropylation reactions. The compound improves the biological, morphological and histochemical aspects of rat liver following CCl4 intossication. At the same time has been successfully used during chronic liver disease in man. With the aim to better clarify the action mechanism of SAMe some aspects concerning its effects on cell permeability in rat liver, by using the perfusion technique, have been investigated. In particular the capacity of this compound to prevent the enzymatic loss (GPT and GOT) during liver perfusion has been studied. 30 perfusions without SAMe, as control, and 6 by infusing 2 mg of compound during the perfusion time have been accomplished. Varing the perfusion time from 0 to 120 min it has been observed that at any time the presence of the SAMe reduced by about 50% the loss of GOT. Similarly the activity of GPT ranging from 2 to 6 mU/ml indicate that no appreciable enzyme output occurs in presence of SAMe.     

Superficial mycoses in Italy

A total of 1244 cases suspected of superficial mycoses were analysed in a period of 12 months in Italy. Dermatophytoses were found in 62.4%; the other common disease was Pityriasis versicolor (44.1%). The predominant speciesEpidermophyton floccosum (34,2%) was strickingly high in relation to other statistics; this species was commonest in tinea cruris. Among the other dermatophytesM. canis was predominant (31.3%) commonest in tinea corporis, followed byT. mentagrophytes (17,8%) andT. rubrum (10,3%). A high rate of yeasts was found in tinea manum (81.6%) and tinea pedis (47.7%).     

Experiences from the accident of Seveso

Provisional data on selected sanitary events which took place at Seveso after July 10 1976 are reported. 187 cases of chloracne, mostly in children, were detected, 50 just after the accident, the others within a year. Most polluted area (zone A) provided almost all "early" and most severe cases, but the territorial distribution of chloracne prevalence rates showed some inconsistencies with the soil TCDD pollution map; interpretations for such findings are discussed. Thirty-eight birth defects were detected in 1977 (none in zones A and B), more than in previous years, but still less than expected in a well controlled "normal" population: no clustering around a given type was observed. Spontaneous abortions, evaluated both as abortion rates and as pregnancy loss rates, showed scattered and statistically non-significant variations, inconsistent with the pollution map. No differences in birth and death rates compared to surrounding areas were observed. Data on ad hoc cytogenetic, neurological and immunological surveys are commented. Limitations of the presently available data are discussed and further research lines are anticipated.     

Analysis and classification of vegetation based on family composition

Plant Ecology - The distributions of 54 plant families in 105 samples were studied to determine their indicator value in the vegetation of the Pacific Northwest. Families may be characteristic of...     

The differential effects of PGE on the immune response in normal and immunosuppressed mice

The effect of 16,16-dimethyl-PGE₂-methyl ester (di-M-PGE₂) on humoral and cellular immunoresponsiveness has been compared in normal mice and in mice immunosuppressed by splenectomy and thymectomy plus antithymocyte serum (ATS). Splenectomy resulted in immunosuppression manifested by augmentation of B-16 melanoma growth; this stimulatory effect was reversed by di-M-PGE₂. In animals immunosuppressed by thymectomy plus ATS, di-M-PGE₂ augmented the humoral and cellular immune responses; this was manifested by slowing of the growth of B-16 melanoma and by stimulating the number of plaque-forming cells, hemagglutinin titers, and delayed-hypersensitivity reactions to sheep erythrocytes. In contrast, in normal (nonthymectomized) mice, di-M-PGE₂ was mildly immunosuppressive. Finally, adriamycin-immunosuppressed normal mice and this suppression were reversed by the addition of di-M-PGE₂ to the treatment regimen.     

Interaction of glutathione transferase from horse erythrocytes with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole

7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity.     

Redox forms of human placenta glutathione transferase

Human placenta glutathione transferase (EC 2.5.1.18) pi undergoes an oxidative inactivation which leads to the formation of an inactive enzymatic form which is homogeneous in several chromatographic and electrophoretic conditions. This process is pH dependent, and it occurs at appreciable rate in alkaline conditions and in the presence of metal ions. Dithiothreitol treatment completely restores the active form. -SH titration data and electrophoretic studies performed both on the oxidized and reduced forms indicate that one intrachain disulfide is formed, probably between the two faster reacting cysteinyl groups of each subunit. By the use of a specific fluorescent thiol reagent the disulfide forming cysteines have been identified as the 47th and 101th residues. The disulfide formation causes changes in the tertiary structure of this transferase as appears by CD, UV, and fluorometric analyses; evidences are provided that one or both tryptophanyl residues of each subunit together with a number of tyrosyl residues are exposed to a more hydrophilic environment in the oxidized form. Moreover, electrophoretic data indicate that the subunit of the oxidized enzyme has an apparent molecular mass lower than that of the reduced transferase, thereby confirming structural differences between these forms.