Induction of 2',5' oligo(A) synthetase in tumor-bearing mice with encephalomyocarditis (EMC) virus or poly(I)poly(C)

Infection of 13 month-old C3H mice with EMC virus or inoculation with the interferon inducer poly(I)poly(C) results in elevated levels of the enzyme 2',5' oligo(A) synthetase only in animals with spontaneous tumors (breast cancer or hepatomas). High enzymatic activities are detected in homogenates from liver, spleen, plasma and neoplastic cells of the animals with breast carcinomas and only in the neoplastic liver cells of the animals with hepatomas.     

Changes induced by hydrazine in optical spectra of cytochrome oxidase

Casein kinase-TS (Ck-TS), a type-2 casein kinase purified from rat liver cytosol which phosphorylates seryl and threonyl residues N-terminal to acidic clusters, is specifically inhibited by polyglutamyl peptides which are ineffective both on type-1 casein kinase and on cAMP-dependent protein kinase. The inhibition is competitive toward the protein substrate and non-competitive toward ATP. Among the polyglutamates tested (Glu)70 is the most effective (Ki 0.11 microM). (Glu)10 and (Glu)5 are also inhibitors, though less powerful than (Glu)70, while (Glu)3, (Glu)2 and free glutamic acid up to 5 mM are ineffective. These results disclose the possibility that naturally occurring polypeptides containing long stretches of acidic residues may act as physiological inhibitors of type-2 casein kinases.     

Isolation of a brain peptide identical to the intestinal PHI (peptide HI)

The isolation of a brain peptide identical to the intestinal peptide PHI (peptide HI) is described. The peptide was isolated from porcine brain extract using a chemical assay method based on its C-terminal isoleucine amide structure. The complete amino acid sequence of the peptide was found to be: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Arg-Leu-Leu-Gly-Gln-Leu-Ser-Ala- Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Ile-NH2. This sequence is identical to the intestinal peptide thus demonstrating PHI to be a brain-gut peptide. The role of PHI in the central nervous system as a neurotransmitter or neuromodulator is discussed.     

Detection of carcinogen-induced DNA breaks by nick translation in permeable cells

A nick-translation reaction with $\text{E. coli}$ DNA polymerase I (pol. I) was used to detect $\text{in situ}$ DNA breaks produced by chemical carcinogens. Normal human fibroblasts treated with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) in various doses were permeabilized with lysolecithin, and were nick translated in the presence of [³H]dCTP and pol. I. The radioactivity incorporated increased with MNNG concentration, and was directly proportional to the poly(ADP-ribose) synthetase activity. Other DNA-damaging agents such as bleomycin or 4-nitroquinoline 1-oxide also caused the nick translation rate to increase. When MNNG-treated cells were cultured in fresh medium containing no MNNG, the increase in the rate of nick translation in permeable cells became less and this decrease was abolished by addition of aphidicolin or cytosine arabinoside. The nick translation method described here may be a useful means for estimating intrinsic DNA breaks in cells treated with carcinogens.     

A 1H-NMR longitudinal relaxation study of the interaction between cytochrome c and cytochrome c oxidase

The interaction between the oxidized forms of cytochrome c and cytochrome c oxidase (EC 1.9.3.1) has been investigated by ¹H-NMR longitudinal relaxation measurements. It is found that relaxation of methyl groups on the heme ring of cytochrome c markedly deviates from a simple exponential behavior in the presence of small amounts of cytochrome oxidase. A comparison with the relaxation behavior of cytochrome c modified by 4-carboxy-3,5-dinitrophenyl at Lys-13 shows that the oxidase induces a conformation in native cytochrome c that is closely related to that of the derivative. It is suggested that this change in conformation consists of a rupture of the salt bridge between Lys-13 and Glu-90 and a concomitant perturbation of the methionine ligand.     

Changes in composition and function of thylakoid membranes as a result of photosynthetic adaptation of chloroplasts from pea plants grown under different light conditions

The hypothesis that chloroplasts having different light-saturated rates of photosynthesis will have different proportions of the intrinsic thylakoid complexes engaged in light-harvesting and electron transport (Anderson, J.M. (1982) Mol. Cell. Biochem. 46, 161–172) has been tested. Peas were grown in light regimes which varied in light intensity, quality and time of irradiance, and ranged from sunlight through red to blue-enriched light of very low radiation. The electron-transport capacity at saturating light of Photosystem I and Photosystem II of chloroplasts isolated from light-adapted peas was 2-fold and 5–6-fold lower, respectively, in the lowest radiation compared to sunlight. There was a marked increase in the amount of total chlorophyll associated with the main chlorophyll $\text{a}\text{b-}\text{proteins}$ (LHCP¹, LHCP² and LHCP³) and a 2-fold decrease in the core reaction centre complex of Photosystem II (CP a) as the radiation decreased; the $\text{LHCP}{}^{\mathrm{1–3}}\text{CP}$ a ratio changed from 3.5 to 9.0. The amount of chlorophyll associated with Photosystem I varied from 34% in sunlight to 27% in the lowest radiation, but the antenna size of Photosystem I was not markedly different; there was a 2-fold decrease in the amount of cytochrome f on a chlorophyll basis, which partly accounted for the decreased electron-transport capacity of Photosystem I. Since the increases or decreases in the levels of each of the components correlated with decreasing radiation, it is clear that the light-adaptation of both light-harvesting and electron-transport components is indeed closely co-ordinated.     

Rapid resolution of transferrin C subtypes through isoelectric focusing with 2-mercaptoethanol

The technique of choice currently used for the detection of serum transferrin molecular polymorphism is isoelectric focusing on polyacrylamide slab gels. However, this procedure is unsatisfactory for routine purposes, since a long pretreatment of the serum with iron-donor compounds or neuraminidase is necessary in order to obtain a complete resolution of the transferrin molecule. A very fast and highly economical standardized procedure for transferrin typing which enables a fair molecular resolution within only 3 1/2 h is reported. Protracted pretreatment of serum with neuraminidase or with iron-donor compounds can be totally avoided. An ultrathin layer of polyacrylamide gel is employed for the run, using pH ranges of 4-6.5 or 5-7. A short pretreatment of serum with a 13% solution of 2-mercaptoethanol is performed before the samples are placed on the gel. This technique has been used to perform transferrin typing in 396 cord serum samples from newborn infants of Arezzo (Tuscany), without occurrence of artifacts or the appearance of extra bands in transferrin patterns.     

Mode of interference of chlorosis-inducing herbicides with peroxisomal enzyme activities

In rye leaves ( Secale cereale L. cv. Petkus "Kustro") bleached in the presence of the chlorosis-inducing herbicides aminotriazole, haloxidine, San 6706 or difunone in white light of 54.2 W m^-2 (5000 lx), catalase activity was very low. In addition, the activities of glycolate oxidase and hydroxypyruvate reductase were strongly diminished in treatments with San 6706 and difunone. The lowering of the peroxisomal enzyme activities was observed in red, but not in blue light and did not occur after treatment with the non-bleaching pyridazinone derivative San 9785. The deficiencies of the peroxisomal enzymes did not appear to be involved in the initiation of the chlorosis. Instead they are probably produced as secondary consequences of the bleaching. Low peroxisomal enzyme activities were also obtained without herbicide treatment by growing the leaves in an atmosphere of 2% O₂ and 3% CO₂, but in this case were not accompanied by an increased sensitivity of the Chl to photooxidative bleaching. The peroxisomal enzymes reached as high activities as in untreated controls when the herbicide-treated leaves were grown at a low light intensity of 0.106 W m^-2 (10 lx). After transfer of herbicide-treated leaves grown under 0.106 W m^-2 to 306 W m^-2 (30 000 lx), catalase was strongly inactivated, even at 0°C. In treatments with San 6706 and difunone the increase of the activities of glycolate oxidase and hydroxypyruvate reductase was either stopped, remaining unchanged, or the enzymes were slightly inactivated after exposure to 306 W m^-2 (30 000 lx). The observations suggest that the inactivation of peroxisomal enzymes results from photooxidative events in the chloroplasts.     

Changes in polyamines and related enzymes with loss of viability in rice seeds

Putrescine, spermidine and spermine of high vigour, low vigour and non-viable (classes 1, 2 and 3 respectively) seeds of Oryza sativa increased with loss of viability. The largest concentration of spermine was found in non-viable embryos. Spermine was absent in the husks of all the three categories of seeds. Arginine decarboxylase was greatest in high vigoured seeds and its activity gradually declined with loss of viability. However, diamine oxidase and polyamine oxidase activities gradually increased with the loss of viability of the seeds while DNA, RNA and protein contents decreased. The total content of polyamines increased on kinetin treatment but declined on ABA treatment. DNA, RNA and protein followed the same trend as polyamines. The polyamine contents increased by ca 3- and 4-fold, respectively, in high vigoured and low vigoured seeds on 10^?4 M kinetin treatment. The activity of ADC followed the same change as that of the polyamines in both cases, but the reverse was observed for the activities of diamine and polyamine oxidases.     

A chemiluminescent method for measurement of activated oxygen forms in biological fluids and homogenates

A chemiluminescent method for measuring the concentration of activated oxygen species (O₂² and H₂O₂) is described. Its main features are: high sensitivity (10^?9 M H₂O₂), its applicability to systems with high optical absorbance in the visible spectral region, a wide linear dynamic range, and the possibility for recording the kinetics of the processes, in which activated oxygen species are involved.