Mutagenic activation of aflatoxin B1 by several forms of purified cytochrome P-450

Metabolic activation by several forms of purified cytochrome P-450 of aflatoxin B1 to a product(s) mutagenic to Salmonella typhimurium TA100 was examined. Of the 5 forms of cytochrome P-450 purified from liver microsomes of untreated and PCB-treated male rats, a constitutive form purified from untreated male rats, P-450-male, and a high-spin form of cytochrome P-450, P-448-H, from PCB-treated rats were highly active.     

Mouse lymphoma L1210 cells acquire a new cystine transport activity upon adaptation in vitro

Summary Mouse lymphoma L1210 cells maintained in vitro at a high cell density for a certain time period adapted themselves to the in vitro environment and were able to grow indefinitely. From these adapted cells, more than 30 clones were isolated. They all had much higher activity to take up cystine than the original L1210 cells, supporting a previous view that the deficiency of the cystine uptake limits the survival and growth of L1210 cells in vitro. The cystine uptake of one cloned cell line was characterized. The enhanced uptake of cystine in these cells was mainly mediated by a Na⁺-independent, saturable system and was potently inhibited by glutamate and some other anionic amino acids, but less by aspartate. Such activity of cystine uptake was not observed in the original L1210 cells. The results suggest that, upon adaptation in vitro, L1210 cells acquire a new cystine transport activity necessary for survival and growth in vitro.     

Effect of clofibrate on peroxisomal and mitochondrial beta-oxidation in chicken liver

The effect of a 0.25% clofibrate diet for 2 weeks on peroxisomal and mitochondrial beta-oxidation in chicken liver was studied. The activities of antimycin antimycin A-insensitive palmitoyl-CoA oxidation (peroxisomal beta-oxidation) and carnitine acetyltransferase increased about two-fold. The activities of palmitoyl-CoA-dependent O2 consumption (mitochondrial beta-oxidation) and carnitine palmitoyltransferase were also slightly activated by the administration of clofibrate, but not significant. Thus, clofibrate may be a typical drug which activates the peroxisomal beta-oxidation more than the mitochondrial one in various species. The effect of clofibrate on peroxisomal carnitine acetyltransferase was the same as that on the mitochondrial one in chicken liver. Serum lipids were not lowered, but hepatomegaly was observed in the present experiment with chicken.     

The unique action for bone metabolism of 1 alpha,25-(OH)2D3-26,23-lactone

[23 (S), 25 (R)]-1 alpha,25-Dihydroxyvitamin D3-26,23-lactone [( 23 (S),25 (R)]-1 alpha,25-(OH) 2D3-26,23-lactone) increased dose-dependently alkaline phosphatase activity in osteoblastic cells, clone MC3T3-E1, in medium containing 0.1% bovine serum albumin. The maximal stimulated enzyme activity per mg protein was 1.6-fold over that of control cultures at 250 pg/ml. The metabolite also increased collagen synthesis in a dose-related fashion. On the other hand, [23 (S),25 (R)]-1 alpha,25-(OH)2D3-26,23-lactone decreased slightly but significantly 45Ca mobilization, and blocked the resorptive action of 1 alpha,25-dihydroxyvitamin D3 but not that of parathyroid hormone, in mouse calvaria in organ culture. These results indicate that [23 (S),25 (R)]-1 alpha, 25-(OH)2D3-26,23-lactone stimulates the differentiation of osteoblasts and inhibits bone resorption in vitro.     

Isolation and characterization of the bacteriophage T4 tail-associated lysozyme.

Direct evidence has been obtained that the tail-associated lysozyme of bacteriophage T4 (tail-lysozyme) is gp5, which is a protein component of the hub of the baseplate. Tails were treated with 3 M guanidine hydrochloride containing 1% Triton X-100, and the tail-lysozyme was separated from other tail components by preparative isoelectric focusing electrophoresis as a peak with a pI of 8.4. The molecular weight as determined from sodium dodecyl sulfate electrophoresis was 42,000. The tail-lysozyme was unambiguously identified as gp5 when the position of the lysozyme was compared with that of gp5 of tube-baseplates from 5ts1/23amH11/eL1ainfected Escherichia coli cells by two-dimensional gel electrophoresis. The tail-lysozyme has N-acetylmuramidase activity and the same substrate specificity as gene e lysozyme; the optimum pH is around 5.8, about 1 pH unit lower than for the e lysozyme. We assume that the tail-lysozyme plays an essential role in locally digesting the peptidoglycan layer to let the tube penetrate into the periplasmic space. The tail-lysozyme is presumably also responsible for "lysis from without."     

Transient glucose intolerance during attacks of thyrotoxic periodic paralysis

In a 19-year-old Japanese male (case 1) with thyrotoxic periodic paralysis (TPP), an increase of plasma glucose concentration together with abnormally high levels of serum immunoreactive insulin (IRI) was observed preceding a spontaneous attack of paralysis. Therefore, the plasma glucose, glucagon, epinephrine, norepinephrine, serum IRI, growth hormone and cortisol levels, and the erythrocyte insulin receptors were measured in case 1 and a 40-year-old Japanese male (case 2) with TPP during attacks of paralysis induced by prolonged glucose loading. In case 1, the serum IRI concentration was elevated to the extraordinarily high level of 655.0 microU/ml at the beginning of paralysis, and at that time, the plasma glucose concentration was 147 mg/dl. However, when paralysis was not induced by a similar glucose loading during methimazole treatment, the serum IRI and plasma glucose levels at the corresponding time after glucose loading were 20.9 microU/ml and 87 mg/dl, respectively. Furthermore, the affinity of the erythrocyte insulin receptors was decreased during the attack. In case 2, plasma glucose and serum IRI concentrations were increased in accordance with the initiation of paralysis although the blood levels of hormones counteracting insulin were not significantly changed. These findings suggest that there is something interacting with the normal action of the insulin in the early phase of paralysis.     

Genome type analysis of adenovirus type 4 isolates, recently obtained from clinically different syndromes in some areas in Japan

DNA cleavage analyses with EcoRI, HindIII and BamHI were carried out to investigate genome types of recent Ad 4 isolates obtained from acute respiratory disease (8 strains), and ocular disease (11 strains) in Japan. DNA cleavage patterns of all 19 isolates studied were identical regardless of whether they were recovered from respiratory tract or conjunctiva, but were distinct from that of the prototype strain.     

Affinity chromatography of urokinase on an agarose derivative coupled with pyroglutamyl-lysyl-leucyl-argininal

Pyroglutamyl-lysyl-leucyl-argininal (Pyr-Lys-Leu-Argal) immobilized on gel matrix through the epsilon-amino group of its lysine residue was shown to be an efficient biospecific affinity adsorbent for purification of urokinase. Pyr-Lys-Leu-Argal dibutylacetal, a precursor of this immobilized ligand, was synthesized by a fragment condensation procedure, in which one of the thermolysin-digestion products of leupeptin dibutylacetal, H-Leu-Argal dibutylacetal, was used as a key intermediate. The precursor was coupled to CH-Sepharose 4B with the aid of a water-soluble carbodiimide, and its acetal protecting group was then removed by mild acid treatment to free the essential aldehyde function. The Sepharose derivative thus prepared was shown to adsorb urokinase selectively and effectively from a crude human urine preparation at neutral pH and to release the bound enzyme under mild acidic conditions. The present technique afforded a highly purified urokinase preparation abundant in the high-molecular form with 90% recovery. The complex formed between urokinase and the immobilized ligand was found to have a dissociation constant of about 2 X 10(-4)M.     

Molecular cloning and nucleotide sequence of the cDNA for rat peroxisomal enoyl-CoA: hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme

For the studies on the mechanism of induction of peroxisomal beta-oxidation enzymes and biogenesis of the organelle, we have isolated cDNA clones for rat peroxisomal enoyl-CoA: hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme. On blotting experiments with liver RNA, the cDNAs hybridized to a 3.0-kilobase RNA which was increased 5-7-fold by the administration of di-(2-ethylhexyl)phthalate to rats. Nucleotide sequencing was carried out for four cloned cDNAs and one obtained by a primer extension method. By overlapping these sequences with each other, we identified 20 nucleotides of 5'-noncoding, 2,166 nucleotides of coding, and 910 nucleotides of 3'-noncoding regions. The deduced amino acid sequence of the enzyme is composed of 722 residues, and the composition agrees with that of the protein data. The sequence was confirmed by the amino acid compositions and sequence analyses of some of the tryptic peptides. The molecular weight of the mature enzyme is calculated to be 78,511 from the predicted amino acid sequence. The enzyme has no terminal peptide extension as a signal for translocation into peroxisomes.