Further evidence for a cell surface proteinase essential to the growth of cultured fibroblasts

Specific antibodies and protein proteinase inhibitors will inhibit cell-surface proteinase activity on human fibroblasts and cause a concomitant inhibition of DNA synthesis and of cell multiplication. An insolubilized proteinase inhibitor also inhibits cell multiplication. The same reagents partially inhibit the multiplication of mouse L cells, both in monolayer and suspension culture, and inhibit the mitogenic effect of epidermal growth factor (EGF) on both types of cell.     

Electrophysiological characteristics of cardiac pacemaker cells of the frog Caudiverbera caudiverbera

1. The cardiac pacemaker cells of the frog Caudiverbera caudiverbera are centrally located in the sinus venosus. These cells are rounded, smaller than contractile fibres and have large nuclei. 2. Intracellular recording confirmed the existence of primary and transitional pacemaker cells. 3. Action potentials from primary cells were resistant to blockade by tetrodotoxin (TTX), but were abolished by verapamil suggesting that their bioelectric activity is dependent on a slow inward current. 4. Transitional cells appeared to have two different inward currents contributing to the upstroke: a fast TTX-sensitive and a slow verapamil-sensitive current.     

Immunochemical studies on human monoclonal macroglobulins with specificities for 3,4-pyruvylated D-galactose and 4,6-pyruvylated D-glucose

Four of six human monoclonal IgM proteins were found to react best with Klebsiella polysaccharides containing 3,4py beta DGal (pyruvic acetalated D-galactopyranose), one with Klebsiella polysaccharides with 4,6pyDGlc; the sixth is uncharacterized. The combining sites of two of these (IgMWEA and IgMNAE) were essentially indistinguishable by quantitative precipitin studies at varying pH and by quantitative precipitin inhibition assays, but the other two differed in specificity of their combining sites from these and from each other. These differences were detected by precipitin inhibition assays with 3,4py beta DGal-containing oligosaccharide alditols, the R and S isomers of methyl 4,6py alpha DGal, the R isomer of methyl 4,6py beta DGal, or the R and S isomers of methyl 4,6py alpha DGlc, and -beta DGlc. In all of these except the S isomer of methyl 4,6pyDGal and R isomer of methyl 4,6pyDGlc, the carboxyl group is axial to the plane of the acetal ring. Their specificity appears to be determined by the nonreducing ends of chains and is considered to be cavity-type.     

Accumulation of pollutants in fish

The amount of radioactivity which derived from 14C-labeled pollutants was determined in liver, kidney, intestine, blood, muscle and gills of carp, exposed for 6, 24 and 72 hr to high external concentrations of urea, methanol, atrazine and PCP. The results allowed one to calculate roughly the uptake rate for these compounds. It was low for urea (0.055 micrograms/g per hr), higher for methanol (0.12) and atrazine (0.16) and highest for PCP (1.5). The bioaccumulation factors (BFs) were determined for the different substances and organs. They correlated with the hydrophilic-lipophilic nature of the chemicals. The more lipophilic the substances the more accumulation occurred in the liver. PCP accumulated the most. BF was 300-400 in most tissues except muscle where it was quite low. The BF was 3-4 for atrazine in liver, kidney and intestine, but just 1 in blood, muscle and gills. There is some evidence that the BF for methanol equals 1 in liver, kidney, gills and intestine. It is less than 1 in blood and muscle. Urea was equally distributed in all organs and in the external medium.     

Xenobiotic oxidation by cytochrome P-450-enriched extracts of Streptomyces griseus

Crude extracts of Streptomyces griseus grown on soybean flour-enriched medium contain high levels of cytochrome P-450. The cytochrome P-450-enriched fractions, obtained by ammonium sulfate fractionation (30-50% saturation), catalyze the NADPH-dependent oxidation of a variety of xenobiotics when complemented with both spinach ferredoxin:NADP+ oxidoreductase and spinach ferredoxin. Reactions observed are aromatic, benzylic and alicyclic hydroxylations, O-dealkylation, non-aromatic double bond epoxidation, N-oxidation and N-acetylation.     

Studies on the structure of yeast phosphofructokinase

In this paper, we describe an efficient procedure for the purification of yeast phosphofructokinase. This procedure eliminates any time delay and enables to obtain an enzyme with minimum proteolytic alterations. The molecular weights of the oligomeric enzyme and of its constitutive subunits were both evaluated by means of several independent methods. However, the accuracy of each measurement was not sufficient to discriminate between an hexameric and an octameric structure of the enzyme oligomer. On the other hand, crosslinking experiments demonstrated the octameric structure of yeast phosphofructokinase. Obviously, some methods of molecular weight determination have led to erroneous results. In particular, our experiments show that the reliability of molecular weight determinations performed by gel filtration of native proteins must be considered with caution.     

Correlation of 19F-NMR spectra of halothane in rat tumor and non-tumor tissues with membrane alterations

The membrane environments in normal and tumor rat tissue and the effect of hyperthermia thereon are studied with 19F-NMR spectroscopy of the general anesthetic halothane. Normal and tumor cell types are clearly differentiated by the halothane resonance. A hydrophobic environment prominent in tumor tissue is more sensitive to heat treatment than the corresponding environments of normal cells. Studies of extracted lipids suggest that this may be due in part to the considerable difference in lipid temperature response which exists between normal and kidney tumor cells.     

Beta-adrenergic receptor-linked adenylate cyclase in rat posterior pituitary

A specific β-adrenergic-stimulated cyclic AMP generating system has been evidenced in rat posterior pituitary. This is clearly demonstrated by: 1) the adenylate cyclase (AC) affinity for stimulants was in the order ISO > NA > DA, and 2) propranolol, a specific β-adrenergic receptor blocker, was the only antagonist of the system. Clonidine and apomorphine were completely inactive, thus excluding an α-adrenergic and/or dopaminergic component in this AC system. Our data also indicate that dopaminergic receptors present in both pituitary lobes are not coupled to an AC.     

Determination of the molecular mass of bacterial genomic DNA and plasmid copy number by high-pressure liquid chromatography

Relatively rapid methods for the determination of relative genome molecular mass (Mr) and the estimation of plasmid copy number have been developed. These methods are based on the ability of the Bio-Rad high-pressure liquid chromatography hydroxylapatite column to separate and quantify single-stranded DNA, double-stranded DNA, and plasmid DNA. Genome Mr values were calculated from reassociation kinetics of single-stranded DNA as measured with the hydroxylapatite column. Bacteriophage T4 DNA was used to establish a C0t (moles of nucleotides times seconds per liter), or standard reassociation value. From this C0t value, C0t values for Escherichia coli B, Beggiatoa alba B18LD, and Streptomyces coelicolor were determined by comparative calculations. From those calculated C0t values, the Mr values of 1.96 X 10(9) for E. coli, 2.02 X 10(9) for B. alba, and 3.28 X 10(9) for S. coelicolor were estimated. Plasmid concentration was determined from cleared lysates by comparing the integrated area under the phosphate buffer-eluted plasmid peak to values obtained with known amounts of plasmid. The plasmid copy number was estimated by multiplying the ratio between the amounts of plasmid and chromosomal DNA by the ratio between the Mr values of the chromosome and the plasmid. A copy number of 29 was obtained from a culture of E. coli HB101 harboring pBR322 grown to a culture density of 1.6 X 10(9) CFU . ml-1.