A new,strikingly patterned Calathea (Marantaceae) from Ecuador

Calathea libbyana from Napo Province, Ecuador, is described. It belongs to the dimorphic-bracted species-group ofCalathea seriesComosae. It is in cultivation under the cultivar name ‘Windows’, which refers to its distinctive leaf pattern with pale, semi-translucent markings.     

Ca2+ dependence of positive inotropic responses of guinea pig isolated cardiac preparations to cAMP-generating and cAMP-independent agonists

The effects of procedures which diminish Ca2+ influx into myocardial cells on responses of isolated cardiac preparations to cAMP-independent histamine H1 receptor stimulation and cAMP-generating beta-receptor stimulation were measured. The histamine response of guinea pig left atria, which appears to be primarily mediated by H1 receptors, was depressed to a greater extent than was the response of this preparation to isoproterenol by decreasing the extracellular Ca2+ concentration, and by the Ca2+ influx blocker D-600. Similarly, while the H1 agonist 2-pyridylethylamine dihydrochloride (PEA) produced increases in tension of a similar magnitude as the partial beta-agonist salbutamol in both left atria and in papillary muscles, responses of both preparations to PEA were depressed to a significantly greater extent by decreasing the extracellular Ca2+ concentration than were responses to salbutamol. Overall, both the basal developed force of papillary muscles and the responses of these preparations to H1 and beta-receptor stimulation appeared to be less depressed by decreasing the extracellular Ca2+ concentration than were those of left atria. These results indicate that responses mediated via cAMP-independent H1 receptors, like those arising from alpha-receptor stimulation, are more sensitive to procedures which diminish Ca2+ influx than are responses arising from stimulation of cAMP-generating beta-receptors. This may reflect differences in the mechanisms by which stimulation of H1, alpha-, and beta-receptors give rise to positive inotropic responses. In addition, left atria may be more dependent than papillary muscles on extracellular Ca2+ for the support of contraction.     

Effect of experimental diabetes on isolated rat heart responsiveness to isoproterenol

The isolated perfused working rat heart was used to study experimental diabetes-induced alterations in the sensitivity and responsiveness of the myocardium to the effects of isoproterenol. Experimental diabetes was induced by intravenous administration of either 65 mg/kg alloxan or 60 mg/kg streptozotocin. The positive inotropic and cardiac relaxant effects of isoproterenol were studied at various time points after the induction of diabetes. There were no changes either in the sensitivity or in the maximum responses of diabetic rat hearts to the positive inotropic effect of isoproterenol at any time point studied. However, the cardiac relaxant effect of isoproterenol was depressed in acute as well as chronic diabetic rat hearts when compared with age-matched controls. Ventricular noradrenaline content was unchanged in 180-day diabetic rat hearts indicating the absence of a diabetes-induced sympathetic neuropathy in the heart. The depressed relaxing effect of isoproterenol may have resulted from alterations in energy utilization and sarcoplasmic reticular function in diabetic rat hearts.     

Differentiation properties of pure populations of human dystrophic muscle cells

The interpretation of the majority of studies of Duchenne muscular dystrophy (DMD) has been complicated by the heterogeneous composition of the cultures used. In addition to muscle cells, muscle tissue contains adipocytes and fibroblasts and the proportion of these cell types varies, especially in disease states. To overcome this problem we developed culture conditions which permitted isolation and characterization of pure populations of clonally derived human muscle cells [1, 2]. Here we report the successful application of these methods to muscle cells from biopsies of individuals with diagnosed DMD. The normal and mutant human muscle cells were used in experiments of muscle differentiation in the same manner as cell lines. Frozen-stored cells were thawed, plated in a series of replicate plates, and allowed to differentiate under similar culture conditions. Yet, in contrast with cell lines, the cells were karyotypically normal, not altered by adaptation to long-term culture, and had a finite lifespan. We have systematically analysed specific properties of the normal and DMD muscle cells which differentiated in culture. The kinetics and extent of myoblast fusion, myotube morphology, and the accumulation and distribution of membrane acetylcholine receptors were monitored. In addition, the isozyme composition of creatine kinase and its intracellular and extracellular distribution were determined. Our results indicate that DMD muscle cells are fully capable of initiating myogenesis in culture and do not differ from normal muscle in several important parameters of differentiation.     

Susceptibilities of Algae and Legionella pneumophila to Cooling Tower Biocides

Nine algal strains and nine Legionella pneumophila strains were tested in laboratory culture for their susceptibility to inhibition by a variety of commercially available microbiocides. The responses ranged from ineffective to effective at 1/100 the manufacturers' recommended pulse doses. Tests were also performed to determine whether the action of the microbiocide was bacteriostatic or bacteriocidal.     

Stage specificity of selenium-mediated inhibition of mouse mammary tumorigenesis

The experiments reported herein examined the inhibitory role of selenium in chemical carcinogen-induced mouse mammary tumorigenesis. The results from four different experiments are presented herein and are summarized briefly. First, the results demonstrated that relatively low doses of dietary selenium (0.5–2.0 ppm) inhibited 7,12-dimethylbenzanthracene (DBMA)-induced mouse mammary tumorigenesis. At 2 ppm Se, the mammary tumor incidence was reduced from 56 to 15%. Second, the results suggested that the later stages of mammary tumorigenesis (preneoplastic to neoplastic transformation and tumor growth) are not as sensitive to selenium-mediated inhibition as the early stages, i.e., the induction and/or expression of mammary preneoplastic lesions. Finally, the results demonstrated that selenium markedly inhibited mammary tumorigenesis (from 42 to 8%) even when the mice were exposed to selenium only after the carcinogen treatments had been concluded. The results from these experiments are discussed from the viewpoint that selenium-mediated inhibition is a result of a direct block of DNA synthesis.     

Status of reduced glutathione in primary cultures of rat hepatocytes and the effect on conjugation of benzo[a]pyrene-7,8-dihydrodiol-9,10-oxide

The intracellular level of reduced glutathione (GSH) and GSH conjugation have been investigated in primary cell cultures of hepatocytes isolated from control rats, phenobarbitone (PB) and 3-methylcholanthrene (MC) treated rats. The data demonstrate that in all cell cultures the GSH concentrations show a triphasic pattern: (i) within 1 h of culture an initial marked decrease to 50% of the levels found in fresh hepatocytes; (ii) recovery of GSH concentrations to above the levels observed in fresh cells. This occurs after 6 h in culture with control cells and after 10-24 h with cells from either PB or MC treated rats and was most prominent in cells from PB-treated rats. (iii) A slow decline to between 30 and 40 nmol GSH/mg protein from 24 to 96 h in culture. Synthesis of GSH was slower in cultured cells from PB treated rats and this was confirmed by the resynthesis rates when diethylmaleate (DEM) was used to deplete GSH. The formation of GSH conjugates with racemic 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) was measured in control cells in suspension and after 3 and 24 h in culture. Despite the decrease in GSH concentrations observed between 1 and 4 h after culture, the conjugation rates were not decreased.     

Karyological and biochemical evidence for chromosomal dedifferentiation in neoplasia

Summary Quantitative analysis of the X-linked enzyme, glucose 6-phosphate dehydrogenase (G-6-PD), was performed on tumor cells lines from two human females. Both tumor cells were hyperdiploid, having complete or redundant C+X groups. One, no. 930, lacked the X chromatin body and exhibited twice the level of G-6-PD as in the X chromatin-positive tumor cells, ME-180. Hence, in the no. 930 cell, reversal of X chromosomal condensation was associated with loss of the X chromatin body and doubling of genetic activity. Cells of no. 930 were subsequently placed in culture where after three passages they developed an X chromatin body (or bodies). G-6-PD determinations made at that time showed enzyme levels comparable to the X chromatin-positive tumor cells (ME-180). This research was supported by United States Public Health Service Grant CA 08791-03.     

Metabolism of Imidazole by a Pseudomonad

Intermediates formed during the microbial degradation of imidazole, namely 4(5)-imidazolone, formiminoglycine, and possibly glycine, are similar to those formed during metabolism of imidazole derivatives.     

Transformation in Bacillus amyloliquefaciens

The methodology and some of the requirements for the deoxyribonucleic acid-mediated transformation of an arginine auxotroph of Bacillus amyloliquefaciens to prototrophy are described.