“Pleiotypic Response”

A hypothesis has been developed to relate stringent control in bacteria to a set of interactions involved in the regulation of growth of transformed and untransformed mammalian cells.     

Inhibition of DNA Synthesis but not of Poly-dAT Synthesis by the Arabinose Analogue of Cytidine <Emphasis Type="Italic">in vitro</Emphasis>

Kimball and Wilson¹ reported that the arabinose analogue of cytidine (ara-C) inhibited DNA polymerase in a crude extract prepared from Ehrlich ascites cells. Furth and Cohen² observed cytosine arabinoside triphosphate (ara-CTP) inhibited DNA polymerase in extracts from either calf thymus or bovine lymphosarcoma tissue, although these investigators³ had already found no effect of ara-CTP on DNA polymerase from Escherichia coli. The inhibition in both of these cases could be substantially reversed by dCTP; but incorporation of the arabinose nucleotide (ara-CMP) into DNA could not be unequivocally demonstrated. Graham and Whitmore⁴ reported the incorporation of ara-C into DNA in vivo and the inhibition of a DNA polymerase from L cells by ara-CTP. They found that ara-CMP was initially incorporated into small DNA strands but subsequently appeared in long strands. Momparler⁵ has presented evidence that, in vitro, ara-C incorporation was limited to the 3′-hydroxyl end of DNA chains. Such incorporation might be expected to block further chain elongation but this expectation was not supported by the evidence presented by Graham and Whitmore.     

Endopeptidase Activity of Phage λ-Endolysin

JACOB and Fuerst^1,2 demonstrated the presence of a bacteriolytic enzyme (λ-endolysin) in the induced cultures of lysogenic Escherichia coli K12 (λ). The enzyme was later identified as the product of gene R; of phage λ³ which is involved in bacterial lysis at the end of a latent period. The enzyme is apt to form spheroplast-like structures in E. coli² and one would therefore expect its substrate to be murein.     

Metabolic dynamics in the human red cell. Part II--Interactions with the environment

The maintenance of human red cell volume under multitude of trying physiological conditions is a self regulated dynamic process. Theoretical and experimental studies on red cell osmotic states have been primarily focussed on three different interdependent areas: the permeative properties of the red cell membrane, the kinetic studies of transmembrane fluxes of various ionic and nonionic chemical constituents of the red cell and plasma, and the ideal and non-ideal thermodynamic formulation of the osmotic states. The primary objective of this work is to provide a general model that converges the above mentioned components of the red cell and its environment under one umbrella. Such a model facilitates the simultaneous interpretation and prediction of quantitative changes in the red cell volume, pH, Donnan ratios, osmotic effects, plasma volume, transmembrane fluxes, and permeable and impermeable solute concentration.     

Response of senescing wheat leaves to ultraviolet a light: Changes in energy transfer efficiency and PS II photochemistry

Response of senescing leaves of wheat seedlings to ultraviolet A (UVA) radiation (365 nm) has been examined. The results indicate that senescence-induced disorganization of thylakoid membrane, decline in carotenoid-to-chlorophyll energy transfer, and enhancement of lipid peroxidation are furthered by radiation. The senescence-induced decline in photochemical activity of photosystem II further declines on irradiation. UVA does not specifically alter any site other than those damaged by senescence.     

Studies on the lipozyme-catalyzed synthesis of butyl laurate

The effects of temperature, speed of agitation, enzyme concentration, etc., on butyl laurate synthessis using Mucor miehei lipase (Lipozymetrade mark) have been studied. Although the soluble enzyme was quite thermcstable in aqeous solution, it deactivated rapidly at and above 40 degrees C in the presence of butanol. This enzyme immobilized on an anion-exchange resin (Lipozymetrade mark) showed enhanced stability (as compared to the soluble form) to denaturation by butanol under the same conditions. The denaturation of M. miehei lipase was found to be a function of the butanol concentration in the aqueous phase, and rapid denaturation takes place at the concentration corresponding to its saturation at that temperature. (c) 1995 John Wiley & Sons, Inc.     

Factors modifying radiation induced stimulation in plants: Pre-irradiation seed moisture content

Summary The effect of moisture content of seeds at the time of irradiation in relation to radiation-induced stimulation was investigated on rice (Oryza sativa c.v. D-6-2-2). The optimum moisture content was 8% for stimulation measured as seedling height. It is concluded that seed moisture at the time of irradiation plays an important role in the expression of stimulation and its reproducibility.     

Protection against acute paraquat toxicity by ambroxol

An expression vector for G-CSF, pASLB3-3, was constructed and introduced into Namalwa KJM-1 cells (Hosoi et al., 1988), and cells resistant to 100 nM of methotrexate (MTX) were obtained. Among them, the highest producer, clone SC57, was selected and the productivity of this clone was further characterized. The maximal production of G-CSF was at the most 1.8 g/ml/day using a 25 cm² tissue culture flask, even though the cell number was above 7×10⁵ cells/ml. The limiting factors at high density were analyzed as the deficiency of nutrients, such as glucose, cysteine and serine, and pH control. The depression of specific G-CSF productivity per cell under the batch culture conditions was overcome by using a perfusion culture system, Biofermenter^TM (Sato, 1983) with modifications of nutrients supplementation by a dialysis membrane and/or dissolved oxygen (DO) supplementation by microsilicone fibers. ITPSGF medium was modified to elevate concentrations of amino acids and glucose by 2.0- and 2.5-times, respectively. Under the control of pH at 7.4 and DO at 3 ppm, the specific G-CSF productivity was not depressed even at high cell density (above 1×10⁷ cells/ml), and the amount of G-CSF reached 41 g/ml. These results indicated the possibility of finding the optimum culture conditions for the production of recombinant proteins by Namalwa KJM-1 cells.Abbreviations ABTS 2,2-Azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid - BSA Bovine Serum Albumin - BSA-PBS Phosphate-buffered Saline without Ca²⁺ and Mg²⁺ containing Bovine Serum Albumin - dhfr Dihydrofolate Reductase - DO Dissolved Oxygen - G-CSF Granulocyte Colony-stimulating Factor - HEPES 4-(2-Hydroxyethyl)-1-piperazineethansulfonic Acid - IFN Interferon - MTX Methotrexate - PBS(-) Phosphate-buffered saline without Ca²⁺ and Mg²⁺ - Tween-PBS Phosphate-buffered saline without Ca²⁺ and Mg²⁺ containing 0.05% of Tween 20     

Isolation of a highly active H+-ATPase from beef heart mitochondria

The lysolecithin extraction procedure originally described by Sadleret al. (1974) has been modified to yield a H⁺-ATPase with high levels of P_i-ATP exchange activity (400–600 nmol × min^–1 × mg^–1). This activity is further enhanced (1400–1600 nmol × min^–1 × mg^–1) following sucrose density gradient centrifugation in the presence of asolectin. This enhancement results in part from a lipid-dependent activation and in part from removal of inactive complexes. The H⁺ translocating activity of the complex has been determined spectrophotometrically using binding of oxonol VI as an indicator of membrane potential. P_i-ATP exchange, ATP hydrolysis, and oxonol binding are sensitive to energy-transfer inhibitors (oligomycin, rutamycin) and/or uncouplers (DNP, FCCP).