Mode of binding of adriamycin with sulfatide-containing liposomes

Association constants and maximum binding numbers of sulfatide- and phosphatidylserine (PS)-containing liposomes for their binding with adriamycin (ADM) were determined by the column equilibration method. Although these liposomes have two kinds of binding sites, hydrophobic and electrostatic, the majority of ADM molecules was associated with the liposomes via their latter binding sites. Since the association constant for the electrostatic binding of ADM was smaller in sulfatide-containing liposomes (3 x 10(3) M-1) than in PS-containing ones (1.1 x 10(4) M-1), high efficiency of sulfatide-containing liposomes for the entrapment of ADM might be explained by the effect of sulfatide making the liposomes rigid, thereby preventing the leakage of the entrapped ADM.     

Acidic fibroblast growth factor prevents death of hippocampal CA1 pyramidal cells following ischemia.

Ischemic insult induces neuronal death in the CA1 subfields of the hippocampus which are designated generally as the most vulnerable brain region. Recent studies have shown that acidic and basic fibroblast growth factors are potent trophic factors that support the survival of neurons in many brain regions including the hippocampus. Here we demonstrate that continuous infusion of acidic fibroblast growth factor into the lateral cerebral ventricles beginning 2 days before ischemia prevents the death of the CA1 pyramidal cells in the hippocampus of gerbils. Furthermore, delayed continuous administration of acidic fibroblast growth factor starting 5 min after ischemia is equally protective. The results suggest a possible physiological function for acidic fibroblast growth factor in the normal support of hippocampal CA1 pyramidal cells and neurons in some other brain regions in considering the broad spectrum of responsive neurons.     

Regulated Expression of a Gene-Fusion Product Derived from the Gene for Phytochrome I from Pisum sativum and the uidA Gene from E. coli in Transgenic Petunia hybrida

The 5'-upstream region (2.4 kb) of the gene for phytochromeI from Pisum sativum (phyl) was fused to the uidA gene fromEscherichia coli that encodes ß-glucuronidase (GUS).The resulting PHY-GUS fusion was introduced into Petunia hybridaand was used as a reporter of the expression of the phyI genewhich was recognized by GUS activity. The PHY-GUS fusion wasexpressed at a relatively high level when transgenic plantswere grown in the dark, while leaves and stems of light-grownplants showed background activity. Flowers of light-grown plantswere shown to have significant levels of GUS activity but rootsdid not have such activity. When light-grown transgenic plantswere transferred to the dark, they expressed the activity atlevels that corresponded to those of dark-grown plants. Lighttreatment prior to growth in darkness revealed red/far-red reversibilityof recovery of the activity. Thus, the 2.4-kb fragment fromthe 5' region of the phyI gene carries the information necessaryfor the light-repressible autoregulation. (Received March 30, 1991; Accepted May 20, 1991)     

Bacterial NADH-quinone oxidoreductases

The NADH-quinone oxidoreductases of the bacterial respiratory chain could be divided in two groups depending on whether they bear an energy-coupling site. Those enzymes that bear the coupling site are designated as NADH dehydrogenase 1 (NDH-1) and those that do not as NADH dehydrogenase 2 (NDH-2). All members of the NDH-1 group analyzed to date are multiple polypeptide enzymes and contain noncovalently bound FMN and iron-sulfur clusters as prosthetic groups. The NADH-ubiquinone-1 reductase activities of NDH-1 are inhibited by rotenone, capsaicin, and dicyclohexylcarbodiimide. The NDH-2 enzymes are generally single polypeptides and contain non-covalently bound FAD and no iron-sulfur clusters. The enzymatic activities of the NDH-2 are not affected by the above inhibitors for NDH-1. Recently, it has been found that both of these types of the NADH-quinone oxidoreductase are present in a single strain of bacteria. The significance of the occurrence of these two types of enzymes in a single organism has been discussed in this review.     

Quantitation of specific mRNA by RNA-RNA hybridization kinetics with single-stranded riboprobes

A quantitative procedure by a solution hybridization involving RNA-RNA hybridization kinetics was developed for measurement of specific mRNA accumulated in particular tissues and cells. For quantitating mouse beta-tubulin mRNA two types of riboprobes were prepared: one was a truncated RNA covering only the coding portion of beta-tubulin cDNA and the other was a non-truncated RNA covering the vector portion as well as the coding portion. These antisense RNAs were hybridized with mouse brain total cellular RNA, yielding heat-stable hybrids. Both the truncated and non-truncated antisense RNA probes showed similar hybridization kinetics. Hybridization of the sense RNA, consisting of the beta-tubulin coding portion, with the antisense RNA probe gave standards for determining the proportion of beta-tubulin mRNA in total brain RNA. By this method, the amounts of beta-tubulin mRNA included in the brains of 10- and 50-day-old mice were quantitated to be 0.0056 and 0.0011% of total RNA, respectively.     

Occurrence in humans and guinea pigs of the gene related to their missing enzyme L-gulono-gamma-lactone oxidase

Humans, other primates, and guinea pigs are missing an enzyme L-gulono-gamma-lactone oxidase which catalyzes the last step of L-ascorbic acid biosynthesis. We have recently isolated a cDNA encoding this enzyme of the rat (T. Koshizaka, M. Nishikimi, T. Ozawa, and K. Yagi (1988) J. Biol. Chem. 263, 1619-1621). Northern blot hybridization using this cDNA as a probe demonstrated that guinea pigs lack mRNA for L-gulono-gamma-lactone oxidase. Nevertheless, existence of a DNA sequence related to this enzyme in the genome of this animal was shown by Southern blot hybridization. The human genome was also found to contain a sequence that is hybridizable with the cDNA probe; however, the degree of hybridization was less than those of hybridization with the L-gulono-gamma-lactone oxidase genes of animals possessing the enzyme, suggesting that the human L-gulono-gamma-lactone oxidase gene has diverged more rapidly than the genes of L-ascorbic acid-synthesizing species. This hypothesis was confirmed by comparison of a partial nucleotide sequence of the human gene with that of the rat one. The L-gulono-gamma-lactone oxidase-related sequences in the guinea pig and human genomes may represent the remnants of the gene of the enzyme that were once active but became nonfunctional during the course of evolution.     

Endothelin: a new inhibitor of renin release

Endothelin is a recently-discovered vasoconstrictor peptide which is produced by endothelium and acts on vascular smooth muscle cells. At present its actions on other organs or cells are unknown. We studied the effect of endothelin on renin release in a dynamic superfusion system of dispersed rat juxtaglomerular (JG) cells. Endothelin in concentrations of 10(-11) M or more inhibited renin release dose-dependently and this inhibitory action vanished in the absence of extracellular Ca. It is suggested that endothelin is an inhibitory regulator of renin secretion from JG cells and its action is Ca-dependent.     

A simple preparation method for apoaspartate aminotransferase from Escherichia coli B, and its application for the assay of pyridoxal and pyridoxamine 5'-phosphate

A simple and rapid preparation method for apoaspartate aminotransferase from Escherichia coli B was developed. A crude extract of the bacterial cells was treated batchwise with DEAE-cellulose. The enzyme fraction obtained was then applied to a pyridoxamine-Sepharose column. Apoaspartate aminotransferase was eluted with 50 mM potassium phosphate buffer (pH 7.0), and found to be electrophoretically homogeneous. The apoenzyme preparation thus obtained showed very low holoenzyme activity (only 0.4% of the activity seen in the fully saturated condition with pyridoxal 5'-phosphate) and was successfully used for assaying pyridoxal and pyridoxamine 5'-phosphate.     

beta-D-Glucosidase from seeds of Japanese cycad, Cycas revoluta Thunb.: properties and substrate specificity

beta-D-Glucosidase was purified from seeds of Japanese cycad by dialysis, chromatography on CM-Sepharose CL-6B, gel filtration on Biogel P-200, and chromatofocusing. By chromatofocusing, beta-D-glucosidase was separated into four components whose isoelectric points were in a very narrow range (7.43-7.68). All these components were glycoproteins. The main component (pI = 7.59) was homogeneous on gel isoelectric focusing, and was crystallized from ammonium sulfate solution. The molecular weight of the crystalline preparation was determined to be 137,000 by gel filtration, and 67,000 by sodium dodecylsulfate polyacrylamide gel electrophoresis, indicating the main component was composed of two subunits with the same molecular weight. The amino acid composition and sugar content of the main component were also determined. All four components hydrolyzed not only o-nitrophenyl beta-D-glucopyranoside but also o-nitrophenyl beta-D-galactopyranoside, o-nitrophenyl beta-D-fucopyranoside, and o-nitrophenyl beta-D-xylopyranoside. Hydrolysis rates of each substrate by the four components were quite similar. Mixed substrate experiments using crystalline preparation proved that a single active site was responsible for the hydrolysis of these substrates.