Effect of catecholamine on aldosterone release in isolated rat glomerulosa cell suspensions

Effect of adrenergic activity on the adrenal steroidogenesis and the modulation by catecholamines of aldosterone release were studied in isolated rat adrenal cell suspensions. Isoproterenol, norepinephrine and epinephrine, but not dopamine, caused statistically significant increase in aldosterone release. Both prazosin (alpha 1 antagonist) and yohimbine (alpha 2 antagonist) suppressed the norepinephrine-induced aldosterone release in a dose dependent manner, respectively. Both atenolol (beta 1 antagonist) and ICI 118-551 (beta 2 antagonist) also blocked (-)-isoproterenol-induced aldosterone release in a dose dependent manner, respectively. Neither (-)-isoproterenol nor (+/-)-norepinephrine at concentrations of 10(-6) M potentiated aldosterone release stimulated by angiotensin II or ACTH. These results suggest that catecholamines stimulate aldosteroidogenesis, but it appears unlikely that aldosterone release induced by ACTH or angiotensin-II is modulated by adrenergic stimulation.     

Developmental Changes in the NGF Content in the Brain of Young,Growing, Low-Birth-Weight Rats

The NGF content in each region of the brain of four-week-old rats was ranked in the decreasing order of cerebral cortex, hippocampus, cerebellum, midbrain/diencephalon, and pons/medulla ob-longata, and the NGF concentration, in the decreasing order of hippocampus, cerebral cortex, cerebellum, midbrain/diencephalon, and pons/medulla oblongata in both AFD and SFD groups. The NGF content and concentration in the cerebral cortex were about the same value at each age between those in the AFD and SFD groups. Those in the hippocampus were a little higher in the SFD group than in the AFD group at the ages of three and four weeks, unlike those in the other regions, where the values for the cerebellum, midbrain/diencephalon and pons/medulla oblongata tended to be somewhat higher in the AFD group than in the SFD group. The NGF concentrations in the hippocampus and cerebral cortex increased with growth: the concentration in the hippocampus at four weeks of age was about 4-fold of that at one week in the AFD group and about 5.7-fold of that at one week in the SFD group; and likewise the concentration in the cerebral cortex at four weeks of age was about 5.3-fold in the AFD group and about 7-fold in the SFD group. The NGF concentrations in the cerebellum decreased, and those in midbrain/diencephalon and pons/medulla oblongata hardly changed with growth in either AFD or SFD group. From these results NGF may have stronger implications for the neuronal growth in the hippocampus compared with those in the lower brain regions of the SFD rats.     

Leptin induces insulin-like signaling that antagonizes cAMP elevation by glucagon in hepatocytes

Although many effects of leptin are mediated through the central nervous system, leptin can regulate metabolism through a direct action on peripheral tissues, such as fat and liver. We show here that leptin, at physiological concentrations, acts through an intracellular signaling pathway similar to that activated by insulin in isolated primary rat hepatocytes. This pathway involves stimulation of phosphatidylinositol 3-kinase (PI3K) binding to insulin receptor substrate-1 and insulin receptor substrate-2, activation of PI3K and protein kinase B (AKT), and PI3K-dependent activation of cyclic nucleotide phosphodiesterase 3B, a cAMP-degrading enzyme. One important function of this signaling pathway is to reduce levels of cAMP, because leptin-mediated activation of both protein kinase B and phosphodiesterase 3B is most marked following elevation of cAMP by glucagon, and because leptin suppresses glucagon-induced cAMP elevation in a PI3K-dependent manner. There is little or no expression of the long form leptin receptor in primary rat hepatocytes, and these signaling events are probably mediated through the short forms of the leptin receptor. Thus, leptin, like insulin, induces an intracellular signaling pathway in hepatocytes that culminates in cAMP degradation and an antagonism of the actions of glucagon.     

Chemical structure of kenaf xylan

Methylation and partial acid hydrolysis of xylans from the bast and core of kenaf (Hibiscus cannabinus) showed that the main chain of these xylans consists of (1 → 4)-linked β-d-xylopyranosyl (Xylp) residues, some of which carry a -1,2-linked 4-O-methyl-glucopyranosyluronic acid (Me-GlcAp) and glucopyranosyluronic acid (GlcAp) residues as side chains. Partial hydrolysis of kenaf xylans afforded two series of aldouronic acids from aldobio- to aldotetraouronic acids. The acids of the first series composed of 4-O-Me-d-GlcAp and d-Xylp residues: 4-O-Me-GlcA-Xyl₃, 4-O-Me-GlcA-Xyl₂ and 4-O-Me-GlcA-Xyl. The second series composed of d-GlcAp and d-Xylp: GlcA-Xyl₃, GlcA-Xyl₂ and GlcA-Xyl.

In addition to these acids, another aldobiouronic acid, 4-O-(-d-GalAp)-d-Xyl was found to be present in the partial hydrolysate.

The molar ratio of GalA, GlcA, 4-O-Me-GlcA, and Xyl residues was calculated to be 1.0:2.0:9.4:119 for the bast xylan and 1.0:1.3:7.9:99.4 for the core xylan.     

Sequence Heterogeneity of the Ten rRNA Operons in Clostridium perfringens

We have cloned and sequenced rRNA operons of Clostridium perfringens strain 13 and analyzed the sequence structure in view of the phylogenesis. The organism had ten copies of rRNA operons all of that comprised of 16S, 23S and 5S rDNAs except for one operon. The operons clustered around the origin of replication, ranging within one-third of the whole genome sequence as it is arranged in a circle. Seven operons were transcribed in clockwise direction, and the remaining three were transcribed in counter clockwise direction assuming that the gyrA was transcribed in clockwise direction. Two of the counter clockwise operons contained tRNA^Ile genes between the 16S and 23S rDNAs, and the other had a tRNA^Ile genes between the 16S and 23S rDNAs and a tRNA^Asn gene in the place of the 5S rDNA. Microheterogeneity was found within the rRNA structural genes and spacer regions. The length of each 16S, 23S and 5S rDNA were almost identical among the ten operons, however, the intergenic spacer region of 16S-23S and 23S-5S were variable in the length depending on loci of the rRNA operons on the chromosome. Nucleotide sequences of the helix 19, helix 19a, helix 20 and helix 21 of 23S rDNA were divergent and the diversity appeared to be correlated with the loci of the rRNA operons on the chromosome.     

Lytic activity and biochemical properties of lysozyme in the coelomic fluid of the sea urchin strongylocentrotus intermedius

Lysozyme was identified in the coelomic fluid including coelomocytes of the sea urchin Strongylocentrotus intermedius, and its lytic activity and biochemical properties were examined in this study. The urchin lysozyme was electrophoretically fractionated to a single lytic band of about 14 kDa. No distinct difference in the lytic activity of this enzyme was found between urchins held at two temperatures, 11 degrees and 25 degrees C. The lysozyme of this species was purified through several procedures: salting out with ammonium sulfate, precipitation by ethanol saturation, gel filtration with a Biogel column, and an affinity chromatography with a heparin Sepharose column. The combination method of Biogel filtration and affinity chromatography resulted in the most purified lysozyme fraction, but we could not obtain a single protein band in SDS-PAGE. In addition, anti-hen egg white lysozyme (HEWL) antibody was produced and confirmed to react specifically with the urchin lysozyme in this study. Therefore, the HEWL antibody may be available for examining the lytic activity of lysozyme at an individual level to determine the biodefense activity of sea urchins. Copyright 1999 Academic Press.     

Reduced Contamination by the Fusarium Mycotoxin Zearalenone in Maize Kernels through Genetic Modification with a Detoxification Gene

Maize is subject to ear rot caused by toxigenic Aspergillus and Fusarium species, resulting in contamination with aflatoxins, fumonisins, trichothecenes, and zearalenone (ZEN). The trichothecene group and ZEN mycotoxins are produced by the cereal pathogen Fusarium graminearum. A transgenic detoxification system for the elimination of ZEN was previously developed using an egfp::zhd101 gene (gfzhd101), encoding an enhanced green fluorescent protein fused to a ZEN-degrading enzyme. In this study, we produced a transgenic maize line expressing an intact copy of gfzhd101 and examined the feasibility of transgene-mediated detoxification in the kernels. ZEN-degrading activity has been detected in transgenic kernels during seed maturation (for a period of 6 weeks after pollination). The level of detoxification activity was unaltered after an additional storage period of 16 weeks at 6°C. When the seeds were artificially contaminated by immersion in a ZEN solution for 48 h at 28°C, the total amount of the mycotoxin in the transgenic seeds was uniformly reduced to less than 1/10 of that in the wild type. The ZEN in the transgenic maize kernels was also efficiently decontaminated under conditions of lower water activity (a_w) and temperature; e.g., 16.9 μg of ZEN was removed per gram of seed within 48 h at an a_w of 0.90 at 20°C. F. graminearum infection assays demonstrated an absence of ZEN in the transgenic maize seeds, while the mycotoxin accumulated in wild-type kernels under the same conditions. Transgene-mediated detoxification may offer simple solutions to the problems of mycotoxin contamination in maize.     

A novel effect of polymorphonuclear leukocytes in the facilitation of angiogenesis

The purpose of this study was to examine whether the adhesion of polymorphonuclear leukocytes (PMNs) to endothelial cells and/or reactive oxygen species (ROS) released from PMNs are responsible for inducing angiogenesis. Angiogenesis was assessed by tube formation using endothelial cells obtained from bovine thoracic aorta (BAECs) grown on a layer of collagen type I. Addition of PMNs to BAECs weakly induced angiogenesis. The angiogenesis induced by PMNs alone was further enhanced by treatment of the PMNs with N-formyl-methionyl-leucyl-phenylalanine (FMLP), a selective activator of PMN. The involvement of PMN adhesion to BAECs via adhesion molecules in angiogenesis was investigated by using monoclonal antibodies against E-selectin and intercellular adhesion molecule-1 (ICAM-1). These antibodies blocked both the PMN adhesion to BAECs and the enhancement of angiogenesis induced by FMLP-treated PMNs. Furthermore, the enhancement of angiogenesis by FMLP-treated PMNs was blocked by catalase, a scavenging enzyme of H2O2, but not by superoxide dismutase (SOD). These results suggest that PMNs induce angiogenesis in vitro, and that the mechanism of stimulation of angiogenesis by PMNs may involve the adherence of PMNs to endothelial cells via E-selectin and ICAM-1, and H2O2, but not superoxide. Thus, activated PMNs in pathological states may not only induce tissue injury, but may also function as regulators of angiogenesis.     

Engineering Cytochrome P450 BM-3 for Oxidation of Polycyclic Aromatic Hydrocarbons

Cytochrome P450 BM-3, a self-sufficient P450 enzyme from Bacillus megaterium that catalyzes the subterminal hydroxylation of long-chain fatty acids, has been engineered into a catalyst for the oxidation of polycyclic aromatic hydrocarbons. The activities of a triplet mutant (A74G/F87V/L188Q) towards naphthalene, fluorene, acenaphthene, acenaphthylene, and 9-methylanthracene were 160, 53, 109, 287, and 22/min, respectively. Compared with the activities of the wild type towards these polycyclic aromatic hydrocarbons, those of the mutant were improved by up to 4 orders of magnitude. The coupling efficiencies of the mutant towards naphthalene, fluorene, acenaphthene, acenaphthylene, and 9-methylanthracene were 11, 26, 5.4, 15, and 3.2%, respectively, which were also improved several to hundreds fold. The high activities of the mutant towards polycyclic aromatic hydrocarbons indicate the potential of engineering P450 BM-3 for the biodegradation of these compounds in the environment.