Effect of sustained limb ischemia on norepinephrine release from skeletal muscle sympathetic nerve endings

Acute ischemia has been reported to impair sympathetic outflow distal to the ischemic area in various organs, whereas relatively little is known about this phenomenon in skeletal muscle. We examined how acute ischemia affects norepinephrine (NE) release at skeletal muscle sympathetic nerve endings. We implanted a dialysis probe into the adductor muscle in anesthetized rabbits and measured dialysate NE levels as an index of skeletal muscle interstitial NE levels. Regional ischemia was introduced by microsphere injection and ligation of the common iliac artery. The time courses of dialysate NE levels were examined during prolonged ischemia. Ischemia induced a decrease in the dialysate NE level (from 19+/-4 to 2.0+/-0 pg/ml, mean+/-S.E.), and then a progressive increase in the dialysate NE level. The increment in the dialysate NE level was examined with local administration of desipramine (DMI, a membrane NE transport inhibitor), omega-conotoxin GVIA (CTX, an N-type Ca(2+) channel blocker), or TMB-8 (an intracellular Ca(2+) antagonist). At 4h ischemia, the increment in the dialysate NE level (vehicle group, 143+/-30 pg/ml) was suppressed by TMB-8 (25+/-5 pg/ml) but not by DMI (128+/-10 pg/ml) or CTX (122+/-18 pg/ml). At 6h ischemia, the increment in the dialysate NE level was not suppressed by the pretreatment. Ischemia induced biphasic responses in the skeletal muscle. Initial reduction of NE release may be mediated by an impairment of axonal conduction and/or NE release function, while in the later phase, the skeletal muscle ischemia-induced NE release was partly attributable to exocytosis via intracellular Ca(2+) overload rather than opening of calcium channels or carrier mediated outward transport of NE.     

Isolation of a cadmium-releasing bacterium and characterization of its novel protease

Microorganisms were screened for their ability to release cadmium from scallop hepatopancreas, which is the main residue after removing of the edible parts of scallop. The isolated strain, 23-0-11, identified as Arthrobacter nicotinovorans, secreted a protease which released cadmium from scallop hepatopancreas into the liquid medium. The molecular mass of the enzyme was estimated to be 27 kDa. The sequence of the 15 N-terminal amino acids of the protease showed no close similarity with any other protein. Compared with a commercial enzyme, the purified protease had greater ability to release cadmium. The enzyme activity was greatest at 50 degrees C and pH 7.0, and was enhanced in the presence of Ca(2+), Mg(2+) and Mn(2+), while being strongly inhibited by Co(2+). The inhibition profile by the serine protease inhibitor, phenylmethylsulphonyl fluoride (PMSF), confirmed that the protease belonged to the serine protease family.     

Free radical theory of apoptosis and metamorphosis

Reactive oxygen species (ROS) are the major factors that induce oxidative modification of DNA and gene mutation. ROS can elicit oxidative stress and affect a wide variety of physiological and pathological processes including embryonal development, maturation and aging.     

Oxygen-Dependent Inhibition of Neutrophil Respiratory Burst by Nitric Oxide

Effect of nitric oxide (NO) on the respiratory burst of neutrophils was examined under different oxygen tensions. Phorbol myristate acetate (PMA) stimulated oxygen consumption and superoxide (O₂^-) generation in neutrophils by a mechanism which was inhibited reversibly by NO. The inhibitory effect of NO increased significantly with a decrease in oxygen tension in the medium. The inhibitory effect of NO was suppressed in medium containing oxyhemoglobin (HbO₂), a NO scavenging agent. In contrast, 3-morpholinosydnonimine (SIN-1), a compound that rapidly generates peroxynitrite (ONOO^-) from the released NO and O₂^-, slightly stimulated the PMA-induced respiratory burst. These results suggested that NO, but not ONOO, might reversibly inhibit superoxide generation by neutrophils especially at physiologically low oxygen tensions thereby decreasing oxygen toxicity particularly in and around hypoxic tissues.     

Contribution of membrane-associated prostaglandin E2 synthase to bone resorption

This study initially confirmed that, among prostaglandins (PGs) produced in bone, only PGE(2) has the potency to stimulate osteoclastogenesis and bone resorption in the mouse coculture system of osteoblasts and bone marrow cells. For the PGE(2) biosynthesis two isoforms of the terminal and specific enzymes, membrane-associated PGE(2) synthase (mPGES) and cytosolic PGES (cPGES) have recently been identified. In cultured mouse primary osteoblasts, both mPGES and cyclooxygenase-2 were induced by the bone resorptive cytokines interleukin-1, tumor necrosis factor-alpha, and fibroblast growth factor-2. Induction of mPGES was also seen in the mouse long bone and bone marrow in vivo by intraperitoneal injection of lipopolysaccharide. In contrast, cPGES was expressed constitutively both in vitro and in vivo without being affected by these stimuli. An antisense oligonucleotide blocking mPGES expression inhibited not only PGE(2) production, but also osteoclastogenesis and bone resorption stimulated by the cytokines, which was reversed by addition of exogenous PGE(2). We therefore conclude that mPGES, which is induced by and mediates the effects of bone resorptive stimuli, may make a target molecule for the treatment of bone resorptive disorders.     

RNase ES of Streptomyces coelicolor A3(2) can complement the rne and rng mutations in Escherichia coli

The Streptomyces coelicolor gene SCC88.10c encodes a protein (RNase ES) which is homologous to endoribonucleases in the RNase E/G family. We expressed S. coelicolor RNase ES as a 6 x His-tagged protein in an Escherichia coli mutant carrying a rng (which encodes RNase G) or a rne (which encodes RNase E) mutation to study whether S. coelicolor RNase ES is able to complement these mutations in host E. coli cells. The results clearly indicated that the S. coelicolor RNase ES can partially abrogate either the rng::cat or rne-1 mutation, as measured by the ability to suppress the several aberrant phenotypes resulting from the rng or rne mutation. Thus, S. coelicolor RNase ES appears to have the dual ability to supplant the functions of both RNase G and RNase E in E. coli.     

Parasiticidal activity of human α-defensin-5 against <Emphasis Type="Italic">Toxoplasma gondii</Emphasis>

Human defensins play a fundamental role in the initiation of innate immune responses to some microbial pathogens. In this paper, we show that human α-defensin-5 displays a parasiticidal role against Toxoplasma gondii, the causative agent of toxoplasmosis. Exposure of the tachyzoite form of T. gondii to defensin induced aggregation and significantly reduced parasite viability in a concentration-dependent peptide. Pre-incubation of tachyzoites with human α-defensin-5 followed by exposure to a mouse embryonal cell line (NIH/3T3) significantly reduced T. gondii infection in these cells. Thus, human α-defensin-5 is an innate immune molecule that causes severe toxocity to T. gondii and plays an important role in reducing cellular infection. This is the first report showing that human α-defensin-5 causes aggregation, leading to Toxoplasma destruction.