Age-related increase of superoxide generation in the brains of mammals and birds

Oxidative stress, an imbalance between endogenous levels of oxygen radicals and antioxidative defense, increases with aging. However, it is not clear which of these two factors is the more critical. To clarify the production of oxygen radicals increases with age, we examined oxygen radical-dependent chemiluminescent signals in ex vivo brain slices using a novel photonic imaging method. The chemiluminescent intensity was significantly decreased by the membrane permeable superoxide dismutase (SOD)/catalase mimic, but not by Cu,Zn-SOD. Inhibitors for complex I, III, and IV of the mitochondrial electron transport chain transiently enhanced the chemiluminescent signal. The superoxide-dependent chemiluminescent intensity in senescence accelerated mouse (SAM) brain tissues increases with age. Moreover, the slope of the age-dependent increase was steeper in SAMP10, a strain characterized by a short lifespan and atrophy in the frontal cerebral cortex, than the senescence-resistant strain SAMR1, which has a longer lifespan. An increase in chemiluminescence with age was also observed in C57/BL6 mice, Wistar rats, and pigeons, although levels of chemiluminescence were lower in the pigeons than murines. The rate of age-related increases of superoxide-dependent chemiluminescence was inversely related to the maximum lifespan of the animals. The activity of superoxide dismutase was unchanged during the aging process in the brain. This suggested that superoxide production itself may increase with age. We speculated that reactive oxygen may be a signal to determine the aging process.     

Scaffold Protein Ahk1, Which Associates with Hkr1, Sho1, Ste11, and Pbs2, Inhibits Cross Talk Signaling from the Hkr1 Osmosensor to the Kss1 Mitogen-Activated Protein Kinase

In the budding yeast Saccharomyces cerevisiae, osmostress activates the Hog1 mitogen-activated protein kinase (MAPK), which regulates diverse osmoadaptive responses. Hkr1 is a large, highly glycosylated, single-path transmembrane protein that is a putative osmosensor in one of the Hog1 upstream pathways termed the HKR1 subbranch. The extracellular region of Hkr1 contains both a positive and a negative regulatory domain. However, the function of the cytoplasmic domain of Hkr1 (Hkr1-cyto) is unknown. Here, using a mass spectrometric method, we identified a protein, termed Ahk1 (Associated with Hkr1), that binds to Hkr1-cyto. Deletion of the AHK1 gene (in the absence of other Hog1 upstream branches) only partially inhibited osmostress-induced Hog1 activation. In contrast, Hog1 could not be activated by constitutively active mutants of the Hog1 pathway signaling molecules Opy2 or Ste50 in ahk1Δ cells, whereas robust Hog1 activation occurred in AHK1⁺ cells. In addition to Hkr1-cyto binding, Ahk1 also bound to other signaling molecules in the HKR1 subbranch, including Sho1, Ste11, and Pbs2. Although osmotic stimulation of Hkr1 does not activate the Kss1 MAPK, deletion of AHK1 allowed Hkr1 to activate Kss1 by cross talk. Thus, Ahk1 is a scaffold protein in the HKR1 subbranch and prevents incorrect signal flow from Hkr1 to Kss1.     

Occurrence of ribitol-containing lipoteichoic acid in Staphylococcus aureus H and its glycosylation

A ribitol-containing lipoteichoic acid was obtained from the 20,000 x g supernatant fraction of Staphylococcus aureus H by extraction with Triton X-100 followed by fractionation on Sepharose 6B and DEAE-cellulose columns. The purified lipoteichoic acid was composed of phosphate, glycerol, glucose, glucosamine, ribitol, and fatty acids in a molar ratio of 1 : 0.9 : 0.06 : 0.03 : 0.09 : 0.07. Based on the structural analysis of fragments from alkali and HF hydrolysis, the lipoteichoic acid appears to consist of three moieties, namely a ribitol phosphate oligomer, poly(glycerol phosphate) which has about 30 glycerol phosphate units, and beta-glucosyl-beta-glucosyl(1 leads to 1)diacylglycerol. N-Acetylglucosamine was linked to the ribitol residues. The lipoteichoic acid serves as an acceptor of glycosyl moieties from UDP-glucose and UDP-N-acetylglucosamine in the enzyme reaction catalyzed by the membrane preparation. The rate of enzymatic glycosylation was increased by prior treatment of the lipoteichoic acid with N-acetyl-beta-D-glucosaminidase. The glycosylation seems to occur at the ribitol residues of the lipoteichoic acid.     

beta-lactamase from Streptomyces cacaoi. Purification and properties

A beta-lactamase was purified to an apparently homogeneous state from Streptomyces cacaoi. The molecular weight calculated from the mobility in sodium dodecyl sulfate polyacrylamide gel electrophoresis was 34,000. pI was 4.7 and the optimal pH was 6.5. The optimum temperature was found to be between 40 degrees C and 45 degrees C, but the enzyme lost activity above 50 degrees C. N-Bromosuccinimide was the strongest inhibitor among the reagents tested, followed by iodine. p-Chloromercuribenzoate showed a weak inhibitory effect. Diisopropylfluorophosphate and sodium chloride did not show any inhibitory effect on the enzyme. The beta-lactamase catalyzed the hydrolysis of methicillin and cloxacillin at two-thirds to one-third the rate of benzylpenicillin. On the other hand, the enzyme hydrolyzed cephalosporins and 7-methoxycephalosporin only slowly. With benzylpenicillin as a substrate, the Km increased sharply with decreasing pH and the pK alpha estimated from the Km versus pH curve was 6.5 to 7.0. In contrast, with cloxacillin as a substrate, the Km showed a minimum at pH 7.5. The Vmax changed with pH in a bell-shaped curve in the case of benzylpenicillin, but the Vmax for cloxacillin changed only within a small range. In addition, the ratio of the hydrolysis rate of benzylpenicillin and cloxacillin at 30 degrees C and 20 degrees C (V30 degrees/V20 degrees) was found to be 1.23 and 1.55, respectively. These results indicate that the S. cacaoi beta-lactamase behaves differently toward benzylpenicillin and cloxacillin, although both are penicillins. S. cacaoi seems to release beta-lactamase into the culture medium soon after its biosynthesis without retaining it in the membrane and the soluble fraction. The possible relationships between beta-lactamases from Streptomyces and those from pathogenic bacteria are discussed.     

Discovery of Power-Law Growth in the Self-Renewal of Heterogeneous Glioma Stem Cell Populations

Background

Accumulating evidence indicates that cancer stem cells (CSCs) drive tumorigenesis. This suggests that CSCs should make ideal therapeutic targets. However, because CSC populations in tumors appear heterogeneous, it remains unclear how CSCs might be effectively targeted. To investigate the mechanisms by which CSC populations maintain heterogeneity during self-renewal, we established a glioma sphere (GS) forming model, to generate a population in which glioma stem cells (GSCs) become enriched. We hypothesized, based on the clonal evolution concept, that with each passage in culture, heterogeneous clonal sublines of GSs are generated that progressively show increased proliferative ability.

Methodology/Principal Findings

To test this hypothesis, we determined whether, with each passage, glioma neurosphere culture generated from four different glioma cell lines become progressively proliferative (i.e., enriched in large spheres). Rather than monitoring self-renewal, we measured heterogeneity based on neurosphere clone sizes (#cells/clone). Log-log plots of distributions of clone sizes yielded a good fit (r>0.90) to a straight line (log(% total clones) = k*log(#cells/clone)) indicating that the system follows a power-law (y = x^k) with a specific degree exponent (k = −1.42). Repeated passaging of the total GS population showed that the same power-law was maintained over six passages (CV = −1.01 to −1.17). Surprisingly, passage of either isolated small or large subclones generated fully heterogeneous populations that retained the original power-law-dependent heterogeneity. The anti-GSC agent Temozolomide, which is well known as a standard therapy for glioblastoma multiforme (GBM), suppressed the self-renewal of clones, but it never disrupted the power-law behavior of a GS population.

Conclusions/Significance

Although the data above did not support the stated hypothesis, they did strongly suggest a novel mechanism that underlies CSC heterogeneity. They indicate that power-law growth governs the self-renewal of heterogeneous glioma stem cell populations. That the data always fit a power-law suggests that: (i) clone sizes follow continuous, non-random, and scale-free hierarchy; (ii) precise biologic rules that reflect self-organizing emergent behaviors govern the generation of neurospheres. That the power-law behavior and the original GS heterogeneity are maintained over multiple passages indicates that these rules are invariant. These self-organizing mechanisms very likely underlie tumor heterogeneity during tumor growth. Discovery of this power-law behavior provides a mechanism that could be targeted in the development of new, more effective, anti-cancer agents.     

Immunohistochemical studies on peptide- and amine-containing endocrine cells and nerves in the gut and the rectal gland of the ratfish Chimaera monstrosa

Summary The occurrence and distribution of endocrine cells and nerves were immunohistochemically demonstrated in the gut and rectal gland of the ratfish Chimaera monstrosa (Holocephala). The epithelium of the gut mucosa revealed open-type endocrine cells exhibiting immunoreactivity for serotonin (5HT), gastrin/cholecystokinin (CCK), pancreatic polypeptide (PP)/FMRFamide, somatostatin, glucagon, substance P or gastrin-releasing peptide (GRP). The rectum contained a large number of closed-type endocrine cells in the basal layer of its stratified epithelium; the majority contained 5HT- and GRP-like immunoreactivity in the same cytoplasm, whereas others were immunoreactive for substance P. The rectal gland revealed closed-type endocrine cells located in the collecting duct epithelium. Most of these contained substance P-like immunoreactivity, although some reacted either to antibody against somatostatin or against 5HT. Four types of nerves were identified in the gut and the rectal gland. The nerve cells and fibers that were immunoreactive for vasoactive intestinal peptide (VIP) and GRP formed dense plexuses in the lamina propria, submucosa and muscular layer of the gut and rectal gland. A sparse network of gastrin- and 5HT-immunoreactive nerve fibers was found in the mucosa and the muscular layer of the gut. The present study demonstrated for the first time the occurrence of the closed-type endocrine cells in the mucosa of the rectum and rectal gland of the ratfish. These abundant cells presumably secrete 5HT and/or peptides in response to mechanical stimuli in the gut and the rectal gland. The peptide-containing nerves may be involved in the regulation of secretion by the rectal gland.     

A point mutation in exon 3 (His 107→Tyr) in two unrelated Japanese patients with carbonic anhydrase II deficiency with central nervous system involvement

We have analyzed two unrelated Japanese patients with carbonic anhydrase II deficiency born to consanguineous parents. We have identified the same mutation as that reported to be homozygous in a Belgian family and compound heterozygous in an American family. It comprises to C-to-T transition that results in the amino acid substitution of Tyr (TAT) for His (CAT) at position 107. This point mutation creates an AccI site that can be conveniently screened by the polymerase chain reaction/restriction fragment length polymorphism method using a restriction enzyme for gene tracking. Our patients exhibit severe mental retardation, not seen in the Belgian and American patients. Received: 23 November 1994 / Revised: 22 May 1995     

Inhibitory effect of long chain fatty acyl CoAs on RNA polymerase from Escherichia coli

RNA polymerase from Escherichia coli was inhibited by long chain fatty acyl CoAs, such as myristoyl CoA (Ki = 17.2 microM), palmitoyl CoA (Ki = 8.9 microM), oleoyl CoA (Ki = 5.5 microM), and stearoyl CoA (Ki = 0.94 microM). The inhibition by these CoA thioesters was non-competitive against nucleoside triphosphates. Short chain fatty acyl CoAs, such as acetyl CoA, propionyl CoA, acetoacetyl CoA, butyryl CoA, and decanoyl CoA, failed to inhibit RNA polymerase. CoA, Na-myristate, Na-palmitate, Na-oleate, Na-stearate, palmitoyl carnitine, and carnitine did not inhibit the enzyme. The inhibition of RNA polymerase by long chain fatty acyl CoAs was competitive against template DNA.     

Detection and Identification of Yersinia pestis by Polymerase Chain Reaction (PCR) Using Multiplex Primers

A PCR method for detection of Yersinia pestis-virulence determinants by the use of multiplex primers was developed. Four pairs of oligonucleotide primers were designed from each gene of three kinds of virulent plasmids and a chromosomal DNA; 60-Md plasmid-located gene (caf1) encoding Y. pestis-specific capsular antigen fraction 1, a Y. pestis-specific region of a yopM gene encoded on 42-Md virulent plasmid, a plasminogen activator gene (pla) encoded on Y. pestis-specific 7-Md plasmid and an invasin protein gene (inv) encoded on chromosomal DNA. This multiplex-primer system was specific for the detection of Y. pestis among pathogenic Yersinia species and other enterobacteriaceae having antigens common to Y. pestis. Since this method is simple and safe, it will be useful to identify and confirm Y. pestis in cases of emergency and for the surveillance of epidemics.