Isolation and Characterization of Alicycliphilus denitrificans Strain BC, Which Grows on Benzene with Chlorate as the Electron Acceptor

A bacterium, strain BC, was isolated from a benzene-degrading chlorate-reducing enrichment culture. Strain BC degrades benzene in conjunction with chlorate reduction. Cells of strain BC are short rods that are 0.6 μm wide and 1 to 2 μm long, are motile, and stain gram negative. Strain BC grows on benzene and some other aromatic compounds with oxygen or in the absence of oxygen with chlorate as the electron acceptor. Strain BC is a denitrifying bacterium, but it is not able to grow on benzene with nitrate. The closest cultured relative is Alicycliphilus denitrificans type strain K601, a cyclohexanol-degrading nitrate-reducing betaproteobacterium. Chlorate reductase (0.4 U/mg protein) and chlorite dismutase (5.7 U/mg protein) activities in cell extracts of strain BC were determined. Gene sequences encoding a known chlorite dismutase (cld) were not detected in strain BC by using the PCR primers described in previous studies. As physiological and biochemical data indicated that there was oxygenation of benzene during growth with chlorate, a strategy was developed to detect genes encoding monooxygenase and dioxygenase enzymes potentially involved in benzene degradation in strain BC. Using primer sets designed to amplify members of distinct evolutionary branches in the catabolic families involved in benzene biodegradation, two oxygenase genes putatively encoding the enzymes performing the initial successive monooxygenations (BC-BMOa) and the cleavage of catechol (BC-C23O) were detected. Our findings suggest that oxygen formed by dismutation of chlorite can be used to attack organic molecules by means of oxygenases, as exemplified with benzene. Thus, aerobic pathways can be employed under conditions in which no external oxygen is supplied.     

STAT4 isoforms differentially regulate Th1 cytokine production and the severity of inflammatory bowel disease

STAT4, a critical regulator of inflammation in vivo, can be expressed as two alternative splice forms, a full-length STAT4alpha, and a STAT4beta isoform lacking a C-terminal transactivation domain. Each isoform is sufficient to program Th1 development through both common and distinct subsets of target genes. However, the ability of these isoforms to mediate inflammation in vivo has not been examined. Using a model of colitis that develops following transfer of CD4(+) CD45RB(high) T cells expressing either the STAT4alpha or STAT4beta isoform into SCID mice, we determined that although both isoforms mediate inflammation and weight loss, STAT4beta promotes greater colonic inflammation and tissue destruction. This correlates with STAT4 isoform-dependent expression of TNF-alpha and GM-CSF in vitro and in vivo, but not Th1 expression of IFN-gamma or Th17 expression of IL-17, which were similar in STAT4alpha- and STAT4beta-expressing T cells. Thus, higher expression of a subset of inflammatory cytokines from STAT4beta-expressing T cells correlates with the ability of STAT4beta-expressing T cells to mediate more severe inflammatory disease.     

Validity of pulse oximetry during maximal exercise in normoxia, hypoxia, and hyperoxia.

During exercise, pulse oximetry is problematic due to motion artifact and altered digital perfusion. New pulse oximeter technology addresses these issues and may offer improved performance. We simultaneously compared Nellcor N-395 (Oxismart XLTM) pulse oximeters with an RS-10 forehead sensor (RS-10), a D-25 digit sensor (D-25), and the Ivy 2000 (Masimo SETTM)/LNOP-Adt digit sensor (Ivy) to arterial blood oxygen saturation (Sa(O(2))) by cooximetry. Nine normal subjects, six athletes, and four patients with chronic disease exercised to maximum oxygen consumption (VO(2 max)) under various conditions [normoxia, hypoxia inspired oxygen fraction (FI(O(2))) = 0.125; hyperoxia, FI(O(2)) = 1.0]. Regression analysis for normoxia and hypoxic data was performed (n = 161 observations, Sa(O(2)) = 73-99.9%), and bias (B) and precision (P) were calculated. RS10 offered greater validity than the other two devices tested (y = 1.009x - 0.52, R(2) = 0.90, B+/-P = 0.3 +/- 2.5). Finger sensors had low precision and a significant negative bias (D-25: y = 1.004x - 2.327, R(2) = 0.52, B+/-P = -2.0 +/- 7.3; Ivy: y = 1.237x - 24.2, R(2) = 0.78, B+/-P = -2.0 +/- 5.2). Eliminating measurements in which heart rate differed by >10 beats/min from the electrocardiogram value improved precision minimally and did not affect bias substantially (B+/-P = 0.5 +/- 2.0, -1.8 +/- 8.4, and -1.25+/-4.33 for RS-10, D-25, and Ivy, respectively). Signal detection algorithms and pulse oximeter were identical between RS-10 and D-25; thus the improved performance of the forehead sensor is likely because of sensor location. RS-10 should be considered for exercise testing in which pulse oximetry is desirable.     

Centrosomes split in the presence of impaired DNA integrity during mitosis

A well-established function of centrosomes is their role in accomplishing a successful mitosis that gives rise to a pair of identical daughter cells. We recently showed that DNA replication defects and DNA damage in Drosophila embryos trigger centrosomal changes, but it remained unclear whether comparable centrosomal responses can be provoked in somatic mammalian cells. To investigate the centrosomal organization in the presence of impaired DNA integrity, live and ultrastructural analysis was performed on gamma-tubulin-GFP and EGFP-alpha-tubulin-expressing Chinese hamster ovary cells. We have shown that during mitosis in the presence of incompletely replicated or damaged DNA, centrosomes split into fractions containing only one centriole. This results in the formation of multipolar spindles with extra centrosome-like structures. Despite the extra centrosomes and the multipolarity of the spindles, cells do exit from mitosis, resulting in severe division errors. Our data provide evidence of a novel mechanism showing how numerous centrosomes and spindle defects can arise and how this can lead to the formation of aneuploid cells.     

Structural insights into the processivity of endopolygalacturonase I from Aspergillus niger

Endopolygalacturonase I is a processive enzyme, while the 60% sequence identical endopolygalacturonase II is not. The 1.70 A resolution crystal structure of endopolygalacturonase I reveals a narrowed substrate binding cleft. In addition, Arg96, a residue in this cleft previously shown to be critical for processivity, interacts with the substrate mimics glycerol and sulfate in several well-defined conformations in the six molecules in the asymmetric unit. From this we conclude that both Arg96 and the narrowed substrate binding cleft contribute to retaining the substrate while it moves through the active site after a cleavage event has occurred.     

Normalization of aortic function during arousal episodes in the hibernating ground squirrel

Hypothermia is commonly used to restrict organ damage during preservation of tissue, but does not offer complete protection. Organ damage after reperfusion/rewarming is amongst others caused by an impairment of vascular properties, particularly endothelium-dependent vasodilatation. We hypothesized that hibernating small animals, which frequently cycle through periods of deep cooling (torpor) and full rewarming (arousal), employ specific mechanisms to preserve vascular function after cooling and reperfusion. Therefore we measured contraction of aortic tissue of hibernating European ground squirrels after 24 h and 7 days of torpor, arousal (1.5 h) and in non-hibernating animals. To assess the role of nitric oxide (NO), experiments were performed in the absence and presence of the NO-synthesis inhibitor, L-NMMA (10(-4) M). Maximum contraction to phenylephrine and angiotensin II was doubled in 7-days torpid animals without a shift in EC50, compared to the other 3 groups. Maximum contraction to KCl was doubled in 7-days torpid animals compared to the arousal group and non-hibernating animals. Relaxation to acetylcholine (ACh) and sodium nitrite in phenylephrine precontracted rings did not differ between groups. In the presence of L-NMMA, the maximum of concentration-response curves for all three vasoconstrictors was increased by about 30% in the arousal group, but unaffected in other groups. L-NMMA completely inhibited ACh-induced relaxation in 24-h torpid animals and non-hibernating animals, but only partially in 7-days torpid animals and in the arousal group. From this we conclude that vascular adaptation proceeds during torpor. Further, increased contractility of aortic tissue during long torpor returns to normal within 1.5 hours of arousal, which is associated with an increased basal NO synthesis. In addition, involvement of NO in agonist-mediated relaxation differs between the various stages of hibernation.Thus, hibernating animals have effectively developed mechanisms to preserve vascular function after cooling and rewarming.     

Role of phospholipase C in development of myogenic tone in rat posterior cerebral arteries

Earlier studies have implicated phospholipase C (PLC) in the development of myogenic tone (MT) based on pharmacological studies in larger arteries. In the present study, we further investigated the cellular effects of PLC inhibition using pharmacological and electrophysiological approaches to provide more quantitative functional evidence for the involvement of PLC in the genesis of MT in small cerebral arteries. The phosphatidylinositol-selective PLC (PI-PLC) inhibitor U-73122 decreased MT by 87% in posterior cerebral arteries from Sprague-Dawley rats with pIC(50) of 6.2 +/- 0.09 (n = 5). Similar potency (pIC(50) of 6.2 +/- 0.04, n = 5) was observed in arteries with MT that were further constricted with 30 nM serotonin. The phosphatidylcholine-specific (PC-PLC) inhibitor D609 had no effect on MT. U-73343, the inactive analog of U-73122, did not show any relaxant effect, but at higher concentrations (>1 microM) it reduced MT. In the presence of 125-500 nM U-73122, the pressure-diameter curves shifted toward that obtained in Ca-free conditions. U-73122-mediated decrease in MT was accompanied by a decrease in mean arterial wall calcium (maximum effect: 77 +/- 3% of 16 mM KCl-mediated decrease, n = 4). This was due to a simultaneous membrane potential hyperpolarization of approximately 9 mV or from -44 +/- 1 to -53 +/- 2 mV (10 microM, P < 0.001, n = 8). In summary, this study provides the first quantitative data suggesting a critical importance of PI-PLC in the genesis of pressure-induced MT in rat cerebral arteries via membrane potential depolarization and increased calcium influx.