Nitrosomonas europaea expresses a nitric oxide reductase during nitrification

In this paper, we report the identification of a norCBQD gene cluster that encodes a functional nitric oxide reductase (Nor) in Nitrosomonas europaea. Disruption of the norB gene resulted in a strongly diminished nitric oxide (NO) consumption by cells and membrane protein fractions, which was restored by the introduction of an intact norCBQD gene cluster in trans. NorB-deficient cells produced amounts of nitrous oxide (N2O) equal to that of wild-type cells. NorCB-dependent activity was present during aerobic growth and was not affected by the inactivation of the putative fnr gene. The findings demonstrate the presence of an alternative site of N2O production in N. europaea.     

Unique effect of arachidonic acid on human neutrophil TNF receptor expression: up-regulation involving protein kinase C,extracellular signal-regulated kinase,and phospholipase A2

Arachidonic acid (AA) regulates the function of many cell types, including neutrophils. Although much emphasis has been placed on agonist-induced down-regulation of TNFR, our data show that AA caused a rapid (10-20 min) and dose-dependent (0.5-30 micro M) increase in the surface expression of both classes of TNFR (TNFR1 and TNFR2) on human neutrophils. This increased TNFR expression correlated with an increase in TNF-induced superoxide production. In contrast, the omega3 fatty acids eicosapentaenoic acid, docosahexaenoic acid, and linolenic acid failed to stimulate TNFR expression. Although fMLP and LPS reduced the neutrophil expression of TNFR, when pretreated with AA, fMLP caused an increase in TNFR expression. Consistent with this result was the finding that AA prevented the fMLP-induced receptor release in neutrophil cultures. AA also caused an increase in TNFR expression in matured HL-60 cells (neutrophil-like cells), but a decrease in nonmatured cells and HUVEC. The AA effects were independent of the lipoxygenase and cyclooxygenase pathways, but dependent on protein kinase C, the extracellular signal-regulated kinases 1 and 2, and cytosolic phospholipase A(2). The data demonstrate a unique effect of AA in the inflammatory reaction, through its action on neutrophil TNFR expression, and suggest that AA may regulate the response of neutrophils to TNF by altering its receptor number.     

The glucose transport facilitator GLUT8 is predominantly associated with the acrosomal region of mature spermatozoa

The glucose transporter 8 (GLUT8) is a recently identified member of the family of sugar transport facilitators. In human tissues GLUT8 is predominantly expressed in testis in a gonadotropin-dependent manner. It is shown here that the onset of mRNA synthesis of GLUT8 during the maturation of mouse testis coincides with the appearance of mature spermatozoa. Furthermore, immunohistochemistry with antiserum against the C-terminus of GLUT8 indicated that the protein was associated with spermatozoa within the seminiferous and the epididymal tubules. The GLUT8 immunoreactivity was detected within the head of mouse and human spermatozoa in the acrosomal region, and appeared to be located at the plasma membrane as well as within the cells. This specific expression and localization of GLUT8 suggests that the transport facilitator plays a major role in the fuel supply of mature spermatozoa, and that it is a potential target for inhibition of sperm cell function.     

Novel and conserved roles for orthodenticle/ otx and orthopedia/ otp orthologs in the gastropod mollusc Patella vulgata

The orthodenticle/ otx and orthopedia/ otp classes of homeobox gene families have been identified in all three major classes of bilaterians: deuterostomes, lophotrochozoans, and ecdysozoans. Otx genes have been studied extensively and play a role in the development of anterior neural structures. Otp genes have been found to be involved in nervous system development in mouse and Drosophila. To date, no members of these genes are known in molluscs. We cloned orthologs of orthodenticle/ otx and orthopedia/ otpfrom the gastropod Patella vulgata, and designated them Pv-otx and Pv-otprespectively. Our analysis of the spatio-temporal expression pattern of otx and otp orthologs during P. vulgata embryogenesis leads to the following conclusions. First, Pv-otx is expressed in and around the stomodaeum and our analysis thus supports the previously suggested conservation of the protostome and deuterostome larval mouth regions. Second, we find that Pv-otp is involved in the development of the larval apical sensory organ, suggesting a conserved role for this gene family in nervous system development. A similar conserved role in nervous system development has been proposed for orthodenticle/otx genes and we suggest that part of the cells expressing Pv-otx are involved in the development of the anterior nervous system. Last, we postulate that otx genes were ancestrally involved in the development of ciliary bands in bilaterians.     

LIF receptor signaling limits immune-mediated demyelination by enhancing oligodendrocyte survival

Multiple sclerosis (MS) is a disabling inflammatory demyelinating disease of the central nervous system (CNS) that primarily affects young adults. Available therapies can inhibit the inflammatory component of MS but do not suppress progressive clinical disability. An alternative approach would be to inhibit mechanisms that drive the neuropathology of MS, which often includes the death of oligodendrocytes, the cells responsible for myelinating the CNS. Identification of molecular mechanisms that mediate the stress response of oligodendrocytes to optimize their survival would serve this need. This study shows that the neurotrophic cytokine leukemia inhibitory factor (LIF) directly prevents oligodendrocyte death in animal models of MS. We also demonstrate that this therapeutic effect complements endogenous LIF receptor signaling, which already serves to limit oligodendrocyte loss during immune attack. Our results provide a novel approach for the treatment of MS.     

Expression of Patella vulgata orthologs of engrailed and dpp-BMP2/4 in adjacent domains during molluscan shell development suggests a conserved compartment boundary mechanism

The engrailed gene is well known from its role in segmentation and central nervous system development in a variety of species. In molluscs, however, engrailed is involved in shell formation. So far, it seemed that engrailed had been co-opted uniquely for this particular process in molluscs. Here, we show that, in the gastropod mollusc Patella vulgata, an engrailed ortholog is expressed in the edge of the embryonic shell and in the anlage of the apical sensory organ. Surprisingly, a dpp-BMP2/4 ortholog is expressed in cells of the ectoderm surrounding, but not overlapping, the engrailed-expressing shell-forming cells. It is also expressed in the anlage of the eyes. Earlier it was shown that a compartment boundary exists between the cells of the embryonic shell and the adjacent ectoderm. We conclude that engrailed and dpp are most likely involved in setting up a compartment boundary between these cells, very similar to the situation in, for example, the developing wing imaginal disc in Drosophila. We suggest that engrailed became involved in shell formation because of its ancestral role, which is to set up compartment boundaries between embryonic domains.     

Proline metabolism in isolated rat liver cells

The metabolism of proline was studied in liver cells isolated from starved rats. The following observations were made. 1. Consumption of proline could be largely accounted for by production of glucose, urea, glutamate and glutamine. 2. At least 50% of the total consumption of oxygen was used for proline catabolism. 3. Ureogenesis and gluconeogenesis from proline could be stimulated by partial uncoupling of oxidative phosphorylation. 4. Addition of ethanol had little effect on either proline uptake or oxygen consumption, but strongly inhibited the production of both urea and glucose and caused further accumulation of glutamate and lactate. Accumulation of glutamine was not affected by ethanol. 5. The effects of ethanol could be overcome by partial uncoupling of oxidative phosphorylation. 6. The apparent K_m values of argininosuccinate synthetase (EC 6.3.4.5) for aspartate and citrulline in the intact hepatocyte are higher than those reported for the isolated enzyme. 7. 3-Mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase (EC 4.1.1.32), greatly enhanced cytosolic aspartate accumulation during proline metabolism, but inhibited urea synthesis. 8. It is concluded that when proline is provided as a source of nitrogen to liver cells, production of ammonia by oxidative deamination of glutamate is inhibited by the highly reduced state of the nicotinamide nucleotides within the mitochondria. 9. Conversion of proline into glucose and urea is a net-energy-yielding process, and the high state of reduction of the nicotinamide nucleotides is presumably maintained by a high phosphorylation potential. Thus when proline is present as sole substrate, the further oxidation of glutamate by glutamate dehydrogenase (EC 1.4.1.3) is limited by the rate of energy expenditure of the cell.     

Retinohypothalamic projection in the mouse: Electron microscopic and iontophoretic investigations of hypothalamic and optic centers

The problem of the direct retinohypothalamic projection in mammals (Moore, 1973) was reinvestigated in the laboratory mouse by electron microscopy and cobalt chloride-iontophoresis. The time-course of the axonal degeneration in the suprachiasmatic nucleus was studied 3, 6 and 12 h, 1, 2, 4, 6, 9 and 12 days after unilateral retinectomy. Specificity of the degenerative changes was controlled by investigation of the superficial layers of the superior colliculus. The ratio of crossed to uncrossed optic fibers could could be determined by counting degenerating structures (axons and terminals) in the optic chiasma and the ipsilateral and contralateral areas of the optic tract, the suprachiasmatic nucleus, and the superior colliculus. The number of degenerating axons in the suprachiasmatic nucleus showed a maximum one day after unilateral retinectomy and was, at all stages studied, two to three times higher in the contralateral than in the ipsilateral nuclear area. In the optic tract and in the superior colliculus the number of degenerating profiles was three times higher in the contralateral than in the ipsilateral area. Retinohypothalamic connections and crossing pattern of retinal fibers were studied light microscopically using impregnation with cobalt sulfide in whole mounts of brains. Most of the optic fibers in the laboratory mouse are crossed crossed (70-80%). A bundle of predominantly crossed optic fibers runs to the suprachiasmatic nucleus.