Strains missing several genes required for chemotaxis toward amino acids, peptides, and certain sugars were tethered and their rotational behavior was analyzed. Null strains (called gutted) were deleted for genes that code for the transducers Tsr, Tar, Tap, and Trg and for the cytoplasmic proteins CheA, CheW, CheR, CheB, CheY, and CheZ. Motor switch components were wild type, flaAII(cheC), orflaBll(cheV). Gutted cells with wild-type motors spun exclusively counterclockwise, while those with mutant motors changed their directions of rotation. CheY reduced the bias (the fraction of time that cells spun counterclockwise) in either case. CheZ offset the effect of CheY to an extent that varied with switch allele but did not change the bias when tested alone. Transducers also increased the bias in the presence of CheY but not when tested alone. However, cells containing transducers and CheY failed to respond to attractants or repellents normally detected in the periplasm. This sensitivity was restored by addition of CheA and CheW. Thus, CheY both enhances clockwise rotation and couples the transducers to the flagella. CheZ acts, at the level of the motor, as a CheY antagonist. CheA or CheW or both are required to complete the signal pathway. A model is presented that explains these results and is consistent with other data found in the literature.Sensory transduction in bacterial chemotaxis involves receipt of information about the external environment, passage of this information across the cytoplasmic membrane, generation of signals that converge on the flagellar motors, and activation of mechanisms that permit adaptation. The concentrations of certain chemicals are sensed by transmembrane receptors, also called transducers or methylaccepting chemotaxis proteins (1, 11,39; for a review, see reference 10). Four transducers are known, one sensitive to aspartate, maltose, and certain repellents (Tar), a second sensitive to serine and certain other repellents (Tsr), a third sensitive to galactose and ribose (Trg), and a fourth sensitive to dipeptides (Tap [17]). Changes in receptor occupancy, through a series of intermediate events that we hope to understand, alter the probability that the flagella spin clockwise (CW) or counterclockwise (CCW). If they spin CW, the cells move erratically with little net displacement (they tumble); if they spin CCW, the cells swim smoothly (they run) (15,16). If a run happens to carry the cell up a spatial gradient of an attractant (e.g., of aspartate), the probability of CW rotation decreases and the probability of CCW rotation increases (4, 5), extending the run. This enables the cell to move toward a more favorable environment (3).How is sensory information transferred from the receptors to the flagella? From measurements of signal propagation in filamentous cells, Segall et al. (31) showed that there is an internal signal but that its range is short, only a few micrometers. To explain this limited range, they suggested that the signal is a small protein or ligand that is inactivated ...

Dialumenes are neutral Al I compounds with Al = Al multiple bonds.Wereport the isolation of an amidophosphinesupported dialumene.O ur X-ray crystallographic,s pectroscopic,a nd computational DFT analyses reveal al ong and extreme trans-bent Al=Al bond with alow dissociation energy and bond order.Insolution, the dialumene can dissociate into monomeric Al I species.Reactivity studies reveal two modes of reaction:asdialumene or as aluminyl monomers.

Background Traumatic brain injury (TBI) is a major cause of death and disability. T cells were shown to infiltrate the brain during the first days after injury and to exacerbate tissue damage. The objective of this study was to investigate the hitherto unresolved role of immunosuppressive, regulatory T cells (Tregs) in experimental TBI. Methods “Depletion of regulatory T cell” (DEREG) and wild type (WT) C57Bl/6 mice, treated with diphtheria toxin (DTx) to deplete Tregs or to serve as control, were subjected to the controlled cortical impact (CCI) model of TBI. Neurological and motor deficits were examined until 5 days post-injury (dpi). At the 5 dpi endpoint, (immuno-) histological, protein, and gene expression analyses were carried out to evaluate the consequences of Tregs depletion. Comparison of parametric or non-parametric data between two groups was done using Student’s t test or the Mann-Whitney U test. For multiple comparisons, p values were calculated by one-way or two-way ANOVA followed by specific post hoc tests. Results The overall neurological outcome at 5 dpi was not different between DEREG and WT mice but more severe motor deficits occurred transiently at 1 dpi in DEREG mice. DEREG and WT mice did not differ in the extent of brain damage, blood-brain barrier (BBB) disruption, or neuronal excitotoxicity, as examined by lesion volumetry, immunoglobulin G (IgG) extravasation, or calpain-generated αII-spectrin breakdown products (SBDPs), respectively. In contrast, increased protein levels of glial fibrillary acidic protein (GFAP) and GFAP+ astrocytes in the ipsilesional brain tissue indicated exaggerated reactive astrogliosis in DEREG mice. T cell counts following anti-CD3 immunohistochemistry and gene expression analyses of Cd247 (CD3 subunit zeta) and Cd8a (CD8a) further indicated an increased number of T cells infiltrating the brain injury sites of DEREG mice compared to WT. These changes coincided with increased gene expression of pro-inflammatory interferon-γ ( Ifng ) in DEREG mice compared to WT in the injured brain. Conclusions The results show that the depletion of Tregs attenuates T cell brain infiltration, reactive astrogliosis, interferon-γ gene expression, and transiently motor deficits in murine acute traumatic brain injury.

HIF-1a is pivotal for cellular homeostasis in response to cerebral ischemia. Pharmacological inhibition of HIF-1a may reduce secondary brain damage by targeting post-translational mechanisms associated with its proteasomal degradation and nuclear translocation. This study examined the neuroprotective effects of 2-methoxyestradiol (2ME2), the involved HIF-1a-dependent response, and alternative splicing in exon 14 of HIF-1a (HIF-1aΔEx14) after traumatic brain injury (TBI) in mice. Intraperitoneal 2ME2 administration 30 min after TBI caused a dose-dependent reduction in secondary brain damage after 24 h. 2ME2 was physiologically tolerated, showed no effects on immune cell brain migration, and mitigated trauma-induced brain expression of neuropathologically relevant HIF-1a target genes encoding for Plasminogen activator inhibitor 1 and tumor necrosis factor alpha. Moreover, TBI-induced expression of pro-apoptotic BNIP3 was attenuated by 2ME2 treatment. Alternatively, spliced HIF-1aΔEx14 was substantially up-regulated from 6 to 48 h after TBI. In vitro, nuclear location and gene transcription activity of HIF-1aΔEx14 were impaired compared to full-length HIF-1a, but no effects on nuclear translocation of the transcriptional complex partner HIF-1b were observed. This study demonstrates that 2ME2 confers neuroprotection after TBI. While the role of alternatively spliced HIF-1aΔEx14 remains elusive, the in vivo data provide evidence that inhibition of a maladaptive HIF-1a-dependent response contributes to the neuroprotective effects of 2ME2. Keywords: 2-methoxyestradiol, alternative splicing, cerebral ischemia, HIF-1, neuroprotection, traumatic brain injury.

Traumatic brain injury (TBI) is a major cause of death and disability. The underlying pathophysiology is characterized by secondary processes including neuronal death and gliosis. To elucidate the role of the NG2 proteoglycan we investigated the response of NG2-knockout mice (NG2-KO) to TBI. Seven days after TBI behavioral analysis, brain damage volumetry and assessment of blood brain barrier integrity demonstrated an exacerbated response of NG2-KO compared to wild-type (WT) mice. Reactive astrocytes and expression of the reactive astrocyte and neurotoxicity marker Lcn2 (Lipocalin-2) were increased in the perilesional brain tissue of NG2-KO mice. In addition, microglia/macrophages with activated morphology were increased in number and mRNA expression of the M2 marker Arg1 (Arginase 1) was enhanced in NG2-KO mice. While TBI-induced expression of pro-inflammatory cytokine genes was unchanged between genotypes, PCR array screening revealed a marked TBI-induced up-regulation of the C-X-C motif chemokine 13 gene Cxcl13 in NG2-KO mice. CXCL13, known to attract immune cells to the inflamed brain, was expressed by activated perilesional microglia/macrophages seven days after TBI. Thirty days after TBI, NG2-KO mice still exhibited more pronounced neurological deficits than WT mice, up-regulation of Cxcl13, enhanced CD45+ leukocyte infiltration and a relative increase of activated Iba-1+/CD45+ microglia/macrophages. Our study demonstrates that lack of NG2 exacerbates the neurological outcome after TBI and associates with abnormal activation of astrocytes, microglia/macrophages and increased leukocyte recruitment to the injured brain. These findings suggest that NG2 may counteract neurological deficits and adverse glial responses in TBI.