Mechanism of rapid-phase insulin response to elevation of portal glucose concentration

The hepatoportal region is important for glucose sensing; however, the relationship between the hepatoportal glucose-sensing system and the postprandial rapid phase of the insulin response has been unclear. We examined whether a rapid-phase insulin response to low amounts of intraportal glucose infusion would occur, compared that with the response to intrajugular glucose infusion in conscious rats, and assessed whether this sensing system was associated with autonomic nerve activity. The increases in plasma glucose concentration did not differ between the two infusions at 3 min, but the rapid-phase insulin response was detected only in the intraportal infusion. A sharp and rapid insulin response was observed at 3 min after intraportal infusion of a small amount of glucose but not after intrajugular infusion. Furthermore, this insulin response was also induced by intraportal fructose infusion but not by nonmetabolizable sugars. The rapid-phase insulin response at 3 min during intraportal infusion did not differ between rats that had undergone hepatic vagotomy or chemical sympathectomy with 6-hydroxydopamine compared with control rats, but this response disappeared in rats that had undergone chemical vagotomy with atropine. We conclude that the elevation of glucose concentration in the hepatoportal region induced afferent signals from undetectable sensors and that these signals stimulate pancreas to induce the rapid-phase insulin response via cholinergic nerve action.     

Loss of the TOR kinase Tor2 mimics nitrogen starvation and activates the sexual development pathway in fission yeast

Fission yeast has two TOR (target of rapamycin) kinases, namely Tor1 and Tor2. Tor1 is required for survival under stressed conditions, proper G(1) arrest, and sexual development. In contrast, Tor2 is essential for growth. To analyze the functions of Tor2, we constructed two temperature-sensitive tor2 mutants. Interestingly, at the restrictive temperature, these mutants mimicked nitrogen starvation by arresting the cell cycle in G(1) phase and initiating sexual development. Microarray analysis indicated that expression of nitrogen starvation-responsive genes was induced extensively when Tor2 function was suppressed, suggesting that Tor2 normally mediates a signal from the nitrogen source. As with mammalian and budding yeast TOR, we find that fission yeast TOR also forms multiprotein complexes analogous to TORC1 and TORC2. The raptor homologue, Mip1, likely forms a complex predominantly with Tor2, producing TORC1. The rictor/Avo3 homologue, Ste20, and the Avo1 homologue, Sin1, appear to form TORC2 mainly with Tor1 but may also bind Tor2. The Lst8 homologue, Wat1, binds to both Tor1 and Tor2. Our analysis shows, with respect to promotion of G(1) arrest and sexual development, that the loss of Tor1 (TORC2) and the loss of Tor2 (TORC1) exhibit opposite effects. This highlights an intriguing functional relationship among TOR kinase complexes in the fission yeast Schizosaccharomyces pombe.     

Flight muscle myofibrillogenesis in the pupal stage of Drosophila as examined by X-ray microdiffraction and conventional diffraction

In the asynchronous flight muscles of higher insects, the lattice planes of contractile filaments are strictly preserved along the length of each myofibril, making the myofibril a millimetre-long giant single multiprotein crystal. To examine how such highly ordered structures are formed, we recorded X-ray diffraction patterns of the developing flight muscles of Drosophila pupae at various developmental stages. To evaluate the extent of long-range myofilament lattice order, end-on myofibrillar microdiffraction patterns were recorded from isolated quick-frozen dorsal longitudinal flight muscle fibres. In addition, conventional whole-thorax diffraction patterns were recorded from live pupae to assess the extent of development of flight musculature. Weak hexagonal fluctuations of scattering intensity were observed in the end-on patterns as early as approximately 15 h after myoblast fusion, and in the following 30 h, clear hexagonally arranged reflection spots became a common feature. The result suggests that the framework of the giant single-crystal structure is established in an early phase of myofibrillogenesis. Combined with published electron microscopy results, a myofibril in fused asynchronous flight muscle fibres is likely to start as a framework with fixed lattice plane orientations and fixed sarcomere numbers, to which constituent proteins are added afterwards without altering this basic configuration.     

Antimalarial activity of 1-aryl-3,3-dialkyltriazenes

The antimalarial activity of 1-aryl-3,3-dialkyltriazenes to Plasmodium berghei NK-65 in infected mice was evaluated at an intraperitoneal dose of 100mg/kgbw. Some of these compounds were found to possess potent antimalarial activity.     

Involvement of p38alpha in kainate-induced seizure and neuronal cell damage

We investigated how p38alpha mitogen-activated protein kinase (p38) is related to kainate-induced epilepsy and neuronal damages, by using the mice with a single copy disruption of the p38 alpha gene (p38alpha(+/-)). Mortality rate and seizure score of p38alpha(+/-) mice administered with kainate were significantly reduced compared with the case of wild-type (WT) mice. This was clearly supported by the electroencephalography data in which kainate-induced seizure duration and frequency in the brain of p38alpha(+/-) mice were significantly suppressed compared to those of WT mice. As a consequence of seizure, kainate induced delayed neuronal damages in parallel with astrocytic growth in the hippocampus and ectopic innervation of the mossy fibers into the stratum oriens in the CA3 region of hippocampus in WT mice, whose changes were moderate in p38alpha(+/-) mice. Likewise, kainate-induced phosphorylation of calcium/calmodulin-dependent kinase II in the hippocampus of p38alpha (+/-) mice was significantly decreased compared to that of WT mice. These results suggest that p38alpha signaling pathway plays an important role in epileptic seizure and excitotoxicity.     

Molecular cloning and characterization of all RND-type efflux transporters in Vibrio cholerae non-O1

Resistance Nodulation cell Division (RND) efflux transporters are thought to be involved in mediating multidrug resistance in Gram-negative bacteria, including Vibrio cholerae non-O1. There are six operons for putative RND-type efflux transporters present in the chromosome of V. cholerae O1 including two operons, vexAB and vexCD, which had already been identified. All of the six operons were cloned from V. cholerae non-O1, NCTC4716 by the PCR method, introduced, and expressed in cells of drug hypersusceptible Escherichia coli KAM33 (DeltaacrAB, DeltaydhE). Only vexEF conferred elevated minimum inhibitory concentrations (MICs) of some antimicrobial agents in the E. coli cells. However, VexEF did not confer increased MIC of any drug tested in tolC-deficient E. coli KAM43 cells. On the other hand, when E. coli KAM43 was transformed with vexAB, vexCD or vexEF together with tolC(Vc) of V. cholerae NCTC4716, we observed elevated MICs of various antimicrobial agents. Among them, E. coli KAM43 expressing both VexEF and TolC(Vc) showed much higher MICs and much broader substrate specificity than the other two. We also observed ethidium efflux activity via VexEF-TolC(Vc), and the activity required Na(+). Thus, VexEF-TolC (Vc) is either a Na(+)-activated or a Na(+)-coupled transporter. To our knowledge, this is the first report on the requirement of Na(+) for an RND-type efflux transporter.     

Molecular analysis of RANKL-independent cell fusion of osteoclast-like cells induced by TNF-alpha, lipopolysaccharide, or peptidoglycan

Focusing on the final step of osteoclastogenesis, we studied cell fusion from tartrate-resistant acid phosphatase (TRAP)-positive mononuclear cells into multinuclear cells. TRAP-positive mononuclear cells before generation of multinuclear cells by cell fusion were differentiated from RAW264.7 cells by treatment with receptor activator of nuclear factor kappa B ligand (RANKL), and then the cells were treated with lipopolysaccharide (LPS), followed by culturing for further 12 h. LPS-induced cell fusion even in the absence of RANKL. Similarly, tumor necrosis factor (TNF)-alpha and peptidoglycan (PGN) induced cell fusion, but M-CSF did not. The cell fusion induced by RANKL, TNF-alpha, and LPS was specifically blocked by osteoprotegerin (OPG), anti-TNF-alpha antibody, and polymyxin B, respectively. LPS- and PGN-induced cell fusion was partly inhibited by anti-TNF-alpha antibody but not by OPG. When TRAP-positive mononuclear cells fused to yield multinuclear cells, phosphorylation of Akt, Src, extracellular signal-regulated kinase (ERK), p38MAPK (p38), and c-Jun NH2-terminal kinase (JNK) was observed. The specific chemical inhibitors LY294002 (PI3K), PP2 (Src), U0126 (MAPK-ERK kinase (MEK)/ERK), and SP600125 (JNK) effectively suppressed cell fusion, although SB203580 (p38) did not. mRNA of nuclear factor of activated T-cells c1 (NFATc1) and dendritic cell-specific transmembrane protein (DC-STAMP) during the cell fusion was quantified, however, there was no obvious difference among the TRAP-positive mononuclear cells treated with or without M-CSF, RANKL, TNF-alpha, LPS, or PGN. Collectively, RANKL, TNF-alpha, LPS, and PGN induced cell fusion of osteoclasts through their own receptors. Subsequent activation of signaling pathways involving PI3K, Src, ERK, and JNK molecules was required for the cell fusion. Although DC-STAMP is considered to be a requisite for cell fusion of osteoclasts, cell fusion-inducing factors other than DC-STAMP might be necessary for the cell fusion.     

Exploration of Pericyte-Derived Factors Implicated in Lung Cancer Brain Metastasis Protection: A Pilot Messenger RNA Sequencing Using the Blood–Brain Barrier In Vitro Model

Cellular and Molecular Neurobiology - Metastatic brain tumors have poor prognoses and pose unmet clinical problems for the patients. The blood–brain barrier (BBB) implication is supposed to...     

Clinical Features and Mortality of COVID-19-Associated Mucormycosis: A Systematic Review and Meta-Analysis

The recent increase of COVID-19-associated mucormycosis (CAM) has been commanding global attention. However, basic epidemiologic characteristics have not firmly been established. In this systematic review and meta-analysis, we sought to determine the clinical manifestations, potential risk factors, and outcomes of CAM. Observational studies reporting CAM were searched with PubMed and EMBASE databases in January 2022. We collected data on comorbidities and treatment for COVID-19, and performed a one-group meta-analysis on the frequency of orbital exenteration procedure and mortality of CAM using a random-effect model. Fifty-one observational studies, including a total of 2,312 patients with proven CAM, were identified. Among the 51 studies, 37 were conducted in India, 8 in Egypt, and 6 in other countries. The most common comorbidity was diabetes mellitus (82%). While 57% required oxygenation, 77% received systemic corticosteroids. Among CAM, 97% were rhino-orbital-cerebral (ROCM), and 2.7% were pulmonary mucormycosis. Usual presentations were headache (54%), periorbital swelling/pain (53%), facial swelling/pain (43%), ophthalmoplegia (42%), proptosis (41%), and nasal discharge/congestion (36%). Regarding the outcomes, orbital exenteration was performed in 17% (95% CI: 12–21%, I²?=?83%) of the COVID-19-associated ROCM patients. The mortality of CAM was 29% (95% CI; 22–36%, I²?=?92%). In conclusion, this systematic review and meta-analysis indicated that the most prevalent type of CAM was ROCM, and most CAM patients had diabetes mellitus and received systemic glucocorticoids. Clinicians in the endemic areas should have a high index of suspicion for this invasive fungal complication of COVID-19 when a diabetic patient who received high-dose systemic glucocorticoids developed rhino-orbital symptoms.