Stress analysis of self-tightness metal sealing against ultrahigh pressure medium.

Stress is one of the most important factors in metal-to-metal sealing. In this paper, two methods (theoretical and empirical) were adopted to calculate the normal stress of the brass sealing surfaces against different ultrahigh pressure liquid. The theoretical formula was derived in terms of force balance, and the empirical formula was obtained by polynomial curve fitting, which the fitted data were from simulated results; besides, the results calculated using the empirical formula agree well with the results by theoretical formula. Meanwhile, the equivalent stresses of the brass seal, normal stress and contact stress on the brass seal surfaces were simulated by finite element method, and the simulated results indicated these stresses are increased with the increase of liquid pressure, and the maximum stresses always appear on the tip of the brass seal.

[The stimulation of human pulmonary artery endothelial cells by cigarette smoke extract contributed to cell senescence and induced human pulmonary artery smooth cell migration].

Objective: To observe the senescent effect of human pulmonary arterial endothelial cells (HPAEC) stimulated by cigarette smoke extract (CSE) and the effect of secretion of senescent cells on human pulmonary arterial smooth muscles cell (HPASMC) proliferation and migration. Methods: HPAEC was treated with different concentrations of CSE in vitro and cell proliferation was determined by CCK8, senescence cells analyzed by detecting the ß-gal activity, and the senescent proteins of cells measured by Western blot. The concentration of senescence-associated secretory phenotype (SASP) was detected by ELISA and the expression of MCP-1 and TGF-ß1 was measured by Real-time PCR. The number of the proliferated cells was measured by Transwell assay and immunoflurescence. Results: The HPAEC was aging with the stimulation concentration of CSE increasing and the stimulation time prolonging (P<0.05). Western blot indicated that the senescent associated protein p53 or p21 increased markedly after 48 h and 72 h CSE-exposure (n=3, P<0.05). The SA-ß-Gal staining showed that the number of senescent cells increased as the exposure time prolonged. Compared with the control group, cell viability of 48 h group(1.8±0.1) and 72 h group (1.8±0.1) decreased significantly. The flow cytometry showed a significant difference between the CSE group(14.1±1.2) and the control group(28.5±1.8) in S phase(P<0.01), indicating cell cycle arrest. The SASP was increasing as the CSE-exposure prolonged. Compared with the control group(177±39), the 48 h group(460±43) and the 72 h group(609±64) showed a marked increase in MCP-1(P<0.05). For TGF-ß1, it had a same tendency and a significant difference between the control group(121±18) and the 48 h group(413±32) or 72 h group(606±67, both P<0.05). In the meantime, the bFGF increased after 48 h stimulation(291±13, P<0.05). Besides MCP-1, TGF-ß1 showed a significant difference between the control group and the 72 h CSE-exposure group (P<0.01). Premature cells could secrete SASP which induced HPASMC proliferation. After different times of conditioned medium stimulation, HPASMC proliferated especially at 72 h(P<0.05) . The immnoflorescence and Transwell assay confirmed this finding. Conclusion: CSE could induce senescence of HPAEC and SASP production which improved HPASMC proliferation and migration.

A study of boronic acid based fluorescent glucose sensors.

Boronic acid based anthracene dyes were designed, synthesized, and immobilized to solid phase, creating a continuous glucose sensor. Glucose sensitivities of dyes can decrease drastically after immobilization, therefore how to immobilize a dye to solid phase without changing the dye property is a key issue in developing the sensor. The glucose sensitivity of the simplest 1st generation sensor, which is based on an immobilized mono-phenylboronate/single-arm type, came short of the sensitivity requirement for practical use, because of the very moderate fluorescence intensity change over the physiological glucose range. However, the 2nd generation, an immobilized bis-phenylboronate/double-arm type sensor, which contained two boronate groups in the dye moiety in expectation of a large intensity change, brought about considerable improvement on its glucose sensitivity. We tried to introduce functional groups onto an anthracene ring in order to improve the dies' fluorescence properties. Acetyl or carboxyl substitution on anthracene contributed to shift the fluorescence wavelength into the more visible range (red-shift) and a divergence of wavelength between an excitation peak and an emission peak. This improvement is advantageous to the design of an optical detection system. Furthermore, single arm immobilization to this carboxyl group, thus linking directly to the fluorophore led to a 3rd generation sensor, an immobilized bis-phenylboronate/single-arm type, that was twice as sensitive as that of the 2nd generation sensor, presumably due to increased mobility of the dye moiety. The results of our study advance closer toward a clinically useful continuous fluorescent glucose sensor.

[Experimental study on effect of congsheng capsule on expression of brain derived neurotrophic factor and tyrosinkinase mRNA in forebrain of rats after cortical devascularization].

OBJECTIVE: To study the effect and mechanism of Congsheng Capsule (CSC) on brain derived neurotrophic factor (BDNF) and tyrosinkinase (trkB) mRNA in forebrain of rats after cortical devascularization. METHODS: The rat devascularization model was established, and expression of BDNF mRNA and trkB mRNA were determined by hybridization in situ method. RESULTS: Expression of BDNF mRNA and trkB mRNA reduced obviously in the cerebral cortex and hippocampus of devascularization model, especially in hippocampal CA1 subregion. There was trkB mRNA but no BDNF mRNA expression in the macrocyte basal nuclei (MBN). CSC significantly increased the decreased BDNF and trkB mRNA in cortex, hippocampus and MBN compared with placebo group. CONCLUSION: CSC could salvage the degenerating neurons and maintain their survival after cortical devascularization by increasing the expression of BDNF and trkB mRNA and improving the synthesis of BDNF mRNA and trkB protein.

Exocytosis from large dense cored vesicles outside the active synaptic zones of terminals within the trigeminal subnucleus caudalis: a possible mechanism for neuropeptide release.

It has been hypothesized that chemical interactions between neurons in the central nervous system can occur in the absence of well defined synaptic complexes, but morphological correlates have been difficult to find. The present study demonstrates exocytotic release from large (70-130 nm) dense cored vesicles at structurally nonspecialized areas along the plasmalemma of structurally different categories of terminals and occasionally from dendrites and axons within the neuropil of the trigeminal subnucleus caudalis. In rats, the marginal (lamina I) and substantia gelatinosa (lamina II) layers contain the central terminals of primary afferent fibers from the infraorbital nerve that supply the skin and whiskers (vibrissae). Different types of interneurons are also present and may modify the input being relayed to higher centers. While exocytotic profiles were present in control animals, they increased significantly (P less than 0.01) on the ipsilateral side 1-24 h after a unilateral skin lesion in the vibrissae area. A second increase (P less than 0.001) occurred 14-15 days after the lesion. Virtually all examples of large vesicle exocytosis were observed at structurally nonspecialized sites while those at the active synaptic zones involved small clear vesicles. Substance P-like immunofluorescence, present in controls and on the ipsilateral side during the first 6 days, subsequently declined until 4 weeks after surgery when some recovery was noted. The increase in large vesicle exocytosis and the decrease in substance P are interpreted to reflect functional adjustments of different neurons in response to the lesion. The exocytosis involving large dense cored vesicles may serve to deliver transmitters and/or neuropeptide modulators to appropriate receptors in a wider area than release into a specialized synaptic cleft would allow.

Exocytosis from large dense cored vesicles as a mechanism for neuropeptide release in the peripheral and central nervous system.

Nerve terminals often contain morphologically distinct populations of large (75-110 nm) and small (45-55 nm) vesicles. The small vesicles are speculated to account for release of transmitter quanta as they accumulate at presynaptic membranes. Large vesicles can co-store neuropeptides and classical transmitters but their function in neurotransmission has been disputed because they do not appear to accumulate at chemical synapses. However, there is now evidence that the large vesicles play a role in neurotransmission or its modulation even though they may not be eminently involved in synaptic release. Thus, exocytosis occurs along the synapse-lacking membranes of peripheral noradrenergic varicosities. Large vesicles may continue to function in peptide release even after the classical transmitter has been depleted as demonstrated in the pig vas deferens. Three days of reserpine administration causes a parallel loss of noradrenaline and small vesicle contents but does not decrease enkephalin-like immunoreactivity or large vesicle electron density. In the central nervous system of the rat, where substance P and enkephalin have been localized to large vesicles, exocytosis occurs from several types of terminals. The large vesicles appear preferentially to release their contents at morphologically non-specialized sites even when characteristic synapses are present. Thus different mechanisms of transmitter and neuropeptide release may coexist. The nonsynaptic discharge may allow substances to diffuse over a wider distance whereas release into a synaptic cleft could restrict receptor interaction.