UV-curable ladder-like diphenylsiloxane-bridged methacryl-phenyl-siloxane for high power LED encapsulation.

A UV curable ladder-like diphenylsiloxane-bridged methacryl-phenyl-siloxane (L-MPS) was synthesized from phenyltrichlorosilane, diphenylsilanediol and methacryloxypropyldimethylmethoxysilane via dehydrochlorination precoupling, supramolecular architecture-directed hydrolysis-condensation and end-capping reactions. The L-MPS has a condensation degree of ∼100%, and can be complete crosslinked by UV curing. XRD, TEM and molecular simulation suggest that the ladder-like molecules are close packed with a periodic distance of ca. 1.2 nm. The L-MPS shows transmittance of 98% and a refractive index of ca. 1.61 at 450 nm. The cured L-MPS with a T d5% value of 465.5 °C showed excellent anti-yellowing and anti-sulfidation properties. The cured L-MPS film and the encapsulated LED samples were compared with those of Dow Corning OE-6630 and OE-7662. It is believed that the dense nano-ladder unit also contributes to the thermal, gas barrier and even optical properties. L-MPS shows promising potential as a high power LED encapsulant and optical coating for use in harsh environments. This work provides an approach to integrate this novel ladder structure with advanced properties.

[Performance evaluation of two N95 filtering-facepiece respirators on decomposition products of sulfur hexafluoride].

OBJECTIVE: To assess the filtration efficiency of two N95 filtering-facepiece respirators (FFRs) for the decomposition products of sulfur hexafluoride (SF6). METHODS: Two types of N95 FFRs (the particulate and the acid-proof respirators) were selected in this study. The decomposition products of SF6, including particles, hydrogen fluoride (HF) and sulfur dioxide (SO2) , were measured under experimental condition by using TSI PortaCount Plus, fluorine ion-selective electrodes and spectrophotometer separately. The filtration efficiency was then calculated and compared. RESULTS: Both two models of N95 respirators had lowest filtration efficiency larger than 95% for particles under airflow ranged from 10 to 95 L/min. When exposed to different concentrations of HF (low: 0.00~1.99 mg/m(3), middle: 2.00~3.99 mg/m(3), high: >4 mg/m(3)) , the acid-proof N95 respirator was more effective than the particulate respirator (P<0.05) with a filtration efficiency of 98.83%, 99.08%, and 99.03% versus 48.44%, 45.71%, and 47.31%. For four SO2 concentration ranges (0.00~2.49 mg/m(3), 2.50~4.99 mg/m(3), 5.00~9.99 mg/m(3), and >10.00 mg/m(3)) , the acid-proof respirator showed a high filtration efficiency within exposure to 1.5 hours: 95.73%, 98.67%, 98.14%, and 97.78%, respectively, when exposure duration extended to 4 hours, the filtration efficiency of the acid-proof respirator decreased to 91.97%, 82.28%, 70.12%, and 58.56%, respectively. CONCLUSION: Both the particulate and the acid-proof N95 FFRs met national standards on the particulate filtration efficiency. The acid-proof N95 respirator demonstrates to be more effective in filtering HF and SO2 than the particulate respirator. The filtration efficiency could decrease to an unsafe condition under longer exposure duration, timely replacement of respirator is recommended at the workplace.

The effect of citalopram on chronic stress-induced depressive-like behavior in rats through GSK3ß/ß-catenin activation in the medial prefrontal cortex.

Antidepressant treatments enhance synaptic connectivity in stress-sensitive brain regions such as the medial prefrontal cortex (mPFC). The mPFC plays a key role in controlling cognition and emotion. While several signaling pathways are involved in this enhancement process, the exact mechanisms are not fully established. In the present study, we evaluated the role of the glycogen synthase kinase 3ß (GSK3ß)/ß-catenin signaling pathway in the antidepressant effect of citalopram in rats exposed to forced swim stress. The acute stress group received the classic, two-day variant of the forced swimming test (FST), whereas the chronic stress group received swim stress for 14 consecutive days. We found that rats exposed to acute swim stress showed depressive-like behaviors and expressed normal GSK3ß and ß-catenin levels in the mPFC. Chronic swim stress, also induced a significant behavior changes but was associated with decreased levels of phosphorylated GSK3ß and ß-catenin in the rat's mPFC. Chronic citalopram treatment alleviated these behavioral changes in chronically stressed rats and normalized the downregulation of GSK3ß/ß-catenin signaling. Our results suggest that GSK3ß/ß-catenin signaling plays an important role in chronic but not acute stress-related depression and contributes, at least in part, to the antidepressant effects of citalopram in distinct brain regions associated with mood regulation.

Dorsal column is not involved in the mechanism of the hypotensive effect by simulating acupuncture on rat hindlimb.

The present study investigated the role of the dorsal column (DC) in the mechanism of the hypotensive effect induced by simulating acupuncture on rat hindlimb. The femoral arterial pressure and electrocardiogram (ECG) of rats were recorded when the hypothalamic paraventricular nucleus (PVN) was electrically stimulated with or without DC lesion. Stimulation of the deep peroneal nerve (DPN) decreased the pressor response elicited by electrical stimulation of the PVN. Thirty minutes after micro-dissection of the right DC, the inhibitory effect of stimulating the right or left DPN on the pressor response induced by stimulation of the contralateral PVN was not altered. Of 6 rats tested, the inhibitory effect of stimulating the right or left DPN could still be observed five days after the right DC was destroyed. The pain responses of both hindlimbs of the rats with the right DC destroyed showed no obvious difference when compared with the sham control rats. These data suggest that the DC is not involved in the inhibitory effect of stimulating the DPN on the pressor response induced by the PVN activation.

Analytical expressions of quadratic and cubic phases in a three-element resonator for kerr-lens mode locking.

We present analytical expressions of quadratic and cubic phases in a three-element resonator for Kerr-lens mode locking. Variation of quadratic and cubic phases with wedge angles of Ti:sapphire and apex angles of a prismatic output coupler are calculated. The results provide a theoretical basis for the design of a three-element cavity.

Gene expression networks underlying retinoic acid-induced differentiation of acute promyelocytic leukemia cells.

To elucidate the molecular mechanism of all-trans-retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) cells, the gene expression patterns in the APL cell line NB(4) before and after ATRA treatment were analyzed using complementary DNA array, suppression-subtractive hybridization, and differential-display-polymerase chain reaction. A total of 169 genes, including 8 novel ones, were modulated by ATRA. The ATRA-induced gene expression profiles were in high accord with the differentiation and proliferation status of the NB(4) cells. The time courses of their modulation were interesting. Among the 100 up-regulated genes, the induction of expression occurred most frequently 12-48 hours after ATRA treatment, while 59 of 69 down-regulated genes found their expression suppressed within 8 hours. The transcriptional regulation of 8 induced and 24 repressed genes was not blocked by cycloheximide, which suggests that these genes may be direct targets of the ATRA signaling pathway. A balanced functional network seemed to emerge, and it formed the foundation of decreased cellular proliferation, maintenance of cell viability, increased protein modulation, and promotion of granulocytic maturation. Several cytosolic signaling pathways, including JAKs/STAT and MAPK, may also be implicated in the symphony of differentiation. (Blood. 2000;96:1496-1504)

Primary structure, tissue distribution, and expression of mouse phosphoinositide-dependent protein kinase-1, a protein kinase that phosphorylates and activates protein kinase Czeta.

Phosphoinositide-dependent protein kinase-1 (PDK1) is a recently identified serine/threonine kinase that phosphorylates and activates Akt and p70(S6K), two downstream kinases of phosphatidylinositol 3-kinase. To further study the potential role of PDK1, we have screened a mouse liver cDNA library and identified a cDNA encoding the enzyme. The predicted mouse PDK1 (mPDK1) protein contained 559 amino acids and a COOH-terminal pleckstrin homology domain. A 7-kilobase mPDK1 mRNA was broadly expressed in mouse tissues and in embryonic cells. In the testis, a high level expression of a tissue-specific 2-kilobase transcript was also detected. Anti-mPDK1 antibody recognized multiple proteins in mouse tissues with molecular masses ranging from 60 to 180 kDa. mPDK1 phosphorylated the conserved threonine residue (Thr402) in the activation loop of protein kinase C-zeta and activated the enzyme in vitro and in cells. Our findings suggest that there may be different isoforms of mPDK1 and that the protein is an upstream kinase that activates divergent pathways downstream of phosphatidylinositol 3-kinase.

[The role of accumbens nucleus in the inhibitory effect of somatic afferent inputs on the defence cardiovascular response and its mechanism].

After Accumbens Nucleus (AC) lesion, the inhibitory effect of deep peroneal nerve (DPN) on the pressor response and ECG-ST changes induced by excitation of dorsomedial nucleus of hypothalamus (DMH) was decreased as compared with that of before lesion (P < 0.05, P < 0.01). Electrical stimulation of AC could elicit prominent depressor response, which could be effectively lessened by microinjection of naloxone into ventral periaqueductal gray (vPAG). Lesion of vPAG could reverse the depressor response to AC stimulation to a slight pressor response (P < 0.01). After lesion of arcuate nucleus of hypothalamus (ARC), the depressor response to AC stimulation almost disappeared, which, again, could be largely mimicked by microinjection of naloxone into ARC.

[Spinal mechanism of the inhibitory effect of somatic input on the cardiac ischemia induced by hypothalamus stimulation].

Experiments were carried out on 58 urethane-chloralose anaesthetized, gallamine triethiodide immobilized and vagotomized rabbits under artificial ventilation. Median nerve (MN) or deep peroneal nerve(DPN) stimulation could inhibit completely or partially the deflection of ischemic ECG ST segment due to stimulation of dorsomedial hypothalamic nucleus (DMH). The inhibitory effect of MN stimulation was more marked than that of DPN stimulation. Intrathecal injection (ith) of morphine (40 micrograms) could also inhibit these ischemic ECG ST segment changes. After ith naloxone (20 micrograms), the inhibitory effect of MN stimulation on DMH stimulation-induced ischemic ECG ST segment changes was abolished. In intact rabbits, it was demonstrated that L-enkephalin (LENK) immunoreactive material was increased in the left or right intermediolateral cell column (IML) of T2-5 spinal cord after stimulation of left MN or DPN for five minutes. In the Cl transected rabbits, stimulation of MN only increased ipsilateral LENK immunoreactive material content in the thoracic IML, while stimulation of DPN produced no such an effect. These results indicate that stimulation of MN or DPN can inhibit cardiac ischemia induced by DMH stimulation and that the effect of MN stimulation is more potent. The inhibitory effects may be mediated by an increase of LENK immunoreactive material in the bilateral IML produced through some supraspinal mechanisms; whereas the effect of MN stimulation may also be mediated by an increase of ipsilateral spinal LENK immunoreactive material in the thoracic IML through segmental mechanism to inhibit the sympathetic activity.

High channel-mediated water permeability in rabbit erythrocytes: characterization in native cells and expression in Xenopus oocytes.

Erythrocytes from several mammalian species contain mercurial-sensitive water transporters. By a stopped-flow light scattering technique, osmotic water permeability (Pf) was exceptionally high in rabbit erythrocytes (0.053 +/- 0.002 cm/s) and reversibly inhibited by 98% by p-(chloromercuri)benzenesulfonate (pCMBS). The activation energy (Ea) was 4.6 kcal/mol (15-37 degrees C). pCMBS inhibition was half-maximal at 0.1 mM (60-min incubation); at 1 mM pCMBS, half-maximal inhibition occurred in 8 min. Pf was also inhibited by HgCl2 and pCMB with greater than 90% inhibition in 5 min. There was no inhibition by high concentrations of phloretin, DNDS, cytochalasin B, amiloride, ouabain, furosemide, and several proteases. In defolliculated Xenopus oocytes microinjected with 50 nL of water or unfractionated mRNA (1 mg/mL) from rabbit reticulocytes, oocyte Pf assayed at 10 degrees C after 72-h incubation increased from (4 +/- 1) X 10(-4) cm/s (water injected) to (18 +/- 2) X 10(-4) cm/s (mRNA injected). Pf increased linearly with [mRNA] (0-75 ng/oocyte) and was inhibited slowly and reversibly by pCMBS and immediately by HgCl2 but not by cytochalasin B, phloretin, or DNDS. Ea was 9.6 kcal/mol (water injected) and 2.6 kcal/mol (mRNA injected). These results demonstrate that rabbit erythrocytes have the highest Pf and the greatest percentage inhibition of Pf by mercurials of any mammalian erythrocyte studied. The characteristics of the expressed and native water channels were similar, suggesting that the erythrocyte water channel is a membrane protein suitable for expression cloning.

[Effect of hypothalamic stimulation on RMBF and SP content in IML of spinal cord in rabbits].

Experiments were performed on 48 urethane-chloralose anaesthetized, gallamine triethiodide immobilized and vagotomized rabbits under artificial ventilation. Radiolabeled microspheres were injected into the left atrium during stimulation of the left or right dorsomedial hypothalamic nucleus (LDMH or RDMH) to measure regional myocardial blood flow (RMBF). RDMH stimulation produced relatively little flow reduction of the left ventricle, whereas LDMH stimulation produced an obvious flow reduction. No significant change occurred in the right ventricle. Meanwhile, LDMH or RDMH stimulation caused increases of mean arterial blood pressure (MABP) and changes of epicardial electrogram (EECG) ST segment, but no significant changes in heart rate. EECG ST segment was elevated in relation to the reduction of RMBF in left ventricle (r = -0.825, P less than 0.001). Linear regression analysis of MABP change in relation to left ventricle RMBF showed no significant correlation. In intact rabbits, it was demonstrated that DMH stimulation caused an decrease of substance P (SP) immunoreactive material in bilateral intermediolateral cell columns (IML) of T2-5 spinal cord concomitantly with an elevation in MABP and EECG ST changes. The results suggest that electrical stimulation of DMH can elicit coronary constriction, decrease in RMBF, elevation of EECG ST segment and increase in MABP, which may be mediated by the release of SP immunoreactive material in the IML of the spinal cord.

Water and urea permeability properties of Xenopus oocytes: expression of mRNA from toad urinary bladder.

The Xenopus oocyte was evaluated as an mRNA expression system for water and urea transporters. Osmotic water permeability (Pf) was measured from the time course of oocyte volume in response to osmotic gradients using a real-time imaging method. Diffusional water permeability (Pd) was measured by 3H2O efflux. In mature oocytes treated with collagenase to remove the follicular cell layer, Pf was 8.6 +/- 0.6 x 10(-4) (SD) cm/s (n = 32) at 25 degrees C and independent of the time after oocyte removal (0-8 days). The activation energy (Ea) for Pf was 10.2 kcal/mol (10-32 degrees C). Pf was independent of osmotic gradient size (50-200 mosmol) in swelling experiments but decreased in an unpredictable manner in shrinking experiments. Pf was not altered by removal of the vitelline membrane but was decreased by 75% when the follicular cell layer was intact. In collagenase-treated oocytes, amphotericin (0-500 micrograms/ml) increased Pf from 8 x 10(-4) to 84 x 10(-4) cm/s in a dose-dependent manner. Pd was 3.4 +/- 0.2 x 10(-4) (SE) cm/s at 25 degrees C, 1.5 +/- 0.2 x 10(-4) cm/s at 4 degrees C, and 5.1 +/- 0.5 x 10(-4) cm/s at 25 degrees C in the presence of 500 micrograms/ml amphotericin; Ea was 6.5 kcal/mol. Thus Pd, but not Pf, is unstirred layer limited.(ABSTRACT TRUNCATED AT 250 WORDS)

Urea transport in freshly isolated and cultured cells from rat inner medullary collecting duct.

Regulation of urea transport by vasopressin in inner medullary collecting duct (IMCD) cells is thought to be important for the urinary concentrating mechanism. Isolated tubule perfusion studies suggest the existence of a saturable urea carrier. We have measured 14C-urea efflux in IMCD cells which were freshly isolated and grown in primary culture. Cells were isolated from rat papilla by collagenase digestion and hypotonic shock. In suspended cells, 14C-urea efflux (Jurea) from loaded cells was exponential with time constant 59 +/- 3 sec (SEM, n = 6, 23 degrees C). Jurea had an activation energy of 4.1 kcal/mole and was inhibited 42 +/- 7% by 0.25 mM phloretin and 30-40% by the high affinity urea analogues dimethylurea and phenylurea. Jurea was increased 40-60% by addition of vasopressin (10(-8) M) or 8-bromo-cAMP (1 mM); stimulated Jurea was inhibited 55 +/- 8% by the kinase A inhibitor H-8. Phorbol esters and epidermal growth factor did not alter Jurea. IMCD cells grown in primary culture were homogeneous in appearance with greater than fivefold stimulation of cAMP by vasopressin. The exponential time constant for urea efflux was 610 +/- 20 sec (n = 3). Jurea was not altered by vasopressin, cAMP or phloretin. Another function of in vivo IMCD cells, vasopressin-dependent formation of endosomes containing water channels, was absent in the cultured cells. These results demonstrate presence of a urea transporter on suspended IMCD cells which is activated by cAMP and inhibited by phloretin and urea analogues. The urea transporter and its regulation by cAMP, and cAMP-dependent apical membrane endocytosis, are lost after growth in primary culture.

Expression of mRNA coding for kidney and red cell water channels in Xenopus oocytes.

The existence and identity of protein water transporters in biological membranes has been uncertain. Osmotic water permeability (Pf) was measured in defolliculated Xenopus oocytes microinjected with water or mRNA from kidney cortex, kidney papilla, reticulocyte, brain, and muscle. Pf was measured by quantitative image analysis from the time course of oocyte swelling in response to an osmotic gradient. When assayed at 10 degrees C, Pf in water-injected oocytes increased from (3.6 +/- 0.9) x 10(-4) cm/s (S.D., n = 16) to 74 x 10(-4) cm/s with addition of amphotericin B, showing absence of unstirred layers. At 48-72 h after injection of 50 ng of unfractionated mRNA, Pf (in cm/s x 10(-4] was: 4.0 +/- 1.5 (rabbit brain, n = 15), 4.2 +/- 1.8 (rabbit muscle, n = 10), 18.4 +/- 6.3 (rabbit reticulocyte, n = 20), 16.1 +/- 5.6 (rat renal papilla, n = 24), 12.9 +/- 6.3 (rat renal cortex, n = 20), 14.4 +/- 6.1 (rabbit renal papilla, n = 15), and 11.8 +/- 3.4 (rabbit renal cortex, n = 8). In oocytes injected with mRNA from rat renal papilla, Pf was inhibited reversibly by 0.3 mM HgCl2 (4.1 +/- 1.6, n = 10); expressed water channels from kidney and red cell had activation energies of less than 4 kcal/mol. These results show functional oocyte expression of water channels from red cell, kidney proximal tubule (cortex), and the vasopressin-sensitive kidney collecting tubule (papilla), indicating that water channels are proteins, and providing an approach for the expression cloning of water channels.

[High performance liquid chromatographic studies of indole alkaloids].

The chromatographic behavior and the relationship between the retention and the structure of 16 indole alkaloids were investigated on a mu-Bondapak C18 column at different pH with different volume ratios of 0.02 mol/L KH2PO4-CH3OH as mobile phase and a photodiode array detector (DAD) was used. The experimental results demonstrate that the plots of the logarithm of capacity factor k' of the indole alkaloids are nonlinear in the volume fraction of methanol and the capacity factors increase with increasing pH of buffer solution from 2 to 6 then decrease. The effect of different kinds of buffer solution on k' has also been examined. Phosphate and citrate buffer showed stronger elution strength for various indole alkaloids but acetate buffer was shown to be relatively weak. Increase of phosphate buffer concentration gives a little decrease on k'. These results indicate that the optimized separation of 12 indole alkaloids studied in this work can be carried out isocratically in the system of pH 7.5 phosphate buffer-methanol (30:70) on a mu-Bondapak C18 column.