Metaraminol use during spinal anaesthesia for caesarean section: a meta-analysis of randomised controlled trials.

INTRODUCTION: During caesarean section, the use of a vasopressor is often required to achieve haemodynamic stability of the parturient. Metaraminol is a vasopressor used in this context in some countries. However, the differences between metaraminol and other vasopressors remain unclear. METHODS: A search of the PubMed, Cochrane Library, and Embase databases was performed to identify randomised controlled trials comparing the use of metaraminol with other vasopressors during spinal anaesthesia at caesarean section. The selected studies were subjected to meta-analysis and risk-of-bias assessment. RESULTS: Four randomised, controlled trials met the selection criteria and 409 parturients who underwent an elective caesarean section were included in this meta-analysis. The quality of these trials was good. Metaraminol was associated with higher umbilical arterial pH (standardised mean difference [SMD] 0.82, 95% CI 0.01 to 1.62, P=0.05); a lower incidence of fetal acidosis (RR 0.08, 95% CI 0.01 to 0.63, P=0.02); and a lower incidence of nausea or vomiting (RR 0.16, 95% CI 0.04 to 0.57, P=0.0005) than was ephedrine. Metaraminol resulted in higher umbilical arterial pH (SMD 0.42, 95% CI 0.15 to 0.68, P=0.002) but a higher incidence of reactive hypertension (RR 1.80, 95% CI 1.32 to 2.46, P=0.0002) than did phenylephrine. CONCLUSION: The results of this study showed that for spinal anaesthesia at elective caesarean section, metaraminol may be a more suitable vasopressor than ephedrine and its effects are at least not inferior to those of phenylephrine.

High-voltage thin-film GaN LEDs fabricated on ceramic substrates: the alleviated droop effect at 670 W/cm(2).

High-voltage thin-film GaN LEDs with the emission wavelength of 455 nm were fabricated on ceramic substrates (230 W/m · K). The high-voltage operation was achieved by three cascaded sub-LEDs with dielectric passivation and metal bridges conformally deposited on the side walls. Under the driving power of 670 W/cm(2), the high-voltage LEDs exhibit much alleviated efficiency droop and the operative temperature below 80 °C. The excellent performances were attributed to the improved current spreading within each sub-LED and the superior heat sinking of the ceramic substrate.

Quantitative MRI analysis of craniofacial bone marrow in patients with sickle cell disease.

BACKGROUND AND PURPOSE: Assessment of bone marrow is most commonly performed qualitatively in the spine or other large long bones. The craniofacial bones are less ideal for bone marrow analysis because of the relatively small bone marrow volume. Because patients with SCD often undergo repeated brain imaging to evaluate for cerebral vaso-occlusive disease, quantitative assessment of craniofacial bone marrow is a reasonable possibility in these patients. The purpose of this study was to investigate specific sickle cell disease changes in craniofacial bone marrow quantitatively by analyzing T1, T2, and secular-T2 relaxation times and volume with the use of quantitative MRI. MATERIALS AND METHODS: Fourteen patients with SCD and 17 control subjects were imaged with the mixed TSE pulse sequence at 1.5T. The craniofacial bones were manually segmented by using 3D Slicer to generate bone marrow volumes and to provide T1, T2, and secular-T2 relaxation times. RESULTS: All subjects exhibited a bimodal T1 histogram. In the SCD group, there was a decrease in amplitude in the first T1 peak and an increase in amplitude in the second T1 peak. The first T1 peak showed a significant increase in relaxation time compared with control subjects (P < .0001), whereas there was no significant difference in the second T1 peak. T2 and secular-T2 relaxation times were significantly shorter in the SCD group (T2, P < .0001; secular-T2, P < .0001). Increasing numbers of blood transfusions resulted in a decrease in T2 and secular-T2 times. Patients with SCD exhibited a larger bone marrow volume compared with control subjects, even after standardization. CONCLUSIONS: Patients with SCD exhibited significant quantifiable changes in the craniofacial bone marrow because of failure of red-to-yellow marrow conversion and iron deposition that can be identified by qMRI relaxometry and volumetry. Both qMRI relaxometry and volumetry may be used as noninvasive tools for assessment of disease severity.

The effects of repeated heat-pressing on properties of pressable glass-ceramics.

The aim of this study was to evaluate the properties of four heat-pressed glass-ceramic materials after repeated heat-pressing. Two commercially available heat-pressed glass-ceramic systems [Optimal pressable glass-ceramics (OPC and 3G) and Empress pressable glass-ceramics (Empress and Empress2)] were selected. Disc samples (14 mm x 1.4 mm) of each tested material were heat-pressed and used as controls. Sprue and button parts of the pressed groups were retrieved and used for repeated heat-pressing to construct specimens of re-pressed group. All the heat-pressed casting procedures were performed according to the manufacturers' instructions. A biaxial flexural strength (BFS) test (ISO 6872) was performed to determine the strength of pressed and re-pressed glass-ceramic disc specimens (n = 10) at a crosshead speed of 0.5 mm min(-1). Ions eluted from etching procedure were collected and examined using inductively coupled plasma mass spectrometer. Surface characteristics were examined with electron probe microanalysis, X-ray diffraction and secondary electron imaging (SEI). The data were analysed statistically (ANOVA + Tukey's HSD post hoc test, P < 0.05). The BFS values obtained ranged from 123.5 +/- 18.5 to 365.9 +/- 35.5 MPa. The re-pressed Empress2 group had a statistically significant higher BFS mean than the pressed control group (P < 0.05). The SEI micrographs of the lithium disilicate-reinforced glass-ceramic material (Empress2) showed a densely packed, interlocking microstructure and an increase in size with preferred orientation of the lithium disilicate crystals after repeated heat-pressing. Repeated heat-pressing treatment produced a statistically significant increase in the flexural strength of Empress2 glass-ceramic material.

K10M4Sn4S17 (M = Mn, Fe, Co, Zn): soluble quaternary sulfides with the discrete [M4Sn4S17]10- supertetrahedral clusters.

Four cubic compounds are reported that contain the supertetrahedral cluster [M(4)Sn(4)S(17)](10)(-) where M = Mn, Fe, Co, Zn. The cluster features a central quadruply bridging sulfide ion (mu(4)-S) that holds together four divalent M atoms in a tetrahedral arrangement. This core is capped with four tridentate [SnS(4)](4)(-) fragments to complete the structure.

alpha- and beta-A2Hg3M2S8 (A = K, Rb; M = Ge, Sn): polar quaternary chalcogenides with strong nonlinear optical response.

The closely related phases alpha- and beta-A(2)Hg(3)M(2)S(8) (A = K, Rb; M = Ge, Sn) have been discovered using the alkali polychalcogenide flux method and are described in detail. They present new structure types with a polar noncentrosymmetric crystallographic motif and strong nonlinear second-harmonic generation (SHG) properties. The alpha-allotropic form crystallizes in the orthorhombic space group Aba2 with a = 19.082(2) A, b = 9.551(1) A, c = 8.2871(8) A for the K(2)Hg(3)Ge(2)S(8) analogue, and a = 19.563(2) A, b = 9.853(1) A, c = 8.467(1) A for the K(2)Hg(3)Sn(2)S(8) analogue. The beta-form crystallizes in the monoclinic space group C2 with a = 9.5948(7) A, b = 8.3608(6) A, c = 9.6638(7) A, beta = 94.637 degrees for the K(2)Hg(3)Ge(2)S(8) analogue. The thermal stability and optical and spectroscopic properties of these compounds are reported along with detailed solubility and crystal growth studies of the alpha-Kappa(2)Hg(3)Ge(2)S(8) in K(2)S(8) flux. These materials are wide gap semiconductors with band gaps at approximately 2.40 and approximately 2.64 eV for the Sn and Ge analogues, respectively. Below the band gap the materials exhibit a very wide transmission range to electromagnetic radiation up to approximately 14 microm. alpha-K(2)Hg(3)Ge(2)S(8) shows anisotropic thermal expansion coefficients. SHG measurements, performed with a direct phase-matched method, showed very high nonlinear coefficient d(eff) for beta-K(2)Hg(3)Ge(2)S(8) approaching 20 pm/V. Crystals of K(2)Hg(3)Ge(2)S(8) are robust to air exposure and have a high laser-damage threshold.

Cycloheximide blocks TGF-beta1-induced apoptosis in murine hepatocytes.

AIM: To study the mechanism of transforming growth factor beta1-induced apoptosis in cultured hepatocytes. METHODS: DNA fragmentation and fluorescent microscopy were used to characterize cell apoptosis. Crystal violet staining was used to assess cell viability. Immunoblotting was used to detect Tak1, p53, and Bax. Dual luciferase assay was used to determine TGF-beta1-induced gene expression. Thin layer chromatography was used to examine ceramide level in AML12 cells. RESULTS: In response to TGF-beta1 treatment, AML12 cells exhibited typical chang es, which was characteristic of apoptosis, such as condensation of chromatin, disintegration of nuclei, and DNA fragmentation. TGF-beta1-induced apoptosis in AML12 cells was completely blocked in the presence of cycloheximide. The inhibitory effect of cycloheximide was accompanied with down-regulation of Tak1 expression and TGF-beta1-induced PAI-1 expression. TGF-beta1 induced p53 expression but not Bax. No increase of ceramide was observed in TGF-beta1-induced apoptosis. CONCLUSION: TGF-beta1-induced apoptosis requires TGF-beta1-induced gene expression.

The involvement of p38 MAPK in transforming growth factor beta1-induced apoptosis in murine hepatocytes.

We reported in this manuscript that TGF-beta1 induces apoptosis in AML12 murine hepatocytes, which is associated with the activation of p38 MAPK signaling pathway. SB202190, a specific inhibitor of p38 MAPK, strongly inhibited the TGF-beta1-induced apoptosis and PAI-1 promoter activity. Treatment of cells with TGF-beta1 activates p38. Furthermore, over-expression of dominant negative mutant p38 also reduced the TGF-beta1-induced apoptosis. The data indicate that the activation of p38 is involved in TGF-beta1-mediated gene expression and apoptosis.

Novel transformations of gamma-silyl nitro compounds.

Introduction of a gamma-silyl group into nitro compounds of dihydrobenzofuran, dihydrobenzo[b]thiophene, and dihydrofuran allowed new transformations to take place in the presence of a Lewis acid to give the corresponding alpha,beta-unsaturated oximes or multisubstituted dihydrofurans, respectively, in good to excellent yields.[reaction: see text]

Characterization, cloning, and expression of porcine alpha B crystallin.

alpha-Crystallin is a major lens protein present in the lenses of all vertebrate species. Recent studies have revealed that bovine alpha-crystallins possess genuine chaperone activity similar to small heat-shock proteins. In order to compare this chaperone-like structural protein from the eye lenses of different mammalian species, we have cloned and expressed one of the main alpha-crystallin subunits, i.e., alpha B crystallin, from the porcine lenses in order to facilitate the structure-function evaluation and comparison of this chaperonin protein. cDNA encoding alpha B subunit chain was obtained using a new "Marathon cDNA amplification" protocol of Polymerase Chain Reaction (PCR). PCR-amplified product corresponding to alpha B subunit was then ligated into pGEM-T plasmid and prepared for nucleotide sequencing by the dideoxy-nucleotide chain-termination method. Sequencing several positive clones containing DNA inserts coding for alpha B-crystallin subunit constructed only one complete full-length reading frame of 525 base pairs similar to human and bovine alpha B subunits, covering a deduced protein sequence of 175 amino acids including the universal translation-initiating methionine. The porcine alpha B crystallin shows only 3 and 7 residues difference to bovine and human alpha B crystallins respectively, revealing the close relatedness among mammalian eye lens proteins. The sequence differences between porcine and sub-mammalian species such as chicken and bullfrog are much greater, especially at the N- and C-terminal regions of these alpha B crystallins. Expression of alpha B subunit chain in E. coli vector generated a polypeptide which can cross-react with the antiserum against the native and purified alpha B subunit from the native porcine lenses albeit with a much lower activity.

Physiological role of the association complexes of alpha-crystallin and its substrates on the chaperone activity.

Previous reports on the chaperone activity of alpha-crystallin to prevent protein denaturation and thermal aggregation have suggested that partially denatured proteins can bind alpha-crystallin in its central region. Likewise, beta- and gamma-crystallin can also be localized to the central cavity of alpha-crystallin particle in vivo, which provides indirect evidence that alpha-crystallin can function as a chaperone in the intact lens. In this study, we have further demonstrated that the binding of the substrate proteins to alpha-crystallin by short-term preincubation may mimic the in vivo conditions of crystallin association. Preheating of alpha-crystallin with its substrate proteins at 60 degrees C for 20 min resulted in the formation of stable complexes between alpha-crystallin and its substrates (8.0% of insulin or 5.3% of gamma-crystallin was involved in complex formation). Under such conditions, the chaperone activity of alpha-crystallin to inhibit dithiothreitol-, ultraviolet-, or oxidation-induced protein aggregation can be greatly enhanced. Since UV-irradiation and oxidative stress are common insults to eye lenses under normal physiological conditions, the presence of alpha/gamma and alpha/beta complex in vivo may play an important role to maintain the lens in a transparent state.

alpha-Crystallin acting as a molecular chaperonin against photodamage by UV irradiation.

alpha-Crystallin, a major protein of the eye lens, is known to have chaperone activity in preventing heat-induced aggregation of enzymes and other crystallins. In this study, we investigate the ability of alpha-crystallin to inhibit UV-light-induced aggregation of other lens proteins and the effect of exposure of alpha-crystallin to UV irradiation on its chaperone activity. The chaperone activities of alpha-crystallin preincubated at different temperatures were found to be different and could be correlated with its change in quaternary structure as determined by the fluorescence probe ANS (8-anilo-1-naphthalene sulfonate). alpha-Crystallin can inhibit the aggregation of gamma-crystallin from UV irradiation at room temperature, and the preheated alpha-crystallins provide more protection than the native one. Upon irradiation by UV light, alpha-crystallin gradually lost its ability to protect beta-crystallin against thermal aggregation. The loss of the chaperone efficacy of alpha-crystallin to protect other lens proteins may shed light on human cataract formation induced by long-term exposure to UV irradiation.

L-Histidine tetrafluoroborate: a solution-grown semiorganic crystal for nonlinear frequency conversion.

The crystal structure, refractive indices, and phase-matching conditions for a new nonlinear optical material, L-histidine tetrafluoroborate (HFB), are reported. HFB grows readily, displays favorable mechanical characteristics, and has adequate birefringence to permit phase-matched parametric processes over much of its transparency range (250 nm to 1300 nm). The phase-matching loci and angular sensitivity for second-harmonic generation of 1064-nm light in single crystals of HFB were measured. The effective nonlinearity for HFB is comparable with that of beta-barium borate (~2 pm/V), and its angular sensitivity [delta(Deltak)/deltatheta] is somewhat smaller.