[Feasibility and safety of bridge therapy with active fixed electrodes connected to external permanent pacemakers for patients with infective endocarditis after lead removal and before permanent pacemaker implantation]

Objective: To analyze the feasibility and safety of bridge therapy with active fixed electrodes connected to external permanent pacemakers (AFLEP) for patients with infective endocarditis after lead removal and before permanent pacemaker implantation. Methods: A total of 44 pacemaker-dependent patients, who underwent lead removal due to infective endocarditis in our center from January 2015 to January 2020, were included. According to AFLEP or temporary pacemaker option during the transition period, patients were divided into AFLEP group or temporary pacemaker group. Information including age, sex, comorbidities, indications and types of cardial implantable electionic device (CIED) implantation, lead age, duration of temporary pacemaker or AFLEP use, and perioperative complications were collected through Haitai Medical Record System. The incidence of pacemaker perception, abnormal pacing function, lead perforation, lead dislocation, lead vegetation, cardiac tamponade, pulmonary embolism, death and newly infection of implanted pacemaker were compared between the two groups. Pneumothorax, hematoma and the incidence of deep vein thrombosis were also analyzed. Results: Among the 44 patients, 24 were in the AFLEP group and 20 in the temporary pacemaker group. Age was younger in the AFLEP group than in the temporary pacemaker group (57.5(45.5, 66.0) years vs. 67.0(57.3, 71.8) years, P=0.023). Male, prevalence of hypertension, diabetes mellitus, chronic renal dysfunction and old myocardial infarction were similar between the two groups (all P>0.05). Lead duration was 11.0(8.0,13.0) years in the AFLEP group and 8.5(7.0,13.0) years in the temporary pacemaker group(P=0.292). Lead vegetation diameter was (8.2±2.4)mm in the AFLEP group and (9.1±3.0)mm in the temporary pacemaker group. Lead removal was successful in all patients. The follow-up time in the AFLEP group was 23.0(20.5, 25.5) months, and the temporary pacemaker group was 17.0(14.5, 18.5) months. In the temporary pacemaker group, there were 2 cases (10.0%) of lead dislocation, 2 cases (10.0%) of sensory dysfunction, 2 cases (10.0%) of pacing dysfunction, and 2 cases (10.0%) of death. In the AFLEP group, there were 2 cases of abnormal pacing function, which improved after adjusting the output voltage of the pacemaker, there was no lead dislocation, abnormal perception and death. Femoral vein access was used in 8 patients (40.0%) in the temporary pacemaker group, and 4 patients developed lower extremity deep venous thrombosis. There was no deep venous thrombosis in the AFLEP group. The transition treatment time was significantly longer in the AFLEP group than in the temporary pacemaker group (19.5(16.0, 25.8) days vs. 14.0(12.0, 16.8) days, P=0.001). During the follow-up period, there were no reinfections with newly implanted pacemakers in the AFLEP group, and reinfection occurred in 2 patients (10.0%) in the temporary pacemaker group. Conclusions: Bridge therapy with AFLEP for patients with infective endocarditis after lead removal and before permanent pacemaker implantation is feasible and safe. Compared with temporary pacemaker, AFLEP is safer in the implantation process and more stable with lower lead dislocation rate, less sensory and pacing dysfunction.

[Advances in the study of programmed cell death protein 1 and its ligand inhibitors in the treatment of late stage HCC]

The treatment of late stage hepatocellular carcinoma (HCC) presently remains a great challenge. A very few drugs have been recently approved for clinical use except sorafenib and lenvatinib. After decades of failure and experience with molecular targeted and immunosuppressive therapy, immune checkpoint inhibitors are becoming one of the potentially effective therapies for patients with HCC, whose tumor is in the middle and late stages. Moreover, immune checkpoint is one of the main mechanisms of tumor immune evasion; of which programmed cell death protein 1 and its ligand (PD1/PD-L1) are important immune checkpoint targets, and its related pathway has shown to have an antitumor effect in a variety of solid or hematologic tumors and its inhibitors can effectively exert antitumor immunosuppressive effects. This review summarizes the current role of PD1/PD-L1 inhibitors in the treatment of late stage HCC, and explores the forecasting value of combined therapy strategy for HCC.

Glassy Dynamics in a heavy ion irradiated NbSe2 crystal

Fascination with glassy states has persisted since Fisher introduced the vortex-glass as a new thermodynamic phase that is a true superconductor that lacks conventional long-range order. Though Fisher's original model considered point disorder, it was later predicted that columnar defects (CDs) could also induce glassiness - specifically, a Bose-glass phase. In YBa2Cu3O7-x (YBCO), glassy states can cause distinct behavior in the temperature (T ) dependent rate of thermally activated vortex motion (S). The vortex-glass state produces a plateau in S(T ) whereas a Bose-glass can transition into a state hosting vortex excitations called double-kinks that can expand, creating a large peak in S(T ). Although glass phases have been well-studied in YBCO, few studies exist of other materials containing CDs that could contribute to distinguishing universal behavior. Here, we report on the effectiveness of CDs tilted ~30° from the c-axis in reducing S in a NbSe2 crystal. The magnetization is 5 times higher and S is minimized when the field is parallel to the defects versus aligned with the c-axis. We see signatures of glassiness in both field orientations, but do not observe a peak in S(T ) nor a plateau at values observed in YBCO. Finally, we discuss the possibility that competing disorder induces a field-orientation-driven transition from a Bose-glass to an anisotropic glass involving both point and columnar disorder.

Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe_{2}

Extremely large magnetoresistance (XMR) was recently discovered in WTe_{2}, triggering extensive research on this material regarding the XMR origin. Since WTe_{2} is a layered compound with metal layers sandwiched between adjacent insulating chalcogenide layers, this material has been considered to be electronically two-dimensional (2D). Here we report two new findings on WTe_{2}: (1) WTe_{2} is electronically 3D with a mass anisotropy as low as 2, as revealed by the 3D scaling behavior of the resistance R(H,θ)=R(ϵ_{θ}H) with ϵ_{θ}=(cos^{2}θ+γ^{-2}sin^{2}θ)^{1/2}, θ being the magnetic field angle with respect to the c axis of the crystal and γ being the mass anisotropy and (2) the mass anisotropy γ varies with temperature and follows the magnetoresistance behavior of the Fermi liquid state. Our results not only provide a general scaling approach for the anisotropic magnetoresistance but also are crucial for correctly understanding the electronic properties of WTe_{2}, including the origin of the remarkable "turn-on" behavior in the resistance versus temperature curve, which has been widely observed in many materials and assumed to be a metal-insulator transition.

Realization of artificial ice systems for magnetic vortices in a superconducting MoGe thin film with patterned nanostructures

We report an anomalous matching effect in MoGe thin films containing pairs of circular holes arranged in such a way that four of those pairs meet at each vertex point of a square lattice. A remarkably pronounced fractional matching was observed in the magnetic field dependences of both the resistance and the critical current. At the half matching field the critical current can be even higher than that at zero field. This has never been observed before for vortices in superconductors with pinning arrays. Numerical simulations within the nonlinear Ginzburg-Landau theory reveal a square vortex ice configuration in the ground state at the half matching field and demonstrate similar characteristic features in the field dependence of the critical current, confirming the experimental realization of an artificial ice system for vortices for the first time.

Catalyst-free growth of millimeter-long topological insulator Bi₂Se₃ nanoribbons and the observation of the π-Berry phase

We report the growth of single-crystalline Bi(2)Se(3) nanoribbons with lengths up to several millimeters via a catalyst-free physical vapor deposition method. Scanning transmission electron microscopy analysis reveals that the nanoribbons grow along the (112̅0) direction. We obtain a detailed characterization of the electronic structure of the Bi(2)Se(3) nanoribbons from measurements of Shubnikov-de Haas (SdH) quantum oscillations. Angular dependent magneto-transport measurements reveal a dominant two-dimensional contribution originating from surface states. The catalyst-free synthesis yields high-purity nanocrystals enabling the observation of a large number of SdH oscillation periods and allowing for an accurate determination of the π-Berry phase, one of the key features of Dirac fermions in topological insulators. The long-length nanoribbons open the possibility for fabricating multiple nanoelectronic devices on a single nanoribbon.

Large magnetoresistance oscillations in mesoscopic superconductors due to current-excited moving vortices

We show in the case of a superconducting Nb ladder that a mesoscopic superconductor typically exhibits magnetoresistance oscillations whose amplitude and temperature dependence are different from those stemming from the Little-Parks effect. We demonstrate that these large resistance oscillations (as well as the monotonic background on which they are superimposed) are due to current-excited moving vortices, where the applied current in competition with the oscillating Meissner currents imposes or removes the barriers for vortex motion in an increasing magnetic field. Because of the ever present current in transport measurements, this effect should be considered in parallel with the Little-Parks effect in low-critical temperature (T(c)) samples, as well as with recently proposed thermal activation of dissipative vortex-antivortex pairs in high-T(c) samples.

Transparent conducting films from NbSe3 nanowires

We have developed methods to disperse and partially size separate NbSe(3) nanowires in aqueous surfactant solutions. These dispersions can easily be formed into thin films. Optical and electrical studies show these films to display sheet resistances and transmittances ranging from (460 Ω/□, 22%) to (12 kΩ/□, 79%) depending on thickness. For thicker films, we measured the transparent conducting figure of merit to be σ(DC, B)/σ(Op) = 0.32, similar to graphene networks. Thickness measurements gave individual values of σ(Op) = 17,800 S m(-1) and σ(DC, B) = 5700 S m(-1). Films thinner than ∼ 70 nm displayed reduced DC conductivity due to percolative effects.

Hydrogen gas sensing with networks of ultrasmall palladium nanowires formed on filtration membranes

Hydrogen sensors based on single Pd nanowires show promising results in speed, sensitivity, and ultralow power consumption. The utilization of single Pd nanowires, however, face challenges in nanofabrication, manipulation, and achieving ultrasmall transverse dimensions. We report on hydrogen sensors that take advantage of single palladium nanowires in high speed and sensitivity and that can be fabricated conveniently. The sensors are based on networks of ultrasmall (<10 nm) palladium nanowires deposited onto commercially available filtration membranes. We investigated the sensitivities and response times of these sensors as a function of the thickness of the nanowires and also compared them with a continuous reference film. The superior performance of the ultrasmall Pd nanowire network based sensors demonstrates the novelty of our fabrication approach, which can be directly applied to palladium alloy and other hydrogen sensing materials.

Hypocholesterolemic effects of Auricularia auricula ethanol extract in ICR mice fed a cholesterol-enriched diet

The cholesterol-lowering properties of Auricularia auricula are commonly attributed to the presence of polysaccharides based on previous research. The present study was designed to investigate the effects of ethanol extract of A. auricula (AAE) on hypercholesterolemia in ICR mice. AAE contained more than 16% (g/g) polyphenolic compounds, excluding other interfering factors such as polysaccharides, water-soluble fibre and protein. Thirty-six mice were randomly assigned to three groups (n = 12). The experimental group was fed cholesterol-enriched diet (CED) with oral administration of AAE (150 mg/kg/d b.w.) for 8-week, normal control group and CED control group received either a regular diet (RD) or CED along with oral administration of equal volume distilled water. Serum lipid profiles and antioxidant status were measured in addition to fecal neutral cholesterol and bile acids. AAE showed a remarkable hypocholesterolemic effect, improving antioxidant status, decreasing the level of total cholesterol and atherosclerosis index, increasing the level of high-density lipoprotein cholesterol and fecal excretion of bile acids. No apparent effects on serum triglycerides, low-density lipoprotein cholesterol, fecal excretion of neutral cholesterol and feeding efficiency were observed among all groups. These results indicated that A. auricula functional components, which prevented hypercholesterolemia contained polyphenolic compounds, in addition to polysaccharides.

Magnetoresistance anisotropy of a one-dimensional superconducting niobium strip

We investigated confinement effects on the resistive anisotropy of a superconducting niobium strip with a rectangular cross section. When its transverse dimensions are comparable to the superconducting coherence length, the angle dependent magnetoresistances at a fixed temperature can be scaled as R(theta,H) = R(H/Hctheta) where Hctheta =Hc0(cos2theta + gamma(-2)sin2theta)(-1/2) is the angular dependent critical field, gamma is the width to thickness ratio, and Hc0 is the critical field in the thickness direction at theta=0 degrees . The results can be understood in terms of the anisotropic diamagnetic energy for a given field in a one-dimensional superconductor.

Onset of motion and dynamic reordering of a vortex lattice

Time resolved transport measurements on a driven vortex lattice in an undoped 2H-NbSe2 crystal show that the response to a current pulse is governed by healing of defects as the lattice evolves from a stationary to a moving steady state and that the response time reflects the degree of order in the initial vortex state. We find that stationary field cooled vortex lattices become more ordered with decreasing temperature and identify a temperature below which a qualitative change in the response signals the disappearance of topological defects.

Nanowires and nanoribbons of charge-density-wave conductor NbSe3

We report synthesis of nanowires and nanoribbons of the charge-density-wave conductor NbSe(3) through direct reaction of Nb and Se powders. The transverse dimension of the obtained nanostructures, as identified with scanning/transmission electron microscopy, ranges from 20 to 700 nm. X-ray and selected area electron diffraction analyses indicate that these nanowires and nanoribbons are single crystalline. Four-probe resistivity measurements confirm the expected charge-density-wave transitions, and furthermore, we find significant enhancement in the depinning threshold fields, which we attribute to a confinement effect.

Observation of the vortex lattice spinodal in NbSe2

Metastable superheated and supercooled vortex states in NbSe2 crystals were probed with fast transport measurements over a wide range of field and temperature. The limit of metastability of the superheated vortex lattice defines a line in the phase diagram that lies below the superconducting transition and is clearly separated from it. This line is identified as the vortex lattice spinodal, and is in good agreement with recent theoretical predictions by Li and Rosenstein [Phys. Rev. B 65, 220504 (2002)]; cond-mat/0305258]. By contrast, no limit of metastability is observed for the supercooled disordered state.

Abnormalities of gallbladder muscle associated with acute inflammation in guinea pigs

Muscle strips from experimental acute cholecystitis (AC) exhibit a defective contraction. The mechanisms responsible for this impaired contraction are not known. The present studies investigated the nature of these abnormalities. AC was induced by ligating the common bile duct of guinea pigs for 3 days. Contraction was studied in enzymatic dissociated muscle cells. Cholecystokinin (CCK) and prostaglandin E2 (PGE2) receptor binding studies were performed by radioreceptor assay. The levels of lipid peroxidation, cholesterol, phospholipid, and H2O2 as well as the catalase and superoxide dismutase (SOD) activities were determined. PGE2 content was measured by radioimmunoassay. Muscle contraction induced by CCK, ACh, or KCl was significantly reduced in AC, but PGE2-induced contraction remained normal. GTPgammaS, diacyglycerol (DAG), and 1,4,5-trisphosphate (IP3), which bypass the plasma membrane, caused a normal contraction in AC. The number of functional receptors for CCK was significantly decreased, whereas those for PGE2 remained unchanged in AC. There was a reduction in the phospholipid content and increase in the level of lipid peroxidation as well as H2O2 content in the plasma membrane in AC. The PGE2 content and the activities of catalase and SOD were also elevated. These data suggest that AC cause damage to the constituents of the plasma membrane of muscle cells. The preservation of the PGE2 receptors may be the result of muscle cytoprotection.

Depinning of a metastable disordered vortex lattice

We report on experiments investigating the depinning dynamics of a strongly pinned vortex lattice in 2H-NbSe2. We find that the depinning process starts at currents that are well below the critical current of the entire lattice and that it is governed by the formation of contiguous channels of mobile vortices connecting the sample edges. We obtain the formation time of the first channel by monitoring the delayed voltage response to a driving current step and by measuring the ramping rate dependence of the critical current. The subsequent increase in the number of moving vortices is determined from the temporal evolution of the voltage response and the critical current.

Gallbladder muscle dysfunction in patients with chronic acalculous disease

BACKGROUND & AIMS

The mechanisms responsible for the abnormalities of gallbladder emptying in patients with chronic acalculous gallbladder disease (AGD) have not been elucidated. This study was designed to determine whether a muscle defect could explain this gallbladder dysfunction.

METHODS

Gallbladder contraction induced by a continuous intravenous cholecystokinin octapeptide (CCK-8) infusion was determined by ultrasonography in control subjects, patients with AGD, pigment stones, and cholesterol stones. Muscle cells were obtained by enzymatic digestion. (125)I-CCK-8 binding and [(35)S]guanosine triphosphate gamma S (GTP gamma S) binding studies were performed.

RESULTS

In vivo gallbladder contraction induced by CCK-8 was significantly lower in AGD (29.4%) and cholesterol stones (28.8%) than in pigment stones (59.8%) and normal controls (57.8%; P < 0.01). In vitro muscle cell contraction induced by CCK-8 was also lower in AGD than in pigment stones. It remained impaired in AGD after stimulation with the G-protein activators GTP gamma S and AlF(4) and with the second messenger 1,2-dioctanoyl-sn-glycerol. However, GTP gamma S binding induced by CCK-8 and vasoactive intestinal polypeptide and the binding capacity of CCK receptors were not different between AGD and pigment stones.

CONCLUSIONS

These findings suggest that there is a good correlation between in vivo and in vitro gallbladder response to CCK-8 in patients with AGD. Unlike those found in cholesterol stones, the muscle defects in AGD appear to reside in the contractile apparatus.

[Experimental research on permeability injury of pulmonary microvascular endothelial cells monolayer induced by tumor necrosis factor]

AIM AND METHODS

To investigate the mechanism of tumor necrosis factor (TNF) induced permeability injury of rat pulmonary microvascular endothelial cells (RPMVEC) monolayer, the effect of TNF on permeability of RPMVEC monolayer was examined with microfilter and the effect of TNF on RPMVEC F-actin was observed with immunocytochemistry. The interfering action of formoterol, anisodamine and cholera toxin on permeability and F-actin changes induced by TNF was also observed.

RESULTS

(1) TNF induced significant increase in permeability of RPMVEC monolayer 30, 60 and 90 minutes after treatment with TNF. (2) F-actin in RPMVEC depolymerized 90 minutes after treatment with TNF. Permeability and F-actin did not change significantly when formoterol, anisodamine or cholera toxin was added separately.

CONCLUSION

TNF can induce permeability injury of RPMVEC monolayer, which is correlated with depolymerization of F-actin. Formoterol, anisodamine and cholera toxin can inhibit the permeability change induced by TNF which may due to their inhibition to the distribution change of F-actin.

Instabilities and disorder-driven first-order transition of the vortex lattice

Transport studies in a Corbino disk suggest that the Bragg glass phase undergoes a first-order transition into a disordered solid. This transition shows sharp reentrant behavior at low fields. In contrast, in the conventional strip configuration, the phase transition is obscured by the injection of the disordered vortices through the sample edges, which results in the commonly observed vortex instabilities and smearing of the peak effect in NbSe2 crystals. These features are found to be absent in the Corbino geometry in which the circulating vortices do not cross the sample edges.

Equilibration and dynamic phase transitions of a driven vortex lattice

We report on the observation of two types of current driven transitions in metastable vortex lattices. The metastable states, which are missed in usual slow transport measurements, are detected with a fast transport technique in the vortex lattice of undoped 2H-NbSe2. The transitions are seen by following the evolution of these states when driven by a current. At low currents we observe an equilibration transition from a metastable to a stable state, followed by a dynamic crystallization transition at high currents.

Defect of receptor-G protein coupling in human gallbladder with cholesterol stones

Human gallbladders with cholesterol stones (ChS) exhibit an impaired muscle contraction and relaxation and a lower CCK receptor-binding capacity compared with those with pigment stones (PS). This study was designed to determine whether there is an abnormal receptor-G protein coupling in human gallbladders with ChS using (35)S-labeled guanosine 5'-O-(3-thiotriphosphate) ([(35)S]GTPgammaS) binding, (125)I-labeled CCK-8 autoradiography, immunoblotting, and G protein quantitation. CCK and vasoactive intestinal peptide caused significant increases in [(35)S]GTPgammaS binding to Galpha(i-3) and G(s)alpha, respectively. The binding was lower in ChS than in PS (P < 0.01). The reduced [(35)S]GTPgammaS binding in ChS was normalized after the muscles were treated with cholesterol-free liposomes (P < 0.01). Autoradiography and immunoblots showed a decreased optical density (OD) for CCK receptors, an even lower OD value for receptor-G protein coupling, and a higher OD for uncoupled receptors or Galpha(i-3) protein in ChS compared with PS (P < 0.001). G protein quantitation also showed that there were no significant differences in the Galpha(i-3) and G(s)alpha content in ChS and PS. We conclude that, in addition to an impaired CCK receptor-binding capacity, there is a defect in receptor-G protein coupling in muscle cells from gallbladder with ChS. These changes may be normalized after removal of excess cholesterol from the plasma membrane.

CCK receptor dysfunction in muscle membranes from human gallbladders with cholesterol stones

Human gallbladders with cholesterol stones exhibit impaired muscle contraction induced by agonists that act on transmembrane receptors, increased membrane cholesterol content, and abnormal cholesterol-to-phospholipid ratio compared with those with pigment stones. The present study was designed to investigate the functions of the CCK receptor of gallbladder muscle membranes by radioreceptor assay and cross-linking. 125I-labeled CCK-8 binding was time-dependent, competitive, and specific. Scatchard analysis showed that the maximum specific binding (Bmax) was significantly decreased in cholesterol compared with pigment stone gallbladders (0.18 +/- 0. 07 vs. 0.38 +/- 0.05 pmol/mg protein, P < 0.05). In contrast, the affinity for CCK was higher in cholesterol than pigment stone gallbladders (0.18 +/- 0.06 vs. 1.2 +/- 0.23 nM). Similar results were observed in binding studies with the CCK-A receptor antagonist [3H]L-364,718. Cross-linking and saturation binding studies also showed significantly less CCK binding in gallbladders with cholesterol stones. These abnormalities were reversible after incubation with cholesterol-free liposomes. The Bmax increased (P < 0.01) and the dissociation constant decreased (P < 0.001) after incubation with cholesterol-free liposomes. In conclusion, human gallbladders with cholesterol stones have impaired CCK receptor binding compared with those with pigment stones. These changes are reversed by removal of the excess membrane cholesterol. These receptor alterations may contribute to the defective contractility of the gallbladder muscle in patients with cholesterol stones.

Downregulation of Galphaq-11 protein expression in guinea pig antral and colonic circular muscle during pregnancy

Pregnancy has an inhibitory effect on motility of the gastrointestinal tract. The present study was designed to examine the mechanisms responsible for antral and colonic hypomotility in pregnant guinea pigs. Circular smooth muscle cells from the antrum and left colon were isolated by enzymatic digestion with collagenase from pregnant and nonpregnant guinea pigs. Contractile responses to agonists were expressed as percent shortening from resting cell length. The function of G proteins in antral and colonic circular smooth muscle was assessed by [35S]guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) binding induced by CCK-8 and G protein quantitation. The contraction of antral and colonic circular smooth muscle from pregnant guinea pigs was reduced in response to CCK-8 and to GTPgammaS but was normal in response to KCl and D-myo-inositol 1,4,5-trisphosphate compared with nonpregnant animals. The stimulation of [35S]GTPgammaS binding to Galphaq-11 induced by 1 microM CCK-8 was significantly lower in antral and colonic circular smooth muscle from pregnant guinea pigs than that in controls. Furthermore, Western blot analysis showed a decreased Galphaq-11 and an increased Gsalpha protein content in both tissues during pregnancy. It is concluded that pregnancy appears to impair gastrointestinal circular smooth muscle contractility by downregulating G proteins such as Galphaq-11 protein, which mediates muscle contraction, and upregulating Gsalpha protein, which mediates muscle relaxation.

Mechanisms of gallbladder hypomotility in pregnant guinea pigs

BACKGROUND & AIMS

Gallbladder muscle contraction becomes impaired during pregnancy. This study was designed to investigate the mechanisms of gallbladder hypomotility induced by pregnancy in guinea pigs.

METHODS

Gallbladder muscle cells were obtained by enzymatic digestion. Cell contraction was expressed as percent shortening of initial control cell length.

RESULTS

Contraction induced by cholecystokinin (CCK)-8 or guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) was reduced in muscle cells from pregnant guinea pigs. The response to KCl or D-myo-inositol 1,4, 5-trisphosphate was not different between controls and pregnant animals. These findings suggest that impaired contraction in pregnancy might be caused by defective G protein activation. The function and content of G proteins were examined by using [35S]GTPgammaS binding and G protein subunit quantitation. In female controls, CCK-8 at 1 micromol/L caused increased [35S]GTPgammaS binding to Galphai3 but not to Galphaq/11, Galphai1-2, or Galphas. GTPgammaS binding to Galphai3 induced by CCK-8 was reduced in gallbladder muscle from pregnant guinea pigs. Measurements of basal G proteins showed that the content of Galphai3 was significantly lower and the Galphas content was higher in muscles from pregnant guinea pigs than in controls.

CONCLUSIONS

Pregnancy may cause down-regulation of contractile G proteins such as Galphai3 and up-regulation of Galphas that mediates relaxation, resulting in impaired gallbladder muscle contraction.

Functional reconstitution of membrane glycoproteins into lipid vesicles using lectin precipitation. Application to the VIP receptor

We studied the interaction of n-octyl-beta-d-glucopyranoside-solubilized VIP receptors (VIPR) with wheat germ agglutinin and found that the addition of the lectin to the detergent extract led to the formation of aggregates that could be pelleted by high speed centrifugation. Resuspension of the pellet in the presence of the competing trisaccharide, N,N', N"-triacetylchitotriose (TAC), dissociated the lectin from the complex without altering the precipitability of VIPR. The final pellet (referred to as TAC pellet) contained an average of 12% of total protein and 96% of total VIP binding activity with a typical rank order of potency for VIP-related peptides. Lipid analysis and electron microscopic examination indicated that the precipitated material was composed of lipid vesicles. VIPR molecules were shown to be integrally inserted in the liposomes because they could not be dissociated from the vesicles at pH 11 or with high salt concentration. By comparing the liposome-associated VIP binding activity in the presence and absence of detergent and by showing accessibility of VIPR to PNGase F, it was concluded that VIP binding sites were not simply trapped within the reconstituted vesicles but likely exposed at the external surface of the liposomes.

[Research progress on regulation of vascular endothelial barrier function]

The regulatory mechanisms of vascular endothelial barrier function are complicated. Inflammatory mediators, such as alpha-thrombin, activate phospholipases to mediate generation of IP3 and other second messengers through receptor-coupled G protein. Protein kinase C and myosin light chain kinase are then activated, leading to phosphorylation of myosin light chains, rearrangement of F-actin skeleton, interendothelial cell gap formation and increased endothelial permeability.

Effect of low-dose endotoxin on pulmonary vascular permeability following acute hemorrhagic shock

The purpose of the current study was to determine the effect of low-dose Escherichia coli lipopolysaccharide (LPS) on pulmonary vascular permeability when administered after hemorrhagic shock (40% of baseline cardiac output) followed by resuscitation. Animals were monitored for 3-4 h after LPS infusion. Thirty minutes prior to termination of the experiment, 3 mCi of 125I-human serum albumin was injected intravenously to calculate a permeability index from the left lung lavage and plasma 125I ratios. The two control groups were (1) shock only (no LPS, n = 4), and (2) LPS only (no shock, n = 8). The permeability index for the shock-only group was 0.0015 +/- 0.0007 (mean +/- SE) and that for the LPS-only group was 0.0035 +/- 0.0014. The permeability index for the experimental group (shock followed by LPS, n = 10) was 0.0071 +/- 0.0030 (p > 0.05). Similarly, there was no difference in the wet-to-dry ratios between the three groups. The shock+LPS group required more intravenous fluids to maintain mean arterial blood pressure at control values than the LPS-only group (p < 0.003). We conclude that hemorrhagic shock and resuscitation do not lead to an acute increased permeability of the lung when it is subsequently challenged by a low dose of bacterial LPS.

Demonstration of endogenous inhibitors for the formation of 14,15-oxido-5,8,11-eicosatrienoic acid from phosphatidylinositol in bovine lung extract

Bovine lung extract contained an enzyme or enzyme system that catalyzed the formation of 14,15-oxido-5,8,11-eicosatrienoic acid from phosphatidylinositol. The enzyme activity increased markedly during the course of purification, apparently due to the removal of two endogenous inhibitors from the enzyme. Using membranes with known molecular weight cut-offs, we estimated the Mr of Inhibitor 1 to be between 10,000 and 100,000 and Inhibitor 2 less than 1,000. Inhibitor 1 appeared to be partially inactivated by trypsin and was heat labile, whereas Inhibitor 2 was resistant to trypsin and was heat resistant. Both inhibitors were hydrophilic.