Internal moisture barrier layer for improving high-humidity reliability of miniature light emitting diode die without encapsulation

Atomic layer deposited Al2O3 films are incorporated into miniature light emitting diodes (mini-LEDs) as an internal moisture barrier layer. The experimental results show that the water vapor transmission rate reaches ≤10-4 g/m2/day when the Al2O3 thickness is ≥40 nm. The mini-LED with a 40 nm-thick Al2O3 layer shows negligible degradation after 1000 h of 85°C/85% relative humidity testing, whereas the device without an Al2O3 layer fails after only 500 h due to delamination occurring at the GaN surface. Current-voltage characteristics of the device without an Al2O3 moisture barrier layer indicate an increase in series resistance and ideality factor. This study provides a simple, light-weighting method to have a satisfactory encapsulation function for miniature LEDs.

Crystallinity Effect on Electrical Properties of PEALD-HfO2 Thin Films Prepared by Different Substrate Temperatures

Hafnium oxide (HfO₂) thin film has remarkable physical and chemical properties, which makes it useful for a variety of applications. In this work, HfO₂ films were prepared on silicon through plasma enhanced atomic layer deposition (PEALD) at various substrate temperatures. The growth per cycle, structural, morphology and crystalline properties of HfO₂ films were measured by spectroscopic ellipsometer, grazing-incidence X-ray diffraction (GIXRD), X-ray reflectivity (XRR), field-emission scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy. The substrate temperature dependent electrical properties of PEALD-HfO₂ films were obtained by capacitance-voltage and current-voltage measurements. GIXRD patterns and XRR investigations show that increasing the substrate temperature improved the crystallinity and density of HfO₂ films. The crystallinity of HfO₂ films has a major effect on electrical properties of the films. HfO₂ thin film deposited at 300 °C possesses the highest dielectric constant and breakdown electric field.

Deposition Mechanism and Characterization of Plasma-Enhanced Atomic Layer-Deposited SnOx Films at Different Substrate Temperatures

The promising functional tin oxide (SnOx) has attracted tremendous attention due to its transparent and conductive properties. The stoichiometric composition of SnOx can be described as common n-type SnO2 and p-type Sn3O4. In this study, the functional SnOx films were prepared successfully by plasma-enhanced atomic layer deposition (PEALD) at different substrate temperatures from 100 to 400 °C. The experimental results involving optical, structural, chemical, and electrical properties and morphologies are discussed. The SnO2 and oxygen-deficient Sn3O4 phases coexisting in PEALD SnOx films were found. The PEALD SnOx films are composed of intrinsic oxygen vacancies with O-Sn4+ bonds and then transformed into a crystalline SnO2 phase with increased substrate temperature, revealing a direct 3.5−4.0 eV band gap and 1.9−2.1 refractive index. Lower (<150 °C) and higher (>300 °C) substrate temperatures can cause precursor condensation and desorption, respectively, resulting in reduced film qualities. The proper composition ratio of O to Sn in PEALD SnOx films near an estimated 1.74 suggests the highest mobility of 12.89 cm2 V−1 s−1 at 300 °C.

Compact Ga2O3 Thin Films Deposited by Plasma Enhanced Atomic Layer Deposition at Low Temperature

Amorphous Gallium oxide (Ga₂O₃) thin films were grown by plasma-enhanced atomic layer deposition using O₂ plasma as reactant and trimethylgallium as a gallium source. The growth rate of the Ga₂O₃ films was about 0.6 Å/cycle and was acquired at a temperature ranging from 80 to 250 °C. The investigation of transmittance and the adsorption edge of Ga₂O₃ films prepared on sapphire substrates showed that the band gap energy gradually decreases from 5.04 to 4.76 eV with the increasing temperature. X-ray photoelectron spectroscopy (XPS) analysis indicated that all the Ga₂O₃ thin films showed a good stoichiometric ratio, and the atomic ratio of Ga/O was close to 0.7. According to XPS analysis, the proportion of Ga³⁺ and lattice oxygen increases with the increase in temperature resulting in denser films. By analyzing the film density from X-ray reflectivity and by a refractive index curve, it was found that the higher temperature, the denser the film. Atomic force microscopic analysis showed that the surface roughness values increased from 0.091 to 0.187 nm with the increasing substrate temperature. X-ray diffraction and transmission electron microscopy investigation showed that Ga₂O₃ films grown at temperatures from 80 to 200 °C were amorphous, and the Ga₂O₃ film grown at 250 °C was slightly crystalline with some nanocrystalline structures.

[Effect of hypochloric acid on Escherichia coli biofilm and the clinical efficacy of hypochloric acid for wounds with Escherichia coli infection]

Objective: To investigate the effect of hypochloric acid on Escherichia coli biofilm and the clinical efficacy of hypochloric acid for wounds with Escherichia coli infection. Methods: One strain of Escherichia coli with the strongest bacterial biofilm forming ability among the strains isolated from specimens in 25 patients (16 males and 9 females, aged 32-67 years) from five clinical departments of the 940th Hospital of the Joint Logistic Support Force was collected for the experimental study from September to December 2019. The Escherichia coli was cultured with hypochloric acid at 162.96, 81.48, 40.74, 20.37, 10.18, 5.09, 2.55, 1.27, 0.64, and 0.32 μg/mL respectively to screen the minimum bactericidal concentration (MBC) of hypochloric acid. The Escherichia coli was cultured with hypochloric acid at the screened MBC for 2, 5, 10, 20, 30, and 60 min respectively to screen the shortest bactericidal time of hypochloric acid. The biofilm formation of Escherichia coli was observed by scanning electron microscopy at 6, 12, 24, 48, 72, and 96 h of incubation, respectively. After 72 h of culture, hypochloric acid at 1, 2, 4, 8, and 16 times of MBC was respectively added to Escherichia coli to screen the minimum biofilm eradicate concentration (MBEC) of hypochloric acid against Escherichia coli. After hypochloric acid at 1, 2, 4, and 8 times of MBEC and sterile saline were respectively added to Escherichia coli for 10 min, the live/dead bacterial staining kit was used to detect the number of live and dead cells, with the rate of dead bacteria calculated (the number of samples was 5). From January to December 2020, 41 patients with infectious wounds meeting the inclusion criteria and admitted to the Department of Burns and Plastic Surgery of the 940th Hospital of Joint Logistic Support Force of PLA were included into the prospective randomized controlled trial. The patients were divided into hypochloric acid group with 21 patients (13 males and 8 females, aged (46±14) years) and povidone iodine group with 20 patients (14 males and 6 females, aged (45±19) years) according to the random number table. Patients in the 2 groups were respectively dressed with sterile gauze soaked with hypochloric acid of 100 μg/mL and povidone iodine solution of 50 mg/mL with the dressings changed daily. Before the first dressing change and on the 10th day of dressing change, tissue was taken from the wound and margin of the wound for culturing bacteria by agar culture method and quantifying the number of bacteria. The amount of wound exudate and granulation tissue growth were observed visually and scored before the first dressing change and on the 3rd, 7th, and 10th days of dressing change. Data were statistically analyzed with one-way analysis of variance, Dunnett-t test, independent sample t test, Mann-Whitney U test, Wilcoxon signed-rank test, chi-square test, or Fisher's exact probability test. Results: The MBC of hypochloric acid against Escherichia coli was 10.18 μg/mL, and the shortest bactericidal time of hypochloric acid with MBC against Escherichia coli was 2 min. Escherichia coli was in a completely free state after 6 and 12 h of culture and gradually aggregated and adhered with the extension of culture time, forming a mature biofilm at 72 h of culture. The MBEC of hypochloric acid against Escherichia coli was 20.36 μg/mL. The Escherichia coli mortality rates after incubation with hypochloric acid at 1, 2, 4, and 8 times of MBEC for 10 min were significantly higher than that after incubation with sterile saline (with t values of 6.11, 25.04, 28.90, and 40.74, respectively, P<0.01). The amount of bacteria in the wound tissue of patients in hypochloric acid group on the 10th day of dressing change was 2.61 (2.20, 3.30)×104 colony forming unit (CFU)/g, significantly less than 4.77 (2.18, 12.48)×104 CFU/g in povidone iodine group (Z=2.06, P<0.05). The amounts of bacteria in the wound tissue of patients in hypochloric acid group and povidone iodine group on the 10th day of dressing change were significantly less than 2.97 (2.90, 3.04)×106 and 2.97 (1.90, 7.95)×106 CFU/g before the first dressing change (with Z values of 4.02 and 3.92, respectively, P<0.01). The score of wound exudate amount of patients in hypochloric acid group on the 10th day of dressing change was significantly lower than that in povidone iodine group (Z=2.07, P<0.05). Compared with those before the first dressing change, the scores of wound exudate amount of patients in hypochloric acid group on the 7th and 10th days of dressing change were significantly decreased (with Z values of -3.99 and -4.12, respectively, P<0.01), and the scores of wound exudate amount of patients in povidone iodine group on the 7th and 10th days of dressing change were significantly decreased (with Z values of -3.54 and -3.93, respectively, P<0.01). The score of wound granulation tissue growth of patients in hypochloric acid group on the 10th day of dressing change was significantly higher than that in povidone iodine group (Z=2.02, P<0.05). Compared with those before the first dressing change, the scores of wound granulation tissue growth of patients in hypochloric acid group on the 7th and 10th days of dressing change were significantly increased (with Z values of -3.13 and -3.67, respectively, P<0.01), and the scores of wound granulation tissue growth of patients in povidone iodine group on the 7th and 10th days of dressing change were significantly increased (with Z values of -3.12 and -3.50, respectively, P<0.01). Conclusions: Hypochloric acid can kill Escherichia coli both in free and biofilm status. Hypochloric acid at a low concentration shows a rapid bactericidal effect on mature Escherichia coli biofilm, and the higher the concentration of hypochloric acid, the better the bactericidal effect. The hypochloric acid of 100 μg/mL is effective in reducing the bacterial load on wounds with Escherichia coli infection in patients, as evidenced by a reduction in wound exudate and indirect promotion of granulation tissue growth, which is more effective than povidone iodine, the traditional topical antimicrobial agent.

Deposition and Characterization of RP-ALD SiO2 Thin Films with Different Oxygen Plasma Powers

In this study, silicon oxide (SiO2) films were deposited by remote plasma atomic layer deposition with Bis(diethylamino)silane (BDEAS) and an oxygen/argon mixture as the precursors. Oxygen plasma powers play a key role in the quality of SiO2 films. Post-annealing was performed in the air at different temperatures for 1 h. The effects of oxygen plasma powers from 1000 W to 3000 W on the properties of the SiO2 thin films were investigated. The experimental results demonstrated that the SiO2 thin film growth per cycle was greatly affected by the O2 plasma power. Atomic force microscope (AFM) and conductive AFM tests show that the surface of the SiO2 thin films, with different O2 plasma powers, is relatively smooth and the films all present favorable insulation properties. The water contact angle (WCA) of the SiO2 thin film deposited at the power of 1500 W is higher than that of other WCAs of SiO2 films deposited at other plasma powers, indicating that it is less hydrophilic. This phenomenon is more likely to be associated with a smaller bonding energy, which is consistent with the result obtained by Fourier transformation infrared spectroscopy. In addition, the influence of post-annealing temperature on the quality of the SiO2 thin films was also investigated. As the annealing temperature increases, the SiO2 thin film becomes denser, leading to a higher refractive index and a lower etch rate.

Properties and Mechanism of PEALD-In2O3 Thin Films Prepared by Different Precursor Reaction Energy

Indium oxide (In₂O₃) film has excellent optical and electrical properties, which makes it useful for a multitude of applications. The preparation of In₂O₃ film via atomic layer deposition (ALD) method remains an issue as most of the available In-precursors are inactive and thermally unstable. In this work, In₂O₃ film was prepared by ALD using a remote O₂ plasma as oxidant, which provides highly reactive oxygen radicals, and hence significantly enhancing the film growth. The substrate temperature that determines the adsorption state on the substrate and reaction energy of the precursor was investigated. At low substrate temperature (100–150 °C), the ratio of chemically adsorbed precursors is low, leading to a low growth rate and amorphous structure of the films. An amorphous-to-crystalline transition was observed at 150–200 °C. An ALD window with self-limiting reaction and a reasonable film growth rate was observed in the intermediate temperature range of 225–275 °C. At high substrate temperature (300–350 °C), the film growth rate further increases due to the decomposition of the precursors. The resulting film exhibits a rough surface which consists of coarse grains and obvious grain boundaries. The growth mode and properties of the In₂O₃ films prepared by plasma-enhanced ALD can be efficiently tuned by varying the substrate temperature.

Suppression of Oxygen Vacancy Defects in sALD-ZnO Films Annealed in Different Conditions

Zinc oxide (ZnO) has drawn much attention due to its excellent optical and electrical properties. In this study, ZnO film was prepared by a high-deposition-rate spatial atomic layer deposition (ALD) and subjected to a post-annealing process to suppress the intrinsic defects and improve the crystallinity and film properties. The results show that the film thickness increases with annealing temperature owing to the increment of oxide layer caused by the suppression of oxygen vacancy defects as indicated by the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra. The film transmittance is seldom influenced by annealing. The refractive index increases with annealing temperature at 300–700 °C, possibly due to higher density and crystallinity of the film. The band gap decreases after annealing, which should be ascribed to the decrease in carrier concentration according to Burstein–Moss model. The carrier concentration decreases with increasing annealing temperature at 300–700 °C since the oxygen vacancy defects are suppressed, then it increases at 800 °C possibly due to the out-diffusion of oxygen atoms from the film. Meanwhile, the carrier mobility increases with temperature due to higher crystallinity and larger crystallite size. The film resistivity increases at 300–700 °C then decreases at 800 °C, which should be ascribed primarily to the variation of carrier concentration.

Effect of Annealing Temperature on Spatial Atomic Layer Deposited Titanium Oxide and Its Application in Perovskite Solar Cells

In this study, spatial atomic layer deposition (sALD) is employed to prepare titanium dioxide (TiO2) thin films by using titanium tetraisopropoxide and water as metal and water precursors, respectively. The post-annealing temperature is varied to investigate its effect on the properties of the TiO2 films. The experimental results show that the sALD TiO2 has a similar deposition rate per cycle to other ALD processes using oxygen plasma or ozone oxidant, implying that the growth is limited by titanium tetraisopropoxide steric hindrance. The structure of the as-deposited sALD TiO2 films is amorphous and changes to polycrystalline anatase at the annealing temperature of 450 °C. All the sALD TiO2 films have a low absorption coefficient at the level of 10-3 cm-1 at wavelengths greater than 500 nm. The annealing temperatures of 550 °C are expected to have a high compactness, evaluated by the refractive index and x-ray photoelectron spectrometer measurements. Finally, the 550 °C-annealed sALD TiO2 film with a thickness of ~8 nm is applied to perovskite solar cells as a compact electron transport layer. The significantly enhanced open-circuit voltage and conversion efficiency demonstrate the great potential of the sALD TiO2 compact layer in perovskite solar cell applications.

Low Reflection and Low Surface Recombination Rate Nano-Needle Texture Formed by Two-Step Etching for Solar Cells

In this study, needle-like and pyramidal hybrid black silicon structures were prepared by performing metal-assisted chemical etching (MACE) on alkaline-etched silicon wafers. Effects of the MACE time on properties of the black silicon wafers were investigated. The experimental results showed that a minimal reflectance of 4.6% can be achieved at the MACE time of 9 min. The height of the nanostructures is below 500 nm, unlike the height of micrometers needed to reach the same level of reflectance for the black silicon on planar wafers. A stacked layer of silicon nitride (SiN_x) grown by inductively-coupled plasma chemical vapor deposition (ICPCVD) and aluminum oxide (Al₂O₃) by spatial atomic layer deposition was deposited on the black silicon wafers for passivation and antireflection. The 3 min MACE etched black silicon wafer with a nanostructure height of less than 300 nm passivated by the SiN_x/Al₂O₃ layer showed a low surface recombination rate of 43.6 cm/s. Further optimizing the thickness of ICPCVD-SiN_x layer led to a reflectance of 1.4%. The hybrid black silicon with a small nanostructure size, low reflectance, and low surface recombination rate demonstrates great potential for applications in optoelectronic devices.

Enhanced Si Passivation and PERC Solar Cell Efficiency by Atomic Layer Deposited Aluminum Oxide with Two-step Post Annealing

In this study, aluminum oxide (Al₂O₃) films were prepared by a spatial atomic layer deposition using deionized water and trimethylaluminum, followed by oxygen (O₂), forming gas (FG), or two-step annealing. Minority carrier lifetime of the samples was measured by Sinton WCT-120. Field-effect passivation and chemical passivation were evaluated by fixed oxide charge (Q_f) and interface defect density (D_it), respectively, using capacitance-voltage measurement. The results show that O₂ annealing gives a high Q_f of - 3.9 × 10¹² cm^-2, whereas FG annealing leads to excellent Si interface hydrogenation with a low D_it of 3.7 × 10¹¹ eV^-1 cm^-2. Based on the consideration of the best field-effect passivation brought by oxygen annealing and the best chemical passivation brought by forming gas, the two-step annealing process was optimized. It is verified that the Al₂O₃ film annealed sequentially in oxygen and then in forming gas exhibits a high Q_f (2.4 × 10¹² cm^-2) and a low D_it (3.1 × 10¹¹ eV^-1 cm^-2), yielding the best minority carrier lifetime of 1097 μs. The SiN_x/Al₂O₃ passivation stack with two-step annealing has a lifetime of 2072 μs, close to the intrinsic lifetime limit. Finally, the passivated emitter and rear cell conversion efficiency was improved from 21.61% by using an industry annealing process to 21.97% by using the two-step annealing process.

Temperature-Dependent HfO2/Si Interface Structural Evolution and its Mechanism

In this work, hafnium oxide (HfO₂) thin films are deposited on p-type Si substrates by remote plasma atomic layer deposition on p-type Si at 250 °C, followed by a rapid thermal annealing in nitrogen. Effect of post-annealing temperature on the crystallization of HfO₂ films and HfO₂/Si interfaces is investigated. The crystallization of the HfO₂ films and HfO₂/Si interface is studied by field emission transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. The experimental results show that during annealing, the oxygen diffuse from HfO₂ to Si interface. For annealing temperature below 400 °C, the HfO₂ film and interfacial layer are amorphous, and the latter consists of HfO₂ and silicon dioxide (SiO₂). At annealing temperature of 450-550 °C, the HfO₂ film become multiphase polycrystalline, and a crystalline SiO₂ is found at the interface. Finally, at annealing temperature beyond 550 °C, the HfO₂ film is dominated by single-phase polycrystalline, and the interfacial layer is completely transformed to crystalline SiO₂.

Surface Passivation of Silicon Using HfO2 Thin Films Deposited by Remote Plasma Atomic Layer Deposition System

Hafnium oxide (HfO₂) thin films have attracted much attention owing to their usefulness in equivalent oxide thickness scaling in microelectronics, which arises from their high dielectric constant and thermodynamic stability with silicon. However, the surface passivation properties of such films, particularly on crystalline silicon (c-Si), have rarely been reported upon. In this study, the HfO₂ thin films were deposited on c-Si substrates with and without oxygen plasma pretreatments, using a remote plasma atomic layer deposition system. Post-annealing was performed using a rapid thermal processing system at different temperatures in N₂ ambient for 10 min. The effects of oxygen plasma pretreatment and post-annealing on the properties of the HfO₂ thin films were investigated. They indicate that the in situ remote plasma pretreatment of Si substrate can result in the formation of better SiO₂, resulting in a better chemical passivation. The deposited HfO₂ thin films with oxygen plasma pretreatment and post-annealing at 500 °C for 10 min were effective in improving the lifetime of c-Si (original lifetime of 1 μs) to up to 67 μs.

Assessment of lateral geniculate nucleus atrophy with 3T MR imaging and correlation with clinical stage of glaucoma

BACKGROUND AND PURPOSE

Although previous animal studies have shown structural changes in ocular hypertension such as atrophy of the LGN, such changes have not been thoroughly studied in human glaucoma patients nor correlation made with clinical stage. Our aim was to investigate prospectively LGN atrophy in patients with POAG using 3T MR imaging and correlation with the clinical stage of disease.

MATERIALS AND METHODS

Twenty-six patients with known POAG and 26 age-matched healthy volunteers were included in this institutional review board-approved study. All subjects underwent imaging on a 3T MR imaging system with a PD and GM sequence. LGN height and volume were measured by 2 blinded neuroradiologists. Measurements were compared and correlated with clinical glaucoma severity as assessed by static threshold visual field parameters.

RESULTS

Average maximum LGN height in patients with glaucoma on PD images was 4.36 ± 0.61 mm (right) and 4.31 ± 0.61 mm (left), significantly less (P < 10⁻³) than respective measurements of 5.05 ± 0.41 and 4.99 ± 0.41 mm in volunteers. With the GM sequences, such respective measurements were also less (P < 10⁻³) in patients with glaucoma (4.20 ± 0.71 mm right, 4.00 ± 0.85 mm left) versus respective measurements in volunteers (4.88 ± 0.51 mm right, 4.77 ± 0.47 mm left). Average LGN volumes in the patient group were 98.0 ± 27.2 mm³ (right) and 93.7 ± 25.8 mm³ (left) with the PD sequence versus respective measurements of 85.2 ± 27.1 and 80.5 ± 23.6 mm³ with the GM sequence. All height and volume measurements were greater in volunteers (P < 10⁻³). In the patient group, both maximum height and volume of the LGN with both sequences were significantly correlated with cumulative clinical glaucoma stage (P < .05).

CONCLUSIONS

MR imaging measurements of LGN height and volume are diminished in patients with glaucoma, with the extent of atrophy correlating to clinical stage, suggesting a novel imaging marker of disease severity.

Human embryonic stem cell-derived cardiomyocytes engraft but do not alter cardiac remodeling after chronic infarction in rats

Previous studies indicated that, in an acute myocardial infarction model, human embryonic stem cell-derived cardiomyocytes (hESC-CM) injected with a pro-survival cocktail (PSC) can preserve contractile function. Because patients with established heart failure may also benefit from cell transplantation, we evaluated the physiological effects of hESC-CM transplanted into a chronic model of myocardial infarction. Intramyocardial injection of hESC-CM with PSC was performed in nude rats at 1 month following ischemia-reperfusion. The left ventricular function of hESC-CM injected rats was evaluated at 1, 2 and 3 months after the cell injection procedure and was compared to 3 control groups (rats injected with serum-free media, PSC only, or non-cardiac human cells in PSC). Histology at 3 months revealed that human cardiomyocytes survive, develop increased sarcomere organization and are still proliferating. Despite successful engraftment, both echocardiography and MRI analyses showed no significant difference in left ventricular structure or function between these 4 groups at any time point of the study, suggesting that human cardiomyocytes do not affect cardiac remodeling in a rat model of chronic myocardial infarction. When injected into a chronic infarct model, hESC-CM can engraft, survive and form grafts with striated cardiomyocytes at least as well as was previously observed in an acute myocardial infarction model. However, although hESC-CM transplantation can attenuate the progression of heart failure in an acute model, the same hESC-CM injection protocol is insufficient to restore heart function or to alter adverse remodeling of a chronic myocardial infarction model.

Dual modulation of cell survival and cell death by beta(2)-adrenergic signaling in adult mouse cardiac myocytes

The goal of this study was to determine whether beta(1)-adrenergic receptor (AR) and beta(2)-AR differ in regulating cardiomyocyte survival and apoptosis and, if so, to explore underlying mechanisms. One potential mechanism is that cardiac beta(2)-AR can activate both G(s) and G(i) proteins, whereas cardiac beta(1)-AR couples only to G(s). To avoid complicated crosstalk between beta-AR subtypes, we expressed beta(1)-AR or beta(2)-AR individually in adult beta(1)/beta(2)-AR double knockout mouse cardiac myocytes by using adenoviral gene transfer. Stimulation of beta(1)-AR, but not beta(2)-AR, markedly induced myocyte apoptosis, as indicated by increased terminal deoxynucleotidyltransferase-mediated UTP end labeling or Hoechst staining positive cells and DNA fragmentation. In contrast, beta(2)-AR (but not beta(1)-AR) stimulation elevated the activity of Akt, a powerful survival signal; this effect was fully abolished by inhibiting G(i), G(beta gamma), or phosphoinositide 3 kinase (PI3K) with pertussis toxin, beta ARK-ct (a peptide inhibitor of G(beta gamma)), or LY294002, respectively. This indicates that beta(2)-AR activates Akt via a G(i)-G(beta gamma)-PI3K pathway. More importantly, inhibition of the G(i)-G(beta gamma)-PI3K-Akt pathway converts beta(2)-AR signaling from survival to apoptotic. Thus, stimulation of a single class of receptors, beta(2)-ARs, elicits concurrent apoptotic and survival signals in cardiac myocytes. The survival effect appears to predominate and is mediated by the G(i)-G(beta gamma)-PI3K-Akt signaling pathway.

beta 2-adrenergic receptor-induced p38 MAPK activation is mediated by protein kinase A rather than by Gi or gbeta gamma in adult mouse cardiomyocytes

Increasing evidence shows that stimulation of beta-adrenergic receptor (AR) activates mitogen-activated protein kinases (MAPKs), in addition to the classical G(s)-adenylyl cyclase-cAMP-dependent protein kinase (PKA) signaling cascade. In the present study, we demonstrate a novel beta(2)-AR-mediated cross-talk between PKA and p38 MAPK in adult mouse cardiac myocytes expressing beta(2)-AR, with a null background of beta(1)beta(2)-AR double knockout. beta(2)-AR stimulation by isoproterenol increased p38 MAPK activity in a time- and dose-dependent manner. Inhibiting G(i) with pertussis toxin or scavenging Gbetagamma with betaARK-ct overexpression could not prevent beta(2)-AR-induced p38 MAPK activation. In contrast, a specific peptide inhibitor of PKA, PKI (5 microm), completely abolished the stimulatory effect of beta(2)-AR, suggesting that beta(2)-AR-induced p38 MAPK activation is mediated via a PKA-dependent mechanism, rather than by G(i) or Gbetagamma. This conclusion was further supported by the ability of forskolin (10 microm), an adenylyl cyclase activator, to elevate p38 MAPK activity in a PKI-sensitive manner. Furthermore, inhibition of p38 MAPK with SB203580 (10 microm) markedly enhanced the beta(2)-AR-mediated contractile response, without altering base-line contractility. These results provide the first evidence that cardiac beta(2)-AR activates p38 MAPK via a PKA-dependent signaling pathway, rather than by G(i) or Gbetagamma, and reveal a novel role of p38 MAPK in regulating cardiac contractility.

Spontaneous activation of beta(2)- but not beta(1)-adrenoceptors expressed in cardiac myocytes from beta(1)beta(2) double knockout mice

Although ligand-free, constitutive beta(2)-adrenergic receptor (AR) signaling has been demonstrated in naive cell lines and in transgenic mice overexpressing cardiac beta(2)-AR, it is unclear whether the dominant cardiac beta-AR subtype, beta(1)-AR, shares the ability of spontaneous activation. In the present study, we expressed human beta(1)- or beta(2)-AR via recombinant adenoviral infection in ventricular myocytes isolated from beta(1)beta(2)-AR double knockout mice, creating pure beta(1)-AR and beta(2)-AR systems with variable receptor densities. A contractile response to a nonselective beta-AR agonist, isoproterenol, was absent in double knockout mouse myocytes but was fully restored after adenoviral beta(1)-AR or adenoviral beta(2)-AR infection. Increasing the titer of adenoviral vectors (multiplicity of infection 10-1000) led to a dose-dependent expression of beta(1)- or beta(2)-AR with a maximal density of 1207 +/- 173 (36-fold over the wild-type control value) and 821+/-38 fmol/mg protein (69-fold), respectively. Using confocal immunohistochemistry, we directly visualized the cellular distribution of beta(1)-AR and beta(2)-AR and found that both subtypes were distributed on the cell surface membrane and transverse tubules, resulting in a striated pattern. In the absence of ligand, beta(2)-AR expression resulted in graded increases in baseline cAMP and contractility up to 428% and 233% of control, respectively, at the maximal beta(2)-AR density. These effects were specifically reversed by a beta(2)-AR inverse agonist, ICI 118,551 (10(-7) M). In contrast, overexpression of beta(1)-AR, even at a greater density, failed to enhance either basal cAMP or contractility; the alleged beta(1)-AR inverse agonist, CGP 20712A (10(-6) M), had no significant effect on basal contraction in these cells. Thus, we conclude that acute beta(2)-AR overexpression in cardiac myocytes elicits significant physiological responses due to spontaneous receptor activation; however, this property is beta-AR subtype specific because beta(1)-AR does not exhibit agonist-independent spontaneous activation.

Culture and adenoviral infection of adult mouse cardiac myocytes: methods for cellular genetic physiology

Rapid development of transgenic and gene-targeted mice and acute genetic manipulation via gene transfer vector systems have provided powerful tools for cardiovascular research. To facilitate the phenotyping of genetically engineered murine models at the cellular and subcellular levels and to implement acute gene transfer techniques in single mouse cardiomyocytes, we have modified and improved current enzymatic methods to isolate a high yield of high-quality adult mouse myocytes (5.3 +/- 0.5 x 10(5) cells/left ventricle, 83.8 +/- 2.5% rod shaped). We have also developed a technique to culture these isolated myocytes while maintaining their morphological integrity for 2-3 days. The high percentage of viable myocytes after 1 day in culture (72.5 +/- 2.3%) permitted both physiological and biochemical characterization. The major functional aspects of these cells, including excitation-contraction coupling and receptor-mediated signaling, remained intact, but the contraction kinetics were significantly slowed. Furthermore, gene delivery via recombinant adenoviral infection was highly efficient and reproducible. In adult beta(1)/beta(2)-adrenergic receptor (AR) double-knockout mouse myocytes, adenovirus-directed expression of either beta(1)- or beta(2)-AR, which occurred in 100% of cells, rescued the functional response to beta-AR agonist stimulation. These techniques will permit novel experimental settings for cellular genetic physiology.

Tyrosine kinase participates in alpha 1A-adrenoceptor-mediated increase of intracellular calcium in human embryo kidney 293 cells

AIM

To determine the role of protein-tyrosine kinase (PTK) in alpha 1A-adrenoceptor-mediated increase of [Ca2+]i (intracellular calcium) in human embryo kidney (HEK) 293 cells expressed alpha 1A-adrenoceptor.

METHODS

Effects of two PTK inhibitors: genistein and tyrphostin, were investigated on the increase of [Ca2+]i by using Fura-2, The activity of PTK was measured and the accumulation of [3H] InsPs were observed.

RESULTS

Norepinephrine stimulated a rapid increase in [Ca2+]i to (371 +/- 31) nmol.L-1 in HEK 293 cells. Norepinephrine-induced increase of [Ca2+]i was inhibited by the tyrosine kinase inhibitors quercetin and tyrphostin by 23.8% and 21.4%, respectively, but the accumulation of [3H]InsPs induced by norepinephrine was not. The activity of the plasma-associated tyrosine kinase was increased to (1.73 +/- 0.72)-fold over the control by norepinephrine 10 mumol.L-1. The norepinephrine-activated PTK was inhibited by calphostin C and depletion of intra- and extra-cellular Ca2+.

CONCLUSION

The PTK participates in mobilization of Ca2+ mediated by alpha 1A-adrenoceptors in HEK 293 cell lines.

Characterization of subtype of alpha 1-adrenoceptor mediating vasoconstriction in perfused rat mesenteric vascular bed

AIM

To characterize the subtype of alpha 1-adrenoceptor mediating vasoconstriction in perfused rat mesenteric vascular bed.

METHODS

The potencies (pA2 values determined by Schild plot) of alpha 1-adrenoceptor-selective antagonists were determined by isolated vasoconstrictive experiment. The pKi values were determined by 125I-BE 2254 binding from the cloned alpha 1A-, alpha 1B-, and alpha 1D-adrenoceptor, stably expressed in human embryonic kidney (HEK) 293 cells.

RESULTS

The pA2 values for alpha 1A-adrenoceptor-selective antagonists, RS-17053, WB 4101, 5-methyl-urapidil, and the alpha 1D-adrenoceptor-selective antagonist, BMY 7378, were 8.98 +/- 0.28, 9.16 +/- 0.20, 8.69 +/- 0.02, and 6.03 +/- 0.26, respectively, with the slope not different from unity. The pA2 values of the above antagonists correlated well with the binding pKi values only for alpha 1A-adrenoceptors (r = 0.97), but not for alpha 1B-adrenoceptors (r = 0.52) and alpha 1D-adrenoceptors (r = 0.04). The concentration-vasopressor response curve for norepinephrine was not affected by pretreatment with chloroethylclonidine (Chl) 50 mumol.L-1 for 30 min.

CONCLUSION

Only alpha 1A-adrenoceptors mediate the norepinephrine-induced vasopressor response in perfused rat mesenteric vascular bed.

Tyrosine kinases participate in alpha 1A-adrenoceptor-mediated vasoconstriction in perfused rat hindlimb

AIM

To determine whether or not tyrosine kinase is involved in the signal transduction of alpha 1A-adrenoceptors.

METHODS

Effects of various pharmacological probes on norepinephrine (NE)-induced vasopressor responses were determined in the perfused rat hindlimb.

RESULTS

The putative tyrosine kinase inhibitors, genistein, and tyrphostin, significantly inhibited the vasopressor responses induced by NE but not that induced by KCl. The protein-tyrosine-phosphatase inhibitor, sodium orthovanadate, selectively potentiated the vasopressor responses induced by NE. Neither genistein nor tyrphostin had effect on the contraction elicited by phorbol 12-myristate 13-acetate. In contrast, both genistein and tyrphostin attenuated the vasopressor responses evoked by NaF.

CONCLUSION

The genistein- and tyrphostin-sensitive tyrosine kinases participate in alpha 1A-adrenoceptor-mediated vasoconstriction in perfused rat hindlimb.

Ca2+-dependence of vasoconstriction mediated by alpha1A-adrenoceptors in perfused rat hindlimb: a pharmacological approach

We investigated the source of Ca2+ for the vasoconstriction mediated by alpha1a-adrenoceptors in perfused rat hindlimb in functional studies. The noradrenaline (NA)-induced maximum response was decreased by 92% following perfusion with Ca2+-free medium. Depletion of intracellular Ca2+-stores with repeatedly application of caffeine and NA in Ca2+-free medium resulted in complete abolishment of NA-response. Nifedipine concentration-dependently inhibited NA-contraction with a maximum inhibition of 65%. The residual nifedipine-insensitive response was further inhibited by Cd2+. Following depletion of Ca2+ stores with cyclopiazonic acid in Ca2+ free medium for 30 min, the NA-response obtained by re-admission of Ca2+ was decreased by 80%. However, re-introduction of Ca2+ to NA-treated tissues in Ca2+-free medium without prior treatment with cyclopiazonic acid normalizes the NA-response. These results suggest that the NA-contraction in this preparation is mediated largely via an influx of extracellular Ca2+, of which the majority utilizes L-type calcium channels. Only a small portion of the contractile response to NA is derived from intracellular stores, which probably also play a modulatory role on Ca2+ influx.

[Effects of naphthylmethyl isoquinoline on contraction and calcium flux of rabbit vascular strips in vitro]

Naphthylmethyl isoquinoline (NI) 1-30 mumol.L-1 inhibited the contraction of rabbit vascular smooth muscle in vitro induced by KCl, CaCl2, and norepinephrine (NE). NI 0.3-30 mumol.L-1 blocked 45Ca2+ influx process in vascular smooth muscle of aorta, mesenteric and femoral arteries by addition of KCl and NE. NI 3-10 mumol.L-1 had no effect on 45Ca2+ efflux from aorta at resting state. These results suggest that the relaxing effect of NI on rabbit blood vessels may be relevant to the inhibition of Ca2+ influx into vascular smooth muscle.