Artificial intelligence-assisted system for the assessment of Forrest classification of peptic ulcer bleeding: a multicenter diagnostic study

BACKGROUND

Inaccurate Forrest classification may significantly affect clinical outcomes, especially in high risk patients. Therefore, this study aimed to develop a real-time deep convolutional neural network (DCNN) system to assess the Forrest classification of peptic ulcer bleeding (PUB).

METHODS

A training dataset (3868 endoscopic images) and an internal validation dataset (834 images) were retrospectively collected from the 900th Hospital, Fuzhou, China. In addition, 521 images collected from four other hospitals were used for external validation. Finally, 46 endoscopic videos were prospectively collected to assess the real-time diagnostic performance of the DCNN system, whose diagnostic performance was also prospectively compared with that of three senior and three junior endoscopists.

RESULTS

The DCNN system had a satisfactory diagnostic performance in the assessment of Forrest classification, with an accuracy of 91.2% (95%CI 89.5%-92.6%) and a macro-average area under the receiver operating characteristic curve of 0.80 in the validation dataset. Moreover, the DCNN system could judge suspicious regions automatically using Forrest classification in real-time videos, with an accuracy of 92.0% (95%CI 80.8%-97.8%). The DCNN system showed more accurate and stable diagnostic performance than endoscopists in the prospective clinical comparison test. This system helped to slightly improve the diagnostic performance of senior endoscopists and considerably enhance that of junior endoscopists.

CONCLUSION

The DCNN system for the assessment of the Forrest classification of PUB showed satisfactory diagnostic performance, which was slightly superior to that of senior endoscopists. It could therefore effectively assist junior endoscopists in making such diagnoses during gastroscopy.

Cd2(IO3)(PO4) and Cd1.62Mg0.38(IO3)(PO4): metal iodate-phosphates with large SHG responses and wide band gaps

The first NLO-active metal iodate-phosphates, namely, Cd₂(IO₃)(PO₄) and Cd_1.62Mg_0.38(IO₃)(PO₄) (1 and 2), with three types of NLO groups, have been reported. 1 and 2 are isostructural and the structure of 1 features a 3D network formed by the Cd₄(IO₃)_8/4(PO₄)_6/3 groups. 1 and 2 with strong SHG signals of 4 × and 3.5 × KH₂PO₄ are promising SHG materials in the visible region.

α- and β-Ag4P2S7: Two Semiconductors with Promising Photocatalytic Hydrogen Production Based on a Density Functional Theory Study

Herein, a new chiral compound with short Ag-Ag distances, namely, β-Ag₄P₂S₇ (P3₁21), has been discovered by a solid-state method. Density functional theory (DFT) calculations show that both α and β phases exhibit suitable band gaps, low reduction potentials, and large visible-light absorption coefficients, as well as excellent band edges for carrier separation, suggesting their promising application in photocatalytic hydrogen production.

MicroRNA-126 Attenuates the Effect of Chemokine CXCL8 on Proliferation, Migration, Apoptosis, and MAPK-Dependent Signaling Activity of Vascular Endothelial Cells Cultured in a Medium with High Glucose Concentration

We studied the mechanisms by which microRNA-126 regulates proliferation and migration of human umbilical vein endothelial cells (HUVEC) cultured in a medium with high glucose concentration and treated with chemokine CXCL8. Cell proliferation, apoptosis, and migration were analyzed by the CCK-8 assay, Annexin V-PI staining, and Transwell assay, respectively. The ratios of p-ERK/ERK, p-P38/P38, p-JNK/JNK were determined by ELISA. HUVEC cells cultured in the presence of high glucose concentration (30 mmol/ml) and treated with CXCL8 (50 ng/ml) demonstrated more intensive proliferation, migration, and p-ERK/ERK, p-P38/P38, and p-JNK/JNK ratios and significantly lower apoptosis rate than control cells (high glucose, no treatment) and cells treated with CXCL8 and transfected with microRNA-126-mimic. Thus, microRNA-126 regulates proliferation and migration of HUVEC cells cultured in the presence of high glucose concentrations and treated with CXCL8 through inhibition of MAPK signaling pathway.

FOXA2 alleviates CCl4-induced liver fibrosis by protecting hepatocytes in mice

The liver-enriched transcription factor Forkhead Box A2 (FOXA2) has been reported to be involved in bile acid homeostasis and bile duct development. However, the role of FOXA2 in liver fibrogenesis remains undefined. In this study, we found that the abundance of FOXA2 was significantly lower in fibrotic livers of patients and mice treated with CCl₄ than in controls. Interestingly, the expression level of FOXA2 decreased in hepatocytes, whereas FOXA2 was elevated in hepatic stellate cells (HSCs) of mouse fibrotic livers. Hepatocyte-specific ablation of FOXA2 in adult mice exacerbated liver fibrosis induced by CCl₄. Either lentivirus LV-CMV-FOXA2 mediated FOXA2 overexpression in the liver or adeno-associated virus AAV8-TBG-FOXA2-mediated hepatocyte-specific upregulation of FOXA2 alleviated hepatic fibrosis. Overexpression of FOXA2 in HSCs did not obviously affect hepatic fibrogenesis. Additionally, FOXA2 knockout in hepatocytes resulted in aberrant transcription of metabolic genes. Furthermore, hepatocyte-specific knockout of FOXA2 enhanced endoplasmic reticulum stress (ER stress) and the apoptosis of hepatocytes, whereas FOXA2 overexpression in hepatocytes suppressed ER stress and hepatocyte apoptosis in mouse fibrotic livers. In conclusion, our findings suggested that FOXA2-mediated hepatocyte protection has a therapeutic role in hepatic fibrosis, and thus may be a new, promising anti-fibrotic option for treating chronic liver diseases.

The fabrication and characteristics of indium-oxide covered porous InP

Uniform and vertical indium-oxide nanotube (IONT) arrays embedded well in n-type InP single crystal have been successfully prepared in situ by porous InP-template-assisted chemical vapor deposition (CVD). This IONT/InP nanostructure reveals high sensitivity to humidity at room temperature, which is ascribed to the ultrahigh surface-to-volume ratio of this nanostructure and the large number of oxygen defected states in IONTs. Such a nanostructure of IONT arrays embedded in a III-V semiconductor substrate could be expected to have potential applications, such as superior gas sensors. This work provides a novel approach for fabricating low-melting metal oxide semiconductor nanotubes.

Polo-like kinase-1 in porcine oocyte meiotic maturation, fertilization and early embryonic mitosis

Polo-like kinases (Plks) are a family of serine/threonine protein kinases that regulate multiple stages of mitosis. Expression and distribution of polo-like kinase 1 (Plk1) were characterized during porcine oocyte maturation, fertilization and early embryo development in vitro, as well as after microtubule polymerization modulation. The quantity of Plk1 protein remained stable during meiotic maturation. Plk1 accumulated in the germinal vesicles (GV) in GV stage oocytes. After germinal vesicle breakdown (GVBD), Plk1 was localized to the spindle poles at metaphase I (MI) stage, and then translocated to the middle region of the spindle at anaphase-telophase I. Plk1 was also localized in MII spindle poles and on the spindle fibers and on the middle region of anaphase-telophase II spindles. Plk1 was not found in the spindle region when colchicine was used to inhibit microtubule organization, while it accumulated as several dots in the cytoplasm after taxol treatment. After fertilization, Plk1 concentrated around the female and male pronuclei. During early embryo development, Plk1 was found to be in association with the mitotic spindle at metaphase, but distributed diffusely in the cytoplasm at interphase. Our results suggest that Plk1 is a pivotal regulator of microtubule organization and cytokinesis during porcine oocyte meiotic maturation, fertilization, and early embryo cleavage in pig oocytes.

Evaluation of alveolar surfactant aggregates in vitro and in vivo

In acute lung injury, a decrease in surface-active large aggregates and an increase in the less surface-active small surfactant aggregates are observed. The objective of the current study was to determine if the increase in small aggregates interfered with the function of large aggregates, thereby independently contributing to lung dysfunction. Isolated large aggregates, small aggregates, and large aggregate+small aggregate combinations were analysed for in vitro surface activity utilizing a pulsating bubble surfactometer. Subsequently, large aggregates, small aggregates, and large aggregate+ small aggregate combinations were administered to surfactant-deficient, adult Sprague-Dawley rats. Physiological parameters were measured during 1 h of ventilation. After sacrifice, the whole lung lavage was analysed for protein concentration, and surface activity of the recovered large aggregates. The minimum surface tension of the large aggregate+small aggregate preparations (10 mN x m(-1)) was significantly higher than large aggregates alone (1 mN x m(-1)), but lower than small aggregates alone (21 mN x m(-1) ) after 100 pulsations. In vivo, rats receiving large aggregates+small aggregates showed immediate increases in oxygenation, similar to animals given large aggregates, whereas animals given small aggregates and control animals maintained low oxygenation values. In conclusion, small aggregates interfered with large aggregates function in vitro, but this was not observed in vivo in this experimental model.

Surfactant treatment for ventilation-induced lung injury in rats: effects on lung compliance and cytokines

The objective of this study was to determine if exogenous surfactant therapy could prevent the harmful effects of ventilation at high tidal volumes without positive end-expiratory pressure (PEEP). Rats were randomized to either a nontreated control group (8 mL/kg 4 cm H2O PEEP), a nontreated injuriously ventilated group (20 mL/kg 0 cm H2O PEEP) or a treatment group of either 50 mg/kg, 50 mg/kg + 5% surfactant-associated protein A, 100 mg/kg exogenous surfactant followed by injurious ventilation. Isolated lungs from animals in all 5 groups were ventilated in a humidified box at 37 degrees C for 2 hours. Pressure-volume curves and light microscopy showed that surfactant treatment reduced the ventilation-induced lung injury (VILI). Inflammatory cytokines (tumor necrosis factor-alpha [TNFalpha], interleukin [IL]-1beta, and IL-6) in the lavage were significantly higher in injuriously ventilated lungs compared to the control group. However the 3 treatment groups had cytokine concentrations that were similar to the injuriously ventilated group. We conclude that surfactant treatment is beneficial in preventing VILI; however, it does not prevent the release of inrflammatory cytokines during mechanical ventilation.

Mechanical ventilation of isolated septic rat lungs: effects on surfactant and inflammatory cytokines

The effects of mechanical ventilation (MV) on the surfactant system and cytokine secretion were studied in isolated septic rat lungs. At 23 h after sham surgery or induction of sepsis by cecal ligation and perforation (CLP), lungs were excised and randomized to one of three groups: 1) a nonventilated group, 2) a group subjected to 1 h of noninjurious MV (tidal volume = 10 ml/kg, positive end-expiratory pressure = 3 cmH(2)O), or 3) a group subjected to 1 h of injurious MV (tidal volume = 20 ml/kg, positive end-expiratory pressure = 0 cmH(2)O). Nonventilated sham and CLP lungs had similar compliance, normal lung morphology, surfactant, and cytokine concentrations. Injurious ventilation decreased compliance, altered surfactant, increased cytokines, and induced morphological changes compared with nonventilation in sham and CLP lungs. In these lungs, the surfactant system was similar in sham and CLP lungs; however, tumor necrosis factor-alpha and interleukin-6 levels were significantly higher in CLP lungs. We conclude that injurious ventilation altered surfactant independent of sepsis and that the CLP lungs were predisposed to the secretion of larger amounts of cytokines because of ventilation.

[The determination of lorazepam in human urine by gas chromatography/nitrogen-phosphorus detector]

A method to assay lorazepam in human urine has been developed. After addition of hydroxyethylflurazepam (internal standard) and hydrolysis with beta-glucuronidase, the lorazepam and hydroxyethylflurazepam were extracted with ethyl ether at pH 10.8. The analysis was performed on an HP-5 capillary column with nitrogen-phosphorus detector(NPD). The detection limit and recovery of analytes in urine were 5 micrograms/L and (83.4 +/- 3.1)% respectively. The method was successfully applied to urine specimens collected from healthy human volunteers who have ingested 2 mg of lorazepam. The method was sensitive enough to assay urine specimen excreted at 32 h after taking the medicine by volunteers.

Evaluation of exogenous surfactant in HCL-induced lung injury

The efficacy of exogenous surfactant administration is influenced by numerous factors, which has resulted in variable outcomes of clinical trials evaluating this treatment for the acute respiratory distress syndrome (ARDS). We investigated several of these factors in an animal model of acid aspiration including different surfactant preparations, and different delivery methods. In addition, high-frequency oscillation (HFO), a mode of mechanical ventilation known to recruit severely damaged lungs, was utilized. Lung injury was induced in adult rabbits via intratracheal instillation of 0.2 N HCl followed by conventional mechanical ventilation (CMV) until Pa(O2)/FI(O2) values ranged from 220 to 270 mm Hg. Subsequently, animals were given one of three surfactants administered via three different methods and physiological responses were assessed over a 1-h period. Regardless of the surfactant treatment strategy utilized, oxygenation responses were not sustained. In contrast, HFO resulted in a superior response compared with all surfactant treatment strategies involving CMV. The deterioration in physiological parameters after surfactant treatment was likely due to overwhelming protein inhibition of the surfactant. In conclusion, various surfactant treatment strategies were not effective in this model of lung injury, although the lungs of these animals were recruitable with HFO, as reflected by the acute and sustained oxygenation improvements.

Effects of alveolar surfactant aggregates on T-lymphocyte proliferation

The effects of alveolar large aggregate (LA) and small aggregate (SA) surfactant subfractions isolated from healthy adult rats on mitogen-stimulated proliferative responses of human peripheral blood mononuclear cells (PBMC) was examined. Various concentrations of total surfactant suppressed proliferation of stimulated lymphocytes by up to 95% of mitogen-stimulated cells alone. LA subfractions of total surfactant had no effect on proliferation, whereas SA significantly enhanced the lymphocyte proliferation at lower concentrations (7.8 microg/ml) compared to mitogen-stimulated cells alone. Higher concentrations of SA (62.5 microg/ml) inhibited lymphocyte proliferation. This concentration-dependent effect of SA on proliferation of PBMC was also present when cells were stimulated with various lectins including anti-CD3, concanavalin A and phytohemagglutinin. Analysis of the supernatant of mitogen-stimulated cell cultures treated with inhibitory concentrations of SA showed decreased amounts of interleukin (IL)-2, compared to cells alone, which could be reversed by adding exogenous IL-2 to the cell cultures with the SA. These results suggest that alveolar surfactant subfractions have distinct functions within the alveoli, both biophysically and with respect to their effects on the host's immunomodulatory responses.

Ovine surfactant protein cDNAs: use in studies on fetal lung growth and maturation after prolonged hypoxemia

cDNAs for ovine surfactant-associated protein (SP) A, SP-B, and SP-C have been cloned and shown to possess strong similarity to cDNAs for surfactant apoproteins in other species. These reagents were employed to examine the effect of fetal hypoxia on the induction of surfactant apoprotein expression in the fetal lamb. Postnatal lung function is dependent on adequate growth and maturation during fetal development. Insulin-like growth factor (IGF) I and IGF-II, which are present in all fetal tissues studied, possess potent mitogenic and proliferative actions, and their effects can be modulated by IGF-specific binding proteins (IGFBPs). Hypoxia can lead to increases in circulating cortisol and catecholamines that can influence lung maturation. Therefore, the effects of mild hypoxia in chronically catheterized fetal lambs at gestational days 126-130 and 134-136 (term 145 days) on the expression of pulmonary surfactant apoproteins and IGFBPs were examined. Mild hypoxia for 48 h resulted in an increase in plasma cortisol that was more pronounced at later gestation, and in these animals, there was a twofold increase in SP-A mRNA. SP-B mRNA levels also increased twofold, but this was not significant. SP-C mRNA was not altered. No significant changes in apoprotein mRNA were observed with the younger fetuses. However, these younger animals selectively exhibited reduced IGFBP-5 mRNA levels. IGF-I mRNA was also reduced at 126-130 days, although this conclusion is tentative due to low abundance. IGF-II levels were not affected at either gestational age. We conclude that these data suggest that mild prolonged fetal hypoxia produces alterations that could affect fetal cellular differentiation early in gestation and can induce changes consistent with lung maturation closer to term.

Alveolar environment influences the metabolic and biophysical properties of exogenous surfactants

Several factors have been shown to influence the efficacy of exogenous surfactant therapy in the acute respiratory distress syndrome. We investigated the effects of four different alveolar environments (control, saline-lavaged, N-nitroso-N-methylurethane, and hydrochloric acid) on the metabolic and functional properties of two exogenous surfactant preparations: bovine lipid extract surfactant and recombinant surfactant-associated protein (SP) C drug product (rSPC) administered to each of these groups. The main difference between these preparations was the lack of SP-B in the rSPC. Our results demonstrated differences in the large aggregate pool sizes recovered from each of the experimental groups. We also observed differences in SP-A content, surface area cycling characteristics, and biophysical activities of these large aggregate forms after the administration of the two exogenous surfactant preparations. We conclude that the alveolar environment plays a critical role, influencing the overall efficacy of exogenous surfactant therapy. Thus further preclinical studies are warranted to investigate the specific factors within the alveolar environment that lead to the differences observed in this study.

An examination of the different variables affecting surfactant aggregate conversion in vitro

Pulmonary surfactant exists in 2 major subtypes, the freshly secreted, surface-active large surfactant aggregates (LA) and their metabolic product, the less surface active, small aggregates (SA). Conversion of LA into SA can be studied using an in vitro technique, surface area cycling, which involves the rotation of a suspension of LA end-over-end so that the surface area of the liquid changes twice each cycle. In order to further elucidate the mechanisms involved in aggregate conversion, we have examined the effects of time, temperature, change in surface area, cycling speed, surfactant concentration, and albumin on aggregate conversion in vitro. Three different surfactant preparations were used; rabbit LA, sheep LA, and an exogenous surfactant preparation, bovine lipid extract surfactant (BLES). Based on our results that showed that these variables affected aggregate conversion, we concluded that the adsorption of surfactant at the changing air-liquid interface was an important step in aggregate conversion. However, the results also indicated that aggregate conversion was not solely due to the adsorption characteristics of the surfactant. Other surfactant properties, such as the activity of serine protease or film stability at the air-liquid interface, may also be important in aggregate conversion.

[Research of the extraction method of morphine from biological fluids]

A solid-phase extraction method of morphine from urine and blood has introduced. The effect of 5 SPE columns, 3 eluents and pH on morphine recovery has been investigated systematically. Derivative GC was used as a method of detection. The result showed that the column and the eluent of such as GDX-301, GDX-403 and C18 chloroform:isopropanol (9:1) had good behaviors to extraction of morphine. When GDX-301 was used as a sorbent, the recovery of morphine from urine was above 90% at pH 9, then went down with the increase of pH. While the recovery from blood was growing with the increase of pH, which reached above 90% in strong alkaline. The extraction method is simple, inexpensive, efficient and reproducible, which provides an effective and practical method to extract morphine and similar illicit drugs from biological fluids.

Effects of surfactant distribution and ventilation strategies on efficacy of exogenous surfactant

The effects of both surfactant distribution patterns and ventilation strategies utilized after surfactant administration were assessed in lung-injured adult rabbits. Animals received 50 mg/kg surfactant via intratracheal instillation in volumes of either 4 or 2 ml/kg. A subset of animals from each treatment group was euthanized for evaluation of the exogenous surfactant distribution. The remaining animals were randomized into one of three ventilatory groups: group 1 [tidal volume (VT) of 10 ml/kg with 5 cmH2O positive end-expiratory pressure (PEEP)]; group 2 (VT of 5 ml/kg with 5 cmH2O PEEP); or group 3 (VT of 5 ml/kg with 9 cmH2O PEEP). Animals were ventilated and monitored for 3 h. Distribution of the surfactant was more uniform when it was delivered in the 4 ml/kg volume. When the distribution of surfactant was less uniform, arterial PO2 values were greater in groups 2 and 3 compared with group 1. Oxygenation differences among the different ventilation strategies were less marked in animals with the more uniform distribution pattern of surfactant (4 ml/kg). In both surfactant treatment groups, a high mortality was observed with the ventilation strategy used for group 3. We conclude that the distribution of exogenous surfactant affects the response to different ventilatory strategies in this model of acute lung injury.

Effects of ventilation strategies on the efficacy of exogenous surfactant therapy in a rabbit model of acute lung injury

We evaluated the effects of various ventilation strategies on the efficacy of exogenous surfactant therapy in lung-injured adult rabbits. Lung injury was induced by repetitive whole-lung saline lavage followed by mechanical ventilation. Three hours after the final lavage, 100 mg lipid/kg bovine lipid extract surfactant was instilled. After confirmation of similar responses to exogenous surfactant, animals were then randomized to one of four ventilation groups; (1) Normal tidal volume (VT) (5 cm H2O): VT = 10 ml/kg, respiratory rate (RR) = 30/min, positive end-expiratory pressure (PEEP) = 5 cm H2O; (2) Normal VT (9 cm H2O): VT = 10 ml/kg, RR = 30/min, PEEP = 9 cm H2O; (3) Low VT (5 cm H2O): VT = 5 ml/kg, RR = 60/min, PEEP = 5 cm H2O; (4) Low VT (9 cm H2O): VT = 5 ml/kg, RR = 60/min, PEEP = 9 cm H2O. Animals were ventilated for an additional 3 h and then killed, and lung lavage fluid was analyzed. Animals ventilated with the low-VT modes (Low VT [5 cm H2O] and Low VT [9 cm H2O]) had higher PaO2 values (430 +/- 7 mm Hg and 425 +/- 18 mm Hg versus 328 +/- 13 mm Hg) and higher percentages of surfactant in large aggregate forms (83 +/- 2% and 82 +/- 2% versus 67 +/- 4%) at 3 h after treatment than did the Normal VT (5 cm H2O) group (p < 0.05). Increasing the PEEP level was beneficial for a short period after surfactant administration to maintain oxygenation, but did not affect exogenous surfactant aggregate conversion. We speculate that ventilation strategies resulting in low exogenous surfactant aggregate conversion will result in superior physiologic responses to exogenous surfactant.

Alterations of the endogenous surfactant system in septic adult rats

Sepsis is the most common factor leading to the acute respiratory distress syndrome (ARDS) and is associated with the highest mortality rate. It has been suggested that the pulmonary surfactant system is altered and contributes to the lung dysfunction associated with ARDS. The objective of this study was to characterize the lung injury, specifically the endogenous surfactant system in septic adult rats. Sepsis was induced in male Sprague-Dawley rats by cecal ligation and perforation and resulted in significant increases in heart rates, respiratory rates, and lactate levels along with positive blood cultures in septic animals compared with a sham control group. Two distinct septic groups were developed, a septic group and a sepsis with lung injury (septic+LI) group. The septic group had no significant differences in oxygenation compared with the sham group, whereas the septic+LI group had significantly lower PaO2 and higher A-a gradient values compared to both the sham and septic groups. The total surfactant pool size was significantly lower in the septic+LI group compared with the sham group. The small surfactant aggregate to large surfactant aggregate ratio was significantly lower in the septic group and was further reduced in the septic+LI group. There were also significantly higher levels of surfactant protein A (SP-A) in both septic and septic+LI groups compared to the sham group. These results demonstrated that the endogenous surfactant system was altered in systemic sepsis without lung dysfunction and is further altered when a lung injury is present.

Effects of lung injury on pulmonary surfactant aggregate conversion in vivo and in vitro

Within the alveolar space pulmonary surfactant is converted from the surface active large aggregates (LA) to the inactive small aggregates (SA). This conversion is affected by a change in surface area, lung injury, breathing pattern, and protease activity. This study examined the effect of N-nitroso-N-methylurethane-induced acute lung injury on aggregate conversion in mechanically ventilated and spontaneously breathing rabbits. Both the in vitro surface area cycling techniques and the in vivo technique of intratracheally injecting radiolabeled LA were used for analyzing aggregate conversion. Mechanical ventilation of injured lungs resulted in increased aggregate conversion and increased surfactant aggregate ratios compared with controls. Spontaneously breathing injured animals had aggregate conversion and aggregate ratios that were not significantly different from controls. In vitro aggregate conversion was slower for LA obtained from injured animals compared with normal animals. We conclude that the mechanical stress of mechanical ventilation results in increased aggregate conversion and aggregate ratios. Furthermore, in vitro conversion of isolated LA does not necessarily reflect the conversion of aggregates within the alveoli.

The dynamic NMR structure of the T psi C-loop: implications for the specificity of tRNA methylation

tRNA (m5U54)-methyltransferase (RUMT) catalyzes the S-adenosylmethionine-dependent methylation of uridine-54 in the T psi C-loop of all transfer RNAs in E. coli to form the 54-ribosylthymine residue. However, in all tRNA structures, residue 54 is completely buried and the question arises as to how RUMT gains access to the methylation site. A 17-mer RNA hairpin consisting of nucleotides 49-65 of the T psi-loop is a substrate for RUMT. Homonuclear NMR methods in conjunction with restrained molecular dynamics (MD) methods were used to determine the solution structure of the 17-mer T-arm fragment. The loop of the hairpin exhibits enhanced flexibility which renders the conventional NMR average structure less useful compared to the more commonly found situation where a molecule exists in predominantly one major conformation. However, when resorting to softer refinement methods such as MD with time-averaged restraints, the conflicting restraints in the loop can be satisfied much better. The dynamic structure of the T-arm is represented as an ensemble of 10 time-clusters. In all of these, U54 is completely exposed. The flexibility of the T psi-loop in solution in conjunction with extensive binding studies of RUMT with the T psi C-loop and tRNA suggest that the specificity of the RUMT/ tRNA recognition is associated with tRNA tertiary structure elements. For the methylation, RUMT would simply have to break the tertiary interactions between the D- and T-loops, leading to a melting of the T-arm structure and making U54 available for methylation.

Ventilation strategies affect surfactant aggregate conversion in acute lung injury

This study evaluated the effects of varying tidal volumes (VT) and positive end-expiratory pressure (PEEP) levels on surfactant aggregate conversion and lung function in an animal model of lung injury induced by N-nitroso-N-methylurethane. Lung-injured adult rabbits were initially ventilated using a VT of 10 ml/kg (VT10), a respiratory rate of 30 breaths/min (RR30), and a PEEP of 3.5 cm H2O. A trace dose of radiolabeled rabbit large surfactant aggregates was instilled after the onset of ventilation, and animals were then ventilated at different ventilator settings for 1 h. Ventilation strategies involving a lower VT (VT5, RR60) resulted in significantly superior oxygenation and lower surfactant aggregate conversion rates than strategies involving a higher VT ([VT10, RR30], [VT15, RR20], p < 0.05). Increasing the PEEP level to 8.0 cm H2O improved oxygenation, but it was sustained only with a low VT (VT5, RR60), and deteriorated with a high VT (VT10, RR30). Varying VT but not PEEP levels resulted in significant changes in surfactant aggregate conversion. We conclude that increased surfactant aggregate conversion resulting from suboptimal ventilation of injured lungs may play an important role in the pathophysiology of ventilation-induced lung dysfunction in acute lung injury.

Evaluation of surfactant treatment strategies after prolonged graft storage in lung transplantation

We have previously documented alterations in endogenous surfactant after lung transplantation and improved graft function in some dogs after instillation of bovine lipid extract surfactant (bLES) into the recipient. To determine the effect of bLES delivery method and timing of treatment on physiologic response and surfactant recovery, 21 canine left lung grafts were divided into four groups: (1) Treatment of the donor for 3 h with aerosolized bLES prior to graft storage (Donor Aerosol); (2) Treatment of the recipient with instilled bLES immediately after transplantation (Recipient Instilled); (3) No bLES treatment (Control); and (4) Aerosolized bLES in donors and instilled bLES in recipients (Combined Therapy). Aerosolized bLES was labeled with [3H]-dipalmitoylphosphatidylcholine (DPPC) and instilled bLES with [14C]-DPPC. Grafts were stored for 36 h, transplanted and reperfused for 6 h. The native right and transplanted left lungs were then lavaged and protein yield, surfactant aggregates, and bLES recovery were measured. After 6 h of reperfusion, PO2/FlO2 ratio was significantly better after Combined Therapy (372 +/- 52 mm Hg) than in the Recipient Instilled (117 +/- 47 mm Hg) and Control groups (87 +/- 26 mm Hg), with intermediate values in Donor Aerosol dogs (232 +/- 64 mm Hg). The recovery of donor aerosolized bLES from transplanted lungs was increased in dogs given Combined Therapy versus Donor Aerosol treatment alone (p = 0.03). Furthermore, with Combined Therapy there was an increased percentage of instilled bLES recovered from transplanted lungs compared with the Recipient Instilled group. We conclude that surfactant treatment strategies influence physiologic response and bLES recovery after prolonged lung preservation. Treatment of lung donors with exogenous surfactant prior to graft storage was associated with less severe lung injury. Combined donor and recipient bLES therapy resulted in a superior physiologic response during reperfusion in this model.

Interactions of integrin GPIIb/IIIa-derived peptides with fibrinogen investigated by NMR spectroscopy

Three peptides derived from platelet receptor glycoprotein alphaIIbBeta3 (GPIIb/IIIa) have been identified recently as fibrinogen-binding sequences: GPIIb 300-314 and 656-667 and GPIIIa 211-223. NMR spectroscopy has been used here to investigate the interactions of these peptides with parent fibrinogen. Based on resonance broadening and chemical-shift changes of peptides in the presence and absence of fibrinogen, interactions in the fast ligand-exchange regime are apparent and interfacial residues can be proposed. Positively charged arginines and histidines, along with several hydrophobic residues, are implicated as being crucial to the binding process. Transferred nuclear Overhauser effects and distance geometry calculations allow discussion of probable conformations in peptide-'bound' states. These identifications are consistent with other biological/chemical data and provide the basis for further studies aimed at understanding fibrinogen-mediated platelet aggregation on the molecular level.

Timing of exogenous surfactant administration in a rabbit model of acute lung injury

The purpose of this study was to evaluate early vs. late administration of exogenous surfactant in an adult rabbit model of acute lung injury. Lung injury was induced by repetitive whole lung saline lavage and subsequent mechanical ventilation. Bovine lipid extract surfactant was instilled either 1 (Early) or 4 h (Late) after the last lavage. Animals were monitored for 7 h after the last lavage. Although arterial PO2 values increased significantly immediately after treatment in both the Early and Late groups, this improvement was not sustained in the Late group. There was also a higher incidence of pneumothoraxes in the Late group vs. both the Early group and a nontreated control group. The ratio of poorly functioning small surfactant aggregates to superior functioning large aggregates was higher in the Late group compared with the Early group. Morphological analysis revealed that early surfactant treatment prevented the progression of lung injury over time. We conclude that administration of exogenous surfactant at an early time point in lung injury resulted in superior responses compared with later treatments.

Surfactant-associated protein A is important for maintaining surfactant large-aggregate forms during surface-area cycling

Alveolar surfactant can be separated into two major subfractions, the large surfactant aggregates (LAs) and the small surfactant aggregates (SAs). The surface-active LAs are the metabolic precursors of the inactive SAs. This conversion of LAs into SAs can be studied in vitro using a technique called surface-area cycling. We have utilized this technique to examine the effect of trypsin on aggregate conversion. Our results show that trypsin increases the conversion of LAs into SAs in a concentration- and time-dependent manner. Immunoblot analysis revealed that surfactant-associated Protein A (SP-A) was the main target of trypsin. To examine further the role of SP-A in aggregate conversion, we tested the effect of Ca2+ and mannan on this process. The absence of Ca2+ (l mM EDTA) and the presence of mannan both increased the formation of SAs. Electron microscopy revealed that highly organized multilamellar and tubular myelin structures were present in samples that converted slowly to SAs. We concluded that SP-A is important for maintaining LA forms during surface-area cycling by stabilizing tubular myelin and multilamellar structures.

Alveolar surfactant aggregate conversion in ventilated normal and injured rabbits

Alveolar surfactant can be separated into two subtypes; large aggregates and small aggregates. Large aggregates represent the surface active form of surfactant and are the metabolic precursors of small aggregates. Previous studies examined the mechanism by which large aggregates are converted into small aggregates in vitro. We used intratracheal injection of radiolabeled large aggregates in rabbits to probe the aggregate conversion in vivo. After this injection, animals were mechanically ventilated for 60 min. After the animals were killed, the lungs were lavaged, and the percentage of radiolabel present in the small aggregate fraction was determined. Our results showed that ventilation resulted in aggregate conversion and that increases in tidal volume, but not in respiratory rate, correlated with increased conversion. Aggregate conversion in rabbits with acute lung injury correlated significantly with severity of injury. We conclude that a change in surface area (i.e., respiration) is necessary for aggregate conversion in vivo and that the ventilation strategy can affect this conversion. Furthermore, increased aggregate conversion in injured lungs might contribute to increased small-to-large aggregate ratios in these lungs compared with normal lungs.

Regulation of mRNA levels for pulmonary surfactant-associated proteins in developing rabbit lung

Gene transcriptional activities and steady-state mRNA levels have been examined for the surfactant-associated proteins SP-A, SP-B and SP-C in developing rabbit lung. It was observed SP-C mRNA levels increase early in gestation, while SP-A and SP-B mRNA levels increase rapidly between 26 and 30 days gestation. Transcriptional activities for all three surfactant apoproteins increase between 26 and 30 days. Studies conducted with fetal lung explants of 26 days gestation demonstrated exposure to low doses of dexamethasone increases SP-A and SP-C mRNA levels, while high doses stimulate transcription, although this only significant for SP-C. Time course studies revealed different temporal patterns and glucocorticoid responses for SP-A and SP-C mRNAs. SP-A and SP-C mRNA production and steady-state levels were reduced after treatment with cycloheximide. In contrast, SP-B gene transcription was selectively stimulated, suggesting involvement of a labile negative regulatory factory. It is concluded that expression of the three surfactant apoproteins is independently regulated. Early in gestation, SP-C mRNA levels may be regulated in vivo through message stabilization. Glucocorticoids can affect SP-A and SP-C mRNA levels in culture at both transcriptional and post-transcriptional levels. The ability of glucocorticoids to influence these processes declines during fetal development.

[The relationship between stereoacuity and contracted visual field]

The stereoacuity (SA) was measured by means of the Titmus test, Random Dot E stereotest and Yan's stereoscopic test charts in 90 cases of glaucoma or retinitis pigmentosa with visual field contraction and 28 normal subjects. Significant reduction in SA was observed in all patients with contracted visual field, and markedly so (> 130") in cases with bilateral or unilateral tubular vision. The SA was reduced with visual field loss of over 30% and there was a positive correlation between the SA reduction and the area of visual field loss.

Expression of mature pulmonary surfactant-associated protein B (SP-B) in Escherichia coli using truncated human SP-B cDNAs

The present communication documents attempts to produce the mature form of human surfactant-associated protein B (SP-B) by modification of the 5' and 3' regions of the cDNA and expression of the truncated cDNAs after insertion into the vector pKK223-3. The 5' end of a cDNA for human SP-B (1407 base pairs) was reconstructed through the ligation of synthetic oligonucleotides to an internal PstI site in the 5' region. This construction coded for the initiation of protein synthesis at a Met codon adjacent to a codon for the N-terminal Phe of the mature polypeptide. Variable amounts of the 3' end of the human SP-B cDNA were deleted with mung bean nuclease and exonuclease III. The resulting blunt-ended 3' fragments were then ligated to a synthetic oligonucleotide linker designed to create a stop codon. The modified 5' and 3' ends were ligated to a short PstI-BamHI fragment isolated from the SP-B cDNA and inserted into the expression vector pKK223-3. In vitro translation of sense mRNAs derived from the truncated SP-B cDNAs yielded oligopeptides of appropriate molecular weights, as indicated by urea - sodium dodecyl sulphate - polyacrylamide gel electrophoresis of either intact or immunoprecipitated reaction mixtures. Expression of SP-B in Escherichia coli was confirmed by Northern blot analysis for the mRNAs corresponding to the truncated cDNAs in appropriately transformed bacteria induced with the galactose analog isopropyl-beta-thiogalactoside. Western blot analysis using rabbit antisera prepared against bovine SP-B confirmed the presence of mature SP-B in lipid extracts of transformed E. coli, but the amounts were very small.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of the cDNA for pulmonary surfactant-associated protein-B (SP-B) in the rabbit

Pulmonary surfactant contains phospholipids including dipalmitoyl-phosphatidylcholine and three surfactant-associated proteins designated SP-A, SP-B and SP-C. A cDNA for rabbit SP-B has been isolated from a fetal (30 days gestation) rabbit lung cDNA library constructed in lambda gt11. The cDNA and deduced amino acid sequences show strong homology with the cDNAs and predicted 40 kDa proproteins for human and canine SP-B. Strong homology is also observed with the amino acid sequences directly determined for the mature 8 kDa bovine and porcine SP-B isolated from lung lavage. SP-B is remarkable for its high cysteine and proline content and for the hydrophobic nature of the organic solvent-soluble, mature protein. In vitro translation of sense but not antisense RNA transcribed from the cDNA led to the production of 40 kDa and 32 kDa proteins. These proteins were immunoprecipitated by an antibody raised against bovine SP-B. Northern blot analysis revealed the mRNA for rabbit SP-B appears in fetal rabbit lung late in gestation and falls slightly in the neonate.