Causal role of gut microbiota in intracranial aneurysm: evidence from a Mendelian randomization study

OBJECTIVE

An increasing number of studies suggest that the alteration of gut microbiota may affect the pathogenesis of intracranial aneurysm (IA). However, the exact causal relationship between gut microbiota and IA has not been confirmed.

MATERIALS AND METHODS

The instrumental variables (IVs) for gut microbiota were obtained from a meta-analysis of a genome-wide association study (GWAS) conducted by the MiBioGen consortium (n = 13,266). The summary of GWAS data for IA was obtained from a large genome-wide meta-analysis involving 23 cohorts. Five Mendelian randomization (MR) methods were used to investigate the causal relationship between gut microbiota and IA (ruptured and unruptured), unruptured intracranial aneurysm only (uIA), and aneurysmal subarachnoid hemorrhage (aSAH) respectively, with inverse variance weighted (IVW) as the main MR method. All MR results were verified through sensitive analyses.

RESULTS

Based on the results of the IVW analyses, it was found that five gut microbiota taxa were causally associated with IA (ruptured and unruptured), seven gut microbiota taxa were causally associated with uIA, and six gut microbiota taxa were causally associated with aSAH. Among these taxa, the genus Bilophila was the only one identified to have significant protective effects against IA (ruptured and unruptured), uIA, and aSAH. The sensitivity analysis did not reveal any significant heterogeneity or horizontal pleiotropy among the included IVs.

CONCLUSIONS

MR analyses identified several gut microbiota taxa that have a causal relationship with IA. Future research should prioritize understanding the mechanisms underlying this causal relationship, as it is expected to contribute to the development of new methods for predicting and treating IA.

The generation of genuine quadripartite Einstein-Podolsky-Rosen steering in an optical superlattice

Einstein-Podolsky-Rosen (EPR) steering is a quantum effect based on quantum entanglement and it is the key resource for building quantum networks because of its useful properties. Based on the criterion for genuine multipartite EPR steering, the genuine quadripartite EPR steering is confirmed and it can be generated by a spontaneous parametric down-conversion cascaded process with two sum-frequency generations in an optical superlattice. This occurs either below the oscillation threshold and without oscillation threshold. The influence of the parameters of cascaded nonlinear process on the quadripartite EPR steering among signal, idler, and two sum-frequency beams are also discussed. Choosing appropriate nonlinear parameters can achieve good quadripartite quantum steering. This scheme of the generation of genuine quadripartite EPR steering has potential applications in quantum communication and computing.

[Comparison of 5-year follow-up outcomes between"one-stop"procedure and long-term oral anticoagulants after radiofrequency catheter ablation in patients with atrial fibrillation]

Objective: To compare the 5-year follow-up outcomes of radiofrequency catheter ablation (RFCA) combined with left atrial appendage closure (LAAC) and long-term oral anticoagulant (OAC) after RFCA in patients with atrial fibrillation. Methods: This retrospective cross-sectional study included patients with atrial fibrillation who underwent"one-stop"procedure in the First Affiliated Hospital of Ningbo University from September 2015 to December 2017 (RFCA+LAAC group). Baseline data of patients were collected. Propensity score matching at the ratio of 1∶1 was used to select patients with atrial fibrillation who took long-term OAC after RFCA (RFCA+OAC group). The maintenance rate of sinus rhythm and the incidence of adverse events during follow-up were compared between the two groups. Results: A total of 110 patients were enrolled in the RFCA+LAAC group and RFCA+OAC group, respectively. Age of patients was (67.4±8.8) years in RFCA+LAAC group, and there were 42 (38.2%) female patients. Age of patients was (67.3±7.9) years in RFCA+OAC group, and there were 47 (42.7%) female patients. The patients were followed up for mean of (5.3±1.1) years. There was no significant difference in the maintenance rate of sinus rhythm (log-rank: χ2=0.277, P=0.602) and incidence of ischemic stroke events (2.7% (3/110) vs. 4.5% (5/110), P=0.719) during follow-up between the two groups. The incidence of bleeding events (6.4% (7/110) vs. 18.2% (20/110), P=0.008) and major bleeding events (1.8% (2/110) vs. 8.2% (9/110), P=0.030) was significantly higher in the RFCA+OAC group than in the RFCA+LAAC group. Conclusion: There is no significant difference between RFCA+LAAC group and RFCA+OAC group in maintenance rate of sinus rhythm and incidence of ischemic stroke events. Patients in the RFCA+LAAC group have a lower risk of bleeding events compared to the RFCA+OAC group.

[Feasibility and safety of closing large left atrial appendage using the LAmbre device]

Objective: To evaluate the feasibility and safety of the LAmbre occluder for large-diameter left atrial appendage occlusion. Methods: This study was a retrospective cohort study. Patients with large orifice of the left atrial appendage (≥31 mm) and occlusion with the LAmbre device in the Arrhythmia Center of Ningbo First Hospital were included from June 2018 to March 2020. Baseline data were collected and major perioperative complications of left atrial appendage occlusion (including death, stroke, instrumental embolism, cardiac tamponade, and major bleeding events) were recorded. Patients were followed up 45 days, 6 months and 12 months after surgery. The shunt and device-related thrombosis were recorded by esophageal cardiac ultrasound or pulmonary vein CT, and the occurrence of postoperative thromboembolism, bleeding events, death and other serious adverse events were recorded. Results: The average age and left atrial appendage ostial dimension of 32 patients (37.5% women) included in this research were (70.4±8.4) years old and (34.4±2.9) mm. The LAmbre device was successfully implanted in 31(96.9%) patients. No major complications occurred during the perioperative period. During the 12-month follow-up, pericardial tamponade occurred in 1(3.2%) patient and was recovered after treatment. There was no occluder edge shunt>5 mm in patients followed up by esophageal echocardiography. No significant peri-device leak, device-related thrombus, thromboembolism or death event has occurred. Conclusion: The LAmbre occluder may be feasible and safe for large-diameter left atrial appendage occlusion.

MiR-486 alleviates hypoxia/reoxygenation-induced H9c2 cell injury by regulating forkhead box D3

OBJECTIVE

Myocardial ischemia-reperfusion injury (IRI) is common in myocardial infarction and is the leading cause of death. Therefore, we investigated the effect of miR-486 on myocardial IRI to explore new targets for clinical treatment of IRI.

MATERIALS AND METHODS

We made a rat myocardial IRI model by obstructing the coronary arteries and detected the change of miR-486 expression in rat myocardial tissue. In addition, we induced injury of rat cardiomyocytes (H9c2 cells) by hypoxia/reoxygenation and transfected H9c2 cells with agomir-miR-486 and antagomir-miR-486 to detect the effects of miR-486 on the viability, inflammation and apoptosis of cardiomyocytes. We also used the Targetscan system to predict the direct target of miR-486 and verified the effect of miR-486 on downstream targets through the Dual-Luciferase reporter assay.

RESULTS

HE staining and the detection of myocardial injury markers and inflammatory factors verified the effectiveness of IRI rat model. The expression of miR-486 in myocardium of IRI rats was significantly lower than that of the control group. The overexpression of miR-486 in H9c2 cells increased the viability of H9c2 cells and reduced the levels of inflammation and apoptosis. MiR-486 is predicted to have a potential binding site to forkhead box D3 (FOXD3). The Dual-Luciferase reporter assay proved that miR-486 can bind and degrade FOXD3 mRNA. In addition, the overexpression of FOXD3 was found to attenuate the protective effect of miR-486 on H9c2 cells.

CONCLUSIONS

MiR-486 protects cardiomyocytes and reduces the levels of inflammation and apoptosis by binding and inhibiting FOXD3 activity. Therefore, miR-486 may become a new target for myocardial IRI therapy.

Hydroxytyrosol suppresses LPS-induced intrahepatic inflammatory responses via inhibition of ERK signaling pathway activation in acute liver injury

OBJECTIVE

Acute liver injury (ALI) leads to inflammatory response and tissue damage. Inflammatory activation of infiltrative macrophages plays a critical role in liver histology destruction and dysfunction. Hydroxytyrosol (3,4-dihydroxyphenil-ethanol, HT), one of the polyphenols extracted from extra virgin olive oil, currently acts as a treatment for neuroinflammatory responses, but its effect on ALI is elusive. The present study aims to examine the mechanism of HT in macrophages inflammation and evaluate treatment effect of HT on ALI.

MATERIALS AND METHODS

In vitro, the expressions of type M1/M2 macrophages biomarkers (CD11c/CD206) and cytokines (TNF-α, IL-1β, IL-6, IL-10, IL-4) following lipopolysaccharide (LPS) stimulation and HT administration were detected using immunofluorescence, quantitative real-time polymerase chain reaction (qRT-PCR), and enzyme-linked immunosorbent assay (ELISA). Mechanically, HT was used to treat cells and phosphorylation level of extracellular-signal-regulated kinase 1/2 (ERK1/2) protein in cells was analyzed using Western blotting. In murine acute liver injury, inflammatory cytokines and liver injury degree were exhibited by qRT-PCR, IHC and HE staining. Furthermore, hepatic function was exhibited via hepatic metabolic enzymes (ALT/AST) and total bilirubin (TBil) in serum.

RESULTS

It was demonstrated that HT treatment attenuated M1 macrophages and increased M2 macrophages after LPS stimulation. Furthermore, the pro-inflammatory cytokine level was descended, while an-inflammatory cytokine was increased via HT suppressing ERK pathway in macrophages. In vivo, HT reduced inflammatory level and mitigated hepatic histological injury, thus ameliorating liver function after acute liver injury.

CONCLUSIONS

HT exerts a hepatoprotective and anti-inflammation effect on acute liver injury, which restrains inflammation by inhibiting ERK pathway and regulating macrophages polarization. Moreover, HT prevents liver tissues from inflammatory injury. Therefore, HT serves as a potential implication to treat ALI through modulating inflammation of macrophages.

The role of quinazoline in ameliorating intervertebral disc degeneration by inhibiting oxidative stress and anti-inflammation via NF-κB/MAPKs signaling pathway

OBJECTIVE

Previous studies have shown that Quinazoline (QNZ) plays extremely important roles in the cellular physiological activity, but it has been rarely examined on cell behavior following intervertebral disc degeneration (IVDD). The aim of this study was to investigate whether QNZ mediates oxidative stress and inflammation contributed to IL-1β-induced nucleus pulposus (NP) cells degeneration in vitro.

PATIENTS AND METHODS

NP were isolated cells from human disc samples collected from patients and the IL-1β-induced NP cells degenerated model was constructed. The cells were randomly divided into 3 groups, namely, Control group, IL-1β group (10 µM), QNZ + IL-1β group (containing 10 nM QNZ and 10 µM IL-1β). Then, the cell viability was determined by CCK-8 assay, and the levels of collagen I, collagen II, aggrecan, p16, p53, β-galactosidase (β-gal), antioxidant enzymes, 8-hydroxy-2-deoxyguanosine (8-OHdG), NF-κB/MAPKs signaling-related proteins and inflammatory factors were examined using Western blot and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in NP cells. Finally, the expressions of IL-1β, IL-6, and TNF-α in the cell supernatants were also determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

This study showed that IL-1β promoted the progress of IDD, with markedly increased expressions of collagen I, p16, p53, and β-gal, as well as decreased expressions of collagen II and aggrecan. However, QNZ treatment could reverse the effects of IL-1β. It was found that cell proliferation was increased, ROS level was decreased, antioxidant enzymes were upregulated, and inflammatory factors were reduced after QNZ stimulation. Moreover, NF-κB/MAPKs signaling proteins IKKβ, IκBα, p65, ERK, JNK, and p38 were significantly dephosphorylated by QNZ.

CONCLUSIONS

These results indicated that QNZ prevented NP degradation via restraining oxidative stress and inflammation through inhibition of the NF-κB/MAPKs signaling pathway. QNZ may become a novel insight into the therapy of IVDD in the future.

Genuine tripartite Einstein-Podolsky-Rosen steering in the cascaded nonlinear processes of third-harmonic generation

Recently, Einstein-Podolski-Rosen (EPR) steering has important application in quantum information processing, and it has been received considerable attention because of its uniqueness. The properties of quantum steering among three output fields generated by cascaded nonlinear processes of quasi-phase-matching third-harmonic generation in an optical cavity are investigated. Based on the criteria for multipartite EPR steering which proposed by He and Reid [PRL, 111, 250403 (2013)], the genuine tripartite EPR steering among pump, second-harmonic, and third-harmonic is demonstrated. The parameters which affect the quantum property are also discussed.

Ultrastructure of intestinal mucosa in diarrhea-predominant irritable bowel syndrome

OBJECTIVES

Impaired intestinal barrier function has been demonstrated in the pathophysiology of diarrhea-predominant irritable bowel syndrome (IBS-D). This study aimed to describe the intestinal ultrastructural findings in the intestinal mucosal layer of IBS-D patients.

METHODS

In total, 10 healthy controls and 10 IBS-D patients were analyzed in this study. The mucosa of each patient's rectosigmoid colon was first assessed by confocal laser endomicroscopy (CLE); next, biopsied specimens of these sites were obtained. Intestinal tissues of IBS-D patients and healthy volunteers were examined to observe cellular changes by transmission electron microscopy (TEM).

RESULTS

CLE showed no visible epithelial damage or inflammatory changes in the colonic mucosa of IBS-D compared with healthy volunteers. On transmission electron microscopic examination, patients with IBS-D displayed a larger apical intercellular distance with a higher proportion of dilated (>20 nm) intercellular junctional complexes, which was indicative of impaired mucosal integrity. In addition, microvillus exfoliation, extracellular vesicle as well as increased presence of multivesicular bodies were visible in IBS-D patients. Single epithelial cells appeared necrotic, as characterized by cytoplasmic vacuolization, cytoplasmic swelling, and presence of autolysosome. A significant association between bowel habit, frequency of abdominal pain, and enlarged intercellular distance was found.

CONCLUSION

This study showed ultrastructural alterations in the architecture of intestinal epithelial cells and intercellular junctional complexes in IBS-D patients, potentially representing a pathophysiological mechanism in IBS-D.

[Predictive value of typical cataplexy+ DQB1*0602 positive to hypocretin-1 reduction in cerebrospinal fluid in patients with narcolepsy]

Objective: To discusses the predictive value of typical cataplexy+ HLA-DQB1*0602 positive to hypocretin-1 (HCRT-1) reduction in cerebrospinal fluid (CSF) in patients with narcolepsy. Methods: A total of 165 narcoleptic patients, who were diagnosed at the Sleep Center of Peking University People's Hospital and Peking University International Hospital from March 2003 to March 2017, were recruited. The CSF HCRT-1 level and DQB1*0602 were measured in all the subjects. The narcoleptic patients were divided into two groups: typical cataplexy+ DQB1*0602 positive were CH group, and others who were not typical cataplexy and DQB1*0602 positive simultaneously were NCH group. The HCRT-1 level in CSF was declared to have a serious reduction when HCRT-1≤110 ng/L. According to this standard, the CH group and NCH group were subdivided into sub-groups and the data was analyzed to investigate the predictive value of typical cataplexy+ HLA-DQB1*0602 positive to HCRT-1 reduction. Results: There were 142 patients in CH group, including 137 patients with HCRT-1 reduction and 5 patients without. There were 23 patients in NCH group, including 15 patients with HCRT-1 reduction and 8 patients without. The positive predictive value of typical cataplexy+ DQB1*0602 positive for the reduction of HCRT-1 in CSF was 96.5%. Typical cataplexy+ DQB1*0602 positive had a good consistency with the HCRT-1 reduction in CSF (χ(2)=26.7, P<0.001). Conclusion: Typical cataplexy+ DQB1*0602 positive has a good predictive value to the HCRT-1 reduction in CSF in patients with narcolepsy.

[The study on the inhibitive effects of recombinant parathyroid hormone (1-34) on osteolysis in a murine calvarial model induced by wear particles]

Objective: To investigate the effect of different doses of recombinant parathyroid hormone (PTH) (1-34) on osteolysis in a murine calvarial model. Methods: In total, 48 adult male C57BL/J6 mice were randomly divided into four groups: the sham group, the vehicle group, the low dose-, and high dose PTH group (n=12 each group). Mice in the PTH groups were treated with local injection of recombinant PTH at 30 or 60 μg·kg^-1·d^-1, intermittent injection 3 times per week for two weeks. Mice in the sham and vehicle groups received local injection of saline daily. Two weeks after surgery, calvarial tissue and peripheral blood were harvested for further analysis. Osteolysis was assessed by micro-computed tomography. The mRNA and protein expression of osteoprotegerin (OPG) and receptor activator for nuclear factor-κB Ligand (RANKL) of calvarial tissue and peripheral blood were tested by real-time PCR and ELISA, respectively. Results: Compared with the vehicle group, PTH treatment significantly inhibited the severity of osteolysis and improved the bone volume. Real time-PCR and ELISA showed that PTH significantly increased the mRNA and protein expression of OPG and reduced the RANKL/OPG ratio. Conclusion: These findings suggest that local application of PTH could effectively inhibit wear-particle-induced-osteolysis in a murine calvarial model.

BDNF modulates intestinal barrier integrity through regulating the expression of tight junction proteins

BACKGROUND

Brain-derived neurotrophic factor (BDNF) may play a vital role in the homeostatic regulation of intestinal barrier integrity. We aimed to investigate the physiological role of BDNF in maintaining the intestinal epithelial barrier using postinflammatory irritable bowel syndrome (PI-IBS) mice and explore the underlying molecular mechanisms using intestinal epithelial cells in vitro.

METHODS

Postinflammatory-IBS mice were induced by intrarectal administration of trinitrobenzene sulfonic acid and allowed to recover for 28 days. Frequency of defecation, fecal water content, colonic epithelial integrity and expressions of BDNF and tight junction (TJ) proteins (occludin, ZO-1, claudin-1, claudin-2) of the PI-IBS mice were investigated. Based on the results of animal studies, we further performed RT-PCR and Western blots to assess how BDNF stimulation and BDNF knockdown impacted TJ proteins in the ht-29 intestinal epithelial cells.

KEY RESULTS

Water content of stools was significantly increased in the PI-IBS mice compared with controls. Colonic mucosa from the PI-IBS mice displayed epithelial barrier defects and exhibited increased protein expressions of BDNF and claudin-2 and decreased protein expressions of occludin, ZO-1 and claudin-1. Furthermore, a siRNA against BDNF in the ht-29 cells could effectively suppress BDNF gene and protein expressions, and subsequently reduce TJ gene and protein levels. When the ht-29 cells were incubated with different doses of exogenous BDNF, significant increases of occludin, ZO-1 and claudin-1 and decreases of claudin-2 protein were observed.

CONCLUSIONS & INFERENCES

BDNF may play a role in regulating intestinal epithelial barrier via affecting the expression of TJ proteins.

Linear dependence of the water proton transverse relaxation rate on the shear modulus of hydrogels

It is found that hydrogelation of peptides enhances the transverse relaxation rate R2 of water protons but has no effect on the longitudinal relaxation rate R1 and the diffusion coefficient D. The magnitude of water proton R2 enhancement increases linearly with the shear modulus G of hydrogels.

Increased cancer risk in patients with haemophilia A: a nationwide population-based 14-year study in Taiwan

Haemostasis is associated with the development and dissemination of cancer. Whether cancer incidence is increased in haemophiliacs remains uncertain; thus, we aimed to further examine this issue. By using data from the National Health Insurance Research Database in Taiwan, we obtained a cohort of 683 patients with haemophilia A, and compared the incidence rate ratio (IRR) of cancer in this cohort with an age- and sex-matched control of 6830 patients. The log-rank test was used to compare Kaplan-Meier curve of the cumulative cancer incidence between two cohorts. Cox regressions were used to identify independent risk factors of cancer in the study patients. The cancer incidence of patients with haemophilia A was significantly higher compared to the control group (IRR 1.95, 95% CI 1.18-3.09, P = 0.008) during the 14-year follow-up period. The non-lymphoma and non-liver cancer incidence in the haemophilia A cohort remained higher than that of the matched control (P = 0.050 by the log-rank test). The multivariate Cox proportional hazards analysis indicated that age (per year, HR 1.09, 95% CI 1.06-1.12, P < 0.001) was the only significant risk factor for cancer development in haemophilia patients. Patients with haemophilia A had higher cancer incidence than the age- and sex-matched patients, especially for the elderly. With increasing life expectancy for haemophiliacs, physicians should be aware of their cancer development.

Meta-analysis of confocal laser endomicroscopy for the detection of colorectal neoplasia

AIM

Confocal laser endomicroscopy (CLE) is a recently developed technique used to image colorectal neoplasia. Trials have shown varied results when it is compared with conventional colonoscopy. A meta-analysis was performed to determine the diagnostic accuracy of CLE in the detection of colorectal neoplasia.

METHOD

A search was performed for studies assessing the accuracy of CLE in colorectal neoplasia. Studies comparing CLE diagnostic accuracy with conventional endoscopy in the detection of colorectal neoplasia were included. Exclusion criteria included case reports or case series, reviews, duplicate reports or insufficient data in the paper. Seventy-eight titles came up in the initial search and six studies were selected. These were subjected to a meta-analysis. In all, 284 patients with 1030 lesions were included. Each patient underwent conventional colonoscopy and CLE. Per-lesion sensitivity and specificity with 95% CI were calculated.

RESULTS

In the individual studies, the sensitivity ranged from 33.3% to 100% and specificity from 71.6% to 99.4%. The weighted and total pooled result (random effects model) for sensitivity was 81% (95% CI 77-85) and for specificity was 88% (95% CI 85-90). The area under the weighted symmetric summary receiver operating curve was 0.9186. In the endoscope-based CLE subgroup, the sensitivity was 82% (95% CI 69-91) and specificity was 94% (95% CI 91-96). In the probe-based CLE subgroup, the sensitivity was 81% (95% CI 76-85) and the specificity was 75% (95% CI 69-81).

CONCLUSION

CLE, using either the endoscope-based CLE or probe-based CLE technique, has high sensitivity and specificity. It could therefore be considered as an alternative endoscopic method to distinguish neoplastic from non-neoplastic lesions.

Meta-analysis of confocal laser endomicroscopy for the detection of colorectal neoplasia

AIM

Confocal laser endomicroscopy (CLE) is a recently developed technique used to image colorectal neoplasia. Trials have shown varied results when it is compared with conventional colonoscopy. A meta-analysis was performed to determine the diagnostic accuracy of CLE in the detection of colorectal neoplasia.

METHOD

A search was performed for studies assessing the accuracy of CLE in colorectal neoplasia. Studies comparing CLE diagnostic accuracy with conventional endoscopy in the detection of colorectal neoplasia were included. Exclusion criteria included case reports or case series, reviews, duplicate reports or insufficient data in the paper. Seventy-eight titles came up in the initial search and six studies were selected. These were subjected to a meta-analysis. In all, 284 patients with 1030 lesions were included. Each patient underwent conventional colonoscopy and CLE. Per-lesion sensitivity and specificity with 95% CI were calculated.

RESULTS

In the individual studies, the sensitivity ranged from 33.3% to 100% and specificity from 71.6% to 99.4%. The weighted and total pooled result (random effects model) for sensitivity was 81% (95% CI 77-85) and for specificity was 88% (95% CI 85-90). The area under the weighted symmetric summary receiver operating curve was 0.9186. In the endoscope-based CLE subgroup, the sensitivity was 82% (95% CI 69-91) and specificity was 94% (95% CI 91-96). In the probe-based CLE subgroup, the sensitivity was 81% (95% CI 76-85) and the specificity was 75% (95% CI 69-81).

CONCLUSION

CLE, using either the endoscope-based CLE or probe-based CLE technique, has high sensitivity and specificity. It could therefore be considered as an alternative endoscopic method to distinguish neoplastic from non-neoplastic lesions.

BCLAF1 is a radiation-induced H2AX-interacting partner involved in γH2AX-mediated regulation of apoptosis and DNA repair

H2AX, a histone H2A variant, has a key role in the cellular response to DNA double-strand breaks (DSBs). H2AX senses DSBs through rapid serine 139 phosphorylation, concurrently leading to the formation of phospho-(γ)H2AX foci with various proteins. However, in the cells with different sensitivity to ionizing radiation (IR)-induced DSBs, still incomplete are those specific proteins selectively recruited by γH2AX to decide different cell fates. Because the abundance of γH2AX indicates the extent of DSBs, we first identified IR-induced dose-dependent H2AX-interacting partners and found that Bcl-2-associated transcription factor 1 (BCLAF1/Btf) showed enhanced association with γH2AX only under high-dose radiation. In acutely irradiated cells, BCLAF1 promoted apoptosis of irreparable cells through disturbing p21-mediated inhibition of Caspase/cyclin E-dependent, mitochondrial-mediated pathways. Meanwhile, BCLAF1 co-localized with γH2AX foci in nuclei and stabilized the Ku70/DNA-PKcs complex therein, facilitating non-homologous end joining (NHEJ)-based DSB repair in surviving cells. In tumor cells, BCLAF1 was intrinsically suppressed, leading to formation of anti-apoptotic Ku70-Bax complexes and disruption of Ku70/DNA-PKcs complexes, all of which contribute to tumor-associated apoptotic resistance and cell survival with defective NHEJ DNA repair. For the first time, our studies reveal that, based on the extent of DNA damage, BCLAF1 is involved in the γH2AX-mediated regulation of apoptosis and DNA repair, and is a γH2AX-interacting tumor suppressor.

Directly produced three-color entanglement by quasi-phase-matched third-harmonic generation

A new scheme is presented to directly produce fundamental, second-, and third-harmonic three-color continuous-variable (CV) entangled beams by cascaded quasi-phase-matched third-harmonic generation (THG) in an optical cavity. THG can be achieved with high efficiency through a coupled sum-frequency process between the second-harmonic and the fundamental fields. It is demonstrated that the three beams (fundamental, second-, and third-harmonic fields) are entangled with each other according to the CV entanglement criterion. In this scheme, only one crystal and one pump field can generate three-color CV entangled beams separated by an octave in frequency through quasi-phase-matched cascaded nonlinear process, which may be very useful for the applications in quantum communication and computation networks.

The effect of a side chain-backbone swap on protein stability

To assess the relative importance of backbone hydrogen bonding (H-bonding) vs. side chain hydrophobicity in protein structural formation, a method called side chain-backbone swap is proposed. Such a method swaps the side chain and backbone portions of certain amino acid residues, such as Asp, Glu, Asn, Gln, Lys, and Arg. Such a swap retains the sequence of a polypeptide and preserves the identity of the backbone linkage. On the other hand, the swap disrupts backbone H-bonding geometry because of the introduction of extra methylene groups into the peptide backbone. In this project, we chose the two-stranded alpha-helical coiled-coil to implement side chain-backbone swap. A pair of 36-residue peptides was designed. The two peptides have identical sequence with four residues in each heptad repeat occupied by glutamyl residues. Each glutamic acid was incorporated either as alpha-glutamyl residue (the peptide is denoted as alpha-Glu-36) or as gamma-glutamyl residue (the peptide is denoted as gamma-Glu-36). The inter-conversion between the two peptides constitutes a side chain-backbone swap. Residues constituting the hydrophobic core of the coiled-coil, however, are left unchanged. The peptide pair was characterized by circular dichroism spectroscopy, reversed-phase liquid chromatography (RPLC), and two-dimensional nuclear magnetic resonance (NMR). The results indicate that alpha-Glu-36 is a two-stranded alpha-helical coiled-coil while gamma-Glu-36 lacks stable structural elements. It is concluded that, at least for coiled-coils where hydrophobic interactions are predominantly long-range, local backbone H-bonding is a required for structural formation, consistent with a hierarchic folding mechanism. The methodological implication of side chain-backbone swap is also discussed.

Cost-effectiveness of postremission intensive therapy in patients with acute leukemia

BACKGROUND

We assessed the cost-effectiveness of high-dose arabinoside (HiDAC)-based and allogeneic stem-cell transplantation (alloSCT)-based therapy in patients with acute leukemia.

PATIENTS AND METHODS

We analyzed the outcome, cost and cost-effectiveness of 106 patients treated from January 1994 to January 2002 [94 acute myelogenous leukemia (AML)/12 acute lymphoblastic leukemia (ALL)]. Forty-two young patients at either intermediate or unknown cytogenetic risk received postremission intensive therapy (24 HiDAC-based/18 alloSCT-based therapy).

RESULTS

After a median follow-up of 50 months, the estimated 7-year overall survival for the HiDAC-based group showed a tendency to be higher than the alloSCT-based group (48% versus 28%, P = 0.1452). The HiDAC-based group spent a significantly lower total cost ($US51,857 versus 75,474, P = 0.004) than the alloSCT-based group. Cost-effectiveness analysis showed that the mean cost per year of life saved for the HiDAC-based group is considerably less expensive than the alloSCT-based group ($US11,224 versus 21,564). The reduced total cost for the HiDAC-based group originated from lower cost in room fees, medication, laboratory and procedure, but not in blood transfusion and professional manpower fees.

CONCLUSION

For the postremission therapy in young AML patients at either intermediate or unknown cytogenetic risk, cost-effectiveness of HiDAC-based therapy compares favorably with that of alloSCT-based therapy, which deserves further clinical trials.

Strategy for olive mill wastewater treatment and reuse with a sewage plant in an arid region

This study was conducted to evaluate the treatability of OMW (olive mill wastewater) with sewage and sewage sludge, which could supplement nutrients and microbes required for OMW treatment and reduce its possible toxicity. The amount of OMW added to an aeration tank was based on the loading difference between the designed and actual COD loads, while the amount added to anaerobic digestion for energy recovery was determined by CH4 production. The COD removal efficiencies were 70-85% for both systems. Compost of OMW with dried sewage sludge also showed a similar temperature profile without OMW addition. This strongly suggested that OMW can be treated at a sewage plant without pretreatment and the treated effluent can be reused in irrigation for an arid region.

Pretreatment prognostic factors and treatment outcome in elderly patients with de novo acute myeloid leukemia

BACKGROUND

Elderly patients with acute myeloid leukemia (AML) generally have an unfavorable clinical course and are under-represented in clinical trials. The aim of this study was to analyze the prognosis and treatment outcome of elderly AML patients.

PATIENTS AND METHODS

We studied 205 AML patients aged 65 years or older at our hospital. Prior to study initiation, we designated 13 variables to be analyzed for their impact on complete remission (CR) rate and overall survival (OS).

RESULTS

Induction regimen (standard chemotherapy) and good performance status (PS) (Eastern Cooperative Oncology Group PS 0-1) independently influenced the achievement of CR. Multivariate analysis also determined five poor prognostic factors for OS: poor PS (score 2-4), presence of comorbidities, elevated serum lactate dehydrogenase level (> or =2x upper normal limit), extreme leukocytosis (> or =100 x 10(9)/l) and marked thrombocytopenia (< or =20 x 10(9)/l). Age was not an independent contributing factor in terms of either CR attainment or OS duration. Low-risk patients, who possessed one or less non-leukocytosis poor prognostic factor, had significantly longer disease-free survival and OS than their high-risk counterparts.

CONCLUSIONS

Elderly AML patients should be risk-stratified at diagnosis. Anthracycline-based induction chemotherapy would be the best therapeutic option for such patients.

Algorithmic Generation of Freely Jointed Hard Sphere Chains and Properties of Inertial Tensors

A statistical algorithm, capable of generating a large number of freely jointed hard sphere chains, is presented. This is the first of a series of algorithms being developed to model unfolded proteins by different modes of hard sphere chains. The aim of these studies is to systematically investigate the effects of different factors, such as atomic radii, bond angles, torsion angles, chain length, etc., on the conformation of unfolded proteins and other random polymers. As continuous models, various types of hard sphere chains enable one to isolate the aforementioned factors one at a time for investigation and thus are advantageous over discrete lattice models. In particular, the freely jointed hard sphere chain model allows one to evaluate the excluded volume effect. As a first step in this endeavor, the average determinant D(N, r) and the average trace T(N, r) of the inertial tensor A of the random chains were calculated at various sphere radii r and chain lengths N. It is found that both the average determinant D(N, r) and the average trace T(N, r) scale linearly with chain length N after logarithmic transformation. However, the critical exponent of D(N, r) increases with r faster than that of T(N, r) as a result of the non-commutativity between the det operator and the average operator < >. The significance of the algorithm and the results obtained on understanding random polypeptide chains are discussed.

Standard state and thermodynamic self-consistency

It is pointed out that even though the standard state for solutions is a fictitious state, it nonetheless should be thermodynamically self-consistent. Using a volumetric constraint, it is shown that the biochemical standard state concentration of 1M is too high for macromolecules like proteins and nucleic acids that it violates volumetric self-consistency. Also, at 1 M standard state, the mole fraction of these macromolecular solutes is not the commonly held value of 1/55.5, but rather a meaningless negative number. Thus, the ideal mixing entropy (also called cratic entropy) cannot be meaningfully calculated for macromolecules at such a standard state. The relevance of this conclusion to the interpretation of standard bimolecular binding entropy is discussed.

Contribution of translational and rotational motions to molecular association in aqueous solution

Much uncertainty and controversy exist regarding the estimation of the enthalpy, entropy, and free energy of overall translational and rotational motions of solute molecules in aqueous solutions, quantities that are crucial to the understanding of molecular association/recognition processes and structure-based drug design. A critique of the literature on this topic is given that leads to a classification of the various views. The major stumbling block to experimentally determining the translational/rotational enthalpy and entropy is the elimination of vibrational perturbations from the measured effects. A solution to this problem, based on a combination of energy equi-partition and enthalpy-entropy compensation, is proposed and subjected to verification. This method is then applied to analyze experimental data on the dissociation/unfolding of dimeric proteins. For one translational/rotational unit at 1 M standard state in aqueous solution, the results for enthalpy (H degrees (tr)), entropy (S degrees (tr)), and free energy (G degrees (tr)) are H (degrees) (tr) = 4.5 +/- 1.5RT, S (degrees) (tr) = 5 +/- 4R, and G (degrees) (tr) = 0 +/- 5RT. Therefore, the overall translational and rotational motions make negligible contribution to binding affinity (free energy) in aqueous solutions at 1 M standard state.

Trapping the monomeric alpha-helical state during unfolding of coiled-coils by reversed-phase liquid chromatography

Reversed-phase liquid chromatography (RPLC) offers a unique opportunity to monitor the transition from the native state (N) to the structural intermediate state (I) for proteins whose secondary structure is comprised entirely of amphipathic helices, such as coiled-coils. During RPLC, the hydrophobicity of the stationary phase and mobile phase results in the unfolding of the tertiary/quaternary structure of coiled-coils but retains alpha-helical secondary structure and thus isolates the I state. A set of five peptides, alphaalpha-36, betabeta-36, alphabeta-36, gammadelta-36 and omegaomega-36, was generated by shuffling guest hydrophobes at equivalent sites in a symmetric host frame. In one of the peptides, omegaomega-36, all the alpha-glutamic residues in the host frame were replaced by gamma-glutamic residues. alphaalpha-36, betabeta-36, alphabeta-36, gammadelta-36 form two-stranded coiled-coils of identical helical content and unfold as a two-state transition during temperature denaturation while the fifth peptide, omegaomega-36, is a random coil and cannot be induced in to an alpha-helical structure even in the presence of a helix inducing solvent, 50% trifluoroethanol. By comparing the stability order of the four coiled-coils in the N-->I transition (measured by RPLC studies) with that in the N-->D (denatured state) transition (measured by calorimetry), it is concluded that there is a direct correlation between the relative stabilities of these peptides in these two unfolding transitions. This result supports a hierarchical folding mechanism for coiled-coils.

Developmental adaptation of rat nociceptive withdrawal reflexes after neonatal tendon transfer

Nociceptive withdrawal reflexes (NWRs) were studied in adult rats in which the movement patterns produced by single muscles had been altered by neonatal tendon transfer. NWRs evoked by cutaneous noxious mechanical and thermal (CO2-laser) stimulation were recorded using electromyography in a decerebrate spinal preparation. The sensitivity distribution within the receptive fields of the NWRs of the extensor digitorum longus and the peronei muscles exhibited changes corresponding to the altered movement patterns. No detectable change of NWRs was found in normal muscles whose receptive fields overlapped that of the modified muscle. Furthermore, NWRs of muscles that regained an essentially normal function after neonatal tendon transfer did not differ from normal. It is proposed that a developmental experience-dependent mechanism, which takes into account the hindlimb movement pattern caused by contraction of single muscles, underlies the functionally adapted organization of adult NWRs.

Protective effect of Oenanthe javanica on the hepatic lipid peroxidation in bromobenzene-treated rats and its bioactive component

To investigate the detoxification of bromobenzene-induced hepatic lipid peroxidation by Oenanthe javanica DC, the hepatic lipid peroxide level and the activities of enzymes responsible for production and removal of epoxide were studied. The level of lipid peroxide elevated by bromobenzene was significantly reduced by the methanol extract (250 mg/kg) and persicarin (5 mg/kg). The methanol extract and persicarin administered daily over 4 weeks before intoxication with bromobenzene did not affect the activities of aminopyrine N-demethylase, aniline hydroxylase, and glutathione S-transferase. Epoxide hydrolase activity was decreased significantly by bromobenzene, which was restored to the control level by pretreatment with persicarin. However, the identical pretreatment with isorhamnetin and hyperoside did not change the enzyme activity or lipid peroxide level. The results suggest that the reduction of bromobenzene-induced hepatic lipid peroxidation by O. javanica under our experimental conditions is effected through enhancing the activity of epoxide hydrolase, an enzyme removing bromobenzene epoxide. In addition, the bioactive component of this plant responsible for the detoxification of bromobenzene, at least in part, is thought to be persicarin.

Overexpression of plasminogen activator inhibitor 2 in human melanoma cells inhibits spontaneous metastasis in scid/scid mice

A metastatic human melanoma cell line that produces urokinase-type plasminogen activator was stably transfected with cDNA encoding human plasminogen activator inhibitor 2 (PAI-2). Transfected clones expressed PAI-2 at levels two to nine times higher than both the parental cell line and mock transfectants, as detected by ELISA of cell lysates and conditioned medium. The clone with the highest PAI-2 expression exhibited complete inhibition of soluble and cell-surface-bound plasminogen activator activity. The level of PAI-2 overexpression in these clonal cell lines correlated positively with the inhibition of their ability to degrade extracellular matrix in vitro. Parental, mock-transfected, and PAI-2-transfected cell lines produced rapidly growing tumors when injected s.c. into the skin of mice with severe combined immunodeficiency. The tumors producing the highest levels of PAI-2 were surrounded by a dense tumor capsule. Both parental cells and mock-transfected cells invariably metastasized from s.c. tumors to lymph nodes and lungs of mice. PAI-2-transfected cell lines produced significantly less or no metastases. Taken together, these data indicate a critical role for plasminogen activator activity in melanoma invasion and metastasis.

Inhibition of invasion of HT1080 sarcoma cells expressing recombinant plasminogen activator inhibitor 2

Plasminogen activators (PA) elaborated by tumor cells play an important role in the complex process of tissue invasion and metastasis. In the present study the effect of the PA inhibitor type 2 (PAI-2) on tissue invasion in vitro and in vivo was investigated. Clones either expressing (B-) or not expressing the endogenous PAI-2 gene (C+) were isolated from the human HT1080 fibrosarcoma cell line and transfected with full-length PAI-2 cDNA. Recombinant PAI-2 (rPAI-2) expressed by these cells completely inhibited receptor-bound urokinase activity and partially neutralized secreted PA activity. Degradation of extracellular matrix proteins by these transfected cells was markedly decreased when compared to mock or untransfected control cells. The rPAI-2-expressing cells did not penetrate a multilayer of rat smooth muscle cells in vitro, which was readily invaded and destroyed by control cells. The PAI-2 transfectants remained tumorigenic in athymic/nude mice, but tumors originating from these cells showed the presence of a thick, collagenous capsule absent in tumors formed by control cells. Thus, expression of rPAI-2 in HT1080 cells resulted in neutralization of receptor-bound urokinase with subsequent inhibition of matrix protein degradation and invasion in vitro and induction of a thick, peritumoral capsule in vivo.

Multiple spinal pathways mediate cutaneous nociceptive C fibre input to the primary somatosensory cortex (SI) in the rat

In the present study, partial lesions of the lower thoracic spinal cord in rats anaesthetized with halothane and nitrous oxide were made in order to elucidate which of the spinal funiculi mediate a nociceptive C fibre input to SI. Field potentials evoked by noxious CO2-laser stimulation were recorded in the left SI. Nociceptive C fibre input from the right hindpaw to SI was propagated by the dorsal funiculi (DF) and the left and right lateral funiculi (LLF and RLF, respectively). Nociceptive C fibre input from the left hindpaw was propagated by LLF and RLF, but not DF. Input from the hindpaws mediated by LLF and RLF caused widespread surface positive potentials throughout most of SI, although potentials in the hindlimb area tended to be larger than those in other areas of SI. Input from the right hindpaw mediated by DF caused surface positive potentials mainly in the hindlimb area of SI. Intracortically, the field potentials reversed polarity in the superficial laminae and had maximal negative amplitudes in laminae III-IV (input transferred by DF and LLF) and in laminae V-VI (input transferred by LLF and RLF). It is concluded that there are multiple spinal pathways which can transfer information from cutaneous nociceptive C fibres to SI in the rat. These ascending pathways seem to activate partly different thalamo-cortical systems.

[Effects of glycine and GABA on primary afferent terminal excitability in mouse spinal cord]

The effects of GABA, glycine and their antagonists on primary afferent terminal excitability were observed on isolated spinal cord of 10-15 day-old mouse. The results indicated that electrical stimulation of an adjacent dorsal root and electrophoresis of GABA, Thip., thiomuscimol and glycine can evoke a fall in threshold, the excitability of single primary afferent terminal was increased. Bicuculline, an antagonist of GABA receptor, can block effects of GABA, Thip. and thiomuscimol, but it has no effect on glycine. However, strychnine, an antagonist of glycine, can block the effect of glycine but not to GABA. These results suggest that there are GABA and glycine receptors on primary afferent terminals of mouse spinal cord and the type of glycine receptor may be the same as neuron body.

Primary afferent terminal excitability in the normal and spastic mutant mouse spinal cord

A microcomputer-based system has been used to apply the technique of excitability testing to the study of the actions of a range of pharmacological agents on the excitability of single primary afferent terminals in the mouse spinal cord in vitro. GABAA analogues all evoked increases in excitability that were bicuculline sensitive. GABA itself also evoked biphasic changes in excitability, or occasionally only suppressed terminal excitability. This latter effect was often enhanced in the presence of bicuculline, and resembled the action of the GABAB agonist, baclofen. The GABAA action could be enhanced by concurrent application of either benzodiazepine, midazolam or flurazepam. Bicuculline alone frequently decreased excitability. This action could be abolished by blocking synaptic activity with a low Ca2+ high Mg2+ superfusate, and was therefore considered to be due to reduction of the tonic action of GABA released at synaptic connections. Comparison of the action of these agents on terminals in the spastic mutant mouse showed an increased sensitivity of the GABA response to the benzodiazepines in mutant animals.

[Radioimmunodetection of human lung cancer xenografts by isotope labeling monoclonal antibody ALT-04 in nude mice]

Three nude mouse models bearing the human lung cancer were established from two fresh surgical specimens and one cell line. Tumor histological structure and cell morphology were similar before and after transplantation. The monoclonal antibody ALT-04 (McAb ALT-04) against human lung cancer was labeled by 125I, 131I and 201Tl. Radioimmunodetection study showed that all the three kinds of xenografts in nude mice were specifically located by McAb ALT-04. Imaging examination confirmed the ability of isotope labeling McAb ALT-04 to detect the presence of transplanted human lung cancer tissues without the aid of background subtraction manipulations. It is suggested that McAb ALT-04 have the possibility of locating in the tumor diagnosis and guiding in the treatment.

[Reactivity of monoclonal antibodies ALT-01 and ALT-04 and identification of lung cancer-associated antigens]

Two IgG1 type monoclonal antibodies ALT-01 and ALT-04 were prepared by two different immunization schedules. ALT-01 was generated by fusing murine myeloma NS-1 cells with splenocytes from a BALB/c mouse immunized by human lung squamous carcinoma cells, which were coated by antisera to mixed human lymphocytes. For preparation of ALT-04, human lung squamous carcinoma xenograft-bearing nude mice were injected I. P. with the spleen cells of normal BALB/c mice in order to acquire immunofunction. The spleen cells from these tumor-bearing nude mice were fused with NS-1 cells. Then, these hybridomas were screened and cloned for 3 times. Two antibodies were shown to recognize the surface antigen on human lung carcinoma cells and several kinds of tumor cell lines but not those on normal cell lines. ALT-01 reacted to neither human lung carcinoma tissue nor its xenograft. ALT-04 reacted to human lung carcinoma tissue, of which, reaction to adenocarcinoma was the strongest but not to various normal tissues. Immunoprecipitation followed by SDS-polyacrylamide gel electrophoresis and autoradiography was used to detect the associated antigen in 35S-labeled human lung carcinoma cells. Antigens, reacting to ALT-01, show one band of Mr 38,000 but those to ALT-04 reveal two bands of Mr 48,000 and 36,000.

[Kinetic observation and analysis of the radioactivity distribution of 125I-labelled F(ab')2 fragments of monoclonal antibody against human lung cancer cells in normal mice]

Radioactivity distribution of 125I-labelled F(ab')2 fragments in 14 organs and tissues of normal mice for 11 time-phases from 0.5 hour to 7 days after injection was observed. The radioactivity-time curves of these organs and tissues were divided into three types according to their characteristics: excreting type (blood and liver), absorbing type (thyroid), absorbing-excreting type (the other organs and tissues). The organs fully perfused with blood had shorter peak-time and higher peak-value, such as heart, lung, kidney and liver. All of the peak-times were equal to or less than 2 days after injection, therefore the image taking should be kept away from this period. The excreting rate constants of slow metabolic component were similar for various organs and tissues except thyroid and brain. The brain had a low peak in the curve and small excreting rate constant. It was demonstrated that F(ab')2 fragments were able to penetrate the blood-brain barrier but absorption and excretion were slower compared with the other organs and tissues. The radioiodine was obviously concentrated in the subcutaneous tissue, which may have been the main cause of the subcutaneous tissue tumor induced by radioiodine. The radioactivity-time curve in which the peak value and inflect point existed simultaneously shows that radioactivity metabolism after injection of 125I-F(ab')2 follows three compartment models. The biological meanings corresponding to three sections of the blood radioactivity-time curve are pure distribution, distribution-recycle and catabolic-excretory phases, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of ethylene production by 2,4-dinitrophenol and high temperature

2,4-Dinitrophenol (DNP) and high temperature (35 to 40 C) are known to inhibit C(2)H(4) production in various plant tissues. The present study was made to determine the step in the C(2)H(4) biosynthetic pathway (methionine --> S-adenosylmethionine [SAM] --> 1-aminocyclopropane-1-carboxylic acid [ACC] --> C(2)H(4)) at which these treatments exert their inhibitory effect. In mung bean hypocotyls the dose-inhibition curves for the effect of DNP on auxin-dependent C(2)H(4) production (in which auxin exerts its effect by stimulating the conversion of SAM to ACC) and on ACC-dependent C(2)H(4) production (in which ACC is directly utilized as precursor) were similar. It was concluded, therefore, that DNP at low concentrations (below 50 micromolar) exerted its effect primarily on the conversion of ACC to C(2)H(4), a step which is common to both systems. This view was further substantiated by quantitative analysis of the intermediates in the biosynthetic sequence. DNP exerted little influence on the content of SAM but caused a significant increase in the ACC content and marked inhibition in C(2)H(4) production, indicating that the conversion of ACC to C(2)H(4) is the crossover point. At higher concentrations (above 100 micromolar), DNP inhibited the conversion of methionine to ACC and to C(2)H(4), and this effect could be attributed to the inhibition of SAM synthesis.The optimal temperature for maximal C(2)H(4) production by apple tissue and mung bean hypocotyl is about 30 C. An increase in temperature to 35 C caused an accumulation of endogenous ACC, whereas C(2)H(4) production was greatly reduced. These results suggest that the conversion of ACC to C(2)H(4) is highly vulnerable to high temperature inhibition.

Biosynthesis of wound ethylene

Untreated mung bean hypocotyls produced very little C(2)H(4) but, upon treatment with 10 millimolar Cu(2+) or 10 millimolar Cu(2+) + 10 millimolar Ca(2+), C(2)H(4) production increased 20- and 40-fold, respectively, within 6 hours. This increase in C(2)H(4) production was preceded and paralleled by an increase in 1-aminocyclopropanecarboxylic acid (ACC) content, but the level of S-adenosylmethionine (SAM) was unaffected, suggesting that the conversion of SAM to ACC is a key reaction in the production of wound-induced C(2)H(4). This view was further supported by the observation that application of aminoethoxyvinylglycine, a known inhibitor of the conversion of SAM to ACC, eliminated the increases in ACC formation and in C(2)H(4) production. A significant increase in C(2)H(4) production was observed in the albedo tissue of orange in response to excision, and it was paralleled by an increase in ACC content. In columella tissue of unripe green tomato fruit, massive increases in the C(2)H(4) production rate (from 0 to 12 nanoliters per gram per hour), in ACC content (from 0.05 to 12 nmoles per gram), and in ACC synthase activity (from 0 to 6.4 units per milligram protein) occurred during the 9-hour incubation period following excision. Infiltration with 0.1 millimolar cycloheximide, an inhibitor of protein synthesis, completely blocked wound-induced C(2)H(4) production, ACC formation, and development of ACC synthase activity. These data indicate that wounding induces the synthesis of ACC synthase, which is the rate-controlling enzyme in the pathway of C(2)H(4) biosynthesis and, thereby, causes accumulation of ACC and increase in C(2)H(4) production.

Auxin-induced Ethylene Production and Its Inhibition by Aminoethyoxyvinylglycine and Cobalt Ion

Auxin is known to stimulate greatly both C(2)H(4) production and the conversion of methionine to ethylene in vegetative tissues, while amino-ethoxyvinylglycine (AVG) or Co(2+) ion effectively block these processes. To identify the step in the ethylene biosynthetic pathway at which indoleacetic acid (IAA) and AVG exert their effects, [3-(14)C]methionine was administered to IAA or IAA-plus-AVG-treated mung bean hypocotyls, and the conversion of methionine to S-adenosylmethionine (SAM), 1-amino-cyclopropane-1-carboxylic acid (ACC), and C(2)H(4) was studied. The conversion of methionine to SAM was unaffected by treatment with IAA or IAA plus AVG, but active conversion of methionine to ACC was found only in tissues which were treated with IAA and which were actively producing ethylene. AVG treatment abolished both the conversion of methionine to ACC and ethylene production. These results suggest that in the ethylene biosynthetic pathway (methionine --> SAM --> ACC --> C(2)H(4)) IAA stimulates C(2)H(4) production by inducing the synthesis or activation of ACC synthase, which catalyzes the conversion of SAM to ACC. Indeed, ACC synthase activity was detected only in IAA-treated tissues and its activity was completely inhibited by AVG. This conclusion was supported by the observation that endogenous ACC accumulated after IAA treatment, and that this accumulation was completely eliminated by AVG treatment. The characteristics of Co(2+) inhibition of IAA-dependent and ACC-dependent ethylene production were similar. The data indicate that Co(2+) exerts its effect by inhibiting the conversion of ACC to ethylene. This conclusion was further supported by the observation that when Co(2+) was administered to IAA-treated tissues, endogenous ACC accumulated while ethylene production declined.

Regulation of Auxin-induced Ethylene Production in Mung Bean Hypocotyls: Role of 1-Aminocyclopropane-1-Carboxylic Acid

Ethylene production in mung bean hypocotyls was greatly increased by treatment with 1-aminocyclopropane-1-carboxylic acid (ACC), which was utilized as the ethylene precursor. Unlike auxin-stimulated ethylene production, ACC-dependent ethylene production was not inhibited by aminoethoxyvinylglycine, which is known to inhibit the conversion of S-adenosylmethionine to ACC. While the conversion of methionine to ethylene requires induction by auxin, the conversion of methionine to S-adenosylmethionine and the conversion of ACC to ethylene do not. It is proposed that the conversion of S-adenosylmethionine to ACC is the rate-limiting step in the biosynthesis of ethylene, and that auxin stimulates ethylene production by inducing the synthesis of the enzyme involved in this reaction.