[Revision rate of periprosthetic joint infection post total hip or knee arthroplasty of 34 hospitals in China between 2015 and 2017: a multi-center survey]

Objective: To investigate the rate of periprosthetic joint infection (PJI) revision surgeries and clinical information of hip-/knee- PJI cases nationwide from 2015 to 2017 in China. Methods: An epidemiological investigation. A self-designed questionnaire and convenience sampling were used to survey 41 regional joint replacement centers nationwide from November 2018 to December 2019 in China. The PJI was diagnosed according to the Musculoskeletal Infection Association criteria. Data of PJI patients were obtained by searching the inpatient database of each hospital. Questionnaire entries were extracted from the clinical records by specialist. Then the differences in rate of PJI revision surgery between hip- and knee- PJI revision cases were calculated and compared. Results: Total of 36 hospitals (87.8%) nationwide reported data on 99 791 hip and knee arthroplasties performed from 2015 to 2017, with 946 revisions due to PJI (0.96%). The overall hip-PJI revision rate was 0.99% (481/48 574), and it was 0.97% (135/13 963), 0.97% (153/15 730) and 1.07% (193/17 881) in of 2015, 2016, 2017, respectively. The overall knee-PJI revision rate was 0.91% (465/51 271), and it was 0.90% (131/14 650), 0.88% (155/17 693) and 0.94% (179/18 982) in 2015, 2016, 2017, respectively. Heilongjiang (2.2%, 40/1 805), Fujian (2.2%, 45/2 017), Jiangsu (2.1%, 85/3 899), Gansu (2.1%, 29/1 377), Chongqing (1.8%, 64/3 523) reported relatively high revision rates. Conclusions: The overall PJI revision rate in 34 hospitals nationwide from 2015 to 2017 is 0.96%. The hip-PJI revision rate is slightly higher than that in the knee-PJI. There are differences in revision rates among hospitals in different regions.

miR-497 inhibits tumor growth and migration of osteosarcoma by targeting plexinA4 and CDK6

MicroRNAs are small non-coding RNAs that regulate gene expression at the post-transcriptional level which have been reported to be involved in the pathogenesis of various cancers. In the present study, we found that miR-497 was downregulated in osteosarcoma tissues. Gain and loss of function studies were carried out to investigate the effect of miR-497 on the growth of osteosarcoma cells. The results indicated that miR-497 inhibited the growth of osteosarcoma cells. Furthermore, bioinformatics analysis predicted plexinA4 and CDK6 as targets of miR-497, which was afterward confirmed by luciferase activity assay and rescue experiments. These findings suggested that miR-497, plexinA4 and CDK6 may serve as novel potential makers for osteosarcoma diagnostics and therapy.

Theoretical investigation on the optical and EPR spectra for Cu2+ -doped ZnO-CdS nanocomposites

The three optical absorption bands and EPR parameters of the [CuO6 ]10- center in the ZnO-CdS composite nanopowders are theoretically studied from the perturbation formulas based on the cluster approach. In the formulas, the contributions to EPR parameters arising from the ligand orbital and spin-orbit coupling interactions via covalence effect are considered. For the studied [CuO6 ]10- cluster, the Cu-O bond lengths are suggested to show a relative elongation ratio ρ (≈ 4.1%) along the z-axis due to Jahn-Teller effect. The defect models suggested in this work are different from the previous assumption that the impurity Cu2+ can replace the host Zn2+ site when it enters the lattices of the ΖnO and ΖnS nanocrystals, forming the tetrahedral [CuΧ4 ]6- clusters (Χ = O, S). The validity of the proposed model is discussed. The differences between the present calculations and the previous ones for the interstitial Cu2+ center in ZnO nanocrystals are analyzed in view of the dissimilar impurity behaviors due to the new composition CdS and distinct preparation conditions.

Determination of InN/Diamond Heterojunction Band Offset by X-ray Photoelectron Spectroscopy

Diamond is not only a free standing highly transparent window but also a promising carrier confinement layer for InN based devices, yet little is known of the band offsets in InN/diamond system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band offset (VBO) of InN/diamond heterostructure. The value of VBO was determined to be 0.39 ± 0.08 eV and a type-I heterojunction with a conduction band offset (CBO) of 4.42 ± 0.08 eV was obtained. The accurate determination of VBO and CBO is important for the application of III-N alloys based electronic devices.

Differential gene expression and functional analysis of pit cells from regenerating rat liver

Hepatic pit cells are a population of large granular lymphocytes that substantially contribute to hepatic immunity. Studies have proven that pit cells have a role in liver regeneration, but the details of the relationship between pit cells and liver regeneration is not clear at present. We subjected rats to a two-third hepatectomy; pit cells with high purity were obtained with Percoll density centrifugation and immunomagnetic bead methods, and the changes in mRNA levels in pit cells from the regenerating liver were monitored up to 168 h using a Rat Genome 230 2.0 Array composed of 25,020 distinct rat liver cDNA clones. Of the 25,020 genes analyzed, 612 known and 358 unknown genes were identified to be associated with liver regeneration. The 612 known genes are classified into up-regulation and down-regulation patterns based on the expression levels; they primarily participate in at least 23 biological activities based on gene ontology analysis. Together with gene function enrichment analysis, cytokines and a growth factor-mediated pathway in pit cells were activated at an early phase of liver regeneration; pit cell proliferation occurred from 24-72 h after liver hepatectomy; the machinery of pit cell differentiation commenced early and came into play late; an immune/inflammatory response was enhanced late. Expression pattern analysis of functionally classified genes in pit cells can give insights into the relationship between pit cells and liver regeneration.

Measurement of w-InN/h-BN Heterojunction Band Offsets by X-Ray Photoemission Spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) of the w-InN/h-BN heterojunction. We find that it is a type-II heterojunction with the VBO being -0.30 ± 0.09 eV and the corresponding conduction band offset (CBO) being 4.99 ± 0.09 eV. The accurate determination of VBO and CBO is important for designing the w-InN/h-BN-based electronic devices.

Orally delivered foot-and-mouth disease virus capsid protomer vaccine displayed on T4 bacteriophage surface: 100% protection from potency challenge in mice

An orally delivered foot-and-mouth disease (FMD) vaccine has not previously been reported. By using a T4 bacteriophage nanoparticle surface gene-protein display system (T4-S-GPDS), we created a foot-and-mouth disease virus (FMDV) entire capsid protein vaccine candidate. On the T4 phage surface SOC site, a full length FMDV capsid precursor polyprotein (P1, 755 aa) and proteinase 3C (213 aa) derived from an infected pig of serotype O strain GD-10 (1999), were separately displayed on different T4 phage particle surfaces through inserting their coding region DNAs into the T4 phage genome, yielding phage strains T4-P1 and T4-3C. We also constructed a series of FMDV sub-full length capsid structural protein (subunit) containing T4 phage recombinant vaccines. Both sucking and young BALB/c mice were used as two kinds of FMDV vaccine potency evaluation models. Many groups of both model mice were vaccinated orally or by subcutaneous injection with varying FMDV-T4 phage recombinant vaccines, with and without addition of adjuvant, then challenged with a lethal dose of cattle source virulent FMDV. In the case of immunization with a mixture of phage T4-P1 and phage T4-3C particles without any adjuvant added, all mice were 100% protected following either oral or injection immunization, whereas 100% of the control, non-immunized mice and mice immunized with only T4 phage vector Z1/Zh(-) or wild-type T4(+)D phage died; in contrast, with FMDV subunit vaccine, less than 75% protection followed the same potency challenge in both mice model groups. In addition, two pigs immunized with a phage T4-P1 and phage T4-3C mix were protected upon housing together with infected pigs. This study represents a clear example of how FMD and other pathogenic disease vaccines can be prepared by a simple and efficient bacteriophage route.

Correlations between cadmium and mineral nutrients in absorption and accumulation in various genotypes of rice under cadmium stress

The absorption and accumulation of Cd2+, Fe3+, Zn2+, Mn2+, Cu2+ and Mg2+ in the roots and leaves of 20 rice cultivars (Oryza sativa L.) with different genotypes under cadmium (Cd) stress were investigated with pot experiments. The results showed that there existed significant differences among the rice cultivars in the contents of six mineral elements in both roots and leaves at both heading and ripening periods. The statistical analysis showed that, for their contents in roots, significant and positive correlations between Cd2+ and Fe3+, Cd2+ and Zn2+, Cd2+ and Mn2+, Cd2+ and Cu2+ existed, but no significant correlation between Cd2+ and Mg2+, at the two periods. In the leaves, Cd also showed significant and positive correlations with Fe3+, Zn2+ and Cu2+ at the both periods, but a significant and negative correlation with Mn2+ and no significant correlation with Mg2+ at heading, a significant and positive correlation with Mg2+ and no significant correlation with Mn2+ at ripening. These results suggested that there were cooperative absorption between Cd2+ and Fe3+, Mn2+, Cu2+, Mn2+ in rice plants. Genotypic differences in Cd uptake and translocation among the rice cultivars suggested that paddy field of some rice cultivars may be irrigated with partially treated sewage water.

Clinical significance of P-glycoprotein immunohistochemistry and doxorubicin binding assay in patients with osteosarcoma

In 45 osteosarcoma patients, mean age 18 (4-61) years and followed for 14 (5-48) months, we studied the sensitivity to doxorubicin as well as P-glycoprotein expression, and compared these with the extent of tumour necrosis following chemotherapy. Doxorubicin assay was positive in 37 patients in whom necrosis induced by chemotherapy was good in 20 and poor in 17. Metastases developed in nine patients. In eight patients in whom doxorubicin assay indicated tumour resistance, chemonecrosis was poor and all developed pulmonary metastases. P-glycoprotein was studied in pre-treatment biopsies and post-treatment resection specimens. Its expression was positive in 16 patients in whom the necrosis induced by chemotherapy was good in four and poor in 12. In 29 patients with negative P-glycoprotein expression, necrosis was good in 16 and poor in 13. The doxorubicin sensitivity had a high correlation with chemonecrosis (P=0.006) and the incidence of metastases (P<0.001). However, P-glycoprotein expression at the time of diagnosis did not correlate statistically with chemonecrosis (P=0.066). Doxorubicin sensitivity prior to treatment is a better determinant of the response to chemotherapy and clinical outcome than is the P-glycoprotein expression.

A case-control study of microsomal epoxide hydrolase, smoking, meat consumption, glutathione S-transferase M3, and risk of colorectal adenomas

We estimated associations between polymorphisms in the gene encoding microsomal epoxide hydrolase (mEH) among 464 cases diagnosed with first occurrence of colorectal adenoma and 510 matched controls. In an analysis controlling only for the matching variables, we found little or no association between adenoma and mEH genotypes defined by polymorphisms at either codon 113 and 139 or mEH activity predicted by both polymorphisms. However, in subsequent analyses, high predicted mEH activity was significantly associated with adenoma among certain subgroups defined by smoking history [odds ratio (OR), 4.27; 95% confidence interval (CI), 1.68-10.81 among current smokers; interaction, P = 0.11], meat consumption (OR, 2.47; CI, 0.99-6.19 among individuals who regularly eat well-done meat; interaction, P = 0.03), and genotypes for the *A/*B polymorphism in the gene encoding glutatione S-transferase M3 (OR, 2.60; CI, 1.28-5.28 among individuals with *A*A genotype; interaction, P = 0.03). These findings are consistent with causal roles for environmental polycyclic aromatic hydrocarbons and genetically encoded variants in enzymes whose actions lead to the production of activated polycyclic aromatic hydrocarbon metabolites.

High-Resolution Study of the (v(1) + 12v(2) + v(3) = 3) Polyad of Strongly Interacting Vibrational Bands of D(2)O

Analysis of the high-resolution Fourier transform spectra of the D(2)O first decade was carried out in the framework of the Hamiltonian model which took into account resonance interactions between the seven states, (300), (201), (102), (003), (220), (121), and (022). Assigned from the experimentally recorded spectrum transitions belonged to the four bands, 2nu(1) + nu(3), 3nu(3), nu(1) + 2nu(2) + nu(3), and 3nu(1), gave the possibility both of obtaining rotational, centrifugal distortion, and resonance interaction parameters of "appeared" states, (201), (003), (121), and (300), and of estimating from the fit band centers, rotational, and resonance interaction parameters of the three "dark" states, (220), (022), and (102). Copyright 2000 Academic Press.

High-Resolution Study of Strongly Interacting Vibrational Bands of HDO in the Region 7600-8100 cm(-1)

The high-resolution Fourier transform spectrum of the HDO molecule was recorded and analyzed in the region 7600-8100 cm(-1) where the weak vibration-rotation bands 3nu(1) and nu(1) + nu(2) + nu(3) are located. Because of the presence of strong local resonance interactions, transitions belonging to the 3nu(2) + nu(3) and 6nu(2) bands were assigned as well. Spectroscopic parameters of all four bands were estimated, which reproduce initial line positions with accuracy close to experimental uncertainties. Copyright 2000 Academic Press.

Absorption Intensity of Stretching Overtone States of Silane and Germane

The band absorbance and line absorbance of R branch transitions are obtained from high-resolution Fourier transform measurement of silane and germane local mode overtones (n000), n = 1-5, under proper sample pressures and absorption lengths. The absorption coefficients of these overtones are derived by linear least-squares fitting. The relative intensities of overtones can be satisfactorily reproduced with the bond dipole model containing two adjustable parameters. Copyright 1998 Academic Press.

Monoamine oxidase gene transcription in human cell lines: treatment with psychoactive drugs and ethanol

In the present study transcriptional activities has been measured with different fragments of the 5'-flanking sequence of the human monoamine oxidase (MAO) genes linked to human growth hormone which was used as a reporter gene. SH-SY5Y neuroblastoma cells and 1242 MG glioma cells were compared under basal conditions as well as after treatments with different drugs. Under basal conditions, the relative reporter activities of the different promoter fragments were similar for both cell lines. No changes in promoter activities, were observed when cells were treated with L-deprenyl, lithium chloride or raclopride. In contrast, increases (2-3-fold) in both reporter gene expression and enzyme activity were observed after ethanol treatment of cells transfected with MAO-B fragments. Gel retardation analysis showed that ethanol caused changes in transcription factor binding to the MAO-B core promoter in both the SH-SY5Y and 1242 MG cell lines in a cell-type specific fashion.

Characterization of the human 5-HT2A receptor gene promoter

The regulation of 5-HT2A receptor (5-HT2AR) expression has been implicated in a variety of pathological processes and has been shown to be extremely complicated and controversial. In order to understand the mechanisms of regulation of this receptor, it is important to characterize its promoter. In this report, the 5' end of the human 5-HT2AR gene was cloned and characterized. Anchored PCR mapped multiple transcription initiation sites at nucleotides -1157, -1137, -1127, and -496. Transfection of chimeric growth hormone plasmids containing various DNA fragments into 5-HT2AR-positive human cell lines (SHSY-5Y, neuroblastoma; HeLa, cervix carcinoma) showed that the 0.74 kb HaeIII/PvuII fragment, which encompasses the initiation sites between -1157 and -1127 and 5' of the downstream initiation site (at -496), exhibited significant promoter activity. This promoter activity was not affected by the sequence upstream of the 0.74 kb fragment. The sequence downstream (the 0.45 kb PvuII/SmaI fragment) strongly repressed this promoter activity, suggesting the presence of a silencer. Sequence analysis combined with gel retardation and Dnase 1 footprinting assay identified multiple cis and trans elements for this fragment, including Sp1, PEA3, cyclic AMP response element (CRE)-like sequence, and E-boxes. Two novel transcription factors have been detected by gel retardation and DNase 1 footprinting assay; one of them may be specific for human. The transcription factors and promoter activities were low in the negative cell line NCI-H460 (human lung large cell carcinoma). Interestingly, the 0.39 kb fragment, isolated from the 3' end of the 0.74 kb fragment, exhibited the highest promoter activity. The possibility that this 0.39 kb fragment may be an alternative promoter is discussed. These new data are essential for further study of the regulation of 5-HT2AR gene expression.

Bidirectional promoter of human monoamine oxidase A (MAO A) controlled by transcription factor Sp1

The core promoter region of human monoamine oxidase (MAO) A has been identified in the two 90 bp repeat sequences, which can be further divided into four imperfect tandem repeats, each containing an Sp 1 binding site in the reversed orientation. Gel retardation and DNase 1 footprinting assays identified Sp 1 to be the major transcription factor binding to MAO A core promoter. In addition, positive association has been observed between cellular Sp1 concentration and MAO A promoter or catalytic activity, indicating that Sp1 is a controlling factor for human MAO A expression. DNA fragments from MAO A core promoter exhibit promoter activity in both orientations in a transient transfection assay, using human growth hormone as the reporter gene. A DNA probe isolated from upstream of the core promoter detected positive signals in a Northern analysis, suggesting that the reverse promoter activity may endogenously transcribe a new gene located upstream of MAO A.

[The measurement of collagen and proteoglycan contents in nucleus pulposus of lumbar intervertebral disc]

The collagen and proteoglycan contents were determined in lumbar intervertebral disc nucleus from 50 cases normal Chinese with accidental death and in that of 50 cases of prolapsed lumbar intervertebral disc (PID). The significance of the work rested with. (1) The normal range of the collagen and proteoglycan contents in the nucleus pulposus of normal Chinese was defined, therefore, it provided a normal parameter and laid a foundation for the study of collagen and proteoglycan metabolic changes in the nucleus pulposus of lumbar intervertebral disc under pathological condition. (2) By comparison of contents between collagen and proteoglycan in the nucleus pulposus of PID, the physiopathology of PID was confirmed further, that is, the content of proteoglycan of the nucleus pulposus in PID decreased, however, that of collagen increased. (3) The collagen contents between fibrocartilage and nucleus pulposus in normal chinese were compared. Analyses were made biomechanically and biochemically.

Development of a real-time adaptive current tomograph

Following the successful development of a multiple-drive electrical impedance tomography system OXPACT-II featuring a voltage-driven current method for in vitro studies, research work currently being undertaken at the EIT research group in Oxford is aimed at developing a real-time multiple-drive adaptive system, called the Oxford Brookes Adaptive Current Tomograph Mark-III (OXBACT-III) which will operate at several frequencies in between 10-160 kHz. The objective of this system development is to enable EIT clinical studies to be undertaken based on the adaptive current method. One of the most important issues addressed in the new system design is to achieve high data acquisition speed while maintaining sufficient system accuracy. This paper will describe the overall data acquisition system structure and relevant system performance specifications.

A high output impedance current source

A high output impedance current source was required for electrical impedance tomography (EIT) applications capable of operating up to 200 kHz. The architecture is based on operational-amplifier power-supply current sensing and produces a predominantly capacitive output impedance, which for the design presented is approximately 1.2 pF.

Identification of human monoamine oxidase (MAO) A and B gene promoters

The promoter of human monoamine oxidase (MAO) A and B genes have been identified. The core promoter region of MAO A is comprised of two 90 bp repeats each of which contains two Sp1 elements and lacks a TATA box. The MAO B core promoter region contains two sets of overlapping Sp1 sites which flank a CACCC element all upstream of a TATA box. The different organization of the MAO A and B promoters may underlie their different cell and tissue specific expression.

[Measurement of collagen content in articular cartilage of normal Chinese]

We determine the collagen contents of fresh articular cartilage from 188 normal Chinese who died in accidents. Among them, the collagen content of femoral head cartilage (104 cases) was 496 +/- 35mg/g, femoral condyle cartilage (62) 456 +/- 38mg/g, and humeral head cartilage 588 +/- 42mg/g. The normal range of collagen contents in Chinese articular cartilage was defined for the pathological studies of collagen metabolic changes in cartilage. The collagen contents of the non-loading areas were evidently higher than those of the loading ones. The more pressure the cartilage beared, the less collagen contents it contained. In our experiment, the disturbances of "free" hydroxyproline were eliminated by analysing hydroxyproline with rehydrolysis after extraction with heated trichloroacetic acid.

Structure and promoter organization of the human monoamine oxidase A and B genes

Monoamine oxidase (MAO) A and B play an important role in regulating levels of biogenic amines. MAO A and B cDNAs have been cloned and the deduced amino acids share 73% sequence identity. The genes for MAOA and B are comprised of 15 exons interspersed by 14 introns, span at least 60 kb and exhibit identical exon-intron organization. These findings suggest that the MAOA and MAOB genes are derived from the duplication of a common ancestral gene. The core promoter region of MAOA is comprised of two 90 bp repeats, each of which contains two Spl elements and lacks a TATA box. The MAOB core promoter region contains two sets of overlapping Spl sites which flank a CACCC element all upstream of a TATA box. The different organization of the MAOA and MAOB promoters may underlie their different cell and tissue specific expression.

Electrical impedance tomography. Electrode current determination from programmable voltage sources

The accuracy requirements for adaptive current electrical impedance tomography (EIT) measurements exceed the capability of available current sources. A new architecture for an EIT system is described in which the electrode current is set indirectly from a voltage-drive structure. A numerically inverted admittance matrix, obtained from current measurements and driving voltages, has been used to achieve the desired current pattern from programmable voltage sources.

Electrical impedance tomography. Improved wideband, high CMRR (common mode rejection ratio) instrumentation amplifier

A wideband high CMRR instrumentation amplifier is described. Based on a previously reported current-mode design, the improved amplifier features excellent CMRR performance of better than 60 dB up to 200 kHz with unity differential gain.

Promoter organization and activity of human monoamine oxidase (MAO) A and B genes

Monoamine oxidase A and B (MAO A and B) play important roles in the metabolism of biogenic and dietary amines and are encoded by two genes derived from a common ancestral gene. The promoter regions for human MAO A and B genes have been characterized using a series of 5' flanking sequences linked to a human growth hormone reporter gene. When these constructs were transfected into NIH3T3, SHSY-5Y, and COS7 cells, the maximal promoter activity for MAO A was found in a 0.14 kilobase (kb) PvuII/DraII fragment (A0.14) and in a 0.15 kb PstI/NaeI fragment (B0.15) for MAO B. Both fragments are GC-rich, contain potential Sp1 binding sites, and are in the region where the MAO A and B 5' flanking sequences share the highest identity (approximately 60%). However, the organization of the transcription elements is distinctly different between these two promoters. Fragment A0.14 consists of three Sp1 elements, all in reversed orientations, and lacks a TATA box. Two of the Sp1 sites are located within the downstream 90 base pair (bp) direct repeat, and the third is located at the 3' end of the upstream 90 bp direct repeat. Fragment B0.15 contains an Sp1-CACCC-Sp1-TATA structure; deletion of any of these elements reduced promoter activity. Additional Sp1 sites, CACCC elements, CCAAT boxes, and direct repeats (four 30 bp direct repeats in MAO A and two 29 bp direct repeats in MAO B) are found in farther-upstream sequences of both genes (1.27 kb for MAO A and mostly in 0.2 kb for MAO B). Inclusion of these sequences decreased promoter activity. The different promoter organization of MAO A and B genes provides the basis for their different tissue- and cell-specific expression.

[Peripheral nerves injection injury: the clinical and experimental study]

The results of operative management of peripheral nerve postinjection injuries in 58 patients are reported. Neurolysis is one effective method in treating nerve postinjection injuries with excellent and good results observed in 64.6 percent of patients in this series. We also investigated the early changes in neurophysiological, histological and ultrastructural studies in the peroneal nerve of the rabbit. The results from early exploration and 0.9% NaCl irrigation were compared with those from late extraneural and intraneural neurolysis. The results showed that the injury occurs early in the nerve following intrafacicular injection and may proceed quickly to a certain degree of severity, so timely operation is advisable early incision of the epineurium with saline irrigation is superior to the neurolysis in treating nerve injuries as proved by the experimental study which suggests that the former can be used as an emergency operation for the management of this type of nerve injuries.

Direct interaction between the internal NADH: ubiquinone oxidoreductase and ubiquinol:cytochrome c oxidoreductase in the reduction of exogenous quinones by yeast mitochondria

The reduction of duroquinone (DQ) and 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB) by NADH and ethanol was investigated in intact yeast mitochondria with good respiratory control ratios. In these mitochondria, exogenous NADH is oxidized by the NADH dehydrogenase localized on the outer surface of the inner membrane, whereas the NADH produced by ethanol oxidation in the mitochondrial matrix is oxidized by the NADH dehydrogenase localized on the inner surface of the inner membrane. The reduction of DQ by ethanol was inhibited 86% by myxothiazol; however, the reduction of DQ by NADH was inhibited 18% by myxothiazol, suggesting that protein-protein interactions between the internal (but not the external) NADH: ubiquinone oxidoreductase and ubiquinol:cytochrome c oxidoreductase (the cytochrome bc1 complex) are involved in the reduction of DQ by NADH. The reduction of DQ and DB by NADH and ethanol was also investigated in mutants of yeast lacking cytochrome b, the iron-sulfur protein, and ubiquinone. The reduction of both quinone analogues by exogenous NADH was reduced to levels that were 10 to 20% of those observed in wild-type mitochondria; however, the rate of their reduction by ethanol in the mutants was equal to or greater than that observed in the wild-type mitochondria. Furthermore, the reduction of DQ in the cytochrome b and iron-sulfur protein lacking mitochondria was myxothiazol sensitive, suggesting that neither of these proteins is an essential binding site for myxothiazol. The mitochondria from the three mutants also contained significant amounts of antimycin- and myxothiazol-insensitive NADH:cytochrome c reductase activity, but had no detectable succinate:cytochrome c reductase activity. These results suggest that the mutants lacking a functional cytochrome bc1 complex have adapted to oxidize NADH.

Unique organization of the human BCR gene promoter

The promoter of the human BCR gene, regulating the transcription of the chimeric BCR/ABL mRNA in leukemia, has been isolated and characterized. A region of 1.1 kb immediately 5' to the transcription start site was analyzed in detail by sequencing, DNase 1 footprinting, gel retardation and functional studies. These experiments localized a minimal promoter to a 650 bp sequence, composed of 270 bp of 5' flanking sequences and 380 bp of exon 1 transcribed sequences. The promoter region includes a TTTAA box, one Sp1 site and a novel protein-binding sequence absolutely necessary for efficient transcription in vivo. Six additional protein-binding regions were identified more to the 5'. Of these, one is found in an inverted repeat in the 3' coding and splice donor region of BCR exon 1.

Characterization of the human ABL promoter regions

Gel retardation and DNAase 1 footprinting experiments have been performed to characterize the promoter sequences of exon 1a and 1b of the human ABL gene. Several Sp1 motifs and CCAAT boxes are found to be protected by nuclear proteins in the 1b promoter but none of the 7 reported Sp1 sites in 1a were found to bind protein. Multiple sets of initiation sites seem to exist in the 1b promoter region which may represent individual initiation sites, distributed over a DNA region of up to 700 bp. Starting with the most distal initiation site, 1a and 1b ABL promoter sequences show a high degree of homology, suggesting that one is derived from the other. However, multiple evolutionary changes in the 1a promoter sequence indicate that type 1a ABL expression may be differently regulated than 1b.

Reduction of exogenous quinones and 2,6-dichlorophenol indophenol in cytochrome b-deficient yeast mitochondria: a differential effect on center i and center o of the cytochrome b-c1 complex

The reduction of duroquinone (DQ), 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB), and dichlorophenol indophenol (DCIP) by succinate and NADH was investigated in yeast mitochondria which have no spectrally detectable cytochrome b. Succinate reduces DB in the cytochrome b-deficient mitochondria at rates comparable to that observed in wild-type mitochondria, suggesting that succinate:ubiquinone oxidoreductase is unaffected by the lack of cytochrome b. In the mutant mitochondria, succinate does not reduce DQ or DCIP at significant rates; however, NADH reduces both DQ and DCIP at rates similar to that of the wild-type mitochondria in a myxothiazol, but not antimycin, sensitive reaction. The Ki for myxothiazol in this reaction is close to that for electron transfer through the cytochrome b-c1 complex. In addition, myxothiazol does not inhibit NADH:ubiquinone oxidoreductase. These results confirm our previous suggestion that the cytochrome b-c1 complex is involved in electron transfer from the primary dehydrogenases to DQ and DCIP and suggest that cytochrome b is not the binding site for myxothiazol.

The interaction of quinone analogues with wild-type and ubiquinone-deficient yeast mitochondria

The interaction of the exogenous quinones, duroquinone (DQ) and the decyl analogue of ubiquinone (DB) with the mitochondrial respiratory chain was studied in both wild-type and a ubiquinone-deficient mutant of yeast. DQ can be reduced directly by NADH dehydrogenase, but cannot be reduced by succinate dehydrogenase in the absence of endogenous ubiquinone. The succinate-driven reduction of DQ can be stimulated by DB in a reaction inhibited 50% by antimycin and 70-80% by the combined use of antimycin and myxothiazol, suggesting that electron transfer occurs via the cytochrome b-c1 complex. Both DQ and DB can effectively mediate the reduction of cytochrome b by the primary dehydrogenases through center o, but their ability to mediate the reduction of cytochrome b through center i is negligible. Two reaction sites for ubiquinol seem to be present at center o: one is independent of endogenous Q6 with a high reaction rate and a high Km; the other is affected by endogenous Q6 and has a low reaction rate and a low Km. By contrast, only one ubiquinol reaction site was observed at center i, where DB appears to compete with endogenous Q6. DB can oxidize most of the pre-reduced cytochrome b, while DQ can oxidize only 50%. On the basis of these data, the possible binding patterns of DB on different Q-reaction sites and the requirement for ubiquinone in the continuous oxidation of DQH are discussed.

Direct interaction between yeast NADH-ubiquinone oxidoreductase, succinate-ubiquinone oxidoreductase, and ubiquinol-cytochrome c oxidoreductase in the reduction of exogenous quinones

The reduction of the following exogenous quinones by succinate and NADH was studied in mitochondria isolated from both wild type and ubiquinone (Q)-deficient strains of yeast: ubiquinone-0 (Q0), ubiquinone-1 (Q1), ubiquinone-2 (Q2), and its decyl analogue 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB), duroquinone (DQ), menadione (MQ), vitamin K1 (2-methyl-3-phytyl-1,4-naphthoquinone), the plastoquinone analogue 2,3,6-trimethyl-1,4-benzoquinone (PQOc1), plastoquinone-2 (PQ2), and its decyl analogue (2,3-dimethyl-6-decyl-1,4-benzoquinone). Reduction of the small quinones DQ, Q0, Q1, and PQOc1 by NADH occurred in both wild type and Q-deficient mitochondria in a reaction inhibited more than 50% by myxothiazol and less than 20% by antimycin. The reduction of these small quinones by succinate also occurred in wild type mitochondria in a reaction inhibited more than 50% by antimycin but did not occur in Q-deficient mitochondria suggesting that endogenous Q6 is involved in their reduction. In addition, the inhibitory effects of antimycin and myxothiazol, specific inhibitors of the cytochrome b-c1 complex, on the reduction of these small quinones suggest the involvement of this complex in the electron transfer reaction. By contrast, the reduction of Q2 and DB by succinate was insensitive to inhibitors and by NADH was 20-30% inhibited by myxothiazol suggesting that these analogues are directly reduced by the primary dehydrogenases. The dependence of the sensitivity to the inhibitors on the substrate used suggests that succinate-ubiquinone oxidoreductase interacts specifically with center i (the antimycin-sensitive site) and NADH ubiquinone oxidoreductase preferentially with center o (the myxothiazol-sensitive site) of the cytochrome b-c1 complex. The NADH dehydrogenase involved in the myxothiazol-sensitive quinone reduction faces the matrix side of the inner membrane suggesting that center o may be localized within the membrane at a similar depth as center i.

Subunit VII, the ubiquinone-binding protein, of the cytochrome b-c1 complex of yeast mitochondria is involved in electron transport at center o and faces the matrix side of the membrane

The functional role and topographical orientation in the inner membrane of subunit VII, the ubiquinone-binding protein, of the cytochrome b-c1 complex of yeast mitochondria has been investigated. The apparent molecular weight of this subunit on sodium dodecyl sulfate-urea gels was calculated to be 15,500, while its amino acid composition was similar to that of the Q-binding proteins present in the cytochrome b-c1 complexes isolated from both beef heart and yeast mitochondria. The specific antibody obtained against subunit VII inhibited 30-47% of the ubiquinol-cytochrome c reductase activity in the isolated cytochrome b-c1 complex and in submitochondrial particles but had no effect on cytochrome c reductase activity in mitoplasts, mitochondria from which the outer membrane has been removed. Furthermore, the antibody against subunit VII strongly inhibited (74%) the reduction of cytochrome b by succinate in the presence of antimycin, an inhibitor of center i, but had no effect on cytochrome b reduction in the presence of myxothiazol, an inhibitor of center o. These results suggest that subunit VII, the Q-binding protein, is involved in electron transport at center o of the cytochrome b-c1 complex of the respiratory chain and that subunit VII is localized facing the matrix side of the inner mitochondrial membrane.

The effect of ring substituents on the mechanism of interaction of exogenous quinones with the mitochondrial respiratory chain

In uncoupled pig-heart mitochondria the rate of the reduction of duroquinone by succinate in the presence of cyanide is inhibited by about 50% by antimycin. This inhibition approaches completion when myxothiazol is also added or British anti-Lewisite-treated (BAL-treated) mitochondria are used. If mitochondria are replaced by isolated succinate:cytochrome c oxidoreductase, the inhibition by antimycin alone is complete. The reduction of a plastoquinone homologue with an isoprenoid side chain (plastoquinone-2) is strongly inhibited by antimycin with either mitochondria or succinate:cytochrome c reductase. The reduction by succinate of plastoquinone analogues with an n-alkyl side chain in the presence of mitochondria is inhibited neither by antimycin nor by myxothiazol, but is sensitive to the combined use of these two inhibitors. On the other hand, the reduction of the ubiquinone homologues Q2, Q4, Q6 and Q10 and an analogue, 2,3-dimethoxyl-5-n-decyl-6-methyl-1,4-benzoquinone, is not sensitive to any inhibitor of QH2:cytochrome c reductase tested or their combined use, either in normal or BAL-treated mitochondria or in isolated succinate:cytochrome c reductase. It is concluded that quinones with a ubiquinone ring can be reduced directly by succinate:Q reductase, whereas those with a plastoquinone ring can not. Reduction of the latter compounds requires participation of either center i or center o (Mitchell, P. (1975) FEBS Lett. 56, 1-6) or both, of QH2:cytochrome c oxidoreductase. It is proposed that a saturated side chain promotes, while an isoprenoid side chain prevents reduction of these compounds at center o.

Rapid redox equilibrium between the mitochondrial Q pool and cytochrome b during triphasic reduction of cytochrome b by succinate

The reliability of monitoring the redox reactions of cytochrome b using the different wavelengths employed by different authors has been reexamined. It was found that 562-575 nm is suitable in succinate: cytochrome c reductase but not in mitochondria, in which case 562-540 nm is a better pair. Direct optical measurements of the redox reaction kinetics of the mitochondrial Q pool using a commercial dual-wavelength spectrophotometer are possible when succinate is used as the electron donor. Using the correct wavelength pair, and with malonate to slow down the electron input, the reduction course of cytochrome b was still triphasic but a plateau or a turn replaced the oxidation phase previously reported by several authors. At the same time, the reduction course of the Q pool was also triphasic, and in perfect match with that of cytochrome b. Destruction of the Rieske iron-sulfur cluster by British anti-Lewisite (BAL) + O2 treatment or prereduction of the high-potential components made the reduction of both Q and b monophasic. The plot of log (Q/QH2) against log (b3+/b2+) gave a straight line with an n value of 1.7 for cytochrome b at pH 7.4. This n value rose to 2.0 at pH 6.5 and dropped to 1.4 at pH 8.5. On the other hand, the mid-point potential of cytochrome b relative to that of the Q pool remained essentially unchanged between pH 6.5 and 8.4. BAL treatment had a small effect on the midpoint potential of cytochrome b relative to that of the Q pool and had no effect on the n value. Addition of quinone homologues and analogues extended the plateau phase in the reduction of cytochrome b, but exogenous quinones did not equilibrate rapidly with cytochrome b. It was concluded that the appearance of the plateau between the two reduction phases of Q and b is caused by the rapid delivery of electrons to the high-potential components of the respiratory chain as envisaged in the Q cycle; the unexpected n value for cytochrome b suggests a concerted reduction by QH2 of two species of cytochromes b-562.

Flash-induced electron transfer through mitochondrial QH2: cytochrome c oxidoreductase in the presence of bacterial reaction centres and cytochrome c. Analysis of subsequent processes and effect of inhibitors

In a system containing reaction centres isolated from Rhodopseudomonas sphaeroides mutant R26, and variable amounts of horse-heart cytochrome c and bovine-heart mitochondrial QH2: cytochrome c oxidoreductase in a medium containing 2 mM ascorbate and 0.1 microM phenazine methosulphate, electron transfer was induced by a single flash. Three distinct phases of electron transfer can be distinguished: the first event is the oxidation of cytochrome c, and this is followed by an equilibration between cytochrome c, cytochrome c1 and the Rieske [2Fe-2S] cluster. The actual rates of these processes depend on the concentrations of cytochrome c and the reductase. The slower third phase is the oxidation of ubiquinol, which can follow two pathways: one sensitive to antimycin and one sensitive to myxothiazole. The antimycin-sensitive pathway (t1/2 approximately equal to 10 ms) is an equilibration between the Q/QH2 couple and cytochrome b, but may also include a direct reduction of cytochrome b by the QB of the reaction centres. The myxothiazole-sensitive pathway is a coupled reduction of cytochrome b and the Rieske [2Fe-2S] cluster which rapidly equilibrates with cytochromes c1 and c. Both pathways are sensitive to 7-(n-heptadecyl)mercapto-6-hydroxy-5,8-quinoline quinone, but with different affinities. In the absence of inhibitors the initial reduction of cytochrome b (via both pathways) is followed by a net oxidation which is the resultant of a continuing reduction (together with the reduction of the Rieske [2Fe-2S] cluster) and an oxidation (via the antimycin-sensitive site) by quinone. The results are discussed in the light of linear and cyclic models proposed to explain electron transfer between cytochromes b and c. It is concluded that only the Q-cycle model fits the present experimental data.

Kinetics of flash-induced electron transfer between bacterial reaction centres, mitochondrial ubiquinol:cytochrome c oxidoreductase and cytochrome c

Ascorbate-reduced horse heart cytochrome c reduces photo-oxidized bacterial reaction centres with a second-order rate constant of (5-8) X 10(8) M-1 X s-1 at an ionic strength of 50 mM. In the absence of cytochrome c, the cytochrome c1 in the ubiquinol:cytochrome c oxidoreductase is oxidized relatively slowly (k = 3.3 X 10(5) M-1 X s-1). Ferrocytochrome c binds specifically to ascorbate-reduced reductase, with a Kd of 0.6 microM, and only the free cytochrome c molecules are involved in the rapid reduction of photo-oxidized reaction centres. The electron transfer between ferricytochrome c and ferrocytochrome c1 of the reductase is rapid, with a second-order rate constant of 2.1 X 10(8) M-1 X s-1 at an ionic strength of 50 mM. The rate of electron transfer from the Rieske iron-sulphur cluster to cytochrome c1 is even more rapid. The cytochrome b of the ubiquinol:cytochrome c oxidoreductase can be reduced by electrons from the reaction centres through two pathways: one is sensitive to antimycin and the other to myxothiazol. The amount of cytochrome b reduced in the absence of antimycin is dependent on the redox potential of the system, but in no case tested did it exceed 25% of the amount of photo-oxidized reaction centres.

Identification of two different Q-binding sites in QH2-cytochrome c oxidoreductase, using the Q analogue n-heptadecylmercapto-6-hydroxy-5,8-quinolinequinone

The pK and mid-point redox potential of the Q-analogue 7-(n-heptadecyl)mercapto-6-hydroxy-5,8-quinolinequinone (HMHQQ) in aqueous medium are so low that under the experimental conditions used for studying the inhibition of electron transfer in submitochondrial particles only the oxidized, anionic form is present. The KD of the analogue, determined by comparing its inhibitory effect with that of n-heptyl-4-hydroxyquinoline N-oxide, is (0.003 + 0.24 x mg protein/ml) microM. The inhibition of succinate oxidation is pH dependent, due to a pH-dependent change in the overcapacity of the QH2-oxidizing system above the Q-reducing system. If the terminal part of the respiratory chain is reduced with ascorbate, the analogue inhibits the reduction of cytochrome b by substrate in the presence of antimycin with a similar KD value. In the absence of ascorbate the KD value is 100-times higher. The reduction of cytochrome b by substrate in particles treated with 2,3-dimercaptopropanol (BAL) + O2 is also sensitive to HMHQQ, with a KD value in between the two values given above. It is concluded that the QH2 oxidase system contains two different sites for interaction with ubiquinone. The site responsible for the inhibition of steady-state electron transfer is near the Fe-S cluster, as is shown by the sensitivity to the redox state of this cluster and by the effect of HMHQQ on the EPR signal of the reduced cluster. The second site, which is similar to the antimycin-binding site, is occupied only at higher concentrations of inhibitor. The affinity of HMHQQ for this site is not affected by the redox state of the Fe-S cluster.

On the role of ubiquinone in the respiratory chain

(1) The V1 (substrate-Q oxidoreductase activity) and V2 (QH2 oxidase activity) for the oxidation of substrates by submitochondrial particles have been measured by using heptylhydroxyquinoline N-oxide (HQNO) as inhibitor of V2. (2) Partial destruction of the Rieske Fe-S cluster by treatment with Bal (2,3-dimercaptopropanol) + O2 has the same effect on the QH2 oxidase activity as partial saturation of the antimycin-binding site with HQNO. (3) The extent of the rapid reduction of cytochrome b in the presence of excess antimycin is proportional to the percentage of intact Rieske Fe-S cluster. (4) The measured rate of oxidation of endogenous ubiquinol (V2) by submitochondrial particles is dependent on the substrate used to reduce ubiquinone, especially at low levels of ubiquinone. (5) Pool-function kinetics in the oxidation of substrate, found both in the presence and absence of free ubiquinone, are due both to the pool of free ubiquinone and to direct collision between Q-loaded Q-reducing and -oxidizing enzymes. At infinite Q content only the former mechanism is operative; at low Q content only the latter. (6) Duroquinone can be reduced directly by NADH dehydrogenase without mediation of ubiquinone, but duroquinol cannot be oxidized in the absence of ubiquinone. On the other hand, the reduction of cytochrome b by duroquinol does not require the presence of ubiquinone. (7) It is suggested that the need for ubiquinone for the oxidation of duroquinol is due to the requirement of ubisemiquinone for the oxidation of cytochrome b, duroquinol not being able to form a stabilized semiquinone.