[Influence of proximal two-wall bone defect on periodontal ligament stresses under normal occlusal forces]

Objective: To study the influence of two-wall bone defect on periodontal ligament stresses under normal occlusal forces, and to analyze the influence of depth and width of bone defect to periodontal ligament stresses. Methods: Three-dimensional finite element models of teeth, periodontal ligament and alveolar bone were created based on cone beam CT images. Proximal two-wall bone defect with different depths (bone defect occupies one third, two thirds, and full length of root) and widths (bone defect occupies one fourth, two fourths, three fourths and full width of buccal lingual width) were simulated by modifying the elastic modulus of elements within defect areas. Occlusal forces with magnitudes of half of the maximum occlusal forces were applied to the model at an angle of 45° to the long axis of tooth, and equivalent stresses of periodontal ligament were analyzed. Results: In the model of no bone defect, the equivalent stresses of periodontal ligament of incisors, canines, premolars and molars were 2.88, 2.31, 8.67 and 7.53 MPa respectively. The equivalent stresses of periodontal ligament increased with the enlargement of depth and width of bone defect. The equivalent stresses of periodontal ligament with maximum bone defect in both depth and width for incisors, canines, premolars and molars were 4.47, 3.62, 11.66 and 8.72 MPa respectively. In the model of width of bone defect was consistent and bone defect develops vertically, the increments of equivalent stresses of periodontal ligament were significantly greater in the early stage bone defect model (from no defect to one third of root length bone defect) than that in the later stage bone defect model (from two thirds to full length of root length bone defect). In the model of bone defect depth was consistent and bone defect develops transversely, the increments of equivalent stresses of periodontal ligament in the early stage bone defect model (from no defect to one fourth of buccal lingual width bone defect) were significantly smaller than that in the later stage bone defect model (from three fourths to full width of buccal lingual width bone defect). Conclusions: Bone defect with shallow depth and that with large width would increase periodontal ligament stresses. Therefore, more attention should be paid to occlusion evaluation and adjustment for teeth with shallow and wide two-wall bone defect.

High-dose dexamethasone or all-trans-retinoic acid restores the balance of macrophages towards M2 in immune thrombocytopenia

Essentials M1/M2 imbalance is involved in many autoimmune diseases, and could be restored. The expressions and functions of M1 and M2 were investigated in an in vitro culture system. A preferred M1 polarization is involved in the pathogenesis of immune thrombocytopenia (ITP). High-dose dexamethasone or all-trans-retinoic acid restores M1/M2 balance in ITP patients.

SUMMARY

Background Immune thrombocytopenia (ITP) is an autoimmune disorder. Deficiency of immune tolerance in antigen-presenting cells and cross-communication between antigen-presenting cells and T cells are involved in the pathogenesis of ITP. Macrophages can polarize into proinflammatory M1 or anti-inflammatory M2 phenotypes in response to different environmental stimuli, and have diverse immunologic functions. Objectives To investigate the M1/M2 imbalance in ITP and whether high-dose dexamethasone (HD-DXM) or all-trans-retinoic acid (ATRA) could restore this imbalance. Methods The numbers of M1 and M2 macrophages in the spleens of ITP patients and patients with traumatic spleen rupture were analyzed by immunofluorescence. Monocyte-derived macrophages were cultured and induced with cytokines and drugs. The expression of M1 and M2 markers and functions of M1 and M2 macrophages before and after modulation by HD-DXM or ATRA were evaluated with flow cytometry and ELISA. Results There was preferred M1 polarization in ITP spleens as compared with healthy controls. Monocyte-derived macrophages from ITP patients had increased expression of M1 markers and impaired immunosuppressive functions. Either HD-DXM or ATRA corrected this imbalance by decreasing the expression of M1 markers and increasing the expression of M2 markers. Moreover, HD-DXM-modulated or ATRA-modulated macrophages suppressed both CD4+ and CD8+ T-cell proliferation and expanded CD4+ CD49+ LAG3+ type 1 T-regulatory cells. HD-DXM or ATRA modulated macrophages to shift the T-cell cytokine profile towards Th2. Treating patients with HD-DXM or ATRA revealed that macrophages induced from responders showed a predominant M2-like phenotype and immunosuppressive function. Conclusions Aberrant macrophage polarization is involved in the pathogenesis of ITP. Either HD-DXM or ATRA is able to correct this imbalance.

[Prediction of drug-target interaction based on fingerprint similarity]

Drugs play the pharmacological effects by combining with target proteins. Identification of drug-target interactions is important for discovering new functions of drugs. In this paper, the target fingerprints based on molecular substructure and the drug-target similarity based on fingerprints are proposed to a random forest-based classification method, in order to identify the drug-target interactions. Experiments on enzymes, ion channels, G protein-coupled receptors and nuclear receptors proved the effectiveness of the proposed method. In addition, the proposed method is applied to predict the interactions between ingredients and targets of traditional Chinese medicines.

[Perfluorinated Compounds in Snow from Downtown Hangzhou, China]

Snow samples were collected from the snow event on January 20-22, 2016 from 11 sites in downtown Hangzhou to explore the occurrence of sixteen perfluorinated compounds (PFCs) in the atmosphere. All samples were prepared by solid-phase extraction with Oasis WAX cartridges and analyzed using ultra performance liquid chromatography interfaced with tandem mass spectrometry (UPLC-MS/MS). The results showed that seven medium- and short-chain PFCs including C₄ and C₈ perfluorinated sulfonates (PFSAs) and C₄-C₆, C₈, and C₉ perfluorinated carboxylic acids (PFCAs) were detected in the snow samples. Total PFC concentrations ranged from 2.85 to 35.1 ng·L^-1, whereas perfluorooctanoic acid (PFOA) dominated, with ranges of 2.15-23.0 ng·L^-1, and perfluorooctane sulfonate (PFOS) was detected at lower levels, ranging from 0 to 0.46 ng·L^-1. As compared to the results from other studies, the PFOA concentrations of the study region were at mid-level and the PFOS concentrations were relatively low. The spatial distribution of PFCs varied, and the pollutant concentrations of the snow samples from the sampling sites located in the urban areas were higher than those in the rural areas. The greatest total PFC concentrations were detected in Fuyang, whereas the lowest concentrations were detected in Jiande and Chun'an. In this study, the high concentrations of PFCs dominated by PFOA that were measured in the Hangzhou snow samples emphasize the importance of atmospheric wet deposition as one of the sources of PFC contamination in this ecological system and should be addressed. The occurrence of PFCs in the air, indicated by their presence in the snow, suggests that the atmospheric environment may be an important contributor in human and ecological exposure to PFCs by local residents.

Cardiotoxicity evaluation of nine alkaloids from Rhizoma Coptis

PURPOSE

Alkaloids derived from Rhizoma Coptis (RC) has been widely applied to clinical treatments in China. However, the toxicity of RC and the alkaloids from RC remained controversial. The research is designed to clarify the cardiotoxic compounds found in RC.

METHODS

In this study, the real-time cellular analysis cardio system and the high-content analysis were applied to monitor the function of cardiomyocytes (CMs) in the treatment of nine alkaloids in RC. Luciferase-coupled adenosine triphosphate (ATP) assay was used to detect cell viability.

RESULTS

The results showed that berberine, palmatine, berbamine, and oxyberberine were cardiotoxic, which resulted in arrhythmia and cardiac arrest on CMs in a time- and dose-dependent manner. Meanwhile, berbamine and oxyberberine caused shrinkage and detachment on CMs at 10 μM. Cytotoxicity was induced by these two compounds with decline in cell index and ATP depletion. Cardiotoxicity or cytotoxicity was not observed in the other five alkaloids within 10 μM.

CONCLUSION

For the first time, the cardiotoxicity of the nine alkaloids was evaluated to clarify the cardiotoxic components in RC. Furthermore, the experimental evidences were provided to support the safety of drug application.

[The efficacy of large spot indirect ophthalmoscopy laser alone or combined with systemic chemotherapy in retinoblastoma therapy]

Objective: To evaluate the efficacy of large spot indirect ophthalmoscopy laser alone or combined with systemic chemotherapy in the treatment of early and middle stage retinoblastoma. Methods: Retrospective series case study. Clinical data of 21 patients (22 eyes) who were diagnosed as retinoblastoma (RB) in Peking University People's Hospital from March 2009 to August 2014 were collected. Medical and family history, ocular ultrasound, orbital and cranial MRI or CT examination of RB Children were detailed recorded. Ocular examination and laser treatment were performed under general anesthesia, once every 3-4 weeks until the tumor was under control. The observation period was at least 3 months after the last treatment. The ocular examination included intraocular pressure measurement, anterior segment and fundus examination and the fundus photography with Retcam. Laser therapeutic instrument was large spot indirect ophthalmoscopy laser of 810nm wavelength. Results: Of the 21 children, 16 were male and 5 were female. The range of age was 3 to 82 months averaged 17.3 months. Among 22 eyes, four with small tumor, eight with medium tumor, and ten with large tumor. Two eyes underwent laser treatment only and 20 eyes underwent laser treatment combined with systemic chemotherapy. During the average observation period of 33.9 months, 15 tumors were treated successfully, but 7 failed. The total success rate was 68.2%. The number and success rate of small, medium and large tumor eyes were 4 (100%), 5 (62.5%) and 5 (50%), respectively. There was one case of tumor brain metastases, and the classification of contralateral eye of the child was E phase.

COMPLICATIONS

Iris burns happened in one eye, obvious vitreous proliferation in one eye and mild vitreous hemorrhage occurred in two eyes, which did not affect the treatment of laser. However, obvious tumor hemorrhage happened in two eyes and affected laser therapy. There was no complicated cataract, iatrogenic retinal hole and tumor intravitreal implant caused by laser blasting effect. Conclusions: Indirect ophthalmoscope laser in 810-nm diode laser with large-spot alone or combined with systemic chemotherapy may be effective treatment for retinoblastoma in earlier than stage C of international classification. It is suitable for large and multiple retinoblastoma.(Chin J Ophthalmol, 2016, 52: 745-748).

[Profiles of cognitive and language impairment of logopenic and non-fluent variant of primary progressive aphasia]

OBJECTIVE

To decipher the cognitive and linguistic feature of logopenic variant primary progressive aphasia (lv-PPA) and nonfluent variant primary progressive aphasia (nfv-PPA) and to explore the extent to which cognitive and language impairment contribute to the dysfunction of activity of daily living(ADL).

METHODS

Seven lv-PPA and five nfv-PPA were enrolled in memory clinic of Xuanwu Hospital, Capital Medical University from January 2015 to January 2016 accordig to the international consensus criteria for PPA and its three subtypes. 20 age-matched normal controls (NC) were included. Both the patients and the NC completed a battery of neuropsychological test, lingusitic test and brain magnetic resonance imaging. All the patients conducted (11)C Pittsburgh compound B (PiB) PET imaging.

RESULT

Lv-PPA patients were characterized by deficits in lexical retrieval and long sentenses repetition, while nfv-PPA were with motor speech apraxia and phonetic distortion. Compared with nfv-PPA, lv-PPA patient displayed more severe cognitive deficit with younger onset of age (56±5 vs 61±5, P<0.05) , rapid decline of MMSE score within 1.5 years and pariental cortex dysfunctions such as ideomotor praxis, Gerstmann syndrome and contructional apraxia. Correlation analysis indicated that there was more significant association between pariental cortex dysfunction and ADL/mini-mental state examination(MMSE) than that of language deficit(r=-0.868, r=-0.922; r=0.312, r=-0.257). All seven lv-PPA were PiB-PET positive and five nfv-PPA were negative.

CONCLUSION

This study enriched the chinical and linguistic characterization of lv-PPA and nfv-PPA, which has implication for diagnosis, disease management and treatment for clinicians.

Performance of the international physical activity questionnaire (short form) in subgroups of the Hong Kong chinese population

BACKGROUND

The International Physical Activity Questionnaire (IPAQ-SF) has been validated and recommended as an efficient method to assess physical activity, but its validity has not been investigated in different population subgroups. We examined variations in IPAQ validity in the Hong Kong Chinese population by six factors: sex, age, job status, educational level, body mass index (BMI), and visceral fat level (VFL).

METHODS

A total of 1,270 adults (aged 42.9 ± SD 14.4 years, 46.1% male) completed the Chinese version of IPAQ (IPAQ-C) and wore an accelerometer (ActiGraph) for four days afterwards. The IPAQ-C and the ActiGraph were compared in terms of estimated Metabolic Equivalent Task minutes per week (MET-min/wk), minutes spent in activity of moderate or vigorous intensity (MVPA), and agreement in the classification of physical activity.

RESULTS

The overall Spearman correlation (ρ) of between the IPAQ-C and ActiGraph was low (0.11 ± 0.03; range in subgroups 0.06-0.24) and was the highest among high VFL participants (0.24 ± 0.05). Difference between self-reported and ActiGraph-derived MET-min/wk (overall 2966 ± 140) was the smallest among participants with tertiary education (1804 ± 208). When physical activity was categorized into over or under 150 min/wk, overall agreement between self-report and accelerometer was 81.3% (± 1.1%; subgroup range: 77.2%-91.4%); agreement was the highest among those who were employed full-time in physically demanding jobs (91.4% ± 2.7%).

CONCLUSIONS

Sex, age, job status, educational level, and obesity were found to influence the criterion validity of IPAQ-C, yet none of the subgroups showed good validity (ρ = 0.06 to 0.24). IPAQ-SF validity is questionable in our Chinese population.

First report of human infection by Rhodoplanes sp., Alphaproteobacteria in China

We isolated a novel strain of Alphaproteobacteria from a patient, who had medical history of chronic rhinitis for more than twenty years and recently experienced local skin abscess and ulcer. He eventually died of multiple organ failure due to multi-antibiotics resistance. We identified the microorganism by 16SrRNA sequencing and found that it belonged to the genus Rhodoplanes. It was named as Rhodoplanes sp. strain ZLJ-0. It is resumed that Rhodoplanes sp. strain ZLJ-0 might be an emerging human pathogen involving in unknown febrile conditions and could cause local infection of any tissues or organs. Differential diagnosis of febrile patients should be conducted in clinical practice and research on emerging pathogens of Alphaproteobacteria should be performed to determine the epidemiology, clinical symptoms and pathogenic features of these pathogens.

Ferrous chelator 2,2'-dipyridyl attenuates cerebral vasospasm after experimental subarachnoid haemorrhage in rabbits

The effect of 2,2'-dipyridyl (DP) on cerebral vasospasm was investigated in a double-injection rabbit model of subarachnoid haemorrhage (SAH). Thirty-six animals were divided between four groups: control (sham-operated), SAH (model alone), SAH + DP (the SAH model in which DP dissolved in dimethyl sulphoxide [DMSO] was injected once daily for 5 days into the cisterna magna), and SAH + DMSO (the SAH model in which DMSO [vehicle] was injected daily for 5 days). There were significant differences in the basilar artery luminal area, wall thickness, neurological deficit score and vasospasm index between the SAH + DP and SAH groups. There was a significant negative correlation between arterial luminal area and arterial wall thickness, and also between the neurological deficit score and vasospasm index. Cells that were positive for terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) and p53 expression were significantly increased in the SAH + DMSO and SAH groups, but not in the SAH + DP group, versus controls. Thus, DP may attenuate cerebral vasospasm after SAH by suppressing p53-induced apoptosis in the cerebral vessels.

Virological response to antiviral therapy at week 12 indicates a great reduction of intrahepatic hepatitis B virus DNA and cccDNA in HBeAg-positive chronic hepatitis B patients

Early virological response is considered to be a predictor for the outcome of anti-hepatitis B virus (HBV) therapy. To analyze its correlation to intrahepatic HBV DNA and covalently closed circular DNA (ccc)DNA, 71 hepatitis B virus e antigen (HBeAg)-positive chronic hepatitis B patients were recruited: 34 patients were treated with lamivudine; 13 with interferon-alpha2b; and 24 with sequential therapy of lamivudine-interferon-alpha2b for 48 weeks. Intrahepatic HBV DNA and cccDNA load were measured at the baseline and at Week 48. Fifty-seven patients had virological response at Week 12. Median decreases of serum HBV DNA in patients with or without virological response at Week 12 were 4.0 log(10) (max. 6.2, min. 2.2) and 1.1 log(10) (max. 2.1, min. 0) (Z = -5.766, P = 0.0000), respectively. At Week 48 they were 4.1 log(10) (max. 7.4, min. 1.0) and 2.3 log(10) (max. 7.5, min. 0.3) (Z = -2.760, P = 0.006), respectively. For intrahepatic HBV DNA load they were 1.3 log(10) (max. 4.3, min. -1.2) and 0.6 log(10) (max. 3.5, min. -0.8), respectively, and for HBV cccDNA load they were 1.1 log(10) (max. 4.8, min. -0.5) and 0.5 log(10) (max. 3.0, min. -0.8) (Z = -2.097, P = 0.036), respectively at Week 48. Step-wise logistic regression analysis indicated that the baseline intrahepatic HBV DNA load effected virological response at Week 12 [odds ratio (OR) 0.405; 95% confidence interval (CI) 0.174-0.944; P = 0.036] and HBeAg seroconversion at Week 48 (OR 0.292; 95% CI 0.131-0.649; P = 0.003). In conclusion, virological response at Week 12 indicated a great reduction of intrahepatic DNA and cccDNA load in HBeAg-positive CHB patients. The baseline intrahepatic HBV DNA load affected virological response at Week 12 and HBeAg seroconversion at Week 48.

Recording Bessel-like beam shapes generated by plasmonics lens

In our study, we spun a negative photoresist layer on top of a plasmonic lens which was formed by adopting a metallic ring structure with a nano-scale width opening. We recorded the beam shape of the Bessel-like beam emitting from the plasmonic lens which formed a high aspect ratio structure. We found that the high aspect ratio structure was higher after exposure as the inner and outer diameter had increased. In addition, we used an oblique incidence on the negative resist metallic ring structure to produce an inclined micro-structure. Different exposure results were obtained with the two different metal thicknesses. Therefore, in our study, we not only proved that it is possible to record the shape of a Bessel-like beam, but we also demonstrated that it is possible to create a plasmonic lens which is capable of creating a high aspect ratio structure through exposure.

Polymorphisms of short tandem repeat of genes and breast cancer susceptibility

AIM

To explore the relationship of short tandem repeat polymorphisms and breast cancer susceptibility.

METHODS

We searched the MEDLINE database (up to June 2006) with the keywords of tandem repeat sequences, gene polymorphisms, breast cancer, cancer susceptibility and microsatellite instability. We reviewed the literature on gene polymorphisms, especially the relationship of short tandem repeat and breast cancer risk.

RESULTS

We focused on the candidate genes sex hormones, steroid hormone and receptors, carcinogen metabolism, cell proliferation regulation and other genes.

CONCLUSIONS

The functional effects of short tandem repeat polymorphisms on cancer susceptibility, especially on breast cancer risk, are identified. The importance of short tandem repeat polymorphisms on development and progression of breast cancer are discussed.

Homeobox genes and their functions on development and neoplasm in gastrointestinal tract

AIM

To describe the role of homeobox genes on development and tumorigenesis in gastrointestinal tract.

METHODS AND RESULTS

We searched the MEDLINE database (until March, 2006) with the keywords of homeobox genes, gastrointestinal tract, development, tumorigenesis, carcinogenesis and therapeutic targets. We reviewed the literature on classification of homeobox genes, development of gastrointestinal tract, carcinogenesis of gastrointestinal tract as well as therapeutic targets.

CONCLUSIONS

The functional effects of homeobox family in development and tumorigenesis of gastrointestinal tract are identified. The importance of homeobox genes and a possibility of therapeutic intervention in clinical medicine are discussed.

[Effects of antiviral effects of agents and prognosis of chronic hepatitis B.]

BACKGROUND

To analyze the effects of difference antiviral agents and the effects of the treatments on long-term prognosis.

METHODS

Retrospective research method was applied.

RESULTS

About 40% of the patients were treated with interferon or lamivudine. After the treatment, in lamivudine group, the negative rate of HBV DNA was the highest. In the interferon group, the sero conversion rates of HBeAg/HBeAb were 22.9%. In the antiviral treatment patients, the disease progression and the occurrence of cirrhosis and liver cancer were much lower than those of the control groups. The mortality of cirrhosis and liver cancer in the HBeAg/HBeAb sero converted group was much lower than that of the group without HBeAg/HBeAb sero conversion groups (P less than 0.05).

CONCLUSION

The antiviral effects of interferon and lamivudine were better than those of the other drug groups. The antiviral drugs could relieve the disease progression and reduce the mortality of cirrhosis and liver cancer.

NF-κB as a molecular target in adjuvant therapy of gastrointestinal carcinomas

AIM

To describe the role of nuclear factor-kappa B (NF-kappaB) in cancer treatment.

METHODS

We searched the Pubmed database (until Oct, 2004) with the keywords of gastrointestinal carcinoma, NF-kappaB, inhibitor, cancer treatment molecular target and chemoresistance. We reviewed the literature in the role of NF-kappaB activation in chemoresistance, tumour growth suppression and enhancement of apoptosis in gastrointestinal carcinomas.

CONCLUSIONS

Several possible strategies for inhibiting NF-kappaB activation are identified. The importance of targeting NF-kappaB as a potential therapeutic approach in clinical medicine was discussed.

Germline mutational analysis of CDH1 and pathologic features in familial cancer syndrome with diffuse gastric cancer/breast cancer proband in a Chinese family

AIMS

Hereditary non-polyposis colorectal cancer, thyroid medullary carcinoma, breast/ovarian cancer and gastric cancer/breast cancer syndrome are encountered in surgery. Some gastric cancer/breast cancer syndrome may be the result of a CDH1 germline mutation. This is the first report of CDH1 germline mutations gastric cancer/breast cancer syndrome in Chinese patients.

METHODS

Peripheral blood from the proband, as well as, her first and second degree relatives was collected and CDH1 gene exon 1-16 mutations were screened. E-cadherin/beta-catenin proteins expression and histopathologic features were examined on gastric cancer/breast cancer tissues from the proband.

RESULTS

A C-->T nucleotide substitution at exon 13 (mRNA 2200 locus, Accession number NM-004360) was found. This was a transition from GCC-->GCT in DNA sequence (Ala154Ala). Diffuse-type gastric cancer and infiltrating ductal breast carcinoma were present. Both tumours preserved E-cadherin/beta-catenin expression immunohistochemically.

CONCLUSIONS

Familial cancer syndrome with diffuse-type gastric cancer/breast cancer proband in Chinese has a propensity of early onset during lifespan. No truncating or splice-site CDH1 mutations had been identified in this family. A silent nucleotide variation in exon 13 of the CDH1 gene may contribute to some forms of cancer susceptibility.

Chemiluminescence detection for hybridization assays on the flow-thru chip, a three-dimensional microchannel biochip

Chemiluminescence (CL) detection is seldom used in two-dimensional solid support microarray platforms because adequate sensitivity and spatial resolution is difficult to achieve. The three-dimensional ordered microchannels of the Flow-thru Chip increase both the sensitivity and spatial resolution required for quantitative CL measurements on microarrays. Enzyme-catalyzed CL reactions for the detection of hybridizations on microchannel glass were imaged using a CCD camera. Signal uniformity, sensitivity, and dynamic range of the detection method were determined. The relative standard deviation of signal intensities across an array of 64 spots was 8.1%. A detection limit of 250 amol of target with a linear dynamic range of 3 orders of magnitude was obtained for a 3-h assay. Similar to two-color fluorescence measurements, multiple enzyme labels were employed to demonstrate two-channel chemiluminescence. A unique method for measuring the relaxation time of a chemiluminescent species is also described.

Interactions of HLA-B27 with the peptide loading complex as revealed by heavy chain mutations

MHC class I heavy chains assemble in the endoplasmic reticulum with beta(2)-microglobulin and peptide to form heterotrimers. Although full assembly is required for stable class I molecules to be expressed on the cell surface, class I alleles can differ significantly in their rates of, and dependencies on, full assembly. Furthermore, these differences can account for class I allele-specific disparities in antigen presentation to T cells. Recent studies suggest that class I assembly is assisted by an elaborate complex of proteins in the endoplasmic reticulum, collectively referred to as the peptide loading complex. In this report we take a mutagenesis approach to define how HLA-B27 molecules interact with the peptide loading complex. Our results define subtle differences between how B27 mutants interact with tapasin (TPN) and calreticulin (CRT) in comparison to similar mutations in other mouse and human class I molecules. Furthermore, these disparate interactions seen among class I molecules allow us to propose a spatial model by which all class I molecules interact with TPN and CRT, two molecular chaperones implicated in facilitating the binding of high-affinity peptide ligands.

Tapasin enhances peptide-induced expression of H2-M3 molecules, but is not required for the retention of open conformers

H2-M3 is a class Ib MHC molecule that binds a highly restricted pool of peptides, resulting in its intracellular retention under normal conditions. However, addition of exogenous M3 ligands induces its escape from the endoplasmic reticulum (ER) and, ultimately, its expression at the cell surface. These features of M3 make it a powerful and novel model system to study the potentially interrelated functions of the ER-resident class I chaperone tapasin. The functions ascribed to tapasin include: 1) ER retention of peptide-empty class I molecules, 2) TAP stabilization resulting in increased peptide transport, 3) direct facilitation of peptide binding by class I, and 4) peptide editing. We report in this study that M3 is associated with the peptide-loading complex and that incubation of live cells with M3 ligands dramatically decreased this association. Furthermore, high levels of open conformers of M3 were efficiently retained intracellularly in tapasin-deficient cells, and addition of exogenous M3 ligands resulted in substantial surface induction that was enhanced by coexpression of either membrane-bound or soluble tapasin. Thus, in the case of M3, tapasin directly facilitates intracellular peptide binding, but is not required for intracellular retention of open conformers. As an alternative approach to define unique aspects of M3 biosynthesis, M3 was expressed in human cell lines that lack an M3 ortholog, but support expression of murine class Ia molecules. Unexpectedly, peptide-induced surface expression of M3 was observed in only one of two cell lines. These results demonstrate that M3 expression is dependent on a unique factor compared with class Ia molecules.

Evaluation of three-dimensional microchannel glass biochips for multiplexed nucleic acid fluorescence hybridization assays

Three-dimensional, flow-through microchannel glass substrates have a potential for enhanced performance, including increased sensitivity and dynamic range, over traditional planar substrates used in medium-density microarray platforms. This paper presents a methodology for the implementation of multiplexed nucleic acid hybridization fluorescence assays on microchannel glass substrates. Fluorescence detection was achieved, in a first instance, using conventional low-magnification microscope objective lenses, as imaging optics whose depth-of-field characteristics match the thickness of the microchannel glass chip. The optical properties of microchannel glass were shown, through experimental results and simulations, to be compatible with the quantitative detection of heterogeneous hybridization events taking place along the microchannel sidewalls, with detection limits for oligonucleotide targets in the low-attomole range.

Association of ERp57 with Mouse MHC Class I Molecules Is Tapasin Dependent and Mimics That of Calreticulin and not Calnexin

Before peptide binding in the endoplasmic reticulum, the class I heavy (H) chain-beta(2)-microglobulin complexes are detected in association with TAP and two chaperones, TPN and CRT. Recent studies have shown that the thiol-dependent reductase, ERp57, is also present in this peptide-loading complex. However, it remains controversial whether the association of ERp57 with MHC class I molecules precedes their combined association with the peptide-loading complex or whether ERp57 only associates with class I molecules in the presence of TPN. Resolution of this controversy could help determine the role of ERp57 in class I folding and/or assembly. To define the mouse class I H chain structures involved in interaction with ERp57, we tested chaperone association of L(d) mutations at residues 134 and 227/229 (previously implicated in TAP association), residues 86/88 (which ablate an N-linked glycan), and residue 101 (which disrupts a disulfide bond). The association of ERp57 with each of these mutant H chains showed a complete concordance with CRT, TAP, and TPN but not with calnexin. Furthermore, ERp57 failed to associate with H chain in TPN-deficient.220 cells. These combined data demonstrate that, during the assembly of the peptide-loading complex, the association of ERp57 with mouse class I is TPN dependent and parallels that of CRT and not calnexin.