Proteomic approach to characterize biochemistry of meat quality defects

Proteomics can be used to characterize quality defects including pale, soft, and exudative (PSE) meat (pork and poultry), woody broiler breast meat, reddish catfish fillets, meat toughness, and beef myoglobin oxidation. PSE broiler meat was characterized by 15 proteins that differed in abundance in comparison to normal broiler breast meat, and eight proteins were differentially expressed in woody breast meat in comparison to normal breast meat. Hemoglobin was the only protein that was differentially expressed between red and normal catfish fillets. However, inducing low oxygen and/or heat stress conditions to catfish fillets did not lead to the production of red fillets. Proteomic data provided information pertaining to the protein differences that exist in meat quality defects. However, these data need to be evaluated in conjunction with information pertaining to genetics, nutrition, environment of the live animal, muscle to meat conversion, meat quality analyses and sensory attributes to understand causality, protein biomarkers, and ultimately how to prevent quality defects.

A Diffusion Tensor Imaging Study on White Matter Abnormalities in Patients with Type 2 Diabetes Using Tract-Based Spatial Statistics

BACKGROUND AND PURPOSE

Patients with type 2 diabetes mellitus have considerably higher risk of developing cognitive impairment and dementia. WM changes in these patients have been reported. Our aim was to demonstrate that gradual and continuous WM change and the associated cognitive decline in patients with type 2 diabetes mellitus can be captured by DTI parameters, which can be used to complement neuropsychological test scores in identifying patients with type 2 diabetes mellitus with and without mild cognitive impairment.

MATERIALS AND METHODS

Forty-two patients with type 2 diabetes mellitus, divided into a group with mild cognitive impairment (n = 20) and a group with normal cognition (n = 22), were enrolled with age-, sex-, and education-matched healthy controls (n = 26). 3T DTI followed by Tract-Based Spatial Statistics analysis was used to investigate the differences in fractional anisotropy, mean diffusivity, axial diffusivity (λ1), and radial diffusivity (λ23) among the groups. A receiver operating characteristic analysis assessed the performance of DTI parameters for separating the 2 groups with type 2 diabetes mellitus.

RESULTS

The whole-brain Tract-Based Spatial Statistics analysis revealed that 7.3% and 24.9% of the WM exhibited decreased fractional anisotropy and increased mean diffusivity (P < .05), respectively, between the diabetes mellitus with mild cognitive impairment and the diabetes mellitus with normal cognition groups, while considerably larger WM regions showed fractional anisotropy (36.6%) and mean diffusivity (58.8%) changes between the diabetes mellitus with mild cognitive impairment and the healthy control groups. These changes were caused primarily by an elevated radial diffusivity observed in the patients with diabetes mellitus with mild cognitive impairment. Radial diffusivity also exhibited subtle but statistically significant changes between the diabetes mellitus with normal cognition and the healthy control groups. Analyses on individual fiber tracts showed pronounced fractional anisotropy reduction and mean diffusivity elevation in regions related to cognitive functions. The receiver operating characteristic analysis on the right cingulum (hippocampus) showed that fractional anisotropy produced a larger area under the curve (0.832) than mean diffusivity (0.753) for separating mild cognitive impairment from normal cognition among patients with type 2 diabetes mellitus. When fractional anisotropy was combined with mean diffusivity, the area under the curve was further improved to 0.857.

CONCLUSIONS

DTI parameters can show a substantial difference between patients with type 2 diabetes mellitus with and without mild cognitive impairment, suggesting their potential use as an imaging marker for detecting cognitive decline in patients with type 2 diabetes mellitus. More important, DTI parameters may capture gradual and continuous WM changes that can be associated with early stages of cognitive decline in patients with type 2 diabetes mellitus before they can be diagnosed clinically by using conventional neuropsychological tests.

Sudden stoppage of rotor in a thermally driven rotary motor made from double-walled carbon nanotubes

In a thermally driven rotary motor made from double-walled carbon nanotubes, the rotor (inner tube) can be actuated to rotate within the stator (outer tube) when the environmental temperature is high enough. A sudden stoppage of the rotor can occur when the inner tube has been actuated to rotate at a stable high speed. To find the mechanisms of such sudden stoppages, eight motor models with the same rotor but different stators are built and simulated in the canonical NVT ensembles. Numerical results demonstrate that the sudden stoppage of the rotor occurs when the difference between radii is near 0.34 nm at a high environmental temperature. A smaller difference between radii does not imply easier activation of the sudden rotor stoppage. During rotation, the positions and electron density distribution of atoms at the ends of the motor show that a sp(1) bonded atom on the rotor is attracted by the sp(1) atom with the biggest deviation of radial position on the stator, after which they become two sp(2) atoms. The strong bond interaction between the two atoms leads to the loss of rotational speed of the rotor within 1 ps. Hence, the sudden stoppage is attributed to two factors: the deviation of radial position of atoms at the stator's ends and the drastic thermal vibration of atoms on the rotor in rotation. For a stable motor, sudden stoppage could be avoided by reducing deviation of the radial position of atoms at the stator's ends. A nanobrake can be, thus, achieved by adjusting a sp1 atom at the ends of stator to stop the rotation of rotor quickly.

Induction of apoptosis by capsaicin in hepatocellular cancer cell line SMMC-7721 is mediated through ROS generation and activation of JNK and p38 MAPK pathways

Capsaicin, one of the major pungent ingredients found in red peppers, has been shown to have anti-carcinogenic effect on various cancer cells through multiple mechanisms. In this study, we investigated the apoptotic effect of capsaicin on human hepatocellular cancer cell line SMMC-7721, as well as the possible mechanisms involved. Treatment of SMMC-7721 cells with capsaicin resulted in a dose-dependent inhibition of cell-viability and induction of apoptosis which was associated with the generation of ROS and persistent disruption of mitochondrial membrane potential. These effects were significantly blocked when cells were pretreated with a general antioxidant N-acetyl cysteine (NAC). We also found that capsaicin induced JNK and p38 MAPK phosphorylation. JNK and p38 MAPK inhibitor effectively blocked capsaicin-induced SMMC-7721 cell apoptosis. In addition, NAC completely blocked phosphorylation of JNK and p38 MAPK induced by capsaicin. Our results indicate that capsaicin induced in SMMC-7721 cell apoptosis through generation of intracellular ROS and activation of JNK and p38 MAPK pathways.

Gradientless temperature-driven rotating motor from a double-walled carbon nanotube

Rotation of the inner tube in a double-walled carbon nanotube (DWCNT) system with a fixed outer tube is investigated and found to be inducible by a relatively high uniform temperature (say, 300 K). We also found the mechanism of a gradientless temperature-driven rotating motor lies in the inner tube losing its geometric symmetry in a high-temperature field. This mechanism can be taken as a guide for designing a motor from such a bi-tube system. Using a computational molecular dynamics (CMD) approach and the adaptive intermolecular reactive empirical bond order (AIREBO) potential, the dynamic behavior of a bi-tube system subjected to uniformly distributed temperature is studied. In particular, the effects of environmental temperature, boundary conditions of the outer tube, and intertube gap on the dynamic behavior of the bi-tube system are investigated. Numerical examples show that a bi-tube system with the inner tube having 0.335 nm of interlayer gap produces the highest rotational speed.

TNF-α acutely upregulates amylin expression in murine pancreatic beta cells

AIMS/HYPOTHESIS

Amylin, a secretory protein mainly produced by pancreatic beta cells, is elevated in the circulation of patients with diseases related to acute and chronic inflammation, including acute pancreatitis, pancreas graft rejection, obesity and insulin resistance. TNF-α is involved in these disorders. We investigated the effect of TNF-α on amylin levels and the underlying mechanisms, using murine pancreatic beta cell line MIN6 and pancreatic islets.

METHODS

Amylin, proinsulin and prohormone convertase 1/3, 2 (Pc1/3, Pc2 [also known as Pcsk1/3 and Pcsk2, respectively]) mRNA levels, and amylin promoter and nuclear factor κB (NF-κB) activation were examined by real-time PCR and luciferase reporter assay, respectively. Amylin protein level and mitogen-activated protein kinase phosphorylation were detected by western blot. Activator protein 1 (AP1) activation was examined by electrophoretic mobility shift assay (EMSA).

RESULTS

TNF-α acutely induced amylin expression at the transcriptional level and increased proamylin and the intermediate form of amylin in MIN6 cells and islets. However, it had no effect on proinsulin, Pc1/3 and Pc2 expression. Studies with (1) MIN6 cells treated with inhibitors of MEK1/2, c-Jun-N-terminal kinase (JNK) or protein kinase Cζ (PKC(ζ)), (2) MIN6 cells expressing a c-Jun-dominant negative construct and (3) islets from Fos knockout mice demonstrated that TNF-α induced amylin expression through the PKC(ζ)-extracellular signal-regulated kinase (ERK)/JNK pathways. EMSA showed that (PKC(ζ)), JNK and ERK1/2 were involved in TNF-α-induced AP1 activation, suggesting that TNF-α induces murine amylin expression through the (PKC(ζ)) - ERK1/2 - AP and PKC(ζ) - JNK - AP1 pathways. Further studies showed that TNF-α also induced murine amylin expression through the phosphatidylinositol 3 kinase-NF-κB signalling pathway and enhanced human amylin promoter activation through NF-κB and AP1.

CONCLUSIONS/INTERPRETATION

TNF-α acutely induces amylin gene expression in beta cells through multiple signalling pathways, possibly contributing to amylin elevation in acute inflammation-related pancreatic disorders.

Lentivirus-mediated expression of MxA in chicken spermatogonial stem cells

The aim of this study was to construct a lentivirus vector that carries the human myxovirus-resistant A (MxA) anti-virus gene for efficiently infecting rooster spermatogonial stem cells (SSCs). A lentiviral vector carrying the enhanced green fluorescent protein (EGFP) and MxA fusion gene (EGFP-MxA) was constructed using TOPO technology in this study. Enhanced green fluorescent protein-MxA was inserted in the right orientation as determined by restriction enzyme digest. No gene recombination in the vector occurred. After infecting 293FT cells, EGFP-MxA fusion protein was expressed as granular green fluorescence characteristic of EGFP-MxA expression, suggesting that the TOPO expression vector was properly constructed and the fusion protein expressed correctly. The EGFP-MxA recombinant lentivirus was packaged by cotransfecting 293FT cells with EGFP-MxA and the packaging plasmids. We also purified SSCs from testicle tissues from 25-day-old roosters for infection with the EGFP-MxA recombinant virus. After infecting rooster SSCs with the recombinant virus for 72 h, EGFP-MxA expression was detected by EGFP expression. Enhanced green fluorescent protein-MxA expression in SSCs was further confirmed at the transcription level by RT-PCR and at the protein level by immunocytochemistry. Staining with Hoechst 33342 showed that infected SSCs differed from the sertoli cells. Similar to stem cells, SSCs were positive for alkaline phosphoric acid enzyme and for stage-specific embryonic antigen-1 stem cell factor. The results demonstrated that the recombinant virus made in our study can infect rooster SSCs efficiently to express the anti-virus protein MxA, establishing the basis of transferring MxA into SSCs to obtain virus-resistant, genetically-modified roosters.

Molecular Biomarkers of Columnar Cell Lesions Identified by Proteomic Approaches

The widespread increase in the use of screening mammography has led to a significant rise in the detection and diagnosis of benign breast disease (BBD), which encompasses a wide variety of non-cancerous changes including columnar cell lesions (CCL). Epidemiologic studies provide evidence for a relationship between BBD and subsequent risk of developing breast cancer. Observational studies have reported CCL are found adjacent to areas of tubular carcinoma and ductal and lobular carcinomas in situ and recently published molecular data state that genetic abnormalities frequently found in low grade ductal carcinoma in situ are also found in CCL. All these data support the hypothesis that CCL are the earliest morphologically distinguishable precursor lesions to low grade ductal carcinoma in situ and invasive carcinoma. However, BBD is heterogeneous and there is limited understanding of the biological importance associated with the spectrum of lesions. The lack of accurate molecular-based risk categories, therefore, hinders the ability of assigning prognostic significance to benign biopsy findings. The purpose of our study was to identify putative molecular markers of cancer progression from epithelial cells of BBD lesions. Regions of ductal hyperplasia (DH) and normal breast epithelium were isolated from mastectomy specimens using laser capture microdissection and extracted proteins were analyzed through proteomic approaches. Of the 1,500 total protein spots resolved by 2-dimensional electrophoresis, 98 were differentially expressed between DH and normal breast epithelial proteomes. Twenty-two proteins or related isoforms were identified using mass spectrometry. Two proteins of particular interest, NAD(P)H: quinone oxidoreductase 1 (NQO1) and galectin-3, were further investigated by immunohistochemistry (IHC) on cases diagnosed with BBD lesions. NQO1 was expressed sporadically in overtly normal epithelial cells lining breast ducts, but was overexpressed in BBD and tumor tissues. Notably, we found that a subpopulation of DH tissues with CCL stained positively for NQO1 and negatively for galectin-3. This finding has significance because CCL can only be diagnosed morphologically and the presence of CCL in biopsy specimens may indicate a precancerous lesion. However, sectioning artifacts associated with core biopsies can hinder morphological diagnosis of CCL, thus a means to additionally identify these lesions using IHC has tremendous value. Together, immunohistochemical staining of NQO1 and galectin-3 may prove to be clinically relevant in the identification of CCL in biopsy samples.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2142.

Mild hypoxic-ischemic injury in the neonatal rat brain: longitudinal evaluation of white matter using diffusion tensor MR imaging

BACKGROUND AND PURPOSE

Selective white matter (WM) damage is a known sequela of mild hypoxic-ischemic (HI) injury in the neonatal rat model. The aim of this study was to evaluate longitudinally mild HI-induced WM damage (represented by the external capsule [EC]) by diffusion tensor MR imaging (DTI) and to correlate the findings with histology.

MATERIALS AND METHODS

Seven-day-old Sprague-Dawley rats (n = 19) underwent unilateral ligation of the left common carotid artery followed by hypoxia for 50 minutes to create mild HI injury. DTI was performed longitudinally at 5 time points from day 1 to day 90 postinjury (n = 19, 16, 13, 11, 9, respectively), and fractional anisotropy (FA), trace, radial diffusivity (lambda( perpendicular)), and axial diffusivity (lambda(//)) of the injury and control contralateral ECs were quantified. Rats were randomly sacrificed (n = 15, in total), and the corresponding ECs were stained with hematoxylin-eosin, Luxol fast blue (LFB), and neurofilament (NF) to evaluate morphologic changes, amount of myelin, and axonal count at every time point. A paired t test was applied to evaluate statistical differences between both ECs, and the Pearson correlation test was used to evaluate the relationships between DTI indices and histologic evaluations. In addition, longitudinal changes in DTI indices and histologic evaluations were analyzed by a linear mixed model and an analysis of variance test, respectively.

RESULTS

We demonstrated significantly decreased FA, increased lambda( perpendicular), and similar lambda(//) in the injury compared with the control EC, which was persistent through all time points. Histologic evaluation by LFB and NF staining showed reduced myelin stain intensity in the injury EC and similar axonal counts in both ECs. Longitudinally, there was an increase in FA, a decrease in lambda( perpendicular) and trace, and stability in lambda(//) in both ECs. Also, there was progressive reduction in the differences in FA, trace, and lambda( perpendicular) between the injury and control EC, especially between day 1 and day 7 postinjury and in tandem with changes in myelin stain. FA was significantly correlated with myelin stain (r = 0.681, P < .01) and axonal count (r = 0.673, P < .01), whereas lambda( perpendicular) was significantly correlated with myelin stain only (r = -0.528, P < .01), and lambda(//), with axonal count only (r = 0.372, P = .043).

CONCLUSIONS

Diffusion indices can reflect dysmyelination in mild HI injury, continual myelination of both injury and control ECs with growth, and the partial recovery of myelin postinjury. We propose that diffusion indices may be used as biomarkers to monitor noninvasively the longitudinal changes of mild HI-induced WM damage.

SINGLE UV EXCITATION OF HOECHST 33342 AND PROPIDIUM IODIDE FOR VIABILITY ASSESSMENT OF RHESUS MONKEY SPERMATOZOA USING FLOW CYTOMETRY

Many fluorescent probes excited by visible light have been used to assess sperm quality by flow cytometry. Developing a viability evaluation method using UV excited stains would be useful for multiparameter analysis of sperm function. This investigation was conducted to determine the efficacy of Hoechst 33342 (H342) and propidium iodide (PI) dual staining for evaluating rhesus monkey sperm viability through use of flow cytometry and excited by a single UV laser. The results showed that the live cells stained only with H342 strongly correlated with expected sperm viability, and flow cytometric analyses were highly correlated with fluorescence microscopic observation. Using H342/PI/SYBR-14 triple staining method, it was found that the live/dead sperm distributions were completely concordant in both H342/PI and SYBR-14/PI assays. In addition, this dual staining was extended with fluorescein isothiocyanate-conjugated peanut agglutinin (FITC-PNA) to simultaneously analyze viability and acrosome integrity of sperm cryopreserved using two different extenders, TTE and TEST, and indicated that TTE offered better preservation of plasma and acrosome integrity than TEST. Therefore, the H342/PI dual staining provides an accurate technique for evaluating viability of rhesus monkey sperm and should be valuable for multiparameter flow cytometric analysis of sperm function.

Critical factors influencing prion inactivation by sodium hydroxide

BACKGROUND AND OBJECTIVES

Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases caused by aberrantly folded cellular proteins (PrP(Sc); prions) that are generally resistant to conventional pathogen-inactivation techniques. To ensure effective decontamination and inactivation of prions that could be present in source material, we investigated critical factors that influence prion inactivation by NaOH.

MATERIALS AND METHODS

A decrease in prion infectivity correlates with the disappearance of the protease-resistant core of PrPSc (PrPRES) observed in biochemical assays. To model prion inactivation, hamster scrapie (strain 263K) brain homogenate (SBH) was incubated for specific periods of time in 0.1 m NaOH at 4 or 18 degrees C, with or without detergent. Neutralized samples were subjected to limited digestion with proteinase K (PK) and then analysed using an endpoint dilution western blot assay and antibody 3F4. Structural changes in prions exposed to NaOH were examined using differential immunoprecipitation.

RESULTS

Treatment of SBH with 0.1 m NaOH for 15 min, in the absence of detergent, at 4 and 18 degrees C caused a reduction in the PrP(RES) signal of 3.5 and 4.0 log10 units, respectively, with some residual signal remaining. The presence of the detergent sarkosyl during a 60-min incubation in NaOH further enhanced PrPRES reduction to > or = 4.5 log10 units (i.e. below the limit of detection). NaOH treatment induced conformational changes in PrP that resulted in the exposure of a hidden epitope and enabled prion immunoprecipitation by antibody 3F4.

CONCLUSIONS

The use of NaOH can effectively reduce prion levels in an in vitro inactivation assay. After pretreatment of SBH with detergent, NaOH completely eliminates the PrPRES signal. Detergent may liberate lipid membrane-protected PrPSc to improve access to NaOH, which can then inactivate PrPSc by altering its structure. In cases of unidentified exposure to PrPSc during manufacturing, sanitizing procedures combining the use of detergent and NaOH may help to ensure minimal levels of contamination carryover in products.

Rat osteoblast functions on the o-carboxymethyl chitosan-modified poly(D,L-lactic acid) surface

In this study, the functions of rat osteoblasts on o-carboxymethyl chitosan-modified poly(D,L-lactic acid) (PDLLA) films were investigated in vitro. The surface characterization was measured by contact angle and electron spectroscopy for chemical analysis (ESCA). Cell adhesion and proliferation were used to assess cell behavior on the modified surface and control. The MTT assay was used to determined cell viability and alkaline phosphatase (ALP) activity was performed to evaluate differentiated cell function. Compared to the control films, cell adhesion of osteoblasts on o-carboxymethyl chitosan-modified PDLLA films was significantly higher (p < 0.05) after 6 and 8 h culture, and osteoblast proliferation was also significantly higher (p < 0.01) between 4 and 7 days. The MTT assay suggested cell viability of osteoblasts cultured on o-carboxymethyl chitosan modified PDLLA films was significantly greater (p < 0.05) than that seeded on control one, and the ALP activity of cells cultured on modified PDLLA films was significantly higher (p < 0.01) than that found on control. These results give the first evidence that o-carboxymethyl chitosan could be used to modify PDLLA surface for improving biocompatibility.

The influence of phorbol ester on the effect of tamoxifen in breast cancer cells

To investigate the correlation between the activity of kinases in the growth factor signal transduction pathway and the development of resistance of breast cancer to tamoxifen, reporter gene regulated by the regulating fragment of CCD1 was transfected into the MCF-7 cells, and the influence of tamoxifen on the reporter gene expression was examined under different conditions of TPA treatment. Our results showed that the reporter gene expression was inhibited by tamoxifen and promoted by TPA. Furthermore, tamoxifen exerts an agonist effect on the reporter gene expression when the cells was treated by TPA previously for 12 h. It is concluded that TPA could induce estrogen-like effect of tamoxifen on estrogen receptor positive breast cancer cells and it may be one of the mechanisms responsible for the development of tamoxifen resistance.

Structure and function in rhodopsin: mapping light-dependent changes in distance between residue 65 in helix TM1 and residues in the sequence 306-319 at the cytoplasmic end of helix TM7 and in helix H8

Spin-labeled double mutants of rhodopsin were produced containing a reference nitroxide at position 65, at the cytoplasmic termination of helix TM1, and a second nitroxide in the sequence of residues 306-319, which includes the cytoplasmic termination of helix TM7 and nearly the entire surface helix H8. Magnetic dipole-dipole interactions between the spins are analyzed to provide interspin distance distributions in both the dark and photoactivated states of rhodopsin. The distributions, apparently resulting from the conformational flexibility of the side chains, are found to be consistent with the structural model of rhodopsin in the dark state derived from crystallography. Photoactivation of the receptor triggers an increase in distance between residues in TM7, but not those in H8, relative to the reference at position 65 in TM1. The simplest interpretation of the result is a movement of the cytoplasmic portion of TM7 away from TM1 by 2-4 A.

Structure and function in rhodopsin: mapping light-dependent changes in distance between residue 316 in helix 8 and residues in the sequence 60-75, covering the cytoplasmic end of helices TM1 and TM2 and their connection loop CL1

Double-spin-labeled mutants of rhodopsin were prepared containing a nitroxide side chain at position 316 in the cytoplasmic surface helix H8, and a second nitroxide in the sequence of residues 60-75, which includes the cytoplasmic loop CL1 and cytoplasmic ends of helices TM1 and TM2. Magnetic dipole-dipole interactions between the spins were analyzed to provide interspin distance distributions in both the dark and photoactivated states of rhodopsin. In the dark state in solutions of dodecyl maltoside, the interspin distances are found to be consistent with structural models of the nitroxide side chain and rhodopsin, both derived from crystallography. Photoactivation of rhodopsin shows a pattern of increases in internitroxide distance between the reference, position 316 in H8, and residues in CL1 and TM2 that suggests an outward displacement of TM2 relative to H8 by approximately 3 A.

Probing the dark state tertiary structure in the cytoplasmic domain of rhodopsin: proximities between amino acids deduced from spontaneous disulfide bond formation between Cys316 and engineered cysteines in cytoplasmic loop 1

A dark state tertiary structure in the cytoplasmic domain of rhodopsin is presumed to be the key to the restriction of binding of transducin and rhodopsin kinase to rhodopsin. Upon light-activation, this tertiary structure undergoes a conformational change to form a new structure, which is recognized by the above proteins and signal transduction is initiated. In this and the following paper in this issue [Cai, K., Klein-Seetharaman, J., Altenbach, C., Hubbell, W. L., and Khorana, H. G. (2001) Biochemistry 40, 12479-12485], we probe the dark state cytoplasmic domain structure in rhodopsin by investigating proximity between amino acids in different regions of the cytoplasmic face. The approach uses engineered pairs of cysteines at predetermined positions, which are tested for spontaneous formation of disulfide bonds between them, indicative of proximity between the original amino acids. Focusing here on proximity between the native cysteine at position 316 and engineered cysteines at amino acid positions 55-75 in the cytoplasmic sequence connecting helices I-II, disulfide bond formation was studied under strictly defined conditions and plotted as a function of the position of the variable cysteines. An absolute maximum was observed for position 65 with two additional relative maxima for cysteines at positions 61 and 68. The observed disulfide bond formation rates correlate well with proximity of these residues found in the crystal structure of rhodopsin in the dark. Modeling of the engineered cysteines in the crystal structure indicates that small but significant motions are required for productive disulfide bond formation. During these motions, secondary structure elements are retained as indicated by the lack of disulfide bond formation in cysteines that do not face toward Cys316 in the crystal structure model. Such motions may be important in light-induced conformational changes.

Probing the dark state tertiary structure in the cytoplasmic domain of rhodopsin: proximities between amino acids deduced from spontaneous disulfide bond formation between cysteine pairs engineered in cytoplasmic loops 1, 3, and 4

To probe proximities between amino acids in the cytoplasmic domain by using mutants containing engineered cysteine pairs, three sets of rhodopsin mutants have been prepared. In the first two sets, a cysteine was placed, one at a time, at positions 311-314 in helix VIII, while the second cysteine was fixed at position 246 (set I) and at position 250 (set II) at the cytoplasmic end of helix VI. In the third set, one cysteine was fixed at position 65 while the second cysteine was varied between amino acid positions 306 and 321 located at the cytoplasmic end of helix VII and throughout in helix VIII. Rapid disulfide bond formation in the dark was found between the cysteine pairs in mutants A246C/Q312C,A246C/K311C and in mutants H65C/C316, H65C/315C and H65C/312C. Disulfide bond formation at much lower rates was found in mutants A246C/F313C, V250C/Q312C, H65C/N310C, H65C/K311C, H65C/F313C, and H65C/R314C; the remaining mutants showed no significant disulfide bond formation. Comparisons of the results from disulfide bond formation in solution with the distances observed in the rhodopsin crystal structure showed that the rates of disulfide bond formation in most cases were consistent with the amino acid proximities as revealed in crystal structure. However, deviations were also found, in particular, in the set containing fixed cysteine at position Cys246 and cysteines at positions 311-314. The results implicate significant effects of structural dynamics on disulfide bond formation in solution.

[Development and application of software in EDXRF spectrometer]

The present paper describes application softwares on file management system, multicomponent linear regression, rapid semi-quantitative analysis, analysis of coating thickness and multifunctional Lucas-tooth intensity correction, developed in EDXRF. Utilization of these software improves the analytical quality, management efficiency and development ability of scientific research.

[Mitochondrial mechanisms of CPT-induced apoptosis in nasopharyngeal carcinoma cells]

OBJECTIVE

To understand whether CPT-induced apoptosis is related to the alteration of mitochondrial transmembrane potentials (delta psi m).

METHOD

A low differentiation human nasopharyngeal carcinoma (NPC) cell line of CNE-2Z cells were used as in vitro model. After treatment with 2 mumol/L CPT for 24 h, the delta psi m was detected by the staining of rhodamine 123 (Rh123), while apoptosis was confirmed by sub-G1 cell content and the double staining of hoechst33258 and propidium iodide (PI).

RESULT

CPT induced delta psi m collapse and apoptosis. With 2 mumol/L CPT treatment for 24 h, delta psi mlow cell was increased to (19.0 +/- 3.0)%, while in the DMSO control, delta psi mlow was (7.0 +/- 1.4)% P < 0.05.

CONCLUSION

The disruption of the delta psi m may be one of the mechanisms of CPT-induced apoptosis in CNE-2Z cells.