Biomedical subjects

X Xu

Publications and source records attributed to X Xu.

At least 55 records · Page 3Linked to original sources

PubMed2005

Expression of endothelial nitric oxide synthase traffic inducer in the placentas of women with pre-eclampsia.

OBJECTIVE: To investigate the expression of endothelial nitric oxide synthase traffic inducer (NOSTRIN) in the placenta of women with pre-eclampsia (PE) and discuss its role in the pathogenesis of PE. METHODS: Western blot analysis was used to detect the expression of NOSTRIN and endothelial nitric oxide synthase (eNOS). The activity of eNOS in placental tissue was assayed by spectrophotometry. Serum and placental NO(2)/NO(3), the stable metabolic end product of NO, was measured using nitrate reductase. RESULTS: Western blot analysis showed that the protein level of NOSTRIN was significantly higher in women with PE than in the control group (P<0.01). However, no significant difference between groups was observed in the expression of placental eNOS (P>0.05). The activity of eNOS was significantly decreased in women with PE (13.727+/-3.58 U/mg) compared with the control group (21.69+/-3.84 U/mg) (P<0.01). The placental levels of NO(2)/NO(3) were significantly lower in women with PE (27.53+/-8.51 micromol/mg) than in the control group (44.38+/-9.59 micromol/mg) (P<0.01). The levels of serum NO(2)/NO(3) were significantly lower in women with PE (48.56+/-8.49 micromol/L) than in the control group (65.37+/-9.61 micromol/L) (P<0.01). A significant negative correlation existed between the expression of NOSTRIN protein and the activity of eNOS in the placental tissues of women with PE (r=-0.57, P<0.01). CONCLUSION: The level of NOSTRIN expression in the placental tissues of women with PE is increased and is negatively correlated with the activity of eNOS-which may play an important role in the pathogenesis of PE.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Primary adenovirus-specific cytotoxic T lymphocyte response occurs after viral clearance and liver enzyme elevation.

The virus-specific cytotoxic T lymphocyte (CTL) response is a major obstacle to effective delivery of adenovirus gene therapy. However, its relative role in viral clearance, transgene elimination and hepatotoxicity remains unclear. In this paper, we present an analysis of viral clearance and liver toxicity in relation to the induction of the virus-specific CD8 T-cell response revealed by an MHC class I tetramer. A surprisingly high number of tetramer+ CD8 T cells were found in the liver and lung and reached peak values at days 8 and 10, respectively, post-infection. Nearly 100% of these tetramer+ CD8 T cells expressed high levels of granzyme B and IFNgamma. Remarkably, liver viral load and liver enzyme elevation peaked early, at days 2 and 4, respectively, post-infection, before the specific CTL response was detectable. After generation of CTLs, there was only minimal liver damage or further decrease in virus titer. These results indicated that the primary peak response of tetramer+ CTLs does not correlate with the elimination of adenovirus or liver cytotoxic response.

Adenoviridae↗

PubMed2005

Effects of vasopressin and long pulse-low frequency gastric electrical stimulation on gastric emptying, gastric and intestinal myoelectrical activity and symptoms in dogs.

The aim of this study was to investigate the effect of vasopressin and long pulse-low frequency gastric electrical stimulation (GES) on gastric emptying, gastric and intestinal myoelectrical activity and symptoms in dogs. The study was performed in eight healthy female dogs implanted with four pairs of gastric serosal electrodes and two pairs of small bowel serosal electrodes, and a duodenal fistula for the assessment of gastric emptying. Each dog was studied in three sessions on three separate days in a randomized order with recordings of gastric and small bowel slow waves. Each study session consisted of 30-min baseline, 30-min stimulation and 30-min recovery period. In sessions 1 and 2, infusion of either saline or vasopressin (0.75 U kg(-1) in 30 mL saline instilled in 30 min) was given during the second 30-min period. The protocol of session 3 was the same as session 2 except long pulse-low frequency GES was performed during the second 30-min period. It was found that: (i) Vasopressin significantly delayed gastric emptying 30 and 45 min after meal and GES did not improve the vasopressin induced delayed gastric emptying; (ii) Vasopressin induced gastric dysrhythmias and GES significantly improved vasopressin induced gastric dysrhythmia; (iii) Vasopressin also induced intestinal slow wave abnormalities but GES had no effect on vasopressin induced small bowel dysrhythmia; (iv) Vasopressin induced symptoms and behaviours suggestive of nausea that were not improved by GES. We conclude that: (i) Vasopressin delays gastric emptying and induces gastric and small bowel dysrhythmias and symptoms in the fed state, and (ii) long pulse-low frequency GES normalizes vasopressin induced gastric dysrhythmia with no improvement in gastric emptying or symptoms.

Animals↗

PubMed2005

Efficiency and efficacy of multi-channel gastric electrical stimulation.

Gastric electrical stimulation (GES) using single channel has been under investigation for its therapeutic potential for gastroparesis. The aim of this study was to study the efficacy and efficiency of multi-channel GES in accelerating gastric emptying in dogs. The study was performed in eight dogs, and gastric emptying of liquid was assessed in three randomized sessions of control, one-channel GES and four-channel GES. It was found that (i) GES of both one-channel and four-channel was able to completely entrain the slow waves in the entire stomach. However, the stimulation energy required by four-channel GES was only 1% of that required by one-channel GES. (ii) Four-channel, but not one-channel, GES significantly and substantially accelerated gastric emptying. An increase of 121.0 and 93.9% was noted with four-channel GES at 30 and 60 min after the meal, respectively. It was concluded that four-channel GES is substantially more efficient and effective than conventional single-channel GES in improving gastric emptying. It is worthy to explore its therapeutic potential for gastroparesis in clinical settings.

Animals↗

PubMed2005

Serum DDT, age at menarche, and abnormal menstrual cycle length.

BACKGROUND: Although dichlorodiphenyl trichloroethane (DDT) exposure is known to affect human endocrine function, few previous studies have investigated the effects of DDT exposure on age at menarche or menstrual cycle length. METHODS: A cross sectional study was conducted to study the effects of DDT exposure on age at menarche and menstrual cycle length among 466 newly married, nulliparous female Chinese textile workers aged 20-34 years enrolled between 1996 and 1998. Serum was analysed for DDT and its major metabolites. Multivariate linear regression was used to estimate DDT exposure effects on age at menarche and multivariate logistic regression was used to estimate DDT exposure effects on odds of experiencing short or long cycles. RESULTS: Relative to those in the lowest DDT quartile, the adjusted mean age at menarche was younger in those in the fourth quartile (-1.11 years). Modeled as a continuous variable, a 10 ng/g increase in serum DDT concentration was associated with an adjusted reduction in age at menarche of 0.20 years. Relative to those in the lowest DDT quartile, odds of any short cycle (<21 days) in the previous year were higher for those in the fourth quartile (odds ratio = 2.78; 95% CI 1.07 to 7.14). There were no associations between serum DDT concentrations and odds of experiencing a long cycle (>40 days). CONCLUSION: Results suggest that DDT exposure was associated with earlier age at menarche and increased risk of experiencing a shortened menstrual cycle.

Adult↗

PubMed2004

Beta-adrenoceptor subtype dependence of chronotropy in mouse embryonic stem cell-derived cardiomyocytes.

Cardiomyocytes derived from embryonic stem cells (ESCM) have potential both as an experimental model for investigating cardiac physiology and as a source for tissue repair. For both reasons it is important to characterise the responses of these cells, and one of the key modulators of contraction is the beta-adrenergic system. We therefore undertook a detailed study of the response of the spontaneous beating rate of ESCM to beta-adrenoceptor (betaAR) stimulation. Embryoid bodies (EBs) were generated from murine ES line E14Tg2a by the hanging drop method, followed by plating. Spontaneously beating areas were seen starting from 9-14 days after differentiation: the experiments described here were performed on EBs between developmental day 19 and 48. Beating cell layers were seeded with charcoal to allow tracking of movement by a video-edge detection system. Experiments were performed in physiological medium containing 1 mM Ca2+ at 37 degrees C. Isoprenaline (Iso) increased beating rate with an EC50 value of 52 nM. Iso (0.3 microM) increased basal rate from 67 +/- 7 beats per minute (bpm) to 138 +/- 18 bpm, P < 0.001, n = 22. At earlier developmental time points the response to Iso was not maintained through 5 min exposure; this spontaneous desensitisation only being observed before day 36. A repeat application of Iso after a wash period of 20 min produced reproducible effects on beating rate. Subtype dependence of the betaAR response was determined by comparing an initial response with a second in the presence of selective beta1- or beta2AR antagonists. In the presence of the specific beta1AR-blocker CGP 20712A (300 nM) the increase in rate with Iso was reduced from 207 +/- 42% of basal to 128 +/- 13%, P < 0.01. With the beta2AR-blocker ICI 118,551 (50 nM) there was no significant change in Iso response. Exposure to the muscarinic agonist, carbachol (10 microM), inhibited the increase in frequency mediated by isoprenaline, but had mixed stimulatory and inhibitory effects on basal rate. This study extends the characterisation of ESCM as a preparation for studying receptor pharmacology, and indicates that the beta1AR is the predominant subtype mediating increases in contraction rate in murine ESCM.

Animals↗

PubMed2004

Temperature-induced gelation of concentrated silicon carbide suspensions.

Due to the steric barrier provided by the adsorption of the dispersant hypermer KD1 (a polyester/polyamine condensation polymer), stable and low-viscosity suspensions of SiC, Y(2)O(3), and Al(2)O(3) powder mixtures could be prepared in methyl ethyl ketone (MEK)/ethanol (E) solvent with solids loading as high as 60 vol%. The solvency of the dispersant in MEK/E decreased dramatically on cooling. Steady shear viscosity and oscillatory measurements were performed as a function of temperature for suspensions with different solids loading. The viscosity and elastic modulus of suspension increased with decreasing temperature and became more sensitive with the increase of solids loading. The suspensions with solids loading higher than 40 vol% could be solidified with decreasing temperature, but gelation temperature and gelation stiffness decreased with decreasing solids loading. The 60 vol% solid-loaded suspension was a stable and free-flowing fluid at 20 degrees C and gradually transformed to a very highly viscous and elastic system upon cooling to about 13 degrees C. Complete solidification occurred when the temperature was decreased to 5 degrees C. The gelation mechanism was mainly based on the collapse of the adsorbed layer as the temperature decreases, which induced incipient flocculation and formed a stiff network. The gelled body was further strengthened by separation of the dispersant from the suspension.

Carbon Compounds, Inorganic↗

PubMed2004

Inheritance and molecular mapping of two fertility-restoring loci for Honglian gametophytic cytoplasmic male sterility in rice (Oryza sativaL.).

The Honglian cytoplasmic male sterility ( cms-HL) system, a novel type of gametophytic CMS in indica rice, is being used for the large-scale commercial production of hybrid rice in China. However, the genetic basis of fertility restoration ( Rf) in cms-HL remains unknown. Previous studies have shown that fertility restoration is controlled by a single locus located on chromosome 10, close to the loci Rf1 and Rf4, which respond to cms-BT and cms-WA, respectively. To determine if the Rf locus for cms-HL is different from these Rf loci and to establish fine-scale genetic and physical maps for map-based cloning of the Rf gene, high-resolution mapping of the Rf gene was carried out using RAPD and microsatellite markers in three BCF(1) populations. The results of the genetic linkage analysis indicated that two Rf loci respond to cms-HL, and that these are located in different regions of chromosome 10. One of these loci, Rf5, co-segregates with the SSR marker RM3150, and is flanked by RM1108 and RM5373, which are 0.9 cM and 1.3 cM away, respectively. Another Rf locus, designated as Rf6(t), co-segregates with RM5373, and is flanked by RM6737 and SBD07 at genetic distances of 0.4 cM. The results also demonstrated these loci are distinct from Rf1 and Rf4. A 105-kb BAC clone covering the Rf6(t) locus was obtained from a rice BAC library. The sequence of a 66-kb segment spanning the Rf6(t) locus was determined by a BLASTX search in the genomic sequence database established for the cultivar 93-11.

Cell Line↗

PubMed2004

Osteoblastic cells express phospholipid receptors and phosphatases and proliferate in response to sphingosine-1-phosphate.

Sphingosine-1-phosphate (S1P) is a naturally occurring polar phospholipid that exerts growth-factor--like effects in a number of cell types, potentially by endocrine, paracrine, and intracrine mechanisms. The biological actions of S1P are mediated in part by its specific binding to at least four members of the edg/lp family of G protein-coupled receptors (edg 1, 3, 6, and 8), and further regulated by the actions of specific cell membrane-bound lipid phosphate phosphatases (LPPs). Recent evidence has suggested that S1P may act as an osteoblast growth factor. In the current study, we demonstrate expression in osteoblastic cells of the S1P receptors edg 1, edg 5 and edg 8; the lipid phosphate phosphatases LPP-1, LPP-2, and LPP-3, and the S1P phosphatase mSPP1. S1P exerts dose-dependent mitogenic effects in cultures of primary rat osteoblastic cells and SaOS-2 cells. S1P also activates p42/44 mitogen-activated protein (MAP) kinases in osteoblastic cells, and the proliferative effects of S1P in these cultures are partially abrogated by PD-98059 and U-0126, specific inhibitors of p42/44 MAP kinase signaling. S1P-induced p42/44 MAP kinase activation in osteoblastic cells is dependent on functional Gi proteins and intracellular calcium fluxes, but not on protein kinase A, phospha-tidylinositol-3 kinase, or protein Kinase C. These data demonstrate (1) the expression by osteoblastic cells of several cell membrane-bound components of phospholipid signaling and (2) that S1P is a potent osteoblast mitogen, the proliferative action of which is mediated by a signaling pathway that involves Gi proteins, intracellular calcium, and p42/44 MAP kinases.

Animals↗

PubMed2004

Prospective study of relationship between cytomegalovirus pneumonia and viral load in renal transplant recipients.

The present study prospectively examined the relationship between cytomegalovirus interstitial pneumonia (CMV-IP) and viral load among 56 renal transplant recipients. We sought to identify the cutoff of viral load to predict CMV-IP. Blood samples were obtained weekly within the first 2 months and every second week during 2 to 6 months after kidney transplantations. A commercial real-time polymerase chain reaction (PCR)-method was applied to quantify CMV-DNA in plasma or in leukocytes. Among 54 renal transplant recipients who were analyzed for CMV-DNA in the blood (96.4%), 8 experienced CMV-IP (14.3%) and 2 died (3.6%). After kidney transplantation, CMV-DNA loads were near 0 in plasma before the week 4 and before the week 3 in leukocytes among both groups. From week 5 (week 4, in leukocytes), plasma CMV-DNA loads in the CMV-IP group increased, the peak value reached at week 8 in plasma and the week 9 in leukocytes. Whereas, the CMV-DNA loads both in plasma and in leukocytes in the non-CMV-IP group fluctuated at lower levels, those in plasma were significantly different between the 2 groups at the weeks 5, 7, and 9. For CMV-DNA in leukocytes, there were significant differences between 2 groups from week 6 to week 11. The present study demonstrated that dynamic determination of CMV-DNA may predict the occurrence of CMV-IP. Viral loads over 10(4) copies/mL plasma continuing for 3 weeks may serve as a cutoff to predict CMV-IP.

Cytomegalovirus↗

PubMed2004

Mast cells and eosinophils have a potential profibrogenic role in Crohn disease.

BACKGROUND: Mast cells and eosinophils have an important role in allergic inflammation and probably also in chronic inflammatory diseases resulting in fibrosis, such as Crohn disease where fibrosis is present as strictures. The involvement of mast cells and eosinophils in Crohn disease fibrosis was investigated. METHODS: Biopsies from diseased foci were stained for mast cells, eosinophils, anti-collagen type IV and VIII, laminin and alpha-smooth muscle actin (alpha-SMA) (IHC). Fibroblasts outgrown from the biopsies and a normal fetal intestinal fibroblast line were cultured in the presence of the human mast cell line HMC-1, or of human peripheral blood eosinophil (MACS, purity > 98%) sonicates, or of selected mediators. Fibroblast proliferation (3H-thymidine), collagen synthesis ([3H]-proline) and collagen gel contraction were evaluated. RESULTS: Mast cells were present in all the biopsies and only faintly positive for extra cellular matrix (ECM) products. Pronounced eosinophilia was detected in only two cases. Mast cell sonicates increased both Crohn disease (alpha-SMA positive) and control fibroblast proliferation, decreased collagen production and increased collagen gel contraction. Eosinophil sonicates increased fibroblast proliferation, gel contraction and collagen production. TNF-alpha decreased collagen production. Histamine, tryptase and chymase had no influence. CONCLUSIONS: These in vitro data show that mast cells and eosinophils could be involved in modulating Crohn disease fibrosis by directly influencing intestinal fibroblast properties.

Cell Communication↗

PubMed2004

Comparative disposition of [14C]ertapenem, a novel carbapenem antibiotic, in rat, monkey and man.

1. The disposition and metabolism of ertapenem, a carbapenem antibiotic, was examined in rat, monkey and man. Sprague-Dawley rats and Rhesus monkeys were given, by intravenous administration, radiolabelled doses of ertapenem (60 and 30 mg kg(-1), respectively), and healthy normal volunteers received a single fixed dose of 1000 mg. Urine and faeces were collected for determination of total radioactivity. 2. In healthy volunteers, [14C]ertapenem was eliminated by a combination of hydrolytic metabolism to a beta-lactam ring-opened derivative and renal excretion of unchanged drug. Approximately equal amounts were excreted as a beta-lactam ring-opened metabolite and unchanged drug (36.7 and 37.5% of dose, respectively). A secondary amide hydrolysis product accounted for about 1% of the dose in man. About 10% of the administered radioactivity was recovered in faeces, which suggested that a minor fraction underwent biliary and/or intestinal excretion. 3. In animals, a greater fraction of the dose was eliminated via metabolism; excretion of unchanged drug accounted for 17 and 5% of dose in rats and monkeys, respectively. In monkeys, the beta-lactam ring-opened and amide hydrolysis metabolites accounted for 74.8 and 7.59% of the dose, respectively, whereas in rats, these metabolites accounted for 31.9 and 20% of dose, respectively. 4. In vitro studies with fresh rat tissue homogenates indicated that lung and kidney were the primary organs involved in mediating formation of the beta-lactam ring-opened metabolite. The specific inhibitor of dehydropeptidase-I, cilastatin, inhibited the in vivo and in vitro metabolism of ertapenem in rats, which suggested strongly that the hydrolysis of ertapenem in lung and kidney was mediated by this enzyme.

Adult↗

PubMed2004

The longitudinal relationship of hemoglobin, fatigue and quality of life in anemic cancer patients: results from five randomized clinical trials.

BACKGROUND: Anemia is common in cancer and has been associated with fatigue and reduced health-related quality of life (HRQOL). We report the association between hemoglobin and fatigue and the impact of reducing fatigue on several domains of HRQOL. PATIENTS AND METHODS: These analyses were based on five randomized trials. Patients completed the Functional Assessment of Cancer Therapy (FACT) Anemia scales and numeric rating scales of Energy, Activity and Overall Health at baseline and after the 12-week treatment period. t-tests and linear regression models were used to evaluate associations. Analyses were stratified into three groups: solid tumor chemotherapy patients, lymphoproliferative malignancy chemotherapy patients and non-chemotherapy patients. RESULTS: Adjusted mean differences (95% CI) in FACT Fatigue change scores between hemoglobin responders (> or =2 g/dl increase) and non-responders were 3.0 (1.2, 4.7), 2.8 (0.6, 5.0) and 5.8 (2.2, 9.5) among the solid tumor, lymphoproliferative malignancy and non-chemotherapy groups, respectively. Significantly greater improvements (P <0.01) were observed in the FACT well-being scales for patients with meaningful improvement in fatigue (FACT Fatigue change score > or =3 points). After controlling for other factors, patients whose fatigue improved reported substantially greater improvements in energy, ability to perform usual activities and overall health (P <0.0001). CONCLUSIONS: Across five trials of cancer patients on and off chemotherapy, hemoglobin response was associated with meaningful improvements in fatigue, which, in turn, was associated with improved physical, functional, emotional and overall well-being.

Adolescent↗

PubMed2004

Lymphatic vessel density is significantly increased in melanoma.

BACKGROUND: Melanoma is well known for its ability to involve regional lymph nodes in the early stage. However, the presence of lymphangiogenesis in melanoma is still controversial due to lack of lymphatic-specific markers. The purpose of this study was to determine the intra- and peritumoral lymphatic vessel density (LVD) using a novel lymphatic vessel-specific marker D2-40 and compare it to general vessel density (GVD) as determined by CD31 immunostaining in a series of melanocytic lesions. METHODS: The intra- and peritumoral GVD and LVD were examined by immunohistochemistry using D2-40 and CD31 antibodies in a series of melanocytic lesions. RESULTS: We found significantly higher intratumoral LVD in melanomas as compared to either common acquired or dysplastic nevi (p < 0.01). Although peritumoral LVD in melanoma and malignant melanoma in situ was higher compared to nevi, the difference did not reach statistical significance (p = 0.059). There was no significant difference in GVD among the various groups of melanocytic lesions. CONCLUSIONS: Our results show that intratumoral LVD is significantly increased in melanomas compared to benign nevi. The higher intratumoral lymphatic density in invasive melanomas suggests that melanoma cells might promote lymphangiogenesis. In addition, assessment of intratumoral LVD may be potentially useful in the differential diagnosis of melanocytic lesions.

Antibodies, Monoclonal↗

PubMed2004

Structural features and hypoglycaemic activity of an exopolysaccharide produced by Sorangium cellulosum.

AIMS: To investigate the structural features and hypoglycaemic activity of an exopolysaccharide (EPS) produced by Sorangium cellulosum NUST06. METHODS AND RESULTS: The chemical structure of the EPS from S. cellulosum NUST06 was determined by gas-liquid chromatography, gas chromatography (GC), GC-mass spectrometry and nuclear magnetic resonance. The EPS was composed of a beta-D-(1-->4)-glucose backbone with alpha-D-(1-->6)-mannose side chains. The molecular weight of the EPS was approx. 2x10(5) Da. Healthy and alloxan-induced diabetic mice were used in the study. Blood glucose levels of the experimental animals during the trial period were analysed by a glucose test kit based on the glucose oxidase method. When 100 and 200 mg kg(-1) day(-1) of purified EPS was orally administered for 7 days, the serum glucose in alloxan-induced diabetic mice was reduced by 35.9 and 41.4% (P<0.01), and the serum glucose in healthy mice was reduced by 27.3 and 30.1% (P<0.05), respectively. CONCLUSIONS: The EPS produced by S. cellulosum NUST06 decreased blood glucose levels distinctly in both healthy and alloxan-induced diabetic mice. SIGNIFICANCE AND IMPACT OF THE STUDY: To elucidated the chemical structure of the EPS from S. cellulosum NUST06 and exploited the anti-diabetic potential of the EPS.

Animals↗

PubMed2004

Stress and dysmenorrhoea: a population based prospective study.

BACKGROUND: Dysmenorrhoea is the most common gynaecological disorder in women of reproductive age. Despite the association between stress and pregnancy outcomes, few studies have examined the possible link between stress and dysmenorrhoea. AIMS AND METHODS: Using a population based cohort of Chinese women, the independent effect of women's perceived stress in the preceding menstrual cycle on the incidence of dysmenorrhoea in the subsequent cycle was investigated prospectively. The analysis included 1160 prospectively observed menstrual cycles from 388 healthy, nulliparous, newly married women who intended to conceive. The perception of stress and the occurrence of dysmenorrhoea in each menstrual cycle were determined from daily diaries recorded by the women. RESULTS: After adjustment for important covariates, the risk of dysmenorrhoea was more than twice as great among women with high stress compared to those with low stress in the preceding cycle (OR = 2.4; 95% CI 1.4 to 4.3). The risk of dysmenorrhoea was greatest among women with both high stress and a history of dysmenorrhoea compared to women with low stress and no history of dysmenorrhoea (OR = 10.4, 95% CI 4.9 to 22.3). Stress in the follicular phase of the preceding cycles had a stronger association with dysmenorrhoea than stress in the luteal phase of the preceding cycles. CONCLUSION: This study shows a significant association between stress and the incidence of dysmenorrhoea, which is even stronger among women with a history of dysmenorrhoea.

Adult↗

PubMed2003

Genetic diversity in the northernmost Oryza rufipogon populations estimated by SSR markers.

To estimate genetic diversity of the residual northern populations of Oryza rufipogon, a total of 232 individuals from six populations were analyzed using microsatellites (SSRs). The O. rufipogon populations with different status included three from Dongxiang (Jiangxi Province) and three from Chaling (Hunan Province) in China. The 23 rice SSR primer pairs selected from the RiceGenes Database detected a total of 115 alleles, indicating that all the SSR loci were polymorphic in this study. The total gene diversity was 0.919 in the six O. rufipogon populations, and the Donxiang populations showed higher diversity than the Chaling populations. More significant genetic differentiation and less gene flow were found among the Dongxiang populations than those from Chaling. The two putative introgressed populations showed relatively high genetic variation. One in situ conserved population from Dongxiang had the lowest level of genetic diversity. The re-introduced population from Chaling restored about 90% of the genetic variation, compared with the original source population. It is concluded from these results that a relatively high level of genetic variation resided in the northern O. rufipogon populations and continued efforts of conservation of these populations are needed; and that the conservation of some Chaling and Dongxiang populations has been effective in preventing gene flow from cultivated rice. Introgression of cultivated rice demonstrated significant impacts on genetic variability of the O. rufipogon populations, and should be carefully considered in conserving this wild rice. This study also suggested that re-introduction to its original habitats is an effective approach to restore O. rufipogon populations.

Base Sequence↗

PubMed2003

Intracellular pH changes in isolated bovine articular chondrocytes during the loading and removal of cryoprotective agents.

The addition and removal of a cryoprotective agent (CPA) are necessary steps in the cryopreservation of natural or engineered tissue products. However, the introduction and removal of CPAs induces dramatic chemical changes inside tissues and cells and these could cause irreversible damage. This study examined the effect of CPA loading and removal on the intracellular pH of isolated bovine articular chondrocytes using a fluorimetric technique. Chondrocytes that had been isolated from bovine articular cartilage were loaded with the pH-sensitive fluorophore 2('),7(')-bis(carboxyethyl)-5(6)-carboxyfluorescein. After removal of the extracellular fluorophore, the intensity of fluorescence was used to measure the intracellular pH according to a pre-determined calibration curve. Changes of intracellular pH in chondrocytes were measured following their exposure to dimethyl sulfoxide (Me(2)SO) and glycerol at concentrations of 0.6, 0.9, and 1.2M and later to the isotonic or hypertonic solutions that were used to remove the CPA. The effect of the presence of NaCl on the intracellular pH during CPA removal was also examined. The temperature was maintained at 37 degrees C. Trypan blue exclusion was used to quantify cell membrane integrity after the addition and removal of CPA. It was found that when the cells were exposed to CPA, the intracellular pH decreased quickly and recovered gradually later. During CPA removal, the intracellular pH rose following exposure to isotonic Hepes-buffered medium, but the opposite was observed if the Hepes buffer solution contained no NaCl; this was ascribed to the role of NaCl in cell membrane transport. It was noted that the change in intracellular pH correlated with the cell volume excursion, which could be estimated by the Kedem-Katchalsky model, and was linked to cell survival. The resulting alteration of pH inside the cells might contribute to cell damage and loss of function after cryopreservation.

Animals↗