Biomedical subjects

Yu Zhang

Publications and source records attributed to Yu Zhang.

At least 253 records · Page 14Linked to original sources

PubMed2004

Biological removal of methanol from process condensate for the purpose of reclamation.

The biological removal of methanol from condensate of ammonia manufacturing processes for the purpose of reclamation using contact type reactor was studied. Methanol of 60 mg/L was removed completely under an HRT of 1.12 h. Optimal inorganic nutrient dose was determined on evaluating methanol removal performance and dehydrogenase activities (DHA) under different nutrition doses. The optimal inorganic nutrient dose only gave an increase of conductivity of ca. 10 micros/cm2 in the effluent on treating synthetic condensate containing methanol of 30 mg/L. The results demonstrated that biological removal of methanol was effective for the purpose of recovering the methanol-bearing condensate.

Ammonia↗

PubMed2004

[Removal of humic substances using cerium-iron adsorbent].

A rare earth metal inorganic adsorbent, cerium-iron adsorbent (CFA), was developed, and its performance for fulvic acid (FA) removal was evaluated. Experimental results show that rare earth metal adsorbent had a relatively high adsorption capacity and good kinetic property for FA ion under the pH range of 3.0-6.5, then the adsorption capacity decreased with the increase of pH. FA seriously inhibited the removal of arsenate, suggesting that the adsorption sites for As(V) and FA were similar. Fourier transform infrared (FTIR) spectra of CFA before and after FA adsorption demonstrated that M-OH groups plays an important role for FA removal. The pH(icp) is 5.6 through the measure of Zeta potential.

Adsorption↗

PubMed2004

[Relationship of cyclooxygenase 2 expression and chemotherapy response and prognosis in human ovarian carcinoma].

OBJECTIVE: To investigate the relationship between expression of cyclooxygenase 2 (COX-2) and chemotherapy response and prognosis of patients with ovarian carcinoma. METHODS: The expression of COX-2 was detected by immunohistochemistry in ovarian carcinoma tissues. Correlations between COX-2 and clinicopathological markers, therapeutic effect and prognosis of the patients with ovarian carcinoma were analyzed by chi(2) test, Kplan-Meire and Cox model. RESULTS: COX-2 positive rate of 70 ovarian carcinomas was 60%. Expression of COX-2 was correlated with lymph nodes metastasis only (P = 0.001). There was no correlation between COX-2 and pathohistological types, clinical stage, pathohistological grade, age at diagnosis (P = 0.397, 0.094, 0.275, 0.394). In patients whose serum CA(125) level did not drop to normal after two courses of chemotherapy, the COX-2 positive rate (76%) was significantly higher than in those whose serum CA(125) level decreased obviously (51%, P = 0.042). The positive rate was also higher in patients with recurrent diseases (67%) than in those without recurrence (46%, P = 0.062). In univariate survival analysis, the expression of COX-2 was associated with a significantly reduced median survival time (P = 0.029). In multivariate survival analysis, COX-2 was an independent prognostic factor for poor survival (P = 0.036). CONCLUSION: COX-2 expression is correlated with poor chemotherapy response and prognostic outcome. It is an independent prognostic factor of ovarian carcinoma.

Adult↗

PubMed2004

[Using platelet-rich plasma (PRP) to improve bone regeneration in implant bone defect].

OBJECTIVE: To evaluate the result of bone regeneration due to using PRP in combination with beta-TCP in bone defect adjacent to oral implantation. METHODS: Ten patients (6 males, 4 females, with an average age of 49.6 years) participated in this study. Seven of them underwent maxillary sinus augmentations, and 3 underwent GBR for peri-implant bone defects. PRP + beta-TCP was used in 4 cases and beta-TCP in other 6 as control. X-ray examinations were carried out prior to operation and in 1 week, at 3 months, 6 months after operation. After 4 - 6 months, 3 biopsy specimens were obtained at the time of the second stage operation in each group. RESULTS: Bone grafts healed well without any infection in all cases. Radiographs showed that bone grafts integrated together with the bone. The histological result showed that new bone was formed among particles of beta-TCP in both groups, but in PRP + beta-TCP group denser and better arranged woven bone was observed, and more new bone was formed into the micropores of the particles. CONCLUSIONS: The result in this study implied that PRP in combination with beta-TCP can improve bone regeneration in bone defect adjacent to oral implantation.

Adolescent↗

PubMed2004

[Effects of allogeneic hematopoietic stem cell transplantation with very-high-dose conditioning regimen for refractory leukemia].

OBJECTIVE: To explore the regimen-related toxicity (RRT) and therapeutic effects of very-high-dose conditioning regimen combined with induction of graft-versus-leukemia (GVL) effects in allogeneic hematopoietic stem cell transplantation (allo-HSCT) for refractory leukemia with unattainable complete remission (CR) before transplantation. METHODS: Eighteen patients who failed to obtain CR before transplantation received very-high-dose conditioning regimen protocol (experimental group), and 62 patients with acute leukemia with CR or with chronic myeloid leukemia in the chronic phase before transplantation received total body irradiation plus cyclophosphamide (CTX) or modified BuCY (hydroxyurea, busulfan, Ara-C, CTX) protocol (control group). In patients with refractory leukemia who did not develop graft-versus-host disease (GVHD) 30 d after the transplantation, GVL was induced by rapid reduction of the dosage of cyclosporin A or by donor lymphocytic infusion. The incidence and mortality of RRT and the rates of CR, GVHD and leukemia relapse after transplantation were investigated. Kaplan-Meier survival analysis model was used to estimate the disease-free survival (DFS) rate at 3 years post-transplantation. RESULTS: Except for one patient in the experimental group and two in the control group who died of transplantation- related complications, all the other patients obtained hematopoietic reconstitution. The total incidence of RRT was 100% in both groups, involving most frequently the stomach and intestines at the rate as high as 83.3% in the experimental group and 85.5% in the control group. RRT involving the oral cavity occurred in 44.4% and 62.9%, and that involving the bladder in 16.7% and 33.9% of the cases in the experimental group and control group, respectively, all similar between the groups (P=0.823, 0.172 and 0.244, respectively). The RRT mortality was 0 and 5% in the experimental and control groups, respectively (P=0.341). With the exception of one patient who died of infection, all the other patients treated with very-high-dose conditioning regimen obtained CR. The incidences of acute/chronic GVHD were 58.8%/92.6% and 40.0%/55.8%, respectively, in the experimental and control groups. The incidence of leukemia relapse was 11.8% and 18.3%, and DFS at 3 years after transplantation was (61.2+/-12.3)% and (65.0+/-7.4)% (P=0.6311) in the two groups, respectively. CONCLUSION: Consecutive very-high-dose conditioning regimen combined with GVL induction after transplantation can increase the rate of CR and DFS, without increasing RRT incidence and mortality in allo-HSCT for the refractory leukemia with unattainable CR pre-transplantation.

Adolescent↗

PubMed2004

[Value of EBNA1-IgA and EA-IgG in serological diagnosis of nasopharyngeal carcinoma].

OBJECTIVE: To evaluate the value of EBNA1-IgA and EA-IgG in serological diagnosis of nasopharyngeal carcinoma (NPC). METHODS: The serum EBNA1-IgA and EA-IgG of 56 patients with NPC and 58 healthy adults were detected by ELISA. The sensitivity, specificity, positive predictive value, accuracy rate and odds ratio of the two tests used singly or in combination were compared with each other. RESULTS: The sensitivity of EBNA1-IgA (91.07%) was higher than that of EA-IgG (87.50%), while the specificity of EA-IgG (87.93%) was higher than that of EBNA1-IgA (84.48%). The combination of EBNA1-IgA and EA-IgG could enhance the specificity (94.83%), positive predictive value (0.9375), likelihood ratio (15.5435) and odds ratio (75.0000) for serological diagnosis of NPC. Forty-five patients showed both positive EBNA1-IgA and positive EA-IgG. A positive EA-IgG was detected in 4 out of 5 patients with negative EBNA1-IgA and a positive EBNA1-IgA was founded in 6 out of 7 patients with negative EA-IgG. CONCLUSION: Although relatively high sensitivity and specificity could be obtained by either EBNA1-IgA or EA-IgG test alone, the combination of these two tests with a complementary effect is able to enhance the reliability of serological diagnosis of NPC as most patients have positive ENBA1-IgA and EA-IgG concurrently.

Adult↗

PubMed2004

Effects of tea polyphenols on hepatic fibrosis in rats with alcoholic liver disease.

BACKGROUND: As an anti-oxidation agent, tea polyphenols may have the effect of anti-fibrosis. This study was designed to observe the effect of tea polyphenols on hepatic fibrosis in rats with alcoholic liver disease and to explore the related mechanisms. METHODS: Sixty healthy Sprague-Dawley rats were divided randomly into normal control group, single alcohol group, and three alcohol groups given different doses of tea polyphenols. Alcohol or isovolumic normal saline and corresponding doses of tea polyphenols were given daily to the rats separately. The rats were sacrificed at the end of the 24th week. Masson staining was performed to observe liver fibrosis, serum endotoxin, and oxidant and anti-oxidant activity. RESULTS: Hepatic fibrosis was less severe in the rats of the alcohol groups given tea polyphenols than in the single alcohol group. Tea polyphenols increased the serum anti-oxidant capacity and decreased the endotoxin level. CONCLUSION: Tea polyphenols show anti-fibrosis effect in rats with alcoholic liver disease, and the mechanism may be related to the clearance of overall oxidant and decrease of the endotoxin level.

Animals↗

PubMed2004

[Therapeutic efficacy of hematopoietic stem cell transplantation in patients with chronic myelogenous leukemia].

OBJECTIVE: To evaluate the clineffects of autologous and allogeneic hematopoietic stem cell transplantation (HSCT) for chronic myelogenous leukemia (CML). METHODS: Fifty-seven patients with CML were treated by HSCT, including 8 patients treated with autologous transplantation in vivo and vitro purging minimal residual disease (MRD), 39 with related donor allogeneic HSCT (allo-HSCT), and 10 with unrelated donor allo-HSCT. For the conditioning regimen, total-body irradiation with cyclophosphamide (CTX) was given in 32 patients, modified BuCY protocol (hydroxyurea, busulfan, Ara-C, CTX) in 24 patients, and MACC protocol (melphalan, Ara-C, CTX and lomustine) in one patient. Cyclosporine (CsA) and methotrexate (MTX) were used in patients with related donor allo-HSCT, and the combination of CsA, MTX , mycophenolate mofetil (MMF), and antithymocyte globulin (ATG) in unrelated donor all-HSCT to prevent graft versus host disease (GVHD). Kaplan-Meier survival analysis model was used to estimate the overall survival and the disease-free survival (DFS) at 5 years after transplantation. RESULTS: In 8 patients with autologous transplantation, 7 obtained partial or complete cytogenetic remission (CR) within 3 months after transplantation and one died of transplantation-related complication. In 49 patients with allo-HSCT transplantation, all patients obtained CR except for two patients, one of whom failed to obtain CR and the other died of hepatic veno-occlusive disease. The incidence of infection and veno-occlusive disease during transplantation was 33.3% and 7.0%, respectively. The incidence of hemorrhagic cystitis and cytomegalovirus interstitial pneumonia after transplantation was 22.8% and 8.8%, respectively. Veno-occlusive disease, hemorrhagic cystitis or cytomegalovirus interstitial pneumonia did not occur in patients with autologous transplantation. The incidence of acute GVHD was 41.0% and 48.6%, and that of chronic GVHD 40.0% and 42.9% in patients with related and unrelated transplantation, respectively. The rate of relapse was 57.1% and 12.8%, with DFS at 5 years of 25.0% and 61.7%, respectively, in patients with autologous and related donor transplantation. The DFS at 5 years was 70.7% and 34.1%, respectively, in patients with chronic/accelerated phases and blast crisis be fore trans plantation. CONCLUSION: allo-HSCT can produce a higher clinical cure rate in CML patients in chronic phase CsA+MTX+MMF+ ATG protocol is more effective for prevention and alleviation of acute GVHD in patients with unrelated donor transplantation. Autologous transplantation with bone marrow purging helps prolong the patients' survival and even obtain clinical cure of CML.

Adolescent↗

PubMed2004

[Sugar metabolism and its regulation in postharvest ripening kiwifruit].

Kiwifruit (Actinidia deliciosa cv. Bruno) was used to investigate starch and sugar metabolism and the mechanisms of regulation by acetylsalicylic acid (AsA 1.0 mmol/L, pH 3.5), low temperature (0 degrees C) and ethylene (100 microL/L) treatments. There was an increase in amylase activity at the initial stage followed by dramatical decrease in starch content and a rapid increase in hexose content at the rapid stage of fruit ripening and softening, which was associated with an increase in SPS activity, a decrease in acid invertase activity, and the accumulation of sucrose. AsA and low temperature treatments inhibited the amylase activity, slowed down the hydrolysis of starch and the accumulation of hexoses, suppressed the rise of SPS activity and the decline of acid invertase activity in the ripening fruit. The accumulation of sucrose was delayed by AsA and low temperature treatments. However, ethylene application induced amylase activity, accelerated starch hydrolysis, and raised the hexose content. The SPS activity also increased and the sucrose accumulated in the presence of ethylene. It is suggested that the SPS may play a key role in sugar metabolism of postharvest kiwifruit, and it could be activated by hexose and feedback-inhibited by sucrose. AsA, low temperature and ethylene treatments regulate sugar metabolism probably through influencing the SPS activity.

Actinidia↗

PubMed2004

[Inactivation of T4 phage in water environment using proteinase].

The inactivation effectiveness of proteinase to viruses was investigated by using T4 phage as a model virus. The results showed that the inactivation effectiveness of proteinase to T4 phage was obvious. In the optimum conditions and 67.5 u/mL concentration, the inactivation rate of proteinase K to T4 phage in sterilized water and in sewage achieved 99.4% and 49.4% respectively in an hour, and achieved >99.9% and 81.1% in three hours. The inactivation rate of the industrial proteinase 1398 to T4 phage in sterilized water achieved 74.4% in an hour. The effects of pH and temperature on the inactivation effectiveness was not evident.

Bacteriophage T4↗

PubMed2004

[Cloning and expression of ethylene receptor gene Ad-ETR1 from kiwifruit].

According to the conserved amino acid sequence from ethylene receptors in other plants, a pair of degenerate primers was designed and a 657-bp cDNA fragment encoding an ethylene receptor fruit was obtained by RT-PCR from ripening kiwifruit (Actinidia deliciosa cv. Bruno) (Fig. 1). The cDNA fragment encoding 219 amino acids was named Ad-ETR1, and its sequences shared high similarity at both nucleotide and polypeptide level with the sequences from the plants of Arabidopsis, tomato, persimmon, avocado, citrus and peach (Fig. 2, Table 1). Northern blot analysis indicated that the levels of Ad-ETR1 mRNA increased during kiwifruit ripening and reached peak at 144 h after treatment, then dropped immediately. The expression of Ad-ETR1 could be induced by ethylene treatment, while acetylsalicylic acid (ASA) treatment inhibited its expression (Fig. 4). In consistency with the changes of Ad-ETR1 mRNA, ethylene or ASA treatment had marked effects on the kiwifruit ethylene production and fruit softening (Fig. 3). The significance of these results was discussed.

Actinidia↗

PubMed2004

[Fabrication of laryngeal cartilage by means of tissue engineering technique].

OBJECTIVE: To explore the method of fabricating tissue engineered laryngeal cartilage. METHODS: The rib and articular cartilage of infant New Zealand white rabbits were harvested in sterile condition. The chondrocytes were separated by collagenase digestion and cultured in vitro for 3 passage. Serial steps of solution casting, extrusion molding and particulate leaching were used to make larynx-shaped biomaterial models with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate, PHBHH). The chondrocytes were seeded onto PHBHH scaffolds to form cell-PHBHH composites, which were subsequently in vitro for one week. After that, the measure of filling inner space of cell-PHBHH composites together with wrapping total composites using either greater omentum (n = 9) or fascia flap and muscle (also n = 9) in experimental groups was taken to implant the larynx-shaped biomaterial models seeded with chondrocytes into the belly and the back of adult New Zealand white rabbits. Control groups (every group n = 3) were the same measure as experimental groups but without chondrocyte on PHBHH scaffolds. Finally, morphological observation, HE staining & special staining and immunohistochemical test were conducted to assess cartilage regeneration and its shape at different period following implantation. RESULTS: The rate of viable cell in the final cell suspension was (93 +/- 2)% after well-controlled prolongation of digestion trypsin. Similar to that by traditional procedures (94 +/- 2)% (P > 0.05). The larynx-shaped PHBHH models with edges and corners of laryngeal cartilage made by us appeared to be hollow half-trumpet shape and its porosity was more than 90%. It showed that chondrocytes equally attached to the surface of porous PHBHH and filled within porousness with scanning electron microscopic examination. Tissue engineered larynx-shaped specimens could alternatively be harvested with the above mentioned two different implantation measures. The specimens presented to be similar to that before implantation in gross shape. It was demonstrated to be cartilaginous tissue through histological and immunohistochemical examination. Furthermore, There was nearly no difference between two kinds of tissue engineered laryngeal cartilage with two measures of implantation in morphology and histology. CONCLUSIONS: The regeneration of tissue engineered cartilage in vivo is not influenced by the chondrocytes harvested by improvement of well-controlled prolonged digestion with trypsin during in vitro cell culture. It seems that PHBHH may be used as scaffold in cartilage tissue engineering and wrapping together with filling method with either greater omentum or fascia flap and muscle is appropriate for fabricating tissue engineered laryngeal cartilage.

Animals↗

PubMed2004

[Effect of heparin on fetal growth restriction].

OBJECTIVE: To investigate the clinical effect and safety of heparin in treating fetal growth restriction (FGR). METHODS: A total of 107 women diagnosed with FGR were randomized into three groups. Group 1 (standard heparin group, n = 37) received 50 - 75 mg standard heparin added to 500 ml 5% glucose sodium chloride, infused intravenously in 6 - 8 hours. Group 2 (low molecular weight heparin group, n = 31) received 0.2 - 0.4 ml low molecular weight heparin given by subcutaneous injection. Control group (n = 39) received 20 ml dan-shen added to 500 ml low-molecular-weight dextran infused intravenously. Fetal growth indices, biophysical score, umbilical artery blood flow, count of platelet (PLT), prothrombin time (PT), activated partial thromboplastin time (APTT), 1-minute Apgar score, body weight and gestational age of the neonates were measured. Babies prognosis was followed-up. RESULTS: (1) Height of fundus of uterus was obviously increased per week in the groups of standard heparin (0.7 +/- 0.6) cm and low molecular weight heparin [(0.7 +/- 0.6) cm]] vs. control group [(0.5 +/- 0.4) cm, P < 0.05]. Biparietal diameter of fetus increased in standard heparin [(2.4 +/- 0.7) mm] and low molecular weight heparin [(2.5 +/- 0.8) mm] groups vs. control [(1.7 +/- 0.6) mm, P < 0.05]. The femur length, head circumference and abdominal circumference of fetus were significantly longer in heparin treated patients than in control group (P < 0.05). (2) Biophysical score improved in groups of standard heparin (9.7 +/- 0.8) and low molecular weight heparin (9.6 +/- 0.6) vs. control group (8.9 +/- 0.7) (P < 0.05). (3) Umbilical blood S/D ratio decreased in standard heparin (2.5 +/- 0.5) and low molecular weight heparin (2.4 +/- 0.5) groups vs. control group (2.9 +/- 0.6) (P < 0.05). Pulsatile index (PI) and resistance index (RI) were significantly lower also (P < 0.05).(4) Rate of one minute Apgar score (8 - 10) was 86% in group 1, 87% in group 2 and 74% in control group, respectively. Body weight of the neonates was significantly increased in group 1(3100 +/- 256 g) and in group 2 [(3080 +/- 225) g] vs. [(2580 +/- 304) g] in control group (P < 0.05). Gestational age was prolonged in group 1 [(38 +/- 3) w] and group 2 [(38 +/- 4) w] vs. control group [(37 +/- 4) w, P < 0.05]. (5) Incidence of term small for gestational age infant in groups of standard heparin and low molecular weight heparin was 5% and 6%, respectively, significantly lower than those in the control group (18%) (P < 0.05). (6) No difference was shown in PLT, PT and APTT before and after heparin treatment (P > 0.05). (7) There was no difference in fetal growth indices, biophysical score, umbilical blood, neonatal outcome between standard heparin and low molecular heparin groups. CONCLUSIONS: Heparin can improve placenta function and obviously increase body weight of fetuses and neonates. It is safe for both pregnant women and their fetuses.

Birth Weight↗

PubMed2004

[Diagnosis of ovarian teratomas with two-dimensional ultrasound].

OBJECTIVE: To investigate the value of two-dimensional ultrasound in the diagnosis of tertoma in the ovary. METHODS: The sonographic images of 278 cases of ovarian teratomas confirmed by surgical pathology were reviewed. RESULTS: According to the surgical pathological results of the 278 cases, 95.3% (265/278) were benign, and 4.7% (13/278) were malignant. Among those, 88.5% (246/278) cases were unilateral, and 11.5% (32/278) were bilateral. Compared with the surgical pathological results, the rate of accurate diagnosis with ultrasound was 95.0% (264/278), the rate of misdiagnosis was 3.6% (10/278), and the rate of missed diagnosis was 1.4% (4/278). Among the benign cases, the rate of accurate dingnosis was 95.1% (252/265); the rate of misdiagnosis was 3.4% (9/265); and the rate of missed diagnosis was 1.5% (4/265). Among the 13 malignant cases, the rate of accurate diagnosis and misdiagnosis were 92.3% (12/13) and 7.7% (1/13), respectively. CONCLUSION: Two-dimensional ultrasound can be the first choice in diagnosing teratoma. Although the sonographic images of ovarian teratoma have specialities, they should be differentiated from other ovarian tumors, such as chocolate cyst of ovary, denaturation of subserous myoma, inflammatory mass, and etc.

Adult↗

PubMed2004

[Expression of transforming growth factor-beta1 in cervical squamous carcinoma cell and stroma].

OBJECTIVE: To explore the significance and expression of transforming growth factor-beta1 (TGFbeta1) in cervical squamous carcinoma. METHODS: The expression of TGFbeta1 in 31 cases of cervical squamous carcinomas were detected by SP immunohistochemical staining. RESULTS: TGFbeta1 expression was found in both cytoplasm and extracellular stroma. TGFbeta1 expression increased when the pathologic grade was getting worse and clinical stage was of later the in extracellular matrix and decreased in cytoplasm. The positive rate of TGFbeta1 in cytoplasm in the low grade group was lower than that in the high and middle grade (P < 0.05). The positive rate of TGFbeta1 in extracellular stroma in the high grade group was significantly lower than that of the other two groups. In cytoplasma, the TGFbeta1 expression was obviously higher in stage I than in stage II and III, while it was lower in extracellular stroma (P < 0.05). There was no significant difference between stage II and III (P > 0.05. CONCLUSION: The decrease of TGFbeta1 expression may play an important role in the differentiation and devepolment of cervical squamous carcinoma. High expressions of TGFbeta1 in extracellular stroma may be related to the matastasis of cervical squamous carcinoma.

Adult↗

PubMed2003

Fundamental role of the Rip2/caspase-1 pathway in hypoxia and ischemia-induced neuronal cell death.

Caspase-1 plays a key role in inflammatory pathways by processing pro-IL-1beta into the active cytokine mature IL-1beta. Given its sequence similarity with the Caenorhabditis elegans cell death gene ced-3,it has long been speculated that caspase-1 may also play a role in cell death. However, an unequivocal role for caspase-1 in cell death has been questioned, and not definitively demonstrated. Furthermore, if caspase-1 does play a role in cell death, its position in the apoptotic hierarchy has not been clearly defined. Previous studies have shown that caspase-1 knockout (KO) mice and transgenic mice expressing a dominant-negative caspase-1 construct are resistant to ischemic brain injury. We provide direct evidence that caspase-1 plays a key role in neuronal cell death and that caspase-1 is an apical activator of the cell death pathway in the premitochondrial collapse stage. Furthermore, we demonstrate that Rip2/Cardiak/Rick is a stress-inducible upstream modulator of pro-caspase-1 apoptotic activation. We provide evidence that Bid cleavage appears to be an important downstream effector of caspase-1-mediated cell death. Our data demonstrate that caspase-1 is an apical mediator of neuronal cell death during in vitro hypoxia, and confirmed in vivo in ischemia, and provide insights into the sequence of events involved in this pathological cell death process.

Animals↗

PubMed2003

Sequence variations of simple sequence repeats on chromosome-4 in two subspecies of the Asian cultivated rice.

Computational screening of the chromosome-4 sequence of the rice cultivar Nipponbare ( Oryza sativa L. japonica) revealed 1,844 tandem simple sequence repeats (SSRs) or microsatellites with SSR motifs >/=20 bp and repeated unit length of 1-6 base pairs. Thus SSRs occur once in every 18.8 kb, on the average, on the chromosome with one SSR per 23.8 kb and 16 kb on the short and long arms, respectively. No SSR was detected in the core region of the centromere. Poly(AT)(n) repeats represented the most abundant and length polymorphic class of SSRs on the chromosome, but it did not occur in the exons. GC-rich trinucleotide repeats were most abundant in the coding regions, representing 71.69% of the SSRs identified in the exons. Two hundred and twenty four SSRs were associated with the repetitive DNA sequences, most of them were poly(AT)(n) tracts. Sequence variations of SSRs between two cultivars, representing the two subspecies of the Asian cultivated rice indica and japonica, were identified, revealing that divergence and convergence of the two subspecies could be traced by the analysis of SSRs. These results provide a great opportunity for SSR-based marker development and comparative genome analysis of the two subspecies of the Asian cultivated rice.

Base Composition↗

PubMed2003

Size dependence of second-order optical nonlinearity of CdS nanoparticles studied by hyper-Rayleigh scattering.

The second-order optical nonlinearity of CdS nanoparticles with different mean diameters of 28.0, 30.0, 31.5, 50.0, and 91.0 A was studied by the incoherent hyper-Rayleigh scattering technique. Results show that the first-order hyperpolarizability beta value per CdS particle decreases with decreasing size from 91.0 to 31.5 A; however, as CdS particle size further decreases, this trend is reversed and the beta value increases. Substantially, the normalized value of the first-order hyperpolarizability per CdS formula unit, beta(0), exhibits systematic enhancement with decreasing size. This is interpreted in terms of a so-called surface contribution mechanism. The two aspects of quantum size effects, the size dependence of optical band-gap and oscillator strength, cannot be adopted to explain the size dependence of the second-order optical nonlinearity of CdS nanoparticles.

Journal Article↗