桂平市竹笋资源及其开发利用

桂平市食用竹笋资源丰富,有大头竹笋、吊丝竹笋、浦竹笋、毛竹笋等十余种,年产鲜笋８５００ｔ以上。原有的加工方法比较落后,现已注意引进新技术,今后还需进一步开发利用。     

羊角椒辣味物质成份分析

用紫外光谱法、红外光谱法和高效液相色谱法分析羊角椒中辣味物质纯度与组成,表明辣味物质由辣椒素、二氢辣椒素和降二氢辣椒素组成。     

Binding of vanadate to human erythrocyte ghosts and subsequent events

Spectroscopic techniques were used to investigate the interaction between vanadate and human erythrocyte ghosts. Direct evidence from ⁵¹V nuclear magnetic resonance (NMR) studies suggested that the monomeric and polymeric vanadate species may bind to the anion binding sites of band 3 protein of the erythrocyte membrane. The results of ⁵¹V NMR studies and the quenching effect of vanadate on the intrinsic fluorescence of the membrane proteins indicated that in the low concentration range of vanadate (<0.6 mm), monomeric vanadate binds mostly to the anion sites of band 3 protein with the dissociation constant close to 0.23 mm. The experiments of sulfhydryl content titration by the method of Ellman and residue sulfhydryl-labeled fluorescence spectroscopies clearly displayed that vanadate reacts directly with sulfhydryl groups. The appearance of the anisotropic election spin resonance (ESR) signal of vanadyl suggests that a small (c. 3%) amount of vanadate was reduced by sulfhydryl groups of membrane proteins. The fluidity and order of intact ghost membrane were reduced by the reaction with vanadate, as shown by the ESR studies employing the protein- and lipid-specific spin labels. It was concluded that although vanadates mainly bind to band 3 protein, a minor part of vanadate may oxidize the residue sulfhydryl groups of membrane proteins, and thus decrease the fluidity of erythrocyte membrane.     

Primary structure of human thromboxane synthase determined from the cDNA sequence.

Polymerase chain reaction techniques have been used to isolate a cDNA clone containing the entire protein coding region of thromboxane A2 synthase (EC 5.3.99.5) from a human lung cDNA library. The cDNA clone hybridizes with a single 2.1-kilobase mRNA species in phorbol ester-induced human erythroleukemia and monocytic leukemia cell lines. A second cDNA, differing only by an insert of 163 base pairs near the 3'-end of the translated region, was also found to be present in the same library. The proteins predicted from both nucleic acid sequences include the three polypeptide sequences determined from amino acid sequencing of the purified human platelet enzyme, five potential sites for N-glycosylation, and a hydrophobic region that may serve to anchor the synthase in the endoplasmic reticulum membrane. The longer predicted protein, designated thromboxane synthase-I, contains 534 amino acids, with a Mr of 60,684, whereas the shorter protein, designated thromboxane synthase-II, contains 460 amino acids and has a Mr of 52,408. Although thromboxane synthase-II lacks the conserved cysteine that serves as the proximal heme ligand in the other cytochromes, significant sequence similarities exist among thromboxane synthase-I and -II and several P450s, particularly those in family 3. The overall amino acid identity is considerably less than 40%, making it likely that thromboxane synthase represents a previously undefined family of cytochrome P450.     

Up-regulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors in murine peritoneal exudate macrophages by both GM-CSF and IL-3.

Murine peritoneal exudate macrophages (PEM) display multiple CSF receptors. In this study, the expression of granulocyte-macrophage (GM)-CSF receptors in PEM was studied. PEM displayed over 5000 single type, high affinity GM-CSF receptors/cell with a Kd = 38 to 42 pM and an apparent molecular mass of 86,000 Da. Treatment of PEM with low, but not high, concentrations of recombinant murine (rMu) GM-CSF continuously for 24 h resulted in a marked up-regulation of GM-CSF receptors in PEM. A similar up-regulation of GM-CSF receptors also was detected in PEM cultures treated with rMuIL-3 (1-100 ng/ml) for 24 h or longer, regardless the doses of rMuIL-3 added in this case. Scatchard analysis of equilibrium binding showed that the enhanced binding activities in both cases were due to an increase in total number of GM-CSF receptors rather than changes in receptor affinity. Contrariwise, treatment with recombinant human macrophage-CSF (greater than 100-1000 ng/ml) partially inhibited the expression of GM-CSF receptors in PEM. Removal of rMuGM-CSF from culture medium 24 h after treatment led to a further up-regulation of GM-CSF receptors over a 4 to 24-h period, depending on the doses of initial treatment. On the other hand, removal of rMuIL-3 from culture medium after prolonged treatment did not result in further increase in GM-CSF receptors. The protein synthesis inhibitor cycloheximide abrogated GM-CSF receptor up-regulation induced by both rMuIL-3 and rMuGM-CSF, whereas actinomycin D inhibited only the second (8-24 h) phase of GM-CSF receptor up-regulation induced by exposure to high concentrations rMuGM-CSF (10 ng/ml). These findings suggest that rMuGM-CSF and rMuIL-3 up-regulate GM-CSF receptors in PEM in part through similar or identical metabolic pathways and provide further evidence of a close linkage between IL-3 and GM-CSF receptors.     

Thrombomodulin as a marker of radiation-induced endothelial cell injury.

Cultured confluent human umbilical vein endothelial cells were irradiated in vitro with 60Co gamma rays at doses from 0 to 50 Gy. After irradiation thrombomodulin was measured at different times over 6 days in the supernatants of endothelial cell culture medium, on the surface of the cells, and within the cells. At 24 h after irradiation, an increase in the release of thrombomodulin from irradiated endothelial cells and an increase in the number of molecules and the activity of thrombomodulin on the surface of the cells were observed; these reactions were dependent on radiation dose. The capacity of the cells to produce and release thrombomodulin was decreased from 2 to 6 days after exposure to 60Co gamma rays. Our data indicate that radiation can injure endothelial cells, and that thrombomodulin may be used as a marker of radiation-induced injury in endothelial cells. The interrelationship between the dysfunction of irradiated endothelial cells and the pathological mechanisms of acute radiation disease is also discussed.     

Rapid and sensitive assay for the phytotoxin rhizobitoxine.

Rhizobitoxine is a phytotoxin synthesized by some strains of the legume symbiont genus Bradyrhizobium and the plant pathogen Pseudomonas andropogonis. We demonstrate here a new enzymatic assay which is 100-fold more sensitive than previous assays and can detect as little as 1.0 pmol of rhizobitoxine. The assay is based on the inhibition of Salmonella typhimurium beta-cystathionase by rhizobitoxine. Interestingly, beta-cystathionase from Bradyrhizobium japonicum is insensitive to rhizobitoxine at concentrations lower than 75 microM.     

Traveling wave solutions in a two-group SIR epidemic model with constant recruitment

Journal of Mathematical Biology - Host heterogeneity can be modeled by using multi-group structures in the population. In this paper we investigate the existence and nonexistence of traveling waves...     

Natural variation in the promoter of OsHMA3 contributes to differential grain cadmium accumulation between Indica and Japonica rice

Rice is a major source of cadmium(Cd) intake for Asian people. Indica rice usually accumulates more Cd in shoots and grains than Japonica rice. However, underlying genetic bases for differential Cd accumulation between Indica and Japonica rice are still unknown. In this study, we cloned a quantitative trait locus(QTL) grain Cd concentration on chromosome 7(GCC7) responsible for differential grain Cd accumulation between two rice varieties by performing QTL analysis and map-based cloning. We found that the two GCC7 alleles, GCC7~(PA64s) and GCC7~(93-11), had different promoter activity of OsHMA3,leading to different OsHMA3 expression and different shoot and grain Cd concentrations. By analyzing the distribution of different haplotypes of GCC7 among diverse rice accessions, we discovered that the high and low Cd accumulation alleles, namely GCC7~(93-11) and GCC7~(PA64s), were preferentially distributed in Indica and Japonica rice,respectively. We further showed that the GCC7~(PA64s)allele can be used to replace the GCC7~(93-11) allele in the super cultivar 93-11 to reduce grain Cd concentration without adverse effect on agronomic traits. Our results thus reveal that the QTL GCC7 with sequence variation in the OsHMA3 promoter is an important determinant controlling differential grain Cd accumulation between Indica and Japonica rice.