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Biomedical subjects

Q Z Li

Publications and source records attributed to Q Z Li.

18 recordsLinked to original sources
PubMed2006

A two-dimensional adsorption kinetic model for thermal hysteresis activity in antifreeze proteins.

Antifreeze proteins (AFPs) and antifreeze glycoproteins (AFGPs), collectively abbreviated as AF(G)Ps, are synthesized by various organisms to enable their cells to survive in subzero environments. Although the AF(G)Ps are markedly diverse in structure, they all function by adsorbing to the surface of embryonic ice crystals to inhibit their growth. This adsorption results in a freezing temperature depression without an appreciable change in the melting temperature. The difference between the melting and freezing temperatures, termed thermal hysteresis (TH), is used to detect and quantify the antifreeze activity. Insights from crystallographic structures of a number of AFPs have led to a good understanding of the ice-protein interaction features. Computational studies have focused either on verifying a specific model of AFP-ice interaction or on understanding the protein-induced changes in the ice crystal morphology. In order to explain the origin of TH, we propose a novel two-dimensional adsorption kinetic model between AFPs and ice crystal surfaces. The validity of the model has been demonstrated by reproducing the TH curve on two different beta-helical AFPs upon increasing the protein concentration. In particular, this model is able to accommodate the change in the TH behavior observed experimentally when the size of the AFPs is increased systematically. Our results suggest that in addition to the specificity of the AFPs for the ice, the coverage of the AFPs on the ice surface is an equally necessary condition for their TH activity.

Adsorption↗
PubMed2006

AUNX1, a novel locus responsible for X linked recessive auditory and peripheral neuropathy, maps to Xq23-27.3.

BACKGROUND: We report here the genetic characterisation of a large five generation Chinese family with the phenotypic features of auditory neuropathy and progressive peripheral sensory neuropathy, and the genetic feature of X linked recessive inheritance. Disease onset was at adolescence (at an average age of 13 years for six affected subjects). The degree of hearing impairment varied from mild to severe, with decreased otoacoustic emissions; auditory brainstem responses were lacking from onset. METHODS: Two-point and multipoint model based linkage analysis using the MILNK and LINKMAP programs of the FASTLINK software package produced maximum two-point and multipoint LOD scores of 2.41 and 2.41, respectively. RESULTS: These findings define a novel X linked auditory neuropathy locus/region (AUNX1, Xq23-q27.3). This region is 42.09 cM long and contains a 28.07 Mb region with flanking markers DXS1220 and DXS8084, according to the Rutgers Combined Linkage-Physical Map, build 35. However, mutation screen of the candidate gene SLC6A14 within the region did not identify the causative genetic determinant for this large Chinese family.

China↗
PubMed2006

Novel selective cytotoxicity of wild sarsaparilla rhizome extract.

Among six fractions, including total extract and fractions of hexane, ethyl acetate, butanol, water and boiling water extracted and separated from wild sarsaparilla rhizome, the hexane fraction (HRW) was the most effective in eliminating four different human cancer cell lines with cellular viability less than 6.8%. HRW exhibited the highest potency against human leukaemia cells with an IC50 (concentration that inhibited the growth rate of cells by 50%) of 3.3 +/- 0.3 microg mL(-1), which was 17.6-fold smaller than that against normal human umbilical vein endothelial cells (IC50, 58.0 +/- 1.5 microg mL(-1)). For its rich natural resources, simple extraction procedure and high yield (3.2%), HRW has the potential to be developed as a selective anti-cancer nutraceutical or pharmaceutical natural health product with low side effects and high economical return.

Antineoplastic Agents, Phytogenic↗
PubMed2004

Expression and bioactivity analysis of recombinant beta-CPP dimer.

Beta-casein phosphopeptide (beta-CPP) is a bioactive peptide that carries different minerals, especially calcium. To investigate more effects of beta-CPP, eukaryotic expression vector of beta-CPP dimer was constructed and transfected into Chinese hamster ovary (CHO) cells. After selection, the cell lines stably expressing beta-CPP dimer were obtained, and the recombinant product was identified and purified. Activity assay of recombinant protein indicated that the recombinant beta-CPP dimer could improve Ca(2+) uptake of sperm, stimulate the proliferation of spleen cells, and induce apoptosis of some malignant tumor cells.

Animals↗
PubMed2001

The prediction of the structural class of protein: application of the measure of diversity.

Based on the concept that the structural class of a protein is mainly determined by its secondary structure sequence, a new algorithm for prediction of the structural class of a protein is proposed. By use of the number of alpha -helices, beta -strands, and betaalphabeta fragments, the structural class of a protein can be predicted by an algorithm based on the increment of diversity (ID), in which the sole prediction parameter-the increment of diversity is used as the index of prediction of structural class of a protein. The results indicate that the high rates of correct prediction are obtained for complete set (standard set) from Brookhaven Protein Data Bank-CD ROM (PDB) published in October 1995 and the test set newly released from Brookhaven Protein Data Bank-CD ROM (PDB) before July 1998, respectively.

Algorithms↗
PubMed2001

Molecular cloning and characterization of the mouse and human TUSP gene, a novel member of the tubby superfamily.

We report here the cloning and characterization of a novel gene belonging to the tubby superfamily proteins (TUSP) in mouse and human. The mouse Tusp cDNA is 9120 bp in length and encodes a deduced protein of 1547 amino acids, while the human TUSP gene is 11,127 bp and encodes a deduced protein of 1544 amino acids. The human and mouse genes are 87% identical for their nucleotide sequences and 85% identical for their amino acid sequences. The protein sequences of these genes are 40-48% identical to other tubby family proteins at the C-terminal conserved 'tubby domain'. In addition, the TUSP proteins contain a tubby signature motif (FXGRVTQ), two bipartite nuclear localization signals (NLSs) at the C-terminal, two proline-rich regions, one WD40 repeat region and one suppressor of cytokines signaling domain. Transfection assay with green fluorescent protein-tagged TUSP expression constructs showed that the complete TUSP protein and the N-terminal portion of TUSP are localized in the cytoplasm but the C-terminal portion with the two NLSs produced distinct dots or spots localized in the cytoplasm. Northern blotting analysis showed that the major transcript with the complete coding sequence is expressed mainly in the brain, skeletal muscle, testis and kidney. Radiation hybrid mapping localized the mouse gene to chromosome 17q13 and the human TUSP gene to chromosome 6q25-q26 near the type 1 diabetes gene IDDM5. However, association analysis in diabetic families with a polymorphic microsatellite marker did not show any evidence for association between TUSP and type 1 diabetes. The precise biological function of the tubby superfamily genes is still unknown; the highly conserved tubby domain in different species, however, suggests that these proteins must have fundamental biological functions in a wide range of multi-cellular organisms.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Molecular cloning and characterization of a novel mammalian endo-apyrase (LALP1).

Here we describe the cloning, localization, and characterization of a novel mammalian endo-apyrase (LALP1) in human and mouse. The predicted human LALP1 gene encodes a 604-amino acid protein, whereas the mouse Lalp1 gene encodes a 606-amino acid protein. The human and mouse genes have 88% amino acid sequence identity. These genes share considerable homologies with hLALP70, a recently discovered mammalian lysosomal endo-apyrase. The human LALP1 gene resides on chromosome 10q23-q24 and contains 12 exons and 11 introns covering a genomic region of approximately 46 kilobase pairs. The subcellular localization and enzymatic activity of LALP1 indicated that LALP1 is indeed an endo-apyrase with substrate preference for nucleoside triphosphates UTP, GTP, and CTP.

Amino Acid Sequence↗
PubMed2001

Rapid decrease of RNA level of a novel mouse mitochondria solute carrier protein (Mscp) gene at 4-5 weeks of age.

We cloned a novel mouse gene that encodes a protein with homology to the mitochondria solute carrier proteins (Mscp). The major full-length Mscp transcript contains 4112 bp of cDNA and a deduced protein of 338 amino acids. The Mscp protein shares 50%, 40%, and 39% sequence identity with the C. elegans hypothetical protein T26089 and the yeast mitochondria carrier proteins MRS3 and MRS4, respectively. It also showed homology with the uncoupling proteins (UCP1, UCP2, and UCP3; 22%, 24%, and 29% identity, respectively). The protein has six transmembrane domains and three mitochondria energy-transfer protein signature motifs, which are conserved among all the members of mitochondria carrier protein family. Northern analysis indicated that the Mscp gene is highly expressed in the spleen. Using cDNA microarray and Northern analysis, we have shown a significant decrease of the splenic Mscp mRNA levels around 4-5 weeks of age in several mouse strains including C57BL/6J, nonobese diabetic (NOD), and several NOD-congenic mice. These results suggest that the Mscp gene is decreased during splenic lymphocyte maturation in these mice.

Amino Acid Sequence↗
PubMed2001

[Effect of Astragalus injection on platelet function and plasma endothelin in patients with early stage diabetic nephropathy].

OBJECTIVE: To study the therapeutic effect of Astragalus injection (AI) in treating early stage diabetic nephropathy (DN) patients. METHODS: The total of 136 early diabetic nephropathy patients were randomly divided into two groups, 50 cases in the conventional treated group and 86 in the AI treated group, the therapeutic course being 3 weeks. Levels of plasma endothelin-1 (ET-1), 24 hrs urinary albumin excretion rate (uAER), and platelet granule membrane protein (GMP-140), 6-keto-prostaglandin F1 alpha(6-keto-PGF1 alpha), and thromboxane B2(TXB2) before and after treatment were determined by radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) respectively. Moreover, the above-mentioned criteria in 26 healthy subjects were also measured for control. RESULTS: The plasma ET-1, GMP-140, TXB2 and uAER levels in DN patients were higher, but 6-keto-PGF1 alpha level was lower than those in healthy subjects. The above elevated criteria in DN patients could be lowered by AI treatment. CONCLUSION: The pathogenesis and development of DN might be closely associated with the changes of plasma ET-1 level and platelet function. Astragalus could improve the above-mentioned changes in patients of early stage DN.

6-Ketoprostaglandin F1 alpha↗
PubMed1995

[The pharmacokinetics and pharmacodynamics of cefotaxime in experimental diabetic rats].

The present paper describes the pharmacokinetics and pharmacodynamics of CTX in both normal control rats and early alloxan-diabetic rats in vivo. The plasma concentrations of CTX were determined with HPLC. The main pharmacokinetic parameters of the two groups were calculated with computer. Compared with the control group, the C(m) and AUC in the diabetic group decreased significantly. Most of the free drug was distributed to tissue fluid because the protein binding of CTX decreased. But, the T1/2ka and T1/2ke of the two groups were not significantly different. It was suggested that the absorption and elimination rate of CTX were not affected in early diabetic rats. The PD50 of CTX against S. Pneumoniae infection was not different significantly between the two groups. This implies that the therapeutic effect of CTX was enhanced as the plasma free concentration could be increased in diabetic rats.

Animals↗
PubMed1993

[The study and protection of mercury contamination in silver amalgam on patient's safety]

The mercury concentration of oeal gas was determinded.Comparison were made on 2 groups consisting of silver amalgam covered cases(n=15) and uncovered cases (n=29) immediately by vaseline after filling silver amalgam,and the concentration of Hg before polishing old silver amalgam and after polishing (n=10),The result showed there are very significant difference (P<0.01).The surface area of filling mercury amalgam did not relate to Hg concentration.The larger volume of polishing old mercury amalgam was,the higher concentration of Hg was.In addition,mercury concentrations of air in four consulting rooms before ventilation were higher than 3.1-6.6 times national hyienic standard,however,it was reduced to 1.2-2.1 times after ventilation.

Journal Article↗
PubMed1989

[A comparison of the efficiency of density gradient and low-speed centrifugation methods for isolating Plasmodium sporozoites].

P. yoelii sporozoites(Sp) in Anopheles stephensi were first isolated with low-speed centrifugation and the Sp suspension was subsequently purified with the density gradient centrifugation. The recovery rates of Sp by the latter method is about 50 approximately 75% of that by the former, but few debris could be found in the Sp suspension and the infectivity of the Sp was not weakened as compared with the Sp obtained by low-speed method. Sp would retain partial infectivity, when its suspension was maintained in medium 199 at 4 degrees C for 48 hrs. When rats and mice were infected with these Sp, pathological changes of hepatocytes such as cloudy swelling or fatty degeneration, which had been evidenced to be induced by mosquito tissues, would be absent or present in the slightest degree.

Animals↗