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Biomedical subjects

T Zhu

Publications and source records attributed to T Zhu.

At least 109 records · Page 6Linked to original sources
PubMed1996

Functional expression of mammalian myosin I beta: analysis of its motor activity.

The motor function of vertebrate unconventional myosins is not well understood. In this study, we initiated the baculovirus expression system to characterize a novel myosin I from bovine adrenal gland that we had previously cloned [Zhu, T., & Ikebe, M. (1994) FEBS Lett. 339, 31-36], which is classified as myosin I beta. The expressed myosin I beta was well extracted when calmodulin was coexpressed in Sf9 cells. The recombinant myosin I beta cosedimented with actin in an ATP dependent manner. The purified myosin I beta was composed of one heavy chain and three calmodulins. The electron microscopic image of myosin I beta confirmed its single-headed structure with a short tail, which is similar to that of brush border myosin I (BBMI). Myosin I beta showed high K+,EDTA--ATPase activity (approximately 0.14 mumol/min/mg) and Ca(2+)-ATPase activity (approximately 0.32 mumol/min/mg), and the KCl/pH dependence of these activities was different from that of conventional myosin. Mg(2+)-ATPase activity of myosin I beta alone was increased above pCa 6, while the actin dependent activity was not affected by Ca2+. Actin sliding velocity of myosin I beta in the absence of Ca2+ was 0.3-0.5 microns/s at 25 degrees C, which is much greater than that of BBMI (< 0.05 microns/s). The actin sliding activity was abolished above pCa 6, and the sliding activity was restored when exogenous calmodulin was added in the absence of Ca2+. Within similar Ca2+ concentrations, one of the three calmodulins was dissociated from myosin I beta. The results suggest that Ca2+ dependent association of calmodulin may function as a regulatory mechanism of myosin I beta motor activity and that the motor activity of mammalian myosin I is largely different among distinct myosin I isoforms.

Actins↗
PubMed1996

Studies on the ossification of compound transplantation of porous TCP ceramics and bone marrow.

Following the culture of human red marrow with porous TCP ceramics in vitro, a large amount culturing marrow cells adhered well to the surface and inner wall of TCP ceramics and spread well over the dish bottom 4 weeks after cultivation. After the compound transplantation of porous TCP ceramics with red marrow into quadriceps femoris muscle of rabbits, a huge amount of new bone and marrow formed in these sites on and in the ceramics 4 weeks after transplantation. These results showed an excellent biocompatibility between TCP ceramics and marrow and an excellent osteogenic effect in the compound transplantation. The mechanism of ossification and clinical significance about the compound transplantation were discussed.

Animals↗
PubMed1996

Epiphyseal lengthening operation--an improved technique.

An improved method of epiphyseal lengthening operation and subsequent outer fixation are presented on the basis of experience in 30 cases. The operative technique is described in detail, including the different options of separative traction and osteotomy at subtrochanteric, distal part of the upper femur and lower tibial levels. The physiological and histological research concerning this method is discussed. The authors believe that this procedure is better than the other methods.

Adolescent↗
PubMed1996

Gel shift assay: demonstration of enhanced binding of oligo(delta)-L-ornithine-oligodeoxynucleotide conjugates to complementary DNA and RNA.

An increase in melting temperature for DNA:DNA duplexes had been observed previously (Zhu et al. Antisense Res. Dev. 3:349-356, 1993) when an oligo(delta)ornithine moiety was covalently appended to a short oligodeoxynucleotide. We now report the analysis of duplex formation by electrophoretic gel shift analysis. In the particular example studied, an increase in Tm of 4 degrees C was found to correspond to about a fivefold increase in binding constant. A similar enhancement by the appended cationic peptide was observed when the target strand was RNA. The use of a competitive assay format for avoidance of adsorptive loss at low concentrations (< 10(-7)M) of the oligonucleotide-oligo(delta)ornithine conjugate is presented.

Base Sequence↗
PubMed1996

Genetic characterization of human immunodeficiency virus type 1 in blood and genital secretions: evidence for viral compartmentalization and selection during sexual transmission.

To explore the mechanism of sexual transmission of human immunodeficiency virus type 1 (HIV-1), we compared HIV-1 gp120 sequences in longitudinal samples from five acute seroconvertors with those from their corresponding sexual partners (transmitters). We used a quantitative homoduplex tracking assay to compare the overall genetic composition of HIV-1 quasispecies in each transmission pair and to track the transmitted viruses during the acute and asymptomatic stages of HIV-1 infection. In the chronically infected transmitters, HIV-1 variants in genital secretions differed from those in blood and variants in cells differed from those in cell-free plasma, indicating remarkable sequence heterogeneity in these subjects as well as compartmentalization of the virus in different bodily sites. Conversely, two of five seroconvertors had only a few related variants and three of five harbored only one viral population, indicating that in these subjects the transmitted viruses were typically homogeneous. Transmitted viruses were evident in the donor's seminal plasma (one of five cases) and even more so in their seminal cells (three of five cases), suggesting that both cell-associated and cell-free viruses can be transmitted. In every pair studied, the transmitted variant(s) represents only a minor population in the semen of the corresponding transmitter, thereby providing evidence that HIV-1 selection indeed occurs during sexual transmission.

Amino Acid Sequence↗
PubMed1996

[Alterations of protein phosphatases, PP2A and PP1, during retinoic acid-induced differentiation of HL-60 cells].

Alterations of protein phosphatases, PP2A and PP1, during the retinoic acid-induced differentiation of HL-60 cells have been investigated. The PP2A activity determined with myelin basic protein (MBP) as a substrate showed a sharp transient increase at 18 h of incubation of the cells with retinoic acid, whereas during incubation without retinoic acid, the activity remained at the initial level. On DEAE-Sepharose column chromatography of the extracts preparted from the cells incubated without retinoic acid, the PP2A activities determined with MBP were eluted at 0.13 M or 0.23 m NaCl, respectively. The PP2A activity of the cells incubated for 18 h with retinoic acid was much more greatly activated by protamine compared with the activity of the cells incubated without retinoic acid. These results strongly suggest a conversion of PP2A holoenzyme from PP2A1 to PP2A0 during the initial process of the retinoic acid-induced differentiation. On the other hand PP2A activity determined with phosphorylase alpha as a substrate showed a sharp transient decrease at 24 h of incubation of the cells, irrespective of the presence or the absence of retinoic acid in the incubation mixtures. This decrease may be related to the synchronization of the cells at S phase, which also occurred irrespective of the retinoic acid stimulation. PP1 activity determined with MBP was transiently increased between 27 and 36 h of the incubation of cells without retinoic acid. The increase was strongly suppressed in the cells incubated with retinoic acid, suggesting a role of PP1 in the cell proliferation, the activity of which was also inhibited by retinoic acid.

Cell Differentiation↗
PubMed1996

[The cloning and analysis of a single gene in Drosophila homologic with human oncogene TTG].

The human TTG/RBTN family is an oncogene family. There are three members in this family: TTG-1/RBTN-1, TTG-2/RBTN-2 and TTG-3/RBTN-3. Two of them, TTG-1/RBTN-1 and TTG-2/RBTN-2 have been isolated at the sites of chromosomal translocations in T-cell leukaemia. This gene family encodes cysteine-rich proteins with two tandem copies of a LIM motif. The function of the LIM motif is unknown. We found that the TTG-2 gene is highly conserved among mammals; Drosophila and yeast. As a first step to obtain a model system for studying the function of the LIM motifs, we isolated the Drosophila homologue dttg. In contrast to human, Drosophila appeared to have only one ttg/rbtn gene. A 2087bp cDNA clone was isolated, encoding a protein of 266 amino acids. A second transcript with an alternative 5' end was identified in RNA from embryos. The Drosophila ttg protein consisted of two tandem copies of the conserved LIM domain characteristic of the human TTG/RBTN family. The amino acid sequence similarity with human TTG-1 and TTG-2 is 79% and 62%, respectively. The dttg, like TTG-1, have an intron in the second LIM encoding region, which is not present in TTG-2.

Adaptor Proteins, Signal Transducing↗
PubMed1996

[The study of the morphology of ultramicrostructure in molecular level of nucleus herniation of lumbar intervertebral disc].

In order to investigate the morphology of ultramicrostructure in molecular level of nucleus herniations, the authors studied the ultramicrostructure of three cases of nucleus herniations of lumbar intervertebral disc which were proved by operations and one case of normal nucleus pulposus of fresh corpse by using of atomic force microscope. The results showed that the arrangement of collagen bundle, collagen fiber and procollagen fiber were different between the two conditions, and the morphology of molecular particles of proteoglycan in nucleus herniations was different from that in the normal condition. In the condition of nucleus herniations, the collagen fiber formed procollagen fiber reticular porous adhering to the molecules of protein and proteoglycan, and the DNA adhering to the monochain of RNA in fiberal cell nuclei, in the form of bichain and multichain three dimensions helix structures. The banded structure (64-78 mm) of the procollagen fiber, and the collagenation and calcification of the degenerated nuclens pulposuses, the quantity of which was significant greater than normal (P < 0.05) indicated that the chronic injury of lumbar intervertebral nucleus pulposuses gave rise to the injury and break of the collagen fiber which resulted in twist (tangle) phenomenon so that nucleus pulposuses lost their normal resistance strength.

Adult↗
PubMed1995

Genomic organization and evolution of the soybean SB92 satellite sequence.

Repetitive DNA sequences comprise a large percentage of plant genomes, and their characterization provides information about both species and genome evolution. We have isolated a recombinant clone containing a highly repeated DNA element (SB92) that is homologous to ca. 0.9% of the soybean genome or about 10(5) copies. This repeated sequence is tandemly arranged and is found in four or five major genomic locations. FISH analysis of metaphase chromosomes suggests that two of these locations are centromeric. We have determined the sequence of two cloned repeats and performed genomic sequencing to obtain a consensus sequence. The consensus repeat size was 92 bp and exhibited an average of 10% nucleotide substitution relative to the two cloned repeats. This high level of sequence diversity suggests an ancient origin but is inconsistent with the limited phylogenetic distribution of SB92, which is found at high copy number only in the annual soybeans. It therefore seems likely that this sequence is undergoing very rapid evolution.

Base Sequence↗
PubMed1995

Doses near the surface in high-energy x-ray beams.

In an irradiation with a high-energy x-ray beam, the absorbed dose near the surface is the combined result of incident contaminating electrons and phantom-generated electrons. We describe an experimental method to characterize these processes under conditions of longitudinal electron disequilibrium but lateral equilibrium. The equilibrium dose at large depths is extrapolated back towards the surface and compared with measured doses. The extrapolation uses an expression that is based on Monte Carlo-calculated kerma values. The technique was applied to a 6-MV and a 25-MV x-ray beam. The dose from phantom-generated electrons increased exponentially with depth from zero at the surface. The dose from contaminating electrons decreased rapidly with depth with an attenuation coefficient that was approximately equal to the corresponding coefficient for the increase of dose from phantom-generated electrons. The surface dose from contaminating electrons increased linearly with the side of the square field at 6 MV but an error-function agreed better with the data at 25 MV.

Electrons↗
PubMed1995

Evidence for coinfection by multiple strains of human immunodeficiency virus type 1 subtype B in an acute seroconvertor.

Sequences encoding the envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1) were amplified by PCR from plasma and peripheral blood mononuclear cells obtained at four time points from an acute seroconvertor. Genetic analyses, including nucleotide sequencing and heteroduplex mobility studies, showed that the patient harbored three distinct populations of HIV-1 clade B envelope sequences, with nucleotide distances ranging from 9.2 to 17.2%. One population of sequences was clearly distinguishable from the others on the basis of phylogenetic analysis. In addition, sequences suggesting recombination between two of the three distinct viral populations were also found. This case of acute seroconversion provides clear and conclusive evidence that coinfection by multiple HIV-1 strains can indeed occur in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Sequence diversity of V1 and V2 domains of gp120 from human immunodeficiency virus type 1: lack of correlation with viral phenotype.

We analyzed by PCR and direct sequencing 57 viral sequences from 47 individuals infected with human immunodeficiency virus type 1, focussing on the V1 and V2 regions of gp120. There was extensive length polymorphism in the V1 region, which rendered sequence alignment difficult. The V2 hypervariable locus also displayed considerable length variations, whereas flanking regions were relatively conserved. Two-thirds of the amino acid residues in these flanking regions were highly conserved (> 80%), presumably reflecting their critical contribution to V2 structure or function. We also characterized the syncytium-inducing properties of the isolates from which we derived sequence information. There was no correlation between V1 or V2 sequences and the viral phenotype, contrary to a previous report (M. Groenink, R. A. M. Fouchier, S. Broersen, C. H. Baker, M. Koot, A. B. van't Wout, H. G. Huisman, F. Miedema, M. Tersmette, and H. Schuitemaker, Science 260:1513-1516, 1993). The sequence heterogeneity described in this study provides information to suggest that it would be most difficult to exploit the V1 and V2 domains for vaccine development.

Amino Acid Sequence↗
PubMed1995

[Analysis of poisonous trace elements in huangwu gongmitai].

A comparative study was made on the dissolved amount of poisonous trace elements mercury and arsenic contained in hydrargyri subchloridum and realgar of gynecological suppository in artificially simulated vaginal acid-base liquid with that contained in hydrargyri subchloridum and realgar in artificial gastric juice stipulated in Pharmacopeia of China. The result shows that the dissolved amount of mercury and arsenic contained in the suppository is much smaller than that stipulated in Pharmacopeia for oral administration.

Arsenic↗
PubMed1995

[Promoting effects of rhizoma Drynariae on the calcification of cultivated chick embryo bone primordium].

It has been discovered by tissue cultivation and isotope tracing that the injection of Rhizoma Drynariae significantly promotes the calcification of chick embryo bone primordium in vitro, increases the ALP activity of cultivated tissues and accelerates the synthesis of proteoglycan. It has also been proved that the promotion of the synthesis of proteoglycan is an important factor of the promotion of calcification.

Alkaline Phosphatase↗