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Biomedical subjects

L Zhao

Publications and source records attributed to L Zhao.

At least 253 records · Page 14Linked to original sources
PubMed1998

Molecular cloning and sequencing of the cDNA of cop1 gene from Pisum sativum.

Cop1 protein plays an important role in seedling development of higher plants. The cDNA of cop1 gene from pea (Pisum sativum) was cloned and sequenced. Cop1 protein of pea is predicted to have 672 amino acids and a molecular mass of 76 kDa. Sequence comparison between Cop1 proteins of pea and Arabidopsis thaliana revealed that the two Cop1 proteins were highly homologous in the regions with functional domains and at the C-terminus. Immunoblotting performed with polyclonal antibodies against recombinant Cop1 of pea showed that Cop1 protein was present in seedlings germinated both in light and darkness.

Amino Acid Sequence↗
PubMed1998

The temporal and spatial features of event-related EEG spectral changes in 4 mental conditions.

Event-related EEG spectral perturbation (ERSP) was studied in 20 right-handed subjects during selective response (SRP) and selective mental arithmetic (SMA). The input signals were one-digit number sounds (single syllable). The subjects were asked to make switch response (for SRP) or accumulative summation (for SMA) as soon as odd numbers (T) were heard and to ignore even ones (N). EEG powers were derived from 3 successive 0.5 s segments post input signal from 9 locations on scalp in 4 conditions (srT, srN, maT and maN). The ERSP was taken as the spectral change relative to that under rest control. The main results were: (i) the power of delta and theta activity increased significantly in the 1st 0.5 s in all 4 conditions but decreased in the following epochs; (ii) the theta activity revealed greatest spatial differentiation, prominent theta activity remained at Fz in the 2nd and 3rd 0.5 s in maT but not in srT; (iii) the power of alpha activity was lowest in the 1st 0.5 s and remained low level during SMA but increased in the 2nd 0.5 s during SRP; (iv) the 11-18 Hz activity augmented after the 1st 0.5 s, its dominance remained at P6 during SMA but switched from P6 to frontal locations during SRP; (v) the power of high frequency activities beyond 30 Hz decreased significantly during SRP at all locations. The temporal and spatial feature of ERSP in the 4 conditions provided further evidence indicating the functional correlates of EEG activities in each frequency band. The high frequency activity might reflect the general attention state. The dynamic change of attentional demand during information processing was probably reflected by alpha activity. The delta, theta and beta activities seemed related to different aspects of cognitive processes.

Adult↗
PubMed1998

A simple efficient method of sequential G-banding and fluorescence in situ hybridization.

Several methods of chromosome identification to be used in combination with G-banding by the trypsin technique with Giemsa staining (G-banding) and fluorescence in situ hybridization (FISH) have been developed in the past few years. Unfortunately, these methods are impractical to use in the clinical laboratory and can provide inconsistent results. We report a simple, efficient, and reliable method of G-banding and FISH for use in clinical cytogenetics. G-banded chromosomes are codenatured with a direct- or indirect-labeled DNA prove (by using either chromosome painting or a chromosome centromeric probe) followed by a hybridization and signal detection. The procedure requires no pretreatment or additional fixation and results in good preservation of chromosome morphology and good intensity of the FISH signal.

Azure Stains↗
PubMed1998

Biomedical imaging using hyperpolarized noble gas MRI: pulse sequence considerations.

Hyperpolarized noble gas MRI is a new technique for imaging of gas spaces and tissues that have been hitherto difficult to image, making it a promising diagnostic tool. The unique properties of hyperpolarized species, particularly the non-renewability of the large non-equilibrium spin polarization, raises questions about the feasibility of hyperpolarized noble gas MRI methods. In this paper, the critical issue of T1 relaxation is discussed and it is shown that a substantial amount of polarization should reach the targets of interest for imaging. We analyse various pulse sequence designs, and point out that total scan times can be decreased so that they are comparable or shorter than tissue T1 values. Pulse sequences can be optimized to effectively utilize the non-renewable hyperpolarization, to enhance the SNR, and to eliminate image artifacts. Hyperpolarized noble gas MRI is concluded to be quite feasible.

Echo-Planar Imaging↗
PubMed1998

Hydroxylation of macrolactones YC-17 and narbomycin is mediated by the pikC-encoded cytochrome P450 in Streptomyces venezuelae.

BACKGROUND: . Streptomyces venezuelae produces two groups of antibiotics that include the 12-membered ring macrolides methymycin and neomethymycin, and the 14-membered ring macrolide pikromycin. Methymycin and pikromycin are derived from the corresponding precursors, YC-17 and narbomycin, respectively, by hydroxylation of the tertiary carbon position (C-10 in YC-17 or C-12 in narbomycin) on the macrolactone ring. In contrast, neomethymycin is derived from YC-17 by hydroxylation of the secondary carbon (C-12) of the propionyl starter unit sidechain. RESULTS: . Using a genetic and biochemical approach we have characterized a single P450 hydroxylase (PikC) in the methymycin/pikromycin biosynthetic gene cluster (pik) from S. venezuelae. Inactivation of pikC abolished production of all hydroxylated macrolides, with corresponding accumulation of YC-17 and narbomycin in the culture medium. The enzyme was produced efficiently and purified as a His-tagged protein from recombinant Escherichia coli cells. Purified PikC effectively converts YC-17 into methymycin and neomethymycin and narbomycin into pikromycin in vitro. CONCLUSIONS: . These results demonstrate that PikC is responsible for the conversion of YC-17 to methymycin and neomethymycin, and narbomycin to pikromycin in S. venezuelae. This substrate flexibility is unique and represents the first example of a P450 hydroxylase that can accept 12- and 14-membered ring macrolides as substrates, as well as functionalize at two positions on the macrolactone system. The broad substrate specificity of PikC provides a potentially valuable entry into the construction of novel macrolide- and ketolide-based antibiotics.

Amino Acid Sequence↗
PubMed1998

Secretion of CSF-1 and its inhibition in rat dental follicle cells: implications for tooth eruption.

Tooth eruption requires the presence of a dental follicle around the unerupted tooth. Before the onset of eruption there is an influx of mononuclear cells into the follicle which, in turn, form osteoclasts that erode the alveolar bone. Eruption can be accelerated by the injection of colony-stimulating factor-one (CSF-1), a molecule that is maximally transcribed and translated in the dental follicle cells at the time of peak influx of mononuclear cells into the follicle of the rat first mandibular molar. To determine if the rat dental follicle cells secrete the CSF-1 needed for these cellular events, conditioned medium was collected from cultures of these cells. Using as a bioassay, a cell line (m-NFS 60) that is responsive to CSF-1 for growth, it was shown that conditioned medium from the follicle cells stimulated growth of the m-NFS 60 cells by almost 33% over the controls. Western blots confirmed that CSF-1 was secreted into the medium. Treating the dental follicle cells with an antisense oligodeoxynucleotide probe against CSF-1 reduced the amount of CSF-1 produced. These results demonstrate that CSF-1 is secreted by the dental follicle cells and that the production of CSF-1 can be reduced with an antisense probe. This secretion by the dental follicle might recruit mononuclear cells into the follicle to initiate tooth eruption.

Alveolar Process↗
PubMed1998

Effects of vascular permeability factor on the permeability of cultured endothelial cells from brain capillaries.

The effects of vascular permeability factor (VPF) on the blood-brain barrier (BBB) permeability were studied in cultured capillary endothelial cells from bovine brain. When VPF was added to the abluminal or brain side of the BBB, a rapid increase in the BBB permeability was observed. This increase in the BBB permeability is dependent on the concentration of the VPF used and is reversible on removal of the VPF. Contrarily, when VPF was added to the luminal or blood side of the BBB, no increase in the BBB permeability was observed. These results suggest that the receptors for VPF are located on the abluminal side of the BBB.

Animals↗
PubMed1998

Effect of CSF-1 on in vivo expression of c-fos in the dental follicle during tooth eruption.

It has been demonstrated that both colony-stimulating factor-one (CSF-1) and the transcription factor, c-fos are required for tooth eruption. Osteopetrotic mutant rats deficient in CSF-1 activity have unerupted teeth which can be induced to erupt by injections of CSF-1, and osteopetrotic mice deficient in c-fos, have unerupted teeth. Both CSF-1 and c-fos are expressed and translated in the dental follicle, the tissue that is required for eruption. Recent in vitro studies indicate that CSF-1 can enhance the expression of the c-fos gene in cultured dental follicle cells, but the effects in vivo are not known. In the present studies. postnatal rats were injected with 10(6) units of CSF-1 at different ages from birth to day 10 and sacrificed 30 min after injection. Isolation of total RNA from the follicle and reverse transcription PCR showed that CSF-1 injection enhanced the expression of c-fos over the non-injected controls. Chronologically, day 3 postnatally appeared to show the greatest increase of c-fos mRNA following CSF-1 injection. These results suggest that one of the functions of CSF-1 in tooth eruption is to enhance the early expression of c-fos. In turn, c-fos might act to promote fusion of monocytes into the osteoclasts needed for alveolar bone resorption and tooth eruption.

Animals↗
PubMed1998

Postsurgical changes of the opening angle of canine autogenous vein graft.

The opening angles of 30 canine autogenous vein grafts were measured to determine the postsurgical change of residual strain in the vein graft. Canine femoral veins were grafted to femoral arteries in the end-to-end anastomosis fashion. When harvested, the vein grafts were cut into short segments and the segments were cut open radially. The opened-up configurations were taken as the zero-stress states of the vessels. Opening angle, defined as the angle between the two lines from the middle point to the tips of the inner wall, was used to describe the zero-stress states. Results show that the opening angles (mean +/- SD) are 63.0 +/- 30.6 deg for normal femoral veins, and -0.4 +/- 4.6, 6.1 +/- 19.4, 25.4 +/- 20.1, and 47.8 +/- 11.4 deg for vein grafts at 1 day, 1 week, 4 and 12 weeks postsurgery, respectively. The postsurgical changes in opening angle reveal nonuniform transmural tissue remodeling in the vascular wall. The relations between the changes in opening angle and the changes in the morphology of the vein grafts are discussed. Intimal hyperplasia is correlated to the opening angle and is suggested to be the main factor for the postsurgical increase in opening angle. The longitudinal strain in the vein graft is found to decrease postsurgically.

Anastomosis, Surgical↗
PubMed1998

Amino-terminal substitutions in the CCR5 coreceptor impair gp120 binding and human immunodeficiency virus type 1 entry.

The CC-chemokine receptor CCR5 is required for the efficient fusion of macrophage (M)-tropic human immunodeficiency virus type 1 (HIV-1) strains with the plasma membrane of CD4+ cells and interacts directly with the viral surface glycoprotein gp120. Although receptor chimera studies have provided useful information, the domains of CCR5 that function for HIV-1 entry, including the site of gp120 interaction, have not been unambiguously identified. Here, we use site-directed, alanine-scanning mutagenesis of CCR5 to show that substitutions of the negatively charged aspartic acid residues at positions 2 and 11 (D2A and D11A) and a glutamic acid residue at position 18 (E18A), individually or in combination, impair or abolish CCR5-mediated HIV-1 entry for the ADA and JR-FL M-tropic strains and the DH123 dual-tropic strain. These mutations also impair Env-mediated membrane fusion and the gp120-CCR5 interaction. Of these three residues, only D11 is necessary for CC-chemokine-mediated inhibition of HIV-1 entry, which is, however, also dependent on other extracellular CCR5 residues. Thus, the gp120 and CC-chemokine binding sites on CCR5 are only partially overlapping, and the former site requires negatively charged residues in the amino-terminal CCR5 domain.

Amino Acid Sequence↗
PubMed1998

Human choriocarcinoma JAR cells constitutively express pro-interleukin-1beta that can be released with Fc(gamma) receptor engagement.

Some authors have suggested that fetally derived syncytiotrophoblasts, which form the barrier between mother and the fetus, are an integral part of a complex macrophage-cytokine network involving maternal leukocytes, decidual cells, placental tissues, and even the fetus itself. We report here that syncytiotrophoblast-like JAR cells, a human choriocarcinoma cell line, share another feature common to cells of the monocyte-macrophage lineage, the ability to secrete IL-1beta when stimulated through their Fc(gamma) receptors. We incubated JAR cells with physiologically relevant concentrations of model BSA-rabbit IgG-anti-BSA immune complexes or monomeric rabbit IgG for periods of up to 72 h. Both monomeric IgG and immune complexes induced IL-1beta from JAR cells, although levels produced by immune complexes were approximately twice those induced by monomeric IgG. IL-1beta secretion was not inhibited by cycloheximide, and Western blots of JAR cell lysates using pro-IL-1beta MAb revealed constitutive expression of a 31-kD protein, whose levels declined within 2 h of stimulation by either IgG or immune complexes, but returned to baseline within 18 h.

Animals↗
PubMed1998

Adhesion and cytosolic dye transfer between macrophages and intestinal epithelial cells.

Activated macrophages (M phi) found in the intestinal lesions of patients with inflammatory bowel disease (IBD) secrete many inflammatory mediators which can regulate intestinal epithelial cell (IEC) function. However, little is known about direct M phi-IEC interactions. Two potential mechanisms by which cells may interact are through specific receptor-ligand binding of adhesion molecules, such as integrins or cadherins, and by exchange of cytoplasmic substances through transmembraneous channels called gap junctions. We investigated whether M phi could adhere to epithelial cells in culture and form transmembrane communication channels as defined by dye transfer. Primary cultures of murine M phi and a M phi cell line, P388D1, adhered to Mode-K and IEC6, but not CMT-93 IEC. Antibody blocking studies determined that P388D1-Mode-K binding was partially dependent on beta 2 integrin (CD18) function, Mode-K constitutively expressed CD106 (VCAM-1) and cell associated fibronectin, while P388D1 expressed low levels of CD49d/CD29 (VLA4) but blocking antibodies to these surface molecules did not inhibit P388D1-Mode-K adherence. Transfer of calcein dye from M phi to IEC was quantitated by flow cytometry and was dependent on M phi-IEC adhesion. Dye transfer was concentration dependent in that the fluorescence intensity of Mode-K was proportional to the number of adherent P388D1 cells as well as the dye load of the M phi. These results indicate that M phi interact with IEC by adhesion and possibly through gap junctions and may thus regulate IEC function by direct cell-cell communication.

Adenocarcinoma↗
PubMed1998

A neural network for the optimization of fed-batch glutamic acid production.

A neural network system, which is composed of a simulation subnetwork and an optimization subnetwork, was constructed to predict and optimize the industrial fed-batch fermentation of glutamic acid. A data-compression and filtration network structure was incorporated into the simulation subnetwork to extract "noise-free" patterns from the input signals. The sole-variant optimization and the multiple-variant optimization can be easily carried out by the neural network developed. A satisfactory result has been achieved.

Computer Simulation↗
PubMed1998

[Epidemiologic features of viral hepatitis in Fujian].

To study the prevalence and the epidemiologic features of viral hepatitis in Fujian, a seroepidemiological survey on five kinds of viral hepatitis infection has been carried out in Fujian province since 1992. Using stratified mulitistage random cluster sampling, 3,809 serum samples were collected from 1,237 families in general population in the disease surveillance points in Fujian province. HBsAg, anti-HBs and anti-HBc were screened by RIA and HBeAg, anti-HAV, anti-HCV anti-HDV anti-HEV were by EIA. The results showed that the standardized prevalence rates of HAV, HBV, HCV, HDV, HEV, HBsAg, anti-HBs, anti-HBc and HBeAg were 76.60%, 77.26%, 3.99%, 2.10%, 18.80%, 17.25%, 34.33%, 68.58% and 8.42% respectively. The HAV, HBV, HEV prevalence rates in rural were higher than in urban areas. The HBsAg prevalence rate among males was higher than females, with peaks evidenced in 5-9 years old and 20-29 years old. There seemed to be significant family clusterings of HBV and HEV infection. There was higher HEV prevalence rate among the young-robusts but lower HAV prevalence rate among children in urban areas. These results suggested that Fujian is a highly prevalent area for HAV, HBV, HCV and HEV infections. Thus HA and HB vaccination should play as the most effective strategy in the prevention of HAV and HBV infections.

Adolescent↗
PubMed1998

[Effects of supplement Zn on levels of Zn in serum, growth hormone and hydroxyproline].

OBJECTIVE: In order to research the effects of supplement Zn on wound healing, the changes of Zn in serum and skin, growth hormone and hydroxyproline of skin were observed in burn rats. METHOD: 80 SD rats were randomly divided into four groups: Control group of 8 rats, N group (diet containing Zn 40 micrograms/g), W group (application of Zn on burn skin), H group (diet containing Zn 80 micrograms/g). 8 rats of each group were killed on 1, 3, 7 days after burn. RESULTS: The levels of serum Zn declined on 1 day postburn in N and W groups, whereas the content of serum Zn in H group elevated and were 2.4, 2.0 times as much as that of N and W groups respectively (P < 0.01). Zn in burn skin increased significantly on 3, 7 days in W group and was 1.3, 1.5 times as much as that of N group. Serum growth hormone increased in all groups postburn. The highest level appeared in H group. Hydroxyproline in burn skin decreased in all groups, but it began to increase on 7 day postburn in W group. CONCLUSION: Supplementation of Zn by diet rapidly raises the levels of Zn in serum, burn skin and growth hormone. It is beneficial to apply Zn to the wound to improve wound healing. Hydroxyproline increased significantly with application of Zn to burn wound. It is better to supply Zn by diet and topical application simultaneously.

Animals↗
PubMed1998

Effects of electroacupuncture and twirling reinforcing-reducing manipulations on volume of microcirculatory blood flow in cerebral pia mater.

Effects of electroacupuncture (EA) and routine acupuncture with twirling reinforcing and reducing manipulation of the needle (RA) both at Zusanli point (St 36) on volume of microcirculatory blood flow in the cerebral pia mater were observed by fenestration of the cranial bone and laser Doppler microcirculatory blood flow analyser. Results showed that both RA and EA could increase the volume of microcirculatory blood flow in the cerebral pia mater; and that the increase in the EA group was superior to that in RA group. This suggests that a moderate and effective stimulation is a key to the production of a regulative effect on the organism.

Acupuncture Therapy↗