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Biomedical subjects

Z G Liu

Publications and source records attributed to Z G Liu.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Behaviour after transplantation of brain cells into monkey models of Parkinson's disease].

OBJECTIVE: To observe the improved degree of pathogenic behaviour in monkey models of Parkinson's disease after transplantation of substantia nigra cells of human fetus. METHOD: 1-methy-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was used to prepare monkey models of hemiparkinson's disease, i.e., early substantia nigra cells of human fetus were stereotaxically transplanted into PD monkey's behaviour for six months, using immuno-electromicroscopy to prove the transplanted survived neuron. RESULTS: After transplantation, the model monkey's motion slow and muscle hypertonia was apparently improved. Limb tremor almost disappeared, Right spontaneous rotation behavior relieved. Rotating frequency caused by APO became less than before transplanytation, and its effect could last a year. Under the immunoelectromicroscope, we observed that transplanted tyrosine hydroxylase positive neuron was connected with the host brain cells in synapse. CONCLUSION: Substantia nigra neuron transplanted into the PD monkey brain can establish synaptic connection with the host nervous cells. Pathogenic symptoms are improved and the effect may remain for a longer time.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1997

[Study on the incidence of thyroid disease in Dun Hua District of Chang Bai mountain area, Jilin Province].

Dun Hua is a district where endemic goiter has been prevalent. Residents commenced to eat iodined salt ten years ago. We studied 469 people in this district and discovered that the incidence of endemic goiter had somehow come down but still kept 10.4%. However, the incidence of thyroid cancer went up to 1.9% with the incidence of thyroiditis 0.85%. Pathological characteristic of endemic goiter frequently appeared adenoniatoid feature with some atypical hyperplasia follicles which facilitates the cancerization in the fibrigenic part. Reasons accounted for the endemic goiter occurrance might not only relate to the insufficient intake of iodined salt but also to the increase of iodine excretion from the body. The increase of iodine excretion may be related to the factors as varieties of subsidiary food and vegetables as well as personal habitualness on food and drinks.

Adolescent↗
PubMed1996

Three distinct signalling responses by murine fibroblasts to genotoxic stress.

Genotoxic stress triggers signalling pathways that mediate either the protection or killing of affected cells. Whereas induction of p53 involves events in the cell nucleus, the activation of transcription factors AP-1 and NF-kappaB by ultraviolet radiation is mediated through membrane-associated signalling proteins, ruling out a nuclear signal. An early event in AP-1 induction by ultraviolet radiation is activation of Jun kinases (JNKs), which mediate the induction of the immediate-early genes c-jun and c-fos. The JNKs have also been proposed to mediate the apoptopic response to genotoxins. The non-receptor tyrosine kinase c-Abl is also activated by genotoxic stress. To understand the relationship between these events, we compared the activation of p53, JNK and c-Abl by several DNA-damaging agents in murine fibroblasts. We found that whereas p53 was induced by every genotoxic stimulus tested, c-Abl was activated by most stimuli except ultraviolet irradiation and JNK was strongly stimulated only by ultraviolet light and the alkylating agent methyl methanesulphonate. Activation of JNK by this alkylating agent was normal in c-Abl-null cells but was reduced in c-Src-null cells. Unlike p53 induction, c-Abl activation occurs in the S phase of the cell cycle and does not affect cell proliferation. These findings show that signals generated by genotoxins are transduced by multiple, independent pathways. Only p53 appears to be a universal sensor of genotoxic stress.

3T3 Cells↗
PubMed1996

Dissection of TNF receptor 1 effector functions: JNK activation is not linked to apoptosis while NF-kappaB activation prevents cell death.

Through its type 1 receptor (TNFR1), the cytokine TNF elicits an unusually wide range of biological responses, including inflammation, tumor necrosis, cell proliferation, differentiation, and apoptosis. We investigated how TNFR1 activates different effector functions; the protein kinase JNK, transcription factor NF-kappaB, and apoptosis. We found that the three responses are mediated through separate pathways. Recruitment of the signal transducer FADD to the TNFR1 complex mediates apoptosis but not NF-kappaB or JNK activation. Two other signal transducers, RIP and TRAF2, mediate both JNK and NF-kappaB activation. These two responses, however, diverge downstream to TRAF2. Most importantly, JNK activation is not involved in induction of apoptosis, while activation of NF-kappaB protects against TNF-induced apoptosis.

Adenocarcinoma↗
PubMed1996

Isolation of a lymphocyte chemotactic factor produced by the murine thymic epithelial cell line MTEC1: identification as a 30 kDa glycosylated form of MCP-1.

A medullary-type murine thymic epithelial cell line (MTEC1) established in our laboratory constitutively produces multiple species of chemotactic factors, which attract lymphocytes, neutrophils, and monocytes. Chemotactic proteins were isolated from MTEC1 supernatant and purified to homogeneity by adsorption to controlled pore glass, heparin-Sepharose chromatography, cation-exchange FPLC and RP-HPLC. A chemotactic factor for both lymphocytes and monocytes was identified as a 30 kDa protein by SDS-PAGE analysis under reducing conditions. After cleavage of the NH2-terminally blocked protein with formic acid, the amino acid sequence of the internal fragment was analysed and found to be identical to the amino acid sequence of mouse MCP-1/JE. The protein is hence identified as a glycosylated natural form of MCP-1/JE secreted by thymic epithelial cells. The 30 kDa glycosylated form of MCP-1 shows lower specific chemotactic activity (CA) for both lymphocytes and monocytes than the 6-7 kDa unglycosylated form of MCP-1.

Amino Acid Sequence↗
PubMed1996

[Analysis of chemokine (S) produced by mouse thymic stromal cell lines].

By using Boyden Chamber and PACS methods, we analysed the chemotactic activity of five mouse thymic stromal cell (MTSC) lines' culture supernatant for neutrophil, monocyte/macrophage and lymphocyte, and the phenotype of the attracted lymphocyes, MTEC 1, MTEC 2, MTEC 3, MTEC 5 are mouse thymus epithelial cell lines. MTDC 4 is a mouse thymus dendritic cell line. The results indicate that all of the five MTSC supernatants have chemotactic activity for the target cells mentioned above but in different degree. Chemokines produced by the MTSC cells can be classified into three categories: (1) Chemokines produced by MTEC 1 and MTEC 2 are more potent for the attraction of neutrophils and lymphocytes. (2) MTDC 4 derived chemokines are highly potent for the attraction of monocytes/macrophages. (3) Chemokines produced by MTEC 3 and MTEC 5 are equally attractive to neutrophils, lymphocytes and monocytes/macrophages. Most of the MTSC-SN are more potent for the migration of B lymphocyte than for T lymphocyte. The MTSC-SN exhibits higher chemotactic activity to CD4-CD8+ T cell subset than to CD4+CD8-T cell subset. The characterization of chemokines in MTSC-SN will benefit the finding of new chemokines and the analysis of the mechanism of thymus homing.

Animals↗
PubMed1995

Comparative studies of the conformation of the N-terminal fragments of staphylococcal nuclease R in solution.

In order to elucidate the folding of nascent peptide, five peptide fragments of staphylococcal nuclease R starting from N-terminal end and of different chain lengths are made by deletion of 47, 39, 28, 14 and 8 amino-acid residues from its C-terminal end, respectively. Changes in conformation of the N-terminal fragments have been compared by using Fourier-transform infrared spectra, far-ultraviolet circular dichroism spectra and analysis of surface hydrophobicity. The experiments indicate that all the five fragments have certain amounts of residual structure; in general, with increasing the peptide chain, the contents of secondary structure and the enzyme's activity of the peptide increase, and the exposed hydrophobic side chains brought about by the deletion of C-terminal residues are gradually buried in the interior of the nuclease. However, the ordered secondary structures do not always increase with increasing the peptide chain. Further growth of the length of the peptide chain could have an important effect on the conformation of the peptide fragment already synthesized, suggesting some structural adjustments should be necessary in order for the newly synthesized polypeptide to attain its final native conformation. These results support Tsou's nascent peptide folding hypothesis (Tsou, C.-L. (1988) Biochemistry 27, 1809-1812).

Circular Dichroism↗
PubMed1995

Transient transfection assays to examine the requirement of putative cell death genes.

In conclusion, this chapter provides a convenient and efficient method for the detection and analysis of transiently transfected cells. Such strategies allow a fast and simple analysis of the requirement for particular genes that have been identified as being induced during apoptosis. Our experience has been that, when screening for "cell death genes," it is easy to isolate genes induced during apoptosis but far more difficult to determine the requirement for any given gene. These protocols have rendered such determinations much simpler to perform.

Antigens, CD↗
PubMed1995

Gene therapy of Parkinson disease model rat by direct injection of plasmid DNA-lipofectin complex.

Lipofectin-mediated gene transfer was used to introduce plasmid harboring the tyrosine hydroxylase (TH) gene into the striatum of rats with lesions of the nigrostriatal pathway. The rotational asymmetry of Parkinson disease model rat was reduced quickly and significantly, suggesting that plasmid-DNA-transfected brain cells can generate L-dopa locally in the striatum in quantities sufficient to compensate partially for the loss of intrinsic striatal dopaminergic input. Immunohistochemical staining and reverse transcription polymerase chain reaction (RT-PCR) also confirm that striatal cells can express exogenous TH gene. Such in vivo plasmid DNA transfer strategy may be useful in other neurologic disease therapy, especially acute brain insults.

Animals↗
PubMed1995

Sulfhydryl involvement in nitric oxide sequestration and nitric oxide induced guanylyl cyclase activation in vascular smooth muscle.

In the present study, the role of vascular smooth muscle sulhydryl groups was investigated with respect to sequestration of nitric oxide (NO) and activation of soluble guanylyl cyclase by NO. Vascular smooth muscle 100,000 x g supernatant (soluble) fraction was prepared in phosphate buffer, using the medial layer of bovine pulmonary artery. The soluble fraction was incubated with 100 pmol NO for 5 min in a sealed flask at 37 degree C under anerobic conditions in the presence or absence of the sulfhydryl reagent, N-ethylmaleimide (NEM, 5 mM). NO sequestration by the soluble fraction was measured as an indicator of NO binding. Total thiol content was measured in the soluble fraction with and without exposure to NEM. Guanylyl cyclase activity was measured in the soluble fraction with and without exposure to NO and a combination of NO and NEM. NEM decreased total thiol content in the soluble fraction from 103.59 nmol/mL to undetectable levels, and decreased guanylyl cyclase activity to below basal levels. The percentage of NO sequestered by the soluble fraction was inhibited by NEM by approximately 25% from a control value of 26.52 +/- 9.39 to 18.72 +/- 8.52, n = 13, p < 0.05. The data indicate that sulfhydryl groups are essential for guanylyl cyclase activation by NO, and are also involved in the sequestration of NO by the vascular smooth muscle soluble fraction.

Animals↗
PubMed1995

[Cost-benefit analysis on immunization of newborns with hepatitis B vaccine in Jinan City].

The decision tree model cost-benefit analysis method was used to analyse the strategies and economic benefits of immunization of newborns with hepatitis B vaccines in Jinan City. The results showed that all the three vaccination strategies could all produce positive benefits. Their BCR were 42.41 to 48.01. Through the decision analysis, it concluded that stress should be laid on the blocking of mother-to-infant transmission, and that if there are sufficient HB vaccines, all newborns should be vaccinated. In addition, the results of sensitivity analysis indicate that the benefits of HB vaccination are outstanding and quite stable.

China↗
PubMed1995

[Fate of human fetal dopamine neurons transplanted into rhesus monkey model of Parkinson's disease: a tyrosine hydroxylase immunocytochemical study].

To predicate the value of human fetal substantia nigra transplantation in clinical treatment of Parkinson's disease (PD), dissociated cells of substantia nigra from 8-12 week old abortive human fetus were grafted into the neostriatum of 5 adult rhesus monkeys with hemiparkinsonism induced by unilateral injection of MPTP. At 2, 5 and 12 months after transplanting the monkeys were sacrificed for tyrosine hydroxylase (TH) immunocytochemistry to examine the survival and possible synaptic contact of transplanted dopamine (DA) neurons. Transplanted TH immunoreactive cells took a pattern of patches scattered in the neostriatum. Each of the cell patches consisted of 3-10 cells. The TH immunoreactive fiber network was seen in the neostriatum. Electron microscopic survey revealed that TH+ buttons arising from grafted DA neurons formed symmetric or asymmetric synapses with TH- dendritic shafts/spines, and TH+ dendrites were seen to form synapses with TH- axons of the host. Additionally, there were a few synapses formed by TH+ axonal terminals with negative buttons. The results suggest that DA neurons from 8-12 week old abortive human fetus are able to survive grafting into the neostriatum of monkey, a species phylogenetically very close to human, and to establish reciprocal synaptic connectivity with the host even at 2 months post-transplanting. It is, therefore, inferable that embryonic human DA neurons transplanted into human neostriatum may have the same fate as in monkeys.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1994

Apoptotic signals delivered through the T-cell receptor of a T-cell hybrid require the immediate-early gene nur77.

Engagement of the T-cell antigen receptor (TCR) on immature thymic T cells induces death by apoptosis. Although several lines of evidence indicate that apoptosis requires de novo gene expression, little is known about the molecular pathways that mediate this response. Here we show that nur77 (refs 4-7), a zinc-finger transcription factor, is expressed in response to TCR engagement in immature T cells and T-cell hybrids. Antisense inhibition of nur77 expression prevents apoptosis in TCR-stimulated cells. nur77 is also expressed in response to mitogens, but in this case transcription is regulated by 5' upstream elements that are distinct from those used for induction of apoptosis. In addition, polyadenylation is only observed on nur77 transcripts found in condemned cells. These data support a role for nur77 in cell death that may be distinct from that of activation.

Animals↗
PubMed1994

[Cytokine production by MTSC 4 cells, an established mouse thymic dendritic cell line].

The cytokine production by MTSC 4 cells, a murine thymic dendritic cell line established in our laboratory, has been investigated. Without exogenous stimulation, the MTSC 4 cells constitutively produce multiple types of cytokines, including IL-1, IL-6, IL-7, CSF, IFN and Chemotactic factor (CF). Of which, IL-6 and IFN were abundant: IL-1 and Chemokine, moderate: IL-7 and CSF at low level. MTSC4 cells could not produce detectable either IL-3 of TNF alpha. The establishment of MTSC 4 may be useful in the analysis of the mechanism of thymus selection, and in the study of the network regulation of autocrined cytokines.

Animals↗
PubMed1994

[Corneal topography of keratoconus].

A computerized video keratoscope (TMS-1) was used to determine the topographic findings of 6 eyes of 4 patients with keratoconus and they were compared with those of 18 normal eyes. The results show that in keratoconus the central corneal refractive power is greater, the difference between the refractive powers of the bilateral central corneas of a case is larger and the inferior cornea is steeper than the superior cornea. The above topographic findings are possibly the characteristics of the corneal topography of keratoconus.

Adolescent↗
PubMed1992

An efficient method for blunt-end ligation of PCR products.

This report presents data demonstrating a simple method that can potentially be extended to a wide range of cloning strategies to increase the yield of insert-containing recombinants. The method requires that the ligation of an insert to a vector does not regenerate the original restriction enzyme recognition sequence. In the example presented, PCR products were blunt-end ligated to a SmaI-cut vector, in the presence of SmaI endonuclease. The addition of the restriction enzyme to the ligation reaction dramatically favored the ligation of insert to vector rather than vector self-ligation.

Cloning, Molecular↗