Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 451 records · Page 25Linked to original sources

PubMed2000

Combined treatment with stereotactic intracavitary irradiation and gamma knife surgery for craniopharyngiomas.

OBJECT: To evaluate the effectiveness of the combined treatment of stereotactic intracavitary irradiation and Gamma Knife surgery on craniopharyngiomas. PATIENTS AND METHODS: Combined treatment with stereotactic instillation of radioisotopes and Gamma Knife surgery was performed on 46 patients with craniopharyngioma between October 1996 and June 1999. There were 13 solid tumors and 33 mixed solid and cystic tumors. RESULTS: 38 patients (10 solid and 28 mixed) were followed up from 6 months to two years. The tumor control rate was 90% in solid tumors, 85.7% in mixed tumors, 92.1% in the solid segment and 89.5% in total. CONCLUSIONS: Gamma Knife surgery plays an important role in the treatment of the solid component of craniopharyngiomas and the combination of treatment is a simple, safe and effective method for treatment of craniopharyngiomas, especially for the recurrent mixed solid and cystic tumors.

Adolescent↗

PubMed2000

A critical role for neutrophil elastase in experimental bullous pemphigoid.

Bullous pemphigoid (BP) is an autoimmune skin disease characterized by subepidermal blisters and autoantibodies against 2 hemidesmosome-associated proteins, BP180 and BP230. The immunopathologic features of BP can be reproduced in mice by passive transfer of anti-BP180 antibodies. Lesion formation in this animal model depends upon complement activation and neutrophil recruitment. In the present study, we investigated the role of neutrophil elastase (NE) in antibody-induced blister formation in experimental BP. Abnormally high levels of caseinolytic activity, consistent with NE, were detected in extracts of lesional skin and blister fluid of mice injected with anti-BP180 IgG. The pathogenic anti-BP180 IgG failed to induce subepidermal blistering in NE-null (NE(-/-)) mutant mice. NE(-/-) mice reconstituted with neutrophils from wild-type mice became susceptible to experimental BP. Wild-type mice given NE inhibitors (alpha1-proteinase inhibitor and Me-O-Suc-Ala-Ala-Pro-Val-CH(2)Cl), but not mice given cathepsin G/chymase inhibitors (alpha1-antichymotrypsin or Z-Gly-Leu-Phe-CH(2)Cl), were resistant to the pathogenic activity of anti-BP180 antibodies. Incubation of murine skin with NE induced BP-like epidermal-dermal detachment. Finally, NE cleaved BP180 in vitro and in vivo. These results implicate NE directly in the dermal-epidermal cleavage induced by anti-BP180 antibodies in the experimental BP model.

Animals↗

PubMed2000

Regulation of meristem organization and cell division by TSO1, an Arabidopsis gene with cysteine-rich repeats.

In higher plants, meristem organization and cell division regulation are two fundamentally important and intimately related biological processes. Identifying and isolating regulatory genes in these processes is essential for understanding higher plant growth and development. We describe the molecular isolation and analyses of an Arabidopsis gene, TSO1, which regulates both of these processes. We previously showed that tso1 mutants displayed defects in cell division of floral meristem cells including partially formed cell walls, increased DNA content, and multinucleated cells (Liu, Z., Running, M. P. and Meyerowitz, E. M. (1997). Development 124, 665-672). Here, we characterize a second defect of tso1 in influorescence meristem development and show that the enlarged influorescence in tso1 mutants results from repeated division of one inflorescence meristem into two or more influorescence meristems. Using a map-based approach, we isolated the TSO1 gene and found that TSO1 encodes a protein with cysteine-rich repeats bearing similarity to Drosophila Enhancer of zeste and its plant homologs. In situ TSO1 mRNA expression pattern and the nuclear localization of TSO1-GFP are consistent with a regulatory role of TSO1 in floral meristem cell division and in influorescence meristem organization.

Amino Acid Sequence↗

PubMed2000

Temporal and spatial gradients of Fgf8 and Fgf17 regulate proliferation and differentiation of midline cerebellar structures.

The midbrain-hindbrain (MHB) junction has the properties of an organizer that patterns the MHB region early in vertebrate development. Fgf8 is thought to mediate this organizer function. In addition to Fgf8, Fgf17 and Fgf18 are also expressed in the MHB junction. Fgf17 is expressed later and broader than either Fgf8 or Fgf18. Disrupting the Fgf17 gene in the mouse decreased precursor cell proliferation in the medial cerebellar (vermis) anlage after E11.5. Loss of an additional copy of Fgf8 enhanced the phenotype and accelerated its onset, demonstrating that both molecules cooperate to regulate the size of the precursor pool of cells that develop into the cerebellar vermis. However, expression patterns of Wnt1, En2, Pax5 and Otx2 were not altered suggesting that specification and patterning of MHB tissue was not perturbed and that these FGFs are not required to pattern the vermis at this stage of development. The consequence of this developmental defect is a progressive, dose-dependent loss of the most anterior lobe of the vermis in mice lacking Fgf17 and in mice lacking Fgf17 and one copy of Fgf8. Significantly, the differentiation of anterior vermis neuroepithelium was shifted rostrally and medially demonstrating that FGF also regulates the polarized progression of differentiation in the vermis anlage. Finally, this developmental defect results in an ataxic gait in some mice.

Animals↗

PubMed2000

p125 focal adhesion kinase promotes malignant astrocytoma cell proliferation in vivo.

p125 focal adhesion kinase (p125FAK) is a cytoplasmic tyrosine kinase that is activated upon engagement of integrin cell adhesion receptors, and initiates several signaling events that modulate cell function in vitro. To determine the biologic role of p125FAK in malignant astrocytic tumor cells, U-251MG human malignant astrocytoma cells were stably transfected with p125FAK cDNA using the TET-ON system, and stable clones isolated that exhibited an estimated 5- or 20-fold increase in p125FAK expression on administration of 0.1 or 2.0 microg/ml doxycycline, respectively. In vitro studies demonstrated that induction of p125FAK resulted in a 2- to 3-fold increase in cell migration, increased p130CAS phosphorylation, localization of exogenous p125FAK to focal adhesions, and a 2-fold increase in soft agar growth. To determine the role of p125FAK in vivo, clones were injected stereotactically into the brains of scid mice. A 4.5-fold estimated increase in p125FAK expression was induced by administration of doxycycline in the drinking water. Analysis of xenograft brains demonstrated that, upon induction of p125FAK, there was a 1.6- to 2.8-fold increase in tumor cell number, and an increase in mAb PCNA-labeling of tumor cells in the absence of a change in the apoptotic index. Compared to normal brain, the expression of p125FAK was elevated in malignant astrocytic tumor biopsies from patient samples. These data demonstrate for the first time that p125FAK promotes tumor cell proliferation in vivo, and that the underlying mechanism is not associated with a reduction in apoptosis.

Agar↗

PubMed2000

A new diterpene glycoside from Rabdosia rubescens.

A new ent-kaurene beta-D-glucoside was isolated from Rabdosia rubescens, together with the known compounds oridonin, ponicidin, and pedalitin. The structure of new compound was determined, on the basis of spectral data and X-ray crystallographic analysis, to be ent-7 beta,20-epoxy-kaur-16-ene-1 beta,6 alpha,7 alpha,14 alpha,15 alpha-pentanol 1-O-beta-D-glucopyranoside.

Crystallography, X-Ray↗

PubMed2000

Novel enantioselective fluorinating agents, (R)- and (S)-N-fluoro-3-tert-butyl-7-nitro-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides.

Enantioselective fluorinating agents, (R)- and (S)-,N-fluoro-3-tert-butyl-7-nitro-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides (BNBT-F, 2) are readily prepared in 3 steps from racemic 3-tert-butyl-7-nitro-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides (5) via optical resolution and fluorination. These agents make accessible both enantiomers of optically active quaternary alpha-fluoro carbonyl compounds in modest to high enantioselectivities. X-ray crystallographic analysis of chiral 2 reveals a unique structure wherein the nitrogen atom is highly pyramidalized and fluorine occupies an axial position.

Crystallography, X-Ray↗

PubMed2000

Collagen structure regulates fibril mineralization in osteogenesis as revealed by cross-link patterns in calcifying callus.

Although >80% of the mineral in mammalian bone is present in the collagen fibrils, limited information is available about factors that determine a proper deposition of mineral. This study investigates whether a specific collagen matrix is required for fibril mineralization. Calcifying callus from dog tibias was obtained at various times (3-21 weeks) after fracturing. At 3 weeks, hydroxylysine (Hyl) levels were almost twice as high as in control bone, gradually reaching normal levels at 21 weeks. The decrease in Hyl levels can only be the result of the formation of a new collagen network at the expense of the old one. The sum of the cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) in callus matched that of bone at all stages of maturation. However, the ratio HP/LP was 2.5-4.5 times higher in callus at 3-7 weeks than in normal bone and was normalized at 21 weeks. Some 40% of the collagen was nonmineralized at the early stages of healing, reaching control bone values (approximately 10%) at 21 weeks. In contrast, only a small increase in callus mineral content from 20.0 to 22.6 (% of dry tissue weight) from week 3 to 21 was seen, indicating that initially a large proportion of the mineral was deposited between, and not within, the fibrils. A strong relationship (r = 0.80) was found between the ratio HP/LP and fibril mineralization; the lower the HP/LP ratio, the more mineralized the fibrils were. Because the HP/LP ratio is believed to be the result of a specific packing of intrafibrillar collagen molecules, this study implies that mineralization of fibrils is facilitated by a specific orientation of collagen molecules in the fibrils.

Amino Acids↗

PubMed2000

Effects of bone marrow cells on hepatocytes: when co-cultured or co-encapsulated together.

Bone marrow cells co-cultured with hepatocytes resulted in hepatocytes that can be maintained in culture for 14-21 days. This is compared to 7-10 days with hepatocytes alone under the same conditions. Similarly, when bone marrow cells are co-encapsulated together with hepatocytes, the viability of hepatocytes in culture medium is prolonged to 28 days. This is compared to 14 days when hepatocytes are encapsulated alone under the same conditions. These results suggest that bone marrow cells can contribute to the viability and maintenance of hepatocytes. It addition, this principle could be applied to other situation as in helping the regeneration of hepatocytes in liver failure and also for other cells and organs.

Animals↗

PubMed2000

Approaches to estimating daily yield from single milk testing schemes and use of a.m.-p.m. records in test-day model genetic evaluation in dairy cattle.

Statistical models were presented to estimate daily yields from either morning or evening test results. The 64,451 test-day records from 10,392 lactations of 8800 cows were available for analysis from experiments that were designed to investigate the accuracy of an alternate morning and evening four-weekly milk-testing scheme. The experiments were conducted in 152 herds from six German states and covered a span from 1994 to 1998. Milk yield, fat, and protein percentage were recorded for all of the morning and evening milkings. Seven statistical models were fitted to the data to derive formulas for estimating daily yields from morning or evening yields. In general, use of evening milkings less accurately estimated yields than did use of morning milkings. Among the three yield traits the lowest accuracy of estimation of daily yield was found for fat yield. Although the models do not differ much in the correlation between estimated and true daily yields, systematic under- and overestimation of daily yield at the beginning and end of lactation were observed in all models with the exception of model 6, which accounted for heterogeneous variances by parity class, milking interval class, and lactation stage by fitting separate regression formulas within each combination of the three factors. A study to validate the models showed that model 6 is also robust for the analyzed populations. Smoothing model 6 regression formulas across lactation stages caused a systematic pattern of estimation error, although loss in accuracy was minimal by fitting far fewer parameters in the regression formulas. Differences in the accuracy of alternate milking schemes to predict daily yields were found between traits, between morning and evening milkings, and between parity classes. Compared with true daily yields from different lactation stages, variances and correlations of the estimated yields were reduced, which must be accounted for in genetic evaluation. The use of estimated daily yields from morning or evening milkings has a smaller impact on estimated breeding values of bulls than cows. As a result of lower heritability and repeatability of estimated daily yields than true daily yields, the weight on own test-day records for estimating cows' breeding values is lower when cows are in a.m.-p.m. than conventional monthly testing schemes. However, the difference in the weights between estimated and true daily yields decreases as lactation progresses. Use of estimated daily yields is less reliable for estimating breeding value than use of true daily yields.

Animals↗

PubMed2000

Mechanisms for neuronal degeneration in amyotrophic lateral sclerosis and in models of motor neuron death (Review).

Amyotrophic lateral sclerosis (ALS), also referred to as motor neurone disease, is a fatal neurological disease that is characterized clinically by progressive muscle weakness, muscle atrophy, and eventual paralysis. The neuropathology of ALS is primary degeneration of upper (motor cortical) and lower (brainstem and spinal) motor neurons. The amyotrophy refers to the neurogenic atrophy of affected muscle groups, and the lateral sclerosis refers to the hardening of the lateral white matter funiculus in spinal cord (corresponding to degeneration of the corticospinal tract) found at autopsy. Because the mechanisms for the motor neuron degeneration in ALS are not understood, this disease has no precisely known causes and no effective treatments. Very recent studies have identified that the degeneration of motor neurons in ALS is a form of apoptotic cell death that may occur by an abnormal programmed cell death (PCD) mechanism. In order to treat ALS effectively, we need to understand the mechanisms for motor neuron apoptosis more completely. Future studies need to further identify the signals for PCD activation in neurons as they relate to the pathogenesis of ALS and to clarify the molecular pathways leading to motor neuron apoptosis in animal and cell culture model systems. These studies should lead to a better understanding of motor neuron death and to the design of new therapeutic experiments critical for the future treatment of ALS.

Amyotrophic Lateral Sclerosis↗

PubMed2000

Differential diagnosis of malignant lymphomas and related disorders by specific pattern of expression of immunophenotypic markers revealed by multiparameter flow cytometry (Review).

The introduction of monoclonal antibodies (mAbs) for cell immunophenotyping and use of flow cytometry with the progressively improving software for multivariate analyses have revolutionized the diagnosis and influenced the classification of hematologic neoplasms. In this review we focus on the practical application of flow cytometry in the diagnosis and classification of malignant lymphomas and related lymphoproliferative disorders with special emphasis on differential diagnosis. A general approach to the utilization of flow cytometry (FC) in hematopathology with an algorithm to diagnose the most common neoplasms is presented. We discuss precursor B-cell neoplasms, mature B-cell neoplasms (SLL/CLL, mantle cell lymphoma, marginal zone lymphoma, hairy cell leukemia, diffuse large B-cell lymphoma, plasma cell dyscrasias and lymphomas with plasmacytic differentiation), precursor T-lymphoblastic leukemia and mature (peripheral) T-cell neoplasms, including T-SLL/PLL, anaplastic cell lymphomas and large granular cell leukemia/lymphoma. The text is accompanied by characteristic FC scatterplots of the discussed entities.

Antibodies, Monoclonal↗

PubMed2000

Detection of sialomucin complex (MUC4) in human ocular surface epithelium and tear fluid.

PURPOSE: To evaluate human ocular surface epithelium and tear fluid for the presence of sialomucin complex (MUC4), a high-molecular-weight heterodimeric glycoprotein composed of mucin (ASGP-1) and transmembrane (ASGP-2) subunits. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis assays were used to identify sialomucin complex RNA in ocular surface epithelia. Immunoprecipitation and immunoblot analysis were used to identify immunoreactive species in human tears and in the corneal and conjunctival epithelia using antibodies specific for carbohydrate and peptide epitopes on the sialomucin complex subunits. Immunofluorescence staining was used to detect sialomucin complex in frozen sections and impression cytology specimens of human cornea and conjunctival epithelia. RESULTS: ASGP-1- and ASGP-2-specific sequences were amplified from RNA extracted from both conjunctival and corneal epithelial biopsies by RT-PCR. Sialomucin complex transcripts were also detected in these tissues by Northern blot analysis, with a greater level of RNA detected in the peripheral than the central corneal epithelium. Sialomucin complex was immunoprecipitated from tear fluid samples and both corneal and conjunctival epithelia and detected by immunoblot analysis with specific anti-ASGP-1 and anti-ASGP-2 antibodies. The ASGP-1 peptide antibody HA-1 stained the full thickness of the corneal and conjunctival epithelia. In contrast, antibody 15H10, which reacts against a carbohydrate epitope on ASGP-1, stained only the superficial epithelial layers of these tissues. No staining was observed in the conjunctival goblet cells. CONCLUSIONS: Sialomucin complex was originally identified in rat mammary adenocarcinoma cells and has recently been shown to be produced by the ocular surface epithelia of rats. Furthermore, it has been identified as the rat homologue of human MUC4 mucin. The present studies show that it is expressed in the stratified epithelium covering the surface of the human eye and is present in human tear fluid. Expression of a carbohydrate-dependent epitope on the mucin subunit (ASGP-1) of sialomucin complex occurs in a differentiation-dependent fashion. Sialomucin complex joins MUC1 as another membrane mucin produced by the human ocular surface epithelia but is also found in the tear fluid, presumably in a soluble form, as found on the rat ocular surface.

Antibody Specificity↗

PubMed2000

Regulation of MMP-9 activity in human tear fluid and corneal epithelial culture supernatant.

PURPOSE: To evaluate human corneal epithelial culture supernatant and tear fluid for the presence of activators and inhibitors of matrix metalloproteinase (MMP)-9, MMP-3, and tissue inhibitor of metalloproteinase (TIMP)-1, respectively, and to evaluate the effect of MMP-3 on the activation of MMP-9 in these specimens. METHODS: Unstimulated tear fluid was collected from patients with ocular rosacea and normal control subjects. Levels of MMP-9, MMP-3, and TIMP-1 were determined by enzyme-linked immunosorbent assay (ELISA) and/or immunoblot analysis. Supernatants from primary human corneal epithelial cultures and human tear fluid were incubated with MMP-3. Cultured epithelial cells and their supernatants were also treated with doxycycline before MMP-3 was added. Gelatin zymography was used to identify activated 82-kDa MMP-9. MMP-9 activity was assessed with a commercial MMP-9 activity assay system. RESULTS: MMP-9 and TIMP-1 were detected at significantly higher concentrations in rosacea-affected than in normal tear fluids. MMP-3 was detected exclusively in the tear fluid of patients with ocular rosacea who had corneal epithelial disease. Treatment of the supernatant and tear fluid with MMP-3 resulted in two bands with molecular weights of 92 kDa and 82 kDa, representing pro-MMP-9 and activated MMP-9, respectively. Doxycycline added to the conditioned media did not affect activation of MMP-9 by MMP-3. However, 24-hour treatment of corneal epithelial cultures with doxycycline resulted in a lower concentration and activity of MMP-9 in their supernatants. CONCLUSIONS: MMP-9 and TIMP-1 are produced by the human corneal epithelium and are present in tear fluid. MMP-3 alone is sufficient to activate MMP-9 on the ocular surface. Doxycycline does not directly inhibit this activation by MMP-3, but it decreases MMP-9 activity when added to corneal epithelial cultures.

Blotting, Western↗

PubMed2000

[Plasma technology for biomedical material applications].

In this paper is introduced the plasma technology for the applications of several species biomaterial such as ophthalmological material, drug delivery system, tissue culture material, blood anticoagulant material as well as plasma surface clearing and plasma sterilization, and so on.

Animals↗

PubMed2000

[A self-adaptable system for acquiring and processing animal ECG parameters].

The present authors have developed a computerized system for acquiring and processing the animal ECG. The system provides many functions in the software design and the users can compile the parameter-analyzing formulae by themselves according to the characteristics of ECG. The system is much more accurate and flexible in analyzing the ECG parameters and can significantly avoid the processing mistakes caused by signal variations and interference. It is especially suitable for continuous ECG monitoring and analysis of animal experiments in physiology, pharmacology and toxicology.

Animals↗

PubMed2000

The time-effect relationship of central action in acupuncture treatment for weight reduction.

PURPOSE: To study the time-effect relationship of action of acupuncture on the satiety center of ventromedial nucleus of hypothalamus (VMH) in rats with experimental obesity. METHODS: Microelectrode recording method of nerve cells and stereotaxic technique for brain were adopted with discharge frequency (Hz/s) of nerve impulse in VMH as the index, and the time-effect of acupuncture action in different periods between groups were observed. RESULTS: Electric activity in acupuncture group was higher than in the obesity model group (P < 0.001) and the normal group (P < 0.01) respectively, and the curve of acupuncture action within 2 hours showed irregular fluctuation. CONCLUSION: Acupuncture can increase excitability of the satiety center, with a better long-term effect.

Acupuncture Therapy↗

PubMed2000

[Cytochrome P450 1A1 and cytochrome P450 2E1 gene polymorphisms in Guangzhou Hans].

OBJECTIVE: To determine the distribution of cytochrome P450 1A1(CYP1A1) and cytochrome P450 2E1(CYP2E1) gene polymorphisms in Guangzhou Hans. METHODS: A total of 150 healthy Guangzhou Hans were studied with PCR-RFLP and ASA techniques. Current results were compared with the data on other ethnic groups. RESULTS: In the 150 individuals tested, the frequencies of the m1(Msp I-) and m2(Msp I+) alleles of the Msp I polymorphic site in the 3' non-coding region of the CYP1A1 gene were found to be 62.33% and 37.67%, respectively. The observed frequencies of the m1m1, m1m2 and m2m2 genotypes were found to be 40%, 44.67% and 15.33%, respectively, which met Hardy-Weinberg equilibrium. The frequencies of the A and G alleles of the exon 7 A4889G polymorphic site in the CYP1A1 gene were found to be 79% and 21%, respectively. The observed frequencies of the AA, AG and GG genotypes were found to be 62.67%, 32.67% and 4.66%, respectively, which met Hardy-Weinberg equilibrium. A close linkage between the Msp I polymorphism and exon 7 A4889G polymorphism was observed in Guangzhou Hans(chi(2)=62.2358, P<0.005). The frequencies of the C1(Rsa I+, Pst I-) and C2(Rsa I-, Pst I+) alleles of the Rsa I polymorphic site in the 5' flanking region of the CYP2E1 gene were found to be 85.3% and 14.7%, respectively. The observed frequencies of the C1C1, C1C2 and C2C2 genotypes were found to be 67.3%, 29.3%, and 3.4%, respectively, which met Hardy-Weinberg equilibrium. CONCLUSION: The frequencies of the CYP1A1 and CYP2E1 gene polymorphisms in Guangzhou Hans were similar to those in Japanese population, but were significantly different from those in European populations.

China↗