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Biomedical subjects

H Liang

Publications and source records attributed to H Liang.

At least 109 records · Page 6Linked to original sources
PubMed1999

Genome-wide transcriptional analysis of aerobic and anaerobic chemostat cultures of Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae is unique among eukaryotes in exhibiting fast growth in both the presence and the complete absence of oxygen. Genome-wide transcriptional adaptation to aerobiosis and anaerobiosis was studied in assays using DNA microarrays. This technique was combined with chemostat cultivation, which allows controlled variation of a single growth parameter under defined conditions and at a fixed specific growth rate. Of the 6,171 open reading frames investigated, 5,738 (93%) yielded detectable transcript levels under either aerobic or anaerobic conditions; 140 genes showed a >3-fold-higher transcription level under anaerobic conditions. Under aerobic conditions, transcript levels of 219 genes were >3-fold higher than under anaerobic conditions.

Aerobiosis↗
PubMed1999

Bone anabolic effects of basic fibroblast growth factor in ovariectomized rats.

The purpose of this study was to characterize the bone anabolic effects of basic fibroblast growth factor (bFGF) in ovariectomized (OVX) rats. Female Sprague Dawley rats were subjected to ovariectomy or sham surgery at 3 months of age and maintained untreated for 2 months post surgery. Groups of OVX rats were then treated iv with bFGF at doses of 100 or 200 microg/kg day for 7 or 14 days. Another group of OVX rats and a group of sham-operated control rats were treated iv with vehicle alone for 14 days. Certain groups of bFGF-treated OVX rats were killed at 7 or 14 days after withdrawal of treatment. The right tibiae were processed undecalcified for quantitative bone histomorphometry. Vehicle-treated OVX rats were characterized by decreased cancellous bone volume associated with increased bone turnover. Treatment of OVX rats with bFGF strongly stimulated bone formation, as indicated by marked increases of at least a factor of 10 in osteoblast surface, osteoid surface, and osteoid volume. Furthermore, new osteoid spicules were observed within the marrow cavity of these animals. Osteoclast surface was markedly decreased in bFGF-treated OVX rats, but this finding may be secondary to the extensive osteoid surface. The strongest bone anabolic effects occurred in OVX rats treated with the higher dose of bFGF for 14 days, but these animals exhibited a bone mineralization defect, as evidenced by abundant osteoid and a lack of double fluorochrome labeling, despite markedly increased osteoblast surface. However, the newly-formed osteoid rapidly calcified after withdrawal of bFGF treatment. The data indicate that bFGF not only stimulates bone formation on pre-existing bone surfaces but also induces de novo formation of bone spicules within the marrow cavity, which results in partial restoration of lost cancellous bone mass in osteopenic OVX rats after only 14 days of treatment with the growth factor. These findings suggest that bFGF merits consideration for development as a potential treatment for patients with severe osteopenia who are unresponsive to conventional osteoporosis therapies.

Animals↗
PubMed1999

Parathyroid hormone and mechanical usage have a synergistic effect in rat tibial diaphyseal cortical bone.

Previous reports showed that bone mass and architecture only partially recovered by remobilization (RM) after immobilization (IM)-induced osteopenia, and that parathyroid hormone (PTH) had an anabolic effect on the skeleton. The aim of this study was to determine whether low doses of PTH could restore IM-induced cortical bone loss and whether a combination of PTH plus loading (RM) treatment would be more effective than the PTH in unloaded (IM) limbs. One hundred and sixty 6-month-old rats were divided into aging and IM groups. The right hindlimb of the rat was immobilized by elastic bandage for 18 weeks, and then groups of rats were either kept IM or RM and treated with 30 microgram or 80 microgram of hPTH(1-38)/kg/day for 2, 10, and 20 weeks. Fluorescent-labeled, undecalcified cross-sections of right tibial shafts were studied. We found that RM for 20 weeks after 18 weeks of IM only partially recovered IM-induced muscle weight loss and PTH had no effect on muscle weight in either IM or RM limbs; that RM for 20 weeks after 18 weeks of IM partially restored some minimal cortical width by stimulating periosteal and endocortical bone formation and decreasing endocortical resorption; that PTH treatment of IM limbs completely restored IM-induced cortical bone loss and added extra bone by stimulating bone formation indices on all bone surfaces and depressing bone resorption on endocortical surface; that PTH treatment of RM limbs produced similar anabolic effects as in IM limbs with 30 microgram/kg/day dose but the 80 microgram/kg/day dose-treated limbs had a higher periosteal bone formation rate, which created a larger cross-sectional area, more cortical bone area, and a thicker cortex than the same dose treated IM limbs; and that PTH 80 microgram/kg/day treatment produced more anabolic effect than the 30 microgram/kg/day in both IM and RM limbs. We concluded that reloading the hindlimb by RM after long-term IM could not recover the cortical bone mass. PTH at employed doses was able to completely restore IM-induced cortical bone loss, and this effect was independent of mechanical stimulation. However, when PTH was combined with mechanical loading (RM), a synergistic anabolic effect on periosteal bone formation occurred which increased the cross sectional area that can increase bone strength.

Aging↗
PubMed1999

Structural features of cell death in atherosclerotic lesions affecting long-term aortocoronary saphenous vein bypass grafts.

Aortocoronary saphenous vein bypass grafts fail because of structural pathologies (thrombosis, intimal hyperplasia and atherosclerosis) within the 'arterialized' vein leading to graft stenosis. This study examined structural characteristics of atherosclerotic alterations in long-term aortocoronary artery saphenous vein bypass grafts with particular attention to the features of cell death in atherosclerotic lesions. Stenotic vein grafts were obtained from 10 patients at redo coronary artery bypass grafting operations. All the grafts were affected by histological abnormalities, with eight out of ten grafts showing evidence of atherosclerotic alterations in the intimal hyperplastic layer. Areas containing foam cells were examined by electron microscopy. Cells with cytoplasmic lipid accumulations were characterized by varying degrees of chromatin condensation, fragmentation or dispersion, by focal areas of oedema and vacuolisation of their cytoplasm, and by plasmalemmal destruction. Some lipid-filled cells exhibiting signs of destruction contained myofilaments and basal membrane fragments, allowing them to be identified as smooth muscle cells. Macrophage foam cells were found to have undergone similar destruction. No cells showing nuclear degeneration were observed to have intact cytoplasmic organelles. Neither were apoptotic bodies identified, but necrotic remnants were frequently seen. The results suggest that cell death in atherosclerotic lesions affecting aortocoronary artery saphenous vein bypass grafts occurs through oncosis rather than by apoptosis.

Adult↗
PubMed1999

[Studies of improving the frequency of wheat transformation by biolistic bombardment] [In Process Citation]

In the present study immature embryos of spring wheat Zhong-60634 were bombarded with gold particles coated with pAHC25 containing Bar and GUS genes. A total of 17 bialaphos-tolerant plants were obtained from 342 immature embryos which were first cultured for 3-4 days and then bombarded and selected. Integration of the introduced genes into the genome of transgenic wheat plants was shown by PCR and Southern analysis and transformation frequency was 0.88%. Furthermore, the present study showed that calli regeneration ability was improved while the embryo culture medium was supplemented with 2 mg/L dicamba instead of 2 mg/L 2,4-D. Meanwhile, in order to keep the calli differentiation ability calli should be transferred to differentiation medium supplemented with 3 mg/L bialaphos from calli selection medium with 5 mg/L bialaphos within a month.

Journal Article↗
PubMed1999

[The suppression of T cell functions and its relationship with the change of signal transduction after trauma].

OBJECTIVE: To study the relationship between the suppression of T cell functions and the change of signal transduction in traumatized mice. METHODS: 60 Balb/c mice were randomized into six groups: normal control, 1st, 2nd, 4th, 7th, 10th day posttrauma (n = 10). A murine closed trauma model was used, T cells were separated from splenocytes using nylon column. T cell functions were determined and their relationship with intracellular signal transduction was investigated. RESULTS: Interleukin 2 (IL-2) mRNA and IL-2 receptor alpha (IL-2R alpha) mRNA levels were decreased in activated T cells from traumatized mice, IL-2 production, IL-2R alpha expression and T lymphocytes transformation were suppressed. cAMP contents in activated T cells were increased after trauma while cGMP contents, free calcium (Ca2+) concentration and protein kinase C (PKC) activities were decreased. These changes were closely related to the suppression of T cell functions. In addition, adenylate cyclase (AC) and protein kinase A (PKA) activities were increased while cAMP-dependent phosphodiesterase (cAMP-PDE), calmodulin (CaM), CaM-dependent protein kinase (CaM-PK) activities were decreased. Levamisole (a stimulator of cGMP), H-8 (an inhibitor of PKA), A23187 (an ionophore of Ca2+) and TPA (an activator of PKC) could in vitro elevate activated T cell functions after trauma in various degrees. CONCLUSIONS: Alteration in the pathway of signal transduction following trauma related to cyclic nucleotide and phosphatidylinositol metabolism in activated T cells participate in mediating the suppressive progress of T cell functions.

Animals↗
PubMed1999

[The effect of riboflavin on lipid peroxidation in rats].

In order to study the effect of riboflavin on lipid peroxidation in rats, randomized block design was used to study the effect of different riboflavin levels on the riboflavin status and lipid peroxidation of S.D. rats. The rats fed with riboflavin deficient diets for 6 weeks had higher levels of BGRAC, blood malondialdehyde and lower levels of GSH than those with riboflavin sufficient diets. The RBC SOD activity is also reduced in riboflavin deficiency rats. It is concluded that riboflavin deficiency increases the extent of lipid peroxidation.

Animals↗
PubMed1999

[Effects of low concentration carbon monoxide on the neurobehavior function in mice].

OBJECTIVE: To study the effect of low concentration CO on neurobehaviour function and the maximal allowable concentration (MAC) in limited time. METHOD: 40 KM (kunming) male mice were randomly divided into groups A, B, C and D. They were exposed to normal air, 30 mg/m3 CO, 300 mg/m3 CO and 600 mg/m3 CO respectively. The changes in neurobehaviour function of the mice before, during and after 72 h exposure in 0.5 m3 static chambers were observed. Four indices were measured: response time (RT) and error rate (ER) in the water maze test, enter check frequency (ECF) and urine or excrement frequency (UEF) in open field test. RESULT: The set upright frequency in group D was smaller than those in groups A, B and C during exposure. RT and ER values went in a direction contrary to pre-exposure the four groups in the second 3 days (6 d) after or out of exposure, while ER values showed that group D > group C > group A > group B in the third 3 days (9 d). RT value was not different among the 4 groups, but its order of numerical value was similar to the ER order. The order of ECF values was that group C > group A and group D in 3 d after or out of exposure and not different among the 4 groups in 6 d and group D < group A and group B in 9 d. UEF values were not different among the 4 groups in 3 d and 9 d, but group D > group A and group B in 6 d after or out of exposure. Comparison with every group itself, showed statistically significance increase in ER values in 9 d out of exposure than before exposure in group D. ECF values showed the statistics significant increase in 9 d in group A and B. CONCLUSION: Low concentration CO may interfere with the learning and memory of mice in the water maze and impede the development of the motor nervous function and disturb the steadiness of emotion of mice in the open field. In addition, low concentration of CO may be of tardy toxicity.

Animals↗
PubMed1999

[An introduction of solvent-free(SPME) technique].

Solid-phase microextraction (SPME) is a solvent-free sample preparation technique in which a fused silica fiber coated with polymeric organic liquid is introduced into the sample. In this paper, theoretical aspects, operating models, factors of influencing sensitivity, applications and future development are introduced briefly with 19 references.

Chromatography, Gas↗
PubMed1999

[Effect of the coordinate micro-environment on the structure of Hg (II)-serum albumin].

Detailed studies on the UV spectra of Hg (II)-HSA or Hg (II)-BSA complexes nearby isoionic point were carried out in this paper. Compared with the spectra at physiological pH, the band nearby 250 nm of Hg (II)-BSA generally disappeared or widened and weakened,but the band at 290 nm of Hg (II)-BSA and Hg (II)-HSA remained nearly unchanged. These results support that these binding sites of Hg (II)-serum albumin may be located at seven pairs of adjacent disulfide bridges and there might be the structure of HgS4 tetrahedral configuration. For the first time, this paper put forward the solid figure of HgS4 tetrahedral configuration, and further discussed the results using the discrepancy of the coordinate micro-environment.

Animals↗
PubMed1999

[Study on the interaction of human serum albumin and Mn (II), Co (II) by fluorescence method].

The interaction of Mn (II), Co(II) and HSA has been studied by fluorescence method at pH 7.4 and 5.3. Based on Forste non-radiative energy transfer theory, the distance between Trp-214 residue of HSA and the first strong binding site to Mn (II), Co (II) in HSA was determined, and it is much larger than that of reference. This notable different result has been discussed according to the binding site of Mn (II), Co (II ) and domain structure in HSA.

Binding Sites↗
PubMed1998

Mapping the subsite preferences of protein tyrosine phosphatase PTP-1B using combinatorial chemistry approaches.

Protein tyrosine phosphatases (PTPases) are important regulators of signal transduction systems, but the specificity of their action is largely unexplored. We have approached this problem by attempting to map the subsite preferences of these enzymes using combinatorial chemistry approaches. Protein-tyrosine peptidomimetics containing nonhydrolyzable phosphotyrosine analogues bind to PTPases with high affinity and act as competitive inhibitors of phosphatase activity. Human PTP-1B, a PTPase implicated to play an important role in the regulation of growth factor signal transduction pathways, was used to screen a synthetic combinatorial library containing malonyltyrosine as a phosphotyrosine mimic. Using two cross-validating combinatorial chemistry screening approaches, one using an iterative method and the other employing library affinity selection-mass spectrometric detection, peptides with high affinity for PTP-1B were identified and subsite preferences were detailed by quantitatively comparing residues of different character. Consistent with previous observations, acidic residues were preferred in subsites X-3 and X-2. In contrast, aromatic substitutions were clearly preferred at the X-1 subsite. This information supports the concept that this class of enzymes may have high substrate specificity as dictated by the sequence proximal to the phosphorylation site. The results are discussed with regards to the use of combinatorial techniques in order to elucidate the interplay between enzyme subsites.

Computer Simulation↗
PubMed1998

Molecular anatomy of chromosome 7q deletions in myeloid neoplasms: evidence for multiple critical loci.

Complete or partial deletions of the long arm of chromosome 7 (7q- and -7) are nonrandom abnormalities seen in primary and therapy-induced myelodysplasia (MDS) and acute myelogenous leukemia (AML). Monosomy 7, occurring as the sole cytogenetic anomaly in a small but significant number of cases, may denote a dominant mechanism involving critical tumor suppressor gene(s). We have determined the extent of allele loss in cytogenetically prescreened MDS and AML patients for microsatellite markers from chromosome 7q22 and 7q31. Whereas >80% of these cases revealed allele loss for the entire region, a rare case of the 7q- chromosome showed allele loss for only the proximal 7q31.1 loci flanked by the markers D7S486 and D7S2456, and a case of monosomy 7 revealed allele loss for loci at both 7q31 and 7q22 with retention of sequences between these sets of loci. Furthermore, a case of AML with no cytogenetic anomaly of chromosome 7 revealed a submicroscopic allelic imbalance for a third distal locus, D7S677. These findings suggest the presence of three distinct critical loci that may contribute alone or in combination to the evolution of MDS and AML. The data also provide molecular evidence for unbalanced translocation with noncontiguous deletions, as an alternate mechanism underlying monosomy 7.

Chromosomes, Human, Pair 7↗
PubMed1998

Subcellular phototoxicity of 5-aminolaevulinic acid (ALA).

BACKGROUND AND OBJECTIVE: 5-aminolaevulinic acid (ALA) is a new, promising photosensitizer for PDT of cancer. Subcellular toxicity induced by ALA and light exposure in single cells was studied to elucidate the mechanism of cell damage. STUDY DESIGN/MATERIALS AND METHODS: CPAE, PTK2, and rat neonatal myocardial cells treated with ALA were examined for localization using fluorescence microscopy and for subcellular phototoxicity using 630 nm laser microbeam irradiation of specific subcellular regions. RESULTS: In CPAE and PTK2 cells, a large amount of fluorescence was detected in the peri-nuclear cytoplasm. In rat neonatal myocardial cells, the sensitizer selectively localized in the large mitochondria. In both cell types, there was little phototoxicity when the peripheral cytoplasmic region was exposed, as compared to considerable phototoxicity with exposure of either the perinuclear or nuclear regions. CONCLUSION: Both the CPAE and PTK2 cells demonstrated that the nucleus followed by the perinuclear cytoplasm are the most sensitive cell areas with no sensitivity in the peripheral cytoplasm.

Aminolevulinic Acid↗
PubMed1998

Transient overexpression of the Microphthalmia gene in the eyes of Microphthalmia vitiligo mutant mice.

The murine microphthalmia gene (Mitf) encodes a basic helix-loop-helix transcription factor thought to regulate transcription of genes encoding proteins of the pigmentation pathway. It may promote pigment cell survival and development. The protein encoded by Mitf appears to be critical for eye development, because mutant alleles demonstrate varying degrees of ocular malformation. One of the mildest of these is the Mitf vitiligo (Mitfvit) mutant allele, which exhibits uneven pigmentation of the retinal pigment epithelium (RPE) and slow, progressive photoreceptor cell loss, eventually leading to blindness. In the present study, the expression of Mitf during early eye development in the Mitfvit mutant was compared with that of pigmented wild type mice. Mitf expression quantified by reverse transcriptase-polymerase chain reaction amplification demonstrated a transient elevation of Mitf between embryonic day 10.5 (E10.5) and E13.5 in the Mitfvit mutant compared with wild type mice. In situ hybridization analysis confirmed this elevation and localized Mitf expression to the neuroepithelium during onset of optic vesicle formation (E9.0-E9.5) and, subsequently, to the RPE during optic cup formation (E10-E11.5) in both mutant and wild type eyes. This is the first report of transient elevation of Mitf in any of the Mitf mutants, and the elevation may be relevant to altered levels of pigmentation proteins as well as to the RPE abnormalities observed in the Mitfvit mutant.

Alleles↗
PubMed1998

[Action of DDPH in the interventional treatment of portal hypertension induced by liver cirrhosis in rabbits].

To explore a new way of utilizing intervential treatment to effectively decrease the portal hypertension, the animal models of liver cirrhosis accompanying portal hypertension were set up by intraportal vein injection of suspensions of Bletilla striata to 10 rabbits by means of prospective investigational method. The catheter filled with heparin solution was remained in theportal vein for infusion of drugs. Three weeks later, DDPH solution was injected into the portal vein via the catheter to determine its effect of decreasing portal vein pressure and its influence of peripheral blood pressure and heart rate. At the same time, other 10 rabbits with liver cirrhosis associated with portal hypertension were subjected to the injection of DDPH solution via the ear vein served as control group. The results showed that administration of DDPH by portal vein could rapidly, safely and effectively decrease the portal hypertenive pressure without side effects and partially reverse liver cirrhosis, as compared with injection of DDPH via peripheral veins. It was concluded that DDPH exerted its alpha 1-adrenoceptor blocking and calcium antagonistic effects, thereby significantly reduce the portal hypertension. Injection of DDPH via portal vein is a completely new and relaible method for the treatment of liver cirrhosis with portal hypertension.

Adrenergic alpha-Antagonists↗