Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 253 records · Page 14Linked to original sources

PubMed2000

Effects of prolactin on osteoblast alkaline phosphatase and bone formation in the developing rat.

The purpose of the current study was to determine whether maternal prolactin (PRL) had any effects on bone formation in the developing rat pup. Because the most prevalent forms of PRL in rats are unmodified and phosphorylated PRL, both recombinant PRL and a molecular mimic of phosphorylated PRL (PP-PRL) were administered to pregnant animals. Blood samples from the dams showed normal estrogen and progesterone and no effect of extra PRL on parathyroid hormone (PTH), calcium, or alkaline phosphatase (AP). In newborn pups, however, there was a 30% decrease in blood AP in both PRL-treated groups, whereas PTH and calcium levels were not different from controls. When primary rat osteoblasts were exposed to both PRLs, AP activity was reduced, with PP-PRL being the more potent form of the hormone. Histological examination of pup bone formation showed reduced calvarial bone and reduced endochondral ossification in pups exposed to PP-PRL. These results are the first to show a direct inhibitory effect of PRL on osteoblast function.

Alkaline Phosphatase↗

PubMed2000

p53-dependent acinar cell apoptosis triggers epithelial proliferation in duct-ligated murine pancreas.

The mechanisms linking acinar cell apoptosis and ductal epithelial proliferation remain unknown. To determine the relationship between these events, pancreatic duct ligation (PDL) was performed on p53(+/+) and p53(-/-) mice. In mice bearing a wild-type p53 allele, PDL resulted in upregulation of p53 protein in both acinar cells and proliferating duct-like epithelium. In contrast, upregulation of Bcl-2 occurred only in duct-like epithelium. Both p21(WAF1/CIP1) and Bax were also upregulated in duct-ligated lobes. After PDL in p53(+/+) mice, acinar cells underwent widespread apoptosis, while duct-like epithelium underwent proliferative expansion. In the absence of p53, upregulation of p53 target genes and acinar cell apoptosis did not occur. The absence of acinar cell apoptosis in p53(-/-) mice also eliminated the proliferative response to duct ligation. These data demonstrate that PDL-induced acinar cell apoptosis is a p53-dependent event and suggest a direct link between acinar cell apoptosis and proliferation of duct-like epithelium in duct-ligated pancreas.

Animals↗

PubMed2000

Beat-to-beat repolarization variability in ventricular myocytes and its suppression by electrical coupling.

Single ventricular myocytes paced at a constant rate and held at a constant temperature exhibit beat-to-beat variations in action potential duration (APD). In this study we sought to quantify this variability, assess its mechanism, and determine its responsiveness to electrotonic interactions with another myocyte. Interbeat APD(90) (90% repolarization) of single cells was normally distributed. We thus quantified APD(90) variability as the coefficient of variability, CV = (SD/mean APD(90)) x 100. The mean +/- SD of the CV in normal solution was 2.3 +/- 0.9 (132 cells). Extracellular TTX (13 microM) and intracellular EGTA (14 mM) both significantly reduced the CV by 44 and 26%, respectively. When applied in combination the CV fell by 54%. In contrast, inhibition of the rapid delayed rectifier current with L-691,121 (100 nM) increased the CV by 300%. The CV was also significantly reduced by 35% when two normal myocytes were electrically connected with a junctional resistance (R(j)) of 100 MOmega. Electrical coupling (R(j) = 100 MOmega) of a normal myocyte to one producing early afterdepolarization (EAD) completely blocked EAD formation. These results indicate that beat-to-beat APD variability is likely mediated by stochastic behavior of ion channels and that electrotonic interactions act to limit temporal dispersion of refractoriness, a major contributor to arrhythmogenesis.

Action Potentials↗

PubMed2000

Ligand activation domain of human orphan growth hormone (GH) secretagogue receptor (GHS-R) conserved from Pufferfish to humans.

Synthetic ligands have been identified that reset and amplify the cycle of pulsatile GH secretion by interacting with the orphan GH-secretagogue receptor (GHS-R). The GHS-R is rhodopsin like, but does not obviously belong to any of the established G protein-coupled receptor (GPCR) subfamilies. We recently characterized the closely related orphan family member, GPR38, as the motilin receptor. A common property of both receptors is that they amplify and sustain pulsatile biological responses in the continued presence of their respective ligands. To efficiently identify additional members of this new GPCR family, we explored a vertebrate species having a compact genome, that was evolutionary distant from human, but where functionally important genes were likely to be conserved. Accordingly, three distinct full-length clones, encoding proteins of significant identity to the human GHS-R, were isolated from the Pufferfish (Spheroides nephelus). Southern analyses showed that the three cloned Pufferfish genes are highly conserved across species. The gene with closest identity (58%) was activated by three synthetic ligands that were chosen for their very high selectivity on the GHS-R as illustrated by their specificity in activating the wild-type human GHS-R but not the E124Q mutant. These results indicate that the ligand activation domain of the GHS-R has been evolutionary conserved from Pufferfish to human (400 million years), supporting the notion that the GHS-R and its natural ligand play a fundamentally important role in biology. Furthermore, they illustrate the power of exploiting the compact Pufferfish genome for simplifying the isolation of endocrinologically important receptor families.

Amino Acid Sequence↗

PubMed2000

The effects of different wire and screw combinations on the stiffness of a hybrid external fixator.

Hybrid external fixators that use tensioned wires in the metaphysis and screws in the diaphysis combine the advantages of both unilateral and circular fixators and provide considerable flexibility in frame construction. This study aims to determine the effects of wire and screw combinations on the mechanical characteristics of such systems. Acrylic rods were used to simulate a long bone with a transverse fracture gap. A standard hybrid fixator design was used to stabilize the fracture in accordance with modern concepts with wires being used on one side of the fracture and screws on the other side. Twelve different wire and screw combinations were tested in axial compression and four-point bending in two planes. All the fixators tested demonstrated stiffening under increasing axial load, the extent of which appeared to correlate inversely with the number of wires used. Increasing the number of wires by one increased the axial stiffness by 7-16 N/mm (average 11 N/mm). The bending stiffness was largely controlled by the number of wires and increased by 0.42-1.03 N m/mm (average 0.74 N m/mm) for each additional wire. The axial stiffness of fixators with three screws was 4-7 N/mm (average 6 N/mm) higher than those with two screws if the offset screw was not in use. When the offset screw was used no stiffness advantages were found for three screws over two screws. The use of an offset screw substantially increased axial stiffness (by 12-26 N/mm, average 20 N/mm) and is recommended for unstable fractures. The two-ring hybrid fixators with four wires in one ring and three screws in the other had stiffness characteristics similar to the conventional four-ring Ilizarov fixator. Knowledge gained regarding the effects of wire and screw combinations on overall stiffness will be helpful both in the construction of frames and in destabilization during fracture healing.

Biomechanical Phenomena↗

PubMed2000

Effects of photoinduced membrane rigidification on the lysosomal permeability to potassium ions.

Mechanism for the photoinduced increase in the lysosomal K+ permeability is still unknown. In this study, we investigated the effect of photodamage-induced membrane rigidification on the lysosomal K+ permeability by measuring the membrane potential with bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol and by monitoring proton leakage with p-nitrophenol. Membrane fluidity was measured by the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene. Methylene blue-mediated photodamage to lysosomes decreased their membrane fluidity and increased their K+ permeability. The photoinduced increase in the K+ permeability can be reversed by fluidizing the rigidified lysosomal membranes with benzyl alcohol. The results suggest that the membrane rigidification induced by photodamage may increase lysosomal K+ permeability. This conclusion is supported by the observation that rigidifying lysosomal membranes by the treatment with membrane rigidifier cholesteryl hemisuccinate also enhanced the lysosomal K+ permeability.

Animals↗

PubMed2000

Transplantation of normal and genetically modified adrenocortical cells.

Cell transplantation techniques have been applied to the study of the biology of the adrenal cortex and to adrenocortical cell proliferation, differentiation, and senescence. Primary bovine adrenocortical cells, primary human adrenocortical cells and genetically modified bovine adrenocortical cells have been transplanted. Successful methods include transplantation of cells beneath the kidney capsule and several subcutaneous cell transplantation procedures. In successful transplants the cells form a functional vascularized tissue structure that allows the host animals to survive adrenalectomy. We show here that subcutaneous cell transplantation does not depend on embedding cells in collagen gel before introduction into the host animal. Subcutaneous transplants secrete both cortisol and aldosterone. However, the variability of plasma aldosterone levels indicates that the factors that determine glomerulosa-type and fasciculata-type cell function in transplant tissues are not well understood.

3T3 Cells↗

PubMed2000

Adenoviral vector-mediated transfer of human heme oxygenase in rats decreases renal heme-dependent arachidonic acid epoxygenase activity.

Intravenous administration of an adenovirus human heme oxygenase (HO)-1 gene construct to rats resulted in functional expression of human HO-1 in brain, heart, lung, liver, and kidney. Because accurate assessment of human HO-1 mRNA in various tissues by Northern analysis is not sufficiently sensitive, we developed a method for quantifying human HO-1 mRNA copies with quantitative reverse transcription- polymerase chain reaction techniques; this allowed us to use the same primers for both the sample and internal standard. Administration of the adenovirus human HO-1 gene resulted in the detection of human HO-1 mRNA in various tissues with the highest levels seen in the kidney followed, in order, by lung > liver > brain > heart. Human HO-1 was detectable for up to 4 weeks in all tissues studied. Administration of adenovirus human HO-1 resulted in maximal increase of HO activity after 1 to 2 weeks in rats. The increase in HO activity due to gene transfer also was associated with a parallel decrease (approximately 25%) in cytochrome P-450 (CYP) content and in CYP-dependent arachidonic acid metabolism. In addition, we investigated the possibility that the human HO-1 gene altered the expression of the endogenous rat enzyme after administration of cobalt chloride s.c. Cobalt chloride administration resulted in increased HO activity in all tissues examined in rats transduced with the human HO-1 gene to the same degree as in nontransduced rats. The metal was a more potent inducer of renal HO activity than was the adenoviral-mediated human HO-1 vector. The increase in HO activity after adenoviral-mediated human HO-1 transfer was associated with a decrease in microsomal heme-CYP and CYP activity. The increase in HO-1 activity after adenovirus-mediated human HO-1 gene transfer may prove useful as a means of selectively increasing enzyme activity in a specific organ and regulating homeostasis by modulation of vasoactive molecules such as carbon monoxide and bilirubin and, in addition, providing a means of delivering the human HO-1 gene for experimental purposes.

Adenoviridae↗

PubMed2000

[Immobilized Ni(2+)-IDA metal chelating affinity membrane chromatography for purification of commercial human serum albumin].

Further purification of commercial human serum albumin was studied on immobilized Ni(2+)-IDA composite membrane cartridge. Effect of pH on HSA binding capacity was examined. A lot of impurities in the commercial HSA had been removed by a single step purification with a recovery of more than 85% of the protein bound on membrane cartridge. The purified HSA was of comparable purity of that from Sigma company analyzed by capillary electrophoresis. The nickel ion retained in the protein solution could be removed efficiently with the N, N, N'-tris (carboxymethyl) ethylenediamine chelating membrane cartridge.

Chelating Agents↗

PubMed2000

The immunomarker of aging and the modulatory effect of Chinese medicinal herbs on the dysfunction of lymphocytes in the elderly.

PURPOSE: This study examined an immunomarker of aging and evaluated the modulatory effect of Chinese medicinal herbs (CMH) on the immune function of lymphocytes in the elderly. METHODS: Forty-seven elderly and fifteen young persons were selected as study subjects. Peripheral blood lymphocytes (PBL) were isolated by Ficoll-Hypaque gradient centrifugation. The responsive proliferation was investigated by means of the 3H-TdR incorporation procedure. The phenotype and receptor of lymphocytes were measured using indirect immunofluorescence. RESULTS: Both Rg1 and Gy-P significantly increased the responsive proliferation of lymphocytes in the elderly, p < 0.001 and p < 0.05, respectively. Rg1 also had a stimulatory effect on the receptor, CD25, and phenotype, CD45RA, CD45RO, in lymphocytes in aged persons. The immunomarker of aging was established by multiparametric indications on the basis of study at the cellular and molecular levels. CONCLUSION: The possibility exists that a lowered immune function can be reversed with modulation. In the near future, a highly purified, nontoxic, and more effective immunomodulator could be produced from CMH as an antiaging drug.

Adjuvants, Immunologic↗

PubMed2000

[Advances in the researches of DNA vaccines against tumors].

The injection of naked plasmid DNA directly into the muscle cells of hosts has been shown to induce potent immune responses, as well as to express large amounts of gene product; this has provided a new way of treatment for tumor. The past ten years have witnessed tremendous growth in the field of gene therapy for cancer using intramuscular injection of plasmid DNA. Many studies have suggested that the immunostimulatory DNA sequences(ISS) in vector backbone of plasmid DNA, delivering adjuvant and mitogenic activity, are necessary for effective intradermal gene immunization. It has been postulated that muscle cells serve as a reservoir of expressed antigen with subsequent transfer to bone marrow-derived APCs. Thus, immunization with plasmid DNA can trigger strong and persistent cell-mediated and humoral immune responses to the antigen encoded by the plasmid. Increasing evidence demonstrates that DNA immunization can prevent or inhibit tumor development. In this review, the present authors presented a discussion on the characteristics of immune response to DNA vaccines and a summary of the effects of immune response against tumors.

Animals↗

PubMed2000

[A novel rabbit endothelin B receptor gene: cloning and sequence analysis].

Endothelin(ET) is the most potent mammalian vasoconstrictor identified to data. As a pathogenic factor, ET is involved in the genesis of many diseases. In this study, a pair of primers was designed and synthesized according to the human ETB receptor gene (hETBR) sequence. A 394 bp of DNA fragment was amplified by polymerase chain reaction(PCR) and labeled with alpha-32P-CTP using Random Primer-Labeling method. With this probe, rabbit lung cDNA library was screened by in situ hybridization and 11 positive clones were identified. Sequencing result showed that a complete reading frame of rabbit ETB receptor(rETBR) cDNA could be produced from three positive clones of eleven. By a series of subcloning, a recombinant plasmid including the 1326 bp of rETBR coding sequences, named pBlu Script-rETBR, was constructed. The deduced amino acid sequence indicated that the rETBR is 441 residues in length, with an expected molecular mass of approximately 49.44 kD. N-terminal 18 residues is the potential signal peptide (Score = 11.11) and therefore the molecular mass of mature rETBR is 47.65 kD with 423 amino acid residues. Analysis of the rETBR hydropathy profile indicates the presence of seven hydrophobic regions, putative transmembrane domains. Potential N-glycosylation sites are the 60th and the 118th. The structure exhibits a significant sequence and topographical similarity with G protein-coupled receptors.

Amino Acid Sequence↗

PubMed2000

Iridoid glucosides from Caryopteris mongholica.

Two new iridoid glucosides, 8-acetyl-6'-O-(p-coumaroyl) harpagide and 6'-O-(p-coumaroyl) antirrinoside, were isolated from the Caryopteris mongholica, together with two known iridoid glucosides, 8-acetylharpagide and harpagide. Their structures were elucidated, mainly by interpretation of their spectroscopic data (UV, IR, MASS, 1H, 13C, 1H/1H-COSY, HMQC, HMBC and NOESY NMR) and chemical methods.

China↗

PubMed2000

Dietary conjugated linoleic acid mixture affects the activity of intestinal acyl coenzyme A: cholesterol acyltransferase in hamsters.

The present study was designed to study the mechanisms by which dietary conjugated linoleic acids (CLA) decrease serum cholesterol. Hamsters were fed a semi-synthetic diet containing 1 g cholesterol/kg diet with or without supplementation with 20 g linoleic acid (LA) and 20 g CLA/kg diet. After 8 weeks, serum fasting total cholesterol (TC) and triacylglycerol (TG) were significantly lower in the LA-supplemented and CLA-supplemented groups compared with those of the control (CTL) hamsters. In contrast to LA, CLA significantly lowered hepatic cholesterol but it increased the level of adipose tissue cholesterol, suggesting that the hypocholesterolaemic mechanism of CLA is different from that of LA. CLA decreased the activity of intestinal acyl CoA:cholesterol acyltransferase (ACAT) whereas LA had no effect on this enzyme. Consequently, CLA supplementation increased the faecal excretion of total neutral sterols, but it had no or little effect on the faecal acidic sterols. If the ACAT is associated with cholesterol absorption, the part of mechanisms by which CLA decreases serum cholesterol may involve down-regulation of intestinal ACAT activity.

Acyl Coenzyme A↗

PubMed2000

New bisabolane sesquiterpenes from Ligularia songarica.

Phytochemical investigation of Ligularia songarica (Compositae) afforded seven new bisabolane-type sesquiterpenes. Their structures were confirmed on the basis of spectroscopic methods, especially 2D-NMR techniques, and compound 7 showed stronger antibacterial activity against Escherichia coli, Pseudomonas acruginosa and Salmonella pullorum.

Anti-Bacterial Agents↗

PubMed2000

[Asymmetric biosynthesis of chiral styrene oxide].

Used styrene as the sole carbon and energy source, 12 strains of aerobic bacterial and two strains of fungi were screened from a series soil samples. These strains were able to convert styrene to styrene oxide. HPLC and chiral GC method were used for determination the substrate, product and e.e value of culture broth. There were obvious effect on the biomass and epoxidase activity under various conditions in the fermentation. Styrene epoxidation of the strain PS-1206 was studied in different reaction time. 35% of conversion yield and 80% e.e value of (R)-styrene oxide could been obtained at the optimum conditions.

Bacteria↗

PubMed2000

[A clinical analysis of combination treatment with brachytherapy and external radiation, plus chemotherapy for the treatment of esophageal cancer].

OBJECTIVE: To analyse the value of various combinations of treatment for esophageal cancer. METHODS: One hundred twenty cases of esophageal cancer were randomly divided into four groups, 30 cases in each group. Group I was treated with external radiation (RT) alone; group II, with RT plus brachytherapy; group III with RT plus chemotherapy, and group IV with RT plus brachytherapy and chemotherapy. RT with 60Co was given 2 Gy daily, 5 times a week, with a total dose of 60-74 Gy. Brachytherapy was given 6-8 Gy once weekly with a total dose of 18-24 Gy. Chemotherapy with carboplatin was given 100 mg/day, five days a week at first and fifth week. RESULTS: The 1, 2, 3-year survival rate in group II, III and IV was higher than that in group I (P < 0.05). The 3-year survival rate of group I-IV patients was 13.3%, 36.7%, 40.0%, 46.7%, respectively. More patients died of cancer recurrence and progression in group I than in any of the other 3 groups of patients (P < 0.05). However, the frequency of distant metastasis was not significantly different. CONCLUSION: The combination treatment with external radiation, brachytherapy and chemotherapy can improve the local control of tumor growth and the survival rate in esophageal cancer patients.

Adenocarcinoma↗

PubMed2000

The regulatory action of the modified Yu Ping Feng Tang on cellular immunity in mice under amputation-induced stress.

To approach the action of modified Yu Ping Feng Tang ([symbol: see text] Jade-Screen Decoction) on cellular immunity, an experiment was conducted in mice under amputation-induced stress. On the 3rd day after amputation, acute atrophy was found in the thymus, the reactivities of T- and B-lymphocytes to Con-A and LPS were decreased, the IL-2 content and its activity reduced and the activity of NK cells lowered. The high, moderate and low concentrations of the modified Yu Ping Feng (YPF) Decoction all have antagonistic action on the above manifestations of immune inhibition.

Adjuvants, Immunologic↗