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Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 703 records · Page 39Linked to original sources
PubMed1994

An immunocytochemical study of bone morphogenetic protein in experimental fracture healing of the rabbit mandible.

A monoclonal antibody raised against bone morphogenetic protein (BMP-McAb) has been used to demonstrate the presence of bone morphogenetic protein (BMP) in experimental fracture healing. Rabbit mandibles were fractured using standardized methods and left to heal for 3, 7, 14, 21 and 24 d, respectively. The avidin-biotin complex (ABC) method demonstrated an accumulation of positively stained primitive mesenchymal cells at the fracture site in the hematoma stage of bone repair. These cells appeared to undergo differentiation into positively-stained chondroblasts and osteoblasts during the phase of callus formation. Undifferentiated mesenchymal cells showed a high positive reactivity in the early post-fracture stages but a much lower reactivity during the remodelling phase. The results of our study suggest that bone inductive processes are accompanied by the presence of BMP in osteoprogenitor cells during fracture healing of the mandible and that BMP may play a significant role in osteogenesis during bone healing.

Animals↗
PubMed1994

Elevations in circulating calcitonin gene-related peptide correlate with hemodynamic deterioration during endotoxic shock in pigs.

Calcitonin gene-related peptide (CGRP) is a potent vasodilatory neuropeptide, which may play a role in vascular dysfunction during septic shock. Sixteen pigs (25-50 kg) were anesthetized with ketamine and isoflurane in O2, and administered 100 micrograms/kg Escherichia coli lipopolysaccharide i.v. (LPS; n = 8) or saline vehicle (n = 8). Pigs were instrumented for hemodynamic determinations and blood sampling for CGRP assay (pg/ml) from the portal vein (PV) and the pulmonary (PA) and carotid (CA) arteries. Blood samples were collected into EDTA and aprotinin before (baseline) and at 60, 120, and 180 min after LPS administration. LPS caused significant deterioration in indices of hemodynamic function and a significant increase in plasma CGRP concentration at all sampling sites by 120 min (P < 0.01). No significant difference between sampling sites was recorded at any time. Plasma CGRP concentrations displayed significant negative correlations with mean arterial pressure, cardiac index, and left ventricular stroke work. These data confirm our previous findings of CGRP elevations in endotoxemic rats, and indicate that 1) LPS is a potent stimulus for the systemic release of CGRP, 2) increasing plasma CGRP concentrations temporally correlates with cardiovascular deterioration during LPS shock, and 3) there is little evidence that the portal circulation is a major source of circulating CGRP levels during LPS shock. Vasoactive neuropeptides, such as CGRP, may interact with other documented mediators of vascular dysfunction in the pathogenesis of septic shock.

Animals↗
PubMed1993

No association between schizophrenia and homozygosity at the D3 dopamine receptor gene.

The D3 dopamine receptor gene is an important candidate gene for schizophrenia, since (because of its almost exclusive expression in the limbic system) it combines the dopamine receptor hypothesis with the limbic system hypothesis of schizophrenia. A BalI restriction fragment length polymorphism of the D3 dopamine receptor gene has been typed in 107 schizophrenic patients and 98 normal controls from Sichuan (China). With regard to alleles or genotypes, no significant differences were obtained between controls from Europe and China, between patients and controls, and between patient subgroups and controls. These results indicate a lack of association between schizophrenia and the D3 dopamine receptor gene in our sample. Our findings are at variance with reports of a significant excess of homozygosity at the D3 dopamine receptor gene in schizophrenic patients from Wales (United Kingdom) and Alsace (France). In conclusion, further studies will be needed with larger samples of patients from Wales and Alsace as well as with samples of different racial groups to prove or disprove the initial positive association between schizophrenia and genotypes of the D3 dopamine receptor gene.

Adolescent↗
PubMed1993

The E1 protein of bovine papilloma virus 1 is an ATP-dependent DNA helicase.

For efficient DNA replication of papillomaviruses, only two viral-encoded proteins, E1 and E2, are required. Other proteins and factors are provided by the host cell. E2 is an enhancer of both transcription and replication and is known to help E1 bind cooperatively to the origin of DNA replication. E1 is sufficient for replication in extracts prepared from permissive cells, but the activity is enhanced by E2. Here we show that purified E1 can act as an ATP-dependent DNA helicase. To measure this activity, we have used strand displacement, unwinding of topologically constrained DNA, denaturation of duplex fragments, and electron microscopy. The ability of E1 to unwind circular DNA is found to be independent of origin-specific viral DNA sequences under a variety of experimental conditions. In unfractionated cellular extracts, E1-dependent viral DNA replication is origin-dependent, but at elevated E1 concentrations, replication can occur on non-origin-containing DNA templates. This conversion from an origin-dependent replication system to a nonspecific initiator system is discussed in the context of the current understanding of the initiation of chromosomal DNA replication.

Adenosine Triphosphate↗
PubMed1993

Epidermal growth factor-mediated signaling of G(i)-protein to activation of phospholipases in rat-cultured hepatocytes.

Hepatocytes were established in tissue culture in order to study the effects of pertussis toxin (PT) on epidermal growth factor (EGF)-mediated cellular responses under in vitro conditions. EGF caused a 3-fold increase of myo-inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) mass and a 50% increase of diacylglycerol mass within the first minute, with the change of diacylglycerol content being 100-fold greater than that of Ins-1,4,5-P3. Diacylglycerol, but not Ins-1,4,5-P3, continued to accumulate over several hours, indicating that EGF increased the hydrolysis of lipids other than phosphatidylinositol 4,5-bisphosphate (PIP2). EGF increased phosphoinositide-specific phospholipase C-gamma (PLC-gamma) tyrosine phosphorylation within 1 min, but no effect was observed with vasopressin, insulin, or glucagon after 5 min. EGF also caused a rapid, tyrosine kinase-dependent association of G(i) alpha with PLC-gamma, which was maximal within 10 min. In contrast to our previous data on fresh hepatocytes, PT had no effect on the EGF-induced tyrosine phosphorylation of PLC-gamma, although Ins-1,4,5-P3 and diacylglycerol production were inhibited. The role of G-proteins in EGF signaling was investigated further by microinjection of G alpha antibodies into single fura-2-loaded hepatocytes. Anti-G(i) alpha (common) antibodies prevented EGF-induced but not vasopressin-induced Ca2+ transients. These results strengthen previous observations that a PT-sensitive G-protein is involved in EGF-mediated phospholipid metabolism in hepatocytes and show that tyrosine phosphorylation of PLC-gamma is an insufficient signal for activation of PIP2 hydrolysis.

Adenosine Diphosphate Ribose↗
PubMed1993

Molecular cloning of cDNA encoding the phenol/aryl form of sulfotransferase (mSTp1) from mouse liver.

The cDNA sequence of the mouse liver phenol/aryl form of sulfotransferase (mSTp1) has been determined. The cloned cDNA consists of 1269 base pairs (bp) and contains an 897 nucleotide open reading frame (ORF) beginning at nucleotide 65, which encodes a 298 amino acid polypeptide of 34.7 kDa. Alignment of mSTp1 to other sulfotransferases shows overall identities of 87% to r-STp, 37% to r-STa, 48% to r-STe, 51% to b-STe, and 37% to h-STa, at the deduced amino acid level.

Amino Acid Sequence↗
PubMed1993

Vibrational CD study of the thermal denaturation of poly(rA).poly(rU).

The vibrational cd (VCD) of a double-stranded RNA, poly(rA).poly(rU), at pH 7 and moderate added salt concentration (0.1 M) has been measured in both the base-stretching and phosphate-stretching regions of the ir as a function of temperature. The data in both cases show two distinct phase transitions. The first is from double- to a triple-stranded form, and the second is from triple- to single-stranded forms, which still retain substantial local order even up to 80 degrees C. The nature of these transitions has been identified by comparison of the VCD and ir absorption spectra of the initially double-stranded samples with those of single-stranded poly(rA) and poly(rU) and with triple-stranded poly-(rA).poly-(rU).poly(rU). The large differences in the VCD band shapes allows positive identification of the intermediate and final states. Thus under VCD-concentration conditions, a simple helix-to-coil transition can be eliminated for poly(rA).poly(rU) while such a two-step transition can be seen at low salt conditions. All of these observations are consistent with previous studies of the phase transitions of poly(rA).poly(rU) under various salt conditions. Additionally, the VCD is indicative of premelting for all the triple-, double-, and single-strand complexes studied. The triple-strand complex did not show disproportionation to double strand on heating under these added salt conditions. The unusual VCD pattern for low temperature poly(rA).poly(rU), as compared to high G--C content RNAs and DNAs, is qualitatively, but not quantitatively, explained using exciton coupling of localized dipolar transitions in each type of base within the strand.

Circular Dichroism↗
PubMed1993

Immunoreactivity of proliferating cell nuclear antigen in salivary gland tumours: an assessment of growth potential.

Immunoreactivity of proliferating cell nuclear antigen (PCNA) was assessed to evaluate growth potential in surgically resected tissue specimens from 70 cases of benign and malignant salivary gland tumours. Three stage streptavidin-biotin immunoperoxidase immunostaining using monoclonal antibody to PCNA showed a heterogeneity of PCNA index and distribution. In normal salivary gland specimens, PCNA was demonstrated in the nuclei of few ductal and acinar cells. In pleomorphic adenoma a multiple nodular growth pattern was observed with positive immunoreactivity restricted to the nuclei of tubulo-ductal structures. Warthin's tumour had positive nuclei in the outer cuboidal cells of epithelial component and germinal centres of lymphoid tissue. Myoepithelioma and acinic cell carcinoma showed slightly differing values and a statistically significant difference in the value of the index was observed in tumour cell aggregates of the cribiform type of adenoid cystic carcinoma and the solid undifferentiated type and between low/intermediate and high-grade mucoepidermoid tumours. PCNA is a useful marker of tumour cell proliferation; the index correlates with the grade of malignancy in salivary gland tumours.

Carcinoma, Squamous Cell↗
PubMed1993

Long-term culture and characteristics of normal rat liver bile duct epithelial cells.

BACKGROUND: A method was established for isolation and long-term culture of bile duct epithelial cells (BDEC) of normal adult rat liver that does not require the preparation of highly purified BDEC. METHODS: After dissociation of the liver parenchyma by collagenase perfusion, the liver remnant containing the intact biliary tree was minced into small fragments, embedded in a rat tail collagen gel, and cultured for 6 days in hormonally defined serum-free Dulbecco's Modified Eagle Medium/F12 medium (SFDM). BDEC cultures were subsequently subcultured and maintained on rat tail collagen gels in SFDM medium containing 5 mumol/L forskolin and 5%-10% Nu Serum IV (Collaborative Research, Bedford, MA). RESULTS: Established BDEC lines continued to express ductal specific markers including gamma-glutamyl transpeptidase, cytokeratins 7 and 19, and a number of monoclonal antibody-defined bile duct antigens, such as OC.2, OC.3, and OV6. CONCLUSIONS: The availability of a method to establish normal BDEC lines will allow further investigation of the function of bile duct cells and their role in normal liver differentiation and carcinogenesis.

Animals↗
PubMed1993

No evidence of linkage between schizophrenia and D3 dopamine receptor gene locus in Icelandic pedigrees.

The D3 dopamine receptor gene is an important candidate gene for schizophrenia, since--because of its almost exclusive expression in the limbic system--it combines the dopamine receptor hypothesis with the limbic system hypothesis of schizophrenia. Pairwise linkage analyses were carried out between the D3 dopamine receptor gene locus (DRD3) and schizophrenia (including major depression among its pleiotropic manifestations). On the basis of these analyses, which assumed a penetrance of 0.71 and a dominant mode of inheritance, we were able to exclude the DRD3 locus with a lod score of -2.50 in four Icelandic pedigrees. The area of exclusion (lod score < -2.00) extended 1.2 centimorgans. We conclude that the genetic predisposition to schizophrenia in these pedigrees is not due to a mutation in the DRD3 locus. However, these results cannot exclude the possibility that a defect in other genes regulating the expression of the D3 dopamine receptor gene could be involved in the pathogenesis of schizophrenia or that linkage analyses in other families or population-based association studies might show a positive result.

Adult↗
PubMed1993

Catecholamines: important factors in the increase of oxidative phosphorylation coupling in rat-liver mitochondria during the early phase of burn injury.

Thirty minutes after Sprague-Dawley rats had been injected subcutaneously with epinephrine or norepinephrine, the respiratory control ratio (RCR), the rate of O2 consumption in state 3 and the rate of ATP formation in liver mitochondria succinate respiratory chain were increased. The rate of O2 consumption in state 4 was increased or only slightly increased. When the rats were injected with the adrenergic blocking agents, timolol or phenoxybenzamine, 1 h before the burn, the activities of the succinate respiratory chain was partly inhibited 30 min postburn. Compared with our previous results, it can be suggested that catecholamines may play an important role in the increase of oxidative phosphorylation coupling in the early phase of burn injury.

Animals↗
PubMed1993

Polyphenols from Rhodiola crenulata.

A novel gallotannin, crenulatin ( 7), has been isolated from RHODIOLA CRENULATA. The structure was elucidated by spectral analyses (including 2D-NMR spectral measurements) and chemical methods. Also six known polyphenols have been isolated and identified.

Journal Article↗