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Biomedical subjects

Y Gao

Publications and source records attributed to Y Gao.

At least 289 records · Page 16Linked to original sources
PubMed1998

[Infrared spectra of Caulis Mahoniae and 6 species of medicinal plants of the same genus].

Based on the IR spectra of the petroleum ether extract, ethyl ether extract and water extract of Caulis Mahoniae and six species of medicinal plants of the same genus, it has been found out that the differences of chemical constituents among the samples can be reflected by the changes of IR spectra. This method can be used as a rapid and exact means to search unknown species with same chemical constituents in the same genus and family.

Drug Contamination↗
PubMed1998

[The effect of retinoic acid on crown morphogenesis of mouse tooth germs in vitro].

OBJECTIVE: To study the effects of retinoic acid on crown morphogenesis of early tooth germs. METHODS: Mouse tooth organ culture model was used and the functions of different retinoic acid concentration on the first mandibular molar germs of 14-day old mouse embryo were examined. RESULTS: The first mandibular molar germ of 14-day old mouse was at the bud stage. After 6 days culture, tooth germs in culture medium (not containing retinoic acid) developed from bud stage to bell stage and formed normal cusps. The morphogenesis of tooth germs in medium containing 1 x 10(-7) mol/L retinoic acid was similar to molar germs in the medium without retinoic acid. When the concentration of retinoic acid increased to 1 x 10(-6) mol/L, the mouse tooth germs still developed from bud stage to bell stage, but normal cusps was not formed. CONCLUSION: The results suggest that high concentration of retinoic acid alter crown morphogenesis of tooth germs.

Animals↗
PubMed1998

[A study of epithelial cell kinetics of the odontogenic keratocyst].

OBJECTIVE: To study epithelial cell kinetics of the odontogenic keratocyst. METHODS: Proliferating cell nuclear antigen (PCNA) immunohistochemistry in 60 cases and cellular nuclear DNA contents cytometry in 40 cases were used to compare the epithelial cell kinetics of the odontogenic keratocyst, radicular cyst, dentigerous cyst, and ameloblastoma. RESULTS: The epithelial cells in odontogenic keratocyst has the potential of active growth instead of passive expanding. CONCLUSION: The authors suggest that the odontogenic keratocyst should be termed as "odontogenic keratocystic tumor" because is aggressive growth potential.

Cell Division↗
PubMed1998

[Basaloid squamous cell carcinoma: clinical pathological and immunohistochemical study].

OBJECTIVE: To investigate the clinicopathological and immunohistochemical characteristics of basaloid squamous cell carcinoma of oral cavity. METHODS: Routine HE staining and immunohistochemical staining. RESULTS: Basaloid squamous cell carcinoma accounted for 1% of oral squamous cell carcinoma and was more common in male. It could be found at anysite of oral mucosa. The tumor was composed of basaloid cells and squamous cells. Basaloid cell, the main tumor cell, arranged in sheets and nests. Mitosis and comedoform necrosis was often seen. Adjacent oral epithelium often exhibited dysplasia. The tumor cells were cytokeratin positive, S-100 negative; PCNA index was high; 50% cases were p53 positive. CONCLUSION: Oral basaloid squamous cell carcinoma was a higher grade malignant tumor as compared with usual squamous cell carcinoma and should be paid great attention both in treatment and in pathological diagnosis.

Adult↗
PubMed1998

[Langerhans cell histiocytosis of jaws: a clinical pathological and immunohistochemical study].

OBJECTIVE: To investigate the pathological and immunohistochemical characteristics of chronic localized Langerhans cell histiocytosis (LCH). METHODS: HE staining and histopathological observation, mitotic counting and immunohistochemical staining. RESULTS: 22 cases of LCH were included in this study. The most prominent histologic feature was nuclear polymorphism of Langerhans cells (LC). Nuclear sulcus was often noted. Intercellular spaces were also obvious. Mitotic figures were commonly seen (the mean mitotic index was 7.1 under 10 high magnification fields). The mean PCNA index of LC was 14.5%. Other histiocytes and multinuclear cells were CD68 and cathepsin D positive. CONCLUSION: The nuclear polymorphism of LC is of diagnostic value for LCH, LC in the lesions is hyperplastic and neoplastic in nature rather than simple accumulation and the S-100 positive LC are immature precursors of Langerhans cell.

Adolescent↗
PubMed1998

[Synthesis and antiulcer activity of 3,4-dihydro-hainanensine analogs].

In order to search for new compounds with new mode of action, high antiulcer activity and lower toxicity, 26(13 pairs of diastereoisomer A and B) 3,4-dihydro-hananensine analogs were synthesized. All compounds were tested in M1 receptor combined assay and gastric ulcer induced by cold-immersion stress in rats. Most compounds showed antiulcer activity, among them IX3A, IX7A, IX8A, IX12A, IX12B and IX13A exhibited more potent antiulcer activity than the control compound cimetidine. Meanwhile, the relationship between their structures and activity was discussed.

Animals↗
PubMed1998

[Studies on the fine stereostructure of taxoids].

The anticancer drug taxol is a new type antimicrotubular drug. The structure-activity relationship study on taxol and its analogs has indicated the importance of the C13 side chain and the C4-C5-C20 epoxypropane group. The crystal structures of 4 taxoids having the basic skeleton with 5/7/6 membered ring and three types of 10 taxoids having the basic skeleton with 6/8/6 membered ring have been analyzed. The effects of the induction by different substructures at C4 on the stereostructures of taxoids were studied, and the relationship between the 6/8/6/4 skeleton and the anticancer activity was discussed from the crystallographic point.

Antineoplastic Agents, Phytogenic↗
PubMed1998

[Research on the mechanism of Yin-enriching and Qi-reinforcing, strengthening body and tonification deficiency syndrome action of radix Panacis quinquefolii].

Radix Panacis Quinquefolii could significantly promote 3H-TdR infiltrating of spontaneously and ConA-stimulated splenic lymphocytes of mice; Promote the splenic lymphocytes capacity of mice in interleukin2 (IL-2) production; Significantly enhance erythropoitin (EPO) level of mice in serum; Markedly promote production of colony stimulating factors (CSFs) in murine spleen-conditioned medium (SCM); And promote production of CSFs in lung-conditioned medium (LCM) of mice. The results suggest that yin-enriching and qi-reinforcing, strengthening body and tonification deficiency syndrome action of Radix Panacis Quinquefolii is in association with its lymphocytes activation-stimulating, IL-2 secrection-promoting, EPO secrection, and CSTs production enhancing effectes.

Animals↗
PubMed1998

Effects of radiation on wound healing.

The pathological changes of radiation on wound healing in rats were observed by macroscopic, microscopic, and electronmicroscopic examination and detection of collagen types. We found that the wound healing process was obviously delayed by irradiation. First, the early phase inflammatory response was severely inhibited. In particular, the number of infiltrating macrophages and neutrophils was decreased, blood vessels were injured, and hemorrhage was evident. Second, the formation and maturation of granulation tissue were slowed down, fibroblasts were injured, and transcription of types and collagen mRNAs and synthesis and secretion of collagen were reduced. Finally, the reepithelialization process was delayed and the healing time was prolonged.

Animals↗
PubMed1998

Overexpression of MDM2, p53, and NCAM proteins in human radiation-induced skin ulcers.

Using immunohistochemistry, we studied the overexpression of MDM2, p53, and NCAM proteins in human radiation-induced skin ulcers. We found that the positive rate of overexpression of MDM2, p53, and NCAM was 36%, 8%, and 32%, respectively. The overexpression of MDM2 protein was mainly observed in the nuclei of fibroblasts in the deeper part of the ulcer; that of p53 protein was in the nuclei of the epidermis and in the cytoplasm of fibroblasts and endothelial cells, whereas that of NCAM was located in the cytoplasm of squamous epithelial cells of the epidermis and in fibroblasts, fibrocytes, endothelial cells, and leiomyocytes in the media of arteriolar walls. The overexpression of MDM2, p53, and NCAM may be related to the poor healing of radiation-induced skin ulcers and the cancer transformation.

Gene Expression↗
PubMed1998

The changes and significance of c-kit expression in the irradiated bone marrow of mice.

There have been only a few studies on the expression of c-kit in bone marrow after radiation and radiation-induced apoptosis of hematopoietic cells. LACA mice were examined after irradiation with a dose of 60Co gamma-rays. Using a light microscope, electron microscope, and immunohistochemistry, we studied radiation-induced apoptosis of hematopoietic cells and the expression of c-kit. We found that 5.5 Gy total body irradiation was a sublethal dose for LACA mice, induced suppression of leukocytes in blood, and of nucleated cells in bone marrow. Apoptosis of the hematopoietic cells occurred within 1 day after irradiation. The expression of c-kit was related to the recovery of hematopoiesis and played an important role in early hematopoiesis.

Animals↗
PubMed1998

Interleukin-3 gene expression in irradiated mouse bone marrow.

The expression of endogenous interleukin-3 (IL-3) gene in mouse bone marrow after whole body irradiation was assessed by immunocytochemistry, in situ hybridization (ISH), and in situ reverse transcription PCR (IS RT-PCR). The results showed obvious injury to the bone marrow followed by recovery 4 weeks after radiation. IL-3 protein was increased in the cytoplasm of recovering hematopoietic cells, especially at 21 days after radiation, while the mRNA was negative, except at 15 days when the mRNA was weakly positive by ISH. IS RT-PCR showed that IL-3 mRNA was strongly positive in the cytoplasm of recovering hematopoietic cells, especially at 10 to 15 days after radiation. We postulate that endogenous IL-3 gene may accelerate hematopoietic recovery in irradiated bone marrow and that IS RT-PCR may objectively report the regulation of IL-3 gene expression.

Animals↗
PubMed1998

Structural changes in lenses of mice lacking the gap junction protein connexin43.

PURPOSE: To investigate the role of the gap junction protein connexin43 (Cx43), which is predominantly expressed in lens epithelial cells in the control of lens development and organization. METHODS: Newborn mice in which the Cx43 gene was disrupted by homologous recombination were used. Lenses from Cx43 (-/-) mice and wild-type littermates were processed by using 2% glutaraldehyde fixation for light and transmission electron microscopy and by freezing in liquid nitrogen for light and confocal microscopy of immunofluorescence in cryosections. RESULTS: In wild-type mice, Cx43 was immunolocalized to apical and lateral regions of lens epithelial cells and throughout the cornea, iris, ciliary body, and retina. In the bow, or equatorial, region of the lens, Cx43 disappeared gradually at the margins of the epithelial layer, whereas major intrinsic polypeptide, MP26, and alpha-crystallins were only detected in differentiated fiber cells. Ultrastructural studies revealed that epithelial cells and epithelial fiber cells were connected by large gap junctions. Lens fiber cells were closely apposed to apical boundaries of epithelial cells and apposed to one another along their entire lengths. In Cx43 (-/-) mice, epithelial cells were connected more loosely. The distribution of MP26 and alpha-crystallin in bow region fiber cells in Cx43 (-/-) lenses was not distinguishable from that in the lenses of wild-type mice. Cx46 and Cx50 were also expressed in superficial and cortical fiber cells, with similar distributions in Cx43 (-/-) and wild-type mice. However, organization of appositional membranes between lens fiber cells and between fiber and epithelial cells differed dramatically in the Cx43 (-/-) lens. In contrast to the close apposition of cells in lenses of normal mice, fiber cells in Cx43 (-/-) lenses were largely separated from apical surfaces of epithelial cells, and large vacuolar spaces were apparent between fiber cells, most prominently in deeper cortical regions. CONCLUSIONS: The normal differentiation of lens fiber cells in the bow region in lenses of Cx43 (-/-) mice, evidenced by similar distributions of Cx46, Cx50, MP26, and alpha-crystallin, suggests that the expression of Cx43 is not required for this process. However, these lenses exhibit grossly dilated extracellular spaces and intracellular vacuoles, indicative of early stages of cataract formation. These changes suggest that osmotic balance within the lens is markedly altered in Cx43 (-/-) animals, highlighting the importance of intercellular communication mediated by lens epithelial Cx43 gap junctions in the function of this tissue.

Animals↗
PubMed1997

The 95-kilodalton membrane glycoprotein overexpressed in novel multidrug-resistant breast cancer cells is NCA, the nonspecific cross-reacting antigen of carcinoembryonic antigen.

Human breast carcinoma MCF-7/AdrVp cells display a novel multidrug resistance phenotype that is characterized by the overexpression of a 95-kDa membrane glycoprotein (p95) and by marked reduction in intracellular anthracycline accumulation, without overexpression of P-glycoprotein or the multidrug resistance protein MRP. p95 is also highly expressed in multidrug-resistant NCI-H1688 cells derived from a human small cell lung carcinoma. Deglycoslyated p95 from NCI-H1688 cells was isolated by two-dimensional gel electrophoresis and then digested with trypsin. The tryptic peptides were analyzed by mass spectrometry and microsequencing. These analyses identified p95 to be identical to NCA-90, the nonspecific cross-reacting antigen related to the carcinoembryonic antigen (CEA). Further confirmation that p95 is indeed NCA-90 was obtained by Northern and Western blot studies using probes or antibodies specific for p95, NCA-90, or CEA family members. Western blot studies also revealed that CEA itself is overexpressed in MCF-7/AdrVp cells compared to parental MCF-7/W cells. The enforced expression of NCA-90 protein in HeLa cells stably transfected with NCA-90 cDNA did not result in increased resistance of the transfected cells to daunorubicin or a decrease in daunorubicin accumulation in the transfected cells compared to cells transfected only with the expression vector. However, a recent report by H. Kawaharata et al. (Int. J. Cancer, 72: 377-382, 1997) of diminished accumulation, retention, and cytotoxicity of doxorubicin in EJNIH3T3 cells in which enforced expression of CEA was accomplished leaves open the possibility that the overexpression of CEA, possibly in combination with that of NCA-90, could account at least in part for the drug resistant phenotype displayed by MCF-7/AdrVp cells.

3T3 Cells↗
PubMed1997

Identification of a critical phenylalanine residue in horseradish peroxidase, Phe179, by site-directed mutagenesis and 1H-NMR: implications for complex formation with aromatic donor molecules.

The functional and structural significance of Phe179 of horseradish peroxidase isoenzyme C (HRP C) has been investigated by site-directed mutagenesis. This residue is located in a structurally variable insertion between helices F and G, a motif unique to peroxidases of higher plants. Results obtained for three recombinant enzymes, with Phe179 substituted by Ala, His, or Ser, provide the first demonstration of the importance of this side chain for the binding of aromatic donor molecules. Experimental parameters for direct comparison with the wild-type enzyme were obtained by extensive solution state characterization using both optical and 1H-NMR spectroscopy. Significant chemical shift variations for resonances associated with the exposed heme edge, notably heme methyl C18H3 and heme propionate C17(1)H2, were recorded in NMR spectra of both the resting and cyanide-ligated states of the three Phe179 mutants. Furthermore, comparison of NOE connectivities in NOESY spectra of cyanide-ligated wild-type and mutant enzymes enabled the elusive assignment of the aromatic side chain in close proximity to heme methyl C18H3 to be made to Phe179. Replacement of Phe179 by Ala resulted in an 80-fold decrease in the binding affinity of the cyanide-ligated enzyme for benzhydroxamic acid, with a Kd value similar to that determined for cyanide-ligated HRP A2 (an acidic isoenzyme with valine at position 179). The binding affinity of Phe179-->Ser was similarly decreased, while that of Phe179-->His was partially restored relative to wild-type HRP C. Cyanide-ligated Phe179-->His HRP C exhibited a unique pH-dependent spectral transition associated with a pKa value of 6.5 +/- 0.2, assigned to the His179 side chain. Two closely related enzyme forms exhibiting different affinities for benzhydroxamic acid were observed at neutral pH and above, indicating that the protonation state of His179 gave rise to microheterogeneity in the aromatic donor molecule binding site.

Benzoates↗
PubMed1997

Enhanced bradykinin-stimulated phospholipase C activity in murine embryonic stem cells lacking the G-protein alphaq-subunit.

The gene coding for the G-protein alphaq subunit was interrupted by homologous recombination in murine embryonic stem cells (alphaq-null ES cells) as detected by Southern analysis and reverse-transcriptase PCR. The bradykinin (BK) B2 receptor was stably transfected into wild-type (WT) alphai-2-null and alphaq-null ES cells. The B2 receptor bound BK with high affinity and mobilized Ca2+. BK also activated phospholipase C (PLC), as determined by total inositol phosphate (IP) accumulation in a Bordetella pertussis toxin- and genistein-insensitive manner. In WT and alphai-2-null ES cells, BK increased IP levels approx. 4-fold above baseline. Most interestingly, in alphaq-null ES cells, BK increased IP accumulation approx. 9-fold above baseline. Re-expression of alphaq in alphaq-null ES cells resulted in normalization of the BK-stimulated IP accumulation (4-fold above baseline). These results suggest that the B2 receptor activates PLC through more than one member of the Gq family. Additionally, the absence of alphaq alters the kinetics of IP generation, which may reflect intrinsic characteristics of individual members of the Gq family or a decreased susceptibility to heterologous regulation in the alphaq-null ES cells, thus allowing for a more sustained generation of IP.

Animals↗