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Biomedical subjects

L Ma

Publications and source records attributed to L Ma.

At least 451 records · Page 25Linked to original sources
PubMed1996

[Treatment of neovascular glaucoma by anterior retinal cryotherapy and trabeculectomy].

OBJECTIVE: To investigate the efficacy of anterior retinal cryotherapy (ARC) for treatment of neovascular glaucoma (NVG). METHODS: 12 eyes (11 patients) with open angle NVG were treated by ARC only, 22 eyes (22 patients) with closed angle NVG were treated by ARC combined with trabeculectomy, and 32 eyes (31 patients) with closed angle NVG were treated by either ARC or cyclocryotherapy as controls. The follow-up period were 6-26 months. RESULTS: Iris new vessels (INV) regressed or disappeared with normal intraocular pressure (IOP) in 92% (11/12) of the eyes with open angle NVG treated simply by ARC. In comparison with closed angle NVG treated by the same method, there was a significant difference in IOP (P < 0.05). The combination of ARC and trabeculectomy showed markedly better results than either ARC or cyclocryotherapy for treatment of closed angle NVG (P < 0.01). In the eyes with closed angle NVG, INV regressed or disappeared with normal IOP in 86% (19/22), 90% (18/20) achieved a marked relief from pain and the visual acuity was better or unchanged in 67% (8/12) that was significantly different from the eyes treated by cyclocryotherapy (P < 0.05). CONCLUSION: The results indicate that ARC is suitable for treatment of NVG at early stage, and ARC combined with trabeculectomy, at later stage.

Adult↗
PubMed1996

[Extraction technology of effervescent granules for arresting cold pain optimized by orthogonal tests].

In the extraction technology of Effervescent Granules for Arresting Cold Pain (Hantongding Paoteng Chongji), the drug combinative modes, solvent pH and drug granularity were optimized by orthogonal tests, with the total alkaloid, paeoniflorin and glycyrrhetinic acid as indexes. The experimental results show that it is better to decoct together all the recipe ingredients, with water of pH2 for the first decoction, then water of pH8 for the second decoction, and to make its granularities ranging from the original herbal pieces to particles which can pass through a No. 2 sieve.

Alkaloids↗
PubMed1996

MR evaluation of the brain in central diabetes insipidus.

OBJECTIVE: To evaluate the role of magnetic resonance (MR) imaging in determining the cause of central diabetes insipidus (CDI) by using MR imaging to describe the findings in the hypothalamic-pituitary area in patients with CDI. METHODS: Thirty-one cases of clinically proved CDI were prospectively studied. A control study was also conducted in 200 normal subjects. MR imaging was performed on a 1.0 T superconductive unit with T1-weighted images obtained in the sagittal, coronal and axial planes. RESULTS: Hypothalamic-pituitary masses or structural changes were identified in 26 cases and normal structures in 5. The normal high signal intensity of the posterior pituitary lobe was absent in 29 cases, but remained unchanged in 2. In the control group, the frequency of the high signal of the posterior lobe was 93%. CONCLUSIONS: The absence of the normal high signal in the posterior pituitary lobe is closely related to the loss of hypothalamic-pituitary function. MR imaging is very sensitive in demonstrating the changes in this area in CDI and it can provide an accurate diagnosis when combined with the clinical information.

Adolescent↗
PubMed1996

[Regulative effects of cytokines on the expression of cell adhesion molecules on human mesangial cells].

OBJECTIVE: To study the regulative effects of rhIL-1 beta or rhTNF-alpha on the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on human mesangial cells (HMC). METHODS: At the 4th, 8th, 16th and 32nd hours after stimulation by rhIL-1 beta (25 ng/ml) or rhTNF alpha (100 ng/ml), the mRNA expression of ICAM-1 and VCAM-1 on HMC was determined with Northern blot, and their protein expression was also tested with cell ELISA analysis. RESULTS: mRNA and protein of both ICAM-1 and VCAM-1 were only basically expressed on HMC at very low levels in the control groups without stimulation. After stimulation by rhIL-1 beta or rhTNF alpha, however, their expression was markedly upregulated. The maximal mRNA expression level of ICAM-1 stimulated by rhTNF alpha was present at the 8th hour, but in the remaining groups the maximal mRNA expression levels of ICAM-1 or VCAM-1 were all present at the 4th hour. Compared with control groups, ICAM-1 protein expression was significantly increased from the 4th hour after rhIL-1 beta stimulation (P < 0.05), but in the remaining groups ICAM-1 or VCAM-1 protein expression was significantly raised from the 8th hour after stimulation (P < 0.001). CONCLUSION: These results suggest that upregulated expression of ICAM-1 and VCAM-1 by inflammatory cytokines IL-1 beta and TNF alpha may play a pathogenic role in glomerulonephritis.

Cells, Cultured↗
PubMed1996

[Alveolar reconstruction in patients with cleft palate].

Repair of the alveolar cleft is one important procedure in team approach of cleft palate. The present paper reports 110 cases repaired by bone grafting. Indications, technique, results evaluation and management before and after operation are discussed. The study proves that bone grafting is effective to repair alveolar cleft and should be popularised. Properly forming the bed of bone grafting and perfectly closing the receipt site are the keys of success. Patients should be treated orthodontically before and after operation. In selection of donor site, the patient's age, tooth age, width of cleft and quantity of bone to be grafted should be considered.

Adolescent↗
PubMed1996

[Studies on sapogenins of Aesculus wilsonii Rehd].

Three sapogenins were isolated from the hydrolysate of the saponin mixture extracted from the seeds of Aesculus wilsonii. They were identified as 21-angeloyl-protoaescigenin., aescigenin and protoaescigenin by physicochemical propertise and spectroscopic analysis.

Drugs, Chinese Herbal↗
PubMed1996

[Determination of five isoflavones in Belamcanda Chinensis by RP-HPLC].

A reversed phase high performance liquid chromatographic method for the quantitative determination of the five isoflavones (tectoridin, iridin, tectorigenin, irigenin and irisflorentin) in the rhizome of Belamcanda and Iris was developed. The column was packed with TSK gel ODS 80 TS (150 mm x 4.6 mm). Methanol-water (36%-60%) was used as mobile phase. The method was rapid, sensitive, precise and has good reproducibility. The five isoflavones in the crude drugs were completely separated within 40 min. Recoveries of the five constituents were 98.41%-101.93%. The crude drugs were analysed as follows: The powdered sample was refluxed with methanol for 6 hours. The extract was transferred into a 2 ml volumetric flask and diluted to mark with methanol. A definite amount of this sample solution was injected into RP-HPLC. The contents of the five constituents in the rhizomes of Belamcanda and Iris were calculated from the relevant peak heights or peak areas. The analytical results of determination for various species and habitats are shown in Tab 2-5.

Chromatography, High Pressure Liquid↗
PubMed1995

Aspartate 698 within a novel cation binding motif in alpha 4 integrin is required for cell adhesion.

The interactions of alpha 4 beta 1 integrin with vascular cell adhesion molecule (VCAM) and fibronectin play important roles in many physiological and pathological processes. To understand the mechanism of alpha 4 beta 1 integrin-mediated cell adhesion, we made mutant alpha 4 constructs. Three aspartic acid (Asp) residues in alpha 4, Asp-489, Asp-698, and Asp-811, were replaced with glutamic acids (Glu). The wild-type and mutant alpha 4 constructs were transfected into K562 cells, and stable transfectants with similar levels of alpha 4 surface expression were established. The Asp-->Glu substitutions did not affect alpha 4 beta 1 association or heterodimer formation as demonstrated by immunoprecipitation analysis. However, the glutamate substitutions at Asp-489 and Asp-698 severely impaired cell adhesion to VCAM and fibronectin, whereas the substitution at Asp-811 had no detectable effect on cell adhesion. In contrast to these results, isolated alpha 4 beta 1, containing the D489E or D698E substitution, was able to bind to VCAM, suggesting that these two residues are not critical for ligand recognition. In searching for a mechanism to explain inhibition of adhesion by Asp-489 and Asp-698 mutations, we found that the sequences flanking Asp-698 resemble the DxxxxxD-S-Sx divalent cation/ligand binding motif in beta integrins and the I-domains of alpha integrins. This suggests that Asp-698 in the alpha 4 integrin, which does not possess an I-domain, may also be involved in cation binding and may be part of a sequence functionally similar to that found in the I-domains of other alpha integrins.

Amino Acid Sequence↗
PubMed1995

The P-selectin glycoprotein ligand functions as a common human leukocyte ligand for P- and E-selectins.

P- and E-selectins belong to a family of Ca(2+)-dependent lectins and function as receptors for myeloid leukocytes. We have described a panel of monoclonal antibodies which recognize a sialoglycoprotein from human neutrophils and HL-60 promyelocytic cells and inhibit adhesion of these cells to P-selectin. In this study, we show that the E-selectin receptor-globulin (E-selectin Rg) affinity chromatography can isolate specifically only one glycoprotein from [3H]glucosamine-labeled HL-60 cells in a Ca(2+)-dependent manner. This protein has a molecular mass of approximately 120 kDa under reducing conditions, which appears to be identical with the previously characterized glycoprotein ligand for P-selectin. The molecule can be cross-depleted by and cross-bound to the E- and P-selectin columns. The chromatographic profile of desialylated O-linked carbohydrates from molecules purified by P- and E-selectin affinity chromatography are identical. Both have five structures at 12.8, 9.8, 6.3, 3.5, and 2.5 glucose units. PL5 monoclonal antibody to the P-selectin sialoglycoprotein ligand, E-selectin Rg, and antiserum to P-selectin glycoprotein ligand-1 (PSGL-1) all recognize the purified P-selectin ligand on ligand blots and immunoblots. Furthermore, PL5 monoclonal antibody blocks adhesion of HL-60 cells and human neutrophils to E-selectin Rg. Taken together, our results demonstrate that the P- and E-selectin ligand defined in this study is PSGL-1 and suggest that this molecule is an important leukocyte ligand for both P- and E-selectins.

Amino Acid Sequence↗
PubMed1995

Direct evidence of involvement of glycosylphosphatidylinositol-anchored proteins in the heavy metal-mediated signal delivery into T lymphocytes.

The biological significance of the action of glycosylphosphatidylinositol (GPI)-anchored proteins in cell physiology and pathology when stimulated with their natural agonists is not known. Here we provide evidence that GPI-anchored proteins play a crucial role in the recently defined heavy metal (HgCl2)-triggered signal delivery to T lymphocytes. Thiol-reactive HgCl2, a multi-potent crosslinker of cell membrane proteins, induced heavy aggregation of Thy-1, a representative GPI-anchored protein, on murine thymocytes, and delivered a signal to induce heavy tyrosine phosphorylation of cellular proteins. This rather unusual signal delivery by HgCl2 is diminished by the pre-treatment of cells with phosphatidylinositol-specific phospholipase C, which partially cleaved GPI-anchored proteins from the cell surface. Direct evidence for the involvement of GPI or GPI-anchored proteins in the HgCl2-mediated signaling is provided by the loss of signaling in a mutant thymoma cell line defective in the phosphatidylinositol glycan-class A gene (PIG-A), and its restoration in a transfectant with PIG-A.

Animals↗
PubMed1995

Phosphorylation of the multidrug resistance associated protein gene encoded protein P190.

Recent studies suggest that multidrug resistance of HL60/ADR cells is related to an overexpression of the MRP (multidrug resistance associated protein) gene which encodes a 190-kDa ATP-binding membrane glycoprotein. In the present study we have further characterized P190 and have examined phosphorylation properties of the protein. The results demonstrate that P190 is highly phosphorylated and that the phosphate groups are metabolically active and undergo cycles of phosphorylation and dephosphorylation in the cell. Serine is the single amino acid phosphorylated in P190 and the phosphate groups are contained in nine tryptic peptides. Experiments have also been conducted to analyze the effect of various protein kinase inhibitors on phosphorylation levels of P190. The results show that H-7, staurosporine, and chelerythrine can reduce the phosphorylation of this protein. In the presence of both H-7 (200 microM) and staurosporine (200 nM) the phosphorylation of P190 is completely blocked. It has also been found that in the presence of these agents there is a major increase in drug accumulation and concomitant inhibition in drug efflux of resistant cells. These results therefore suggest the possibility that certain phosphate groups of protein P190 play an important role in modulating drug accumulation in resistant cells.

ATP-Binding Cassette Transporters↗
PubMed1995

Cloning and sequence analysis of the human mitochondrial translational initiation factor 2 cDNA.

Complete cDNAs encoding human mitochondrial translational initiation factor 2 (IF-2mt) have been obtained from liver, heart, and fetal brain cDNA libraries. These cDNAs have a long open reading frame 2181 residues in length encoding a protein of 727 amino acids. Overall, human IF-2mt has 30-40% identity to the corresponding prokaryotic factors. Surprisingly, it is no more homologous to yeast IF-2mt than to the IF-2s from bacterial sources. The greatest region of conservation lies in the G-domain of this factor with less conservation in the COOH-terminal half of the protein and very little homology near the amino terminus. The 5'-untranslated leaders of the liver and heart cDNAs contain a number of short open reading frames. These sequences may play a role in the translational activity of the IF-2mt mRNA. Northern analysis indicates that the IF-2mt gene is expressed in all tissues but that the level of expression varies over a wide range.

Amino Acid Sequence↗
PubMed1995

Ricin disturbs calcium homeostasis in the rabbit heart.

Ricin, a toxic lectin from the castor bean, affects the cardiovascular system. Because calcium is very important in cardiotoxicity and cell intoxication, we studied the effects of ricin pretreatment to rabbits on basal intracellular calcium levels and calcium uptake and release from isolated papillary muscle, microsomes, and mitochondria. An increase in basal intracellular calcium levels was observed. Ricin pretreatment nearly doubled the intracellular-free Ca2+ concentration as measured by fura-2 fluorescence microscopy in isolated myocytes (p = 0.002). Ricin did not alter basal calcium efflux in isolated papillary muscles. However, ricin inhibited the NE-induced calcium efflux (expressed as fractional efflux ratios) in papillary muscles from rabbits receiving the minimum lethal dose of ricin at 25-35 minutes (p = 0.002 and 0.003, respectively). Ricin depressed basal calcium uptake into isolated papillary muscles at 5 minutes (mean +/- SEM, mumol/g wet weight) (control: 3.68 +/- 0.57; ricin: 2.31 +/- 0.28, p = 0.045, n = 6). Ricin pretreatment significantly depressed calcium uptake into microsomes (mean +/- SEM, mumol/g protein) (control: 9.9 +/- 1.9; ricin: 3.1 +/- 1.9, p = 0.025, n = 6). Calcium uptake into mitochondria was increased at the beginning (2 minutes, p = 0.048), but not thereafter. Thus, administration of ricin disturbed calcium homeostasis in the rabbit heart, which may be at least partially responsible for altering cardiac function and myocardial cell death.

Animals↗
PubMed1995

Multiphasic modulation of signal transduction into T lymphocytes by monoiodoacetic acid as a sulfhydryl reagent.

Actions of monoiodoacetic acid (MIA) as a sulfhydryl reagent on the different stages of the T cell receptor (TCR)-mediated signal transduction were examined. MIA (1 mM) prevented anti-TCR (CD3) monoclonal antibody (mAb)-induced energy-dependent receptor capping but at the same time promoted the anti-CD3 mAb/mitogen-induced tyrosine phosphorylation of the T cell activation-linked cellular proteins of 120, 80, 70, 56, and 40 kDa. Relatively low concentration (0.01 mM) of MIA further promoted anti-CD3 mAb-induced transcription of c-fos, production of IL-2, and cell surface expression of IL-2 receptors. The MIA-promoted TCR-mediated IL-2 production actually required signal transduction that could be inhibited by cyclosporin A, genistein, or H-7. In contrast, the same concentration of MIA as promoted the signal transduction for cell activation severely inhibited the anti-CD3 mAb-triggered signal delivery for cell proliferation, selectively at its early stage. We conclude from these results that MIA differentially affects various steps of signaling into T lymphocytes, suggesting that there exist multiple sites of MIA-sensitive or redox-linked control in the signal cascade.

Animals↗
PubMed1995

Escherichia coli alkaline phosphatase: X-ray structural studies of a mutant enzyme (His-412-->Asn) at one of the catalytically important zinc binding sites.

The X-ray structure of a mutant version of Escherichia coli alkaline phosphatase (H412N) in which His-412 was replaced by Asn has been determined at both low (-Zn) and high (+Zn) concentrations of zinc. In the wild-type structure, His-412 is a direct ligand to one of the two catalytically critical zinc atoms (Zn1) in the active site. Characterization of the H412N enzyme in solution revealed that the mutant enzyme required high concentrations of zinc for maximal activity and for high substrate and phosphate affinity (Ma L, Kantrowitz ER, 1994, J Biol Chem 269:31614-31619). The H412N enzyme was also inhibited by Tris, in contrast to the wild-type enzyme, which is activated more than twofold by 1 M Tris. To understand these kinetic properties at the molecular level, the structure of the H412N (+Zn) enzyme was refined to an R-factor of 0.174 at 2.2 A resolution, and the structure of the H412N(-Zn) enzyme was refined to an R-factor of 0.166 at a resolution of 2.6 A. Both indicated that the Asn residue substituted for His-412 did not coordinate well to Zn1. In the H412N(-Zn) structure, the Zn1 site had very low occupancy and the phosphate was shifted by 1.8 A from its position in the wild-type structure. The Mg binding site was also affected by the substitution of Asn for His-412. Both structures of the H412N enzyme also revealed a surface-accessible cavity near the Zn1 site that may serve as a binding site for Tris.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗