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Biomedical subjects

H Ding

Publications and source records attributed to H Ding.

At least 109 records · Page 6Linked to original sources
PubMed1998

Mechanisms of insulin-like growth factor-I-induced accelerated recovery in experimental ischemic acute renal failure.

Exogenous administration of recombinant human insulin-like growth factor I (rhIGF-I) to normal rats or humans increases renal blood flow and glomerular filtration rate (GFR). In rats with ischemic acute renal failure (iARF) the peptide accelerates the recovery of renal function and tubular integrity. These latter effects may be caused by renal hemodynamic actions of IGF-I or may result from direct actions of IGF-I on injured tubular cells. To examine this hypothesis, in vivo studies were performed in rats with iARF and in vitro experiments were conducted using a model of anoxia/reoxygenation injury in primary cultures of rat proximal tubular cells. In rats with iARF, IGF-I ameliorates the rise in serum creatinine, improves GFR, increases the rate of bromodeoxyuridine (BrdU) incorporation and the mitosis score, and reduces the number of apoptotic bodies. In acutely injured proximal tubular cells, IGF-I receptor mRNA levels decrease, but the remaining receptors are functional as indicated by ligand-induced phosphorylation of the IGF-I receptor beta-subunit. In anoxia/reoxygenation-injured cells, exogenous rhIGF-I improves ATP repletion, increases 3H-thymidine and BrdU incorporation and reduces the incidence of apoptosis as determined by the TUNEL method. We conclude that rhIGF-I accelerates the recovery of renal function in rats with iARF probably through hemodynamic effects, but in addition through direct metabolic, mitogenic and antiapoptotic actions on injured tubules.

Acute Kidney Injury↗
PubMed1998

Glutathione-related enzyme activities in human fetal adrenal, liver, and kidney.

AIM: To understand the capacity of fetal adrenal to catalyze reaction metabolites. METHODS: Subcellular fractions were prepared by differential centrifugation in fetal adrenal and liver. Glutathione (GSH)-transferase, reductase, and peroxidase were measured. RESULTS: The mean values (mumol.min-1/g protein) of GSH-transferase activities in adrenal microsome (112 +/- 34), mitochondria (62 +/- 35), and cytosol (191 +/- 89) were 373%, 270%, and 167%, respectively, higher than those in the corresponding fractions of fetal liver. Adrenal microsomal GSH-transferase was positively correlated with adrenal microsomal P-450 (r = 0.821, P < 0.01), and with adrenal microsomal aminopyrine N-demethylase (r = 0.829, P < 0.01). The GSH reductase contents (mumol.min-1/g protein) in adrenal mitochondria (24 +/- 14), and in S9 (36 +/- 15) were almost 5 times higher, compared with that in liver. Selenium-dependent GSH peroxidase was present in all the adrenal. CONCLUSION: Fetal adrenal, with greater capacities than those of liver in detoxifying reaction, may act as a drug-metabolizing organ during development.

Adrenal Glands↗
PubMed1998

[Effects of high dietary zinc on liver function, hepatic drug metabolism enzymes and membrane fluidity in mice].

Mice were fed with high zinc diet (15 g/kg) for 3 weeks. High zinc could cause liver toxicity: 1. inhibiting the activity of GOT and GPT in liver homogenate, reducing GSH and glycogen contents. 2. increasing the activity of aniline hydroxylase and inhibiting the activities of NADPH-cytochrome C reducease, benzo-phytamine-N-demethylase and glutathione S-transferase. The activities of cytochrome P450 and cytochrome b5 were not obviously changed 3. increasing microsomal membrane fluidity in the superficial layers, but not in the deep layers.

Animals↗
PubMed1998

[In situ hybrid detection of p16 mRNA in primary breast carcinoma: its clinicopathologic significance].

OBJECTIVE: To investigate the expression of p16 mRNA in primary breast carcinoma and its clinicopathological significance. METHODS: In vitro transcriptional RNA probe labeled with biotin and in situ hybridization method were used in this study to detect p16 mRNA in the paraffin embedded tissue of human primary breast carcinoma from 120 cases. RESULTS: 85 breast carcinomas showed expression of p16 mRNA with a positive rate of 70.8%. The p16 mRNA expression was not obviously correlated with patient age, tumor size, estrogen and progesterone receptor status (P > 0.05), but the positive rate of 54.4% for the lymph node metastasis group was significantly lower than 85.7% of the non-metastasis group (P < 0.001). Moreover, the positive rate of 58.3% for the poor differentiate invasive duct carcinoma was also lower than that 89.7% for the well differentiated (P < 0.05). The patients after operation were followed up. The mortality of 25% (21/85) in the p16 mRNA positive group was significantly lower than that of the negative group 57% (20/35) (P < 0.01). CONCLUSION: Abnormal expression of p16 mRNA may play an important role in the development of human breast carcinoma.

Adult↗
PubMed1998

[The relationship between laminin and laminin receptor expression to metastasis and survival of breast carcinomas].

OBJECTIVE: To investigate the relationship between laminin (LN) and LN receptor (LN-R) expression to breast carcinoma metastasis and survival. METHOD: The LSAB immunohistochemical method was used to study cytoplasm of primary breast cancer tissue from 109 cases and 37 axillary lymph nodes with metastasis. RESULTS: Immunostaining of LN was detected in 32 (29.4%) primary breast carcinoma and in 5 (13.7%) axillary nodes with metastasis. The expression of LN-R was significantly lower in primary breast carcinomas (55.0%) than in the node-positive tissues (83.8%) (P < 0.05). Among the 64 cases followed up none of the 6 patients with LN positive alone died after 3 years. Whereas, the LN-R positive (including LN-R positive alone or both LN and LN-R positive) cases had a significantly poorer prognosis when compared with the LN-R negative cases (P < 0.001). Multivariate analysis of clinical and pathological data by Cox regression method demonstrated that both LN-R expression and lymph node status were independent factors affecting the survival of breast cancer patients, but the former had a higher risk (odds ratio = 4.375) than the latter (OR = 2.810). CONCLUSION: These results suggest that LN-R expression is an important biofactor for predicting the prognosis of breast cancer.

Adult↗
PubMed1998

[Expression of p16 gene in malignant lymphoma detected by immunohistochemical and in situ hybridization techniques].

OBJECTIVE: To investigate the expression of p16 gene in non-Hodgkin's lymphoma (NHL) and its clinicopathological significance. METHODS: Paraffin embedded biopsies from 64 patients with NHL were analysed for p16 gene expression by immunohistochemical methods and in situ hybridization technique. RESULTS: Of the 64 NHL cases, 34(53.1%) were positive for p16 protein, 30(46.9%) lacked p16 protein, most of the positive signals were seen in the nuclei; 45(70.3%) were p16 mRNA positive, 19(29.7%) lost p16 mRNA and p16 mRNA was clearly observed in the cytoplasm of lymphocytes. p16 expression did not show correlation with such factors as sex, age and immunophenotype in NHL, but there was a significant difference between the pattern of expression of p16 in well differentiated lymphomas and poorly differentiated lymphomas (P < 0.05). Moreover, 42 patients were followed postoperatively for over 3 years, both p16 protein and mRNA correlated with the prognosis of these patients. CONCLUSION: There was a higher incidence of negative expression of p16 mRNA and protein in NHL, which indicates that p16 gene inactivation may play an important role in the genesis and development of some NHL. The frequency of negative expression of p16 mRNA was lower than that of p16 protein suggests that it may be due to post-transcriptional regulation or the unsteadiness of mRNA or protein expressed. The positive expression of both p16 mRNA and p16 protein may be features for favorable prognosis in patients with NHL.

Adolescent↗
PubMed1998

[Non-invasive determination of human oxygen metabolism during exercise].

Human muscle oxygenation during exercise was studied with near - infrared spectroscopy (NIRS). Ten athletes performed a 12 min aerobic cycling exercise with increasing workloads. Muscle oxygen content (OC), blood lactate (Bla) and heart rate (HR) were measured continuously throughout the test. The values measured showed a linear correlation (r = -0.962) between Bla and OC during aerobic exercise. The athletes and controls were also selected to compare the variation of OC, Bla and HR under exercise of the same workload. In addition, the muscle oxygen decrease and recovery during sprint were determined and discussed. The results demonstrated that NIRS provides an advantageous method for evaluation of oxygen supply and consumption in working muscles during exercise of varying intensity.

Evaluation Studies as Topic↗
PubMed1998

[Fate of massive retrieved human bone allografts].

OBJECTIVES: To study retrieved massive human allograft specimen after they had been in situ for four to sixty-five months, and to investigate the changes union, bone replacement and degradation of articular cartilage. METHOD: BMP gene expression in the specimen was also studied with in situ hybridization, immunohistochemical methods, and the observations were correlated with the clinical and isotope scan date. RESULT: The union between the allograft and the host was achieved by the formation of an external callus derived from the cortex of the host. New bone replacement took place slowly. Analysis of the articular cartilage revealed evidence that some chondrocytes had survived in non bearing area of the articular. The expression of BMP in the surface of the cortex and united callus was positive 4 months after implantation. But it was negative in the center of cortex after it had been implanted for over 12 months. An external callus formed from the cortex of the host. Some chondrocytes survived in non-bearing area of the articular. Neovasculature penetrated into osteoarticular. CONCLUSION: Bone absorption may be the cause of collapse of articular surface. The results suggest that large allografts in humans are osteo-conductive rather than inductive. Incomplete repair of osteon may be related to slowed replacement of massive human allograft.

Adolescent↗
PubMed1998

Growth factors and acute renal failure.

During acute renal injury, there are alterations in the expression of several growth factors and their receptors in the kidney. The increased expression of several growth factors and/or their receptors at sites of nephron injury suggests important contributions to repair. Exogenous administration of some growth factors, such as IGF-I, EGF and HGF, accelerates recovery of renal function in experimental acute renal failure (ARF). In ARF growth factors act through several mechanisms, which may include altered cell cycle regulation and mitogenesis, differentiation of recovered cells, regulation of apoptosis, improved renal hemodynamics, and others. There is evidence for interactions of growth factors with other growth factors as well as with other genes resulting in complex orchestration of biologic events contributing to recovery from ARF.

Acute Kidney Injury↗
PubMed1997

Effect of a chemical modification on the hydrated adenosine intermediate produced by adenosine deaminase and a model reaction for a potential mechanism of action of 5-aminoimidazole ribonucleotide carboxylase.

Using the hydrated adenosine intermediate (6R)-6-amino-1, 6-dihydro-6-hydroxy-9-(beta-D-ribofuranosyl)purine (2) produced by adenosine deaminase (ADA, EC 3.5.4.4) as a starting point, the active site probe and inhibitor platform 5-(formylamino)imidazole riboside (FAIRs, 4) was designed by removal of the-C6(OH)(NH2)-molecular fragment of 2 generated by the early events of the enzyme-catalyzed hydrolysis. FAIRs was synthesized directly from the sodium salt of 5-amino-1-(beta-D-ribofuranosyl)imidazole-4-carboxylic acid (CAIR) along a reaction sequence involving a tandem N-formylation/decarboxylation that may have a mechanistic connection to the Escherichia coli purE-catalyzed constitutional isomerization of N5-CAIR to CAIR. The physical and spectral properties of FAIRs were elucidated, its X-ray crystal and NMR solution structures were determined, and its interaction with ADA was investigated. Crystalline FAIRs exists solely as the Z-formamide rotamer and exhibits many of the same intramolecular hydrogen bonding events known to contribute to the association of Ado to ADA. In water and various organic solvents, however, FAIRs exists as NMR-distinct, slowly interconverting Z and E rotamers. This truncated enzymatic tetrahedral intermediate analog was determined to be a competitive inhibitor of ADA with an apparent Ki binding constant of 40 microM, a value quite close to that (33 microM) of the natural substrate's K(m). The actual species selected for binding by ADA, though, is likely the minor hydroxyimino prototropic form of Z-FAIRs possessing a far lower true Ki value. As the structural features of FAIRs appear well-suited to support its use as a template for constructing active site probes of both ADA and AIR carboxylases, a variety of carbohydrate-protected versions of FAIRs suitable for facile aglycon elaborations were synthesized. The N3-alkylation, N3-borane complexation, and C4-iodination of some of these were investigated in order to assess physicochemical properties that may assist in the elucidation of mechanisms for the AIR carboxylases. The survey of these properties taken together with a reasonable mechanism for the model CAIRs-->FAIRs synthetic transformation is interpreted to support a mechanism for the purE-catalyzed N5-CAIR-->CAIR biosynthetic one that involves a carboxylative sp3-rehybridization of the imidazole C4 atom rather than one possessing a dipole-stabilized C4 sp2 carbanionic intermediate.

Adenosine↗
PubMed1997

Endothelial-dependent mechanisms regulate leukocyte transmigration: a process involving the proteasome and disruption of the vascular endothelial-cadherin complex at endothelial cell-to-cell junctions.

Although several adhesion molecules expressed on leukocytes (beta1 and beta2 integrins, platelet endothelial cell adhesion molecule 1 [PECAM-1], and CD47) and on endothelium (intercellular adhesion molecule 1, PECAM-1) have been implicated in leukocyte transendothelial migration, less is known about the role of endothelial lateral junctions during this process. We have shown previously (Read, M.A., A.S. Neish, F.W. Luscinskas, V.J. Palambella, T. Maniatis, and T. Collins. 1995. Immunity. 2:493-506) that inhibitors of the proteasome reduce lymphocyte and neutrophil adhesion and transmigration across TNF-alpha-activated human umbilical vein endothelial cell (EC) monolayers in an in vitro flow model. The current study examined EC lateral junction proteins, principally the vascular endothelial (VE)-cadherin complex and the effects of proteasome inhibitors (MG132 and lactacystin) on lateral junctions during leukocyte adhesion, to gain a better understanding of the role of EC junctions in leukocyte transmigration. Both biochemical and indirect immunofluorescence analyses of the adherens junction zone of EC monolayers revealed that neutrophil adhesion, not transmigration, induced disruption of the VE-cadherin complex and loss of its lateral junction localization. In contrast, PECAM-1, which is located at lateral junctions and is implicated in neutrophil transmigration, was not altered. These findings identify new and interrelated endothelial-dependent mechanisms for leukocyte transmigration that involve alterations in lateral junction structure and a proteasome-dependent event(s).

Acetylcysteine↗
PubMed1997

In vivo kinetics of a redox-regulated transcriptional switch.

SoxR is a transcription activator governing a cellular response to superoxide and nitric oxide in Escherichia coli. SoxR protein is a homodimer, and each monomer has a redox-active [2Fe-2S] cluster. Oxidation and reduction of the [2Fe-2S] clusters can reversibly activate and inactivate SoxR transcriptional activity. Here, we use electron paramagnetic resonance spectroscopy to follow the redox-switching process of SoxR protein in vivo. SoxR [2Fe-2S] clusters were in the fully reduced state during normal aerobic growth, but were completely oxidized after only 2-min aerobic exposure of the cells to superoxide-generating agents such as paraquat. The oxidized SoxR [2Fe-2S] clusters were rapidly re-reduced in vivo once the oxidative stress was removed. The in vivo kinetics of SoxR [2Fe-2S] cluster oxidation and reduction exactly paralleled the increase and decrease of transcription of soxS, the target gene for SoxR. The kinetic analysis also revealed that an oxidative stress-linked decrease in soxS mRNA stability contributes to the rapid attainment of a new steady state after SoxR activation. Such a redox stress-related change in soxS mRNA stability may represent a new level of biological control.

Bacterial Proteins↗
PubMed1997

Isolated P-selectin glycoprotein ligand-1 dynamic adhesion to P- and E-selectin.

Leukocyte adhesion to vascular endothelium under flow involves an adhesion cascade consisting of multiple receptor pairs that may function in an overlapping fashion. P-selectin glycoprotein ligand-1 (PSGL-1) and L-selectin have been implicated in neutrophil adhesion to P- and E-selectin under flow conditions. To study, in isolation, the interaction of PSGL-1 with P- and E-selectin under flow, we developed an in vitro model in which various recombinant regions of extracellular PSGL-1 were coupled to 10-microm-diameter microspheres. In a parallel plate chamber with well defined flow conditions, live time video microscopy analyses revealed that microspheres coated with PSGL-1 attached and rolled on 4-h tumor necrosis factor-alpha-activated endothelial cell monolayers, which express high levels of E-selectin, and CHO monolayers stably expressing E- or P-selectin. Further studies using CHO-E and -P monolayers demonstrate that the first 19 amino acids of PSGL-1 are sufficient for attachment and rolling on both E- and P-selectin and suggest that a sialyl Lewis x-containing glycan at Threonine-16 is critical for this sequence of amino acids to mediate attachment to E- and P-selectin. The data also demonstrate that a sulfated, anionic polypeptide segment within the amino terminus of PSGL-1 is necessary for PSGL-1-mediated attachment to P- but not to E-selectin. In addition, the results suggest that PSGL-1 has more than one binding site for E-selectin: one site located within the first 19 amino acids of PSGL-1 and one or more sites located between amino acids 19 through 148.

Animals↗
PubMed1997

Cysteine-to-alanine replacements in the Escherichia coli SoxR protein and the role of the [2Fe-2S] centers in transcriptional activation.

The Escherichia coli soxRS regulon activates oxidative stress and antibiotic resistance genes in two transcriptional stages. SoxR protein becomes activated in cells exposed to excess superoxide or nitric oxide and then stimulates transcription of the soxS gene, whose product in turn activates>/=10 regulon promoters. Purified SoxR protein is a homodimer containing a pair of [2Fe-2S] centers essential for soxS transcription in vitro . The [2Fe-2S] centers are thought to be anchored by a C-terminal cluster of four cysteine residues in SoxR. Here we analyze mutant SoxR derivatives with individual cysteines replaced by alanine residues (Cys-->Ala). The mutant proteins in cell-free extracts bound the soxS promoter with wild-type affinity, but upon purification lacked Fe or detectable transcriptional activity for soxS in vitro . Electron paramagnetic resonance measurements in vivo indicated that the Cys-->Ala proteins lacked the [2Fe-2S] centers seen for wild-type SoxR. The Cys-->Ala mutant proteins failed to activate soxS expression in vivo in response to paraquat, a superoxide- generating agent. However, when expressed to approximately 5% of the cell protein, the Cys-->Ala derivatives increased basal soxS transcription 2-4-fold. Overexpression of the Cys119-->Ala mutant protein strongly interfered with soxS activation by wild-type SoxR in response to paraquat. These studies demonstrate the essential role of the [2Fe-2S] centers for SoxR activation in vivo ; the data may also indicate oxidant-independent mechanisms of transcriptional activation by SoxR.

Alanine↗
PubMed1997

CD45RA-RO+ (memory) but not CD45RA+RO- (naive) T cells roll efficiently on E- and P-selectin and vascular cell adhesion molecule-1 under flow.

This study examines the molecular mechanisms that underlie the observed preferential interactions of memory vs naive T cells with activated vascular endothelium. Many more CD4+ CD45RO+ (memory) cells adhered to 6-h TNF-alpha-activated human umbilical vein endothelium under flow than CD4+CD45RA+ (naive) cells. Adhesion studies were performed using Chinese hamster ovary (CHO) cell monolayers expressing human E- or P-selectin (CHO-E and CHO-P, respectively) or with soluble vascular cell adhesion molecule-1 (VCAM-1)-coated glass surfaces. Under flow at 1.8 dynes/cm2, RO+ T cells rolled extensively at low velocity on both CHO-P and CHO-E monolayers and VCAM-1, whereas very few RA+ T cells interacted with these surfaces. VCAM-1-dependent rolling was blocked completely by anti-very late Ag-4 (VLA-4) Abs. Purified CD4+RA+ T cells could be converted to RO+ cells by mitogen stimulation and 7-day culture in vitro, and this correlated with the acquisition of the ability to roll on E- or P-selectin, but not on VCAM-1 under flow. In summary, these data indicate that CD45RO+ cells interact with E- and P-selectins and VCAM-1 much more effectively than do CD45RA+ cells under flow conditions, and these adhesion pathways may contribute, either individually or in combination, to the preferential recruitment of memory T cells to peripheral sites of inflammation.

Animals↗
PubMed1997

Substitutions at position 146 of cytochrome b affect drastically the properties of heme bL and the Qo site of Rhodobacter capsulatus cytochrome bc1 complex.

The cytochrome (cyt) b subunit of ubihydroquinone: cytochrome c oxidoreductase (bc1 complex) contains four invariant glycine (G) residues proposed to be essential for proper packing of the high and low potential (bH and bL) hemes of the bc1 complex. One of these residues, G146 located in the transmembrane helix C of cyt b of Rhodobacter capsulatus, was substituted with A and V using site-directed mutagenesis, and the effects of these substitutions on the properties of the ubiquinone oxidation (Qo) site and heme bL of the bc1 complex were analyzed. The mutants G146A and V produced properly assembled but catalytically defective bc1 complexes that are unable to support photosynthetic growth. The steady-state ubihydroquinone: cytochrome c reductase activities of the mutant complexes were about one-tenth of that of a parental strain overproducing the wild-type enzyme. Similarly, their light-activated single turnover rates were significantly lower than those of a wild-type complex. The dark potentiometric titrations revealed no significant changes in the redox midpoint potentials (Em.7) of the high (bH) and low (bL) potential hemes of cyt b in both G146A and V mutants. However, EPR spectroscopy of the [2Fe-2S] cluster of the bc1 complex indicated that the Qo site of the mutant enzymes were unoccupied. Moreover, the gz signal of heme bL, but not that of heme bH, was modified both in G146A and V, suggesting that the geometry of its ligands has been distorted. These findings indicate that this region of cyt b must be well packed around heme bL since even a slight increase in the size of the amino acid side chain at position 146 (such as G to A) greatly perturbs the spatial conformation of heme bL, alters substrate accessibility and binding to the Qo site, and renders the bc1 complex inactive.

Alanine↗
PubMed1997

Redox signal transduction: mutations shifting [2Fe-2S] centers of the SoxR sensor-regulator to the oxidized form.

SoxR is a [2Fe-2S] transcription factor triggered by oxidative stress and activated in vitro by one-electron oxidation or assembly of the iron-sulfur centers. To distinguish which mechanism operates in cells, we studied constitutively active SoxR (SoxRc) proteins. Three SoxRc proteins contained [2Fe-2S] centers required for in vitro transcription and, like wild-type SoxR, were inactivated by chemical reduction. However, in vivo spectroscopy showed that even without oxidative stress, the three SoxRc proteins failed to accumulate with reduced [2Fe-2S] (< or = 4% compared to > or = 40% for wild type). One SoxRc protein had a redox potential 65 mV lower than wild type, consistent with its accumulation in the oxidized (activated) form in vivo. These results link in vitro and in vivo approaches showing novel redox regulation that couples an iron-sulfur oxidation state to promoter activation.

Aerobiosis↗