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Biomedical subjects

H Gong

Publications and source records attributed to H Gong.

At least 91 records · Page 5Linked to original sources
PubMed1997

Hyaluronic acid in the normal and glaucomatous optic nerve.

Eighteen normal human eye-bank eyes (age: 18-81 years), five fetal eyes (16-24 weeks), 11 primary open-angle glaucoma (POAG) eyes (age: 76-89 years), and two Schnabel's cavernous optic atrophy eyes were examined using a biotinylated-hyaluronan binding protein to study the changes in the distribution of hyaluronic acid (HA) in the fetal, adult and glaucomatous optic nerve head. The vitreous body served as a positive control. Sections treated with Streptomyces hyaluronidase were used to confirm specificity. Monoclonal antibodies to myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) were used as additional controls. In fetal optic nerve, HA was localized in blood vessels, peripapillary sclera and the pial septae in the retrolaminar nerve. No staining was associated with axons. Staining for MBP was negative. In adults, HA was found surrounding the myelin sheaths in the retrolaminar nerve; staining decreased with age. In contrast, HA staining in myelinated peripheral nerves (e.g. ciliaries) remained unchanged with age. HA also was localized to the adventitia of arteries and veins throughout the posterior segment. Compared to age-matched normal eyes, HA staining was virtually absent around myelin sheaths of the retrolaminar nerve in POAG eyes. Similar changes were not found in other HA positive structures. In Schnabel's cavernous optic atrophy. HA was present in increased amount in the atrophic area, but virtually absent in the remaining retrolaminar nerve. HA staining was invariably positive in vitreous, and Streptomyces hyaluronidase treated sections were negative. In adults, staining of MBP was associated with the myelin sheath in the retrolaminar nerve. In contrast to HA, staining of MBP was unchanged with age and in POAG. In Schnabel's atrophy, MBP staining disappeared only in the atrophic area. HA in the retrolaminar optic nerve appears to be associate with the space-filling matrix between myelin sheaths. HA is not present in the axon bundles prior to myelination of the optic nerve. HA in the retrolaminar optic nerve appears to decrease with age and is further reduced in POAG; however, corresponding changes are not found in MBP or in peripheral nerves. Perhaps, decreased amounts of HA is related to a higher susceptibility to elevated intraocular pressure or to optic nerve atrophy. In Schnabel's cavernous optic atrophy, HA is present in increased amount only in the atrophic area while MBP is markedly decreased, suggesting in situ production of HA in areas of optic nerve atrophy.

Adolescent↗
PubMed1997

The role of soluble proteins in generating aqueous outflow resistance in the bovine and human eye.

Previous research has shown that wash-out in bovine and primate eyes can be greatly reduced by perfusing with buffer containing 5-15% serum. It was suggested that protein diffusion from the iris root might raise the in vivo protein concentration in the trabecular meshwork to a level much higher than in the anterior chamber. In this study, we investigated the protein concentration in effluent from the outflow pathways in bovine and human eyes, its possible relationship to wash-out, and whether the reduction of wash-out was caused by a bulk protein effect. Bovine and human eyes were placed under silicone oil and perfused with buffer. Outflow facility was continuously determined while effluent was periodically collected from the surface of the eye, and the soluble protein concentration in the effluent was determined. Separate studies were conducted perfusing either albumin or gamma-globulin through bovine eyes. Theoretical models were developed to study the transport of protein into the perfusion fluid. In the bovine eyes, the initial protein concentration in the collected effluent was approximately 1% that of serum, much lower than the 10-15% buffer in serum required to prevent wash-out. Furthermore, the rate of change of outflow facility showed a different dependence on perfused volume than did the protein concentration. Human eyes showed a much higher level of protein in the perfusate, that decayed over a much longer time period. A statistically significant correlation existed between outflow resistance and soluble protein concentration in both bovine and human eyes. However, modelling studies suggested that this correlation might be due to flow resistance setting the flowrate which then determines the protein concentration of the effluent. Separate experiments indicated that the decreased rate of wash-out caused by perfusion of 10-15% serum in buffer was not due to either albumin or gamma-globulin alone. These results suggest that the reduction of wash-out observed in previous studies when serum proteins were perfused through bovine and monkey eyes was not due to the general level of serum proteins but may instead be due to interactions of a particular protein(s).

Animals↗
PubMed1997

Intraocular pressure and outflow facility are unchanged following acute and chronic intracameral chondroitinase ABC and hyaluronidase in monkeys.

We determined the effect of chronic and acute loss of glycosaminoglycans from the aqueous outflow pathway on intraocular pressure (IOP) and outflow facility in the subhuman primate eye. For the study of the chronic effects of the GAGases, cynomolgus monkeys received intracameral injections of hyaluronidase (Streptomyces, 5 or 50 units, n=2) or chondroitinase ABC (0.05 or 0.25 units, n=2) biweekly for 8 months (4 months for each dose). IOP was measured at 3, 7, 10 and 14 days after each injection. Outflow facility (2-level constant pressure) was determined at 2, 4, 6, and 8 months. Monkeys were killed 6 days after the last injection. The changes in the distribution of hyaluronic acid and sulfated proteoglycans in the outflow pathway were examined using substrate-specific histochemical techniques. The acute effects of these enzymes on outflow facilities (30 min or 2 hr after enzyme) were determined in another group of animals (n=4 for each time enzyme-1). IOP and outflow facility were unchanged compared to controls (heat inactivated enzyme) at any time in the chronically or acutely treated monkeys. Hyaluronic acid staining was absent in the outflow pathways of eyes treated chronically with hyaluronidase compared with control eyes, while collagen-associated sulfated proteoglycans were decreased but not completely removed by the chronic chondroitinase ABC treatment. Chronic loss of these glycosaminoglycans from the trabecular meshwork does not appear to contribute to the IOP elevation and decrease in outflow facility that accompanies open-angle glaucoma. Most importantly, no increase in outflow facility was found with acute hyaluronidase or chondroitinase treatment.

Animals↗
PubMed1997

The non-uniform distribution of albumin in human and bovine cornea.

In our previous studies, we noted a non-uniform distribution of protein tracer preferentially entering the anterior stromal lamellae of the cornea from the limbus. Given other differences reported previously between the anterior and posterior lamellae of the cornea, and the number of corneal disorders in which abnormalities are preferentially confined to either the anterior or posterior lamellae, we were prompted to examine the distribution of albumin in normal human and bovine cornea. The distribution of albumin in bovine and human cornea was studied immunohistochemically. Total soluble protein and albumin in the anterior 1/3 and posterior 2/3 of the central, middle and peripheral cornea of bovine eyes was measured biochemically. To aid in interpreting the findings, a theoretical model was developed based upon the combined effects of diffusive and convective transport. Using immunohistochemical methods, in both bovine and human eyes, intense staining of albumin was found in the anterior 1/3 of the corneal stroma. There was a gradual reduction in staining intensity from the limbus to the central cornea in the anterior corneal stroma. Less staining was found in the posterior 2/3 of corneal stroma. Additionally, a greater concentration of soluble protein and albumin was found in the anterior stroma than in the posterior stroma of the bovine eyes by biochemical analyses. The theoretical model demonstrated that this distribution of protein required a difference in excluded volume fraction between the anterior and posterior stroma and was consistent with a convective flux originating at the limbus and passing through the corneal stroma. The soluble proteins of the bovine and human cornea are preferentially concentrated in the anterior cornea and near the limbus. This distribution is likely due to differences in excluded volume fraction between the anterior and posterior stroma and a small convective flux passing through the cornea.

Albumins↗
PubMed1997

The effectiveness of once-daily dosing of inhaled flunisolide in maintaining asthma control.

OBJECTIVE: The purpose of this study was to evaluate the feasibility of switching to once-daily (qd) administration of flunisolide in patients with asthma that was controlled by twice-daily (bid) dosing of this inhaled steroid. METHODS: Three hundred sixty-six adults and children with bronchial asthma that was controlled with inhaled steroids were recruited for this prospective, double-blind, parallel-group study. After a 4-week, stable baseline period of flunisolide administration, 2 inhalations (500 microg) twice daily, each patient was randomized into one of four 12-week flunisolide treatment groups: group 1, 2 inhalations (500 microg) bid; group 2, 4 inhalations (1000 microg) qd in the morning; group 3, 4 inhalations (1000 microg) qd in the evening; or group 4, 2 inhalations (500 microg) qd in the morning. Outcome measures included morning and evening asthma symptoms (scale of 0 to 3), daytime and nighttime albuterol use, morning and evening peak expiratory flow rate (PEFR), FEV1, and methacholine PC20. In addition, a subset of patients in each group had 24-hour urinary cortisol levels measured before and after randomization. RESULTS: Outcome measures in the four groups were not significantly different at baseline before randomization. The three groups that received maintenance therapy with flunisolide, 1000 microg daily, did not show significant changes from baseline values and remained comparable in all outcome areas. Asthma control in the group randomized to flunisolide 500 microg qd, however, deteriorated significantly: morning symptoms increased by 0.21 units (48%), evening symptoms increased by 0.15 units (31%), daytime albuterol use increased by 0.42 inhalations per day (37%), nighttime albuterol use increased by 0.48 inhalations per night (91%), morning PEFR decreased by 17.1 L/min (4%), and evening PEFR decreased by 12.6 L/min (3%). There were no significant changes in PC20 or 24-hour urinary cortisol levels in any group. CONCLUSIONS: For patients with asthma that was stabilized by 2 inhalations of flunisolide (500 microg) bid, switching to 4 inhalations (1000 microg) qd in either the morning or evening is effective in maintaining asthma control. Reducing the dose to 2 inhalations (500 microg) qd in the morning, however, leads to a deterioration in asthma control.

Administration, Inhalation↗
PubMed1997

Projection of health benefits from ambient ozone reduction related to the use of methyl tertiary butyl ether (MTBE) in the reformulated gasoline program.

To estimate potential public health benefits from ozone (O3) pollution reduction attributable to the use of methyl tertiary-butyl ether (MTBE) in gasoline, O3 dose-response estimates from the biomedical literature were combined with model estimates of O3 reduction. Modeling employed EPA MOBILE5a and Complex models to predict emission changes, industry AQIRP techniques to predict ambient O3 changes, and the National Exposure Model to predict human exposures. Human health effects considered were lung function decrements and respiratory irritant symptoms (using dose-response functions measured in laboratory and field studies), and increased death rates (using concentration-response functions inferred statistically from public-health data). Other reported health effects, such as lung inflammation, increases in asthma attacks, and hospitalizations, were not addressed because of inadequate dose-response information. Even for the health responses considered, quantitation of improvements due to MTBE use is problematical, because MTBE affects only a small percentage of existing O3 pollution, and because exposure-response relationships are not well understood for population subgroups most likely to be affected. Nevertheless, it is reasonable to conclude that even small MTBE-associated reductions in peak ambient O3 levels (1-5 ppb, according to model estimates) should yield considerable public health benefits. Tens of millions of Americans are potentially exposed to O3 in the concentration range associated with health effects. Even if only a small percentage of them are susceptible, any incremental reduction in O3 (as with MTBE use) must mitigate or prevent effects for a meaningful number of people. Better quantitative estimates of benefit must await a more detailed understanding of each link in the chain of causation.

Air Pollutants↗
PubMed1997

[HBsAg autologous red cell agglutination assay].

Three lot of HBsAg autologous red cell agglutination kits (ARCA kit) have been qualified in lab, clinical trial and the stability confirmation have been performed. The sensitivity of the kits is 1ng/ml HBsAg. A, B, O, AB type of peripheral blood or antiagglutinated specimens can be used for assay. No Holk effect has been found. The repeated rate of 10 samples assayed for five times reached 100%. The specimens collected from HAV, HCV, Schistosoma Japonicum infected patients or RF positive patients do not interfere the test. The specificity of the kits is very high. 1712 clinical specimens were inspected comparing with the EIA kits in market. The relativity between the two methods is 0.985. 18 of the 26 specimens which two methods did not accord with each other have been confirmed. The false positive and missing detected for ARCA kits is 1, 3 and for EIA kits are 6, 8 respectively. ARCA kits are stable in 4 degrees C and 22 degrees C for more than one year. The kits can stand in 35 degrees C, 45 degrees C for 45 and 10 days without losing activity respectively.

Hemagglutination Tests↗
PubMed1997

[Measurement and analysis of tumor tissue autofluorescence spectra].

Measurement results of laser induced autofluorescence spectra of tumor tissue from little rat are given in this paper it is compared with normal tissue of the same body After analyzing the origin of tumor tissue autofluorescence and the difference with normal tissue spectra, it is concluded that autofluorescence spectra of tissue may reflect the features of tumor tissue and be utilized to diagnose the tumor.

Animals↗
PubMed1997

Control of lymphoproliferative and autoimmune disease in MRL-lpr/lpr mice by brequinar sodium: mechanisms of action.

Brequinar sodium (BQR) was originally developed as an antitumor drug and subsequently as an immunosuppressant for controlling transplant rejection. It has been widely accepted that the antitumor and immunosuppressive activities of BQR are dependent on its ability to inhibit the enzymatic activity of dihydroorotate dehydrogenase, the fourth enzyme in the de novo pyrimidine synthesis pathway. Recently, we discovered that BQR has the ability to inhibit protein tyrosine phosphorylation in anti-CD3-stimulated murine T lymphocytes and to inhibit the activity of src-related protein tyrosine kinases, p56lck and p59fyn. We examined the in vivo activities of BQR in MRL-lpr/lpr mice. We report that the dose of BQR (10 mg/kg/day) that induced anemia, controlled lymphadenopathy and inhibited autoantibody production, also selectively reduced the pyrimidine nucleotide levels in the bone marrow and in the lymph nodes. Coadministration of uridine (1000 mg/kg/day) with BQR completely normalized pyrimidine nucleotide levels in the bone marrow and lymph nodes, and prevented BQR-induced anemia. However, coadministration of uridine with BQR only partially reversed the anti-proliferative effects of BQR, and did not antagonize the inhibitory effect of BQR on autoantibody production. Finally, we report that BQR markedly reduced protein tyrosine phosphorylation in lymph nodes of MRL-lpr/lpr mice. These results collectively suggest that the control of lymphadenopathy and autoantibody production in MRL-lpr/lpr mice by BQR is only partially dependent on inhibition of pyrimidine nucleotide synthesis, and suggest a critical role for in vivo inhibition of protein tyrosine phosphorylation.

Animals↗
PubMed1997

Interendothelial junctions in normal human Schlemm's canal respond to changes in pressure.

PURPOSE: To determine if changes in the structure and complexity of junctions between endothelial cells lining Schlemm's canal (SC) occur in normal human eyes with changes in perfusion pressure. METHODS: Twelve normal human eyes were either perfusion-fixed (at 15 or 45 mm Hg) or immersion-fixed (0 mm Hg) in modified Karnovsky's fluid. 'Outflow facility was measured continually during the perfusion fixation. The intercellular junctions of the endothelial cells of SC were ultrastructurally examined in thin sections, including serial sections and freeze-fracture replicas. Morphometric data on the number of junctional strands per total length of tight junction were documented and categorized by the number of strands (one, two, or three or more). The length of endothelial cell overlap was measured on thin sections. RESULTS: In freeze-fracture replicas, perfusion-fixed eyes demonstrated less complex junctions. At 15 mm Hg, 18.06% of the total junctional length was represented by three or more strands; at 45 mm Hg, this percentage decreased to 8.59%. In immersion-fixed eyes, 24.17% of the total junctional length was represented by three or more strands. These differences were statistically significant (P < 0.0012). In sections, the amount of endothelial cell overlap, and thus the length of paracellular pathway, was reduced in perfusion-fixed versus immersion-fixed eyes (P < 0.02). Extensive serial sectioning demonstrated that giant vacuoles were formed, either by individual endothelial cells or by two or more adjacent endothelial cells. CONCLUSIONS: When compared with specimens fixed at zero pressure, overlap between endothelial cells of SC is reduced significantly when this cell layer is under conditions of flow similar to those encountered in vivo. The tight junctions between cells of the inner wall of SC become less complex with increasing pressure. Our data suggest that the paracellular pathway into SC in the normal eye is sensitive to modulation within a range of physiologically relevant pressures.

Aged↗
PubMed1997

Construction and application of a prokaryotic vector which expresses the protein that can be quickly purified by IMAC.

A vector was constructed by inserting a pair of complementary oligo nucleotides encoding 6 histidine residues into the polylinker's upstream of the prokaryotic high expression vector pBV220. The resultant vector is named pBV222. Proteins expressed by this vector will have a 6-histidine tail as an affinity handle fused to their N-terminus and can be quickly purified by one-step immobilized metal affinity chromatography (IMAC). This plasmid was verified by restriction mapping and DNA sequencing. When GM-CSF and IL-2 cDNA were closed into pBV222, expressed proteins in the inclusion body showed the predicted molecular weight and biological activity. The expressed bacteria were dissolved in 6 mol/L guanidine.HCl and the supernatant was loaded directly to IMAC. IL-2 and GM-CSF fusion proteins were eluted by the pH gradient, and over 90% purity was achieved.

Chromatography, Affinity↗
PubMed1996

Two activities of the immunosuppressive metabolite of leflunomide, A77 1726. Inhibition of pyrimidine nucleotide synthesis and protein tyrosine phosphorylation.

Previous studies have demonstrated that the active metabolite of leflunomide, A77 1726 [N-(4-trifluoromethylphenyl-2-cyano-3-hydroxycrotoamide)], is capable of inhibiting the activities of tyrosine kinases and dihydroorotate dehydrogenase (DHO-DHase). In the present study, we define the relative contribution of these activities to the ability of A77 1726 to inhibit proliferation of the murine leukemia cell line LSTRA. A77 1726 inhibited LSTRA cell growth and proliferation (IC50 = 10-30 microM); this inhibition, however, could be reversed by the addition of exogenous uridine, suggesting that the anti-proliferative activity of A77 1726 may be due to inhibition of de novo pyrimidine nucleotide synthesis. Quantitation of nucleotide levels revealed that A77 1726, at an IC50 of about 10 microM, selectively inhibited pyrimidine nucleotide but not purine nucleotide synthesis. In vitro enzyme assays confirmed that A77 1726 directly inhibited the activity of DHO-DHase, the fourth enzyme in the de novo pathway of pyrimidine nucleotide synthesis (IC50 = 220 nM). LSTRA cells overexpress p56lck and have elevated levels of tyrosine phosphorylated intracellular proteins. A77 1726 reduced the intracellular levels of tyrosine phosphorylated proteins with relatively high IC50 values ranging from 50 to 100 microM. A77 1726 also inhibited p56lck activity in LSTRA membrane preparation and immunoprecipitates; the IC50 values for inhibition of immunoprecipitated p56lck autophosphorylation and exogenous substrate histone 2B were 80 and 40 microM, respectively. The anti-tyrosine phosphorylation activity of A77 1726 was not affected by uridine. These studies therefore demonstrate the two activities of A77 1726: inhibition of pyrimidine nucleotide synthesis and interference with tyrosine phosphorylation.

Animals↗
PubMed1996

Uncommon causes of occupational interstitial lung diseases.

Uncommon causes of occupational interstitial lung disease, or pneumoconiosis, are being increasingly recognized and diagnosed. The fibrogenic potential of numerous types of respirable inorganic particles remains poorly understood but is significantly determined by lung deposition and clearance, the agent's size and solubility, host susceptibility, and other factors. Microanalytic techniques have improved the identification of uncommon or unusual biopersistent particles or elements in fibrotic lung tissue. Recent findings in workers exposed to manmade vitreous fibers, silicon carbide, talc, titanium, cerium, and polyvinyl chloride provide new clinical insights into not only their specific fibrogenic capabilities but also in the broader appreciation that many cases of unexplained interstitial lung disease may be caused by occupational exposures to one or more uncommon airborne substances.

Air Pollutants, Occupational↗
PubMed1996

Standardization of multiple spirometers at widely separated times and places.

We designed a system for a multiyear longitudinal study of lung function in 12 widely separated communities, intending to minimize variation in instrument-related data. We used multiple rolling-seal spirometer/personal computer systems. Calibrations were checked before, during, and after each day's field testing, using multiple calibration syringes with electronic readouts. The syringes were rotated to obtain data for each syringe-spirometer combination. Before and after each annual field testing season, a laboratory reference spirometer system was calibrated against a water-displacement device and an electronic frequency counter, and then compared against each field spirometer and syringe. Field equipment consistently met American Thoracic Society (ATS) specifications. Variance among spirometers exceeded variance among syringes. A spirometer occasionally changed its volume readout by approximately 1 to 2 %. More rarely, a syringe changed its delivered volume by approximately 1%. Syringes' electronic readouts tracked changes in delivered volume. Syringe readouts were the most stable component of the system, and were more reproducible than the laboratory water-displacement calibration. We conclude that variation in spirometers may limit the reliability of epidemiologic findings, even when these spirometers meet ATS specifications. Frequent calibration checks traceable to an independent standard, and adjustment of individual test results, can reduce measurement error.

Calibration↗
PubMed1996

Effect of inhaled salmeterol on sulfur dioxide-induced bronchoconstriction in asthmatic subjects.

UNLABELLED: This study tested the capability of a single 42-microgram dose of inhaled salmeterol xinafoate, a long-acting beta 2-agonist, to protect against bronchoconstrictive effects of exposure to 0.75 ppm sulfur dioxide (SO2) during exercise, for up to 24 h. Ten SO2-responsive adult volunteers with stable asthma were studied under 4 conditions of drug pretreatment/exposure, administered in random order, double-blind: salmeterol/SO2, placebo/SO2, salmeterol/clean air, and placebo/clean air. Each subject underwent 10-min exposure/exercise challenges in a chamber 1, 12, 18, and 24 h after pretreatment. Exercise ventilation rates averaged 29 L/min. Response was measured as the decrement in FEV1 between preexposure and postexposure (lowest value within 30 min). After salmeterol, mean decrement post-SO2 was 7% at 1 h and 12% at 12 h. At 18 and 24 h after salmeterol, and at all times after placebo, mean decrements were 25 to 30%. After 18 and 24 h, salmeterol still improved base-line FEV1 relative to placebo, although improvement was not statistically significant at 24 h. Acute symptom increases accompanied FEV1 decrements. CONCLUSION: In our asthmatic subjects, pretreatment with salmeterol imparted clinically and statistically significant (p < 0.01) protection against bronchoconstriction induced by SO2/exercise for at least 12 h, and maintained an improvement in lung function for as much as 18 h.

Administration, Inhalation↗
PubMed1996

[The usefulness of three-dimensional helical CT for the detection of abnormalities of the auditory ossicles].

To evaluate the usefulness of three-dimensional (3D) helical CT for the detection of abnormalities of the auditory ossicles, 3D helical CT of the middle ear was performed in seven patients with hearing disorder. It revealed that 4 patients had congenital deficiency of the auditory ossicles, 2 patients with chronic otitis media had shortening of the incus and one patient with head injury had doubtful fracture of the incus. This study indicated that 3D helical CT of the middle ear can represent the auditory ossicles objectively and can offer detailed diagnosis.

Adolescent↗