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Biomedical subjects

R Yu

Publications and source records attributed to R Yu.

At least 145 records · Page 8Linked to original sources
PubMed1995

Ascorbic acid transport and distribution in human B lymphocytes.

Ascorbic acid (vitamin C) transport was investigated in human B lymphocytes. The vitamin was transported by two components. The first was a high-affinity activity with an apparent Km of 7-10 microM and Vmax of 0.14 mM/h (3.11 x 10(-4) mumol x h-1 x mg protein-1). The activity was concentration and temperature dependent, saturable, and inhibited by carbonylcyanide-p-trifluoromethoxyphenylhydrazone and ouabain and generated ascorbic acid accumulation against a concentration gradient. Kinetics for the second component were indeterminate because ascorbate was not accumulated against a concentration gradient. Subcellular fractionation revealed that intracellular ascorbic acid in human B lymphocytes was > 90% localized to the cytosol and not protein bound. Kinetic parameters of high-affinity ascorbic acid transport could operate effectively with plasma concentrations normally found in humans.

Ascorbic Acid↗
PubMed1995

Visualization of the thyrotropin-releasing hormone receptor and its ligand during endocytosis and recycling.

Endocytosis and recycling of both thyrotropin-releasing hormone (TRH) and its G-protein-coupled receptor were visualized by conventional and confocal fluorescence microscopy in pituitary cells using a rhodamine-labeled TRH analog (Rhod-TRH) and indirect immunofluorescent staining of cells stably transfected with an epitope-tagged TRH receptor (TRHR). The epitope-tagged TRHR was confined to the cell surface prior to agonist treatment. Both Rhod-TRH and TRHR were also localized on the plasma membrane after agonist binding at 0 degrees C. Ligand binding at 37 degrees C resulted in rapid endocytosis, and both Rhod-TRH and the epitope-tagged TRHR appeared in cytoplasmic vesicles within 5 min. Fluorescently labeled TRH and transferrin colocalized in the same endocytotic vesicles, and internalization of Rhod-TRH and TRHR was inhibited by hypertonic medium, suggesting that endocytosis occurred by a clathrin-dependent mechanism. Internalized TRHRs returned to the membrane within 20 min after removal of TRH, and cycloheximide did not block receptor recycling. A mutant TRHR truncated at Cys335 signaled but did not internalize Rhod-TRH, confirming the importance of the carboxyl terminus of the TRHR in receptor-mediated endocytosis. Thus, the TRH-TRHR complex is endocytosed via clathrin-coated vesicles and the receptor is recycled to the plasma membrane.

Amino Acid Sequence↗
PubMed1995

Biochemical analysis of lactoferrin receptors in the Neisseriaceae: identification of a second bacterial lactoferrin receptor protein.

Bacterial transferrin receptors that have been described in the families Pasteurellaceae and Neisseriaceae are composed of two receptor proteins, transferrin binding proteins 1 and 2 (Tbp1 and Tbp2). In contrast, bacterial lactoferrin receptors have only been described for human pathogens in the family Neisseriaceae, and were believed to consist of a single protein, Lbp1, which is highly homologous to Tbp1. We describe a modified affinity isolation procedure that facilities isolation of a second lactoferrin receptor protein Lbp2 (a presumptive Tbp2 homologue) from Neisseria meningitidis, Moraxella catarrhalis and Moraxella bovis using immobilized lactoferrin. Antiserum specific for either the M. catarrhalis Tbp1+2 molecules, the M. catarrhalis Lbp1 molecule, or for a commercial preparation of human lactoferrin did not react on western blots with the same organisms' affinity purified Lbp2. In addition, the M. catarrhalis Lbp2 could be isolated in a functional form without contaminating Lbp1 or Tbp1+2. We also demonstrate that the bovine pathogen, M. bovis, produces functional transferrin and lactoferrin receptors specific for the bovine forms of these glycoproteins. A putative lbpB gene, recently speculated to reside immediately upstream of the N. meningitidis Lbp1 structural gene, lbpA, likely encodes the newly isolated Lbp2 protein from this bacterial species.

Animals↗
PubMed1995

Chronic neurosteroid treatment decreases the efficacy of benzodiazepine ligands and neurosteroids at the gamma-aminobutyric acidA receptor complex in mammalian cortical neurons.

The effect of chronic 5 alpha-pregnane-3 alpha-ol-20-one (5 alpha 3 alpha; neurosteroid) treatment was investigated on the gamma-aminobutyric acid (GABA), 5 alpha 3 alpha, and ligands that bind to the benzodiazepine (BZ) site on GABA-induced [36Cl-]influx in intact cultured mammalian cortical neurons. Chronic 5 alpha 3 alpha treatment (1 microM; 5 days) decreased the efficacy of GABA, because its Emax (maximal response) value was decreased, whereas the EC50 (potency) value was not altered. Chronic 5 alpha 3 alpha treatment also decreased the Emax value of BZ agonists like diazepam to potentiate GABA-induced [36Cl-] influx, and decreased the -Emax (maximal inhibitory response) value of inverse agonists like methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3'-carboxylate to inhibit GABA-induced [36Cl-] influx, whereas not altering their EC50/IC50 values. Furthermore, chronic 5 alpha 3 alpha treatment decreased the Emax value of 5 alpha 3 alpha to potentiate GABA-induced [36Cl-] influx, without altering its EC50 value. The decreased efficacy of GABA and 5 alpha 3 alpha were reversed by concomitant exposure of the neurons to R 5135 (3 alpha-hydroxy-16-imino-5 beta-17-androstan-11-one; a competitive GABA antagonist). Taken together, these findings suggest that chronic 5 alpha 3 alpha treatment produces decreased efficacy of GABA, ligands that bind to the BZ site, and neurosteroids at the GABAA-BZ receptor complex. The decreased efficacy is heterologous in nature and involves mediation via the GABAA receptor site.

Animals↗
PubMed1995

Chronic neurosteroid treatment produces functional heterologous uncoupling at the gamma-aminobutyric acid type A/benzodiazepine receptor complex in mammalian cortical neurons.

We have investigated the effects of chronic treatment with the neurosteroid 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha) on the gamma-aminobutyric acid (GABA)A receptor complex in cultured mammalian cortical neurons. Chronic 5 alpha 3 alpha treatment (up to 2 microM, 5 days) did not produce any changes in the morphological appearance or the cell protein content of cortical neurons. The basal binding of [3H]flunitrazepam, [3H]Ro15-1788, and [3H]Ro15-4513 was not altered after the chronic treatment. Chronic 5 alpha 3 alpha treatment did not alter the Kd or Bmax values of [3H]flunitrazepam binding to intact cortical neurons. However, chronic 5 alpha 3 alpha treatment produced uncoupling between GABA, barbiturate, and neurosteroid sites and the benzodiazepine site. The EC50 values of these ligands were not significantly altered; however, their Emax values were decreased after chronic 5 alpha 3 alpha treatment. The 5 alpha 3 alpha-induced uncoupling was time and concentration dependent. The binding of [3H]GABA and t-[35S]butylbicyclophosphorothionate was also decreased after chronic 5 alpha 3 alpha treatment. Chronic 5 alpha 3 alpha treatment decreased the Bmax of the low affinity GABAA receptor sites, without affecting the high affinity sites, and decreased the Bmax of t-butylbicyclophosphorothionate binding sites. The EC50 value for GABA-induced 36Cl- influx was not altered, whereas the Emax value was decreased after chronic 5 alpha 3 alpha treatment. Furthermore, the 5 alpha 3 alpha-induced uncoupling was reversed by concomitant exposure of the cortical neurons to 5 alpha-pregnan-3 beta-ol-20-one or R5135, suggesting an involvement of the neurosteroid and GABA recognition sites in the observed uncoupling. Taken together, these results suggest that chronic 5 alpha 3 alpha treatment produces heterologous uncoupling at the GABAA receptor complex.

Androstanes↗
PubMed1995

Effects of chronic pentobarbital treatment on the GABAA receptor complex in mammalian cortical neurons.

In this study we examined the binding characteristics of the gamma-aminobutyric acid (GABAA) receptor complex after chronic pentobarbital sodium treatment in cultured mammalian cortical neurons. Chronic pentobarbital sodium treatment (200 microM, 5 days) did not alter the basal binding of ligands like [3H]flunitrazepam, [3H]ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo [1,5 alpha][1,4]-BZ-3-carboxylate and [3H]ethyl-8-azido-5,6-dihydro- 5-methyl-6-oxo-4H-imidazo [1,5 alpha][1,4]BZ-3-carboxylate that bind to the benzodiazepine (BZ) recognition site of the GABAA receptor complex. Similarly, chronic pentobarbital sodium treatment did not alter the basal binding of [3H]GABA and t-butylbicyclophosphoro[35S]thionate. However, chronic pentobarbital sodium treatment produced uncoupling between GABA, barbiturate and neurosteroid sites with the BZ site. The efficacy (Emax) values of GABA, pentobarbital and neurosteroid, 5 alpha-pregnan-3 alpha-ol-20-one, on [3H]flunitrazepam binding were significantly decreased, whereas their potency (EC50) values were not altered after chronic pentobarbital sodium treatment. Taken together, these results suggest that chronic pentobarbital sodium treatment produces heterologous uncoupling of the GABA-BZ receptor ionophore complex.

Animals↗
PubMed1995

[Retrograde insertion of a spherical headed silicon tube through nasolacrimal duct].

PURPOSE: Chronic dacryocystitis or obstruction of nasolacrimal duct is one of the common and refractory eye diseases. The present operations have large destruction to lacrimal passage and unsatisfactory effects. The purpose of this research is to explore a simple and easy surgical method that makes small injuries and good curative effects. METHODS: Prob a self-made lumbar puncture needle (No. 7) through the lacrimal drainage system, inject fluid and put a thread into the inferior meatus. Guided by the thread, a special robe is retrogradely pulled through the nasolacrimal duct to dilate the meatus to about 3 mm. Then a silicon tube with a spherical head was inserted in the same may. RESULTS: 37 cases with chronic dacryocystitis or obstruction of nasolacrimal duct were treated by the method and followed up from 6 to 17 months. The result showed that the naso meatus was unobstructed postoperatively. The curative rate was 83.7%, which is better than that of other surgical methods. CONCLUSION: This operation is simple and painless for patients; has good curative effects and no severe complications: seldomly injures the normal lacrimal drainage system; can be done repeatedly or replaced by dacryocystorhinostomy if the procedure fails and will become the primarily elected method th treat the patients with chronic dacryocystitis and obstruction of the nasolacrimal duct.

Adult↗
PubMed1994

Evaluation of assays for the identification and quantitation of muconic acid, a benzene metabolite in human urine.

Muconic acid (MA) is a urinary metabolite of benzene and has been used as a biomarker of exposure to benzene in humans exposed to levels as low as 1 ppm. We have modified a high-pressure liquid chromatography (HPLC) based assay for urinary MA (Ducos et al., 1990) by the use of a diode array detector. This modification increases the specificity of the HPLC-based assay by identifying false positives. In addition, we have developed a gas chromatography (GC) based assay that uses a flame ionization detector (GC-FID). Both assays identified and quantified MA in human urine at concentrations greater than 40-50 ng/ml. Assay precision was within 10% relative standard deviation for MA concentrations above 90 ng/ml using the HPLC assay and above 40 ng/ml using the GC-FID assay. Quantitative accuracy of the assays was evaluated by determining MA in human urine samples using both methods and also a gas chromatography-mass spectrometry (GC-MS) procedure. Numerical correlation among the three assays was good at MA concentrations above 100 ng/ml.

Benzene↗
PubMed1994

Transferrin receptors on ruminant pathogens vary in their interaction with the C-lobe and N-lobe of ruminant transferrins.

The interaction between ruminant transferrins and receptor proteins on the surface of the ruminant pathogens Pasteurella haemolytica, Haemophilus somnus, Pasteurella multocida, Haemophilus agnii, and Moraxella bovis was evaluated by a combination of binding assays and affinity isolation procedures. Membranes isolated from P. haemolytica, P. multocida, and H. agnii were capable of binding sheep, goat, and cattle transferrins whereas binding by membranes from H. somnus and M. bovis was specific for bovine transferrin. Proteolytically derived bovine transferrin C-lobe was capable of inhibiting the interaction between bovine transferrin and both Tbp1 and Tbp2 from P. haemolytica and M. bovis but only Tbp1 from H. somnus and P. multocida. Proteolytically derived N-lobe inhibited the binding of P. multocida and H. somnus Tbp2 to bovine transferrin and the binding of bovine transferrin to the single receptor protein identified in H. agnii. The implications of these results regarding the nature of the ligand-receptor interaction and similarities of this interaction with ligand-receptor interactions in different species are discussed.

Animals↗
PubMed1994

[Experimental and clinical observation on wrinkle correction by medical cosmetic collagen injection].

Medical cosmetic collagen is a new biomaterial for soft tissue augmentation, such as wrinkle correction, It consists of highly purified human collagen. The ratio of type I and type III collagen is 44/56. The persistence of collagen in rats is more than one year. Rat cells and capillaries grew into the injections. Fibroblasts synthesized rat collagen. Capillaries established blood supply. The clinical observation on 123 cases proved the safety of this product. No adverse reactions developing from the use of the collagen were found. It was effective in correcting contour deformities of the skin. More than 90% correction results were excellent or good.

Adult↗
PubMed1994

The distribution of ascorbic acid and dehydroascorbic acid during tissue regeneration in wounded dorsal skin of guinea pigs.

The distribution of L-ascorbic acid AA and dehydroascorbic acid DHA in wounded and intact skin of guinea pig was investigated to elucidate the utilization of AA during tissue regeneration. Male guinea pigs fed an AA-free diet for 14 days were surgically injured on the dorsal skin, followed by intraperitoneal supplementation of AA (0.5, 5 and 50 mg/day/animal) for 4 days. The wounded skin, its surroundings and intact skin in each animal were removed for the determination of AA, DHA and collagen. The collagen content in wounded and intact skin increased in dose-dependent manner up to 5 mg AA/day, although neither the wounded nor the intact skin of the group supplemented with 50 mg AA had a higher content of collagen than those supplemented with 5 mg. In each group, the wounded skin had only about half the collagen of intact skin. AA content in the wounded skin of the groups supplemented with 5 and 50 mg AA were significantly lower than that in the other parts of their skin, whereas DHA content in wounded skin increased markedly. These results indicate that other factors besides collagen synthesis may enhance the oxidation of AA in the early stage of tissue regeneration.

Animals↗
PubMed1993

Immunocytochemical localization of androgen receptors in human skin using monoclonal antibodies against the androgen receptor.

Androgen receptors were localized in cryostat sections of human skin using monoclonal antibodies to the human androgen receptor. Bound antibodies were detected using biotinylated rabbit anti-rat IgG, peroxidase-conjugated streptavidin, and diaminobenzidine as chromogen. In the neonatal foreskin, antibody to androgen receptor bound to keratinocytes in the epidermis and to fibroblasts and vascular endothelial cells in the dermis. Immunohistochemical staining was stronger in nuclei than in cytoplasm. This staining was specific, because there was no significant staining when antibody to the androgen receptor was replaced with IgG from nonimmunized rats or with buffer, or when antibody to androgen receptor was incubated, prior to immunostaining, with a trp E-human androgen-receptor fusion protein used as immunogen. Incubation of androgen receptor antibody with trp E alone did not affect staining. Androgen-receptor antibody also bound to keratinocytes, fibroblasts, and endothelial cells in skin from adult men and women. Skin from the scalp, nose, lip, back, and chest gave positive staining for androgen receptor. Antibody to androgen receptor also bound to the coil and ductal cells of eccrine glands, external root sheath of hair follicles, epithelium in the hair bulb, dermal papilla cells, and sebocytes. There was no significant binding to adipocytes, collagen, or stratum corneum. These results show that androgen receptor is present in cells that are known to be targets for androgens and also in cells in which the biologic effects of androgens are yet to be characterized.

Adult↗
PubMed1993

Gamma delta T lymphocytes in oriental cutaneous leishmaniasis: occurrence and variable delta gene expression.

It has been suggested that T lymphocytes expressing gamma delta T-cell receptors could play an important role in defence against some intracellular infectious pathogens. The present study was undertaken to characterize the occurrence and variable delta gene expression of T lymphocytes expressing the gamma delta T-cell receptor in oriental cutaneous leishmaniasis. Eleven cases of oriental cutaneous leishmaniasis were investigated by immunohistological analysis using an alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique. In three cases, we observed an increased percentage of gamma delta T cells (about 20% of CD3+ cells). In these cases gamma delta T cells generally expressed the V delta 2 segment, and only rarely the V delta 1 gene product. V delta 2+ cells were predominantly localized in the dermis, and were virtually absent in the epidermal compartment. The rare gamma delta T cells observed in the epidermis were almost exclusively V delta 1+. This study demonstrates that an increase of gamma delta T cells may be found in oriental cutaneous leishmaniasis, although it is not a constant feature of the disease. The finding of a preferential expansion of the V delta 2 subset suggests that this subpopulation of gamma delta T cells might be selectively involved in the recognition of Leishmania antigens. The distinct compartmentalization of gamma delta T-cell subpopulations indicates that these subsets may recognize distinct sets of antigens.

Antigens, Protozoan↗