Search PubMed⌕ Search

Biomedical subjects

D Han

Publications and source records attributed to D Han.

At least 163 records · Page 9Linked to original sources
PubMed1995

Elucidation of antioxidant activity of dihydrolipoic acid toward hydroxyl radical using a novel hydroxyl radical generator NP-III.

The photosensitive organic hydroperoxide, NP-III, which produces hydroxyl radicals on illumination by UVA light, was used to examine the antioxidant activity of dihydrolipoic acid toward hydroxyl radical. Apolipoprotein (apo-B) of human low density lipoprotein (LDL), and bovine serum albumin (BSA), were irradiated with UVA in the presence of NP-III and dihydrolipoic acid. The oxidation of BSA and apo-B of LDL by NP-III was completely inhibited by dihydrolipoic acid. ESR studies using dimethylpyrroline oxide (DMPO) as a spin trapping reagent also revealed that in the presence of dihydrolipoic acid, the DMPO-OH adduct produced from the irradiation of NP-III and DMPO completely disappeared. Hence, the scavenging activity of dihydrolipoic acid is not due to its chelating activity toward transition metals (ferrous ions). The results lead us to conclude that dihydrolipoic acid is an efficient hydroxyl radical scavenger through the direct reaction of dihydrolipoic acid with hydroxyl radical.

Antioxidants↗
PubMed1995

[Recurrent meningitis and spontaneous cerebrospinal fluid otorrhea].

Five children with recurrent meningitis were surgically confirmed to have vestibular fistula and spontaneous cerebrospinal fluid (CSF) otorrhea. The vestibular fistulas were successfully repaired under general anaesthesia. No complications were found after follow-up for 3-8 years. The etiology of CSF otorhinorrhea, location of fistulas, diagnosis and treatment of spontaneous vestibular CSF otorrhea were discussed.

Cerebrospinal Fluid Otorrhea↗
PubMed1995

[Endoscopic sinus surgery in children].

Thirty-seven cases (67 sides) of chronic sinusitis treated with endoscopic sinus surgery (ESS) at the age of 8 to 17 years were evaluated in the paper. All the patients after ESS were followed up for a period of 2 to 24 months. Twenty-four out of 37 cases were primarily healed, 7 cases had delayed healing and 2 cases still had persistent inflammation during the period of follow-up. Among the 37 cases, 17 recovered completely and 20 recovered incompletely. The necessity, feasibility and indications of ESS in children were discussed.

Adolescent↗
PubMed1995

[Early diagnosis of acoustic neuroma].

The diagnostic findings in 31 patients (32 ears) with acoustic neuromas are reported. In patients suspicious of acoustic neuroma, case history and clinical examination are important. In our material of 31 patients with acoustic neuromas, hearing loss was presented in 94% (slow onset 87%, sudden onset 10% and fluctuating 3%), tinnitus in 91%, vestibular symptoms (dizziness or vertigo) in 62%. It should be stressed that in patients with unilateral hearing loss (or tinnitus) or vestibular symptoms, it is necessary to exclude the presence of an acoustic neuroma. In addition, the trigeminal never was affected in 34%, which was encountered in tumours larger than 26-40 mm. There was a positive correlation between duration of symptoms and size of the tumour, but there was no correlation between hearing loss and size of the tumour. Brainstem response audiometry (ABR) exhibited a very high sensitivity (100%), making it a suitable single test for screening patients suspected to have an acoustic neuroma.

Adolescent↗
PubMed1994

Alpha-lipoic acid reduction by mammalian cells to the dithiol form, and release into the culture medium.

Lipoic acid has been reported recently to be an effective antioxidant in biological systems. It may act in vivo through reduction to its dithiol form, dihydrolipoic acid. Using a dual Hg/Au electrode, and HPLC with electrochemical detection, a method was developed which allowed simultaneous measurement of lipoic acid and dihydrolipoic acid, at nanomolar levels. (RS)-alpha-Lipoic acid was added to human cells in tissue culture (Jurkat T-lymphocytes and primary neonatal diploid fibroblasts). Lipoic acid was converted rapidly by the cells to dihydrolipoic acid, which accumulated in the cell pellet. Monitored over a 2-hr interval, dihydrolipoic acid was released, and several-fold more dihydrolipoic acid could be found in the medium than in the pellet.

Chromatography, High Pressure Liquid↗
PubMed1994

Reassessment of digoxin and other low-dose positive inotropes in the treatment of chronic heart failure.

Digoxin and other low doses of drugs that have inotropic properties may have an important role to play in the therapy of patients with chronic heart failure. There is convincing evidence that digoxin is effective in relieving the signs and symptoms of heart failure due to systolic dysfunction. While earlier results with some of the other agents have been disappointing, recent data suggest that a reevaluation of these agents is necessary. There is now compelling evidence that lower doses of these agents may be clinically useful without necessarily having any significant hemodynamic effects. The recent experience with vesnarinone is especially promising in showing that therapy with these agents may improve survival in addition to improving clinical status. It is becoming recognized that hemodynamic activity should not necessarily be a prerequisite for clinical utility for those agents. The neuroendocrine and electrophysiologic effects of many of these agents, including digitalis, remain incompletely characterized and may play an important role in their therapeutic benefit. It appears that certain drugs that have inotropic properties may be effective only when their inotropic effects are not readily demonstrated. Further research into the appropriate mechanisms of action and proper dosing of these drugs may lead to a renewed interest in the use of positive inotropes for chronic heart failure.

Adrenergic beta-Agonists↗
PubMed1994

Binding of [3H]triamcinolone acetonide to glucocorticoid receptors in brain cytosol fractions of rats with intact adrenals.

Binding of [3H]triamcinolone acetonide (TA) increased with prolongation of incubation periods of up to 5 h after the onset of incubation at 2 degrees C, with a plateau thereafter persisting for at least up to 48 h in brain cytosol fractions of rats with intact adrenals. Elevation of incubation temperature to 30 degrees C resulted in a marked reduction of the binding at equilibrium which persisted for only 1 to 2 h with complete abolition thereafter. The addition of sodium molybdate was effective in doubling the maximal value at 30 degrees C without markedly affecting the binding at 2 degrees C. [3H]TA binding at equilibrium determined at 2 degrees C was a reversible, saturable and structure selective process with uneven distribution profiles in rat brain. Among a variety of steroid hormones tested, TA was the most potent displacer with progressively less potent displacement by dexamethasone, deoxycorticosterone, progesterone, prednisolone, hydrocortisone and corticosterone. Among discrete brain regions examined, the highest density was detected in the cerebellum followed by the hippocampus, cerebral cortex, midbrain, striatum, hypothalamus and medulla-pons in a rank order of decreasing density. In contrast, both the cerebellum and medulla-pons had significantly higher affinities for [3H]TA than the cerebral cortex. Moreover, the binding was markedly inhibited by Zn2+ ions at 10 microM due to a decrease in the affinity. These results suggest that [3H]TA labels a ligand recognition domain on the cytoplastic glucocorticoid receptor complex with different affinities in rat brain.

Adrenal Glands↗
PubMed1994

Discrimination by added ions of ligands at ionotropic excitatory amino acid receptors insensitive to N-methyl-D-aspartate in rat brain using membrane binding techniques.

The addition of potassium thiocyanate almost quadrupled binding of [3H]DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) to an AMPA-sensitive subclass of brain excitatory amino acid receptors in rat brain synaptic membranes, treated with Triton X-100. Among several ligands tested, quisqualic acid (QA) was the most potent displacer of [3H]AMPA binding in the absence of added SCN- ions, followed by AMPA, 6,7-dinitroquinoxaline-2,3-dione (DNQX), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), glutamic (Glu) and kainic (KA) acids in a rank order of decreasing potency. The addition of SCN- ions was effective in significantly reducing the potencies of antagonists such as DNQX and CNQX, without affecting those of agonists including QA, AMPA, Glu and KA. On the other, the addition of Ca2+ ions significantly inhibited [3H]KA binding in a concentration-dependent manner at concentrations of above 2.5 mM. Calcium ions were also effective in significantly potentiating potencies to displace [3H]KA binding of antagonists such as DNQX and CNQX, with concomitant reduction of those of agonists including KA, QA and Glu. However, N-methyl-D-aspartic acid (NMDA) did not affect binding of both radioligands at concentrations of below 0.1 mM. These results suggest that both SCN- and Ca2+ ions may be useful to discriminate agonists and antagonists among a variety of displacers of ligand binding to the non-NMDA receptors in the brain.

Animals↗
PubMed1994

How interleukin-2 can affect human fibroblasts behaviour.

The alpha and beta chains of the Interleukin 2 receptor (IL2R alpha and IL2R beta) were detected at the surface of cultured fibroblastic cells by flow cytometry, using monoclonal antibodies (mAbs) directed against the IL2R alpha and the IL2R beta. These cells bound FITC-IL2 and this binding was inhibited by an excess of cold ligand and by mAbs recognizing the IL2 binding sites of the alpha and beta chains. Internalisation studies show that the fibroblastic IL2R/IL2 complex is internalized at 37 degrees C. By Northern Blot analysis we detected the presence of specific transcripts for the IL2R alpha and IL2R beta genes. Finally, the addition of exogenous IL2 specifically modified the surface expression of different antigens involved in the process of immunosurveillance. Indeed, IL2, at concentrations affecting the high affinity IL2R, caused the down regulation of ICAM-1 protein. IL2 also decreased the surface expression of the class I and class II HLA. By contrast, the use of IL2 concentrations which saturate the intermediate affinity IL2R beta caused the up regulation of the surface expression of the ICAM-1 protein. ICAM-1 is the natural ligand for the LFA-1 integrin expressed at the surface of lymphoid cells. ICAM-1/LFA-1 interactions favour homotypic and heterotypic cell-cell adhesion. Since human fibroblasts express an LFA-1 like molecule, we propose that in these cells IL2 can modify homotypic and heterotypic interactions acting on the surface expression of ICAM-1 protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Line↗
PubMed1994

Preferential induction by stress of the N-methyl-D-aspartate recognition domain in discrete structures of rat brain.

Immobilization stress in water for 3 h was effective in inducing significant potentiation of [3H](+)-5-methyl-10,11-dihydro-5H- dibenzo [a,d] cyclohepten-5,10-imine ([3H]MK-801) binding 5 days after the stressful manipulation in rat hypothalamus and cerebellum when determined before equilibrium in the absence of any added agonists, in addition to resulting in marked reduction of rearing behaviors of animals. However, the stressful manipulation failed to modulate the [3H]MK-801 binding in other central regions examined, and binding of either [3H]DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid or [3H]kainic acid was not significantly affected in all brain structures studied 5 days after the stress application. In contrast, the stressful procedures potentiated binding of both L-[3H]glutamic ([3H]Glu) and [3H]DL-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic ([3H]CGP-39653) acids in the hypothalamus and cerebellum 5 days later, without affecting binding of [3H]-glycine and 5,7-dichloro[3H]kynurenic acid. The systemic administration of corticosterone mimicked the stress manipulation at doses of 5-50 mg/kg in terms of inducing significant enhancement of binding of both [3H]Glu and [3H]CGP-39653 in the hypothalamus and cerebellum when determined 5 days after the single administration. The translation inhibitor cycloheximide was effective in preventing the stress-induced potentiation of [3H]Glu binding in the cerebellum, without altering that in the hypothalamus. Furthermore, the stressful handling significantly increased the densities of [3H]Glu binding sites in the hypothalamus and cerebellum, with the affinities being unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1994

IL-2 production by myofibroblasts from post-radiation fibrosis in breast cancer patients.

The origin of cell activation in post-radiation fibrosis and its chronic extension are still poorly understood. Since local IL-2 cancer treatment sometimes triggers intraperitoneal fibrosis we have analyzed three myofibroblastic cell strains from post-radiation skin fibrosis (FPR7, FPR10 and FPR15) for their interactions with IL-2. In these cells we have observed the surface expression of the two chains of the IL-2R (IL-2R alpha beta), the presence of the 0.9 kb transcript specific for the IL-2 gene and, by flow cytometry with anti-IL-2 mAbs, the presence of IL-2 immunoreactive material inside the cells up to 8 days after subculture. The FPR cell lines secreted IL-2, as determined by ELISA. The secreted IL-2 is biologically active since it sustains the proliferation of the IL-2-dependent murine lymphoid cell line CTLL2 and preincubation with anti-IL-2 blocking mAbs completely abolishes this activity. Overnight incubation of FPR cells with polyclonal anti-IL-2 antibodies leads to a decreased expression of the membrane adhesion molecules ICAM-1 and CD44, suggesting the existence of an autocrine/paracrine loop involved in the surface expression of these antigens. By contrast, in normal adult skin fibroblasts we did not detect IL-2 gene activation. In vivo, IL-2 secretion by post-radiation fibrosis fibroblasts and the subsequent up-regulation of ICAM-1 and CD44 may represent key events during the process that leads to radiation fibrosis.

Breast Neoplasms↗
PubMed1994

Enzymic and non-enzymic antioxidants in epidermis and dermis of human skin.

We measured enzymic and non-enzymic antioxidants in human epidermis and dermis from six healthy volunteers undergoing surgical procedures. Epidermis was separated from dermis by curettage and antioxidants were measured by high-performance liquid chromatography (HPLC) or standard spectrophotometric methods. The concentration of every antioxidant (referenced to skin wet weight) was higher in the epidermis than in the dermis. Among the enzymic antioxidants, the activities of superoxide dismutase, glutathione peroxidase, and glutathione reductase were higher in the epidermis compared to the dermis by 126, 61 and 215%, respectively. Catalase activity in particular was much higher (720%) in the epidermis. Glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, which provide reduced nicotinamide adenine dinucleotide phosphate (NADPH), also showed higher activity in the epidermis than the dermis by 111% and 313%, respectively. Among the lipophilic antioxidants, the concentration of alpha-tocopherol was higher in the epidermis than the dermis by 90%. The concentration of ubiquinol 10 was especially higher in the epidermis, by 900%. Among the hydrophilic antioxidants, concentrations of ascorbic acid and uric acid were also higher in the epidermis than in the dermis by 425 and 488%, respectively. Reduced glutathione and total glutathione were higher in the epidermis than in the dermis by 513 and 471%. Thus the antioxidant capacity of the human epidermis is far greater than that of dermis. As the epidermis composes the outermost 10% of the skin and acts as the initial barrier to oxidant assault, it is perhaps not surprising that it has higher levels of antioxidants.

Aged↗
PubMed1994

Dose-response effects of acute ultraviolet irradiation on antioxidants and molecular markers of oxidation in murine epidermis and dermis.

There has not as yet been an integrated, comprehensive study of the responses of dermis and epidermis in vivo to a wide range of ultraviolet (UV) doses, encompassing all major antioxidants and a sensitive marker of oxidative damage. We have irradiated hairless mice with simulated solar light at doses of 2, 5, 12.5, and 25 J/cm2 combined UVA and UVB (0.8 to 10 MED) and measured enzymic and non-enzymic antioxidants as well as lipid hydroperoxides in both epidermis and dermis to elucidate the response of cutaneous antioxidant defense mechanisms to UV stress. Among the nonenzymic antioxidants two different dose-response patterns were seen. Ascorbate was rapidly depleted at doses between 0 and 5 J/cm2 but was less affected between 5 and 25 J/cm2. In contrast, glutathione, ubiquinol/one, and alpha-tocopherol levels remained approximately equal to control levels between 0 and 5 J/cm2, then decreased to varying degrees from 5 to 25 J/cm2; ubiquinol was almost completely depleted, whereas alpha-tocopherol dropped only 30%. The concentration of lipid hydroperoxides increased throughout the dose range. These results may be explained partly by direct destruction of some antioxidants by UV light, partly by the separate antioxidant functions of the compounds, and partly by recycling of some antioxidants (e.g., alpha-tocopherol) at the expense of others (e.g., ubiquinol). Even at the lowest dose (0.8 MED) lipid hydroperoxide formation was observed. Among the enzymic antioxidants, superoxide dismutase activity decreased significantly (to 63.6% of initial activity for epidermis and 51.5% for dermis at 25 J), whereas activities of glutathione peroxidase and glutathione reductase decreased slightly. Catalase activity decreased dramatically at doses above 5 J (to 11.8% of initial activity in epidermis and 27.7% in dermis at 25 J). The dramatic loss of catalase is almost entirely accounted for by direct destruction by the simulated solar light, but superoxide dismutase was unaffected by direct exposure; hence its destruction must be due to indirect effects, either mediated by free radicals or other harmful species formed upon irradiation. At low doses of UV light many components of the cutaneous antioxidant system were damaged, whereas at high doses all components were damaged and some were almost completely destroyed.

Animals↗
PubMed1994

Characterization of effector cells against B16 melanoma in mice inoculated with allogeneic spleen cells.

Inbred C57BL/6 (B6) mice which had received an inoculation of allogeneic spleen cells showed remarkable antitumor activity against syngeneic tumor challenge with B16 melanoma cells 3 days after the allogeneic cell inoculation. This antitumor activity was not specific to the inoculated alloantigen, since the challenging B16 cells are syngeneic to B6 mice and since it was induced by BALB/c spleen cells as well as C3H/He spleen cells. The antitumor activity was sensitive to an in vivo treatment with anti-asialo GM1 (AGM1) antiserum or anti-Thy.1 monoclonal antibody (mAb) just before the tumor challenge and was resistant to an in vivo treatment with anti-CD8 (Ly.2) mAb. These results suggest that AGM1+Thy.1+CD8- activated natural killer (NK) cells were generated by alloantigen inoculation and took an important part in the antitumor effect of the alloantigen inoculation.

Animals↗
PubMed1994

[Nasal endoscopic middle meatal antrostomy].

Middle meatal antrostomy under nasal endoscope, a functional procedure which conforms to paranasal sinus physiology, has provided a new approach to reestablishing the ventilation and drainage of nasal cavity and paranasal sinus. A 3-15 month's follow-up of 75 patients with chronic sinusitis and polyps who had undergone endoscopic sinus surgery shows a higher patency rate of 86.7% and a lower closure rate of 13.3%. While for patients who received inferior meatal antrostomy the patency rate was 54.7% and the closure rate 45.3%. There was a significant difference (P < 0.01) between the two groups in patency rate and closure rate respectively. So the antrostomy of middle meatus appears to be better than that of inferior meatus. The clinical significance of middle meatal antrostomy on the basis of anatomy and physiology of paranasal sinus is emphasized in discussion.

Adolescent↗
PubMed1994

Recovery of antioxidants and reduction in lipid hydroperoxides in murine epidermis and dermis after acute ultraviolet radiation exposure.

In previous studies we have found that a single acute dose of ultraviolet radiation to murine skin causes a large degree of destruction of enzymic and non-enzymic antioxidants immediately after irradiation. In the present study, we wished to elucidate the recovery of antioxidants after a single dose of ultraviolet (UV) radiation. We measured antioxidants and lipid hydroperoxides (as a marker of membrane damage) in murine epidermis and the dermis at 0, 3, 12, 24, 72 and 120 h after exposure to UV radiation (25 J/cm2, UVA+UVB). Lipid hydroperoxides showed the highest values immediately after UV exposure and returned to control values within 24 h in both epidermis and dermis. The activities of catalase, glutathione peroxidase and glutathione reductase showed the lowest activities immediately after UV exposure; superoxide dismutase activities reached a minimum at 3 h postexposure. The pattern of recovery was different for each enzyme and for epidermis and dermis. The activities of superoxide dismutase and catalase decreased remarkably and recovered slowly. Superoxide dismutase in the dermis recovered full activity by 120 h and in the epidermis by 12 h. Catalase activity in both epidermis and dermis had returned to only 50% of control activity at 120 h, although the epidermis showed a temporary increase (to 93%) at 24 h. Glutathione peroxidase and glutathione reductase were slightly decreased immediately after irradiation, recovered to 100% at 3 h and then increased to 200-250% in both the epidermis and the dermis at various times; values had returned to 100% in epidermis by 120 h but remained elevated in dermis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Vitamin E recycling in human erythrocyte membranes.

Vitamin E, the major lipid chain-breaking antioxidant in erythrocyte membranes, is present in low concentration, suggesting that mechanisms should exist to protect against its loss. Enzymatic pathways for the recycling of vitamin E from its tocopheroxyl radical have been observed previously in inner membranes of mitochondria and microsomes. These pathways use electron transport enzymes and their substrates to regenerate vitamin E. Erythrocyte membranes also contain significant NADH-cytochrome c reductase activity, as well as cytochrome b5, the function of which is not yet known. Using an enzymatic oxidation system composed of lipoxygenase and arachidonic acid, free radicals were produced in human erythrocyte membranes, and their reaction with chromanols was followed by ESR and high performance liquid chromatography (HPLC). Since the endogenous vitamin E content of the membranes is very low, we used a vitamin E homologue lacking the hydrocarbon chain (2,2,5,7,8-pentamethyl-6-hydroxychromane) as a probe molecule for ESR measurements. However, parallel HPLC determinations of lipid hydroperoxides and of endogenous vitamin E confirmed the results obtained by ESR. It was found that protection against the loss of vitamin E can be provided either by NADH-cytochrome b5-dependent enzymatic recycling or by a nonenzymatic pathway involving ascorbate and dihydrolipoic acid.

Arachidonic Acid↗