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Biomedical subjects

B Han

Publications and source records attributed to B Han.

At least 91 records · Page 5Linked to original sources
PubMed1999

Age- and growth hormone-induced alterations in renal sulfate transport.

The effects of growth hormone (GH) treatment on renal sodium sulfate cotransport (NaSi-1) were studied in adult (9-10 months) and old (22-23 months) male Fischer 344 rats. All animals received twice-daily s.c. injections of recombinant human GH (hGH; 4 mg/kg) for up to 6 days. Animals were sacrificed by exsanguination on days 0, 1, 2, 3, 4, 5, and 6. Kidneys were removed, and kidney cortex was trimmed immediately and used for RNA and membrane preparations. Plasma hGH concentrations were significantly lower in old rats during the hGH treatment (P <.05). Insulin-like growth factor-I (IGF-I) levels were significantly increased and remained stable after day 2 of hGH treatment in both age groups (P <.05). There was no significant difference in plasma IGF-I levels between age groups. Plasma IGF-I binding protein 3 (IGFBP-3) concentrations were significantly higher in 9- to 10-month-old rats compared with that in 22- to 23-month-old animals (P <.001). There were no significant differences in plasma IGFBP-3 concentrations between days of hGH treatment. The NaSi-1 mRNA levels were significantly lower in 22- to 23-month-old rats compared with that in 9- to 10-month-old animals (P <.001). The NaSi-1 mRNA levels were significantly increased on days 2 and 3 of hGH treatment (P <.05) and then gradually decreased to the control value. The NaSi-1 protein levels in old animals (22-23 months) were also significantly lower than that of 9- to 10-month-old animals and were significantly increased from day 2 of hGH treatment, reaching a maximum level on day 3 or 4 and then returning to the baseline level in both age groups. From these results, it was concluded that 1) NaSi-1 mRNA and protein levels are lower in old animals and increase in both adult and aged rats after hGH treatment, 2) plasma IGF-I levels are similar in adult and aged rats and increase after hGH treatment, and 3) plasma IGFBP-3 levels are lower in old rats and remain unchanged after hGH treatment.

Aging↗
PubMed1999

Aluminum uptake and effects on transferrin mediated iron uptake in primary cultures of rat neurons, astrocytes and oligodendrocytes.

Transferrin (Tf) is known primarily for its role in the transport and cellular uptake of iron (Fe). Tf is also the major serum binding protein for Al. In this study, primary rat oligodendrocyte, neuron and astrocyte cultures were found to differ in Tf mediated Fe and Al uptake and in the effect of Al-Tf on Fe-Tf uptake during 4 h incubation periods. When incubated with Al-Tf (1.25 microM), oligodendrocytes displayed a 3- to 4-fold increase (p=.0002) in Al, neurons demonstrated a much smaller (p=.06) increase, and no increase was seen for astrocytes. When incubated with equimolar Al citrate or Al chloride, no increase in cellular Al was seen in any of the three cell types. Oligodendrocytes, astrocytes and neurons all demonstrated greater 59Fe uptake from Fe-Tf than Fe chloride. This uptake could be inhibited by excess Fe-Tf in oligodendrocytes and neurons, but not astrocytes. A small but significant inhibition of 59Fe uptake from Fe-Tf was seen after addition of Al-Tf to the incubation medium of oligodendrocytes, but not neurons or astrocytes. Oligodendrocytes may be particularly vulnerable to the accumulation of excess intracellular Al, and to interference of Al with Fe uptake. Such effects could contribute to Al-induced neurotoxicity if they result in altered myelin formation or maintenance.

Aluminum↗
PubMed1999

[The development of a RF electrical pole catheter for heart ablation].

This article describes a RF electrical pole catheter for heart ablation. There is a device in the catheter, that can adjust the bending of the catheter tip on which there are a pair of electrical poles that is able to record and map the electrical potential of the heart, and to transfer 50 W electrical energy for focus ablution of heart disease.

Cardiac Surgical Procedures↗
PubMed1998

Brain-wave recognition of sentences.

Electrical and magnetic brain waves of two subjects were recorded for the purpose of recognizing which one of 12 sentences or seven words auditorily presented was processed. The analysis consisted of averaging over trials to create prototypes and test samples, to each of which a Fourier transform was applied, followed by filtering and an inverse transformation to the time domain. The filters used were optimal predictive filters, selected for each subject. A still further improvement was obtained by taking differences between recordings of two electrodes to obtain bipolar pairs that then were used for the same analysis. Recognition rates, based on a least-squares criterion, varied, but the best were above 90%. The first words of prototypes of sentences also were cut and pasted to test, at least partially, the invariance of a word's brain wave in different sentence contexts. The best result was above 80% correct recognition. Test samples made up only of individual trials also were analyzed. The best result was 134 correct of 288 (47%), which is promising, given that the expected recognition number by chance is just 24 (or 8.3%). The work reported in this paper extends our earlier work on brain-wave recognition of words only. The recognition rates reported here further strengthen the case that recordings of electric brain waves of words or sentences, together with extensive mathematical and statistical analysis, can be the basis of new developments in our understanding of brain processing of language.

Adult↗
PubMed1998

Repin-induced neurotoxicity in rodents.

Russian knapweed is a perennial weed found in many parts of the world, including southern California. Chronic ingestion of this plant by horses has been reported to cause equine nigropallidal encephalomalacia (ENE), which is associated with a movement disorder simulating Parkinson's disease (PD). Repin, a principal ingredient purified from Russian knapweed, is a sesquiterpene lactone containing an alpha-methylenebutyrolactone moiety and epoxides and is a highly reactive electrophile that can readily undergo conjugation with various biological nucleophiles, such as proteins, DNA, and glutathione (GSH). We show in this study that repin is highly toxic to C57BL/6J mice and Sprague-Dawley rats and acutely induces uncoordinated locomotion associated with postural tremors, hypothermia, and inability to respond to sonic and tactile stimuli. We also show that repin intoxication reduces striatal and hippocampal GSH and increases total striatal dopamine (DA) levels in mice. Striatal microdialysis in rats, however, has demonstrated a significant reduction of extracellular DA levels. These findings, coupled with the absence of any demonstrable change in striatal DOPAC levels, suggest that repin acts by inhibiting DA release, a hypothesis that is further supported by our demonstration that, in cultured PC12 cells, repin inhibits the release of DA without affecting its uptake. We believe, therefore, that inhibition of DA release represents one of the earliest pathogenetic events in ENE, leading eventually to striatal extracellular DA denervation, oxidative stress, and degeneration of nigrostriatal pathways. Since the neurotoxic effects of repin appear to be mediated via oxidative stress, and since repin is a natural product isolated from a plant in our environment that can cause a movement disorder associated with degeneration of nigrostriatal pathways, clarification of the mechanism of repin neurotoxicity may provide new insights into our understanding of the pathogenesis of PD.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

Estimation of target hazard quotients and potential health risks for metals by consumption of seafood in Taiwan.

The purpose of this paper is to describe the impact of metal pollution on the main seafood and assess the potential health risk from consuming the contaminated seafood in Taiwan. The results of geometric mean (GM) metal concentrations in various seafood showed that the copper, zinc, and arsenic concentrations in oysters were significantly (p < 0.001) higher than those in the other seafood by about 1,057, 74.3, and 56.2 times, respectively. The green color found in the oysters was due to high GM copper and zinc concentrations of 909 (ranging from 113-2,805) and 1,293 (ranging from 303-3,593) microg/g dry wt, respectively. In addition, using a maximum consumption rate of 139 g/day of oysters for individuals, calculations yield target hazard quotients (daily intake/reference dose) of below 1 for cadmium and mercury and high values of 1.61, 9. 33, and 1.77 for inorganic arsenic, copper, and zinc in adults, respectively. The various lifetime cancer risks for inorganic arsenic (maximum exposed individuals risk ranging from 9.93 x 10(-6) to 3.11 x 10(-4)) might be caused by consuming different seafood in Taiwan. The highest risk estimate for inorganic arsenic was 5.10 x 10(-4) for consumption of oysters by Machu Islands residents. The long-term exposure of metals through consumption of oysters, especially for some high-risk groups, could be dangerous. Taking inorganic arsenic for example, a 10(-6) upper limit on lifetime risk as the health protection standard would require maximum oyster residue levels of approximately 0.0076-0.056 microg/g wet wt, for consumption rates of 139-18.6 g/d. In the light of known risks to public health, the government should issue an immediate warning to the public to refrain from eating all seafood harvested from the Taiwan coastal areas, especially the Hsiangshan area and the Machu Islands.

Environmental Exposure↗
PubMed1998

Detection and quantitation of a sodium-dependent sulfate cotransporter (NaSi-1) by sandwich-type enzyme-linked immunosorbent assay.

The sodium-dependent sulfate transporter (NaSi-1) DNA has been recently identified from rat kidney cortex. The objective of this study was to develop a quantitative assay for the NaSi-1 transporter protein. The NaSi-1 antigen was prepared by fusion protein techniques following analysis of the primary sequence for antigenicity. Polyclonal and monoclonal antibodies against the NaSi-1 antigen were raised in rabbits and mice, respectively. The specificity of the raised antibodies was examined by Western analysis using brush-border membrane (BBM) and basolateral membrane (BLM) purified from rat kidney cortex. Both NaSi-1 polyclonal and monoclonal antibodies detected a 69-kDa protein in the BBM. Using the purified monoclonal antibody as the capture antibody and the polyclonal antibody as the detecting antibody, a simple and sensitive sandwich-type enzyme-linked immunosorbent assay was developed to quantitate NaSi-1 transporter protein levels in tissue. The specificity of the assay was examined using BBM, BLM and NaSi-1-transfected Madin-Darby canine kidney cells. The assay was capable of detecting NaSi-1 at levels as low as 6.58 fmol. The concentration of NaSi-1 transporter protein in crude membrane isolated from rat kidney cortex was 0.094+/-0.014 fmol/ microg protein (mean+/-SD of three preparations).

Animals↗
PubMed1998

The use of a chimera HIV-1/HIV-2 envelope protein for immunodiagnosis of HIV infection: its expression and purification in E. coli by use of a translation initiation site within HIV-1 env gene.

A chimera HIV-1/HIV-2 envelope sequence composed of multiple conserved immunodominant epitopes of HIV-1 envelope protein (HIV-1 IIIB: env482-518 + env548-675) and the HIV-2 gp36 immunodominant epitope (env592-603), was constructed and directly over-expressed in E. coli by using a prokaryotic translation initiation sequence contained within the gene of HIV-1 envelope. The recombinant product was purified and applied in antibody-screening assay. The purified chimera antigen reacted with all the thirty-eight HIV-1 positive serum samples, the two HIV-2 serum samples, and had no cross-reaction with all the eighty-eight normal healthy serum sample. The results indicated that this recombinant chimera HIV-1/HIV-2 envelope protein could be useful for diagnostic purposes of HIV infection.

AIDS Serodiagnosis↗
PubMed1998

Inhibition of cathepsin B does not affect the intracellular activation of trypsinogen by cerulein hyperstimulation in isolated rat pancreatic acinar cells.

Activation of trypsinogen is thought to trigger the autodigestive process in acute pancreatitis. The lysosomal enzyme cathepsin B was suggested to cause the activation of trypsinogen because it is known that cathepsin B is able to activate trypsinogen in special circumstances and that lysosomal and digestive enzymes are colocalized within intracellular vacuoles in the early stage of pancreatitis. As yet this hypothesis has been difficult to prove because activated trypsin is difficult to quantify in pancreatitis by conventional enzymatic measurements. We therefore employed an ELISA for trypsin activating peptide (TAP), which is a small peptide cleaved during the activation of trypsinogen and can be determined reliably. Supraphysiological concentrations of cerulein (1 nM-1 microM) resulted in a marked increase in TAP in freshly isolated pancreatic acinar cells, indicating activation of trypsinogen. This activation as determined by the TAP increase was significantly reduced by the serine protease inhibitor Fut-175 but not by the cathepsin B inhibitors E-64 and NCO-700. The concentrations of NCO-700 and E-64 abolished the cathepsin B activity of pancreatic acinar cells but did not significantly reduce the trypsin activity (after enterokinase preincubation); correspondingly the concentrations of Fut-175 used abolished the trypsin activity but did not reduce the cathepsin B activity. The results indicate that an autoactivation of trypsin rather than an activation of trypsinogen by cathepsin B triggers trypsin activation by supramaximal cerulein concentrations.

Animals↗
PubMed1998

User-friendly and versatile software for analysis of protein hydrophobicity.

We have developed a simple and flexible program to analyze regional hydrophobicity of a protein from its amino acid (aa) sequence. This program runs as a Microsoft Excel document into which aa sequence can be copied from any Windows-compatible or Macintosh word processor. The program returns the hydrophobicity index of each aa residue and other analyses that can be used to predict transmembrane domains, amphiphilic alpha helices and putative antigenic epitopes in a protein using established algorithms. The program can also be easily modified to test user-defined algorithms and to accommodate non-conventional aa residues or ambiguities in the aa sequence. Simple modification of the program allows direct use of nucleic acid sequence information for various analyses. Graphic visualization of the results is readily achieved using the graphics function of Microsoft Excel. Alternatively, the data can be imported into other graphics software for preparation of publication-quality figures. By running as a document in Microsoft Excel, which can be found in virtually all personal computers, this program provides easy access even to the computer novice.

Amino Acid Sequence↗
PubMed1997

Brain wave recognition of words.

Electrical and magnetic brain waves of seven subjects under three experimental conditions were recorded for the purpose of recognizing which one of seven words was processed. The analysis consisted of averaging over trials to create prototypes and test samples, to both of which Fourier transforms were applied, followed by filtering and an inverse transformation to the time domain. The filters used were optimal predictive filters, selected for each subject and condition. Recognition rates, based on a least-squares criterion, varied widely, but all but one of 24 were significantly different from chance. The two best were above 90%. These results show that brain waves carry substantial information about the word being processed under experimental conditions of conscious awareness.

Brain↗
PubMed1997

Studies on Interaction of Dodecyltrimethylammonium Bromide with Na- and Al-Montmorillonite

The adsorption isotherms and adsorption enthalpies of dodecyltrimethylammonium bromide (DDTMAB) on Na- and Al-montmorillonite were determined in the pH range 2-12. The basal spacings of the clays were also studied by X-ray diffraction. Interactions of DDTMAB with the two montmorillonites predominate mostly through cation exchange in the pH range studied. In the case of Na-montmorillonite, the amount of adsorption increases with pH, but adsorption enthalpy decreases with pH. For Al-montmorillonite, adsorption enthalpy exhibits nonmonotonic variation with pH, although the amount of adsorption increases with pH monotonously. The adsorption enthalpies of DDTMAB on the clays are negative. The adsorbed DDTMAB molecules in clay interlayers present a bilayer arrangement at saturation. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Capture and expansion of bone marrow-derived mesenchymal progenitor cells with a transforming growth factor-beta1-von Willebrand's factor fusion protein for retrovirus-mediated delivery of coagulation factor IX.

Mesenchymal stem cells give rise to the progenitors of many differentiated phenotypes, including osteocytes, chrondocytes, myocytes, adipocytes, fibroblasts, and marrow stromal cells, which are capable of self-renewal and undergo expansion in the presence of transforming growth factor-beta1 (TGF-beta1). The present study was designed to test the concept that mesenchymal progenitor cells could be selected and expanded by virtue of their intrinsic physiologic responses to TGF-beta1. Human bone marrow aspirates were initially cultured, under low serum conditions, in collagen pads or gels impregnated with a genetically engineered TGF-beta1 fusion protein bearing an auxiliary von Willebrand's factor-derived collagen-binding domain (TGF-beta1-vWF). Histologic examination of TGF-beta1-vWF-supplemented collagen pads from 8-day cultures revealed the selective survival of a population of mononuclear blastoid cells. The TGF-beta-responsive cells were expanded to form stromal/fibroblastic colonies by serum reconstitution, and further to form osteogenic colonies upon supplementation with osteoinductive factors. In comparative studies, both marrow-derived progenitor cells and mature stromal cells were transduced with a retroviral vector bearing a human factor IX construct. Both the transduced progenitor cells and mature stromal cells expressed the factor IX transgene at levels comparable to those reported for human fibroblasts. Transplantation of murine progenitor cells bearing the human factor IX vector into syngeneic B6CBA mice resulted in detectable circulating levels of the human factor IX antigen. Taken together, these data demonstrate a novel physiologic approach for the selection of mesenchymal precursor cells followed by mitotic expansion, transduction, and transplantation of these progenitor cells with retroviral vectors bearing therapeutic genes.

Animals↗
PubMed1997

Factors which affect the calcification of tissue-derived bioprostheses.

Mineralization of implanted bioprostheses poses a major clinical problem. Crosslinking of collagenous matrices, a process used to render tissues relatively inert and nonbiodegradable, seems to encourage calcification. Residual, noncovalently bound glutaraldehyde, as well as glutaraldehyde crosslinks which can be degraded with time, seem to play a role in this connection. Our findings demonstrate the need to carefully remove noncovalently or labile-associated glutaraldehyde by thorough rinsing or neutralization before implantation. Components of a valve prosthesis such as cusps and aortic wall, which are known to vary in their proportions of collagen, elastin, and noncollagenous proteins and to calcify to different extents, can both be prevented from calcifying if treated with a biphosphonate before implantation. Calcification can also be reduced by selective enzymatic removal of noncollagenous materials. In addition to the age of rats, animals usually used to evaluate calcification, the strain of animal can markedly affect the response. The Fischer-344 rat, a highly inbred animal, will not calcify exhaustively rinsed implants. Our findings suggest that multifactorial approaches may have to be combined to generate the most ideal bioprostheses. These should include careful removal of noncovalently bound glutaraldehyde, neutralization of the nonbifunctionally reacted residues, removal of lipids and noncollagenous proteins (and possibly the more antigenic nonhelical collagen telopeptides), as well as inclusion of agents such as biphosphohates, which by interfering with crystal growth prevent the accumulation of mineral in the interstices of the tissue.

Animals↗
PubMed1997

Enthalpy of Adsorption and Isotherms for Adsorption of Naphthenic Acid onto Clays

The enthalpies of adsorption and the isotherms for adsorption of naphthenic acid onto Na-montmorillonite, Na-kaolinite, and Na-illite were studied by means of calorimetry and the static method at 298.15 K. The results show that the enthalpies of adsorption and saturated adsorption amounts of naphthenic acid on different clays change in the order Na-montmorillonite > Na-illite > Na-kaolinite. The interaction between naphthenic acid and clays is discussed.

Journal Article↗
PubMed1997

Collagen content is significantly lower in restenotic versus nonrestenotic vessels after balloon angioplasty in the atherosclerotic rabbit model.

BACKGROUND: It is recognized that restenosis is primarily due to alterations in geometric remodeling of the extracellular matrix rather than intimal hyperplasia. Prior studies have shown that angioplasty stimulates an increase in both synthesis and degradation of collagen in the atherosclerotic vessel. However, differences in collagen content and metabolism between restenotic and nonrestenotic vessels have not been examined. METHODS AND RESULTS: Four weeks after angioplasty in an atherosclerotic rabbit model, collagen content in restenotic and nonrestenotic vessels was measured both biochemically by hydroxyproline quantitation and histologically by a digital subtraction method with the use of circularly polarized images of picrosirius red-stained sections. Collagenase and gelatinase activity also were measured in the same restenotic and nonrestenotic vessels by use of a radiosubstrate assay. Collagen content was found to be significantly lower in restenotic vessels than in nonrestenotic vessels both biochemically (127.0 +/- 32.6 versus 212.6 +/- 84.3 micrograms/mg tissue; n = 11 vessels; P < .05) and histologically (67.3 +/- 7.9% versus 76.3 +/- 11.8% area fraction; n = 20 sections from 6 vessels; P = .05). There was a significant inverse correlation between biochemically determined collagen content and gelatinase activity (P = .02) and a significant correlation between histologically determined lumen are and percent collagen content (P = .0071). CONCLUSIONS: Collagen content is significantly decreased in restenotic versus nonrestenotic vessels after angioplasty in the atherosclerotic rabbit model. The increased collagen content in nonrestenotic vessels was associated with preserved lumen area and may play a role in geometric remodeling after angioplasty.

Angioplasty, Balloon↗
PubMed1997

Adsorption Enthalpy and Adsorption Isotherm of Tetradecylpyridinium Bromide on Na-Montmorillonite

The adsorption enthalpy and the adsorption isotherm of tetradecylpyridinium bromide (TPB) onto a Na-montmorillonite suspension and the dilution enthalpy of the TPB solution have been determined at 298.15 K. The dilution process is endothermic and the adsorption process is exothermic. For ion exchange adsorption, the interaction between TP+ and the montmorillonite is much stronger than that between Na+ and the montmorillonite because the cumulative adsorption enthalpy increases dramatically with adsorption amount. For molecular adsorption, however, the interaction between TPB and the clay is much weaker.

Journal Article↗