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Biomedical subjects

B Han

Publications and source records attributed to B Han.

At least 55 records · Page 3Linked to original sources
PubMed2000

Orchestrated transcription of key pathways in Arabidopsis by the circadian clock.

Like most organisms, plants have endogenous biological clocks that coordinate internal events with the external environment. We used high-density oligonucleotide microarrays to examine gene expression in Arabidopsis and found that 6% of the more than 8000 genes on the array exhibited circadian changes in steady-state messenger RNA levels. Clusters of circadian-regulated genes were found in pathways involved in plant responses to light and other key metabolic pathways. Computational analysis of cycling genes allowed the identification of a highly conserved promoter motif that we found to be required for circadian control of gene expression. Our study presents a comprehensive view of the temporal compartmentalization of physiological pathways by the circadian clock in a eukaryote.

Arabidopsis↗
PubMed2000

MRG1 expression in fibroblasts is regulated by Sp1/Sp3 and an Ets transcription factor.

MRG1 (melanocyte-specific gene 1 (MSG1)-related gene), a ubiquitously expressed transcription factor that interacts with p300/CBP, TATA-binding protein and Lhx2, is the founding member of a new family of transcription factors. Initial characterization of this newly discovered transcription factor has underscored its potential involvement in many important cellular processes through transcriptional modulation. We previously demonstrated that MRG1 can be induced by various biological stimuli (Sun, H. B., Zhu, Y. X., Yin, T., Sledge, G., and Yang, Y. C. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 13555-13560). As a first step in understanding its role in different biological processes, we investigated mechanisms that regulate transcription of the mouse MRG1 gene in fibroblasts. Transient transfection of Rat1 fibroblast cells with sequential 5'-deletions of mouse MRG1 promoter-luciferase fusion constructs indicated that the -104 to +121 region contains the full promoter activity. Deletion and site-directed mutations within this region revealed that the Ets-1 site at -97 to -94 and the Sp1 site at -51 to -46 are critical for MRG1 expression in fibroblasts. Gel mobility shift and supershift assays performed with Rat1 nuclear extracts identified nucleoprotein complexes binding to the Ets-1 site and the Sp1 site. In Drosophila SL2 cells, which lack the Sp and Ets family of transcription factors, expression of Sp1, Sp3, and Ets-1 or Elf-1 functionally stimulated MRG1 promoter activity in a synergistic manner. These results suggest that multiple transcription factors acting in synergy are responsible for MRG1 expression and the responsiveness of cells to different biological stimuli.

Animals↗
PubMed2000

Lifelong feeding of a high aluminum diet to mice.

In three experiments, high aluminum diets (1000 microg Al/g diet) were fed to mice throughout their life span to determine whether neurodegenerative changes were seen with aging. Brain Al concentrations were slightly lower in Al-treated mice than controls. Generally, no increased mortality or gross evidence of neurodegeneration was seen in Al-treated mice. Eighteen and 24 month old Swiss Webster mice fed the high aluminum diet differed from controls on some neurobehavioral tests, but differences were no greater than previously seen with shorter term exposure in younger mice. Both brain Al concentration and susceptibility to oxidative damage, as measured with TBARS, were lower in the Al-treated aged mice than in controls. In addition, Al-treated aged Swiss Webster and C57BL/6J mice showed somewhat enhanced performance in the Morris water maze. Finally, Al treatment did not exacerbate the effect of MPTP treatment on a grip strength measure in either 66 or 235 day old male mice. Swiss Webster and C57BL/6J mice do not appear to provide useful models for studying Al-induced neurodegenerative changes in aging.

Aluminum↗
PubMed2000

Brain-wave representation of words by superposition of a few sine waves.

Data from three previous experiments were analyzed to test the hypothesis that brain waves of spoken or written words can be represented by the superposition of a few sine waves. First, we averaged the data over trials and a set of subjects, and, in one case, over experimental conditions as well. Next we applied a Fourier transform to the averaged data and selected those frequencies with high energy, in no case more than nine in number. The superpositions of these selected sine waves were taken as prototypes. The averaged unfiltered data were the test samples. The prototypes were used to classify the test samples according to a least-squares criterion of fit. The results were seven of seven correct classifications for the first experiment using only three frequencies, six of eight for the second experiment using nine frequencies, and eight of eight for the third experiment using five frequencies.

Acoustic Stimulation↗
PubMed2000

Phosphine-induced oxidative damage in rats: attenuation by melatonin.

Phosphine (PH(3)), from hydrolysis of aluminum, magnesium and zinc phosphide, is an insecticide and rodenticide. Earlier observations on PH(3)-poisoned insects, mammals and a mammalian cell line led to the proposed involvement of oxidative damage in the toxic mechanism. This investigation focused on PH(3)-induced oxidative damage in rats and antioxidants as candidate protective agents. Male Wistar rats were treated ip with PH(3) at 2 mg/kg. Thirty min later the brain, liver, and lung were analyzed for glutathione (GSH) levels and lipid peroxidation (as malondialdehyde and 4-hydroxyalkenals) and brain and lung for 8-hydroxydeoxyguanosine (8-OH-dGuo) in DNA. PH(3) caused a significant decrease in GSH concentration and elevation in lipid peroxidation in brain (36-42%), lung (32-38%) and liver (19-25%) and significant increase of 8-OH-dGuo in DNA of brain (70%) and liver (39%). Antioxidants administered ip 30 min before PH(3) were melatonin, vitamin C, and beta-carotene at 10, 30, and 6 mg/kg, respectively. The PH(3)-induced changes were significantly or completely blocked by melatonin while vitamin C and beta-carotene were less effective or inactive. These findings establish that PH(3) induces and melatonin protects against oxidative damage in the brain, lung and liver of rats and suggest the involvement of reactive oxygen species in the genotoxicity of PH(3).

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Glial cell line-derived neurotrophic factor protects against ischemia/hypoxia-induced brain injury in neonatal rat.

Ischemic/hypoxic brain damage induced in 7-day-old rats was significantly attenuated in a dose-dependent manner by intracerebral injection of glial cell line-derived neurotrophic factor (GDNF; 2 or 4 microg) within 30 min after the insult. Whereas the great majority of the vehicle-treated animals showed massive infarction involving more than 75% of the affected cerebral hemisphere, GDNF injection resulted in a remarkable reduction in both the incidence and severity of the brain damage (incidence ranging from 76% to 93% in controls to 34% to 64% in the 2.0-microg group and 7% to 29% in 4.0-microg group). The induction of immunoreactive 70-kDa heat shock protein (HSP70) in cerebral cortical neurons was also significantly reduced in GDNF-treated animals as compared to controls. The mechanisms responsible for the neuroprotective effects of GDNF remain unknown, although it has been speculated that these may be endogeneous. The higher expression of GDNF and its mRNA in developing brains may be one of the factors responsible for the relative resistance to ischemia of fetal and neonatal as opposed to adult brains. GDNF may possibly act by protecting against oxidative stress or by scavenging free radicals generated during ischemia. The results of our study strongly suggest that GDNF may prove to be an effective and potent protective agent against perinatal ischemic/hypoxic encephalopathy.

Animals↗
PubMed2000

Application of Live Monocells from Macroalgae to Shellfish Seed Production.

Monocells were isolated from several macroalgae, Porphyra yezoensis, Undaria pinnatifida, and Laminaria japonica, by digestion with alga-tool enzymes. The monocells were then used to feed the parents or larvae of bay scallop Argopecten irradians, blood cockle Arca inflata, and abalone Haliotis discus juveniles. Results showed that the parents of bay scallop and blood cockle fed with Porphyra monocells could mature and discharge eggs and spermatozoa and their larvae could metamorphose; the survival rate of abalone juveniles fed with isolated cells from Laminaria and Undaria increased by 100% compared with that of those fed with artificial food.

Journal Article↗
PubMed2000

Menadione-induced oxidative stress inhibits cholecystokinin-stimulated secretion of pancreatic acini by cell dehydration.

The present study evaluated the effects of free radicals generated by menadione on morphology and function of pancreatic acinar cells focusing on enzyme secretion, stimulus-secretion coupling, and cell hydration. Various experiments evaluated morphology and function of isolated rat pancreatic acinar cells exposed to menadione. Menadione instantaneously generated free radicals (luminol and deoxyribose assays) followed by a time-dependent cell injury (uptake of trypan blue). Early ultrastructural changes included vacuolization and alterations of mitochondria, endoplasmic reticulum, and nucleus. Menadione caused a rapid glutathione oxidation followed by a depletion in reduced glutathione. An increase in lipid peroxides and a depletion of adenosine triphosphate were seen only after 30-60 minutes. Menadione markedly inhibited amylase release stimulated by cholecystokinin (CCK) and carbachol and simultaneously caused cell shrinkage after a few minutes. Similar degrees of cell shrinkage induced by hyperosmolar incubation and by menadione inhibited amylase secretion to a similar extent. CCK binding and its effect on calcium and inositol 1,4,5-trisphosphate (IP3) were not affected by menadione. Menadione (without CCK) induced an instantaneous increase of intracellular calcium followed by a slow constant increase. In single cells, menadione induced calcium oscillations with a frequency lower than that seen after CCK stimulation. Some morphologic and functional alterations owing to menadione-induced oxidative stress may be caused by adenosine triphosphate and glutathione depletion, lipid peroxidation, and changes in cytosolic calcium. The marked inhibition of secretagogue-stimulated enzyme secretion owing to menadione may be mediated to a large part by cell dehydration, whereas classical steps of stimulus-secretion coupling like receptor binding, calcium release, and IP3 generation remained unchanged.

Adenosine Triphosphate↗
PubMed2000

CCK stimulates mob-1 expression and NF-kappaB activation via protein kinase C and intracellular Ca(2+).

Supraphysiological concentrations of cholecystokinin (CCK) induce chemokine expression in rat pancreatic acini through the activation of the transcription factor NF-kappaB. In the current study, the intracellular signals involved in these pathophysiological effects of CCK were investigated. CCK induction of mob-1 expression in isolated rat pancreatic acini was blocked by the protein kinase C (PKC) inhibitors GF-109203X and Ro-32-0432 and by the intracellular Ca(2+) chelator BAPTA. CCK induced NF-kappaB nuclear translocation, and DNA binding was also blocked by GF-109203X and BAPTA. Direct activation of PKC with TPA induced mob-1 chemokine expression and activated NF-kappaB DNA binding to a similar extent as did CCK. Increasing intracellular Ca(2+) using ionomycin had no effect on mob-1 mRNA levels or NF-kappaB activity. Both CCK and TPA treatments decreased inhibitory kappaB-alpha (IkappaB-alpha) levels, whereas ionomycin had no effect. However, the effects of TPA on IkappaB-alpha degradation were less complete than for CCK. In combination, TPA and ionomycin degraded IkappaB-alpha to a similar extent as CCK. Therefore, activation of NF-kappaB and mob-1 expression by supraphysiological CCK is likely mediated by both PKC activation and elevated intracellular Ca(2+).

Animals↗
PubMed2000

Treatment margins for prostate brachytherapy.

The purpose of this article was to determine what planned treatment margin (TM) would allow for implant-related prostate volume changes and still achieve an adequate periprostatic cancercidal dose. Twenty consecutive, unselected patients who underwent (125)I implantation (144 Gy prescription dose) were studied. The treated volume (TV) was calculated as the volume encompassed by the 144 Gy isodose distribution. A post-implant computed tomography scan was obtained the following day, using 5-mm images at every 5 mm. The distances between the prostate margin (GTV) and TV were determined by measuring the distance between the ultrasound-defined prostatic margin and the prescription isodose, perpendicular to the prostatic margin. The lateral, anterior, and posterior TM margins were determined at the base, mid-level, and apex of the prostate. The pre-implant TV was nearly twice as large as the GTV, ranging from 36 to 199 mL (median, 73 mL). The anterior, lateral, and posterior planned TMs varied substantially between patients, due to lack of a consistent policy the magnitude of the CTV and the acceptable CTV-to-TV distance. For all measurement points, the median planned treatment margin was 3 mm (range, -16 mm to 14 mm). Overall, there was only a loose correlation between pre- and post-implant treatment margins primarily due to variable, implant-related prostatic dimensional changes. Patients with a greater implant-related volume increase tended to have smaller post-implant treatment margins. The post-implant TMs were negatively correlated with dimensional changes, and the negative correlation was most marked for the anterior and posterior TMs due to predominant anterior-posterior dimensional increase. As expected, the post-implant target coverage was higher when larger planning TMs were used, but the correlation was loose due to the unpredictable, highly variable degree of implant-related volume increase. We currently are using 5-mm TMs around the GTV, as identified on pre-implant transrectal ultrasonography or computed tomography. However, the poor correlation between planned and actual post-implant TMs call into question any attempt to make a rational recommendation regarding optimal TMs.

Brachytherapy↗
PubMed2000

[Changes of hepatic energy metabolism following partial hepatopetal blood occlusion].

OBJECTIVE: To evaluate the changes of hepatic energy metabolism by temporary occlusion of partial hepatopetal blood. METHODS: The animal mode of partial hepatopetal blood occlusion (PBO) was established without portal stasis. The hepatic energy metabolism parameters including adenosine triphosphate, respiratory control ratio, P/O ratio, and arterial ketone bodies ratio were studied following 30 min ischemia or 1, 6, and 24 h of reperfusion. The total hepatopetal blood occlusion (TBO) and sham groups served as control. RESULTS: The parameters of hepatic motochondrial function reflecting hepatic damage to ischemia-reperfusion showed different in PBO comparing with TBO group. The functional lesion was restored progressively in PBO-30 min group, but it was maintained low level in TBO-30 min group. CONCLUSION: The results suggest that it is beneficial to restoration of the hepatic energy metabolism in the ischemia-reperfusion injury by partial hepatopetal blood occlusion.

Adenosine Triphosphate↗
PubMed2000

[Behavior response of four Leis axyridis varieties to volatiles from tea and Toxoptera aurantii].

The behavior response of the adults of four Leis axyridis varieties to kairomone from Taxoptera aurantii was determined by Y-shape olfaction instrument. The results showed that when supplied with two-two-combinations of Taxoptera aurantii, Brevicoryne brassicae and Lipaphis erysimi, tea aphids plus aphid-damaged vs. normal shoots, and aphid-damaged vs. normal shoots, Leis axyridis had a preference for tea aphids, tea aphids plus aphid-damaged tea shoots, or aphid-damaged tea shoots. There existed a Logistic curve relationship(P < 0.01) between odor source tendency rate of Leis axyridis and odor source quality, when 8-9 kinds of odor gradients including tea aphids plus aphid-damaged tea shoots, aphid-damaged tea shoots and tea aphids were used as odor sources. The tendency rates of Leis axyridis ab. bimaculata, Leis axyridis ab. conspicua and Leis axyridis var. novemdecimpunctata showed single left-tilting peak curves to the aphid number(P < 0.01). Ether and n-hexane ringes of Toxoptera aurantii body surface also showed an attraction to all varieties. Leis axyridis var. spectabilis was the most sensitive variety.

Animals↗
PubMed1999

Invariance of brain-wave representations of simple visual images and their names.

In two experiments, electric brain waves of 14 subjects were recorded under several different conditions to study the invariance of brain-wave representations of simple patches of colors and simple visual shapes and their names, the words blue, circle, etc. As in our earlier work, 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. A least-squares criterion of fit between prototypes and test samples was used for classification. The most significant results were these. By averaging over different subjects, as well as trials, we created prototypes from brain waves evoked by simple visual images and test samples from brain waves evoked by auditory or visual words naming the visual images. We correctly recognized from 60% to 75% of the test-sample brain waves. The general conclusion is that simple shapes such as circles and single-color displays generate brain waves surprisingly similar to those generated by their verbal names. These results, taken together with extensive psychological studies of auditory and visual memory, strongly support the solution proposed for visual shapes, by Bishop Berkeley and David Hume in the 18th century, to the long-standing problem of how the mind represents simple abstract ideas.

Adult↗
PubMed1999

Invariance between subjects of brain wave representations of language.

In three experiments, electric brain waves of 19 subjects were recorded under several different experimental conditions for two purposes. One was to test how well we could recognize which sentence, from a set of 24 or 48 sentences, was being processed in the cortex. The other was to study the invariance of brain waves between subjects. As in our earlier work, 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. A least-squares criterion of fit between prototypes and test samples was used for classification. In all three experiments, averaging over subjects improved the recognition rates. The most significant finding was the following. When brain waves were averaged separately for two nonoverlapping groups of subjects, one for prototypes and the other for test samples, we were able to recognize correctly 90% of the brain waves generated by 48 different sentences about European geography.

Brain↗
PubMed1999

Structural and Thermodynamic Properties of Solutions of Butane in Aqueous Sodium Dodecyl Sulfate: A Study Using Neutron Scattering and Solubility Measurements.

The solubility of n-butane at a pressure of 1.013 bar in aqueous solutions of sodium dodecyl sulfate (SDS) has been measured over a range of concentration from below the critical micelle concentration (CMC) at about 8 mol kg(-1) to about 90 mol kg(-1) at three different temperatures. The free energy, enthalpy, and entropy of transfer of butane from water to the micelle were respectively -19.0 kJ mol(-1), 5.5 kJ mol(-1), and 80 J K(-1) mol(-1). At 68 mol kg(-1) a transition was found with a free energy of about -400 J mol(-1). Small-angle neutron experiments were used to study the effect of butane on the state of aggregation of the SDS. For each butane molecule incorporated into a micelle, the aggregation number of the SDS increased by an average of about 1.4 molecules. Thus, at 1.013 bar of butane and 50 mM SDS, where the solubility is about 1 butane to 10 SDS, the average micelle increases in size by about 20%, most of which comes from the additional SDS molecules. The aggregation behavior is qualitatively similar to that reported for hexane, heptane, and octane, but the effect seems to be larger for butane for a given volume of solute hydrocarbon. Small-angle scattering did not observe any substantial change in structure across the phase transition at 68 mol kg(-1). Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

The release of acetylcholine receptor inducing activity (ARIA) from its transmembrane precursor in transfected fibroblasts.

Acetylcholine receptor inducing activity (ARIA) is made by motoneurons and is released at the neuromuscular synapse to stimulate the synthesis of acetylcholine receptors by skeletal muscle. ARIA is derived from a transmembrane precursor (pro-ARIA) via proteolytic cleavage of the ectodomain. We studied requirements in the amino acid sequence at the cleavage site with various substitution and deletion mutations. Wild type (WT) and mutant proteins were transiently expressed in COS cells, and release of ARIA into the conditioned medium was measured by tyrosine phosphorylation of its receptor, p185, in L6 cells. Removal of all potential cleavage sites between the extracellular epidermal growth factor domain and the transmembrane domain by substitution and small deletions (<11 amino acid residues out of 21) did not significantly reduce ARIA release, whereas larger deletions abolished it. We propose that cleavage occurs independently of amino acid sequence at a short distance from the epidermal growth factor domain, unless sterically hindered by the nearby secondary structure. A mutant with shorter cytoplasmic domain ("c" isoform) released significantly less ARIA than the WT ("a" isoform), suggesting that the c isoform may be suitable for signaling through direct cell-cell contact. Alternatively, proteolytic conversion of the a isoform to the c isoform may rapidly down-regulate release of ARIA.

Amino Acid Sequence↗