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Biomedical subjects

B Han

Publications and source records attributed to B Han.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1999

A recombinant human TGF-beta1 fusion protein with collagen-binding domain promotes migration, growth, and differentiation of bone marrow mesenchymal cells.

A continuous source of osteoblasts for normal bone maintenance, as well as remodeling and regeneration during fracture repair, is ensured by the mesenchymal osteoprogenitor stem cells of the bone marrow (BM). The differentiation and maturation of osteoprogenitor cells into osteoblasts are thought to be modulated by transforming growth factors-beta (TGF-beta1 and TGF-beta2) and TGF-beta-related bone morphogenetic proteins (BMPs). To define the responses of mesenchymal osteoprogenitor stem cells to several growth factors (GFs), we cultured Fischer 344 rat BM cells in a collagen gel medium containing 0.5% fetal bovine serum for prolonged periods of time. Under these conditions, survival of BM mesenchymal stem cells was dependent on the addition of GFs. Recombinant hTGF-beta1-F2, a fusion protein engineered to contain an auxiliary collagen binding domain, demonstrated the ability to support survival colony formation and growth of the surviving cells, whereas commercial hTGF-beta1 did not. Initially, cells were selected from a whole BM cell population and captured inside a collagen network, on the basis of their survival response to added exogenous GFs. After the 10-day selection period, the surviving cells in the rhTGF-beta1-F2 test groups proliferated rapidly in response to serum factors (10% FBS), and maximal DNA synthesis levels were observed. Upon the addition of osteoinductive factors, osteogenic differentiation in vitro was evaluated by the induction of alkaline phosphatase (ALP) expression, the production of osteocalcin (OC), and the formation of mineralized matrix. Concomitant with a down-regulation of cell proliferation, osteoinduction is marked by increased ALP expression and the formation of colonies that are competent for mineralization. During the induction period, when cells organize into nodules and mineralize, the expression of OC was significantly elevated along with the onset of extracellular matrix mineralization. Differentiation of BM mesenchymal stem cells into putative bone cells as shown by increased ALP, OC synthesis, and in vitro mineralization required the presence of specific GFs, as well as dexamethasone (dex) and beta-glycerophosphate (beta-GP). Although rhTGF-beta1-F2-selected cells exhibited the capacity to mineralize, maximal ALP activity and OC synthesis were observed in the presence of rhBMPs. We further report that a novel rhTGF-beta1-F2 fusion protein, containing a von Willebrand's factor-derived collagen binding domain combined with a type I collage matrix, is able to capture, amplify, and stimulate the differentiation of a population of cells present in rat BM. When these cells are subsequently implanted in inactivated demineralized bone matrix (iDBM) and/or diffusion chambers into older rats they are able to produce bone and cartilage. The population of progenitor cells captured by rhTGF-beta1-F2 is distinct from the committed progenitor cells captured by rhBMPs, which exhibit a considerably more differentiated phenotype.

Alkaline Phosphatase↗
PubMed1999

Effects of Chain Length and Structure of Cationic Surfactants on the Adsorption onto Na-Kaolinite.

The adsorption of a series of alkylammonium bromides (RR1N(CH3)2Br) with different chain lengths R and R1 on a nonswelling clay surface (sodium kaolinite) has been studied by microelectrophoresis and adsorption isotherms. An increase in the number of CH2 groups in the shorter alkyl chain of the double-chain surfactant, or the introduction of another kind of alkyl group (phenyl group), was found to have much less effect on the adsorption behavior than changing the length of the alkyl chain in the single-chain surfactants. It is inferred that the effective hydrophobicity of the shorter chains in these double-chain surfactants is reduced by their intramolecular association with the longer chain. Comparison of adsorption and micellization leads to an empirical quantitative description of the effects of alkyl chain length and structure on adsorption. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Processing of ARIA and release from isolated nerve terminals.

The neuromuscular junction is a specialized synapse in that every action potential in the presynaptic nerve terminal results in an action potential in the postsynaptic membrane, unlike most interneuronal synapses where a single presynaptic input makes only a small contribution to the population postsynaptic response. The postsynaptic membrane at the neuromuscular junction contains a high density of neurotransmitter (acetylcholine) receptors and a high density of voltage-gated Na+ channels. Thus, the large acetylcholine activated current occurs at the same site where the threshold for action potential generation is low. Acetylcholine receptor inducing activity (ARIA), a 42 kD protein, that stimulates synthesis of acetylcholine receptors and voltage-gated Na+ channels in cultured myotubes, probably plays the same roles at developing and mature motor endplates in vivo. ARIA is synthesized as part of a larger, transmembrane, precursor protein called proARIA. Delivery of ARIA from motor neuron cell bodies in the spinal cord to the target endplates involves several steps, including proteolytic cleavage of proARIA. ARIA is also expressed in the central nervous system and it is abundant in the molecular layer of the cerebellum. In this paper we describe our first experiments on the processing and release of ARIA from subcellular fractions containing synaptosomes from the chick cerebellum as a model system.

Animals↗
PubMed1999

Sensitive detection of the binding of E2F to its promoter by exonuclease III- and BssHII-protection PCR assays.

For the non-radioactive, sensitive detection of the binding of transcription factor E2F to its binding site (E2 promoter), exonuclease III (ExoIII)- and BssHII-protection PCR assays were established. The binding of glutathione S-transferase E2F-1 (GST-E2F-1) fusion protein to its promoter protected the promoter against ExoIII- and BssHII-digestion. For the BssHII-protection PCR assay, a BssHII restriction site was made in the E2 promoter sequence by changing one base-pair next to its sequence. To detect E2F binding in ExoIII- or BssHII-protection PCR assays, the use of 3.13 fmol (5.00 ng) or 2.33 fmol (4.62 ng) of DNA (containing E2 promoters) and 0.325 microg (3.70 pmol) or 0.175 microg (2.00 pmol) of GST-E2F-1 protein, respectively, were found to be sufficient.

Carrier Proteins↗
PubMed1999

Quantification of iNOS mRNA with reverse transcription polymerase chain reaction directly from cell lysates.

Inducible nitric oxide synthase (iNOS) is a member of a family of primary inflammatory response genes. Quantitative measurement of iNOS mRNA levels is important for the study of gene expression of this enzyme during the process of inflammation. We report here a method for quantitative measurement of iNOS mRNA levels with rtPCR directly from cells lysed with a single step phenol/chloroform/ether extraction. Using a mouse macrophage cell line, J774.2, which expresses iNOS mRNA upon LPS + IFN-gamma treatment as the model, the effects of the extraction on iNOS mRNA recovery and cytosolic RNase removal have been studied. The cells are lysed and RNases denatured and removed by phenol/chloroform extraction. Trace amounts of the phenol partitioned in the samples are then removed by ether extraction. After the extraction, the samples can be used directly for reverse transcription and PCR without further purification of RNA. The recovery of specific mRNA is not affected by the extraction procedure and externally added iNOS cRNA shows no degradation by the extracted cell lysates. Measurement of iNOS mRNA with this procedure is linear using serially double-diluted cells in the range from 94 to 6000 cells. The efficiencies of rtPCR of iNOS wild-type and deletion cRNAs are also compared in our study. By controlling the molecular size of the deletion construct to within 10% of that of the wild type and maintaining PCR cycling below 25 cycles, the rtPCR efficiencies of iNOS wild type and deletion are identical. The detection of rtPCR products is enhanced by hybridization with specific probes. Under these conditions, iNOS mRNA concentration can directly be calculated from the internal standard in each tube without a standard curve. We conclude that our procedure provides an accurate method for quantitative measurement of iNOS mRNA from limited amount of cells without complete RNA isolation.

Animals↗
PubMed1999

Requirement for the homeobox gene Hb9 in the consolidation of motor neuron identity.

The homeobox gene Hb9, like its close relative MNR2, is expressed selectively by motor neurons (MNs) in the developing vertebrate CNS. In embryonic chick spinal cord, the ectopic expression of MNR2 or Hb9 is sufficient to trigger MN differentiation and to repress the differentiation of an adjacent population of V2 interneurons. Here, we provide genetic evidence that Hb9 has an essential role in MN differentiation. In mice lacking Hb9 function, MNs are generated on schedule and in normal numbers but transiently acquire molecular features of V2 interneurons. The aberrant specification of MN identity is associated with defects in the migration of MNs, the emergence of the subtype identities of MNs, and the projection of motor axons. These findings show that HB9 has an essential function in consolidating the identity of postmitotic MNs.

Animals↗
PubMed1999

Solid-substrate fermentation of soybeans with Rhizopus spp.: comparison of discontinuous rotation with stationary bed fermentation.

Tempe is a soybean food obtained by stationary solid-substrate fermentation using moulds (mainly Rhizopus spp.) as starter organism. Traditionally, tempe is fermented in static layer trays or wrapped packages. Due to heat and mass transfer limitations, gradients of temperature and gas atmosphere will result. Agitated fermentation can help to level heat and mass gradients, yielding better homogeneity. This type of process will not result in traditional tempe, but in individually fermented soybeans that could be processed into food ingredients. This report deals with the comparative effect of stationary versus agitated solid-substrate fermentation of soybeans on some chemical indices of substrate modification. For agitated solid-substrate fermentation, a 450-l size rotary-drum bioreactor was designed and constructed. Of two Rhizopus spp. tested, R. microsporus tolerated agitation quite well, as judged by changes of pH, amino nitrogen, ammonia, and soluble dry matter. The other species, R. oligosporus was strongly affected by agitation. This resulted in less pH increase (difference approx. 1.5 units), lower amino nitrogen levels (30-50% of levels in static fermentation), and lower levels of water-soluble non-lipid dry matter (30-50% of levels in static fermentation) with R. oligosporus agitated fermentation of soybeans controlled at 30 and 37 degrees C, compared to static fermentation at temperatures ranging between 25-35 and 30-40 degrees C, respectively.

Journal Article↗
PubMed1999

The linoleic acid metabolite, 13-HpODE augments the phosphorylation of EGF receptor and SHP-2 leading to their increased association.

In previous studies with Syrian hamster embryo fibroblasts, we found that a specific lipoxygenase metabolite of linoleic acid, 13(S)-hydroperoxyoctadecadienoic acid (HpODE), enhanced epidermal growth factor (EGF) signal transduction in a tumor suppressor gene plus phenotype (supB+); with a diminished response to 13(S)-HpODE in a tumor suppressor gene minus phenotype (supB-). This differential response was attributed to differences in the rate of EGF receptor (EGFR) dephosphorylation. To further define the molecular basis for these observations, in this report we examine the interaction of phosphorylated EGFR with the SH2 domain-containing protein tyrosine phosphatase, SHP-2, a positive modulator of EGF dependent cell growth. SHP-2 associated with phosphorylated EGFR to a greater extent in supB+ cells when compared to supB-. This differential association could not be accounted for by differences between suppressor gene phenotypes in SHP-2 protein level or mutations in the molecular sequence. The addition of 13(S)-HpODE stimulated a concentration-dependent increase in EGF-dependent phosphorylation of SHP-2 and its association with EGFR. A more dramatic response was observed in the supB+ cells. Differences in SHP-2 interaction with EGFR may account, in part, for phenotypic differences in the growth rates and responsiveness to EGF between the supB+ and supB- cells. EGFR-SHP-2 association appears to play an important role in the regulation of EGFR signal transduction.

Animals↗
PubMed1999

Supraphysiologic concentrations of cerulein induce apoptosis in the rat pancreatic acinar cell line AR4-2J.

Little is known as yet about the role of apoptosis in pancreatic damage. This study evaluated the effects of supraphysiologic concentrations of the cholecystokinin (CCK) analog, cerulein, which causes cell damage in vitro and acute pancreatitis in vivo, on cell proliferation and DNA fragmentation in the rat pancreatic acinar cell line AR4-2J. Cerulein inhibited the cell proliferation of AR4-2J time- and dose-dependently to approximately 60% of the control level at 10(-6) M after 72 h. DNA fragmentation, as assessed by both electrophoresis and enzyme-linked immunosorbent assay (ELISA), occurred at cerulein concentrations > or = 10(-8) M. The maximal DNA fragmentation as measured by ELISA was reached after 24 h. Cerulein at concentrations > or = 10(-9) M induced wild-type p53. Glutathione (1 mM) diminished the effects of cerulein on both cell proliferation and DNA fragmentation, whereas spermine (100 microM), which partially attenuated DNA fragmentation, did not have an effect on cell proliferation. The CCK-A-receptor antagonist loxiglumide completely abolished the effect of cerulein on DNA fragmentation. The serine-protease inhibitor FUT-175 (10 microM), the cysteine-protease inhibitor NCO-700 (5 mM), and ethylene glycol tetraacetic acid (EGTA; 500 microM) all had no effects on the changes in cell proliferation and DNA fragmentation induced by cerulein. The data suggest that supraphysiologic concentrations of cerulein rapidly induce apoptosis in AR4-2J cells and only later inhibit cell proliferation. These effects are mediated by CCK-A receptors. Cerulein-induced apoptosis may involve the induction of wild-type p53 or glutathione depletion or both.

Animals↗
PubMed1999

Cholecystokinin induction of mob-1 chemokine expression in pancreatic acinar cells requires NF-kappaB activation.

Inflammatory mediators are involved in the early phase of acute pancreatitis, but the cellular mechanisms responsible for their generation within pancreatic cells are unknown. We examined the role of nuclear factor-kappaB (NF-kappaB) in cholecystokinin octapeptide (CCK-8)-induced mob-1 chemokine expression in pancreatic acinar cells in vitro. Supraphysiological, but not physiological, concentrations of CCK-8 increased inhibitory kappaB (IkappaB-alpha) degradation, NF-kappaB activation, and mob-1 gene expression in isolated pancreatic acinar cells. CCK-8-induced IkappaB-alpha degradation was maximal within 1 h. Expression of mob-1 was maximal within 2 h. Neither bombesin nor carbachol significantly increased mob-1 mRNA or induced IkappaB-alpha degradation. Thus the concentration, time, and secretagogue dependence of mob-1 gene expression and IkappaB-alpha degradation were similar. Inhibition of NF-kappaB with pharmacological agents or by adenovirus-mediated expression of the inhibitory protein IkappaB-alpha also inhibited mob-1 gene expression. These data indicate that the NF-kappaB signaling pathway is required for CCK-8-mediated induction of mob-1 chemokine expression in pancreatic acinar cells. This supports the hypothesis that NF-kappaB signaling is of central importance in the initiation of acute pancreatitis.

Adenoviridae↗
PubMed1999

Family caregiving for patients with stroke. Review and analysis.

BACKGROUND: The literature on family caregiving for stroke patients is reviewed with the goals of (1) evaluating the effects of stroke caregiving on caregivers' well-being, (2) outlining deficiencies and methodological limitations of current research, and (3) outlining policy and practice implications of current studies. SUMMARY OF REVIEW: A total of 20 published stroke caregiving research articles were included in this review. Across studies, the effects of stroke caregiving on caregivers' well-being and the significant predictors of caregivers' depression were analyzed. Current evidence suggests that stroke caregivers have elevated levels of depression at both the acute stroke phase and the chronic stroke phase. However, major gaps are apparent in this literature, with few studies addressing such areas as caregiver physical health, ethnicity, and caregiver interventions. CONCLUSIONS: Given the increasing prevalence of stroke as well as the increasing pressures on families to provide care, more research is needed to guide policy and practice in this understudied topic.

Caregivers↗
PubMed1999

Induction of apoptosis by Coprinus disseminatus mycelial culture broth extract in human cervical carcinoma cells.

Extract of Coprinus disseminatus (pers. Fr.) (C. disseminatus) culture broth (EDCB) inhibits proliferation and induces apoptosis in the human cervical carcinoma cells at 5 microg/ml. To determine whether the cell death induced by the EDCB recruits caspases or not, one of the exclusive pathways in cell death, we examined caspase-3 activity in this cell death process. The activity of caspase-3 was remarkably increased when the cell was treated with EDCB, and this activity was nullified by Z-VAD-FMK, a well known caspase-3 inhibitor. From these results, we would expect the EDCB to contain substances with the ability to induce apoptosis in the human cervical carcinoma cells. The extent of the EDCB induced apoptosis is cell line-dependent.

Amino Acid Chloromethyl Ketones↗
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↗