Biomedical subjects

S H Nam

Publications and source records attributed to S H Nam.

At least 19 recordsLinked to original sources

PubMed2005

Bran extracts from pigmented rice seeds inhibit tumor promotion in lymphoblastoid B cells by phorbol ester.

Using flow cytometry, we quantitatively evaluated anti-tumor-promoting activity of rice bran extracts by measuring inhibition of Epstein-Barr virus early-antigen activation (EBV-EA) induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). This assay measures anti-tumor-promoting activity and cytotoxicity of target substances using the same batch of cells. Using this short-term procedure, we have determined the anti-tumor-promoting activity of 70% ethanol-water extracts of bran (outer layer) from seeds of five pigmented rice cultivars: Jumlalocal-1, DZ 78, Elwee, LK1-3-6-12-1-1, and LK1A-2-12-1-1. The results show that, compared to an extract from the non-pigmented white cooking rice variety Chuchung, the extracts from the pigmented varieties strongly inhibited phorbol ester-induced tumor promotion in marmoset lymphoblastoid cells B95-8 in vitro. These findings may facilitate development and use of new health-promoting rice varieties.

Animals↗

PubMed2004

A novel splice acceptor mutation in the DSPP gene causing dentinogenesis imperfecta type II.

The dentin sialophosphoprotein (DSPP) gene (4q21.3) encodes two major noncollagenous dentin matrix proteins: dentin sialoprotein (DSP) and dentin phosphoprotein (DPP). Defects in the human gene encoding DSPP cause inherited dentin defects, and these defects can be associated with bilateral progressive high-frequency sensorineural hearing loss. Clinically, five different patterns of inherited dentin defects are distinguished and are classified as dentinogenesis imperfecta (DGI) types I, II, and III, and dentin dysplasia types I and II. The genetic basis for this clinical heterogeneity is unknown. Among the 11 members recruited from the studied kindred, five were affected with autosomal dominant DGI type II. The mutation (g.1188C-->G, IVS2-3C-->G) lay in the third from the last nucleotide of intron 2 and changed its sequence from CAG to GAG. The mutation was correlated with the affection status and was absent in 104 unaffected individuals (208 alleles) with the same ethnic and geological background. The proband was in the primary dentition stage and presented with multiple pulp exposures. The occlusal surface of his dental enamel was generally abraded, and the dentin was heavily worn and uniformly shaded brown. The dental pulp chambers appeared originally to be within normal limits without any sign of obliteration, but over time (by age 4), the pulp chambers became partially or completely obliterated. The oldest affected member (age 59) showed mild hearing loss at high-frequency (8 kHz). Permanent dentition was severely affected in the adults, who had advanced dental attrition, premature loss of teeth, and extensive dental reconstruction.

Adolescent↗

PubMed2003

Non-linear registration for brain images by maximising feature and intensity similarities with a Bayesian framework.

The objective of this work was to provide a new, precise registration of the cortical mantle with a non-linear transformation. Image registration is broadly classified into two types, using intensity similarity and feature similarity. Whereas the former approach has merit in global brain matching, the latter provides a fast registration centred on a region of interest. The hybrid registration proposed in this paper was achieved using a Bayesian framework, which consisted of a likelihood model including intensity similarity and a prior model including feature information and a smoothing constraint. In this approach, each voxel was spatially transformed, so that the distance between corresponding features was shortened and also so that the intensity correlation was maximised. The result of the hybrid method clearly showed a good match of global brain (r = 0.930) by including intensity similarity. Moreover, this method compensated for the approximated sulcus of the feature-based method with intensity information, so that the geometric shape and thickness of the sulcus at the feature-defined region was likely to be registered. The accuracy in the feature-defined area was improved by 33.4% and 7.5% compared with feature-based and intensity-based methods, respectively.

Bayes Theorem↗

PubMed2001

Rapid fractionation of bovine transferrin using immobilized gangliosides.

Bovine transferrin (BTF) was fractionated from bovine whey using ganglioside affinity chromatography. After loading the immobilized matrix with a 2% whey solution, the matrix was washed with sodium acetate buffer at pH 4 containing 1 M NaCl before elution of BTF with sodium phosphate buffers at pH 7. Concanavalin-A affinity and ion exchange chromatography were used for further purification. The ganglioside column showed a 74.2% BTF recovery from whey and BTF was enriched to 61% purity with ion exchange chromatography. Bovine transferrin was identified by SDS-PAGE and western analysis. The Concanavalin-A affinity and ion exchange chromatography steps enriched BTF in the samples and removed other whey proteins from ganglioside purified fractions. These results indicate that immobilized ganglioside can be used to fractionate BTF from bovine whey. Our novel ganglioside affinity chromatography is rapid and efficient for the fractionation of BTF from whey.

Animals↗

PubMed2001

Affinity enrichment of bovine lactoferrin in whey.

Bovine lactoferrin was enriched in various whey samples by affinity chromatography using immobilized gangliosides. Bovine gangliosides were isolated from fresh buttermilk using a combination of ultrafiltration and organic extraction. Isolated gangliosides were covalently immobilized onto controlled-pore glass beads. The immobilized matrix contained 66 micrograms of gangliosides per gram of beads. After loading the matrix with reconstituted whey protein isolate (WPI) or whey protein concentrate (WPC), the matrix was washed with sodium phosphate buffer (pH 7) followed by sodium acetate buffer (pH 4) before elution of lactoferrin with 1 M NaCl in sodium acetate buffer. From the intensities of the protein bands in SDS-PAGE, lactoferrin constituted a minimum of 40% of the total protein in the salt eluted sample. WPI, pretrated by heating and ultrafiltration, showed the highest lactoferrin purity among protein sources, while WPI (10% wt/vol) showed the highest recovery. These results show that immobilized gangliosides can be used to enrich the lactoferrin content of whey.

Animals↗

PubMed2001

Differential expression patterns of Runx2 isoforms in cranial suture morphogenesis.

Runx2 (previously known as Cbfal/Pebp2alphaA/AML3), a key transcription factor in osteoblast differentiation, has at least two different isoforms using alternative promoters, which suggests that the isoforms might be expressed differentially. Haploinsufficiency of the Runx2 gene is associated with cleidocranial dysplasia (CCD), the main phenotype of which is inadequate development of calvaria. In spite of the biological relevance, Runx2 gene expression patterns in developing calvaria has not been explored previously, and toward this aim we developed three probes: pRunx2, which comprises the common coding sequence of Runx2 and hybridizes with all isoforms; pPebp2alphaA, which specifically hybridizes with the isoform transcribed with the proximal promoter; and pOsf2, which hybridizes with the isoform transcribed with the distal promoter. These probes were hybridized with tissue sections of mouse calvaria taken at various time points in development. Runx2 expression was localized to the critical area of cranial suture closure, being found in parietal bones, osteogenic fronts, and sutural mesenchyme. Pebp2alphaA and Osf2 showed tissue-specific expression patterns. The sites of Pebp2alphaA expression were almost identical to that of pRunx2 hybridization but expression was most intense in the sutural mesenchyme, where undifferentiated mesenchymal cells reside. The Osf2 isoform was strongly expressed in the osteogenic fronts, as well as in developing parietal bones, where osteopontin (OP) and osteocalcin (OC) also were expressed. However, in contrast to Pebp2alphaA, Osf2 expression did not occur in sutural mesenchyme. Pebp2alphaA also was expressed prominently in primordial cartilage that is found under the sutural mesenchyme and is not destined to be mineralized. Thus, Osf2 isoforms contribute to events later in osteoblast differentiation whereas the Pebp2alphaA isoform participates in a wide variety of cellular activities ranging from early stages of osteoblast differentiation to the final differentiation of osteoblasts.

Animals↗

PubMed2001

The changes in delivered oxygen fractions using laerdal resuscitator bag with different types of reservoir.

One of the disadvantages of the Laerdal resuscitator bag is that it does not deliver a high concentration of oxygen without a reservoir and an appropriate technique of ventilation. With a specific device that is able to compress a resuscitator bag mechanically at a regular volume, ventilator rate, and speed, we evaluated the effects of various factors (the tidal volume, the ventilator rate, the oxygen flow rate, the type of reservoir) of the Laerdal resuscitator bag during positive pressure ventilation that affect the delivered oxygen fraction (FDO2) and also whether 250 mL and 500 mL corrugated tubes could be used as substitutes for the reservoir bag. The 250 mL corrugated tube increased the FDO2 to over 96% with an oxygen flow rate of 15 L/min. The 500 mL corrugated tube increased the FDO2 to over 96% with an oxygen flow rate of 10 L/min regardless of the ventilator rate at a fixed tidal volume of 500 mL. At the identical fixed tidal volume of 500 mL, the 1,600 mL reservoir bag increased the FDO2 to over 92% with an oxygen flow rate of 5 L/min and to over 96% at 7.5 L/min regardless of the ventilator rate. We concluded that the FDO2 of the Laerdal resuscitator bag depends on various factors such as tidal volume, ventilator rate, oxygen flow rate, and type of reservoir and both the 250 mL and 500 mL corrugated tubes can be used as substitutes.

Equipment Design↗

PubMed1997

The bovine guanylate cyclase GC-E gene and 5' flanking region.

The gene encoding the bovine guanylate cyclase isoform E (GC-E) was isolated as a single 18 kb genomic clone and shown to have 20 exons and 19 introns. Comparison of the structure of the GC-E gene with structures of other membrane guanylate cyclase genes indicates that the GC-E is most closely related to the subfamily of sensory guanylate cyclases. Comparison of the GC-E structure with that of the more distantly related guanylate cyclase isoform A (GC-A) gene shows the most divergence in the extracellular and C-terminal regions, but general conservation of introns and exons in the intracellular kinase-like and catalytic domains. RT-PCR from several bovine tissues shows that GC-E is expressed only in the retina. Consistent with this pattern of expression, elements for the retinal-specific transcription factors RET-1, RET-2 and Talpha-1 are located in the 5' flanking promoter region.

Amino Acid Sequence↗

PubMed1997

Markers of bone and cementum formation accumulate in tissues regenerated in periodontal defects treated with expanded polytetrafluoroethylene membranes.

Guided tissue regeneration (GTR) is a concept that evolved from the development of membrane-barrier techniques, which allow the repopulation of periodontal wounds by specific cells, resulting in a new attachment apparatus. To help understand the biological mechanisms involved in membrane barrier-led periodontal healing, the present study investigated the macromolecules phenotypic of bone and cementum formation in tissues grown under the GTR barrier by immunolocalization. Periodontal regeneration was initiated by placing barriers on experimentally induced periodontal defects in a Rhesus monkey model. Samples were harvested 6 wk after healing and sections of soft tissues grown under GTR barriers (membrane tissue) were stained with antibodies to bone morphogenetic proteins-2 and 4 (BMP-2, BMP-4), bone morphogenetic protein-7 (OP-1), cementum attachment protein (CAP), osteonectin (OTN) and bone sialoprotein (BSP). Tissues grown in the absence of any barrier device served as a control (control tissue). Membrane periodontal tissues from beneath the ePTFE membrane were comprised of spindle-shaped fibroblast-like cells encased in a dense fibrillar extracellular matrix (ECM). Round-shaped cells aggregated to form nodules. Newly formed hard tissue was conspicuous. A similar, but very disorganized, fiber network was observed in control tissues, but neither nodule formation nor hard tissue was observed. Osteonectin staining was observed in the ECM of membrane tissues and particularly in the area of the connective tissue adjacent to newly formed hard tissue. The dense network of connective tissue fibers was also stained. In control tissues, cells and fiber network had a significantly weaker signal for osteonectin. An intense reaction was observed in membrane tissues stained for BSP, particularly the connective tissue adjacent to the newly formed hard tissue, while the control tissues did not stain for BSP. Cementum attachment protein (CAP) was observed in the connective tissue adjacent to the newly formed hard tissue of the membrane tissues whereas control tissues exhibited no CAP staining. In membrane tissues, BMP-2 and 4 distribution was found to concentrate in nodule areas, in the newly formed hard tissue and in the fiber network, while very faint staining was observed in control sections. The distribution of OP-1 in membrane and control tissues was found to mimic the BMP-2 pattern, but staining was more distributed in hard tissue matrix. When the profile of BMP-2, BMP-4, OP-1, OTN, CAP and BSP staining was analyzed on membrane tissue sections, striking similarities were noted in the connective tissue adjacent to the newly formed hard tissue and in nodular areas. In addition, the localization of BMP-2 and BMP-4 mRNA was investigated in both tissues by in situ hybridization. An intense expression of BMP-2 and 4 transcripts was observed in membrane tissues while control tissues never yielded any positive hybridization signal. The correlation between these histochemical findings strongly suggests that the forming soft tissues under ePTFE membranes contain cells and ECM macromolecules normally associated with bone and cementum.

Alveolar Process↗

PubMed1997

Varus and internal rotational deformity of the ankle secondary to distal tibial physeal injury.

Nine children who sustained Lauge-Hansen's supination-inversion injury of distal tibial physeal injury with intact distal fibular physis, were followed until their maturity. The average varus deformity was 39 degrees (maximum, 80 degrees) with 23 degrees of internal rotational deformity. The longitudinal growth of the fibula was retarded compared with opposite normal leg. There was early closure of the medial distal tibial physis, gradual upward migration of medial malleolus, and eventually medial subluxation of the ankle; these resulted in gradual varus and internal rotational deformities of the injured ankle. It is thought that the resultant disabling deformity of ankle should be prevented by any means, though presently there are no available effective methods of treatment. It is suggested that the repeated corrective osteotomy should be carried out before epiphyseal deformity of the distal tibia and subluxation of the ankle joint develop.

Ankle Joint↗

PubMed1997

Valgus ankle secondary to acquired fibular pseudoarthrosis in children. Long-term results of the Langenskiöld operation.

Nine cases of acquired absence of the fibular shaft were studied to determine the growth contribution of the distal fibula; in 6 cases the absence was caused by osteomyelitis and in 3 cases by trauma. The average valgus and external rotational deformities were 15.2 degrees and 10 degrees, respectively. In 3 of 7 cases surgically treated with Langenskiöld operation or supramalleolar corrective osteotomy, the valgus deformity recurred during the postoperative growth period. The speculated causes of gradual valgus deformity are the loss of physiologic thrust from the proximal to distal fibula, the tethering effect of contracted soft tissue on distal fibula and early physeal closure of the lateral part of the distal tibia due to continuous, uneven axial overloading. The Langenskiöld operation was found effective for the stability of ankle joint in the initial period, but could not prevent the postoperative revascularization of the ankle. However, it is strongly recommended that any types of prophylactic surgery should be carried out before the development of an epiphyseal deformity of distal tibia, and to prevent secondary osteoarthritis of the ankle joint.

Adolescent↗

PubMed1996

A status report on helium inductively coupled plasma mass spectrometry.

The current status of helium inductively coupled plasma - mass spectrometry (He ICPMS) is examined, its potentials and limitations are reviewed, and a summary of fundamental properties of atmospheric pressure He ICP discharges is presented. Also included are results of He ICPMS studies with a new helium plasma torch (18 mm i.d.) operated at four sets of operating conditions. Under the "cold plasma" condition (600 W forward power), no secondary discharge is observed and ion kinetic energies ranging from 2.0 eV to 9.5 eV for 6 elements (mass range: 39-208) are measured. At higher power levels, the secondary discharge still is strong. In general, detection limits for certain elements are improved by 1-3 orders of magnitude compared to previous data acquired in 1993 with a 13-mm He ICP torch. Elements such as K, Fe, Cr, Mn, Ni, and Co that suffer from spectral interferences in Ar ICPMS can be detected at pg/mL-levels with an analogue detector and a prototype ICPMS instrument having no photon stops or obstacles present in the ion trajectory path.

Journal Article↗

PubMed1993

Characterization of ribosomal frameshifting for expression of pol gene products of human T-cell leukemia virus type I.

For study of the pol gene expression of human T-cell leukemia virus type I (HTLV-I), RNA was transcribed in vitro from proviral DNA and translated in rabbit reticulocyte lysates. This cell-free translation resulted in two major translation products representing the Gag and Gag-Pro polyproteins. By contrast, the Gag-Pro-Pol polyprotein could be readily observed only when translation was performed with mutant mRNA in which the protease (pro) reading frame was aligned to gag to eliminate the frameshifting event in the gag-pro overlap. The results indicated that two independent ribosomal frameshifting events are required for expression of the HTLV-I pol gene product. Studies with mutant DNAs facilitated the characterization of the primary structure of the HTLV-I mRNA responsible for the ribosomal frameshift in the pro-pol overlap and demonstrated that the frameshift occurs at the signal sequence UUUAAAC. Direct amino acid sequencing of the transframe protein localized the site of the frameshift to the asparagine codon AAC.

Amino Acid Sequence↗

PubMed1989

Identification of HTLV-I gag protease and its sequential processing of the gag gene product.

The full-length provirus of human T-cell leukemia virus type I (HTLV-I) was isolated from MT-2, a lymphoid cell line producing HTLV-I. In transfected cells, structural proteins of HTLV-I, the gag and env products, were formed and processed in the same manner as observed in MT-2 cells. The nucleotide sequence was determined for a region between the gag and pol genes of the proviral DNA clone containing an open-reading frame. The deduced amino acid sequences show that this open-reading frame encodes a putative HTLV-I protease. The protease gene (pro) of HTLV-I was investigated using a vaccinia virus expression vector. Processing of 53k gag precursor polyprotein into mature p19, p24, and p15 gag structural proteins was detectable with a recombinant plasmid harboring the entire gag- and protease-coding sequence. We demonstrated that the protease processed the gag precursor polyprotein in a trans-action. A change in the sequence Asp(64)-Thr-Gly, the catalytic core sequence among aspartyl proteases, to Gly-Thr-Gly was shown to abolish correct processing, suggesting that HTLV-I protease may belong to the aspartyl protease group. The 76k gag-pro precursor polyprotein was identified, implying that a cis-acting function of HTLV-I protease may be necessary to trigger the initial cleavage event for its own release from a precursor protein, followed by the release of p53 gag precursor protein. The p53 gag precursor protein is then processed by the trans-action of the released protease to form p19, p24, and p15.

Amino Acid Sequence↗

PubMed1989

Direct determination of chromium(III) and chromium(VI) with ion chromatography using direct current plasma emission as element-selective detector.

A method is described that utilizes direct current plasma atomic emission spectrometry as an element-selective method of detection for ion chromatographic determination of chromium(III) and chromium(VI) species. The eluting chromium-containing species are detected on the basis of the atomic emission of chromium without any species conversion. Both anion and cation separator columns give similar results when used with varying sample matrices. By employing an on-column preconcentration procedure, the detectable concentrations of the chromium species are reduced to less than 1.0 ppb. This method is applied to the determination of chromium species in human serum, natural water, and industrial process stream samples.

Chromatography↗

PubMed1989

Pulse oximetry during shunt surgery in pediatric patients with tetralogy of fallot.

Pulse oximetry is a noninvasive technique for measuring O2 saturation (SpO2) continuously. We applied pulse oximetry to 9 pediatric patients with tetralogy of Fallot during shunt surgery. Arterial oxygen tensions (PaO2) and saturations (SaO2) were also measured at the time of postinduction, just before the shunt, after the shunt and at the end of the operation. The SpO2 and SaO2 levels were identically changed in all 4 periods. The PaO2 was increased a little without statistical significance after the shunt procedure and at the end of the operation compared with the values before the shunt. However, SaO2 values increased with statistical significance after the shunt procedure and SpO2 values also showed similar increases with significance. In conclusion, continuous monitoring of SpO2 by pulse oximetry, instead of PaO2, is a very useful and reliable method to assess the improvement of perfusion after shunt, particularly in cyanotic cases.

Child, Preschool↗

PubMed1988

Sequence requirements for nucleolar localization of human T cell leukemia virus type I pX protein, which regulates viral RNA processing.

The posttranscriptional regulator (p27x-III) of human T cell leukemia virus type I (HTLV-I) is located predominantly in the cell nucleolus. A highly basic amino-terminal sequence (NH2-Met-Pro-Lys-Thr-Arg-Arg-Arg-Pro-Arg-Arg-Ser-Gln-Arg-Lys-Arg-Pro-Pro -Thr- Pro) in this protein, when fused to the amino termini of beta-galactosidase and p40x of HTLV-I, acts as an autonomous signal capable of directing the hybrid proteins to the cell nucleolus.

Amino Acid Sequence↗

PubMed1988

Processing of gag precursor polyprotein of human T-cell leukemia virus type I by virus-encoded protease.

The biological activity encoded in the putative protease gene (pro) of human T-cell leukemia virus type I was investigated by using a vaccinia virus expression vector. The 53-kilodalton gag precursor polyprotein was processed into the mature p19, p24, and p15 gag proteins when the gag and protease-coding sequence was expressed under the control of a vaccinia virus promoter, suggesting that the protease may be synthesized through the mechanism of ribosomal frame shifting. The processing defect of a protease mutant could be complemented by cointroduction of a wild-type construct into the cell, demonstrating that the pro gene encodes the biologically active protease molecules which are capable of processing the gag precursor polyprotein in vivo in trans. A study involving the use of a variety of mutants constructed in vitro revealed that the protease consists of a nonessential carboxy-terminal region and a part essential for its activity, including the putative catalytic residue, aspartic acid. Furthermore, a cluster of adenine residues positioned at the overlapping region between the gag and pro genes was shown to be involved in the ribosomal frameshifting event for the synthesis of protease. To mimic the formation of the 76-kilodalton gag-pro precursor polyprotein formed by ribosomal slipping, the coding frames of the gag and pro gene were adjusted. The processing of the gag-pro precursor polyprotein depended on an intact protease gene, implying that a cis-acting function of human T-cell leukemia virus type I protease may be necessary to trigger the initial cleavage event that leads to the release of protease from the precursor protein.

Amino Acid Sequence↗