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Biomedical subjects

K M Lim

Publications and source records attributed to K M Lim.

10 recordsLinked to original sources
PubMed2005

Plant uptake and downward migration of 85Sr and 137Cs after their deposition on to flooded rice fields: lysimeter experiments with and without the addition of KCl and lime.

In order to study the plant uptake and downward migration of radiostrontium and radiocesium deposited on to a flooded rice field, 85Sr and 137Cs were applied to the standing water over an acidic sandy soil in planted lysimeters. The plant uptake was quantified with the areal transfer factor (TFa, m2 kg(-1)-dry plant). Following the spiking 14 days after transplanting, the TFa values for the hulled seeds were 3.9 x 10(-4) for 85Sr and 1.4 x 10(-4) for 137Cs, whereas those for the straws were 1.3 x 10(-2) and 3.2 x 10(-4), respectively. The 137Cs TFa from the spiking at the anthesis/milky-ripe stage was several times higher than that from the earlier spiking, whereas the difference was much less in the 85Sr TFa. Such an increase in the 137Cs TFa was attributed mainly to an enhanced plant-base uptake. The addition of KCl and lime after the spiking significantly reduced the TFa values of both radionuclides. The reducing effect was greater for the later spiking. An appreciable fraction of the applied activity leached out of the lysimeter for 85Sr, whereas a negligible fraction leached for 137Cs. The leaching was remarkably increased by the KCl and lime addition for both. A conspicuous localization of 137Cs with respect to the soil surface was observed. In a batch experiment, the 137Cs concentration in the standing water decreased more rapidly than that of 85Sr, both of which were fitted to the power functions of the elapsed time. To add KCl and lime slowed such decreases to lessen the distribution coefficients (Kd) of both 85Sr and 137Cs.

Biological Transport↗
PubMed2005

Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages.

Soil blocks from 18 paddy fields around three Korean nuclear power plant sites were put into lysimeters. Greenhouse experiments were carried out to investigate the (137)Cs transfer from these paddy soils to rice plants for its deposition at different growth stages. A solution of (137)Cs was applied to the flooded lysimeters at 2-3 different stages. The applied (137)Cs was mixed with the topsoil only at the pre-transplanting application. The transfer was quantified with a transfer factor based on the unit-area deposition (TF(a), m(2)kg(-1)-dry). The TF(a) in the pre-transplanting application showed a remarkable variation with the soils. However, the differences in the mean values among the study sites were not statistically significant. The straw TF(a) was 2-3 times higher than the corresponding seed value. The early-tillering stage and booting stage applications resulted in a higher transfer than the pre-transplanting application by factors of, on an average, 2 and 16 for the straws, and 3 and 25 for the hulled seeds, respectively. The (137)Cs transfer was found to correlate negatively with the soil pH and positively with the organic matter content. Based on the present results, the representative (137)Cs TF(a) values for the rice are proposed for use in the whole of Korea for the deposition at three different growth stages.

Cesium Radioisotopes↗
PubMed2002

Induction of marked apoptosis in mammalian cancer cell lines by antisense DNA treatment to abolish expression of DENN (differentially expressed in normal and neoplastic cells).

We previously reported the isolation of the novel human DENN gene, which is differentially expressed in normal and neoplastic cells. DENN is identical to MADD (mitogen-activated protein kinase-activating death domain), which interacts with tumor necrosis factor receptor 1 through their death domains. DENN is also homologous to Rab3 GEP, a rat Rab3 GDP/GTP exchange protein. Real-time reverse transcription-polymerase chain reaction analysis showed that DENN expression in cancer cell lines was 26-50 times that in normal cells. The Jurkat human leukemia, PLC/PRF/5 human hepatoma, and NS-1 mouse myeloma cell lines as well as the MRC-5 human fetal lung and Vero monkey kidney cell lines were treated successfully with four separate DENN-targeted antisense oligodeoxynucleotides (ODNs) to abrogate DENN expression. Quantitative assessment of cell viability and apoptosis by flow cytometry via fluorescein diacetate and propidium iodide membrane-integrity tests, terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate-biotin nick end-labeling, and annexin V assays showed that antisense silencing of DENN resulted in markedly more pronounced cell death in cancer cells compared with nonmalignant cells. Antisense-treated cell lines exhibited extensive loss of DNA content, forming distinct sub-G(1) peaks, while cell proliferation diminished significantly. Ultrastructural features of programmed cell death in cells subjected to antisense ODNs were authenticated by electron microscopy. In contrast, transfection of cell lines with a plasmid construct to achieve DENN overexpression augmented cellular proliferation and could reverse the apoptotic effect of antisense and staurosporine treatment. Our findings suggest that DENN is intimately involved in anti-apoptotic and cell-survival processes.

Animals↗
PubMed2002

Tissue free water tritium and organically bound tritium in the rice plant acutely exposed to atmospheric HTO vapor under semi-outdoor conditions.

Potted rice plants were exposed to atmospheric HTO in a box outdoors for 1 h at 9 different times from booting to yellow-ripe stages. It is indicated that the leaf TFWT concentration may reach equilibrium within 1 h in clear weather. The plant TFWT concentration decreased at a rapid rate for the first several hours and at a much slower rate thereafter. The decrease till harvest was by factors of 600-95,000 depending on the plant parts and exposure times. The time course of the ear OBT concentration was characterized by the exposure time. After exposure at the booting to heading stages, the leaf OBT concentration decreased rapidly for the first several hours and then very slowly. The plant OBT concentration was initially about 2 orders of magnitude lower, but at harvest an order of magnitude higher, than the TFWT concentration. The OBT concentration in hulled seeds at harvest varied with exposure times by a factor of 70, being highest in the exposure performed at the earlier stage of rapid grain growth. Also in this exposure, the plant total OBT was greatest due to the seed OBT.

Environmental Exposure↗
PubMed1999

Prostaglandin H synthase and lipoxygenase mediated activation of xenobiotics in platelets.

To investigate the involvement of prostaglandin H synthase (PHS) and lipoxygenase (LPO) in the activation of xenobiotics in platelets, platelet sonicates were preincubated with alpha-naphthol. Protein covalent binding of alpha-naphthol was measured following addition of arachidonic acid. Protein covalent binding was increased in a dose-dependent manner until it plateaued at 500 microM arachidonic acid. Pretreatment by two inhibitors of PHS, aspirin and indomethacin, resulted in a dose-dependent inhibition of alpha-naphthol-induced covalent binding, confirming PHS involvement. In addition, pretreatment by a LPO inhibitor, nordihydroguaiaretic acid (NDGA), also prevented covalent binding substantially, showing that LPO may be an alternative pathway for xenobiotic activation in platelets. Furthermore, combined treatment of aspirin and NDGA almost abolished the increase of alpha-naphthol-induced covalent binding, suggesting that PHS and LPO are both major pathways for xenobiotic activation in platelets.

Animals↗
PubMed1998

The human DENN gene: genomic organization, alternative splicing, and localization to chromosome 11p11.21-p11.22.

We have previously isolated and sequenced the cDNA of a novel gene, DENN, that exhibits differential mRNA expression in normal and neoplastic cells. The open reading frame of 4761 nucleotides encodes a putative hydrophilic protein of 1587 amino acids with a calculated molecular mass of 176,431 Da. Within DENN cDNA lies an alternative exon segment of 129 nucleotides encoding 43 amino acids, which may be excluded from some transcripts by alternative splicing. The serine- and leucine-rich DENN protein possesses a RGD cellular adhesion motif and a leucine-zipper-like motif associated with protein dimerization, and shows partial homology to the receptor binding domain of tumor necrosis factor alpha. DENN is virtually identical to MADD, a human MAP kinase-activating death domain protein that interacts with type I tumor necrosis factor receptor. DENN displays significant homology to Rab3 GEP, a rat GDP/GTP exchange protein specific for Rab3 small G proteins implicated in intracellular vesicle trafficking. DENN also exhibits strong similarity to Caenorhabditis elegans AEX-3, which interacts with Rab3 to regulate synaptic vesicle release. Composed of 15 exons (ranging in size from 73 to 1230 bp) and 14 introns (varying from about 170 bp to 5.3 kb), the DENN gene is estimated to span at least 28 kb. The alternative splicing event was traced to an alternative 5' donor site involving exon 7. DENN was mapped to chromosome region 11p11.21-p11.22 by FISH. Using polyclonal antibodies against a synthetic peptide, Western blotting of MOLT-4 T-lymphoblastic leukemic cell proteins and immunoblotting of subcellular fractions of MOLT-4 cells and PLC/PRF/5 liver cancer cells yielded data corroborating the alternative splicing mechanism that generates two variant isoforms of the DENN protein that display differential expression in cells of different lineages.

Alternative Splicing↗
PubMed1991

Determinants of spatial priming in environmental memory.

Spatial priming in recognizing objects in experimentally learned environments has been proposed as strong evidence for spatial organization of environmental memory. However, in all studies showing recognition priming effects, encoding and rehearsal contiguity may have coincided with spatial proximity, and thus priming may have been due to temporal associations formed during rehearsal, not encoded spatial relations per se. We investigated this question in four experiments, using a trip trial learning method in which temporal contiguity and spatial relations were independent. In Experiment 1, no spatial priming in recognition was found, even though indirect evidence suggested that subjects had encoded spatial relations. In Experiment 2, the trip trial method was compared with the free study procedure commonly used in previous priming studies. Spatial priming occurred only for free study subjects, even though the two groups were equivalent on direct measures of encoding accuracy. In Experiment 3, spatial priming in recognition was obtained with a modification of the trip trial method in which temporal and spatial contiguity were deliberately confounded. In Experiment 4, the unmodified trip trial method produced spatial priming in a location-decision task. Taken together, our results suggest that environmental memory may be spatially organized, but retrieval of object identities does not necessarily activate encoded spatial relations.

Adult↗
PubMedDate not supplied

Superior vena cava syndrome and tracheal obstruction due to multinodular goiter.

Tracheal obstruction and superior vena cava (SVC) syndrome are rare complications of retrosternal goiter. These two conditions present a difficult diagnostic and therapeutic challenge. Malignancy is the most common cause of SVC syndrome. Determining whether SVC syndrome is due to a benign or malignant process is imperative before instituting treatment, but this determination may be difficult. We present a case of a patient presenting with upper airway obstruction and SVC syndrome with a large mediastinal mass. The mass was determined to be a multinodular goiter. The patient was managed by surgical removal of the goiter with complete resolution of symptoms. This case illustrates the need for careful preoperative evaluation and the importance of establishing a histologic diagnosis prior to initiating treatment for SVC syndrome.

Airway Obstruction↗
PubMedDate not supplied

Cochlear model with three-dimensional fluid, inner sulcus and feed-forward mechanism.

A three-dimensional model of the guinea pig cochlea using the phase-integral method is presented. This model incorporates the viscous fluid effects in the cochlea, dimensional and material property variation along the cochlear duct and the active feed-forward mechanism of the outer hair cells. Two degrees of freedom of the basilar membrane are considered, which results in two traveling waves propagating along the duct for a given frequency. Basilar membrane response with the active feed-forward mechanism compares favorably with published experimental measurements.

Acoustic Stimulation↗