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Biomedical subjects

J K Kim

Publications and source records attributed to J K Kim.

At least 55 records · Page 3Linked to original sources
PubMed2001

Insulin resistance and a diabetes mellitus-like syndrome in mice lacking the protein kinase Akt2 (PKB beta).

Glucose homeostasis depends on insulin responsiveness in target tissues, most importantly, muscle and liver. The critical initial steps in insulin action include phosphorylation of scaffolding proteins and activation of phosphatidylinositol 3-kinase. These early events lead to activation of the serine-threonine protein kinase Akt, also known as protein kinase B. We show that mice deficient in Akt2 are impaired in the ability of insulin to lower blood glucose because of defects in the action of the hormone on liver and skeletal muscle. These data establish Akt2 as an essential gene in the maintenance of normal glucose homeostasis.

Animals↗
PubMed2001

Generation of macrophages from early T progenitors in vitro.

Early T progenitors in the thymus have been reported to have the capacity to develop into B cells, thymic dendritic cells, and NK cells. Here we describe conditions that induce early T progenitors to develop into macrophages. Initially, we observed that early T progenitors could be induced to develop into macrophages by cytokines produced from a thymic stromal cell line, TFGD, and later we found that the cytokine mixture of M-CSF plus IL-6 plus IL-7 also induced macrophage differentiation from pro-T cells. M-CSF by itself was unable to induce macrophage differentiation from early T progenitors. To correlate this observation with the developmental potential of early T progenitors, mouse embryonic thymocytes were sorted into four populations, pro-T1 to pro-T4, based on the expression of CD44 and CD25, and then cultured with TFGD culture supernatant. We found that pro-T1 and pro-T2 cells, but not pro-T3 and pro-T4 cells, generate macrophages. Limiting dilution analysis of the differentiation capability of sorted pro-T2 cells also confirmed that pro-T2 cells could generate macrophages. These results suggest that T cells and thymic macrophages could originate from a common intrathymic precursor.

Animals↗
PubMed2001

Curcuminoids from Curcuma longa L. (Zingiberaceae) that protect PC12 rat pheochromocytoma and normal human umbilical vein endothelial cells from betaA(1-42) insult.

beta-Amyloid (betaA) induced oxidative stress is a well-established pathway of neuronal cell death in Alzheimer's disease. From turmeric, Curcuma longa L. (Zingiberaceae), three curcuminoids, curcumin, demethoxycurcumin, and bisdemethoxycurcumin, were found to protect PC12 rat pheochromocytoma and normal human umbilical vein endothelial (HUVEC) cells from betaA(1-42) insult, as measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction assay. ED(50) values of curcumin, demethoxycurcumin, and bisdemethoxycurcumin toward PC12 and HUVEC cells were 7.1+/-0.3, 4.7+/-0.1, 3.5+/-0.2 microg/ml and 6.8+/-0.4, 4.2+/-0.3, and 3.0+/-0.3 microg/ml, respectively. These compounds were better antioxidants than alpha-tocopherol as determined by DPPH radical trapping experiment. alpha-Tocopherol did not protect the cells from betaA(1-42) insult even at>50 microg/ml concentration. The results suggest that these compounds may be protecting the cells from betaA(1-42) insult through antioxidant pathway.

Alzheimer Disease↗
PubMed2001

Overexpression of the LAR (leukocyte antigen-related) protein-tyrosine phosphatase in muscle causes insulin resistance.

Previous reports indicate that the expression and/or activity of the protein-tyrosine phosphatase (PTP) LAR are increased in insulin-responsive tissues of obese, insulin-resistant humans and rodents, but it is not known whether these alterations contribute to the pathogenesis of insulin resistance. To address this question, we generated transgenic mice that overexpress human LAR, specifically in muscle, to levels comparable to those reported in insulin-resistant humans. In LAR-transgenic mice, fasting plasma insulin was increased 2.5-fold compared with wild-type controls, whereas fasting glucose was normal. Whole-body glucose disposal and glucose uptake into muscle in vivo were reduced by 39-50%. Insulin injection resulted in normal tyrosyl phosphorylation of the insulin receptor and insulin receptor substrate 1 (IRS-1) in muscle of transgenic mice. However, phosphorylation of IRS-2 was reduced by 62%, PI3' kinase activity associated with phosphotyrosine, IRS-1, or IRS-2 was reduced by 34-57%, and association of p85alpha with both IRS proteins was reduced by 39-52%. Thus, overexpression of LAR in muscle causes whole-body insulin resistance, most likely due to dephosphorylation of specific regulatory phosphotyrosines on IRS proteins. Our data suggest that increased expression and/or activity of LAR or related PTPs in insulin target tissues of obese humans may contribute to the pathogenesis of insulin resistance.

Animals↗
PubMed2001

Induction and repair of DNA damage as measured by the Comet assay and the yield of somatic mutations in gamma-irradiated tobacco seedlings.

The advantage of using the tobacco (Nicotiana tabacum var. xanthi) mutagenicity assay is the ability to analyze and compare on the same plants under identical treatment conditions both the induced acute DNA damage in somatic cells as measured by the Comet assay and the yield of induced leaf somatic mutations. Gamma-irradiation of tobacco seedlings induced a dose-dependent increase in somatic mutations from 0.5 (control) to 240 per leaf (10Gy). The increased yield of somatic mutations was highly correlated (r = 0.996) with the increased DNA damage measured by the Comet assay immediately after irradiation. With increased dose of gamma-irradiation, the averaged median tail moment values ( +/- S.E.) significantly increased from 1.08 +/- 0.10 (control) to 20.26 +/- 1.61 microm (10Gy). Nuclei isolated from leaves 24h after irradiation expressed tail moment values that were not significantly different from the control (2.08 +/- 0.11). Thus a complete repair of DNA damage induced by gamma-irradiation and measurable by the Comet assay was observed, whereas the yield of somatic mutations increased in relation to the radiation dose. Data on the kinetics of DNA repair and of DNA damage induced by gamma-radiation on isolated tobacco nuclei, and on nuclei isolated from irradiated leaves and roots are presented.

Comet Assay↗
PubMed2001

Characterization of mouse brain-specific angiogenesis inhibitor 1 (BAI1) and phytanoyl-CoA alpha-hydroxylase-associated protein 1, a novel BAI1-binding protein.

Previously, PAHX-AP1 (PAHX-associated protein 1) was isolated as a novel protein to interact with Refsum disease gene product (phytanoyl-CoA alpha-hydroxylase, PAHX) and specifically expressed in mouse brain. PAHX-AP1 is also suggested to be involved in the development of the central neurologic deficits of Refsum disease. To clarify its function, we have searched for proteins that associate with PAHX-AP1 via yeast two-hybrid system. We found that PAHX-AP1 interacts with the cytoplasmic region of human brain-specific angiogenesis inhibitor 1 (hBAI1), and isolated murine homolog of hBAI1. Structural analysis of the PAHX-AP1 with three reported hBAI-associated proteins (BAP) revealed no homology among them, and we designated PAHX-AP1 as BAP4. The ability of BAP4 to interact with BAI1 was confirmed by pulling-down BAI1 with GST-BAP4 protein and immunoprecipitation study using brain lysate. Northern and Western blot analyses demonstrated a unique pattern of BAI1 expression in the brain. The peak level of BAI1 was observed 10 days after birth. In situ hybridization analyses of the brain showed the same localization of BAI1 as BAP4, such as most neurons of cerebral cortex, hippocampus, and V, VI, VII, VIII, and XII nuclei. Because BAI1 possessed thrombospondin-type 1 repeats in its extracellular region, changes of BAI1 expression were examined in the focal cerebral ischemia model. The BAI1 expression decreased on the ischemic side after 24 h but BAP4 was not changed after the time-course of ischemia. Our results indicate that expression and localization of BAI1 in the brain is correlated with BAP4, and that BAI1 is involved in inhibition of angiogenesis and neuronal differentiation.

Angiogenesis Inhibitors↗
PubMed2001

Relative biological efficiency for the induction of various gene mutations in normal and enriched with 10B Tradescantia cells by neutrons from 252Cf source.

The effectiveness of neutrons from a Californium-252 source in the induction of various abnormalities in the Tradescantia clone 4430 stamen hair cells (Trad-SH assay) were studied. A special attention was paid to check whether any enhancement in effects is visible in the cells enriched with boron ions. Inflorescences, normal or pretreated with chemicals containing boron, were irradiated in the air with neutrons from a 252Cf source at KAERI, Taejon, Korea. To estimate the relative biological effectiveness (RBE) of the beam under the study, numbers of Tradescantia inflorescence without chemical pretreatment were irradiated with various doses of X-rays. The ranges of radiation doses used for neutrons were 0-1.0Gy and for X-rays 0-0.5Gy. Following the culturing according to standard procedures screening of gene and lethal mutations in somatic cells of stamen hairs was done in the extended period, between days 7 and 19 after exposures. Maximal RBE values for the induction of pink, colorless and lethal mutations were evaluated from comparison of the slopes in linear parts of the dose response curves obtained after irradiation with X-rays and californium source. The RBE(max) value or the induction of gene mutation was estimated as 7.2 comparing the value 5.6 in the studies reported earlier. The comparison of dose-response curves and its alteration, due to changes in the cells and plants environment during and after irradiation, explains the observed differences. Inflorescence pretreated with borax responded to neutrons differently depending on the biological end points. Although, for the induction of pink mutations no significant difference was observed, though, in the case of cell lethality, pretreated with boron ion plants have shoved a statistically significant increase of the RBE value from 5.5 to 34.7, and in the case of colorless mutations from 1.6 to 5.6.

Boron↗
PubMed2001

Adipose-selective targeting of the GLUT4 gene impairs insulin action in muscle and liver.

The earliest defect in developing type 2 diabetes is insulin resistance, characterized by decreased glucose transport and metabolism in muscle and adipocytes. The glucose transporter GLUT4 mediates insulin-stimulated glucose uptake in adipocytes and muscle by rapidly moving from intracellular storage sites to the plasma membrane. In insulin-resistant states such as obesity and type 2 diabetes, GLUT4 expression is decreased in adipose tissue but preserved in muscle. Because skeletal muscle is the main site of insulin-stimulated glucose uptake, the role of adipose tissue GLUT4 downregulation in the pathogenesis of insulin resistance and diabetes is unclear. To determine the role of adipose GLUT4 in glucose homeostasis, we used Cre/loxP DNA recombination to generate mice with adipose-selective reduction of GLUT4 (G4A-/-). Here we show that these mice have normal growth and adipose mass despite markedly impaired insulin-stimulated glucose uptake in adipocytes. Although GLUT4 expression is preserved in muscle, these mice develop insulin resistance in muscle and liver, manifested by decreased biological responses and impaired activation of phosphoinositide-3-OH kinase. G4A-/- mice develop glucose intolerance and hyperinsulinaemia. Thus, downregulation of GLUT4 and glucose transport selectively in adipose tissue can cause insulin resistance and thereby increase the risk of developing diabetes.

Adipocytes↗
PubMed2001

SPIN90 (SH3 protein interacting with Nck, 90 kDa), an adaptor protein that is developmentally regulated during cardiac myocyte differentiation.

In the yeast two-hybrid screening, we have isolated a cDNA clone from a human heart library using Nck Src homology 3 (SH3) domains as bait. The full-length cDNA, which encoded 722 amino acids, was identified as a VIP54-related gene containing an SH3 domain, proline-rich motifs, a serine/threonine-rich region, and a long C-terminal hydrophobic region. We refer to this protein as SPIN90 (SH3 Protein Interacting with Nck, 90 kDa). The amino acid sequence of the SH3 domain has the highest homology with those of Fyn, Yes, and c-Src. SPIN90 was broadly expressed in human tissues; in particular, it was highly expressed in heart, brain, and skeletal muscle, and its expression was developmentally regulated during cardiac myocyte differentiation. SPIN90 is able to bind to the first and third SH3 domains of Nck, in vitro, and is colocalized with Nck at sarcomere Z-discs within cardiac myocytes. Moreover, treatment with antisera raised against SPIN90 disrupted sarcomere structure, suggesting that this protein may play an important role in the maintenance of sarcomere structure and/or in the assembly of myofibrils into sarcomeres.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Dissolution of poorly crystalline apatite crystals by osteoclasts determined on artificial thin-film apatite.

Poorly crystalline apatite (PCA) crystals introduced into bone tissue should be stable for a definite period before they are dissolved as a result of a host response. In this report, the dissolution of PCA crystals by the action of osteoclasts was studied on artificial thin films. These consisted of PCA crystals having similar crystallographic properties to bone crystals which were developed for assaying the osteoclast activity in vitro. The dissolution of minerals by osteoclasts decreased along with the decreased amount of labile phosphate and hydrogen phosphate domains of apatite crystals, which were caused by the crystal maturation temperature. A profound effect on mineral dissolution by pH in the culture medium was also shown. Low acidity considerably increased mineral dissolution, whereas a slight alkalinity totally blocked mineral dissolution. There was little difference in the mineral dissolution behavior of osteoclasts near the physiologic pH. In addition, it was determined whether mineral dissolution by osteoclasts was dependent on the destruction of the organic matrix. Nocodazole was introduced to inhibit the secretion of hydrolytic enzymes, and acetazolamide was added to inhibit acid production by the osteoclasts. There was no significant change as a result of nocodazole addition on mineral dissolution or by the addition of acetazolamide on degradation of collagen. These results indicate that small changes in the physicochemical properties of apatite crystals can decrease resorption by osteoclasts, which can be highly activated at low pH. These results also suggest that mineral dissolution and organic degradation by osteoclasts are self-regulating.

Acetazolamide↗
PubMed2001

Influence of enterotoxin on mucosal intranet: selective inhibition of extrathymic T cell development in intestinal intraepithelial lymphocytes by oral exposure to heat-labile toxin.

We tested the possibility that heat-labile enterotoxin of Escherichia coli (LT) affects the development of extrathymic T cells in the intraepithelial lymphocyte (IEL) compartment. After oral administration of LT, the number of extrathymic CD8alphaalpha+ IEL was selectively and significantly diminished when compared with the corresponding cells in phosphate-buffered saline-fed control mice. To clarify the mechanism behind this selective reduction of CD8alphaalpha+ IEL, we analyzed the expression of essential cytokines and their corresponding receptors for the mucosal intranet formed by intestinal epithelial cells (IEC) and IEL. The expression levels of stem cell factor, interleukin (IL)-7, and IL-15 in IEC, and their corresponding receptors, i. e. c-kit, IL-7 receptor, and IL-15 receptor, in CD8alphaalpha+ IEL were reduced following oral feeding with LT. These findings suggest that LT negatively regulates development of CD8alphaalpha+ IEL via the disruption of mucosal intranet-associated cytokine and cytokine receptors, which are required for the development and/or expansion of extrathymically developed T cells. Further, LT-induced destruction of the mucosal intranet resulted in the impairment of IEC generation via an increase of apoptosis.

Administration, Oral↗
PubMed2001

Ovarian expression of melatonin Mel(1a) receptor mRNA during mouse development.

Melatonin, secreted by the pineal gland, is involved in the regulation of many physiological functions of various species of animals. In the present study, the expression of gene for melatonin Mel(1a) receptor (MelR) was evaluated in the ovary, hypothalamus, and pituitary according to the developmental stages in female mice. Semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) and in situ PCR techniques were applied. According to the developmental stages, gene for MelR was differently expressed on ovary, hypothalamus, and pituitary. MelR gene was first expressed on pituitary prior to the expression in hypothalamus and ovary. Ovarian MelR gene started to express at birth. Unlike hypothalamic expression of MelR gene which was identified after birth, in pituitary, it was expressed at 16 days post coitum. In the ovary, the expression signal of MelR gene was identified on granulosa cells. However, the signal was not detected in the theca cells. It was weak in the primordial and atretic follicles. Taken together, it can be considered that melatonin has a pivotal role in the folliculogenesis.

Animals↗
PubMed2001

Differential distribution of ganglioside GM3 in seminiferous tubule and epididymis of adult rats.

Gangliosides are ubiquitous membrane components in mammalian cells and are suggested to play important roles in various functions such as cell-cell interaction, adhesion, cell differentiation, growth control and signaling. Among all ganglio-series gangliosides, GM3 has the simplest carbohydrate structure, and has been shown as a major ganglioside in male reproductive system. To study GM3 distribution in the seminiferous tubule and epididymis, frozen sections were stained with specific monoclonal antibody (MAb) against ganglioside GM3. In the seminiferous tubule of testis, pachytene spermatocytes and spermatids expressed ganglioside GM3, but not in spermatogonia and sertoli cells. Spermatogonia and sertoli cells near the basement membrane were negatively reacted to anti-GM3. In the epididymis, GM3 was expressed only in some interstitial cells. Taken together, these results suggest that the expression of ganglioside GM3 in rat seminiferous tubule and epididymis is spatio-temporally regulated during spermatogenesis.

Animals↗
PubMed2001

Mechanism of refractory ceramic fiber- and rock wool-induced cytotoxicity in alveolar macrophages.

OBJECTIVES: Man-made vitreous fibers (MMVFs) can induce cytotoxicity in a way similar to that of other particles, including silica and asbestos fibers. However, as yet the mechanism of MMVF-induced cytotoxicity is still not clear. This report aims to clarify the mechanism of MMVF-induced cytotoxicity in the alveolar macrophage (AM). In this mechanism, an attempt to prove the involvement of the adenosine triphosphate (ATP) generation system and the polyinosinic acid-inhibitable scavenger receptors was made. METHODS: Several parameters were observed for cytotoxicity, such as cell viability, the release of lactic dehydrogenase (LDH) and ATP levels in rat AM's that were treated with refractory ceramic fibers (RF2) and rock wool (RW1). A specially designed ATP generation system was used to determine the effect of MMVF on ATP generation. A scavenger receptor ligand was applied to evaluate the relationship between scavenger receptors and MMVF-induced ATP depletion. RESULTS: A 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay indicated that both RF2 and RW1 caused a decrease in cell viability and this decrease was concentration-dependent. RF2 and RW1 increased the release of LDH with increasing fiber concentration. From these parameters, RF2 was shown to exhibit greater cytotoxicity than did RW1. Both fibers decreased the intracellular ATP content and this decrease was concentration-dependent. The decrease was more pronounced in RW1 than in RF2 at all fiber concentrations. These fibers suppressed succinate-triggered oxygen consumption. Polyinosinic acid, a ligand of the scavenger receptor, inhibited the MMVF-induced decrease in ATP concentration. CONCLUSION: These results suggest that RF2 and RW1 can induce cytotoxicity and ATP depletion in the AM through the polyinosinic acid-inhibitable scavenger receptor. ATP depletion was the important factor in MMVF cytotoxicity, especially by RW1.

Adenosine Triphosphate↗
PubMed2001

Expression of brain-derived neurotrophic factor in rat dorsal root ganglia, spinal cord and gracile nuclei in experimental models of neuropathic pain.

Chronic constriction injury of the sciatic nerve and lumbar L5 and L6 spinal nerve ligation provide animal models for pain syndromes accompanying peripheral nerve injury and disease. In the present study, we evaluated changes in brain-derived neurotrophic factor (BDNF) immunoreactivity in the rat L4 and L5 dorsal root ganglia (DRG) and areas where afferents from the DRG terminates (the L4/5 spinal cord and gracile nuclei) in these experimental models of neuropathic pain. Chronic constriction injury induced significant increase in the percentage of small, medium and large BDNF-immunoreactive neurons in the ipsilateral L4 and L5 DRG. Following spinal nerve ligation, the percentage of large BDNF-immunoreactive neurons increased significantly, and that of small BDNF-immunoreactive neurons decreased markedly in the ipsilateral L5 DRG, while that of BDNF-immunoreactive L4 DRG neurons of all sizes showed marked increase. Both chronic constriction injury and spinal nerve ligation induced significant increase in the number of BDNF-immunoreactive axonal fibers in the superficial and deeper laminae of the L4/5 dorsal horn and the gracile nuclei on the ipsilateral side. Considering that BDNF may modulate nociceptive sensory inputs and that injection of antiserum to BDNF significantly reduces the sympathetic sprouting in the DRG and allodynic response following sciatic nerve injury, our results also may suggest that endogenous BDNF plays an important role in the induction of neuropathic pain after chronic constriction injury and spinal nerve ligation. In addition, the increase of BDNF in L4 DRG may contribute to evoked pain which is known to be mediated by input from intact afferent from L4 DRG following L5 and L6 spinal nerve ligation.

Animals↗
PubMed2001

Selection of a potential probiotic Lactobacillus strain and subsequent in vivo studies.

The probiotic potential of a Lactobacillus strain, isolated from pig faeces, was assessed as a probiotic in piglets. The strain was examined for resistance to pH 2.0, 0.5% oxgall and antibiotics, and antimicrobial activities against enteric pathogenic bacteria. The probiotic strain, L. reuteri BSA131, was administered through the feed to 25 1-month-old Landrace piglets. The piglets were divided into five groups of five piglets each and fed with different diets for 28 days. The daily consumption of L. reuteri BSA131 was assigned into two groups by the concentration of 10(6) or 10(8) freeze-dried bacteria. Fecal samples were collected before, during, and after consumption. Lactobacilli and enterobacteria cell counts were determined in the fecal samples. The liveweight gains and feed consumption of the piglets were recorded daily. This study showed that strain BSA131 enhanced liveweight gains and feed conversion rates in piglets. It also showed a significant increase in lactobacilli cell counts and decreases in enterobacterial numbers in the fecal samples. Strain BSA131 was considered to be a potential probiotic for piglets, especially after weaning.

Animal Feed↗
PubMed2001

Peritoneal dialysis in diabetic patients.

Diabetic nephropathy is the leading cause of end-stage renal disease worldwide. Although death rates of diabetic patients on hemodialysis and peritoneal dialysis (PD) have decreased substantially, they remain higher than rates in nondiabetics on both modalities. PD offers equal or better survival than hemodialysis for younger diabetic patients during early years of dialysis. PD technique survival does not appear different between diabetic and nondiabetic patients but is inferior to hemodialysis technique survival. PD may accelerate changes in peritoneal membrane structure and function in diabetics. Peritonitis and conventional PD solutions containing high glucose and glucose degradation products are implicated in PD technique failure. Increased peritoneal expression of vascular endothelial growth factor and transforming growth factor-beta1 and excessive accumulation of advanced glycosylation end products may be involved in the progressive increase in membrane permeability, loss of ultrafiltration, and peritoneal fibrosis. Nonglucose PD solutions or solutions containing low glucose degradation products may prevent or delay alterations in peritoneal membrane structure and function in diabetic as well as nondiabetic patients during long-term PD.

Diabetic Nephropathies↗