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J Y Kwon

Publications and source records attributed to J Y Kwon.

At least 19 recordsLinked to original sources
PubMed2003

Cloning and gene expression of P450 17alpha-hydroxylase,17,20-lyase cDNA in the gonads and brain of the fathead minnow Pimephales promelas.

P450 17alpha-hydroxylase,17,20-lyase (P450c17) is a key steroidogenic enzyme in the production of androgens and, therefore, is also indispensable for the production of oestrogens (that are produced from the aromatisation of androgens). In this study, P450c17 cDNA was cloned from the ovary of the fathead minnow (FHM) and its gene expression was examined in the gonads and brains of male and female FHM at different stages of gonadal development with a view to developing an understanding of its involvement in the reproductive physiology in this species. The FHM-P450c17 cDNA sequence cloned was 1812 bp in length, with an open reading frame of 1554 nucleotides encoding a protein of 518 amino acids. Amino acid identity of FHM-P450c17 with P450c17s in other animals was up to 81.8% in other teleosts (channel catfish), 62% in elasmobranches (spiny dogfish), 64% in birds (chicken), and up to 48.8% in mammals (human). FHM-P450c17 gene expression occurred in the ovary, testis, and also in the brain (both male and female) at all stages of sexual development studied. Expression in the brain was at least 30-fold lower than in the gonads, but consistent in all fish life stages studied. In the testis, FHM-P450c17 gene expression was negatively correlated with gonadal development, but there was no obvious association between P450c17 gene expression and sexual development in the ovary, or brain (in both males and females). The results from this study demonstrate the expression of P450c17 in the brain for the first time in fish. Enzymatic studies are now needed to investigate the possible role of P450c17 in neurosteroid production in teleosts.

Amino Acid Sequence↗
PubMed2003

Physical mapping of the brain and ovarian aromatase genes in the Nile Tilapia, Oreochromis niloticus, by fluorescence in situ hybridization.

Cytochrome P450-aromatase enzyme (CYP19), which catalyses the conversion of androgens to oestrogens, is critical in ovarian differentiation and hence in the sex differentiation pathways of non-mammalian vertebrates. As in other fish species, distinct ovarian and brain aromatase genes have been identified in the Nile Tilapia, Oreochromis niloticus. Here we demonstrate by in situ hybridization that the two aromatase genes of this species are present on different chromosomes and that neither are located on the sex chromosomes. Hence, the aromatase genes are not the primary sex determination genes in O. niloticus.

Animals↗
PubMed2001

The MED-7 transcriptional mediator encoded by let-49 is required for gonad and germ cell development in Caenorhabditis elegans.

Transcription mediators are evolutionarily conserved from yeast to human. We previously reported the specific in vivo roles of mediators during development. Transcriptional mediators including med-6, med-7, and med-10 were shown to be involved in the regulated transcription of specific genes, but not in the transcription of ubiquitous genes. In this report we have identified and characterized the Caenorhabditis elegans med-7 gene. A genetic mutation in the med-7 gene was identified by comparing genetic and physical maps and determining the molecular lesion. let-49 was found to have a nonsense mutation in the coding region of the med-7 gene. The identification of let-49 as the med-7 gene was confirmed by rescue experiments. The phenotype of the let-49 mutation indicated that the med-7 gene is required for normal postembryonic development. RNAi experiments showed that med-7 is also involved in embryogenesis and the gonad and germ cell development.

Animals↗
PubMed2001

Cloning of brain aromatase gene and expression of brain and ovarian aromatase genes during sexual differentiation in genetic male and female Nile tilapia Oreochromis niloticus.

A brain aromatase gene was identified from the Nile tilapia Oreochromis niloticus. The cDNA sequence of this gene differed from that of the ovarian aromatase gene previously reported from this species. Tissue specific expression for both brain and ovarian aromatase genes was examined in the tissues of adult tilapia. Brain aromatase mRNA was expressed in the brain, kidney, eye, ovary, and testis, but not in the liver and spleen. Ovarian aromatase mRNA was expressed in the brain, spleen, ovary, and testis but not in the eye, kidney, and liver. Differential aromatase gene expression between the sexes was investigated in all-male (XY) and all-female (XX) groups of tilapia fry from fertilisation throughout the sexual differentiation period. Semi-quantitative RT-PCR analysis revealed that the initiation of expression of both aromatase genes lay between 3 and 4 dpf (days post fertilisation) in both sexes. The level of brain aromatase mRNA gradually increased throughout the period studied with little difference between the sexes. This contrasted with marked sexual dimorphism of ovarian aromatase mRNA expression. In females, the expression level was maintained or increased gradually throughout ontogeny, while the level in males was dramatically down-regulated between 15 and 27 dpf. Subsequently, the level of ovarian aromatase mRNA expression fluctuated slightly in both sexes, with the expression in females always being higher than in males. These findings clearly suggest that ovarian aromatase plays a decisive role in sexual differentiation in this species and that this is achieved by down-regulation of the expression of this gene in males. Mol. Reprod. Dev. 59: 359-370, 2001.

Amino Acid Sequence↗
PubMed2001

Analysis of underivatized amino acid mixtures using high performance liquid chromatography/dual oscillating nebulizer atmospheric pressure microwave induced plasma ionization-mass spectrometry.

A dual oscillating capillary nebulizer (OCN) in conjunction with an atmospheric pressure microwave induced plasma ionization (AP-MIPI) source was applied to the analysis of underivatized amino acid mixtures. It was found that, compared to the single OCN, the dual OCN enhanced the sensitivity of detection several fold. Enhanced sensitivity was compound dependent. For small molecules, such as amino acids, it was 2-5 times more sensitive, while for larger molecules such as peptides it was more than an order of magnitude. The increase in sensitivity was attributed to the enhanced nebulization of the new torch. By using water/ acetonitrile containing 0.1% nonafluoropentanoic acid as the high performance liquid chromatography (HPLC) mobile phase and a C18 column, all common amino acids were separated and detected. A comparison between the results obtained using microwave induced plasma, atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) at flow rates compatible with micro LC (10-100 microL/min) showed a higher sensitivity of detection with the AP-MIPI technique for the analysis of underivatized amino acids.

Journal Article↗
PubMed2001

Calreticulin, a calcium-binding molecular chaperone, is required for stress response and fertility in Caenorhabditis elegans.

Calreticulin (CRT), a Ca(2+)-binding protein known to have many cellular functions, including regulation of Ca(2+) homoeostasis and chaperone activity, is essential for heart and brain development during embryogenesis in mice. Here, we report the functional characterization of Caenorhabditis elegans calreticulin (crt-1). A crt-1 null mutant does not result in embryonic lethality but shows temperature-dependent reproduction defects. In C. elegans CRT-1 is expressed in the intestine, pharynx, body-wall muscles, head neurons, coelomocytes, and in sperm. crt-1 males exhibit reduced mating efficiency and defects late in sperm development in addition to defects in oocyte development and/or somatic gonad function in hermaphrodites. Furthermore, crt-1 and itr-1 (inositol triphosphate receptor) together are required for normal behavioral rhythms. crt-1 transcript level is elevated under stress conditions, suggesting that CRT-1 may be important for stress-induced chaperoning function in C. elegans.

Animals↗
PubMed2001

Molecular characterization of putative yolk processing enzymes and their expression during oogenesis and embryogenesis in rainbow trout (Oncorhynchus mykiss).

Vitellogenin is the major yolk protein precursor in fish, but little is known about its processing pathway in the oocyte, nor about mobilization of yolk proteins during embryogenesis. In this study we cloned three putative yolk processing enzymes; specifically, cathepsin B and L, and lipoprotein lipase (LPL), from the rainbow trout ovary and determined their patterns of gene expression, together with cathepsin D, during oogenesis and embryogenesis using reverse transcription-polymerase chain reaction. The approximate sizes of both cathepsin B and cathepsin L transcripts were estimated as 1.7-1.8 kilobases by Northern blot analysis. Cathepsin D mRNA and cathepsin L mRNA were expressed constitutively throughout vitellogenesis and embryogenesis, showing the highest levels of expression at around fertilization. Cathepsin B and LPL were expressed exclusively during oogenesis. Quantitatively, expression of cathepsin D mRNA was higher than cathepsin B, cathepsin L, and LPL mRNA throughout the period studied. The different patterns of expression for these genes during oogenesis and embryogenesis signify specific temporal roles in yolk protein processing.

Amino Acid Sequence↗
PubMed2001

Biological significance of a universally conserved transcription mediator in metazoan developmental signaling pathways.

Transcription mediators are known to be required for regulated transcription in yeast and higher eukaryotes. However, little is known about the specific roles of mediators in vivo during development. In this report, we have characterized the biological functions of the C. elegans gene med-6, which is the homolog of the yeast mediator med-6. We first identified a genetic mutation in the med-6 gene by comparing genetic and physical maps and determining the molecular lesion. Next, we demonstrated that med-6 plays an important role in metazoan development by regulating the transcription of genes in evolutionarily conserved signaling pathways. We showed that med-6 is involved in the transcription of genes of the Ras pathway by showing that med-6 RNAi suppressed phenotypes associated with gain-of-function alleles of let-23 and let-60, and enhanced those associated with a reduction-of-function allele of lin-3. We also found that med-6 is involved in male ray development, which is partly mediated by the Wnt pathway. As MED-6 is universally conserved, including in yeast, and the mediator-related proteins that function in vulval and male ray development are metazoan specific, our results suggest the role of med-6 as a point of convergence where signals transmitted through metazoan-specific mediator-related proteins meet. In addition, RNAi experiments in rde-1 background showed that maternal and zygotic med-6 activities have distinct roles in development.

Alleles↗
PubMed2000

Masculinization of genetic female nile tilapia (Oreochromis niloticus) by dietary administration of an aromatase inhibitor during sexual differentiation.

A series of experiments was carried out in which genetically female Nile tilapia (Oreochromis niloticus) fry were treated with Fadrozole, a nonsteroidal aromatase inhibitor (AI), in the diet during the period of sexual differentiation. Batches of tilapia fry treated with AI during the first 30 days following yolk-sac resorption (7-37 days post hatch, dph) showed a dose-dependent increase in the percentage of males from 0 to 200 mg. kg(-1). The percentage of males remained approximately constant (92.5-96.0%) from 200 to 500 mg. kg(-1). Any continuous 2- or 3-week treatment with 500 mg. kg(-1) AI in this 4-week period successfully masculinized the majority of the treated fish (>80%). Treatments of 1 week duration revealed that the most sensitive time to AI lies in the first week (between 7 and 14 dph). Progeny testing of males from AI-treated groups gave results indicating that these were XX males, as expected. These experiments strongly implicate aromatase activity as a key factor in sexual differentiation in the Nile tilapia.

Animals↗
PubMed2000

8-O-Methylsclerotiorinamine, antagonist of the Grb2-SH2 domain, isolated from Penicillium multicolor.

A new secondary metabolite, 8-O-methylsclerotiorinamine (1), was isolated from a strain of Penicillium multicolor, and its structure was established using NMR spectroscopy and chemical evidence. The metabolite inhibited significantly the binding between the Grb2-SH2 domain and the phosphopeptide derived from the Shc protein and also blocked the protein-protein interactions of Grb2-Shc in cell-based experiments, with IC(50) values of 5.3 and 50 microM, respectively.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Effects of pentobarbital and isoflurane on conditioned learning after transient global cerebral ischemia in rabbits.

BACKGROUND: The acquisition of a conditioned eyeblink response has been used extensively to study the neurologic substrates of learning and memory. We examined the effects of the anesthetics isoflurane and pentobarbital, or hypothermia (30 degrees C), on the ability of rabbits to acquire an eyeblink conditioned response after 6.5 min of cerebral ischemia. METHODS: New Zealand white rabbits (n = 48) were randomly assigned to sham, normothermic, hypothermic, isoflurane, or pentobarbital groups. In the normothermic, hypothermic, isoflurane, and pentobarbital groups, 6.5 min of global cerebral ischemia was produced. In animals randomized to the isoflurane and pentobarbital groups, a pattern of burst suppression was achieved on the electroencephalogram before the start of the ischemic episode. Animals in the hypothermia group were cooled to 30 degrees C before ischemia. Seven days after ischemia, eyeblink training was started using an audible tone presented for 100 ms as the conditioned stimulus. The unconditioned stimulus was an air puff directed at the cornea. The delay between the end of conditioned stimulus and the start of the unconditioned stimulus (the trace interval) was 300 ms in duration. A conditioned response was defined as an eyeblink that was initiated during the trace interval. Eighty trials per day and 15 days of training were delivered. RESULTS: Neurologic deficits were greatest in the normothermia group, and these animals also had fewer conditioned responses than those in the sham, hypothermia, or pentobarbital groups. Animals in the isoflurane group had an intermediate number of conditioned responses that was not significantly different from the normothermia group. CONCLUSIONS: This study demonstrates that a brief episode of cerebral ischemia results in the impairment of associative learning. Hypothermia and burst-suppressive doses of pentobarbital were able to improve neurobehavioral outcome as measured by ability to acquire a trace conditioned response.

Adjuvants, Anesthesia↗
PubMed2000

cis-fumagillin, a new methionine aminopeptidase (type 2) inhibitor produced by Penicillium sp. F2757.

Selective inhibition against the yeast MetAP2 (methionine aminopeptidase type 2) was detected in the fermentation broth of a fungus F2757 that was later identified as Penicillium janczewskii. A new compound cis-fumagillin methyl ester (1) was isolated from the diazomethane treated fermentation extracts together with the known compound fumagillin methyl ester (2). The cis-fumagillin methyl ester, a stereoisomer of fumagillin methyl ester at the C2'-C3' position of the aliphatic side chain, selectively inhibited growth of the map1 mutant yeast strain (MetAP1 deletion strain) at a concentration as low as 1 ng. However, the wild type yeast w303 and the mutant map2 (MetAP2 deleted) strains were resistant up to 10 microg of the compound. In enzyme experiments, compound 1 inhibited the MetAP2 with an IC50 value of 6.3 nM, but it did not inhibit the MetAP1 (IC50 >200 microM). Compound 2 also inhibited the MetAP2 with an IC50 value of 9.2 nM and 105 microM against MetAP1.

Aminopeptidases↗
PubMed1999

Caenorhabditis elegans mediator complexes are required for developmental-specific transcriptional activation.

Mediator proteins are required for transcriptional regulation of most genes in yeast. Mammalian Mediator homologs also function as transcriptional coactivators in vitro; however, their physiological role in gene-specific transcription is not yet known. To determine the role of Mediator proteins in the development of complex organisms, we purified putative Mediator complexes from Caenorhabditis elegans and analyzed their phenotypes in vivo. C. elegans Mediator homologs were assembled into two multiprotein complexes. RNA interference assays showed that the CeMed6, CeMed7, and CeMed10/CeNut2 gene products are required for the expression of developmentally regulated genes, but are dispensable for expression of the ubiquitously expressed genes tested in this study. Therefore, the gene-specific function of Mediator as an integrator of transcriptional regulatory signals is evolutionarily conserved and is essential for C. elegans development.

Amino Acid Sequence↗
PubMed1999

Effects of hypothermia and lamotrigine on trace-conditioned learning after global cerebral ischemia in rabbits.

Acquisition of the trace-conditioned eye blink response (CR) is mediated by a variety of brain structures, including the cerebellum, the hippocampus, and brain stem nuclei. We examined the effects of a neuronal sodium channel antagonist (lamotrigine) on the ability of rabbits to acquire an eye blink CR after 6.5 min of cerebral ischemia. New Zealand white rabbits (n = 31) were randomly assigned to sham (S), normothermic ischemia (N), hypothermic (30 degrees C) ischemia-(H), or lamotrigine (50 mg/kg) treated (L) groups. In the N, H, and L groups, 6.5 min of global cerebral ischemia was produced using an inflatable neck tourniquet. Trace conditioning was started on the 7th postischemic day. The conditioned stimulus consisted of a tone (85 dB, 6 kHz) presented for 100 ms. The unconditioned stimulus was an air puff (150 ms duration) directed at the cornea. The interval between the end of the conditioned stimulus and the start of the unconditioned stimulus (the trace interval, TI) was 300 ms in duration. A trace-conditioned response was defined as an eye blink that was initiated during the TI. Eighty trials were delivered daily for 15 days. Neurologic deficits were greatest in the N group, and these animals had fewer CRs (149 +/- 157) than animals in the S (509 +/- 214) or H (461 +/- 149) groups (P < 0.05 by analysis of variance). Animals in the L group had a total number of CRs (380 +/- 253) that was intermediate between the S and N groups. Histologic evidence of neural injury was greatest in the N group. This study demonstrates that a brief episode of cerebral ischemia results in the impairment of this test of neurobehavioral function. Both hypothermia and lamotrigine were able to attenuate the impairment of eye blink trace-conditioned responses produced by cerebral ischemia.

Animals↗
PubMed1999

Changes in lymphatic function after complex physical therapy for lymphedema.

Twenty-two extremities of 19 lymphedema patients (6 arms, 16 legs) were treated by 2 weeks of complex physical therapy (CPT) and self home maintenance therapy (bandage/wearing of elastic garment and exercise). In addition to the clinical response of volume reduction before and 3 months after CPT, we analyzed the functional changes of the peripheral lymphatic system by use of lymphoscintigraphy (LS). Before CPT, the main LS findings of lymphedema included dermal backflow (100%), absent or faintly visualized regional lymph nodes (95.5%), presence of collateral lymphatic vessels (68.2%), and no or barely visualized lymphatic vessels (27.3%). LS findings suggesting improved lymphatic function after CPT were a decrease in dermal backflow (72.7%), an increase in radioisotope uptake by lymphatic vessels (27.3%), and an increase in radioisotope uptake by lymph nodes (9.1%). 81.8% of limbs showed improved lymphoscintigraphic findings and no change in 9.1%. In the others (9.1%), LS findings appeared worse. There was, however, no correlation between LS "improvement" and the amount of limb volume reduction.

Antimony↗
PubMed1998

Riluzole does not attenuate increases in hippocampal glutamate concentrations in a rabbit model of repeated transient global cerebral ischemia.

UNLABELLED: The aim of the present study was to examine the ability of riluzole to inhibit glutamate release during episodes of transient global cerebral ischemia. New Zealand White rabbits (n = 36) were anesthetized with halothane and mechanically ventilated to maintain normocarbia. Microdialysis catheters were inserted bilaterally into the dorsal hippocampus and perfused with artificial cerebrospinal fluid at 2 microL/min. Animals were randomly assigned to control, hypothermia (30 degrees C), or riluzole (2 or 8 mg/kg; R2 and R8) groups. Two episodes of transient global cerebral ischemia (each lasting 10 min) were produced by inflating the pneumatic tourniquet combined with induced hypotension. Dialysate was collected throughout the periischemic period, and glutamate concentrations were determined by using high-performance liquid chromatography. Peak levels were compared by using the Kruskal-Wallis test. Glutamate concentrations significantly increased by twofold to fourfold during the second ischemic period for the control, R2, and R8 groups. Glutamate concentrations in the hypothermic group were significantly lower than those in the other three groups and remained at baseline levels during the entire experiment. This study demonstrates that the sodium channel blocker riluzole does not inhibit ischemia-induced glutamate accumulation. The previously reported neuroprotective ability of riluzole may be caused by mechanisms other than the presynaptic inhibition of glutamate release during ischemia. IMPLICATIONS: Glutamate, an excitatory neurotransmitter, is released in excessive amounts during brain ischemia and may result in neuronal injury and death. Riluzole, a neuronal sodium channel blocker, has neuroprotective properties in some animal models of brain ischemia, possibly because of its ability to inhibit the release of glutamate from synaptic vesicles. However, this microdialysis study failed to demonstrate any attenuation of glutamate release during transient global ischemia after the administration of either 2 mg/kg or 8 mg/kg of riluzole.

Animals↗
PubMed1998

Effects of temperature on cerebral tissue oxygen tension, carbon dioxide tension, and pH during transient global ischemia in rabbits.

BACKGROUND: A decrease in brain temperature (Tbrain) causes a decrease in the cerebral metabolic rate for oxygen (CMRO2) and provides potent neuroprotection against ischemic damage. In the present study, the effects of mild to moderate hypothermia on cerebral tissue oxygen tension (PO2 brain), carbon dioxide tension (PCO2 brain), and pH (pHbrain) were monitored during short episodes of global cerebral ischemia. METHODS: After approval by the Animal Care and Use Committee, 10 New Zealand white rabbits were anesthetized (1% halothane in air) and mechanical ventilation was adjusted to maintain the arterial carbon dioxide tension at 35 mmHg (alpha-stat). A sensor to measure PO2 brain, PCO2 brain, pHbrain, and Tbrain was inserted into the brain through a burr hole in the skull. Tbrain was adjusted to 38 degrees C, 34.4 degrees C, and 29.4 degrees C in a random sequence in each animal. PO2 brain, PCO2brain, and pHbrain (all variables are reported at the actual Tbrain) were recorded every 10 s during a 5-min baseline, 3 min of cerebral ischemia induced by inflation of a neck tourniquet, and 10 min of reperfusion at each level of Tbrain. Analysis of variance and Dunnett's test were used for statistical analysis. Data are presented as means +/- SD. RESULTS: During ischemia, PO2 brain decreased from 56 +/- 3 to 33 +/- 2 mmHg at 38 degrees C, from 58 +/- 3 to 32 +/- 3 mmHg at 34.4 degrees C, and from 51 +/- 2 to 32 +/- 2 mmHg at 29.4 degrees C (p = NS). PCO2 brain increased by 6.7 +/- 2 mmHg at 38 degrees C, by 5.1 +/- 1.4 mmHg at 34.4 degrees C, and by 2.3 +/- 0.8 mmHg at 29.4 degrees C. pHbrain inversely followed the trend of PCO2 brain. CONCLUSIONS: The attenuated increase in PCO2 brain during hypothermic ischemia results from the reduced CMRO2. The similar decrease in PO2 brain at all temperature levels indicates that despite the reduction in CMRO2, PO2 brain is no better preserved during brief episodes of hypothermic ischemia than during normothermic ischemia.

Analysis of Variance↗