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Biomedical subjects

D H Kim

Publications and source records attributed to D H Kim.

At least 109 records · Page 6Linked to original sources
PubMed2001

Neurocognitive symptoms and impairment in an HIV community clinic.

BACKGROUND: Neurocognitive impairment is a frequent complication of HIV infection and heralds a poor survival prognosis. With the availability of highly active antiretroviral therapy (HAART), survival times for HIV-infected patients have markedly increased although the effects of HAART on the prevalence of neurocognitive impairment remain uncertain. OBJECTIVE: To determine the relationship between self-reported neurocognitive symptoms and neuropsychological (NP) performance together with the impact of HAART among HIV-infected patients. METHODS: A cross-sectional study was performed in which patients without previously documented neurocognitive impairment attending an HIV community clinic were questioned about neurocognitive symptoms and a NP test battery was administered. RESULTS: Of the eighty-three patients examined, neurocognitive symptoms were reported by 34% of patients and were associated with a shorter duration of HAART and higher viral loads. Patients reporting neurocognitive symptoms were also more likely to exhibit impaired NP performance (p<0.005) with NP impairment being detected in 46% of all patients examined (12% with HIV-associated dementia). Neuropsychological impairment was directly correlated with age (p<0.001), plasma viral load (p<0.005) and inversely correlated with the number of prescribed antiretroviral drugs (p<0.01). CONCLUSIONS: These results suggest that neurocognitive symptoms are predictive of impaired NP performance and that NP impairment remains a frequent finding among older patients with higher viral loads. An increased number of antiretroviral drugs may be neuroprotective.

Adult↗
PubMed2001

Annomolin and annocherimolin, new cytotoxic annonaceous acetogenins from Annona cherimolia seeds.

Two new cytotoxic annonaceous acetogenins, annomolin (1) and annocherimolin (2), were isolated from an ethanolic extract of the seeds of Annona cherimolia. Annomolin has a mono-THF ring with one flanking hydroxyl and possesses a 1,2-diol at C-7/8 of the aliphatic chain. Annocherimolin has a mono-THF ring with two flanking hydroxyls and possesses a double bond at C-21/22. Their structures were elucidated by spectral data and chemical derivatization. Compound 1 showed cytotoxic selectivity for the human prostate tumor cell line (PC-3), with a potency of over 10,000 times that of adriamycin. Compound 2 showed cytotoxic potencies about 10,000 times those of adriamycin in the breast (MCF-7) and colon (HT-29) cancer cell lines.

Adenocarcinoma↗
PubMed2001

Protective effect of harmaline and harmalol against dopamine- and 6-hydroxydopamine-induced oxidative damage of brain mitochondria and synaptosomes, and viability loss of PC12 cells.

The present study elucidated the protective effect of beta-carbolines (harmaline, harmalol and harmine) against oxidative damage of brain mitochondria, synaptosomes and PC12 cells induced by either dopamine or 6-hydroxydopamine. Harmaline, harmalol and antioxidant enzymes (superoxide dismutase/SOD and catalase) decreased the alteration of mitochondrial swelling and membrane potential induced by 200 microM dopamine or 100 microM 6-hydroxydopamine. Deprenyl attenuated the dopamine-induced mitochondrial dysfunction but did not reduce the effect of 6-hydroxydopamine. While beta-carbolines inhibited the electron flow in mitochondria, they did not enhance the depressant effect of catecholamines. beta-Carbolines and antioxidant enzymes reversed the depression of synaptosomal Ca2+ uptake induced by 10 microM catecholamines. The compounds inhibited the catecholamine-induced thioredoxin reductase inhibition, thiol oxidation and carbonyl formation in mitochondria and synaptosomes. beta-Carbolines decreased the reactive species-induced deoxyribose degradation. Harmaline and harmalol reduced the catecholamine-induced loss of the transmembrane potential and of cell viability in PC12 cells. beta-Carbolines alone did not show a significant cytotoxic effect on PC12 cells. The results suggest that beta-carbolines may attenuate the dopamine- or 6-hydroxydopamine-induced alteration of brain mitochondrial and synaptosomal functions, and viability loss in PC12 cells, by a scavenging action on reactive oxygen species and inhibition of thiol oxidation.

Animals↗
PubMed2001

Evidence for direct involvement of beta-catenin in phorbol ester-induced neurite outgrowth in GT1-1 hypothalamic neurones.

Gonadotropin-releasing hormone (GnRH) is a pivotal neuroendocrine regulator controlling reproductive functions. However, the scattered distribution of GnRH neurones in the mammalian brain has hindered studies on the development and differentiation of GnRH neurones. In the present study, we used the immortalized GnRH-producing GT1-1 cells to examine whether activation of protein kinase C (PKC) pathway with 12-O-tetradecanoyl-13-acetate (TPA) induces morphological and functional differentiation of GnRH neurones. TPA induced neurite outgrowth and inhibited proliferation of GT1-1 cells that were specifically antagonized by cotreatment of PKC inhibitor, calphostin C. The functional significance of TPA-induced differentiation of GT1-1 cells was manifested in part by the changes in the effects of gamma-aminobutyric acid (GABA) on intracellular Ca2+ levels. In untreated GT1-1 cells, activation of GABA-A receptor with 10 microM muscimol increased intracellular Ca2+ levels, whereas such stimulatory effects disappeared in GT1-1 cells bearing neurites. Accordingly, muscimol could not stimulate GnRH release in TPA-treated GT1-1 cells. To elucidate the molecular mechanism underlying TPA-induced neurite outgrowth, we performed differential display reverse transcription-polymerase chain reaction. Among several genes that are affected by TPA treatment, we found a significant induction of beta-catenin mRNA expression. Along with the rapid induction of beta-catenin protein levels, we observed that beta-catenin was reallocated from cell-cell adhesion sites to the growth cones within 3 h of TPA treatment. Transient transfection studies with green fluorescent protein as a reporter gene demonstrated that beta-catenin overexpression alone can promote neurite outgrowth in GT1-1 cells. Moreover, TPA was found to increase the transcription-activational roles of beta-catenin. Together, these data provide evidence that beta-catenin is involved in the TPA-induced functional differentiation of immortalized GnRH neurones.

Calcium↗
PubMed2001

Purification and characterization of acharan sulfate lyases, two novel heparinases, from Bacteroides stercoris HJ-15.

Two novel acharan sulfate lyases (ASL1 and ASL2: no EC number) have been purified from Bacteroides stercoris HJ-15 which was isolated from human intestinal bacteria with glycosaminoglycan (GAG) degrading enzymes. These enzymes were purified to apparent homogeneity by a combination of QAE-cellulose, DEAE-cellulose, carboxymethyl-Sephadex C-50, hydroxyapatite and HiTrap SP Sephadex C-25 column chromatography with the final specific activity of 50.5 and 76.7 micromol.min-1.mg-1, respectively. Both acharan sulfate lyases are single subunits of 83 kDa by SDS/PAGE and gel filtration. ASL1 showed optimal activity at pH 7.2 and 45 degrees C. ASL1 activity was inhibited by Cu2+, Ni2+ and Co2+, but ASL2 activity was inhibited by Cu2+, Ni2+and Pb2. Both enzymes were slightly inhibited by some agents that modify histidine and cysteine residues, but activated by reducing agents such as DL-dithiothreitol and 2-mercaptoethanol. Both purified bacteroidal acharan sulfate lyases acted to the greatest extent on acharan sulfate, and to a lesser extents on heparan sulfate and heparin. They did not act on de-O-sulfated acharan sulfate. These findings suggest that the biochemical properties of these purified acharan sulfate lyases are different from those of the previously purified heparin lyases, but these enzymes belong to heparinase II.

Amino Acid Sequence↗
PubMed2001

Internalization of tenecin 3 by a fungal cellular process is essential for its fungicidal effect on Candida albicans.

Tenecin 3 is a glycine-rich, antifungal protein of 78 residues isolated from the insect Tenebrio molitor larva. As an initial step towards understanding the antifungal mechanism of tenecin 3, we examined how this protein interacts with the pathogenic fungus Candida albicans to exert its antifungal action. Tenecin 3 did not induce the release of a fluorescent dye trapped in the artificial membrane vesicles and it did not perturb the membrane potential of C. albicans by the initial interaction. Fluorescence confocal microscopy and flow cytometric analysis revealed that tenecin 3 is rapidly internalized into the cytoplasmic space in energy-dependent and temperature-dependent manners. This internalization is also dependent on the ionic environment and cellular metabolic states. These results suggest that the internalization of tenecin 3 into the cytoplasm of C. albicans is mediated by a fungal cellular process. The internalized tenecin 3 is dispersed in the cytoplasm, and the loss of cell viability occurs after this internalization.

Amino Acid Sequence↗
PubMed2001

In vitro anti-Helicobacter pylori activity of irisolidone isolated from the flowers and rhizomes of Pueraria thunbergiana.

The inhibitory effect of isoflavones isolated from the flowers and rhizomes of Pueraria thunbergiana (Leguminosae) on the growth of Helicobacter pylori (HP) was investigated. Isoflavone glycosides did not inhibit the growth of HP. However, their aglycones, irisolidone, tectorigenin and genistein, inhibited HP growth. Among them, irisolidone had the most potent inhibitory activity against HP and its MIC was 12.5-25 micrograms/ml. Genistein only weakly inhibited the urease of HP and H+/K(+)-ATPase of rat stomach: its IC50 were 0.43 and 0.89 mg/ml, respectively.

Animals↗
PubMed2001

Effect of an extract of the root of Scutellaria baicalensis and its flavonoids on aflatoxin B1 oxidizing cytochrome P450 enzymes.

The inhibition of aflatoxin B1 (AFB1) metabolism by a water extract of the root of Scutellaria baicalensis and its flavonoids was examined in liver microsomes. AFB1 is known to be metabolized to aflatoxin M1 (AFM1), aflatoxin Q1 (AFQ1), and AFB1-8,9-epoxide (AFBO). The water extract potently inhibited the production of AFM1 by cytochrome P450 (CYP)1A1/2 and slightly reduced AFBO formation by CYP1A1/2, CYP2B1, CYP2C11 and CYP3A1/2 in TCDD-treated rat liver microsomes. IC50 values for AFM1 and AFBO formation were 6.8 and 122.4 microg/ml, respectively. Wogonin showed the highest inhibitory activity towards AFM1 formation among the flavonoids isolated from the extract. On the other hand, the extract had no effects on the formation of AFBO and AFQ1 in human liver microsomes, and on the activities of CYP2B1, CYP2C11 and CYP3A1/2 which were detected by hydroxylation patterns of testosterone. These results demonstrated that the extract of the root of Scutellaria baicalensis has a specific inhibitory effect on CYP1A1/2 among CYP enzymes involved in AFB1 metabolism by rat and human microsomes.

Aflatoxin B1↗
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

Image-guided hypo-fractionated stereotactic radiosurgery to spinal lesions.

OBJECTIVE: This article demonstrates the technical feasibility of noninvasive treatment of unresectable spinal vascular malformations and primary and metastatic spinal tumors by use of image-guided frameless stereotactic radiosurgery. METHODS: Stereotactic radiosurgery delivers a high dose of radiation to a tumor volume or vascular malformation in a limited number of fractions and minimizes the dose to adjacent normal structures. Frameless image-guided radiosurgery was developed by coupling an orthogonal pair of x-ray cameras to a dynamically manipulated robot-mounted linear accelerator that guides the therapy beam to treatment sites within the spine or spinal cord, in an outpatient setting, and without the use of frame-based fixation. The system relies on skeletal landmarks or implanted fiducial markers to locate treatment targets. Sixteen patients with spinal lesions (hemangioblastomas, vascular malformations, metastatic carcinomas, schwannomas, a meningioma, and a chordoma) were treated with total treatment doses of 1100 to 2500 cGy in one to five fractions by use of image-guided frameless radiosurgery with the CyberKnife system (Accuray, Inc., Sunnyvale, CA). Thirteen radiosurgery plans were analyzed for compliance with conventional radiation therapy. RESULTS: Tests demonstrated alignment of the treatment dose with the target volume within +/-1 mm by use of spine fiducials and the CyberKnife treatment planning system. Tumor patients with at least 6 months of follow-up have demonstrated no progression of disease. Radiographic follow-up is pending for the remaining patients. To date, no patients have experienced complications as a result of the procedure. CONCLUSION: This experience demonstrates the feasibility of image-guided robotic radiosurgery for previously untreatable spinal lesions.

Adolescent↗
PubMed2001

A new dynamin-like protein, ADL6, is involved in trafficking from the trans-Golgi network to the central vacuole in Arabidopsis.

Dynamin, a high-molecular-weight GTPase, plays a critical role in vesicle formation at the plasma membrane during endocytosis in animal cells. Here we report the identification of a new dynamin homolog in Arabidopsis named Arabidopsis dynamin-like 6 (ADL6). ADL6 is quite similar to dynamin I in its structural organization: a conserved GTPase domain at the N terminus, a pleckstrin homology domain at the center, and a Pro-rich motif at the C terminus. In the cell, a majority of ADL6 is associated with membranes. Immunohistochemistry and in vivo targeting experiments revealed that ADL6 is localized to the Golgi apparatus. Expression of the dominant negative mutant ADL6[K51E] in Arabidopsis protoplasts inhibited trafficking of cargo proteins destined for the lytic vacuole and caused them to accumulate at the trans-Golgi network. In contrast, expression of ADL6[K51E] did not affect trafficking of a cargo protein, H(+)-ATPase:green fluorescent protein, destined for the plasma membrane. These results suggest that ADL6 is involved in vesicle formation for vacuolar trafficking at the trans-Golgi network but not for trafficking to the plasma membrane in plant cells.

Amino Acid Sequence↗
PubMed2001

Identification of a signal that distinguishes between the chloroplast outer envelope membrane and the endomembrane system in vivo.

Certain small outer envelope membrane proteins of chloroplasts are encoded by the nuclear genome without a cleavable N-terminal transit peptide. We investigated in vivo the targeting mechanism of AtOEP7, an Arabidopsis homolog of the small outer envelope membrane protein. AtOEP7 was expressed as a fusion protein with the green fluorescent protein (GFP) either transiently in protoplasts or stably in transgenic plants. In either case, fluorescence microscopy of transformed cells and protein gel blot analysis of fractionated proteins confirmed that the AtOEP7:GFP fusion protein was targeted to the chloroplast outer envelope membrane. In vivo targeting experiments revealed that two regions, the transmembrane domain (TMD) and its C-terminal neighboring seven-amino acid region, were necessary and sufficient for targeting to the chloroplast outer membrane. Substitution of aspartic acid or lysine residues with glycine residues or scrambling of the amino acid sequence of the seven-amino acid region caused mistargeting to the plasma membrane. Although the amino acid sequence of the TMD is not important for targeting, amino acid residues with large side chains inhibited targeting to the chloroplasts and resulted in the formation of large aggregates in the protoplasts. In addition, introduction of a proline residue within the TMD resulted in inhibition of targeting. Finally, a fusion protein, AtOEP7:NLS:GFP, was targeted efficiently to the chloroplast envelope membranes despite the presence of a nuclear localization signal. On the basis of these results, we conclude that the seven-amino acid region and the TMD are determinants for targeting to the chloroplast outer envelope membrane. The seven-amino acid region plays a critical role in AtOEP7 evading the endomembrane system and entering the chloroplast pathway, and the TMD plays critical roles in migration to the chloroplasts and/or subsequent insertion into the membrane.

Amino Acid Sequence↗
PubMed2001

Trafficking of phosphatidylinositol 3-phosphate from the trans-Golgi network to the lumen of the central vacuole in plant cells.

Very limited information is available on the role of phosphatidylinositol 3-phosphate (PI[3]P) in vesicle trafficking in plant cells. To investigate the role of PI(3)P during the vesicle trafficking in plant cells, we exploited the PI(3)P-specific binding property of the endosome binding domain (EBD) (amino acids 1257 to 1411) of human early endosome antigen 1, which is involved in endosome fusion. When expressed transiently in Arabidopsis protoplasts, a green fluorescent protein (GFP):EBD fusion protein exhibited PI(3)P-dependent localization to various compartments--such as the trans-Golgi network, the prevacuolar compartment, the tonoplasts, and the vesicles in the vacuolar lumen--that varied with time. The internalized GFP:EBD eventually disappeared from the lumen. Deletion experiments revealed that the PI(3)P-dependent localization required the Rab5 binding motif in addition to the zinc finger motif. Overexpression of GFP:EBD inhibited vacuolar trafficking of sporamin but not trafficking of H(+)-ATPase to the plasma membrane. On the basis of these results, we propose that the trafficking of GFP:EBD reflects that of PI(3)P and that PI(3)P synthesized at the trans-Golgi network is transported to the vacuole through the prevacuolar compartment for degradation in plant cells.

Arabidopsis↗
PubMed2001

Roles of dimerization in folding and stability of ketosteroid isomerase from Pseudomonas putida biotype B.

Equilibrium and kinetic analyses have been performed to elucidate the roles of dimerization in folding and stability of KSI from Pseudomonas putida biotype B. Folding was reversible in secondary and tertiary structures as well as in activity. Equilibrium unfolding transition, as monitored by fluorescence and ellipticity measurements, could be modeled by a two-state mechanism without thermodynamically stable intermediates. Consistent with the two-state model, one dimensional (1D) NMR spectra and gel-filtration chromatography analysis did not show any evidence for a folded monomeric intermediate. Interestingly enough, Cys 81 located at the dimeric interface was modified by DTNB before unfolding. This inconsistent result might be explained by increased dynamic motion of the interface residues in the presence of urea to expose Cys 81 more frequently without the dimer dissociation. The refolding process, as monitored by fluorescence change, could best be described by five kinetic phases, in which the second phase was a bimolecular step. Because <30% of the total fluorescence change occurred during the first step, most of the native tertiary structure may be driven to form by the bimolecular step. During the refolding process, negative ellipticity at 225 nm increased very fast within 80 msec to account for >80% of the total amplitude. This result suggests that the protein folds into a monomer containing most of the alpha-helical structures before dimerization. Monitoring the enzyme activity during the refolding process could estimate the activity of the monomer that is not fully active. Together, these results stress the importance of dimerization in the formation and maintenance of the functional native tertiary structure.

Dimerization↗
PubMed2001

Enhanced iron uptake of Saccharomyces cerevisiae by heterologous expression of a tadpole ferritin gene.

We genetically engineered Saccharomyces cerevisiae to express ferritin, a ubiquitous iron storage protein, with the major heavy-chain subunit of tadpole ferritin. A 450-kDa ferritin complex can store up to 4,500 iron atoms in its central cavity. We cloned the tadpole ferritin heavy-chain gene (TFH) into the yeast shuttle vector YEp352 under the control of a hybrid alcohol dehydrogenase II and glyceraldehyde-3-phosphate dehydrogenase promoter. We confirmed transformation and expression by Northern blot analysis of the recombinant yeast, by Western blot analysis using an antibody against Escherichia coli-expressed TFH, and with Prussian blue staining that indicated that the yeast-expressed tadpole ferritin was assembled into a complex that could bind iron. The recombinant yeast was more iron tolerant in that 95% of transformed cells, but none of the recipient strain cells, could form colonies on plates containing 30 mM ferric citrate. The cell-associated concentration of iron was 500 microg per gram (dry cell weight) of the recombinant yeast but was 210 microg per gram (dry cell weight) in the wild type. These findings indicate that the iron-carrying capacity of yeast is improved by heterologous expression of tadpole ferritin and suggests that this approach may help relieve dietary iron deficiencies in domesticated animals by the use of the engineered yeast as a feed and food supplement.

Animals↗
PubMed2001

Dietary induction of angiotensin-converting enzyme in proximal and distal rat small intestine.

Induction of angiotensin-converting enzyme was examined in proximal and distal intestinal segments of rats fed a low-protein (4%) diet and then switched to a high-protein (gelatin) diet. Animals were killed at varying time points, and brush-border membranes and total RNA were prepared from the segments. In the proximal intestine, there was a fivefold increase in angiotensin-converting enzyme levels after 14 days but only a twofold change in mRNA. In the distal intestine, there was no increase in enzyme activity but mRNA increased 2.4-fold. Organ culture was used to measure changes in enzyme biosynthesis. There was a 5- to 6-fold increase in the biosynthesis of angiotensin-converting enzyme in the proximal intestine 24 h after the switch to the gelatin diet and a 1.6-fold increase in mRNA levels. No change in biosynthesis was observed in the distal small intestine despite an increase in mRNA. These results support the conclusion that rapid dietary induction of intestinal angiotensin-converting enzyme is differentially regulated in proximal and distal segments of the small intestine.

Animals↗
PubMed2001

Cloning and sequencing of the astA gene encoding arylsulfate sulfotransferase from Salmonella typhimurium.

Arylsulfate sulfotransferase (ASST) transfers a sulfate group from a phenolic sulfate ester to a phenolic acceptor substrate. In the present study, the gene encoding ASST was cloned from a genomic library of Salmonella typhimurium. The gene was subcloned into the vector pKF3 and was sequenced. A recombinant clone harboring the gene was directly identified using a fluorescent assay. Sequencing revealed two contiguous open reading frames (ORFs) on the same strand. Based on amino acid sequence homology, ORF1 and ORF2 are designated as astA and dsbA, respectively. The deduced amino acid sequence of astA from S. typhimurium was highly similar to those of the Enterobacter amnigenus, Klebsiella, and Campylobacter jejuni ASSTs, encoded by the astA genes. However, an ASST activity assay revealed a different acceptor specificity. Using p-nitrophenyl sulfate (PNS) as a donor substrate, phenol is the best acceptor substrate, followed by alpha-naphthol, resorcinol, tyramine, acetaminophen, and tyrosine.

Amino Acid Sequence↗