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Biomedical subjects

Y Kang

Publications and source records attributed to Y Kang.

At least 127 records · Page 7Linked to original sources
PubMed1998

Derivation and functional characterization of a consensus DNA binding sequence for the tas transcriptional activator of simian foamy virus type 1.

Although DNA binding sites specific for the Bel-1 and Tas transcriptional activators, encoded, respectively, by the human and simian foamy viruses, have been mutationally defined, they show little evident sequence identity. As a result, the sequence determinants for DNA binding by both Bel-1 and Tas have remained unclear. Here, we report the use of a novel in vivo randomization and selection strategy to identify a Tas DNA binding site consensus. This approach takes advantage of the fact that Tas can effectively activate gene expression in yeast cells via a Tas DNA binding site derived from the simian foamy virus type 1 (SFV-1) internal promoter. The defined Tas DNA binding site consensus extends over approximately 25 bp and contains a critical core sequence of approximately 5 bp. Positions adjacent to this core sequence, while clearly also subject to selection, show a significantly higher level of sequence variation. Surprisingly, the wild-type SFV-1 internal promoter Tas DNA binding site fails to conform to the consensus at several positions. Further analysis demonstrated that the consensus sequence bound Tas more effectively than did the wild-type sequence in vitro and could mediate an enhanced Tas response in vivo when substituted into the SFV-1 internal promoter context. These findings explain the limited sequence identity observed for mutationally defined Tas or Bel-1 response elements and should facilitate the identification of Tas DNA target sites located elsewhere in the SFV-1 genome.

Amino Acid Sequence↗
PubMed1998

Determination of encephalomyocarditis viral diabetogenicity by a putative binding site of the viral capsid protein.

The molecular mechanism by which some, but not all, variants of encephalomyocarditis (EMC) virus selectively infect pancreatic beta-cells in mice and induce IDDM has been an enigma for more than a decade. We report here that the binding site of the EMC viral capsid protein VP1 determines viral diabetogenicity. Recombinant chimeric EMC viruses containing threonine, serine, proline, aspartic acid, or valine at position 152 of the major capsid protein VP1 bind poorly to beta-cells. In contrast, recombinant chimeric EMC viruses containing alanine or glycine at position 152 of the VP1 bind efficiently to and infect beta-cells, resulting in the development of diabetes. Three-dimensional molecular modeling reveals that the van der Waals interactions are greater and the residues surrounding position 152 of the VP1 are more closely packed in recombinant chimeric viruses containing threonine, serine, proline, aspartic acid, or valine at position 152 than in recombinant chimeric viruses containing alanine or glycine at the same position. Our studies reveal that the surface areas surrounding alanine or glycine at position 152 of the VP1 are more accessible, thus increasing the availability of the binding sites for attachment to beta-cell receptors and resulting in viral infection and the development of diabetes.

Animals↗
PubMed1998

Spinal meningeal melanocytoma presenting with superficial siderosis of the central nervous system. Case report and review of the literature.

Meningeal melanocytoma is a benign melanocytic tumor that originates most frequently from the melanocytes in the posterior fossa or along the spinal cord. This tumor generally occurs as an extraaxial mass that compresses adjacent neural structures to produce various neurological signs. The authors describe an unusual case in which a patient with a meningeal melanocytoma located at the thoracic spinal cord presented with superficial siderosis of the central nervous system (CNS). Extensive neuroradiological studies identified the presence of a spinal cord tumor, and postsurgical histological examination revealed the meningeal melanocytoma as a bleeding source. After surgery, lumbar puncture demonstrated normalization of the patient's cerebrospinal fluid; however, no neurological improvement occurred. The neurological deficits seem irreversible. Meningeal melanocytoma is biologically benign and can be cured by complete surgical resection; therefore, this tumor should be included in the differential diagnosis of pigmented lesions of the CNS. The authors reviewed 14 cases of well-documented meningeal melanocytoma in the literature and discuss the clinical, radiological, and pathological features of the present case to emphasize the importance of early diagnosis and identification of the source of bleeding in patients with superficial siderosis.

Brain Diseases↗
PubMed1998

[The effect of chitosan in prevention of fibrous scar tissue formation after laminectomy].

OBJECTIVE: To study the effect of chitosan in the prevention of fibrous scar formation in the epidural space after laminectomy. METHOD: Fourty-eight SD rats were used as the animal model. Laminectomy was performed in lumber 1, and the exposed dura was covered with hyaluronate (group A), free fat (group B), chitosan (group C), and saline solution (group D) respectively. At 4, 8 and 12 weeks postoperation, scar formation was observed. RESULT: The results revealed that scar formed in the group D at the fourth week reached a peak at the eighth week and began to soften and constrict at the twelfth week. Sodium hyaluronate and chitosan had a significant efficacy in the prevention of scar formation, but the effect of chitosan was superior to that of sodium hyaluronate. CONCLUSION: The findings of this study indicate that chitosan has a preventive effect on scar tissue formation.

Animals↗
PubMed1998

Neural activity of the superior salivatory nucleus in rats.

We recorded the neural activity of the superior salivatory (SS) neurons in brain slice preparations from neonatal rats in vitro and in decerebrate anesthetized rats in vivo. In the in vitro experiment, the SS neurons were retrogradely labeled by the injection of Rhodamine into the chorda-lingual nerve (labeling SS neurons innervating the submandibular and intra-lingual ganglia) or into the anterior part of the tongue. The SS neurons labeled from the nerve were classifiable into two types: Type-I, tonic firing at a frequency of up to 30 Hz; and Type-II, phasic firing at a higher frequency of up to 70 Hz followed by tonic firing at 30-50 Hz. All of the SS neurons labeled from the tongue were Type-II. Since the anterior tongue is a non-glandular area, the type of cells may be involved in vasodilatation. Type-I neurons, which did not innervate the tongue, may be responsible for salivation. In the in vivo experiment, the reflex activity evoked by taste or mechanical stimulation was recorded from the axons of the SS neurons innervating the submandibular ganglia. These fibers also displayed two firing patterns. One was a tonic firing pattern discharging at 5-30 Hz. The other consisted of a transient firing (about 80 Hz) at the beginning of stimulation and then a prolonged firing at 5-40 Hz. The latter firing pattern was similar to that of the Type-II neurons. These findings suggest that the parasympathetic nerves of the salivary glands contain both the secretory- and vasodilator-type of SS neuron.

Action Potentials↗
PubMed1997

Involvement of endogenous opioids and ATP-sensitive potassium channels in the mediation of carbachol-induced antinociception at the spinal level: a behavioral study in rats.

The effects of intrathecally administered (i.t.) atropine, glibenclamide, a blocker of ATP-sensitive potassium channels, or naloxone on the antinociception produced by i.t. carbachol or morphine were observed in rats by tail-flick (TF) test. The results showed that: (1) i.t. carbachol produced a dose-dependent antinociception and it could be antagonized by i.t. atropine; (2) the antinociception produced by i.t. carbachol could be blocked dose-dependently by i.t. glibenclamide or i.t. naloxone; (3) the antinociception produced by i.t. morphine could be blocked dose-dependently by i.t. glibenclamide, but not by i.t. atropine. The results suggest that the antinociception produced by activation of muscarinic receptors at the spinal level might be mediated by endogenous opioids and ATP-sensitive potassium channels in a cascade form.

Adenosine Triphosphate↗
PubMed1997

Role of macrophages and macrophage-derived cytokines in the pathogenesis of Kilham rat virus-induced autoimmune diabetes in diabetes-resistant BioBreeding rats.

The diabetes-resistant BioBreeding (DR-BB) rat, derived from diabetes-prone forebears, does not normally develop spontaneous insulitis or diabetes, but when infected with Kilham rat virus (KRV) this animal develops autoimmune diabetes similar to the diabetes-prone BioBreeding (DP-BB) rat. In this study, we attempted to determine whether macrophages and macrophage-derived cytokines play a role in the development of KRV-induced diabetes in DR-BB rats. Seventy-eight percent of DR-BB rats treated with KRV and poly(I:C) develop diabetes, whereas depletion of macrophages with liposome-encapsulated dichloromethylene diphosphonate (lip-Cl2MDP) in KRV and poly(I:C)-treated DR-BB rats results in the near-complete prevention of insulitis and diabetes. Measurement of the macrophage-derived cytokines IL-12, TNF-alpha, and IL-1beta revealed a selective increase of their expression, after KRV infection, in the splenic lymphocytes and the pancreatic islets. Measurement of CD4+ T cell-derived cytokines revealed that IL-2 and IFN-gamma cytokine gene expression closely correlates with an elevation of IL-12, but IL-4 and IL-10 do not change. Depletion of macrophages before the isolation of splenic lymphocytes from DR-BB rats treated with KRV and poly(I:C) resulted in the loss of ability to transfer diabetes to young DP-BB rats. On the basis of these observations, we conclude that macrophages and macrophage-derived cytokines play a critical role in the cascade of events leading to the destruction of pancreatic beta cells, culminating in the development of insulin-dependent diabetes mellitus.

Animals↗
PubMed1997

Cloning/brain localization of mouse glutamylcysteine synthetase heavy chain mRNA.

Glutathione (GSH) is considered the primary molecule responsible for peroxide removal from the brain. Inhibition of its rate-limiting synthetic enzyme, glutamylcysteine synthetase (GCS), results in morphological damage to both cortical and nigral neurons in rodents. Here, we report cloning of the catalytic heavy chain GCS mRNA from mouse and its localization in the murine brain. Heavy chain GCS appears to be localized in glial populations in the hippocampus, cerebellum and olfactory bulb, with lower levels of expression in the cortex and substantia nigra. Variations in GCS levels and subsequent GSH synthesis may explain differences in susceptibility to neuropathology associated with oxidative stress noted in these various brain regions.

Amino Acid Sequence↗
PubMed1997

Depolarization-induced slow potentiation of depolarizing afterpotential.

Effects of strong membrane depolarization on the excitability of regular spiking (RS) non-pyramidal cells in layer VI of the cat motor cortex were examined in in vitro slice preparations. RS non-pyramidal cells that expressed depolarizing afterpotential (DAP) following spikes displayed either of the two distinct responses: immediate and successive potentiation of DAP in association with repetition of firing, or slow enhancement of DAP after repetitive injections of strong depolarizing current pulses leading to burst firing. In those neurones that displayed the immediate potentiation of DAP, slow potentiation was never induced. This difference in changes of DAP was consistent with morphological differences. DAP-lacking RS non-pyramidal cells displayed neither immediate nor slow changes in excitability.

Action Potentials↗
PubMed1997

Characterization of the solubilized oocyte membrane receptor for insecticyanin, a biliprotein of the hawkmoth, Manduca sexta.

We report the solubilization and characterization of the oocyte membrane receptor for insecticyanin, a blue biliprotein of the hawkmoth Manduca sexta. The insecticyanin receptor was solubilized using 40 mM CHAPS. Strong binding affinity of [125I]insecticyanin to its solubilized receptor was demonstrated to be heat-labile, pH-dependent, Ca2+-dependent, and saturable. The binding was inhibited by excess unlabeled insecticyanin, but not by two other major hemolymph and oocyte proteins, vitellogenin and lipophorin. The receptor for insecticyanin showed tissue specificity: it was present only in oocyte membranes, not in membranes of fat body, midgut or ovariole sheath. The equilibrium data for the solubilized receptor, K(d) and B(max), were estimated to be 17 nM and 11.4 pmol/mg solubilized proteins, respectively. The results from co-immunoprecipitation showed that the apparent molecular mass for the insecticyanin receptor is approximately 185 kDa while chemical crosslinking of the insecticyanin-receptor complex revealed a product with a molecular mass near 10(3) kDa. This suggests that the insecticyanin receptor has a multimeric structure, or that four receptor molecules can bind to one insecticyanin tetramer.

Animals↗
PubMed1997

In vitro evaluation of antiproliferative potential of calcium channel blockers in human Tenon's fibroblasts.

The calcium cation has been known to play a central and diverse role in the proliferation of numerous types of cells including fibroblasts. Therefore, ib1p4llows that calcium channel blockers (CCBs) may potentially inhibit fibroblast attachment and proliferation. The time and dose-related effects of five commonly used CCBs-verapamil, diltiazem, nicardipine, trifluoperazine, and dantrolene-on human Tenon's fibroblast attachment and proliferation were studied. Fibroblasts were incubated with different concentrations of each drug. To evaluate the effect of each drug on fibroblast attachment, cell density was quantified by Coulter counter and hexosaminidase assays after 24 hours of incubation. To evaluate the effect of each drug on fibroblast proliferation, cell density was quantified by Coulter counter, hexosaminidase, and 3H-thymidine uptake assays on days 1, 3, and 7. Dantrolene had minimal effect, failing to cause even 20% inhibition at 10(-5) M, the highest concentration tested. Verapamil, diltiazem, nicardipine, and trifluoperazine all inhibited fibroblast attachment and proliferation. Trifluoperazine was the most potent inhibitor of attachment and proliferation with ID50S in the 10(-5) M range. Verapamil, diltiazem, and nicardipine had similar potency in inhibiting attachment and proliferation with ID50S in the 10(-4) M range. Because CCBs seem to inhibit fibroblast attachment and proliferation, future clinical studies may show that these agents reduce collagen production, scar formation, and bleb failure following glaucoma filtration surgery.

Calcium Channel Blockers↗
PubMed1997

Complete sequence of the UPP gene encoding uracil phosphoribosyltransferase from Mycobacterium bovis BCG.

The nucleotide sequence of a 799 bp fragment of Mycobacterium bovis BCG containing the putative upp gene that encodes a uracil phosphoribosyltransferase (UPRTase [EC 2.4.2.9]) has been determined. The upp gene of BCG has an open reading frame (ORF) of 621 bp (207 amino acids) starting with GTG (position 112) and ending with TGA (position 733), and its molecular mass was calculated to be 21,864 Da. Comparative analyses of the deduced amino acid sequence of BCG UPRTase with the UPRTase of six bacterial genera revealed that 24% (50/211) of the residues are perfectly conserved and 32% (67/211) of the residues are well conserved.

Amino Acid Sequence↗
PubMed1997

Differential expression of ferritin heavy chain in THP-1 cells infected with Mycobacterium bovis BCG.

To identify the host genes induced or suppressed by infection of mycobacteria, the reverse transcriptase polymerase chain reaction (RT-PCR) and the differential display reverse transcriptase polymerase chain reaction (DD RT-PCR) methods were used. In this study, cDNAs complement to mRNA extracted from human peripheral monocyte derived naive THP-1 cells, THP-1 cells infected with live Mycobacterium bovis BCG, THP-1 cells treated with heat-killed BCG, and THP-1 cells incubated with IgG-coated glass-beads were compared on the sequencing gel. One (TG2-1) of the clones selected by DD RT-PCR is 446 bp long and is identical to human ferritin heavy (H) chain gene. Northern blot analysis confirmed that ferritin H chain gene has been markedly over-expressed in monocytic THP-1 cells incubated with live and dead M. bovis BCG. Differential display techniques of host genes whose expression levels were varied by infection of mycobacteria could provide information about the response of macrophages to mycobacterial infection.

Amino Acid Sequence↗
PubMed1997

Gain or loss of diabetogenicity resulting from a single point mutation in recombinant encephalomyocarditis virus.

Molecular pathogenic mechanisms for virus-induced disease have received considerable attention. Encephalomyocarditis (EMC) virus-induced diabetes in mice has been extensively studied to elucidate the cellular and molecular mechanisms involved in the development of this disease. In this study, we report for the first time that a single point mutation at nucleotide position 3155 or 3156 of the recombinant EMC viral genome, located on the major capsid protein VP1, which causes an amino acid change, results in the gain or loss of viral diabetogenicity. A G base at nucleotide position 3155 (alanine at amino acid position 776 of the EMC virus polyprotein [Ala776]; GCC) results in viral diabetogenicity, whereas the substitution of other bases at the same or next position results in a loss of viral diabetogenicity. This finding provides clear evidence that a point mutation at a critical site in a viral genome affects the ability of the virus to cause a cell-specific disease.

Alanine↗
PubMed1997

Identification of gene loci controlling pectate lyase production and soft-rot pathogenicity in Pseudomonas marginalis.

Pseudomonas marginalis is an important postharvest pathogen capable of causing soft rot in a wide variety of harvested fruits and vegetables. Following transposon mutagenesis, we isolated two groups of P. marginalis CY091 mutants deficient in production of pectate lyase (Pel) and soft-rot pathogenicity in plants. The first group, designated Pel-, was caused by the insertion of Tn5 into a pel structural gene, and the second group, designated LemA-, was caused by the insertion of Tn5 into a regulatory locus corresponding to the lemA gene previously identified in other Gram-negative bacteria. The LemA- mutants also exhibited alteration in colony morphology and showed deficiency in production of protease (Prt). A cosmid clone pCIC carrying the P. marginalis lemA gene was isolated and characterized. pCIC was capable of restoring Pel production and soft-rot pathogenicity in LemA- mutants of P. marginalis and Pseudomonas viridiflava, indicating that the function of lemA gene in these two pseudomonads was similar and interchangeable. Using MudI-mediated mutagenesis, we isolated a third group of P. marginalis mutants deficient in production of Pel, Prt, and soft-rot pathogenicity. Mutants in this group (designated GacA-1) contained an insertion of MudI in a locus corresponding to the gacA gene of P. viridiflava. Like LemA- mutants, GacA- mutants also exhibited alteration in colony morphology and showed deficiency in production of Pel and Prt. However, GacA- mutants produced much lower levels of levan and fluorescent pyoverdine siderophore than the wild type and LemA- mutants. These results provide the first genetic evidence that P. marginalis produces a single alkaline Pel for maceration of plant tissue and demonstrate that production of Pel, Prt, levan, and pyoverdin by this bacterium is mediated by the two-component lemA/gacA gene system.

Bacterial Proteins↗