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Biomedical subjects

B Choi

Publications and source records attributed to B Choi.

At least 55 records · Page 3Linked to original sources
PubMed1999

Antiretroviral antibodies: implications for schizophrenia, schizophrenia spectrum disorders, and bipolar disorder.

BACKGROUND: Some retroviral antigens share structural homology within a group of related retroviruses. It is possible that antibodies directed against one virus may cross-react with antigens from a different virus in the group. METHODS: Using this principle, the human immunodeficiency virus 1 (HIV-1) Western blot assay was used as an available source of human retroviral antigens to screen serum samples from an archived collection to ascertain whether there was an association between serum antiretroviral antibodies and mental illnesses. RESULTS: A statistically significant proportion (28/54, 52%) of patients suffering from psychiatric disorders had serum antibodies that recognized at least one antigen present on the blot, culminating in indeterminate HIV-1 tests. The majority of the reactive samples were directed against the HIV-1 group antigens p24 and p17. These findings contrast with those of nonpsychiatric patients, who had 4/16 (25%) indeterminate blots. CONCLUSIONS: The results suggest exposure to retroviral antigens related to those of HIV-1 in subpopulations of schizophrenic, schizophrenic spectrum disorder, and bipolar disorder patients.

Antibodies, Viral↗
PubMed1999

Radiometric surface temperature measurements during dye-assisted laser skin closure: in vitro and in vivo results.

BACKGROUND AND OBJECTIVE: A thermal camera was used to measure surface temperatures during laser skin welding to provide feedback for optimization of the laser parameters. STUDY DESIGN/MATERIALS AND METHODS: Two-centimeter-long, full-thickness incisions were made in guinea pig skin in vitro and in vivo. India ink was applied to the incision edges, which were then mechanically apposed. Continuous-wave, 1.06-microm Nd:YAG laser radiation was scanned over the incisions, producing an effective pulse duration of approximately 100 msec. Cooling durations between scans of 1.6, 4.0, and 8.0 sec were studied in vitro. A 5-mm-diameter laser spot was used with the power kept constant at 10 W. Thermal images were obtained at 30 frames per second with a thermal camera detecting 3-5 microm radiation. Surface temperatures were recorded at 0, 1, and 6 mm from the center line of the incision. RESULTS/CONCLUSIONS: Cooling durations of 1.6 and 4.0 seconds in vitro resulted in temperatures at the weld site that remained above approximately 65 degrees C for prolonged periods of time. Cooling durations of 8.0 seconds were sufficient both in vitro and in vivo to prevent a significant rise in baseline temperatures at the weld site over time.

Animals↗
PubMed1999

Identification of a cytoplasmic targeting/retention signal in a retroviral Gag polyprotein.

Retroviral capsid assembly can occur by either of two distinct morphogenic processes: in type C viruses, the capsid assembles and buds at the plasma membrane, while in type B and D viruses, the capsid assembles within the cytoplasm and is then transported to the plasma membrane for budding. We have previously reported that a single-amino-acid substitution of a tryptophan for an arginine in the matrix protein (MA) of Mason-Pfizer monkey virus (MPMV) converts its capsid assembly from that of a type D retrovirus to that of the type C viruses (S. S. Rhee and E. Hunter, Cell 63:77-86, 1990). Here we identify a region of 18 amino acids within the MA of MPMV that is responsible for type D-specific morphogenesis. Insertion of these 18 amino acids into the MA of type C Moloney murine leukemia virus causes it to assemble an immature capsid in the cytoplasm. Furthermore, fusion of the MPMV MA to the green fluorescent protein resulted in altered intracellular targeting and a punctate accumulation of the fusion protein in the cytoplasm. These 18 amino acids, which are necessary and sufficient to target retroviral Gag polyproteins to defined sites in the cytoplasm, appear to define a novel mammalian cytoplasmic targeting/retention signal.

3T3 Cells↗
PubMed1998

Role of potassium in human immunodeficiency virus production and cytopathic effects.

Acute infection of CD4+ lymphoid cells by human immunodeficiency virus type 1 (HIV-1) induces an increase in the intracellular concentration of potassium (K+). Media containing reduced or elevated concentrations of K+ were used to investigate the role of this ion in HIV-1 production and cytopathology. Incubation of CD4+ lymphoblastoid cells acutely infected by HIV-1 (strain LAI) in low K+ medium resulted in an approximately 50% decrease in HIV-1 production and markedly diminished HIV-1 induced cytopathic effects (CPE) relative to cells incubated in medium containing a normal K+ concentration (approximately 5 mM). Incubation of HIV-1 infected cells in media containing elevated concentrations of K+ medium. Cells mM) increased HIV-1 production by two- to fivefold over the amount produced in cells incubated in normal K+ medium. Cells incubated in high K+ media also displayed enhanced HIV-1-induced cytopathology. The decrease in HIV-1 production by low K+ medium and increase by high K+ media could be a accounted for by effects on HIV-1 reverse transcription. However, low K+ medium inhibited HIV-1 protein synthesis and high K+ media increased HIV-1 protein synthesis. These results suggest that the HIV-1-induced increase in intracellular is required for efficient viral replication and to induce cytopathology.

CD4-Positive T-Lymphocytes↗
PubMed1998

Inhibition of HIV type 1 production by hygromycin B.

HIV infection alters the cellular uptake of ions and other small molecules. This study was designed to determine whether hygromycin B, a low molecular weight (MW 527) aminoglycoside protein synthesis inhibitor that is normally impermeable to mammalian cells at micromolar concentrations, can selectively inhibit HIV expression and cytopathology. CD4+ T lymphoblastoid cells (H9) and peripheral blood mononuclear cells (PBMCs) were infected with HIV-1, then incubated in medium containing various concentrations of hygromycin B. HIV-1-induced formation of multinucleated giant cells and single cell killing were dramatically reduced in the presence of micromolar concentrations of hygromycin B. Hygromycin B also inhibited HIV-1 production in a dose-dependent manner during acute infection. G418, a larger and more hydrophobic aminoglycoside (MW 692), did not display the same selective inhibition of HIV-1 production as hygromycin B. Relative to mock-infected cells, protein synthesis in acutely infected H9 cells was selectively inhibited by hygromycin B. Hygromycin B also reduced HIV production in PBMCs and in H9 cells persistently infected with HIV. PCR analysis demonstrated that hygromycin B did not inhibit HIV-1 reverse transcription. These results demonstrate that HIV-1 infection renders cells more sensitive to hygromycin B than uninfected cells, and provides support for the hypothesis that HIV-1 induces an alteration of plasma membrane permeability. The HIV-modified cell membrane may be a potential target for antiviral intervention and chemotherapy.

Anti-Bacterial Agents↗
PubMed1998

Imaging of the irradiation of skin with a clinical CO2 laser system: implications for laser skin resurfacing.

BACKGROUND AND OBJECTIVE: Several published reports describe the benefits of using the carbon dioxide laser for cutaneous resurfacing. The mechanisms on which skin resurfacing work are still not completely understood. This study was performed to obtain quantitative and qualitative information describing the thermal response of skin during high-energy, short-pulsed CO2 laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: A Tissue Technologies TruPulse CO2 laser was used to irradiate an in vivo rat model. The laser parameters that were used were a 100-micros pulse width, a 1-Hz repetition rate, a 3 mm x 3 mm square spot size, and 2.4 J/cm2 and 3.9 J/cm2 radiant exposures. A 3-5 microm thermal camera was used to obtain temperature information during irradiation. Single spots were irradiated with one pulse, and the temperature-time history was obtained. In a different experiment, 15 pulses were applied to single spots, and both thermal and video images were obtained. RESULTS: Irradiation with one pulse at 2.4 J/cm2 and 3.9 J/cm2 led to peak temperatures >100 degrees C. The temperature relaxation time was approximately 25-150 ms. Multiple-pulse irradiation at 2.4 J/cm2 led to a slight rise in the peak temperature with each pulse. At 3.9 J/cm2, the peak temperature increased with successive pulses until pulse 10, after which the peak temperature oscillated between 300 and 400 degrees C. Video images showed concurrent burning events that occurred during pulses 10-15. CONCLUSION: Temperatures >100 degrees C were measured during CO2 laser irradiation of skin. Pulse stacking can lead to peak temperatures approaching 400 degrees C and to tissue charring with as few as three stacked pulses. It is crucial for the physician to manipulate the laser handpiece at parameters with which he or she can avoid pulse overlap.

Animals↗
PubMed1997

A synthetic peptide corresponding to the carboxy terminus of human immunodeficiency virus type 1 transmembrane glycoprotein induces alterations in the ionic permeability of Xenopus laevis oocytes.

The carboxy-terminal 29 amino acids of the human immunodeficiency virus type 1 transmembrane glycoprotein (HIV-1 TM) are referred to as lentivirus lytic peptide 1 (LLP-1). Synthetic peptides corresponding to LLP-1 have been shown to induce cytolysis and to alter the permeability of cultured cells to various small molecules. To address the mechanisms by which LLP-1 induces cytolysis and membrane permeability changes, various concentrations of LLP-1 were incubated with Xenopus laevis oocytes, and two-electrode, voltage-clamp recording measurements were performed. LLP-1 at concentrations of 75 nM and above induced dramatic alterations in the resting membrane potential and ionic permeability of Xenopus oocytes. These concentrations of LLP-1 appeared to induce a major disruption of plasma membrane electrophysiological integrity. In contrast, concentrations of LLP-1 of 20-50 nM induced changes in membrane ionic permeability that mimic changes induced by compounds, such as the bee venom peptide melittin, that are known to form channel-like structures in biological membranes at sublytic concentrations. An analog of LLP-1 with greatly reduced cytolytic activity failed to alter the electrophysiological properties of Xenopus oocytes. Thus, by altering plasma membrane ionic permeability, the carboxy terminus of TM may contribute to cytolysis of HIV-1-infected CD4+ cells.

Animals↗
PubMed1997

Effect of adrenergic receptor activation on post-herpetic neuralgia pain and sensory disturbances.

Patients with acute herpes zoster, and to a lesser extent post-herpetic neuralgia (PHN), have been reported to respond to local anesthetic blockade of the sympathetic nervous system. In animal models of nerve injury, local injection of adrenergic agonists after nerve injury, but not before, excites nociceptors. In some patients with chronic neuropathic pain, local application of norepinephrine evokes pain. In 15 subjects with PHN, the role of adrenergic receptors in PHN pain was assessed in a two-session double blind study comparing the response to cutaneous infiltration of epinephrine or phenylephrine (30 micrograms in 3 ml) with the response to normal saline in both the painfully affected skin and mirror-image normal skin. Two adjacent sites were studied on each side of the body, one site for injection and the other for measuring sensory effects of the injection. In the morning part of each session, mirror-image normal skin was injected. In the afternoon portion of each session, skin in the most painful area affected by PHN was injected. Injection of saline or the adrenergic agonist in normal skin produced mild and transient pain without development of allodynia and without affecting overall PHN pain intensity. In PHN skin, injection of saline and the adrenergic agonist produced an equivalent degree of transient pain that was slightly greater than injection into mirror-image normal skin. After injection of the adrenergic agonist into PHN skin, both overall PHN pain and allodynia severity were significantly greater than after saline injection, peaking at 10-15 min post-injection. Even when PHN has been present for years, adrenergic receptor stimulation in PHN skin increases pain, most likely through direct activation of C-nociceptors in the painful skin. Increased allodynia is most likely mediated centrally and driven by the increase in C-nociceptor input.

Adrenergic alpha-Agonists↗
PubMed1997

[Study for searching equilibrium point in dentulous hemimandibulectomy patients].

Occlusal registration for prosthodontic rehabilitation in dentulous hemimandibulectomy patient has various difficulties due to mandibular instability. The purpose of this study was to find the occlusal contact position for remaining dentition to stabilize the hemiresected mandible during clenching. Three hemimandibulectomized subjects without surgical bony construction were selected and custom-made Gothic-arch typed apparatus was fabricated. Mandibular movements during clenching were recorded with jaw movement tracking device with six degrees of freedom. The results were as follows: 1. The direction of the mandibular rotation around each coordinate axis in 3-dimensional space during clenching was constant in each subject, regardless of stylus position. 2. The most stable points on the hemimandibules during clenching did not necessarily correspond to the mid-portion of the remaining dentition of the mandible. 3. When referred to the maxillary arch, the point was lined up within the distal half of the second premolar and the mesial third of the first molar in mid-sagittal plane along the long axis of the remaining dentition. 4. Rotational axis during clenching existed on the horizontal plane. 5. It was assumed that the most stable point of the mandible in a hemimandibulectomy patient may be useful in interocclusal registration in clinical dental practice.

Carcinoma, Squamous Cell↗
PubMed1996

Iron metabolism-related genes and mitochondrial genes are induced during involution of mouse mammary gland.

To understand molecular mechanisms of mammary gland involution, several clones were isolated after the primary differential screening of a total 40,000 pfu of involution-specific cDNA library, and further characterized. The partial sequences and Northern analysis revealed that iron metabolism-related genes and mitochondrial genes were induced during mammary gland involution. The expression of the lactoferrin gene was induced at involution days 1, 2, and 3. The expression of ferritin heavy chain gene was induced at involution days 1, 2, 3 and 4. Cytochrome oxidase subunit 1 and cytochrome oxidase subunit 2 genes were induced at involution days 4 and 7. The expression of cytochrome b gene was induced at involution day 7. These results imply that iron metabolism and mitochondrial function may be altered during mammary gland involution.

Animals↗
PubMed1996

Alteration of intracellular potassium and sodium concentrations correlates with induction of cytopathic effects by human immunodeficiency virus.

Increases in intracellular concentrations of potassium ([K+]i) and sodium ([Na+]i) occur concomitantly with cytopathic effects induced in a CD4+ T-lymphoblastoid cell line acutely infected by human immunodeficiency virus (HIV). This [K+]i increase was greater in cells infected by cytopathic HIV strains than in cells infected by less cytopathic strains. T cells persistently infected by HIV had an increased [K+]i but displayed an [Na+]i similar to that of mock-infected cells. HIV induced increases in [K+]i and [Na+]i after cytopathic infection of human peripheral blood mononuclear cells, but the magnitude of the Na+ changes did not correlate with the extent of the cytopathic effect. Enhanced movement of cations may osmotically drive water entry, resulting in balloon degeneration and lysis of HIV-infected cells. These observations offer potential approaches for antiviral therapies.

CD4-Positive T-Lymphocytes↗
PubMed1996

Toxoplasma antibody titers by ELISA and indirect latex agglutination test in pregnant women.

The seroepidemiologic studies on anti-Toxoplasma antibody titers were carried out using ELISA and indirect latex agglutination test. Among 899 sera prepared from pregnant women, 39 cases (4.3%) revealed positive reaction and 218 sera from middle school students showed 4 positive reaction (1.8%) by ELISA. By LAT (newly established by National Veterinary Research Institute. Korea), the sera of 7 pregnant women (0.8%) showed positive reaction. When 80 sera showing > or = 1:8 by LAT were used for comparing the results obtained from LAT and Toxotest-MT (Eiken Chemical Co., Japan), 7 cases and 8 sera were positive, respectively. All of 11 sera of proven toxoplasmosis patients showed positive reaction in both tests. Overall proportion of agreement between LAT kit and Toxotest-MT was 0.94 (kappa-index = 0.632, p < 0.011, and LAT was considered to be useful for the screening of toxoplasmosis.

Adolescent↗
PubMed1995

Genetic determinants of feline leukemia virus-induced multicentric lymphomas.

Three discrete forms of feline leukemia virus (FeLV)-associated lymphoma have been described clinically: (1) thymic, (2) alimentary, and (3) multicentric. The most common and best-characterized lymphomas are of T-cell origin, generally occurring in the thymus. These tumors typically contain mature T-cells, involve the activation of a distinctive set of proto-oncogenes, and contain FeLV proviruses whose long terminal repeat (LTR) sequences contain tandemly repeated enhancers. Previous studies of a small group of extrathymic, multicentric lymphomas implicated a different set of genetic determinants. The present study expands those observations by examining the lineage of origin, the involvement of proto-oncogenes, and the structure of LTR and env gene sequences in a set of 11 natural, extrathymic lymphomas of the multicentric type. A pattern of genetic events associated with FeLV-positive multicentric lymphomas emerges from this analysis that is clearly distinct from the pattern associated with thymic lymphomas. The tumors do not contain T-cells or B-cells, as evidenced by the germ line organization of TCR beta and IgH loci. Proto-oncogenes strongly implicated in T-cell lymphomagenesis are not involved in these tumors. Rather, a distinct set of proto-oncogenes may be involved. Most striking is the repeated occurrence of an FeLV isolate whose LTR and env gene bear unique sequence elements.

Amino Acid Sequence↗
PubMed1995

Expression of protein kinase C isozymes that are required for chondrogenesis of chick limb bud mesenchymal cells.

Protein kinase C (PKC) has been suggested to be involved in the chondrogenesis of chick limb bud mesenchymal cells. This study examined the expression and the role of PKC isozymes in chondrogenesis. Multiple PKC isozymes such as conventional PKC (cPKC alpha and gamma), new PKC (nPKC epsilon), and atypical PKC (aPKC zeta, lambda, and tau) were expressed in chondroblasts but cPKC beta and nPKC delta were not detected. The amounts of expressed cPKC and nPKC isozymes, namely cPKC alpha and gamma and nPKC epsilon, were increased as chondrogenesis proceeds while the level of aPKC isozymes was not changed. Treatment of cells with specific PKC inhibitors blocked chondrogenesis. Prolonged exposure of cells to phorbol ester which down regulates both cPKC and nPKC also blocked chondrogenic differentiation. The inhibition of chondrogenesis was the most effective when PKC activity was blocked at the early stage of chondrogenesis (i.e., for the first 24 hours of micromass culture). Down regulation of PKC blocked both proliferation of cells and synthesis of sulfated proteoglycans, indicating that expression of cPKC and nPKC is required at early stage of chondrogenesis.

Animals↗
PubMed1992

Characterization of catechol 2,3-dioxygenases.

Three catechol 2,3-dioxygenases for biphenyl, naphthalene/salicylate, and toluene/xylene oxidation were cloned from Achromobacter xylosoxidans KF701, Pseudomonas putida (NAH7), and Pseudomonas sp. (pWWO). The cloned catechol 2,3-dioxygenases were identified by enzymatic activity assay in addition to yellow bands on polyacrylamide gel after electrophoresis and activity staining. All of the cloned catechol 2,3-dioxygenases exhibited their highest activities on catechol as a substrate compared with catechol derivatives including 4-chlorocatechol, 3-methylcatechol, and 4-methylcatechol. The cloned catechol 2,3-dioxygenases are not fused proteins but were significantly different from one another in their electrophoretic mobilities on nondenaturing 7.5%-polyacrylamide gel.

Alcaligenes↗