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Biomedical subjects

J Choi

Publications and source records attributed to J Choi.

At least 181 records · Page 10Linked to original sources
PubMed1996

Physical activity increases mRNA for brain-derived neurotrophic factor and nerve growth factor in rat brain.

Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) support the viability and function of many types of neurons, and are likely mediators of activity-dependent changes in the CNS. We examined BDNF and NGF mRNA levels in several brain areas of adult male rats following 0, 2, 4, or 7 nights with ad libitum access to running wheels. BDNF mRNA was significantly increased in several brain areas, most notably in the hippocampus and caudal 1/3 of cerebral cortex following 2, 4, and 7 nights with exercise. Significant elevations in BDNF mRNA were localized in Ammon's horn areas 1 (CA1) and 4 (CA4) of the hippocampus, and layers II-III of the caudal neocortex and retrosplenial cortex. NGF mRNA was also significantly elevated in the hippocampus and caudal 1/3 of the cortex, affecting primarily the dentate gyrus granular layer (DG) and CA4 of the hippocampus and layers II-III in caudal neocortex.

Analysis of Variance↗
PubMed1996

An alternative splice variant of human IL-4, IL-4 delta 2, inhibits IL-4-stimulated T cell proliferation.

Alternative splicing of mRNA can generate protein isoforms that are preferentially expressed in different tissues or during different states of cell differentiation or activation. Protein isoforms may have different functions. In this study, we cloned, expressed, and tested functional effects of a naturally occurring splice variant of human IL-4, called IL-4 delta 2. In IL-4 delta 2, the second exon of IL-4 is omitted by alternative splicing, with exons 1, 3, and 4 joined in an open reading frame. We found that IL-4 delta 2 RNA is expressed in the PBMC of all donors tested, usually in lower amounts than IL-4 RNA. In contrast, IL-4 delta 2 RNA is expressed in much higher levels than IL-4 RNA in thymocytes and bronchoalveolar lavage cells, suggesting tissue specificity of expression. IL-4 delta 2 cDNA was expressed in yeast. Recombinant human (rh) IL-4 delta 2 was partially purified and found to be glycosylated, with a protein core of 13 to 15 kDa. Unlike rhIL-4, rhIL-4 delta 2 did not act as a costimulator for T cell proliferation. However, rhIL-4 delta 2 inhibited the ability of rhIL-4 to act as a T cell costimulator. Inhibition was independent of glycosylation and was not mediated by toxicity. Iodinated IL-4 delta 2 was found to bind specifically to human PBMC and tumor lines known to express IL-4 receptors. Excess unlabeled IL-4 inhibited cellular binding of labeled IL-4 delta 2. Thus, rhIL-4 delta 2 is a naturally occurring splice variant of IL-4 that is preferentially expressed in the thymus and airways and inhibits function of complete IL-4. The balance between IL-4 and IL-4 delta 2 may be important in the regulation of IL-4 effects.

Amino Acid Sequence↗
PubMed1996

Normal adult swallowing of liquid and viscous material: scintigraphic data on bolus transit and oropharyngeal residues.

Scintigraphic data are provided for 20 normal control subjects, 39-65 years of age. Each subject swallowed 10 cc of water and 10 cc of a more viscous material (1,100 centipoise) consisting of apple juice thickened with Thick-It, a commercial food thickener. The test substances were combined with 2.5 mCi Tc-99m sulfur colloid. Scintigraphic data were acquired in dynamic mode for 10 sec at 25 frames/sec as the subject swallowed. Time-activity (TA) data were used to compute transit times, percentage residues in the mouth and pharynx, percent ingested, and a derived swallow efficiency score. The liquid was ingested in a single swallow by all subjects, and 9 cc was actually transferred to the esophagus. In contrast, for the viscous material, 11/20 subjects performed a second clearing swallow within the 10-sec interval. On the first swallow with the viscous substance, an average of 7 cc was transferred to the esophagus. Scintigraphy offers an excellent technique for determining natural and preferred volumes for swallowing a variety of bolus consistencies, since it can quantify the volume of each swallow or partial swallow. In this group of subjects the oral discharge time was shorter with the viscous material than with the water, but the pharyngeal transit times were not significantly different for the two bolus consistencies. Numerical efficiency scores were lower for the viscous material, indicating that such a measure is bolus dependent.

Adult↗
PubMed1996

Elementary events of InsP3-induced Ca2+ liberation in Xenopus oocytes: hot spots, puffs and blips.

Liberation of sequestered Ca2+ ions in Xenopus oocytes by the second messenger inositol 1,4,5-trisphosphate (InP3) occurs from functionally discrete sites, which are spaced at intervals of several microns and probably represent clusterings of InsP3 receptor/channels (InsP3R) in the endoplasmic reticulum. As well as requiring InsP3, opening of release channels is regulated by dual positive and negative feedback by cytosolic Ca2+, leading to regenerative Ca2+ transients. Because the sensitivity of this process is determined by [InsP3], the ability of Ca2+ ions diffusing from one location to activate increasingly distant InsP3R is enhanced by increasing [InsP3]. Together with the spatial distribution of receptors, this results in generation of a hierarchy of Ca2+ release events, which may involve individual InsP3R (Ca2+ 'blips'), concerted activation of several receptors within a single release site (Ca2+ 'puffs'), and recruitment of successive sites by Ca2+ diffusing over micron distances to produce propagating Ca2+ waves. Thus, Ca2+ signalling in the oocyte is organized as at least two sizes of elemental 'building blocks'; highly localized Ca2+ transients that arise autonomously and stochastically from discrete sites at low [InsP3], but which become coordinated at higher [InsP3] to produce global Ca2+ responses.

Animals↗
PubMed1996

Scintigraphic quantification of aspiration reduction with the Passy-Muir valve.

The Passy-Muir "speaking" tracheostomy valve has been noted to aid in swallowing, based on videofluoroscopy to assess aspiration. In this study scintigraphy was used to quantify the amount of material aspirated. Eleven patients were studied who currently had a tracheostomy in place and were either known to aspirate or were suspected of aspirating. Most were post-treatment head and neck cancer patients who were tumor free at the time of testing. Swallowing was evaluated using videofluoroscopy and scintigraphy. Videofluoroscopy was performed to assess anatomy and determine whether aspiration had occurred. Scintigraphic testing was then performed when the patient had the one-way valve on, and again with it off and tracheostomy open. Following a swallow, the amount (%) of aspirate with the valve in place was found to be significantly less than with the tracheostomy open. A one-way valve can be helpful in reducing aspiration in patients who are at risk for aspiration and who require that their tracheostomy be open.

Humans↗
PubMed1996

Purification and characterization of a fibrinolytic enzyme produced from Bacillus sp. strain CK 11-4 screened from Chungkook-Jang.

Bacillus sp. strain CK 11-4, which produces a strongly fibrinolytic enzyme, was screened from Chungkook-Jang, a traditional Korean fermented-soybean sauce. The fibrinolytic enzyme (CK) was purified from supernatant of Bacillus sp. strain CK 11-4 culture broth and showed thermophilic, hydrophilic, and strong fibrinolytic activity. The optimum temperature and pH were 70 degrees C and 10.5, respectively, and the molecular weight was 28,200 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The first 14 amino acids of the N-terminal sequence of CK are Ala-Gin-Thr-Val-Pro-Tyr-Gly-Ile-Pro-Leu-Ile-Lys-Ala-Asp. This sequence is identical to that of subtilisin Carlsberg and different from that of nattokinase, but CK showed a level of fibrinolytic activity that was about eight times higher than that of subtilisin Carlsberg. The amidolytic activity of CK increased about twofold at the initial state of the reaction when CK enzyme was added to a mixture of plasminogen and substrate (H-D-Val-Leu-Lys-pNA). A similar result was also obtained from fibrin plate analysis.

Amino Acid Sequence↗
PubMed1996

Regional Transcatheter Therapy of Hepatic Neoplasms.

BACKGROUND: Surgical resection of hepatocellular carcinomas and metastases to the liver cannot always be performed, and systemic therapies for these entities are of limited value. The techniques of chemoembolization and hepatic artery infusion have been used for patients who are not candidates for surgery. METHODS: Chemoembolization uses percutaneous intra-arterial infusion of chemotherapeutic agents and embolic material. This provides longer contact of the agents with the tumor cells and induces ischemia. Hepatic arterial chemoinfusion uses the knowledge that hepatic cancers are supplied predominantly by the hepatic artery. RESULTS: Chemoembolization using Lipiodol, doxorubicin, and Gelfoam has promoted necrosis of unresectable hepatocellular tumors and may have prolonged patient survival. Hepatic arterial infusion with fluorinated pyrimidines produces more objective responses than systemic chemotherapy but probably does not alter survival. CONCLUSIONS: The nonsurgical treatments of chemoembolization and hepatic arterial infusion of chemotherapy have expanded our armamentarium to manage many primary and metastatic tumors in the liver. Additional approaches are needed.

Journal Article↗
PubMed1996

Safe and effective early postoperative feeding and hospital discharge after open colon resection.

Recent articles have stressed early postoperative feeding and hospital discharge as major benefits of laparoscopic colon surgery. From March 1993 to December 1994, an early feeding protocol after open colon resection consisting of clear liquid diet on postoperative Day (POD) 2, then advancing to regular diet on POD 3, and discharging home as tolerated was applied to 41 patients (Group A). We reviewed the charts of 41 consecutive patients from January 1992 to February 1993 who were operated immediately before the protocol and whose diet was started by traditional methods (Group B). Both groups were similar in age and types of procedures performed. Clear liquid diet was started earlier in Group A than Group B (all patients on POD 2 versus average POD 4.9 (range, 4-7 days), but it was tolerated by a similar number of patients in both groups (90% versus 85%). The mortality and morbidity in both Groups were similar. In Group B, four patients (9.8%) did not tolerate diet and needed nasogastric tube, whereas none required nasogastric tube in Group A. The average hospital stay was 4.2 days (range, 3-8 days) in group A versus 6.7 days (range, 5-34 days) in Group B. In Group A, 67 per cent were discharged home by POD 4 versus none in Group B. Neither group had readmission within 2 weeks for recurrent nausea or vomiting. The early postoperative feeding and hospital discharge are safe and effective after open colon surgery.

Adolescent↗
PubMed1996

Galeal flap: clinical application in periorbital and orbital reconstruction.

We report the use of a galea flap in the reconstruction of the orbit and the periorbital in region three representative cases. Two patients, who had communication between the orbit, paranasal sinuses, and cranium following orbital and periorbital tumor resection, required a physical barrier to partition these compartments and an immunological barrier to prevent infection. A third patient, who had a contracted socket and had been on systemic steroids chronically, required a tissue with intrinsic blood supply to sustain an implant and promote healing. The outcome in all three patients was gratifying. The surgical anatomy is reviewed, the surgical technique detailed, and potential applications and complications discussed.

Adult↗
PubMed1995

A temperature-sensitive IE1 protein of Autographa californica nuclear polyhedrosis virus has altered transactivation and DNA binding activities.

The temperature-sensitive mutant tsB821 of Autographa californica nuclear polyhedrosis virus has two nucleotide transitions in the transregulatory ie1 gene (Ribiero et al. (1994) J. Virol. 68, 1075-1084). These mutations result in two conservative amino acid substitutions in the encoded protein. To determine whether the mutations affect the ability of IE1 to interact with viral enhancer elements, electrophoretic mobility shift assays were performed using extracts prepared from infected cells and a fragment of the viral enhancer element hr5. When binding reactions were assembled on ice, the extracts prepared from tsB821-infected cells showed wild-type levels of DNA binding activity, whether the infected cells were grown at the permissive or nonpermissive temperature. However, when binding reactions were incubated at 33 degrees, enhancer binding activity was significantly reduced in the ts extract. This suggests that the ts phenotype results from reduced interactions of tsIE1 with the viral enhancer elements. Site-directed mutagenesis was used to construct plasmids encoding IE1 with both of the amino acid substitutions (tsIE1) and with each of the single substitutions. tsIE1 was expressed in transient assays and exhibited thermolabile enhancer binding activity. However, proteins with single substitutions did not accumulate to detectable levels and did not exhibit enhancer binding activity. Temperature shift-up experiments with tsB821 indicated that late genes were expressed at wt levels when cells were shifted to the nonpermissive temperature during the early phase. This suggests that IE1 is not directly and continuously required for expression of late genes. However, polyhedrin expression was decreased in the mutant-infected cells when the temperature was shifted during the early or late phases of infection. Together, these results suggest that IE1 may differentially affect expression of these two classes of genes.

Animals↗
PubMed1995

Expression of the IE1 transactivator of Autographa californica nuclear polyhedrosis virus during viral infection.

The immediate-early IE1 protein of Autographa californica nuclear polyhedrosis virus (AcMNPV) is an important regulator of viral gene transcription. To provide a tool for further analysis of the expression and function of IE1, a polyclonal antiserum was raised against IE1 expressed in bacteria. Immunoblot analysis of infected cell lysates was used to monitor the accumulation of IE1 throughout the viral life cycle. When extracts were prepared in the presence of phosphatase inhibitors, only one protein band was detected on SDS-polyacrylamide gels. However, in the absence of phosphatase inhibitors, at least four distinct electrophoretic species were detected. Mobility shift assays were conducted using an enhancer DNA probe and whole cell extracts prepared at different times postinfection. Results indicated that the enhancer-binding activity of IE1 increased from 4 to 72 hr postinfection. DNA-protein complexes formed with infected cell extracts migrated more slowly than those formed with transfected cell extracts. This effect was more pronounced with extracts prepared in the presence of phosphatase inhibitors. Supershift experiments with IE1 antiserum confirmed that IE1 was a component of DNA-protein complexes in both transfected and infected cell extracts. A titration experiment was done to determine the minimal amounts of IE1 required for activation of the 39k promoter in the presence and absence of a cis-linked enhancer element. These analyses indicated that the intracellular levels of IE1 are not sufficient for enhancer-independent activation of the 39k promoter during the early phase of viral infection. Quantitative immunoblots revealed that the amount of IE1 in budded virus was less than 0.68 mole per mole of viral DNA, suggesting that IE1 is not a structural protein of AcNPV.

Animals↗
PubMed1995

Quantal puffs of intracellular Ca2+ evoked by inositol trisphosphate in Xenopus oocytes.

1. Ca2+ liberation induced in Xenopus oocytes by a poorly metabolized derivative of inositol 1,4,5-trisphosphate (3-deoxy-3-fluoro-D-myo-inositol 1,4,5-trisphosphate; 3-F-InsP3) was visualized using a video-rate confocal microscope to image fluorescence signals reported by the indicator dye calcium green-1. 2. Low (10-30 nM) intracellular concentrations of 3-F-InsP3 evoked Ca2+ release as localized transient 'puffs'. Progressively higher concentrations (30-60 nM) gave rise to abortive Ca2+ waves triggered by puffs, and then (> 60 nM) to a sustained elevation of Ca2+ followed by the appearance of propagating Ca2+ waves. At concentrations up to that giving waves, the frequency of puffs increased as about the third power of [InsP3], whereas their amplitudes increased only slightly. 3. The rise of cytosolic Ca2+ during a puff began abruptly, and peaked within about 50 ms. The peak free Ca2+ level was about 180 nM, and the total amount of Ca2+ liberated was several attomoles (10(-18) mol), too much to be accounted for by opening of a single InsP3-gated channel. The subsequent decline of Ca2+ occurred over a few hundred milliseconds, determined largely by diffusion of Ca2+ away from the release site, rather than by resequestration. Lateral spread of Ca2+ was restricted to a few micrometres, consistent with an effective diffusion coefficient for Ca2+ ions of about 27 microns2 s-1. 4. The peak amplitudes of puffs recorded at a given site were distributed in a roughly Gaussian manner, and a small proportion of sites consistently gave puffs much larger than the main population. Intervals between successive puffs at a single site were exponentially distributed, except for a progressive fall-off in puffs seen at intervals shorter than about 10 s. Thus, triggering of puffs appeared to be stochastically determined after recovery from a refractory period. 5. There was little correlation between the occurrence of puffs at sites more than a few micrometres apart, indicating that puff sites can function autonomously, but closely (ca 2 microns) adjacent sites showed highly correlated behaviour. 6. Puffs arose from sites-present at a density of about 1 per 30 microns2 in the animal hemisphere, located within a narrow band about 5-7 microns below the plasma membrane. 7. We conclude that Ca2+ puffs represent a 'quantal' unit of InsP3-evoked Ca2+ liberation, which may arise because local regenerative feedback by cytosolic Ca2+ ions causes the concerted opening of several closely clustered InsP3 receptor channels.

Animals↗
PubMed1995

Congenital syphilis mimicking child abuse.

It has been reported that fractures complicating congenital syphilis can mimic child abuse. We present such a finding in an 8-week-old infant who presented with paralysis of the left arm.

Child Abuse↗
PubMed1995

Antiphospholipid antibodies lead to increased risk in cardiovascular surgery.

BACKGROUND: Antiphospholipid (APL) antibodies are a heterogenous group of antibodies that have been associated with an increase in bleeding complications and a marked increase in thrombotic events, both of which result in significant patient morbidity and mortality. PATIENTS AND METHODS: A retrospective analysis of patients identified to be positive for APL via a university thrombosis registry who had cardiovascular surgery between 1989 and 1994. RESULTS: Seventy-one patients positive for APL antibodies were identified. Of those patients, 19 had cardiovascular surgical procedures (11 women and 8 men, mean age 58.4 years, range 38 to 78). A total of 48 cardiovascular surgical procedures (mean 2.5 procedures/patient) were performed in the 19 patients. These procedures included 13 lower-extremity reconstructions, 11 upper-extremity reconstructions/fistulas, 8 cardiac valve replacements, 5 coronary artery bypass procedures, 5 major amputations, 4 infrarenal aortic reconstructions, and 2 carotid endarterectomies. Sixteen of the 19 patients (84.2%) suffered major postoperative complications. These included 16 thrombosed grafts, 5 strokes, 5 major bleeding events, 2 pulmonary emboli, and 2 myocardial infarctions. Ultimately, 12 of the 19 patients (63.2%) died of complications related to surgery. CONCLUSIONS: This series of patients confirms that patients with circulating APL antibodies are prone to excessive postoperative morbidity and mortality after cardiovascular surgical procedures. The presence of APL antibodies may be a maker of increased risk of complications after cardiovascular surgery.

Adult↗
PubMed1995

Localization of the epitope in methamphetamine and its antibody use for the detection of methamphetamine and benzphetamine by polarization fluoroimmunoassay.

An antibody was prepared, using a four carbon-bridged methamphetamine molecule as an immunogen in order to develop a polarization fluoroimmunoassay for urine screening of methamphetamine and benzphetamine. Also, its binding characteristics were investigated to locate epitope sites of methamphetamine. The study showed that the antibody was highly capable of eliciting a polarization fluoroimmunoassay response. However, the detection limit was much greater for benzphetamine (0.05 ppm) than for methamphetamine (0.2 ppm) and weakly antibody binding was found with methamphetamine. This difference in sensitivity may reflect the similarity of benzphetamine to the immunogen used to produce the antibody. Both benzphetamine and the immunogen have a tertiary amine attached to a carbon bridges whereas methamphetamine has only a secondary amine and amphetamine has a primary amine group. The difference of cross-reactivity data between phenylethylamine drugs and beta-hydroxyl phenylethylamine drugs indicates that the beta-carbon position have a major influence on the antibody interaction. Thus, the substitution of hydroxyl group on beta-carbon resulted in virtually no antibody affinity, even if a tertiary amine or secondary amine group was present in the molecule. This suggests that the beta-carbon chain plays a primary role as the epitope site with cooperative binding site of tertiary amine or secondary amine in alpha-carbon position. A hydroxyl group at the beta-carbon position plays an important inhibitory role to the antibody binding.

Antibody Affinity↗
PubMed1995

The baculovirus transactivator IE1 binds to viral enhancer elements in the absence of insect cell factors.

The transregulatory IE1 protein of Autographa californica nuclear polyhedrosis virus binds to the viral enhancer element hr5. To test whether IE1 binds independently of host cell factors, IE1 was translated in rabbit reticulocyte extracts and tested for DNA binding activity by an electrophoretic mobility shift assay. Complexes with the hr5 probe were detected with translation reaction mixtures primed with ie1 RNA but not with control translation reaction mixtures. However, the DNA-protein complexes formed with IE1 translated in vitro migrated more slowly than complexes formed with IE1 that was transiently expressed in insect cells. Phosphatase treatment of the translation reactions resulted in an increase in the mobility of the DNA-protein complexes, suggesting that hyperphosphorylation was responsible for the altered migration. To further verify that IE1 was capable of binding DNA in the absence of host cell factors, an N-terminal truncation of IE1 was synthesized in vitro, and shown to interact with hr5. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of IE1 translated in vitro revealed that the mobility of the protein was heterogeneous. This pattern was altered by translation in the presence of an oligonucleotide corresponding to the IE1 specific binding site but was not affected by translation in the presence of a nonspecific DNA. These results suggest that binding of IE1 to DNA causes a conformational change in the protein that alters the accessibility of IE1 to protein kinases.

Animals↗