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Biomedical subjects

H Cho

Publications and source records attributed to H Cho.

At least 37 records · Page 2Linked to original sources
PubMed2000

Comparison of two commercially available near-infrared spectroscopy instruments for cerebral oximetry. Technical note.

Two near-infrared spectroscopy (NIRS) devices were compared with regard to their responses to changes in cerebral hemoglobin oxygenation induced by hypoxia and hypercapnia in five healthy volunteers. Sensors belonging to each NIRS device were placed on opposite sides of the volunteer's forehead. The INVOS-3100A device, approved by the United States Food and Drug Administration, records the percentage of oxyhemoglobin (HbO2) saturation and the investigational NIRO500 device records absolute changes in HbO2, deoxyhemoglobin, and total hemoglobin in micromolar concentrations referenced to an arbitrary baseline. The volunteers breathed separate mixtures of 7% CO2 in O2 and 10% O2 for 5 minutes in random order. Arterial blood pressure, end-tidal CO2 (ETCO2), arterial O2 saturation, and electrocardiographic data were continuously monitored. Hypercapnia increased (p < 0.01) ETCO2 from 42+/-2 to 56+/-3 mm Hg (mean +/- standard deviation), resulting in a 7.3+/-0.2% increase (p < 0.005) in cerebral HbO2 saturation detected by the INVOS3100A device and an 11.6+/-3 microM increase (p < 0.0008) in HbO2 detected by the NIRO500. Hypoxia decreased (p < 0.01) arterial HbO2 saturation from 98+/-1 to 87+/-3%, causing a 5.1+/-1.2% decrease (p < 0.01) in the percentage of HbO2 saturation detected by the INVOS3100A device and a 9.7+/-6.3 microM decrease in HbO2 detected by the NIRO500. The responses of the NIRO500 and the INVOS3100A instruments to changes in cerebral oxygenation resulting from hypercapnia and hypoxia were generally similar; however, responses tended to be greater when recorded by the NIRO500 device, perhaps because, unlike the INVOS3100A device, the NIRO500 does not correct for skin and bone contamination.

Blood Gas Monitoring, Transcutaneous↗
PubMed2000

[Combined 5-FU and CDDP in a gastric cancer patient undergoing hemodialysis--pharmacokinetics of 5-FU and CDDP].

The pharmacokinetics of 5-FU and CDDP was examined in a gastric cancer patient receiving regular hemodialysis (HD) for renal failure. The patient received combination chemotherapy of 5-FU and CDDP, then on the day of HD we measured the plasma concentration of 5-FU, total platinum, and non-protein-bound platinum of the patient. In the present case, the 5-FU concentration was kept at an almost even level during HD. Non-protein-bound platinum disappeared after being maintained in blood for a certain time when HD was started 30 minutes after the end of CDDP administration. From these findings, we conclude that combined 5-FU and low-dose CDDP therapy should be done by decreasing the dose of 5-FU, administrating CDDP only on the day the patient undergoes HD, and starting HD 30 minutes after the end of CDDP administration.

Adult↗
PubMed1999

Signaling pathways mediating insulin-stimulated glucose transport.

A major action of insulin is to accelerate the rate of uptake of sugar into muscle and adipose cells following a meal. The biochemical mechanism by which this is accomplished has been a subject of intense experimentation, although elucidation of the pathways has remained elusive. In recent years, numerous signaling molecules and cascades modulated by insulin have been identified, although few have been definitively established as important to the metabolic actions of the hormone. An exception to this is the lipid kinase phosphatidylinositide 3'-kinase, which, under many conditions, appears absolutely required for insulin to stimulate hexose uptake into adipocytes. Akt/PKB, a serine/threonine protein kinase activated by insulin in a phosphatidylinositide 3'-kinase-dependent manner, has been implicated as a critical mediator of insulin's actions on metabolism and cell survival. Nonetheless, Akt/PKB's role in many insulin effects, particularly accelerated glucose transport, remains controversial. Interestingly, soluble analogues of ceramide antagonize both insulin's activation of Akt/PKB as well as its stimulation of glucose transport, consistent with a causal relationship between the two.

Animals↗
PubMed1999

On the design of BSB neural associative memories using semidefinite programming.

This article is concerned with the reliable search for optimally performing BSB (brain state in a box) neural associative memories given a set of prototype patterns to be stored as stable equilibrium points. By converting and/or modifying the nonlinear constraints of a known formulation for the synthesis of BSB-based associative memories into linear matrix inequalities, we recast the synthesis into semidefinite programming problems and solve them by recently developed interior point methods. The validity of this approach is illustrated by a design example.

Association↗
PubMed1999

Diagnosis of stridor in children.

Stridor is a sign of upper airway obstruction. In children, laryngomalacia is the most common cause of chronic stridor, while croup is the most common cause of acute stridor. Generally, an inspiratory stridor suggests airway obstruction above the glottis while an expiratory stridor is indicative of obstruction in the lower trachea. A biphasic stridor suggests a glottic or subglottic lesion. Laryngeal lesions often result in voice changes. A child with extrinsic airway obstruction usually hyperextends the neck. The airway should be established immediately in children with severe respiratory distress. Treatment of stridor should be directed at the underlying cause.

Algorithms↗
PubMed1999

Differentiation-dependent suppression of platelet-derived growth factor signaling in cultured adipocytes.

A critical component of vertebrate cellular differentiation is the acquisition of sensitivity to a restricted subset of peptide hormones and growth factors. This accounts for the unique capability of insulin (and possibly insulin-like growth factor-1), but not other growth factors, to stimulate glucose uptake and anabolic metabolism in heart, skeletal muscle, and adipose tissue. This selectivity is faithfully recapitulated in the cultured adipocyte line, 3T3-L1, which responds to insulin, but not platelet-derived growth factor (PDGF), with increased hexose uptake. The serine/threonine protein kinases Akt1 and Akt2, which have been implicated as mediators of insulin-stimulated glucose uptake, as well as glycogen, lipid, and protein synthesis, were shown to mirror this selectivity in this tissue culture system. This was particularly apparent in 3T3-L1 adipocytes overexpressing an epitope-tagged form of Akt2 in which insulin activated Akt2 10-fold better than PDGF. Similarly, in 3T3-L1 adipocytes, only insulin stimulated phosphorylation of Akt's endogenous substrate, GSK-3beta. Other signaling molecules, including phosphatidylinositol 3-kinase, pp70 S6-kinase, mitogen-activated protein kinase, and PHAS-1/4EBP-1, did not demonstrate this selective responsiveness to insulin but were instead activated comparably by both insulin and PDGF. Moreover, concurrent treatment with PDGF and insulin did not diminish activation of phosphatidylinositol 3-kinase, Akt, or glucose transport, indicating that PDGF did not simultaneously activate an inhibitory mechanism. Interestingly, PDGF and insulin comparably stimulated both Akt isoforms, as well as numerous other signaling molecules, in undifferentiated 3T3-L1 preadipocytes. Collectively, these data suggest that differential activation of Akt in adipocytes may contribute to insulin's exclusive mediation of the metabolic events involved in glucose metabolism. Moreover, they suggest a novel mechanism by which differentiation-dependent hormone selectivity is conferred through the suppression of specific signaling pathways operational in undifferentiated cell types.

3T3 Cells↗
PubMed1999

A protein phosphatase functions to recycle RNA polymerase II.

Transcription is regulated by the state of phosphorylation of a heptapeptide repeat known as the carboxy-terminal domain (CTD) present in the largest subunit of RNA polymerase II (RNAPII). RNAPII that associates with transcription initiation complexes contains an unphosphorylated CTD, whereas the elongating polymerase has a phosphorylated CTD. Transcription factor IIH has a kinase activity specific for the CTD that is stimulated by the formation of a transcription initiation complex. Here, we report the isolation of a cDNA clone encoding a 150-kD polypeptide, which, together with RNAPII, reconstitutes a highly specific CTD phosphatase activity. Functional analysis demonstrates that the CTD phosphatase allows recycling of RNAPII. The phosphatase dephosphorylates the CTD allowing efficient incorporation of RNAPII into transcription initiation complexes, which results in increased transcription. The CTD phosphatase was found to be active in ternary elongation complexes. Moreover, the phosphatase stimulates elongation by RNAPII; however, this function is independent of its catalytic activity.

Amino Acid Sequence↗
PubMed1999

Off-resonance multiple-pulse dynamics in solid-state NMR spectroscopy: A revised coherent averaging theory analysis

The standard coherent averaging theory treatment of the resonance offset interaction is compared to exact calculations for multiple-pulse solid-state NMR experiments. Significant differences between coherent averaging approximations and exact results are revealed, even for idealized conditions. A revision of the standard analysis is proposed as a way of improving the description of the off-resonance dynamics in these experiments. We use the insights obtained from this investigation to derive a qualitatively new type of homonuclear decoupling sequence, and evaluate the performance and advantages of this sequence with both simulations and experimental tests. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Effect of DA-6034, a derivative of flavonoid, on experimental animal models of inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a multifactorial disorder with unknown etiology and pathogenesis. DA-6034, 7-carboxymethyloxy-3', 4', 5-trimethoxy flavone, is a synthetic flavonoid known to possess anti-inflammatory activity. This study was performed to evaluate the oral therapeutic effect of DA-6034 in three experimental animal models of IBD: two chemical-induced IBD models of rats and the human leukocyte antigen (HLA)-B27 transgenic rat model known to develop spontaneous colitis without the use of exogenous agents. Acute chemical colitis was induced by intracolonic instillation of 1.2 ml of 4% acetic acid solution. Prednisolone (1 mg/kg), sulfasalazine (100 mg/kg) and DA-6034 (0.3 to approximately 3 mg/kg) were orally administered twice daily for 6 days in these rats. In addition, chronic chemical colitis was induced by intracolonic administration of trinitrobenzene sulfonic acid (TNBS) 30 mg in 50% ethanol and agents were orally administered for 6 or 20 days. In chemical-induced IBD models, all of these agents reduced the severity of colitis and specially, DA-6034 (3 mg/kg) showed more potent effect than other drugs in macroscopic lesion score. In HLA-B27 transgenic rats, DA-6034 (3 mg/kg) and prednisolone (0.5 mg/kg) were treated orally twice daily for 6 weeks. The HLA-B27 transgenic rats showed only mild colitis, compared with the chemical-induced colitis models. DA-6034 ameliorated the loose stool and decreased microscopic damage, which is the important indicator of this model. In conclusion, oral therapy of DA-6034 attenuated the macroscopic and histologic damages of the colon in all three experimental models of IBD, which suggest that DA-6034 could be a promising drug in the treatment of IBD.

Acetic Acid↗
PubMed1999

2- or 6-(1-azidoalkyl)-5,8-dimethoxy-1,4-naphthoquinone: synthesis, evaluation of cytotoxic activity, antitumor activity and inhibitory effect on DNA topoisomerase-I.

6-(1-azidoalkyl)-DMNQ derivatives compared to 2-(1-azidoalkyl)-DMNQ isomers, exhibited higher cytotoxic activity against L1210 mouse leukemia cells and stronger inhibition of DNA topoisomerase-I (TOPO-I), suggesting involvement of steric hindrance. However, similar antitumor activity against mice bearing S-180 cell was shown by 2- and 6-(1-azidoalkyl)-DMNQ derivatives.

Animals↗
PubMed1999

The general transcription factors IIA, IIB, IIF, and IIE are required for RNA polymerase II transcription from the human U1 small nuclear RNA promoter.

RNA polymerase II transcribes the mRNA-encoding genes and the majority of the small nuclear RNA (snRNA) genes. The formation of a minimal functional transcription initiation complex on a TATA-box-containing mRNA promoter has been well characterized and involves the ordered assembly of a number of general transcription factors (GTFs), all of which have been either cloned or purified to near homogeneity. In the human RNA polymerase II snRNA promoters, a single element, the proximal sequence element (PSE), is sufficient to direct basal levels of transcription in vitro. The PSE is recognized by the basal transcription complex SNAPc. SNAPc, which is not required for transcription from mRNA-type RNA polymerase II promoters such as the adenovirus type 2 major late (Ad2ML) promoter, is thought to recruit TATA binding protein (TBP) and nucleate the assembly of the snRNA transcription initiation complex, but little is known about which GTFs other than TBP are required. Here we show that the GTFs IIA, IIB, IIF, and IIE are required for efficient RNA polymerase II transcription from snRNA promoters. Thus, although the factors that recognize the core elements of RNA polymerase II mRNA and snRNA-type promoters differ, they mediate the recruitment of many common GTFs.

Animals↗
PubMed1999

Treatment of severe postpartum hemorrhage by rectally administered gemeprost pessaries.

OBJECTIVE: To assess the efficacy of rectally administered gemeprost pessaries in the treatment of severe postpartum hemorrhage. DESIGN: Retrospective analysis of a twelve month period in which all patients having postpartum hemorrhage treated with rectal gemeprost were analyzed. SETTING: Royal Darwin Hospital, Northern Territory, Australia. POPULATION: Fourteen women with established postpartum hemorrhage not responding to oxytocine and ergometrine regimens, or not responsive to oxytocine and having contraindications to ergometrine. MAIN OUTCOME MEASURES: Per vaginum bleeding with continued postpartum hemorrhage; adverse patient reactions to gemeprost; need for operative intervention. RESULTS: All patients who were treated with rectally administered gemeprost pessaries had cessation of bleeding per vaginum. There were no adverse side effects noted from the medication and no patient required surgical treatment. CONCLUSIONS: Rectally administered gemeprost administered pessaries appear to be safe and effective method of treating severe postpartum hemorrhage in those patients in whom the standard oxytocic regimens fail. This form of treatment may avoid the need for parenteral prostaglandins or surgical intervention.

Administration, Rectal↗
PubMed1999

Role of p53 gene mutation in tumor aggressiveness of intracranial meningiomas.

The mutations that occur in the p53 tumor suppressor gene have been studied in various human malignant tumors. However, little is known about this gene in meningiomas. To investigate the relationship and frequency of p53 gene mutations, the p53 polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) and immunohistochemical study were performed on the 41 intracranial meningiomas (21 benign, 11 atypical, and 9 malignant). The higher the p53 protein expression rate, the poorer the histologic grade (9.5%, 72.7%, and 88.9% in benign, atypical and malignant meningioma, respectively) (p=0.000). The p53 protein expression rate was higher in recurrent meningioma (71.4%) than in nonrecurrent meningioma (10.5%) (p=0.002). PCR-SSCP method was performed in positive p53 protein immunoreactivity cases. p53 gene mutation rate was higher in the atypical (62.5%) and malignant (25%) meningiomas than in the benign meningioma (0%) (p=0.232). Also, the rate was higher in recurrent menigioma (20%) than in nonrecurrent meningioma (0%) (o=0.495). Among five to eight exons of the p53 gene, the mutation was observed on exon 7 more frequently. In conclusion, p53 immunoreactivity and p53 gene mutation are closely correlated with histologic grade and histologic atypia of intracranial meningiomas. p53 gene mutation would be considered as a useful marker to detect the progression of intracranial meningiomas.

Brain Neoplasms↗
PubMed1999

Comparison of rocuronium and vecuronium pretreatment for prevention of fasciculations, myalgia and biochemical changes following succinylcholine administration.

BACKGROUND: The purpose of this study was to assess the effect of rocuronium pretreatment on the succinylcholine-induced fasciculations, myalgia and biochemical changes, and to compare it with vecuronium pretreatment. METHODS: We have studied 60 female patients undergoing minor elective surgery, in a prospective double blinded method. Three groups of 20 patients each was pretreated with either saline (control group), rocuronium 0.05 mg/kg (rocuronium group) or vecuronium 0.007 mg/kg (vecuronium group). Three min after the pretreatment, 1.5 mg/kg succinylcholine was injected. Single twitch responses to electrical stimulation were measured. Serum potassium and creatine kinase were respectively measured 5 min after succinylcholine and 24 h after operation. Fasciculations and myalgia on postoperative day 1 and day 2 were evaluated. RESULTS: The incidence of fasciculations was lowest in the rocuronium group, followed by the vecuronium group, and was highest in the control group. The incidence of myalgia on postoperative day 1 was lower in the rocuronium and vecuronium groups than the control group. The increase of serum creatine kinase was similar among the three groups, but there was no increase in serum potassium concentration in any group. No differences of the single twitch responses to electrical stimulation were found between the rocuronium and vecuronium groups. CONCLUSIONS: Rocuronium pretreatment was more effective in reducing fasciculations than was vecuronium pretreatment, but both were equally effective in preventing myalgia on postoperative day 1. This difference may reflect the differential activities of rocuronium and vecuronium at the neuromuscular junction. The increase of creatine kinase was not attenuated by any regimen.

Adult↗
PubMed1998

Evidence for the location of bicyclomycin binding to the Escherichia coli transcription termination factor Rho.

The commercial antibiotic bicyclomycin (Bcm) has been shown to target the essential transcription termination factor Rho in Escherichia coli. Little is known about the Bcm binding domain in Rho. A recent structure-activity relationship study led us to evaluate the reductive amination probe, 5a-(3-formylanilino)dihydrobicyclomycin (FD-Bcm). Biochemical studies showed that FD-Bcm possessed inhibitory activities comparable to Bcm in Rho-dependent ATPase and transcription termination assays. Incubation of Rho with FD-Bcm, ATP, and poly(C) followed by NaBH4 reduction and dialysis led to an appreciable loss of ATPase activity. Inclusion of Bcm with FD-Bcm in the reductive amination reaction protected Rho, indicating that Bcm and FD-Bcm competed for the same binding site in Rho. Incubation of Rho with FD-Bcm and poly(C) followed by NaBH4 reduction provided a sample with residual ATPase activity (12%). Mass spectrometric analysis indicated the presence of two proteins in an approximate 1.2:1 ratio, whose masses corresponded to wild-type Rho (47,010 Da) and lysine-modified Rho (47,417 Da), respectively. Trypsin digestion of the Rho sample followed by high performance liquid chromatography separation and tandem mass spectrometry analysis identified the site of modification as Lys181 within the combined tryptic fragment, Gly-Leu-Ile-Val-Ala-Pro-Pro-Lys-Ala-Gly-Lys (residues 174-184). Similar analysis of a lesser modified sample (following incubation with inclusion of ATP) showed that addition had again occurred at Lys181. These findings provide the first structural information concerning the site of Bcm binding in Rho.

Adenosine Triphosphatases↗
PubMed1998

Elucidation of conditions allowing conversion of penicillin G and other penicillins to deacetoxycephalosporins by resting cells and extracts of Streptomyces clavuligerus NP1.

Using resting cells and extracts of Streptomyces clavuligerus NP1, we have been able to convert penicillin G (benzylpenicillin) to deacetoxycephalosporin G. Conversion was achieved by increasing by 45x the concentration of FeSO4 (1.8 mM) and doubling the concentration of alpha-ketoglutarate (1.28 mM) as compared with standard conditions used for the normal cell-free conversion of penicillin N to deacetoxycephalosporin C. ATP, MgSO4, KCl, and DTT, important in cell-free expansion of penicillin N, did not play a significant role in the ring expansion of penicillin G by resting cells or cell-free extracts. When these conditions were used with 14 other penicillins, ring expansion was achieved in all cases.

Adenosine Triphosphate↗
PubMed1998

Auditory pathway and auditory brainstem response in mice lacking NMDA receptor epsilon 1 and epsilon 4 subunits.

There is considerable evidence that the N-methyl-D-aspartate receptor (NMDAR) is a component of excitatory amino acid synapses in the ascending auditory pathway. The availability of mice that are defective in NMDAR epsilon 1 or NMDAR epsilon 4 subunit paves the way for investigations on the role of this receptor in auditory function. Non-radioactive in situ hybridization was used in the parent C57/6J wild strain to determine if these subunits are normally expressed in cochlear nucleus (CN) and superior olivary complex (SOC) and to confirm their absence in the respective mutant mice. Evoked auditory brainstem response (ABR) to normal acoustic stimulation was investigated to assess function. In situ hybridization revealed the expression of NMDAR epsilon 1 and epsilon 4 subunits mRNAs in major neuronal types in the CN and SOC of the wild type mice while epsilon 1 and epsilon 4 expression were absent in their respective mutant mice. The ABR threshold for the epsilon 1 mutant mice was similar to that of wild type mice however the threshold for the epsilon 4 mutant mice was significantly elevated. These results suggest a role for the NMDAR epsilon 4 in normal auditory functions while the NMDAR epsilon 1 may have a less critical function under normal conditions.

Animals↗