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Biomedical subjects

T Cho

Publications and source records attributed to T Cho.

At least 37 records · Page 2Linked to original sources
PubMed1998

New methods for semiconductor charge-diffusion-length measurements using synchrotron radiation.

The extension of a new theory on the X-ray energy response of semiconductor detectors is carried out to characterize the X-ray response of a multichannel semiconductor detector fabricated on one silicon wafer. Recently, these multichannel detectors have been widely utilized for position-sensitive observations in various research fields, including synchrotron radiation research and fusion-plasma investigations. This article represents the verification of the physics essentials of a proposed theory on the X-ray response of semiconductor detectors. The three-dimensional charge-diffusion effects on the adjoining detector-channel signals are experimentally demonstrated at the Photon Factory for two types of multichannel detectors. These findings are conveniently applicable for measuring diffusion lengths for industrial requirements.

Journal Article↗
PubMed1998

Characterization and interpretation of the quantum efficiencies of multilayer semiconductor detectors using a new theory.

On the basis of a new theory of semiconductor X-ray detector response, a new type of multilayer semiconductor detector was designed and developed for convenient energy analyses of intense incident X-ray flux in a cumulative-current mode. Another anticipated useful property of the developed detector is a drastic improvement in high-energy X-ray response ranging over several hundred eV. The formula for the quantum efficiency of multilayer semiconductor detectors and its physical interpretations are proposed and have been successfully verified by synchrotron radiation experiments at the Photon Factory. These detectors are useful for data analyses under strong radiation-field conditions, including fusion-plasma-emitting X-rays and energetic heavy-particle beams, without the use of high-bias applications.

Journal Article↗
PubMed1998

Aminoglycoside pharmacokinetics in African-Americans with normal renal function.

OBJECTIVE: To compare aminoglycoside pharmacokinetics in African-Americans with normal renal function with published adult population values. DESIGN: An Institutional Review Board approved concurrent study. SETTING: The study was conducted at Howard University Hospital, Washington DC. SUBJECTS: All subjects had serum creatinine levels of 1.5mg/dl or less and were receiving aminoglycoside for suspected or documented Gram-negative infection, had no obvious underlying disease condition that could influence aminoglycoside pharmacokinetics and were aged 18 years or older. MAIN OUTCOME MEASURES: Volume of distribution (Vd), half-life (t1/2), elimination rate constant (Ke) and total body clearance (Cl) were calculated using a one-compartment, open, linear pharmacokinetic model. Using an unpaired Student's t-test, the pharmacokinetic values of our patients were compared with general population values. INTERVENTIONS: Patients receiving aminoglycosides were identified by the pharmacist through the hospital's standard antibiotic order sheet. Twenty-five patients were enrolled after they met the inclusion criteria. Pharmacists made recommendations for dose change as part of standard of care when inappropriate doses were ordered. In collaboration with medical and nursing staff, the amount and time of dose administration, and steady-state peak and trough serum drug levels were stringently measured, documented on a data collection form and used to calculate pharmacokinetic values for our patients. The form was also used to document demographic information. RESULTS: The following values were obtained: Vd 0.27+/-0.15 litres/kg, t(1/2) 1.93+/-1.38h, Ke 0.31+/-0.134/h (gentamicin), Ke 0.22 +/- 0.10/h (tobramycin), Cl 103.95+/-62.98ml/kg/h (gentamicin) and Cl 118.96+/-84.83ml/kg/h (tobramycin). These values are not significantly different from general population values. Following a mean tobramycin or gentamicin dose of 1.32+/-0.32mg/kg ideal body weight (IBW)/ dose or 1.11+/-0.33 mg/kg actual body weight (ABW)/ dose every 8h, patients achieved a mean peak and trough serum drug levels of 6.6+/-3.86mg/litre and 1.03+/-0.68mg/litre, respectively. Wide interpatient pharmacokinetic variability was also observed. CONCLUSIONS: We conclude that aminoglycoside pharmacokinetics in African-Americans seem to be consistent with the published general population values. Thus, initiating aminoglycoside regimens using population dosing guidelines appears to be appropriate. However, due to the observed wide interpatient pharmacokinetic variability, individualized dosing is required with very close monitoring, to avoid or minimize toxicity.

Adult↗
PubMed1998

Mediation between the shamanistic model and the psychiatric model in a shamanistic climate: a viewpoint of medical anthropology.

It is suggested that any clinician working on the Miyako islands, Okinawa, Japan, be a mediator or a negotiator between two worlds, namely the shamanistic and the modern psychiatric ones. On these islands, to subscribe to either is possible only by ignoring conflicting clinical realities. The main point is to summarize the complementary practices of these two medical systems on these islands. Psychiatric illness attributed to kamidaari is introduced. The initiatory illness for seeing a shaman is called kamidaari or kamburi. From the viewpoint of medical anthropology, aspects of the treatment of such patients in a shamanistic 'climate' (which is called fudo in Japanese), will be reported. In the shamanistic fudo, it must be recognized that, at a critical moment, shamanistic epistemology and psychiatric epistemology penetrate each other, and they exist together in a clinical 'mesh'. Two epistemologies must join in a coalition to access, and build continuity into, psychiatric and shamanistic medical care. It is demonstrated that these two worlds almost merge in dialogue but do not fuse, and that clinical relations occur on the boundary between these two epistemologies. 'Climatic' specific therapeutic stances are introduced and are clinically illustrated.

Adult↗
PubMed1998

Quinine and mefloquine in the treatment of multidrug-resistant Plasmodium falciparum malaria in pregnancy.

Between 1991 and 1996, 372 pregnant women with uncomplicated, multidrug-resistant Plasmodium falciparum malaria, living on the western border of Thailand, were treated with either mefloquine (N = 194), quinine (N = 93) or both drugs (N = 85). Antimalarial treatment was generally well tolerated; the most common side-effects were dizziness (42%) and tinnitus (35%) following quinine, and anorexia (23%) and dizziness (36%) following mefloquine. In the patients treated for primary infections with melfloquine, 6% failed to clear their parasitaemia by day 7 and 28% failed by day 42. The corresponding figures for quinine were 4% and 23%, respectively. The failure rates in the 117 women treated for recrudescent infections were higher, the increase being significant for quinine (38%; P = 0.03) but not for mefloquine (37%). The percentage of pregnant women who had patent gametocytaemia on presentation ranged from 4%-19%. Over 50% of the patients were anaemic (haematocrit < 30%) on presentation and 52% of those not anaemic on enrolment developed anaemia during follow-up. Mefloquine and quinine, the only antimalarials generally available for the treatment of highly drug-resistant P. falciparum in pregnancy, give unsatisfactory treatment responses when used as single agents. New, safe and effective regimens are needed for the treatment of pregnant women with multidrug-resistant falciparum malaria.

Adolescent↗
PubMed1995

Regulation of neurotensin receptor mRNA expression by the receptor antagonist SR 48692 in the rat midbrain dopaminergic neurons.

In this study, we demonstrated that the tyrosine hydroxylase-like immuno-reactive (possibly dopaminergic) neurons express neurotensin receptor mRNA in the rat substantia nigra and in the ventral tegmental area. Additionally, 2 weeks treatment with the neurotensin receptor antagonist SR 48692 increased mRNA levels in the substantia nigra. These data suggest that neurotensin receptor expression in the perikarya and in the terminal regions of dopaminergic neurons is regulated by its endogenous agonist in vivo.

Animals↗
PubMed1995

Regulation of daily rhythm of body temperature by neurotensin receptor in rats.

It is proposed that neurotensin receptor mediated signal transduction may play an important role in the thermoregulatory control in the brain. In this study, a significant increase in body core temperature was observed with SR 48692, a neurotensin receptor antagonist, after treatment of rats at light phase when the temperature is regulated low. On the other hand, SR 48692 delayed the physiological decline of body core temperature at dark phase when the temperature is highly regulated. We also found slight daily rhythmicity, though not significant, in neurotensin/neuromedin N precursor protein mRNA levels in the medial preoptic nucleus using in situ hybridization technique. Our results support the hypothesis that endogenous neurotensin receptor agonists play a physiological role in the central modulation of body core temperature in rats.

Animals↗
PubMed1994

Activation of blood clotting factors by microbial proteinases.

There are very few reports on the involvement of bacterial proteinases on the blood clotting system using both human plasma and purified clotting factors. We studied whether microbial proteinases from the opportunistic pathogens Candida albicans, Pseudomonas aeruginosa and Serratia marcescens activate the blood clotting cascade by using normal human plasma, human plasmas deficient in clotting factor XII or X, and also by using purified clotting factors XII, X and prothrombin. All proteinases tested activated either clotting factor XII or prothrombin in vitro, thus resulting in generation of thrombin. Clotting factor X was converted to the active form (Xa) by both Candida and Pseudomonas proteinases, but not by Serratia proteinase. These results suggest that peripheral and systemic blood circulation may be impaired by activation of the blood clotting cascade by microbial infections, especially in septic patients, which would enhance disseminated intravascular coagulation and multi-organ failure.

Amino Acid Sequence↗
PubMed1994

The relationship between the glucose uptake system and growth cessation in Candida albicans.

It is thought that dimorphic Candida albicans undergoes changes in its intracellular metabolic state prior to yeast-mycelial transformation. Cells grown in budding form to mid-exponential phase could not be induced to form germ tubes when grown in glucose medium. However, cells in which growth was initially inhibited by either starvation or inhibitors (0.1% hydroxyurea, 4% sodium malonate or 4% 2-deoxy-D-glucose) could be induced to form germ tubes in the same medium. The effects of these initial treatments on the intracellular state in mid-exponential phase cells were analysed by measuring the kinetics of D-glucose uptake. D-glucose uptake in mid-exponential phase and stationary phase cells was measured. The untreated mid-exponential phase cells exhibited only a high Km (6.9 mM). However, mid-exponential phase cells, in which growth was initially inhibited, exhibited both a high Km (3.2-6.2 mM) and a low Km (0.40-0.78 mM) simultaneously. In addition, the stationary phase cells exhibited both a high Km (5.6 mM) and a low Km (0.56 mM). These results suggest that there are two kinetically distinct systems of glucose transport in C. albicans and that changes in the glucose uptake system in C. albicans may be related to intracellular changes prior to transition from the budding to the mycelial form.

Candida albicans↗
PubMed1994

[Blind duplication of the ureter. Apropos of a case].

The authors report on a case of a 24 year-old man with a double-blind duplication of the ureter, which was diagnosed in the workup of a microscopic hematuria. The patient who had no symptoms and a normal renal function has been followed up at regular intervals. The diagnosis of this malformation is difficult as long as it is asymptomatic and does not affect the excretory function.

Adult↗
PubMed1994

[Pharmacokinetics of carboplatin in a patient under hemodialysis].

A patient with ovarian cancer under long-term hemodialysis was treated with carboplatin at 240 mg/m2 via intravenous drip infusion for 30 min. Hemodialysis was performed 1 or 2 hrs after the administration of carboplatin. The pharmacokinetics of carboplatin were determined, plasma total and free carboplatin-derived platinum (total Pt and free Pt) levels declined rapidly in the former. The AUC, T1/2 and Cmax of total and free Pt were estimated to be 7.14 and 3.14 mg/ml x min, 35.1 and 18.2 h, and 15.1 and 10.0 micrograms/ml, respectively. Plasma total and free Pt levels showed the same as normal control in the latter. The AUC, T1/2 and Cmax of total and free Pt were estimated to be 8.70 and 5.09 mg/ml x min, 27.6 and 21.9 h, and 13.2 and 13.2 micrograms/ml, respectively. No severe side effect was observed after administration of carboplatin. In conclusion, carboplatin may be given to the patient 2 hrs before hemodialysis in view of the pharmacokinetics.

Carboplatin↗
PubMed1993

Vascular permeability enhancing activity of Porphyromonas gingivalis protease in guinea pigs.

Porphyromonas gingivalis protease, which had been isolated from a culture supernatant, caused vascular permeability enhancement in a dose-dependent manner when injected into guinea pig skin. The permeability-enhancing reaction caused by the protease was not affected by treatment with antihistamine, but was greatly augmented by simultaneous injection of a kinin potentiator, carboxypeptidase N inhibitor. However, the reaction was inhibited by soybean trypsin inhibitor or alpha 2-antiplasmin, although both of these inhibitors could not inhibit P. gingivalis protease at all by themselves. A bradykinin-degrading enzyme, carboxypeptidase B, weakened this vascular reaction. Results described indicate that the permeability-enhancing reaction induced by the protease is caused by activation, of the kallikrein-kinin cascade in the tissue.

Animals↗
PubMed1992

The relationship between cyclic adenosine 3',5'-monophosphate and morphology in exponential phase Candida albicans.

The relationship between changes in cyclic AMP content and germ tube formation in exponential phase Candida albicans was investigated using two simple media containing glucose plus ammonium chloride, or N-acetyl-D-glucosamine (GlcNAc). The glucose medium did not promote germ tube formation unless the cells were starved before inoculation, whereas the GlcNAc medium promoted germ tube formation in both non-starved and starved cells. The cyclic AMP content of exponential phase cells, non-starved cells and starved cells was 0.21, 0.34 and 0.64 pmol mg-1 dry wt, respectively. In glucose medium, cyclic AMP content in both non-starved cells and starved cells increased for a period of 60 min after inoculation, but then decreased for a further 120 min. The cyclic AMP content of non-starved cells and starved cells was 0.16 and 0.29 pmol mg-1 dry wt, respectively, after 180 min. The maximum percentage of non-starved cells with germ tubes was around 20%. Starved cells with germ tubes were observed after 40 min and reached a maximum (around 90%) after 140 min. The number of germ tubes remained constant for the next 40 min. In GlcNAc medium, the cyclic AMP content of both non-starved cells and starved cells showed a tendency to increase for 180 min. The content of non-starved cells and starved cells was 2.02 and 1.75 pmol mg-1 dry wt, respectively, after 180 min. Germ tube formation in non-starved cells started after 70 min, reached around 80% after 150 min, and remained stable for the next 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosamine↗