Biomedical subjects

K Kim

Publications and source records attributed to K Kim.

At least 235 records · Page 13Linked to original sources

PubMed1999

Analysis of cyclic boronated and trimethylsilylated phenolalkylamines by gas chromatography and electron impact mass spectrometry

The side chain of phenolalkylamines containing a bifunctional group was derivatized as the cyclic boronate, and then the residual phenolic group was trimethylsilylated. The resulting derivatives were single reaction products in each case, with good gas chromatographic properties and informative mass spectra to afford prominent molecular ions by gas chromatography with electron impact mass spectrometry (GC/EI-MS). The cyclic boronated-trimethylsilylated derivatives yielded the isotope pattern for boron ((10)B:(11)B =-1:4.2) and characteristic ions [M](+), [M - H](+), [M - CH(3)](+), [M - RBO](+), [M - TMSO](+), and [M - TMSO - C(6)H(5)](+) ions in the mass spectra. In order to distinguish between m- and p-phenolalkylamines, the mass spectra of the cyclic phenylboronated-trimethylsilylated (PBA-TMS) derivatives were compared with those of the trimethylsilylated (TMS) derivatives. The TMS derivatives of octopamine (p-) and norfenefrine (m-) showed identical mass spectra, while the PBA-TMS derivatives had mass spectra sufficiently different from one other to distinguish between the isomers. The most prominent ion of the PBA-TMS derivative is the [M - H](+) ion (m/z 310) for octopamine and the [M](+) ion (m/z 311) for norfenefrine. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed1999

Predictors of safety belt use among crash-involved drivers and front seat passengers: adjusting for over-reporting.

Police-reported crash data are rarely used to investigate safety belt use and its predictors, even though these data have a number of advantages over data collected in roadside surveys. It has been widely recognized that motorists tend to over-report their safety belt use to police when mandatory belt use becomes law. In this paper, we use a logistic regression model that allows for misclassification errors in outcome variable to examine predictors of safety belt use among crash-involved drivers and front seat passengers. Our analysis shows significant associations between occupant characteristics, driving circumstances, and safety belt use. Alcohol involvement has the strongest negative association with safety belt use, but this association would be considerably underestimated without adjusting for the over-reporting of safety belt use in police-reported crash data. The adjusted belt use rate among front seat occupants with at least nonincapacitating injuries is about 81%, compared to 90% in police-reported crash data.

Accidents, Traffic↗

PubMed1999

Synthesis and hybridization property of sugar and phosphate linkage modified oligonucleotides.

1-[3-Deoxy-5-O-(4,4'-dimethoxytriphenylmethyl)-3-C-hydroxymethyl-2 -O-(2-methoxyethoxymethyl)-beta-D-erythro-pentofuranosyl]thymine (13) was synthesized from 1,2-isopropylidene-D-xylose (1) as a building block of modified oligonucleotides. Three types of novel oligonucleotides were synthesized from 13 and their T(m)s were compared with those of the corresponding natural oligonucleotides. It was found that our synthesized oligomers had lower affinity to DNA and RNA than the natural oligomers.

Base Sequence↗

PubMed1999

Molecular cloning, expression, and functional characterization of a 2Cys-peroxiredoxin in Chinese cabbage.

A cDNA (C2C-Prx) corresponding to a 2Cys-peroxiredoxin (2Cys-Prx) was isolated from a leaf cDNA library of Chinese cabbage. The predicted amino acid sequence of C2C-Prx has 2 conserved cysteines and several peptide domains present in most of the 2Cys-Prx subfamily members. It shows the highest sequence homology to the 2Cys-Prx enzymes of spinach (88%) and Arabidopsis (86%). Southern analysis using the cDNA insert of C2C-Prx revealed that it consists of a small multigene family in Chinese cabbage genome. RNA blot analysis showed that the gene was predominantly expressed in the leaf tissue of Chinese cabbage seedlings, but the mRNA was generally expressed in most tissues of mature plant, except roots. The expression of C2C-Prx was slightly induced by treatment with H2O2 (100 microM) or Fe3+/O2/DTT oxidation system, but not by ABA (50 microM) or GA3 (10 microM). The C2C-Prx is encoded as a preprotein of 273 amino acids containing a putative chloroplast-targeting signal of 65 amino acids at its N-terminus. The N-terminally truncated recombinant protein (deltaC2C-Prx) migrates as a dimer in a non-reducing SDS-polyacrylamide gel and as a monomer in a reducing condition. The deltaC2C-Prx shows no immuno cross-reactivity to antiserum of the yeast thiol-specific antioxidant protein, and vice versa. The deltaC2C-Prx prevents the inactivation of glutamine synthetase and the DNA cleavage in the metal-catalyzed oxidation system. In the yeast thioredoxin system containing thioredoxin reductase, thioredoxin, and NADPH, the deltaC2C-Prx exhibits peroxidase activity on H2O2.

Amino Acid Sequence↗

PubMed1999

Negative regulation of gonadotropin-releasing hormone and gonadotropin-releasing hormone receptor gene expression by a gonadotrophin-releasing hormone agonist in the rat hypothalamus.

There exists evidence for the presence of ultrashort loop feedback circuits of gonadotropin-releasing hormone (GnRH) secretion in the hypothalamus. It is, however, uncertain whether a similar mechanism is involved in the regulation of GnRH gene expression in vivo. Furthermore, little is known about the regulation of GnRH receptor (GnRHR) expression in the brain. In the present study, we examined the regulation of GnRH and its receptor gene expression by GnRH in vivo. A GnRH agonist, [D-Ala6, des-Gly10]GnRH-ethylamide (des-Gly GnRH), was administered by intracerebroventricular (i.c.v.) injection via the lateral ventricle of ovariectomized and estradiol (OVX + E)-treated rats. The amounts of GnRH and GnRHR mRNA were measured in the preoptic area (POA) and posterior mediobasal hypothalamus (pMBH) micropunch samples from individual rat brain slices by respective competitive reverse transcription-polymerase chain reactions. The i.c.v. administration of des-Gly GnRH significantly decreased GnRH and GnRHR mRNA expression in a dose-and time-related manner: des-Gly GnRH (6 ng) suppressed GnRH and GnRHR mRNA expression within 2 h, and the suppression was maintained without significant variation until 8 h after treatment. Treatment with Antide, [N-Ac-D-Nal(2)1, pCl-D-Phe2, D-Pal(3)3, Lys(Nic)5, D-Lys(Nic)6, Lys(iPR)8, D-Ala10]GnRH (10 ng), a potent GnRH antagonist, did not alter GnRH mRNA expression, but prevented des-Gly GnRH-induced suppression of GnRH mRNA expression. Antide alone decreased GnRHR mRNA expression, but failed to alter agonist-induced suppression of GnRHR mRNA expression. These results demonstrate the existence of an ultrashort loop feedback mechanism for GnRH gene expression in the POA, along with homologous down-regulation of GnRHR mRNA expression in the pMBH.

Animals↗

PubMed1999

Disruption of the Toxoplasma gondii bradyzoite-specific gene BAG1 decreases in vivo cyst formation.

The bradyzoite stage of the Apicomplexan protozoan parasite Toxoplasma gondii plays a critical role in maintenance of latent infection. We reported previously the cloning of a bradyzoite-specific gene BAG1/hsp30 (previously referred to as BAG5) encoding a cytoplasmic antigen related to small heat shock proteins. We have now disrupted BAG1 in the T. gondii PLK strain by homologous recombination. H7, a cloned null mutant, and Y8, a control positive for both cat and BAG1, were chosen for further characterization. Immunofluorescence and Western blot analysis of bradyzoites with BAG1 antisera demonstrated expression of BAG1 in the Y8 and the PLK strain but no expression in H7. All three strains expressed a 116 kDa bradyzoite cyst wall antigen, a 29 kDa matrix antigen and the 65 kDa matrix reactive antigen MAG1. Mice inoculated with H7 parasites formed significantly fewer cysts than those inoculated with the Y8 and the PLK strains. H7 parasites were complemented with BAG1 using phleomycin selection. Cyst formation in vivo for the BAG1-complemented H7 parasites was similar to wild-type parasites. We therefore conclude that BAG1 is not essential for cyst formation, but facilitates formation of cysts in vivo.

Animals↗

PubMed1999

Expression of interleukin-1 receptors in the later period of foetal thymic organ culture and during suspension culture of thymocytes from aged mice.

Interleukin-1 has been reported to be involved in thymocyte development by exerting a variety of effects on immature CD4-CD8- double-negative (DN) thymocytes. In contrast to the well-documented involvement of IL-1 in thymocyte development, expression of IL-1 receptors (IL-1R) on thymocytes has not been well demonstrated. In the present study, expression of IL-1R on the developing thymocytes was investigated. Although normal thymocytes barely express IL-1R, expression of IL-1R (type I) substantially increased at days 12-15 of foetal thymic organ culture (FTOC), with an increase of the DN subset. The CD4/CD8 profile of the IL-1R (type I)+ cells showed that these cells were mostly restricted to the DN and CD4+CD8+ subsets. Interestingly, in vitro culture of the thymocytes from an aged mouse, but not those from young adult or newborn mice, revealed similar results to those of FTOC. In addition, half of the IL-1R+ cells that increased in the later period of FTOC were gammadelta thymocytes. These results demonstrate IL-1R expression on thymocytes during ex vivo culture and suggest that IL-1R is expressed in a certain environment during normal thymocyte differentiation.

Aging↗

PubMed1999

Poor recovery sleep after sleep deprivation in delayed sleep phase syndrome.

To clarify disturbances in sleep regulation in patients with delayed sleep phase syndrome (DSPS), we studied three patients with DSPS and seven healthy controls. Sleep propensity and melatonin rhythms after 24-h sleep deprivation were investigated under dim light condition by using the ultra-short sleep-wake schedule. The sleep propensity curves displayed clear differences between DSPS patients and the controls. During the subjective day when melatonin was not produced, recovery sleep after the sleep deprivation did not occur in DSPS patients, while recovery sleep occurred during the subjective day in controls. This suggests that DSPS may involve problems related to the homeostatic regulation of sleep after sleep deprivation.

Adult↗

PubMed1999

Diurnal fluctuation of sleep propensity across the menstrual cycle.

Most women experience sleep changes across the menstrual cycle. We applied the ultra-short sleep-wake schedule to healthy females to compare their 24-h sleep propensity rhythms in the follicular and luteal phases. The daytime (09.00-16.30 h) subjective sleepiness and the number of slow wave sleep-containing nap trials increased in the luteal phase compared to the follicular phase, but the mean sleep propensity did not change. During the periods of 17.00-00.30 h and 01.00-08.30 h there were no differences between the two phases. These results suggest that increased daytime sleepiness in the luteal phase may be related to brain mechanisms controlling slow wave sleep.

Adult↗

PubMed1999

Correlation between the circadian sleep propensity rhythm and hormonal rhythms under ultra-short sleep-wake cycle.

The aim of this study was to clarify effects of hormonal and temperature rhythms on circadian fluctuations of sleep propensity. Ten healthy females underwent 24-h sleep deprivation and entered the circadian sleep propensity assessment setting under the ultra-short sleep-wake schedule. During the experiment, sleep propensity rhythm, rectal temperature, and 24-h serum hormone profiles (melatonin, cortisol and thyroid-stimulating hormone) were investigated. The circadian sleep propensity rhythms had two apparent peaks (afternoon and nocturnal peaks) and a trough (nocturnal sleep gate). The timings of the nocturnal sleep gate and the nocturnal peak were correlated exclusively with temperature and melatonin rhythms (P < 0.05), while that of the afternoon peak was significantly correlated with habitual wake time and melatonin rhythm. These results indicate that the circadian sleep propensity rhythm is influenced not only by the circadian pacemaker, but also by sleep habit.

Adult↗

PubMed1999

Lifestyles and sleep disorders among the Japanese adult population.

To clarify the effects of daily stress, habitual exercise, drinking and smoking on the prevalence of sleep disorders, we selected 4000 residents (> or =20 years) in Japan by stratified random sampling and carried out structured interviews (response rate 75.8%). Frequencies of sleep disorders (difficulty initiating sleep: DIS; difficulty maintaining sleep: DMS; early morning awakening and hypnotic medication use) were treated as dependent variables. Significant effects of stress were prevalent in all sleep disorders. Habitual exercise had significant negative association with DIS and DMS. Drinking and smoking did not affect sleep disorders.

Adult↗

PubMed1999

Driver compliance with stop signs at pedestrian crosswalks on a university campus.

Pedestrians on college campuses interact continuously with various motorized vehicles. Rates of compliance with stop signs at pedestrian crosswalks and noncomplying vehicles were monitored in spring 1996 on a large urban campus. The number of pedestrians, pedestrian clearance, type of vehicle, hour of day, and day of week were monitored at 3 pedestrian crosswalks. The overall compliance rate for stop signs was 22.8 per 100 vehicles, ranging from 1.4 per 100 for bicycles to 46.2 per 100 for commuter vans. Compliance increased to 53 per 100 vehicles when pedestrians were present in the crosswalk. Several differences in compliance rates were found among the observation sites. Lowest compliance was observed for bicycles and motorcycles. Pedestrians on this and other college campuses risk injuries because of violations of pedestrian right-of-way laws. The problem calls for appreciable educational efforts by college health personnel.

Automobile Driving↗

PubMed1999

A study on the rotational torque movement of mandible in patients with TMJ closed lock.

The mandibular rotational angle and distance were measured during various movements of temporomandibular joint (TMJ) closed lock patients (17 women, 23.9 +/- 6.6 years). The measurements were compared with those of the healthy controls (18 women, 24.0 +/- 1.4 years) using the BioPAK system (BioResearch Inc. Milwaukee, USA), which can analyze mandibular rotational torque movements. During maximum mouth opening movement, the parameters of the patient group were significantly larger than those of the control group in horizontal plane (p < 0.05) but vice versa in frontal plane (p < 0.001). During protrusive movement, the parameters of patients were significantly larger than those of control group in frontal and horizontal plane (p < 0.01, p < 0.05). During lateral excursive movement to the affected side of patients, the parameters were significantly larger than those to the unaffected side in frontal plane (p < 0.05).

Adult↗

PubMed1999

Cervical cancer screening knowledge and practices among Korean-American women.

Cervical cancer is one of the most common cancers of American women. The Papanicolaou (Pap) smear test for cervical screening is a widely used and effective means to reduce the morbidity and mortality rate from cervical cancer through early detection. Despite these benefits, many women have never been screened or are not screened at regular intervals. The purpose of this study was to examine cervical cancer screening knowledge and practices of Korean-American women. The sample consisted of 159 Korean-American women, 40 to 69 years of age. The 1987 Cancer Control Supplement questionnaire was translated into Korean and used to collect data. Twenty-six percent of the respondents never heard of the Pap smear test. Only 34% of respondents reported having had a Pap smear test for screening. The most frequently cited reason for not having had a Pap smear test was absence of disease symptoms. Results indicate that education and usual sources of health care were significant factors related to having heard of or having had a Pap smear test. The findings from this study have important implications for health practitioners and policy makers who serve this ethnic population.

Adult↗

PubMed1999

Potentiation of cholecystokinin and secretin-induced pancreatic exocrine secretion by endogenous insulin in humans.

To investigate the effects of endogenous insulin on pancreatic exocrine secretion in humans, we evaluated the pure pancreatic juice obtained by endoscopic cannulation of the main pancreatic duct in 21 healthy subjects (14 men and seven women). Samples of pancreatic juices were collected after intravenous injection of either glucose (50%, 40 ml), secretin (0.25 CU/kg), and cholecystokinin-8 (CCK) (40 ng/kg), or a combination of glucose, secretin, and CCK in six 5-min periods. The responses of plasma glucose, insulin, and C-peptide to intravenous administration of glucose were measured. After infusion of glucose, the plasma insulin and C-peptide levels were significantly increased and remained at high levels during 30-min experiments, intravenous administration of secretin and CCK resulted in significant increases of pancreatic secretion including volume, bicarbonate, and protein output. When glucose was simultaneously administered with secretin and CCK, pancreatic secretion was significantly increased, more than the effects achieved by the secretin and CCK. However, glucose alone did not increase basal pancreatic secretion. These observations suggest that endogenous insulin intensifies pancreatic secretion stimulated by secretin and CCK in humans.

Adult↗

PubMed1999

Neuropeptide gene families in the nematode Caenorhabditis elegans.

Neuropeptides have diverse roles in the function and development of the nervous system. With the completion of the sequencing of the C. elegans genome, rapid identification of nematode neuropeptide genes is possible. To date, 41 C. elegans neuropeptide genes have been identified. Of these genes, 20 genes, named flp (FMRFamide-like peptide) genes, encode FMRFamide-related proteins (FaRPs). Deletion of one of the flp genes, flp-1, results in several behavioral defects, suggesting that at least one flp gene is not functionally redundant with other flp genes. Twenty-one genes, named neuropeptide-like protein (nlp) genes, encode peptides distinct from the FaRP family. The predicted nlp-1 and nlp-2 neuropeptides have modest similarity to buccalin and myomodulin, respectively. Cellular expression patterns and genetic analysis of flp and nlp genes suggest that neuropeptides in nematodes also have widespread and varied roles in nervous system function.

Amino Acid Sequence↗

PubMed1999

Characterization of binding of adenylate cyclase toxin to target cells by flow cytometry.

Adenylate cyclase (AC) toxin from Bordetella pertussis intoxicates eukaryotic cells by increasing intracellular cyclic AMP (cAMP) levels. In addition, insertion of AC toxin into the plasma membrane causes efflux of intracellular K(+) and, in a related process, hemolysis of sheep erythrocytes. Although intoxication, K(+) efflux, and hemolysis have been thoroughly investigated, there is little information on the nature of the interaction of this toxin with intact target cells. Using flow cytometry, we observe that binding of AC toxin to sheep erythrocytes and Jurkat T lymphocytes is dependent on posttranslational acylation of the toxin. Extracellular calcium is also necessary, with a steep calcium concentration dependence similar to that required for intoxication and hemolysis. Binding of AC toxin is concentration dependent but unsaturable up to 50 micrograms/ml, suggesting that if there is a specific receptor molecule with which the toxin interacts, it is not limiting. Visualization of cells by fluorescence microscopy supports the data obtained by flow cytometry and reveals a peripheral pattern of toxin distribution. AC toxin binds to erythrocytes at both 0 and 37 degrees C; however, the total binding at 0 degrees C is less than that at 37 degrees C. In human erythrocytes, AC toxin does not cause an increase in K(+) efflux or hemolysis. While AC toxin exhibits reduced potency to increase cAMP in these cells than in sheep erythrocytes, there is only a modest reduction in the binding of the toxin as measured by flow cytometry. Further use of this technique will provide new approaches for dynamic and functional analysis of the early steps involved in intoxication, K(+) efflux, and hemolysis produced by AC toxin.

Adenylate Cyclase Toxin↗

PubMed1999

Correlation of activity regulation and substrate recognition of the ADP-ribosyltransferase that regulates nitrogenase activity in Rhodospirillum rubrum.

In Rhodospirillum rubrum, nitrogenase activity is regulated posttranslationally through the ADP-ribosylation of dinitrogenase reductase by dinitrogenase reductase ADP-ribosyltransferase (DRAT). Several DRAT variants that are altered both in the posttranslational regulation of DRAT activity and in the ability to recognize variants of dinitrogenase reductase have been found. This correlation suggests that these two properties are biochemically connected.

ADP Ribose Transferases↗