Biomedical subjects

K P Park

Publications and source records attributed to K P Park.

8 recordsLinked to original sources

PubMed1998

Development of vimentin filaments in the cells of the articular disc of the rat squamosomandibular joint with age.

Age-related changes in the vimentin filaments were studied by immunohistochemistry and electron microscopy. In 2-week-old rats, cells showed only weak labelling for vimentin. A few intermediate filaments but well-developed rough endoplasmic reticulum and Golgi apparatus were observed in the cytoplasm. As the age of the rats advanced from 4-weeks to adulthood, labelling intensity increased and the cytoplasm of articular-disc cells was gradually filled with intermediate filaments surrounding degraded cytoplasmic organelles in the cytosol. Articular-disc cells in adult rats showed intense vimentin labelling and their cytoplasm was filled with closely packed intermediate filaments aligned in alternating layers. This age-related accumulation of vimentin filaments in articular-disc cells may be an adaptive response to compressive forces.

Adaptation, Physiological↗

PubMed1998

Changes in sleep patterns during He-O2 saturation dives.

During simulated hyperbaric saturation diving experiments of He-O2 mixture at the depths of 150, 180 and 230 m the standard polysomnography of four divers, as well as their subjective feelings of fatigue, were recorded for 268 nights. In all three diving conditions, during the bottom period and the decompression period, wakes after sleep onset and Stage 1 sleep increased while Stage 4 sleep decreased. In deeper diving conditions stage 4 sleep tended to decrease and subjective feelings of fatigue increased. When the results are considered it can be assumed that the deeper the diving depths, the increased sleep disturbances and fatigue. However, it is believed that a fundamental sleep pattern will be maintained.

Adult↗

PubMed1998

Evaluation of human activities and sleep-wake identification using wrist actigraphy.

The purpose of this study is to investigate the count-characteristics of wrist actigraphy in basic human activities and to discuss the agreement of sleep-wake identification between polysomnography (PSG) and wrist actigraphy during nocturnal sleep. There was a distinct distribution of actigraphy counts over the studied activities. The evaluation of sleep-wake scoring using the wrist actigraphy agreed 96.9% with the polysomnographic scoring during nocturnal sleep.

Activity Cycles↗

PubMed1998

Effects of aging on morningness-eveningness and sleep habits in Korean and Japanese workers.

The Morningness-Eveningness Questionnaire and Life Habits Inventory were given to Korean and Japanese workers. The distributions of scores on the questionnaire for these two groups were normal and its mean slightly moved to the Morning type with aging. It is noteworthy, however, that the mean scores of Korean workers was lower than those of the Japanese workers. The self-reported waking times and bedtimes for the two groups gradually became earlier with aging. From these results it could be said that aging was an factor that led to the difference of circadian phase.

Adult↗

PubMed1998

Sleep in relation to age, sex, and chronotype in Japanese workers.

The Morningness-Eveningness Questionnaire and Life Habits Inventory were administered to 622 Japanese workers matched for sex and age. We investigated the distributions of the scores on the Morningness-Eveningness Questionnaire and sleep-wake habits by age and sex. Subjects were classified into five age groups and three chronotypes. The distributions and mean scores on the questionnaire advanced slightly toward the Morning type from the young to the aged group. The habitual bedtimes and waking times were significantly earlier in all the chronotypes from the young to the aged group, and the preferred bedtimes and waking times were also clearly earlier from the young to the aged group. The length of sleep was shorter for the Evening than the Morning types, especially in the group below 24 yr. The differences in habitual and preferred sleep length were greater than 1 hour for all age groups, especially the two groups under 34 yr. The number of awakenings during night sleep increased from the young to the aged group for all chronotypes. The older Evening type tended more toward frequent napping and longer naptime. The variabilities of bedtime and sleep length were larger for the young and Evening type than for the old group and Morning types. Further, the mood upon waking and satisfaction with sleep length were better in the aged Evening type than the young Morning type. The women under 44 yr. woke up earlier than the men of the same age, and the women of the 35-54 yr. groups had a shorter length of sleep than others. These may be related to childcare and housework. These results indicated that the phase of circadian rhythms had moved forward from the young to the aged group, and the individual's rhythm, of those that were aged Morning types, showed better agreement with sleep-wake rhythms than did others.

Adult↗

PubMed1997

Identification of gamma-aminobutyric acid-immunoreactive axon endings associated with mesencephalic periodontal afferent terminals and morphometry of the two types of terminals in the cat supratrigeminal nucleus.

A previous study has shown that mesencephalic periodontal afferent terminals receive contacts more frequently from axonal endings containing pleomorphic, synaptic vesicles (P-endings) in the supratrigeminal nucleus (Vsup) than in the trigeminal motor nucleus, suggesting that interneurons in Vsup play an important role in modulating the jaw-closing reflex. The present study was attempted to identify neurotransmitters in P-endings associated with mesencephalic periodontal afferents in cat Vsup through the use of intracellular staining of horseradish peroxidase combined with the postembedding immunogold methods. A morphometric analysis was carried out to compare the ultrastructural features of these two types of terminals. Serial sections of 31 labeled boutons and of their associated 38 P-endings were examined. They were processed for postembedding immunogold labeling with antibodies to the neurotransmitter gamma-aminobutyric acid (GABA). The 38 P-endings presynaptic to periodontal afferents showed GABA-like immunoreactivity, but the afferent terminals were free from the labeling. The morphometric analysis indicated that bouton volume, apposed surface area, total active zone size, and mitochondrial volume were smaller in GABA-immunoreactive P-endings than in periodontal afferents, but the pooled data of the two types of terminals showed that each synaptic parameter was highly correlated in a positive, linear manner with bouton volume. These observations provide evidence that P-endings presynaptic to mesencephalic periodontal afferents contain the neurotransmitter GABA and that their axoaxonic synapses are organized in accordance with the ultrastructural "size principle" proposed by Pierce and Mendell (Pierce and Mendell [1993] J. Neurosci. 13:4748-4763) on Ia-motoneuron synapses.

Animals↗

PubMed1997

Scores on morningness-eveningness and sleep habits of Korean students, Japanese students, and Japanese workers.

The Morningness-Eveningness Questionnaire and Life Habits Inventory were given to three groups of the same mean age: 533 Korean students, 468 Japanese students, and 311 Japanese workers. The distributions of scores on the questionnaire for these three groups are normal; however the Japanese students' distribution was slightly skewed towards the Evening type. The self-reported waking times and bedtimes for the three groups were late in the order of Morning, Intermediate, and Evening types. It is noteworthy, however, that the Korean students woke earlier than the Japanese students, and the workers always went to bed and woke earlier than the students. For the groups the variations in bedtime, waking time, and length of sleep were large, the sleep latency was long, and mood of the participants upon waking was bad in the order of the Morning. Intermediate, and Evening types. The scores of the Korean students were distributed more highly in the Morning type than were the Japanese students', but the students' sleep habits in both countries were quite similar. The subjects categorized as Evening types had more irregular sleep habits than those of the Morning type. In comparison with the student groups, Japanese workers of the same mean age had higher scores and slightly different sleep habits. The change in sleep habits could be seen as a result of the demands of employment, and the probable basis for difference in scores.

Adolescent↗

PubMed1994

Ca(2+)-activated K+ channels are involved in regulatory volume decrease in acinar cells isolated from the rat lacrimal gland.

The volumes of acinar cells isolated from rat lacrimal gland were measured on computer by video-imaging. Cells were found to swell on exposure to hypotonic solutions; they subsequently exhibited a regulatory volume decrease (RVD). RVD was inhibited in the absence of extracellular Ca2+, and by the K+ channel blocker tetraethylammonium chloride (2 mM TEA+). The possible involvement of K+ channels in RVD was further investigated in cell-attached patches. Exposing the cells to a hypotonic solution activated channels with a conductance of 141 +/- 6 pS (n = 11). These channels were partially blocked by 0.5 mM TEA+, and channel activation was not observed in the absence of extracellular Ca2+. Experiments in the inside-out patch configuration demonstrated that the channels activated by hypotonic stress were "maxi" Ca(2+)-activated K+ channels. It is concluded that the opening of these channels plays an important role in RVD, by facilitating K+ loss from the cell.

Animals↗