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Biomedical subjects

K Ohtsuka

Publications and source records attributed to K Ohtsuka.

At least 181 records · Page 10Linked to original sources
PubMed1992

Burst discharges of fastigial neurons in macaque monkeys are driven by vision- and memory-guided saccades but not by spontaneous saccades.

Discharges from 61 saccadic burst neurons in the fastigial oculomotor region were recorded for two trained macaque monkeys during vision-guided or memory-guided saccades or spontaneous saccades in the dark. Although these neurons exhibited vigorous, burst discharges during both vision-guided and memory-guided saccades, only weak bursts were observed during spontaneous saccades in the dark. Especially in 10 of the 61 neurons, saccadic burst discharge was almost completely absent during spontaneous saccades in the dark. These findings suggest that the cerebellum plays an important role in the control of vision-guided saccades as well as memory-guided saccades, but not of spontaneous saccades in the dark.

Animals↗
PubMed1992

Burst discharges of mossy fibers in the oculomotor vermis of macaque monkeys during saccadic eye movements.

Mossy fiber activity was recorded from the oculomotor vermis (lobules VIc and VII) during visually guided saccades. Saccade-related activities of 99 mossy fiber units were observed in two alert macaque monkeys. Ninety-six units were characterized by high-frequency bursts of firing in response to visually guided saccades (burst unit). These units were silent during all periods of fixation in any gaze position. Three units showed eye position-related tonic discharges with saccadic bursts. The lead time of saccadic bursts ranged from 2.6 to 80.5 ms (mean 27.9 ms, SD 16.6 ms). About 75% of the burst units exhibited a long lead burst characterized by a slow buildup, while the remaining units showed short lead bursts with a sharp onset. About 80% of the units showed burst in association with contralaterally directed saccades. The remaining units exhibited bursts in association with ipsilateral saccades. Preferred directions in this population covered the entire field including the vertical and the oblique. About 68% of long lead burst units exhibited the movement field which consists of a whole sector of the entire oculomotor range (directional type). About 32% of long lead burst units showed the movement field which is a closed area within the oculomotor range (vectorial type). On the other hand, peak frequency of short lead burst units increased in proportion to saccade amplitude. The end of the burst in all units always preceded the completion of saccade. The end of burst was time-locked to the completion of saccade, so that the lead time from the end of burst to the end of saccade was consistent among these units and, was constant regardless of saccadic amplitude. The duration between the peak and the offset of burst was correlated with the amplitude of saccade (0.63 < or = r < or = 0.83). Long lead burst of mossy fibers was almost comparable to burst activity in the nucleus reticularis tegmenti pontis (NRTP), while short lead burst of mossy fibers closely resembles activity of excitatory burst neurons in the paramedian pontine reticular formation (PPRF). These findings suggest that the cerebellum receives command signal from the superior colliculus via the NRTP and feedback signal from the PPRF.

Animals↗
PubMed1992

Cerebellar peduncle lesion without saccadic abnormalities.

A 66-year-old woman had a unilateral infarction in the cerebellar peduncle. Saccadic eye movements were intact in this patient, while smooth-pursuit eye movements were impaired. Magnetic resonance imaging disclosed that the lesion was well localized in the superior cerebellar peduncle and the juxtarestiform body. These findings support the idea that saccade signals from the cerebellum project to the brainstem through the hook bundle, which was recently confirmed in the monkey.

Aged↗
PubMed1992

Intracellular localization and partial amino acid sequence of a stress-inducible 40-kDa protein in HeLa cells.

We earlier discovered a novel 40-kDa protein (hsp40) induced by heat shock and other stresses in mammalian and avian cells. In this report, we purified the hsp40 in HeLa cells, using modified two-dimensional gel electrophoresis, and determined the amino terminal amino acid sequence of this protein. The hsp40 is homologous to DnaJ, an Escherichia coli heat-shock protein, as well as to DnaJ-homologous proteins in yeast such as SCJ1, Sec63/Np11, YDJ1 and SIS1. Indirect immunofluorescence staining using an anti-hsp40 polyclonal antibody demonstrated that hsp40 was localized faintly throughout the cell in non-heat-shocked cells and was accumulated in nuclei and nucleoli in heat-shocked cells. The intracellular localization of hsp40 was very similar to that of hsp70, suggesting that these two hsps colocalize in heat-shocked HeLa cells.

Amino Acid Sequence↗
PubMed1992

Effects of continuous heating at mild temperatures on the translocation of hsp70 and protein synthesis in NRK cells.

We investigated intracellular translocation of hsp70 and total protein synthesis during heating at mild temperatures in NRK (normal rat kidney) cells. When cells were heated at 41 degrees C, the hsp70 was translocated into the nuclei/nucleoli, then returned gradually to the cytoplasm during heating. Concomitantly, total protein synthesis first decreased to 80% of the control level, then recovered by 2 hr. This indicates the acquisition of translational thermotolerance during heating at 41 degrees C. The return of hsp70 to the cytoplasm seems to be related to the recovery of total protein synthesis. Similar relationships were obtained at 42 degrees C heating in the presence of glycerol. These results suggest that translocation of hsp70 into the nuclei/nucleoli is important for the recovery of protein synthesis (acquisition of translational thermotolerance) during heating at mild temperatures.

Acclimatization↗
PubMed1992

Cortical area related to lens accommodation in cat.

Lens accommodation was evoked by microstimulation in the lateral suprasylvian (LS) area in cats. The accommodative response was monitored continuously with an infrared optometer. The low threshold areas related to lens accommodation were located in the lower parts of the medial banks of the middle suprasylvian sulcus from A1 to A4, and also in the fundus of the sulcus at A8 in the stereotaxic coordinates. The latency of the onset of the accommodative responses evoked by stimulating the caudal area (A1-A4) was shorter than that evoked by stimulating the rostral area (around A8). Electrical stimulation was also attempted at the subcortical area in order to study the output pathway from the LS area. It was determined that the low threshold sites in the LS cortex of A1-A4 extend rostrally along the lateral ventricle in the brainstem, then ventrally into the midbrain. These findings suggest that there are two cortical areas related to lens accommodation: caudal and rostral, and the caudal accommodation area may provide the output signal for the subcortical system.

Accommodation, Ocular↗
PubMed1992

[Pulmonary function and exercise tolerance in patients treated with bone marrow transplantation (BMT)].

We assessed pulmonary function and exercise tolerance in 10 BMT patients. Their underlying disorders were as follows; chronic myeloid leukemia 5 cases, acute lymphoblastic leukemia 2 cases, aplastic anemia, acute myeloid leukemia and non-Hodgkin's lymphoma one case each. Their mean age was 26 +/- 9 years old. When the patients were healthy and free of serious complications and anemia, arterial blood gas examination, pulmonary function tests and incremental treadmill exercise test were examined repeatedly. Although %VC and FEV1.0% kept within normal range, PaO2 at rest, %DLCO, VO2max, VO2max/kg and O2-pulsemax remained low at one year after BMT. There were significant correlations between VO2max and O2-pulsemax [r = 0.955 (p < 0.001)], %VC [r = 0.758 (p < 0.02)], VE/VO2max [r = -0.749 (p < 0.02)] and delta SaO2/VO2/kg [r = -0.731 (p < 0.02)], suggesting that exercise intolerance in BMT patients may be based on both cardiac and gas exchange abnormalities. To evaluate cardiac dysfunction, we compared exercise parameters obtained at an exercise level of 75% predicted heart rate max in five age-matched normal subjects to those in six BMT patients who did not demonstrate desaturation during exercise. As a result, the mean values of VO2max/kg and O2-pulse/m2 in BMT patients were significantly lower than those in normal subjects, suggesting that cardiac dysfunction may be due to insufficiency of stroke volume during exercise. It is concluded that exercise intolerance in BMT patients may be mainly due to cardiac dysfunction.

Adolescent↗
PubMed1991

The effect of microstimulation of the oculomotor vermis on discharges of fastigial neurons and visually-directed saccades in macaques.

The present study confirmed our previous reports that neurons in the fastigial oculomotor region (FOR) of the macaque show presaccadic bursts during contralateral saccades and that the burst duration is closely related to the duration of the accompanying saccade. Furthermore, when the burst duration was reduced by subthreshold electrical stimulation applied to the oculomotor vermis prior to the onset of the burst, the impending visually-directed saccade became hypometric. The reduction in the burst duration was closely related to the degree of the hypometria. Since saccadic burst neurons in the FOR constitute the sole output channel for saccadic signals of the oculomotor vermis, the findings support the hypothesis that the cerebellum can regulate the amplitude of eye movements.

Animals↗
PubMed1991

Saccadic burst neurons in the oculomotor region of the fastigial nucleus of macaque monkeys.

1. The discharge of 255 neurons in the fastigial nuclei of three trained macaque monkeys was investigated during visually guided saccades. Responses of these neurons were examined also during horizontal head rotation and during microstimulation of the oculomotor vermis (lobules VIc and VII). 2. One hundred and two units were characterized by bursts of firing in response to visually guided saccades. Ninety-eight of these (96.1%) were located within the anatomic confines of the fastigial oculomotor region (FOR), on the basis of reconstruction of recording sites. During contralateral saccades, these neurons showed bursts that preceded the onset of saccades (presaccadic burst), whereas, during ipsilateral saccades, they showed bursts associated with the end of saccades (late saccadic burst). They were hence named saccadic burst neurons. Sixty-one saccadic burst neurons (62.2%) were inhibited during microstimulation of the oculomotor vermis with currents less than 10 microA. 3. All saccadic burst neurons were spontaneously active, and the resting firing rate varied considerably among units, ranging from 10 to 50 imp/s. The tonic levels of activity did not correlate significantly with eye position. 4. The presaccadic burst started 18.5 +/- 4.7 (SD) ms (n = 45) before the onset of saccades in the optimal direction (the direction associated with the maximum values of burst lead time, number of spikes per burst, and burst duration). Optimal directions covered the entire contralateral hemifield, although there was a slightly higher incidence in both horizontal and upper-oblique directions in the present sample. The duration of the presaccadic burst was highly correlated with the duration of saccade (0.85 less than or equal to r less than or equal to 0.97). 5. The late saccadic burst was most robust in the direction opposite to the optimal in each unit (the nonoptimal direction). Its onset preceded the completion of ipsilateral saccade by 30.4 +/- 5.9 ms. The lead time to the end of saccade was consistent among different units and was constant also for saccades of various sizes. Thus the late saccadic burst started even before the saccade onset when the saccade duration was less than 30 ms. Unlike the presaccadic burst, its duration was not related to the duration of saccade. 6. Discharge rates of saccadic burst neurons were correlated neither to eye positions during fixation nor to the initial eye positions before saccades. 7. Eye-position units and horizontal head-velocity units were located rostral to the FOR.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

Pursuit deficits in bilateral pulvinar lesions.

A 58-year-old man had bilateral pulvinar infarctions. The patient developed smooth pursuit deficits in both the horizontal and vertical directions, while metrics of saccadic eye movements were normal. The gain of optokinetic nystagmus was slightly reduced. These findings strongly support the idea that the efferent fibers from the cortical pursuit center pass through the pulvinar in the human brain, in the same manner as previously described in the monkey cerebrum.

Cerebral Infarction↗
PubMed1991

Utilization and metabolism of [U-14C]4' galactosyllactose (O-beta-D-galactopyranosyl-(1----4)-O-beta-D-galactopyranosyl-(1----4)- D-glucopyranose) in rats.

O-beta-D-Galactopyranosyl-(1----4)-O-beta-D-galactopyranosyl- (1----4)-D-glucopyranose (designated as 4'GL) are produced from lactose with Cryptococcus laurentii OKN-4. Excretion and metabolism of 4'GL in rats were examined using a radioisotope technique. [U-14c]4'GL was synthesized from [U-14C]lactose by Cryptococcus laurentii OKN-4. The 14CO2 in expired air was counted after oral administration of [U-14C]4'GL or [U-14C]lactose in conventional rats, rats treated with antibiotics and germ-free rats. The rate of 14CO2 excretion from conventional rats given [U-14C]4'GL was slower than that from those administered [U-14C]lactose. When [U-14C]4'GL was orally administered to rats given antibiotics, there was a 2-h delay in 14CO2 excretion, as compared to conventional rats. In germ-free rats, total excretion of 14CO2 from [U-14C]-4'GL decreased to about one-third of that of conventional rats during a 24-h period. Radioactivities in the serum, liver, and carcass of the [U-14C]4'GL oral administration group were lower than those of the [U-14C]lactose oral administration group. Radioactivities in the feces and urine however, were higher in [U-14C]4'GL group than in [U-14C]lactose group.

Animals↗
PubMed1991

Translocation of hsp-70 and protein synthesis during continuous heating at mild temperatures in HeLa cells.

We have investigated intracellular translocation of hsp-70 and the synthesis of hsp-70 and total protein during heating at moderate temperatures in HeLa cells. When cells were heated at temperatures above 41 degrees C, hsp-70 translocated from the cytoplasm into the nuclei and apparently accumulated in nucleoli within 10 min. At temperatures above 42 degrees C, hsp-70 remained in the nuclei during heating. When cells were heated at 41 degrees C, the hsp-70 which had translocated into the nuclei returned gradually to the cytoplasm during heating. Synthesis of hsp-70 increased to three- to fourfold that in control cells, then decreased to the control level by 6-8 h. Total protein synthesis first decreased to 60% of the control level, then gradually recovered by 4 h. This indicates the acquisition of translational tolerance during heating at 41 degrees C. The return of hsp-70 to the cytoplasm is related to the recovery of total protein synthesis. Similar results were obtained at 42 degrees C heating in heat-induced thermotolerant cells. From these results, it is suggested that translocation of hsp-70 into the nuclei is very important for the recovery of protein synthesis (acquisition of translational tolerance) during heating at moderate temperatures. Also, cycloheximide and puromycin appeared to lower the temperature threshold about 1 degree C with respect to the translocation of hsp-70.

Cycloheximide↗
PubMed1991

[HSP 70 is associated with abnormal cytoplasmic inclusions characteristic of neurodegenerative diseases].

Several degenerative diseases of the central nervous system are characterized by the presence of neuronal inclusions. One of these inclusions, neurofibrillary tangles in Alzheimer's disease, has been shown to contain ubiquitin that belongs to a group of proteins known as heat shock proteins. Subsequent studies revealed that ubiquitin is also associated with various neuronal inclusions including Lewy bodies, Pick bodies and hyaline inclusions. Very recently, ubiquitin has been found also to be associated with glial inclusions that are unique to multiple system atrophy. The close association of ubiquitin with varying cellular inclusions, together with its function in the proteolytic process, raised the hypothesis that ubiquitin may be involved in the degradation of abnormal proteins appearing in the damaged neurons and glial cells. In central nervous system, a group of heat shock proteins collectively known as HSP 70 is also present which is constitutive and/or inducible. Since HSP 70 has been suspected to play a crucial role degradation and repair of abnormal intracellular proteins, we hypothesized that HSP 70 may be associated with those inclusions, as the case with ubiquitin. To test this we performed immunohistochemical studies on brain tissues from patients with various neurodegenerative conditions by using specific polyclonal antibody to HSP 70. Brain tissues were obtained at autopsy from each three patients with Alzheimer's disease, Pick's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS) and multiple system atrophy. Tissues were fixed in buffered formalin and embedded in paraffin. Immunostaining was performed by the standard ABC method using diaminobenzidine as a chromogen. Sections were lightly stained with hematoxylin. Polyclonal antibodies were raised in rabbits against mouse HSP 70.(ABSTRACT TRUNCATED AT 250 WORDS)

Alzheimer Disease↗
PubMed1990

A novel 40-kDa protein induced by heat shock and other stresses in mammalian and avian cells.

When HeLa cells were exposed to heat shock or other stresses, a 40-kDa protein (p40) was induced in addition to the classical heat shock proteins with molecular sizes of 110-, 90-, 70-, and 47-kDa. The p40 was induced not only by heat shock but by arsenite and 2-azetidine carboxylic acid. Also, it was induced in rat, mouse and chick cells by these stresses. The p40 was a basic protein (pI divided by 9.2) as judged by two-dimensional gel electrophoresis. To our knowledge, p40 is a novel heat shock protein in mammalian and avian cells.

Animals↗
PubMed1990

Novel ATP-binding heat-inducible protein of Mr = 37,000 that is sensitive to transformation in BALB/3T3 cells.

Using affinity chromatography on ATP-agarose, we have identified a major ATP-binding protein in Nonidet P-40 extracts of avian and mammalian cells labeled with [35S]methionine. After washing ATP-agarose beads with high-ionic-strength buffer (0.4 M NaCl), the 37-kD protein was shown to be one of the major ATP-binding proteins while p72 and grp78, which are members of the hsp70 family, also bound to ATP-agarose. This protein consisted of several spots on two-dimensional gel electrophoresis. The isoelectric point of the most basic spot was approximately 9.2 in chick embryo fibroblasts, whereas it was about 8.8 in mouse 3T3 cells. The identities of these proteins in mouse and chick cells were confirmed by peptide mapping. After heat-shock treatment of BALB/3T3 cells, the major heat-shock protein, hsp70, was shown to be induced very rapidly after heat shock and was recovered in the ATP-binding fraction. Besides hsp70, a 37-kD protein was also found to be induced by heat shock. This protein was drastically induced by treating the cells with alpha,alpha'-dipyridyl, an iron chelating reagent, but not with sodium arsenite, calcium ionophore, or tunicamycin. The synthesis and the total amount of this ATP-binding protein increased in mouse 3T3 cells transformed by simian virus 40, methylcholanthrene, or activated c-Ha-ras oncogene compared to their normal counterparts. The incorporation of [32P]orthophosphate was not detected in either normal or transformed cells. These studies established that a major ATP-binding protein of Mr = 37,000 is a heat-inducible protein and that the synthesis of this protein is regulated by malignant transformation.

2,2'-Dipyridyl↗