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Y Ohki

Publications and source records attributed to Y Ohki.

At least 37 records · Page 2Linked to original sources
PubMed1996

Inhibitory input to pause neurons from pontine burst neuron area in the cat.

Extra- and intracellular recordings were made from pontine pause neurons (PNs) in the cat. Spontaneous spikes of PNs were suppressed after single shock stimulation of excitatory burst neuron (EBN) area immediately rostral to the abducens nucleus. The most effective stimulation site for the suppression was the region where long-lead burst neurons (LLBNs) were predominantly located. Intracellular recordings from PNs showed that stimulation of the LLBN area induced short-latency inhibitory postsynaptic potentials (IPSPs) in PNs and that steep hyperpolarization of PNs associated with quick phases of nystagmus occurred prior to an abrupt change in abducens nerve activity. Results suggest that a pause of PN spikes associated with quick phases is, at least in part, produced by inhibitory action mediated through LLBNs.

Abducens Nerve↗
PubMed1996

Two-dimensional electrophoresis of plant proteins and standardization of gel patterns.

Proteins of two plants, Arabidopsis thaliana and rice (Oryza sativa) were subjected to two-dimensional electrophoresis analysis with two modifications: (i) comigration of external standard marker proteins with resultant horizontal and vertical stripes in the gel, and (ii) deblocking with a vapor of aqueous heptafluorobutyric acid for N-acetylserine. Approximately 5000 protein spots were separated from both the five tissues of Arabidopsis and the nine tissues of rice. Over one hundred spots were electroblotted for N-terminal sequencing. Among the newly sequenced proteins, 62 were from Arabidopsis and 51 from rice.

Amino Acid Sequence↗
PubMed1996

Convergence of skin reflex and corticospinal effects in segmental and propriospinal pathways to forelimb motoneurones in the cat.

The organization of facilitatory convergence from cutaneous afferents (Skin) and the corticospinal tract (pyramidal tract, Pyr) in pathways to forelimb motoneurones of mainly distal muscles was studied in anaesthetized cats by analysing postsynaptic potentials (PSPs), which were spatially facilitated by combinations of stimuli to the two sources at different time intervals. Conditioning Pyr volleys facilitated Skin-evoked PSPs of fixed (1.2-3.6 ms) central latencies (Skin PSPs), suggesting that disynaptic and polysynaptic skin reflex pathways are facilitated from the pyramidal tract. The shortest latencies (1.2-1.7 ms) of pyramidal facilitation suggested direct connection of pyramidal fibres with last order neurones of skin reflex pathways. Conditioning Skin volleys facilitated Pyr-evoked PSPs of fixed, mostly disynaptic latencies (1.0-2.5 ms; Pyr PSPs), suggesting that pyramido-motoneuronal pathways are facilitated from Skin at a premotoneuronal level. The shortest pathway from skin afferents to the premotor neurones appeared to be monosynaptic. Although Pyr and Skin volleys were mutually facilitating, the facilitation curve of Pyr PSPs and that of Skin PSPs were discontinuous to each other, with the peak facilitation at different Skin-Pyr volley intervals. Transection of the dorsal column (DC) at the C5/C6 border had little effect on the latencies or amplitudes evoked by maximal stimulation and the pyramidal facilitation of Skin PSPs. In contrast, the facilitation of Pyr PSPs by Skin stimulation was greatly decreased after the DC transection, and the facilitation curve of Pyr PSPs was continuous to that of Skin PSPs, with no separate peak. Latencies of Pyr PSPs ranged similarly to those in DC intact preparations. More rostral DC transection (C4/C5 border) reduced Skin-facilitated Pyr excitatory PSPs (EPSPs) less than C5/C6 lesions, suggesting that the C5 segment also contains neurones mediating Skin-facilitated Pyr EPSPs. The results show that convergence from skin afferents and the corticospinal tract occurs at premotor pathways of different cervical segments. We suggest that corticospinal facilitation of skin reflex occurs mostly in the brachial segments and Skin facilitation of cortico-motoneuronal effects takes place largely in the rostral cervical segments and partly in the brachial segments.

Animals↗
PubMed1995

Delayed gastric emptying in a neonate, associated with a partial defect in the gastric smooth muscle.

A girl born after 36 weeks' gestation had emesis 15 hours after birth. She required total parenteral nutrition (TPN) because of persistent gastric retention. When milk was given, the volume of gastric aspirate 3 hours after feeding often was greater than the volume given. Domperidon and erythromycin were ineffective. Upper gastrointestinal series showed slow gastric emptying but no abnormalities in the stomach. No stenosis or obstruction below pylorus was found. Endoscopy showed normal gastric mucosa. Manometry showed normal antroduodenal motility patterns. Transpyloric feeding, which started at age 73 days, was successful and enabled cessation of the TPN. Laparotomy at 119 days of age showed partial absence of the muscle and serosal layer in the anterior wall of the gastric body (1 x 4 cm). The mucosal layer was intact and partly adhered to the peritoneum and the left lobe of the liver. The defect was surgically corrected by plicating the place. The postoperative course was excellent, and oral feeding was fully established within 2 weeks. Although the cause of the partial muscle defect in the case is unclear, this case suggests that this rare condition can cause severe chronic gastric retention.

Female↗
PubMed1995

Input-output organization in the hand area of the human motor cortex.

The primate motor cortex consists of efferent zones which receive sensory information from a portion of limb in close anatomical relation to the muscle to which they project. To investigate a similar input-output relation in humans, we studied the effect of tactile stimuli on the size of motor evoked potentials (MEPs) elicited by transcranial magnetic and electrical stimulation. For tactile stimuli we applied air to the skin. The sizes of MEP of 3 finger muscles (flexor pollicis brevis, first dorsal interosseous, and abductor digiti minimi) with and without air stimuli were compared. Air stimuli applied to the tip of one finger facilitated mainly the magnetically evoked MEP of a muscle attached to that finger. A less obvious facilitatory effect was observed when giving stimuli on the dorsal aspect of the hand. Air stimuli had no facilitatory effect on electrically evoked MEPs. In one subject, there was no facilitatory effect even to magnetically evoked MEPs. In this subject, D-waves had the lowest threshold for magnetic and electrical stimulation. These results suggested that the effect was produced at the cortical level. This effect may correspond to the input-output relation found in the primate motor cortex.

Electric Stimulation↗
PubMed1995

Site of interaction between saccade signals and vestibular signals induced by head rotation in the alert cat: functional properties and afferent organization of burster-driving neurons.

1. Extracellular spikes of burster-driving neurons (BDNs) were recorded within and immediately below the prepositus hypoglossi nucleus in the alert cat. BDNs were characterized by short-latency activation after stimulation of the contralateral vestibular nerve (latency: 1.4-2.7 ms) and the ipsilateral superior colliculus (latency: 1.7-3.5 ms). Convergence of vestibular and collicular inputs was found in all of 85 BDNs tested. Firing of BDNs increased during contralateral horizontal head rotation and decreased during ipsilateral rotation. A burst of spikes was induced in association with contralateral saccades and quick phases of nystagmus. 2. BDNs showed irregular tonic discharges during fixation. There was no significant correlation between the firing rate during fixation and horizontal or vertical eye position in most BDNs. During horizontal sinusoidal head rotation, the change in firing rate was approximately proportional to and in phase with contralateral head velocity. The phase lag of the response relative to head angular velocity was 13.8 +/- 20.1 degrees (mean +/- SD) at 0.5 Hz and 7.2 +/- 13.5 degrees at 0.2 Hz on the average. The gain was 0.88 +/- 0.25 (spikes/s)/(degrees/s) at 0.5 Hz and 1.19 +/- 0.49 (spikes/s)/(degrees/s) at 0.2 Hz. 3. Quantitative analysis of burst activity associated with saccades or quick phases indicated that the ON direction of BDNs was contralateral horizontal. The number of spikes in the burst was linearly related to the amplitude of the contralateral component of rapid eye movements. The slope of regression line was, on the average, 1.14 +/- 0.48 spikes/deg. There was no significant difference between the mean slopes for saccades and quick phases. The number of spikes depended on the difference between initial and final horizontal eye positions and not on the absolute eye position in the orbit. The mean burst firing rate was proportional to the mean velocity of the contralateral component of rapid eye movements. The slope of the regression line was 0.82 +/- 0.34 (spikes/s)/(degrees/s). Significant correlation was also found between intraburst instantaneous firing rate and instantaneous component eye velocity. 4. Objects presented in the contralateral visual field elicited a brief burst of spikes in BDNs independent of any eye movement. Contralateral saccades to the target were preceded by an early response to the visual stimulus and subsequent response associated with eye movement. 5. Excitation of BDNs produced by stimulation of the ipsilateral superior colliculus was facilitated by contralateral horizontal head rotation. Therefore saccadic signals from the superior colliculus to BDNs may be augmented by vestibular signals during head rotation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

[Arrhythmias, autonomic function and spectral analysis of heart rate variation in patients with stable chronic pulmonary disease].

Autonomic function, the frequencies of arrhythmias, and outcome were studied in patients with stable chronic pulmonary disease (n = 67. Old tuberculosis, n = 35. Chronic pulmonary emphysema, n = 32) and in age-matched healthy elderly. The frequencies of arrhythmias were computed and spectral analysis was done with data obtained from 24-hour Holter ECG monitoring. The minimum heart rates of the patients were high. The minimum heart rate fell at night in the controls, but not in the patients. The patients had more PVCs than the controls, however sudden death due to arrhythmias did not occur. The LF/HF ratios obtained by spectral analysis of heart rate were lower in the patients than in the controls. There were no significant differences in age, respiratory rate, arterial blood gases, pulmonary-function tests, arrhythmias, or in the hourly distribution of the minimum heart rate between patients who died within 3 years and those who lived for more than 5 years. However, the LF/HF ratio in those who died was significantly lower than in the other groups. These results suggest that functional disturbance of the autonomic nervous system is related to outcome in patients with stable chronic pulmonary disease.

Aged↗
PubMed1994

Excitation of the motor cortex associated with the E2 phase of cutaneous reflexes in man.

We investigated excitability changes of the motor cortex associated with the E2 phase of cutaneous reflexes in the first dorsal interosseous muscle using transcranial electrical and magnetic stimulation of the motor cortex in humans. EMG responses to combined cutaneous and weak magnetic cortical stimulation, which were elicited during the E2 phase of cutaneous reflexes, were larger than those by the same magnetic cortical stimulation alone. This facilitatory effect was reduced or even inhibitory effect was seen when the intensity of cortical stimulation was increased. Responses to weak electrical cortical stimulation were less affected by the combined cutaneous stimulation. The same facilitatory effect on responses to weak magnetic cortical stimulation was also observed in single motor unit recordings, too. Dissociation between facilitatory effects on the responses evoked by weak magnetic and weak electrical cortical stimulations suggests that the motor cortical excitability is increased in association with the E2 phase. The present results are consistent with the hypothesis that the E2 phase is a kind of transcortical reflex.

Adult↗
PubMed1993

Candidate premotor neurones of skin reflex pathways to T1 forelimb motoneurones of the cat.

This study explored the locations and input-output properties of a large population of putative premotor neurones of skin reflex pathways in the cat. These neurones, interneurones excited by forelimb skin afferents and antidromically from the T1 motor nucleus (MN) and/or the lateral funiculus (LF, C8/T1 border), termed antidromic cells, were extracellularly recorded at C6-8. Selection of this site was based on data showing that cells retrogradely HRP labelled from the T1 MN were most numerous in C6-8 and the observation that transection of LF at the C8/T1 border abolished most skin-evoked postsynaptic potentials of T1 motoneurones. Antidromic cells were located in laminae IV-V, VI and VII. The latencies of antidromic excitation ranged from 0.4 to 1.8 ms, with a tendency for laminae IV-V cells to show longer latencies than laminae VI and VII cells. Latency of skin-evoked excitation ranged from 0.6 ms (IV-V cells), 0.8 ms (VI) and 1.4 ms (VII) to greater than 5 ms. The sum of the ortho- and antidromic latencies (estimated central latency) of individual cells explained the central latencies of skin-evoked postsynaptic potentials in T1 motoneurones. Skin-evoked firing responses (average of eight to ten cells) were earliest and largest in laminae IV-V antidromic cells, and latest and smallest in lamina VII cells. The antidromic cells who received inputs from muscle afferents and descending tracts. The following three results support the suggestion that the sampled antidromic cells are mostly premotor neurones. (1) Projection to the T1 MN via LF was verified in six laminae IV-VII antidromic cells, as tested with threshold mapping for antidromic excitation. (2) Three skin-excited axons of the middle LF projected to T1 MN, as revealed by intra-axonal staining (HRP). (3) PHA-L injection in laminae I-V of C8 anterogradely labelled terminals in lamina IX and LF axons at T1. It is suggested that last-order neurones of skin reflex pathways to T1 motoneurones are widely distributed in laminae IV-VII of C6-8 and consist of a variety of neurones with different locations and input patterns.

Animals↗
PubMed1992

Structural analysis of non-volatile compounds by liquid chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry: thermal isomerization of benzylpenicillin in a Plasmaspray interface.

Isomerization and degradation of benzylpenicillin ((2S,5R,6R)-3,3-dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1- azabicyclo[3.2.0]heptane-2-carboxylic acid) were studied using a combination of Plasmaspray (PSP) liquid chromatography/tandem mass spectrometry (LC/MS/MS) and liquid secondary ion tandem mass spectrometry (LSI MS/MS). Benzylpenicillin was isomerized to benzylpenicillenic acid (3-mercapto-N-[[5-oxo-2-(phenylmethyl)-4(5H)- oxazolylidene]methyl]valine) in the PSP interface/ion source. The isomerization was inferred from the probe temperature dependence of PSP LC tandem mass spectra and discrepancies in the daughter ions between PSP LC and LSI tandem mass spectra. High temperature at the PSP interface was responsible for the isomerization, since the difference between PSP LC and LSI tandem mass spectra became smaller as the probe temperature was lowered. It was also found that benzylpenicillin was decomposed to benzylpenilloic acid (5,5-dimethyl-2-[(phenylacetamido)methyl]thiazolidine-4-carboxylic acid), N-(phenylacetyl)glycine, N-(phenylacetyl)glycinal and 3-mercaptovaline in the PSP interface/ion source. The degradation products formed in the interface/ion source were identical to those formed in acidic solution. The results show that degradation of penicillins can be investigated by PSP LC/MS and PSP LC/MS/MS.

Chromatography, Liquid↗
PubMed1992

The dawn phenomenon: comparison between normal and insulin-dependent diabetic adolescents.

To determine the role of insulin clearance in the dawn phenomenon, we studied 10 adolescents with IDDM in comparison to 10 healthy, matched control subjects reported previously. In diabetics, metabolic clearance rate of insulin was calculated during i.v. infusion of insulin from 0100 to 0430 h and from 0430 to 0800 h (0.17 and 0.33 mU/kg/min, respectively), with a Harvard pump, while maintaining nocturnal euglycemia. In controls, metabolic clearance rate of insulin was calculated from the prehepatic insulin secretion rate based on C-peptide levels. In diabetic and control subjects, plasma glucose, free insulin, and glucagon concentrations were similar and did not change during the dawn period. However, metabolic clearance rate of insulin increased during the dawn period in diabetic (9.42 +/- 0.91 to 19.89 +/- 1.52 mL/kg/min, p less than 0.0001) and control subjects (4.87 +/- 1.11 to 9.30 +/- 1.50 mL/kg/min, p = 0.008). Plasma cortisol and adrenocorticotropic hormone levels increased and growth hormone (GH) decreased significantly during the dawn period. Diabetic adolescents had significantly higher plasma GH levels than control subjects throughout the night. We conclude the 1) increased insulin clearance is responsible for the dawn phenomenon in healthy and diabetic adolescents and 2) insulin resistance due to GH is an unlikely cause for the dawn phenomenon because diabetic subjects, despite higher GH levels, maintain plasma glucose levels similar to control subjects without requiring higher plasma free insulin concentrations.

Adolescent↗
PubMed1992

[Studies on insulin secretion and clearance in obese and diabetic children (7-11 years old) and adolescents (12-16 years old) investigation by oral glucose tolerance tests (O-GTT)].

We analyzed O-GTT obtained from 375 children (group A; 7-11 years old) and adolescents (group B; 12-16 years old), including 96 normal non-obese cases, 266 simple obese cases (172 with normal O-GTT, 79 with border line type O-GTT and 15 with diabetic type O-GTT), 8 obese NIDDM cases and 5 non-obese NIDDM cases. The results were as follows; 1) The levels of epsilon CPR (in terms of total sum of the values measured at 0, 30, 60, 120 and 180 minutes on O-GTT) in the obese children and adolescents were only 1.5 and 1.2 times as high as in the control group. The levels of epsilon CPR/epsilon IRI molar ratio in the control group were 2.0 and 2.3 times as high as in the obese children and adolescents. These data suggest that hyperinsulinemia in the obese children and adolescents is caused mainly by decreased hepatic insulin extraction rather than by increased insulin secretion. 2) In the non-obese NIDDM adolescents, the levels of epsilon CPR decreased to about 3/4 of those in the control group; in contrast, the epsilon CPR/epsilon IRI molar ratio increased. Therefore, it seems that there is increased hepatic insulin extraction as well as decreased insulin secretion in the non-obese NIDDM adolescents. 3) In the obese NIDDM adolescents, the levels of epsilon CPR were nearly the same as in the control group and the epsilon CPR/epsilon IRI molar ratios were slightly lower as the disease state of NIDDM counterbalanced obesity.

Adolescent↗