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Biomedical subjects

A Sakaguchi

Publications and source records attributed to A Sakaguchi.

At least 37 records · Page 2Linked to original sources
PubMed1989

Sympathetic nervous function and erythrocyte cation transport systems in normotensive individuals with family history of hypertension.

To investigate the influence of heredity to the sympathetic nervous function and the cell membrane cation transport systems, we studied the blood pressure and plasma catecholamine response to supine exercise testings by bicycle ergometer, the pressure response to noradrenaline infusion tests and the heart rate response to isoproterenol infusion tests in 88 healthy Japanese sedentary normotensive men with and without a family history of essential hypertension [FHH(+) and FHH(-)]. Several erythrocyte monovalent cation transport parameters were also measured in 74 of these individuals. In the results, (1) the systolic blood pressure response to exercise testings and noradrenaline infusion tests were larger in FHH(+) than FHH(-): (2) there was no difference between FHH(+) and FHH(-) in the heart rate response to isoproterenol infusion tests: (3) there was no significant difference between FHH(+) and FHH(-) in the increased plasma catecholamine levels to exercise testings: (4) the intraerythrocytic sodium content was significantly higher in FHH(+) than in FHH(-): and (5) several erythrocyte monovalent cation transport systems (Li-Na countertransport, Na-K cotransport and Na-K pump activity) were clearly accelerated in FHH(+). We concluded that in spite of normotension there were abnormalities of sympathetic nervous function, intracellular sodium content and several cell membrane cation transport systems in individuals with a family history of essential hypertension.

Adult↗
PubMed1988

Sodium sensitivity of blood pressure and baroreceptor reflex function in patients with essential hypertension.

In order to define the role of the baroreceptor reflex function in the sodium sensitivity of blood pressure in patients with mild essential hypertension, 25 patients were classified into two groups, salt-sensitive and salt-insensitive, depending on the difference in the averages of the resting systolic blood pressure, taken hourly on the fifth day of 7 days of sodium depletion and on the fifth day of 7 days of repletion. Increases in urinary sodium excretion and body weight and a decrease in haemotocrit during the sodium repletion period were similar in both groups. Baroreceptor reflex function, estimated from the baroreceptor slope and the blood pressure change on a 70 degrees tilting test, was enhanced by the sodium repletion period in the sodium-insensitive group but not in the sodium-sensitive group. These results suggest that sodium sensitivity might be due to differences in the ability of the baroreceptor reflex function to become sensitized during a high sodium intake.

Blood Pressure↗
PubMed1988

[Two cases of cloacogenic carcinoma of the anal canal: chemotherapeutic effect of cis-dichlorodiammine-platinum].

Cloacogenic carcinoma, originating from the remnant of the cloaca, is a rare malignant tumor, comprising 2-3% of cancers of the anal canal. We reported here two cases of cloacogenic carcinoma whose pulmonary and hepatic metastases were successfully treated with CDDP administration, in spite of limited effect on primary lesions of the rectum. The promising usage of CDDP for cloacogenic carcinoma, especially for distant metastasis was discussed.

Anus Neoplasms↗
PubMed1986

Interruption of projections from the medial geniculate body to an archi-neostriatal field disrupts the classical conditioning of emotional responses to acoustic stimuli.

We have previously found that the coupling of changes in autonomic activity and emotional behavior to acoustic stimuli through classical fear conditioning survives bilateral ablation of auditory cortex but is disrupted by bilateral lesions of the medial geniculate nucleus or inferior colliculus in rats. Auditory fear conditioning thus appears to be mediated by the relay of acoustic input from the medial geniculate nucleus to subcortical rather than cortical targets. Since the medial geniculate nucleus projects, in addition to auditory cortex, to a striatal field, involving portions of the posterior neostriatum and underlying archistriatum (amygdala), we have sought to determine whether interruption of connections linking the medial geniculate nucleus to this subcortical field also disrupts conditioning. The conditioned emotional response model studied included the measurement of increases in mean arterial pressure and heart rate and the suppression of exploratory activity and drinking by the acoustic conditioned stimulus following delayed classical conditioning, where the footshock unconditioned stimulus appeared at the end of the conditioned stimulus. The peak increase in arterial pressure and the duration of activity and drinking suppression were greater in unoperated animals subjected to delayed conditioning than in pseudoconditioned controls, where the footshock was randomly rather than systematically related to the acoustic stimulus. Increases in heart rate, however, did not differ in conditioned and pseudoconditioned groups. While the arterial pressure and behavioral responses therefore reflect associative conditioning, the heart rate response does not. Rats were prepared with bilateral lesions of the medial geniculate nucleus, bilateral lesions of the striatal field or asymmetrical unilateral lesions destroying the medial geniculate nucleus on one side and the striatal field on the contralateral side. The latter preparation leaves one medial geniculate nucleus and one striatal field intact but disconnected and thus produces a selective auditory deafferentation of the intact striatal field. Control groups included animals with unilateral lesion of the medial geniculate nucleus, with unilateral lesion of the medial geniculate nucleus combined with lesion of the ipsilateral striatal field, unilateral lesion of the medial geniculate combined with lesion of the contralateral anterior neostriatum (a striatal area outside of the medial geniculate nucleus projection field).(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1984

Strain difference in fear between spontaneously hypertensive and normotensive rats is mediated by adrenal cortical hormones.

In the present study we sought to determine whether the strain difference in fear reactivity between spontaneously hypertensive rats (SHR) and strain-matched WKY controls might be related to adrenocortical function. SHR and WKY were subjected to adrenalectomy prior to classical fear conditioning. Adrenal cortical steroids were replaced in some animals. Adrenalectomy produced comparable effects on conditioned fear reactivity in SHR and WKY and steroid replacement reversed the effects of adrenalectomy in both strains. However, a larger dose was required to compensate for adrenalectomy in SHR. These date implicate functions related, directly or indirectly, to the adrenal cortex, in the maintenance of the strain difference in fear reactivity.

Adrenal Cortex Hormones↗
PubMed1984

Experimental vasospasm: experiences with a canine model and failure of naloxone therapy.

Experimental vasospasm was studied in a canine model utilizing subarachnoid injection of autologous blood. Alterations in the size of the basilar artery were noted angiographically. Naloxone, an opioid receptor antagonist, has been reported to have a beneficial effect on neurological dysfunction secondary to cerebral ischemia. No significant change in the diameter of the basilar artery was noted in dogs either with or without spasm when treated with naloxone. We have concluded that naloxone has no detectable vasodilatory effect on the cerebral arteries of dogs.

Animals↗
PubMed1984

Subcortical efferent projections of the medial geniculate nucleus mediate emotional responses conditioned to acoustic stimuli.

The purpose of this study was to identify the afferent link in the neural pathway which mediates emotional responses coupled to auditory stimuli. We evaluated whether autonomic and behavioral responses elicited by acoustic conditioned emotional stimuli are based on afferent information derived from the auditory cortex or from the auditory thalamic relay station, the medial geniculate nucleus (MG), in rats. The rat auditory cortex was defined through anterograde neuroanatomical tracing studies involving the injection of HRP into MG. Lesions were then placed in the auditory cortex or in MG. After 10 to 20 days the rats were subjected to classical fear conditioning trials involving the pairing of a pure tone with electric footshock. Changes in mean arterial pressure and heart rate and the duration of immobilization ("freezing") and drink suppression elicited by presentation during extinction trials (no footshock) of the acoustic conditioned emotional stimulus were measured. Auditory cortex lesions did not affect the magnitude of the mean arterial pressure or heart rate conditioned responses nor the duration of freezing or drink suppression. In contrast, lesions of MG suppressed the magnitude of both the autonomic and somatomotor (behavioral) conditioned emotional responses but did not affect either autonomic or somatic responses elicited by the footshock unconditioned stimulus. Lesions of the inferior colliculus, the primary source of afferent input to MG, replicated the effects of MG lesions. These findings demonstrate that lesions of MG and lower auditory centers, but not lesions of the auditory cortex, block autonomic and behavioral conditioned emotional responses coupled to acoustic stimuli and indicate that subcortical rather than cortical efferents of MG sustain these responses. Our concurrent observation that MG projects to several subcortical areas (central and lateral amygdala; caudate-putamen; ventromedial hypothalamus) involved in emotional behavior and autonomic function suggests hypotheses concerning subsequent links in this emotional processing pathway.

Acoustic Stimulation↗
PubMed1983

Strain differences in fear between spontaneously hypertensive and normotensive rats.

The purpose of this study was to determine whether the reduced conditioned fear response in spontaneously hypertensive rats (SHRs) relative to Wistar-Kyoto controls (WKYs); (a) reflects a decrease in fear in SHRs or an increase in fear in WKYs, relative to other strains; (b) is secondary to strain differences in cardiovascular regulation; (c) represents a weaker conditioned response or a weaker memory trace; and (d) generalizes beyond tests of conditioned fear. SHRs, WKYs and Sprague-Dawley (SD) rats were subjected to classical fear conditioning (30 trials) involving the pairing of a tone conditioned emotional stimulus (CES: 800 Hz, 82 dB, 10 s) with an electric footshock unconditioned stimulus (US: 1.5 mA, 0.5 s). Cardiovascular responses elicited by the CES (without the US) were assessed through computer assisted techniques in chronically instrumented animals. Conditioned fear behavior was assessed as the proportion of time accounted for by crouching or freezing during a 300 s presentation of the CES without the US. Unconditioned fear reactivity was examined using the open field test. Conditioned fear reactivity (% freezing during 300 s CES) was reduced (P less than 0.01) in SHRs relative to both WKYs and SDs, which did not differ (SHR: 57% +/- 5; WKY 85% +/- 3; SD: 93% +/- 4). Young (7 week) and mature (14 week) animals within each strain differed in resting mean arterial pressure (MAP, in mm Hg) (WKY: young , 102 +/- 1; mature, 133 +/- 2; P less than 0.01; SHR: young, 124 +/- 3; mature, 153 +/- 5; P less than 0.01) but did not differ in conditioned fear reactivity (WKY: young, 91% +/- 3; mature, 93% +/- 3; SHR: young, 47% +/- 3; mature, 62% +/- 8.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗