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Biomedical subjects

T Tsukada

Publications and source records attributed to T Tsukada.

At least 253 records · Page 14Linked to original sources
PubMed1985

Endogenous opioids and related peptides: from molecular biology to clinical medicine. The Sir Henry Dale lecture for 1985.

Advances in techniques in molecular biology have facilitated the research into endogenous opioids and related peptides in several ways. The organization and expression of genes and the primary structure of three precursor proteins of opioid peptides have been elucidated. These studies predicted the presence of potentially bioactive peptides, which has been confirmed by later studies. Advances in techniques in protein chemistry have helped to elucidate the distribution and molecular forms of endogenous opioids and related peptides in the body, and the processing of precursor proteins. Studies on the function of these peptides have shown a broad spectrum of actions. Leumorphin, a newly identified peptide, has been shown to exhibit unique biological activities. In spite of extensive studies, the physiological and pathophysiological significance of opioid peptide systems are not yet completely understood. This is mainly due to the paucity of our knowledge about opioid receptors. Further studies on the subtypes of opioid receptors will help to elucidate all aspects of the function of endogenous opioids and related peptides.

Animals↗
PubMed1985

Mechanism of the hypotensive effect of a new beta-adrenergic blocking drug, arotinolol (S-596) in anesthetized rabbits.

The mechanism of the hypotensive effect of arotinolol (dl-2-(3'-t-butylamino-2'-hydroxypropylthio)-4-(5'-carbamoyl-2'-th ienyl) thiazole hydrochloride, S-596), a new beta-adrenergic blocking drug with a weak alpha-adrenergic blocking activity, was studied in anesthetized rabbits. Intravenously administered arotinolol produced hypotension at doses above 3 micrograms/kg. Postganglionic renal nerve impulses (RNI) were effect-dependently at doses of 3 and 30 micrograms/kg but augmented after 300 micrograms/kg of arotinolol. The effects of the lower doses of arotinolol were similar to those of clonidine or propranolol, while the effects of the higher doses were similar to those of nitroprusside or phentolamine. The regression line representing the relation between the per cent change of the resting blood pressure and that of the numbers of RNI produced by the lower doses of arotinolol coincided with that of propranolol. Arotinolol blocked the pressor response to phenylephrine but not that to noradrenaline. Administration of arotinolol via the carotid artery produced a hypotension and a concomitant decrease of the numbers of RNI at doses of 3 to 30 micrograms/kg. The above results suggest that the hypotension produced by lower doses of arotinolol was attributable to a decreased sympathetic nervous activity, as is the case with propranolol, while the hypotension by higher doses was peripheral in origin, occurring as a consequence of the blocking effect on the alpha 1-adrenoceptor.

Adrenergic beta-Antagonists↗
PubMed1985

[Anti-platelet therapy in ischemic cerebrovascular disorder--clinical and hematological study].

Anti-platelet therapy (Aspirin 250 mg/every other day approximately 1000 mg/day + Dipyridamole 150 mg/day) was performed on 51 patients with ischemic cerebrovascular disorders (ICVD). Among these patients, 41 cases showed no recurrence of ICVD attack, whereas the remaining 10 cases had re-attacks. These 2 groups were compared from the viewpoint of various risk factors and other clinical findings: e.g. CT scan and angiographic appearance. But there was no statistically significant difference between them. Platelet aggregability and platelet survival time were examined in twenty-eight patients out of cases. We used a simple nonradioisotope technic for the determination of platelet survival time. Platelet survival time was shortened in 22 of 28 (79%) patients. On the other hand, platelet aggregability was found to have no definite tendency. In 9 of 10 cases, platelet survival time was revealed to be prolonged several months after administration of anti-platelet drugs. There was no re-attack in 7 of these 9 patients. Some reports also showed that platelet survival time was shortened in various thromboembolism and recovered by anti-platelet drugs. Measurement of platelet survival time is thought to be an important method as to the indication and the monitoring of anti-platelet therapy.

Adult↗
PubMed1984

Serotonin involvement in the inhibition of luteinizing hormone (LH) release during immobilization in castrated male rats.

The involvement of serotonin in mediating the inhibitory effect of immobilization stress on LH secretion in castrated male rats was examined by employing p-chlorophenylalanine (PCPA, 320 mg/kg, ip), an inhibitor of serotonin synthesis, and 5,6-dihydroxytryptamine (5,6-DHT, 50 micrograms, icv), a drug toxic to the indoleaminergic system. Immobilization stress suppressed pulsatile LH release and decreased mean plasma LH levels. Pretreatment with PCPA or 5,6-DHT apparently eliminated the inhibitory effect of immobilization stress on LH release. These results suggest the possible involvement of a serotoninergic mechanism in mediating the suppression of LH release induced by immobilization stress in castrated male rats.

Animals↗
PubMed1984

Determination of fragment D-dimer derivatives in serum reactive with antiserum against human fragment D-dimer.

A previous study demonstrated the preparation of an antiserum having enough specificity and sensitivity for a radioimmunoassay to determine fragment D-dimer derivatives. Using the antiserum the contents of fragment D-dimer derivatives in the sera of normal subjects and patients were determined. The content in normal subjects was 0.260 +/- 0.07 micrograms/ml (mean +/- SD) an that in patients with elevated levels of FDP ranged from 0.30 to 28 micrograms/ml. The values of fragment D-dimer derivatives and FDP in sera of some patients did not necessarily change in parallel, although there seems to be generally a positive correlation between them.

Antigen-Antibody Reactions↗
PubMed1984

Role of the pudendal nerves on the dynamics of micturition in the dog evaluated by pressure flow EMG and pressure flow plot studies.

The role of the pudendal nerves on the dynamics of micturition was studied using 16 decerebrated dogs. The voiding cycles were analyzed by pressure flow EMG and pressure flow plot studies under 3 conditions: control, after unilateral, and after bilateral pudendal nerve transection. In the control condition, highly reproducible reflex micturition with bladder contraction and spasmodic rhythmic sphincter contractions was demonstrated. Two patterns were noted following pudendal nerve transection: reflex micturition and overflow incontinence. Even though reflex micturition could be achieved in 9 out of 16 dogs after bilateral transection, there was decreased bladder emptying as well as absence of spasmodic rhythmic sphincter contractions. Overflow incontinence developed in the remaining 7 dogs (5 dogs after bilateral transection and 2 dogs after unilateral transection). It appears that the pudendal nerves play an important role in emptying the bladder of the dog.

Animals↗
PubMed1984

Plasma disappearance of ovine corticotrophin-releasing factor in man.

Disappearance of immunoreactive ovine corticotrophin-releasing factor (IR-oCRF) from plasma after a single intravenous injection of ovine corticotrophin-releasing factor (oCRF) was studied in man in the morning and evening. Synthetic oCRF (80 micrograms) was injected intravenously to four normal male volunteers at 0900 h or at 2200 h. Blood samples were drawn before and 2, 5, 10, 15, 30, 45, 60, 90 and 120 min after the oCRF injection. Plasma IR-oCRF was measured by a specific radioimmunoassay for OCRF. Plasma concentrations of IR-oCRF after oCRF injections in the morning and in the evening did not differ significantly (P greater than 0.05). Disappearance of IR-oCRF was modelled with a two-exponent function by using a non-linear least squares computer program. The metabolic clearance rate, the apparent initial volume of distribution, the plasma half-life for the fast component and that for the slow component calculated from all eight tests in the morning and evening were 1.49 +/- 0.05 ml/min X kg, 44.4 +/- 1.7 ml/kg, 6.8 +/- 0.7 min and 46.2 +/- 2.3 min (mean +/- SEM), respectively. This relatively long half-life may be responsible for the prolonged biological effect of oCRF administered intravenously. There were no significant differences between parameters of IR-oCRF disappearance curves in the morning and those in the evening (P greater than 0.05).

Adult↗
PubMed1984

Plasma adrenocorticotropin and cortisol responses to ovine corticotropin-releasing factor in patients with adrenocortical insufficiency due to hypothalamic and pituitary disorders.

Plasma ACTH and cortisol responses to intravenous injection of 100 micrograms synthetic ovine corticotropin-releasing factor (CRF) were studied in 4 patients with hypothalamic hypopituitarism, 2 patients with Sheehan's syndrome, 2 patients with isolated ACTH deficiency and 10 normal subjects. All 4 patients with hypothalamic hypopituitarism had exaggerated plasma ACTH responses to CRF compared to normal subjects and gradual but definite increases in plasma cortisol from low basal levels. Of 2 patients with Sheehan's syndrome, one had slight ACTH and cortisol increases after CRF injection, whereas the other had no increase in either. In 2 patients with isolated ACTH deficiency, plasma ACTH and cortisol remained undetectable (ACTH less than 10 pg/ml, cortisol less than 0.6 microgram/dl) after CRF injection. These results suggest that the CRF test is a useful tool in evaluating patients with secondary adrenocortical deficiency.

Adolescent↗
PubMed1984

[Role of the striated urethral sphincter in the voiding cycle of the decerebrated dog].

The role of the striated urethral sphincter on the dynamics of micturition was studied using 4 decerebrated dogs. The voiding cycles were analyzed by pressure flow EMG and pressure flow plot studies before and after the administration of suxamethonium. In the control condition, highly reproducible reflex micturition with bladder contraction and spasmodic rhythmic sphincter contractions was demonstrated. After the administration of suxamethonium reflex micturition occurred, but there was decreased bladder emptying as well as absence of spasmodic rhythmic sphincter contractions. The striated urethral sphincter would seen to play an important role in bladder emptying of decerebrated dogs.

Animals↗