Search PubMed⌕ Search

Biomedical subjects

N Murakami

Publications and source records attributed to N Murakami.

At least 559 records · Page 31Linked to original sources
PubMed1984

Thyroid hormone maintains normal circadian rhythm of blood corticosterone levels in the rat by restoring the release and synthesis of ACTH after thyroidectomy.

The role of thyroid hormone in maintenance of the circadian adrenocortical rhythm was studied in the rat. The amplitude of the circadian rhythm of blood corticosterone levels gradually decreased with time after thyroidectomy, and by 5 weeks the rhythm disappeared. However, the circadian peak elevation constantly occurred just before the onset of the dark period until 4 weeks. Three weeks after thyroidectomy, daily overall treatment with thyroxine (T4) or 3,5,3'-triiodothyronine (T3) completely restored the amplitude of the circadian adrenocortical rhythm to the previous level within 2 weeks. Thyroidectomy did not affect the circadian rhythm in water intake. However, thyroidectomy resulted in a loss of significant difference of plasma adrenocorticotrophin (ACTH) levels between the morning and the evening, by decreasing the evening levels. Similarly, pituitary ACTH content was decreased by thyroidectomy. Replacement of T4 completely restored the decreased ACTH levels to the previous ones. These results suggest that thyroid hormone plays an important role in maintenance of the normal amplitude in circadian adrenocortical rhythm in the rat, by affecting ACTH synthesis.

Adrenal Cortex↗
PubMed1984

Flow cytometric analysis of deoxyribonucleic acid (DNA) content in adult leukemia.

Flow cytometric analysis of the bone marrow cellular DNA content was performed in 40 adult patients with acute leukemia. Twenty-eight had AML (29 previously untreated and 9 relapse) and 12 ALL (8 previously untreated and 4 relapse). For the whole series, the mean G1/0-phase compartment was 82 +/- 1.3%, the mean S-phase compartment 14 +/- 1%, and the mean G2 +M-phase compartment 4 +/- 0.7%. The percentage of cells in the S-phase had a positive correlation with the LDH level, but not with other parameters. Patients at relapse had significantly lower percentages of cells in the S-phase in AML and significantly higher in ALL. The changes of the S-phase size of the same patients at the first and relapse phases varied. Patients who obtained complete remission had significantly higher percent S phase than patients who did not. This difference was more significant in ALL. Percent cytoreduction had no correlation with the remission rate or S-phase size. Therefore, we analyzed changes of cells in the S-phase of patients with untreated AML during chemotherapy. The reduction rate of cells in the S-phase of patients who obtained complete remission was significantly higher than that of patients who did not.

Adolescent↗
PubMed1984

[Studies on background radioactivity in the Niigata City area--identification of natural nuclides present in underground (well) water samples].

Background radioactivity levels in Niigata city area were studied through the years of 1981-1984. As the results, it was found that the gross beta-radioactivity in underground (well) water samples were comparatively higher than those of other ground water samples. Ion chromatographic and gamma-ray spectroscopic determination revealed that this higher radioactivities were contributed by 40K rather than radium or thorium series nuclides or fallout originated 90Sr.

Background Radiation↗
PubMed1983

Circadian rhythm of adenosine-3',5'-monophosphate content in suprachiasmatic nucleus (SCN) and ventromedial hypothalamus (VMH) in the rat.

Twenty-four hour patterns of adenosine-3',5'-monophosphate (cAMP) contents in the suprachiasmatic nucleus (SCN) and the ventromedial hypothalamus (VMH) were determined at 3 h intervals under various conditions in adult male rats. The cAMP levels in both the nuclei showed a circadian variation with a clear peak time, which shifted under constant conditions (blinded and constant illumination). Under both entrained and free-running conditions, a consistent phase-angle difference of 9 h in peak time was observed between cAMP rhythms in the SCN and VMH. Under the LD cycle, the peak time of cAMP rhythms in the SCN and VMH appeared at 16.00 h and 07.00 h, respectively. The cAMP rhythm in the VMH synchronized with a restricted feeding time, when the rats were subjected to restriction of access to food under constant light. On the contrary, that in SCN did not synchronize with the restricted feeding time. These results indicate that the 24-h patterns of cAMP contents in SCN and VMH are the manifestation of endogenous circadian rhythms. However, the generating mechanism of cAMP rhythm may be different between SCN and VMH, as the restricted feeding regime affected the cAMP patterns of both the nuclei in different ways.

Animals↗
PubMed1983

Identification of calcium-independent myosin kinase with casein kinase II.

A crude myosin fraction from bovine brain has been found to contain a Ca2+-independent myosin kinase that catalyzes the phosphorylation of 20,000-Da light chain of gizzard myosin. The myosin kinase has been separated from the myosin by Sepharose CL-4B gel filtration and purified further by chromatography on phosphocellulose, Sephacryl S-300, and hydroxylapatite. The myosin kinase was found to copurify with casein kinase II and show the same substrate specificity with the casein kinase. These results indicate that the myosin kinase is identical to casein kinase II. The purified myosin kinase catalyzed the preferential phosphorylation of the threonyl residues of 20,000-Da light chains of gizzard and brain myosins. The 17,000-Da light chains of these myosins and the mixed light chains of skeletal and cardiac muscle myosins were not phosphorylated by the enzyme to an appreciable extent.

Amino Acids↗
PubMed1983

Effect of hypothalamic cooling on the tonic vibration reflex of gastrocnemius muscle in cats.

The tonic vibration reflex (TVR) in a medial gastrocnemius muscle (MG) was analyzed in 28 cats anesthetized with pentobarbital sodium while the preoptic-anterior hypothalamic region (PO-AH) was locally cooled or warmed in a thermoneutral environment. Cooling of the PO-AH did not produce shivering or changes in rectal and skin temperatures, but it brought about facilitation (16/28 cats) or inhibition (9/28) of the TVR in the MG. A few cats (3/28) showed inconsistent alteration of the TVR. Warming of the PO-AH did not produce any changes in the TVR of the MG. Histological identification of thermode placements revealed that in cats having the facilitatory response of the TVR, the thermodes were localized at regions caudal to A 14.0 mm and most of the thermodes in those having the inhibitory response were rostral to A 14.0 mm, except for two cases. Bilateral microinjection of a small quantity of anesthetic agent into the medial forebrain bundle (MFB) at the level of the mamillary body abolished the facilitatory effect of PO-AH cooling on the TVR. The results suggest that the spinal motor system is influenced by the PO-AH's sensitivity to local temperature and that the MFB constitutes part of the efferent pathway of the hypothalamic influence.

Animals↗
PubMed1983

Immunoelectron microscopic localization of thyroglobulin (TG) in the thyroid gland in Basedow's disease.

An electron microscopic immunohistochemical localization of thyroglobulin (TG) using PAP methods from Epok-812 embedded tissues has been made in human thyroids obtained from 15 patients with treated Basedow's disease aged 13 to 43 years. Follicular cells vary considerably in shape and content of cytoplasmic organelles depending mainly upon the size of follicles. Reaction product for TG coincided well with previous investigations studied by electron microscopic autoradiography and is strongly positive in most follicular lumina having no relation to their size, reabsorbed colloid droplets or small subapical vesicles. The reabsorbed colloid droplets are rarely observed in cells surrounding distended follicles and more frequently appeared in small follicles. The reabsorbed colloid droplets after fusion with lysosomes show a variable amount of reaction products from intense deposition to a complete absence of product indicating hydrolysis of TG by lysosomal enzymes. There is no reaction product in rough endoplasmic reticulum or Golgi apparatus in spite of positive reaction product in the subapical vesicles. These subapical vesicles are composed of both endocytotic and exocytotic vesicles.

Adolescent↗
PubMed1983

Cervical thymoma and incidence of cervical thymus.

A case of cervical thymoma in a 51-year-old female is reported. The tumor was located on the left side of the anterior neck just beneath the left lower lobe of the thyroid gland and there was no connection to the mediastinal thymus gland. It was well encapsulated and lobulated on the cut-surface. Histologically, the tumor showed a mixed proliferation of lymphocytes and epithelial cells. Mitoses were frequently seen. Several tiny fragments of ectopic thymic tissue were found around the tumor. Cervical thymic tissue, considered to be the original site of the cervical thymoma, was studied and found macroscopically in 12 out of 657 patients with Basedow's disease (1.8%).

Female↗
PubMed1983

Immunoelectron microscopic localization of thyroglobulin in human follicular adenoma.

An electron microscopic immunohistochemical localization of thyroglobulin (TG) using PAP methods has been made in 15 cases of cold follicular adenoma. All cases of follicular adenoma showed organ specific functions such as synthesis, storage, reabsorption, and hydrolysis of thyroglobulin except for an area composed of follicular cells with trabecular arrangement. Immuno-reaction product for TG was precisely demonstrated in follicular lumina, subapical vesicles and reabsorbed colloid droplets. The reaction product observed in the follicular lumen was clearly demarcated from the cytoplasm of the follicular cells by the apical plasma membrane. The subapical vesicles ranging approximately from 50 millimicrons to 300 millimicrons in diameter were rarely observed in follicular adenoma and some of them fused with the reabsorbed colloid droplets. The reabsorbed colloid droplets usually had the intense reaction product and hydrolyzed colloid droplets had a vacuole containing floccular low electron dense materials. There is no reaction product in rough endoplasmic reticulum and Golgi complexes.

Adenoma↗
PubMed1983

Melatonin accelerates the reentrainment of the circadian adrenocortical rhythm in inverted illumination cycle.

The effect of melatonin, para-chlorophenyl alanine (PCPA), gamma-aminobutyric acid (GABA) and dibutyryl-cAMP (d-cAMP) on the photoentrainment of the circadian adrenocortical rhythm was studied by the intrahypothalamic (near the SCN) implantation of a paraffin pellet mixed with each agent, in the rat. 2 weeks after implantation, the rats were moved to a room with a reversed lighting cycle (from LD to DL). Blood samples were taken from individual rats at 4-hour intervals for 24 h, and 2, 4, 6 and 10 days after movement, by the tail tip incision method. The effects of implantation of PCPA, GABA and d-cAMP on the reentrainment to the illumination cycle reversed were indistinguishable from those due to implantation of a pellet of paraffin alone. In these groups, more than half of the rats did not reentrain to the light cycle reversed in 4 (less than 18.1%) and 6 days (less than 36.3%), but did reentrain in 10 days. However, melatonin caused reentrainment of the circadian adrenocortical rhythm to reversed illumination between 4 (45.4%) and 6 days (72.7%). Pinealectomized rats receiving a melatonin pellet also exhibited an accelerated reentrainment to the light cycle reversed, when compared with the rat which received a pellet of paraffin alone. However, pinealectomized rats which received a pellet of paraffin alone did not require more time than intact rats to reentrain to the light cycle reversed. These results indicate that melatonin accelerates the reentrainment of the circadian adrenocortical rhythm to the light cycle reversed.

Animals↗
PubMed1983

Enhancement of corticosterone release by repeated injections of ACTH in the dexamethasone pre-treated rat.

To examine the possibility that pulsatile secretion of adrenocorticotrophic hormone (ACTH) enhances the responsiveness of the adrenal, the blood corticosterone response to repeated injections of ACTH was determined in the dexamethasone-nembutal pre-treated rat. Treatment with dexamethasone (100 micrograms/100 g body weight) at 13.00 h for 2 days decreased corticosterone levels and completely abolished these daily variations in both the blood and adrenal. Under these conditions, four or five successive iv injections of 0.2 or 2 mIU ACTH were given at 1/2 or 1 h intervals. Blood samples were taken immediately before and at frequent intervals after injection. A significant increase of blood corticosterone levels was observed 10 min after the second injection of 0.2 mIU ACTH. Further increases in blood corticosterone levels were observed after the subsequent injections. In addition, repeated injections of 2 mIU ACTH augmented the responsiveness of the adrenal to ACTH. The second or the third injections of 2 mIU ACTH produced a greater increase in adrenal corticosterone content than did the first ACTH injection. These results suggest that when ACTH acts on the adrenal gland in a pulsatile fashion, the steroidogenic response of the adrenal to ACTH increases markedly.

Adrenal Glands↗