Biomedical subjects

C Fukuhara

Publications and source records attributed to C Fukuhara.

31 records · Page 2Linked to original sources

PubMed1993

Endogenous circadian rhythmicity of somatostatin like-immunoreactivity in the rat suprachiasmatic nucleus.

The suprachiasmatic nucleus (SCN) of the hypothalamus has been established as the locus of the circadian pacemaker in mammals. The SCN is histochemically divided into two subdivisions: dorsomedial and ventrolateral subfields. The dorsomedial SCN is characterized, in part, by dense somatostatin-like immunoreactivity (SS-LI), but its functional significance in circadian pacemaking remains unclear. Our previous study revealed that 24 h SS-LI contents of the SCN in rats kept under light-dark (LD) conditions or blinded by orbital enucleation showed a distinct circadian rhythm. In the present study, 24 h SS-LI contents of the SCN in sighted rats kept under constant darkness (DD) conditions for prolonged periods were measured by enzyme immunoassay. Cellular contents of SS-LI exhibited a clear circadian rhythm on the third day of constant darkness (DD) with a peak at circadian time (CT) 5, corresponding to the time of peak levels found in LD conditions and in enucleated animals. This endogenous free-running rhythm continued to oscillate without attenuation of the amplitude even at 14 days in constant darkness. Moreover, SS-LI rhythm was found to be similar to the vasopressin rhythm in the SCN. In summary, these findings further strengthen the idea that the cellular content of SS-LI in the SCN is under the control of the endogenous circadian pacemaker.

Animals↗

PubMed1993

Processing of photic information within the intergeniculate leaflet of the lateral geniculate body: assessed by neuropeptide Y immunoreactivity in the suprachiasmatic nucleus of rats.

Entrainment of the circadian pacemaker in the suprachiasmatic nucleus is accomplished by two neural pathways, the retinohypothalamic and geniculohypothalamic tracts. The geniculohypothalamic tract, which originates from the intergeniculate leaflet and a portion of the ventral lateral geniculate nucleus, is composed of fibers immunoreactive to neuropeptide Y. To assess the processing of photic information by the geniculohypothalamic tract, neuropeptide Y immunoreactivity in the suprachiasmatic nucleus of rats kept under various external lighting conditions was determined by enzyme immunoassay of micropunched tissues. Neuropeptide Y levels in the suprachiasmatic nucleus steadily increased when rats were exposed to continuous light and reached a peak in 2 h before returning to basal level. The amount of increase did not depend on intensity and duration of light exposure. A light pulse as short as 5 min elicited a similar rise in neuropeptide Y, indicating that the response is due to the sudden transition from dark to light. This response, however, was only observed when the dark to light transition occurred at circadian time 0 (subjective dawn) of the pacemaker. A light pulse at circadian time 0, which effectively induces the increase in neuropeptide Y level, does not significantly shift the phase of the circadian rhythm. This observation indicates that the photic pathway utilizing neuropeptide Y may be functional only when the endogenous circadian rhythm is synchronized to external light and dark cycles. Administration of an excitatory amino acid antagonist (MK-801) blocked the increase of neuropeptide Y by light, while an agonist (N-methyl-D-aspartate) induced similar facilitatory effects to that of light on the neuropeptide Y level in the rat suprachiasmatic nucleus. These results suggest that the geniculohypothalamic tract processes photic information so as to facilitate distinction of the transition between light and darkness that occurs either at subjective dawn or dusk.

Animals↗

PubMed1992

Circadian rhythms of vasopressin content in the suprachiasmatic nucleus of the rat.

The suprachiasmatic nucleus (SCN) of the anterior hypothalamus contains a circadian pacemaker in mammals. We determined the circadian profiles of arginine-vasopressin (AVP), a major peptide in the dorsomedial SCN, in rats under light-dark (LD), constant dark (DD) and constant light (LL) conditions. Under LD conditions, AVP levels in the SCN showed circadian rhythmicity with a peak at early light phase and a broad trough during the dark phase. This rhythm in the AVP contents was maintained even after 14 days of free-running under DD conditions and 3 days under LL conditions. These circadian patterns of AVP are similar to those of somatostatin, another peptide in the dorsomedial SCN. This indicates a common mode of regulation for peptides in this subfield of the SCN.

Animals↗

PubMed1990

Effects of chelators on copper therapy of macular mouse, a model animal of Menkes' kinky disease.

Effects of chelators on the copper(Cu) therapy for the mutant mouse, Macular, which is a model animal of Menkes' disease were studied. Simultaneous administration of some chelators reduced the necessary dose of Cu (10 mg/kg) for the survival of the mice to one tenth. By this treatment the Cu concentration in the brain was increased but Cu in the kidney was not increased as much as Cu administration without chelator. Surviving mice showed normal growth in terms of body weight and fertility. Furthermore same effects were observed even when the chelator was administered without Cu. In the chelators tested, derivatives of carbamic acid like dimethyldithiocarbamate, which forms a lipophilic complex with Cu, were effective.

Animals↗

PubMed1988

Experience with Ikuta's phalangeal compression-distraction-fixation device.

Proper bony reduction and anatomic alignment without rotational deformity are sometimes difficult to achieve during phalangeal bone lengthening procedures. We report our experience with Ikuta's phalangeal compression-distraction-fixation device, which can be used to achieve proper bony reduction and good alignment and without any rotational deformity.

Adult↗

PubMed1987

Synthesis and degradation of erythrocyte metallothionein in cadmium-administered mice.

The origin of erythrocyte metallothionein (MT) in cadmium (Cd) administered mice and its fate were studied in connection with erythrocyte kinetics. It was shown that Cd-MT in the erythrocyte is synthesized in the precursor cells of the erythropoietic tissues, and Cd-MT containing erythrocytes come into the circulation after maturation. In regard to the degradation, it was found that Cd-MT is stable in the erythrocyte, but decomposed in the spleen or liver with the breakdown of erythrocyte when its life span is over.

Animals↗

PubMed1986

Fate of erythrocyte Cd-metallothionein in mice.

Degradation of metallothionein (MT), which appears in erythrocytes following cadmium (Cd) administration, was investigated in mice. Cd-MT underwent only slight decomposition by hemolysate in an in vitro experiment unlike an 800g supernatant fraction of the liver homogenate. In an in vivo study, [3H]diisopropylfluorophosphate was given to mice which had received 109CdCl2 to investigate the relationship between the decay of 109Cd-MT in the erythrocyte and the life span of the erythrocyte. A similar reduction pattern of radioactivity of 109Cd and 3H was observed. Erythrocytes containing 109Cd-MT obtained from mice preadministered with 109CdCl2 was transfused to normal mice. The 109Cd radioactivity of erythrocytes decreased in a manner similar to Cd in erythrocytes of 109CdCl2-administered mice. Contrary to this decrease of erythrocyte Cd in the transfused mice, Cd concentration of the spleen increased markedly. Cd increased also in the liver. These results indicate that erythrocyte MT degrades along with the erythrocyte. The Cd from this MT is deposited in the spleen and liver where blood cells are catabolized.

Animals↗

PubMed1986

Concentrations of metallothionein and metals in malignant and non-malignant tissues in human liver.

Concentration of metallothionein in the malignant and non-malignant tissues of the human liver was determined by the Cd-hem method. The concentration of metallothionein was high in the non-malignant tissue (471 +/- 306 micrograms/g). Metallothionein in the non-malignant tissue was mainly Zn-thionein and metallothionein-bound Zn was a major chemical form of Zn in the non-malignant tissue. The concentration of metallothionein in the malignant tissue was 75.6 +/- 79.6 micrograms/g, and significantly lower than that in the nonmalignant tissue. A strong, positive relationship was observed between the Zn and metallothionein concentrations, and the regression equation was MT (microgram/g) = -94.7 + 11.9 Zn (micrograms/g).

Adult↗

PubMed1985

The origin of metallothionein in red blood cells.

The origin of metallothionein (MT) in red blood cells (RBCs) from a mouse given cadmium was studied in connection with RBC kinetics. Plasma Cd concentration rapidly decreased 3 hr following 109CdCl2 (2 mg/kg, sc) administration, whereas RBC Cd increased from 2 to 4 days, followed by a gradual decrease. RBC Cd was found to be distributed more in the high-molecular-weight fraction than in the MT fraction 12 hr after administration. But, thereafter, Cd increased rapidly in the MT fraction to show changes with time similar to Cd level in RBCs. Hepatic damage induced in a mouse given 21 injections of Cd, with resultant marked elevation of plasma MT concentrations, did not cause any change in RBC Cd concentration. MT was hardly transferred to RBC when a mouse RBC suspension was incubated with mouse hepatic MT. To examine the relationship of Cd-MT and erythropoietic function, mice in the normal group, the phenylhydrazine-induced anemia group (PH), the transfusion-induced plethora group (TR), and the erythropoietin administered plethora group (TR + EP) were given 109CdCl2. Three days after administration, Cd concentration in its RBCs and its MT fraction remarkably increased in the PH group, and was greatly decreased in the TR group. A significant increase was noted in the TR + EP group as compared with the TR group. These results indicate that MT in the RBCs is formed in erythroblasts.

Anemia, Hemolytic↗

PubMed1981