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Biomedical subjects

N Kamiya

Publications and source records attributed to N Kamiya.

106 records · Page 6Linked to original sources
PubMed1978

Cyclic production of tension force in the plasmodial strand of Physarum polycephalum and its relation to microfilament morphology.

Cyclic contraction and relaxation of plasmodial strands of Physarum polycephalum were measured under both isotonic and isometric conditions, and their relation to changes in microfilament (MF) morphology was investigated. The contraction-relaxation rhythm of a strand segment was insignificant and irregular immediately after isolation from the mother plasmodium. It became regular half an hour later when local minute rhythms were synchronized spontaneously. If a strand kept under isotonic conditions was loaded with a heavier weight or a strand kept under isometric conditions was stretched a few times, the amplitude of each contraction wave was enhanced. After a strand had been thus conditioned, it was fixed at a selected phase of the contraction-relaxation cycle under both isotonic and isometric conditions. The state of MFs changed strikingly according to the phase of the contraction cycle. In the shortening phase of the strand under isotonic contractions, MFs with a diameter of 6--7 nm were arranged parallel to each other to form large compact bundles in which adjacent filaments were bridged with cross linkages. Among these MFs, thicker filaments were sporadically scattered. At about the phase of minimal strand length, most of the MFs became kinky and formed networks. In the elongating phase, new loose bundles of MFs developed from the network. These loose bundles became compact again when the strand reached its maximal elongation phase. In the isometric contraction, MFs in the increasing tension phase were nearly the same as those in the shortening phase in isotonic contraction. Around the maximal tension phase, dense areas of MFs appeared along the bundles in place of the network formed in the isotonic contraction phase. These areas were closely packed, with MFs arranged parallel to each other. In the decreasing and minimal tension phases in isometric contraction, MFs were arranged similarly to those in the elongating and maximally elongated phases, respectively, in isotonic contraction. Alternation between the straight bundle and fine network configuration of the MFs observed in isotonic contraction was inconspicuous in isometric contraction. This was probably due to spatial restriction of shortening under isometric contraction. The results are interpreted in terms of cyclic changes of the aggregation pattern of the MFs in the form of F-actin, as opposed to the possibility that the contraction-relaxation cycles depend on cyclic G-F transformation of actin.

Biomechanical Phenomena↗
PubMed1978

Studies on adrenocorticotropic hormone receptor using isolated rat adrenocortical cells.

To clarify the function of ACTH receptors, the actions of ACTH on cyclic AMP formation, Ca2+-influx across cell membrane, and corticoidogenesis were examined using dispersed adrenocortical cells prepared from the rat adrenal gland. 1) There are two types of ACTH receptors from Scatchard analysis of 125I-ACTH1-24 binding to the cell, the one receptor is of high affinity and low capacity (dissociation constant (Kd1) = 2.6 x 10(-19) M and 7,350 sites per cell), and the other one is of low affinity and high capacity (dissociation constant (Kd2) = 7.1 x 10(-9)M and 57,400 sites per cell). 2) Both apparent dissociation constants derived from the effects of ACTH on corticoidogenesis and Ca2+ influx well correspond with Kd1 of the high affinity receptor, 3) Apparent dissociation constant obtained from the effect of ACTH on cyclic AMP formation is in good agreement with Kd2 of the low affinity receptor. Thus it could be deduced from these data that the high affinity receptor is concerned with an increased Ca2+-influx to regulate corticoidogenesis at physiological levels of ACTH, whereas the low affinity receptor is coupled to adenylate cyclase at supraphysiological concentrations of ACTH.

Adrenal Cortex↗
PubMed1977

Pancreatolithiasis and pancreatic carcinoma. Evaluation of pancreatic excretion test with 5,5-dimethyl-2,4-oxazolidinedione.

The pancreatic excretion test with a weak acid of 5, 5-dimethyl-2,4-oxazolidinedione (DMO) was performed concomitantly with the pancreozymin-secretin test in 28 patients with pancreatolithiasis, 14 patients with pancreatic carcinoma, and 67 healthy subjects. The DMO concentration and total output of duodenal content after secretin stimulation, when corrected to the simultaneously determined plasma DMO concentration, were significantly reduced in the patients. While the pancreozymin-secretin test was abnormal in 96% of patients with pancreatolithiasis and in 86% of those with pancreatic carcinoma, the pancreatic DMO excretion test gave abnormal results in 100% of the patients. This suggests that the new test may well become effective in detecting early stages of pancreatic disease including carcinoma and chronic pancreatitis.

Calculi↗
PubMedDate not supplied

Experimental study on interactions between selenium and tin in mice.

The organ distributions of tin and selenium, and their excretion into urine and feces, were determined in mice. There were four groups; (A) control, (B) Sn (5 mumol/kg/d) ip injection, (C) Se (5 mumol/kg/d) sc injection, and (D) Sn plus Se (5 mumol/kg/d, each). Animals received injections once a day for 12 consecutive days. The results were the following (1) Simultaneous injection of Sn and Se enhanced accumulation of both elements in the body, i.e., in group B, 14.1% of the total injected amount of Sn was excreted into urine and feces; in group C, 46.2% of total injected Se was excreted into urine and feces; in group D, 10.9% of total Sn and 37.5% of total Se were found in excreta. (2) Large amounts of Sn were found in bone, liver, spleen, and kidney in group B. When Se was administered jointly with Sn, the concentrations of Sn in bone and liver were suppressed, whereas those in spleen and pancreas were increased. (3) The effects of Se-injections at this dose on concentrations of Se in organs were small. (4) In plasma, chemical reduction of selenite by stannous chloride was not observed.

Animals↗
PubMedDate not supplied

Catalytic and structural properties of surfactant-horseradish peroxidase complex in organic media.

A surfactant-horseradish peroxidase (HRP) complex that is catalytically active in organic media has been successfully prepared by a method utilizing water-in-oil (W/O) emulsions. To optimize conditions for preparation of the HRP complex, the effects of some key parameters in the aqueous phase of W/O emulsions were investigated. The surfactant-HRP complex prepared with a nonionic surfactant exhibited a high catalytic activity compared to those with a cationic or anionic surfactant in anhydrous benzene. At the preparation step, the pH of the aqueous solution had a prominent effect on the enzymatic activity of the HRP complex in organic media. Several kinds of salts present in the HRP complex could be employed to enhance the catalytic performance in organic media. However, anionic ions present in the preparation process appeared to lower the catalytic activity owing to the complexation with heme iron. UV-visible absorption spectra of the HRP complex in benzene, which were prepared from a KCN solution (pH 7.0) or an alkaline solution (pH 12), were comparable with those of native HRP in aqueous solution under the same conditions. Resonance Raman spectroscopic studies also revealed that no significant change in the coordination state of the heme iron occurred even after coating the enzyme with surfactant molecules, lyophilization, and solubilization in nonaqueous media.

Benzene↗
PubMedDate not supplied

Differential expression of dentin matrix protein 1, type I collagen and osteocalcin genes in rat developing mandibular bone.

The expression of dentin matrix protein 1 (Dmp1) mRNA has been compared with that of type I collagen and osteocalcin mRNAs during bone formation in the rat mandible, using in situ hybridization. At embryonic day 15 (E15), type I collagen and osteocalcin mRNAs were expressed by the majority of newly-differentiated osteoblasts attached to unmineralized bone matrices, whereas Dmp1 mRNA expression was confined to only a few osteoblasts. Expression of these genes increased as the number of osteoblasts increased in specimens from E16 to E18. At E20, expression of Dmp1, type I collagen and osteocalcin was also observed in osteocytes. Dmp1 expression continued in osteocytes as they matured up to the 90-day-old specimens, whereas type I collagen and osteocalcin expression in osteocytes almost disappeared at 30 days of postnatal life. In contrast, osteoblasts continued to express type I collagen and osteocalcin in 90-day-old rats, but transiently expressed Dmp1 mRNA, which was seen in the minority of osteoblasts at 14 days of postnatal life. These data show that the developmental expression patterns of Dmp1 in osteogenic differentiation differ from those of type I collagen and osteocalcin, and Dmp1 appears to be expressed by osteocytes throughout ossification in the skeleton. These observations indicate that Dmp1 may serve unique biological functions in osteocyte and bone metabolism.

Animals↗
PubMedDate not supplied

Differential regulation of stromelysin-1 (matrix metalloproteinase-3) and matrilysin (matrix metalloproteinase-7) in baboon endometrium.

OBJECTIVE: To investigate in vivo expression of matrix metalloproteinase enzymes (MMP), MMP-3 and MMP-7, by the baboon endometrium in relation to the process of tissue remodeling that accompanies menstruation in the primate. METHODS: Endometrial tissues and uterine fluids obtained from reproductively intact cycling baboons, cycling baboons treated with an anti-progestin, and ovariectomized steroid-treated baboons were evaluated for MMP mRNA expression and protein production by using multiple analytic techniques. RESULTS: The pattern of MMP protein production matched the pattern of MMP mRNA expression. In intact cycling baboons, MMP mRNA expression and protein production were specific to cell type and stage of the menstrual cycle. Endometrial stroma expressed minimal amounts of MMP-3 during the proliferative and secretory stages, whereas endometrial epithelia expressed MMP-7 during the proliferative stage. Expression of stromal MMP-3 and epithelial MMP-7 increased during early menses. Administration of anti-progestin beginning on the day of the LH surge increased MMP-7 but not MMP-3 expression at the mid secretory phase. Expression of MMP-3 and MMP-7 in the ovariectomized steroid-treated animals paralleled that of the intact cycling animals. CONCLUSIONS: These results highlight the similarity of human and baboon endometrial MMP-3 and MMP-7 production, providing further evidence for use of the baboon as a model for studying events associated with hormonally regulated changes during the menstrual cycle. These results also demonstrate that endometrial epithelial MMP-7 is suppressed by progesterone in the baboon endometrium, but endometrial stromal MMP-3 is regulated by a different mechanism.

Amino Acid Sequence↗