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Biomedical subjects

S Kakuta

Publications and source records attributed to S Kakuta.

52 records · Page 3Linked to original sources
PubMed1988

[Study of species differences on chemical sympathectomy: rats and guinea pigs].

Chemical sympathectomy induced by guanethidine or 6-hydroxydopamine (6-OHDA) and reserpinization were investigated by their influences on the cardiovascular system in urethane-anesthetized rats and guinea pigs and on nerve endings in the atrium or aorta and adrenaline-containing granules in the adrenal medulla. In rats, guanethidine and 6-OHDA significantly lowered the basal blood pressure, but reserpine did not. In guinea pigs, none of them affected the basal blood pressure, and with the exception of the potentiation of adrenaline-induced pressor responses, the influences of all 3 drugs on adrenaline- and tyramine-induced responses in blood pressure and heart rate were weaker than those in rats, but influences of treatments with guanethidine for 1 week were more striking than those for 5 weeks. There were significant differences between rats and guinea pigs in classified forms of nerve endings in the right atrium and of adrenaline-containing granules in the adrenal medulla or differences in the influences on the adrenal medulla by all 3 drugs. Only 6-OHDA induced injury in rat atrium. The above results suggest that there are species differences between rats and guinea pigs, not only in the chemical sympathectomized animals but also in the normal condition and that the pharmacodynamic effect of chemical sympathectomy is more prominent in rats than in guinea pigs.

Adrenal Medulla↗
PubMed1986

Redox studies of the epiphyseal growth cartilage: pyridine nucleotide metabolism and the development of mineralization.

The objective of this investigation was to examine the redox status of chondrocytes in normal and rachitic growth cartilages and to relate energy metabolism to cell maturation and the initiation of mineralization. The redox status was evaluated by chemical analysis and by microfluorimetric scanning of rapidly frozen, freeze-fractured tibial growth cartilages. In the normal epiphysis, the redox pattern of both avian and lagomorph cartilages were very similar. Thus, in the proliferative tissue zone the NAD/NADH ratio was high; in the hypertrophic zone, the cells appeared to be reduced. The sharp border between the two zones suggested that the redox shift may be associated with development of hypoxia. Induction of rickets resulted in a fivefold decrease in the total concentration of pyridine nucleotides in the proliferating and hypertrophic zones. Furthermore, the NAD/NADH ratio was profoundly disturbed. In the mineralizing zone, there was an accumulation of reduced pyridine nucleotide. Healing, initiated by administration of vitamin D to the rachitic birds, caused a rapid increase in NAD and NADH in all zones of the growth cartilage. It was concluded that vitamin D deficiency leads to changes in the energy metabolism of growth cartilage and that these changes were related to the defective mineralization of the rachitic tissue.

Animals↗
PubMed1986

Morphological studies on the forming processes and patterns of the platelet demarcation membrane system in the megakaryocytic series of embryonic rat livers.

Using injections of horseradish peroxidase (HRP) and the osmium-tannic acid method, megakaryocytic cells in the livers of rat embryos at 12-16 days of gestation were examined for the purpose of classification of the stages of formation of the platelet demarcation membrane. Megakaryoblasts were classified into the following three types according to the formation patterns of the demarcation membrane. The P-type megakaryoblasts showed plate-like membrane invaginations in large localized areas at early stages. The invaginating membrane developed toward the periphery of the nucleus. The L-type megakaryoblasts showed localized labyrinthine membrane invaginations but no definite direction in its development. The T-type megakaryoblasts had tubular invaginations at multiple sites on the plasma membrane. The P- and L-type cells were observed at 12 and 13 days of gestation. The T-type cells were found after the 14th day. In all the types of megakaryoblasts the membrane invagination occurred in the areas making contact with hepatocytes. It was agreed that the cells of the megakaryocytic series in which the demarcation membrane developed contrary to the basic pattern were ordinary promegakaryocytes. The megakaryocytes forming networks of the demarcation membrane dividing into platelet areas were small in cell size. Examination of the patterns of formation of the demarcation membrane proved useful for classifying the megakaryocytic series at each stage of maturation.

Animals↗
PubMed1985

Morphochemical analysis of phosphorus pools in calcifying cartilage.

The objective of this investigation was to measure phosphorus (P) levels in the epiphyseal growth cartilage and to relate pool sizes to chondrocyte maturation and tissue mineralization. To carry out these studies, we utilized a morphochemical technique that permitted measurements of insoluble mineral phosphate, soluble inorganic phosphate (Pi), low and high molecular weight phosphorylated macromolecules and lipid P in freeze-trapped histological sections. Analysis of the sections revealed that very low levels of P are present in pre-mineralized cartilage; at the mineralization front, a large increase in Pi is correlated with mineral formation. Moreover, with calcification of the cartilage, a decrease in the concentration of low molecular weight compounds was observed. It is suggested that these latter components may provide the initial source of Pi for the development of mineral. The results of the study support the view that metabolic regulation of P pool size may be a rate-limiting factor in the mineralization of cartilage.

Animals↗
PubMed1985

Isolation of matrix vesicles by isoelectric focusing in Pevikon-Sephadex.

We have investigated the use of an isoelectric focusing (IEF) technique for isolating and characterizing matrix vesicles. Focusing was performed on crude preparations of matrix vesicles isolated from collagenase digests of chick epiphyseal cartilage and purified by discontinuous sucrose gradient centrifugation. Crude and partially purified vesicle preparations were subjected to flat bed IEF in a slurry of Pevikon-Sephadex. Partially purified matrix vesicles focused as a narrow band (pI congruent to to 6.5). Alkaline phosphatase, solubilized from matrix vesicles, focused with a pl of 4.0-4.5. The IEF profile of matrix vesicles also differed from that of chondrocyte membranes. Thus, the membrane pls were congruent to to 5.4 and 6.6-7.8, respectively. The latter peak probably corresponded to the pl of the matrix vesicle preparation. This observation lends support to the view that vesicles originate from distinct regions of the chondrocyte membrane.

Alkaline Phosphatase↗
PubMed1982

Initiation of endochondral calcification is related to changes in the redox state of hypertrophic chondrocytes.

The level of pyridine nucleotides (NADH and NAD+) in the mineralizing growth plate of the chick was ascertained by high-resolution scanning microfluorimetry and biochemical analysis. Scanning electron microscopy and light microscopy were used to relate the concentrations of NADH and NAD+ to stages of chondrocyte maturation. A dramatic increase was found in the relative concentration of reduced pyridine nucleotides in the hypertrophic zone. On either side of this zone, in proliferating and calcifying cartilage, there was a decrease in NADH fluorescence, and the NADH/NAD+ ratio was depressed. The finding that NADH accumulated in the tissue zone associated with the earliest deposition of bone mineral supports the hypothesis that a change in the redox state initiates tissue mineralization.

Animals↗
PubMed1975

Effects of parathyroid hormone on the accumulation of cyclic AMP in bone of vitamin D-deficient rats.

The mechanism of skeletal refractoriness to parathyroid hormone (PTH) in vitamine D-deficient animals was studied in terms of the adenylate cyclase-cyclic AMP system in rat calvaria. In vitamin D-deficient, thyroparathyroidectomized rats, plasma calcium concentration was not elevated by iv administration of PTH, while responsiveness to the hormone was recovered within 24 h after a single dose (2.5 mug) of vitamin D3. In spite of the remarkable dependency of PTH on vitamin D for mobilization of calcium from bone, PTH stimulated adenylate cyclase activity in particulate bone cell fractions in vitro. PTH also enhanced the levels of cyclic AMP in the skeletal tissues of vitamin D-deficient rats in vivo and in vitro to an extent similar to those found in rats given 2.5 mug of D3. Administration of theophylline or dibutyryl cyclic AMP to the vitamin D-deficient rats did not cause any significant hypercalcemic effects, while these drugs enhanced plasma calcium concentration significantly in the rats given vitamin D3. These data strongly indicate that the cause of the skeletal refractoriness to PTH in vitamin D-deficient animals is not a defective activation of adenylate cyclase, but must be related to a later step or steps in the biochemical events leading to bone cell activation.

Adenylyl Cyclases↗