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Biomedical subjects

S Yamashiro

Publications and source records attributed to S Yamashiro.

At least 145 records · Page 8Linked to original sources
PubMed1986

Proliferation of myogenic cells in the diaphragm of the fetal rabbit.

Diaphragms obtained from 40 fetal rabbits at gestational ages of 20, 22, 25 and 30 days were examined by light and transmission electron microscopes. The percentage of myogenic cells undergoing mitosis was calculated by counting mitotic nuclei in 1 micron sections. At 20 and 22 days gestation, myogenic cells (myoblasts and satellite cells) were actively proliferating with 2.66 +/- 0.41% (n = 15) and 2.18 +/- 0.20% (n = 23), of the cells in division, respectively. The myogenic cells undergoing mitosis appeared to be of both myoblasts and satellite cells at these stages of the development. The myotubes on day 20 of gestation contained a large number of lipid droplets and an abundance of glycogen particles which were reduced by day 22 of gestation. The mitotic rate on day 25 of gestation was reduced to 1.16 +/- 0.11% (n = 28). The muscle fibers were well differentiated at this stage and the majority of the dividing cells were considered to be satellite cells. In diaphragms from the full term fetuses (day 30), the mitotic rate was reduced to 0.31 +/- 0.05% (n = 24). It was suggested that myoblasts of the fetal rabbit diaphragm proliferated for the myotube formation during the earliest stage of the development (day 20 of gestation) and then the number of satellite cells increased after day 22 of gestation. Growth of the organ after day 25 of gestation appeared to be mostly due primarily to the hypertrophy and differentiation of the muscle fibers rather than proliferation of myoblasts.

Animals↗
PubMed1985

Copper-induced myopathy in rabbits: ultrastructural observations.

Mature rabbits were injected intra-muscularly into the hamstring (HS) muscles with doses of 1.66 mg Cu/kg/day, as cupric acetate, in aqueous solution. Similar doses of Na acetate were injected into control rabbits. Skeletal (HS) and cardiac (MYO) muscles were examined by scanning electron microscopy, transmission electron microscopy and a microanalyzer and energy dispersive X-ray (MEDX). Na-injected rabbits showed slight myofibrillar lesions in HS after four injections, and mitochondrial inclusions in MYO were noted after two or seven injections. No Cu was found with MEDX. Cu-injected rabbits showed that the severity of lesions of myofibrillar degeneration and mitochondrial inclusions in HS increased with the number of injections and days the rabbits had been on experiment. After seven days on experiment signs of muscle regeneration were seen. Cu was found first to localize in the nucleus of HS after one day, thereafter it localized in the mitochondria after three and seven days. MYO lesions were found in the mitochondria after six or seven days after Cu-injection. With MEDX less Cu was found than had been found in HS. This Cu first localized in the nucleus of MYO after one day and then disappeared from the tissue altogether.

Animals↗
PubMed1984

Ultrastructural study of developing rabbit diaphragm.

Diaphragms obtained from forty rabbit fetuses during the last third of gestation and from five rabbits one week old were studied ultrastructurally. Four gestational ages were chosen for the investigation. The diaphragm at 20 days gestation revealed early myogenesis which was characterised by many myogenic cells in the process of mitosis and by fusion of myoblasts to form myotubes. A large number of lipid droplets and a moderate quantity of glycogen were observed in the myotubes. These myotubes contained a few myofibrils peripherally. At 22 days of gestation, the myotubes exhibited a relatively large number of myofibrils and large amounts of glycogen. They also showed sarcolemmal modifications which appeared to be developing motor end plates. Mitosis of the myogenic cells persisted even after fusion. At 25 days of gestation, connective tissue sheaths appeared around the muscle fibres as well as further differentiation of the muscle fibres. At 30 days of gestation, the muscle fibres exhibited nearly complete differentiation, with the formation of myotendinous junctions. At one week post partum, the diaphragm showed full development of its muscle fibres. These morphological observations suggest a very rapid functional differentiation of the rabbit diaphragm during the last third of gestation.

Animals↗
PubMed1983

Ultrastructural study of Ni3S2-induced tumors in rats.

An ultrastructural study was conducted on a total of 24 tumors selected from 70 tumors induced by intramuscular injection of Ni3S2 in Fischer and Hooded rats. Well differentiated rhabdomyosarcomas were predominantly composed of strap-like cells containing numerous myofilaments occasionally forming S-line-like structures, whereas poorly differentiated rhabdomyosarcomas were made up mainly of round or oval cells with abundant cytoplasm. Embryonal rhabdomyosarcomas contained cells resembling the mast cells in myxomatous areas as well as spindle-shaped myoblast-like cells. Mesenchymal tumors exhibited morphological characteristics of the lymphoid cells. The tumor cells from leiomyosarcoma-like tumors showed myoblast-like appearance. Tumors diagnosed as fibrosarcoma-like tumors at the light microscopic level demonstrated the ultrastructural characteristics of fibrosarcomas. The possibility of a multicentric origin of the tumor cells in Ni3S2-induced tumors has been discussed.

Animals↗
PubMed1983

Plasma and erythrocyte volumes of newborn rabbits delivered after 30 days of gestation.

The plasma and erythrocyte volumes of 18 rabbit fetuses delivered by caesarean section on day 30 of gestation were measured by a double labelling radioisotope technique after separation from the placenta. These late gestation fetuses were viable. A negative correlation was found between the bodyweight of the neonate and its blood volume expressed as a percentage of bodyweight. The equation of the linear regression line was Y = 92.3 - 3.9X. The haematocrit was 0.494 +/- 0.029 l/l.

Animals↗
PubMed1983

Effect of dietary supplementation with stearic acid on the severity of myocardial lesions.

Histological studies were conducted on ventricular myocardium obtained from male rats of the Sprague-Dawley strain after 16 weeks of feeding diets containing 20 per cent (w/w) soybean oil, low erucic acid rapeseed oil or high erucic acid rapeseed oil. Additional groups of rats were fed similar diets supplemented with up to 8 g/kg of tristearin. Increasing dietary intake of stearic acid normalised the plasma ratio of C16:0 to C18:0 for rapeseed oil treatments to ratios analogous to that observed for rats fed soybean oil. Tristearin supplementation did not have a significant effect on myocardial lesion incidence but decreased the severity of lesions observed for rapeseed oil treatments.

Animals↗
PubMed1983

The effects of cesarean section anesthesia on heat loss and heat production in the newborn rabbit.

The newborn of some smaller animals rely upon heat produced by nonshivering thermogenesis in the brown fat to prevent a fall in body temperature after birth. Because of their pharmacological properties, some drugs may affect nonshivering thermogenesis. Therefore, in this study, the ability of newborn rabbits delivered under Innovar-Vet, ketamine hydrochloride, methoxyflurane and epidural anesthesia to maintain the rectal, subcutaneous interscapular and lumbar temperature was investigated at an ambient temperature of 35 degrees C or 22 degrees C and the results compared with control newborns delivered without anesthesia. When the newborns were exposed to 35 degrees C, the anesthetics studied had no effect on the ability of the newborn to maintain the rectal temperature and the subcutaneous temperature over the interscapular fat pad was similar to the lumbar subcutaneous temperature thereby indicating that nonshivering thermogenesis was not activated. However, at an ambient temperature of 22 degrees C Innovar-Vet or methoxyflurane reduced the temperature difference between interscapular and lumbar temperatures to 1.6 degrees C compared to 2.5 degrees C in controls and the difference between core temperature and ambient temperature to 3.5 degrees C greater compared to 7.5 degrees C in controls. Ketamine hydrochloride or lidocaine hydrochloride plus meperidine has less effect because these compounds lack adrenergic blocking properties. These data suggest that newborns delivered under anesthetics or tranquillizers that have adrenergic blocking properties require a warm (35 degrees C) environment to prevent a fall in core temperature.

Anesthesia, Obstetrical↗
PubMed1983

Rapid method for the examination of platelet morphology.

A simple, rapid method is described for preparing platelets of domestic animals for light and electron microscopic examinations. The method involves the isolation of the platelet rich plasma (PRP) by centrifugation of the whole blood for five minutes followed by recentrifugation of PRP in a Wintrobe tube at 4500 rpm for 20 minutes to separate the blood components into four distinct layers composed exclusively of plasma, leucocytes, platelets and erythrocytes. A short fixation (20 minutes) by replacing the plasma layer with glutaraldehyde before breaking the bottom of the tube with a glass cutter allows the cellular contents to be gently pushed out of the tube in the form of a cylindrical semisolid pellet, with a wooden applicator stick. A further three hour fixation of the pellet in fresh glutaraldehyde before cutting out the middle layer for routine processing for light and electron microscopy provides pure preparation of platelets with a minimum of morphological distortion.

Animals↗
PubMed1982

Ultrastructural alterations of the liver of Pekin ducks fed methyl mercury-containing diets.

This report describes the ultrastructural alterations of the liver of 24 male and 24 female Pekin ducks fed 0.0, 0.5, 5.0, and 15.0 ppm of methyl mercury chloride (MeHgCl), mixed in a mash diet, for 12 wk. Birds were weighed weekly and observed for neurologic symptoms daily. Samples of blood, liver, kidney, skeletal muscle and brain were analyzed for Hg residue by atomic absorption spectrophotometry. Livers were fixed in situ by perfusion with glutaraldehyde fixative and processed for electron microscopy. The percent decreases in mean body weights between wk 0 and wk 7 were statistically not significant except for males fed 5.0 ppm MeHgCl. Leg paralysis and convulsions in males treated with 15.0 ppm began at wk 5 and in females at wk 8, but were more severe in the latter. The dose-residue response for the three dose levels in all five tissues was linear, with liver and kidney containing the highest and the brain the least amount of Hg. Hepatocytes in 0.5- and 5.0-ppm MeHgCl treatment groups showed little morphologic changes, while liver cells in the 15.0-ppm group had several ultrastructural alterations, including remarkable increase in peribiliary lysosomal bodies. The mitochondria of some hepatocytes exhibited lysis of both inner and outer membranes. Changes also occurred in endothelial and Kupffer cells. These results indicate that dosing Pekin ducks with 15.0 ppm causes ultrastructural alterations indicative of toxic injury to the liver.

Animals↗
PubMed1982

Dietary factors affecting the incidence of dietary fat-induced myocardial lesions.

Histological study of ventricular muscle was conducted on Sprague-Dawley male rats fed diets containing 20% (w/w) of either soybean oil, low erucic acid rapeseed oil or high erucic acid rapeseed oil. Purified diets providing two levels of intake for choline and inositol or magnesium were fed for 16 weeks to determine whether increased intake of these nutrients reduced myocardial lesion incidence. Diets containing high erucic acid rapeseed oil resulted in a high incidence of degenerative focal myocardial lesions, whereas low erucic acid rapeseed oil feeding resulted in less severe cardiopathological changes. Dietary supplementation providing 0.475% (w/w) choline and 0.635% (w/w) inositol reduced incidence of myocardial lesion for both rapeseed oil treatments indicating that lesion incidence may also be altered by the nutrient composition of the purified diet. Nutritional adaptation by increasing the animals dietary fat intake from 6% (w/w) to 20% (w/w) over an 8-week period had no effect on lesion incidence.

Animals↗
PubMed1980

Effects of methionine supplementation on the incidence of dietary fat induced myocardial lesions in the rat.

Purified diets were prepared to evaluate the effect of methionine supplementation on the incidence and severity of vegetable oil-induced myocardial lesions in the rat. The unsupplemented basal diet fed was similar in nutrient composition to typical semipurified diets currently utilized for cardiopathogenic evaluation of dietary rapeseed oils and contained 1.276 mg of S-amino acid per kilocalorie. The methionine-supplemented diet contained an additional 0.25% (w/w) L-methionine or a total of 1.815 mg of S-amino acid per kilocalorie. Feeding trials were conducted in which weanling rats were fed either a diet containing 20% (w/w) soybean oil (SBO), low erucic acid rapeseed oil (LER) or high urucic acid rapeseed oil (HER) for 16 or 28 weeks. Dietary supplementation with methionine was found to reduce the incidence of focal myocardial lesions in SBO-fed animals to zero. These results suggest that marginal deficiencies in methionine may interact with the frequency and severity of myocardial changes reported for Sprague-Dawley rats fed various dietary oils. The results indicate that levels of essential nutrients should be adjusted when the energy level of the diet is increased.

Amino Acids, Sulfur↗
PubMed1980

Nickel sulphide-induced rhabdomyosarcomata in rats.

Fifty-nine Fischer rat tumors and eleven Hooded rat tumors induced by intramuscular injection of Ni3S2 were examined and their histopathologic and cytologic characteristics studied. Nine out of eleven Hooded rat tumors metastasized whereas 15 out of 59 Fischer rat tumors metastasized within 30 days. Histopathological characterization of the Ni3S2-induced tumors was made according to their preponderant cellular constitution. They were grouped into six types: well-differentiated rhabdomyosarcomas, poorly-differentiated rhabdomyosarcomas, embryonal rhabdomyosarcomas, mesenchymal tumors, leiomyosarcoma-like tumors and fibrosarcoma-like tumors. Forty-seven of total of 70 were rhabdomyosarcomas. Tumors with shorter latent periods in Fischer rats and tumors with fleshy and soft texture demonstrated a higher incidence of metastases.

Animals↗