Biomedical subjects
Publications and source records attributed to A Ohtsuka.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
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Scanning electron microscopy of vascular casts showed that in the mouse, rat, and guinea pig, the pancreatic endocrine islets were frequently interlobular in position and emitted insulo-venous efferent vessels directly draining into veins. In these animals, the intralobular islets, located within the exocrine lobules, issued insulo-acinar portal vessels continuous with the lobular capillaries in addition to the insulo-venous efferent vessels. In humans, monkeys, cows, pigs, dogs, cats, and rabbits, essentially all islets in the pancreas were intralobular in location and emitted the insulo-acinar portal vessels only. In man and animals examined, especially in the murine species, many lobules lacked an islet, therefore the insular control over the exocrine pancreas seemed to be effected in more or less restricted areas of lobules.
Scanning electron microscopy of vascular casts prepared by arterial injections of intentionally reduced amounts of resin showed that in the rat pancreas, the casting medium fills blood capillaries in the endocrine islets more promptly than those in the exocrine lobules and secretory ducts. Furthermore, the exocrine lobules containing endocrine islets allowed a more rapid resin flow through the insulo-acinar portal route than those lobules lacking an islet. The capillaries of secretory ducts were the last portions to be filled with resin. Since the resin used in this study was as viscous as blood and injected under a physiological pressure, the microcirculatory patterns demonstrated by the present method reflect the physiological flow pattern of blood in the pancreas.
Testicular and plasma testosterone levels were found to be decreased markedly in streptozotocin diabetic rats compared with those of controls. Treatment with 6 units NPH insulin daily for one week almost normalized plasma testosterone levels parallel to the increase in body and liver weights in diabetic rats, while testosterone levels in testicles were not significantly changed. Plasma prolactin and LH levels were unchanged among control, diabetic and diabetic insulin-treated rats. Thus, testosterone reduction in the testis might play a role in diabetic impotence.
We measured the characteristic curve, modulation transfer function (MTF), and the Wiener spectrum of a commercially available computed radiographic (CR) system with photostimulable phosphor plate (imaging plate, IP). The characteristic curve (system response) obtained by an inverse-square x-ray sensitometry showed a wide dynamic range (order of 10(3) in maximum). The slit technique was employed to determine the MTF's, such as IP MTF, presampling MTF including the unsharpness of the detector (IP) and the blurring effect of the sampling aperture, and laser-printer MTF. It was found that the MTF of the standard type of IP was comparable to that of medium-speed screen/film systems. The noticeable degradation of resolution in our CR system, however, occurred at the stage of image data sampling: the presampling MTF was inferior to the IP MTF due to the effect of the scattering and resultant spreading of the incidence laser beam and the emitted luminescence. The noise was characterized by means of digital Wiener spectrum using uniformly exposed noise data. Exposure ranges could be separated into different sections depending upon the noise sources, such as quantum mottle at low exposure and system structure noise at high exposure.
We studied the responses of cultured endothelial cells to mechanical shearing force directly applied to those cells in vitro to determine changes in the concentration of intracellular calcium ion (Ca++), one of the factors that transfers information within the cell. Cultured bovine fetal aortic endothelial cells containing the Ca++ fluorescence indicator, Fura-2, were rubbed with a latex balloon in a specially designed system, and changes in the fluorescence of Fura-2 caused by this shear stimulation were determined by photometric fluorescence microscopy. Immediately after shear stimulation, the concentration of Ca++ in the cells was increased and reached a peak (511 +/- 165 nM, n = 12) within 15 seconds after stimulation. After the peak, the concentration was gradually restored to the resting level (55 +/- 17 nM, n = 12). The magnitude of the Ca++ response was dependent on the intensity of the shear force applied. Analysis of fluorescence images of Fura-2 revealed that the cells showed this Ca++ reaction without being injured or desquamated, although there were slight differences in the degree and duration of reaction among cells. This reaction appeared even when the cells were placed in the air with no contact with the fluid. This result suggests that neither the fluid flow associated with the balloon movement nor chemical substances in the fluid are involved in the reaction, but that pure physical force alone is responsible for the Ca++ reaction. Further, it suggests that endothelial cells have the ability to perceive such physical stimulation as shear force and to transfer this information to the interior of the cell via changes in the intracellular Ca++ concentration.