Biomedical subjects

T Nakahari

Publications and source records attributed to T Nakahari.

6 recordsLinked to original sources

PubMed1992

Osmotically inactive space during hyperosmotic stress in the perfused submandibular gland of the rat.

Cell volume changes were measured by an impedance method during hyperosmotic stress in the perfused rat submandibular gland. When the perfusate osmolarity was raised to 484 mosmol, the cell volume decreased and remained at a plateau level (79%). The decrease was smaller than expected from the extracellular fluid osmolarity change. Furthermore, the potassium content of the gland increased by 7% during the hyperosmotic stress. These results suggest that the cell volume changes observed during hyperosmotic stress are affected by the existence of an osmotically inactive space and by an increase in the intracellular solute content.

Animals↗

PubMed1992

Effect of alpha-tocopherol on oxidative hemolysis, as evaluated by impedance measurement.

Using a hypoxanthine-xanthine oxidase (HX-XOD) reaction system, the effect of vitamin E (VE) on oxidative membrane injury was studied by the impedance method. Both VE-sufficient and VE-deficient erythrocytes showed an elevation of low frequency permittivity in the early phase of reaction. In the later phase of reaction, VE-sufficient erythrocytes showed a sustained elevation in permittivity, while VE-deficient erythrocytes showed a decrease in permittivity with time. These changes consisted with the process of hemolysis in the HX-XOD system. The similarity of early phase change between VE-sufficient and VE-deficient erythrocytes indicates that the HX-XOD system exerted a similar effect on both erythrocytes in the early phase. The difference in changes of later phase between the two types of erythrocytes suggests that VE suppressed the reduction in permittivity. When the results were analyzed by the Pauly-Schwan's theory based on the assumption that erythrocytes are spherical, the product of VE-deficient or VE-sufficient erythrocyte size (R) and membrane capacity (Cm) showed a change similar to that in permittivity.

Algorithms↗

PubMed1991

Dose effects of acetylcholine on the cell volume of rat mandibular salivary acini.

The effects of acetylcholine (ACh) on the cell volume of the isolated rat mandibular acini were studied stereologically using video-enhanced contrast optical microscopy. The lengths of major and minor axes of the acini were measured in the successive video images, from which the relative volume change was estimated. ACh induced a rapid shrinkage of the acinar cell to reach minimum volume within 1 min. Simultaneously, the acinus and acinar clump shrunk in the same proportion as the acinar cell. The initial volume decrease induced by ACh was dose dependent: 0.92 at 10(-8) M, 0.91 at 10(-6) M, 0.77 at 10(-5) M, 0.78 at 10(-4) M, and 0.75 at 10(-3) M (the relative volume compared with the resting control). During sustained stimulation by ACh for 3 min, the volume of acinar cell remained at the plateau level at concentrations lower than 10(-5) M ACh, whereas the volume increased by 0.1-0.15 at concentrations higher than 10(-4) M ACh. The dose-dependent manner of the cell volume coincided with the fluid secretion measured in the isolated perfused gland. The findings on the dose effects of ACh are discussed in connection with the intercellular communication and the movement of electrolytes.

Acetylcholine↗

PubMed1990

Decrease in rat submandibular acinar cell volume during ACh stimulation.

Changes in acinar cell volume were measured in the perfused submandibular gland of the rat at 23 degrees C during salivary secretion induced by acetylcholine (ACh). Cellular volume was monitored by two methods: the impedance method and the morphometric method using video-enhanced contrast optical microscopy. Both measurements revealed a decrease in acinar cell volume in response to 1 microM ACh. Within the 1st min of stimulation, secretion increased to the initial maximum (initial secretion), and cell shrinkage occurred. During sustained stimulation, secretory rate and cell volume were maintained at the plateau level (steady secretion). The decrease in cell volume was 71.8 +/- 2.9% of resting volume (means +/- SE, n = 8) as measured by the impedance method and 76.1 +/- 2.0% (n = 20) as measured by the morphometric method. With the removal of ACh, cell volume increased to 111.6 +/- 2.7% (n = 8) of the prestimulation level as measured by the impedance method and 108.8 +/- 1.5% (n = 20) as measured by the morphometric method, and then recovered to the prestimulation level slowly. The weight of the gland decreased significantly during stimulation. These findings proved that volume decrease occurred during stimulation. The measurement of cell volume gave the net fluid flux of the acinar cell compartment. The net fluid flux and the rate of salivary secretion gave an estimation of the fluid influx across the basolateral membrane. These findings suggest that a transcellular route for fluid secretion exists in the salivary gland.

Acetylcholine↗

PubMed1989

Shrinkage of rat mandibular acinar cell with acetylcholine detected by video-enhanced contrast microscopy.

Changes in acinar cell volume during secretion were observed in the perfused rat mandibular gland by the video-enhanced contrast (VEC) microscopy. The acinar cell shrank (81.3 +/- 4.9% (mean +/- S.D., n = 5] during acetylcholine stimulation and swelled (107.4 +/- 2.3% (n = 5] after cessation of the stimulation. These evidences suggested that a large amount of fluid is transported via transcellular route in the salivary gland.

Acetylcholine↗

PubMed1988

Continuous measurements of tissue impedance during secretion in dog submandibular gland.

The electrical impedance of the dog submandibular gland, as an indicator of changes in extracellular fluid (ECF) volume, was measured at 5 kHz, 500 kHz, and 5 MHz at intervals of 10 s during secretory stimulation, because the conductivity calculated from impedance at low frequencies reflected the ECF volume. The decrease in conductivity occurred in the first minute of stimulation. Its decrease was more marked during stimulation after circulatory arrest. Salivary secretion under intact circulation consists of two phases: an initial secretion occurring in the first minute of stimulation with a high secretory rate and a steady secretion continuing during stimulation at a constant rate. A decrease in conductivity occurred in the initial secretion. Within a few minutes following the cessation of stimulation, the conductivity increased to a level higher than the resting one with an intact circulation, while the blood flow remained several times higher than in the resting state. The conductivity of the gland slowly recovered to the prestimulation level over a 30-min period. The histological examination revealed that the main compartment of the ECF change was the interlobular space. Impedance and histological studies showed that the ECF volume of salivary glands changes dynamically during secretion. On the other hand, the cellular volume also increased in the initial secretion of an isolated gland. Its increase suggested that the fluid was transported to the lumen via a cellular pathway as well as a paracellular pathway in the initial secretion.

Animals↗