PubMed Health⌕ Search

Biomedical subjects

O Noi

Publications and source records attributed to O Noi.

6 recordsLinked to original sources
PubMed1999

Comparison between the intravenous and esophageal-gastric administration of glycerol in changing cochlear blood flow and serum osmolarity in the guinea pig.

The effects of glycerol on cochlear blood flow and serum osmotic pressure were studied in healthy guinea pigs. Laser Doppler flowmetry of cochlear blood flow after the esophageal-gastric administration of 50% glycerol demonstrated a greater increase in blood flow for a longer time than with the intravenous infusion of 50% glycerol. The intravenous infusion of glycerol did increase systemic blood pressure, which changed partially in parallel with the change in cochlear blood flow. The change in systemic blood pressure after esophageal-gastric administration was slight. In another experiment designed to observe the changes in serum osmotic pressure after glycerol administration, the esophageal-gastric route also caused a greater and longer increase in serum osmolarity than intravenous infusion. The increase in cochlear blood flow after glycerol administration was thought to be due to an increase in the osmotic gradient between the blood in the cochlear vessels and the interstitial fluid, or to the high osmolarity of the blood itself. The possible mechanisms underlying local blood flow increase caused by high serum osmolarity are discussed. Systemic blood pressure increase induced by glycerol could be an influential factor for the cochlear blood flow increase during intravenous infusion.

Animals↗
PubMed1998

Comparative effects of glycerol and Urografin on cochlear blood flow and serum osmolarity.

Glycerol, an osmotic diuretic, has been used for the diagnosis and treatment of endolymphatic hydrops. Hearing improvements in hydropic ears are attributed to its dehydrating effect. In addition to this effect, glycerol also increases cochlear blood flow. Urografin, another hyperosmotic agent used for vasography, is similarly known to increase local blood flow. The present study compared these two hyperosmotic agents, glycerol and Urografin, in their effects on cochlear blood flow and serum osmolarity. Laser Doppler flowmetry on the lateral wall of the cochlea revealed that the increase in cochlear blood flow with a 30-min infusion (0.025 ml/min) of 76% Urografin continued for a longer time than with a 30-min infusion (0.025 ml/min) of 50% (v/v) glycerol. The significant increases appeared at 20 and 30 min after the infusion with the former; 10, 20, 30, 40, 50 and 60 min after the infusion with the latter. Intravenous infusion of these agents also caused elevation in serum osmolarity. This elevation was appreciably greater with Urografin infusion (maximal increase: about 30 mOsm on average) than with glycerol infusion (maximal increase: about 6 mOsm on average), and the former elevation appeared to be longer lasting than the latter. These differences were ascribed to differences between glycerol and Urografin with respect to the creation of an osmotic gradient across the capillary walls of cochlear blood vessels. Since glycerol penetrates the interstitial space and moves into inner ear fluids, the gradient may decline faster. It would be assumed that a higher concentration of the hyperosmotic agent in the capillary blood causes more vasodilatation and lowering of blood viscosity. Alternatively, direct action of these agents on the vascular wall may affect some biological processes, leading to vasodilatation in different degrees and durations with different agents. Hearing improvement with glycerol administration in hydropic ears was also discussed from the perspective of cochlear blood flow.

Animals↗
PubMed1991

Relationship between cochlear blood flow and perilymphatic oxygen tension.

To clarify the characteristics of the blood circulation in the cochlea, we correlated cochlear blood flow and perilymphatic oxygen tension at various blood pressures. Cochlear blood flow was measured in guinea pigs by laser Doppler flowmetry, and perilymphatic oxygen tension by polarography. Blood pressure changes were induced by angiotensin II injection, trimetaphan camsylate injection and blood withdrawal. Cochlear blood flow generally paralleled systemic blood pressure, indicating a close correlation. In contrast, perilymphatic oxygen tension was slower to increase and decrease. However, when systemic blood pressure was lowered more gradually, perilymphatic oxygen tension did not show the same lag. These findings indicate that perilymphatic oxygen tension parallels systemic blood pressure when changes induced are slower and in a physiological range.

Angiotensin II↗
PubMed1991

Feasibility of pulse oxymetry to measure arterial O2 saturation in studies on cochlear blood circulation.

To understand the characteristics of oxygen transport to the inner ear, the relationship between arterial O2 saturation and cochlear microcirculation was investigated under different respiratory condition in guinea pigs. To monitor arterial O2 saturation a pulse oxymeter instead of an arterial blood gas analyzer was used. When the arterial O2 saturation was measured in the foot pad by a pulse oxymeter under different respiratory conditions, the data showed a close correlation with the results of blood gas analysis. For the measurement of cochlear microcirculation, a pulse oxymeter was found to be a feasible respiratory monitor for animal experiments. With this apparatus our study demonstrated a slower reaction in the decrease of perilymphatic oxygen tension than of cochlear blood flow during stepwise induction of hypoventilation monitored by a pulse oxymeter. Under certain conditions of hyperventilation in which arterial O2 saturation and perilymphatic oxygen tension increased gradually, cochlear blood flow was found to decrease. This decrease of cochlear blood flow could be attributed to chemical controls which are regulated, as in the cerebral blood circulation, by the content of CO2 and H+ in the vascular bed in the cochlea.

Animals↗
PubMed1988

Effects of prostaglandins on perilymphatic oxygenation. Enhancement of cochlear autoregulation by prostacyclin.

Effects of prostaglandin E1, prostacyclin, a prostacyclin analogue (OP-2507), and an inhibitor of thromboxane A2 synthetase (OKY-046) on the perilymphatic oxygen tension were measured in the feline tympanic perilymph under various respiratory conditions and blood pressure ranges. Factors influencing the capacity of the autoregulative properties of the inner ear vessels to accommodate changes in systemic blood pressure were also examined. Intravenous administration of prostacyclin, OP-2507, and OKY-046 prevented a decrease in perilymphatic oxygen tension when the systemic blood pressure decreased. Even a negative correlation of the differential coefficients between the perilymphatic oxygen tension and the systemic blood pressure was noticed during the administration of prostacyclin. Thus, prostacyclin enhanced the autoregulative property of the inner ear vessels. Furthermore, correlation studies between perilymphatic oxygen tension and cochlear blood flow demonstrated a partial dissociation, indicating the presence of autoregulation in the mean systemic blood pressure range under 80 mmHg.

Alprostadil↗