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Biomedical subjects

H Hosomi

Publications and source records attributed to H Hosomi.

At least 109 records · Page 6Linked to original sources
PubMed1984

Sensitivity of rapidly acting arterial pressure control system in conscious adult rabbits at different ages.

Changes in sensitivity of the rapidly acting arterial pressure control (AP) system with aging were investigated. Two catheters, one for pressure measurement and the other for inducing hemorrhage from the aorta, were chronically implanted in 25 rabbits from the same colony (aged 6 to 30 months). A few days after the operations, each animal was quickly bled (2 ml/kg body weight) while it was conscious. The hemorrhage experiment was repeated 16 times and the mean arterial pressure responses were sampled with an A/D-converter and stored in a digital computer, the 16 strings of data being pooled for each animal. The overall open-loop gain (G) of the AP-system was estimated from the individually pooled responses. In the present study, aging exerted no significant effect on the value of G (7.1) as evaluated by Kruskal-Wallis' non-parametric one criterion variance analysis (p greater than 0.05). The reflex sensitivity of the AP-system over the pressure ranges used in this experiment thus appears to be unaffected by aging over the range from 6 to 30 months.

Aging↗
PubMed1983

Overall open-loop gain of rapidly acting arterial pressure control system in rabbits.

We estimated the overall open-loop gain of the rapidly acting arterial pressure control system without surgically or pharmacologically opening the reflex loop in rabbits. Animals anesthetized by intravenous injection of Nembutal (27.5 mg X kg-1 body weight) and heparinized were bled by 2 ml X kg-1 body weight within 1-2 s through a catheter inserted into the aortic arch. Arterial pressure change after the quick mild hemorrhage was monitored via a catheter placed in the right subclavian artery for more than 2 min. The overall open-loop gain of the lumped arterial pressure control system determined from the mean arterial pressure response to the hemorrhage was 7.3. It was almost constant over the range between 12.9 and 22.2 kPa systemic pressure.

Animals↗
PubMed1982

Lack of time-dependent augmentation of carotid sinus baroreflex system after vagotomy.

The purpose of this experiment was to study whether the carotid sinus baroreflex system (CS system) increases its gain with time after vagotomy in compensation for the loss of the vagally mediated arterial pressure control system (V system). In 7 dogs anesthetized with pentobarbital sodium we determined the responsiveness of the V system by repeatedly measuring the overall open-loop gain (G) of the negative feedback control system. G was assessed as (delta API/delta APS) -- 1, where delta API and delta APS are, respectively, the immediate and steady-state falls in arterial pressure at the aortic arch following a stepwise reduction in blood volume. delta API, delta APS, and G in intact condition were -12.0 +/- 1.8 mmHg, -1.1 +/- 0.2 mmHg, and 10.1 +/- 0.7 (SD), respectively. delta API, delta APS, and G after vagotomy, i.e., G of the CS system (GCS), were -15.6 +/- 3.6 mmHg, -6.4 +/- 1.9 mmHg, and 1.6 +/- 0.4 GCS did not change with time over 4 h after vagotomy. We conclude that the CS system cannot augment its ability to restore arterial pressure in compensation for the lost function of the V system within 4 h after vagotomy in the anesthetized dog.

Animals↗
PubMed1981

Estimation of open-loop gain of canine arterial pressure control system by a new method.

We developed a method to estimate an overall open-loop gain of the arterial pressure control system without surgically opening the reflex loop. Dogs anesthetized by intravenous injection of Nembutal (35 mg/kg body wt) were bled by 2 ml/kg body wt within 2-3 s through a catheter inserted into the abdominal aorta. Arterial pressure change after the quick hemorrhage was monitored via a catheter placed in the aortic arch for more than 2 min. The overall open-loop gain of the lumped arterial pressure control system was assessed as (delta API/delta APs)-1, where delta API is the immediate fall and delta APs the steady-state fall in mean arterial pressure obtained by a filter with a 2-s time constant. The advantage of this method is that the overall open-loop gain can be estimated under the closed-loop condition in which the baroreceptor reflexes operate naturally around the existing range of systemic arterial pressure. This enables one to study time-varying characteristics of the reflex gain. The disadvantage is that the substantial constituents of the lumped reflex system remain to be confirmed.

Animals↗
PubMed1981

Time-dependent changes in open-loop gains of baroreflex systems after massive hemorrhage.

To quantify the effects of massive hemorrhage (5 ml/kg body weight) on the individual arterial baroreflex systems in the dog, changes in the open-loop gains of the intact arterial pressure control system (Gintact), the carotid sinus baroreflex system (GCS), and the vagally mediated and aortic arch baroreflex systems (GV) were measured repeatedly from the response to quick mild hemorrhage (2 ml/kg body weight) before and after massive hemorrhage. Fifteen mongrel adult dogs were divided into 3 groups. i.e., the control, vago-aortic nerve-severed, and carotid sinus-denervated groups. The dogs anesthetized with Nembutal (35 mg/kg body weight) were bled by 2 ml/kg body weight within 2 sec through a catheter inserted into the abdominal aorta. The arterial pressure change after mild hemorrhage was monitored via a catheter placed in the aortic arch. The open-loop gain of the baroreflex system was assessed as (delta API/delta APS--1), where delta API and delta APS are the immediate and steady-state falls in arterial pressure following mild hemorrhage. The mean values of Gintact, GCS, and GV before massive hemorrhage were 7.8, 2.0, and 1.8, respectively. Since Gintact is not a simple summation of GCS and GV, it is speculated that the carotid sinus baroreflex system interacts in a facilitatory way with the vagally mediated and aortic arch baroreflex systems. After massive hemorrhage, Gintact changed along a time course of parabolic form, whereas GCS did not change and GV decreased. These results suggest that the time-dependent change of Gintact after massive hemorrhage depends on the change in the open-loop gain of the baroreflex system making a facilitatory interaction.

Animals↗
PubMed1980

The blood supply of the facial nerve in the human temporal bone.

The gross blood supply and intrinsic vascular anatomy of the facial nerve in the temporal bone are described, and their significance is discussed. At the vertical part of the facial nerve, the stylomastoid artery lies on its anteromedial side as far as the upper third of the nerve. The artery then loops around the lateral or medial side of the nerve, and divides into several branches. At the convex aspect of the genu, these branches anastomose with one another to form an arterial network, passing to the horizontal part. The petrosal branch of the middle meningeal artery reaches the geniculate ganglion and forms a profuse, fine arterial network. The main arterial trunk extends toward the second bend in the nerve, but it never reaches the vertical part. Studies on the draining veins are also described. Duplication of blood vessels from different sources was seen at the horizontal part of the nerve. This would suggest a special vulnerability of this area to vascular injury, since in our topographical study of Bell's palsy within two weeks of its onset, 72 out of 117 cases (61.5%) were found to have suprastapedial lesions.

Cadaver↗
PubMed1979

Effect of pentobarbital anesthesia on hypotension after 10% hemorrhage in the dog.

The effect of pentobarbital anesthesia, 30 mg.kg body wt-1, on the rapidly acting arterial pressure control system was studied on splenectomized dogs chronically instrumented with catheters for pressure measurement and hemorrhage and with a flow probe for measurement of aortic flow. The dogs were subjected to 10% hemorrhage in 30 s under conscious and anesthetized states before and after denervation of the carotid sinus nerves (CS) and/or the vagi (V). In the intact nerve condition, arterial pressure fall (delta AP) at 1-2 min after hemorrhage was 8.0 +/- 1.3 (mean +/- SE) mmHg in conscious dogs and 9.4 +/- 2.0 mmHg in dogs under anesthesia. There was no significant difference between these delta APs or other pairs of delta APs in conscious and anesthetized states at any stage of denervation. As long as the CS reflex was intact, heart rate and total peripheral resistance increased in response to hemorrhage as in the intact condition. In conclusion, the pentobarbital anesthesia had little effect on the rapidly acting arterial pressure control system as far as its capacity to restore mean arterial pressure after the brief 10% hemorrhage is concerned.

Animals↗
PubMed1979

Sinovagal interaction in arterial pressure restoration after 10% hemorrhage.

The summation between the carotid sinus baroreceptor reflex system (CS system) and the vagally mediated reflex system (V system) was studied as they restore mean arterial pressure (MAP) after 10% quick hemorrhage in splenectomized conscious dogs chronically instrumented with catheters for pressure measurement and hemorrhage. The experiment was repeated under nerve-intact condition (intact), with cold block of the vagi ([V]), after carotid sinus denervation (CS), and CS plus [V] situations. MAP falls at 1.5 min after the hemorrhage were 7.2 in intact, 24.7 in [V], 36.0 in CS, and 67.6 in CS + [V] mmHg. When we calculated the open-loop gains of CS and V systems assuming a simply additive summation between them a self-contradiction occurred. To avoid this contradiction, it was necessary to assume that CS and V systems interact in a facilitatory manner. Mean open-loop gains calculated under this assumption were 1.64 for the CS system alone, 0.89 for the V system alone, and 6.59 for the interacting component between them. These intriguing results warrant further analysis of the summation between the two reflex systems.

Animals↗
PubMed1978

Overall characteristics of arterial pressure control system studied by mild hemorrhage.

The overall, static, open-loop gain of the negative-feedback arterial pressure control system was determined repeatedly in anesthetized cats under normal and hypovolumic states. The gain, H, was assessed as (deltaAPI/deltaAPS)-1, where deltaAPI is the immediate fall and deltaAPS the steady-state fall in arterial pressure following a stepwise reduction in blood volume. When the step size was increased from 1.25 to 25% of the total blood volume, H decreased from 30 to less than unity. Considering this amplitude dependence of H, a small amount (1.25%) of quick (in less than 0.3 s) hemorrhage was used to determine H throughout the rest of the experiments. Time-dependent variation of H was evident after a large amount (6.25%) of blood loss. During the initial 10 min, H increased to 126% of the control value, decreased to 43% over the subsequent 20--70 min, and showed a trend toward recovery. The small signal analysis permits a quantitative characterization of the time and input size dependent nature of the arterial pressure control system after various degrees of hemorrhage.

Animals↗
PubMed1978

Unstable state of the arterial pressure control system after a mild hemorrhage.

The stability of the arterial pressure control system after a mild hemorrhage (5 ml/kg body wt) was studied in 10 anesthetized cats by analyzing the responses of arterial pressure and of heart rate and the dead time (L) of heart rate response to a minute, rapid test hemorrhage (1 ml/kg body wt). The overall open-loop gain (H) of the arterial pressure control system was estimated from the ratio of arterial pressure fall immediately after the quick hemorrhage over the steady-state fall. Increases in H and L were correlated with the tendency of the arterial pressure control system to be unstable and oscillate. Oscillation in arterial pressure was always accompanied by a marked increase in heart rate (deltaHR), which represents an enhanced activity of the sympathetic nervous system and serves to restore arterial pressure toward the prehemorrhage level. The present study indicates that the magnitude of deltaHR also serves as a good predictor of arterial pressure oscillation.

Animals↗
PubMed1976

[Classification of oscillatory states of blood pressure after bleeding in cats (author's transl)].

Blood pressure and heart rate responses were recorded on bleeding of blood volume of 1 ml/kg body weight (test input) from the abdominal aorta of cat. Forward path gain, backward path gain and minification were determined from blood pressure responses to test input. Oscillations in blood pressure were elicited spontaneously or artificially after bleeding of blood volume of 5 ml/kg body weight (conditioning input). The oscillatory states are classified into latent state, underdamped oscillatory state and harmonic oscillatory state. Open loop gain decreased in the latent state but increased in the other states. Therefore, oscillation was hard to elicit in the latent state. Minification, however, enlarged in the latent state, making the system irritable to disturbances and reducing its control accuracy. In the latent state, an insensible disturbance increased backward path gain and open loop gain to induce the oscillations. There was an increase of heart rate at an elicitation of oscillation in any state and a decrease of heart rate made it damped. Therefore, the heart rate regulatory system plays a main role in the feedback path of the blood pressure regulatory system and an increase of heart rate by an insensible disturbance or test input increases backward path gain.

Animals↗
PubMed1976

Control of blood pressure oscillation elicited by bleeding.

1) A control objective regarding the blood pressure oscillation is to decrease the heart rate. 2) The transfusion of a small amount of blood at the bottom of a cycle in the oscillation is usually useful as a control plan for the blood pressure oscillation. 3) A partial occlusion of the abdominal aorta is effective in arresting the oscillation, but the oscillation starts again after releasing the abdominal aorta from the partial occlusion.

Animals↗