Search PubMed⌕ Search

Biomedical subjects

K Tamiya

Publications and source records attributed to K Tamiya.

At least 37 records · Page 2Linked to original sources
PubMed1986

A new approach to defining regional work of the ventricle and evaluating regional cardiac function: mean wall stress-natural logarithm of reciprocal of wall thickness relationship.

A new method of defining regional mechanical work done by a unit volume of myocardium of the ventricular wall and evaluating regional cardiac function is proposed. This method uses the relationship between mean wall stress (sigma) and the natural logarithm of the reciprocal of wall thickness (ln(1/H)). 1/H at a point on the epicardial surface is proportional to the regional area (A) of the ventricular wall containing that point. The value for regional work obtained from the relationship between the sigma and ln A or sigma and ln(1/H) has a true dimension of work, i.e., [J/m3]. The sigma-ln(1/H) relationship was studied in ten anesthetized dogs. Wall thickness and internal diameter of the left ventricle were measured with ultrasonic dimension gauges. Regional work per unit volume of myocardium multiplied by the total myocardial volume of the left ventricle correlated well with the total mechanical work of the entire left ventricle calculated from the pressure-volume relationship during pressure loading, contractility change, and volume loading. During pressure loading, the end-systolic sigma-ln(1/H) relationship showed linearity. After bolus injection of isoproterenol the sigma-ln(1/H) loop shifted to the left. We concluded that the sigma-ln(1/H) relationship provides a method of characterizing regional function normalized to the unit volume of myocardium. In addition, our methods have a potential for echocardiographic application.

Animals↗
PubMed1986

Technique with lock-in amplifier for real-time measurement of tricuspid valve annulus area.

A new measuring system that permits real-time registration of the tricuspid valve annular area (TVA) using lock-in amplifier is devised and applied in open-chest anesthetized dogs. The tricuspid valve annulus was stitched with a fine, pliable, metal thread made of 10 30-micron urethane resin-coated copper wires during inflow occlusion. Both ends of the thread were guided out from the right atrium through a single pinhole in the right atrial wall. The signal intensity induced in the sense loop is linearly related to the area encircled by the thread, i.e., the area of the tricuspid annulus. During control state, TVA varied by an average of 24.5% (3.8-46.5%) of its maximum. Presystolic peak and valley of TVA due to atrial contraction and a decrease in TVA during ventricular ejection were generally observed. An increase in TVA during the initial portion of isovolumic contraction phase was prominent in dogs with filariasis, whereas in the other dogs it was not.

Acetylcholine↗
PubMed1985

Regional work of the ventricle: wall tension--area relation.

We clarified that the set of the isotropic component (T) of wall tension and the area (A) of a selected region of the left ventricular wall expresses the regional work with sufficient accuracy. The area surrounded by the locus of the T-A relation in the T-A plane is approximately equal to the real work done by that region. The behavior of the T-A loop was studied in nine anesthetized dogs under various conditions. The regional area and diameter of the left ventricle were measured with ultrasonic crystal pairs. The wall tension was calculated from measured left ventricular pressure and diameter by a generalized Laplace's equation for a thick-walled model. During volume loading, administration of methoxamine, and aortic constriction, the regional work per stroke increased with the increase in end-diastolic regional area, which is considered to be the regional Frank-Starling mechanism. With the development of ischemia, the T-A loop for the ischemic region shifted to the right and the work done by that region decreased. After a certain stage in the development of ischemia, the work done by the ischemic region became negative. When only one of the segmental lengths, rather than the area, is measured, difficulty arises in the physical interpretation of pressure-length or tension-length data in some cases. The T-A loop diagram resolves such difficulty by defining the regional work correctly. We conclude that the T-A loop diagram is a useful tool for analyzing the regional ventricular function.

Animals↗
PubMed1984

A mechanical model of mitral insufficiency using canine papillary muscle preparation.

A canine papillary muscle is loaded to mimic the load of the myocardium in the wall of the left ventricle with atrio-ventricular valvular insufficiency. This mechanical model which simulates the atrio-ventricular valvular regurgitation is based on two simple assumptions. The assumptions arranged for the papillary muscle experiment are as follows: 1) the force that the myocardium encounters during muscle shortening is proportional to the muscle shortening velocity due to regurgitation through a narrow regurgitant orifice; and 2) the myocardium exerts a constant force while the aortic valve is open. The muscle shortening except the isotonic phase is ascribed solely to regurgitation since the aortic valve is closed during these phases. In the combined antegrade/retrograde ejection phase, which is characterized by a constant muscle force, the shortening velocity due to regurgitation is constant because of the assumed functional relation between the muscle force and shortening velocity. The amount of shortening assigned to regurgitation in this phase is given by the product of the velocity at the beginning point of the isotonic phase and the duration of this phase. The present in-vitro studies offer an alternative explanation for decrease in the regurgitant fraction as total load was reduced at a constant preload. The regurgitant fraction decreased as preload was increased at a constant total load in the present study. The regurgitant fraction also decreased by either isoproterenol or CaCl2 administration via the coronary artery.

Animals↗
PubMed1984

[Contractility].

Explore the source record for details and available documents.

Animals↗
PubMed1984

[Progress and problems in pediatric surgery--the Association of Pediatric Anesthesiologists].

From the first meeting of the Japanese Society of Pediatric Surgeons in 1964 a small group discussion on anesthetic problems and patient care was held by some anesthesiologists at night. The Association of Pediatric Anesthesiologists (started in 1971) has undertaken the night meeting ever since the twelfth Annual Meeting of the Society of Pediatric Surgeons in 1975. The problems about pediatric respiratory management, neonatal emergency surgery and pediatric anesthesia were discussed frequently by doctors in different specialties. The recent decrease of mortality in neonatal surgery is thought to have come from the improvement of pediatric respiratory management. This night meeting of anesthesiologists has had a major role in the resolution of problems in pediatric respiratory impairment. The problems to be resolved in an emergency--persistent fetal circulation, barotrauma, nutritional problems in long term ventilatory support and so on--, will be discussed in the future. The purpose of this association is to elevate the quality of pediatric anesthesiologists by discussion with the other specialists of medicine and to make clear their responsibility in Children's Hospitals or Centers.

Anesthesiology↗
PubMed1983

[Caerulein-induced contraction of the ileal longitudinal smooth muscle isolated from various animal species].

An effect of caerulein was studied on a contractile response of the ileal longitudinal smooth muscle isolated from seven animal species, monkey, dog, rabbit, guinea-pig, rat, vole and mouse. In isotonic recording, caerulein induced a contraction in the muscle isolated from all animal species. Sensitivities of ileal strips to caerulein in the contractile response was divided into three groups. That is, a high sensitive group; dog and guinea-pig, a middle sensitive group; rabbit and vole, a low sensitive group; monkey, rat and mouse. In another series of experiment, effect of several antagonists was examined on the caerulein-induced contraction in ileal muscle of dog, rabbit or guinea-pig. TTX inhibited the contractions in all the ilea. As the contraction was inhibited by atropine and scopolamine in dog ileum but not in rabbit one, the contraction may be due to an excitation of the cholinergic neuron or an excitation of non-cholinergic excitatory neuron, respectively. On the other hand, it is supposed that the contraction in guinea-pig ileum is involved to both the neurons because the contraction was inhibited partially by scopolamine and not by atropine. In conclusion, the ilea isolated from seven animal species showed species differences in sensitivity to caerulein in contractile response, and caerulein seems induces the contractions involving to different nervous systems in dog, rabbit or guinea-pig ileum, respectively.

Animals↗
PubMed1977

Maximum rate of tension fall during isometric relaxation at end-systolic fiber length in canine papillary muscle.

We measured the characteristics of the decline in tension during isometric relaxation of canine papillary muscle. In the intact heart, relaxation begins with the isovolumic phase, but in experiments on papillary muscle previously reported the isotonic phase preceded the isometric phase during the course of relaxation. In our experiments, however, the isotonic bar was locked at the instant the muscle reached the end-systolic fiber length in order to hold the fiber at the length during the succeeding relaxation process. Therefore, we obtained a relaxation process similar to that occurring in the intact heart. The major results of these experiments are: (1) Maximum rate of the decline in tension (-dT/dtmax) is linearly related to the magnitude of total load. (2) -dT/dtmax is augmented by positive inotropic interventions and diminished by negative inotropic interventions. (3) An increase in preload results in only a slight increase in -dT/dtmax. (4) End-systolic fiber length itself is not a principal determinant of -dT/dtmax. (5) -dT/dtmax divided by total load is independent of the amount of muscle shortening. We, therefore, suggest that -dT/dtmax divided by total load cand be a useful index of the relaxation characteristics of cardiac muscle.

Animals↗