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Biomedical subjects

A Shibata

Publications and source records attributed to A Shibata.

At least 577 records · Page 32Linked to original sources
PubMed1984

[Met-enkephalin-like immunoreactivity-containing nerve elements in the canine pancreas--a histochemical study].

Met-enkephalin-like immunoreactivity-containing nerve elements in the canine pancreas was investigated by immunocytochemistry. Anti-Met-enkephalin (Met-Enk) serum used as the primary anti-serum was raised against synthetic Met-Enk conjugated with bovine serum albumin by a glutaraldehyde method. For light microscopic immunocytochemistry, Bouin-fixed and paraffin-embedded sections not exceeding 20 micrometers in thickness were stained by the PAP method. For electron microscopy, the fixative used was 4% paraformaldehyde plus 1% glutaraldehyde in a 0.067 M phosphate buffer. Ultra-thin sections of Araldite-embedded materials were stained by a protein A-colloidal gold method. The main localization of Met-Enk-like immunoreactivity-containing nerve fibers and ganglion cell somas was as follows: a) on the surface of ganglion cell somas, b) among nerve fiber bundles in the connective tissue septum, c) around blood vessels in the exocrine parenchyma, and d) in the islet of Langerhans. Electron microscopic immunocytochemistry showed that colloidal gold particles representing a Met-Enk-like substance were concentrated on secretory type granules of the ganglion cell somas and nerve terminals around the blood capillaries. Met-Enk-like immunoreactivity was eliminated by preincubation of the primary anti-serum with Met-Enk (nerve fibers: 0.1 X 2(-3) g/l, ganglion cells: 0.1 X 2(-2) g/l of the diluted antiserum, 1:2000) before application to tissue sections. The functional significance of Met-Enk-like immunoreactivity-containing nerve elements in both the endocrine and exocrine pancreas was discussed.

Animals↗
PubMed1984

Three-dimensional characteristics of the intramyocardial microvasculature of hypertrophied human hearts.

The three-dimensional architecture of the intramyocardial microvasculature was demonstrated in hypertrophied human hearts using Evan's method: scanning electron microscopic observation of the cardiac muscle chemically digested by hydrochloric acid and collagenase. Twenty autopsied hearts, which had already been fixed in 10% formalin, were investigated, including 17 hypertrophied hearts (mean cardiac weight, 587 g) and three control hearts (mean cardiac weight, 238 g). The luminal surfaces of the arterioles were characterized by the coiled arrangement of their smooth muscle cells. The structure of these vessels was not significantly different in hypertrophied and normal hearts. The capillaries showed great changes in the hypertrophied muscle: capillaries running on the body of the myofibres, in loop form on disorganized myofibres, and protruding into myofibres and/or probably penetrating through them. These features indicated an increase in the ratio of capillary/myofibre in hypertrophied human hearts. In hypertrophied hearts the venules had a more developed system than normal hearts, but without change in their basic architecture.

Adult↗
PubMed1984

Optimal pacemaker sensing with respect to amplitude and slew rate of intracardiac electrograms: theoretical analysis by computer simulation.

The optimal amplitude and slew rate of intracardiac electrograms for pacemaker sensing were examined on a theoretical basis by computer simulation. The simulation was based on the concept that it is the voltage at the position of the pacing electrode in an electrical field of a moving electrical dipole. By changing the distance between the electrode and the myocardium and the moving velocity of the electrical dipole, simulated ECGs with arbitrary amplitudes and slew rates were generated by the computer and fed to a bandpass filter. This filter was equivalent to those assembled in some models of permanent pacemakers and had a center pass-band frequency of 50 Hz and a Q of 1.0. The outputs of the filter were measured. The results showed that, for pacemakers sensing, simulated intracardiac electrograms with high amplitude should have high slew rates and those with low amplitudes should have low slew rates, although the absolute values depend on the characteristics of the bandpass filter and the sensing threshold of the pacemaker.

Computers↗
PubMed1984

A new pacemaker for monitoring asystole and prevention of Adams-Stokes syndrome and sudden cardiac death.

Patients with suspected Adams-Stokes syndrome are examined by Holter monitoring. During the monitoring, there is the danger of syncopes occurring and there are even reports of sudden cardiac death. We therefore developed a pacemaker for cardiac arrest monitoring and the prevention of Adams-Stokes syndrome and sudden cardiac death, which has the following functions: (1) the longest escape interval of the pacemaker not exceeding the value at which syncope is induced is determined by the decline of the mean heart rate including the asystole to a certain threshold rate; (2) once the pacemaker escapes from the interval it continues pacing for a while at a physiological rate to allow recover from ischemias in organs or tissues; and (3) to prevent overdrive suppression to the heart, the pacing rate gradually declines and stops pacing until the next asystole. This pacemaker is useful not only in the diagnosis of Adams-Stokes syndrome but also in pharmacological and pathophysiological studies and in determining when pacing should cease.

Adams-Stokes Syndrome↗
PubMed1984

Different response of left ventricular dimensions to nitroglycerin in patients with artificial pacemaker. A possible significance of reflex tachycardia for the reduction of LV cavity after nitroglycerin.

The effects of nitroglycerin (NTG) on cardiac function can be evaluated by echocardiography. In this paper, we discuss the effects of NTG on cardiac function in two groups of subjects, one with artificial pacemakers implanted with a fixed heart rate, and the other examined as the control group. Left ventricular dimension was obtained in the standard manner using the electronic sector scanning system of Toshiba SSH-11A. Left ventricular end-diastolic and end-systolic dimensions (Dd and Ds) were obtained in each case and the ejection fraction was calculated. After the sublingual administration of NTG (0.6 mg), the blood pressure decreased in both groups. The ventricular rate was fixed in the pacemaker group but increased significantly in the control group. Dd and Ds were found to decrease only in the control group. The ejection fraction showed an increase in the majority of the control group but remained unchanged in the pacemaker group. Heart rate change therefore may play a role in dimensional change and pumping function of heart after NTG.

Adolescent↗
PubMed1984

The causative mechanisms of mitral valve prolapse in progressive muscular dystrophy in reference to thorax and thoracic spine deformities and left ventricular dysfunction.

The causative mechanisms of mitral valve prolapse (MVP) were evaluated in 58 patients with progressive muscular dystrophy (PMD). Two possible causes, 1) left ventricular (LV) dysfunction and 2) thoracic spine and thorax deformities were assessed. Patients were classified into three groups by echocardiographic findings. Group 1: 31 patients without MVP, group 2: 11 patients with MVP confirmed only by M-mode echocardiogram, group 3: 16 patients with MVP confirmed by both two-dimensional and M-mode echocardiograms. LV functions evaluated by systolic time intervals and fractional shortening showed no significant differences among the three groups. Scoliosis of the thoracic spine was not related to the incidence of MVP. Lordotic or straight spines were found in 32.3%, 100%, 93.8% of cases in group 1, group 2 and group 3, respectively, and the incidences of MVP in cases with kyphosis, straight spine and lordosis were 4.8%, 66.7% and 77.8%, respectively. The shape of the thorax as evaluated by the ratio of anteroposterior internal diameter to transverse diameter was more flattened in groups 2 and 3 than in group 1. From these results, we concluded that LV dysfunction was not related to the incidence of MVP and that the lordotic or straight spine and the flattened thorax were supposed to be the major factors in the occurrence of MVP in PMD.

Adolescent↗
PubMed1984

Chronic intermittent atrial standstill with intraatrial block and split atrial potentials.

A 24-year-old male with chronic atrial standstill underwent an electrophysiologic study. No atrial activity was recorded from the right atrium which did not respond to stimulation with up to 10 volts. After the administration of atropine, non-localized split atrial potentials appeared, and intraatrial phase 4 block and atrial flutter with intraatrial 2:1 block were observed. The atrium then responded to electrical stimulation (less than 2 volts). Persistent sinus node activity with intraatrial block was found during post-pacing atrial pauses.

Action Potentials↗
PubMed1984

Further characterization of platelet-type von Willebrand's disease in Japan.

We studied four patients who showed aggregation of platelets in platelet-rich plasma at lower concentrations of ristocetin than those required for normal platelet-rich plasma and who demonstrated an increased capacity of the platelets to bind normal von Willebrand factor. The four patients were from two Japanese families. Platelets from one family aggregated spontaneously in vitro, and platelets from both families aggregated upon the addition of normal plasma and cryoprecipitate, in the absence of ristocetin or other agonists. Analysis of the multimeric composition of von Willebrand factor by sodium dodecyl sulfate-agarose gel electrophoresis revealed a decrease in large multimers or a decrease in both large and intermediate multimers in plasma, but normal multimers in platelets. 1-Deamino-[8-D-arginine]-vasopressin caused by an immediate appearance of larger multimers in plasma, followed by the rapid disappearance of these multimers from circulating plasma. Analysis of platelet membrane glycoproteins from the patients showed that there were two distinct bands in the glycoprotein I region; one migrated in a slower region and the other in a faster region than normal glycoprotein Ib. We suggest that the platelet receptor abnormality in these patients is related to this abnormality of glycoprotein Ib.

Deamino Arginine Vasopressin↗
PubMed1984

Hemorrhagic cystitis after conditioning for bone marrow transplantation and its prophylaxis.

The situation regarding hemorrhagic cystitis after conditioning for bone marrow transplantation (BMT) in Japan was surveyed and analyzed. Thirty-seven of 110 patients (33.6%) developed hemorrhagic cystitis after conditioning for BMT with cyclophosphamide (CY) and total body irradiation. In two of these 37 patients the cystitis was virus (adenovirus)-induced. In the others it was diagnosed as CY-induced. The severity and duration of CY-induced hemorrhagic cystitis were related to its onset. The delayed type of hemorrhagic cystitis induced by CY seemed to have a poor prognosis and often continued until the patient died. Therefore, late-onset hemorrhagic cystitis should be followed carefully and its prophylaxis may be important. 2-Mercaptoethane sulphonate (mesna) injections for prophylaxis of CY-induced hemorrhagic cystitis were found to be effective in reducing the incidence of the delayed type in 21 (53.8%) of 39 patients treated, but did not reduce the total incidence of CY-induced hemorrhagic cystitis.

Bone Marrow Transplantation↗