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Biomedical subjects

A Sakai

Publications and source records attributed to A Sakai.

At least 415 records · Page 23Linked to original sources
PubMed1982

A study on the localization of the sternocleidomastoid and trapezius motoneurons in the rat by means of the HRP method.

The sternocleidomastoid and trapezius muscles of the rat, which are innervated by the spinal accessory nerve (SAN) and cervical spinal nerve (CSN), consist of five smaller muscles: the sternomastoid, cleidomastoid, clavotrapezius, acromiotrapezius, and spinotrapezius. In this study, the location of cell somata of the motoneurons supplying each of these smaller muscles and the peripheral course of their axons have been studied by means of the horseradish peroxidase retrograde axonal transport technique (the HRP method) in combination with cutting of the SAN. The sternocleidomastoid and trapezius motoneurons formed three cell columns, column-M, -L, and -5, in the ipsilateral ventral horn of the cervical spinal cord. Column-M and -L extend longitudinally in the medial nucleus of C1 and C2 and in the ventrolateral nucleus from the middle of C2 to the middle of C6, respectively. These columns consist of the motoneurons whose axons pass through the SAN and they merge in the caudal C2 to constitute the spinal accessory nucleus. Column-5, which consists of the motoneurons passing through the CSN, extends longitudinally from C3 to C5 close to column-L in the ventrolateral nucleus. Motoneurons supplying the sternomastoid, cleidomastoid, clavotrapezius, acromiotrapezius, and spinotrapezius muscles showed a rostrocaudal somatotopic distribution in the spinal accessory nucleus and in column-5 in this order, though the sternomastoid motoneurons were not found in column-5.

Animals↗
PubMed1982

DNA polymerases of Tetrahymena pyriformis. I. Characterization of two N-ethylmaleimide-sensitive DNA polymerases from exponentially growing cells.

Two DNA polymerase activities, polymerases A and B, were separated from the Triton-treated cell homogenate of exponentially growing Tetrahymena pyriformis by phosphocellulose column chromatography. Their properties were as follows. Polymerase A: The molecular weight was about 140,000, the sedimentation value was about 6.2S, the optimum Mg2+ concentration was 15 mM, the optimum K+ (or Na+) concentration was 20 mM, and the optimum pH was 7.4. The enzyme activity was inhibited by cytosine-beta-D-arabinofuranoside-5'-triphosphate (araCTP) or aphidicolin, but not by 2'-3'-dideoxythymidine-5'-triphosphate (ddTTP). Polymerase B: The molecular weight was about 70,000, the sedimentation value was 4.3S, the optimum Mg2+ concentration was 15 mM, the optimum K+ (or Na+) concentration was 150 mM, and the optimum pH was 8.4. The enzyme activity was inhibited by ddTTP, but not by araCTP or aphidicolin. Polymerases A and B were both found to be N-ethylmaleimide-sensitive. These results indicate that at least two N-ethylmaleimide-sensitive DNA polymerases, A and B, are present in exponentially growing Tetrahymena cells. Polymerase A bears many similarities to DNA polymerase alpha of higher eukaryotes and polymerase B also bears similarities to DNA polymerase beta except as regards N-ethylmaleimide sensitivity. Based on the properties of polymerases A and B, the relation of Tetrahymena DNA polymerases reported by several investigators is discussed.

Animals↗
PubMed1982

Tetrahymena alpha-type DNA polymerase A: purification and subunit analysis.

DNA polymerase A (an alpha-type polymerase) from the ciliate, Tetrahymena pyriformis, has been purified 260,000-fold (40,000 units/mg protein). The polymerase A did not show any heterogeneity in terms of size and charge during purification. Enzymatic properties of the DNA polymerase A remained unchanged during the purification. Two-dimensional gel electrophoresis revealed that in the first dimension (isoelectric focusing agarose gel), the activity of the purified enzyme was focused at around pH 5.5 and that in the second dimension (sodium dodecyl sulfate-polyacrylamide gel), 135,000- and 66,000-dalton polypeptides emerged from the activity peak at a stoichiometric ratio of about 1:3. The native molecular weight of the DNA polymerase A estimated from the stoichiometric subunit ratio approximately coincided with that estimated from gel filtration on Sephadex G-200 under low ionic strength conditions. The present results strongly suggest the existence of a common high-molecular-weight catalytic core subunit in alpha-type polymerases of eukaryotes.

Animals↗
PubMed1982

Hemodynamic responses to prostacyclin (PGI2) in the conscious sheep.

Hemodynamic responses to prostacyclin (PGI2) were studied in sheep in the conscious state as well as under pentobarbital-halothane anesthesia. PGI2 in doses of 0.02-1.0 microgram/kg were administered as a bolus into the right or left atrium in the conscious sheep. PGI2 decreased systemic arterial pressure (PSA), systemic (SVR) and pulmonary vascular resistance (PVR) and increased cardiac output (CO) and heart rate (HR) in a dose-dependent manner. The changes of each parameter were almost similar regardless of the sites of administration. Pulmonary arterial pressure (PPA) was increased. There was no change in left (PLA) or right atrial pressure (PRA). A bolus administration of 0.5 microgram/kg of PGI2 in the anesthetized sheep produced a decrease in PSA, SVR and PVR, and increase in CO and HR. PPA remained unchanged when administered into the right atrium and increased slightly when administered into the left atrium. PLA and PRA did not change. Comparing hemodynamic responses to 0.5 microgram/kg of PGI2 of the conscious and anesthetized states, decrease in PSA was smaller and increases in CO and HR were greater in the former. Decreases in SVR and PVR were similar in both states. Increase in PPA was greater in the conscious sheep. This data confirms that PGI2 dilates the systemic as well as the pulmonary circulation of the sheep and an inactivation of this compound in the lungs is minimal. Furthermore, it may be suggested that general anesthesia significantly alters hemodynamic responses to PGI2 in the sheep.

Animals↗
PubMed1982

[Evaluation of diastolic phase by left ventricular volume curve using S2-gated equilibrium method in radioisotope angiography].

S2-gated (the second heart sound) method was designed by authors. In 6 normal subjects and 16 patients (old myocardial infarction 12 cases, hypertension 2 cases and aortic regurgitation 2 cases), radioisotope (RI) angiography using S2-gated equilibrium method was performed. In RI angiography, 99mTc-human serum albumin (HSA) 555MBq (15 mCi) as tracer, PDP11/34 as minicomputer and PCG/ECG synchronizer (Metro Inst.) were used. Then left ventricular (LV) volume curve by S2-gated and electrocardiogram (ECG) R wave-gated method were obtained. Using LV volume curve, left ventricular ejection fraction (EF), mean ejection rate (mER, s-1), mean filling rate (mFR, s-1) and rapid filling fraction (RFF) were calculated. mFR indicated mean filling rate during rapid filling phase. RFF was defined as the filling fraction during rapid filling phase among stroke volume. S2-gated method was reliable in evaluation of early diastolic phase, compared with ECG-gated method. There was the difference between RFF in normal group and myocardial infarction (MI) group (p less than 0.005). RFF in 2 groups were correlated with EF (r = 0.82, p less than 0.01). RFF was useful in evaluating MI cases who had normal EF values. The comparison with mER by ECG-gated and mFR by S2-gated was useful in evaluating MI cases who had normal mER values. mFR was remarkably lower than mER in MI group, but was equal to mER in normal group approximately. In conclusion, the evaluation using RFF and mFR by S2-gated method was useful in MI cases who had normal systolic phase indices.

Adult↗