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Y Saeki

Publications and source records attributed to Y Saeki.

At least 217 records · Page 12Linked to original sources
PubMed1986

Length-tension relation of cat heart muscle studied by a segment-control method.

We studied the effects of the damaged ends on the length-tension relationship of the cat right ventricular papillary muscle during twitch contraction (30/min) using a newly developed segment-control system. The segment length (SL), defined as the distance between two thin black films attached to the central surface of the muscle with silicone grease, was measured by a Hamamatsu Photonics Width Analyzer (C1170) and Camera (C1000) and controlled with a servoactuator. The marker distance was determined to be either the central 24%-30% (short marker distance) or 47%-56% (long marker distance) of the muscle length (ML) at which the maximum developed twitch tension was observed (MLmax). The muscle was lengthened and shortened in a triangular fashion under both ML and SL isometric twitch modes over a period of 250s. The relationship between ML or SL and developed tension (DT, total minus resting tension) was obtained from the twitch tension data during the lengthening. The DT in the SL isometric twitch was always greater than that in the ML isometric twitch over the range of lengths studied. The slope of the SL-DT relation curve was much less steep than that of the ascending limb of the ML-DT relation curve. The gradient of the SL-DT relationship curve was greater for the long marker than for the short marker distance. The percentage shortening of SL in the ML isometric twitch increased with decreasing ML; it was greater for the short marker than for the long marker distance, particularly at shorter MLs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Very long-chain fatty acids in erythrocyte membrane sphingomyelin: detection of ALD hemizygotes and heterozygotes.

We used mass fragmentography to analyze a very long-chain fatty acid composition of erythrocyte membrane sphingomyelin. The content of hexacosanoic acid (C26:0), tetracosanoic acid (C24:0) and docosanoic acid (C22:0) in adrenoleukodystrophy (ALD) hemizygotes and heterozygotes was significantly higher than in controls. Although the ratio of C26:0 to C22:0 in 18 of the 46 controls was in the range of ALD heterozygotes, the absolute content of C26:0 and C24:0 in controls did not overlap with ALD hemizygotes or heterozygotes. The content of C26:0 and C24:0 is more reliable for detection of ALD hemizygotes and heterozygotes than the ratio of C26:0 to C22:0 when red cell sphingomyelin is used for diagnosis.

Adolescent↗
PubMed1986

Barosensory neurons in the ventrolateral medulla in rabbits and their responses to various afferent inputs from peripheral and central sources.

In 55 anesthetized and paralyzed adult rabbits, 161 spontaneously active neurons which responded to electrical stimulation of A-fibers of the aortic nerve were found within the ventrolateral medulla (VLM). They were termed barosensory VLM neurons, since the aortic nerve A-fibers were considered to consist exclusively of afferents from arterial baroreceptors. Forty percent of barosensory VLM neurons tested (49/123) were activated antidromically by stimulation of the dorsolateral funiculus indicating that they send descending bulbospinal projections. Spontaneous discharges of barosensory VLM neurons were invariably inhibited by stimulation of aortic nerve A-fibers. Ninety-three percent of 80 neurons tested also responded to stimulation of aortic nerve C-fibers, a mixture of barosensory and nonbarosensory afferents. Natural stimulation of carotid sinus baroreceptors by an intravenous injection of phenylephrine in 19 vagotomized rabbits with aortic nerves disrupted inhibited spontaneous activity of all the 50 barosensory VLM neurons tested. By contrast, pharmacological stimulation of right or left carotid body chemoreceptors by close arterial injection of NaCN into the carotid sinus augmented activity of 93% of barosensory VLM neurons tested (41/44). The neuronal response was always greater to stimulation of chemoreceptors in the contralateral carotid sinus. Seven out of 8 barosensory VLM neurons tested (88%) were orthodromically excited by stimulation of the posterior hypothalamic area. In 74% of the 97 neurons examined in 29 vagotomized animals, a distinct respiratory-related rhythm, locked to that of phrenic nerve activity, was discerned. Thus, spontaneous activity of barosensory VLM neurons is inhibited by afferent inputs from aortic and carotid sinus baroreceptors, but is excited by incoming signals from carotid body chemoreceptors and the posterior hypothalamic area. It is also subject to the influence of the central mechanism generating the respiratory rhythm.

Afferent Pathways↗
PubMed1986

[Diagnosis of minimal breast cancer by diagnostic hormonal treatment].

After diagnostic hormonal treatment of 129 patients, 11 (8.5%) were revealed to have breast cancer. The diagnostic accuracy in the case of a lesion of less than 1.0 cm in diameter was 11.8% for palpation, 18.2% for mammography, 33.3% for ultrasonography; the accuracy of this method is 66.6%. Minimal breast cancer was present in eight out of nine cases. Thus, diagnostic hormonal treatment was found to be useful in the diagnosis of minimal breast cancer that coexists with mastopathy.

Adult↗
PubMed1985

Ca2+ sensitivities and transient tension responses to step-length stretches in feline mechanically-stripped single-fibre jaw-muscle preparations.

At a muscle length, Lo (just taut), isometric tension at constant levels of various Ca2+ activations and transient tension responses to rapid length stretches (less than 1 per cent of Lo within 2 ms) at maximal Ca2+ activation level were measured in temporal, masseter and digastric (anterior belly) muscles (2-3 mm long and 24-48 micron in diameter). Steady isometric tension increased in a sigmoid fashion with increasing Ca2+ concentration from about pCa 7.28 to 4.49 in temporalis, from about pCa 6.18 to 4.40 in masseter and from about pCa 5.82 to 4.40 in digastric. The maximum tension was 75.5 +/- 10.2 g/mm2 in temporalis, 44.7 +/- 14.1 g/mm2 in masseter, and 46.1 +/- 20.1 g/mm2 in digastric. In the resting state, the sarcomere length at Lo was 2.34 +/- 0.06 micron in temporalis, 2.20 +/- 0.08 micron in masseter, and 2.20 +/- 0.00 micron in digastric. When the sarcomere length was stretched from 2.20 to 2.34 micron (the sarcomere length of temporalis at Lo) in the masseter and digastric, the Ca2+ sensitivity increased without significant change of the maximum tension in either muscle. The transient tension responses in all three muscles showed two distinct phases; an immediate tension increase coincident with the length stretch followed by an exponential tension decrease. The mean value of the time constant in the second phase was 58.5 +/- 19.7 ms in temporalis, 58.5 +/- 12.6 ms in masseter, and 362.6 +/- 16.8 ms in digastric. Thus temporalis showed a higher Ca2+ sensitivity at Lo and a greater maximum tension-producing capability than the other muscles and the cross-bridge turnover rate appears to be slower in digastric than in the others.

Animals↗
PubMed1985

Purification and properties of NADH oxidase from Bacillus megaterium.

NADH oxidase, which catalyzes the oxidation of NADH, with the consumption of a stoichiometric amount of oxygen, to NAD+ and hydrogen peroxide was purified from Bacillus megaterium by 5'-AMP Sepharose affinity chromatography to homogeneity. The enzyme is a dimeric protein containing 1 mol of FAD per mol of subunit, Mr = 52,000. The absorption maxima of the native enzyme (oxidized form) were found at 270, 383, and 450 with a shoulder at 475 nm in 50 mM KPi buffer, pH 7.0. The visible absorption bands at 383 and 450 nm disappeared on the addition of NADH under anaerobic conditions and reappeared upon the introduction of air. Thus, the non-covalently bound FAD functioned as a prosthetic group for the enzyme. We tentatively named this new enzyme NADH oxidase (NADH:oxygen oxidoreductase, hydrogen peroxide forming). This enzyme stereospecifically oxidizes the pro-S hydrogen at C-4 of the pyridine ring of NADH.

Adenosine Diphosphate Ribose↗
PubMed1985

Spontaneous immunoglobulin A secretion and lack of mitogen-responsive B cells in systemic lupus erythematosus.

In an analysis of lymphocyte functions of systemic lupus erythematosus (SLE) patients, B cell abnormalities such as a lack of mitogen-responsive B cells and a predominance of spontaneous IgA-secreting cells (SC) were found. Lymphocyte functions of 20 SLE patients were studied. Impaired proliferative response to B cell mitogen, Staphylococcus aureus strain Cowan I (Cowan I), was observed, whereas the response to T cell mitogen phytohemagglutinin was normal. High levels of spontaneous IgA-SC were observed in SLE patients (greater than 10(2) cells/10(4) peripheral blood mononuclear cells [PBMC]), whereas spontaneous IgM-, IgG-, or IgE-SC were not proportionately increased. The number of spontaneous IgA-SC decreased with time in culture and became undetectable by day 5 of culture. In contrast, spontaneous immunoglobulin- (IgM, IgG, and IgA) SC were not observed in healthy volunteers (less than 10 cells/10(4) PBMC). Moreover, in SLE patients failure of induction of immunoglobulin-secreting cells (ISC) was observed when B cells were stimulated by Cowan I and B cell differentiation factor at any day tested, whereas ISC were induced in healthy volunteers on day 6 of culture. Depletion of T cells or macrophages did not affect the results obtained. These results suggest that the abnormalities observed in SLE B cells are not due to the in vitro direct effects of suppressor macrophages or suppressor T cells, and that the condition of the predominance of spontaneous IgA-SC and the unresponsiveness to exogenous stimulation may be emblematic of hyperactive B cells in SLE.

Antibody-Producing Cells↗
PubMed1985

Vascular effects of 15-hydroperoxyeicosatetraenoic acid and 15-hydroxyeicosatetraenoic acid on canine arteries.

The vascular effects of 15-hydroperoxyeicosatetraenoic acid (15-HPETE) and 15-hydroxyeicosatetraenoic acid (15-HETE) were investigated on isolated helical strips of canine cerebral and coronary arteries. 15-HPETE caused strong concentration-related contraction of cerebral arteries under resting tension. After contraction with prostaglandin F2 alpha (PGF2 alpha), 15-HPETE caused marked relaxation of coronary arteries. The effects of 15-HETE on isolated canine arteries were similar to those of 15-HPETE. The relaxation of coronary arteries caused by both 15-HPETE and 15-HETE was completely inhibited in the presence of aspirin, but not in the presence of tranylcypromine. Preincubation of coronary and cerebral arterial strips with 15-HPETE or 15-HETE resulted in suppression of the production of 6-keto-PGF1 alpha from exogenously added arachidonic acid; and 15-HPETE, but not 15-HETE, enhanced the production of HETE(s) significantly. Aspirin blocked 15-HPETE induced HETE(s) production in coronary arteries. On cerebral angiography, strong contraction of intracranial arteries was observed after intracisternal injection of 15-HPETE. On the other hand, 15-HETE had little effect on intracranial arteries in vivo. The mechanism of the vascular effects of 15-HPETE and 15-HETE will be discussed.

Animals↗
PubMed1984

Transient length responses of heart muscle in Ba2+-contracture to step tension reductions.

The transient length response of the cat papillary muscle in Ba2+-contracture to step tension reduction was found to comprise four different phases. It is tentatively suggested that the transient response is mostly determined by the kinetics of the attachment and detachment of cross-bridges between actin and myosin filaments, which vary appreciably with activation level of the muscle.

Animals↗
PubMed1984

Effects of Ba2+ on the mechanical properties of glycerinated heart muscle.

At a muscle length, L0 (just taut), isometric tension and tension transients in response to rapid step stretches in length (mostly less than 1.2% of L0 within 2 ms) were measured at constant levels of Ba2+ activation of varying magnitude in glycerinated cat right-ventricular papillary muscles (2-3 mm long, 130-200 micron in diameter). The majority of the experiments were carried out at room temperature (26-27 degrees C) and at a pH of 6.8. The steady isometric tension increased as Ba2+ was varied from slightly below pBa 6 to about pBa 4. The concentration range of Ba2+-activated muscle was roughly 10 times higher than that of Ca2+-activated muscle. Maximum Ba2+-activated isometric tension was 79.0 +/- 4.2% (mean +/- SD, n = 8) of that activated with Ca2+. The tension transients in Ba2+-activated muscle were characterized by at least three distinct phases; an immediate tension increase coincident with the stretch, a rapid exponential tension decrease (time constant, tau 1 = 7.3 +/- 1.0 ms, n = 5) and a delayed exponential tension rise (tau 2 = 104 +/- 5.7 ms, n = 5). The profile of tension response was quite similar to that of Ca2+-activated muscle. These results suggest that in Ba2+-activated glycerinated heart muscle the cross-bridge turnover is taking place as in the Ca2+-activated muscle, but the number of active cross-bridges at maximally activated state is smaller than that of Ca2+-activated muscle.

Animals↗
PubMed1984

Mechanical properties of glycerinated guinea-pig temporal and masseter muscles.

At a muscle length, L0 (just taut), isometric tension and tension transients in response to rapid step stretches in length (less than 1 per cent of L0 within 2 ms) were measured at constant levels of Ca2+ activation of various magnitudes in glycerinated temporal and masseter muscles (1.7-2.5 mm long, 48-96 micron in diameter) from guinea pigs. The experiments were at 20 and 30 degrees C, and pH 6.8. Steady isometric tension increased in a sigmoid fashion as Ca2+ varied from about pCa 6.6 to 4.4 in both muscles. However, the maximum tension of temporal muscle was about 4.4 times greater than that of masseter muscle at 20 degrees C. The tension transients showed an immediate tension increase coincident with the stretch (the first phase) and an exponential-like tension decrease (the second phase). The time constant of the second phase was about 87.5 ms in temporalis and 3.7 ms in masseter at 30 degrees C. Decreasing temperature from 30 to 20 degrees C markedly increased the time constant of the tension response in the second phase (Q10 of about 3.4 in temporalis and 2.2 in masseter). Although there was a difference in the sarcomere length between the two muscles at L0 (2.14 micron in temporalis and 1.84 micron in masseter), the mechanical characteristics were almost independent of the muscle length. Thus the cross-bridges in temporalis appear to cycle more slowly and produce more isometric tension than those in masseter muscle.

Animals↗
PubMed1984

Isotonic length transient of cat heart muscle in Ba2+-induced contracture.

To characterize mechanical properties of activated heart muscle, the length response to step (4 ms) decrease in tension in Ba2+-induced contracture in kitten papillary muscle was analyzed. The amplitudes of tension steps were varied at the maximum contracture level (Tc), different initial muscle lengths [0.90 Lmax to Lmax], and different temperatures (20-35 degrees C). When the tension decrease was less than 0.7 Tc, the length response comprised four different phases. The amplitude of shortening in the second phase, after the initial rapid shortening in the first phase, increased up to approximately 3.5% of the initial muscle length quite linearly with increasing amplitude of tension reduction. The amount of lengthening in the third phase, however, increased to a maximum (up to approximately 1.4% initial length) at the tension reduction of approximately 0.4 Tc. The third phase of lengthening was larger at shorter initial muscle length. Increasing temperature markedly decreased the amplitude and shortened the duration of the length response in the second and third phase independently of initial muscle length. Unlike that of the muscle in contracture, the length response of the resting and of the rigor muscle changed in a nearly stepwise fashion. One explanation of these phenomena is that the transient length responses following a rapid tension reduction are mostly determined by the kinetics of the attachment and detachment of cross bridges between actin and myosin filaments.

Animals↗