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M Yoshii

Publications and source records attributed to M Yoshii.

158 records · Page 9Linked to original sources
PubMed1976

Two components of the calcium current in the egg cell membrane of the tunicate.

The Ca current of the egg cell membrane of a certain tunicate, Halocynthia roretzi Drasche, was studied by the voltage-clamp technique. 2. The Ca current in the standard artificial sea water (ASW) was produced at the critical membrane potential of -10 mV after inactivating the Na current by conditioning depolarization, -30 to -15 mV. The Ca current was abolished by replacing Ca in ASW with Mg2+ or Mn2+. The Ca current was not significantly influenced by replacing Na in ASW with choline or Cs. 3. The relation of Ca current to the external Ca concentration was a monotonously increasing function, but was not linear. The current tended to saturate above 50 mM-Ca. In 100 mM-Ca ASW, the maximum peak inward current of Ca ranged from 1 to 7 X 10(-9) A. 4. The kinetics of Ca current was accurately analysed because of the small contribution of K outward current and was found to be relatively slow in comparison with the Na current. The peak time and the half-decay time of the maximum Ca current at about 25 mV were about 25 and 100 msec respectively in 100 mM-Ca ASW at 15 degrees C. 5. Addition of 20 mM-Co2+ to 100 mM-Ca ASW reduced Ca current to one fourth and 1 mM-La3+ to 100 mM-Ca ASW abolished the current. 6. Sr and Ba could substitute for Ca in Ca channels. The selectivity ratios for the 'Ca channels's were Ca (1-00):Sr(1-17):Ba(0-71) at a potential level of +40 mV. The Ca current in the egg cell membrane appeared to be essentially the same as the Ca current in the common excitable membranes, such as the crustacean muscle fibre. 7. The polyvalent cations including Ca ion and monovalent H+ ion showed the stabilizing effect upon both Na and Ca currents, by shifting V-I relations along the voltage axis. From the prediction of a theory of the diffuse double layer, the shift in the V-I relation induced by those cations should be directly related to their binding powers to the membrane. Thus, the sequence of the binding powers was inferred as H+ greater than La3+ greater than Co2+ greater than Mn2+ greater than Ca2+ greater than Sr2+ larger than or equal to Ba2+ greater than Mg2+. 9. In Na-free ASW, such as isotonic Ca ASW, Ca current was composed of two components. The one component was the Ca current described in 1 to 6. The other was also dependent upon the external Ca concentration, but showed the more negative critical membrane potential and the faster kinetics. It was concluded that this component should be the Ca current through Na channels. 10. The selectivity among Ca, Sr and Ba for 'Ca' current through 'Na channels' was significantly different from that of 'Ca' current through 'Ca channels', being Ca greater than Sr larger than or equal to Ba = 0.

Animals↗
PubMed1974

Analysis of non-linearity observed in the current-voltage relation of the tunicate embryo.

1. In the gastrula of the tunicate (Halocynthia aurantium) the resting potential of the embryonic membrane was about -70 mV in both std ASW and Na-free ASW.2. The potential responses to depolarizing current in the early gastrula embryo showed distinct potential jumps from about -50 to about +40 mV during the application of current and from about 0 to resting level after its cessation thus forming a plateau at about 0 mV. Those jumps were not altered significantly by the removal of both Na and Ca ions from ASW except for the duration of the plateau after the cessation of current.3. Blastomeres in an embryo were tightly coupled with each other electrotonically at the blastula and gastrula stages. The fact that the coupling ratio was nearly 1.0 made it reasonable to treat an embryo as one cell as far as electrical properties are concerned.4. The I-V relation of the embryonic membrane consisted of an inward rectifying region, outward rectifying region and transitional zone between the two, resulting in a S-shaped curve as in the egg cell membrane. But in the gastrula embryo, the transitional zone actually included the discontinuous part of the I-V curve (from about -50 to about +40 mV) due to the potential jump.5. The ionic current (I(i)) during the potential jump in Na-free ASW was estimated from the slope of the potential response based on the assumption of constant capacitance during the membrane potential changes. The calculated I(i)-V curve complemented the interrupted I-V curve smoothly and showed the existence of a negative resistance region from about -50 to about 0 mV in the steady-state I-V relation.6. The steady-state I-V relation was altered significantly by changing the K concentration in ASW, and the existence of the negative resistance can be reasonably explained by the marked inward-going rectification or anomalous rectification of K conductance.7. The replacement of K with Rb in ASW produced the marked suppression of the inward-going rectification of the embryonic membrane.

Animals↗
PubMedDate not supplied

Bile acid profiles in bile, urine, and feces of a patient with cerebrotendinous xanthomatosis.

Bile acid profiles of bile, urine, and feces obtained from a patient with cerebrotendinous xanthomatosis on the same day have been analyzed by gas-liquid chromatography-mass spectrometry after fractionation into groups by mode of conjugation by an ion-exchange chromatography. The predominant biliary bile acid was cholic acid conjugated with glycine and taurine. Lesser amounts of the amino acid conjugates of chenodeoxycholic acid, ursodeoxycholic acid, 7-ketodeoxycholic acid, allocholic acid, and deoxycholic acid, and of unconjugated norcholic acid and allonorcholic acid were also present in the bile. The major fecal bile acid was 7-epicholic acid. Relatively large amounts of bile acids were excreted in the urine. Unconjugated 7-epicholic acid, norcholic acid, allonorcholic acid, and cholic acid predominated. The bile acid profiles of the patient were different from those of normal subjects and should be useful for the diagnosis.

Bile↗
PubMedDate not supplied

Artifact removal procedure distorts multifocal electroretinogram.

PURPOSE: To study whether the Artifact Removal procedure available for eliminating artifacts in multifocal electroretinograms (mERG) works correctly or not. METHODS: A test response was made using a photo-diode circuit. mERGs were recorded from 3 well-trained normal subjects using the Veris III system, and were then analyzed by the procedure that is included in the Veris Science (Artifact Removal) software program. The stimuli consisted of densely arranged arrays of 103 or 37 hexagonal elements. It took a total of 8 minutes to obtain one mERG record, and 16 sessions were required to complete this record. The first-order as well as the second-order kernel response components were extracted by Veris Science software, and the Artifact Removal procedure was used for both components. RESULTS: The Artifact Removal procedure influenced both the test response on the center element as well as the neighboring traces just around the test response. After the repetitions of the Artifact Removal procedure, the shape of the test response changed considerably. Some of the traces of the second-order kernel response components elicited from a normal subject changed irregularly when the Artifact Removal procedure was repeatedly used. The noise increased at the first iteration of the Artifact Removal procedure. CONCLUSION: This procedure has been considered useful for eliminating artifact distortion in mERG, but should be carefully checked by well-established testing methods before clinical use.

Adult↗
PubMedDate not supplied

Analysis of second-order kernel response components of multifocal electroretinograms elicited from normal subjects.

PURPOSE: It has been reported that the second-order kernel response components of multifocal electroretinograms (mERGs) reflect the electrical activity of the inner retinal layers. In this study, we have investigated whether the amplitudes of the second-order kernel response components correlate with the spatial distribution of human retinal ganglion cells. METHODS: Multifocal electroretinograms were recorded using the Veris III system from 5 healthy subjects with different stimulus and recording parameters. The mERGs were analyzed using the Veris Science software programs. The stimuli consisted of densely arranged arrays of 103, 61, 37 or 19 hexagonal elements. Four minutes were required to record one set of mERG responses using 8 sessions, and 8 minutes using 16 sessions. The second-order kernel response components were extracted and analyzed using the Veris Science program. RESULTS: The signal-to-noise ratio of the first-order kernel response components was improved considerably by the summation of the nine reproducible responses from the same subject but the second-order kernel response components were not. The summation of the nine reproducible responses was insufficient to identify an array of the second-order kernel response components. Both the first- and second-order kernel response components were larger when fewer hexagonal elements were used. There was no significant difference in the individual responses between the 4-minute and the 8-minute recordings. A response density analysis revealed a weak correlation between the amplitude distribution of the second-order kernel response components and the spatial distribution of human retinal ganglion cells. CONCLUSIONS: The distribution of the amplitudes of the second-order kernel response components of the mERGs elicited from normal subjects did not correlate with the distribution of human ganglion cells. This suggests that the theory that second-order kernel response components arise from the activity of retinal ganglion cells should be reconsidered.

Adult↗
PubMedDate not supplied

Relationship between visual field defect and multifocal electroretinogram.

We investigated the effect of artificial parafoveal scotomata on the multifocal electroretinogram (M-ERG). M-ERGs were recorded from normal subjects using a monitor with several different sizes of black paper attached. A lower response density area around the 10 to 15 degree parafoveal region was not recognized for scotomata up to 3 degrees but was observed in scotomata above 5 degrees (visual angle) in the field topography of M-ERG. The shape of the scotomata was not circular but somewhat oval. The results from two cases of parafoveal retinal degeneration accorded well with this basic study.

Adult↗
PubMedDate not supplied

A basic investigation of multifocal electroretinogram: reproducibility and effect of luminance.

PURPOSE: To investigate the reproducibility as well as the effect of luminance in multifocal electroretinogram (mERG). METHODS: Multifocal electroretinogram recordings were repeated on different days in 6 normal subjects using the Veris III system. The mean luminance of the monitor displaying the stimuli was randomly varied by five kinds of neutral density (ND) filters. RESULTS: The standard deviation of mERG amplitude from the macular region was approximately 10% of the mean value for each normal subject. Reproducibility largely depended on the condition of the subject and placement of the contact lens electrode. With decreases in the mean luminance of the monitor, the amplitude of mERG decreased exponentially, whereas the peak latency increased linearly. mERGs elicited from a patient with mild cortical cataract resembled the mERGs obtained from the control group using an ND filter between -0.30 and -0.52 log, whereas two patients with typical retinitis pigmentosa showed much lower response densities in mERGs. CONCLUSIONS: It is necessary to pay attention to the reproducibility and the luminance effect to obtain reliable mERGs.

Adult↗
PubMedDate not supplied

Comparison of the effects of amlodipine and losartan on 24-hour ambulatory blood pressure in hypertensive patients.

Effects of amlodipine (AML), a long-acting calcium antagonist, and losartan (LOS), an angiotensin II receptor antagonist, on 24-hr blood pressure profile were compared in 15 patients with essential hypertension. After 4 weeks of placebo period, the patients were treated with AML or LOS in a random crossover design for 12-16 weeks each. Either drug was given once daily at 0800 and the doses were titrated so that the office blood pressure was reduced lower than 140/90mmHg. At the end of each period, 24-hr blood pressure was monitored. Average office blood pressure was lowered from 158 +/- 2/ 98 +/- 2 mmHg to 134 +/- 1/87 +/- 1 mmHg by AML and 134 +/- 2/88 +/- 1 mmHg by LOS. Average 24-hr blood pressure was also reduced from 144 +/- 3/ 92 +/- 2 mmHg to 131 +/- 2/84 +/- 2 mmHg by AML and 135 +/- 3/85 +/- 2 mmHg by LOS. The averaged 24-hr systolic blood pressure was significantly lower in AML than in LOS (p < 0.05). Then, the 24-hr blood pressure was analyzed for four segments; morning (0530-0900 h), daytime (0930-1800 h), evening (1830-2300 h) and night (2330-0500 h). Although the daytime blood pressure was comparable between AML and LOS, systolic blood pressure in the evening and morning hours were lower in AML than in LOS (133 +/- 2 vs. 138 +/- 3mmHg,p<0.01; 129 +/- 3 vs. 134 +/- 4,p<0.05). Troughtopeakratio of antihypertensive effect on systolic blood pressure was significantly greater in AML than in LOS (62 +/- 5% vs. 55 +/- 4%, p < 0.05). Either drug did not cause reflective increase in pulse rate over 24 hours. These results suggest that both AML and LOS are equally effective in lowering daytime blood pressure without eliciting reflex tachycardia, however, the antihypertensive effect of AML lasts longer than that of LOS. Such information seems important to achieve 24-hr blood pressure control using these drugs.

Adult↗
PubMedDate not supplied

Functional expression of Fas and Fas ligand on human colonic intraepithelial T lymphocytes.

The expression of Fas, a cell surface receptor directly responsible for triggering cell death by apoptosis, and its ligand (FasL) was investigated on both human colonic intraepithelial T lymphocytes (IELs) and peripheral blood mononuclear lymphocytes (PBMLs). FACS analysis indicated that IELs have increased expression of Fas compared with PBMLs, together with the progress activation marker, CD45RO. A discrete fraction of freshly isolated IELs also constitutively expressed FasL, perhaps as a result of recent in vivo activation. Using monoclonal antibody APO2.7, which detects mitochondrial 7A6 antigen specifically expressed by cells undergoing apoptosis, we further investigated the apoptosis-inducing effect of anti-Fas monoclonal antibody (CH11) on both IELs and PBMLs. FACS analysis revealed that CH11 increased the percentage of apoptotic cells, in IELs but not in PBMLs. Culture with anti-FasL monoclonal antibody (4H9) significantly recovered cell viability in IELs, but not in PBMLs. These results indicate that IELs constitutively express both Fas and FasL and that Fas crosslinking generates signals resulting in apoptosis, outlining a potential mechanism involved in intestinal tolerance.

Adult↗