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Biomedical subjects

Y Katayama

Publications and source records attributed to Y Katayama.

At least 649 records · Page 36Linked to original sources
PubMed1989

Adenosine 5'-triphosphate modulates membrane potassium conductance in guinea-pig myenteric neurones.

1. Intracellular recordings were made from myenteric neurones isolated from the guinea-pig small intestine to study actions of adenosine 5'-triphosphate (ATP). ATP was applied by superfusion (10 nM-100 microM) or pressure ejection from ATP-containing glass pipettes. 2. Myenteric neurones have been classified into two groups: type I/S neurones and type II/AH neurones. ATP produced a membrane hyperpolarization in 80% of AH neurones and a membrane depolarization in 90% of S neurones in a dose-dependent manner. Adenosine caused responses similar to those induced by ATP in both AH and S neurones, but was less effective than ATP. 3. The ATP-induced hyperpolarization was associated with a fall in input resistance, but the ATP-induced depolarization was accompanied by an increase in input resistance. Both responses reversed in polarity near the potassium equilibrium potential (-84 to -87 mV) and the reversal potential varied with extracellular potassium concentration, as predicted by the Nernst equation. These results indicate that the hyperpolarization is due to an increase, while the depolarization is due to a decrease in potassium conductance. 4. Both the hyperpolarization and the depolarization induced by ATP persisted in calcium-free solution containing 1.2 mM-magnesium, but were markedly reduced or abolished in calcium-free solutions containing 3.7-10 mM-magnesium and by 1 mM-nickel or cobalt. Both responses to ATP persisted in tetraethylammonium (1-10 mM) or tetrodotoxin (1-3 microM)-containing solutions. 5. Quinine and quinidine (1-100 microM) reversibly depressed both the ATP-induced responses. Caffeine (100 microM), theophylline (100 microM) and 3-isobutyl-1-methylxanthine (1-10 microM) did not significantly affect the ATP-induced depolarization but did reversibly depress the ATP-induced hyperpolarization. 6. These results suggest that the ATP-induced hyperpolarization may be due to activation, and the ATP-induced depolarization to inactivation, of a calcium-sensitive potassium conductance.

Action Potentials↗
PubMed1989

Bullfrog dorsal root ganglion cells having tetrodotoxin-resistant spikes are endowed with nicotinic receptors.

1. Intracellular recordings were made from bullfrog dorsal root ganglion (DRG) neurons in vitro. They were divided into three types, As, Ar, and C, according to their conduction velocity and their sensitivity to tetrodotoxin [TTX (less than or equal to 1 microM)]; an As neuron had a fast conduction velocity (13-50 m/s, mean = 31 m/s, n = 73) and TTX-sensitive sodium soma spikes: an Ar neuron showed a fast conduction velocity (4-28 m/s, mean = 14 m/s, n = 52) and TTX-resistant sodium soma spikes; and a C neuron had a slow conduction velocity (0.16-0.8 m/s, mean = 0.4 m/s, n = 49) and TTX-resistant sodium-calcium soma spikes. 2. Superfusion of acetylcholine [ACh (0.3 microM-1 mM)] produced a fast depolarization in 70% of Ar and in 50% of C neurons. No As neuron showed a fast depolarization in response to ACh. The ACh-induced fast response persisted in calcium-free or TTX-containing solutions. 3. The response in both Ar and C neurons was similar except in time course; the response was always more rapid in C than in Ar neurons. The response was always associated with a decreased membrane resistance and reversed in polarity at about -30 mV. The reversal potential varied with both sodium and potassium concentrations of the superfusing solutions. 4. Nicotine, (+)-tubocurarine [(+)-TC], and hexamethonium reversibly blocked the ACh fast response.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1989

[The effect of the interval from dinner until retiring on the concentration of lithogenic substances during sleep].

The relationship between the interval from dinner until retiring and the concentration of various substances secreted into the urine during sleep was studied in 69 healthy men who had eaten the same meal. The specific gravity and the concentrations of creatinine, uric acid and magnesium in the morning spot urine were highest in subjects who had retired within 2 hours after dinner. The concentrations of calcium and oxalate in the morning spot urine were highest in those who had retired between 2 and 4 hours. The specific gravity and urinary concentrations of creatinine, uric acid and oxalate were markedly higher in those with the interval less than 4 hours than in those 4 hours or longer. The concentrations of calcium, magnesium and citrate were not significantly different between the two groups. From these results, we recommend that the interval from dinner until retiring be prolonged and fluid be drunk before going to bed to decrease the concentration of lithogenic substances during sleep.

Adult↗
PubMed1989

[Treatment of prosthetic valve endocarditis--analysis of eleven cases].

A retrospective examination was made of eleven patients that developed prosthetic valve endocarditis (PVE) during the period from January 1960 to December 1987. Infection occurred in one patient within 60 days after surgery and in 10 thereafter. Causative organism was found in 6 patients. As organism, Staphylococcus species were noted in 4 patients and Peptstreptococcus was noted in one patient and Aspergyllus was noted in one patient. Three of eleven patients received medical treatment only and the other 8 patients were received surgical treatment. Mortality rate was 67% in medical group and 29% in surgical group. Two patients with medical treatment died of cerebral infarction about 40 days after the onset of PVE. In surgical group one patient died of uncontrollable Aspergillus infection and the other one died of dyspnea. No survivors who was treated surgically have developed reinfection or relapse of infection but four of them developed perivalvular leakage and needed reoperation. Absolute removal and closure of the valve ring abscess and reconstruction of defect should be considered for those needed surgical treatment to prevent reinfection and relapse developing.

Adolescent↗
PubMed1989

[Dietary habits of Japanese renal stone formers and clinical effects of prophylactic dietary treatment].

The daily consumption of various nutrients and the daily habits of 241 male stone formers were investigated. The patients (especially uric acid stone formers and hypercalciuric (greater than or equal to 300 mg/day) calcium stone formers) ingested much more total protein and animal protein than healthy Japanese. However, the amount of ingested calcium by the patients (470 mg) was less than that of healthy subjects (553 mg) and did not reach the level of the daily nutritive requirement (600 mg). The amount of ingested nutrients during the evening meal by the patients was about 50% of the daily amount with over 60% of the daily animal protein being ingested at dinner. This tendency was high in subjects who were in their 20's to 40's. The interval from dinner until retiring in the patients was not different from that of healthy males, but it was under 4 hours in over 50% of those in their 30's and 40's in both groups. From these results, we thought that a rapid change in nutritional status and dietary style in the short period after World War II had strongly affected the incidence of renal stone disease in Japan. Therefore, we have established the following general guidelines: 1) increased fluid intake, especially after dinner, 2) correct and avoid unbalanced diet (the diet should include all kinds of food, with vegetables being eaten at every meal and avoidance of an excessive intake of meat), 3) eat three meals a day and avoid an excessive intake at dinner, and 4) extend the interval from dinner until retiring. By following these individual dietary guidelines, the 5-year stone recurrence rate and the stone episode rate decreased remarkably in the period of not only outpatient visits but also in the period when the outpatient visits were discontinued. From these results, we conclude that individual dietary management should be the primary measure for the prophylaxis of renal stone disease in Japan.

Adult↗
PubMed1989

[A case of atresia hymen with urinary retention].

A case of atresia hymen with urinary retention was reported. The patient was a 13-year-old female, who visited our clinic complaining of urinary retention and constipation. Examination of the external genitalia revealed atresia hymen . Intravenous pyelography showed hydronephrosis was not present. The symptoms disappeared completely after a hymenal incision was made. This case indicates necessity for caution concerning urological symptoms in females.

Adolescent↗
PubMed1989

[Multiple myeloma in a patient with primary hyperparathyroidism].

A 50-year-old man presented with knee pain and general fatigue and was found to have severe hypercalcemia and renal failure. Hyperparathyroidism was suspected by hypercalcemia and a nodular lesion of the thyroid gland with CT-scan of the patient's neck. Exploration of the neck disclosed two slightly enlarged parathyroid glands. After surgery, the patient's serum calcium levels remained normal for two weeks, but after that his serum calcium levels rose again and renal failure continued. So needle biopsy of the kidney was enforced, and myeloma of the kidney was suspected. Multiple myeloma was diagnosed by bone marrow puncture.

Humans↗
PubMed1989

[Surgical treatment of left ventricular aneurysm associated with mitral regurgitation].

The purpose of this study is to analyze the early and late results of left ventricular aneurysmectomy in patients with mitral regurgitation secondary to myocardial infarction. Twenty patients who had left ventricular aneurysm combined with mitral regurgitation underwent the isolated or combined aneurysmectomy during the last 10 years. There were 18 male cases and 2 female cases, and their age ranged from 31 to 64 (mean age 52.6 years). In 19 cases, the left ventricular aneurysm were caused secondary to antero-septal infarction due to the occlusion of the left anterior descending coronary artery. In one case, the coronary spasm of circumflex artery provoked the posterolateral myocardial infarction and the tendon rupture of posterior papillary muscle. The isolated left ventricular aneurysmectomy were performed in 6 cases and the combined operations were coronary artery bypass grafting in 11 cases, mitral annuloplasty in 1 case, mitral annuloplasty and bypass grafting in 1 case, and mitral replacement in 1 case. There were no operative death cases. The preoperative mean functional class (NYHA classification) was 2.9 and the postoperative class was 1.4. The preoperative mitral regurgitation of grade 1 in Sellers' classification was observed in 11 cases. Grade 2 regurgitation was observed in 6 cases, grade 3 in 2 and grade 4 in 1. After surgery, mitral regurgitation more than grade 2 was recognized in 3 cases (group A) and regurgitation less than grade 1 was seen in 17 cases (group B).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The two-component, ATP-dependent Clp protease of Escherichia coli. Purification, cloning, and mutational analysis of the ATP-binding component.

The ATP-binding component (Component II, hereafter referred to as ClpA) of a two-component, ATP-dependent protease from Escherichia coli has been purified to homogeneity. ClpA is a protein with subunit Mr 81,000. It has an intrinsic ATPase activity and activates degradation of protein substrates only in the presence of a second component (Component I, hereafter referred to as ClpP), Mg2+, and ATP. The amount of ClpA varies by less than a factor of 2 in cells grown in different media and at temperatures from 30 to 42 degrees C. ClpA does not appear to be a heat-shock protein since its synthesis is not dependent on htpR. Antibodies against purified ClpA were used to identify lambda transducing phage bearing the clpA gene. The cloned gene contains a DNA sequence expected to code for the first 28 amino acids of ClpA, which were determined by protein sequencing of purified ClpA. The clpA gene in the phage was mutated by insertion of delta kan defective transposons and the mutations were transferred to E. coli by homologous recombination. The clpA gene was mapped to 19 min on the E. coli chromosome. Mutant cells with insertions early in the gene produce no ClpA protein detectable in Western blots, and extracts of such mutant cells have no detectable ClpA activity. clpA- mutants grow well under all conditions tested and are not defective in turnover of proteins during nitrogen starvation nor in the turnover of such highly unstable proteins as the lambda proteins O, N, and cII, or the E. coli proteins SulA, RcsA, and glutamate dehydrogenase. The degradation of abnormal canavanine-containing proteins is defective in clpA mutants especially in cells that also have a lon- mutation. Extracts of clpA- lon- cells have ATP-dependent casein degrading activity.

ATP-Dependent Proteases↗
PubMed1988

Late slow outward currents following hyperpolarizing commands are associated with intracellular Ca2+ increase in guinea-pig submucous neurons: investigations with fura-2.

Intracellular recordings were made from submucous neurons in the guinea-pig isolated caecum. A hyperpolarization lasting several seconds followed the termination of a strong hyperpolarizing current pulse; this was always accompanied by a decrease in input resistance. In neurons voltage-clamped at -30 mV, a late slow outward current (LSOC) flowed for more than 10 s, following the termination of a hyperpolarizing command (-100 mV, 2 s). This current was dependent on extracellular K+ concentration, but was not affected by tetraethylammonium, D-tubocurarine and 4-aminopyridine, and was reversibly blocked by low calcium/high magnesium solution. Intracellular calcium concentration ([Ca2+]i) was measured by using a fluorescent calcium indicator, fura-2. In voltage-clamped neurons, [Ca2+]i decreased during the hyperpolarizing command pulse, but increased above the original level at the end of the command. The time course of the change in [Ca2+]i was almost the same as that of the LSOC. Intracellular injection of cesium ions depressed the LSOC, but did not affect the change in [Ca2+]i. The present results indicate that the LSOC is due to activation of calcium-sensitive potassium conductance.

Animals↗
PubMed1988

Measurement of the intracellular calcium concentration in guinea-pig myenteric neurons by using fura-2.

Intracellular free calcium concentration [( Ca2+]i) was measured in guinea-pig myenteric neurons by using the fluorescent calcium indicator, fura-2; at the same time, intracellular recordings were made from the myenteric neurons. The [Ca2+]i of the myenteric neurons was about 100 nM at the resting state. The slow after-hyperpolarization that followed an action potential was associated with an increase in [Ca2+]i [Ca2+]i decreased during superfusion with calcium-free/high (6 mM) magnesium solution, and increased during superfusion with high (20 mM) potassium solution. However, [Ca2+]i did not change when the depolarizations caused in the high potassium solution were prevented by passing inward current through the recording electrode. The present experiments provide direct evidence that depolarization of the myenteric neurons allows calcium to enter the cell, and that rises in intracellular calcium concentration hyperpolarize the neuron.

Animals↗
PubMed1988

Methionine enkephalin presynaptically facilitates and inhibits bullfrog sympathetic ganglionic transmission.

The effects of [Met5]enkephalin (ME) on the fast excitatory postsynaptic potential (EPSP) in bullfrog sympathetic ganglion cells were studied with intracellular recording in vitro. The variance and failure methods were used to calculate quantal content and quantal size of the fast EPSP in a low Ca2+/high Mg2+ solution. High concentrations of ME (1 and 10 microM) decreased the amplitude and the mean quantal content of the fast EPSP, whereas low concentrations (10 pM to 10 nM) of the peptide increased EPSP amplitude and quantal content. The mean quantal size of the EPSP was not changed by ME. The inhibitory effect of ME at high concentration (10 microM) was reversibly antagonized by the same concentration of naloxone; the facilitatory effect of ME at low concentration (1 nM) was not affected by 10 times higher concentration of naloxone (10 nM), but inhibited by 10 microM naloxone. A low concentration of naloxone (100 pM) itself increased the amplitude and the mean quantal content of the fast EPSP without changing the mean quantal size. The other concentrations of naloxone used in this study (1 pM to 10 microM) caused no significant change in the fast EPSP. ME (100 fM to 10 microM) and naloxone (1 pM to 10 microM) did not change the resting membrane potential or input resistance, the amplitude and duration of action potentials, and the sensitivity to the acetylcholine applied by iontophoresis. These results indicate that ME may act on preganglionic nerve terminals either to facilitate or to depress transmitter release; the inhibitory action is naloxone sensitive, whereas the facilitatory action is less sensitive to naloxone.

Action Potentials↗