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Biomedical subjects

C Yamamoto

Publications and source records attributed to C Yamamoto.

At least 217 records · Page 12Linked to original sources
PubMed1989

[Memory, learning and glutamate receptor].

After a brief tetanic stimulation of an excitatory pathway in the hippocampus, synaptic transmission through the tetanized pathway is facilitated for a long period. This phenomenon is called long-term potentiation (LTP), and has been regarded as a neuronal correlate with learning and memory. Features of LPT in Schaffer collateral-CA1 neuron are calcium-dependency, input-specificity, cooperativity and sensitivity to blockers of N-methyl-D-aspartate (NMDA) receptors. These features can be explained by properties of NMDA receptors. LTP in mossy fiber-CA3 neuron has features different from those in field CA1: It is insensitive to blockers of NMDA receptors and does not show cooperativity. Quantal analysis of transmission through mossy fiber synapses before and after generation of LTP reveals that LTP resulted from facilitated release of transmitter. Participation of the metabotropic glutamate receptor is suggested.

Animals↗
PubMed1989

[A case of eosinophilic pneumonia with acute progressive dyspnea and diffuse small nodular shadows on chest X-ray film].

A 52-year-old man was admitted to our hospital with high-grade fever, dry cough and severe dyspnea. Chest X-ray films revealed diffuse small nodular shadows in all lung fields, prominently in the middle and lower lung fields. On examination, peripheral blood eosinophilic leukocytosis and severe hypoxemia were demonstrated. His clinical condition improved during five days after the admission without any therapy but oxygen inhalation. The abnormal shadows decreased in several days, and disappeared completely in thirty days. Bronchoalveolar lavage fluid revealed increased total cell counts, mostly with eosinophils (60%) and lymphocytes (21%). Histologically, the transbronchial lung biopsy specimen showed that the walls of pulmonary arteries and bronchioli were markedly infiltrated with eosinophils, and that alveolar septa were edematous with mononuclear and eosinophilic cells infiltration. There were no prominent changes in the alveolar lumen except few macrophage exudates. Our case was of importance for two reasons: first, eosinophilic pneumonia could take the form of interstitial pneumonia both roentgenologically and histologically; second, Crofton's classification of P.I.E. could not be applied to this case.

Acute Disease↗
PubMed1989

[Pharmacokinetic and clinical studies on sulbactam/ampicillin in children].

Laboratory and clinical studies of sulbactam/ampicillin (SBT/ABPC) in children have been carried out, and the following results were obtained. 1. Antibacterial effect MICs of SBT/ABPC were only one-tube less than or similar to those of ABPC against susceptible organisms. Against ABPC-resistant organisms at the inoculum size of 10(8) cells/ml however, SBT/ABPC was superior to ABPC when evaluated in terms of their MIC values. When MICs of SBT/ABPC were compared to those of ABPC against organisms with high beta-lactamase producing activities, it was found that many of ABPC-resistant organisms were much susceptible to SBT/ABPC. 2. Absorption and urinary excretion In 2 cases to which 50 mg/kg and 20 mg/kg SBT/ABPC were respectively given over 30 minutes by drip infusion, peak serum levels were obtained at the end of the drip infusion with peak levels of SBT of 45.5 micrograms/ml, 12.5 micrograms/ml, respectively and those of ABPC of 83.0 micrograms/ml, 22.9 micrograms/ml, respectively. The half-lives of SBT and ABPC were 0.94 hour and 0.98 hour, respectively. The mean urinary excretion rates in the first 6 hours after the end of administration were 84.4% for SBT and 63.1% for ABPC. 3. Clinical results Clinical efficacies were evaluated in 24 cases including 9 cases of pneumonia, 2 cases of upper respiratory infection, 7 cases of urinary tract infection and 1 case each of bronchopneumonia, pyothorax, tonsillitis, streptococcal infection, ++ phlegmon and staphylococcal scalded skin syndrome. Clinical efficacies were excellent or good in 19 cases with an overall efficacy rate of 86.4%. Adverse effect was found in 1 case with nausea and vomiting, and abnormal laboratory test values observed were 2 cases each of eosinophilia, slight elevation of GOT and GPT and elevation of LDH, but they were not serious.

Adolescent↗
PubMed1988

Synthetic omega-conotoxin blocks synaptic transmission in the hippocampus in vitro.

The effects of some organic calcium channel blockers and a toxin on synaptic transmission were examined in hippocampal slices from the guinea pig. omega-Conotoxin fraction GVIA, a novel peptide that blocks N and L type voltage-sensitive calcium channels, blocked synaptic transmission from mossy fibers to CA3 neurons at very low concentration (100 nM). However, organic calcium channel blockers such as verapamil (100 microM) and nifedipine (10 microM), which block L type calcium channels, had little effect on the synaptic transmission. Phenytoin (100 microM, T type calcium channel blocker) was also ineffective to block the synaptic transmission. These results suggest that presynaptic calcium channels which cause transmitter release may be N type calcium channel.

Animals↗
PubMed1988

Left ventricular dysfunction after prolonged strenuous exercise in healthy subjects.

To determine whether depressed left ventricular (LV) contractile function can occur after prolonged and strenuous exercise, 12 healthy men, 26 +/- 1 years old (mean +/- standard error of the mean) were studied. The subjects exercised on a treadmill at 69 +/- 1% of maximal O2 uptake until exhaustion (170 +/- 10 minutes). Hemodynamic variables were measured before and 10 minutes after exhausting exercise. Baseline systolic blood pressure decreased from 124 +/- 2 to 113 +/- 3 mm Hg (p less than 0.001) after exhausting exercise. LV end-diastolic diameter, measured by echocardiography, decreased from 51 +/- 1.0 to 47 +/- 1.0 mm (p less than 0.005) but LV end-systolic diameter did not change (34 +/- 1.0 vs 34 +/- 1.0 mm). Both LV fractional shortening and the mean velocity of circumferential fiber shortening decreased (33 +/- 1 vs 28 +/- 1%; p less than 0.01 and 1.09 +/- 0.4 vs 0.97 +/- 0.05 circ/s; p less than 0.025) despite a lower end-systolic wall stress (sigma es = 88 +/- 4 vs 82 +/- 5, X 10(3) dynes/cm2; p less than 0.05) after prolonged exhausting exercise. A repeat bout of exercise of the same intensity but brief in duration (10 minutes) resulted in increases in LV fractional shortening (p less than 0.001) and mean velocity of circumferential fiber shortening (p less than 0.001), and a decrease in LV end-diastolic diameter (50 +/- 1.0 to 48 +/- 1.0 mm; p less than 0.05) at heart rates comparable to those attained after prolonged exhausting exercise. The results suggest that prolonged strenuous exercise may result in impaired LV function in healthy young subjects.

Adult↗
PubMed1988

Kainic acid induces long-lasting depolarizations in hippocampal neurons only when applied to stratum lucidum.

The actions of alpha-kainic acid (KA) were reexamined in thin sections of the hippocampus and the cerebellum of the guinea pig in view of various discrepancies between our previous findings and reports from other laboratories. Brief pulses of KA ejected in st. lucidum in the CA3 region induced short- and long-lasting depolarizations in neurons nearby, whereas those ejected in st. radiatum or st. oriens induced only short-lasting responses. Neurons in CA1 region and Purkinje cells in the cerebellum generated only short-lasting depolarizations in response to KA pulses ejected in their dendritic fields. The short-lasting KA responses in CA1 region were sensitive to gamma-D-glutamylglycine and pentobarbital. The slow KA responses were suppressed by kynurenic acid. They were not accompanied by increases in extracellular potassium concentration. These results suggest that the mossy fiber-innervated portions of the surface membrane of CA3 neurons have a type of KA receptor different from those ubiquitously distributed in central neurons.

Action Potentials↗
PubMed1988

Additive feature of long-term potentiation and phorbol ester-induced synaptic enhancement in the mossy fiber-CA3 synapse.

Application of phorbol esters, selective activators of protein kinase C (PKC), causes a long-lasting enhancement of synaptic transmission in the hippocampus. We examined the relationship between this phorbol ester-induced enhancement of synaptic transmission and long-term potentiation (LTP) quantitatively in the mossy fiber-CA3 synapse of the guinea pig hippocampus in vitro. Potentiating action of 0.5 microM phorbol 12,13-diacetate (PDAc) on synaptic transmission was almost unaffected by preceding tetanic stimuli which had caused a full development of LTP. Tetanic stimulation induced LTP even after synaptic transmission had been enhanced by 0.5 microM PDAc. Quantitative estimations revealed that PDAc-induced synaptic enhancement and LTP were simply additive to each other. The relation between LTP and PKC activation is discussed.

Action Potentials↗
PubMed1988

Effect of 6 d of exercise training on responses to maximal and sub-maximal exercise in middle-aged men.

Nine sedentary men (53 +/- 3 yr) were studied before and after 6 d of endurance exercise training to determine the effects on maximal oxygen uptake (VO2max), and on the heart rate, blood pressure, and metabolic responses to a standard bout of steady-state sub-maximal exercise. The subjects exercised approximately 1 h.d-1 at about 68% of VO2max. The 6-d protocol elicited no improvement in VO2max (2.50 +/- 0.14 before vs 2.58 +/- 0.15 l.min-1 after training). Heart rates were significantly lower by 5 to 8 b.min-1, systolic blood pressures were reduced by 16 to 19 mm Hg, and blood lactate concentrations were 25 to 35% less at the same exercise intensities (60, 70, and 80% of VO2max) after 6 d of exercise. Rate pressure product was about 15% lower at the same exercise intensity after 6 d of training (P less than 0.05). The respiratory exchange ratio during submaximal exercise was 0.02 to 0.04 units lower (P less than 0.05; P less than 0.01) after 6 d of exercise, indicating a shift in substrate utilization favoring fat oxidation. These findings suggest that short-term endurance training can induce heart rate, blood pressure, and metabolic adaptations to sub-maximal exercise before there is a significant increase in VO2max in sedentary, middle-aged men who are capable of vigorous exercise.

Blood Pressure↗
PubMed1988

Blood vascular architecture of the rat extra-adrenal cortical body: a scanning electron microscopic study of corrosion casts.

A well developed extra-adrenal cortical body with an axis of 200-700 micron was found in eighteen of thirty adult male Wistar rats under a stereomicroscope. All eighteen bodies were located between the kidneys. Blood vascular beds of sixteen of the eighteen bodies were reproduced with a methacrylate casting medium and observed with a scanning electron microscope. The extra-adrenal cortical body was found to contain remarkably numerous capillaries which anastomosed with each other to form a conglomerated network; it received one afferent vessel and issued one to three (usually, one) efferent vessels. The blood capillaries were of sinusoidal and uniform calibers, and resembled those of the adrenal cortex. The network with an axis of 300-700 micron possessed a typical, deep efferent rootlet which corresponds to the central vein of the adrenal gland. Histological examination of the two bodies treated with Orth's or Helley's fixative confirmed that they consisted of non-chromaffin cells similar to those of the adrenal cortex. These findings suggest that in the rat, the extra-adrenal cortical bodies persist throughout life, actively producing cortical hormones.

Adrenal Cortex↗
PubMed1988

Homology of the adductor pollicis and contrahentes muscles: a study of monkey hands.

The deep palmar muscles in monkey hands were studied. The contrahentes muscles mainly arose from the capitate bone, descended palmar to the deep palmar branch of the ulnar nerve and the palmar metacarpophalangeal nerves, and attached to the proximal phalanges or wing tendons of the second, fourth and fifth fingers. In relation to the deep palmar branch of the ulnar nerve and the palmar metacarpophalangeal nerves, the contrahentes muscles are homologous with the adductor pollicis and flexor indicis radialis muscles. The contrahentes muscles occasionally gave off some accessory slips which blended with the interosseous muscles. These findings suggest that the human adductor pollicis muscle is a well-developed remnant of a contrahens muscle, and that the human interosseous muscles contain some remnant of the contrahentes muscle. In fact, a well-developed remnant of a contrahens muscle was found in the fourth finger of a human hand. It is further considered that the human adductor pollicis muscle contains an element of the interosseous muscle of the thumb.

Animals↗
PubMed1988

Improvement in glucose tolerance after 1 wk of exercise in patients with mild NIDDM.

We investigated the effects of 1 wk of intense exercise on glucose tolerance in 10 men with abnormal glucose tolerance [7 had mild non-insulin-dependent diabetes mellitus (NIDDM), and 3 had impaired glucose tolerance]. The 7 days of exercise did not result in significant changes in body weight or maximal oxygen uptake. Plasma glucose concentration at 120 min averaged 227 +/- 23 mg/dl in an oral glucose tolerance test (OGTT) before and 170 +/- 18 mg/dl after the 7 days of exercise (P less than .001). There was a 36% reduction in the area under the glucose tolerance curve. Plasma insulin concentration at 120 min of the OGTT averaged 172 +/- 27 microU/ml before and 106 +/- 13 microU/ml after 7 days of exercise (P less than .001); the area under the insulin curve was decreased by 32%. In contrast to the response to 7 days of exercise, one bout of exercise did not result in an improvement in glucose tolerance. These results provide evidence that regularly performed, vigorous exercise can be effective in decreasing insulin resistance and improving glucose tolerance within 7 days in some patients with mild NIDDM.

Blood Glucose↗
PubMed1988

Effect of physical training on immunoreactive gamma-glutamyltransferase in human plasma.

The effects of 10-week physical training on both the activity and concentration of gamma-glutamyltransferase (gamma-GT) in plasma were investigated on 7 sedentary healthy male students. The training consisted of running over 5 km, 6 times/week. The maximal oxygen uptake (Vo2max) and 12-min field performance increased significantly after training, from 43.5 and 2,683.7 to 48.1 ml.kg-1.min-1 and 2,931.1 m, respectively. After training the resting plasma gamma-GT concentration decreased to half, whereas the gamma-GT activity did not vary substantially. The training did not affect the response to the Vo2max test of either concentration or activity of gamma-GT. These results may suggest that plasma gamma-GT concentration is useful as an index of the extent of physical training.

Adolescent↗
PubMed1987

Enzymatic determination of bilirubin fractions in serum.

Novel enzymatic methods using bilirubin oxidase from Myrothecium verrucaria are described for the determination of bilirubin fractions in serum. These fractions include an unconjugated form (Bu), a conjugated form (Bc), and a delta fraction of bilirubin that reacts with direct diazo reagent and is irreversibly bound to serum albumin (B delta). The determination is based on the different reactivities of the enzyme to bilirubin fractions at different pH in the presence or absence of anionic detergent such as sodium dodecyl sulfate (SDS) or sodium cholate. Thus, in the absence of detergents, Bc and B delta are oxidized at acidic pH, while Bc is oxidized at alkaline pH; Bu is not oxidized at either acidic or alkaline pH. The first approach is based on measuring the decreased absorbance of bilirubin colour at 450 nm caused by the enzymatic oxidation. Total bilirubin is measured at pH 8.0 in the presence of SDS. Direct bilirubin is measured at pH 3.7 and Bc is measured at pH 10.0 in the absence of SDS, respectively. The second approach is made by coupling the diazo reaction with the enzyme reaction. Total and direct bilirubin are determined by a conventional diazo method without prior treatment by the enzyme. B delta is determined with a direct diazo method after the serum sample is treated at pH 10.0 by the enzyme to oxidize the Bc fraction. The precision and the accuracy of these methods were compared with a diazo method, an HPLC method and a slide method, and good results were obtained.

Bilirubin↗
PubMed1987

Quantal analysis of potentiating action of phorbol ester on synaptic transmission in the hippocampus.

The mechanism of the potentiating action of phorbol diacetate on synaptic transmission in the hippocampus was studied by the quantal analysis technique. Thin transverse sections were prepared from guinea pig hippocampus and intracellular potentials were recorded from CA3 neurons. Unitary excitatory postsynaptic potentials (EPSPs) were induced in the impaled neurons by brief glutamate pulses administered to granule cells. The amplitude of the unitary EPSPs fluctuated according to Poisson distribution. From the mean and variance of the amplitude of the unitary EPSPs, the mean quantal content (m) and the mean quantal amplitude (q) were calculated. Before phorbol diacetate administration, the values of m and q were 9.7 +/- 1.4 and 1.1 +/- 0.28 mV (mean +/- S.D.), respectively. Potentiation of synaptic transmission by phorbol diacetate was accompanied by increases in the value of m. The value of q remained unchanged in most neurons and decreased in some. These results indicate that the phorbol ester causes an increase in release of neurotransmitter and thereby potentiates synaptic transmission.

Animals↗
PubMed1987

The effect of 7 years of intense exercise training on patients with coronary artery disease.

The purpose of this study was to evaluate the effects of long-term exercise training on maximal aerobic exercise capacity, evidence of myocardial ischemia and plasma lipid-lipoprotein concentrations in patients with coronary artery disease. Nine men with coronary artery disease, aged 57 +/- 2 years, who had completed 12 months of supervised intense exercise training were restudied after 6 additional years during which they continued to exercise. The first 12 months of training resulted in a 44% increase in maximal oxygen consumption (VO2max) from 25.0 +/- 1.3 to 35.9 +/- 1.5 ml X kg-1 X min-1 (p less than 0.001). The VO2max after 6 additional years (total 7 years) of intense training was 36.8 +/- 2.4 ml X kg-1 X min-1. Plasma high density lipoprotein (HDL)-cholesterol concentration increased from 38 +/- 3 to 45 +/- 4 mg X dl-1 at 12 months and rose further to 53 +/- 5 mg X dl-1 at 6 years of follow-up (p less than 0.05). The atherogenic index (total cholesterol/HDL-cholesterol ratio) decreased from 5.8 +/- 0.4 to 4.9 +/- 0.4 by 12 months (p less than 0.01) and to 4.1 +/- 0.4 after 6 additional years of training (p less than 0.05). Although the maximal heart rate-pressure product was 14% higher after 12 months of training, maximal ST segment depression was significantly less, 0.27 +/- 0.06 versus 0.19 +/- 0.04 mV (p less than 0.05); this improvement was maintained after 6 years of additional training. These data provide evidence that the beneficial effects of a program of intense exercise training can be maintained for long periods in some motivated patients with coronary artery disease who continue to exercise.

Blood Pressure↗