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Biomedical subjects

A Yoshida

Publications and source records attributed to A Yoshida.

At least 307 records · Page 17Linked to original sources

Heart rate variability before spontaneous episodes of ventricular tachycardia originating from right ventricular outflow tract in patients without organic heart disease.

Ventricular tachycardia (VT) originating from the right ventricular outflow tract (RVOT) has been reported to be induced by exercise or isoproterenol and is considered to be related to catecholamines. This study was designed to examine the role of autonomic tone in spontaneous episodes of VT originating from RVOT. High frequency (HF; peak power of 0.20-0.40 Hz) and low frequency (LF; peak power of 0.05-0.15 Hz) spectral components of heart rate variability were calculated from RR intervals in a 30-min period before 33 episodes of VT during 24-h Holter monitoring in 8 patients. One VT episode was sustained, 20 were incessant and 12 were nonsustained. The ratio of LF and HF power and heart rate increased significantly from 8 min before the onset of VT, whereas the HF power gradually decreased but this decrease did not reach the statistical significance. In conclusion, an increase of the ratio of LF and HF power preceding VT suggests that activation of sympathetic tone plays an important role in the occurrence of VT originating from the RVOT.

Adolescent↗

Role of N-acetylglutamate turnover in urea synthesis by rats treated with the thyroid hormone.

We determined whether the synthesis and degradation of N-acetylglutamate would regulate urea synthesis when the thyroid status was manipulated. Experiments were done on three groups of rats, each being given 6-propyl-2-thiouracil (PTU, a thyroid inhibitor) without a triiodothyronine (T3) treatment, treated with PTU + T3, or receiving neither PTU nor T3 (control). The plasma concentration and urinary excretion of urea, the liver concentration of N-acetylglutamate, and the liver N-acetylglutamate synthesis in rats given PTU alone were each significantly higher than in the control rats. Compared with the control rats, the liver N-acetylglutamate degradation was significantly lower in those rats given PTU without the T3 treatment. Treatment of the PTU-treated rats with T3 reversed the effects of PTU to the values of the control rats. N-Acetylglutamate synthesis in the liver was closely correlated with the excretion of urea, and inverse correlation between the liver N-acetylglutamate degradation and urea excretion was found. These results suggest that the greater synthesis and lower degradation of N-acetylglutamate in the hypothyroid (PTU alone) rats would be likely to increase the hepatic concentration of this compound and stimulate urea synthesis.

Animals↗

Different expression of Tn and sialyl-Tn antigens between normal and diseased human gastric epithelial cells.

Thomsen-Friedenreich antigen (T antigen) has been supposed to be a cancer-specific carbohydrate antigen. We have previously shown that one third of the Japanese population normally expressed T antigen in gastric surface epithelia and the other two thirds expressed fucosyl-T antigen. Their sialylation and blocked-synthesis were associated with diseased conditions. In the present study, we studied gastric surface epithelial expression of monosaccharide antigen Tn, i.e., a precursor of T antigen, and sialyl-Tn. Normal fundic and pyloric epithelia, respectively, expressed Tn supranucleally and cytoplasmically, but did not express sialyl-Tn. In the intestinal metaplasias and intestinal-type adenomas, goblet cells expressed sialyl-Tn in their vacuoles, and absorptive cells expressed Tn apically. In gastric-type adenomas, Tn, but not sialyl-Tn, was detected. Intestinal-type cancers expressed Tn and sialyl-Tn more often than the diffuse-type cancers. Five cancers did not express Tn, sialyl-Tn, or the T-related antigens. In these, four were diffuse-type cancers. We concluded that: a) normal gastric epithelial cells express Tn; b) metaplastic differentiation is associated with sialylation of Tn and c) expression of Tn and sialyl-Tn is depressed in the gastric cancers.

Adenoma↗

Studies of repeated administration of FK-506 on myocardial metabolism in rats.

The effect of a 14-day administration of FK-506 at 1 or 3 mg/kg on plasma lipids and myocardial energy and glucose metabolism in rats was investigated. FK-506 increased the level of blood glucose in rats when given daily at an oral dosage of 3 mg/kg for 14 days. The plasma level of total cholesterol was significantly increased by FK-506 at either 1 or 3 mg/kg, whereas that of triglyceride was not changed. There was no significant difference in energy charge potential and the lactate/pyruvate ratio of the myocardial tissue between FK-506- and solvent-treated groups. Because FK-506 administration for 14 consecutive days did not disturb myocardial energy and glucose metabolism, its cardiotoxic side effects were not recognized in the present experimental toxicological evaluation of rats.

Animals↗

Hematuria in patients with renal hypouricemia.

The characteristics of urate metabolism in renal hypouricemic patients with hematuria were studied to clarify the risk factors for hematuria in patients with renal hypouricemia. In 16 Japanese patients with isolated renal hypouricemia, urate metabolism was measured using the urate clearance study and the subtype of renal hypouricemia [defective presecretory reabsorption (Pre), defective postsecretory reabsorption (Post), enhanced tubular secretion (Secretion) and defective presecretory and postsecretory reabsorption (Pre&Post)] were determined by the pharmacological tests. Hematuria was seen in 7 out of the 16 patients (44%), all of whom were females (58%). Serum urate and urinary urate concentrations were significantly higher in the group with hematuria (Sur = 1.76 +/- 0.31 mg/dl and Uur/Ucr = 0.75 +/- 0.12: p<0.05) than in the group without hematuria (Sur = 1.44 +/- 0.46 mg/dl and Uur/Ucr = 0.56 +/- 0.04), although there was no difference in the urate excretion rate between the two groups. Hematuria was more likely to be accompanied by Post (75%) and Secretion (75%), which showed significantly higher urinary urate concentration (Uur/Ucr = 0.75 +/- 0.1 and 0.69 +/- 0.13, respectively) than by Pre (25%) and Pre&Post (0%), which showed lower urinary urate concentration (0.61 +/- 0.06 and 0.62 +/- 0.05, respectively). The risk factors for hematuria in patients with renal hypouricemia are the elevation of urinary urate concentration and the subtypes of Post and Secretion.

Adult↗

Heart failure in 3 patients with acromegaly: echocardiographic assessment.

We evaluated 3 patients with acromegaly who developed heart failure. Heart failure appeared to be due to acromegalic cardiomyopathy in 2 patients who did not have hypertension or evidence of coronary artery disease, and it was possibly due to acromegalic cardiomyopathy combined with familiar hypertrophic cardiomyopathy in 1 patient. The common echocardiographic findings in the present three cases were: 1) enlargement of the left atrium, 2) markedly dilated left ventricular cavity with diffuse hypokinesis, 3) decrease of indices of the left ventricular systolic function, and 4) no evidence of left ventricular hypertrophy. Echocardiographic findings in acromegaly with congestive heart failure resemble those of idiopathic dilated cardiomyopathy.

Acromegaly↗

Excess urate excretion correlates with severely acidic urine in patients with renal hypouricemia.

We evaluated the renal handling of urate in 12 Japanese renal hypouricemia patients, and studied the relationship between the renal handling of urate and the urinary pH. The patients were classified into the 4 subtypes of renal hypouricemia: (defective presecretory reabsorption (Pre), defective postsecretory reabsorption (Post), enhanced tubular secretion (Secretion), and defective presecretory and postsecretory reabsorption (Pre&Post) as based on a pharmacological test. Seven patients showed acid urine with a urinary pH of less than 5.9, although this was not accompanied by any abnormality of blood pH, partial pressure of carbon dioxide (PaCO2), or blood HCO3-. The urinary pH in the morning significantly correlated with the ratio of urate clearance to creatinine clearance in the morning, whereas the urinary urate concentration in the morning did not correlate with the urinary pH in the morning. In the Pre&Post patients, the urate excretion was higher and the urinary pH was more acidic compared to the other subtypes. The administration of K+-, Na+-citrate significantly alkalized the urinary pH in the patients with renal hypouricemia. These results suggest that the acidic urine was significantly related to the Pre&Post subtype of renal hypouricemia with the higher urate excretion, and that this subtype might be a risk factor for complications in renal hypouricemia. The alkalization of urine might be a useful treatment for the complication of renal hypouricemia.

Adult↗

Effect of posture change on control of ventilation.

To clarify the control mechanism of ventilation during posture change, ventilatory parameters, PETCO2, and ventilatory response to CO2 were examined in 11 healthy male subjects at supine (0 degrees) and 75 degrees head-up tilt positions. Minute expiratory ventilation (V.E), tidal volume (VT), respiratory frequency (f), end-tidal and transcutaneous PCO2 and CO2 output (V.CO2), and ventilatory response to CO2 were measured during a steady state condition. V.E (V.A) and VT increased significantly at 75 degrees tilt with significant decrease in PETCO2 from 40.1 mmHg (0 degrees) to about 36.1 mmHg (75 degrees). Transcutaneous PCO2 also decreased during tilt, by 3.3 mmHg. Physiological dead space (VD/VT) and V.CO2, however, remained unchanged, and ventilatory equivalent (V.E/V.CO2, V.A/V.CO2) increased significantly. The CO2-ventilatory response curve shifted upward (or leftward) without significant change in the response slope. At 75 degrees tilt, EMG activity of gastro-cnemius muscle increased. These findings suggested that PETCO2 decreased because of increased V.E (V.A) with a leftward shift of CO2-ventilatory response curve. Various signals such as afferents from lower extremities might have net stimulatory effects on a CO2-ventilation control system to reset the controlled level of PETCO2 to a lower range, but without significant change in CO2-ventilatory response during upright position.

Adult↗

Effects of intracoronary caffeine on left ventricular mechanoenergetics in Ca2+ overload failing rat hearts.

How different the effects of caffeine on cardiac mechanoenergetics in failing hearts are from those of normal hearts remains to be fully elucidated. First we successfully instituted a new experimental model of acute mild heart failure in the rat by 0.005 mM Ca2+ Tyrode perfusion. These failing hearts neither decreased left ventricular end-systolic pressure nor increased left ventricular end-diastolic pressure, indicating unchanged left ventricular mechanics. However, their myocardial mitochondrial respiratory function examined by respiratory control index (RCI) and oxygen consumption rate in state III (State III O2) was significantly depressed compared with normal hearts. From these results, we judged that this Ca2+ protocol could make mild Ca2+ overload acute failing hearts and that this model would be appropriate for comparing the effects of caffeine on cardiac mechanoenergetics between normal hearts and these failing hearts. We investigated the effects of caffeine on cardiac mechanoenergetics above a concentration of 0.05 mM that corresponds to the maximum blood concentration after a healthy human subject drinks a cup of coffee or tea. We obtained results indicating that caffeine depressed left ventricular systolic and diastolic functions and decreased a measure of total mechanical energy per beat in terms of systolic pressure-volume area (PVA) more severely in these failing hearts at concentrations (20-fold higher than the concentration in a cup of coffee) lower than those in normal hearts. This result implies that these acute failing hearts are Ca2+ overloaded.

Animals↗

Subarachnoid hemorrhage caused by Aspergillus aneurysm as a complication of transcranial biopsy of an orbital apex lesion--case report.

A 62-year-old male complaining of unilateral visual disturbance and pain in the involved eye had a small mass at the right orbital apex which was identified as an Aspergillus granuloma by transcranial biopsy. One month later, the patient became comatose because of fatal subarachnoid hemorrhage due to a newly developed aneurysm. Autopsy showed a ruptured aneurysm on the right internal carotid-posterior communicating artery. Histological examination demonstrated prominent Aspergillus invasion of the arterial wall. Aspergillus infection must be taken into consideration in patients with orbital apex syndrome, which may lead to serious cerebrovascular consequences. If sino-orbital lesions are detected by neuroimaging techniques, biopsy using an extradural approach should be performed to obtain a definitive diagnosis.

Aneurysm, Infected↗

The use of scanning laser ophthalmoscope microperimetry to detect visual impairment caused by macular photocoagulation.

BACKGROUND AND OBJECTIVE: To demonstrate the effectiveness of scanning laser ophthalmoscope (SLO) microperimetry in detecting retinal sensitivity and in describing areas of unstable fixation following photocoagulation therapy. PATIENTS AND METHODS: Two patients with iatrogenic vision loss resulting from photocoagulation therapy underwent a fundus examination, SLO microperimetry, and fluorescein angiography. One patient also underwent indocyanine green angiography. RESULTS: Two types of visual acuity decrease--sudden-onset and late-onset--were demonstrated following macular photocoagulation, the former resulting from incorrect identification of the fixation point, and the latter from enlarging photocoagulation scars placed in close proximity to the fovea. In one case, SLO microperimetry detected dense scotoma corresponding to the patient's symptoms and an unstable fixation point. In the other case, different retinal sensitivities were found in the photocoagulation scars. No differences were found with fluorescein angiography or indocyanine green angiography. CONCLUSION: SLO microperimetry might be effective for quantitative assessment of retinal sensitivity in photocoagulation scars and for detecting fixation points and determining their stability.

Diabetic Retinopathy↗

Expression of Shaker-type voltage-gated potassium channel genes in the guinea-pig.

Few potassium channel genes have been isolated in the guinea-pig despite detailed electrophysiological characterization of potassium channels in the guinea-pig heart. We obtained partial clones of Shaker-type potassium channel genes in the guinea-pig and demonstrated their tissue distribution. Partial clones of the Shaker-type potassium channel genes were obtained by RT-PCR or genomic PCR. mRNA expression was measured by RNase protection assays in the heart, brain, and skeletal muscle. Three of the five obtained channel genes were expressed in the guinea-pig heart; Kv1.2, Kv1.3, and Kv1.6. Kv 1.6 expression was markedly at a higher level in the atrium than in the ventricle. Expression of the channel genes in the guinea-pig was different from that in human and rat, which may contribute to the species-specific action potential waveform.

Animals↗

[The importance of informed consent in the field of ophthalmology].

Ocular diseases have some characteristics that are different from diseases of other organs. First, patients clearly can judge for themselves whether or not they can see better postoperatively. Second, because several parameters such as visual acuity and intraocular pressure, are obtained from patients, patient's families and others can objectively judge the post-treatment status. Therefore, clinical information is easily available to others besides the physician. Third, except for acute ocular diseases such as retinal detachment, acute glaucoma, and ocular trauma that easily can result in blindness, ophthalmologists usually treat eyes that will maintain a certain visual acuity level. These are the primary reasons why patients and families complain about unfavorable post-treatment subjective symptoms. Because of these three characteristics of ocular disease, informed consent (IC) is extremely important in the field of ophthalmology. I studied ophthalmology and IC at Harvard Medical School, Boston, from 1980 to 1983, and again in 1989. Strict IC is mandatory in the United States. However, the concept of IC in the US cannot always be adapted to fit Japanese culture. The different legal concepts of IC in the two countries are discussed in this paper. Since I returned to Japan, our Department of Ophthalmology incorporated several new concepts into our clinical practice. For example, we now broadcast live surgeries of patients with severe proliferative diabetic retinopathy by closed-circuit TV to their families in the hospital. This has fostered great communication and confidence among patients, their families, and doctors. In 1994, we also began inter-hospital and international IC via telemedicine and telescience. The video conferencing system VisionSeries (Panasonic Broadcast and Television System Company) is used to communicate between Asahikawa Medical University and 10 branch hospitals. INS net 1500 or INS net 64 (3 lines) transmits full-motion (30 frames/second) color fundus images and biomicroscopic images. Ocular surgeries performed by ophthalmologists using operating microscopes at each branch hospital also are transmitted to Asahikawa Medical University to facilitate consultation with more experienced ophthalmologists. The transmitted images of the fundus and biomicroscopic findings are satisfactory, and they allow surgeons to conduct useful discussions among themselves and with the family members during the surgeries in real time. When the patients' families are in local cities, surgeons can transmit the operations via the telemedicine system link to the nearby hospital, and the ophthalmologists there can narrate the surgeries in real time. On November 14, 1996, our technology was used internationally for the first time to transmit ocular images and live ocular surgeries between Asahikawa Medical University, Japan, and the Schepens Eye Research Institute, Harvard Medical School, Boston, MA, USA. Telemedicine and telesurgery will be useful scientific tools in the field of Ophthalmology in the near future. We believe that this technology literally opens up the world to scientific and medical collaboration. Patients with vision deficiencies and blinding disease are certain to be the ultimate beneficiaries of these interactions. Lastly, ideal implementation of IC in the field of Ophthalmology are discussed in this paper.

Cataract Extraction↗

Role of NF-kappaB-mediated interleukin-8 expression in intraocular neovascularization.

PURPOSE: To investigate the role of interleukin (IL)-8 in intraocular neovascularization and the mechanism of its production. METHODS: Interleukin-8 was measured with enzyme-linked immunosorbent assays in vitreous and aqueous fluid obtained from patients with neovascular diseases. Localization of IL-8 was examined by immunohistochemistry. An in vitro angiogenesis assay was performed on collagen gels, by using bovine aortic endothelial cells to determine the effect of the vitreous fluid. In bovine retinal glial cells under hypoxia, NF-kappaB activation was evaluated by immunoblot analysis and by electrophoretic mobility shift assay, and IL-8 and vascular endothelial growth factor (VEGF) mRNA expression was determined by semiquantitative reverse transcription-polymerase chain reaction. RESULTS: The concentration of IL-8 in vitreous fluid of patients with retinal neovascularization was significantly higher than that of patients without neovascular disease. Interleukin-8 immunostaining was detected in vascular endothelial cells and glial cells in the retinas with neovascularization. Vitreous fluid with high concentrations of IL-8 induced tubular morphogenesis in endothelial cells, and this effect was inhibited to a similar extent by neutralizing antibodies to IL-8 or to VEGF. In glial cells, in vitro, hypoxia induced NF-kappaB activation and increased IL-8 and VEGF mRNA. Furthermore, pyrrolidine dithiocarbamate, a specific inhibitor of NF-kappaB activation, prevented the induction of the IL-8 gene, but not that of the VEGF gene. CONCLUSIONS: These results suggest that IL-8 induced by hypoxia and mediated by NF-kappaB may contribute to the pathogenesis of intraocular neovascularization.

Animals↗

[Improvement of detectability of microcalcifications by magnification digital mammography].

Our aim in this study was to evaluate the potential utility of magnification mammography with a CR system by investigating the basic imaging parameters and detectability of microcalcifications in comparison with those of conventional screen-film systems. The basic imaging parameters were evaluated by measuring scatter fraction, modulation transfer function (MTF), Wiener spectrum, and incident dose for the various magnification factors. The detection of simulated microcalcifications in radiographs of a mammographic phantom and breast specimens were evaluated subjectively and quantitatively for screen-film and CR techniques with various magnification factors. The scatter fraction of digital magnification mammography decreased with increasing magnification factor. MTF of magnification digital mammography improved with increasing magnification factor. The detectability of microcalcifications with the CR system was significantly improved by magnification technique. From the above results, it is expected that the use of magnification mammography with a CR system will improve the detectability of microcalcification.

Breast Diseases↗

Expression of human aldehyde dehydrogenase-3 associated with hepatocellular carcinoma: promoter regions and nuclear protein factors related to the expression.

The human ALDH3 gene is constitutively expressed in stomach, lung, esophagus, and cornea, but hardly detectable in the normal liver. However, it is highly activated in the hepatocellular carcinoma tissues from approximately 50% of patients. The nuclear DNA binding factors exist in both ALDH3-positive cancerous liver and ALDH3-positive HepG2 cells, but not in ALDH3-negative Hep3B cells and normal liver tissues. South-western blot hybridization showed the existence of two nuclear-binding protein components, 35 and 14 kDa, in ALDH3-positive cancerous liver tissues. These two DNA binding proteins were not found in normal stomach tissues and stomach carcinoma KATO III cells. DNaseI footprint analysis identified two protective regions within the ALDH3 promoter. The first protected region has one putative CCAAT-box and one putative Sp1-site. The second protected region contains a putative HiNF-A binding sequence. These findings suggest that a high level of expression of ALDH3 in cancerous liver tissues resulted from the expression or activation of at least two nuclear proteins reacting to the ALDH3 promoter region.

Alcohol Dehydrogenase↗

[Tuberculosis of the endocrine system].

Tuberculosis now rarely affects the endocrine system. Adrenal tuberculosis is responsible for Addison's disease, but now fewer cases are affected. Although the symptoms and signs of Addison's disease appear when most of the adrenal glands have been functionally destroyed, adrenal tuberculosis results in not only chronic adrenal insufficiency but also acute adrenal failure. Dissemination of M. tuberculosis is responsible for adrenal tuberculosis, other tuberculous lesions (including the past lesions) should be evaluated. Bilateral adrenal calcification and/or enlargement which are often pointed out on abdominal CT, are important signs of adrenal tuberculosis. Thyroid gland is rarely affected, but thyroid function impairment is uncommon even if it is affected. Hypopituitarism due to intracranial tuberculoma or tuberculous meningitis are also reported. Tuberculosis of the endocrine system is a part of disseminated infection, so it should not be overlooked in miliary spread tuberculosis.

Adrenal Gland Diseases↗

Identification of gamma-aminobutyric acid-immunoreactive axon endings associated with mesencephalic periodontal afferent terminals and morphometry of the two types of terminals in the cat supratrigeminal nucleus.

A previous study has shown that mesencephalic periodontal afferent terminals receive contacts more frequently from axonal endings containing pleomorphic, synaptic vesicles (P-endings) in the supratrigeminal nucleus (Vsup) than in the trigeminal motor nucleus, suggesting that interneurons in Vsup play an important role in modulating the jaw-closing reflex. The present study was attempted to identify neurotransmitters in P-endings associated with mesencephalic periodontal afferents in cat Vsup through the use of intracellular staining of horseradish peroxidase combined with the postembedding immunogold methods. A morphometric analysis was carried out to compare the ultrastructural features of these two types of terminals. Serial sections of 31 labeled boutons and of their associated 38 P-endings were examined. They were processed for postembedding immunogold labeling with antibodies to the neurotransmitter gamma-aminobutyric acid (GABA). The 38 P-endings presynaptic to periodontal afferents showed GABA-like immunoreactivity, but the afferent terminals were free from the labeling. The morphometric analysis indicated that bouton volume, apposed surface area, total active zone size, and mitochondrial volume were smaller in GABA-immunoreactive P-endings than in periodontal afferents, but the pooled data of the two types of terminals showed that each synaptic parameter was highly correlated in a positive, linear manner with bouton volume. These observations provide evidence that P-endings presynaptic to mesencephalic periodontal afferents contain the neurotransmitter GABA and that their axoaxonic synapses are organized in accordance with the ultrastructural "size principle" proposed by Pierce and Mendell (Pierce and Mendell [1993] J. Neurosci. 13:4748-4763) on Ia-motoneuron synapses.

Animals↗