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Biomedical subjects

M Maeda

Publications and source records attributed to M Maeda.

At least 37 records · Page 2Linked to original sources
PubMed1992

Effectiveness of planar image and single photon emission tomography of thallium-201 compared with gallium-67 in patients with primary lung cancer.

A comparative study of planar images and single photon emission tomography (SPET) of thallium-201 chloride and gallium-67 citrate was performed in 38 patients with proven primary lung cancer to detect the primary lung tumour and to establish the presence of metastasis in the lung hilum and mediastinum. The findings of planar images and SPET were compared with the pathological findings after thoracotomy. It was shown that 201Tl studies were superior to 67Ga studies for evaluation of the primary lesion and lymph node metastases.

Aged↗
PubMed1992

Intracerebral distribution of albumin after transient cerebral ischemia: light and electron microscopic immunocytochemical investigation.

The blood-brain barrier breaks down following cerebral ischemia, but the exact sequence of events for extravasation of serum proteins and their parenchymal distribution remain uncertain. We studied the distribution of serum albumin in the hippocampus of the gerbil brain using light and electron microscopic immunocytochemical techniques. With light microscopy, there was no reaction for albumin for the first 12 h after unilateral common carotid artery occlusion for 10 min and reperfusion. At 12 h, the reaction was weak and limited to the neuropil in the subiculum-CA1 region (between the subiculum and the medial CA1 region). After 24 h, the reaction became intense in the neuropil and neuronal perikarya in the subiculum-CA1 and medial CA1 regions. The electron microscopic immunocytochemical study of the subiculum-CA1 and medial CA1 regions revealed electron-dense immunoprecipitates in the extracellular space and the peripheral part of the apical dendrites as early as 30 min after reperfusion and in the astrocytic cytoplasm after reperfusion for 1 h. However, immunoprecipitates were not found in the neuronal perikarya until after reperfusion for 24 h. The present study demonstrated prompt appearance of albumin in the extracellular space of the brain parenchyma after re-establishment of cerebral circulation and prompt accumulation in the peripheral part of the dendrites with spreading to neuronal perikarya, likely in the process of degeneration and death.

Animals↗
PubMed1992

Retrograde cerebral perfusion through a superior vena caval cannula protects the brain.

Retrograde cerebral perfusion through a superior vena caval cannula is a new technique for protecting the brain during aortic arch operations. In mongrel dogs (n = 10; 13 to 15 kg) we have performed retrograde cerebral perfusion (300 mL/min) by infusing blood through a superior vena caval cannula with aortic and inferior vena caval drainage. We have measured the cerebral tissue blood flow, oxygen consumption, and carbon dioxide exudation during retrograde cerebral perfusion at normothermia (NT, 37 degrees C) and hypothermia (HT, 20 degrees C) and have compared these values with values obtained in dogs during cardiopulmonary bypass (1,200 mL/min). Cerebral tissue blood flow was measured by the hydrogen clearance method. During retrograde cerebral perfusion about 20% of the superior vena caval perfusate was returned through the aorta and the rest drained from the inferior vena cava. Cerebral vascular resistance during retrograde cerebral perfusion was lower than that during cardiopulmonary bypass (NT, 63.8 +/- 52.5 versus 126.9 +/- 58.4; HT, 28.4 +/- 32.8 versus 69.5 +/- 28.7 x 10(3) dynes.s.cm(-5). Retrograde cerebral perfusion provided half the cerebral tissue blood flow of cardiopulmonary bypass (NT, 14.7 +/- 6.4 versus 34.3 +/- 7.8; HT, 17.6 +/- 5.6 versus 37.2 +/- 10.6 mL/min). Retrograde cerebral perfusion also provided a third of the oxygen (NT, 4.4 +/- 2.1 versus 12.3 +/- 7.1; HT, 1.4 +/- 0.8 versus 4.2 +/- 1.3 mL/min) and discharged 20% of the carbon dioxide (NT, 0.24 +/- 0.08 versus 1.19 +/- 0.58; HT, 0.15 +/- 0.06 versus 0.51 +/- 0.17 mmol/min) when compared with cardiopulmonary bypass. Retrograde cerebral perfusion may reduce ischemic damage during interruption of cerebral blood flow.

Animals↗
PubMed1992

A study on optimal temperature for isolated lung preservation.

Fifty-two heart-lung blocks (grafts) of New Zealand white rabbits were used for determining optimal temperature in lung preservation. Grafts were inflated with room air and preserved by simple surface cooling at arbitrarily determined temperatures for 18 hours. Graft function was assessed by nonrecirculated perfusion with autologous blood. Segmented regression models between functional parameters and preservation temperature (T) were applied for determining optimal temperature. Graft ability was also assessed from the point of view of pulmonary circulation by indocyanine green dilution rate of effluent and histological distribution of carbon particles. Significant segmented regression curves and lines between parameters of effluent oxygen tension (PO2) and wet-dry weight ratio (W/D), and T were obtained as follows: PO2 = 150/(1 + 3208.1[e-1.17T]), p less than 0.01; PO2 = -13.8T + 222.6, p less than 0.05; W/D = 5.0 + 1.5/(1 + 0.0028[e0.94T]), p less than 0.01; W/D = 0.075T + 4.52, p less than 0.05. Optimal temperature for lung preservation by topical cooling was calculated as 8 degrees to 9 degrees C from each intersecting point of regression equations. Analysis of regression curves suggested that the most common hypothermic ischemic injury during preservation by topical cooling is pulmonary vascular obstruction, which might be induced at temperatures lower than the critical temperature of 6 degrees to 7 degrees C. Indocyanine green dilution rate and histological findings supported the results of graft functional parameters.

Animals↗
PubMed1992

Role of the amino terminal region of the epsilon subunit of Escherichia coli H(+)-ATPase (F0F1).

Escherichia coli strain KF148(SD-) defective in translation of the uncC gene for the epsilon subunit of H(+)-ATPase could not support growth by oxidative phosphorylation due to lack of F1 binding to Fo (M. Kuki, T. Noumi, M. Maeda, A. Amemura, and M. Futai, 1988, J. Biol. Chem. 263, 17, 437-17, 442). Mutant uncC genes for epsilon subunits lacking different lengths from the amino terminus were constructed and introduced into strain KF148(SD-). F1 with an epsilon subunit lacking the 15 amino-terminal residues could bind to F0 in a functionally competent manner, indicating that these amino acid residues are not absolutely necessary for formation of a functional enzyme. However, mutant F1 in which the epsilon subunit lacked 16 amino-terminal residues showed defective coupling between ATP hydrolysis (synthesis) and H(+)-translocation, although the mutant F1 showed partial binding to Fo. These findings suggest that the epsilon subunit is essential for binding of F1 to F0 and for normal H(+)-translocation. Previously, Kuki et al. (cited above) reported that 60 residues were not necessary for a functional enzyme. However, the mutant with an epsilon subunit lacking 15 residues from the amino terminus and 4 residues from the carboxyl terminus was defective in oxidative phosphorylation, suggesting that both terminal regions affect the conformation of the region essential for a functional enzyme.

Amino Acid Sequence↗
PubMed1992

The effect of mixed live vaccines of Newcastle disease and infectious bronchitis on the chicken respiratory tract.

The effect of mixed live vaccines of Newcastle disease (ND) and infectious bronchitis (IB) on specific pathogen-free chickens aged 7 days was investigated. The chickens were inoculated intranasally with mixed live vaccines with and without Escherichia coli, or with E. coli alone. "Vaccine 1" consisted of ND virus strain B1 and IB virus strain ON; "vaccine 2" consisted of ND virus strain B1 and IB virus strain H120. The tracheas of chickens inoculated with the vaccines and E. coli and with the vaccines alone showed multiplication of E. coli and histological lesions (loss of cilia, degeneration and hyperplasia in epithelial cells and cellular infiltration of subepithelial tissues). In the tracheas of chickens inoculated with vaccines and E. coli, multiplication of E. coli was greater than in chickens given vaccine alone. There were no histological lesions, and only mild, transient multiplication of E. coli in chickens inoculated with E. coli alone. The results suggest that these mixed live vaccines, especially vaccine 2, play a role in inducing or enhancing colibacillosis in the chicken.

Animals↗
PubMed1992

Data processing for multi-channel optical recording: action potential detection by neural network.

Using a neural network, we have developed a program for fast and precise detection of action potentials (AP) in raw multi-channel optical recording data. The AP detection was performed in two steps: first, peaks were detected in raw optical data, and, second, the peaks were classified by the neural network into APs, noise and undecided peaks. The network was optimized and trained by the backpropagation learning algorithm, employing some thousands of manually classified peaks. The performance of the optimized network was found to be not completely satisfactory, although it was better than the classification by template matching and nearest-neighbor rules. The addition of a signal-to-noise ratio (SNR) of a peak to the network classification improved the classification performance: in comparison with the manual classification results, 96% of manually classified APs were detected. The causes of classification errors were discussed. In spite of the fact that the program required a slight amount of human intervention for undecided peaks, the program could allow mostly automatic AP detection.

Action Potentials↗
PubMed1992

Sympathetic and metabolic mechanisms of the cerebrovasomotor function of the caudal ventrolateral medulla in rats.

We attempted to elucidate the cerebrovasomotor function of the caudal ventrolateral medulla. Sixty-one rats were anaesthetized, paralysed and artificially ventilated. The microsphere method was employed for the measurement of blood flow. Microinjection of an antagonist of excitatory amino acids, kynurenate (2 nmol), into functionally identified depressor sites within the caudal ventrolateral medulla produced arterial hypertension of about 140 mmHg. We found that the cerebral blood flow was substantially increased, but was maintained at the same level (17 rats) as that observed under phenylephrine-induced hypertension (26 rats). Bilateral severing of the cervical sympathetic trunks resulted in a further increase in blood flow in all brain regions studied (18 rats). The response was most significant in the cerebral parasagittal cortex (164 +/- 31% of baseline without, and 211 +/- 43% with sympathectomy; mean +/- S.D.; P < 0.001). The contributions of the cerebral metabolic mechanism to this flow increase under denervation was minimal, as evidenced by the observation of disproportionately smaller changes in cerebral metabolic rate for oxygen during any type of hypertension. We conclude that the cerebrovasomotor functions of the caudal ventrolateral medulla may operate to keep an equilibrium between simultaneously working tonic inhibitions against sympathetic vasoconstriction as well as against vasodilatation. This dual effect is mediated by excitatory amino acid receptors located within this particular brain area. The vasodilator mechanism may be of neurogenic origin. When the function of the brain area is suppressed, the subsequently disinhibited vasodilator mechanism dominates the cerebrovascular autoregulatory function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Synthesis and biodistribution of a fluorine-18 labeled analogue of D-talose: 2-deoxy-2-[18F]fluoro-D-talose.

A fluorine-18 labeled analogue of D-talose, 2-deoxy-2-[18F]fluoro-D-talose ([18F]FDT), was synthesized via nucleophilic fluorination with [18F]fluoride ion and its biodistributions in animals were examined. Radiofluorination of benzyl 3,5,6-tri-O-benzyl-2-O-(trifluoromethanesulfonyl)-alpha-D-galac tof uranoside (5) with aminopolyether supported potassium [18F]fluoride (K18F/Kry222) in acetonitrile followed by deprotection of the [18F]fluorinated intermediate (6) with boron tribromide in CH2Cl2 gave [18F]FDT in an average radiochemical yield of 29% with a radiochemical purity greater than 98%. Biodistribution studies of [18F]FDT in mice bearing fibrosarcoma showed the highest uptake of radioactivity in the liver (34.9% dose/g), followed by the kidney (15.9%dose/g), the small intestine (12.9%dose/g) and fibrosarcoma (5.7%dose/g), at 30 min after i.v. administration. Although the radioactivity in the kidney and small intestine decreased with time, the uptake in the liver and the tumor slightly increased until 120 min. The high liver uptake of [18F]FDT was also observed in normal rats and this uptake was strongly inhibited by co-administration of D-galactose. These preliminary results suggest that [18F]FDT might be metabolized through the galactose metabolic pathway as analogously observed with 2-deoxy-2-[18F]fluoro-D-galactose which is an isomer with respect to carbon-2 of [18F]FDT, and that it may be another candidate for studying liver function by positron emission tomography.

Animals↗
PubMed1992

Positron labeled antioxidants: synthesis and tissue biodistribution of 6-deoxy-6-[18F]fluoro-L-ascorbic acid.

A one-pot synthesis of 6-deoxy-6-[18F]fluoro-L-ascorbic acid (18F-DFA) has been developed via nucleophilic displacement of a cyclic sulfate with no-carrier-added [18F]fluoride ion. Isolated radiochemical yields of around 15% were obtained with radiochemical purity of over 99% after overall synthesis time of 90 min. Tissue distribution studies with 18F-DFA in rats showed high uptake of radioactivity in the adrenals, kidneys, liver and small intestine--organs known to have high concentrations of L-ascorbic acid. The slow and low uptake of radioactivity in the brain was observed between 10 and 120 min after i.v. injection. In vivo behavior of 18F-DFA in mice bearing 3-methylcholanthrene-induced fibrosarcoma demonstrated its ability to accumulate in the tumor.

Animals↗
PubMed1992

In vitro comparison of the spiral Z stent and the Gianturco Z stent.

A new spiral Z stent is described, and its characteristics are compared in vitro with those of the modified Gianturco Z stent. The spiral Z stent has a more uniform expansile force throughout its effective length; is more compressible, thus allowing for use of a smaller introductory catheter; and is more stable than the modified Z stent. Flexibility of both stent types is similar. Advantages of the spiral Z stent promise to be beneficial for clinical use.

Equipment Design↗
PubMed1992

Silicone-covered expandable metallic stents in the esophagus: an experimental study.

Modified silicone-covered Gianturco expandable metallic stents were placed in the normal esophagus of six young pigs. Following endoscopic examination, the stents were placed using endoscopic and fluoroscopic control. The animals were observed for eating behavior and weight gain. Stents appeared to be tolerated well based on these parameters. Three stents remained in position for the full study period, and three stents migrated into the stomach during the study. The pigs were sacrificed at four weeks and postmortem examination performed. Esophageal wall thickening and nodular inflammation were noted at the sites where the wire skirts penetrated the mucosa. Injury was limited to the region of the wire skirts and there was no injury due to the radial force of the stent body. There was no free perforation. This preliminary study suggests that endoscopic and fluoroscopic placement of modified silicone-covered Gianturco stents in the esophagus is feasible and safe. More extensive animal studies, followed by clinical investigation for palliation of malignant strictures, are warranted.

Animals↗
PubMed1992

Effect of colostomy on the utilisation of dietary nitrogen in the fowl fed on a low protein diet.

1. The effect of the inhibition of urine back-flow into the colon and caeca by colostomy on the utilisation of dietary nitrogen by fowls fed on a low protein diet and receiving free or restricted water supply was investigated. 2. Colostomy caused an increase in water excretion and a resultant increase in water intake to maintain water balance. 3. Colostomy tended to decrease nitrogen balance and nitrogen utilisation (N balance/N intake) to negative values, and these decreases became significant when water was restricted (P less than 0.05). 4. Excretory uric acid, ammonia, urea and total nitrogen were significantly increased after colostomy in water-restricted fowls (P less than 0.05), but such significant effects were not observed, except for ammonia, in fowls given water ad libitum. 5. It is concluded that the back-flow of urine into the caeca plays a significantly useful role in the utilisation of nitrogen in the fowl fed on a low protein diet especially when water intake is restricted.

Animals↗
PubMed1992

Occurrence of intraportally-infused urea-15N in the urine of domestic fowl.

1. Measurements were made in situ to determine the occurrence of intraportally infused urea-15N in ureteral urine of the fowl. 2. Of the total amount of infused urea-15N, 15% was excreted intact into the urine (90% of urinary total 15N) whereas 9% remained unchanged in the blood (78% of blood non-protein-15N). 3. The proportions of non-protein-15N in the blood, liver and kidney were 12, 3 and 1%, respectively of the infused 15N. Protein-15N was 3% of that infused in blood and much less in liver and kidney. 4. About 1% of the infused 15N was observed in the urinary uric acid, and 3% of the infused 15N in non-protein N, other than urea, ammonia and glutamine amide N, of blood and liver. 5. No appreciable amounts of 15N were present in ammonia and glutamine amide N of blood, liver or kidney and in uric acid of liver or kidney. 6. The caecal contents contained about 1% of the infused 15N with 15% of this as ammonia-15N. 7. It is concluded that intraportal urea is mostly excreted unchanged into ureteral urine of the fowl.

Animals↗
PubMed1992

Dipeptidyl peptidase IV as a differentiation marker of the human endometrial glandular cells.

To investigate the involvement of membrane-bound peptidases in the human endometrial function, we examined the expression of dipeptidyl peptidase (DPP) IV and its enzyme activity. Immunohistological studies revealed that DPP IV was detected on human endometrial glandular cells and endometrial surface epithelium, but not on endometrial stromal cells or decidual cells in the first trimester of pregnancy. DPP IV expression on glandular cells and surface epithelium was weak in the proliferative phase, began to increase gradually in the early secretory phase, and was strong in mid-to late secretory phase and in the first trimester of pregnancy. DPP IV enzyme activity was detected histochemically in glandular cells and surface epithelium in the mid-secretory phase, and became stronger in the late secretory phase, but was rarely detected in the proliferative phase and early secretory phase. During the first trimester of pregnancy DPP IV enzyme activity in glandular cells and surface epithelium was slightly weaker than in the late secretory phase. Endometrial stromal cells and decidual cells, however, had no detectable DPP IV enzyme activity at any time throughout the menstrual cycle or during the first trimester of pregnancy. These findings indicate that DPP IV is a differentiation marker for glandular cells and surface epithelium and that active DPP IV is present in both areas during the peri-implantation period and thereafter.

Adult↗
PubMed1992

Expression of aminopeptidase N and neutral endopeptidase on the endometrial stromal cells in endometriosis and adenomyosis.

Indirect immunofluorescence staining revealed that endometrial stromal cells (ESC) in the ectopic endometrium of patients with endometriosis or adenomyosis expressed aminopeptidase N/cluster of differentiation (CD) 13 antigen and neutral endopeptidase/CD10 antigen, both of which are expressed on ESC in the normal endometrium throughout the menstrual cycle. Thus, ESC in the ectopic endometrium resembled ESC in the normal endometrium not only morphologically but also antigenically. Both peptidase antigens may be useful markers for the histological diagnosis of endometriosis and adenomyosis.

Adult↗