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Biomedical subjects

Y Sakurai

Publications and source records attributed to Y Sakurai.

At least 253 records · Page 14Linked to original sources
PubMed1997

Soldering strength of post-soldering of palladium-based metal-ceramic alloys.

To evaluate the post soldering of metal-ceramic alloys that have palladium as their main component, palladium-based metal-ceramic alloys with different compositions were used to assess soldering strength. Four palladium-based metal ceramic alloys were selected: Pd-Cu system, Pd-Ag system, Pd-Ni system, and Pd-Sb system, and gold-silver-palladium alloy was also used. As soldering materials, 12 k gold solder and 16 k gold solder were used. After post-soldering by butt joint samples that had been heat treated (equivalent to the porcelain firing cycle), soldering strength was evaluated by measuring the flexural strength. The yield strength had a range of 300 to 800 MPa, and the ultimate strength was in the range of 350 to 1,000 MPa; the Pd-Ag type showed the highest value. There was no correlation between the yield strength of the metal-ceramic alloys and that of the soldering samples. When the soldering strength of 12 k gold solder and 16 k solder were compared, the samples soldered with 12 k gold solder showed higher values in all cases. Samples in which heating was prolonged for 10 seconds had a high strength, within 100 to 500 MPa in yield strength and 100 to 800 MPa in ultimate strength.

Analysis of Variance↗
PubMed1997

Corrosion resistance of the soldering joint of post-soldering of palladium-based metal-ceramic alloys.

To evaluate the corrosion resistance of post soldering of metal-ceramic alloys, four commercially available palladium-system metal-ceramic alloys (Pd-Cu, Pd-Ni, Pd-Ag, and Pd-Sb systems) and two types of solder (12 k gold solder and 16 k gold solder) with different compositions and melting points were used. The corrosion resistance of the soldered joint was evaluated by anodic polarization. The electrochemical characteristics of soldered surface were measured using electrochemical equipment. Declines in corrosion resistance were not detectable with Pd-Cu, Pd-Ag and Pd-Sb types, but break down at low potential occurred with Pd-Ni type.

Corrosion↗
PubMed1996

Complete amino acid sequence and identification of the platelet glycoprotein Ib-binding site of jararaca GPIb-BP, a snake venom protein isolated from Bothrops jararaca.

Jararaca GPIb-BP, a snake venom protein composed of alpha and beta subunits purified from Bothrops jararaca, binds to platelet glycoprotein (GP)Ib and functions as a receptor blocker for von Willebrand factor binding to GPIb (Fujimura, Y., Ikeda, Y., Miura, S., Yoshida, E., Shima, H., Nishida, S., Suzuki, M., Titani, K., Taniuchi, Y., and Kawasaki, T. (1995) Thromb. Haemostasis 74, 743-750). We present here the entire 142- and 123-residue amino acid sequence of the respective alpha and beta subunits and also demonstrate that the platelet GPIb-binding site resides on the beta and not on the alpha subunit based on an enzyme-linked immunosorbent assay using biotin-labeled jararaca GPIb-BP and competing ligands. Sequences of the alpha and beta subunits were determined by analysis of the intact S-pyridylethylated proteins and their peptides generated by digestion with Achromobacter protease I, Staphyloccocus aureus V8 protease, pepsin, endoproteinase Asp-N, or L-1-tosylamino-2-phenylethyl chloromethyl ketone-trypsin. A 38-39% identity of amino acid sequence between the alpha and beta subunits of jararaca GPIb-BP was observed, as well as a high degree of sequence identities (38-64%) with the respective subunits of botrocetin (Usami, Y., Fujimura, Y., Suzuki, M., Ozeki, Y., Nishio, K., Fukui, H., and Titani, K (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 928-932) and the beta-chain of echicetin (Peng, M., Holt, J. C., and Niewiarowski, S. (1994) Biochem. Biophys. Res. Commun. 205, 68-72).

Amino Acid Sequence↗
PubMed1996

Inhibition assay for the binding of biotinylated von Willebrand factor to platelet-bound microtiter wells in the presence of ristocetin or botrocetin.

We developed a solid-phase inhibition assay for the binding of biotinylated von Willebrand factor (vWF) to platelet glycoprotein (GP)Ib based on an enzyme-linked immunosorbent assay (ELISA) with platelet-bound microtiter wells. Washed platelets were immobilized onto the microplates via the anti-GPIIb/IIIa monoclonal antibody (mAb) VNR-5. In the presence of an antibiotic ristocetin (1 mg/ml, final) or the snake venom botrocetin (2 micrograms/ml, final), biotinylated vWF bound to the affixed platelets with half-maximal binding occurring at a vWF concentration of approximately 2 micrograms/ml. Several specific inhibitors of the binding of vWF to GPIb abolished the interaction of biotinylated vWF with GPIb in a dose-dependent fashion, with comparable protein concentrations to those seen in the liquid-phase inhibition assay using 125I-vWF. These inhibitors included mAb against vWF (NMC-4), mAb against GPIb (AP-1), and two vWF fragments containing vWF's putative GPIb-binding domain, namely a 39/34-kDa dispase-digested vWF fragment and a recombinant vWF fragment. Thus, this new assay is a convenient alternative to the conventional inhibition assay using 125I-vWF.

Anti-Bacterial Agents↗
PubMed1996

K-ras point mutations in cancerous and noncancerous biliary epithelium in patients with pancreaticobiliary maljunction.

BACKGROUND: Pancreaticobiliary maljunction (PBM), an anomalous union of the pancreatic duct with the common bile duct, has frequently been shown to be associated with biliary carcinoma. However, the mechanism of carcinogenesis is unknown. METHODS: Mutations of the K-ras oncogene were examined in cancerous and noncancerous biliary tract epithelium of 20 patients with PBM by an extraction of DNA from surgically resected histologic specimens. DNA was analyzed by a polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) method and direct sequencing. RESULTS: An abnormally mobilized DNA band was detected not only in cancerous epithelium but also in hyperplastic, metaplastic, and inflammatory epithelium of the gallbladder and/or common bile duct in patients with PBM. Among the biliary epithelium of patients with PBM, point mutation of K-ras oncogenes were detected in 4 of 5 (80%) cancerous epithelium, 7 of 12 (58%) hyperplastic and metaplastic epithelium, and 8 of 18 (44%) inflammatory epithelium, whereas no point mutation of the K-ras oncogene was detected in the gallbladder epithelium in 3 control patients without PBM. Direct sequence analysis of the K-ras oncogene revealed the mutation at codon 12 substituting the wild-type glycine (GGT) for aspartic acid (GAT) in all cancerous lesions of patients with PBM. Simultaneous two-point mutations from the wild-type glycine (GGC) to arginine (CGC) at codon 13 associated with the mutation at codon 12 were also found in one case of gallbladder carcinoma and one case of bile duct carcinoma. CONCLUSIONS: K-ras gene mutation is involved in the carcinogenesis of biliary tract epithelium in patients with PBM, and appears to be a high risk factor for carcinogenesis of the biliary tract.

Adult↗
PubMed1996

Hippocampal and neocortical cell assemblies encode memory processes for different types of stimuli in the rat.

The objective of this study was to determine whether each of several different memory processes is encoded exclusively by specific single neurons (single-neuron coding) or by overlapped groups of neurons (population coding by cell assembly). Single neuronal activity was recorded from the rat hippocampal formation (CA1, CA3, dentate gyrus) and temporal cortex during the performance of simple auditory, simple visual, and configural auditory-visual discrimination tasks. All the tasks employed the identical apparatus and time parameters and differed only in the type of stimuli to be processed for correct performance. Single neurons showing significantly differential activity among the discriminative stimuli in each task were judged to be task-related and involved in the memory process of the task. Of the total number of neurons recorded from the hippocampal formation and temporal cortex, 21-26% of the neurons showed task-related activity in only one task, in two tasks, or in all three tasks. This result indicates some overlapping among the neurons involved in each of teh different memory processes. A cross-correlation analysis tested activity correlations among the neurons recorded simultaneously. Most pairs of the hippocampal neurons related to the same tasks (same memory processes) showed correlations during performance of the related tasks. This result showing coactivation of the same types of task-related neurons, together with the result showing the overlapping of task-related neurons, supports the concept of population coding by cell assemblies specifically in the hippocampal formation during memory processing.

Acoustic Stimulation↗
PubMed1996

Primary structure of alboaggregin-B purified from the venom of Trimeresurus albolabris.

The complete amino acid sequences of alpha and beta subunits of alboaggregin-beta are presented. The alpha and beta subunits were separated by reversed-phase HPLC after reduction and S-pyridylethylation, and their sequences were determined by analysis of peptides generated by enzymatic or chemical digestion. The alpha and beta subunits consist of 133 and 123 amino acid residues, respectively. The sequences are highly homologous to each other (41.4% identity) and also to those of the alpha and beta subunits of botrocetin (a von Willebrand factor modulator) and the A and B chains of factor IX/X binding protein from other snake venoms. It is also homologous to C-type lectins with a homodimeric structure, but it shows no lectin-like activity.

Amino Acid Sequence↗
PubMed1996

Spontaneous hemopneumothorax.

BACKGROUND: Spontaneous hemopneumothorax is a rare disorder, occurring in 1% to 12% of patients with spontaneous pneumothorax. We studied our previously treated patients to determine the nature of optimal operative management. METHODS: This was a retrospective case study. From 1987 to 1994, of 428 cases of spontaneous pneumothorax that occurred in 234 patients treated at our institution, hemopneumothorax developed in 10 patients (2.3%). The clinical features of these patients were studied. RESULTS: The amount of bleeding ranged from 600 to 1,600 mL, and 3 patients exhibited symptoms of shock, such as sweating, nausea, and syncope. Six patients underwent operation within 7 days from the onset, and this involved resection of the bullae or pneumorrhaphy, or both. The source of bleeding was identified in 5 patients. Pathologic examination showed marked fibrosis with alcian blue-positive deposits of aberrant vessels. All 6 patients continue to be well postoperatively without recurrence or complications. Four patients did not undergo early thoracotomy. However, decortication was required in 3 of these patients because of a reactive fluid collection in the pleural space, which led to impaired lung expansion. CONCLUSIONS: Early surgical repair should be considered once diagnosis of a spontaneous hemopneumothorax is confirmed, because this provides better long-term results. Video-assisted thoracoscopic surgery as well as minithoracotomy should be considered as surgical options because of the improved quality of life they confer.

Adolescent↗
PubMed1996

Population coding by cell assemblies--what it really is in the brain.

One of the central questions in neuroscience concerns the basic code for information processing in the brain. Much experimental evidence and theoretical consideration have suggested that single-neuron coding is no longer a tenable hypothesis. The present review explains why population neuronal coding is valid and discusses how it is carried out in the brain. The main context is experimental access to real features of the coding in working brains as deduced from experimental research. Several recent studies recording neuronal activities from behaving animals have shown that ensemble activity of neurons represents specific information, indicating the reality of population coding by many neurons. The key concept which can integrate the experimental evidence is the 'cell assembly', i.e., overlapped populations of neurons with flexible functional connections within and among the populations. Correlated activity among the neurons constructs the functional connection. In order to see features of the cell-assembly coding, two main properties of cell assemblies in processing several different kinds of information must be investigated, that is, the overlapping of neurons and the dynamics of synaptic connections. This manner of coding can provide both the experimental and theoretical framework to detect the real dynamic features of information processing by the brain.

Animals↗
PubMed1996

Metabolic response to radiation therapy in patients with cancer.

The effect of radiation therapy on substrate metabolism was evaluated in five patients with head and neck or lung cancer. Stable isotope tracer methodology was used to determine urea, amino acid, glucose, and lipid kinetics during postabsorptive conditions before initiation, near the midpoint (after receiving 2,672 +/- 36 rads), and at completion (after receiving 6,072 +/- 307 rad) of a 6- to 8-week course of radiation therapy. Nutritional status was maintained throughout the treatment period by providing supplemental enteral feedings as needed. Postabsorptive plasma insulin, catecholamine, and amino acid concentrations did not change during the course of treatment. Before radiation therapy was initiated, values for the plasma rate of appearance (Ra) of urea (3.35 +/- 0.33 micromol x kg(-1) x min(-1)), alpha-ketoisocaproate ([alpha-KIC] 2.16 +/- 0.19 micromol x kg(-1) x min(-1)), phenylalanine (0.59 +/- 0.052 micromol x kg(-1) x min(-1)), and glucose (10.56 +/- 1.31 micromol x kg(-1) x min(-1)) were in the normal range. However, glycerol and palmitate Ra values (3.11 +/- 0.30 and 2.01 +/- 0.33 micromol x kg(-1) x min(-1), respectively) were 25% higher than values observed previously in normal subjects. Substrate flux did not change during radiation therapy, and measurements obtained during the midpoint and at completion of treatment were similar to initial values. These results demonstrate that large doses of radiation therapy, administered over 6 to 8 weeks to the upper body, do not cause significant metabolic stress.

Amino Acids↗
PubMed1996

An animal model for measurement of protein metabolism in the skin.

BACKGROUND: A suitable in vivo approach with which to quantify skin protein metabolism has not been found, and consequently no information exists relating protein synthesis to protein breakdown in the fasted state. METHODS: Stable isotope-labeled phenylalanine was infused into five fasted rabbits, and amino acid and protein kinetics were calculated from a three-compartment model with the rabbit ear used as an arteriovenous balance mode. Results were compared with the more traditional but limited direct incorporation technique to measure synthesis. RESULTS: The model-derived skin protein synthesis rate was 0.34%/hr +/- 0.04%/hr, which was almost identical to the value of 0.30%/hr +/- 0.01%/hr determined by the direct incorporation method. The model-derived skin protein breakdown rate was only slightly higher than the synthesis rate, meaning protein balance was generally maintained in the fasted state because of the efficient reuse of amino acids from protein breakdown. CONCLUSIONS: The newly described rabbit ear model is a reliable approach to the determination of the amino acid and protein kinetics in the skin in vivo. Efficient reuse of amino acids released from proteolysis explains the maintenance of skin integrity during brief fasting.

Animals↗
PubMed1996

Regulation of the acid-labile subunit of the insulin-like growth factor ternary complex in patients with insulin-dependent diabetes mellitus and severe burns.

OBJECTIVE: Little information is available regarding the regulation of serum acid-labile subunit (ALS) in human disease. We have studied alterations in serum ALS of the insulin-like growth factor (IGF) ternary complex in children with untreated insulin-dependent diabetes mellitus (IDDM) and subjects with severe burns before and after insulin therapy. In addition, we have investigated the effect of insulin plus GH on serum ALS in burn patients. DESIGN: Serum samples were obtained from children with newly diagnosed and untreated IDDM before the initiation of insulin therapy and 1 month thereafter. Serum samples were also obtained from adult patients with severe burns who were on a continuous infusion of a carbohydrate-rich enteral diet via nasogastric and duodenal catheters under basal conditions, after a 1-week period of continuous insulin infusion, and after an additional week of insulin plus recombinant GH. PATIENTS: Twenty children and adolescents with untreated IDDM, aged 1.2-16 years, and 6 young adult patients with severe burns aged 17-28 years were studied longitudinally. Control sera were obtained from age, sex and pubertal status matched subjects (for children with IDDM) and from fed healthy adults. MEASUREMENTS: Serum insulin, GH, cortisol and IGF-I were measured by radioimmunoassay, and serum ALS levels were assessed by Western immunoblot before and after treatment periods. RESULTS: Serum ALS levels were lower in untreated children with IDDM (69 +/- 6% of control children). Insulin therapy significantly increased serum ALS (79 +/- 5%, P < 0.05) in these children. Patients with severe burns also had lower serum ALS levels (79 +/- 10% of control adults). After one week of insulin therapy serum ALS levels increased to 90 +/- 15% of control values (P < 0.05). Addition of GH to insulin therapy for another week did not significantly further increase serum ALS levels (95 +/- 27%). Serum IGF-I concentrations increased nearly 2.5-fold in diabetic subjects and fourfold in burn subjects at the end of the study periods. There were no proteolytic fragments of ALS in the sera studied. The deglycosylation pattern of ALS did not differ between diabetic and control sera. CONCLUSION: Serum ALS levels were diminished in children with untreated IDDM and were partially restored after the initiation of insulin therapy. Serum ALS levels were also diminished in patients with severe burn injury and restored by insulin treatment. Addition of GH to insulin therapy did not significantly increase serum ALS levels over levels obtained during insulin therapy alone. These decreases in serum ALS were smaller than the decrease in serum IGF-I concentrations in both conditions, suggesting that IGF-I is the limiting factor for the ternary complex formation in the catabolic states. Insulin may regulate circulating ALS levels in catabolic states and helps to restore the IGF system.

Acute Disease↗
PubMed1996

Cytoplasmic calcium levels and membrane fluidity of platelets in contact with polyether-polyamide multiblock-copolymer surfaces.

Cytoplasmic calcium levels and the membrane fluidity of rabbit platelets stored in mini blood bags of crystalline-amorphous microstructured polymers (polyether-polyamide multiblock-copolymers) were studied. Fluorescent dye (Fura 2 or 1,6-diphenyl-1,3,5-hexatriene)-loaded platelet suspensions were stored at 37 degrees C for 1 h in the blood bags, and metabolic changes in the platelets during storage were evaluated by the fluorescent spectroscopic technique. The surfaces of poly(vinyl chloride) and polyolefin elastomers, which are used for commercially available blood bags, enhanced the progress of platelet metabolism; i.e., there was a dramatic decrease in membrane fluidity and an increase in [Ca2+]i. Furthermore, the decrease in membrane fluidity was observed prior to the increase in [Ca2+]i. These results suggest that the decrease in membrane fluidity of platelets in contact with polymer surfaces can be the dominant stage in the activation of these platelets. In contrast, the surfaces of polyether-polyamide multiblock-copolymers exhibited few changes in either membrane fluidity or [Ca2+]i levels. These results suggest that the platelets in contact with the crystalline-amorphous microstructured copolymer surfaces can be inert and inactivated in terms of the prevention of a decrease in membrane fluidity.

Animals↗
PubMed1996

An isotopic method for measurement of muscle protein fractional breakdown rate in vivo.

We have developed a novel method to measure the fractional breakdown rate (FBR) of muscle protein. This method involves infusing isotope tracer to reach an isotopic equilibrium and then observing its decay in the arterial blood and muscle intracellular pool. The calculation of FBR is based on the rate at which tracee released from breakdown dilutes the intracellular enrichment using a modified precursor-product equation. To test this method, L-[1,2-13C2]leucine and L-[ring-13C6]phenylalanine were infused into six dogs for measurement of FBR and fractional synthesis rate (FSR), respectively. Leucine and phenylalanine kinetics in the hindlimb were measured simultaneously using the arteriovenous (A-V) balance method. The measured FBR (0.17 +/- 0.02%/h) and FSR (0.10 +/- 0.01%/h) were in agreement with the results from the A-V balance method. In conclusion, our new method provides a feasible approach for measurement of muscle protein FBR. This method can be combined with the tracer incorporation method to measure both breakdown and synthesis in the same infusion study.

Animals↗
PubMed1996

TNF directly stimulates glucose uptake and leucine oxidation and inhibits FFA flux in conscious dogs.

We tested the hypothesis that the metabolic changes in glucose, lipid, and protein metabolism seen during tumor necrosis factor (TNF) infusion were due to the increase in plasma glucagon concentration rather than to the direct effects of TNF. We employed a pancreatic clamp technique to keep plasma insulin and glucagon concentrations constant throughout a 4-h isotope infusion. Glucose, lipid, and protein kinetics were measured by means of the primed, constant infusion of [6,6-2H]glucose, [2H5]glycerol, [2H2]palmitic acid, and [1-13C]leucine. After a 2-h baseline period (period 1), TNF was infused as a primed, constant infusion (prime, 2.5 micrograms/kg; constant infusion, 62.5 ng.kg-1.min-1) for 2 h (period 2). Whereas plasma glucose concentration dropped significantly during TNF infusion, endogenous glucose production did not change. The decrease in glucose concentrations was due to a stimulation of glucose clearance (P < 0.05). The rate of lipolysis did not decrease significantly, but free fatty acid (FFA) flux and plasma FFA concentration significantly decreased during TNF infusion (P < 0.05). The rate of appearance of leucine was not affected by TNF infusion, but TNF caused a significant increase in 13CO2 excretion (P < 0.05) and leucine oxidation (P < 0.05). The calculated rates of whole body protein synthesis decreased. We concluded that TNF did not directly affect glucose production. Furthermore, changes in protein and lipid kinetics during TNF infusion were not mediated by changes in insulin or glucagon and may have reflected direct effects of TNF.

Animals↗
PubMed1996

A clinical profile of corticobasal degeneration presenting as primary progressive aphasia.

We report a patient with primary progressive aphasia who first presented with amnesic aphasia that developed over the course of 3 years into nonfluent aphasia with buccofacial apraxia, followed in the next year by cognitive impairment and parkinsonism. Pathological findings were typical for corticobasal degeneration except for the distribution of cortical atrophy. This case suggests that corticobasal degeneration should be included in the differential diagnosis of primary progressive aphasia, especially in association with parkinsonism.

Aphasia, Primary Progressive↗
PubMed1996

Amine effect on phenylboronic acid complex with glucose under physiological pH in aqueous solution.

A new "intelligent' polymer system was developed utilizing the binding and exchange of phenylboronic acid (PBA) with polyols and/or glucose. In this improved system, an amine component was incorporated into the polymer chain along with PBA, to enhance binding between PBA and glucose under physiological conditions. The PBA-based polymer was formed by free-radical copolymerization of 3-methacrylamidophenylboronic acid (MAPB) with comonomers, N,N-dimethylaminopropylacrylamide (DMAPAA) and acrylamide (AAm) in the presence of N,N'-methylenebis(acrylamide) (Bis-AAm) as a cross-linker. The proportion of the amount of PBA groups complexed with glucose vs total amount of PBA groups was determined by the batch method. Compared to PBA copolymers synthesized without amine component, the proportion increased as a function of the amine content as well as the pH of the buffer. These results confirm that the interaction of neighboring amines (unprotonated) to PBA strengthens the binding with glucose, especially at pH 7.4 and above. This new PBA-amine copolymer is promising as a material useful for polyol separation, protection of polyols, and possibly, as an insulin delivery device.

Acrylamide↗