• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.725-732
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• 1998

In order to elucidate the molecular mechanism of the intracellular $Ca^{2+}$ overload frequently reported from diabetic heart, diabetic rats were induced by the administration of streptozotocin, the membrane vesicles of junctional SR (heavy SR, HSR) were isolated from the ventricular myocytes, and SR $Ca^{2+}$ uptake and SR $Ca^{2+}$ release were measured. The activity of SR $Ca^{2+}-ATPase$ was $562{\pm}14$ nmol/min/mg protein in control heart. The activity was decreased to $413{\pm}30$ nmol/min/mg protein in diabetic heart and it was partially recovered to $485{\pm}18$ nmol/min/mg protein in insulin-treated diabetic heart. A similar pattern was observed in SR $^{45}Ca^{2+}$ uptakes; the specific uptake was the highest in control heart and it was the lowest in diabetic heart. In SR $^{45}Ca^{2+}$ release experiment, the highest release, 45% of SR $^{45}Ca^{2+}$, was observed in control heart. The release of diabetic heart was 20% and it was 30% in insulin-treated diabetic heart. Our results showed that the activities of both SR $Ca^{2+}-ATPase$ and SR $Ca^{2+}$ release channel were decreased in diabetic heart. In order to evaluate how these two factors contribute to SR $Ca^{2+}$ storage, the activity of SR $Ca^{2+}-ATPase$ was measured in the uncoupled leaky vesicles. The uncoupling effect which is able to increase the activity of SR $Ca^{2+}-ATPase$ was observed in control heart; however, no significant increments of SR $Ca^{2+}-ATPase$ activities were measured in both diabetic and insulin-treated diabetic rats. These results represent that the $Ca^{2+}$ storage in SR is significantly depressed and, therefore, $Ca^{2+}-sequestering$ activity of SR may be also depressed in diabetic heart.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.88-93
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• 2013

In order to construct a controlled release system of drugs and to reduce toxic side effects of 5-fluorouracil, the novel ramose chitosan-based-5-fluorouracil microspheres (CS-FU-MS) were prepared. Firstly, using chitosan (CS) as carriers and 5-fluorouracil (5-FU) as a model drug, ramose chitosan-based-5-fluorouracil (CS-FU) was efciently synthesized by chemical crosslinking method through microwave irradiation, drug loading was 10.6%; Secondly, CS-FU-MS were prepared by CS-FU self-assembled under the dialysis conditions and the free 5-FU was encapsulated further at the same time. The size dispersivity of particles is uniform, and the average diameter of the CS-FU-MS was $4{\mu}m$. The drug encapsulation efficiency was 76.1%, and the drug loading was increased to 26.22%. CS-FU-MS maintain the zero-order release time in PBS (pH = 7.4) and HCl/KCl (pH = 1.2) dialysis medium was 40h and 34h respectively, and the cumulative release were 58.89% and 79.33% in 182 h. The results showed that CS-FU-MS have excellent sustained release properties.

• Archives of Pharmacal Research
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• v.12 no.2
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• pp.88-93
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• 1989

In order to obtain some informations about the effect of molecular weight on the release rate of drug from drug carrier, two types of poly-L-glutamic acid (PLGA)-cytarabine (ara-C) conjugates, PLGA-ara-C:I and PLGA-ara-C:II, were synthesized using two types of PLGA having different average molecular weight, 43,000 and 77,800, respectively. The PLGA-ara-C conjugates were synthesized by mixed anhydride method and found to be covalently linked. Both types of conjugates charged negatively at biological pH. The pH-dependent release rate of ara-C was observed in both cases, and the release rate was accelerated in basic, acidic conditions (the k values were 0.015 $day^{-1}$ at pH 7.0, 0.024 $day^{-1}$ at pH 5.0, and 0.059 $day^{-1}$ at pH 9.0 in the case of PLGA-ara-C:I) and in the presence of pretense. The time required for the release of 16.5% of ara-C from PLGA-ara-C:I were 8 hr and 144 hr in the presence and absence of protease, respectively. Although both types of conjugates showed similar drug substitution ratio, they showed different release rates. Between the two types of conjugates, PLGA-ara-C:II showed the faster release rate (0.030 vs 0.042 $day^{-1}$ in pH 7.4 phosphate buffer solution at $37^{\circ}C$) and the smaller activation energy for the release of drug (12.5 vs 7.7 Kcal/mol) than PLGA-ara-C:I. The characteristic effect of molecular weight on the release rates of PLGA-ara-C conjugates suggests that the drug release rate might be effectively controlled over a prolonged period of time by the combined use of the different types of PLGA-ara-C conjugates having different molecular weights.

• The Korean Journal of Physiology
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• v.25 no.1
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• pp.61-67
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• 1991

In order to determine possible relationships between the renin-angiotensin system and nephron heterogeneity, we compared the response of renin release and the angiotensin-converting enzyme (ACE) activity from different areas of the rat kidney. We used the renal cortical slices from the capsular surface to the juxtamedullary junction. Slices from outer one-third of the cortex were designated as outer cortical slices (OC), middle one-third as midcortical slices (MC), and inner one-third as inner cortical slices (IC). The renal renin content markedly decreased from OC and MC to IC. The basal lenin release was higher in OC than in MC or IC. On the contrary the percent change of renin release in response to L-isoproterenol was significantly higher in MC than in OC or IC. By TMB-8, the renin release in MC by $231{\pm}21%$ was higher than OC by $171{\pm}19%$ or IC by $$162{\pm}19. Angiotensin II suppressed renin release in OC and MC by $68{\pm}2,\;71{\pm}4%$ respectively, but only $40{\pm}7%$ in IC. The ACE activity was higher in IC than in OC, MC, medulla and papilla. The present data indicate that renin content and basal lenin release gradulally decreased from outer (OC) to inner (IC) cortex. The renin release in response to beta-adrenergic agonist, L-isoproterenol and intracellular calcium antagonist, TMB-8 were higher in MC than in OC and IC, but angiotensin II suppressed renin release less in IC than in OC and MC. It is suggested that juxtaglomerular cells of outer, mid-and inner cortices show a difference in renin release response to the stimuli.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.4047-4054
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• 2010

We studied the release characteristics of the marine sediment which could facilitate sea eutrophication through some lab-scale simulation experiments. Environmental indicators such as pH, ORP(oxidation reduction potential), nitrogens, and phosphates were measured in order to calculate the corresponding release rates. $CaO_2$, an oxygen releasing compound was used to determine how it would effect on the natural process of sedimental release. COD, ammonia nitrogen, phosphorous compounds were less released under the oxic environment caused by $CaO_2$. This basic data will help developing methodology for reducing marine eutrophication which may be initiated by the sedimental release.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.377-380
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• 2001

A recent trend in flexible manufacturing systems(FMS) is to compose of the identical versatile-machines and to use dynamic tool allocation strategy, sharing tools between machines with fast tool delivery system. Unlike a conventional FMS where parts are fed to the machines with the required tools, tools are acquired from other machines using a tool delivery system and parts can be finished on the same machine in these FMS. Therefore it is more important problem to plan tool flow using tool delivery system in these FMS rather than part flow in conventional FMS. According to existing study, in FMS 20~30 percent of the total management cost is the cost related with tools and it is possible to reduce the tool inventory by 40 percent using efficient tool allocation. In this study, in FMS under dynamic tool allocation strategy, a new method of part release considering tool flow at the stage of part release is proposed. In order to prove the efficiency of the proposed part release it is compared with other part release through simulation experiments. Performance measures in these experiments are the throughput and the number of tardy parts.

• Journal of the Korean Society of Clothing and Textiles
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• v.3 no.2
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• pp.29-36
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• 1979

In order to control free formaldehyde release from fabric finished with urea-formaldehyde precondensate, the resin finished fabric was padded in urea or acylamide solution, dried and cured at $140^{\circ}C$. The effect of aftertreatment with urea or acrylamide on free formaldehyde release and on characteristics of resin finished fabric were examined. It was shown that aftertreatment with urea was effective to control free formaldehyde release, the free formaldelyde content in aftertreated fabric could be reduced from 900 ppm to 200 ppm and formaldehyde release under accelerated storage condition was also reduced from 8000 ppm to 1000 ppm. Polyacrylamide formed in the fiber during aftertreatment appeared to be a formaldehyde capture. Especially by washing the aftertreated fabric, the ability to control formaldehyde release under accelerated condition was not dimimished in contrast with aftertreated with unea. It suggests that polyacrylamide can be used as a formaldehyde capture which withstand diminution from washing.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.2
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• pp.89-94
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• 1999

In this study small glass columns with 2.5cm inner diameter and 24.5cm length were used as many as the sample numbers to study the effects of initial pH, temperature, dissolved oxygen concentration, and sediment depth on the release of phosphorus from lake sediment. No phosphorus release occurred at $10^{\circ}C$ with all pHs, and release rate at $25^{\circ}C$ was higher than that at $35^{\circ}C$ with pH 4 and reverse trends were observed at pH 7 and 10. Under all conditions, DO concentrations were decreased and equilibrium was obtained after 4-8 days when phosphorus release started and the Do concentrations were less than 1 mg/l. Sediment depth had little effect on phosphorus release rate. It was found that relation between released SRP(Soluble Reactive Phosphorus) concentration and time was zero order reaction and reaction rate coefficients were obtained. The amount of phosphorus release from lake sediment can be predicted by considering these k values.

• Journal of Pharmaceutical Investigation
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• v.22 no.1
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• pp.33-40
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• 1992

This study was aimed to control the release characteristics of ketoprofen by microencapsulating $ketoprofen-{\beta}-cyclodextrin\;(KF-{\beta}-CyD)$ solid dispersion with Eudragit RS by the phase separation method using a nonaqueous vehicle. KF alone was also microencapsulated with Eudragit RS by the evaporation process in water phase. The results obtained showed that it was not possible to microencapsulate KF alone by phase separation in a chloroform-cyclohexane system while it was easy to microencapsulate $(KF-{\beta}-CyD)$ solid dispersion system. For the microcapsules, the release test was performed in the first fluid (pH 1.2) and the second fluid (pH 6.8) of K.P.V disintegration medium at $37^{\circ}C$. The release of KF from $(KF-{\beta}-CyD)$ solid dispersion microcapsules (1:1 core wall ratio) was more sustained than that from KF microcapsules, and followed zero-order kinetics. Especially, solid dispersion microcapsules showed pH-independent release patterns with higher wall to core ratio (1:1 w/w).

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.323-327
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• 1999

To protect ${\beta}-carotene$ at the stomach and to release rapidly at the intestine we prepared alginate beads containing ${\beta}-carotene$. ${\beta}-carotene$ and alginate solution was homogenized and prepared o/w emulsion was prepared. It was poured into $Ca^{2+}$ solution through syringe needle. The gel was formed spontaneously and alginate beads containing ${\beta}-carotene$ were prepared. ${\beta}-Carotene$ was incorporated into the beads more than 95%. The release rate of ${\beta}-carotene$ was dependent on the concentration of $Ca^{2+}$, ${\beta}-carotene$ and surfactants. However, the concentration of alginate did not affect the release rate of ${\beta}-carotene$. The high concentration of $Ca^{2+}$ slowed down the release rate of ${\beta}-carotene$. The addition of surfactants in the ${\beta}-carotene$beads increased the release rate of ${\beta}-carotene$ in the order of Tween 80 > Cremophor > Span 20. The contents of ${\beta}-carotene$ and diameter of ${\beta}-carotene$ beads did not change significantly at $50^{\circ}C$ for 20 days.