Biomedical subjects

J-Y Lee

Publications and source records attributed to J-Y Lee.

24 records · Page 2Linked to original sources

PubMed2003

Influence of TachoComb in comparison to local hemostyptic agents on epidural fibrosis in a rat laminectomy model.

This animal experimental study was designed to examine the effects of TachoComb, a fixed combination of collagen with tissue adhesive, as an interposition membrane on the development of spinal epidural fibrosis in comparison to other hemostyptic materials. In 10 Wistar rats, four laminectomies were performed at lumbar and sacral vertebrae. Alternately, a piece of TachoComb, Spongostan, or Tabotamp was placed into each laminectomy site. One laminectomy site served as an empty control (n = 10). 8 weeks later, the animals were sacrificed, and the spinal column including surrounding muscle tissue was removed en bloc from each rat and fixed in formaldehyde. After decalcification and staining the specimens were graded by a neuropathologist in a blindfold test for severity of epidural fibrosis as "light-moderate" or "marked". Epidural scarring of variable density was seen in all laminectomy sites. Light epidural fibrosis, without any adhesion to dura, as only noted in cases after application of TachoComb (n = 4/10) and Spongostan (n = 1/10). All other slices showed marked epidural fibrosis with dura adherence regardless of the implanted material. Statistical analysis revealed significantly lower epidural fibrosis after application of TachoComb compared to all other groups (p < 0.05). In this series, TachoComb is more effective in reducing the epidural fibrosis than Spongostan, and Tabotamp. However, complete prevention of scar tissue formation was not achieved.

Animals↗

PubMed2003

Muscle cell-mediated gene delivery to the rotator cuff.

Rotator cuff lesions are one of the most common causes of upper extremity disability. Surgical therapy addresses mostly the extrinsic etiology, but not intrinsic factors such as aging, structural changes, low vascularity, and inflammatory processes. In this study, genetically engineered, highly purified muscle-derived cells (MDCs) were characterized and injected into the supraspinatus tendons of nude rats. The injected cells were monitored for 3 weeks. In vitro, the engineered, highly purified MDCs do not express vimentin; 98% of them are positive for the beta-galactosidase marker gene, and 99% hybridize with the specific pancentromeric mouse probe. beta-Galactosidase marker gene expression of the injected cells was detected up to 21 days. From day 7 after injection, the cell nuclei became spindle shaped, cells were integrated into the tendon collagen bundles, and the cells showed differentiation into vimentin-expressing fibroblastic cells. The results indicate that the rotator cuff tendon matrix and its original cellular components modulated the injected MDCs toward a fibroblastic phenotype. The compatibility and ability of MDCs to differentiate into other cell lineages, such as fibroblasts, might have high potential utility in tissue-engineering applications for tendon healing. This approach facilitates the application of muscle-derived progenitor cells and ex vivo gene therapy for the treatment of rotator cuff lesions.

Animals↗

PubMed2002

Active insulin infusion using optimal and derivative-weighted control.

Close control of blood glucose levels significantly reduces vascular complications in Type I diabetes. A control method for the automation of insulin infusion that utilizes emerging technologies in blood glucose biosensors is presented. The controller developed provides tighter, more optimal control of blood glucose levels, while accounting for variation in patient response, insulin employed and sensor bandwidth. Particular emphasis is placed on controller simplicity and robustness necessary for medical devices and implants.A PD controller with heavy emphasis on the derivative term is found to outperform the typically used proportional-weighted controllers in glucose tolerance and multi-meal tests. Simulation results show reductions of over 50% in the magnitude and duration of blood glucose excursions from basal levels. A closed-form steady state optimal solution is also developed as a benchmark, and results in a flat glucose response. The impact and trade-offs associated with sensor bandwidth, sensor lag and proportional versus derivative-based control methods are illustrated. Overall, emerging blood glucose sensor technologies that enable frequent measurement are shown to enable more effective, automated control of blood glucose levels within a tight, acceptable range for Type I and II diabetic individuals.

Blood Glucose↗

PubMed2002

The prototype of sex chromosomes found in Korean populations of Rana rugosa.

The seventh largest chromosome in Japanese populations of the frog Rana rugosa morphologically evolved as a sex chromosome. The sex chromosome is XX/XY type in one geographic form and ZZ/ZW type in another. In contrast, the seventh chromosomes are still homomorphic between the sexes in the other two geographic forms: they are more subtelocentric in the Kanto form and subtelocentric in the western Japanese form. To identify a prototype of the sex chromosomes, we extended our investigation in this study to the Korean form, which is supposed to be close to the phylogenetic origin of this species. The karyotype, a sex-linked gene sequence, and mechanisms of sex determination and gonadal differentiation were all examined. In addition, phylogenetic analyses were performed based on mitochondrial gene sequences and the results of crossings between the Korean and Japanese forms. As a consequence, the more subtelocentric seventh chromosome, shared by the Korean and Japanese Kanto forms, was concluded to be the prototype of the sex chromosomes. Starting at the prototype, a whole process of morphological sex chromosome evolution was reconstructed.

Animals↗

PubMedDate not supplied

Differential regulation of protein kinase C activity by modulating factors and Euonymus alatus (Thunb.) Sieb in human myometrial and uterine leiomyomal smooth muscle cells.

Human myometrial smooth muscle cells (MSMC) showed high protein kinase C (PKC) activity when a maximal dose of PKC-activating phorbol ester was used, while uterine leiomyomal cells (ULMC) showed only 6-12% of PKC activity. MSMC exhibited a low proliferation rate, whereas ULMC exhibited a high proliferation rate. These different cell types of MSMC and ULMC responded to 10 U/mL thrombin, with a twofold stimulation of PKC activity. Downregulation of PKC activity was found when MSMC were treated with phorbol ester or with transforming growth factor-beta2. We concluded that differences in PKC activity exist between MSMC and ULMC, which may be related to their different proliferative activity. ULMC treated with Euonymus alatus (Thunb.) Sieb (EA), known as "gui-jun woo" in Korea, which is used for leiomyomal tumors, exhibited a much lower proliferation rate than untreated cells, suggesting that EA inhibited the cellular proliferation of ULMC. The PKC activity of MSMC by EA treatment (50 microg/mL) changed little. ULMC showed increased PKC activity by addition of EA, indicating that PKC is activated by EA. The EA-treated ULMC were differentiated into phenotypes characteristic for normal untransformed cells, since the EA-treated cells possess higher PKC activity than untreated cells.

Cell Proliferation↗

PubMedDate not supplied

Overexpression and incorporation of GagPol precursor does not impede packaging of HIV-1 tRNA(Lys3) but promotes intracellular budding of virus-like particles.

We have recently demonstrated that alteration of the human immunodeficiency virus type 1 (HIV-1) Gag/GagPol ratio in virus-producing cells reduces the infectivity of progeny viruses and hinders the formation of stable virion RNA dimers without impairing virion packaging of the viral genomic RNA. In addition, we have previously shown that the expression of GagPol mediates the selective packaging of tRNA(Lys3). In this study we report that overexpression of uncleaved GagPol in the virus-producing cell did not alter the packaging levels of tRNA(Lys3). Similarly, altering the virion-associated Gag/GagPol ratio did not affect the virion packaging of the HIV-1 envelope protein nor cyclophilin A. Thin section electron microscopy analysis of the cells overexpressing protease-defective [PR(-)] GagPol revealed immature virions but no mature virions. These immature virions were seen both extracellularly and in membrane-bound cytoplasmic vacuoles. Furthermore, an accumulation of electron-dense material was occasionally found at the plasma membrane and associated with intracytoplasmic membranous vacuoles in cells expressing excess PR(-) GagPol. No intracellular HIV was seen in the wild-type control. Density gradient analysis showed that the overall density of these mutant virions with excess PR(-) GagPol was identical to that of the wild-type HIV-1. The findings indicate that overexpression of PR(-) GagPol, in the presence of Gag synthesis, promotes intracellular budding of the mutant virions and inhibits virus maturation.

Cell Line↗