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Biomedical subjects

Y G Kim

Publications and source records attributed to Y G Kim.

141 records · Page 8Linked to original sources
PubMed1978

Stratification, specialization, and proliferation of primary keratinocyte cultures. Evidence of a functioning in vitro epidermal cell system.

A population of neonatal mouse keratinocytes (epidermal basal cells) was obtained by gentle, short-term trypsin separation of the epidermal and dermal skin compartments and discontinuous Ficoll gradient purification of the resulting epidermal cells. Over 4--6 wk of culture growth at 32--33 degrees C, the primary cultures formed a complete monolayer that exhibited entire culture stratification and upper cell layer shedding. Transmission and scanning electron microscopy demonstrated that the keratinocyte cultures progressed from one to two cell layers through a series of stratification and specialization phenomena to a six to eight cell layer culture containing structures characteristic of epidermal cells and resembling in vivo epidermal development. The temporal development of primary epidermal cell culture specialization was confirmed by use of two histological techniques which differentially stain the specializing upper cell layers of neonatal mouse skin. No detectable dermal fibroblast co-cultivation was demonstrated by use of the leucine aminopeptidase histochemical technique and routine electron microscope surveillance of the cultures. Incorporation of [3H]thymidine ([3H]Tdr) was greater than 85% into DNA and was inhibited by both 20 micron cytosine arabinoside (Ara-C) and low temperature. Autoradiography and 90% inhibition of [3H]Tdr incorporation by 2 mM hydroxyurea indicated that keratinocyte culture DNA synthesis was scheduled (not a repair phenomenon). The primary keratinocytes showed an oscillating pattern of [3H]Tdr incorporation into DNA over the initial 23--25 days of growth. Autoradiography demonstrated that the cultures contained 10--30% proliferative stem cells from days 2-25 of culture. The reproducibility of both the proliferation and specialization patterns of the described primary epidermal cell culture system indicates that these cultures are a useful tool for investigations of functioning epidermal cell homeostatic control mechanisms.

Cell Division↗
PubMed1969

The effects of time-varying blood flow on diffusional resistance to oxygen transfer in the pulmonary capillaries.

The effects of the persistence of pulsatile blood flow in the pulmonary capillaries on the over-all diffusing capacity and alveolar-arterial oxygen tension gradient were studied. A mathematical analysis was made of the oxygen transfer process using an undamped cardiac flow pulse in the capillaries and taking into account the finite rate of reaction of oxygen with hemoglobin.In five cases of both normal and low oxygen atmospheres, combined with varying degree of exercise, it was found that the alveolar-arterial oxygen tension gradients were not affected by the time-varying blood flow, while in cases of breathing air the over-all diffusing capacity of the lung increased 10-15% over the diffusing capacity obtained with constant blood flow rate in the pulmonary capillaries.

Atmospheric Pressure↗
PubMedDate not supplied

Expression of cytochrome P-450s and glutathione S-transferases in the rat liver during water deprivation: effects of glucose supplementation.

Pharmacokinetic profiles of therapeutic agents change in dehydrated animals. The present study was designed to determine the expression of xenobiotic-metabolizing enzymes in the rat liver and the effect of glucose supplementation during water deprivation. Deprivation of water intake, which reduced food intake, resulted in no significant change in the cytochrome P-450 1A2, 2B1/2, 2C11 and 3A1/2 expression. Cytochrome P-450 2E1, however, was three-fold induced with an increase in the mRNA. Rehydration of 48-h water-deprived rats for the next 24 h with free access to foods restored the P-450 2E1 level to that of the control, although rehydration with 20% food supply failed to normalize the P-450 2E1 expression. Water deprivation caused a reduction in the plasma insulin level, which was prevented by rehydration with a sufficient food supply. The plasma insulin level was inversely related to the P-450 2E1 expression. Glucose feeding instead of foods during dehydration prevented P-450 2E1 induction in the absence of recovering the plasma insulin level. Western blot analysis revealed that the hepatic rGSTA2 level was 30% decreased in dehydrated rats, whereas the rGSTA3, M1 and M2 expression was not affected. Suppression of rGSTA2 accompanied a reduction in the mRNA. Glucose feeding further reduced rGSTA2 expression. The data indicated that expression of major P-450s and glutathione S-transferases, except P-450 2E1, was not greatly affected by water deprivation and that the P-450 2E1 induction and a decrease in plasma insulin resulted from the reduction in food intake but not from dehydration per se. Glucose supplementation restored P-450 2E1 expression but further suppressed rGSTA2 expression during water deprivation.

Animals↗
PubMedDate not supplied

Kinetic resolution of racemic alpha-methyl-beta-propiothiolactone by lipase-catalyzed hydrolysis.

Kinetic resolution of racemic alpha-methyl-beta-propiothiolactone (rac-MPTL) using lipases in organic solvent was studied. The lipase from Pseudomonas cepacia (PCL) showed the highest (S)-enantioselectivity (E > 100), and cyclohexane containing 1% (v/v) buffer was identified as the best reaction medium for maintaining high enantioselectivity as well as high reaction rate. While the substrate inhibition was not observed up to 300 mM rac-MPTL, severe product inhibition was observed even at 50 mM racemic 3-mercapto-alpha-methyl propionic acid (rac-MMPA), which made the use of high substrate concentration difficult. To overcome the product inhibition, the products, (R)-MMPA, were neutralized by addition of a dilute basic solution. Although the resolution reaction proceeded further by the base titration, the enantioselectivity of the reaction decreased as a result of nonenantioselective hydrolysis of rac-MPTL in the basic solution. Under these conditions, 200 mM rac-MPTL was successfully resolved to above 95% ee(S) with 53% conversion.

Burkholderia cepacia↗
PubMedDate not supplied

Chimeric restriction enzyme: Gal4 fusion to FokI cleavage domain.

Gal4, a yeast protein, activates transcription of genes required for metabolism of galactose and melibiose. It binds as a dimer to a consensus palindromic 17-base pair DNA sequence. It is a member of the third family of proteins that contain zinc-mediated peptide loops that interact specifically with nucleic acids. Gal4 has a very distinctive zinc coordination profile and mode of DNA-binding. Here, we report the creation of a novel site-specific endonuclease by linking the N-terminal 147 amino acids of Gal4 to the cleavage domain of FokI endonuclease. The fusion protein is active and under optimal conditions, binds to a 17 bp consensus DNA site and cleaves near this site. As expected, the cleavage occurs on either side of the consensus binding site(s).

Base Sequence↗
PubMedDate not supplied

Effects of cysteine on the pharmacokinetics of intravenous adriamycin in rats with protein-calorie malnutrition.

In rats with protein-calorie malnutrition (PCM, 5% caseine diet for 4 weeks), hepatic cytochrome P450 levels suppressed markedly and cytochrome P450 mRNAs decreased significantly compared with those in control rats (23% caseine diet for 4 weeks), however, the values completely (or partially) returned to control levels by a week (from fourth week) of cysteine supplementation (rats with PCMC) (Cho, Kim et al., Arch. Biochem. Biophys. 1999, 372: 150-158). The formation of aglycone metabolites of adriamycin and adriamycinol, M3 and M4, respectively, seemed to be induced (Lee and Lee, Res. Commun. Mol. Pathol. Pharmacol. 1999, 105: 87-96) by pretreatment with dexamethasone (possibly by hepatic cytochrome P450 RL 33/cDEX, Komori and Oda, J. Biochem. 1994, 116: 114-120) in rats. Adriamycin, 16 mg/kg, was administered intravenously in 1-min to control rats and rats with PCM and PCMC. In rats with PCM, the plasma concentrations of adriamycin was higher (the area under the plasma concentration-time curve from time zero to 12 hr, AUC(0-12 hr), tended to be higher) and 24-hr urinary excretion of M3 (including its 'conjugates') seemed to increase than those in control rats, suggested that the formation of M3 was inhibited in rats with PCM. In rats with PCMC, the plasma concentrations of adriamycin were lower (the AUC(0-12 hr) was significantly smaller) and 24-hr urinary excretion of M3 (including its 'conjugates') were significantly greater than those in rats with PCM, suggested that the formation of M3 increased significantly by cysteine supplementation by restoring the enzyme system(s) that metabolize adriamycin to M3. The altered pharmacokinetic parameters of adriamycin mentioned above in rats with PCM returned to greater than those of control rats after cysteine supplementation (rats with PCMC). Above data suggested that other hepatic cytochrome P450 isozyme(s) which catalyze(s) the formation of M3 from adriamycin could be induced by cysteine supplementation.

Animals↗
PubMedDate not supplied

Dissociation between clearances of small and middle molecules in incremental peritoneal dialysis.

OBJECTIVE: To evaluate the peritoneal clearance of middle molecules in comparison with the peritoneal clearance of small molecules in incremental peritoneal dialysis (PD). STUDY DESIGN: Peritoneal clearances of creatinine and beta2-microgloblulin (B2M) were compared in 57 continuous ambulatory PD patients on full dose of 4 exchanges, and 54 incremental PD patients with 2 or 3 exchanges over 24 hours. Clearances were also compared when there were changes in the PD regimen, such as in the number of exchanges and the duration of the dwell time. SETTING: Tertiary-care university hospital. RESULTS: Peritoneal creatinine clearance increased almost linearly with the increase in the number of exchanges. In contrast, peritoneal clearance of B2M was 9.1 +/- 3.6 L/week, 8.8 +/- 4.4 L/week, and 7.9 +/- 2.5 L/week with 2,3, and 4 exchanges, respectively, per day, amounts that were not different from each other. Peritoneal clearance of B2M did not change when there was an increase in the number of dialysate exchanges from 2 to 3 and from 3 to 4 over a period of 24 hours; whereas the peritoneal clearance of creatinine increased. Peritoneal clearance of B2M almost doubled, from 5.4 +/- 2.7 L/week with 2 exchanges over 12 hours per day, to 9.5 +/- 4.4 L/week with the same 2 exchanges over 24 hours. The creatinine clearance did not change. CONCLUSION: In contrast to peritoneal clearance of small molecules, such as creatinine, which was dependent on the number of dialysate exchanges, peritoneal clearance of middle molecules, such as B2M, depended mainly on the total dwell hours of PD and not on the number of exchanges of peritoneal dialysate in incremental PD. This might be another advantage of incremental PD, since peritoneal clearance of middle molecules in incremental PD over 24 hours can be comparable to that in full dose PD.

Adult↗
PubMedDate not supplied

An HSVtk-mediated local and distant antitumor bystander effect in tumors of head and neck origin in athymic mice.

The "bystander effect," produced by ganciclovir-mediated killing of cells transduced with a herpes simplex virus thymidine kinase (HSVtk) gene, defines the cooperative killing of non-HSVtk-transduced cells. In vitro, a major contributor to this phenomenon is metabolic cooperation involving transfer of cytotoxic small molecules between cells via gap junctions. In this study, the bystander effect was assessed in vivo using cells of oral squamous cell carcinoma origin. Mixtures of HSVtk+ and HSVtk- tumor cells were implanted subcutaneously in the left flank of nude mice, and naive HSVtk- cells were implanted subcutaneously in the right flank. When tumors attained a size of 0.5 to 1 cm, the animals were treated with ganciclovir on a daily basis. The tumors comprised of mixed cells in the left flank resolved, consistent with a predicted bystander effect. The naive tumors in the right flank either resolved or became cytostatic showing little further growth compared to controls. Similar results were obtained when naive tumors were grown in both flanks and the tumor in the left flank received intratumoral injection of HSVtk retroviral producer cells or PA317 (HSVtk+) packaging cells, but not parental NIH 3T3 cells. Concomitant treatment with dexamethasone impaired the antitumor effect on the contralateral side. When these experiments were performed in SCID-Beige mice, there was a reduced antitumor effect on the ipsilateral flank and no antitumor response in the contralateral flank. Together with histology of regressing tumors, which showed an infiltration of lymphoid cells, these results are suggestive of an immune-related antitumor response that could account for the distant bystander effect.

3T3 Cells↗