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Biomedical subjects

S Ryu

Publications and source records attributed to S Ryu.

At least 55 records · Page 3Linked to original sources
PubMed1999

In-vitro synergy of paromomycin with metronidazole alone or metronidazole plus hydroxymetronidazole against Helicobacter pylori.

The in-vitro activities of paromomycin and metronidazole alone or paromomycin and metronidazole plus hydroxymetronidazole (2:1 ratio) were studied against 19 Helicobacter pylori isolates using an in-vitro chequerboard technique. Partial synergy was demonstrated for the majority of isolates (11/19) for both combinations tested. When hydroxymetronidazole was added to the parent compound, the number of metronidazole-sensitive isolates demonstrating synergy increased to 5/12, compared with 1/12 for the combination that did not include the metabolite. In metronidazole-resistant isolates there was a shift from an additive effect to partial synergy for the combination containing hydroxymetronidazole. The in-vitro activity of paromomycin and the synergic effect that is achieved in combination with metronidazole and hydroxymetronidazole render paromomycin suitable for further investigation as a treatment option for H. pylori infection.

Anti-Bacterial Agents↗
PubMed1999

Bactericidal activity and postantibiotic effect of levofloxacin against anaerobes.

The bactericidal activity and postantibiotic effect (PAE) of levofloxacin against nine anaerobes were determined. Levofloxacin at concentrations of the MIC and twice the MIC was bactericidal at 24 h to five of nine and nine of nine strains, respectively. The PAE of levofloxacin following a 2-h exposure ranged from 0.06 to 2.88 h.

Anti-Infective Agents↗
PubMed1999

Precocious estrus and reproductive ability induced by PG 600 in prepuberal gilts.

A total of 29 SPF Large White prepuberal gilts (mean age 152 days at treatment) were examined for estrous and ovulatory responses after PG 600 treatment. After treatment, 85.2% of the gilts showed standing estrus within 6 days. Whereas the treatment-to-estrus interval and duration were 3.7 and 1.9 days respectively. As ovulation occurred on Day 5 to 6, appropriate timing of artificial insemination would be about 4 days after treatment. Fertility of gilts revealed to be excellent, giving rise to a high percentage of normal embryos, 85.3%. Meanwhile, development and growth of fetuses were mostly normal. Other reproductive performances recorded were: mean litter size 6.8; mean birth weight 1.26 kg; weaning-to-return estrus interval 5 to 8 days. In conclusion, PG 600 was found to be useful in inducing fertile estrus in prepuberal gilts, a result which will be of interest for commercial pig farms.

Animals↗
PubMed1998

Retention of intracellular fibronectin expression in primary and metastatic thyroid carcinoma: an immunohistochemical study.

We previously showed that thyroid carcinoma distinctively expresses intracellular fibronectin (FN) compared to other carcinomas. To determine the persistency of such FN accumulation in metastasis, we immunohistochemically examined the accumulation of intracellular FN in 92 cases of different carcinomas originating from the thyroid gland, lung and kidney, 44 of which showed metastasis to other organs. In all of the cases, normal epithelial cells adjacent to carcinomas did not show intracellular FN. Almost all of the cases (31/32) of thyroid carcinoma with/without metastasis to the lung and/or kidney showed intracellular FN in both the primary and metastatic lesions. Few cases (2/38) of lung carcinoma and none of the 22 cases of kidney carcinoma showed intracellular FN in the primary and metastatic lesions. In conclusion, the intracellular accumulation of FN acquired after carcinogenic transformation is not a common phenomenon in carcinomas, but rather is distinctive for thyroid carcinoma, even when it metastasizes to other organs. The immunohistochemical detection of intracellular FN may be useful for diagnosing thyroid carcinoma, even in metastatic lesions.

Adult↗
PubMed1998

GalR-mediated repression and activation of hybrid lacUV5 promoter: differential contacts with RNA polymerase.

The GalR repressor regulates expression of genes of the gal regulon in Escherichia coli. We studied the regulatory effect of GalR in vitro on a heterologous promoter, lacUV5, by placing the GalR-binding site, OE, at different locations upstream of this promoter. Despite the fact that the lacUV5 promoter is transcribed efficiently by RNA polymerase (RNP) alone, GalR modulated transcription from many of the PlacUV5 variants. Depending on the location of OE and the neighboring DNA sequence, GalR repressed, activated or had no effect on the promoter. Both repression and activation involved formation of GalR-RNP-DNA ternary complexes and required an intact c-domain of the alpha subunit of the holoenzyme. These results support the differential contact model of a regulator action, in which a regulator differentially binds to, and lowers the energy of, intermediates of transcription initiation either to hinder or to facilitate a step of initiation. The nature of the contacts depends upon the context, i.e. the geometry of the ternary complex. The observed repression and activation effect of GalR on a heterologous promoter also underscores the point that a regulator is not a dedicated protein for repression or for activation.

Binding Sites↗
PubMed1998

CRP.cAMP-dependent transcription activation of the Escherichia coli pts Po promoter by the heat shock RNA polymerase (Esigma32) in vitro.

The P0 promoter of the Escherichia coli pts operon that is activated during growth in the presence of glucose contains a recognition sequence for the RNA polymerase holoenzyme containing sigma 70 (Esigma70) which is the RNA polymerase holoenzyme responsible for the transcription of heat shock genes, and a putative recognition element for Esigma32, the Esigma32 was found to be able to transcribe from the pts P0 promoter with in vitro transcription assays using purified RNA polymerase holoenzymes. Esigma32 and Esigma70 used the same transcriptional start site and both RNA polymerases were activated in the presence of a cAMP receptor protein (CRP) and cAMP complex (CRP.cAMP). These results suggest the possibility that the contact between CRP.cAMP and the alpha subunit of the RNA polymerase can be made regardless of the kind of sigma subunit that is associated with the core RNA polymerase.

Base Sequence↗
PubMed1998

In vitro radiosensitization of human cervical carcinoma cells by combined use of 13-cis-retinoic acid and interferon-alpha2a.

BACKGROUND: Significant antitumor activity has been reported with the combined use of 13-cis-retinoic acid (cRA) and interferon-alpha2a (IFN-alpha) in the treatment of advanced-stage cervical cancers and skin cancers. Since IFN-alpha has been shown to be a modest radiation enhancer for selected malignant tumor cells and the cytotoxic activity is more enhanced by combining cRA and IFN-alpha, we hypothesized that the exposure of selected human carcinoma cells to combined cRA and IFN-alpha would render the cells highly radiosensitive. METHODS AND MATERIALS: Two human cervical carcinoma cell lines, ME-180 and HeLa-S3, were chosen for the present study because of the different characteristics of the retinoic acid receptor status of the cell lines. To demonstrate the effects of combined cRA and IFN-alpha treatment on radiation response, we exposed the cells to cRA, IFN-alpha, or a combination of the drugs for 72 h before radiation. Experiments were carried out at minimally cytotoxic concentrations of the drug for radiation studies. End points of the study were cell growth inhibition and clonogenic ability of the single-plated cells. Effects of cRA and IFN-alpha on radiation response were quantitatively analyzed by constructing the radiation cell survival curves of ME-180 and HeLa cells. RESULTS: ME-180 cells exhibited varying degrees of cytotoxicity with cRA and IFN-alpha, while HeLa cells showed no toxic effects with the same treatment. Combined treatment of cRA and IFN-alpha produced an additive cytotoxic effect in ME-180 cells. Radiosensitization was minimal when ME-180 cells were treated with either cRA or IFN-alpha before radiation. When ME-180 cells were exposed to 10 microM cRA for 48 h and 1000 U/ml IFN-alpha for 24 h prior to radiation, there was a significant enhancement in radiation-induced cell killing; the dose modification factor was 2.1 +/- 0.9 at the 1% cell-survival level. On the other hand, HeLa-S3 cells exhibited no increased cytotoxicity or radiation enhancement under the same experimental conditions. CONCLUSION: The present data provide a radiobiological basis for using cRA and IFN-alpha as a combination radiosensitizer in selected human carcinoma cells.

Antineoplastic Agents↗
PubMed1998

A survey of human serum samples for antibody against Clostridium perfringens type A enterotoxin in humans in Korea.

Serum samples from humans in Chongju City, Korea, were tested for the presence of Clostridium perfringens enterotoxin antibody by enzyme linked immunosorbent assay (ELISA). About half of the 1054 samples tested had high ELISA readings, which could be the result of exposure to enterotoxin produced by C. perfringens. The high prevalence of the antibody among the Korean population suggests that foodborne illnesses caused by C. perfringens may be common in Korea even though the occurrence has not been monitored.

Adolescent↗
PubMed1998

Analysis of the gene encoding cyclomaltodextrinase from alkalophilic Bacillus sp. I-5 and characterization of enzymatic properties.

The gene encoding cyclomaltodextrinase (CDase) was cloned from alkalophilic Bacillus sp. I-5. The nucleotide sequence of the gene was determined and the physicochemical properties of the enzyme were investigated. The gene had an open reading frame of 559 amino acids with a predicted molecular weight of 64,884. The enzyme was purified to near homogeneity from Escherichia coli cells carrying a recombinant plasmid that contained the CDase gene. The enzyme hydrolyzed cyclomaltoheptaose (beta-CD) 13 times better than starch and 33 times better than pullulan, and it had transglycosylation activity. The enzyme also hydrolyzed acarbose, a pseudotetrasaccharide inhibitor of glucosidases. The enzyme was stabilized by Ca2+ and the activity was increased more than twofold in the presence of 5 mM EDTA. The optimum temperature of the enzyme was elevated from 40 to 50 degrees C by Ca2+ ion and the thermal activity was maintained more than 80% at 60 degrees C in the presence of Ca2+. Comparison of known amino acid sequences of several amylolytic enzymes with cyclomaltodextrinase activity, site-directed mutagenesis of the enzyme, and substrate specificity of the enzyme imply that the region between the third and the fourth conserved regions of the enzyme may play an important role in binding and degradation of cyclomaltodextrin.

Acarbose↗
PubMed1997

Thyroid carcinoma distinctively expresses intracellular fibronectin in vivo.

Fibronectin is a multifunctional protein that plays a role in tumor invasion. We immunohistochemically examined the in vivo expression of fibronectin in thyroid carcinoma in comparison with other carcinomas, such as hepatocellular carcinoma, transitional cell carcinoma and gastric adenocarcinoma. Intracellular localization of fibronectin was found in almost all cases of thyroid carcinoma. In contrast, hepatocellular carcinoma showed a lower expression rate and the other carcinomas were all negative. These results indicate that the intracellular expression of fibronectin is not a common phenomenon in carcinoma, but rather is distinctive for thyroid carcinoma.

Adenocarcinoma↗
PubMed1997

In vitro synergy testing of clarithromycin and 14-hydroxyclarithromycin with amoxicillin or bismuth subsalicylate against Helicobacter pylori.

The activity of clarithromycin-14-hydroxyclarithromycin (2:1 ratio) and bismuth subsalicylate or amoxicillin against Helicobacter pylori was determined by the checkerboard technique in vitro. Clarithromycin-14-hydroxyclarithromycin and amoxicillin resulted in additive effects in 7 of 22 isolates, compared to 14 of 22 isolates when bismuth subsalicylate was substituted for amoxicillin. Synergy was not demonstrated and is probably not responsible for the clinical success of treatment combinations containing clarithromycin.

Amoxicillin↗
PubMed1996

Preferential radiosensitization of human prostatic carcinoma cells by mild hyperthermia.

PURPOSE: Recent cell culture studies by us and others suggest that some human carcinoma cells are more sensitive to heat than are rodent cells following mild hyperthermia. In studying the cellular mechanism of enhanced thermosensitivity of human tumor cells to hyperthermia, prostatic carcinoma cells of human origin were found to be more sensitive to mild hyperthermia than other human cancer cells. The present study was designed to determine the magnitude of radiosensitization of human prostatic carcinoma cells by mild hyperthermia and to examine whether the thermal radiosensitization is related to the intrinsic thermosensitivity of cancer cells. METHODS AND MATERIALS: Two human prostatic carcinoma cell lines (DU-145 and PC-3) and other carcinoma cells of human origin, in particular, colon (HT-29), breast (MCF-7), lung (A-549), and brain (U-251) were exposed to temperatures of 40-41 degrees C. Single acute dose rate radiation and fractionated radiation were combined with mild hyperthermia to determine thermal radiosensitization. The end point of the study was the colony-forming ability of single-plated cells. RESULTS: DU-145 and PC-3 cells were found to be exceedingly thermosensitive to 41 degrees C for 24 h, relative to other cancer cell lines. Ninety percent of the prostatic cancer cells were killed by a 24 h heat exposure. Prostatic carcinoma cells exposed to a short duration of heating at 41 degrees C for 2 h resulted in a substantial enhancement of radiation-induced cytotoxicity. The thermal enhancement ratios (TERs) of single acute dose radiation following heat treatment 41 C for 2 h were 2.0 in DU-145 cells and 1.4 in PC-3 cells. The TERs of fractionated irradiation combined with continuous heating at 40 degrees C were similarly in the range of 2.1 to 1.4 in prostate carcinoma cells. No significant radiosensitization was observed in MCF-7 and HT-29 cells under the same conditions. CONCLUSION: The present data suggest that a significant radiosensitization of prostatic cancer cells could be obtained by the combined treatment of radiation and mild hyperthermia. Future clinical trials should be aimed at achieving mild heating and fractionated radiation therapy.

Combined Modality Therapy↗
PubMed1996

A case of malignant pleural mesothelioma with metastasis to the orbit.

A 58-year-old woman with malignant mesothelioma metastatic to the orbit is reported. Malignant pleural mesothelioma was diagnosed by pleural biopsy. Marked reduction of pleural effusion was obtained with intrapleural interleukin-2 therapy. Systemic chemotherapy failed to elicit a response after the first recurrence of the tumor. Multiple systemic metastasis, including metastasis to the orbit, developed and the patient died one year and 4 months after the initial diagnosis. Although malignant mesothelioma is known to spread hematogenously, sometimes producing brain metastasis, there have been few reports of orbital metastasis, and in fact the present report may be the first clinically documented account of its kind.

Female↗