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Biomedical subjects

S Ryu

Publications and source records attributed to S Ryu.

At least 73 records · Page 4Linked to original sources
PubMed1996

Amelioration of hyperglycemia in streptozotocin-induced diabetic rats receiving a marginal mass of islet grafts by troglitazone, an oral antidiabetic agent.

Troglitazone, a novel oral antidiabetic agent, was evaluated to determine whether it could have hypoglycemic effects in streptozotocin (STZ)-induced diabetic rats when a marginal mass of islets was transplanted and hyperglycemia persisted after transplantation. Lewis rats (RT1(1)) were used as both donors and recipients. Five hundred fresh islets were transplanted beneath the kidney capsule of STZ-induced diabetic recipients. Troglitazone was administered orally (0.34 mmol/kg/day) for 7 days before and for 60 days after islet transplantation. Neither troglitazone treatment without islet transplantation (n = 8) nor islet transplantation alone (n = 7) could produce normoglycemia (< 11 mmol/L) in diabetic recipients by 60 days after transplantation. In marked contrast, seven of 10 rats receiving islet grafts and treated with troglitazone became normoglycemia at 26.9 +/- 16.4 days (mean +/- SD; n = 7) after transplantation. Removal of the kidney bearing the grafts promptly resulted in the normoglycemic recipients (n = 4) becoming diabetic again. Light and electron microscopically, the intact islets with well-granulated beta cells could be observed in the transplant site of the normoglycemic recipients. These findings clearly demonstrate that the hyperglycemia in STZ-induced diabetic rats receiving an insufficient number of islet grafts to reverse diabetes was ameliorated by troglitazone treatment.

Animals↗
PubMed1996

Necrotizing fasciitis due to group A streptococci: a clinicopathological study of six patients.

The recent worldwide appearance of invasive group A streptococcal infections has again called attention to streptococcal necrotizing fasciitis. However, in contrast to polymicrobial necrotizing fasciitis, the streptococcal form has not been thoroughly studied clinically. The objective of the study was to elucidate the characteristic features of recent cases of necrotizing fasciitis due exclusively to pure group A streptococci. We encountered six patients with these criteria at a single hospital in Japan during the last 12 years. A clinicopathological analysis was performed in these six patients. In three patients, the clinical signs and the laboratory findings were characteristic of systemic toxicity. In this group, the clinical presentation was a pale or blue-gray lesion associated with severe intravascular coagulation histologically involving the vessels in the lesion. In the three patients without signs of systemic toxicity, a swollen, erythematous skin lesion persisted for as long as one week; histologically, the intravascular coagulation within these lesions was mild. In clinicopathological terms, the entity in these six patients could be clearly classified as either fulminant or subacute. In the fulminant type, immediate surgical debridement of necrotic fascia is required; in the subacute type, incision and drainage alone are sufficient.

Adult↗
PubMed1996

The effects of work intensity on adolescent mental health, achievement, and behavioral adjustment: new evidence from a prospective study.

This article examines the effects of work intensity on adolescent mental health, academic achievement, and behavioral adjustment. Questionnaire data were collected yearly from an initial panel of 1,000 randomly selected ninth graders (14-15 years old). Consistent with other studies, students who worked at higher intensity engaged in more alcohol use. The methodological strengths of this research (a representative panel studied prospectively over a 4-year period with minimal attrition and an analysis incorporating key control and lagged variables) provide strong evidence that adolescent work fosters alcohol use. The contention that work of high intensity has deleterious effects on mental health, academic achievement, and 2 other indicators of behavioral adjustment did not withstand our stringent tests. However, high school seniors who worked at moderate intensity (1-20 hours per week) had higher grades than both nonworkers and students who worked more hours per week.

Achievement↗
PubMed1996

[Current diagnosis and treatment of early pancreatic cancer].

In the present study our current experience of early pancreatic cancer is described. The early pancreatic cancer was defined when the tumor was located within the pancreas and/or less than 2 cm in diameter. Between 1983 and 1995, 9 out of 183 cases with pancreatic cancer were fulfilled with the criteria of early pancreatic cancer. Among the diagnostic modalities including US, CT, ERP, balloon ERP-CS and EUS, the balloon ERP-CS as well as EUS appears the most valuable procedure for making diagnosis of small pancreatic cancer. Currently, 8 out of 9 patients are alive at 1-10 years after surgery.

Adult↗
PubMed1995

Effect of the FruR regulator on transcription of the pts operon in Escherichia coli.

The promoters of the pts operon of Escherichia coli are controlled by the cyclic AMP receptor protein (CRP) complexed with cAMP (CRP.cAMP). In addition, glucose stimulates pts operon expression in vivo. The pts promoter region has a fructose repressor (FruR)-binding site (the FruR box) that partially overlaps with one of the CRP.cAMP-binding sites. The effects of the pleiotropic transcriptional regulator FruR on pts operon expression were studied to determine whether the in vivo glucose effect on pts operon expression is mediated by FruR. In vitro, FruR can repress P1b transcription, which is activated by CRP.cAMP, and restore P1a transcription, which is repressed by CRP.cAMP. FruR can displace CRP.cAMP from its binding site in the presence of RNA polymerase even though FruR and CRP.cAMP can bind simultaneously to their partially overlapping binding sites in the absence of RNA polymerase. FruR had very little effect on the transcription of the P0 promoter, which is most important for regulation by glucose. Consistent with the in vitro results, pts P0 transcription did not increase as much in cells grown in the presence of fructose or in fruR- mutant cells as in cells grown in the presence of glucose. These results suggest that FruR alone does not mediate the in vivo glucose effect on pts operon expression.

Bacterial Proteins↗
PubMed1995

CRP-DNA complexes: inducing the A-like form in the binding sites with an extended central spacer.

The consensus DNA sequence for binding of the Escherichia coli cyclic AMP receptor protein (CRP) has two symmetrically related inverted recognition elements TGTGA:TCACA, separated by a variable spacer, normally 6 bp long. We have shown that the CRP-cAMP complex, when bound to synthetic binding sites with an extended 8 bp spacer segment, induces an increase in the DNA circular dichroism (CD). The CD change at lambda > 275 nm agrees with the shift of approximately one helical turn of DNA into A-like form. The B-conformation is preserved for CRP binding sites similar to that in the lac and uxaCA promoters with 6 bp spacers. Another effect accompanying DNA binding is a dramatic increase of the negative CD magnitude in the spectral region of the ligand cAMP, at lambda < 272 nm. This effect is observed when CRP binds to specific sites with 6 or 8 bp spacers as well as to non-specific DNA. We reason that the A-like form arises by compressing and unwinding the DNA in CRP-DNA complexes having 8 bp central spacers. This serves to maintain a fixed length and twisting angle and is controlled by the protein's relatively rigid frame. This model is consistent with the observation that some binding sites with 6 bp spacers may also show the CD increase inherent to the sites with the extended 8 bp spacers. These 6 bp spacers are characterized by an increased twisting angle that requires their unwinding to bind to CRP. We propose that a mutual adaptation between CRP and binding sites by local untwisting and a B-->A-like transition in the DNA is of general importance and may occur in other protein-DNA complexes, such as the complex of RNA polymerase with promoter DNA.

Base Sequence↗
PubMed1995

Elevation of cystathionine gamma-lyase activity in the serum of rats treated with a single dose of carbon tetrachloride.

Cystathionine gamma-lyase activity in the sera of rats subjected to experimental hepatotoxicity after intraperitoneal administration of carbon tetrachloride (CCl4) was measured and compared with activities of aspartate aminotransferase (GOT) and alanine aminotransferase (GPT), which have been clinically used for detecting liver damage. In the experimental subjects, serum levels of cystathionine gamma-lyase showed a similar behavior to GOT and GPT, increasing markedly with respect to the controls after administration of CCl4 and reaching a maximum at 24 hours. No such cystathionine gamma-lyase activity was detected immunochemically in the control subjects. These data suggest that measurement of serum cystathionine gamma-lyase activity could be used as a sensitive and specific marker of hepatic cytolysis.

Animals↗
PubMed1994

Estramustine: a novel radiation enhancer in human carcinoma cells.

PURPOSE: Estramustine (EM), an antimicrotubule agent, binds microtubule-associated proteins, causes spindle disassembly, and arrests cells at the late G2/M phase of the cell cycle. Since cells in the G2/M phase are the most radiosensitive and some human cancer cells contain high level of EM-binding protein, experiments were carried out to determine whether radiation sensitization could be obtained in human carcinoma cells. METHODS AND MATERIALS: Cells containing a high level of EM-binding protein such as prostate carcinoma (DU-145), breast carcinoma (MCF-7), and malignant glioma (U-251) were used to demonstrate radiosensitization. Cervical carcinoma (HeLa-S3) and colon carcinoma (HT-29) cells which are not known to contain EM-binding protein were also employed. Cell survival was assayed by the colony forming ability of single plated cells in culture to obtain dose-survival curves. RESULTS: Pretreatment of DU-145, MCF-7, and U-251 cells to a nontoxic concentration (5 microM) of EM for more than one cell cycle time, substantially enhanced the radiation-induced cytotoxicity. The sensitizer enhancement ratio of these cells ranged from 1.35-1.52. The magnitude of the enhancement was dependent on the drug concentration and exposure time. The rate of cell accumulation in G2/M phase, as determined by flow cytometry, increased with longer treatment time in the cell lines which showed radiosensitization. Other antimicrotubule agents such as taxol and vinblastine caused minimal or no radiosensitization at nontoxic concentrations. CONCLUSION: The data provide a radiobiological basis for using EM as a novel radiation enhancer, with the property of tissue selectivity.

Breast Neoplasms↗
PubMed1994

An arcane role of DNA in transcription activation.

The mechanism by which the cAMP receptor protein (CRP) activates transcription has been investigated using the lac promoter of Escherichia coli. For transcription activation, an interaction between DNA-bound CRP and RNA polymerase is not sufficient. CRP must bind to a site in the same DNA and close to the promoter. CRP action requires an intact spacer DNA to provide a rigid support in building a CRP-RNA polymerase protein bridge or to allow a conformational change in the DNA to be transmitted to the lac promoter using the protein bridge as a structural support.

Base Sequence↗
PubMed1994

Clinical and biological studies of estramustine phosphate as a novel radiation sensitizer.

PURPOSE: Estramustine phosphate (EMP), a nor-nitrogen mustard carbamate derivative of estradiol-17 beta-phosphate, causes G2/M phase arrest in treated cells through its specific binding to microtubule associated proteins. Since cells in the G2/M phase are the most radiosensitive, cell culture experiments were performed to determine whether EMP would enhance the radiosensitivity of related human tumor cells. Based on the cell culture findings and well known pharmacokinetic data in humans, a Phase II prospective study of concomitant radiotherapy (RT) and EMP plus Velban for locally advanced carcinoma of the prostate was carried out. METHODS AND MATERIALS: Three established human tumor cells, DU-145 cells (prostate), MCF-7 cells (breast), and U-251 cells (malignant glioma), were used to determine cell survival curves with and without the drug. Flow cytometry was used to obtain the cell cycle distribution of cells that were exposed to the drug for periods of 1 day to 1 week. Patients with locally advanced prostate cancer (Stages B2, C, D1) were entered into the Phase II study. All patients received a total tumor dose of 65-70 Gy over 7 weeks. Oral EMP was administered daily and Velban was administered weekly, concomitantly during the course of RT. RESULTS: Radiosensitization was dependent on the exposure time and the drug concentration prior to radiation. No radiosensitization was obtained when cells were exposed to the drug after irradiation. The enhancement ratios varied from 1.3-1.6 at the 10% survival level. All patients who received the combined RT and EMP plus Velban achieved complete response (n = 27). The rate of PSA (prostate specific antigen) reduction was very prompt compared to that of the RT alone group. There was not disproportionately enhanced side effects for the combined regimen. CONCLUSION: EMP enhances radiation induced cytotoxicity in several human tumor cells in culture. The effect is most significant after prolonged exposure to the drug before irradiation. Documented G2/M phase cell cycle block by EMP is the likely mechanism of radiosensitization. The preliminary clinical findings with the combined RT and drugs are highly encouraging.

Adenocarcinoma↗
PubMed1994

Photodynamic therapy and/or external beam radiation therapy for roentgenologically occult lung cancer.

BACKGROUND AND METHODS: Thirty-nine roentgenologically occult lung cancers in 29 patients were treated using photodynamic therapy (PDT) and/or thoracic radiotherapy (TRT) from January 1986 to March 1992. With the exception of one mixed-tumor case, all were squamous cell carcinomas. RESULTS: Initial PDT achieved complete responses in 25 of 39 (64%) of the cancers. Of the remaining 14 cancers that showed less than complete response (CR), 10 of the 14 (71.4%) showed a CR when subsequently treated with TRT, yielding an overall CR rate of 89.7% for cancers treated. Although nine patients experienced recurrences, six of these had CR when treated with PDT and/or TRT. To date, 22 patients are alive. Causes of death in the patients enrolled in this study are as follows: pyothorax (2); heart failure due to pulmonary hypertension (1); chronic respiratory insufficiency (1); subsequent primary brain cancer (1); and subsequent primary lung cancer (1). Only one died of primary lung cancer. CONCLUSIONS: These findings suggest that PDT and/or TRT may be used as an alternative to surgery in the treatment of selected patients with roentgenologically occult lung cancer.

Adult↗
PubMed1994

Promoter switch in the Escherichia coli pts operon.

The ptsH operon of Escherichia coli is controlled by two promoters P0 and P1, each of which is regulated by cyclic AMP receptor protein (CRP) complexed with cAMP (CRP.cAMP). We have studied the in vitro as well as in vivo transcriptional regulation of these two promoters. Each promoter exhibits a switching mechanism in vitro, where, depending upon the presence or absence of CRP.cAMP, transcription is initiated from different start sites termed a and b. P0 (P0a) is affected by supercoiling: when the template is linear, transcription initiation is switched to a site 3 base pairs upstream (P0b) and becomes more CRP.cAMP dependent. Transcription from the P1 promoter (P1a) switches initiation sites to 7 base pairs downstream (P1b) in the presence of CRP.cAMP. Most transcription in vivo was from P1a, and P0b could not be detected in vivo. Glucose has independent positive effects on pts expression in vivo. The results indicate that the two different regulatory mechanisms (one through CRP.cAMP, the other through glucose) are working together for fine control of pts expression.

Base Sequence↗
PubMed1994

Acetylcholine regulates glucagon secretion from human glucagonoma cells.

Human glucagonoma cells were isolated and maintained in vitro. Incubation experiments showed that carbachol (Cch) induced the simultaneous release of glucagon, VIP (vasoactive intestinal polypeptide), and pancreatic polypeptide (PP) at levels significantly higher than basal levels. Atropine abolished the stimulatory effect of Cch on glucagon, VIP, and PP release. An immunohistological study of the tumor tissues revealed that the cells contained glucagon, VIP, and PP. These findings demonstrate, for the first time, the in vitro release of glucagon from glucagonoma cells by Cch stimulation.

Carbachol↗