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Biomedical subjects

H Choi

Publications and source records attributed to H Choi.

216 records · Page 12Linked to original sources
PubMed1976

Influence of hippocampectomy on gastric ulcer in rats.

Hippocampectomized male rats were prepared, and the incidence as well as severity of gastric ulceration upon restraint were compared with those of normal control animals and controls with localized damage to the cortex over the hippocampus. In another experiment, observations on gastric ulceration were made without restraint in hippocampectomized animals, normal controls, controls with cortical damage, vagotomized animals and animals that received hippocampectomy as well as vagotomy. Both in restrained and unrestrained states, the incidence of animals with ulcer as well as the number and the total area of ulcers per stomach were significantly larger in the hippocampal animals than they were in the other animal groups. Vagotomy abolished the effect of hippocampectomy upon gastric ulceration in the unrestrained state. We infer that the hippocampus helps to protect the stomach from ulceration partly by controlling vagal activity.

Animals↗
PubMed1976

Influence of ginseng on mating behavior of male rats.

Experiment on the mating behavior of male albino rats paired with receptive females established that in comparison with control animals, males under the influence of ginseng (a) began ejaculation earlier and repeated the action more often in a 45-minute observation period and (b) deposited more copulation plugs in 10 days. The data suggest that ginseng facilitates the mating behavior of male rats.

Animals↗
PubMed1975

Effect of hippocampectomy on sleep patterns in cats.

The study was planned to see if the hippocampus has an influence on fast wave sleep (FWS) as well as on slow wave sleep (SWS). From 8 male cats EEG, EMG and EOG were recorded for 24 h, first under normal conditions, secondly after cortical damage to the dorsal marginal portion of posterior ectosylvian gyrus, and thirdly following hippocampectomy done through the cortical damage. From the records, SWS, FWS and the sleep state (defined as a sequence of SWS or SWS-FWS phases between two successive waking states) were measured in terms of their occurrence, the mean duration and the total time they occupied in the day, night and 24 h. In addition, sleep sequences were classified according to the number of constituent sleep phases. Cortical damage did not affect SWS, FWS, or sleep state with regard to their occurrence, the mean duration, and the total time they occupied in 24 h. Nor did it affect the proportion of short and long sequences. The circadian variation of sleep was clearly retained. Hippocampectomy significantly reduced the total time occupied by sleep state, SWS and FWS, increased the occurrence of sleep state and SWS phase against decreased incidence of FWS phase, and reduced the mean duration of sleep state and SWS phase. Hippocampectomy also significantly increased the occurrence of sleep sequences with only one SWS phase at the cost of sequences with alternating SWS and FWS phases. Following hippocampectomy, the circadian variation of sleep was not only retained, but actually exagerated. The hippocampus in inferred to facilitate the FWS as well as the SWS phase of sleep.

Animals↗
PubMedDate not supplied

Glycosaminoglycans and proteoglycans induce gap junction expression and restore transcription of tissue-specific mRNAs in primary liver cultures.

Normal rat hepatocytes maintained on tissue culture plastic and in serum-supplemented medium lose their gap junctions within 12 hr and expression of their tissue-specific functions within 24 to 72 hr. The gap junctions are lost via internalization and degradation, and the differentiated functions due to loss of synthesis and to rapid degradation of tissue-specific mRNAs. Near normal levels of tissue-specific mRNAs can be achieved by stabilization of the mRNAs but not by transcription (for most genes), if the cells are cultured in a serum-free, hormonally defined medium and on substrata of tissue culture plastic, fibronectin or laminin, or on various purified collagens. The hormonally defined medium also extends the life-span of the gap junctions to about 24 hr. Certain glycosaminoglycans, proteoglycans and anionic polysaccharides have proven to be potent inducers of gap junction expression and function, to increase abundance of tissue-specific mRNAs, and to lower abundance of common gene mRNAs, a level of gap junctions and a pattern of gene expression similar to that in vivo. Addition to the hormonally defined medium of 10 micrograms per ml of hyaluronates, dermatan sulfates, bovine lung heparan sulfate, chondroitin 4-sulfate or chondroitin 6-sulfate resulted in a weak response in induction of gap junctions (5 to 15% of the cells became dye and electrically coupled) and in gene expression. An intermediate response in gap junction expression (30 to 50% coupled cells) and in gene expression was observed with 50 to 100 micrograms per ml of heparins or hyaluronates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

MR imaging characteristics of noncancerous lesions of the prostate.

Radical prostatectomy specimens from 53 men with clinical stage A or B prostate cancer were retrospectively reviewed and compared with correlative axial T2-weighted magnetic resonance (MR) images obtained just before surgery. Non-cancerous lesions were evaluated for signal intensity and location. Focal high-signal-intensity areas (n = 72) were present in 81% of patients. The 26% of lesions seen in the central gland all correlated with cystic atrophy. Of the 53 lesions seen in the peripheral prostate, 47 (89%) were cystic atrophy without associated cancer, four (7.5%) cystic atrophy with cancer, and two (3.8%) focal inflammation. Focal low-signal-intensity areas (n = 42) were present in 60% of patients. Of the 31% of lesions in the central prostate, one-fifth correlated with benign prostatic hyperplasia (BPH) and four-fifths with fibrous tissue. Of the 69% of peripheral lesions, 83% corresponded to fibrous tissue, 10% to BPH, and 7% to normal tissue. Mixed lesions (n = 42) were present in 64% of patients; 86% of these were located centrally and 14% peripherally. All mixed central lesions were BPH; the peripheral lesions were areas of combined cystic atrophy and fibrosis. BPH of low or mixed signal intensity can extend into the peripheral prostate and mimic cancer. High-intensity cystic atrophy associated with cancer can mimic normal tissue.

Aged↗
PubMedDate not supplied

Cultural marginality: a concept analysis with implications for immigrant adolescents.

Society in the United States is becoming increasingly culturally diverse. In 1996, almost 1 in 10 people living in the United States was a foreign-born immigrant and the number of foreign-born in the population exceeded 25 million. However, the lack of mutual understanding between health care providers and immigrants, particularly children and adolescents, has impeded progress in research and practice for this population. To facilitate nurses' understanding of immigrant adolescents' unique experiences, this article explores the concept of cultural marginality. Cultural margin ality is defined by the author as "situations and feelings of passive betweeness when people exist between two different cultures and do not yet perceive themselves as centrally belonging to either one." Using Walker and Avant's (1995) method as a framework, my article identifies attributes, antecedents, and consequences of cultural marginality in the context of immigrant adolescents' experiences. To clarify the abstract concept, cases are provided that distill meanings of the concept in life. A conceptual model has been synthesized to illustrate relationships among attributes, antecedents, and consequences and to highlight areas for further inquiry. Concept analysis is a critical step for the develop ment of nursing knowledge. The process of concept analysis is demonstrated through clarification of the concept of cultural marginality, which offers guidance for nursing research and practice within the immigrant adolescent population.

Adolescent↗
PubMedDate not supplied

A fatality due to injection of tiletamine and zolazepam.

A 22-year-old male with more than 28 needle marks on his right arm was found dead. First, he was suspected as a drug abuser. Blood, urine, spleen, and injection-site tissue was collected during autopsy. The blood and urine specimens were screened for drugs. Immunoassay studies did not show any illegal drugs. However, two unidentified peaks were isolated in both of these biological fluids by routine gas chromatography-flame-ionization detection (GC-FID) and thermionic specific detection. Additional gas chromatography-mass spectrometry analysis determined these two peaks to be tiletamine and zolazepam. These two agents are used in combination as veterinary anesthesia. The concentrations of these drugs in blood were quantitated by GC-FID and found to be 0.85 mg/L of tiletamine and 3.3 mg/L of zolazepam. In urine, tiletamine and its metabolite, 2-(ethylamino)-2-(2-thionyl) cyclohexanol, were identified to be present along with zolazepam. The concentrations of tiletamine and zolazepam in spleen were revealed to be 0.92 and 3.5 mg/kg, respectively. Injection-site tissue concentrations were determined to be 25.1 mg/kg tiletamine and 23.3 mg/kg for zolazepam. The cause of death in this case was determined to be due to the multiple drug intoxication of tiletamine and zolazepam.

Adult↗
PubMedDate not supplied

Multi-institutional phase 2 study of TLK286 (TELCYTA, a glutathione S-transferase P1-1 activated glutathione analog prodrug) in patients with platinum and paclitaxel refractory or resistant ovarian cancer.

The purpose of this study was to determine the safety and efficacy of TLK286 (TELCYTA(TM)), a glutathione analog prodrug, in patients with platinum and paclitaxel refractory or resistant ovarian carcinoma. Thirty-six patients with measurable disease were enrolled. TLK286 was administered at 1000 mg/m2 intravenously every 3 weeks. The endpoints were objective response rate assessed by Response Evaluation Criteria in Solid Tumors (RECIST) and survival. Adverse events were graded using the National Cancer Institute Common Toxicity Criteria. Thirty-four platinum refractory or resistant patients (94%) were evaluable for objective tumor response. Five patients (15%) had objective tumor responses, including one durable complete response (CR) of greater than 3 years and continuing. The disease stabilization rate was 50%, including one CR (3%), four partial responses (12%), and 12 durable disease stabilizations (35%). Responses were accompanied by improvement in clinical symptoms and Eastern Cooperative Oncology Group Performance Status (ECOG PS) and decline in CA125 levels. Median survival was 423 days with survival of 60% at 1 year and 40% at 18 months. TLK286 was well tolerated in this population. TLK286 is an active agent in chemotherapy-resistant ovarian cancer. Further studies of TLK286 in platinum and paclitaxel refractory or resistant ovarian cancer are in progress.

Adult↗
PubMedDate not supplied

Leaching characteristics of heavy metals from sewage sludge by Acidithiobacillus thiooxidans MET.

An acidophilic, sulfur-oxidizing Acidithiobacillus thiooxidans MET bacterium was isolated from anaerobically digested, dewatered sewage sludge. This bacterium showed sulfur-oxidizing ability at both acidic and neutral conditions, and allowed metal leaching even at a high (130 g L(-1)) sludge solids concentration. We found that low metal leaching efficiency at high solids concentration was mainly due to an increase in buffering capacity resulting in retardation of pH reduction. Therefore, metal leaching was mainly influenced not by sludge solids concentration, but by the pH (or sulfate concentration per unit sludge mass) of the sludge solutions. The relationship between the pH of the sludge solution and the efficiency of metal leaching was obtained by quantitatively investigating the effect of pH reduction or the amount of sulfate produced per unit sludge mass on leaching of each metal. Furthermore, the relationship between total metal content in the sludge and metal leached to the solution was obtained for each metal. Such a relationship allowed estimation of leachable metal at various amounts of total metal content in sludge.

Gammaproteobacteria↗
PubMedDate not supplied

Development of a new plasmid vector with PSA-promoter and enhancer expressing tissue-specificity in prostate carcinoma cell lines.

Differential expression of the desired gene product in the target tissue is central to the concept of gene therapy. One approach is to use a tissue-specific promoter to drive therapeutic genes, such as the p53 tumor suppressor gene. To determine the feasibility of tissue-specific gene therapy for prostate cancer using prostate specific antigen (PSA) promoter and/or enhancer, in this study, we developed a tissue specific expression vector using a PSA promoter and enhancer. Our results showed that the cloned PSA promoter actively drives gene expression in the PSA-producing prostate cancer cell line (LNCaP). However, barely any promoter activity was detected in the non-PSA producing prostate cancer cell lines (DU145, PC-3) or the non-prostate cell lines (HEK-293, SAOS-2). The wild-type p53 gene driven by this PSA-promoter efficiently suppressed the growth of LNCaP. Moreover, p53 driven by the PSA enhancer-promoter cassette more efficiently suppressed the growth of the PSA-producing prostate cancer cell line (LNCaP) in vitro. This suggest that we were able to manage the tissue specificity by PSA enhancer and promoter. Additionally, the juxtaposed enhancer-promoter cassette showed great enhancement of p53 expression and apoptosis in vitro. Taken together, these results show that PSA enhancer-promoter may be a potential tool for gene therapy for prostate cancer.

Adenocarcinoma↗
PubMedDate not supplied

Passivity of fit and marginal opening in screw- or cement-retained implant fixed partial denture designs.

The relationship of stress generation upon placement of cement-retained or screw-retained implant restorations has not been thoroughly investigated. Passivity of fit and marginal discrepancies of screw- and cement-retained implant fixed partial denture (FPD) designs were determined using a photoelastic model of a partially edentulous posterior mandibular arch with 3 screw-type implants. Buccal and lingual marginal openings, measured with a traveling microscope before cementation or screw tightening, revealed no statistical difference in adaptation between designs. Screw tightening caused a reduction in marginal opening (changes significant, P < .05). The opening with the cemented FPDs was similar before and after cementation. Photoelastic evaluation of the FPDs showed that cement-retained FPDs exhibited a more equitable stress distribution than did their screw-retained counterparts.

Cementation↗
PubMedDate not supplied

Asiatic acid derivatives protect cultured cortical neurons from glutamate-induced excitotoxicity.

Asiatic acid, a triterpene of Centella asiatica (L.) Urban (Umbelliferae), has been patented as a treatment for dementia and an enhancer of cognition by the Hoechst Aktiengesellschaft (EP 0 383 171 A2). We modified the chemical structure of asiatic acid and obtained 36 derivatives of asiatic acid in an attempt to prepare neuroprotective compounds that were more efficacious than asiatic acid itself. The neuroprotective activities of these derivatives were evaluated using primary cultures of rat cortical neurons insulted with the neurotoxin, glutamate, as an in vitro screening system. Among the semi-synthesized derivatives, three derivatives significantly mitigated the neurotoxicity induced by glutamate in this screening system. The neuroprotective activities of these 3 derivatives appeared to be more powerful than that of asiatic acid itself. These 3 derivatives significantly attenuated decreases in the levels of glutathione, glutathione peroxidase and other enzymes, which participate in the cellular defense mechanisms blunting oxidative stress. Furthermore, they significantly reduced the overproduction of NO induced by glutamate. These results showed that these derivatives of asiatic acid exerted significant neuroprotective effects on cultured cortical cells by their potentiation of the cellular oxidative defense mechanism. Therefore, these agents may prove to be efficacious in protecting neurons from the oxidative damage caused by exposure to excess glutamate.

Animals↗
PubMedDate not supplied

Necrotizing arteriolitis of ileum, as the initial manifestation of malignant hypertension in childhood.

Intestine is seldom a site of clinical manifestation of malignant hypertension, particularly in childhood. This report deals with a case of malignant nephrosclerosis superimposed on benign nephrosclerosis which probably resulted from a unilateral obstructive uropathy and chronic pyelonephritis. Clinical features included severe hypertension, neuroretinopathy with retinal exudate and hypertensive encephalopathy. An acute abdomen due to transmural infarction of the ileum caused by multiple thrombotic occlusion of necrotizing arteritis involving bowel wall and the mesentery was noted.

Arterioles↗
PubMedDate not supplied

The effect of promoter strength in adenoviral vectors containing herpes simplex virus thymidine kinase on cancer gene therapy in vitro and in vivo.

The use of adenoviral vectors to deliver the herpes simplex virus thymidine kinase (HSVtk) gene followed by treatment with the prodrug ganciclovir (GCV) has promise for a variety of applications where excess cell proliferation is detrimental such as treatment of tumors and vascular restenosis. Optimizing this system is thus an important goal. The purpose of this study was to determine if the induction of higher levels of HSVtk expression would augment the sensitivity to GCV. This was accomplished by generating adenoviral vectors that expressed HSVtk from promoters of different efficiencies (the CMV versus RSV promoters). Despite higher levels of HSVtk expression per cell with the CMV promoter, there was no significant enhancement of antitumor effects between RSV- and CMV-driven adenovirus vectors in in vitro and in vivo studies indicating that simply increasing HSVtk enzyme levels per cell above a minimal threshold level will not be effective in augmenting the HSVtk/GCV system. These results suggest that other strategies, e.g., the use of higher doses of GCV, augmentation of the "bystander effect," the generation of mutant HSVtk genes with higher substrate affinities, the discovery of improved vectors with increased transduction efficiencies, or the development of new prodrugs with higher affinities for HSVtk will therefore be needed to enhance therapeutic responses.

Adenoviridae↗