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Biomedical subjects

H Shih

Publications and source records attributed to H Shih.

31 records · Page 2Linked to original sources
PubMed1995

Data clustering and other archive retrieval strategies for teleradiology and picture archiving and communication systems.

A key advantage in the conversion from film-based to digital radiology is the possibility of a long-term on line electronic archival of patient studies. The popular approach based on optical disk jukeboxes for the long-term archive and magnetic disk storage for data caching is not economically attractive because of the cost of both the jukebox and the medium. Strategies for extending the archival system design with a tape jukebox have been studied. The proposed strategy calls for the use of high-ratio lossy compression together with low-cost tape storage to make long-term on line archiving more affordable. An intelligent prefetching algorithm based on hospital information system and radiologic information system triggers, which in turn are augmented by manual case preparation, can effectively overcome the longer latency of ad hoc retrievals. This longer latency is caused by both system-level bottlenecks and the sequential access constraint of the tape drive. Strategies for image clustering and tape allocation by patient classification also enhance retrieval efficiency. This archival design using image compression, prefetching, and clustering could be implemented in many of the existing teleradiology and picture archiving and communication systems.

Algorithms↗
PubMed1994

Crystallization and preliminary X-ray analysis of anti-digoxin antibodies.

The Fab fragments of several monoclonal antibodies that bind digoxin and other cardiac glycosides have been screened for crystallization conditions. We have crystallized two of these in forms suitable for X-ray analysis. The anti-digoxin antibody 40-50 in complex with ouabain crystallizes with symmetry consistent with space group C2, with a = 92.6, b = 85.0, c = 73.0 A and beta = 131.7 degrees. This crystal form shows considerable non-isomorphism between crystals. A second anti-digoxin antibody, 49-10, crystallizes with symmetry consistent with space group P2(1)2(1)2, with a = 95.3, b = 147.1 and c = 76.2 A.

Journal Article↗
PubMed1994

Definition of the carbohydrate response element of the rat S14 gene. Context of the CACGTG motif determines the specificity of carbohydrate regulation.

Transcription of the S14 gene in primary hepatocytes is stimulated in response to increased carbohydrate metabolism. We have demonstrated previously that a 30-base pair (bp) segment of the S14 gene from -1457 to -1428 is a carbohydrate response element (ChoRE). This element contains a (5')CACGTG motif that is essential for control. DNase I footprinting experiments with liver nuclear extract revealed two factors binding within the S14 ChoRE. In transient transfection experiments, mutation of the upstream site between -1457 and -1450 did not affect the response to elevated glucose, whereas the downstream 21-bp site between -1448 and -1428 was sufficient to mediate the glucose induction. Electrophoretic mobility shift assays indicated that the hepatic factor binding to this site in vitro is closely related or identical to the major late transcription factor (MLTF). However, replacement of the 21-bp S14 ChoRE with the authentic MLTF binding site from the adenovirus major late promoter failed to elicit the glucose response. By systematically exchanging bases between the functional S14 and nonresponsive adenovirus sites, the sequence (5')CACGTGNNNGCC was found to be essential for carbohydrate regulation. A segment containing this specific motif from the rat fatty acid synthase gene, another carbohydrate-responsive gene in hepatocytes, conferred a carbohydrate response when linked to the S14 promoter. Thus, the context of the CACGTG motif provides the specificity for regulation by carbohydrate metabolism.

Animals↗
PubMed1993

Relative specificities in binding of Watson-Crick base pairs by third strand residues in a DNA pyrimidine triplex motif.

The specificity of binding of Watson-Crick base pairs by third strand nucleic acid residues via triple helix formation was investigated in a DNA pyrimidine triplex motif by thermal melting experiments. The host duplex was of the type A10-X-A10: T10-Y-T10, and the third strand T10-Z-T10, giving rise to 16 possible triplexes with Z:XY inserts, 4 duplexes with the Watson-Crick base pairs (XY) and 12 duplexes with mismatch pairs (XZ), all of whose stabilities were compared. Two Z:XY combinations confirm the primary binding of AT and GC target pairs in homopurine.homopyrimidine sequences by T and C residues, respectively. All other Z:XY combinations in the T:AT environment result in triplex destabilization. While some related observations have been reported, the present experiments differ importantly in that they were performed in a T:AT nearest neighbor environment and at physiological ionic strength and pH, all of which were previously untested. The conclusions now drawn also differ substantially from those in previous studies. Thus, by evaluating the depression in Tm due to base triplet mismatches strictly in terms of third strand residue affinity and specificity for the target base pair, it is shown that none of the triplet combinations that destabilize qualify for inclusion in the third strand binding code for the pyrimidine triplex motif. Hence, none of the mismatch triplets afford a general way of circumventing the requirement for homopurine.homopyrimidine targets when third strands are predominated by pyrimidines, as others have suggested. At the same time, the applicability of third strand binding is emphasized by the finding that triplexes are equally or much more sensitive to base triplet mismatches than are Watson-Crick duplexes to base pair mismatches.

DNA↗
PubMed1992

Renal effects of N-(3,5-disubstitutedphenyl)-succinimides in the Fischer 344 rat.

Previous studies have demonstrated the importance of substitution at the 3- and 5-positions of the phenyl ring in N-phenylsuccinimides for the production of nephrotoxicants in this series of compounds. The purpose of this study was to determine if the electronic nature of the 3,5-substituents is an important determinant for nephrotoxic potential. Male Fischer 344 rats (four rats per group) were administered a single intraperitoneal injection of a succinimide (0.4 or 1.0 mmol kg-1) or vehicle, and the renal function was monitored for 48 h. Only N-(3,5-dichlorophenyl)succinimide (0.4 or 1.0 mmol kg-1) induced marked changes in renal function. Urine volume, BUN concentration and proteinuria were increased following N-(3,5-dinitrophenyl)succinimide (1.0 mmol kg-1) treatment but other renal parameters and renal morphology were unchanged in this treatment group. These results indicate that the presence of halogen atoms at the 3- and 5-positions of the phenyl ring in N-phenylsuccinimides is more important for nephrotoxic potential than the presence of non-halogen substituents. The reason why halogen substitution is an important determinant for N-phenylsuccinimide nephrotoxicity is unknown.

Animals↗
PubMed1991

The compensatory 'rebound' of reactive astrogliosis: glial fibrillary acidic protein immunohistochemical analysis of reactive astrogliosis after a puncture wound to the brain of rats with portocaval anastomosis.

This study was designed to compare the degree of reactive astrogliosis occurring around a puncture wound in the brain of normal rats and at different intervals after a similar puncture wound in rats with a portocaval anastomosis. The gliosis was evaluated by the number of astrocytes, the thickness of their processes and the intensity of the glial fibrillary acidic protein immunoreactivity. After the puncture wound in the brain of rats with a portocaval anastomosis, the gliosis varied at different intervals being: (1) decreased at 10 days, (2) markedly increased at 5 weeks and (3) significantly decreased at 8, 12, and 16 weeks. These findings suggest that 5 weeks after portocaval anastomosis, an active proliferation of the metabolically altered astrocytes occurs with heightened synthesis of glial fibrillary acidic protein in the period of adaptive compensation, the so-called compensatory 'rebound'. At 8 weeks or more after portocaval anastomosis, these altered astrocytes were considered to be in the phase of decompensation and incapable of maintaining the reactive response which occurred in normal rats. The compensatory rebound and decompensatory 'decline' illustrate the dynamic plasticity of the reactive astrogliosis.

Ammonia↗
PubMed1991

Kaposi's sarcoma presenting as linitis plastica.

A 31-yr-old woman presenting with abdominal complaints and fever was found to have linitis plastica on upper gastrointestinal series. Endoscopic studies confirmed these findings; however, pathology revealed the diagnosis to be Kaposi's sarcoma. We believe this to be the first case report of linitis plastica presenting as Kaposi's sarcoma.

Adult↗
PubMed1990

Heteronuclear 3D NMR and isotopic labeling of calmodulin. Towards the complete assignment of the 1H NMR spectrum.

New methods are described that permit detailed analysis of the NMR spectra of calmodulin, an alpha-helical protein with a molecular weight of 16.7 kD. Two complementary approaches have been used: uniform labeling with 15N and labeling of specific amino acids with either 15N or 13C. It is demonstrated that uniform 15N labeling permits the recording of sensitive three-dimensional (3D) NMR spectra that show far better resolution than their conventional two-dimensional analogs. Selective 15N labeling of amino acids can be used for identifying the type of amino acid, providing information that is essential for the analysis of the 3D spectra. Simultaneous selective labeling with both 15N and 13C can provide a number of unique backbone assignments from which sequential assignment can be continued.

Amino Acid Sequence↗
PubMed1989

Acute nephrotoxicity induced by N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid in Fischer 344 rats.

N-(3,5-Dichlorophenyl)succinimide (NDPS) induces nephrotoxicity via one or more metabolites which arise from oxidation of the succinimide ring. The purpose of this study was to examine the nephrotoxic potential of N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid (3-NDHSA), a potential metabolite of NDPS and a positional isomer of N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA), a known nephrotoxic metabolite of NDPS. Male Fischer 344 rats were administered a single intraperitoneal injection of 3-NDHSA (0.2 or 0.4 mmol/kg) or sesame oil (2.5 mmol/kg), and renal function was monitored at 24 and 48 h. Both doses of 3-NDHSA induced diuresis, increased proteinuria, glucosuria and hematuria, elevated blood urea nitrogen (BUN) concentrations and kidney weights, decreased organic ion accumulation by renal cortical slices, and induced proximal tubular necrosis. The characteristics of 3-NDHSA-induced nephrotoxicity were identical to NDPS-induced nephropathy, but were evident at lower doses with 3-NDHSA. These results demonstrate that 3-NDHSA is a nephrotoxicant which might contribute to NDPS-induced nephropathy.

Animals↗