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D Y Chen

Publications and source records attributed to D Y Chen.

At least 73 records · Page 4Linked to original sources
PubMed1993

The induction and suppression of c-fos expression in the rat brain by cholecystokinin and its antagonist L364,718.

Immunohistochemical techniques were used to map c-fos expression in the rat brain after the i.p. administration of CCK-8 (8 micrograms/kg). C-fos expression was observed in the rostral and the caudal parts of the nuclei of the solitary tract (NTS), and the paraventricular nuclei (PVN) in the hypothalamus. The c-fos expression in these areas was suppressed by the administration of L364,718 (120 micrograms/kg). Since L364,718 is known to be a powerful selective antagonist to the peripheral CCK-A receptors, these data suggest that the effects produced by exogenous CCK are due to peripheral receptors that project to the NTS.

Animals↗
PubMed1993

The function of tyrosine 74 of cytochrome b5.

Tyrosine 74, which is part of a hydrophobic patch on the surface of rat cytochrome b5, also forms van der Waals contacts with the heme prosthetic group of the protein. In addition it is a member of an aromatic network of amino acids which includes Phe-35 and the axial ligand, His-39. Because of its strategic location in the protein, the Tyr-74 residue was mutated to a lysine in order to investigate how it affected the interaction of heme with the protein and whether it might be an alternative binding site and an electron transfer path which cytochrome b5 would use with its amphipathic electron transfer partners cytochrome P450 and its corresponding NADPH cytochrome P450 reductase. The mutant protein receives electrons from NADPH cytochrome P450 reductase and provides the second electron to cytochrome P450 to catalyze the metabolism of methoxyflurane, a substrate which requires cytochrome b5 for its metabolism, at the same rate as the wild type protein. The Tyr74Lys mutant exhibits a normal redox potential and spectroscopic properties identical to those of the wild type protein. Under equilibrium conditions in the presence of urea, heme dissociation and denaturation occur simultaneously with a free energy of 3.4 kcal/mol. The free energy of activation of heme dissociation from the wild type protein is 22.7 kcal/mol. The free energy and free energy of activation of the Tyr74Lys mutant are 1.4 kcal/mol less than the wild type values, indicating that the mutant binds heme 10-fold less tightly and dissociates heme 10 times faster than the wild type protein. Heme transfer experiments demonstrate that heme spontaneously dissociates 6 times faster from the mutant than the wild type protein (t1/2 = 1.9 and 11.5 h, respectively). The most likely conformation of Lys-74 in the mutant protein was determined by calculating the Lys-74 rotamer with the minimal energy using an energy-based conformation search method. This conformation was subsequently modeled on the computer graphics. Not unexpectedly, the side chain of Lys-74 is shifted toward the surface of the protein to allow solvation of the positive charge on the epsilon amino group of lysine. This movement of the lysine residue results in the formation of a cavity on the surface of the cytochrome b5 molecule, which exposes a heme methyl and vinyl group to aqueous solvent thereby destabilizing the binding between the protein and its hydrophobic prosthetic heme group.

Animals↗
PubMed1993

[Effect of movement of cervical spine on compressed spinal cord-meningeal complex].

The compression of spinal cord-meningeal complex after the injury of cervical spine was simulated in seven intact fresh adult cadaver spines. In this study, a hole was drilled from the anterior part to the posterior in vertebral body C6 to accommodate a transducer which was pushed into the canal. The measurement of the pressure on the spinal cord-meningeal complex was made in different canal acclusion during the extension-flexion and rotation movements of the cervical spine. The results showed that the flexion and axial rotation of the cervical spine increased damage stress to the spinal cord under compression. The distribution of the stress on the spinal cord was discussed, and the strict immobilization and keeping the cervical spine in the natural-extension position were recommended for the injury of cervical spine.

Adult↗
PubMed1993

Crusted scabies in systematic lupus erythematosus: a case report.

Crusted scabies (Norwegian scabies) is uncommon in clinical practice and may present as papulosquamous dermatosis. A case of crusted scabies in systemic lupus erythematosus (SLE) is described. The skin lesions simulated those of subacute cutaneous lupus erythematosus of the papulosquamous type, and became the source of epidemic scabies in the hospital. The colonization with Staphylococcus aureus within crusted lesions may have contributed to the patient's sepsis. This case illustrates the pitfalls in recognition of crusted scabies and the importance of rapid diagnosis.

Humans↗
PubMed1992

Formamide modified polyacrylamide gels for DNA sequencing by capillary gel electrophoresis.

Compressions are occasionally found during the separation of DNA sequencing fragments, particularly in G/C-rich regions and in gels operated at room temperature. Addition of at least 10% formamide to urea/polyacrylamide sequencing gels improves the denaturing capacity of the gel, minimizing compressions. Addition of 20% or more formamide decreases the separation rate, theoretical plate count, and resolution for normally migrating fragments. An optimum concentration of 10% formamide improves resolution of compressed regions without degrading the other characteristics of the gel. Operation of gels at room temperature simplifies the engineering associated with automated sequencers based on capillary gel electrophoresis.

Base Sequence↗
PubMed1992

Treatment of pigmented villonodular synovitis with yttrium-90: changes in immunologic features, Tc-99m uptake measurements, and MR imaging of one case.

Pigmented villonodular synovitis (PVNS) is an uncommon proliferative disease of synovium. We report a 35-year-old male with diffuse form of PVNS of left knee, treated with intraarticular injection of 5 mCi of yttrium-90 (Y-90) silicate colloid consisting of two doses with a 3-month interval between them. During follow-up, the affected knee showed clinical improvement and was accompanied by a decrease of the levels of soluble interleukin-2 receptor in sera and synovial fluids (SF). When compared to osteoarthritis subjects, SF lymphocyte subsets of this case before Y-90 therapy showed a lower CD4:CD8 cell ratio and absence of suppressor inducer cells (CD4+ 2H4+). The Tc-99m pertechnetate knee uptake indexes correlated well with clinical improvement. Serial magnetic resonance imaging revealed significant change one year after Y-90 therapy. The findings of immunological assessment suggested that immunoregulatory dysfunction may be related to the pathogenesis of PVNS.

Adult↗
PubMed1992

Cholecystokinin antagonist and lipid intake as a function of caloric density and familiarity.

The effect of treatment with the cholecystokinin antagonist L364,718 on intake of different dilutions of corn oil emulsion was tested under two levels of familiarity with the oil emulsion. No increase in intake was observed. To see if the CCK antagonist was effective under our conditions, exogenous CCK was administered under the same conditions. A complete suppression of the large reduction produced by CCK on intake was found.

Animals↗
PubMed1992

Determinants of rotavirus stability and density during CsCl purification.

The stability of rotavirus infectivity during CsCl gradient purification and subsequent storage was examined using our standard SA11 wild type (SA11-Cl3), the SA11 4F variant (SA11-4F), bovine rotavirus B223, and a panel of bi- and triparental reassortants derived from these parental viruses. Viral stability was determined by the recovery of infectivity at each step during a standard CsCl purification protocol. SA11-4F was the most stable parent (91-93% recovery), SA11-Cl3 had intermediate stability (10-21% recovery), and B223 was least stable (0.5-7% recovery). Among the reassortants, the recovery varied from 0.5 to 88.6% of the initial infectivity and was determined primarily by the parental origin of genome segment 4. The greatest loss of infectivity occurred during Freon extraction, with smaller losses during the CsCl gradient, and the smallest loss during the virus pelleting step. Comparison of the stability of viruses grown in the presence or absence of exogenous trypsin revealed that, in general, viruses grown in the absence of trypsin were more stable during purification. During 4-5 months storage at 4 degrees, the differences in stability of parental and reassortant viruses were not as dramatic as during purification and were not significantly affected by the presence or absence of trypsin during growth. However, survival during storage was as low as 4% and as high as 100% and was also primarily dependent on the parental origin of genome segment 4. It was noted that bovine rotavirus B223 had higher density in CsCl than either SA11-Cl3 or SA11-4F. The observation of heterogeneity in density was investigated using reassortants. These results indicated that all reassortants had intermediate density and suggested that physical interactions among the structural proteins were responsible for the heterogeneity in density. The possible roles of viral structural proteins in rotavirus stability and the relationship between the stability and the density are discussed.

Centrifugation, Density Gradient↗
PubMed1992

Specific interactions between rotavirus outer capsid proteins VP4 and VP7 determine expression of a cross-reactive, neutralizing VP4-specific epitope.

We previously reported that the expression of rotavirus phenotypes by reassortants was affected by recipient genetic background and proposed specific interactions between the outer capsid proteins VP4 and VP7 as the basis for the phenotypic effects (D. Chen, J. W. Burns, M. K. Estes, and R. F. Ramig, Proc. Natl. Acad. Sci. USA 86:3743-3747, 1989). A neutralizing, cross-reactive VP4-specific monoclonal antibody (MAb), 2G4, was used to probe the protein-protein interactions. The VP4 specificity of 2G4 was confirmed by immunoblot analysis. MAb 2G4 reacted with both standard (SA11-C13) and variant rotavirus SA11 (SA11-4F) but did not react with bovine rotavirus B223 as determined by plaque reduction neutralization (PRN) and enzyme-linked immunosorbent assay (ELISA). When a panel of SA11-4F/B223 and SA11-Cl3/B223 reassortants in purified or crude lysate form that had been grown in the presence or absence of trypsin was analyzed with MAb 2G4 by PRN and ELISA, the results with some reassortants were unexpected. That is, MAb 2G4 reacted with VP4 of SA11 parental origin (4F or C13) when it was assembled into capsids with the homologous SA11 VP7 but failed to react with VP4 of SA11 assembled into capsids with heterologous B223 VP7. Conversely, MAb 2G4 failed to react with VP4 of B223 parental origin when it was assembled into capsids with homologous B223 VP7 but did react with B223 VP4 assembled into capsids with the heterologous SA11 VP7. Similar reactivity was observed when 2G4 was used to immunoprecipitate purified double-shelled virions. When soluble unassembled viral proteins were analyzed by ELISA, the 2G4 reactive pattern was as predicted from the parental origin of VP4. That is, 2G4 reacted with the soluble VP4 of reassortants having VP4 from SA11-Cl3 or SA11-4F and failed to react with VP4 of B223 origin, regardless of the origin of VP7. PRN and ELISA results obtained with nonglycosylated viruses revealed that the unexpected reactivity of 2G4 with virus particles was not the result of differential glycosylation of VP7 and epitope masking. These results indicate that the 2G4 epitope existed in the soluble form of VP4 encoded by SA11-Cl3 or SA11-4F but not in soluble B223 VP4. On the other hand, in assembled virions, the presentation of the 2G4 epitope on VP4 was unexpected in some reassortants and was affected by the specific interactions between VP4 and VP7 of heterologous parental origin.

Animals↗
PubMed1991

Three DNA sequencing methods using capillary gel electrophoresis and laser-induced fluorescence.

Capillary gel electrophoresis is demonstrated for the four-spectral-channel sequencing technique of Smith, the two-spectral-channel sequencing technique of Prober, and the one-spectral-channel sequencing technique of Richardson and Tabor. Sequencing rates up to 1000 bases/h are obtained at electric field strengths of 465 V/cm. At lower electric field strengths, capillary electrophoresis produces useful data for fragments greater than 550 nucleotides in length with 2 times better resolution than slab gel electrophoresis. An on-column detector produces detection limits of 200 zmol (1 zmol = 10(-21) mol = 600 molecules) for the four-spectral-channel technique. A postcolumn detector, based on the sheath flow cuvette, produces detection limits of 20 and 2 zmol for the two- and one-spectral-channel techniques, respectively.

Base Sequence↗
PubMed1991

Low-cost, high-sensitivity laser-induced fluorescence detection for DNA sequencing by capillary gel electrophoresis.

A low cost, 0.75-mW helium neon laser, operating in the green region at 534.5 nm, is used to excite fluorescence from tetramethylrhodamine isothiocyanate-labelled DNA fragments that have been separated by capillary gel electrophoresis. The detection limit (3 sigma) for the dye is 500 ymol [1 yoctomole (1 ymol) = 10(-24) mol] or 300 analyte molecules in capillary zone electrophoresis; the detection limit for labeled primer separated by capillary gel electrophoresis is 2 zmol [1 zeptomole (1 zmol) = 10(-21) mol]. The Richardson-Tabor peak-height encoded sequencing technique is used to prepare DNA sequencing samples. In 6% T, 5% C acrylamide, 7 M urea gels, sequencing rates of 300 bases/hour are produced at an electric field strength of 200 V/cm; unfortunately, the data are plagued by compressions. These compressions are eliminated with addition of 20% formamide to the sequencing gel; the gel runs slowly and sequencing data are generated at a rate of about 70 bases/hour.

Base Sequence↗
PubMed1991

Varicocele in the rat: a new experimental model. Effect on histology, ultrastructure and temperature of the testis and the epididymis.

With no consistent animal prototype for the study of varicocele, we set out to create a model in the rat by complete ligation of the main branch of left spermatic vein (MBSV) or by partial ligation of the left renal vein. Three months later, the histology, ultrastructure and temperature of the testis and epididymis were studied. Microscopically, spermatogenic arrest was the most frequent anomaly seen. The most frequently noted ultrastructural change of the testis was distension of smooth endoplasmic reticula in Sertoli cells. The microvilli of columnar epithelia in epididymis were sparse and showed local defects. Lesions and increased temperatures in the testis and epididymis induced by the ligation of the left MBSV were similar to those seen in partial ligation of the left renal veins, with no significant differences between left and right. Significant differences were found, however, on comparison with the controls.

Animals↗
PubMed1991

High-sensitivity laser-induced fluorescence detection for capillary electrophoresis.

Capillary electrophoresis provides very high efficiency separations of biological molecules. Laser-induced fluorescence produces very high sensitivity detection. The combination of the two techniques results in an analytical tool with unprecedented properties: separations with more than a million theoretical plates and detection limits of a few hundred analyte molecules. This paper considers the design of high-sensitivity laser-induced fluorescence detection for capillary zone electrophoresis separation of labeled amino acids and capillary gel electrophoresis separation of DNA sequencing fragments.

Amino Acids↗
PubMed1991

Erythrocyte Li transport following different storage conditions.

Erythrocyte Na-Li countertransport has been shown to be elevated in subjects with essential hypertension and has been proposed as a genetic marker. It is also modified by other factors which may exist in the plasma under physiological or pathophysiological conditions. In this investigation, we studied the comparison of storage conditions in plasma and isotonic KCl solution (which has been used as a preservation solution for erythrocyte's Li transport) for cellular Na economy and Na-Li countertransport in erythrocytes from normotensive and hypertensive subjects. We found that plasma-stored cells exhibited higher cellular Na concentration and higher rates of Na-Li countertransport as well as Li leak, than that of KCl solution-stored cells after 20 hr. It is likely that both Na pump and leak permeabilities are changed during plasma storage but the detailed mechanisms involved require further investigation. We also confirmed the usefulness of isotonic KCl solution as a preservation media for erythrocytes in transport studies for up to three days.

Biological Transport↗
PubMed1991

Healing potential of experimental meniscal tears in the rabbit. Preliminary results.

This study assessed the healing potential of longitudinal or transverse incisions in the peripheral, central, and inner rim regions of rabbit medial menisci. Longitudinal and transverse incisions were made in 48 male New Zealand white rabbits. The incisions were either repaired with sutures or left open. The effect of joint motion on repair was also evaluated. In one group, longitudinal incisions were made in the peripheral, central, and inner rim regions of the meniscus. Some of these incisions were sutured, whereas others were not repaired. In another group, transverse incisions were made in the meniscus, extending from the inner rim to the middle of the meniscus or to the peripheral attachment (radial tear). Again, the lesions were left open or repaired. The effect of joint motion on healing was assessed by immobilizing several knees from each group with Kirschner wires temporarily for ten weeks. Suture of the meniscus incision did not substantially affect the rate of healing. When the healing rates of menisci at the periphery, body, and rim were compared, incisions at the periphery healed significantly better than incisions at the meniscal body and central rim regions. K-wire immobilization did not substantially affect the rate of healing. The difference in healing with regard to the type of incision, either longitudinal or transverse, was not statistically significant.

Animals↗