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Biomedical subjects

S Ding

Publications and source records attributed to S Ding.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Study on T lymphocyte recognition of tumor antigens on autologous CML cells].

OBJECTIVE: To investigate the existence of cytotoxic precursor cells in previously untreated or remissive chronic myelogenous leukemia(CML) patients,and identify their phenotypical and functional characteristics. METHODS: Bone marrow or peripheral blood mononuclear cells from CML patients were stimulated with autologous CML cells by using mixed lymphocyte tumor cell coculture. RESULTS: A kind of cytotoxic T lymphocytes could be generated from bone marrow or peripheral blood of CML patients. These T cells showed differential cytotoxicities against autologous and allogeneic CML cells and no activity to autologous and allogeneic normal bone marrow cells. They also exhibited no inhibitive effect on CFU-GM yields. LAK cells had no effect on autologous CML cells, but showed intensive cytotoxic activity to allogeneic CML cells. The T lymphocytes obtained were CD3+ CD56+ non-MHC restricted or CD3+ CD56- MHC restricted. HLA-DR and CD25 were expressed in a significantly larger proportion of T lymphocytes stimulated with autologous CML cells than those not stimulated. The T lymphocytes showed low proliferative response to autologous CML cell stimulation and no or least response to allogeneic CML cells, they showed also no response to EB virus-transformed autologous B cells(obtained in remission) pulsed with peptides corresponding to the BCR-ABL joining region. CONCLUSION: There is probably a common tumor antigen among CMLs, this leukemia-specific antigen can be recognized by T cells,and it shows no indication to be a p210 fusion sequence.

Amino Acid Sequence↗
PubMed1996

Coexpression of a human P450 (CYP3A4) and P450 reductase generates a highly functional monooxygenase system in Escherichia coli.

The catalytic activities of recombinant cytochrome P450s expressed in E. coli have been impeded by the absence of endogenous P450 reductase. To solve this problem, we coexpressed P450 reductase with CYP3A4. Membranes from this strain contained 215 pmol P450/mg protein and a reductase activity of 1315 nmol cytochrome c reduced/min per mg. We detected 6beta-hydroxylation of testosterone and oxidation of nifedipine in vivo with turnover numbers of 15.2 and 17.3 min(-1), respectively. These values compare favourably with those obtained using an optimally reconstituted system. Our data demonstrate that a catalytically efficient human P450 system can be generated in E. coli.

Base Sequence↗
PubMed1996

A modified sub-second fast-STEAM sequence incorporating bipolar gradients for in vivo diffusion imaging.

A modified high-speed stimulated-echo acquisition mode (STEAM) diffusion sequence (90 degrees-TE/2-90 degrees-TM-[alpha-TE/2-STE]n) incorporating bipolar diffusion gradients that are less sensitive to macroscopic motion-induced artifacts is presented. Diffusion encoding was performed only during the first echo interval (TE1) with bipolar gradients that were implemented on all three mutually orthogonal axes. Calibration measurements on phantoms filled with water, isopropanol, and dimethyl sulfoxide yielded apparent diffusion coefficients (ADC) consistent with published values. Non-ECG-triggered in vivo images acquired on rat brain with relatively high b values (approximately 450 s/mm2) indicated minimal motion artifacts. Evaluated ADCs averaged over the cortex, left mid-brain, right mid-brain, regions yielded (0.91 +/- 0.02), (1.06 +/- 0.02), (1.01 +/- 0.03) x 10(-3) mm2s-1, respectively.

Animals↗
PubMed1995

Expression and alternative splicing of the cytochrome P-450 CYP2A7.

In order to investigate the relative levels of expression of human cytochrome P-450 (P-450) CYP2A genes and determine how this relates to polymorphism in coumarin hydroxylase activity, cDNA clones for members of the CYP2A gene family were isolated. These clones were CYP2A6, CYP2A7 and an alternatively spliced version of CYP2A7 (CYP2A7AS). The latter clone was missing exon 2, but contained a 10 bp segment of intron 1. Translation of CYP2A7AS resulted in an in-frame deletion of 51 amino acids. The expression of these cDNAs in COS-7 cells showed that both CYP2A6 and CYP2A7 generated a protein of molecular mass 49 kDa, whereas the protein product of CYP2A7AS was about 44 kDa. Only the CYP2A6 had coumarin hydroxylase activity. The relative level of CYP2A7 and CYP2A7AS mRNA was investigated by reverse transcription followed by PCR (RT-PCR) using human liver RNAs and an RNA sample from a human skin fibroblast cell line. In one of five liver RNAs studied, the aberrantly spliced CYP2A7 mRNA was 3-4-fold more abundant than the normal mRNA. The other samples contained very low levels of this mRNA species. Interestingly, CYP2A7AS mRNA was the major CYP2A7 mRNA detected in the fibroblast cell line. In this case only a protein band of 44 kDa was observed by Western-blot analysis. The relative of mRNA encoding CYP2A6 and CYP2A7 was established in seven human liver samples by RT-PCR and found to range between 1:0.5 and 1:3. These data strength the previous findings that alternative splicing is an important factor in determining the levels of many human P-450s and that this may be subject to tissue-specific effects. Whether in this case the protein product has some function remains to be determined.

Alternative Splicing↗
PubMed1995

The apparent diffusion constant measured by MRI correlates with pO2 in a RIF-1 tumor.

As tissue oxygen tension (pO2) is an important variable in cancer therapy, it would be of major clinical benefit to be able to measure pO2 noninvasively. Current methods for determining pO2 in clinical settings are limited to superficial tumors. The authors measured the apparent diffusion constant (ADC) in an implanted murine fibrosarcoma (RIF-1) using magnetic resonance imaging and correlated the ADC with tissue pO2 measured by electron paramagnetic resonance oximetry. The ADC correlates significantly with tissue pO2 in this tumor (r = 0.89; n = 14) and so may provide a noninvasive index of pO2 in tumors.

Animals↗
PubMed1995

High resolution renal diffusion imaging using a modified steady-state free precession sequence.

A modified steady-state free precession (SSFP) diffusion sequence is proposed for high resolution renal imaging. A pair of bipolar diffusion gradients was used to minimize the errors in measured apparent diffusion coefficient (ADC) caused by variations in T1, T2, and RF flip angle that have been observed with previously employed SSFP diffusion sequences. Motion sensitivity was reduced by the use of compensated gradients, frame-by-frame averaging, and a repetition time of 22 ms, which for a single-acquisition 128 x 128 image requires only 3 s. High resolution was achieved by signal averaging. The modified sequence was applied to in vivo diffusion measurements. In six normal rat kidneys the ADCs (mean +/- SD; x 10(-3) mm2/s) of the cortex, outer medulla, and inner medulla were 2.28 +/- 0.05, 2.38 +/- 0.10, and 2.95 +/- 0.05, respectively. The technique requires relatively large gradients to achieve adequate diffusion weighting.

1-Propanol↗
PubMed1995

A longitudinal study on electrophysiological properties of atrioventricular accessory pathways in infants and children.

In this study the electrophysiological developmental changes of accessory pathway (AP) properties in infants and children are examined. Intracardiac and/or transesophageal electrophysiological studies were performed on seven infants (group 1, mean age 2 months) and four children (group 2, mean age 9 y; study 1), and documented orthodromic atrioventricular tachycardia in all cases. At follow-up study (study 2), supraventricular tachycardia was induced in three of seven (43%) cases in group 1 and in all four cases in group 2. Changes in antegrade conduction properties of AP were documented by loss of pre-excitation (two of four cases in group 1) or change to intermittent pre-excitation (one of two cases in group 2).

Age of Onset↗
PubMed1995

[Tuberculous lymphadenitis: a sarcoidosis-like variation].

By means of polymerase chain reaction technique to amplify DNA sequence specific for mycobacterium tuberculosis (M. TB-PCR), BCG immunohistochemistry (BCG-IHC) as well as acid fast stain (AF), mycobacterium other than tuberculosis (MOTT) and mycobacterium tuberculosis (M. TB) were detected in paraffin blocks from 12 cases diagnosed by consultant pathologists as lymph node "sarcoidosis". Of the 5 cases which consulting pathologists unanimously agreed to the lymph node "sarcoidosis" diagnosis, 1 case showed BCG-IHC (+) and M. TB-PCR (+); Of the 7 cases which most of the consulting pathologists agreed to be "sarcoidosis", 1 case showed AF (+), BCG-IHC (+) and M. TB-PCR (+). The results suggest: (1) some tuberculous lymphadenitis cases may present as "sarcoidosis"-like lesions; (2) lymph node sarcoidosis may be related to MOTT and M. TB infection.

Adult↗
PubMed1995

Treatment of 23 patients with advanced gastric cancer by intravenously transfer of autologous tumor-infiltrating lymphocytes combined with rIL-2.

Tumor-infiltrating lymphocytes (TIL) isolated from metastatic lymph nodes in patients with nonoperable advanced gastric cancer were induced to become LAK-like cytotoxic activity of TIL after in vitro culture with rIL-2. Twenty-three patients with advanced gastric cancer were treated by intravenously transfer of autologous TIL combined with rIL-2. The tumor focus disappeared (complete remission, CR) in 3 patients (13.0%) and significantly decreased (partial remission, PR) in 5 patients (21.7%). Fifteen patients did not respond to the treatment. The amount of soluable IL-2 receptor in serum was significantly decreased after treatment, the cytotoxicity of NK cells and OT test were significantly increased. No significant difference in CD4/CD8 was found between before and after treatment. No serious side effect was observed in the treatment.

Adenocarcinoma↗
PubMed1995

[Evaluation of the combined assay of alpha-feto protein and gamma-glutamyl transpeptidase isoenzyme II in the diagnosis of primary hepatic carcinoma].

Serum alpha-feto protein (AFP) and gamma-glutamyl transpeptidase isoenzyme II (gamma-GTP-II) were assayed in 104 patients with primary hepatic carcinoma (PHC), gamma-GTP-II had a higher specificity of 95.7%, while AFP a higher sensitivity of 84.6%. There was no significant difference in the positive diagnostic rate of the two markers in patients with AFP > or = 400 micrograms/L and with AFP < 400 micrograms/L. Nor was there any difference if the patients were divided into four groups according to the serum AFP levels of 200 micrograms/L, 400 micrograms/L and 1,000 micrograms/L. Altogether 97 of the 104 PHC patients were detected when the two markers were assayed in combination (40 out of 42 PHC patients with AFP > or = 400 micrograms/L and 57 out of 62 PHC patients with AFP < 400 micrograms/L). These results suggest that combined assay of the two serum PHC markers will increase the detecting rate of PHC and be of value especially in those patients with normal or low serum level of AFP.

Adolescent↗
PubMed1995

[Removal of petrous bone cholesteatoma and obliteration with adipose tissue].

Three cases of petrous bone cholesteatoma removed through translabyrinthine-cochlear approach with the surgical defect obliterated by using adipose tissue covered with superficial temporalis fasia flap were reported. The average follow-up period was two years without any sign of recurrence. The etiology, diagnosis and methods of surgical treatment were discussed.

Adipose Tissue↗
PubMed1993

Quantitation of hydroperoxides in the aqueous solutions of non-ionic surfactants using polysorbate 80 as the model surfactant.

The application of coupled oxidation of NADPH to peroxide quantitation in non-ionic surfactant solutions is demonstrated using polysorbate 80 as the model surfactant. The linearity, precision, accuracy, and sensitivity of the method are discussed. The method has the following advantages over the traditional iodimetric method: (1) it is not affected by the non-ionic surfactant present in the solution; (2) it is reactive to less reactive hydroperoxides; (3) it is not light sensitive; and (4) it is carried out at near physiological pH in aqueous solutions. The method was employed to monitor the peroxide concentration of polysorbate 80 solutions stored under three different conditions. The effects of light and heat on peroxide concentration are more pronounced in more dilute solutions (0.1 and 1%). The peroxide concentration determined in the freshly prepared polysorbate 80 solution can be converted to the peroxide number of the raw material, which is not available from the supplier of polysorbate 80.

Glutathione Peroxidase↗
PubMed1993

Corrections to the cross-polarization dynamics in solids. The effect of nonsecular terms of heteronuclear dipolar interaction on cross-relaxation.

The dynamic theory of cross-polarization in solids is modified by considering the contribution of the nonsecular terms of the heteronuclear dipolar interaction Hamiltonian in the laboratory frame to cross-relaxation. This contribution is evaluated numerically and confirmed experimentally. It is shown that these nonsecular terms may play a considerable role in cross-relaxation in many systems, especially in those with fast internal molecular motion. The complication in the cross-polarization process is further revealed.

Amino Acids↗
PubMed1992

Inhomogeneous interactions in solids under slow off-magic angle spinning.

The central band of an inhomogeneous interaction under slow off-magic angle spinning (off-MAS) is no longer a scaled static spectrum with scaling factor P2(cos upsilon), that is, the spectrum distortion occurs in comparison with that under the rapid rotation condition. The dependence of this distortion in the chemical shift spectrum, for instance, on anisotropy, the asymmetry parameter, spinning rate and the angle between the spinning axis and the applied magnetic field is studied in this paper. It is shown that the distortion can be partly eliminated by using TOSS in certain circumstances. Experimental evidence is presented in this study.

Carbon↗
PubMed1992

The chemical shift interaction under weak radio frequency pulses.

The chemical shift anisotropy of a nuclear spin system in a strong magnetic field can be comparable to the strength of the rf pulse (weak pulse condition). In this case, the commonly used assumption that the chemical shift interaction Hamiltonian in the duration of a rf pulse can be neglected is no longer effective. The rf response characteristics of a spin-1/2 system under a weak pulse condition is studied in detail. The relationships between the distortion of the chemical shift powder spectrum and the relative rf field amplitude under various conditions are given. The suppression of sidebands of a MAS spectrum is analysed as an example of solid multiple pulse experiments. The experimental results are in good agreement with computer simulations.

Alanine↗
PubMed1992

Precorneal sampling techniques for ophthalmic gels.

Drug-cornea contact time is a critical issue in ocular drug delivery. Existing methods for its experimental determination are developed mainly for eye drops and ointments, and have not been reported for ophthalmic gels. The present study evaluated two tear film sampling techniques (capillary tubes and Schirmer strips) and one recovery technique (cotton swab) for their suitability for the determination of precorneal drug concentration as a function of time for ophthalmic gels. The study was conducted using the rabbit eye model, and the gel studied was a commercial polyacrylate-based gel containing pilocarpine HCl. The three techniques explored yield similar results with respect to drug-cornea contact time, about one hour for the gel studied. The strip method suffers from a gel-carry-over problem at the early time points; therefore it is not recommended for tear sampling until most of the gel is cleared from the cul-de-sac. Successful tear sampling was accomplished using capillary tubes. Drug concentration in the tear film as a function of time determined using this technique reveals not only the duration of contact between the drug and the cornea, but also demonstrates a nonuniform drug distribution in the tear film at the early time points (10 and 30 minutes). Finally the cotton swab technique is gentle, easy, and nondestructive. It recovers total drug remaining in the cul-de-sac but does not yield information for the tear film.

Animals↗