Search PubMed⌕ Search

Biomedical subjects

S Shen

Publications and source records attributed to S Shen.

At least 163 records · Page 9Linked to original sources
PubMed1996

Accurate measurement of copper-67 in the presence of copper-64 contaminant using a dose calibrator.

UNLABELLED: The use of 67Cu-labeled antibodies for the treatment of cancer has advanced to the clinical trial phase. Quantitation of 67Cu radiopharmaceuticals is complicated by the presence of the radioimpurity of 64Cu in 67Cu supplies. Here we report a method to assay 67Cu and 64Cu in a mixed sample with a commonly available instrument, the ionization chamber dose calibrator. METHODS: The activities of 67Cu and 64Cu in a mixed sample can be calculated from a single-dose calibrator measurement. The calculation requires (1) instrument-specific response coefficients D67 and D64, generated by gauging the instrument for the efficiency of measurement of 67Cu and 64Cu, and (2) a value for the ratio of 67Cu to 64Cu in the sample, routinely provided by major suppliers of 67Cu. D67 and D64 were empirically determined by measuring samples containing known amounts of 67Cu and 64Cu. The samples were also assayed by gamma ray spectroscopy to verify the isotope ratios given by the suppliers. RESULTS: This method generated accurate response coefficients. At the recommended dose calibrator setting for the measurement of 67Cu, at which D67 = 1.0, the measurement for D67 with this method was 1.02 (+/- 0.04). Isotope ratios provided by the radionuclide suppliers were corroborated by gamma ray spectroscopy. CONCLUSION: A method is presented by which 67Cu and 64Cu in a mixed sample can be assayed using a dose calibrator. Although the derived numeric constants are only correct for a specific dose calibrator and setting, the method can be adapted for use with any dose calibrator.

Calibration↗
PubMed1996

A locus for Fanconi anemia on 16q determined by homozygosity mapping.

We report the results of a genomewide scan using homozygosity mapping to identify genes causing Fanconi anemia, a genetically heterogeneous recessive disorder. By studying 23 inbred families, we detected linkage to a locus causing Fanconi anemia near marker D16S520 (16q24.3). Although -65% of our families displayed clear linkage to D16S520, we found strong evidence (P = .0013) of genetic heterogeneity. This result independently confirms the recent mapping of the FAA gene to chromosome 16 by Pronk et al. Family ascertainment was biased against a previously identified FAC gene on chromosome 9, and no linkage was observed to this locus. Simultaneous search analysis suggested several additional chromosomal regions that could account for a small fraction of Fanconi anemia in our families, but the sample size is insufficient to provide statistical significance. We also demonstrate the strong effect of marker allele frequencies on LOD scores obtained in homozygosity mapping and discuss ways to avoid false positives arising from this effect.

Chromosome Mapping↗
PubMed1996

[Frequency dependence of substance P release by electroacupuncture in rat spinal cord].

Previous studies in our laboratory have shown that electroacupuncture (EA) using different frequencies produced differential opioid peptides release in the spinal cord of rats and human beings. In the present study we observed the frequency dependence of substance P (SP) release from rat spinal cord, with the frequencies of EA set at 2, 4, 8, 15, 30 and 100 Hz. The spinal perfusate was collected in 3 periods of 30 min before, during and after EA, and the immunoreactive SP (SP-ir) was measured by radioimmunoassay (RIA). The effectiveness of EA-induced analgesia was assessed by tail flick latency (TFL). Rats showing an increase of TFL over 40% was considered as EA responder. The results showed that in the responders, SP-ir in spinal perfusate showed a moderate decrease during 2 Hz EA, (P < 0.01 compared with baseline level), no change in the 4 Hz EA group, and a marked increase during 8, 15, 30 and 100 Hz EA (P < 0.01), with maximal increase occurring at 15 Hz (P < 0.001). The above results suggest that EA may induce upward or downward modulation in SP-ir release depending on the frequency of EA. However in the non-responder rats no change in spinal fluid SP-ir content was observed. This suggests that changes in SP-ir release have same causal relation with the analgesia induced by EA stimulation.

Acupuncture Analgesia↗
PubMed1996

[Incidence of insulin dependent diabetes mellitus in children of Shanghai, China].

A retrospective study on incidence of insulin dependent diabetes mellitus (IDDM) in children aged 1-14 was conducted in urban districts of Shanghai in 1989-1993. There were 1,401,664 children aged 0-14 in the urban area of Shanghai in 1990. 58 cases of IDDM, 28 boys and 30 girls, were traced from hospitals, primary and high schools, kindergartens and nurseries in the city during 1989 to 1993 with a "capture-recapture" method in line with DIAMOND protocol sponsored by WHO with independent validation of complete case ascertainment, with an average crude incidence of 0.83/100,000 (95% CI of 0.61/100,000-10.4/100,000), and a corrected incidence of 0.96/100,000 (95% CI of 0.71/100,000-1.18/100,000). Peak incidence of IDDM was in 1992 and at age of nine. Age of onset in boys (a median of 8.0 years) was earlier than that in girls (9.7 years). Incidence of IDDM was increasing in Shanghai as compared with the studies in 1980-1991, but it still is placed in the lowest throughout the world.

Adolescent↗
PubMed1996

Prediction of radiation doses from therapy using tracer studies with iodine-131-labeled antibodies.

UNLABELLED: Tracer pharmacokinetic studies are often used in treatment planning for radionuclide therapy including radioimmunotherapy. This study evaluates the validity of using tracer studies to predict radiation doses from therapy with the same radiolabeled antibody. METHODS: Quantitative imaging and blood radioactivity were used to obtain the pharmacokinetics and radiation doses that were delivered to the total body, blood, marrow, lungs, liver, kidneys, thyroid, spleen and tumors. Tracer and therapy data for eight patients with lymphoma and one patient with breast cancer were compared using linear regression statistics. Doses of 131I-labeled antibody for the tracer studies ranged from 0.1 to 0.4 GBq (2 to 10 mCi), and therapy doses ranged from 0.7 to 5.6 GBq (20 to 150 mCi). RESULTS: Radiation doses to tissues and, in particular, the bone marrow and tumors were reliably predicted from tracer studies. In this group of patients, median dose to marrow from marrow targeting, total body and blood was 9.2 cGy/GBq for tracer studies and 7.6 cGy/GBq for therapy studies with a median difference of 0.5 cGy/GBq. Median dose to tumors was 81.1 cGy/GBq for tracer studies and 70.3 cGy/GBq for therapy studies with a median difference of 5.9 cGy/GBq. CONCLUSION: In these patients, tracer studies were predictive of the radiation doses from therapy for total body, major organs and tumors. The radiation doses to marrow and tumors, which are the usual determinants of the therapeutic index, correlated well between tracer and therapy studies (r > or = 0.95).

Antibodies, Monoclonal↗
PubMed1996

[Development of genetically engineered chimeric and single chain antibodies against human brain glioma: a preliminary report].

In order to improve the clinical usefulness of mAb of mouse origin in targeting diagnosis and therapy for human brain glioma, it is necessary to humanize it and reduce its molecular size. By means of RT-PCR technique, a 348 bp heavy chain variable domain (VH), and a 318 bp light chain variable domains (VL) cDNA fragments were cloned from mouse hybridoma cell line SZ39 secreting mAb against human brain glioma. By recombinant DNA technique, the two cDNA fragments were linked to human IgG1 heavy chain CH1 and light chain kappa constant regions, respectively, to form a chimeric gene which was then inserted into an expression vector pHEN1-SZ39 Fab/Hu. In addition, the two cDNA fragments were connected directly with a universal linker and inserted to an expression vector pHEN1-SZ39 ScFv. The two expression vectors were separately introduced into E. coli HB2151 to secrete chimeric antibodies and single-clain antibodies, respectively. On ELISA and Western blot, the two genetically engineered antibodies bond to the same 180,000 cell surface membrane antigen on human brain glioma cell line SHG44 as did the parental mAb SZ39.

Amino Acid Sequence↗
PubMed1996

[Treatment of oral leukoplakia with retinamide].

Inhibition of buccal pouch carcinogenesis induced by dimethyl-benzanthracene in hamsters with retinamide was studied. Group A received oral retinamide at a dosage of 20mg/kg, every day for eight weeks. Group B was treated by retinamide orally at the same dosage, plus topical treatment by retinamide. Group C was treated by retinamide topically for eight weeks. Experiments exhibited that under the action of retinamide the incidence of tumor was lowered significantly. All the Group A, B and C had a good response. Clinically 80 patients were randomly arranged into two groups. One group received placebo and served as controls and the other group was treated by retinamide. Results indicate that retinamide is effective against leukoplakia and the response rate is as high as 84.0%. By contrast, only 16.7% of patients receiving placebo showed some improvement.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

[Angiotensin II release and anti-electroacupuncture analgesia in spinal cord].

Changes in the content of angiotensin II (A II) immunoreactivity (ir) in rat spinal perfusate induced by electroacupuncture (EA) stimulation of different frequencies were measured by radioimmunoassay (RIA). The results were analyzed in relation to the role of opioid receptor. (1) 2 Hz EA produced a 20% (P > 0.05) decrease in A II -ir content in the spinal perfusate. 15 Hz EA produced an even more decrease (62%, P < 0.01), whereas 100 Hz produced a significant increase (65%, P < 0.05). (2) The release in spinal A II -ir produced by 15 Hz EA was reversed by the opioid antagonist naloxone to a of 125% highter than that of the control (P < 0.05), suggesting that 15 Hz EA may accelerate the release of endogenous opioids to suppress the release of A II. (3) This was substantiated by the finding that intrathecal (i.t.) injection of the selective mu agonist ohmefentanyl produced a dramatic suppression (20%, P < 0.05) of A II release, but not by delta and kappa agonist. (4) Intrathecal injection of salarasin, the angiotensin receptor antagonist, produced a significant potentiation of the analgesia produced by 100 Hz EA, but not that produced by 2 or 15 Hz EA. It is concluded that 15 Hz EA may induce the release of endogenous opioids acting on mu opioid receptor so as to suppress A II release, and that 100 Hz EA may accelerate the release of A II serving as a brake for 100 Hz EA-induced analgensia. Removal of the brake by angiotensin antagonist may be advised as an adjunct for the potentiation of 100 Hz EA-induced analgesia.

Acupuncture Analgesia↗
PubMed1995

Yttrium-90 chimeric L6 therapy of human breast cancer in nude mice and apoptosis-related messenger RNA expression.

Radioimmunotherapy (RIT) in breast cancer patients using I-131-chimeric L6 (ChL6) and in human breast cancer xenografts in nude mice using Y-90-1,4,7,10-tetraazacylododecant N,N',N",N"'-tetraacetic acid-peptide ChL6 (Y-90-ChL6) has shown promise. Tumor cell response to low-dose rate (5-25 rads/h) irradiation from Y-90-ChL6 RIT, therefore, was correlated with levels of tumor cell mRNA for selected genes linked to programmed cell death (apoptosis). Three groups of 10-16 mice with 1-2 HBT 3477 xenograft tumors were treated with 100, 150, or 250 microCi Y-90-ChL6. Three tumors were taken before and two tumors each were taken 3, 6, and 24 h after injection of 150 microCi Y-90-ChL6. Tumor expression of mRNA was amplified by PCR for p53, PIC1, c-myc, and transforming growth factor-beta 1; quantitated; and standardized to N-ras. Tumors received radiation doses of 2000, 3000, and 5000 rads, respectively, for the groups of mice that received 100, 150, and 250 microCi Y-90-ChL6, and tumor regression occurred in each group, with mean tumor volumes decreased by 10, 50, and 95% at nadir after Y-90-ChL6 injection. At the highest dose level, 30% of mice had complete remissions, and no treatment deaths occurred, although tumors subsequently recurred. Continuous up-regulation of transforming growth factor-beta 1 and c-myc mRNA expression was observed from 3 to 24 h after treatment. Expression of p53 and PIC1 increased at 3 h and subsequently decreased to the untreated control levels. These observations are consistent with previous observations of early responses of p53 and PIC1 to cellular DNA damage and subsequent G1 cell cycle arrest or apoptosis. Apoptosis-associated gene expression patterns observed in this tumor model provide evidence that changes are initiated in the first 24 h of RIT associated with radiation doses of 100-700 rads. These preliminary data suggest that insight into the molecular basis of RIT-induced tumor regression may be gained by further studies using different radiation doses.

Animals↗
PubMed1995

Prognostic factors for radioimmunotherapy in patients with B-lymphocytic malignancies.

The Ann Arbor staging classification has proven less useful in nonHodgkin's lymphoma, because this malignancy is inherently a multifocal disorder. Since 1985, 57 adult patients with advanced B-lymphocytic malignancies that progressed despite standard therapy entered into one of three different therapy trials using radiolabeled Lym-1 antibody. Tumor regression in 31 (54%) of these patients fulfilled conventional requirements for an oncological response to the therapy. To define the role of radioimmunotherapy in B-lymphocytic malignancies better and to find opportunities for improving its therapeutic efficacy, the records of these patients were reviewed to assess the significance of various parameters as prognostic indicators. Twenty-one pretherapy characteristics were evaluated, including age at diagnosis, age at study entry, sex, Karnofsky performance status, prior chemotherapy and radiation therapy, interval since diagnosis, histology, constitutional B symptoms, extranodal malignancy (excluding marrow), bone marrow malignancy, tumor bulk, and circulating malignant cells; blood tests included lymphocyte, granulocyte, platelet, hematocrit, serum lactate dehydrogenase (LDH), interleukin 2 receptor, and human antimouse antibody levels. In the multivariate analysis, LDH and Karnofsky performance status were the parameters that best predicted survival, complete and partial remission, and time to progression; interleukin 2 receptor and LDH best predicted complete remission. These prognostic factors for radioimmunotherapy outcome are consistent with the pretherapy characteristics observed to be significant for chemotherapy.

Adult↗
PubMed1995

Functional assessment of specific amino acid residues of cytochrome P4501A1 using anti-peptide antibodies.

Several positively charged amino acid residues in cytochrome P450 have been shown to be involved in the electrostatic association with NADPH-cytochrome P450 reductase. For cytochrome P4501A1, five regions were proposed as the putative binding sites for the reductase (Shen, S., and Strobel, H. W. (1993) Arch. Biochem. Biophys. 304, 257-265). To elucidate the specific roles of each of these amino acid residues, five anti-peptide antibodies defined as 1A, 4A, 5A, 6A, and 7A were generated against these regions containing 8-13 amino acids and were affinity-purified using a peptide-Sepharose 4B column. Analysis by enzyme-linked immunosorbent assay and protein immunoblot techniques demonstrated that three of five anti-peptide antibodies have specific binding to the peptides as well as to cytochrome P4501A1. Incubation of the various anti-peptide antibodies with cytochrome P450 followed by reconstitution with reductase, lipid, and NADPH resulted in significant inhibition of P450 activity for antibodies 5A and 6A, but not for 1A, 4A, or 7A. Antibody 5A also exhibited inhibition of P450 activity supported by cumene hydroperoxide, though the inhibition was 45 to 30% less than the inhibition of reductase-supported activity at each of the increasing concentrations of antibody. Kinetic studies with antibody 5A revealed no change in the Km for the substrate ethoxycoumarin, but rather a dramatic effect on the Vmax of the cytochrome P4501A1 system whether reconstituted with reductase or supported by cumene hydroperoxide. Characterization of the effects of antibody 5A on cytochrome P4501A1 suggested that the binding of antibody 5A to P4501A1 may change the binding of P4501A1 with reductase. Furthermore, the binding of 5A to cytochrome P4501A1 also lowered the Vmax of the P450. These results are consistent with the roles for the regions of cytochrome P4501A1 from amino acid residues 269 to 281 (peptide 5) and 454 to 463 (peptide 6) in cytochrome P4501A1 hydroxylation activity.

Amino Acid Sequence↗
PubMed1995

Design and synthesis of new naphthalenic derivatives as ligands for 2-[125I]iodomelatonin binding sites.

New melatonin-like agents were designed from the frameworks of 2,5-dimethoxyphenethylamine, an important structural moiety for the 5-HT receptor, and (2-methoxynaphthyl)-ethylamine. The compounds were synthesized by classical methods and evaluated in binding assays with chicken brain membranes using 2-[125I]iodomelatonin as the radioligand. Preliminary studies on the series of N-acyl-disubstituted phenethylamines showed the favorable role of the methoxy group in the ortho position of the side chain on the affinity for the receptor (Ki = 8 +/- 0.2 nM) for N-[2-(2-methoxy-5-bromophenyl)ethyl]propionamide (3o). This effect was confirmed in a series of the naphthalene derivatives, a bioisosteric moiety of the indole ring, and several potent ligands for melatonin binding sites were prepared such as N-[2-(2-methoxynaphthyl)ethyl]propionamide (4b) (Ki = 0.67 +/- 0.05 nM) and N-[2-(2,7-dimethoxynaphthyl)ethyl]cyclopropylformamide (Ki = 0.05 +/- 0.004 nM) (4k). Structure-activity relationships are discussed with regard to melatonin and bioisosteric naphthalenic compound 2. The Ki value for 4b was affected to a similar extent to that of melatonin by GTP-gamma-S or Mn2+ in competition experiments, suggesting an agonist profile for this compound.

Animals↗
PubMed1995

Denaturation of cytochrome P450 2B1 by guanidine hydrochloride and urea: evidence for a metastable intermediate state of the active site.

A metastable intermediate was found in the course of the denaturation of purified cytochrome P450 2B1 by increasing concentrations of guanidine hydrochloride (GuHCl). The metastable intermediate has no or low absorbance at 450 nm in the reduced carbon monoxide difference spectrum and has no absorbance at 420 nm. The intermediate is easily converted to P420 by increasing concentrations of GuHCl. Before it becomes P420, the cytochrome can be completely reconverted to native P450 by dilution and incubation at 4 degrees C. Cytochrome P420 resulting from exposure to higher concentrations of GuHCl (> 3 M) failed to be reconverted to P450 by dilution. Denaturation of P450 2B1 by exposure to low concentrations of urea (< 2 M) is also completely reversible but no obvious intermediate is detectable. An intermediate is observed, however, when the urea denaturation is conducted in the presence of 1 M NaCl. As is the case with higher concentrations of GuHCl, cytochrome P450 denatured by exposure to 5 M or higher concentrations of urea is not reversible. The failure of reconversion of P420 denatured by exposure of cytochrome P450 to high concentrations of GuHCl or urea is probably attributable to the extensive unfolding of the apoprotein, which favors aggregation, rather than to heme loss. Our results also suggest that the active site is more sensitive to denaturants than other regions of the protein.

Animals↗
PubMed1995

Expression of multiple forms of brain cytochrome P450.

Multiple forms of cytochrome P450 (P450) in brain tissue have been demonstrated to be expressible in brain tissue using polymerase chain reaction (PCR) techniques, Northern blotting, hydroxylation activity assessment and cloning approaches. The antidepressant drug imipramine is metabolized by brain microsomes to multiple products by pathways inhibitable by quinidine, 7,8-benzoflavone, and ketoconazole, well-known inhibitors of P450-catalyzed reactions. Moreover, PCR studies revealed that a number of P450s are expressible in brain tissue and in glioma C6 cells. Quantitative PCR studies further demonstrated the response of many of these forms to induction in agreement with hydroxylation activity results.

Animals↗
PubMed1995

Estimation of radiation absorbed doses to the red marrow in radioimmunotherapy.

Myelotoxicity is the dose-limiting factor in radioimmunotherapy. Traditional methods most commonly used to estimate the radiation adsorbed dose to the bone marrow of patients consider contributions from radionuclide in the blood and/or total body. Targeted therapies, such as radioimmunotherapy, add a third potential source for radiation to the bone marrow because the radiolabeled targeting molecules can accumulate specifically on malignant target cells infiltrating the bone marrow. A non-invasive method for estimating the radiation absorbed dose to the red marrow of patients who have received radiolabeled monoclonal antibodies (MoAb) has been developed and explored. The method depends on determining the cumulated activity in three contributing sources: 1) marrow; 2) blood; and 3) total body. The novel aspect of this method for estimating marrow radiation dose is derivation of the radiation dose for the entire red marrow from radiation dose estimates obtained by detection of cumulated activity in three lumbar vertebrae using a gamma camera. Contributions to the marrow radiation dose from marrow, blood, and total body cumulated activity were determined for patients who received an I-131 labeled MoAb, Lym-1, that reacts with malignant B-lymphocytes of chronic lymphocytic leukemia and nonHodgkin's lymphoma. Six patients were selected for illustrative purposes because their vertebrae were readily visualized on lumbar images. The radiation doses to the marrow contributed by nonpenetrating emissions in the marrow blood and penetrating emissions in the total body were similar in these patients with a mean of 0.2 and 0.3 rads per administered mCi from the blood and total body, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Marrow↗
PubMed1995

Immunohistochemical staining for endotoxin using horseshoe crab factor C in fecal peritonitis.

The object of the present study was to apply a new immunohistochemical staining method to the in vivo determination of endotoxin localization. The immunohistochemical staining method requires factor C (an initiation factor in the Limulus clotting system which is mediated by endotoxin) as a specific ligand of endotoxin, and a newly developed murine monoclonal antibody to factor C. The blood endotoxin level and endotoxin localization in the rat were determined before and at 6, 12 and 24 h after intraperitoneal injection of 0.25 g/kg of fresh rat feces. The greatest blood endotoxin level was achieved at 12 h after the injection, and uptake of endotoxin was evident in Kupffer cells in the liver at 24 h after the injection. There has been no report on determining endotoxin localization in cases of endotoxemia attributed to fecal peritonitis. This new immunohistochemical staining method for determining endotoxin localization will contribute to the histopathological diagnosis of endotoxemia in humans.

Animals↗
PubMed1995

Structure and oxygen sensitivity of nifLA promoter of Enterobacter cloacae.

The nucleotide sequence of the nifLA promoter of Enterobacter cloacae E26 was determined, and the transcription start site of nifLA was mapped by the primer extension. Studies on the oxygen regulation of E. cloacae nifLA promoter with the nifL'-lacZ fusion showed that the nifLA promoter was sensitive to oxygen as Klebsiella pneumoniae nifLA promoter reported previously. Comparison between the nifLA promoter sequences of E. cloacae and K. pneumoniae revealed the presence of an 11-bp conserved sequence between the -24/-12 consensus of sigma 54-dependent promoter and NtrC binding motif. The 11-bp sequence is speculated to be involved in the oxygen regulation of the nifLA promoter of both enteric bacteria.

Base Sequence↗