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Biomedical subjects

S Sun

Publications and source records attributed to S Sun.

At least 217 records · Page 12Linked to original sources
PubMed1997

[The enrichment of polycyclic aromatic hydrocarbons in water samples by solid-phase extraction].

Solid-phase extraction (SPE) is an emerging chromatographic sample preparation technique. The novel extraction technique can reduce the time and volume of organic solvents required, and alleviate problems associated with the formation of emulsions as compared to conventional liquid-liquid extractions. This study was designed to demonstrate the utility of SPE for trace enrichment of polycyclic aromatic hydrocarbons (PAHs) in water samples. The results showed that dichloromethane and benzene are the preferred elution solvents for the adsorbed PAHs. The recoveries of PAHs with SPE are in the range of 87% to 102%. When the elution solvent is selected, the variation of recoveries as a function of the volume of elution solvent used can be determined. Meanwhile, further studies showed that recoveries become worse as the number of rings of PAH increased. The decrease of solubility and adsorption onto container surface may be responsible for bad recoveries. The addition of 20% (V/V) methanol or ethanol into the sample prior to spiking can greatly improve the recoveries of larger PAHs. Recoveries of 89%-108% can be obtained.

Polycyclic Aromatic Hydrocarbons↗
PubMed1997

[Study on the tribochemistry of antiwear additive BA1 by FTIRM].

This paper studied the tribochemistry of antiwear additive BA1 by FTIR microscope technique. We observed the changes of physical properties, interpreted the infrared spectra of the products in the track and concluded the chemical mechanism through the change of BA1 concentration, load and rubbing time. The results shows that the BA1 was decomposed, oxided and a thin film was produced when rubbed. This film makes the rubbing efficiency less.

English Abstract↗
PubMed1997

[Study on self-activation of phosphorylated amino acids to form peptides by FTIR].

The self-activation of six phosphorylated amino acids to form peptides was studied in i-propyl alcohol by FTIR. The results indicated that the phosphorylated amino acids could be self-activated to form peptides in alcohol and the FTIR method in the study on the self-activation of phosphorylated amino acids to form peptides can provide useful information for life process.

2-Propanol↗
PubMed1997

[TR-FTIRS study of crystal phase transformation in polyvinylidene fluoride].

The study of polyvinylidene fluoride (PVDF) by time-resolved Fourier transform infrared spectroscopy (TR-FTIRS) was reported. The instantaneous change and process of both alpha-form and beta-form during transformation were studied under the pulse electric field excitation. Transformation of alpha-form to beta-form was indicated by the increasing of the peak at 508cm(-1), the decreasing of the peak at 528cm(-1) and a shift of those peaks. The transient change time was about 5ms. The decreasing of the peak at 528cm(-1) was nonlinear. A hysteresis-like loop was observed, which was related with the biaxially orientated property of PVDF and was in good agreement with its polarizated hysteresis loop.

English Abstract↗
PubMed1997

Study on enzyme electrode biosensor of choline.

Choline oxidase was immobilized at a hydrogen peroxide electrode and the enzyme electrode was used for the amperometric determination of choline. The linear range is 0-200 mg/L with a response time of 40 seconds and a 25-microliter sample injection. The relative standard deviation (RSD) is less than 1.5% in 20 assays. The enzyme membrane can be used continuously at 25 degrees C for 60 days. The recovery rate of this method is 100.3-102.3%.

Alcohol Oxidoreductases↗
PubMed1997

Synthesis of 3'-thioribonucleosides and their incorporation into oligoribonucleotides via phosphoramidite chemistry.

Oligoribonucleotides containing 3'-S-phosphorothiolate linkages are valuable probes in nucleic acid biochemistry, but their accessibility has been limited because 3'-thioribonucleoside phosphoramidites have not been available. We synthesized 3'-thioribonucleoside derivatives (C, G, and U) via glycosylations of nucleoside bases with 3-S-thiobenzoyl-5-O-toluoyl-1,2-O-diacetylfuranose 5, which was obtained from 1 ,2-O-isopropylidene-5-O-toluoyl-3-trifluoromethane-sulfonyl-alpha-D-x ylofuranose 2 by SN2 displacement with sodium thiobenzoate. Additionally, a 3'-thioinosine derivative was prepared from inosine via direct modification of the ribose, analogous to the previously reported synthesis of 3'-thioadenosine, except that the intermediate 2',3'-epoxide 9 was first protected as the 5'-O-tert-butyldiphenylsilyl ether prior to subsequent synthetic steps. This hydrophobic silyl group facilitated extraction and isolation of synthetic intermediates. After removal of the protecting groups, the 3'-thionucleosides (C, G, U, and I) were treated with 2,2'-dipyridyl disulfide to protect the free thiol group as a disulfide. The 3'-thionucleosides were converted to the corresponding phosphorothioamidites using procedures analogous to those for standard phosphoramidites. The amino groups of 3'-thiocytidine and 3'-thioguanosine were protected as benzoyl and isobutyryl amides, respectively, and the 5'- and 2'-hydroxyl groups of each nucleoside were protected as dimethoxytrityl and tert-butyldimethylsilyl ethers, respectively. The 3'-thiol group was deprotected by reduction with DTT and phosphitylated to afford analytically pure 3'-S-phosphorothioamidites 15, which were incorporated into oligoribonucleotides by solid-phase synthesis. Chemical assays and mass spectrometry of the synthetic RNA showed that ribose-3'-S-phosphorothiolate linkages were installed correctly and efficiently into RNA oligonucleotides using phosphoramidite chemistry.

Glycosylation↗
PubMed1997

Early intervention improves intellectual development in asphyxiated newborn infants. Intervention of Asphyxiated Newborn Infants Cooperative Research Group.

OBJECTIVE: To evaluate the effect of early intervention on the intellectual development in asphyxiated newborn infants. METHODS: Full term asphyxiated infants (Apgar score < or = 6 at 5 minutes after birth) were randomly assigned to early intervention group (34 cases) and conventional care (30 cases) group. The normal control group consisted of 38 infants. Sex, mother's educational background, environmental condition and physical development were not significantly different in the 3 groups. Zero to two years early intervention program was compiled on basis of the national and foreign material about 1 month ahead of average development of the child. It included motor, cognitive, speech development and social behavior. Parents were instructed to carry out early intervention. RESULTS: At the age of 1.5 years, average score of mental development index (MDI) in early intervention group was 14.6 higher than that in conventional care group (F = 18.86, P < 0.0001). MDI score in early intervention group caught up with that in normal control group (F = 2.17, P > 0.05). Conventional care group was 9.7 lower than normal control group (F = 10.14, P < 0.01). Two of 30 cases (6.7%) in conventional care group was mentally retarded while none was mentally retarded in the early intervention group. CONCLUSIONS: The results showed that the early intervention could promote intellectual development of asphyxiated infants and be of much benefit to the prevention of mental retardation.

Asphyxia Neonatorum↗
PubMed1997

[Sequential changes in diamine oxidase activity after burn].

We invistigated the sequntial changes in plasma and intestinal diamine oxidase (DAO) levels in animals and patients after burn injury. The results were as follows: 1. The plasma DAO level in patients was increased significantly at 1, 3, 7, 14 d and returned to normal at 21 d postburn; 2. In pigs, the elevation of plasma DAO level was also found during the whole experiment, but only significantly so at 72 h postburn; 3. In scald rats, the DAO level was increased in plasma and decreased in intestine. The above results suggested that intestinal mucosa injury and DAO release into blood occurred after burn injury. The activity of DAO in plasma might be one of the marker to reflect injury of intestinal mucosa.

Adult↗
PubMed1996

Repression of transcriptional enhancer factor-1 and activator protein-1-dependent enhancer activity by vascular actin single-stranded DNA binding factor 2.

Transcriptional repression of the murine vascular smooth muscle alpha-actin gene in fibroblasts results from the interaction of two sequence-specific single-stranded DNA binding activities (VACssBF1 and VACssBF2) with opposite strands of an essential transcriptional enhancer factor-1 (TEF-1) element (Sun, S., Stoflet, E. S., Cogan, J. G., Strauch, A. R., and Getz, M. J. (1995) Mol. Cell. Biol. 15, 2429-2436). Here, we identify a sequence element located within a protein-coding exon of the gene that bears structural similarity with the TEF-1 enhancer. This includes a 30-base pair region of purine-pyrimidine asymmetry encompassing a perfect 6-base pair GGAATG TEF-1 recognition motif. Unlike the enhancer, however, the exon sequence exhibits no TEF-1 binding activity nor does the pyrimidine-rich strand bind VACssBF1. However, VACssBF2 interacts equally well with the purine-rich strand of both the enhancer and the exon sequence. To test the ability of VACssBF2 to independently repress transcription, the exon sequence was placed upstream of a deletionally activated promoter containing an intact TEF-1 binding site. The exon sequence repressed promoter activity, whereas a mutant deficient in VACssBF2 binding did not. Moreover, VACssBF2 similarly repressed activator protein-1-dependent transcription of a heterologous tissue factor promoter. These results suggest that VACssBF2 possesses an intrinsic ability to disrupt enhancer function independently of the enhancer-binding proteins involved.

3T3 Cells↗
PubMed1996

Effect of tacrolimus on hemodynamics and absorption of experimental small intestinal transplants.

We have previously reported the adverse effects of cyclosporine on small intestine transplant physiology. In this study, we report for the first time the effect of tacrolimus (FK) on graft intestinal blood flow and intramural distribution, vascular resistance, and absorptive function. Isogeneic small intestine transplantation was performed in Lewis rats. Animals were grouped based upon the following treatment schedules: no treatment for 1 week in group 1; 0.6 ml/kg/day i.m. polyethylene glycol (PEG) for 1 week in group 2; 2 mg/kg/day i.m. FK for 1 week in group 3; 0.6 ml/kg/day PEG for 1 week and then 0.3 ml/kg/day for 5 weeks in group 4; 2 mg/kg/day FK for 1 week and then 1 mg/kg/day for 5 weeks in group 5. Group 6 was the same as in group 5 but FK was withdrawn for 1 week prior to assessment. Maltose absorption was measured to evaluate graft absorptive function. Blood flow and its intramural distribution to mucosal and serosal/muscularis layers were determined using the radioactive microsphere technique. Perfusion pressure was measured to calculate vascular resistance. One week of FK administration in group 3 did not change graft hemodynamics and absorption significantly. Prolonged FK treatment up to 6 weeks in group 5 resulted in a significant increase in mucosal vascular resistance (71.0 +/- 9.6 versus 47.7 +/- 6.7 U/g, P<0.01) and significant decreases in mucosal blood flow (1.14 +/- O.15 versus 1.69 +/- 0.24 ml/g/min, P<0.01) and maltose absorption (30 min after loading. 155.4 +/- 26.9 versus 216.4 +/- 29.6, P<0.01; 60 min after loading: 172.9 +/- 24.5 versus 229.1 +/- 32.6 glucose mg/dl P<0.01). The serosal/muscularis layer remained relatively unaffected. Withdrawal of FK for 1 week after prolonged treatment in group 6 resulted in restorations of all parameters measured to normal ranges. We conclude that a short course of FK is safe, but prolonged FK administration has harmful effects on the hemodynamics and function of small intestinal transplants. Complete recovery is achieved when FK is discontinued.

Animals↗
PubMed1996

Thickness measurement of hydrated and dehydrated cryosections by EELS.

Electron energy-loss spectroscopy (EELS) provides a useful method for determining the thickness of frozen-hydrated and dehydrated cryosections in terms of the inelastic mean free path. Cryosection thickness is an important parameter because plural inelastic scattering limits the sensitivity of elemental microanalysis based on core-loss EELS, and because overlapping structures can affect interpretation of microanalytical data as well as the quality of electron images. The purpose of this work was to establish the minimum practical thickness for cutting cryosections and to explain the measured values for hydrated and dehydrated specimens. Hydrated sections were typically found to be between 1.5-2.5 times thicker than expected from the nominal microtome setting; this difference can be largely explained by compression during cutting. Comparison of micrographs from hydrated and dehydrated cryosections of rapidly-frozen, vitrified liver revealed a lateral shrinkage of approximately 20% on drying. The measured compression and shrinkage factors are consistent with dark-field scanning transmission electron microscopy (STEM) mass measurements on freeze-dried sections. Freeze-dried cryosections, cut to a nominal thickness of 90 nm and supported on thin Formvar/carbon films, had a relative thickness t/lambda i in the range of 0.5 for cytoplasm to 0.9 for mitochondria when analyzed at 100 keV beam energy. Mass loss of approximately 30% occurring at high electron dose enabled useful core-loss spectra to be recorded even from high-mass compartments such as mitochondria without excessive plural scattering.

Animals↗
PubMed1996

Active immunization against vasoactive intestinal peptide prevents photo-induced prolactin secretion in turkeys.

Photostimulation initiates and maintains the rise in circulating prolactin (PRL) observed during the reproductive cycle of the female turkey. Vasoactive intestinal peptide (VIP) is the principal PRL-releasing factor. This study tested the hypothesis that gonadal stimulatory photoperiods stimulate PRL secretion by releasing hypothalamic VIP. Therefore, an experiment was designed to determine if VIP immunoneutralization altered photo-induced PRL secretion. Reproductively quiescent female turkeys were divided into two groups comprising turkeys actively immunized with synthetic VIP conjugated to keyhole limpet hemocyanin (VIP-KLH; immunized; n = 48) or KLH alone (control; n = 48). The first immunization was administered 6 weeks before photostimulation. Blood samples were collected at frequent intervals prior to and following photostimulation, and plasma PRL concentrations were determined. Vasoactive intestinal peptide antibody titer was estimated from the percentage of 125I-labeled VIP bound to plasma diluted 1:1000. At the onset of photostimulation (Day 0), plasma PRL levels were similar for immunized and control turkeys (9.1 +/- 0.3 versus 8.9 +/- 0.3 ng/ml, respectively). Plasma PRL of control birds increased (P < 0.05) by Day 16 of photostimulation, reaching a peak value of 724.9 +/- 90.1 ng/ml on Day 84. In contrast, plasma PRL remained essentially unchanged in immunized birds. Titer of anti-VIP antibodies expressed as 125I-VIP bound by plasma in immunized birds was 10.9 +/- 1.5% on the day of photostimulation. Incubation behavior was blocked in immunized birds, whereas 75% of controls exhibited incubation behavior. The control group laid 1.83 eggs/ week/hen compared to 3.40 eggs/week/hen in immunized hens. These findings suggest that photoperiodic modulation of PRL secretion in the turkey is influenced by hypothalamic VIP neuronal system.

Animals↗
PubMed1996

Smaller alveolar-arterial O2 gradients in Tibetan than Han residents of Lhasa (3658 m).

Previous studies have indicated that native Tibetans have a larger lung capacity and better maintain arterial O2 saturation during exercise than Han ("Chinese") acclimatized lowlanders. To test if differences in ventilation or alveolar-arterial O2 gradient (A-aDO2) were responsible, we compared 10 lifelong Tibetan and 9 Han acclimatized newcomer residents of Lhasa (3658 m) at rest and during progressive exercise. Resting blood gas tensions and arterial O2 saturation in the two groups were similar. During exercise the Tibetans had lower total ventilation and higher arterial CO2 tensions than the Han (both P < 0.01) and markedly lower A-aDO2 (7 +/- 1 vs. 11 +/- 1, 13 +/- 1 vs. 18 +/- 1, and 14 +/- 1 vs. 20 +/- 1 mmHg at light, medium, and heavy workloads respectively, all P < 0.01). The Tibetans' narrower A-aDO2 compensated for their lower exercise ventilation such that arterial O2 tension and saturation were raised above acclimatized newcomer values and better maintained during exercise. We concluded that the Tibetans exhibited more efficient pulmonary gas exchange which compensated for reduced ventilation and lessened respiratory effort.

Acclimatization↗
PubMed1996

Nucleotide-free diet suppresses antigen-driven cytokine production by primed T cells: effects of supplemental nucleotides and dietary fatty acids.

Our previous studies suggest that nucleotides modulate T-helper (Th) cell-mediated antibody (Ab) production. This nucleotide action is influenced by dietary fatty acids. Herein, we report the effects of nucleotide-free (NF) diets normal or high in saturated fatty acid on antigen-driven Th cell activation by using cytokine production as an indicator. C57BL/6 mice were fed a NF diet, a NF diet plus mononucleotide and nucleoside mixture (OG-VI), a NF diet high in saturated fatty acid (NF-SFA), or a NF-SFA diet plus OG-VI. Mice were then challenged with neoantigen, a keyhole limpet hemocyanin (KLH). Regional draining lymph nodes were collected 5-7 d following antigen (AG) priming, rechallenged with KLH in the culture, and resultant cytokine production was measured. IFN gamma and IL-5 production was lower in mice fed a NF diet at protein and mRNA levels. IL-4 and IL-2 mRNA expression was also lower in mice fed a NF diet. IFN gamma protein levels were higher in mice fed a NF-SFA diet than in mice fed a NF diet, but production of other cytokines was equally suppressed in those fed a NF-SFA diet. In vivo OG-VI supplementation prevented aberrant cytokine production in mice fed a NF or NF-SFA diet. Polynucleotides added to the culture restored impaired IFN gamma and IL-5 production in mice fed a NF diet but did not further augment cytokine production in mice of other diet groups. These results indicate a potential role of nucleotides in Ag-driven Th-cell activation, and this nucleotide action is partly under the influence of dietary fatty acids.

Animals↗
PubMed1996

Polymorphisms in P21CIP1/WAF1 are not correlated with TP53 status in sporadic ovarian tumours.

In breast cancers and sarcomas, a variant polymorphism in the cell cycle inhibitor P21CIP1/WAF1 is under-represented in those individuals whose tumours contain mutated TP53. The aim of this study was to determine whether this variant polymorphism was also under-represented in those with ovarian carcinoma and TP53 mutations. We studied lymphocyte DNA from 104 women with ovarian carcinoma, 15 with borderline tumours and 16 with benign tumours, using a previously-reported PCR-RFLP technique. 96 of the ovarian carcinoma cases had been previously examined for mutations in TP53 and/or for overexpression of the TP53 protein. The variant allele was seen in 11 out of 104 women (10.6%) with ovarian carcinoma. There was no significant difference in the distribution of the variant allele in the women whose tumours had (7/47) or did not have (4/49) TP53 mutations (P = 0.523). It does not appear that the presence of this variant allele of P21CIP1/WAF1 has any aetiological role in ovarian carcinomas. Studies in other tumours support this finding.

Alleles↗