Biomedical subjects

S Song

Publications and source records attributed to S Song.

At least 109 records · Page 6Linked to original sources

PubMed1999

Differential depression at excitatory and inhibitory synapses in visual cortex.

The function of cortical circuits depends critically on the balance between excitation and inhibition. This balance reflects not only the relative numbers of excitatory and inhibitory synapses but also their relative strengths. Recent studies of excitatory synapses in visual and somatosensory cortices have emphasized that synaptic strength is not a fixed quantity but is a dynamic variable that reflects recent presynaptic activity. Here, we compare the dynamics of synaptic transmission at excitatory and inhibitory synapses onto visual cortical pyramidal neurons. We find that inhibitory synapses show less overall depression than excitatory synapses and that the kinetics of recovery from depression also differ between the two classes of synapse. When excitatory and inhibitory synapses are stimulated concurrently, this differential depression produces a time- and frequency-dependent shift in the reversal potential of the composite postsynaptic current. These results indicate that the balance between excitation and inhibition can change dynamically as a function of activity.

Analysis of Variance↗

PubMed1999

Fast C18 solid-phase desalting/delipidation of the human serum apolipoproteins for matrix-assisted laser desorption ionization and electrospray ionization mass spectrometric analysis.

A new method for the delipidation of human serum lipoproteins involving the use of a reversed-phase C18 solid-phase extraction (SPE) cartridge is introduced for use with matrix-assisted laser desorption ionization and electrospray ionization mass spectrometry. This method is compared with two other methods of lipoprotein delipidation. The SPE method of delipidation produces a higher and more reproducible protein yield than the conventional liquid-liquid methanol-diethyl ether delipidation technique. Furthermore, the SPE method implements a fast, sequential, desalting and delipidation of the lipoproteins for subsequent mass spectrometric analysis providing high quality spectra.

Apolipoproteins↗

PubMed1999

Computational Studies on Interaction between Air Bubbles and Hydrophobic Mineral Particles Covered by Nonpolar Oil.

Computations based on the extended DLVO theory are carried out on the potential energies of interactions between air bubbles and talc particles covered by nonpolar oil. It is shown that the major role of nonpolar oil in this system is to greatly increase the depth of the primary energy valley, giving rise to a much stronger bubble-particle aggregate that can support greater aggregate-rupture force fields from turbulent flows. Also, due to nonpolar oil involvement, the energy barrier between bubbles and mineral particles sharply collapses down and further separates, indicative of a greater probability of attachment of mineral particles to air bubbles. A linear relationship is found between the primary energy valley and the contact angles of oil or bubbles, and thus a simple and approximate formula is presented to evaluate the depth of the primary energy valley. In addition, it is found that the primary energy valley and the energy barrier are directly proportional to the effective particle radius, but the barrier location is independent of the effective particle radius. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Supercritical fluid extraction and gas chromatography/mass spectrometry for the analysis of tobacco-specific nitrosamines in cigarettes.

A method for measuring four tobacco-specific nitrosamines (TSNAs), an important group of compounds in tobacco products, was developed. These compounds were extracted using supercritical fluid extraction (SFE) and purified by a sodium hydroxide wash of the ethyl acetate eluting solvent and solid-phase extraction. Quantitation was performed using gas chromatography/mass spectrometry (GC/MS). Spiking experiments were carried out to determine the recovery, precision, and limits of detection of this method. The detection limits were 0.04 microgram per sample for N'-nitrosonornicotine and N'-nitrosoanatabine and 0.02 microgram for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosoanabasine. This method was used to measure TSNAs in various brands of cigarette tobacco with excellent reproducibility. The variation of TSNA levels among the cigarettes of different packs and types was significantly smaller than that among different brands. Comparable TSNA levels were obtained with SFE and liquid extraction methods. Signal-to-noise levels were similar for GC/MS and GC/thermal energy analysis when low-level tobacco samples were analyzed.

Gas Chromatography-Mass Spectrometry↗

PubMed1999

Impaired proteolytic processing of presenilin-1 in chromosome 14-linked familial Alzheimer's disease patient lymphocytes.

Many cases of early-onset familial Alzheimer's disease (FAD) are caused by mutations in the presenilin 1 (PS1) and PS2 genes. PS1 protein is generated as a 47 kDa protein and is endoproteolytically cleaved into N-terminal 28 kDa and C-terminal 19 kDa fragments in vivo. To examine whether mutated PS1 protein is abnormally metabolized, we performed immunoblot analysis of lymphoblasts from familial Alzheimer's disease patients and controls. More full-length PS1 was apparently detected in samples from PS1 mutants than those from PS2 mutant and controls. This result suggests that impaired proteolysis of PS1 may be associated with the pathogenesis of FAD. Moreover, our simple test using lymphocytes from FAD patients might be useful from a diagnostic point of view.

Alzheimer Disease↗

PubMed1999

Role of CCAAT enhancer-binding protein beta in the thyroid hormone and cAMP induction of phosphoenolpyruvate carboxykinase gene transcription.

Transcription of the gene for phosphoenolpyruvate carboxykinase (PEPCK) is stimulated by thyroid hormone (T3) and cAMP. Two DNA elements in the PEPCK promoter are required for T3 responsiveness including a thyroid hormone response element and a binding site called P3(I) for the CCAAT enhancer-binding protein (C/EBP). Both the alpha and beta isoforms of C/EBP are highly expressed in the liver. C/EBPalpha contributes to the liver-specific expression and cAMP responsiveness of the PEPCK gene. In this study, we examined the ability of C/EBPbeta when bound to the P3(I) site to regulate PEPCK gene expression. We report that C/EBPbeta can stimulate basal expression and participate in the induction of PEPCK gene transcription by T3 and cAMP. The cAMP-responsive element-binding protein and AP1 proteins that contribute to the induction by cAMP are not involved in the stimulation by T3. A small region of the transactivation domain of C/EBPbeta is sufficient for the stimulation of basal expression and cAMP responsiveness. Our results suggest that C/EBPalpha and C/EBPbeta are functionally interchangeable when bound to the P3(I) site of the PEPCK promoter.

Base Sequence↗

PubMed1999

Oxidative DNA damage in the aging mouse brain.

The brain exhibits regional vulnerabilities to many insults, and age itself has differential effects on neuronal populations as exemplified by the age-dependent loss of dopaminergic neurons in the nigrostriatal system. We hypothesized that oxidative damage to DNA was more likely to occur in the nigrostriatal system which undergoes significant neurochemical and functional changes with age. To test this hypothesis, oxidative damage to DNA, indicated by levels of 8-hydroxy2'-deoxyguanosine (oxo8dG), was measured in pons-medulla (PM), midbrain (MB), caudate-putamen (CP), hippocampus (HP), cerebellum (CB), and cerebral cortex (CX) at 3, 18, and 34 months of age in C57/b1 mice. Steady-state levels of oxo8dG increased significantly with age in MB, CP, and CB, but not in PM, HP, or CX. Manganese superoxide dismutase (MnSOD) activity decreased with age in MB, CP, and HP, but not in PM, CB, or CX. Regional activities of Cu/Zn superoxide dismutase (Cu/Zn SOD) and glutathione peroxidase (Glut Px) did not change significantly with age. Concomitant with the regional alterations in DNA damage, there was a significant age-dependent decline in locomotor activity, motor coordination, and striatal dopamine content especially during the interval between 18 and 34 months. In conclusion, oxyradical-associated damage to DNA did not accumulate uniformly across brain regions with age and was highest in brain regions that subserve spontaneous locomotor activity and motor coordination.

Age Factors↗

PubMed1999

Effect of SJAMP on ATP release of platelet.

The aggregation and ATP release of placelet of normal subjects were measured by platelet lumi-aggregometer. It was found that the aggregation curve induced by SJAMP at the concentration of 100 mg/L was a typical second phase aggregation. There existed a certain lag between platelet aggregation and secretion. The secretion actually began slightly after the second phase of aggregation, suggesting that the second phase aggregation induced by SJAMP is not dependent upon the release of contents of dense granule alone. If platelets were incubated with cyclo-oxygenase inhibitor, the second phase aggregation was inhibited and no ATP was released. The results indicated that the aggregation and release reaction induced by SJAMP were dependent upon the generation of prostaglandin endoperoxides and TXA2 in normal subjects. The amount of ATP release was 0.69 +/- 0.22 nmol/10(8) platelets as stimulated with SJAMP (100 mg/L). But the amount of ATP release were 1.60 +/- 0.25 and 1.37 +/- 0.15 nmol/10(8) platelets when platelets were stimulated with ADP (5 mumol/L) and collagen (5 mg/L). The amount of ATP release induced by SJAMP was significantly lower than that of ADP and collagen. These findings indicated that SJAMP was a weaker agonist than ADP in terms of platelets release reaction.

Adenosine Triphosphate↗

PubMed1999

Multidrug resistance P-glycoprotein function of bone marrow hematopoietic cells and the reversal agent effect.

The multidrug resistance P-glycoprotein (P-gp) expression and function in hematopoietic stem/progenitor cells were studied to investigate whether the inhibition of hematopoietic cell P-gp function by multidrug resistance reversal agent increases the cytotoxicity of chemotherapy drugs on the hematopoietic cells. The expression of P-gp on the surface of CD34+ cells from healthy human marrow was examined by flow cytometry. The multidrug resistance reversal agent MS-209 was used to measure the effects of MS-209 on the Rhodamin-123 uptaking of CD34+ hematopoietic cells. By using methylcellulose semi-solid culture, normal human granulocyte-macrophage clonal formation unit (CFU-GM) was cultured. The changes in CFU-GM inhibitory rate caused by daunorubicin were determined in the presence or absence of MS-209. The results showed that the P-gp expression rate of bone marrow CD34+ cells was 13.3%. MS-209 obviously increased the Rhodamin-123 uptake of CD34+ positive cells. The mean inhibitory rate of daunorubicin for CFU-GM was 29.6%, but it was increased to 43.3% in the presence of MS-209 with the difference being significant (P < 0.05). It was concluded that hematopoietic cells expressed P-gp protein and possessed active function. MS-209 could inhibit the membrane efflux pump and increase the cytotoxicity of chemotherapy drugs to the clonal growth of hematopoetic stem cells, suggesting the side effects of these drugs on the hematopoietic system should be taken into consideration in the clinical use.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed1999

Detection of the level of urinary FPA in chronic nephritis with renal failure and its clinical implication.

The level of urinary FPA was assayed by high performance liquid chromatography (HPLC) in 42 normal controls, 57 cases of chronic glomerulonephritis, including 24 with normal renal function, 12 with renal insufficiency and 21 with uremia. Their levels were 24.40 +/- 10.30 micrograms/L, 26.99 +/- 5.77 micrograms/L, 38.81 +/- 6.28 micrograms/L, 79.74 +/- 18.76 micrograms/L, respectively. The level of urinary FPA in renal insufficiency function group was significantly higher than those of the control group and normal renal function group (P < 0.01). The patients with uremia presented dramatically higher level of urinary FPA than those in the renal insufficiency group (P < 0.01). A positive correlation was found between the level of urinary FPA and the blood creatine (r = 0.9120, P < 0.01). It was suggested that a hypercoagulable state existed in the patients with chronic nephritis with renal failure, in which the severity was closely related with the occurrence and development of the disease. The urinary FPA could serve as a good indicator for renal function.

Biomarkers↗

PubMed1999

Immunohistochemical study of T lymphocyte subsets on frozen substituted plastic embedding section of the bone marrow from patients with myelodysplastic syndrome and its clinical implication.

An immunohistochemical study of T lymphocyte subsets on frozen substituted plastic embedding bone marrow sections obtained from 10 patients with myelodysplastic syndrome (MDS) was presented. The results of qualitative and quantitative immunohistochemical analysis are as follows: (1) Labile antigens of T lymphocytes were well preserved, thus allowing analysis of distribution of T lymphocyte subsets in situ: (2) the average number of T3, T4 and T8 lymphocyte of the diffuse infiltrate was about 2%, 0.4%, 0.5%, respectively, of all nucleated cells in bone marrow, and T4/T8 of T cells were below 1.0 in patients with MDS; (3) there were cases of RAS showing T lymphocyte aggregation in bone marrow, but no patient exhibited progressive refractory anemia with excess of blasts (RAEB) and RAEB in transformation (RAEBT). These findings indicated that the immunological abnormalities are of importance in the evaluation of pathogenesis and prognosis of MDS.

Aged↗

PubMed1999

Features of syndrome X develop in transgenic rats expressing a non-insulin responsive phosphoenolpyruvate carboxykinase gene.

AIMS/HYPOTHESIS: Obesity, glucose intolerance, dyslipidaemia and hypertension are a cluster of disorders (syndrome X) affecting many people. It has been hypothesised that these abnormalities are caused by insulin resistance, but definitive proof is lacking. We have developed transgenic rats in which the rate-limiting gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, is non-insulin responsive. The aim of our study was to investigate whether syndrome X develops in these animals and if a high-fat diet interacts with this genetic defect. METHODS: Chow-fed transgenic and control rats aged 1, 3, 6 and 17 months and a subgroup of transgenic and control rats fed chow plus cafeteria foods for 6 months were examined for features of syndrome X. RESULTS: At 3 months, transgenic rats had fasting and postprandial hyperinsulinaemia, mild obesity (in abdominal and, to a lesser extent, peripheral regions) and fasting hypercholesterolaemia. Hypertriglyceridaemia was evident after 6 months while hyperglycaemia was apparent at 17 months. Hypertension had not developed by 17 months. The effect of a high-fat diet on insulin, glucose, body weight and body fat was more dramatic than the effect of the transgene alone while the effect of a high-fat diet on cholesterol and triglyceride was similar to the transgene. This illustrates that a high-fat diet is a potent catalyst for many abnormalities associated with syndrome X. There was no evidence of an additive effect of the high-fat diet plus transgene. CONCLUSION/INTERPRETATION: Therefore rats genetically-engineered with a non-insulin responsive gluconeogenic enzyme develop several aspects of syndrome X, supporting the hypothesis that insulin resistance initiates this cluster of disorders.

Animals↗

PubMed1999

Paraspinal abscess following facet joint injection.

Injection to the zygapophysial joint is a procedure which is performed frequently for diagnostic or therapeutic reasons in the management of back pain. It is generally considered to be free of significant complications. We report a patient who developed a paraspinal abscess following a lumbar facet joint injection.

Abscess↗

PubMed1999

Different responses of epidermal and hair follicular cells to radiation correlate with distinct patterns of p53 and p21 induction.

Different parts of the skin respond to ionizing radiation with different sensitivities. To examine the mechanisms underlying these different responses, we investigated various cellular parameters in the skin after exposure of mice to 5 Gy of ionizing radiation. Epidermal cells responded to radiation by undergoing growth arrest, whereas the cells in the matrix of hair follicles underwent apoptosis but not growth arrest. These distinct responses correlated with differential increases in p53 and p21 proteins in these two populations of cells; whereas an increase in p53 protein levels was observed in both epidermis and hair follicular matrix, especially in the latter, the induction of p21 was strong in the epidermis but absent in the follicular matrical cells. Studies using p53-null and p21-null mice demonstrated that the radiation-induced apoptosis in the hair follicles was fully dependent on p53, and growth arrest in the epidermis was only partially dependent on p53 but fully dependent on p21. These results indicate that two epithelial cell types respond to radiation by different pathways that are governed in part by the differential p53- and p21-dependent responses of these cells; high-level induction of p53 in the absence of p21 induction led to apoptosis, whereas intermediate induction of both p53 and p21 led to growth arrest.

Animals↗

PubMed1999

Comparison of 2D conventional, 3D conformal, and intensity-modulated treatment planning techniques for patients with prostate cancer with regard to target-dose homogeneity and dose to critical, uninvolved structures.

The purpose of this study was to compare 2-dimensional (2D), 3-dimensional (3D) and intensity-modulated radiation therapy (IMRT) techniques for external-beam radiation treatment for prostate cancer. Dose homogeneity within the target volume and doses to critical, uninvolved anatomic structures were evaluated. Computed tomography (CT) scans of 3 patients with localized prostate cancer (T2NOM0) were acquired and transferred to the treatment planning systems. The target volume and uninvolved structures were contoured on axial CT slices throughout the volume of interest. A comparison of the 3 treatment techniques was performed using isodose distributions, dose statistics, and dose-volume histograms. Dose homogeneity was found to be most uniform with the 2D technique; however, the 2D technique delivers unnecessary radiation doses to the rectum and bladder. The dose conformity observed with IMRT is increased compared with that observed with the 3D technique, as is the sparing of critical uninvolved structures; however, dose homogeneity appears to be worse with IMRT than with the 3D technique. Overall, of the 3 techniques, IMRT offers the most conformity in delivery of tumoricidal doses to the prostate while sparing dose to critical, uninvolved structures. Association of Medical Dosimetrists.

Femur Head↗

PubMed1999

One of two unstructured domains of Ii becomes ordered in complexes with MHC class II molecules.

We studied the role of the invariant chain (Ii) protein's structure in its ability to form complexes with major histocompatibility complex class II molecules. Multidimensional nuclear magnetic resonance experiments demonstrated that Ii contains two unstructured, flexible domains: a 39 residue sequence that contains a region (CLIP) critical for Ii/class II complex formation and becomes rapidly ordered when Ii/class II complexes are assembled, and a 30 residue sequence that contains the insertion point for a protease inhibitor domain included in an alternative splice form of Ii. Mobility of these domains guarantees accessibility to CLIP and the inhibitor insert, and ordering of the CLIP-containing domain may provide protection against proteolysis and contribute, along with Ii's compact 118-192 domain, to allotype-independent class II binding.

Amino Acid Sequence↗

PubMed1999

p38 MAPK is activated but not necessary in porcine von Willebrand factor-dependent platelet activation.

We have investigated the role of p38 mitogen-activated protein kinase (MAPK) in von Willebrand factor (VWF)-dependent platelet activation. The interaction of platelets with subendothelial VWF, especially under high shear stress, is considered to be the first activation step which primes platelets for subsequent haemostatic events. As a model of VWF-dependent platelet activation, porcine VWF was employed. Porcine VWF induced p38 MAPK activation by 1 min post-addition; assessed by phosphorylation of a recombinant p38 MAPK fusion protein substrate termed glutathione S-transferase-MAPK activated protein kinase-2. To determine if p38 MAPK was necessary for porcine VWF-induced platelet activation, we functionally inhibited p38 MAPK activity with SB203580 before exposure of the platelets to porcine VWF. Inhibition of p38 MAPK had no effect on VWF-induced platelet alpha or lysozomal granule release, expression of activated GPIIb IIIa, modulation of membrane glycoprotein CD41, expression of phosphatidylserine as assessed by annexin V binding, microparticle formation, or platelet agglutination. It was concluded that SB203580-inhibitable p38 MAPK activity induced by porcine VWF is not necessary for platelet activation.

Humans↗

PubMed1999

Traumatic cervical distraction complicated by delayed reduction due to traumatic vertebral artery pseudo-aneurysm.

A 23-year-old male involved in a high-speed collision acquired, among other injuries, a wide fracture distraction at C2/C3. Reduction was delayed by an enlarging vertebral artery pseudo-aneurysm at the site of injury which was successfully treated by proximal endovascular occlusion with a detachable polymer-filled balloon. A traumatic arachnoid cyst or pseudomeningocele was also demonstrated at the injury site but intervention was not required. The treatment and outcome of these three uncommon injuries in the literature is reviewed and discussed. Given the severity of the injury, the absence of severe long-term neurological disability is notable.

Accidents, Traffic↗