Biomedical subjects

S Song

Publications and source records attributed to S Song.

At least 145 records · Page 8Linked to original sources

PubMed1998

Priority of pentose utilization at the level of transcription: arabinose, xylose, and ribose operons.

When E. coli cells were grown in minimal medium supplemented with D-ribose and D-xylose, a diauxic growth preferring D-xylose was observed. Transcription of the ribose (rbs) operon was repressed in the presence of D-xylose, phenotypically similar to catabolite repression by D-glucose, although D-ribose did not affect transcription of the xylose (xyl) operon. Complementation analysis with xylR revealed that the repression of the rbs operon by D-xylose is exerted at the transcriptional level through XylR, suggesting a novel mechanism for catabolite repression. Furthermore, it was shown that L-arabinose reduced transcriptions of both xyl and rbs operons, whereas the arabinose operon was not affected by D-xylose or D-ribose, suggesting a priority mechanism for pentose utilization.

Arabinose↗

PubMed1998

Utilization of D-ribose through D-xylose transporter.

An Escherichia coli mutant defective in high-affinity D-ribose transport is able to utilize the sugar as a sole carbon source, suggesting that other transport systems for D-ribose exist. In order to search for such transporters, transposon mutagenesis was carried out in an rbsB-negative strain containing ribokinase (rbsK) for sugar phosphorylation. Insertions showing an enhanced ribose growth were isolated and mapped in xylA and its promoter region. The mutations increased not only the ribose uptake but also the expression of xylFGH encoding an ABC (ATP-binding cassette)-type transporter for D-xylose. Secondary mutations abolishing the ribose-utilizing phenotype were obtained both in the xylFG genes coding for the xylose high-affinity transporter and in xylR that is required for the xyl gene expression. Ribose uptake was also reduced by the secondary mutations. An overexpression of xylFGH under Ptrc promoter supported enhanced growth on ribose. These results indicate that D-ribose can be transported through the XylFGH transporter.

ATP-Binding Cassette Transporters↗

PubMed1998

Modulation of rat rotational behavior by direct gene transfer of constitutively active protein kinase C into nigrostriatal neurons.

The modulation of motor behavior by protein kinase C (PKC) signaling pathways in nigrostriatal neurons was examined by using a genetic intervention approach. Herpes simplex virus type 1 (HSV-1) vectors that encode a catalytic domain of rat PKCbetaII (PkcDelta) were developed. PkcDelta exhibited a constitutively active protein kinase activity with a substrate specificity similar to that of rat brain PKC. As demonstrated in cultured sympathetic neurons, PkcDelta caused a long-lasting, activation-dependent increase in neurotransmitter release. In the rat brain, microinjection of HSV-1 vectors that contain the tyrosine hydroxylase promoter targeted expression to dopaminergic nigrostriatal neurons. Expression of pkcDelta in a small percentage of nigrostriatal neurons (approximately 0.1-2%) was sufficient to produce a long-term (>/=1 month) change in apomorphine-induced rotational behavior. Nigrostriatal neurons were the only catecholaminergic neurons that contained PkcDelta, and the amount of rotational behavior was correlated with the number of affected nigrostriatal neurons. The change in apomorphine-induced rotational behavior was blocked by a dopamine receptor antagonist (fluphenazine). D2-like dopamine receptor density was increased in those regions of the striatum innervated by the affected nigrostriatal neurons. Therefore, this strategy enabled the demonstration that a PKC pathway or PKC pathways in nigrostriatal neurons modulate apomorphine-induced rotational behavior, and altered dopaminergic transmission from nigrostriatal neurons appears to be the affected neuronal physiology responsible for the change in rotational behavior.

Animals↗

PubMed1998

Human papillomavirus type 16 E6 and E7 oncogenes abrogate radiation-induced DNA damage responses in vivo through p53-dependent and p53-independent pathways.

E6 and E7 oncoproteins from high risk human papillomaviruses (HPVs) transform cells in tissue culture and induce tumors in vivo. Both E6, which inhibits p53 functions, and E7, which inhibits pRb, can also abrogate growth arrest induced by DNA-damaging agents in cultured cells. In this study, we have used transgenic mice that express HPV-16 E6 or E7 in the epidermis to determine how these two proteins modulate DNA damage responses in vivo. Our results demonstrate that both E6 and E7 abrogate the inhibition of DNA synthesis in the epidermis after treatment with ionizing radiation. Increases in the levels of p53 and p21 proteins after irradiation were suppressed by E6 but not by E7. Through the study of p53-null mice, we found that radiation-induced growth arrest in the epidermis is mediated through both p53-dependent and p53-independent pathways. The abrogation of radiation responses in both E6 and E7 transgenic mice was more complete than was seen in the p53-null epidermis. We conclude that E6 and E7 each have the capacity to modulate p53-dependent as well as p53-independent cellular responses to radiation. Additionally, we found that the conserved region (CR) 1 and CR2 domains in E7 protein, which are involved in the inactivation of pRb function and required for E7's transforming function, were also required for E7 to modulate DNA damage responses in vivo. Thus pRb and/or pRb-like proteins likely mediate both p53-dependent and p53-independent responses to radiation.

Animals↗

PubMed1998

Cloning and characterization of the promoter for the liver isoform of the rat carnitine palmitoyltransferase I (L-CPT I) gene.

Carnitine palmitoyltransferase I (CPTI) catalyses the transfer of long chain fatty acids to carnitine for translocation across the mitochondrial inner membrane. The cDNAs of two isoforms of CPT I, termed the hepatic and muscle isoforms, have been cloned. Expression of the hepatic CPT I gene (L-CPT I) is subject to developmental, hormonal and tissue specific regulation. We have cloned the promoter of the L-CPTI gene from a rat genomic library. In the L-CPTI gene, there are two exons 5' to the exon containing the ATG that initiates translation. Exon 1 and the 5' end of exon 2 contain sequences that were not previously described in the rat L-CPTI cDNA. There is an alternatively spliced form of the L-CPTI mRNA in which exon 2 is skipped. The proximal promoter of the L-CPTI gene is extremely GC rich and does not contain a TATA box. There are several putative Sp1 binding sites near the transcriptional start site. A 190 base pair fragment of the promoter can efficiently drive transcription of luciferase and CAT (chloramphenicol acetyltransferase) reporter genes transiently transfected into HepG2 cells. Sequences in both the first intron and the promoter contribute to basal expression. Our results provide the foundation for further studies into the regulation of L-CPTI gene expression.

Alternative Splicing↗

PubMed1998

cDNA cloning and tissue-specific expression of the gene encoding human adenylate kinase isozyme 2.

We isolated two kinds of cDNAs encoding human adenylate kinase (AK) isozyme 2 from a HeLa cell cDNA library using bovine AK2 cDNA as a probe. Nucleotide sequencing revealed that the cDNAs encoded 239- and 232-amino acid proteins with deduced molecular mass of 26.5 (AK2A) and 25.6kDa (AK2B), respectively. Northern blot analysis demonstrated that AK2 mRNA is strongly expressed in liver, heart, skeletal muscle and pancreas, and moderately in kidney, placenta and brain, and weakly in lung. However, Western blot analysis showed that AK2 protein was present in large amounts in liver, heart, kidney, and in a small amount in lung, and undetectable in brain and skeletal muscle. These results suggested the presence of the tissue-specific gene-expression including post-transcriptional regulation in expression of the AK2 gene.

Adenylate Kinase↗

PubMed1998

Toxicity of dieldrin for dopaminergic neurons in mesencephalic cultures.

Dieldrin can be retained for decades in lipid-rich tissue and has been measured in some postmortem PD brains. Dieldrin has been reported to deplete brain monoamines in several species and has been shown to inhibit mitochondrial respiration. To further investigate the possibility that it may be involved in the pathogenesis of parkinsonism, its toxicity for dopaminergic (DA) neurons was assessed in a mesencephalic cell culture model. Primary neuronal cultures of mesencephalic neurons were prepared from fetal rats or fetal mice, grown for 1 week and incubated with Dieldrin (0.01-100 microM) for 24 or 48 h. Toxicity for DA neurons was determined by measuring density of surviving tyrosine hydroxylase immunoreactive (TH-ir) cells. Toxicity for gamma-aminobutyric acid (GABA)-ergic neurons was determined by measuring survival of glutamate decarboxylase (GAD)-ir neurons. General, nonselective cytotoxicity was determined by counting cells visualized by phase contrast microscopy or by DAPI-stained cells with fluorescence microscopy. Dieldrin exposure for 24 h resulted in a dose-dependent decrease in survival of TH-IR cells (DA neurons) with a 50% decrease (EC50) produced by 12 microM in rat mesencephalic cultures. Dieldrin also produced a dose- and time-dependent decrease in mouse DA-ergic and GABA-ergic neurons in mouse mesencephalic cultures. GABA-ergic neurons were less sensitive to the toxin compared to DA-ergic neurons. Cellular uptake of 3H-DA was also affected by lower concentrations of Dieldrin (EC50 = 7.98 microM) than uptake of 3H-GABA (EC50 = 43 microM). Thus, Dieldrin appears to be a relatively selective DA-ergic neurotoxin in mesencephalic cultures. Dieldrin, which may be ubiquitous in the environment, is proposed as an agent which can initiate and promote dopaminergic neurodegeneration in susceptible individuals.

Animals↗

PubMed1998

Effect of SJAMP on human platelet cytoplasmic Ca2+.

Using the method of dual-wavelength measurement of platelet [Ca2+]i and Fura-2 as the Ca2+ fluorophore probe, we measured the effect of acidic Mucopolysaccharide from Sticopus Japonicus Selenka (SJAMP) on platelet [Ca2+]i. The results showed that the most significant increase in platelets [Ca2+]i was seen when the concentration of SJAMP was 100 micrograms/ml and the elevation of normal platelet [Ca2+]i was 93.96 +/- 10.24 nmol/L (n = 10). In the presence of extracellular Ca2+ (1 mmol/L), the magnitude of platelet [Ca2+]i response to SJAMP was increased and the [Ca2+]i could reach 116.72 +/- 10.66 nmol/L (n = 10). On the other hand, the magnitude of increased platelet [Ca2+]i induced by SJAMP was smaller and the duration of [Ca2+]i reaching the highest level was longer when compared with other platelet aggregation agents. In the mean time, if platelets were first incubated with cyclooxygenase inhibitor, the rise of [Ca2+]i evoked by SJAMP was inhibited. The results indicated that the mechanism of the rise of [Ca2+]i induced by SJAMP might be dependent upon the generation of prostaglandin endoperoxides and(or) TXA2.

Animals↗

PubMed1998

Study on the hypercoagulable state in patients with angina and myocardial infarction.

The molecular markers of platelet activation, coagulation and fibrinolysis were detected in 60 cases of coronary heart disease (CHD), including 15 cases of stable angina (SA), 21 cases of unstable angina (UA) and 24 cases of acute myocardial infarction (AMI). The results showed that the platelet granule membrane protein 140 (GMP-140) level increased obviously in CHD groups compared with normal control, suggesting that platelet activation existed in CHD. Prothrombin fragment F1 + 2 and fibrinopeptide A (FPA) were examined to observe the activation of coagulation. No difference was found between SA group and normal controls, while their levels in both UA group and AMI group were significantly higher than in normal control and SA group (both P < 0.05). D-D dimer and alpha 2-plasma inhibitor (alpha 2-PI) were detected to observe fibrinolytic state. The results showed that no difference existed between SA group and normal controls, while both D-D dimer and alpha 2-PI in UA group and AMI group were significantly elevated than those in SA group and normal controls (P < 0.05).

Angina Pectoris↗

PubMed1998

Serotonin receptors in the caudal brainstem are necessary and sufficient for the anorectic effect of peripherally administered mCPP.

The role of caudal brainstem 5-HT receptors in mediating the anorectic effect of the direct 5-HT2C/1B agonist, mCPP [1-(3-chlorophenyl)piperazine dihydrochloride], was evaluated. We demonstrated, first, that systemic injections of mCPP yielded a dose-related suppression of intra-oral intake of 12.5% glucose in intact rats and in chronically maintained supracollicular decerebrate rats. The results of the decerebrate experiment suggest that 5-HT receptors in the caudal brainstem are sufficient for mediating the drug's intake effect. We also showed a dose-related intake suppression when mCPP was delivered to the fourth ventricle of intact rats, with potent suppression obtained at doses well below threshold for systemic administration. Whether and to what extent the 5-HT2C/2A antagonist, mesulergine reverses the intake suppression that follows systemic or 4th i.c.v. injection of mCPP was examined. Fourth i.c.v. co-administration of mesulergine (60 microg) and mCPP (40 microg) eliminated the approximately 50% intake suppression observed when mCPP was delivered alone, a result that affirms the receptor selectivity of the 4th i.c.v. agonist effect. We showed, further, that 4th i.c.v.mesulergine (60 microg) completely reversed the intake suppression produced by systemic mCPP (2 mg/kg). The latter result indicates that stimulation of 5-HT receptors in the caudal brainstem is necessary for the intake suppression produced by systemic administration of this 5-HT agonist in the intact rat.

Animals↗

PubMed1998

The porcine insulin-like growth factor system: at the interface of nutrition, growth and reproduction.

The IGF system is implicated in the regulation of cellular response to protein- and energy-restriction. Although it is clear that the IGF and their binding proteins are profoundly influenced by dietary factors, a number of important questions remain about this relationship. In particular, although studies to date have focused on nutritional modulation of hepatic IGF gene expression, the molecular mechanisms underlying metabolic regulation of liver IGF and IGF binding protein genes remain relatively unknown. Moreover, the potential effects of altered nutrition on the expression and/or actions of IGF system components in tissues other than the liver have been examined only in cursory fashion. Many of these studies have used rats, an admittedly important model, but one which differs from the human in a potentially significant way: rats lack circulating IGF-II and IGFBP-2 during post-weaning and adult life. Here, we summarize current research on the porcine IGF system and highlight the particular usefulness this system may offer for unraveling the complex relationships of nutrition and systemic/local IGF expression and actions that are relevant to human nutritional physiology.

Amino Acid Sequence↗

PubMed1998

Mechanism of mitochondrial import of adenylate kinase isozymes.

Adenylate kinase (AK) is a ubiquitous enzyme that contributes to the homeostasis of the cellular adenine nucleotide composition. Three isozymes, AK1, AK2, and AK3, have so far been characterized in vertebrates. They are located in different tissues, while their primary and tertiary structures are similar. Among them, AK2 and AK3 are located in mitochondria, but unlike most mitochondrial proteins, both proteins lack a cleavable presequence. In this study, we first confirmed that AK2 is distributed in liver cells in both the cytosol and the intermembrane space of mitochondria, while AK3 is localized exclusively in the mitochondrial matrix. Next, we analyzed the process of import of AK2 and AK3 by incubating isolated rat mitochondria with proteins that were synthesized in a reticulocyte lysate translation system. The results indicated that both AK2 (an intermembrane-space-targeting protein) and AK3 (a matrix-targeting protein) require an inner membrane electrochemical potential for their import. This finding for AK2 is in contrast with those of other noncleavable intermembrane-space-targeting proteins such as cytochrome c and cytochrome c heme lyase, which do not require the membrane potential for their import. In the transport process, AK2 and AK3 competed with the adrenodoxin precursor, which is imported into the matrix through a mechanism common to other mitochondrial matrix proteins. Thus, AK2 and AK3 were thought to be translocated into mitochondria through the same pathway as that for most mitochondrial protein precursors. Neither AK2, that was previously synthesized in reticulocyte lysates, nor AK2, that was purified from an Escherichia coli overexpression system, was imported into mitochondria in a post-translational import manner. In contrast, AK3 was imported into mitochondria after completion of protein synthesis. Thus, the import of AK2 is likely to be co-translational, and the co-translational import mechanism might contribute to the bi-topological distribution of AK2 in both the cytosol and mitochondria.

Adenylate Kinase↗

PubMed1998

A distal regulatory region of the insulin-like growth factor binding protein-2 (IGFBP-2) gene interacts with the basic helix-loop-helix transcription factor, AP-4.

Insulin-like growth factor binding protein-2 (IGFBP-2), the predominant IGFBP in the fetal circulation and an induced protein during several types of malignancies, belongs to a family of structurally related proteins that bind the mitogens, IGF-1 and IGF-2. The present study focused on functional analysis of the 5 '-flanking region (approximately 1.3 kb) of the IGFBP-2 gene to identify nuclear factors that mediate hepatic transcription of this gene. Luciferase (LUC) reporter constructs containing progressive deletions of 5'-flanking DNA and the intact promoter of the porcine IGFBP-2 gene were examined for functional activity by transient transfection of human HepG2 liver cells. LUC activity of the transfected reporter gene driven by the IGFBP-2 promoter and flanking sequences to -1397 (numbering relative to initiation codon at +1) was 22-fold higher than that of promoterless parent LUC vector. This activity was decreased by 60% with deletion of sequences to -874 bp, and dropped to basal levels with further truncation to -764 bp. The region between -874 and -765 bp (110 bp) functioned as a potent stimulator of heterologous SV40 promoter activity (110 bp/SV40-LUC construct) and was found to contain two noncontiguous basic helix-loop-helix (bHLH) transcription factor binding motifs (E-boxes [CAN NTG]: CACCTG and CAAATG). In electrophoretic mobility shift assays, nuclear proteins prepared from HepG2 cells formed two complexes (C1, C2) with double-stranded oligonucleotides containing either HLH sequence, mutations of which resulted in loss of complex formation. Southwestern blot analysis identified an HepG2 nuclear protein with molecular mass of 48 kDa, similar to that of the bHLH transcription factor AP-4, which bound the CACCTG motif. Cotransfection of HepG2 cells with the 110-bp/SV40-LUC construct and an expression vector encoding human AP-4 increased IGFBP-2 fragment-dependent SV40 promoter activity by 16-fold. This AP-4-mediated stimulation was lost following block mutation of both bHLH motifs within the IGFBP-2 110-bp fragment. Results demonstrate the functional importance of sequences upstream of the promoter in IGFBP-2 gene transcription and identify a novel mechanism by which bHLH proteins potentially may affect cell proliferation and differentiation via induction of IGFBP-2 synthesis.

DNA-Binding Proteins↗

PubMed1998

[Major blood vessel excision and reconstruction in the treatment of retroperitoneal neoplasms].

OBJECTIVE: To summarize the experience in the treatment of retroperitoneal tumors involving major blood vessels. METHODS: Twenty five cases with retroperitoneal tumors involving major blood vessels were treated by excision of the tumor and the major blood vessel involved followed by vascular reconstruction. RESULTS: After a careful preoperative evaluation and necessary preparation, the tumor together with the involved blood vessels in all patients are successfully resected and the severed major blood vessels reconstructed. There was no operative death. CONCLUSION: Retroperitoneal neoplasm involving major blood vessels is not a contraindication for surgical resection. The tumor and the involved vessel can be removed en bloc followed by vascular reconstruction. The risk of local tumor recurrence can thus be minimized and better survival achieved.

Adolescent↗

PubMed1998

[Treatment of avascular necrosis of femoral head by periosteal cell transplantation: an experimental study].

OBJECTIVE: To investigate the effect of periosteal cell transplantation on the repair of avascular necrosis of femoral head (ANFH). On the basis of successful culture of periosteal cells in vitro. METHODS: The tibial periostea of new born dog were excised and cultured under aseptic conditions. Eight adult dogs were used and divided into 2 groups: experimental group and control group. The animal model of ANFH was made by transferring the freed femoral head into the muscle under the ilium on one side in each dog. Two weeks after the establishment of ANFH, the cultured periosteal cells were collected and transplanted into the necrotic femoral heads in the experimental group, and the femoral heads without periosteal cell transplantation served as the control. Six weeks after cell transplantation, the femoral heads were taken out and histological examination was made. RESULTS: There was active bone formation in the experimental group. The new bone was arranged into bone trabeculae, most of which were covered by a monolayer of osteoblasts. Between bone trabeculae were fibrous tissue rich in blood vessels. In the control group, the bone trabeculae withered and remained necrotic. There were fibrous tissues with few blood vessels between bone trabeculae. CONCLUSION: Periosteal cell transplantation can improve the repair of ANFH.

Animals↗

PubMed1998

[Study of activated protein C resistance(APC-R) and FV Leiden in healthy blood donors and patients with thrombosis].

OBJECTIVE: To study activated protein C resistance (APC-R) and FV Leiden in Chinese and their role in the pathogenesis of thrombophilia. METHODS: APC-R was detected by activated partial thromboplastin time (APTT) in the presence and absence of APC. FV Leiden mutation was detected by PCR amplification with sequence-specific primers and restriction enzyme digestion. The subjects included 32 healthy blood donors (control), 38 patients with thrombosis in Wuhan, China, 106 patients with thrombosis in Homburg, Germany. FV Leiden mutation was screened in 12 patients in Wuhan and 106 in Homburg. RESULTS: There was no significant difference for APC-R between healthy controls and the patients in Wuhan. No FV Leiden mutation was found in 12 patients in Wuhan. The APC-R frequency of the patients in Homburg was significantly higher than those in Wuhan (22.6% and 7.9%, respectively). Eleven patients in Hombery had FV Leiden mutation. CONCLUSION: APC-R and FV Leiden mutation varied in different regions and races. FV Leiden may not be the main cause of thrombophilia in Chinese.

Activated Protein C Resistance↗

PubMed1998

[Study on the cellular immune function and cytokines in aplastic anemia patients].

OBJECTIVE: To evaluate the effects of cellular immune function and cytokines on the pathogenesis of aplastic anemia (AA) and its clinical significance. METHODS: T lymphocyte subsets and HLA-DR antigen expression in the peripheral blood cells were assayed, and the levels of G-CSF, IL-6, TNF alpha, IFN alpha and IL-8 in the PBMNC culture supernatants were determined in 38 AA patients and 20 normal control with APAAP and ELISA methods. RESULTS: CD4+ cells, CD4+/CD8+ cells and G-CSF level were lower, and CD8+ cells, HLA-DR+ cells and IL-6, TNF alpha, IFN alpha and IL-8 levels were higher in AA patients than in normal controls. The level of G-CSF was positively correlated with CD4+ cells and CD4+/CD8+ cells and negatively with IFN alpha level. IL-6 level was negatively correlated with WBC count and CD4+ cells. TNF alpha level was positively correlated with CD8+ cells and negatively with CD4+/CD8+ cells. IL-8 level was positively correlated with CD8+ cells and HLA-DR+ cells. CONCLUSION: The cellular immune dysfunction and cytokine aberration participate in the pathogenesis of AA.

Adult↗

PubMed1998

[Resection and reconstruction of inferior vena cava and renal vein in surgical treatment of retroperitoneal tumours: a report of 11 cases].

OBJECTIVE: To improve the surgical resection rate of complicated retroperitoneal tumors which depends on handling of celiac major blood vessel. METHODS: 219 retroperitoneal tumours were resected from 1990 to 1997. Eleven of them were resected in combination of resections and reconstructions of inferior vena cava (IVC) and renal veins (RV). IVC below RV was resected in 5 cases, IVC below liver with resections of right kidney in 3 cases, IVC above RV in 1 case, major partial resections of left RV with anastomosis to left ovarian vein in 2 cases, and 1 of them with IVC resection. RESULTS: Follow-up showed transient bilateral lower limbs edema in 3 cases. The values of blood urea nitrogen and creatinine were normal after operations, no changes were found in the kidneys under ultrasonic examination. CONCLUSION: As the left renal vein has many branches and constant anastomotic branches that connect with peripheral veins, it can be ligated proximally; and it even can be resected when at least one of its branches (routinely lift sexual gland vein) can be kept to maintain the blood circulation. Reconstruction of IVC and RV is usually not necessary after the resection of IVC, unless the bilateral renal veins were obstructed.

Adult↗