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Biomedical subjects

S Peng

Publications and source records attributed to S Peng.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Melatonin inhibits TRH-stimulating prolactin gene expression of anterior pituitary cells in newborn rat in vitro].

OBJECTIVE AND METHODS: This work was to investigate whether melatonin (MEL) plays a role in the gene expression of prolactin (PRL), by the Method of in situ hybridyzation. RESULTS: Our results indicated that, at a higher concentration, MEL not only inhibits TRH (thyrotropin releasing hormone) stimulating PRL gene expression of anterior pituitary cell in newborn rat, but also exerts a direct inhibitory effect on PRL gene expression in vitro. CONCLUSION: These results suggest that MEL may be a regulator of PRL synthesis and secreting in vivo.

Animals↗
PubMed1997

Study of the expression of the gene encoding Ki-67 antigen in human pancreatic cancer using non-radioactive in situ hybridization and immunohistochemistry.

OBJECTIVE: To investigate, at transcriptional and translational level in situ, whether the gene expression of the Ki-67 protein in pancreatic carcinoma specimens is altered to get insight of the gene structure and function. METHODS: Forty pancreatic cancer, 5 normal pancreatic and 4 chronic pancreatitis tissues were used in this experiment. A 435 bp cDNA fragment located in codon 2, exon 13 of Ki-67 antigen gene was amplified by the polymerase chain reaction (PCR). The DIG-labeled cRNA probes were transcribed using a commercial DIG RNA labeling kit. Localization of the Ki-67 protein and the specific mRNA was performed by combining immunohistochemistry (ICH) with DIG-labeled in situ hybridization (ISH). RESULTS: Successful localization of the Ki-67 protein mRNA in pancreatic tissue sections, routinely formalin-fixed and paraffin-embedded, was first accomplished in this experiment. Analysis of the Ki-67 mRNA transcription in 17 pancreatic cancer specimens with Ki-67 ICH labeling index > 20% revealed stronger mRNA signals in poorly differentiated specimens with Ki-67 index > 50% than in well differentiated cases with the ICH labeling index of 20%-50%. A high expression of both the mRNA and the protein was observed in pancreatic adenocarcinomas with poor differentiation. CONCLUSIONS: This is the first study in which the abnormal overexpression of the gene encoding Ki-67 protein was detected not only at the protein level, but also at the mRNA level in pancreatic tumours. The abnormal overexpression of the Ki-67 protein might be correlated with the central part, exon 13, of the gene.

Adenocarcinoma↗
PubMed1996

Engineering stabilized ion channels: covalent dimers of alamethicin.

The peptide alamethicin forms channels with a variety of conductance states. Selective stabilization of a particular state should simplify the task of understanding conductance in terms of channel structure. We synthesized two different covalent dimers of alamethicin in which peptides were linked at their C-terminal ends by flexible tethers. Both dimeric peptides formed channels with conductances that matched those of alamethicin channels. Particular conductance states were selectively stabilized, however, with lifetimes up to 170-fold longer than the same states observed with monomers. In addition, tethering appeared to limit the size of the structures formed so that, even at higher peptide concentrations, a single predominant conductance state was obtained. We suggest this state corresponds to a channel made from six alamethicin molecules (three dimers).

Alamethicin↗
PubMed1996

Hemorrhage in intracranial epidermoid cyst.

A case of intracranial epidermoid cyst with intracystic hemorrhage is reported. A 63-year-old woman sustained a head injury after a fall; obtundation and ataxia were noted later. Computed tomography revealed a heterogeneous hyperdense lesion in the posterior and middle cranial fossas. Magnetic resonance imaging showed a lesion with increased signal intensity both on T1 and T2 weighted images. Two craniotomies revealed an intracranial epidermoid cyst with about 6 mL of clotted blood. Pathologic study showed hemosiderin-laden macrophages and neovascularity in the cystic wall granulation tissue, which indicated rupture of the cystic wall with intracystic hemorrhage, which later correlated with the diagnostic image findings. The patient tolerated the two operations well and her postoperative course was smooth. She was discharged in good health without obvious neurologic deficits.

Brain Diseases↗
PubMed1996

[Studies on relationship between toxicity of trichothecene toxin T-2 and its structure].

Toxic action of mycotoxin T-2 and its metabolite T-2 tetraol and deepoxy T-2; tetraol was studied by cytotoxicity and animal toxicity tests to explore the relationship between toxin T-2 and its structure. Restults showed that proliferation of LLC-PK1 cells and synthesis of DNA could be inhibited by both toxin T-2 and T-2 tetraol. Toxicity of toxin T-2 was 100 times greater than that of T-2 tetraol. There was no obvious toxicity to the proliferation of LLC-PK1 cells and synthesis of DNA in a dose of 10 mg/L deepoxy T-2 tetraol. But, toxin T-2 caused obvious damage in heart muscle and articular cartilage of chicken embryos, and T-2 tetraol and deepoxy T-2 tetraol in heart muscle, but not in articular cartilage. T-2 tetraol produced by hydrolysis of toxin T-2 had toxicity to certain extent, but its strength was significantly less than that of the latter. It suggests that the epoxide group in toxin T-2 played a determinant role for its toxicity. If epoxy cycle of the basic nucleus of the molecule is open, its toxicity will change significantly.

Animals↗
PubMed1996

[A genetic epidemiological study on lung cancer].

Segregation ratio, heritability and relative risk of genetic susceptibility were estimated for 355 families of lung cancer in matched pair with genetic epidemiological methods. Results showed that segregation ratio for lung cancer was 0.09-0.12 (95% confidence interval, CI) and heritability of lung cancer was (40.58 +/- 4.01)% and (27.58 +/- 4.76)% for smokers and non-smokers, respectively. Relative risks of genetic susceptibility to lung cancer were 4.73 (95% CI 3.90-5.74) and 2.61 (95% CI 2.18-3.13) in their first and second degree relatives, respectively, after adjustment of smoking with a logistic regression model. It was also found that there was an interaction between smoking habit and genetic background of lung cancer. Thus, it is believed that genetic background is one of the multifactorial causes in lung cancer.

China↗
PubMed1996

[Effects of preoperative transcatheter hepatic arterial chemoembolization (TAE) on the prognosis of patients with hepatic carcinoma undergoing tumor resection].

This study consists of 77 hepatocellular carcinoma patients. Twenty-six (Group A) received preoperative TAE and 51 did not (Group B). Group A and B were further divided into two subgroups according to their tumor size i.e. Group A1 and B1 (tumor size 3-8 cm); Group A2 and B2 (tumor size > 8 cm). The 1-, 2-, 3-year disease free survival rates were 50.0%, 33.3%, 16.6% for Group A1 and 72.7%, 54.2%, 39.7% for Group B1; 75.0%, 56.2%, 45.0% for Group A2 and 38.9%, 32.4%, 10.8% for Group B2 respectively. The 1-, 3-, 5-years survival rates were 85.7%, 31.2%, 0 for Group A1 and 84.8%, 58.7%, 27.9% for Group B1; 91.6%, 82.5%, 53.0% for Group A2 and 77.8%, 30.1%, 0 for Group B2 respectively. There were significant differences between Group A2 and B2 both in disease free survival rate and 5-year survival rate (P < 0.05). The results also demonstrated that the preoperative TAE did worsen the prognosis of patients with tumor size between 3-8 cm (Group A1) with disease free survival rate and 5-year survival rate shorter than that of Group A2.

Antineoplastic Agents↗
PubMed1995

Cationic lipids for reporter gene and CFTR transfer to rat pulmonary epithelium.

Increasing evidence indicates that cationic liposomes are capable of safely transferring foreign genes to pulmonary epithelium in vitro and in vivo. To transfer reporter genes and the cystic fibrosis transmembrane conductance regulator (CFTR) to mammalian respiratory epithelium we used two cationic lipid formulations: N-[1-(2,3-dioleoyloxy)propyl] N,N,N-triethylammonium chloride (DOTMA), and 1,2-dimyristyloxy-propyl-3-dimethylhydroxyethylammonium bromide (DMRIE) at a 1:1 molar ratio with dioleoyl phosphatidylethanolamine (DOPE). Lipid-DNA conjugates containing either CFTR or LacZ were instilled directly into the airways of Sprague-Dawley rats. Rats treated with LacZ cDNA in vivo demonstrated expression in 30-50% of the large and medium-sized airways, with some airways showing high efficiency gene transfer and expression (in the most proximal airways, 70-80% of surface epithelial cells were positive for expression of a nuclear targeted LacZ). While control and LacZ treated tracheas mounted in Ussing chambers showed minimal stimulation of transepithelial chloride (Cl)-currents by cAMP (suggesting low levels of endogenous rat CFTR activity), tracheas taken from animals receiving CFTR exhibited significant forskolin-stimulated currents at 72 h after gene transfer. Human CFTR gene expression was also detected by polymerase chain reaction (PCR) analysis of reverse transcribed lung RNA. These results, together with previous studies using lipid-mediated gene transfer in mice, help confirm the potential for cationic lipid-mediated gene transfer in the gene therapy of cystic fibrosis in humans.

Animals↗
PubMed1995

Expression of human interleukin-11 cDNA in E. coli.

A 551-bp hIL-11 gene fragment that includes no nucleotide sequences encoding signal polypeptide and the initial 8 amino acids of the mature protein was cloned into a high-level expression vector pEx31B of E. coli. The authors identified the recombinant plasmid, designated pEx31-IL11, by restriction endonucleases digestion and DNA sequencing. The resulting recombinant plasmids were then used to transform E. coli strain HB101, and expression in the PL promoter system, which is temperature-regulated, was achieved. The expressed fusion protein amounts to 50% of total bacterial proteins. The hIL-11 protein expressed in E. coli was fused to the N-terminal 99 amino acids of the MS2 polymerase to form the inclusion body. These recombinant proteins can be purified to about 80% by extracting inclusion body with urea. One IL-6-dependent cell line 7 TD1 was used for bioassay. The recombinant hIL-11 protein was preliminarily purified and renatured to a specific activity of 10(5)U/mg, even in the presence of an excess of a neutralizing anti-IL-6 antibody.

DNA, Complementary↗
PubMed1995

[Morphological transformation of BHK-21 cells by nickel titanium shape memory alloy particles encapsulated by titanium oxide].

The special treatment process formed a compact titanium oxide thin film on the surface of medical nickel titanium shape memory alloy (NiTiSMA) particles (< or = 5 microns). The BHK-21 cells were cultivated in 10% infant calf serum containing NiTiSMA particles and NiTiSMA particles encapsulated by titanium oxide respectively, and morphological transformation clones were observed. The results showed that NiTiSMA particles induced obviously morphological transformation clones, and that NiTiSMA particles induced obviously morphorogical transformation of BHK-21 cells (the rate of morphological transformation clones was 13.46%), especially in TPA medium. The rate of morphological transformation in the group containing NiTiSMA particles was not more significantly different than that in the positive control group. The rate of morphological transformation in the group containing NiTiSMA particles encapsulated by titanium oxide was not more significantly different than that in the negative control group, but significantly different than that in the NiTiSMA particles group. Therefore, it is possible that NiTiSMA particles are directly carcinogenic and that NiTiSMA particles encapsulated by titanium oxide are not potentially carcinogenic.

Alloys↗
PubMed1995

[Surgical treatment for iatrogenic damage at the confluence of hepatic duct].

Since 1989, 4 patients with iatrogenic bile duct injuries at the level of bifurcation were treated. Among them, the bifurcation together with both right and left hepatic duct had had wrongly been resected in 2 cases. The bifurcation was partially resected in the other 2 cases. The establishment of a permanent hepaticoentertostomy is essential. Abnormal bile flow would impede surgical effect, hence in the author's opinion, peripheral hepaticoenterostomy such as Longmire's procedure is unsuitable for iatrogenic bile duct injuries. The author's special technique for adequate exposure and accurate dissection of intrahepatic bile ducts is described. Four cases have been followed up for 7 months to 5 years with good result.

Adult↗
PubMed1995

Cloning, expression and purification of the ligand-binding region of human IL-6R in E. coli and its preliminary functional identification.

The ligand-binding region of human IL-6R is taken as the target gene fragment to be cloned and expressed. With pET-3b as expressing vector, two recombinants pET-6R(B) and pET-6R(B)4 have been constructed encoding the ligand-binding region (28 kD) of hIL-6R and its dimmer (53 kD), respectively. After induction with IPTG, they produced two proteins rIL6R-28 of 28 kD and rIL6R-53 of 53 kD amounting to 50% and 30% of total bacteria proteins, respectively. The expressed products were mainly recovered as inclusion bodies. After purification and renaturation, both of them were capable of augmenting the growth-stimulating effect of IL-6 on 7TD1 cells, an IL-6 dependent cell line. The result of ELISA also revealed that both rIL6R-28 and rIL6R-53 had the obvious ligand-binding activity.

Antigens, CD↗
PubMed1995

Identification of 2-[125I] iodomelatonin binding sites in the thymus of mice and its significance.

The melatonin binding sites in membrane preparations of the mouse thymus were demonstrated using 2-[125I] iodomelatonin as a radioligand. The binding sites were stable, saturable, reversible and of high affinity. Studies on specificity of 2-[125I] iodomelatonin binding suggested that the 2-[125I] iodomelatonin binding sites are highly specific for melatonin. These binding sites fulfilled the standard criteria for receptors. Our work suggested that melatonin should have direct regulatory action on immune system mediated through the melatonin binding sites. Studies on the circadian rhythm showed that there existed the circadian rhythm in the binding capacity for 2-[125I] iodomelatonin in the mouse thymus with the peak values at 12:00-16:00 and the trough values between 00:00 and 4:00. The subcellular distribution of 2-[125I] iodomelatonin binding sites in the mouse thymus was in the following descending order: nuclear > mitochondrial > microsomal > cytosolic fraction. There was also an age-related decrease in 2-[125I] iodomelatonin binding in the mouse thymus. This is correlated with the involution of the thymus.

Age Factors↗
PubMed1994

Nanometric design of extraordinary hydrophobic-induced pKa shifts for aspartic acid: relevance to protein mechanisms.

Commonly a key element enabling proteins to function is an amino acid residue or residues with functional side chains having shifted pKa values. This article reports the results on a set of protein-based polymers (model proteins) that exhibit hydrophobic folding and assembly transitions, and that have been designed for the purpose of achieving large hydrophobic-induced pKa shifts by selectively replacing Val residues by Phe residues. The high molecular weight polypentapeptides, actually poly(tricosapeptides) with six varied pentamers in fixed sequence, were designed and synthesized to have the same amino acid compositions but different proximities between a single aspartic acid residue and 5 Phe residues per 30 residues. With the 5 Phe residues distal from the Asp residue, the observed pKa shift was 2.9 when compared to the Val-containing reference. With the 5 Phe residues within 1 nm of the Asp residue, the pKa shift was 6.2. This represents a free energy of interaction of 8 kcal/mole. To our knowledge, this is the largest pKa shift documented for an Asp residue in a polypeptide- or protein-water system. Data are reviewed that do not support the usual electrostatic arguments for pKa shifts of charge-charge repulsion and/or unfavorable ion self-energies arising from displacement of water by hydrophobic moieties, but rather the data are interpreted to indicate the presence of an apolar-polar repulsive free energy of hydration, which results from a potentially highly cooperative competition between apolar and polar species for hydration.

Amino Acid Sequence↗
PubMed1994

Tumor cell bystander killing in colonic carcinoma utilizing the Escherichia coli DeoD gene to generate toxic purines.

Inefficiency of gene delivery, together with inadequate bystander killing, represent two major hurdles in the development of a toxin-mediated gene therapy for human malignancy. The product of the Escherischia coli DeoD gene (purine nucleoside phosphorylase, PNP) differs from the mammalian enzyme in its substrate specificity and is capable of catalyzing the conversion of several non-toxic deoxyadenosine analogs to highly toxic adenine analogs. We have found that expression of E. coli PNP in < 1% of a human colonic carcinoma cell line leads to the death of virtually all bystander cells after treatment with 6-methyl-purine-2'-deoxyribonucleoside, a deoxyadenosine analog that is a substrate for E. coli PNP but not human PNP. Minimal toxicity was observed in non-transfected or E. coli LacZ transfected cells that were treated with this compound. These results establish a rational approach to achieve significant bystander killing, even after gene transfer to only a small fraction of tumor cells.

Base Sequence↗
PubMed1993

One-step affinity isolation of recombinant protein using the baculovirus/insect cell expression system.

We have developed two baculovirus transfer vectors which allow single-step affinity isolation of recombinant proteins after expression in insect cells. Using these vectors, recombinant proteins are synthesized as fusions with glutathione-S-transferase and are amenable to enrichment from a crude insect cell lysate using glutathione affinity agarose. After affinity isolation, glutathione-S-transferase can be cleaved from the recombinant polypeptides of interest at an engineered thrombin cleavage site. We used this approach to successfully isolate glutathione-S-transferase, the human low density lipoprotein receptor, two large polypeptides containing cytoplasmic domains of the cystic fibrosis transmembrane conductance regulator (CFTR), and the full-length CFTR. The approach has potential advantages over prokaryotic overexpression of foreign polypeptides, including: (i) eukaryotic post-translational modification of expressed protein, (ii) increased solubility of recombinant fusion proteins synthesized in insect cells leading to increased affinity yield under mild conditions, and (iii) production of large and/or complex polypeptides which might be difficult to purify from prokaryotic cells. The method also allows enrichment of recombinant protein representing a small fraction (less than 5%) of total insect cell protein produced and provides a general method for eukaryotic protein synthesis and isolation which is independent of the particular protein being expressed.

Animals↗