Biomedical subjects

Z Sun

Publications and source records attributed to Z Sun.

At least 199 records · Page 11Linked to original sources

PubMed1997

Distinct signaling from stem cell factor and erythropoietin in HCD57 cells.

A recent report (Wu, H., Klingmuller, U., Besmer, P., and Lodish, H. F. (1995) Nature 377, 242-246) documents the interaction of the erythropoietin (EPO) receptor (EPOR) with the stem cell factor (SCF) receptor (c-KIT) and suggests that SCF acts through the EPOR. To elucidate the ability of SCF to affect the erythropoietin signaling pathway, we studied the effect of SCF on EPOR phosphorylation, SHC/ERK-1 activity, and cell proliferation and apoptosis in EPO-dependent HCD57 cells. Treatment of these cells with SCF resulted in phosphorylation of the EPOR. However, SCF-dependent phosphorylation of the EPOR did not initiate an EPO-like intracellular signal. SCF induced proliferation, SHC phosphorylation, and activation of ERK-1 but did not activate the JAK/STAT pathway. SCF stimulated SHC phosphorylation and ERK-1 activation independent of the EPOR in cells where the EPOR was down-regulated; the presence of the EPOR appeared to facilitate SCF activation of SHC and ERK-1. Furthermore, treatment of HCD57 cells with SCF increased cell number over a 3-day treatment, but apoptosis was observed in these cells. These data may illustrate two distinct pathways for erythroid cell proliferation and prevention of apoptosis in response to EPO, thereby providing a system to discriminate these intracellular signals.

Apoptosis↗

PubMed1997

Acid-Base Properties of Aqueous Illite Surfaces

In this paper, the acid-base properties of illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of illite suspensions can be successfully represented by proton reactions of Al(H2O)63+ and Si(OH)4 in water solutions. For illustrating the acidic characteristics of aqueous illite surfaces, two surface protonation models are proposed: (1) one site-one pKa model, identical withSOH right arrow over left arrow identical withSO- + H+, pKaint = 4.12-4.23; (2) two sites-two pKas model, identical withSIOH right arrow over left arrow identical withSIO- + H+, pKintaI = 4.17-4.44, and identical withSIIOH right arrow over left arrow identical withSIIO- + H+, [dipKintaII = 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the illite surfaces, they suggest that the surface behavior of the illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.

Journal Article↗

PubMed1997

Adsorption of Copper at Aqueous Illite Surfaces

In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free illite suspensions can be explained by the formation of mononuclear surface complexes, identical withSOCu+ and identical withSOCuOH, and a multinuclear surface complex, identical withSOCu2(OH)2+, followed by the formation of a bulk precipitate, Cu(OH)2(s), or a surface precipitate, identical withSOCu2(OH)3(sp). For the illite suspensions containing carbonates, we propose that the copper-illite interaction can be depicted by the formation of mononuclear surface complexes, identical withSOCu+ and identical withSOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu2(OH)2CO3(s), rather than a copper hydroxide precipitate. The existence of Cu2(OH)2CO3(s) in the carbonate-containing illite suspensions was identified by FT-IR analysis.

Journal Article↗

PubMed1997

Experimental study on the effects of aprotinin on myocardial ischemia and reperfusion.

Direct effects of a high-dose aprotinin on the normally perfused hearts and the myocardial protection after ischemia and reperfusion were investigated in an isolated working rat heart model. In trial I, hearts had no ischemia and were perfused with either K-H solution or the K-H solution containing aprotinin (200 KIU/ml) for 55 min. No statistically significant difference was observed in hemodynamics between the two groups. In trial II, hearts were exposed to 150 min period of global ischemia at 15 degrees C with 4 degrees C multidose St. Thomas' II solution (STS). The control group I received normal K-H solution; the group II was treated with the solution with aprotinin added. The group III was similar to the group I and received the STS enriched with aprotinin. On reperfusion, the recovery of hearts in group III was significantly better than those of the group I and II, as reflected by better hemodynamics and myocardial ATP levels and milder myocardial ultrastructural injury. There was no difference between the group I and II. These results suggest that the aprotinin a dose of 200 KIU/ml has no harmful effects on normally perfused hearts and has a marked myocardial protective effect on the prolonged myocardial ischemia when used in cold crystalloid cardioplegia.

Animals↗

PubMed1997

Mutations in SPK1/RAD53 that specifically abolish checkpoint but not growth-related functions.

SPK1/RAD53/SAD1/MEC2 encodes an essential protein kinase of Saccharomyces cerevisiae and is required for the execution of checkpoint arrest at multiple stages of the cell cycle. We have isolated two mutant alleles of SPK1 (spk1K227A and spk1-1A208P) that are defective for checkpoint-arrest functions but retain wild-type levels of SPK1-associated growth activity. Both mutations occur within conserved regions of the kinase domain of SPK1 resulting in a substantial reduction in the catalytic activity of Spk1. Thus, while minimal levels of Spk1 kinase activity are capable of supporting normal rates of growth, higher levels are required for checkpoint functions. In addition, using deletional analysis we have identified a region within the N-terminus of Spk1 outside of the conserved kinase domain that is required for checkpoint functions. Interestingly, this region may be important in the regulation of Spk1 kinase activity.

Alleles↗

PubMed1997

Effect of chronic treatment with propranolol on the cardiovascular responses to chronic cold exposure.

The purpose of this study was to determine whether beta-adrenergic receptors are involved in the elevation of blood pressure, tachycardia, and cardiac hypertrophy in rats chronically exposed to cold (5 degrees C). Four groups of rats were used. Two groups of rats were exposed to 5 degrees C and the other 2 groups were kept at 25 degrees C. In each temperature condition, one group received regular food while the other received food to which a nonspecific beta-adrenoceptor antagonist, d,l-propranolol, was added. The blood pressure of the untreated, cold-exposed group increased significantly within 3 weeks of exposure to cold and remained elevated until the end of the experiment. Chronic treatment with d,l-propranolol decreased the rate of cold-induced elevation of blood pressure at doses of 1.0 and 1.2 g/kg of food, and produced a complete reversal of hypertension at a higher dose ( 1.5 g/kg of food). Propranolol also prevented tachycardia in cold-exposed rats. The fact that propranolol decreased the elevation of blood pressure and prevented tachycardia suggests that both beta1- and beta2-adrenoceptors are blocked in cold-exposed rats. Propranolol, however, did not affect cold-induced cardiac hypertrophy.

Adrenergic beta-Antagonists↗

PubMed1997

Long-term results of surgery for active infective endocarditis.

OBJECTIVE: This paper was undertaken to determine the long-term outcome of active infective endocarditis treated with antibiotic and radical excision of infected tissues by surgery. METHODS: From October 1978 to August 1994, 122 consecutive patients were operated on during the acute phase of infective endocarditis. There were 85 men and 37 women whose mean age was 50 years, ranging from 20 to 79. Surgery was needed because of one or more of the following complications: cardiogenic/septic shock in 19 patients, congestive heart failure in 68, persistent sepsis in 64, peripheral embolization in 20, and cerebral embolization in 10. The offending microorganism was identified in 110 patients, staphylococci were the most common ones. Seventy-six patients had native valve endocarditis and 46 had prosthetic valve endocarditis. Simple valve replacement or repair was performed in 60 patients and radical resection of the valve and surrounding tissues with reconstruction of the heart with either fresh autologous pericardium or glutaraldehyde-fixed bovine pericardium was performed in 62 with paravalvular abscess. Pulmonary autograft and aortic homograft were used in only three patients, the remaining patients had either bioprostheses or mechanical heart valves if valve repair was not feasible. RESULTS: There were nine deaths, for an operative mortality of 7.4%. Logistic regression analysis identified preoperative shock and renal failure as predictors of operative mortality. Operative survivors were followed up from 4 to 173 months, mean of 56.4. The actuarial survival at 10 years was 61 +/- 6%. Logistic regression analysis identified preoperative New York Heart Association functional class IV and perioperative renal failure as predictors of late mortality. Eight patients developed recurrent endocarditis 10-102 months postoperatively. The freedom from recurrent endocarditis at 10 years was 79 +/- 9%. All patients who developed this late complication had paravalvular abscess at the time of original operation. CONCLUSIONS: These data suggest that surgery for active infective endocarditis yield a high probability of eradicating the infection with relatively low operative mortality and good long-term results.

Abscess↗

PubMed1997

Prediction of protein supersecondary structures based on the artificial neural network method.

The sequence patterns of 11 types of frequently occurring connecting peptides, which lead to a classification of supersecondary motifs, were studied. A database of protein supersecondary motifs was set up. An artificial neural network method, i.e. the back propagation neural network, was applied to the predictions of the supersecondary motifs from protein sequences. The prediction correctness ratios are higher than 70%, and many of them vary from 75 to 82%. These results are useful for the further study of the relationship between the structure and function of proteins. It may also provide some important information about protein design and the prediction of protein tertiary structure.

Amino Acid Sequence↗

PubMed1997

Inefficient secretion of human H27A-prolactin, a mutant that does not bind Zn2+.

Human PRL binds Zn2+, but the function of the binding is not known. We investigated the effect on PRL production in pituitary cells by obtaining clones of GH4C1 cells stably transfected with human H27A-PRL, a mutant that does not bind Zn2+. Unexpectedly, clones transfected with the mutant human PRL made little rat PRL. Untransfected GH4C1 cells made between 0.5 to 10 microg rat PRL/10(5) cells in 24 h. Clones transfected with vector alone (four of four), wild type human PRL (six of six), or with human K69A-PRL (two of two) made amounts of rat PRL in the same range. Clones transfected with human H27A-PRL (five of five) made 0.003-0.1 microg rat PRL/10(5) cells in 24 h, and the production of rat PRL mRNA was reduced. Human H27A-PRL was not efficiently secreted; 20-40% newly synthesized H27A-PRL was degraded by 60 min, and there was usually a delay in release of newly synthesized H27A-PRL. Reduction of rat PRL production is not mediated through the PRL receptor, because no sequences for the receptor in GH4C1 cells were detected by RT-PCR. Proteins involved in folding, such as BiP, were not specifically elevated in the H27A-PRL clones. In transient transfections, in which cells have not undergone selection, we found no evidence for disulfide-bonded aggregates of the mutant protein. The results indicate that Zn2+ binding stabilizes PRL in the secretory pathway; the instablility of the mutant protein may trigger effects that suppress rat PRL production directly or that indirectly result in selection of clones with low rat PRL production.

Animals↗

PubMed1997

[Transformation of rat hepatocytes in an in vitro primary culture by aflatoxin B1].

Aflatoxin B1 (AFB1) is one of the major causative factors of hepatocellular carcinoma. In this study, the combined effects of AFB1 activated by human cytochrome p450 IA2 and c-myc in transformation of rat hepatocytes were investigated in an in vitro primary culture system. The expression vectors, Xm-6/c-myc was first constructed and their expression possibilities were examined in Alexander cells by immunocytochemistry. Then both c-myc and human cytochrome p450 IA2 expression vectors were sequentially transfected into newborn rat liver cells in serum-free primary culture. Results showed that p450 IA2 could activate AFB1 at concentrations as low as 5 ng/ml, and the activated AFB1 coupled with exogenous c-myc could induce rat hepatocytes to survive and grow beyond two-month limit in primary culture. During long-term in vitro culturing including four-month in crisis, one of the randomly selected transformed hepatocytes with the growth advantage became immortalized. Immunocytochemical assays for CK-18 and rat albumin plus observed electron microscopic features clearly confirmed these cells derived from epithelial hepatocytes. Further characterization showed that the process of immortalization was associated with chromosomal abnormalities and elevated expression of TGF alpha.

Aflatoxin B1↗

PubMed1997

[Diagnosis and treatment of congenital choledochal cysts in adults].

We report the experience with 97 adult patients with bile duct cysts in the past 30 years (1965-1995). The median age at time of initial therapy in our department was 37 years (range, 16 to 78 years). Clinical symptoms in most cases were non-specific, resulting in delayed diagnosis. 74 patients (76%) had coexistent pancreaticohepatobiliary disease. Carcinoma of the biliary duct occurred in 16 patients (17%). Abnormal pancreatobiliary duct junction (APBDJ) was found in 28 patients. 94 patients underwent a total of 169 biliarytract procedures. Cyst excision with Roux-en-y hepaticojejunostomy and internal drainage were the main procedures. The result of long-term follow-up shows that internal drainage frequently resulted in recurrent cholangitis and cyst malignancy which need reoperation. In contrast, cyst excision was associated with a significantly lower incidence of recurred cholangitis and lower occurrence of malignancy. Thus, cyst excision with Roux-en-y hepaticojejunostomy is recommended as the treatment of choice for adult patient.

Adolescent↗

PubMed1997

[Diagnosis and treatment of postrenal acute renal failure].

52 cases of postrenal acute renal failure (ARF) from 1985 to 1995 were studied. 50 cases underwent emergency operation, and 2 were drained with ureter intubation by cystoscope. 37 cases (71.2%) were cured, 14 (26.9%) were improved, and 1 (1.9%) died. Oliguria, anuria and progressive increase of blood urea nitrogen and serum creatinine are the main points of diagnosis. Renal percussive pain is the important sign. B-ultrasonography examination is the first choice and often indicate the increase of the volume of kidney and mild hydronephrosis. Obstruction should be removed as quickly as possible, infection should be prevented and treated to protect renal function. The way of treatment should be adopted according to the variant causes and conditions of disease. The etiology, clinical findings, diagnosis, operating methods and cautions were discussed.

Acute Kidney Injury↗

PubMed1997

[p53 gene mutations in BALB/c 3T3 cells transformed by crocidolite].

This study sought to address the relationship between crocidolite and p53 gene mutation. The mutations of p53 gene in 8 BALB/c 3T3 cell lines transformed by crocidolite were analysed. Altogether 11 exons of the gene from 8 cell lines were detected by PCR-SSCP. 7 alterations were found; 2 of them were located in exon 4-6, and 5 in 9-11. Most of the mutations (5/7) were of one more band than that of wild cell from SSCP, and alterations were randomly scattered among the crocidolite doses groups. The results suggest that the presence of a p53 alteration is not related to the dose of crocidolite used. Besides, p53 mutation may occur in a relatively later period of the growth of the transformed cell lines. The results also showed that the mutations occurred predominantly in exons 9-11. This was different from that seen in human mesothelioma where mutations in the exon 5-8 of p53 gene were more frequently observed.

3T3 Cells↗

PubMed1997

[PCR-SSCP analysis of p53 gene in human primary brain tumor].

In this study PCR-SSCP alalysis was made to detect the mutation of the exon 5-7 of p53 gene in 37 cases of human primary brain tumor. The results showed that 10 human primary brain tumors had mutation, of which 9 were gliomas (37.5%) and 1 was meningioma (7.7%), and that the higher the grade of tumor was, the higher would be the frequency of mutation. These results suggest that human primary brain tumor is related to p53 gene mutation and such mutation may be the major reason for human primary brain tumor genesis and malignancy.

Astrocytoma↗

PubMed1997

[The uncinate process: ultrastructural and CT studies].

To provide further understanding of uncinate process, 15 uncinate processes were examined under scanning electron microscope, and 32 high-resolution coronal CT scans were studied in patients with septal deformity or sinusitis. It was found that(1)pathological ultrastructural changes of uncinate process were noted in patients with chronic sinusitis; (2) medially deviated, laterally deviated, pneumatization and hypertrophy of uncinate process were demonstrated. The following conclutions were drawn(1)the anatomic variations in ostiomeatal complex is responsible for the formation of chronic sinusitis; (2)for patients with chronic sinusitis, uncinatectomy is the treatment of choice; (3)preoperative and intraoperative studies of CT scans are mandatory for avoidance of complications.

Adolescent↗

PubMed1997

[Purification and properties of inulinase from Aspergillus niger].

The main component of inulinase was purified from fermentation broth of Aspergillus niger 319 to homogeneity by using ammonium sulfate fraction, ion-exchange chromatography on DEAE-cellulose column and Sephadex G-100 gel filtration. The specific activity was as 67 folds at the fermentation broth, and the yield was 25.5%. The inulinase, containing 13.92% of carbohydrate, was a monomer protein with a molecular weight of 28,000 Dalton; and its isoelectric point was pH 5.4. The optimal pH and temperature of the inulinase was pH 5.0 and 60 degrees C, respectively. The enzyme was strongly inhibited by heavy metal ions of Hg2+, Pb2+ and Cu2+. The optimal substrate for the enzyme was inulin and the product was only fructose, but it also had invertase activity with the I/S of 0.348. The Km and Vm of the inulinase was 6.25 mmol/L and 67.11 mumol.mg-1.min-1, respectively.

English Abstract↗

PubMed1997

[Preparation of liposomes of superoxide dismutase].

The liposomes of SOD were prepared by reverse-phase evaporation. By examining the important effects on preparation we obtained the liposomes of SOD. The encapsulation of SOD was more than 60%, and the stability of the liposomes was excellent.

Delayed-Action Preparations↗

PubMed1997

Gallstones and their chemical types in relation to serum lipids and apolipoprotein levels.

OBJECTIVE: To determine the profile of lipidemia in patients with gallstones and the characteristics of lipidemia in different kinds of gallstone in gallbladder for predicting high risk subjects predisposed to gallstone formation by means of some serum parameters. METHODS: Serum lipids and apolipoproteins levels in 47 patients with stone in gallbladder (stone group) were compared with those in 19 inpatients without stone (control group). The characteristics of lipidemia in different kinds of gallbladder stones were also compared. RESULTS: Serum apolipoprotein (Apo) A1, C2 and E levels in the stone group significantly increased as compared with the control group (P < 0.01), but there were no statistically significant differences in TC, TG, LDL-C, HDL-C, HDL-C/TC, LDL-C/HDL-C, Apo A2, B and C3 and Apo A1/Apo B levels between the stone and control groups (P > 0.05). Increased levels of serum LDL-C and Apo B and the LDL-C/HDL-C ratio (P < 0.05) were characterized as an index of cholesterol stones, while elevated levels of serum TG and Apo C2 (P < 0.05) as an index of pigment stones. CONCLUSIONS: Serum apolipoproteins might be more sensitive parameters as compared with serum lipids in distinguishing patients with stones from subjects without stones. There are different profiles of serum lipids and apolipoproteins in different chemical types of gallbladder stones.

Adult↗