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S Shi

Publications and source records attributed to S Shi.

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

In situ compositional analysis of acidocalcisomes in Trypanosoma cruzi.

We measured the elemental content of different compartments in Trypanosoma cruzi epimastigotes using quick freezing, ultracryomicrotomy, and electron probe microanalysis. Vacuoles identified by high electron density contained (in units of mmol/kg dry weight +/- S.E.) large amounts of phosphorus (1390 +/- 13), magnesium (646 +/- 19), calcium (171 +/- 5), sodium (161 +/- 18), and zinc (148 +/- 6). No other compartment had appreciable calcium or zinc content. Iron (128 +/- 16 mmol/kg) was detected only in vacuoles distinct from the electron-dense vacuoles and other organelles. Incubation of cells for 70 min in culture medium in the presence of ionomycin plus nigericin led to a very significant 3- or 2-fold increase in potassium in the electron-dense vacuoles and the iron-rich vacuoles, respectively, with no significant change in the other elements investigated. This indicated the acidic nature of the vacuoles and demonstrated that the electron-dense vacuoles correspond to what were described previously as acidocalcisomes, i.e. acidic compartments rich in Ca2+. The acidocalcisomes were investigated by separation of epimastigote fractions on Percoll gradients in combination with Triton WR-1339 treatment. This detergent caused a rapid vacuolation; these vacuoles were shown by electron microscopy to be largely transparent, with a diffuse matrix. Percoll gradient fractionation demonstrated decreases in the density of various organelle markers in detergent-treated cells compared with controls. Large decreases in the density of the acidocalcisome and the mitochondrion were seen, as well as smaller decreases in the density of the other markers. Conventional electron microscopy of epimastigotes loaded with gold-labeled transferrin indicated that the endosomal system was separate from vacuoles that probably corresponded to the calcium-containing organelles detected by electron probe microanalysis. The combined results provide evidence that acidocalcisomes are organelles different from lysosomes or other organelles previously described in these parasites.

Animals↗
PubMed1997

Creation and removal of embedded ribonucleotides in chromosomal DNA during mammalian Okazaki fragment processing.

Mammalian RNase HI has been shown to specifically cleave the initiator RNA of Okazaki fragments at the RNA-DNA junction, leaving a single ribonucleotide attached to the 5'-end of the downstream DNA segment. This monoribonucleotide can then be removed by the mammalian 5'- to 3'-exo-/endonuclease, a RAD2 homolog-1 (RTH-1) class nuclease, also known as flap endonuclease-1 (FEN-1). Although FEN-1/RTH-1 nuclease often requires an upstream primer for efficient activity, the presence of an upstream primer is usually inhibitory or neutral for removal of this 5'-monoribonucleotide. Using model Okazaki fragment substrates, we found that DNA ligase I can seal a 5'-monoribonucleotide into DNA. When both ligase and FEN-1/RTH-1 were present simultaneously, some of the 5'-monoribonucleotides were ligated into DNA, while others were released. Thus, a 5'-monoribonucleotide, particularly one that is made resistant to FEN-1/RTH-1-directed cleavage by extension of an inhibitory upstream primer, can be ligated into the chromosome, despite the presence of FEN-1/RTH-1 nuclease. DNA ligase I was able to seal different monoribonucleotides into the DNA for all substrates tested, with an efficiency of 1-13% that of ligating DNA. These embedded monoribonucleotides can be removed by the combined action of RNase HI, cutting on the 5'-side, and FEN-1/RTH-1 nuclease, cleaving on the 3'-side. After FEN-1/RTH-1 action and extension by polymerization, DNA ligase I can join the entirely DNA strands to complete repair.

Animals↗
PubMed1997

Mineralized nodule formation by human dental papilla cells in culture.

Human dental papilla cells were enzymatically separated from deciduous tooth germs of an 8-month-old embryo legally aborted. The second passage cells were cultured up to 35 days in 3 groups. The beta-GP group was cultured in the Dulbecco MEM containing ascorbic acid and beta-glycerophosphate supplemented with 15% fetal bovine serum. The Dex group was in the same medium, in addition containing dexamethasone. The control group contained none of the 3 chemicals. Mineralized nodules were formed after 15 days in the beta-GP and Dex groups. Only in the presence of ascorbic acid and organic phosphate did they mineralize. The addition of dexamethasone caused a significant increase in the number of nodules. By electron microscopy, the nodules contained needle-shaped crystals associated with a network of collagen fibrils. Calcium and phosphorus were detected by energy-dispersive X-ray microanalysis in the nodules. Furthermore, the crystalline material exhibited a pattern consistent with hydroxyapatite and dentin when examined by X-ray diffractometry. Cells showed high levels of alkaline phosphatase activity, which was increased 2-3 times in the presence of the 3 chemicals. These results indicated that human dental papilla cells have the ability to form dentin in culture. The formation of mineralized nodules by human dental papilla in vitro provides a useful model for studying the morphogenesis and differentiation of dental papilla ectomesenchyme.

Alkaline Phosphatase↗
PubMed1997

Mechanisms of ionomycin-induced endothelial cell barrier dysfunction.

Myosin light chain (MLC) phosphorylation catalyzed by the Ca(2+)- calmodulin-dependent MLC kinase (MLCK) is critical to thrombin-mediated endothelial cell gap formation and barrier dysfunction. We have tested the hypothesis that the Ca2+ ionophore ionomycin stimulates MLCK-dependent endothelial cell contraction and permeability. Ionomycin significantly increased albumin clearance and decreased electrical resistance across confluent bovine pulmonary microvascular and macrovascular endothelial cell monolayers in a concentration-dependent manner that was temporally similar to that produced by thrombin. In contrast, however, ionomycin produced a significant Ca(2+)-dependent reduction in the levels of phosphorylated MLC with evidence of serine/threonine phosphatase activation. Potential MLCK-independent mechanisms of endothelial cell permeability were examined with little evidence to support a role for stimulated nitric oxide synthase or phospholipase A2 activities. Importantly, ionomycin produced 1) reductions in the activities of the barrier protective adenylate cyclase and the adenosine 3',5'-cyclic monophosphate-dependent protein kinase A, 2) dramatic dose- and time-dependent inhibition of endothelial cell tyrosine kinase activities, and 3) marked decreases in the phosphotyrosine content of the p125 focal adhesion kinase. These data indicate that ionomycin produces endothelial cell barrier dysfunction by mechanisms that are independent of MLCK activation and may involve reductions in endothelial cell tethering forces via inhibition of protein kinase A and tyrosine kinase activities, especially the p125 focal adhesion kinase.

Adenylyl Cyclases↗
PubMed1997

[The expression of AT1A receptor and its modulation by benazepril in the renal tubulointerstitial lesions induced by ureteral obstruction].

OBJECTIVE: To study the expressions of angiotensin II 1A receptor (AT1A) both at the mRNA level and the protein level and their modulation by an angiotensin converting enzyme inhibitor, benazepril, in the renal tubulointerstitial injuries induced by unilateral ureteral obstruction (UUO) in rats. METHODS: Six SD rats (UUO-T) were administered benazepril in the drinking water (50mg/L). Additional 6 rats were used as untreated controls (UUO-C). Mean arterial Prossure (MAP) was measured at the 10th day after UUO, and then all animals were sacrificed. The expressions of AT1A were examined both at the mRNA level by in situ hybridization using a subtype-specific probe and at the protein level by an immunohistochemistry methods using AT1 receptor antibody in normal rat kidneys and the obstructed rat kidneys. RESULTS: MAP was 14.2 +/- 0. 6kPa in the UUO-T and 16.6 +/- 0.7kPa in the UUO-C (P < 0.05). Benazepril slowed the tubulointerstitial fibrosis (TIF) and reduced the expression of AT1A in the renal tubular epithelial cells, the interstitial areas, and the walls of renal arteriole in the UUO-T group. CONCLUSION: The increased expressions of AT1A were found in the acute renal tubulointerstitial pathogenesis induced by UUO. Benazepril may retard the progression of TIF and decrease the expression of AT1A in the obstructed kidneys. We conclude that the effects of Ang II on the obstructed kidneys may be due to its binding with AT1A.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Collecting duct carcinoma of the kidney.

OBJECTIVE: To describe the clinical, pathologic and immunohistochemical characteristics of collecting duct carcinoma (CDC) of the kidney. METHODS: Five cases of CDC (3 males and 2 females, aged 41 to 67 years) were identified between January, 1990 and December, 1994. Routine histopathologic study and immunohistochemical examinations of the surgical specimens were performed. RESULTS: Four patients underwent radical nephrectomy; 3 have been alive without evidence of recurrence for 3 months, 2 years and 2.5 years, respectively after the operation. Bone metastasis was noted 2 months after the operation in 1 case. One patient was submitted to simple nephrectomy because of extensive regional node involvement and died of lung metastasis 14 months after the surgery. Grossly, the tumors were usually grey-whitish in color and located in the renal medulla. Microscopically, the characteristic structure of tubulo-papillary pattern could be identified. Marked desmoplastic reaction was noted and atypical hyperplastic changes were found in the adjacent collecting ducts. Immunohistochemical studies revealed positive results to epithelial membrane antigen, high molecular weight cytokeratin and peanut agglutinin. CONCLUSION: CDC of the kidney is a rare disease with a poor prognosis. Radical nephrectomy is recommended even if the tumor is small.

Adult↗
PubMed1997

Identification of a novel missense mutation in Wilson's disease gene.

OBJECTIVE: To investigate the allelic heterogeneity of the ATP7B gene in Chinese patients with Wilson's disease (WD). METHODS: Exons of the ATP7B gene from 141 WD patients' DNA were amplified with polymerase chain reaction (PCR) 887-890. Mutations were then screened by single strand conformation polymorphism (SSCP) analysis and further identified by sequencing. RESULTS: The molecular structure of exon 7 of the ATP7B gene from 141 WD patients was analyzed. The same band shift in electrophoretic pattern of 4 cerebral type patients was identified with SSCP and subsequently sequenced. The results showed missense mutation at the second base of the codon as Ser 662 Cys, which is caused by a C to G transversion. CONCLUSIONS: Mutations of the ATP7B gene were investigated for the first time in China and a novel missense mutation was identified in four cases.

Adolescent↗
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

The role of type I collagen in the regulation of the osteoblast phenotype.

Evidence from a variety of sources indicates that the extracellular matrix forms an important part of a feedback loop governing the migration, proliferation, and differentiation of the cells that produce it. In keeping with this, we showed previously that the extracellular matrix of a multipotential mesenchymal clonal cell line (ROB-C26) induced to differentiate into a more osteoblastic cell type by the addition of exogenous retinoic acid produces an extracellular matrix capable of osteoinductive activity in vivo and of stimulating alkaline phosphatase activity in vitro. Since type I collagen is the major structural component of this extracellular matrix, we sought to determine whether and to what extent this protein is responsible for the previously observed inductive/stimulatory activity. To this end, C26 cells are cultured on plastic, in the presence of retinoic acid, on a type I collagen film, or on an extracellular matrix from retinoic acid-treated C26 cells, and cell differentiation is assessed by measuring changes in the abundance of a number of osteoblast-related mRNAs. These determinations are made by RNAse protection assay after 3 or 6 days of incubation and include measurements of the RNAs for type I collagen, alkaline phosphatase, osteopontin, transforming growth factor alpha 1 and beta 2, and Vgr-1/BMP-6. In addition, C26 cells are incubated in the presence of retinoic acid and several established inhibitors of the synthesis or assembly of extracellular matrix components and the effects on induced alkaline phosphatase activity determined. Our data show that while the collagen substrate mimics some of the effects of retinoic acid and the extracellular matrix, it cannot reproduce all of them. Specifically, while the latter two culture conditions increase the abundance of all six mRNAs, type I collagen film increases the levels of only three of the six (collagen I, alkaline phosphatase, and osteopontin). Moreover, while type I collagen film produces an increase in alkaline phosphatase message, it falls to produce a similar change in alkaline phosphatase activity, an effect seen with both retinoic acid and extracellular matrix. However, interruption of collagen I synthesis by cis-4-hydroxy-L-proline blocks the increase in alkaline phosphatase activity associated with retinoic acid treatment. Thus, it appears likely that type I collagen is a necessary but, by itself, insufficient factor to elicit the comprehensive expression of the osteoblastic phenotype in immature mesenchymal cells.

Alkaline Phosphatase↗
PubMed1996

[Effects of aspirin and nifedipine alone or in combination on hemodynamics in anesthetized dogs].

AIM: To study the effects of the combination of aspirin (Asp) and nifedipine (Nif) on hemodynamics in 8 anesthetized dogs. METHODS: Tension time index (TTI), left ventricular work index (LVWI), mean arterial pressure (MAP), and total peripheral vascular resistance (TPVR), femoral artery blood flow (FBF), ventricular systolic pressure (LVSP), maximum of its first derivative (dp/dt(max)), left ventricular end diastolic pressure (LVEDP) and heart rate (HR) were recorded on polygraph and electromagnetic flowmeter. RESULTS: Asp 5, 10 mg.kg-1, i.v. exerted a significant effect on the hemodynamic indices, wheras Nif 15 micrograms.kg-1, i.v. decreased TTI, LVWI, MAP, and TRVR, increased FBF distinctively, and slightly affected LVSP, dp/dt(max), LVEDP, and HR. The effects of Asp in combination with Nif on hemodynamics were similar to those of Nif alone. CONCLUSION: The improvement of cardiovascular function caused by Nif was not affected by the presence of Asp.

Animals↗
PubMed1996

[Uterine papillary serous carcinoma and papillary endometrial carcinoma: analysis of clinical biological behaviors of 56 cases].

OBJECTIVE: To characterize the clinical biological behavior and the pathological morphology of uterine papillary serous carcinoma and papillary endometrial carcinoma. METHODS: This is a retrospective analysis of 56 patients with papillary endometrial cancer treated at Cancer Hospital. Chinese Academy of Medical Sciences from January, 1981 to December, 1993. Of the 56 cases, 15 were uterine papillary serous carcinomas (UPSC), 41 papillary endometrial carcinomas (PEC). One hundred and sixty patients with endometrial adenocarcinoma (AC) were submitted as control group. RESULTS: 26.7% of UPSC, 14.6% of PEC and 5.6% of AC patients had stage III or IV by clinical examination (P < 0.05), whereas 53.3% of UPSC, 20.8% of PEC and 12.1% of AC patients has extrauterine disease at surgery (P < 0.01). Deep myometrial invasion occurred in 75.0% of UPSC, 41.7% of PEC, and 32.3% of AC patients (P < 0.01). An increasing gradient of 5 year survival rate (life table method) was observed from UPSC (45.7%) to PEC (61.9%) to AC (90.3%) in their early stage (stage I-II) (P < 0.01). Upper abdominal spread was a common finding in UPSC which had a high rate of persistent disease (46.2%). The pelvis was the predominant involving site in PEC with a high frequency of recurrence and metastasis (31.0%). CONCLUSIONS: The presence of papillary features in endometrial carcinoma is an important prognostic indicator. The prognosis of PEC is better than UPSC, but worse than AC.

Adult↗
PubMed1996

[Constituents of essential oil of imported myrrh and gum opoponax].

The constitutents of essential oil in two kinds of Myrrha were analyzed by GC-MS. Fifteen compounds in Myrrh and thirty-three compounds in Gum opoponax were identified with their percent contents given. The main constituent of Myrrh is furanoeudesma-1,3-diene, and the main constituent of Gum opoponax is beta-trans-ocimene.

Drugs, Chinese Herbal↗
PubMed1996

[A simplified theory of protrusive balanced occlusion in complete denture and its application].

Based the study of the theory of protrusive balanced occlusion in complete denture construction and clinical experience the author established a new simplified theory named "the three principle factors and three laws for protrusive balanced occlusion in complete denture" to guide us to arrange teeth for balanced occlusion in complete denture construction. Based this theory the phenomena of protrusive occlusal disharmony appeared in the process of teeth arrangement and denture insertion can be corrected easily.

Dental Occlusion, Balanced↗
PubMed1996

[The analysis of clinical dental crown of primary molar teeth].

For providing the anatomical data of primary molar teeth in China and using for the reference of clinical orthodontics, we measured and analysed the clinical crown of first and second primary molar teeth in 167 children of 4-6 years old finely. Each tooth was measured for 7 items with 9,228 in total. The heights of teeth crowns on buccal site were much taller than that on glossopalatal site except E. The mesial, distal and buccoglossal lenths were much longer on the enlarged part of crown than on the occlusive part. The mean values of symmetric teeth on both sites almost were of no difference. The mean values were not different in age groups (4.5 or 6 years old) either.

Anthropometry↗
PubMed1996

[Effects of aspirin and nifedipine alone or in combination on mesenteric microcirculation of rats].

AIM: To study the effects of the combination of aspirin (Asp) and nifedipine (Nif) on mesenteric microcirculation of rats. METHODS: Acute microcirculation disturbance (AMD) was produced by high molecular weight dextran (M(r) 480,000, 360 mg.kg-1 i.v.). Arteriole and venule blood flow velocity and diameter (ABFV, VBFV, AD, VD) and blood flow state (BFS) were observed by intravital microcirculation method. RESULTS: Asp 2.5, 5 mg.kg-1, Nif 0.05, 0.1 mg.kg-1, Asp + Nif (1 + 0.025), (2.5 + 0.05) mg.kg-1, i.v. had the significant increase of 11.1%, 31.3%, 18.5%, 19.3%, 30.5%, 39.8% of ABFV and 12.5%, 25.7%, 12.6%, 15.2%, 29.6%, 36.1% of VBFV respectively, the marked improvement of BFS, and the distinctive increase of 4.3%, 17.9%, 35.9%, 39.7%, 15.2%, 42.8% of AD and 2.2%, 4.2%, 26.2%, 27.4%, 3.4%, 28.9% of VD separately, and got a raise in the number of capillaries. Asp + Nif (1 + 0.025), 2.5 + 0.05) mg.kg-1 i.v. could reverse AMD. CONCLUSION: Asp was superior to Nif in the increase of BFV, but Nif was superior to Asp in expansion of blood vessel. Asp in combination with Nif produced marked synergistic action and protection againist AMD.

Animals↗
PubMed1995

[Study on Gong Dingguo].

It is proved through textual researches that Gong Dingguo, the author of Neifu Michuan Jingyan Nuke, was the son of gong Tingxian, a famous physician of the late Ming Dynasty.

China↗