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Biomedical subjects

D Shi

Publications and source records attributed to D Shi.

At least 55 records · Page 3Linked to original sources
PubMed2000

[The morphological characteristics of desmoplastic fibroblastoma].

OBJECTIVE: To study the clinical and pathological characteristics of desmoplastic fibroblastoma. METHODS: Three cases of desmoplastic fibroblastoma were evaluated by light microscopy and immunohistochemistry. RESULTS: The patients were all adults, 2 males and 1 female, age range 46 - 62 years (mean 53 years). Clinically, the tumors presented as slowly growing painless masses, which were located in the deep soft tissue of the lower extremity, the subcutaneous tissue of the forearm and the ankle respectively. Grossly, they were well-circumscribed neoplasms with a firm consistency. Histologically, the tumors were composed of paucicellular spindle or stellate-shaped fibroblastic cells embedded in a densely fibrous or fibromyxoid stroma. The neoplastic fibroblastic cells resembled the reactive fibroblasts by containing fine chromatin and small distinct nucleoli without cellular atypia or mitotic figures. Immunohistochemically, the neoplastic cells showed diffuse and strong immunoreactivity for vimentin, focal staining for alpha-SMA, MSA and desmin. CONCLUSION: Desmoplastic fibroblastoma is a benign fibroblastic neoplasm with distinctive clinical and pathological characteristics. It should be differentiated from a variety of reactive or low-grade fibroblastic lesions.

Actins↗
PubMed2000

[Effect of xiongshao capsule on proliferation and apoptosis of vascular smooth muscle cells in rabbits observed by serum pharmacological method].

OBJECTIVE: To observe the effect of Xiongshao Capsule (XSC) on proliferation and apoptosis of aortic smooth muscle cells (SMC) of rabbits by serum pharmacological method. METHODS: SMC were isolated from thoracic aorta of the normal rabbits and passaged. The SMC proliferation model was established by endothelin (ET). The medicated serum was prepared after given the normal rabbits suspension of XSC through gastrogavage for 10 days. The proliferation and apoptosis of SMC were observed by methyl thiazolyl tetrazolium (MTT) colorimetry, flow cytometry and agarose gel electrophoresis. RESULTS: ET obviously promoted proliferation of SMC, and the serum medicated with XSC could lower the proportion of SMC in S + G2 phase and markedly inhibited the proliferation of SMC caused by ET in dose dependent manner. It also had certain effect on inducing apoptosis of SMC. CONCLUSION: XSC could markedly inhibit the proliferation of SMC caused by ET and induce apoptosis of SMC, which might be the mechanism of preventing coronary restenosis after interventional treatment.

Animals↗
PubMed1999

Images of oligomeric Kv beta 2, a modulatory subunit of potassium channels.

The Shaker type voltage-gated potassium (K+) channel consists of four pore-forming Kv alpha subunits. The channel expression and kinetic properties can be modulated by auxiliary hydrophilic Kv beta subunits via formation of heteromultimeric Kv alpha-Kv beta complexes. Because each (Kv alpha)4 could recruit more than one Kv beta subunit and different Kv beta subunits could potentially interact, the stoichiometry of alpha-beta and beta-beta complexes is therefore critical for understanding the functional regulation of Shaker type potassium channels. We expressed and purified Kv beta 2 subunit in Sf9 insect cells. The purified Kv beta 2, examined by atomic force and electron microscopy techniques, is found predominately as a square-shaped tetrameric complex with side dimensions of 100 x 100 A2 and height of 51 A. Thus, Kv beta 2 is capable of forming a tetramer in the absence of pore-forming alpha subunits. The center of the Kv beta 2 complex was observed to be the most heavily stained region, suggesting that this region could be part of an extended tubular structure connecting the inner mouth of the ion permeation pathway to the cytoplasmic environment.

Amino Acid Sequence↗
PubMed1999

Coating of hydroxyapatite on porous alumina substrate through a thermal decomposition method.

A thin film of hydroxyapatite (HA) was uniformly coated onto a highly porous substrate of alumina through the thermal decomposition method. Calcium 2-ethyl hexanoate and bis(2-ethyhexyl) phosphite were used as starting materials. Scanning electron microscopy, X-ray diffraction, and infrared spectroscopy were used to characterize the chemical and structural evolution of the coating. In vitro tests were conducted to evaluate the reactivity of the synthetic HA. It was found that the sintering process greatly influenced the in vitro behavior of HA. High temperature sintering may reduce the reactivity of HA, suggesting that the reactivity is structure dependent.

Aluminum Oxide↗
PubMed1999

Crystal structure of bullfrog M ferritin at 2.8 A resolution: analysis of subunit interactions and the binuclear metal center.

Ferritins concentrate and store iron as a mineral in all bacterial, plant, and animal cells. The two ferritin subunit types, H or M (fast) and L (slow), differ in rates of iron uptake and mineralization and assemble in vivo to form heteropolymeric protein shells made up of 24 subunits; H/L subunit ratios reflect cell specificity of H and L subunit gene expression. A diferric peroxo species that is the initial reaction product of Fe(II) in H-type ferritins, as well as in ribonucleotide reductase (R2) and methane monooxygenase hydroxylase (MMOH), has recently been characterized, exploiting the relatively high accumulation of the peroxo intermediate in frog H-subunit type recombinant ferritin with the M sequence. The stability of the diferric reaction centers in R2 and MMOH contrasts with the instability of diferric centers in ferritin, which are precursors of the ferric mineral. We have determined the crystal structure of the homopolymer of recombinant frog M ferritin in two crystal forms: P4(1)2(1)2, a = b = 170.0 A and c = 481.5 A; and P3(1)21, a = b = 210.8 A and c = 328.1 A. The structural model for the trigonal form was refined to a crystallographic R value of 19.0% (Rfree = 19.4%); the two structures have an r.m.s.d. of approximately 0.22 A for all C alpha atoms. Comparison with the previously determined crystal structure of frog L ferritin indicates that the subunit interface at the molecular twofold axes is most variable, which may relate to the presence of the ferroxidase site in H-type ferritin subunits. Two metal ions (Mg) from the crystallization buffer were found in the ferroxidase site of the M ferritin crystals and interact with Glu23, Glu58, His61, Glu103, Gln137 and, unique to the M subunit, Asp140. The data suggest that Gln137 and Asp140 are a vestige of the second GluxxHis site, resulting from single nucleotide mutations of Glu and His codons and giving rise to Ala140 or Ser140 present in other eukaryotic H-type ferritins, by additional single nucleotide mutations. The observation of the Gln137xxAsp140 site in the frog M ferritin accounts for both the instability of the diferric oxy complexes in ferritin compared to MMOH and R2 and the observed kinetic variability of the diferric peroxo species in different H-type ferritin sequences.

Amino Acid Sequence↗
PubMed1999

Expression of gp145trkB in the early stage of Schwann cell tube formation.

We investigated the expression of tyrosine kinase receptors (trkBs) and their ligand, brain-derived neurotrophic factor (BDNF), in isolated sciatic nerve segments of rat in a silicone chamber model devoid of axonal contact, using an immunohistochemical technique. The receptor gp 95trkB was not detected during the first 3 weeks but was strongly expressed in the nerve stumps on day 21. In contrast, gp 145trkB immunoreactivity was readily detected in the Schwann cells in the nerve stumps between days 1 and 7 after isolation. Immunohistochemical analysis using anti-S-100 antibody demonstrated that Schwann cell tube formation within the silicone chamber had been completed by the third week, which suggested that gp 95trkB began to be produced by Schwann cells after completion of Schwann cell tube formation. Considering the low level of BDNF production during the first week, molecules other than BDNF may be ligands for gp 145trkB in the silicone chamber model devoid of axonal contact.

Animals↗
PubMed1999

Karyological and dental identification of Microtus limnophilus in a large focus of alveolar echinococcosis (Gansu, China).

A study of voles (Arvicolidae, Rodentia) from Gansu (China) designed to identify a potential host of Echinococcus multilocularis, responsible for human alveolar echinococcosis, leads to a general analysis of Microtus limnophilus population karyotypes, M1 of M. oeconomus populations from all of Eurasia and of M. limnophilus of Mongolia. The Microtus of Gansu belonging to the nominal subspecies M. limnophilus limnophilus (2n = 38; NF = 58) differs markedly in size and shape of M1 from the M. limnophilus of Mongolia, which must therefore be considered as a new subspecies M. limnophilus of malygini nov. ssp. (2n = 38; NF = 60) and the M. oeconomus of Mongolia should be ranked as M. oeconomus kharanurensis nov. ssp. (2n = 30; NF = 60).

Animals↗
PubMed1999

Chronic effects of xanthines on levels of central receptors in mice.

1. Chronic ingestion of caffeine causes a significant increase in levels of A1-adenosine, nicotinic and muscarinic receptors, serotonergic receptors, GABAA receptors and L-type calcium channels in cerebral cortical membranes from mice NIH Swiss strain mice. 2. Chronic theophylline and paraxanthine had effects similar to those of caffeine except that levels of L-type channels were unchanged. Chronic theobromine, a weak adenosine antagonist, and 1-isobutyl-3-methylxanthine (IBMX), a potent adenosine antagonist and phosphodiesterase inhibitor, caused only an increase in levels of A1-adenosine receptors. A combination of chronic caffeine and IBMX had the same effects on receptors as caffeine alone. Chronic 3,7-dimethyl-1-propargylxanthine (DMPX), a somewhat selective A2A-antagonist, caused only an increase in levels of A1-adenosine receptors. Pentoxifylline, an adenosine-uptake inhibitor inactive at adenosine receptors, had no effect on receptor levels or calcium channels. 3. A comparison of plasma and brain levels of xanthines indicated that caffeine penetrated more readily and attained somewhat higher brain levels than theophylline or theobromine. Penetration and levels were even lower for IBMX, paraxanthine, DMPX, and pentoxyfylline. 4. The results suggest that effective blockade of both A1 and A2A-adenosine receptors is necessary for the full spectrum of biochemical changes elicited by chronic ingestion of xanthines, such as caffeine, theophylline, and paraxanthine.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Neocognitron's parameter tuning by genetic algorithms.

The further study on the sensitivity analysis of Neocognitron is discussed in this paper. Fukushima's Neocognitron is capable of recognizing distorted patterns as well as tolerating positional shift. Supervised learning of the Neocognitron is fulfilled by training patterns layer by layer. However, many parameters, such as selectivity and receptive fields are set manually. Furthermore, in Fukushima's original Neocognitron, all the training patterns are designed empirically. In this paper, we use Genetic Algorithms (GAs) to tune the parameters of Neocognitron and search its reasonable training pattern sets. Four contributions are claimed: first, by analyzing the learning mechanism of Fukushima's original Neocognitron, the correlations amongst the training patterns are claimed to affect the performance of Neocognitron, tuning the Neocognitron's number of planes is equivalent to searching reasonable training patterns for its supervised learning; second, a GA-based supervised learning of the Neocognitron is carried out in this way, searching the parameters and training patterns by GAs but specifying the connection weights by training the Neocognitron; third, other than traditional GAs which are unsuitable for the large searching space of training patterns set, the cooperative coevolution is incorporated to play this role; fourth, an effective fitness function is given out when applying the above methodology into numeral recognition. The evolutionary computation in our initial experiments is implemented based on the original training pattern set, e.g. the individuals of the population are generated from Fukushima's original training patterns during initialization of GAs. The results prove that our correlation analysis is reasonable, and show that the performance of a Neocognitron is sensitive to its training patterns, selectivity and receptive fields, especially, the performance is not monotonically increasing with respect to the number of training patterns, and this GA-based supervised learning is able to improve Neocognitron's performance.

Cognition↗
PubMed1999

[The association of radiation-induced apoptosis with radiosensitivity of cervical carcinoma].

OBJECTIVE: To study the relationship between apoptosis, radiation-induced apoptosis and radiosensitivity of cervical carcinoma and find new markers for predicting radiosensitivity. METHODS: TdT-mediated bio-dUTP nick end labeling (TUNEL) method was used to check apoptosis cells. The association of radiation-induced apoptosis with tumor volume shrinkage, radiation damage grade and local control rate was analysed. RESULTS: There was no relationship between apoptosis before radiation and tumor volume shrinkage(P > 0.05); Radiation-induced apoptosis had a significant association with tumor volume shrinkage (P < 0.01); In patients with radiation-induced apoptosis 10 or more, the grade of radiation damage IIb-III accounted for 76% (13/17), while for less than 10, it was 39% (5/13, P < 0.05); After 6 months of radiotherapy, local control rate was 88% (15/17) in the former, 69% (9/13) in the latter, respectively (P > 0.05). CONCLUSION: Radiation-induced apoptosis has some reference value for predicting radiosensitivity of cervical carcinoma.

Apoptosis↗
PubMed1999

[Prognostic value of cell proliferation and apoptosis in uterine cervical cancer treated with radiation].

OBJECTIVE: To study the prognostic value of cell proliferation and apoptosis in cervical cancer patients treated with radiation. METHODS: A retrospective study was done in 40 radiotherapy-uncontrolled cases of squamous-cell carcinoma of the cervix uteri and an equal number of cases, matched in age, clinical stage, tumor size and histologic grade, which had been cured by radiotherapy. Cell proliferation was judged by the proliferating cell nuclear antigen (PCNA)-positively stained cell number x intensity of staining, and number of cells in mitosis per 10 high-power microscopic fields (HPF). Apoptotic cells were identified by TUNEL method and the result was expressed as the number of cells undergone apoptosis per 10 HPF. RESULTS: The average level of PCNA expression was 5.38 +/- 3.21 in the cured patients and 7.50 +/- 3.16 in the radiotherapy-uncontrolled patients (P < 0.01). The number of mitotic cells/10 HPF was 6.33 +/- 5.15 in the cured patients and 11.33 +/- 7.50 in the uncontrolled patients (P < 0.001). The number of apoptotic cells/10 HPF was 20.90 +/- 8.19 in the cured patients and 27.13 +/- 17.28 in the uncontrolled patients (P < 0.05). The ratio of number of apoptotic cells to that of mitotic cells (A/M) was 4.97 +/- 3.31 in the cured and 3.36 +/- 2.83 in the uncontrolled (P < 0.05). CONCLUSION: In cervical cancer, PCNA expression, the number of cells in mitosis and that of cells in apoptosis are significantly increased while the A/M ratio is significantly decreased in radiotherapy-uncontrolled patients compared to those of patients cured by radiotherapy. These parameters may be of value of predict response to radiotherapy and prognosis of patients with cervical cancer.

Apoptosis↗
PubMed1999

[Histological grading in ductal carcinoma in situ of the breast].

OBJECTIVE: To study the significance of histological grading as a prognostic factor in ductal carcinoma in situ of the breast. METHODS: According to Van Nuy's classification, 32 cases of ductal carcinoma in situ (DCIS) of the breast were divided into three grades. RESULTS: Low grade (well differentiated, low grade DCIS) 12 patients (37.5%); Intermediate grade, 9 patients (28.1%); High grade (poorly differentiated DCIS) 11 patients (34.4%). Among the high grade DCIS, the histological subtypes were comedo (9 patients), micto papillary (1 patient) and solid (1 patient). The positive expression of c-erbB-2, p53 and MIB-1 in high grade DCIS was higher than that in intermediate and low grade DCIS. The difference between high grade and low grade DCIS was significant (P < 0.05). The expression of ER in high grade DCIS was lower than that in intermediate and low grade DCIS. CONCLUSIONS: Histological grading of breast ductal carcinoma in situ may be a good prognostic factor.

Adult↗
PubMed1998

Three-dimensional crystals of Ca2+-ATPase from sarcoplasmic reticulum: merging electron diffraction tilt series and imaging the (h, k, 0) projection.

Electron crystallography offers an increasingly viable alternative to X-ray crystallography for structure determination, especially for membrane proteins. The methodology has been developed and successfully applied to 2D crystals; however, well-ordered thin, 3D crystals are often produced during crystallization trials and generally discarded due to complexities in structure analysis. To cope with these complexities, we have developed a general method for determining unit cell geometry and for merging electron diffraction data from tilt series. We have applied this method to thin, monoclinic crystals of Ca2+-ATPase from sarcoplasmic reticulum, thus characterizing the unit cell and generating a 3D set of electron diffraction amplitudes to 8 A resolution with tilt angles up to 30 degrees. The indexing of data from the tilt series has been verified by an analysis of Laue zones near the (h, k, 0) projection and the unit cell geometry is consistent with low-angle X-ray scattering from these crystals. Based on this unit cell geometry, we have systematically tilted crystals to record images of the (h, k, 0) projection. After averaging the corresponding phases to 8 A resolution, an (h, k, 0) projection map has been calculated by combining image phases with electron diffraction amplitudes. This map contains discrete densities that most likely correspond to Ca2+-ATPase dimers, unlike previous maps of untilted crystals in which molecules from successive layers are not aligned. Comparison with a projection structure from tubular crystals reveals differences that are likely due to the conformational change accompanying calcium binding to Ca2+-ATPase.

Calcium-Transporting ATPases↗
PubMed1998

1.85-A resolution crystal structure of human ornithine transcarbamoylase complexed with N-phosphonacetyl-L-ornithine. Catalytic mechanism and correlation with inherited deficiency.

The crystal structure of human ornithine transcarbamoylase complexed with the bisubstrate analog N-phosphonacetyl-L-ornithine has been solved at 1.85-A resolution by molecular replacement. Deleterious mutations produce clinical hyperammonia that, if untreated, results in neurological symptoms or death (ornithine transcarbamylase deficiency). The holoenzyme is trimeric, and as in other transcarbamoylases, each subunit contains an N-terminal domain that binds carbamoyl phosphate and a C-terminal domain that binds L-ornithine. The active site is located in the cleft between domains and contains additional residues from an adjacent subunit. Binding of N-phosphonacetyl-L-ornithine promotes domain closure. The resolution of the structure enables the role of active site residues in the catalytic mechanism to be critically examined. The side chain of Cys-303 is positioned so as to be able to interact with the delta-amino group of L-ornithine which attacks the carbonyl carbon of carbamoyl phosphate in the enzyme-catalyzed reaction. This sulfhydryl group forms a charge relay system with Asp-263 and the alpha-amino group of L-ornithine, instead of with His-302 and Glu-310, as previously proposed. In common with other ureotelic ornithine transcarbamoylases, the human enzyme lacks a loop of approximately 20 residues between helix H10 and beta-strand B10 which is present in prokaryotic ornithine transcarbamoylases but has a C-terminal extension of 10 residues that interacts with the body of the protein but is exposed. The sequence of this C-terminal extension is homologous to an interhelical loop found in several membrane proteins, including mitochondrial transport proteins, suggesting a possible mode of interaction with the inner mitochondrial membrane.

Amino Acid Sequence↗
PubMed1998

Transcription factor AP-2gamma regulates murine adenosine deaminase gene expression during placental development.

Trophoblast cells are specialized extra-embryonic cells present only in eutherian mammals. They play a major role in the implantation and placentation processes. To understand better the molecular mechanisms that control the development and function of trophoblast cells, we sought to identify the transcription factors that regulate murine adenosine deaminase (ADA) gene expression in the placenta. Here we report a detailed characterization of a placenta-specific footprinting region (FP1) in the Ada placental regulatory element. The sequence of FP1 was mapped by DNase I footprinting and was found to match a consensus AP-2 transcription factor-binding site. Electrophoretic mobility shift assays demonstrated that FP1 interacted with AP-2-like proteins. Further analysis using AP-2 antibody confirmed that AP-2 protein was indeed present in the placenta and bound to FP1. Mutation at the AP-2 site in FP1 abolished the ability of the Ada placental regulatory element to bind AP-2 proteins and failed to target chloramphenicol acetyltransferase reporter gene expression to placentas in transgenic mice, indicating that AP-2 is required for Ada expression in the placenta. In addition, RNase protection assays demonstrated that AP-2gamma was the predominant AP-2 family member expressed in the placenta. In situ hybridization analysis revealed that AP-2gamma expression was enriched in the trophoblast lineage throughout development, suggesting that AP-2gamma may be critical for trophoblast development and differentiation.

Adenosine Deaminase↗
PubMed1998

Localized unfolding at the junction of three ferritin subunits. A mechanism for iron release?

How and where iron exits from ferritin for cellular use is unknown. Twenty-four protein subunits create a cavity in ferritin where iron is concentrated >10(11)-fold as a mineral. Proline substitution for conserved leucine 134 (L134P) allowed normal assembly but increased iron exit rates. X-ray crystallography of H-L134P ferritin revealed localized unfolding at the 3-fold axis, also iron entry sites, consistent with shared use sites for iron exit and entry. The junction of three ferritin subunits appears to be a dynamic aperture with a "shutter" that cytoplasmic factors might open or close to regulate iron release in vivo.

Amino Acid Substitution↗