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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
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↗
PubMed1998

Expression of the mouse metallothionein-I gene conferring cadmium resistance in a transgenic cyanobacterium.

This paper reports the construction of a transgenic strain of cyanobacterium aimed at removing heavy metal pollution in waters. The mouse metallothionein-I (mMT-I) gene was inserted in the vector pRL-439 downstream of the strong psbA promoter. The resulting plasmid pRL-MT was ligated at the EcoRI site of the shuttle vector pKT-210 to generate the shuttle expression vector pKT-MT. This recombinant plasmid was introduced into Anabaena sp. PCC 7120 by triparental conjugative transfer. After selection on streptomycin, a stable transgenic Anabaena strain was obtained. The presence of the mMT-I gene was confirmed by DNA/DNA hybridization and its expression was demonstrated by immunodetection with specific antibodies. A metal tolerance experiment showed that this transgenic Anabaena strain had acquired higher metal resistance.

Anabaena↗
PubMed1998

Coating of hydroxyapatite on highly porous Al2O3 substrate for bone substitutes.

A thin film of hydroxyapatite (HA) was successfully coated onto a highly porous substrate of alumina by using a novel solution technique. The coated HA bonded strongly to the substrate through a glass sintering aid with an intermediate thermal expansion coefficient. The coating was also found to be microstructurally and chemically uniform on the surfaces of the interconnected pores in the matrix of the substrate. Mechanical property testing results showed that the strength of the HA-coated composite was significantly improved, indicating a high potential for structural bone substitutes in hard tissue prosthetics.

Aluminum Oxide↗
PubMed1998

Deficits in smooth-pursuit eye movements after muscimol inactivation within the primate's frontal eye field.

To evaluate smooth-pursuit (SP) function in the primate frontal eye field (FEF), microinjections of muscimol, a gamma-aminobutyric acid (GABA) agonist, were used to reversibly deactivate physiologically characterized sites in FEF. SP was severely impaired by deactivation at sites in the FEF's smooth eye movement region (FEFsem) located in the fundus and posterior bank of the macaque monkey's arcuate sulcus. These SP deficits were apparent immediately after the muscimol injection and persisted for several hours but recovered by the next day. SP was most drastically and consistently impaired for directions similar to the injected site's elicited smooth eye movement direction or to the optimal SP direction for its neuronal responses. Targets moving in these directions, usually ipsilateral to the injected hemisphere, were tracked primarily with saccades after the muscimol injection, the peak SP velocity being only 10-30% of preinjection velocity. SP in other directions, including contralateral, was less strongly affected. Initial SP acceleration in response to target motion onset was also significantly diminished, generally by approximately the same proportion as peak SP velocity. In contrast, saccades were largely unaffected by muscimol injections in FEFsem; nor was there an immediate effect on SP when control sites in the saccadic region of FEF (FEFsac) were deactivated, although a SP deficit often appeared 30-60 min after FEFsac injections, possibly reflecting diffusion of muscimol into neighboring FEFsem. These reversible SP deficits produced by muscimol inactivation within FEFsem are similar to permanent deficits caused by large aspiration lesions of FEF and indicate that inclusion of FEFsem is the critical factor determining whether FEF lesions impair SP. The severity of the reversible deficits found here indicates how extremely critical FEFsem is for normal highgain SP.

Animals↗
PubMed1998

Clinical observation on 84 cases of ventricular premature beat with deficiency syndrome treated by qi lu tang.

From August 1989 to May 1994, 84 cases of ventricular premature beat (VPB) with deficiency syndrome were treated with our empirical prescription called Qi Lü Tang Decoction for Improving Abnormal Heart Beat). The total effective rate was 88.10%, being significantly different from that of the control group treated with the Western drug propafenone (P < 0.01). Qi Lü Tang exhibited a better therapeutic effect in cases of VPB with deficiency of qi, deficiency of both qi and blood, and deficiency of both qi and yin.

Adult↗
PubMed1998

[The comparison of radiosensitivity between uterine cervical squamous carcinoma and adenocarcinoma].

OBJECTIVE: To compare the radiosensitivity of uterine cervical squamous carcinoma and adenocarcinoma. METHODS: The shrinkage of tumor and the radiation-induced damage were compared between cervical squamous carcinoma and adenocarcinoma after twice afterloading radiotherapy. Proliferating cell nuclear antigen index (PI), detected immunohistochemically, was compared before and after radiotherapy between the two tumors. RESULTS: Patients of squamous carcinoma with tumor shrinkage 50% or more accounted for 70% (21/30) and patients of adenocarcinoma accounted for 27% (4/15), which was statistically significant (P < 0.01). The radiation-induced damage grade II b-III accounted for 60% (18/30) in squamous carcinoma and for 20% (3/15) in adenocarcinoma, which was statistically significant (P < 0.05); PI decreased from 53.50% +/- 4.34% to 39.30% +/- 4.02% after radiotherapy in squamous carcinoma (P < 0.001), while PI decreased from 35.47% +/- 3.83% to 31.80% +/- 3.06% in adenocarcinoma (P > 0.05). CONCLUSIONS: The radiosensitivity of cervical squamous carcinoma is higher than that of adenocarcinoma. The decrease of PI after radiotherapy may be a biological basis of radiosensitivity for uterine cervical squamous carcinoma.

Adenocarcinoma↗
PubMed1998

[Nucleoside diphosphate kinase/nm23H1 expression in ovarian epithelial carcinoma: retroperitoneal lymphatic metastasis and survival].

OBJECTIVE: To determine the relationship between NDPK(A) expression and retroperitoneal lymph node metastasis (LNM) and the significance of the prognosis in epithelial ovarian carcinoma. METHODS: NDPK(A) expression of formalin-fixed parafin-beded samples, which included 74 primary, 31 intraperitoneal and 18 retroperitoneal lymph node metastatic tumors, were examined by ABC immunohistochemisty in 74 patients with primary ovarian cancer. RESULTS: In the 74 primary lesions, 22 samples showed positive staining of NDPK(A) (30%). Positive staining was higher in patients without LNM(46%) than those with LNM (17%, P = 0.008); it was lower in menopausal patients (19%) than in menstruant (44%, P = 0.022). Compared with primary tumor, NDPK(A) expression appeared to decrease in lymph-node lesion(28% vs 39%, P > 0.1) but to increase in intraperitoneal metastastic tumor (32% vs. 19%, P > 0.5). Multivariance analysis confirmed that the important risk factors for LNM were lower expression of NDPK(A), more large residual tumor and poor differentiation. But there was no any corelation between NDPK(A) expression and survia. CONCLUSION: The study suggested that increased expression of NDPK(A)/nm23H1 is inversely related to LNM in epithelial ovarian carcinoma, but it can not confirm the prognostic significance of NDPK(A).

Female↗
PubMed1998

[Effect of purified Xuefu capsule on cardiac haemodynamics and oxygen consumption in acute myocardial ischemia of experimental dogs].

OBJECTIVE: To investigate the effect of Purified Xuefu Capsule (PXC) on cardiac haemodynamic and oxygen consumption in acute myocardial ischemia of experimental dogs. METHODS: The coronary arteries was ligated to create the myocardial ischemic modle and gave them PXC through the duodenum. The effect of PXC on the systolic and diastolic function, volume of blood flow in coronary arteries and cardiac output of acute ischemic heart of experimental dogs were examined. RESULTS: After ligation of the coronary artery the myocardial ischemia was formed, the systolic and diastolic function, volume of blood flow in coronary arteries and cardiac output were decreased significantly in the control group, whereas these indexes in high-dose and low-dose PXC group were improved to some extent, the effect of high-dose PXC group was better than that of the low-dose PXC group. Furthermore high-dose PXC could reduce the oxygen consumption. CONCLUSIONS: PXC could prevent the cardiac pump function from acute myocardial ischemia of experimental dogs. The mechanism may be related to reduce the oxygen consumption and increase the blood supplement to myocardium.

Animals↗
PubMed1998

[Observation on the surface characteristics of the leaves of Dysosma and its related genus by scanning electronic microscope].

OBJECTIVE: To observe the surface characteristics of leaves of Dysosma and its related genus by SEM for identification. METHOD: Leaf surface characteristics of seven species of Dysosma and tow species of its related genus were observed by scanning electronic microscopic method. RESULT: The leaf surface characteristics of upper epidermis and lower epidermis of the nine plants are different from each other. A key and illustrations were listed. CONCLUSION: The leaf surface characteristics observed by SEM can be used for identification of Dysosma and its related plants.

Magnoliopsida↗