Biomedical subjects
Publications and source records attributed to X Tang.
A new model for mitotic dynamics of eukaryotic cells is proposed. In the kinetochore motor-midzone motor model two kinds of motors, the kinetochore motors and the midzone motors, play important roles in chromosome movement. Using this model the chromosome congression during prometaphase, the chromosome oscillation during metaphase and the chromatic segregation during anaphase are described in a unified way.
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A reaction kinetic model is proposed for immobilized S. aureofacien's protoplasts which can facilitate the conversion of lincomycin into clindamycin. The simulation result of the model has been given. Effects of various kinetic parameters of the reaction on the conversion rate are given in the formula. The formulas which can be used to calculate the maximum conversion rate and the optimal reaction time have been given. The results of model simulation are in good agreement with the experimental results.
OBJECTIVE: To investigate osteoclastic resorption in trabeculae of osteoporotic femoral head. METHODS: Osteoporotic femoral heads were collected from 7 aged women with an average age of 72.4 years, who underwent endoprosthetic replacement for intracapsular hip fracture. Femoral head trabeculae from 3 young adults killed in traffic accidents served as control. The two types of specimens were processed and studied under scanning electron microscope. RESULTS: The trabeculae of femoral head formed round or roundish arch structure. The columnar trabeculae of femoral head in the aged women showed overt osteoclastic resorption, manifested in thinning, tapering and perforation, resulting in formation of icicle-like trabeculae, which then became rounded, lost height and eventually turned into small tubercle. As a result, the inter-trabecular space enlarged markedly. Under high magnification, the trabeculae could be discerned oval, narrow oval or spindle-shaped. Howship resorption lacunae, which varied in size, depth and content, but all revealed punched-out margin. During bone resorption, the inorganic and organic components were successively resorbed. In the Howship lacunae and surrounding areas, newly formed collagen fibrils and bone tissues emerged, signifying reversal and new bone formation phases after bone resorption phase. CONCLUSION: Osteoclastic resorption markedly compromises the structural integrity and strength of the trabeculae of the arch structure of the femoral head in the aged women.
Eight alkaloids were isolated from the bulb of Fritillaria Wabuensis S.Y. Tang et S.C. Yueh the best "Chuan Bei" cultivated in Sichuan province, which is efficacious against cough. Five of them are known, identified as imperialine (I), peimisine (II), ebeinone (III), isoverticine (IV), and imperialine-beta-N-oxide (V). All the signals for both 1H and 12C-NMR spectra of base (V) were assigned by 2D NMR experiments, and an X-ray structural data of alkaloid (V) was obtained for the first time.
OBJECTIVE: To reveal the sequence of events of osteoclastic resorption taking place in the cortical bone of the femoral neck in aged women. MATERIAL AND METHODS: The cross sections of cortical bones of the femoral neck from 7 aged women who underwent endoprosthetic replacement for intracapsular hip fracture, were processed and subjected to scanning electron microscopic observation. RESULTS: The cortical bone sections revealed enlargement of the Haversian canals. On the inner linings of the enlarged canals many oval resorption lacunae could be found, reflecting osteoclastic resorption of the Haversian systems. The osteoclastic resorption with subsequent enlargement of the Haversian canals into round or oval cavities took place first over the inner portions of the cortical sections, thereby rendering these areas porotic (cancellization). These processes of the Haversian systems and canals then gradually emerged over the central and eventually over the outer areas of the cortical bone, and the entire cortical bone became porotic. Meanwhile, the inner porotic portion of the cortex turned into trabeculae (trabecularization) and became gradually resorbed, resulting in thinning of the medial cortex. CONCLUSIONS: Cortical cancellization, trabecularization and thinning compromised the material strength of the femoral neck so that fracture would ensue even with trivial injury.
Burn, tumor or congenital reasons may cause coloboma of conjunctiva. We were seeking for a thin membrane to cover the coloboma that would make the survival peripheral conjunctiva to grow and self-repair so that mucosa transplantation could be avoided. A polytetrafluoroethylene membrane of 0.1 mm thickness, 2-3 mm larger in diameter than the coloboma was sutured in place. After 2-3 weeks the membrane was removed. A total of 16 patients underwent the operation. Of them there were 2 of plasmacytoma, 5 of symblepharon, 6 of contracture of socket of eyeball and 3 of complex pterygium. In two to three weeks, the region of coloboma of conjunctiva was found being repaired. On an average 12 months' follow-up study, the eyeball movements in all cases were normal and the eyes looked symmetric. No symblepharon was found. We conclude that the polytetrafluoroethylene is a non-toxic, smooth, non-adhesive and non-distort substance resistant to high and low temperatures. When used as a substitute for conjunctiva at the region of coloboma of conjunctiva, it makes the peripheral normal conjunctiva tissues to grow and repair the coloboma.
Changes in the number of calcium channels in two subcellular fractions, the sarcolemma and the light vesicle, of rat cardic cells were studied during sepsis. Sepsis was induced by cecal ligation and puncture (CLP). The results showed that some of the calcium channels in the light vesicle translocated to the sarcolemma during the early sepsis (9 h after CLP) while during the late sepsis (18 h after CLP), some of these in the sarcolemma translocated to the light vesicle. The mechanisms of redistribution of the calcium channels in the sarcolemma and the light vesicle during sepsis was not associated to the phosphorylation of the calcium channels by cAMP dependent protein kinase (PKA), Ca2+/calmodulin dependent protein kinase (PKM) and protein kinase C (PKC). Since beta-adrenergic receptors, muscarinic cholinergic receptors and Na+/K(+)-ATPase were also redistributed during sepsis, it is suggested that the redistribution might be non-specific.
Endothelin-1 (ET-1) receptors of normal adrenal gland (ADR, 6 cases), aldosterone-producing adenoma (APA, 5 cases), idiopathic hyperaldosteronism (IHA, 4 cases) and pheochromocytoma (PHE, 6 cases) in human were measured by radioligand binding assay (RBA) of receptors. Binding studies using 125I-ET-1 as a radio ligand showed the presence of a single class of high-affinity binding sites for ET-1 in all of the above tissues. The values of dissociation constant (Kd) of ET-1 for its receptor were similar in ADR, APA and IHA (28.3 +/- 2.5, 27.9 +/- 6.1, 27.7 +/- 1.9 pmol/L, respectively), but the maximal binding capacity (Bmax) of ET receptor tended to be lower in APA tissue (107.2 +/- 13.2 fmol/mg protein) in comparison with ADR (P < 0.01) and IHA (P < 0.05, 274.9 +/- 40.8, 247.0 +/- 19.8 fmol/mg protein, respectively). Both the Kd (50.8 +/- 5.1 pmol/L) and Bmax (675.3 +/- 93.7 fmol/mg protein) in PHE were higher than those in ADR (P < 0.01), APA (P < 0.01) or IHA (P < 0.05 for Kd, P < 0.01 for Bmax). Our data may suggest that there is the down-regulation for ET-1 receptor in APA and support the concept of an important role of ET-1 in the paracrine-autocrine regulation of aldosterone and catecholamine secretion in the adrenal and adrenal tumors.
Positive ion mode matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was used to explore nonspecific interactions between proteins and oligonucleotides. The formation of noncovalent complexes showed correlation with the type of oligonucleotide bases and with the amino acid composition of the proteins. Among the four DNA homooligomers, abundant protein-nucleic acid complexes were detected for pd(T)n, whereas negligible attachment was evident for pd(A)n, pd(C)n, and pd(G)n. Mixed base sequence nucleic acids (pd(AGCTCAGCTT) and d(TTAGCAGCTT) also showed affinity to Arg-Lys. The protein affinity of pd(T)n turned out to be nonspecific and produced a larger variety of complexes when the number of basic residues in the protein was increased. Complexation of pd(T)n with small basic dipeptides (Arg-Lys or His-His) led to significant improvement in the mass resolution for positive ions. For example, the mass resolution of the pd(T)20/Arg-Lys complex exhibited about 4 times improvement over pd(T)20 alone. The protein--oligonucleotide interactions were also pH and matrix dependent. Lowering the pH from its original value (pH = 1.7) led to diminishing complex related signal, whereas increasing the pH resulted in the appearance of a larger variety of complexes. 2,5-Dihydroxybenzoic acid matrix demonstrated much greater tendency to produce complex ions than did the three other matrix materials we tested. A possible explanation of the observed phenomena was based on pH-controlled ion pair formation between oligonucleotides and proteins.
Genetic screening in fission yeast has identified a gene named stp1+ that rescues cdc25-22 [Mondesert et al. (1994) J. Biol. Chem. 269, 27996-27999]. This gene encodes a 17.4 kDa protein that is 42% identical to members of the low molecular weight protein tyrosine phosphatases (low M(r)PTPases) previously known to exist only in mammalian species. A simple and efficient purification procedure was developed to obtain the homogeneous recombinant yeast low M(r)PTPase, Stp1, in large quantities suitable for kinetic and structural studies. Authentic Stp1 was produced as judged by amino terminal protein sequencing and electrospray ionization mass spectrometry analyses. Stp1 was shown to possess intrinsic phosphatase activity toward both aryl phosphates (such as phosphotyrosine) and alkyl phosphates (such as phosphoserine). Stp1 also dephosphorylated phosphotyrosyl peptide/protein substrates. The yeast enzyme was 6-fold slower than the mammalian enzymes, which made it amenable to pre-steady-state stopped-flow spectroscopic kinetic analysis at 30 degrees C and pH 6.0. Burst kinetics was observed with Stp1 using p-nitrophenyl phosphate as a substrate, suggesting that the rate-limiting step corresponds to the decomposition of the phosphoenzyme intermediate. Interestingly, the bovine heart low M(r)PTPase was capable of removing phosphate groups from both phosphotyrosyl and phosphoseryl/threonyl protein substrates with comparable efficiencies. The low M(r)PTPases, like the Cdc25 family of phosphatases, may represent a new group of dual specificity phosphatases which may be involved in cell cycle control.
The effects of the E1A protein of adenovirus-5 on the differentiation program of F9 teratocarcinoma cells were examined by the stable introduction of plasmids that expressed wild-type or mutated forms of E1A. Constitutive expression of plasmids for most of the mutant E1As induced loss of expression of the cell-surface antigen SSEA-1 and the enhanced expression of genes specific for the differentiated phenotype of F9 cells, such as genes for laminin B1, tissue-type plasminogen activator (tPA) and type IV collagen, as well as the altered cell morphology that is associated with the differentiated state. However, such changes were not observed in the case of genes for mutant proteins from which a conserved region (CR1) of E1A had been deleted. Furthermore, no significant induction of expression of the c-jun gene or transactivation of the c-jun-CAT reporter gene were observed when the sequence that encodes CR1 of E1A had been deleted. A palindromic sequence element (DRE) of the c-jun promoter was essential for the E1A-mediated up-regulation of the c-jun gene. These results imply that CR1 is required for activation of the c-jun gene and that it is implicated in the growth arrest, expression of parietal endoderm-specific functions and the orderly differentiation of F9 cells.
In primary rodent cells transformed by the E1A region of the highly oncogenic adenovirus type 12, repression of transcription mediated by the far upstream TATA-like element was observed only in conjunction with either possible juxtaposition of a CAA repeated element in the presence of E1A and was dependent upon the relative arrangement of both the TATA-like and CAA repeated motifs in both homologous and heterologous promoter constructs. A gel shift competition study demonstrated that the TATA-binding protein (TBP) or a TBP-like protein can bind to both the upstream TATA-like sequence and the regular TATA box on the H-2Kb basal promoter. Moreover, employing immunoselection and cyclic amplification and selection of targets (CASTing) methods with nuclear extracts derived from Ad12-E1A transformants, we have identified a high affinity binding site in the H-2Kb class I promoter for E1A-associated DNA-binding proteins. The sequences of the binding sites were identified and were found to contain both the upstream TATA-like motif and the CAA repeated motifs. Our results suggest that the TATA-like sequence in the far upstream region of the H-2Kb gene is one of the elements that is required for Ad12-E1A-mediated negative repression.
Extensive immunohistochemical analyses of the hyperplastic human palatine tonsil disclosed variegated B cell phenotypes on the lymphoid cells among the crypt epithelium. The reticular epithelial network was evident by cytokeratin immunostaining. The reticular epithelium near the crypt lumen was positive for lysozyme. Secretory component was negative, while HLA-DR was frequently expressed. Intramucosal small lymphocytes, densely distributed in the luminal side, consisted mainly of B cells expressing CD19, CD20, CD21, CD22, CD45R, CD74, DBB42, HLA-DR, HLA-DQ, bcl-2 protein and surface IgM. Some B cells revealed mantle zone phenotypes (surface IgD+, CD5+, CD24+, DBA44+, CD10-, DNA7-). Cells of germinocyte phenotype (CD10+, DNA7+) were sparsely seen. A good number of intramucosal lymphoid cells were further labeled for CD11b, a phenotype of so-called B-1 cells. Plasma cells were clustered within the basal half. IgG was their major immunoglobulin class, followed by IgA, IgM and IgD classes. A smaller number of T cells (CD2+, CD3+, CD5+, CD45RO+, TCR alpha beta+) were identified among the epithelium. CD4+ cells predominated over CD8+ cells. TCR gamma delta+ cells were rare. Macrophages (CD68+), dendritic histiocytes (S-100 protein+, CD1+), and natural killer cells (CD16+ or CD57+) were also dispersed. Another unique feature of this lymphoepithelial complex was the existence of HLA-DR- intramucosal intramucosal microvasculature, where lymphocyte recirculation was suggested. Proliferating cell nuclear antigen was detected commonly in the epithelial cells but rarely in the lymphoid cells. Possible lymphoepithelial interactions and morphologic similarities to the thymic medulla are discussed.
A rapidly growing mandibular tumor occurred in a 17 month old female infant. Tumor outgrowth showing a periosteal reaction was radiographically seen on the lower surface (base) of the mandible. Under the biopsy diagnosis of osteosarcoma, high-dose chemotherapy with methotrexate was performed, resulting in little effect. The right hemimandibulectomy specimen disclosed intraosseous infiltrative growth of pleomorphic adenoma of salivary gland type, associated with chondroid stroma and reactive bone formation. The highly proliferative small-sized cells retained immunohistochemical features of myoepithelial cells, with positive reactivity of cytokeratin, vimentin, S-100 protein, alpha-smooth muscle actin, epithelial membrane antigen, CA15-3, type IV collagen, laminin and p53 protein. No heterotopia of the salivary gland was identified within the bone tissue. The tumor recurred 2 months later. Due to uncontrollable local growth, the patient died 8 months after operation. At autopsy, reactive ossification was closely associated with malignant myoepithelial proliferation. No distant metastasis was noted. This osteosarcoma-like tumor can be regarded as myoepithelial carcinoma in pleomorphic adenoma, originating from intramandibular heterotopic salivary gland tissue.
In the neurological mutant mouse weaver (wv/wv), the majority of males are infertile due to hypospermatogenesis. Heterozygous weaver mice (wv/+) cease mating successfully when males reach an average age of 3.5 months. The contents of epididymal fluid were scored for the number of sperm and sperm motility in wv/wv, wv/+ and controls. Testes were examined in mice of the three genotypes at various ages using light and electron microscopy. In wv/+ males, sperm counts were significantly lower than in controls and were significantly higher than in wv/wv. The seminiferous epithelium in weaver mice appears depleted soon after puberty and a wide range of degenerative changes was identified in both germ cells and Sertoli cells. Analogous cellular aberrations were detected in heterozygous males, but they appeared at an older age and were not as severe as in wv/wv. We hypothesize that in weaver homo- and heterozygosity the damage of Sertoli cells may induce degeneration of germinal cells and particularly affect the most advanced spermatogenic cells.
In the present study, rat cardiac sarcoplasmic reticulum (SR) phospholamban (PLB) phosphatase was partially purified by chromatography on DEAE-Sephacel. This PLB phosphatase was indentical to phosphatase-1. It was shown on electrophoresis of SDS-PAGE autoradiography that the PLB phosphatase in rats during early sepsis (ES) depressed dephosphorylation of substrates (32P-phosphorylase a and 32P-SR). However, dephosphorylation of the substrates by the partially purified phosphatase during late sepsis (LS) was same as that in control rats. The partially purified PLB phosphatase activity in ES rats was significantly decreased, but showed no change in LS rats. The results above were confirmed by a studing of the substrate concentration (enzyme concentration, time)--enzyme reaction velocity curve in showing that both affinity and maximum initial velocity (Vmax) of the phosphatase in the ES rats were decreased, but had no change in those in the LS rats.
In 1979, in view of the widespread resistance of Plasmodium falciparum to chloroquine in the island of Hainan, China, it use as an antimalarial was suspended throughout the island. A longitudinal survey of the chloroquine-sensitivity of P. falciparum was carried out over the period 1981-91 to investigate whether its resistance had changed from the 1979 level. In-vitro assays were carried out every 2-3 years, while in-vivo tests were performed annually over the period 1981-83 and also in 1991. Resistance to chloroquine declined progressively after its use had stopped. The in-vitro tests indicated that the rate of chloroquine-resistant P. falciparum was 97.9% in 1981, but dropped to 60.9% in 1991 (P < 0.001). The mean concentration of chloroquine for complete inhibition of schizont formation was 10.4 pmol/microliters in 1981, but decreased to 3.0 pmol/microliters in 1991 (P < 0.001). The proportion of samples taken from malaria cases that required high concentrations ( > 6.4 pmol/microliters) of chloroquine for complete inhibition of schizont formation was 83.3% in 1981, but only 17.4% in 1991 (P < 0.001); at low concentrations ( > 1.6 pmol/microliters), the corresponding proportions increased from 4.2% in 1981 to 60.8% in 1991 (P < 0.001). In the 4-week in-vivo test, the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 40% in 1991 (P < 0.001). RII + RIII cases represented 59.4% of the total resistant cases in 1981, but decreased to 37.5% in 1991 (0.02 > P > 0.01).