[Summary of the National Symposium on Menopausal and Postmenopausal Problems].
Explore the source record for details and available documents.
Aged↗
Biomedical subjects
Y Shi
Publications and source records attributed to Y Shi.
Some changes of receptor and postreceptor signal transduction regulated by somatostatin in pituitary hGH-secreting adenomas.
OBJECTIVE: To investigate the disturbance in the function of SRIF receptor, Gi protein and Ca2+ channel in hGH adenoma cells and to evaluate their significance in the pathogenesis of pituitary hGH adenomas. METHODS: All 25 patients with pituitary hGH adenoma who were involved in this study had typical acromegalic manifestation and high fasting serum hGH levels of > 5.0 micrograms/L which were not suppressed to < 3.0 micrograms/L by oral glucose tolerance test. The pituitary hGH adenoma tissue obtained from transphenoidal operation was digested by collagenase and the dispersed adenoma cells were cultured in the monolayer. The effects of octreotide (SMS), a long-acting agonist of somatostatin, on hGH secretion and intracellular cAMP level were observed and the influences of pertussis toxin (PT), an inhibitor of Gi protein, and Ca2+ ionophore A23187 or KCl on the inhibitory action of octreotide on hGH secretion were also investigated in the cultured pituitary hGH adenoma cells. RESULTS: A total of 16.0% (4/25) of cultured pituitary hGH adenomas did not respond to octreotide (100 nmol). The inhibitory effect of octreotide on hGH secretion was not blocked by PT (50 ng/ml) and A23187 (10 mumol) or KCl (22.5 nmol) in 31.6% (6/19) and 35% (7/20) of hGH adenomas, respectively. The effects of octreotide on hGH secretion and intracellular cAMP levels were studied in 10 cultured hGH adenomas. Octreotide suppressed both hGH secretion and cAMP levels in 5 cases; inhibited only hGH secretion or the cAMP level in 3 cases and 1 case respectively; and affected neither hGH secretion nor cAMP level in the last case. CONCLUSION: There were abnormalities in the SRIF receptor and/or postreceptor signal transduction in 16.0% of hGH adenomas which did not respond to octreotide. The defects in Gi and/or Ca2+ channels were found in 52.4% (11/21) of hGH adenomas which had responded to octreotide. These defects might induce diminution of the inhibitory action of SRIF on hGH secretion and might be the causes of hypersecretion in some pituitary hGH adenomas.
Adenoma↗
[Adhesive proteins and endothelialization of biomaterials].
Explore the source record for details and available documents.
Animals↗
Phospholamban-dependent effects of C12E8 on calcium transport and molecular dynamics in cardiac sarcoplasmic reticulum.
We have studied the effects of the nonionic detergent C12E8 on Ca-ATPase enzymatic activity and oligomeric state (detected by time-resolved phosphorescence anisotropy, TPA) in skeletal and cardiac sarcoplasmic reticulum (SR). In skeletal, SR, C12E8 inhibits the CA-ATPase, both at high (micromolar and above) and low (submicromolar) Ca. In cardiac SR, C12E8 inhibits at high Ca but activates at low Ca. Thus C12E8 activates enzymatic activity only in cardiac SR and only under conditions (submicromolar Ca) where phospholamban (PLB) regulates (inhibits) the enzyme [Lu, Y.-Z., & Kirchberger, M.A. (1994) Biochemistry 33, 5056-5062]. TPA of skeletal SR at low and high Ca demonstrates that C12E8 induces aggregation of ATPase monomers and small oligomers. C12E8 also aggregates the Ca-ATPase in cardiac SR at high Ca. In cardiac SR at low Ca, the Ca-ATPase is already highly aggregated, and C12E8 partially dissociates these aggregates. Thus the TPA results provide a simple physical explanation for the functional effects: C12E8 inhibits the ATPase when it aggregates the enzyme (skeletal SR at high and low Ca; cardiac SR at high Ca), and the detergent activates when it dissociates ATPase oligomers (cardiac SR at low Ca). C12E8 stabilizes the E2P conformation of the Ca-ATPase with respect to the E2 conformation, and this stabilization is PLB-dependent. Both the physical and functional effects of C12E8 on the Ca-ATPase are PLB-dependent, with C12E8 reversing the effects of PLB. The results provide insight into the mechanism by which PLB regulates the Ca-ATPase in cardiac SR.
Animals↗
Alloreactive anti-HLA-B7 cytolytic T cell clones use restricted T cell receptor genes.
Most alloreactive T cells specifically recognize peptides bound to donor MHC molecules. In addition to peptides, solvent accessible MHC residues also may stimulate alloreactive T cells. We studied T cell receptor (TCR) usage by 16 independent anti-HLA-B7 alloreactive cytolytic T lymphocyte (CTL) clones. Most or all of these CTL clones recognized unique peptides bound to HLA-B7. Despite the diversity of peptides recognized, 11 out of 15 CTL clones analyzed expressed TCR V(alpha) gene segment (AV) subgroups 1 and 3. Within AV subgroup 1, four of six clones expressed AV2; within AV subgroup 3, three clones used AV6. Ten of 14 CTL clones analyzed expressed V(beta) gene segment (BV) subgroups 4 and 1. In subgroup 4, BV14 was expressed by four of five alloreactive CTL clones. Similar AV and BV usage restriction was not found in mitogen-stimulated peripheral blood T cells from the major donor of the CTL clones. TCR A and TCR B junctional region sequences were quite diverse in length and sequence, although two CTL clones expressed nearly identical TCR B chains. We found no correlation between TCR AV or TCR BV usage and CTL recognition of 81 HLA-B7 variants. These results are consistent with models of TCR structure, in which very diverse TCR CDR3 regions contact very diverse peptides, and moderately diverse TCR CDR1 and CDR2 regions contact moderately diverse MHC alpha-helices.
Amino Acid Sequence↗
Adventitial myofibroblasts contribute to neointimal formation in injured porcine coronary arteries.
BACKGROUND: The adventitia undergoes remodeling changes after a deep medial coronary injury. Because this process is associated with the formation of adventitial myofibroblasts, which resemble medial smooth muscle (SM) cells, we have examined myofibroblast involvement in the development of neointima. METHODS AND RESULTS: In a porcine model, severe endoluminal coronary injury resulted in fibroblast proliferation and adventitial remodeling. Significant adventitial responses were associated with increased neointimal formation (P < .01). To examine the contribution of adventitial cells to the development of neointima, proliferating cells were labeled with bromodeoxyuridine (BrdU) at 12 and 24 hours after injury, and their subsequent localization was determined by immunohistochemistry (n = 24). At 2 to 3 days after severe injury, the adventitia contained numerous BrdU-labeled cells (37 +/- 4%), whereas the media demonstrated infrequent labeled cells (4 +/- 1%). Adventitial cells lacked alpha-SM actin and desmin, which distinguished them from medial SM cells. At 7 to 8 days, some labeled cells acquired characteristics of myofibroblasts expressing alpha-SM actin. They were found to translocate to the gap between dissected media and contributed to the formation of neointima (76 +/- 19%). At 18 to 35 days, labeled cells were abundant in the neointima (86 +/- 5%). They showed uniform immunostaining for alpha-SM actin but not for desmin, thereby differing from medial SM cells and blood-borne cells. CONCLUSIONS: This study demonstrates translocation of adventitial fibroblasts to neointima, their phenotypic modulation to myofibroblasts, and distinct characteristics of myofibroblasts within neointima after severe endoluminal coronary injury. These findings suggest the significance of vascular fibroblasts in the process of arterial repair.
Animals↗
The differential adhesion forces of anterior cruciate and medial collateral ligament fibroblasts: effects of tropomodulin, talin, vinculin, and alpha-actinin.
We have determined the effects of tropomodulin (Tmod), talin, vinculin, and alpha-actinin on ligament fibroblast adhesion. The anterior cruciate ligament (ACL), which lacks a functional healing response, and the medial collateral ligament (MCL), a functionally healing ligament, were selected for this study. The micropipette aspiration technique was used to determine the forces needed to separate ACL and MCL cells from a fibronectin-coated surface. Delivery of exogenous tropomodulin, an actin-filament capping protein, into MCL fibroblasts significantly increased adhesion, whereas its monoclonal antibody (mAb) significantly decreased cell adhesiveness. However, for ACL fibroblasts, Tmod significantly reduced adhesion, whereas its mAb had no effect. mAbs to talin, vinculin, and alpha-actinin significantly decreased the adhesion of both ACL and MCL cells with increasing concentrations of antibody, and also reduced stress fiber formation and cell spreading rate as revealed by immunofluorescence microscopy. Disruption of actin filament and microtubule assembly with cytochalasin D and colchicine, respectively, also significantly reduced adhesion in ACL and MCL cells. In conclusion, both ACL and MCL fibroblast adhesion depends on cytoskeletal assembly; however, this dependence differs between ACL and MCL fibroblasts in many ways, especially in the role of Tmod. These results add yet another possible factor in explaining the clinical differences in healing between the ACL and the MCL.
Actinin↗
Differential interactions of the CREB/ATF family of transcription factors with p300 and adenovirus E1A.
The adenovirus E1A-associated protein p300 is a transcriptional cofactor that interacts with YY1 and mediates the relief of YY1 transcriptional repression by E1A. These observations raise the possibility that p300 may function as a bridging factor between E1A and cellular transcription factors. Here we show that p300, but not a mutant defective for binding to E1A, activated cAMP-responsive element-binding protein/activating transcription factor (CREB/ATF) binding site-mediated transcription in the presence of E1A. Among proteins that can recognize the CREB/ATF site, CREB appeared to be modulated by E1A in a p300 binding-dependent manner. This effect of E1A was correlated with a specific physical interaction between CREB and p300. These results suggest that p300 plays a crucial role in mediating the functional interplay between E1A and certain members of the CREB/ATF family. Two separate domains within p300 were identified that are capable of activating transcription. One of the domains interacted with the basal factor TFIIB, suggesting that p300 may function as a coactivator by making contacts with both sequence-specific transcription factors and the basal transcriptional machinery. This pivotal role of p300 may make it a prime target for viral proteins such as E1A in programming the cellular transcription machinery.
Activating Transcription Factors↗
Cell cycle progression out of G1 sensitizes primary-cultured nontransformed T cells to TCR-mediated apoptosis.
Shortly after primary activation and IL-2-induced entry into cell cycle, splenic or lymph node T cells can be induced to undergo apoptosis by recrosslinking of the TCR complex using anti-TCR antibodies. We demonstrate here that primary-activated T cells induced to undergo apoptosis by TCR recrosslinking during the G1 phase of the cell cycle did not arrest in the G1 phase of the cell cycle. Instead, the cells continued to progress through the cell cycle and underwent at least one mitosis before dying. Rapamycin, an inhibitor of IL-2-induced S phase entry, prevented this apoptotic death. Prevention of cell death correlated with delayed entry into S phase from G1 following TCR religation in the rapamycin-treated cultures. Addition of rapamycin after cells had entered S phase or had already divided failed to prevent cell death. Treatment of activated T cells with dibutyryl cAMP or forskolin, which also block primary-activated T lymphocytes in G1, also inhibited TCR-induced cell death. In contrast, treatment of TCR-religated cells with reagents that blocked cell cycle progression in S phase (aphidicolin, deferoxamine) after TCR religation failed to prevent apoptotic cell death. Activated T cells sorted for S + G2/M DNA content following Hoechst 33342 staining were also found to be more sensitive to TCR-induced apoptosis than cells sorted for G1 DNA content. Rapamycin inhibited apoptosis in G1-sorted cells, but not in S + G2/M-sorted cells. Together, these results suggest that factors regulating cell cycle progression also control the induction of TCR-mediated apoptosis. Primary-activated T cells may become committed to programmed cell death only after progressing into S phase of the cell cycle.
Animals↗
T cells commit suicide, but B cells are murdered!
In addition to self tolerance, the immune system needs to be regulated when a response has been initiated. Recent data suggest that activated T and B cells, as well as immature lymphocytes, are susceptible to programmed cell death and that Fas:Fas ligand (FasL) interactions play an important role in this process. However, while T cells may kill themselves via a Fas-dependent pathway, we propose that B cells undergo activation-induced apoptosis independent of Fas, yet can be susceptible to T cell-mediated, FasL-induced death. Therefore, T cells can "commit suicide," but B cells are "murdered" during the regulation of an immune response! Further evidence is presented to support the hypothesis that T cell and B cell apoptosis, are initiated through fundamentally different pathways.
Animals↗
DNA unwinding induced by zinc finger protein binding.
Zinc finger domains of the Cys2His2 type are found in a large number of eukaryotic proteins. Various proteins containing these domains have been shown to bind specifically to DNA, RNA, and DNA-RNA hybrids. Structural studies of zinc finger protein-DNA complexes have revealed that the DNA molecules are underwound relative to canonical B-form. It has not been clear if zinc finger proteins recognize preexisting underwound conformations of DNA or if they induce such conformations upon binding. We report that the DNA binding domains of Sp1 and several designed zinc finger proteins unwind DNA upon binding. The extent of unwinding is consistent with that observed in zinc finger protein-DNA cocrystal structures. These DNA deformations may be important in determining overall binding affinities as well as influencing binding site preferences. Furthermore, changes in DNA conformation upon zinc finger protein binding may affect protein-protein interactions important for transcriptional regulation and other activities of zinc finger proteins.
Base Sequence↗
Axon-Schwann cell interactions regulate the expression of c-jun in Schwann cells.
The transcription factor c-jun is selectively expressed by non-myelinating Schwann cells in normal peripheral nerve, and be "denervated," previously myelinatng Schwann cells, after axotomy. When axons regenerate into the distal nerve-stump, the expression of c-jun declines as Schwann cells remyelinate axons. Treating cultured Schwann cells with forskolin, a drug that mimics many of the effects of axon-Schwann cell interactions, decreases the expression of myelin-specific genes. Overexpressing c-jun in cultured Schwann cells, however, does not decrease the expression of a myelin basic protein promoter-reporter construct, indicating that c-jun expression may not directly regulate myelin-specific gene expression. These data suggest that c-jun is invloved in regulating the phenotype of non-myelinating and denervated Schwann cells.
Animals↗
GLUT1 transmembrane glucose pathway. Affinity labeling with a transportable D-glucose diazirine.
We synthesized a transportable diazirine derivative of D-glucose,3-deoxy-3,3-azi-D-glucopyranose (3-DAG), and studied its interaction with purified human erythrocyte facilitative glucose transporter, GLUT1. 3-DAG was rapidly transported into human erythrocytes and their resealed ghosts in the dark via a mercuric chloride-inhibitable mechanism and with a speed comparable with that of 3-O-methyl-D-glucose (3-OMG). The rate of 3-DAG transport in resealed ghosts was a saturable function of 3-DAG concentration with an apparent Km of 3.2 mM and the Vmax of 3.2 micromol/s/ml. D-Glucose inhibited the 3-DAG flux competitively with an apparent KI of 11 mM. Cytochalasin B inhibited this 3-DAG flux in a dose-dependent manner with an estimated KI of 2.4 x 10(-7) M. Cytochalasin E had no effect. These findings clearly establish that 3-DAG is a good substrate of GLUT1. UV irradiation of purified GLUT1 in liposomes in the presence of 3-DAG produced a significant covalent incorporation of 3-DAG into glut1, and 200 mM D-glucose abolished this 3-dag incorporation. Analyses of trypsin and endoproteinase Lys-C digestion of 3-DAG-photolabeled GLUT1 revealed that the cleavage products corresponding to the residues 115 183, 256 300, and 301 451 of the GLUT1 sequence were labeled by 3-DAG, demonstrating that not only the C-terminal half but also the N-terminal half of the transmembrane domain participate in the putative substrate channel formation. 3-DAG may be useful in further identification of the amino acid residues that form the substrate channel of this and other members of the facilitative glucose transporter family.
Affinity Labels↗
CD28 costimulation inhibits TCR-induced apoptosis during a primary T cell response.
Murine splenic T cells undergo apoptosis when the TCR complex is re-cross-linked in the absence of costimulation during a primary immune response. However, if the CD28 complex is also cross-linked, growth continues without induction of apoptosis. Prevention of apoptosis by CD28 costimulation was associated with increased expression of bcl-xL, while overexpression of bcl-2 in T cells from bcl-2 transgenic mice was not protective. In both situations, surviving cells can be recovered in a growth arrested state following the primary response, many more if CD28 was also religated. When these cells were restimulated in secondary response, those surviving TCR religation without CD28 costimulation could not be induced to proliferate further. In contrast, cells given CD28 costimulation during the primary response proliferated well after restimulation. Thus, the CD28 signaling pathway may function not only in the initial activation of naive T cells, but also in maintaining their viability and responsiveness during a primary immune response. In addition, the results further suggest that bcl-2 and bcl-xL regulate T cell survival under different conditions, with bcl-xL being perhaps more important in maintaining viability of activated T cells traversing the cell cycle.
Animals↗
The galvanization of biology: a growing appreciation for the roles of zinc.
Zinc ions are key structural components of a large number of proteins. The binding of zinc stabilizes the folded conformations of domains so that they may facilitate interactions between the proteins and other macromolecules such as DNA. The modular nature of some of these zinc-containing proteins has allowed the rational design of site-specific DNA binding proteins. The ability of zinc to be bound specifically within a range of tetrahedral sites appears to be responsible for the evolution of the side range of zinc-stabilized structural domains now known to exist. The lack of redox activity for the zinc ion and its binding and exchange kinetics also may be important in the use of zinc for specific functional roles.
Amino Acid Sequence↗
The effects of oral myelin basic protein and dexamethasone treatment on experimental autoimmune encephalomyelitis.
Explore the source record for details and available documents.
Administration, Oral↗
Adventitial remodeling after coronary arterial injury.
BACKGROUND: Intraluminal thrombus formation and medial smooth muscle (SM) cell proliferation are recognized responses of the arterial system to injury. In contrast to these well-characterized processes during vascular repair, changes involving the adventitia have been largely neglected in previous studies. Hence, the goal of this investigation was to assess the response of the adventitia to coronary arterial injury. METHODS AND RESULTS: Adventitial changes in porcine coronary arteries subjected to medial injury were characterized by immunohistochemistry, histochemistry, and microscopic morphometry. The rapid development of a hypercellular response in the adventitia was evident 3 days after balloon-induced medial injury. Cell proliferation, as assessed by proliferating cell nuclear antigen immunostaining, reached the maximum level in the adventitia at 3 days, whereas at 14 and 28 days, the number of replicating cells reverted toward the baseline. The proliferating activity in the adventitia exceeded that seen in the media at all times after injury. To further define the changes in the phenotype of adventitial cells, the expression of three cytoskeletal proteins (vimentin, alpha-SM actin, and desmin) was characterized. Fibroblasts in normal adventitia expressed vimentin but no alpha-SM actin or desmin. After injury, these cells acquired characteristics of myofibroblasts expressing alpha-SM actin, which peaked at 7 and 14 days. Desmin expression was patchy in the adventitia, as opposed to its homogeneous distribution in medial SM cells. The modulation of fibroblast phenotype was transient, inasmuch as alpha-SM actin immunostaining declined at 28 days after injury, when dense, collagen-rich scar was evident within the adventitia. The above-described changes involving hypercellularity of the adventitia, myofibroblast formation, and fibrosis were associated with a significant focal adventitial thickening at 3, 7, 14, and 28 days after injury (P < .01 versus uninjured coronary arteries). CONCLUSIONS: This study demonstrates the involvement of the adventitia in the vascular repair process after medial injury. The hypercellularity of the adventitial layer, proliferation of fibroblasts, and modulation of their phenotype to myofibroblasts are associated with the development of the thickened adventitia. It is postulated that these phenomena affect vascular remodeling and may provide an important insight into the mechanisms of vascular disorders.
Actins↗
Scanning electron microscopy of human cerebral meningeal stomata.
The human dura mater and pia mater were studied by using a scanning electron microscope and a computer image processing system (C.I.P.). The human cerebral meningeal stomata are located between the mesothelial cells of the cerebral meninges. They are round or oval in shape with diameters of 0.33-2.98 microns. The cerebral meningeal stomata are stable structures, scattered or clustered together. Their density in the dura mater is greater than in the pia mater (P < 0.01), and they are regularly distributed. The statistical analysis showed that the stomata diameter and distribution density in the dura mater are 1.34 microns and 381.55/0.1 mm2; while in the pia mater they are 0.88 micron and 195.06/0.1 mm2 respectively. The cerebral meningeal stomata are probably part of the cerebral prelymphatic capillary system, which undertakes the cerebral lymph drainage because there are no lymphatic vessels in the brain although yet there is lymph drainage. Thus, we believe that the cerebral meningeal stomata are involved in maintaining the physiological function of the brain as part of the cerebrospinal fluid (CSF) which absorbs the cerebral interstitial fluid.
Dura Mater↗