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C L Wang

Publications and source records attributed to C L Wang.

At least 109 records · Page 6Linked to original sources
PubMed1996

(i, i + 4) Ion pairs stabilize helical peptides derived from smooth muscle caldesmon.

The central region of smooth muscle caldesmon contains 10 repeats of a 13-amino-acid residue motif that is rich in charged side chains. This region has been predicted to have a strong alpha-helical propensity, and the helical structure was thought to be stabilized by the interactions between oppositely charged side chains of residues at positions i and i + 4 (Wang, C.-L. A., Chalovich, J.M., Graceffa, P., Lu, R.C., Mabuchi, K, and Stafford, W.F., J.Biol. Chem. 266, 13958-13963, 1991). Two synthetic peptides corresponding to these repeats, each containing 25 and 60 amino acid residues, indeed assume an alpha-helical conformation that is stable over a wide range of salt concentration and pH, and exhibit a typical helix-coil transition upon heating. Most significantly, when the amino acid sequence of the 25-mer is randomized without losing the i-to-i + 4 ion pairs, the peptide maintains a helical content comparable to that of the wild-type peptide, whereas another peptide variant with a sequence rearranged to eliminate all i-to-(i + 4) ion pairs has much less helicity, suggesting that specific interactions between residues with (i,i + 4) spacings are important determinants for the maintenance of secondary structure in this region of caldesmon.

Amino Acid Sequence↗
PubMed1996

Ca2+-dependent binding of calcyclin to muscle tropomyosin.

The interaction of calcyclin with tropomyosin and tropomyosin-actin was studied with fluorescence titrations and photo-reactive crosslinking experiments. Titrations of pyreneiodoacetamide-labeled tropomyosin alone or with actin showed binding of calcyclin to tropomyosin with muM dissociation constants when Ca2+ was present. UV irradiation of mixtures of calcyclin and gizzard beta beta-tropomyosin labeled with benzophenone-iodoacetamide at Cys36, with or without actin, produced crosslinks between tropomyosin chains and calcyclin monomers only in the presence of Ca2+. These data provide direct evidence for a Ca+2-dependent tropomyosin-calcyclin interaction at or near Cys36 of tropomyosin and indicate that calcyclin binding to tropomyosin-actin does not cause tropomyosin dissociation.

Actins↗
PubMed1996

Cloning of the cDNA and genomic clones for glutathione synthetase from Arabidopsis thaliana and complementation of a gsh2 mutant in fission yeast.

Glutathione is essential for protecting plants from a range of environmental stresses, including heavy metals where it acts as a precursor for the synthesis of phytochelatins. A 1658 bp cDNA clone for glutathione synthetase (gsh2) was isolated from Arabidopsis thaliana plants that were actively synthesizing glutathione upon exposure to cadmium. The sequence of the clone revealed a protein with an estimated molecular mass of 53858 Da that was very similar to the protein from higher eukaryotes, was less similar to the gene from the fission yeast, Schizosaccharomyces pombe, and shared only a small region of similarity with the Escherichia coli protein. A 4.3 kb SstI fragment containing the genomic clone for glutathione synthetase was also isolated and sequenced. A comparison of the cDNA and genomic sequences revealed that the gene was composed of twelve exons. When the Arabidopsis cDNA cloned in a special shuttle vector was expressed in a S. pombe mutant deficient in glutathione synthetase activity, the plant cDNA was able to complement the yeast mutation. Glutathione synthetase activity was measurable in wild-type yeast cells, below detectable levels in the gsh2- mutant, and restored to substantial levels by the expression of the Arabidopsis cDNA. The S. pombe mutant expressing the plant cDNA had near wild type levels of total cellular thiols, 109Cd2+ binding activity, and cadmium resistance. Since the Arabidopsis cDNA was under control of a thiamine-repressible promoter, growth of the transformed yeast on thiamine-free medium increased expression of the cDNA resulting in increases in cadmium resistance.

Amino Acid Sequence↗
PubMed1996

Immunocytochemical localization of caldesmon and calponin in chicken gizzard smooth muscle.

The distribution of caldesmon and calponin in chicken gizzard smooth muscle was investigated with immunofluorescence and immunogold electron microscopy. Immunofluorescence microscopy showed that in verapamil treated (relaxed) muscles the distributions of caldesmon and myosin appeared to be uniform throughout the cytoplasm, but clearly more textured than that of actin filaments as revealed by the distribution of tropomyosin. In shortened muscles both caldesmon and myosin became segregated, in contrast to the distribution of actin, which remained uniform. The distribution of calponin was even more textured, with no similarity to those of caldesmon or myosin. Instead, considerable overlap was observed between calponin and the cytoskeletal protein desmin and, to a lesser extent, beta-actin. By immunogold electron microscopy caldesmon appeared mostly near and around myosin filaments in both relaxed and shortened muscle. Calponin, on the other hand, was found primarily at the periphery of cytoskeletal structures in the same general region as desmin, and very often adjacent to beta-actin, which is mainly in the core. These observations indicated that caldesmon and calponin are associated with different subsets of actin filaments, caldesmon with contractile actin, while calponin with cytoskeletal actin. Thus the in situ localization of caldesmon is consistent with its proposed regulatory function. Calponin, on the other hand, is unlikely to directly regulate actomyosin interactions in these cells; instead, it may function as a bridging protein between the actin and the intermediate filament networks.

Animals↗
PubMed1996

Affinity and structure of complexes of tropomyosin and caldesmon domains.

The interaction of caldesmon domains with tropomyosin has been studied using x-ray crystallography and an optical biosensor. Only whole caldesmon and the carboxyl-terminal domain of caldesmon (CaD-4, chicken gizzard residues 597-756) bound to tropomyosin with greater than millimolar affinity at 100 and 150 microM salt. Under these conditions the affinities of whole caldesmon and CaD-4 were both in the micromolar range. Data from the x-ray studies showed that whole caldesmon bound to tropomyosin in several places, with the region of tightest interaction being at tropomyosin residues 70-100 and/or 230-260. Studies with CaD-4 revealed that this region corresponded to the strong binding site seen with whole caldesmon. Weaker association of other regions of caldesmon to tropomyosin residues 180-210 and 5-50 was also observed. The results suggest that the carboxyl-terminus of caldesmon binds tightly to tropomyosin and that other regions of caldesmon may interact with tropomyosin tightly only when they are held close to tropomyosin by the carboxyl-terminal domain. Four models are presented to show the possible interactions of caldesmon with tropomyosin.

Animals↗
PubMed1996

Prevalence and clinical significance of antibodies to ribonucleoproteins in systemic lupus erythematosus in Malaysia.

One hundred and seventy patients with systemic lupus erythematosus (SLE) were studied for the prevalence of antibodies to the small RNA-associated proteins Ro/SSA, La/SSB, Sm, U1RNP and Sm. The relationship of these autoantibodies to different races, sexes and clinical manifestations of SLE was evaluated. Passive immunodiffusion was employed using human spleen extract as antigen source for Ro and rabbit thymus extract for La, Sm and U1RNP. We found the prevalence of antibodies to be as follows: anti-Ro/SSA, 36%; anti-La/SSB, 8%; anti-Sm, 15% ; anti-U1RNP, 21%. Except for a low prevalence of anti-La, the prevalence of these antibodies was similar to that in Western studies, The prevalence of anti-Ro/SSA is similar to that reported in the Western studies, but lower than that reported in the Oriental patients from Singapore and Hong Kong. Linkages of anti-Ro with anti-La antibodies were usual; however, although anti-Sm antibodies were usually associated with anti-U1RNP, they were more frequently associated with anti-Ro antibodies. The Malay patients had a high prevalence of anti U1RNP compared to other races. No gender difference was detected. Anti-Sm antibody was associated with serositis and anti-U1RNP antibodies with Raynaud's phenomenon. No association was found between the presence of skin renal or cerebral manifestations and any specific antibodies or combination of antibodies.

Adolescent↗
PubMed1996

Altered muscle insulin sensitivity in the male offspring of protein-malnourished rats.

Insulin sensitivity of skeletal muscle was studied in male offspring of rat dams fed either a 20% (control) or 8% (low-protein) diet during pregnancy and lactation. Freshly isolated muscle strips took up more [3H]methylglucose from low-protein animals than from controls (19.2 +/- 2.5 and 4.26 +/- 0.45 nmol.min-1.mg muscle-1, respectively, P < 0.001). However, after a 60-min preincubation there was no significant difference in basal glucose transport (4.02 +/- 0.42 and 4.23 +/- 0.35 nmol.min-1.mg-1 for control and low-protein animals, respectively). Insulin (300 pM) had a significantly greater (P < 0.001) effect on stimulation of glucose transport into preincubated low-protein muscle strips than into controls (to 14.14 +/- 1.25 and 9.61 +/- 0.71 nmol.min-1.mg-1, respectively). There were no differences in total GLUT-4 protein content. However, subcellular fractionation revealed significantly (P < 0.001) more GLUT-4 in muscle plasma membranes of low-protein animals compared with controls. Insulin increased (P < 0.001) the GLUT-4 content of control plasma membranes but had no effect in low-protein animals. There were twofold more insulin receptors in low-protein muscle membranes compared with controls (2.35 +/- 0.17 x 10(11) and 1.28 +/- 0.10 x 10(11) and insulin receptors/mg muscle membrane protein, respectively, P < 0.01). These results suggest that programming of muscle insulin sensitivity can occur during fetal life.

Animals↗
PubMed1996

When do human macrophages release nitric oxide? Variable effects of certain in vitro cultural and in vivo resident conditions.

Nitric oxide (NO) release from mouse and rat macrophages is implicated in tumor cell cytotoxicity and the killing of intracellular organisms. Evidence, however, suggests that human monocyte-derived macrophages or myeloid leukemic cells differentiated along the monocytic lineage do not consistently release NO. Results presented herein that human monocyte-derived macrophages in response to lipopolysaccharide can release NO, but markedly less than mouse macrophages (1.26 +/- 0.20 vs 42.5 +/- 6.3 microM). Different in vitro and in vivo conditions have variable effects on NO production by human macrophages. Monocytes cultured in plastic wells, but not teflon beakers, for 7 days can release NO (1.22 +/- 0.13 vs 0.14 +/- 0.07 microM). In addition, human resident macrophages derived from patients with certain diseases possess a calcium- and protein kinase C-dependent pathway to produce NO, in contrast to the calcium-independent and phosphatase-dependent NO release in murine macrophages. Above results suggest that the mechanism of producing NO by macrophages in humans is not only different from that in mice, but also depends on certain in vitro and in vivo conditions.

Adult↗
PubMed1996

SS-A/Ro antibodies in Chinese patients with systemic lupus erythematosus and Sjögren's syndrome.

Serum from 53 patients with systemic lupus erythematosus (SLE) and 23 patients with primary Sjögren's syndrome (SS) were studied for anti-52-kDa SS-A/Ro, anti-60-kDa SS-A/Ro, and anti-SS-B/La antibodies by immunoblotting and enzyme-linked immunosorbent assay (ELISA). By immunoblotting, anti-SS-A/Ro was detected in 16 (30%) patients with SLE and 17 (74%) patients with SS. Anti-SS-B/La was detected in 22 (41%) patients with SLE and 15 (65%) patients with SS. Serum from 14 of the 16 SLE patients with anti-SS-A/Ro reacted with the 60-kDa protein and 15 serum samples from these patients recognized the 52-kDa protein. Serum with anti-60-kDa SS-A/Ro alone was not found. Serum from all of the 17 SS patients with anti-SS-A/Ro reacted with the 52-kDa protein, whereas serum from only two of these patients recognized the 60-kDa protein. By ELISA, the frequency of anti-SS-A/Ro (antibodies to the 60-kDa and/or 52-kDa of SS-A/Ro proteins) in patients with SLE and SS was 43/53 (81%) and 15/23 (65%), respectively. Anti-48-kDa SS-B/La was found in 28% and 48% of SLE and SS patients, respectively. Serum from 77% of SLE patients and 48% of SS patients reacted with the 60-kDa SS-A/Ro protein. Serum from 45% of SLE patients and 52% of SS patients reacted with the 52-kDa SS-A/Ro protein. Patients with SLE had significantly higher titers of antibodies to 60-kDa SS-A/Ro compared with patients with SS. Anti-SS-A/Ro and anti-SS-B/La are common in both SLE and SS. The different reactivities of anti-52-kDa and anti-60-kDa antibodies in serum from patients with SLE and SS may represent differences in conformation-dependent epitopes of SS-A/Ro autoantigens.

Adult↗
PubMed1996

[Experimental and ultrastructural study of synapses in the substantia gelatinosa after electrical acupuncture].

Ultrastructural changes of synapses in the rat substantia gelationsa of the spinal caudal trigeminal nucleus were quantitatively examined following electrical acupuncture at "Sibai" for 30 minutes. Various structural changes were observed: Spherical synaptic vesicles were clustered toward the presynaptic membrane, the number of the vesicles tended to decrease, the width of the postsyiincreased and mitochondria were also increased in the bouton. These various types of synaptic alterations related to boutons are interpreted as the morphological changes induced by the acupuncture in the region corresponding to "Sibai".

Acupuncture Points↗
PubMed1995

Identification of the functionally relevant calmodulin binding site in smooth muscle caldesmon.

The C-terminal region of smooth muscle caldesmon (CaD) interacts with calmodulin (CaM) and reverses CaD's inhibitory effect on the actomyosin ATPase activity. We have previously shown that the major CaM-binding site (site A) in this region is within the segment from Met-658 to Ser-666 (Zhan, Q., Wong, S. S., and Wang, C.-L. A. (1991) J. Biol. Chem. 266, 21810-21814). Recently, another segment (site B), Asn-675 to Lys-695, was reported to bind CaM (Mezgueldi, M., Derancourt, J., Calas, B., Kassab, R., and Fattoum, A. (1994) J. Biol. Chem. 269, 12824-12832). To assess the functional relevance of these two putative CaM-binding sites, we have examined three synthetic peptides regarding their effects on CaM's ability to reverse CaD-induced inhibition of actomyosin ATPase activity: GS17C (Gly-651 to Ser-667), VG29C (Val-685 to Gly-713), each containing one CaM-binding site, and MG56C (Met-658 to Gly-713), which contains both sites. We found that although VG29C did bind CaM, its affinity was weakened by GS17C, and it failed to compete with CaD for CaM under the conditions where GS17C effectively displaced CaD from CaM. MG56C had an effect similar to that of GS17C. These experiments demonstrated that site A for CaM binding is involved in regulating the inhibitory property of CaD.

Amino Acid Sequence↗
PubMed1995

Interaction between caltropin and the C-terminal region of smooth muscle caldesmon.

Caltropin (CaT) binds caldesmon (CaD) in a Ca(2+)-dependent manner with an affinity higher than that of calmodulin (CaM). Photo-crosslinking between CaT and a benzophenone-labeled C-terminal CaD fragment (27K) results in a 35-kDa protein that corresponds to the 1:1 adduct between CaT and 27K. In the absence of Ca2+, no crosslinking is obtained. This result is similar to that obtained with CaM and 27K. The apparent affinity of CaM for GS17C, a CaM-binding peptide of CaD, is weakened by CaT, suggesting CaT competes with CaM for the peptide. In contrast to CaM, CaT does not induce changes in the tryptophan fluorescence of GS17C. Thus although the two Ca(2+)-binding proteins behave similarly, there are differences in their interactions with CaD.

Animals↗
PubMed1995

Monoclonal antibody X18A4 identifies an oncofetal fibronectin epitope distinct from the FDC-6 binding site.

OBJECTIVE: Oncofetal fibronectin reactive with antibody FDC-6 has been associated with trophoblastic implantation and chorion structural stability. Abnormal release of this fibronectin into cervical and vaginal secretions has identified patients at risk for preterm labor and delivery. The aim of this study was to determine whether trophoblast-derived oncofetal fibronectin contains other novel epitopes distinct from the FDC-6 binding site. STUDY DESIGN: Antitrophoblast fibronectin hybridomas were generated and screened by comparative immunoassays. One specific monoclonal antibody, X18A4, was identified and compared with antibody FDC-6 by immunocytochemical and immunoblot analyses. Both antibodies were also evaluated in "sandwich"-type double monoclonal immunosorbent assays. RESULTS: X18A4 and FDC-6 bind avidly and noncompetitively to distinct epitopes within oncofetal fibronectin. They exhibit similar immunohistochemical staining of the extracellular matrix within placental tissue, ovarian epithelial tumors, and cultured trophoblasts. However, in contrast to FDC-6, X18A4 has no detectable binding activity to human plasma fibronectin, and its binding to oncofetal fibronectin was unaffected by enzymatic deglycosylation. Immunoblot analyses of oncofetal fibronectin proteolytic digests suggest that X18A4 binds near or within the alternatively spliced type III connecting segment domain. CONCLUSIONS: X18A4 identifies and binds with high affinity to a new epitope within oncofetal fibronectin, distinct from the FDC-6 binding site. Because X18A4 displays no detectable binding to plasma fibronectin, it could be used as an important adjunctive antibody for enhancing the specificity of clinically based oncofetal fibronectin diagnostic assays.

Animals↗
PubMed1995

Contact areas and pressure distributions in the subtalar joint.

We investigated how foot position and ankle arthrodesis affect the contact characteristics of the subtalar joint. Nine fresh-frozen specimens of amputated lower legs were used. Pressure-sensitive films were inserted into the anterior and posterior articulation of the subtalar joint. The contact areas and pressure for various foot positions and under axial loads of 600, 1200, and 1800 N were determined based on the gray level of the digitized film. In neutral position and under a 600 N load, the maximum contact pressure in the subtalar joint was 5.13 +/- 1.16 MPa. The contact area (1.18 +/- 0.35 cm2) was only 12.7% of the whole subtalar articulation area (9.31 +/- 0.66 cm2), and the total force (348.5 +/- 41.7 N) transmitted via this contact area was about 58% of the applied load (600 N). Dorsiflexion of the foot increased the contact area and the force transmitted, but decreased the average contact pressure in the subtalar joint, while the reverse occurred in plantar flexion. Eversion increased the subtalar contact stress, whereas inversion up to 10 degrees decreased it. Ankle joint arthrodesis shifted the contact areas in the subtalar joint posteriorly in all inversion/eversion positions. Moreover, total force transmitted through the subtalar joint as well as the contact pressure increased.

Adult↗
PubMed1995

Phosphotyrosine-dependent targeting of mitogen-activated protein kinase in differentiated contractile vascular cells.

Tyrosine phosphorylation has been linked to plasmalemmal targeting of src homology-2-containing proteins, activation of mitogen-activated protein (MAP) kinase, nuclear signaling, and proliferation of cultured cells. Significant tyrosine phosphorylation and MAP kinase activities have also been reported in differentiated cells, but the signaling role of tyrosine-phosphorylated MAP kinase in these cells is unclear. The spatial and temporal relation between phosphotyrosine and MAP kinase immunoreactivity was quantified in differentiated contractile vascular smooth muscle cells by using digital imaging microscopy. An initial association of MAP kinase with the plasmalemma required upstream protein kinase C activity but occurred in a tyrosine phosphorylation-independent manner. Subsequent to membrane association, a delayed redistribution of MAP kinase, colocalizing with the actin-binding protein caldesmon, occurred in a tyrosine phosphorylation-dependent manner. The apparent association of MAP kinase with the contractile proteins coincided with contractile activation. Thus, tyrosine phosphorylation appears to target MAP kinase to cytoskeletal proteins in contractile vascular cells. This targeting mechanism may determine the specific destination and thereby the specialized function of MAP kinase in other phenotypes.

Animals↗
PubMed1995

Ovarian failure in oral cyclophosphamide treatment for systemic lupus erythematosus.

Ninety-two women with systemic lupus erythematosus treated with oral cyclophosphamide were studied to ascertain the prevalence and the factors associated with ovarian dysfunction. Menstrual disturbance during treatment occurred in 55% of patients: 36% had amenorrhoea and 19% had oligomenorrhoea. Sustained oligomenorrhoea occurred in 12% patients. Permanent amenorrhoea (> 12 months) after cessation of oral cyclophosphamide occurred in 27% of patients. Hormonal studies in these patients were consistent with ovarian failure. Older age at initiation of treatment and high cumulative dose of cyclophosphamide were found to be associated with this outcome. There was a trend towards linear relationship between the age of initiation of cyclophosphamide therapy and frequency of amenorrhoea. A statistically significant association between amenorrhoea and cumulative dose of cyclophosphamide after adjustment for age was found whereas no such association was linked to the duration of treatment. Fourteen of the 23 women who wished to become pregnant after cessation of treatment conceived resulting in 20 live births and two abortions.

Abortion, Spontaneous↗