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Biomedical subjects

C L Wang

Publications and source records attributed to C L Wang.

At least 163 records · Page 9Linked to original sources
PubMed1989

Ultrastructure and synaptic architecture of spinal motoneurons in the frog (Rana catesbeiana).

An electron-microscopic analysis of spinal motoneurons and their synapses was carried out in a frog (Rana catesbeiana). Six different types of boutons (S, F, M, P, C and GS) have been identified. Their distribution on spinal motoneuron somata and proximal dendrites is described. The mean linear percentage of the surface area covered by boutons is 26.1 +/- 1.9%. S-type boutons are preferentially concentrated on the soma and proximal dendrites. The relative number of S-type boutons (58.7%) was greater (p less than 0.01) than that of F-type boutons (41.3%). This is in contrast to mammalian spinal motoneurons where F-type boutons are much more numerous on the soma than S-type boutons. F-type boutons are randomly distributed and the average ratio of S:F-type boutons is 20:14 (S:F ratio = 1.4). In contrast, M-type boutons synapse exclusively on the distal part of the dorsal dendrites and are restricted to the intermediate zone or to the dorsal horn. P-type boutons form synapses upon the large M-type boutons. The polarity of these axoaxonic synapses is always from P to M. Similarities and differences between the synaptology of frog and mammalian spinal motoneurons are discussed.

Animals↗
PubMed1989

A new active saponin from Phytolacca esculenta.

A new water-soluble saponin (esculentoside H) has been isolated from the roots of Phytolacca esculenta and identified as 3-O-[beta-D-glucopyranosyl-(1----4)-beta-D-xylopyranosyl]-28-O-beta-D- glucopyranosyl phytolaccagenin.

Drugs, Chinese Herbal↗
PubMed1989

[Treatment of retinal neovascularization secondary to branch vein occlusion with argon laser photocoagulation].

20 cases (22 eyes) of retinal neovascularization (RNV) secondary to branch vein occlusion were treated with argon laser photocoagulation. The RNV and the area of nonperfusion in these eyes were detected by fluorescein angiography. The results showed that argon laser photo coagulation was a highly effective therapy for RNV which was refractory to treatment. Photocoagulation minimized or resolved RNV and prevented recurrent vitreous hemorrhage. The relationship of RNV with the area of nonperfusion, the selection of the direct or indirect modality, and the points of note for success and prevention of complications were discussed.

Adult↗
PubMed1988

Photocrosslinking of calmodulin and/or actin to chicken gizzard caldesmon.

The two sulfhydryl groups of chicken gizzard caldesmon were specifically labeled with a photoreactive crosslinker, benzophenone-maleimide, to study its interactions with calmodulin and/or actin. When incubated with F-actin caldesmon crosslinks to a single actin monomer; it can, however, crosslink to up to two calmodulin molecules in the presence, but not in the absence, of Ca2+. Thus caldesmon may have two calmodulin-binding sites, each containing, or being near, one of the two thiol residues. One of these two sites may also be adjacent to the actin-binding site. A calmodulin-binding fragment of caldesmon resulting from cyanogen bromide digestion crosslinks to a single calmodulin molecule, also in a Ca2+-dependent manner. Crosslinking of calmodulin to caldesmon does not prevent the latter from binding F-actin, suggesting that calmodulin and actin do not compete with each other for the same binding site(s) on the caldesmon molecule.

Actins↗
PubMed1988

Caldesmon. Molecular weight and subunit composition by analytical ultracentrifugation.

A wide range of values has been reported for the subunit and molecular weights of smooth muscle caldesmon. There have also been conflicting reports concerning whether caldesmon is a monomer or dimer. We attempted to resolve these uncertainties by determining the molecular weight of chicken gizzard smooth muscle caldesmon using the technique of sedimentation equilibrium in the analytical ultracentrifuge. Unlike previous methods that have been used to estimate the molecular weight of caldesmon, the molecular weight determined by equilibrium sedimentation does not depend upon assumptions about the shape of the molecule. We concluded that caldesmon in solution is monomeric with a molecular mass of 93 +/- 4 kDa, a value that is much less than those previously reported in the literature. This new value, in conjunction with sedimentation velocity experiments, led to the conclusion that caldesmon is a highly asymmetric molecule with an apparent length of 740 A in solution. The mass of a cyanogen bromide fragment, with an apparent mass of 37 kDa from sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was determined to be 25.1 +/- 0.6 kDa using sedimentation equilibrium. These results imply that the reported molecular weights of other fragment(s) of caldesmon have also been overestimated. We have determined an optical extinction coefficient for caldesmon (E1%(280 nm) = 3.3) by determining its concentration from its refractive index which was measured in the analytical ultracentrifuge. From the above values of the molecular weight and the extinction coefficient, we redetermined that the caldesmon molecule has two cysteines and recalculated the stoichiometric molar ratio of actin/tropomyosin/caldesmon in the smooth muscle thin filament to be 28:4:1.

Amino Acids↗
PubMed1988

Transmission of the Ca2+-regulatory signal in skeletal muscle thin filaments.

Studies dealing with some aspects of the thin-filament based regulatory mechanism of striated muscle are discussed. A key event is a Ca2+-induced shift of TnI from a binding site on actin to TnC, as indicated by optical and crosslinking experiments. The regions concerned involve residues 1-12 in actin, residues 96-116 in TnI, and residues 89-100 in TnC. These changes in interaction are accompanied by changes in TnC and TnI that occur on a millisecond time scale which is consistent with their being part of the regulatory processes underlying regulation in vivo.

Actin Cytoskeleton↗
PubMed1987

pH-dependent structural transition in rabbit skeletal troponin C.

Although the crystal structure of troponin C is known (Herzberg, O., and James, M. N. G. (1985) Nature 313, 653-659; Sundaralingam, M., Bergstrom, R., Strasburg, G., Rao, S. T., Roychowdhury, P., Greaser, M., and Wang, B. C. (1985) Science 227, 945-948), its structure in solution, particularly under physiological conditions, has not been established. We examined the conformation of troponin C under a variety of conditions by measuring the distance between sites located in the N- and C-terminal domains using the technique of resonance energy transfer. The donor was the luminescent lanthanide ion Tb3+ bound at the low affinity metal sites in the N-terminal domain. The acceptor was 4-dimethylaminophenylazophenyl-4'-maleimide attached at Cys-98 in the C-terminal domain. The distance between these sites was found to be greater than 5.2 nm at pH 5.0, 2.7 nm at pH 6.8 for uncomplexed troponin C, and 4.1 nm for troponin C complexed with troponin I at pH 6.8. These findings suggest that uncomplexed troponin C undergoes a pH-dependent transition from an elongated conformation, compatible with the crystal structure at acidic pH, to a more compact conformation at neutral pH. When complexed with troponin I, troponin C adopts a conformation of intermediate length compared to the uncomplexed molecule at pH 6.8 and 5.0.

Animals↗
PubMed1987

Projection pattern of vestibulocerebellar fibers in the anterior vermis of the cat: an anterograde wheat germ agglutinin-horseradish peroxidase study.

The distribution of mossy fiber terminals of vestibulocerebellar fibers was studied in the anterior lobe following a unilateral injection of wheat germ agglutinin-horseradish peroxidase into the medial and descending vestibular nuclei in the cat. In the transverse plane 3 groups of labeled terminals were seen bilaterally: group 1 located in the midline region, group 2 at 0.5 mm, and group 3 between 0.75 and 1.5 mm lateral to the midline. Reconstruction of the distribution in the horizontal plane revealed that the labeled terminals were distributed in 3 areas extending apicobasally in the basal part of the lobules.

Animals↗
PubMed1987

Influence of microgravity on cellular differentiation in root caps of Zea mays.

We launched imbibed seeds of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on cellular differentiation in root caps. The influence of microgravity varied with different stages of cellular differentiation. Overall, microgravity tended to 1) increase relative volumes of hyaloplasm and lipid bodies, 2) decrease the relative volumes of plastids, mitochondria, dictyosomes, and the vacuome, and 3) exert no influence on the relative volume of nuclei in cells comprising the root cap. The reduced allocation of dictyosomal volume in peripheral cells of flight-grown seedlings correlated positively with their secretion of significantly less mucilage than peripheral cells of Earth-grown seedlings. These results indicate that 1) microgravity alters the patterns of cellular differentiation and structures of all cell types comprising the root cap, and 2) the influence of microgravity on cellular differentiation in root caps of Zea mays is organelle specific.

Cell Differentiation↗
PubMed1987

Influence of microgravity on root-cap regeneration and the structure of columella cells in Zea mays.

We launched imbibed seeds and seedlings of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on 1) root-cap regeneration, and 2) the distribution of amyloplasts and endoplasmic reticulum (ER) in the putative statocytes (i.e., columella cells) of roots. Decapped roots grown on Earth completely regenerated their caps within 4.8 days after decapping, while those grown in microgravity did not regenerate caps. In Earth-grown seedlings, the ER was localized primarily along the periphery of columella cells, and amyloplasts sedimented in response to gravity to the lower sides of the cells. Seeds germinated on Earth and subsequently launched into outer space had a distribution of ER in columella cells similar to that of Earth-grown controls, but amyloplasts were distributed throughout the cells. Seeds germinated in outer space were characterized by the presence of spherical and ellipsoidal masses of ER and randomly distributed amyloplasts in their columella cells. These results indicate that 1) gravity is necessary for regeneration of the root cap, 2) columella cells can maintain their characteristic distribution of ER in microgravity only if they are exposed previously to gravity, and 3) gravity is necessary to distribute the ER in columella cells of this cultivar of Z. mays.

Endoplasmic Reticulum↗