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W Lehman

Publications and source records attributed to W Lehman.

At least 37 records · Page 2Linked to original sources
PubMed1993

Three-dimensional reconstruction of caldesmon-containing smooth muscle thin filaments.

Caldesmon is known to inhibit actomyosin ATPase and filament sliding in vitro, and may play a role in modulating smooth muscle contraction as well as in diverse cellular processes including cytokinesis and exocytosis. However, the structural basis of caldesmon action has not previously been apparent. We have recorded electron microscope images of negatively stained thin filaments containing caldesmon and tropomyosin which were isolated from chicken gizzard smooth muscle in EGTA. Three-dimensional helical reconstructions of these filaments show actin monomers whose bilobed shape and connectivity are very similar to those previously seen in reconstructions of frozen-hydrated skeletal muscle thin filaments. In addition, a continuous thin strand of density follows the long-pitch actin helices, in contact with the inner domain of each actin monomer. Gizzard thin filaments treated with Ca2+/calmodulin, which dissociated caldesmon but not tropomyosin, have also been reconstructed. Under these conditions, reconstructions also reveal a bilobed actin monomer, as well as a continuous surface strand that appears to have moved to a position closer to the outer domain of actin. The strands seen in both EGTA- and Ca2+/calmodulin-treated filaments thus presumably represent tropomyosin. It appears that caldesmon can fix tropomyosin in a particular position on actin in the absence of calcium. An influence of caldesmon on tropomyosin position might, in principle, account for caldesmon's ability to modulate actomyosin interaction in both smooth muscles and non-muscle cells.

Actin Cytoskeleton↗
PubMed1992

Proteus syndrome.

Proteus syndrome is a rare congenital disorder that is characterized by a wide variety of deformities including macrodactyly. Skin and soft tissue lesions are common; they may increase in size as the child develops and may assume tremendous proportions. The syndrome is often mistaken for other more commonly recognized conditions such as neurofibromatosis. Unlike neurofibromatosis, the soft tissue masses in Proteus syndrome are not nerve tumors but, rather, are hamartomas composed primarily of lipomatous tissue. The hand surgeon should be aware of this condition when evaluating a child with macrodactyly.

Diagnosis, Differential↗
PubMed1992

The future of electronic billing.

A comprehensive patient accounting system is vital to achieving timely reimbursement. Industry-wide standardization of intermediary requirements can further aid the process.

Accounts Payable and Receivable↗
PubMed1990

Caldesmon and the structure of smooth muscle thin filaments: electron microscopy of isolated thin filaments.

Native and synthetic vertebrate smooth muscle thin filaments have been examined by electron microscopy in order to determine the arrangement of the regulatory protein caldesmon. In synthetic filaments of actin-caldesmon, long slender molecules were sometimes seen running along the thin filament, suggesting that caldesmon can associate with actin along its length, while at other times lateral projections were observed. In native filaments, containing actin, caldesmon and tropomyosin, we found no evidence for lateral projections extending from the filaments, suggesting that caldesmon does not act as a crosslinking protein in vivo. In contrast, elongated molecules were clearly seen following the long pitch actin helices. We suggest that these may represent an association of caldesmon and tropomyosin. Antibodies developed against an N-terminal fragment of caldesmon caused thin filaments to aggregate laterally into arrays displaying approximately 35-38 nm repeats; thin filament aggregates with this periodicity were obtained previously (Lehman et al., 1989) using antibodies to the C-terminal segment of caldesmon. These results suggest that both ends of caldesmon are closely associated with the shaft of the thin filament, supporting a model in which the elongated caldesmon molecule runs along the filament, possibly interacting with tropomyosin, following the long pitch actin helices.

Animals↗
PubMed1989

Characterization of the Ca2+-switch in skeletal and cardiac muscles.

To determine the significance of the global structure of the regulatory proteins in the mechanism of the Ca2+-switch in cardiac and skeletal muscle contractions, the properties of a family of Ca2+-binding proteins with 4 or 3 EF-hand motifs have been studied with desensitized skinned fiber preparations. Proteins with 4 EF hands (such as troponins C - TnCs) are dumb-bell shaped, those with 3 EF hands (parvalbumin) being ellipsoidal. The number of active sites varied between four and two. We find that the ability to anchor in the fiber is limited to proteins with 4 EF hands and, at least, two active Ca2+-binding sites, one each in the N- and C-termini. The results suggest that the dumb-bell shaped global structure is critical for the switching action in muscular contraction, and a trigger site in the N-terminus and a structural site in the C-terminus need to be active in order to regulate contractility.

Animals↗
PubMed1989

35 kDa proteins are not components of vertebrate smooth muscle thin filaments.

A 35 kDa protein present in vertebrate smooth muscle and capable of binding to purified actin does not appear to be a constituent of smooth-muscle thin filaments in vivo; instead, it is more likely to be a component easily solubilized from particulate material which then spuriously interacts with actin.

Actin Cytoskeleton↗
PubMed1989

Caldesmon and the structure of smooth muscle thin filaments: immunolocalization of caldesmon on thin filaments.

Antibodies reacting with chicken gizzard caldesmon were used to determine the distribution of caldesmon on smooth muscle thin filaments. Antibodies developed against both the intact caldesmon molecule and a 40 kilodalton proteolytic fragment cause thin filaments to aggregate laterally. Aggregates produced with the latter antibody display regular periodic labelling with a repeat of approximately 38 nm, a distribution characteristic of proteins associated with tropomyosin on thin filaments. The stoichiometry of caldesmon on thin filaments has been critically reevaluated and alternative models of caldesmon distribution on thin filaments are proposed.

Animals↗
PubMed1989

Development and testing of a statistical and graphics-enhanced nutrient analysis program.

The authors have developed and tested a nutrient analysis program that will compute and present graphically summary statistics of population and population subgroup nutrient intakes. The program analyzes for 44 nutrients from 5,800 separate food items. Capabilities of the program include: storage of large numbers of diet records and evaluations of their nutrients; calculation of nutrient means and standard deviations; data sorting based on subject characteristics, such as age, sex, and supplement use; and generation of bar graphs and line plots for individual and/or group data. To test this computerized nutrient analysis program, two sets of 3-day diet records from 200 elderly individuals were analyzed. The program was then used to generate means, differences between means, and distribution frequencies of designated nutrients for various population subgroups (e.g., men greater than or equal to 65 years vs. men greater than or equal to 80 years) as well as comparisons with individual files (e.g., Mr. Smith vs. all men greater than or equal to 65 years). The statistical and graphics capabilities also function within the context of recipe analysis and menu planning, which enhances the application of this program in institutional and community nutrition settings.

Aged↗
PubMed1988

Reversal of caldesmon function by anti-caldesmon antibodies confirms its role in the calcium regulation of vascular smooth muscle thin filaments.

Direct evidence that caldesmon is the Ca2+-regulated inhibitory component of native smooth muscle thin filaments is provided by studies using caldesmon-specific antibodies as antagonists. The antibodies reverse caldesmon inhibition of actomyosin ATPase and abolish Ca2+-regulation of native aorta thin filament activation of myosin ATPase. This effect is a result of antibody binding to the caldesmon on the filament thereby inactivating it and not due to antibody-induced caldesmon dissociation from the filament. The antibodies, however, neutralise caldesmon only in systems using skeletal muscle myosin and not in those using smooth muscle myosin; this implies that smooth muscle myosin prevents appropriate antibody binding to caldesmon perhaps because smooth muscle myosin binds to caldesmon thus preventing access of antibody to antigenic sites.

Actin Cytoskeleton↗
PubMed1987

Diversity in smooth muscle thin filament composition.

Two classes of smooth muscle thin filament can be identified and separated based on their interaction with antibodies specific either to filamin or to caldesmon. One type is composed of actin, tropomyosin and filamin and the other of actin, tropomyosin and caldesmon.

Actins↗
PubMed1986

The effect of calcium on the aggregation of chicken gizzard thin filaments.

Electron microscopy demonstrates that thin filaments isolated from chicken gizzard smooth muscle in the absence of Ca2+ are aggregated into networks. In contrast, thin filaments isolated in the presence of Ca2+ are dissociated from each other. Electron microscopy also reveals that the respective state of aggregation in each type of preparation is reversible and dependent on Ca2+ concentration. Corresponding viscosity measurements indicate that network formation is associated with an increase in thin filament viscosity. We propose that thin filament aggregation in vivo may be responsible for the tension maintenance of smooth muscle during relaxation.

Animals↗
PubMed1985

Caldesmon is a Ca2+-regulatory component of native smooth-muscle thin filaments.

Thin-filament preparations from four smooth muscle types (gizzard, stomach, trachea, aorta) all activate myosin MgATPase activity, are regulated by Ca2+, and contain actin, tropomyosin and a 120000-140000-Mr protein in the molar proportions 1:1/7:1/26. The 120000-140000-Mr protein from all sources is a potent inhibitor of actomyosin ATPase activity. Peptide-mapping and immunological evidence is presented showing that it is identical with caldesmon. Quantitative immunological data suggest that caldesmon is a component of all the thin filaments and that the thin-filament-bound caldesmon accounts for all the caldesmon in intact tissue. The myosin light-chain kinase content of thin-filament preparations was found to be negligible. We propose that caldesmon-based thin-filament Ca2+ regulation is a physiological mechanism in all smooth muscles.

Adenosine Triphosphatases↗