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Biomedical subjects

W Lehman

Publications and source records attributed to W Lehman.

At least 55 records · Page 3Linked to original sources
PubMed1984

The characterization of invertebrate troponin C.

TNCs from lobster, mussel, and squid migrated with rabbit TNC at an apparent mol. wt of 18,000. Electrophoretic mobilities in the presence or absence of Ca2+ were compared: the electrophoretic mobility of rabbit TNC was greater in the presence of Ca2+ than it its absence, but all invertebrate TNCs tested migrated identically, whether Ca2+ was present or not. The Ca2+-binding capacity of invertebrate TNCs was only one Ca2+ ion per molecule. The alpha-helix contents in the presence or absence of Ca2+ were compared: rabbit TNC changed by a value of 16% and invertebrate TNCs by 4%. Antibodies to loligo TNC did not cross-react with rabbit TNC, but did interact with their molluscan TNCs.

Animals↗
PubMed1983

The ionic requirements for regulation by molluscan thin filaments.

Initial studies on molluscan muscle regulation indicated that thin filaments do not confer Ca2+-dependence on vertebrate myosin ATPase, and hence that molluscan muscles do not possess thin filament-linked regulatory systems. Subsequently it was shown that molluscan thin filaments do, in fact, impart Ca2+-sensitivity but only at Mg2+ concentrations greater than those used in the earlier studies. In the present study it is shown that Mg2+ prevents significant dissociation of tropomyosin and troponin subunits from thin filaments at the low monovalent ion concentrations typically employed to assay actomyosin ATPase; as a result Mg2+ allows expression of the molluscan thin filament regulatory system under these conditions.

Adenosine Triphosphatases↗
PubMed1983

The distribution of troponin-like proteins on thin filaments of the bay scallop, aequipecten irradians.

Antibodies reacting either with bay scallop troponin-C-like protein or both bay scallop troponin-I-like protein and a possible scallop troponin-T were used to determine the distribution of the troponin complex on bay scallop striated muscle thin filaments. Both antibodies cause thin filaments to associate laterally and electron microscopy of such aggregates indicates a periodicity of approximately 38 nm, a distribution characteristic of proteins comprising the troponin complex in vertebrate and arthropod striated muscle. These studies therefore provide additional evidence for the presence of thin filament-linked regulation in bay scallops.

Animals↗
PubMed1983

Retention in outpatient drug free treatment clinics.

This study examined time in treatment and the percentage of clients who quit or were expelled from drug treatment clinics as dependent measures in a general model including socioecological aspects of the clinic neighborhood environment, the clinic structure (attributes, e.g., size, and services and staffing), and the client composition of the clinic (sociodemographic and deviance). In this study the clinic was the unit of analysis. The data were analyzed by means of path analysis, for (1) drug free outpatient, nonopiate orientation (DFO-N) and (2) drug free outpatient, opiate orientation (DFO-O). There were 204 DFO-N and 130 DFO-O clinics. The path analytic model proved to be useful for the explanation of clinic retention outcomes. The socioecological variables predicted the types of clients who entered treatment. These in turn along with clinic attributes were significant predictors of clinic retention. Clinic attributes also predicted clinic services and staffing. The results suggested that both clinic variables and client composition variables are important predictors of clinic retention.

Adult↗
PubMed1983

Agency differences in posttreatment outcomes: a follow-up of drug abuse treatment clients.

The present study examined variations in posttreatment outcomes for clients treated in the same modality but in different treatment agencies located across the United States. Three modalities were studied, represented by seven methadone maintenance (MM) programs, seven therapeutic community (TC) programs, and nine outpatient drug-free (DF) programs. Agency differences within MM and TC programs were not significantly different on posttreatment outcomes for opioid use, nonopioid use, alcohol use, productive activities, and criminality. There were significant outcome differences among the DF agencies, but they were explained by variations in the background characteristics of the particular types of clients served by each agency. In particular, these posttreatment outcome differences appeared to be related to programs treating primarily opioid addicts versus primarily nonopioid users.

Alcoholism↗
PubMed1982

Addict death rates during a four-year posttreatment follow-up.

Mortality rates were examined among 3,324 Black and White daily opioid drug users for a four-year period following treatment in community-based agencies located across the United States. A total of 179 of these addicts died during this follow-up period, yielding a death rate of 15.2 per 1,000 person-years at risk. When adjusted for age, addict death rates were found to be three to 14 times higher than those in the general US population. Life table analysis was also used to examine these rates in relation to client demographic, background, and treatment variables obtained prospectively, both prior to and during treatment. Age, alcohol use, and criminal history were positively associated with higher death rates. With regard to causes of death, age proved to be the only significant predictor; older addicts (over 30) had the highest percentages of deaths due to "natural" causes, while over three-fourths of the deaths among younger addicts were drug related or involved violence.

Adult↗
PubMed1980

The stoichiometry and location of troponin I- and troponin C-like proteins in the myofibril of the bay scallop, Aequipecten irradians.

Localization and quantification studies were carried out on bay-scallop (Aequipecten irradians) striated-muscle troponin C- and troponin I-like proteins. Indirect immunofluorescence microscopy of scallop myofibrils stained with either rabbit anti-(scallop troponin I) or anti-(scallop troponin C) antibodies shows staining of all I-bands observed. The results of quantification studies using sodium dodecyl sulfate poly-acrylamide-gel electrophoresis of untreated scallop myofibrils, washed scallop myofibrils, and isolated scallop thin filaments indicate an actin/tropomyosin/troponin-C molar rationn of 7:1:1. The molar ratio for troponin I could not be determined in untreated myofibrils because of interfering bands; in washed myofibrils a value of 0.6 mol of troponin I/mol of tropomyosin was found. Purified scallop troponin C binds Ca2+ and interacts with scallop troponin I to relieve troponin I-induced inhibition of actomyosin ATPase. Although scallop troponin C is an acidic protein, it appears to be less acidic than troponin C from higher organisms. A calmodulin-like protein has been isolated from scallop striated muscle that activates bovine brain phosphodiesterase to the same extent as does brain calmodulin. Its amino acid composition and its electrophoretic mobility on alkaline 6 M-urea/polyacrylamide gels differs from that of scallop troponin C, and it appears not to be associated with thin filaments.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

Troponin-like proteins from muscles of the scallop, Aequipecten irradians.

Ca2+ regulation of molluscan actomyosin adenosine triphosphatase is known to be associated with the myosin molecule. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, however, also suggests the possible presence of troponin, a thin-filament-linked Ca2+-regulatory complex. In the present study, scallop troponin and tropomyosin were prepared and complexed with rabbit actin; the resulting synthetic thin filaments form a Ca2+-dependent actomyosin adenosine triphosphatase with Ca2+-insensitive rabbit myosin, indicating that the troponin in scallops is potentially functional. Scallop troponin I was isolated and mixed with chicken troponin C and troponin T, forming a functional hybrid troponin complex, indicating that scallop and vertebrate troponins may act by a common mechanism. Densitometry of sodium dodecyl sulphate/polyacrylamide gels reveals that in synthetic thin filaments there are larger amounts of troponin than are present in native thin filaments. Amounts present in the intact muscle were not determined.

Actins↗
PubMed1977

Calcium ion-dependent myosin from decapod-crustacean muscles.

Ca2+ regulation of arthropod actomyosin adenosine triphosphatase is associated with both the thin filaments, as in vertebrates, and with the myosin, as in molluscs. The actomyosin of decapod-crustacean fast muscles was previously considered to be an exception, displaying only a Ca2+-regulatory system linked to the thin filaments and not a myosin-linked regulatory system. In the present study, myosin regulation is demonstrated in a variety of decapod muscles when they are tested under more physiological ionic conditions. Myosin regulation is shown by using mixtures of pure rabbit actin with myofibrils, with actomyosin and with purified myosin, and in each case the adenosine triphosphatase is Ca2+ dependent. Myosin regulation may also occur in vertebrate striated muscle, but seemingly is lost during purification of the myosin.

Actomyosin↗
PubMed1976

The stoichiometry of the components of arthropod thin filaments.

Limulus thin filaments confer calcium sensitivity on calcium-independent myosins and contain in addition to actin and tropomyosin, three troponin components. The molar ratio of actin:tropomyosin:troponin sub-unit T (TN-T): troponin sub-unit C (TN-C) is approximately 7:1:1:1, as in vertebrates, but twice the amount of the troponin sub-unit I (TN-I) may be present. Arthropod troponin binds approximately 1 mole Ca/mol troponin, a significantly smaller amount than bound by vertebrate troponin.

Actins↗