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P S Cassidy

Publications and source records attributed to P S Cassidy.

10 recordsLinked to original sources
PubMed1994

Data verification in the residue laboratory.

Residue analysis frequently presents a challenge to the quality assurance (QA) auditor due to the sheer volume of data to be audited. In the face of multiple boxes of raw data, some process must be defined that assures the scientist and the QA auditor of the quality and integrity of the data. A program that ensures that complete and appropriate verification of data before it reaches the Quality Assurance Unit (QAU) is presented. The "Guidelines for Peer Review of Data" were formulated by the Residue Analysis Business Center at Ricerca, Inc. to accommodate efficient use of review time and to define any uncertainties concerning what are acceptable data. The core of this program centers around five elements: Study initiation (definitional) meetings, calculations, verification, approval, and the use of a verification checklist.

Chemistry Techniques, Analytical↗
PubMed1981

Exogenous calmodulin increases Ca2+ sensitivity of isometric tension activation and myosin phosphorylation in skinned smooth muscle.

We have investigated the effect of exogenous calmodulin on chicken gizzard or rabbit ileum smooth muscle functionally skinned by mechanical grinding or exposure to Triton X-100 detergent. We found that specific protein inhibitor, modulator binding protein, caused a loss of Ca2+-activated tension which was restored by subsequent treatment with calmodulin. Calmodulin at 5 microM increased 10-fold the speed of development of isometric tension while it had no significant effect on the rate of relaxation or on maximum tension at high Ca2+ concentrations. The Ca2+ sensitivity of steady state tension and LC20 phosphorylation were also increased by 5 microM calmodulin. These results are consistent with a calmodulin-regulated light chain kinase/phosphatase system being responsible for activation of tension in smooth muscle.

Animals↗
PubMed1981

Calcium-regulatory mechanisms. Functional classification using skinned fibers.

The primary purpose of this study was to determine whether various agents (adenosine 3-thiotriphosphate [ATP gamma S], trifluoperazine [TFP], troponin I, the catalytic subunit of the cyclic adenosine 3',5'-monophosphate dependent protein kinase [C-subunit], and calmodulin [CaM]) could be used to classify skinned fiber types, and then to determine whether the proposed mechanisms for Ca2+ regulation were consistent with the results. Agents (ATP gamma S, TFP, C-subunit, CaM) expected to alter a light chain kinase-phosphatase system strongly affect the Ca2+-activated tension in skinned gizzard smooth muscle fibers, whereas these agents have no effect on skinned mammalian striated and scallop adductor fibers. Troponin I, which is known to bind strongly to troponin C and CaM, inhibits Ca2+ activation of skinned mammalian striated and gizzard fibers but not scallop adductor muscle. The results in different types of skinned fibers are consistent with proposed mechanisms for Ca2+ regulation.

Adenosine Triphosphate↗
PubMed1980

Calcium-activated tension: the role of myosin light chain phosphorylation.

Small strips of intestinal or arterial smooth muscle composed of many functionally skinned muscle cells (nonfunctional sarcolemma), skinned skeletal single fibers, or bundles of skinned cardiac fibers were used to test the hypothesis that a myosin light chain kinase/phosphatase system is responsible for the activation of contraction. The results showed that in smooth muscle: 1) there is a close correlation between the degree of phosphorylation of the myosin light chains and tension development: 2) irreversible thiophosphorylation of myosin light chain results in irreversible activation of tension; and 3) inhibition of the light chain kinase by phenthiazines results in dephosphorylation of the myosin light chains and inactivation of tension in the presence of Ca2+. In contrast, in skinned striated muscle fibers 1) there is no correlation between phosphorylation and tension, 2) light chains could not be thiophosphorylated, and 3) phenothiazines did not affect Ca2+-activated tension. These findings indicate a Ca2+-sensitive light chain kinase/phosphatase system is responsible for the activation of smooth muscle, but no similar evidence was found for such a system in striated muscle.

Animals↗
PubMed1979

Chicken gizzard: relation between calcium-activated phosphorylation and contraction.

Of the proteins in mechanically disrupted chicken gizzard fibers (no functional sarcolemma) only the 20,000-dalton light chains of myosin underwent large Ca2+-and Sr2+-dependent changes in phosphorylation. Phosphorylation closely corresponded with the Ca2+- and Sr2+-activated tensions. Adenosine 5'-O (3'-thiotriphosphate) only in the presence of Ca2+ induced irreversible Ca2+-insensitive activation of tension and thiophosphorylation of the 20,000-dalton light chains, and blocked incorporation of 32P from [gamma-32P]adenosine triphosphate into the myosin light chains.

Animals↗
PubMed1976

Transformation of mouse cells by fusion with chronic granulocytic leukemia cells: possible role of human chromosome.

In vitro properties of somatic cell hybrids between non-malignant B82 mouse fibroblasts and human chronic granulocytic leukemia spleen cells include lack of cell density-dependent growth inhibition and growth in soft agar. These phenotypic expressions of cell transformation appear linked to the retention by the cells of chromosome 7 from the human leukemic genome.

Animals↗