Search PubMed⌕ Search

Biomedical subjects

P Cummins

Publications and source records attributed to P Cummins.

53 records · Page 3Linked to original sources
PubMed1981

The effect of prolonged administration of propranolol and timolol on the growth and the heart of growing rabbits.

1. The effect of prolonged administration of beta-adrenoreceptor-blocking agents was studied in growing rabbits. Equivalent doses of propranolol and timolol were given parenterally for 8 weeks. 2. Animals given propranolol had a significantly lower heart rate than that in the controls. After subcutaneous injection, plasma propranolol levels were twice those obtained after intraperitoneal injection. 3. Growth rate of animals given propranolol intraperitoneally was significantly less than controls, whereas animals given propranolol subcutaneously or timolol intraperitoneally grew normally. Reduced growth rate was associated with reduced food intake and was not related to the beta-adrenoreceptor-blocking activity of the drugs. 4. At the end of the experiment the heart and other organs were examined. beta-Adrenoreceptor blockade produced no significant changes in ventricular size or water content, and no significant changes in ultrastructure were found.

Animals↗
PubMed1981

Radioimmunoassay of human cardiac tropomyosin in acute myocardial infarction.

1. Tropomyosin was prepared from fresh human myocardium and antisera raised in rabbits. A sensitive radioimmunoassay was developed for the detection of human cardiac tropomyosin in human sera down to levels of 1 ng/ml. 2. Values for human cardiac tropomyosin in normal patients ranged from less than 1 to 3 ng/ml. In 18 patients with acute myocardial infarction all had elevated tropomyosin levels ranging from 41 to above 200 ng/ml with a mean peak level of 101 ng/ml. In this study there were no false positive or false negative results. 3. In the initial stages of infarction the time course of appearance and peak levels of cardiac tropomyosin, total creatine kinase and creatine kinase MB isoenzyme were similar. Although total creatine kinase and creatine kinase MB isoenzyme levels were normal after 72 h in patients with single, uncomplicated infarction, cardiac tropomyosin levels were still significantly elevated above normal after this time, being 30-60% of peak values. 4. Radioimmunoassay of human cardiac tropomyosin may prove useful in the diagnosis and in the management of patients with acute myocardial infarction, particularly in the long-term postinfarction period.

Adult↗
PubMed1981

Heart antibodies in cardiomyopathies.

The reported frequency of circulating heart reactive antibodies in cardiomyopathies has varied and their significance is unknown. In this study such antibodies were sought in patients with primary congestive and hypertrophic cardiomyopathies and other heart diseases. Standard "single sandwich" and the more sensitive "double sandwich" indirect immunofluorescence techniques failed to disclose a significant difference between any cardiomyopathic group and controls in repeated experiments. With both techniques results were subject to considerable method-specific artefacts and observer variation. No published work associating heart antibodies detected by immunofluorescence methods with cariomyopathies adequately takes these into account.

Autoantibodies↗
PubMed1980

Human atrial and ventricular myosin light-chains subunits in the adult and during development.

1. Myosin was isolated from human right- and left-atrial and -ventricular myocardium, and examined both in adult subjects and at different stages during pre- and post-natal development. 2. The myosin light-chain subunits in the atria and ventricles were different when characterized by isoelectric focusing and subsequent two-dimensional poly-acrylamide-gel electrophoresis. 3. No differences were observed between the light-chain subunits in the right and left ventricle at any stage of development. 4. The foetal ventricle contained a characteristic light chain that was a major component throughout the latter half of gestation. This foetal light chain, which disappeared in the postnatal period, could not be distinguished from adult atrial light chain 1 on two-dimensional electrophoresis. 5. Myosin in the adult atria, particularly the left, contained components similar to ventricular light-chain components. 6. The possible stimuli for the observed changes in myosin light-chain expression are discussed in relation to the known physiological changes occurring during development.

Adult↗
PubMed1980

Foetal myosin light chain in human ventricle.

Myosin light chain subunits from adult human atria and ventricle were characterized by two-dimensional gel electrophoresis. Atrial (ALC-1 and ALC-2) differed from ventricular (VLC-1 and VLC-2) light chains. Foetal (18--21 week) ventricle contained VLC-1 plus a foetal light chain (FLC-1) which could not be distinguished from adult ALC-1. Myosin FLC-1 was gradually lost from the ventricle and replaced by VLC-1 during foetal development and in the immediate postnatal period.

Age Factors↗
PubMed1980

Myosin adenosinetriphosphatase activity and light chain subunit composition of human right and left ventricle.

Myosin was isolated from the free right and left ventricular wall of normal adult human myocardium and purified until actin contamination was considered negligible as judged by sodium dodecyl sulphate polyacrylamide gel electrophoresis and adenosine triphosphatase assay in the presence of magnesium chloride. Ca2+ and K+ ethylenediaminetetra-acetic acid activated adenosine triphosphatase activities were determined in the presence of 3 mmol.litre-1 adenosine triphosphate. Myosin light chain subunits, VLC-1 and VLC-2, were analysed by polyacrylamide gel electrophoresis using: (i) sodium dodecyl sulphate at pH 7.0; (ii) 6 mol.litre-1 urea at pH 8.5; and (iii) isoelectric focusing in 9.2 mol.litre-1 urea over the pH range 4 to 6. No inherent differences in enzymic or physiochemical properties of the myosins from the human right and left ventricle were observed. Similar results were obtained in the baboon and dog.

Adenosine Triphosphatases↗
PubMed1979

Crystal structure and molecular interactions of tropomyosin.

The three-dimensional structure of tropomyosin filaments has been determined by X-ray crystallography. The ends of the molecules were located by reference to the single pair of cysteine residues. Departures from the alpha-helical-coiled coil conformation may occur in localised domains along the molecule as well as at the overlapping ends.

Amino Acid Sequence↗
PubMed1978

Troponin I from human skeletal and cardiac muscles.

1. Myofibrils from human skeletal muscle contained regulatory proteins exhibiting similar electrophoretic behaviour to those present in rabbit skeletal muscle. 2. All human skeletal muscles examined contained two forms of troponin I corresponding to the forms already characterized in fast and slow rabbit muscle. 3. The ratios of the amounts of the two forms of troponin I in different human skeletal muscles were not identical with the ratios for the type 1 to type 2 fibres published in the literature. The ratios could, however, be arranged in the same rank order. 4. Primate heart contained a single form of troponin I different in molecular weight and amino acid composition from the skeletal forms. 5. A monospecific antiserum to human cardiac troponin I was prepared in the sheep and shown not to react with the fast or slow skeletal-muscle forms of troponin I from human and other species. 6. The anti-(human cardiac-muscle troponin I) reacted with the cardiac troponin I from the human, baboon, rabbit and rhesus monkey. Positive reactions were also obtained with urea extracts of whole cardiac tissue.

Amino Acids↗
PubMed1974

Chemical and immunochemical characteristics of tropomyosins from striated and smooth muscle.

1. On electrophoresis in dissociating conditions the tropomyosins isolated from skeletal muscles of mammalian, avian and amphibian species migrated as two components. These were comparable with the alpha and beta subunits of tropomyosin present in rabbit skeletal muscle. 2. The alpha and beta components of all skeletal-muscle tropomyosins contained 1 and 2 residues of cysteine per 34000g respectively. 3. The ratio of the amounts of alpha and beta subunit present in skeletal muscle tropomyosins was characteristic for the muscle type. Muscle consisting of slow red fibres contained a greater proportion of beta-tropomyosin than muscles consisting predominantly of white fast fibres. 4. Mammalian and avian cardiac muscle tropomyosins consisted of alpha-tropomyosin only. 5. Mammalian and avian smooth-muscle tropomyosins differed both chemically and immunologically from striated-muscle tropomyosins. 6. Antibody raised against rabbit skeletal alpha-tropomyosin was species non-specific, reacting with all other striated muscle alpha-tropomyosin subunits tested. 7. Antibody raised against rabbit skeletal beta-tropomyosin subunit was species-specific.

Amphibians↗
PubMed1973

The subunits and biological activity of polymorphic forms of tropomyosin.

1. Free thiol groups were shown to be essential for tropomyosin to effect maximum inhibition of the Ca(2+)-stimulated ATPase (adenosine triphosphatase) of desensitized actomyosin but not for its activity in the regulatory-protein system. 2. The activity of tropomyosin on the Mg(2+)-stimulated ATPase in the regulatory-protein system was more susceptible to enzymic digestion and thermal denaturation than its effect on the Ca(2+)-stimulated ATPase of actomyosin. 3. Rabbit skeletal tropomyosin migrated as two distinct electrophoretic components in the presence of sodium dodecyl sulphate and urea and as four components on isoelectric focusing in urea. 4. The two main subunits present in rabbit skeletal tropomyosin, which have been named the alpha- and beta-chains, were separated by chromatography on CM-cellulose in urea at pH4.0. They were shown to be virtually identical in amino acid composition, except for their cysteine contents. The alpha(2) and beta(2) forms of tropomyosin possessed all the biological activities characteristic of normal tropomyosin preparations. 5. In skeletal muscle the alpha and beta components of tropomyosin were present in the proportion of 4:1. Somewhat lower ratios were obtained in skeletal muscle of sheep, pig and cow. 6. Tropomyosin isolated from cardiac muscle and Pecten maximus adductor muscle migrated as one band only. These tropomyosins possessed similar biological activities to those isolated from skeletal muscle.

Actomyosin↗
PubMedDate not supplied

A comparison of the serologic responses to oral and injectable trivalent poliovirus vaccines.

United States children two months of age were randomly assigned to two groups that received either the commercially available oral trivalent poliovirus vaccine ( OPV ) or an injectable (inactivated) trivalent poliovirus vaccine (IPV) with a confirmed minimum D-antigen content of 27, 3.5, and 29 units for poliovirus types 1, 2, and 3, respectively. Vaccine was given at two, four, and 18 months of age. Sera obtained from 439 children at two, four, and six months of age and from 85 children at 18 and 20 months of age were examined for neutralizing antibodies. The percentage of children with detectable antibodies and the reciprocal geometric mean titers were similar for both groups at two months of age for antibodies to all three poliovirus types. At 20 months of age, all children but one had detectable antibodies to all three poliovirus types. Significantly higher geometric mean titers against types 2 and 3 were noted at 20 months of age for the IPV group.

Age Factors↗