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Biomedical subjects

P Cummins

Publications and source records attributed to P Cummins.

At least 37 records · Page 2Linked to original sources
PubMed1990

Uptake of radioiodinated cardiac specific troponin-I antibodies in myocardial infarction.

STUDY OBJECTIVE: To examine the potential diagnostic value of the cardiac myofibrillar protein troponin-I as a target for radiolabelled antibodies in detecting heart damage, the uptake of 131I labelled polyclonal cardiac troponin-I Fab was investigated in necrotic myocardial cells in canine myocardial infarction. DESIGN: Cardiac specific troponin-I Fab was prepared by immunoaffinity chromatography and injected 5 h after coronary artery ligation. Whole body gamma camera scintigraphic images were taken after the injection, and heart slices were examined for the presence of labelled antibody. SUBJECTS: Adult dogs of either sex (n = 6) were used. MEASUREMENTS AND MAIN RESULTS: Scintigraphic whole body images at 24 and 40 h after troponin-I Fab injection showed increased 131I-localisation over the apical region of the heart which corresponded to the infarcted areas. Localisation in infarcted tissue was confirmed in isolated heart and histochemically stained heart slice images. Uptake of 131I Fab was up to 24 times greater in necrotic than in normal myocardium and was inversely related to regional blood flow as determined by 141cerium microsphere distribution. Confirmation that 131I Fab uptake was due to direct binding to troponin-I in necrotic cells was obtained by coinjection of non-immune 125I labelled Fab. CONCLUSIONS: Results indicate that troponin-I could act as a suitable target for detecting myocardial necrosis.

Animals↗
PubMed1988

Effects of chronic sympathectomy on muscle fibre composition ISO-myosin patterns, protein synthesis and calcium content in canine gracilis muscle.

We have previously reported functional and histological studies in five beagle dogs with unilateral lumbar sympathectomy. Three months later, fatiguability in the gracilis muscles was increased on the denervated sides, and this was associated with an increase in the relative distribution of FT fibres. Biochemical studies now show that these changes were associated with an increase in cytosolic protein without change in DNA content; this is consistent with an increase in cell size. There was a reduction in the proportion of slow myosin light chain isoforms from 50 +/- 7 to 34 +/- 6%. Noradrenaline levels were increased on the denervated sides but this may reflect greater vascularity. Calcium content did not correlate with fibre type but there was a positive relation with both noradrenaline content (r = 0.73; P less than 0.05) and DNA content (r = 0.84; P less than 0.05). It is concluded that sympathectomy induces several biochemical changes in skeletal muscle which constitute a change and increase in fast myosin light chain synthesis and a corresponding fibre type transformation.

Animals↗
PubMed1987

Cardiac-specific troponin-I radioimmunoassay in the diagnosis of acute myocardial infarction.

The cardiac isotype of the myofibrillar contractile protein, troponin-I, is located specifically in the mammalian heart. A sensitive radioimmunoassay has been developed to detect human and nonhuman primate cardiac troponin-I in serum down to 10 ng/ml. Immunochemical cross reactivity with skeletal troponin-I was only 2% and was species nonspecific. Normal patient levels of cardiac troponin-I are about 10 ng/ml. In patients with acute myocardial infarction (n = 32), serum cardiac troponin-I was elevated within 4 to 6 hours, reached a mean peak level of 112 ng/ml (range 20 to 550 ng/ml) at 18 hours, and remained above normal for up to 6 to 8 days following infarction. Peak cardiac troponin-I correlated with peak creatine kinase (CK) MB isoenzyme (r = 0.75). In subjects (n = 34) with skeletal muscle damage (total CK = 338 to 5384 IU/L), cardiac troponin-I levels were not elevated above normal, although CK-MB isoenzyme was elevated in some patients. Cardiac troponin-I levels were normal or slightly elevated in patients with ischemic heart disease and were normal in patients with chest pain of noncardiac origin. Immunoassay of cardiac troponin-I could be a valuable diagnostic aid in the cardiac-specific detection of cell necrosis.

Adult↗
PubMed1987

Cardiac specific troponin-I release in canine experimental myocardial infarction: development of a sensitive enzyme-linked immunoassay.

A canine model of experimental myocardial infarction has been used to investigate the release of troponin-I as a specific diagnostic indicator of cardiac necrosis. An enzyme-linked immunoassay was established to detect canine cardiac troponin-I in serum. Polyclonal antisera to cardiac troponin-I showed low cross-reactivity with skeletal muscle troponin-I which was completely removed by immunoadsorption. The cardiac specific ELISA time was 5 to 6 h. Assay sensitivity was 4 ng cardiac troponin-I/ml with an upper limit of 200 ng/ml in neat serum. Mean normal circulating levels of cardiac troponin-I were 15.6 ng/ml compared with an estimated 11 ng/ml in man [Cummins, B. et al. Am Heart J 113, 1333-1344 (1987)]. After experimental infarction, cardiac troponin-I was detectable within 4 to 6 h and peaked between 10 to 16 h post-ligation. Cardiac specific creatine kinase-MB isoenzyme was released with a similar initial time course. Mean peak cardiac troponin-I and CK-MB were elevated 6- and 10-fold respectively. Cardiac troponin-I levels were elevated for up to 200 h post-ligation compared to a maximum of 100 h for CK-MB. The prolonged time course of troponin-I release was comparable to that seen clinically [Cummins, B., et al. Am Heart J 113, 1333-1344 (1987)]. Histochemical infarct size correlated well with CK-MB but less so with troponin-I release. This may reflect the complex nature of intracellular troponin-I degradation and loss from necrotic cardiac tissue.

Animals↗
PubMed1987

Comparison of serum cardiac specific troponin-I with creatine kinase, creatine kinase-MB isoenzyme, tropomyosin, myoglobin and C-reactive protein release in marathon runners: cardiac or skeletal muscle trauma?

Problems arise in distinguishing skeletal from cardiac muscle trauma on the basis of serum enzyme tests following severe muscle exercise. The contributions of cardiac and skeletal sources have been assessed in eleven marathon runners by measuring pre- and post-race serum levels of cardiac-specific myofibrillar troponin-I together with total creatine kinase, creatine kinase-MB isoenzyme, myoglobin, myofibrillar tropomyosin and C-reactive protein. Total creatine kinase, creatine kinase-MB isoenzyme, tropomyosin and myoglobin were significantly elevated above pre-race levels in all runners between 1 h and 128 h post-race. Neither mean cardiac troponin-I nor C-reactive protein was elevated post-race. Nine out of sixty-three samples fulfilled conventional positive criteria for cardiac muscle damage on the basis of combined creatine kinase and creatine kinase-MB isoenzyme levels. Six runners had one or more positive samples. No samples had levels above twice the upper normal limit for either cardiac troponin-I or C-reactive protein. Correlation analysis of levels in each sample indicated skeletal and not cardiac muscle as the source of raised serum protein.

Athletic Injuries↗
PubMed1986

A comparison of myosin light chain subunits in the atria and ventricles of mammals.

An SDS-electrophoretic comparison of atrial and ventricular myosin light chain isotypes was performed in mouse, rat, rabbit, dog, pig, rhesus monkey, baboon, human and cow heart. Light chains 1 and 2 in atria and ventricles differed in all species with the possible exception of the rhesus monkey. Relative migration of atrial and ventricular LC-2 isotypes was similar in all species but LC-1 isotypes varied in relative migration rates suggesting increased primary sequence heterogeneity. Order of migration was VLC-1 less than ALC-1 less than ALC-2 less than VLC-2 in mouse, rat, rabbit, dog, baboon and cow and ALC-1 less than VLC-1 less than ALC-2 less than VLC-2 in pig and human heart. No obvious relationship existed between electrophoretic pattern and phylogenetic evolution.

Animals↗
PubMed1986

Cardiac myosin light and heavy chain isotypes in tetralogy of Fallot.

Myosin isotype composition was examined in ventricular infundibular muscle from 40 patients with tetralogy of Fallot, aged from 7 months to 38 years. Results were compared with normal samples of ventricular infundibulum from subjects in the same age range, from 18-20 week old fetuses to 6 month old neonates, and from 43-81 year old adults. Myosin light chain isotypes were examined by one dimensional and two dimensional gel electrophoresis and quantified densitometrically. Heavy chain isotypes were examined by electrophoresis of whole heavy chains and peptide mapping after limited proteolytic digestion with chymotrypsin. At mid-gestation in normal tissues, only ventricular light chain 2 was present but light chain 1 consisted almost equally of atrial and ventricular isotypes. Amounts of atrial light chain 1 declined towards birth and disappeared during the first year after birth, gradually being replaced by ventricular light chain 1. Relative amounts of total light chains 1 and 2 remained equal. In tetralogy of Fallot atrial light chain 1 expression did not cease neonatally with mean values of 11.8% of total light chain 1 present between 7 months and 2 years, decreasing to 1.7% at 6.5-12 years and then increasing again to 3.4% in adults. A value of 34% atrial light chain 1 was present in one subject. As in normal subjects, equimolar amounts of total light chains 1 and 2 were retained. No evidence of new light chain isotypes was found in tetralogy of Fallot. Heavy chain expression was constant in normal infundibulum with only beta-heavy chain (V3 isozyme) present in the fetus, neonate, and adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Myosin transitions in the bovine and human heart. A developmental and anatomical study of heavy and light chain subunits in the atrium and ventricle.

Transitions in cardiac myosin isotypes occur in response to a variety of stimuli. These are well documented in small, but less so in larger, mammals where data on quantitative isotype composition of normal atria and ventricles are scarce. In this study, heavy and light chain isotypes were examined in fetal, neonatal, and adult bovine and human hearts. Defined anatomical areas of chambers were studied, and detailed mapping of isotypes was conducted on bovine atria. Heavy chain isotype quantification was carried out electrophoretically either after peptide mapping or by a new technique for separating whole cardiac alpha- and beta-heavy chains capable of detecting 5% of either isotope. Atrial and ventricular light chains were resolved electrophoretically, and all isotypes were quantified densitometrically. Beta-Heavy chain was almost exclusively expressed (greater than 95%) in the ventricles at all ages except in the bovine neonate. Ventricular light chains predominated in the adult ventricle, but atrial light chain 1 was present at mid-gestation. This was replaced by ventricular light chain 1 in the neonate with no transitions in light chain 2 isotypes. Transitions were more marked in the atria. Only alpha-heavy chains were detected at mid-gestation, but beta-heavy chain increased toward birth. After a decline in the neonatal period, beta-heavy chain levels usually increased in the adult. Atrial light chains were the main isotypes in the atria, but ventricular light chain 2 was the major adult bovine atrial isotype. Transitions in isotypes were significant at birth as in smaller mammals. No close relationship existed between heavy and light chain transitions. Significant anatomical variation in bovine atrial isotype expression was present, and may reflect functional demand in each area.

Adolescent↗
PubMed1985

Isolation of cardiac myosin light-chain isotypes by chromatofocusing. Comparison of human cardiac atrial light-chain 1 and foetal ventricular light-chain 1.

Cardiac myosin light chain isotypes have been resolved using chromatofocusing, a new preparative column chromatographic technique. The method relies on production of narrow-range, shallow and stable pH gradients using ion-exchange resins and buffers with even buffering capacity over the required pH range. Light chains were resolved in order of decreasing isoelectric point in the pH range 5.2-4.5. Gradients of delta pH = 0.004-0.006/ml elution volume were achieved which were capable of resolving light chains with isoelectric point differences of only 0.03. Analytical isoelectric focusing of light chains in polyacrylamide gels could be used to predict the results of preparative chromatofocusing for method development. Chromatofocusing was capable of resolving human and bovine cardiac light chain 1 and 2 subunits, atrial (ALC) and ventricular (VLC) light chain isotypes and homologous VLC-2 and VLC-2* light chains. The technique was used to purify and resolve the human foetal ventricular light chain 1 (FLC-1) from adult ventricular light chain 1 (VLC-1) present in foetal ventricles and the atrial light chain 1 (ALC-1) in adult atria. Comparative peptide mapping studies and amino acid analyses were carried out on FLC-1 and ALC-1. No differences were detected between FLC-1 and ALC-1 using three different proteases and amino acid compositions were similar with the exception of glycine content. The studies indicate that FLC-1 and ALC-1 are homologous, and possibly identical, light chains. Comparison of human FLC-1/ALC-1 with VLC-1 suggested marked structural and chemical differences in these light chain isotypes, in particular in the contents of methionine, proline, lysine and alanine residues. Differences in the contents of these residues were also apparent in the corresponding bovine atrial and ventricular light chains [Wikman-Coffelt, J. & Srivastava, S. (1979) FEBS Lett. 106, 207-212]. The latter three residues are known to be rich in the N-termini of cardiac and skeletal light chain 1 isotypes, an area that has been implicated in actin binding, suggesting that atrial and ventricular light chains may differ functionally in this region.

Amino Acids↗
PubMed1984

Regulatory proteins of the myocardium. Atrial and ventricular tropomyosin and troponin-I in the developing and adult bovine and human heart.

The myofibrillar regulatory proteins, troponin-I and tropomyosin were isolated from human and bovine atria and ventricles and studied in the adult and during foetal development. A number of analytical electrophoretic procedures were employed to detect possible atrial, ventricular or foetal specific forms of these proteins. Biological activity of the regulatory protein complex during development was monitored by measuring the calcium sensitivity of the myofibrillar Mg2+ activated ATPase. No evidence was obtained for unique or foetal specific forms of either troponin I or the alpha and beta subunits of tropomyosin. Although the atria and ventricles possess markedly different contractile properties, no difference was observed between the two chambers at any developmental stage in the relative amounts of alpha and beta tropomyosin present. However, the relative amount of beta tropomyosin increased by 50% in both atria and ventricles during the transition from foetus to adult. A strong inverse correlation existed (r = -0.92) between beta tropomyosin content and heart rate in different species and at different developmental stages in both cardiac chambers. The relative invariance of tropomyosin and troponin I forms in the myocardium was reflected in the high and constant level of calcium sensitivity of myofibrillar Mg2+ ATPase retained in the atria and ventricles throughout development. The implications of these results in relation to control of cardiac contraction are discussed.

Adenosine Triphosphatases↗
PubMed1984

The effects of acute and chronic beta-adrenoceptor blockade on the myofibrillar contractile system in the dog heart.

Electrophoretic and enzyme techniques have been used to study the structure and function of the contractile protein system in the myocardium of dogs before and after beta-adrenoceptor blockade. Animals were examined after acute beta-adrenoceptor blockade by using intravenous atenolol (0.2 mg/kg) and following chronic therapy with oral atenolol (100 mg twice daily) for a mean period of 106 days. Two-dimensional polyacrylamide-gel electrophoretic techniques were used to examine the myocardial contractile and regulatory proteins present in endomyocardial biopsy specimens obtained after acute and chronic beta-adrenoceptor blockade. No differences in charge, molecular weight or the relative proportions of actin, myosin light chains, tropomyosin or troponin-C were seen after either acute or chronic beta-adrenoceptor blockade. The maximal activity and calcium sensitivity of the myofibrillar adenosine triphosphatase (ATPase) was also unchanged after acute and chronic atenolol therapy. It is concluded that beta-adrenoceptor blockade has no significant adaptive effect on the structural or functional properties of the myofibril.

Adenosine Triphosphatases↗
PubMed1984

Contractile protein transitions in human cardiac overload: reality and limitations.

Attention has focused on possible defects at the level of the contractile proteins in myocardial hypertrophy and failure. In small mammals such as the rat and rabbit, myofibrillar and myosin ATPases are depressed in situations of decreased contractility. Converse increases in enzymic activity together with enhanced contractility are seen in the hyperthyroid state. The molecular basis for these changes in enzymic activity is now known to result from transitions in three heavy chain isoenzymes of myosin, V1, V2 and V3 which possess different ATPase activities. Transitions in isoenzyme composition occur during hypertrophy, thyrotoxicosis and development in the myocardium of small mammals. In larger animals such as the rhesus monkey, baboon, cow and in particular, man, only V3, the lowest ATPase isoenzyme can be detected in the normal ventricle and this is the only form present throughout development. Confirmation of the lack of developmental transitions in myosin heavy chains expressed in man is also obtained by sensitive peptide mapping techniques. Changes in myosin heavy chain isoenzymes in large mammals as an explanation of depressed contractile function cannot therefore be made on the presently available evidence. Indeed, evidence for lowered ATPase activities in the failing human myocardium is equivocal. Evidence is however provided for transitions in light chain isoenzymes of myosin in situations of cardiac overload. Caution should be exercised in using small animals as models of myocardial hypertrophy and failure in man.

Adenosine Triphosphatases↗
PubMed1984

Metabolic changes in the autotransplanted baboon heart.

Chronic denervation of the heart leads to depletion of tissue catecholamines, giving rise to metabolic abnormalities, including a reduction in cardiac glucose oxidation. Impaired glucose oxidation could cause an increased oxidation of fat, which in turn could lead to development of coronary artery disease. Cardiac glucose oxidation (using 14C-(U),D-glucose) was studied in female baboons, before, and three to five weeks after, autotransplantation. Systemic arterial and coronary sinus samples were analyzed for total CO2 content, O2 content, 14CO2, glucose, lactate, pH, PCO2, and PO2. Tissue for metabolite assays (adenosine-5'-triphosphate [ADP] and creatine phosphate [CP]; glucose-6-phosphate [G6P] and fructose 6-phosphate [F6P] was obtained from the right ventricle before and after autotransplantation in some animals. There were no significant changes. Tissue was also obtained postmortem for analysis of noradrenaline, soluble tyrosine hydroxylase activity, and contractile and regulatory proteins. There was a large decrease in tissue noradrenaline, suggesting almost total sympathetic denervation. The level of tyrosine hydroxylase activity shows that the denervated heart can synthesize dopamine. There were no detectable changes in the contractile or regulatory proteins. In six of the nine baboons successfully studied, there was a distinct decrease in the oxidation of glucose after autotransplantation (P less than 0.05). This indicates that the removal of the sympathetic and parasympathetic nerve supply to the heart affects the ratio of glucose oxidized to other substrates.

Adenosine Triphosphate↗
PubMed1983

Myosin light chain phosphorylation during regional myocardial ischemia.

The extent of cardiac myosin light chain phosphorylation was measured during regional myocardial ischemia in the dog. A multiple-projectile cutter was used to sample adjacent biopsies from the normal and ischemic areas of the myocardium in an open-chested dog heart following 30 min of coronary artery ligation. Measurement of metabolite levels and blood flow in the individual biopsies clearly defined the border zone between normal and ischemic myocardium. Myosin light chain phosphorylation was measured after isoelectric focusing of biopsy samples and subsequent densitometric analysis. A 50% increase in phosphorylation was observed in the ischemic zone which may correlate with the reduced contractility which is a feature of the ischemic myocardium.

Animals↗
PubMed1982

Transitions in human atrial and ventricular myosin light-chain isoenzymes in response to cardiac-pressure-overload-induced hypertrophy.

1. The light-chain subunits of human atrial and ventricular cardiac muscle were examined by two-dimensional polyacrylamide-gel electrophoresis and limited proteolytic digestion. The light-chain patterns in the normal right and left atria were identical. 2. Myosin preparations isolated from right or left atria that had been subjected to cardiac-pressure-overload-induced hypertrophy also contained ventricular light-chain subunits. These were identified by peptide mapping in sodium dodecyl sulphate. 3. Ventricular light chain-2 was the major species in hypertrophied atria, although light chain-1 subsequently appeared in severe pressure-overload-hypertrophied cases. Evidence is presented for the existence of more than one form of ventricular light chain-2. 4. The transition from atrial to ventricular myosin light chains correlated with the degree of pressure-overload hypertrophy in 83 examples of surgically excised atria. 5. The adult atrial light chain-1 was shown to be homologous to the human foetal ventricular light chain-1 [Price, Littler & Cummins (1980) Biochem. J. 191, 571-580] by peptide mapping. 6. A scheme of atrial/ventricular myosin light-chain isoenzyme transitions is discussed in relation to changing contractile properties in cardiac muscle, together with implications for the role of light-chain subunits.

Blood Pressure↗
PubMed1982

Serum levels of acute phase and cardiac proteins after myocardial infarction, surgery, and infection.

C-reactive protein and four other acute phase reactant proteins of non-cardiac, origin (orosomucoid, alpha 1- antitrypsin, heptoglobin, and alpha 2- macroglobulin) were studied serially by laser immunonephelometric assay in sera from 17 patients with myocardial infarction. A similar comparison was made in 57 patients undergoing surgery and 72 patients with acute infection. C-reactive protein was consistently the most sensitive acute phase reactant in all three conditions. After myocardial infarction, a raised serum C-reactive protein level was found on admission in four patients before a rise in creatine kinase MB isoenzyme (CK MB). The peak C-reactive protein level was reached on the third post-infarct day and it then declined over seven days with a half-life similar to myocardial tropomyosin. Serial monitoring of serum C-reactive protein, in parallel with cardiac proteins of short half-life (CK MB) and long half-life (tropomyosin), provides maximal information for diagnosis and for detecting post-infarct complications.

Alpha-Globulins↗