Search PubMed⌕ Search

Biomedical subjects

R J Ellis

Publications and source records attributed to R J Ellis.

At least 109 records · Page 6Linked to original sources
PubMed1986

Purification and properties of ribulosebisphosphate carboxylase large subunit binding protein.

The large subunit binding protein, an abundant plastid protein implicated in the assembly of ribulose-1,5-bisphosphate carboxylase-oxygenase (RubisCO), has been highly purified from leaves of Pisum sativum. The 720 kilodaltons purified binding protein is composed of two types of subunits of 60 and 61 kilodaltons. Highly specific polyclonal antibodies have been raised against the binding protein. The antibodies do not cross-react with the large subunit nor do anti-RubisCO antibodies cross-react with the binding protein. A higher molecular weight form of the binding protein is immunoprecipitated from products of P. sativum polysomes translated in a wheat-germ system, indicating that the binding protein is synthesized by cytoplasmic ribosomes. Immunoblotting reveals the presence of binding protein in extracts of tobacco, wheat and barley leaves and castor bean endosperm.The previously reported dissociation of the binding protein-large subunit complex upon addition of ATP in vitro has been confirmed and the fates of the dissociated subunits further investigated. The dissociated binding protein subunits are not phosphorylated or adenylated in vitro by added ATP.

Journal Article↗
PubMed1985

Transport of proteins into chloroplasts. The effect of incorporation of amino acid analogues on the import and processing of chloroplast polypeptides.

We have synthesized abnormal precursors of imported chloroplast proteins by incorporating amino acid analogues during translation in a cell-free wheat germ system. Incorporation of analogues of either proline, arginine or leucine markedly inhibits both the import of Pisum sativum ribulosebisphosphate carboxylase small subunit precursor by isolated chloroplasts and processing to the mature size by the purified processing enzyme. One effect of the arginine analogue is to remove a positive charge(s) in the precursor essential for efficient recognition by the processing enzyme. Incorporation of a lysine analogue results in moderate inhibition of the import of small subunit precursor but complete inhibition of import of the chlorophyll a/b-binding polypeptide precursor. The effect of carboxymethylation on the import of chloroplast proteins is also analyzed. The results indicate that residues essential for transport of the imported proteins by the chloroplast vary among different protein precursors.

Amino Acids↗
PubMed1985

Significance of the pericardium in human subjects: effects on left ventricular volume, pressure and ejection.

To assess the effect of the pericardium, left ventricular systolic function and diastolic compliance were studied in 15 patients before and after pericardiotomy during coronary artery surgery. Using first pass radionuclide angiography, curves for left ventricular systolic function (stroke work versus end-diastolic volume) and a measure of diastolic compliance (pulmonary capillary wedge pressure versus end-diastolic volume) were generated by changing body position to alter venous return. Left ventricular end-diastolic volume ranged from 41 to 111 ml/m2 and pulmonary capillary wedge pressure from 0 to 24 mm Hg. No significant changes were found in blood pressure (150/83 to 148/82 mm Hg), heart rate (66.7 to 67.1 beats/min), cardiac index (2.38 to 2.41 liters/min per m2), ejection fraction (0.56 to 0.54), end-systolic volume index (31.4 to 32.2 ml/m2), end-diastolic volume index (65.9 to 69.5 ml/m2) or pulmonary capillary wedge pressure (7.5 to 7.3 mm Hg). The pericardium did not affect the curves relating stroke work and end-diastolic volume or those relating pulmonary capillary wedge pressure and end-diastolic volume. Thus, when filling pressure and volume are normal or only moderately elevated, the pericardium does not appear to affect left ventricular systolic function or diastolic compliance in patients.

Adult↗
PubMed1984

Transport of proteins into chloroplasts. Partial purification of a chloroplast protease involved in the processing of important precursor polypeptides.

We have partially purified a soluble protease from Pisum sativum chloroplasts involved in the processing of precursor polypeptides imported into the organelle. The enzyme processes precursors of both stromal and thylakoid proteins to the mature size, but is inactive against all proteins so far tested other than precursors destined for the chloroplast. The enzyme processes precursors from wheat and barley, and is therefore not species-specific. It has a relative molecular mass of about 180 000 and a pH optimum near 9. The enzyme is inhibited by ethylenediamine tetraacetate and 1,10-phenanthroline but not by serine- or thiol-protease inhibitors.

Biological Transport↗
PubMed1984

Transport of proteins into chloroplasts. The precursor of small subunit of ribulose bisphosphate carboxylase is processed to the mature size in two steps.

The precursor of the small subunit of ribulose bisphosphate carboxylase in Pisum sativum (relative molecular mass 20 000) is processed to the mature size (relative molecular mass 14 000) by the purified processing enzyme in two steps. The maturation proceeds via an intermediate of Mr 18 000. Both processing reactions may be carried out by the same enzyme although different residues are involved in the two cleavage sites. The second cleavage is inhibited if the precursor is pre-incubated with iodoacetate. The processing intermediate cannot be detected during the uptake of the precursor by intact isolated chloroplasts but iodoacetate-treated precursor is taken up and converted to a number of polypeptides of Mr 18 000 and below.

Biological Transport↗
PubMed1984

Non-equilibrium thermodynamics and degenerate disease.

Non-equilibrium thermodynamics, biochemistry and physiology can be associated to form a possible foundation for a theory of nutritional medicine. The theory predicts a new class of diseases. The relationship between this new class and cancer is discussed.

Disease↗
PubMed1984

Photoregulation of the biosynthesis of ribulose bisphosphate carboxylase.

Chloroplast development in higher plants is light dependent, and is accompanied by the synthesis of chlorophyll and the accumulation of many chloroplast polypeptides. There is a 100-fold greater content of the photosynthetic enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase, in light-grown seedlings of Pisum sativum than in dark-grown seedlings. Following the illumination of dark-grown seedlings, there is a parallel increase in the content of both the mRNA and the polypeptide of the small subunit of the carboxylase; this subunit is a product of the nuclear genome. The increases in the mRNA and the polypeptide of the large subunit, which is a product of the chloroplast genome, show less synchronicity. Studies with isolated leaf nuclei show that the increase in small subunit mRNA is mediated primarily at the level of transcription. Three distinct effects of light on transcription of small subunit genes have been found; a rapid (approximately 1 h) burst, followed by a decline, when etiolated plants are first exposed to light; a slow (approximately 36 h) development of the competence to transcribe rapidly after the initial burst; rapid (approximately 20 min) switches in both directions when fully greened plants are exposed to light-dark transitions.

Chloroplasts↗
PubMed1983

Computer-derived treadmill exercise score quantifies the degree of revascularization and improved exercise performance after coronary artery bypass surgery.

A computer-derived treadmill exercise score (TES) that quantifies the severity of the ischemic ST response to exercise was used to detect noninvasively graft occlusion or the progression of new lesions after coronary artery bypass surgery. Three months after surgery TES completely normalized in 68% of patients and improved by more than 70% in another 18% of patients, thus reflecting excellent improvement in exercise-induced ischemia in 87% of patients. Surgical results correlated well with completeness of revascularization as shown by repeat coronary angiography. When TES, done serially up to 4 years after surgery, remained unchanged, grafts were patent and no new critical lesions had occurred. Deterioration in TES always predicted either late graft occlusion or appearance of new, high-grade lesions in the native vessels. Thus TES provides a new, accurate method that quantifies the ischemic response to exercise and detects graft occlusion or new obstructive lesions in the native coronary arteries.

Arterial Occlusive Diseases↗
PubMed1983

Evaluation of varicella-zoster immune globulin: protection of immunosuppressed children after household exposure to varicella.

Varicella-zoster immune globulin (VZIG), an immunoglobulin prepared from normal donor plasma selected for high titer of antibody to varicella-zoster virus (VZV), and zoster immune globulin (ZIG), prepared from the plasma of donors convalescing from herpes zoster, were compared in a double-blind, randomized clinical trial to determine their relative efficacy in protecting immunosuppressed children from severe varicella. VZV infection occurred in 49 (60.4%) of 81 recipients of VZIG and in 57 (68.6%) of 83 recipients of ZIG. These rates and the clinical severity of varicella were not significantly different; however, the subclinical infection rate was significantly higher in ZIG recipients (31.3% vs. 16.0%). This difference was accounted for by a subgroup of patients receiving immunosuppressive therapy for nonneoplastic diseases. Doubling the dose of VZIG administered reduced the rate of subclinical infection. These data indicate that VZIG can be used to protect immunosuppressed children from severe chicken pox.

Chickenpox↗
PubMed1982

General occurrence and structural similarity of the rapidly synthesized, 32,000-dalton protein of the chloroplast membrane.

A rapidly metabolized membrane protein from Spirodela, with an apparent molecular weight of 32,000, has been implicated in allosterically regulating electron transport and mediating diuron herbicide sensitivity in the chloroplast (Mattoo, A. K., Pick, U., Hoffman-Falk, H., and Edelman, M. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 1572-1576). Rapid synthesis of a 32,000-dalton plastid membrane protein is demonstrated for several diverse angiosperms and the alga, Chlamydomonas. Comparative partial proteolytic mapping of the polypeptide showed similar patterns for all species tested. In some cases, a 33,500-dalton precursor polypeptide was identified which also displayed interspecific structural homologies. Lastly, in situ analysis of the surface-exposed 32,000-dalton membrane protein yielded a common trypsinization pattern for the organisms studied. These findings point toward a broad distribution and phylogenetic similarity of the 32,000-dalton thylakoid protein of the chloroplast at levels of precursor maturation, membrane orientation, and primary structure.

Chloroplasts↗
PubMed1982

Light-stimulated transcription of genes for two chloroplast polypeptides in isolated pea leaf nuclei.

Nuclei isolated from both light-grown and dark-grown leaves of Pisum sativum by Percoll density gradient centrifugation incorporate labelled UTP into RNA when supplemented with the other three nucleoside triphosphates. The RNA is heterodisperse, with transcripts up to at least 25S in size. Among these transcripts are sequences hybridizing to cloned DNA probes for wheat rRNA and two abundant chloroplast polypeptides of Pisum, viz. the small subunit of ribulose bisphosphate carboxylase and a polypeptide of the light-harvesting chlorophyll a/b binding complex. Transcription of small subunit and light-harvesting complex sequences is greater (18-fold and 9-fold, respectively) in nuclei from light-grown leaves than in nuclei from dark-grown leaves. Transcription of ribosomal genes, by contrast, is only doubled by growth in the light. Small subunit and light-harvesting complex sequences transcribed in dark-grown nuclei are not degraded in a 120 min chase. These results suggest that the stimulation of accumulation of small subunit and light-harvesting complex mRNAs by exposure of Pisum seedlings to light is mediated by an increase in transcription rather than by a decrease in RNA degradation.

Journal Article↗
PubMed1981

Reduction of myocardial wall tension during cold pressor stress after myocardial revascularization.

The effects of myocardial revascularization on cardiac function remain controversial despite clinical improvement. A study was designed to determine the effects of revascularization on the myocardial response to stress. Stress was induced using the cold pressor (CP) test in which th patient places his arm in ice water for one minute. All patients were tested before and one week and six months after surgery. Ejection fraction and cardiac index were determined with a noninvasive nuclear technique. Fifteen patients were studied (five patients received propranolol hydrochloride therapy after surgery, and ten patients did not receive this therapy). Cuff systolic blood pressure (BP) was obtained simultaneously with the nuclear study. The double product (heart rate x systolic BP) was calculated and used as an index of stress induced by the CP test. The results indicate that, during stress, myocardial wall tension is significantly reduced after adequate revascularization (565 dynes/cm from a preoperative value of 458 dynes/cm [P less than .001].) Patients achieved a higher cardiac index (3.58 L/min/sq m as compared with a preoperative value of 2.51 L/min/sq m) and double product (13,600 as compared with a preoperative value of 11,900) while, at the same time, tension was reduced. This suggest that increasing coronary blood flow through bypass surgery reduces myocardial wall tension during stress. This may be the reason myocardial revascularization achieves a lower incidence in late myocardial infarction when compared with medical therapy.

Blood Pressure↗