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Biomedical subjects

R Barr

Publications and source records attributed to R Barr.

At least 109 records · Page 6Linked to original sources
PubMed1976

Evidence for multiple sites of ferricyanide reduction in chloroplasts.

Various sites of ferricyanide reduction were studied in spinach chloroplasts. It was found that in the presence of dibromothymoquinone a fraction of ferricyanide reduction was dibromothymoquinone sensitive, implying that ferricyanide can be reduced by photosystem I as well as photosystem II. To separate ferricyanide reduction sites in photosystem II, orthophenanthroline and dichlorophenyl dimethylurea inhibitions were compared at various pHs. It was noted that at low pH ferricyanide reduction was not completely inhibited by orothophenanthroline. At high pH's, however, inhibition of ferricyanide reduction by orthophenanthroline was complete. It was found that varying concentration of orthophenanthroline at a constant pH showed different degrees of inhibition. In the study of ferricyanide reduction by photosystem II various treatments affecting plastocyanin were performed. It was found that Tween-20 or KCN treatments which inactivated plastocyanin did not completely inactivate ferricyanide reduction. These data support the conclusion that ferricyanide accepts electrons both before and after plastoquinone in photosystem II.

Binding Sites↗
PubMed1976

Organization of Electron Transport in Photosystem II of Spinach Chloroplasts According to Chelator Inhibition Sites.

The organization of electron transport in photosystem II of spinach (Spinacia oleracea) chloroplasts was studied by means of various chelators and uncouplers. The partial reactions used included H(2)O-->methyl viologen, H(2)O-->silicomolybdic acid H(2)O-->ferricyanide, and H(2)O-->dimethylbenzoquinone. Three types of chelator inhibition were found (a) inhibition common to all pathways and presumably affecting the Mn or water oxidation site in photosystem II (salicylaldoxime, dithizone, acridine, 4,4,4-trifluoro-1-(2-thienyl)-1,1-butanedione, 4,4,4-trifluoro-0-(2-furyl)-1,3-butanedione; (b) strong inhibition of the H(2)O-->silicomolybdic acid pathway in presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea by lipophilic chelators (bathocuproine, tertoctylcatechol) but stimulation by orthophenanthroline; and (c) 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone-insensitive dimethylbenzoquinone reduction inhibited by all phenanthrolines while ferricyanide reduction was remarkably stimulated by bathophenanthroline but inhibited by orthophenanthroline and bathocuproine. The action of lipophilic chelators on silicomolybdic acid reduction presumes the presence of a metallo protein in photosystem II. The differential action of bathophenanthroline on dimethylbenzoquinone and ferricyanide reduction indicated the possible existence of a metalloprotein in this pathway which is different from the site of orthophenanthroline inhibition.

Journal Article↗
PubMed1976

Intraoperative autotransfusion in major elective vascular operations: a clinical assessment.

Six patients undergoing major elective vascular operations received an average of 1,700 ml. of intraoperative autotransfusion of shed blood. The patients were anticoagulated systemically during operation. The mean platelet count (156,000 per cubic millimeter and fibrinogen value (257 mg. per 100 ml.) were normal in autotransfused blood and the mean hemoglobin level was slightly below normal (11.5 Gm. per 100 ml.). Plasma hemoglobin values were variable. No patient suffered any complication that could be attributed to autotransfusion. Donor blood transfusion was avoided in five of the six patients by salvage and reinfusion of shed blood. No evidence of coagulopathy was found in any patient as measured by platelet count, fibrinogen level, prothrombin time, partial thromboplastin time, euglobulin clot lysis, and fibrin degradation products. The technique of intraoperative autotransfusion is described in detail.

Blood Coagulation↗
PubMed1975

Vanadium compounds and ferrocyanide as ionic redox agents in photosynthesis.

The effect of such ionic redox agents as ferrocyanide and several vanadium compounds was determined on photosynthetic reactions of spinach chloroplasts. It was found that: 1. Vanadyl sulfate like ferrocyanide in moderately high concentrations (0.03 M) donates electrons to Photosystem II. 2. Decavanadate in the presence of 2,5-dibromothymoquinone accepts electrons in Photosystem II. 3. In the absence of a block between the two photosystems, decavanadate accepts electrons in Photosystem I in the vicinity of plastocyanin or beyond. 4. Vanadite and ferrocyanide in high concentrations (0.32 M) donate electrons to Photosystem I. 5. On the basis of chelator inhibition and polyoxyethylene sorbitan monolaureate treatment, the vanadite oxidation site is located near plastocyanin while the ferrocyanide site is between plastocyanin and P-700.

Chloroplasts↗
PubMed1975

The exodus of long-stay psychiatric patients.

Increasing criticism is being made of the policy of discharging long-stay psychiatric patients to the community. A study of such ex-patients who had left Callan Park Hospital was undertaken to assess this policy in New South Wales. The majority were unemployed pensioners, living in convalescent homes and boarding houses, who stated that they were happier than when living in Callan Park Hospital. It would appear that one type of institution has been substituted for another, and that greater responsibility for the care and rehabilitation of such ex-patients needs to be offered.

Age Factors↗
PubMed1975

Dichlorophenylurea-insensitive Reduction of Silicomolybdic Acid by Chloroplast Photosystem II.

The photoreduction of silicomolybdate and other heteropoly ions by chloroplasts is insensitive to 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (DCMU). Both water and diphenylcarbazide can be used as electron source for the reduction. Three different assays for silicomolybdate reduction are described including oxygen evolution, formation of a reduced heteropoly blue silicomolybdate, or an indirect assay for reduced silicomolybdate by redox indicators, such as ferricyanide or cytochrome c. The effects of detergents and tris washing are consistent with silicomolybdate reduction through photosystem II before the DCMU site. The effects of orthophenanthroline and bathophenanthroline indicate chelator-sensitive sites in photosystem II before the site of DCMU action.

Journal Article↗
PubMed1975

The effects of discharge on long-stay psychiatric hospital patients.

One hundred and forty long-stay patients discharged from Callan Park Hospital were followed up. All except nine were accounted for and 90 who were living outside hospital at the time of the study were interviewed. Thirty percent of the total sample were readmitted during the mean follow up period of 20.4 months. Most of those living outside hospital said that they were happier than when living in hospital. They formed a relatively homogeneous socio-economic group with the majority living in boarding houses and convalescent homes and being unemployed.

Age Factors↗
PubMed1972

The Ultrastructure of Chloroplasts in Mineral-deficient Maize Leaves.

The ultrastructure of mesophyll chloroplasts in full-nutrient and mineral-deficient maize (Zea mays) leaves was examined by electron microscopy after glutaraldehyde-osmium tetroxide fixation. Nitrogen, calcium, magnesium, phosphorus, potassium, and sulfur deficiencies were induced by growing the plants in nutrient culture. Distinctive chloroplast types were observed with each deficiency. Chloroplasts from nitrogen-deficient plants were reduced in size and had prominent osmiophilic globules and large grana stacks. Magnesium deficiency was characterized by the accumulation of osmiophilic globules and the progressive disruption of the chloroplast membranes. In calcium deficiency, the chloroplast envelope was often ruptured. Chloroplasts from potassium- or phosphorus-deficient plants possessed an extensive system of stroma lamellae. Sulfur deficiency resulted in a pronounced decrease of stroma lamellae, an increase in grana stacking, and the frequent occurrence of long projections extending from the body of the chloroplast. These morphological changes were correlated with functional alterations in the chloroplasts as measured by photosystem I and II activities. In chloroplasts of the nitrogen- and sulfur-deficient plants an increase in grana stacking was associated with an increase in photosystem II activity.

Journal Article↗
PubMed1970

Comparative Studies on Plastoquinones: V. Changes in Lipophilic Chloroplast Quinones during Development.

Changes of lipophilic chloroplast quinones in corn, oats, peas, and Vicia faba are reported after 0, 4, 8, 12, 16, 20, 24, 48, 72, or 96 hours of exposure to light. There is a pronounced increase in plastoquinone A and chlorophyll levels and slight increase, in plastoquinone C(1-6), vitamin K(1), and alpha-tocopherylquinone content. Coenzyme Q levels, on the other hand, show little change upon exposure to light.THE SEQUENCE IN WHICH INDIVIDUAL QUINONES APPEAR DURING DEVELOPMENT IS AS FOLLOWS: plastoquinone A instantaneously after exposure to light, plastoquinone C(1-6) from 4 to 24 hours, vitamin K(1) from 12 to 24 hours, alpha-tocopherylquinone from 0 to 24 hours of illumination. Small amounts (<0.01 mumole/g, dry wt) of plastoquinone A and plastoquinone B are found in seeds and etiolated tissues. After exposure to light, the quinone tentatively identified as a member of the plastoquinone B series by reverse phase thin layer chromatography disappears and can be detected again in small amounts during maturity and toward senescence of the leaf.

Journal Article↗