Nursing with a difference.
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Consultants↗
Biomedical subjects
J Barber
Publications and source records attributed to J Barber.
Mouth and genital ulcers with inflamed cartilage: MAGIC syndrome. Five patients with features of relapsing polychondritis and Behçet's disease.
Five patients with features of coexistent relapsing polychondritis and Behçet's disease are described. Review of the literature supports the overlap of the clinical manifestations of these two conditions. A common immunologic abnormality is likely, and elastin is cited as a possible target antigen. The "mouth and genital ulcers with inflamed cartilage (MAGIC) syndrome" is the proposed name for this entity.
Adult↗
Does unilateral dopamine deficit contribute to depression?
A system of emotional control of behavior is believed to be lateralized to the right hemisphere. Given that dopaminergic pathways are involved in affective behavior, depression, which is recognized as an integral part of Parkinson's disease, may be associated with a dopamine imbalance. The present study examined this hypothesis in patients with unilateral symptomatology indicating either left hemisphere parkinsonism (LHP) or right hemisphere parkinsonism (RHP). Sixteen patients were tested on a battery of neuropsychological tests and several scales for evaluating mood. The two groups did not differ significantly on either cognitive or emotional measures. However, RHP patients rated themselves higher on the Present Scale of Cantril, and showed some neglect of the left visual field, as compared to LHP patients.
Affect↗
The light-intensity-dependence of the efficacy of 2-(3-chloro-4-trifluoromethyl)-anilino-3,5-dinitrothiophene (Ant2p) to inhibit the photosystem 2 reactions of chloroplasts.
The mechanism by which Ant2p [2-(3-chloro-4-trifluoromethyl)anilino-3, 5-dinitrothiophene] inhibits the oxygen evolution capacity of chloroplasts is thought to be due to a rapid reduction of the S2 and S3 oxidation states of the oxygen-evolving complex mediated by the oxidation of endogenous donors such as cytochrome b559. The results presented in this paper show that the degree of inhibition by Ant2p of the photosystem 2-supported electron transfer reactions, registered by the light-dependent rate of dichlorophenolindophenol reduction, varies according to the actinic light intensity. Moreover, a similar intensity-dependence can be detected in the extent of the Ant2p-induced cytochrome b559HP photo-oxidation. We show, however, that the dependence of the cytochrome oxidation is not due to the oxidation per se, but reflects changes in the high light-driven re-reduction reaction. The close correlation between the two Ant2p reactions is interpreted as indicating that the effect of Ant2p might be due to an inhibition of the S-state turnovers and not necessarily due to a deactivation process.
2,6-Dichloroindophenol↗
Evidence that phosphorylation and dephosphorylation regulate the distribution of excitation energy between the two photosystems of photosynthesis in vivo: Photoacoustic and fluorimetric study of an intact leaf.
State 1-state 2 transitions in an intact tobacco leaf were monitored by the photoacoustic method. Modulated oxygen evolution yield and its enhancement by continuous far-red light ("Emerson enhancement") were used to characterize the balance of light distribution between the two photosystems. These measurements were additionally supported by fluorimetry. Adaptation of the leaf to far-red light (lambda [unk] 700 nm), mainly absorbed in photosystem I (light 1), results in state 1, where short-wavelength light (light 2) is distributed in favor of photosystem II. This is shown by a low yield of oxygen evolution, a high extent of Emerson enhancement, a concomitantly high extent of fluorescence quenching by far-red light, and a low ratio of the 77 K emission peaks at 730 and 695 nm. The magnitudes of these parameters were reversed when the leaf was adapted to light 2 (state 2), indicating a change towards a more equal distribution of the excitation between the two photosystems. Preincubation of an intact leaf with NaF, a specific phosphatase inhibitor, stimulated the extent of adaptation to light 2, shown by all the above criteria, and completely abolished adaptation to light 1. Light 1 preillumination prior to NaF treatment resulted initially in state 1, but then a transition to state 2 was irreversibly induced by any light. The NaF effect was specific because NaCl did not affect the state 1-state 2 transitions. Leaching out the NaF restored the original physiological transitions of the leaf. NaF presumably acts here in the same way as it acts in isolated thylakoids-by blocking the dephosphorylation of membranal proteins (particularly the chlorophyll a/b-protein complex) phosphorylated by a light 2-activated kinase. Our results give direct support to the suggestion [Allen, J. F., Bennett, J., Steinback, K. E. & Arntzen, C. J. (1981) Nature (London) 291, 25-29] that it is the phosphorylation level of thylakoid proteins that controls the light distribution between the two photosystems in vivo, shown previously in isolated thylakoids.
Journal Article↗
Very early intervention with beta-blockade in acute myocardial infarction.
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Clinical Trials as Topic↗
Keratitis in relapsing polychondritis.
An 11-year-old girl developed peripheral corneal thinning and superficial pannus formation with no other ocular or systemic signs. During the subsequent two years she developed inflammation of both ears, progressive collapse of the nasal cartilage, and polyarthritis. A clinical diagnosis of relapsing polychondritis was made. A spontaneous perforation of her right eye secondary to progression of peripheral ulcerative keratitis was successfully repaired. Treatment with dapsone, a nonsteroidal anti-inflammatory agent resulted in remission of her ocular and systemic disease.
Cartilage Diseases↗
EDTA-induced release of manganese and proteins from inside-out thylakoid vesicles and the inhibition of oxygen evolution.
Washing of inside-out, but not right-way-round, pea chloroplast thylakoid vesicles with 2 mM EDTA inhibits O2 evolution. Artificial electron donor/acceptor studies indicate that the site of inhibition is on the oxidising side of photosystem two (PS2), a conclusion reinforced by chlorophyll fluorescence measurements. Evidence is presented that the EDTA inhibition of O2 evolution is linked partly to the removal of one Mn atom per PS2 reaction centre and partly to the removal of extrinsic membrane proteins having apparent molecular weights between 58 and 70 kdaltons.
Chloroplasts↗
Growth temperature effects on thylakoid membrane lipid and protein content of pea chloroplasts.
The lipid composition and level of unsaturation of fatty acids has been determined for chloroplast thylakoid membranes isolated from Pisum sativum grown under cold (4 degrees /7 degrees C) or warm (14 degrees /17 degrees C) conditions. Both the relative amounts of lipid classes and degree of saturation were not greatly changed for the two growth conditions. In cold-grown plants, there was a slightly higher linolenic and lower linoleic acid content for the glycolipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol. In contrast to thylakoid membranes, a non-thylakoid leaf membrane fraction including the chloroplast envelope, had a higher overall level of fatty acid unsaturation in cold-grown plants due mainly to an increase in the linolenic acid content of MGDG, DGDG, phosphatidylglycerol, and phosphatidylcholine. The most clear cut change in the thylakoid membrane composition was the lipid to protein ratio which was higher in the cold-grown plants.
Journal Article↗
State 1-State 2 Transitions in a Unicellular Green Algae : Analysis of In Vivo Chlorophyll Fluorescence Induction Curves in the Presence of 3-(3,4-Dichlorophenyl)-1, 1-dimethylurea (DCMU).
A study has been made on the State 1-State 2 transitions exhibited by the unicellular green algae Chlorella pyrenoidosa. Chlorophyll fluorescence induction curves from algae adapted to State 1 or State 2 have been analyzed and a comparison made with similar curves produced by decreasing the intensity of light going to the photosystem II reaction centers. In both cases, quenching of the maximum fluorescence yield (F(m)) and the initial fluorescence yield (F(o)) were observed so that the F(v)/F(m) ratio and the area above the induction curve (A(max)) remained constant. The State 1-State 2 transition also produced changes in the beta(max) component indicative of some alteration within photosystem II organization. The implications of these experiments on the in vivo mechanism for energy redistribution between the two photosystems are discussed in terms of changes in absorption cross-section rather than being due to spillover from photosystem II to photosystem I. These changes may reflect the phosphorylation of the light-harvesting chlorophyll a/b protein complex and its subsequent migration away from the photosystem II core leading to its closer association with photosystem I.
Journal Article↗
Properties and organisation of photosynthetic pigments.
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Bacteria↗
Ocular herpes simplex virus infection is diminished by depletion of B lymphocytes.
Rabbit anti-mouse mu-chain serum was used to deplete specifically IgM-bearing B cells and B cell function in BALB/c mice. B cell-depleted and normal littermates were infected via the cornea with herpes simplex virus type 1 (HSV-1) at 4 to 5 wk of age. B cell-depleted mice had a reduced number of lymphocytes bearing surface immunoglobulin and a greatly reduced ability to produce antibody. Mortality was reduced from 89% in normal controls to 42% in B cell-depleted mice (p less than 0.001) and peak virus shedding from eyes was also reduced as much as 90% in the B cell-depleted mice (p less than or equal to 0.0005). These results support the hypothesis that a B cell function of normal mice somehow contributes directly or indirectly to the enhanced mortality of mice infected with HSV.
Animals↗
The control of membrane organization by electrostatic forces.
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Cell Membrane↗
Interactions between photosystem I and II.
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Chemical Phenomena↗
Possible effects of the detachment of stromal lamellae from granal stacks on salt-induced changes in spillover. A study by sonication of chloroplasts.
Salt-induced chlorophyll fluorescence and spillover changes in control and briefly sonicated chloroplasts have been studied under conditions where Photosystem II traps are closed. In a low-salt medium containing 10 mM KCl, control envelope-free chloroplasts exhibited good spillover, as measured by low chlorophyll fluorescence yield at room temperature, a high ratio of the fluorescence peaks F735/F685 at 77 K, and increased Photosystem I activity in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea and Photosystem II light. In contrast, when stacked chloroplasts were briefly sonicated and subsequently diluted into a low-salt medium, a high fluorescence yield at room temperature and a low ratio of F735/F685 at 77 K persisted. When unstacked chloroplasts were sonicated and then diluted into a high-salt medium, the room temperature fluorescence yield remained low. The results are interpreted in terms of a model relating the changes in chlorophyll fluorescence with the lateral diffusion of Photosystem I and Photosystem II chlorophyll-protein complexes in the plane of the thylakoid membrane creating randomized or segregated domains, depending on the degree of electrostatic screening of surface charges (Barber, J. (1980) FEBS Lett. 188, 1-10). It is argued that brief sonication of stacked chloroplasts separates stromal membranes from granal stacks, thus limiting the inter-mixing of the photosystems via lateral diffusion even when the ionic composition of the medium is varied. Consequently energy transfer from Photosystem II to Photosystem I is relatively poor and chlorophyll fluorescence from Photosystem II is enhanced. The loss of the salt effect on sonicated unstacked membranes can also be accommodated by the model. In this case it seems that the generation of small membrane fragments does not allow the normal salt-induced phase separation of the pigment-protein complexes to occur.
Chloroplasts↗
Salt-induced microscopic changes in chlorophyll fluorescence distribution in the thylakoid membrane.
Addition of 3 mM MgCl2 to isolated pea thylakoids suspended in a medium of low osmotic strength at room temperature induces an increase in chlorophyll fluorescence similar to that observed with unswollen thylakoids. Fluorescence microscopy indicates that the MgCl2 induced increase in the emission intensity involves the formation of highly fluorescent patches on the swollen vesicles. The data seems to give additional support ton the concept that salt induced chlorophyll fluorescence changes involves the lateral movement of pigment-proteins within the thylakoid membrane in such a way as to form discrete domains.
Chlorophyll↗
Experimental and theoretical considerations of mechanisms controlling cation effects on thylakoid membrane stacking and chlorophyll fluorescence.
The roles of specific cation binding, charge neutralization and electrostatic screening mechanisms in controlling salt-induced stacking and chlorophyll fluorescence changes in thylakoid membranes are examined in the light of new experimental evidence and theoretical calculations of the forces between membrane surfaces. A comparison of the biphasic stacking and fluorescence phenomena generated by organic mono- and divalent cations known sterically to inhibit specific binding with the effects generated by inorganic mono- and divalent cations suggests that the observed salt-induced changes at pH greater than or equal to 7.5 are predominantly governed by the electrostatic screening mechanism in agreement with previous work (e.g. Barber, J., Mills, J.D. and Love, A. (1977) FEBS Lett. 74, 174-181). Detailed calculations of the coulombic double layer repulsive force between negatively charged membrane surfaces immersed in a mixed electrolyte of valence type Z1+/Z1-,Z2+/Z1- were performed both under the constraints of fixed surface charged density and fixed surface potential. From a close comparison of the theoretical results with new experimental data on salt-induced stacking and fluorescence changes and a consideration of the contributions of the 'hydration' repulsive force and the van der Waals attractive force, it is argued that a reduction in surface charge density alone by lateral diffusion is probably insufficient to realize membrane stacking and that an increase in the van der Waals attractive force is necessary to account for the experimental observations perhaps through the formation of protein rich domains. In view of the complexity of the thylakoid membranes, the conclusions are to be considered qualitative. Nevertheless, these calculations give support to a model in which the cation induced chlorophyll fluorescence and stacking changes can be explained by lateral diffusion of two types of pigment protein complexes in the lipid matrix of the membrane. Such diffusion gives rise to changes in energy transfer between Photosystem II and Photosystem I and also to the creation of domains having low and high electrical surface charge density.
Cations↗
9-Aminoacridine as a fluorescent probe of the electrical diffuse layer associated with the membranes of plant mitochondria.
1. Mitochondria from Jerusalem artichoke (Helianthus tuberosus) tubers and Arum maculatum spadices caused a quenching of the fluorescence of 9-aminoacridine when mixed in a low-cation medium (approximately 1 mM-K+) and addition of chelators further decreased the fluorescence. Salts released the quenching of the 9-aminoacridine fluorescence and the efficiency of the release appeared to be mainly dependent on the valency of the cation (C3+ greater than C2+ greater than C+). 2. The results are consistent with the theory of charge screening and demonstrate that 9-aminoacridine is a convenient probe of the behaviour of cations on the membranes of mitochondria and in the diffuse layer associated with these membranes. 3. The concentration of salt required to achieve half-maximal release of quenching of 9-aminoacridine fluorescence was proportional to the concentration of mitochondria in the solution and theoretical considerations show this effect to be inherent in the Gouy-Chapman theory. 4. 9-Aminoacridine was removed from the bulk of the solution by the mitochondria to a far greater extent than was Na+ or K+, which is suggested to be due to the formation of bi- and poly-valent cations by aggregation of 9-aminoacridine molecules in the diffuse layer. This would have implications for the use of 9-aminoacridine to determine delta pH across membranes. 5. Jerusalem-artichoke mitochondria removed from 9-aminoacridine and Ca2+ from the bulk of the solution and required more ions to screen the membranes than did an equal concentration (mg of protein/ml) of Arum mitochondria, indicating that Jerusalem-artichoke mitochondria contain more negative charges per mg of protein.
Aminacrine↗