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Biomedical subjects

J Barber

Publications and source records attributed to J Barber.

At least 181 records · Page 10Linked to original sources
PubMed1989

psbG is not a photosystem two gene but may be an ndh gene.

A gene of the chloroplast genome has been designated the psbG gene on the basis that in maize the gene product is a 24-kDa polypeptide of photosystem two (PS2) (Steinmetz, A. A., Castroviejo, M., Sayre, R. T., and Bogorad, L. (1986) J. Biol. Chem. 261, 2485-2488). We have located and sequenced the equivalent gene in wheat (Triticum aestivum) and have raised specific antibodies to the gene product following its expression in Escherichia coli as a beta-galactosidase fusion protein. Using these antibodies, we have investigated the location of the gene product in various thylakoid membrane fractions of pea (Pisum sativum). The gene product of apparent molecular mass 27-28 kDa is severely depleted in PS2-enriched membrane preparations and its distribution between stromal and granal regions of the membrane is distinct to that of the psbC gene product which is known to be a core polypeptide of PS2. We therefore conclude that psbG does not code for a component of PS2 but instead suggest that it is present in a novel protein complex of the thylakoid membrane. On the basis of 1) the conserved overlap between psbG and ndhC, a chloroplast gene which shows significant homology to a mitochondrial gene that codes for a subunit of the NADH-ubiquinone oxidoreductase of mitochondria, and 2) sequence similarity between the psbG gene product and the ndh gene product of E. coli, which codes for a respiratory NADH dehydrogenase, we propose that this ill-defined complex functions as a NADH or NADPH-plastoquinone oxidoreductase.

Amino Acid Sequence↗
PubMed1989

Effect of alkaline pH on photosynthetic water oxidation and the association of extrinsic proteins with Photosystem Two.

Incubation of a membrane preparation enriched in Photosystem Two (PSII) at alkaline pH inhibited the water-splitting reactions in two distinct steps. Up to pH 8.5 the inhibition was reversible, whereas at higher alkalinities it was irreversible. It was shown that the reversible phase correlated with loss and rebinding of the 23 kDa extrinsic polypeptide. However, after mild alkaline treatments a partial recovery was possible without the binding of the 23 kDa polypeptide when the assay was at the optimal pH of 6.5 and in a medium containing excess Cl-. The irreversible phase was found to be closely linked with the removal of the 33 kDa extrinsic protein of PSII. Treatments with pH values above 8.5 not only caused the 33 kDa protein to be displaced from the PSII-enriched membranes, but also resulted in an irreversible modification of the binding sites such that the extrinsic 33 kDa protein could not reassociate with PSII when the pH was lowered to 6.5. The results obtained with these more extreme alkaline pH treatments support the notion that the 23 kDa protein cannot bind to PSII unless the 33 kDa protein is already bound. The differential effect of pH on the removal of the 23 kDa and 33 kDa proteins contrasted with the data of Kuwabara & Murata [(1983) Plant Cell Physiol. 24, 741-747], but this discrepancy was accounted for by the use of glycerol in the incubation media.

Electron Transport↗
PubMed1989

Diurnal weight gain in chronic psychosis.

We found diurnal weight gain to be abnormal among 93 chronically psychotic patients, most of whom had schizophrenia. They were weighed at 7 a.m. and 4 p.m. weekly for 3 weeks. We normalized the diurnal weight gain (NDWG) as a percentage by subtracting the 7 a.m. weight from the 4 p.m. weight, multiplying the difference by 100, and dividing the result by the 7 a.m. weight. NDWG was 1.7 +/- 1.0 percent for the study sample, 0.6 +/- 0.4 percent for 16 acutely psychotic controls, and 0.5 +/- 0.4 percent for 29 normals. More than 60 percent of the study sample had abnormal NDWG values. NDWG related to antipsychotic drug dose (r = 0.290, p = 0.005) with variability in drug dose accounting for 8 percent of the variability in NDWG. This report provides yet another piece of evidence that disordered water balance is common in chronic psychiatric patients. The etiology is unknown, but it may relate to subtle brain abnormalities in the regulation of fluid intake and excretion.

Adult↗
PubMed1989

[Esophagocoloplasty in the treatment of total caustic stenosis of the esophagus].

Since October 1986 until January 1988 we have treated 3 patients with corrosive strictures of the esophagus, by substitution of esophagus with vascularized colon. Two females (4 and 8 years) and one male (5 years) had been treated on others hospitals by means of gastrostomy and periodically retrogradual dilatations; in two of them for more than 24 months. The surgical treatment was indicated upon the evolution time, the degree of dysphagia and the size of the affected segment. The coloesophagoplasty by retrosternal approach with proximal anastomosis in the neck, has been the operative technique performed in the male case. On the others two cases, colon interposition by extrapleural thoracic approach, combined with laparotomy was carried out. We think that the coloesophagoplasty by retroesternal way should only be advised in cases were superior anastomosis in the neck is indicated, conditioned by the height of the stricture. On the other hand, colon interposition by extrapleural approach, is the elective way for the others cases.

Burns, Chemical↗
PubMed1989

Suffering children hurt us.

This paper examines the consequences of our attitudes toward children's pain and suffering, both on that pain and suffering and on children's response to treatment. Examples are offered for alternative ways we can cope with suffering children. Attention is paid to the importance of self-awareness on the part of clinicians, and of its relevance to good clinical care.

Biopsy, Needle↗
PubMed1988

The molecular basis of kirromycin (mocimycin) action; a 1H NMR study using deuterated elongation factor Tu.

The binding of the antibiotic kirromycin (mocimycin) to its target protein, bacterial elongation factor Tu (EF-Tu), has been studied by 1H NMR spectroscopy using deuterated protein. Narrow lines were observed in the spectrum of the unbound protein (due to residual protons) and in the spectrum of the kirromycin-EF-Tu complex. The spectrum of the complex has been compared with the spectra of the unbound protein and the unbound drug, and the results are interpreted in terms of the mode of antibiotic action of kirromycin.

Deuterium↗
PubMed1987

131I labeled diphosphonates for the palliative treatment of bone metastases--IV. Syntheses of benzylidenediphosphonates and their organ distribution in rats.

Palliative treatment of bone pain induced by disseminated bone metastases can be performed with osteotropic, beta(-)-emitting radionuclides. Newly developed 131I labeled benzylidenediphosphonic acid (BDP) derivatives show osteotropic characteristics which suggest that they might possibly be useful radiopharmaceuticals for that purpose. Six BDP derivatives were synthesized with H, OH or NH2 in the 4- and alpha-position. Syntheses were performed by the formal addition of 2 mol of phosphorous acid in the presence of PBr3 to 1 mol of the respective benzonitrile. Transformation of the 4-methoxy and 4-nitro substituents, which were stable during the diphosphonate formation, to 4-HO and 4-NH2 was achieved by hydrolytic ether cleavage in boiling HBr and catalytic hydrogenation with Pd/C, respectively. Transformation of the alpha-amino to alpha-hydroxy group was achieved by the action of NaNO2 in HCl. 4-Hydroxybenzylidenediphosphonic acid (9) was formed unexpectedly during the reaction of 4-hydroxybenzoic acid with H3PO3/PBr3. The addition of 2 mol of phosphorous acid to the benzoic acid was accompanied by an additional reduction at the alpha-carbon. The new BDP derivatives were analyzed by HPLC, NMR and elemental analysis. After labeling with 131I the BDP derivatives were tested in female Sprague-Dawley rats to obtain organ uptake and kinetic data. The various substituents showed an influence on the bone affinity and the uptake in other organs. Among the BDP derivatives tested alpha-amino-(3-[131I]iodo-4-hydroxybenzylidene)diphosphonate (4a) showed the best biological characteristics.

Animals↗
PubMed1987

A method for estimating lateral diffusion coefficients in membranes from steady-state fluorescence quenching studies.

The Stern-Volmer theory, in which the quantum yield ratio (Io/I) depends linearly on the quencher concentration, will typically be inapplicable to fluorescence quenching in membranes. Numerical analysis shows that diffusion-controlled quenching results in a nonlinear concentration dependence for diffusion coefficients less than or of the order of 10(-6) cm2 s-1 and probe fluorescence lifetimes in the region of 10-100 ns. Lateral diffusion coefficients in membranes are typically overestimated an order of magnitude or more by the Stern-Volmer theory. An alternative empirical method is presented, which represents nonlinear concentration curves by a single parameter linear approximation determined by a least-squares analysis. The fitting parameter, P, depends on the interaction distance, the membrane thickness, the maximum extent of quenching and, in the case of biexponential probe fluorescence decay, the fluorescence kinetic parameters. P is presented in tabular form for a useful range of these parameters. The method is used to estimate diffusion coefficients for plastoquinone and plastoquinol from pyrene fluorescence quenching in soya bean phosphatidylcholine liposomes. It is found that the diffusion coefficients are nearly equal and in the region of 1.3-3.5 X 10(-7) cm2 s-1 for interaction radii of 1.5-0.5 nm, respectively.

Diffusion↗
PubMed1987

Dynamics of Photosystem II and Its Light Harvesting System in Response to Light Changes in the Halotolerant Alga Dunaliella salina.

A photosystem two (PSII) core complex consisting of five major polypeptides (47, 40, 32, 30, and 10 kilodaltons) and a light harvesting chlorophyll a/b complex (LHC-2) have been isolated from the halotolerant alga Dunaliella salina. The chlorophyll and polypeptide composition of both complexes were compared in illuminated and dark-adapted cultures. Dark adaptation is accompanied by a decrease in the chlorophyll a to chlorophyll b (Chl a/Chl b) ratio of intact thylakoids without any change in total chlorophyll. These changes occur with a half-time of 3 hours and are reversed upon reillumination. Analyses of PSII enriched membrane fragments suggest that the decrease in the Chl a/Chl b is due partly to an increase in the Chl b content of LHC-2 and partly to changes in the relative levels of the two complexes. Apparently during dark adaptation there is: (a) a net synthesis of chlorophyll b, (b) removal of PSII core complexes resulting in a 2-fold drop in the PSII cores to LHC-2 chlorophyll ratio. These changes should dramatically increase the light harvesting capacity of the remaining PSII reaction centers. Presumably this adjustment of antenna size and composition is a physiological mechanism necessary for responding to shade conditions. Also detected, using (32)P, are light-induced phosphorylation of the LHC-2 (consistent with the ability to undergo State transitions) and of the 40 and 30 kilodalton subunits of the PSII core complex. These observations indicate that additional mechanisms may also exist to help optimize the interception of quanta during rapid changes in illumination conditions.

Journal Article↗
PubMed1987

Absence of carbamazepine-induced hyponatremia among patients also given lithium.

Of 33 chronically psychotic patients in a state hospital, 17 received carbamazepine, 13 received carbamazepine and lithium, and three received carbamazepine and then the combination. There was a significant difference in serum sodium level between the patients receiving carbamazepine alone (mean +/- SD = 138.4 +/- 4.3 meq/liter) and those also receiving lithium (141.8 +/- 1.6 meq/liter). (A similar difference was seen for the patients who received the two treatments serially.) Age, sex, diagnosis, age at diagnosis, seizure disorder, antipsychotic drugs, and serum carbamazepine level did not explain this difference. The protection against hyponatremia provided by the carbamazepine-lithium combination occurred despite lithium's tendency to increase polyuria.

Adult↗
PubMed1986

Evidence that pyrene excimer formation in membranes is not diffusion-controlled.

Kinetic and steady-state measurements of pyrene fluorescence in a variety of model membranes are evaluated in terms of the theory of collisional excimer formation. In the region of 10(-3)-0.1 M pyrene, molecular fluorescence decay in membranes is biphasic and the two component lifetimes do not depend on the pyrene concentration. The lifetime data are consistent with the rate constant for collisional excimer formation being of the order 10(6) M-1 X s-1 or less. The concentration dependence of the component amplitudes is inconsistent with the theory of collisional excimer formation and suggests that pyrene exists in two forms in membranes: a slowly diffusing monomeric form and an aggregated form. The component of molecular fluorescence decay associated with aggregated pyrene is highly correlated with steady-state excimer fluorescence, suggesting that excimer fluorescence in membranes arises from aggregated pyrene in which excimers are formed by a static rather than a collisional mechanism. It is suggested that the concentration dependence of excimer to molecular fluorescence intensity ratios in membranes is related to the equilibrium constant for exchange between monomeric and aggregated pyrene forms rather than to the collisional excimer formation rate constant.

Chloroplasts↗