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Biomedical subjects

R J Kessler

Publications and source records attributed to R J Kessler.

15 recordsLinked to original sources
PubMed1990

Models of disease and the diagnosis of schizophrenia.

DSM-III criteria for schizophrenia represent a significant advance in diagnostic reliability and relevance to course and treatment outcome. However, the underlying, predominantly biomedical model, if exclusively applied, encourages the making of more malignant diagnoses and in particular the over-diagnosing of schizophrenia. This occurs by virtue of an associated declining interest in the content and context of symptoms, a disavowal of "psychology" and a failure of empathy. A psychodynamic viewpoint can help to redress the diagnostic imbalance that the use of the biomedical model can engender.

Humans↗
PubMed1988

Binding of calcium to the proteolipid phosphorin.

Phosphorin is a phosphate-binding proteolipid isolated from rabbit kidney brush border membrane vesicles that binds inorganic phosphate with high affinity and specificity. This binding of phosphate has a Hill coefficient of 1.92 and an absolute requirement for the presence of a divalent metal. We now describe the binding of Ca2+ to phosphorin that had been depleted of endogenous divalent metal. The dependence of the binding of Ca2+ over the concentration range of 5-100 microM produced a sigmoidal curve, yielding a Hill coefficient of 2.46. (Ruthenium red and La3+ were also potent inhibitors of Ca2+ binding). The divalent metals Mn2+ and Mg2+ were able to inhibit binding of Ca2+ and produced Hill coefficients of 1.75 and 1.98; however, Ba2+ and Sr2+ were less effective in their ability to inhibit binding. In addition, the amine-reactive reagent, 4,4'-diisothiocyano-2,2'-disulfonic acid (DIDS), which had previously been found to inhibit binding of phosphate to phosphorin, also completely inhibited binding of Ca2+. We propose that a phosphorin-Me2+ complex forms the molecular species that binds phosphate.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1986

Interference by lipids in the determination of protein using bicinchoninic acid.

Bicinchoninic acid forms the basis of an analytical method for the determination of protein. The reagent produces a purple complex with cuprous ion (Cu+) in an alkaline environment and is the basis for the monitoring of cuprous ions produced in the reactions of proteins with alkaline Cu2+. This method of protein determination was reported to have greater tolerance to many commonly encountered interfering compounds, when compared to the Lowry technique. However, we have found the bicinchoninic acid technique to produce erroneously high values for protein when common membrane phospholipids were included in the assay. Phospholipids in the presence of bicinchoninic acid produced an absorbance peak similar to that produced by protein. This absorbance was linear with concentration, however, the slope varied for individual phospholipids. The combined absorption of phospholipid and protein was not strictly additive. The results indicate that the presence of appreciable quantities of lipid in samples can cause significant error in the analysis of protein by the bicinchoninic acid procedure.

Copper↗
PubMed1986

Artifactual phosphate binding due to impurities in [32P]orthophosphate.

Many commercial preparations of [32P]orthophosphate contain radioactive impurities that interfere with binding and transport studies in biological systems. One type of impurity is micro-particulate whereas another may be pyrophosphate. Methods of removing these impurities from radiolabeled orthophosphate solutions are described.

Diphosphates↗
PubMed1984

Divalent metal is required for both phosphate transport and phosphate binding to phosphorin, a proteolipid isolated from brush-border membrane vesicles.

The Na+-dependent phosphate transport system in the brush border of rabbit kidney exhibits a positive requirement for a divalent metal ion. Treatment of the brush-border membrane vesicles (BBMV) with a divalent metal chelator in combination with the divalent metal ionophore A23187 dramatically and selectively decreased the Na+-dependent uptake of phosphate; Na+-independent uptake of phosphate was not affected. The combination of chelator plus A23187 also inhibited uptake of phosphate in the presence of Na+ but in the absence of a gradient for sodium across the BBMV. This indicates that the inhibitor is not a result of an alteration in the Na+ gradient by chelator plus ionophore. The inhibited Na+ gradient-dependent transport of phosphate was restored by removing the chelator and adding Mn2+ to the BBMV. The phosphate-binding proteolipid (phosphorin) isolated from rabbit kidney BBMV binds inorganic phosphate with high affinity and specificity. Binding of phosphate to phosphorin is also inhibited by divalent metal chelators and can be restored by addition of a divalent metal. We conclude that a divalent metal ion is required both for the Na+-dependent phosphate transport in BBMV and for the binding of phosphate to the proteolipid phosphorin. These findings are consistent with our suggestion that phosphorin is a component of the Na+-dependent phosphate transport system in renal brush-border membranes.

Animals↗
PubMed1982

Phosphate-binding proteolipid from brush border.

A proteolipid that binds inorganic phosphate with high affinity and specificity has been extracted from rabbit kidney brush-border membranes. This proteolipid has been partially purified by chromatography on LH-20. The molecular weight of the proteolipid is approximately 3000 as determined by urea-sodium dodecyl sulfate gel electrophoresis. This proteolipid can bind and transport phosphate into an organic phase. The K0.5 for phosphate binding is 8 microM with a Hill coefficient of 1.92. Arsenate inhibits phosphate binding in a competitive manner with a KI of 27.5 microM. The aminoreactive reagent 2,4-dinitrofluorobenzene inhibits phosphate binding to the proteolipid. Similarly, 2,4-dinitrofluorobenzene inhibited Na+-driven Pi uptake in renal brush-border membrane vesicles. In contrast to the mitochondrial phosphate binder, this proteolipid is not inhibited by sulfhydryl reagents. We suggest that this molecular species is a likely candidate for involvement in phosphate uptake in the renal tubule.

Animals↗
PubMed1977

Uncouplers and the molecular mechanism of uncoupling in mitochondria.

Uncouplers are molecules with protonophoric and ionophoric capabilities that mediate coupled cyclical transport of cations--a transport that takes precedence over all other coupled processes. Uncouplers form cation-containing complexes with electrogenic ionophores that potentiate cyclical transport of cations. The molecular mechanism of uncoupling sheds strong light on the mechanism of coupling.

Adenosine Triphosphatases↗
PubMed1977

Coupling in cytochrome c oxidase.

Cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase; EC 1.9.3.1) can be resolved into an electron transfer complex (ETC) and an ionophore transfer complex (ITC). Coupling requires an interaction between the moving electron in the ETC and a moving, positively charged ionophore-cation adduct in the ITC. The duplex character of cytochrome oxidase facilitates this interaction. The ITC mediates cyclical cation transport. It can be replaced as the coupling partner by the combination of valinomycin and nigericin in the presence of K(+) when cytochrome oxidase is incorporated into liposomes containing acidic phospholipids or by the combination of lipid cytochrome c and bile acids in an ITC-resolved preparation of the ETC. Respiratory control can be induced by incorporating cytochrome oxidase into vesicles of unfractionated whole mitochondrial lipid. The activity of the ITC is suppressed by such incorporation and this suppression leads to the emergence of respiratory control. The ionophoroproteins of the ITC can be extracted into organic solvents; some 50% of the total protein of cytochrome oxidase is extractable. The release of free ionophore is achieved by tryptic digestion of the ionophoroprotein. Preliminary to this release the ionophoroprotein is degraded to an ionophoropeptide. Electrogenic ionophores, as well as uncoupler, are liberated by such proteolysis. The ITC contains a set of ionophoroproteins imbedded in a matrix of phospholipid.

Animals↗
PubMed1977

Isolation of an electrogenic K+/Ca2+ ionophore from an ionophoroprotein of beef heart mitochondria.

A K+/Ca2+ electrogenic ionophore has been isolated from an ionophoroprotein of beef heart mitochondria and identified as a neutral peptide of molecular weight 1600. The amino acid composition and cationic specificity of the ionophore have been determined. The free ionophore was released from the ionophoroprotein as a consequence of tryptic digestion. The ionophoroprotein can be converted to an ionophoro peptide (molecular weight 5,100) by proteolysis without release of the free ionophore. The isolation of a K+/Ca2+ ionophore thus provides an introduction to the general technology of extracting ionophoro proteins and ofreleasing ionophores from these proteins by proteolytic digestion.

Animals↗
PubMed1976

Mechanism of uncoupling in mitochondria: uncouplers as ionophores for cycling cations and protons.

Classical uncouplers such as 2,4-dinitrophenol have been shown to be ionophores with the capability for transporting monovalent or divalent cations with equal efficiency. The conditions appropriate for the maximal expression of this ionophoric capability have been explored. Two critical factors are the polarity of the organic phase and the pH of the aqueous phase that is equilibrated with the organic phase. The demonstrated cationic ionophoric capability of uncouplers, taken in conjunction with the known ability of uncouplers to cycle protons across a membrane phase, provides the experimental basis for the thesis that uncoupling of electron flow from ATP synthesis via classical uncouplers involves the substitution of one coupled process by another. Uncoupling thus reduces to the replacement of one driven reaction (ATP synthesis) by the driven reaction (cyclical transport) mediated by the uncoupler.

Animals↗