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Biomedical subjects

D E Green

Publications and source records attributed to D E Green.

At least 91 records · Page 5Linked to original sources
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

Phospholipids as ionophores.

The ionophoretic capabilities of phospholipids have been examined by direct measurement in a Pressman cell of the phospholipid-mediated translocation of cations across an organic phase separating two aqueous phases. Cardiolipin and phosphatidic acid were the most active inonophores among the phospholipids tested, with activities comparable to that of X537A in respect to the translocation of divalent cations. Cardiolipin translocates both divalent and monovalent cations at approximately equal rates. The ionophoretic activity of cardiolipin could be modulated by other phospholipids (inhibition), by butacaine (stimulation), by complexation with cytochrome c (inhibition), and by ruthenium red and lanthanum (inhibition). The rate of translocation of cations mediated by cardiolipin was independent of pH over a wide pH range (5.4 to 8.3). The same general pattern of properties observed for cardiolipin applied to phosphatidic acid except for stimulation by butacaine. Complexation of phospholipid mixtures, such as asolectin or mitochondrial lipid, with reduced cytochrome c, enhanced the ionophoretic capability of these phospholipids by 1 order of magnitude. The complex thus formed has the properties of a polyionophore. The possible physiological significance of this enormous ionophoretic potential of phospholipids is examined.

Calcium↗
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↗
PubMed1976

Automated analysis of phencyclidine in urine by probability based matching GC/MS.

A novel form of selected ion recording mass spectrometry using a microcomputer-managed mass spectrometer was employed to automatically identify and quantitate phencyclidine (PCP) in cyclohexane extracts of urine by Probability Based Matching. Seventy urine samples from known abusers were assayed for PCP content. The positively identified PCP concentrations ranged from 0.01 to 10.5 mug/ml for 65 samples, 26% of which fell in the 0.35-1.0 mug/ml range and 30% in the 1.0-3.4 mug/ml range. Five specimens had no detectable PCP (less than 10 mug/ml). Cyclohexane extraction efficiency for PCP in urine exceeded 95%. Selected ion monitoring was found to be necessary in order to avoid gas chromatographic interferences produced by co-elution of contaminants at the same retention time as PCP.

Autoanalysis↗
PubMed1976

Quantitation of cannabinoids in biological specimens using probability based matching GC/MS.

The results from these urine studies and a few other isolated extracts we have run may be generalized as follows: The hexane fractions showed low levels of delta9-THC (ca. 10 ng/ml) with marginal Confidence Indices (25-30), but both the quantities and the K-scores were well above the values seen in extracts of control urines; the hexane fractions showed similar levels of CBN (ca. 12-25 ng/ml) with significant K-scores (60-80); the ether-extractable neutral fraction contained 8alpha, 11-dihydroxy-delta9-THC (25-150 ng/ml) with low conficdence and sometimes a suggestion of 8beta-hydroxy-delta9-THC (15 ng/ml) with a marginal identification; and the E-II fraction (ether-extractable, weak acids) usually contained a strong indication (CONF 60-95) of delta9-THC-11-oic acid (100-200 ng/ml.

Animals↗
PubMed1976

The passage of 14C-delta-9-tetrahydrocannabinol into the milk of lactating squirrel monkeys.

Lactating squirrel monkeys chronically receiving 2 mg/kg delta-9-tetrahydrocannabinol (THC) orally either two or five times weekly were given a tracer dose of 14C-delta-9-THC mixed with the delta-9-THC. This permitted radioquantitation of the THC in milk specimens collected 1 to 24 hr after administration of the labeled dose. Correlated specimens of urine and feces were also collected individually from mothers and infants and were subjected to radioquantitation and exploratory TLC. During the 24-hr observation period, approximately 0.2% of the labeled delta-9-THC appeared in the milk, whereas 42% and 1% were excreted in the feces and urine, respectively. Infants that suckled during the 6 hr immediately after their mothers were administered the labeled compound excreted an average of 0.01% and 0.12% of the mother's dose in the urine and feces, respectively, during the 18 hr after suckling.

Animals↗