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S Abou-Khalil

Publications and source records attributed to S Abou-Khalil.

29 records · Page 2Linked to original sources
PubMed1980

Mitochondrial metabolism in normal, myeloid, and erythroid hyperplastic rabbit bone marrow: effect of chloramphenicol.

Protein synthesis, respiration, and oxidative phosphorylation were studied in mitochondria isolated from normal, myeloid, and erythroid hyperplastic bone marrow of rabbits. Mitochondria from normal and myeloid hyperplastic marrow showed a similar degree of 14C-leucine incorporation while a threefold higher activity was demonstrated in mitochondria from erythroid marrow. The incorporation was mitochondrial-concentration-dependent and in all cases was inhibited by low concentrations of chloramphenicol (CAP). The respiratory activity of mitochondria isolated from either myeloid or erythroid marrow was twice as high as the normal, but in all cases respiration and phosphorylation were unaffected by concentrations of CAP which totally inhibited protein synthesis.

Adenosine Triphosphate↗
PubMed1979

Energy-linked Sulfate Uptake by Corn Mitochondria via the Phosphate Transporter.

Corn shoot mitochondria possess an energy-linked transport system for sulfate uptake as demonstrated by osmotic swelling and [(35)S]SO(4) (2-) accumulation. Maximum uptake is secured in the presence of Mg(2+) and oligomycin with sucrose for osmotic support. Neither phosphate nor dicarboxylate anions are required. When added simultaneously, millimolar concentrations of phosphate block [(35)S]SO(4) (2-) uptake after the initial minute. Mersalyl, N-ethylmaleimide, and 2,4-dinitrophenol are strong inhibitors of sulfate uptake; n-butylmalonate is a weak inhibitor. These inhibitors act in the same fashion on phosphate uptake. It is concluded that sulfate uptake in the absence of phosphate is by the phosphate transporter.

Journal Article↗
PubMed1979

Energy-linked Adenosine Diphosphate Accumulation by Corn Mitochondria: I. General Characteristics and Effect of Inhibitors.

Corn mitochondria show respiration-linked net accumulation of [(3)H]ADP in the presence of phosphate and magnesium, especially if the formation of ATP is blocked with oligomycin. Inhibition of ADP-ATP exchange by carboxyatractyloside also activates ADP accumulation, and addition of carboxyatractyloside or palmitoyl-coenzyme A to oligomycin-blocked mitochondria produces additional ADP uptake. With carboxyatractyloside the accumulated ADP is phosphorylated to ATP. With oligomycin, only a little ATP is formed. Millimolar concentrations of ADP are required for maximum uptake, and the K(m) (3.77 millimolar) for ADP translocation is independent of whether oligomycin or carboxyatractyloside is used. This is not true for ADP concentrations in the 0.05 to 0.25 millimolar range. Accumulated [(3)H]ADP rapidly exchanges with unlabeled AMP, ADP, or ATP, but not with other diphosphate nucleotides or 2 millimolar substrate anions. [(3)H]AMP is not accumulated, but [(3)H]ATP is accumulated to about one-half the extent of [(3)H]ADP. Tricarboxylate substrates inhibit ADP net uptake, and inhibition by citrate is competitive with K(i) = 10 millimolar. The evidence suggests the presence of a pathway, carboxyatractyloside-insensitive and different from the translocase, which operates to maintain adenine nucleotides in the matrix.

Journal Article↗
PubMed1979

Energy-linked Adenosine Diphosphate Accumulation by Corn Mitochondria: II. Phosphate and Divalent Cation Requirement.

The requirement for phosphate and Mg(2+) in energy-linked [(3)H] ADP accumulation by corn mitochondria has been studied. Arsenate will fully substitute for phosphate; sulfate partially substitutes; acetate, bicarbonate, and pyrophosphate are ineffective. Phosphate is also taken up by the mitochondria, but the ADP/Pi ratio varies widely with experimental treatments. ADP does not exchange with endogenous labeled phosphate, although Pi/(32)Pi exchange occurs.Mg(2+) is also accumulated during ADP uptake. Mg(2+) can be substituted with varying efficiency by other divalent cations, but not monovalent cations. Effective cations typically increase phosphate uptake, particularly Ca(2+) . Ca(2+) -activated ADP accumulation is insensitive to carboxyatractyloside over a wide range of Ca(2+) concentrations. When Ca(2+) is substituted for Mg(2+) it is not necessary to block ATP formation to secure high levels of ADP accumulation, since Ca(2+) will divert energy from ATP formation into ion uptake.It is suggested that the transport mechanism may carry out a concerted transport of ADP and phosphate with bound divalent cation. The phosphate transporter may be involved, or alternatively a special mechanism for trivalent anion transport may exist which acts cooperatively with the phosphate transporter.

Journal Article↗
PubMed1975

Special features of Pi transport in pig heart and rat liver mitochondria as revealed by 6,6'-dithiodinicotinic acid (CPDS).

CPDS (6,6'-dithiodinicotinic acid), a non permeant thiol agent which affects several mitochondrial functions in a way different to that of mersalyl [18-19] revealed striking differences between the phosphate translocating systems of pig heart and rat liver mitochondria. Pi entry was measured either by swelling in 0.12 M ammonium phosphate or by rapid centrifugation in 32Pi medium. Pi efflux was measured after preloading of mitochondria with 32Pi, by exchange against Pi or malate; the "ATP-FCCP" system has been tested previously [19]. In pig heart mitochondria, Pi entry seems to proceed exclusively via the Pi/OH- carrier; CPDS completely inhibits this transport and the energy-linked functions. In contrast n-butyl-malonate does not affect the Pi-entry and the energy-linked functions. The Pi efflux is not affected either by CPDS or mersalyl, which do not produce a swelling in the "ATP-uncoupler system". In rat liver mitochondria, CPDS inhibits only the Pi/OH- carrier; both CPDS and n-butylmalonate are necessary to inhibit completely Pi entry. CPDS as well as mersalyl provokes a swelling in the presence of the "APT-uncoupler system". The results suggest two distinct functions of phosphate transport in both types of mitochondria.

Animals↗