Abstract Cancer cells have a greater need for energy and a ready supply of the building blocks necessary for the synthesis of macromolecules (nucleotides, protein, lipids) in order to duplicate ...genome and biomass. The hypothesis can be postulated that those precursors for synthetic processes, which can only be furnished by glycolysis, cannot be sufficiently recruited from external sources (the blood stream) and that glycolysis is necessarily markedly activated. It can also be hypothesized that the Krebs cycle, which also furnishes precursors for macromolecule synthesis to meet the requirements of proliferating cells, is depleted of intermediates. In view of its cyclic nature requiring not only pyruvate but also oxalacetate as the “last” metabolite of the reaction sequence for its sustenance, the Krebs cycle may be partially inactivated. While anaplerotic reactions and other sources (amino acids and fatty acids) could supply the cycle with intermediates, those pathways constitute futile cycles for amino and fatty acids as they would be partially degraded in the cycle and the intermediates thus obtained would be exported into the cytoplasm for synthetic processes with no advantage for the cell. It is also hypothesized that glutamine, an important fuel for cancer cells and playing a critical role in anaplerosis, may not contribute to reinforce the cycle; malate and α-ketoglutarate, two products of glutamine metabolism, might be exported from the mitochondria as precursors of biosynthetic pathways. It is possible then that malate, used for NADPH production required in the biosynthetic pathways, and glycerol–phosphate, too used for biosynthetic purposes (lipid biosynthesis), are unable to sustain the mitochondrial redox shuttles reducing the respiratory capacity of the mitochondria. Low shuttle capacity implies that NADH generated by glycolysis needs to be continuously re-oxidized in the cytoplasm via lactate dehydrogenase to maintain glycolysis fully activated, causing the abnormal lactate production observed in cancer. The paper goes onto discuss the essential role of glucose in cancer cell proliferation also in inducing the Crabtree effect. It is finally hypothesized that respiration inhibition after cancer cells have been supplied with glucose is due to reactivation in a suited medium of biosynthetic pathways with the consequences described above.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Rheumatic carditis is a sequela of group A streptococcal throat infection. Although the pathogenic mechanisms which lead to heart damage in acute rheumatic fever (ARF) are not well understood, ...autoimmune processes have been implicated, involving molecular mimicry between streptococci and the human heart. We have studied the immunological cross-reactions between the group A Streptococcus and human heart to understand their molecular and immunological basis. Human and mouse monoclonal antibodies (mAb) and affinity-purified anti-myosin antibodies from acute rheumatic fever sera were characterized and shown to cross-react with group A streptococcal M protein and myosin. Studies of proteolytic fragments of human cardiac myosin identified sites of cross-reactivity in the rod region of the myosin heavy chain. Murine monoclonal antibodies cross-reactive with streptococcal M protein and myosin recognized epitopes located in the S2 and light meromyosin (LMM) subfragments of the heavy chain. None of the cross-reactive monoclonal antibodies recognized the S1 subfragment. One broadly cross-reactive monoclonal antibody was highly cytotoxic for heart cells in vitro and reactive with the LMM fragment. The data suggest that the cross-reactive epitopes recognized by these antibodies are conformational, dependent upon their alpha-helical structures, and potentially damaging to host tissues.
Δ∼μ
H has been determined in steady state mitochondria, by measuring the magnitude of ΔpH on the distribution of acetate and of Δψ on the distribution of K
+, tetraphenylphosphonium, Ca
2+, Sr
2+ and ...Mn
2+.
1.
(1) The matrix concentration of divalent cations has been calculated from the total cation uptake, from the increase of matrix volume and from the ESR sextet signal of Mn(H
2O)
6
2+. The cat
2+
i based on osmotic data is about five times higher than that based on ESR measurements. The cat
2+
i based on total uptake is much higher than that based on osmotic data at low cation/protein ratios.
2.
(2) In the presence of 10 mM acetate the maximal Δψ on Ca
2+ is about 130 mV and on Sr
2+ is 95 mV. Δψ on Mn
2+ is 91 or 109 mV, according to whether cat
2+
i is calculated from ESR or osmotic data. Under the same conditions, ΔpH is about 60 mV. Hence, Δ∼μ
H on divalent cations is between 151 and 190 mV.
3.
(3) Δψ on K
+, in valinomycin treated mitochondria with 10 mM acetate or 2 mM Pi, drops from 200 mV, at low K
+
o to almost zero parallel to the increase of K
+
o. ΔpH is 30 mV at low K
+ and about 42 mV at 600 μM K
+. Hence Δ∼μ
H drops from 227 mV to lower values with the increase of K
+
o.
4.
(4) Maximal Δψ on triphenylmethylphosphonium is 143 mV.
5.
(5) When Δ∼μ
H is measured simultaneously on divalent cations and on K
+, the values on K
+ tend to approach those on Ca
2+, while those on Sr
2+ are about 50 mV lower.
6.
(6) It is concluded that the steady state mitochondrial energy potential is equivalent to a Δ∼μ
H between 150 and approx. 190 mV.
Three effects concerning the organic cations, the aggregation, the metachromasy and the
pK
α
shift, have been studied in comparison at high dye concentrations, with natural and synthetic polyanions ...and with energized submitochondrial particles.
The metachromatic effect has been obtained by increase of the free cationic dye concentration or by interaction of the dye with natural, synthetic polyanions and energized submitochondrial particles. The metachromatic effect is dependent on the pH of the medium, the presence of ionized acidic groups, and the ionic strength of the medium.
The polyanion‐induced metachromasy requires the ionization of the acidic groups of the polyelectrolyte. The metachromasy with neutral red requires an acidic pH if induced by increase of the dye concentration or by chondroitin sulphuric acid, whereas it takes place also at alkaline pH if induced by polystyren sulphonic acid or by energized particles. It is inhibited by increase of ionic strength in the case of agar and chondroitin sulphuric acid, but not in the case of the energized particles or polystyrene sulphonic acid.
Interaction of neutral red with polystyrene sulphonic acid or energized particles results also in a large apparent
pK
α
shift, which represents the mechanism for obtaining the metachromatic effects at alkaline pH. The apparent
pK
α
, as measured from the extinction of the alkaline band is: 6.0 at 400 μM neutral red, 6.7 at 20 μM neutral red, 7.0 with chondroitin sulphuric acid, 7.1 with the deenergized particles, 8.0 with polystyrene sulphonic acid and 8.1 with energized particles. From thermodynamic considerations it is suggested that the
pK
α
shift requires a decrease of the activity coefficient of the dye following the formation of ion pairs with anionic groups of the membrane. The
pK
α
shift may be taken as a tool for discriminating between a dyeinduced and a membrane‐induced metachromatic effect.
A model is proposed for the energized membrane, based upon electrostatic and hydrophobic interactions of the cationic dyes with a layer of oriented nucleophilic sites in an environment of intermediate polarity.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
The Membrane Structure Studied with Cationic Dyes Dell' Antone, Paolo; Colonna, Raffaele; Azzone, Giovanni Felice
European journal of biochemistry,
January 1972, Volume:
24, Issue:
3
Journal Article
Peer reviewed
Open access
Three effects concerning the organic cations, the aggregation, the metachromasy and the pKα shift, have been studied in comparison at high dye concentrations, with natural and synthetic polyanions ...and with energized submitochondrial particles.
The metachromatic effect has been obtained by increase of the free cationic dye concentration or by interaction of the dye with natural, synthetic polyanions and energized submitochondrial particles. The metachromatic effect is dependent on the pH of the medium, the presence of ionized acidic groups, and the ionic strength of the medium.
The polyanion‐induced metachromasy requires the ionization of the acidic groups of the polyelectrolyte. The metachromasy with neutral red requires an acidic pH if induced by increase of the dye concentration or by chondroitin sulphuric acid, whereas it takes place also at alkaline pH if induced by polystyren sulphonic acid or by energized particles. It is inhibited by increase of ionic strength in the case of agar and chondroitin sulphuric acid, but not in the case of the energized particles or polystyrene sulphonic acid.
Interaction of neutral red with polystyrene sulphonic acid or energized particles results also in a large apparent pKα shift, which represents the mechanism for obtaining the metachromatic effects at alkaline pH. The apparent pKα, as measured from the extinction of the alkaline band is: 6.0 at 400 μM neutral red, 6.7 at 20 μM neutral red, 7.0 with chondroitin sulphuric acid, 7.1 with the deenergized particles, 8.0 with polystyrene sulphonic acid and 8.1 with energized particles. From thermodynamic considerations it is suggested that the pKα shift requires a decrease of the activity coefficient of the dye following the formation of ion pairs with anionic groups of the membrane. The pKα shift may be taken as a tool for discriminating between a dyeinduced and a membrane‐induced metachromatic effect.
A model is proposed for the energized membrane, based upon electrostatic and hydrophobic interactions of the cationic dyes with a layer of oriented nucleophilic sites in an environment of intermediate polarity.
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
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