Acid titrations of poly(dG-dC).poly(dG-dC) in aqueous solution and in a w/o microemulsion.

The model polynucleotide poly(dG-dC).poly(dG-dC) (polyGC) was titrated with a strong acid (HCl) in aqueous unbuffered solutions and in the quaternary w/o microemulsion CTAB/n-pentanol/n-hexane/water. The titrations, performed at several concentrations of NaCl in the range 0.

Titration of poly(dA-dT) . poly(dA-dT) in solution at variable NaCl concentration.

CD and uv absorption data showed that high molecular weight poly(dA-dT) . poly(dA-dT), at 298 K, undergoes an acid-induced transition from B-double helix to random coil in NaCl solutions of different concentrations, ranging from 0.005 to 0.

Protective effect of procaine hydrochloride on cisplatin-induced alterations in rat kidney.

Efforts have been made to reduce the undesirable side effects of cisplatin, mainly nephro- and neurotoxicity, but their reduction is usually accompanied by a concomitant inhibition of antitumor activity. The local anesthetic procaine hydrochloride (P.HCl) improves the therapeutic index of cisplatin not only by the reduction of its nephro- and hemotoxicity, but also by an increase of its antitumor activity.

Hyperammonemia and chronic hepatic encephalopathy: an in vivo PMRS study of the rat brain.

The brain energy metabolism of rats affected by chronic hepatic encephalopathy due to portacaval shunting was monitored by in vivo 31P-nuclear magnetic resonance spectroscopy before and after ammonium acetate administration. With respect to healthy unoperated and to sham operated controls, portacaval shunting decreased the levels of the nuclear magnetic resonance (NMR) visible brain phosphocreatine and nucleoside phosphates, and the intracellular [free Mg(2+)]. Ammonium acetate induced a further decrease of the levels of the NMR detectable phosphocreatine and nucleoside triphosphates and of the [free Mg(2+)], while the PMR spectra of the brain of non-shunted rats did not show any significant change even after treatment with ammonium acetate.

Sodium ion distribution in the vitreous body.

We have studied the nuclear magnetic resonance (NMR) relaxation behavior, and thus the dynamic properties, of the sodium ion in the vitreous body at different temperatures. The 23Na NMR spectrum exhibits a resonance, the intensity of which accounts for an ion visibility of 100%. The 23Na longitudinal and transverse relaxation times, at all temperatures but the highest, present two components, suggesting that the sodium ions are present in two states of different mobility, whose populations are in slow exchange on the NMR time scale.

Phospholipid-based reverse micelles.

Physicochemical investigations on the aggregation of phospholipids (mainly phosphatidylcholines) in organic solvents are reviewed and compared with the aggregation behaviour of phospholipids in aqueous medium. In particular we review the data showing that phosphatidylcholines (lecithins) form reverse micellar structures in certain apolar solvents. In these systems not only low molecular weight compounds but also catalytically active enzymes and entire cells can be solubilized.

NMR monitoring of the anaerobic metabolism of frog muscle at rest.

The time dependence of Lactate (Lac), H+, Adenosine-triphosphate (ATP), Phosphocreatine (PCr), Hexose-monophosphate (PME), and Inorganic Phosphate (Pi) levels has been obtained for frog muscle at rest in anaerobic conditions by multinuclear NMR. All information has been collected on the same samples alternatively tuning the probehead on 1H- and 31P-NMR frequencies. ATP, PCr and H+ levels show the same time dependence for all the samples, while PME, Pi and Lac levels vary in time differently from one sample to another.

An approach to noninvasive fiber type determination by NMR.

In vivo 31P NMR spectroscopy was used to determine the ratios of creatine phosphate (PCr) to adenosine triphosphate (ATP) and inorganic phosphate (Pi) in leg and arm muscles of four sprinters, one marathon runner, and two sedentary subjects. Both ratios were definitely higher in the sprinters indicating that, since muscle ATP and Pi concentrations are constant, the PCr muscle content of these athletes is higher than usual. Sprinters are known to have higher percentages of fast-twitch fibers, which are richer in PCr than slow-twitch fibers.

Nucleotide pool and the proliferative process: an NMR study of the liver regeneration.

The metabolic changes occurring during liver regeneration after partial hepatectomy have been followed by examination of the perchloric extracts by means of NMR spectroscopy. Proton spectra show an abrupt decrease of glycogen, glucose and nucleotides, which are essentially ribonucleotides, in the first hours after hepatectomy. Nucleotides begin to store up again in the third day after hepatectomy, while glucose and glycogen storage builds up from the second day.

Characterization of human pathological papillary muscles by 1H-NMR spectroscopic and histologic analysis.

Two groups of human pathological papillary muscle samples were analyzed by 1H-NMR spectroscopy and histology. The first group, mainly characterized by hypertrophy of the myocardial cells, interstitial edema and intracellular lipoperoxide accumulation showed similar T1 as well as T2 values. The second group, mainly characterized by hypertrophy of the myocardial cells, fibrosis and areas of necrosis showed T1 values longer than those of the first group while no appreciable differences were evident in the T2 values.

Interactions of ubiquinones with membrane models.

The effect of the insertion of coenzyme Q10 and some of its shorter chain homologues in membrane models (Reverse Micelles, Small Unilamellar Vesicles and Liposomes) has been studied by NMR and IR spectroscopies. By 1H-NMR we have found that the stretched conformation of the isoprenoid side-chain observed in solution is maintained in membrane models. Interaction between the quinonoid moiety of the Q's and the phosphatidic groups of the phospholipids has been evidenced by 31P-NMR.

Proton NMR study of erythrocytes of essential hypertensives.

Proton NMR studies (saturation transfer experiments and longitudinal relaxation time determinations) indicate that substantial differences exist between erythrocytes of essential hypertensives and normotensive subjects. A higher degree of intracellular organization has been found for the hypertensives and several factors are proposed as contributing to the observed behaviour.

Natural abundance 13C-NMR study of liver regeneration in rats.

13C-NMR spectra of liver samples of partially hepatectomized rats have been obtained at 50 MHz. The tissue specimens, fixed in buffered formaldehyde solution, were obtained for NMR spectroscopy at various time intervals between 6 and 72 hours after hepatectomy. Several metabolites were identified from the spectra and their concentrations were determined as a function of time.

Time dependence of the proton relaxation times of regenerating rat liver.

The proton longitudinal relaxation time of regenerating rat liver has been found to increase during the first 24 hours after hepatectomy and to drop back to normal in the following hours. The decreased relaxation rate may be related to the increase of the water mobility due to the expansion of the intercellular spaces during the massive proliferation of the first day, or to the increased cell hydration which is known to occur during active cell proliferation. Equations have been derived for the proliferation process, and the competing inhibition process, active from the 24th hour, which can quantitatively account for the proton relaxation behaviour.

Modified proton relaxation behaviour in erythrocytes from spontaneously hypertensive rats.

The proton NMR parameters of suspensions of erythrocytes from normotensive (MNS and WKY strains) and spontaneously hypertensive (MHS and SHR strains) rats have been compared: a marked difference in the relaxation behaviour has been observed for the two classes of strains. Various factors which may give rise to the difference found in dynamic behaviour are discussed.

Ubiquinones: stereochemistry and biological implications.

Proton NMR and 13C-NMR studies on the configuration of CoQn homologues show that the polyisoprenoid side-chain is in the all-trans configuration and confers a higher degree of rigidity to the quinones with respect to the acyl-chains of the phospholipids within the membrane bilayer. The quinonoid ring appears to be specifically involved in the redox function of the coenzyme while the side-chain length only affects the lipophilicity of the molecule. LIS data show that the ring strongly interacts with metals as a consequence of the high pi-electron density on the carbonyls that is somewhat larger on the carbonyl oxygen to alpha to the isoprenoid chain.