Effects of cadmium ions on synaptic transmission in the frog tectum

The effects of cadmium ions on synaptic transmission in the frog tectum were investigated in acute experiments using quantal EEG recording techniques (readings of extracellular monosynaptic potential induced by activating the synapses of a single axon) [1]. Superfusion of the tectum by 10–200 µM CdCl₂ reversibly inhibits EEG quanta, reduces their duration (measured at 50% amplitude level) and increases synaptic delay. The results of this study confirm the concept formed from in vitro experiments of votage-dependent calcium channels as one of the likely Cd²⁺ action sites at central synapses. It is concluded that cadmium-induced industrial pollution may also pose a threat in the form of damaging action on the central nervous system.Medical Institute, Ministry of Public Health of the Lithuanian SSR, Kaunas. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 756–765, November–December, 1989.     

Effects of sedation on the controlled pulmonary circulation

The pulmonary circulatory effects of sedatives and groups of sedatives in dosages commonly employed as pre cardiac catheterization sedatives were evaluated. The sedatives included: meperidine, thiamylal, hydroxyzine, promethazine, meperidine + chlorpromazine + promethazine and meperidine + hydroxyzine. An animal preparation with constant pulmonary blood flow and left atrial pressure was employed. This preparation has the unique advantage of permitting measurement of the active pulmonary vascular resistance change since passive effects are controlled. In order to establish the significance of a given change in active PVR, a dose response relationship for serotonin was established and the effect of the sedatives was calibrated against it. PVR increased following infusion of all sedatives tested except hydroxyzine and chlorpromazine.A technique was detailed to permit subtraction of passive PVR change from total PVR change in intact, unsedated animals. Results of active change in PVR of previous investigations in intact, unsedated animals were compared to the active change observed in this experiment and were found to be similar in direction and magnitude. This investigation stresses the need to consider possible effects of sedatives on the pulmonary circulation.     

Effects of octopamine on pulmonary circulation of the pig]

The perfusion of octopamine in pig produces an increase of cardiac output with decrease of pulmonary vascular resistances. The changes in lung circulation depend by a direct action of this drug on nervous control of vascular walls because when the pulmonary shunt increase the effect is not correlated to changes a pattern of breathing.     

Effects of nociceptive stimuli on the pulmonary circulation in the ovine fetus

The fetus is able to exhibit a stress response to painful events, and stress hormones have been shown to modulate pulmonary vascular tone. At birth, the increased level of stress hormones plays a significant role in the adaptation to postnatal life. We therefore hypothesized that pain may alter pulmonary circulation in the perinatal period. The hemodynamic response to subcutaneous injection of formalin, which is used in experimental studies as nociceptive stimulus, was evaluated in chronically prepared, fetal lambs. Fetal lambs were operated on at 128 days gestation. Catheters were placed into the ascending aorta, superior vena cava, and main pulmonary artery. An ultrasonic flow transducer was placed around the left pulmonary artery. Three subcutaneous catheters were placed in the lambs' limb. The hemodynamic responses to subcutaneous injection of formalin, to formalin after fetal analgesia by sufentanil, and to sufentanil alone were recorded. Cortisol and catecholamine concentrations were also measured. Pulmonary vascular resistances (PVR) increased by 42% (P < 0.0001) after formalin injection. Cortisol increased by 54% (P = 0.05). During sufentanil infusion, PVR did not change significantly after formalin. Cortisol increased by 56% (P < 0.05). PVR did not change during sufentanil infusion. Norepinephrine levels did not change during any of the protocols. Our results indicate that nociceptive stimuli may increase the pulmonary vascular tone. This response is not mediated by an increase in circulating catecholamine levels. Analgesia prevents this effect. We speculate that this pulmonary vascular response to nociceptive stimulation may explain some hypoxemic events observed in newborn infants during painful intensive care procedures.     

Interaction of alkaline-earth metal ions with calf thymus DNA. Volume and compressibility effects in diluted aqueous solutions

The binding of Mg2+, Ca2+, Sr2+ and Ba2+ ions to calf thymus DNA in solutions has been investigated by ultrasonic and densimetric techniques. The obtained parameters, the apparent molar volume, phiV, and the apparent molar adiabatic compressibility, phiK(S), are very sensitive to hydration of investigated molecules. The interaction between the cations and DNA is accompanied by overlapping their hydration shells and consequently releasing the water molecules from hydration shells to bulk state. The change in the hydration is reflected in the measured parameters, phiV and phiK(S). The magnitude of these hydration changes is determined by the position of the cation relative to DNA atomic groups involved in the binding, and thus can characterize the structure of cation-DNA complexes. The values of the dehydration effects of the binding, deltaphiV and deltaphiK(S), correspond to two direct or higher number of indirect contacts between calf thymus DNA and the cations.     

DNA conformational equilibrium in the presence of Zn2+ ions in neutral and alkaline solutions

Effect of Zn(2+) ions on DNA transition from B-form to a metallized form (m-DNA) in Tris and tetraborate buffers at pH 8.5 has been studied by visible and differential UV-spectroscopy and by thermal denaturation. The results have been compared to those obtained at pH 6.5 in cacodylate buffer. It was found that in alkaline solutions Zn(2+) ions induced a hypochromicity of the DNA absorption in the whole spectral range monitored, which was attributed to DNA transition from B- to the m-form. Complete metallization occurred only upon heating the DNA solutions containing more than ~2×10(-4) M of Zn(2+) ions. Phase diagrams of the DNA-zinc complexes at pH 6.5 and 8.5 have been obtained for the first time. The m-DNA form showed higher thermal stability compared to B-DNA.     

Effects of ionized cyclodextrin on decomposition of allyl isothiocyanate in alkaline solutions

The secondary hydroxyl ion (alkoxide) ion for cyclodextrin (CD) may affect the decomposition of allyl isothiocyanate (AITC) in alkaline solutions. The equilibrium and kinetic parameters involved in the reaction processes were measured. It was found that the interaction between the alkoxide ion for CD and the included AITC occurred more than pKa 12.7. From the identified kinetic parameters and discussion, it was suggested that the reaction site of AITC was located in the vicinity of one of the secondary hydroxyl groups of CD in the cavity.