[Mechanism of local anesthesia: long-range orientation effects]

The orientation interaction of a molecule of a local anesthetic with a biomembrane and cell-like liquid was studied, based on the model of adsorption of the anesthetic from a cell-like solution on the surface of a biomembrane for compounds of the trimecaine series. A statistically significant correlation equation was obtained, which relates the minimum blocking concentration to the projection of the dipole moment of the anesthetic on the plane X(1)0X2 of the principal axes of inertia. A model is prosed according to which the "anesthetic-biomembrane" interaction is most effective the molecule of the anesthetic rotates around the axis of the maximum moment of inertia.

Inhibition of membrane-bound carbonic anhydrase decreases subretinal pH and volume

PURPOSE

The lipophilic carbonic anhydrase (CA) inhibitor acetazolamide has been shown to enhance subretinal fluid resorption, reduce subretinal pH, and can improve cystoid macular edema, but its clinical use is limited by systemic side effects. While these are most likely a result of inhibiting intracellular CA isoenzymes, retinal pigment epithelial (RPE) transport is thought to be modulated via membrane-bound CA. This study investigates whether benzolamide, a hydrophilic CA inhibitor that does not readily penetrate cell membranes, is sufficient to modulate subretinal volume and pH.

METHODS

Volume and pH were assessed in the subretinal space (SRS) of the perfused chick retina-RPE-choroid preparation by calculating these variables from data obtained with two different double-barreled, ion-selective electrodes (H+ for pH and the extracellular space marker tetramethylammonium (TMA+) for SRS volume). Light induced variations and changes in baseline measurements were recorded before and after addition of 10(-4) M acetazolamide or benzolamide to the basal perfusion.

RESULTS

Basal perfusion with either drug induced both an acidification of the SRS by 0.02-0.04 pH units, which occurred within 60 s, as well as an increase in the amplitude of the light-induced alkalinisation of the SRS. TMA+ concentration in the SRS increased steadily over a period of several minutes after basal perfusion with either of the CA inhibitors, and the calculated SRS volume was reduced by 40% within 8-10 min.

CONCLUSION

The observation that benzolamide had effects equal to acetazolamide suggests that inhibition of membrane-bound CA at the basolateral membrane of the RPE is sufficient to decrease subretinal pH and volume. This may represent a clinically important mechanism for the resorption of sub- and intraretinal fluid.

A circadian clock regulates the pH of the fish retina

Although it is generally accepted that the acid/base ratio of tissue, as represented by the pH, is strictly regulated to maintain normal function, recent studies in the nervous system have shown that neuronal activity can result in significant shifts in pH. In the vertebrate retina, many cellular phenomena, including neuronal activity, are regulated by a circadian clock. We thus investigated whether a circadian clock regulates the pH of the retina. pH-sensitive microelectrodes were used to measure the extracellular pH of the in vitro goldfish retina superfused with a bicarbonate-based Ringer solution in the subjective day and night; that is, under conditions of constant darkness. These measurements demonstrated that a circadian clock regulates the pH of the vertebrate retina so that the pH is lower at night compared to the day. This day-night difference in retinal pH was observed at two different values of Ringer solution pH, indicating that the circadian phenomenon is independent of the superfusion conditions. The circadian-induced shift in pH was several times greater than light-induced pH changes and large enough to influence synaptic transmission between retinal neurons. These findings indicate that a circadian clock regulates the pH of the vertebrate retina. Thus, an intrinsic oscillator in neural tissue may modulate metabolic activity and pH as part of normal daily function.

Light-induced changes of extracellular ions and volume in the isolated chick retina-pigment epithelium preparation

To better understand the mechanisms of extracellular space volume regulation and their possible effects on retinal function, light-induced changes in the concentrations of the principal extracellular ions (Na+, K+, Ca2+, and Cl-) were measured with ion-sensitive microelectrodes in the chick retina-pigment epithelium-choroid preparation. Changes of extracellular space volume were assessed by measuring the concentration of an impermeant marker, tetramethylammonium. In the inner retina, transient ON/OFF Na+ decrease was about twice as large as K+ increase, and the charge difference was compensated by a decrease in Cl- concentration. The ion changes were accompanied by extracellular space-volume decreases here. In the subretinal space, [Na+]o increase was about twice as large as K+ decrease, yet [Cl-]o, also decreased; this was accompanied by a sustained extracellular space-volume increase. The ionic changes in the inner retina are consistent with a model of extracellular space-volume regulation which assumes that neuronal depolarization causes net uptake of NaCl, cell swelling, and extracellular space shrinkage. However, to prevent the apparent violation of electroneutrality in the subretinal space, our simple model should be expanded to include the involvement of unidentified anion(s). Substantial changes in the subretinal space volume may influence interaction between the neural retina and pigment epithelium. Among ionic changes, only the light-induced [K+]o decrease around the photoreceptors and the [Ca2+]o increase near the photoreceptor bodies and synaptic terminals are large enough (-25% and 7.5%, respectively) to be likely candidates for integrated intercellular signaling.

[Genetic analysis of pathogenic streptococci groups A and B]

The study deals with the genetic mapping of chromosomal DNA of groups A (AS) and B (BS) pathogenetic Streptococci. Its stages are presented and considered. The maps of these microorganisms are compared. A collection of epidemic AS and BS was analyzed by employing pulsed field gel electrophoresis. AS and BS were found to show heterogeneity of DNA sequences and the common pattern of gene location on the chromosomes.

Energetic neutron and gamma-ray spectra under the earth radiation belts according to "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686" orbital complex and "CORONAS-I" satellite data

The spectra of neutrons >10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686", are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm-2 s-1 for neutrons, 0.8 cm-2 s-1 for gamma-rays at the equator and 1.2 cm-2 s-1, 1.9 cm-2 s-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from "CORONAS-1" data are near those for albedo particles.

[The cloning and expression of the phospholipase D gene from Corynebacterium pseudotuberculosis]

In a number of consecutive gene engineering operations a DNA fragment having a size of about 2.8 kb was cloned in Escherichia coli by means of Blue-script II SK+ used as vector. The insert contained pld gene coding the synthesis of phospholipase D, one of the key factors of C. pseudotuberculosis virulence. The stable and active expression of this gene in E.coli was achieved. High phospholipase A activity was accumulated in the periplasmatic space. The molecular weight of the synthesized protein was 31 kD. The product obtained by gene engineering methods was found to possess the biological activity of the natural product: it induced the hemolysis of sheep red blood cells in the presence of equi factor of Rhinococcus equi and inhibited the hemolytic activity of Staphylococcus aureus beta-hemolysin (phospholipase C). The pld gene cloned in these experiments differed from that of another C.pseudotuberculosis strain. Further research is underway with a view of searching for the limits of pls gene.

Mathematical model of TMA+ diffusion and prediction of light-dependent subretinal hydration in chick retina

PURPOSE

To derive a mathematical model of TMA+ diffusion across the retina that can be used to estimate the amplitude and kinetics of the light-evoked increase in subretinal hydration and its effect on the concentration of other ions.

METHODS

All experimental data were obtained in chick retina-pigment epithelium-choroid preparations as described in the accompanying paper.

RESULTS

Diffusional properties of the retina were derived from the time course of [TMA+]o in the subretinal space (SRS) after changes in the retinal perfusate. Then, the SRS volume changes underlying the light-induced [TMA+]o response can be derived using a mathematical model of TMA+ diffusion. Complete retinal depth series of light-evoked [TMA+]o responses could be simulated by producing a corresponding expansion of the SRS. Volume changes inferred from the diffusion model were 2.2 to 3.8 times larger and more prolonged than could be derived directly from delta [TMA+]o. The model predicted up to a 20% peak increase in subretinal-space hydration during illumination. The effects of this volume increase on subretinal K+ and Ca2+ were estimated. These predictions were supported by inhibiting the volume increase with DIDS, which blocks retinal pigment epithelium basal membrane Cl- conductance.

CONCLUSIONS

The primary source of light-evoked changes in extracellular TMA+ concentration recorded throughout the retina is an increase in hydration (volume) of the subretinal space. The response spreads to the inner retina by diffusion. Effects of TMA+ diffusion lead to large underestimates of the underlying volume changes. The light-evoked volume change alters the composition of the subretinal space and light-induced responses of other ions.

[The effect of baclofen on the nociceptive reactions of the blood pressure in waking rats]

The effect of baclophen (5-10 mg/kg) on the background arterial blood pressure (AP), amplitude of nociceptive AP reactions under electrostimulation of the tail's proximal part and the time of AP normalization after the nociceptive action was studied in the experiments of awaking rats with implanted arterial catheters. Baclophen in the range of analgesic doses causes persistent hypertension depending on the drug dose and the level of emotional reactivity of the rats. Simultaneously with the above mentioned effects the amplitude and the duration of the nociceptive AP reactions are decreased. The blockade of the alpha-adrenoreceptors (phenoxybenzamine, 5 mg/kg) abolishes the hypertensive effect of baclophen but increases its inhibitory effect on the nociceptive AP changes.

[Mechanism of the action of baclofen on the contractile activity of the myocardium and blood vessels]

The cardiovascular effects of GABA-analogous-baclofen (10(-5) M) have been investigated in the experiments on isolated myocardium and vessels of the rats. The spontaneous contraction of vena porta segments and contraction of papillary muscle and arterial rings segments induced by electrostimulation were registered. Baclofen induced the growth of arterial tonus, decreased the amplitude of phase contraction as well as resulted in positive inotropic effects in myocardium and vena porta. The obsidan did not influence the baclofen effects, but alpha-adrenolytic dihydroergotoxine inhibited the inotropic effects of the drug. It is supposed that hypertensive baclofen effect which is observed during system injection may be caused not only by central, but also by peripheral regulation of calcium change in the myocytes. The latter (possible) kind of regulation may consist in the drug binding with adrenoreceptor and/or direct influence on the calcium transport across sarcolemma.

[Hormonal aspects of cathepsin D regulation in seminal follicles]

Androgen-dependent regulation of cathepsin D activity was studied in rat seminal follicles. Cathepsin D, isolated from the follicles by means of ammonium sulfate fractionation, chromatography on Hb-Sepharose and Sephadex G-200, was similar to the enzyme from other tissues in molecular mass, Km for hemoglobin, pH optimum of activity, thermolability. Concentration of androgens in tissues affected the properties of purified cathepsin D: the enzyme activity, its sensitivity to thermoinactivation and to chymotryptic hydrolysis were increased as well as the pH optimum was expanded after orchidectomy. Testosterone restored the initial enzyme properties altered after castration.

[The spectrum of analgesic activity of baclofen and tolibut]

Spectrum of the analgetic activity of GABA derivatives baclofen (2.5-10.0 mg/kg) and tolibut (12.5-100.0 mg/kg) was studied in experiments on albino mice and rats. Baclofen and especially tolibut showed a dose-dependent inhibition of perceptive, emotional and autonomic manifestations of nociceptive reactions at the tail's thermal and electrical stimulation and enhancement of the analgetic effect of promedol. The regressive analysis made it possible to show dependence of the analgetic effect on the level of pain sensitivity and emotional reactivity of the animals. Tolibut deepens and prolongs sombrevin anesthesia, baclofen fails to alter it.

[Evaluation of the pain-alleviating properties of a combination of analgesic and tranquilizer using multiple stepwise regression]

A method for preclinical evaluation of the optimal ratio (for analgesia) of an analgesic to a tranquilizer has been devised. It is based on the drug threshold dose decrease on the drug combined use. The multiple stepwise regression analysis of the data discovered the correlations between diazepam and promedol, optimal for pain perception decrease and nociceptive emotional responsiveness inhibition.

[Slow P III component of the electroretinogram resulting from the interaction of photoreceptors and cells of Müller in the retina]

Simultaneously recorded slow PIII (sPIII) and the late receptor potential of the frog isolated aspartate-treated retina were studied under different intensity and duration of light stimuli. The earlier suggested model of the sPIII generation in Müller's cells showed that the sPIII kinetic had to be the same as the light photo-receptor-induced decrease in the extracellular potassium ions concentration. There were some differences between the real sPIII time-course and the theoretical one within the photopic range that were, probably, due to infringement of interrelationships proposed by Matsuura et al. for potassium fluxes through the photoreceptor membrane.

[Extracellular potassium in the frog retina and its light-induced changes]

Similar downhill gradients of [K]0 were revealed in the aspartate--treated dark--adapted frog retina and in the eye cup without aspartate. [K]0 in the receptor layer is 8 X 10(-3) M, while in the proximal retina it is nearly 2.7 X 10(-3) M. Illumination decreased [K]0 in the receptor layer to 2.5 X 10(-3) M. The dark level and the light-induced changes of [K]0 were practically unaltered when Ba2+ ions suppressed the slow PIII and the resting transretinal glia potential blocking up the Müller cells permeability for K+. The findings suggest that [K]0 around the receptor space is regulated by red rods with no interference from the Müller cells or pigment epithelial cells. The amplitude of [K]0 changes seems to be physiologically significant.

[Analysis of the role of various factors of the initial status of the body in the analgesic action of promedol]

A comprehensive approach is suggested to the assessment of the analgetic action of analgetics during screening. This approach lies in the study of the drug effects on the emotional, vegetative and motor manifestations of the painful reactions. Based on multiple and regression analysis the role of different factors of the initial status of the body in the development of analgesia is demonstrated. Application of the given approach is examplified by the reference analgetic promedol.

[Effect of hormonal preparations on lysosome enzyme activity in rat tissues]

Experiments on white male rats were made to study and compare the action of hormonal drugs (testosterone propionate, retabolil and chorionic gonadotropin) on lysosomal enzymes of different tissues. There were differences in the changes in the activity of acid phosphatase, ribonuclease, cathepsins and beta-galactosidase after a single administration of testosterone and after a course of drug treatment. Retabolil and chorionic gonadotropin acted on lysosomal enzymes of spermatic vesicles similarly to testosterone given in a single dose. As far as the activity of liver cathepsins and beta-galactosidase is concerned retabolil was found to produce an opposite effect as compared to that of testosterone.

[Effect of stimulation of the central gray substance of the midbrain on hemodynamic nociceptive reactions]

Experiments on unrestrained rats were made to study the influence of central gray matter of the midbrain, whose activation evokes analgesia, on hemodynamic manifestations of pain reactions under tooth pulp irritation. Electrical stimulation of the brain "analgetic areas" that does not change the animals' behavior or vegetative indices at rest decreased or abolished nociceptive arterial pressure reactions and tachycardia. Possible mechanisms of central gray matter of the midbrain influence on the pain-evoked vegetative reactions are discussed.