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Biomedical subjects

E Varga

Publications and source records attributed to E Varga.

At least 91 records · Page 5Linked to original sources
PubMed1989

Effects of precocene analogs on the nematode Caenorhabditis remanei (var. Bangaloreiensis). I. Structure/activity relations.

Precocenes (PI and PII) and 114 of their analogs (PAs) were synthetized and tested on C. remanei embryos for their precocene-like (P-like) activities resulting in unusual development at sublethal doses. The P-like activity was quantitated by plotting the probit of the percentage of the developmentally affected survivors against the (log) dose to obtain the EC plot and the half effective concentration (EC50). All five PAs (PI, PII, 7-ethoxy-PII, 7-(prop-2-ynyloxy)-PI, and 6-methoxy-7-(prop-2-ynyloxy)-PII) which exert both antiallatal activity in insects and P-like activity in nematodes are 7-alkoxy-substituted 2,2-dimethylchromenes. Both activities can be enhanced by an additional 6-MeO-substitution or by an asymmetric 6,7-dialkoxy-substitution, on condition that R-7 is longer than R-6. There are many more similarities than dissimilarities in the structural requirements needed for antiallatal and P-like activities. All but three nonantiallatal PAs effective in nematodes are 7-prop-2-ynyloxy-subsituted; two are symmetrically 6,7-disubstituted, and one is heterosubstituted (thio-PI). All PAs with antiallatal but without P-like activity are 7-monosubstituted with a relatively long alkoxy group. Certain substitutions favor antiallatal activity and others P-like activity. The severe nematocidal effect of 6,7-methylenedioxy-2,2-dimethylchromene (inert in insects) is not accompanied by P-like activity. The present findings lend some indirect support to the supposition that JH-producing cells and/or JH-dependent function(s) might exist in the nematodes.

Animals↗
PubMed1989

Effects of oxymorphazone in frogs: long lasting antinociception in vivo, and apparently irreversible binding in vitro.

Oxymorphazone (at doses of 50-200 mg/kg) was found to be a relatively weak antinociceptive drug in intact frog (Rana esculenta) when acetic acid was used as pain stimulus. Frogs remained analgesic for at least 48 hrs following oxymorphazone (200 mg/kg) administration. The ligand increased the latency of wiping reflex in spinal frogs too. These effects were blocked by naloxone. In equilibrium binding studies (3H)oxymorphazone had high affinity to the opioid receptors of frog brain and spinal cord as well (apparent Kd values were 8.9 and 10.6 nM, respectively). Kinetic experiments show that only 25% of the bound (3H)oxymorphazone is readily dissociable. Preincubation of the membranes with labeled oxymorphazone results in a washing resistant inhibition of the opioid binding sites. At least 70% of the (3H)oxymorphazone specific binding is apparently irreversible after reaction at 5 nM ligand concentration, and this can be enhanced by a higher concentration of tritiated ligand.

Analgesics↗
PubMed1989

Cation and guanine nucleotide effects on ligand binding properties of mu and delta opioid receptors in rat brain membranes.

Monovalent cations such as Na+, K+ and Li+ at 100 mM concentration inhibit the binding of mu and delta opioid agonists (e.g. (3H) dihydromorphine and (3H) D-Ala2-Leu5-enkephalin), enhance opioid antagonist [(3H) naloxone] binding in rat brain membranes. Divalent cations have an opposite effect: Mg2+ or Mn2+ (2mM) increase both mu and delta agonist binding, and decrease the antagonist binding. The effect of guanosine 5'-triphosphate and its non-hydrolysable analogue 5'-guanylyl-imidodiphosphate at micromolar concentrations is similar to that of sodium ion. In kinetic experiments, guanine nucleotides promote the dissociation of radiolabelled agonists from their binding sites by increasing the rate of dissociation. Equilibrium saturation binding studies show that only binding of the opioid agonist ligands are significantly inhibited by 5'-guanylyl-imidodiphosphate.

Animals↗
PubMed1988

Synthesis of 3H-Tyr-D-Ala-Gly-N(Me)Phe chloromethyl ketone--an opioid affinity label.

A radioactive enkephalin affinity reagent, selective for the mu opioid receptor subtype, was synthesized by a fragment condensation method. 3H-BOC-Tyr-D-Ala-Gly-OH was prepared by catalytic tritiation of the protected iodinated tripeptide. The protected tritiated tripeptide and N(Me)Phe-CH2Cl were condensed by the mixed anhydride method. The protecting group was removed by HCl/acetic acid. The tritiated tetrapeptide has a specific radioactivity of 56.8 Ci/mmole (2.1 TBq/mmole).

Affinity Labels↗
PubMed1988

Enkephalin photoaffinity probes: synthesis and binding properties.

The diazomethyl ketone derivative of D-Ala2-Leu-enkephalin and Leu-enkephalin were synthesized. Replacement of the C-terminal carboxyl group with CO-CHN2 resulted in a potency decrease, the new compounds display micromolar affinities to 3H-naloxone and 3H-DALE binding sites. Photolysis of the ligands bound to rat brain membranes resulted in an approximately 30% irreversible loss of the receptors. Photoinactivation was prevented by the opiate antagonist, naloxone, thus providing that the ligands are specific photoaffinity probes of the opioid receptors.

Affinity Labels↗
PubMed1988

Characterization of human placental opioid receptors by 3H-ethylketocyclazocine and 3H-naloxone binding.

The human placenta contains membrane bound opioid receptors. The binding of the antagonist naloxone and the fairly kappa-selective agonist EKC were studied in the microvillous membrane fraction. In both cases high affinity binding sites were detected with Kd values in the nanomolar range. A series of kappa-selective ligand (PD-117302, EKC, and U-50, 488H) were tested in displacement experiments, and found to be potent inhibitors of agonist and antagonist binding. It was confirmed that large percentage of the binding is associated with the kappa sub-type which is of current interest, in that it shows distinctive pharmacology and distribution and is selective for the natural opioid polypeptide, dynorphin.

Analgesics, Opioid↗
PubMed1988

The effect of chlorhexidine irrigation on the incidence of dry socket: a pilot study.

A pilot study was conducted to measure the reported incidence of dry socket following pre-operative irrigation and mouthrinsing with either 0.2% (w/v) chlorhexidine gluconate or normal saline or with no irrigation (control). Three hundred and twenty-four patients presenting for the single extraction of a lower premolar or molar under local anaesthesia were divided into three equal groups; no irrigation, irrigation with saline and irrigation with a 0.2% (w/v) chlorhexidine gluconate solution. After administration of the local anaesthetic agent, 10 ml of the test solutions were applied to the gingival crevice using a blunted needle. The solutions were retained in the patients mouth for 2 min following irrigation. Pre-operative irrigation of the gingival crevice and mouthrinsing with 0.2% (w/v) chlorhexidine gluconate significantly reduced the number of dry sockets. There was no significant reduction in the number of dry socket cases following irrigation and rinsing with normal saline. The irrigation technique, using 0.2% (w/v) chlorhexidine gluconate is safe, inexpensive, easy to apply and can be recommended for routine use in dental practice, to reduce the incidence of dry socket.

Bicuspid↗
PubMed1987

Synthesis and binding of 3H-oxymorphazone to rat brain membranes.

Oxymorphazone is a 14-hydroxydihydromorphinone derivative which contains a C-6 hydrazone group and hence could serve as an irreversible label for opioid receptors. 3H-oxymorphazone was synthesized by the reaction of 3H-oxymorphone with excess hydrazine. A specific radioactivity of 640 GBq/mmol (17,3 Ci/mmol) was achieved. Both the unlabelled compound and the tritiated ligand show high affinity to mu and kappa opiate receptor subtypes in rat brain membranes. Two binding sites were detected by equilibrium binding studies, with apparent Kd values of 0.62 nM and 28 nM. About 20% of the H-oxymorphazone specific binding is irreversible after reaction at 1 nM ligand concentration, and this can be enhanced by a higher concentration of tritiated ligand. No azine formation was detected. Preincubation of the membranes with unlabelled oxymorphazone resulted in an irreversible blockade of the high affinity 3H-naloxone binding sites.

Animals↗
PubMed1987

The chronically furosemide-treated mouse as a possible ultrastructural model for cystic fibrosis.

The effect of chronic furosemide treatment on the structure of the secretory cells in the mouse pancreas was studied using electron microscopy. The number of the zymogen granules increased in the cytoplasm of acinar cells; they were more densely packed and had a less electron-dense appearance than the controls. Because these ultrastructural findings resemble the changes observed in exocrine glands of patients with cystic fibrosis, the chronic furosemide-treated mouse is proposed as an experimental model for this disease.

Animals↗
PubMed1987

Effects of phlorizin and phloretin on passive and dynamic electrical properties in muscle membrane.

The effects of phlorizin and phloretin on the cable properties were investigated in frog sartorius muscle by conventional cable analysis. Actions of phloretin on voltage-dependent ionic conductances were also studied by analysis of the phase plane trajectories. Both drugs evoked a significant decrease in specific membrane resistance (Rm) in chloride-containing Ringer's solution. The linear membrane capacitance increased by about 30%. On the contrary, in the presence of the non-penetrating anion, glutamate, a slight increase in Rm was induced by phlorizin. It is suggested that these drugs may increase the chloride conductance in the muscle membrane. Under the effect of phloretin the resting membrane potential remained unchanged but the amplitude of the action potential was lowered and the rate of repolarization was significantly reduced. The rate of depolarization during the "foot" of the action potential and the conduction velocity calculated from the rate constant of depolarization decreased. The maximum Na conductance was not altered by phloretin but K conductance was reduced. The time constant (tau K) reflecting the kinetic properties of K conductance was increased about seven-fold. It is suggested that great importance may be attributed to the dipole properties of these drugs in the actions presented above.

Action Potentials↗
PubMed1987

Chloride-dependence of the actions of phlorizin on frog skeletal muscle membrane.

The effects of phlorizin on the membrane potential changes induced by cevadine were compared in the presence and absence of external chloride anions in frog skeletal muscle. The action of the drug on 24Na-efflux was also studied in chloride-free medium. In accordance with previous results, it was found that phlorizin reduced the frequency of the membrane potential oscillation (1 mmol/l) or fully inhibited the rhythmic activity (2 mmol/l) in the presence of chloride anions. Replacing the total chloride content of bathing fluid with non-penetrating anions (glutamate, isethionate or sulphate) the inhibitory action of phlorizin on the membrane potential oscillation failed to appear while it reappeared rapidly if the chloride ions were partially restored in the incubating medium. The membrane potential changes evoked by changing the chloride concentration of Ringer solution at constant [K]0 were more expressed in the presence of phlorizin. The action of phlorizin on 24Na-transport proved to be a chloride-independent phenomenon. This finding indicates that the inhibitory effect of phlorizin on Na-transport processes may not be the reason of its blocking action on membrane potential oscillation. Furthermore, it suggests that failure of the drug to inhibit the membrane potential oscillation in the absence of chloride anions may not be accounted for the lack of phlorizin-binding under those circumstances. It is therefore assumed that the increase in chloride conductance may play a causal role in the inhibitory effect of phlorizin on membrane potential oscillation.

Animals↗
PubMed1986

[Scleromyxedema].

In a 51-year-old man scleromyxedema developed gradually from mucinosis papulosa over 13 years. Paraproteins of the type IgG-lambda were discovered in this patient.

Biopsy↗
PubMed1986

[Experience with percutaneous needle muscle biopsy in pediatrics: alternatives to open biopsy?].

Over 14 months the authors have performed 22 needle muscle biopsies using the Bergström needle. Sufficient material was obtained for histological, histochemical and electron microscopic examination. The biopsies can be done as an outpatient procedure under local anesthetic, and with sedation in infants and young children. The technique is safe, quick and well tolerated and leaves only a very small scar. It provides adequate information for almost all diagnostic purposes in neuromuscular disease. The few indications for open muscle biopsy are discussed.

Adolescent↗
PubMed1986

Inhibition of sodium for sodium exchange by phlorizin in frog sartorius muscle.

The effects of phlorizin (2 X 10(-3) mol X l-1) on the Na transport of frog (Rana esculenta) sartorius muscle were investigated in glucose-free medium. Phlorizin decreased the rate coefficient of 24Na efflux by about 40%. The degree of inhibition was comparable to that caused by ouabain (10(-4) mol X l-1). Phlorizin could evoke a further reduction in the 24Na efflux also in the presence of ouabain. The intracellular Na content of the phlorizin-treated muscles remained unchanged, in contrast to a 60% increase induced by ouabain. 42K uptake was not affected by phlorizin. Data indicate that the ouabain-sensitive Na-K pump was not involved in the action of phlorizin. At the same time, phlorizin failed to alter the residual 24Na efflux measured in Li-Ringer solution containing ouabain. When Na: Na exchange was restored by replacing Na into the washout solution in the presence of ouabain, the increase of 24Na efflux was significantly diminished by phlorizin. Phlorizin reduced the 24Na uptake into a compartment with a half time of 6 min by about 40% without affecting the intracellular compartment. The results suggest that phlorizin inhibits the ouabain-insensitive Na: Na exchange in a superficial Na compartment.

Animals↗
PubMed1986

Preparation of [3H]-oxymorphazone and its binding to rat brain membranes.

Oxymorphazone is a 14-hydroxydihydromorphinone derivative which contains C-6 hydrazone group and hence could serve as an irreversible label for opioid receptors. 3H-oxymorphazone was synthesized by the reaction of 3H-oxymorphone with excess hydrazine, with 640 GBq/mmol specific radioactivity. Both the unlabelled compound and the tritiated ligand show high affinity to mu and kappa opiate receptor subtypes in rat brain membranes. Two binding sites were detected by equilibrium binding studies. About 60% of the 3H-oxymorphazone specific binding is irreversible at 10nM ligand concentration. Preincubation of the membranes with unlabelled oxymorphazone resulted in an irreversible blockade of the high affinity 3H-naloxone binding sites.

Animals↗