A comparative study of the effects of muscimol and diazepam on the recall of noxious events

Muscimol induced in rats a recall deficit which possibly results from a dissociation of learning. In one out of the 2 experimental conditions studied, a cross dissociation of learning was found between diazepam and muscimol.     

Conditioned suppression: Dissociation of learning in baclofen treated rats

Summary In rats, baclofen induced a memory deficit related to a dissociation of learning. Baclofen given prior to training or prior to testing had no effect on the amnesia elicited by diazepam.     

Determination of odour affinities based on the dose-response relationships of the frog's electro-olfactogram

Summary Electro-olfactograms (EOG's) recorded from the frog's olfactory epithelium for 11 substances were used to calculate dissociation constants which in turn serve as an index for the affinity between odorant and receptor site. These constants were calculated with and without a correction for the odour partition between water and air. For a homologous series of 7 n-alcohols these values decrease up to 1-heptanol. The dose-response relationships were based on the peaks of the EOG's since the peak/plateau-ratio was concentration-dependent for some of the substances.This work was supported by Z.W.O. grant number 12-24-12 of the Dutch Government.     

Dissociation-constants of metat-ion-complexes with alkaline phosphatase from pig kidney.

Using metal-ion buffers it was possible to remove Zn2+, Mg2+ and Mn2+ ions of pig kidney alkaline phosphatase reversibly. The dissociation constants obtained are KEMg: 4 X 10(-7) M, KEMn: 4 X 10(-8) M and KEZn: 8 X 10(-13) M (22 degrees C, pH: 9.6, mu: 0.07).     

The in vitro stability in human plasma of two different technetium-99m-fibrinogen compounds

Two 99mTc -labeling methods of human fibrinogen resulted in different complexes. This was concluded from different dissociation rates in human plasma. The dissociation could be described by a simple exponential function.     

The in vitro stability in human plasma of two different technetium-99m-fibrinogen compounds

Summary Two^99mTc-labeling methods of human fibrinogen resulted in different complexes. This was concluded from different dissociation rates in human plasma. The dissociation could be described by a simple exponential function.     

Demonstration of dopaminergic receptors in human pituitary adenomas secreting prolactin]

3H Domperidone binding on cellular membranes from human prolactin adenomas demonstrates the presence of two dopaminergic binding sites. The mean value of the dissociation constant (Kd) for five adenomas is of 0.29 +/- 0.14 nM for the first site and of 4.19 +/- 1.56 nM for the second site. The maximal number of binding sites (Bmax) varies from one adenoma to another. The binding is completely displaced at 30 nM of tritiated Domperidone by apomorohine, a specific dopaminergic agonist.     

Offset rate of action of muscarinic antagonists depends on their structural flexibility.

Time course measurements of the action of muscarinic antagonists were performed in the spontaneously beating carp atrium. Several high affinity drugs, which embody the quinuclidine structure were examined. The structural flexibility of these molecules was reflected in the dissociation of the drugs from the muscarinic receptor. The dissociation of rigid drugs was very much prolonged as compared to flexible drugs of the same affinity.     

Dissociation of glucocorticoid effects of C-21 steroids at high concentrations in thymocytes

A dissociation between inhibition of RNA synthesis and cell lysis was observed when thymocytes of adrenalectomized rats were incubated with high concentrations of pregn-4-ene-11 beta-ol-3,20-dione and pregna-1,4-diene-11 beta-ol-3,20-dione. In contrast, no dissociation of these effects was found with the typical glucocorticoids cortisol and corticosterone, nor with their 1,4-diene analogs under the same conditions.     

Offset rate of action of muscarinic antagonists depends on their structural flexibility

Summary Time course measurements of the action of muscarinic antagonists were performed in the spontaneously beating carp atrium. Several high affinity drugs, which embody the quinuclidine structure were examined. The structural flexibility of these molecules was reflected in the dissociation of the drugs from the muscarinic receptor. The dissociation of rigid drugs was very much prolonged as compared to flexible drugs of the same affinity.We thank Prof. S. Lifson for helpful discussion and Mrs M. Bendikovsky for technical assistance. This work was supported by a USA-Israel Binational Science Foundation (BSF-Jerusalem) grant to Y. Lass.     

Action of D-penicillamine on immunocomplexes containing rheumatoid factor

Summary The affinity between purified rheumatoid factors (RF) and native or heat aggregated human IgG has been studied in vitro by polarization florescence in the presence and in the absence of D-penicillamine. The value of the dissociation constant was the same using native and heat aggregated IgG suggesting that binding to the aggregated protein is not dependent on the exposure of a new determinant lacking in the native molecule. The results obtained in the presence of D-penicillamine suggest that the concentration of the drug necessary to get a pronounced effect on the apparent dissociation constant of the immunocomplex between IgG and RF is not reached in vivo, in clinical situations.     

A comparative study of the differentiation of dissociated nerve cells under different culture conditions.

In vitro differentiation of chick embryo brain cells was compared under several culture conditions. Morphological observations and acetylcholinesterase histochemical staining revealed that the development was similar in all conditions tested if cells have been derived from 7 days embryos. Considering the cultures from 11 days embryos, the cell dissociation by trypsin and the plastic surface proved to be the most favourable conditions in contrast to mechanical dissection and collagen surface.     

Increased activity of the ribosomal dissociation factor in the pre-replicative phase of liver regeneration after partial hepatectomy.

The activity of the ribosomal dissociation factor and the formation in vitro of free 60S and 40S subunits increased in the first 12--48 h after partial hepatectomy. This suggests an accelerated reconversion into active subunits of ribosomes that complete a translation cycle in the early phases of liver regeneration.     

Consequences of acute ischemia for the electrical and mechanical function of the ventricular myocardium. A brief review

Reduction or interruption of the blood supply to the myocardium leads to marked disturbances of electrical and mechanical function within a few seconds. Electrical dysfunction is characterized by an initial depolarization of the resting membrane, and a decrease of the amplitude, the upstroke velocity and the duration of the action potential. Both depolarization and depression of the action potential are closely associated with intracellular metabolic acidosis. After this initial phase, electrical cell-to-cell uncoupling develops, probably as a consequence of increased cytosolic free [Ca++]. Mechanical dysfunction is characterized by a dissociation of the initial decrease of active force development from the subsequent ischemic contracture. Active force development in acute ischemia is inhibited by the accumulation of ischemic metabolic products (H+, inorganic phosphate (Pi), Mg++) but not by a marked decrease of [ATP]. The subsequent ischemic contracture is probably initiated by release of Ca++ from intracellular stores. This release causes rapid consumption of ATP and the development of rigor within 1-2 minutes.     

Binding site of activators of the cystic fibrosis transmembrane conductance regulator in the nucleotide binding domains

The use of substances that could activate the defective chloride channels of the mutant cystic fibrosis transmembrane conductance regulator (CFTR) has been suggested as possible therapy for cystic fibrosis. Using epithelia formed by cells stably transfected with wildtype or mutant (G551D, G1349D) CFTR, we estimated the apparent dissociation constant, K_D, of a series of CFTR activators by measuring the increase in the apical membrane current. Modification of apparent K_D of CFTR activators by mutations of the nucleotide-binding domains (NBDs) suggests that the binding site might be in these regions. The human NBD structure was predicted by homology with murine NBD1. An NBD1-NBD2 complex was constructed by overlying monomers to a bacterial ABC transporter NBD dimer in the head-to- tail conformation. Binding sites for CFTR activators were predicted by molecular docking. Comparison of theoretical binding free energy estimated in the model to free energy estimated from the apparent dissociation constants, K_D, resulted in a remarkably good correlation coefficient for one of the putative binding sites, located in the interface between NBD1 and NBD2.Received 21 September 2004; received after revision 6 December 2004; accepted 10 December 2004     

Monoclonal antibodies to L-asparaginase

Five hybridomas secreting monoclonal antibody to E. coli L-asparaginase were isolated. These monoclonal antibodies were classified into 3 different subclasses; Ig G1 (1 clone), Ig G2 (2 clones) and Ig G3 (2 clones). One of them possessed anti-L-asparaginase neutralizing activity. Four antibodies examined demonstrated a linear Langmuir binding plot and binding affinities, with equilibrium dissociation constant (Kd) ranging between 2.5 X 10(-9) M and 6.3 X 10(-10) M. The monoclonal antibodies should be useful probes for investigation of the enzyme activity.     

The effect of ligand on the kinetics of the sulfhydryl groups of human hemoglobin with p-mercuribenzoate

The rate of reaction of PMB with the masked sulfhydryls of human hemoglobin derivatives correlates well with the extent of dissociation for various ligands. It is suggested that the alpha1beta2 dimer of hemoglobin participates in the slow step of the reaction with PMB.     

A comparative study of the differentiation of dissociated nerve cells under different culture conditions

Summary In vitro differentiation of chick embryo brain cells was compared under several culture conditions. Morphological observations and acetylcholinesterase histochemical staining revealed that the development was similar in all conditions tested if cells have been derived from 7 days embryos. Considering the cultures from 11 days embryos, the cell dissociation by trypsin and the plastic surface proved to be the most favourable conditions in contrast to mechanical dissection and collagen surface.M. Sensenbrenner is Maitre de Recherche au CNRS.     

Characterization of apoptosis induced by marine natural products in non small cell lung cancer A549 cells

The effects of different marine derived agents were studied in A549 cell growth. These drugs induced cell cycle arrest at the G2-M phase associated with the up-regulation of GADD45alpha-gamma and down-regulation of c-Myc. In treated cells, GADD45alpha-gamma and c-Myc were up- and down-regulated, respectively. A cascade of events leading to apoptotic mitochondrial 'intrinsic' pathway was observed in treated cells: (1) dephosphorylation of BAD serine136; (2) BAD dissociation from 14-3-3 followed by its association with BCL-XL; (3) cytochrome c release; (4) caspase-3 activation, and (5) cleavage of vimentin. Caspase(s) inhibitor prevented the formation of cleavage products and, in turn, apoptosis was inhibited through a p53-independent mechanism. Moreover, these compounds did not activate NF-kappaB. Our findings may offer new insights into the mechanisms of action of these agents in A549 cells. The better understanding of their effects might be important to fully exploit the potential of these new drugs.