[Effect of 1,5-benzodiazepine derivatives on the electrical activity of neurons of the Helix albescens Rossm].

Using a standard technique for intracellular recording of potentials, we investigated the influence of two new derivatives of 1,5-benzodiazepine-2-one on the electrical activity of neurons of the Helix albescens Rossm. These substances possess neurotropic properties, the effects were concentration dependent in the concentration range 10(-6) M -10(-2) and did not depend on the type of neurons. We defined the threshold, optimum and toxic concentrations for the compounds investigared. Analysis of the total ion current showed that the compounds reduce the rate of inward Na+- and Ca2+ currents and of outward K+-currents.

[Effect of benzimidazole and its derivatives on electrical activity of Helix albescens Rossm neurons and behavior of rats].

We studied concentration dependency and the mechanisms of the effect of bezimidazole and its new derivatives on electrical processes in Helix albescens Rossm. neurons. These compounds appeared to have neurotropic properties dependent on their chemical structure and the types of neurons. We determined the threshold, optimal and toxic concentration values of the tested substances. Benzimidazole and 2-trifluoromethylbenzimidazole at concentrations of 10(-3) and 10(-2) M elicit both excitatory and inhibitory postsynaptic potentials on soma membrane of some pacemaker and non-pacemaker neurons and even cause a strong depolarization. The membrane of pacemaker neurons (namely, neuron RPa2) was found to have at least two spatially separated trigger sites with different trigger mechanism of action potential. After single intraperitoneal injection (50 mg/kg) of the substance solution, the tested compounds based on the discovered effects were separated into two groups. The first group inhibits locomotion and psychoemotional state of rats, the second group elicits the opposite effect. We found that at 100 and 150 mg/kg all tested substances inhibit the animal's activity.

Studies on anti-human immunodeficiency virus oligonucleotides that have alternating methylphosphonate/phosphodiester linkages.

Preliminary investigations of the physical properties of oligonucleotide analogs that contain alternating methylphosphonate/phosphodiester linkages are described. An alternating oligo-2'-O-methylribonucleoside methylphosphonate, oligomer 1676, whose sequence is complementary to the upper hairpin region of human immunodeficiency virus TAR RNA, has been synthesized. This 15-mer forms a very stable duplex with its complementary RNA target, whose melting temperature is 71 degrees C. Introduction of two mismatched bases reduces the melting temperature by 16 degrees C. Similar results were obtained with the all-phosphodiester version of oligomer 1676, which demonstrates that introduction of the methylphosphonate linkages does not significantly perturb the ability of the oligo-2'-O-methylribonucleoside methylphosphonate to bind to RNA. Unlike the phosphodiester oligomer, however, oligomer 1676 is completely resistant to hydrolysis by the 3'-exonuclease activity found in mammalian serum. The interactions between nuclease-resistant, 5'-psoralen-derivatized, alternating oligo-2'-deoxypyrimidine methylphosphonates and double-stranded DNA were also studied. A 15-mer that contains thymine, 5-methylcytosine, and 5-propynyl-uracil forms a triplex with a polypurine tract found in the env gene of human immunodeficiency virus proviral DNA with an apparent dissociation constant of 400 nM at 22 degrees C. Maximal triplex formation by these oligomers is observed at approximately 2.5 mM magnesium, whereas maximal triplex formation by the corresponding all-phosphodiester oligomers occurs between 10 and 20 mM magnesium. This reduced magnesium dependence most likely results from reduced charge repulsion between the backbones of the methylphosphonate oligomer and purine strand of the target. The nuclease stability and ability of the methylphosphonate oligomers to form stable complexes with their target nucleic acids suggest that these oligomers are potential candidates for use as antisense or antigene agents in cell culture.

Syntheses of alternating oligo-2'-O-methylribonucleoside methylphosphonates and their interactions with HIV TAR RNA.

Oligonucleotide analogues 15-20 nucleotides in length have been prepared, whose sequences are complementary to nucleotides in the upper hairpin of HIV TAR RNA. These alternating oligonucleoside methylphosphonates, mr-AOMPs, contain 2'-O-methylribonucleosides and alternating methylphosphonate and phosphodiester internucleotide linkages. The methylphosphonate and phosphodiester linkages of these oligomers are highly resistant to hydrolysis by exonuclease activity found in mammalian serum and to endonucleases, such as S1 nuclease. The oligomers were prepared using automated phosphoramidite chemistry and terminate with a 5'-phosphate group, which provides an affinity handle for purification by strong anion exchange HPLC. A 15-mer mr-AOMP, 1676, that is complementary to the 5'-side of the TAR RNA hairpin, including the 3-base bulge and 6-base loop region, forms a 1:1 duplex with a complementary RNA 18-mer, mini-TAR RNA. The T(m) of this duplex is 71 degrees C, which is similar to that of the duplex formed by the corresponding all phosphodiester 15-mer. Introduction of two mismatched bases reduces the T(m) by 17 degrees C. The apparent dissociation constant, K(d), for the 1676/mini-TAR RNA duplex as determined by an electrophoretic mobility shift assay at 37 degrees C is 0.3 nM. Oligomer 1676 also binds tightly to the full length TAR RNA target under physiological conditions (K(d) = 20 nM), whereas no binding was observed by the mismatched oligomer. A 19-mer that is complementary to the entire upper hairpin also binds to TAR RNA with a K(d) that is similar to that of 1676, a result that suggests only part of the oligomer binds. When two of the methylphosphonate linkages in the region complementary to the 6-base loop are replaced with phosphodiester linkages, the K(d) is reduced by approximately a factor of 10. This result suggests that interactions between TAR RNA and the oligomer occur initially with nucleotides in the 6-base loop, and that these interactions are sensitive to presence and possibly the chirality of the methylphosphonate linkages in the oligomer. The high affinities of mr-AOMPs for TAR RNA and their resistance to nuclease hydrolysis suggests their potential utility as antisense agents in cell culture.

Multiple protein domains contribute to the action of the copper chaperone for superoxide dismutase.

The copper chaperone for superoxide dismutase (SOD1) inserts the catalytic metal cofactor into SOD1 by an unknown mechanism. We demonstrate here that this process involves the cooperation of three distinct regions of the copper chaperone for SOD1 (CCS): an amino-terminal Domain I homologous to the Atx1p metallochaperone, a central portion (Domain II) homologous to SOD1, and a short carboxyl-terminal peptide unique to CCS molecules (Domain III). These regions fold into distinct polypeptide domains as revealed through proteolysis protection studies. The biological roles of the yeast CCS domains were examined in yeast cells. Surprisingly, Domain I was found to be necessary only under conditions of strict copper limitation. Domain I and Atx1p were not interchangeable in vivo, underscoring the specificity of the corresponding metallochaperones. A putative copper site in Domain II was found to be irrelevant to yeast CCS activity, but SOD1 activation invariably required a CXC in Domain III that binds copper. Copper binding to purified yeast CCS induced allosteric conformational changes in Domain III and also enhanced homodimer formation of the polypeptide. Our results are consistent with a model whereby Domain I recruits cellular copper, Domain II facilitates target recognition, and Domain III, perhaps in concert with Domain I, mediates copper insertion into apo-SOD1.