Setting a maximum allowable concentration for urea in reclaimed potable water and evaluating the nature of its biological action

The purpose of the study was to identify maxim allowable concentrations of urea in reclaimed potable water. The urea concentration equal to 80 mg/l is the threshold dose influencing the taste and flavor of water. Urea is a low toxicity substance (LD50 = 14,300 mg/kg), the effect of which is not cumulative. However, when used in high doses it affects bioenergetic and cholinergic processes and causes changes in ECG, higher nervous activity and visceral structure. It has been shown that when applied to warm-blooded animals the acting dose of urea is 14.3 and 1.43 mg/kg (1/1000 and 1/10000 LD50), the threshold dose is 0.72 mg/kg (1/20000 LD50), and the ineffective dose is 0.36 mg/kg (1/40000 LD50) which amounts to the concentration of 10 mg/l. In terms of toxic effects the dose equal to 10 mg/l is taken to be the maximally allowable concentration of urea. It is recommended to use the Laham biotest for measuring urea in water.     

Antiviral Drug Ivermectin at Nanomolar Concentrations Inhibits Glycine-Induced Chloride Current in Rat Hippocampal Neurons

Bulletin of Experimental Biology and Medicine - Ivermectin (IVM) belongs to the class of macrocyclic lactones, which is used as an antiparasitic agent. At present, the researchers focus on...     

Protein Synthesis Is Required for Induction of Amnesia Elicited by Disruption of the Reconsolidation of Long-Term Memory

Studies on common snails previously trained to an associative skill consisting of rejecting a defined foodstuff addressed the effects of NMDA glutamate receptor antagonists (MK-801 and APV) and protein synthesis inhibitors (cycloheximide and anisomycin) on long-term memory reconsolidation processes. Injections of each of the study compounds before the reminding procedure 24 h after training were found to lead to impairment of the reproduction of the acquired skill, which lasted at least three weeks. Repeat training of these animals to reject the same foodstuff as used in the initial training did not lead to acquisition of the skill. However, simultaneous injections of a protein synthesis inhibitor and an NMDA receptor antagonist (MK-801 + cycloheximide or APV + anisomycin) did not impair the skill. In subsequent experiments, snails received cycloheximide at different times after exposure to MK-801/reminding. Administration of cycloheximide 3 and 6 h after MK-801/reminding led to the development of incomplete amnesia and repeat training of the animals led to rapid restoration of memory. Administration of cycloheximide 9 h after MK-801/reminding evoked the development of stable amnesia characterized by impairment of skill formation on repeat training. We propose that the mechanisms of amnesia induced by the NMDA glutamate receptor antagonist, by analogy with the mechanisms of other long-term adaptive rearrangements of the brain, depend on translation and can be suppressed by inhibitors of translation. The “time window” for the dependence of amnesia induction processes on the synthesis of protein molecules was 6–9 h after exposure to MK-801/reminding.     

Selective suppression of the slow-inactivating potassium currents by nootropics in molluscan neurons

The role of the voltage-gated K+ channels in the effect of some nootropics was investigated. Earlier, the multiple effect of high concentrations of two nootropics, piracetam and its peptide analogue GVS-111 [Seredenin et al. (1995), US Patent No. 5,439,930], on Ca2+ and K+ currents of molluscan neurons was shown [Solntseva et al. (1997), General Pharmacology 29, 85-89]. In the present work, we describe the selective effect of low concentrations of these nootropics as well as vinpocetine on certain types of K+ current. The experiments were performed on isolated neurons of the land snail Helix pomatia using a two-microelectrode voltage-clamp method. The inward voltage-gated Ca2+ current (ICa) and three subtypes of the outward voltage-gated K+ current were recorded: Ca2+-dependent K+ current (IK(Ca)), delayed rectifying current (IKD), and fast-inactivating K+ current (IA). It has been found that I Ca was not changed in the presence of 30 microM vinpocetine, 100 microM piracetam or 10 nM GVS-111, while slow-inactivating, TEA-sensitive IK(Ca) and IKD were inhibited (IK(Ca) more strongly than IKD). In contrast, the fast-inactivating, 4-AP-sensitive K+ current (IA) was not diminished by low concentrations of piracetam and GVS-111, while vinpocetine even augmented it. A possible role of slow-inactivating subtypes of the K+ channels in the development of different forms of dementia is discussed.     

Human microecology studies at Department of Microbiology with Virology and Immunology, I.M. Sechenov Moscow Medical Academy

Studies of human microflora in health and disease and during exposure to professional and ecological factors is a traditional problem solved for many years by staff members of Department of Microbiology with Virology and Immunology, I. M. Setchenov Moscow Medical Academy. The purpose of research is to develop methods and means for diagnosis and prevention of human microbiocenosis disorders. Fundamental and applied research in cooperation with prophylactic and clinical institutions and departments yielded data contributing to solution of many pressing problems in prevention and diagnosis of infectious diseases.