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At least 379 records · Page 21Linked to original sources
PubMed1980

In vitro inhibition of cyclic 3' 5',-AMP-phosphodiesterase by a group of structural analogues of glaucine.

Both glaucine and six of its structural analogues applied in increasing concentrations produced a concentration-dependent inhibiton of cyclic 3' 5'-AMP-phosphodiesterase in homogenates from different organs of guinea-pigs and rats. At one and the same concentration of the compound tested the percentage of inhibition varied within wide ranges depending on the compound used, as well as on the organ and on the Km of phosphodiesterase. The changes in the chemical structure of glaucine and the changes in the inhibitory effects on phosphodiesterase activity of tissue homogenates were compared. Some of the compounds applied in appropriate concentrations showed a twice higher inhibitory activity than glaucine. This finding is of particular importance having the mind the much lower toxicity of these compounds compared with glaucine. Essential differences in the dynamics of the concentration-dependent phosphodiesterase inhibition between the compounds were established. The observed peculiarities of the inhibitory effects of the compounds tested favour the concept of the multiple nature of phosphodiesterase. The data from the pharmacological investigation on glaucine and its semisynthetic analogues led us to believe that the effect of 2 compound on phosphodiesterase activity of homogenates from intestinal smooth muscles does not justify any definitive conclusions about the character of its effect on the smooth-muscle activity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

Concepts of drugs: differences in conceptual structure across groups with different levels of drug experience.

Seventy-seven college students varying in degree of drug use experience rated the perceived similarities of all possible combinations of 16 drugs classes (cigarettes, other tobacco, alcohol, marijuana, barbiturates, minor and major tranquilizers, amphetamines, amphetamine derivatives, cocaine, heroin, opiates, hallucinogens, inhalants, PCP, anti-depressants). Multi-dimensional scaling (INDSCAL) and network models (PFNET) indicated that abstainers had only one pharmacological category involving sedatives/depressants, and that they attached more importance to whether drugs were licit vs. illicit than to whether they were depressants vs. stimulants. Conceptions became more coherent, differentiated and based on pharmacological properties for more experienced drug users. In line with previous work, groups with greater experience with drugs had more sophisticated conceptions not only about the drugs they had used, but also about drugs they had not used. These findings suggest that early on in drug behavior sophisticated and interrelated concepts are developing that should be taken into account when designing interventions and information campaigns.

Adult↗
PubMed1989

[The sequential structures of social behavior and their developmental changes in rats bidirectionally selected for emotionality].

Eighteen colonies of Tsukuba High Emotional (THE) and 17 colonies of Low Emotional (TLE), each one composing of one female and two male rats, were reared for about two months. During this period, intruder tests and intra-colony observations were conducted once a week. Social behavior of colony residents was coded sequentially with 17 items in a microcomputer. Transitions in chi 2 tests were visualized in a tree structure. The sequential structures of social behavior were compared between two strains of rat in the course of social dominance organization. Although TLE males were more aggressive than THE males, dominant males of both strains had almost the same transition structure constructed of four common sequentially bound item-groups; alpha group (bite, lunge, aggressive groom), beta group (on-top related items), gamma group (chase, lateral display, boxing, on-back), and delta group (flight, retreat, defensive upright). beta items were found to be sequentially located after bite in alpha group. delta group was disappeared with dominance organization. But there were some differences in inter- and intra-group structures between THE and TLE.

Aggression↗
PubMed2002

Multicenter clinical research in adult critical care.

OBJECTIVE: To describe the development, organization, and operation of several collaborative groups conducting investigator-initiated multicenter clinical research in adult critical care. DESIGN: To review the process by which investigator-initiated critical care clinical research groups were created using examples from Europe, Australia, the United States, and Canada. Various models of group structure and function are discussed, highlighting complementary approaches to protocol development, multicenter study management, and project funding. DATA SOURCES: Published peer review research and unpublished terms of reference documents on the structure and function of these groups. DATA SYNTHESIS: The overall goal of clinical critical care research groups engaged in multicenter studies is to improve patient outcomes through conducting large, rigorous investigations. Research programs we reviewed included the following: a) multicenter epidemiologic studies and surveys; b) technology evaluations of mechanical ventilation; c) investigations focused on three priority fields (acute lung injury, infection, and acute brain injury); d) a series of randomized trials of treatments for one syndrome (acute respiratory distress syndrome); and e) diverse methodologies addressing several clinical problems. The structure and function of these research groups differ according to their historical development, research culture, and enabling resources. Specific protocols emerge from clinical questions generated by investigators or from collectively prioritized research agendas. Project funding includes government support, peer-review grants, intensive care foundations, industry, local hospital funds, and hybrid models. Infrastructure for study management varies widely. CONCLUSIONS: Several national and international groups have engaged in investigator-initiated multicenter critical care research. The development, organization, and operational methods of these groups illustrate several collaborative models for clinical investigations in the intensive care unit. Common characteristics of these groups are a cohesive spirit, a sense of mission to achieve shared research goals, and acknowledgment that such an organization is much more than the sum of its parts.

Adult↗
PubMed2006

A novel bacterium Saprospira sp. strain PdY3 forms bundles and lyses cyanobacteria.

A helical filamentous cyanobactericidal bacterium was isolated from Dianchi Lake, a eutrophic freshwater lake in Kunming City of the Yunnan Province in China using a special solid medium. This species was designated strain PdY3. This bacterium was identified as a novel Saprospira sp. on the basis of its morphological characteristics and 16S rDNA sequence. Strain PdY3 showed apparent group behavior on the solid medium, forming orderly, bundle-like group structures. These bundles moved as groups. Individuals in a bundle responded to the bundle as a whole. PdY3 also showed group behavior and formed a three-dimensional reticular structure when co-cultured with Anabaena in liquid media. This helical bacterium lysed cyanobacteria through direct contact and its group behavior greatly accelerated the cyanobactericidal process. Our experiments showed that PdY3 caused lysis of 64% of Anabaena cells within 1 day and that its cyanobactericidal range was broad. These results underscore potential application of Saprospira on the control of blooms of cyanobacteria. PdY3 group behavior might allow a more efficient capture of bacterial prey.

Anabaena↗
PubMed1982

The dual effects of GABA and related amino acids on the electrical threshold of ventral horn group Ia afferent terminations in the cat.

Amino acids were administered microelectrophoretically near the unmyelinated terminations of extensor muscle Ia afferent terminations stimulated electrically in the vicinity of lumbar motoneurones in anaesthetized cats. The predominant effect of one group (structurally related to GABA, poor substrates for in vitro amino acid uptake systems) was a reduction in the threshold (depolarization). The second group (including GABA and structural analogues which are substrates for GABA transport systems in vitro) had biphasic effects, an initial reduction being followed by an increase in threshold. The third group (structurally unrelated to GABA, substrates for amino acid uptake systems) only increased Ia termination thresholds. Reductions in termination thresholds, but not increases, were associated with diminution of synaptically evoked primary afferent depolarization, and were decreased by bicuculline methochloride. Many amino acids increased the electrical resistance of the intraspinal medium near the orifices of the barrels of seven barrel micropipettes, and for L-histidine, one of the third group of amino acids, both this effect and the increased threshold of terminations were reversibly modified by microelectrophoretic ouabain. These observations suggest that GABA-mimetics depolarize Ia terminations by interacting with bicuculline-sensitive receptors similar to those at hyperpolarizing gabergic synapses upon spinal interneurones. In addition, under the experimental conditions used, these and other amino acids increase termination thresholds, probably in the absence of any change in membrane conductance, an effect resulting from alterations in the ionic constitution of the extracellular medium around the orifices of micropipettes ejecting amino acids consequent upon the ouabain-sensitive co-transport of amino acids and sodium ions into neurones and glia.

Afferent Pathways↗
PubMed2003

Non-Watson Crick base pairs might stabilize RNA structural motifs in ribozymes -- a comparative study of group-I intron structures.

In recent decades studies on RNA structure and function have gained significance due to discoveries on diversified functions of RNA. A common element for RNA secondary structure formed by series of non- Watson/Watson Crick base pairs, internal loops and pseudoknots have been the highlighting feature of recent structural determination of RNAs. The recent crystal structure of group-I introns has demonstrated that these might constitute RNA structural motifs in ribozymes, playing a crucial role in their enzymatic activity. To understand the functional significance of these non-canonical base pairs in catalytic RNA, we analysed the sequences of group-I introns from nuclear genes. The results suggest that they might form the building blocks of folded RNA motifs which are crucial to the catalytic activity of the ribozyme. The conservation of these, as observed from divergent organisms, argues for the presence of non-canonical base pairs as an important requisite for the structure and enzymatic property of ribozymes by enabling them to carry out functions such as replication, polymerase activity etc. in primordial conditions in the absence of proteins.

Animals↗