Analysis of the form of cortical neuron reaction to acetylcholine

Reaction patterns of 90 cortical neurons to acetylcholine approximated by two parabolas have been divided on simple and complex. The participation of different types of cholinoreceptors in complex reactions to transmitter is proposed.     

Inhibition of NADH-dehydrogenase by low concentrations of NAD+]

Low concentrations of NAD+ inhibit the NADH: acceptor reductase reactions catalyzed by soluble NADH dehydrogenase from bovine heart mitochondria. The degree of incomplete inhibition of the enzyme depends on the nature and concentration of artificial electron acceptors and is manifested only at low concentrations of the latter. Marked inhibition was demonstrated for the 2.6-dichlorophenolindophenol-, ferricyanide- and O2-reductase reactions, being weakly pronounced during the measurement of the NADH: cytochrome c reductase activity. The inhibition of the above reactions by oxidized NAD+ isn't competitive towards NADH. A kinetic scheme is proposed, which postulates NADH: acceptor reductase reactions occurrence via two mechanisms, namely, a ping-pong mechanism and oxidation of the product-enzyme complex by the acceptor. It was shown that low concentrations of NAD+ also inhibit the NADH oxidase reaction catalyzed by complex I.     

Expression of the glucose transporter isoform GLUT 4 is insufficient to confer insulin-regulatable hexose uptake to cultured muscle cells.

Glucose transporter isoform expression was studied in the skeletal muscle-like cell line, C2C12. Northern and Western blot analysis showed that the insulin-responsive muscle/fat glucose transporter isoform, GLUT 4, was expressed in these cells at very low levels, whereas the erythrocyte isoform, GLUT 1, was expressed at readily detectable levels. Insulin did not stimulate glucose transport in this cultured muscle cell line. The C2C12 cells were then transfected separately with either GLUT 1 or GLUT 4, and stable cell lines expressing high levels of mRNA and protein were isolated. GLUT 1-transfected cells exhibited a 3-fold increase in the amount of the GLUT 1 transporter protein which was accompanied by a 2- to 3-fold increase in the glucose uptake rate. However, despite at least a 10-fold increase in GLUT 4 mRNA and protein detected after GLUT 4 cDNA transfection, the glucose uptake of these cells was unchanged and remained insulin-insensitive. By laser confocal immunofluorescence imaging, it was established that the transfected GLUT 4 protein was localized almost entirely in cytoplasmic compartments. In contrast, the GLUT 1 isoform was detected both at the plasma membrane as well as in intracellular compartments. These results suggest that acute insulin stimulation of glucose transport is not solely dependent on the presence of the insulin receptor and the GLUT 4 protein, and that the presence of some additional protein(s) must be required.     

Tonic component of the conditioned reflex process and its functional role

Tonic background activity of 266 neurones in the hippocampus and different neocortical areas was studied in freely moving rabbits in the process of defensive and food instrumental conditioned performance and during switching-over of instrumental and classical food and defensive reflexes. Associations of CS and reinforcement evoke background activity changes in most of recorded cortical neurones preceding the development of other conditioned manifestations. Conditioned reflex was performed only after reaching the background firing rate of almost every examined neurone optimal for its realization. The performance of different conditioned reflexes was associated with different background activity levels of cortical neurones. The above mentioned data form the experimental basis for the identification of the tonic component in conditioned process which reflects tonic character of temporary connection formation and function.     

Insulin-regulated glucose uptake in rat adipocytes is mediated by two transporter isoforms present in at least two vesicle populations

We have recently described a monoclonal antibody (1F8) that recognizes a form of glucose transporter unique to fat and muscle (James, D. E., Brown, R., Navarro, J., and Pilch, P. F. (1988) Nature 333, 183-185), tissues that respond acutely to insulin by markedly increasing their glucose uptake. Here, we report that rat adipocytes possess two immunologically distinct glucose-transporters: one recognized by 1F8, and one reactive with antibodies raised against the human erythrocyte glucose transporter. Immunoadsorption experiments indicate that these glucose transporters reside in different vesicle populations and that both transporter isoforms translocate from intracellular sites to the plasma membrane in response to insulin. The insulin-regulatable transporter resides in a unique vesicle that comprises 3% or less of the low density microsomes of fat cells and has a limited protein composition that does not include the bulk of another translocatable protein, the insulin-like growth factor II receptor. Immunoprecipitation with 1F8 of microsomal glucose transporters photoaffinity labeled with [3H]cytochalasin B brings down 90% of the label. Similarly, immunoprecipitation with 1F8 of glucose transporters from insulin-stimulated plasma membranes photolabeled with 3-[125I]iodo-4-azidophenethylamido-7-O-succinyldeacetyl-f ors kolin, another transporter-selective reagent, results in 75% of the labeled transporter localized in the immunoprecipitate. Thus, insulin action involves the combined effect of translocation from at least two vesicle pools each containing different glucose transporters. The 1F8-reactive transporter comprises the majority of the total transporter pool that is responsible for the insulin-induced increase in glucose transporter number.     

Scale dependency and the expression of hierarchical structure in Delphinium patches

Hierarchy theory has provided a valuable conceptual framework for studies of heterogeneity. However, there have been few empirical studies of hierarchical structure and little is known about how hierarchical structure originates or varies among systems. Here, I explore how scale dependency can influence the detection of hierarchical structure. Specifically, I compared how heterogeneity changed with scale in patches of larkspur (Delphinium spp). The distribution of Delphinium nelsonii inflorescences was quite uniform over the range of measured scales (1 m²-2500 m²) and only a single level of patchiness was observed. Aggregations of D. barbeyi inflorescences were much more pronounced and this patchiness was evident at many scales. The number of hierarchical levels and the scales at which patchiness occurred varied both within and between plots of D. barbeyi. Because patchiness was not strongly scale-dependent for either species, discrete patch boundaries and well-defined hierarchical levels were not usually apparent even when multiple scales of patchiness were present. In several cases, the scales of detected patchiness depended on the difference in scale between grain (resolution) and extent. I predict that because of the lack of dominant and strongly scale-dependent processes, microlandscapes such as Delphinium meadows, may be less likely to exhibit well-defined hierarchical structure than larger-scale landscapes, especially those heavily altered by human activities.     

Models of learning based on the plastic properties of the "placing reaction" in cats]

A possibility of functional reorganization of initial sensorimotor connections of the forepaw has been shown on seven cats. The main initial relationships between the afferent tactile input and motor output for the ulnar joint of the cat forepaw are as follows: tactile stimulation of the dorsal surface of the paw produces a flexion in the ulnar joint ("placing reaction"), and that of the ventral surface, an extension of the paw in the ulnar joint ("magnetic reflex"); simultaneous tactile stimulation of the ventral surface of the paw blocks the "placing reaction" evoked by a touch of the dorsal side. Extinction was produced of the above unconditioned connections and elaboration of a new "cross" connection consisting in that tactile stimulation of the ventral side of the paw resulted in flexion in the ulnar joint.     

Aromatic crown ethers as phase transfer catalysts in the synthesis of N-acetylglucosamine beta-aryl glycosides

The crown ether-catalyzed glycosylation of phenol, 4-methoxyphenol, and 4-nitrophenol was studied under phase transfer conditions in solid-liquid system. The asymmetric dibenzocrown esters are superior to [3.3]dibenzo-1 8-crown-6 and 15-crown-5 in the catalysis of these reactions. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 3; see also http://www.maik.ru.