This article describes studies on the glucose-induced responses of intracellular Ca2+ concentration ([Ca2+]i), insulin release, and redistribution of calbindin-D28k, a calcium-binding regulatory protein, in beta-cells of pancreatic islets of calbindin-D28k knockout (KO) and wild-type mice (C57BL6) as well as in betaHC-13 control cells and betaHC-13 CaBP40 cells (beta-cell line overexpressing calbindin-D28k). Upon increasing the glucose concentration from 2.8 to 30 mM, islets of KO mice showed a significantly greater increase in [Ca2+]i (mean increase in [Ca2+]i, i.e., delta[Ca2+]i, was 296 nM) compared with wild-type mice (delta[Ca2+]i = 97 nM). betaHC-13 CaBP40 cells showed little change in [Ca2+]i upon elevation of glucose from 5.5 to 32.7 mM, whereas betaHC-13 control cells exhibited significant increases in [Ca2+]i, (delta[Ca2+]i = 510 nM). Similarly, upon addition of 30 mM glucose, the rate of insulin release increased from 25.2 (basal rate) to 145.2 pg/mL/min in betaHC-13 control cells, whereas in betaHC-13 CaBP40 cells the rate of insulin release was only 27.5 pg/mL/min in high glucose. Thus, levels of calbindin-D28k in beta-cells affect both [Ca2+]i and insulin secretion in response to glucose. The three-dimensional reconstruct of confocal immunofluorescent images showed that glucose caused redistribution of calbindin-D28k resulting in co-localization in the region of L-type voltage-dependent calcium channels (VDCC). This co-localization may be an important regulatory function concerning Ca2+ influx via L-type VDCC and exocytosis of insulin granules.
Decreases in load are important cues in the control of posture and walking. We recorded activities of the tibial campaniform sensilla, receptors that monitor forces as strains in the exoskeleton, in the middle legs of freely moving cockroaches. Small magnets were attached to the thorax and body load was changed by applying currents to a coil below the substrate. Body position was monitored by video recording. The tibial sensilla are organized into proximal and distal subgroups that have different response properties and reflex effects: proximal sensilla excite extensor motoneurons while distal receptors inhibit extensor firing. Sudden load decreases elicited bursts from distal sensilla, while increased load excited proximal receptors. The onset of sensory discharges closely approximated the time of peak velocity of body movement in both load decreases and increases. Firing of distal sensilla rapidly adapted to sustained unloading, while proximal sensilla discharged tonically to load increases. Load decreases of small amplitude or at low rates produced only inhibition of proximal activity while decrements of larger size or rate elicited distal firing. These response properties may provide discrete signals that either modulate excitatory extensor drive during small load variations or inhibit support prior to compensatory stepping or initiation of swing.
Monosodium glutamate (MSG) is one of the most widely spread food additives that might cause male infertility. However, Nigellasativa L. seeds (NSS) could provide a solution. This study was designed to investigate the potential effects of NSS on rats ingesting MSG. To achieve this aim, adult male albino rats were randomly equally assigned into three groups for 21 days: control group received no treatment, MSG group received MSG as 30 g/kg feed, and MSG + NSS group received MSG as 30 g/kg and NSS as 30 g/kg feed. Testis histomorphometry showed marked deterioration by MSG as atrophic seminiferous tubules with degeneration of their lining cells, damaged Leydig cells and decreased germ cells number. Periodic Acid Schiff stain indicated irregular interrupted basement membranes. Glutathione reductase, superoxide dismutase 2 (SOD2), and caspase-3 immuno-expressions increased in testicular cells. Testosterone levels were significantly decreased in MSG challenged rats along with significant increase in luteinizing hormone levels, whereas NSS normalized this hormonal profile. MSG exposure also caused significantly increased lipid peroxides (LPO), glutathione-S-transferase, and total antioxidant capacity (TAC) whereas nitric oxide and SOD2 were significantly decreased. NSS succeeded in rebalance LPO and TAC and ameliorated the histoarchitectural disturbances. NSS mitigated MSG-induced testicular impairment by its antioxidant and cytoprotective activities.
We studied the mechanisms underlying support of body load in posture and walking in serially homologous legs of cockroaches. Activities of the trochanteral extensor muscle in the front or middle legs were recorded neurographically while animals were videotaped. Body load was increased via magnets attached to the thorax and varied through a coil below the substrate. In posture, tonic firing of the slow trochanteral extensor motoneuron (Ds) in each leg was strongly modulated by changing body load. Rapid load increases produced decreases in body height and sharp increments in extensor firing. The peak of extensor activity more closely approximated the maximum velocity of body displacement than the body position. In walking, extensor bursts in front and middle legs were initiated during swing and continued into the stance phase. Moderate tonic increases in body load elicited similar, specific, phase dependent changes in both legs: extensor firing was not altered in swing but was higher after foot placement in stance. These motor adjustments to load are not anticipatory but apparently depend upon sensory feedback. These data are consistent with previous findings in the hind legs and support the idea that body load is countered by common motor mechanisms in serially homologous legs.
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