1,721,446 research outputs found
Regional variation in the current flow across an insect blood-brain barrier
No full textOne notable characteristic of the insect and vertebrate central nervous system is the presence of a clearly defined blood-brain barrier. In the insect this barrier is made up of the perineurial glial cells, and shows a heterogeneity in structure and possibly function between the connectives and ganglia. In this paper we have used a two-dimensional vibrating probe to investigate the net flow of electrical current across the barrier at various locations in the abdominal nervous system. The results show clear differences between different areas. There is a strong and consistent outward current flow (3.16 microA cm-2) perpendicular to the ganglion surface over the equatorial plane. Current returns through the peripheral nerves and the connectives. A detailed study of the latter shows that the net inward flow is principally over the initial section, immediately adjacent to the ganglia (2.11 microA cm-2). The different current polarities can be correlated with structural differences in the underlying glial cells. <br/
Glial toxin effect on protein synthesis in an insect connective
No full textAnalysis of electron autoradiographs from the nerve cord of the insect, Periplaneta americana (L.) shows a significant incorporation of 3H-labelled protein in the axons. The axonal activity is greatly reduced after treatment of the cord with the glial toxin ethidium bromide. This is interpreted as substantiating the possibility that adaxonal glia can transfer proteins to the axons
Role of V-ATPase-rich cells in acidification of the male reproductive tract
No full textSpecialized proton-secreting cells play important physiological roles in a variety of tissues. On the basis of the immunocytochemical detection of carbonic anhydrase and V-ATPase in distinct epithelial cells of the epididymis and vas deferens, we predicted that the vacuolar V-ATPase that is located on the apical membrane of these cells should be a major contributor to luminal acidification in parts of the male reproductive tract. Physiological studies using the proton-selective vibrating probe in the vas deferens confirmed this hypothesis. As discussed recently, maintenance of the pH of the reproductive tract is probably under tight physiological control, by analogy with the situation in the kidney. Manipulation of luminal pH might, therefore, provide a point of intervention for the regulation of male fertility. In addition, it is possible that some cases of unexplained male infertility might result from defective acidification, resulting either from pathological states or potentially from environmental factors that may inhibit proton secretory pathways
Sustaining olfaction at low salinities: mapping ion flux associated with the olfactory sensilla of the blue crab Callinectes sapidus
No full textTo test the hypothesis of a diffusion-generated, ionic/osmotic microenvironment within the olfactory sensilla (aesthetases), flux gradients of Ca2+ and K+ associated with the external surfaces of these sensilla were spatially mapped using self-referencing, ion-selective microelectrodes. Blue crabs (Callinectes sapidus) acclimated to low-salinity conditions (15% sea water and fresh water) showed a net efflux of ions from the aesthetases. The region of maximum flux associated with each aesthetase conformed to that predicted from structural data and corresponded to the permeable region of the cuticle separating the olfactory dendrites from the external environment. Estimates of net flux from the entire tuft of aesthetases for both Ca2+ and K+ fell within the predicted range on the basis of comparisons with (22)Na+ flux measured previously and assuming a passive diffusion model of ion movement from the hemolymph to the sensillar lymph and, ultimately, to the external environment. The maximum concentrations of these ions measured deep within the tuft are discussed in the light of a potential across the aesthetases that may limit ion efflux at low salinities
Mechanisms of glial regeneration in an insect central nervous system
No full textAs in other repairing systems, glial regeneration in insect central nervous connectives, following selective chemical lesioning, involves both exogenous and endogenous elements. Our current evidence, including that obtained with monoclonal antibodies, indicates that the reactive, granule-containing cells are derived from a sub-population of circulating haemocytes which, within 24 h, invade, and are restricted to, the lesion zone. The granule-containing cells are involved in the initial repair of the perineurial region. They also contribute to the first stage in the restoration of the blood-brain barrier and are responsible for recruiting reactive endogenous glia, apparently from the vicinity of the anterior abdominal ganglion. The granule-containing cells transform into or are replaced by functional glia between 3 and 5 days after selective glial disruption, coincident with the appearance in the lesion zone of dividing reactive cells
Development of self-referencing oxygen microsensor and its application to single pancreatic HIT cells: effects of adenylate cyclase activator forskolin on oxygen consumption
No full textNoninvasive measurement of hydrogen and potassium ion flux from single cells and epithelial structures
No full textThis review introduces new developments in a technique for measuring the movement of ions across the plasma membrane. With the use of a self-referencing ion-selective (Seris) probe, transport mechanisms can be studied on a variety of preparations ranging from tissues to single cells. In this paper we illustrate this versatility with examples from the vas deferens and inner ear epithelium to large and small single cells represented by mouse single-cell embryos and rat microglia. Potassium and hydrogen ion fluxes are studied and pharmacological manipulation of the signals are reported. The strengths of the self-referencing technique are reviewed with regard to biological applications, and the expansion of self-referencing probes to include electrochemical and enzyme-based sensors is discussed
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