Inadequate brain glycogen or sleep increases spreading depression susceptibility.

OBJECTIVE: Glycogen in astrocyte processes contributes to maintenance of low extracellular glutamate and K+ concentrations around excitatory synapses. Sleep deprivation (SD), a common migraine trigger, induces transcriptional changes in astrocytes, reducing glycogen breakdown. We hypothesize that when glycogen utilization cannot match synaptic energy demand, extracellular K+ can rise to levels that activate neuronal pannexin-1 channels and downstream inflammatory pathway, which might be one of the mechanisms initiating migraine headaches. METHODS: We suppressed glycogen breakdown by inhibiting glycogen phosphorylation with 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) and by SD. RESULTS: DAB caused neuronal pannexin-1 large pore opening and activation of the downstream inflammatory pathway as shown by procaspase-1 cleavage and HMGB1 release from neurons. Six-hour SD induced pannexin-1 mRNA. DAB and SD also lowered the cortical spreading depression (CSD) induction threshold, which was reversed by glucose or lactate supplement, suggesting that glycogen-derived energy substrates are needed to prevent CSD generation. Supporting this, knocking down the neuronal lactate transporter MCT2 with an antisense oligonucleotide or inhibiting glucose transport from vessels to astrocytes with intracerebroventricularly delivered phloretin reduced the CSD threshold. In vivo recordings with a K+ -sensitive/selective fluoroprobe, Asante Potassium Green-4, revealed that DAB treatment or SD caused a significant rise in extracellular K+ during whisker stimulation, illustrating the critical role of glycogen in extracellular K+ clearance. INTERPRETATION: Synaptic metabolic stress caused by insufficient glycogen-derived energy substrate supply can activate neuronal pannexin-1 channels as well as lower the CSD threshold. Therefore, conditions that limit energy supply to synapses (eg, SD) may predispose to migraine attacks, as suggested by genetic studies associating glucose or lactate transporter deficiency with migraine. Ann Neurol 2018;83:61-73.

Potassium up-regulates antioxidant metabolism and alleviates growth inhibition under water and osmotic stress in wheat (Triticum aestivum L).

Pot experiments were conducted to find out the effectivity of K on Triticum aestivum L cultivars. Polyethylene glycol 6000 (PEG 6000) was used as an osmoticum to induce osmotic stress under sand culture setting up the water potential of external solution at -3 and -5 bars. In pots, plants were raised under restricted and normal irrigation and K was applied in varying doses (0, 20, 40, 60 kg ha-1) and estimation of different physiological and biochemical parameters was done at two developmental stages, i.e., preflowering and flowering. Supplementation of K resulted in obvious increase in growth and activity of antioxidant enzymes in both normal and stressed plants. Added potassium increased total phenols and tannins thereby strengthening the components of both the enzymatic as well as non-enzymatic antioxidant system. Under both normal and stressed conditions, K-fed plants experienced significant increase in the synthesis of osmolytes like free proline, amino acids, and sugars which assumes special significance in growth under water stress conditions. Wheat plants accumulating greater K were able to counteract the water stress-induced changes by maintaining lower Na/K ratio.

Modulation by K+ Plus NH4+ of microsomal (Na+, K+)-ATPase activity in selected ontogenetic stages of the diadromous river shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).

We investigate the synergistic stimulation by K(+) plus NH4 (+) of (Na(+), K(+))-ATPase activity in microsomal preparations of whole zoea I and decapodid III, and in juvenile and adult river shrimp gills. Modulation of (Na(+), K(+))-ATPase activity is ontogenetic stage-specific, and particularly distinct between juveniles and adults. Although both gill enzymes exhibit two different sites for K(+) and NH4 (+) binding, in the juvenile enzyme, these two sites are equivalent: binding by both ions results in slightly stimulated activity compared to that of a single ionic species. In the adult enzyme, the sites are not equivalent: when one ion occupies its specific binding site, (Na(+), K(+))-ATPase activity is stimulated synergistically by ≈ 50% on binding of the complementary ion. Immunolocalization reveals the enzyme to be distributed predominantly throughout the intralamellar septum in the gill lamellae of juveniles and adults. Western blot analyses demonstrate a single immunoreactive band, suggesting a single (Na(+), K(+))-ATPase α-subunit isoform that is distributed into different density membrane fractions, independently of ontogenetic stage. We propose a model for the modulation by K(+) and NH4 (+) of gill (Na(+), K(+))-ATPase activity. These findings suggest that the gill enzyme may be regulated by NH4 (+) during ontogenetic development in M. amazonicum.

Contributions of Kv7-mediated potassium current to sub- and suprathreshold responses of rat layer II/III neocortical pyramidal neurons.

After block of Kv1- and Kv2-mediated K(+) currents in acutely dissociated neocortical pyramidal neurons from layers II/III of rat somatosensory and motor cortex, the remaining current is slowly activating and persistent. We used whole cell voltage clamp to show that the Kv7 blockers linopirdine and XE-991 blocked a current with similar kinetics to the current remaining after combined block of Kv1 and Kv2 channels. This current was sensitive to low doses of linopirdine and activated more slowly and at more negative potentials than Kv1- or Kv2-mediated current. The Kv7-mediated current decreased in amplitude with time in whole cell recordings, but in most cells the current was stable for several minutes. Current in response to a traditional M-current protocol was blocked by muscarine, linopirdine, and XE-991. Whole cell slice recordings revealed that the Q10 for channel deactivation was ∼2.5. Sharp electrode current-clamp recordings from adult pyramidal cells demonstrated that block of Kv7-mediated current with XE-991 reduced rheobase, shortened the latency to firing to near rheobase current, induced more regular firing at low current intensity, and increased the rate of firing to a given current injection. XE-991 did not affect single action potentials or spike frequency adaptation. Application of XE-991 also eliminated subthreshold voltage oscillations and increased gain for low-frequency inputs (<10 Hz) without affecting gain for higher frequency inputs. These data suggest important roles for Kv7 channels in subthreshold regulation of excitability, generation of theta-frequency subthreshold oscillations, regulation of interspike intervals, and biasing selectivity toward higher frequency inputs.

Fluid and electrolyte management in the premature infant.

Caring for the premature infant in the NICU requires knowledge and understanding of the physiologic adaptation to extrauterine life and how prematurity affects that transition. Nurses play an integral role in managing fluid and electrolyte balance in these infants. This article addresses postnatal adaptation and all aspects of fluid and electrolyte management of the preterm infant.

The voltage-clamp fluorometry technique.

Ion channels are the cell's gatekeepers. These proteins selectively allow ionic current to flow down its electrochemical gradient. In some cases, specialized chemical or voltage sensing domains respond to environmental changes and signal the cell to adjust its internal chemistry in response to its surroundings. Because of their importance in cell function, channels have been the focus of intense study at the functional and structural level. Here we describe the optical technique voltage-clamp fluorometry (VCF) which is used to monitor the functional state and probe the structural rearrangements that take place as ion channels are activated by voltage. VCF combines electrophysiology, molecular biology, chemistry, and fluorescence into a single technique. Our focus is on voltage-gated ion channels, but the technique described can be applied to other proteins. We describe the cut open vaseline gap configuration (COVG) for VCF recording.

Knowledge of phosphorus compared with other nutrients in maintenance dialysis patients.

OBJECTIVE: This study's objective was to assess knowledge of phosphorus compared with other nutrients in patients undergoing maintenance dialysis (MD). DESIGN: We compared knowledge of phosphorus vs. other nutrients important to the MD diet (potassium, sodium, and protein) in patients undergoing hemodialysis (HD) and peritoneal dialysis (PD). We further measured gender, age, education level, and functional health literacy to assess correlations in patient nutrient knowledge. Nutrient knowledge was measured using a 25-item Chronic Kidney Disease Knowledge Assessment Tool for Nutrition (CKDKAT-N), and functional health literacy was measured using the short form of the Test of Functional Health Literacy in Adults (S-TOFHLA). SETTING AND PATIENTS: Patients received maintenance outpatient PD or HD at Wisconsin Dialysis, Inc. (Madison, WI). MAIN OUTCOME MEASURE: The main outcome measure was knowledge of phosphorus vs. knowledge of potassium, sodium, and protein. RESULTS: Forty-seven MD patients participated in the study (29 undergoing HD, 18 undergoing PD, 30 males, 17 females, average age of 58.6 (SD, 13.8) years, and average grade level of 1.4 (SD, 2.6) years of post-secondary education). Thirty-five participants had adequate health literacy, 4 had marginal health literacy, and 8 had inadequate health literacy. The CKDKAT-N scores ranged from 6-21 for 25 items, with a mean score of 13 (SD, 2.91). Knowledge of phosphorus compared with knowledge of other nutrients was poor (0.38 vs. 0.72, P = .003). In a comparison of HD vs. PD patient knowledge, both phosphorus (0.37 vs. 0.42, P = .231) and other nutrients (0.69 vs. 0.80, P = .115) were the same. CONCLUSION: Despite regular dietary instruction, patients undergoing MD have a poor knowledge of dietary phosphorus content, compared with knowledge of other nutrients important in chronic kidney disease. Interestingly, there was no difference in nutrition knowledge when comparing PD and HD patients, despite differences in education level and health literacy between groups.

Area-specific resonance of excitatory networks in neocortex: control by outward currents.

During disinhibition or low [Mg++](o) buffer, 7-14 Hz ( approximately 10 Hz) oscillations are generated by excitatory networks of interconnected pyramidal cells in motor (agranular) cortex but are absent in barrel (granular) cortex. Here we studied if the inability of barrel cortex to produce approximately 10 Hz oscillations during these conditions is because barrel cortex networks lack the necessary cellular mechanisms or, alternatively, because those mechanisms are inhibited by outward currents. The results show that blockers of slowly inactivating voltage-dependent K+ currents unmask approximately 10 Hz oscillations in barrel cortex, and this occurs in unison with the unmasking of intrinsic inward Ca++ currents that are kept suppressed by the outward currents. Moreover, the approximately 10 Hz oscillations unmasked in barrel cortex occur independently in upper and lower layers indicating that the approximately 10 Hz oscillation mechanisms are kept suppressed in multiple networks. The results reveal that the propensity of distinct excitatory networks of neocortex to generate epileptiform oscillatory activities is controlled by outward currents.

Potassium sensitivity test (PST) as a measurement of treatment efficacy of painful bladder syndrome/interstitial cystitis: a prospective study with cyclosporine A and pentosan polysulfate sodium.

AIMS: Potassium sensitivity test (PST) has been used as an optional tool in diagnosing painful bladder syndrome/interstitial cystitis (PBS/IC). The role of PST in the follow-up of patients with PBS/IC is elusive. We performed PST before and after treatment of PBS/IC with cyclosporine A (CyA) or pentosan polysulfate sodium (PPS), to test whether the result of repeated PST correlates with alleviation of PBS/IC-related symptoms. MATERIALS AND METHODS: Sixty-four patients who participated in a randomized clinical study comparing CyA and PPS in the treatment of PBS/IC were recruited to the present study. Patients underwent 0.4 M PST before and after 6 months of treatment. The primary end point was a change from positive PST to negative among patients who responded to both treatments determined by global response assessment (GRA). RESULTS: Potassium sensitivity test (PST) was more likely to change from positive to negative among patients who responded to their treatment according to GRA (P < 0.001). The PST change follows the clinical course (ICSI score, voiding frequency, VAS score), which was more beneficial in the CyA-treated patients. CONCLUSIONS: Potassium sensitivity test (PST) reflects symptom severity of PBS/IC patients. Change of pre-treatment positive PST to negative correlates well with clinical alleviation of PBS/IC-related symptoms. In patients with persistent symptoms it may be painful and does not offer additional information. Thus, we do not recommend PST to be used as a routine clinical test in monitoring of PBS/IC treatment efficacy.

Developmental regulation of K accumulation in pollen, anthers, and papillae: are anther dehiscence, papillae hydration, and pollen swelling leading to pollination and fertilization in barley (Hordeum vulgare L.) regulated by changes in K concentration?

The presence of potassium (K) in pollen, anthers and papillae from barley (Hordeum vulgare L.) flowers with different levels of developmental stages starting from boot stage to fully mature flower, was studied by using the K-sensitive fluorescent dye PBFI (potassium-binding benzofuran isophthalate) and confocal laser scanning microscopy. The presence of heavy K fluorescence was detected only at the aperture area of the mature pollen. Similarly, the presence of K increased with the progression from immature to mature anther and papillae. In addition, a higher concentration of K was observed only at the stomium area (the place of anther dehiscence) of mature anthers. Keeping in view the role of K as an active osmoticum and the consistent and synchronized appearance of K in mature pollen, anthers, and papillae, it was concluded that K may regulate anther dehiscence, pollen imbibition, and papillae hydration leading to pollination and fertilization.

Electrical perception of the 'death message' in Chara: characterization of K+ -induced depolarization.

When the nodal end of an internodal cell of Chara corallina was subjected to a pulse treatment with artificial cell sap, a depolarization lasted in artificial pond water. This depolarization could also be induced by pulse treatment with KCl solution, indicating that K+ in the artificial cell sap is responsible (K+ -induced depolarization). The depolarization was prolonged in the presence of 2 mM KCl and the prolonged depolarization was terminated by supplementing with either CaCl2, MgCl2 or NaCl. These results supported the hypothesis that K+ released from the killed cell is responsible for generation of the wound-induced membrane depolarization.

Bioenergetic analysis of cerebellar granule neurons undergoing apoptosis by potassium/serum deprivation.

Apoptosis induced by K+/serum deprivation (low K+) in cerebellar granule neurons has been extensively investigated. The mitochondria play a key role in apoptosis by releasing proapoptotic factors into the cytoplasm, and mitochondrial dysfunction has been proposed as an early or initiating event in this model. To directly test this hypothesis, cellular and mitochondrial bioenergetics were quantified by determining the respiratory parameters of coverslip-attached neurons. While oxidative phosphorylation rate decreased 39-49% in low K+, this was due to decreased cellular ATP demand rather than impaired ATP/ADP exchange or respiratory chain inhibition. From 3 to 5 h in low K+, apoptosis progressed from 13 to 40% despite no appreciable change in respiratory parameters. Changes in steady-state O2-, assessed with dihydroethidium, were seen in granule but not hippocampal neurons. The O2- change correlated with changes in [Ca2+]c, but not mitochondrial respiration. Thus, early mitochondrial dysfunction can be excluded in this common model of neuronal apoptosis.

Assessing the generality of global leaf trait relationships.

Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation-climate models. A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus concentrations, as well as leaf potassium, photosynthetic N-use efficiency (PNUE), and leaf N : P ratio. While mean trait values differed between plant functional types, the range found within groups was often larger than differences among them. Future vegetation-climate models could incorporate this knowledge. The core leaf traits were intercorrelated, both globally and within plant functional types, forming a 'leaf economics spectrum'. While these relationships are very general, they are not universal, as significant heterogeneity exists between relationships fitted to individual sites. Much, but not all, heterogeneity can be explained by variation in sample size alone. PNUE can also be considered as part of this trait spectrum, whereas leaf K and N : P ratios are only loosely related.

Radial transport of water and abscisic acid (ABA) in roots of Zea mays under conditions of nutrient deficiency.

Radial water (J(V)) and abscisic acid (ABA) flows (J(ABA)) through maize root seedlings have been investigated under different conditions of nutrient deficiency. Whereas J(V) was reduced under nitrogen deficiency, potassium deficiency stimulated J(V). A substantial increase of J(ABA) was observed in roots kept under potassium deficiency. The observed changes of J(V) might have resulted from changed barrier properties of the endodermis. Nitrogen and potassium deficiency also caused an accumulation of endogenous ABA in root tissues. Under all conditions studied, except under K(+)-deficiency, external ABA (100 nM) caused an increase of J(V). The data of this study were used to analyse the relations between internal and endogenous root ABA, J(V), and J(ABA). The internal ABA of root tissues was positively correlated with J(V) and was highly significant (P <0.001 for internal and P=0.03 for endogenous root ABA) within the range 2-300 pmol g(-1) FW. It was also highly positively correlated to the radial ABA flows. There was also a highly positive correlation between J(V) and J(ABA). The data of this study indicate, for the first time, the relations between internal ABA, water, and ABA flows. Independent of treatment with external ABA, an ABA transport by solvent drag across the endodermis is confirmed.

Excitatory effects of thyrotropin-releasing hormone in the thalamus.

The activity of the thalamus is state dependent. During slow-wave sleep, rhythmic burst firing is prominent, whereas during waking or rapid eye movement sleep, tonic, single-spike activity dominates. These state-dependent changes result from the actions of modulatory neurotransmitters. In the present study, we investigated the functional and cellular effects of the neuropeptide thyrotropin-releasing hormone (TRH) on the spontaneously active ferret geniculate slice. This peptide and its receptors are prominently expressed in the thalamic network, yet the role of thalamic TRH remains obscure. Bath application of TRH resulted in a transient cessation of both spindle waves and the epileptiform slow oscillation induced by application of bicuculline. With intracellular recordings, TRH application to the GABAergic neurons of the perigeniculate (PGN) or thalamocortical cells in the lateral geniculate nucleus resulted in depolarization and increased membrane resistance. In perigeniculate neurons, this effect reversed near the reversal potential for K+, suggesting that it is mediated by a decrease in K+ conductance. In thalamocortical cells, the TRH-induced depolarization was of sufficient amplitude to block the generation of rebound Ca2+ spikes, whereas the even larger direct depolarization of PGN neurons transformed these cells from the burst to tonic, single-spike mode of action potential generation. Furthermore, application of TRH prominently enhanced the afterdepolarization that follows rebound Ca2+ spikes, suggesting that this transmitter may also enhance Ca2+-activated nonspecific currents. These data suggest a novel role for TRH in the brain as an intrinsic regulator of thalamocortical network activity and provide a potential mechanism for the wake-promoting and anti-epileptic effects of this peptide.

A "synaptoplasmic cistern" mediates rapid inhibition of cochlear hair cells.

Cochlear hair cells are inhibited by cholinergic efferent neurons. The acetylcholine (ACh) receptor of the hair cell is a ligand-gated cation channel through which calcium enters to activate potassium channels and hyperpolarize the cell. It has been proposed that calcium-induced calcium release (CICR) from a near-membrane postsynaptic store supplements this process. Here, we demonstrate expression of type I ryanodine receptors in outer hair cells in the apical turn of the rat cochlea. Consistent with this finding, ryanodine and other store-active compounds alter the amplitude of transient currents produced by synaptic release of ACh, as well as the response of the hair cell to exogenous ACh. Like the sarcoplasmic reticulum of muscle, the "synaptoplasmic" cistern of the hair cell efficiently couples synaptic input to CICR.

A novel potassium deficiency-induced stimulon in Anabaena torulosa.

Potassium deficiency enhanced the synthesis of fifteen proteins in the nitrogen-fixing cyanobacterium Anabaena torulosa and of nine proteins in Escherichia coli. These were termed potassium deficiency-induced proteins or PDPs and constitute hitherto unknown potassium deficiency-induced stimulons. Potassium deficiency also enhanced the synthesis of certain osmotic stress-induced proteins. Addition of K+ repressed the synthesis of a majority of the osmotic stress-induced proteins and of PDPs in these bacteria. These proteins contrast with the dinitrogenase reductase of A. torulosa and the glycine betaine-binding protein of E. coli, both of which were osmo-induced to a higher level in potassium-supplemented conditions. The data demonstrate the occurrence of novel potassium deficiency-induced stimulons and a wider role of K+ in regulation of gene expression and stress responses in bacteria

Exclusive postsynaptic action of hypocretin-orexin on sublayer 6b cortical neurons.

The hypocretin-orexin (hcrt-orx) neurons are thought to maintain wakefulness because their loss results in narcolepsy. This role may be fulfilled by the excitatory action that the hcrt-orx peptide exerts on multiple brainstem and forebrain systems that, in turn, promote cortical activation. Here, we examined whether hcrt-orx may also exert a postsynaptic excitatory action at the level of the cortex, where hcrt-orx fibers project. However, we found that neurons in layers 2-5 in the primary somatosensory cortex (SSp) were unresponsive to hcrt-orx. We then found that although all neurons tested in sublayer 6a were also unresponsive to hcrt-oxr, all those tested in sublayer 6b were highly sensitive to the peptide. The sublayer selectivity of hcrt-oxr was not restricted to the somatosensory cortex, because it was also found to be present in the primary visual cortex, the motor cortex, and the cingulate cortex. In the SSp, in which the hcrt-oxr effect was investigated further, it was demonstrated to be postsynaptic, to result from an interaction with Hcrtr2-OX2 receptors and to depend on the closure of a potassium conductance. Similar to the selectivity of action in the thalamus, where hcrt-oxr excites the nonspecific thalamocortical projection neurons and not the specific sensory relay neurons, here in the cortex, it excites a specific subset of cortical neurons which, through corticocortical projections, may also be involved in promoting widespread cortical activation.