Vastus lateralis NA+‐K+‐ATpase activity,protein, and isoform distribution in chronic obstructive pulmonary disease

In this study we investigate the hypothesis that protein abundance, isoform distribution, and maximal catalytic activity of sodium–potassium–adenosine triphosphatase (Na⁺‐K⁺‐ATPase) would be altered in muscle of patients with moderate to severe chronic obstructive pulmonary disease (COPD). Tissue samples were obtained from the vastus lateralis of 10 patients with COPD (mean ± SE: age = 67 ± 2.9 years; FEV₁ = 39 ± 5.5%) and 10 healthy, matched controls (CON: age = 68 ± 2 years; FEV₁ = 114 ± 4.2%). The samples were assessed for maximal catalytic activity (V_max) of the enzyme using the K⁺‐stimulated 3‐O‐methylfluorescein‐phosphatase (3‐O‐MFPase) assay, enzyme abundance using the [³H]‐ouabain assay, and isoform content of both α (α₁, α₂, α₃) and β (β₁, β₂, β₃) using Western blot techniques. A 19.4% lower (P < 0.05) V_max was observed in COPD compared with CON (90.7 ± 6.7 vs. 73.1 ± 4.7 nmol · mg protein^?1 h^?1). No differences between groups were observed for pump concentration (259 ± 15 vs. 243 ± 17 pmol · g wet weight). For the isoforms, α₁ was decreased by 28% (P < 0.05), and α₂ was increased by 12% (P < 0.05) in COPD compared with CON. No differences between groups were observed for α₃ or for the β isoforms. We conclude that moderate COPD compromises V_max, which occurs in the absence of changes in pump abundance. The reduction in V_max could be due to a shift in isoform expression (α₁, α₂), alterations in intrinsic regulation, or to structural changes in the enzyme. The changes observed in the catalytic activity of the pump could have major effects on membrane excitability and fatigability, which are typically compromised in COPD. Muscle Nerve, 2009     

Contributions of the Na+/K+‐ATPase,NKCC1, and Kir4.1 to hippocampal K+ clearance and volume responses

Network activity in the brain is associated with a transient increase in extracellular K⁺ concentration. The excess K⁺ is removed from the extracellular space by mechanisms proposed to involve Kir4.1‐mediated spatial buffering, the Na⁺/K⁺/2Cl^? cotransporter 1 (NKCC1), and/or Na⁺/K⁺‐ATPase activity. Their individual contribution to [K⁺]_o management has been of extended controversy. This study aimed, by several complementary approaches, to delineate the transport characteristics of Kir4.1, NKCC1, and Na⁺/K⁺‐ATPase and to resolve their involvement in clearance of extracellular K⁺ transients. Primary cultures of rat astrocytes displayed robust NKCC1 activity with [K⁺]_o increases above basal levels. Increased [K⁺]_o produced NKCC1‐mediated swelling of cultured astrocytes and NKCC1 could thereby potentially act as a mechanism of K⁺ clearance while concomitantly mediate the associated shrinkage of the extracellular space. In rat hippocampal slices, inhibition of NKCC1 failed to affect the rate of K⁺ removal from the extracellular space while Kir4.1 enacted its spatial buffering only during a local [K⁺]_o increase. In contrast, inhibition of the different isoforms of Na⁺/K⁺‐ATPase reduced post‐stimulus clearance of K⁺ transients. The astrocyte‐characteristic α2β2 subunit composition of Na⁺/K⁺‐ATPase, when expressed in Xenopus oocytes, displayed a K⁺ affinity and voltage‐sensitivity that would render this subunit composition specifically geared for controlling [K⁺]_o during neuronal activity. In rat hippocampal slices, simultaneous measurements of the extracellular space volume revealed that neither Kir4.1, NKCC1, nor Na⁺/K⁺‐ATPase accounted for the stimulus‐induced shrinkage of the extracellular space. Thus, NKCC1 plays no role in activity‐induced extracellular K⁺ recovery in native hippocampal tissue while Kir4.1 and Na⁺/K⁺‐ATPase serve temporally distinct roles. GLIA 2014;62:608–622     

Plasmalemmal and mitochondrial Na+‐Ca2+ exchange in neuroglia

In the absence of the electrical signaling for which neurons are so highly specialized, GLIA rely on the slow propagation of ionic signals to mediate network events such as Ca²⁺ and Na⁺ waves. Glia differ from neurons in another important way, they are replete with a high density of ionic‐transport proteins that are essential for them to fulfil their basic functions as guardians of the intra and extra‐cellular milieux. Both the signaling and the homeostatic properties of glial cells are therefore particularly dependent upon the regulation of the two principle physiological metal cations, Ca²⁺ and Na⁺. For both ions, glia express high‐affinity/low capacity ATP‐fuelled pumps that can rapidly move small numbers of ions against an electro‐chemical gradient. For both Ca²⁺ and Na⁺ regulation, a single transporter family, the Na⁺‐Ca²⁺ exchanger (NCX), is used to maintain cellular ion homeostasis over the longer term and under conditions of prolonged or acute ionic dysregulation in astrocytes, oligodendroglia and microglia. Our understanding of glial NCX, both plasmalemmal and mitochondrial, is undergoing the kind of transformation that our understanding of glial cells, in general, has undergone in recent decades. These exchange proteins are becoming increasingly recognized for their essential roles in intracellular homeostasis while their signaling functions are starting to come to light. This review summarizes these key aspects and highlights the many areas where work has yet to begin in this rapidly evolving field. GLIA 2016;64:1646–1654     

Membrane-bound enzymes of erythrocytes in human muscular dystrophy: (Na+ + K+-ATPase, Ca2+-ATPase, K+- and Ca2+-p-nitrophenylphosphatase.

Four enzyme activities were studied in erythrocyte membranes from patients with Duchenne and congenital myotonic muscular dystrophy. (Na⁺ + K⁺)-stimulated, Mg²⁺-dependent adenosinetriphosphatase, measured in two different media, showed normal activity and ouabain inhibition, as did K⁺-stimulated p-nitrophenylphosphatase. The specific activity of Ca²⁺-stimulated p-nitrophenylphosphatase was twice normal in Duchenne membranes. Ca²⁺-stimulated, Mg²⁺-dependent adenosine-triphosphatase was augmented in membranes from both Duchenne and congenital myotonic muscular dystrophic patients. The cause of the increased activities may be the necessity for compensating an alteration in the calcium metabolism in the dystrophic erythrocytes.Several kinetic parameters of the two Ca²⁺-stimulated enzyme activities were studied in Duchenne and control membranes. Most were not changed, with the exception of the Na⁺-stimulation of Ca²⁺-ATPase. In Duchenne membranes two affinity sites were present with half maximal activating concentrations of 58 ± 4 and 4 ± 1 mM Na⁺. In control membranes only one affinity site was found with K_a = 26 ± 9 mM Na⁺.     

For K+ channels, Na+ is the new Ca2+

Although K+ channels activated by Ca2+ have long been known to shape neuronal excitability, evidence is accumulating that K+ channels sensitive to intracellular Na+, termed K(Na) channels, have an equally significant role. K(Na) channels contribute to adaptation of firing rate and to slow afterhyperpolarizations that follow repetitive firing. In certain neurons, they also appear to be activated by Na+ influx accompanying a single spike. Two genes encoding these channels, Slick and Slack, are expressed throughout the brain. The spatial localization of K(Na) channels along axons, dendrites and somata appears to be highly cell-type specific. Their molecular properties also suggest that these channels contribute to the response of neurons to hypoxia.     

Myokymia,neuromyotonia, dermatomyositis,and voltage-gated K+ channel antibodies

A young woman presented with facial myokymia in association with dermatomyositis. There was no evidence of peripheral neuropathy. Needle electromyography showed prominent myokymic discharges and brief neuromyotonic discharges in addition to many small-amplitude, short-duration motor unit potentials. Myokymia and dermatomyositis both responded to immunosuppressive treatment. The presence of antibodies to voltage-gated potassium channels and the association with dermatomyositis indicated an autoimmune cause for myokymia, which may have been due to reversible peripheral nerve hyperexcitability.     

Na+‐Activated K+ Channels in Rat Supraoptic Neurones

The magnocellular neurosecretory cells (MNCs) of the hypothalamus secrete the neurohormones vasopressin and oxytocin. The systemic release of these hormones depends on the rate and pattern of MNC firing and it is therefore important to identify the ion channels that contribute to the electrical behaviour of MNCs. In the present study, we report evidence for the presence of Na⁺‐activated K⁺ (K_Na) channels in rat MNCs. K_Na channels mediate outwardly rectifying K⁺ currents activated by the increases in intracellular Na⁺ that occur during electrical activity. Although the molecular identity of native K_Na channels is unclear, their biophysical properties are consistent with those of expressed Slick (slo 2.1) and Slack (slo 2.2) proteins. Using immunocytochemistry and Western blot experiments, we found that both Slick and Slack proteins are expressed in rat MNCs. Using whole cell voltage clamp techniques on acutely isolated rat MNCs, we found that inhibiting Na⁺ influx by the addition of the Na⁺ channel blocker tetrodotoxin or the replacement of Na⁺ in the external solution with Li⁺ caused a significant decrease in sustained outward currents. Furthermore, the evoked outward current density was significantly higher in rat MNCs using patch pipettes containing 60 mm Na⁺ than it was when patch pipettes containing 0 mm Na⁺ were used. Our data show that functional K_Na channels are expressed in rat MNCs. These channels could contribute to the activity‐dependent afterhyperpolarisations that have been identified in the MNCs and thereby play a role in the regulation of their electrical behaviour.     

The effects of trimethyltin on the Ca+2, Mg+2 and Ca+2 + Mg+2-dependent ATPases of human neuroblastoma GM 3320

Data presented here indicate neuroblastoma GM 3320 tissue homogenates exhibit ouabain insensitive Ca+2-dependent, Mg+2-independent, Mg+2-dependent, Ca+2-independent and Ca+2 + Mg+2-dependent ATPase activities. Inclusion of trimethyltin in homogenate preparations of these cells appears to discriminate between these various ATPase activities. At low concentrations (25 microM), trimethyltin preferentially stimulated the Ca+2-dependent, Mg+2-independent ATPase activity while inhibiting the Ca+2 + Mg+2-ATPase activity approximately 70%. At 75 microM trimethyltin, the Ca+2 + Mg+2-dependent ATPase activity is inhibited greater than 95% while the Ca+2-dependent, Mg+2-independent activity is essentially unchanged from control activity and the Mg+2-dependent, Ca+2-independent activity is inhibited approximately 50%. At concentrations greater than 75 microM, trimethyltin significantly inhibits the Ca+2-dependent, Mg+2-independent ATPase activity. Thus, at trimethyltin concentrations of 50-75 microM, preferential inhibition of the Mg+2-dependent, Ca+2-independent and Ca+2 + Mg+2-dependent ATPase activities of neuroblastoma GM 3320 is achieved.     

Histamine facilitates GABAergic transmission in the rat entorhinal cortex: Roles of H1 and H2 receptors,Na+‐permeable cation channels,and inward rectifier K+ channels

In the brain, histamine (HA) serves as a neuromodulator and a neurotransmitter released from the tuberomammillary nucleus (TMN). HA is involved in wakefulness, thermoregulation, energy homeostasis, nociception, and learning and memory. The medial entorhinal cortex (MEC) receives inputs from the TMN and expresses HA receptors (H₁, H₂, and H₃). We investigated the effects of HA on GABAergic transmission in the MEC and found that HA significantly increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) with an EC₅₀ of 1.3 µM, but failed to significantly alter sIPSC amplitude. HA‐induced increases in sIPSC frequency were sensitive to tetrodotoxin (TTX), required extracellular Ca²⁺, and persisted when GDP‐β‐S, a G‐protein inactivator, was applied postsynaptically via the recording pipettes, indicating that HA increased GABA release by facilitating the excitability of GABAergic interneurons in the MEC. Recordings from local MEC interneurons revealed that HA significantly increased their excitability as determined by membrane depolarization, generation of an inward current at ?65 mV, and augmentation of action potential firing frequency. Both H₁ and H₂ receptors were involved in HA‐induced increases in sIPSCs and interneuron excitability. Immunohistochemical staining showed that both H₁ and H₂ receptors are expressed on GABAergic interneurons in the MEC. HA‐induced depolarization of interneurons involved a mixed ionic mechanism including activation of a Na⁺‐permeable cation channel and inhibition of a cesium‐sensitive inward rectifier K⁺ channel, although HA also inhibited the delayed rectifier K⁺ channels. Our results may provide a cellular mechanism, at least partially, to explain the roles of HA in the brain. © 2017 Wiley Periodicals, Inc.     

急性脑梗死患者CD19+-CD25+、CD19+-CD25-B淋巴细胞、免疫球蛋白和补体C3的检测及临床意义

目的 检测急性脑梗死患者CD19+-cD25+、CD19+-CD25-B 淋巴细胞、免疫球蛋白和补体C3的含量并探讨其临床意义.方法 根据病史及头颅CT或MRI明确疾病诊断.抽取69例急性脑梗死、115例脑出血患者、41例正常对照者静脉血各4 mL,采用流式细胞仪检测CD19+-CD25+、CD19+-CD25-B淋巴细胞百分比,采用散射比浊法检测免疫球蛋白和补体C3含量,并结合不同的病程、不同影像学评分和不同的神经功能评分进行分析比较.结果 脑梗死和脑出血急性期CD19+-CD25+、CD19+-CD25-B淋巴细胞、免疫球蛋白和补体C3的差异无统计学意义(P均＞0.05).脑梗死急性期CD19+-CD25+B淋巴细胞百分比、IgG、补体C3含量均较恢复期及对照组显著增高(P均＜0.05).脑梗死恢复期各项体液免疫指标与对照组之间差异无统计学意义(P均＞0.05).不同影像学评分患者之间CD19+-CD25+、CD19+-CD25-B淋巴细胞百分比差异有统计学意义(P均＜0.05).脑梗死急性期神经功能评分与各体液免疫指标间无相关(P均＞0.05).结论 脑梗死与脑出血存在着同样的体液免疫功能改变.这种改变可能与应激、病变部位及病变范围有关.脑梗死病灶越大,体液免疫改变越明显;随着应激的消逝,体液免疫功能逐渐恢复.     

Double autosomal trisomy: case report (48, XX, +18, +21) and review of the literature.

A twelve-months-old female is reported with double trisomy of the autosomes 18 and 21 (48,XX,+18,+21), exhibiting the clinical features of mongolism. The findings of this patient and the data of fourteen previously reported cases with double autosomal trisomy, twelve of them mosaics, may be summarised as follows: The mean birth weight was lower than in the single trisomies D, E, and G. The distribution of the maternal ages at birth of the patients was striking: six mothers were younger than 21 years, seven mothers were older than 34 years. In those patients with prevalence of one of the two extra chromosomes in their karyotypes, the corresponding trisomy syndrome also predominated clinically. In those cases with an equal proportion of both additional chromosomes there were as many patients with clinical predominance of the one as of the other trisomy syndrome. Survival beyond the second half of the first year of life was seen only in those patients who showed the clinical picture of mongolism.     

Learning using privileged information: SVM+ and weighted SVM

Prior knowledge can be used to improve predictive performance of learning algorithms or reduce the amount of data required for training. The same goal is pursued within the learning using privileged information paradigm which was recently introduced by Vapnik et al. and is aimed at utilizing additional information available only at training time—a framework implemented by SVM+. We relate the privileged information to importance weighting and show that the prior knowledge expressible with privileged features can also be encoded by weights associated with every training example. We show that a weighted SVM can always replicate an SVM+ solution, while the converse is not true and we construct a counterexample highlighting the limitations of SVM+. Finally, we touch on the problem of choosing weights for weighted SVMs when privileged features are not available.     

Loss of β1 accessory Na+ channel subunits causes failure of carbamazepine,but not of lacosamide,in blocking high‐frequency firing via differential effects on persistent Na+ currents

Purpose: In chronic epilepsy, a substantial proportion of up to 30% of patients remain refractory to antiepileptic drugs (AEDs). An understanding of the mechanisms of pharmacoresistance requires precise knowledge of how AEDs interact with their targets. Many commonly used AEDs act on the transient and/or the persistent components of the voltage‐gated Na⁺ current (I_NaT and I_NaP, respectively). Lacosamide (LCM) is a novel AED with a unique mode of action in that it selectively enhances slow inactivation of fast transient Na⁺ channels. Given that functional loss of accessory Na⁺ channel subunits is a feature of a number of neurologic disorders, including epilepsy, we examined the effects of LCM versus carbamazepine (CBZ) on the persistent Na⁺ current (I_NaP), in the presence and absence of accessory subunits within the channel complex. Methods: Using patch‐clamp recordings in intact hippocampal CA1 neurons of Scn1b null mice, I_NaP was recorded using slow voltage ramps. Application of 100 μm CBZ or 300 μm LCM reduced the maximal I_NaP conductance in both wild‐type and control mice. Key Findings: As shown previously by our group in Scn1b null mice, CBZ induced a paradoxical increase of I_NaP conductance in the subthreshold voltage range, resulting in an ineffective block of repetitive firing in Scn1b null neurons. In contrast, LCM did not exhibit such a paradoxical increase, and accordingly maintained efficacy in blocking repetitive firing in Scn1b null mice. Significance: These results suggest that the novel anticonvulsant LCM maintains activity in the presence of impaired Na⁺ channel β₁ subunit expression and thus may offer an improved efficacy profile compared with CBZ in diseases associated with an impaired expression of β sub‐units as observed in epilepsy.