Altered gating and conductance of Na+ channels in hyperkalemic periodic paralysis

Electrophysiological studies on muscle fibres from patients with hyperkalemic periodic paralysis with myotonia have shown that the episodes of weakness are caused by a sustained depolarization of the sarcolemma to potentials between -40 and -60 mV. In muscle fibre segments from three such patients this sustained depolarization was caused by noninactivating Na⁺ channels with reduced single-channel conductance blocked by TTX and procainamide. As the chloride conductance was normal, myotonia may be best explained with the abnormal reopenings of the Na⁺ channels. The recently described genetic linkage between hyperkalemic periodic paralysis with myotonia and the gene coding for the TTX-sensitive Na⁺ channel suggests an altered primary structure of this channel causing its abnormal function.     

含有十二烷基磺酸钠的生物制剂的内毒素检测不能采用鲎试验

重组人ＩＬ－２在大肠杆菌表达时形成包含体，需经过变性和复性才具有生物学活性，在分离提取过程中常加一定量的ＳＤＳ，最低浓度每毫升不小于０．２５ｍｇ；低于此浓度会发生沉淀。鲎试验（ＬＡＬ试验）是一种灵敏度很高的检查生物制剂中致热源的常规方法。我们发现，当样本中ＳＤＳ的浓度＞０．０２５ｍｇ／ｍｌ时，可抑制尝试制的酶反应，使阳性结果转变为阴性。据此，我们建议，凡生物制剂中含有ＳＤＳ或其他酶抑制剂的产品，以尝试验来检查内毒素含量是没有意义的。     

Human myeloma light chains with increased molecular weight: high frequency among lambda chains

The discovery of a human myeloma protein comprising a kappa L-chain with an increased mol. wt of 30,000) (Bouvet et. al., 1980) prompted investigations on the incidence of such heavier L-chains among other human myeloma proteins. In 105 samples examined, 34 were found to have L-chains heavier than normal (23,000-24,000), ranging from 25,000 up to 31,000, and five of lighter mol. wt (21,000-22,000). These mol. wt abnormalities were detected by electrophoresis in sodium dodecyl sulfate 10% polyacrylamide gels (SDS-PAGE) after reduction with 2-mercaptoethanol. The mol. wt of three of the heavier kappa or lambda chains was also estimated by filtration through a Sephadex G100 column and by sedimentation equilibrium. All three methods indicated a mol. wt increase of about 15-25% as compared with the usual mol. wt. The distribution of the high mol. wt chains among all L-chains examined was found to be 11 out of 62 kappa chains (17.7%) and 23 out of 43 lambda chains (53%) (P less than 0.001). A preferential association of such L-chains with H-chains producing multiple bands in SDS-PAGE (P less than 0.01) and an association between multiple L-chain and multiple H-chain band (P less than 0.05) were also observed. In contrast, no abnormal L-chain was found in immunoglobulins from normal subjects. Spontaneous degradation of the normal H-chains sometimes yielded fragments of 30,000 mol. wt. These fragments were easily distinguishable from abnormal L-chains. The nature of extra mol. wt in heavy L-chains was investigated for the presence of carbohydrate moiety. Four large and three normal size L-chains were examined for amino-sugar and sialic acid content. A small amount (one residue per molecule) of amino-sugar was detected only in two normal and two heavy L-chains, whereas sialic acid was only found in the heaviest (27,000-30,000) L-chains (Lh) and in small percentage (one or two residues per molecule). Total sugar estimation in one Lh chain indicated a proportion not exceeding three or four residues per L-chain (mol. wt 1,000) and this is insufficient to explain the 15-25% (3,600-6,000) mol. wt increase. It is therefore possible that, at least in some heavy myeloma L-chains, an additional peptide is expressed. Whatever the nature of the increase it would be of interest to elucidate whether this is a marker of malignant process or of an intermediate step of normal Ig synthesis.     

The influence of sodium on growth in infancy

Sodium (Na) is an important growth factor, stimulating cell proliferation and protein synthesis and increasing cell mass. Sodium chloride (NaCl) deprivation inhibits growth, as reflected by reduced body and brain weight, length, muscle and brain protein and RNA content and brain lipid content compared with controls. This is not due to deficiency of other nutrients since control and experimental diets were identical except for NaCl content. Subsequent NaCl supplementation restores growth velocity to control values but does not induce catch-up growth. In humans, salt loss causes growth failure and subsequent salt repletion improves growth. Preterm infants <32 weeks' gestation at birth are renal salt losers in the first 2 weeks of post-natal life and are vulnerable to hyponatraemia. This can be prevented by increasing Na intake, which also produces accelerated weight gain that persists beyond the period of supplementation. Early nutrition in preterm infants can affect subsequent growth and also cognitive function: this is probably multifactorial, but NaCl intake differed substantially between study groups and is likely to be an important factor. The mechanism whereby Na promotes cell growth is not understood, but stimulation of the membrane Na⁺,H⁺-antiporter with alkalinization of the cell interior is a likely possibility.     

31P and23Na nuclear magnetic resonance study on forebrain ischemia in rats with shift reagent Dy(TTHA)

³¹P and ²³Na nuclear magnetic resonance (NMR) spectroscopy was employed to study the dynamic changes in intracellular high-energy phosphates and sodium during 15min of forebrain ischemia and recirculation in in vivo rat brain. In the presence of the shift reagent Dysprosium triethylenetetramine-N,N,N,N,N,N-hexaacetic and [Dy(TTHA)], the sodium peak separated into two peaks, unshifted and shifted. During 15min of ischemia, the unshifted sodium peak decreased and the shifted sodium peak increased. With recirculation, the unshifted and the shifted sodium peaks returned to the preischemia level within 10min, but the shifted one increased during 30–60min. Intracellular high-energy phosphates and intracellular pH (pHi) decreased during 15min of ischemia and returned to the preischemia levels within 20min of recirculation. We conclude that the decrease in unshifted sodium peak during ischemia is due to the decrease in subarachnoid sodium and the cellular influx of interstitial sodium would be minimum. The increase in shifted sodium peak during ischemia is considered to be due to the dilatation of cerebral blood vessels and the increase in interstitial sodium which was transported from subarachnoid space.(Kurata M: ³¹P and ²³Na nuclear magnetic resonance study on forebrain ischemia in rats with shift reagent Dy(TTHA). J Anesth 7: 325–333, 1993)     

Increased sodium requirement following early postnatal surgical correction of congenital uropathies in infants

Serum electrolyte equilibrium and plasma aldosterone concentrations were monitored in 19 infants who had severe obstructive uropathy or grade 5 vesico-ureteral reflux and were undergoing surgical correction in the first 2 months of life. Before surgery high plasma aldosterone levels were observed in 8 patients, but serum sodium and potassium concentrations were normal. Plasma concentrations of aldosterone were elevated in all patients during the week following surgery and 7 patients developed severe hyponatraemia, hyperkalaemia and weight loss despite very high plasma aldosterone concentrations. As a consequence 5 infants were infused with sodium chloride (4 mEq/kg per day) before and for 36h after surgery; this prevented metabolic imbalance. We conclude that infants undergoing surgical correction of uropathies may require a high sodium intake to maintain electrolyte balance and adequate growth.     

Conotoxin GIIIA: selective inhibition of 22Na influx via voltage-dependent Na channels in adrenal medullary cells

Summary Conotoxin GIIIA and GIIIB from the marine snail Conus geographus have been reported to inhibit voltage-dependent Na channels in skeletal muscle and postganglionic sympathetic neuron, but have no effect on Na channels in brain, giant axon and heart. In eel electroplax, conotoxins were also shown to share the common binding sites with saxitoxin (see review Gray et al. 1988).In bovine adrenal medullary cells, conotoxin GIIIA inhibited veratridine-induced influx of ²²Na, ⁴⁵Ca and secretion of catecholamines with an IC₅₀ of 6 mol/l, while saxitoxin suppressed veratridine-induced responses with an IC₅₀ of 6.3 nmol/l. [³H]Saxitoxin binding to the cells was inhibited by unlabeled saxitoxin with an IC₅₀ of 5.1 nmol/l, but was slightly reduced by 10 mol/l conotoxin GIIIA. Conotoxin GIIIA, at 10 mol/l, did not alter carbachol-induced influx of ²²Na, ⁴⁵Ca and secretion of catecholamines as well as high K-induced ⁴⁵Ca influx and catecholamine secretion.These results indicate that conotoxin GIIIA, at concentrations 950 fold higher than saxitoxin, inhibits Na influx via voltage-dependent Na channels, but has no effect on the nicotinic receptor-ion channel complex or the voltage-dependent Ca channels. Conotoxin GIIIA seems to bind at the sites which are distinct from saxitoxin, but are functionally linked to the voltage-dependent Na channels. Conotoxins may be useful for the classification of Na channels in excitable cell membranes. Send offprint requests to A. Wada at the above address     

血管瘤不同治疗方法的疗效评价

目的　评价四种不同方法治疗血管瘤远期疗效。方法　取 1992～ 1998年共七年间我院门诊及住院分别患有毛细血管瘤、海绵状血管瘤、蔓状血管瘤病人 2 33例 ,分别采取血管瘤营养血管结扎 平阳霉素注射、5 %鱼肝油酸钠注射、平阳霉素 强的松龙注射、平阳霉素 5 %鱼肝油酸钠注射 4种治疗方法 ,并对上述 4种方法血管瘤注射后进行随访及疗效评定。结果　血管瘤营养血管结扎 平阳霉素注射组总有效率及显效率均较其余 3组高 ,而单纯应用鱼肝油酸钠血管瘤注射组较其余 3组无论是总有效率或显效率均低。结论　联合用药较单一用药治疗血管瘤效果好 ,而血管瘤远期疗效与药物在瘤体内存留时间长短有关 ,停留时间愈长 ,其有效率愈高 ,而缝扎血管瘤营养血管后无疑为药物在血管瘤内长时间停留提供条件。     

手性修饰的硼氢化钠对前手性酮的不对称还原

研究了以Ｎ－苄基－（３Ｓ,４Ｓ）－３,４－二羟基四氢吡咯修饰的硼氢化钠对前手性酮的不对称还原反应,合成了五个光学活性醇,同时研究了添加路易斯酸对还原反应光学产率的影响。     

Release of the antioxidants ascorbate and urate from a nitrergically-innervated smooth muscle

1. The main object of the present study was to determine whether ascorbate, an antioxidant which has been shown to protect nitric oxide (NO) from attack by scavenger molecules, might be released from nitrergically-innervated smooth muscle; ascorbate release from the rat anococcygeus was measured by use of h.p.l.c. with electrochemical detection.
2. Incubation of rat anococcygeus muscles in normal physiological salt solution (PSS; 30 min) resulted in release of ascorbate into the bathing medium (7.7±0.9 nmol g⁻¹ tissue). This release was increased by 96% when muscles were incubated in high K⁺ (70 mM) PSS. The resting release of ascorbate was unaffected by tetrodotoxin (TTX; 1 μM), ω-conotoxin GVIA (10 nM) or omission of calcium ions from the PSS (with addition of 0.2 mM EGTA), but all three procedures attenuated the increased release observed under depolarizing conditions. Resting release of ascorbate was unaffected by glutamate (100 μM), aspartate (100 μM), γ-aminobutyric acid (100 μM) or carbachol (50 μM).
3. A second h.p.l.c. peak, which always preceded the ascorbate peak, was identified as urate. Urate release from the anococcygeus, following 30 min incubation in normal PSS, was 64.6±12.7 nmol g⁻¹ tissue but, unlike ascorbate, urate release was unchanged in high K⁺ PSS. In functional experiments, urate (100–400 μM) partially protected NO (15 μM)-induced relaxations of the rat anococcygeus from inhibition by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO; 50 μM), but not from inhibition by hydroquinone or duroquinone (both 100 μM).
4. Muscles chemically sympathectomized with 6-hydroxydopamine (6-OHDA, 500 μM; 2 h) still exhibited release of ascorbate (2.5±0.4 nmol g⁻¹ tissue) and urate (22.2±2.9 nmol g⁻¹ tissue); in both cases the release was similar to that observed in time-matched control tissues not exposed to 6-OHDA. High K⁺ PSS produced a TTX-sensitive increase in release of ascorbate, but not urate, from 6-OHDA-treated muscles.
5. The results demonstrate that significant amounts of ascorbate and urate are released from the rat anococcygeus muscle. Ascorbate, but not urate, release appears to be enhanced by activation of nerves which are resistant to 6-OHDA pretreatment. Since both antioxidants can protect NO from attack by scavenger molecules, their release in nitrergically-innervated tissues may be important for the provision of the correct redox environment to allow NO to fulfill its proposed neurotransmitter role.