江西省猪和啮齿动物宿主小肠结肠炎耶尔森菌病原学研究

目的 了解江西省不同宿主动物中小肠结肠炎耶尔森菌的分布以及病原特征,为该菌防控提供科学依据。方法 采集江西省不同年份的屠宰猪与鼠类标本,对foxA筛检阳性的标本进行分离培养,对分离到的小肠结肠炎耶尔森菌进行血清型、生物型、毒力基因与脉冲场凝胶电泳(PFGE)分析。结果　从1 018份标本中分离到79株小肠结肠炎耶尔森菌,阳性率为7.76%(79/1018)。猪的阳性率为20.86%(63/302),均为O∶3血清型;鼠的阳性率为2.24%(16/716),血清型为O∶5、O∶8和未分型,生物型均为1A型。79株小肠结肠炎耶尔森菌中,致病性菌株均来自猪,占总分离菌株数的79.75%(63/79),其中59株(ystA+、ystB-、yadA+、virF+、ail+、rfbc+),4株(ystA+、ystB-、yadA-、virF-、ail+、rfbc+);非致病性菌株均来自鼠,占总分离菌株数的20.25%(16/79),其中12株(ystA-、ystB+、yadA-、virF-、ail-、rfbc-)、4株(ystA-、ystB-、yadA-、virF-、ail-、rfbc-)。致病性菌株可分为6种带型,以K6GN11C30021为主要型别,占比80.95%(51/63)。结论　在江西省的不同宿主动物中,致病性小肠结肠炎耶尔森菌的主要携带者为生猪。应加强江西地区以生猪为宿主的小肠结肠炎耶尔森菌的监测。     

云南省玉溪市家鼠疫源地小肠结肠炎耶尔森菌监测分析

目的 了解云南省玉溪市家鼠鼠疫疫源地小肠结肠炎耶尔森菌的分布、病原学特征及对抗生素的敏感性。方法 从元江、新平两县采集褐家鼠、黄胸鼠、小家鼠、树鼩的盲肠和舌根以及猪咽拭标本、猪粪便和腹泻病人粪便,分离小肠结肠炎耶尔森菌及毒力基因检测。结果 从3 431份标本中分离到小肠结肠炎耶尔森菌71株,总检出率为2.07%。分离株包含15株致病株和56株非致病株,有3种生物型(1A、2、3型)、3种以上血清型(O∶3、O∶5、O∶8及未分型)及3种毒力基因型别。致病株均为3/O∶3生物血清型,毒力基因以ail^＋、ystA^＋、ystB^－、yadA^＋、virF^＋为主;非致病株,血清型属于O∶5、O∶8及未分型,毒力基因以ail^－、ystA^－、ystB^＋、yadA^－、virF^－为主;分离株对阿莫西林、阿莫西林/克拉微酸、氨苄西林高度耐药,对其他大部分常用抗生素敏感性较高。结论 小肠结肠炎耶尔森菌病在玉溪家鼠鼠疫疫原地宿主中传播流行;分离菌株的血清型/生物型,毒力基因型别多样性;头孢三、四代,喹诺酮类或氨基糖甙类抗生素适宜治疗小肠结肠炎耶尔森菌引起的感染。     

我国牛羊主产区小肠结肠炎耶尔森菌的病原特征研究

目的 对2018-2020年我国牛羊主产区牛羊源小肠结肠炎耶尔森菌进行病原特征研究,为该菌的防控提供科学依据。方法 对来自于6个地区的2 291份样本进行分离培养、PCR鉴定、玻片凝集以及药敏试验,以掌握其感染情况、毒力基因型和血清型的分布以及耐药情况。结果 在2 291份样本中,共分离出该菌109株,总检出率为4.76%,其中辽宁地区检出率最高(20.42%),并且各地区检出率差异有统计学意义(χ²=288.153,P<0.01),而各种类样本检出率差异无统计学意义(χ²=1.734,P>0.05)。在本次分离菌株中,ystB基因为优势毒力基因,O∶5,27为优势血清型,菌株对氨苄西林、红霉素、磺胺异恶唑和头孢噻吩耐药率为100%,对多粘菌素B和氟苯尼考敏感率为100%。结论 牛、羊源小肠结肠炎耶尔森菌在全国牛、羊主产区分布不广泛,但其多重耐药率较高,建议加强对该菌耐药性的监测与管理。     

The L-type Ca2+ channel is involved in microvesicle-mediated glutamate exocytosis from rat pinealocytes

Abstract: Pinealocytes, parenchymal cells of the pineal gland, secrete glutamate through microvesicle-mediated exocytosis upon depolarization by KC1 in the presence of Ca²⁺, which is involved in a novel paracrine-like intercellular signal transduction mechanism in neuroendocrine organs. In the present study, we investigated whether or not the L-type Ca²⁺ channel is involved in the microvesicle-mediated glutamate secretion from cultured rat pinealocytes. Nifedipine, a specific antagonist of the L-type Ca²⁺ channel, inhibited the Ca²⁺-dependent glutamate exocytosis by 48% at 20 uM. Other L-type Ca²⁺ channel antagonists, such as nitrendipine, showed similar effects. 1,4-Dihydro-2,6-dimethyl-5-nitro-4[2-(trifluoromethyl)-phenyl]-3-pyridinecarboxylic acid methyl ester (BAY K8644), an agonist of the L-type Ca²⁺ channel, at 1 uM, on the other hand, stimulated the glutamate exocytosis about 1.6-fold. Consistently, these Ca²⁺ channel antagonists inhibited about 50% of the Ca²⁺ uptake, whereas BAY K8644 increased the uptake 5.3-fold. An antibody against the carboxyl-terminal region of the rabbit L-type Ca²⁺ channel recognized polypeptides of pinealocytes with apparent molecular masses of 250 and 270 kDa, respectively, and immunostained the plasma membrane region of the pinealocytes. These results strongly suggested that the entry of Ca²⁺ through L-type Ca²⁺ channel(s), at least in part, triggers microvesicle-mediated glutamate exocytosis in pinealocytes.     

A requirement for calcium in the caspase-independent killing of Burkitt lymphoma cell lines by Rituximab

The therapeutic monoclonal antibody rituximab has previously been shown to kill B cells in a caspase-independent manner. The signalling pathways underpinning this novel death pathway are unknown. The present study showed that rituximab treatment of Burkitt lymphoma cell lines induced a slow rise in intracellular calcium ([Ca²⁺]_i). This rise was only witnessed in cell lines that were killed by antibody, suggesting a critical role for Ca²⁺ in mediating rituximab-driven caspase-independent cell death. Inhibition of the two main intracellular store-located Ca²⁺ channels, i.e. the ryanodine and inositol-1,4,5-triphosphate receptor channels by dantrolene and xestospongen-c respectively did not prevent the rise in Ca²⁺ seen with rituximab or protect cells from subsequent death. In sharp contrast, inhibition of Ca²⁺ entry via plasma membrane channels with (2-aminoethoxy) diphenylborate or SKF-96365 or complete chelation of extracellular Ca²⁺ with ethyleneglycol bis (aminoethylether) tetra-acetate inhibited the rise in [Ca²⁺]_i and increased cell viability. Together, these data suggest that ligation of the CD20 receptor with rituximab allows a slow sustained influx of Ca²⁺ from the external environment that under certain conditions can lead to cell death.     

Shortcomings of current models of glucose-induced insulin secretion

Glucose-induced insulin secretion by pancreatic β-cells is generally schematized by a 'consensus model' that involves the following sequence of events: acceleration of glucose metabolism, closure of ATP-sensitive potassium channels (K_ATP channels) in the plasma membrane, depolarization, influx of Ca²⁺ through voltage-dependent calcium channels and a rise in cytosolic-free Ca²⁺ concentration that induces exocytosis of insulin-containing granules. This model adequately depicts the essential triggering pathway but is incomplete. In this article, we first make a case for a model of dual regulation in which a metabolic amplifying pathway is also activated by glucose and augments the secretory response to the triggering Ca²⁺ signal under physiological conditions. We next discuss experimental evidence, largely but not exclusively obtained from β-cells lacking K_ATP channels, which indicates that these channels are not the only possible transducers of glucose effects on the triggering Ca²⁺signal. We finally address the identity of the widely neglected background inward current (Cl⁻ efflux vs. Na⁺ or Ca²⁺ influx through voltage-independent channels) that is necessary to cause β-cell depolarization when glucose closes K_ATP channels. More attention should be paid to the possibility that some components of this background current are influenced by glucose metabolism and have their place in a model of glucose-induced insulin secretion.     

Evidence for the involvement of complement proteins in platelet aggregation by Streptococcus sanguis NCTC 7863

We investigated the mechanisms of platelet aggregation by the type strain of Streptococcus sanguis (NCTC 7863). This species is one of the major aetiological agents of infective endocarditis. S. sanguis NCTC 7863 caused aggregation of normal human platelets in vitro following a lag period that varied between donors (7–19 min). Platelet aggregation was dependent on one or more plasma consistuents and all the necessary factors gradually became bound to the bacterial surface during the lag period. The length of the lag period was determined by the plasma of the donor and not by a feature of their platelets. Platelet aggregation by S. sanguis NCTC 7863 could be inhibited by heating plasma at 56°C, by treating plasma with cobra venom factor, or by incubating with soluble Complement Receptor 1, all of which inhibit or deplete complement. Complement activation required Mg²⁺, but not Ca²⁺ ions and the the cleavage fragment, Ba, of factor B was produced, indicating that the alternative pathway was operative. Zymosan- and S. sanguis -induced aggregation showed similarities, including the same variability in lag times among donors, and absorption of plasma with zymosan prevented the plasma from supporting platelet aggregation by S. sanguis . C3, C9 and vitronectin were found to bind to S. sanguis NCTC 7863, but the latter two were present at very low levels on a non-aggregating strain of S. sanguis , SK96. The rate of assembly of the C5b–9 complex on the NCTC 7863 bacterial surface correlated with the lag time. These data suggest a role for the complement pathway in platelet aggregation by the type strain of S. sanguis .     

In vivo and in vitro effects of the pineal gland and melatonin on [Ca2++ Mg2+]-dependent ATPase in cardiac sarcolemma

Abstract: The possible diurnal variation in cardiac [Ca²⁺+ Mg²⁺]-dependent ATPase (Ca²⁺ pump) activity and the influence of pinealectomy and melatonin on this enzyme in rat heart have been studied. Lowest levels of cardiac sarcolemma] membrane [Ca²⁺+ Mg²⁺]-dependent ATPase activity were measured in late afternoon in rats kept under a 14:10 light:dark cycle. Late in the dark phase the enzyme activity began to increase with the rise continuing until 0900, 3 hr after light onset. These time-dependent changes in [Ca²⁺+ Mg²⁺]-dependent ATPase activity did not occur in either pinealectomized or light-exposed rats suggesting that melatonin, secreted from the pineal gland during the night, induces the change in [Ca²⁺+ Mg²⁺]-dependent ATPase activity. In vitro studies in which cardiac tissue was incubated in the presence of melatonin over a wide range of doses showed that this indole stimulated the Ca²⁺ pump. The half-maximal effect of melatonin was observed at a melatonin concentration of 28 ng/ml. These findings suggest that the daily change in [Ca²⁺+ Mg²⁺]-dependent ATPase activity in the sarcolemma of heart tissue is a result of the circadian rhythm in pineal melatonin production and secretion. These findings may be applicable to normal cardiac physiology.     

Age-related alterations in Ca2+ signals and mitochondrial membrane potential in exocrine cells are prevented by melatonin

Abstract:  Information regarding age-induced Ca²⁺ signal alterations in nonexcitable cells is limited. In addition, little evidence exists on the ability of melatonin to palliate the effects of aging on Ca²⁺ signals and mitochondrial potential, a parameter involved in both Ca²⁺ signaling and aging. We studied the ability of melatonin to prevent the effects of aging on intracellular Ca²⁺ homeostasis and mitochondrial potential in exocrine cells. Pancreatic acinar cells were obtained from adult (3 months old) and aged (22–24 months old) mice by collagenase dispersion. Ca²⁺ signals, in situ mitochondrial potential and in vitro amylase secretion were determined. Secretion in response to increasing levels of the secretagogues, acetylcholine and cholecystokinin (CCK), were impaired in aged pancreatic acini. This decrease was accompanied by an inhibition in the amplitude of the peak response to maximal concentrations of the agonists, and by a decrease in the pattern of Ca²⁺ oscillations induced by postprandial levels of CCK. Both the size of the calcium pools, assessed by low levels of ionomycin, and capacitative calcium entry, induced by depletion of the stores with thapsigargin, were diminished in aged cells. These changes in Ca²⁺ homeostasis were associated with depolarization of intracellular mitochondria. Oral administration of melatonin for 3 months to aged mice restored the secretory response, the amplitude and frequency of Ca²⁺ responses, the size of intracellular calcium pools, the capacitative calcium entry, and the mitochondrial potential. In conclusion, melatonin restores secretory function, Ca²⁺ signals and mitochondrial potential of aged exocrine cells.     

小肠结肠炎耶尔森菌尿素酶基因多态性及尿素酶活性分析

目的 了解小肠结肠炎耶尔森菌尿素酶基因的多态性以及不同致病力菌株尿素酶活性之间的关联性。方法 选取43株不同致病能力的小肠结肠炎耶尔森菌用PCR扩增尿素酶基因并进行序列测定。连同4株NCBI上尿素酶基因参考序列一起进行比对和构建聚类树。同时选取8株不同致病力的小肠结肠炎耶尔森菌进行尿素酶活性实验。 结果 在低致病性小肠结肠炎耶尔森菌中,全部的18株O∶3血清型菌株的尿素酶基因7个开放读码框(ureABCEFGD)的基因序列完全一致;在全部17株O∶9血清型菌株中,尿素酶基因7个开放读码框(ureABCEFGD)的基因序列完全一致的有16株,仅1株2/O∶9(NX1997-IE419)与其他血清型菌株的尿素酶基因序列不同;高致病性的O∶8血清型小肠结肠炎耶尔森菌以及非致病菌的尿素酶基因序列与低致病性O∶3、O∶9血清型菌株的尿素酶基因序列不同且各菌株之间基因序列差异也较大。尿素酶活性实验显示不同致病能力的小肠结肠炎耶尔森菌尿素酶活性存在多样性,无明显的规律发现。结论 低致病性O∶3、O∶9血清型的小肠结肠炎耶尔森菌的尿素酶基因分别表现出高度的保守性,NX1997-IE419的尿素酶基因可能是由O∶3血清型小肠结肠炎耶尔森菌的尿素酶基因演变而来。高致病性的1B/O∶8小肠结肠炎耶尔森菌及非致病性小肠结肠炎的尿素酶基因相对不保守。尿素酶活性试验提示我们小肠结肠炎耶尔森菌的尿素酶活性大小与其致病性的强弱可能无关联。     

Protective effect of melatonin on Ca2+ homeostasis and contractility in acute cholecystitis

Abstract:  Impaired Ca²⁺ homeostasis and smooth muscle contractility co-exist in acute cholecystitis (AC) leading to gallbladder dysfunction. There is no pharmacological treatment for this pathological condition. Our aim was to evaluate the effects of melatonin treatment on Ca²⁺ signaling pathways and contractility altered by cholecystitis. [Ca²⁺]_i was determined by epifluorescence microscopy in fura-2 loaded isolated gallbladder smooth muscle cells, and isometric tension was recorded from gallbladder muscle strips. Malondialdehyde (MDA) and reduced glutathione (GSH) contents were determined by spectrophotometry and cycloxygenase-2 (COX-2) expression was quantified by western blot. Melatonin was tested in two experimental groups, one of which underwent common bile duct ligation for 2 days and another that was later de-ligated for 2 days. Inflammation-induced impairment of Ca²⁺ responses to cholecystokinin and caffeine were recovered by melatonin treatment (30 mg/kg). This treatment also ameliorated the detrimental effects of AC on Ca²⁺ influx through both L-type and capacitative Ca²⁺ channels, and it was effective in preserving the pharmacological phenotype of these channels. Despite its effects on Ca²⁺ homeostasis, melatonin did not improve contractility. After de-ligation, Ca²⁺ influx and contractility were still impaired, but both were recovered by melatonin. These effects of melatonin were associated to a reduction of MDA levels, an increase in GSH content and a decrease in COX-2 expression. These findings indicate that melatonin restores Ca²⁺ homeostasis during AC and resolves inflammation. In addition, this indoleamine helps in the subsequent recovery of functionality.     

Effect of Glutathione on Inositol 1,4,5-Triphosphate-Induced Ca2+ Release in Permeabilized Hepatocytes from Control and Chronic Ethanol-Fed Rats

The effect of oxidized and reduced glutathione on inositol 1,4,5-trisphosphate (InsP3)-induced Ca²⁺ release from endoplasmic reticular Ca²⁺ stores was studied in digitonin-permeabilized hepatocytes from chronically ethanol-fed rats and pair-fed control animals. The fractional Ca²⁺ release induced by a subsaturating concentration of lnsP3 was significantly enhanced in cells from ethanol-fed rats in the absence of a change in maximal lnsP3-releasable Ca²⁺ pool size, and this difference was not affected by preincubation with reduced glutathione. Incubation with oxidized glutathione (1 mM) increased the efficacy of Ca²⁺ release by subsaturating concentrations of lnsP3 in both control preparations and in cells from ethanol-fed rats. The shift in the InsP3 dose-response curve was not significantly different between the two preparations. These findings suggest that the enhanced efficacy of InsP3-induced Ca²⁺ release in hepatocytes from ethanol-fed rats is not caused by the oxidation of protein-bound thiol groups on the lnsP3 receptor.     

从生猪中分离小肠结肠炎耶尔森菌病原学研究

目的 了解河南省登封市生猪中小肠结肠炎耶尔森菌的病原学特征。方法 以采集的1346份猪咽拭子所分离的331株小肠结肠炎耶尔森菌为研究对象,进行系统生化鉴定、血清学分型和毒力基因PCR检测。结果 采集的1346份猪咽拭子中共筛查、分离出小肠结肠炎耶尔森菌331株,分离率为24.59℅（331/1346）;鉴定出O:3、O:5、O:8三种血清型（84.6% ,2.1% 和1.8%）和1A、3、4三个生物型;毒力基因分布特征为ail+、ystA+、ystB-、yadA+、virF+占80.67℅（267/331）,ail+、ystA+、ystB-、yadA-、virF-占3.32℅（11/331）且均为血清型O:3;其它型的为16.01℅（53/331）。结论 生猪为携带小肠结肠炎耶尔森菌的主要宿主,且多携带致病性菌株,提示在今后疫情控制中应加强生猪的监测、检疫和管理。     

Abnormal cAMP-induced phosphorylation of rap 1, protein in grey platelet syndrome platelets

Summary We previously demonstrated abnormal Ca²⁺ transport by microsomes in platelets from a grey platelet syndrome patient. Here, we investigated the platelet Ca²⁺ ATPases that mediate this transport, as well as its possible regulation by rap 1 protein. We showed that grey platelet syndrome platelets expressed the same two distinct Ca²⁺ ATPases as those recently described in normal platelets; the 100 kD SERCA_2-b isoform (Sarco/Endoplasmic Reticulum Ca²⁺ATPase) and a new 97 kD SERCA isoform. The two Ca²⁺ ATPases formed similar amounts of transient phosphorylated intermediates. The expression of these two Ca²⁺ ATPases was compared by Western blotting using specific antibodies, which again emerged in similar amounts in normal and grey platelet syndrome platelets. As regards the protein phosphorylated by cAMP, it was found to be identical to rap 1 protein when it was immunoprecipitated with an antibody raised against a synthetic peptide specific for rap 1 protein. Although the expression of rap 1 protein was similar in membranes isolated from grey platelet syndrome and normal platelets, its exogenous phosphorylation by cAMP was abnormal, with a concentration (10 μg/ml) of the catalytic subunits of the cAMP-dependent protein kinase (C.Sub.), as it decreased to half the control level.
It is concluded that the abnormal Ca²⁺ transport found in grey platelet syndrome platelets is not due to the abnormal expression of the Ca²⁺ ATPases, but is associated with an abnormality of rap 1 protein phosphorylation by cAMP.     

Na+/Ca2+ Exchanger Expression and Function in a Rabbit Model of Myocardial Infarction

Introduction: In general, sarcolemmal Na⁺/Ca²⁺ exchanger (NCX) protein and activity is increased in hearts with ventricular dysfunction. However, in a subset of studies, reduced activity of NCX has been reported. Left ventricular dysfunction (LVD) was induced in the rabbit eight weeks after an apical myocardial infarction.
Methods: Using single microelectrode voltage clamp to assess the NCX activity in isolated ventricular cells, a decrease in NCX activity by ∼30% was observed. Immunoblot analysis indicated increased NCX protein levels by ∼20% in the LVD group. The cause of this paradox is unknown. Overexpression of the protein sorcin increased the activity of NCX without affecting NCX protein levels.
Results: Sorcin protein (dimer) levels were significantly lower in the LVD group (0.67 ± 0.05 n = 15, P < 0.05) compared to sham (1.0 ± 0.16, n = 15). Sorcin monomer levels were not significantly different (sham: 1.0 ± 0.26, LVD: 0.83 ± 0.13). Mathematical modeling of NCX suggests that a reduction of NCX activity during diastole to that in LVD could be achieved by holding the diastolic membrane potential at −60 mV instead of −80 mV. Holding E_m at −60 mV decreased NCX-mediated Ca²⁺ efflux rates to values comparable to those seen in LVD and increased SR Ca²⁺ content and peak systolic [Ca²⁺] in sham and LVD cardiomyocytes.
Conclusions: In conclusion, reduced sorcin expression may be linked to the lower NCX activity in the rabbit model of LVD. Reduced NCX activity during diastole increases SR Ca²⁺ content and Ca²⁺ transient amplitude.     

Ethanol and Cocaine Cause Additive Inhibitory Effects on the Calcium Transients and Contraction in Single Cardiomyocytes

The heart is a major locus for the toxic actions of cocaine and ethanol, each of which has been shown to interfere with excitation-contraction coupling in cardiac muscle cells. Because these drugs are frequently used in combination, the present study was designed to investigate how they interact to modify the Ca²⁺ transient and associated contraction in fura2-loaded cardiomyocytes. A high-speed imaging technique using a charge-coupled device as detector and short-term image store was used to measure cytosolic Ca²⁺ and contraction simultaneously from fluorescence images obtained during the contractile cycle. Ethanol (100 mM) and cocaine (50 μM) caused reversible reductions in Ca²⁺ transient amplitude of 24.3 ± 3.0% and 25.1 ± 3.6%, respectively. Neither agent modified basal Ca²⁺. Ethanol treatment decreased peak shortening by 44.3 ± 3.5%, whereas the contractile depression by cocaine was 31.4 ± 5.3%. The relatively greater effect of ethanol on contraction resulted from a Ca²⁺-independent component of ethanol action on contractility. When cardiomyocytes were exposed simultaneously to ethanol and cocaine, Ca²⁺ transient amplitude was reduced by 38.7 ± 3.0%, and peak contraction was decreased by 55.1 ± 3.5%. These values represent a significantly greater inhibition than observed with either drug alone (p < 0.02) and are compatible with additive effects of the two drugs acting at distinct loci within the excitation-contraction coupling pathway. Thus, simultaneous use of cocaine and ethanol leads to an enhanced depression of myocardial contractility, which is likely to contribute to the cardiotoxic actions of the combination of these two drugs.     

Regulation of calcium influx and phospholipase C activity by indoleamines in dinoflagellate Crypthecodiniurn cohnii

Abstract: Exogenous indoleamines such as melatonin and 5-methoxytryptamine have been shown to induce cyst formation (encystment) in many species of dinoflagellate. Induction of inositol phosphates formation by indoleamine has previously been demonstrated in Crypthecodiniurn cohnii . In addition, depletion of extracellular Ca²⁺ blocks the indoleamine-induced encystment. In the present study, 12 indoleamines (including melatonin and related compounds) were examined for their abilities to induce Ca²⁺ influx, inositol phosphates formation, and encystment in C. cohnii . The results showed that melatonin, 5-methoxytryptamine, and the peptide toxin mastoparan stimulated ⁴⁵Ca²⁺ influxes in dose- and time-dependent manners. The EC₅₀ values of 5-methoxytrypramine and mastoparan to stimulate ⁴⁵Ca²⁺ uptake were 2 mM and 35 μM, respectively. The 5-methoxytryptamine- and mastoparan-induced ⁴⁵Ca²⁺ influx were partially attenuated by the calcium channel blockers, verapamil and ruthenium red. A series of indoleamines were examined for their structure-activity relationship on the induction of encystment and formation of inositol phosphates. Melatonin-induced inositol phosphates formation was completely blocked by U73122, indicating the possible involvement of phospholipase C. Taken together, we conclude that indoleamines may induce encystment of the dinoflagellate C. cohnii via parallel activation of phospholipase C and Ca²⁺ influx signaling pathways. However, activation of phospholipase C and Ca²⁺ influx are not always necessary or sufficient for inducing encystment. Also, these data provided the first direct evidence of a Ca²⁺ influx regulating mechanism in dinoflagellate C. cohnii .     

利用J+H噬菌体鉴定小肠结肠炎耶氏菌的评价

使用J+H噬菌体检查192株通过生化反应作出鉴定的小肠结肠炎耶氏菌和类小肠结肠炎耶氏菌,其裂解率为77.1％,比血清定型率(73.5％)为高,属于致病性血清型的裂解率为95.7％,其中O:3和O:9血清型38株的裂解率为100％;属于非致病性血清型的裂解率为59.6 ％。实验证明这株J+H噬菌体用于临床和流行病学调查致病性小肠结肠炎耶氏菌,非常简便和实用。     

Role of L-Type Calcium Channel Window Current in Generating Current-Induced Early Afterdepolarizations

Ionic Mechanism of EADs. Introduction: Early afterdepolarizations (EADs) can give rise to triggered activity and thereby produce cardiac arrhythmias. We used the whole-cell patch clamp technique to examine the relationship between L-type Ca²⁺ channel window current and the generation of EADs in single ventricular myocytes isolated from guinea pig hearts.
Methods and Results: With a high concentration of EGTA in the internal solution and Na⁺-containing physiologic external solution, EADs were induced in unclamped cells by injecting intracellular depolarizing current pulses. During voltage clamp protocols designed to simulate action potentials interrupted by EADs, we recorded an inward shift in total current up to 0.7 pA/pF over 400 msec at test steps in the range of the take-off potential for EADs. Cd^2t (0.2 mM) blocked most of the inward shift of current during the test steps and abolished EADs. When the same voltage clamp protocol was used following perfusion with an Na⁺-free, K⁺-free external solution, the Cd²⁺-sensitive inward currents recorded during the test steps were similar to those obtained in physiologic external solution. The overlapping range of potentials for partial activation of the d and f variables of L-type Ca²⁺ current ("window" region) measured in Na⁺-free, K⁺-free external solution was virtually the same as the voltage range of the Cd²⁺–sensitive inward currents.
Conclusion: Our experiments suggest that: (1) EADs can arise under conditions of high EGTA buffering of intraccllular [Ca²⁺]; and (2) under these conditions, L-type Ca²⁺ channel window current plays a major role in the initiation of EADs.     

Action Potential Duration, Rate of Stimulation, and Intracellular Sodium

In the first section of this short review the change of the cardiac action potential (APD) with the rate of stimulation under physiological conditions is described and mechanistically analyzed. A fast phase of adaptation is mainly caused by changes in gating characteristics of ionic currents, and rapid modulation of the Na⁺/Ca²⁺ exchanger. The slower phase is largely conditioned by incomplete recovery from inactivation of the late Na⁺ current (late I_Na) and changes in ion concentrations of [K⁺]_e, [Na⁺]_i, and [Ca²⁺]_i, which cause secondary changes in the permeation and the gating of ion channels and flux through transporters. In a second section, an analysis is presented of the rate dependence of APD in pathological conditions and its importance in the genesis of arrhythmias in hypertrophy, heart failure, congenital, and acquired LQT syndromes is summarized. The role of the late I_Na, Na⁺, and Ca²⁺ overload is emphasized. Special attention is given to the paradoxical transient lengthening of APD in LQT3 syndrome for the sudden increase in rate in this setting. The third section consists of a short commentary on Na⁺ and Ca²⁺ overload and drugs which block the late I_Na.