Detection of Francisella tularensis and analysis of bacterial growth in ticks in Japan.

UNLABELLED: Francisella tularensis is distributed in the Northern hemisphere and it is the bacterial agent responsible for tularaemia, a zoonotic disease. We collected 4 527 samples of DNA from ticks in Japan, which were then analysed by real-time PCR and nested PCR. Francisella DNA was detected by real-time PCR in 2·15% (45/2 093) of Ixodes ovatus, 0·66% (14/2 107) of I. persulcatus, 8·22% (6/73) of I. monospinosus and 0·72% (1/138) of Haemaphysalis flava specimens. Finally, Francisella DNA was detected by nested PCR in 42 and five samples I. ovatus and I. persulcatus, respectively, which were positive according to real-time PCR. Phylogenetic analysis showed that the sequence from I. ovatus and I. persulcatus were clustered with F. tularensis type B strains distributed in Eurasia. Microinjected live F. tularensis persisted in ticks, whereas heat-killed F. tularensis decreased. Microinjected F. tularensis hlyD mutant decreased in ticks significantly compared to parent strain, thereby suggesting that HlyD in F. tularensis contributes to the adaptation or survive of bacterial infection in ticks. SIGNIFICANCE AND IMPACTS OF THE STUDY: Francisella tularensis has been detected in ticks, suggesting that it is a tick-borne pathogen. However, F. tularensis has not been detected in ticks in Japan since 1991. In this study, we performed a large-scale analysis of DNA isolated from ticks in Japan and detected F. tularensis by real-time polymerase chain reaction (PCR) and nested PCR. We found that F. tularensis could survive in ticks based on an experimental tick-infection model. We also identified a bacterial factor that contributes to survival in ticks. Our results suggest that ticks are candidate vectors that mediate F. tularensis infection in Japan.

Inhibition of cardiac delayed rectifier K+ currents by an antisense oligodeoxynucleotide against IsK (minK) and over-expression of IsK mutant D77N in neonatal mouse hearts.

The IsK (minK or KCNE1) protein is known to co-assemble with the KvLQT1 (KCNQ1) protein to form a channel underlying the slowly activating delayed rectifier K+ current (IKs). Controversy remains as to whether the IsK protein assembles with ERG (the ether-a-go-go-related gene) products to form or modulate the channel-underlying the rapidly activating delayed rectifier K+ current (IKr). We investigated the effects of antisense oligodeoxynucleotides (AS-ODN) against IsK and its mutant D77N [which underlies a form of long QT syndrome (LQT5) in humans] on the delayed rectifier K+ current (IK) of neonatal mouse ventricular myocytes in primary culture. Patch-clamp experiments on these cells showed that IK consists of IKs and IKr. IK was not recorded from ventricular cells transfected with AS-ODN, while it was recorded from cells transfected with the corresponding sense oligodeoxynucleotides (S-ODN). IK was not recorded from cells transfected with the D77N mutant, and the action potential duration was much longer than in cells transfected with wild-type IsK. Furthermore, HERG could not induce currents in COS-1 cells co-expressed with the D77N mutant and HERG (the human form of ERG). These results indicate that the IsK protein associates with both KvLQT1 and ERG products to modulate IKr and IKs in cardiac myocytes.

Mechanisms of CSF secretion by the choroid plexus.

The epithelial cells of the choroid plexus secrete cerebrospinal fluid (CSF), by a process that involves the movement of Na(+), Cl(-) and HCO(3)(-) from the blood to the ventricles of the brain. This creates the osmotic gradient, which drives the secretion of H(2)O. The unidirectional movement of the ions is achieved due to the polarity of the epithelium, i.e., the ion transport proteins in the blood-facing (basolateral) are different to those in the ventricular (apical) membranes. Saito and Wright (1983) proposed a model for secretion by the amphibian choroid plexus, in which secretion was dependent on activity of HCO(3)(-) channels in the apical membrane. The patch clamp method has now been used to study the ion channels expressed in rat choroid plexus. Two potassium channels have been observed that have a role in maintaining the membrane potential of the epithelial cell, and in regulating the transport of K(+) across the epithelium. An inward-rectifying anion channel has also been identified, which is closely related to ClC-2 channels, and has a significant HCO(3)(-) permeability. This channel is expressed in the apical membrane of the epithelium where it may play an important role in CSF secretion. A model of CSF secretion by the mammalian choroid plexus is proposed that accommodates these channels and other data on the expression of transport proteins in the choroid plexus.

Properties of the inward-rectifying Cl- channel in rat choroid plexus: regulation by intracellular messengers and inhibition by divalent cations.

The properties of the inward-rectifying Cl- conductance in rat choroid plexus epithelial cells were investigated to allow comparisons to be made with ClC-2. All experiments were performed using the whole-cell configuration of the patch-clamp method. The conductance was transiently activated using an electrode solution which contained 375 nM catalytic subunit of protein kinase A (PKA). PKA failed to activate the conductance, however, when cells were pre-incubated with phorbol esters, which activate protein kinase C [1 microM phorbol 12-myristate 13-acetate (PMA) and 1 microM phorbol 12,13-dibutyrate (PDBu)]. Sustained activation of the conductance by PKA was observed in Ca2+-free conditions (5 mM BAPTA in the electrode solution), or when 100 nM calphostin C, a PKC inhibitor, was added to the electrode solution. The inward-rectifying Cl- conductance in choroid plexus is therefore similar to ClC-2 in that it is inhibited by PKC. The inward-rectifying conductance was blocked when Cd2+ (30 and 300 microM) and Zn2+ (1, 30 and 300 microM) were added to the bath solution. ClC-2 channels are also blocked by Zn2+ and Cd2+. The magnitude of the inward conductance was dependent on the concentration of ATP in the electrode solution. The conductance was not observed when ATP in the electrode was replaced with non-hydrolysable ATP analogues [adenosine 5'-O-(3-thiotriphosphate) (ATP[gamma-S]) and 5'-adenylylimidodiphosphate (AMP-PNP)), but it was supported by UTP and GTP. These data contrast with those of previous studies in which ClC-2 channels were activated in the absence of ATP. In conclusion, the inward-rectifying Cl- channel in rat choroid plexus shares some properties with ClC-2 (inhibition by PKC and block by divalent cations), but differs in that it depends on intracellular ATP.

The chloride channel ClC-2 contributes to the inwardly rectifying Cl- conductance in cultured porcine choroid plexus epithelial cells.

1. The contribution of ClC-2 protein to the inwardly rectifying Cl- conductance in cultured porcine choroid plexus epithelial cells was investigated using Western analysis and whole-cell current recordings. 2. Inwardly rectifying currents were elicited by hyperpolarizing voltage at a potential more negative than -50 mV in the presence of intracellular protein kinase A (PKA). The relative halide selectivity estimated from the shift in the reversal potential (Erev) was I- > Br- > Cl- > F-. 3. Extracellular vasoactive intestinal peptide (VIP) activated the same currents in a dose-dependent manner with a half-maximal concentration of 167.3 nM. H-89 (a PKA inhibitor) interfered with the current activation by VIP. 4. The Cl- channel was inhibited by external Cd2+, Ba2+or H+, but only weakly inhibited by known Cl- channel blockers including glibenclamide, NPPB, DIDS and anthracene-9-carboxylic acid (9AC). 5. A specific antibody to ClC-2 detected a 79 kDa protein in porcine choroid plexus cells, which was reduced in cells treated with antisense oligodeoxynucleotide for ClC-2. Both PKA and VIP failed to activate the inwardly rectifying Cl- currents in cells transfected with the antisense oligodeoxynucleotide, while they activated the currents in cells transfected with GFP alone or the control oligodeoxynucleotide randomized from antisense oligonucleotide. 6. It is concluded that ClC-2 protein contributes to the inwardly rectifying Cl- conductance in porcine choroid plexus epithelial cells.

Biological and biochemical properties of Ret with kinase domain mutations identified in multiple endocrine neoplasia type 2B and familial medullary thyroid carcinoma.

Several mutations were identified in the kinase domain of the RET proto-oncogene in patients with multiple endocrine neoplasia (MEN) 2B, familial medullary thyroid carcinoma (FMTC) or sporadic medullary thyroid carcinoma. We introduced seven mutations (glutamic acid 768-->aspartic acid (E768D), valine 804-->leucine (V804L), alanine 883-->phenylalanine (A883F), serine 891-->alanine (S891A), methionine 918-->threonine (M918T), alanine 919-->proline (A919P) and E768D/A919P) into the short and long isoforms of RET cDNA and transfected the mutant cDNAs into NIH3T3 cells. The transforming activity of the long isoform of Ret with each mutation was much higher that that of its short isoform. Based on the levels of the transforming activity, these mutant RET genes were classified into two groups; a group with high transforming activity (A883F, M918T and E768D/A919P) and a group with low transforming activity (E768D, V804L, S891A and A919P) (designated high group and low group). Interestingly, the level of transforming activity correlated with clinical phenotypes; high group Ret with the A883F or M918T mutation and low group Ret with the E768D, V804L or S891A mutation were associated with the development of MEN 2B and FMTC, respectively. In addition, we found that substitution of phenylalanine for tyrosine 905 present in the kinase domain abolished both transforming and autophosphorylation activities of low group Ret whereas it did not affect the activities of high group Ret.

Whole cell Cl- conductances in mouse choroid plexus epithelial cells do not require CFTR expression.

Whole cell patch-clamp studies were performed with tissue isolated from the cystic fibrosis (CF) transgenic Cftrm1cam mouse, to determine whether anion currents in choroid plexus epithelial cells require the expression of cystic fibrosis transmembrane conductance regulator (CFTR). Inclusion of 0.25 mM adenosine 3',5'-cyclic monophosphate (cAMP) and 375 nM protein kinase A (PKA) in the pipette solution caused a significant activation of a Cl(-)-selective, inward-rectifying conductance in cells from wild-type and CF mice. The small, outward currents observed in wild-type and CF animals, however, were not activated by cAMP-PKA. There were no significant differences in the size of currents between wild-type, heterozygote, and CF cells in the presence or absence of cAMP-PKA. A second whole cell conductance was activated when cells from wild-type mice were swollen. These volume-activated currents were Cl- selective and exhibited outward rectification. They were Ca2+ independent and ATP dependent and blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid. The volume-activated channels were also activated in CF mutant cells, and there was no significant difference in the size of the volume-activated currents between wild-type, heterozygote, and CF cells. It is concluded that CFTR neither contributes to the whole cell conductance nor regulates the other anion conductances in choroid plexus epithelial cells.

Inhibition of the inward-rectifying Cl- channel in rat choroid plexus by a decrease in extracellular pH.

1. The sensitivity of the inward-rectifying Cl- channel in choroid plexus to changes in external pH (pHo) was examined. 2. Cl- currents were recorded using whole-cell patch-clamp methods. The inward-rectifying channel was activated by 375 nM of the catalytic subunit of protein kinase A which was added to the electrode solution. 3. Reducing pHo from 7.3 to 6.5 inhibited the inward-rectifying Cl- currents, whereas an increase in current was observed when pHo was elevated to 8.5. The inhibition of the conductance exhibited a sigmoidal relationship with decreasing pH over a range of 8.5 to 5.5. A half-maximal inhibition of the current was observed at pH 7.3. 4. The inhibition of the whole-cell current by reducing pHo suggests that it is carried by channels which are distinct from other inward-rectifier Cl- channels, e.g. ClC-2, phospholemman and the channel in Xenopus oocytes.

A mini Cl- channel sensitive to external pH in the basolateral membrane of guinea-pig parietal cells.

1. Voltage-independent whole-cell Cl- currents were recorded from both single, isolated parietal cells and parietal cells within gastric glands obtained from the fundus of guinea-pig stomach. 2. The Cl- currents were rapidly suppressed by a Cl- channel blocker, NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate), added to the (basolateral) bathing solution in a concentration-dependent manner with a half-maximal inhibition concentration of 12 microM. 3. The selectivity sequence among anions was I- > Br- > Cl- > F-, corresponding to Eisenman's sequence I. 4. The Cl- currents were independent of cytosolic Ca2+, cyclic AMP, cyclic GMP, GTP-gamma-S and cell volume, and were not affected by application of acid secretagogues, omeprazol, arachidonic acid or prostaglandin E2. 5. Reduction of pH in the (basolateral) bathing solution immediately inhibited the Cl- current with a pK (-log of KD) of 6.3, whereas changes in intracellular pH had no effect. 6. The single-channel conductance was estimated to be 0.46-0.6 pS by variance noise analysis during inhibition of whole-cell Cl- currents by NPPB or acidic pH. 7. It is concluded that pH-sensitive 'mini' Cl- channels, with a sub-picosiemens unitary conductance, exist in the basolateral membrane of guinea-pig parietal cells.

A maxi Cl- channel coupled to endothelin B receptors in the basolateral membrane of guinea-pig parietal cells.

1. To study endothelin (ET) receptors in guinea-pig stomach, ET-binding assays and in vitro autoradiography were performed on fundic cell suspensions and on sections of the fundus, respectively. ETA and ETB receptor subtypes were found to coexist in the parietal cells. 2. Endothelin 1 (ET-1) added to the (basolateral) bathing solution was found to activate noisy whole-cell Cl- currents within about 1 min in both single, isolated parietal cells and those within gastric glands obtained from the fundus. 3. ET-1-induced Cl- currents were rapidly blocked by a Cl- channel blocker (NPPB) added to the (basolateral) bathing solution in a concentration-dependent manner with a half-maximum inhibition concentration of 33 microM. 4. The anion selectivity sequence of the ET-1-induced conductance was I- > Br- > Cl- > F-, corresponding to Eisenman's sequence I. 5. Changes in extracellular pH between 5 and 8 did not affect the ET-1-induced activation of Cl- currents. 6. Similar activating effects were also observed with ET-3 and a specific ETB receptor agonist (IRL1620). An ETB receptor antagonist (IRL1720) prevented the ET-1 effect, whereas an ETA-selective antagonist (FR139317 or BQ123) failed to antagonize the ET-1 effect. 7. In the whole-cell mode, unitary Cl- channel events could be observed in association with ET-1-activated macroscopic currents. The single-channel conductances were around 200 and 350 pS at negative and positive membrane potentials, respectively. 8. It is concluded that gastric parietal cells of guinea-pig possess pH-insensitive 'maxi' Cl- channels coupled to ETB receptors in the basolateral membrane.

Endothelin-induced activation of Cl- channels of guinea pig parietal cells.

The addition of endothelin-1 to the bath solution dose-dependently increased the whole-cell Cl- currents in single parietal cells isolated from guinea pig stomach. NPPB dose-dependently inhibited the current. Endothelin-3 was also effective, though less than endothelin-1.

[Clinical evaluation of endoscopic variceal ligation (EVL)].

From August 1992 through February 1993, we treated 21 patients with endoscopic variceal ligation (EVL). Two patients had a history of the esophageal variceal bleeding, but 19 patients did not have bleeding episodes. To evaluate preventive effect of bleeding, we selected the patients who had grade F2 or red color sign positive varices. We repeated EVL until varices improved into grade F0 or F1 and red color sign negative. The therapeutic goal was sometimes changed according to patient's general condition. No additional therapy was performed to eradicate varices, such as endoscopic injection sclerotherapy. As a result of our therapy, eradication rate was 73.7% and period of hospitalization were 25 +/- 11 days. No major complications were found during and after EVL. EVL affected neither liver function test nor size of gastric varices. Recurrent varices with red color sign were found in 4 patients, but easily controlled by retreatment with EVL. EVL seems to be convenient and effective therapy in our short-term study, and useful for preventive therapy of the esophageal variceal bleeding.

Role of the medical museum in teaching medical students.

We describe the Educational Museum of Modern Medicine of Kawasaki Medical School of Kurashiki, Japan, and its use in medical education. The extraordinary speed of recent medical advances confronts medical educators with many difficulties. With the aim of improving medical education at our school, we have imposed some roles of medical education, especially regarding pathology, on the medical museum, because it has attracted students to a greater extent and facilitated their independent learning in a more fruitful way than the audiovisual materials previously available in our library. We hope to provide some insights for the improvement of medical education and lead to enthusiastic discussion of this matter.