Postoperative decrease of regional volumetric bone mineral density measured by quantitative computed tomography after lumbar fusion surgery in adjacent vertebrae

We investigated the effect of posterior lumbar fusion surgery on the regional volumetric bone mineral density (vBMD) measured by quantitative computed tomography. Surgery negatively affected the regional vBMD in adjacent levels. Interbody fusion was independently associated with vBMD decline and preoperative epidural steroid injections (ESIs) were associated with less postoperative vBMD decline.

INTRODUCTION

Few studies investigate postoperative BMD changes after lumbar fusion surgery utilizing quantitative computed tomography (QCT). Additionally, it remains unclear what preoperative and operative factors contribute to postoperative BMD changes. The purpose of this study is to investigate the effect of lumbar fusion surgery on regional volumetric bone mineral density (vBMD) in adjacent vertebrae and to identify potential modifiers for postoperative BMD change.

METHODS

The data of patients undergoing posterior lumbar fusion with available pre- and postoperative CTs were reviewed. The postoperative changes in vBMD in the vertebrae one or two levels above the upper instrumented vertebra (UIV+1, UIV+2) and one level below the lower instrumented vertebra (LIV+1) were analyzed. As potential contributing factors, history of ESI, and the presence of interbody fusion, as well as various demographic/surgical factors, were included.

RESULTS

A total of 90 patients were included in the study analysis. Mean age (±SD) was 62.1 ± 11.7. Volumetric BMD (±SD) in UIV+1 was 115.4 ± 36.9 mg/cm³ preoperatively. The percent vBMD change in UIV+1 was - 10.5 ± 12.9% (p < 0.001). UIV+2 and LIV+1 vBMD changes showed similar trends. After adjusting with the interval between surgery and the secondary CT, non-Caucasian race, ESI, and interbody fusion were independent contributors to postoperative BMD change in UIV+1.

CONCLUSIONS

Posterior lumbar fusion surgery negatively affected the regional vBMDs in adjacent levels. Interbody fusion was independently associated with vBMD decline. Preoperative ESIs were associated with less postoperative vBMD decline, which was most likely a result of a preoperative decrease in vBMD due to ESIs.

Quantitative evaluations of the contribution of the excitatory ionic conductance to repetitive spiking in a mathematical model of medial vestibular nucleus neurons

Medial vestibular nucleus neurons show spontaneous repetitive spiking. This spiking activity was reproduced by a Hodgkin-Huxley-type mathematical model, which was developed in a previous study. The present study performed computer simulations of this model to evaluate the contribution of the excitatory ionic conductance to repetitive spiking. The present results revealed the difference in the influence of the transient sodium, persistent sodium, and calcium conductance on spiking activity. The differences between the present and previous results obtained from other neuronal mathematical models were discussed.

Effect of sodium conductance variations on electrical behavior of a neocortical neuron model

Neocortical pyramidal neurons are capable of intrinsic regenerative firing. A mathematical model introduced by Delord et al. [2] of these neurons based on the Hodgkin-Huxley formalism, varied the values of two parameters of the model, i.e. the maximal persistent sodium conductance (gNaP) and the leakage one (gl), and revealed the (gNaP, gl) parameter space supporting regenerative firing. The present study focused on another parameter of this model, i.e. the maximal fast sodium conductance (gNa), to investigate the (gNaP, gNa) parameter space involved in regenerative firing. When gNa was completely blocked, regenerative firing was suppressed. In addition, the gNa threshold necessary to induce regenerative firing was almost independent of the gNaP level. Finally, our results were compared with those of other types of neurons.

Novel types of bistability in a model of a bursting pacemaker neuron RPa1 from the snail, Helix pomatia

The RPa1 neuron identified in the snail, Helix pomatia, produced a variety of electrical activities (e.g. bursting and spiking). A previously developed mathematical model, which described these activities, revealed bistability between bursting and chaotic spiking, where chaotic spiking was transformed into bursting by a short-lasting external stimulus, and vice versa. The present study used this model to detect other types of bistability, i.e. bistability between bursting and period-2 spiking and between bursting and period-4 spiking (period-2 and -4 spiking are generated by period-doubling bifurcation). This contributes to our understanding of the electrophysiological properties of RPa1.

Analysis of the electrosensory pyramidal cell bursting model for weakly electric fish: model prediction under low levels of dendritic potassium conductance

Pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish produce burst discharge. A Hodgkin-Huxley-type model, called ghostburster, consisting of two compartments (soma and dendrite) reproduces ELL pyramidal cell bursting observed in vitro. A previous study analyzed the ghostburster by treating Is and gDr,d as bifurcation parameters (Is: current injected into the somatic compartment and gDr,d: maximal conductance of the delayed rectifying potassium current in the dendritic compartment) and indicated that when both Is and gDr,d are set at particular values, the ghostburster shows a codimension-two bifurcation at which both saddle-node bifurcation of fixed points and saddle-node bifurcation of limit cycles occur simultaneously. In the present study, the ghostburster was investigated to clarify the bursting that occurred at gDr,d values smaller than that at the codimension-two bifurcation. Based on the number of spikes per burst, various burst patterns were observed depending on the (Is, gDr,d) values. Depending on the (Is, gDr,d) values, the burst trajectory in a phase space of the ghostburster showed either a high or a low degree of periodicity. Compared to the previous study, the present findings contribute to a more detailed understanding of ghostburster bursting.

Probing the metal-insulator phase transition in the (DMEDO-EBDT)2PF6 single crystal by optical measurements

The temperature and polarization dependence of the optical reflectivity  spectra of a quasi-one-dimensional 1/4-filled band system, (DMEDO-EBDT)(2)PF(6), have been investigated. We observed clear anisotropy in the electronic structures corresponding to the anisotropic transport properties. The appearance of a charge gap (E(g) > 0.1 eV) and transfer of the spectral weight accompanied by the metal-insulator phase transition were clearly observed. In addition, a split of the intramolecular vibrational modes was observed, which strongly suggested the existence of charge disproportionation in the low temperature phase. We also observed a photoinduced reflectivity change, which implied the occurrence of a photoinduced phase transition from the low temperature insulating phase to the high temperature metallic phase.

Evaluation of a new fiber-grating vision sensor for assessing pulmonary functions in healthy and COPD subjects

Spirometry is practically the only tool to evaluate pulmonary functions. Other automatic systems comparable to spirometry are expected. A fiber-grating (FG) vision sensor is a non-contact respiratory monitoring system to detect changes in volumes by measuring the movement of laser spots on the body surface. We examined the contributions of the FG sensor to evaluating pulmonary functions. The FG sensor showed a linear correlation with spirometry in tidal volumes (TV) obtained from five controls (R = 0.98, P < 0.0001). We also showed agreement of TV between the two devices using Bland-Altman analysis. TV measured by the FG sensor were reproducible and applicable to distinct subjects. To detect airway obstruction, we performed forced expiration in controls (n = 16) and chronic obstructive pulmonary disease (COPD) patients (n = 18) with the FG sensor and spirometry. Forced expiratory volume in 1 s (FEV(1)) and FEV(1)/forced vital capacity in COPD patients were lower than those in controls by the FG sensor. In addition, prolonged expiration in natural breathing by the FG sensor was related to airflow limitation by spirometry. The FG sensor was helpful to measure volume changes and to evaluate pulmonary functions in controls and patients with COPD. Its upcoming clinical applications are promising for simplicity and feasibility.

The effect of variations in sodium conductances on pacemaking in a dopaminergic retinal neuron model

Dopaminergic neurons in the retina show spontaneous tetrodotoxin-sensitive pacemaking, which has been explained by a reduced Hodgkin-Huxley-type computer model. The present study used this model to investigate the effect of variations in transient and persistent sodium conductance values on pacemaking, under variable leakage conductance levels. This study indicated that transient sodium conductance plays an indispensable role in pacemaking, which occurs under conditions in which only a persistent sodium conductance is considerably reduced, thus contributing to a detailed understanding of the relationship between sodium conductance and pacemaking.

The effect of hyperpolarizing inputs on the dynamics of a bursting pacemaker neuron model in the pre-Bötzinger complex

The pre-Bötzinger complex (pre-BötC), a subregion of the ventrolateral medulla involved in respiratory rhythm generation, contains intrinsically bursting pacemaker neurons. A previous study proposed Hodgkin-Huxley type minimal models for pacemaker neurons and predicted the effect of a hyperpolarizing input on the dynamics of a model under certain conditions. In this model, bursting is explained by the dynamics of a persistent sodium current. In the present study, the effect of a hyperpolarizing input on the dynamics of a model was investigated under variable conditions. It was observed that immediately after an input of sufficient intensity and duration, an increase in the maximal value of the gating variable h of a persistent sodium current was brought about by a decrease in the timing of the hyperpolarizing input. This corresponds to an observation that immediately after the input, a monotonic increase in the number of spikes in the neuron model was brought about by a decrease in the timing of the hyperpolarizing input. In addition, the dependency of burst duration immediately after the input on the timing of the hyperpolarizing input varied depending on the condition of input. The present study is the first to elucidate that the influence of hyperpolarizing inputs on the number of spikes within a burst in a pacemaker neuron model in the pre-BötC is dependent on the timing of the hyperpolarizing input and to clarify the possible mechanism of this influence, thereby facilitating a detailed understanding of the dynamics of a pacemaker neuron model in the pre-BötC.

Simulation of rabbit A-type retinal horizontal cell that generates repetitive action potentials

Rabbit A-type retinal horizontal cells are classified into at least two types: cells that generate repetitive action potentials and those that do not. A mathematical model of these two types of cells based on the ionic current mechanisms has been proposed. Although the response of the former cell to 1-s positive current injection has so far been investigated by both electrophysiological and computational approaches, how this cell responds to much longer current injection has not been investigated. In the present study, I use this model to investigate the response of the former cell to a much longer current injection. Computer simulation indicates that when the stimulation period is relatively short, the membrane potential returns to the resting potential after current injection. In this case, the cell can repeatedly generate repetitive action potentials in response to stimulation. In contrast, when the stimulation period is relatively long, the membrane potential does not return to the resting potential but maintains the depolarized level even after current injection. In this case, the cell cannot repeatedly generate repetitive action potentials. When the present results were compared with those of the previous study, the difference in the response pattern after stimulation between the two types of horizontal cells was revealed.

Depletion of serotonin selectively impairs short-term memory without affecting long-term memory in odor learning in the terrestrial slug Limax valentianus

The terrestrial slug Limax is able to acquire short-term and long-term memories during aversive odor-taste associative learning. We investigated the effect of the selective serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) on memory. Behavioral studies indicated that 5,7-DHT impaired short-term memory but not long-term memory. HPLC (high-performance liquid chromatography) analysis revealed that 5,7-DHT significantly reduced serotonin content in the central nervous system. The present study suggests that acquisition, retention, and/or retrieval of short-term memory involves serotonin, and neither acquisition nor retrieval of long-term memory requires serotonin at a level as high as that required for short-term memory.

Protective immunity of SpaA-antigen producing Lactococcus lactis against Erysipelothrix rhusiopathiae infection

AIMS

To develop an economical, safe and simple vaccination system against swine erysipelas using SpaA-antigen producing Lactococcus lactis.

METHODS AND RESULTS

The spaA gene of Erysipelothrix rhusiopathiae was inserted into a shuttle plasmid pSECE1 to construct pSECE1.3. The SpaA produced in L. lactis maintained a stable antigenicity without degrading in growth. After mice were inoculated intranasally and orally with pSECE1.3-carrying L. lactis cells, IgG and IgA specific to SpaA were detected, and all the mice survived a challenge with 100 LD(50) of E. rhusiopathiae Tama-96 in the inner thigh.

CONCLUSIONS

SpaA-producing L. lactis appears useful as an effective subunit vaccine against swine erysipelas.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this vaccination system, purification of the antigen and injection are unnecessary, leading to a reduced production cost, reduced labour and less stress to the animals. This vaccination system of the lactic acid bacteria should be a safe and suitable vehicle for a polyvalent vaccine.

Distribution of serotonin-like immunoreactive neurons in the slug Limax valentianus

Immunohistochemical techniques were used to study the distribution of serotonin-containing neurons in the nervous system of the slug Limax valentianus. Approximately 350 serotonin-like immunoreactive cell bodies were found in the central nervous system. These were located in the cerebral, pedal, visceral and right parietal ganglia. Most serotonin-like immunoreactive neurons had small cell bodies, which were aggregated into discrete clusters. A pair of previously identified metacerebral giant cells were found on the anterior side of the cerebral ganglion, and two additional pairs of uniquely identifiable, serotonin-like immunoreactive cells were found on the posterior side of the cerebral ganglion. The whole-mount maps of these stained neurons will be useful in further physiological and biochemical studies of olfactory learning at the cellular level in Limax valentianus.

Effects of rearing conditions on the colonization of Salmonella enteritidis in the cecum of chicks

Salmonella enteritidis is the cause of human salmonellosis associated with contaminated eggs. In this study, we artificially challenged S. enteritidis to chicks just after hatching, and the effects of breeding conditions on the intestinal carriage of S. enteritidis were examined. S. enteritidis was not directly detected from spleen, liver and blood, but were constantly isolated from the cecal contents throughout the experiment. When chicks were reared in the unsanitary conditions and in the high housing density, the numbers of S. enteritidis increased. The subsequent experiment was undertaken to examine whether the antibacterial additive in a feed would have any impact on S. enteritidis colonization in chicks. Some antibiotic effective on the growth promotion had an influence on S. enteritidis colonization.

A simple and sensitive detection system for Bacillus anthracis in meat and tissue

AIMS

To detect and isolate Bacillus anthracis from meat and tissue by rapid and simple procedures.

METHODS AND RESULTS

Bacillus anthracis Pasteur II cells were added to 1 g lymph node and pig meat, which were then cut into small pieces and suspended in PBS. Aliquots were spread on Bacillus cereus selective agar (BCA) plates to isolate B. anthracis cells, and incubated in trypticase soy broth. The enrichment culture was used for nested PCR with B. anthracis specific primers, which were to confirm the presence of B. anthracis chromosomal DNA and the pXO1/pXO2 plasmids.

CONCLUSION

One cell of B. anthracis was detected by nested PCR from 1 g of the samples, and was also isolated on BCA plates according to colony morphology within two days.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results could be useful for detecting animals with latent anthrax, and meat contaminated with B. anthracis, rapidly and simply.

Phylogenetic diversity and similarity of active sites of Shiga toxin (stx) in Shiga toxin-producing Escherichia coli (STEC) isolates from humans and animals

Nucleotide sequences of Shiga toxin (Stx) genes in STEC from various origins were determined and characterized by phylogenetic analysis based on Shiga toxin (Stx) with those deposited in GenBank. The phylogenetic trees placed Stx1 and Stx2 into two and five groups respectively, and indicated that Stx1 in sheep-origin STEC were placed into a different group from those in other STEC, and that Stx2 of deer-origin STEC also belonged to the unique group and appeared to be distantly related to human-origin STEC. On the other hand, Stx of STEC isolated from cattle, seagulls and flies were closely related to those of human-origin STEC. Such a diversity of Stx suggested that STEC might be widely disseminated in many animal species, and be dependent on their host species or their habitat. In addition, the active sites in both toxins were compared; the active sites in both subunits of Stx in all the animal-origin STEC were identical to those in human-origin STEC, suggesting that all the toxin of STEC from animals might be also cytotoxic, and therefore, such animal-origin STEC might have potential pathogenicity for humans.

Genetically modified Shiga toxin 2e (Stx2e) producing Escherichia coli is a vaccine candidate for porcine edema disease

Porcine edema disease (ED) is an enterotoxaemia in pigs after weaning, caused by Shiga toxin 2e (Stx2e) producing Escherichia coli. Recently in Japan, outbreaks of ED are re-emerging in pig production. In this study we constructed a mutant that retained immunogenicity but lost Vero cell cytotoxicity, which produced genetically modified toxin (Stx2e*) by replacing glutamate with glutamine at position 167 and arginine with leucine at position 170 of the A subunit. The stx(2e)* gene was replaced with the stx(2e)gene of the wild type virulent strain by homologous recombination. As the parent wild strain was pathogenic to pigs but the mutant was not, the mutant named as YT106 was given to the pigs to examine its protective immunity against ED. All 20 pigs vaccinated with YT106 survived, but only eight of the 20 non-vaccinated pigs survived after the challenge with a wild strain. Also, the eight pigs that survived had decreased rates of gain relative to those of the controls. Blood IgG and intestinal IgA titres increased 3.3 and 1.6 times more than the control, respectively, showing that YT106 might be a good candidate of a live attenuated vaccine strain to protect against ED.

Does enterohemorrhagic Escherichia coli O157:H7 enter the viable but nonculturable state in salted salmon roe?

An outbreak caused by salted salmon roe contaminated with enterohemorrhagic Escherichia coli O157 occurred in Japan in 1998. Since about 0.75 to 1.5 viable cells were estimated to cause infection, we presumed that O157 might enter the viable but nonculturable (VNC) state in salted salmon roe and consequently that viable cell numbers might be underestimated. Although patient-originating O157 cells could not grow on agar plates after 72 h of incubation in 13% NaCl, they were resuscitated in yeast extract broth, and more than 90% of the cells were shown to be viable by fluorescent staining, suggesting that almost all of them could enter the VNC state in NaCl water. Roe-originating O157 was resistant to NaCl because it could grow on agar after 72 h of incubation in NaCl water, but about 20% of cells appeared to enter the VNC state. Therefore, germfree mice were infected with O157 to examine the resuscitation of cells in the VNC state and the retention of pathogenicity. O157 that originated in roe, but not patients, killed mice and was isolated from the intestine. However, these isolates had become sensitive to NaCl. O157 cells of roe origin incubated in normal media also killed mice and were isolated from the intestine, but they also became transiently NaCl sensitive. We therefore propose that bacterial cells might enter the VNC state under conditions of stress, such as those encountered in vivo or in high salt concentrations, and then revive when those conditions have eased. If so, the VNC state in food is potentially dangerous from a public health viewpoint and may have to be considered at the time of food inspection. Finally, the establishment of a simple recovery system for VNC cells should be established.

Detection and characterization of Shiga toxin-producing Escherichia coli from seagulls

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains isolated from a seagull in Japan were examined. A total of 50 faecal samples was collected on a harbour bank in Hokkaido, Japan, in July 1998. Two different STEC strains, whose serotypes were O136:H16 and O153:H-, were isolated from the same individual by PCR screening; both of them were confirmed by ELISA and Vero cell cytotoxicity assay to be producing active Stx2 and Stx1, respectively. They harboured large plasmids, but did not carry the haemolysin or eaeA genes of STEC O157:H7. Based on their plasmid profiles, antibiotic resistance patterns, pulsed-field gel electrophoresis analysis (PFGE), and the stx genes sequences, the isolates were different. Phylogenic analysis of the deduced Stx amino acid sequences demonstrated that the Stx toxins of seagull-origin STEC were closely associated with those of the human-origin, but not those of other animal-origin STEC. In addition, Stx2phi-K7 phage purified from O136 STEC resembled Stx2phi-II from human-origin O157:H7, and was able to convert non-toxigenic E. coli to STEC. These results suggest that birds may be one of the important carriers in terms of the distribution of STEC.

Antibacterial activity of chaff vinegar and its practical application

Since enterohemorrhagic Escherichia coli O157, Salmonella, etc., sometimes contaminate animal feces and may cause infectious diseases to humans, it is important to remove pathogenic bacteria from domestic animal waste. For the purpose, we examined the antibacterial activity of chaff vinegar. We found that the chaff vinegar inhibited the growth of pathogenic bacteria immediately in vitro but not efficiently spores and lactic acid bacteria. Further, it removes bacteria, especially Enterobacteriaceae, from animal feces and the surface of the concrete-floor in the cattle barn. Chaff vinegar is advertised as a natural chemical substance for a soil conditioner, to promote the composting and to deodorize their smell. Chaff vinegar may be useful for organic agriculture without enteric pathogenic bacteria.

Surface antigen, SpaA, of erysipelothrix rhusiopathiae binds to Gram-positive bacterial cell surfaces

In a previous study, we isolated the spaA gene encoding the surface protective antigen A, SpaA, of Erysipelothrix rhusiopathiae, and found that the N-terminal region of SpaA was responsible for protective immunity against erysipelas and that the C-terminal region contained eight repeat units consisting of 20 amino acids comprising the binding domain on the Erysipelothrix cell surface. In this study, using recombinant SpaA proteins, we showed that the repeat region bound to the cell surfaces of various Gram-positive bacterial cells, SpaA was a membrane-associated protein, this association depended on the interaction with choline residues in teichoic acid, and SpaA bound to lipoteichoic acid (LTA) of Bacillus subtilis and Staphylococcus aureus. These results showed that LTA was required for the surface association of SpaA in E. rhusiopathiae and that such an association might be common among Gram-positive bacterial cells. We suggested that an LTA-SpaA complex might have an important role in the E. rhusiopathiae infection process.

Complement receptor type 3 plays an important role in development of protective immunity to primary and secondary Corynebacterium pseudotuberculosis infection in mice

The present study was performed to investigate the role of CR3, the type 3 complement receptor, in host defense against primary and secondary Corynebacterium (C.) pseudotuberculosis infection in mice. Treatment of mice with 5C6, an anti-CR3 monoclonal antibody (mAb), resulted in unrestricted multiplication of bacteria in the organs and dramatically increased mortalities of the infected mice. Histological examinations showed the inflammation, degeneration and necrosis of organs and revealed that the infection-enhancing effect of 5C6 mAb was associated with the failure of mice to focus mononuclear phagocytes at sites of bacterial multiplication. These results suggest that CR3 plays an important role in host defense against primary as well as secondary C. pseudotuberculosis infection in mice.

Tumor necrosis factor alpha and gamma interferon are required for the development of protective immunity to secondary Corynebacterium pseudotuberculosis infection in mice

The production and role of endogenous cytokines during the course of secondary Corynebacterium (C.) pseudotuberculosis infection were investigated in mice. When immunized mice were challenged on day 28 after primary infection, tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) were found to appear at 3 hr and to reach the maximum at 24 hr after challenge. Spleen cells of mice primarily infected from 2 to 8 weeks before produced a significant amount of TNF-alpha and IFN-gamma when stimulated with formalin-killed bacteria. However, they could not produce detectable amounts of IL-4. The administration of anti-TNF-alpha monoclonal antibody (MAb) and IFN-gamma MAb increased bacterial proliferation in the organs of immune mice and exacerbated the secondary infection. Injection of anti-CD4 MAb alone or anti-CD4 plus anti-CD8 MAbs resulted in significantly increased mortality and a marked suppression of bacterial elimination as well as cytokine production of secondarily infected mice, while the treatment with anti-CD8 MAb alone showed no effect on either the resistance or cytokine production of mice. These results suggest that CD4, probably Th1 T cells, play an important role for establishment of protective immunity against secondary C. pseudotuberculosis infection by secreting TNF-alpha and IFN-gamma.

Establishment of the PCR system specific to Salmonella spp. and its application for the inspection of food and fecal samples

We established the PCR detection system specific to Salmonella species using Salmonella enterotoxin gene (stn). The detection limit was one bacterial cell per one gram of fecal and minced-meat samples using enrichment procedure by Tripticase soy broth or Salmonella enrichment broth, respectively. We concluded that this PCR system is useful for the practical application in the field of the public hygiene.

Molecular epidemiological study on tetracycline resistance R plasmids in enterohaemorrhagic Escherichia coli O157:H7

Restriction patterns obtained with EcoRI and Southern hybridization were used for the differentiation of tetracycline-resistant (Tet(r)) R plasmids in enterobaemorrhagic Escherichia coli (EHEC) O157:H7 isolates from a mass outbreak at a kindergarten in Obihiro-City, Hokkaido, Japan, 1996. Two kinds of Tet(r) R plasmids of 50 and 95 kb were detected. The 50-kb plasmids were identical to each other, while the 93-kb plasmids were of three types that were very similar to each other. The tet genes of both 50- and 95-kb R plasmids were 100% identical to the tet gene of pSC101 and all plasmids hybridized to a probe for tet. Because food-origin O157 strains were sensitive to tetracycline, we concluded that such Tet(r) R-plasmids might transfer to drug-sensitive O157 strains in the infected individuals.

Molecular epidemiological study of a mass outbreak caused by enteropathogenic Escherichia coli O157:H45

We made a molecular analysis of O157:H45 Escherichia coli isolated from a mass outbreak that occurred in Obihiro City. Using DNA analysis, we confirmed this infection case as a mass outbreak. Although the isolates expressed O157 antigen, they did not produce Vero toxin. We concluded they were enteropathogenic E. coli (EPEC) because they had a bfp gene and an EAF plasmid, and further they exhibited local adherence to HEp-2 cells. We believe this is the first report of a mass outbreak by O157 EPEC, and we suggest that PCR using eae- and bfp-specific primers and HEp-2 adherence assay are useful to identify EPEC.

Detection and genetical characterization of Shiga toxin-producing Escherichia coli from wild deer

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains isolated from wild deer in Japan were examined. A total of 43 fecal samples were collected 4 times from 4 different sites around Obihiro City, Hokkaido, Japan, in June and July 1997. Seven STEC strains were isolated by PCR screening, all of them were confirmed by ELISA and Vero cell cytotoxicity assay to be producing only active Stx type 2 (Stx2). Moreover, they seemed to carry the hemolysin and eaeA genes of STEC O157:H7, and some isolates harbored large plasmids which were similar to the 90-kilobase virulence plasmid of STEC O157:H7. Based on their plasmid profiles, antibiotic resistance patterns, PCR-based DNA fingerprinting data obtained by using random amplified polymorphic DNA (RAPD) and the stx2 gene sequences, all isolates were divergent from each other except for 3 isolates from the first and second samplings. A DNA sequence analysis of representative isolates revealed that deer originating STEC strains were closely related to each other, but not to the Stx2-producing STEC strains isolated from a mass outbreak in Obihiro at the same time. A phylogenic analysis of the deduced Stx2 amino acid sequences demonstrated that three distinct clusters existed in the deer originating STEC strains and that the Stx of deer originating STEC was closely associated with that originating from humans, but not those of STEC originating from other animals. These results suggest that STEC contamination of deer carcasses should be considered as a potential source of human infection and adequate sanitary inspection of meat for human consumption is also essential for wild animals.

Role of endogenous tumor necrosis factor alpha and gamma interferon in resistance to Corynebacterium pseudotuberculosis infection in mice

The production and roles of endogenous tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) in the infection of Corynebacterium (C.) pseudotuberculosis were investigated in mice. The maximum levels of TNF-alpha and IFN-gamma were detected on day 4 after infection. The administration of anti-TNF-alpha monoclonal antibody (mAb) as well as anti-IFN-gamma mAb increased bacterial proliferation in the organs, leading to the death of infected mice, but anti-IFN-gamma mAb showed a less marked effect than anti-TNF-alpha mAb. The suppressive effect of anti-TNF-alpha and anti-IFN-gamma mAbs on anticorynebacterial resistance was augmented by the simultaneous administration of these antibodies. Anti-TNF-alpha mAb was found to be highly effective when administered on day 0 and day 4, suggesting that TNF-alpha produced during the early stage of infection is critical for the generation of resistance. Histologically, many microabscesses, severe follicular swelling and lymphocyte destruction were observed in mice treated with anti-TNF-alpha or anti-IFN-gamma mAb. Injection of anti-CD4 or anti-CD8 mAb also resulted in significantly increased mortality and a marked suppression of IFN-gamma production, but had no effect on TNF-alpha production. Carrageenan also showed a marked effect on the exacerbation of infection. Taken together, these results suggest that endogenously produced TNF-alpha and IFN-gamma are both essential to the host defense against C. pseudotuberculosis infection and that these cytokines may have an additive effect.

Detection and long-term existence of Shiga toxin (Stx)-producing Escherichia coli in sheep

The isolation and characterization of Shiga-like toxin (Stx)-producing Escherichia coli (STEC) from sheep are described. The distribution of stx genes in E. coli isolates was detected by PCR. When brain heart infusion (BHI) broth and novobiocin supplemented m-EC broth (N-mEC) were used as enrichment culture for the isolation of STEC, N-mEC, compared to BHI, showed clearly lower efficiency. Finally, 5 STEC isolates from 4 sheep were isolated and characterized by biochemical and genetical analysis. All of them were confirmed by ELISA and Vero cell cytotoxicity assay for the production of Stx. Moreover, some strains carried hemolysin and eaeA genes and harbored large plasmids. Based on their plasmid profiles, antibiotic patterns and PCR-based DNA fingerprinting analysis using random amplified polymorphic DNA (RAPD), all isolates were different from each other. Three of the isolates were identified to belong to serogroups O2, O153 and O165, respectively, and the STEC strains belonging to these serogroups had been isolated from STEC outbreaks in humans. Four months after the first isolation in July 1997, STEC from sheep #1 was isolated again. A new isolate, HI-11, was identified as STEC O2:Hnt. Simultaneously, 2 STEC, which were genetically and phenotypically different from each other, were isolated from the same sheep at intervals of 4 months. These results demonstrate that sheep may be an important animal for studying human STEC infections, and that further epidemiological surveys on STEC are necessary.

Isolation of acriflavine resistant Erysipelothrix rhusiopathiae from slaughter pigs in Japan

Erysipelothrix rhusiopathiae is the causative agent of swine erysipelas. Although an attenuated vaccine is used in Japan, recent increases in disease occurrence have cast doubts on its efficacy. We investigated the similarity between the vaccine strain and E. rhusiopathiae field isolates by the analysis of acriflavine resistance (the vaccine strain marker), serotype, DNA fingerprinting and pathogenicity to mice. Although 7 acriflavine resistant E. rhusiopathiae isolates were separated from arthritic lesions of slaughter pigs, we were unable to prove that they were identical to the vaccine strain.

Properties of repeat domain found in a novel protective antigen, SpaA, of Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae is a small gram-positive rod bacterium that causes erysipelas in swine and a variety of diseases in other animals and humans. Although live-attenuated or bacterin vaccines are effective in protecting against erysipelas, the genetic construction of their active antigen has not been identified. To clarify the surface antigen(s) involved in protective and arthritic response, using monoclonal antibody I2A against the surface proteins of E. rhusiopathiae, we identified a protective antigen, which consists of 606 amino acids. Analysis of deletion derivatives of the gene, spaA(surface protective antigen), showed that the SpaA protein binds tightly to the bacterial cell surface via eight repeat units with a GW-module consisting of 20 amino acids at the C-terminus. Although DeltaSpaA lacking their repeat units lost its ability to induce protection against E. rhusiopathiae infection, intact SpaA protein showed the protection. We conclude that the presence of repeat units is essential both for the binding of SpaA to the bacterial cell surface and for protection. We believe that the repeat region at the C-terminus should be a candidate for a subunit vaccine against erysipelas.

[Enterohemorrhagic Escherichia coli O157 outbreak in Obihiro-City--study on antibiotic susceptivity and plasmid profiles]

The drug-resistance patterns and plasmid profiles of 147 isolates (patient origin 142 and food origin 5 isolates) from the outbreak of enterohemorrhagic Escherichia coli (EHEC) O157:H7 infection in Obihiro-city Hokkaido in late October, 1996, were examined. Thirty-six isolates were resistant to tetracycline (TC) (24.5%), 15 of which were resistant to both streptomycin and TC. The minimal growth inhibitory concentration (MIC) of fosfomycine (FOM) was examined, confirming that MIC changed by the cultivation conditions, that is 12.5 micrograms/ml at the aerobic condition, 1.6 micrograms/ml at the anaerobic condition and 3.2 micrograms/ml on blood agar plates. Furthermore, though E. coli O157 could not be detected once by the FOM medication, FOM sensitivity of the patient origin O157 isolates who became O157-positive again was examined. Any changes in FOM sensitivity were not observed. Plasmid profiles of all isolates were divided by 4 patterns from A to D. The most dominant pattern was type A, and plasmid profiles of food origin O157 belonged to pattern A. In 9 examples of the person-to-person infection in the family, plasmid patterns of O157 isolates were the same to each other, even though drug-resistant patterns were different. In 13 patients developing the duration of excretion of EHEC, the changes of the drug-resistance patterns were correlated with the changes of plasmid profiles. By comparing plasmid profiles and TC resistance, it was suggested that TC resistance was controlled on a plasmid. Since food origin O157 isolates were sensitive to all drugs and presenting the same plasmid profiles, demonstrating that TC resistance and plasmid are newly added to the bacterial cells while food origin O157 isolates passe inside the human body.

[Enterohemorrhagic Escherichia coli O157 outbreak in Obihiro-city--biological and molecular characteristics among O157 isolates]

The outbreak of enterohaemorrhagic Escherichia coli (EHEC) O157:H7 infection in Obihiro City, Japan, occurred in late October 1996. The infection affected a total of 169 kindergarten pupils and school staff members in a private kindergarten. Twenty-one children (12.4%) progressed into hemolytic uremic syndrome (HUS). Moreover, the person-to-person infections in 9 families and the duration of excretion of EHEC in 13 patients were observed. The contaminated food was identified as the potato-salad served at lunch. Analysis of biological characteristics, the ability of toxin production, and the DNA analysis by PCR-based fingerprinting, the RAPD tests, among all clinical isolates, clarified a homologous origin of contamination.

The distribution of G and P types within isolates of bovine rotavirus in Japan

Various combinations of G type and P type were observed in 76 bovine rotavirus (BRV) strains isolated from 235 diarrheal calves in three prefectures of Japan in 1992-1994. The most prevalent combination was G6:P5 (46/76, 60.5%), followed by G10:P11 (13/76, 17.1%), G6:P11 (7/76, 9.2%) and G10:P5 (5/76, 6.6%). No G6:P1 strain of BRV was recognized from the isolates in the present study, though this type of BRV is well known as a suitable vaccine strain against BRV infection.

Antigenic and genetic analyses of the hemagglutinin of influenza viruses isolated from pigs in 1993

Three strains of influenza A virus (H3N2) were isolated from pigs in Hokkaido, Japan in 1993. The hemagglutinin (HA) antigen of the three isolates was related to that of recent H3N2 viruses of human origin. The reactivity patterns of two of the isolates (A/sw/Obihiro/1/93 and A/sw/Obihiro/2/93) with monoclonal antibodies to the hemagglutinin of A/Bangkok/1/79 strain were similar to that of the human H3N2 strain isolated in Hokkaido in 1988, while that of the other one (A/sw/Obihiro/3/93) was similar to human H3N2 strains of 1993. In the phylogenetic analysis based on the nucleotide sequences of the HA1 regions, the HA genes of the two isolates were shown to be closely related to those of human H3N2 viruses isolated between 1986 and 1988. The remaining one isolate was shown to be closely related to those of current human H3N2 viruses. We have also found serological evidence that the A/sw/Obihiro/1/93 virus is circulating extensively in Obihiro swine. It is clear from these findings that pigs were infected with the recent H3N2 influenza virus during the human epidemic and that the virus has been maintained in pigs for at least five years.

Prevalence of antibodies to type A influenza viruses in swine sera 1990-1994

A total of 3,120 swine sera collected for the years 1990-94 were tested for the presence of hemagglutination-inhibition (HI) antibodies against swine (H1N1) and human (H1N1 and H3N2) strains of influenza virus. No HI antibody against the swine strains was recognized during 18 months, though a slight prevalence (1.5-9.2%) of the antibodies was observed over the entire period. A wide variance in the incidence (0-26.3%) of antibodies against the human H3N2 strains was observed among the swine population.

Persistence of a single electropherotype and serotype (G6P5) of bovine rotavirus in calves on a closed dairy farm from 1990 to 1993

A virologic survey was conducted on calves with diarrhea associated with bovine rotavirus (BRV) on a closed dairy farm. The BRV was detected from 32 of 219 (14.6%) fecal specimens repeatedly collected from 56 calves born during the years 1992-1993, regardless of whether they had diarrhea. Most of the 32 strains were isolated from fecal specimens obtained from 2- to 6-week-old calves. After electrophoresis of double-stranded viral RNA from the 32 strains, genomic RNA migration patterns were similar to those of the predominant BRV strains isolated at the same farm during the years 1990-1991. All representative strains were identified as G serotype 6 (G6) and P type 5 (P5) by results of the virus-neutralization test and polymerase chain reaction procedure. Thus, BRV had no change in genomic RNA electropherotypes and serologic antigenicities in a closed dairy herd over a period of several years.

Antigenic and genetic characteristics of H1N1 human influenza virus isolated from pigs in Japan

Two strains of influenza A virus were isolated from pigs in northern Japan in 1992. Serological tests showed that the haemagglutinin (HA) and neuraminidase (NA) antigens were more closely related to those of recent human H1N1 viruses than to those of swine H1N1 viruses. The HA and NA genes of isolate A/sw/Obihiro/5/92 were shown to be closely related to those of current human H1N1 viruses. Evolutionary trees constructed from nucleotide sequences showed that the HA and NA genes of A/sw/Obihiro/5/92 were apparently on a branch cluster containing human strains isolated between 1990 and 1992.

CD8+ T lymphocytes are the major cell population involved in the early gamma interferon response and resistance to acute primary Toxoplasma gondii infection in mice

Gamma interferon (IFN-gamma) is known to be a major mediator influencing host defense against Toxoplasma (T.) gondii. To evaluate lymphocyte populations involved in this cytokine-mediated early resistance to T. gondii, the effects of in vivo administration of monoclonal antibodies (MAbs) against T-cell subsets and anti-asialo GM1 antibody on the course of infection and IFN-gamma response were investigated in mice infected acutely with this parasitic protozoan. A single injection of anti-CD8 MAb on day -1 or day 4 severely exacerbated the infection, in accordance with a marked suppression of endogenous IFN-gamma production. Moreover, the administration of anti-IFN-gamma MAb on day 0 but not later than day 4 resulted in a total abrogation of resistance to T. gondii, suggesting that endogenous IFN-gamma produced during the first several days of infection is critical for the generation of antitoxoplasmal resistance in mice. In contrast, no significant increase in mortality was observed when injected with either anti-CD4 MAb or anti-asialo GM1 antibody on day -1, while these antibodies reduced significantly the ability of mice to produce IFN-gamma. Indeed, simultaneous depletion of CD4+ and CD8+ cells had no greater suppressive effect on host defense and endogenous IFN-gamma production than depletion of CD8+ cells alone. Together, these results suggest that CD8+ T cells play a central role for resolution of acute toxoplasmosis by participating in endogenous IFN-gamma production. The possible role of early produced IFN-gamma in the development of protective immune response to T. gondii is also discussed.

Interferon-gamma production of mitogen stimulated peripheral lymphocytes in perinatal cows

The production of interferon-gamma (IFN-gamma) in bovine peripheral blood mononuclear cells (PBMC) during the perinatal period was studied. IFN-gamma activity was neutralized with monoclonal antibodies (MoAb) to recombinant bovine IFN-gamma. IFN-gamma production was apparently suppressed by treatment of the PBMC with MoAb to bovine pan-T cell. IFN-gamma was more susceptible to treatment with MoAb to CD4+ than that with MoAb to bovine CD8+, suggesting that the CD4+ T-cell subset was the major producer of the lymphokine formed in the culture. IFN-gamma production by concanavalin A (Con A) stimulation was found to be significantly depressed throughout the perinatal period (from 5 weeks before to 7 weeks after parturition) when compared to that of the non-pregnant control group, but phytohemagglutinin (PHA)-induced IFN-gamma production was markedly depressed from 3 weeks before to 2 weeks after calving. The addition of recombinant human interleukin 2 (100 IU/ml) to the PBMC cultures from perinatal cows resulted in the augmentation of IFN-gamma production by stimulation with Con A or PHA.

Importance of early gamma interferon production in Propionibacterium acnes-induced resistance to Toxoplasma gondii infection in mice

Treatment of mice with heat-killed Propionibacterium (P.) acnes conferred transient protection against Toxoplasma infection. To investigate the mechanism of this nonspecific resistance, the production of gamma interferon (IFN-gamma) by P. acnes-injected mice was evaluated in comparison with that by noninjected controls upon infection with Toxoplasma. Mice pretreated with this bacterium produced significantly more IFN-gamma than that produced by control mice up to 24 hr of infection. A single injection of anti-IFN-gamma MAb on day 0 but not later than day 3 of infection resulted in a total abrogation of the resistance conferred by P. acnes. Likewise, daily injection of cyclosporin A (Cs-A), a potent inhibitor of T cell function, during the first 3 days of Toxoplasma infection severely exacerbated the infection, in accordance with a marked suppression of the early IFN-gamma production. In contrast, the administration of Cs-A for 3 consecutive days starting at day 4 had no significant consequence on P. acnes-induced anti-toxoplasma resistance, while it reduced greatly the ability of P. acnes-injected mice to produce IFN-gamma in the later phase of infection. Moreover, no significant increase in mortality and suppression of IFN-gamma production was noted in mice receiving anti-asialo GM1 antibody. These results suggest that the early IFN-gamma production by T cells is an essential event for the establishment of P. acnes-induced anti-toxoplasma resistance in mice.

Characterization of a G14 equine rotavirus (strain CH3) isolated in Japan

Antigenic and genomic properties of equine rotavirus strain CH3 isolated in Japan were studied by cross-neutralization tests and nucleotide sequence determination of the VP4 and VP7 genes. It was shown that the strain CH3 belongs to G14 and shares VP4 genotype with strain H2.

Preventive administration of bovine colostral immunoglobulins for foal diarrhea with rotavirus

Foal diarrhea due to serotype 3 rotavirus broke out on a foal-raising farm in the years 1987 and 1989. In 1989, all of the foals, regardless of whether or not they suffered from diarrhea, received bovine colostral immunoglobulin (Ig) powder orally for 3 to 5 days during the epidemic. The morbidity of the diarrhea was lower than that observed in 1987, when the Ig powder was not administered to foals. These data suggested that the administration of Ig powder might partially prevent foal diarrhea with rotavirus infection.

A minor prevalent strain in a severe outbreak of foal diarrhea associated with serotype 3 rotavirus

An epizootic of foal diarrhea due to serotype 3 rotavirus (RV) was observed in 89 of 168 cases (53%) during the period from March to July in 1987. A total of 51 strains of RV were isolated from the 62 diarrheal feces examined, and one isolate (CH-3) showed a unique electropherotype of viral RNA which differed from the others that widely prevailed on this farm. No positive reaction was observed between strain CH-3 and each of the antisera against serotypes 1 to 12 of human and animal RV in neutralization tests. However, dsRNAs of the CH-3 virus were hybridized with a probe prepared from a strain of equine serotype 3 RV.

Enhancement by recombinant human interleukin 2 of host resistance to Toxoplasma gondii infection in pregnant mice

The lymphokine production by pregnant mice infected with a lethal dose of Toxoplasma gondii was evaluated in comparison with that by virgin mice infected with a sublethal dose of this protozoan parasite. Splenocytes taken from mice before and on the day after infection produced considerable amounts of IL-2 in response to concanavalin A (Con A) stimulation, but the titers rapidly declined in both pregnant and virgin mice as infection progressed. A trace amount or undetectable level of IL-2 was produced by splenocytes from acutely infected mice when stimulated with Toxoplasma lysate antigen (TLA). In contrast to the kinetics of IL-2 production, the levels of IFN-gamma produced by splenocytes cultured with Con A or TLA increased steadily in the later stage of infection in both pregnant and virgin mice. Thus, the response to Con A or TLA of splenocytes to produce IL-2 and IFN-gamma differed strikingly in acute toxoplasmosis in mice. The administration of rHuIL-2 resulted in a significant decrease in the mortality of pregnant mice infected with a lethal dose of Toxoplasma. The combination of rHuIL-2 and rMuIFN-gamma increased the survival rate slightly but not significantly compared with pregnant mice receiving either rHuIL-2 or rMuIFN-gamma. Moreover, exogenously administered rHuIL-2 enhanced the production of both IFN-alpha and IFN-gamma in the bloodstreams of pregnant mice, in accordance with the decreased mortality. These results indicate that IL-2 may play a significant role in modulating the host defense against Toxoplasma infection in pregnant mice.

Establishment of an antitoxoplasma state by stable expression of mouse indoleamine 2,3-dioxygenase

Indoleamine 2,3-dioxygenase (IDO), a tryptophan-degrading enzyme, is inducible by various interferons (IFNs). IDO-mediated tryptophan degradation, but not the formation of IDO-catalyzed tryptophan metabolites, has been suggested as a mechanism for the antiparasitic action of IFN-gamma. To determine whether the IFN-gamma-induced IDO alone is sufficient for establishing the antiparasitic state, we constructed a mouse IDO expression plasmid containing a heavy metal-responsive metallothionein promoter and obtained a stable transformant (C6) by transfection of this plasmid into mouse rectal cancer (CMT-93) cells. In the presence of 100 microM ZnSO4, C6 cells yielded a high level of IDO; and after a 2-day culture period, the enzyme induction resulted in complete depletion of tryptophan from the culture medium. Under these conditions, the growth of Toxoplasma gondii in C6 cells infected with the organisms on day 3 after enzyme induction was completely blocked. In the absence of ZnSO4, however, IDO induction was negligible in C6 cells, and T. gondii continued to grow. Furthermore, in a transformant (CC10) carrying an antisense mouse IDO plasmid or in parental CMT-93 cells, IDO was not induced at all even in the presence of 100 microM ZnSO4, and T. gondii continued to grow in these cells as well. These results taken together indicate that complete depletion of tryptophan from the culture by IDO alone is sufficient to establish the antitoxoplasma state in mouse cells.

Antibody responses of Japanese horses to influenza viruses in the past few years

A total of 305 horse sera collected in the Hidaka district of Hokkaido in the years 1988-90 were tested for the presence of hemagglutination-inhibition (HI) antibodies to A/equine/Newmarket/1/77 (H7N7), A/equine/Tokyo/2/71 (H3N8) and A/equine/Kentucky/1/81 (H3N8, Kentucky) strains of equine influenza (EI) virus. Antibodies to the 3 strains were detected in hardly of the 45 sera from 2-years-old horses which were collected before vaccination. Many of the 51 horses, after vaccination with inactivated EI virus, had HI antibodies to the 3 strains in 37 to 88 per cent. However, the number of positive reactors among the horses aged 3 to 23 years gradually decreased with the advance in age. In particular, no antibody response was found in the 60 horses over 9 years of age, except for 3 cases with HI antibody of low titer, with the Kentucky strain which has recently been prevalent among the horse populations in many countries. In a complement-fixing test, antibodies to the soluble antigen of type A influenza virus were detected in the sera collected from the horses which were exposed to an outbreak of EI virus infection, but not in the sera from the vaccinated horses examined.

Correlation between increased susceptibility to primary Toxoplasma gondii infection and depressed production of gamma interferon in pregnant mice

To explore a possible mechanism of pregnancy-associated suppression of T cell-mediated immunity to Toxoplasma gondii, acquired resistance and gamma interferone (IFN-gamma) production in pregnant mice were compared with those in virgin mice after infection with the S-273 strain of this protozoan parasite. The 50% lethal dose of this strain was less than 200 tachyzoites for pregnant mice and 2,800 organisms for virgin controls. Toxoplasma-induced production of both IFN-alpha and IFN-gamma in the bloodstream of pregnant mice was significantly depressed as compared with that in virgin controls. The administration of recombinant murine IFN-gamma (rMuIFN-gamma) resulted in a significant decrease of mortality and parasitic growth in the organs of pregnant mice infected with a lethal dose of S-273 strain tachyzoites. Thus, the impairment of T cell-mediated immune responses was evident in pregnant mice from the impaired IFN-gamma-generating capacity and poor survival rate after primary infection with Toxoplasma. When mice with chronic Toxoplasma infection were injected with specific antigen, the resultant production of IFN-gamma was also significantly suppressed during pregnancy. However, there was no direct correlation between the serum levels of IFN-gamma and susceptibility to reinfection, since the mortality rate of chronically infected pregnant mice after the challenge with the high virulent RH strain was not significantly higher than that of virgin controls.