Toxic epidermal necrolysis with tracheobronchial and pulmonary complications

A 55-year-old man developed multiple erythematous skin lesions after surgery for acoustic neurinoma. Necrosis and detachment of the epidermis developed and a diagnosis of toxic epidermal necrolysis (TEN) was made. Progressive dyspnea was evident two days after the onset of the skin lesions. Chest X-ray revealed diffuse interstitial shadows in both lung fields. On bronchoscopic examination, erosion, vesicle formation, necrosis and desquamation of the epidermis were seen in the tracheobronchial mucosa. Therapy, including prednisolone, improved the skin lesions as well as the chest X-ray and bronchoscopic findings. Tracheobronchial and pulmonary lesions were followed before, during and after treatment of TEN.

[Pharmacokinetics of paclitaxel in experimental animals. Part 2. Tissue distribution]

In S 180 bearing male mice, paclitaxel was rapidly distributed to various tissues within 10 minutes. The highest AUC was seen in the liver, and relatively high in the pancreas, kidney, thymus, intestine, stomach and lung. The concentration of paclitaxel in tumor tissue was not so high early time after administration, but was sustained for a long time with a half life of 12.3 hr. Elimination from the testis and thymus was also slow. The drug level in the brain was very low. In M 109 bearing female CDF1 mice, the distribution and elimination profile of paclitaxel was comparable to that in S 180 mice. The concentration of paclitaxel in the ovary, lung and uterus decreased slowly. In M 109 tumor, which was very sensitive to paclitaxel, the drug had a higher and long lasting distribution compared with S 180 tumor. In S 180 tumor bearing mice pretreated with CCl4, the paclitaxel level was found to be lower in the liver and higher in the other tissues including tumor, plasma, urine and bile than in non-treated mice.

[Pharmacokinetics of paclitaxel in experimental animals. Part 1. Blood level]

The plasma disposition of paclitaxel in rabbits (7 mg/kg, 1 h i.v. inf.) was biphasic with half-lives of 0.36 and 6.36 h, and AUC was 9.46 micrograms.hr/ml. K12 value was larger than K21 and V2 was larger than V1, suggesting that paclitaxel had a favorable distribution profile in tissues. In S 180 bearing male ICR mice (30 mg/kg, i.v. bolus), the biphasic plasma disposition was also observed. The half-lives and AUC were 0.25 h, 2.23 h and 117.93 micrograms.hr/ml. Paclitaxel distributed widely in plasma rather than blood cells. The biliary level of paclitaxel in the enlarged gallbladder of ICR mice was markedly high, about 10-fold higher than the urinary level and 100-fold higher than the plasma level. The bioavailability with oral administration to ICR mice was poor. AUC(oral)/AUC(i.v.) ratio in the bile, liver, tumor and plasma was 18.91, 6.71, 0.83 and 0.45%, respectively.

Regulation of beta-globin mRNA accumulation by heme in dimethyl sulfoxide (DMSO)-sensitive and DMSO-resistant murine erythroleukemia cells

The level of mRNA encoding beta-globin was examined in dimethyl sulfoxide (DMSO)-sensitive (DS), and DMSO-resistant (DR) murine erythroleukemia (MEL) cells. DR cells lack erythroid-specific delta-aminolevulinate (ALA) synthase (AL-AS-E), and fail to undergo erythroid differentiation following treatment with DMSO. Treatment of cells with DMSO markedly increased ALAS-E mRNA in DS cells, while the same treatment downregulated the nonspecific ALA synthase (ALAS-N) mRNA levels in both DS and DR cells. The levels of beta-globin mRNA, heme content, and hemoglobin in DS cells increased, while those in DR cells decreased following treatment with DMSO. Treatment of DR cells with hemin caused an increase in beta-globin mRNA and hemoglobin, and partially restored the DMSO-mediated suppression of beta-globin mRNA and hemoglobin synthesis. DMSO treatment decreased heme oxygenase (HO) mRNA in hemin-treated DS cells, but not in hemin-treated DR cells. These findings indicate that heme is necessary for accumulation of the beta-globin transcript during erythroid differentiation, and that hemin-mediated HO induction becomes markedly downregulated in differentiated erythroid cells, presumably because less free heme is available for HO induction by a greater demand for the synthesis of hemoglobin.

Tetanus toxin and Clostridium perfringens enterotoxin as tools for the study of exocytosis

The role of calmodulin in exocytotic secretion was studied using digitonin-permeabilized bovine adrenal chromaffin cells to examine the effect of calmodulin directly introduced into the cells and using tetanus toxin as a specific inhibitor of exocytotic secretion. Addition of calmodulin to the permeabilized cells increased Ca(2+)-dependent norepinephrine release in a dose-dependent manner. The enhancement of release by calmodulin was specific to calmodulin: bovine serum albumin, actin, and caldesmon had no such effect. Enhancement of release by calmodulin occurred at Ca2+ concentrations of more than 10(-6) M and increased with an increase of Mg2+ concentration. The release of norepinephrine enhanced by calmodulin was inhibited by tetanus toxin. These results indicate directly that calmodulin plays an important role in exocytotic secretion from chromaffin cells. Exocytosis is known to occur by fusion of plasma membrane with limiting membranes of secretory vesicles following an increase in intracellular Ca2+. We used the enterotoxin of Clostridium perfringens type A as a specific tool to modify plasma membrane permeability to induce calcium influx. Multigranular exocytosis was recognized electron-microscopically in addition to the single-granular exocytosis in rat anterior pituitary cells and pancreatic acinar cells treated with the enterotoxin in the presence of extracellular Ca2+. The treatment with the enterotoxin did not induce any drastic change in the fine membrane structures of both types of cells. The enterotoxin-treated anterior pituitary cells and pancreatic acinar cells should provide a useful system for studying the molecular mechanism of fusion of membranes in exocytosis.

Cold agglutinin disease following allogeneic bone marrow transplantation

We describe a case of cold agglutinin disease (CAD) following allogeneic bone marrow transplantation. This 36-year-old male developed CAD 3 weeks after allogeneic bone marrow transplantation for chronic myelogenous leukemia. Cyclosporin A and methotrexate had been administered to prevent graft-versus-host disease. Other agents administered included cytomegalovirus hyperimmune globulin and recombinant human G-CSF. Pericarditis preceded the development of CAD. The characterization of cold agglutinin (CA) was monoclonal IgM-kappa with anti-Pr antigen specificity, probably derived from the engrafted donor lymphocytes. The administration of prednisolone led to transient improvement. The CA titer decreased without further treatment 12 weeks after transplant.

First isolation of a rickettsia closely related to Japanese spotted fever pathogen from a tick in Japan

In May 1993, we collected unfed ticks in Anan, Tokushima Prefecture, Shikoku District, Japan, a highly endemic area of Japanese spotted fever (JSF). We isolated JSF rickettsiae from these ticks by inoculating tick-emulsions into L-929 cells. Of the four genera and seven species of ticks examined, only one larva of Dermacentor taiwanensis Sugimoto yielded a rickettsial isolate. The isolate (DT-1 strain) was found to belong to the serotype common to the causative agent of JSF. This was based on its specific reactivity to mouse antisera and to a monoclonal antibody to JSF rickettsiae from the Shikoku District. This is the first tick-borne spotted fever group of rickettsia isolated in Japan. However, all stages of D. taiwanensis infrequently parasitize humans. Some ticks in the genus Haemaphysalis commonly infest humans and are frequently found to be rickettsia-positive in the hemolymph test when using the monoclonal antibody mentioned above. Therefore, the vectors of JSF rickettsiae to humans may be a complex of tick species.

Resolution properties of a 2048 x 2048 matrix image intensifier-TV based digital radiography system

Spatial resolution properties of a 2048 x 2048 matrix image intensifier (II) TV based real-time digital radiography (DR) system were investigated. The presampling modulation transfer function (MTF), which includes the unsharpness of the detector and the blurring effect of the sampling aperture, was measured by a slit method. Also determined was the limiting resolution using a bar pattern. It was found that, the spatial resolution in this system is substantially improved relative to previous II-TV based DR systems, and is comparable or even superior to that in a computed radiography system depending on the imaging plate employed. However, the presampling MTF for 2048 x 2048 matrix is comparable to that for 1024 x 1024 matrix in this DR system, because the same sampling aperture is assumed to be used for both matrices. Even under these conditions obtained the improved clinical image since the Nyquist frequency is doubled for 2048 x 2048 matrix. It should be noted that the resolution property in the II-TV based DR system depends on the signal current from the TV image pickup tube (level of image pixel value) and also on the size of the iris in the TV lens. We must pay attention to these parameters when acquiring clinical images and evaluating the resolution properties. Finally, it was demonstrated that smaller focus than that used in a screen-film system can be employed in the DR system due to its high sensitivity, so the geometric unsharpness can be reduced. Therefore, the image resolution of our system was found to be superior to a screen-film system at some geometric magnification factors.

Lymph node metastasis and recurrence in patients with a carcinoma of the thoracic esophagus who underwent three-field dissection

The indication, efficacy, and extent of extended lymphadenectomy for a carcinoma in the thoracic esophagus remain controversial and under clinical investigation. Here we report the frequency and mode of lymph node metastasis at operation and of lymph node recurrence after operation in 70 patients who underwent three-field dissection and 75.7% of whom suffered from metastasis or recurrence in the lymph nodes (metastasis in 71.4% and recurrence in 21.4%). Metastasis or recurrence in the cervical and cervicothoracic nodes were found in 18.6% and 41.4%, respectively. The frequency of cervical and cervicothoracic lymph node metastasis or recurrence was, respectively, 40.0% and 90.0% for a carcinoma in the upper thoracic esophagus, 21.6% and 37.8% for a carcinoma in the middle thoracic esophagus, and 4.3% and 26.1% for a carcinoma in the lower thoracic esophagus. Lymph node metastasis at operation was most frequently found in the right recurrent nerve nodes, right paracardiac nodes, periesophageal nodes, and lesser curvature nodes, whereas lymph node recurrence after operation was found in the left upper recurrent nerve nodes and the right supraclavicular, celiac, and abdominal paraaortic nodes. Metastasis or recurrence was rarely found in the internal jugular, pretracheal, greater curvature, common hepatic, or splenic nodes. This finding suggests the need for recurrent nerve node dissection for all cases and for three-field dissection for a carcinoma in the upper or middle thoracic esophagus.

A possible mechanism for vascular endothelial cell injury elicited by activated leukocytes: a significant involvement of adhesion molecules, CD11/CD18, and ICAM-1

To clarify the mechanism of vascular endothelial cell injury induced by activated leukocytes, we investigated the intracellular peroxide level in endothelial cells and the effect of antibodies against adhesion molecules on it. The change in the intracellular peroxide level was measured using the fluorescence of 2,7-dichlorofluorescein diacetate. The fluorescence intensity of the endothelial cells exposed to PMA-stimulated leukocytes increased with time up to 15 min, although neither PMA alone nor unstimulated leukocytes alone showed such increase at all. When catalase, which degrades hydrogen peroxide produced by leukocytes, was added to this system, the peroxide level in endothelial cells decreased significantly. On the other hand, pretreatment of endothelial cells with allopurinol, a specific inhibitor of xanthine oxidase, also caused significant inhibition of the increase in peroxide level in the endothelial cells. The monoclonal antibodies against CD11a, CD11b, CD18, and ICAM-1 showed almost complete inhibition of the increase in intracellular peroxide levels of the endothelial cells exposed to PMA-stimulated leukocytes. In contrast, the anti-CD11c antibody could not block the increase in fluorescence intensity due to peroxides. The endothelial injury elicited by activated leukocytes was partially inhibited by catalase alone (approximately 40%) and allopurinol alone (approximately 60%), but it was completely inhibited by the concomitant treatment of endothelial cells with catalase and allopurinol. The specific antibodies against such adhesion molecules as ICAM-1 and CD11/CD18 except CD11c/CD18 also blocked the endothelial cell injury significantly. These data suggest that there is a good correlation between the early increase in intracellular peroxides and endothelial cell injury elicited by PMA-stimulated leukocytes and that the adhesion of activated leukocytes to endothelial cells via CD11a/CD18-ICAM-1 must be deeply involved in these phenomena.

A prediction of hospital mortality after surgical treatment for esophageal cancer

A series of 100 patients with thoracic esophageal cancer who underwent subtotal esophagectomy through a right thoracotomy between 1986 and 1989, were statistically analyzed to assess the risk factors predicting hospital mortality from complications. Hospital mortality was termed as "complication death", and the analyzed factors were age, pulmonary function [% vital capacity (%VC) or % forced expiratory volume1.0 (%FEV1.0)], cardiac function [ECG and Master test], renal function [creatinine clearance (CCR)], hepatic function [15' indocyanine green test (R15.ICG)], diabetes mellitus [75 g oral glucose tolerance test (75OGTT)], depth of tumor invasion [T-factor], and the type of operative procedure [operation]. Each patient was scored according to risk severity on a scale from 0-3, with the higher numbers representing higher risk. Patients not succumbing to complication death had less than 8 points in the total score, while those who suffered a complication death had 8 or more points. Through stepwise logistic regression analysis, we produced a prediction formula. In cases where eight or more points are scored by the semi-quantitative analysis, or 0 or more, by the prediction formula, the operative procedure should be changed to a less radical one for improved prognosis. The introduction of this semi-quantitative analysis for postoperative risk reduced the incidence of complication death from 6% to 3%, and of hospital mortality from 13% to 3%.

Plasmin converts pro-form of group I phospholipase A2 into receptor binding, active forms

Treatment of zymogen of pancreatic-type group I phospholipase A2 (PLA2-I) by plasmin, a fibrinolytic enzyme, increases PLA2 activity as well as receptor binding activity in a dose- and time-dependent manner. Separation of plasmin-treated pro-PLA2-I by HPLC and amino acid sequence analysis of the products revealed that, in addition to an authentic mature PLA2-I produced by trypsin, plasmin produced active products which had been modified in the C-terminal region. Thus, PLA2-I may be involved in physiologic processes which accompany the formation of plasmin.

[Malignant lymphoma with various neuropsychological symptoms]

A case of malignant lymphoma presented with various neuropsychological symptoms which made it difficult to achieve the diagnosis and therapy. A 9-year-old boy was referred to our hospital with complaints of psychological symptoms, impairment of consciousness and generalized convulsive seizures. A lumbar puncture revealed infiltration of numerous blasts which were positive for immature B cell markers. CT scan showed a mass in the right ethmoidal sinus, but no space occupying lesion in the brain. The tumor cells in the right ethmoidal sinus had the same phenotypes as those in the CSF. Thus a diagnosis of non-Hodgkin's lymphoma, developing in the right ethmoidal sinus and infiltrating into the central nervous system, was established. The blast cells in the liquor and the tumor of the right ethmoidal sinus disappeared after induction of systemic chemotherapy, irradiation and intrathecal chemotherapy. However, intracranial bleeding occurred during the chemotherapy. He died of respiratory failure 10 months after the start of treatment.

Methionine PET for follow-up of radiation therapy of primary lymphoma of the brain

Positron emission tomography (PET) with carbon-11 methionine, computed tomography (CT), and magnetic resonance (MR) imaging were performed in 10 patients with histologically verified central nervous system (CNS) lymphoma before and after radiation therapy to compare the radiologic findings and to evaluate the usefulness of PET in monitoring tumor response to radiation therapy. Methionine PET clearly depicted CNS lymphoma before radiation therapy as an increased accumulation of C-11 methionine. The extent of increased accumulation of the radiotracer in tumor tissue markedly decreased after radiation therapy. The area of increased uptake was larger than the enhancing lesions on CT or MR images in most cases. One patient was confirmed to have tumor recurrence at the region of residual increased accumulation on methionine PET images. Methionine PET is useful for the delineation of CNS lymphoma and for monitoring the therapeutic effect of irradiation.

Slow hemodialysis performed during the day in managing renal failure in critically ill patients

Slow hemodialysis (HD) was performed for 10 h during the day in 11 critically ill patients with renal failure. The dialysis method was a modification of the pump-driven continuous venovenous HD. A nonsterile bicarbonate-containing hemodialysate was passed into the EVAL membrane dialyzer at a flow rate of 30 ml/min. No patient developed further hemodynamic instability during the treatment. The serum urea level was maintained below 20 mmol/l within 4 days of initiating the treatment. It allowed the patients to rest without interruption at night. This method was safely conducted by general nursing staff under the supervision of nephrologists on duty during the day. This schedule offers an approach to renal replacement therapy for hemodynamically unstable patients without any potential problem in the extracorporeal circulation at night.

Factors affecting leakage following esophageal anastomosis

Esophageal anastomotic leaks remain the most serious problem following extirpative procedures for esophageal carcinoma. We conducted a retrospective analysis of 352 patients with carcinoma in the thoracic esophagus who had undergone esophageal anastomosis following esophagectomy at the Kurume University Hospital between 1981 and 1990. Of these, 94 patients (27%) developed anastomotic leaks, and out of this subgroup, 21 (6%) died as a direct result of the leak. A further 20 patients (6%) underwent repair of the leak, after which they were able to tolerate oral intake. The anastomotic leak healed spontaneously in the other 53 patients (15%). The risk factors predisposing to leaks from esophageal anastomoses were determined as: (1) the anastomosis being performed via a retrosternal or subcutaneous route as opposed to an intrathoracic route, (2) the use of colonic interposition as opposed to a gastric pedicle, (3) performing a manual anastomosis as opposed to a mechanical anastomosis, and (4) employing an end-to-end anastomosis, as opposed to an end-to-side anastomosis, using a mechanical method. By introducing an anastomotic stapling device, a microvascular technique, a staged operation based on the preoperative risk analysis, and improvement in pre- and postoperative management, the incidence of anastomotic leakage could be decreased from 35% to 14%, and that of consequent hospital mortality, from 9% to 2%.

O6-alkylguanine-DNA alkyltransferase activity of human malignant glioma and its clinical implications

Activity of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) is an important determinant of responsiveness of tumor cells to chloroethylnitrosoureas (CENUs), representative chemotherapeutic agents for primary malignant gliomas. In order to assess the real states of this repair protein in human malignant gliomas, we assayed AGT activity in surgically extirpated 42 malignant glioma samples and studied the distribution of the activity under certain clinical conditions. There were wide variations in AGT activity between individuals. No significant difference in AGT activity on average was seen either between glioblastoma and anaplastic astrocytoma, nor between primary and recurrent tumors. Among 42 malignant gliomas, 7 samples (16.7%) had low AGT activity less than 0.1 pmoles/mg protein. In the case of glioblastoma, tumors possessing higher AGT activity tended to be less responsive to post-operation remission-induction therapy including CENUs. The result of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) chemosensitivity assay by using the corresponding surgical specimens suggested a close relationship between cellular resistance to CENUs and AGT activity. It was found to be unlikely that a short term administration of CENUs had a significant effect on AGT activity of brain tumors in human body. We could detect a bit of definite evidences of the relevance of AGT to resistance to CENUs and need to conduct further investigations for other resistance factors.

Cerebral uptake of 99mTc-bicisate in patients with cerebrovascular disease in comparison with CBF and CMRO2 measured by positron emission tomography

The regional brain uptake of 99mTc-N,N'-(1,2-ethylenediyl)bis-L-cysteine diethyl ester (99mTc-bicisate) measured by single photon emission computed tomography (SPECT) was compared with the regional CBF and CMRO2 measured by positron emission tomography in patients with cerebrovascular disease. Nine patients with the diagnosis of cerebral ischemic disorders (n = 7) or cerebral hemorrhage (n = 2) were studied. 99mTc-Bicisate brain uptake correlated with CBF and CMRO2. However, 99mTc-bicisate uptake did not reflect CBF in the single lesion showing luxury perfusion, which seemed to resemble a CMRO2 image. Though quantitative analysis showed the nonlinear correspondence of 99mTc-bicisate brain uptake with CBF and CMRO2, this correspondence could be corrected into a more linear relationship using a correction factor. 99mTc-Bicisate washout from the brain had no correlation to CBF and CMRO2. This diffuse decreasing washout rate was approximately 15% during the first hour after injection. By using the lipophilic fraction of arterial blood and a linearized correction of 99mTc-bicisate SPECT images, the feasibility of obtaining a factor-related CBF and CMRO2 was suggested from our data. These results suggested that 99mTc-bicisate had good characteristics for routine clinical use with SPECT to display the brain function in patients with neurological disorders.

Fibronectin inhibits platelet aggregation independently of RGD sequence

Fibronectin binds to platelet membrane glycoprotein (GP) IIb-IIIa in Arg-Gly-Asp (RGD)-dependent and -independent manner. We have isolated and characterized the 29-kDa dispase fragment of fibronectin. Binding of 125I-fibronectin to thrombin-stimulated platelets was inhibited by the 29-kDa fragment and the GRGDSPA peptide with IC50 values of 1.5 +/- 0.4 and 8.1 +/- 0.9 microM, respectively. The NH2-terminal sequence of this fragment gave this result: Ala-Val-Thr-Thr-Ile-Pro-Ala-Pro-Thr-Asp. This established the position of this peptide within fibronectin as beginning with the residue tentatively designated 1597. Neither the RGDS sequence nor the RGD-independent binding domain of fibronectin (Bowditch, R. D., Halloran, C. E., Aota, S., Obara, M., Plow, E. F., Yamada, K. M., and Ginsberg, M. H. (1991) J. Biol. Chem. 266, 23323-23328) was contained in this fragment. The 29-kDa fragment inhibited ADP-induced aggregation of platelets and binding of fibrinogen to activated platelets. The fragment bound to immobilized GPIIb-IIIa. The 125I-labeled 29-kDa fragment directly bound to thrombin-stimulated platelets with 98,000 +/- 4,600 molecules/platelet (Kd = 4.6 +/- 0.5 x 10(-6) M). Direct binding was inhibited by the unlabeled 29-kDa fragment but was not blocked by either the GRGDSPA peptide or the monoclonal anti-GPIIb-IIIa antibody. These results indicate that the additional RGD-independent binding domain(s) to GPIIb-IIIa are present on fibronectin. This additional binding domain(s) on fibronectin may prevent thrombus formation by interfering with the interaction of fibrinogen with GPIIb-IIIa.

Computerized EEG and brain imaging studies in untreated schizophrenic patients: a report of seven cases

We undertook routine EEG, Z-map, CT and PET scans in seven acute untreated schizophrenics. Routine EEGs showed slower activity in only one case. However, the Z-map showed slower activity in all the cases. CT demonstrated brain atrophy in three of the cases, and PET revealed hypofrontality in two, right hypoparietality in four, and both conditions in one case. There was no relation between CT and PET or the Z-map. However, a significant increase in alpha 1 activity was demonstrated on the Z-map in cases who were found to be the parietal type on PET; this was not conspicuous in the frontal type on PET. Moreover, in three of the patients, the Z-map findings were similar to the lesion indicated on PET.

Haem is necessary for a continued increase in ferrochelatase mRNA in murine erythroleukaemia cells during erythroid differentiation

The level of mRNA encoding ferrochelatase (FeC) was examined in two murine erythroleukaemia (MEL) clones, DS and DR, a DMSO-sensitive, and a DMSO-resistant clone, respectively. DS cells undergo erythroid differentiation by DMSO treatment with a marked increase in haem synthesis, while DR cells fail to do so due to the lack of the erythroid-specific delta-aminolaevulinate synthase (ALAS-E). Both DS and DR cells showed an increase in the level of FeC mRNA within 18 h of DMSO treatment. The level of FeC mRNA in DR cells was then decreased, while that in DS cells continued to increase for 72 h. Treatment with haemin significantly increased FeC mRNA in DR cells. When cells were treated with both DMSO and haemin, the level of FeC mRNA in DR cells increased to a level comparable to that in DS cells. These findings suggest that the failure to maintain increased FeC mRNA DR cells after DMSO treatment may be due to a deficiency of haem in these cells.

The entry and intracellular multiplication of Francisella tularensis in cultured cells: its correlation with virulence in experimental mice

Five acriflavine agglutination test-positive (acf+) colonies and five negative (acf-) colonies were isolated from each of the four strains (Ebina, CMB2, N9, and Schu) of Francisella tularensis, and the correlation between the virulence in experimental mice and the entry and intracellular multiplication in cultured mouse fibroblast cells (L-929 cells) was examined. All of the acf- colonies derived from the Ebina and CMB2 strains were highly virulent in mice, readily entering and growing well in the cells, while all of the acf- colonies from N9 and Schu strains were of low virulence and neither entered nor grew in the cells effectively. On the other hand, regardless of their parent strains, the acf+ colonies were low virulent and most of those colonies did neither enter nor grow in L-929 cells. In addition, two acf- colonies, one from the N9 and the other from the Schu strain, gained virulence through several passages in mice, and in parallel, their entry and multiplication also improved. However, two acf+ colonies from the Ebina strain and one acf+ colony from the N9 strain showed a moderate degree of the entry and multiplication although they were all low virulent. The overall results indicate that the entry and multiplication in cells are important factors regulating the virulence of F. tularensis. The results also showed, however, that they were not sole factors to elucidate the virulence of the bacterium in mice.