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Biomedical subjects

J Fujii

Publications and source records attributed to J Fujii.

At least 73 records · Page 4Linked to original sources
PubMed1999

Brainstem mechanisms of autonomic dysfunction in encephalopathy-associated Shiga toxin 2 intoxication.

Acute encephalopathy is the major determinant of death in an early stage of Shiga toxin (Stx)-producing Escherichia coli infection. Rapid progress toward refractory hypotension and dysfunction of breathing implies autonomic center dysfunction of patients. To clarify whether autonomic dysfunction becomes an ultimate cause of death in Shiga toxemia, we injected purified Stx2 (20 microg/kg) intravenously into rabbits, and monitored changes in cardiovascular and respiratory function together with renal sympathetic nerve activity (RSNA) in the conscious state. After an approximately 24-hour silent (lag) period, all rabbits given Stx2 developed hemorrhagic diarrhea (25.7 +/- 1.1 hours) and limb paralysis (31.2 +/- 1.3 hours). This limb paralysis was observed initially in the hind legs, and then it gradually extended to the forelegs. After 23.2 +/- 2.3 hours, RSNA increased gradually, and arterial blood pressure was maintained within normal limits together with an increase in the maximum gain of baroreflex response. Severe hypotension developed within 34.8 +/- 2.2 hours, without any increase in heart rate; RSNA significantly increased by 39.5 +/- 0.9 hours. In the final stage, RSNA decreased concurrently with decreases in arterial blood pressure, heart rate, and baroreflex response, suggesting dysfunction of the baroreflex control system. Thereafter, all rabbits died within 47.8 +/- 1.2 hours after the intravenous Stx2 injection. Magnetic resonance imagings of the central nervous system (T2-weighted images) showed high-intensity areas in the dorsal two-thirds of the cervical spinal cord and brainstem 48 hours after Stx2 administration. These results show that the cause of death is circulatory failure caused by impairment of the cardiovascular center in the medulla. We believe that this animal model helps to clarify the mechanism of rapid progress to death of patients with Shiga toxin-producing E. coli infection.

Animals↗
PubMed1998

Specific detections of the early process of the glycation reaction by fructose and glucose in diabetic rat lens.

The glycation reaction by fructose, as well as that by glucose, in control and diabetic rat lens was analyzed by using antibodies which specifically recognize adducts of lysine with fructose and with glucose. Levels of fructose adducts in diabetic rat lens were 2.5 times that of the control, and correlated with sorbitol levels. This was mainly due to enhanced glycation of beta- and gamma-crystallins by fructose under diabetic conditions. These data suggest that glycation by fructose may also play a role in cataract formation under conditions of diabetes and aging.

Animals↗
PubMed1998

Immunological detection of fructated proteins in vitro and in vivo.

An antibody has been raised against fructated lysine in proteins by immunizing fructated lysine-conjugated ovalbumin in rabbits. The affinity-purified antibody specifically recognized proteins incubated with fructose but not with other reducing sugars such as glucose, galactose or ribose, as judged by immunoblotting and ELISA techniques. Competitive binding to this antibody was observed specifically by fructated lysine but not by glucated lysine, glucose, fructose or lysine. The antibody binds specifically to fructated lysine residues in the protein but not to borohydride-reduced material or advanced glycation end products, indicating that the antibody recognizes only the reducing, carbonyl-containing forms produced in the early stage of the fructation reaction. When BSA was incubated with various concentrations of fructose, the reactivity of the antibody increased in a dose- and time-dependent manner. When soluble proteins prepared from either normal or streptozotocin-induced diabetic rat eyes were analysed by ELISA with this antibody, an increase in the reactive components was observed as a function of aging as well as under diabetic conditions. Western blotting analysis showed that lens crystallin reacted highly with this antibody. Because fructose is biosynthesized largely through the polyol pathway, which is enhanced under diabetic conditions, and lens is known to have a high activity of enzymes in this pathway, this antibody is capable of recognizing fructated proteins in vivo. Thus it is a potentially useful tool for investigating two major issues that seem to be involved in diabetic complications, namely the glycation reaction and the polyol pathway.

Animals↗
PubMed1998

Reactive oxygen species enhances the induction of inducible nitric oxide synthase by sphingomyelinase in RAW264.7 cells.

The sphingomyelin pathway, activated by stimuli, such as inflammatory cytokines, results in the formation of ceramide, a second messenger molecule. The purpose of the present study was to examine the mechanism by which macrophage-type nitric oxide synthase (NOS II) is induced by stimulation of the sphingomyelin pathway. When RAW264.7 cells were incubated with sphingomyelinase (SMase), nitrite production, NOS II activity, and NOS II mRNA were increased in a dose-dependent manner. Sphingosine, dihydrosphingosine, N-acetylsphingosine (C2-ceramide), and N-acylsphingosine (natural ceramide) had no effect on nitrite production, suggesting that signal molecules other than these were concomitantly produced by SMase treatment and required for NOS II induction. We then investigated the possible involvement of intracellular reactive oxygen species (ROS) in gene induction. SMase treatment increased the level of intracellular ROS, as assessed by flow cytometric analysis using a ROS-sensitive dye, dichlorofluorescin diacetate. Antioxidants, such as N-acetyl-l-cysteine and alpha-tocopherol, inhibited gene induction as well as nitrite production by SMase. These results suggest that activation of the sphingomyelin pathway induces gene expression and that the elevated ROS were somehow involved in this process.

Acetylcysteine↗
PubMed1998

Neurotoxicity of intrathecal Shiga toxin 2 and protection by intrathecal injection of anti-Shiga toxin 2 antiserum in rabbits.

The initial brain lesions in rabbits given intravenous Shiga toxin 2 (Stx2) were noted at 24 h in an area around the third ventricle (Fujii et al., Infect Immun 1996, 64: 5053-60). This result implied that Stx2 is present in the cerebrospinal fluid (CSF) despite the fact that the toxin was administered intravenously. We measured Stx2 activity in CSF by using a Vero cell cytotoxicity assay at various times after an intravenous injection of Stx2. Stx2 was detected from 2 h after the injection, and its concentration in CSF remained at a high level for a further 6 h. Fifty percent lethal doses (LD 50) of Stx2 were measured in rabbits after intravenous and intrathecal Stx2 injections; The LD 50 after an intrathecal injection of Stx2 was 0. 36 microg/kg, which was 9.2-fold lower than that of an intravenous injection of Stx2 (3.4 microg/kg). Magnetic resonance images obtained after an intrathecal Stx2 injection (5 microg/kg) were compared with those obtained after an intravenous Stx2 injection (5 microg/kg). At 48 h, the cerebellar lesions had spread from the area in contact with the CSF on a T2-weighted image, which suggests that the intrathecal Stx2 may invade the cerebellum directly. We then examined whether anti-Stx2 antiserum injected intrathecally protects rabbits against brain damage. Eighty percent of the rabbits infected with Stx2 at 5 microg/kg died within 8 days from brain damage. Rabbit anti-Stx2 sera (with titres of x16 and x64 by the Ouchterlony precipitation method) were administered into the CSF space through the cisterna magna. All the rabbits ( n=10) survived when they were given an intrathecal injection of rabbit anti-Stx2 antiserum 2 h before the intravenous injection of Stx2. Our results suggest that a leakage of Stx2 into the CSF from the choroid plexus causes brain damage, and that an intrathecal injection of anti-Stx2 antiserum could be a therapy for acute encephalopathy caused by Stx2-producing Escherichia coli.

Animals↗
PubMed1998

A defect in the mitochondrial import of mutant Mn-superoxide dismutase produced in Sf21 cells.

Wild-type and several mutant human manganese superoxide dismutases (Mn-SODs) were produced in a baculovirus/insect cell system and characterized. The enzymatic activity of a homogenate of Sf21 cells, infected with baculovirus carrying wild-type Mn-SOD and grown in the conventional medium, was indistinguishable from that of control cells, but was augmented by supplementation with Mn2+. The protein produced was largely imported into the mitochondria, as judged from the enrichment in the mitochondrial fraction, the mobility of the protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the results of N-terminal processing, which was confirmed by sequencing of the purified enzyme. However, a significant amount of precursor was also detected by an antibody raised against the human Mn-SOD signal peptide. While both Mn2+ and Fe3+ stimulated Mn-SOD accumulation within mitochondria, the active form was produced in the presence of submillimolar Mn2+ only. Amino acid substitutions at a signal peptide-cleavage site, His-Ser-Leu4 to Pro-Met-Va14, in the mature Mn-SOD prevented the processing of the precursor protein, and thus resulted in the accumulation of the precursor protein within mitochondria, as judged on immunostaining with an anti-Mn-SOD antibody. Mutant Mn-SODs with a truncated signal peptide or carboxyl region (8, 13, and 42 amino acid residues in the mature form) were barely solubilized, even with a nonionic detergent, and exhibited no activity, suggesting inappropriate folding of these mutant SODs. They were also susceptible to proteolytic degradation, while the wild-type and precursor forms were resistant. Thus, the baculovirus/insect cell expression system appears to be adequate for the analysis of mitochondrial import using intact cells as well as for the large scale production of active Mn-SOD.

Amino Acid Sequence↗
PubMed1998

Remission of hypertension: retrospective observations over a period of 20 years.

To clarify the background and outcome of hypertensive patients who have remission of their elevated blood pressure (BP) after a course of antihypertensive drug therapy, we designed a retrospective observational study. The clinical records of 106 hypertensive men and women (BP, 164.3/104.4 mmHg) given antihypertensive drug treatment and subsequently examined every 1 to 3 mo for more than 20 yr were reviewed. The patients were divided into two groups: those who had remission (R-group) and those who did not have remission (N-group). Patients were considered in remission if no significant elevation in BP was observed for more than 1 yr after withdrawing their medication. Remissions ranging in duration from 1.6 to 21.7 yr (average duration, 6.3 yr) occurred in 19 of 106 patients (17.9%). However, anti-hypertensive drug treatment was eventually restarted in 17 of the 19 patients. Before treatment, comparison of the R-group and N-group revealed no differences with respect to age, body weight, BP, or serum creatinine. In contrast, the proportion of patients who lacked high-voltage deflections in their electrocardiograms (ECG) as well as that of patients whose BP was well-controlled by a single medication was significantly greater in the R-group than in the N-group (12/19 vs. 22/87, p < 0.05 and 10/19 vs. 13/87, p < 0.001, respectively). In addition, body weight in the R-group decreased significantly by the time drug therapy was withdrawn (p < 0.01). Finally, significantly more patients (14 of 19 patients) entered remission in the spring and summer (p < 0.05) than at other times of the year. We conclude that remission occurs in a subset of well-controlled hypertensive patients and may persist for several years or more. However, in the majority of patients, antihypertensive drug treatment will usually need to be restarted at some point. Patients who lack ECG high-voltage deflections and who are successfully treated with a single therapeutic agent are most likely to experience remission. Moreover, it appears that withdrawing patients from drug therapy in the spring or summer is more likely to yield a favorable outcome than at other times of the year.

Adult↗
PubMed1998

Sustained hemoconcentration in patients with chronic atrial fibrillation, a potential risk for stroke and thromboembolic complications. A retrospective study.

Hemoconcentration has been observed during paroxysms of atrial fibrillation and at the early stage of chronic atrial fibrillation. The present study was designed to determine how long the hemoconcentration continues after complete transition to atrial fibrillation from sinus rhythm by retrospective long-term observation of 9 patients with chronic atrial fibrillation and 18 age-gender matched control patients. Hematocrit levels significantly increased with transition to chronic atrial fibrillation from sinus rhythm (from 44.88 +/- 0.87% to 46.87 +/- 1.12%, p < 0.01) and remained high for at least another 4 years. They remained unchanged throughout the observation period in the control patients. There is a significant difference in the hematocrit level between patients with chronic atrial fibrillation and control patients (p < 0.001). The hemoconcentration may present a potential risk for stroke and thromboembolic complications.

Aged↗
PubMed1998

A marked increase in free copper levels in the plasma and liver of LEC rats: an animal model for Wilson disease and liver cancer.

Most of copper present in rat plasma and liver binds to caeruloplasmin and metallothionein, respectively, and is not redox active. However, free forms of copper including loosely bound forms to other molecules are redox active. We assessed the free copper in Long-Evans rats with a cinnamon-like coat color (LEC rats), an animal model of Wilson disease and liver cancer. Compared to those of control rats, the liver and plasma of LEC rats showed a marked elevation of free copper, especially at the stage of acute hepatitis, in parallel with an increase of total copper levels in the livers and a decrease of plasma caeruloplasmin (ferroxidase I) activity. At the onset of jaundice, the total copper levels, however, decreased in liver, but increased in plasma, while free copper levels in both liver and plasma remained higher. Free iron levels in both liver and plasma were also determined and did not change significantly, except for the case of plasma in jaundiced rats. The data are consistent with a proposal in which increased levels of redox active free copper in the liver of LEC rats catalyze Fenton-type reactions, producing a large flux of hydroxyl radicals that would play an important role in the observed liver dysfunction, leading to acute hepatitis, and finally, hepatocarcinoma. This is the first demonstration that the free copper may participate in the pathophysiology of the LEC rats and Wilson disease.

Animals↗
PubMed1998

A high expression of heme oxygenase-1 in the liver of LEC rats at the stage of hepatoma: the possible implication of induction in uninvolved tissue.

We have examined changes in the expression of heme oxygenase-1 (HO-1), an inducible isoform and HO-2, a constitutive isoform, in the liver of Long-Evans with a Cinnamon-like color (LEC) rat, a mutant strain which spontaneously develops acute hepatitis and hepatoma. HO-1 expression was highly enhanced in the LEC rat livers with jaundice, and then decreased slightly, but overall remained at a higher level than in the Long-Evans with Agouti color (LEA) control rats, as judged by Northern blotting analysis of the whole liver extract. The high expression of HO-1 in the LEC rat liver was, however, not due to the actual cancer lesion but, rather, due to the surrounding uninvolved tissues including hepatocytes. Immunohistochemical analysis also supported this conclusion. Among normal tissues, the expression of HO-1 but not HO-2 was high in only the spleen of both LEC and LEA rats. The high expression observed in the stage of acute hepatitis and hepatoma stages in the LEC rat is probably due to the oxidative stress caused by the accumulation of free copper and free iron levels which has been reported earlier by our group (Suzuki et al., Carcinogenesis, 1993, 14, 1881-1884 and Koizumi et al., Free Radical Research, in press) as well as by free heme levels. The inflammatory cytokines produced by the surrounding tissue at the hepatoma stage would also be expected to play a role in the induction mechanism. The physiological relevance of HO-1 induction might be an adaptive response to oxidative stress and vasodilatory effect of carbon monoxide on sinusoidal circulation.

Age Factors↗
PubMed1998

[Effects of antihypertensive treatment on the thickening of the basal portion of the interventricular septum in essential hypertension].

Previous echocardiographic studies have indicated that the basal portion of interventricular septum is locally thickened in many patients with essential hypertension. This retrospective study investigated whether this localized thickening is decreased by antihypertensive treatment. Twenty-four patients with mild essential hypertension (15 males, 9 females, mean [+/- SD] 55 +/- 9 years) were selected who had local thickening at the basal portion of interventricular septum (> or = 11 mm) on echocardiograms recorded within 3 months after the first visit and were followed up by echocardiography 6 months or more after the start of antihypertensive treatment. Interventricular septal wall thickness at the mid portion (IVST), posterior wall thickness (PWT), left ventricular mass index (LVMI), aorto-septal angle, blood flow velocity in left ventricular outflow tract, and the thickness of the basal portion of interventricular septum (septal wall maximum thickness within 1.5 cm apex side from the joint of interventricular septum and aorta in the long-axis view of B-mode echocardiograms) were measured. Blood pressure was significantly decreased from 152.7 +/- 8.7/93.1 +/- 8.0 mmHg to 140.0 +/- 8.2/86.6 +/- 8.2 mmHg by treatment (p < 0.0001). The thickness of the basal interventricular septum was significantly reduced by treatment from 12.3 +/- 1.7 mm to 10.3 +/- 1.4 mm (p < 0.0001). Mean IVST, PWT and LVMI were slightly reduced by treatment, but the differences were not statistically significant. These results suggest that the thickening of basal interventricular septum is induced by high blood pressure, and the measurement of the thickness of basal interventricular septum might be a useful tool to estimate and monitor the effect of antihypertensive treatment in patients with mild essential hypertension.

Adult↗
PubMed1998

[Transient mitral regurgitation induced by vagal stimulation in rabbits: a Doppler echocardiographic study].

Cervical vagal stimulation in rabbits frequently causes systolic murmur with bigeminy due to premature ventricular contractions. The bigeminy disappears in a few minutes, but the systolic murmur persists for a few days. The present study used Doppler echocardiography to examine whether or not this systolic murmur is due to mitral regurgitation. Electrocardiographic monitoring was performed on anesthetized rabbits forced into the supine position. Doppler echocardiography was performed in the animals which showed systolic murmur 6 hours, 3 days, and 1, 2, 3 and 4 weeks after vagal stimulation. Six hours after vagal stimulation, phonocardiography detected systolic click and late systolic murmur, and Doppler echocardiography detected marked mitral regurgitation. The systolic murmur and mitral regurgitation were attenuated and the papillary muscle was swollen 3 days after vagal stimulation. The mitral regurgitation disappeared within a week and swelling of the papillary muscle improved 3 weeks after vagal stimulation. Doppler echocardiography confirmed that the systolic murmur observed in rabbits after vagal stimulation is due to transient mitral regurgitation.

Animals↗