Disulfide bond formation and secretion of Escherichia coli heat-stable enterotoxin II

The Escherichia coli heat-stable enterotoxin II (STII) is a typical extracellular toxin consisting of 48 amino acid residues, of which 4 are cysteine. There are two disulfide bonds, one between Cys-10 and Cys-48 and one between Cys-21 and Cys-36. We examined the involvement of DsbA in the formation of the disulfide bonds of STII and the role of each in the secretion of STII. A dsbA mutant was transformed with a plasmid harboring the STII gene, and STII was not detected either in the cells or in the culture supernatant. Reducing the level of STII brought about the dsbA mutation restored by introducing the wild-type dsbA gene into the mutant strain. These results showed that DsbA is involved in forming the disulfide bonds of STII and that STII without these disulfide bonds is degraded during secretion. We substituted these four cysteine residues in vivo by oligonucleotide-directed site-specific mutagenesis. The amino acid sequence of the purified STII (C48S) and pulse-chase studies revealed that two intermolecular disulfide bonds must be formed to be efficiently secreted and that cleavage between amino acid residues 14 and 15 is probably the first step in the proteolytic degradation of STII.

Dilated cardiomyopathy associated with hyperthyroidism

We report a case of dilated cardiomyopathy with hyperthyroidism. A 28-year-old man was admitted because of congestive heart failure and atrial fibrillation, and was newly diagnosed as having hyperthyroidism. Despite administration of antithyroid medication, he developed recurrent congestive heart failure. An echocardiogram revealed a moderately dilated left ventricle with diffuse hypokinesis. Though his thyroid function normalized, the patient's cardiac dysfunction did not improve. Beta-blocker therapy was begun with subsequent improvement in clinical symptoms. This suggests that beta-blocker treatment may be effective in patients with atrial fibrillation associated with cardiomyopathy and hyperthyroidism.

Involvement of prostaglandin E2 synthesis in the intestinal secretory action of Escherichia coli heat-stable enterotoxin II

The prostaglandin response of mouse intestinal epithelial cells after exposure to Escherichia coli heat-stable enterotoxin II was examined. The quantity of prostaglandin E2 produced by the intestinal cells was directly related to the dose of heat-stable enterotoxin II. The change in the amount of prostaglandin E2 over time correlated to that of the volume of fluid released into the intestinal lumen. We then demonstrated that administration of heat-stable enterotoxin II into the intestinal loops of mice induced elevation of arachidonic acid and phosphatidic acid levels in intestinal epithelial cells. These results show that heat-stable enterotoxin II stimulates arachidonic acid metabolism in intestinal epithelial cells and that the synthesized prostaglandin E2 functions as a mediator of fluid secretion induced by this enterotoxin.

Stimulation of cell proliferation and autoregulation of elastin expression by elastin peptide VPGVG in cultured chick vascular smooth muscle cells

Synthetic elastin peptides, VPGVG or its polymer (VPGVG)n, enhanced the proliferation of smooth muscle cells 1.5-fold during 48 h treatment at the concentrations over 10(-6) M or 1.0 microgram/ml, respectively. Monomeric and polymeric VPGVG sequences reduced elastin synthesis and its mRNA level to one-third and one-half of control respectively under the conditions in which the proliferation of cells were enhanced, but did not change collagen synthesis as measured by bacterial collagenase digestion. The elastin-specific autoregulation by elastin fragments may reflect the feedback regulation of elastin expression which may play an essential role in elastin metabolism under the normal and diseased conditions.

[Geographical epidemiologic studies on factors associated with centenarians in Japan]

To explore factors associated with longevity, we studied geographic distribution of centenarians in Japan, based on 1990 the population census. We calculated the proportion of centenarians from ratio of number of centenarian to that of population aged 65 years or older. Centenarians in Japan consisted of number 4,152 persons. By prefecture, Tokyo had the most centenarians (383), followed by Okinawa (193) and Fukuoka (151) prefectures. Fukui had the least (24), followed by Akita (26) and Ishikawa (29) prefectures. The proportion of centenarians in Japan was 21.6 (per 100,000 populations) in 1990. By prefecture, the highest proportion lived in Okinawa (133.8), whereas the fewest were found in Akita (8.9). The relationship between geographic distribution of centenarians and environmental factors and nutritional factors were analyzed. Correlation coefficients between proportion of centenarians and mean temperature, high quality of welfare work and of medical services, and having much leisure time were positively significant. As for nutritional factor, correlation coefficients between proportion of centenarians and protein (% of energy) was positively significant, while intake of total energy was negatively significant.

Human cathepsin O2, a novel cysteine protease highly expressed in osteoclastomas and ovary molecular cloning, sequencing and tissue distribution

A 1.6-kilobase full-length cDNA of a novel human cysteine protease has been isolated and sequenced. The nucleotide sequence encodes a polypeptide of 329 amino acids composed of a 15-residue N-terminal signal peptide, a 99-residue propeptide, and a mature protein of 215 amino acids. The deduced amino acid sequence contains two potential N-glycosylation sites, one located in the proregion and one in the mature enzyme. Comparison of the amino acid sequence of cathepsin O2 with that of known human lysosomal cysteine proteases revealed a substantial degree of similarity to cathepsins L and S. Northern blot analysis indicates predominant levels of expression in osteoclastomas and ovary and therefore the enzyme was named cathepsin O2. The extremely high expression levels of human cathepsin O2 in osteoclastomas suggest a major role of this novel enzyme in bone remodelling and bone related diseases.

31P nuclear magnetic resonance evaluation of rat liver preserved in UW solution

A persistent problem in orthotopic liver transplantation is primary nonfunction (PNF) of the hepatic allograft. In an attempt to reduce the incidence of graft failure, the feasibility of pretransplant assessment of graft viability was investigated by 31P nuclear magnetic resonance (NMR) spectroscopy. The level of adenosine triphosphate (ATP) was measured as an indicator of liver function by 31P NMR spectroscopy after a 30 min normothermic reperfusion following cold-storage in University of Wisconsin (UW) solution. The mean +/- SD beta-ATP/Pi ratio after preservation for 0, 12, 24 or 48 h was 1.40 +/- 0.34, 0.85 +/- 0.27, 0.64 +/- 0.14 and 0.38 +/- 0.09, respectively. Significance was observed between 12h and 24h and between 12h and 48h of preservation. These results correlated well with the morphological changes in endothelial cells and sinusoidal lining cells examined by transmission electron microscopy. It is suggested strongly that microcirculatory disturbances due to endothelial cell injury impairs the recovery of ATP levels after reperfusion, and that ATP determination by 31P NMR spectroscopy, as a non-invasive modality, may help in the prediction of PNF after liver transplantation.

The role of renal dopamine in the reduction of high blood pressure by beta 1-selective beta-blocker with intrinsic sympathomimetic activity in spontaneously hypertensive rats

The present experiments were undertaken to clarify the difference of renal dopamine production from beta 1-selective beta-blocker with and without intrinsic sympathomimetic activity (ISA). Either beta-blocker with ISA, celiprolol (100 or 300 mg/kg/day; CEL-100 or CEL-300) or beta-blocker without ISA, atenolol (50 mg/kg/day; ATE-50) was administered to the SHR from 19 to 26 weeks. Degrees of lowering blood pressure in CEL-300 SHR and in ATE-50 SHR were similar, but decrease in heart rate was significantly less in CEL-300 SHR than in ATE-50 SHR. Urine output, which was significantly less in control SHR than in control WKY, was significantly greater in CEL-100 SHR and CEL-300 SHR, but not in ATE-50 SHR. Urinary excretions of noradrenaline (u-NA) and dopamine (u-DA) were significantly higher in control SHR than in control WKY and a comparable u-DA/u-NA ratio was found in these two groups. U-DA and the ratio of u-DA/u-NA were significantly elevated in CEL-100 SHR and CEL-300 SHR, but not in ATE-50 SHR. There was a significant positive correlation between u-DA/u-NA ratio and urine output and a significant negative correlation between the ratio of u-DA/u-NA and change of blood pressure in control SHR, CEL-100 SHR and CEL-300 SHR. These results suggest that an enhancement of renal dopamine production by ISA (beta 2 stimulation) of beta 1-selective beta-blocker may contribute, at least in part, to the antihypertensive effect of this drug.

Natural course of diabetic peripheral neuropathy in spontaneous-onset diabetic Chinese hamsters

We investigated metabolic and pathological changes in the peripheral nerve of the spontaneous-onset diabetic Chinese hamster. Electrophysiological examination revealed that the motor nerve conduction velocity was significantly decreased at 10 months and afterwards, however, the F-wave latency was significantly increased at 5 months and afterwards. Concerning sciatic nerve contents of sorbitol, myo- and scyllo-inositol, the content of sorbitol was not significantly increased at 5 months, but, myo- and scyllo-inositol were significantly decreased at 5 months and thereafter. At 10 and 15 months, however, sciatic nerve content of sorbitol was significantly increased. On morphological examination, loss of large myelinated fiber and reciprocal increase in degenerative fiber were also seen in sciatic nerve, but not in tibial nerve, at 5 months. At 15 months, these morphological changes were also found in the tibial as well as the sciatic nerve. Thus, we may hypothesize that F-wave latency is useful in the detection of initial diabetic neuropathy, and that the initial pathological changes in diabetic neuropathy of diabetic Chinese hamsters are predominantly found in the proximal site of peripheral nerves.

The complete mitochondrial DNA sequence of Hansenula wingei reveals new characteristics of yeast mitochondria

The complete 27,694-bp mitochondrial (mt) DNA sequence of Hansenula wingei, which is a typical budding yeast and contains circular mitochondrial DNA, has been determined. The mt sequence contains genes encoding large and small ribosomal RNAs, 25 tRNAs, three subunits of cytochrome c oxidase (subunits 1, 2 and 3), three subunits of ATPase (subunits 6, 8 and 9), apocytochrome b, seven subunits of NADH dehydrogenase (subunits 1, 2, 3, 4, 4L, 5 and 6), and a ribosomal protein, VAR1. The VAR1 gene is considered to be a typical yeast type. This is consistent with data on DNA and the deduced amino-acid sequence homology comparisons of genes ubiquitous in yeast and fungi. However, we have identified seven genes encoding NADH dehydrogenase subunits, which are not found in other yeast mitochondrial genomes, thus placing the H. wingei mitochondrial genome in a unique position. In addition the H. wingei mitochondrial genome also encodes one tRNA pseudogene and one short unidentified ORF. The genome is compact with only two introns both of which contain an ORF. One intron lies in the large rRNA gene while the other is situated in the cytochrome c oxidase subunit-1 gene. The conserved nonanucleotide motif (A/T)TATAAG (T/A)(A/T), which is a transcription start signal in Saccharomyces cerevisiae mitochondria, has also been found in the H. wingei mitochondrial genome. The codon assignments for ATA and CTN in H. wingei mitochondria are different from those in S. cerevisiae mitochondria. These results indicate a unique and novel structure for the H. wingei mitochondrial genome in terms of characteristics which are typical for both yeast and for filamentous fungi. This is the first complete mt DNA sequence report in yeast.

Generation of effector T cells in Hymenolepis nana-infected, FK-506-treated BALB/c mice

FK-506 administered into mice daily at a dose of 10.0 mg/kg (but not 1.0 and 5.0 mg/kg) caused suppression of protective immunity to Hymenolepis nana, when the agent was injected intraperitoneally during the induction phase of protective immunity. Daily administration of 10.0 mg/kg FK-506, during the course of larval development from challenge, also suppressed protective immunity. Inhibition of protective immunity was only observed in mice that received FK-506 for 6 days at a daily dose of 10.0 mg/kg and were challenged 24 h after the final FK-506 injection. FK-506 did not inhibit formation of effector cells that mediate delayed-type hypersensitivity (DTH) to H. nana egg antigen when the agent was administered intraperitoneally at a dose of 10.0 mg/kg/day for 6 days before cell preparation. However, FK-506 did inhibit DTH effector cell activation when cells prepared from infected, saline-injected mice were transferred into 10.0 mg/kg FK-506-treated recipient mice. These results strongly indicate that FK-506 cannot inhibit the generation of effector cells but will suppress their function in vivo.

Partial type of common atrioventricular canal defect associated with mitral stenosis

We report a 63-year-old woman, with a partial type of common atrioventricular canal and mitral stenosis, who was hospitalized because of dyspnea on exertion. Two-dimensional echocardiogram showed an ostium primum atrial septal defect with two well-formed AV valves located at the same level. However, both anterior and posterior mitral leaflets were markedly thickened with a thickened subvalvular apparatus, and the commisures were fused. Echocardiographic measurements demonstrated a mitral valve area of 1.48 cm2 with mild mitral regurgitation. Cardiac catheterization demonstrated mild pulmonary artery hypertension with a large left to right shunt (72%) at the atrial level. The combination of the partial type of common atrioventricular canal and mitral stenosis is rare; only one similar case has been reported previously in the literature.

Age-related changes in ConA-induced cytokine production by splenocytes from senescence accelerated mice SAMP8

In vitro production of interleukin-2 (IL-2), IL-4, IL-5 and interferon-gamma (IFN-gamma) by splenocytes stimulated with concanavalin A (ConA) was studied in senescence-accelerated mice (SAMP8; 2-14.5 months old) by employing AKR (2-9 months old), origin of SAM strain, as controls. Male and female SAMP8 mice showed an age-related decrease in IL-2 production from the age of 9 months and the phenomena were accompanied by an increase in IFN-gamma production with a large increment. AKR mice showed no decrease in IL-2 production even at 9 months of age, but there was an increase in IFN-gamma production showing levels lower than those in SAMP8 mice. Between IL-2 and IFN-gamma production during the ages of 2-9 months, there were negative correlations in male and female SAMP8 mice and a positive correlation in female AKR mice. The levels of IL-4 production were lower in SAMP8 than in AKR mice, although there was no difference in IL-5 production between SAMP8 and AKR mice. Male and female SAMP8 mice showed a positive correlation between IL-5 and IFN-gamma production. Only in SAMP8 females was an increase in IFN-gamma accompanied by an increase in IL-4. From these changes in the cytokine production profile was it concluded that SAMP8 mice were senescence-accelerated in immuno-responses in comparison with AKR mice and had some functional deficiency with respect to IL-4 production, a part of which resulted from over-production of IFN-gamma.

Mechanism of inhibition of xanthine oxidase with a new tight binding inhibitor

The mechanism of inhibition of milk xanthine oxidase and xanthine dehydrogenase by the tight binding inhibitor, sodium-8-(3-methoxy-4-phenylsulfinylphenyl)pyrazolo[1,5-a]-1,3,5- triazine-4-olate monohydrate (BOF-4272), was studied after separation of the two isomers. The steady state kinetics showed that the inhibition by these compounds was a mixed type. One of the isomers had a Ki value of 1.2 x 10(-9) M and a Ki' value of 9 x 10(-9) M, while the other isomer had a Ki value of 3 x 10(-7) M and a Ki' value of 9 x 10(-6) M. Spectral changes were not observed by mixing either the oxidized or reduced form of the enzyme with BOF-4272. The stopped-flow study and the effects of BOF-4272 on various substrates showed that BOF-4272 bound to the xanthine binding site of the enzyme. Kd values of the enzyme and one of the isomers, which has a higher affinity for the enzyme, were also found to be 2 x 10(-9) M for the active form of the enzyme and 7 x 10(-9) M for the desulfo-form using fluorometric titration, and the binding has stoichiometry of 1:1. The inhibitor could not bind to the enzyme when the enzyme was previously treated with oxipurinol.

Effect of Picibanil (OK-432) on the scavenging effect of free radicals produced during liver regeneration in the rat

We administered a biological response modifier Picibanil (OK-432), attenuated Streptococcus pyogenes, via the dorsal vein of the penis after 70% hepatectomy in rats, and clarified the scavenging effect of Picibanil on free radicals generated in the regenerating liver. A group of 5 rats was intravenously administered with 25 KE/kg of OK-432 after hepatectomy, while the control group was given saline after hepatectomy. Serum levels of aspartate aminotransferase and alanine aminotransferase and the value of thiobarbituric acid-reactive substances in serum and hepatic tissue after hepatectomy were serially measured, and these values were significantly lower in Picibanil treated animals than in control animals. Free radical production in the regenerating liver was also measured by electron spin resonance spectrometry, and OK-432 injection significantly reduced free radical production. These results suggested that OK-432 reduced hepatocellular damage in regenerating liver by inhibiting lipid peroxidation.

Chemoprevention of azoxymethane-induced intestinal carcinogenesis by a novel synthesized retinoidal butenolide, 5-hydroxy-4-(2-phenyl-(E)-ethenyl)-2(5H)-furanone, in rats

The present study was designed to investigate the modifying effects of dietary 5-hydroxy-4-(2-phenyl-(E)-ethenyl)-2(5H)-furanone (KYN-54), a new synthetic retinoidal butenolide, during the post-initiation phase on azoxymethane (AOM)-induced rat intestinal carcinogenesis. The number of aberrant crypt foci (ACF) in rat colon, colonic ornithine decarboxylase (ODC) activity and bromodeoxy-uridine (BrdUrd) labeling index in rat colonic epithelium were also assessed. At 7 weeks of age, male F344 rats (except the KYN-54 alone and control groups) were given weekly s.c. injections of AOM at 15 mg/kg body wt for 3 weeks. Starting 1 week after the last injection of AOM, rats (except the control group) were fed a diet containing KYN-54 at concentrations of 100 or 200 p.p.m. throughout the experiment. All animals were necropsied at 32 weeks after the start of the experiment. Compared with the AOM alone group, KYN-54 at both doses reduced the incidence and multiplicity of tumors in entire intestine (small and large intestines). In the 200 p.p.m. KYN-54 fed group especially, tumor incidence and multiplicity in the entire intestine were lower compared with the AOM alone group (P < 0.005 and P < 0.05 respectively). Also, the number of ACF/cm2 colon in the groups of rats treated with AOM and KYN-54 at both doses were significantly lower than that of rats treated with AOM alone (P < 0.05). Colonic ODC activity and BrdUrd labeling index in the groups of rats treated with AOM and KYN-54 at both doses were slightly lower than those treated with AOM alone. KYN-54 at 200 p.p.m. significantly lowered BrdUrd labeling index induced by AOM (P < 0.005). These results suggest that KYN-54 might be a promising chemopreventive agent for intestinal neoplasia.

Regulation of the major histocompatibility complex class I mRNA expression by bile acids in cultured human hepatoma cells

We investigated the effect of bile acids on major histocompatibility complex (MHC) class I gene expression in the cultured human hepatoma cell HepG2. Not only chenodeoxycholic acid, but its stereoisomer ursodeoxycholic acid as well, increased steady state level of MHC class I mRNA. When various bile acids were studied, inducibility of MHC class I mRNA was closely associated with the hydrophobicity of the corresponding bile acids. Pretreatment of the cells with a protein kinase C (PKC) inhibitor H7 suppressed induction of MHC class I mRNA by those bile acids. Furthermore, treatment of the cells with chenodeoxycholic acid significantly induced translocation of PKC from cytosol to membrane. In summary, our data strongly indicate up-regulatory effect of bile acids on MHC class I mRNA expression, most probably via activation of PKC-dependent pathway.

DIF-1, morphogen of Dictyostelium discoideum, induces the erythroid differentiation in murine and human leukemia cells

The structure of morphogen of Dictyostelium discoideum, DIF-1, which was elucidated by Morris et al. proved to be closely similar to that of differanisole A which had been isolated by us from the metabolites of a simple eucaryote, Chaetomium, as the differentiation-inducer of murine and human undifferentiated tumor cells. This fact seemed to suggest the molecular structure playing an important part in differentiation and development beyond species. We have already examined whether differanisole A induces the differentiation in Dictyostelium discoideum, and it was morphologically and biochemically confirmed. In this study, we examined whether DIF-1 induces the differentiation in murine and human leukemia cells. Above the concentration of 2 micrograms/ml (6.5 microM), DIF-1 induced the differentiation in murine erythroleukemia B8 cells and in human leukemia K562 cells into the hemoglobin-synthesizing erythrocyte-like cells.

Effect of substitution for arginine residues near position 146 of the A subunit of Escherichia coli heat-labile enterotoxin on the holotoxin assembly

Escherichia coli heat-labile enterotoxin (LT) is a holotoxin which consists of one A and five B subunits. Although B subunit monomers released into periplasm can associate into pentameric structures in the absence of the A subunit, the A subunit accelerates the assembly. To express the function, A subunit constructs the proper spatial structure. However, the regions involved in the construction are unknown. To identify the regions, we substituted arginine residues near position 146 of the A subunit with glycine by oligonucleotide-directed site-specific mutagenesis and obtained the mutants expressing LT(R141G), LT(R143G), LT(R146G), LT(R143G, R146G), LT(R141G, R143G, R146G) and LT(R143G, R146G, R148G). We purified these mutant LTs by using an immobilized D-galactose column and analyzed the purified mutant LTs by SDS-PAGE to examine the amount of A subunit associated with B-subunit oligomer. The substitution of an arginine residue at any position did not induce a significant alteration in the amount of A subunit associated with B-subunit oligomer. However, the substitution of more than two arginine residues induced a significant decrease in the amount of A subunits associated with the B-subunit oligomer. Subsequently, we measured the level of the intracellular B-subunit oligomer of these mutant strains. The measurement revealed that the amount of B-subunit oligomer in cells decreased as the number of substituted arginine residues increased. These results show that all arginine residues near position 146 are important for the construction of the functional A subunit, and thus for holotoxin formation, although each individual arginine residue is not an absolute requirement.

Parvalbumin-positive small myelinated fiber bundles in anterior marginal areas in the human cervical cord

During pathological examinations of amyotrophic lateral sclerosis (ALS) patients, we noticed that bundles of dense small myelinated fibers were relatively well preserved in the anterior marginal areas of the cervical cords in a few ALS patients with diffuse myelin pallor. Moreover, these fibers were strongly immunostained by anti-parvalbumin antiserum. These parvalbumin-positive fiber bundles were also seen in other ALS and non-ALS patients, and they were continuously traced up to the spinothalamic tract areas of the medulla oblongata. Therefore, it is suggested that these fiber bundles belong mainly to the ventral spinothalamic tract. We considered that these fiber bundles became conspicuous in shape since other areas in the anterolateral funiculus showed myelin pallor in such ALS patients.