Structures of the N-linked sugar chains in PAS-7 glycoprotein sharing the same protein core with PAS-6 glycoprotein from the bovine milk fat globule membrane

Glycoproteins PAS-6 (50 kDa) and -7 (47 kDa) from the bovine milk fat globule membrane share a common protein core but differ in their carbohydrate moiety. We here analyzed and proposed the structures of the N-linked sugar chains of PAS-7. The N-linked sugar chains were liberated from PAS-7 by hydrazinolysis and, after modifying the reducing ends with 2-aminopyridine (PA), were separated into one neutral (7N, 55%) and two acidic (7M, mono-, 43%; 7D, di-, 2%) sugar chain groups. The latter were converted into neutral groups (7MN and 7DN) by sialidase digestion. 7N was finally separated into 5 chains (7N1A, 7N1B-1, 7N1B-2, 7N2A, and 7N2B), and 7MN and 7DN were separated into 3 (7MN1, 7MN2, and 7MN3) and 2 (7DN1 and 7DN2) chains, respectively. The structure of each of these PA-neutral sugar chains was determined by sugar analysis, sequential exoglycosidase digestion, partial acetolysis, and 1H-NMR spectroscopy. The results show that the 10 sugar chains were of the biantennary complex type with and without fucose. The structure of 7N2A, one of the major sugar chains, was proposed as; [structure: see text] A structural comparison between PAS-6 and -7 indicated that, although they shared the same protein core, their sugar moiety was markedly different, involving the existence of a different pathway during the post-transcriptional modification.

Non-involvement of the K-ras mutation in colon carcinogenesis promoted by dietary deoxycholate in azoxymethane-treated rats

Fisher-344 rats, whose ileum or jejunum had been surgically removed to change the influx of bile acids into the colon, were intraperitoneally administered with azoxymethane and fed on a diet containing deoxycholate for 39 weeks to induce colon cancer. Fecal bile acids in the ileum-resected group were 1.5-times and serum bile acids were about half of those in the jejunum-resected group. As a result, the incidence and number of tumors were higher in the ileum-resected group. In the total of 59 colon tumors (40 were in the ileum-resected group and 19 in the jejunum-resected group), 56 were carcinomas, including two well-differentiated invasive and two mucinous carcinomas found in the ileum-resected rats. However, only three carcinomas, two invasive and one non-invasive, had the K-ras mutation. These results demonstrate that the K-ras mutation was not essentially involved in deoxycholate-promoted colon carcinogenesis.

Soybean resistant proteins interrupt an enterohepatic circulation of bile acids and suppress liver tumorigenesis induced by azoxymethane and dietary deoxycholate in rats

We found that azoxymethane and dietary deoxycholate induced liver tumors in rats. The incidence and the development of the tumor were closely related to the enterohepatic circulation of bile acids. The feeding of a high-molecular-weight fraction of soy protein digest (HMF) suppressed the tumorigenesis, probably due to the inhibitory effect of soybean resistant protein on reabsorption of bile acids in the intestine.

Prevalence of Barrett's esophagus and expression of mucin antigens detected by a panel of monoclonal antibodies in Barrett's esophagus and esophageal adenocarcinoma in Japan

Barrett's esophagus (BE) is an acquired disorder associated with a high incidence of adenocarcinoma of the lower esophagus. Moreover, it has been reported that short-segment BE may be associated with adenocarcinoma of the esophagogastric junction. The objective of this study was to define the prevalence of BE and the mucin profile in BE, including the short-segment type, and to compare the mucin profile in BE with the profiles of Barrett's adenocarcinoma and distal esophageal adenocarcinoma among Japanese. In total, 650 adult subjects underwent endoscopic examination for evaluation of BE. Although the prevalence of traditional (long segment) BE was 0.62%, the overall prevalence of BE including short-segment type was 15.7%. In Barrett's epithelium, the short-segment type predominantly had gastric type mucin, while the middle- and long-segment types possessed intestinal mucin, especially colonic type mucin (sulfo-Lewis(a)), with high frequency. In Barrett's epithelium with adenocarcinoma, all Barrett's epithelium adjacent to carcinomas showed a predominance of immunoreactivity to sulfo-Lewis(a). In Barrett's adenocarcinomas, colonic type mucin was detected in 100% by monoclonal antibody (MoAb) 91.9H. Small-intestinal mucin and gastric mucin were stained in 50% and 12.5% of the subjects, respectively. Colonic type mucin was also detected with high frequency (80%) in distal esophageal adenocarcinomas without Barrett's epithelium. These data suggest that the epitope, not of small-intestinal type or gastric type mucin, but of colonic type mucin (sulfo-Lewis(a)), may be associated with, at least in part, the malignant phenotype of BE.

Engraftment of genetically engineered amniotic epithelial cells corrects lysosomal storage in multiple areas of the brain in mucopolysaccharidosis type VII mice

Cell-mediated gene therapy for visceral lesions of lysosomal storage diseases is promising; however, the treatment of central nervous system (CNS) lesions remains a challenge. In this study, we generated rat amniotic epithelial cells (AEC) that overexpress and secrete human beta-glucuronidase (GUSB) following transduction with an adenoviral vector encoding human GUSB. The AEC were used as donor cells for cell-mediated gene therapy of CNS lesions in mice with mucopolysaccharidosis type VII (MPSVII), a lysosomal storage disorder caused by an inherited deficiency of GUSB activity. After confirmation that the secreted GUSB was taken up mainly via mannose 6-phosphate receptors in primary cultured neurons, the AEC were transplanted into the brains of adult MPSVII mice. Histochemical analysis showed extensive GUSB activity throughout the ipsilateral hemisphere of the recipient brains, and pathological improvement of the lysosomal storage was observed even in regions far from the site of injection. These results suggest that intracerebral transplantation of genetically engineered AEC has therapeutic potential for the treatment of CNS lesions in lysosomal storage disorders.

Role of p38 MAP kinase in endothelial cell alignment induced by fluid shear stress

The p38/mitogen-activated protein (MAP) kinase-activated protein kinase 2 (MAPKAP kinase 2)/heat shock protein (HSP)25/27 pathway is thought to play a critical role in actin dynamics. In the present study, we examined whether p38 was involved in the morphological changes seen in endothelial cells (EC) exposed to shear stress. Cultured bovine aortic EC were subjected to 14 dyn/cm(2) laminar steady shear stress. Peak activation of p38, MAPKAP kinase 2, and HSP25 were sixfold at 5 min, sixfold at 5 min, and threefold at 30 min compared with static control, respectively. SB-203580 (1 microM), a specific inhibitor of p38, abolished the activation of MAPKAP kinase 2 and HSP25 as well as EC elongation and alignment in the direction of flow elicited by shear stress. The mean orientation angle of cells subjected to shear without SB-203580, with SB-203580, or static control were 17, 50, and 43 degrees, respectively (P < 0. 05). EC transfected with the dominant negative mutant of p38-alpha aligned randomly with no stress fiber formation despite exposure to shear stress. These data suggests that the pathway of p38/MAPKAP kinase 2/HSP25/27 is activated in response to shear stress, and this pathway plays an important role in morphological changes induced by shear stress.

[Molecular cell biology on morphogenesis of the fovea and evolution of the central vision]

Since Charles Darwin wrote "On the Origin of Species by Means of Natural Selection", it had been assumed that various eye types, from the compound eye to the camera eye, had originated independently in at least 40-60 different phyletic lines. However, the finding of Pax 6, the master control gene for eye morphogenesis, and the fact that its sequence is highly conserved throughout the animal kingdom indicated that the prototype eye in a primitive animal originated only once in evolution, and various eye types arose from the same origin. We recently found a Pax 6 mutation in a pedigree with foveal hypoplasia. Thus, the Pax 6 that appeared in light sensory cells of a primitive animal in ancient times may play a role in morphogenesis of the fovea, the most highly developed visual receptor. The fovea first appeared in evolution in the temporal retina of fishes. Then, in birds, the nasal fovea and bifoveal system with nasal and temporal foveas developed. The fovea disappeared in primitive mammals, and reappeared in primates. A residue of the fovea is conserved in the visual streak, and the disappearance and reappearance of the fovea, in primitive mammals and primates respectively, correlates with degeneration and restoration of cone pigment genes in photoreceptors. Humans inherited the temporal fovea that had first originated in fish eyes. Pax 6 is expressed in the entire eyeball at an early stage of development, and is also expressed widely in the retina to determine its differentiation. To determine the position of the fovea, retinal cells are abundant in the visual streak, probably because expression of Pax 6 is regulated by patterning of the dorsoventral axis of the eyeball. Signaling molecules, discharged from the front of the face, also regulate Pax 6 expression, and determine position of the fovea, visual axis, angle gamma, growth of the eyeball, and shape of the visual field. Further investigation of nerve pathfinding system from the fovea to the central nervous system will clarify the origin of the central vision, and contribute to human welfare.

Role of mitogen-activated protein kinases in pulmonary endothelial cells exposed to cyclic strain

The aim of this study was to examine the role of mitogen-activated protein kinases (MAPKs) activation in bovine pulmonary arterial endothelial cells (EC) exposed to cyclic strain. EC were subjected to 10% average strain at 60 cycles/min. Cyclic strain induced activation of extracellular signal-regulated kinase (ERK; 1.5-fold), c-Jun NH(2)-terminal protein kinase (JNK; 1.9-fold), and p38 (1. 5-fold) with a peak at 30 min. To investigate the functional role of the activated MAPKs, we analyzed cells after treatment with PD-98059, a specific ERK kinase inhibitor, or SB-203580, a catalytic inhibitor for p38, and after transient transfection with JNK(K-R), and MEKK(K-M) the respective catalytically inactive mutants of JNK1 and MAPK kinase kinase-1. Cyclic strain increased activator protein-1 (AP-1) binding activity, which was blocked by PD-98059 and SB-203580. Activity of AP-1-dependent luciferase reporter driven by 12-O-tetradecanoyl-phorbol-13-acetate-responsive element (TRE) was induced by cyclic strain, and this was attenuated by PD-98059, MEKK(K-M), JNK(K-R), and SB-203580. PD-98059 and SB-203850 did not inhibit cell alignment and migration induced by cyclic strain. MEKK(K-M) and JNK(K-R) transfection did not block cyclic strain-induced cell alignment. In conclusion, cyclic strain activates ERK, JNK, and p38, and their activation plays a role in transcriptional activation of AP-1/TRE but not in cell alignment and migration changes in bovine pulmonary arterial EC.

Endothelial cell response to different mechanical forces

PURPOSE

Endothelial cells (ECs) are subjected to the physical forces induced by blood flow. The aim of this study was to directly compare the EC signaling pathway in response to cyclic strain and shear stress in cultured bovine aortic ECs.

MATERIALS AND METHODS

The ECs were seeded on flexible collagen I-coated silicone membranes to examine the effect of cyclic strain. The membranes were deformed with a 150-mm Hg vacuum at a rate of 60 cycle/min for up to 120 minutes. For a comparison of the effect of shear stress, ECs from the same batch as used in the strain experiments were seeded on collagen I-coated silicone sheets. The ECs were then subjected to 10 dyne/cm(2) shear with the use of a parallel flow chamber for up to 120 minutes. Activation of the mitogen- activated protein kinases was assessed by determining phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK), and p38 with immunoblotting.

RESULTS

ERK, JNK, and p38 were activated by both cyclic strain and shear stress. Both cyclic strain and shear stress activated JNK with a similar temporal pattern and magnitude and a peak at 30 minutes. However, shear stress induced a more robust and rapid activation of ERK and p38, compared with cyclic strain.

CONCLUSIONS

Our results indicate that different mechanical forces induced differential activation of mitogen-activated protein kinases. This suggests that there may be different mechanoreceptors in ECs to detect the different forces or alternative coupling pathways from a single receptor.

Ultrastructural and immunohistochemical findings in five patients with vitreomacular traction syndrome

OBJECTIVE

To evaluate pathologic features of vitreomacular traction syndrome (VMT).

METHODS

Preretinal membranes removed from five patients during vitreous surgery for VMT syndrome were evaluated by electron microscopy (n = 4) and immunohistochemistry (n = 1).

RESULTS

Electron microscopic examination revealed large segments of internal limiting lamina (ILL) in three of the four cases. Other extracellular features included two types of abnormal collagen fibrils, determined to be type I and fibrous long-spacing collagen. The myofibrocyte was the predominant cell type in all cases. Collagen types I, II, and III, as well as glial fibrillary acidic protein and vimentin, were identified by immunohistochemistry.

CONCLUSIONS

Epiretinal membranes in eyes with VMT syndrome adhered tightly to the ILL with abnormal collagen and contractile elements that included myofibrocytes.

High accumulation of plasminogen and tissue plasminogen activator at the flow surface of mural fibrin in the human arterial system

PURPOSE

We assessed the fibrinolytic activity of the organized mural thrombus lining of aneurysms and prosthetic grafts.

METHODS

Between May 1995 and April 1998, the full-thickness mural thrombi of aneurysms and the pseudointima lining of vascular grafts were obtained from 12 patients, ranging from 55 to 78 years in age, who underwent elective surgery. These included five aortic arch aneurysms, four abdominal aortic aneurysms, and three patent synthetic vascular grafts. The specimens were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/immunoblot and immunohistochemistry for human plasmin/plasminogen, tissue plasminogen activator (tPA), and fibrin degradation product (D-dimer).

RESULTS

In the SDS-PAGE/immunoblot, 25- and 27-kd bands appeared specifically in experimental fibrin plates after limited digestion by plasmin and were also recognized in the mural thrombi. The presence of bands at 25 and 27 kd, which were most prominent in sections near the flow surface layer, was consistent with the hypothesis that the mural fibrin was digested by the endogenous plasmin. Apparent immunoreactivity was found at the flow surface of the masses at a thickness of 10 to 400 micrometer suggesting the presence of a plasminogen and tPA-rich layer, with D-dimer as a consequential product of fibrinolysis.

CONCLUSION

The hypothesis that fibrin surfaces in the arterial system acquire fibrinolytic activity because of digestion by circulating endogenous plasmin was confirmed; this may contribute to the antithrombogenicity of these flow surfaces.

Role of caveolin in hemodynamic force-mediated endothelial changes

BACKGROUND

Caveolin has been shown to play an important role in signal transduction and nitric oxide synthase production. The purpose of this study was to investigate whether caveolin was tyrosine phosphorylated or activated by shear stress or cyclic strain in bovine aortic endothelial cells (BAECs).

MATERIALS AND METHODS

BAECs were subjected to an average of 10% strain at a rate of 60 cycles/min or a laminar shear stress of 10 dyn/cm(2) for up to 4 h. Immunoblotting with anticaveolin antibody was performed to assess activation of caveolin. Coimmunoprecipitation of anticaveolin antibody with anti-tyrosine phosphorylation antibody was performed to detect the tyrosine phosphorylation of caveolin.

RESULTS

Neither cyclic strain nor shear stress at physiologic levels altered the level of caveolin protein. Tyrosine phosphorylation of caveolin could not be observed at any time under either cyclic strain or shear stress condition.

CONCLUSION

Although hemodynamic forces alter nitric oxide synthase production and activate signal transduction, caveolin levels or activity is not altered in endothelial cells exposed to shear stress or cyclic strain.

Autoepitopes on autoantigen centromere protein-A (CENP-A) are restricted to the N-terminal region, which has no homology with histone H3

Anti-centromere autoantibodies (ACA) are commonly found in the serum of patients with a limited type of scleroderma and other systemic autoimmune diseases. CENP-A is one of the major antigens against ACA and a histone H3-like protein. To analyse the autoantigenic epitopes of CENP-A, a series of truncated peptides of human CENP-A were expressed in Escherichia coli and immunoblotting analysis was performed with 91 ACA+ sera. Eighty sera (88%) with the ACA reacted to the 52-amino acids N-terminal region which is not homologous to H3, while no sera reacted to the C-terminus which has a sequence similarity with H3. Moreover, ELISA was also employed in this study using two synthetic peptides corresponding to the amino acid sequences 3-17 (peptide A) and 25-38 (peptide B). Peptides A and B were reactive to 78 (86%) and 79 (87%) of ACA, respectively. Core antigens of hepatitis B virus (HBV) and hepatitis C virus (HCV) have similar sequences to peptide A and/or peptide B, but three sera containing HBV without ACA and five sera containing HCV without ACA were found to be reactive to neither peptide. Centromere localization of CENP-A is dependent on the H3-like C-terminal domain which is not autoantigenic, while the antigenic N-terminal domain, which might play unidentified functional roles, should be an important region for the induction of ACA.

Antitumorigenic effects of several food proteins in a rat model with colon cancer and their reverse correlation with plasma bile acid concentration

In order to obtain information on the preventive effects of various food proteins against colonic cancer, six groups of azoxymethane-initiated mature Fischer rats (n = 10) were fed respective diets different in protein sources such as bovine milk casein (casein), high-molecular-weight fraction from protolytic digest of soy protein isolate (soybean HMF), hen's yolk defatted protein (yolk protein), wheat gluten and codfish meat, which had been supplemented with sodium deoxycholate (hereinafter, DCA) as a cancer promoter except for an additional DCA-unfed casein group. All of the living rats at checkpoints during the feeding period were examined by the use of a bronchus fiberscope for colonic tumor incidence at 6 wk intervals between the 10th and 34th wk, from which both blood and feces samples were taken at times of endoscopy. Tumorigenesis in the colon was perceived by endoscopy at wk 22 in the group fed DCA casein only and at wk 28 in the other groups except the DCA-unfed casein group. At wk 34, both soybean HMF and yolk protein groups ranked inferior to the DCA-unfed group in tumor incidence. When plasma steroid or lipid concentration was plotted against tumor incidence at wk 28 or 34, positive correlations were found between plasma bile acid concentration and tumor incidence at both weeks. With the exception of the DCA-unfed casein group, plasma bile acid concentration was reversely correlated to fecal bile acid excretion. Taken altogether, these results suggest that bile acids at higher concentrations in the plasma may serve as risk factors of colon tumor incidence.

Purification of membrane-bound lactoferrin from the human milk fat globule membrane

Although lactoferrin is known as a basic soluble glycoprotein, the presence of the membrane-bound form of this protein has also been demonstrated in human milk. Membrane-bound lactoferrin was extracted from the human milk fat globule membrane with a detergent mixture of 1% Tween-20, 0.5% C12E8, and 0.5 M KCl in 20 mM Tris-HCl (pH 7.4). Lactoferrin in the detergent-soluble fraction was purified by affinity chromatography with Concanavalin A and by hydrophobic chromatography with phenyl-Superose. The purified protein gave a single band of 80 kDa by SDS-PAGE. Its N-terminal amino acid sequence was consistent with that of human lactoferrin.

Mutations of a human homologue of the Drosophila eyes absent gene (EYA1) detected in patients with congenital cataracts and ocular anterior segment anomalies

The Drosophila eyes absent gene ( eya ) is involved in the formation of compound eyes. Flies with loss-of-function mutations of this gene develop no eyes and form the ectopic eye in the antennae and the ventral zone of the head on target expression. A highly conserved homo-logous gene in various invertebrates and vertebrates has been shown to function in the formation of the eye. In contrast, a human homologue, EYA1, has been identified by positional cloning as a candidate gene for branchio-oto-renal (BOR) syndrome, in which phenotypic manifestations are restricted to the areas of branchial arch, ear and kidney, with usually no anomalies in the eye. We have examined genomic DNA isolated from patients with various types of developmental eye anomaly for EYA1 mutations by the use of polymerase chain reaction-single-strand conformation polymorphism and sequencing. We identified three novel missense mutations in patients who had con-genital cataracts and ocular anterior segment anomalies. One of the patients had clinical features of BOR syndrome as well. This result implies that the human EYA1 gene is also involved in eye morphogenesis, and that a wide variety of clinical manifestations may be caused by EYA1 mutations.

Preventive effect of soybean resistant proteins against experimental tumorigenesis in rat colon

The insoluble 'high-molecular-weight' fraction (HMF) centrifugally separable after digestion of soy protein isolate with a microbial protease of the exo-type, of which about a quarter is regarded as an indigestible 'resistant protein,' was examined for its preventive effect against colonic tumorigenesis in a model system with male F-344 rats. The rats were intraperitoneally injected with azoxymethane (15 mg/kg BW) once a week for 3 wk and were fed a 20.6% HMF diet (+0.4% DL-Met) or 14.7% casein diet (+0.3% DL-Met) supplemented with 0.2% sodium deoxycholate (DCA) or without supplementation. Twelve wk later, 5 rats of each group were inspected for formation of tumors but no tumors were visible to the naked eye. The DCA-fed casein group was conspicuous for a low count of aberrant crypt foci. At 39 wk, 6 rats of the DCA-fed casein group (n = 10) and 3 rats of the DCA-fed HMF group (n = 9) had a total of 18 tumors with a major axis of 4.0 +/- 0.4 mm and 3 tumors with an axis of 2.0 +/- 0.1 mm, respectively, in contrast to only a single tumor for the DCA-unfed casein group (nil for the DCA-unfed HMF group). The difference in tumor number and size was considered significant between these DCA-fed casein and HMF groups; that is to say, HMF feeding retarded tumor development despite the frequent occurrence of pre-neoplastic lesions. In addition, fecal bile acid excretion was much more elevated by HMF feeding than by casein feeding. It can be assumed from these observations that the antitumorigenicity of HMF is due to the inhibitory effect of soybean resistant proteins on reabsorption as well as the mucosal contact of bile acids in the intestine.

Mitogen-activated protein phosphorylation in endothelial cells exposed to hyperosmolar conditions

The effect of hyperosmolarity on the induction of the mitogen-activated protein kinases (MAPK) was studied in bovine aortic endothelial cell (EC). Different types of agents were used to differentiate the effects of osmolarity from other variables. Hypertonic treatment with physiologically relevant levels of NaCl (350 mOsm/kg H(2)O) significantly increased the level of expression of p38 within 2 min, and ERK-1/2 and JNK after 10 min. The inductions peaked between 30 and 60 min and returned to baseline levels within 2 h. A similar pattern of induction occurred with ionic contrast agent. p38 induction by glucose and mannitol showed a similar pattern, although the level of ERK-1/2 phosphorylation was not as robust, and JNK was not induced by glucose. Urea did not affect the level of induction of the MAPK isoforms. It is concluded that MAPK plays an important role in hyperosmolality-induced signal transduction. Different osmotic agents induce MAPK expression differently. No MAPK induction with urea implies that cell shrinkage may be an important component of hyperosmolality-induced MAPK phosphorylation.

Local antibody response in Peyer's patches to the orally administered dietary protein antigen

To understand local antibody production to dietary protein antigens in the gut, the reactivity of the monoclonal antibodies (mAbs) from Peyer's patches of BALB/c mice raised against orally administered hen egg lysozyme (HEL) was studied. These mAbs were of IgG1 (7 clones), IgA (5 clones) and IgM (13 clones) isotypes. Some of the HEL-binding mAbs preferentially reacted with reduced, carboxy-methylated HEL, rather than with native HEL. MAbs of the IgA and IgM isotypes had cross-reactivity with other unrelated environmental antigens such as E. coli, single-strand DNA, and soluble components of mouse food. In contrast, the IgG1 mAbs did not cross-react with these antigens. The average of the Kd values for HEL of these mAbs was in the order of 10(-6) M, which is moderately higher than those of mAbs from the preimmune repertoire. These results suggest that, under normal physiological conditions, orally administered dietary proteins predominantly induce the local production of polyreactive IgA/IgM antibodies cross-reacting with environmental luminal antigens.

Soybean curd refuse alleviates experimental tumorigenesis in rat colon

Adult Fischer-344 rats which underwent administration of azoxymethane were fed diets containing soybean curd refuse (SCR) or a high-molecular-weight fraction of soy protein digest (HMF), or Hammarsten casein (CAS) as a protein source over a period of 34 weeks. All the living rats of each group at 22, 28 or 34 weeks were endoscopically inspected for tumor incidence in the colon. SCR turned out to be comparable to HMF in anti-tumorigenicity, or rather better than HMF.

Flagellar proteins and type III-exported virulence factors are the predominant proteins secreted into the culture media of Salmonella typhimurium

We analysed all major proteins secreted into culture media from Salmonella typhimurium. Proteins in culture supernatants were collected by trichloroacetic acid precipitation, separated in SDS-polyacrylamide gels and analysed by amino acid sequencing. Wild-type strain SJW1103 cells typically gave rise to nine bands in SDS gels: 89, 67, 58, 52, 50, 42, 40, 35 and (sometimes) 28 kDa. A search of the sequences in the available databases revealed that they were either flagellar proteins or virulence factors. Six of them were flagella specific: FlgK or HAP1 (58 kDa), FliC or flagellin (52 kDa), FliD or HAP2 (50 kDa), FlgE or hook protein (42 kDa), FlgL or HAP3 (35 kDa) and FlgD or hook-cap protein (28 kDa). The other four bands were specific for virulence factors: SipA (89 kDa), SipB (67 kDa), SipC (42 kDa) and InvJ (40 kDa). The 42 kDa band was a mixture of FlgE and SipC. We also analysed secreted proteins from more than 30 flagellar mutants, and they were categorized into four groups according to their band patterns: wild type, mot type, polyhook type and master gene type. Virulence factors were constantly secreted at a higher level in all flagellar mutants except a deltamot (motAB deletion) mutant, in which the amounts were greatly reduced. A new morphological pathway of flagellar biogenesis including protein secretion is presented.

Elimination of Na+-dependent bile acid transporter from small intestine by ileum resection increases [correction of increase] colonic tumorigenesis in the rat fed deoxycholic acid

Ileal Na+-dependent bile acid transporter (ISBT) constituting a gateway to enterohepatic circulation of bile acids occurs exclusively at the distal site of the small intestine. In the present study, we examined colonic tumorigenesis promoted by deoxycholic acid in relation to the expression of the ISBT. For this purpose, the small intestine of a Fischer-344 rat was resected a length of 20 cm above the ileo-cecal valve (ileal resection) or below the duodenum (jejunal resection). Then, rats were treated with an intraperitoneal injection of azoxymethane (15 mg/kg body wt.) once a week for 3 weeks and fed a 20% casein diet supplemented with 0.2% deoxycholate for 39 weeks. Northern blot analysis demonstrated that the ISBT mRNA was hardly detectable in ileum-resected rats. The excretion of fecal bile acids was 1.5-fold higher in the ileum-resected group than in the jejunum-resected group (P < 0.05). On the contrary, the serum bile acids concentration of ileal-resected rats was about one-half of that of jejunum-resected animals (P < 0.05). The tumor incidence and the total tumor number were significantly higher in the ileum-resected group than in the jejunum-resected one (P < 0.05). Interestingly, no tumor was found at the proximal colon in the jejunum-resected group while tumors developed frequently at the proximal site as well as mid and distal colon in the ileum-resected group. These observations demonstrate that malabsorption of bile acids owing to the lack of ISBT enhanced colon tumorigenesis.

Missense mutation in the alternative splice region of the PAX6 gene in eye anomalies

The PAX6 gene is involved in ocular morphogenesis, and PAX6 mutations have been detected in various types of ocular anomalies, including aniridia, Peters anomaly, corneal dystrophy, congenital cataract, and foveal hypoplasia. The gene encodes a transcriptional regulator that recognizes target genes through its paired-type DNA-binding domain. The paired domain is composed of two distinct DNA-binding subdomains, the N-terminal subdomain (NTS) and the C-terminal subdomain (CTS), which bind respective consensus DNA sequences. The human PAX6 gene produces two alternative splice isoforms that have the distinct structure of the paired domain. The insertion, into the NTS, of 14 additional amino acids encoded by exon 5a abolishes the DNA-binding activity of the NTS and unmasks the DNA-binding ability of the CTS. Thus, exon 5a appears to function as a molecular switch that specifies target genes. We ascertained a novel missense mutation in four pedigrees with Peters anomaly, congenital cataract, Axenfeldt anomaly, and/or foveal hypoplasia, which, to our knowledge, is the first mutation identified in the splice-variant region. A T-->A transition at the 20th nucleotide position of exon 5a results in a Val-->Asp (GTC-->GAC) substitution at the 7th codon of the alternative splice region. Functional analyses demonstrated that the V54D mutation slightly increased NTS binding and decreased CTS transactivation activity to almost half.