Identification of Helicobacter pylori infection in symptomatic patients in Surabaya, Indonesia, using five diagnostic tests.

SUMMARY The prevalence of Helicobacter pylori infection in Indonesia is controversial. We examined the H. pylori infection rate in 78 patients in a hospital in Surabaya using five different tests, including culture, histology, immunohistochemistry, rapid urease test, and urine antibody test. Furthermore, we analysed virulence factors in H. pylori strains from Indonesia. The H. pylori infection rate was only 11.5% in all patients studied, and 2.3% of Javanese patients and 18.0% of Chinese patients were infected (P = 0.01). Although severe gastritis was not observed, activity and inflammation were significantly higher in patients positive for H. pylori than in patients negative for H. pylori. Among genotypes identified from five isolated strains, cagA was found in four; two were vacA s1m1. All cagA-positive strains were oipA 'on' and iceA1 positive. We confirmed both a low H. pylori infection rate and a low prevalence of precancerous lesions in dyspeptic patients in a Surabaya hospital, which may contribute to the low incidence of gastric cancer in Indonesia.

Ras-related C3 botulinum toxin substrate 1 (RAC1) regulates glucose-stimulated insulin secretion via modulation of F-actin.

AIMS/HYPOTHESIS: The small G-protein ras-related C3 botulinum toxin substrate 1 (RAC1) plays various roles in mammalian cells, such as in the regulation of cytoskeletal organisation, cell adhesion, migration and morphological changes. The present study examines the effects of RAC1 ablation on pancreatic beta cell function. METHODS: Isolated islets from pancreatic beta cell-specific Rac1-knockout (betaRac1(-/-)) mice and RAC1 knockdown INS-1 insulinoma cells treated with small interfering RNA were used to investigate insulin secretion and cytoskeletal organisation in pancreatic beta cells. RESULTS: BetaRac1(-/-) mice showed decreased glucose-stimulated insulin secretion, while there were no apparent differences in islet morphology. Isolated islets from the mice had blunted insulin secretion in response to high glucose levels. In RAC1 knockdown INS-1 cells, insulin secretion was also decreased in response to high glucose levels, consistent with the phenotype of betaRac1(-/-) mice. Even under high glucose levels, RAC1 knockdown INS-1 cells remained intact with F-actin, which inhibits the recruitment of the insulin granules, resulting in an inhibition of insulin secretion. CONCLUSIONS/INTERPRETATION: In RAC1-deficient pancreatic beta cells, F-actin acts as a barrier for insulin granules and reduces glucose-stimulated insulin secretion.

The atomic and electronic structures of NiO(001)∕Au(001) interfaces.

The atomic and electronic structures of NiO(001)∕Au(001) interfaces were analyzed by high-resolution medium energy ion scattering (MEIS) and photoelectron spectroscopy using synchrotron-radiation-light. The MEIS analysis clearly showed that O atoms were located above Au atoms at the interface and the inter-planar distance of NiO(001)∕Au(001) was derived to be 2.30 ± 0.05 Å, which was consistent with the calculations based on the density functional theory (DFT). We measured the valence band spectra and found metallic features for the NiO thickness up to 3 monolayer (ML). Relevant to the metallic features, electron energy loss analysis revealed that the bandgap for NiO(001)∕Au(001) reduced with decreasing the NiO thickness from 10 down to 5 ML. We also observed Au 4f lines consisting of surface, bulk, and interface components and found a significant electronic charge transfer from Au(001) to NiO(001). The present DFT calculations demonstrated the presence of an image charge beneath Ni atoms at the interface just like alkali-halide∕metal interface, which may be a key issue to explain the core level shift and band structure.

Impaired glucose tolerance in mice with a targeted impairment of insulin action in muscle and adipose tissue.

Type 2 diabetes is a complex metabolic disorder characterized by peripheral insulin resistance and impaired beta cell function. Insulin resistance is inherited as a non-mendelian trait. In genetically predisposed individuals, resistance of skeletal muscle and adipose tissue to insulin action precedes the onset of clinical diabetes, and is thought to contribute to hyperglycaemia by leading to impaired beta cell function and increased hepatic glucose production. It is not clear whether beta cell and liver defects are also genetically determined. To test the hypothesis that insulin resistance in muscle and fat is sufficient to cause type 2 diabetes in the absence of intrinsic beta cell and liver abnormality, we generated transgenic mice that were insulin-resistant in skeletal muscle and adipose tissue. These mice developed all the prodromal features of type 2 diabetes but, despite the compounded effect of peripheral insulin resistance and a mild impairment of beta cell function, failed to become diabetic. These findings indicate the need for a critical re-examination of the primary site(s) of insulin resistance in diabetes.

Osteoporotic changes of subchondral trabecular bone in osteoarthritis of the knee: a 3-T MRI study.

SUMMARY: Subchondral trabecular bone structure was analyzed in knee osteoarthritis (OA) patients using 3-T MRI to investigate structural features of subchondral trabecular bone of knee OA. With OA progression, osteoporotic changes were observed in the lateral joint, showing a higher correlation than sclerotic changes in the medial joint. INTRODUCTION: To investigate structural features of subchondral trabecular bone of knee osteoarthritis (OA). METHODS: Sixty knees with KL grade 0-4 (all female) were examined. Fast imaging employing steady-state acquisition-cycled phases (FIESTA-c) and FatSat Spoiled gradient recalled acquisition in the steady state (SPGR) images were acquired by 3-T MRI. At four sites (the medial femur, medial tibia, lateral femur, and lateral tibia), subchondral trabecular bone structure was analyzed by FIESTA-c imaging, cartilage area was measured by SPGR imaging, and their correlation was analyzed. In addition, the subjects were classified into four groups from the cartilage area measured by SPGR imaging, and subchondral trabecular bone structure in each group was compared. RESULTS: As cartilage area decreased in the medial joint, bone volume fraction and trabecular thickness in the medial tibia increased, and bone volume fraction, trabecular thickness, number, and connectivity in the lateral femur and lateral tibia decreased (r ≥ 0.4 or ≤-0.4, p ≤ 0.001). Compared to medially, the changes laterally showed a higher correlation. When the medial-lateral ratio of trabecular thickness in the tibia was determined, it had the highest correlation coefficient (r=-0.7, p < 0.001). These changes were not significantly detected in the early stage. CONCLUSIONS: To more sensitively detect OA changes in subchondral trabecular bone structure, a focus on osteoporotic changes in the lateral joint and the medial-lateral ratio would be useful. Detectability of early OA remains unknown, but based on a strong correlation with the degree of OA progression, trabecular structural analysis of subchondral bone may be a useful parameter to evaluate OA severity and evaluate treatment.

The source of the Ti 3d defect state in the band gap of rutile titania (110) surfaces.

The origin of the Ti 3d defect state seen in the band gap for reduced rutile TiO(2)(110) surfaces has been excitingly debated. The probable candidates are bridging O vacancies (V(O)) and Ti interstitials (Ti-int) condensed near the surfaces. The aim of this study is to give insights into the source of the gap state via photoelectron spectroscopy combined with ion scattering and elastic recoil detection analyses. We have made three important findings: (i) The intensity of the gap state observed is well correlated with the sheet resistance measured with a 4-point probe, inversely proportional to the density of Ti-int. (ii) Sputter∕annealing cycles in ultrahigh vacuum (UHV) lead to efficient V(O) creation and condensation of Ti-int near the surface, while only annealing below 870 K in UHV condenses subsurface Ti-int but does not create V(O) significantly. (iii) The electronic charge to heal a V(O) is almost twice that to create an O adatom adsorbed on the 5-fold Ti row. The results obtained here indicate that both the V(O) and Ti-interstitials condensed near the surface region contribute to the gap state and the contribution to the gap state from the Ti-int becomes comparable to that from V(O) for the substrates with low sheet resistance less than ∼200 Ω∕square.

The mechanism of emerging catalytic activity of gold nano-clusters on rutile TiO2(110) in CO oxidation reaction.

This paper reveals the fact that the O adatoms (O(ad)) adsorbed on the 5-fold Ti rows of rutile TiO(2)(110) react with CO to form CO(2) at room temperature and the oxidation reaction is pronouncedly enhanced by Au nano-clusters deposited on the above O-rich TiO(2)(110) surfaces. The optimum activity is obtained for 2D clusters with a lateral size of ∼1.5 nm and two-atomic layer height corresponding to ∼50 Au atoms∕cluster. This strong activity emerging is attributed to an electronic charge transfer from Au clusters to O-rich TiO(2)(110) supports observed clearly by work function measurement, which results in an interface dipole. The interface dipoles lower the potential barrier for dissociative O(2) adsorption on the surface and also enhance the reaction of CO with the O(ad) atoms to form CO(2) owing to the electric field of the interface dipoles, which generate an attractive force upon polar CO molecules and thus prolong the duration time on the Au nano-clusters. This electric field is screened by the valence electrons of Au clusters except near the perimeter interfaces, thereby the activity is diminished for three-dimensional clusters with a larger size.

Association between BIA-derived Phase Angle and Sarcopenia and Improvement in Activities of Daily Living and Dysphagia in Patients undergoing Post-Stroke Rehabilitation.

OBJECTIVES: To investigate the predictive value of the BIA-derived phase angle with respect to the functional prognosis and baseline sarcopenia in patients undergoing post-stroke rehabilitation. DESIGN: Retrospective cohort study. SETTING AND PARTICIPANTS: Overall, 577 Japanese patients admitted to a post-acute care hospital from 2016 to 2020 were recruited. MEASUREMENTS: Body composition analysis, which included BIA-derived phase angle and skeletal muscle mass, was performed using bioelectrical impedance analysis (BIA). Study outcomes included physical function assessed using the Functional Independence Measure (FIM-motor) and the level of dysphagia assessed using the Food Intake LEVEL Scale (FILS). Sarcopenia was defined as the loss of skeletal muscle mass and decreased muscle strength. Receiver operating characteristic curves were used to calculate the optimal cutoff value of BIA-derived phase angle to diagnose sarcopenia. Multivariate analyses were used to determine whether the BIA-derived phase angle at admission was associated with outcomes at discharge and baseline sarcopenia. RESULTS: After enrollment, 499 patients (mean age: 74.0 ± 13.1 years; 52.0% men) were examined. The median FIM-motor and FILS scores at admission were 47 (20-69) and 8 (7-10), respectively. Sarcopenia was observed in 43.2% of patients. After adjusting for potential confounders, BIA-derived phase angle was positively associated with FIM-motor scores at discharge (ß = 0.134, P < 0.001), FIM-motor score gain (ß = 2.504, P < 0.001), and FILS scores at discharge (ß = 0.120, P = 0.039). BIA-derived phase angle was negatively associated with the sarcopenia diagnosis at baseline (odds ratio = -0.409, P < 0.001); its cutoff value was 4.76° (sensitivity 0.800, specificity 0.790, P < 0.001) for sarcopenia diagnosis in men and 4.11° (sensitivity 0.735, specificity 0.829, P < 0.001) in women. CONCLUSION: BIA-derived phase angle was positively associated with the recovery of physical function and dysphagia level and negatively associated with baseline sarcopenia in patients undergoing post-stroke rehabilitation. The BIA-derived phase angle cutoff for sarcopenia diagnosis was 4.76° for men and 4.11° for women.

Distinct and overlapping functions of insulin and IGF-I receptors.

Targeted gene mutations have established distinct, yet overlapping, developmental roles for receptors of the insulin/IGF family. IGF-I receptor mediates IGF-I and IGF-II action on prenatal growth and IGF-I action on postnatal growth. Insulin receptor mediates prenatal growth in response to IGF-II and postnatal metabolism in response to insulin. In rodents, unlike humans, insulin does not participate in embryonic growth until late gestation. The ability of the insulin receptor to act as a bona fide IGF-II-dependent growth promoter is underscored by its rescue of double knockout Igf1r/Igf2r mice. Thus, IGF-II is a true bifunctional ligand that is able to stimulate both insulin and IGF-I receptor signaling, although with different potencies. In contrast, the IGF-II/cation-independent mannose-6-phosphate receptor regulates IGF-II clearance. The growth retardation of mice lacking IGF-I and/or insulin receptors is due to reduced cell number, resulting from decreased proliferation. Evidence from genetically engineered mice does not support the view that insulin and IGF receptors promote cellular differentiation in vivo or that they are required for early embryonic development. The phenotypes of insulin receptor gene mutations in humans and in mice indicate important differences between the developmental roles of insulin and its receptor in the two species.

Unique role of SNT-2/FRS2beta/FRS3 docking/adaptor protein for negative regulation in EGF receptor tyrosine kinase signaling pathways.

The membrane-linked docking protein SNT-2/FRS2beta/FRS3 becomes tyrosine phosphorylated in response to fibroblast growth factors (FGFs) and neurotrophins and serves as a platform for recruitment of multiple signaling proteins, including Grb2 and Shp2, to FGF receptors or neurotrophin receptors. We previously reported that SNT-2 is not tyrosine phosphorylated significantly in response to epidermal growth factor (EGF) but that it inhibits ERK activation via EGF stimulation by forming a complex with ERK2. In the present report, we show that expression of SNT-2 suppressed EGF-induced cell transformation and proliferation, and expression level of SNT-2 is downregulated in cancer. The activities of the major signaling molecules in EGF receptor (EGFR) signal transduction pathways, including autophosphorylation of EGFR, were attenuated in cells expressing SNT-2 but not in cells expressing SNT-2 mutants lacking the ERK2-binding domain. Furthermore, SNT-2 constitutively bound to EGFR through the phosphotyrosine binding (PTB) domain both with and without EGF stimulation. Treatment of cells with MEK inhibitor U0126 partially restored the phosphorylation levels of MEK and EGFR in cells expressing SNT-2. On the basis of these findings, we propose a novel mechanism of negative control of EGFR tyrosine kinase activity with SNT-2 by recruiting ERK2, which is the site of negative-feedback loop from ERK, ultimately leading to inhibition of EGF-induced cell transformation and proliferation.

Tissue-specific insulin resistance in mice with mutations in the insulin receptor, IRS-1, and IRS-2.

Type 2 diabetes is characterized by abnormalities of insulin action in muscle, adipose tissue, and liver and by altered beta-cell function. To analyze the role of the insulin signaling pathway in these processes, we have generated mice with combined heterozygous null mutations in insulin receptor (ir), insulin receptor substrate (irs-1), and/or irs-2. Diabetes developed in 40% of ir/irs-1/irs-2(+/-), 20% of ir/irs-1(+/-), 17% of ir/irs-2(+/-), and 5% of ir(+/-) mice. Although combined heterozygosity for ir/irs-1(+/-) and ir/irs-2(+/-) results in a similar number of diabetic mice, there are significant differences in the underlying metabolic abnormalities. ir/irs-1(+/-) mice develop severe insulin resistance in skeletal muscle and liver, with compensatory beta-cell hyperplasia. In contrast, ir/irs-2(+/-) mice develop severe insulin resistance in liver, mild insulin resistance in skeletal muscle, and modest beta-cell hyperplasia. Triple heterozygotes develop severe insulin resistance in skeletal muscle and liver and marked beta-cell hyperplasia. These data indicate tissue-specific differences in the roles of IRSs to mediate insulin action, with irs-1 playing a prominent role in skeletal muscle and irs-2 in liver. They also provide a practical demonstration of the polygenic and genetically heterogeneous interactions underlying the inheritance of type 2 diabetes.

Preserved pancreatic beta-cell development and function in mice lacking the insulin receptor-related receptor.

Receptors of the insulin/insulinlike growth factor (IGF) family have been implicated in the regulation of pancreatic beta-cell growth and insulin secretion. The insulin receptor-related receptor (IRR) is an orphan receptor of the insulin receptor gene (Ir) subfamily. It is expressed at considerably higher levels in beta cells than either insulin or IGF-1 receptors, and it has been shown to engage in heterodimer formation with insulin or IGF-1 receptors. To address whether IRR plays a physiologic role in beta-cell development and regulation of insulin secretion, we have characterized mice lacking IRR and generated a combined knockout of Ir and Irr. We report that islet morphology, beta-cell mass, and secretory function are not affected in IRR-deficient mice. Moreover, lack of IRR does not impair compensatory beta-cell hyperplasia in insulin-resistant Ir(+/-) mice, nor does it affect beta-cell development and function in Ir(-/-) mice. We conclude that glucose-stimulated insulin secretion and embryonic beta-cell development occur normally in mice lacking Irr.

Predictive assay of neoadjuvant chemotherapy in management of oral cancer.

Neoadjuvant chemotherapy (NAC) for oral squamous cell carcinoma has a positive impact on organ preservation and/or survival only in patients who achieve an excellent anti-tumour effect with this therapy. Predictive assay for NAC can play an important role in establishing tailor-made treatments for oral squamous cell carcinoma. In this retrospective study, the anti-tumour effects of cisplatin-based NAC in 70 patients with oral squamous cell carcinoma were reviewed in relation to biological markers of tumour cell proliferation activity: tumour grade, cellular DNA content, mitotic index, apoptotic index, ki-67 positive rate, and p53 and Bax expression. Tumour grade, Bax expression, apoptotic index and cellular DNA content were significantly correlated with the anti-tumour effects of NAC in univariate analysis. Tumour grade, Bax expression and apoptotic index were selected as independent predictive factors by means of multiple logistic analysis. Using the regression equation from these results, the prediction rate for anti-tumour effects was 70%. For patients in whom NAC is predicted to be ineffective, it may be necessary to choose another treatment option in order to improve their survival and quality of life.

Modulation of cytotoxicity and cellular pharmacology of 1,2-diaminocyclohexane platinum (IV) complexes mediated by axial and equatorial ligands.

Isomers (R,R-, S,S-, and cis-) of 1,2-diaminocyclohexane (DACH) platinum(IV) complexes with selected axial and equatorial ligands were synthesized and evaluated for in vitro antitumor activity, cellular uptake, and total DNA-Pt adducts. L1210 cells, sensitive to cis-diamminedichloroplatinum(II) (CDDP) and tetraplatin (L1210/0), 160-fold resistant to CDDP [L1210/diamminedichloroplatinum (DDP)], or 70-fold resistant to tetraplatin (L1210/DACH), were used in conjunction with compounds having the general structure DACH-Pt(IV)-X2Y2, where X and Y are axial and equatorial ligands and X2Y2 are specifically Cl2Cl2,Ac2Cl2, (TFA)2Cl2, (OH)2Cl2, and Cl2CBDCA (Cl, chloro; Ac, acetato; TFA, trifluoroacetato; OH, hydroxo; CBDCA, 1,1-cyclobutanedicarboxylato). Comparison of cytotoxicities between isomers of Cl2Cl2,Ac2Cl2, or Cl2CBDCA indicated that R,R-isomers were the most effective against all three cell lines. The relatively lower activity of the S,S- and cis-isomers was cell line dependent: against L1210/DACH, both isomers of Cl2Cl2 were only 2- to 3-fold less effective, and this contrasted with 7- and 26-fold lower cytotoxicities, respectively, against L1210/DDP. Cross-resistance factors in the L1210/DDP and L1210/DACH lines depended on both isomeric form and the nature of axial or equatorial ligand. The L1210/DDP cells were 6- to 9-fold cross-resistant to the R,R-isomer, 8- to 15-fold to S,S-isomer, and 13- to 38-fold to cis-isomer. The L1210/DACH line was only 4- to 7-fold cross-resistant to the three isomers of Ac2Cl2 but cross-resistance to the isomers was 47- to 79-fold for Cl2Cl2 and 22- to 56-fold for Cl2CBDCA complexes. Compared with CDDP, accumulation (2 h at 100 microM drug concentration) of Ac2Cl2 in the three L1210 cell lines was 26-50%, while uptake of Cl2Cl2 and (TFA)2Cl2 was 100-170% and 320-570%, respectively. The greatest DNA binding was seen with Cl2Cl2 in all cell lines, followed by (TFA)2Cl2, CDDP, and Ac2Cl2. DNA binding correlated directly with potency (1/concentration producing 50% inhibition) in the L1210/0 model (r = 0.973, P < 0.016) but not in the L1210/DDP and L1210/DACH models. Accumulation and DNA-binding studies indicated that binding efficiency to DNA was: Cl2Cl2 > Ac2Cl2 > CDDP > (TFA)2Cl2. In a nonreducing environment, the Pt(IV) complexes (20 microM) did not react with salmon sperm DNA. Reduced glutathione (100 microM), as a reducing agent, rendered full binding capacity to Cl2Cl2; binding was 25-30% of the expected maximum for (TFA)2Cl2, while Ac2Cl2 remained inert.(ABSTRACT TRUNCATED AT 400 WORDS)

Estradiol sensitivity test using contact-sensitive plates of confluent BALB/c 3T3 cell monolayers.

We have attempted to develop an in vitro assay system for predicting estradiol sensitivity of clinical cancer cells by measuring the effects of estradiol on the net DNA synthesis of primary culture cells. Superinoculation of neoplastic and normal cells onto confluent monolayers of a contact-sensitive cell line, which have been designated as contact-sensitive plates (CSPs), resulted in both the specific growth of the neoplastic cells and the growth inhibition of contact-sensitive normal cells. The applicability of CSPs to an estradiol sensitivity test was examined in the known estradiol-sensitive, estrogen receptor-possessing cell lines, MCF-7 breast cancer and KSE-1 esophageal cancer cells. The responses of each cancer cell to estradiol were sufficiently evaluated in this assay and clearly demonstrated stimulative and inhibitive growth regulatory effects of the estradiol in MCF-7 and KSE-1 cells, respectively. A total of 38 clinical carcinomas (33 of the breast and 5 of the esophagus) were tested for their estradiol sensitivity. A statistically significant increase of cancer cell growth (P less than 0.1) in nontreated culture from the 48th to the 96th h of the primary culture on CSPs was observed in 28 of 38 overall cases (73.7%), and the evaluable data were obtained within 5 days by a sampling of 5 X 10(3) cancer cells. Most of the breast carcinomas exhibited a positive correlation between the growth-stimulative effect of estradiol in this assay and the estrogen receptor levels in the resected specimens. On the other hand, a clinical case of esophageal cancer with an estrogen receptor showed a growth inhibition of primary carcinoma cells by estradiol treatment. These results therefore indicate the feasibility of predicting individual tumor response to estradiol by using a rapid sensitivity test in vitro.

Decreased activation of carcinogens in the liver of carcinogen-resistant rats.

We have developed a new strain of rats (resistant rat) which exhibit resistance against the carcinogenic action of several carcinogenic compounds. In the present study, we compared the ability of resistant rat liver to activate 3'-methyl-4-dimethylaminoazobenzene and 2-acetylaminofluorene to highly reactive metabolites, which can covalently bind to DNA, with that of carcinogen-sensitive parent strain rats (sensitive rat), using in vitro DNA binding assay. The covalent binding of these carcinogens to calf thymus DNA, catalyzed by the hepatic 9000 x g supernatant fraction from resistant rats pretreated with 3-methylcholanthrene, was about one-half of that catalyzed by the 9000 x g supernatant from sensitive rats which had received the same treatment. These results suggest that the ability of resistant rat liver to activate the carcinogens decreases compared to sensitive rat liver. Further experiments revealed that this decreased activation of the carcinogens in resistant rat livers is due to a low inducibility of 3-methylcholanthrene-inducible forms of cytochrome P-450 mRNA. The hepatic cytosolic Ah receptor concentrations in resistant rats were shown to be significantly lower than those of sensitive rats. Scatchard plot analysis demonstrated, however, that there is no significant difference between the affinity of Ah receptors for 2,3,7,8-tetrachlorodibenzo-p-dioxin in these two strains. These data implicate that the hepatic Ah receptor level may be an important factor in determining carcinogen sensitivity in rats.

Genetic modifiers of the insulin resistance phenotype in mice.

Insulin resistance can result from genetic interactions among susceptibility alleles. To identify genetic loci predisposing to insulin resistance, we used crosses between different strains of mice with a targeted null allele of the insulin receptor gene. On the genetic background of B6 mice, the insulin receptor gene mutation causes mild hyperinsulinemia. In contrast, on the genetic background of 129/Sv mice, the same mutation causes severe hyperinsulinemia, suggesting that the 129/Sv strain harbors alleles that interact with the insulin receptor mutation and predispose to insulin resistance. As a first step to identify these alleles, we generated an F2 intercross between insulin receptor heterozygous mutant mice on B6 and 129/Sv backgrounds (B6IR x 129IR) and performed a genome-wide scan with polymorphic markers at a 20-cM resolution. We report the identification of loci on chromosomes 2 (logarithm of odds [LOD] 5.58) and 10 (LOD 5.58) that show significant evidence for linkage to plasma insulin levels as a quantitative trait. These findings indicate that targeted mutations in knockout mice can be used to unravel the complex genetic interactions underlying insulin resistance.

Amplification of distinct subfamilies of short interspersed elements during evolution of the Salmonidae.

There are at least three different kinds of short interspersed repetitive elements in salmonid genomes. Of these, members of the HpaI family are found to be most widely distributed in salmonid species. The HpaI family is present with high copy numbers in all members of the subfamily Salmoninae, such as salmon, trout and charr. In order to determine whether the amplification of the Hpa sequence occurred rapidly within a short evolutionary period or gradually, over the long term, a search was made for Hpa sequences in primitive salmonids; namely, grayling and whitefish. A grayling species has fivefold fewer copies of these sequences than the Salmoninae species, whereas several whitefish species have 200-fold to 20-fold fewer copies than the Salmoniae species. Characterization of the Hpa sequences in these species allowed us to recognize two distinct Hpa subfamilies on the basis of diagnostic substitutions as well as a new short interspersed element with an Hpa-related sequence. The distribution of these sequences revealed that distinct members of the HpaI or Hpa-related family were amplified during establishment of each subfamily lineage in a manner very similar to the amplification of the human Alu family. We provide evidence for the validity of a model that involves "multiple source genes" to explain diagnostic substitutions of the Hpa subfamilies and the timing of their appearance during evolution.

A newly isolated family of short interspersed repetitive elements (SINEs) in coregonid fishes (whitefish) with sequences that are almost identical to those of the SmaI family of repeats: possible evidence for the horizontal transfer of SINEs.

The SmaI family of repeats is present only in the chum salmon and the pink salmon, and it is not present in five other species in the same genus or in other species in closely related genera. In the present study, we showed that another short interspersed repetitive elements (SINEs) family, which is almost identical to the SmaI family, is present in all fishes in the subfamily Coregoninae, being regarded as the most primitive salmonids. This new family of SINEs was designated the SmaI-cor family (SmaI family of repeats in coregonids). The consensus sequence of the SmaI-cor family was found to be 98.6% homologous to that of the SmaI family. Accordingly, it is difficult to explain the high degree of homology between these two families of SINEs by any mechanism other than the horizontal transfer of SINEs. The estimates of the rate of neutral mutation of nuclear genes, comparing chum salmon and European whitefish, confirmed this possibility. Our results strongly suggest that a member(s) of the SmaI-cor family might have been transferred horizontally from one coregonid species to a common ancestor of chum and pink salmon or to these two species independently, to allow subsequent amplification of the SmaI family in their respective genomes.

Shc phosphotyrosine-binding domain dominantly interacts with epidermal growth factor receptors and mediates Ras activation in intact cells.

The adaptor protein Shc contains a phosphotyrosine binding (PTB) domain and a Src homology 2 (SH2) domain, both of which are known to interact with phosphorylated tyrosines. We have shown previously that tyrosine 1148 of the activated epidermal growth factor (EGF) receptor is a major binding site for Shc while tyrosine 1173 is a secondary binding site in intact cells. In the present study, we investigated the interaction between the PTB and SH2 domains of Shc and the activated human EGF receptor. Mutant 52-kDa Shc with an arginine-to-lysine substitution at residue 175 in the PTB domain (Shc R175K) or 397 in the SH2 domain (Shc R397K) was coexpressed in Chinese hamster ovary cells overexpressing the wild-type or mutant EGF receptors that retained only one of the autophosphorylation sites at tyrosine 1148 (QM1148) or 1173 (QM1173). Shc R397K was coprecipitated with the QM1148 and QM1173 receptors, was tyrosine-phosphorylated, and associated with Grb2 and Sos. In contrast, coprecipitation of Shc R175K with the mutant receptors was barely detectable. In cells expressing the QM1173 receptor, Shc R175K was tyrosine-phosphorylated and associated with Grb2, while association of Sos was barely detectable. In cells expressing the QM1148 receptor, tyrosine phosphorylation of Shc R175K was markedly reduced. When both Shc R175K and 46-kDa Shc R397K were coexpressed with the mutant receptors, p46 Shc R397K was dominantly tyrosine-phosphorylated. In cells expressing the wild-type receptor, Shc R397K, but not Shc R175K, translocated to the membrane in an EGF-dependent manner. In addition, Ras activity stimulated by the immunoprecipitates of Shc R397K was significantly higher than that by the immunoprecipitates of Shc R175K. The present results indicate that tyrosine 1148 of the activated EGF receptor mainly interacts with the Shc PTB domain in intact cells. Tyrosine 1173 interacts with both the PTB and SH2 domains, although the interaction with the PTB domain is dominant. In addition, Shc bound to the activated EGF receptor via the PTB domain dominantly interacts with Grb2-Sos complex and plays a major role in the Ras-signaling pathway.