4F2 (CD98) heavy chain is associated covalently with an amino acid transporter and controls intracellular trafficking and membrane topology of 4F2 heterodimer

4F2, also termed CD98, is an integral membrane protein consisting of a heavy chain linked to a light chain by disulfide bond. We have generated a monoclonal antibody to the mouse 4F2 light chain and cloned the cDNA. It encodes a mouse counterpart of rat L-type amino acid transporter-1, and induces system L amino acid transport in Xenopus oocytes in the presence of 4F2 heavy chain. Transfection studies in mammalian cells have indicated that the 4F2 heavy chain is expressed on the plasma membrane on its own, whereas the 4F2 light chain can be transported to the surface only in the presence of 4F2 heavy chain. 4F2 heavy chain is expressed diffusely on the surface of fibroblastic L cells, whereas it is localized selectively to the cell-cell adhesion sites in L cells expressing cadherins. These results indicate that the 4F2 heavy chain is associated covalently with an amino acid transporter and controls the cell surface expression as well as the membrane topology of the 4F2 heterodimer. Although 4F2 heavy and light chains are expressed coordinately in most tissues, the light chain is barely detected by the antibody in kidney and intestine, despite the presence of heavy chain in a complex form. The results predict the presence of multiple 4F2 light chains.

Detection of Man5GlcNAc and related free oligomannosides in the cytosol fraction of hen oviduct

The presence of free oligomannosides in cytosol has been demonstrated by metabolic radiolabeling, and Manalpha1-2Manalpha1-2Manalpha1-3(Manalpha1-6)++ +Manbeta1-4GlcNAc was detected as the main free oligomannoside in Chinese hamster ovary cells [Kmiécik, D., Herman, V., Stroop, C.J.M., Michalski, J.C., Mir, A.M., Labiau, O., Verbert, A., and Cacan, R. (1995) Glycobiology, 5, 483-494]. In the present paper, the isomeric structures and amounts of oligomannosides in the cytosol fraction of hen oviduct were analyzed by pyridylamination and exoglycosidase digestion. Hen oviduct was used since our group has already characterized the cytosolic neutral alpha-mannosidase and endo-beta-N-acetylglucosaminidase obtained from the same source. The amounts of Man2GlcNAc, Man3GlcNAc, Man4GlcNAc, and Man5GlcNAc were 0.6, 0.6, 0.5, and 0.8 nmol/g tissue, respectively, but Man6GlcNAc-Man9GlcNAc were not detected. The isomeric structures of the Man3GlcNAc-Man5GlcNAc found were (Manalpha1-2)0-2Manalpha1-3(Manalpha1-6)Manbeta1 -4GlcNAc, which were compatible with the substrate specificities of cytosolic endo-beta-N-acetylglucosaminidase and neutral alpha-mannosidase, indicating that these enzymes participate in the formation of the oligomannosides present in the cytosol.

[An elderly patient with an insulinoma who had prolonged dementia-like symptoms]

A 77-year-old woman had suffered from memory disturbance and disorientation for two years before she was admitted to the hospital because of confusion. Her score on the Hasegawa dementia scale revised (HDS-R) was 12 points at the time of the first medical examination. No other abnormalities could be found except for a blood glucose concentration of 34 mg/ dl. A Magnetic Resonance Image (MRI) of the brain showed some small lacunae on both sides in the frontal white matter and basal ganglia. After hospitalization, glucose was administered and the blood glucose concentration increased, but the dementia-like symptoms did not resolve. She was discharged because the symptoms were too difficult to control in the general hospital. Although dementia-like symptoms were present even after discharge, they did not necessarily appear during fasting. Six months later she was rehospitalized. The insulin-blood sugar ratio was at least 0.3 and abdominal echogram showed a 1-cm tumor at the tail of pancreas. The pancreas tail was removed and the tumor cells were reacted with anti-insulin-antibodies. One month after the operation, the dementia-like symptoms had resolved. The HDS-R score was improved to 27 points (normal range) 40 days after the operation. The amount of the slow waves in the electroencephalogram decreased 5 months after the operation. The dementia-like symptoms observed in this case could be regarded as the Durchgangssyndrom of Wieck. This syndrome is observed transiently at the time of recovery of deterioration of disturbances of consciousness. But it is treatable. This patient was an interesting case that showed Durchgangssyndrom mimiking dementia associated with insulinoma.

Prognostic significance of progesterone receptor immunohistochemistry in endometrial carcinoma

OBJECTIVE

The aim of this study was to evaluate the prognostic significance of steroid hormone receptors in endometrial carcinoma using immunohistochemical staining for progesterone receptor (PR) and estrogen receptor (ER).

METHODS

We evaluated the correlation between PR/ER immunohistochemistry and age, clinical stage, tumor grade, myometrial tumor invasion, and disease-free survival in a series of 92 cases of endometrioid adenocarcinoma.

RESULTS

Fifty (54.4%) endometrial carcinomas were PR-positive and 44 (47.8%) were ER-positive. PR immunohistochemistry of endometrial carcinoma was statistically correlated with the International Federation of Gynecology and Obstetrics (FIGO) stage (I, II vs III, IV, P = 0.001), FIGO grade (G1 vs G2 vs G3, P = 0.007), the depth of myometrial tumor invasion (< or = 1/2 vs > 1/2, P = 0.006), and disease-free survival (living vs dead, P = 0.0025). In contrast, ER immunohistochemistry had significant correlations with the depth of myometrial tumor invasion (P = 0.026) and disease-free survival (P = 0.032). Multivariate analysis of PR/ER immunohistochemistry, stage, grade, and myometrial invasion showed that the PR immunohistochemistry was a significant prognostic factor for survival (P = 0.026).

CONCLUSION

PR/ER immunohistochemistry was significantly related to survival and PR immunohistochemistry appeared to be the most reliable means for predicting survival in endometrioid adenocarcinoma of the endometrium, independent of other clinicopathological parameters.

Effects of mesenchyme on epithelial tissue architecture revealed by tissue recombination experiments between the submandibular gland and lung of embryonic mice

Lung epithelium during morphogenesis maintains a sheet structure of polarized cells lining a lumen, in which E-cadherin, beta-catenin and tight junctional proteins are localized at the cell-cell contact sites. On the other hand, the submandibular gland epithelium at early stages of development forms a non-cavitated mass of cells where E-cadherin/beta-catenin are present on the entire cell surfaces and tight junctional proteins are almost absent or weakly scattered. In the present study, tissue recombination experiments were performed between the two organs to explore roles of mesenchyme in the architectural development of the epithelium. Homotypic recombinants of both submandibular gland and lung showed the tissue architecture as observed in the intact organs. In contrast, 11-day lung epithelium cultured with 13-day submandibular mesenchyme formed multilayers of cells with the lumen being less visible. It was accompanied by redistribution of E-cadherin/beta-catenin along the entire cell surfaces and by an irregular distribution of tight junctional proteins. A similar redistribution of these molecules was observed in 15-day lung epithelium cultured with the submandibular mesenchyme, although the epithelial sheet structure lining the lumen was formed. On the other hand, the tissue architecture of submandibular gland epithelium was little affected by lung mesenchyme, although the epithelium was flattened and showed branching morphogenesis.

Iron-dependent oxidation, ubiquitination, and degradation of iron regulatory protein 2: implications for degradation of oxidized proteins

The ability of iron to catalyze formation of reactive oxygen species significantly contributes to its toxicity in cells and animals. Iron uptake and distribution is regulated tightly in mammalian cells, in part by iron regulatory protein 2 (IRP2), a protein that is degraded efficiently by the proteasome in iron-replete cells. Here, we demonstrate that IRP2 is oxidized and ubiquitinated in cells before degradation. Moreover, iron-dependent oxidation converts IRP2 into a substrate for ubiquitination in vitro. A regulatory pathway is described in which excess iron is sensed by its ability to catalyze site-specific oxidations in IRP2, oxidized IRP2 is ubiquitinated, and ubiquitinated IRP2 subsequently is degraded by the proteasome. Selective targeting and removal of oxidatively modified proteins may contribute to the turnover of many proteins that are degraded by the proteasome.

Lung tumor induced by long-term inhalation or intratracheal instillation of diesel exhaust particles

A series of long-term inhalation studies of diesel exhaust and intratracheal instillation of diesel particles was conducted on female SPF F344 rats. A particulate but not gaseous component in the inhalation studies provoked inflammatory changes and tumors in the lung, and the intratracheally instilled particles showed similar findings. Adenoma and adenocarcinoma were the main histologic types of the tumors which developed and they showed the phenotype of surfactant apoprotein-producing cells, suggesting that the tumor cell origin was a Type II alveolar cell. The tumor incidence rate correlated with the cumulative concentration of inhaled particles per week and with the amount of particles deposited in the lung. In the instillation studies, the carbon core of diesel particles obtained after exhaustive extraction of tarry matter showed a slightly lower positive rate of lung tumor formation than the rate in untreated diesel particles, indicating an important role of carbon core in the diesel particle-induced tumor. In the intratracheal instillation studies, point mutation of K-ras oncogene was detected in a significant percentage in the tumor cells.

Human SPA-1 gene product selectively expressed in lymphoid tissues is a specific GTPase-activating protein for Rap1 and Rap2. Segregate expression profiles from a rap1GAP gene product

Mouse Spa-1 gene with a region homologous to the human rap1GAP gene is transcriptionally induced in the lymphocytes by mitogenic stimulation. Herein we have cloned a cDNA for its human counterpart. SPA-1 cDNA encodes a 130-kDa protein (p130(SPA-1)) consisting of proline-rich regions and rap1GAP-related domain followed by a coiled-coil stretch. Baculovirally expressed p130(SPA-1) exhibited GTPase-activating protein (GAP) activity for Rap1 and Rap2, but not for Ras, Rho, Cdc42, Rac, and Ran, with comparable specific activity to the rap1GAP gene product (p85/95(rap1GAP)). In the cells, p130(SPA-1) was mostly localized at the perinuclear membranous region co-localizing with Rap1 and Rap2. Expression of SPA-1 and rap1GAP genes tended to be segregate in various tissues, lymphoid tissues expressing abundant SPA-1 transcript without rap1GAP, while those such as brain, kidney, and pancreas exhibiting rap1GAP mRNA with little SPA-1. Promyelocytic HL-60 cells, which expressed p130(SPA-1) with little p85/95(rap1GAP) in uninduced state, showed progressive decline in p130(SPA-1) and conversely drastic increase in p85/95(rap1GAP) as they ceased from proliferation and differentiated into macrophages by 12-O-tetradecanoylphorbol-13-acetate. These results suggested that products of SPA-1 and rap1GAP genes, albeit comparable GAP activity for Rap1 and Rap2, functioned in the distinct contexts depending on cell types and/or states.

Prethrombotic state due to hypercoagulability in patients with permanent transvenous pacemakers

Venous thrombosis is a relatively usual but serious complication of permanent transvenous pacing. However, the pathogenesis has not been defined. To clarify underlying abnormalities in the coagulation-fibrinolysis system in patients with permanent transvenous pacemakers, we measured serum levels of fibrinopeptide A (FPA), thrombin-antithrombin III complexes (TATs), plasmin-alpha 2 plasmin inhibitor complexes (PICs), D-dimer (D-D), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4) in 53 patients with permanent transvenous pacemakers and 10 control subjects. The patients were divided into two groups, as follows, according to the presence of mural thrombus documented along the pacing lead(s) by digital subtraction angiography and transesophageal echocardiography: Group Th (-), patients without venous route thrombus; and Group Th (+), patients with venous route thrombus. FPA and TAT levels increased significantly even in Group Th (-), and further increased in Group Th (+) compared with control subjects (FPA: 7.5 +/- 4.9, 15.3 +/- 8.8 vs 3.0 +/- 1.4 ng/mL, respectively, P < 0.05; TAT: 2.9 +/- 1.3, 4.8 +/- 2.3 vs 1.7 +/- 0.6 ng/mL, respectively, P < 0.05). There were no differences in levels of D-D, PIG, beta-TG, and PF4 among control subjects, Group Th (-), and Group Th (+). These findings suggest that the hypercoagulable state appears in patients with permanent transvenous pacemakers, even without apparent venous thrombosis. The patients with permanent transvenous pacemakers are thought to be in the prethrombotic state even if they have no venous route thrombosis.

Talc and amosite/crocidolite preferentially deposited in the lungs of nonoccupational female lung cancer cases in urban areas of Japan

To analyze the correlation between asbestos lung burden and lung cancer, lungs of 211 female cases with and without lung cancer were examined. Phase-contrast microscopic (PCM) counting of ferruginous (FBs) and uncoated fibers (UFs), which had length longer than 5 microns and aspect ratios greater than 3:1, revealed a significantly higher level of FBs plus UFs in urban lung cancer cases than urban non-lung cancer cases (1380.5 vs. 550.3; p < 0.001). No difference was noted between rural lung cancer and non-lung cancer cases. Analytical electron microscopic studies identified various kinds of mineral fibers with an aspect ratio greater than 3:1 in the lung tissue including chrysotile, actinolite/tremolite, amosite/crocidolite, fibrous talc, mica, silica, iron, wollastonite, chlorite, kaoline, and others. The most frequently detected fibers were thin, short chrysotile fibers, most of which could not be found by PCM, followed by relatively thick, long actinolite/tremolite fibers, fibrous talc, and in a smaller number, amosite/crocidolite of intermediate length and width. Amosite/crocidolite and fibrous talc counts in urban lung cancer cases were greater than those of urban non-lung cancer cases, rural lung cancer, and rural non-lung cancer cases; these findings were consistent with PCM analysis. Therefore, it is suggested that fibers detected in PCM observation may be mainly amosite/crocidolite with some parts fibrous talc and that fibrous talc in urban environments may be another candidate for carcinogenic or cocarcinogenic factors of female lung cancer.

Involvement of reactive oxygen intermediates in spontaneous and CD95 (Fas/APO-1)-mediated apoptosis of neutrophils

Apoptosis is well known to be mediated by oxidative stress. To evaluate the functional role of reactive oxygen intermediates (ROI) produced by neutrophils, we compared the rates of apoptosis in neutrophils isolated from normal donors and from patients with chronic granulomatous disease (CGD), a hereditary defect in ROI production. Spontaneous cell death in CGD neutrophils in vitro was significantly inhibited relative to normal neutrophils. The acceleration of apoptosis induced by anti-Fas monoclonal antibody (MoAb) in CGD neutrophils was much slower than that seen in normal neutrophils. These findings suggest that the apoptosis of neutrophils may be mediated by endogenous oxidative products. This suggestion was confirmed by observation that apoptosis of normal neutrophils was markedly inhibited by reduction of intracellular levels of hydrogen peroxide (H2O2). The inhibition of apoptosis in normal neutrophils by adding catalase occurred regardless of the presence of anti-Fas MoAb. H2O2 increased both spontaneous apoptosis and Fas-mediated apoptosis of the CGD neutrophils in proportion to that seen in normal neutrophils. Although several factors that mediate the apoptosis of neutrophils remain to be determined, these results suggest that ROI are major mediators of the apoptosis in neutrophils and may be involved in Fas-mediated signal transduction pathway.

Mitogen-inducible SIPA1 is mapped to the conserved syntenic groups of chromosome 19 in mouse and chromosome 11q13.3 centromeric to BCL1 in human

Sipa1, previously called Spa1, is transcriptionally induced in the murine lymphoid cells following mitogenic stimulation and encodes a protein with a domain related to Rap1 GTPase activating protein (Rap1GAP) at the N-terminus and to PEST sequences followed by a leucine zipper motif at the C-terminus. Herein mouse genomic Sipa1, which consisted of 16 exons, was cloned. Gene linkage analysis using (BXD) recombinant inbred strains indicated that Sipa1 was mapped to the most centromeric region of chromosome 19 syntenic with the long arm of human chromosome 11. Human SIPA1 cDNA exhibited a striking homology to that of mouse throughout the entire region, with the overall identity being 90% at the amino acid level. Human genomic clones, which hybridized with both mouse and human SIPA1 cDNA but not with RAP1GAP cDNA, were then isolated. Fluorescence in situ hybridization (FISH) analysis using the human genomic clones indicated that SIPA1 was indeed mapped to chromosome 11q13, most likely to the 11q13.3 subregion. It was further indicated by double-color FISH that SIPA1 was located in the centromeric neighborhood of CCND1/ PRAD1, a presumed BCL1 oncogene.

Clinical presentation of pulmonary tuberculosis associated with acquired immunodeficiency syndrome in metropolitan Tokyo

The clinical features of pulmonary tuberculosis associated with acquired immunodeficiency syndrome (AIDS) in Japan were surveyed utilizing questionnaires completed by 48 institutes around the Tokyo metropolitan area. We found 11 Japanese and six foreign patients. The average number of patients per institute was 0.37. The Japanese patients had advanced human immunodeficiency virus (HIV) infection. A middle aged man, with fever and cough, nonspecific chest X-ray infiltrates, decreased lymphocyte counts, and a negative tuberculin skin test was the typical presentation of the Japanese patients. The clinical diagnosis was often difficult. The smear positive rate was high among those from whom smears were obtained, suggesting high communicability. None of the isolates indicated multidrug-resistant tuberculosis at the time of diagnosis. In conclusion, sputum smear and culture remain the keys to diagnosing tuberculosis in patients with AIDS, although the clinical picture may be atypical for pulmonary tuberculosis.

Mouse embryonic submandibular gland epithelium loses its tissue integrity during early branching morphogenesis

During the development of the mouse submandibular gland, the epithelium undergoes not only shape changes to produce extensively branched lobules and stalk, but also changes in cell arrangement from a cell mass to a cavitated cell sheet. The present study examined the organization in the developing epithelium of intercellular adhesion systems and of actin-containing microfilaments. E-cadherin and beta-catenin, which are components of cell-to-cell adherens junctions in epithelial cells, were distributed along the cell periphery of almost the entire epithelium of the submandibular gland at all stages examined and were mainly localized at the apical region of the oral epithelium. Actin-containing microfilaments, which are associated with cell-to-cell adherens junctions, showed a distribution similar to that of those molecules. In contrast, although the distributions of desmoplakins I/II, major desmosomal proteins, and ZO-1 (a tight junction protein) were seen in the oral epithelium and proximal stalk of the submandibular gland epithelium, signals representing these molecules were absent from or much reduced in the submandibular gland epithelium of the cell mass at the 12- and 13-day stages. In the 14-day gland, they strongly appeared in the cells facing the appearing lumens, whereas they were weakly scattered within the terminal lobules that were still a part of the cell mass. These findings suggest that cell-to-cell adhesion systems are differentially regulated during the epithelial morphogenesis of the submandibular gland and that the integrity of the submandibular gland epithelium is lost during the early stages of development, indicating the tissue to be a rather plastic structure.

Identification of a conserved and functional iron-responsive element in the 5'-untranslated region of mammalian mitochondrial aconitase

Iron-responsive elements (IREs) are RNA stem-loop motifs found in genes of iron metabolism. When cells are iron-depleted, iron regulatory proteins (IRPs) bind to IREs in the transcripts of ferritin, transferrin receptor, and erythroid amino-levulinic acid synthetase. Binding of IRPs to IRE motifs near the 5' end of the transcript results in attenuation of translation while binding to IREs in the 3'-untranslated region of the transferrin receptor results in protection from endonucleolytic cleavage. Iron deprivation results in activation of IRE binding activity, whereas iron replete cells lose IRE binding activation. Here, we report the identification of a conserved IRE in the 5'-untranslated region of the transcript of the citric acid cycle enzyme mitochondrial aconitase from four different mammalian species. The IRE in the transcript of mitochondrial aconitase can mediate in vitro translational repression of mitochondrial aconitase by IRPs. Furthermore, levels of mitochondrial aconitase are decreased in mice maintained on a low iron diet, whereas levels of mRNA remain unchanged. The decrease in levels of mitochondrial aconitase is likely due to activation of IRP binding and consequent attenuation of translation. Thus, expression of the iron-sulfur protein mitochondrial aconitase and function of the citric acid cycle may be regulated by iron levels in cells.

Superior vena cava syndrome due to a permanent transvenous pacing lead

Superior vena cava (SVC) syndrome after pacemaker implantation is a very rare complication. We present a 56-year-old man with severe swelling of the face, neck, and upper arms about 6 years after pacemaker implantation. Digital subtraction angiography showed occlusion of the left innominate vein and severe stenosis of the SVC. The patient eventually required surgical treatment, since anticoagulant therapy and balloon venoplasty were not effective. We conclude that surgical repair is the most effective method for treating similar patients.

Recovery of impaired left ventricular function in patients with acute myocardial infarction is predicted by the discordance in defect size on 123I-BMIPP and 201Tl SPET images

A discrepancy between myocardial perfusion defect and wall motion abnormalities is frequently found early after coronary reperfusion in patients with acute myocardial infarction. The purpose of this study was to assess recovery of impaired left ventricular function by reference to the discordance in defect size between myocardial fatty acid uptake and myocardial perfusion using combined single-photon emission tomographic (SPET) imaging early after coronary perfusion therapy. In 37 patients with acute myocardial infarction, iodine-123 15-(p-iodophenyl)-3(R, S)-methylpentadecanoic acid (BMIPP) and thallium-201 SPET scans were performed early after coronary reperfusion. A severity score was determined from the extent of the imaging defect with each tracer. Left ventricular wall motion score (WMS) and ejection fraction (EF) were obtained at admission and at 4 weeks after the onset of infarction. In 32 of the 37 patients, discordance in defect sizes delineated with the two SPET studies was found during the acute stage. The severity score for BMIPP was larger than that for 201Tl during the acute stage (7. 7+/-2.4 vs 4.4+/-2.5, P <0.001). There was a fair correlation between the severity score for BMIPP and WMS (r=0.82, P <0.0001), but a poor correlation between that for 201Tl and WMS. The extent of discordance in severity scores between BMIPP and 201Tl during the acute stage correlated well with the extent of the improvement in WMS (r=0.86, P <0.0001) and that of EF (r=0.85, P <0.0001). We conclude that the discordance in defect size on BMIPP and 201Tl SPET images during the acute stage of infarction is an early predictor of the viability of the myocardium at risk of infarction.

Recovery of apparent diffusion coefficient after ischemia-induced spreading depression relates to cerebral perfusion gradient

BACKGROUND AND PURPOSE

Transient decreases of the apparent diffusion coefficient (ADC) of water as measured by fast diffusion-weighted imaging (DWI) in the ischemic border zone are thought to reflect cellular swelling associated with spreading depression. DWI and dynamic contrast-enhanced MRI were applied to study the characteristics of spreading depression and the correlation between ADC recovery time and tissue perfusion in focal ischemia.

METHODS

Serial DWI was performed during remote middle cerebral artery occlusion in rats (n = 5) with an echo-planar imaging technique. ADC maps were calculated and ADC values displayed as a function of time in user-defined regions of interest with a time resolution of 12 to 16 seconds. Dynamic contrast-enhanced MRI was performed for qualitative correlation of ADC changes with tissue perfusion.

RESULTS

Recovery time of transient ADC decreases correlated with the degree of the perfusion deficit (r = .81, P < .001). Slowly recovering ADC declines were found close to the ischemic core and correlated with severe perfusion deficit, while short-lasting ADC declines were typically found in moderately malperfused or normal tissue. Transient ADC decreases originated in the subcortical and cortical ischemic border zones and propagated along the cortex with a velocity of 2.9 +/- 0.9 mm/min.

CONCLUSIONS

The variation in the recovery time of transient ADC decreases in the ischemic periphery reflects the gradient of the tissue perfusion. Severely delayed recovery time after spreading depression is thought to represent the ischemic penumbra.

Differences in the RNA binding sites of iron regulatory proteins and potential target diversity

Posttranscriptional regulation of genes of mammalian iron metabolism is mediated by the interaction of iron regulatory proteins (IRPs) with RNA stem-loop sequence elements known as iron-responsive elements (IREs). There are two identified IRPs, IRP1 and IRP2, each of which binds consensus IREs present in eukaryotic transcripts with equal affinity. Site-directed mutagenesis of IRP1 and IRP2 reveals that, although the binding affinities for consensus IREs are indistinguishable, the contributions of arginine residues in the active-site cleft to the binding affinity are different in the two RNA binding sites. Furthermore, although each IRP binds the consensus IRE with high affinity, each IRP also binds a unique alternative ligand, which was identified in an in vitro systematic evolution of ligands by exponential enrichment procedure. Differences in the two binding sites may be important in the function of the IRE-IRP regulatory system.