Properties of the naturally occurring soluble surface glycoprotein of ecotropic murine leukemia virus: binding specificity and possible conformational change after binding to receptor

Ecotropic murine leukemia virus (MuLV) infection is initiated by the interaction between the surface glycoprotein (SU) of the virus and its cell-surface receptor mCAT-1. We investigated the SU-receptor interaction by using a naturally occurring soluble SU which was encoded by the envelope (env) gene of a defective endogenous MuLV, Fv-4(r). Binding of the SU to mCAT-1-positive mouse cells was completed by 1 min at 37 degrees C. The SU could not bind to mouse cells that were persistently infected by ecotropic MuLVs (but not amphotropic or dualtropic MuLVs) or transfected with wild-type ecotropic env genes or a mutant env gene which can express only precursor Env protein that is restricted to retention in the endoplasmic reticulum. These cells were also resistant to superinfection by ecotropic MuLVs. Thus, superinfection resistance correlated with the lack of SU-binding capacity. After binding to the cells, the SU appeared to undergo some conformational changes within 1 min in a temperature-dependent manner. This was suggested by the different properties of two monoclonal antibodies (MAbs) reactive with the same C-terminal half of the Fv-4(r) SU domain, including a proline-rich motif which was shown to be important for conformation of the SU and interaction between the SU and the transmembrane protein. One MAb reacting with the soluble SU bound to cells was dissociated by a temperature shift from 4 to 37 degrees C. Such dissociation was not observed in cells synthesizing the SU or when another MAb was used, indicating that the dissociation was not due to a temperature-dependent release of the MAb but to possible conformational changes in the SU.

OTX2 directly interacts with LIM1 and HNF-3beta

Otx2 is a paired-class homeobox gene, and its functions in anterior visceral endoderm and/or anterior mesendoderm have been suggested to be vital for head development in mammals. Several transcription factors are expressed in these tissues, and mutant mice analyses have suggested the interactions of the Otx2 gene cascade with the Lim1 or HNF-3beta cascade. Here we show that OTX2 directly associates with LIM1 and HNF-3beta; OTX2 binds to the LIM1 homeodomain (HD) with its C-terminal region, whereas both HD and C-terminal regions of OTX2 bind to the HNF-3beta fork head domain or OTX2 HD. The luciferase assay with the P3C sequence, a specific DNA binding sequence for paired-class homeobox genes, has demonstrated that LIM1 enhances, but HNF-3beta represses, OTX2-directed gene expression. Direct interactions of OTX2 with LIM1 or HNF-3beta may play important roles in anterior visceral endoderm and/or anterior mesendoderm to constitute transcriptional regulatory networks for head development.

Cutting edge: absence of expression of RAG1 in peritoneal B-1 cells detected by knocking into RAG1 locus with green fluorescent protein gene

It has been proposed that Ig gene rearrangement in the peritoneal cavity (Pc) B-1 cells might be involved in autoantibody generation. To study possible secondary B cell maturation, we prepared mice carrying a target integration of gfp gene into a rag1 locus (rag1/gfp mice). The GFP+ cells express rag1 mRNA and are undergoing Ig gene rearrangement. RAG1 expression was studied in Pc B-1 cells to detect cells during the stage of Ig gene rearrangement. In contrast to previous reports, Pc B-1 cells did not show RAG1 expression in adolescent or elderly mice. RAG1 expression was not induced in Pc B-1 cells in vivo after stimulation by oral or i.p. administration of LPS. Our results suggest that RAG1 expression in Pc B-1 cells is inhibited for a long period under normal condition and that this suppression is an essential state which maintains allelic exclusion of Ig genes.

A spaceflight experiment for the study of gravimorphogenesis and hydrotropism in cucumber seedlings

Seedlings of Cucurbitaceae plants form a protuberance, termed peg, on the transition zone between hypocotyl and root. Our spaceflight experiment verified that the lateral positioning of a peg in cucumber seedlings is modified by gravity. It has been suggested that auxin plays an important role in the gravity controlled positioning of a peg on the ground. Furthermore, cucumber seedlings grown in microgravity developed a number of the lateral roots that grew towards the water containing substrate in the culture vessel, whereas on the ground they oriented perpendicular to the primary root growing down. The response of the lateral roots in microgravity was successfully mimicked by clinorotation of cucumber seedlings on the three dimensional clinostat. However, this bending response of the lateral roots was observed only in an aeroponic culture of the seedlings but not in solid medium. We considered the response of the lateral roots in microgravity and on clinostat as positive hydrotropism that could easily be interfered by gravitropism on the ground. This system with cucumber seedlings is thus a useful model of spaceflight experiment for the study of the gravimorphogenesis, root hydrotropism and their interaction.

Clinicopathological study of pheochromocytoma of the urinary bladder: immunohistochemical, flow cytometric and ultrastructural findings with review of the literature

Pheochromocytomas usually arise from the adrenal medulla but may also arise from the carotid body, the retroperitoneum, the urinary bladder, and other locations. We report three cases of pheochromocytoma of the urinary bladder with clinicopathological, immunohistochemical, flow cytometric, and ultrastructural findings. Case 1, a 13-year-old boy presented with hematuria. He underwent partial cystectomy, 31 years later he presented with a tumor in the thoracic vertebra. Case 2, a 35-year-old woman presented with headache, nausea, vomiting, palpitations, and diaphoresis on evacuation. She underwent total cystectomy and regional lymph adenectomy. She survived for 10 years without recurrence or metastasis; however, she died from another disease. Case 3, a 31-year-old man presented with dysuria. He underwent total cystectomy and regional lymph adenectomy. The tumor metastasized to the lymph nodes, and the patient died after 4 years. The urinary bladder tumors in these three cases protruded into the lumen and invaded deeper than the middle of the muscle layer. The tumor of the urinary bladder, metastatic lymph nodes, and thoracic vertebra showed alveolar and trabecular patterns, and tumor cells were surrounded by capillaries. The tumor cells were moderate in size with ovoid nuclei and abundant eosinophilic cytoplasm that contained acidophilic granules reactive to Grimelius stain. Vascular invasion was observed in cases 1 and 2. Immunohistochemically, tumor cells showed reactivity for chromogranin, Leu 7, and S-100 protein. In each of the three cases, the DNA ploidy pattern on flow cytometry was aneuploid. Ultrastructural examination revealed several neurosecretory granules, rough endoplasmic reticulum, and a few mitochondria within the cytoplasm. It is difficult to determine whether pheochromocytoma of the urinary bladder is malignant on the basis of histological, immunohistochemical, and flow cytometric findings. Long-term follow up is necessary.

Inhibition of root elongation in microgravity by an applied electric field

Roots grown in an applied electric field demonstrate a bidirectional curvature. To further understand the nature of this response and its implications for the regulation of differential growth, we applied an electric field to roots growing in microgravity. We found that growth rates of roots in microgravity were higher than growth rates of ground controls. Immediately upon application of the electric field, root elongation was inhibited. We interpret this result as an indication that, in the absence of a gravity stimulus, the sensitivity of the root to an applied electric stimulus is increased. Further space experiments are required to determine the extent to which this sensitivity is shifted. The implications of this result are discussed in relation to gravitropic signaling and the regulation of differential cell elongation in the root.

Growth and development, and auxin polar transport in higher plants under microgravity conditions in space: BRIC-AUX on STS-95 space experiment

The principal objectives of the space experiment, BRIC-AUX on STS 95, were the integrated analysis of the growth and development of etiolated pea and maize seedlings in space and a study of the effects of microgravity conditions in space on auxin polar transport in these segments. Microgravity significantly affected the growth and development of etiolated pea and maize seedlings. Epicotyls of etiolated pea seedlings were the most oriented toward about 40 to 60 degrees from the vertical. Mesocotyls of etiolated maize seedlings were curved at random during space flight but coleoptiles were almost straight. Finally the growth inhibition of these seedlings in space was also observed. Roots of some pea seedlings grew toward to the aerial space of Plant Growth Chamber. Extensibilities of cell walls of the third internode of etiolated pea epicotyls and the top region of etiolated maize coleoptiles, which were germinated and grown under microgravity conditions in space, were significantly low as compared with those grown on the ground of the earth. Activities of auxin polar transport in the second internode segments of etiolated pea seedlings and coleoptile segments of etiolated maize seedlings were significantly inhibited and promoted, respectively, under microgravity conditions in space. These results strongly suggest that auxin polar transport as well as the growth and development of plants is controlled under gravity on the earth.

Effect of water temperature on the fit of provisional crown margins during polymerization

STATEMENT OF PROBLEM

When fabricating a provisional crown with the direct technique, dentists are concerned with margin discrepancies that result from polymerization shrinkage.

PURPOSE

This in vitro study examined the effect of water temperature on the fit of provisional crown margins during resin polymerization.

MATERIAL AND METHODS

The experiment was designed to simulate a direct technique to fabricate provisional crowns. After mixing autopolymerizing methyl methacrylate resin, the material was placed in a preformed polycarbonate crown. The crown was seated on a prepared premolar-shaped die with a shoulder margin. After 1 minute and 50 seconds, the crown was removed and polymerization was continued under the following conditions: 20 degrees C air, and water at 0 degrees C, 10 degrees C, 20 degrees C, 30 degrees C, 40 degrees C, 60 degrees C, and 80 degrees C. Six minutes after polymerization, the crown was trimmed and reseated on the die. Discrepancy of crown margin was measured with a 3-dimensional digitizer.

RESULTS

Margin discrepancy varied with the condition during resin-polymerization (ANOVA, P <.001). The crowns polymerized in 20 degrees C and 30 degrees C water revealed the best margin fit, showing 3 times more accurate margin fit than those polymerized in 20 degrees C air (Bonferroni/Dunn procedure, P <.01).

CONCLUSION

Conditions during resin polymerization were significant factors that affected margin fit of provisional crowns using the direct technique. Water temperatures of 20 degrees C and 30 degrees C produced the best fit at the margin of the provisional crown.

Morphogenesis of rice and Arabidopsis seedlings in space

Seedlings of rice (Oryza saliva L.) and Arabidopsis (A. thaliana L.) were cultivated for 68.5 hr in the RICE experiment on board during Space Shuttle STS 95 mission, and changes in their growth and morphology were analyzed. Microgravity in space stimulated elongation growth of both rice coleoptiles and Arabidopsis hypocotyls by making their cell walls extensible. In space, rice coleoptiles showed an inclination toward the caryopsis in the basal region and also a spontaneous curvature in the same direction in the elongating region. These inclinations and curvatures were more prominent in the Koshihikari cultivar compared to a dwarf cultivar, Tan-ginbozu. Rice roots elongated in various directions including into the air on orbit, but two thirds of the roots formed a constant angle with the axis of the caryopsis. In space, Arabidopsis hypocotyls also elongated in a variety of directions and about 10% of the hypocotyls grew into the agar medium. No clear curvatures were observed in the elongating region of Arabidopsis hypocotyls. Such a morphology of both types of seedlings was fundamentally similar to that observed on a 3 D clinostat. Thus, it was confirmed by the RICE experiment that rice and Arabidopsis seedlings perform an automorphogenesis under not only simulated but also true microgravity conditions.

Anti-HIV effect of saquinavir combined with ritonavir is limited by previous long-term therapy with protease inhibitors

Combination therapy of saquinavir (SQV) and ritonavir (RTV) seems to have a strong antiretroviral effect pharmacokinetically. The purpose of this study was to examine the effectiveness of combined therapy using SQV and RTV in patients previously treated with protease inhibitors (PIs) and to identify the factors compromising the response to such combination therapy. Nineteen HIV-infected Japanese patients participated in this trial between June 1997 and July 1998, and were monitored until November 1998. Patients were treated with SQV (400 mg twice daily) and RTV (300 or 400 mg twice daily). Among the 17 patients who continued such therapy for longer than 3 months, 6 were responders. Among nonresponders, the duration of PI therapy was longer and a higher frequency of preexisting PI resistance viral mutations was detected than in responders. No significant differences were found in previous use of reverse transcriptase inhibitor therapy, CD4+ and CD8+ T cell counts, viral load at baseline, and plasma concentrations of SQV and RTV between responders and nonresponders. Our results suggest that the response to SQV combined with RTV therapy is complicated by previous long-term treatment with PIs, probably owing to multiple PI resistance mutations. Even in patients with a PI-sensitive HIV genotype, however, resistance mutations can develop during therapy and abrogate the effect of high plasma SQV concentrations.

Reduction in interleukin-2-producing cells but not Th1 to Th2 shift in moderate and advanced stages of human immunodeficiency virus type-1-infection: direct analysis of intracellular cytokine concentrations in CD4+ CD8- T cells

Previous studies have suggested that CD4+ T lymphocytes shift from the Th1 type to the Th2 type during disease progression in patients with the human immunodeficiency virus type-1 (HIV-1). In the present study, we used a modified method that allowed a direct measurement of intracellular cytokines in CD4+ CD8- T cells. A total of 48 HIV-1-infected (HIV+) and 16 HIV-1-uninfected (HIV-) individuals were studied. The percentages of CD4+ CD8- T cells producing interleukin-2 (IL-2), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), or interleukin-5 (IL-5) in HIV+ and HIV- subjects were 23.6% versus 34.9% (P < 0.01), 13.7% versus 13.2%, 1.3% versus 1.0%, and 1. 2% versus 0.9%, respectively. The population of IL-2-producing cells decreased proportionately with reductions in CD4 counts (< 200/mm3, 200-500/mm3, and > 500/mm3 to 18.0%, 23.5%, and 30.5%, P < 0.05, respectively). There was an inverse correlation between the percentage of IL-2-producing cells and plasma viral load (r = - 0. 446, P < 0.05). However, the percentages of CD4+ CD8- T cells producing other cytokines were not different between HIV+ and HIV-. Our cross-sectional study demonstrated a decrease in IL-2-producing cells but not the Th1 to the Th2 shift in the CD4+ CD8- T cell population in the moderate and advanced stages of HIV-1-infection.

Gangliosides are the binding substances in neural cells for tetanus and botulinum toxins in mice

We used the knockout mice lacking gangliosides and evaluated their response to tetanus and botulinum toxins. We found that tetanus toxin and botulinum type A or B toxin was less toxic in the knockout mice. We conclude that the toxins bind to the gangliosides on the synapses in the initial step of intoxication prior to penetration of the toxins into the neural cells.

PPAR gamma mediates high-fat diet-induced adipocyte hypertrophy and insulin resistance

Agonist-induced activation of peroxisome proliferator-activated receptor gamma (PPAR gamma) is known to cause adipocyte differentiation and insulin sensitivity. The biological role of PPAR gamma was investigated by gene targeting. Homozygous PPAR gamma-deficient embryos died at 10.5-11.5 dpc due to placental dysfunction. Quite unexpectedly, heterozygous PPAR gamma-deficient mice were protected from the development of insulin resistance due to adipocyte hypertrophy under a high-fat diet. These phenotypes were abrogated by PPAR gamma agonist treatment. Heterozygous PPAR gamma-deficient mice showed overexpression and hypersecretion of leptin despite the smaller size of adipocytes and decreased fat mass, which may explain these phenotypes at least in part. This study reveals a hitherto unpredicted role for PPAR gamma in high-fat diet-induced obesity due to adipocyte hypertrophy and insulin resistance, which requires both alleles of PPAR gamma.

NADH shuttle system regulates K(ATP) channel-dependent pathway and steps distal to cytosolic Ca(2+) concentration elevation in glucose-induced insulin secretion

The NADH shuttle system is composed of the glycerol phosphate and malate-aspartate shuttles. We generated mice that lack mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH), a rate-limiting enzyme of the glycerol phosphate shuttle. Application of aminooxyacetate, an inhibitor of the malate-aspartate shuttle, to mGPDH-deficient islets demonstrated that the NADH shuttle system was essential for coupling glycolysis with activation of mitochondrial ATP generation to trigger glucose-induced insulin secretion. The present study revealed that blocking the NADH shuttle system severely suppressed closure of the ATP-sensitive potassium (K(ATP)) channel and depolarization of the plasma membrane in response to glucose in beta cells, although properties of the K(ATP) channel on the excised beta cell membrane were unaffected. In mGPDH-deficient islets treated with aminooxyacetate, Ca(2+) influx through the plasma membrane induced by a depolarizing concentration of KCl in the presence of the K(ATP) channel opener diazoxide restored insulin secretion. However, the level of the secretion was only approximately 40% of wild-type controls. Thus, glucose metabolism through the NADH shuttle system leading to efficient ATP generation is pivotal to activation of both the K(ATP) channel-dependent pathway and steps distal to an elevation of cytosolic Ca(2+) concentration in glucose-induced insulin secretion.

Myelination and behaviour of tenascin-C null transgenic mice

The extracellular matrix glycoprotein tenascin-C is widely expressed during development and repair, making it surprising that few abnormalities have been found in transgenic mice lacking this molecule. We have therefore re-examined the transgenic mice described by Saga et al. [Saga, Y., Yagi, T., Ikawa, Y., Sakakura, T. & Aizawa, S. (1992) Genes Dev., 6 1821-1831] in which tenascin-C was knocked-out by homologous recombination, focusing on two aspects of the nervous system likely to reveal any abnormalities that might follow the loss of tenascin-C. First, we have determined the pattern of myelin and distribution of oligodendrocyte precursor cells in those areas, such as the optic nerve and retina where local concentrations of tenascin-C have been proposed to act as barriers to oligodendrocyte precursor migration and so prevent inappropriate myelination. Secondly, we have examined the behaviour of the mice in a number of well-characterized tests, e.g. beam-walking, passive avoidance and the Morris water maze. We find no abnormalities of myelination or oligodendrocyte precursor distribution in adult mice, showing that local concentrations of tenascin-C are not the sole mechanism responsible for the pattern of myelination in these regions of CNS. However, we do find a number of behavioural abnormalities in these mice and show that hyperlocomotion and deficits in coordination during beam walking can be ascribed to tenascin-C deficiency. The effects on coordination are, however, not seen on a 129 genetic background. Taken together, these results significantly extend the phenotype associated with tenascin-C deficiency but argue against a role in myelination.

[Usefulness of MT-2 assay to decide when to start anti-HIV therapy]

It is well known that the emergence of syncytium inducing (SI) variant correlates accelerated CD4 decline and disease progression during the course of HIV infection. We have conducted a clinical study to investigate whether or not detection of SI by MT-2 cells (MT-2 assay) can be a clinical marker to decide when to start anti-HIV therapy since 1995. We examined 483 blood samples obtained from 172 HIV-infected patients by the MT-2 assay. SI was detected from 20 patients. There were five untreated patients whose CD4 counts were 300/microliter or more. Anti-HIV combination therapies were started soon after detection of SI in all of them. We have followed their clinical courses for more than 4 years, so far, in three of them. Their CD4 counts and clinical courses were both stable. In contrast, in another patient who could not receive any anti-HIV therapy even though SI positive, decline of CD4 was very rapid (200/microliter/year) and the disease progressed to AIDS within one year as like other SI positive cases before the era of several approved anti-HIV drugs. According to these distinct prognosis, the MT-2 assay might be a useful clinical marker for deciding anti-HIV therapy at least in our limited cases.

Effect of hook subunit concentration on assembly and control of length of the flagellar hook of Salmonella

The flagellar hook of Salmonella is a filamentous polymer made up of subunits of the protein FlgE. Hook assembly is terminated when the length reaches about 55 nm. After our recent study of the effect of cellular levels of the hook length control protein FliK, we have now analyzed the effect of cellular levels of FlgE itself. When FlgE was overproduced in a wild-type strain, a fliC (flagellin) mutant, or a fliD (hook-associated protein 2 [HAP2], filament capping protein) mutant, the hooks remained at the wild-type length. In a fliK (hook length control protein) mutant, which produces long hooks (polyhooks), the overproduction of FlgE resulted in extraordinarily long hooks (superpolyhooks). In a flgK (HAP1, first hook-filament junction protein) mutant or a flgL (HAP3, second hook-filament junction protein) mutant, the overproduction of FlgE also resulted in longer than normal hooks. Thus, at elevated hook protein levels not only FliK but also FlgK and FlgL are necessary for the proper termination of hook elongation. When FlgE was severely underproduced, basal bodies without hooks were often observed. However, those hooks that were seen were of wild-type length, demonstrating that FlgE underproduction decreases the probability of the initiation of hook assembly but not the extent of hook elongation.

Distinctive roles of Fyn and Lyn in IgD- and IgM-mediated signaling

Src family kinases Fyn and Lyn associate with the B cell antigen receptor (BCR). Accumulating data show that Lyn plays important roles in BCR-mediated signaling, while the role of Fyn remains obscure. Here we dissected the role of Fyn and Lyn in BCR signaling using B cells from fyn(-/-), lyn(-/-) and fyn/lyn double-deficient (fyn(-/-)lyn(-/-)) mice. In contrast to previous reports, fyn(-/-) B cells were slightly hyporeactive to both anti-IgM and anti-IgD-dextran. Although lyn(-/-) B cells were hyper-reactive to anti-IgM, anti-IgD-induced proliferation was impaired in lyn(-/-) B cells. Most of the other phenotypes of fyn(-/-)lyn(-/-) mice were similar to that of lyn(-/-) mice, except that proliferative responses of B cells to various stimuli, such as BCR cross-linking and lipopolysaccharide, were significantly lower in fyn(-/-)lyn(-/-) mice than in lyn(-/-) mice. Finally, immune responses to thymus-independent type 2 antigen were affected in these mutant mice. These observations suggest that Fyn and Lyn are involved in B cell functions, and play similar, but partly distinct, roles in BCR signaling.

Exacerbation of influenzavirus pneumonia by intranasal administration of surfactant in a mouse model

Although surfactant-secreting type II alveolar cells have been shown to be damaged during influenzavirus pneumonia, little is known about the effects of surfactant replacement therapy. We have developed a mouse influenza model, in which viral infection can be localized to the upper respiratory tract or to both the upper and lower respiratory tract depending on the volume (rather than infectious dose) of intranasal inocula of influenzavirus. In this model, only mice infected with a large inocula die with massive infection in the lung. Using this model, we unexpectedly found that intranasal administration of surfactant dramatically exacerbated influenzavirus infection causing fatal disease even in mice inoculated with a small inocula. This exacerbation resulted from enhancement of intrabronchial and intraalveolar spread of virus, as confirmed by immunohistochemical detection of viral antigen in lungs. Assuming this experimental model in mice recapitulates naturally occurring disease in humans, extreme caution is warranted in surfactant-replacement treatment of influenzavirus pneumonia in humans.