Regulated expression of a gene encoding a nuclear factor, IRF-1, that specifically binds to IFN-beta gene regulatory elements

Expression of the interferon-beta (IFN-beta) gene is induced by a variety of agents, including viruses. Evidence has been provided that a mouse nuclear factor, termed interferon regulatory factor-1 (IRF-1), specifically binds to the upstream regulatory region of the human IFN-beta gene and mediates virus-induced transcription of the gene. In this study, we describe the molecular cloning and characterization of the mouse and human cDNAs encoding IRF-1. Our results suggest that IRF-1 is also involved in the regulation of other genes such as IFN-alpha and MHC class I genes. Surprisingly, IRF-1 gene expression is dramatically induced by Newcastle disease virus in mouse L929 cells and by Concanavalin A in spleen cells. We show here that the IRF-1 gene possesses virus-inducible promoter.

Structurally similar but functionally distinct factors, IRF-1 and IRF-2, bind to the same regulatory elements of IFN and IFN-inducible genes

Viral infections commonly induce expression of type I interferon (IFN) genes. The induction is transient and involves transcriptional activation wherein a positive factor, IRF-1, binds to upstream regulatory cis elements. In the present study we report the isolation of a cDNA encoding a novel factor, termed IRF-2, that interacts with the same nucleotide sequence elements as IRF-1. Both genes are inducible not only by virus but also by IFN. Unlike IRF-1, IRF-2 does not function as an activator; rather, it suppresses the function of IRF-1 under certain circumstances. Our results suggest that transcription of the IFN and IFN-inducible genes is regulated by two similar trans-acting factors that apparently compete for the same cis-acting recognition sequences, but which have opposite effects.

Intracytoplasmic sperm injection in the mouse

Intracytoplasmic sperm injection (ICSI) was successful in the mouse when a piezo-driven micropipette was used instead of a mechanically driven conventional pipette. Eighty percent of sperm-injected oocytes survived, and approximately 70% of them developed into blastocysts in vitro. When 106 embryos at the 2- to 4-cell stage were transferred to eight naturally mated foster mothers, 30% of the embryos (25-43%, depending on the host) reached the full term. Except for two that were cannibalized soon after birth, all of the young (30 pups) grew into normal adults. Studies of this type on the mouse may increase understanding of the fertilization process and of how ICSI works.

T cell-specific loss of Pten leads to defects in central and peripheral tolerance

PTEN, a tumor suppressor gene, is essential for embryogenesis. We used the Cre-loxP system to generate a T cell-specific deletion of the Pten gene (Pten(flox/-) mice). All Pten(flox/-) mice develop CD4+ T cell lymphomas by 17 weeks. Pten(flox/-) mice show increased thymic cellularity due in part to a defect in thymic negative selection. Pten(flox/-) mice exhibit elevated levels of B cells and CD4+ T cells in the periphery, spontaneous activation of CD4+ T cells, autoantibody production, and hypergammaglobulinemia. Pten(flox/-) T cells hyperproliferate, are autoreactive, secrete increased levels of Th1/Th2 cytokines, resist apoptosis, and show increased phosphorylation of PKB/Akt and ERK. Peripheral tolerance to SEB is also impaired in Pten(flox/-) mice. PTEN is thus an important regulator of T cell homeostasis and self-tolerance.

Surface of bacteriorhodopsin revealed by high-resolution electron crystallography

Bacteriorhodopsin is a transmembrane protein that uses light energy, absorbed by its chromophore retinal, to pump protons from the cytoplasm of bacteria such as Halobacterium salinarium into the extracellular space. It is made up of seven alpha-helices, and in the bacterium forms natural, two-dimensional crystals called purple membranes. We have analysed these crystals by electron cryo-microscopy to obtain images of bacteriorhodopsin at 3.0 A resolution. The structure covers nearly all 248 amino acids, including loops outside the membrane, and reveals the distribution of charged residues on both sides of the membrane surface. In addition, analysis of the electron-potential map produced by this method allows the determination of the charge status of these residues. On the extracellular side, four glutamate residues surround the entrance to the proton channel, whereas on the cytoplasmic side, four aspartic acids occur in a plane at the boundary of the hydrophobic-hydrophilic interface. The negative charges produced by these aspartate residues is encircled by areas of positive charge that may facilitate accumulation and lateral movement of protons on this surface.

Induction of endogenous IFN-alpha and IFN-beta genes by a regulatory transcription factor, IRF-1

Interferons (IFNs) have an important role in cell growth and differentiation. The most well-known function of IFNs is their antiviral activity; viral infections result in induction of the transcription of the IFN-alpha and IFN-beta genes. Recently we isolated the gene encoding a transcription factor, IRF-1, that may play a part in the induction of IFN genes. Interestingly, the IRF-1 gene itself is virus-inducible, suggesting the importance of de novo production of IRF-1 in IFN gene induction. Here we show that high-level expression of the cloned mouse IRF-1 gene in monkey COS cells results in the induction of endogenous IFN-alpha and IFN-beta genes without viral stimulation. Furthermore, we demonstrate the induction of these genes by an IRF-1/yeast GAL4 chimaeric transcription factor. This may be the first demonstration of the specific induction of silent chromosomal genes by transfection of a single transcription factor gene in mammalian cells.

The outcome of hepatitis C virus infection is predicted by escape mutations in epitopes targeted by cytotoxic T lymphocytes

CD8(+) cytotoxic T lymphocytes (CTL) are thought to control hepatitis C virus (HCV) replication and so we investigated why this response fails in persistently infected individuals. The HCV quasispecies in three persistently infected chimpanzees acquired mutations in multiple epitopes that impaired class I MHC binding and/or CTL recognition. Most escape mutations appeared during acute infection and remained fixed in the quasispecies for years without further diversification. A statistically significant increase in the amino acid replacement rate was observed in epitopes versus adjacent regions of HCV proteins. In contrast, most epitopes were intact when hepatitis C resolved spontaneously. We conclude that CTL exert positive selection pressure against the HCV quasispecies and the outcome of infection is predicted by mutations in class I MHC restricted epitopes.

Regulation of Toll-like receptor-mediated inflammatory response by complement in vivo

Toll-like receptors (TLRs) and complement are 2 components of innate immunity that are critical for first-line host defense and elicitation of adaptive immune responses. Many pathogen-associated molecular patterns activate both TLR and complement, but whether and how these 2 systems, when coactivated in vivo, interact with each other has not been well studied. We demonstrate here a widespread regulation of TLR signaling by complement in vivo. The TLR ligands lipopolysacharride (TLR4), zymosan (TLR2/6), and CpG oligonucleotide (TLR9) caused, in a complement-dependent manner, strikingly elevated plasma interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and IL-1beta, and/or decreased plasma IL-12 levels in mice deficient in the membrane complement inhibitor decay-accelerating factor (DAF). A similar outcome was observed in wild-type mice cotreated with the TLR ligands and cobra venom factor, a potent complement activator. The regulatory effect of complement on TLR-induced cytokine production in vivo was mediated by the anaphylatoxin receptors C5aR and C3aR. Additionally, changes in lipopolysaccharide (LPS)-induced cytokine production in DAF-deficient mice correlated with increased mitogen-activated protein kinase and nuclear factor-kappaB activation in the spleen. These results reveal a strong interaction between complement and TLR signaling in vivo and suggest a novel mechanism by which complement promotes inflammation and modulates adaptive immunity.

Evidence for a nuclear factor(s), IRF-1, mediating induction and silencing properties to human IFN-beta gene regulatory elements

Transcription of the human interferon-beta (IFN-beta) gene is induced by a variety of agents such as viruses, dsRNA and some cytokines. In this study, we describe a nuclear factor, termed interferon regulatory factor-1 (IRF-1), that is involved in the transcription of IFN-beta and possibly other genes. We demonstrate that IRF-1 functions in virus-induced transcription by interacting with previously identified, IFN-beta regulatory DNA elements. Our data suggest that IRF-1 participates in the transient formation of an induction-specific complex(es) with the regulatory elements. IRF-1 may also be involved in silencing the function of the SV40 enhancer juxtaposed to the regulatory elements in uninduced cells.

Oxidative stress by tumor-derived macrophages suppresses the expression of CD3 zeta chain of T-cell receptor complex and antigen-specific T-cell responses

One of the important mechanisms of immunosuppression in the tumor-bearing status has been attributed to the down-modulation of the CD3 zeta chain and its associated signaling molecules in T cells. Thus, the mechanism of the disappearance of CD3 zeta was investigated in tumor-bearing mice (TBM). The decrease of CD3 zeta was observed both in the cell lysate and intact cells. Direct interaction of T cells with macrophages from TBM (TBM-macrophages) induced the decrease of CD3 zeta, and depletion of macrophages rapidly restored the CD3 zeta expression. We found that treatment of such macrophages with N-acetylcysteine, known as antioxidant compound, prevented the decrease of CD3 zeta. Consistent with this result, the addition of oxidative reagents such as hydrogen peroxide and diamide induced the decrease of CD3 zeta expression in T cells. Consequently, the loss of CD3 zeta resulted in suppression of the antigen-specific T-cell response. These results demonstrate that oxidative stress by macrophages in tumor-bearing status induces abnormality of the T-cell receptor complex by cell interactions with T cells. Therefore, our findings suggest that oxidative stress contributes to the regulation of the expression and function of the T-cell receptor complex.

Mouse oocytes injected with testicular spermatozoa or round spermatids can develop into normal offspring

Genomic imprinting occurs in both male and female gametes during gametogenesis, but the exact time when imprinting begins and ends is unknown. In the present study we injected nuclei of testicular spermatozoa and round spermatids into mature mouse oocytes to see whether these nuclei are able to participate in syngamy and normal embryonic development. If the injected oocytes develop into normal fertile offspring, imprinting in the male germ cells used must have been completed by the time of injection. Ninety-two percent of mouse oocytes injected with testicular spermatozoa survived and 94% of these were fertilized normally (extrusion of the second polar body and formation of male and female pronuclei). When 44 two-cell embryos so created were transferred to 5 foster mothers, 24 (54.5%) developed into normal offspring. Unlike testicular spermatozoa, round spermatids could not activate the oocytes, and therefore the oocytes had to be activated artificially either before or after spermatid injection. The highest rate (77%) of normal fertilization was obtained when the oocytes were first activated by electric current, then injected individually with a single spermatid nucleus. When 131 two-cell embryos were transferred to 15 foster mothers, 37 (28.2%) reached full term. All but two grew into healthy adults. Thus, it would appear that gametic imprinting in mouse spermatogenic cells is completed before spermiogenesis begins. Under the experimental conditions employed, spermatid nuclei were less efficient than testicular sperm nuclei in producing normal offspring, but perhaps this was due to technical rather than inherent problems.

Induction of the transcription factor IRF-1 and interferon-beta mRNAs by cytokines and activators of second-messenger pathways

Nuclear protein IRF-1 (interferon regulatory factor 1) was earlier shown to bind to cis-acting regulatory elements present on interferon (IFN)-alpha/beta genes and some IFN-inducible genes. Here we show that in both human FS-4 and murine L929 cells, steady-state levels of IRF-1 mRNA were increased by treatment with tumor necrosis factor (TNF), interleukin 1 (IL-1), poly(I).poly(C), or IFN-beta. IRF-1 mRNA induction was also demonstrated in cells treated with calcium ionophore A23187 or with phorbol 12-myristate 13-acetate, but not with epidermal growth factor, dibutyryl-cAMP, or the adenylate cyclase activator forskolin. To determine whether stimulation of IRF-1 mRNA levels correlates with IFN-beta induction, we compared IRF-1 and IFN-beta mRNA levels in cells exposed to various stimuli. In L929 cells, treatment with poly(I).poly(C) under conditions that failed to induce significant levels of IFN-beta mRNA led to a very low induction of IRF-1 mRNA, but "priming" cells with IFN prior to the addition of poly(I).poly(C) greatly increased both IRF-1 and IFN-beta mRNAs. In FS-4 cells an increase in IFN-beta mRNA (examined by the polymerase chain reaction) was seen after treatment with TNF, IL-1, A23187, or poly(I).poly(C), but not with IFN-beta, epidermal growth factor, dibutyryl-cAMP, or forskolin. Thus, all treatments that increased steady-state levels of IFN-beta mRNA also enhanced IRF-1 mRNA levels. However, treatment with IFN-beta, which caused a marked stimulation in IRF-1 mRNA, failed to produce a detectable increase in IFN-beta mRNA. It appears that IRF-1 may be necessary but not sufficient for IFN-beta induction. The ability of TNF and IL-1 to increase both IRF-1 and IFN-beta mRNAs may be responsible for some similarities in the actions of TNF, IL-1, and the IFNs.

Neuronal circuits are subdivided by differential expression of type-II classic cadherins in postnatal mouse brains

A number of type-II classic cadherin cell-cell adhesion molecules are expressed in the brain. To investigate their roles in brain morphogenesis, we selected three type-II cadherins, cadherin-6 (cad6), -8 (cad8) and -11 (cad11), and mapped their expressions in the forebrain and other restricted regions of postnatal mouse brains. In the cerebral cortex, each cortical area previously defined was delineated by a specific combinatorial expression of these cadherins. The thalamus and other subcortical regions of the forebrain were also subdivided by differential expression of the three cadherins; e.g., the medial geniculate body expressed only cad6; the ventral posterior thalamic nucleus, cad6/cad11; and the anteroventral thalamic nucleus, cad6/cad8. Likewise, in the olivocerebellar system, each subdivision of the inferior olive expressed a unique set of the three cadherins, and the cerebellar cortex had parasagittal stripes of cad8/cad11 expressions. Close analysis of these cadherin expression patterns revealed that they are correlated with neuronal connection patterns. Examples of these correlations include that cad6 delineates the auditory projection system, cad6/cad8/ cad11 are expressed by part of the Papez circuit, and cad6/cad8 are expressed by subdivisions of the olivo-nuclear circuit. Together with the recent finding that the cadherin adhesion system is localized in synaptic junctions, our findings support the notion that cadherin-mediated cell-cell adhesion plays a role in selective interneuronal connections during neural network formation.

Resveratrol isolated from Polygonum cuspidatum root prevents tumor growth and metastasis to lung and tumor-induced neovascularization in Lewis lung carcinoma-bearing mice

Resveratrol is a naturally occurring phytoalexine found in medicinal plants. We found that resveratrol, at doses of 2.5 and 10 mg/kg, significantly reduced the tumor volume (42%), tumor weight (44%) and metastasis to the lung (56%) in mice bearing highly metastatic Lewis lung carcinoma (LLC) tumors, but not at a dose of 0.6 mg/kg. Resveratrol did not affect the number of CD4(+), CD8(+) and natural killer (NK)1.1.(+) T cells in the spleen. Therefore, the inhibitory effects of resveratrol on tumor growth and lung metastasis could not be explained by natural killer or cytotoxic T-lymphocyte activation. In addition, resveratrol inhibited DNA synthesis most strongly in LLC cells; its 50% inhibitory concentration (IC(50)) was 6.8 micromol/L. Resveratrol at 100 micromol/L increased apoptosis to 20.6 +/- 1.35% from 12.1 +/- 0.36% (P < 0.05) in LLC cells, and decreased the S phase population to 22.1 +/- 1.03% and 29.2 +/- 0.27% from 35.2 +/- 1.72% (P < 0.05) at concentrations of 50 and 100 micromol/L, respectively. Resveratrol inhibited tumor-induced neovascularization at doses of 2.5 and 10 mg/kg in an in vivo model. Moreover, resveratrol significantly inhibited the formation of capillary-like tube formation from human umbilical vein endothelial cells (HUVEC) at concentrations of 10-100 micromol/L; the degree of the inhibition of capillary-like tube formation by resveratrol was 45.5% at 10 micromol/L, 50.2% at 50 micromol/L and 52.6% at 100 micromol/L. Resveratrol inhibited the binding of vascular endothelial growth factor (VEGF) to HUVEC at concentrations of 10-100 micromol/L, but not at concentrations of 1 and 5 micromol/L. The degree of inhibition of VEGF binding to HUVEC by resveratrol was 16.9% at 10 micromol/L, 53.2% at 50 micromol/L and 47.8% at 100 micromol/L. We suggest that the antitumor and antimetastatic activities of resveratrol might be due to the inhibition of DNA synthesis in LLC cells and the inhibition of LLC-induced neovascularization and tube formation (angiogensis) of HUVEC by resveratrol

A single receptor encoded by vzg-1/lpA1/edg-2 couples to G proteins and mediates multiple cellular responses to lysophosphatidic acid

Extracellular lysophosphatidic acid (LPA) produces diverse cellular responses in many cell types. Recent reports of several molecularly distinct G protein-coupled receptors have raised the possibility that the responses to LPA stimulation could be mediated by the combination of several uni-functional receptors. To address this issue, we analyzed one receptor encoded by ventricular zone gene-1 (vzg-1) (also referred to as lpA1/edg-2) by using heterologous expression in a neuronal and nonneuronal cell line. VZG-1 expression was necessary and sufficient in mediating multiple effects of LPA: [3H]-LPA binding, G protein activation, stress fiber formation, neurite retraction, serum response element activation, and increased DNA synthesis. These results demonstrate that a single receptor, encoded by vzg-1, can activate multiple LPA-dependent responses in cells from distinct tissue lineages.

Phospholamban inhibitory function is activated by depolymerization

Phospholamban (PLN), a homopentameric, integral membrane protein, reversibly inhibits cardiac sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) activity through intramembrane interactions. Here, alanine-scanning mutagenesis of the PLN transmembrane sequence was used to identify two functional domains on opposite faces of the transmembrane helix. Mutations in one face diminish inhibitory interactions with transmembrane sequences of SERCA2a, but have relatively little effect on the pentameric state, while mutations in the other face activate inhibitory interactions and enhance monomer formation. Double mutants are monomeric, but loss of inhibitory function is dominant over activation of inhibitory function. These observations support the proposal that the SERCA2a interaction site lies on the helical face which is not involved in pentamer formation. Four highly inhibitory mutants are effectively devoid of pentamer, suggesting that pentameric PLN represents a less active or inactive reservoir that dissociates to provide inhibitory monomeric PLN subunits. A model is presented in which the degree of PLN inhibition of SERCA2a activity is ultimately determined by the concentration of the inhibited PLN monomer.SERCA2a heterodimeric complex. The concentration of this inhibited complex is determined by the dissociation constant for the PLN pentamer (which is mutation-sensitive) and by the dissociation constant for the PLN/SERCA2a heterodimer (which is likely to be mutation-sensitive).

A novel brain-specific p53-target gene, BAI1, containing thrombospondin type 1 repeats inhibits experimental angiogenesis

The genetic alteration of p53 is associated with neovascularization during progression of glioma to its more malignant form, glioblastoma. Hence, one or more of the genes transactivated by p53 is likely to function as an angiogenesis inhibitors. We isolated a novel p53-inducible gene that encodes a 1584-amino-acid product containing five thrombospondin type 1 (TSP-type 1) repeats and is specifically expressed in the brain. A recombinant protein corresponding to the TSP-type 1 repeats of this gene product inhibited in vivo neovascularization induced by bFGF in the rat cornea. The expression of this gene, designated BAI1 (brain-specific angiogenesis inhibitor 1) was absent or significantly reduced in eight of nine glioblastoma cell lines, suggesting BAI1 plays a significant role in angiogenesis inhibition, as a mediator of p53.

VCP/p97 in abnormal protein aggregates, cytoplasmic vacuoles, and cell death, phenotypes relevant to neurodegeneration

Neuronal cell death, abnormal protein aggregates, and cytoplasmic vacuolization are major pathologies observed in many neurodegenerative disorders such as the polyglutamine (polyQ) diseases, prion disease, Alzheimer disease, and the Lewy body diseases, suggesting common mechanisms underlying neurodegeneration. Here, we have identified VCP/p97, a member of the AAA+ family of ATPase proteins, as a polyQ-interacting protein in vitro and in vivo, and report on its characterization. Endogenous VCP co-localized with expanded polyQ (ex-polyQ) aggregates in cultured cells expressing ex-polyQ, with nuclear inclusions in Huntington disease patient brains, and with Lewy bodies in patient samples. Moreover, the expression of VCP mutants with mutations in the 2nd ATP binding domain created cytoplasmic vacuoles, followed by cell death. Very similar vacuoles were also induced by ex-polyQ expression or proteasome inhibitor treatment. These results suggest that VCP functions not only as a recognition factor for abnormally folded proteins but also as a pathological effector for several neurodegenerative phenotypes. VCP may thus be an ideal molecular target for the treatment of neurodegenerative disorders.

Triterpene alcohol and sterol ferulates from rice bran and their anti-inflammatory effects

Six novel feruloyl esters of triterpene alcohols and sterols, viz., two trans-ferulates, cycloeucalenol and 24-methylenecholesterol trans-ferulates, and four cis-ferulates, cycloartenol, 24-methyelenecycloartanol, 24-methylcholesterol, and sitosterol cis-ferulates, besides five known trans-ferulates, cycloartenol (CAR), 24-methylenecycloartanol (24-MCA), 24-methylcholesterol, sitosterol, and stigmastanol trans-ferulates, and one known cis-ferulate, stigmastanol cis-ferulate, were isolated from the methanol extract of edible rice bran. These and eight other synthetic trans- and cis-ferulates of triterpene alcohols and sterols, along with the corresponding free alcohols, were evaluated with respect to their anti-inflammatory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation (1 microg per ear) in mice. All of the ferulates showed marked inhibitory activity, and their 50% inhibitory dose (ID(50)) was 0. 1-0.8 mg per ear. On the other hand, whereas two free triterpene alcohols, CAR and 24-MCA, showed strong inhibition (ID(50) 0.2-0.3 mg/ear), eight free sterols examined showed weaker activity (ID(50) 0.7-2.7 mg/ear) than their corresponding ferulates.

Cyclooxygenase-2 overexpression enhances lymphatic invasion and metastasis in human gastric carcinoma

OBJECTIVE

Recent epidemiological studies indicate that there is reduced risk of all digestive carcinomas in patients who regularly take nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin. Cyclooxygenase (COX) is a target enzyme for NSAIDs. We investigated the role of two isoforms, COX-1 and COX-2, in the development and metastasis of gastric carcinoma.

METHODS

Fifteen gastric carcinoma tissue specimens and accompanying adjacent mucosa specimens were obtained from surgical resections. COX-1 and COX-2 protein expression were evaluated using Western blotting analysis, and their relative band densities were semi quantified using standard densitometry scanning techniques.

RESULTS

Compared with paired noncancerous specimens, COX-2 was overexpressed in 10 of 15 carcinoma tissue specimens (66.7%). Overall, COX-2 levels in carcinoma tissue were significantly higher. Two early carcinomas (confined to the mucosa and submucosa) and three of 13 advanced carcinomas (extended below the submucosa into the muscular wall) had weak or similar COX-2 expression in paired tissue specimens. COX-2 overexpression in tumors significantly correlated with tumor invasion into the lymphatic vessels in the gastric wall and metastasis to the lymph nodes. Furthermore, the stage grouping in the TNM classification significantly correlated with COX-2 overexpression. In contrast, COX-2 overexpression did not correlate with histopathological grading, surface size, and venous vessel invasion of the tumors. COX-1 levels were similar between paired tissues.

CONCLUSION

COX-2 overexpression might enhance lymphatic invasion and metastasis in patients with gastric carcinoma, implicating a poor prognosis. Therefore, the use of COX-2-specific inhibitor to suppress lymphatic metastasis in humans should be investigated.

The structure of bacteriorhodopsin at 3.0 A resolution based on electron crystallography: implication of the charge distribution

Electron crystallography has the potential to visualise the charge status of atoms. This is due to the significantly different scattering factors of neutral and ionised atoms for electrons in the low-resolution range (typically less than 5 A). In previous work, we observed two different types of densities around acidic residues in the experimental (|Fo|) map of bacteriorhodopsin (bR), a light-driven proton pump. We suggested that these might reflect different states of the acidic residues; namely, the protonated (neutral) and the deprotonated (negatively charged) state. To evaluate the observed charge more quantitatively, we refined the atomic model for bR and eight surrounding lipids using our electron crystallographic data set between 8.0 and 3.0 A resolution, where the charge effect is small. The refined model yielded an R-factor of 23.7% and a free R-factor of 33.0%. To evaluate the effect of charges on the density map, we calculated a difference (|Fo|-|Fc|) map including data of a resolution lower than 8.0 A resolution, where the charge effect is significant. We found strong peaks in the difference map mainly in the backbone region of the transmembrane helices. We interpreted these peaks to come from the polarisation of the polar groups in the main chain of the alpha-helices and we examined this by assuming a partial charge of 0.5 for the peptide carbonyl groups. The resulting R and free R-factors dropped from 0.250 and 0.341 to 0.246 and 0.336, respectively. Furthermore, we also observed some strong peaks around some side-chains, which could be assigned to positively charged atoms. Thus, we could show that Asp36 and Asp102 are likely to interact with cations nearby. In addition, peaks found around the acidic residues Glu74, Glu194 and Glu212 have different features and might represent positive charges on polarised water molecules or hydroxonium ions.

Long-term effects of radiation exposure on health

Late-onset effects of exposure to ionising radiation on the human body have been identified by long-term, large-scale epidemiological studies. The cohort study of Japanese survivors of the atomic bombings of Hiroshima and Nagasaki (the Life Span Study) is thought to be the most reliable source of information about these health effects because of the size of the cohort, the exposure of a general population of both sexes and all ages, and the wide range of individually assessed doses. For this reason, the Life Span Study has become fundamental to risk assessment in the radiation protection system of the International Commission on Radiological Protection and other authorities. Radiation exposure increases the risk of cancer throughout life, so continued follow-up of survivors is essential. Overall, survivors have a clear radiation-related excess risk of cancer, and people exposed as children have a higher risk of radiation-induced cancer than those exposed at older ages. At high doses, and possibly at low doses, radiation might increase the risk of cardiovascular disease and some other non-cancer diseases. Hereditary effects in the children of atomic bomb survivors have not been detected. The dose-response relation for cancer at low doses is assumed, for purposes of radiological protection, to be linear without a threshold, but has not been shown definitively. This outstanding issue is not only a problem when dealing appropriately with potential health effects of nuclear accidents, such as at Fukushima and Chernobyl, but is of growing concern in occupational and medical exposure. Therefore, the appropriate dose-response relation for effects of low doses of radiation needs to be established.

Fertilization and development of mouse oocytes injected with isolated sperm heads

To determine whether spermatozoa must be structurally intact before microsurgical injection into oocytes for normal fertilization, intact spermatozoa, as well as sperm heads separated from tails by sonication, were individually injected into oocytes. When whole spermatozoa were injected immediately after their immobilization, the majority of the oocytes were fertilized and developed normally. Sonication in the presence or absence of Triton X-100 decapitated more than 95% of spermatozoa. Although all decapitated spermatozoa were diagnosed as "dead" by live/dead sperm staining, separated sperm heads (nuclei) could participate in normal embryo development when injected into the oocytes. The ability of isolated sperm heads (nuclei) to participate in normal embryo development was maintained under cryopreservation conditions that were not suitable for the survival of plasma membrane-intact spermatozoa. These results indicate that 1) spermatozoa do not need to be structurally intact for intracytoplasmic injection, 2) the plasma and acrosomal membranes and all tail components are not essential for normal embryo development, at least in the mouse, and 3) the cryopreservation conditions required for maintenance of the genetic integrity of sperm nuclei are less stringent than those necessary for keeping plasma membrane-intact spermatozoa alive.