CD4+ T cell--mediated tumor rejection involves inhibition of angiogenesis that is dependent on IFN gamma receptor expression by nonhematopoietic cells

Immunity against MHC class II tumors can be mediated by CD4+ T cells in the effector phase through an unknown mechanism. We show that this is IFN gamma dependent but does not require IFN gamma receptor (IFN gamma R) expression on tumor cells, T cells, or other hematopoietic cells and that IFN gamma R expression is not necessary in the priming phase. However, tumor immunity requires IFN gamma R expression on nonhematopoietic cells in the effector phase and involves inhibition of tumor-induced angiogenesis. This shows that an effective anti-tumor response involves communication between CD4+ T cells and nonhematopoietic cells, most likely within the tumor stroma, and that tumor immunity must not entirely rely on direct tumor cell killing.

B cells inhibit induction of T cell-dependent tumor immunity

Cytotoxic T lymphocyte (CTL) mediated tumor immunity against major histocompatibility antigen (MHC) class I-positive but class II-negative tumors often requires help from CD4+ T cells. These CD4 cells are activated by MHC class II-positive cells that present tumor derived antigens. Considering that different antigen presenting cells, such as B cells, macrophages and dendritic cells compete for antigen and influence the outcome of an immune response, we analyzed tumor immunity in B cell-deficient mice. These mice appear normal with regard to T cell immunity and tolerance to some pure foreign antigens. We show here that the low immunogenicity of tumors is caused by B cells whose presence in the priming phase results in disabled CD4+ T cell help for CTL mediated tumor immunity. Instead, in the presence of B cells, a non-protective humoral immune response is induced. Our results may explain the enigmatic observation that tumor-reactive antibodies occur frequently in cancer patients.

Chemical investigation of hassium (element 108)

The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes (269)Hs (refs 8, 9) and (270)Hs (ref. 10) in the fusion reaction between (26)Mg and (248)Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO(4), for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO(4). These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table.

Mechanisms of rejection induced by tumor cell-targeted gene transfer of interleukin 2, interleukin 4, interleukin 7, tumor necrosis factor, or interferon gamma

Interleukin (IL)-2, IL-4, IL-7, tumor necrosis factor (TNF), or interferon-gamma (IFN-gamma) has been shown to be able to induce tumor rejection if produced locally by the tumor cells after gene transfer. To analyze whether the cellular rejection mechanisms are different or redundant we have expressed the cytokines in the same tumor cell line (J558L). Cell depletion experiments revealed that all cytokines required CD8+ T cells for complete long-term tumor eradication, although effective but transient host-dependent tumor suppression was also observed in the complete absence of CD8+ T cells. The transient tumor suppression induced by IL-2, IL-4, TNF, or IFN-gamma was also operative in nude and severe combined immunodeficient mice, whereas only tumor suppression induced by IL-7 was dependent on the presence of CD4+ T cells and was not evident in nude mice. The T-cell-independent effector arm of IL-2 and IFN-gamma but not IL-4 and TNF was mediated in part by natural killer cells. The transience of tumor suppression in the absence of T cells reflected loss of cytokine production in the case of TNF, IL-2, and IL-4 but not IFN-gamma. Immunohistologic analysis revealed all cytokine-producing tumors to be heavily infiltrated by macrophages. IL-4 and IL-7 tumors additionally contained eosinophils. The infiltration by T cells did not necessarily reflect their contribution to tumor rejection. Thus, the different cytokines activate heterogeneous transient tumor-suppressive mechanisms but always require CD8+ T cells for complete tumor rejection.

HER2 exon 20 insertions in non-small-cell lung cancer are sensitive to the irreversible pan-HER receptor tyrosine kinase inhibitor pyrotinib

BACKGROUND

Effective targeted therapy for non-small-cell lung cancer (NSCLC) patients with human epidermal growth factor receptor 2 (HER2) mutations remains an unmet need. This study investigated the antitumor effect of an irreversible pan-HER receptor tyrosine kinase inhibitor, pyrotinib.

PATIENTS AND METHODS

Using patient-derived organoids and xenografts established from an HER2-A775_G776YVMA-inserted advanced lung adenocarcinoma patient sample, we investigated the antitumor activity of pyrotinib. Preliminary safety and efficacy of pyrotinib in 15 HER2-mutant NSCLC patients in a phase II clinical trial are also presented.

RESULTS

Pyrotinib showed significant growth inhibition of organoids relative to afatinib in vitro (P = 0.0038). In the PDX model, pyrotinib showed a superior antitumor effect than afatinib (P = 0.0471) and T-DM1 (P = 0.0138). Mice treated with pyrotinib displayed significant tumor burden reduction (mean tumor volume, -52.2%). In contrast, afatinib (25.4%) and T-DM1 (10.9%) showed no obvious reduction. Moreover, pyrotinib showed a robust ability to inhibit pHER2, pERK and pAkt. In the phase II cohort of 15 patients with HER2-mutant NSCLC, pyrotinib 400 mg resulted in a objective response rate of 53.3% and a median progression-free survival of 6.4 months.

CONCLUSION

Pyrotinib showed activity against NSCLC with HER2 exon 20 mutations in both patient-derived organoids and a PDX model. In the clinical trial, pyrotinib showed promising efficacy.

CLINICAL TRIAL REGISTRATION

NCT02535507.

T helper cell type 1-associated and cytotoxic T lymphocyte-mediated tumor immunity is impaired in interleukin 4-deficient mice

It is widely accepted that cellular immune responses are induced by CD4(+) T helper 1 (Th1) cells secreting interleukin (IL)-2 and interferon (IFN)-gamma. Tumor immunity is often mediated by cytotoxic T lymphocytes (CTLs) whose activation is supported by Th1 cytokines. Since IL-4 directs Th2 development and has been shown to inhibit Th1-dominated responses, we assumed that IL-4-deficient (IL-4(-/-)) mice would develop vigorous CTL-mediated tumor immunity compared with IL-4-competent (IL-4(+/+)) mice. Surprisingly, IL-4(-/-) mice were severely impaired to develop tumor immunity to both a mammary adenocarcinoma line and a colon carcinoma line. The lack of tumor immunity in IL-4(-/-) mice was associated with reduced IFN-gamma production, diminished levels of tumor-reactive serum IgG2a, and undetectable CTL activity, indicating a defective Th1 response in the absence of endogenous IL-4. Anti-IL-4 monoclonal antibody blocked tumor immunity in IL-4(+/+) mice when administered at the time of immunization but not at the time of challenge. Additionally, tumor immunity could be induced in IL-4(-/-) mice, if IL-4 was provided by gene-modified cells together with immunizing tumor cells. These results demonstrate that tumor immunity requires IL-4 in the priming phase for the generation of effector cells rather than for their maintenance and exclude secondary, developmental defects in the "knockout" strain. Together, our results demonstrate a novel and previously unanticipated role of IL-4 for the generation of Th1-associated, CTL-mediated tumor immunity.

Inhibition of TNFalpha attenuates infarct volume and ICAM-1 expression in ischemic mouse brain

The purpose of our study was to determine whether inhibiting the action of tumor necrosis factor-alpha (TNFalpha) attenuates brain injury and reduces inflammatory responses in the mouse during ischemia and reperfusion. Mice underwent middle cerebral artery occlusion (MCAO) for 1 h followed by 23 h reperfusion. Monoclonal neutralizing anti-murine TNFalpha antibody (mAb) was administrated intraventricularly in the mouse with temporary MCAO. Infarct volume in the anti-TNFalpha mAb treated mice was significantly smaller than that in the control group (p < 0.05). The number of intercellular adhesion molecule-1 (ICAM-1)-positive vessels in the ischemic area of the anti-TNFalpha mAb-treated group was significantly less than that in the control group. Our study demonstrated that blocking TNFalpha reduced brain injury and attenuated ICAM-1 expression during transient cerebral ischemia.

Loss of conformational stability in calmodulin upon methionine oxidation

We have used electrospray ionization mass spectrometry (ESI-MS), circular dichroism (CD), and fluorescence spectroscopy to investigate the secondary and tertiary structural consequences that result from oxidative modification of methionine residues in wheat germ calmodulin (CaM), and prevent activation of the plasma membrane Ca-ATPase. Using ESI-MS, we have measured rates of modification and molecular mass distributions of oxidatively modified CaM species (CaMox) resulting from exposure to H2O2. From these rates, we find that oxidative modification of methionine to the corresponding methionine sulfoxide does not predispose CaM to further oxidative modification. These results indicate that methionine oxidation results in no large-scale alterations in the tertiary structure of CaMox, because the rates of oxidative modification of individual methionines are directly related to their solvent exposure. Likewise, CD measurements indicate that methionine oxidation results in little change in the apparent alpha-helical content at 28 degrees C, and only a small (0.3 +/- 0.1 kcal mol(-1)) decrease in thermal stability, suggesting the disruption of a limited number of specific noncovalent interactions. Fluorescence lifetime, anisotropy, and quenching measurements of N-(1-pyrenyl)-maleimide (PMal) covalently bound to Cys26 indicate local structural changes around PMal in the amino-terminal domain in response to oxidative modification of methionine residues in the carboxyl-terminal domain. Because the opposing globular domains remain spatially distant in both native and oxidatively modified CaM, the oxidative modification of methionines in the carboxyl-terminal domain are suggested to modify the conformation of the amino-terminal domain through alterations in the structural features involving the interdomain central helix. The structural basis for the linkage between oxidative modification and these global conformational changes is discussed in terms of possible alterations in specific noncovalent interactions that have previously been suggested to stabilize the central helix in CaM.

Tumor necrosis factor alpha expression produces increased blood-brain barrier permeability following temporary focal cerebral ischemia in mice

Alteration of blood-brain barrier (BBB) function occurs in both permanent and temporary cerebral ischemia. Studies in vivo and in vitro have shown that tumor necrosis factor-alpha (TNFalpha) is involved in changes of BBB permeability. However, the relationship between TNFalpha expression and BBB disruption during reperfusion is unclear. The aim of this study is to find the cell source of TNFalpha and to determine the relationship between TNFalpha expression and BBB disruption following temporary focal cerebral ischemia in mice. Adult CD-1 mice received 1 h middle cerebral artery occlusion (MCAO) followed by 2 h, 6 h, 12 h, 24 h, and 48 h of reperfusion. MCAO was achieved using an intraluminal suture technique and reperfusion was performed by the suture withdrawal. Neutralizing monoclonal anti-mouse TNFalpha antibody was administrated intraventricularly immediately after reperfusion. TNFalpha expression was determined by double labeling immunohistochemistry. BBB permeability was determined by albumin immunostaining. TNFalpha immunoreactivity (IR) was observed in the ipsilateral hemisphere from 1 h MCAO with 2 h reperfusion. TNFalpha positive cells included neurons, astrocytes, and ependymal cells. BBB disruption was detected beginning at 6 h reperfusion but was not present at 2 h of reperfusion. The areas of BBB disruption were significantly enlarged at 12 h reperfusion and plateaued at 24 h to 48 h reperfusion. BBB disruptions were significantly attenuated in the anti-TNFalpha antibody treated mice (p<0.05). Our results demonstrate that TNFalpha IR existed in neurons, astrocytes, and ependymal cells during reperfusion. TNFalpha IR following temporary focal cerebral ischemia precedes increased BBB permeability. Treatment with TNFalpha antibody reduces BBB disruption, suggesting TNFalpha may be an important mediator in altering BBB permeability during reperfusion.

IL6 derived from cancer-associated fibroblasts promotes chemoresistance via CXCR7 in esophageal squamous cell carcinoma

Various factors and cellular components in the tumor microenvironment are key drivers associated with drug resistance in many cancers. Here, we analyzed the factors and molecular mechanisms involved in chemoresistance in patients with esophageal squamous cell carcinoma (ESCC). We found that interleukin 6 (IL6) derived mainly from cancer-associated fibroblasts played the most important role in chemoresistance by upregulating C-X-C motif chemokine receptor 7 (CXCR7) expression through signal transducer and activator of transcription 3/nuclear factor-κB pathway. CXCR7 knockdown resulted in the inhibition of IL6-induced proliferation and chemoresistance. In addition, CXCR7 silencing significantly decreased gene expression associated with stemness, chemoresistance and epithelial-mesenchymal transition and suppressed the proliferation ability of ESCC cells in three-dimensional culture systems and angiogenesis assay. In clinical samples, ESCC patients with high expression of CXCR7 and IL6 presented a significantly worse overall survival and progression-free survival upon receiving cisplatin after operation. These results suggest that the IL6-CXCR7 axis may provide a promising target for the treatment of ESCC.

Tumor rejection by disturbing tumor stroma cell interactions

The stroma of solid tumors is a complex network of different cell types. We analyzed stroma cell interactions in two tumor models during cyclophosphamide (Cy)-induced tumor rejection. In growing tumors, tumor infiltrating macrophages (TIMs) produced interleukin (IL)-10. Beginning 6 h after Cy-treatment T cells in the tumor were inactivated and TIMs switched to interferon (IFN)-gamma production. Both, IL-10 production before and IFN-gamma production after Cy-treatment by TIMs required T cells. With the same kinetics as TIMs started to produce IFN-gamma the tumor vasculature was destroyed which required IFN-gamma receptor expression on host but not tumor cells. These events preceded hemorrhagic necrosis and residual tumor cell elimination by T cells. Together, T cells regulate the function of TIMs and tumor rejection can be induced by disturbing the stroma network.

Heterogeneity of mRNA and protein products arising from the protein 4.1 gene in erythroid and nonerythroid tissues

Immunologically cross-reactive isoforms of the cytoskeletal element protein 4.1 have been identified in many tissues in which they exhibit heterogeneity of molecular weight, abundance, and intracellular localization. To examine the basis for isoform production in erythroid and nonerythroid tissues, we have compared the structure and expression of cDNAs isolated from human erythroid and nonerythroid sources. We have encountered cDNAs representing many distinct mRNA sequences. These exhibit complete nucleotide sequence homology along most of their lengths. Differences were confined to five sequence blocks designated Motifs I-V, which were present or absent in each mRNA moiety. Motif I was expressed only in erythroid cells; it encodes 21 amino acids in a well-characterized spectrin/actin binding domain. Motif II, located near the COOH terminus of the 80-kD "erythroid" protein 4.1 molecule is present in the vast majority of transcripts from both erythroid and nonerythroid cells. Motifs IV and V alter the 5' untranslated region: simultaneous insertion of Motif IV and deletion of Motif V in the untranslated region inserts a new initiator methionine and establishes a contiguous open reading frame encoding a novel 135-kD protein 4.1 molecule. By immunochemical analysis we have identified the longer isoform in cells. Our results are most consistent with tissue-specific alternative mRNA splicing of transcripts of the protein 4.1 gene to yield numerous isoforms. These isoforms exhibit tissue specificity and alter strategic portions of the molecule. Moreover, we describe a novel high molecular weight form of protein 4.1 that arises by splicing events which allow translation at an upstream site.

The Gfi-1B proto-oncoprotein represses p21WAF1 and inhibits myeloid cell differentiation

Gfi-1 is a cellular proto-oncogene that was identified as a target of provirus integration in T-cell lymphoma lines selected for interleukin-2 (IL-2) independence in culture and in primary retrovirus-induced lymphomas. Gfi-1 encodes a zinc finger protein that functions as a transcriptional repressor. Here we show that Gfi-1B, a Gfi-1 related gene expressed in bone marrow and spleen, also encodes a transcriptional repressor. IL-6-induced G1 arrest and differentiation of the myelomonocytic cell line M1 were linked to the downregulation of Gfi-1B and the parallel induction of the cyclin-dependent kinase inhibitor p21WAF1. Experiments addressing the potential mechanism of the apparent coordinate regulation of these genes revealed that Gfi-1B represses p21WAF1 directly by binding to a high-affinity site at -1518 to -1530 in the p21WAF1 promoter. Forced expression of Gfi-1B, but not of Gfi-1B deletion mutants lacking the repressor domain, blocked the IL-6-mediated induction of p21WAF1 and inhibited G1 arrest and differentiation. We conclude that Gfi-1B is a direct repressor of the p21WAF1 promoter, the first such repressor identified to date, and that sustained expression of Gfi-1B blocks IL-6-induced G1 arrest and differentiation of M1 cells perhaps because it prevents p21WAF1 induction by IL-6.

Self-assembly of polymer and sheet structures from palladium(II) complexes by hydrogen bonding between carboxamide substituents

The self-assembly of supramolecular structures from either neutral or cationic palladium(II) complexes containing primary or secondary carboxamide groups as substituents on pyridine ligands has been explored. The displacement of PhCN in trans-[PdCl(2)(PhCN)(2)] by L = N-methylnicotinamide (MNA), isonicotinamide (INA), or nicotinamide (NA) gave the corresponding complexes trans-[PdCl(2)L(2)] 1-3, respectively. Complex 1.H(2)O forms a 2D sheet network via amide-amide hydrogen bonding supported by chloride ligand-to-water hydrogen-bonding interactions. Several cationic complexes, [Pd(L'L')L(2)](2+) 4-9 and 11-16, containing the above ligands and with PPh(3), dppp, dppm, or bu(2)bipy as ancillary ligand(s) were prepared. Complex 4 (L = MNA, L'L' = dppp) forms dimers through amide-amide hydrogen bonding, forming macrocycles which further propagate to form chains via weak C-H...O=C hydrogen bonding. Complex 6 (L = NA, L'L' = dppp) forms zigzag chains connected by amide head-to-head hydrogen bonds. Complex 8 (L = INA, L'L' = dppm) gives interesting double-stranded ribbons linked by two types of amide--amide hydrogen-bonding interactions. Complex 13 (L' = PPh(3), L = NA) forms an infinite chain via complementary amide-amide hydrogen bonds. Complex 14 (L = MNA, L'L' = bu(2)bipy) forms infinite ribbons via the combination of amide hydrogen bonding mediated by a BF(4) anion and weak C-H...O=C hydrogen bonding. Complex 15 (L = INA, L'L' = bu(2)bipy) gives a ladder polymer formed through amide--amide hydrogen bonds. The structure of cis-[Pd(PPh(3))(2)(OH(2))(2)] (OTf)(2) (10) is also reported.

Zebrafish (Danio rerio) gill neuroepithelial cells are sensitive chemoreceptors for environmental CO2

Adult zebrafish exhibit hyperventilatory responses to absolute environmental CO(2) levels as low as 0.13% ( mmHg), more than an order of magnitude lower than the typical arterial levels (40 mmHg) monitored by the mammalian carotid body. The sensory basis underlying the ability of fish to detect and respond to low ambient CO(2) levels is not clear. Here, we show that the neuroepithelial cells (NECs) of the zebrafish gill, known to sense O(2) levels, also respond to low levels of CO(2). An electrophysiological characterization of this response using both current and voltage clamp protocols revealed that for increasing CO(2) levels, a background K(+) channel was inhibited, resulting in a partial pressure-dependent depolarization of the NEC. To elucidate the signalling pathway underlying K(+) channel inhibition, we used immunocytochemistry to show that these NECs express carbonic anhydrase (CA), an enzyme involved in CO(2) sensing in the mammalian carotid body. Further, the NEC response to CO(2) (magnitude of membrane depolarization and time required to achieve maximal response), under conditions of constant pH, was reduced by 50% by the CA-inhibitor acetazolamide. This suggests that the CO(2) detection mechanism involves an intracellular sensor that is responsive to the rate of acidification associated with the hydration of CO(2) and which does not require a change of extracellular pH. Because some cells that were responsive to increasing also responded to hypoxia with membrane depolarization, the present results demonstrate that a subset of the NECs in the zebrafish gill are bimodal sensors of CO(2) and O(2).

Replication at the telomeres of the Streptomyces linear plasmid pSLA2

The Streptomyces linear plasmid pSLA2 initiates DNA replication bidirectionally towards its telomeres from a site located near the centre of the molecule; at the telomeres, the recessed ends of lagging strands are filled in by non-displacing DNA synthesis. Here, we report experiments that test three proposed mechanisms for lagging-strand fill-in. We present data inconsistent with recombinational or terminal hairpin models for the formation of full-length duplex pSLA2 DNA. Instead, we find that deletions in short, distantly separated homologous palindromes in the leading-strand 3' overhang prevent propagation of linear pSLA2 DNA, implicating a mechanism of palindrome-mediated leading-strand fold-back in telomere replication. We further show that circularized pSLA2 DNA molecules are opened in vivo precisely at the terminal nucleotides of telomeres, generating functional linear replicons containing native telomeres covalently bound to a protein at their 5' DNA termini. Together, our results support a model in which pairing of multiple widely separated pSLA2 palindromes anchors the 3' end of the leading-strand overhang to a site near the overhang's base -- providing a recognition site for terminal-protein-primed DNA synthesis and subsequent endonucleolytic processing. Thus, the replication of Streptomyces plasmid telomeres may have features in common with the mechanism proposed for telomere replication in autonomous parvoviruses.

Nuclear chemistry. Synthesis and detection of a seaborgium carbonyl complex

Experimental investigations of transactinoide elements provide benchmark results for chemical theory and probe the predictive power of trends in the periodic table. So far, in gas-phase chemical reactions, simple inorganic compounds with the transactinoide in its highest oxidation state have been synthesized. Single-atom production rates, short half-lives, and harsh experimental conditions limited the number of experimentally accessible compounds. We applied a gas-phase carbonylation technique previously tested on short-lived molybdenum (Mo) and tungsten (W) isotopes to the preparation of a carbonyl complex of seaborgium, the 106th element. The volatile seaborgium complex showed the same volatility and reactivity with a silicon dioxide surface as those of the hexacarbonyl complexes of the lighter homologs Mo and W. Comparison of the product's adsorption enthalpy with theoretical predictions and data for the lighter congeners supported a Sg(CO)6 formulation.

Rev3, the catalytic subunit of Polζ, is required for maintaining fragile site stability in human cells

It has been long speculated that mammalian Rev3 plays an important, yet unknown role(s) during mammalian development, as deletion of Rev3 causes embryonic lethality in mice, whereas no other translesion DNA synthesis polymerases studied to date are required for mouse embryo development. Here, we report that both subunits of Polζ (Rev3 and Rev7) show an unexpected increase in expression during G₂/M phase, but they localize independently in mitotic cells. Experimental depletion of Rev3 results in a significant increase in anaphase bridges, chromosomal breaks/gaps and common fragile site (CFS) expression, whereas Rev7 depletion primarily causes lagging chromosome defect with no sign of CFS expression. The genomic instability induced by Rev3 depletion seems to be related to replication stress, as it is further enhanced on aphidicolin treatment and results in increased metaphase-specific Fanconi anemia complementation group D type 2 (FANCD2) foci formation, as well as FANCD2-positive anaphase bridges. Indeed, a long-term depletion of Rev3 in cultured human cells results in massive genomic instability and severe cell cycle arrest. The aforementioned observations collectively support a notion that Rev3 is required for the efficient replication of CFSs during G₂/M phase, and that the resulting fragile site instability in Rev3 knockout mice may trigger cell death during embryonic development.

Ultrasound backscattering from non-aggregating and aggregating erythrocytes--a review

The objective of the present paper is to provide a detailed review of theoretical, experimental and clinical works aimed at understanding the scattering of ultrasound by red blood cells (RBC). The paper focuses on the role of biofluid mechanics and blood biorheology on the scattering mechanisms. The influence of RBC aggregation on the ultrasound backscattered power is specifically addressed. After a short introduction, the paper presents the theory of Rayleigh scattering and summarizes theoretical models on ultrasound backscattering by RBC. The particle, continuum and hybrid models are presented along with reported packing factors used to consider the orderliness in the spatial arrangement of RBC. Computer models of ultrasound backscattering by RBC are also presented in this section. In the second section, experimental factors affecting the ultrasound backscattered power from blood are presented. The influence of the volume of the scatterers, ultrasound frequency, hematocrit, orientation of the scatterers, flow turbulence, flow pulsatility, and concentration of fibrinogen and dextran is discussed. The third section focuses on the use of ultrasound to characterize RBC aggregation. Three aspects are reported: the shear rate dependence of the backscattered power, the "black hole" phenomenon, and the kinetics of RBC rouleau formation. The fourth section reports in vivo observations of the "smoke like" echo in mitral valve disease, and blood echogenicity and backscattered power in veins and arteries. In the last section, new areas of research, clinical applications of ultrasound backscattering, and areas of potential future developments are presented.

Roles of sequential ubiquitination of PCNA in DNA-damage tolerance

Living organisms not only repair DNA damage induced by environmental agents and endogenous cellular metabolites, but have also developed mechanisms to survive in the presence of otherwise lethal lesions. DNA-damage tolerance (DDT) is considered such a mechanism that resumes DNA synthesis in the presence of replication-blocking lesions. Recent studies revealed that DDT in budding yeast is achieved through sequential ubiquitination of DNA polymerase processivity factor, proliferating cell nuclear antigen (PCNA). It is generally believed that monoubiquitinated PCNA promotes translesion DNA synthesis, whereas polyubiquitinated PCNA mediates an error-free mode of lesion bypass. This review will discuss how ubiquitinated PCNA modulates different means of lesion bypass.

Cellular localization of tumor necrosis factor alpha following focal cerebral ischemia in mice

Tumor necrosis factor alpha (TNFalpha) is a pleiotrophic cytokine with diverse proinflammatory actions. Focal cerebral ischemia induces rapid and dramatic increases in TNFalpha levels within and surrounding the focus of damaged brain both in striatum and cortex. The actions of TNFalpha during cerebral ischemia may be related to the cell types which deliver and/or accept TNFalpha signals. However, the cellular sources of TNFalpha following cerebral ischemia have not been fully elucidated. The present study was designed to determine the cellular localization of TNFalpha following permanent middle cerebral artery occlusion (MCAO) in mice. As judged by immunohistochemistry, TNFalpha expression in the ischemic hemisphere was increased at 3 h following MCAO, peaked at 6 to 12 h, and decreased at 24 h. Double immunostaining for TNFalpha and neuron specific enolase (NSE) or glial fibrillary acidic protein (GFAP) showed that TNFalpha positive neurons were observed in both the ischemic core and perifocal region, while TNFalpha positive astrocytes were observed in the outer cortical layer, the corpus callosum, the molecular layer of the hippocampus, and periventricular areas. The presence of TNFalpha immunoreactivity in neurons and nerve fibers following MCAO suggests that TNFalpha expressed in ischemic neurons might be delivered via axonal transport, while TNFalpha immunoreactivity in astrocyte end-feet and ependymal cells following MCAO suggests that TNFalpha may be involved in blood-brain barrier disruption and the initiation of inflammation in the brain.

Double suicide gene (cytosine deaminase and herpes simplex virus thymidine kinase) but not single gene transfer allows reliable elimination of tumor cells in vivo

Suicide genes such as cytosine deaminase (CD) and herpes simplex virus thymidine kinase (TK) encode products that convert nontoxic substances (prodrugs) into toxic metabolites. Suicide gene transfer is currently being used in cancer therapy or can be used as a safety modality. To analyze the reliability of suicide genes as a safety modality for a vaccination study with viable cytokine/B7 gene-modified tumor cells, the individual and combined efficacy of the two suicide genes was compared for in vitro and in vivo cell killing of a murine mammary adenocarcinoma cell line (TS/A). To adapt the system to an in vivo gene delivery situation, bulk cultures cotransfected with the CD and TK gene were used instead of selected clones. In vitro, both CD and TK conferred sensitivity to the respective prodrug but the combined cytotoxic effects of both gene products were always superior. For in vivo analysis BALB/c mice were injected subcutaneously with CD- and TK-modified TS/A cells, treated with prodrugs, and tumor size was evaluated for a period of 100 days. In the in vivo situation the combination of both enzyme/prodrug systems was again most effective. The highest single concentration of 5-FC (500 mg/kg) or GCV (100 mg/kg) was not able to fully protect the animals from developing tumors, whereas a combination of 5-FC (250 mg/kg) and GCV (50 mg/kg) resulted in complete tumor eradication. In nude mice treated in the same way, most CD/TK tumors could not be eliminated. Furthermore, BALB/c mice cured of TS/A-CD/TK tumors developed a systemic tumor immunity against challenge with parental TS/A cells. These findings indicate that reliable tumor elimination by the suicide genes depends on T cells. The cooperative effect of both suicide genes was confirmed in vitro with the human renal cell carcinoma line RCC26. We conclude that TK and CD together, but neither gene alone, act as a safety mechanism for the elimination of tumor cells in a reliable fashion and suggest that a rapid and quantitative antigen release by effective TK- and CD-mediated tumor destruction is necessary for T cell immunity to develop.

Serotypes, genotypes and antimicrobial resistance patterns of human diarrhoeagenic Escherichia coli isolates circulating in southeastern China

Diarrhoeagenic Escherichia coli (DEC) infection is a major health problem in developing countries. The prevalence and characteristics of DEC have not been thoroughly investigated in China. Consecutive faecal specimens from outpatients with acute diarrhoea in nine sentinel hospitals in southeastern China were collected from July 2009 to June 2011. Bacterial and viral pathogens were detected by culture and RT-PCR, respectively. DEC isolates were further classified into five pathotypes using multiplex PCR. The O/H serotypes, sequence types (STs) and antimicrobial susceptibility profiles of the DEC isolates were determined. A total of 2466 faecal specimens were collected, from which 347 (14.1%) DEC isolates were isolated. DEC was the dominant bacterial pathogen detected. The DEC isolates included 217 EAEC, 62 ETEC, 52 EPEC, 14 STEC, one EIEC and one EAEC/ETEC. O45 (6.6%) was the predominant serotype. Genotypic analysis revealed that the major genotype was ST complex 10 (87, 25.6%). Isolates belonging to the serogroups or genotypes of O6, O25, O159, ST48, ST218, ST94 and ST1491 were highly susceptible to the majority of antimicrobials. In contrast, isolates belonging to O45, O15, O1, O169, ST38, ST226, ST69, ST31, ST93, ST394 and ST648 were highly resistant to the majority of antimicrobials. DEC accounted for the majority of bacterial pathogens causing acute diarrhoea in southeastern China, and it is therefore necessary to test for all DEC, not only the EHEC O157:H7. Some serogroups or genotypes of DEC were highly resistant to the majority of antimicrobials. DEC surveillance should be emphasized.

Membrane structure of protein kinase C and calmodulin binding domain of myristoylated alanine rich C kinase substrate determined by site-directed spin labeling

Cysteine-substituted peptides based on the membrane, calmodulin, and protein kinase C binding domain of the myristoylated alanine rich C kinase substrate (MARCKS) were synthesized and derivatized with a sulfhydryl reactive proxyl nitroxide. These spin-labeled peptides were used in combination with continuous wave power saturation electron paramagnetic resonance (EPR) spectroscopy to determine the position and structure of the peptide on membranes containing phosphatidylserine. These peptides bind at the membrane interface, with nitroxide side chains in the central and C-terminal regions lying several angstroms below the level of the head group. In contrast, the N-terminus of the peptide is extended out of the membrane interface so that the two N-terminal residues are positioned on the aqueous side of the head group. When bound to the membrane, the N-terminal segment of this peptide is sensitive to the membrane surface charge density. Higher charge densities decrease the amplitude of side chain motions at the N-terminus and bring this end of the peptide closer to the membrane interface. When the location of successive residues along the bilayer normal is compared, no helical trend is seen, and no evidence for aggregation of the peptide is found. The EPR spectra of double spin-labeled peptides also show no evidence for a helical structure. Thus, these basic peptides are in an extended configuration at the membrane interface with hydrophobic side chains oriented inward toward the membrane hydrocarbon.