Expansion Kinetics Research Articles

Molecular dissection of the male germ cell lineage identifies putative spermatogonial stem cells in rhesus macaques

BACKGROUNDThe spermatogonial stem cell (SSC) pool in the testes of non-human primates is poorly defined.METHODSTo begin characterizing SSCs in rhesus macaque testes, we employed fluorescence-activated cell sorting (FACS), a xenotransplant bioassay and immunohistochemical methods and correlated our findings with classical descriptions of germ cell nuclear morphology (i.e. Adark and Apale spermatogonia).RESULTSFACS analysis identified a THY-1+ fraction of rhesus testis cells that was enriched for consensus SSC markers (i.e. PLZF, GFRα1) and exhibited enhanced colonizing activity upon transplantation to nude mouse testes. We observed a substantial conservation of spermatogonial markers from mice to monkeys [PLZF, GFRα1, Neurogenin 3 (NGN3), cKIT]. Assuming that molecular characteristics correlate with function, the pool of putative SSCs (THY-1+, PLZF+, GFRα1+, NGN3+/−, cKIT−) comprises most Adark and Apale and is considerably larger in primates than in rodents. It is noteworthy that the majority of Adark and Apale share a common molecular phenotype, considering their distinct functional classifications as reserve and renewing stem cells, respectively. NGN3 is absent from Adark, but is expressed by some Apale and may mark the transition from undifferentiated (cKIT−) to differentiating (cKIT+) spermatogonia. Finally, the pool of transit-amplifying progenitor spermatogonia (PLZF+, GFRα1+, NGN3+, cKIT+/−) is smaller in primates than in rodents.CONCLUSIONSThese results provide an in-depth analysis of molecular characteristics of primate spermatogonia, including SSCs, and lay a foundation for future studies investigating the kinetics of spermatogonial renewal, clonal expansion and differentiation during primate spermatogenesis.

Interleukin-18-Related Genes Are Induced during the Contraction Phase but Do Not Play Major Roles in Regulating the Dynamics or Function of the T-Cell Response toListeria monocytogenesInfection

Proinflammatory cytokines, such as gamma interferon (IFN-gamma), impact aspects of T-cell responses after infection, including expansion, contraction, and memory formation. Interleukin-18 (IL-18) functions as a proinflammatory cytokine by stimulating the production of IFN-gamma from multiple cell types and accentuating the development of Th1 CD4 T-cell responses. Focused microarray analyses revealed upregulation of IL-18 and IL-18 receptor genes in CD8 T cells during the contraction phase. Based on these findings we investigated if and how signaling through the IL-18 receptor influences the development and kinetics of antigen (Ag)-specific CD8 and CD4 T-cell responses following infection. IL-18Ralpha(-/-) and IL-18(-/-) mice developed frequencies and total numbers of Ag-specific CD8 T cells after Listeria monocytogenes infection that were similar to those of wild-type C57BL/6 mice. The kinetics of expansion, contraction, and memory CD8 T-cell maintenance were also similar. When IL-18Ralpha deficiency was isolated to Ag-specific CD8 T cells, the kinetics of the expansion and contraction phases were also normal. These basic findings were confirmed by examining the response to vaccinia virus infection. In contrast, the expansion of Ag-specific CD4 T cells was slightly curtailed by the absence of IL-18Ralpha; however, contraction and the maintenance of memory were not altered. Importantly, both memory Ag-specific CD8 and CD4 T cells generated in the absence of IL-18Ralpha expanded appropriately after secondary antigen exposure and were protective, indicating that signaling through the IL-18 receptor is not required for normal T-cell response kinetics and survival of immunized mice challenged with a lethal L. monocytogenes infection.

Two-dimensional Calorimetry: Imaging Thermodynamics and Kinetics of Phase Transitions of Biological Membranes

Differential scanning calorimetry (DSC) is a relatively rapid and informative biophysical method for studying thermotropic phase behavior of biological membranes. More recently a pressure perturbation calorimetry has been introduced. The latter method is capable of characterizing membrane thermal volume expansion coefficient and kinetics associated with the phase transition. Notably, pressure perturbation calorimetry requires both pressure jump accessory and, most importantly, fast and sophisticated temperature control system to ensure constant sample temperature upon the pressure jump. Here we describe a calorimetry procedure and associated method of data analysis to characterize sample thermal properties as a two-dimensional (2D) object (temperature-time thermal image) whereas data obtained by conventional calorimetry are essentially one-dimensional. In brief, the method utilizes mathematical formalism of the Radon transform (back-projecting algorithm) to separate temperature and time dimensions from a series of thermal flux measurements obtained by a conventional DSC calorimeter at different scanning rates. By this manner static and time-dependent (i.e., relaxation) thermodynamic parameters of an object become resolved and displayed as a single 2D temperature-time thermal image. There are two main advantages of our 2D-calorimetry method: 1) 2D temperature-time thermal image separates and characterizes equilibrium and non-equilibrium thermal properties of a sample; 2) the method improves signal-to-noise ratio for conventional DSC measurements of equilibrium heat capacity as a function of temperature. We demonstrate these advantages of the 2D calorimetry method on examples of imaging thermodynamics and heat relaxation properties of lipid bilayers composed from single and mixed phospholipids with and without cholesterol. We also show that confining lipid bilayers inside nanopores of ca. 175 nm in diameter results in heterogeneous heat transfer kinetics while conventional equilibrium calorimetry curves remain unperturbed. Supported by the DOE Contract DE-FG02-02ER15354.

A Liposomal Formulation of KRN7000 (RGI-2001) Potently Reduces GvHD Lethality through the Expansion of CD4+Foxp3+ Regulatory T Cells in Murine Models

KRN7000 is a potent synthetic derivative of alpha-galactosylceramide and ligand for CD1d molecules expressed on antigen-presenting cells. Subsequent presentation of KRN7000 by CD1d to invariant natural killer T (iNKT) cells, a subset of natural killer T cells expressing invariant T cell receptor alpha, results in the rapid release of Th1, Th2, or immune regulatory cytokines and initiation of multiple downstream cellular events such as T cell polarization and expansion of dendritic cell subsets. Previously we have demonstrated that liposomal formulation of KRN7000 containing a model antigen induces antigen specific immune tolerance by way of regulatory dendritic cells and induction of Foxp3+ regulatory T (Treg) cells. In this study, we examined the ability of KRN7000 embedded in a liposomal bilayer (RGI-2001) to prevent acute graft-versus-host disease (aGvHD), as Tregs have been shown to have a pivotal role in regulating immune responses to alloantigens. RGI-2001 demonstrated potent activity in reducing GvHD lethality in mice that received fully mismatched bone marrow cells (BMC) and whole spleen cells (WSC). A single intravenous administration of RGI-2001 given on day 0 reproducibly demonstrated efficacy in prolonging the survival of mice relative to untreated mice in a total of 16 independent experiments using lethally-irradiated (9 Gys) Balb/c (H-2d) recipients transplanted with 5×10e6 C57BL/6 (H-2b) T cell depleted BMC with 5×10e6 or 2.5×10e6 WSC. Statistically significant prolongation by Log-rank test was observed at the doses > 1 ng/kg in mice that received 2.5×10e6 WSC, and at the doses > 10 ng/kg in those that received 5×10e6 WSC. Investigation of mice that survived greater than 100 days demonstrated multi-lineage hematopoietic reconstitution by donor derived cells. Next, we investigated the kinetics of Treg expansion following BMT using the model receiving 2.5×10e6 WSC. The results revealed significantly accelerated expansion of donor-derived Tregs in RGI-2001 treated animals as compared with untreated animals. In a representative experiment, 3–4 fold higher percentages of Foxp3+ cells were found in H-2b+CD4+ cells in RGI-2001 treated animals on day 15 post BMT as follows: untreated (n=5) vs RGI-2001 (n=5), 4.5±0.7 % vs 20.7±6.0% (spleen), 2.4±1.3% vs 10.6±5.0% (mesenteric lymph nodes) and 5.4±2.8% vs 15.7±6.0% (peripheral lymph nodes). Furthermore, allo-responses of RGI-2001 treated spleen cells were suppressed in an antigen-specific manner. Proliferation of RGI-2001 treated spleen cells was significantly reduced when stimulated with host (Balb/c) antigen presenting cells (APCs) in vitro while responsiveness to a third party (C3H) APCs remained. Based on these findings, we investigated if the second injection of RGI-2001 on day 15 could further support the expansion/maintenance of Tregs post BMT. Results demonstrated further improvement in the survival as well as clinical score of mice that received RGI-2001 treatment on both day 0 and day 15 as compared to those received the treatment only on day 0. Taken together, these results strongly suggest that RGI-2001 promotes the expansion of donor-derived Tregs which specifically suppress T-cell responses against host alloantigens, thereby reducing the GvHD lethality.

TET2 Is a Novel Tumor Suppressor Gene Inactivated in Myeloproliferative Neoplasms: Identification of a Pre-JAK2 V617F Event

Abstract Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell (HSC) malignancies with increased expansion of myeloid lineages. JAK2 and MPL mutations are detected in MPN patients’ HSCs but their biological consequences appear to rather target the terminal myeloid differentiation than the early steps of hematopoiesis. Analysis of CD34+CD38− multipotent progenitors, CD34+CD38+ committed progenitors and mature cells, led us to identify two subsets of JAK2 V617F MPN at diagnosis with distinct kinetics of hematopoietic expansion. The first subset (85% of patients) is characterized by a late expansion of the malignant clone –i.e downstream the committed progenitor stage. In contrast, the second subset of patients (15%) has an early expansion of the clone, upstream the committed progenitor stage. The hallmark of this early expansion is a high percentage (>80%) of JAK2 V617F positive multipotent or committed progenitors, contrasting with low percentages (<50%) in other MPN patients (Dupont et al, Blood 2007). We hypothesized that the second subset of patients had a pre-existent molecular defect able to promote the early expansion of the malignant clone. With high resolution SNP arrays (Affymetrix 500K) and CGH arrays (Agilent 244K), we compared malignant granulocyte or erythroblast DNA with paired non malignant lymphocyte DNA from five patients with such a phenotype. Three/5 harbored an acquired loss of heterozygosity (LOH) on the long arm of chromosome 4. In 2 patients, the LOH spanned a large region from the 4q22 band to the telomeric end, without copy number variation. In contrast, in the third patient the LOH was restricted to the 4q24 region and was due to a 325 kb microdeletion. This minimal candidate region contains only one single gene, TET2 (Ten-Eleven Translocation–2), which belongs to a family of three genes of unknown function. Sequencing of the coding region of TET2 in the two patients with large LOH revealed a mutation leading to a stop codon in exon 3 and a 9 nucleotide deletion in exon 6 resulting in the loss of 3 evolutionary-conserved residues. TET2 coding sequence was normal in the patient with the 325 kb deletion and in the samples from the 2 patients without 4q24 LOH. Analysis of lymphocyte DNA demonstrated that TET2 defects were acquired. To extend our results we sequenced TET2 in a series of 181 unselected JAK2 V617F MPN patients. We found TET2 deletions, frame shifts, stop codons or conserved amino-acid substitutions, in 25 MPN (3/10 primary myelofibrosis, 14/98 polycythemia vera, 8/73 essential thrombocythemia), resulting in an overall 14% frequency. In the majority of MPN patients our results suggest that the two copies are affected, indicating that TET2 behaves as a tumor suppressor gene. To determine whether TET2 inactivation was an early, pre-JAK2 V617F molecular event, we analyzed single clones grown from CD34+CD38− and CD34+CD38+ cells in five patients with TET2 mutations. We showed that TET2 defects target both multipotent and committed progenitors, some of them being TET2 mutated in the absence of JAK2 V617F. This indicates that TET2 inactivation is a pre-JAK2 V617F event in these five patients. Finally, TET2-mutated HSCs from MPN patients have an increased capacity to repopulate non obese diabetic-severe combined immunodeficient (NOD-SCID) mice, suggesting that TET2 regulates HSC properties. In conclusion we have identified TET2 as a probable new tumor suppressor gene altered in 14% of MPN patients. This gene may have key functions in hematopoiesis and HSC biology.

Kinetic Analysis by Real-Time PCR of Hepatitis C Virus (HCV)-Specific T Cells in Peripheral Blood and Liver after Challenge with HCV

Intrahepatic virus-specific CD8(+) T cells are thought to be important for the control of hepatitis C virus (HCV) infection, yet the precise kinetics for the expansion of epitope-specific T cells over the course of infection are difficult to determine with currently available methods. We used a real-time PCR assay to measure the frequency of clonotypic HCV-specific CD8(+) T cells in peripheral blood and snap-frozen liver biopsy specimens of two chimpanzees (Pan troglodytes) with previously resolved HCV infection who were rechallenged with HCV. In response to rechallenge, the magnitude of each clonotypic response was 10-fold higher in the liver than in the blood, and the peak clonotype frequency was concurrent with the peak viral load. The higher frequency of HCV-specific clonotypes in the liver than in peripheral blood was maintained for at least 3 months after the clearance of viremia. After antibody-mediated CD8(+) T-cell depletion and another viral challenge, the rebound of these clonotypes was seen prior to an appreciable reconstitution of CD8(+) T-cell values and, again, at higher frequencies in the liver than in peripheral blood. These data demonstrate the importance of intrahepatic virus-specific CD8(+) T cells for the clearance of infection and the rapid kinetics of expansion after virus challenge.

To the kinetics of photoinduced volume changes in chalcogenide glasses

Recent experimental data on the dynamics of photoinduced volume changes in chalcogenide glasses are analyzed within a simple phenomenological model. Both kinetics of the volume expansion under continuous irradiation and that of the relaxation after the illumination is switched off are considered. Comparison between theoretical results and experimental data provides a quantitative estimate of the local conversion rate of structural units responsible for the effect into the expanded states. Furthermore, this comparison shows that the conversion rate in a-As2Se3 is several times smaller than that in a-Se.

Complement Factor H-Binding Protein, a Putative Virulence Determinant of Borrelia hermsii, Is an Antigenic Target for Protective B1b Lymphocytes

Vaccination is the most effective way to control infectious diseases. A variety of microbial pathogens use antigenic variation, an immune evasion strategy that poses a challenge for vaccine development. To understand protective immune responses against such pathogens, we have been studying Borrelia hermsii, a bacterium that causes recurrent bacteremia due to antigenic variation. An IgM response is necessary and sufficient to control B. hermsii infection. We have recently found a selective expansion of B1b cells concurrent with the resolution of B. hermsii bacteremia. B1b cells from convalescent but not naive mice confer long-lasting immunity, but the Ag(s) driving the protective IgM responses is unknown. Herein we demonstrate that convalescent B1b cell-derived IgM recognizes complement factor H-binding protein (FhbA), a B. hermsii outer-surface protein and putative virulence factor that does not undergo antigenic variation and is expressed by all clinical isolates. A progressive increase in the IgM response to FhbA correlated with the kinetics of B1b cell expansion, diminished the severity of bacteremic episodes, and led to the eventual resolution of the infection. These data indicate that FhbA is a specific target for protective B1b cell responses. Ags recognized by B1b cells may be considered as an important component in vaccination strategies.

Kinetics of stress fibers

Stress fibers are contractile cytoskeletal structures, tensile actomyosin bundles which allow sensing and production of force, provide cells with adjustable rigidity and participate in various processes such as wound healing. The stress fiber is possibly the best characterized and most accessible multiprotein cellular contractile machine. Here we develop a quantitative model of the structure and relaxation kinetics of stress fibers. The principal experimentally known features are incorporated. The fiber has a periodic sarcomeric structure similar to muscle fibers with myosin motor proteins exerting contractile force by pulling on actin filaments. In addition the fiber contains the giant spring-like protein titin. Actin is continuously renewed by exchange with the cytosol leading to a turnover time of several minutes. In order that steady state be possible, turnover must be regulated. Our model invokes simple turnover and regulation mechanisms: actin association and dissociation occur at filament ends, while actin filament overlap above a certain threshold in the myosin-containing regions augments depolymerization rates. We use the model to study stress fiber relaxation kinetics after stimulation, as observed in a recent experimental study where some fiber regions were contractile and others expansive. We find that two distinct episodes ensue after stimulation: the turnover–overlap system relaxes rapidly in seconds, followed by the slow relaxation of sarcomere lengths in minutes. For parameter values as they have been characterized experimentally, we find the long time relaxation of sarcomere length is set by the rate at which actin filaments can grow or shrink in response to the forces exerted by the elastic and contractile elements. Consequently, the stress fiber relaxation time scales inversely with both titin spring constant and the intrinsic actin turnover rate. The model's predicted sarcomere velocities and contraction–expansion kinetics are in good quantitative agreement with experiment.

USE OF HUMAN NEURAL TISSUE FOR THE GENERATION OF PROGENITORS

Accumulating evidence suggests that a better understanding of normal human brain stem cells and tumor stem cells (TSCs) will have profound implications for treating central nervous system disease during the next decade. Neurosurgeons routinely resect excess surgical tissue containing either normal brain stem cells or TSCs. These cells are immediately available for expansion and use in basic biological assays, animal implantation, and comparative analysis studies. Although normal stem cells have much slower kinetics of expansion than TSCs, they are easily expandable and can be frozen for future use in stem cell banks. This nearly limitless resource holds promise for understanding the basic biology of normal brain stem cells and TSCs, which will likely direct the next major shift in therapeutics for brain tumors, brain and spinal cord injury, and neurodegenerative disease. This report reviews the progress that has been made in harvesting and expanding both normal and tumor-derived stem cells and emphasizes the integral role neurosurgeons will play in moving the neural stem cell field forward.

The change in effective stress associated with swelling during carbon dioxide sequestration on natural gas recovery

Abstract The sequestration of CO 2 by pumping it into deep coal seams is being investigated. It is therefore worthwhile to gather the information available on the interactions of CO 2 with coals and the effects of CO 2 on coals' properties in order to attempt a prediction of the long-term effects of sequestration. In the experiment, the volumetric changes of the coal matrix were monitored for a low-rank coal (C daf 84.14; V daf 33.4) for mixtures of CO 2 and CH 4 of different proportions and single gases. In the case of the sorption of a mixture of gases, the course of the kinetics of expansion of the coals studied indicates a lack of visible deformation of the coal structure. The observed phenomenon of a higher affinity to CO 2 and displacement of CH 4 by this sorbate may , provide one of the reasons for abrupt disturbances in the rock, by changes in the bed permeability, caused by competitive processes of sorption and desorption.

Classifying the Expansion Kinetics and Critical Surface Dynamics of Growing Cell Populations

We systematically study the growth kinetics and the critical surface dynamics of cell monolayers by a class of computationally efficient cellular automaton models avoiding lattice artifacts. Our numerically derived front velocity relationship indicates the limitations of the Fisher-Kolmogorov-Petrovskii-Piskounov equation for tumor growth simulations. The critical surface dynamics corresponds to the Kardar-Parisi-Zhang universality class, which disagrees with the interpretation by Bru et al. of their experimental observations as generic molecular-beam-epitaxy-like growth, questioning their conjecture that a successful therapy should lead away from molecular beam epitaxy.

Self Renewal and Proliferative Signals in the Bone Marrow Microenvironment Promote Homeostatic Peripheral Expansion of Donor-Derived T Cell Subsets Following Stem Cell Transplantation.

The bone marrow (BM), in addition to its role in providing hematopoietic stem cell support, is becoming increasingly recognized as a significant reservoir for T cells. Recent data have shown the BM to be the predominant site for homeostatic peripheral expansion (HPE). Constitutive HPE is a mechanism which allows maintenance of T cell numbers, while lymphopenia-induced HPE restores T cell numbers following T cell-depleting measures such as myelosuppression. While the role of BM in constitutive HPE in non-irradiated mice has been well documented, little is known of the role of BM in HPE following myeloablation. In the present study, we examined the contribution of BM to lymphopenia-induced HPE following myeloablative radiation conditioning and HSC transplantation, and documented the kinetics of expansion of donor-derived T cell subsets in the irradiated marrow and spleen. To this end, C57BL/6 and BoyJ congenic mice, differing in CD45 allelic expression, were used to track donor-derived T cell subsets using 8 color flow cytometry 5 days after transplantation of 10–20 × 10e6 low density BM cells (non-T cell depleted) into lethally-irradiated recipients (950cGy). At the time of analysis (d5 post transplant) the percentage of total donor cells in BM was approximately 20%, and 10% in the spleen. Of interest, an enhanced migration of CD8+ cells to BM was observed, increasing from 3±0.6% in steady state marrow to 8±3.3% of donor cells in transplanted mice. While only 10.1±1.0% of CD8+ cells in steady state BM exhibited a central memory phenotype (TCM, CD44hi, CD45RBhi, CD62Lhi), this percentage increased to 90±2.7% of donor CD8+ cells in day 5 transplanted BM (p<0.05). This preferential migration of TCM to irradiated BM is in contrast to the spleen, which contained approximately equal percentages of donor CD8+ naïve (CD44lo, CD62Lhi), effector (CD44hi, CD45RBlo, CD62Llo), and TCM cells. The reported increase in SDF-1 expression in irradiated BM relative to spleen may contribute to the enhanced TCM migration to BM, since TCM are more responsive to SDF-1 than naive cells. In experiments where donor cells were stained with CFSE prior to transplantation, proliferation of the different CD8+ subsets was followed. While the majority (∼97%) of BM TCM proliferated and lost CFSE fluorescence by day 5, a small percentage (2.8%) remained quiescent, exhibiting bright CFSE fluorescence (CFSEbright). In contrast, 10–20% of spleen TCM remained quiescent. These findings are in support of data documenting the BM as the predominant site for HPE, and illustrate the highly proliferative environment in the BM compared to spleen for expansion of TCM cells. Despite the higher degree of proliferation in the BM, 2-fold more BM CFSEbright TCM cells express IL7Ralpha, a molecule important in self renewal, compared to spleen CFSEbright cells. Given that TCM cells reportedly possess a similar self renewal genetic profile as hematopoietic stem cells, it is possible that TCM cells migrating through the BM following HSC transplantation are responsive to some of the same self renewal signals important for HSC self renewal, which would be presumably plentiful in the post-irradiation/transplantation BM microenvironment. In this regard, expression of IL7Ralpha by BM-homed TCM may allow for significant expansion while maintaining a self renewal phenotype, requirements which may be important for efficient HPE following myeloablation and stem cell transplantation.

Time–temperature superposition for foaming kinetics of Al-alloy foams

Abstract Applicability of time–temperature superposition principle to the foaming kinetics of aluminum (Al)-alloy foams produced by powder metallurgical method was investigated. Foaming kinetics above melting temperatures of Al–Si–Cu–Mg foams was studied. The expansion data at various furnace temperatures were collected. Well-known superposition parameters such as Larson-Miller, Orr-Sherby-Dorn, Goldhoff-Sherby and Manson-Succop were established based on the linear iso-expansion lines in plots of log(heating time) versus furnace temperature and log(heating time) versus inverse furnace temperature. In order to study the expansion kinetics of the Al-alloy foams, the expansions were measured in terms of pore fraction using an image analyzer. Finally, the linear relationship between the porosity and the superposition parameters was established.

Anti‐CD3/28 mediated expansion of macaque CD4+ T cells is polyclonal and provides extended survival after adoptive transfer

Our lab has previously shown that adoptive transfer of in vitro expanded autologous purified polyclonal CD4(+) T cells using anti-CD3/CD28 coated beads induced antiviral responses capable of controlling simian immunodeficiency virus (SIV) replication in vivo. Expansion on anti-CD3/28 coated beads was found to induce a true polyclonal expansion as CFSE labeled cells uniformly showed dilution of the dye over several days of culture, in contrast to aliquots of the same cells subjected to mitogen stimulation. Of interest was the finding that CD4(+) T cells collected before and during early chronic SIV infection or AIDS stage did not show any or only modest differences in proliferative response or expansion kinetics. The reason for such excellent expansion properties was analyzed by the quantitation of telomerase activity in aliquots of expanding CD4(+) T cells from sample collected at various times post-infection. First, anti-CD3/28 expanded CD4(+) T cells exhibited telomerase levels 2- to 20-fold higher than the starting population of CD4(+) T cells. Moreover, while telomerase activity in ex vivo tested CD4(+) T cells was found to decrease following SIV infection and disease progression, anti-CD3/28 expansion appeared to restore significant levels of telomerase activity as no difference was noted in telomerase expression between CD4(+) T cells expanded from samples collected before or during the chronic SIV infection. When such expanded and CFSE labeled T cells were autologously transferred to monkeys, evidence for extended survival in vivo was provided as CFSE labeled cells were detected to relatively high levels in blood and spleen at 1 week post-infection. In summary, the data suggest that anti-CD3/28 mediated expansion of CD4(+) T cells retains its immunotherapeutic potential not only during the early stages of lentiviral infection but also at more advanced stages of disease.

Effects of poly (ethylene glycol) chains conformational transition on the properties of mixed DMPC/DMPE-PEG thin liquid films and monolayers

Foam thin liquid films (TLF) and monolayers at the air–water interface formed by DMPC mixed with DMPE-bonded poly (ethylene glycol)s (DMPE-PEG 550, DMPE-PEG 2000 and DMPE-PEG 5000) were obtained. The influence of both (i) PEG chain size (evaluated in terms of Mw) and mushroom-to-brush conformational transition and (ii) of the liposome/micelle ratio in the film-forming dispersions, on the interfacial properties of mixed DMPC/DMPE-PEG films was compared. Foam film studies demonstrated that DMPE-PEG addition to foam TLFs caused (i) delayed kinetics of film thinning and black spot expansion and (ii) film stabilization. At the mushroom-to-brush transition, due to steric repulsion increased DMPE-PEG films thickness reached 25 nm while pure DMPC films were only 8 nm thick Newton black films. It was possible to differentiate DMPE-PEG 2000/5000 from DMPE-PEG 550 by the ability to change foam TLF formation mechanism, which could be of great importance for “stealth” liposome design. Monolayer studies showed improved formation kinetics and equilibrium surface tension decrease for DMPE-PEG monolayers compared with DMPC pure films. SEM observations revealed “smoothing” and “sealing” of the defects in the solid-supported layer surface by DMPE-PEGs adsorption, which could explain DMPE-PEGs ability to stabilize TLFs and to decrease monolayer surface tension. All effects in monolayers, foam TLFs and solid-supported layers increased with the increase of PEG Mw and DMPE-PEG concentration. However, at the critical DMPE-PEG concentration (where mushroom-to-brush conformational transition occurred) maximal magnitude of the effects was reached, which only slightly changed at further DMPE-PEG content and micelle/liposome ratio increase.

Unique features of Vγ2Vδ2 T cell memory provides for bridge immunity to infections (44.16)

Abstract Human Vγ2Vδ2 T cells play important roles in mediating immunity against microbial pathogens and have potent anti-tumor activity. They recognize prenyl pyrophosphates such as isopentenyl pyrophosphate (IPP). We and others find that hydroxymethyl-butenyl pyrophosphate (HMBPP) is the major Vγ2Vδ2 antigen for many eubacteria. HMBPP is an intermediate in the MEP pathway for isoprenoid biosynthesis used by bacteria and protozoans. HMBPP was a 30,000-fold more potent antigen than IPP. The ubiquitous presence of prenyl pyrophosphates results in unique features of Vγ2Vδ2 T cell memory. Although exhibiting similar kinetics of expansion as CD8 αβ T cells after infections, almost all adult γδ T cells are memory cells that can be distinguished by expression of CD28, CD27 and CD45RA. High proportions of intermediate/late effector memory cells can be found in some donors even in early adulthood. Each memory subset displays distinct functional properties and chemokine receptors. Intermediate/late memory cells express CXCR1, CXCR2 and CX3CR1, whereas early central memory cells express CXCR6, CCR1 and CCR2. Late effector cells proliferate poorly compared with early and intermediate cells. Thus, different inflammatory chemokines attract distinct Vγ2Vδ2 memory subsets with different functional capabilities. The rapid conversion from naïve to memory T cells due to the recognition of a widespread microbial metabolite allows Vγ2Vδ2 T cells to mount memory responses to primary infections by bacteria and parasites using the MEP pathway.

Integrating phenological, chemical and biotic defences in ant-plant protection mutualisms: a case study of two myrmecophyte lineages

We examined the role of plant phenology in the evolution of anti-herbivore defence in symbiotic ant-plant protection mutualisms. Phenology of the host-plant affects traits of its herbivores, including size, growth rate, development time, and gregariousness. Traits of herbivores in turn determine what traits ants must have to protect their host. Diversity in plant phenological traits could thus help explain the great ecological diversity of coevolved ant-plant mutualisms. We explored the postulated causal chain linking phenology of the plant, herbivore adaptations to phenology, and ant adaptations for protection, by comparing two myrmecophytes presenting strong contrasts in phenology. In Leonardoxa africana, a slow-growing understory tree, growth at each twig terminal is intermittent, the rapid flushing of a single leaf-bearing internode being followed by a pause of several months. In contrast, axes of Barteria nigritana, a tree of open areas, grow continuously. Analysis of the phenology (kinetics of expansion) and chemistry of leaf development (contents of chlorophylls, lignin, and nitrogen during leaf growth) showed that these two species exhibit strongly contrasting strategies. Leonardoxa exhibited a delayed greening strategy, with rapid expansion of leaves during a short period, followed by synthesis of chlorophylls and lignins only after final leaf size has been reached. In contrast, leaves of Barteria expanded more slowly, with chlorophylls and lignin gradually synthesised throughout development. Differences in the phenology of leaf development are reflected in differences in the duration of larval development, and thereby in size, of the principal lepidopteran herbivores observed on these two plants. This difference may in turn have led to different requirements for effective defence by ants. The strategy of phenological defence may thus affect the evolution of biotic defence.

링거액 주입시의 부피팽창 효과에 대한 모델링

In this work the kinetics of volume changes of fluid spaces associated with infusion of Ringer`s solution are analyzed using the body fluid space model. During infusion of Ringer`s solution, the human body is assumed to be characterized by the fluid space model into which fluid is fed and from which fluid is left. Various infusion types were tested to accommodate different medical situations. Volunteers were given Ringer`s solution and the changes in blood hemoglobin were detected. From the comparison with experimental data, the single- and two-fluid space models were found to represent adequately the kinetics of human volume expansion during infusion of Ringer`s solution.

Kinetics of volume expansion during infusion of Ringer’s solution based on two volume model

Kinetics of volume expansion during infusion of Ringer’s solution based on two volume model