bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency of D8/17 B lymphocyte alloantigen in North Indian patients with rheumatic heart disease
Authors: GANGULY N. K. , ANAND I. S. , KOICHA M. , JINDAL S. , WAHI P. L.
Published: July 2007

Ninety patients with rheumatic heart disease and 50 age‐ and sex‐matched healthy human volunteers representing a North Indian population were typed for the B cell alloantigen D8/17 using a monoclonal antibody and a single step immunofluorescence technique. This alloantigen was expressed in 66.44% patients with RHD as compared with 14% of the normal population. A high relative risk (RR = 11.13) indicated a strong association of D8/17 B cell alloantigen with rheumatic heart disease. Increase in the frequency of the marker was observed with increasing age up to the fifth decade (40–49 years) in these patients. However, the frequency of this alloantigen, in the present study, in North Indian patients with rheumatic heart disease is lower than that reported in the American population.
Evaluation of thrombus detection in a rabbit model using a technetium‐99M‐labelled anti‐fibrin monoclonal antibody
Authors: LEE F‐T. , MILNER L. J. , BONIFACE G. R. , BAUTOVICH G. J. , WEEDON A. R. J. , BUNDESEN P. G. , RYLATT D. B. , WALKER K. Z.
Published: July 2007

Technetium‐99 m (99mTc)‐labelled conjugates of an anti‐fibrin monoclonal antibody, DD‐3B6/22, have been assessed for their detection of vascular thrombi in a rabbit model. DD‐3B6/22 binds to a D‐dimer epitope present on cross‐linked fibrin but absent from the fibrin monomer or fibrinogen. Injection of a 99mTc‐label led Fab′ fragment of DD‐3H6/22 allowed delineation of model thrombi as early as 30 min postinjection (p.i.) with optimal localization at 4–5 h. Thrombus label uptake at 4 h p.i. was 0.304 ± 0.106% injected dose/g (% ID/g) compared with 0.022 ± 0.001% ID/g after the injection of a control Fab′ fragment. These results suggest that the 99mTc‐labelled Fab′ fragment of DD‐3B6/22 has excellent potential for scintigraphic detection of vascular thrombi in humans.
Structural basis of antigenic variation: Studies of influenza virus neuraminidase
Authors: COLMAN P. M.
Published: July 2007

Recent studies of the structural basis of antigenic variation in influenza virus neuraminidase and of the structure of neuraminidase‐antibody complexes are summarized.
Increased release of interleukin‐1 and tumour necrosis factor by interleukin‐2‐induced lymphokine‐activated killer cells in the presence of cisplatin and FK‐565
Authors: BASU SUNANDA , SODHI AJIT
Published: July 2007

The supernatants of peripheral blood lymphocytes cultured in interleukin‐2 (IL‐2) for 4 days contained tumour necrosis factor (TNF) and interleukin‐1 (IL‐1). Addition of cisplatin (CP) or FK‐565 to these cultures increased the level of both of these cytokines in culture supernatants. Furthermore, when the LAK cells induced by culture with IL‐2 in the presence or absence of CP/FK‐565 were co‐cultured with tumour cells, the production of these cytokines was significantly enhanced. The level of enhancement depended on the ratio of LAK cells to tumour cells used and the length of coincubation of the two cell types. Culture supernatants of LAK cells and LAK cells stimulated by tumour cells were also cytotoxic to MCF‐7 and U937 cells in 72 h cytotoxic assay, and antibodies specific for TNF and IL‐1 inhibited the supernatant‐mediated cytotoxicity. These results suggest that, in addition to the up‐regulation of IL‐2‐induced LAK activity, treatment of PBL with CP/FK‐565 leads to enhanced production of various cytokines with potential antitumour and immunoregulatory activity.
T cell receptor α‐chain polymorphic allele frequencies in Caucasians and Polynesians
Authors: GEURSEN A. , COUPER A. , ABBOTT W. G. H. , CAIRNS L. M.
Published: July 2007

Restriction length polymorphisms in the variable and constant regions of the T cell receptor α‐chain were examined in 42 Caucasians, 29 Maoris and 27 Pacific Islanders. Southern blots of Tag I digested DNA were hybridized with the T cell receptor α‐chain probe pY14. Our results confirm that a 1.4 kb T cell receptor α chain‐Tag 1 band is allelic to a 0.5 kb band. A significant difference in the frequency of the 1.4 and 0.5 kb alleles of the variable region of the α‐chain was detected in Caucasians when compared with Maoris or Pacific Islanders (P < 0.0001). No differences in the frequency of the 2.0 and 7.0 kb alleles of the constant region gene were detected between any of the racial groups. These data may be relevant to ethnic differences in susceptibility to immune disorders.
Parasite‐induced changes to localized erythrocyte membrane deformability in Plasmodium falciparum cultures
Authors: NAUMANN KELLIE M. , JONES GRAHAM L. , SAUL ALLAN , SMITH ROSS
Published: July 2007

The effect of intra‐erythrocytic development of the Plasmodium falciparum parasite on local deformability of human erythrocyte membranes was studied by aspiration of cells into 0.56 μm diameter pores in polycarbonate filters and examination, after fixing, with a scanning electron microscope. As the aspiration pressure increased, the erythrocyte membrane was extruded into the filter pores. The pressure dependence of the protrusion length and the minimum pressure required to produce any deformation provided measures of the membrane shear and the bending moduli, respectively. At the trophozoite and, to a greater extent, schizont stage of development, host cell membrane deformability was significantly decreased. There was no appreciable difference between uninfected and ring‐infected erythrocytes.
Limiting dilution analysis in leprosy
Authors: MULLINS RAYMOND J. , ROCHE PAUL , ADAMS ELIZABETH , JONES PHILLIP , CHEN SHARON , THEUVENET WIM , BASTEN ANTONY
Published: July 2007

Peripheral blood mononuclear cells (PBM) obtained from leprosy patients and healthy controls were cultured with Mycobacterium leprae and the control antigens, BCG and SKSD. Parallel cultures were supplemented with additional interleukin‐2 (IL‐2). On the basis of the level of response to M. leprae, leprosy patients could be divided into low, intermediate and high responders. The addition of IL‐2 resulted in enhanced proliferation to antigen only by cells from intermediate responders. This effect was neither antigen specific nor was it confined to cells from leprosy patients. When limiting dilution analyses were performed on cells from 26 patients across the leprosy spectrum, no M. leprae‐reactive lymphocytes were detected in cells from subjects with lepromatous disease. The precursor frequency for cultures containing M. leprae plus IL‐2 was no greater than that of cultures containing IL‐2 alone, thereby excluding the possibility of clonal anergy reversible with IL‐2. This was observed in both untreated patients and those on long‐term treatment, which made sequestration of antigen‐reactive cells within leprosy lesions an unlikely explanation. On the other hand, M. leprae‐reactive lymphocytes were detected in patients with tuberculoid and borderline tuberculoid disease and in two subjects with borderline lepromatous leprosy in type I reversal reaction. IL‐2 reactive cells were detected in all patients regardless of clinical classification. Three 'suppressor’curves were obtained but were not confined to cells from lepromatous patients. Taken together, these findings suggest that the non‐responsiveness to M. leprae characteristic of the great majority of multibacillary patients is due to an absence of antigen‐sensitive T cells.
Antibodies to 65 kDa and 70 kDa heat shock proteins in rheumatoid arthritis and systemic lupus erythematosus
Authors: PANCHAPAKESAN JAI , DAGLIS MALAMA , GATENBY PAUL
Published: July 2007

To test the potential role of autoimmunity to the highly conserved heat shock proteins (HSP) in immune arthritides, the sera from 99 patients with rheumatoid arthritis (RA), 48 patients with systemic lupus erythematosus (SLE) and 65 normal controls were examined by ELISA for IgG and IgM antibodies to the 65 kDa and 70 kDa heat shock proteins from Mycobacterium bovis (Bacille Calmette‐Guerin; BCG). In RA sera there are significant numbers of individuals with increased IgM anti‐65 kDa and anti‐BCG reactivity as well as IgG anti‐70 kDa when compared with controls. In SLE both IgM and IgG anti‐BCG, together with IgM anti‐65 kDa, differed significantly from controls. The results were compared with previous reports in similar groups of patients, and it is clear that no consistent pattern of reactivity emerges. While further work may be justified looking carefully at the disease duration and other subsets of both RA and SLE, it is difficult at this stage to conclude that antibodies to autologous HSP that cross‐react with mycobacterial HSP play a major role in disease pathogenesis.
Local immunity in the male reproductive tract
Authors: CLIFTON VICKI L. , HUSBAND ALAN J. , KAY DAVID J.
Published: July 2007

In previous studies we have demonstrated that the male urinary tract forms part of the common mucosal immune system, and that the gut contributes to local defences at this site.1 The question arises as to the extent to which the reproductive tract also forms part of the common mucosal immune system. Rats were immunized by a variety of routes designed to stimulate a local response in the intestine and/or the reproductive tract. Rats immunized only by the intratesticular (i.t.) route yielded no antibody‐containing (ACC) response in any of the tissues examined. Intestinal immunization using intraperitoneal priming followed by intraduodenal challenge (i.p./i.d.) yielded a substantial IgA‐specific ACC response in the jejunum, but no ACC were detectable in any of the reproductive tract tissues. However, when intestinal and testicular immunizations were combined, large numbers of IgA‐specific antibodies were detected in all tissues examined. Chronic drainage of the thoracic lymphatic duct throughout the post‐challenge period abrogated the ACC response in all tissues of the reproductive tract, indicating that the ACC appearing at these sites after immunization were of gut origin. The IgA‐specific anti‐OVA antibody detectable in serum, saliva and testis homogenate reflected the ACC counts in histological sections. The studies reported here confirm that the male reproductive tract does form part of a common mucosal immune system and that gut‐associated lymphoid tissues may contribute cellular precursors for ACC, particularly those of IgA specificity, appearing in the tract after local challenge. The implications of these findings to infectious disease involving the urogenital tract are obvious and investigation of oral vaccines to control sexually transmitted disease as well as acquired urinary tract infections deserves further attention. There are further implications, however, for the understanding and management of male infertility.
In vitro metabolic inhibition of the human lymphocyte: Influence on the expression of interleukin‐2 receptors
Authors: KARLSSON H. , NÄSSBERGER L.
Published: July 2007

We have investigated the effects of energy depletion in human lymphocytes on the expression of the membrane‐bound interleukin‐2 receptor (IL‐2R) and the release of soluble IL‐2R. Concanavalin‐A (Con‐A) and IL‐2‐transformed lymphocytes were incubated with sodium fluoride, inhibiting the Embden‐Meyerhof pathway, rotenone and 2,4‐dinitrophenol (2,4‐DNP), which are known to disturb mitochondria 1 high energy production. Rotenone was found to be the most potent inhibitor, with a half maximal effect at 10 nmol/L. 2,4‐DNP and sodium fluoride, although not as potent as rotenone, showed marked inhibitory effects in higher concentrations, with half maximal effects at 50 μmol/L and 5 mmol/L respectively. No difference in the inhibition pattern for membrane‐bound IL‐2R compared with sIL‐2R was observed. It is concluded that intracellular synthesis, transport and subsequent membrane insertion or release of receptors important for immunoregulation require high energy phosphate compounds and are sensitive to disturbances in intracellular energy levels.
T cell memory: A role for MHC class II molecules on T cells?
Authors: ZOLA HEDDY
Published: July 2007

A proportion of human T cells express MHC class II molecules. In this paper, the hypothesis is advanced that these MHC class II molecules present antigenic peptides acquired from interaction with other antigen‐presenting cells (e.g. during the primary response) and can therefore interact in a cognitive manner with T cells with the same specificity. Memory is maintained in the physical form as clusters of T cells expressing T cell receptors and the cognate peptide‐MHC class II complex; by virtue of their cognate interaction with each other these cells turn over gradually and return to the cluster when they recirculate. When fresh antigen is introduced, it is presented to some of these T cells by non‐T antigen‐presenting cells that provide a second signal leading to vigorous activation of the T cell. The proximity and cognate interaction of other T cells of the same specificity allows a chain reaction to occur, leading to rapid development of the secondary response. The hypothesis, which is testable, is proposed because of doubts concerning the current concept of memory as applied to T cells, and a need to understand the consequences of the expression of MHC class II molecules by a subset of T cells.
An hypothesis to explain why cell‐mediated immunity alone can contain infections by certain intracellular parasites and how immune class regulation of the response against such parasites can be subverted
Authors: BRETSCHER PETER A.
Published: July 2007

Cells with a low density of parasite‐specific antigens on their surface are postulated to be susceptible to a cell‐mediated attack but not to effector mechanisms normally activated following the binding of specific antibody to the infected cell. It is further postulated that such infected cells normally induce a cell‐mediated response, and that cells infected with slow‐growing intracellular parasites have a low density of parasite‐specific antigens on their surface. Despite these general postulates, cell‐mediated immunity is not invariably induced following natural infection by certain slow‐growing parasites, such as those responsible for leprosy, tuberculosis, and the leishmaniases, and antibody can be induced that is exclusive of a strong, cell‐mediated response. It is proposed that certain events in such cases subvert the normal regulatory processes that control the class of immunity induced. In these cases, the parasite‐infected cells, bearing a low representation of parasite antigens, induce antibody even though they are not susceptible to antibody‐dependent effector mechanisms, and so they are not eliminated. In this case, chronic infection and uncontrolled growth of the parasiteoccurs, often with fatal consequences.
Value issues in biomedical science: Public concerns and professional complacency
Authors: BELLETT A.J.D.
Published: July 2007

Biomedical research was once an unquestioned good, and generous funding for a short time allowed researchers to work on whatever interested them. Two contradictory pressures have changed this. As costs have risen and economic rationalism has become politically dominant, governments, private corporations and granting agencies have increasingly demanded compliance with their own priorities, instrumental values and performance criteria. On the other hand, social and ethical critics have characterized biomedical research as being out of touch with real health needs and community values and as being an agent of social control that entrenches the power of a technocratic hegemony. The profession has largely acquiesced in bureaucratic and corporate intervention in exchange for continued funding, and assumed that social concerns could be allayed by ‘top down’ paternalistic education of the public. However, this response tends to add weight to the criticism that biomedicine is an agent of social control. What is needed is a spirited defence of the value of independent scholarship and research that is not limited to science but includes the humanities. Equally important is a process of community education in which scientists not only transmit their knowledge and enthusiasm to the public, but themselves become open to the social and ethical concerns of the community.
Lymphoid tissue in rat oral mucosa: Structure and function
Authors: SMINIA TAEDE , SWART SIEBE J. , STEENBERGEN JOKE J. E. , BIEWENGA JEIKE
Published: July 2007

Lymphocyte and macrophage/dendritic cell populations in the oral cavity of the rat were studied by immunohistochemistry. Furthermore, the reactivity of the oral mucosa towards antigen and its position in the mucosal immune system was investigated by staining antibody‐forming cells and comparing serum and saliva antibody titres. Although numerous lymphocytes and non‐lymphoid cells were present in the oral mucosa, organized lymphoid tissue could not be found. The majority of the lymphocytes are T cells, particularly of the T‐helper phenotype. Macrophages were found only in the connective tissue, whereas dendritic cells also occurred in the epithelium. The possible functions of the cells in the different sites of the oral mucosa are discussed. Antibody‐forming cells were mainly detected in the draining superficial and posterior cervical lymph nodes and in the submandibular glands. The roles of the various compartments of the oral mucosal immune system are discussed with particular reference to the epithelium and connective tissue as induction sites, the draining lymph nodes as sites of proliferation and differentiation, and the submandibular glands as effector sites.
What is the selective pressure that maintains the gene loci encoding the antigen receptors of T and B cells? A hypothesis
Authors: LANGMAN RODNEY E. , COHN MELVIN
Published: July 2007

The dominant view is that the gene loci encoding the B cell antigen receptor (BAr) or the T cell antigen receptor (TAr) specify a vast array of combining sites. The ‘germline’ repertoire is estimated to be > 1010 by multiplying numbers of subunit complements by DN‐region variability. This implies that the germline can be maintained by a selection imposed by all or most of the antigenic universe. Its unchallenged popularity, notwithstanding, this neo‐germline view is untenable and hence the need for a competing concept, as presented here. The immunoglobulin (Ig) loci are under a totally different selection from the T loci. The Ig loci are selected upon largely by carbohydrate determinants on pathogens that vary more slowly than the proteins produced by the Ig loci, which are necessary to rid these selective antigens. By contrast, the T loci are selected to recognize the allele‐specific determinants on restricting elements encoded in the major histocompati‐bility complex (MHC). The expression of the germline results in a high copy number (HCN) repertoire; this repertoire is the substrate for ‘mutation’ that yields the low copy number (LCN) repertoire. For the B cell, these two repertoires interact to optimize the response to the unexpected. For the T cell, only the LCN repertoire is functional. The immunoglobulin (Ig) loci are selected upon as light(L)‐heavy (H) pairs; the T loci are selected upon as single units α or β (i.e. the VT‐gene segments act as a single pool). This competing concept carries with it many important and testable consequences.
Macrophages in protective immunity to Hymenolepis nana in mice
Authors: ASANO K. , MURAMATSU K. , ITO A. , OKAMOTO K.
Published: July 2007

When mice were treated with carrageen just before infection with eggs of Hymenolepis nana, they failed to exhibit sterile immunity to the egg challenge, with evidence of a decrease in the number of peripheral macrophages (Mø) and the rate of carbon clearance. Although there were high levels of interleukin‐1 (IL‐1) released into the intestinal tracts of the parasitized mice at challenge infection, there was almost no release of IL‐1 in those treated with carrageen just before challenge. These results strongly suggest that Mo have an important role in protective immunity to H. nana in mice.
A transgenic window on peripheral T cell tolerance
Authors: MILLER JACQUES F. A. P.
Published: July 2007

There is convincing evidence for the imposition of self‐tolerance by means of the clonal deletion of self‐reactive T cells within the thymus. Since not all self components may be encountered there, the question must be asked whether tolerance can occur post‐thymically. To test this, we have used transgenic technology to direct expression of a‘non‐self gene, H‐2Kb, to the insulin‐producing β cells of the pancreas in mice. These‘RIP‐Kb’transgenic mice were specifically tolerant of H‐2Kb‐bearing skin grafts. To test the fate of potentially reactive H‐2Kb ‐specific T cells in these tolerant mice, the RIP‐Kb mice were mated to a second series of transgenic mice with rearranged T cell receptor (TCR) genes encoding an H‐2Kb‐specific TCR to produce‘double transgenic’offspring. The TCR was detectable by a clonotype‐specific antibody. Although there was some evidence of intrathymic deletion of those T cells that expressed the highest density of the H‐2Kb‐specific TCR, lower density cells were present in the periphery. These may have been either indifferent to the H‐2Kb molecule expressed on the p cells or functionally silenced by it. Further experiments are planned to determine which of these two situations exists.
Is erratic bud-break in grapevines grown in warm winter areas related to disturbances in mitochondrial respiratory capacity and oxidative metabolism?
Authors: Pérez Francisco J. , Rubio Sebastián , Ormeño-Núñez Juan
Published: July 2007

Bud-break and the length and depth of endodormancy (ED) were studied in grapevine (Vitis Vinifera L.) cv. Thompson Seedless (Sultana) grown in the Elqui (warm winter) and in the Maipo (temperate winter) valleys of north and central Chile, respectively. High maximum daily winter temperatures, ordinarily occurring in the Elqui valley, reduced the depth without affecting the length of ED in comparison to buds grown in the Maipo valley. Furthermore, high winter temperatures during the ED period altered the oxidative metabolism of buds by increasing its mitochondrial respiratory capacity and increasing its levels of H2O2. Moreover, a reduced expression in alternative oxidase transcript was also observed at the end of the ED period in buds collected from the warmer Elqui valley in relation to those collected from the temperate Maipo valley. In controlled environments, the bud-break response of ecodormant (ECD) buds depended on the climatic zones from which buds were sampled (temperate or warm winter), and on whether growth chamber temperatures were held constant or fluctuated. Mitochondrial respiratory capacity of dormant grapevine buds was raised by warmer winter temperatures, and higher subsequent H2O2 levels at the ECD phase appeared to be related to the erratic breaking of latent buds in subtropical areas such as the Elqui valley.
Ascorbate and glutathione metabolism during development and desiccation of orthodox and recalcitrant seeds of the genus Acer
Authors: Pukacka Stanislawa , Ratajczak Ewelina
Published: July 2007

The ascorbate–glutathione system was studied during development and desiccation of seeds of two Acer species differing in desiccation tolerance: Norway maple (Acer platanoides L., orthodox) and sycamore (Acer pseudoplatanus L., recalcitrant). The results showed remarkable differences in the concentration and redox balance of ascorbate and glutathione between these two kinds of seeds during development, and a significant dependence between glutathione content and acquisition of desiccation tolerance in Norway maple seeds. There were relatively small differences between the species in the activities of enzymes of the ascorbate–glutathione cycle: ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.6.4.2). At the end of seed maturation, ascorbic acid content and the activities of the above enzymes was about the same in both species The electrophoretic pattern of APX isoenzymes was also similar for both species, and the intensity of the bands decreased at the end of seed maturation in both species. When sycamore seeds were desiccated to a moisture content of less than 26%, there was a marked decrease in seed viability and an increase in the production of reactive oxygen species. During desiccation, Norway maple seeds had a more active defence system, which was reflected in a higher glutathione content, a higher glutathione redox status, a higher ascorbate redox status, and higher activities of APX, MR, DHAR, GR and GPX (glutathione peroxidase). During desiccation, sulfhydryl-to-disulfide transition into proteins was more intense in Norway maple seeds than sycamore seeds. All of these results suggest that, in orthodox seeds, the ascorbate–glutathione cycle plays an important role in the acquisition of tolerance to desiccation, in protein maturation, and in protection from reactive oxygen species.
The aerodynamics of
Argentavis
, the world's largest flying bird from the Miocene of Argentina
Authors: Chatterjee Sankar , Templin R. Jack , Campbell Kenneth E.
Published: July 2007

We calculate the flight performance of the gigantic volant bird
Argentavis magnificens
from the upper Miocene (≈6 million years ago) of Argentina using a computer simulation model.
Argentavis
was probably too large (mass ≈70 kg) to be capable of continuous flapping flight or standing takeoff under its own muscle power. Like extant condors and vultures,
Argentavis
would have extracted energy from the atmosphere for flight, relying on thermals present on the Argentinean pampas to provide power for soaring, and it probably used slope soaring over the windward slopes of the Andes. It was an excellent glider, with a gliding angle close to 3° and a cruising speed of 67 kph.
Argentavis
could take off by running downhill, or by launching from a perch to pick up flight speed. Other means of takeoff remain problematic.
Natural killer cells actively patrol peripheral lymph nodes forming stable conjugates to eliminate MHC-mismatched targets
Authors: Garrod Kym R. , Wei Sindy H. , Parker Ian , Cahalan Michael D.
Published: July 2007

Natural killer (NK) cells are known to reject MHC-mismatched targets within blood organs, yet their role in peripheral lymphoid tissue remains unresolved. Here we address the capacity of NK cells to migrate within lymph nodes (LN) using two-photon microscopy to characterize cell velocities and interaction dynamics within the native lymphoid-tissue environment. Adoptively transferred unmanipulated NK cells were highly motile (6–7 μm/min) and capable of forming transient contacts with both syngeneic and allogeneic B cells. Stable conjugate interactions (lasting >5 min) formed preferentially with allogeneic cells, resulting in diminished motility and subsequent elimination of the target cell. In marked contrast to unmanipulated cells, NK cells purified by CD49b-positive selection exhibited only limited motility (2–3 μm/min). This velocity impairment arose largely because CD49b cross-linking enhanced NK cell adhesion to collagen fibers within the node. Moreover, CD49b cross-linking prevented NK cells from reconstituting effector cytolytic function
in vivo
, inhibited target cell lysis
in vitro
, and augmented IFN-γ responses to IL-2 activation
in vitro
. Taken together our data demonstrate that NK cells are a functionally important component of the LN microenvironment, and that cell motility and effector function are strongly modulated via CD49b manipulation.
Structural consequences of disease-causing mutations in the ATRX-DNMT3-DNMT3L (ADD) domain of the chromatin-associated protein ATRX
Authors: Argentaro Anthony , Yang Ji-Chun , Chapman Lynda , Kowalczyk Monika S. , Gibbons Richard J. , Higgs Douglas R. , Neuhaus David , Rhodes Daniela
Published: July 2007

The chromatin-associated protein ATRX was originally identified because mutations in the ATRX gene cause a severe form of syndromal X-linked mental retardation associated with α-thalassemia. Half of all of the disease-associated missense mutations cluster in a cysteine-rich region in the N terminus of ATRX. This region was named the
A
TRX-
D
NMT3-
D
NMT3L (ADD) domain, based on sequence homology with a family of DNA methyltransferases. Here, we report the solution structure of the ADD domain of ATRX, which consists of an N-terminal GATA-like zinc finger, a plant homeodomain finger, and a long C-terminal α-helix that pack together to form a single globular domain. Interestingly, the α-helix of the GATA-like finger is exposed and highly basic, suggesting a DNA-binding function for ATRX. The disease-causing mutations fall into two groups: the majority affect buried residues and hence affect the structural integrity of the ADD domain; another group affects a cluster of surface residues, and these are likely to perturb a potential protein interaction site. The effects of individual point mutations on the folding state and stability of the ADD domain correlate well with the levels of mutant ATRX protein in patients, providing insights into the molecular pathophysiology of ATR-X syndrome.
Packing contacts can mediate highly specific interactions between artificial transmembrane proteins and the PDGFβ receptor
Authors: Ptacek Jennifer B. , Edwards Anne P. B. , Freeman-Cook Lisa L. , DiMaio Daniel
Published: July 2007

We used proteins with randomized transmembrane (TM) domains to explore the role of hydrophobic amino acids in mediating specific interactions between transmembrane helices. The 44-aa bovine papillomavirus E5 protein, which binds to the TM domain of the PDGFβ receptor (PDGFβR) was used as a scaffold to construct a library encoding small dimeric proteins with randomized, strictly hydrophobic TM domains, and proteins were selected that induced focus formation in mouse C127 cells by activating the PDGFβR. Analysis of these proteins identified a motif of two hydrophobic residues that, when inserted into a 17-residue polyleucine TM domain, generated a protein that activated the PDGFβR and transformed cells. In addition, we identified transforming proteins that activated the wild-type PDGFβR but did not activate a series of PDGFβR TM point mutants that were efficiently activated by the E5 protein, indicating that these proteins were more specific than the E5 protein. Our results implied that multiple van der Waals interactions distributed along the entire length of the TM domains were required for productive interaction between the PDGFβR and some small proteins lacking hydrophilic TM residues. Our results also suggested that excluding hydrophilic residues from small TM proteins and peptides is a strategy to increase the specificity of heteromeric TM helix–helix interactions.
Expression of IL-7 receptor α is necessary but not sufficient for the formation of memory CD8 T cells during viral infection
Authors: Hand Timothy W. , Morre Michel , Kaech Susan M.
Published: July 2007

During many acute viral and bacterial infections, IL-7 receptor α-chain (IL-7Rα) is expressed on a subset of effector CD8 T cells that preferentially develop into long-lived memory CD8 T cells. These cells functionally require IL-7Rα, but it is unclear whether IL-7Rα acts mainly to induce their differentiation into memory cells or to sustain their long-term survival. To examine this question, IL-7Rα was constitutively overexpressed on all antigen-specific effector CD8 T cells during viral infection. Constitutive IL-7Rα expression had minimal effects on the numbers or function of effector and memory CD8 T cells formed. This indicated that IL-7Rα expression is not sufficient to drive memory cell development. In particular, the forced IL-7Rα expression did not rescue the killer cell lectin-like receptor G1 (KLRG1)
hi
short-lived effector CD8 T cells from death, showing that the majority of effector CD8 T cells die in an IL-7Rα-independent manner. Moreover, we found that, regardless of the ectopic expression of IL-7Rα, the KLRG1
hi
, but not the KLRG1
lo
effector CD8 T cells, were unable to proliferate well to IL-7, which may be due to increased amounts of p27
kip
in KLRG1
hi
cells. Because IL-7 can destabilize p27
kip
, this result suggested that KLRG1
hi
and KLRG1
lo
effector CD8 T cells naturally differ in their ability to transmit IL-7 signals. Altogether, these results reveal that IL-7Rα expression is permissive, but not instructive, to the creation of memory CD8 T cells.
Mycobacterium tuberculosis
DosS is a redox sensor and DosT is a hypoxia sensor
Authors: Kumar Ashwani , Toledo Jose C. , Patel Rakesh P. , Lancaster Jack R. , Steyn Adrie J. C.
Published: July 2007

A fundamental challenge to the study of oxidative stress responses of
Mycobacterium tuberculosis
(
Mtb
) is to understand how the protective host molecules are sensed and relayed to control bacilli gene expression. The genetic response of
Mtb
to hypoxia and NO is controlled by the sensor kinases DosS and DosT and the response regulator DosR through activation of the dormancy/NO (Dos) regulon. However, the regulatory ligands of DosS and DosT and the mechanism of signal sensing were unknown. Here, we show that both DosS and DosT bind heme as a prosthetic group and that DosS is rapidly autooxidized to attain the met (Fe
3+
) form, whereas DosT exists in the O
2
-bound (oxy) form. EPR and UV-visible spectroscopy analysis showed that O
2
, NO, and CO are ligands of DosS and DosT. Importantly, we demonstrate that the oxidation or ligation state of the heme iron modulates DosS and DosT autokinase activity and that ferrous DosS, and deoxy DosT, show significantly increased autokinase activity compared with met DosS and oxy DosT. Our data provide direct proof that DosS functions as a redox sensor, whereas DosT functions as a hypoxia sensor, and that O
2
, NO, and CO are modulatory ligands of DosS and DosT. Finally, we identified a third potential dormancy signal, CO, that induces the
Mtb
Dos regulon. We conclude that
Mtb
has evolved finely tuned redox and hypoxia-mediated sensing strategies for detecting O
2
, NO, and CO. Data presented here establish a paradigm for understanding the mechanism of bacilli persistence.
AMP-activated protein kinase (AMPK) action in skeletal muscle via direct phosphorylation of PGC-1α
Authors: Jäger Sibylle , Handschin Christoph , St.-Pierre Julie , Spiegelman Bruce M.
Published: July 2007

Activation of AMP-activated kinase (AMPK) in skeletal muscle increases glucose uptake, fatty acid oxidation, and mitochondrial biogenesis by increasing gene expression in these pathways. However, the transcriptional components that are directly targeted by AMPK are still elusive. The peroxisome-proliferator-activated receptor γ coactivator 1α (PGC-1α) has emerged as a master regulator of mitochondrial biogenesis; furthermore, it has been shown that PGC-1α gene expression is induced by exercise and by chemical activation of AMPK in skeletal muscle. Using primary muscle cells and mice deficient in PGC-1α, we found that the effects of AMPK on gene expression of glucose transporter 4, mitochondrial genes, and PGC-1α itself are almost entirely dependent on the function of PGC-1α protein. Furthermore, AMPK phosphorylates PGC-1α directly both
in vitro
and in cells. These direct phosphorylations of the PGC-1α protein at threonine-177 and serine-538 are required for the PGC-1α-dependent induction of the PGC-1α promoter. These data indicate that AMPK phosphorylation of PGC-1α initiates many of the important gene regulatory functions of AMPK in skeletal muscle.
Structural modules for receptor dimerization in the
S
-locus receptor kinase extracellular domain
Authors: Naithani Sushma , Chookajorn Thanat , Ripoll Daniel R. , Nasrallah June B.
Published: July 2007

The highly polymorphic
S
-locus receptor kinase (SRK) is the stigma determinant of specificity in the self-incompatibility response of the Brassicaceae. SRK spans the plasma membrane of stigma epidermal cells, and it is activated in an allele-specific manner on binding of its extracellular region (eSRK) to its cognate pollen coat-localized
S
-locus cysteine-rich (SCR) ligand. SRK, like several other receptor kinases, forms dimers in the absence of ligand. To identify domains in SRK that mediate ligand-independent dimerization, we assayed eSRK for self-interaction in yeast. We show that SRK dimerization is mediated by two regions in eSRK, primarily by a C-terminal region inferred by homology modeling/fold recognition techniques to assume a PAN_APPLE-like structure, and secondarily by a region containing a signature sequence of the
S
-domain gene family, which might assume an EGF-like structure. We also show that eSRK exhibits a marked preference for homodimerization over heterodimerization with other eSRK variants and that this preference is mediated by a small, highly variable region within the PAN_APPLE domain. Thus, the extensive polymorphism exhibited by the eSRK not only determines differential affinity toward the SCR ligand, as has been assumed thus far, but also underlies a previously unrecognized allelic specificity in SRK dimerization. We propose that preference for SRK homodimerization explains the codominance exhibited by a majority of SRKs in the typically heterozygous stigmas of self-incompatible plants, whereas an increased propensity for heterodimerization combined with reduced affinity of heterodimers for cognate SCRs might underlie the dominant–recessive or mutual weakening relationships exhibited by some SRK allelic pairs.
Advancing the analysis of treatment process
Authors: Stout Robert L.
Published: July 2007

Aims To review the role of process research in clinical research, to summarize progress in statistical methods for process analyses, and to describe a dynamic analytical approach that can provide new insights into the processes responsible for the effects of treatments and other variables.

Summary Process research helps us to understand what happens during our interventions, and can yield valuable knowledge regardless of whether an intervention is found to have significant effects. This is a review of recent statistical advances for dealing with missing data, tests for mediation and hierarchical modeling and demonstrate how these advances can help process researchers overcome obstacles that had limited past studies. However, the standard paradigm for process analysis, although conceptually sound, is based upon a static model that does little justice to the dynamics of treatment. Therefore, it is proposed that the paradigm is extended to study the time–course of dynamic processes, using existing statistical methods. Hierarchical linear modeling, structural regression modeling and event history methods are among the most promising tools for more advanced process analyses because of their ability to incorporate time‐varying predictors.

Conclusions The function of process analysis is to probe into the mechanisms of action of treatment to locate both weaknesses and strengths, but methods for process research are still rudimentary. By conceptualizing process analysis as a problem of relating multiple time‐series, many new analytical opportunities, and challenges, present themselves. Modern statistical methods can help to lead to broad advances in our understanding of the processes that affect treatment success.
Disentangling social selection and social influence effects on adolescent smoking: the importance of reciprocity in friendships
Authors: Mercken Liesbeth , Candel Math , Willems Paul , De Vries Hein
Published: July 2007

Aims  The goal of this study was to examine social selection and social influence within reciprocal and non‐reciprocal friendships, and the role of parents and siblings, as factors explaining similarity of smoking behaviour among adolescent friends. A new social selection–social influence model is proposed.

Design  Longitudinal design with two measurements.

Setting  Data were gathered among Dutch high school students in the control group of the European Smoking prevention Framework Approach (ESFA) study.

Participants  The sample consisted of 1886 adolescents with a mean age of 12.7 years.

Measurements  The main outcome measures were the smoking behaviours of the respondents, best friends, parents and siblings. We tested the social selection–social influence model with structural equation modelling techniques.

Findings  Social selection and social influence both played an important role in explaining similarity of smoking behaviour among friends. Within non‐reciprocal friendships, only social selection explained similarity of smoking behaviour, whereas within reciprocal friendships, social influence and possibly also social selection explained similarity of smoking behaviour. Sibling smoking behaviour was a more important predictor of adolescent smoking behaviour than parental smoking behaviour.

Conclusions  Social selection and social influence both promote similarity of smoking behaviour, and the impact of each process differs with the degree of reciprocity of friendships. These insights may contribute to further refinement of smoking prevention strategies.
Effect of acute paracetamol overdose on changes in serum and urine electrolytes
Authors: Pakravan N. , Bateman D. N. , Goddard J.
Published: July 2007

What is already known about this subject

• Paracetamol causes renal failure in overdose. Experimental studies have shown that paracetamol can inhibit COX II systemically in a manner similar to selective COX‐II inhibitors.

• In overdose nonsteroidal anti‐inflammatory drugs such as ibuprofen, cause dose‐dependent increase in urinary potassium excretion (FeK) and sodium retention, probably due to vasoconstriction.

What this study adds

• Paracetamol overdose is associated with dose‐related hypokalaemia and kaliuresis of short duration (<24 h), suggesting a specific renal effect of paracetamol in overdose.

• This effect seems likely to be via cyclo‐oxygenase inhibition and may be separate from the nephrotoxic effects of paracetamol.

Aims

To investigate the effects of acute paracetamol overdose on renal function, serum and urine electrolyte excretion in man.

Methods

Two studies were performed in patients admitted with paracetamol overdose: a retrospective study examining changes in serum electrolytes, and a prospective study evaluating changes in serum and urine electrolytes. A control group with SSRI overdose was included in the prospective study.

Results

There was a significant dose‐dependent relationship between admission (4 h) paracetamol concentration and fall in serum potassium in the retrospective study (P < 0.01) and a significant positive relationship between serum paracetamol at 4 h and fractional excretion of potassium at 12 h postingestion (P < 0.01) in the prospective study. No changes were seen in the control group. No cases developed renal failure.

Conclusions

Paracetamol overdose is associated with dose‐related hypokalaemia, and kaliuresis of short duration (<24 h), suggesting a specific renal effect of paracetamol in overdose perhaps via cyclo‐oxygenase inhibition. This effect seems distinct from any nephrotoxic effect of paracetamol.
Pharmacokinetic interaction between TMC114/ritonavir and tenofovir disoproxil fumarate in healthy volunteers
Authors: Hoetelmans Richard M. W. , Mariën Kris , De Pauw Martine , Hill Andrew , Peeters Monika , Sekar Vanitha , De Doncker Piet , Woodfall Brian , Lefebvre Eric
Published: July 2007

What is already known about this subject

• Tenofovir disoproxil fumarate and some of the HIV protease inhibitors show drug–drug interactions that cannot be predicted based on their metabolic profiles.

• Tenofovir disoproxil fumarate and HIV protease inhibitors are often combined as part of antiretroviral therapy.

What this study adds

• TMC114 (darunavir) is the latest HIV protease inhibitor approved by the US Food and Drug Administration and is used in combination with low‐dose ritonavir.

• This study shows for the first time the extent of the drug–drug interaction between tenofovir disoproxil fumarate and TMC114 combined with low‐dose ritonavir and compares the interaction observed with other HIV protease inhibitors.

Aim

TMC114 is a new HIV protease inhibitor, used in combination with low‐dose ritonavir (TMC114/r) as a pharmacokinetic enhancer. Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor. Both antiretrovirals show activity against wild‐type and resistant HIV. An open‐label crossover study was conducted in HIV – healthy volunteers to investigate the potential for a pharmacokinetic interaction between TMC114/r and tenofovir.

Methods

Two groups, each of six volunteers, were evaluated in two consecutive sessions. In session 1, volunteers received TMC114/r (300/100 mg bid) for 7 days, followed by a wash‐out period of at least 6 days. In session 2, volunteers received TMC114/r (300/100 mg bid) plus TDF (300 mg qd).

Results

When TMC114/r and TDF were coadministered, tenofovir plasma concentrations (Cmin and Cmax), and area under the curve (AUC24 h) increased by 37%, 24% and 22%, respectively. When TDF and ritonavir were coadministered, TMC114 plasma Cmin, Cmax and AUC12 h increased by 24%, 16% and 21%, respectively. There were no changes in the urinary excretion of unchanged tenofovir or TMC114 during coadministration. Administration of TMC114/r in HIV– healthy volunteers with or without TDF was well tolerated.

Conclusions

The interaction between TMC114/r and tenofovir is not clinically relevant and no dose adjustments are required when these drugs are coadministered.
The pharmacokinetics and effects of a long‐acting preparation of superoxide dismutase (PC‐SOD) in man
Authors: Broeyer F. J. F. , Van Aken B. E. , Suzuki J. , Kemme M. J. B. , Schoemaker H. C. , Cohen A. F. , Mizushima Y. , Burggraaf J.
Published: July 2007

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Reactive oxygen species (ROS), like superoxide anion, play an important role in different disease states.

• Superoxide dismutase (SOD) acts as a free radical scavenger by catalysing the dismutation of superoxide.

• Over the last decade, therapeutic use of SOD has been explored, but the results of these experiments have indicated that this has been of limited value, probably due to unfavourable pharmaceutical characteristics of the compounds.

WHAT THIS STUDY ADDS

• Single intravenous administrations of PC‐SOD (SOD covalently linked to lecithin) in doses up to 80 mg was well tolerated and biologically active for a period of 19 ± 6 h in healthy White volunteers.

• This suggests that PC‐SOD has pharmaceutically appropriate characteristics and may be a possible protective agent for patients in clinical conditions characterized by acute high radical overload.

AIM

To study the pharmacokinetics (PK), safety and tolerability of single rising doses up to 80 mg of superoxide dismutase covalently linked to lecithin (PC‐SOD) in healthy White volunteers.

METHODS

This double‐blind, placebo‐controlled, four‐period cross‐over study was performed in eight healthy volunteers (four male/four female). Three doses of PC‐SOD (20, 40 and 80 mg) and placebo were administered intravenously in randomized order. Serum and urinary PC‐SOD concentrations were measured predose and up to 96 h after dosing. In addition to standard safety measurements, the urinary excretion of N‐acetyl‐β‐glucosaminidase, α‐glutathione S‐transferase (α‐GST) and π‐GST was measured to evaluate renal function. The PK of PC‐SOD was analysed using noncompartmental and compartmental methods.

RESULTS

All treatments were well tolerated, and no obvious relationship between adverse events and treatment was observed. No effects of PC‐SOD on renal function could be detected. Dose normalized Cmax and AUC were not different between the different dosages, indicating linearity of plasma concentrations with dose. Estimated PC‐SOD clearance was 2.54 ml min−1[95% confidence interval (CI) 2.07, 2.83]. The terminal half‐life was estimated to be 1.54 days (95% CI 0.93, 2.15). SOD activity was elevated above baseline for 19 ± 6 h after the 80‐mg dose.

CONCLUSIONS

Single intravenous administrations of PC‐SOD in doses up to 80 mg were well tolerated in healthy White male and female volunteers. With the doses used, SOD activity was linearly related to the dose; after the 80‐mg dose it was present for an appreciable period. These findings suggest that it is worthwhile to investigate PC‐SOD in clinical conditions characterized by a high radical overload.