bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibitory effects of elevated endogenous cytokinins on nitrate reductase in ipt‐expressing tobacco are eliminated by short‐term exposure to benzyladenine
Authors: Lexa Matej , Genkov Todor , Brzobohatý Břetislav
Published: March 2003

Using a novel system for expressing ipt gene from Agrobacterium tumefaciens in tobacco (Nicotiana tabacum L., cv. Petit Havana SR1), we were able to grow seedlings and teratoma‐like tissue with increased content of cytokinins. This material enabled us to investigate new regulatory aspects of nitrate reduction. We grew control plants and plants with elevated cytokinins on MS media, with or without nitrate and benzyladenine (BA). We determined in vitro nitrate reductase (EC 1.6.6.1) activity (NRA) in this plant material. Initially, we found that ipt‐expressing plants always displayed lowered levels of NRA when compared to wild‐type SR1 plants. We determined that long‐term exposure of tobacco plants and tissue to cytokinins caused up to 60% decrease in NRA. Exposure to 40 mM nitrate was able to induce the activity in such plants 3‐fold, increasing the activity in SR1 plants more than 5‐fold. We were able to restore wild‐type levels of NRA in ipt‐expressing plants by simultaneous induction of NR with BA and nitrate. Our results suggest that regulation of NR by nitrate and cytokinin is a result of overlaying cytokinin‐driven regulatory processes, with those acting in the short‐term having a positive effect on NRA, and those acting over extended periods of time having inhibitory effects on NRA.
In situ analysis of enzymes involved in sucrose to hexose‐phosphate conversion during stolon‐to‐tuber transition of potato
Authors: Appeldoorn Niek J.G. , Sergeeva Lidiya , Vreugdenhil Dick , Van Der Plas Linus H.W. , Visser Richard G.F.
Published: March 2003

An in situ study of enzymes involved in sucrose to hexose‐phosphate conversion during in vitro stolon‐to‐tuber transition of potato (Solanum tuberosum L. cv. Bintje) was employed to follow developmental changes in spatial patterns. In situ activity of the respective enzymes was visualized by specific activity‐staining techniques and they revealed distinct spatially and developmentally regulated patterns. Two of the enzymes studied were also subject to in situ investigations at the transcriptional level. During the stages of stolon formation high hexokinase (EC 2.7.1.1) and acid (cell wall‐bound) invertase (EC 3.2.1.26) activities were restricted to the mitotically active (sub)apical region, suggesting a possible importance of these enzymes for cell division. At the onset of tuberization sucrose synthase (EC 2.4.1.13) and fructokinase (EC 2.7.1.4) were strongly induced (visualized at transcriptional and translational level) and the acid invertase activities disappeared from the swelling subapical region as expected. The high degree of similarity in the spatial pattern and the temporal induction of sucrose synthase and fructokinase suggests a tightly co‐ordinated coarse (up)regulation, which may be subject to a sugar‐modulated mechanism(s) by which genes involved in the metabolic sucrose‐starch converting potential are co‐ordinately regulated during tuber growth. The overall activity of uridine‐5‐diphosphoglucose pyrophosphorylase (EC 2.7.7.9) was present in all tissues during stolon and tuber development, implying that its coarse control is not subject to (in)direct developmental regulation.
Drought survival, summer dormancy and dehydrin accumulation in contrasting cultivars of Dactylis glomerata
Authors: Volaire Florence
Published: March 2003

To study survival under prolonged and severe drought in the perennial grass Dactylis glomerata we compared dormant, resistant and sensitive cultivars (cvs.) in both field and glasshouse experiments. Water status, membrane stability and expression of dehydrins were assessed in the immature leaf bases, which are the last surviving organs. Analysis of leaf elongation and senescence of aerial tissues showed that dormancy was exhibited by the potentially dormant cultivar (cv.) only in the field. This cultivar exhibited a high survival rate, similar levels of dehydration and expression of a low‐molecular weight (22–24 kDa) dehydrin in both drought and irrigated plants, whether fully dormant or not. At the same level of soil water deficit, there were no differences between the non‐dormant drought resistant and drought sensitive cultivars in plant water status and membrane stability. However, the accumulation of dehydrins as drought progressed was markedly different between these cultivars and was associated with their contrasting survival. The possible role of the major low‐molecular dehydrins in maintenance of cell integrity under dehydration is discussed with reference to both summer dormancy and survival under severe drought.
Profiles of photosynthesis within red and green leaves of  Quintinia serrata
Authors: Gould Kevin S. , Vogelmann Thomas C. , Han Tao , Clearwater Michael J.
Published: March 2003

We have measured photosynthesis at the cellular, tissue, and whole leaf levels to understand the role of anthocyanin pigments on patterns of light utilization. Profiles of chlorophyll fluorescence through sections of red and green leaves of Quintinia serrata showed that anthocyanins in the mesophyll restricted absorption of green light to the uppermost palisade mesophyll. The distribution was further restricted when anthocyanins were also present in the upper epidermis. Mesophyll cells located beneath a cyanic light‐filter assumed the characteristic photosynthetic features of shade‐adapted cells. As a result, red leaves showed a 23% reduction in CO2 assimilation under light‐saturating conditions, and a lower threshold irradiance for light‐saturation, relative to those of green leaves. The photosynthetic characteristics of red leaves are comparable to those of shade‐acclimated plants.
Rice receptor for chitin oligosaccharide elicitor does not couple to heterotrimeric G‐protein: Elicitor responses of suspension cultured rice cells from Daikoku dwarf (d1) mutants lacking a functional G‐protein α‐subunit
Authors: Tsukada Koji , Ishizaka Masumi , Fujisawa Yukiko , Iwasaki Yukimoto , Yamaguchi Takeshi , Minami Eiichi , Shibuya Naoto
Published: March 2003

We present evidence that the rice receptor for N‐acetylchitooligosaccharide elicitor does not couple to heterotrimeric G‐protein (G‐protein), one of the most important signal transducers from the cell surface to down‐stream effectors in various cellular responses of many organisms. Using mutant rice cells lacking functional G‐protein α‐subunit, cellular responses of suspension‐cultured rice cells derived from Daikoku dwarf (d1) mutants that were shown to contain mutations in the coding region of the G‐protein α‐subunit (Fujisawa et al. 1999) to N‐acetylchitooligosaccharide (oligochitin) elicitor were compared with those of the corresponding parent cell lines. All the elicitor‐induced cellular responses, such as medium alkalinization, generation of reactive oxygen species, expression of early responsive genes, PAL and PR genes, and production of phytoalexin, were basically identical in the mutant and wild type cell lines. Considering the reported presence of a single copy gene for the G‐protein α‐subunit in many plant species including rice, these results strongly support the above conclusion.
Ultraviolet‐B radiation effects on plants: induction of morphogenic responses
Authors: Jansen Marcel A. K.
Published: March 2003

Plants raised under field conditions are acclimated to ambient levels of solar UV‐B radiation. Morphogenic responses are part of the UV‐B acclimation process and have been hypothesized to contribute to UV avoidance. UV‐B induced morphogenic responses include inhibition of hypocotyl and stem elongation, leaf curling, leaf thickening and increased axillary branching. So far, neither the photosensory nor the signal transduction mechanism involved in UV‐B mediated morphogenesis has been identified. The combination of classical photobiological techniques and Arabidopsis genetic resources comprises a powerful tool for the analysis of morphogenic responses. However, no morphogenic mutants, specifically altered in their response to UV‐B, have yet been identified. In this paper we discuss the possibility that some UV‐B driven morphogenic responses do not involve a dedicated photosensory system, but rather are a consequence of UV‐B induced changes in secondary metabolism. UV‐B induced flavonoid aglycones and phenol‐oxidizing peroxidases can affect, respectively, polar auxin transport and auxin catabolism, and hence plant architecture. Integration of genetic, photobiological, biochemical and physiological approaches is necessary to fully appraise the ecophysiological role of UV‐B radiation in controlling plant architecture.
Low vapour pressure deficit reduces the beneficial effect of elevated CO2 on growth of N2‐fixing alfalfa plants
Authors: Luis Iñaki De , Irigoyen Juan José , Sánchez‐Díaz Manuel
Published: March 2003

Plant responses to elevated CO2 can be modified by many environmental factors, but very little attention has been paid to the interaction between CO2 and changes in vapour pressure deficit (VPD). Thirty‐day‐old alfalfa plants (Medicago sativa L. cv. Aragón), which were inoculated with Sinorhizobium meliloti 102F78 strain, were grown for 1 month in controlled environment chambers at 25/15°C, 14 h photoperiod, and 600 µmol m−2 s−1 photosynthetic photon flux (PPF), using a factorial combination of CO2 concentration (400 µmol mol−1 or 700 µmol mol−1) and vapour pressure deficit (0.48 kPa or 1.74 kPa, which corresponded to relative humidities of 85% and 45% at 25°C, respectively). Elevated CO2 strongly stimulated plant growth under high VPD conditions, but this beneficial effect was not observed under low VPD. Under low VPD, elevated CO2 also did not enhance plant photosynthesis, and plant water stress was greatest for plants grown at elevated CO2 and low VPD. Moreover, plants grown under elevated CO2 and low VPD had a lower leaf soluble protein and photosynthetic activity (photosynthetic rate and carboxylation efficiency) than plants grown under elevated CO2 and high VPD. Elevated CO2 significantly increased leaf adaxial and abaxial temperatures. Because the effects of elevated CO2 were dependent on vapour pressure deficit, VPD needs to be controlled in experiments studying the effect of elevated CO2 as well as considered in the extrapolations of results to a warmer, high‐CO2 world.
The impact of elevated ozone and carbon dioxide on young Acer saccharum seedlings
Authors: Gaucher Catherine , Costanzo Nadine , Afif Dany , Mauffette Yves , Chevrier Normand , Dizengremel Pierre
Published: March 2003

The effects of high O3 (200 nl l−1 during the light period) and high CO2 (650 μl l−1 CO2, 24 h a day) alone and in combination were studied on 45‐day‐old sugar maple (Acer saccharum Marsh.) seedlings for 61 days in growth chambers. After 2 months of treatment under the environmental conditions of the experiment, sugar maple seedlings did not show a marked response to the elevated CO2 treatment: the effect of high CO2 on biomass was only detected in the leaves which developed during the treatment, and assimilation rate was not increased. Under high O3 at ambient CO2, assimilation rate at days 41 and 55 and Rubisco content at day 61 decreased in the first pair of leaves; total biomass was reduced by 43%. In these seedlings large increases (more than 2‐fold) in glucose 6‐phosphate dehydrogenase (G6PDH, EC 1.1.1.49) activity and in anaplerotic CO2 fixation by phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) were observed, suggesting that an enhanced reducing power and carbon skeleton production was needed for detoxification and repair of oxidative damage. Under high O3 at elevated CO2, a stimulation of net CO2 assimilation was observed after 41 days but was no longer observed at day 55. However, at day 61, the total biomass was only reduced by 21% and stimulation of G6PDH and PEPC was less pronounced than under high O3 at ambient CO2. This suggests that high CO2 concentration protects, to some extent, against O3 by providing additional carbon and energy through increased net assimilation.
Cytomegalovirus maculopapular eruption in a kidney transplant patient
Authors: Trimarchi Hernán , Casas Gabriel , Jordan Rosana , Martínez Jorge , Schropp Juan , Freixas Emilio Ar , Efrón Ernesto
Published: March 2003

Abstract: Cytomegalovirus (CMV) is the most important viral agent in kidney transplantation. Clinical manifestations of CMV disease in transplantation include hepatitis, pneumonitis, pancreatitis, kidney allograft dysfunction, colitis, and meningoencephalitis. However, skin involvement is rare. We describe a severely compromised cadaveric‐kidney transplant recipient who developed renal failure, colonic ulcers, and a maculopapular rash accompanied by fever and malaise 4 months after transplantation. Only the skin biopsy was diagnostic and consistent with CMV disease. Intravenous ganciclovir administration resulted in clinical improvement of CMV‐induced skin lesions; kidney function normalized and the patient became asymptomatic after 14 days of ganciclovir therapy. Nephrologists should consider the diagnosis of CMV disease in the febrile immunosuppressed patient with skin involvement. Skin biopsy must be considered as a useful and safe procedure in patients with a rash to obtain a prompt diagnosis and efficiently treat this immunocompromised population.
Anti‐B cell and anti‐cytokine therapy for the treatment of post‐transplant lymphoproliferative disorder: past, present, and future
Authors: Durandy A.
Published: March 2003

Abstract: Epstein–Barr virus (EBV)‐induced post‐transplant lymphoproliferative disorder (PTLD) is a rare but severe complication of solid organ and bone‐marrow transplantation. When possible, reduction of immunosuppressive treatment or surgery for localized disease may cure PTLD. Therapeutic approaches using chemotherapy or antiviral drugs have limited effects on survival. Adoptive immunotherapy with donor T cell infusions has shown promising results in bone‐marrow transplantation. The use of anti‐B cell monoclonal antibodies is herein reported as a safe and efficient therapy for severe PTLD. Because IL6 has been described as a growth factor for EBV‐infected B cells, anti‐IL6 monoclonal antibody therapy was also tested in a phase I–II clinical trial, the results of which are summarized.
Aspergillus galactomannan antigen levels in allogeneic haematopoietic stem cell transplant recipients given total parenteral nutrition
Authors: Blijlevens N.M.A. , Donnelly J.P. , Meis J.F.G.M. , Verweij P.E. , De Pauw B.E. , Blijlevens N.M.A. , Donnelly J.P. , Meis J.F.G.M. , Verweij P.E. , De Pauw B.E.
Published: March 2003

Abstract: False‐positive tests for Aspergillus galactomannan have been reported in neutropenic patients. We failed to detect any circulating antigen during the 2 weeks following allogeneic haematopoietic stem cell transplantation of 12 patients who had severe mucositis but were unable to eat.
Xenograft rejection of fetal porcine islet‐like cell clusters in the rat: effects of active and passive immunization
Authors: Korsgren Olle , Wallgren Anna Carin , Satake Masahiro , Karlsson‐parra Alex
Published: March 2003

The process of islet xenograft rejection is still poorly understood. To elucidate further possible mechanism(s) involved in xenograft rejection, the effect of different immunization protocols was investigated. Fetal porcine islet‐like cell clusters (ICCs) were transplanted under the kidney capsule in otherwise untreated rats, rats pre‐immunized by s.c. injections of ICCs and in rats passively immunized with immune serum. The rejection process was evaluated with regard to antibody and complement deposition in the graft, as well as to morphology and phenotype of the infiltrating cells. In otherwise untreated animals, a moderate perigraft mononuclear cell infiltrate was seen after 3 days. Graft destruction became evident on day 6 with marked intragraft infiltration by macrophages (ED1 positive), whereas T cells were in the minority and mainly located in the perigraft area. In contrast to the findings in non‐immunized rats, the rejection process in pre‐immunized rats was characterized by marked intragraft infiltration by macrophages 3 days after transplantation. Moreover, both T cells and macrophages heavily infiltrated the adjacent kidney parenchyma, and major histocompatibility complex (MHC) class II expression in surrounding kidney tubular cells was concomitantly enhanced. Syngeneic rat islets mixed with porcine ICCs escaped the rejection process in non‐immunized rats but were affected in pre‐immunized animals. Thus, the specificity of the rejection process in non‐immunized animals seems to be lost in pre‐immunized animals. The early macrophage infiltration was also accelerated in rats passively immunized with immune serum, but no early switch from perigraft to intragraft infiltration or subsequent cellular infiltration in the adjacent kidney parenchyma was seen. Circulating xenoreactive antibodies of the IgG isotype increased after transplantation in normal and otherwise untreated rats. No distinct IgG deposition in the ICC xenografts was observed until day 12 after transplantation in untreated rats, whereas perigraft deposition of IgG was found 1 day after transplantation in pre‐immunized rats and in rats given immune serum. No deposition of complement was observed within the ICC xenograft in any of the groups during the observation period. The dependence on T cells, the massive infiltration of macrophages with a unique phenotype, the cellular distribution, and the loss of specificity (bystander killing) of the rejection process in immunized rats suggest that ICC xenograft rejection shares some of its main characteristics with a delayed type hypersensitivity‐like (DTH) immune response.
An approach to the control of disease transmission in pig‐to‐human xenotransplantation
Authors: Onions D. , Cooper D. K. C. , Alexander T. J. L. , Brown C. , Claassen E. , Foweraker J. E. , Harris D. L. , Mahy B. W. J. , Minor P. D. , Osterhaus A. D. M. E. , Pastoret P.‐P. , Yamanouchi K.
Published: March 2003

Abstract: Although several major immunologic hurdles need to be overcome, the pig is currently considered the most likely source animal of cells, tissues and organs for transplantation into humans. Concerns have been raised with regard to the potential for the transfer of infectious agents with the transplanted organ to the human recipient. This risk is perceived to be increased as it is likely that the patient will be iatrogenically immunocompromised and the organ‐source pig may be genetically engineered in such a way to render its organs particularly susceptible to infection with human viruses. Furthermore, the risk may not be restricted to the recipient, but may have consequences for the health of others in the community. The identification of porcine endogenous retroviruses and of hitherto unknown viruses have given rise to the most concern. We document here the agents we believe should be excluded from the organ‐source pigs. We discuss the likelihood of achieving this aim and outline the potential means by which it may best be achieved.
Productive infection of primary human endothelial cells by pig endogenous retrovirus (PERV)
Authors: Martin U. , Winkler M. E. , Id M. , Radeke H. , Arseniev L. , Takeuchi Y. , Simon A. R. , Patience C. , Haverich A. , Steinhoff G.
Published: March 2003

Abstract: The potential risk of viral transmission in the setting of xenotransplantation has gained major attention. Different porcine cell types have been shown to release retroviral particles, which are infectious for human cell lines in vitro. However, there are only a few data on whether PERV (pig endogenous retrovirus) is able to infect primary human cells. In this study we have analyzed endothelial cells, vascular fibroblasts, mesangial cells, mononuclear cells, hematopoetic stem cells and bone marrow stromal cells for PERV transmission. We now provide evidence for primary human endothelial cells, vascular fibroblasts, and mesangial cells to be susceptible to PERV transmission. PERV infection was productive in endothelial cells and mesangial cells. Our data confirm and extend former reports concerning the PERV infection of human cells. The PERV infection of different primary human cells represents further significant evidence for a viral risk during xenotransplantation. In this context, special attention should be directed towards productive infection of human endothelial cells: in the setting of xenotransplantation this cell type will have close contact with porcine cells and PERV particles.
Oral delivery of xeno‐antigen combined with non‐depleting anti‐CD4 monoclonal antibody induces significantly prolonged survival of concordant skin xenograft
Authors: Niimi M. , Shirasugi N. , Hamano K. , Esato K. , Matsumoto K. , Ikeda Y. , Shatari T. , Takami H. , Kodaira S.
Published: March 2003

Abstract: Oral administration can induce unresponsiveness to protein antigens. Therefore, we examined whether oral administration of xeno‐antigen could induce the prolonged survival of xenogeneic skin grafts. CBA mice were given 1 × 107 SD rat splenocytes orally, 7 days before transplantation of a SD rat skin in the presence or absence of a non‐depleting anti‐CD4 monoclonal antibody (mAb) (YTS177, 200 µg/dose, −8 and −7 days relative to transplantation). All skin grafts survived with a median survival time (MST) of 62 days when xeno‐antigens were administered orally in combination with anti‐CD4 mAb. Mice treated with anti‐CD4 mAb alone or oral administration of xeno‐antigen alone induced modest prolonged survival of rat skin grafts (MST = 18 and 19 days, respectively) while naive mice rejected rat skin acutely (MST = 12 days). Oral administration alone or combined with anti‐CD4 mAb reduced the level of xeno‐antibody production compared with that in untreated mice after transplantation. Xenogeneic mixed leukocyte response was reduced when splenocytes from mice pre‐treated with oral administration of xenogeneic cells were used as the responder compared with that in untreated mice. Oral delivery of xeno‐antigen plus non‐depleting anti‐CD4 mAb can induce prolongation of concordant xenogeneic skin grafts.
Xenogeneic human NK cytotoxicity against porcine endothelial cells is perforin/granzyme B dependent and not inhibited by Bcl‐2 overexpression
Authors: Matter‐Reissmann Ulrike B. , Forte Pietro , Schneider Mårten K. J. , Filgueira Luis , Groscurth Peter , Seebach Jörg D.
Published: March 2003

Because of organ shortages in clinical allotransplantation, the potential of pig‐to‐human xenotransplantation is currently being explored showing a possible critical role for natural killer (NK) cells in the immune response against xenografts. Therefore, we analyzed the cytotoxic pathways utilized by human natural killer cells (hNK) against porcine endothelial cells (pEC). Transmission electron microscopy of pEC cocultured with hNK cells showed both apoptotic and necrotic cell death, whereas soluble factors such as Fas ligand or TNFα did not induce apoptosis in pEC. NK lysis of pEC was abrogated by concanamycin A and ammonium chloride, reagents inhibiting the perforin/granzyme B (grB) pathway, but only partially blocked by caspase inhibition with z‐VAD‐fmk. Overexpression of bcl‐2 protected pEC against apoptosis induced by staurosporine or actinomycin D, but failed to prevent hNK cell‐mediated lysis. In conclusion, pEC are lysed in vitro by hNK cells via the perforin/grB pathway and are not protected from NK lysis by overexpression of bcl‐2.
Reduction of α‐galactosyl xenoantigen by expression of endo‐β‐galactosidase C in pig endothelial cells
Authors: Ogawa Haruko , Kobayashi Takaaki , Yokoyama Itsuo , Nagatani Naoki , Mizuno Masaaki , Yoshida Jun , Kadomatsu Kenji , Muramatsu Hisako , Nakao Akimasa , Muramatsu Takashi
Published: March 2003

Background: Elimination of the Galα1–3Galβ1–4GlcNAc (αGal) epitope has been considered to be essential for successful pig‐to‐human xenotransplantation but, unfortunately, has not been achieved. Endo‐β‐galactosidase C (EndoGalC) is an endoglycosidase which cleaves the Galβ1–4GlcNAc linkage in the αGal epitope and digests out the Galα1–3Gal disaccharide. Because of its potent activity in physiological pH conditions, EndoGalC can remove αGal epitopes expressed on the cell surface of pig erythrocytes and vascular endothelial cells almost completely. In vivo or ex vivo administration of EndoGalC successfully reduced αGal expression in pig kidneys to an undetectable level, but αGal epitopes soon reappeared. Gene expression of EndoGalC in pig cells was attempted to solve this problem. As the terminal αGal is transferred in the trans‐Golgi network by α‐1,3‐galactosyltransferase (α1,3GT), colocalization of the EndoGalC gene with the α1,3GT gene was expected to be one of the most reliable ways to eliminate the αGal epitope. Methods and results: The sequence of pig α1,3GT, including the cytoplasmic tail, transmembrane domain and stem region, was ligated upstream of EndoGalC, and the conjugated gene was expressed in pig aortic endothelial cells and COS7 cells. Following the introduction of the gene, the αGal epitope on pig aortic endothelial cells was effectively reduced. Transfection studies in COS7 cells using EndoGalC combined with α1,3GT showed that the expressed EndoGalC was localized not only inside, but also outside, the cells. The expression of EndoGalC conjugated with a murine immunoglobulin (Igκ)‐chain signal sequence also showed a similar effect. Conclusions: These results suggest the effectiveness of gene transfer with EndoGalC into pig endothelial cells, and strongly encourage us to produce transgenic animals with the expressed enzyme.
Siblicide, starvation and nestling growth in the laughing kookaburra
Authors: Legge Sarah
Published: March 2003

I examined the growth of surviving nestlings in broods of the cooperatively breeding laughing kookaburra Dacelo novaeguineae, which has complex patterns of brood reduction. Laughing kookaburras usually lay three eggs that hatch asynchronously. Brood reduction occurs in nearly half of all broods and always affects the youngest nestling. In most cases, the youngest nestling is killed within a few days of hatching by aggressive attacks from its older siblings. In a smaller proportion of nests, the youngest nestling dies from starvation, rather than physical attack, much later in the nestling period when nestling growth rates and adult feeding rates peak (about 20 days post‐hatching). These mechanistically and temporally distinct episodes of brood reduction were associated with very different patterns of growth in the senior nestlings. Seniors that killed their youngest sibling reached higher asymptotic weights than seniors that did not commit siblicide. In contrast, if the youngest nestling was not killed by its older siblings, but later starved to death, the surviving seniors were skeletally smaller and had retarded feather development compared to seniors from other broods. These differences in nestling growth may have longer‐term fitness consequences, because kookaburra fledging weight is positively associated with both juvenile survival and successful recruitment into the breeding population. Therefore, although parents of broods without mortality produce the highest number of fledglings and also the highest number of independent juveniles, if parents are unable to raise a full brood, early siblicide may represent the best brood reduction option. Early siblicide is at least associated with high quality young that have enhanced survival and recruitment prospects. In contrast, the poor growth of seniors in broods where the youngest nestling starved suggests that parents overestimated the size of the brood they could provision.
Ly49 and CD94/NKG2: developmentally regulated expression and evolution
Authors: Takei Fumio , McQueen Karina L. , Maeda Motoi , Wilhelm Brian T. , Lohwasser Stefan , Lian Rebecca H. , Mager Dixie L.
Published: March 2003

Summary: Murine natural killer (NK) cells express two families of MHC class I‐specific receptors, namely the Ly49 family and CD94/NKG2 heterodimers. Stochastic co‐expression of these receptors generates diverse receptor repertoires in adult NK‐cell populations, whereas fetal NK cells have much more limited receptor diversity as they mostly express CD94/NKG2A but not Ly49. These receptors are also expressed on CD8+ T cells and NK1.1+ T cells and regulate their functions, but their expression pattern on NK cells is significantly different from those on T cells. Thus, expression of Ly49 and CD94/NKG2 is developmentally regulated. NK cells acquire the Ly49 family of receptors in an orderly manner as they differentiate from bone marrow progenitors in vitro. Similarly, acquisition of CD94 and NKG2 by NK cells as they differentiate from embryonic stem cells is also orderly. To gain insight into the mechanisms regulating Ly49 expression, potential regulatory regions of several Ly49 genes have been examined. Ly49 genes with different expression patterns have remarkably similar sequences in the putative regulatory regions. Finally, a functional Ly49 gene has been identified in baboon, and primate comparisons suggest that functional extinction of the Ly49 gene in the human lineage seems to have been a relatively recent event.

This research was supported by the National Cancer Institute of Canada and the Medical Research Council of Canada with core support from the BC Cancer Agency. KM and BW were supported by studentships from the University of British Columbia and the National Science and Engineering Research Council of Canada. RL is a recipient of a Leukemia Research Fund of Canada fellowship. SL was supported by the Deutsche Forschungsgemeinschaft.
Human cytomegalovirus and natural killer‐mediated surveillance of HLA class I expression: a paradigm of host–pathogen adaptation
Authors: López‐Botet Miguel , Llano Manuel , Ortega Mara
Published: March 2003

Summary: Among various strategies to evade the host immune response, some viruses like human cytomegalovirus (HCMV) interfere with surface MHC class I expression and antigen presentation to T lymphocytes. The ability of natural killer (NK) cells to detect MHC class I molecules through inhibitory receptors can be envisaged as an adaptation of the immune system for responding to such pathological alterations. To fulfil that role, rodents use members of the Ly49 C‐type lectin superfamily, whereas primates employ killer immunoglobulin‐like receptors and the immunoglobulin‐like transcript 2/leucocyte immunoglobulin‐like receptor‐1 receptor. CD94/NKG2 lectin‐like heterodimers represent the most conserved receptor system for MHC class I molecules; by interacting with human HLA‐E or murine Qa‐1b, CD94/NKG2A inhibitory receptors broadly probe the biosynthesis pathway of other class I molecules. Reciprocally, HCMV has developed mechanisms to evade the NK response while modulating HLA class Ia expression. The ability of HCMV to maintain surface levels of HLA‐E and to express an HLA class I surrogate (UL18) are herein discussed in the context of the interplay with human NKR systems.

This work was supported by grants FIS 00/0181 and SAF98‐0006. We thank Dr A. Angulo for helpful discussion.
The KIR and CD94/NKG2 families of molecules in the rhesus monkey
Authors: LaBonte Michelle L. , Hershberger Karen L. , Korber Bette , Letvin Norman L.
Published: March 2003

Summary: Natural killer (NK) cells and a subset of T cells express families of receptors that are capable of detecting major histocompatibility complex (MHC) class I expression on the surface of cells. Molecules of the killer cell immunoglobulin‐like receptor (KIR) family bind directly to MHC class I, while those of the CD94/NKG2 family recognize MHC class I signal sequences bound to HLA‐E. Both the KIR and CD94/NKG2 families are composed of activating and inhibitory molecules that serve to regulate the function of NK cells as a result of their MHC class I recognition. Here we review the recently described KIR and CD94/NKG2 family members in the rhesus monkey.
Synaptotagmin regulates mast cell functions
Authors: Baram Dana , Mekori Yoseph A. , Sagi‐Eisenberg Ronit
Published: March 2003

Summary: Synaptotagmin(s) (Syts), are products of a gene family implicated in the control of Ca2+‐dependent exocytosis. Mast cells, specialized secretory cells that release mediators of inflammatory and allergic reactions in a process of regulated exocytosis, express Syt homologues and SNAREs (Soluble NSF Attachment proteins Receptors), which together with Syt constitute the core complex which mediates exocytotic vesicle docking and fusion. Rat basophilic leukemia cells (RBL‐2H3), a tumor analogue of mucosal mast cells, express the Syt homologues Syt II, Syt III and Syt V. Expression of Syt I, the neuronal Ca2+ sensor, in the RBL cells, resulted in its targeting to secretory granules and in prominent potentiation and acceleration of Ca2+‐dependent exocytosis. Syt II is localized to an amine‐free lysosomal compartment, which is also subjected to regulated exocytosis. Lysosomal exocytosis is negatively regulated by Syt II: overexpression of Syt II inhibited Ca2+‐triggered exocytosis of lysosomes, while suppression of Syt II expression markedly potentiated this release. These findings implicate Syt homologues as key regulators of mast cell function.

We thank Drs. T.C. Sudhof, R.H. Scheller and M. Takahashi for their generous gifts of antibodies and cDNAs.
Migration and differentiation of CD8+ T cells
Authors: Weninger Wolfgang , Manjunath N. , Von Andrian Ulrich H.
Published: March 2003

Summary: Antigen‐specific responses by CD8+ T cells require direct cell–cell interactions between T cells and antigen‐presenting cells (APC). Initially, naïve T cells must communicate with APC in lymphoid organs. Once stimulated, the resulting effector cells interact with APC in peripheral tissues. To this end, T cells must migrate to discrete sites throughout the body where antigen may be found. Recent progress in the field has revealed that the migratory abilities of T cells are critically dependent on their differentiation state, which is shaped by a multitude of factors. Thus, naïve T cells are normally restricted to recirculate between the blood and secondary lymphoid tissues, although in some autoimmune diseases they may also accumulate in chronically inflamed tissues. When CD8+ T cells encounter antigen and differentiate into short‐lived effector CTL, they lose the ability to home to lymph nodes but gain access to peripheral tissues and sites of inflammation. Long‐lived memory cells exist in (at least) two flavors: central memory cells that migrate to both lymphoid organs and peripheral sites of inflammation, and effector memory cells that are preferentially localized in non‐lymphoid tissues. Our current understanding of the interplay of T cell differentiation and migration has been boosted by the development of T‐GFP mice, in which transgenic green fluorescent protein is expressed selectively in naïve and central memory T cells, but not in effector cytotoxic T cells (CTL). This review will focus on recent studies in which T‐GFP mice were used to dissect the traffic signals for naïve T cell homing to secondary lymphoid organs, the factors that influence the differentiation of naïve CD8+ T cells into cytotoxic and memory cells, as well as the in vivo trafficking routes of antigen‐experienced subsets.
Divergent models of lymphoid lineage specification: do clonal assays provide all the answers?
Authors: Spangrude Gerald J.
Published: March 2003

Summary: Hematopoietic stem cells that drive blood development in mouse and man have been well characterized in recent years. In contrast, detailed analysis of the next stages of development, the progenitor cells that have begun to differentiate along specific hematopoietic lineages, is now only in its infancy. The process of myeloid differentiation has been relatively accessible to experimental manipulation due to the availability of culture systems able to support the progenitors for myeloid lineages, and the identification of cytokines capable of driving myeloid differentiation. Studies of early lymphoid differentiation, however, have lagged behind. In particular, the characterization of the first progenitors for the lymphoid lineages is far from complete, due mainly to inefficient assay systems for growing these cell lineages in vitro. Two laboratories have published conflicting data regarding the specification of lymphoid lineages in the mouse. Both groups of investigators utilize elegant clonal approaches to characterize progenitor cell subsets. While these experiments define lineage potential in the most rigorous manner possible, the divergent results suggest that clonal assays must be supplemented with more physiologic studies in order to define the actual differentiation pathways that function in vivo.
Multiple pathways to tumor immunity and concomitant autoimmunity
Authors: Turk Mary Jo , Wolchok Jedd D. , Guevara‐Patino José A. , Goldberg Stacie M. , Houghton Alan N.
Published: March 2003

Summary: The immune repertoire contains T cells and B cells that can recognize autologous cancer cells. This repertoire is directed against self, and in some cases altered self (mutations). Priming immune responses against self antigens can be difficult. Strategies are presented using altered self to elicit immunity against self in poorly immunogenic tumor models. Mechanisms underlying immunity to self antigens on cancer cells show that the immune system can use diverse strategies for cancer immunity, in both the immunization and the effector phases. CD4+ T cells are typically, but not always, required for immunization. The effector phase of tumor immunity can involve cytotoxic T cells, macrophages with activating Fc receptors, and/or killer domain molecules. This diversity in the effector phase is observed even when immunizing with conserved paralogs. A consequence of tumor immunity is potentially autoimmunity, which may be undesirable. Autoimmunity uses similar mechanisms as tumor immunity, but tumor immunity and autoimmunity can uncouple. These studies open up strategies for active immunization against cancer.
The roles of membrane microdomains (rafts) in T cell activation
Authors: Hor̆ejs̆í Václav
Published: March 2003

Detergent‐resistant membrane microdomains enriched in sphingolipids, cholesterol and glycosylphosphatidylinositol‐anchored proteins play essential roles in T cell receptor (TCR) signaling. These ‘membrane rafts’ accumulate several cytoplasmic lipid‐modified molecules, including Src‐family kinases, coreceptors CD4 and CD8 and transmembrane adapters LAT and PAG/Cbp, essential for either initiation or amplification of the signaling process, while most other abundant transmembrane proteins are excluded from these structures. TCRs in various T cell subpopulations may differ in their use of membrane rafts. Membrane rafts also seem to be involved in many other aspects of T cell biology, such as functioning of cytokine and chemokine receptors, adhesion molecules, antigen presentation, establishing cell polarity or interaction with important pathogens. Although the concept of membrane rafts explains several diverse biological phenomena, many basic issues, such as composition, size and heterogeneity, under native conditions, as well as the dynamics of their interactions with TCRs and other immunoreceptors, remain unclear, partially because of technical problems.
Quantitative testing of liver function in patients with cirrhosis due to chronic hepatitis C to assess disease severity
Authors: Herold C. , Heinz R. , Radespiel‐Tröger M. , Schneider H. T. , Schuppan D. , Hahn E. G.
Published: March 2003

Abstract: Background/Aims: Quantitative testing of liver function (QTLF) may allow a prognostic assessment of patients with various liver diseases. However, there are insufficient data about patients with liver cirrhosis due to hepatitis C. Patients/Methods: 86 consecutive patients (58 males, 28 females, age: 48.3±11.7 years) with chronic hepatitis C (HCV RNA pos.) underwent sonographically guided liver biopsy to confirm the diagnosis of cirrhosis. QTLF included aminopyrine breath test (microsomal liver function), galactose elimination capacity (cytosolic liver function), sorbitol clearance (liver plasma flow) and indocyanine green clearance (liver perfusion). Values were correlated with the Child‐Pugh classification. Results: 55% of the patients (n=47) had cirrhosis of Child‐Pugh grade A, 28% of grade B (n=24) and 17% of grade C (n=15). QTLF showed a steady decrease from Child‐Pugh grade A to grade B and to grade C. Contrary to markedly reduced tests of metabolic liver function in Child‐Pugh grade patients, surrogate tests of hepatic perfusion were at the lower normal limit. All QTLF were significantly reduced in Child‐Pugh grade B and C patients compared to healthy controls. Differences between the three Child grades were significant. Conclusion: In patients with cirrhosis due to hepatitis C, QTLF correlated inversely with Child‐Pugh grades. Since in cirrhosis of grade A, surrogate tests of hepatic perfusion remained at the lower normal limit, whereas those of metabolic function were decreased, QTLF may be a tool to predict prognosis or complications in early cirrhosis due to chronic hepatitis C.
Suppression of hepatitis B virus replication mediated by hepatitis A‐induced cytokine production
Authors: Van Nunen Andeltje B. , Pontesilli Oscar , Uytdehaag Fons , Osterhaus Albert D. M. E. , De Man Robert A.
Published: March 2003

Abstract: Background: Acute hepatitis A virus (HAV) infection can cause severe hepatitis especially in patients with underlying chronic liver disease. In patients with pre‐existing chronic hepatitis B (HBV) acute HAV infection can suppress HBV replication. The exact mechanism of HBV suppression during acute HAV infection is still a subject of debate. One mechanism may be the production of HAV infection‐induced cytokines leading to suppression of HBV replication and viral clearance. Aim: To evaluate cytokine production and HBV‐specific lympho‐proliferative responses (LPR) during acute HAV infection in a patient with chronic HBV infection‐clearing markers of active HBV replication. Design: Early detection of a case of acute HAV infection in an HBeAg‐positive, HBV DNA‐positive chronic HBV patient treated with lamivudine. Results: At the time of HAV infection a sharp peak in the gamma‐interferon (IFN‐γ) level occurred just before the rise in serum transaminase activity. This was subsequently followed by a decrease in HBV DNA and HBeAg below the limit of detection of the assay. However the HBV‐specific T‐cell response was not modified. After resolution of the acute HAV infection and withdrawal of antiviral therapy HBV replication relapsed. Conclusion: The sharp rise in IFN‐γ production mediated by the acute HAV infection may be pivotal in the suppression of HBV replication in chronic hepatitis B.
Estrogen receptor levels and lipid peroxidation in hepatocellular carcinoma with hepatitis C virus infection
Authors: Shimizu Ichiro , Inoue Hiroshi , Yano Mitsuyasu , Shinomiya Hirohiko , Wada Satoshi , Tsuji Yasuhiro , Tsutsui Akemi , Okamura Seisuke , Shibata Hiroshi , Ito Susumu
Published: March 2003

Abstract: Aims/Background. Our preliminary studies showed that estradiol suppresses hepatic carcinogenesis and fibrogenesis in animal models. Hepatic estrogen receptors (ERs) medicate estradiol action in the liver. This study was performed to assess possible implications of menopause and hepatic ER levels for the development of cirrhosis with hepatocellular carcinoma (HCC). Methods. One thousand, one hundred and ninety‐nine consecutive HCC patients with hepatitis C virus (HCV)‐related cirrhosis were divided into two groups, based on a menopausal age of 49 years. Liver tissues were obtained during surgical resection of HCC and metastatic liver tumor. Results. The proportion of females among the HCC subjects ≤49 years of age was significantly lower (15.0%) than was the proportion of females among subjects >49 years of age (29.8%). Univariate analysis showed that HCV‐related cirrhotic patients who developed HCC were more likely to have low hepatic levels of ER and copper‐zinc superoxide dismutase (CuZn‐SOD) protein and a high hepatic level of a lipid peroxidation product, malondialdehyde (MDA). Logistic regression identified age greater than 49 years (odds ratio [OR]: 7.9, 95% confidence interval [CI]: 2.8–21.3), male sex (OR: 3.5, 95% CI: 1.3–10.2), a decreased ER level (OR: 16.8, 95% CI: 7.3–34.6), and an increased MDA (OR: 8.3, 95% CI: 2.8–24.0) as the variables independently associated with the development of HCC in HCV‐infected patients with cirrhosis. ER level was significantly correlated with CuZn‐SOD level (r=0.583) and was inversely proportional to MDA level (r=−0.553). The study also showed that ER levels in the cirrhotic livers from premenopausal females were significantly higher than in male cirrhotic livers. Conclusions. These findings suggest that increased lipid peroxidation and impaired SOD function in the liver may be associated with decreased hepatic ER levels in HCV‐infected patients with cirrhosis and HCC, and that HCV‐related cirrhotic women before menopause might have the ability to protect against developing HCC via hepatic ER.
Artificial and bioartificial support systems for liver failure: a Cochrane Hepato‐Biliary Group Protocol
Authors: Liu Jianping , Kjaergard Lise Lotte , Als‐Nielsen Bodil , Gluud Christian
Published: March 2003

Abstract: Aims/Background: Liver support systems may bridge patients to liver transplantation or recovery from liver failure. This review is to evaluate the beneficial and harmful effects of artificial and bioartificial support systems for acute and acute‐on‐chronic liver failure.

Data Sources: Randomized trials on any support system versus standard medical therapy will be included irrespective of publication status or language. Non‐randomized studies are included in explorative analyses. Trials will be identified through bibliographies, correspondence with original investigators, and electronic searches (Cochrane Hepato‐Biliary Group Controlled Trials Register, Cochrane Controlled Trials Register, MEDLINE, EMBASE, and The Chinese Biomedical Database).

Methods of the review: The extracted data will include characteristics of trials, patients, interventions, and all outcome measures. Methodological quality will be assessed by the randomization, follow up, and blinding. The RevMan and STATA will be used for statistical analyses. Sources of heterogeneity and methodological quality in the assessment of the primary outcome will be explored by sensitivity analyses and meta‐regression.