bluuebunny/crossref_metadata_2025 huggingface dataset:
Different morphotypes of functional dentition in the lower molar region of tabby (EDA) mice
Authors: Kristenová P , Peterka M , Lisi S , Gendrault J‐L , Lesot H , Peterková R
Published: March 2003

Structured Abstract

Authors –
Kristenová P, Peterka M, Lisi S, Gendrault J‐L, Lesot H, Peterková R

Objectives –
To sort and classify the highly variable lower molar dentition in tabby (Ta) mice postnatally. The Ta syndome is homologous to the anhidrotic (hypohidrotic) ectodermal dysplasia (EDA) in human and includes severe developmental defects of teeth, hair and sweat glands.

Design –
Analysis of tooth shape and cusp pattern and measurement of the mesio‐distal crown length.

Setting and sample population –
Institute of Experimental Medicine, Academy of Sciences, Prague. Fixed heads of 107 tabby (Ta) homozygous and hemizygous mice and 90 wild type mice aged from post‐natal day 11 to adulthood, collected during 1995–2001.

Outcome Measure –
Identification of distinct morphotypes of Ta dentition. Reduced tooth length in Ta teeth and specific differences in tooth length between distinct morphotypes.

Results –
The variable dentitions in the lower molar region of Ta mice were classified in two basic morphotypes I and II. The morphotype I was further subdivided into particular morphotypes Ia, Ib and Ic. Proportion of the basic morphotypes I and II was different in the offspring of heterozygous (84% and 12%) compared with homozygous + hemizygous (45% and 52%) mothers. The proportions of particular morphotypes within a basic morphotype were similar in both offspring groups.

Conclusion –
The identification of the distinct morphotypes made possible to classify the structural variability of the mandibular functional dentition in Ta mice.
Collectins and pulmonary innate immunity
Authors: Crouch Erika , Hartshorn Kevan , Ofek Itzhak
Published: March 2003

Summary: The surfactant‐associated proteins SP‐A and SP‐D are members of a family of host defense lectins, designated collectins. There is increasing evidence that these pulmonary, epithelial‐derived proteins are important components of the innate immune response to microbial challenge and participate in other aspects of immune and inflammatory regulation within the lung. Both proteins bind to glycoconjugates and/or lipid moieties expressed by a wide variety of microorganisms, and to certain organic particles, such as pollens. SP‐A and SP‐D have the capacity to modulate leukocyte function and, in some circumstances, to opsonize and enhance the killing of microorganisms. The biologic activity of cell wall components, such as Gram‐negative bacterial polysaccharides, or viral glycoproteins, such as the hemagglutinin of influenza viruses, may be altered by interactions with collectins. In addition, complementary or cooperative interactions between SP‐A, SP‐D and other host defense lectins could contribute to the efficiency of this defense system. Collectins could play particularly important roles in settings of inadequate or impaired specific immunity, and acquired alterations in the levels of active collectins within the airspaces and distal airways may increase susceptibility to infection.
Ligands for natural killer cell receptors: redundancy or specificity
Authors: Cerwenka Adelheid , Lanier Lewis L.
Published: March 2003

Summary: Several inhibitory and activating receptors involved in natural killer cell activation have been characterized. The increasing knowledge about their ligands, including classical MHC class I molecules, non‐classical MHC class I molecules and MHC class I‐related molecules, is shedding new light on the targets of innate immune recognition. While classical MHC class I molecules are constitutively expressed, some MHC class I‐related (MIC) molecules, however, are stress‐induced by ill‐defined stimuli. Two families of ligands for the human activating NKG2D receptor have been identified. These are the MIC proteins encoded by two highly polymorphic genes within the MHC class I and the retinoic acid‐inducible early gene‐1‐like (also designated UL16‐binding) proteins encoded by genes outside the MHC. For the mouse NKG2D receptor, one family, containing at least five distinct ligands, has been described. A better understanding about how targets signal their distress, which renders them susceptible to natural killer (NK)‐cell attack, will help to define the role of NK cells in antimicrobial and antitumor immunity and transplantation.

Supported by NIH grants CA89294 and CA89189
CD4+CD25+ regulatory cells in acquired MHC tolerance
Authors: Field Elizabeth H. , Matesic Damir , Rigby Shawn , Fehr Tricia , Rouse Todd , Gao Quiglan
Published: March 2003

Summary: Tolerance to self‐antigens is an ongoing process that begins centrally during T‐cell maturation in the thymus and continues throughout the cell's life in the periphery by a network of regulated restraints. Remaining self‐reactive T‐cells that escape intrathymic deletion may be silenced within the peripheral immune system by specialized regulatory CD4+ cells. By analogy, regulatory CD4+ cells that control immunity to “acquired self” should arise in circumstances where the immune system acquires tolerance to foreign MHC, such as the tolerance that develops following the exposure to foreign MHC antigens during the neonatal period. We have used this classic model of neonatal tolerance to examine the role of regulatory CD4+ cells in acquired tolerance to disparate class I and class II MHC. Adoptive transfer of unfractionated but not CD4+‐depleted spleen cells from neonatal tolerant mice into SCID recipients inhibited skin graft rejection by immunocompetent CD8+ T cells. Using 5‐bromo‐2′‐deoxyuridine incorporation, standard cytotoxic T‐lymphocyte assays, short‐term interferon‐γ ELISPOT, and intracellular FACS analysis to study CD8+ T‐cell effector function, we demonstrated that neonatal tolerant mice contain CD4+CD25+ cells that suppress the development of anti‐donor CD8+ T‐cell responses in vitro. We conclude that regulatory CD4+CD25+ cells initiate and/or maintain tolerance by preventing the development of CD8+ T‐cell alloreactivity.
Neuroendocrine responses regulating susceptibility and resistance to autoimmune/inflammatory disease in inbred rat strains
Authors: Tonelli Leonardo , Webster Jeanette I. , Rapp Kimberly L. , Sternberg Esther
Published: March 2003

Summary: Rodent animal models of inflammatory and autoimmune disease have been important tools in the study of the interaction between neuroendocrine physiology and the immune responses. The rat has been particularly useful in part because, in contrast to other species, most rat models of autoimmune/inflammatory disease are induced rather than spontaneous. This allows for systematic and controlled manipulations of the neuroendocrine system in relation to exposure to the antigen or pro‐inflammatory trigger. The most frequently used immune challenges include lipopolysaccharide‐induced septic shock, carrageenan‐induced local inflammation and adjuvant or bacterial cell wall‐induced arthritis. By analyzing the responses to these challenges in different strains of rats and mice it has been possible to define the relationships between the neuroendocrine and immune systems and to identify some mechanisms through which these connections confer susceptibility and resistance to autoimmune and inflammatory diseases. The present review will discuss data obtained from rodent physiology, indicating that an important component in the susceptibility or resistance to development of these diseases is due to dysfunctional regulation of the immune response by the neuroendocrine hypothalamic–pituitary–adrenal axis. In particular, the importance of neurons of the paraventricular hypothalamic nucleus in determining susceptibility or resistance to autoimmune and inflammatory disease will be discussed.
Human retroviruses after 20 years: a perspective from the past and prospects for their future control
Authors: Gallo Robert C.
Published: March 2003

Summary: Among viruses the human retroviruses may be of special interest to immunologists, because they target cells of the immune system, particularly mature CD4+ T cells, impair their function and cause them to grow abnormally (human T‐cell leukemia virus, HTLV) or to die (human immunodeficiency virus, HIV). Human retroviruses cause disease ranging from neurological disorders and leukemias (HTLV‐1) to AIDS (acquired immunodeficiency virus) (HIV) and promote development of several types of malignancies (HIV). They share many common features, but their contrasts are greater, especially the far greater replication and variation of HIV associated with its greater genomic complexity. Both have evolved striking redundancy for mechanisms which promote their survival. Thus, HTLV has redundant mechanisms for promoting growth of provirus containing T cells needed for virus continuity, because it is chiefly through its cellular DNA provirus that HTLV replicates and not through production of virions. Conversely, HIV has redundancy in its mechanisms for promoting virion replication and escape from the host immune system. It is via these redundant mechanisms that they produce disease: leukemias from mechanisms promoting T‐cell proliferation (HTLV‐1) and AIDS from mechanisms promoting virus replication and T‐cell death (HIV). The practical challenges for the future are clear. For HTLV‐1, education and control of breastfeeding. For HIV, the formidable tasks now ahead in part demand new kinds of talent, talents that will foster greater insights into the development of therapy for the developing countries, new forms of less toxic therapies for all infected persons, a continued and expanded commitment to education, and a persistent ‘never say die’ commitment to the development of a truly preventive vaccine with all the scientific and nonscientific challenges that these objectives face.
Rapid leukocyte integrin activation by chemokines
Authors: Laudanna Carlo , Kim Ji Yun , Constantin Gabriela , Butcher Eugene C.
Published: March 2003

Summary: Chemokines control selective targeting of circulating leukocytes to the microvasculature by triggering inside‐out signal transduction pathways leading to integrin‐dependent adhesion. Integrin activation by chemokines is very rapid, is downmodulated within minutes and appears to involve both enhanced heterodimer lateral mobility on the plasma membrane, facilitating encounters with dispersed ligand, as well as induction of a high‐affinity state. These two modalities of integrin activation by chemokines involve distinct signaling pathways in the cell, yet complement each other functionally, allowing binding of rolling cells under conditions of low as well as high ligand density. Recent data show that chemokines generate both pro‐ and anti‐adhesive intracellular signaling events, whose equilibrium is likely to be relevant to the kinetics of adhesion and de‐adhesion, and to cell movement during diapedesis and chemotaxis. Importantly, chemokines utilize different signaling mechanisms to modulate the activity of distinct integrin subtypes. These recent advances suggest that chemokines may regulate adhesive responses of immune cells based not only on patterns of chemokine receptor expression, but also on variable signaling pathways that can modulate the pro‐adhesive responses of leukocytes as a function of their differentiated state, and of the local microenvironment.
The immunological synapse: integrins take the stage
Authors: Sims Tasha N. , Dustin Michael L.
Published: March 2003

Summary: Adhesive interactions play important roles in coordinating T‐cell migration and activation, specifically in the formation of the immunological synapse (IS), a specialized cell‐cell junction. Recent demonstrations show several molecules implicated in T‐cell signaling, including Vav, ADAP, and Rap‐1, have major roles in integrin regulation and place adhesion molecules at center stage in addressing the question: what are the signals involved in the formation of the IS and full T‐cell activation? This review focuses on the role of integrins as an essential system for both physical adhesion and signaling in T‐cell activation. The role of integrins appears to be quite distinct from classical costimulation and has been largely overlooked due to the ubiquitous use of serum in lymphocyte functional assays. Each major signal transduction pathway has branches leading to the nucleus and others that feed back on cytoskeletal and membrane regulation at the IS.
Notch signaling in hematopoiesis and early lymphocyte development
Authors: Allman David , Aster Jon C. , Pear Warren S.
Published: March 2003

Summary:  Notch signals regulate multiple cell fate decisions during metazoan development. During hematopoiesis, Notch affects both hematopoietic stem cells and committed progenitors. In hematopoietic stem cells, Notch signaling has the propensity to expand the stem cells, promote their self‐renewal, and influence their survival. In committed progenitors, Notch signaling plays a key role in determining lymphoid cell fates. This review focuses on recent developments to understand the role of Notch signaling in early events in hematopoiesis.
Cancer/testis antigens: an expanding family of targets for cancer immunotherapy
Authors: Scanlan. Matthew J. , Gure. Ali O. , Jungbluth. Achim A. , Old. Lloyd J. , Chen. Yao‐Tseng
Published: March 2003

Summary: Cancer/testis (CT) antigens are a category of tumor antigens with normal expression restricted to male germ cells in the testis but not in adult somatic tissues. In some cases, CT antigens are also expressed in ovary and in trophoblast. In malignancy, this gene regulation is disrupted, resulting in CT antigen expression in a proportion of tumors of various types. Since their initial identification by T‐cell epitope cloning, the list of CT antigens has been greatly expanded through serological expression cloning (SEREX) and differential mRNA expression analysis, and approximately 20 CT antigens or antigen families have been identified to date. Characteristics commonly shared by CT antigens, aside from the highly tissue‐restricted expression profile, include existence as multigene families, frequent mapping to chromosome X, heterogeneous protein expression in cancer, likely correlation with tumor progression, induction of expression by hypomethylation and/or histone acetylation, and immunogenicity in cancer patients. Spontaneous humoral and cell‐mediated immune responses have been demonstrated against several CT antigens, including NY‐ESO‐1, MAGE‐A, and SSX antigens. Since CT antigens are immunogenic and highly restricted to tumors, their discovery has led directly to the development of antigen‐specific cancer vaccines, and clinical trials with MAGE‐A and NY‐ESO‐1 are in progress.
The killer cell immunoglobulin‐like receptor (KIR) genomic region: gene‐order, haplotypes and allelic polymorphism
Authors: Hsu Katharine C. , Chida Shohei , Geraghty Daniel E. , Dupont Bo
Published: March 2003

Summary: Recent genetic studies have established that the killer cell immunoglobulin‐like receptor (KIR) genomic region displays extensive diversity through variation in gene content and allelic polymorphism within individual KIR genes. It is demonstrated by family segregation analysis, genomic sequencing, and gene order determination that genomic diversity by gene content alone gives rise to more than 20 different KIR haplotypes and at least 40–50 KIR genotypes. In the most reductionist format, KIR haplotypes can be accommodated within one of 10 different prototypes, each with multiple permutations. Our haplotype model considers the KIR haplotype as two separate halves: the centromeric half bordered upstream by KIR3DL3 and downstream by 2DL4, and the telomeric half bordered upstream by 2DL4 and downstream by 3DL2. There are rare KIR haplotypes that do not fit into this model. Recombination, gene duplication, and inversion can however, readily explain these haplotypes. Additional allelic polymorphism imposes extensive individual variability. Accordingly, this segment of the human genome displays a level of diversity similar to the one observed for the human major histocompatibility complex. Recent application of immunogenetic analysis of KIR genes in patient populations implicates these genes as important genetic disease susceptibility factors.
Morphological mechanisms for regulating blood flow through hepatic sinusoids
Authors: McCuskey Robert S.
Published: March 2003

Abstract: This review summarizes what is known about the various morphological sites that regulate the distribution of blood flow to and from the sinusoids in the hepatic microvascular system. These sites potentially include the various segments of the afferent portal venules and hepatic arterioles, the sinusoids themselves, and central and hepatic venules. Given the paucity of smooth muscle in the walls of these vessels, various sinusoidal lining cells have been suggested to play a role in regulating the diameters of sinusoids and influencing the distribution and velocity of blood flow in these vessels. While sinusoidal endothelial cells have been demonstrated to be contractile and to exhibit sphincter function, attention has recently focused on the perisinusoidal stellate cell as the cell responsible for controlling the sinusoidal diameter. A very recent study, however, suggested that the principal site of vasoconstriction elicited by ET‐1 was the pre‐terminal portal venule. This raised the question of whether or not the diameters of sinusoids might decrease due to passive recoil when inflow is reduced or eliminated and intra‐sinusoidal pressure falls. In more recent in vivo microscopic studies, clamping of the portal vein dramatically reduced sinusoidal blood flow as well as the diameters of sinusoids. The sinusoidal lumens rapidly returned to their initial diameters upon restoration of portal blood flow suggesting that sinusoidal blood pressure normally distends the sinusoidal wall which can recoil when the pressure drops. Stellate cells may be responsible for this reaction given the nature of their attachment to parenchymal cells by obliquely oriented microprojections from the lateral edges of their subendothelial processes. This suggests that care must be exercised when interpreting the mechanism for the reduction of sinusoidal diameters following drug administration without knowledge of changes occurring to the portal venous and hepatic inflow.
Systemic and splanchnic endothelin‐1 plasma levels in liver cirrhosis before and after transjugular intrahepatic portosystemic shunt (TIPS)
Authors: Nolte Wilhelm , Ehrenreich Hannelore , Wiltfang Jens , Pahl Karoline , Unterberg Knut , Kamrowski‐Kruck Heike , Schindler Christian G. , Figulla Hans‐Reiner , Buchwald Arnd B. , Hartmann Heinz , Ramadori Giuliano
Published: March 2003

Abstract: Aims/Background: Endothelin‐1 (ET‐1) may be a mediator for portal hypertension in liver cirrhosis. The aim of the present study was to determine the concentrations of ET‐1 in the systemic and splanchnic circulation before and after reduction of portal hypertension by transjugular intrahepatic portosystemic shunt implantation (TIPS). Methods: Plasma concentrations of immunoreactive ET‐1 were measured in peripheral venous blood samples from 25 patients with liver cirrhosis before and at 1, 3, 9 and 15 months after TIPS. Furthermore, acute effects of TIPS on ET‐1 were studied in plasma samples from the hepatic vein, the portal vein 30 minutes before and after TIPS and in the femoral artery (only after TIPS) in a subgroup of 15 patients. In addition, the portocaval pressure gradient was determined before and after TIPS. Results: Before TIPS peripheral venous plasma ET‐1 concentrations (n=25; median 4.2 pg/ml; range 1.9–14.7) were significantly increased in patients with refractory ascites (n=7; median 7.8, range 3.5–14.7) compared to patients with repetitive bleeding (n=18; median 3.4; range 1.9–7.1) (p=0.003). Furthermore, peripheral ET‐1 concentrations correlated with the degree of liver dysfunction according to the Child‐Pugh classification (Spearman's r=0.46; p=0.02). Following TIPS, peripheral ET‐1 concentrations remained unchanged during a follow‐up of 15 months. Before TIPS, a positive gradient of ET‐1 concentrations from portalvenous to hepatovenous and peripheral venous levels was found (p<0.03). Immediately after TIPS, arterial ET‐1 concentrations reached markedly increased levels in individual patients (88, 92 and 103 pg/ml). Severe systemic reactions to these high levels were not observed. Peripheral venous, hepatovenous and portalvenous ET‐1 concentrations did not correlate with portocaval pressure gradients. Conclusion: Cirrhotic patients demonstrated unchanged peripheral venous ET‐1 concentrations up to 15 months after TIPS. Portal congestion was associated with increased ET‐1 levels in the prehepatic splanchnic area. The effect of portal decompression on splanchnic and systemic ET‐1 levels deserves further investigation.
Mitochondrial diseases represent a risk factor for valproate‐induced fulminant liver failure
Authors: Krähenbühl Stephan , Brandner Sebastian , Kleinle Stephanie , Liechti Sabina , Straumann Dominik
Published: March 2003

Abstract: We report on 3 siblings (2 females and 1 male) with chronic progressive external ophthalmoplegia (CPEO), compatible with inherited mitochondrial cytopathy. The younger of the two sisters died at the age of 37 due to progressive respiratory failure. The older one presented with a status epilepticus at the age of 39 and was treated with valproate. Five months after the start of treatment, she developed fulminant liver failure and died. The brother has suffered from CPEO since early childhood but has had so far no other symptoms of a mitochondrial disease. A muscle biopsy from the younger sister revealed ragged‐red fibers and decreased activities of complex I and IV of the respiratory chain but no pathogenic mutations in the mitochondrial tRNA genes or in several locations in the coding region of the mitochondrial genome. In the older sister's liver (obtained post‐mortem), mitochondrial DNA was fragmented and could not be investigated. The clinical presentation and the biochemical findings suggest that all 3 siblings suffered from a mitochondrial cytopathy. Since mitochondrial cytopathies and valproate‐induced fulminant liver failure are both rare events, an association between them is likely. Mitochondrial diseases should therefore be considered as a risk factor for valproate‐induced liver failure and be excluded before treatment with valproate.
Hepatic sinusoidal endothelial fenestrae express plasma membrane Ca++pump and Ca++Mg++‐ATPase
Authors: Yokomori Hiroaki , Oda Masaya , Ogi Mariko , Kamegaya Yoshitaka , Tsukada Nobuhiro , Nakamura Masahiko , Ishii Hiromasa
Published: March 2003

Abstract: Background/Aim: In general, intracytoplasmic free calcium ions (Ca++) are maintained at a very low concentration in mammalian tissue by extruding Ca++ against a high concentration of extracellular Ca++, mainly through the activity of the plasma membrane Ca++pump‐ATPase. The aim of the present study was to demonstrate by electron cytochemical and immunogold methods the ultrastructural localization of two different types of plasma membrane Ca++‐ATPase, i.e. Ca++Mg++‐ATPase and Ca++pump‐ATPase in the hepatic sinusoidal endothelium. Methods: Liver tissues and the isolated hepatic sinusoidal endothelial cell (SEC)s were subjected to the following procedures. The ultrastructural localizations of Ca++Mg++‐ATPase were examined by an electron cytochemical method. The ultrastructural localization of Ca++pump‐ATPase was identified by an electron immunogold method. Results: The cytochemical reaction of Ca++Mg++‐ATPase was found to be localized on the outer sites of the plasma membrane of sinusoidal endothelial fenestrae (SEF). The immunogold particles indicating the presence of Ca++ pump‐ATPase were identified on the inner sites (cytoplasmic) of the invaginated plasma membrane of SEF. Conclusions: Both Ca++Mg++‐ATPase and Ca++pump‐ATPase demonstrated on the SEF plasma membrane may be involved in the regulation of intracytoplasmic Ca++ concentration.
Expression of uncoupling protein‐2 in biliary epithelial cells in primary biliary cirrhosis
Authors: Taniguchi Eitaro , Harada Masaru , Kawaguchi Takumi , Koga Hironori , Kumemura Hiroto , Hanada Shinichiro , Shishido Shoichiro , Baba Shinji , Kumashiro Ryukichi , Ueno Takato , Sakisaka Shotaro , Sata Michio
Published: March 2003

Abstract: Background/Aims: Uncoupling proteins are thought to protect cells from oxidative stresses. Because uncoupling protein‐2 is expressed in liver and reactive oxygen species are involved in pathogenesis of various liver diseases, this protein may protect liver cells from disease‐associated oxidative stress. However, uncoupling protein‐2 expression in human liver has not been examined. Methods: We investigated hepatic uncoupling protein‐2 distribution in various liver diseases including primary biliary cirrhosis, autoimmune hepatitis, chronic viral hepatitis, and histologically normal liver by immunohistochemistry.Results: Uncoupling protein‐2 was expressed in some hepatocytes, however, the degree of hepatocytic uncoupling protein‐2 expression did not differ significantly among liver diseases and normal liver. Uncoupling protein‐2 was abundant in biliary epithelial cells in primary biliary cirrhosis but not in other liver specimens. Enhanced uncoupling protein‐2 expression in biliary epithelial cells was specific for primary biliary cirrhosis and did not result simply from cholestasis. The percentage of uncoupling protein‐2 positive bile ducts in primary biliary cirrhosis patients treated with ursodeoxycholic acid was significantly lower than in untreated patients.Conclusions: These results suggest that uncoupling protein‐2 is involved in the pathogenesis of primary biliary cirrhosis.
Haematology and blood chemistry of Cebus apella in relation to sex and age
Authors: Riviello M. Cristina , Wirz Annarita
Published: March 2003

An effective health care program entails the prevention, diagnosis and treatment of medical problems. A knowledge of baseline values in clinically normal individuals is essential for determining the limits between good health and disease and for understanding the changes produced by pathogenic agents. However, very little information is currently available concerning the blood chemistry and haematological values of different species of monkeys, particularly new‐world primates. The values of some haematological and chemical parameters in Cebus apella were determined. The aim of the present work was to verify the effect of age and sex on normal blood values. Blood samples were collected once a year for two successive years from 36 monkeys living in large captive social groups. Significant differences between males and females were found for AST, GGT, urea nitrogen and creatinine, erythrocytes, haemoglobin and haematocrit. Significant differences between juveniles and adults were found for calcium, AST, alkaline phosphatase, inorganic phosphorus, glucose, neutrophils, lymphocytes and serum protein parameters.
Ovarian stimulation of marmoset monkeys (Callithrix jacchus) using recombinant human follicle stimulating hormone
Authors: Marshall V.S. , Browne M.A. , Knowles L. , Golos T.G. , Thomson J.A.
Published: March 2003

To reduce the number of animals required for controlled studies of marmoset oocytes and early embryos, a superovulation protocol was developed for the common marmoset. Females were given up to 50 i.u./day recombinant human follicle stimulating hormone (FSH) – (r‐hFSH) for 6 days. Ovaries were visualized by a modified laparoscopic technique and follicular aspiration was performed using a needle and suction apparatus inserted directly through an otoscope speculum. The number of follicles + ovulation points (± S.E.) was 2.9 (± 0.2) in controls and 14.1 (± 1.6; P≤0.001) in the 50 i.u. r‐hFSH per day animals. Oocytes, typically at the germinal vesicle stage at collection, extruded a first polar body within 26 hours. In vitro fertilization was performed and embryos developed to the hatched blastocyst stage (34%). With many high quality oocytes and the ability to synchronize cycles, the marmoset is a valuable primate model for examining nuclear reprograming and early embryonic events.
Thermodynamics of liquid and undercooled liquidAl–Cr–Ni alloys
Authors: Saltykov Pavlo , Witusiewicz Victor T. , Arpshofen Ingo , Fabrichnaya Olga , Seifert Hans Jürgen , Aldinger Fritz
Published: March 2003

The partial and the integral enthalpies of mixing of liquid ternary Al–Cr–Ni alloys have been determined by high temperature iso‐peribolic calorimetry at 1718–1731 K. Measurements for ternary alloys were performed along 4 isopleths with xCr:xNi of 0.20:0.80, 0.50:0.50, 0.70:0.30, and 0.85:0.15. The results were analytically described by the thermodynamically adapted power series according to the Kohler interpolation geometry as well as by the regular association model using the parameters for the constituent binaries and assuming that ternary association reactions with the stoichiometry Al2Cr1Ni1 take place in the liquid state. The results were also compared with the calculated ones using the database for the Al–Cr–Ni system. The Gibbs energy of mixing of liquid and undercooled liquid Al–Cr–Ni alloys were estimated in the whole composition range. The latter function demonstrates that the minimum (−41.5 kJ · mol−1) shows up near the ternary composition Al0.48Cr0.04Ni0.48.
Hot rolling in ferrite region
Authors: Kawalla Rudolf , Lehnert Wolfgang
Published: March 2003

Hot forming or rolling in the ferrite region (HRF) is a special kind of thermomechanical treatment with a remarkable potential for innovation. By this technology it is possible to produce hot rolled strips from low‐carbon steels with new quality parameters, on the one hand, and in a thinner thickness dimension, on the other hand. The changes in microstructural morphology must be suitably influenced and controlled according to the specific material importance. Scientific understanding and control of this process is not as far developed as in other cases of thermomechanical treatment. Therefore, it is necessary to simulate the complete process and microstructure evolution by experimental and mathematical methods. An overview of the specifics and characteristics of HRF is given, and some results are demonstrated.
Liquidus temperatures and viscosities of FeO‐Fe2O3‐SiO2‐CaO‐MgO slags at compositions relevant to nickel matte smelting
Authors: Ducret A. C. , Rankin W. J.
Published: March 2003

Although the liquidus temperatures and viscosities of iron silicate slags are critical in the operation of many pyrometallurgical processes, there is relatively little published data relating to complex, multi‐component systems. In this study, liquidus temperatures and viscosities in the FeO‐Fe2O3‐SiO2‐CaO‐MgO slag system were determined at conditions relevant to base metal smelting processes. The classical quench technique was used to measure liquidus temperatures at Fe/SiO2 ratios of 1.3 to 1.8, CaO contents up to 9 wt%, MgO contents up to 12 wt% and at oxygen partial pressures of 10−11 and 10−8 atm. The addition of MgO was found to lead to large increases in liquidus temperature. The addition of CaO generally led to a moderate fall in liquidus temperature but the magnitude and direction of the change depended on the Fe/SiO2 ratio and MgO content. At CaO contents greater than about 3%, increasing the oxygen partial pressure of the system raised the liquidus temperature moderately and lowered the ability of CaO to depress the liquidus temperature. The viscosity of the slags was measured over similar composition ranges at iron saturation by means of a coaxial, cylindrical cup and bob arrangement. The slags were found to be Newtonian in behaviour above their liquidus temperatures. Viscosity decreased significantly as the Fe/SiO2 ratio was increased in the range 1.3 to 2.00. The addition of low levels of CaO or MgO lowered the viscosity but the addition of further MgO increased the viscosity. The MgO content at which the viscosity began to increase decreased with increased CaO content.
Spatially heterogeneous refugia and predation risk in intertidal salt marshes
Authors: Lewis David B. , Eby Lisa A.
Published: March 2003

The effect of habitat structure on interactions between predators and prey may vary spatially. In estuarine salt marshes, heterogeneity in refuge quality derives from spatial variation in vegetation structure and in tidal inundation. We investigated whether predation by blue crabs on periwinkle snails was influenced by distance from the seaward edge of the salt marsh and by characteristics of the primary habitat structure, smooth cordgrass (Spartina alterniflora). Spartina may provide refuge for snails and interfere with foraging by crabs. Furthermore, predation risk should decline with distance from the seaward edge because landward regions require more travel time for crabs during tidal inundation. We investigated these processes using a comparative survey of snails and habitat traits, an experiment that assessed the crab population and measured predation risk, and a size‐structured model that estimated encounter rates. Taken together, these approaches indicated that predation risk for snails was lower where Spartina was present and was lower in a landward direction. Furthermore, Spartina architecture and distance from the seaward edge interacted. The strength of the predation gradient between seaward and landward regions of the marsh was greater where Spartina was tall or dense. These predation gradients emerge because vegetation and distance inland decrease encounter rates between crabs and snails. This study suggests that habitat modification, a process not uncommon in salt marshes, may have consequences for interactions among intertidal fauna.
Conundrums of competitive ability in plants: what to measure?
Authors: Aarssen LonnieW. , Keogh Teri
Published: March 2003

A survey of recent literature indicates that competitive ability in plants has been measured, in most studies, only in terms of the relative intensity of size suppression experienced by competitors within one growing season. Far fewer studies have recorded relative success in terms of survival and even fewer studies have recorded fecundity under competition. Differences in size suppression are usually assumed to reflect differences in relative abilities to deny resources to competitors. However, most previous studies have failed to control or account for other sources of variation in the size suppression that plants experience under competition, i.e. variation between mixtures in the resource supply/demand ratio (approach to carrying capacity), or variation in the degree of niche overlap between competitors, or variation in the intensity of concurrent facilitative interactions between competitors. For future studies, much greater caution is required in recognizing these inherent limitations of traditional measures of competitive ability and, hence, guarding against unfounded conclusions or predictions about potential for competitive success that are based on these measures. There is also a significant challenge for future studies to adopt empirical approaches for minimizing these limitations. Some initial recommendations are considered here based on an emerging view of competitive ability measured in terms of traits associated with all three conventional components of Darwinian fitness, i.e. not just growth (plant size) but also survival and fecundity allocation (offspring production per unit plant size per unit time). According to this model, differences in competitive ability imply differences in the ability, despite intense competition (i.e. low resource supply/demand ratio), to recruit offspring into the next generation and thereby limit offspring recruitment by other plants. The important traits of competitive ability, therefore, are not only those that allow a plant to deny resources to competitors, suppress their sizes and hence, maximize the plant's own size, but also those traits that allow the plant to withstand suppression from competition enough to persist, both as an individual (through survival) and across generations (through descendants).
Climate patterns and the stochastic dynamics of migratory birds
Authors: Jonzén Niclas , Hedenström Anders , Hjort Christian , Lindström Åke , Lundberg Per , Andersson Arne
Published: March 2003

We analyse time series data of 17 bird species trapped at Ottenby Bird Observatory, Sweden, during spring migration 1972–1999. The species have similar demography but respond differently to variation in the North Atlantic Oscillation (NAO) – a strong determinant of winter climate in the northern Hemisphere. Species wintering in northern Europe, compared to species having winter quarters in the Mediterranean area, tend to respond positively to variation in NAO. The variation within each group is high due to wide‐ranging winter‐distribution in many species, probably smoothing out the effect of spatial variation in NAO. Whereas mild winters (high NAO) is benign for many – but not all – birds wintering in northern Europe, the effect of drier‐than‐normal conditions in the Mediterranean area during high NAO index winters are uncertain. The work presented here goes beyond simple correlative studies and help identifying which species that are most affected by variation in winter climate. This is a first important step that calls for a more mechanistic approach when analysing possible changes to climate change.
Benefits of the Carbon‐Nutrient Balance Hypothesis
Authors: Lerdau Manuel , Coley Phyllis D.
Published: March 2003

The carbon‐nutrient balance hypothesis (CNBH) is one of a number of approaches to understanding patterns of resource allocation in plants. Numerous empirical tests of the CNBH's predictions have led to certain key refinements and to the recognition that some of the simplifications inherent in the model limit its utility. However, as long as the model is applied to compounds with large pools, and the biosynthetic pathways of secondary metabolites are considered, the CNBH still serves as a useful guide for ecological research on resource allocation. One of the model's values is that it attempts to explain the plasticity of individuals but does not assume that all responses of individuals are optimal in terms of maximizing fitness.
Treating the nestedness temperature calculator as a “black box” can lead to false conclusions
Authors: Fischer Joern , Lindenmayer David B.
Published: March 2003

We used the nestedness temperature calculator to examine patterns of nestedness in two datasets on birds in fragmented landscapes in southeastern Australia. During our initial analyses, we found that the nestedness calculator was susceptible to detect nestedness as an artifact of passive sampling. To examine this problem in more detail, we created random matrices that simulated a situation where nestedness did not occur, and we re‐analysed two previously published datasets. Our results showed that the nestedness calculator may (1) overestimate the degree of nestedness and its statistical significance, and (2) consider some datasets which include both ubiquitous and rare species to be significantly nested although they are not. Our results highlight the danger of blindly relying on the p‐values generated by analytical packages such as the nestedness calculator. We suggest that users of analytical packages (often field ecologists) will need to be more critical in future and familiarise themselves in more detail with the packages they use. In addition, the developers of analytical packages (often theoretical ecologists) will need to communicate more clearly the limitations and assumptions underlying analytical tools such as the nestedness calculator.
Biodiversity and ecosystem function: the consumer connection
Authors: Duffy J. Emmett
Published: March 2003

Proposed links between biodiversity and ecosystem processes have generated intense interest and controversy in recent years. With few exceptions, however, empirical studies have focused on grassland plants and laboratory aquatic microbial systems, whereas there has been little attention to how changing animal diversity may influence ecosystem processes. Meanwhile, a separate research tradition has demonstrated strong top‐down forcing in many systems, but has considered the role of diversity in these processes only tangentially. Integration of these research directions is necessary for more complete understanding in both areas. Several considerations suggest that changing diversity in multi‐level food webs can have important ecosystem effects that can be qualitatively different than those mediated by plants. First, extinctions tend to be biased by trophic level: higher‐level consumers are less diverse, less abundant, and under stronger anthropogenic pressure on average than wild plants, and thus face greater risk of extinction. Second, unlike plants, consumers often have impacts on ecosystems disproportionate to their abundance. Thus, an early consequence of declining diversity will often be skewed trophic structure, potentially reducing top‐down influence. Third, where predators remain abundant, declining diversity at lower trophic levels may change effectiveness of predation and penetrance of trophic cascades by reducing trait diversity and the potential for compensation among species within a level. The mostly indirect evidence available provides some support for this prediction. Yet effects of changing animal diversity on functional processes have rarely been tested experimentally. Evaluating impacts of biodiversity loss on ecosystem function requires expanding the scope of current experimental research to multi‐level food webs. A central challenge to doing so, and to evaluating the importance of trophic cascades specifically, is understanding the distribution of interaction strengths within natural communities and how they change with community composition. Although topology of most real food webs is extremely complex, it is not at all clear how much of this complexity translates to strong dynamic linkages that influence aggregate biomass and community composition. Finally, there is a need for more detailed data on patterns of species loss from real ecosystems (community “disassembly” rules).
Northern bats, Eptesicus nilssonii, use vision but not flutter‐detection when searching for prey in clutter
Authors: Eklöf Johan , Svensson A. Monica , Rydell Jens
Published: March 2003

We investigated the detection cues used by the aerial‐hawking bat Eptesicus nilssonii foraging in a cluttered environment. The bats can detect and attack rapidly moving targets within the clutter, i.e. below grass panicles, by using prey motion as a cue. Stationary objects are attacked only above the grass, but still within the clutter overlap zone. To test if the bats were guided by flutter from moth wings or by vision when searching for stationary targets, they were presented with male ghost swifts mounted on top of steel wires. There was no difference in attack frequency on live, fluttering moths compared to dead and spread ones. However, when comparing white and dark moths, we found a significantly higher attack frequency on white ones. As the attacks always were guided by echolocation calls, we hypothesize that northern bats, at least in the initial search phase, use visual cues as a complement to detect stationary ghost swifts.
Using niche‐based GIS modeling to test geographic predictions of competitive exclusion and competitive release in South American pocket mice
Authors: Anderson Robert P. , Peterson A. Townsend , Gómez‐Laverde Marcela
Published: March 2003

Geographic studies addressing the role of competition in determining species’ macrodistributions have been limited by only simple or subjective means of identifying regions of suitable habitat. Now, ecological‐niche models of species’ potential distributions present a possible approach to testing for the geographic patterns predicted under competitive exclusion and competitive release. Previously, we modeled the potential distributions of two spiny pocket mice (Heteromys australis and H. anomalus) in northwestern South America using specimen localities, environmental data, and the Genetic Algorithm for Rule‐Set Prediction (GARP). Here we superimpose the models to examine known distributional records in areas of potential sympatry between the two species, thus testing the geographic predictions of competitive exclusion. In addition, we examine environmental characteristics of known localities, testing for data consistent with competitive release. Areas of potential sympatry are minimal, lying in regions of intermediate water balance. Only records of H. australis are known from areas of potential sympatry in regions where the species’ ranges meet, consistent with exclusion of H. anomalus by H. australis. Heteromys anomalus inhabits areas ecologically suitable for both species only in the isolated Sierra Nevada de Santa Marta, in which H. australis is not present (most likely for historical reasons). Furthermore, environmental characteristics of localities of H. anomalus in biogeographic regions where H. australis is absent fit the pattern predicted under competitive release. In contrast, localities of H. australis show no indication of competitive release. Although the results of present analyses do not conclusively demonstrate competitive exclusion or release, they provide directional hypotheses that can now be tested in experimental field and laboratory studies.
Myofibroblasts and matrix components in healing palatal wounds in the rat
Authors: Cornelissen Anne M. H. , Stoop Reinout , Hoff Hans W. , Maltha Jaap C. , Kuijpers‐Jagtman Anne Marie
Published: March 2003

Abstract: In order to identify wound contraction and scar formation during palatal mucoperiosteal wound healing in growing rats, the temporal and spatial distribution of myofibroblasts and matrix components were determined immunohistochemically. Myofibroblasts were found in the mucosal part of the palatal wound tissue between 4 and 22 days, with the highest density at 8 days post‐wounding. The number of collagen type I and type III fibers gradually increased until about 8 days post‐wounding, and thereafter the staining intensity of collagen type III decreased. At 60 days post‐wounding there were more transversely oriented collagen type I fibers and less type III fibers and elastin present in the submucosa than in normal tissue. The results suggest that in this model wound contraction mainly takes place in the mucosa between 4 and 22 days post‐wounding. Furthermore, palatal wounds made in young rats heal with distinct scar tissue formation. Therefore, this model is useful to test the effects of therapies that aim to reduce wound contraction and scarring after cleft palate surgery.
Penetration of N‐nitrosonornicotine (NNN) across oral mucosa in the presence of ethanol and nicotine
Authors: Du X. , Squier C. A. , Kremer M. J. , Wertz P. W.
Published: March 2003

Abstract: The effects of ethanol concentrations of 5, 15, 20, 25, 27, 30 and 50% on the penetration of the tobacco‐specific carcinogen, nitrosonornicotine (NNN), across porcine oral mucosa were examined using an in vitro perfusion system. Concentrations of ethanol of 25% and above significantly increased the permeability of oral mucosa to NNN, although this increase ceased with 50% ethanol, possibly due to a fixative effect. Nicotine is a consistent component of smoked and smokeless tobacco; the presence of 0.2% nicotine significantly increased the permeability of oral mucosa to NNN and 2% nicotine caused a further increase. Combined use of nicotine and ethanol significantly increased the penetration of NNN across oral mucosa over that of ethanol alone until the concentration of ethanol reached 50%. The results of this study suggest that the synergy between tobacco and alcohol in the etiology of oral cancer may be explained, at least in part, by the local permeabilizing effects of alcohol on the penetration of tobacco‐specific (and other) carcinogens across oral mucosa.