bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequence polymorphism in the bovine major histocompatibility complex DQB loci
Authors: Nasir L , Ndiaye M , Seely C , Stear M J
Published: December 2003

Polymorphism in DQB sequences of the bovine major histocompatibility complex was investigated in 22 British Friesian cattle. The first domain exon was amplified, cloned and sequenced. Eight different sequences were identified, six of which had not been identified previously. The high proportion of novel sequences suggests that additional polymorphisms within the DQB loci remain to be discovered in this breed. One sequence was present in at least 21 of the 22 cattle. This sequence, or a closely related sequence, has also been found in American Holstein Friesian, Swedish Red and White and Japanese Black cattle. The remarkably high sequence conservation suggests that the bovine DQB region may contain a locus with a low level of polymorphism and be more similar to the human DQB region than previously supposed. One sequence with three widely spaced frameshift insertions appeared to be a pseudogene.
Some new variants of serum protease inhibitors in Meishan pigs
Authors: Stratil A , C˘epica S , C˘íz˘ová‐Schröffelová D , Geldermann H
Published: December 2003

Serum samples of Meishan (13 animals) and Meishan x Wild Boar crosses (361 animals) were analysed by means of two‐dimensional electrophoresis. Some new variants in protease inhibitor systems PO1A, PO1B and PI2 are reported.
Mapping genes located on human chromosomes 2 and 12 to porcine chromosomes 15 and 5
Authors: Rohrer G A , Alexander L J , Beattie C W
Published: December 2003

Informative microsatellites associated with two genes on HSA12 (lysozyme, LYZ; tumour necrosis factor receptor, TNFR) and one gene on HSA2 (glutamic acid decarboxylase 1, GAD1) were mapped in the US Meat Animal Research Center (MARC) swine reference population and the physical assignment of a‐lactalbumin (LALBA) was determined. A comparative map for HSA2 and HSA12 with SSC15 and SSC5, respectively, was developed by combining the results from this study with published type I loci mapped in both species. One rearrangement between HSA2 and SSC15 was detected while the number of rearrangements between HSA12 and SSC5 were numerous. These results indicated that conservation of synteny does not imply a conservation of gene order and that additional type I markers need to be mapped in the pig to fully understand the chromosomal rearrangements that occurred during the evolution of mammals.
AFLP™ markers for DNA fingerprinting in cattle
Authors: Ajmone‐Marsan P , Vecchiotti‐Antaldi G , Bertoni G , Valentini A , Cassandro M , Kuiper M
Published: December 2003

This work reports on use of the recently described amplified fragment length polymorphism (AFLP) technology for DNA fingerprinting in cattle. The AFLP technology produces molecular markers through the high‐stringency polymerase chain reaction (PCR)‐amplification of restriction fragments that are ligated to synthetic adapters and amplified using primers, complementary to the adapters, which carry selective nucleotides at their 3' ends. While, for plants, the double digestion of genomic DNA with EcoRI and MseI is suggested, in mammals the enzyme combination EcoRI/TaqI produces clearer and more polymorphic AFLP patterns. In a sample of 47 Italian Holstein genotypes, 16 EcoRI/TaqI primer combinations identified 248 polymorphic bands in a species known for its low level of restriction polymorphism. In spite of the low information content carried by each AFLP polymorphism (average polymorphism information content = 0·31), the number of fragments revealed by each primer combination increased significantly the level of genetic information gained in each experiment. AFLP patterns are reproducible in independent experiments and polymorphic fragments segregate in cattle families according to Mendelian rules.
New microsatellite markers in chicken optimized for automated fluorescent genotyping
Authors: Crooijmans R P M A , Dijkhof R J M , Poel J J van der , Groenen M A M
Published: December 2003

We have isolated and developed 180 new polymorphic chicken microsatellite markers. In addition, primers have been developed for 91 microsatellites derived from the GenBank sequence database (isolated by the laboratory of Terry Burke, Leicester University), of which 89 were polymorphic, and six existing polymorphic markers (HUJ) have been modified. The primer sequences were designed to allow optimal performance of the markers, in sets containing multiple microsatellites, on ABI sequencers. The average number of alleles for the 275 polymorphic markers described was 4·0. Of these markers, 93% were polymorphic in the Wageningen resource population whereas 57% of the markers were polymorphic in the East Lansing reference population and only 44% could be mapped in the Compton reference population. The microsatellite markers described in this paper, in combination with the microsatellite markers published previously, are particularly well suited for performing a total genome scan for the detection of quantitative trait loci (QTL).
Exclusion probabilities of 22 bovine microsatellite markers in fluorescent multiplexes for semiautomated parentage testing
Authors: Heyen D W , Beever J E , Da Y , Everts R E , Green C , Lewin H A , Bates S R E , Ziegle J S
Published: December 2003

Six multiplexes developed for semiautomated fluorescence genotyping were evaluated for parentage testing. These multiplexes contained primer pairs for the amplification of 22 microsatellites on 17 bovine autosomes. Exclusion probabilities were determined from genotypes of 1022 Holstein cattle and 311 beef cattle belonging to five breeds. Two cases were considered: case 1, genotypes are known for an alleged parent and an offspring but genotypes of a confirmed parent are unknown; and case 2, genotypes are known for an alleged parent, a confirmed parent and an offspring. If the alleged parent is not the true parent, then the 22 markers will exclude the alleged parent with a probability of >0·9986 for case 1 and with a probability of >0·99999 for case 2. On the basis of these exclusion probabilities, the probability that an alleged parent will be falsely included as a parent is in the range of 1/716 to 1/2845 for case 1 and 1/1·2 million to 1/159753 for case 2. In addition to these results, a rapid and efficient non‐organic method for extraction of DNA from semen is described.
‘True’ antimitochondrial antibody-negative primary biliary cirrhosis, low sensitivity of the routine assays, or both?
Authors: MURATORI P , MURATORI L , GERSHWIN M E , CZAJA A J , PAPPAS G , MACCARIELLO S , GRANITO A , CASSANI F , LORIA P , LENZI M , BIANCHI F B
Published: December 2003

Anti-mitochondrial antibody (AMA) is considered the serological hallmark of primary biliary cirrhosis (PBC), but may be missing in a proportion of these patients. We assessed sensitivity and specificity of the currently available techniques for AMA detection in a large series of PBC patients and controls, and analysed their clinical and immunological features according to the AMA status. By indirect immunofluorescence on rat tissue sections and HEp-2 cells, Western immunoblot with bovine submitochondrial particles, and two ELISAs with AMA-specific recombinant proteins, we evaluated the presence of AMA in 127 PBC patients, 166 patients with type 1 autoimmune hepatitis and 100 with non alcoholic fatty liver disease. In PBC patients Western immunoblot detects AMA significantly more often than indirect immunofluorescence on HEp-2 cells (85%versus 72%, P = 0·02) or rodent tissue sections (71%, P = 0·01); both ELISAs are only slightly less sensitive than Western immunoblot (81% and 78%). Ten patients with non alcoholic fatty liver disease were AMA-positive by indirect immunofluorescence, but none recognized AMA-specific epitopes in Western immunoblot or in ELISAs. Twelve patients with type 1 autoimmune hepatitis were AMA-positive by indirect immunofluorescence, but only 6 (3·6%) reacted by Western immunoblot and ELISAs. Western immunoblot or ELISA should be regarded as first-line assay for the detection of AMA. Up to 15% of PBC patients are consistently AMA-negative, yet they share the same clinical, biochemical and histological features of AMA-positive PBC. Detection of AMA in type 1 autoimmune hepatitis might identify a subset of patients at risk of developing a hepatitic/cholestatic syndrome.
IgE-dependent enhancement of Th2 cell-mediated allergic inflammation in the airways
Authors: MAEZAWA Y , NAKAJIMA H , SETO Y , SUTO A , KUMANO K , KUBO S , KARASUYAMA H , SAITO Y , IWAMOTO I
Published: December 2003

T helper 2 (Th2) cell-derived cytokines, including interleukin (IL)-4, IL-5 and IL-13, play important roles in causing allergic airway inflammation. In contrast to Th2 cells, however, the role of IgE and mast cells in inducing allergic airway inflammation is not understood fully. In the present study, we addressed this point using transgenic mice expressing trinitrophenyl (TNP)-specific IgE (TNP–IgE mice), which enable us to investigate the role of IgE without the influence of antigen-specific T cell activation and other immunoglobulins. When the corresponding antigen, TNP–BSA, was administered intranasally to TNP–IgE mice, a large number of CD4+ T cells were recruited into the airways. In contrast, TNP–BSA administration did not induce eosinophil recruitment into the airways or airway hyperreactivity. Furthermore, when ovalbumin (OVA)-specific Th2 cells were transferred to TNP–IgE mice and the mice were challenged with inhaled OVA, TNP–BSA administration increased OVA-specific T cell recruitment and then enhanced Th2 cell-mediated eosinophil recruitment into the airways. These results indicate that IgE-induced mast cell activation principally induces CD4+ T cell recruitment into the airways and thus plays an important role in enhancing Th2 cell-mediated eosinophilic airway inflammation by recruiting Th2 cells into the site of allergic inflammation.
Quantitative and functional characteristics of intestinal-homing memory T cells: analysis of Crohn's disease patients and healthy controls
Authors: HART A L , KAMM M A , KNIGHT S C , STAGG A J
Published: December 2003

Circulating memory T cells can be subdivided on the basis of β7 integrin expression. The β7+ population contains cells primed in the intestine capable of homing back to the gut. We hypothesized that cytokine production by β7+ memory T cells reflects the specialized mucosal compartment in which they were primed. Flow cytometry of whole blood was used to assess numbers of β7+ (β7hi and β7int) and β7– memory T cells and their production of Th1 and regulatory cytokines in healthy controls and Crohn's disease patients. In controls, β7+ and β7– memory T cells displayed a similar qualitative profile of cytokine production but the β7+ population was enriched for cytokine-producing effector cells. In addition, the β7hi population contained more cytokine-producing cells than the β7int population, suggesting a gradient of cytokine production based on β7 integrin expression. In active Crohn's disease, there was altered expression of β7 integrin with a decrease in intestinal-homing memory T cells and an increase in systemic memory T cells. Furthermore, there was a selective loss of IL-10 and increase in TGF-β in both β7+ and β7– memory T cell subsets which may contribute to the pathogenesis of the inflammatory process in Crohn's disease.
Tumour necrosis factor-αconverting enzyme (TACE) activity in human colonic epithelial cells
Authors: KIRKEGAARD T , PEDERSEN G , SAERMARK T , BRYNSKOV J
Published: December 2003

Tumour necrosis factor (TNF)-α converting enzyme (TACE) releases biologically active, soluble TNF-α from transmembrane pro-TNF-α and has attracted interest as a specific therapeutic target in inflammatory bowel disease (IBD). Strong immunoreactivity for TACE protein was demonstrated recently in human colonic epithelium, but the function is unknown. We investigated if human colonic epithelial cells express functional TACE activity and how TACE expression is regulated in response to cytokine stimulation. TACE and TNF-α mRNA and protein expression were measured in HT-29 and DLD-1 colonic epithelial cells by reverse-transcription polymerase chain reaction, western blotting or enzyme-linked immunosorbent assay. Monocytic THP-1 cells served as positive control. Functional TACE activity was identified and quantified in detergent extracts of cell lines and freshly isolated colonocytes from 14 IBD patients and five controls by a hydrolysis assay using an oligopeptide spanning the cleavage site in pro-TNF-α. HT-29 and DLD-1 cells spontaneously expressed TACE mRNA and the active form of TACE protein at levels similar to those of monocytic cells. Functional TACE activity was demonstrated in all cell lines and in cells of controls or IBD patients irrespective of disease activity. TACE mRNA expression and functional activity remained unchanged in cell lines after stimulation with TNF-α despite clear induction of TNF-α mRNA expression and release of soluble TNF-α protein. The release of soluble TNF-α protein was almost completely abolished by CH4474, a synthetic TACE inhibitor. We conclude that functional TACE activity is constitutively expressed in human colonic epithelial cells and responsible for processing of the mature, soluble form of TNF-α in response to cytokine stimulation.
POSSIBLE SEX‐CORRELATED TRANSMISSION OF MATERNAL CLASS I HLA HAPLOTYPES
Authors: KOMLOS L. , KOROSTISHEVSKY M. , HALBRECHT I. , VARDIMON D. , BEN‐RAFAEL Z. , KLEIN T.
Published: December 2003

Forty‐seven alleles of class I HLA‐AB loci (14 for locus A and 33 for locus B) were identified in 787 participants in two groups of unrelated families. Group I included parents and children typed for bone marrow transplantation. Group II included families typed for renal transplantation. Before statistical evaluation, the A locus alleles were grouped into eight classes according to broad specificity, and the B locus alleles were grouped according to HLA epitopes into two classes. Significant differences in HLA‐AB haplotype frequencies were found between male and female offspring. When families with children of both sexes were analysed, the frequencies of maternally inherited HLA‐AB haplotypes were found to be significantly different in brothers and sisters. The results suggest the possibility that the transmission of specific AB haplotypes from mother to offspring may be correlated to children’s sex. The major histocompatibility complex has been shown to be involved in the expression of H‐Y male‐specific minor histocompatibility antigens. The possible selection in the transmission of specific maternal HLA‐AB haplotypes to male offspring may contribute to the avoidance of maternal cytotoxic reactions toward the male foetus.
HLA‐DQ ASSOCIATIONS AND T‐CELL RECEPTOR V‐GENE USAGE IN PERIPHERAL BLOOD OF SWEDISH MYASTHENIA GRAVIS PATIENTS
Authors: HJELMSTRÖM P. , GISCOMBE R. , LEFVERT A. K. , GRÜNEWALD J. , PIRSKANEN R. , SANJEEVI C. B.
Published: December 2003

To characterize better the functional aspects of the HLA class II associations with myasthenia gravis (MG), T‐cell receptor (TCR) Vα/β elements were studied in peripheral blood in 29 Swedish MG patients. HLA typing had previously been done using polymerase chain reaction with sequence‐specific primers (PCR‐SSP) or combined with sequence‐specific oligonucleotide probes (PCR‐SSO). The TCR V gene expression was determined by fluorescence‐activated cell sorter (FACS) analysis using 12 monoclonal antibodies (mAb) that detected 30–40% of CD4+ and CD8+ T cells. No correlation between HLA‐DQ genotype and TCR V elements could be found, nor was any restricted V gene usage seen. Fourteen (48%) of the patients had T cells showing signs of abnormal expansion in peripheral blood. There was an increased expression of TCR V gene elements in CD8+ T cells in patients (13/29) compared with CD4+ T cells in patients (5/29) (P < 0.05) and in unthymectomized patients compared with controls (14/56) (P < 0.005). TCR V gene expression was also increased in the CD8+ population in unthymectomized (7/8) compared with thymectomized patients (6/21) (P < 0.01). There was an increased expression in both CD4+ and CD8+ populations in unthymectomized patients (7/8, 88%), compared with thymectomized patients (7/21) (P < 0.05). We conclude that the abnormal T‐cell expansion in peripheral blood could be a reflection of non‐specific pathogenic processes in the muscle and thymus.
ALLELIC POLYMORPHISM OF TWO MULTIFUNCTIONAL REGIONS IN THE CENTRAL HUMAN MHC: TENASCIN X, XB‐S AND YB, AND THEIR DUPLICATED FRAGMENTS XA AND YA
Authors: WEISSENSTEINER T. , LANCHBURY J.S.
Published: December 2003

Two highly polymorphic sequences have been discovered in the complement C4 region of the human major histocompatibility complex (MHC). They are part of a duplicated unit of overlapping genes, transcribed in opposite directions and containing the sequences of tenascin X (XB), XB‐S, XA, YB and YA. Fragments of 1014 bp and 894 bp were co‐amplified by polymerase chain reaction (PCR) and digested with two different restriction enzymes. This preliminary study provides evidence for more than five different alleles each of XA (YA) and XB (XB‐S, YB), and at least 11 XA–XB haplotypes. Their association with extended HLA‐B–DR haplotypes, C4 complotypes, and C4 region restriction fragment length polymorphisms (RFLP) is discussed. X gene polymorphisms are a complement region marker system that should be uniquely suited for PCR‐based typing methods. They could become a useful addition to HLA class I and class II markers in the mapping of candidate genes for MHC‐associated diseases, including the X and Y genes themselves.
REPORT FROM THE HLA CLASS II TYPING BY PCR‐SSP MULTICENTRE STUDY
Authors: ZETTERQUIST H. , BENGTSSON M. , BÄCKSTRÖM G. , EGLE‐JANSSON I. , EKDAHL A.‐M. , GRUNNET N. , GUSTAFSSON I. , KNUTSEN I. , KUHLE A. , RYDBERG L. , SPURKLAND A. , STEFFENSEN R. , STORGÄRDS M. , SZOJMER E. , SÖDERHOLM G. , THURESSON B. , TURESSON §§H. , OLERUP O.
Published: December 2003

Results from 360 HLA‐DR and ‐DQ ‘low‐resolution’ typings with polymerase chain reaction sequence‐specific primers (PCR‐SSP), performed by nine laboratories, were analysed for their overall utility in routinely defining the HLA‐DR1–DR18, DR51–DR53 and DQ1–DQ9 specificities in less than 2.5 h. Thirty EDTA blood samples and 10 DNA samples were distributed and analysed by each laboratory. DNA was extracted using a rapid bromide salt extraction protocol. Complete HLA‐DR and ‐DQ typings were performed, three by three, on pre‐aliquoted 96‐tube PCR trays. When compared with reference typing, 351/360 (98%) correct DR typings were obtained, whereas 320/360 (89%) of the DQ phenotypes were correctly assigned. The time for three complete HLA‐DR and ‐DQ ‘low‐resolution’ typings, including DNA extraction, ranged from 2.0 h to 2.3 h. Unfortunately, an unusually high level of PCR amplification failures was observed (3%), probably due to diffusion and a significant volume loss from some of the pre‐aliquoted primer mixes. Consequently, only 52% of the typings were without any amplification failure, and 0–2 amplification failures where found in 88% of the PCR‐SSP typings performed. The number of HLA‐DR–DQ retypings needed was 7 and 8%, respectively, reflecting the low number of typings where allelic identification was directly affected by the relatively high level of amplification failures in this study. Thus, a 91–98% success rate of correctly identified HLA‐DR and ‐DQ alleles could be maintained, even under suboptimal typing conditions.
THE SPECIFICITY OF ANTI‐HLA CLASS II MONOCLONAL ANTIBODIES IN CATTLE
Authors: NILSSON PH. R. , MARSH S. G. E. , JOOSTEN I. , NIEUWLAND M. G. B. , HENSEN E. J. , GROSFELD‐STULEMEYER M. C. , MIKKO S. , GELHAUS A. , SCHREUDER G. M. TH.
Published: December 2003

At the Eleventh International HLA Histocompatibility Workshop, numerous anti‐HLA class II monoclonal antibodies (mAb) were tested. For several of the polymorphic mAb, one epitope for binding has been mapped within the antigen‐binding site of the class II molecules. Screening of the available bovine DRB3 and DQB exon 2 sequences revealed that some of the key amino acid (AA) motifs of these epitopes were present in cattle as well, and the question was raised whether this sharing of key AA motifs might cause interspecies cross‐reactivity. Eight polymorphic anti‐HLA class II mAb (seven anti‐HLA DRB1 and one anti‐HLA DQB) were selected for analysis of their reactivity towards bovine lymphocytes. In addition, the monomorphic anti‐HLA class II mAb, 7.5.10.1, was selected for analysis, as this mAb was described to detect class II polymorphism in cattle. Flow cytometry and lymphocyte microcytotoxicity testing revealed that five of the polymorphic anti‐HLA mAb were reactive with bovine lymphocytes. Furthermore, the anti‐bovine reactivity of 7.5.10.1 was confirmed. These findings were supported by biochemical analysis. The anti‐bovine reaction of the anti‐HLA mAb did not correspond with the expected reaction, which was based on the presence of the AA, postulated to be responsible for recognition. Therefore, we suggest that the patterns of reactivity of the anti‐HLA mAb are not always determined by one epitope.
POLYMORPHISMS OF TAP1 AND TAP2 GENES IN GERMAN PATIENTS WITH TYPE 1 DIABETES MELLITUS
Authors: RAU H. , NICOLAY A. , DONNER H. , USADEL K. H. , BADENHOOP K.
Published: December 2003

Type 1 diabetes mellitus (IDDM) is an autoimmune disorder in which the alleles HLA DQA1*0501–DQB1*0201 and DQA1*0301–DQB1*0302 confer strong susceptibility. The genes for transporters associated with antigen processing (TAP1 and TAP2) are located near HLA DQ and display only a limited degree of polymorphism. Since polymorphisms of TAP might influence susceptibility to IDDM possibly by selection of different antigen peptides, we investigated sequence variants of TAP1 and TAP2 genes in 120 German patients with IDDM and 218 random healthy German controls by polymerase chain reaction (PCR) followed by sequence‐specific oligonucleotide analysis (SSO), single‐strand conformation polymorphism (SSCP) analysis and amplification refractory mutation system (ARMS). TAP1*02011 (16% vs. 4% in controls, P = 0.001, RR = 5.0) and TAP2*0101 (96% vs. 69% in controls, P < 0.0001, RR = 10.6) showed a positive association with IDDM. However, these associations disappeared when patients and controls were matched for predisposing HLA DQA1 or DQB1 alleles as well as for DRB1*0401. In conclusion, our findings indicate that the observed association of TAP variants with IDDM in German patients is due to linkage disequilibrium with HLA DQ alleles/DRB1*04 subtypes.
SEQUENCE OF A NEW HLA‐DR ALLELE, DRB5*0106
Authors: KERVAIRE B. , TIERCY J.‐M.
Published: December 2003

We report here the exon 2 sequence of a new HLA‐DRB5 allele, DRB5*0106, that was identified in two volunteer bone marrow donors from the Swiss national registry. This new allele differs from DRB5*0101 by five amino acids at positions 67, 70, 71, 85 and 86. It is associated with DRB1*1501 and DQB1*0602. This unusual DRB1*1501–DRB5*0106 association increases the complexity of the DR2 group, although it appears to be very rare, at least in our population. HLA‐DRB5*0106 can be readily detected upon DR generic oligotyping, provided the two probes that mark the major DRB5 subtypes, DRB5*0101 and DRB5*02, respectively, are included in the assay.
Systematics of the ITEX species
Authors: MURRAY D.F.
Published: December 2003

ITEX research was begun to develop generalizations on the growth of tundra plants through synthesis of data from distant arctic and alpine sources gathered by strict protocols. Target species have been selected from among widely distributed ones with attention to those without serious unresolved taxonomic problems, since valid comparisons and generalizations rest on data reported consistently from the same species. The consortium of researchers must firmly establish the identity of the experimental subjects to preserve the integrity of the ITEX synthesis. Documentation is possible only when voucher specimens are conserved. Notes on taxonomy and biology are provided as background for 14 primary, five secondary, and three additional candidate ITEX species.
Tundra plants and climate change: the International Tundra Experiment (ITEX)
Authors: HENRY G.H.R. , MOLAU U.
Published: December 2003

The International Tundra Experiment (ITEX) was established in late 1990 at a meeting of arctic tundra ecologists as a response to predictions that the human‐enhanced greenhouse warming would occur earliest and most intensely at high latitudes. The initial objective of ITEX was to monitor phenology, growth and reproduction in major circumpolar vascular plant species in response to climate variations and environmental manipulations at sites throughout the tundra biome. The manipulations involve passive warming of tundra plots in open‐top chambers (OTCs), and manipulating snow depth to alter growing season length. Standard protocols were developed for measurements, experimental design and statistical analyses, and published in an ITEX Manual. The standard methods ensure comparable data are collected at all sites. This special issue of Global Change Biology is based on papers developed from the 6th ITEX Workshop, held at the University of Ottawa, Ottawa, Canada, 7–11 April 1995. The papers compare short‐term responses (1–3 years) of common species to climate variations and manipulations at ITEX sites. The OTCs increase mean near‐surface temperatures by 1–3°C during the growing season, simulating predictions from global circulation models. All species investigated responded to the temperature increase, especially in phenology and reproductive variables. However, these short‐term responses were individualistic, and no general pattern in type or magnitude of response was noted for functional types or phenology class. Responses were generally similar among sites, although the magnitude of response tended to be greater in high Arctic sites. Early snowmelt increased carbon:nutrient ratios in plants. Sustained growth and reproductive responses to warming will depend on nutrient supply, and increased carbon:nutrient ratios in litter could buffer nutrient cycling, and hence plant growth. Ongoing, long‐term research at ITEX sites, linked to other global change initiatives, will help elucidate probable effects of climate change at the ecosystems level in arctic and alpine tundra.
Response to simulated climatic change in an alpine and subarctic pollen‐risk strategist, Silene acaulis
Authors: ALATALO J.M. , TOTLAND Ø.
Published: December 2003

The aim of this study was to test if early flowering species respond with increased seed production to climate warming as is predicted for late‐flowering seed‐risk strategists. Experimental climate warming of about 3°C was applied to two populations of the cushion‐forming plant Silene acaulis (L.) Jacq. The experiment was run at one subarctic site and one alpine site for 2 years and 1 year, respectively, using open‐top chambers (OTC).

The 2‐year temperature enhancement at the subarctic site had a marked effect on the flowering phenology. Cushions inside the OTC started flowering substantially earlier than control cushions. Both the male and female phases developed faster in the OTCs, and maturation of capsules occurred earlier. The cushions also responded positively in reproductive terms and produced more mature seeds and had a higher seed/ovule ratio. After 1 year temperature enhancement at the alpine site there was a weak trend for earlier flowering, but there was no significant difference in seed production or seed/ovule ratio.
Responses of the clonal sedge, Carex bigelowii, to two seasons of simulated climate change
Authors: STENSTRÖM A. , JÓNSDÓTTIR I.S.
Published: December 2003

The effect of enhanced temperature was studied in open‐top chambers on the arctic clonal sedge Carex bigelowii Torr. ex Schwein. at Latnjajaure Field Station, Swedish Lapland for two growing seasons. The flowering phenology of C. bigelowii accelerated during the first field season that the open‐top chambers were erected. After the second season of perturbation the sexual reproductive investment was higher in the open‐top chambers than in the controls and flowering phenology was still accelerated. Leaf phenology and the growth of vegetative tillers followed the same pattern in the open‐top chambers as in the controls, but the leaves were longer in the open‐top chambers from the end of June until the end of August. The results suggest that relatively late flowering clonal graminoids may be favoured by warmer climate, at least in the short term.
Effects of experimental warming on arctic willows (Salix spp.): a comparison of responses from the Canadian High Arctic, Alaskan Arctic, and Swedish Subarctic
Authors: JONES M.H. , BAY C. , NORDENHÄLL U.
Published: December 2003

Three species of dwarf, prostrate willow (Salix arctica, S. rotundifolia and S. herbacea) were subjected to experimental summer warming in high arctic Canada, arctic Alaska, and subarctic Sweden, respectively, as part of the International Tundra Experiment. Phenological and growth responses of these species were compared for the second season of the experiment. Stigmas became receptive and pollen dispersal occurred significantly earlier for S. rotundifolia and S. herbacea in the ITEX open‐top chambers, but not for S. arctica. Warming had no effect on the timing of seed dispersal, leaf yellowing, or leaf senescence. The length and dry weight of the largest leaves were greater for warmed plants, and was significant for S. rotundifolia. The number of catkins/plot did not differ among species or treatments, but the fruit : flower ratio was reduced in the experimental plots.
Open‐top designs for manipulating field temperature in high‐latitude ecosystems
Authors: MARION G.M. , HENRY G.H.R. , FRECKMAN D.W. , JOHNSTONE J. , JONES G. , JONES M.H. , LÉVESQUE E. , MOLAU U. , MØLGAARD P. , PARSONS A.N. , J. SVOBODA  , VIRGINIA R.A.
Published: December 2003

Passive open‐top devices have been proposed as a method to experimentally increase temperature in high‐latitude ecosystems. There is, however, little documentation on the efficacy of these devices. This paper examines the performance of four open‐top chambers for altering temperature at six sites in the Arctic and Antarctica. Most of the heating effect was due to daytime warming above ambient; occasional night‐time cooling below ambient, especially of air temperatures, depressed mean daily temperature. The mean daily temperatures at four arctic sites were generally increased by 1.2–1.8 °C; but occasionally, temperature depressions also occurred. Under optimal conditions at the antarctic site (dry soils, no vegetation, high radiation) mean daily soil temperatures were increased by +2.2 °C (–10 cm) to +5.2 °C (0 cm). Protection from wind may play a more important role than temperature per se in providing a favourable environment for plant growth within open‐top devices. Wind speed had a generally negative impact on mean daily temperature. Daily global radiation was both positively and negatively related to chamber temperature response. The effect of chambers on snow accumulation was variable with the Alexandra Fjord site showing an increased accumulation in chambers but no difference in the date of snowmelt, while at Latnjajaure in a deep snowfall site, snowmelt occurred 1–2 weeks earlier in chambers, potentially increasing the growing season. Selection of a passive temperature‐enhancing system requires balancing the temperature enhancement desired against potential unwanted ecological effects such as chamber overheating and altered light, moisture, and wind. In general, the more closed the temperature‐enhancing system, the higher is the temperature enhancement, but the larger are the unwanted ecological effects. Open‐top chambers alter temperature significantly and minimize most unwanted ecological effects; as a consequence, these chambers are a useful tool for studying the response of high‐latitude ecosystems to warming.
Arctic soils and the ITEX experiment
Authors: MARION G.M. , BOCKHEIM J.G. , BROWN J.
Published: December 2003

The objectives of this paper are broadly to examine arctic soils and specifically to examine soil properties at ITEX sites. The Arctic is dominated by cold, wet, shallow soils often characterized by surficial organic horizons. Seven of 11 soil orders in Soil Taxonomy are present in the circumarctic and alpine zones of the ITEX Project. Soil organic matter is highly correlated to soil carbon (sink or source of atmospheric CO2), soil moisture (surficial energy balance), and soil nitrogen (plant limiting nutrient). Because of these vital roles, soil organic matter is a keystone that will influence the future response of arctic ecosystems to climate change.
Responses to natural climatic variation and experimental warming in two tundra plant species with contrasting life forms: Cassiope tetragona and Ranunculus nivalis
Authors: MOLAU U.
Published: December 2003

Two circumpolar tundra plant species, the evergreen dwarfshrub Cassiope tetragona and the perennial herb Ranunculus nivalis, were studied at Latnjajaure in northern Swedish Lapland during three consecutive growing seasons (1993–95) as a contribution to the ITEX programme. Open‐top chambers (OTCs) were used in a passive heating experiment, and the performance of the plants in unmanipulated controls was correlated with climatic fluctuations among the years. Phenological, vegetative, and reproductive variables were measured. In both species phenological responses were controlled mainly by ambient air temperature. In the evergreen C. tetragona vegetative growth was controlled mainly by the influx of global solar radiation and was not temperature‐dependent, whereas the opposite applied in the herbaceous R. nivalis. Vegetative growth in C. tetragona was rather stable among years as well as between treatments, whereas it was strongly influenced by annual climate in R. nivalis. Both species increased their reproductive success with increasing temperature, but R. nivalis was also radiation‐dependent in this case, probably because of its green, photosynthetic nutlets. Ovule number in R. nivalis increased steadily in the experimentally heated plots during the study in response to the constant temperature amelioration above the ambient. At the community level, evergreen C. tetragona seems to have low competitive ability under warmer conditions. The situation for vernal low‐growing herbs like R. nivalis is more complex; despite a strong positive response to increased temperature, they may exhibit decreased reproductive success if overgrown by a vigorous graminoid canopy.
Response to experimental warming in a population of Papaver radicatum in Greenland
Authors: MØLGAARD P. , CHRISTENSEN K.
Published: December 2003

In an attempt to simulate the effect of a global climatic change, temperature manipulations were carried out in a natural population of Papaver radicatum from a low arctic area on Disko Island, West Greenland. The manipulations were carried out by means of ITEX corners, which are angular plexiglass screens placed around individual plants. The corners were placed with openings towards four directions and different microclimatic conditions were obtained. The corners increase the summer temperature to different degrees in the four directions. In addition they are windscreens and eventually accumulate snow, dependent on the wind directions.

Dataloggers in a set of corners measured temperatures at the end of one growing season and at the beginning of the next. Spring was delayed in all corners due to increased snow cover duration, especially in those facing East and North. Nevertheless, temperatures were increased in the corners during the season, and highest temperature sums were obtained in those facing South and West. No temperature increase was found in the North‐facing corners.

No effect was seen on the plants the first year after application of the ITEX corners. In the second year an increased biomass was observed in corners facing West and South in accordance with the higher temperatures experienced in these directions. In the third biomass year plants in corners facing West decreased and those facing North slightly increased compared to previous years. After 4 years plants in corners facing West, South and East had attained significantly higher biomass than the control plants and the plants in corners facing North.

An earlier onset of flowering was seen in the corners compared to control, and South‐facing corners had more flowers. An early onset of the growth period is an advantage to flowering, more so than increased temperatures during the season. Flowering was prolonged in the corners compared to controls, but there was a higher risk of frost damage to the flowers in the corners.
Exsertion, elongation, and senescence of leaves of Eriophorum vaginatum and Carex bigelowii in Northern Alaska
Authors: SHAVER G.R. , LAUNDRE J.
Published: December 2003

The seasonal patterns of leaf exsertion, elongation, and senescence were described and compared for two of the most abundant graminoid species of Alaskan moist tussock tundra, Eriophorum vaginatum and Carex bigelowii. In addition the responses of both species to NPK fertilizer and to variation in site fertility (water track vs. non‐track areas) were also assayed and compared. The research was done over two full growing seasons at two sites near Toolik Lake, Alaska, where other aspects of the ecology of both species have been the subject of intensive and ongoing research.

Both species showed the typical graminoid pattern of sequential leaf growth, in which the exsertion and elongation of new leaves is coincident with the senescence of old leaves. However, the rates of these processes were much slower and steadier in Eriophorum than in Carex, with much greater overlap in the life histories of individual leaf cohorts. The total and green leaf lengths of whole tillers in Eriophorum were also less variable over the entire year than in Carex. The conclusion is that leaf growth in Carex should depend more on external storage of carbon and nutrients than Eriophorum, with a much greater seasonal variation in demands on storage and retranslocation to and from leaves.

The effects of fertilizer and the water track on leaf growth dynamics and turnover rates were largely nonsignificant, despite major effects on total tiller size and productivity. This is in contrast to previous research on evergreen leaf dynamics, but similar to results of previous research on overall production and biomass regulation in Eriophorum. It is concluded that the graminoid response to increased nutrient availability in the Arctic is to dilute the greater amounts of nutrient uptake by greater growth, so that nearly the same metabolic homeostasis is achieved as under low nutrient availability, but at a higher biomass.
Experimental manipulations of snow‐depth: effects on nutrient content of caribou forage
Authors: WALSH N.E. , McCABE T.R. , WELKER J.M. , PARSONS A.N.
Published: December 2003

We investigated the potential effects of global climate change on arctic tundra vegetation used as caribou forage. A total of 96 experimental plots was established at six sites on the coastal plain of the Arctic National Wildlife Refuge, Alaska, in 1993 and 1994. We erected snow‐fences to increase the amount of snow deposition, and therefore delay the date of the snowmelt on 48 plots (referred to as increased snow/late melting plots). We used black mesh netting on the surface of the snow to increase the rate of melting on 24 plots; the remaining 24 plots served as controls. In July 1994, we collected green leaves from Eriophorum vaginatum, Salix planifolia, and Betula nana and analysed these samples for total carbon and total nitrogen content. Ratios of carbon to nitrogen differed among treatments for all three species. Generally, C:N ratios for B. nana and E. vaginatum on increased snow/late melting plots were lower than on control plots. C:N ratios for S. planifolia on increased snow/late melting plots did not differ from controls, but were lower than on plots which started to melt early. These results may be due to the timing of nitrogen translocation from leaf and stem tissue into storage organs, or due to an increase in available nitrogen input to the system. Further sampling is needed to adequately determine the mechanism responsible for increased nitrogen content of caribou forage in areas with increased amount of snow and delayed snowmelt.
Responses of Dryas octopetala to ITEX environmental manipulations: a synthesis with circumpolar comparisons
Authors: WELKER J.M. , MOLAU U. , PARSONS A.N. , ROBINSON C.H. , WOOKEY P.A.
Published: December 2003

We have examined organismic responses of Dryas octopetala to simulated changes in the summer climate at four tundra sites as part of the International Tundra Experiment (ITEX). Our study sites are located in the High Arctic, on Svalbard, Norway, in the Low Arctic at Abisko, Sweden, and at Toolik Lake, Alaska, USA and our temperate alpine site is at Niwot Ridge, Colorado, USA. These sites represent a range of tundra temperature and precipitation regimes, being generally cold and dry in the High Arctic and warmer and wetter at Toolik Lake and Niwot Ridge. Results from our studies indicate organismic attributes such as flowering shoot length varies by 30% between low and high arctic populations and that experimental warming results in significant increases in shoot height at three of four sites. We find that phenological development of Dryas is accelerated under experimentally warmed conditions which corresponds with a lengthening of the growing season in autumn, greater degrees of seed set and a higher likelihood of colonization of bare ground. We also observe that Dryas dominated ecosystems which are exposed to experimental manipulations are capable of exhibiting net carbon sequestration in late autumn, and that Dryas photosynthesis and green leaf biomass is significantly greater under warmer as opposed to ambient temperature conditions. Dryas leaf nitrogen is also significantly lowered under warmer conditions resulting in senescent leaves having a higher C:N ratio than those under ambient conditions. Together these findings indicate that Dryas phenology and carbon flux may be altered to the greatest degree in spring and again in autumn by higher summer temperatures and that simultaneously both positive and negative feedback effects may result from changes in plant and ecosystem performance.
Response of Saxifraga oppositifolia L. to simulated climate change at three contrasting latitudes
Authors: STENSTRÖM M. , GUGERLI F. , HENRY G.H.R.
Published: December 2003

Saxifraga oppositifolia, a widespread circum‐arctic and alpine plant species, was exposed to increased temperature at three ITEX sites of different latitudes: Val Bercla in the Swiss Alps (46°N), Latnjajaure in mid‐alpine Northern Sweden (68°N), and Alexandra Fjord, Ellesmere Island (79°N) in the Canadian High Arctic. Phenology, growth, and reproduction were monitored for 2 or 3 consecutive years. Increased temperature had little influence on the phenology of S. oppositifolia, although flowering period was somewhat longer and pollination earlier in the experimental plots. A decrease in the density of flowers on each plant was noted at two sites over 3 years, with a slightly larger decrease in the warmed plots. The few changes observed in reproductive variables (e.g. fruit : flower ratio) are mostly assigned to increased shading by taller growing neighbouring plants of other species, thus limiting performance of the shade‐intolerant S. oppositifolia. It is assumed that survival of this species, especially at the lower limits of its altitudinal and latitudinal distribution, will depend on seed dispersal to new, open habitats.
Phenological and growth responses of Papaver radicatum along altitudinal gradients in the Canadian High Arctic
Authors: LÉVESQUE E. , HENRY G.H.R. , SVOBODA J.
Published: December 2003

Phenology and growth of Papaver radicatum Rottb. was monitored over four summers (1990–1993) at 12 sites, along a dolomitic and a granitic altitudinal gradient (330 m a.s.l.–770 m a.s.l.) at Sverdrup Pass, central Ellesmere Island, Canada. The gradients provided substantial differences in environmental characteristics. Three of the four seasons (1990, 1991 and 1993) had more than 400 thawing degree‐days (TDD) in the valley, while the 1992 season had less than 300. The granitic sites had consistently higher temperatures than the dolomitic sites, despite their northerly aspect. Increasing elevation reduced total degree‐day accumulation (c. 40 degree‐days/100 m) and length of potential growing season. The proportion of the population producing flower buds was similar at all sites in any given year, but there were differences among years. Production of flowers and fruits per site, decreased with altitude along the dolomitic gradient in 1991 and 1992. There was no difference in the number of buds or flowers produced per plant with increasing altitude, although larger plants with multiple flowers were found only on low elevation granitic sites. Plants from the dolomitic sites were smaller and flowered, on average, after the site accumulated 150 degree‐days, while plants on the granitic sites were larger and bloomed after 200 degree‐days. Papaver is able to grow and reproduce over a wide range of environmental conditions and moderate climate warming would likely promote its growth and establishment, unless other factors, especially snow‐free periods and water availability, become limiting.
Short‐term effects of simulated environmental change on phenology, leaf traits, and shoot growth of alpine plants on a temperate mountain, northern Japan
Authors: SUZUKI S. , KUDO G.
Published: December 2003

In order to assess the responses of circumpolar and semicircumpolar plants growing around their southern distribution margins to artificial warming, we set up 11 open‐top chambers (OTCs) on a fell‐field (1680 m a.s.l.) in the Taisetsu Mountains, northern Japan. The OTCs increased mean air temperature by 1.3°C through the growing season (June–September) and extended the length of the growing season. We examined phenology and leaf traits of plants in the OTCs and control plots during the first season under artificial warming treatment using two deciduous and three evergreen species. Ledum palustre (evergreen shrub), Vaccinium uliginosum, and Arctous alpinus (deciduous shrubs) showed earlier leaf emergence and/or flowering in the OTCs. Deciduous shrubs had longer individual leaf longevity and an extended foliage period in the OTCs than in the control plots. There were no significant differences in specific leaf area and leaf size for many species between the OTCs and the control plots. Vaccinium vitis‐idaea (evergreen shrub), L. palustre, A. alpinus, and Empetrum nigrum (evergreen shrub) had lower leaf nitrogen concentration in the OTCs than in the control plots, whereas it was higher in V. uliginosum. Only E. nigrum showed larger annual shoot growth in the OTCs. No clear differences in response to the warming effect were detected between evergreen and deciduous species in the first season. Circumpolar plants growing in temperate alpine regions may be more affected by season length rather than temperature itself.