| 131. |
- Shefferson, Richard P., et al.
(författare)
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Drivers of vegetative dormancy across herbaceous perennial plant species
- 2018
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Ingår i: Ecology Letters. - : WILEY. - 1461-023X .- 1461-0248. ; 21:5, s. 724-733
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Tidskriftsartikel (refereegranskat)abstract
- Vegetative dormancy, that is the temporary absence of aboveground growth for 1year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.
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| 132. |
- Soininen, E.M., et al.
(författare)
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Location of studies and evidence of effects of herbivory on Arctic vegetation: a systematic map
- 2021
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Ingår i: Environmental Evidence. - : BioMed Central (BMC). - 2047-2382. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Herbivores modify the structure and function of tundra ecosystems. Understanding their impacts is necessary to assess the responses of these ecosystems to ongoing environmental changes. However, the effects of herbivores on plants and ecosystem structure and function vary across the Arctic. Strong spatial variation in herbivore effects implies that the results of individual studies on herbivory depend on local conditions, i.e., their ecological context. An important first step in assessing whether generalizable conclusions can be produced is to identify the existing studies and assess how well they cover the underlying environmental conditions across the Arctic. This systematic map aims to identify the ecological contexts in which herbivore impacts on vegetation have been studied in the Arctic. Specifically, the primary question of the systematic map was: “What evidence exists on the effects of herbivores on Arctic vegetation?”.Methods: We used a published systematic map protocol to identify studies addressing the effects of herbivores on Arctic vegetation. We conducted searches for relevant literature in online databases, search engines and specialist websites. Literature was screened to identify eligible studies, defined as reporting primary data on herbivore impacts on Arctic plants and plant communities. We extracted information on variables that describe the ecological context of the studies, from the studies themselves and from geospatial data. We synthesized the findings narratively and created a Shiny App where the coded data are searchable and variables can be visually explored.Review findings: We identified 309 relevant articles with 662 studies (representing different ecological contexts or datasets within the same article). These studies addressed vertebrate herbivory seven times more often than invertebrate herbivory. Geographically, the largest cluster of studies was in Northern Fennoscandia. Warmer and wetter parts of the Arctic had the largest representation, as did coastal areas and areas where the increase in temperature has been moderate. In contrast, studies spanned the full range of ecological context variables describing Arctic vertebrate herbivore diversity and human population density and impact.Conclusions: The current evidence base might not be sufficient to understand the effects of herbivores on Arctic vegetation throughout the region, as we identified clear biases in the distribution of herbivore studies in the Arctic and a limited evidence base on invertebrate herbivory. In particular, the overrepresentation of studies in areas with moderate increases in temperature prevents robust generalizations about the effects of herbivores under different climatic scenarios.
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| 133. |
- Sun, MW, et al.
(författare)
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Haplotype structures and large-scale association testing of the 5 ' AMP-activated protein kinase genes PRK4A2, PRKAB1, and PRK4B1 with type 2 diabetes
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 55:3, s. 849-855
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Tidskriftsartikel (refereegranskat)abstract
- AMP-activated protein kinase (AMPK) is a key molecular regulator of cellular metabolism, and its activity is induced by both metformin and thiazolidinedione antidiabetic medications. It has therefore been proposed both as a putative agent in the pathophysiology of type 2 diabetes and as a valid target for therapeutic intervention. Thus, the genes that encode the various AMPK subunits are intriguing candidates for the inherited basis of type 2 diabetes. We therefore set out to test for the association of common variants in the genes that encode three selected AMPK subunits with type 2 diabetes and related phenotypes. Of the seven genes that encode AMPK isoforms, we initially chose PRKAA2, PRKAB1, and PRKAB2 because of their higher prior probability of association with type 2 diabetes, based on previous reports of genetic linkage, functional molecular studies, expression patterns, and pharmacological evidence. We determined their haplotype structure, selected a subset of tag single nucleotide polymorphisms that comprehensively capture the extent of common genetic variation in these genes, and genotyped them in family-based and case/control samples comprising 4,206 individuals. Analysis of single-marker and multi-marker tests revealed no association with type 2 diabetes, fasting plasma glucose, or insulin sensitivity. Several nominal associations of variants in PRKAA2 and PRKAB1 with BMI appear to be consistent with statistical noise.
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| 134. |
- Suviolahti, E, et al.
(författare)
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The SLC6A14 gene shows evidence of association with obesity
- 2003
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Ingår i: Journal of Clinical Investigation. - 0021-9738. ; 112:11, s. 1762-1772
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Tidskriftsartikel (refereegranskat)abstract
- In our previous genome-wide scan of Finnish nuclear families, obesity was linked to chromosome Xq24. Here we analyzed this 15-Mb region by genotyping 9 microsatellite markers and 36 single nucleotide polyp morphisms (SNPs) for 11 positional and functional candidate genes in an extended sample of 218 obese Finnish sibling pairs (sibpairs) (BMI > 30 kg/m(2)). Evidence of linkage emerged mainly from the obese male sibpairs, suggesting a gender-specific effect for the underlying gene. By constructing haplotypes among the obese male sibpairs, we restricted the region from 15 Mb to 4 Mb, between markers DXS8088 and DXS8067. Regional functional candidate genes were tested for association in an initial sample of 117 cases and 182 controls. Significant evidence was observed for association for an SNP in the 3'-untranslated region of the solute carrier family 6 member 14 (SLC6A14) gene (P = 0.0002) and for SNP haplotypes of the SLC6A14 gene (P = 0.0007-0.006). Furthermore, an independent replication study sample of 837 cases and 968 controls from Finland and Sweden also showed significant differences in allele frequencies between obese and non-obese individuals (P = 0.003). The SLC6A14 gene is an interesting novel candidate for obesity because it encodes an amino acid transporter, which potentially regulates tryptophan availability for serotonin synthesis and thus possibly affects appetite control.
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| 135. |
- Tedersoo, Leho, et al.
(författare)
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Global patterns in endemicity and vulnerability of soil fungi.
- 2022
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Ingår i: Global change biology. - : Wiley. - 1365-2486 .- 1354-1013. ; 28:22, s. 6696-6710
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Tidskriftsartikel (refereegranskat)abstract
- Fungi are highly diverse organisms, which provide multiple ecosystem services. However, compared with charismatic animals and plants, the distribution patterns and conservation needs of fungi have been little explored. Here, we examined endemicity patterns, global change vulnerability and conservation priority areas for functional groups of soil fungi based on six global surveys using a high-resolution, long-read metabarcoding approach. We found that the endemicity of all fungi and most functional groups peaks in tropical habitats, including Amazonia, Yucatan, West-Central Africa, Sri Lanka, and New Caledonia, with a negligible island effect compared with plants and animals. We also found that fungi are predominantly vulnerable to drought, heat and land-cover change, particularly in dry tropical regions with high human population density. Fungal conservation areas of highest priority include herbaceous wetlands, tropical forests, and woodlands. We stress that more attention should be focused on the conservation of fungi, especially root symbiotic arbuscular mycorrhizal and ectomycorrhizal fungi in tropical regions as well as unicellular early-diverging groups and macrofungi in general. Given the low overlap between the endemicity of fungi and macroorganisms, but high conservation needs in both groups, detailed analyses on distribution and conservation requirements are warranted for other microorganisms and soil organisms.
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| 136. |
- Thorén, Magnus, et al.
(författare)
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Resource availability affects investment in carnivory in Drosera rotundifolia
- 2003
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 159:2, s. 507-511
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Tidskriftsartikel (refereegranskat)abstract
- Carnivory in plants is restricted to nutrient-poor and open habitats presumably because of high benefits and/or low costs of carnivory in these conditions. Carnivory is costly because the plants need specific adaptations to capture prey. Drosera rotundifolia produces sticky substances on its leaf surface to catch prey. These substances are primarily carbon-based, and their production can be expected to be lower in shade. The benefit of carnivory is in terms of the increased nutritional gain which will be low when inorganic nutrients are available in the growth medium. We expected that investment in carnivory would be lower in shade and nutrient-rich conditions. A factorial experiment involving shading and the addition of inorganic nutrients confirmed these predictions in the carnivorous, perennial herb D. rotundifolia . Plants growing in shade or in media with nutrients added had less sticky leaves and had reduced their investment in carnivory. Interestingly, the observed changes in the stickiness of the leaves were in accord with the carbon/nutrient balance theory, whereas a carbon-based secondary compound, 7-methyljuglone, in the leaves did not respond to shading or nutrient addition.
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| 137. |
- Tripathy, Devjit, et al.
(författare)
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Familiality of metabolic abnormalities is dependent upon age at onset and phenotype of the type 2 diabetic proband.
- 2003
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Ingår i: American Journal of Physiology: Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 285:6, s. 1297-1303
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Tidskriftsartikel (refereegranskat)abstract
- To determine the impact of a family history of the common form of type 2 diabetes and the phenotype of the proband on anthropometric and metabolic variables in normoglycemic first degree relatives, we studied 2100 first degree relatives of patients with the common form of type 2 diabetes (FH+) and 388 subjects without a family history of diabetes (FH-). All subjects participated in an oral glucose tolerance test to allow measurement of insulin secretion (30min incremental insulin /glucose, I/G 30), and insulin sensitivity (HOMA insulin resistance). A subset participated in a euglycemic clamp (n=75) and an intravenous glucose tolerance test (n=300). To study the effect of a particular phenotype of the proband, insulin secretion and sensitivity were also compared between first degree relatives of diabetic probands with high and low waist to hip ratio (WHR) and probands with early and late onset of diabetes. FH+ subjects were more insulin resistant as seen from higher HOMA-IR index (P=0.007) and lower rate of insulin-stimulated glucose uptake (P=0.001) and had more features of the metabolic syndrome (P=0.02, P=0.0002) compared with FH- subjects. Insulin secretion adjusted for insulin resistance (disposition index, DI) was also lower in the FH+ vs FH- subjects (P=0.04). Relatives of diabetic probands with a high WHR had reduced insulin mediated glucose uptake compared with relatives of probands with a low WHR (P = 0.04). Relatives of diabetic patients with age at onset < 44 years had higher HOMA IR (P < 0.005) and lower DI (P < 0.005) than relatives of patients with age at onset >65 yrs (highest quartile). We conclude that early age at onset of type 2 diabetes and abdominal obesity have a significant influence on the metabolic phenotype in the non-diabetic firstdegree relative
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| 138. |
- Tripathy, Devjit, et al.
(författare)
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Importance of obtaining independent measures of insulin secretion and insulin sensitivity during the same test - Results with the Botnia clamp
- 2003
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Ingår i: Diabetes Care. - 1935-5548. ; 26:5, s. 1395-1401
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE - To validate and apply a method for independent assessment of insulin secretion and insulin sensitivity (S-l) during file same test that is, an intravenous glucose tolerance test followed by a euglycemic-hyperinsulinemic clamp, also called the Botnia clamp. This test was then applied to nondiabetic subjects with (FH+)and without (FH-) a first-degree family history of diabetes. RESEARCH DESIGN AND METHODS - The Botnia clamp measures the first-phase insulin response (FPIR) to 0.3g/k, glucose i.v. and insulin sensitivity (NI-value) front a 2-h euglycemic clamp begun 60 ruin alter the glucose bolus. The W-value obtained during the Botnia clamp was compared With M-values obtained during a regular euglycemic clamp without prior glucose bolus. Repeated tests were performed in random order in subjects with normal and abnormal glucose tolerance, Finally, the test was applied to subjects with and without a family history of type 2 diabetes. RESULTS - S-l and insulin secretion from this test showed a high degree of reproducibility, and the M-value obtained with the Botnia clamp correlated strongly,with the M-value from a euglycemic clamp without prior glucose bolus (r - 0.953, P < 0.005). FH+ subjects showed decreased S-l (P = 0.02), hut similar FPIR, compared with FH- subjects, However, insulin Secretion adjusted for file degree of insulin resistance was significantly impaired (P = 0.04). CONCLUSIONS - In conclusion, the Botnia clamp provides reliable and independent measures of S-l and beta-cell function during, the same test. As illustrated above, knowledge of the degree of S-l is mandatory When presenting data on insulin secretion.
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| 139. |
- Tuomi, T, et al.
(författare)
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Improved prandial glucose control with lower risk of hypoglycemia with nateglinide than with glibenclamide in patients with maturity-onset diabetes of the young type 3
- 2006
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Ingår i: Diabetes Care. - : American Diabetes Association. - 1935-5548 .- 0149-5992. ; 29:2, s. 189-194
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE - To study the effect of the short-acting insulin secretagogue nateglinide in patients with maturity-onset diabetes of the young type 3 (MODY3), which is characterized by a defective insulin response to glucose and hypersensitivity to sulfonylureas. RESEARCH DESIGN AND METHODS - We compared the acute effect of nateglinide, glibenclamide, and placebo on prandial plasma glucose and serum insulin, C-peptide, and glucagon excursions in 15 patients with MODY3. After an overnight fast, they received on three randomized occasions placebo, 1.25 mg glibenclamide, or 30 mg nateglinide before a standard 450-kcal test meal and light bicycle exercise for 30 min Starting 140 min after the ingestion of the first test drug. RESULTS - insulin peaked earlier after nateglinide than after glibenclamide or placebo (median [interquartile range] time 70 [50] vs. 110 [20] vs. 110 [30] min, P = 0.0002 and P = 0.0025, respectively). Consequently, compared with glibenclamide and placebo, the peak plasma glucose (P = 0.031 and P < 0.0001) and incremental glucose areas under curve during the first 140 min of the test (P = 0.041 and P < 0.0001) remained lower after nateglinide. The improved prandial glucose control with nateglinide was achieved with a lower peak insulin concentration than after glibenclamide (47.0 [26.0] vs. 80.4 [71.7] mU/l; P = 0.023). Exercise did not induce hypoglycemia after nateglinide or placebo, but after glibenclamide six patients experienced symptomatic hypoglycemia and three had to interrupt the test. CONCLUSIONS - A low dose of nateglinide prevents the acute postprandial rise in glucose more efficiently than glibenclamide and with less stimulation of peak insulin concentrations and less hypoglycemic symptoms.
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| 140. |
- Tuominen, M., et al.
(författare)
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Nature and occurrence of defects in 6H-SiC Lely crystals
- 2001
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 225:1, s. 23-33
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Tidskriftsartikel (refereegranskat)abstract
- Synchrotron white beam topography has been applied to study defects in 6H-SiC platelets grown by the Lely method. In addition, high resolution X-ray diffraction, chemical etching, capacitance-voltage and photoluminescence measurements were carried out to confirm and complement the topography results. The occurrence of structural defects such as various misorientations, dislocations, stacking faults and precipitates are classified into grown-in and post-growth defects. The results are related to the assumed growth process of the differently shaped platelets. © 2001 Published by Elsevier Science B.V.
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