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1.
Composition of the winter diet, habitat selection and population fluctuations in the mountain hare Lepus timidus were studied in the Värriötunturi fell area, Eastern Finnish Forest Lapland, during the winters 1968/69–1984/85. The three population lows recorded during this 17-year period followed each other at intervals of 4 and 8 years. During the lows the hares occurred only in the most favoured (forest-covered) habitats and in two of them they behaved according to the concept of the refuge theory. The mountain birch Betula pubescens ssp. tortuosa appeared to be the most important, but not the most favoured winter food item. When the population crashed, the proportion of birch in the diet decreased, and was replaced especially by juniper which is one of the secondary food items (and is for this reason often discarded although cut). It is suggested that the quality and/or quantity of the winter food (i.e. winter pastures) are one of the driving forces in the population fluctuation of the mountain hare in this area. 相似文献
2.
Jaakko Lumme Aila Oikarinen Seppo Lakovaara Risto Alatalo 《Journal of insect physiology》1974,20(10):2023-2033
Drosophila littoralis overwinters in the adult stage in a reproductive diapause. During the warm season there are one or two generations in Finland. The diapause appears to be a prolongation of the post-eclosion immaturity of young females. The termination of diapause is controlled by a combination of adequate temperature and sufficiently long photophases. The diapausing status of females is ascertained by inspecting the developmental stage of their ovaries. In laboratory experiments the maturity of ovaries is not closely correlated with the receptivity of females. 相似文献
3.
Summary Conditions were used where the action of porcine pancreatic phospholipase A2 on phospholipids can be followed in the absence of added calcium and the catalytic activity is supported by the calcium brought with the nanomolar enzyme. Therefore, alterations in the enzyme velocity resulting from the presence of spermine or spermidine could be specifically studied using 1-palmitoyl-2-(pyren-1-yl)hexanoyl-sn-glycero-3-phosphocholine (PPHPC) and 1-palmitoyl-2-(pyren-1-yl)hexanoyl-sn-glycero-3-phosphoglycerol (PPHPG) as substrates. Both spermine and spermidine activated the hydrolysis of PPHPG fourfold at polyamine/phospholipid molar ratios of approximately 11 and 121, respectively. Double-reciprocal plots of enzyme activityvs. PPHPG concentration revealed the enhancement to be due to increased apparentV
max while the apparentK
m
was slightly increased. In the presence of 4mm CaCl2 inhibition by polyamines of PPHPG hydrolysis by phospholipase A2 was observed. Using synthetic diamines we could further demonstrate that two primary amino groups are required for the activation. In the absence of exogenous CaCl2 polyamines inhibited the hydrolysis of PPHPC by phospholipase A2. The presence of 4mm CaCl2 reversed this inhibition and a twofold activation was observed at 10 m spermine. The results obtained indicate that the activation of PLA2 by spermine and spermidine is produced at the level of the substrate, PPHPG. This implies the formation of complexes of phosphatidylglycerol and polyamines with defined stoichiometries. 相似文献
4.
Cells from liver, thymus, and spleen of human fetuses at different stages of development were capable of a proliferation response against xenogeneic and allogeneic lymphocytes. The kinetics of fetal responses against rat lymphocytes were identical to those of fetal and adult responses against allogeneic cells. With all of the cell types studied, including adult lymphocytes, allogeneic responses were stronger than xenogeneic. Xenogeneic responses against lymphocytes from rat, mouse, or sheep were stronger than those against lymphocytes from rabbit, chicken, snake, or frog. These results are interpreted to indicate that recognition of foreign lymphocytes by human lymphocytes depends on the phylogenetic position of the species used as a source of stimulating cells. The degree of recognition decreases as the phylogenetic distance increases. Specific elimination of responding cells and restimulation with another cell population was used to study the specificity of proliferation responses against mouse and rat lymphocytes. Responses by prethymic liver cells from human fetuses were not due to the existence of specifically recognizing subpopulations. Thymus and spleen at 16 weeks' gestation contained specific subpopulations capable of differentiating between xenogeneic and allogeneic cells, as well as between xenogeneic cells with different intraspecies histocompatibility patterns. Generation of receptor diversity on T lymphocytes is discussed briefly in the light of these findings. 相似文献
5.
Mart Roosimaa Taavi Põdramägi Lumme Kadaja Arno Ruusalepp Kalju Paju Raivo Puhke Margus Eimre Ehte Orlova Andres Piirsoo Nadežda Peet Frank N. Gellerich Enn Seppet 《Mitochondrion》2013,13(5):399-409
Cardiac energy metabolism with emphasis on mitochondria was addressed in atrial tissue from patients with overload-induced atrial dilation. Structural remodeling of dilated (D) atria manifested as intracellular accumulation of fibrillar aggregates, lipofuscin, signs of myolysis and autophagy. Despite impaired complex I dependent respiration and increased diffusion restriction for ADP, no changes regarding adenylate and creatine kinase occurred. We observed 7-fold overexpression of HK2 gene in D atria with concomitant 2-fold greater activation of mitochondrial oxygen consumption by glucose, which might represent an adaption to increased energy requirements and impaired mitochondrial function by effectively joining glycolysis and oxidative phosphorylation. 相似文献
6.
A single bout of exercise with high mechanical loading induces the expression of Cyr61/CCN1 and CTGF/CCN2 in human skeletal muscle. 总被引:1,自引:0,他引:1
Riikka Kivel? Heikki Kyr?l?inen Harri Sel?nne Paavo V Komi Heikki Kainulainen Veikko Vihko 《Journal of applied physiology》2007,103(4):1395-1401
High mechanical loading was hypothesized to induce the expression of angiogenic and/or lymphangiogenic extracellular matrix (ECM) proteins in skeletal muscle. Eight men performed a strenuous exercise protocol, which consisted of 100 unilateral maximal drop jumps followed by submaximal jumping until exhaustion. Muscle biopsies were taken 30 min and 48 h postexercise from the vastus lateralis muscle and analyzed for the following parameters: mRNA and protein expression of ECM-associated CCN proteins [cysteine-rich angiogenic protein 61 (Cyr61)/CCN1, connective tissue growth factor (CTGF)/CCN2], and mRNA expression of vascular endothelial growth factors (VEGFs) and hypoxia-inducible factor-1alpha. The mRNA expression of Cyr61 and CTGF increased 30 min after the exercise (14- and 2.5-fold, respectively; P < 0.001). Cyr61 remained elevated 48 h postexercise (threefold; P < 0.05). The mRNA levels of VEGF-A, VEGF-B, VEGF-C, VEGF-D, or hypoxia-inducible factor-1alpha did not change significantly at either 30 min or 48 h postexercise; however, the variation between subjects increased markedly in VEGF-A and VEGF-B mRNA. Cyr61 protein levels were higher at both 30 min and 48 h after the exercise compared with the control (P < 0.05). Cyr61 and CTGF proteins were localized to muscle fibers and the surrounding ECM by immunohistochemistry. Fast fibers stained more intensively than slow fibers. In conclusion, mechanical loading induces rapid expression of CCN proteins in human skeletal muscle. This may be one of the early mechanisms involved in skeletal muscle remodeling after exercise, since Cyr61 and CTGF regulate the expression of genes involved in angiogenesis and ECM remodeling. 相似文献
7.
Minna Ruokonen Laura Kvist Tomas Aarvak Juha Markkola Vladimir V. Morozov Ingar J. Øien Eugeny E. Syroechkovsky Jr. Petteri Tolvanen Jaakko Lumme 《Conservation Genetics》2004,5(4):501-512
The lesser white-fronted goose is a sub-Arctic species with a currently fragmented breeding range, which extends from Fennoscandia to easternmost Siberia. The population started to decline at the beginning of the last century and, with a current world population estimate of 25,000 individuals, it is the most threatened of the Palearctic goose species. Of these, only 30–50 pairs breed in Fennoscandia. A fragment of the control region of mtDNA was sequenced from 110 individuals from four breeding, one staging and two wintering areas to study geographic subdivisions and gene flow. Sequences defined 15 mtDNA haplotypes that were assigned to two mtDNA lineages. Both the mtDNA lineages were found from all sampled localities indicating a common ancestry and/or some level of gene flow. Analyses of molecular variance showed significant structuring among populations (
ST 0.220, P < 0.001). The results presented here together with ecological data indicate that the lesser white-fronted goose is fragmented into three distinctive subpopulations, and thus, the conservation status of the species should be reconsidered. 相似文献
8.
Clathrin isoform CHC22, a component of neuromuscular and myotendinous junctions, binds sorting nexin 5 and has increased expression during myogenesis and muscle regeneration
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Towler MC Gleeson PA Hoshino S Rahkila P Manalo V Ohkoshi N Ordahl C Parton RG Brodsky FM 《Molecular biology of the cell》2004,15(7):3181-3195
The muscle isoform of clathrin heavy chain, CHC22, has 85% sequence identity to the ubiquitously expressed CHC17, yet its expression pattern and function appear to be distinct from those of well-characterized clathrin-coated vesicles. In mature muscle CHC22 is preferentially concentrated at neuromuscular and myotendinous junctions, suggesting a role at sarcolemmal contacts with extracellular matrix. During myoblast differentiation, CHC22 expression is increased, initially localized with desmin and nestin and then preferentially segregated to the poles of fused myoblasts. CHC22 expression is also increased in regenerating muscle fibers with the same time course as embryonic myosin, indicating a role in muscle repair. CHC22 binds to sorting nexin 5 through a coiled-coil domain present in both partners, which is absent in CHC17 and coincides with the region on CHC17 that binds the regulatory light-chain subunit. These differential binding data suggest a mechanism for the distinct functions of CHC22 relative to CHC17 in membrane traffic during muscle development, repair, and at neuromuscular and myotendinous junctions. 相似文献
9.
Rudra-Ganguly N Reddy ST Korge P Herschman HR 《The Journal of biological chemistry》2002,277(42):39259-39265
Diesel exhaust particles (DEP) and their organic constituents modulate the immune system and exacerbate allergic airway inflammation. We investigated the role of DEP extract and associated polycyclic aromatic hydrocarbons (PAHs) on prostaglandin synthesis in endotoxin-activated murine macrophages and in mitogen-stimulated fibroblasts. In both macrophages and fibroblasts, DEP extract, phenanthrene, anthracene, phenanthrenequinone, and beta-napthoflavone inhibit prostaglandin production from endogenous arachidonic acid in response to ligand stimulation. However, DEP extract and PAHs do not block ligand induction of cyclooxygenase-2 (COX-2) protein, either in mitogen-stimulated fibroblasts or endotoxin-treated macrophages. Release of total arachidonic acid and total lipid products is not reduced by DEP or PAHs following ligand stimulation of macrophages or fibroblasts. DEP extract and the PAHs inhibit the activity of purified COX-2 enzyme in vitro but do not inhibit COX-1 activity. Thus, DEP and PAHs do not affect ligand-induced COX-2 gene expression, phospholipase activation, or arachidonic acid release in macrophages and fibroblasts but exert their inhibitory effect on prostaglandin production by preferentially blocking COX-2 enzyme activity. 相似文献
10.