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991.
Martin Stock und Frank Hofeditz 《Journal of Ornithology》1997,138(4):387-411
Zusammenfassung Der Einfluß von Störreizen auf das Energiebudget von Ringelgänsen wurde im Frühjahr 1991 in zwei Vorland-Salzwiesen des Nationalparks Schleswig-Holsteinisches Wattenmeer vergleichend untersucht. Die Häufigkeit störreizbedingter Reaktionen der Gänse (Störreizhäufigkeit) wurde als Index für die anthropogene Beeinflussung der Gebiete herangezogen. Die Beeinflussung war in Westerhever mit 1,5±0,7 Reaktionen/h signifikant größer als vor dem Norderheverkoog (1,0±0,6 Reaktionen/h). Mit zunehmender Aktivitätszeit wurde in beiden Gebieten im Verlauf des Frühjahres mehr umsetzbare Energie aufgenommen. In Westerhever haben die Gänse im Vergleich zu denen vor dem Norderheverkoog mit Ausnahme des Mai jeweils mehr umsetzbare Energie aufgenommen. Die energetischen Kosten (DEE) der Gänse wurden anhand der Zeit-Energie-Budget Methode und über die gemessene Körpermasseentwicklung von Fänglingen berechnet. Beide Methoden erzielten vergleichbare Ergebnisse; die Unterschiede betrugen je nach Gebiet 0,4 bis 4,5 %. In Westerhever verzeichneten die Gänse im Vergleich zu denen vor dem Norderheverkoog im Monatsmittel höhere energetische Kosten. Aus dem budgetierten Energieüberschuß (E) wurde die theoretisch mögliche Reservestoffanlagerung (Änderung der Körpermasse) der Gänse berechnet. In Westerhever konnten die Gänse im Verlauf des Frühjahres 357 g Körperreserven anlagern. Bei den Gänsen vor dem Norderheverkoog waren es 399 g. Der Unterschied betrug 11,7 %, war aber nicht signifikant. Anhand von Fangdaten ist bekannt, daß Ringelgänse im langjährigen Mittel Körperreserven von 380 bis 400 Gramm anlagern. Die Störreizhäufigkeit des Tages bewirkte eine signifikante Veränderung der Budgetparameter DME und DEE und E auf stündlicher Basis. In Westerhever stieg die Aufnahme an umsetzbarer Energie signifikant mit steigender Störreizhäufigkeit an. Vor dem Norderheverkoog verringerte sich diese jedoch signifikant. Die Energieaufwendungen stiegen in beiden Gebieten signifikant mit steigender Reizhäufigkeit an. Der Überschuß in der Energiebilanz der Gänse in Westerhever war an Tagen mit einer großen Störreizhäufigkeit um 8,7 % gegenüber den Tagen mit einer geringen Reizhäufigkeit verringert. Aufgrund fehlender kompensatorischer Nahrungsaufnahme war der Überschuß bei den Gänsen vor dem Norderheverkoog um maximal 27,5 % vermindert. Die Gänse in Westerhever haben störreizbedingte Zeitverluste bei der Nahrungsaufnahme und erhöhte energetische Kosten durch Verhaltensänderung und eine erhöhte Nahrungsaufnahme pro Zeit kompensiert. Aufgrund physiologischer Zwänge sind sie jedoch in dem stark vom Menschen beeinflußten Gebiet an die Grenzen ihrer Kompensationsmöglichkeit angelangt. Die errechnete Reservestoffanlagerung und auch der Jungvogelanteil im nachfolgenden Herbst waren geringer als bei den Gänsen vor dem Norderheverkoog.
Compensatory limits: energy budgets of Brent Geese,Branta b. bernicla, the influence of human disturbance
The impact of human disturbances on the energy budget of Brent Geese,Branta b. bernicla, during spring migration was investigated in two different salt marsh areas within the national park Schleswig-Holsteinisches Wattenmeer, Germany. We used the frequency of disturbance-related reactions of the birds as an indicator of the anthropogenic influencing of the sites. The disturbance frequency was significantly higher in the Westerhever salt marsh (1,5±0,7 reactions/h) than in the Norderheverkoog area (1,0±0,6 reactions/h). Monthly activity and energy budgets of the birds were calculated from March to May, based on several simultaneous day-round field observations per month. The amount of daily metabolizable energy (DME) was calculated via dropping rate and digestability of the food. The daily energy expenditure (DEE) was calculated by means of the time-energy-budget methods and by calculations, using the bodymass changes of caught birds during spring. With both methods very similar results were obtained; they varied between 0,4 to 4,5 % per areas and month. The daily energy budget (Æ E) was calculated from DEE — DME. Due to an increasing daily activity time from March to Mai the DME increased in both areas. Compared to the Norderheverkoog area the DME of the birds in Westerhever was higher in March and April, and similar in Mai. DEE increased in both areas too and was in all months higher in Westerhever than in Norderheverkoog. The calculated bodymass changes of the birds during spring was 357 g for the birds in Westerhever and 399 g for the birds in Norderheverkoog. Bodymass measures from caught birds revealed a mean mass gain of 380 to 400 g during spring. The daily disturbance frequency caused a significant change in the budget parameters DME, DDE and E on a hourly base. In Westerhever DME/h increased, while in Norderheverkoog DME/h decreased significantly with increasing disturbance frequency. At the same time DEE/h increased in both areas significantly. As a consequence E/h was reduced at days with a high disturbance frequency; in Westerhever by 8,7 % and in Norderheverkoog by 27,5%. In the disturbed area the birds compensated the time-loss during feeding and the higher energetic costs during disturbance-related flights by a change in activity pattern and by an increased food consumption per time unit. Based on physiological constraints the birds reached their compensatory abilities. The calculated bodymass gain and the proportion of young birds in the flocks was reduced in autumn.相似文献
992.
Glucose Transporter (GLUT-4) Is Targeted to Secretory Granules in Rat Atrial Cardiomyocytes 总被引:6,自引:2,他引:4
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Jan W. Slot Gabriella Garruti Sally Martin Viola Oorschot George Posthuma Edward W. Kraegen Ross Laybutt Gatan Thibault David E. James 《The Journal of cell biology》1997,137(6):1243-1254
The insulin-responsive glucose transporter GLUT-4 is found in muscle and fat cells in the transGolgi reticulum (TGR) and in an intracellular tubulovesicular compartment, from where it undergoes insulindependent movement to the cell surface. To examine the relationship between these GLUT-4–containing compartments and the regulated secretory pathway we have localized GLUT-4 in atrial cardiomyocytes. This cell type secretes an antihypertensive hormone, referred to as the atrial natriuretic factor (ANF), in response to elevated blood pressure. We show that GLUT-4 is targeted in the atrial cell to the TGR and a tubulo-vesicular compartment, which is morphologically and functionally indistinguishable from the intracellular GLUT-4 compartment found in other types of myocytes and in fat cells, and in addition to the ANF secretory granules. Forming ANF granules are present throughout all Golgi cisternae but only become GLUT4 positive in the TGR. The inability of cyclohexamide treatment to effect the TGR localization of GLUT-4 indicates that GLUT-4 enters the ANF secretory granules at the TGR via the recycling pathway and not via the biosynthetic pathway. These data suggest that a large proportion of GLUT-4 must recycle via the TGR in insulin-sensitive cells. It will be important to determine if this is the pathway by which the insulin-regulatable tubulo-vesicular compartment is formed. 相似文献
993.
994.
Carol A. Sheppard Peter B. Simpson Alan H. Sharp Frederick C. Nucifora Christopher A. Ross †G. David Lange James T. Russell 《Journal of neurochemistry》1997,68(6):2317-2327
Abstract: We have examined the mechanisms that underlie Ca2+ wave propagation in cultured cortical astrocytes. Norepinephrine evoked Ca2+ waves in astrocytes that began at discrete initiation loci and propagated throughout the cell by regenerative amplification at a number of cellular sites, as shown by very high Ca2+ release rates at these regions. We have hypothesized previously that domains displaying elevated Ca2+ release kinetics in astrocytes may correspond to sites of high inositol 1,4,5-trisphosphate receptor (InsP3 R) density. To examine this possibility, we compared the distribution pattern of endoplasmic reticulum (ER) and InsP3 Rs with Ca2+ release kinetics in subcellular regions during propagation of norepinephrine-evoked waves. 3,3'-Dihexyloxacarbocyanine iodide staining revealed that the ER in astrocytes exists as a meshwork of membranes extending throughout the cells, including fine processes. A specific antibody directed against type 2 InsP3 Rs (InsP3 R2) detected a 260-kDa band in western blotting of astrocyte membranes. Immunocytochemistry using this antibody stained the entire ER system in a punctate, variegated manner. When Ca2+ responses and InsP3 R2 immunofluorescence were compared in the same cell, domains of elevated Ca2+ response kinetics (high amplitude and rapid rate of rise) showed significant positive correlation with high local intensity of InsP3 R2 staining. It appears, therefore, that specializations in the ER responsible for discrete local Ca2+ release sites that support regenerative wave propagation include increased levels of InsP3 R2 expression. 相似文献
995.
996.
Giselle P. Lim Michael J. Russell Michael J. Cullen † Zoltán A. Tökés 《Journal of neurochemistry》1997,68(4):1606-1611
Abstract: We have previously reported that the amount of the neuronal matrix metalloproteinase (MMP) MMP-9, capable of cleaving β-amyloid1–40 predominantly at Leu34 -Met35 , is increased in a latent form in hippocampal specimens from AD patients and have suggested that the lack of activation of this enzyme may contribute to the deposition of β-amyloid in plaques. The current study addresses whether similar matrix proteinases are detectable in amyloid-positive and -negative brain specimens of aged beagles. Using quantitative zymography, three major neutral proteinases with molecular masses of 60, 95, and 280 kDa were readily detected. These enzymes have the characteristics of MMPs because they were inhibited by EDTA and 1,10-phenanthroline, and their activities were restored by addition of both Ca2+ and Zn2+ . The 95- and 280-kDa proteinases cross-reacted with specific monoclonal antibodies to human MMP-9 (gelatinase B; EC 3.4.24.35). Canine MMP-9 was latent because activation by organomercurial treatment resulted in a characteristic decrease in molecular mass. Statistical analysis revealed no difference in the 60-kDa proteinase activity in amyloid-positive and -negative brain specimens. However, significantly increased amounts of latent MMP-9 were observed in amyloid-positive brain specimens ( p ≤ 0.05) compared with amyloid-negative brain specimens. The observations document that changes in MMP-9 expression in amyloid-positive beagle brains are similar to those reported in the human Alzheimer's disease hippocampus and suggest the possibility that insufficient activation of MMP-9 may contribute to β-amyloid accumulation, a hypothesis that needs to be further investigated. 相似文献
997.
Krishnan Bharath S.; Clemens Ron E.; Zintel Trevor A.; Stockwell Martin J.; Gallagher Charles G. 《Journal of applied physiology》1997,83(1):82-88
Krishnan, Bharath S., Ron E. Clemens, Trevor A. Zintel,Martin J. Stockwell, and Charles G. Gallagher. Ventilatory response to helium-oxygen breathing during exercise: effect of airwayanesthesia. J. Appl. Physiol. 83(1):82-88, 1997.The substitution of a normoxic helium mixture(HeO2) for room air (Air) during exercise results in a sustained hyperventilation, which is present evenin the first breath. We hypothesized that this response is dependent onintact airway afferents; if so, airway anesthesia (Anesthesia) shouldaffect this response. Anesthesia was administered to the upper airwaysby topical application and to lower central airways by aerosolinhalation and was confirmed to be effective for over 15 min. Subjectsperformed constant work-rate exercise (CWE) at 69 ± 2 (SE) % maximal work rate on a cycle ergometer on three separate days: twiceafter saline inhalation (days 1 and3) and once after Anesthesia(day 2). CWE commenced after a briefwarm-up, with subjects breathing Air for the first 5 min (Air-1),HeO2 for the next 3 min, and Airagain until the end of CWE (Air-2). The resistance of the breathingcircuit was matched for Air andHeO2. BreathingHeO2 resulted in a small butsignificant increase in minute ventilation(I) anddecrease in alveolar PCO2 in both theSaline (average of 2 saline tests; not significant) and Anesthesiatests. Although Anesthesia had no effect on the sustainedhyperventilatory response to HeO2breathing, theI transientswithin the first six breaths ofHeO2 were significantly attenuatedwith Anesthesia. We conclude that theI response to HeO2 is not simply due to areduction in external tubing resistance and that, in humans, airwayafferents mediate the transient but not the sustained hyperventilatoryresponse to HeO2 breathing duringexercise. 相似文献
998.
Christopher S. Campbell Michael J. Donoghue Bruce G. Baldwin Martin F. Wojciechowski 《American journal of botany》1995,82(7):903-918
We used sequences from both internal transcribed spacers (ITS) and a small portion of the 5.8S gene of nuclear ribosomal DNA (nrDNA) for phylogenetic reconstruction of 19 genera of Maloideae and four potential outgroups from the Rosaceae. Parsimony analyses indicate that Maloideae are not monophyletic; Vauquelinia, which is traditionally placed in Spiraeoideae, and two genera of the Maloideae, Eriobotrya and Rhaphiolepis, form a well-supported clade that is the sister to the remainder of the subfamily. Although our ITS phylogenetic hypothesis is highly resolved, there is considerable homoplasy, and support, as indicated by bootstrap values and decay indices, is relatively weak for all groups except four: Eriobotrya-Rhaphiolepis-Vauquelinia, Crataegus-Mespilus, Amelanchier-Peraphyllum-Malacomeles, and Cydonia-Pseudocydonia. Our DNA sequence data do not support a broad interpretation of Sorbus. Intergeneric hybridization, which is prevalent in Maloideae, occurs between genera that are far removed from one another on our most-parsimonious trees. We infer an overall phylogeny from separate analyses of ITS DNA sequences and recently published morphological and wood anatomical studies of Maloideae and from analyses after pooling these data sets. The four most strongly supported clades of the ITS phylogeny appear in the phylogeny based on pooled data. 相似文献
999.
Mitochondrial DNA sequence evolution in sharks: rates, patterns, and phylogenetic inferences 总被引:8,自引:0,他引:8
Abundant representation of sharks in the fossil record makes this group a
superb system in which to investigate rates and patterns of molecular
evolution and to explore the strengths and weaknesses of phylogenetic
inferences from molecular data. In this report, the molecular evolution of
the cytochrome b gene in sharks is described and the information related to
results from phylogenetic analysis of the data evaluated in the light of a
phylogeny derived independently of the molecular data. Across divergent
lineages of sharks there is evidence for significant substitution rate
variation, departure from compositional equilibrium, and substantial
homoplasy; nevertheless, the signal of evolutionary history is evident in
patterns of shared transversions and amino acid replacements.
相似文献
1000.
There is marked heterogeneity of nucleotide composition in mitochondrial
DNA across divergent animals. Differences in nucleotide composition
presumably reflect differences in directional nucleotide substitution for
A+T or G+C nucleotides. In mitochondrial DNA, there is A+T directional
nucleotide substitution in most (if not all) animals surveyed, and the
magnitude of directional A+T nucleotide substitution differs greatly within
and among groups. Differences in directional nucleotide substitution among
lineages of mammals can be explained by changes in metabolic physiology.
This relationship is thought to be mediated by the effect of oxygen
radicals because these toxic compounds are by-products of aerobic
metabolism and are known mutagens. Association between metabolism and
nucleotide composition provides additional evidence in favor of the
hypothesis that rates and patterns of nucleotide substitution in
mitochondrial DNA can be influenced by factors that impinge on rates of
endogenous DNA damage.
相似文献