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Zusammenfassung 1. Das Tauchen als Methode zur Untersuchung von Plankton und Echostreuschichten wird durch vier Beispiele erläutert: (a) Visuelle Beobachtungen an Wasserschichtungen und Grenzschichten durch Schwimmtaucher. (b) Untersuchung von Echostreuschichten durch Freitaucher, wobei sich ergab, daß angesammeltes biogenes Material in den untersuchten Sprung- beziehungsweise Streuschichten die Schallreflektion nicht beeinflußt. (c) Beobachtung von Großplankton und Feststellung von Planktonund Sestonkonzentrationen beim Tauchen mit dem Bathyscaph. (d) Untersuchung der Tiefenstreuschicht (deep scattering layer) durch Beobachtung der Vertikalwanderung bestimmter Arten des Großplanktons mit den Tauchbooten Bathyscaph und Soucoupe Plongeante. Physonectide Siphonophoren und Myctophiden standen in deutlicher Beziehung zur Tiefenstreuschicht und wurden als Echogeber erkannt.2. Die Möglichkeiten, von Tauchbooten aus quantitative und qualitative Proben von Plankton und auch vom Benthos zu nehmen, sind zur Zeit noch unzureichend. Die Entwicklung entsprechender Geräte für den wahlweisen und mehrfachen Einsatz bei demselben Tauchgang wird empfohlen.
Diving observations on plankton and on scattering layers
Diving techniques are employed as a research tool in plankton investigations carried out in shallow water of the western Baltic Sea. Observations and samplings were made by skin divers on scattering layers corresponding to the discontinuity layers. Biogene materials, sometimes concentrated at the thermocline, are not responsible for this special kind of scattering, but rather discontinuity of salinity and temperature (Lenz 1965). For observations in deep water the use of undersea vehicles is recommended. From the Bathyscaph and the diving saucer, single plankton organisms and plankton concentrations were observed (e. g.Bernard 1958); investigations on the deep scattering layer have shown physonectid siphonophores and myctophids to be scatterers (Barham 1966). The equipment for sampling plankton and benthos from undersea vehicles is poorly developed. We need urgently gear for quantitative and qualitative sampling and for manifold use during single dives, i. e., multiple sampling gear and magazins for storage of samples.相似文献
3.
Circadian variations in melatonin-binding sites in discrete areas of the male rat brain 总被引:2,自引:0,他引:2
The binding of 125I-melatonin to synaptosomes prepared from whole brains of male rats of the CD strain and from the brain, hypothalamus and striatum of male rats of the Sabra-Wistar strain was assessed throughout a 24 h period. The animals were maintained under a daily schedule of 14 h light (05:00-19:00 h) and 10 h darkness. In whole brain preparations the density of binding sites at 18:00 h was higher by about 70% than at 02:00 h with no variations in apparent affinity of the binding sites throughout the daily period. Specific binding of 125I-melatonin was found in both hypothalamus and striatum of the male rat with a distinct diurnal variation in binding site density in the hypothalamus only. The density of 125I-melatonin-binding sites in the hypothalamus was maximal between 10:00 and 18:00 h and dropped sharply after the lights went off. The apparent 125I-melatonin-binding affinities in these regions were constant and very similar to those in whole brain preparations. The daily variations in densities of 125I-melatonin-binding sites in discrete brain areas may represent a diurnal rhythmicity in the responsiveness of the neuroendocrine axis to melatonin. 相似文献
4.
Nava Zisapel Moshe Laudon 《Biochemical and biophysical research communications》1982,104(4):1610-1616
Microdissected slices of rat hypothalamus were incubated with 3H -dopamine and then subjected to two successive sets of electrical field stimulation in a superfusion chamber. Neurotransmitter release was found to be calcium dependent and the amount of release was determined by scintillation counting of the effluent buffer. The release obtained following the first train of stimuli served as an internal reference. The samples were exposed to drugs during the interval between the two sets of stimuli. Using this technique, as well as K+-evoked depolarization, we were able to show that subnanomolar concentrations of melatonin, the hormone secreted from the pineal gland, inhibits dopamine release from hypothalamic slices. The possibility that melatonin modulates neurotransmission in the brain is therefore indicated. 相似文献
5.
The surface properties of spinach chloroplasts, both of intact chloroplasts with surrounding envelope and broken chloroplasts consisting of the inner lamellar system, have been studied by partitioning them between two aqueous phases, especially using counter-current distribution technique. The two-phase system consists of poly(ethyleneglycol), dextran and water. The two polymers are enriched in opposite phases and by binding deoxycholate or palmitate to one of the polymers the affinity of chloroplasts for the corresponding phase is strongly enhanced. The partition of the two classes of chloroplasts, however, is not affected to the same degree and the affinity of the chloroplast envelope for deoxycholate and palmitate is stronger than that of the lamellar system. This has been correlated to the chemical composition of the two types of membranes. By studying the effect of salts on the partition it has been found that the lamellar system bears a larger number of negative charges as compared to the envelope of the intact chloroplast. 相似文献
6.
Jinshu Chi Mats B. Nilsson Hjalmar Laudon Anders Lindroth Jrgen Wallerman Johan E. S. Fransson Natascha Kljun Tomas Lundmark Mikaell Ottosson Lfvenius Matthias Peichl 《Global Change Biology》2020,26(4):2353-2367
The boreal biome exchanges large amounts of carbon (C) and greenhouse gases (GHGs) with the atmosphere and thus significantly affects the global climate. A managed boreal landscape consists of various sinks and sources of carbon dioxide (CO2), methane (CH4), and dissolved organic and inorganic carbon (DOC and DIC) across forests, mires, lakes, and streams. Due to the spatial heterogeneity, large uncertainties exist regarding the net landscape carbon balance (NLCB). In this study, we compiled terrestrial and aquatic fluxes of CO2, CH4, DOC, DIC, and harvested C obtained from tall‐tower eddy covariance measurements, stream monitoring, and remote sensing of biomass stocks for an entire boreal catchment (~68 km2) in Sweden to estimate the NLCB across the land–water–atmosphere continuum. Our results showed that this managed boreal forest landscape was a net C sink (NLCB = 39 g C m?2 year?1) with the landscape–atmosphere CO2 exchange being the dominant component, followed by the C export via harvest and streams. Accounting for the global warming potential of CH4, the landscape was a GHG sink of 237 g CO2‐eq m?2 year?1, thus providing a climate‐cooling effect. The CH4 flux contribution to the annual GHG budget increased from 0.6% during spring to 3.2% during winter. The aquatic C loss was most significant during spring contributing 8% to the annual NLCB. We further found that abiotic controls (e.g., air temperature and incoming radiation) regulated the temporal variability of the NLCB whereas land cover types (e.g., mire vs. forest) and management practices (e.g., clear‐cutting) determined their spatial variability. Our study advocates the need for integrating terrestrial and aquatic fluxes at the landscape scale based on tall‐tower eddy covariance measurements combined with biomass stock and stream monitoring to develop a holistic understanding of the NLCB of managed boreal forest landscapes and to better evaluate their potential for mitigating climate change. 相似文献
7.
Pingping He Xinping Ouyang Shouhong Zhou Weidong Yin Chaoke Tang Moshe Laudon Shaowen Tian 《Hormones and behavior》2013
Previous studies have shown that melatonin is implicated in modulating learning and memory processing. Melatonin also exerts neuroprotective activities against Aβ-induced injury in vitro and in vivo. Neu-P11 (piromelatine, N-(2-(5-methoxy-1H-indol-3-yl)ethyl)-4-oxo-4H-pyran-2-carboxamide) is a novel melatonin (MT1/MT2) receptor agonist and a serotonin 5-HT1A/1D receptor agonist recently developed for the treatment of insomnia. In the present study we firstly investigated whether Neu-P11 and melatonin enhance memory performance in the novel object recognition (NOR) task in rats, and then assessed whether Neu-P11 and melatonin improve neuronal and cognitive impairment in a rat model of Alzheimer' disease (AD) induced by intrahippocampal Aβ(1–42) injection. The results showed that a single morning or afternoon administration of Neu-P11 enhanced object recognition memory measured at 4 or 24 h after training. Melatonin was effective in the memory facilitating effects only when administered in the afternoon. Further results showed that intrahippocampal Aβ(1–42) injection resulted in hippocampal cellular loss, as well as decreased learning ability and memory in the Y maze and NOR tasks in rats. Neu-P11 but not melatonin attenuated cellular loss and cognitive impairment in the rat AD model. The current data suggest that Neu-P11 may serve as a novel agent for the treatment of AD. 相似文献
8.
Jena R. Hickey Janet Nackoney Nathan P. Nibbelink Stephen Blake Aime Bonyenge Sally Coxe Jef Dupain Maurice Emetshu Takeshi Furuichi Falk Grossmann Patrick Guislain John Hart Chie Hashimoto Bernard Ikembelo Omari Ilambu Bila-Isia Inogwabini Innocent Liengola Albert Lotana Lokasola Alain Lushimba Fiona Maisels Joel Masselink Valentin Mbenzo Norbert Mbangia Mulavwa Pascal Naky Nicolas Mwanza Ndunda Pele Nkumu Valentin Omasombo Gay Edwards Reinartz Robert Rose Tetsuya Sakamaki Samantha Strindberg Hiroyuki Takemoto Ashley Vosper Hjalmar S. Kühl 《Biodiversity and Conservation》2013,22(13-14):3085-3104
Habitat loss and hunting threaten bonobos (Pan paniscus), Endangered (IUCN) great apes endemic to lowland rainforests of the Democratic Republic of Congo. Conservation planning requires a current, data-driven, rangewide map of probable bonobo distribution and an understanding of key attributes of areas used by bonobos. We present a rangewide suitability model for bonobos based on a maximum entropy algorithm in which data associated with locations of bonobo nests helped predict suitable conditions across the species’ entire range. We systematically evaluated available biotic and abiotic factors, including a bonobo-specific forest fragmentation layer (forest edge density), and produced a final model revealing the importance of simple threat-based factors in a data poor environment. We confronted the issue of survey bias in presence-only models and devised a novel evaluation approach applicable to other taxa by comparing models built with data from geographically distinct sub-regions that had higher survey effort. The model’s classification accuracy was high (AUC = 0.82). Distance from agriculture and forest edge density best predicted bonobo occurrence with bonobo nests more likely to occur farther from agriculture and in areas of lower edge density. These results suggest that bonobos either avoid areas of higher human activity, fragmented forests, or both, and that humans reduce the effective habitat of bonobos. The model results contribute to an increased understanding of threats to bonobo populations, as well as help identify priority areas for future surveys and determine core bonobo protection areas. 相似文献
9.
Karen?van Eunen Catharina?M.?L.?Volker-Touw Albert?Gerding Aycha?Bleeker Justina?C.?Wolters Willemijn?J.?van Rijt Anne-Claire?M.?F.?Martines Klary?E.?Niezen-Koning Rebecca?M.?Heiner Hjalmar?Permentier Albert?K.?Groen Terry?G.?J.?Derks Barbara?M.?BakkerEmail author 《BMC biology》2016,14(1):107
Background
Defects in genes involved in mitochondrial fatty-acid oxidation (mFAO) reduce the ability of patients to cope with metabolic challenges. mFAO enzymes accept multiple substrates of different chain length, leading to molecular competition among the substrates. Here, we combined computational modeling with quantitative mouse and patient data to investigate whether substrate competition affects pathway robustness in mFAO disorders.Results
First, we used comprehensive biochemical analyses of wild-type mice and mice deficient for medium-chain acyl-CoA dehydrogenase (MCAD) to parameterize a detailed computational model of mFAO. Model simulations predicted that MCAD deficiency would have no effect on the pathway flux at low concentrations of the mFAO substrate palmitoyl-CoA. However, high concentrations of palmitoyl-CoA would induce a decline in flux and an accumulation of intermediate metabolites. We proved computationally that the predicted overload behavior was due to substrate competition in the pathway. Second, to study the clinical relevance of this mechanism, we used patients’ metabolite profiles and generated a humanized version of the computational model. While molecular competition did not affect the plasma metabolite profiles during MCAD deficiency, it was a key factor in explaining the characteristic acylcarnitine profiles of multiple acyl-CoA dehydrogenase deficient patients. The patient-specific computational models allowed us to predict the severity of the disease phenotype, providing a proof of principle for the systems medicine approach.Conclusion
We conclude that substrate competition is at the basis of the physiology seen in patients with mFAO disorders, a finding that may explain why these patients run a risk of a life-threatening metabolic catastrophe.10.
Ammie?K.?KalanEmail author Alex?K.?Piel Roger?Mundry Roman?M.?Wittig Christophe?Boesch Hjalmar?S.?Kühl 《Frontiers in zoology》2016,13(1):34