Bern, 17.05.2013 - Das BAFU lehnt den Antrag des Kantons Wallis zur Regulation des Biberbestands im...

Categoria: biologia | Fonte: jagd & natur

Liebe Leserin, lieber Leser Innerhalb weniger Jahre hat das Naturbild der jungen Generation...

Categoria: biologia | Fonte: jagd & natur

Investigators typically study one function of the circadian visual system at a time, be it photoreception, transmission of photic information to the suprachiasmatic nucleus (SCN), light control of rhythm phase, locomotor activity, or gene expression. There are good reasons for such a focused approach, but sometimes it is advantageous to look at the broader picture, asking how all the parts and functions complete the whole. Here, several seemingly disparate functions of the circadian visual system are examined. They share common characteristics with respect to regulation by light and, to the extent known, share a common input neuroanatomy. The argument presented is that the 3 hypothalamically mediated effects of light for which there are the most data, circadian clock phase shifts, suppression of nocturnal locomotion ("negative masking"), and suppression of nocturnal pineal function, are regulated by a common photic input pathway terminating in the SCN. For each, light triggers a relatively fixed interval response that is irradiance-dependent, the effective stimulus can be very brief light exposure, and the response continues to completion in the absence of additional light. The presence of a triggered, fixed-length response interval is of particular importance to the understanding of the circuitry and mechanisms regulating circadian rhythm phase shifts because it implies that the SCN clock response to light is not instantaneous. It also may explain why certain stimuli (neuropeptide Y or novel wheel running) administered many minutes after light exposure are able to block light-induced phase shifts. The understanding of negative masking is complicated by the fact that it can be represented as a positive change, that is, light-induced sleep, not just as a reduction in locomotion. Acute nocturnal light exposure also induces adrenal hormone secretion and a rapid drop in body temperature, physiological responses that appear to be regulated similarly to the other light effects. The likelihood of a common regulatory basis for the several responses suggests that additional light-induced responses will be forthcoming and raises questions about the relationships between light, SCN cellular anatomy, the molecular clockworks of SCN neurons, and SCN throughput mechanisms for regulating disparate downstream activities.

Categoria: biologia | Fonte: journal of biological rhythms

There is little evidence for the involvement of microRNAs (miRs) in the regulation of circadian rhythms, despite the potential relevance of these elements in the posttranscriptional regulation of the clock machinery. The present work aimed to identify miRs targeting circadian genes through a predictive analysis of conserved miRs in mammals. Besides 23 miRs previously associated with circadian rhythms, we found a number of interesting candidate genes, equally predicted by the 3 software programs used, including miR-9, miR-24, miR25, miR-26, miR-27, miR-29, miR-93, miR-211, miR-302, and miR-346. Moreover, several miRs are predicted to be regulated by circadian transcription factors, such as CLOCK/BMAL, DEC2, and REV-ERBalpha. Using real-time PCR we demonstrated that the selected candidate miR-27b showed a daily variation in human leukocytes. This study presents predicted feedback loops for mammalian molecular clock and the first description of an miR with in vivo daily variation in humans.

Categoria: biologia | Fonte: journal of biological rhythms

Hans Hoppeler On 16 December 2012, a group of editors and publishers of scholarly journals gathered together at the Annual Meeting of The American Society for Cell Biology in San Francisco, CA, USA to discuss current issues related to how the quality of research output is evaluated and how the primary scientific literature is cited. The outcome of the meeting and further discussions is a set of recommendations that is referred to as the San Francisco Declaration on Research Assessment, published in May 2013. The Journal of Experimental Biology (JEB) fully supports this initiative. In concordance with the recommendations of the Declaration, JEB provides impact factor alongside a variety of other journal-based metrics, requests an author contribution statement for all Research Articles, places no restrictions on the reuse of reference lists, and has no limitations on the number of references in Research Articles.

Categoria: biologia | Fonte: journal of experimental biology

Hironobu Uchiyama, Hiroko Awata, Michiyo Kinoshita, and Kentaro Arikawa The Northeast-Asian Wood White Leptidea amurensis (Lepidoptera, Pieridae) belongs to Dismorphiinae, a subfamily of the family Pieridae. We here studied the structure of the compound eye in this species through a combination of anatomy, molecular biology and intracellular electrophysiology, with a particular focus on the evolution of butterfly eyes. We found that their eyes consist of three types of ommatidia, with a basic set of one short, one middle and one long wavelength-absorbing visual pigment. The spectral sensitivities of the photoreceptors are rather simple, and peak in the ultraviolet, blue and green wavelength regions. The ommatidia have neither perirhabdomal nor fluorescent pigments, which modulate photoreceptor spectral sensitivities in a number of other butterfly species. These features are primitive, but the eyes of Leptidea exhibit another unique feature: the rough appearance of the ventral two-thirds of the eye. The roughness is due to the irregular distribution of facets of two distinct sizes. As this phenomenon exists only in males, it may represent a newly evolved sex-related feature.

Categoria: biologia | Fonte: journal of experimental biology