Variation in Collar Spine Number of Echinostoma revolutum from the Muskrat

1969 ◽  
Vol 55 (2) ◽  
pp. 380
Author(s):  
George P. Doerksen

1988 ◽  
Vol 18 (2) ◽  
pp. 179-181 ◽  
Author(s):  
Bernard Fried ◽  
Jane E. Huffman ◽  
Jose Franco


1984 ◽  
Vol 62 (7) ◽  
pp. 1329-1339 ◽  
Author(s):  
D. M. Blouw ◽  
D. W. Hagen

The goal of our research is to investigate the adaptive significance of a polymorphism for the number of dorsal spines in Apeltes quadracus, the fourspine stickleback. One approach we take is to search for correlations between phenotypes and environments. To this end we collected Apeltes and scored environments at 570 sites in the Maritime Provinces of Canada. In this paper we describe geographic variation in spine number and evaluate how reliably it reflects genetic differentiation among sites. Morph frequencies are highly differentiated geographically. We describe four kinds of variation: relatively constant frequencies, gentle clines, steep clines, and remarkably abrupt changes (called "intrusions") where frequencies at some sites differ greatly from those at a larger number of surrounding sites. Most of the variation among sites is due to differences in the frequencies of the four- and five-spined morphs. However, a remarkable result is that the three-spined morph, which is rare or absent elsewhere in the range, reaches very high frequencies in Bras D'Or Lake. Our evidence suggests this variation among sites reflects substantial genetic differentiation. The differentiation is favorable for detecting selective agents, if indeed selection is responsible.









1937 ◽  
Vol 23 (4) ◽  
pp. 423 ◽  
Author(s):  
Paul Beaver


1968 ◽  
Vol 54 (5) ◽  
pp. 942 ◽  
Author(s):  
Bernard Fried ◽  
Marshall D. Kramer


2020 ◽  
Vol 382 (1) ◽  
pp. 185-199 ◽  
Author(s):  
Marta Zagrebelsky ◽  
Charlotte Tacke ◽  
Martin Korte

Abstract Dendritic spines are tiny membrane specialization forming the postsynaptic part of most excitatory synapses. They have been suggested to play a crucial role in regulating synaptic transmission during development and in adult learning processes. Changes in their number, size, and shape are correlated with processes of structural synaptic plasticity and learning and memory and also with neurodegenerative diseases, when spines are lost. Thus, their alterations can correlate with neuronal homeostasis, but also with dysfunction in several neurological disorders characterized by cognitive impairment. Therefore, it is important to understand how different stages in the life of a dendritic spine, including formation, maturation, and plasticity, are strictly regulated. In this context, brain-derived neurotrophic factor (BDNF), belonging to the NGF-neurotrophin family, is among the most intensively investigated molecule. This review would like to report the current knowledge regarding the role of BDNF in regulating dendritic spine number, structure, and plasticity concentrating especially on its signaling via its two often functionally antagonistic receptors, TrkB and p75NTR. In addition, we point out a series of open points in which, while the role of BDNF signaling is extremely likely conclusive, evidence is still missing.



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