1,720,969 research outputs found
Tissue-specific evaluation of suitable reference genes for RT-qPCR in the pond snail, Lymnaea stagnalis
No full textTyrosine hydroxylase messenger RNA corroborates protein localization in the nervous system of the pond snail, Lymnaea stagnalis
No full textCatecholaminergic neurons are abundant in molluscs and are involved in a variety of behaviors such as feeding, respiration, learning, and locomotion. However, previous identification of these neurons has relied almost exclusively on immunohistochemistry using antibodies, which have not been fully validated for use in molluscs. We employed tissue-specific quantitative PCR in adults of Lymnaea stagnalis (a pulmonate gastropod) and whole-mount in situ hybridization in larvae to both quantify and visualize messenger RNA of the catecholamine synthesis enzyme, tyrosine hydroxylase (TH). TH messenger RNA was found to localize primarily in the foot and the central nervous system, with smaller quantities present in the cephalic sensory organs. Additionally, we performed western blots that validated a popular antibody used as a marker for catecholaminergic neurons in molluscs. Taken together, these data indicate that TH messenger RNA is present in the central and peripheral nervous system of L. stagnalis and support the specificity of past immunohistochemical labeling of the TH protein. These findings have potentially broad implications, given the wide range of biological processes that have been studied in L. stagnalis
Ribbed mussel (Geukensia demissa) demographics and interactions with cord grass (Sporobolus alterniflorus) in the southern Gulf of St. Lawrence, Nova Scotia
Full text linkClimate change and sea level rise have impacted coastal plant communities in estuaries of the southern Gulf of St. Lawrence and resulted in conspicuous marsh erosion. The ribbed mussel (Geukensia demissa) has as its primary habitat the lower marsh fringe where it is attached to the rhizomes of the cordgrass Sporobolus alterniflorus. In numerous sites, the salt marsh is eroding, resulting in the death of the cordgrass and thereby a loss of the primary mussel habitat. I investigated population density and mussel size in 16 populations in the southern Gulf of St. Lawrence from Pugwash Harbour in the west to Cheticamp Harbour in the northeast. Population metrics were measured in three marsh elevation zones: (1) a dead, low elevation zone with intact peat but no living Sporobolus shoots, (2) an intermediate zone with low density of living Sporobolus, and (3) a higher elevation, dense zone of Sporobolus. Mussel size was related to position, with the youngest mussels occurring in the intermediate zone and the oldest mussels occurring in the dense zone. Higher mussel density occurred in intermediate zones primarily at the western end of the sampled salt marshes in Nova Scotia. Marshes with extensive dead zones had the oldest mussels and lower population densities. Low mussel density and absence of relatively small mussels, i.e. < 3 cm, occurred at the most degraded marsh sites. I conclude that as sea level rise impacts the lower marsh fringe that populations of the ribbed mussel are becoming less able to recruit and maintain healthy populations. A symbiosis was described in New England in which Geukensia and Sporobolus have a mutualistic interaction. A 12-month long field experiment tested this facultative mutualism at Fox Harbour, where Geukensia is the most abundant in northern Nova Scotia. I found no evidence to support the mutualism and suggest that mussel density at ~100 m-2 may be too low to allow for the mutualism to persist in this region
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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