1,720,956 research outputs found
Effect of Chronic Melatonin Pretreatment on Neural and Behavioral Consequences of Global Ischemia in Male Gerbils
Get PDFMelatonin has been shown to be an effective neuroprotectant against the neural and behavioral consequences of global ischemia in previous research; however, there is little information as to how melatonin may be used as a chronic prophylactic treatment against ischemic injury in male gerbils The current study sought to determine if chronic melatonin treatment (via a time-released subcutaneous pellet) initiated 2 weeks prior to ischemia attenuates ischemia-induced CA1 cell loss, locomotor hyperactivity, and changes in spontaneous alternation. Gerbils were divided into either a sham, placebo-treated, or melatonin-treated ischemic groups. Ischemic groups were subjected to 5-minute bilateral occlusion of the carotid arteries. Global ischemia produced significant neuronal loss in the CA1 and resulted in a significant increase in locomotor hyperactivity. Exploratory and anxiety-like behavior were not affected by global ischemia. Spontaneous alternation behavior was also unaltered. Chronic melatonin treatment did not afford neuronal protection or decrease locomotor hyperactivity. Analysis of the global ischemic injury revealed a high mortality rate and variable injury in the current sample. This is thought to be due to increasing anatomical variability in the gerbil global ischemia model. The low sample size and inconsistent ischemic injury suggest that the insignificant results of the current study are not definitive of chronic melatonin’s pretreatment potential. Future research using larger sample sizes to account for the increasing variability in the gerbil model is encouraged to clarify the chronic prophylactic potential of melatonin
BEHAVIORAL EFFECTS OF CHRONIC RISPERIDONE TREATMENT ON JUVENILE MALE RATS
No full textDespite substantial increases in the use of antipsychotics, there is a lack of literature regarding the long-term effects of early treatment. Some studies have indicated that early administration results in differential alterations to neurotransmission systems, but few studies have been conducted to investigate the long-term behavioral modifications. Therefore, the aim of the current work was to examine the behavioral effects of low dose risperidone (a commonly used antipsychotic) treatment in rodents. Twenty-four male Sprague-Dawley rats were randomly assigned to either a subcutaneously implanted continuous release risperidone treatment (.04 mg/day) or a sham pellet condition. To encompass the peri-adolescent to adolescent time frame (postnatal days 40-60), thought to be important for brain development (Schneider, 2013; Spear, 2000) male rats began risperidone treatment at post-natal day 35. Following a 6-week treatment period, adult rats (Wiley, 2008), were given a battery of behavioral assessments. No significant differences were found between groups in the Open field, Object recognition, Spatial recognition or Morris water maze tasks. Additionally, Y-maze yielded no differences in percentage of spontaneous alternation and alternate arm return patterns. However, significant differences were found between groups in the number of same arm returns, which has been proposed to be indicative of working memory deficits. Since this is likely the first study of its kind using this route of administration, more work needs to be done to determine if early exposure to risperidone may lead to differences in spatial working memory in adulthood. However, these findings seem to indicate that early low dose risperidone treatment does not severely impair behavior in later adulthood
Effect of pinealectomy on the behavioural and neuropathological consequences of chronic hypoperfusion in the rat.
No full textEffect of Melatonin on Neurobehavioral Functioning in Middle-aged Female Rats
Get PDFMiddle-aged female rats were purchased from a reputable breeding center (Charles River). Animals underwent either subcutaneous melatonin pellet implantation or a sham surgery. All rats were then tested on many behavioral tasks (measuring learning and memory). Upon completion of the project, animals were euthanized, and their brains removed and embedded in paraffin for future analyses. Using SPSS (statistical software) the data was analyzed to determine statistical significance.The percentage of Americans over 65 is expected to increase from 56 million to 72 million in 2050. Of importance will be to better understand normal age-related declines in neurocognitive functioning and develop potential interventions that aim to prevent or retard progression to pathological aging (such as Mild Cognitive Impairment or Alzheimer’s disease). Among those diagnosed with these neurodegenerative conditions, women exhibit faster cognitive decline compared to men. Melatonin is an important pineal hormone that not only has chronological properties but has also been found to be a potent neuroprotectant in the brain. Melatonin levels decline with age. Hence, when neurodegenerative conditions are at their peak, melatonin levels are at their lowest. A plethora of animal studies have demonstrated the effectiveness of melatonin in protecting against many central nervous system disorders such as stroke. There is scant information regarding whether melatonin supplementation affects neurobehavioral functioning in normal middle-aged rodents. Hence, the purpose of the present study was to examine whether chronic melatonin administration (50 mg, 90-day pellets implanted s.c.) impacts neurobehavioral functioning in middle-aged (12 months) female rats. Age-matched non-treated middle-aged female rats were also included (sham operated controls). Approximately 44 days following pellet or sham pellet implantation, rats were tested on an open field, object recognition, spatial recognition, Morris Water Maze, and Y-maze task. Melatonin at the dosage used, did not improve spatial or visual memory in middle-aged female rodents. Although melatonin did not affect behavior, further study will need to examine whether melatonin positively affected the brain. Melatonin is known to have neurogenic properties; hence it will be of interest to examine the brain of these animals to determine whether neurogenesis was positively impacted by treatment. As well, older women also show a decline in estrogen with age. Hence, it will be of interest to determine whether combined melatonin and estradiol replacement would affect neurobehavioral functioning
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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