1,721,066 research outputs found
alpha Latrotoxin of black widow spider venom binds to a specific receptor coupled to phosphoinositide breakdown in PC12 cells
No full textalpha Latrotoxin of black widow spider is known to bind with high affinity to surface sites of rat pheochromocytoma (PC12) cells, thereby causing depolarization, calcium influx and massive neurotransmitter release. We show here that the toxin causes the accumulation of inositol phosphates, the products of phosphoinositide breakdown. Inositol 1,4,5, trisphosphate was predominantly accumulated shortly after toxin application. Phosphoinositide breakdown appears to be a direct consequence of toxin binding because high K+ and ionophores (which induce depolarization, calcium influx and transmitter release by different mechanisms) were without such effect. Phosphoinositide breakdown is known as an event coupled to the activation of receptors of various hormones and transmitters. We suggest therefore that the alpha latrotoxin binding site is a receptor coupled across the membrane to the phosphoinositide hydrolysing system
Serum, bradykinin and vasopressin stimulate release of inositol phosphates from human fibroblasts
No full textThe mitogens serum, vasopressin and bradykinin stimulate a significant rise in the inositol phosphate content of cultured human fibroblasts within 10 seconds, while serum- and bradykinin-stimulated arachidonic acid release does not occur until after 30 seconds. The release of inositol phosphates is not secondary to a rise in Ca activity since the Ca ionophore ionomycin does not stimulate release of inositol phosphates. Moreover, we show that phospholipase C in human fibroblasts is activated by these mitogens at resting Ca levels since TMB-8, which blocks the mitogen-induced rise in Ca activity, does not affect the serum-stimulated accumulation of inositol phosphates
Inhibition of inositol phosphate production is a late, Ca2+-dependent effect of D2 dopaminergic receptor activation in rat lactotroph cells
No full textThe effect of dopamine, working through the activation of D2 receptors, on inositol phosphate production induced by thyrotropin-releasing hormone (TRH) was investigated in rat pituitary lactotroph cells. Dopamine (10 microM) did not modify the initial rapid stimulation of inositol 1,4,5-triphosphate and inositol bisphosphate observed within the first 15 s after TRH addition, but progressively inhibited the later inositol phosphate production induced by the neurohormone. This kinetics of inhibition was independent of dopamine preincubation time (from 2 to 10 min). The effect was still visible when dopamine was added after TRH. It was sensitive to pertussis toxin, was unchanged by increasing cellular cAMP levels with 8-Br-cAMP, but was greatly affected by treatments that modify the cytosolic free Ca2+ concentration. Specifically, the dopamine-induced inhibition was prevented by treatment of the cells with the Ca2+ ionophore ionomycin (100-200 nM) and was mimicked either by withdrawal of Ca2+ from the incubation medium or by blockade of voltage-gated Ca2+ channels with verapamil. The dopamine treatment did not decrease the cellular levels of the various phosphoinositides, strongly suggesting that the inhibition of inositol phosphate production is not due to precursor depletion. In isolated membranes, however, dopamine was unable to counteract the inositol phosphate accumulation triggered by TRH. Taken together, the data indicate that inhibition of inositol phosphate production is not a primary event triggered by D2 receptor activation, but is a late consequence, due to the previously demonstrated (Malgaroli, A., Vallar, L., Reza Elahi, F., Pozzan, T., Spada, A., and Meldolesi, J. (1987) J. Biol. Chem. 262, 13920-13927) inhibition by dopamine of the prolonged cytosolic free Ca2+ concentration increase induced by TRH via the activation of voltage-gated Ca2+ channels. These results are inconsistent with the possibility of a direct inhibitory coupling of D2 receptors to phospholipase C in rat pituitary lactotroph cells
Protein kinase C-mediated feed back inhibition of the Ca2+ response at the EGF receptor
No full textActivation of the EGF receptor in A431 cells induces the hydrolysis of phosphoinositides and a transient rise of the cytosolic Ca2+ concentration, [Ca2+]i, which are completely inhibited by acute pretreatment with activators of protein kinase C, such as phorbol esters. Down regulation of the enzyme (by long-term pretreatment of the cells with phorbol esters) causes the [Ca2+]i response to EGF to increase in magnitude and, especially, to become much more persistent (average t1/2 of [Ca2+]i decline 9 min with respect to 2.3 min in controls). These results demonstrate that the activation of protein kinase C induced by EGF in intact A431 cells is sufficient to trigger a feed back, autolimitative regulation of the EGF receptor that might play a prominent physiological role in the definition of the mitogenic activity of the growth factor
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
PEER LEARNING TO DEVELOP STUDENT’S SKILLS, SHARE KNOWLEDGE AND 5553 FOSTER A SENSE OF COMMUNITY IN UNDERGRADUATE DESIGN STUDIOS
No full textThe study examines different peer learning methods and strategies implemented in two courses of the Design School of the Politecnico di Milano to increase student involvement and collaboration during the training activities. The paper aims to highlight the different activities and results obtained during the design studios to show some strategies specifically conceived to encourage students to cooperate, provide knowledge sharing and help build a sense of community.
The experiment took place with two different types of students, during the course in full presence mode, after the interruptions due to the covid-19. The interruptions alienated students and, in some cases, made it more difficult for class members to get to know each other and to collaborate with different groups, affecting the importance of peer learning to develop students' skills in communication, critical thinking, and self-confidence.
The experimentation took place with two types of students with different needs and backgrounds:
Experiment 1: Second-year students of the Master's Degree in Interior and Spatial Design of Politecnico di Milano, within the design studio named "Contest Design Studio". The class was composed of international students, mainly working together for the first time, who attended the first year partly remotely.
Experiment 2: First-year students of the Bachelor's Degree in Interior Design of Politecnico di Milano, within the design studio named "Elementi Visivi del Progetto". The class comprised national students who had already worked together in small groups during the first semester, partly remotely. The majority met physically for the first time during the course.
The topics the two design studios addressed are different, while the structure is similar; in both cases, the courses envisage the development of a project and consist of: lectures held by the various professors of the course, talks held by guests, guided tours and extracurricular experiences, classroom review of the projects carried out by groups, with four students each.
During the first phase of the course, more time is dedicated to frontal and theoretical lessons. In contrast, the second phase focuses on the project and the revisions, a tool to increase the student's skills and put the acquired theoretical knowledge into practice.
The revision is an essential moment of growth and learning; unfortunately, students are increasingly reluctant to participate in the revisions of other groups, the last two years of distance learning have made collaboration more complex, and students often consider revisions as private moments in which the single group meets with the teacher's team.
The paper aims to illustrate the various activities that have led to positive results demonstrating favourable aspects of peer learning, including increased confidence and competence.
Students belonging to different groups collaborated; after the first difficulties encountered, students proved to be proactive in finding ways for project debate through peer-to-peer review, and being able to expand their design and comparing abilities, also increasing the sense of belonging to the class, weakened by previous events
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
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