1,720,973 research outputs found
The transfer of phosphatidylserine from rat brain microsomes to mitochondria is regulated by microsomal lipid pattern
No full textWe label the phosphatidylserine of rat brain microsomes through the base-ex-
". change reaction and study the export of this lipid to mitochondria in a reconstituted
system. We fuse microsomes to liposomes to vary the lipid composition
of donor membranes and investigate the effect of membrane lipid pattern
on phosphatidylserine movement.
The specific radioactivity of the phosphatidylserine transferred to mitochondria
is higher than that of microsomal phosphatidylserine. This finding supports
the hypothesis that the lipid is compartmented in microsomes and that
the radioactive, newly synthesized phosphatidylserine is much better exported
than the bulk of microsomal phospholipid. The transfer of phosphatidylserine
from microsomes, where it forms through the base-exchange reaction,
to mitochondria, where it decarboxylates to phosphatidylethanolamine,
is enhanced by phosphatidylserine itself, and by other lipid classes.
This is proposed as a part of a possible mechanism for regulating phosphatidylserine
metabolism in the brain
Erectile dysfunction and NO: variations of NO penile blood levels before and after sildenafil treatment
No full textErectile dysfunctions are not uncommon, especially in patients suffering from metabolic syndrome and from a number of circulatory and psychiatric problems. cGMP diesterase inhibitors, such as sildenafil, have proven to be beneficial in the treatment of many such conditions. Our patients, all of them complaining of erectile dysfunction, were treated with sildenafil (50 mg, thrice a week for 6 weeks). All patients reported beneficial effects and were not clinically distinguishable (interview and Doppler scores). We sampled blood for systemic circulation (cubital vein) and from penis (corpora cavernosa) before and after prolonged sildenafil treatment, and measured nitrate (+nitrite) levels in plasma and in red blood cells (RBCs). Hemoglobin is a powerful catalyst of NO oxidation to nitrate, and we thought that nitrate in RBC might be a more sensitive parameter than plasma nitrate. We found that the ratio of penile vs systemic blood plasma nitrate was similar in all patients before or after sildenafil treatment. On the other hand, the same parameter measured in RBC showed that, at the beginning of treatment, patients could be divided into two groups: one with a high ratio and the other with a low ratio. Therefore, clinically similar patients could be biochemically divided into two populations. The difference disappeared after treatment, thus hinting at a curative effect of the drug. The mechanisms underlying this behavior are still unknown and the clinical implication of two populations that can be distinguished by RBC nitrate is yet to be evaluated
Transport of phosphatidylserine from microsmes to the inner mitochondrial membrane in brain tissue
No full textPhosphatidylserine was labeled by incubating rat
brain homogenates with [3-I4C]serine in the presence of
Ca2+ (base-exchange conditions). Some labeled phosphatidylethanolamine
also forms, in spite of the inhibition of
Ca" on phosphatidylserine decarboxylase. Phosphatidylserine
labeling and decarboxylation also occur on incubating
a mixture of purified mitochondria and microsomes,
suggesting that no soluble factors are necessary for the synthesis
and the decarboxylation of phosphatidylserine. Ca2+
favors the transfer of phosphatidylserine from microsomes
(where it forms) to mitochondria (where it is decarboxylated).
The specific radioactivity of the phosphatidylserine
transferred to mitochondria is higher than that of microsoma1
phosphatidylserine. This finding supports the hypothesis
that the lipid is compartmentalized in microsomes
and that radioactive, newly synthesized phosphatidylserine
is much better exported than the bulk of microsomal phospholipid.
Key Words: Phosphatidylserine-Base-exchange
reactions-Phosphatidylserine decarboxylase-Mitochondria-
Microsomes-Brain. Corazzi L. et al. Transport of
phosphatidylserine from microsomes to the inner mitochondrial
membrane in brain tissue. J. Neurochem. 60,50-
56 (1 993)
Erectile dysfunction and NO: variations of NO penile blood levels before and after sildenafil treatment
No full textErectile dysfunctions are not uncommon, especially in patients suffering from metabolic syndrome and from a number of circulatory and psychiatric problems. cGMP diesterase inhibitors, such as sildenafil, have proven to be beneficial in the treatment of many such conditions. Our patients, all of them complaining of erectile dysfunction, were treated with sildenafil (50 mg, thrice a week for 6 weeks). All patients reported beneficial effects and were not clinically distinguishable (interview and Doppler scores). We sampled blood for systemic circulation (cubital vein) and from penis (corpora cavernosa) before and after prolonged sildenafil treatment, and measured nitrate (nitrite) levels in plasma and in red blood cells (RBCs). Hemoglobin is a powerful catalyst of NO oxidation to nitrate, and we thought that nitrate in RBC might be a more sensitive parameter than plasma nitrate. We found that the ratio of penile vs systemic blood plasma nitrate was similar in all patients before or after sildenafil treatment. On the other hand, the same parameter measured in RBC showed that, at the beginning of treatment, patients could be divided into two groups: one with a high ratio and the other with a low ratio. Therefore, clinically similar patients could be biochemically divided into two populations. The difference disappeared after treatment, thus hinting at a curative effect of the drug. The mechanisms underlying this behavior are still unknown and the clinical implication of two populations that can be distinguished by RBC nitrate is yet to be evaluated. © 2009 Nature Publishing Group
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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