1,721,032 research outputs found
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
A temperature-sensitive strain of Histoplasma capsulatum has an altered Δ9-fatty acid desaturase geneacid desaturase gene
No full textWe have isolated and characterized the Delta(9)-desaturase gene (Ole1), which codes for a key enzyme involved in regulating membrane fluidity in animal cells and microorganisms, from two strains of Histoplasma capsulatum, one that is temperature-tolerant (G217B) and the other temperature-susceptible (Downs). These pathogenic fungi are dimorphic in that they undergo a morphologic transition from the mycelial to yeast-like form when the temperature of incubation is switched from 25 to 37 degrees C or when they infect a susceptible host. The coding sequences of the two genes, both containing an intron of 93 nucteotides, are virtually identical and analogous to the dg-desaturase gene of Saccharomyces cerevisiae and those of the rat, mouse and human. Ole1 transcription of the thermotolerant G217B and thermosensitive Downs strains is similar in yeast phase cells and during the temperature shift down from 34, 37, or 40 to 25 degrees C (yeast-to-mycelia transition). Nevertheless, the Delta(9)-desaturase gene is transcriptionally inactive in mycelia of G217B at 25 degrees C while it is actively transcribed in the Downs strain at the same temperature. These results are in agreement with the finding that membranes of the Downs strain have a higher level of oleic acid. The differential expression of Delta(9)-desaturase genes is discussed in relationship to differences in thermosensitivity in the fungal isolates and in regulating the level of expression of heat shock genes
Renal involvement in adrenal insufficiency (Addison disease): can we always recognize it?
No full textAddison disease is due to the destruction or dysfunction of the entire adrenal cortex. Nowadays, the causes of adrenal insufficiency are autoimmune disease for 70–90% and tuberculosis for 7–20%. Many typical signs and symptoms, such as hyponatremia, hyperkalaemia, or renal insufficiency can represent the reasons for a nephrology consultation, especially in conditions of urgency, and they can easily be confused with other causes. Moreover, the fact that in a short time range we have diagnosed the three cases described as a guide in this review, has aroused our attention as nephrologists on a disease in which we have probably already encountered but without recognizing it. The blood tests showed in all three patients severe electrolyte disorders and acute renal failure which will be discussed in their physiopathogenetic mechanisms. In a peculiar way, these alterations were not controlled with repolarizing solutions, fluid replacement and increased volemia, but only after steroid administration. In conclusion, in this review all the known pathogenic mechanisms causing disorders of nephrological interest in adrenal insufficiency are discussed
Heat shock and cold adaptation in antarctic fishes: a molecular approach
No full text1. 1. The restriction patterns of three different Antarctic fish DNA (P. bernacchi, N. rossi and C. kathleene) have been analysed. 2. 2. The restricted DNAs have been probed for the presence of the heat shock 70 sequence (hsp70) by using the corresponding Drosophila sequence. The three patterns are closely related for the presence of several bands in common, though a closer arrangement for the hsp70 gene is present in P. bernacchi and N. rossi. The analysis with different stringency conditions has also suggested that in these fishes more than one copy of hsp70 per genome is present. 3. 3. Poly-A RNA analysis with Northern blot have shown that the hsp70 gene is transcribed, upon temperature increase, between 5 and 12°C with a maximum of expression at 8°C. © 1988
Heat shock 70 gene is differentially expressed in Histoplasma capsulatum strains with different levels of thermotolerance and pathogenicity
No full textThe response to heat shock has been examined In two strains of the dimorphic pathogenic fungus Histoplasma capsulatum, which differ considerably in thermotolerance and pathogenicity. The gene for the 70 kD heat shock protein (hsp70) was isolated using a Drosophila hsp70 gene to screen a cosmid library of the DNA from the temperature‐sensitive Downs strain (low level of thermotolerance for mice). Using the cloned gene as a probe, we have measured the transcription of the endogenous hsp70 gene at 25°C and in response to temperature shift to 34°, 37° and 40°C, temperatures that trigger the mycelial to yeast phase transition in this fungus. The gene is constitutively transcribed at low levels, both in the yeast and the mycelial stages. Synthesis of hsp70 mRNA was transiently increased 1 to 3 h after the temperature shifts. By Northern analysis, peak levels of transcription were shown to occur at 34°C in the Downs strain and at 37°C in the more pathogenic G222B strain. Our results are consistent with reports in which it has been shown that heat shock gene expression is part of temperature adaptation and probably developmental processes. The low levels of transcription of the hsp70 gene in the Downs strain at 37°C correlate with its greater temperature sensitivity and low level of virulence. Copyright © 1987, Wiley Blackwell. All rights reserve
Temperature- and cyclic nucleotide-induced phase transitions of Histoplasma capsulatum
No full textThe transition from yeast to mycelia of H. capsulatum could be accomplished by shifting the temperature of incubation from 37 to 25°C. It was accompanied by many changes in cellular metabolism, including changes in respiration, intracellular cyclic adenosine 3',5'-monophosphate (cAMP) levels, and activities of two enzymes specific for the yeast phase, cystine reductase (EC 1.6.4.1) and cysteine oxidase (EC 1.13.11.20). Even at 37°C, the yeast to mycelial transition could be induced by cAMP and agents which raise the intracellular levels of cAMP (theophylline, acetylsalicylic acid, prostaglandin E 1, and nerve growth factor). During this morphogenesis the same pattern of changes occurred as in the temperature-induced transition. Therefore, these changes were not simply dependent on a shift in temperatures, but rather were part of the process of the phase transition
Image Analysis Workflow for 2-D Electrophoresis Gels Based on ImageJ
Full text linkA number of commercial software packages are currently available to perform digital two-dimensional electrophoresis
(2D-GE) gel analysis. However, both the high cost of the commercial packages and the unavailability of a standard data analysis
workflow, have prompted several groups to develop freeware systems to perform certain steps of gel analysis. Unfortunately, to the
best of our knowledge none of them offer a package that performs all the steps envisaged in a 2D-GE gel analysis. Here we describe an
ImageJ-based procedure, able to manage all the steps of a 2D-GE gel analysis. ImageJ is a free available image processing and analysis
application developed by National Institutes of Health (NIH) and widely used in different life sciences fields as medical imaging,
microscopy, western blotting and PAGE. Nevertheless no one has yet developed a procedure enabled to compare spots on 2D-GE gels.
We collected all used ImageJ tools in a plug-in that allows us to perform the whole 2D-GE analysis. To test it, we performed a set of
2D-GE experiments on plasma samples from 9 patients victims of acute myocardial infarction and 8 controls, and we compared the
results obtained by our procedure to those obtained using a widely diffuse commercial package, finding similar performances
Incidence of histoplasmin skin test reactivity in Somalia: An epidemiological study
No full textHistoplasmosis is an important systemic mycotic infection with a wide geographic distribution. Its occurrence has been mostly studied in the US (6) and in Central America (6), but very little is known about its distribution in Africa, where a specific variant exists. Skin test surveys in the Democratic Republic of Somali indicate that Histoplasma capsulatum or a closely related agent has a focus in this east African country. © 1987 Martinus Nijhoff/Dr W. Junk Publishers
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