344 research outputs found
Feyerabend’s Formative Years. Volume 2. Feyerabend on Logical Empiricism, Bohm & Kuhn
No full textThe authors Matteo Collodel and Eric Oberheim take the reader on a journey through the early life of the famous Austrian philosopher Paul Feyerabend, whose groundbreaking work Against the Method forged new paths in the philosophical understanding of science.
Collodel and Oberheim's book contains the translated correspondence of Feyerabend (1924-1994) with equally influential philosophers and scientists of the time, including Rudolf Carnap, Herbert Feigl, Carl G. Hempel, J.J.C. Smart, David Bohm, and Thomas Kuhn.
This book offers an entirely unique approach to the philosopher Paul Feyerabend. Informative, challenging and profound, it immerses the reader deeply in the mind of a truly revolutionary philosopher of science.
The main focus lies on the explanation of Paul Feyerabend's ideas on logical empiricism and quantum mechanics, which he developed especially in the 1960s. In order to appreciate the celebrated work of the philosopher, it is important to create an understanding of these formative years in Feyerabend's life and work.
Anyone who knows similar discussions, like the paradigm shift of Thomas Kuhn, or has a passion for history, philosophy and science will be fascinated by the works of Paul Feyerabend. As scientists and followers of Feyerabend, Collodel and Oberheim strive to pay respect to the philosopher and to make his work accessible to a whole new generation
In Vitro Effect of Gold or Silver Nanoparticles on Meiotic and Postmeiotic Fractions of Rat Germinal Cells
No full textThe cytotoxicity of Au or Ag nanoparticles (NPs) on rat germinal cells was investigated in vitro. Rat germ cells separated by the STAPUT method in two different populations, pachytene spermatocytes (F5) and round spermatids (F3), were incubated (37°C, 60'-120') with 60 μM, 125 μM, 250 μM and 500 μM of Au/Ag-NPs. Cell viability was assessed with the Eosin Y test. Au or Ag-NPs were investigated with FEG-STEM/EDS and TEM. A dose-dependent effect on the viability of F3 and F5 populations was observed after incubation with Au-NPs or Ag-NPs (P<0.001). A significant decrease in cell viability was observed in F5 fractions compared to F3 fractions (P<0.05), except for the samples treated with 60μM of Au-NPs, and the decrease was also significant in all the samples treated with Ag-NPs compared to those incubated with Au-NPs (P< 0.05). Au-NPs were localized in spermatocytes and spermatids whereas Ag-NPs were undetectable. In conclusion, Au- NPs and Ag-NPs seem to exert a negative effect on rat germ cells, particularly on spermatocytes, that appeared significantly more compromised than spermatids. Further research is needed, mainly to carefully explore the possible genotoxicity of these NPs on germinal cells. © Collodel et al
Three cases of genetic defects affecting sperm tail: a FISH study
No full textSubmicroscopic alterations in the cytoskeletal structure of sperm flagellum are associated with severely reduced or completely absent motility in subfertile or infertile men. Sometimes these alterations can be related to well known genotypic defects when the same anomaly affects the whole sperm population. Transmission electron microscopy (TEM) is the only tool able to specifically characterize the morphological features of genetic sperm defects. In this study, the frequencies of aneuploid and diploid spermatozoa were identified in three patients showing specific flagellar anomalies, each of them affecting the whole sperm population: dysplasia of the fibrous sheath, primary ciliary dyskinesia and absence of fibrous sheath. All these defects were highlighted by TEM. Fluorescence in situ hybridization (FISH) analysis was performed on decondensed sperm nuclei for chromosomes 18, X and Y, highlighting higher diploidies and sex chromosome disomies in cases of dysplasia of the fibrous sheath and primary ciliary dyskinesia, in agreement with other reports. We have also described FISH results in spermatozoa with absence of fibrous sheath. In this case, the only one reported due to the rarity of this defect, the aneuploidies and diploidies were within normal range. These data contribute to the growing evidence that genetic sperm defects of sperm flagella are generally correlated with meiotic segregation derangement. For this reason, genetic counseling is advisable, although all the genes involved and the possible mechanisms of these mutations have not yet been fully characterize
Morphology and meiotic segregation in spermatozoa from men of proven fertility
No full textEstimates of semen parameters are important for defining normal ranges, which are currently established by 1999 World Health Organization guidelines. However, it is well known that semen evaluation is questionable because it is necessary for only 1 sperm to be able to reach and fertilize the oocyte. Spermiogram parameters and sperm morphology, evaluated by transmission electron microscopy (TEM), were performed on semen samples from 25 men of proven fertility. Despite a generally normal sperm concentration, progressive motility was reduced in 9 cases. Sperm characteristics were evaluated with an established technique, and the mean of the percentages of sperm pathologies were confirmed by comparing to previous reports. A comparison of apoptosis and necrosis in the samples, as detected by TEM and an annexin V/propidium iodide assay, was also performed. Fluorescence in situ hybridization was carried out on the same samples using probes for chromosomes 18, X, and Y. The mean value of the frequency of total aneuploidy in the analyzed group was 0.627% (25th percentile = 0.563%; median = 0.625%; 75th percentile = 0.690%). This study of the incidence of disomy and diploidy in spermatozoa from fertile, apparently normal individuals is important for making comparisons with infertile cohorts to determine the real increase of aneuploidy in those cohorts
Promiscuous coupling and involvement of protein kinase C and extracellular signal-regulated kinase 1/2 in the adenosine A1 receptor signalling in mammalian spermatozoa
No full textMammalian spermatozoa require a maturational event after ejaculation that allows them to acquire the capacity for fertilisation. This process occurs spontaneously during the transit through the female reproductive tract where spermatozoa are in contact with micromolar concentrations of adenosine that might act as a capacitative effector. This study shows that the adenosine A1 receptor agonist, 2-chloro-N6-cyclopentyladenosine, can induce capacitation, i.e., the ability to undergo the acrosome reaction and to become fertile. This receptor, already known to be bound to Galpha(i2), is also bound to G(q/11). These G proteins are functional in the signalling pathway elicited by the A1 receptor and correlate with the multiple intracellular events that follow its activation. The use of protein kinase C isoform inhibitors and MEK inhibitors, resulting in the abolition of the biological response to the selective agonist, indicates the involvement of protein kinase C and MEK in its signalling. In agonist-treated spermatozoa an extracellular calcium influx, involvement of alpha and gamma PKC isoforms and transient phosphorylation of ERK1/2 have been observed. Our results, besides showing that adenosine A1 receptor prompts mammalian spermatozoa to undergo the acrosome reaction hence supporting a role for adenosine as agent for fertilisation, show that 2-chloro-N6-cyclopentyladenosine triggers signalling mechanisms that involve both Galpha(i2) and G(q/11), extracellular calcium influx, modulation of classical Ca2+-dependent PCK isoforms and up-regulation of the ERK1/2 phosphorylation
Spermatozoa and chronic treatment with finasteride: a TEM and FISH study
No full textFinasteride is a specific inhibitor of the 5alpha reductase enzyme originally approved for the treatment of benign prostatic hypertrophy and also for the treatment of androgenetic alopecia (AGA) in men at a dose of 1 mg/day. We report on three cases of young men recruited at our Centre for Male Infertility who had used finasteride for five years. Semen quality was investigated by light microscopy to evaluate sperm concentration and motility. Sperm morphology was performed by transmission electron microscope (TEM) and the data were analyzed. The presence of Y microdeletions was investigated by PCR. Meiotic segregation was explored by fluorescence in situ hybridization (FISH). Patient 1 was azoospermic, patients 2 and 3 showed a normal sperm concentration and severely reduced progressive motility. TEM analysis revealed altered sperm morphology consistent with necrosis and FISH data revealed elevated diploidy and sex chromosome disomy frequencies. This examination was repeated 1 year after the men had suspended the use of finasteride, without receiving any other treatment. A recovery of spermatogenetic process was observed. Motility and morphology improved whereas the meiotic pattern did not change presenting elevated diploidy and sex chromosome disomy frequency
Effects of chondroitin sulfate on chondrocytes
No full textA number of in vitro studies have been performed to determine the mode of action of chondroitin sulfate (CS). It has been demonstrated that CS possesses both anabolic effects on cartilage metabolism and anticatabolic properties. In various models of cartilage culture or of isolated chondrocytes, CS has demonstrated the capacity to stimulate the synthesis of proteoglycans (PGs), aggrecanases, and hyaluronic acid at a high‐molecular weight. In the cultures of human osteoarthritic chondrocytes, CS inhibits collagenolytic activity and the synthesis of stromelysin (matrix metalloproteinases‐3) and it counteracts the negative effects of IL‐1β on PG, collagen type 2, and PGE2 synthesis. CS is also able to prevent the apoptosis of chondrocytes induced in vitro by nitric oxide. Additional in vitro experiments have demonstrated that CS interacts with the elastase of human leukocytes and that it determines a partial inhibition of activity. The effects of CS on various mediators of inflammation and the degradation of cartilage can probably be explained based on its capacity to reduce the nuclear translocation of the transcription factor, NF‐ κB, induced by IL‐1β
- …
