1,720,964 research outputs found
Histological, histochemical, enzyme histochemical and ultrastructural investigations of the testis of Pagogobius martensi between annual breeding seasons
No full textFrom July to March, the testis of the spring-spawning freshwater goby Padogobius martensi is characterized by spermatogonial proliferation. A close correlation exists among type of proliferating spermatogonia, gonado-somatic (IG) profiles and morphological and functional variations of the Leydig cells. The IG reach their minimal levels by the end of summer and increase progressively but modestly during autumn and winter. Declining IG levels are associated with proliferation of primary spermatogonia only, whereas increasing IG levels are associated with predominant proliferation of secondary spermatogonia. Minimal IG levels are reached when the germinal epithelium is formed by a continuum of primary spermatogonia and associated Sertoli cells. The proliferation of secondary spermatogonia begins only at this time. Spermatogenesis in autumn occurs when spermatogonial cysts contain at the most 16 cells and it rarely results in the maturation of several cysts so that the amount of sperm cells produced is either negligible or scarce. A number of degenerating cells are usually present within the spermatogonial and meiotic cysts. Leydig cells are the unique cells that display features of steroidogenic cells: mitochondria with tubular cristae, extensive smooth endoplasmic reticulum (SER), 3ß-hydroxysteroid dehydrogenase (3ß-HSD) and glucose-6-phosphate dehydrogenase (G6PD) activity and sudanophilia. Light and dark Leydig cell varieties are always present. During regression, Leydig cells undergo a marked decrease in SER amount, mitochondrial sizes and number of mitochondrial cristae. In parallel, the 3ß-HSD and G6PD activities and sudanophilia decrease progressively until they become undetectable by the end of regression. In autumn, mitochondria increase in size, reaching sizes similar to those observed at the end of the spawning season in the light cells, but not in the dark cells. The SER, on the contrary, undergoes a modest and irregular increase only in a part of the Leydig cells, mostly of the light type. In parallel, the 3ß-HSD and G6PD activities increase until they become moderately intense by the end of autumn. At the end of winter, the SER is extensive and regularly dilated in both Leydig cell types, whereas mitochondria still have sizes similar to those observed in December. The 3ß-HSD and G6PD activities are strong and sudanophilia is again detectable. Sertoli cells undergo changes in shape and position in relation to the proliferation of primary spermatogonia and the development of cysts. A junction modulation occurs in association with these changes. Sertoli cells also undergo changes indicative of a decrease in activity immediately after spawning (loss of mitochondrial cristae and clarification of the mitochondrial matrix) and of an increase in activity by the end of the regressing phase (darkening of the mitochondrial matrix and increase in mitochondrial cristae, rough endoplasmic reticulum (RER) and free ribosomes). In addition, they are involved in the phagocytosis of degenerating germ cells at all stages of their development. Macrophages are found in the testis interstitium only, where they are usually adjacent to Leydig cells, myoid cells and blood capillaries and do not participate in the phagocytosis of degenerating germ cells. Myoid cells do not undergo ultrastructural changes except for an increase in the amount of heterochromatin by the end of spawning. The meaning of the autumnal spermatogenic wave and the relationships between the development of the germinal epithelium and the changes of the Leydig and Sertoli cells are discussed
Identification and localization of hormone-producing cells in the pituitary of male Padogobius martensi (Pisces, Gobiidae): a histochemical and immunocytochemical study
No full textThe adenohypophysial cell types of the adult male freshwater goby Padogobius martensi were identified and localized using histochemical and immunocytochemical techniques. Lactotropes were arranged in an irregular mass which occupied a major portion of the rostral pars distalis(RPD). Lead haematoxylin (PbH) stained the corticotropes selectively. These cells formed large clusters or islets between the neurohypophysial branches penetrating the RPD and the lactotropes. In addition, few isolated or clustered corticotropes were observed in the proximal pars distalis(PPD). Corticotropes showed a moderate immunoreactivity to synthetic anti-human adrenocorticotropic hormone 1–24 but a strong immunoreactivity with antiserum to human α-melanocyte-stimulating hormone, which so far has not been observed in any other teleosts. Of the two mouse monoclonal antibodies to the human thyrotropin β subunit used, one failed to bind the thyrotropes, while the other stained selectively but very weakly cells in the dorsal-anterior part of the proximal pars distalis(PPD) indicating that thyrotropes were probably located in this region. Somatotropes were arranged mainly in a multicellular layer bordering the neurohypophysial processes penetrating the PPD, but some were isolated throughout the PPD. The antiserum to rainbow trout Oncorhynchus mykiss gonadotropin I β subunit bound to gonadotropes located in the central and ventral part of the PPD, and along the external periphery of the pars intermedia(PI). The cells reacting to the antiserum to rainbow trout gonadotropin II β subunit largely showed the same distribution as gonadotropes I, but some were also found isolated or in small clusters between somatolactotropes and melanotropes at the interface PI/neurohypophysis (NH) and throughout the PI, as well as intermingled with thyrotropes in the dorsal-anterior part of the PPD, and with lactotropes and corticotropes in the RPD. These results indicate the presence of two types of both gonadotropins and gonadotropes in P. martensi, but do not exclude some degree of gonadotropin I and gonadotropin II colocalization in the same cells. A distribution of gonadotropes II throughout the adenohypophysis similar to that found in P. martensi has not yet been observed in other teleosts; it suggests the possibility of local interactions between these cells and all the other adenohypophysial cell types. The PI contained somatolactotropes, which were distributed along the neurohypophysial border, and melanotropes which were arranged in clusters mostly located further away from the neural tissue. Melanotropes did not react to PbH and showed positive immunostaining to both anti-human ACTH 1–24 and anti-human α-MSH
Anatomical study of the effect of cooking on differently pigmented rice varieties
Get PDFIn recent years, the consumption of wholemeal rice, and in particular pigmented varieties, has received increased interest because of its content in nutritionally relevant compounds. However, thermal treatment can modify the structure of the matrix, influencing the accessibility and possibly the localization of antioxidants and other compounds. Therefore, in this study the effect of two different cooking methods (i.e. ‘‘risotto’’ and boiling) on the anatomical structure of three differently pigmented wholemeal rice varieties was evaluated. The presence and the localization of tannin inclusions were also analyzed. Cooking caused the formation of voids in the grains and, in particular, black rice presented the highest proportion of voids among the varieties analyzed. After both thermal treatments, a significant increase in the tannin inclusions in endosperm was observed, suggesting a partial resorption of the leached compounds. These observations suggest that an evaluation of the anatomical structure may help to better understand the behavior of cereals during domestic cooking, which in turn, affects their nutritional quality also in terms of compound accessibility
N,N'-bis-(2,3-methylenedioxyphenyl)urea and N,N'-bis-(3,4-methylenedioxyphenyl)urea enhance adventitious rooting in Pinus radiata and affect expression of genes induced during adventitious rooting in the presence of exogenous auxin
No full textWe have analyzed the effect of N,N′-bis-(2,3-methylenedioxyphenyl)urea (2,3-MDPU) and N,N′-bis-(3,4-methylenedioxyphenyl)urea (3,4-MDPU), two symmetrically substituted diphenylurea derivatives with no auxin or cytokinin-like activity, on the rooting capacity of Pinus radiata stem cuttings. Results indicate that both diphenylurea derivatives enhance adventitious rooting in the presence of exogenous auxin (indole-3-butyric acid, IBA), even at low auxin concentration, in rooting-competent cuttings, but have no effect on the adventitious rooting of low or null competent-to-root cuttings. Histological analyses show that, in the simultaneous presence of MDPUs and low concentration of exogenous auxin, adventitious root formation is induced in the cell types that retain intrinsic competence to form adventitious roots in response to auxin. The time course of cellular events leading to root formation and the time of root emergence are closely similar to that observed in cuttings treated only with higher auxin concentration. In addition, the mRNA level of a P. radiata SCARECROW-LIKE gene, which is significantly induced in the presence of the optimal concentration (10 μM) of exogenous auxin needed for cuttings to root, is increased in the presence of MDPUs and low concentration of exogenous auxin (1 μM). The expression of a P. radiata SHORT-ROOT gene in rooting-competent cuttings during adventitious rooting is also affected by the presence of MDPUs when combined with auxin. As MDPUs do not affect the expression of either gene in the absence of exogenous auxin, but only in its presence, we suggest that MDPUs could interact, directly or indirectly, with the auxin-signalling pathways in rooting-competent cuttings during adventitious rooting
Visualizing the relevance of bacterial blue- and red-light receptors during plant-pathogen interaction
Get PDFThe foliar pathogen Pseudomonas syringae pv.
tomato DC3000 (Pst) leads to consistent losses in
tomato crops, urging to multiply investigations
on the physiological bases for its infectiveness. As
other P. syringae pathovars, Pst is equipped with
photoreceptors for blue and red light, mimicking the
photosensing ability of host plants. In this work
we have investigated Pst strains lacking the
genes for a blue-light sensing protein (PstLOV),
for a bacteriophytochrome (PstBph1) or for hemeoxygenase-
1. When grown in culturing medium, all
deletion mutants presented a larger growth than wildtype
(WT) Pst under all other light conditions, with the
exception of blue light which, under our experimental
conditions (photon fluence rate = 40 mol m−2 s−1),
completely suppressed the growth of the deletion
mutants. Each of the knockout mutants shows
stronger virulence towards Arabidopsis thaliana than
PstWT, as evidenced by macroscopic damages in the
host tissues of infected leaves. Mutated bacteria
were also identified in districts distant from the
infection site using scanning electron microscopy.
These results underscore the importance of Pst
photoreceptors in responding to environmental light
inputs and the partial protective role that they exert
towards host plants during infection, diminishing
virulence and invasiveness
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
Adventitious rooting adjuvant activity of 1,3-di(benzo[d]oxazol-5-yl) urea and 1,3-di(benzo[d]oxazol-6-yl)urea: new insights and perspectives
No full textHere we report new insights on the adventitious
rooting adjuvant activity of 1,3-di(benzo[d]oxazol-5-
yl)urea (5-BDPU) and 1,3-di(benzo[d]oxazol-6-yl)urea (6-
BDPU), both symmetrically substituted urea derivatives
that do not show either auxin- or cytokinin-like activity per
se. Our data demonstrate that these synthetic molecules
enhance adventitious rooting in distantly-related herbaceous
and woody species, in the presence of endogenous or
exogenous auxin. For the first time, we report that BDPUs
enhance adventitious rooting in the presence of either
indole-3-butyric acid (IBA) or 1-naphtalene acetic acid and
that their optimal concentration depends on the strength of
the exogenous auxin. Trying to understand the mode of
action of BDPUs, we also show that their adventitious
rooting adjuvant activity correlates with high mRNA levels
of auxin-responsive genes related to the adventitious
rooting process at the very early stages of adventitious
rooting, before the activation of cell divisions in pine
hypocotyls cuttings. The high mRNA levels are measured
in the presence of low auxin concentrations and BDPUs.
The mRNA levels quantified in these conditions are similar
to those measured in the presence of high auxin concentrations
but in the absence of BDPUs. In addition, the
spatial distribution of endogenous auxin is localized in
globular-shaped structures of cell divisions located centrifugal
to the resin canals, at the positions of adventitious
root formation, in the presence of urea derivatives and IBA
after 6 days of the root induction process
- …
