2,478 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
No full textIn 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
Visualizing the relevance of bacterial blue- and red-light receptors during plant-pathogen interaction
No full textThe 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
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
Pseudomonas syringae pv. tomato bacteriophytochromes downregulate bacterial motility and infectivity during plant-pathogen interaction
No full textThe foliar hemibiotrophic pathogen Pseudomonas syringae pv. tomato DC3000 (Pst) leads to consistent losses in tomato crops and this urges to multiply the researches on the physiological bases of its infectiveness. It has been already demonstrated that light perception plays a crucial role in many physiological processes, even in nonphototrophic organisms. Pst is equipped with red/far-red (R/FR) light sensing bacteriophytochromes (BphP), binding biliverdin as chromophore and mimicking the photosensing ability of host plants. Here we report the study of the effect of different light conditions on the swarming motility of mutant strains of P. syringae lacking of the photosensory Bphy1 or Bphy2 or both proteins or heme-oxygenase-1 (HO) catalysing formation of bilins, respectively, as regards to the wild type (WT). Each of the mutants shows stronger virulence than PstWT evidenced by the macroscopic damages caused in the infected leaves of tomato plants. Moreover, they rapidly move inside the infected plants, as necrotic spots in host tissues distant from the infection site appear faster than that due to the WT infection. These results indicate that bacteriophytochromes downregulate bacterial infectivity and invasiveness within the infected leaves and underscore the importance of Pst photoreceptors in responding to environmental light inputs
Education and Training in St.Lucia: A Partially Annotated Bibliography
No full textThis bibliography on “Education and Training in St. Lucia” has been specifically prepared for the UWI School of Continuing Studies’ St. Lucia Country Conference. An attempt has been made to be as comprehensive as possible, but because of the weak bibliographical coverage of the literature of the region, important items may have been omitted. This is especially true for policy documents emanating from official sources. It covers all aspects of education and training in St.Lucia including distance education, educational finance,health and family life education and educational reform
Columbus Square, St. Lucia
No full textLandscape, black & white, 4 x 6 in.No. 18.
Columbus Square, St. Lucia.
Columbus Square, St. Lucia, located in the heart of the capital city, Castries was formerly the site of the Place D’Armes, which was renamed Promenade Square before being renamed the Columbus Square. The Square is currently named after a St. Lucian author Derek Walcott. This spot also pays respect to residents who lost their lives in battle.
On the Postcard; “Columbus Square, St. Lucia.” people can be seen congregating in the Square under the trees.
Information at the back of the Post Card:
Union Postale Universelle
Sarah Cameron, 2013. Footprint Focus. St Lucia & Dominica with Fort-de-France
The language of the cataloguer (part 1). The author
No full textThe paper analyses the evolution of the language of cataloguing, focusing on the concept of authorship. It evaluates cataloguing principles, rules and theory, from Cutter to ICP 2016, in order to study the modification of the idea of author in cataloguing and the emerging importance of non-authorial responsibilities as access points for the organization of catalogues
The causes and the effects of the deficiency in the Pre-Legislative and Legislative scrutiny processes in St. Lucia
No full textThis dissertation argues that there is a significant deficiency in the pre-legislative and legislative scrutiny processes in St. Lucia, caused by the failure of Parliament to utilize the Standing Orders in the manner in which they were intended and develop and follow a more systematic scrutiny process. The author explains how this has hindered St. Lucia’s ability to gain more benefit from the legislative process and improve the quality of legislation produced with less likelihood of amendments
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