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No full textMorphological, Glycohistochemical, and Immunohistochemical Studies on the Embryonic and Adult Bovine Testis
Get PDFIn the present study, the testes of 32 bovine embryos with different crown-rump length (2.5-
90 cm CRL) and of 15 sexually mature bulls (Deutsches Fleckvieh) were investigated using
light- and electron microscope as well as glycohistochemical and immunohistochemical
methods. The gestation period was divided into 3 stages; early, mid, and late gestation.
Developmental changes in the testicular morphogenesis were therefore analyzed in details
during these phases.
Generally, embryonic development of bovine testis involves the same mechanism described
in other mammals. At the first stage of this study (2.5 cm CRL/43 dpc), the anlage of the
testes protruded to the coelomic cavity as paired bean-shaped structures on either side of the
dorsal mesentery medial to the mesonephros. It consists of primitive testicular cords,
interstitium, and rete testis blastema. Proceeding with fetal age, these basic testicular
structures are further differentiated. The tunica albuginea is separated into two layers: an outer
fibrous layer (tunica fibrosa) with some mesenchymal cells, numerous fibroblast, and much
fibrous content and an inner cellular layer with several blood vessels (tunica vasculosa). The
testicular cords are surrounded by a marked basal lamina and peritubular cells and lined by
two types of cells: a large number of dark polygonal cells with irregular nuclei, pre-Sertoli
cells and small number of large light round cells with relatively round nuclei, the
prespermatogonia. The average number of the germ cells per cross section of cord increases,
particularly form 3.5 to 14 cm CRL, resulting in a germ cell maximum at the end of this stage
(14 cm CRL). Although most of the germ cells are located toward the periphery of the cord,
some are also found in the center. Pre-Sertoli cells form a complete layer at the periphery of
the cords. Generally, these cells are irregular in shape and numerous but considerably smaller
than the germ cells. Unlike prespermatogonia, mitotic figures are seen in pre-Sertoli cells
during the whole embryonic life. As a consequence of the expansion in the interstitium, the
seminiferous cords are progressively separated from each other. The testicular interstitium is
rapidly differentiated and is composed of several islets or clusters of polygonal Leydig cells,
peritubular flattened cells surrounding the testicular cords, connective tissue cells, and
numerous blood vessels. In the present study, fetal Leydig cells were first recognized at 3.5
cm CRL. Thereafter, the average number of these cells is rapidly increased to attain their maximum with the end of the first gestation period (14 cm CRL). This generation of Leydig
cells however dedifferentiates progressively with developmental age. A continuous system of
basal lamina joins the testicular cords with rete strands from 10 cm CRL and onwards. This
system establishes the first connection between these two testicular components via ill-developed uncanalized straight tubules (tubuli recti). Rete testis channels are lined by simple
layer of cuboidal epithelium with round nuclei occupying most of the cytoplasm and enclosed
by well-defined basal lamina.
The adult bovine testis is enclosed by a connective tissue capsule, tunica albuginea, composed
predominantly of collagen fibers and few elastic fibers. Most of the testicular parenchyma is
made up of the convoluted seminiferous tubules (tubuli seminiferi contorti), two-ended
convoluted loops, with both ends opening into the rete testis via specialized terminal
segments. The seminiferous tubules of sexually mature bulls are enclosed by a distinct lamina
propria and are lined by two cell populations, non-proliferating Sertoli cells and highly
proliferating spermatogenic cells. The bovine lamina propria consists of basal lamina,
collagen and elastic fibers, and 3-5 layers of partially overlapping myofibroblasts.
Additionally, fibrocytes, collagen fibrils, and fibroblasts-like cells form the outermost border
of the tubulus. Sertoli cells are easily identifiable elements of the seminiferous epithelium.
Adult Sertoli cells are large irregularly shaped cells with their broad bases resting on the basal
lamina while the remaining cytoplasmic processes extend upward to the tubular lumen. They
are characterized by round or oval euchromatin-rich nuclei situating in the basal portion near
the basal lamina of the seminiferous tubules. Adult bovine germ cells are present in four
morphologically different groups, i.e., spermatogonia, spermatocytes, spermatids, and
spermatozoa. The seminiferous cycle stages are identified using changes in the germ cell
nuclei as well as location and shape of spermatids. According to this method, eight stages are
defined in the seminiferous epithelium of bovine. The interstitial or intertubular tissue of adult
bovine testis consists of Leydig cells, macrophages, scattered lymphocytes and plasma cells,
and contains numerous blood and lymph vessels. Not all Leydig cells have contact to blood or
lymph capillaries.
The excurrent duct system of the adult bovine testis consists of terminal segment of the
convoluted seminiferous tubules, straight tubules, and rete testis. The terminal segment can be
further subdivided into a proximal (transitional) region, middle portion, and distal part
(terminal plug). The proximal region is lined by typical Sertoli cells while the last two parts
are lined by modified Sertoli cells. The tubulus rectus of adult bovine testis is composed of
three morphologically different regions: a proximal cup-shaped region, a middle narrow stalk,
and a distal festooned portion. The rete testis is a complicated centrally positioned meshwork
of intercommunicating channels that lies within the mediastinum testis parallel to the long
axis of epididymis. The simple cuboidal epithelium of straight tubules and rete testis is shown
to contain some lymphocytes and macrophages.
The cellular distribution of glycoconjugates within the fetal and adult bovine testis was
investigated using thirteen (ConA, PSA, LCA, PNA, GSA-I, ECA, DBA, SBA, HPA, VVA,
WGA, UEA-I, LTA) different fluorescein isothiocyanate (FITC) conjugated lectins. In fetal
testes, detection of sugar moieties by lectins was carried out on Bouin õ s-fixed paraffin-embedded sections while in adult it was performed on both Bouin õ s-fixed paraffin-embedded and acetone-fixed frozen sections. Only five lectins (PSA, PNA, GSA-I, DBA, WGA) showed a positive reaction in the embryonic testes. PNA, GSA-I, DBA, and WGA were detected in the germ cells whereas PSA, DBA and WGA labeled the fetal Leydig cells. None of the lectins used was observed in the pre-Sertoli cells. Further on, some lectins were seen in tunica albuginea (PSA, PNA, GSA-I, WGA), basal lamina of testicular cords (PSA, WGA), interstitial blood vessels (PSA, GSA-I, WGA), mediastinum testis (PSA, PNA, WGA) and rete testis epithelium (PNA). In adult animals, spermatogonia and spermatocytes were positively stained with PSA, LCA, DBA, SBA, and VVA. All the lectins investigated except that of the fucose-binding lectin (UEA-I and LTA) were definitely detected in the acrosome of round and elongated spermatids. These results indicate a role for carbohydrates in spermiogenesis. Apical Sertoli cells processes and Leydig cells were weakly stained with
PSA and LCA as well. DBA binding sites were also seen in the Leydig cells.
Immunohistochemical studies were performed using the Avidin-Biotin-Peroxidase Complex
(ABC) method for localization of fibroblast growth factor-1 (FGF-1), fibroblast growth
factor-2 (FGF-2), S-100, laminin, alpha-smooth muscle actin (á -SMA), vascular endothelial
growth factor (VEGF), connexin 43 (Cx43), CD4, CD8, CD68, angiotensin-converting
enzyme (ACE), and galactosyltransferase (GalTase) in the bovine testis. The expression of
FGF-1 and FGF-2 was further investigated in the adult bovine testis using in situ
hybridization and PCR. Immunohistochemically, FGF-1 was seen in the Sertoli cells, Leydig
cells, endothelium of the blood vessels, and epithelium of straight tubules and rete testis of
fetal and adult testis. It was additionally detected in spermatogonia and spermatids of sexual
mature animals. FGF-2 exhibited a striking positive reaction in fetal (from 6 to 30 cm CRL)
and adult Leydig cells. Moreover, it showed marked reaction in the endothelium of blood
vessels and in the epithelium of tubulus rectus and rete testis. FGF-2 was also localized in
some spermatogonia, and myofibroblasts. By means of in situ hybridization, FGF-1 and FGF-2 mRNA were found in Leydig and Sertoli cells as well as in the modified Sertoli cells of the
terminal segment. FGF-1 transcripts were additionally recognized in the straight tubules and
rete testis epithelium. Distinct S100 immunostaining was observed in the Sertoli cells,
endothelium of blood vessels and in the rete testis epithelium of fetal and adult testis. Laminin
was localized to the basal lamina of seminiferous tubules, blood vessels, myofibroblasts, and
rete testis. Although á -SMA was detected in smooth muscle cells of the blood vessels, no
immunoreactivity was seen in the peritubular cells during the whole gestation period. The
myofibroblasts surrounding the seminiferous tubules and rete testis showed intense positive
reaction for á -SMA in the adult testis. VEGF was detected in the acrosomes of the elongating
spermatids. Connexin 43 was localized to gap junctions between Leydig cells in the fetal and
adult life as well as to the seminiferous epithelium apical to spermatogonia and basal to
spermatocytes, a position correlating with Sertoli-Sertoli cell junctions. The detection of cells
positive for CD4, CD8, CD68 within the adult testis interstitium clearly indicate the presence
of lymphocytes and macrophages within this testicular compartment. GalTase showed
striking positive reaction in the Golgi complex of Sertoli cells, Leydig cells, and some
spermatocytes as well as at the cell membrane of elongating spermatids and in the simple
cuboidal epithelium of rete testis. ACE positive reaction was found in the prespermatogonia
(only at 6-10 cm CRL) and in fetal and adult testicular blood vessels. The functional
significance of these immunocytochemically-demonstrated proteins is discussed
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
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