Discrimination of LH, FSH, TSH and ACTH in dissociated porcine anterior pituitary cells by light and electron microscope immunocytochemistry

MiR-7 Mediates the Zearalenone Signaling Pathway Regulating FSH Synthesis and Secretion by Targeting FOS in Female Pigs

Zearalenone (ZEA) acts as an environmental endocrine disruptor (EED) to cause health detriments. miRNAs were reported to influence the synthesis and secretion of pituitary hormones. However, the interactions between ZEA and miRNAs and related mechanisms remain unclear. The aims of this study were to determine whether and how miR-7 affects animal reproduction by its interactions with ZEA in the pig pituitary, which is sensitive to ZEA and has been used as an important animal model in medical research. Expressions of miRNA were detected by real-time PCR, in situ hybridization, and immunohistochemistry. The effects of ZEA, miR-7, and their interactions in the pituitary gland were identified by using an ovariectomized pig model, transfecting miR-7 mimics and inhibitor, radioimmunoassay, luciferase reporter assay, and Western blotting. The ZEA dosage was 7.5 mg/kg body weight in vivo and 1 μM in vitro. Our results demonstrate miR-7 acts to regulate gonadotropin synthesis and secretion. Furthermore, we found that ZEA leads to reproductive defects by enhancing miR-7 expression, which subsequently inhibits FSH synthesis and secretion. In vitro and in vivo experiments revealed that the effects of ZEA rely on G protein-coupled estrogen receptor 1, and miR-7 functions by mediating ZEA signaling pathway and targeting the Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog (FOS) gene. These findings show that miRNAs are key intrinsic factors regulating pituitary gonadotropins by mediating EED signaling in pituitary glands, and the actions of miRNAs and EEDs should be seriously considered in related studies about medical practice and animal production.

Social dominance in tilapia is associated with gonadotroph hyperplasia

Tilapias are emerging as one of the most important fish in worldwide aquaculture and are also widely used as model fish in the study of reproduction and behavior. During the reproductive season, male tilapia are highly territorial and form spawning pits in which the dominant males court and spawn with available females. Non-territorial males stand a much lower chance of reproducing. Using transgenic tilapia in which follicle stimulating hormone (FSH) gonadotrophs were fluorescently labeled with enhanced green fluorescent protein (EGFP), we studied the effect of social dominance on the hormonal profile and pituitary cell populations in dominant and non-dominant males. Immunofluorescence studies showed that FSH-EGFP-transgenic fish reliably express EGFP in FSH-secreting cells. EGFP expression pattern differed from that of luteinizing hormone. Dominant males had larger gonads as well as higher levels of androgens and gonadotropins in the plasma. Pituitaries of dominant males exhibited higher gonadotropin content and gene expression. Flow cytometry revealed pituitary hyperplasia as well as FSH cell hyperplasia and increased granulation. Taken together, these findings suggest that gonadotroph hyperplasia as well as increased production by individual cells underlie the increased reproductive activity of dominant tilapia males.

Amplification methods for the immunolocalization of rare molecules in cells and tissues

The needs to precisely assign macromolecules to specific locations and domains within tissues and cells and to reveal antigens which are present in low or even in trace amounts, led to the elaboration of a wide spectrum of immunocytochemical amplification procedures. These arise from the successive improvements of tissue preparation techniques, of antigen retrieval procedures and of immunological or non-immunological detection systems. Improvement of detection systems may be the most active in the development of amplification techniques. Since the early work of Coons, in which by the introduction of the indirect technique has started amplifying the signal, different systems have succeeded in increasing the sensitivity of antigens detection. Indeed, amplification techniques such as the multiple antibody layers, the multiple bridges, the enzyme complexes, the avidin-biotin, the silver intensification, and the numerous variations and combinations among these have increased the sensitivity for the detection of scarce tissue antigens. However, as shown by the recent progress carried out with new approaches such as the catalyzed reporter deposition (CARD) and the enhanced polymer one-step staining (EPOS), more efficient methods are still needed. In electron microscopy, few techniques have reached the resolution afforded by the post-embedding immunogold approach. In spite of this and in order to further increase its sensitivity, new probes and novel approaches are allowing combination of the gold marker with the amplification capacity of enzymes afforded by the CARD technique. Immunogold amplification strategies, such as the multiple incubations with the primary antibody and the use of an anti-protein A antibody have also led to enhanced signals displaying the advantages in terms of resolution and possibilities of quantification inherent to the colloidal gold marker.

A morphometric analysis of the subcellular distribution of LH beta and FSH beta in secretory granules in the pituitary gonadotrophs of the frog (Rana japonica)

Immunohistochemical localization of lutropin beta (LH beta) and follitropin beta (FSH beta) in the pituitary gland of the frog Rana japonica was studied by the peroxidase-anti-peroxidase method and the two-face, double-labeling method with different-sized gold particles at the light- and electron-microscopic levels, respectively, using monoclonal antibodies against bullfrog LH beta and FSH beta. Light-microscopic immunohistochemistry indicated that approximately 66.0% of all the gonadotrophs in the pituitary contained both LH beta and FSH beta, whereas 33.4% of gonadotrophs contained only LH beta, and 0.6% contained only FSH beta. The staining intensity of LH beta and FSH beta varied from cell to cell. The gonadotrophs were classified into four types (Types I-IV) in terms of their ultrastructural and immunolabeling characteristics. Moreover, several secretory granule types were recognized according to differences in their shape and electron density. In all the cell types, both LH beta and FSH beta were often seen in the same secretory granules, but the proportion of granules bearing both hormones ranged from 5.5% in Type I to 32.7% in Type IV. Most secretory granules in Types I and II were immunolabeled with LH beta alone, whereas a small number of granules were immunolabeled with FSH beta alone. More immunolabeled FSH beta granules were present in Types III and IV than in Types I and II.

Hormonal storage patterns and morphological heterogeneity of porcine gonadotrope cells during postnatal development

Previous reports indicate that gonadotrope cells of the porcine pituitary gland can be separated into three subpopulations of low- (1.049 g/cm3), middle- (1.062 g/cm3) and high- (1.087 g/cm3) density in a continuous Percoll density gradient. The aim of this work was to study the hormonal storage patterns and morphological features of these subpopulations at three representative ages of the postnatal development: neonatals (30-day-old animals), prepubertals (5-6-month-old animals) and matures (16-18-month-old animals). The low-density subpopulation, present at the three ages studied, was mainly composed of bihormonal LH/FSH cells in neonatal and monohormonal LH cells in prepubertal and mature animals. On the other hand, middle- (only present in prepubertal and mature animals) and high-density subpopulations (only present in neonatal and prepubertal animals) were mainly composed of bihormonal LH/FSH gonadotropes. In ultrastructural terms, these subpopulations exhibit a correlation between density and morphology irrespective of the animal's age. The low-density subpopulation was composed of poorly granulated cells with highly developed biosynthetic machinery (rough endoplasmic reticulum and Golgi complex), while high-density cells were of opposite morphology, with a highly granulated cytoplasm and poorly developed rough endoplasmic reticulum and Golgi complex. The middle-density subpopulation was composed of poorly granulated cells with scarcely developed biosynthetic machinery. In conclusion, these results indicate that porcine gonadotrope cells during postnatal development are composed of three subpopulations of different hormonal storage patterns and morphology. The presence of these subpopulations at the different stages of postnatal development strongly suggests that their proportions may play a major role in the endocrine control process.

Application of a Percoll density gradient to separate and enrich porcine pituitary cell types

The application of a Percoll density gradient cell separation procedure to the pituitary gland of neonatal, prepubertal and mature pigs is described. After enzymatic dispersion, cell viability was 90% to 98% as determined by uptake of Trypan Blue. Recovery of dissociated cells after application of the gradient ranged from 80% to 95%. The dissociated cells were separated in several fractions that were characterized immunocytochemically using different antisera. We obtained highly enriched fractions of gonadotrope (gonadotropins), somatotrope (growth hormone) and lactotrope (prolactin) cells for each age. Concentration of the cell types (purity) was higher than 60% in the following fractions: 1) gonadotropin cells, fraction 15 (1.033 g/cc of density) from mature animals; 2) growth hormone cells, fraction 3 (1.121 g/cc of density) from neonatal animals and fraction 9 (1.087 g/cc) from prepubertal animals; and 3) prolactin cells, fraction 7 (1.094 g/cc) and 10 (1.082 g/cc) from neonatal animals and fraction 14 (1.051 g/cc) from mature pigs. In thyrotrope (thyroid-stimulating hormone) and corticotrope (adrenocorticotropin) cells, enriched fractions were also obtained, although the values of purity were lower (20% to 58%). In conclusion, the proposed cell separation and enrichment technique is suitable for the isolation, purification and examination of porcine pituitary cell types and subpopulations, and offers major advantages such as simplicity, rapidity, efficiency and reproducible results.

Visualisation of CGRP and ChAT-like immunoreactivity in identified trigeminal neurones by combined peroxidase and alkaline phosphatase enzymatic reactions

We report here a method that allows simultaneous visualisation of two antigens within single neurones. In essence this involves the combined use of horseradish peroxidase and alkaline phosphatase reactions to visualise two markers. Using this method we show that ChAT-and CGRP-like immunoreactivity can be co-localised within single neurones of the V to VII motor nuclei. In the case of the V motor nucleus, we show that each marker can be localised in motoneurones labelled with horseradish peroxidase.

Immunocytochemical demonstration of pituitary cell types in the teleost Poecilia latipinna, by light and electron microscopy

Using the unlabelled antibody method at the light microscope level, and the immunogold method at the electron microscope level, the distribution of the different adenohypophysial cells was demonstrated in the teleost Poecilia latipinna, by means of antisera to both teleostean and mammalian pituitary hormones and their subunits. Anti-salmon prolactin, but not anti-rat or -ovine prolactin, gave a specific staining of the acidophils of the rostral pars distalis (RPD), while anti-trout growth hormone (GH), but not anti-rat GH, stained similar but always separate cells in the proximal pars distalis (PPD). Antisera to the whole molecules of mammalian glycoprotein hormones stained the entire population of basophils in the PPD, but separate populations of gonadotrophs and thyrotrophs could be discriminated using anti-salmon gonadotrophin and anti-human thyrotrophin beta subunit. Antisera to ACTH (1-24) and (11-24) sequences, as well as beta-endorphin and met-enkephalin, stained the lead haematoxylin-positive cells of the RPD and pars intermedia (PI), whereas anti-alpha-MSH stained only the PI cells. Ultrastructural examination showed that these immunoreactivities were present in the same secretory granules, and were always greater in pale granules rather than electron dense granules. In the RPD, blebs of ACTH-immunoreactive cytoplasm were found to protrude through the gaps in the basement membrane into the neurohypophysis. The second "PAS-positive" cell type of the PI showed a strong cross-reaction with anti-salmon gonadotrophin, suggesting that it may produce a glycoprotein chemically related to the gonadotrophin(s).

Light microscopic histochemistry on plastic sections

As compared with conventional paraffin, celloidin, and frozen sections, semithin plastic sections offer a superior quality of the light microscopic image in terms of better resolution, absence of distortion and shrinkage artifacts, and suitability for calcified tissues. Application of histochemical methods to such sections often encounters, however, serious difficulties resulting from a considerably reduced reactivity of plastic-embedded biological material. Factors involved include a poor penetration of reagents into plastic embedding media due to a steric or hydrophobic hindrance, as well as a blockade of the reactive chemical groups in the sample due to interactions with fixatives and plastics. Embedding in polar (hydrophilic) plastics, such as glycol methacrylate, permits carrying out a large number of histochemical reactions, including the demonstration of enzymatic activities, directly on sections, but is less suitable for combined light/electron microscopic studies because of an imperfect ultrastructural preservation of tissues. Embedding in nonpolar epoxy resins, particularly if combined with a double aldehyde-osmium fixation, results in a high quality ultrastructure but almost fully inhibits the histochemical reactivity of the embedded material. In order to restore this reactivity, i.e. to unmask chemical groups bound by the polymerized resin, semithin epoxy sections require the removal of the embedding matrix by alkoxides prior to the histochemical procedure. Additional steps are also often necessary: treatment of osmium-fixed sections with oxidative agents, e.g., hydrogen peroxide or periodate which reoxidize the bound osmium and remove it from tissue, and a controlled proteolytic digestion, especially useful in immunocytochemical studies, which probably cleaves the bonds between the primary aldehyde fixative, and the reactive sites. This article reviews histochemical methods which have been successfully applied to plastic-embedded material. Using polar methacrylates and/or nonpolar epoxy resins as embedding media, it has been possible to demonstrate proteins and aminoacid residues, carbohydrates, lipids, nucleic acids, biogenic amines, inorganic ions, and some enzymes, although the spectrum of methods found as suitable for plastic-embedded material is far narrower than that available for paraffin or frozen sections.(ABSTRACT TRUNCATED AT 400 WORDS)

Light microscopic immunocytochemical demonstration of peroxisomal enzymes in epon sections

A procedure is described for light microscopic immunocytochemical localization of catalase and three enzymes of peroxisomal lipid beta-oxidation: acyl-CoA oxidase, enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase in semi-thin sections of rat liver processed for routine electron microscopy. Satisfactory immunostaining required the removal of the epoxy resin with sodium ethoxide, controlled digestion of deplasticized sections with proteases and, in case of osmiumfixed tissue, bleaching with oxidants. Resin removal was essential for successful immunostaining, and protease treatment enhanced markedly the intensity of the reaction. This study shows that tissues processed for conventional ultrastructural studies can be used for postembedding immunocytochemical demonstration of various peroxisomal enzymes.

Immunohistochemical localization of FSH and LH in the pars distalis of vervet (Cercopithecus aethiops) and baboon (Papio hamadryas) pituitaries

Antisera against oLH, beta oLH and beta hFSH were used to localize gonadotropic cells in the pars distalis of Cercopithecus aethiops and Papio hamadryas. Three separate cell types were observed for FSH and LH: 85% of immunohistochemically identified gonadotropic cells reacted to all the various antisera; 10% reacted with the anti-beta oLH antibody only; and 5% with the anti-beta hFSH antibody only. Comparisons between adjacent serial sections treated with various antisera, other than anti-gonadotropic hormones, demonstrated that the "gonadotropic cells" of these monkeys did not respond to these antisera.

An immunocytochemist's view of gonadotropin storage in the adult male rat: cytochemical and morphological heterogeneity in serially sectioned gonadotropes

This study was designed to elucidate hormone storage patterns in gonadotropes with the use of ultrastructural immunocytochemistry on serial ultrathin sections. Sets of six serial sections were strained for beta chains of LH, FSH, or the C-Terminal sequence of ACTH, and 430 cells cut in triple or double serial section were collected from a group of seven normal adult male rats. Approximately 50--80% of the cells contained both LH and FSH, and most of these were Type I cells which are distinguished by their round shape and heterogeneous populations of secretion granules. Cells containing only FSH or LH constituted, on average, 19% of the population. These were a mixed group, morphologically, and included Type II cells distinguished by their angular shape and population of secretion granules, 250 nm in average diameter. Also among the FSH cells (and a few LH cells in two of the rats) were Type III cells, which resemble the corticotrope. On average, 10% of the serially sectioned cells contained only ACTH. Our findings show the presence of subpopulations of gonadotropes containing only one of the hormones, in numbers large enough to support the hypothesis that they may be partly responsible for the nonparallel release of gonadotropins. Also, the FSH-LH cells seemed to vary in their staining intensity for the two hormones, suggesting that the gondaotropes are a fluid, heterogeneous population of cells capable of storing both or only one of the hormones.