Changes in the ultrastructural distribution of prolactin and growth hormone mRNAs in pituitary cells of female rats after estrogen and bromocriptine treatment, studied using in situ hybridization with biotinylated oligonucleotide probes

Three-dimensional Imaging of the Intracellular Localization of Growth Hormone and Prolactin and Their mRNA Using Nanocrystal (Quantum Dot) and Confocal Laser Scanning Microscopy Techniques

Semiconductor nanocrystals (Quantum dots, Qdots) have recently been used in biological research, because they do not fade on exposure to light, and they enable us to obtain multicolor imaging because of a narrow emission peak that can be excited via a single wavelength of light. There have been no reports of simultaneous localization of mRNA and protein using Qdots. We successfully applied these advantages of Qdot and confocal laser scanning microscopy (CLSM) to three-dimensional images of the intracellular localization of growth hormone and prolactin and to their mRNA. In situ hybridization and immunohistochemistry using Qdots combined with CLSM can optimally illustrate the relationship between protein and mRNA simultaneously in three dimensions. Such an approach enables us to visualize functional images of proteins in relation with mRNA synthesis and localization.

Molecular morphology of pituitary cells, from conventional immunohistochemistry to fluorescein imaging

In situ hybridization (ISH) at the electron microscopic (EM) level is essential for elucidating the intracellular distribution and role of mRNA in protein synthesis. EM-ISH is considered to be an important tool for clarifying the intracellular localization of mRNA and the exact site of pituitary hormone synthesis on the rough endoplasmic reticulum. A combined ISH and immunohistochemistry (IHC) under EM (EM-ISH&IHC) approach has sufficient ultrastructural resolution, and provides two-dimensional images of the subcellular localization of pituitary hormone and its mRNA in a pituitary cell. The advantages of semiconductor nanocrystals (quantum dots, Qdots) and confocal laser scanning microscopy (CLSM) enable us to obtain three-dimensional images of the subcellular localization of pituitary hormone and its mRNA. Both EM-ISH&IHC and ISH & IHC using Qdots and CLSM are useful for understanding the relationships between protein and mRNA simultaneously in two or three dimensions. CLSM observation of rab3B and SNARE proteins such as SNAP-25 and syntaxin has revealed that both rab3B and SNARE system proteins play important roles and work together as the exocytotic machinery in anterior pituitary cells. Another important issue is the intracellular transport and secretion of pituitary hormone. We have developed an experimental pituitary cell line, GH3 cell, which has growth hormone (GH) linked to enhanced yellow fluorescein protein (EYFP). This stable GH3 cell secretes GH linked to EYFP upon stimulation by Ca²⁺ influx or Ca²⁺ release from storage. This GH3 cell line is useful for the real-time visualization of the intracellular transport and secretion of GH. These three methods from conventional immunohistochemistry and fluorescein imaging allow us to consecutively visualize the process of transcription, translation, transport and secretion of anterior pituitary hormone.

In situ detection of specific gene expression during and immediately after transcription at electron microscopic level

In situ hybridization (ISH) is a widely applied technique used for visualizing specific nucleic acid sequences at chromosomal, cytologic, and histologic levels. It sometimes fails, however, to demonstrate precise cell identity, early stages of gene expression and variants of alternative splicing because of its limited resolution. To overcome this shortcoming, we have developed an improved ISH technique at the electron microscopic (EM) level by conducting en bloc hybridization before embedding (pre-embedding) and immuno-EM detection after ultra-thin sectioning (post-embedding). We applied this technique to demonstrate both the dynamic expression of interleukin (IL)-6 mRNA immediately after lipopolysaccharide (LPS) treatment, and the static expression of osteonectin mRNA in a differentiating osteoblastic cell linage. Tissue samples were diced into 1mm cubes, fixed with 4% paraformaldehyde, and then successively hybridized en bloc with the digoxigenin (DIG)-labeled single-stranded probe measuring 200-300 bp with the aid of microwave treatment. After washing, for EM observation, the cubes were embedded in epon for ultra-thin sectioning, and a gold-colloid-labeled anti-DIG antibody was used for post-embedding immuno-EM; some of the cubes was directly incubated with anti-DIG antibody and developed en bloc for stereoscopic and light microscopic observation. IL-6 mRNA during and immediately after transcription was demonstrated in the nuclei of the alveolar macrophages and in neutrophils of mouse lung tissue as early as 15 min after LPS treatment, which was of better sensitivity than that by Northern blot or nuclear run-on techniques. Moreover, in mouse calvaria tissue, osteonectin mRNA both in the nucleus and the cytoplasm was observed in a differentiating osteoblastic cell linage in a differentiation-specific manner. This technique is useful in identifying specific cell types during and immediately after transcribing specific mRNA based on ultrastructural morphology.

Pathology of pituitary tumors

Pituitary adenomas are benign neoplasms originating in adenohypophysial cells. They represent the most common neoplasm of the sellar region, comprising approximately 15% of all primary intracranial tumors. Depending on the studies of unselected adult autopsy material, their frequency as an incidental finding varies between 5% and 20%. The first part of this article summarizes the immunohistochemistry of nontumorous human adenohypophysis. In the second part, the classification of pituitary tumors is discussed, followed by the immunohistochemical and electron microscopic findings of pituitary adenomas and pituitary carcinomas.

Cytochemical and molecular biological aspects of the pituitary and pituitary adenomas--cell differentiation and transcription factors

The anterior pituitary is composed of several cell types, each responsible for the production of specific hormones. Each hormone secreting cells is defined by the activation of its respective hormone genes in a temporally and spatially regulated manner. Recent development in cytochemistry and molecular biology have provided various aspects of human pituitary adenomas, i.e., functional differentiation and classification. The molecular factors that determine hormone production have now been identified as transcription factors. Many novel transcription factors that play a role in anterior pituitary development are implicated. In this review, we focus on the transcriptional factors roles on functional differentiation of the pituitary cells and adenomas and the contribution of cytochemistry and recent development in molecular biological techniques.

Applications of plastic embedding to electron microscopic immunocytochemistry and in situ hybridization in observations of production and secretion of peptide hormones

Plastic embedding has been used to localize various antigens in conjunction with immunohistochemistry. Peptide hormones have been among the antigens that have been studied extensively. Recent application of water-soluble plastics such as LR White and Lowicryl has extended the ranges of detectable antigens and enabled the observation of antigen-antigen or mRNA-antigen combinations. This review article deals with technical aspects, procedures, and applications in endocrine cells.

Ultrastructural localization of beta-actin and amphoterin mRNA in cultured cells: application of tyramide signal amplification and comparison of detection methods

We describe a nonradioactive preembedding in situ hybridization protocol using digoxigenin-labeled RNA probes and tyramide signal amplification to increase the sensitivity of detection. The protocol is sensitive enough for electron microscopic localization of endogenous messenger RNAs encoding beta-actin and amphoterin. Three visualization methods were compared: diaminobenzidine enhanced by nickel, Nanogold enhanced by silver and gold toning, and fluorescently labeled tyramides. Diaminobenzidine and Nanogold can be used in both light and electron microscopy. The nickel-enhanced diaminobenzidine was the most sensitive visualization method. It is easy to accomplish but a drawback is poor spatial resolution, which restricts its use at high magnifications. Nanogold visualization has considerably better spatial resolution and is therefore recommended for electron microscopy. Fluorescent tyramides, especially TRITC-tyramide, offer a good detection method for fluorescence and confocal microscopy. The methods were used to localize amphoterin and beta-actin mRNAs in motile cells. Both mRNAs were found in the soma and cell processes. In double labeling experiments, beta-actin mRNA localized to filamentous structures that also contained ribosomal proteins. Especially in the cortical cytoplasm, beta-actin mRNA was associated with actin filaments. Direct localization to microtubules was only rarely seen. (J Histochem Cytochem 47:99-112, 1999)

Electron Microscopic and Confocal Laser Scanning Microscopic Observation of Subcellular Organelles and Pituitary Hormone mRNA: Application of Ultrastructural In Situ Hybridization and Immunohistochemistry to the Pathophysiological Studies of Pituitary Cells

Nonradioisotopic electron microscopic (EM) in situ hybridization (ISH) (EM-SH) with biotinylated oligonucleotide probes is utilized for the ultrastructural visualization of pituitary hormone mRNA in rat pituitary cells. EMISH is an important tool for clarifying the intracellular localization of mRNA and the exact site of specific hormone synthesis on the rough endoplasmic reticulum. The simultaneous visualization of mRNA and encoded protein in the same cell using preembedding EM-ISH and subsequent postembedding immunoreaction with protein A colloidal gold complex can provide an important clue for elucidating the intracellular correlation of mRNA translation and secretion of translated protein. Another focus of this review is the utilization of a recently developed imaging system of confocal laser scanning microscopy (CLSM). The combination of CLSM and image analysis system (lAS) enables us to visualize an individual dimensional image of the intracellular distribution of mRNA and subcellular organelles successfully at any optional cross sections of light microscopic ISH studies, and can be another useful tool for the ultrastructural ISH study of mRNA.

An improved ultrastructural double-staining method for rat growth hormone and its mRNA using LR White resin: a technical note

An improved new method for the simultaneous visualization of mRNA and encoded protein in LR White resin-embedded specimens is described. This pre-embedding electron microscopical in situ hybridization (procedure) localized rat growth hormone mRNA specifically as high electron-density products on the polysomes of the rough endoplasmic reticulum. A subsequent post-embedding immunoreaction, using protein A colloidal gold particles, identified growth hormone as gold particles both in the cisternae of the rough endoplasmic reticulum and on the secretory granules. In our previous report, we used Epon resin for tissue embedment, which required an etching process using hydrogen peroxide or sodium periodate for immunoreactivity retrieval. In general, osmification and embedment in Epon resin are reported to decrease the immunoreactivity of the targeted protein, and the etching process using hydrogen peroxide or sodium periodate results in deosmification and shades off the signals of mRNA. To resolve these problems, we have recently used LR White resin for tissue embedment. In LR White resin-embedded tissues, retrieval of immunoreactivity using hydrogen peroxide or sodium periodate is not required, and, therefore, the gradation of the signals of mRNA can be avoided.

Application of confocal laser scanning microscopy (CLSM) to visualize prolactin (PRL) and PRL mRNA in the normal and estrogen-treated rat pituitary glands using non-fluorescent probes

In the present study, we performed concomitant visualization of immunohistochemistry (IHC) and in situ hybridization (ISH) on the materials processed for conventional light microscopic specimens using non-fluorescent Confocal Laser. Scanning Microscopy (CLSM). CLSM was used in the reflection confocal mode using horseradish peroxidase (HRP)-3-3'diaminobenzidine (DAB)-osmium (osmium black) and nitroblue tetrazolium (NBT) as non-fluorescent detection methods (probes). To obtain clearer images of the organelles, images that were built up as electronic signals in CLSM were processed in an image analysis system (IAS). By using the combination of CLSM and IAS, in IHC, immunohistochemical localization of prolactin (PRL) was in well-developed lamellar or whorling rough endoplasmic reticula (RER), Golgi apparatus, and secretory granules. With ISH, the expression and distribution of PRL messenger ribonucleic acid (mRNA) was observed in a fashion suggesting polysome-like structures on RER. These observations were confirmed by immunoelectron microscopy and electron microscopic ISH. The herein-described method is expected to be useful to perform the concomitant observation of IHC and ISH at subcellular levels using the conventional light microscopic specimens.

Invasive pituitary tumors in female F344 rats induced by estradiol dipropionate

To clarify the histopathological progression of invasive tumors in the pituitary pars distalis due to estrogen, female Fischer 344 (F344) rats were treated subcutaneously with 5 mg/animal of estradiol dipropionate (ED) once every 2 wk for 13 wk. The animals were killed serially at 2-wk intervals during the investigation. The pituitaries with surrounding tissues were examined light microscopically. At week 7, pituitary cells showed proliferation and atypia with formation of blood-filled spaces. Lesions with these characteristics were diagnosed as adenomas. At week 9 or later, neoplastic cells exhibited extensive proliferation and infiltration into the surrounding tissues, suggesting development of carcinoma. Both proliferating cell nuclear antigen (PCNA) and 5-bromo-2'-deoxyuridine (BrdU) labeling index, markers of cell proliferation, were significantly increased in animals with adenoma or carcinoma. To detect sequential changes in pituitary weight, its signal intensity was periodically monitored in identical rats by using magnetic resonance (MR) imaging. The estimated pituitary weights revealed by MR imaging were comparable to the tumor weights obtained from rats at scheduled sacrifices. These results indicate that ED possesses the potential to cause carcinoma in rat pituitary and MR imaging is an effective tool for estimating the pituitary weight.

Modulation of protein kinases and microtubule-associated proteins and changes in ultrastructure in female rat pituitary cells: effects of estrogen and bromocriptine

This study focused on the intracellular signal transduction system and microtubule-associated proteins (MAPs), such as MAP-2 and Tau protein. The modulation of these proteins and their correlation with ultrastructural changes were investigated in rat pituitary prolactin (PRL) cells. Adult female Wistar rats were treated with estrogen and bromocriptine and their pituitary glands were removed for analysis of the expression of tubulin, MAP-2, Tau protein, protein kinase C (PKC), and calcium calmodulin (CaM) kinase. Western blot analysis showed that estrogen increased and bromocriptine decreased the expression of PKC alpha, beta 1, beta 2, CaM kinase alpha, beta, MAP-2, and Tau protein. MAP-2 and Tau protein, which are cytosolic proteins, being translated on free ribosomes, were associated with the membrane of whirling rough endoplasmic reticulum (RER) in estrogen-treated cells and dissociated with vesiculated RER induced by bromocriptine. These results suggested that the modulation of MAP-2 and Tau protein may reflect changes of PKC and CaM kinase, and that the quantitative changes and intracellular modulation of MAPs induced by estrogen and bromocriptine, i.e., estrogen-induced association and bromocriptine-induced dissociation of MAP-2 and Tau protein with membrane of RER, may reflect the dynamics of microtubules and are associated with structural changes in the RER and changes in the synthesis and intracellular transport of PRL.

Simultaneous ultrastructural identification of growth hormone and its messenger ribonucleic acid using combined immunohistochemistry and non-radioisotopic in situ hybridization: a technical note

The present electron microscopical study is concerned with the simultaneous visualization of messenger ribonucleic acid (mRNA) and its encoded protein in the same specimen. Pre-embedding electron microscopical in situ hybridization (EM-ISH) on rat pituitary gland tissue localized growth hormone mRNA in the polysomes of the rough endoplasmic reticulum, and subsequent postembedding immunolabelling using protein A-colloidal gold particles identified growth hormone mainly in the secretory granules. We believe that our report provides the first simultaneous ultrastructural identification of mRNA and its encoded protein using combined pre-embedding EM-ISH and immunohistochemistry. In this method, the signals for mRNA were localized specifically as highly electron dense products on the polysomes of the endoplasmic reticulum, and those for its encoded protein were recognized as gold particles both in the cisternae of the reticulum and in the secretory granules. Our ultrastructural double labelling method for mRNA and protein may provide a tool to find important clues for elucidating the intracellular correlation of mRNA translation and secretion of translated protein, because of its high resolution, good morphological preservation, and the specific localization of the reaction products.