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The influence of lactation and weaning on the number, distribution, and structure of mammotroph cells (PRL cells) in ewes was studied using immunocytochemical procedures for light and electron microscopy, as well as morphometric and stereological techniques. The adenohypophyseal gland of 12 ewes of the Segureña breed at different stages of milk production and weaning were analysed, while the same organ of 3 ewes in anestrus served as control. During lactation, PRL cells increased in number and decreased in size. Ultrastructurally, these cells showed a well-developed rough endoplasmic reticulum (RER) and Golgi complex (GC), and large secretory granules. These findings point to increased synthesis and secretion activities during lactation, and a decrease after weaning. One day after weaning ‘storage’ cells increased in number, and crinophagy became evident 7 days after weaning, when the first ‘inactive’ cells were seen (10% of total cells). In anestrus these last cells represented 40% of the total, and showed scarce granules, signs of inactivity, lysosomes and lipid droplets.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The structural and ultrastructural characteristics of adenohypophyseal growth hormone (GH)-, prolactin (PRL)- and GH-PRL (SMT)-secreting cells were studied using immunocytochemical techniques in two normal and one lactating male goat. SMT cells were found in both types of males, which showed the same characteristics as those reported for the female. PRL and SMT cells were more frequent in the lactating male, which reflects their greater galactopoietic activity. GH cells did not seem to influence this process significantly. [ABSTRACT FROM AUTHOR]

The distribution of different celltypes (A, B, D and PP cells) of the endocrine pancreas was studied in both the normal and in the experimental diabetic non-pregnant and pregnant rat. In the normal rat the head (juxta duodenal part) of the pancreas contained more PP cells than the tail (12.5±1.1 versus 5.2±2.2) but fewer glucagon cells (19.0 ±3.5 versus 14.3±3.6). This difference disappeared during pregnancy, when the total B cell mass increased (2.05 versus 0.82). In the diabetic rat no difference was found in the number of endocrine cells between the tail and the juxta duodenal part of the pancreas. Unlike the non-diabetic rat, the number of B cells did not increase in the pancreas of the pregnant diabetic rat. An absolute increase in the number of glucagon (A) cells was demonstrated in the islets of the pregnant diabetic rat as compared to the non-diabetic rat (35 versus 21.2). [ABSTRACT FROM AUTHOR]

Different immunohistochemical techniques were used to identify the prolactin and growth hormone producing cells (STH cells) in the pituitary of normal guinea pigs at the ultrastructural level. Prolactin cells revealed two main aspects: 1. Cells with granules from 2500 to 3500 Å in diameter some of which are irregularly shaped. These granulations are scattered throughout the whole cytoplasm. The rough endoplasmic reticulum is well developed and organized in parallel lamellae. 2. In cells of the second type the granules are less numerous and smaller in diameter (1800 to 2500 Å) and the rough endoplasmic reticulum is less well developed. The cytoplasm of the STH cells contains many more round granules (generally grouped) which also range from 2500 to 3500 Å in diameter. The prolactin molecules and the STH molecules are essentially confined to the granules but with the immunocytochemical technique before embedding a slightly diffuse reaction appeared in the entire cytoplasm. These results are discussed. [ABSTRACT FROM AUTHOR]

Three different immunocytoenzymatic techniques were used to identify and characterize the thyrotropic cells in the pituitary of normal guinea pigs at the ultrastructural level (superimposition technique, immunocytochemical technique using P.A.P. and indirect immunohistoenzymatic method before embedding). These cells are characterized by a dark cytoplasm with granules ranging from 1500 to 2000 Å in diameter. The appearance of these granules is very variable: some display a marked electron density and are homogeneous but some have a less marked electron density with a more electron dense peripherally situated region. The TSH molecules are essentially confined to the granules but when the immunocytochemical reactions are carried out before embedding, positive staining is also seen in the cytoplasm and the outer surface of most of the rough endoplasmic reticulum membranes. These results are discussed. [ABSTRACT FROM AUTHOR]

Immunocytochemical techniques applied at both light- and electron microscopical levels are valuable in the study of regulatory peptide distribution in normal and diseased tissue, whether in the form of sections or whole cell preparations. Successful immunolocalisation depends on 1) adequate preservation of the peptide antigen and the tissue structure in which it resides; 2) a suitably specific and sensitive labelled antibody detecting system. In general, peptides are stable molecules, most of which retain their antigenicity after conventional cross-linking fixation and tissue processing, allowing standard immunocytochemical methods to be used for light- and electron microscopy. Regulatory peptides are derived from precursor molecules and several 'families' of structurally similar peptides are now generally recognised. Region-specific antibodies may be needed to overcome problems of cross-reactivity or to identify a bioactive form in the presence of its precursor. Multiple co-localisation of different related and unrelated peptides in the same cell or even storage granule is now recognised and can be identified by immunocytochemistry. [ABSTRACT FROM AUTHOR]