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 58,342 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human NK activity is known to be associated with a population of large granular lymphocytes (LGL) exhibiting several immunophenotypic surface markers including Leu-11a (NKP-15), Leu-7 (HNK-1), Leu-3a (T4), and Leu-2a (T8). Based upon correlation with cytolytic activity, Leu-11a is now considered the most specific antigenic marker for human NK cells. Present investigation compared the ultrastructure of cells expressing Leu-11a, Leu-7, Leu-3a, and Leu-2a, both in human peripheral blood lymphocytes (PBL) and the purified LGL fraction. Subcellular cytochemical reactions were investigated in Leu-7+ or Leu-11a+ PBL or LGL and in cells conjugated with K562 targets (indicating NK cytolytic potential). The surface markers, localized with monoclonal antibodies, were detected by immunoelectron microscopy by using direct or indirect avidin-biotin-peroxidase (ABC) or colloidal gold methods. A peroxidase-colloidal gold double-labeling system was used to identify subsets of Leu-7+ or Leu-11a+ cells. Previously described ultrastructural features of LGL including a villous surface, reniform nuclei, low nuclear/cytoplasm ratios, and abundant cytoplasm with vesicles, vacuoles, electron-dense granules, parallel tubular arrays (PTA), or paracrystalline inclusions were associated with Leu-7+, Leu-11a+, Leu-7+/Leu-11a+, Leu-7+/Leu-11a-, and Leu-7-/Leu-11a+ PBL or LGL. Results showed that the Leu-7+/Leu-11a+ cells were the most abundant NK cells in PBL. Lymphocyte subsets with Leu-3a or Leu-2a surface marker showed some ultrastructural features including PTA similar to Leu-7+ cells and Leu-11a+ cells, and their subsets. These T-cells appeared ultrastructurally more similar to the Leu-7+/Leu-11a- subset. Cytochemical studies showed that electron-dense cytoplasmic granules and PTA typical of the Leu-11a+ cells and Leu-7+ cells contained glycoprotein, acid phosphatase, and arylsulfatase. Large cytoplasmic vacuoles were heterogeneous and typically contained electron-dense material with DAB reactivity, membranous material, PTA, and/or paracrystalline inclusions. Glycoprotein, acid phosphatase, and arylsulfatase, and peroxidase reactive material were also found in these vacuoles. These features suggested that the vacuoles could be secondary lysosomes. The coexistence of intact PTA or degenerating PTA in the same vacuoles with paracrystalline inclusions suggested that the latter are possibly derived from PTA.
Anat Rec 1987 Mar
PMID:Immunoultrastructural studies of human NK cells: I. Ultracytochemistry and comparison with T cell subsets. 355 61

This study has examined the fine structure and some cytochemical characteristics of the endodermal and mesothelial cells of the rhesus monkey yolk sac between 25 and 66 days of gestation. The endodermal cells were characterized by abundant granular endoplasmic reticulum, some agranular endoplasmic reticulum, a well-developed Golgi apparatus, and numerous large mitochondria. During the earlier part of the period studied, endodermal cells had a few acid phosphatase and arylsulfatase-positive lysosomes and moderate numbers of catalase-positive microperoxisomes. During the later stages of development, large granules (believed to be lysosomes) with a heterogeneous content were numerous in the cytoplasm. Mesothelial cells showed fewer development changes. Throughout this period they were usually flattened cells with long microvilli, small mitochondria, and limited amounts of granular endoplasmic reticulum. The mesothelial cells had acid phosphatase reaction product in the Golgi region and occasional large vesicles, but were negative for arylsulfatase and catalase. One specimen was incubated at 37 degrees C in the presence of horseradish peroxidase in order to examine endocytosis. Both the mesothelial cells and endodermal cells internalized the peroxidase into a variety of cytoplasmic vesicles. Based on their cytology, the endodermal cells may function in the synthesis of serum proteins during this period, as has been suggested in other species. They may also be involved in lipid metabolism. The mesothelial cells appeared less synthetically active, but evidence suggested that they may be involved in collagen and extracellular matrix production. The endocytic activity displayed by both cell types may indicate a role in fluid and metabolite transfer across the epithelia. The cytology of both cell types was very similar to that described for human yolk sacs, suggesting that the rhesus monkey may be a useful species in which to study the maturation of yolk sac function.
Anat Rec 1983 Feb
PMID:A fine structural and cytochemical study of the rhesus monkey yolk sac: endoderm and mesothelium. 684 66

Secretory granules, which are released by exocytosis and are speculated to contain progesterone, have been described in luteal cells of sheep and other large domestic animals. These granules are small and densely staining. Gemmell and Stacy ('79) suggested that luteal cells of guinea pigs also contain secretory granules, although they could not document exocytosis of granule content at the fine structural level. For the present study, quantitative methods were used to reexamine the possibility that luteal cells of guinea pigs possess secretory granules. Ovaries of guinea pigs were fixed in situ by vascular perfusion at the time of maximum progesterone secretion, when such granules would be most abundant, as well as other stages. Two types of granules that might be confused with secretory granules are microperoxisomes and lysosomes. Therefore, slices of perfusion-fixed corpora lutea were incubated for the fine structural localization of a peroxisomal enzyme, catalase, or for the lysosomal enzymes, acid phosphatase (ACPase) and arylsulfatase. Other tissue was prepared for conventional electron microscopy. Granule types were classified on the basis of size, morphology, and enzyme content. Quantitation of granule types was carried out on both cytochemically reacted and conventionally prepared luteal tissue. More than 5500 microperoxisomes, 2800 lysosomes, and 1100 multivesicular bodies (MVBs) were tabulated. The results indicate that luteal cells of guinea pigs have three main types of granules: 1) Microperoxisomes, about 0.2 micrometer in diameter and containing catalase; 2) lysosomes, about 0.5 micrometer in diameter and positive for ACPase and arylsulfatase; and 3) MVBs, about 0.4 micrometer in diameter and containing small vesicles. At the time of peak steroid secretion during pregnancy and the estrous cycle, the granule population in luteal cells of guinea pigs consists of 73-80% microperoxisomes, 13-17% lysosomes, and 7-9% MVBs. These proportions are similar in tissue reacted for cytochemistry and tissue prepared by conventional means. Greater than 99% of the small 0.2-0.3 micrometer diameter granules in guinea pig luteal cells are catalase reactive. This finding eliminates from further consideration most of the prime candidates for secretory granules in these cells. Finally, neither a sequential appearance of granules nor exocytosis of secretory product was detected. Our data thus argue against the suggestion that luteal cells of guinea pig have secretory granules of the type observed in corpora lutea of large domestic animals.
Anat Rec 1981 Sep
PMID:Cytoplasmic granules in luteal cells of pregnant and non-pregnant guinea pigs. A cytochemical study. 730 15