Morphometry of feline neutrophil granule genesis

During neutrophil granule genesis, the formation of primary granules is generally thought to be limited to the promyelocyte stage; whereas synthesis of secondary granules is thought to occur only at the myelocyte stage. This hypothesis was tested morphometrically in feline neutrophils that are known to contain both granule types. Marrow specimens obtained from six cats were stained with peroxidase for identification of neutrophil primary granules and counterstained with periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) for identification of secondary granules. By regression analysis using arithmetic models, numbers of cytoplasmic granules in 311 cells were correlated with the degree of nuclear chromatin condensation, which was shown to be an adequate parameter for cell maturation. Promyelocytes and myelocytes had similar mean numbers of peroxidase-positive granules per unit area. A significant increase (p less than or equal to 0.0001) in the numbers of peroxidase-positive granules was noted between the metamyelocyte and the mature neutrophil stage, despite the lack of peroxidase activity in endoplasmic reticulum and Golgi lamellae. By contrast, a significant increase of peroxidase-negative granules between the metamyelocyte and the mature neutrophil stage was not clearly established with these methods. The increase in peroxidase-positive granules may indicate continued production of peroxidase-containing granules and/or redistribution of peroxidase among lysosomal organelles in late feline neutrophils.     

Light and electron microscopic studies on the enzyme cytochemistry of leucocytes of eels, Anguilla species

The leucocytes of three anguillid eels were studied using enzyme cytochemistry. Leucocytes were stained for peroxidase, alkaline phosphatase, acid phosphatase, aryl sulphatase, β-glucuronidase, N-acetyl-β-glucosaminidase, β-galactosidase, lysozyme, a variety of non-specific esterases, chloroacetate esterase and two proteases. All cells were negative for aryl sulphatase, β-glucuronidase, N-acetyl-β-glucosaminidase, and β-galactosidase. Very few neutrophils, thought to be mature, and all eosinophils contained peroxidase-positive granules, and some monocytes showed very weak peroxidase staining. All leucocytes lacked alkaline phosphatase, but all cells except lymphocytes and thrombocytes of A. dieffenbachii contained acid phosphatase. Neutrophil acid phosphatase released into phagosomes was associated with Escherischia coli bacteriolysis. Neutrophils also secrete lysozyme and, with monocytes, produce and secrete a variety of esterases. The possible interaction of lysozyme, acid phosphatase and esterases in bacteriolysis is discussed.     

Ultrastructural Cytochemistry of Secretory Granules of Esophageal Glands of Meloidogyne incognita

Ultrastructural cytochemical tests for several enzymes, proteins, carbohydrates, and nucleic acids were conducted on secretory granules o£ dorsal and subventral esophageal glands of preparasitic second-stage juveniles and the dorsal gland of adult females of Meloidogyne incognita. Secretory granules in the subventral glands of juveniles stained positive for acid phosphatase. Peroxidase, DNase, RNase, cellulase, and nucleic acids were not detected in these granules. Secretory granules in the dorsal gland of adult females stained positive for peroxidase (pH 7.6) in < 50% of the tests, Acid phosphatase, β-glucuronidase, DNase, RNase, polyphenoloxidase, cellulase, and carbohydrates were not detected in dorsal gland granules in adult females. Positive staining with cobalt thiocyanate, a stain for amino groups of basic proteins, occurred in secretory granules in the dorsal gland, ribosomes, and chromatin in adult females. Ribosomes, nuclei, and secretory granules of the dorsal gland of adult females intensely stained when incubated in three reagents specific for nucleic acid.     

Ultrastructural localization of complex carbohydrates in odontoblasts, predentin, and dentin

Glycosaminoglycans (GAGs) and glycoproteins (GPs) are essential components for dentinogenesis. We have examined rat odontoblasts, predentin, and dentin decalcified with EDTA and stained with: 1) Spicer's hig-iron diamine-thiocarbohydrazide-silver proteinate (HID-TCH-SP) method for sulfated glycoconjugates, and 2) Thiéry's periodate-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method for vicinal glycol-containing glycoconjugates. HIS-TCH-SP stained distended portions of Golgi saccules and secretory granules. The predentin contained three times the number of HID-TCH-SP stain precipitates when compared to the mineralization front of the dentin matrix. PA-TCH-SP weakly stained membranes of Golgi saccules and cisternae of rough endoplasmic reticulum (RER), whereas stronger staining was observed in secretory granules, lysosomes, and multivesicular bodies (MVBs). Collagen fibrils in predentin demonstrated moderate PA-TCH-SP staining. In contrast, strong PA-TCH-SP staining was observed on and between collagen fibrils in the mineralization front of the dentin matrix. TCH-SP controls of unosmicated specimens lacked significant staining, however, osmicated control specimens did contain some TCH-SP stain deposits in the mineralization front. These results indicate that sulfated and vicinal glycol-containing glycoconjugates are packaged in the same type of secretory granule and released into the extracellular matrix; subsequently vicinal glycol-containing glycoconjugates concentrate in the calcification front, whereas sulfated glycoconjugates accumulate in the predentin and are either removed or masked to staining in the dentin.     

Cytochemical characterization of leucocytes from the seawater teleost,gilthead seabream (Sparus aurata L.)

The cytochemical characterization of head-kidney and peripheral blood leucocytes of gilthead seabream (Sparus aurata L.) was studied by light and electron microscopy. Neutrophilic granulocytes show some cytoplasmic granules, which are positive for alkaline phosphatase and peroxidase but acid phosphatase negative. The scarce granules found in the cytoplasm of the circulating neutrophils and their cytochemical features seem to be indicative of an immature stage. Acidophils are also alkaline phosphatase and peroxidase positive at pH 11.0. They are strongly positive for acid phosphatase and acid phosphatase activity may thus be considered a cytochemical marker to characterize and differentiate neutrophilic from acidophilic granulocytes in this fish species. Three granule populations are characterized in the cytoplasm of the gilthead seabream acidophils: the first is positive only for peroxidase and the second contains a dense core with acid and alkaline phosphatase activities, surrounded by a thin peroxidase positive electron-dense halo. The third granule type contains an eccentric core, which is strongly positive for acid and alkaline phosphatase and peroxidase. As regards their cytochemical features, the first and second granule types seem to correspond respectively to the azurophilic and specific granules found in acidophils of mammals and could be involved in phagocytic processes, thus playing an important microbicidal role in this species. The monocytes, monocyte-macrophages and macrophages show different cytochemical features. The first have scarce acid phosphatase-positive lysosomes, while blood monocyte-macrophages and macrophages are positive for acid and alkaline phosphatases and for peroxidase; the monocyte-macrophages show scarce lysosomes.     

Characteristics on staining of leukocytes in experimental animals]

The staining characteristics of the peripheral blood cells from mouse, rat, guinea pig, rabbit, dog, marmoset and monkey were studied. In marmoset, it is easy to distinguish neutrophils from eosinophils by using the phosphate-buffered solution of pH 5 or 6. It was found in the special staining methods that neutrophil granules showed intense peroxidase and Sudan black B reactions in marmoset in comparison with those in the other species of experimental animals. Neutrophil granules rabbit was, however, intensely stained with esterase and acid phosphatase.     

Tannic acid-metal salt sequences for light and electron microscopic localization of complex carbohydrates.

Use of tannic acid (TA), in sequence with ferric chloride, uranyl acetate or gold chloride resulted in staining of selective but sometimes different sites in paraffin sections. TA-uranyl acetate of TA-ferric chloride stained sites rich in complex carbohydrates, wherease TA-gold chloride stained the collagen of various connective tissues different shades of red-purple to gray-black. Applied to epoxy-embedded thin sections of tissues fixed with glutaraldehyde and not post-osmicated, TA-uranyl acetate and TA-ferric chloride imparted density to subcellular sites known to contain a high concentration of mucosubstances, such as secretory granules and cisternae of the Golgi complex of certain cells. TA-gold chloride proved unsatisfactory for ultracytochemistry because of its tendency to form globular precipitates on thin sections. The effect of blockage procedures at the light microscopic level indicated that vicinal glycols are not required for binding of TA to tissue sites. Electrostatic forces were shown to be of minimal significance, whereas hydrogen bonding appeared to play a part in both TA-tissue and TA-metal binding mechanisms.     

Identification of Normal and Leukemic Granulocytic Cells with Merocyanine 540

After fixation in a modified Bouin's solution, the acid dye merocyanine 540 stained granules in granulocytic cells intensely. In immature granulocytes, such as promyelocytes and myelocytes, granules stained pink to violet. In some leukemic myeloblasts, promyelocytos and monocytes, granules also stained deep pink to violet. In more mature granulocytes, such as metamyelocytes, bands, and neutrophils, granules stained bright red to orange. In eosinophils and basophils, granules stained deep red. Granules of the type described were not visualized in normal plasma cells, lymphocytes, monocytes, or megakaryocytes. In normoblasts, cytoplasm stained diffusely red. Cytoplasmic staining in crythroblasts became darker as the cell matured, probably reflecting hemoglobin content. Used as a single a p t stain, merocyanine 540 may be useful in distinguishing normal and leukemic granulocytic cells from other types of blood cells.     

Identification of normal and leukemic granulocytic cells with merocyanine 540

After fixation in a modified Bouin's solution, the acid dye merocyanine 540 stained granules in granulocytic cells intensely. In immature granulocytes, such as promyelocytes and myelocytes, granules stained pink to violet. In some leukemic myeloblasts, promyelocytes and monocytes, granules also stained deep pink to violet. In more mature granulocytes, such as metamyelocytes, bands, and neutrophils, granules stained bright red to orange. In eosinophils and basophils, granules stained deep red. Granules of the type described were not visualized in normal plasma cells, lymphocytes, monocytes, or megakaryocytes. In normoblasts, cytoplasm stained diffusely red. Cytoplasmic staining in erythroblasts became darker as the cell matured, probably reflecting hemoglobin content. Used as a single agent stain, merocyanine 540 may be useful in distinguishing normal and leukemic granulocytic cells from other types of blood cells.     

DIFFERENCES IN ENZYME CONTENT OF AZUROPHIL AND SPECIFIC GRANULES OF POLYMORPHONUCLEAR LEUKOCYTES : I. Histochemical Staining of Bone Marrow Smears

Histochemical procedures for PMN granule enzymes were carried out on smears prepared from normal rabbit bone marrow, and the smears were examined by light microscopy. For each of the enzymes tested, azo dye and heavy metal techniques were utilized when possible. The distribution and intensity of each reaction were compared to the distribution of azurophil and specific granules in developing PMN. The distribution of peroxidase and six lysosomal enzymes (acid phosphatase, arylsulfatase, β-galactosidase, β-glucuronidase, esterase, and 5'-nucleotidase) corresponded to that of azurophil granules. Progranulocytes contained numerous reactive granules, and later stages contained only a few. The distribution of one enzyme, alkaline phosphatase, corresponded to that of specific granules. Reaction product first appeared in myelocytes, and later stages contained numerous reactive granules. The results of tests for lipase and thiolacetic acid esterase were negative at all developmental stages. Both types of granules stained for basic protein and arginine. It is concluded that azurophil and specific granules differ in their enzyme content. Moreover, a given enzyme appears to be restricted to one of the granules. The findings further indicate that azurophil granules are primary lysosomes, since they contain numerous lysosomal, hydrolytic enzymes, but the nature of specific granules is uncertain since, except for alkaline phosphatase, their contents remain unknown.     

Ultrastructural visualization of carbohydrates in oxytalan fibers in monkey periodontal ligaments

Fullmer's oxytalan fibers appear to be special connective tissue fibers belonging to elastic system fibers. We have ultrastructurally examined carbohydrates in oxytalan fibers in monkey periodontal ligaments after glutaraldehyde fixation and ethylenediaminetetraacetic acid (EDTA) decalcification using: Thiéry's periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method for thin-section staining of vicinal glycol-containing complex carbohydrates, and the concanavalin A-ferritin (Con A-ferritin) and Con A-horseradish peroxidase (Con-A-HRP) en bloc staining methods specific for alpha-D-mannosyl and alpha-D-glucosyl groups. PA-TCH-SP stained collagen fibrils weakly to moderately and stained oxytalan fibers moderately. Con A-ferritin and Con A-HRP stained collagen fibrils weakly or moderately and stained oxytalan fibers intensely within the superficial region of specimen blocks. The penetration of staining reagents was improved by prior saponin treatment and/or chondroitinase ABC digestion. Thus, these studies demonstrate that PA-TCH-SP and Con A staining of carbohydrates is very useful in identifying oxytalan fibers at the ultrastructural level and that more carbohydrate components are present in oxytalan fibers than in collagen fibrils.     

Unmasking and redistribution of lysosomal sulfated glycoconjugates in phagocytic polymorphonuclear leukocytes

Rabbit heterophil and human neutrophil primary granules contain sulfated glycosaminoglycans (GAGs) and acid phosphatase, which can be readily stained in immature but not mature lysosomes. To determine whether this loss of staining represents masking of reactive components or removal of these components, we examined rabbit heterophils to see if high-iron diamine (HID)-reactive sulfate and acid phosphatase staining reappears in phagocytic vacuoles. Rabbit heterophils, obtained by peritoneal lavage, were incubated in vitro with latex beads or Pseudomonas aeruginosa for 15-60 min. Pre-embedment HID staining was enhanced in thin sections of unosmicated specimens with thiocarbohydrazide and silver proteinate (TCH-SP). Phagocytosis of latex beads or bacteria was progressively more prominent with time. Primary granules that were degranulated or in the process of degranulating into phagocytic vacuoles demonstrated intense sulfate staining with large (13 +/- 7 nm) HID-TCH-SP stain deposits. Smaller (6 +/- 1 nm) HID-TCH-SP stain deposits were present in tertiary granules, which were less frequently observed degranulating into phagosomes. Acid phosphatase staining was most intense during early phagolysosome formation. HID-TCH-SP staining was also observed in extracellular degranulated lysosomal matrices and on the surface of many peritoneal heterophils. These results indicate that loss of sulfate staining in mature heterophil granules is the result of masking by intragranular substances rather than of removal, and that these components may be unmasked during phagocytosis and/or redistributed to the cell surface after exocytosis.     

Analysis of human neutrophil granule protein composition in chronic myeloid leukaemia by immuno-electron microscopy

Summary In this study immuno-electron microscopy was used to assay, semi-quantitatively, the granule contents of elastase, lactoferrin, lysozyme and myeloperoxidase in human peripheral blood neutrophils from 13 chronic myeloid leukaemia patients in the chronic phase of the disease and from normal non-smoking donors. The fixation conditions that adequately preserved the antibody binding capacities of these antigens and reasonably preserved the ultrastructure of the neutrophils were selected by light-microscopic immunoperoxidase cytochemistry on cytospin smears. Immunogold cytochemistry on LR White resin sections localised elastase and myeloperoxidase to the primary granules, lactoferrin to the secondary granules and lysozyme to both types of granule. When applicable, peroxidase cytochemistry was combined with immunogold staining making it easier to distinguish the primary from the secondary granules. A comparison of the immunolabelling density values obtained for the leukaemic and normal states revealed no significant abnormalities in the immunoreactivity patterns for any of these neutrophil granule antigens in the leukaemic patients. All 13 patients gave normal immunostaining reactivities for these neutrophil granule proteins. Consequently the distribution patterns of these proteins, as shown in this study, cannot be used as indices in distinguishing chronic myeloid leukaemic neutrophils from normal neutrophils.     

Granulation staining and cytochemistry of peripheral blood leucocytes in healthy carp (Cyprinus carpio L.) II: Monocytes

Granulation staining and cytochemistry of peripheral blood monocytes in healthy carp ( Cyprinus carpio L.) are described. Blood smears were stained for periodic acid-Schiff (PAS), peroxidase, oxidase, alkaline and acid phosphatase, α-naphthyl acetate esterase, α-naphthyl-butyrate esterase, naphthol-AS-chloroacetate esterase (AS-D), naphthol-AS-acetate esterase and β-glucuronidase. For representation of different granulations triazide-staining for eosinophil and neutrophil granules and aqueous methylere-blue staining for basophil granules were used. Lipids were shown by sudan-black-reaction. Monocytes showed only basophil granulation and weak lipid reaction. All tested enzymes were detected, with the exception of peroxidase. The PAS reaction for glycogen proof was negative.     

Secretory granules of B-cells in the synovial membrane

Summary Ultrastructural and cytochemical studies have been made on secretory granules of B-cells (fibroblast-like cells) in the knee-joint synovium. The secretory granules were membrane-bounded spherical or slightly elongated bodies, 150 to 350 nm (average 230 nm) in diameter and had a homogenous matrix with several cores. These granules were found in B-cells of all animal species examined; they were numerous in mice and rats, and few in guinea pigs, rabbits and man. Ultrastructural and cytochemical examinations revealed that the Golgi apparatus was involved in the formation of the secretory granules. Unlike lysosomes, they showed no acid phosphatase activity. The granule matrix was positively stained by Thiéiy's periodic acid-thiocarbohydrazidesilver proteinate technique, and the cores were digested by protease. These findings suggest that the granule matrix contains mucopolysaccharide(s) and/or glycoprotein(s) and the core material is largely proteinaceous in nature.     

Cytochemical observations of coelomocytes from the earthworm, Lumbricus terrestris.

Synopsis Coelomocytes of the earthworm,Lumbricus terrestris, were stained by cytochemical techniques to determine the biochemical composition of the seven different cell types and subtypes. The enzymes acid phosphatase and -glucuronidase are present in all types of coelomocytes, but are especially abundant in basophils and neutrophils; the differences in enzyme amounts correlate well with the differences in phagocytic activity of the various cell types. No peroxidase is present. The cytoplasmic basophilia of basophils is due primarily to ribonucleic acid. Basophils also contain large deposits of glycogen, with neutrophils and chloragogen cells containing somewhat lesser amounts. The predominant granules of the two types of acidophils and of granulocytes are composed of a basic protein and a neutral mucopolysaccharide or glycoprotein. A second granule population, present in low numbers in acidophils and granulocytes, but in larger numbers in basophils and neutrophils, is small in size and lipid-positive and may, in part, represent lysosomes.Lipid is especially abundant in the vesicles and granules of the two types of chloragogen cells. Some granules of chloragogen cells also contain ferrous and ferric iron and a substance with pseudoperoxidase activity. The cytoplasm contains protein, glycogen, and a neutral mucopolysaccharide. In addition, acid mucopolysaccharides are variably present in the cytoplasm of chloragogen cells, the only coelomocytes to contain this class of substances.     

Investigation of granulocytopoietic kinetics by microdensitometric evaluation of primary granule naphthol-AS-D-chloroacetate esterase activity

Using a scanning microscope photometer we determined quantitatively the enzymecytochemical reaction product for naphthol-AS-D-chloroacetate esterase in neutrophilic granulocytes and their precursors in man. Evaluation of neutrophilic cells from three healthy donors resulted in a logarithm-normal distribution. After subdivision of these cells in their morphologically defined maturational stages no statistically bimodal distribution was shown within the single cell groups. Myelocytes showed twice the amount of the polymorphonuclear neutrophil absorption values. The highest promyelocyte obsorptions were double the values of the myelocyte absorptions. The standard deviation of the absorbance obtained with promyelocytes (which encompass cells already producing granules up to cells reaching their maximal granule content) was significantly higher than the standard deviation of the myelocytes. As already known, primary granules are only synthesized at the promyelocyte stage and - according to the present knowledge - their chloracylesterase and peroxidase activities are not lost during further maturation. Consequently, our results indicate that only enzyme-rich, late promyelocytes undergo mitosis transforming into myelocytes. Correspondingly, their absorption value was halved. Since the absorbance from myelocytes to polymorphonuclears is again halved, myelocytes divide only once. Metamyelocyte absorptions in part correspond to that of myelocytes. This indicates that no distinction can be made between myelocytes with mitotic capacity and "true" if only the size and the nuclear shape are considered metamyelocytes which are not longer capable of undergoing mitosis.     

Subcellular localization and properties of pyridoxal phosphate phosphatases of human polymorphonuclear leukocytes and their relationship to acid and alkaline phosphatase

Using a novel fluorimetric assay for pyridoxal phosphate phosphatase, human polymorphonuclear leucocytes were found to exhibit both acid an alkaline activities. The neutrophils were homogenised in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density gradient centrigfugation. The alkaline pyridoxal phosphate phosphatase showed a very similar distribution to alkaline phosphatase an was located solely to the phosphasome granules. Fractionation experiments on neutrophils treated with isotonic sucrose containing digitonin and inhibitor studies with diazotised sulphanilic acid and levamisole further confirmed that both enzyme activities had similar locations and properties. Acid pyridoxal phosphate phosphatase activity was located primarily to the tertiary granule with a partial azurophil distribution. Fractionation studies on neutrophils homogenised in isotonic sucrose containing digitonin and specific inhibitor studies showed that acid pyridoxal phosphate phosphatase and acid phosphatase were not the result of a single enzyme activity, Neutrophils were isolated from control subjects, patients with chronic granulocytic leukaemia and patients in the third trimester of pregnancy. The specific activities (munits/mg protein) of alkaline pyridoxal phosphate phosphatase an alkaline phosphatase varied widely in the three groups and the alterations occurred in a parallel manner. The specific activities of acid pyridoxal phosphate phosphatase and of acid phosphatase were similar in the three groups. These results, together with the fractionation experiments and inhibition studies strongly suggest that pyridoxal phosphate is a physiological substrate for neutrophil alkaline phosphatase.     

The professional phagocytes of sea bass (Dicentrarchus labrax L.): cytochemical characterisation of neutrophils and macrophages in the normal and inflamed peritoneal cavity

In order to identify the phagocytic cells of sea bass, the peritoneal leucocyte population of fish injected intraperitoneally with Photobacterium damselae subspecies piscicida was studied by light microscopy using cytocentrifuge preparations stained by the Antonow technique for peroxidase detection. Among the leucocytes present in the peritoneal exudate of the infected fish (macrophages, neutrophils, eosinophilic granular cells, lymphocytes and thrombocytes), macrophages and neutrophils were the only phagocytic cells. Neutrophils were easily distinguished from macrophages in Antonow stained preparations by the pattern of peroxidase positivity. Using ultrastructural cytochemistry, neutrophils were found to have abundant cytoplasmic granules positive for peroxidase and arylsulphatase and were negative for alpha-naphthyl butyrate (ANB) esterase. In contrast, ANB esterase activity was detected in macrophages. These leucocytes were typically negative for peroxidase, but ocasionally, some macrophages with peroxidase or arylsulphatase-positive vacuoles were observed. Both phagocytes had cytoplasmic granules positive for acid phosphatase. Glycogen particles were found in the cytoplasm of the two phagocytic cells, but they were much more abundant in neutrophils. Macrophages were much more abundant than neutrophils in the peritoneal cavity of non-injected sea bass but early after the intraperitoneal injection of bacteria, the number of neutrophils increased quickly and extensively. Higher numbers of intraperitoneally injected bacteria were found inside macrophages as compared to neutrophils because macrophages strongly predominated in the peritoneal population at the time of injection. However, when the bacteria were injected into peritoneal cavities with high numbers of neutrophils (attracted by a previous injection of 12% casein), the percentage of neutrophils with phagocytosed bacteria increased, approaching that of infected macrophages. Taken together, these results show that in sea bass, as in many other organisms, in addition to macrophages, neutrophils are important phagocytic cells, the relative participation of each of the two phagocytes in defense mechanisms against infection depending on the opportunity to encounter the invading infectious agents.     

Glycoconjugate localization with lectin and PA-TCH-SP cytochemistry in rat hypophysis

Glycoconjugates were localized by light microscopy with lectin-peroxidase conjugates and by electron microscopy with the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) sequence in immunocytochemically or morphologically identified cell types in rat pituitary. Lectin histochemistry demonstrated sialic acid and glycoconjugates with N-glycosidically linked oligosaccharides in gonadotrophs, thyrotrophs, and corticotrophs. Galactose penultimate to sialic acid was observed mostly in gonadotrophs. The terminal galactose-N-acetylgalactosamine disaccharide was detected in a few gonadotrophs and in a moderate number of mammotrophs. Fucose was localized in only corticotrophs with two fucose-binding lectins and in thyrotrophs with another. Several different monosaccharides were seen in glycoconjugates in melanotrophs and in Herring bodies. Melanotrophs displayed heterogeneous staining with fucose-binding lectins. A small number of nonsecretory cells were also visualized in the pars distalis by virtue of their glycogen content. PA-TCH-SP staining revealed complex carbohydrates in secretory granules and some Golgi cisternae in all types of hormone-producing cells in the pars distalis except for the somatotrophs. Melanotrophs of pars intermedia exhibited stained secretory granules and irregular dense bodies containing a stained meshwork. Corticotrophs of the pars distalis lacked the latter bodies, although they form the same glycoprotein precursor hormone as melanotrophs. Lectin conjugates and the PA-TCH-SP sequence stained some groups of secretion granules in Herring bodies, possibly representing vasopressin-containing granules as well as other cell types in the pars nervosa.