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PubMed1994

Actinobacillus pleuropneumoniae in gnotobiotic piglets: ultrastructural changes in the pulmonary alveoli with dose and time.

The ultrastructural changes in pulmonary alveoli produced by transtracheal inoculation of 10(6) and 10(8) CFU of Actinobacillus pleuropneumoniae serotype 5 in gnotobiotic piglets were studied after 1 and 4 h. At 1 h postinoculation (p.i.) with 10(6) or 10(8) CFU, no gross change in lung and no evidence of infiltration of cells into alveoli was observed. At 4 h p.i., at a dose of 10(6) CFU, a generalized red mottling occurred in the dorsal half of the caudal lobe, which revealed ultrastructural evidence of neutrophil infiltration into alveoli along with fibrin and a few erythrocytes. At 4 h p.i., at a dose of 10(8) CFU, there was a bilateral lung lesion characterized by a generalized mottling and congestion, within which we observed ultrastructural evidence of bacteria and cellular debris in the alveoli and fibrin clots and cellular necrosis in the alveolar septum. By using gnotobiotic piglets and visualizing the effects of bacterial inoculum on cellular ultrastructure of the lung, we have demonstrated that both dose and time play roles in the early pathogenesis of experimental porcine pleuropneumonia. The developing lesion in lungs of gnotobiotic piglets infected with pure cultures of A. pleuropneumoniae can be controlled experimentally. This experimental procedure can provide a base of reproducible, sequential, ultrastructural changes with which to compare the role of inflammatory mediators in the lung and the effects of drugs on immunologic events in the lung.

Actinobacillus Infections↗
PubMed1997

Ultrastructure of the human APUD cells.

The present article summarises the results of our studies on the ultrastructure of the APUD cells at an early embryonic stage of development. Twenty eight 8-week-old human embryos were selected. The early forms of the APUD cells in the epithelium of certain embryonic organs of endoblast origin, i.e., stomach, small intestine, liver and lung (bronchi), were distinguished and examined by transmission electron microscopy. The ultrastructure of these premature cells was compared with the ultrastructure of mature APUD cells from adult human organisms. Differences regarding number, size and location of the secretory granules were established. The form and ultrastructure of the granules were found to be identical in both cell types studied. The ultrastructural characteristics and identification of the embryonic APUD cells may serve as a reliable criterion in complex morphological explorations of the human prenatal development.

APUD Cells↗
PubMed1986

Progressive symmetric erythrokeratodermia. Histological and ultrastructural study of patient before and after treatment with etretinate.

Progressive symmetric erythrokeratodermia is a rare inherited cornification disorder characterized by symmetric erythematous hyperkeratotic plaques. Approximately 25 cases have been reported, but the ultrastructural features have not been well characterized. In this article, we describe the clinical, histologic, and ultrastructural findings noted in our patient. Biopsy specimens taken before treatment with etretinate showed hyperkeratosis with a well-preserved granular layer and acanthosis. Ultrastructural examination disclosed that granular cells contained markedly swollen mitochondria and that corneocytes contained many lipidlike vacuoles. After initiation of treatment, considerable clinical improvement was observed, but without significant histologic modification. The principal posttreatment ultrastructural changes observed were the reduction of mitochondrial swelling in granular cells and the reduction in the number of lipidlike vacuoles in corneocytes.

Adult↗
PubMed1995

Bart's syndrome. Ultrastructure and genetic linkage.

BACKGROUND AND DESIGN: Bart's syndrome, originally described in a large family in 1966, consists of congenital localized absence of skin, blistering, and associated nail abnormalities. Since then, several descriptions of patients with similar clinical findings have suggested that this syndrome may represent any of the three subtypes of epidermolysis bullosa: epidermal, junctional, or dermal. Because no histologic or ultrastructural studies were done in Bart's kindred, and neither immunohistologic nor genetic linkage technology was available at that time, classification of the syndrome has been unclear. We report the findings of clinical, ultrastructural, immunohistologic, and genetic linkage studies of the original kindred and their descendants. We contacted original family members and their descendants by telephone and questionnaire. Skin biopsy specimens adjacent to blisters were obtained for ultrastructural and immunochemical analysis. Blood samples were drawn from affected members and their spouses and children for genetic linkage studies. RESULTS: The clinical findings seen in the descendants of the original family with Bart's syndrome were similar to those described in 1966. We did, however, detect persistence of blistering into adult life and mild atrophic scarring and milia formation at sites of blistering in some family members, a finding not noted in the original study. Hypertrophic scarring and albopapuloid lesions were not detected. Ultrastructural analysis of skin from affected family members showed poorly formed anchoring fibrils and cleavage below the lamina densa. Immunohistochemical staining localized type IV collagen at the roof of blistered skin. Staining for type VII collagen was found to have a normal distribution in nonblistered skin. Genetic linkage studies mapped the gene for the disease in this family to chromosome 3p at or near the site of the gene encoding type VII collagen. CONCLUSION: Bart's syndrome is a subtype of dominantly inherited dystrophic epidermolysis bullosa.

Adult↗
PubMed1998

An ultrastructural comparison of mechanical dermabrasion and carbon dioxide laser resurfacing in the minipig model.

OBJECTIVE: To compare the histological and ultrastructural changes in skin collagen with mechanical dermabrasion and pulsed carbon dioxide laser resurfacing in the minipig model. SETTING: Academic medical center. SUBJECTS: Yucatan minipig animal skin model. MAIN OUTCOME MEASURES: Comparison of light microscopic and ultrastructural (electron microscopic) changes in the skin following the 2 resurfacing modalities. RESULTS: No significant difference in collagen histological characteristics or ultrastructure was detected between the 2 comparison groups. CONCLUSIONS: When mechanical dermabrasion or pulsed carbon dioxide laser resurfacing is used with similar-depth injury to the dermis in this model, the histological changes seen via light microscopy and ultrastructural changes seen via electron microscopy are similar between the 2 treatment modalities.

Animals↗
PubMed1999

Ultrastructural change at rat cerebellothalamic synapses associated with volitional motor adaptation.

Our ability to develop or modify motor skills is thought to involve persistent changes in the efficacy of synaptic transmission (synaptic plasticity) in the cerebellum. Previous work from our laboratory and others, examining synapses between neurons in the deep cerebellar nuclei and neurons in the thalamus revealed ultrastructural characteristics that have been implicated in the expression of synaptic plasticity at other locations in the brain. The present study sought evidence of ultrastructural plasticity at cerebellothalamic synapses associated with volitional motor adaptation. Adult rats were subject to 21 days of training, throughout which a novel load (overcome by predominantly shoulder adduction) was applied to the left forelimb while they fed (the right forelimb acted as an internal control). The behavioral paradigm was observed to produce a profound unilateral motor adaptation that was complete by day 15. Three days before the end of training, intracortical microstimulation was performed to identify the regions of primary motor cortex responsible for execution of shoulder adduction movements on the experimental (right) and control (left) sides of the brain. A retrograde neuronal tracer was injected into these cortical regions and the animals were returned to the training cage. Following training, small blocks of thalamic tissue containing retrogradely labeled cells were removed from the brains for ultrastructural analyses of presumed cerebellothalamic synapses (see Materials and Methods section). The only ultrastructural change observed to occur in association with the volitional motor adaptation was an increase in the proportion of dendritic shaft active zone with docked synaptic vesicles.

Adaptation, Physiological↗
PubMed1998

Gonadotropic and thyrotropic cells from the Mediterranean yellowtail (Seriola dumerilii; Risso, 1810): immunocytochemical and ultrastructural characterization.

BACKGROUND: Gonadotropins GTH I and GTH II from the pituitary of Mediterranean (M.) yellowtail (Seriola dumerilii) were isolated and characterized, and antisera to the whole GTH II molecule (anti-My alpha,betaGTH II) and to its beta-subunit (anti-My betaGTH II) were obtained. At the light microscopic level, anti-My alpha,betaGTH II reacted with My betaGTH II-immunoreactive cells (GTH II cells), thyroid-stimulating hormone (TSH) cells, and a third cell population, which could have been GTH I cells. The aim of this study was the ultrastructural characterization of GTH and TSH cells in M. yellowtail using the immunogold method in order to provide a basis for future research into reproduction of this species. METHODS: Pituitaries from mature male and female specimens reared in captivity were dissected out and processed for electron microscopy. The immunogold method was carried out by using anti-My alpha,betaGTH II, anti-My alpha,betaGTH II preabsorbed with the alpha subunit of the M. yellowtail GTH (My alphaGTH-subunit), anti-My betaGTH II, anti-human (h) alpha,betaTSH, and anti-h betaTSH sera to reveal gonadotropic and thyrotropic cells. RESULTS: M. yellowtail gonadotropic cells were very heterogeneous with regard to their size, shape, and ultrastructural features. Cells were found with numerous, round, variably electron-dense, secretory granules and globules; others were found with their cytoplasm occupied mostly by dilated cisternae of rough endoplasmic reticulum (RER) and scarce secretory granules; and other intermediate cell forms were found that showed varying proportions of secretory granules and dilated RER. The secretory granules and globules were immunogold labeled with anti-My alpha,betaGTH II, and the reaction was weaker in the latter. A similar immunogold-labeling pattern was found with anti-My betaGTH II and with anti-My alpha,betaGTH II preabsorbed with the My alphaGTH-subunit, although some cells that showed the same ultrastructural features described above were not immunogold labeled and could have been GTH I cells. Thyrotropic cells had small, round, secretory granules of medium or high electron density that were immunogold labeled with anti-My alpha,betaGTH II, anti-h alpha,betaTSH, and anti-h betaTSH sera, but not with anti-My betaGTH II or anti-My alpha,betaGTH II serum preabsorbed with the My alphaGTH-subunit. All of the cell forms described for gonadotropes and thyrotropes were also found in a state of involution. CONCLUSIONS: Gonadotropes that are of a single morphological type but that vary in ultrastructure are present in the pituitary of captive M. yellowtail. GTH II- and putative GTH I-producing cells were distinguishable from one another and from TSH cells by their different reactions to anti-My alpha,betaGTH II, anti-My betaGTH II, and anti-My alpha,betaGTH II preabsorbed with the My alphaGTH-subunit.

Animals↗
PubMed1975

Ultrastructure of human bronchiolo-alveolar cell carcinoma.

Ultrastructural features were correlated with a series of special staining reactions in eight cases of bronchiolo-alveolar carcinoma. Ultrastructural, all tumors were similarly composed of large cells with abundant cytoplasm and small nuclei in close contact with each other. Straight membranes or complex interdigitations occurred within adjacent tumor cells, attached to each other by scattered desmosomes. Microvilli or cilia abutted from free surfaces of the cells, and were noted in different stages of evolution. Numerous organelles were seen in the cytoplasm, including prominent mitochondria and single or coalescent secretory vacuoles with granular matrix resembling mucin. Other cytosomes less commonly found were irregular, partially lamellated inclusions and dark, homogeneous structures without limiting membranes. The stroma of the tumors was rich in elastin and collagen. Both the number of secretory vacuoles in the cytoplasm of tumor cells and the amount of connective tissue fibrils in the stroma of the tumors correlated well with the findings in the series of special staining reactions. No definite ultrastructural feature was present to identify the tumors as orginating from Type II alveolar epithelial cells, but the possibility exists that they arose in the bronchiole, from undifferentiated basal cells or mucinous cells per se. Our impression in these eight cases studied is consistent with the view that bronchiolo-alveolar carcinomas are indistinguishable at the ultrastructural level from other bronchogenic adenocarcinomas.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1978

Ultrastructural observations in pleomorphic liposarcoma.

An ultrastructural study of pleomorphic liposarcoma with an unusual clinical presentation is described. A 69-year-old Caucasian female presented with recurrent superficial phlebitis of left leg, which responded only partially to conventional therapy. Following investigations, a mass was excised. Diagnosis of pleomorphic liposarcoma was made on microscopic examination. Numerous lipid droplets in the cytoplasm and often within intranuclear extensions of cytoplasm were seen on oil red O stain of frozen sections. Ultrastructural features are quite distinctive. The cells varied from small to often large pleomorphic cells with numerous lipid spaces without limiting membrane, large pleomorphic nuclei, and an abundance of cytoplasmic organelles. Centrioles were very prominent, in close proximity to nuclei, and collections of autophagocytic inclusions. Intercellular collagen was immature and scant. These features are compared to ultrastructural features of malignant fibrous histiocytoma, pleomorphic rhabdomyosarcoma, and cardiac myxoma, indicating that ultrastructural features are distinctive and help differentiate similar soft tissue tumors.

Aged↗
PubMed1980

Osteogenic sarcoma: a study of the ultrastructure.

Ultrastructural examination of 26 osteogenic sarcomas has revealed that in addition to the basic osteoblast comprising the tumor, five additional cell types may be identified. These include chondroblasts, osteocytes, undifferentiated cells and myofibroblasts. The latter cell type has not been reported in previous studies of medullary osteosarcomas. The relative portions of the cell types varied as to the type of osteogenic sarcoma studied. Osteoid production, the single diagnostic feature of these tumors, was evident and the various ultrastructural appearances of this material are shown. One case of an osteogenic sarcoma that arose in Paget's disease of bone is described and did not differ ultrastructurally from the conventional medullary osteogenic sarcoma. Our studies have shown that osteogenic sarcoma may share common ultrastructural features with other sarcomas involving bone and soft tissue and that the basic difference between osteogenic sarcoma and soft-tissue sarcomas is the presence of osteoid in the former and differing cytoplasmic differentiation in the latter category of tumors.

Bone Neoplasms↗
PubMed1980

A pigmented differentiating neuroblastoma: a light and ultrastructural study.

An unusual case of a 4-year-old girl with a differentiating neuroblastoma arising in a thoracic sympathetic ganglion in which the neoplastic cells contained large amounts of melanin is described. Ultrastructural study showed the melanin granules were not associated with premelanosomes but appeared to be of lysosomal origin similar to neuromelanin seen normally in neurons of the substantia nigra and elsewhere in the central and peripheral nervous systems. The melanin in this neoplasm ws ultrastructurally distinct from that demonstrated in other types of pigmented neural crest neoplasms which have been studied ultrastructurally. The melanin in these latter neoplasms has been associated with premelanosomes and appears identical to melanin formed in epidermal melanocytes, so-called cutaneous or neural-crest-type melanin. The ultrastructural findings in this case demonstrate that neuromelanin can occur in melanotic tumors of neural crest origin, although its occurrence is much less common than that of cutaneous (neural crest) melanin.

Child, Preschool↗
PubMed1994

Ultrastructure of nonspecific cytotoxic cells in teleosts. I. Effector-target cell binding in a marine and a freshwater species (seabream: Sparus aurata L., and carp: Cyprinus carpio L.).

BACKGROUND: Fish cytotoxic effectors form a cell population whose ultrastructure and properties of conjugation with target cells have not been completely established. We report the ultrastructure of the nonspecific cytotoxic cells in a seawater teleost (Sparus aurata L.) and compare it to a freshwater species (Cyprinus carpio L.). METHODS: Blood leucocytes were incubated with HeLa or B16 melanoma cells. Samples were processed for transmission electron microscopic study. RESULTS: Conjugates consisting of leucocytes binding targets were regularly observed after 30 min, 1 hr, or 2 hr of incubation. In both species leucocytes binding to targets showed ultrastructural features of either monocyte-like or lymphocyte-like cells. Monocyte-like cells usually appeared flattened against the targets and seemed to enclose fragments of the target to form cytoplasmic vesicles and the content of their scarce cytoplasmic granules seemed to be delivered into these vesicles. In the seabream lymphocyte-like cells, dense cytoplasmic granules occurred only occasionally, and neither microvilli nor cell processes were present at the contact areas with the targets. In the carp, the contacts were more numerous and formed regularly interdigitating contact areas and the lymphocytes showed granules with characteristic dense and fibrillar contents. CONCLUSIONS: We conclude that seabream and carp have a leucocyte cell population with ultrastructural features of either monocytes or lymphocytes showing nonspecific cytotoxic ability.

Animals↗
PubMed1996

Human synovial mast cells. I. Ultrastructural in situ and in vitro immunologic characterization.

OBJECTIVE: To examine the ultrastructure of human synovial mast cells in situ, to identify immunologic and nonimmunologic stimuli that activate these cells in vitro, and to quantify a number of preformed and de novo-synthesized mediators. METHODS: We conducted an ultrastructural study of synovial mast cells in situ and performed immunoelectron microscopy localization of tryptase and chymase. Isolated synovial mast cells were analyzed biochemically, immunologically, and functionally in vitro and compared with cells from human lung, heart, and skin. RESULTS: Ultrastructural study of synovial tissue revealed mast cells with homogeneously dense, scrolled, crystal, and mixed granules, and lipid bodies in the cytoplasm. A small percentage of mast cells showed evidence of degranulation. Immunoelectron microscopy demonstrated the subcellular localization of tryptase and chymase over granules of > 90% of the mast cells, which were of the MCTC subtype. Isolated synovial mast cells released histamine in response to immunologic (anti-IgE and anti-Fc epsilon receptor I [anti-Fc epsilon RI]) and nonimmunologic (substance P, recombinant human stem cell factor, and 48/80) stimuli, but did not respond to recombinant human C5a in vitro. Synovial mast cells differed from those isolated from other human tissues, in a variety of immunologic and biochemical features. There was a linear correlation between the percentage of histamine secretion and tryptase release (r = 0.79, P < 0.001) induced by cross-linking of Fc epsilon RI. Cross-linking of IgE with anti-IgE on synovial mast cells induced de novo synthesis of prostaglandin D2 (mean +/- SEM 87.5 +/- 4.9 ng/10(6) cells) and of leukotriene C4 (57.6 +/- 17.8 ng/10(6) cells). CONCLUSION: Mast cells ultrastructurally characterized in situ in synovial tissue were seen to differ from mast cells previously isolated from other human tissues. This raises the possibility that the local microenviroment influences their phenotype. Isolation of mast cells from human synovia can be useful for studying their role and their mediators in patients with arthritis.

Adult↗
PubMed1988

Ultrastructural organization of normal and transplanted rat fascia dentata: I. A qualitative analysis of intracerebral and intraocular grafts.

Few studies have dealt with the general ultrastructure and synaptic organization of grafted brain tissue. This study was therefore performed to extend current light microscopic observations on intracerebral and intraocular grafts of hippocampal tissue to the ultrastructural level. Blocks of tissue containing the hippocampus and fascia dentata from day 21 embryonic rats were grafted into the brain of developing and adult rats and to the anterior eye chamber of adult rats. After 100 or 200 days of survival the recipient rat brains or eyes were processed for electron microscopy. Tissue containing the graft dentate molecular layer and adjacent granule cell layer was selected for ultrastructural analysis, together with a few samples of the hilus and CA3. Normal dentate tissue was analyzed as control. At the light microscopic level most intracerebral and intraocular grafts displayed an organotypic organization with clearly recognizable cell and neuropil layers. Under the electron microscope the grafted granule cells had normal-appearing dendrites bearing the normal types of spines and forming the normal types of synapses. This was the case even in the absence of the normal major extrinsic afferents like the perforant path. The graft dentate granule cells formed axons and terminals with characteristics of the normal mossy fiber system in the hilus and CA3, in addition to aberrant supragranular mossy fiber terminals known from light microscopic studies of dentate transplants. Abnormal structures included a few dendritic growth cones and an increased occurrence of polyribosomes in spines. Their occurrence indicates ongoing dendritic plasticity even 100 days after transplantation. There was also an increased density of glial elements, particularly in the intraocular grafts. In some of these grafts the granule cells displayed immature traits in terms of nuclear indentations. Dentate interneurons of the basket cell type were present in both the intracerebral and the intraocular grafts. We conclude that grafted dentate granule cells, in different surroundings and without the normal, major perforant path input, can develop a basically normal cellular morphology, which includes the normal ultrastructural characteristics of the dendrites with spines and synapses, and the mossy fibers and its terminals.

Animals↗
PubMedDate not supplied

Liver ultrastructure in mitochondrial urea cycle enzyme deficiencies and comparison with Reye's syndrome.

The liver ultrastructural findings in two girls with partial carbamyl phosphate synthetase I (CPS) deficiency and their heterozygote parents and two siblings with ornithine transcarbamylase (OTC) deficiency are described. Liver ultrastructure in the four patients with inherited deficiencies of urea cycle enzymes showed minimal alterations with essentially normal mitochondria when biopsy was performed during periods of good control of their hyperammonemia. Mitochondrial ultrastructure was also essentially normal in the heterozygotes for carbamyl phosphate synthetase I deficiency. These findings are in contrast to the marked alterations in mitochondrial ultrastructure found in the study of two cases of Reye's syndrome in which severe depression of ornithine transcarbamylase and carbamyl phosphate synthetase I activities was noted.

Adolescent↗
PubMed2003

The effect of sintered dicalcium pyrophosphate on osteoclast metabolism: an ultrastructural study.

Sintered dicalcium pyrophosphate (SDCP), a synthetic compound, has proved to be both bioabsorbable and biocompatible in vivo. Recent work in our institute also has demonstrated that the ingestion of SDCP can increase bone mass in the ovariectomized rat. In this study, we used an in vitro cell culture model to investigate the ultrastructural changes and fate of osteoclasts induced by SDCP. Quantitative evaluation of osteoblasts and osteoclasts after administration of SDCP was performed. We studied immunohistochemical and ultrastructural features of osteoclasts undergoing apoptosis. The results showed that at 10(-4) M SDCP, the osteoblast cell count increased significantly, whereas the osteoclast population decreased significantly. Apoptosis of the osteoclast population was well demonstrated by immunohistochemical study. Ultrastructural study showed that the Golgi apparatus was degraded or dispersed in the cytoplasm. Later, osteoclasts revealed pyknotic nuclei showing condensation and margination of heterochromatins and DNA fragmentation, which are typical features of apoptosis. In addition, disruption of nuclear envelopes leading to leakage of nuclear contents into the cytoplasm was observed in the late stage of apoptosis. In conclusion, SDCP-induced apoptosis of osteoclasts was characterized by ultrastructural changes of the nucleus accompanied by degradation of cellular organelles.

Animals↗
PubMed1991

Ultrastructure of spontaneous and transplanted pituitary tumors in laboratory animals.

The present review examines ultrastructural studies of pituitary tumors in laboratory animals. Such studies have been facilitated by the development of newer techniques such as immunocytochemistry and in situ hybridization. Using these methods it has been possible to correlate morphological features with function by characterizing specific pituitary hormones in secretory granules and analyzing the messenger ribonucleic acids produced by specific cell types. Analyses of spontaneous and experimentally induced tumors have provided a great deal of insight into the function and ultrastructure of these neoplasms. The description of tumor cells producing more than one hormone has been facilitated by immunocytochemical analyses. Studies of transgenic models of pituitary hyperplasia and tumor development are expanding our knowledge about the ultrastructure and about other aspects of pituitary tumors in a more controlled experimental setting. The production of various hormones by the same pituitary tumors and even the same tumor cells indicates that complex regulatory mechanisms must be analyzed by a combination of ultrastructural and other techniques to learn more about growth and hormone secretion in pituitary neoplasms.

Animals↗
PubMed2003

Immunocytochemical and ultrastructural characterization of mammosomatotrope-, growth hormone-, and prolactin-cells from the gilthead sea bream (Sparus aurata l., Teleostei): an ontogenic study.

Growth hormone (GH), prolactin (PRL), and mammosomatotrope (MS) cells of gilthead sea bream, Sparus aurata, a teleost fish, were studied in specimens from hatching to 15 months (adults) using conventional electron microscopy and an immunogold method using anti-tilapia GH sera and anti-chum salmon PRL serum. MS cells, immunoreactive to both anti-GH sera and anti-PRL sera, had been first identified in fish in a previous study in newly hatched larvae and in older larvae and juvenile specimens of Sparus aurata by light microscopic immunocytochemistry. In the present work, MS cells reacted positively to immunogold label only in older larvae and juveniles and their secretory granules immunoreacted with both GH and PRL antisera or with only one of them. MS cells were ultrastructurally similar to the PRL cells, with which they coincided in time. This is the first report on the ultrastructural characterization of MS cells in fish. In adults, the secretory granules of GH cells (immunoreactive to anti-GH serum) were mainly round, of variable size, and had a homogeneous, highly electron-dense content. Irregularly shaped secretory granules were also present. PRL cells (immunoreactive to anti-PRL serum) were usually observed in a follicular arrangement; they showed few, small, and mainly round secretory granules with a homogeneous and high or medium electron-dense content. Some oval or elongated secretory granules were also observed. GH and PRL cells that showed involutive features were also found. In newly hatched larvae, GH, PRL, and MS cells could not be distinguished either by their ultrastructure or by the immunogold labeling of the secretory granules. In 1-day-old larvae, presumptive GH and PRL cells were observed according to their position in the pituitary gland. In 2-day-old larvae, a few cells showed some of the ultrastructural features described for GH and PRL cells of adults. During development, the number, size, and shape of the secretory granules in both cell types clearly increased and the organelles developed gradually. Some GH cells were found undergoing mitosis.

Animals↗