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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In long-term cultures of bone marrow, the adherent stromal cells provide support for the proliferation and maintenance of hemopoietic stem cells. These stromal cells and their interactions were characterized by means of scanning (SEM) and transmission (TEM) electron microscopy in correlation with functional studies. Cultures were initiated by establishing the adherent stromal layer as a "soil" which was then "seeded" after 3 weeks by the addition of another marrow-cell suspension. Clonal assay of the supernatant demonstrated the continuous proliferation of the hemopoietic stem cell. The stroma essentially consisted of two cell types, macrophages and epithelioid cells. Macrophages were smaller, 10-15 microns, phagocytosed latex and carbon particles, and contained lysosomes. Their surface did not stain with polycationic ferritin (PCF). Epithelioid cells were much larger, more than 100 microns; contained numerous thin, elongated mitochondria; did not phagocytose latex particles; but did display strong surface staining with PCF. The appearance of epithelioid cells in TEM depended on their state of development and whether the section was parallel or perpendicular to the substratum. Epithelioid cells displayed a maturational spectrum, at two ends of which were synthetic and storage phases. In the synthetic phase, the cell contained numerous profiles of rough endoplasmic reticulum, and in the storage phase, numerous storage granules. These two phases were best appreciated in sections perpendicular to the substratum, demonstrating synthetic cells on top settling over the substratum upon maturation into the storage cells. Both macrophages and epithelioid cells contained fat globules which increased in number and size with the addition of hydrocortisone to the culture medium. A distinct fat-cell type, as has been claimed, was not found in this study. Granulopoiesis was observed in the culture system in the absence of colony-stimulating activity in the supernatant, suggesting direct cellular interaction or short-range factors in the induction of granulopoiesis. Widespread cellular interactions were noted between macrophages and epithelioid cells, the latter often completely embracing the former and both extending cytoplasmic processes toward each other. This is reminiscent of the cooperative interaction of endoderm and mesoderm in chick embryo hemopoiesis and may be necessary for the maintenance of stem cells in these cultures.
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PMID:Morphological studies on long-term culture of marrow cells: characterization of the adherent stromal cells and their interactions in maintaining the proliferation of hemopoietic stem cells. 710 79

Twenty-three spontaneous pituitary tumors in 58 rats of Wistar/Furth/Ico strain were studied. The incidence is 38% in rats older than 10 months; it rises with age, with a maximum at 28-32 months (68.7%) and is higher in females (71.4%) than in males (35%) over 17 months. Light-microscopic and immunocytochemical studies revealed 20 prolactinomas in 19 rats (19/58, 32.7%) and 3 spongiocytic nonimmunostaining adenomas (3/58, 5.2%). The prolactinoma is often hemorrhagic. The cells, often arranged in sheets and agranular, are mostly positive with anti-rat prolactin (rPRL) serum. They have few polymorph granules and a well-developed rough endoplasmic reticulum. In the spongiocytic adenoma, the cells are arranged in cords. Their cytoplasm is slightly vacuolated. In prolactinoma-bearing rats, the mean plasma PRL value was 213 +/- 72.5 microgram/1 (SEM) (N = 15 +/- 1.8 microgram/1 [SEM]). A linear correlation was found between the logarithm of the tumoral pituitary weight or of the tumor size and the logarithm of the prolactinemia. Because of the analogies between these rat prolactinomas and 57 human prolactinomas, the Wistar/Furth/Ico rat strain is considered as a good animal model.
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PMID:Spontaneous pituitary tumors in the Wistar/Furth/Ico rat strain. An animal model of human prolactin adenoma. 712 8

A study in rats demonstrated that morphologic changes in the bone osteocytes and osteoblasts are produced following parathyroid hormone (PTH) injection into thyroparathyroidectomized animals. It further showed that similar changes occur in normal rats as the result of of extended fasting. Plasma calcium concentrations were determined at sacrifice to ascertain that these changes in bone occurred at times when plasma calcium is rising as the result of parathyroid hormone stimulation. Tibias from these animals were removed and prepared for morphologic observation using both transmission (TEM) and scanning (SEM) electron microscopy. Specific structural features characterized bone cells stimulated by exogenous or endogenous PTH. The most significant morphologic alterations involved surface microvilli and blebs as determined by SEM. TEM studies showed alterations in the cisternae of the rough endoplasmic reticulum (RER). Additionally, cell shape varied markedly from the control cuboidal morphology. These morphologic changes occurred during peak periods of plasma calcium change and returned to control morphology as plasma calcium levels normalized. Use of an extracellular electron-dense tracer (lanthanum) confirmed the patency of the intercellular channels and the presence of a fluid space between the bone cell plasma membranes and the mineralized surface. PTH stimulation modified cell activity such that the tracer material entered the cell more readily, possibly by inducing increased pinocytosis (endocytosis). This study supports the concept that the osteocytes and lining cells on the surface of bone play a role in maintenance of plasma calcium concentrations.
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PMID:Influence of parathyroid hormone on bone cell ultrastructure. 722 63

Urinary bladders of BALB/c male mice treated with 250 ppm of 2-acetylaminofluorene for 1, 3, 5, 7, and 14 days were examined for early scanning (SEM) and transmission electron microscopic (TEM) changes. SEM observations at days 1, 3, and 5, and TEM observations at days 1 and 3 revealed no significant changes. The bladders of the mice treated for 7 days contained an occasional focus showing irregularity in the shape and size of the superficial cells and SEM revealed ropey microridges in an occasional cell. The bladders of mice treated for 14 days had a greater irregularity of cell size on SEM. TEM changes were evident as early as 5 days with an increase in severity at 7 and 14 days. A numerical reduction of fusiform vesicles, asymmetric membrane plaques and Golgi apparatus along with an increase in membranous whorls, endoplasmic reticulum, cytolysosomes, and small rounded vesicles was evident. The study may aid in a better understanding of early morphologic changes of urothelium in response to a carcinogen.
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PMID:A scanning and transmission electron microscopic study of urinary bladders of mice treated with 2-acetylaminofluorene. 725 18

Three dimensional structure of intracellular elements were observed by the Osmium-DMSO-Osmium method and by a field emission SEM equipped with a high resolution device. (1) Rough endoplasmic reticulum: Their cisternae were closely opposed to form a lamellar system of flat cavities and they were supported at regular interval by fine thread-like structures. They were also connected to the cell membrane with similar threads. (2) Golgi complex: The Golgi cisternae of the serous cell of rat submandibular gland showed a bell-shape fitting one above another. The most characteristic structure of this Golgi complex was its foot-like tubuli which projected to all sides from the periphery of the cisternae. (3) Synaptic vesicles: The synaptic vesicles of rat retina were observed at the direct magnification from 100,000 to 200,000 fold with the field emission SEM. The vesicles ranged from 30 to 50 nm in diameter, and their shapes were also various, such as spherical, cocoon-like and kidney-shape. The synaptic vesicles were studded with several granules, about 10 nm in diameter. In addition, the fine structure of mitochondria and centrioles were examined.
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PMID:Demonstration of intracellular structures by high resolution scanning electron microscopy. 732 22

Granulosa cells from porcine ovarian follicles were cultured in vitro in standard medium and in medium supplemented with HCG. After culture the cellular 3 beta HSD enzymatic activity was evaluated and the cells were studied by TEM and SEM. A stereological evaluation of the smooth and rough endoplasmic reticulum was carried out. The results indicate that the cultured cells undergo a luteinization process which is more evident in the presence of HCG. In fact, in comparison with the controls, in these cells the enzymatic activity is higher, the rough endoplasmic reticulum decreases and the smooth endoplasmic reticulum increases, the cytoplasm shows lipid droplets and vesicular mitochondria. The cell surface develops a number of microvillus-like evaginations.
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PMID:On the structural changes of granulosa cells cultured in vitro. Histochemical, ultrastructural and stereological observations. 733 47

Intraocular pressure was artificially raised to 60--70 mmHg in 7 albino rabbits for periods of 15 minutes to 4 hours. The corneal endothelium of these eyes was studied by transmission and scanning electron microscopy. A correlation between exposure time to elevated IOP, clinical signs observed by slit-lamp examination, and extent of morphological damage is clearly shown. In eyes exposed to high pressure for 15 and 30 minutes corneas remained transparent and only minimal changes could be detected by SEM, which consisted of small areas of cell with unevenness of their surface, occasional cellular ruptures, and diminution of cilia and microvilli. After 1--2 hours of exposure small, solitary corneal opacifications appeared. In these eyes more severe morphological changes affecting larger areas were observed, with additional cellular blebbing, excariocytosis, cellular rupture, disintegration, and disappearance seen in SEM. Thin sections revealed swelling of mitochondria, disorganisation of endoplasmic reticulum, and the existence of myelin bodies. In eyes exposed for 3 and 4 hours to high IOP corneal haziness, implying stromal oedema, appeared. In these eyes the areas affected were larger, the extent of damage being more severe. Many areas were bare of endothelium, surrounded by scattered cellular debris, and showed cells with ballooning surfaces and multiple ruptures. Even in severe cellular damage cellular junctions appeared intact. It is assumed that endothelial cells are more sensitive to IOP elevation than the cellular junctions and that injury to the active pump system due to morphological damage is responsible for the resultant corneal oedema.
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PMID:Corneal endothelial changes under induced intraocular pressure elevation: a scanning and transmission electron microscopic study in rabbits. 738 48

Intracellular Ca2+ pools contribute to changes in cytosolic [Ca2+] ([Ca2+]i), which play an important role in endothelial cell signaling. Recently, endothelial ryanodine-sensitive Ca2+ stores were shown to regulate agonist-sensitive intracellular Ca2+ pools. Since caffeine binds the ryanodine Ca2+ release channel on the endoplasmic reticulum in a variety of cell types, we examined the effect of caffeine on [Ca2+]i in human aortic endothelial cell monolayers loaded with the fluorescent probe indo 1. Under baseline conditions, 10 mmol/L caffeine induced a small increase in [Ca2+]i from 86 +/- 10 to 115 +/- 17 nmol/L (mean +/- SEM); this effect was similar to that of 5 mumol/L ryanodine and was unaffected by buffer Ca2+ removal. After depletion of an intracellular Ca2+ store by the irreversible endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (1 mumol/L), ryanodine did not affect [Ca2+]i. In contrast, caffeine induced a large rapid increase in [Ca2+]i (176 +/- 19 to 338 +/- 35 nmol/L, P < .001) after thapsigargin exposure; this effect of caffeine was only observed when extracellular Ca2+ was present. A similar increase in [Ca2+]i was induced by caffeine after depletion of ryanodine- and histamine-sensitive Ca2+ stores or after pretreatment with the endoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (10 mumol/L). Thus, under baseline conditions the effect of caffeine on [Ca2+]i is similar to that of ryanodine and appears to be due to the release of an intracellular store. However, after depletion of an endoplasmic reticulum Ca2+ store, caffeine, but not ryanodine, stimulates Ca2+ influx, resulting in a large increase in [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Endoplasmic reticulum Ca2+ depletion unmasks a caffeine-induced Ca2+ influx in human aortic endothelial cells. 755 46

Morphodynamics of oocyte follicle cells association during the development of human ovarian follicles were studied by transmission electron microscopy and high resolution scanning electron microscopy including the ODO method. For this study primordial, primary, growing preantral and antral follicles were systematically analysed in a total of 20 adult and fetal (3-8 months and at term) ovaries. In early stages of follicle development (primordial and primary stages) the flattened and/or polyhedral cells, closely associated with the growing oocyte, project an increasing number of microvillous processes. These are in apposition with the oolemma, and form bulbous terminals presenting attachment zones such as zonula adherens, desmosomes and communicating junctions (gap junctions). "Focal contacts" between oolemma, and lateral microvillous extensions of follicle cells were also present. Unusual forms of contact between follicle cell microvilli and oocytes in the early stages of growing primordial and primary follicles were also observed. These consist of long, thin extensions penetrating into the oocyte through deep invaginations of the oolemma. The aid of high resolution SEM of specimens subjected to the ODO method clearly reveals their 3-D arrangement within the ooplasm. They appear as long tortuous microvilli coming very close to the nucleus, and in their course are closely associated with a variety of organelles such as Golgi vesicles, endoplasmic reticulum membranes and nascent forms of smooth endoplasmic reticulum. Using integrated observations by TEM and SEM, there may be as many as 3-5 "intraooplasmic processes" even in only one plane of fracture of an oocyte. Therefore, if the total volume of the oocyte and associated cells is considered, their amounts appear to be higher than previously reported. Thus, they have to be considered as normal devices of deep contact between the ooplasm and associated follicle cell extensions. The presence of such structures within the ooplasm in early developing follicles well coincides with the great increase in volume of the oocyte. Although it is commonly believed that the activation of the growing oocyte may depend on the numerous contacts between the oolemma and follicle cells (mostly via gap junctions), the finding of these additional intraoocytic extensions suggests that they may in someway contribute to the initiation of growth in the human. In fact, these microvilli penetrate deep into the ooplasm, much like a sword in its sheath.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Oocyte follicle cells association during development of human ovarian follicle. A study by high resolution scanning and transmission electron microscopy. 788 May 91

Leydig cells were isolated from adult male guinea-pig testes using a multi-step procedure involving enzymatic dissociation and Percoll-gradient centrifugation. The following description is the first account of a successful isolation of adolescent guinea-pig Leydig cells. The enriched Leydig-cell preparation routinely isolated from six intact testicles yielded approximately 5.0 x 10(6) +/- 0.7 x 10(6) (+/- SEM) Leydig cells with a viability of 98.0 +/- 0.4% as determined using the trypan-blue exclusion method. The purity of the isolated cell population as assessed by 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) staining averaged 82.5 +/- 0.8%. Under light microscopy, guinea-pig Leydig cells were polyhedral in shape with a large prominent nucleus and a distinct nucleolus. The acidophilic cytoplasm contained numerous lipid-filled vesicles. Ultrastructurally, guinea-pig Leydig cells displayed an eccentrically located ovoid nucleus with dark-staining peripheral heterochromatin. Large quantities of mitochondria, smooth endoplasmic reticulum and particulate-laden lipid droplets were also evident. The steroidogenic potential of the isolated Leydig cells was verified using a maximally stimulating dose of ovine LH (100 ng ml-1) and human CG (200 mIU ml-1). Leydig cells incubated in a shaking (120 cycles min-1) water bath for 3 h at 37 degrees C in capped polypropylene microcentrifuge tubes produced 233 +/- 21 ng and 223 +/- 18 ng testosterone per 1 x 10(6) cells when maximally stimulated with oLH or hCG, respectively. The inclusion of low (1-5 microM) levels of sodium ascorbate during culture enhanced significantly Leydig-cell viability vs. control values.
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PMID:Isolation and culture of highly enriched populations of Leydig cells from guinea-pig (Cavia porcellus) testes. 797 73


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