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

Herpetomonas megaseliae grown in the presence of hydroxyurea showed a decline in population during the first 24 hr, eventually increasing slightly over the 7-day incubation. Throughtout the 7-day incubation period the population of the treated organisms never equaled that of the control organisms. The percentage of promastigotes, as opposed to para-and opisthomastigotes, in the treated cultures did not differ from that in the control cultures through the first 3 days in incubation. Thereafter, the percentage of promastigotes in the treated cultures dropped significantly below that of the controls. At the light microscope level, the treated organisms showed an increase in size with associated striations at the anterior end. A multiflagellate (nondividing) condition was also observed in the hydroxyurea-treated organisms. TEM and SEM studies showed pellicular convolutions, which were interpreted as the striations observed under the light microscope. The differnces in population number, kinetoplast number and position and pellicular morphology between control and experimental cultures suggests that enhanced differentiation and abortive cytokinesis are the net effects of hydroxyurea on Herpetomonas megaseliae.
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PMID:Differentiation of Herpetomonas megaseliae: effects of hydroxyurea on morphology and growth. 95 31

The effects of temporary vascular occlusion with surgical clips on the underlying endothelial lining were studied with scanning (SEM) and transmission (TEM) electron microscopy. Twenty-five rabbits were anesthetized and both common carotid arteries exposed. A Heifetz clip was used to occlude the right carotid artery for 5, 15, and 30 minutes, and 2 hours in five animals each. The clips were removed and the vessels immediately perfused with glutaraldehyde. In five remaining animals, the right carotid arteries were occluded for 30 minutes followed by removal of the clip and resumption of blood flow for 30 minutes prior to fixation. Combined SEM and TEM examination of the endothelium of compressed segments revealed "craters" and "balloons", blebs and vacuoles, swollen mitochondria, dilated granular endoplasmic reticulum, and subendothelial edema. There were also areas of endothelial cell flattening, discontinuity, and desquamation exposing the subendothelial tissues. Following restoration of flow, platelets and fibrin were found adherent to altered endothelial cells and to exposed subendothelial tissues. Endothelial craters and balloons were also found distal and, significantly less frequently, proximal to the site of occlusion. It is suggested that antiplatelet aggregating agents may prove beneficial for the prevention of thrombus formation at the site of the clip as well as craters and balloons distal to the clip following procedures requiring temporary vascular occlusion.
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PMID:Endothelial cell damage by temporary arterial occlusion with surgical clips. Study of the clip site by scanning and transmission electron microscopy. 97 35

Ultrastructural analysis including scanning and transmission electron microscopic studies (SEM and TEM) were carried out on oyster gill tissue after exposure either to serum fractions from individuals homozygous or heterozygous for cystic fibrosis (CF), to comparable serum fractions from normal individuals, or to sea water. In 4 of the experiments examined topologically (SEM), the CF sera (either heterozygous or homozygous) stimulated the production of mucus that was found in close association with the cilia. The association of excessive mucus with the cell surface could be responsible, in part, for the well-known inhibition of ciliary activity by a factor in CF serum. In 3 additional SEM experiments involving shorter treatment times, very little difference could be observed between homozygous CF, heterozygous CF, and normal serum-fraction-treated oyster tissues. In parallel experiments, ultrathin sections of gill tissue were examined by means of TEM. Those samples that were responsive, as determined by TEM, displayed several characteristic features, including enlarged and partially exuded goblet cells, altered mucus structure along with twisted and matted cilia. An overall swelling of the gill filament was also observed in the responsive tissues. From TEM analysis no detectable alteration in fine structure was apparent in gill tissues that were treated with sera from heterozygous or normal individuals.
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PMID:Effects of cystic fibrosis serum ciliary inhibitor on oyster gill ultrastructure: analysis by scanning and transmission electron microscopy. 99 86

Normal primary neural induction has been further studied by TEM and SEM. A single mesoderm cell is usually in contact with several ectoderm cells. The mesoderm cells are also contacting other mesoderm cells. It is suggested that ectoderm cells are induced in groups and that induction is synchronized by these contacts. At the points of contact between mesoderm and ectoderm cells cytoplasmic changes are present in the induced tissue.
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PMID:A transmission and scanning electron microsope study of primary neural induction. 102 57

Histopathology of dentinogenesis imperfecta shows a haphazard distribution of dentinal tubules as well as changes in their diameters, sometimes narrowed, sometimes widened. These tubules appear as bundles or sheaves. This kind of dentine is often similar to secondary (also called tertiary) dentine, only mantle dentine preserving a normal structure. There is a complete obliteration of the pulp chamber and an almost complete obliteration of the root canal. Through SEM, the tubules appear to be few in number, their diameters are small and their fine ramifications are intricate through all planes. An heterogenous intertubular substance can be seen. Through TEM, collagenous fibers appear to be uncalcified or incompletely calcified, with a haphazard distribution. There are wide differences in the sizes of crystals and numerous spaces appear between crystals and collagen. Differences between the ultrastructure of human dentinogenesis imperfecta and the dentine of some lower vertebrates are clearly pointed out.
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PMID:[Dentinogenesis imperfecta: a structural and ultrastructural study]. 106 Dec 68

When the dorsal surface of the young chick embryo is examined by SEM, long threads are visible, each of which appears to connect pairs of cells; these cells may be separated from each other by several intervening cells. Many of the threads possess a bead-like structure about half way along their length. When sections of the beads are examined by TEM they are found to resemble midbodies. Furthermore, the threads possess longitudinally arranged structures within them, which are probably the remnants of the microtubules which were part of a mitotic spindle. It is concluded that each bead is a midbody and that each beaded thread is the remains of a telophase bridge connecting two daughter cells which were incompletely separated after mitosis had taken place. The possible function of the beaded threads is considered.
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PMID:Midbodies and beaded threads. 115 64

Morphological changes on the ovarian surface of different mammals both before and during ovulation have been examined by scanning electron microscopy. Preovulatory follicles were blisterlike structures that protruded markedly from the ovarian surface. Basal areas of preovulatory follicles were covered with polyhedral cells containing numerous microvilli, whereas on the lateral surfaces, superficial cells were elongated and possessed few microvilli. At the apex of the follicle, cells were very flattened and possessed few microvilli, which were present only in regions of intercellular contact. In some apical areas, cells appeared to be degenerating, whereas in other regions, groups of cells had "sloughed off." In addition, a fluidlike material was observed to exude from intercellular spaces of the superficial epithelium and to cover some apical cells. By transmission electron microscopy, the same fluidlike material was observed to (1) infiltrate the connective tissue of the tunica albuginea, (2) accumulate under the basal lamina, and (3) distend intercellular spaces of the superficial epithelium. Just prior to ovulation, large, irregular areas of the apex were ruptured and the oocyte, covered with a large amount of fluid, appeared to emerge from the follicle. At ovulation, the oocyte was not completely covered with follicle cells and the zona pellucida was clearly evident. The surface of the zona was quite irregular and contained numerous infoldings, channels and crypts. Follicle cells had polyhedral or star shapes and possessed large cytoplasmic evaginations that obliquely penetrated the zona. Both the zona pellucida and corona cells were covered with a fine layer of granular material. The SEM results and parallel TEM observations suggest that a local increase of fluids (edema) may be an important factor in the final decomposition of the distended and weakened apex of the preovulatory follicle. In addition, the participation of follicle cells, smooth muscle cells and the oviduct in the escape of the oocyte from the ruptured follicle is discussed.
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PMID:A scanning electron microscopic study of the luteo-follicular complex. II. Events leading to ovulation. 117 Jul 53

Normal primary neural induction has been studied by scanning electron microscopy and the results compared with those obtained by TEM. Mesoderm cells are usually in contact with several other cells, both mesodermal and endodermal in origin. By SEM the ectoderm layer has been shown to be in contact with the underlying mesoderm cells. Tufts of fibrous basement membrane are also present between the two cell types. TEM specimens also show an intermediate basement membrane.
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PMID:Primary neural induction as studied by scanning electron microscopy. 121 73

Rats with a nephrotoxic serum nephritis reveal changes of proteinuria and content of serum proteins as well as serum cholesterol in the direction of a nephrotic syndrome as is seen after Daunomycin. Nevertheless, the morphological findings with TEM and especially with SEM are quite different. A striking feature of the nephritis is the rather good preservation of cell processes through all the time of experiment in spite of the elevated proteinuria. Moreover, podocytes with furrowed or ribbed surfaces originate and are most numerous when the signs of inflammation are most pronounced. These furrowed podocytes are interpreted as representing a special reactive, perhaps mobilized form. With SEM it is evident that the glomeruli are altered focally and segmentally in the nephrotoxic serum nephritis.
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PMID:Podocytes of rat kidneys with nephrotoxic serum nephritis. A combined transmission and scanning electron microscopic study. 121 24

The effect of IH764-3, a potent component isolated from Salvia miltiorrhiza, on the proliferation and function of cultured fibroblasts was studied. It was found that the fibroblast growth curve had a dose-dependent relationship with IH764-3 concentration. The incorporation of 3H-TdR and 3H-proline into fibroblasts was significantly inhibited by IH764-3, and calmodulin, fibronectin and thrombospondin contents in the test group were obviously lower than those in the control group. Flow cytometry showed that in the IH764-3-treated group, the percentage of cells in G0/G1 phase was higher than that in the control. Electron microscopic observation (TEM and SEM) showed that in the treated group, collagen secretion was decreased. All of these results indicate that IH764-3 exerts a direct inhibitory effect on fibroblast proliferation and affects their ability to synthesize collagen.
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PMID:The effect of IH764-3 on fibroblast proliferation and function. 128 82


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