Scanning electron microscopy of yolk absorption in early chick embryos

Fresh pullet eggs (White Leghorn Strain) were incubated from 6–19 hours. Blastoderms were fixed in situ with aldehyde fixative, post-osmicated in 2% OsO₄, dehydrated in acetone, criticalpoint-dried, mounted ventral side up, coated with palladium-gold wire and observed in a Cambridge Stereoscan S4 scanning electron microscope. Large extracellular yolk granules had a smooth surface and appeared to break up into smaller particles. Similar particles have been observed intracellularly in transmission electron microscopy. Numerous microappendages, mostly ruffles, suggest phagocytosis as a method of absorption of yolk granules into the cells. Absorption of yolk by the cells of the blastoderm involves an initial break up of yolk granules followed by phagocytosis.     

Scanning electron microscopy of the development of the mesoderm layer in chick embryos

Summary The distribution of mesoderm, the structure of mesoderm cells and relationship between mesoderm and ectoderm were examined by SEM in embryos at stages 3 to 5. The mesoderm was displayed by removal of the endoderm and by fracturing the embryos through mesoderm containing regions. Within the mesoderm layer four zones could be distinguished by their cell shape and arrangement — the primitive streak, a multilayered compact area around the margins of the area pellucida, multilayered and loosely arranged cells near the primitive streak and a flattened monolayer of cells around the advancing lateral and anterior edges of the mesoderm sheet. Secretion of basement membrane by the ectoderm was seen to precede the arrival of mesoderm cells. This suggests that ectoderm alone can synthesize basement membrane without mesodermal contribution.     

Scanning electron microscopy

The technology of scanning electron microscopy (SEM) is described in brief. Its application to the study of cell and tissue structure is demonstrated and the evolution of the concept of 'topographical histology' is discussed. Some current literature on the applications of SEM is reviewed under the headings of experimental pathology and human pathology. While SEM has become an indispensable technique for the experimental morphologist, its application to diagnostic pathology and cytology is still at an early exploratory stage.     

Scanning electron microscopy of normal, neoplastic and inflamed human bladder

Scanning electron microscopy (SEM) was used to compare the topographic fine structure of urothelium from normal, neoplastic and inflamed human bladders. The three groups of patients show different patterns. The normal bladder lining is characterized by regularly arranged large superficial cells with ridged surfaces. By contrast, the surface cells of a transitional cell carcinoma are rounded up and covered with microvilli. In some patients with cystitis or post inflammatory hyperplasia SEM appearances intermediate between normal and neoplastic patterns are encountered. However, except in extremely severe cystitis it is possible on SEM to differentiate between inflamed and neoplastic urothelium. Surface microvilli provide a useful malignant marker for transitional cell carcinoma. However, severe inflammation of the bladder, when diagnosed on cystoscopic examination, can and must be excluded by light microscopy before this marker is considered diagnostic for neoplasia.     

Cryptosporidiosis of the bursa of fabricius and trachea in broilers

Cryptosporidial parasitisation of the bursa of Fabricius and trachea is described in broilers. The response in both tissues was of epithelial hyperplasia and inflammatory cell infiltration. No clinical signs were reported.     

北京鸭法氏囊囊素的分离纯化

从2～3月龄北京鸭法氏囊得到的粗提物,经Se(?)hadex G-15和Molselect G-10两步分子筛层析后,得到了部分纯化的促PFC活性因子,该因子的分子量小于750dal。用高压液相色谱(HPLC)进一步分离活性组分,表明活性物质带有较多正电荷,极性较强。     

Antiserum specific for reticulin of the bursa of fabricius.

Antiserum produced by immunizing rabbits with embryonic chicken spleen cells showed, after appropriate absorption with cell suspensions, specificity for fetal spleen cells in membrane immunofluorescence tests. However, when the original antiserum was absorbed with tissue homogenates and tested on cryostat tissue sections, it reacted specifically with the reticular framework which separates the cortical and medullary lymphocytes in the follicles of the adult bursa of Fabricius. It is suggested that the reticulin may influence bursal lymphoid differentiation.     

Scanning electron microscopy of synaptonemal complexes

The novel application of scanning electron microscopy to study whole-mount surface-spread synaptonemal complex complements of rye (Secale cereale) and rat (Rattus norvegicus) is described. Scanning electron microscopy is able to resolve the third dimension in such preparations and improve the tracing of the continuity of lateral elements without losing information that could be obtained by conventional transmission electron microscopy. This improvement is likely to benefit detailed studies of chromosome synapsis and karyology, and may provide a means of circumventing technical obstacles inhibiting the use of surface-spreads as substrates forin situ hybridization under the electron microscope.     

Scanning and transmission electron microscopy of the rat kidney

This study utilized scanning and transmission electron microscopy of renal tissue to provide new information on the gross and microscopic structure of the kidney. The luminal surface of the proximal convoluted tubule was characterized not only by the border of microvilli, but also by crater-like depressions, and circumferential folds. In tissue processed for scanning electron microscopy the proximal tubular cells separated along their lateral surfaces clearly exposing the topography of the lateral cell projections of cytoplasm which have been generally unavailable for viewing because of their interdigitation with adjacent cells. The various segments of the nephron were identified on the basis of position in the kidney, general morphology, and the distribution and form of apical microvilli, cilia, or flaps. The external surface of the papillary tip had several parallel furrows into which the collecting ducts opened. Large plaquelike depressions lined the papillary surface. The opposed surface of the renal pelvis had small plaque-like depressions separated by narrow ridges. Transmission electron microscopy of plastic-embedded tissue specimens which had been previously dehydrated by the critical point drying method demonstrated that little damage occurred from this procedure.     

Scanning electron microscopy of lymphoid cells from leukemia virus-infected mice

Spleen, lymph node, bone marrow, and thymus cells from Friend leukemia virus (FLV)-infected mice were examined by scanning electron microscopy. Whereas splenocytes from normal, noninfected animals showed the expected morphological classes of lymphocytes, including cells with numerous villous projections and smoother cell types, spleen cells from mice infected with FLV showed a rapid alteration of surface morphology. Shortly after infection, a decrease in the number and percentage of villous cells occurred, with a concomitant increase in the number of cells that were larger and smoother. Within 10 to 20 days after infection, the majority of splenocytes were smooth, large cells showing many distinct morphological charges, including surface "holes" and a "spongy" appearance. By days 25 to 35 after infection, most splenocytes were abnormal in appearance. Similar changes occurred in the lymph nodes after FLV infection, but the rate of change was much lower. Abnormal and larger smooth-surfaced cells did not become prominent until after week 2 or 3 infection. Thymus and bone marrow cells showed little if any change in surface morphology until late in the infectious process. However, even at that time only a few of the cells were abnormal in appearance. The changes in cell population in the spleen but not the lymph nodes paralleled the rapid decrease in the percentage of cells which stained positive for surface immunoglobulin and theta antigen. Futhermore, FLV antigen rapidly appeared on spleen cells after infection; fewer lymph node cells were positive, and only low numbers of marrow and thymus cells stained positive for FLV antigen. The marked immunosuppression induced by FLV infection paralleled and in some instances preceded the marked morphological changes.     

Scanning electron microscopy in oral cytology

Sixty-three cell smears from oral mucosa were studied by scanning electron microscopy. Among them, smears from ten healthy controls showed three kinds of cells: flat (superficial) cells with linear anastomosing microridges and microvilli; polygonal (intermediate) cells with well-defined crests between their faces and numerous microvilli; and round (parabasal) cells entirely covered by microvilli. Twenty-five smears from patients with untreated squamous-cell carcinoma showed enlarged polymorphous cells (round, globular, and elongated); microvilli, variable in their dimensions, were irregularly distributed on their surfaces. Eighteen smears from patients with severe epithelial dysplasia showed polymorphous cells with discontinuous but obvious edges separating their faces and with irregular microvilli and ridges. Nine smears were also performed in patients with various other mucosal lesions (lichen planus, leukoplakia, white sponge naevus, pemphigus vulgaris, and herpes). All of these smears were studied comparatively between examination of smears and biopsies by light microscopy. The smears were truly reliable, particularly for distinguishing between dysplastic and tumoral cells.