Electron-lucent Halo Research Articles

An Ultrastructural Study of Spontaneous Chronic Lung Lesions in Asymptomatic Rabbits

An electron microscopical study of chronic lung lesions in 12 clinically healthy, purpose bred laboratory rabbits (eight of which were free from infections with known respiratory pathogens but 4 of them carried a natural B. bronchiseptica infection) revealed focal chronic interstitial pneumonia, vascular changes and focal chronic bronchiolitis. In addition, severe endothelial changes and intravascular deposition of collagen were observed in septal capillaries. In type I pneumocytes and septal capillary endothelium we noticed numerous rounded structures, 70-90 nm in diameter, which consisted of a limiting two layer membrane enclosing an irregularly rounded electron-dense centre surrounded by a more electron-lucent halo. These structures appeared free in the cytoplasm, or they were attached to or apparently budding from membranes other than the plasmalemma. Particles located extracellularly were not found. Whether the structures described were involved in the genesis of the lesions found remains to be elucidated.

Electron microscopic immunolocalization of seminal vesicle-specific antigen in human seminal vesicle.

Seminal vesicle-specific antigen (SVSA) has been shown to be a polymorphic antigen represented by multiple immunoreactive peptides when fresh human semen is probed with monoclonal antibody (MHS-5) on Western blots. Semen samples collected directly into sodium dodecyl sulfate (SDS) demonstrate major immunoreactive peptide bands at 69-71 kDa and 58 kDa as well as a series of peptides of lower molecular mass. As semen liquefies, the higher molecular mass forms of SVSA are transformed into lower molecular mass bands, with 10-13 kDa immunoreactive peptides predominating after 8 h of liquefaction (McGee and Herr, Biol. Reprod. 37:431-439, 1987). In the present study, the 10-13 kDa form of SVSA was purified by preparative electrophoresis from SDS gels and a polyclonal antibody was generated in guinea pigs. Human seminal vesicle was fixed by immersion in combinations of glutaraldehyde and paraformaldehyde and embedded in Araldite or LR Gold. Both the guinea pig polyclonal antibody and the murine monoclonal antibody MHS-5 were employed to localize SVSA in human seminal vesicle by immunoelectron microscopy using Protein-A gold complexes. Gold particles were quantified in various subcellular compartments by a Videoplan computer. With either antibody probe, SVSA was found predominantly in the central electron-dense cores of secretory granules, with no staining evident over the electron lucent halo surrounding the granule core. With preimmune serum, the mean number of gold particles overlying secretory granules was 3/microns2; with polyclonal anti-SVSA, the mean number of particles observed over secretory granules was 182/microns2. This study represents, to our knowledge, the first fine-structural localization of a specific secretory protein to the electron-dense cores of secretory granules in principal cells of the human seminal vesicle.

Fungus Invasion into Human Hair Tissue in Black Dot Ringworm: Light and Electron Microscopic Study

In order to investigate the morphology of fungi invading into the human hair tissue, three cases of black dot ringworm caused by Trichophyton violaceum and Trichophyton glabrum were studied by light and electron microscopy. Fungal elements were mainly present in the hair cortex and showed a constant morphologic change during the differentiation of hair layers. The fungal elements, located deep in the keratogenous zone of the cortex, showed less electron dense non-septate hyphae. Distally, the hyphae showed septation and contained several scattered dense bodies in the cytoplasm. At the level where the Huxley's layer was keratinized, the fungal elements were transformed into arthrospores, which occupied the large volume of the cortex; each spore was surrounded by a fiber- and melanosome-free, electron lucent halo. Fungal elements occasionally invaded the keratinized hair cuticle and keratinized inner root sheath in a few hair follicles. Fungi do not invade the hair germinative cells. There seems to be a distinct relationship between the morphology of the invading fungi and the cortical cell differentiation in black dot ringworm; a balance between the fungus proliferation and the cortical cell development may be present.

The origin of psammoma bodies in the human arachnoid villi.

The fine structure of the human arachnoid villi was studied to clarify the origin of psammoma bodies. Within the villous surface layer, collagen fibrils and fine granular material clustered forming microcores of variable caliber measuring up to 10 microns. An early stage of psammoma body formation was seen more frequently in these villous microcores than in the meningocytic whorls. The villous microcores contained a large number of membrane-free matrix granules as well as a small number of membrane-bound matrix vesicles and matrix minerals. The matrix granules were irregularly oval structures with electron-lucent halo, measuring 0.05-0.70 micron in diameter. Hydroxyapatite crystals were frequently precipitated within and around the matrix granules which aggregated with calcifying matrix vesicles and matrix minerals. Numerous calcifying matrix granules were present within and around enlarging psammoma bodies. The matrix granules may serve as the principal calcification nidi of psammoma bodies in the human arachnoid villi. The possible mechanisms of matrix granule biogenesis are extrusion of preformed arachnoid cell structures or secretion of fine granular material with its extracellular assemblage.

Localization of glucagon-like peptide (GLP) immunoreactants in human gut and pancreas using light and electron microscopic immunocytochemistry.

The distribution of peptide immunoreactivities predicted from the sequence of the human preproglucagon gene in enteroglucagon (EG; glicentin-like immunoreactant-containing) cells of the human gut and A cells of the pancreas has been determined by light and electron microscopic immunocytochemistry. At light microscopy the application of peroxidase-antiperoxidase and immunogold-silver staining methods has revealed that glucagon-like peptide (GLP-1 and GLP-2) immunoreactivities coexist with a glicentin-related immunodeterminant in human colorectal EG cells and pancreatic A cells. Using single and double colloidal gold probe electron immunocytochemistry, we have been able to show the coexistence of glicentin, GLP-1, and GLP-2 immunoreactivities within single EG cell secretory granules. No morphologic segregation of the proglucagon immunoreactants was observed in EG cells of the colonic mucosa. In pancreatic A cells we have localized GLP-1, GLP-2, and glucagon-[16-29] immunoreactivities solely to the electron-dense core of the secretory granules, whereas glicentin-related immunoreactivity was restricted to the electron-lucent halo. The results obtained in the present study have shown that the peptide immunoreactivities predicted from cDNA sequencing of the human preproglucagon gene are indeed expressed in colorectal EG and pancreatic A cells. The topographical segregation of immunoreactivities in the A cell secretory granule shows that antigenic determinants derived from the C-terminal portion of proglucagon are stored with glucagon in the core of the secretory granule.

Electrical and anatomic characteristics of cells of ferret paratracheal ganglion.

A preparation has been developed for study of the electrical properties of the neurons of the ferret paratracheal ganglia. Two cell types were identified. AH cells were characterized by the presence of a single action potential in response to cathodal current pulses, followed by a profound after hyperpolarization that lasted for several hundred milliseconds. Electrical stimulation of branches of the laryngeal nerves produced a fast excitatory postsynaptic potential (EPSP) that was often followed by an apparent inhibitory postsynaptic potential (IPSP). A similar response was seen with electrical stimulation of interganglionic nerve trunks. Hexamethonium reversibly inhibited fast EPSPs in these cells. Type B cells could not be excited by intracellular current injections. At least some of these cells appear to be neurons as electrical stimulation of nerve trunks resulted in a slow EPSP and, rarely, a fast IPSP. Ganglia have between 10 and 20 cell bodies, and their diameters are between 15 and 40 microns. Two types of nerve endings were seen: 1) those with mainly round agranular vesicles 50-60 nm in diameter, and 2) those with large dense-cored vesicles of approximately 100 nm with an electron-lucent halo around the core.

The effect of prostaglandins on the lysosomal function in the cervix uteri.

Local or systemic prostaglandin (PG) administration leads to the known softening and dilatation of the cervix uteri. Lysosomal enzymes are involved in connective tissue degradation. The question arises whether the effect of PG on the cervix uteri is mediated by lysosomes. Five pregnant women (volunteers after informed consent) in the first trimester received 500 micrograms of PGE2-derivative (Nalador) i.m. at 12 and 8 h before termination by curettage. Five pregnant women without PG-treatment served as controls. Small biopsies were obtained from the endocervical canal and were immediately immersed in cold 2.5% glutaraldehyde and after further preparations examined under a Zeiss electron microscope 9S-2. A second portion of tissue was sliced and prepared for histochemical analysis of the acid phosphatase on lysosomes. Examination of the ultrastructure of the cervix uteri showed vesicles in the extracellular matrix. These were surrounded by a single membrane and contained either fine granular material of myelin-like whorls of membranes. These vesicles lay between collagen fibers, showed the reaction product of acid phosphatase and were often surrounded by an electron-lucent halo. We conclude that these matrix vesicles were "matrix lysosomes" extruded from the cervical myo-fibrocytes into the extracellular space as a result of the PG-E2-administration. Here they are not under cellular control and can initiate the proteolytic degradation of connective tissue. This might be the crucial step in cervical dilatation which, on ultrastructural examination, can be seen as decreasing electron density of the extracellular ground substance near the matrix lysosomes. The relationship between PGE2 and collagenase production is generally accepted. If one believes that lysosomal cathepsin D and cathepsin B act synergistically with collagenase, it can be assumed that PGE2 is involved in a lysosomal degradation of the connective tissue. The morphological sign of this occurrence is the release of matrix lysosomes by PGE2 as described in the present study. Extracellular lysosomes and their physiological significance in cervical function are discussed in detail.

The human fetal pituitary: An ultrastructural analysis

An ultrastructural study was performed on 25 human fetal pituitaries to document the development of cell differentiation and hormone production in the adenohypophysis.At 5 weeks' gestation, Rathke's cleft was lined by columnar epithelium 3-4 cells deep (Fig. 1). The cells were poorly differentiated, with abundant cytoplasmic glycogen, numerous free ribosomes and occasional secretory granules. Terminal bars were formed on the lateral cell surfaces near the luminal surface of Rathke's cleft; desmosomes formed junctions between cells.By 6 weeks' gestation, cells resembling corticotrophs were identified (Fig. 2). They contained moderately developed, rough endoplasmic reticulum and numerous secretory granules of variable size, shape and electron density. In 8-week-old fetuses, type I microfilaments were found in those cells. Welldifferentiated somatotrophs were seen in the adenohypophyses of 8-9-week-old fetuses. They contained scattered profiles of rough-surfaced endoplasmic reticulum and spherical, evenly electron dense secretory granules, measuring 300-600 nm in diameter. Cells with dilated rough endoplasmic reticulum containing flocculent material and small, dense, round secretory granules with peripheral electron lucent halos were seen in the adenohypophysis of a 14-week-old fetus; these features are characteristic of the glycoprotein hormone cell line. Typical prolactin cells were not recognizable before 23 weeks' gestation.

Quick-freeze fixation and freeze-drying of isolated rat pancreatic islets: application to the ultrastructural localization of inorganic phosphate in the pancreatic beta cell.

A bounce-free mechanical quick-freeze assembly and a Coulter-Terracio freeze-dry apparatus were successfully coupled to obtain high quality ultrastructural preservation of pancreatic beta cells in a simple and dependable manner. Except for obvious shrinkage spaces, morphological relationships at the tissue, cellular, and subcellular levels were all intact. Beta cell secretory granules demonstrated a dense core surrounded by an electron lucent halo as typically described in specimens after aqueous fixation. Cell membranes and intracellular membranes demonstrated a trilaminar appearance. Golgi apparatus were well preserved. Two clearly defined populations of mitochondria were found. One group of very dark mitochondria had extremely dense matrices in which cristae were barely visible. A second group of mitochondria had light matrices with prominent cristae. The combined quick-freeze fixation and freeze-drying was applied to reevaluate the ultrastructural localization of inorganic phosphate that had been precipitated with lead in the beta cells of pancreatic islets. Accumulation of inorganic phosphate adjacent to the plasma membrane and over the nucleolus of the beta cell in nonstimulated islets was documented with better detail than heretofore possible.

Electron microscopic findings in four cases of nasopharyngeal fibroma

Light and electron microscopic investigations of four cases of juvenile nasopharyngeal fibroma revealed characteristic structures; a fibrous stroma, an inclination to hyalinisation and formation of scar like tissue, a lacunar thin walled vascular component, large numbers of mast cells and of fibroblasts. The tumor fibroblasts contained different nuclear bodies and particles. There existed five different types of more or less complex spherical bodies. The previously described nuclear electron dense particles with an electron lucent halo could be divided into four groups measuring 60, 90, 150, and 300 nm in diameter. In addition to the previously described ultrastructural properties of the tumors, the nuclei of the tumor fibroblasts were found to contain virus like particles. These particles were less electron dense, measuring 40 to 55 nm in diameter and arranged in groups throughout the nucleoplasm; they were different from chromatin condensations and from perichromatin granules. The structure and the size of the smallest particles was not comparable with the other nuclear inclusions.

Studies on the fat body of oncopeltus fasciatus invaded by pseudomonas aeruginosa1

A fatal disease in laboratory cultures of Oncopeltus fasciatus is caused by Pseudomonas aeruginosa , which invades the fat body and destroys it. The cellular breakdown was studied by electron microscopy. Infected fat body tissue shrinks, disintegrates, and dissolves. The nuclei, apparently, remain intact until immediately before cell death. Bacteria, which are found singularly in cytoplasm, form an expanding electron-lucent halo. Within this halo, free ribosomes and ribosomes of rough endoplasmic reticulum (ER) disappear. The changes are presumably caused by proteolytic activity of the parasite, which results in the destruction of the fat body and death of the host. Lipid droplets dissolve, apparently pass into the matrix of cytoplasm, and may be discharged. The fate of carbohydrates is unclear. When whole clusters of bacteria colonize a cell, they are embedded in a stroma. Bundles of fibers are formed in and around it. They outlive the cellular breakdown and enclose numerous bacteria. The significance of the fiber production is not clear. Blood cells do not attack invading bacteria.

Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis. Ultrastructural changes in basophils and eosinophils at the site of infection.

Basophil and eosinophil leucocytes infiltrate the small intestinal lamina propria of guinea-pigs infected with the nematode Trichostrongylus colubriformis. By comparing the morphology of both cell types at the site of infection with bone marrow and buffy coat cells, it was found that, after entering the lamina propria, basophils developed an electron lucent halo beneath the granule-limiting membrane while the characteristic orderly periodicity of the granules changed to a fibrillar or amorphous appearance. The granules also tended to coalesce but remained within the cell. Approximately half the eosinophils at the site of infection developed deficiencies in the amorphous outer matrix of their granules but showed no obvious change in the central electron-dense cores.

The effects of selective partial pancreatectomy on pancreatic islet cell morphology in the Japanese quail

The A- and B-islet containing splenic lobe of the Japanese quail pancreas was examined by light and electron microscopy after surgical removal of the ventral or third pancreatic lobe, and after a sham operation. Removal of the ventral lobe, which contains only B-islets, resulted in time-dependent alterations in the B-cell granules. Electron opaque material within the crystalline and ring-shaped secretory granules was less abundant in B-cells 2 hr after ventral lobectomy than after a sham operation. The uniformly opaque B-granules, however, were not altered until 6 hr after lobe removal. In contrast, extirpation of the A-islet containing third pancreatic lobe, but not the sham operation, resulted in granule alterations within the A-cells. Two and six hours after third-lobectomy decreases in electron opacity were observed at the peripheries of A-granules. These changes did not result in the formation of electron lucent halos around the majority of A-granule cores suggesting that a nonglucagon component exists within these granules. After removal of either the ventral or third pancreatic lobe increased amounts of rough endoplasmic reticulum, enlargement of Golgi profiles and increased granule numbers were noted in B- and A-cells, respectively, during the 12–48 hr interval following surgery. During this study no granule changes were observed in D- or Type IV cells. These results demonstrate that selective partial pancreatectomy may be used to produce specific cytological alterations in A- or B-cells of the endocrine pancreas of this species. Furthermore, these observations suggest that intracytoplasmic dissolution of secretory granules may play a role in the release of insulin and glucagon from B- and A-cells of the Japanese quail.

HISTOCHEMICAL AND ULTRASTRUCTURAL STUDIES ON HELA CELL CULTURES EXPOSED TO SPINDLE INHIBITORS WITH SPECIAL REFERENCE TO THE INTERPHASE CELL.

Mammalian cells of the HeLa (S3) strain, when exposed to spindle inhibitors, have been found to undergo several morphological transformations during interphase as well as during mitosis. Some of these have been studied both histochemically and ultrastructurally. The lysosomes, represented by the multivesicular bodies in HeLa cells, form clusters and become circumferentially disposed instead of occupying the polarized juxtanuclear position characteristic of these organelles. In the electron microscope it is seen that they have acquired a dense osmiophilic core that is separated from the bounding unit membrane by an electron lucent halo. The Golgi apparatus fragments under the influence of spindle inhibitors and also takes up a circumferential distribution in a pattern similar to that of the lysosomes. On the ultrastructural level, no significant modifications in this organelle are seen. Also noted in the interphase cell are numerous 60-80 Å fibrils coursing through the cytoplasm as well as a paucity of spindle our microtubules. A striking similarity has been pointed out between the behavior of the lysosomes in the drugtreated interphase cell and the untreated, normal mitotic cell. A possible explanation of some of the changes noted has been given in terms of an interruption of protoplasmic flow resulting from the disappearance of microtubules.