Electron-dense Masses Research Articles

Morphological and ultrastructural description of Nematopsis spisula sp. nov. (Apicomplexa) inhabiting Spisula solida (Bivalvia) on the Portuguese Atlantic coast

This study describes the morphology and ultrastructure of the oocysts of a new species of the genus Nematopsis infecting different organs of the surf clam Spisula solida (Linnaeus, 1758) (Mollusca, Bivalvia) on the Portuguese Atlantic coast. Each oocyst [14.3 (SD 0.2) μm long and 10.3 (SD 0.3) μm wide] contains a single uninucleate vermiform sporozoite. Single and grouped oocysts enveloped by a parasitophorous vacuole occur enclosed within host phagocytes externally, surrounded by a complex reticular ring-like structure formed by juxtaposed and parallel cysterns containing numerous small electron dense masses regularly distributed in their lumen. More advanced stages of infection show phagocytic degradation characterized by cytoplasmic vacuolarization and rupture of the parasitophorous vacuole membrane. Morphological and ultrastructural observations combined with host reaction specificity supports the erection of a new species, namely Nematopsis spisula sp. nov.

Postulated Process of Axoneme Organization in the Male Gametogenesis of Malaria Parasite Plasmodium berghei.

The ultrastructural features of axoneme organization within the cytoplasm and exflagellation were investigated in detail in microgametes of a malaria parasite, Plasmodium berghei, by electron and fluorescence microscopy. The kinetosomes (basal bodies) of the microgamete were characterized by an electron dense mass in which singlet microtubules (MTs) were embedded. Around the kinetosomes, several singlet and doublet MTs were recognized in transverse sections. Incomplete doublets with growing B-tubule were also observed. As precursors of the axoneme, arrays of over three doublets showed a tendency to encircle the central pair MTs. Some of the doublet MTs were already equipped with inner and outer dynein arms. In the microgamete, which lacks an intraflagellar transport (IFT) system, self-assembly of microtubular and associated components appeared to proceed stepwise from singlet MTs through arrays of one to nine doublet MTs, surrounding the central pair, to form the complete axoneme in a quite short time. At exflagellation, some extra doublets were occasionally included between the axoneme and the flagellar membrane. At high magnification, the outer dynein arm of the Plasmodium microgamete had a pistol-like shape representing a three-headed dynein molecule like that of other Alveolata.

THE CHANGES OF WOUND MACROPHAGES IN PATIENTS WITH DIABETES

Purulent-necrotic lesions of the extremities require amputation in 30-50% of cases. Among all cases of lower extremity amputations 50-70% are due to diabetes. Moreover, 5 out of 6 amputations, not related to the traumatic injury of the limb, are performed in patients with diabetes. The mortality rate among patients with diabetes, who undergo amputation varies from 28 to 40%, and 5-year surveillance is only 10-25%. The study of ultrastructural changes of macrophages on the 3rd day of treatment revealed masses of chaotically located fibrillar structures in the cytoplasm of macrophages that occasionally had an increased electron density. This phenomenon was observed in the purulent-necrotic areas of soft tissues of patients from the main group, compared to the control group. In all cases, mitochondria were enlarged in size, swollen, with a light matrix and contained a reduced amount of cristae. The cristae were deformed and shortened. Swollen matrix in mitochondria led to the formation of vacuoles on their place containing fine-grained contents. The nucleus had a usual form and size with the presence of single invaginations. Chromatin was predominantly concentrated in the form of solid electron-dense masses or evenly distributed throughout the nucleus. There were nuclei with partial chromatin dispersion. The contents of the nuclei included granular, fibrillar, and fine vacuolar material. The nuclear membrane folding did not fluctuate significantly. The folds did not cover the whole surface of the nucleus. In some areas invaginates were represented by the continuation of perinuclear space only. The nuclear envelop pores, which connect the contents of the cytoplasm and nucleoplasm, have been observed. The cytoplasm between the zones of the plate complex was occupied by small mitochondria, single polysomal rosettes, and cisternae of granular endoplasmic reticulum, which was represented by extended intracellular channels and vacuolar formations. The smooth endoplasmic reticulum was predominantly located in the central part. The surface of macrophages in the process of their differentiation from monocytes was relatively plane. Occasionally there occurred small processes or pseudopodia. The number of pinocytic vesicles surrounded by a border was reduced in poorly differentiated cells. Ozone therapy stimulates the functional activity of wound macrophages, as it causes destructive changes in these cells without necrotic lesions. Intravenous introduction of ozonized saline con-tributes to the elimination of wound macrophag-es, mainly through genetically programmed cell death (apoptosis), which plays a significant role in the regulatory mechanisms of the inflammato-ry process.

Subcellular distribution of calcium during spermatogenesis of zebrafish, Danio rerio.

Calcium plays a variety of vital regulatory functions in many physiological and biochemical events in the cell. The aim of this study was to describe the ultrastructural distribution of calcium during different developmental stages of spermatogenesis in a model organism, the zebrafish (Danio rerio), using a combined oxalate-pyroantimonate technique. Samples were treated by potassium oxalate and potassium pyroantimonate during two fixation stages and examined using transmission electron microscopy to detect electron dense intracellular calcium. The subcellular distribution of intracellular calcium was characterized in spermatogonium, spermatocyte, spermatid, and spermatozoon stages. The area which is covered by intracellular calcium in different stages was quantified and compared using software. Isolated calcium deposits were mainly detectable in the cytoplasm and the nucleus of the spermatogonium and spermatocyte. In the spermatid, calcium was partially localized in the cytoplasm as isolated deposits. However, most calcium was transformed from isolated deposits into an unbound pool (free calcium) within the nucleus of the spermatid and the spermatozoon. Interestingly, in the spermatozoon, calcium was mainly localized in a form of an unbound pool which was detectable as an electron-dense mass within the nucleus. Also, sporadic calcium deposits were scattered in the midpiece and flagellum. The proportional area which was covered by intracellular calcium increased significantly from early to late stages of spermatogenesis. The extent of the area which was covered by intracellular calcium in the spermatozoon was the highest compared to earlier stages. Calcium deposits were also observed in the somatic cells (Sertoli, myoid, Leydig) of zebrafish testis. The notable changes in the distribution of intracellular calcium of germ cells during different developmental stages of zebrafish spermatogenesis suggest its different homeostasis and physiological functions during the process of male gamete development.

Ultrastructure and molecular phylogeny of Pleistophora hyphessobryconis (Microsporidia) infecting hybrid jundiara (Leiarius marmoratus × Pseudoplatystoma reticulatum) in a Brazilian aquaculture facility.

A microsporidian infecting the skeletal muscle of hybrid jundiara (Leiarius marmoratus × Pseudoplatystoma reticulatum) in a commercial aquaculture facility in Brazil is described. Affected fish exhibited massive infections in the skeletal muscle that were characterized by large opaque foci throughout the affected fillets. Histologically, skeletal muscle was replaced by inflammatory cells and masses of microsporidial developmental stages. Generally pyriform spores had a wrinkled bi-layer spore wall and measured 4·0 × 6·0 µm. Multinucleate meronts surrounded by a simple plasma membrane were observed. The polar filament had an external membrane and a central electron dense mass. The development of sporoblasts within a sporophorous vesicle appeared synchronized. Ultrastructural observations and molecular analysis of 16S rDNA sequences revealed that the microsporidian was Pleistophora hyphessobryconis. This study is the first report of a P. hyphessobryconis infection in a non-ornamental fish.

Ultrastructure of antennal sensilla of an autoparasitoid Encarsia sophia (Hymenoptera: Aphelinidae)

Encarsia sophia (Hymenoptera: Aphelinidae) is a parasitoid utilized for biological control of Bemisia tabaci, with selection of prey aided by chemoreceptor organs. The morphology and distribution of the antennal sensilla (chemoreceptors) of E. sophia were examined using Transmission electron micrographs. The total antennal length for E. sophia was 429.28±0.95μm for females and 437.19±8.21 for males, and each antennae was found to consist of seven sensilla of different types. Both sexes possessed sensilla chaetica, sensilla trichodea, basiconic capitate peg sensilla, multiporous grooved-surface placoid sensilla (MG-PS), uniporous rod-like sensilla, nonporous finger-like sensilla, and sensilla coeloconica. Transmission electron micrographs of longitudinal sections of female antennae showed that they were composed of fat body, cuticle, mesoscutello-metanotal muscles, neurons, and glandular tissue, and cross-sections of the basal MG-PS showed sensillar lymph cavities and dendrites. The MG-PSs were imbedded in an electron-dense mass with cuticular invaginations which acted as pores that connected to a central lumen. The possible function of each type of sensilla is discussed.

Expression of a Testis-Specific Nuclear Protein, TRA98, in Mouse Testis during Spermatogenesis. A Quantitative and Qualitative Immunoelectron Microscopy (IEM) Analysis

TRA98 is a testis-specific nuclear protein, but its biological role is unclear. We analyzed the localization of TRA98 in developing spermatogenic cells using immunofluorescence (IF) and immunoelectron microscopy (IEM). TRA98 was localized exclusively to the nuclei. In spermatocytes, IF staining was associated with certain sub-nuclear structures to show a reticular pattern; the XY body was strongly stained. In spermatids, both reticular and punctate staining patterns were observed. In late spermatids, staining decreased as cell dif-ferentiation proceeded. However, epididymal sperm were strongly stained when smear preparations were not fixed, or followed by treatment with 4 M urea or 2% mercaptoethanol. IEM showed that gold signals were closely associated with electron-dense masses but not with the nucleoli. We then investigated the expression of TRA98 in differentiating spermatocytes using a quantitative IEM technique. A small expression peak was observed around stage II-III and a second large peak was noted at stage XI. In spermatids, a single expres-sion peak was observed at step 5; labeling density then decreased gradually but did not reach zero. In early spermatids, heterochromatin was stained much more than euchromatin. The results suggest that the function of TRA98 increases at three points during spermatogenesis. In addition, TRA98 is maintained in the sperm head and carried into the egg after fertilization.

Development of secretory cells and crystal cells in Eichhornia crassipes ramet shoot apex

The distribution and development of secretory cells and crystal cells in young shoot apexes of water hyacinth were investigated through morphological and cytological analysis. The density of secretory cells and crystal cells were high in parenchyma tissues around the vascular bundles of shoot apexes. Three developmental stages of the secretory cells can be distinguished under transmission electron microscopy. Firstly, a large number of electron-dense vesicles formed in the cytoplasm, then fused with the tonoplast and released into the vacuole in the form of electron-dense droplets. As these droplets fused together, a large mass of dark material completely filled the vacuole. To this end, a secretion storage vacuole (SSV) formed. Secondly, an active secretion stage accompanied with degradation of the large electron-dense masses through an ill-defined autophagic process at periphery and in the limited internal regions of the SSV. Finally, after most storage substances were withdrawn, the materials remaining in the spent SSV consisted of an electron-dense network structure. The distribution and development of crystal cells in shoot apical tissue of water hyacinth were also studied by light and electron microscopy. Crystals initially formed at one site in the vacuole, where tube-like membrane structures formed crystal chambers. The chamber enlarged as the crystal grew in bidirectional manner and formed needle-shaped raphides. Most of these crystals finally occurred as raphide bundles, and the others appeared as block-like rhombohedral crystals in the vacuole. These results suggest that the formation of both secretory cells and crystal cells are involved in the metamorphosis of vacuoles and a role for vacuoles in water hyacinth rapid growth and tolerance.

Spermatogenesis and sperm structure of Acerella muscorum, (Ionescu, 1930) (Hexapoda, Protura)

The general organization of the male genital system, the spermatogenesis and the sperm structure of the proturan Acerella muscorum have been described. At the apex of testis apical huge cells are present; their cytoplasm contains a conventional centriole, a large amount of dense material and several less electron-dense masses surrounded by mitochondria. Spermatocytes have normal centrioles and are interconnected by cytoplasmic bridges. Such bridges seem to be absent between spermatid cells and justify the lack of synchronization of cell maturation. Spermatids are almost globular cells with a spheroidal nucleus and a large mass of dense material corresponding to the centriole adjunct. Within this mass a centriole is preserved. Mitochondria of normal structure are located between the nucleus and the plasma membrane. The spermatids are surrounded by a thick membrane. No flagellar structure is formed. Sperm have a compact spheroidal nucleus, a large cap of centriole adjunct material within which a centriole is still visible. A layer of mitochondria is located over the nucleus. The cytoplasm is reduced in comparison to spermatids; many dense bodies are interspersed with sperm in the testicular lumen. The sperm are small, immotile cells of about 2.5–3 μm in diameter.

In vivo encystation of Blastocystis hominis

Blastocystis from infected stools of a person who showed chronic symptoms of abdominal discomfort and diarrhea were examined over a 6-month period, using transmission electron microscopy, for the ultrastructural changes from vacuolar to cystic stage. The study confirms the irregular shedding phenomenon of the organism previously reported, and for the first time, records sequential changes in encystation in stools collected over a time period. The study also confirms the existence of a precystic stage which has an immature cell wall consisting of a layer of a homogenous electron-dense mass surrounding the cell which acts as a intermediatory stage between the vacuolar and cystic stage.

Immunolocalisation of PrP Sc in scrapie-infected N2a mouse neuroblastoma cells by light and electron microscopy

The causative agent of transmissible spongiform encephalopathies (TSE) is PrP Sc, an infectious, misfolded isoform of the cellular prion protein (PrP C). The localisation and trafficking of PrP Sc and sites of conversion from PrP C to PrP Sc are under debate, particularly since most published work did not discriminate between PrP C and PrP Sc. Here we describe the localisation of PrP C and PrP Sc in a scrapie-infected neuroblastoma cell line, ScN2a, by light and electron microscopic immunolocalisation. After eliminating PrP C with proteinase K, PrP Sc was detected at the plasma membrane, endocytosed via clathrin-coated pits and delivered to early endosomes. Finally, PrP Sc was detected in late endosomes/lysosomes. As we detected PrP Sc at the cell surface, in early endosomes and in late endosomes/lysosomes, i.e. locations where PrP C is also present, our data imply that the conversion process could take place at the plasma membrane and/or along the endocytic pathway. Finally, we observed the release of PrP C/PrP Sc via exocytotic pathways, i.e. via exosomes and as an opaque electron-dense mass which may represent a mechanism of intercellular spreading of infectious prions.

Localization of mucilaginous polysaccharides in mulberry leaves

Mulberry tree leaves were shown to have mucilaginous polysaccharides. The extracted water-soluble mucilage was separated into three fractions via a cetylpyridinum chloride complex and purified by anion-exchange chromatography. Five acidic polysaccharides were separated from these fractions, one of which was a major polysaccharide (Mp-3) that was structurally analyzed and used for antibody preparation. The Mp-3 polysaccharide contained rhamnose, galactose, glucose, galacturonic acid, and glucuronic acid in a molar ratio of 1 : 0.2 : 0.5 : 2.3 : 1.5 as constituent monosaccharides. Methylation and gas chromatography-mass spectrometry analysis indicated that the polysaccharide was a rhamnogalacturonan mainly consisting of 1,2,3-linked rhamnose residues, 1,3,4- and 1,4-linked uronic acid residues, and terminal uronic acid residues. Its molecular weight was estimated to be 5.5 x 10(5). Immunohistological observation revealed that the Mp-3 polysaccharide is specifically localized in inner epidermal cells situated in adaxial leaves, and electron microscopy showed that its subcellular location is between the plasma membrane and the cell wall. In young leaves, numerous secretory vesicles were present in a shrunken cytoplasm that was surrounded by fibers. In mature leaves, more than 20% of total epidermal cells were these inner cells in which polysaccharide deposition was significantly increased. The deposits appeared as a rounded electron-dense mass throughout the inner cells by electron microscopy.

Rosenthal Fiber Encephalopathy in a Dog Resembling Alexander Disease in Humans

A young male Bernese mountain dog presented with neurologic abnormalities consisting of nonambulatory tetraparesis, generalized tremors, and depressed mental status. At necropsy only a mild enlargement of the lateral ventricles was seen. The histologic examination revealed the presence of eosinophilic deposits consistent with Rosenthal fibers (RFs) throughout the white matter of the central nervous system. There was also a marked proliferation of abnormally large astrocytes and limited myelin changes. RFs were most prominent in perivascular, subpial, and subependymal areas, where they were perpendicularly located, producing a pallisaded arrangement. Immunohistochemically, RFs were strongly positive for glial fibrillary acidic protein (GFAP), and when they were examined ultrastructurally they appeared as electron-dense amorphous masses located within the processes of astrocytes, most particularly in the perivascular feet. The histologic and immunohistochemical findings of this canine case were consistent with the published neuropathologic descriptions of Alexander disease in humans and in a few dogs, a rare condition that in humans has been shown to be caused by dominant mutations in the GFAP gene.

Ultrastructural pathology of prion diseases revisited: brain biopsy studies

We report here a detailed ultrastructural comparison of brain biopsies from 13 cases of Creutzfeldt-Jakob disease (CJD) and from one case of fatal familial insomnia (FFI). The latter disease has not heretofore benefited from ultrastructural study. In particular, we searched for tubulovesicular structures (TVS), 35-nm particles regarded as the only disease-specific structures at the level of thin-section electron microscopy. Our material consisted of brain biopsies obtained by open surgery from one FFI case from a new French family, one case of variant CJD (vCJD), nine cases of sporadic CJD (sCJD), two cases of iatrogenic (human growth hormone) CJD and one case of hereditary CJD (Val203Iso). The ultrastructural picture of the cerebral cortex of the FFI patient was virtually indistinguishable from that of CJD. TVS were found, albeit only after prolonged search. Typical spongiform change was observed, consisting of intracellular membrane-bound vacuoles containing secondary chambers (vacuoles within vacuoles) and amorphous material. Neuronal degeneration was widespread: some processes contained degenerating mitochondria and lysosomal electron-dense bodies and these met the criteria for neuroaxonal dystrophy. Other processes contained branching cisterns; still others were filled with electron-dense masses and amorphous vesicles. The overall ultrastructural appearance of variant CJD was similar to that of FFI cerebral cortex, except for a much higher number of cellular processes containing TVS. We detected TVS in the majority of sCJD cases that, in addition to typical spongiform change and robust astrocytic reaction, showed widespread neuritic and synaptic degeneration and autophagic vacuoles. We conclude that TVS are readily found in FFI, vCJD and sCJD and that widespread neuritic degeneration is a part of ultrastructural pathology in prion diseases.

Rice stripe virus 23.9 K protein aggregates and forms inclusion bodies in cultured insect cells and virus-infected plant cells.

The genome of Rice stripe virus (RSV, genus Tenuivirus) contains seven open reading frames (ORFs). Little is known about the products of four of these ORFs, including the 23.9 K protein encoded by the virus-sense ORF of RNA3. Western blotting revealed that the 23.9 K protein was synthesized in the host plant and also in the planthopper vector of RSV. Using a baculovirus vector, the 23.9 K protein was expressed, both unfused and fused with red-shifted green fluorescent protein, in Spodoptera frugiperda cells. Inclusion bodies were observed by light microscope in cells expressing fused or unfused proteins. Inclusion bodies in cells expressing the fused protein fluoresced under blue light. By immunoelectron microscopy, electron-dense inclusion bodies in cells expressing the unfused protein were specifically labeled with 23.9 K protein antiserum. Moreover, electron-dense masses labeled with 23.9 K protein antiserum were observed in virus-infected wheat tissue by electron microscopy. This paper thus demonstrates that RSV 23.9 K protein can aggregate in vivo and form inclusion bodies in infected plant tissue.

Genetic and Ultrastructural studies in bone marrow and testis of mice cells under the effect of Glurenor drug

Mutagenetic effects and ultrastructural changes of antidiabetic Glurenor drug were studied in vivo in the highly sensitive micronucleus test. Eight groups of forty male mice used in this study to detect chromosomal abnormalities in somatic and germ cells. Three groups orally administrate therapeutic doses of Glurenor at (30, 60, 120) mg/kg daily the fourth group act as control group. Control group and the treated group with 120 mg/kg were used for ultrastructural examination. While the other four groups were used for bone marrow micronucleus test which receives successive doses of Glurenor as (0.0 & 30) mg/kg for 1, 10 &20 days. A cytogenetic examination of treated and untreated mice showed a significant increase of total chromosomal aberrations (P< 0.01) in both somatic and germ cells at dose 120 mg/kg. when compared by control group. Also Glurenor induced micronucleus polychromatic erythrocytes. Glurenor revealed ultrastructural changes in liver cells represented by deep condensation in the nucleus which revealed by the appearance of a large gap around the nucleus. The condensed chromatin appeared as large sharply marginated electron dense mass that a butted on the nuclear envelope. In addition to electron dark distanced elsewhere (prenuclear), swollen endoplasmic reticulum, Also, observed enlarged nucleolus, and thickening the nuclear membrane. Large vacuoles "hydropic degeneration" also was noticed in the cytoplasm. Our studies had the objective of examining experimentally whether the supposed mutagenic effect of Glurenor can be demonstrated and verified by methods of mutagenicity testing using expermintal mammals. In conclusion, this study revealed that Glurenor gave a positive reaction with a clear dose response in mice. Glurenor gave a mutagenic response from of the chromosomal aberration in somatic and germ cells as well as in micronucleus test. Glurenor showed ultrastructural changes in the liver cells of mice.

Genetic and Ultrastructural studies in bone marrow and testis of mice cells under the effect of Glurenor drug

Mutagenetic effects and ultrastructural changes of antidiabetic Glurenor drug were studied in vivo in the highly sensitive micronucleus test. Eight groups of forty male mice used in this study to detect chromosomal abnormalities in somatic and germ cells. Three groups orally administrate therapeutic doses of Glurenor at (30, 60, 120) mg/kg daily the fourth group act as control group. Control group and the treated group with 120 mg/kg were used for ultrastructural examination. While the other four groups were used for bone marrow micronucleus test which receives successive doses of Glurenor as (0.0 & 30) mg/kg for 1, 10 &20 days. A cytogenetic examination of treated and untreated mice showed a significant increase of total chromosomal aberrations (P< 0.01) in both somatic and germ cells at dose 120 mg/kg. when compared by control group. Also Glurenor induced micronucleus polychromatic erythrocytes. Glurenor revealed ultrastructural changes in liver cells represented by deep condensation in the nucleus which revealed by the appearance of a large gap around the nucleus. The condensed chromatin appeared as large sharply marginated electron dense mass that a butted on the nuclear envelope. In addition to electron dark distanced elsewhere (prenuclear), swollen endoplasmic reticulum, Also, observed enlarged nucleolus, and thickening the nuclear membrane. Large vacuoles hydropic degeneration also was noticed in the cytoplasm. Our studies had the objective of examining experimentally whether the supposed mutagenic effect of Glurenor can be demonstrated and verified by methods of mutagenicity testing using expermintal mammals. In conclusion, this study revealed that Glurenor gave a positive reaction with a clear dose response in mice. Glurenor gave a mutagenic response from of the chromosomal aberration in somatic and germ cells as well as in micronucleus test. Glurenor showed ultrastructural changes in the liver cells of mice.

Lamellar Body Formation in Normal and Surfactant Protein B-Deficient Fetal Mice

Surfactant protein B (SP-B) −/− mice die of lethal respiratory distress syndrome shortly after birth. Alveolar type II epithelial cells in SP-B–deficient mice are characterized by a complete absence of lamellar bodies, the intracellular storage form of pulmonary surfactant, and the presence of inclusions containing numerous small vesicles and electron-dense masses. The present study was undertaken to characterize the formation of these inclusions during fetal lung development and clarify their relationship to lamellar bodies. In wild-type and SP-B +/− mice, small lamellar bodies with loosely organized lamellae and distinct limiting membranes were first detected on day 16 to 16.5 of gestation. SP-B −/− mice were readily identified on day 16 by the absence of immature lamellar bodies, the appearance of vesicular inclusions similar to those previously described in late gestation SP-B −/− mice, and the accumulation of misprocessed SP-C protein. Vesicular inclusions were rarely detected in SP-B +/− mice and were never detected in wild-type littermates. Classical multivesicular bodies were observed fusing with lamellar bodies in wild-type mice, and with the vesicular inclusions in SP-B −/− mice that occasionally contained a few membrane lamellae. On day 18, the airways of SP-B −/− mice lacked tubular myelin and were filled with vesicles and electron-dense masses, suggesting that the contents of the vesicular inclusions were secreted. Taken together, these observations suggest that vesicular inclusions in SP-B −/− mice are disorganized lamellar bodies in which the absence of SP-B leads to failure to package surfactant phospholipids into concentric lamellae.

Ultrastructure Abnormalities in Proteoglycans, Collagen Fibrils, and Elastic Fibers in Normal and Myxomatous Mitral Valve Chordae Tendineae

Normal and myxomatous chordae tendineae were studied using light and electron microscopy, to assess the alterations in the appearance and mutual arrangement of proteoglycans, collagen fibrils, and elastic fibers. Specific staining with ruthenium red and cuprolinic blue in a critical electrolyte concentration mode were used to localize proteoglycans. Fresh tissues were fixed in glutaraldehyde containing the cationic dyes and embedded into Spurr resin. Semithin sections of LR White (London Resin Co., Basingstoke, U.K.)–embedded tissue were used for histochemistry. In normal chordae tendineae, the fibrosa comprised close-packed collagen fibrils intermixed with elastic fibers. These were surrounded by a thin layer of elastic fibers and collagen fibrils, both of which were closely associated with proteoglycans. In myxomatous chordae tendineae, alterations were observed in the connective tissue. Proteoglycans were more abundant and were distributed throughout the tissue. The outermost layer was transformed into an undifferentiated electron-dense mass surrounding the central fibrosa, which contained degraded elastic fibers and collagen fibrils. Collagen fibrils had faint banding or lacked a banding pattern altogether. Spaces between collagen fibrils were occupied by abnormal proteoglycans or proteoglycan aggregates. Elastic fibers showed varying degrees of degeneration and were occasionally replaced by electron-lucent spaces containing microfibrils. Accumulation of abnormal proteoglycan was also observed around degenerated elastic fibres and collagen fibrils.

Images in clinical medicine. An apoptotic eosinophil.

Figure 1. A peripheral-blood eosinophil undergoing apoptosis displays the characteristic condensation of nuclear chromatin into large, electron-dense masses surrounding the central, relatively electron-lucent nuclear matrix. Other changes that are not necessarily related to the apoptotic process include the swelling and breakage of plasma and perinuclear membranes and the release of the contents of granules from swollen, enlarged, electron-lucent granule containers within secretory cells. A single osmiophilic lipid body is present in the cytoplasm. (×18,500.)