Electron-lucent Vacuoles Research Articles

エトレチナートによる催奇形実験 ラットの全はい培養法を用いて

Whole rat embryos with visceral yolk sac on days 9.5 and 10.5 of gestation were explanted and cultured for 36 and 24 hours respectively, in rat serum containing 0, 10, and 20μg/ml etretinate (ETR) dissolved in 0.125% dimethyl sulfoxide. The effects of ETR on the development and morphogenesis of embryos were examined by light and electron microscopy.When embryos were cultured in the medium containing 20μg/ml ETR, various abnormalities were observed: The diameter of visceral yolk sac, crown-rump length, head length, and number of somites were significantly decreased, and incidences of embryos failing to close the neural tube and turn the body axis, as well as, hypoplasia of maxillary and mandibular swellings were increased, compared with control or low ETR-containing (10μg/ml) cultures. Microscopically, embryos treated with 20μg/ml ETR, showed a decreased number of neuroepithelial and interstitial cells. Occasionally, there were cells exhibiting some degenerative changes including electron dense nuclei and cytoplasm, dispersed chromatin, dark mitochondria with dilated cristae, and large phagosomes. These findings suggest that the failure to close the neural tube, as well as, hypoplasia of maxillary and mandibular swelling may be due to cytological disturbances including cell death induced by ETR.Besides these findings, vascular formation was extensively suppressed in the viceral yolk sac of the embryos cultured with 20μg/ml ETR. In addition, endodermal cells of the yolk sac contained an abundance of electron-lucent vacuoles, lipid dropletes, and dark mitochondria with dilated cristae. Considering that the visceral yolk sac of early embryos plays an important role in nutritional supply, the findings of the present study strongly suggest that ETRinduced dysfunctions of the visceral yolk sac can partly be causes for abnormal development of embryos.

Protein storage in large peripheral vesicles in Phytophthora zoospores and its breakdown after cyst germination

The fate of large vesicles that line the periphery of Phytophthora cinnamomi zoospores was monitored by immunogold labeling during encystment and germination. Labeling was carried out using a monoclonal antibody, Lpv-1, directed against glycoprotein components of these vesicles. The results show that the vesicles are retained inside the zoospores during encystment, but their contents are degraded after germination. During initial stages of degradation, the large peripheral vesicles dilate to form small vacuoles containing fine electron-dense fibrillar material which is immunoreactive. Eventually, these small vacuoles fuse together to form large electron-lucent vacuoles which contain very little immunoreactive material. Immunoblot analysis of germinating cysts with Lpv-1 shows that the level of glycoprotein components in the vesicles declines dramatically following germination. It is proposed on the basis of this evidence that the large peripheral vesicles contain storage protein which acts as an endogenous supply of nitrogen reserves for the growing germ tube. Lpv-1 also labels peripheral vesicles in two other species of Phytophthora, P. parasitica var. nicotiana and P. nicotiana var. nicotiana. As in P. cinnamomi, these vesicles do not undergo exocytosis during encystment. The large peripheral vesicles thus appear to be analogous to protein bodies found in seeds of higher plants, and they may be a common feature of Phytophthora zoospores.

Clear cell basal cell carcinoma

We describe a case of clear cell basal cell carcinoma of the superficial type, presenting as a crusted eruption on the abdomen. Histological examination showed a solid proliferation of clear cells attached to the under-surface of an atrophied epidermis. In addition, distinct pagetoid infiltration was seen within the overlying epidermis. A focal connection between the clear cell portion and a deeper lying nodular basal cell carcinoma was demonstrated, elucidating the true nature of the lesion. Immunohistochemical studies and electronmicroscopy confirmed the epithelial derivation of the tumour. The clear cell appearance was due to multiple cytoplasmic electronlucent vacuoles which were not surrounded by membranes.

Skin pigmentation from clofazimine therapy in leprosy patients: A reappraisal

Skin biopsy specimens from two lepromatous leprosy patients with dark brown pigmentation who were receiving long-term clofazimine therapy were studied. Ceroid-lipofuscin pigment was demonstrated inside macrophages that contained numerous phagolysosomes. These contained lipids and clofazimine that appeared as electron-lucent vacuoles and a lipofuscin pigment that was electron dense, granular, and lamellated. Although the presence of the drug in tissues contributed to the skin pigmentation, the main cause was a drug-induced, reversible ceroid lipofuscinosis.

The effects of host age, virus dose, and virus strain on heterologous rotavirus infection of suckling mice

Seven-day-old suckling CD-1 mice, born to seronegative dams, were orally inoculated with a number of animal and human rotaviruses. Simian (SA11), rhesus (RRV), and bovine (B223) rotaviruses were found to replicate and cause severe disease. Canine (K9), bovine (B641), and human (Wa) rotaviruses either replicated minimally and caused minimal disease (K9, B641) or failed to replicate or cause disease (Wa). The features of SA11 infection of mice were examined in greater detail. Suckling mice were susceptible to infection and disease from 1 day of age to 13–15 days of age. Restriction of disease occurred at an earlier age (13 days) than restriction of replication (15 days). Dose-response studies in seven-day-old mice showed that virus replication and disease could be induced with doses as low as 1 × 10 2 pfu/mouse; however, both intestinal virus titers and severity of disease increased in parallel with virus dose. Intestinal virus replication appeared to be restricted in SA11 infections. Only at very low doses (1 × 10 2 pfu/mouse) did virus replication occur to levels above the inoculated dose. While light microscopic examination showed classical features of rotavirus infection in the ileum, electron microscopic examination revealed only the accumulation of large numbers of electron-lucent vacuoles in the ileal enterocytes of infected mice. Structures typical of rotavirus morphogenesis were not detected in enterocytes from mice infected with rotavirus SA11.

Alveolitis due to inhalation of acrylic polymers: Report of a case

Acrylic polymers are increasingly used in dental laboratories for preparation of prostheses. In the past, dental technicians have developed pneumoconiosis due to inhalation of silica dust or heavy metal alloys, but to our knowledge, no other cases of lung disease due to inhalation of acrylic dust have been previously reported.The patient, a dental student, was admitted to the Hospital of the University of Pennsylvania for evaluation of persistent bilateral interstitial infiltrates and cough. An open lung biopsy was performed to determine the cause of the infiltrate. The biopsy specimen revealed interstitial lymphocytic infiltrates and intra-alveolar accumulation of “foamy” macrophages (Fig. 1) suggesting lipoid pneumonia. Since he did not use medications containing mineral oil or had obstructive lesions of the airways, electron microscopy examination of the biopsy specimen was performed. Transmission electron microscopy (TEM) revealed accumulation of macrophages in the alveolar space and interstitium, containing numerous electron-lucent vacuoles of varying size (Fig. 2).

Rapid analytical and preparative isolation of functional endosomes by free flow electrophoresis.

Endosomes are prelysosomal organelles that serve as an intracellular site for the sorting, distribution, and processing of receptors, ligands, fluid phase components, and membrane proteins internalized by endocytosis. Whereas the overall functions of endosomes are increasingly understood, little is known about endosome structure, composition, or biogenesis. In this paper, we describe a rapid procedure that permits analytical and preparative isolation of endosomes from a variety of tissue culture cells. The procedure relies on a combination of density gradient centrifugation and free flow electrophoresis. It yields a fraction of highly purified, functionally intact organelles. As markers for endosomes in Chinese hamster ovary cells, we used endocytosed horseradish peroxidase, FITC-conjugated dextran, and [35S]methionine-labeled Semliki Forest virus. Total postnuclear supernatants, crude microsomal pellets, or partially purified Golgi fractions were subjected to free flow electrophoresis. Endosomes and lysosomes migrated together as a single anodally deflected peak separated from most other organelles (plasma membrane, mitochondria, endoplasmic reticulum, and Golgi). The endosomes and lysosomes were then resolved by centrifugation in Percoll density gradients. Endosomes prepared in this way were enriched up to 70-fold relative to the initial homogenate and were still capable of ATP-dependent acidification. By electron microscopy, the isolated organelles were found to consist of electron lucent vacuoles and tubules, many of which could be shown to contain an endocytic tracer (e.g., horseradish peroxidase). SDS PAGE analysis of integral and peripheral membrane proteins (separated from each other by condensation in Triton X-114) revealed a unique and restricted subset of proteins when compared with lysosomes, the unshifted free flow electrophoresis peak, and total cell protein. Altogether, the purification procedure takes 5-6 h and yields amounts of endosomes (150-200 micrograms protein) sufficient for biochemical, immunological, and functional analysis.

Ultrastructural studies on the effect of Triton WR-1339 on macrophage-mycobacteria interaction.

Mycobacterium bovis (BCG organisms) suspended in saline or a 5% solution of a non-ionic detergent, Triton WR-1339, was injected intraperitoneally into mice. Electron-microscopic observation was carried out on peritoneal exudate cells harvested therefrom. Electron-lucent vacuoles limited by the membrane structure were found in macrophages of the mice injected with BCG suspended in the detergent, but not in polymorphonuclear leukocytes or lymphocytes. Mycobacterial cells were present within such vacuoles. Without the detergent, the ingested mycobacterial cells were in close contact with the phagosomal membrane. Within the electron-lucent vacuoles, however, such close contact was not present. These observations, together with other collateral findings, led us to a view that Triton WR-1339 may inhibit the interaction between mycobacteria and the phagosomal membrane by intervening between them thus making the progress of infection delayed.

Ultracytochemical localization of X-prolyl-dipeptidyl (amino)peptidase in microglobules and endoplasmic membranes accumulated in pep4-3 mutant of Saccharomyces cerevisiae

The ultracytochemical localization of X-prolyl-dipeptidyl (amino)peptidase (DPP) activity was studied in a late exponential culture of a haploid (alpha) wild-type strain of Saccharomyces cerevisiae and its pep4-3 mutant. Yeast cells were fixed for 20 min in cold 1% glutaraldehyde buffered with 50 mM TES buffer to pH 7.0 and then incubated for 80 min with 1.2 mM L-alanyl-L-proline-4-methoxy-2-naphthylamide (Ala-Pro-MNA) or Lys-Pro-MNA as cytochemical substrates plus 0.06% hexazonium p-rosaniline (HPR) buffered with 160 mM cacodylate to pH 7.0. The osmiophilic azoindoxyl complex was formed by coupling HPR with MNA liberated by DPP activity and was then osmicated during an overnight post-fixation of cells in cold 1% OsO4. In the wild-type strain, conspicuous deposits of DPP reaction product were observed in vacuolar membranes. When compared with the parent strain, the pep4-3 mutant cells were enriched in endoplasmic reticulum (ER), cytoplasmic lipoprotein, and microcompartments: membranous vesicles and microglobules. In the mutant, DPP reaction product was found in about 50% of non-vacuolated cells at the following sites: the nuclear envelope, polar layers of ER sheets and of membranous vesicles (diameter, 40-90 nm), the surface or the lumen of these vesicles, the cytoplasmic membrane (under some bud scars) and the periplasmic space. The largest amount of reaction product was found in microglobules (diameter, 20-50 nm) that were mainly observed in the cytoplasmic matrix but were also present in nuclei (nucleoli) and mitochondria. These microglobules had a single-line boundary and appeared to be composed of lipoprotein. The surface ultrastructure of sectioned microglobules in the cytoplasmic matrix was similar to that of the coated vesicles found in mammalian cells. Only sparse amounts of DPP reaction product were seen in budding yeast. In all pep4-3 cells with electron-lucent vacuoles, the reaction product was confined to the vacuolar membranes (i.e. homologous to the ER), microglobules and the periplasmic space. Polysaccharides with free vic-groups were shown by the cytochemical reaction to be present on the surface of ER membranes, in microglobules, in the periplasmic space and in the cell wall. Our cytochemical results indicate that microglobules participate in the exocytosis of both DPP and glycoproteins, and reveal new features of vacuolar morphogenesis in yeast.

In vitro cultivation of Toxoplasma gondii cysts in astrocytes in the presence of gamma interferon.

Long-term culturing of Toxoplasma gondii cysts was accomplished in vitro in association with murine astrocytes and intermittent additions of gamma interferon to the media. Phase-contrast microscopy was used to follow the stages of cyst development, and electron microscopy confirmed the presence of morphologic characteristics of T. gondii cysts. T. gondii cysts formed in vitro had a single trilaminar membrane during both intracellular and extracellular existence and contained amorphous electron-dense material either throughout the cyst or in a uniform layer under the trilaminar membrane. The bradyzoites were similar to previous descriptions of tachyzoites in vitro except that they were smaller and contained numerous electron-lucent vacuoles. Gamma interferon is not necessary for cyst formation, but it controls the division of tachyzoites and may allow cysts to remain for prolonged periods without rupturing. In vitro-cultivated T. gondii cysts will be useful for producing bradyzoite and cyst antigens and for measuring the effects of antimicrobial agents and immune modulators on the viability of intracystic T. gondii.

Neuronal survival or death after dendrite transection close to the perikaryon: correlation with electrophysiologic, morphologic, and ultrastructural changes.

We investigated the probability of survival of mouse spinal neurons in monolayer cultures after transection lesions of dendrites made within 400 microns of the perikarya. Based on a total of 650 lesioned neurons, the following observations were made. First, neuronal survival is a function of lesion distance from the perikaryon and of process diameter at the lesion site. For an average lesion diameter of 3 microns, dendrite transections at 50 microns, 100 microns, and 150 microns were associated with survival probabilities of 30%, 53%, and 70%, respectively. Second, the fate of the injured cells was definitely established 24 hours after injury and very likely was determined as early as 2 hours. Third, early stages of deterioration leading to cell death were associated with cytoplasmic phase brightness on light microscopy, correlating with an appearance of numerous, small, electron-lucent vacuoles and swollen mitochondria on electron microscopy. The cytoplasm of these moribund cells stained darkly and contained no visible microtubules or neurofilaments. Fourth, the magnitude and time course of injury potentials recorded at the somata were a function of the lesion distance and did not return to prelesion levels within 30 minutes after transection. Fifth, at 24 hours after injury, the average membrane potential of lesioned neurons was 8% below that of control neurons. Sixth, at a lesion distance of approximately 300 microns both the injury potential and the probability of cell death approach zero. We conclude that, in the model system used, neuronal survival after dendrite amputation depends on physical parameters of the lesion that determine the magnitude of the injury current reaching the soma. Survival is not assured if the injury is inflicted within 250 microns of the cell body, and cell death is likely for lesions within 50 microns of the soma. The below-normal membrane potentials at 24 hours after injury suggest a possible greater vulnerability of recovering neurons to secondary insults. The characteristic mitochondrial disruption and loss of microtubules implies that the calcium component of the injury current contributes to cell death.

Ultrastructural changes associated with renin secretion from the juxtaglomerular apparatus of mice.

Thin sections and freeze-fracture replicas were used to investigate the ultrastructural changes associated with renin secretion from the juxtaglomerular part of the afferent arteriole of male mice. Adrenalectomized animals in which renin secretion was stimulated by furosemide application and bleeding were also studied. Exocytosis of mature electron-dense granules was found in all experimental groups. Before extrusion, the region of granule facing the cell membrane changed, with vesicular and/or stacked membrane-like profiles and a small local protrusion of the granule membrane appearance of. Concomitantly, punctuate sites of fusion between the cell and granule membranes were observed. Later, unaltered amorphous, and altered membrane-like granule content was released from omega-shaped cavities into the extracellular space. In stimulated animals the alteration and extrusion of several closely apposed granules was reminiscent of compound exocytosis. Coated pits were frequently seen, suggesting specific retrieval of the former granule membrane. The collapsing silhouette of a depleted granule very rarely took the form of a saccule whose narrow membrane-bounded neck was continuous with the extracellular space. Observed were two additional events by which active and inactive renin may be released. Small electron-lucent vacuoles of undetermined origin fused with the cell membrane and, in stimulated kidneys, some epithelioid cell processes disintegrated. However, the interpretation of the related ultrastructural phenomena was uncertain.

Regeneration of an identified central neuron in the cricket. II. Electrical and morphological responses of the soma

The cell body of the medial giant interneuron (MGI) in the cricket normally does not spike in response to injected depolarizing currents. When axotomized 1 mm or more from the cell body (distant axotomy), the membrane properties of the soma remain unchanged. However, after axotomy close to the cell body (200 to 500 micron), the soma membrane becomes capable of generating action potentials by 6 hr after lesion. These regenerative spikes are 1 to 1.5 msec in duration and may reach 100 mV in peak amplitude. Ion substitutions indicate that these action potentials are primarily sodium dependent. A calcium-dependent component of soma membrane excitability that is normally present appears to be unaffected by axotomy. By 48 hr, the close axotomized MGI somata have lost the ability to generate action potentials and the membrane electrical properties return to normal. By 2 days after axotomy close to the soma, large, membrane-bound, electron-lucent vacuoles appear in the cytoplasm of the MGI cell body. Such vacuoles then disappear from axotomized MGI somata by 10 days. In addition, numerous arrays of densely packed, darkly staining microtubules are observed in the cell body, especially concentrated near the initial neurite. Neither of these specialized structures is observed in control, intact MGI somata. We propose that close axotomy disrupts the mechanisms which regulate the stability of the fully mature, differentiated neuron. The characteristic morphological and physiological stability of the MGI is lost: the dendritic arborization has been shown previously to be altered by extensive new outgrowth (Roederer, E., and M. J. Cohen (1983) J. Neurosci. 3: 1835-1847); there is a transient increase in soma membrane excitability, and new cytoplasmic organelles are induced.

Ultrastructure of aerial stalk formation by the ciliated protozoanSorogena stoianovitchae

Sorogena stoianovitchaeBradbury andOlive is an unusual kinetophragminophoran ciliate characterized by the aggregation of individual trophic cells to form a multicellular sorogen that rises aerially from the medium surface to produce a sorocarp. A light and electron microscope study of sorogenesis revealed how the sorogenic cells produce the stalk. The feeding ciliates contain numerous subpellicular expansions of rough endoplasmic reticulum cisternae that are only one element of the secretory system necessary for stalk formation. Upon aggregation, the stalk secretory system develops further, initially with the proliferation of the subpellicular expansions. Then, during later aggregation and early sorogenesis, other secretory elements appear: stalk material vesicles, dense granule vesicles, and electron lucent vacuoles. These are all derived from the rough endoplasmic reticulum. Only the subpellicular expansions and stalk material vesicles appear to add to the stalk matrix. The dense granule vesicles could be precursors of the stalk material vesicles; the electron lucent vacuoles, which can be demonstrated to contain fibrillar material, are perhaps by-products of the secretory process. Sorogenesis inSorogena occurs by a mechanism unique among the stalk-producing protists that have been studied.

Secretory cells of the oviduct of the pig-tailed monkey, Macaca nemestrina, during the menstrual cycle and after estrogen treatment.

The secretory cells of the oviductal epithelium in the pig-tailed monkey, Macaca nemestrina, have been studied by light and electron microscopy. Changes during the menstrual cycle and after ovariectomy, with and without subsequent estrogen treatment, have been documented. During the early follicular phase the epithelium is recovering from deciliation and secretory cell atrophy that occur in the late luteal phase. A few fimbrial and a moderate number of ampullar and isthmic cells contain a few electron-dense, homogeneous secretory granules in their apical cytoplasm. During the late preovulatory and early post-ovulatory periods, secretory cell structure varies considerably. Fimbrial cells typically display apical protrusions that contain no or a few small, mainly homogeneous, secretory granules. The cytoplasm is crowded with elements of the Golgi complex, with granular endoplasmic reticulum profiles often intimately associated with mitochondria, and with variable numbers of polysomes and glycogen granules. In ampullar and isthmic cells secretory granules are more abundant than in fimbrial cells, and electron-lucent vacuoles appear. The granules are of two types: 1) those having an electron-dense, homogeneous matrix, and 2) those possessing lamellar structures within moderately dense matrices. The lamellae of the second type course in parallel arrays separated by a distance of approximately 15.5 nm and exhibit a periodicity of approximately 11.3 nm. Possible transitional stages between the lamellar granules and the vacuoles containing lamellar fragments are observed. Secretion occurs by exocytosis. During the late luteal phase no fimbrial cells have secretory granules. In the ampulla many of the cells have poor development of the organelles involved in secretory activity and have few or no secretory granules. In others, a moderate number of secretory granules are present; in one animal, exocytosis is observed. In the untreated ovariectomized animal no secretory granules occur, and the organelle content is much less than in the cycling and the estrogen-treated monkeys. In ovariectomized, estradiol-treated monkeys, some areas of all three oviductal segments are well stimulated whereas others display little or no secretory activity.

Corticosteroid alteration of human monocyte to macrophage differentiation.

Human monocyte to macrophage differentiation in vitro is associated morphologically with an increased cell size, an increased number of lysosomes, and rough endoplasmic reticulum. Functional changes associated with monocyte to macrophage differentiation include increased tumoricidal activity and increased cell protein, acid phosphatase, and 5'-nucleotidase. Hydrocortisone succinate (HCS) at 2.5 microM markedly altered monocyte to macrophage differentiation: HCS inhibited the development of tumoricidal activity and the increased levels of cell protein, acid phosphatase, and 5'-nucleotidase. By transmission electron microscopy, macrophages incubated with HCS failed to develop an increased complement of lysosomes and developed an increased number of membrane-bound electron lucent vacuoles. Dexamethasone inhibited the development of tumoricidal activity at a 10-fold lower concentration than HCS. HCS also markedly inhibited monocyte 3H-uridine incorporation. Mechanisms of HCS alteration of monocyte differentiation are discussed. These data suggest that corticosteroid alteration of monocyte differentiation may be a mechanism of HCS immunosuppression in vivo.

Cytochemical demonstration of amine-storing vacuoles and lysosomes in the chicken thrombocytes.

A combined electron microscopic and cytochemical study of the thrombocytes of the chicken has clearly identified the amine-storing organelles and lysosomes. A chromaffin positive-reaction product was observed on the inner surface and the granules of the large electron-lucent vacuoles. No acid phosphatase activity was localized in these amine-storing vacuoles. However, the acid phosphatase activity was observed in the small vesicles, the primary lysosomes, and in the large electron dense inclusions with myelin which may be secondary lysosomes. The results of this study suggest that the large empty vacuoles, with one or two very dense osmiophilic peripherally-situated granules, in the chicken thrombocytes are comparable to the vesicles with electron dense materials called "dense bodies" in mammalian thrombocytes.

Oligosaccharides accumulated in the kidney of a goat with β-mannosidosis: Mass spectrometry of intact permethylated derivatives

Two oligosaccharides accumulate in the kidney of a goat with β-mannosidosis. These oligosaccharides were isolated and purified from kidney extracts by Bio-Gel P2 gel permeation column chromatography. Their structures were characterized as Manβ1 → 4GlcNAc and Manβ1 → 4G1cNAcβ1 → 4G1cNAc by mass spectrometry of the permethylated intact oligosaccharide alcohols and permethylated native oligosaccharides. Carbohydrate composition analysis, methylation linkage studies, and enzymatic hydrolysis were also performed. Stored in 1 g of kidney were 1.6 μmol of disaccharide and 7.6 μmol of trisaccharide, which was three times that found in the brain of this affected animal ( M. Z. Jones and R. A. Laine, 1981, J. Biol. Chem., 256, 5181–5184 ). In both the brain and kidney of the affected goat, oligosaccharide accumulation was evidently represented by membrane-bound, electron-lucent vacuoles in numerous cell types. While lesions in the brain were associated with profound neurological deficits, functional impairment of the kidney was not apparent. Similar oligosaccharides excreted in urine may be derived from those stored in the kidney. The mass spectrometric methods utilized in this investigation will facilitate comparison of oligosaccharide composition in different tissues and biological samples in β-mannosidosis and other disorders of glycoprotein catabolism.

Renal pathology of fetuses with congenital nephrotic syndrome of the Finnish type. 2. A qualitative and quantitative electron microscopic study.

A qualitative and quantitative transmission electron microscopic study was performed on kidneys of fetuses with congenital nephrotic syndrome of the Finnish type (CNF) and controls obtained from elective pregnancy terminations. The gestational age of the fetuses ranged from 16–22 weeks. A consistent qualitative change of CNF glomeruli was the nearly total loss of epithelial cell foot processes, with smudging of epithelial cytoplasm as broad masses on the glomerular basement membrane. Adjacent to the basement membrane there were increased amounts of fibrillar material in the epithelial cytoplasm. The number of pinocytic droplets was increased both in epithelial and endothelial cytoplasm and some of the capillary loops showed swelling of endothelial cells with poor fenestrations in cases of CNF. Mesangial hyperplasia was focally evident in the most mature CNF glomeruli with an increase of the mesangial matrix. A striking qualitative feature in CNF, only rarely seen in controls, was the occurrence of electron lucent vacuoles and heteromorphic residual bodies in the mesangial cell cytoplasm. The total thickness of the glomerular basement membrane was comparable in CNF and controls but the width of the lamina densa was significantly smaller in CNF than controls. Lamina rara interna of the basement membrane showed irregular widening with accumulation of coarse granular material. Reabsorption droplets of proximal tubular cytoplasm were significantly increased in CNF. With the dilatation of the tubule the droplets almost totally disappeared. Based on the results of the study it is suggested that the basic pathogenetic defect in CNF lies in faulty development of the lamina densa of the glomerular basement membrane and, secondary to this, various glomerular and tubular changes occur. In addition to evidence of extensive foot process fusion, mesangial cell cytoplasmic vacuoles represent a diagnostically important qualitative change in the glomeruli of fetal CNF.

The corpus luteum of the guinea pig. IV. Fine structure of macrophages during pregnancy and postpartum luteolysis, and the phagocytosis of luteal cells

Little information is available on the ultrastructure of macrophages in the corpus luteum or their importance in the regression of luteal tissue. In the present study, the fine structure of activated luteal macrophages during pregnancy and the postpartum period was examined by electron microscopy of guinea pig ovaries fixed by vascular perfusion. In these corpora lutea, macrophages can readily be distinguished from luteal cells. Activated macrophages typically display three prominent inclusions in their cytoplasm: (1) heterophagic vacuoles, (2) distinctive large dense inclusions, and (3) large and small electron-lucent vacuoles. In addition, they contain numerous smaller lysosome-like dense bodies. Activated macrophages in corpora lutea also characteristically show many surface protrusions, such as processes, folds or pseudopodia, which often occur in close contact with nearby luteal cells. Generally, nuclei of macrophages are irregular in shape and display a dense border of heterochromatin, thus differing from those of luteal cells. Macrophages seem to be most abundant in regressing corpora lutea, where they commonly display heterophagic vacuoles containing recognizable luteal cell fragments, evidence that these phagocytes ingest senescent luteal cells. The digestion of luteal cell components in heterophagic vacuoles presumably gives rise to the distinctive large dense inclusions typically seen in macrophages. The findings of this study indicate that macrophages play a central role in luteolysis by phagocytizing luteal cells or their remnants. They therefore appear to bring about the reduction in volume of the corpus luteum that occurs as this tissue regresses. These results taken together with those previously published (Paavola, '78) further indicate that breakdown of the corpus luteum during postpartum luteolysis in guinea pigs involves both autophagy and heterophagy.