Release of merozoite dense granules during erythrocyte invasion by Plasmodium knowlesi

We used immunoelectron microscopy to study the fate of dense granules during the invasion of erythrocytes by Plasmodium knowlesi merozoites. When merozoites entered host cells, dense granules moved to the pellicle, released their contents into the parasitophorous vacuole space, and then moved into fingerlike channels of the vacuole membrane. This is the first report showing that the content of dense granules of P. knowlesi is different from the contents of rhoptries and micronemes and is associated with the formation of channels from the parasitophorous vacuole.

Ultrastructural demonstration of exocytosis in the intact rat adrenal medulla

Evidence is presented for morphological proof of exocytosis in the rat adrenal medulla in situ. Techniques were modified to allow perfusion of the intact adrenal gland with secretagogues (or electrical stimulation) followed by tannic acid. Unstimulated specimens demonstrated exocytotic (omega-shaped) profiles filled with flocculent material. This flocculation was also seen in the intercellular space. Stimulation of the adrenal medulla also resulted in the appearance of exocytotic profiles and an accumulation of the flocculent mass. This was often most evident in the subendothelial space. This is the first demonstration of exocytosis in the rat adrenal medulla by electron microscopy. The techniques used in this study will be useful for studying the pathway of secretory products of the adrenal chromaffin cell before they enter the vascular system.

Transcellular transport and membrane insertion of the C5b-9 membrane attack complex of complement by glomerular epithelial cells in experimental membranous nephropathy

Deposition of the C5b-9 complex of C in glomeruli of rats with experimental membranous nephropathy (MN) is essential for the development of proteinuria. In this investigation C5b-9 was localized in the passive Heymann nephritis (PHN) by immunoelectron microscopy with a mAb specific for C5b-9(m) neoantigen. Its distribution was compared with that in another model of MN induced by successive injections of cationic human IgG and rabbit anti-human IgG into rats. In PHN C5b-9 was found: 1) in the immune deposits (ID), and on the cell membranes of foot processes close to the ID; 2) in clathrin-coated pits of the glomerular epithelial cells (GEC) close to the ID and in membrane vesicles in the cytoplasm, separated from sheep IgG and the gp330 Ag; 3) in high concentration in multivesicular bodies of GEC; and 4) in association with membrane vesicles in the urinary space which presumably are the exocytosed content of membrane vesicular bodies. By contrast, in the cationic IgG-MN model C5b-9 was found mostly in ID, but rarely within the GEC. By freeze-fracture electron microscopy we have further identified 200- to 250-A intramembrane particles in PHN in the cell membranes of the "soles" of the foot processes which resemble membrane inserted human C5b-9(m). Degradation products of C5b-9 were further detected by immunoblotting of a 100,000 x g pellet of PHN rat urine. These results indicate that, in PHN, C5b-9 is inserted into the cell membranes of GEC, and that it is selectively endocytosed and transported across GEC by a cellular mechanism which apparently protects the cell from accumulation of membrane-inserted C5b-9.

The parathyroid glands in the rat as seen by ultrathin step and serial sectioning

Parathyroid cells exhibit ultrastructural heterogeneity. This has been interpreted as an indication that the cells are undergoing secretory cycles, varying in synthetic activity. By electron microscopy we examined step sections at 1 and 2 micron intervals and serial sections of parathyroids from normocalcemic rats of three different age groups. The secretory cells in all three age groups exhibit structural polarity: nuclei and secondary lysosomes are generally located towards the interstitial tissue, whereas the Golgi is confined mainly to regions in the interior of the cell sheets. Cell surfaces facing the interstitial tissue are smooth, whereas plasma membranes in the interior of the cell sheets form tortuous areas. Consequently, an individual cell profile may show quite different appearance depending on section level. Our results do not support the concept that the observed heterogeneity is necessarily due to differences in organelle contents between the cells. The present investigation thus offers an alternative explanation to the ultrastructural variability among secretory parathyroid cells in the rat.

Lipoprotein lipase in myocytes and capillary endothelium of heart: immunocytochemical study

Lipoprotein lipase was immunolocalized by electron microscopy in hearts of young mice; 78% of lipoprotein lipase was in myocytes, 3-6% in extracellular space, and 18% in capillary endothelium. Lipoprotein lipase in myocytes was located primarily in sarcoplasmic reticulum, Golgi sacs, and transport vesicles and also in secretory vesicles at the cell periphery. Lipoprotein lipase in extracellular space was present near the orifice of secretory vesicles of myocytes and in narrow zones spanning the space between myocytes and capillary endothelium. The lowest concentration of lipase associated with endothelial cells was at the basal plasma membrane, whereas the highest concentration was at the surface of luminal projections. Lipoprotein lipase was associated with chylomicrons at the capillary surface but not with chylomicron remnants. Fasting mice for 48 h increased, in heart, lipoprotein lipase activity by 120% and immunolocalized lipase by 270%. The greatest increase (5-fold) occurred at the surface of intraluminal endothelial projections. The findings indicate that lipoprotein lipase in heart is synthesized by myocytes, transferred across extracellular space along cell surfaces and across endothelial cells via vesicles or intracellular channels, and concentrated at the surface of luminal projections of endothelium where the enzyme hydrolyzes triacylglycerol of chylomicrons and very low-density lipoproteins.

Direct visualization of the interrelationship between intramembrane and extracellular structures

The apical surface of the toad urinary bladder is covered by an interconnected mesh of glycocalyx, which appears to attach to the plasma membrane bilayer. To evaluate the interrelationship between these extracellular elements and intramembrane structures, a strategy was devised to produce composite replicas that allow the simultaneous visualization of intramembrane particles by freeze-fracture while the glycocalyx mesh is replicated by rotary shadowing of the extracellular surface after freeze-drying. Evaluation of these composite replicas by electron microscopy reveals that contacts occur between extracellular filamentous elements and intramembrane particles. This structural organization may be important for stabilizing intramembrane components and for anchoring extracellular elements to the membrane.

Discontinuities of the external limiting membrane in the fovea centralis of the primate retina

In the center of the fovea centralis of retinas of three cynomolgus monkeys, one baboon and one male human, the external limiting membrane contains circumscribed areas in which zonulae adherentes are lacking between cone inner segments and apices of Müller cells. These discontinuities of the external limiting membrane begin about 300 microns from the foveolar center, involving only a few cones. Towards the center of the fovea the discontinuities become larger.

Electron-microscopic study of systemic myonecrosis due to poisoning by tropical rattlesnake (Crotalus durissus terrificus) in humans

This article describes the ultrastructural study of skeletal muscle biopsy specimens from five patients following envenomization by tropical rattlesnake (Crotalus durissus terrificus). All the patients were bitten in the leg and the biopsy specimens were obtained from the contralateral gastrocnemius muscle in the middle of the lower leg. A wide spectrum of detailed ultrastructural changes involving muscle fibers and microvasculature was demonstrated. Essentially, such lesions included widespread necrotic myofibers intermixed with intact fibers, accompanied by changes in the endothelial lining of the intramuscular blood capillaries and small arterial vessels, reducing their lumens. Since these alterations were observed in biopsy specimens from the limb contralateral to the site of the bite, they clearly demonstrate the systemic myonecrotic action of the venom of a tropical rattlesnake. On the basis of these data, the mechanism of venom-induced myopathy is described. It is postulated that the pathogenesis of systemic myonecrosis due to poisoning by C durissus terrificus is a complex one, probably due to direct damage to cells by the myotoxins of the venom, as well as indirect effects due to ischemia.

Age-related changes in the internal branch of the rat superior laryngeal nerve

This investigation was initiated to provide data on the ultrastructural basis for neurologic age-related changes in laryngeal sensory function. In the present study, an animal model (female Wistar rats: age range: young [Y], 3 to 5 months; old [O], 25 months; and very old [VO], 29 to 30 months) was used to examine systematically changes in the internal branch of the superior laryngeal nerve with age using electron microscopic morphometric techniques. Total fiber counts, fiber populations (size categories), and mean fiber size for myelinated and unmyelinated fibers did not change with age. Qualitative changes were consistent with segmental demyelination and axonal degeneration in the older animals. There was also a significant age-related increase in the volume fraction of adaxonal Schwann cell cytoplasm (Y, 0.019; O, 0.041; and VO, 0.042). Ultrastructural correlates of intracellular support and axonal transport showed a significant decrease in the numerical density of neurofilaments (Y, 0.126/micron2; O, 0.073/micron2; and VO, 0.078/micron2) in the older animals, but no change in the numerical density of microtubules. Energy metabolism correlates in the form of mitochondrial volume fraction did not change with age. There was a significant increase in the volume fraction of the intrafascicular extracellular space (Y, 0.224; O, 0.271; and VO, 0.301), indicating a late, age-related change in the extracellular environment. These changes could lead to decreased conduction velocity or complete fiber dysfunction. A number of these changes resembled those of aged human peripheral nerves already examined.

A light and electron microscopy study of normal human stratum corneum with particular reference to the intercellular space

Intercellular and skin-surface substances, and exfoliating corneocytes, were clearly visualized by both light and electron microscopy. The intercellular space constituted an essential part of the normal human stratum corneum, in the basal and middle zones of which this space was filled with substances producing a compact appearance. The intercellular constituents were a nonhomogeneous substance, intact, single and "compound" lamellar granules and an intensely stained, membrane-like material that in some parts, but not in others, had a lamellar pattern. The artifacts produced by ultrathin sectioning for electron microscopy were too small to provide sufficient explanation for the porous appearance of the superficial zone. More important factors seemed to be enlargement of the intercellular space with decrease in the number of desmosomes and alterations of the intercellular substances, with decrease in the amount of nonhomogeneous substance and transformation of the single and "compound" lamellar granules into single and "compound" vesicular bodies. The hypothesis is advanced that the single and "compound" vesicular bodies together with the decreased amount of nonhomogeneous substance may contribute to maintain the patency of the intercellular space in the superficial zone (stratum disjunctum), thereby facilitating absorption of surface-applied agents into the stratum corneum by some shunt mechanism, while the content of the intercellular space in the basal and middle zones (stratum compactum) forms the principal barrier to free diffusion.

Intra- and extracellular lysosomes in tendon tissue of the mouse after treatment with an anabolic steroid hormone. Ultrastructural and cytochemical study

Ultrastructural observations of fibroblasts from 6-week-old mouse tendons were carried out at different times after treatment with an anabolic steroid. The characteristic response of the fibroblasts involves the appearance of great numbers of intracellular lysosomes and the emergence of matrix vesicles, some of which could be identified ultrastructurally by their positive reaction for acid phosphatase as extracellular lysosomes. It is suggested that this fine structural gradient after treatment with the anabolic steroid results from, and may be directly the cause of, an increased level of cyclic AMP. The experimental design and the discussion of the findings consider, on the one hand, the use of anabolic steroid hormones in clinical practice and, on the other hand, the appearance of a collagen dysplasia in competitive sports.

Localization of neural cell adhesion molecule in denervated muscle to both the plasma membrane and extracellular compartments by immuno-electron microscopy

The location of neural cell adhesion molecule in mouse skeletal muscle has been investigated using two immuno-electron microscopical techniques. In the first method, 6-micron frozen sections of a normal and a hemi-denervated gluteus muscle were stained by an indirect immunoperoxidase method using a rabbit-derived polyclonal antiserum to neural adhesion molecule as the primary antibody. The stain was visualized with the electron-dense chromogen, diaminobenzidine and the sections fixed, osmicated and processed for electron microscopy whilst still on the slide. Ultrathin sections were cut and viewed in the electron microscope, where the reaction product appeared to be localized in the plasma membrane and on the basal lamina of the muscle fibres. The second method, using a 5-nm immunogold-labelled secondary antibody, confirmed and extended these initial observations. In these experiments, the primary antibody to neural cell adhesion molecule was applied in vivo to hemi-denervated mouse gluteus muscles. The muscles were dissected out 24 h later, divided into denervated and innervated halves and then into junctional and extrajunctional regions. Together with the junctional and extrajunctional regions of normal, control pieces of muscle which had not been incubated with anti-neural cell adhesion molecule, they were lightly fixed, and incubated with the secondary gold-labelled antibody, before further fixation and processing for electron microscopy. Semi-thin, 0.5-micron sections of each were cut and viewed at 20,000 x magnification. Randomly sampled fibres from the extrajunctional regions of the denervated and innervated halves of the hemi-denervated gluteus and the normal, control gluteus were photographed for quantitative analysis. Five micrographs were randomly selected from each group and in these, the numbers, density and position of gold particles were measured using a digitizing tablet. By far the highest number of gold particles was found in the denervated half of the gluteus muscle, there being much less in the innervated half and practically none in the control. The density of gold particles in the denervated muscles was maximal in the plasma membrane-basal lamina complex, but most were located in the extracellular spaces outside this region, where they usually occurred in clusters apparently in association with collagen fibres. We conclude that neural cell adhesion molecule in denervated skeletal muscle is present not only in the plasma membrane but also in the basal lamina and extracellular space.

A morphometric analysis of extracellular space in the developing spinal cord of the chick embryo

The developmental changes in the amount and distribution of the expanded extracellular space (ECS) (i.e. wider than 100 nm) were analyzed in the cervical spinal cord of chick embryos between stage 9 and 29, using electron micrograph montages, which cover one half of the cross-sectional area of the cord. The percentage of the ECS expansion to the whole cross-sectional area of the cord was 11.0% at stage 9, 7.7% at stage 11, 7.8% at stage 15, and 9.7% at stage 17. It decreased markedly to 3.0% at stage 22 and 1.3% at stage 29. The highest percentage at stage 9 may reflect the dynamic structural changes associated with neural groove closure which takes place around this time. The marked decrease after stage 22 is associated with the rapid overall growth of the cord. Until stage 19, the ECS expansions were mostly elongated and arranged radially with respect to the central canal. The ECS became scarce and arranged randomly thereafter. Throughout the stages examined, especially between stages 17 and 19, percentage was higher in the outer half of the cord than in the inner half. The outer glial limiting membrane was not established by stage 29. Between stages 17 and 22, the percentage was higher in the dorsal region than in the ventral region. This appears to be associated with the regional difference in neuronal maturation. The first blood vessels penetrated the ventromedial portion of the cord around stage 22, where the ECS expansions were relatively scarce. The successive rapid decrease in the amount of ECS expansions can be correlated to the development of vascularization.

Possible role of a proteinase in endosporulation of Coccidioides immitis

We previously reported isolation of a serine proteinase from the soluble conidial wall fraction of Coccidioides immitis. The purified proteinase was identified as a polypeptide band of 36,000 Mr by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In this study, we raised monospecific antiserum in rabbits against the purified proteinase for use in immunoelectron microscopy. We showed that immunolabel was localized in the cell wall of both the saprobic and parasitic phases but was most concentrated in the wall of the segmentation apparatus of spherules just prior to endospore differentiation. The total wall fractions of the mycelial phase, as well as those of presegmented and endosporulating spherules, were isolated from in vitro grown cells and then treated with a proteinase inhibitor (phenylmethylsulfonyl fluoride [PMSF]) which irreversibly binds to the residual proteolytic enzyme in the wall isolates. Each fraction was dialyzed, lyophilized, and separately incubated with the active, purified 36,000-Mr proteinase. The reaction mixtures were examined spectrophotometrically (A280) for decomposition of the substrates. Only the PMSF-treated wall isolated from endosporulating spherules was significantly digested. Active, 36,000-Mr proteinase was isolated from intact and viable, endosporulating spherules by brief extraction of the cells with 1% octyl-beta-D-thioglucoside, a nonionic detergent. The serine proteinase may be partly responsible for autolysis of the segmentation apparatus of mature spherules, a morphogenetic process which is pivotal for release of endospores and subsequent proliferation of the pathogen.

Morphology of the isolated rat hindquarter preparation: tissue preservation, perfusion heterogeneity and a note on the effect of fixative osmolality

The isolated rat hindquarter preparation often used for physiological studies was subjected to morphological examination. A two-hour perfusion with balanced oxygenated dextran solution was followed by perfusion fixation with aldehydes. Fixation was performed at isogravimetry when an isotonic fixative was used (2.5% glutaraldehyde in 0.05 M Na cacodylate + 4% dextran 70). Muscle specimens were prepared for light and electron microscopy. Most muscle tissue was well perfused but a limited tissue volume could retain blood after the perfusion period. Within perfused tissue the perfusion result varied macroscopically with some regions apparently not being reached by fixative. Non-fixed tissue was estimated to amount to maximally one fourth of the total tissue mass. Also within macroscopically well-fixed tissue the microscopy indicated varying patency of perfused capillaries. Thus a marked perfusion flow heterogeneity prevailed in the fixed specimens which is compatible with earlier functional findings of a 50% reduction of capillary surface area during isogravimetric fixation. The possible relation with prefixation flow heterogeneity in the vasodilated preparation is discussed. There were no obvious alterations of endothelial ultrastructure after prolonged artificial perfusion. Isogravimetrically fixed muscle had narrow extracellular spaces which were evidently compressed further after use of absorbing hyperosmolar fixative. Extracellular expansion and intracellular oedema followed after hypo-osmolar fixation. Muscle cells often exhibited insufficient mitochondrial fixation, probably as a result of tissue hypoxia.

Subunits in zonulae adhaerentes and striations in the associated circumferential microfilament bundles in chicken retinal pigment epithelial cells in situ

This study shows that the zonula adhaerens in chicken retinal pigment epithelial (RPE) cells in situ consists of independent subunits which are composed of extracellular intermembrane discs sandwiched between cytoplasmic plaques. These zonula adhaerens complexes (ZACs) are hexagonally arranged within the junction. Previous immunocytochemical studies suggest that the zonula adhaerens region, composed of ZACs, contains the actin associated proteins vinculin and alpha-actinin. The intermembrane discs of ZACs likely mediate cell-to-cell adhesion whereas the cytoplasmic plaques are probably involved in binding the microfilaments of the relatively large circumferential microfilament bundles (CMBs), associated with the zonula adhaerens, to the cell membrane. The CMBs of chicken RPE cells in situ show striations similar to those found in stress fibers of other cell types and in CMBs of cultured epithelial cells. The observation that in the striated regions of CMBs the adjacent junctional membranes tend to follow an undulating path suggests that the CMBs are attached intermittently to the cell membrane and are contractile. The structural similarities between CMBs and stress fibers and the fact that they share similar actin associated proteins support the view that CMBs and stress fibers are related structures.

Collagen phagocytosis by fibroblasts in the periodontal ligament of the mouse molar during the initial phase of hypofunction

This study was undertaken in order to determine whether hypofunction of teeth is associated with changes in collagen phagocytosis by fibroblasts of the periodontal ligament. In mice, the lower right molars were extracted and the animals killed one, two, three, four, or seven days later. The maxillary first molars with their surrounding periodontium were processed for electron microscopy and their periodontal ligament subjected to morphometric analysis. It was observed that, whereas the volume density of extracellular collagen in the ligament of the hypofunctional molars decreased from 50% to 30% during the course of the experiment, the fraction of fibrillar collagen ingested by the cells increased over two-fold. This increase was already manifest very shortly after the onset of the experiment and offers an explanation for the net loss of collagen fibrils from the extracellular space.

Ultrastructural changes in isolated perfused proximal tubules during osmotic water flow

Steady-state effects of osmotic gradients on extracellular spaces and cell volumes were studied by ultrastructural morphometry in isolated perfused Ambystoma proximal tubules. Solute clamping, high-resolution pressure and flow control of lumen and bath solutions were all ascertained before and during fixation. Isosmotic removal of organic substrates in the lumen reversibly abolished transport, as confirmed by transepithelial potential decrease from -4.7 +/- 0.5 to -0.5 +/- 0.2 mV (n = 8) but had no effect on ultrastructural parameters. The walls of the extracellular spaces are therefore not deformed by spontaneous solute-coupled water transport. A hyperosmolar lumen generated a streaming potential of -1.56 +/- 0.15 mV (n = 8), reduced cell volume to 65%, reduced lateral intercellular space (LIS) volume to 20%, and LIS volume density to 29% of control without significant effects on the volume of the basal extracellular labyrinth (BEL). A hyperosmolar bath generated a streaming potential of +1.96 +/- 0.30 mV (n = 7), reduced cell volume to 68%, and increased LIS volume density to 236% of control. BEL volume was 55% larger during lumen-to-bath flow than during bath-to-lumen flow. Because cell volume reduction is very similar for both directions of osmotic water flow, the oppositely directed volume changes in the extracellular spaces are secondary to transepithelial water flow. The greater change in volume of LIS compared with BEL indicates that the outermost parts of the LIS are more resistive to transepithelial water flow than the slitlike communications of the BEL with the peritubular space.

Influence of the rate of ventricular enlargement on the ultrastructural morphology of the white matter in experimental hydrocephalus

The influence of the rate of ventricular enlargement on the morphology of hydrocephalic white matter was studied and correlated with previous studies of water content. Different rates of ventricular enlargement were obtained in two groups of cats by opening either the calvaria or the calvaria and the dura mater before injecting kaolin into the cisterna magna. Animals from each group underwent in vivo fixation of brain 2, 3, and 6 weeks after hydrocephalus was induced. Specimens of white matter were taken 1, 2, and 3 mm lateral to the ependymal surface of the lateral ventricles, imbedded, and examined using transmission electron microscopy. The ultrastructural changes associated with ventricular enlargement varied with the model used and the duration of hydrocephalus. Marked expansion of the extracellular space extending 2 mm lateral from the ependyma was found in the craniectomy-durectomy preparations examined 2 to 3 weeks after kaolin injection. Time-matched craniectomy preparations had less enlargement of the extracellular space that was confined to the white matter immediately adjacent to the ventricle. Marked glial reaction was observed in these areas in the early craniectomy preparations. When studied 6 weeks after hydrocephalus induction, both models had less expansion of the extracellular spaces compared to early observations. Glial reaction was found in both models, but was greater in the craniectomy model. The correlation of these morphological findings with the rate of ventricular enlargement and earlier studies of water content are discussed.

Morphological changes in the human corneal epithelium associated with surgical corneal clouding

Light microscopy and electron microscopy were used to define morphological changes occurring in human corneal epithelium during surgery. No correlation was established between preoperative medication or peroperative fluids and corneal epithelial clouding. It is suggested that the changes we observed in relation to epithelial clouding were the direct result of disturbance to endothelial pump functions.

Ultrastructure of the bronchial epithelium in adult patients with cystic fibrosis

The respiratory epithelium of large airways was studied in biopsy specimens obtained by bronchoscopy in seven patients with cystic fibrosis (CF). All but one of these patients were chronically colonised with Pseudomonas aeruginosa. Biopsy specimens were also obtained from the large airways of 10 control patients with or without signs of chronic bronchitis. All samples were studied by transmission electron microscopy. Morphometry was applied to assess the volume density of various cell types and intercellular spaces and for quantification of microvilli of ciliated cells. In CF patients, the average number of microvilli per ciliated cell was decreased by 17% compared to patients with chronic bronchitis and by 34% compared to patients with apparently normal bronchi (p less than 0.02, respectively), but otherwise no abnormalities were found. In particular, the volume density of goblet cells was not increased. Thus the ultrastructure of the airway epithelium may be nearly normal in CF, even in adult patients with chronic respiratory infection.

Extra-axonal environment and fibre directionality in the early development of the chick embryo optic chiasm: a light and scanning electron microscopic study

The events that occur during the early development of the optic chiasm of the chick embryo have been studied by light and scanning electron microscopy. In developmental stages previous to the arrival of the first optic fibres in the floor of the diencephalon, as well as during the arrival of the leading fibres, extracellular spaces can be seen in the diencephalon ventral wall. These spaces are defined by external cell prolongations which end in a foot-shaped formation. During stages 25 and 26 a prechiasmic degenerative centre appears in the area immediately rostral to the early chiasm, leading to a notable degree of disorganization in the diencephalon wall. This centre appears to be related to the reorganization of the system of external cell processes and extracellular spaces which become progressively more irregularly distributed, coinciding with the arrival of the first optic fibre fascicles to the midline of the floor of the diencephalon. The optic fibre fascicles change their latero-medial directionality in the medial-most regions of the ventral diencephalon, where their course becomes rostrocaudal. This reorientation of the optic fibres seems to be mediated by primitive glial cells which first appear in the ventrorostral region of the early chiasm (previously occupied by the system of external cell processes and extracellular spaces) in stage 26, increasing in number from this stage on. The morphology of the primitive glial cells is laminar in nature and the cells are seen to be densely packed together with no large extracellular spaces between them.

Adrenergic stimulation of ciliary process epithelium causes surface membrane internalization

An ultrastructural change induced in the nonpigmented epithelium (NPE) of the ciliary processes by adrenergic stimulation in the albino rabbit was studied. Thirty min after topical treatment with 2% isoproterenol, an extensive intracellular membranous network, previously reported to be smooth endoplasmic reticulum, was revealed by electron microscopy. It was postulated that this network originated from the plasma membrane. Using cationized ferritin (CF) as an ultrastructural tracer, freshly isolated anterior segments were incubated in buffer containing 10(-5) M isoproterenol and 0.2% CF. As early as 10 min, and for at least 30 min, the isoproterenol-treated NPE cells contained a membranous network that was morphologically similar to that which occurs in vivo. CF particles were present within the network, indicating that the membranous network had originated at the cell surface. This labeling was prevented by pretreatment with the beta-adrenergic antagonist timolol maleate. In both treated and control ciliary processes, CF was present in the ciliary canals between the NPE and the underlying pigmented epithelium after 10 min incubation. This suggests that the NPE is able to transport CF from its basilar to apical surface. These experiments imply that the NPE is able to internalize rapidly large amounts of plasma membrane in response to adrenergic stimulation. This response may be part of the mechanism of adrenergic receptor desensitization, alteration of aqueous humor production, or another adrenergic response.

Morphologic study of ventricular trabeculation in the embryonic chick heart

This paper presents a morphologic study of ventricular trabeculation in chick embryo hearts between days 2 and 5 of incubation. Trabeculation appears to be the expression of three closely interrelated events: the formation of endocardial outgrowths that eventually invade the myocardium; the development of large intercellular spaces between the myocytes, and the decrease in thickness of the cardiac jelly. Endocardial cells present morphologic differences between trabeculated and nontrabeculated areas of the ventricular region. The elongation of the endocardial cells in the endocardial outgrowths and the presence of mitoses suggest that the endocardium grows out by means of an increase in cell number and by redistribution and elongation of the preexisting endocardial cells. The intercellular spaces of the myocardium appear filled with abundant extracellular material. It is suggested that the continuous synthesis of extracellular material by the myocytes may increase the hydrostatic pressure within the myocardium, inducing the formation and the enlargement of these intercellular spaces. The development and later rupture of endocardium-covered cords is described here. These cords are made up of a core of cardiac jelly material revested by endocardium. The cords may be engaged in the removal of substantial amounts of cardiac jelly during the formation of the trabeculae.

Cytologic diagnosis of prostatic malakoplakia. Report of three cases

Three cases of prostatic malakoplakia are reported. The cytologic findings in the smears obtained by transrectal fine needle aspiration biopsy are compared with the histologic findings obtained by simultaneously performed transrectal punch biopsy. The striking cytologic finding was the presence of large isolated histiocytes with abundant foamy cytoplasm. The concentrically laminated Michaelis-Gutmann bodies that are characteristic of malakoplakia were seen both within the histiocytes and, occasionally, in the extracellular background. The smears were further characterized by a granulomatous inflammatory reaction, consisting of large numbers of polymorphonuclear leukocytes, lymphocytes and plasma cells. These findings appear to be sufficient to make a diagnosis of this rare lesion in a prostatic aspirate. To our knowledge, this is the first description of the cytology of prostatic malakoplakia.

Electron microscopy of simian cerebral arteries after subarachnoid hemorrhage and after the injection of horseradish peroxidase

A large unilateral subarachnoid hemorrhage (SAH) was created in 21 monkeys, and horseradish peroxidase (HRP) was injected into the cisterna magna or left internal carotid artery in 3 others (normals). Cerebral fixation was performed on Day 14 after SAH or 15 minutes after HRP injection. The major cerebral arteries from both the nonclot (control) and clot sides and the normal animals were examined with scanning and transmission electron microscopy (SEM and TEM). SEM of the adventitial surfaces of control and normal arteries revealed tunnel-like structures along the longitudinal axis. No vasa vasorum were seen, but adventitial rounded openings were observed, 10 to 35 micron in diameter in vessels of the anterior circulation and up to 80 micron in diameter in the basilar arteries. The stomas, numbering 5 to 10/mm of specimen, appeared to connect the subarachnoid and intraadventitial spaces or pathways. In SAH arteries, the tunica adventitia was coated with cellular remnants of hematoma or dense, well-organized blood clots, the removal of which revealed blocked stomas. TEM showed HRP in the vessel walls after injection into the cisterna magna, but not after injection into the carotid artery. TEM of control arteries revealed Virchow-Robin (intraadventitial) spaces lined by simple planar epithelium-like cells; Virchow-Robin spaces contained sparse nerve fiber bundles and connective tissue fibers. In SAH arteries, these spaces were almost filled with strands of connective tissue and fibroblasts; no nerve fibers were detected. Vasogenic substances probably reach smooth muscle cells via the adventitial stomas. SAH occluding the stomas may block the cerebrospinal fluid circulation, disturbing nutrition of the arterial wall or removal of wastes from it, thereby aggravating vasospasm.

A cell surface desmosome-associated component: identification of tissue-specific cell adhesion molecule

Autoantibodies in the serum of patients suffering the blistering skin disease pemphigus vulgaris recognize a 140-kDa glycoprotein (GP) present in enriched fractions of bovine tongue epidermal desmosomes. Immunofluorescence observations of cryostat sections of bovine tongue epidermis reveal that affinity-purified rabbit antibodies to the 140-kDa GP generate a punctate intercellular stain that is similar to that generated by antibodies directed against a desmosome plaque component (desmoplakin). In cultured mouse keratinocytes, the antibodies against 140-kDa GP recognize desmosomes along areas of cell-cell contact. Double immunofluorescence of cultured keratinocytes with these antibodies and a desmoplakin antiserum reveals that the antibodies against the 140-kDa GP stain a single fluorescent line along areas of cell-cell contact. This single fluorescent line lies between double fluorescent lines generated by the desmoplakin antiserum. Immunogold ultrastructural localization reveals that the 140-kDa antigen is localized not only along the intercellular area of the desmosome but also is found along the whole epidermal cell surface. The antibodies to the 140-kDa GP are able to induce a disruption of cell-cell contact in cultured keratinocytes that possess desmosomes. We propose that the 140-kDa GP is a cell adhesion molecule (CAM). Furthermore we discuss the heterogeneity of desmosomes in the light of our findings that antibodies against the 140-kDa GP recognize specific stratified squamous epithelial tissues.

Reaggregates of cells from rat testis resemble developing gonads

Reaggregates prepared from newborn rat testis cells in Moscona-type rotation cultures were analyzed and compared with normal fetal (12-21 days) and newborn testes at the light and electron microscope level. After 25 h of culture, the aggregates resembled normal testicular tissue. The cells of the surface layer were spindle-shaped and connected by adherent junctions. The epithelial cords were composed exclusively of Sertoli cells and were surrounded by elongated cells resembling the developing myoid cells in newborn testes. The basal aspect of the cords was covered by a layer of flocculent material which, in places, was organized like an ordinary basement membrane. Individual spermatogonia with pseudopodes were observed in the interstitial tissue. Some Leydig cells were organized into small clusters like those typical in newborn testes. The present observations indicate that, histologically, the reaggregation of separated testicular cells resembles the differentiation of embryonic male gonads.

Ultrastructural study of the final cerebrospinal fluid pathway in human arachnoid villi

Human arachnoid villi were studied ultrastructurally to clarify the mechanism of cerebrospinal fluid absorption. Arachnoid villi of humans showed quite different features from those of animals. The former were not always invested with endothelial linings as previously reported in the latter. Instead, there was a covering layer of arachnoid cells which consisted of both an electron-lucent outer zone and an electron-dense inner zone. The outer zone had less cytoplasmic filaments and desmosomes than the inner zone. The inner zone was basically indistinguishable from the arachnoid membrane and had numerous cytoplasmic filaments and a series of desmosomes. Often, the covering layer was further encompassed by the thin fibrous capsule which reflected from the dura mater or sinus wall. Both the outer and inner zones were characterized by numerous extracellular cisterns which appeared, electron-optically, to be empty or contain a little 'fuzzy' material. In the villi affected by subarachnoid hemorrhage, extracellular cisterns were distended by intact of disintegrating erythrocytes which appeared to be natural tracers of cerebrospinal fluid. The size of these cisterns measured approximately 10 microns in the maximum diameter. It is suggested that extracellular cisterns may contribute to the bulk outflow of cerebrospinal fluid.

Massive retinal gliosis. A reactive proliferation of Müller cells

Both Müller cells and astrocytes have been implicated in the dispute over the histogenesis of massive retinal gliosis. We studied three cases of massive retinal gliosis by light and electron microscopy and immunocytochemistry. Spindle fibrillary glial cells were joined by zonulae adherentes resembling those of the external limiting membrane of the retina. Furthermore, these cells produced a continuous basement membrane around an extracellular space filled with fine filaments, which was highly suggestive of vitreous cavity. In the proliferating cells, immunoperoxidase technique disclosed the presence of carbonic anhydrase isoenzyme C, characteristically found only in Müller cells. The glial cells in the preretinal membrane away from the gliotic nodule showed similar characteristics. We concluded that both the nodule of massive retinal gliosis and the associated preretinal glial membrane resulted from the proliferation and migration of Müller cells.

Evaluation of the endothelium of human donor corneas by induced dilation of intercellular spaces and trypan blue

The endothelium of 30 pairs of human cadaver corneas was stained by trypan blue and the intercellular spaces were visualized by induced dilation prior to corneal culture. Trypan blue staining and induced dilation of intercellular spaces by 0.9% and 0.45% NaCl were found to be atraumatic. Only a fraction of damaged cells were stained by trypan blue. Endothelial cell losses in culture did not correlate with the number of trypan-blue stained cells, the post-mortem time, or donor age.

Immunolocalization of elastase in human emphysematous lungs

The current working hypothesis concerning the pathogenesis of human pulmonary emphysema proposes that neutrophils migrate through the alveolar interstitium and degranulate, releasing proteolytic enzymes into the interstitium. These enzymes, in particular elastase, can bind to and degrade interstitial elastin. This report describes an immunohistochemical, ultrastructural technique that utilizes polyclonal antibodies to localize neutrophil elastase in human lungs. Using both the immunoperoxidase and the immunogold methods on thin, embedded sections of surgically resected human emphysematous lung tissue, elastase was localized in neutrophils in the lung interstitium and extracellularly in association with interstitial elastic fibers in human lungs that showed local emphysema of varying severity. Quantitative morphometric data were obtained from the lungs of eight patients undergoing lobectomy for removal of pulmonary carcinomas. Patients had preoperative forced expiratory volume (FEV1)% levels ranging from 55 to 77. There was a correlation between a quantitative measure of the local distribution of neutrophil elastase in contact with alveolar interstitial elastin and the local presence of emphysematous change as determined by mean linear intercept of the various histologic sections. These data support the validity of the "protease-protease inhibitor balance hypothesis" as an explanation of the pathogenesis of human pulmonary emphysema.

Epidermal permeability barrier: transformation of lamellar granule-disks into intercellular sheets by a membrane-fusion process, a freeze-fracture study

Freeze-fracture replication of lamellar granules and intercellular sheets of the horny layer in mouse, chicken, and snake epidermis reveals a pattern of serial fracture faces which is highly suggestive of polar lipids in a bilayer configuration. The occurrence of alternating wide and narrow fracture faces separated by intervening steps supports the view that epidermal barrier bilayers display lipid asymmetry similar to membranes. Within the lamellar granules, bilayers arrange to form disks which in fact are equivalent to flattened unilamellar liposomes. Stacking of the disks in turn gives rise to the lamellar pattern. After exocytosis into the intercellular space, the disks are arranged parallel to the cell membranes. In tangentially fractured specimens, the cleavage plane jumps back and forth from the plasma membrane to a disk-bilayer, thereby giving rise to the known phenomenon of EF-ridges (on the extracellular fracture face) and PF-grooves (in the plasmatic fracture face) which both represent the level of the plasma membrane sur- or subjacent to the aisles between disks. Concomitantly with the upward movement of the keratinocytes, the ridges and grooves become narrower until they fade away by the second or third cell layer of the stratum corneum. This phenomenon is explained by the fusion of adjacent disks at their highly curved brims due to a mechanism similar to the process of membrane fusion which causes the formation of wide, uninterrupted sheets.

[Ultrastructural study of the ureter smooth muscle of the cat]

Morphological specializations of smooth muscles from the middle part of the cat ureter have been examined by electron microscopy using thin sections and freeze-fracture replicas. It is notable that there were many gap junctions which were characteristic in being formed on the surface of blunt cytoplasmic projections protruded from each neighboring cells. In addition to gap junctions, there were two other different junctions, i.e, intermediate junctions and "focal attachments". The latter represents the cell attachment in which two apposing plasma membranes are attached to each other without the intervension of basal lamina in the narrow intercellular space. Caveolae were lined in rows which were intervened by dense band zones parallel to the long axis of the muscle fibre as seen by freeze-fracture replica. Gap junctions were noted to be localized within or along the caveolar zones, being elliptical in shape with the long axis parallel to muscle fibres. As observed in thin sections, gap junctions in freeze-fracture replicas were noted on the top of cytoplasmic protrusions. No membrane specializations were observed in freeze-fracture replicas which corresponded to the "focal attachment" or intermediate junction as seen in thin sections. As to the innervation, the autonomic nerve terminals were in abundance, closely apposed to the smooth muscles. In addition to autonomic nerve terminals, sensory nerve terminals were observed between muscle fibres, consisting of axon terminals and lamellar cells, the same structure as mechanoreceptive lamellar corpuscles known in other organs.

Glial cells of an insect ganglion

The rapid development of the study of insect neurobiology, which is currently occurring principally because individual neurons can be re-identified and because their activities can be recorded in situ and related to behavior, is generating a demand for more knowledge concerning insect glial cells and their functional relationships with neurons. This study examines the ultrastructure of glial cells in locust metathoracic ganglia in relation to general locale within the ganglion and also to specific identified neurons and neuron types. Seven major types of glial cell form are recognized, with subdivisions, requiring a new scheme for classification. Glial invaginations into neurons are of four different kinds: regular, chunky, filigree, and ridge (found only at axon hillocks). They also range from only intrusive to fully reciprocal. In addition, some neurons make projections of various lengths into surrounding glia and between neighboring neuron somata, and some glia make long, branched projections into other glial cells. The differences show that insect glial cells develop highly specific functional specializations; they may not be interchangeable. The complexity and intimacy of relationships of glia with neurons suggest that some glial cells may have roles other than that of nursemaids, possibly in modulation of behavior-determining neural activity, and in learning and other adaptive acts.

The chronology of lesion repair in the developing rat brain: biological significance of the pre-existing extracellular space

We observed the histological peculiarities of the repair process in a destructive lesion of the developing rat brain during neurogenesis. Degeneration was induced selectively in certain cells of the proliferating phase in the rat fetal neopallium on embryonic day 16 by transplacental administration of ethylnitrosourea. Successive elimination of necrotic cells and the restoration process were observed. The repair process was divided into the following steps: elimination of individually affected cells by phagocytes in the pre-existing extracellular space; successive restoration of the disintegrated area by cells which differentiated from remaining matrix cells. No reactive gliosis, fibrosis, abnormal vascularization or infiltration of granulocytes and lymphocytes was observed at any time. The thinned neopallium on postnatal day 21 revealed only a small number and abnormal distribution of the cortical neurons. It may be assumed that the fetal brain owes its unique repair features to the presence of a vast extracellular space under normal conditions. In this pre-existing extracellular space, every kind of cell seems to exist separately without the intracellular adhesions characteristic of the adult brain. When degeneration occurs in certain cells the phagocytes would be able to eliminate the degenerate cells completely in this space without having to break intercellular adhesions. As a result, after the completion of cell elimination, the injured brain is restored to its original state with no cell reaction, giving the appearance of a small brain with normal-looking histological architecture, save only for the sparseness of cells.

Electron dense mitochondrial inclusions in a pituitary oncocytoma

A 65-year-old man had a pituitary adenoma with a large expansion of the sella turcica; computerized tomography demonstrated suprasellar extension. The tumor, removed surgically, was diagnosed as nonsecretory partly chromophobic, partly acidophilic adenoma by light microscopy and immunocytology. Electron microscopic investigation revealed a pituitary oncocytoma with an unusual mitochondrial abnormality. Some mitochondria harbored single or multiple electron dense bodies which were also found in the cytoplasm as well as in the extracellular space. It appears that these bodies were originally formed in the mitochondria, then extruded into the cytoplasm and subsequently to the extracellular space.

Regeneration of central nervous system axons into an acellular tube in the absence of distal tissue

To differentiate between local and distant influences on central nerve regeneration, an impervious, stainless-steel cannula, 12 mm long, was placed in the path of severed axons within the corpus callosum of adult rats. The cannula was occluded for 1 week after implantation to prevent herniation of tissue into its lumen. The extracranial end of the tube was plugged with Gelfoam rather than tissue. Inflammatory cells within the tube decreased in number with time and all animals survived for the experiment's duration of 4 to 16 weeks. Some callosal axons grew into the cannula and eventually extended about 1.3 mm. After 8 to 16 weeks, the lumen of the cannula contained many unmyelinated axons, some of which formed fascicles, myelinated axons, demyelinating axons, a few oligodendrocytes, and many astrocytic processes, macrophages, and blood vessels. A striking feature was the linear orientation of cells and their processes. The distal tip of the core resembled a central nervous system explant: it included an appreciable number of growth cones, synaptic terminals embedded in a generous extracellular space, and occasional remyelinating axons. Thus, within an impervious, acellular conduit and in the absence of distal tissue, intrinsic, neuronal processes can be redirected, fasciculate, myelinate, and can regrow alongside glia and endothelium. An indwelling tube, isolating the growth from surrounding brain fluid, may permit assessment of glial, neuronal, and extracellular contributions to the directed regeneration of adult, central axons.

Light and electron microscopy of the new born sagittal suture

Morphogenesis and maturation of the sagittal suture in newborn C57B1/6J strain mice were studied using light and electron microscopy. Morphodifferentiation of the murine parietal bones progresses radially with the interposed sagittal suture, assuming a greater level of maturity at birth at a midpoint along its length. The presumptive suture develops in a sulcus, deeper posteriorly, more shallow anteriorly. Cells at the osteogenic front (OF) are distinguished from the surrounding fibrocytic cells by a number of distinctive characteristics: 1. increased cytoplasmic density; 2. extensive endoplasmic reticulum; 3. dispersed nuclear chromatin aggregates; 4. extensive surface projections; 5. close approximation. Mineralization of the developing parietal bone occurs extracellularly with the initial deposits of apatite crystals exhibiting no oriented relationship to either cellular or extracellular fibrillar elements. The majority of collagen fibers lie superior and inferior to the presumptive suture, oriented anteroposteriorly with their long axes parallel to the ectocranial surface. Other fiber bundles more intimately associated with the developing suture display a more random orientation.

Ultrastructural investigation of extracellular structures in subcapsular white corrugated cataract (anterior capsular cataract)

Electron microscopic investigations were performed on six extracted lenses from patients undergoing operative treatment of subcapsular white corrugated cataract. The lens capsule itself was unaltered. There was a pronounced extracellular space under the capsule. In this area collagenous aggregations equivalent in size to collagenous fibres and fibrils could be seen. Collagenous microfibrils and delicate microfilaments were also present. The latter could be observed with and without cross-striations. The fibrous structures are distinguished by considerable variations in shape and diameter. The precursor stages of these fibrous materials are produced by myofibroblast-like cells, probably derived from the lenticular epithelium.

Biochemical and microscopic evidence for the internalization and degradation of heparin-containing mast cell granules by bovine endothelial cells

Incubation of [35S]heparin-containing mast cell granules with cultured bovine endothelial cells was followed by the appearance of 35S-granule-associated radioactivity within the endothelial cells and a decrease in radioactivity in the extracellular fluid. These changes occurred during the first 24 hours of incubation and suggested ingestion of the mast cell granules by the endothelial cells. Periodic electron microscopic examination of the monolayers confirmed this hypothesis by demonstrating apposition of the granules to the plasmalemma of endothelial cells, which was followed by the engulfment of the granules by cytoplasmic projections. Under light microscopic examination, mast cell granules within endothelial cells then appeared to undergo degradation. The degradation of [35S]heparin in mast cell granules was demonstrated by a decrease in the amount of intracellular [35S]heparin proteoglycan after 24 hours and the appearance of free [35S]sulfate in the extracellular compartment. Intact endothelial cells were more efficient at degrading [35S]heparin than were cell lysates or cell supernatants. These data provide evidence of the ability of endothelial cells to ingest mast cell granules and degrade native heparin that is presented as a part of the mast cell granule.

Intercellular fibrillar skeleton in the basal interdigitations of kidney tubular cells

The tubular cells from the thick ascending limb of the loop of Henle in rabbit kidney medulla contain in their basal-lateral surfaces a complex system of interdigitations. Within these interdigitations, the plasma membranes are separated by extracellular spaces of relatively constant width that contain a previously undescribed fibrillar system. The structural organization and distribution of this intercellular fibrillar skeleton was studied using freeze-fracture etch and then section electron microscopy. The skeleton is comprised of discrete strands with a density of 300 to 400 per micron 2 evenly distributed along the entire basal-lateral region. Each strand has the shape of a brace and it is constructed from up to eight finer filaments each having a width of about 2 nm. The filaments are tightly joined together along their shafts for about 30 nm but they separate at both ends for about 10 nm before contacting the external surface of the plasma membrane. We propose that this intercellular fibrillar skeleton is responsible for maintaining the wide (about 50 nm) and uniform plasma membrane separation along the entire length of the basal-lateral region of the tubular cells of the thick ascending limb.

Connections between the sensory retina and the retinal pigment epithelium

The study reports on the presence of connections between the visual receptor outer segments and the apical villi on the retinal pigment epithelium in the human eye. The mechanisms underlying sensory retinal adhesion to the pigment epithelium, recognition and attachment of visual receptor outer segments to the pigment epithelium during phagocytosis, and communication and transport of substances between the two layers of retina have been difficult to define, and molecular connections between the two layers of retina could play an important role in these processes.

Digestion of prey in foraminifera is not anomalous: a correlation of light microscopic, cytochemical, and HVEM technics to study phagotrophy in two allogromiids

Correlative light, high-voltage electron and conventional electron microscopic methods were used to investigate digestion in two allogromiid foraminiferans, Allogromia sp., strain NF, and A. laticollaris Arnold. Microscopic observations showed that bacterial prey are phagocytosed by reticulopodia and are transported to the allogromiid cell body within blister-like phagosomes. Larger prey (algae, diatoms) are transported along the reticulopodial surface and are either stored extrathalamously or phagocytosed at the oral opening (peduncle). Studies of allogromiids optimally fixed and labeled with an extracellular-space label (colloidal thorium) showed that phagocytosed prey are completely enclosed by a plasma membrane envelope; this finding was corroborated by a serial-section three-dimensional reconstruction of the oral zone of one allogromiid. Cytochemical staining for acid phosphatase showed that lysosomes are absent from reticulopods but abundant in the cell body, particularly in the oral zone cytoplasm. We conclude that digestion in allogromiid foraminiferans is accomplished by a vacuole-based digestive apparatus and not by extracellular digestion within a lacunary system, as has been suggested in earlier studies.

An ultrastructural study of the vascular alterations within the carotid bodies of spontaneously hypertensive rats (SHR)

Electron microscopic studies of the fine structural changes of the arterioles within the carotid bodies of spontaneously hypertensive rats (SHR) in the established phase of hypertension revealed partly hyperplastic endothelial cells. In the subendothelial space a multiplication of the basal laminae was observed often of a whirl-like shape. The smooth muscle cells of the media were hypertrophied, bizarre and with numerous projections. They exhibited a marked increase in cell organelles. The extracellular space was extensively enlarged and partly vacuolated. It contained a basement membrane-like material which was connected with the basal laminae of the myocytes. All these alterations produced a pad-like thickening of the arteriolar wall which narrowed the vessel lumen. These findings and their possible effects on carotid body function are discussed.