Lipoblastic meningioma: a light and electron microscopic study

A patient with intracranial lipoblastic meningioma in the right frontal lobe is reported. The tumor was entirely made up of vacuolated cells. The nature of this rare neoplasm has been verified by light and electron microscopic studies.     

Obstructive lesions of distal mesenteric arteries. A light and electron microscopic study

Two cases of "nonocclusive" intestinal infarction are reported. No thrombosis or significant atherosclerosis was identified and proximal mesenteric arteries were widely patent. However, distal mesenteric arteries were thickened and had pinpoint lumens. Light microscopic findings suggested that this marked luminal narrowing was due to prominent intimal fibromuscular proliferation, medial hypertrophy and mild structural disarray, focal periarterial fibrosis, and transmural elastosis. Electron microscopic findings indicated that the endothelium was normal but the basal lamina was irregularly thickened. The predominant cellular component of the thickened intima consisted of smooth muscle cells, and smooth muscle cells of the media were seen to migrate through an extensively disrupted and degenerated internal elastic lamina. Deposits of young elastic fibers, collagen, and ground substance were also noted, particularly in the intima. The need for careful sectioning and microscopic examination of small distal mesenteric arteries in cases of so-called nonocclusive intestinal infarction is emphasized.     

Laminin localization in enterocytic basement membrane of rat small bowel grafts. A light and electron microscopic study

In vitro laminins stimulate numerous biological effects, such as cell migration, proliferation, attachment and differentiation. In vitro laminins influence immunocompetent cells and in vivo possibly play an important role in graft rejection. To establish how laminins could be involved in the regulation of acute rejection of small bowel allografts (with and without immunosuppression), we investigated laminin distribution in rat small bowel allografts four days after transplantation, i.e., before the onset of histological signs of rejection, using antibodies against alpha1, beta1, gamma1 chain of laminin-1. In immunosuppressed allografts, the ultrastructure of the enterocytic basement membrane appeared normal, but no laminin staining was seen in this membrane, although basement membranes of intramural blood vessels and muscle cells were normally stained. In non-operated immunosuppressed rats, laminin staining was clearly reduced in the enterocytic basement membrane, demonstrating that cyclosporin A is able to affect this membrane. Since only rats in which laminin is altered survive, this laminin alteration in the enterocytic basement membrane presumably plays an important role in overcoming the acute rejection.     

Paravertebral muscles in experimental scoliosis: a light and electron microscopic study

Experimental structural dextroconvex scoliosis was produced in rabbits by costotransversolisis with transversectomy and releasing of paravertebral muscles between TVII and TX on the right side. Two compensatory curves developed on the upper dorsal and lumbar levels. Biopsies of paravertebral muscles in experimental animals included, besides areas of normal tissue, a considerable derangement of the cell contractile apparatus with sarcoplasmic dilation and eventual cell disintegration and necrosis. Histological changes varied along levels, the convexity being more affected. The severity of changes and reduction in body weight and length were correlated with the degree of scoliosis. A selective atrophy of slow-twitch fibers was observed in experimental animals, especially at the level of the main curve, whereas fast-twitch fiber atrophy was more important caudally. Control animal biopsies always appeared normal. Our experimental model shows an overt participation of paravertebral muscles in the establishment of compensatory processes following scoliosis, although the role that paravertebral muscles play in the etiopathogenesis of human idiopathic scoliosis requires further investigation.     

Immunocytochemical localization of substance P receptor in rat periaqueductal gray matter: a light and electron microscopic study

The distribution of substance P receptor (SPR) protein in the rat periaqueductal gray matter (PAG) was investigated with a polyclonal antibody in the four subdivisions obtained by cytochrome-oxidase histochemistry (Co-hi). At light microscopic analysis, immunoreactivity appeared particularly dense in the dorsal subdivision of the PAG, was less intense in the other subdivisions, and formed several longitudinally organized columns. SPR-like immunoreactivity (SP(R-i)) was localized mostly to cell bodies and dendrites of small and medium-sized neurons, which constituted about 6% of the total neuronal population of the PAG. At the electron microscopic level, SP(R-i) could be observed on postsynaptic as well as on nonsynaptic regions of both cell bodies and dendrites. A small proportion of axons (4.2%) and axon terminals (5.3%) showed SP(R-i), the majority of labeled axon terminals, amounting to about 70% of synapsing elements, formed asymmetric synapses with dendrites. Rare astroglial processes displaying SP(R-i) were also observed scattered throughout the neuropil of all PAG subdivisions. Our observations suggest that 1) also in the PAG, SP may act in a diffuse, nonsynaptic manner, probably on targets that are distant from its sites of release; and 2) SP may modulate excitatory neurotransmission acting presynaptically on those labeled axons that form asymmetric synapses.     

Regional differences in the pineal gland of the cotton rat, Sigmodon hispidus: light microscopic, electron microscopic, and immunohistochemical observations

Light microscopic, electron microscopic and immunohistochemical observations of the various portions of the pineal gland of the cotton rat (Sigmodon hispidus) were made. The volume of the proximal half occupied about 30% of the whole organ, and pinealocytes were slightly smaller in size in the proximal portion than elsewhere. The distal and intermediate portions contained few interstitial cells and numerous astrocytes, but the proximal portion lacked interstitial cells and had more abundant astrocytes than elsewhere. Astrocytes, which were immunoreactive for glial fibrillary acidic protein, mainly lined the pericapillary spaces in the distal and intermediate portions, but in the proximal portion these cells often surrounded isolated or groups of pinealocytes. In the distal and intermediate portions, abundant sympathetic fibers and less numerous non-sympathetic, peptidergic fibers were mainly localized in the pericapillary spaces; these fibers were sparsely distributed in the parenchyma close to interstitial cells or astrocytes. In the proximal portion, non-sympathetic fibers were scarce and sympathetic fibers were distributed abundantly and almost exclusively in the parenchyma. Most of the sympathetic fibers were adjacent to astrocytes and, occasionally, made specialized contact with them. Fenestrae in the capillary endothelium were numerous in the distal portion but absent in the proximal portion. Thus, marked differences in structure existed between the distal and proximal portions of the pineal gland of the cotton rat suggesting that both portions are functionally dissimilar. In addition, the present study indicates that the proximal portion of the cotton rat was well developed and showed morphological features similar to the deeply situated pineal glands of other mammals.     

Identification of orbital lymphatics: enzyme histochemical light microscopic and electron microscopic studies

The presence of orbital lymphatics in the primate model is demonstrated using light and electron microscopic enzyme histochemistry. In addition, strictly morphological definitions of lymphatics, such as discontinuous basal lamina, thin and irregular walls, anchoring filaments, and attenuated endothelial cell cytoplasm, were applied. This study confirmed the presence of conjunctival lymphatics reported by others. It also clearly demonstrated the presence of orbital arachnoid and lacrimal gland lymphatics that have not been previously described. A few areas of the extraocular muscles and connective tissue at the orbital apex also showed evidence of the presence of lymphatic vessels. Additional work is needed to define the nature and extent of orbital lymphatics as well as their connection to the extraorbital lymphatic system.     

Muscarinic receptor subtypes in the lateral geniculate nucleus: a light and electron microscopic analysis

Neural activity in the dorsal lateral geniculate nucleus of the thalamus (DLG) is modulated by an ascending cholinergic projection from the brainstem. The purpose of this study was to identify and localize specific muscarinic receptors for acetylcholine in the DLG. Receptors were identified in rat and cat tissue by means of antibodies to muscarinic receptor subtypes, ml-m4. Brain sections were processed immunohistochemically and examined with light and electron microscopy. Rat DLG stained positively with antibodies to the m1, m2,and m3 receptor subtypes but not with antibodies to the m4 receptor subtype. The m1 and m3 antibodies appeared to label somata and dendrites of thalamocortical cells. The m1 immunostaining was pale, whereas m3-positive neurons exhibited denser labeling with focal concentrations of staining. Strong immunoreactivity to the m2 antibody was widespread in dendrites and somata of cells resembling geniculate interneurons. Most m2-positive synaptic contacts were classified as F2-type terminals, which are the presynaptic dendrites of interneurons. The thalamic reticular nucleus also exhibited robust m2 immunostaining. Cat DLG exhibited immunoreactivity to the m2 and m3 antibodies. The entire DLG stained darkly for the m2 receptor subtype, except for patchy label in the medial interlaminar nucleus and the ventralmost C laminae. The staining for m3 was lighter and was distributed more homogeneously across the DLG. The perigeniculate nucleus also was immunoreactive to the m2 and m3 subtype-specific antibodies. Immunoreactivity in cat to the m1 or m4 receptor antibodies was undetectable. These data provide anatomical evidence for specific muscarinic-mediated actions of acetylcholine on DLG thalamocortical cells and thalamic interneurons.     

Testicular histopathology in congenital lipoid adrenal hyperplasia: a light and electron microscopic study

During the 1980s, interest was shown in North America as to how Intensive Care Nurses use their work time, in response to a shortage of trained nurses. These studies were developed to investigate the amount of nursing time that could be saved by computerised recording systems. Similar pressures are now present in the United Kingdom, but there are no published work load studies of Intensive Care Nurses. This study used a five category tool to examine the work load of nurses in a cardiothoracic ICU. The methodology was designed so that comparison could be made with the earlier American studies. The 36 nurses studied spent 41% of their time in direct nursing care, 22% in patient assessment, 19% in clerical duties, 11% in time outside the unit and 7% in non-nursing duties. These findings were compared with the North American studies. Similarities were found which give some support to the reliability and validity of the tool.     

Lateral nucleus of the rat amygdala is reciprocally connected with basal and accessory basal nuclei: a light and electron microscopic study

Information flow within the intra-amygdaloid circuitry has been generally believed to be unidirectional rather than reciprocal, in which case sensory inputs entering the amygdala via the lateral nucleus would not be modulated by inputs from other amygdaloid regions. In the present study we extend our earlier findings which indicated that the lateral nucleus of the rat amygdala is reciprocally connected with the basal and accessory basal nuclei. The type of synaptic contacts made by these connections is also characterized at the ultrastructural level. An anterograde tracer, Phaseolus vulgaris leucoagglutinin, was injected into the basal (n=22) or accessory basal nuclei (n=12) of the rat amygdala. The results demonstrate that the ventrolateral division of the lateral nucleus receives projections from the basal nucleus, while the medial division receives projections from the accessory basal nucleus. Electron microscopic analyses revealed that axons projecting from the basal nucleus formed both asymmetric and symmetric contacts within the ventrolateral division of the lateral nucleus, whereas axons projecting from the accessory basal nucleus to the medial division of the lateral nucleus formed only asymmetric synapses with their targets. These findings suggest that the lateral nucleus receives both inhibitory and excitatory intra-amygdaloid projections and indicate that information flow within the amygdala is not unidirectional as previously thought. The results of this study provide evidence that the early phase of sensory processing within the amygdala is already modified by inputs from other amygdaloid nuclei.     

A light and electron microscopic study of the rat superior cervical ganglion cells by intracellular HRP-labeling

Horseradish peroxidase (HRP) was injected intracellularly into single neurons of the isolated rat superior cervical ganglia. Intracellular iontophoresis of HRP did not seem to damage the sympatheticneurons or to affect synaptic transmission. Under the light microscope, 9 of the 27 HRP-labeled sympathetic neurons exhibited varicosities in their dendrites, but not in their axons; the varicose dendrites came into close contacts with adjacent non-labeled neurons. With the electron microscope, the varicose dendrites of 3 separate neurons lightly stained with HRP, morphological features of synapses could be identified at the contact site: clusters of vesicles in the varicose dendrites, intercellular space of about 20 nm separating the apposed membranes, and an intermediate density on the postjunctional membrane. These findings suggest at the ultrastructural level the occurrence of dendrodendritic and dendro-somatic synapses in mammalian sympathetic ganglia.     

True synovial metaplasia of breast implant capsules: a light and electron microscopic study

High resolution chromosome analysis, molecular cytogenetics, and study of the association between specific chromosome rearrangements and single gene disorders have provided a chromosomal basis to a number of mendelian diseases. Deletions and duplications of small regions, usually less than 3 Mb in size, result in an alteration of normal gene dosage of a number of unrelated genes physically close to each other and are responsible for contiguous gene syndromes. For example, haploinsufficiency is implicated for del 8q24.1 in Langer-Giedion syndrome, del 17p13.3 in Miller-Dieker syndrome, and del 22q11.2 in DiGeorge and Velo-cardiofacial syndromes. Another chromosomal mechanism causing mendelian phenotypes is translocation, which may eventually interrupt a disease gene. It is assumed that translocation breakpoints are running through a relevant gene, hindering the production of the gene product. An example is breakage 16p13.3 associated with Rubinstein-Taybi syndrome. Females with X/autosome translocations have an almost exclusive inactivation of the normal X. Interruption of a disease gene in the translocated X causes the expression of a mendelian phenotype in the presence of an allelic recessive mutation onto the nonrearranged X. Finally, if a human gene shows exclusive expression from a single parental homologue, ie, it is imprinted, deletion of the chromosomal segment containing the active allele results in structural monosomy and functional nullisomy. This situation is illustrated by Prader-Willi and Angelman syndromes. Over seventy human genes have been precisely assigned to chromosomal regions using a cytogenetic approach. Chromosome techniques combined with molecular methods have proved to have powerful and sensitive diagnostic capabilities.     

Renal proliferative arteriopathies and associated glomerular changes: a light and electron microscopic study

This presentation reports the light and electron microscopic findings relating to the vascular and glomerular changes in the kidney in a series of 25 patients having malignant hypertension, the hemolytic-uremic syndrome, scleroderma, or toxemia of pregnancy. The pathologic changes were generally similar in each of the diseases studied, the changes being related more to the severity and duration of injury than to the specific disease. Vascular narrowing was due mainly to intimal thickening, and by light microscopy the lesions were categorized as onionskin, mucinous, or fibrous with or without associated elastosis. Intimal erythrocyte extravasation, fibrinoid necrosis, and luminal thrombosis were also seen. Electron microscopy provided additional morphologic information: Myointimal cells were found to be the cellular component in each type of intimal thickening; it was possible to distinguish collagen from large intimal accumulations of basement membrane material; mucinous intimal material was characterized ultrastructurally; and fibrinoid necrosis was identified as a lesion inconstantly associated with cellular necrosis and consisting mainly of fibrinoid material and small deposits of fibrin. It seems likely that there is a common pathogenesis for intimal thickening in a variety of diseases and that this involves endothelial cell damage and increased permeability, leakage of serum and erythrocytes into the intima, and a healing reaction of the vessel wall was developing from migration of smooth muscle cells into the intima with subsequent myointimal cell proliferation and fibrogenesis. A common glomerular change in all diseases studied was a striking accumulation of electron lucent material between the endothelium and the lamina densa of the basement membrane. This lesion was interpreted as a manifestation of acute ischemia.     

An electron microscopic study of plasmatic arterionecrosis in the human cerebral arteries

An electron microscopic study of the intracerebral arteries from 9 hypertensive cases was performed in order to elucidate the morphogenesis of the plasmatic arterionecrosis which was considered to be the direct cause of hypertensive intracerebral hemorrhage. In the preceding stage of the arterial lesions, marked necrosis of medial smooth muscle cells and increase of basement membrane-like substance in the intima and media were observed. The lumina of these arteries were slightly dilated. The dilatation and hemodynamic factors were supposed to cause endothelial injury resulting in blood plasma insudation into the intima through the opened spaces between endothelial cells. The insudated blood plasma dispersed and dissolved the basement membrane-like substance, collagen and elastic fibers in the arterial wall, leading to the development of the plasmatic arterionecrosis.     

Calretinin immunoreactivity in the cerebral cortex of the lizard Psammodromus algirus: a light and electron microscopic study

The present study describes the distribution and structural features of calretinin-immunoreactive neurons and fiber plexuses in the cerebral cortex of a lacertid lizard, at the light and electron microscopic levels, and also examines the colocalization of calretinin with parvalbumin and gamma-aminobutyric acid (GABA) in certain cortical regions. Calretinin-immunoreactive neurons are present throughout the cerebral cortex of Psammodromus and can be classified according to morphological and neurochemical criteria. Neurons in the medial cortex are small, spine-free and lack parvalbumin, whereas in the lateral cortex, calretinin-immunoreactive neurons display sparsely spiny dendrites and also lack parvalbumin. The dorsomedial and dorsal cortices contain most of the calretinin cortical neurons, which were located almost exclusively in the deep plexiform layer. These neurons are large, with an extensive spine-free dendritic tree. Most of the calretinin-immunoreactive neurons of dorsomedial and dorsal cortices are GABAergic and contain parvalbumin. Calretinin-immunoreactive fibers form two main afferent systems in the cortical areas. One probably intrinsic inhibitory system, arising from the calretinin and parvalbumin GABAergic neurons in the dorsomedial and dorsal cortices, makes symmetrical synapses on the soma and proximal dendrites of neurons located in the cell layers of the same cortical areas. The other system is formed by extremely thin axons running within the superficial plexiform layers of the medial, dorsomedial and dorsal cortices. These axons make asymmetrical synapses on dendrites or dendritic spines. We suggest that this system, probably extrinsic excitatory, arises from neurons located in the basal forebrain.     

Structure of a juxtaglomerular cell tumor: the presence of a neural component: a light and electron microscopic study

A 15-year-old girl with hypertension, markedly elevated plasma renin activity, and normal aortogram had a well encapsulated tumor nodule removed from the right kidney. Following surgery, the plasma renin activity and blood pressure became normal and have remained so for the past 12 months. The tumor consisted of juxtaglomerular cells filling the interstitium between endothelium-lined vascular spaces. Electron microscopy disclosed the presence in the interior of the tumor, of unmyelinated nerve bundles with varicosities containing the small, densely cored vesicles characteristic of adrenergic nerves. Nerve terminals were in contact with the juxtaglomerular tumor cells. No basement membrane material was interposed between the nerve endings and the tumor cell; the width of the gap between the two plasma membranes was approximately 150 A. The presence of sympathetic fibers in the juxtaglomerular cell tumor underscores the close biologic relationship between the sympathetic and renin systems.     

Histogenesis and diagnostic of kidney cancer in the light of electron microscopic data

Electron microscopic examinations of human renal carcinoma showed that both light and dark (granular) differentiated tumour cells may have ultrastructural features of the cells of any nephron segment. In the light of these results and concepts of the capacity of undifferentiated tumour cells for specific differentiation, the decisive importance in histogenesis (cytogenesis) of the renal carcinoma belongs not to the site of its origin in one or another nephron segment but to the level of differentiation of stem cells (polypotent or monopotent) undergoing malignization and to the direction of their further differentiation. The paper presents concrete ultrastructural differential diagnostic features of renal carcinoma cells.     

Changes in muscularis externa of rat small intestine after myenteric ablation with benzalkonium chloride: electron microscopic and morphometric study

The influence of the intrinsic innervation on the muscularis externa of the rat small intestine was studied by chemical ablation of the myenteric plexus with benzalkonium chloride (BAC). The resulting severe hypertrophy (cell hypertrophy of 96-133% and hyperplasia) differs from working hypertrophy by the distribution and degree of muscle thickening and by characteristics of the extracellular matrix: narrowing of muscle interspaces of 43%; lack of increased collagen; changes in the ratio of interstitial cells of Cajal (ICCs) to fibroblasts from 1.6:1 to 0.8:1 with no numerical decrease in either type of cell; decreased interconnections of ICCs to muscles and nerves due to deformed ICCs; a 197% increase in vascularization (capillaries, venules) and lymphatics in both muscle layers and in the myenteric plexus cleft, possibly initiated by release of fibroblast growth factor from myelin fragmentation after nerve damage; and increased macrophages, plasma cells, monocytes and mast cells in the myenteric plexus cleft. These all signify the neural influence on the morphodifferentiation of the muscularis externa in concert with the extracellular matrix components.     

Localization of cholecystokinin-like peptide in neuroendocrine cells of mammalian lungs: a light and electron microscopic immunohistochemical study

Mixing of starved cells of complementary mating types of Tetrahymena thermophila induces shortening of their longitudinal length within 10 min of mixing. This early morphogenetic transformation in preconjugant sexual interaction (costimulation period) was named "costimulation-induced rounding" (CIR). CIR is the earliest morphological change that has ever been found in the costimulation period and differs from "synchronous rounding" in the vegetative cell cycle, because CIR cells are still able to form food vacuoles, while cells in synchronous rounding do not have this ability. When sexual cell-to-cell collisions between two mating types were hampered by unidirectional stirring for 20 min after mixing of the two mating types, both CIR and conjugation were delayed by 20 min. When secreted materials needed for the onset of costimulation were removed by washing the cells with 10 mM Tris-HCl, pH 7.4, before mixing the two mating types, both CIR and conjugation were delayed by about 30 min. CIR-like rounding was not induced by cell-free medium either from the opposite mating type or from mixed costimulated cells. These results indicated that CIR is induced when cells are activated to form conjugating pairs by cell-to-cell collisions between complementary mating types in the presence of secreted molecules.     

Involvement of nitric oxide in acute spinal cord injury: an immunocytochemical study using light and electron microscopy in the rat

The crystal structure of an acidic neurotoxin, BmK M8, from Chinese scorpion Buthus martensii Karsch was determined at 0.25 nm resolution. The X-ray diffraction data of BmK M8 crystals at 0.25 nm resolution were collected on a Siemens area detector. Using molecular replacement method with a basic scorpion toxin AaH II in a search model, the cross-rotation function, PC-refinement and translation function were calculated by X-PLOR program package. The correct orientation and position of BmK M8 molecule in crystal were determined in a resolution range of 1.5-0.35 nm. The crystallographic refinement was further performed by stereo-chemical restrict least-square technique, followed by simulated annealing, slow-cooling protocols. The final crystallographic R-factor at 0.8-0.25 nm is 0.171. The standard deviations of bond length and bond angle from ideality are 0.0017 nm and 2.24 degrees, respectively. The final model of BmK M8 structure is composed of a dense core of secondary structure elements by a stretch of alpha-helix with two and a half turns (residues 19-28) and a three-stranded antiparallel beta-sheet (residues 2-4, 32-37, 45-51). In addition, three loops protruded from the structural core. The general folding properties of BmK M8 molecule were described; a common structure motif which may appear in all scorpion neurotoxins was identified. The conserved aromatic residues and charged residues were found to be distributed on two roughly opposite surfaces of the molecule. The relationship between these two faces and receptor-binding sites are also discussed.