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.     

Transmission electron microscopy study on the cross-sectional microstructure of an lon-nitriding layer

The cross-sectional microstructure of an ion-nitrided layer on an A₃ steel (C = 0.15, Si = 0.2, Mn = 0.5, and balance Fe, in wt pct) was studied by transmission electron microscopy (TEM), and its electron diffraction patterns were analyzed. It has been shown that the compound layer consists of columnar ε-Fe_2-3 N and γ-Fe₄N. The former precipitates thin γ-Fe₄N phases related to each other by a 180 deg turning twin, and the orientation relationship between ε-Fe_2-3N and γ-Fe₄N is $$\{ 111\} _{\gamma '} //(0001)_\varepsilon ,\left\langle {1\bar 10} \right\rangle _{\gamma '} //\left\langle {11\bar 20} \right\rangle _\varepsilon $$ The columnar γ′-Fe₄N has a stacking fault substructure and accompanying lattice distortion. There are islandlike ferrite crystals between the columnar crystals. Near the compound layer is mostly γ′-Fe₄N with a coexisting small amount of α-Fe. The diffuse layer is composed of Guinier-Preston (GP) zones, α″-Fe₁₆N₂, γ-Fe₄N, and α-Fe. The γ′-Fe₄N with long period structure considered as the ordering of the stacking fault was found. The characters and transformation mechanism of the case were discussed.     

Sintering study of silver particles by in situ electron microscopy

Micron size silver spherical particles were sintered in the hot stage of an electron microscope between 370 and 720°C. In the 370 to 520°C temperature range, sintering can be explained either by grain-boundary diffusion or dislocation slip. At higher temperatures, the controlling mechanism changes from surface or grain-boundary diffusion to volume diffusion from 570 to 720°C. These conclusions are based on observations of neck growth and shrinkage and on analyses of the shapes of the sintering curves.     

Cardiac rhabdomyosarcoma: a clinicopathologic and electron microscopy study

The use of imaging techniques including gamma scintigraphy to follow the behaviour of drug formulations has revolutionized our knowledge of absorption and distribution in drug delivery. The development of gamma camera techniques as physiological tools to explore organ function became routine by the mid-seventies. Several research groups started to explore the applications of technique in drug delivery. Within 5 years, the utility of the technique became obvious and scintigraphy is now widely accepted as an important investigation tool in formulation research. Gamma scintigraphy is especially useful in exploring sources of inter-subject variation, especially in examining food effects in pharmacokinetic estimations and establishing windows of absorption for oral delivery. As a tool to examine drug delivery to the lung and to the eye, scintigraphy is the method of choice. Magnetic Resonance Imaging (MRI) became more generally employed in medicine two decades after the gamma camera. The superior soft-tissue contrast and resolution compared to computed X-ray tomography rapidly established MRI in clinical investigation. Recent applications in oral drug research has allowed the pharmaceutical scientist to explore new facets of delivery and ultimately combine MRI and scintigraphy in human clinical trials.     

Blood flow patterns in the rat pancreas: a simulative demonstration by injection replication and scanning electron microscopy

Scanning electron microscopy of vascular casts prepared by arterial injections of intentionally reduced amounts of resin showed that in the rat pancreas, the casting medium fills blood capillaries in the endocrine islets more promptly than those in the exocrine lobules and secretory ducts. Furthermore, the exocrine lobules containing endocrine islets allowed a more rapid resin flow through the insulo-acinar portal route than those lobules lacking an islet. The capillaries of secretory ducts were the last portions to be filled with resin. Since the resin used in this study was as viscous as blood and injected under a physiological pressure, the microcirculatory patterns demonstrated by the present method reflect the physiological flow pattern of blood in the pancreas.     

Diagnosis and epidural hematoma by brain scan and perfusion study: case report

By using the arterial and venous phases of an anterior cerebral perfusion study, which showed downward displacement of the sagittal sinus, and the finding of a "rim" on the delayed scans, the specific diagnosis of epidural hematoma was established.     

Cholesterol ester in corpus luteum of rat observed by analytical color fluorescence electron microscopy

We used an analytical color fluorescence electron microscope to observe cathodoluminescence (CL) in the corpus luteum of rat. CL was emitted from lipid droplets and has a typical spectrum of two peaks at wavelengths of 320 and 430 nm. The intensity of CL at 320 nm (CL320) in the corpus luteum showed a regular change during an estrous cycle: it was very weak at the newly formed stage, gradually increased, reached the maximum at diestrus 2, and then began to diminish at proestrus except in the patches of degenerated cells. CL320 decreased during early stages of pregnancy or after prolonged treatment with 4-aminopyrazolo-pyrimidine; CL at 430 nm (CL430) remained clearly visible. CL320 showed a strong emission from degenerated luteal cells 10 days after hypophysectomy, but was diminished in cells rescued by injection of 50 IU pregnant mare's serum gonadotropin. In the luteal cells of luteinized ovary 2 hr after intravenous injection of 10 IU luteinizing hormone, CL was barely detected. CL320 in interstitial cells was also weak in the rats hypophysectomized and then treated with pregnant mare's serum gonadotropin, and in the 4-aminopyrazolo-pyrimidine-treated rats, although it has little change through a natural estrous cycle. The results are consistent with the assumption that the content of cholesterol ester is reflected by the intensity of CL320 emitted from the lipid droplets of rat luteal cells. The possibility was shown that the condition of steroidogenesis can be monitored through CL analysis by microscopy.     

Sequential bilateral isolated lung perfusion in the rat: an experimental model

BACKGROUND: A model of isolated single-lung perfusion in the rat has been established in our laboratory to study the chemotherapeutic treatment of pulmonary metastases. A sequential bilateral isolated lung perfusion model was designed to investigate the feasibility of staged perfusions in the rat. METHODS: Twenty-four Fischer rats were randomized into three experimental groups of 8 rats each. All rats underwent left isolated lung perfusion. One, 2, or 3 weeks later, the rats in groups I, II, and III, respectively, underwent contralateral (right) perfusion. Five control animals (group IV) underwent sequential bilateral sham thoracotomies 1 week apart. Arterial blood gas analysis was performed 1 week after the second operation in the rats in groups I and IV. RESULTS: All animals survived the first operation, with 100% (8/8), 75% (6/8), and 100% (8/8) of the animals in perfusion groups I, II, and III, respectively, surviving the second operation. All control animals (group IV) survived the second sham thoracotomy. Arterial blood gas analysis did not show a significant difference in the oxygen or carbon dioxide partial pressure or the pH between group I and IV (p = 0.32, 0.96, and 0.76, respectively). CONCLUSIONS: Our experiments demonstrate that sequential bilateral isolated lung perfusion is safe in and well tolerated by the rat. This model can be used to investigate the safety and efficacy of staged perfusions with chemotherapeutic agents in the treatment of bilateral pulmonary metastases in the rat.     

Ferritin in Crohn's disease tissue: detection by electron microscopy

Using immune electron microscopy, an attempt has been made to visualise viral particles in Crohn's disease tissue and faeces. No particles resembling viruses were observed, but in the absence of a specific antiserum a negative result does not exclude the presence of a virus, particularly if it is sparsely distributed. Compared with controls, an abundance of a 12 nm particle was found in all Crohn's disease tissue and one small intestinal lymphoma. This particle has been identified as ferritin and is unlikely to be of aetiological significance.     

Synaptology of prefrontal cortical projections to the basolateral amygdala: an electron microscopic study in the rat

Elevated extracellular concentrations of the potassium ion ([K+]o) stimulate glycogenolysis in primary cultures of mouse astrocytes that have been grown in the presence of dibutyryl cyclic AMP but not in corresponding cultures which have not been treated in this manner. The response is potently inhibited by nifedipine, suggesting that it is evoked by entry of calcium ions through voltage dependent L-channels. The benzodiazepine midazolam, which is known to enhance calcium entry at concentrations of [K+]o causing submaximum calcium entry, increases the glycogenolytic effect by such levels of [K+]o.     

Glial activation and white matter changes in the rat brain induced by chronic cerebral hypoperfusion: an immunohistochemical study

Activation of glial cells and white matter changes (rarefaction of the white matter) induced in the rat brain by permanent bilateral occlusion of the common carotid arteries were immunohistochemically investigated up to 90 days. One day after ligation of the arteries, expression of the major histocompatibility complex (MHC) class I antigen in microglia increased in the white matter including the optic nerve, optic tract, corpus callosum, internal capsule, anterior commissure and traversing fiber bundles of the caudoputamen. After 3 days of occlusion, MHC class I antigen was still elevated and in addition MHC class II antigen and leukocyte common antigen were up-regulated in the microglia in these same regions. Astroglia, labeled with glial fibrillary acidic protein, increased in number in these regions after 7 days of occlusion. A few lymphocytes, labeled with CD4 or CD8 antibodies, were scattered in the neural parenchyma 1 h after occlusion. Activation of glial cells and infiltration of lymphocytes persisted after 90 days of occlusion in the white matter and the retinofugal pathway. However, cellular activation and infiltration in microinfarcts of the gray matter was less extensive and was substantially diminished 30 days after occlusion. The white matter changes were most intense in the optic nerve and optic tract, moderate in the medial part of the corpus callosum, internal capsule and anterior commissure, and slight in the fiber bundles of the caudoputamen. These results indicated that chronic cerebral hypoperfusion induced glial activation preferentially in the white matter. This activation seemed to be an early indicator of the subsequent changes in the white matter.     

Quantitation of microvascular plasma perfusion and neuronal microtubule-associated protein in ischemic mouse brain by laser-scanning confocal microscopy

In an exposition of the technique of calculating distribution volumes from laser-scanning confocal microscopic (LSCM) data, three-dimensional images of the distribution of one or two fluorescent markers in mouse brain specimens were generated by LSCM and processed by a system developed for morphometric analysis of fixed and stained serial brain histologic samples. To determine the volume of perfused cerebral capillaries, one of two fluorescent plasma markers, either fluorescein isothiocyanate (FITC)-dextran or Evans blue, was intravenously administered to mice subjected to 1 hour of embolic middle cerebral artery (MCA) occlusion (n = 9) and to mice that were not operated on (n = 3); after 1 minute of circulation, brains were removed, immersion-fixed, and processed for LSCM. In some of these animals (n = 5), the volume of endogenous microtubule-associated protein-2 (MAP2) fluorescence was also determined using immunohistochemical staining. For mice that were not operated on, this methodology yielded highly localized volumes of (1) microvascular plasma, which agree with those determined for rodents by other techniques, and (2) MAP2 expression, which appears physiologically and morphologically reasonable. After 1 hour of MCA occlusion, the MAP2 volumes of distribution were less than 10% of normal in the ipsilateral hemisphere in which plasma perfusion essentially ceased. In conclusion, precise colocalization and quantitation of early ischemic neuronal damage and cerebral plasma perfusion deficit can be done with this three-dimensional, microphysiologic and microanatomic methodology.     

Reflux esophagitis in children: a scanning and transmission electron microscopy study

In children, excess of gastroesophageal reflux causes lesions of the esophageal mucosa that we have studied by scanning and transmission electron microscopy (SEM and TEM respectively) in 27 grasp biopsies prelevated during endoscopic procedures. Ultrastructural lesions can be graded on the basis of their severity. In grade I, epithelial cells are well preserved in the deepest layers whereas the superficial cells display ultrastructural alterations such as irregular microridges or reduced intercellular junctions. In grade II, the surface is composed of extruding cells and in the intermediate layer, large intercellular spaces containing lympho-monocytic cells are visible. In grade III, the mucosal surface is characterized by crater-like erosions, degenerating cells are visible in all the layers; in two patients columnar epithelium-lined areas (Barrett's esophagus) have been identified. Our results suggest that in patients with reflux esophagitis, ultrastructural examination of grasp biopsies prelevated by pediatric endoscopes allows a grading of the anatomical lesions providing data that can not be obtained by conventional histology.     

An electron microscopy study of carbide precipitation in vanadium

The precipitation of carbon from supersaturated solid solution in vanadium has been investigated using transmission electron microscopy techniques on thin foils. High purity vanadium strip was doped to a carbon content of about 0.2 at. pct and rapidly quenched in high vacuum, followed by aging treatments for various times in the temperature range from 300° to 600°C. The strip was then thinned for transmission electron microscopy. The carbon is observed to precipitate initially as very finely dispersed carbides visible through structure factor contrast. With increasing aging the precipitate distribution coarsens, and the carbides appear as very thin coherent platelets on {310} planes, showing a pronounced displacement fringe contrast. The coherent precipitate appears to have a bcc structure closely related to that of the matrix. With further aging these platelets are observed to thicken and partially lose coherency, punching out prismatic dislocation loops and helices having axes in 〈111〉 directions. This semicoherent precipitate is found to be the hexagonal V₂C phase described by other researchers, and its orientation relationship with the matrix may be expressed: (110)v‖(00.1)v₂c, [•111]v‖[•110] v₂C. The dislocation loops are a result of the specific volume difference between the V₂C precipitation and the matrix, and have Burgers vector b = a/2〈111〉. Formerly Research Assistant, Department of Metallurgy and Mining Engineering, University of Illinois at Urbana-Champaign, Urbana Ill.     

Congenital neutropenia: an intrinsic cell defect demonstrated by electron microscopy of soft agar colonies

In an attempt to define the molecular events involved in induction of interferon, various parameters of chick cells infected with human adenovirus type 5 were analysed. It was shown by digestion with various proteolytic enzymes and by disruption of the purified virus that induction of interferon requires the interaction of infectious virus with the chick cells. Analysis of adenovirus-infected chick cells by immunological and biochemical techniques indicated that most of the cells produce some virus-specific components, and that temperature sensitive mutants which fail to induce interferon at the restrictive temperature fail to synthesize late components at that temperature. However, since it has been shown that interferon can be induced in the absence of DNA synthesis, these studies conclude that interferon induction results from an early interaction between virus (or virus product) and chick cells and moreover that this interaction is also necessary for the synthesis of virus DNA in this system.     

Neuronal death induced by SIN-1 in the presence of superoxide dismutase: protection by cyclic GMP

OBJECTIVES: To test whether femoral ostectomy level, subtrochanteric bone mass removal, and stemsize selection significantly affect stem positioning in canine total hip replacement, and to determine ability of the femoral stem component to restore geometry of the normal femoral head and neck. SAMPLE POPULATION: Femurs from 8 adult mixed-breed canine cadavers. PROCEDURE: Femurs were systematically prepared, using 8 combinations of 3 surgical preparation techniques that included level of ostectomy (cervical isthmus vs lesser trochanter), subtrochanteric bone block removal, and femoral stem size (recommended, undersized). Computer-aided analysis of specimen photographs was used to evaluate femoral head offset and position and variability of femoral stem positioning for each of the preparation combinations. RESULTS: Original femoral head offset and position were reconstructed to within a mean of 0.052 and 0.031 cm, respectively, using an undersized femoral stem after ostectomy at the level of the lesser trochanter. Implantation of an undersized femoral stem after subtrochanteric bone block removal improved ability to centralize the distal tip of the implant and reduce the angle between the femoral diaphyseal and implant axes. Ostectomy at the level of the cervical isthmus tended to force femoral implants into a varus position, and ostectomy at the level of the lesser trochanter tended to force implants into a valgus position. CONCLUSIONS: Geometry of normal canine femurs was most closely reconstructed by implantation of an undersized femoral component after ostectomy at the level of the lesser trochanter. Implantation of an undersized femoral component after subtrochanteric bone block removal resulted in the best alignment and centralization of the stem.     

A study of the interface between bone and acrylic cement by scanning electron microscopy

The influence of different pretreatments upon locomotor stimulation, induced by injection of ergometrine into the nucleus accumbens of rats, was investigated. The noradrenergic antagonists phenoxybenzamine and propranolol and the serotonin antagonist methysergide produced no clear changes. Reserpine, alone or in combination with alpha-MPT, considerably shortened the delay between injection of ergometrine and start of locomotor stimulation. Ro-DOPA, but not Ro-5-HTP, clearly antagonized the locomotor stimulation. The effect of ergometrine was strongly diminished following injection of haloperidol directly into the nucleus accumbens. A strong inhibition was also observedfollowing intracerebral administration of the imidazoline derivative (3,4-dihydroxy-phenylamino)-2-imidazoline (DPI), but not after injection of the structurally related compound clonidine. DPI by itself and also the ergot derivatives ergocornine, bromocryptine, LSD, dihydroergotamine and methysergide in doses 5--10 times as high as that of ergometrine failed to produce locomotor stimulation following injection into the nucleus accumbens. The results are discussed, especially with regard to the role of dopamine.