The myofibrillar M-band in the cryo-section—analysis of section thickness

Information regarding the formation and the thickness of cryo-sections is of importance for an adequate interpretation of cryo-sectioned biological material. In this study we have taken advantage of the regular arrangement of filaments in myofibrils in an analysis of these matters. It is concluded that the sections are formed partly by fracturing in a way similar to that visualized in replicas made by the freeze-fracturing and -etching procedure.     

Surfaces with high solar reflectance and high thermal emittance on structured silicon for spacecraft thermal control

Presented here is an examination of unstructured and structured (by anisotropic etching), monocrystalline silicon wafers coated with sputter deposited aluminum and chemical vapor deposited silicon dioxide for high solar reflectance and high thermal emittance, respectively. The topography of the samples was characterized with optical and scanning electron microscopy. Optical properties were examined with reflectance and transmittance spectroscopy, partly by usage of an integrating sphere. The measurement results were used to estimate the equilibrium temperature of the surfaces in space. The suitability of the surfaces with high solar reflectance and high thermal emittance to aid in the thermal control of miniaturized, highly integrated components for space applications is discussed. A silicon dioxide layer on a metal layer results in a slightly lower reflectance when compared to surfaces with only a metal layer, but might be beneficial for miniaturized space components and modules that have to dissipate internally generated heat into open space. Additionally, it is an advantage to microstructure the emitting surface for enhanced radiation of excess heat.     

Preparing sections of skeletal muscle for transmission electron analytical microscopy (TEAM) of diffusible elements.

Comparative morphological examination and elemental analysis were carried out in structural compartments of sections of skeletal muscles. These had been prepared either by conventional plastic embedding technique or by various methods of cryo-ultramicrotomy. The analyses were performed in a Philips EM 301 with an Edax energy-dispersive X-ray spectrometer. Spectra obtained from sections of plastic-embedded muscle depended on the reagents used for fixation and staining and were absent if these were omitted. Brief fixation with glutaraldehyde resulted in gross ionic changes, and sectioning of frozen material with trough liquid led to extraction of elements. Sections cut from unfixed and frozen muscle without trough liquid showed numerous peaks. (Mg, P, S, Cl, K, Ca). In the superficial parts of the fibres of freeze-dried sections reproducible spectral differences were found between different structures. Thus, rapid freezing of unfixed tissue, dry cutting in the frozen state, and freeze-drying should be the procedure of choice if data on diffusible ions are desired.     

Morphological observations on motor end-plates in rabbits with experimental myasthenia

The morphology of motor end-plates in rabbits immunized with Torpedo nicotinic acetylcholine receptor (nAChR) has been studied by light and electron microscopy. Rabbits were studied either after one period of paralysis, some in parallel with electrophysiological recordings of MEPPs and EPPs and of Naja naja alpha-neurotoxin binding properties or after recovery followed by a second paralysis. Changes in the sub-neural apparatus were noted after cholinesterase staining only in the latter group. Ultrastructurally, however, most end-plates in both groups contained a wide range of abnormalities. Many were similar in appearance to those observed in human myasthenia gravis (MG). This further supports the theory that immunized rabbits can be used as a model for myasthenia gravis. In the rabbits with 1 period of paralysis an acute stage of influence on the neuromuscular junction seemed to be present while simplified motor end-plates typical for human MG were mostly found in rabbits with 2 periods of paralysis. Short post-synaptic folds in conjugation with thickeneed membrane-bound vesicles at their tops, inside the basement membrane, were frequently observed. These were interpreted as if the crests of the folds containing nAChR had degenerated and had been budded off. If so, a large number of receptor sites had been lost which would be one possible explanation for the lowered capacity of the muscles to bind Naja naja alpha-neurotoxin. Membrane thickenings with projections and striations were interpreted as reflecting ACh receptors and were observed in the post-junctional membrane without proximity to the nerve terminal. The degeneration of the top of the post-synaptic folds and the occurrence of receptors at other locations within the motor end-plate will result in a widened distance between the nerve terminal and the receptors, which can explain previous interpretations of a presynaptic defect in MG.     

Freeze-fracture and immunomorphological analysis of spiral ganglion cells

Freeze-fracture analysis of adult spiral ganglion cells of CBA/CBA mice revealed two types of membrane specializations. Most cells (type I) had a smooth surface and were surrounded by Schwann cells. Type II spiral ganglion cells showed numerous membrane specializations with well-delineated indentations similar to those previously found on hair cells adjacent to afferent and efferent nerve endings. Immunomorphological analysis (using well-defined monoclonal antibodies directed against different subclasses of intermediate filament proteins) revealed a unique co-expression of neurofilaments, vimentin and cytokeratins in spiral ganglion cells of 8-to 22-week human fetuses.     

Anisotropy-independent through micromachining of quartz resonatorsby ion track etching

A method to achieve deep and crystal cut-independent structuring of arbitrary lateral geometry in single crystalline quartz is demonstrated. It is based on local etching of the latent track-induced anisotropy resulting from heavy ion bombardment, and is close to independent of crystallographic orientation. Previous results are briefly reviewed and a more systematic and thorough study is presented. Miniature tuning fork structures of various sizes and directions have been realized, and the suitability for frequency control device production is discussed     

Presence of laminin alpha5 chain and lack of laminin alpha1 chain during human muscle development and in muscular dystrophies

There is currently a great interest in identifying laminin isoforms expressed in developing and regenerating skeletal muscle. Laminin alpha1 has been reported to localize to human fetal muscle and to be induced in muscular dystrophies based on immunohistochemistry with the monoclonal antibody 4C7, suggested to recognize the human laminin alpha1 chain. Nevertheless, there seems to be no expression of laminin alpha1 protein or mRNA in developing or dystrophic mouse skeletal muscle fibers. To address the discrepancy between the results obtained in developing and dystrophic human and mouse muscle we expressed the E3 domain of human laminin alpha1 chain as a recombinant protein and made antibodies specific for human laminin alpha1 chain (anti-hLN-alpha1G4/G5). We also made antibodies to the human laminin alpha5 chain purified from placenta. In the present report we show that hLN-alpha1G4/G5 antibodies react with a 400-kDa laminin alpha1 chain and that 4C7 reacts with a 380-kDa laminin alpha5 chain. Immunohistochemistry with the hLN-alpha1G4/G5 antibody and 4C7 revealed that the two antibodies stained human kidney, developing and dystrophic muscle in distinct patterns. Our data indicate that the previously reported expression patterns in developing, adult, and dystrophic human muscle tissues with 4C7 should be re-interpreted as an expression of laminin alpha5 chain. Our data are also consistent with earlier work in mouse, indicating that laminin alpha1 is largely an epithelial laminin chain not present in developing or dystrophic muscle fibers.     

Characterization of Glycosphingolipids in the Human Parathyroid and Thyroid Glands

As part of a systematic investigation of the glycosphingolipids in human tissues, acid and non-acid glycosphingolipids from human thyroid and parathyroid glands were isolated and characterized with mass spectrometry and binding of carbohydrate-recognizing ligands, with a focus on complex compounds. The glycosphingolipid patterns of the human parathyroid and thyroid glands were very similar. The major acid glycosphingolipids were sulfatide and the gangliosides GM3, GD3, GD1a, GD1b, GT1b and Neu5Ac-neolactotetraosylceramide, and the major non-acid glycosphingolipids were globotriaosylceramide and globoside. We also found neolactotetra- and neolactohexaosylceramide, the x₂ glycosphingolipid, and complex glycosphingolipids with terminal blood group O and A determinants in both tissues. A glycosphingolipid with blood group Le^b determinant was identified in the thyroid gland, and the parathyroid sample had a glycosphingolipid with terminal blood group B determinant. Immunohistochemistry demonstrated the expression of blood group A antigens in both the thyroid and parathyroid glands. A weak cytoplasmatic expression of the GD1a ganglioside was present in the thyroid, while the parathyroid gland had a strong GD1a expression on the cell surface. Thus, the glycosylation of human thyroid and parathyroid glands is more complex than previously appreciated. Our findings provide a platform for further studies of alterations of cell surface glycosphingolipids in thyroid and parathyroid cancers.