The positive staining pattern of skin collagen in chronic haemodialysis patients

The positive staining pattern of skin collagen fibrils from chronic haemodialysis patients was studied by measn of electron microscopy. Such staining patterns were compared with those from normal control subjects. These visual comparisons reveal that in chronic haemodialysis, fibrils retain normal banding periodicity. Disturbances of collagen molecular or fibril architecture brought about by chronic haemodialysis are also discussed.     

An autoradiographic and electron microscopic study of collagen synthesis in differentiating cartilage

Summary The synthesis of the proline-rich collagen component of cartilage matrix has been studied by autoradiography using both the light and electron microscope. Amblystoma maculatum larvae had their forelimbs amputated, were allowed to regenerate for 12–15 days, and then injected intraperitoneally with tritiated proline. The animals were fixed at various times (1 min. to 28 days) after the injection and sections of the developing limbs were coated for autoradiography by dipping in Ilford L 4 or Gevaert 3.07 emulsion. The sequential labeling of the organelles of the cartilage cell which occurred is illustrated in light and electron micrographs. Radioactive products first appeared in the ergastoplasm and were associated with the cisternae of the endoplasmic reticulum. Twenty to thirty minutes after the injection, labeled material began to appear in the Golgi zone. There, the newly synthesized protein accumulated within large vacuoles. The fibrillar material within the vacuoles may represent collagen and the more amorphous material, mucoprotein. The vacuoles subsequently (2 hrs. later) discharge their labeled contents into the extracellular space. The secreted protein is probably soluble collagen (tropocollagen) for it diffuses readily through the matrix to polymerize into striated collagen fibrils some distance from the cell. These findings contradict some widely held opinions that the fibrillar component of the matrix arises by excortication and appositional growth of fibrils originating from the ectoplasm of chondrocytes. It seems reasonable to conclude that the secretory pathway by which extracellular proteins are produced in cartilage is analogous to that suggested for epithelial gland cells.Supported by grants CA 05196-04S1 and GM-K3-13, 979-C1-A from the United States Public Health Service.The results reported in this paper were presented at the second annual meeting of the American Society for Cell Biology, November 6, 1962.     

Scanning electron microscopic visualization of collagen fibers in embryonic chick skin.

The disposition of collagen fibers in embryonic chick skin can be visualized by use of scanning microscopy (SEM). Chick back skin was removed from 8-day embryos, the epithelial and mesenchymal components were separated, and the mesenchyme was subjected to 10% trypsin treatment (Stuart, E. S., and Moscona, A. A. (1967) Science 157, 947–948), after which it was prepared for SEM by critical point drying and coating. Such preparations were largely free of cellular material. Cavities which presumably had contained the cells were present in a network of fibers. Skin of the scaleless mutant was also studied. In this mutant the collagen network was more irregular and collagen fiber diameter was more variable. These findings are discussed in connection with the formation of feather germ pattern.     

Variations in collagen fibril structure in tendons

Variation of collagen fibril structure in tendon was investigated by x-ray diffraction. Anatomically distinct tendons from single species, as well as tendons from different species, were examined to determine the variations that exist in both the axial and lateral structure of the collagen fibrils. The meridional diffraction is derived from the axial collagen fibril structure. Anatomically distinct tendons of a particular species give meridional patterns that are indistinguishable within experimental error. The meridional diffraction patterns from tendons of different mammals are similar but show small species-specific variations, most noticeably in the 14th–18th orders. Tendons of birds also give meridional patterns that are similar to each other, but the avian patterns differ considerably from the mammalian ones. Avian tendons give stronger odd and weaker even low orders, a feature consistent with a reduced gap:overlap ratio, and have a distinctive intensity pattern for the higher meridional orders. Interpretation of these differences has been approached using biochemical data, diffraction by reconsituted fibers of purified collagen, and Fourier transform analysis. From these methods, it appears that the variations observed in the lower orders (2nd–8th) and in the higher orders (29th–52nd) are probably related to differences in the primary structure of the Type I collagen found in the different species. The variations observed in the 14th–18th orders appear not to be related to features within the triple-helical domain of the molecule. Equatorial diffraction yields information on the lateral packing of collagen molecules in the fibrils, and considerable variation was seen in different tendons. Rat tail tendon gives sharp Bragg reflections, demonstrating the presence of a crystalline lateral arrangement of molecules in the fibril. For the first time, sharp lattice reflections similar to those in rat tail tendon have been observed in nontail tendons, including rat achilles tendon, rabbit leg tendon, and wing and leg tendons of quail. In the rabbit and quail tendons, one of the strong equatorial reflections characteristic of the rat tendon pattern, at 1.26 nm, was absent. The positions of the equatorial maxima, which are a measure of intermolecular spacing, varied considerably, being smallest in the specimens displaying crystalline packing. The intermolecular distance in chiken and turkey leg tendons is longer than that found in mammalian tendons, or in avian wing tendons, which supports the hypothesis that a larger intermolecular spacing is characteristic of tendons that calcify. Thus, x-ray diffraction indicates there are reproducible differences in both the axial and lateral structure of collagen fibrils among different tendons. This work on tendon, a tissue containing almost exclusively Type I collagen as its major component, should serve as a basis for analyzing the structure of other connective tissues, which contain different genetic types of collagen and larger amounts of noncollagenous components.     

Cytophotometric and electron microscopic study of chronic human skin lymphomas. I. A study of skin manifestations

Electron microscopic and cytophotometric studies of low-grade malignant cutaneous lymphomas and non-malignant skin diseases revealed substantial differences between these groups of diseases. In the latter case, the DNA content per nucleus is diploid but in the former an atypical distribution of DNA content per nucleus (more than 5% aneuploid and polyploid nuclei) is observed in addition to a significant excess of the mean DNA content per nucleus above the diploid standard level. In lymphomas electron microscopy reveals clusters of atypical lymphoid cells with irregularly shaped nuclei, nuclear pockets, nuclear extrusions, network of cytoplasmic microfilaments. These features never occur with skin diseases. The data obtained can be helpful in the diagnostics of the low-grade malignant cutaneous lymphomas.     

An electron microscopic study of the structure of Erwinia carotovora 268 bacteria

The electron-microscopic studies have shown that the bacterium Erwinia carotovora 268 (a producer of L-asparaginase) does not differ essentially from other representatives of enterobacteria. When growing on the artificial nutrient medium M9, the division of bacteria is inhibited and the bacterial cell itself elongates. Certain functionally specified structural peculiarities such as the formation of the protein microcapsule, formation of cavities and compacted sites of the cytoplasm and mucus on the cell poles are typical of bacteria, that is associated with the synthesis of L-asparaginase and erwiniocinogeny.     

Morphometric evaluation of collagen fibril dimensions in expanded human breast skin

A great innovation in plastic surgery in recent years has been skin expansion, which has provided the discipline with new possibilities for skin reconstruction. At present, little is known about the biology of skin expansion although it is clear that cell proliferation occurs both in the epidermis and the dermis. During previous morphological investigations of skin under expansion we recorded a number of signs comparable with those seen in wound healing. In the present study, the collagen fibril diameter of of skin before and under expansion has been recorded using an IBAS computer-based morphometric system. Preferentially, we have studied the papillary dermis where the most conspicuous morphological events occur.     

The structure of fibrin. An electron microscopic investigation

An electron microscopic investigation on the structure of fibrin is reported. Fibrin morphology was investigated in a wide variety of experimental conditions, and by carefully controlled staining procedures. Two main band patterns A (230-Å-spaced main dark bands) and B (230-Å-spaced main light bands) are observed for stained fibrin; it is shown that the former results from the superimposition of both positive and negative staining, and the latter is given by positive staining. By suitable denaturation experiments, it was found that the fiber is composed of a regular alternation of lose and dense regions along the axis. We have assumed that the monomer of fibrin is described by the three-nodular model of Hall and Slayter, as supported by recent investigations. The monomers are arrayed according to a head-to-tail sequence along the fiber, and to a staggered lateral association. This model accounts for all the experimental observations, and predicts well the high-resolution band pattern of fibrin. It further agrees with the results of a recent work on the early stages of the fibrinogen-to-fibrin conversion.     

An electron microscopic study of surface polysaccharides in Bacteroides

The electron microscopic appearance of the cell surface of Bacteroides strains and Klebsiella pneumoniae stained with ruthenium red or colloidal iron is described. The effect of polymyxin B (PMB) was also registered. It was found that all Bacteroides strains have a polysaccharide lined 'micro-capsule' external to the outer membrane which could aggregate and form blebs. The blebs so formed were distinct from other types of bleb formed in Klebsiella involving the outer membrane and induced by PMB. Such types of PMB alterations were not induced in Bacteroides.