Scanning electron microscopy最新文献

Implantation of bits of marrow in ectopic sites is followed by reorganization of tissue and the formation of a hemopoietic nodule surrounded by a shell of bone. This regenerative process is reminiscent of marrow ontogeny and the model can serve to study marrow ontogeny in a relatively short period of time. Early events during this regeneration were studied by scanning (SEM) and transmission electron microscopy (TEM). Within 24 hours the implant elicited an angiogenic reaction and new vessels penetrated the implant. Intense circulation, thus established, divested the implant from hemopoietic cells, leaving the stroma behind. Stromal cells proliferated and the impetus for this proliferation appeared to result from an impulse caused by the presence of bony fragments outside and within the stromal cells. Previous studies of this model have not appreciated the presence of non-viable bone in the implant, although the fact that non-viable bone can trigger osteogenesis and new bone marrow formation is well-known. This experimental model lends itself to the study of the interrelationship of hemopoietic cells and their supporting stroma as well as the interrelationship of bone and hemopoiesis.

This paper is intended as an introduction to the field of proton microprobe analysis with special emphasis on applications in biological sciences. It is mainly intended for users of electron microscopes equipped with microprobes or other analytical equipment. The basic principles of Particle Induced X-ray Emission analysis are discussed as well as the instrumental requirements for the proton microprobe. The analytical characteristics including quantification procedures are compared with those of the electron microprobe and a review is given of various analytical applications of the proton microprobe within biology and medicine.

To investigate the microstructure of in situ (eutopic) and autotransplanted (ectopic) splenic remnants, adult Sprague-Dawley rats were studied 60 days after subtotal (approximately 80%) splenectomy, total splenectomy followed by single or multiple remnant intraperitoneal autotransplantation, or sham operation. Total nucleated cell counts were determined in excised splenic remnants, and immunohistochemical staining using monoclonal antibodies to rat B- and T-cell antigens was performed in serial tissue sections. Immunoarchitecture of eutopic remnants was indistinguishable from that of intact spleens and total nucleated cell counts remained proportional to weight. In contrast, ectopic remnants showed sparsity and abnormal mixing of B and T lymphocyte subpopulations with widespread loss of follicles and periarteriolar lymphoid sheaths in addition to lower density and marked reduction of total nucleated cells. These findings provide immunohistologic evidence that preservation of intact vasculature is critical to splenic architecture, which may account in part for the demonstrable functional inferiority of ectopic remnants.

Cystic fibrosis (CF) is a generally lethal, congenital, genetic disease of unknown etiology. It is likely that a defective regulation of ion and water transport in exocrine glands and possibly also in other epithelial cells has a central role in the pathogenesis of this disease. Calcium has been implicated in the basic defect underlying CF because of findings of abnormally high calcium levels in some secreted fluids and some cells of CF patients. Using X-ray microanalysis, we have demonstrated elevated calcium concentrations in cultured fibroblasts and in goblet cells of the bronchial epithelium of CF patients. A factor produced by CF fibroblasts in culture can increase the calcium concentration in healthy cells, although this may be an indirect effect. In animal models for CF, such as the chronically reserpinized rat and the chronically isoproterenol-treated rat, abnormally high calcium levels in the acinar cells of the submandibular gland could be demonstrated, similar to the situation in CF patients. In the acinar cells of the parotid gland in these animal models, the calcium levels are, however, abnormally low. This suggests that the changes in cell calcium content are secondary to other changes, possibly changes in the secretory proteins. A study of the effect of the serum calcium level and of the calciotropic hormone calcitonin suggested that neither of these factors could be directly linked with CF. It is concluded that several lines of evidence point to a secondary rather than a primary role for calcium in the pathogenesis of CF.

We studied two aspects of the human gastric mucosa: the surface morphology of mucous cells, as viewed by scanning electron microscopy (SEM); the glycosidic components of intracellular mucins, characterized by means of lectins. The latter were conjugated with fluorescein isothiocyanate and with colloidal gold-silver for the visualization of the reaction products in light microscopy (LM) and in SEM (backscattered mode) respectively. The surface morphology of mucous cells appears to be correlated to the secretory state. In gastric ulcers we found a prevalence of non-secreting cells. A decrease in glycosidic receptors for fucose-binding lectin and galactose-(1-3)-N-acetyl-galactosamine-binding lectin was also observed. This suggests the presence of an impaired mucus secretion which may play a role in the pathogenesis of gastric ulcer. Spiral bacteria, supposed to be aetiologically related to peptic ulcer and gastritis, were easily detected by SEM. Intestinal metaplasia defined "complete" in LM showed surface morphology and glycosidic components different from those of true intestinal mucosa. This implies the necessity of taking into account also these parameters when classifying this lesion. The same applies to polyps. Our data indicate that correlative SEM may contribute further information on the pathogenesis and pathology of gastric diseases.

The events involved in the histogenesis of the primitive nervous system involve precise control over cell shape changes, cellular migrations, cell-cell and cell-extracellular matrix interactions. The coordinated procession of these events results in the elevation of the neural folds, and their apposition and fusion in the dorsal midline, forming the primary neural tube. This is followed by a second series of cellular migrations and rearrangements (collectively called secondary neurulation) which result in lengthening of the caudal neural tube. After a brief consideration of the mechanisms involved in neurulation, the effects of gene or teratogen induced perturbations of these events are presented and reviewed. New data are presented on neurulation in the delayed Splotch mutant embryo and on the effects of altering mesenchymal or neuroepithelial basal lamina constituents on primary and secondary neurulation.

The relationship of polyploidization (DNA content) to differentiation is not well defined. We have developed centrifugal elutriation and Percoll density gradient centrifugation to obtain large numbers of highly-purified megakaryocytes which subsequently were stained for DNA content with Hoechst 33342 and sorted by FACS into 8C, 16C and 32C ploidy classes for correlated analysis of cell surface structures by scanning electron microscopy. Each ploidy class revealed unique surface characteristics that reflect differentiation occurring in megakaryocytes independent of their DNA content.

The intracellular structure of the outer hair cells of the normal guinea pig organ of Corti was investigated three dimensionally by scanning electron microscope. Freeze fracturing technique followed by maceration with a 0.1% OsO4 solution (osmic maceration method) was used. Among the cell organelles, the endoplasmic reticulum (ER) showed the most interesting features, such as subsurface cisternae and lamellar bodies. The subsurface cisterna which formed a stratiform network covered the inner surface of the cell membrane and the stratiform structure disappeared at the infranuclear region. Variously shaped mitochondria (spherical, cylindrical and branched) were found on the innermost layer of the subsurface cisterna. The lamellar body which was located beneath the cuticular plate consisted of dilated cisternae and tubular ER and was surrounded by mitochondria. The tubular ER of the lamellar body were continuous with the subsurface cisterna.

Nerve terminals often contain morphologically distinct populations of large (75-110 nm) and small (45-55 nm) vesicles. The small vesicles are speculated to account for release of transmitter quanta as they accumulate at presynaptic membranes. Large vesicles can co-store neuropeptides and classical transmitters but their function in neurotransmission has been disputed because they do not appear to accumulate at chemical synapses. However, there is now evidence that the large vesicles play a role in neurotransmission or its modulation even though they may not be eminently involved in synaptic release. Thus, exocytosis occurs along the synapse-lacking membranes of peripheral noradrenergic varicosities. Large vesicles may continue to function in peptide release even after the classical transmitter has been depleted as demonstrated in the pig vas deferens. Three days of reserpine administration causes a parallel loss of noradrenaline and small vesicle contents but does not decrease enkephalin-like immunoreactivity or large vesicle electron density. In the central nervous system of the rat, where substance P and enkephalin have been localized to large vesicles, exocytosis occurs from several types of terminals. The large vesicles appear preferentially to release their contents at morphologically non-specialized sites even when characteristic synapses are present. Thus different mechanisms of transmitter and neuropeptide release may coexist. The nonsynaptic discharge may allow substances to diffuse over a wider distance whereas release into a synaptic cleft could restrict receptor interaction.

The enamel ultrastructure of multituberculate mammals has been sampled extensively and studied intensively and is better known than for any other group of early mammals. The enamel of the earliest multituberculates, those of the Late Triassic-Early Jurassic suborder Haramiyoidea and the Late Jurassic-early Early Cretaceous suborder Plagiaulacoidea, is "preprismatic." With only two exceptions, all Late Cretaceous and early Tertiary genera of multituberculates examined have prismatic enamel. Prisms are either small with circular (complete) boundaries or large with arc-shaped (incomplete) boundaries. There is a remarkably consistent relationship between enamel ultrastructural type and subordinal taxa in that small, circular prisms are usually found within the suborder Ptilodontoidea and large, arc-shaped prisms are usually found in the suborder Taeniolabidoidea and in six Late Cretaceous-Early Tertiary genera of indeterminate subordinal status. Research currently in progress suggests that both small, circular prisms and large, arc-shaped prisms are homologous in all multituberculates in which they occur, with one exception. Neoliotomus, a taeniolabidoid, appears to have evolved small, circular prisms independently. In addition, it appears that large, arc-shaped prisms represent the primitive condition in multituberculates with prismatic enamel, not small, circular prisms as has been proposed previously.