Endothelial cell ultrastructure after aortic aneurysm rupture: an electron microscopy study.

Endothelial cell activation as an early response to hypovolaemic shock may be important in the pathogenesis of coagulopathy and multiple organ failure after aortic aneurysm rupture. The aim of this study was to determine whether any evidence could be found of changes in endothelial cell ultrastructure in patients undergoing operation for ruptured aneurysm and to establish a model for future studies of endothelial cells in these patients. At the start of operation, fat samples from the anterior abdominal wall were taken from five patients with ruptured abdominal aortic aneurysms and in an identical fashion from five control patients undergoing elective surgery. Endothelial cells lining capillaries were examined by transmission electron microscopy. Photomicrographs were taken of all capillaries present and these were assessed blindly by three independent observers. When compared with controls it was found that the luminal surface of the endothelial cells in patients with aneurysm rupture was more convoluted, with more frequent processes projecting into the lumen of the capillary. Budding of the luminal surface of the endothelial cell was seen in 11 of 45 capillaries in the rupture group and in none of 44 capillaries in the control group (P < 0.005). Budding was seen in at least one capillary of all five patients presenting with rupture but in none of the control group (P < 0.05). In conclusion, at the ultrastructural level there are changes within endothelial cells in capillaries at an early stage after ruptured abdominal aortic aneurysm.

Eyelid development, fusion and subsequent reopening in the mouse.

The process of eyelid development was studied in the mouse. The critical events occur between about 15.5 d postcoitum (p.c.) and 12 d after birth, and were studied by conventional histology and by scanning electron microscopy. At about 15.5 d p.c. the cornea of the eye is clearly visible with the primitive eyelids being represented by protruding ridges of epithelium at its periphery. Over the next 24 h, eyelid development proceeds to the stage when the cornea is completely covered by the fused eyelids. Periderm cells stream in to fill the gap between the developing eyelids. Their proliferative activity is such that they produce a cellular excrescence on the outer surface of the line of fusion of the eyelids. This excrescence had almost disappeared by about 17.5 d p.c. Keratinisation is first evident at this stage on the surface of the eyelids and passes continuously from one eyelid to the other. Evidence of epidermal differentiation is more clearly seen in the newborn, where a distinctive stratum granulosum now occupies about one third of its entire thickness. Within the subjacent dermis, hair follicles are differentiating. By about 5 d after birth, a thick layer of keratin extends without interruption across the junctional region. While a noticeable surface indentation overlies the latter, a similar depression is only seen on the conjunctival surface by about 10 d after birth. Keratinisation is also observed to extend in from the epidermal surface to involve the entire region between the 2 eyelids at about this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural and histochemical changes in the murine zona pellucida during the final stages of oocyte maturation prior to ovulation.

The ultrastructural morphology of the mouse zona pellucida was studied in preovulatory follicles from the ovaries of immature mice treated with exogenous gonadotrophins. The ovaries were fixed in the presence of cetylpyridinium chloride, which precipitates carbohydrates, so that their loss during fixation and processing is substantially reduced. The semi-thin araldite sections obtained from osmicated material were viewed by conventional light microscopy, while the ultra-thin sections were examined by transmission electron microscopy. A parallel series of semi-thin sections of non-osmicated ovaries was deresined and subsequently stained with periodic acid Schiff (PAS). The morphological appearance of the zona pellucida in preovulatory oocytes changed during the final stages of oocyte maturation. A close correlation was observed between the ultrastructural appearance of the zona pellucida and that observed following PAS staining during the period studied. Real differences were observed in the location, density, and distribution of glycoconjugates within the zona pellucida during the final stages of oocyte maturation prior to and immediately following germinal vesicle breakdown. Similar changes in the zona were observed in adult females autopsied during proestrus and oestrus. The changes in the density and distribution of glycoconjugates are likely to have important consequences for fertilization by affecting sperm-zona binding and sperm-egg interactions.

Ultrastructural analysis of abnormalities in the morphology of the second meiotic spindle in ethanol-induced parthenogenones.

A high frequency of parthenogenetic activation occurs when ovulated mouse oocytes are briefly exposed to a dilute solution of ethanol in vitro. Cytogenetic analyses of parthenogenones at metaphase of the first cleavage division have confirmed that parthenogenetic activation, per se, does not increase the incidence of chromosome segregation errors during the completion of the second meiotic division. Ethanol-induced activation, however, significantly increases the incidence of aneuploidy. The ultrastructural changes that occur in the morphology and organization of the second meiotic spindle apparatus in ethanol- and hyaluronidase-activated oocytes is reported here. Abnormalities in the arrangement of microtubule arrays and chromosome position were principally observed in ethanol-activated oocytes at anaphase and telophase of the second meiotic division, but were only rarely observed in hyaluronidase-activated oocytes. It is proposed that the abnormalities in spindle morphology and chromosome displacement observed in ethanol-activated oocytes represent the initial events that lead to chromosome segregation errors following exposure to this agent.

Macrophages related to leptomeninges and ventral nerve roots. An ultrastructural study.

In immature rats active macrophages were frequently seen projecting into the subarachnoid space from the surface of the leptomeninges. They also occurred between the layers of the pia and within the nerve roots. They were most frequent during the first two weeks after birth, which is a period of rapid neural growth and myelination in ventral roots. In contrast, they were much fewer at later stages. The ultrastructural characteristics of these cells are described. It is suggested that these cells take part in tissue growth and remodelling by the removal of material which degenerates or becomes redundant during development. For example, they may ingest effete leptomeningeal cells or fragments of them. Those within the ventral roots may phagocytose abnormal Schwann cells, or the myelin of sheaths which have failed to develop normally. It is also suggested that macrophages may be involved in the excavation of the subarachnoid space. Another possible function in which they may be involved is the ingestion of material, possibly of a protein nature, from the cerebrospinal fluid.