Morphometric study of the plasmalemmal vesicles of the capillaries of the rat cerebellum, heart, diaphragm and lung during perinatal growth.

1. Morphometric techniques were used to determine the variation in number of plasmalemmal vesicles, their area and the area of the endothelium in capillaries of the cerebellum, heart, diaphragm and lung of rat fetuses aged 17, 19, 20 and 21 days and of newborn rats. 2. A curve fitting procedure showed that the evolution of vesicle number could be properly expressed by equations of the type y = aoekx, where y = number of vesicle images per capillary section or number of vesicles per micron3 of capillary wall, and x = age in days. The time necessary for the numerical density of the vesicles to duplicate in the capillary wall is on average 1.1-1.3 days in the lung, 1.4-1.9 days in the muscular organs and 2.3 days in the cerebellum. 3. Capillary maturation was characterized by thinning of the endothelium, especially for those at the base of the lung, and by increased numbers of vesicles. 4. The ratios: number of plasmalemmal vesicle images/endothelial area, plasmalemmal vesicle image area/endothelial area, and number of plasmalemmal vesicle images/plasmalemmal image area increased with age. The third parameter tended to reach 1 due to the increased area of the vesicles as a function of their numbers, even though there was a decrease in individual vesicle size.

Ultrastructural changes in rat lung arterioles in conditions of altered permeability.

By means of the colloidal carbon technique and injection of a barium-gelatin mixture into the pulmonary artery, the ultrastructure of lung arterioles in a state of increased permeability has been studied. In certain conditions pulmonary arteriolar permeability changes are frequent and the carbon particles adhere to the endothelium. Leakage of carbon into the interstitial space is observed only rarely. It is concluded that the pulmonary and systemic vessels have different patterns of response to altered permeability.

Comparative study of the ultrastructural alterations in the pulmonary vessels of rats treated with alpha-naphthylthiourea (ANTU) and ammonium sulphate.

A comparative study of the ultrastructural changes in rat pulmonary vessels was made in two different situtations of increased vascular permeability: one caused by alpha-naphthylthiourea (ANTU) and the other induced by ammonium sulphate (AS). AS had a more destructive effect on the capillaries but showed little alteration in vessels larger than capillaries. ANTU provoked milder ultrastructural lesions but acted on capillaries, arterial and venous structures. In both conditions intravenously injected carbon particles adhered to the vessel wall and leakage into the interstitial space was rarely seen despite the presence of endothelial gaps. It was concluded that ANTU and AS provoke different ultrastructural alterations and that pulmonary and systemic vessels react differently when undergoing changes in permeability.

Schistosoma mansoni: structural damage after treatment with oxamniquine.

The effects of a single dose (100 mg/kg-body weight of mouse) of oxamniquine on the worm's tegument and paranchyma in relation to the process of immunological granulomatous reaction of the host's liver are described under light and electron microscopy (EM). The lesions caused by the drug are sequentially and simultaneously described in form of swelling, surface bulble and disruption with erosions. Ulceration in the tubercules with loss of spines is often more extensive and severe in male worms and concentration of host's mononuclear cells is observed. The possible role of host's immune response is discussed.

Effect of trypsin and 2-mercaptoethanol on the exposure of sugar residues on the surface of Leishmania donovani chagasi.

Using transmission electron microscopy, gold-labeled lectins, morphometry and enzyme-linked lectin assay, we could show that treatment of promastigotes of Leishmania donovani chagasi with trypsin did not interfere with the binding of lectins (concanavalin A, peanut agglutinin, wheat germ agglutinin and Ricinus communis agglutinin) to the parasite surface. These observations are in agreement with results we previously obtained using a biochemical approach. Treatment of fixed promastigotes with 2-mercaptoethanol induced a significant increase in the density of concanavalin A (Con A) receptors on the surface of L. d. chagasi in relation to the control. We suggest that this increase is due to the unfolding of one or more surface glycoproteins after cleavage of disulfide bonds between cystein residues in adjacent protein loops, exposing second-order Con A receptors that are otherwise hidden in the protein quaternary structure.