Structural and ultrastructural analysis of gills and gut of Hexagenia rigida nymphs (ephemeroptera) in relation to contamination mechanisms.

In the context of an experimental approach to organic and inorganic mercury bio-accumulation by burrowing mayfly nymphs-Hexagenia rigida-, gills and different parts of the gut were investigated by light and electron microscopes. In the gut, two regions were studied: (1) mesenteron (midgut) characterized by cells with microvilli and a peritrophic membrane throughout this part, a lot of fungal hyphae being found on it; (2) proctodeum (hindgut) characterized by macrovilli, the apical face of cells being covered by a thick layer of chitin; many bacteria were observed at the bottom of macrovilli. The stomodeum (foregut) is extremely short. The gills are made up of six pairs of lamellae fringed with long filaments which are arranged on both sides of the long axis. Gills are constituted by tracheae and tracheoles, with a large canal for haemolymph circulation; muscle masses and nerve bundles were also observed. This structural approach shows that the nymph interface with the external environment, at gill and gut barrier levels, are quite different. Links between this structural and ultrastructural analysis and contamination mechanisms, via the trophic or direct route, are discussed; gills and gut could be transfer routes for mercury absorption, but also target organs for metal accumulation.

Eccentric localization of von Willebrand factor in an internal structure of platelet alpha-granule resembling that of Weibel-Palade bodies.

Immunogold staining was used to study the ultrastructural distribution of von Willebrand factor (vWF) in unstimulated platelets. vWF was detected in the alpha-granules with a specific eccentric distribution pattern opposite the nucleoids. Similar findings were obtained with a polyclonal antibody or a pool of monoclonal antibodies to human vWF. This labeling coincided with the presence of tubular structures located at the periphery of the alpha-granules. These structures were better visualized on platelets treated for standard electron microscopy: they formed a group of one to four tubules ranging from 200 A to 250 A in diameter. They closely resembled the internal tubular structures found in Weibel-Palade bodies, which are the storage organelles of vWF in endothelial cells.

[Effect of flurbiprofen and acetylsalicylic acid on the ultrastructure of blood platelets]. / Effet du flurbiprofène et de l'acide acétylsalicylique sur l'ultrastructure des plaquettes sanguines.

Flurbiprofene or acetylsalicylic acid did not change the structure of inactivated platelets. With flurbiprofene 50% aggregation inhibition was obtained at 10(-6) to 10(-5) M concentrations. To obtain the same result with acetylsalicylic acid, 10(-4) to 10(-3) M concentrations were necessary. With both agents, shape change was inhibited. The platelets in the small aggregates did not have the normal stretched dumb-bell shape but remained globulous and emitted a broad pseudopode containing normally-repolymerized microtubules.

Ultrastructure of a model of thrombogenesis induced by mechanical injury.

Injured cortical arteries were observed by electron microscopy. Haemostasis was brought about by both platelets and fibrin, but the intravascular thrombus contained only platelets. Some platelets adhered to the exposed subendothelium but did not form a continuous layer. Such platelet adhesion does not provoke a thrombus, which appears only at the opening in the artery. There was a gap of 7 micrometers between the thrombus and the intact arterial wall. The thrombus was built up progressively by concentric accumulation around the main injury. Central platelets were closely packed and the more distal ones loosely gathered but not touching and not activated. This structure was very different from that observed in in vitro aggregates which formed rapidly and whose platelets are all at the same stage of development and disposed radially. This implies a different sequence in the physiological evolution of platelets submitted to either mode of activation. The results obtained with the present model differ in several respects from those obtained with other models.

[Ultrastructural study on the effect of an inhibitor of platelet aggregation (author's transl)]. / Ultrastrukturelle Untersuchung der Wirkung eines Aggregationshemmers auf die Blutplättchen.

10-Methoxy-1,6-dimethyl-ergoline-8 beta-methanol-(5-bromonicotinate) (nicergoline, Sermion) is introduced into human platelet-rich plasma at different stages of collagen-, ADP- or epinephrine-induced aggregation. Ultrastructural fixation is processed while aggregation on the same plasma sample is recorded. If introduced before the aggregating agent, nicergoline completely neutralises its action and the platelets become spherical. The microtubule marginal bundle is disorganized and both open and dense canalicular systems are modified. If intoduced after the aggregating agent, nicergoline immediately stops the aggregation and disaggregation follows, with complete separation of the platelets. Morphology of microtubules and canalicular systems depend on the time before application of nicergoline. Nicergoline stops the induction of aggregation as well as ADP release. Disaggregation is an active process involving the microtubules.

[Platelet volume in essential thrombopenia]. / Problèmes posés par la mesure des volumes plaquettaires dans les grandes thrombopénies.

The electronic method for measuring platelet volume using the Coulter Z BI Counter coupled with a Channelyser C 1000 has been standardized. The distribution of platelet volumes was studied in 28 cases of idiopathic thrombocytopenic purpura (ITP) and in 59 cases of thrombocytopenia attributed to a failure of platelet production. Results showed that the volumetric distribution curve of platelet rich plasma (PRP) was altered in 40 cases, by the presence of small particles interfering with platelets of small volume and/or by residual red cells modifying its terminal segment. These abnormalities seem linked to the degree of thrombopenia, but independent of its central or peripheral origin. A method of isolation and concentration of platelets in an albumin gradient allowed the restoration of the classical volume distribution in 24 cases out of 40. Simulated thrombopenias obtained by dilution of platelets in their own platelet poor plasma (PPP) showed that the abnormalities in the small volume range could be reproduced in vitro by modifying the proportion of platelets and of small residual elements in the PRP. When the albumin gradient method was used, the classical distribution of platelet volumes was found. Preliminary electron-microscopy studies show that the small elements in the PRP of thrombopenic subjects could be formed by red cell fragments. Cytoenzymologic studies should be able to confirm this. Volumetric parameters were determined from the asymmetric and unimodual distribution of platelets, either directly on PRP or after concentration and separation of platelets in an albumin gradient. They showed that platelet volumes were very often increased in ITP but also occasionnally in thrombopenia of attributed to a failure of production.

[Ultrastructural study of 11 cases of obstructive myocardiography of the left ventricle]. / Etude ultra-structurale de 11 cas myocardiopathie obstructive du ventricule gauche

A fragment of septum was removed for biopsy in 11 patients with obstructive cardiomyopathy who were undergoing surgery. Electron microscopi revealed an increase in the numbers of mitochondria, deposits of glycogen, and deforming fibrosis. As far as the components of muscle fibres are concerned, both lysis and synthesis of neosarcomeres are to be found, together with abnormalities of the Z band and disorientation of the myofibrils. The number and severity of these abnormalities were found to vary from patient to patient and also in different sections. Although these features are virtually constant in cases of obstructive cardiomyopathy, they are not specific for this condition; they are also found in cases of non-obstructive hypertrophic cardiomyopathy.

[Megakaryocytes and platelets in congenital thrombopathies]. / Mégacaryocytes et plaquettes dans les thrombopathies constitutionnelles

Different HT have been studied with the electron microscope and the findings compared to those in the literature. Five patients with thrombasthenia and three with Willebrand's diseases showed various disorders, usually anisocytosis and hypertrophic open canalicular system, in relation to regenerative states. Thirteen young children with 21-trisomy (2 with leukemia) and 13/15 trisomy (1 case) had enlarged platelets with abnormalities of membranes and vacuoles indicating some metabolic disorders and necrotic lesions. One child with Cooley's anemia showed a few granules and necrotic lesions. All these symptoms were related to regenerative or primitive megakaryocytopathias. The lesion of these latter cell appears in other HT: aberrations of membranes in giant platelets syndroms (J. Bernard and J. P. Soulier syndrome), disorders in membranes and/or granules in thrombopenic thrombopathias, the short platelet life span in May-Hegglin anomaly, storage pool disease in Hermansky-Pudlak syndrome. Finally the ultrastructural abnormalities of the platelets mainly help to distinguish several diseases of megakaryocytes.

[Ultrastructure of the blood platelets in the newborn infant and in the young mongolian child. Study of 13 cases]. / Ultrastructure des plaquettes sanguines chez le nouveau-né et le jeune enfant mongolien. Etude de 13 cas

Blood platelets from infant and new born mongolians were examined and compared taking into consideration existing or non existing haematologic anomalies, such as transitory leucoblastosis with or without hyperthrombocytosis and acute leucosis without thrombopenia. These abnormalities were correlated with the analysis of control samples from haematologically normal new-born and premature children as well as samples from adult mongolian, patients with other chromosomal alterations (13-15, phi) and new-born or adults with thrombocytosis. The presence of dysmorphic platelets could be observed in variable degrees and numbers in all the mongolian samples. The characters of the morphologic abnormalities, constantly observed with variations due to pathological causes, denote either metabolic or structural thrombopathy.