Search PubMed⌕ Search

Biomedical subjects

C Combes

Publications and source records attributed to C Combes.

At least 37 records · Page 2Linked to original sources
PubMed1998

Rupture during treatment of recently ruptured aneurysms with Guglielmi electrodetachable coils.

BACKGROUND AND PURPOSE: We describe four cases of aneurysmal rupture during embolization with Guglielmi electrodetachable coils (GDCs) in an attempt to identify those aneurysms whose rupture during embolization represents a life-threatening risk; our emphasis is on emergency management, in particular, ventriculostomy. METHODS: Medical records were reviewed retrospectively for 91 aneurysms treated with GDCs 0 to 21 days after subarachnoid hemorrhage. Rupture was ascertained by the presence of extravascular effusion of contrast medium. RESULTS: Of the perforated aneurysms, two involved the anterior communicating artery, one the posterior inferior communicating artery, and one the basilar artery. Only two patients, whose aneurysms were located in the posterior fossa, had major complications (arterial hyperpressure, mydriasis, angiographically documented circulatory arrest or slowing). One of these patients died and the other improved after emergency ventriculostomy. CONCLUSION: Aneurysmal perforation during embolization may be accompanied by severe intracranial hypertension, which causes either a decrease or arrest of cerebral perfusion, the duration of which determines clinical outcome. Emergency ventriculostomy (which should be performed in the angiographic suite) is an effective means to reduce intracranial pressure. Recognition of aneurysms associated with a high risk of mortality by rupture in the course of embolization (recently ruptured small aneurysms, posterior fossa aneurysms, associated ventricular dilatation, massive cisternal hemorrhage) and use of proper logistics should ensure the effective management of this devastating complication.

Adult↗
PubMed1997

Fitness of parasites: pathology and selection.

Parasites improve their fitness as a result of the selection of traits which determine their relationships with their hosts. Some of these relationships are examined briefly. There is a cost of virulence for parasites, paralleling the cost of resistance for hosts, which implies that the good health of the host can be a component of parasite fitness; conversely, some transmission modes imply that the host be markedly weakened by the parasite. Pathogenicity can be influenced by characters such as a transmission of the parasite from parents to offspring, or the demographic characteristics of the host populations. Important components of parasite fitness are: the complexity of the life-cycle; the degree of specialization for a more or less open host range; the conspicuousness or discretion of the infective and parasitic stages. However, the best possible adaptation to a particular host is not always selected: when a parasite exploits several host species, the gene flows between parasites which have developed in different hosts may be responsible for "maladaptation". This may be important for an understanding of the pathogenicity of certain human parasitic diseases.

Animals↗
PubMed1997

[Host spectrum and virulence].

In an anthropozoonoses distribution of an infectious agent population into several host species at each generation can be considered to result in a fragmented anthropozoonoses environment. Insofar as reproductive success may vary between host species, gene flow becomes asymmetric and a source-sink anthropozoonoses system may be created. Under these conditions optimal virulence may be occur in any host species so that the source host species exerts the strongest selective pressure on the infectious agent. In the sink host species the virulence of the parasite may be sub- or super-optimal (stable misadaptation). This explains the gravity of parasitic infections that man shares with animals and the fact that virulence does not diminish with time.

Adaptation, Physiological↗
PubMed1996

A simple computer-assisted method to identify schistosome cercariae.

Several methods have been suggested to identify schistosome cercariae. In the present work, a new method is proposed, based on the analysis of the distribution of sensory endings (sensillae) on the body of the cercariae, revealed by an impregnation with silver nitrate. We determined the mutual distances between the sensillae and calculated the mean values, standard deviations, coefficients of asymmetry, and of kurtosis of the distribution of these mutual distances. Applied to two species, Schistosoma mansoni from Brazil and S. intercalatum from Cameroon, these mutual distances had the same mean value and the same standard deviation but quite different coefficients of symmetry (0.34 +/- 0.11 versus 0.73 +/- 0.08; P < 0.0001) and of kurtosis (-0.82 +/- 0.27 versus -0.58 +/- 0.31; P < 0.0001). The latter two indices were therefore very effective for discriminating the two species. The present method can be applied to other species and to hybrids in the field.

Animals↗
PubMed1995

[Imagery of human immunodeficiency virus (HIV) encephalitis].

The authors present the different aspects of HIV encephalitis in CT and MR in a series of 15 patients with anatomopathological proof. Atrophy was the most commonly found lesion (12 patients) and could rapidly be evolutive. White matter lesions (9 patients) were more of ten nodular than diffuse. They were better demonstrated by MRI and did not enhance after intra-venous injection of DOTA-gadolinium. A frequent association with opportunistic infections (toxoplasmosis: 10 patients, CMV:2 patients), lymphoma (4 patients), or PML (3 patients) was observed which emphasized the low specificity of brain imaging in patients with HIV encephalitis.

AIDS Dementia Complex↗
PubMed1993

[Schistosoma, water and man].

The biology of schistosomes is increasingly better known due to the research works conducted since the early 1980s. Numerous data have been collected on: the structure of the genome; the genetic variability of natural populations; the causes of geographical distribution of Schistosoma species; the acquisition, probably recent, of the parasite as by modern man's ancestors; and even some aspects of development, such as the behaviour of larvae and the migrations in the circulatory system. Substantial advances have also been made in the maintenance of laboratory strains. Yet, multiple and fascinating problems are still raised by schistosomes. In the present state of our knowledge the origin and relationship of human parasitizing species are still hypothetical. Several features of reproduction, such as the existence of separate sexes and permanent couples cannot be explained. Quantitative data concerning the dynamics of transmission are much too vague to establish satisfactory mathematical models and to contribute usefully to strategies of control. Finally, the fact that schistosomes can develop either in man alone or in numerous mammals remain a mystery for immunologists and specialists of evolution.

Animals↗
PubMed1993

Genetic variability and evolution of the Schistosoma genome analysed by using random amplified polymorphic DNA markers.

The usefulness of random amplified polymorphic DNA markers (RAPD) was assayed in an attempt to discriminate among species, strains and individuals within the genus Schistosoma. Depending on the species, 40-50 arbitrary decamer oligonucleotides were used as primers to amplify total DNA by the polymerase chain reaction (PCR). An important polymorphism was observed among 5 species, allowing a phylogenetic tree to be outlined. These differences can be used for rapid and accurate identification. A limited but easily detectable polymorphism was revealed among 3 strains of a single species (Schistosoma mansoni). Minor differences were observed among individuals of a single strain. A RAPD marker allows sexual discrimination between individuals from the terminal spined-egg species group. Although a limited number of strains have been examined, the results already indicate clearly that RAPD markers constitute a powerful tool for the analysis of genetic variability. This new tool will considerably extend the information available from morphology, isozyme and limited restriction fragment length polymorphism data and opens the way to genetic analysis of these species.

Animals↗
PubMed1993

Experimental host-induced selection in Schistosoma mansoni strains from Guadeloupe and comparison with natural observations.

Allelic frequency variation at the malate dehydrogenase (E.C.1.1.1.37) polymorphic locus (Mdh-1) was analysed during several successive generations in four strains of Schistosoma mansoni from Guadeloupe, maintained experimentally on mice. A rapid evolution of the frequency of the Mdh-1a allele is interpreted as being the result of an interaction between experimental drift and selection induced by the murine laboratory host. These experimental results are compared to the genetic structures observed among the corresponding natural populations of S. mansoni in Guadeloupe (West Indies). They strengthen the hypothesis of a natural host-induced selection by the murine host (Rattus rattus), which, in Guadeloupe, plays the role of host reservoir for this human schistosome.

Alleles↗
PubMed1993

[Arguments for the modification of the genome (introgression) of the human parasite Schistosoma haematobium by genes from S. bovis, in Niger].

Characterization of schistosome populations from human in eastern Niger, through intra-uterine egg morphology of female parasites and phenotopic analyses of worms observed for acid phosphatase using electrophoretic separation, renders results that suggest an intogression of S. haematobium from man by genes of S. bovis, a parasite of domestic livestock. The origin of this introgression, that could implicate S. curassoni as well, another livestock parasite that hybridize with S. bovis, is discussed.

Animals↗
PubMed1992

Molecular evidence linking hominid evolution to recent radiation of schistosomes (Platyhelminthes: Trematoda).

Molecular phylogenies for seven species of schistosomes, including four species infecting man, were constructed from PCR-amplified sequences of two ribosomal genes: one nuclear (internal transcribed spacer 2 in the ribosomal multigenic family) and one mitochondrial (16S rDNA). The two phylogenies obtained are congruent, and the data suggest that the mitochondrial sequence evolves about three times faster than the nuclear sequence. We propose a calibration of the phylogenetic tree of schistosomes that dates "human capture" of these parasites from other animal hosts (rodents and ruminants) in Africa to 1-10 million years ago, when the first hominids invaded savanna areas, which are the favorable environment for parasite transmission.

Africa↗
PubMed1992

Abundance/host size relationship in a fish trematode community.

The abundance of six species of trematodes: Aphanurus stossichi, Bacciger israelensis, Diphterostomum israelense, Plagioporus idoneus, Leprocreadium album and L. pegorchis, parasitic in the digestive tract of marine teleostei (Sparidae) collected near Jounieh (east Mediterranean), was analysed as a function of the host-size. In two parasite/host systems, infections were observed from the lowest size classes of the sample, with a clear tendency to an increase of abundance in older fish. In four others, parasites appear only above a rather high threshold class, young individuals never being infected. In the last three parasite/host systems, host invasion may occur early or late, but infection decreases above a well defined size class, old fishes rarely or never being infected. A given trematode species, when parasitizing several host species, shows similar abundance/host size relationships, e.g., P. idoneus in Diplodus vulgaris and Oblada melanura. When more than one species of trematode infects a single host species, curves can be markedly distinct; for instance, L. pegorchis was collected from Pagellus erythrinus below 15 cm. whereas D. israelense parasitized the same fish approximately above the same size. There is no evidence that such a replacement of one trematode by another in the course of host growth is a result of inter-specific competition.

Animals↗