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Biomedical subjects

N Vidal

Publications and source records attributed to N Vidal.

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

Weighting and congruence: a case study based on three mitochondrial genes in pitvipers.

Weighting strategies in a total evidence approach are often conducted in order to remove homoplasy, with the implicit hope to increase congruence between data partitions. Incongruence was measured using the test of Farris et al. (J. S. Farris, M. Källersjö, A. G. Kluge, and C. Bult, 1995, Cladistics 10, 315-319) within and between three mitochondrial genes from pitvipers (Crotalinae) in partitioning each codon position for the coding genes. Incongruence between codon positions of a gene can be worse than incongruence between genes at analogous positions. Third positions of codons behave very differently in terms of incongruence from one gene to another while showing similar patterns in saturation tests. Instead of removing characters in order to discard homoplasy, which is hopeless and does not increase general congruence, we advocate for the removal of those substitutions that are incongruent with the rest. The genus Calloselasma and its sister group the genus Hypnale are the most basal Crotalinae. Asiatic pitvipers are paraphyletic, while American pitvipers are monophyletic.

Animals↗
PubMed1997

Genetic diversity of simian immunodeficiency viruses from West African green monkeys: evidence of multiple genotypes within populations from the same geographical locale.

High simian immunodeficiency virus (SIV) seroprevalence rates have been reported in the different African green monkey (AGM) subspecies. Genetic diversity of these viruses far exceeds the diversity observed in the other lentivirus-infected human and nonhuman primates and is thought to reflect ancient introduction of SIV in the AGM population. We investigate here genetic diversity of SIVagm in wild-living AGM populations from the same geographical locale (i.e., sympatric population) in Senegal. For 11 new strains, we PCR amplified and sequenced two regions of the genome spanning the first tat exon and part of the transmembrane glycoprotein. Phylogenetic analysis of these sequences shows that viruses found in sympatric populations cluster into distinct lineages, with at least two distinct genotypes in each troop. These data strongly suggest an ancient introduction of these divergent viruses in the AGM population.

Amino Acid Sequence↗
PubMed1995

Regulatory genes of simian immunodeficiency viruses from west African green monkeys (Cercopithecus aethiops sabaeus).

The high seroprevalence of simian immunodeficiency viruses (SIVs) in African green monkeys (AGMs) without immunological defects in their natural hosts has prompted consideration of SIV-infected AGMs as a model of apathogenic SIV infection. Study of the molecular mechanisms of SIVagm asymptomatic infection could thus provide clues for understanding the pathogenesis of human immunodeficiency viruses. Regulatory genes could be candidates for genetic control of SIVagm apathogenicity. We have characterized Vpr, Tat, Rev, and Nef genes of two SIVagm strains isolated from naturally infected sabaeus monkeys captured in Senegal. The results provide further evidence that SIVagm from West African green monkeys is the most divergent class of AGM viruses, with structural features in long terminal repeat sequences and Vpr and Tat genes that distinguish them from viruses isolated from other AGM species (vervet, grivet, and tantalus monkeys).

Africa, Western↗
PubMed1994

Trichomonas vaginalis: repeated DNA target for highly sensitive and specific polymerase chain reaction diagnosis.

Trichomoniasis is recognised as a major sexually transmitted disease (STD) in the world and may act as an acquired immunodeficiency syndromes (AIDS) co-factor by enhancing the transmission of human immunodeficiency virus (HIV). Diagnosis of Trichomonas vaginalis can be achieved by several methods, but sensitive detection means are still lacking. In this study a 2000-bp repeated DNA fragment of T. vaginalis was cloned. Part of a conserved region of this insert was sequenced, two primers (TVK3 and TVK4) were chosen and a highly sensitive detection by polymerase chain reaction (PCR) was then developed for T. vaginalis. All strains of T. vaginalis analysed with these primers gave the expected 350-bp fragment and a 450-bp additional fragment. Sequence analysis of these PCR amplification products revealed that the 450-bp fragment contained the 350-bp with a 100-bp insertion characterised by a TGG microsatellite. A second primer set, namely TVK3 and TVK7 (determined at the border of the insertion), yielded PCR products of expected sizes. After amplification we were able to detect a single parasite. We also detected T. vaginalis in vaginal fluids of patients with STD. There was no reaction with human DNA or other infectious agents. It appears that the two set primers are highly specific of T. vaginalis and provide a useful tool for PCR diagnosis in asymptomatic and symptomatic patients especially among the HIV at risk individuals.

Animals↗
PubMed1992

What teachers want to know about students with cancer.

This article reports the results of a survey of classroom teachers in elementary and high schools in the San Francisco Bay Area. The teachers were asked to respond to questions about their informational needs and concerns related to students in their classroom who were diagnosed with cancer or receiving cancer treatment. Findings indicated that classroom teachers perceive themselves to be ill prepared to address the needs of the student with cancer. Specific concerns clustered around information deficits regarding the students' physiological and physical vulnerability, physical limitations/alterations following treatment, psychological responses to cancer treatment, and peer interactions. Utilizing data from the survey, a conceptual approach and collaborative intervention scheme were developed.

Humans↗
PubMed1986

Influence of Ca2+e on 5-HT2- and alpha 1-induced arterial contraction and phosphoinositide metabolism.

Serotonin and phenylephrine were found to induce contractile responses and inositol phosphate (IP) formation in isolated rat tail artery. Both processes displayed similar concentration dependence in the presence of 2.5 mM external calcium (Ca2+e) and both were respectively inhibited by either ketanserine or prazosin, depending on the agonist used. In the absence of Ca2+e the amines no longer produced a contractile effect. In addition, lack of Ca2+ caused a shift to the right in the dose-response curve for phenylephrine-induced IP formation whereas serotonin-induced IP formation was not affected by changes in Ca2+e. The results suggest that alpha 1- and 5-HT2-induced contractions are quantitatively related to phosphatidylinositol metabolism. Contraction, but not IP formation requires the presence of Ca2+e. Different effects of Ca2+e on phenylephrine- and serotonin-induced IP formation could be related to a differential Ca2+ effect on binding of alpha 1- or 5-HT2 agonists.

Animals↗
PubMed1986

Biochemical and physiological evidences for antiserotonergic properties of naftidrofuryl.

In experimental and clinical investigations, 2-(diethylamino)ethyl-tetrahydro-alpha-(1-naphthyl-methyl)-2-furanpro pionate (naftidrofuryl, Praxilene) appears to improve blood flow and microcirculation in ischemic areas. In order to define the mechanism by which the drug may exert its vascular effects, the binding affinity of naftidrofuryl toward various receptors was studied. From this biochemical study, it appeared that, in therapeutic doses, naftidrofuryl selectively inhibited the binding of spiperone or ketanserin to serotonin S2 receptors. This finding was corroborated in physiological models such as isolated rat caudal arteries or preparations of aortic myocytes. Naftidrofuryl effectively blocked the constrictive effect of serotonin on the artery in a dose-dependent, competitive manner. It also strongly inhibited the formation of serotonin-stimulated inositol triphosphate in the myocytes. From these good correlations between biochemical and physiological data it is concluded that the beneficial effects of naftidrofuryl on ischemic tissue perfusion may be partly explained on the basis of selective antiserotonergic S2 properties.

Animals↗