Biomedical subjects

M Séguin

Publications and source records attributed to M Séguin.

7 recordsLinked to original sources

PubMed2003

Suicide and serotonin: study of variation at seven serotonin receptor genes in suicide completers.

Suicide is an important public health problem, accounting for a significant proportion of total mortality among young people, particularly males. There is growing and consistent evidence suggesting that genetic factors play an important role in the predisposition to suicide. Based on several lines of evidence supporting a reduced serotonergic neurotransmission in subjects who committed suicide, we investigated variation at genes that code for serotonin receptor 1B (5-HTR1B), 1Dalpha (5-HTR1Dalpha), 1E (5-HTR1E), 1F (5-HTR1F), 2C (5-HTR2C), 5A (5-HTR5A), and 6 (5-HTR6) in a total sample of 106 suicide completers and 120 normal controls. No differences were observed in allelic or genotypic distributions between groups for any of the loci investigated. Moreover, further analysis according to suicide method or psychopathology also failed to reveal differences between groups. Our results do not support a substantial role of these serotonergic receptors in suicide completion.

Alleles↗

PubMed2002

Frequency of alleles conferring resistance to Bt maize in French and US corn belt populations of the European corn borer, Ostrinia nubilalis.

Farmers, industry, governments and environmental groups agree that it would be useful to manage transgenic crops producing insecticidal proteins to delay the evolution of resistance in target pests. The main strategy proposed for delaying resistance to Bacillus thuringiensis ( Bt) toxins in transgenic crops is the high-dose/refuge strategy. This strategy is based on the unverified assumption that resistance alleles are initially rare (<10(-3)). We used an F(2) screen on >1,200 isofemale lines of Ostrinia nubilalis Hübner (Lepidoptera: Crambidae) collected in France and the US corn belt during 1999-2001. In none of the isofemale lines did we detect alleles conferring resistance to Bt maize producing the Cry1Ab toxin. A Bayesian analysis of the data indicates that the frequency of resistance alleles in France was <9.20 x 10(-4) with 95% probability, and a detection probability of >80%. In the northern US corn belt, the frequency of resistance to Bt maize was <4.23 x 10(-4) with 95% probability, and a detection probability of >90%. Only 95 lines have been screened from the southern US corn belt, so these data are still inconclusive. These results suggest that resistance is probably rare enough in France and the northern US corn belt for the high-dose plus refuge strategy to delay resistance to Bt maize.

Alleles↗

PubMed2001

TPH and suicidal behavior: a study in suicide completers.

An association between the gene that codes for tryptophan hydroxylase (TPH)-the rate-limiting enzyme in the synthesis of serotonin-and suicidal behavior has been investigated with some detail in samples of living subjects who attempted suicide. In this study, we investigated TPH and suicide completion, the most severe form of suicidal behavior. A relatively large sample of suicide completers (n = 101) was genotyped at three TPH loci (two polymorphisms in the promoter region, A-6526G and G-5806T, and one in intron 7, A218C) and compared to psychiatrically normal living controls (n = 129). Although no significant differences were found between groups for genetic variation at single loci, haplotype analysis revealed that one haplotype (-6526G -5806T 218C) was significantly more frequent among suicide cases than in normal controls (chi(2) = 11.30, df = 2, P = 0.0008; OR = 2.0 CI: 1.30-3.6). Further analyses suggested that this haplotype is particularly more frequent among subjects who committed suicide using violent methods. Similar results were observed in recent haplotype analyses in suicide attempters, which found that the equivalent of haplotype -6526G -5806T 218C was more frequent in impulsive attempters (Rotondo et al, Mol Psychiatry 1999; 4: 360-368). Our results replicate in suicide completers previous data observed in suicide attempters. These and other results continue to point to the substantial role that the gene that codes for TPH may play in the neurobiology of suicidal behavior.

Genetic Predisposition to Disease↗

PubMed1999

Prediction of level of serotonin 2A receptor binding by serotonin receptor 2A genetic variation in postmortem brain samples from subjects who did or did not commit suicide.

OBJECTIVE: Postmortem studies have indicated that suicide victims have greater serotonin receptor 2A (5-HTR2A) binding in prefrontal brain regions. However, there remains some controversy regarding the biological specificity of these findings. The authors hypothesized that the variance observed in brain 5-HTR2A binding is genetically mediated, at least in part. METHOD: Postmortem data from 56 subjects who had committed suicide and 126 normal comparison subjects were studied; brain tissue was available from 11 subjects who committed suicide and 11 comparison subjects. Homogenate binding assays were carried out with [3H]ketanserin. Variation at the 5-HTR2A gene (HTR2A) was investigated by means of two polymorphisms: T102C and A-1438G. RESULTS: 5-HTR2A binding was greater in the prefrontal cortex of the subjects who committed suicide. In addition, the findings suggest that HTR2A variation significantly affects 5-HTR2A binding. However, no interaction between suicidal behavior and this locus was observed. CONCLUSIONS: These results confirm previous reports of greater 5-HTR2A binding in subjects who committed suicide; they also provide preliminary evidence suggesting that the number of 5-HTR2A receptors is genetically mediated.

Adult↗

PubMed1995

History of early loss among a group of suicide survivors.

Suicide-bereaved families have been described as more depression-prone and their bereavement process as more complicated and difficult. Few studies have aimed specifically to investigate the history of transgenerational childhood loss in suicide survivor families as an indicator of greater vulnerability. Childhood separation experiences are associated with difficulties in forming and maintaining attachments. Bonding difficulties are also associated with greater vulnerability to depression and may constitute a suicide risk factor. This exploratory study (n = 32) focused on two groups, each of 16 mothers who had lost a son to suicide and car accidents, respectively. History of loss and early separation experiences were investigated through a clinical interview of the bereaved mothers and through a psychological autopsy of the deceased sons. Results indicate significant transgenerational indices of loss, separation, and inadequate child-rearing. Pre-death life events and adversities in the family may be as important to bereavement outcome as post-death happenings. The cycle of these events, the role of fathers and the role of protective factors must be further studied using detailed life-course reconstructions.

Adolescent↗

PubMed1995

Parental bereavement after suicide and accident: a comparative study.

In what way is the bereavement process following suicide different from other types of bereavement? The participants were 30 survivors of suicide and 30 survivors of car accidents who were interviewed twice at an average of six months, and the second measure was taken at an average of nine months after the death, with standardized questionnaires to measure depression and grief reaction. Measures of shame, social support, family adaptation, psychological distress, and prior losses were also obtained during the second interview. All survivors were parents who had lost a son aged between 18 and 35 years. The results indicate that suicide survivors were more depressed than accident survivors at the first measure but this difference disappeared at the second measure. Survivors of suicide experienced greater feelings of shame and had experienced more life events after the death than did accident survivors. There was also a greater history of loss in parents bereaved by suicide. Parental bereavement after suicide appears to differ in several ways from other types of bereavement and appears to happen more often in vulnerable families.

Accidents, Traffic↗

PubMed1994

[After suicide: a unique mourning experience?].

Canada's national task force on suicide suggests that people who mourn a suicide make up a group that is itself at risk. Literature shows that mourners of a suicide have a suicide rate that is nine times higher than average. While some authors suggest that this type of mourning is more intense and of a longer duration that for other types of mourning, other authors doubt this hypothesis. But what happens in reality? Is suicide mourning truly different from other types of mourning? Is it really a unique mourning experience? These are some of the questions the authors of this article have attempted to answer. Following an in-depth review of studies on the matter, the authors conclude that the mourning of a suicide encompasses certain characteristics that manifest themselves especially in more vulnerable people.

Bereavement↗