Biomedical subjects

K Bertrand

Publications and source records attributed to K Bertrand.

11 recordsLinked to original sources

PubMed2001

Potential accuracy of genetic evaluation for calving difficulty with incomplete data on calving difficulty and/or birth weight using a bivariate threshold-linear animal model.

The purpose of this study was to evaluate the potential loss of accuracy in direct and maternal predicted breeding values (PBV) for calving difficulty (CD) with different levels of missing records of CD and/or birth weight (BW), using a bivariate threshold-linear animal model. Data obtained from the American Gelbvieh Association included 84,420 first-parity records with both CD and BW available. The final pedigree file included 178,858 animals. The model included fixed calf-sex-dam-age, random herd-year-season, and animal direct and maternal effects. Different levels of missing observations for CD and BW were obtained by randomly deleting 0, 25, 50, 75, and 100% of records for both traits in various combinations. Correlation estimates between PBV for CD obtained with complete and incomplete data were used to measure the changes in PBV for different levels of missing records. Reported correlations are means of three replicates. The results suggest that the information on direct and maternal PBV provided by CD records is more reliable than the information provided by BW records. The difference was especially large when a high proportion of CD records were missing. Correlations above 0.96 and 0.95 for direct and maternal PBV, respectively, when missing 25% or 0% of the CD or BW records suggest that small changes would be predicted with a low proportion incomplete data. For genetic prediction of popular sires (with > 100 pogeny), a higher proportion of missing records could be tolerated. The results suggest that the bivariate threshold-linear animal model is useful for routine genetic evaluation of CD with incomplete field data.

Journal Article↗

PubMed2000

[Resilience factors in the victims of sexual abuse: state of affairs].

OBJECTIVE: The aim of this literature review is to examine factors leading to the recovery of child sexual abuse survivors. METHOD: This paper provides a definition of resilience and presents the individual and environmental protective factors. A methodological examination of the studies is carried through. RESULTS: Researchers have documented that 20% to 44% of adult who were sexually abused during their childhood show no apparent signs of negative outcome. However, very few studies as been interested in resilient women and their protective mechanisms. Recent research on protective factors reveal that searching for support, disclosing the abuse and giving a meaning to the abuse are all adaptative cognitive strategies. Furthermore, the perception of benefits and having an external attributional style are both related to less psychological distress. Social support, in general and after the revelation, also appears as a determinant of resilience. However, avoidance, even if victims find it very useful, proves to be a non-adaptative strategy, which may lead to be a catalyst to victims' symptomatology. Definitional problems and the lack of longitudinal studies limit the conclusions that can be drawn. CONCLUSION: The rare studies involving resilient victims show that social support as well as certain cognitive coping strategies may lead to recovery. However the extent of their contribution remains unknown.

Adaptation, Psychological↗

PubMed1994

Air cavity effects on the radiation dose to the larynx using Co-60, 6 MV, and 10 MV photon beams.

PURPOSE: To determine the perturbation effect in the surface layers of lesions located in the air-tumor tissue interface of larynx using 60Co, 6 MV, and 10 MV photon beams. METHODS AND MATERIALS: Thermoluminescent dosimeters (TLDs), were embedded at 16 measurement locations in slab no. 8 of a humanoid phantom and exposed to two lateral-opposed beams using standard small 7 x 7 cm fields. Similarly, radiographic and radiochromic films were placed between slabs no. 7 and no. 8 of the humanoid phantom and exposed to two lateral-opposed radiation beams. The dosimeters were irradiated with 60Co, 6 MV, and 10 MV photon beams. Computer tomography (CT) treatment planning without inhomogeneity correction was performed. RESULTS: At the tissue-air interface, the average measured percentage dose (% dosem) is about (108.7 +/- 4.8)% with TLD data, (96.8 +/- 2.5)% with radiographic film data, and (100.8 +/- 4.9)% with radiochromic film data. Similarly, in the central part of the cavity, the % dosem is (98.4 +/- 3.1)% with TLD data, (94.3 +/- 3.3)% with radiographic film data, and (91.7 +/- 5.0)% with radiochromic film data. Using the CT-based generated dose distribution (without inhomogeneity correction), the average calculated percentage dose (% dosec) is (98.7 +/- 1.0)% at the tissue-air interface and 98% in the central part of the air cavity. CONCLUSION: For the beam energies studied, the variation from the % dosem at the tissue-air interface for a given dosimetry technique is relatively small [< 5% (TLD), < 3% (radiographic), and < 5% (radiochromic)] and therefore should not be significant in clinical settings. The variation from the % dosem at the tissue-air interface is more significant for lower energies [8% (60Co), 7.3% (6 MV)]. This variation is about 4.3% for 10 MV photon beam, therefore, while our institutional practice favors lower energy (60Co to 6 MV) for node-negative glottic cancers, physical/dosimetric evidence offers no disadvantage to the use of higher energy photons.

Humans↗

PubMed1992

Molecular biology of African trypanosomes: development of new strategies to combat an old disease.

African trypanosomes are protozoan parasites that cause a number of diseases of man and domesticated animals in large regions of sub-Saharan Africa. The diseases have proven to be particularly difficult to prevent or to effectively treat due to features of both the trypanosome and the insect vector, the tsetse fly. The habitat of the tsetse and its resistance to insecticides have rendered vector control efforts ineffective. Attempts to develop a vaccine against the African trypanosomes has been dwarfed by the parasite's ability to change the composition of its exposed surface antigens. This process of antigenic variation allows the parasite to avoid the host's immune response and presents the host with a seemingly endless antigenic repertoire. Since conventional approaches to the control of African trypanosomiasis have largely met with failure, there has been a renewed interest in identifying novel aspects of the biology, biochemistry, and molecular biology of trypanosomes that might be exploited to develop new targets for vaccines or chemotherapy. Importantly, this research has opened a virtual Pandora's box of exciting biochemical and molecular surprises, which makes the African trypanosomes not only important medical pathogens but also an exciting experimental system for the basic scientist. In this review, the authors will describe some of the most recent and intriguing developments in the field of molecular parasitology.

Animals↗

PubMed1981