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Biomedical subjects

D Gauthier

Publications and source records attributed to D Gauthier.

At least 19 recordsLinked to original sources
PubMed1995

Live cell image segmentation.

A major requirement of an automated, real-time, computer vision-based cell tracking system is an efficient method for segmenting cell images. The usual segmentation algorithms proposed in the literature exhibit weak performance on live unstained cell images, which can be characterized as being of low contrast, intensity-variant, and unevenly illuminated. We propose a two-stage segmentation strategy which involves: 1) extracting an approximate region containing the cell and part of the background near the cell, and 2) segmenting the cell from the background within this region. The approach effectively reduces the influence of peripheral background intensities and texture on the extraction of a cell region. The experimental results show that this approach for segmenting cell images is both fast and robust.

Algorithms↗
PubMed1994

Ultrasonographic detection of abnormal fetal growth with the gestational age-independent, transverse cerebellar diameter/abdominal circumference ratio.

OBJECTIVES: We prospectively evaluated the accuracy of a gestational age-independent method of detecting abnormal growth, the transverse cerebellar diameter/abdominal circumference ratio, and compared this with standard ultrasonographic methods of growth assessment. STUDY DESIGN: We prospectively studied 825 low-risk obstetric patients and 250 patients having risk factors for fetal macrosomia (n = 92) or growth retardation (n = 158). Measured fetal parameters included the biparietal diameter, head circumference, transverse cerebellar diameter, abdominal circumference, and femur length. The estimated fetal weight, head circumference/abdominal circumference, cerebellar diameter/abdominal circumference, and femur length/abdominal circumference ratios were calculated. Reference curves for these parameters were created from a cross-sectional analysis of the low-risk group. Univariate analysis was used to determine the sensitivity, specificity, predictive values, and odds ratios of each individual parameter in identifying a small- or large-for-gestational-age infant. A multivariate logistic regression model with a variable selection procedure was then used to determine whether significance remained when we controlled for other parameters. RESULTS: Within the low-risk group, the transverse cerebellar/abdominal circumference ratio was gestational age independent between 14 and 42 weeks with a mean of 13.68 +/- 0.96. A value exceeding 2 SD of the mean was significantly associated with birth or a small-for-gestational-age infant, being abnormal in 98% and 71% of asymmetrically and symmetrically growth-retarded infants, respectively. Significance was maintained in the multivariate regression model. The ratio was not helpful in detecting the large-for-gestational-age infant. CONCLUSION: The fetal transverse cerebellar diameter/abdominal circumference ratio is an accurate, gestational age-independent method of identifying the small-for-gestational-age but not the large-for-gestational-age infant.

Abdomen↗
PubMed1993

Detection of fetal cocaine exposure by analysis of amniotic fluid.

OBJECTIVE: To determine whether analysis of amniotic fluid (AF) using solid-phase extraction and high-performance liquid chromatography is useful in detecting fetal exposure to cocaine and its metabolites. METHODS: Amniotic fluid and urine samples were obtained from 23 subjects with documented cocaine abuse during pregnancy and five subjects without a history of cocaine abuse. Urine samples were also collected from all newborns. Urine samples were screened using conventional immunoassay techniques and confirmed with thin-layer chromatography. Using a modified solid-phase extraction procedure, we removed cocaine and its metabolites from all AF samples and from the newborn urine samples in which the initial screening was positive. Subsequently, we analyzed the extracts with high-performance liquid chromatography. RESULTS: Cocaine or benzoylecgonine was detected in 74% of AF samples taken from the 23 known cocaine abusers. In these subjects, conventional maternal and neonatal urine toxicology screens were positive in 61 and 35%, respectively. Concentrations in AF ranged from 400 to greater than 5000 ng/mL for benzoylecgonine and from trace to 250 ng/mL for cocaine. Mean benzoylecgonine recovery from AF was significantly greater than from newborn urine (1800 versus 280 ng/mL, respectively; P < .0001). CONCLUSION: Analysis of AF appears to be useful in detecting gestational cocaine exposure.

Amniotic Fluid↗
PubMed1992

Isolation and characterization of hamster brain polyribosome-cytomatrix complexes.

We have developed a method for the isolation of a brain subcellular fraction enriched in both highly aggregated polyribosomes and cytoskeletal proteins. This method is based on gentle dispersion of brain tissue and low speed centrifugation. This fraction is enriched in typical cytoskeletal proteins as glial fibrillary protein, neurofilament proteins and actin. Messenger RNA did not seem to be involved in the polyribosome association to the cytomatrix as shown by the effect of exposure to micrococcal nuclease. On the other hand, in vivo disruption of protein synthesis by acute experimental phenylketonuria, hypothermia or heat-shock did not cause the release of ribosomes from the cytomatrix.

Actins↗
PubMed1991

In vitro translation in a hamster brain cell-free system.

We have developed a cell-free translation system derived from hamster brain tissue. The optimal incorporation conditions were 160 mM K+, 2 mM Mg2+ and microM spermine. The absence of this latter compound could be compensated only by doubling (to 4 mM) Mg2+ concentration. This system was inhibited by cycloheximide and emetine (elongation inhibitors) as well as NaF and aurintricarboxilic acid (ATA) (initiation inhibitors). The nature of the ATA inhibiting effect was studied by kinetic comparison with cycloheximide and polyribosome sedimentation pattern.

Adenosine Triphosphate↗
PubMed1991

Gastro-intestinal parasitism of cattle in native pasture grazing system in Guadeloupe (French West Indies).

Gastro-intestinal parasitism of creole cows and calves, Limousin x creole cross calves and Brahman x creole cross calves was recorded during seasons of calving in a native grazing system in Guadeloupe, a wet tropical area. Calvings were pooled during the dry season for two herds and during the rainy season for two other herds. For each calving season, calves of one herd were drenched monthly with anthelmintic. A marked periparturient rise in egg excretion was observed in cows. Coccidial infection was always present in calves, but no clinical signs were observed. The main parasites during the first 2 months of life were Strongyloides papillosus and Toxocara vitulorum. Then, Haemonchus placei, Trichostrongylus spp. and Cooperia spp. were the dominant species encountered. Brahman cross calves were the most heavily infested animals. There was no clear relationship between third stage larvae (L3) population size on pasture and worm burdens in calves, except during the second month of life. Despite medium levels of infestation, parasitism inhibited the growth of creole calves: -10.5 kg of bodyweight at weaning (-59 g day-1 of daily bodyweight gain from birth to weaning). The pathological effects of subclinical parasitism were confirmed by a lower packed cell volume and albuminaemia in parasitized calves than in treated calves.

Animals↗
PubMed1989

Immunological and chemical characterization of hamster brain polyribosomes-cytomatrix complexes.

We have studied the cytoskeletal nature of a brain subcellular fraction previously shown to contain polyribosomes. We have identified the major proteins of this fraction by electrophoretic comparison to a standard cytoskeletal fraction and by immunodetection. These methods have shown the presence of actin, glial fibrillary acidic protein, and neurofilament triplet proteins. We have also studied the effect of various ions and nonionic detergents on the stability of this structure. It was stable in presence of Triton X-100 up to 2% but disrupted by 200 mM K+ acetate.

Actins↗
PubMed1989

In vitro localization of the protein synthesis defect associated with experimental phenylketonuria.

We have used a cell-free system derived from hamster brain to investigate protein synthesis during experimental phenylketonuria. In such a system the elongation inhibitor emetine impeded translation in extracts derived from both treated and control animals. On the other hand the initiation inhibitor aurintricarboxylic acid showed no effects on protein synthesis activity of treated hamsters, although it was severely inhibiting in controls. This suggests that initiation is the altered step in brain protein synthesis failure consecutive to phenylketonuria.

Animals↗
PubMed1989

Isolation of hamster brain polyribosomes-cytoskeleton complexes.

We have developed a method for the isolation of a brain subcellular fraction enriched in both highly aggregated polyribosomes and cytoskeletal proteins. This method is based on gentle homogenization of brain tissue and low speed centrifugation. The mechanism of association of polyribosomes to cytoskeletal structures has been studied by in vitro treatment of this fraction with polyribosome-disaggregating agents. RNase and EDTA, while succeeding in completely disrupting them into monosomes or subunits, did not release them from cytoskeleton. Puromycin showed no noticeable effect.

Animals↗
PubMed1987

Efficacy of RNase inhibitors during brain polysome isolation.

We have investigated the efficiency of heparin, polyvinyl sulfate and yeast RNA (as competitive RNase inhibitors), liver extract (as crude preparation of liver RNase inhibitors) and DEPC (as irreversible non-competitive inhibitor) for the preparation of rat brain polysomes. Sucrose gradient sedimentation profiles, obtained from PMS, were used to determine the optimal concentration of each inhibitor. Diethylpyrocarbonate, whatever the composition of isolation buffer, was found detrimental for brain polysomes. Most of the other inhibitors where found useless or even harmful. A slight positive effect was observed with heparin 0.75 mg/mL both for total yield and sedimentation pattern. It is concluded that the utilisation of most of the widely used RNase inhibitors is of questionnable effectiveness for brain polysome preparation.

Animals↗
PubMed1986

Polysomes during early postnatal development of brain in the rat.

We have attempted to show eventual modifications in the brain protein synthesis apparatus of rat during the first three weeks after birth. Through this time we noted a steady decrease (about 60%) in the free polysomes, when expressed relative to tissue weight. This decrease does not correlate with changes in the polysome profile, indicating that no loss in the efficiency of protein synthesis was involved. Translation in a reticulocyte lysate also failed to reveal differences.

Animals↗
PubMed1986

The influence of season and shade on oestrous behaviour, timing of preovulatory LH surge and the pattern of progesterone secretion in FFPN and Creole heifers in a tropical climate.

The aim of this work was to study the duration of oestrous behaviour, timing of the LH surge and the progesterone pattern with and without shelter during January and again in July in FFPN and Creole heifers in a tropical environment. From days 21 to 28 after a synchronization treatment (progesterone + PMSG), ten Creole heifers and ten FFPN heifers were checked for oestrus and sampled for blood every 3 h to assay plasma LH levels and every day from that oestrus to the following one to assay plasma progesterone content. Five heifers in each group were housed in a covered corral and five were exposed to the sun in a corral without shelter. The mean duration of oestrus for all the heifers was 14.0 h. There was a significant breed/season interaction: 21 h in July and 15 h in January for FFPN heifers. Sun exposure did not significantly affect the mean duration of oestrus. The distribution of onset of heat with respect to time of day was not uniform: 29% of the oestruses began between 5 and 8 a.m. and 19% between 8 and 11 p.m. The mean interval between onset of heat and maximal LH value (3.58 h) only varied significantly with the season (1.6 h in January and 6.0 h in July; P less than 0.05) but was equivalent to those obtained by other authors. The plasma progesterone levels of both breeds were lower than those described for cows in temperate countries and were lower for shaded FFPN heifers in January (2.8 ng/ml) than in July (3.93 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effect of underfeeding on testosterone-LH feedback in the bull.

This study was conducted to investigate the hypothesis that the low LH pulsatility induced by underfeeding may result from an altered negative-feedback response to testosterone in cattle. Eight 21-month-old Aubrac bulls were divided into two equal groups. The first group (group H) received a high level of nutrition (producing a gain in weight of 570 g/day) and the second group (group L) a low level of nutrition (producing a loss in weight of 330 g/day). After 52 days of underfeeding the bulls were hemicastrated, castrated 7 days later and then injected with 30 mg testosterone daily for 14 days, 10 mg daily for 7 days and 2.5 mg daily for 7 days. After hemicastration, LH pulsatility was higher (P less than 0.001) in group H (9.0 pulses in 24 h) than in group L (5.3 pulses in 24 h). After castration this value was the same in the two groups (24 pulses in 24 h). When the bulls were injected daily with 30 or 10 mg testosterone, the number of LH pulses in 24 h was lower (P less than 0.05) in group L (14.3 and 9.8 pulses in 24 h with 30 mg, and 17.3 pulses in 24 h with 10 mg) than in group H (27.8 and 25.5 pulses in 24 h with 30 mg, and 24.0 pulses in 24 h with 10 mg). When the animals received 2.5 mg testosterone daily, the number of LH pulses was the same in both groups (20.3 pulses in 24 h). These results indicate that the negative-feedback response of the LH-releasing system to testosterone is modified by underfeeding in the bull.

Animals↗
PubMed1985

Lung angiotensin converting enzyme activity in chronically hypoxic rats.

A study was carried out to test the hypothesis that the reduced lung angiotensin converting enzyme (ACE) activity which occurs in chronic hypoxia is related to the development of pulmonary hypertension rather than to hypoxia per se. Right ventricular mean systolic pressure (Prvs, mm Hg) and ACE activity (nmol/mg protein/min) in lung tissue homogenates were measured in seven groups of four rats placed in a hypobaric chamber (380 mm Hg; 51 kPa) for two to 24 days. Identical measurements were made on 11 groups of four rats, which were placed in the chamber for 24 days and then allowed to recover in room air for one to 153 days. After two days of hypoxia the mean Prvs (25.5 (SD 3.7] and the mean lung ACE activity (56 (4.6] did not differ significantly from control values. Exposure to hypoxia for four to 24 days caused a progressive increase in mean Prvs to 44.4 (5.9) and a progressive reduction in mean lung ACE activity to 34 (4.0). During recovery lung ACE activity increased and Prvs decreased, so that normal values were achieved by 15 and 56 days respectively. Decreased lung ACE activity may be related to haemodynamic factors associated with pulmonary hypertension rather than to hypoxia.

Animals↗
PubMed1985

[Induction of post-partum ovulation in creole cows by using a Norgestomet implant and temporary removal of the calf].

Two treatments were used to attempt to induce ovulation in anoestrous post-partum creole cows. The use of a Norgestomet implant for 7 days followed by removal of the calf for 48 h induced ovulation in 91, 83 and 71% of anoestrous creole cows treated respectively at 37, 48 and 51 days post partum (implant insertion). In the same time, the cycling rates of the control groups were 30, 35 and 35%, respectively. But calf removal for 48 h at 60 and 80 days without progestagen priming failed to increase the number of cycling cows compared to the control group. Whatever the treatment and the post-partum day, calf growth was not different between the treated and the control groups at 30, 60 and 90 days post-partum, and there was no mastitis.

Animals↗