Synthetic MRI is not yet ready for morphologic and functional assessment of patellar cartilage at 1.5Tesla.

PURPOSE: The purpose of this study was to compare morphologic assessment and relaxometry of patellar hyaline cartilage between conventional sequences (fast spin-echo [FSE] T2-weighted fat-saturated and T2-mapping) and synthetic T2 short-TI inversion recovery (STIR) and T2 maps at 1.5T magnetic resonance imaging (MRI). METHOD: The MRI examinations of the knee obtained at 1.5T in 49 consecutive patients were retrospectively studied. There were 21 men and 28 women with a mean age of 45±17.7 (SD) years (range: 18-88 years). Conventional and synthetic acquisitions were performed, including T2-weighted fat-saturated and T2-mapping sequences. Two radiologists independently compared patellar cartilage T2-relaxation time on conventional T2-mapping and synthetic T2-mapping images. A third radiologist evaluated the patellar cartilage morphology on conventional and synthetic T2-weighted images. The presence of artifacts was also assessed. Interobserver agreement for quantitative variables was assessed using intraclass correlation coefficient (ICC). RESULTS: In vitro, conventional and synthetic T2 maps yielded similar mean T2 values 58.5±2.3 (SD) ms and 58.8±2.6 (SD) ms, respectively (P=0.414) and 6% lower than the expected experimental values (P=0.038). Synthetic images allowed for a 15% reduction in examination time compared to conventional images. On conventional sequences, patellar chondropathy was identified in 35 patients (35/49; 71%) with a mean chondropathy grade of 4.8±4.8 (SD). On synthetic images, 28 patients (28/49; 57%) were diagnosed with patellar chondropathy, with a significant 14% difference (P=0.009) and lower chondropathy scores (3.7±4.9 [SD]) compared to conventional images. Motion artifacts were more frequently observed on synthetic images (18%) than on conventional ones (6%). The interobserver agreement was excellent for both conventional and synthetic T2 maps (ICC>0.83). Mean cartilage T2 values were significantly greater on synthetic images (36.2±3.8 [SD] ms; range: 29-46ms) relative to conventional T2 maps (31.8±4.1 [SD] ms; range: 26-49ms) (P<0.0001). CONCLUSION: Despite a decrease in examination duration, synthetic images convey lower diagnostic performance for chondropathy, greater prevalence of motion artifacts, and an overestimation of T2 values compared to conventional MRI sequences.

Effect of Previous Nitrate Deprivation on (15)N-nitrate Absorption and Assimilation by Wheat Seedlings.

Nitrate uptake and assimilation were examined in intact 18 days old wheat (Triticum aestivum, cv Capitole) seedlings either permanently grown on nitrate (high-N seedlings) or N-stressed by transfer to an 0 N-solution for the final 7 days (low-N seedlings). The N-stressed seedlings were characterized by a lower organic N content (2.5 mg instead of 4.9 mg per seedling) and an increased root dry weight. The seedlings received (15)NO(3)K for 7 h in the light. Nitrate uptake was 2.8 times higher in low-N than in high-N seedlings. The assimilation rate was 35 and 16 µmol NO(3)(-)·(h-1)· g(-1) dry weight respectively. Partitioning of NO(3)(-) to reduction and assimilation was the very same in both kinds of seedlings. The results support the view that 50 % of the nitrate reduction in Triticum aestivum, cv Capitole could be achieved in the roots. The present observations are interpreted as evidence that factors closely associated with the seedling N-status may have a major role in regulating NO(3)(-) uptake and assimilation. In low-N seedlings, the high amount of carbohydrates in roots may add its stimulus to the specific inducing effect of nitrate whereas in high-N seedlings, excess of nitrate or amino-acids may set the pace by negative feedback control.

Nitrogen Isotope Fractionation Associated with Nitrate Reductase Activity and Uptake of NO(3) by Pearl Millet.

Nitrogen isotope fractionation by Pearl Millet (Pennisetum americanum L. and P. mollissimum L.) grown on nitrate was associated with nitrate reductase activity. Fractionation was evidenced at the step of nitrate reduction when the substrate-to-enzyme ratio was high (possibly saturating for the active sites of the nitrate reductase enzyme), for instance in young seedlings having a low nitrate reductase activity or in seedlings grown on high nitrate concentration.When the substrate concentration was low (and, hence, the active sites of the enzyme were possibly not saturated), the isotopic discrimination could only be associated with the uptake of nitrate into the cell. In that case, isotopic fractionation was null. It is concluded that the uptake of nitrate does not discriminate among nitrogen isotopes.

[Olfactory stimulation in the relationship between child and mother]. / Les stimulations olfactives dans les relations entre l'enfant et la mère.

In this paper, we report new data on mutual olfactory recognition between mother and child. Newborn infants were filmed since birth. When awakening in the mother's room at the Clinical Hospital, they were confronted with a cotton pad impregnated with diverse secretions of the mother and a cotton pad impregnated with the same secretions of another mother or a pad with no specific odour. We used a double-blind technique. By analyzing the films, frame by frame, we found that the whole area swept by the nose and the arms was significantly decreased in the child whose nose came into contact with the "mother" pad. The method could be used to study other sensory abilities in the baby. The olfactory abilities of the mother in relation to the baby were also tested with the double-blind principle. We found (i) on the 3rd and 4th days after birth, most mothers recognized the baby's odour, (ii) this faculty decreased from the 4th to the 6th day, and finally (iii) increased from the 8th day. These results are discussed. We also found that one-third of 3 to 5 years old children more often chose a tee-shirt worn against the mother's skin for 2 to 3 days than any other tee-shirt (worn by an alien mother or with no specific odour). It appears that olfactory cues can play a role in the attachment of the baby to its mother, and that they still are involved in that process when the child is between 3 and 5 years old.

[Biological characteristics of the spirulines].

The biological characteristics of Spirulina are reported in this study. The cellular structure and photosynthetic membrane structure of Spirulina (Cyanoschizophyta) were viewed by electron microscopy after freeze-etching. Special characteristics of the alga, its ecological behavior in natural carbonated water and its energetic behaviou in the laboratory cultures are also reported.