Prenatal and adult growth hormone gene expression in rat lymphoid organs.

Growth hormone (GH) exerts its immune effects on mature lymphocytes through an autocrine/paracrine mechanism. We investigated the prenatal synthesis of GH mRNA in rat lymphoid organs using the sensitive in situ RT-PCR methodology. We show that GH transcripts are detectable in the thymus and liver of the 18-day fetus. At this stage, all thymocytes are immature and express the GH gene. In fetal liver, GH gene expression was localized in circulating lymphocytes and in hematopoietic cells surrounding GH mRNA-negative hepatocytes. In situ GH gene expression in fetal lymphoid organs was confirmed by in vitro RT-PCR showing that the amplified product from fetal lymphoid tissues was similar to the product obtained from the pituitary. Moreover, GH gene expression was detected in the thymus, spleen, and ileum Peyer's patches of adult rat, with a localization restricted to the lymphocytes and endothelial and smooth muscle cells of blood vessels. The autocrine/paracrine expression of the GH gene by lymphoid and hematopoietic cells during fetal growth might influence the generation of regulatory cells involved in immunity and hematopoiesis.

[Endovascular treatment of an extralobar sequestration with cardiac failure]. / Traitement endovasculaire d'une séquestration extralobaire avec insuffisance cardiaque.

Extralobar sequestration usually presents during the first months or years of life by respiratory distress, cyanosis or infection. Cardiac failure is a rare mode of presentation. If surgery is the usual treatment, radiological endovascular treatment has occasionally been described. We report the case of a newborn who underwent endovascular treatment at 19 days. Clinical status is excellent at 5.5 year follow-up.

[Ultrasound and dynamic contrast-enhanced MR imaging of a multifocal hemangioendothelioma in an infant]. / Echographie et IRM dynamique avec injection d'un hémangioendothéliome multifocal chez un nourrisson.

Multifocal liver hemangioendothelioma is a rare tumor occurring in children less than 6-months-old. It can be life threatening during the first year of life because of possible hemorrhage or high output heart failure. Slow and often spontaneous recovery is the rule. The association of ultrasound and contrast-enhanced dynamic MR seems sufficient to establish the diagnosis.

In situ reverse transcription-polymerase chain reaction. Applications for light and electron microscopy.

Since its discovery in 1986 by Mullis, the polymerase chain reaction (PCR) has been extensively developed by morphologists in order to overcome the main limitation of in situ hybridization, the lack of sensitivity. In situ PCR combines the extreme sensitivity of PCR with the cell-localizing ability of in situ hybridization. The amplification of DNA (PCR) or a cDNA (RT-PCR) in cell or tissue sections has been developed at light and electron microscopic levels. A successful PCR experiment requires the careful optimization of several parameters depending on the tissue (or of cell types), and a compromise must be found between the fixation time, pretreatments and a good preservation of the morphology. Other crucial factors (primer design, concentration in MgCl2, annealing and elongation temperatures during the amplification steps) and their influence on the specificity and sensitivity of in situ PCR or RT-PCR are discussed. The necessity to run appropriate controls, especially to assess the lack of diffusion of the amplified products, is stressed. Current applications and future trends are also presented.