Recent investigations have shown that cortical nerve growth factor (NGF) infusions during the critical period inhibit ocular-dominance plasticity in the binocular portion of the rat visual cortex. The mechanisms underlying the effects of NGF on visual cortical plasticity are still unclear. To investigate whether during normal development intracortical and/or extracortical cells possess uptake/transport mechanisms for the neurotrophin, we injected 125I-NGF into the occipital cortex of rats at different postnatal ages. Within the cortex, only a few labelled cells were observed. These cells were confined to the vicinity of the injection site and their number depended on the animal's age at the time of injection. Labelled cells were absent at postnatal day (PD) 10 but could be detected between PD 14 and PD 18. They then decreased in number over the following period and were not detected in adult animals. Outside the cortex, neurons of the lateral geniculate nucleus (LGN) were not observed to take up and retrogradely transport NGF at any age after birth. In contrast, retrogradely labelled neurons were found in the basal forebrain. Labelled cells were first observed here at PD 14 and then increased in number until reaching the adult pattern. Our results show that intrinsic and extrinsic neurons are labelled following intracortical injections of iodinated NGF. In both neuronal populations, the uptake and transport of NGF is present over a period corresponding to the critical period for visual cortical plasticity. These findings suggest that NGF may play a role, both intra and extracortically, in plasticity phenomena.

Aging↗

PubMedDate not supplied

Hematologic values of fetal blood obtained by means of cordocentesis.

Fetal blood values were evaluated from 541 cordocenteses. Simple regressions were used to find a correlation between blood values and gestational age. We found a linear increase in hemoglobin concentration and hematocrit throughout gestation; a linear decrease of the mean corpuscular volume with the gestation was evidenced as a regular decrease in mean corpuscular hemoglobin. Lastly, the mean corpuscular hemoglobin concentration was constant during the gestation; a linear increase of the platelet count and the nucleated cells was also evidenced. We suggest that each fetal medicine unit should have its own reference ranges. It will permit to accurately diagnose fetal infection, fetal anemia, or any fetal disease where alterations of hematopoiesis have been described.

Cordocentesis↗

PubMedDate not supplied

[Is it possible to prevent pulmonitis?].

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Air Pollutants↗