Dominique Maiter

Maternal protein restriction early in rat pregnancy alters brain development in the progeny

We assessed the effects of a dietary protein restriction (5% vs. 20% casein in diet) initiated at conception and imposed during the first 2 weeks of rat gestation on postnatal brain development. At the end of the malnutrition period, protein-restricted animals exhibited significantly smaller fetal body weight and brain cortical thickness than controls. At birth and thereafter, body weight was normalized in the progeny. Similarly, brain weight and cytoarchitecture were normal in postnatal animals. In contrast, we observed, during the first 2 postnatal weeks, several abnormalities of brain development which affected all the studied areas for most of the studied parameters: (i) delayed astrocytogenesis as shown by a reduced GFAP staining; (ii) delayed production of hyaluronan in the extracellular matrix studied with binding of biotinylated hyaluronectin; (iii) abnormal neuronal differentiation as shown by reduced expression of MAP-5 and increased expression of MAP-1; (iv) abnormal synaptogenesis as shown by the increased expression of synaptophysin in the basal ganglia; (v) decreased programmed cell death. In adult prenatally protein-restricted animals, all the above parameters were normalized excepted MAP-1 labeling which remained high. In addition, we observed slight alterations of the ventilatory response to hypoxia in adult animals. The present study demonstrates that early protein malnutrition during embryonic development induces multiple, transient alterations of brain development. However, the almost complete normalization in adults of brain architecture and differentiation as well as our physiological data strongly suggest a remarkable plasticity of the developing brain following an early aggression.

Cyclic feeding behaviour and changes in hypothalamic galanin and neuropeptide Y gene expression induced by zinc deficiency in the rat.

Dietary zinc‐deficiency induces a striking reduction and a cyclic pattern of food intake in rodents. To elucidate the mechanisms for these effects, we studied the hypothalamic content, synthesis, and distribution of galanin (GAL) and neuropeptide Y (NPY) during zinc deficiency and refeeding in the rat. In Wistar rats, three weeks of zinc‐deprivation consistently induced a reduction and a cyclic pattern of night‐and day‐time food intake, as well as of water intake. This was accompanied in zinc‐deficient (ZD) rats, and to a lesser extent in pair‐fed (PF) rats, by a decrease of hypothalamic GAL mRNA concentration (CTR: 100±8, ZD: 61±4, PF: 78±2 arbitrary densitometric units, ADU, P<0.01) and an increase of hypothalamic NPY (CTR: 100±11, ZD: 154±10, PF: 126±4 ADU, P<0.05), without peptide modification. The two neuropeptidergic systems were not affected by the cycles of feeding, with the exception of the NPY‐immunoreactivity in the suprachiasmatic nuclei (geniculo‐hypothalamic tract), that was inversely correlated to the food intake in both ZD and PF animals. In a second experiment, we showed that zinc‐repletion for 4 days suppressed the behaviour induced by a two‐week zinc‐deprivation, and reversed the increase of NPY mRNA in ZD animals. We finally demonstrated that zinc‐deficiency induced a similar behaviour in Zucker rats. However, in these rats whose synthesis of NPY is constitutively up‐regulated, no change of NPY synthesis was observed in ZD rats, suggesting that the increase observed in Wistar is adaptative rather than instrumental to the abnormal food intake. In conclusion, we have further characterized the cyclic feeding behaviour of the zinc‐deficient Wistar rats, and shown in these animals a decreased activity of the GAL system and an increased activity of the NPY system, likely corresponding to a compensatory response of the two neuropeptidergic systems, as observed in food‐deprived animals. As spontaneous food intake of ZD rats does not increase, a resistance to NPY could also be present. These behavioural and neuropeptidergic changes were partially reversed by reintroduction of zinc in the diet. In Zucker rats, the same behaviour occurred despite an insensitivity of the NPY system to the zinc‐deficiency. In addition, we describe a nutritional regulation of the NPY‐immunoreactivity in the geniculo‐hypothalamic tract, that could constitute the substrate of circadian rhythm modulation by timed feeding.

Continuous administration of growth hormone does not prevent the decrease of IGF-I gene expression in zinc-deprived rats despite normalization of liver GH binding.

To determine the role of reduced liver GH binding (GHR) in the decreased IGF-I observed in zinc-deficient (ZD) animals, we investigated the effects of GHR restoration on growth, insulin-like growth factor I (IGF-I) and its binding proteins (IGFBPs) in ZD rats. Rats were fed for 4 weeks a zinc-deficient diet (ZD Zn, 0 ppm) or a Zinc-normal diet (pair-fed or PF; Zn, 75 ppm). ZD rats received continuous s.c. infusion of bovine growth hormone (bGH) (100 microg/d) for the 4 weeks or for the last week of the study. Compared with pair-fed rats, zinc deficiency produced attenuated weight gain (-43%, P < 0.001), lower serum IGF-I and liver IGF-I mRNA (-52%, P < 0.001 and -44%, P < 0.05), lower serum IGFBPs (IGFBP-3 -66%, IGFBP-4 -48%, 34-29 kDa IGFBP cluster -53%, P < 0.05), lower liver GHR and its mRNA (-20 and -34%, P < 0.05) and lower serum growth hormone binding protein (GHBP) and its mRNA (-56 and -48%, P < 0.05; all comparisons vs PF rats). Exogenous bGH given continuously normalized the liver GHR, serum GHBP and their liver mRNAs, as well as circulating IGFBPs. Despite restoration of GHR and GHBP to normal, growth, serum IGF-I and its liver mRNA were not stimulated by GH infusion in ZD rats, indicating that IGF-I synthesis requires the presence of zinc in addition to GH, and that the lack of growth-promoting action of GH in zinc-deprived rats results from a defect beyond GH binding to its liver receptors.

After portal branch ligation in the rat, cellular proliferation is associated with selective induction of c-Ha-ras, p53, cyclin E, and Cdk2.

BACKGROUND In liver regeneration after portal branch ligation we previously showed that early cellular changes are observed in both the proliferating and atrophying liver lobes. They are therefore not indicative of future proliferative response. In this study we attempted to define precisely, in the same model, the time at which the cellular processes diverge between the lobes by measuring various parameters associated with cellular proliferation. We also investigated the possible role of inhibitors of cell proliferation in the absence of progression towards the S phase in the atrophying lobes. AIMS Expression of p53, c-Ha-ras, cyclin E, cyclin dependent kinase (Cdk2), transforming growth factor (TGF)-β, and interleukin (IL)-1α and IL-1β were assessed in relation to their potential role in proliferating and atrophying cellular phenomenons. METHODS Immunohistochemistry, northern blotting, western blotting, and reverse transcription-polymerase chain reaction were performed, mainly at time points corresponding to mid-G1/S phase progression (8–24 hours after surgery). RESULTS The common and thus most likely non-specific response was still evident 5–8 hours after surgery and included an increase in IL-1 mRNA as well as p53 and cyclin E proteins. From 12 hours onwards, p53, c-Ha-ras, cyclin E, and Cdk2 were selectively induced in proliferating lobes whereas IL-1β was predominantly activated in atrophying lobes. No changes in TGF-β or IL-1α expression were observed at the same time points in any of the liver lobes. CONCLUSIONS The initial response to portal branch ligation and thus probably to partial hepatectomy seems to be non-specific for at least eight hours. Thereafter, p53, c-Ha-ras, cyclin E, and Cdk2 seem to drive cellular proliferation while IL-1β is associated with cellular atrophy. In contrast, TGF-β and IL-1α do not seem to play a role in determining the commitment of cells towards atrophy or proliferation.

Serum Lactate Dehydrogenase Activity Increases in both Endogenous and Exogenous Hypercorticisms

Abstract Both endogenous and exogenous hypercorticisms are associated with a modest increase of the activity of serum lactate dehydrogenase. Considering both the wide use of this parameter and the frequent prescription of corticosteroids in clinical practice, awareness of this phenomenon is useful to avoid unnecessary investigations.