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L Gualandris

Publications and source records attributed to L Gualandris.

10 recordsLinked to original sources
PubMed1991

Urinary albumin excretion in normal pregnancy and pregnancy-induced hypertension.

We measured the urinary excretion of albumin in 67 healthy primigravidae, at monthly intervals, from 16 to 36 weeks of gestation and 12 weeks postpartum. Of the 67 primigravidae, 55 completed a normal pregnancy and 12 developed pregnancy-induced hypertension. In the latter group, an additional measurement of urinary albumin excretion was performed at 24 weeks postpartum. The aims of the study were: to look for changes of urinary albumin excretion during the progression of normal pregnancy; to assess if microalbuminuria could be an early feature of pregnancy-induced hypertension; to evaluate the effects of physical activity on the excretion of albumin in normal pregnancy and pregnancy-induced hypertension. In contrast with glomerular hyperfiltration and increased urinary total protein, two recognized characteristics of the pregnant state, we found that normal primigravidae, during the day, excrete significantly less albumin (p between less than 0.01 and less than 0.001) in comparison with the postpartum period and nonpregnant women. Normal primigravidae, as a group, showed parallel changes of urinary albumin excretion and diastolic blood pressure throughout pregnancy and postpartum, suggesting an important physiologic role of hemodynamic factors in regulating glomerular permeability to albumin. The daytime urinary albumin excretion in patients developing pregnancy-induced hypertension was significantly higher (p between less than 0.005 and less than 0.001) than in normal pregnancy from the 28th gestational week onwards. The increased urinary albumin excretion preceded the onset of hypertension and tended to persist long after blood pressure had returned to normal levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1990

From presumptive ectoderm to neural cells in an amphibian.

As an immediate consequence of neural induction during gastrulation, some neuroectodermal cells acquire the ability to develop a number of specific neuronal and astroglial features, without requiring subsequent chordamesodermal cues. Thus, cholinergic, dopaminergic, noradrenergic, gabaergic, somatostatinergic, enkephalinergic, etc. traits are expressed in cultures of neural plate and neural fold isolated from amphibian late gastrulae immediately after induction and cultured in a defined medium. These results strongly suggest that at the late gastrula stage, the neural precursor population does not yet constitute a homogeneous set of cells. It was of interest to know the origin of this heterogeneity. Is it a direct result of the process of neural induction itself, stochastic phenomena being involved or not at the cellular level, or does it reflect a pre-existing heterogeneity in the presumptive ectoderm? At the early gastrula state, presumptive ectoderm can be neuralized consecutively to its dissociation into single cells. Using this experimental model, we have demonstrated by means of immunological probes that neuralized presumptive ectodermal cells, without any intervention of the chordamesoderm (natural inducing tissue), can develop autonomously into glial and neuronal lineages. These data suggest the existence of diverse predispositions of presumptive ectodermal cells. Competent ectoderm seems to be a heterogeneous structure with cells presenting distinct neural predispositions that can emerge as a consequence of a permissive inductive signal without real specificity (such as a target tissue dissociation). Moreover, such a differentiated neuronal population includes neurons of the GABAergic and enkephalinergic phenotypes but not of the cholinergic, catecholaminergic, somatostatinergic, etc. phenotypes. These data show that the developmental program of ectodermal cells induced without interaction with the chordamesoderm appears restricted compared to the naturally induced ectoderm. Experiments are now under way to analyze such sequential neural events.

Amphibians↗
PubMed1987

Alterations in lateral lipid mobility in the plasma membrane of urodelean ectodermal cells during gastrulation.

The mobility characteristics of lipids were studied in the plasmalemma of dissociated presumptive ectodermal cells from embryos of Pleurodeles Waltl at different stages of development, from early blastula to early neurula, using a Fluorescence Recovery After Photobleaching technique (FRAP), after incorporation of the lipophilic fluorescent probe 5N-(hexadecanoyl)-aminofluoresceine (HEDAF) into the cell plasma membrane. At all stages of development, fluorescence recovery was found to extrapolate to 100%, which suggested that the lipid phase in these plasma membranes can be regarded as dynamically homogeneous (no immobilized fraction). It appears as a continuum over a wide cell surface area, in which lipids are free to move laterally. The lateral diffusion coefficient of the probe, obtained from statistical analysis of the fluorescence recovery data, was found to decrease significantly from blastula to gastrula, slightly increasing at the neurula stage. These changes in the dynamic properties of the lipid probe HEDAF during gastrulation suggest that the lipid phase of the plasma membrane of these ectodermal cells undergo structural changes. The results lend support to the idea that the plasma membrane of these cells is actively involved in the morphogenetic movements which characterize the development of the embryo.

Animals↗
PubMed1987

Cross-linking of membrane glycoconjugates is not a sufficient condition for neural induction by concanavalin A.

Tetravalent native concanavalin A (Con A) has a neural inducing effect on amphibian presumptive ectoderm. The divalent dimeric form of this lectin, succinylated Con A (Succ-Con A), is devoid of neuralizing action on this target tissue in Pleurodeles waltlii. These results suggested that cross-linking of Con A receptors on the cell membrane (which is not provoked by the divalent lectin) might be required for neural induction. To test this possibility, Succ-Con A binding sites were experimentally cross-linked after binding of Succ-Con A to the target cell surface, using anti-Con A antibodies. The combination of these two agents mimics the cross-linking of Con A. The results showed that cross-linking alone, either by treatment with Succ-Con A and anti-Con A antibodies, or with the lectins WGA and PHA, which also cross-link cell surface binding sites, was not able to induce neuralization. This suggested that the inductive action of Con A cannot be explained in terms of receptor cross-linking.

Animals↗
PubMed1987

Structural alteration of the target plasma membrane affects reception but not expression of the neural inductive signal.

We have previously reported that incubation of presumptive neuroectoderm in a solution of lectin (soybean agglutinin or garden pea agglutinin at 50 micrograms ml-1, 30 min) prior to its association with blastoporal lip inhibits neural induction (Duprat et al., 1982). We have also shown that incubation of presumptive ectoderm immediately after its association with blastoporal lip does not prevent neural induction. The same pattern of fluorescence on the ectodermal surface was observed when incubation with lectin was carried out before or after association of ectoderm with blastoporal lip. Although a particular molecular organization of the plasma membrane of the target ectoderm appears to be essential for reception or initiation of neural induction, the subsequent transmission and expression of this neural information does not appear to be affected by structural modifications of the target membrane. Similar studies performed using the inducer Con A indicated that the experimentally induced signal differed from the natural one.

Animals↗
PubMed1986

Neural induction and in vitro initial expression of neurofilament and tetanus toxin binding site molecules in amphibians.

Tetanus toxin (Tt) binding site and neurofilament (NIF), the intermediate-sized filaments, are neuronal markers essentially described in mammals and birds; are these molecular markers present in urodela neuronal cells and are they expressed immediately after neural induction? Our findings are based on immunofluorescent localization of NIF and Tt proteins using three previously characterized antisera against 200 kDa and 70 kDa neurofilament components and against fragment IIc derived from purified tetanus toxin. Embryonic undifferentiated neuronal cells from Pleurodeles waltlii neural plate and/or neural fold (early neurula stage) are cultured isolated in vitro without further chordamesodermal influence. At the beginning of the culture none of the undifferentiated neuronal precursors bind antibodies against NIF or Tt components. The binding is detected when phenotypical differentiation takes place (2/3-day cultures). Both the cell bodies and the cell processes are stained. After 2-3 weeks, immunostaining of the neurones is very distinctive and bright; the non-neuronal cultured cells do not exhibit any labelling. These observations indicate the early acquisition of NIF and Tt binding site expression by neuronal precursor cells (late gastrula stage).

Animals↗
PubMed1986

Effect of short-term cyclosporine administration in rats on renin-angiotensin and thromboxane A2: possible relevance to the reduction in glomerular filtration rate.

A short-term treatment with Cyclosporine A (CyA) induces a decrease in glomerular filtration rate (GFR), promptly reversible after withdrawal of the drug. Several lines of evidence are now available as to indicate that this phenomenon is dependent on a hemodynamic perturbation resulting in a renal vasoconstriction. With the present work we have examined the relationship between the reduction in GFR which follows a short-term administration of CyA in rats and the biochemical changes in renin-angiotensin system and renal arachidonic acid metabolism. Our results show that CyA administration (25 mg/kg/day) for 45 days stimulates renin-angiotensin system with an increase in plasma renin activity. These changes are not accompanied by a parallel increase in the renal synthesis of vasodilatory prostaglandin E2 and prostacyclin as it occurs in other conditions of renin-angiotensin stimulation. At variance glomerular synthesis and urinary excretion of thromboxane A2 (TxA2) are increased progressively during CyA treatment. These changes in renal Tx precede the increase in serum creatinine and the decrease in GFR thus indicating that TxA2 might be an additional factor potentiating the effect of angiotensin II on glomerular hemodynamics. In conclusion the early reduction in GFR which follows daily administration of CyA in rats might be the result of a synergic action of angiotensin II and TxA2 on vascular tone and mesangial contraction which is not modulated by an increase in glomerular vasodilatory prostaglandins. If this explanation may be applied to early reduction in GFR observed in humans treated with CyA before tubular toxicity develops needs to be investigated further.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Neural induction: embryonic determination elicits full expression of specific neuronal traits.

In Pleurodeles waltl, the early neuronal differentiation of precursor cells from late gastrula stage has been studied by culture in vitro from either isolated neural plate (NP) or isolated neural fold (NF). The aim of this study was to delineate the information acquired by ectodermal target cells during neural induction. By culturing these cells in vitro either with or without the underlying chordamesoderm, we showed that in the absence of chordamesodermal influence such NP or NF cells exhibited a high degree of biochemical and morphological differentiation as revealed by the synthesis and the storage of neurotransmitters, the activity of specific enzymes, as well as by the expression of neuronal markers: specific changes in cell surface carbohydrates, tetanus toxin binding sites and neurofilament polypeptides. Remarkable changes in the cell adhesive properties were the first events observed in the different central (NP) and peripheral (NF) types. In cocultures the chordamesodermal cells exert a beneficial influence on this differentiation, specially increasing acetylcholine synthesis. There are some differences between central (NP) or peripheral (NF) neuroblast response to this further notochord or mesodermal influence.

Acetylcholine↗
PubMedDate not supplied

Neural induction.

The molecular mechanism of neural induction of embryonic cells is an important but poorly understood problem in neuroembryology. Glycoconjugates in the target cell plasma membrane and/or its structural organization play a key role in the reception of the inductive signal. It is the competent target tissue itself which probably contains the capacity and specificity for neuralization. However, the mechanism of transmission of the signal which leads to activation of the intracellular machinery involved in the process of neural determination remains to be elucidated. With respect to the information acquired by the target cells during neural induction, and the early events in differentiation, neuronal precursor cells have been shown to have acquired the potential to display a high degree of biochemical and phenotypic differentiation, even in the absence of further embryonic influences.

Animals↗