Pierre Leymarie

Drainage networks from grid digital elevation models

Current algorithms that deduce the drainage network from a digital elevation model (DEM) represented by a regular array of surface elevations share a fault: Unless the terrain is rugged, the derived water channels tend to flow in parallel lines along preferred directions engendered by the sampling grid orientation. We present a simple solution to the problem. A second difficulty is the presence of noise that creates artificial pits. We briefly describe a method which deals with pits in what we believe to be a more efficient manner for virtual memory environments than previous efforts. Our system has treated DEMs of nearly 9,000,000 pixels. We show how depth first search of the resulting drainage network permits segmentation of the DEM into basins by various criteria, analysis of stream-sediment anomaly dilution profiles, improved hydrological models and other applications.

Fetuses with Down's Syndrome detected by prenatal screening are more likely to abort spontaneously than fetuses with Down's Syndrome not detected by prenatal screening.

Objective Pregnancy with Downs Syndrome is often terminated by miscarriage. We have investigated whether prenatal screening would lead preferentially to the identification of fetuses with Downs Syndrome prone to abort spontaneously.

Involvement of the phospholipase C second messenger system in the regulation of steroidogenesis in small bovine luteal cells

We have previously suggested that the interaction between luteinizing hormone (LH) and its receptor, in addition to stimulating adenylate cyclase, is able to trigger a negative regulatory signal at a step beyond cAMP synthesis (Benhaim et al. (1987) FEBS Lett. 223, 321-326). The present study was conducted to determine whether the phospholipase C system is involved in this phenomenon. Small bovine luteal cells from pregnant cows were incubated with phospholipase C, A23187, an ionophore of calcium and/or phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), in the presence or absence of bovine luteinizing hormone or dibutyryl cyclic AMP (dbcAMP). A23187 associated with PMA was able to mimic the stimulatory effect of phospholipase C on basal progesterone production, whereas neither A23187 nor PMA alone had any effect. In the presence of high doses of LH, phospholipase C inhibited progesterone and cAMP production in a dose-dependent manner. A23187 and PMA were able to mimic the inhibition of progesterone synthesis but stimulated LH-induced cAMP accumulation. When cells were stimulated by high doses of dbcAMP, phospholipase C and A23187 but not PMA inhibited progesterone synthesis. These observations suggest that (1) phospholipase C can mimic the post-cAMP negative regulatory signal induced in vitro by high doses of LH, in the presence of an activation of PKC; (2) phospholipase C is also able to mimic in vitro the luteolytic properties of prostaglandin F2 alpha that we previously described (Benhaim et al. (1987) Prostaglandins 33, 227-239); and (3) under basal conditions or in the presence of low doses of LH, the phospholipase C system slightly stimulates steroidogenesis.

Maternal serum pregnancy‐associated plasma protein A (PAPP‐A) but not pregnancy‐specific β1‐glycoprotein (SP1) is a useful second‐trimester marker for fetal trisomy 18

The usefulness of early second‐trimester serum determinations of pregnancy‐associated plasma protein A (PAPP‐A) and pregnancy‐specific β1‐glycoprotein (SP1) in suspected cases of fetal trisomy 18 was examined in a retrospective, cross‐sectional study. Maternal serum PAPP‐A and SP1 in 20 cases of fetal trisomy 18 between 15 and 20 weeks of pregnancy, and in 40 controls matched for gestational age and storage time were determined and compared with hCG and free oestriol (uE3). In trisomy 18, the reduction in serum concentration was found to be more pronounced for PAPP‐A than for hCG and free oestriol. While none of the 40 control sera had a MoM below 0.2 for either PAPP‐A, hCG or uE3, in the trisomy 18 group (20 cases) 17 (85 per cent) of the PAPP‐A but only 5 (25 per cent) of the hCG and 4 (20 per cent) of the uE3 results were below the 0.2 MoM threshold. SP1 did not distinguish between controls and trisomy 18. This chromosomal abnormality is too rare a condition to justify maternal serum PAPP‐A determination in the second trimester as a routine procedure, but such a test can play a useful role whenever the risk of trisomy 18 is found to be only marginally increased after hCG and uE3 measurements. Copyright

The usefulness of hCG and unconjugated oestriol in prenatal diagnosis of trisomy 18

Objective To evaluate the usefulness of the two maternal serum markers, human chorionic gonadotrophin (hCG) and unconjugated oestriol (uE3), in the prenatal diagnosis of trisomy 18.

Androstenedione and testosterone biosynthesis by the adrenal cortex of the horse

An homogenate from cortical tissue of mare adrenals was incubated in the presence of tritiated pregnenolone. The (3H) androstenedione and the (3H) testosterone synthesized during the incubation were extracted, purified, and co-crystallized to constant specific activity in the presence of unlabeled carriers. The rate of conversion of pregnenolone to androstenedione and testosterone was of the order of 5 and 0.15 per cent respectively. The high ratio of (3H) androstenedione to (3H) testosterone observed in this study suggests that androstenedione is the main androgen produced by mare adrenals. It is concluded that adrenals could contribute to the production of blood androgens in normal as well as hyperandrogenic mares.

Stimulation by LH of cyclic AMP-dependent protein kinase activity in bovine corpus luteum slices

In vitro stimulation of corpus luteum slices by bovine pituitary LH is known to increase markedly the de novo synthesis of progesterone [l] . This specific action of LH has been shown to be mediated by an activation of the adenyl cyclase system [2] which increases the intracellular level of cyclic AMP [3], but the mechanism by which the cyclic nucleotide modulates the steroidogenic response to LH is still unknown. Recently a cyclic AMP dependent protein kinase has been partially purified by Menon [4] from the cytosolic fraction of cow corpus luteum. Its activation mechanism takes place according to the equation: R-C t Cyclic AMP e R-Cyclic AMP + C, where R and C represent regulatory and catalytic subunits respectively. Such a system is present in a large variety of tissues [5-l 31 . In the adrenal cortex it is activated by ACTH [ 141, in the testis [ 151 and the ovary [ 161 it can be activated by FSH and LH, and in the thyroid it is activated by TSH [ 171. Moreover this enzyme has been demonstrated to mediate the glycogenolytic effect of epinephrine and glucagon in liver [ 181, epinephrine in muscle [ 191 and the lipolytic effect of epinephrine in adipose tissue [20]. The present report demonstrates a specific in vitro stimulation by LH of the cytosolic protein kinase activity in slices of corpora lutea obtained from pregnant cows. Discrepancies between results obtained with low and high ionic strength homogenization media are discussed. 2. Materials and methods

Angiotensin II receptor type 1 on granulosa and thecal cells of rabbit preovulatory follicles

Specific, high-affinity angiotensin II (A II) receptors were observed on granulosa and thecal cells of preovulatory ovarian follicles from immature PMSG-treated rabbits. Scatchard analysis of 125I-[Sar1,Ile8]A II binding to freshly prepared cells was indicative of only one class of binding sites. Kd values were 0.26 +/- 0.11 nM and 0.18 +/- 0.02 nM, densities of A II receptors were 0.06 +/- 0.02 fmol/10(5) cells and 0.08 +/- 0.01 fmol/10(5) cells for granulosa and thecal cells, respectively. When cells were incubated for 48 h with hCG, Kd values were of the same order of magnitude, but the amount of A II receptors was increased 2-fold in granulosa and 4-fold in theca. Using subtype specific ligands (Losartan for AT1 and PD 123319 for AT2) in competitive binding experiments, A II receptors were found to be of the AT1 type on both granulosa and thecal cells freshly prepared or incubated 48 h in vitro. These results establishing the existence of high affinity AT1 receptors on the two cell types of the rabbit preovulatory follicles contrast with previous observations showing the presence of AT2 receptors on granulosa or theca from several species.

Effects of phorbol esters on steroidogenesis in small bovine luteal cells

The possible influence of an activator of protein kinase C, the tumor‐promoting phorbol ester, PMA (phorbol‐12‐myristate‐13‐acetate), upon small bovine luteal cell steroidogenesis was investigated in vitro. PMA had no significant effect on basal and dibutyryl cyclic AMP (dbcAMP)‐stimulated progesterone production but markedly modulated the LH‐stimulated progesterone and cAMP productions. PMA potentiated the LH‐stimulated cAMP accumulation whatever the dose of LH used. It also potentiated the LH‐induced progesterone production in the presence of low doses of LH. Paradoxically, in the presence of maximal or submaximal effective doses of LH, PMA exerted a time‐ and dose‐dependent inhibition of progesterone synthesis. Diacylglycerol was able to mimic the effects of PMA on LH‐induced steroidogenesis. These observations suggest that the Ca2+‐ and phospholipid‐dependent protein kinase C can modulate the regulation by LH of small bovine luteal cell steroidogenesis at a step before the synthesis of cAMP. They also suggest that the interaction between LH and its receptor is able to trigger a negative regulatory signal which would be only expressed for high doses of LH and in the presence of an activator of PKC.

Stimulation by LH of cytosolic protein phosphorylation in bovine luteal cells

It is now well established that LH exerts its stimulatory action on steroidogenesis in luteal tissue by increasing the intracellular level of cyclic AMP (CAMP) [I]. Moreover the CAMP dependent protein kinase activity has been shown to increase in the cytosol of bovine luteal tissue incubated in the presence of LH [2]. Two points suggest the implication of this type of enzyme in the stimulation of steroidogenesis. On one hand, the enzyme has been shown to mediate in other tissues several hormonal effects involving CAMP such as the glycogenolytic effect of epinephrine and glucagon in liver [3], epinephrine in muscle [4] and the lipolytic effect of epinephrine in adipose tissue [5]. On the other hand, two partially purified luteal enzymes, possibly involved in the steroidogenesis regulation by LH, have been shown to be slightly stimulated by incubation in the presence of CAMPdependent protein kinase. These enzymes are a “reconstituted” cholesterol side chain cleavage enzyme [6] and a sterol ester hydrolase enzyme [7]. In vitro hormonal induction of intracellular protein phosphorylation has been demonstrated for a small number of hormones: glucagon on hepatocytes [8,9] luteinizing hormone on Leydig cells [IO], and norepinephrine on adipocytes [ 111. The present work was an attempt to extend this latter type of findings to luteal cells stimulated in vitro by LH and to bring some further argument in favor of the implication of the CAMP-dependent protein kinase in the mechanism of the hormone action. Using a suspension of small bovine luteal cells which are known to be highly sensitive to LH [ 121 we have been able to demonstrate a dose-dependent stimulatory effect of this hormone on 32P incorpora-