Juana Gutiérrez de Diego

Effect of Pinealectomy on Liver Insulin and Glucagon Receptor Concentrations in the Rat

The studies described here were undertaken to characterize the hepatic insulin and glucagon receptors of control (C), pinealectomized (Pn), and melatonin‐treated pinealectomized (Pn + Mel) rats. Compared with C rats, an increase in plasma glucose and glucagon levels and a reduction in circulating concentrations of insulin in Pn animals were observed. Melatonin treatment of Pn rats reverses all three parameters toward the normal values. In liver membranes, insulin binding was lower in Pn than in C rats, and glucagon binding was greater in Pn than in C animals; in Pn + Mel rats both insul in and glucagon binding reverse toward the normal values that were observed in C rats. The modifications in hormone binding reflect changes in the number of receptors but not in the affinity constants. The time courses of hormone association and dissociation from liver membranes were similar in all three experimental groups. The degradation of both hormones by liver membranes was similar in all three groups. Insulin receptor degradation also was similar in the three groups, while glucagon receptor degradation was similar in the liver membranes of C and Pn rats but smaller in Pn + Mel animals. These findings suggest that the pineal gland may modulate the circulating levels and liver receptor concentrations of insulin and glucagon. In addition, our results indicate that insulin and glucagon did not induce a down‐regulation of liver receptors in Pn rats.

Effect of Pinealectomy and of Diabetes on Liver Insulin and Glucagon Receptor Concentrations in the Rat

The studies described in this paper were undertaken to characterize the circulating and hepatic insulin and glucagon receptor concentrations of control (C), diabetic (Db), and pinealectomized‐diabetic (Pn + Db) rats. Compared with C rats, an increase in plasma glucose and glucagon levels and a reduction in circulating insulin concentrations in Db animals was observed; these differences were greater in Pn + Db rats. In liver membranes, insulin binding was lower in Db and in Pn + Db than in C rats, and glucagon binding was greater in Db and in Pn + Db than in C rats. The modifications in hormone binding did not reflect changes in the affinity constants. The time courses of hormone association and dissociation from liver membranes were similar in all three experimental groups. The degradation of both hormones and their receptors was similar in all three groups. These findings indicate that in either pinealectomized‐diabetic or diabetic rats there were significant changes in the circulating and liver insulin and glucagon receptor concentrations and that the changes in the circulating levels of both pancreatic hormones were more pronounced in pinealectomized‐diabetic animals. In addition, the absence in Db and in Pn + Db rats of the insulin and glucagon down‐regulation of their own receptors could further modify metabolic activities in these animals.

Modeling the Arabidopsis seed shape by a cardioid: Efficacy of the adjustment with a scale change with factor equal to the Golden Ratio and analysis of seed shape in ethylene mutants

A new model for the description of Arabidopsis seed shape based on the comparison of the outline of its longitudinal section with a transformed cardioid is presented. The transformation consists of scaling the horizontal axis by a factor equal to the Golden Ratio. The elongated cardioid approximates the shape of the Arabidopsis seed with more accuracy than other figures. The length to width ratio in wild-type Columbia Arabidopsis dry seeds is close to the Golden Ratio and decreases over the course of imbibition. Dry seeds of etr1-1 mutants presented a reduced length to width ratio. Application of the new model based on the cardioid allows for comparison of shape between wild-type and mutant genotypes, revealing other general alterations in the seeds in ethylene signaling pathway mutants (etr1-1).

Characterization of glucagon receptors in liver membranes and isolated hepatocytes during rat ontogenic development

We studied the functional properties of hepatic glucagon receptors during rat development. Glucagon binding to liver membranes and isolated hepatocytes was significantly less in foetuses and weaning rats than in adult animals, reflecting changes in the number of receptors rather than any change in receptor affinity for the hormone. After correcting for the smaller surface area of foetal hepatocytes, glucagon receptor concentrations were still lower in foetuses than in adult rats. The time courses of glucagon association to liver membranes and of glucagon receptor degradation of prenatal and postnatal rats were similar, while inactivation of glucagon by liver membranes was significantly lower in foetal than in adult rats. Also, glucagon-stimulated production of cAMP was smaller in younger rats. These findings suggest that, according to several criteria, glucagon receptors in the foetus are functionally normal and their delayed development may be important for the metabolic processes occurring during the perinatal age.

Expression of cysteine proteinase mRNA in chickpea (Cicer arietinum L.) is localized to provascular cells in the developing root

Summary A full-length cDNA clone encoding a chickpea (Cicer arietinum L.) cysteine proteinase, homologous to rd21gene of Arabidopsis as well as to cysteine proteinase genes from legumes, was isolated. Expression of the mRNA in growing radicles has been located in a very precisely defined longitudinal zone in the stele, corresponding to the area of differentiation of vascular tissues. This result suggests that the encoded proteinase may be involved in programmed cell death events that precede vascular development.

Dynamic analysis of Arabidopsis seed shape reveals differences in cellulose mutants

In a previous work, the shape of Arabidopsis seed was described as a cardioid modified by a factor of Phi. In addition, J index was defined as the similarity of the seed (in an orthogonal, bi-dimensional image) to a cardioid, thus allowing the quantitative comparison of seed shape in seeds of varieties and mutants at different stages of development. Here, J index is used for modeling changes in seed morphology during the dynamic process of seed imbibition before germination. The analysis was carried out by means of a general linear model with two fixed factors (genotype and time) applied to two Arabidopsis varieties: Columbia and Wassilewskija and two mutants in cellulose synthesis: prc1-1 (CESA6 in Columbia) and kor1-1 (in Wassilewskija). Equations representing the changes in seed form during imbibition are given. The analysis of changes in seed shape by this procedure provides (1) a quantitative method to record changes in seed shape and to compare between genotypes or treatments showing the time points with maximum differences, and (2) the observation of remarkable differences between wild-type seeds and mutants in cellulose biosynthesis, indicating new phenotypic characteristics previously unknown in the latter. While wild-type seeds increase their J index values during imbibition, in the cellulose mutants J index values decrease. In addition, shape comparisons were done with other mutants. Seeds of ga1-1 mutants behave like cellulose mutants, whereas different ethylene mutants present varied responses. Quantitative analysis of seed morphology is a new basis for the record of differences between wild-type and mutants as well as for phenotypic characterization.

In vitro evaluation of the antielastase activity of polycyclic β-lactams.

A series of bi- and tricyclic β-lactam compounds was synthesized and evaluated as inhibitors of cleavage of synthetic substrates in vitro by the serine proteases Human Leukocyte Elastase (HLE), Human Leukocyte Proteinase 3 (HLPR3) and Porcine Pancreatic Elastase (PPE). The obtained results have permitted us to describe a homobenzocarbacephem compound as HLE and HLPR3 inhibitor, to observe the positive effect that the styryl group exerts on the HLE inhibitory activity in polycyclic β-lactam compounds and to conclude that the hydroxyl function decreases the HLE inhibitory activity or rules it out completely.

Characterization of glucacon receptors in Golgi fractions of fetal rat liver

The present study was designed to determine if Golgi fractions from fetal rat liver contain glucagon receptors and to characterize the properties of such receptors. Purification patterns of liver plasma membranes and Golgi fractions from fetal and adult rats were similar, as verified by morphological and biochemical approaches. Glucagon binding was greater in plasma membranes of adult than fetal rats, while in Golgi fractions glucagon binding was similar in both groups. The modifications in glucagon binding reflect changes in glucagon receptors. Glucagon association and glucagon receptor inactivation by liver membranes were similar in the two groups of animals, while glucagon degradation was lower in fetal than in adult rats.

Mitochondrial structures during seed germination and early seedling development in Arabidopsis thaliana

Abstract Mitochondrial morphology and evolution have been observed during seed germination and early seedling development in Arabidopsis thaliana line 43a9 (ecotype Columbia) expressing green fluorescent protein in these organelles. Fluorescence, confocal and electronic microscopy images reveal that mitochondrial development goes through different stages, and that the organelle structure varies with cell types during these processes. Mitochondria develop from larger, isodiametric structures pre-existent in the dry seed called promitochondria. After germination, variations in mitochondrial morphology occur synchronously with cell differentiation and cell division in the course of early root development. Some promitochondria develop into intermediate structures resembling the syncytial organelles. These structures have been described in certain plants under hypoxia as intermediates for the formation of mature mitochondria. On the other hand, other promitochondria temporarily remain in the cells of the root apex