Marisa Puerta | Universidad Complutense de Madrid (original) (raw)

Papers by Marisa Puerta

Thermal Balance in Health and Disease, 1994

The great heat generating power of brown adipose tissue (BAT) has a profound influence in energy ... more The great heat generating power of brown adipose tissue (BAT) has a profound influence in energy balance. Cold-acclimated animals become hyperphagic to sustain the high substrate combustion in brown fat depots without reducing body energy stores. On the other hand, the low activity of brown fat in obese animals contributes to the low energy expenditure and the development of obesity. Reproduction is one of the major energy challenges in the mammalian life cycle. On viewing the profound influence of BAT in energy balance, it seems not surprising that brown adipose tissue is suppressed during late pregnancy and lactation as a way to save substrates for growth of mother and litter (1,13). Female sex steroids, 17s-oestradiol and progesterone seem to be involved in such disactivation. Brown adipocytes isolated from female rats with high plasma levels of sex steroids show a lower responsiveness to noradrenaline (NA) -as revealed by the lower increase in respiration rate after NA addition to the incubation medium-than that displayed by adipocytes isolated from untreated controls (10). The decreased responsiveness of brown adipocytes when plasma levels of oestradiol are high leads to a reduction of BAT thermogenic activity in cold-acclimated rats (11). This poses two additional questions, i.e., are oestradiol-treated females rats hypothermic? or are there alternative adjustments that compensate for the low BAT thermogenesis? On the contrary, progesterone impairment of responsiveness to NA does not decrease BAT thermogenesis (9). This raises another question, how progesterone treated animals maintain BAT thermogenesis despite the low responsiveness of brown adipocytes to NA? As in the case of oestradiol a compensatory adjustment was hypothesized.

Canadian Journal of Zoology, 2001

In this study two experiments were run in parallel. To evaluate the possible influence of moult a... more In this study two experiments were run in parallel. To evaluate the possible influence of moult and age on differential white blood cell (WBC) counts, we captured juvenile and adult house sparrows (Passer domesticus) and housed them in outdoor aviaries. Blood was collected twice, before and after moult. Numbers of basophils, lymphocytes, and monocytes were higher in juveniles than in adults, whereas numbers of eosinophilic cells were similar in the two age groups. Moult induced an increase in basophils and monocytes in both juveniles and adults. This indicates that moult and age impose different immunological challenges on house sparrows. To evaluate the effect of testosterone on differential WBC counts, some house sparrows in aviaries received testosterone during the moult period. Testosterone administration reduced, though not significantly, the number of all WBC types in juveniles, and therefore appeared to have an nonspecific effect. However, the number of lymphocytes increased only in adults, which suggests a specific effect on this cell type in this age group.

Female birds may adjust their offspring phenotype to the specific requirements of the environment... more Female birds may adjust their offspring phenotype to the specific requirements of the environment by differential allocation of physiologically active substances into yolks, such as androgens. Yolk androgens have been shown to accelerate embryonic development, growth rate and competitive ability of nestlings, but they can also entail immunological costs. The balance between costs and benefits of androgen allocation is expected to depend on nestling environment. We tested this hypothesis in a multibrooded passerine, the spotless starling, Sturnus unicolor. We experimentally manipulated yolk androgen levels using a between-brood design and evaluated its effects on nestling development, survival and immune function. Both in first and replacement broods, the embryonic development period was shorter for androgen-treated chicks than controls, but there were no differences in second broods. In replacement broods, androgen-treated chicks were heavier and larger than those hatched from control eggs, but this effect was not observed in the other breeding attempts. Androgen exposure reduced survival with respect to controls only in second broods. Regarding immune function, we detected nonsignificant trends for androgen treatment to activate two important components of innate and adaptive immunity (IL-6 and Ig-A levels, respectively). Similarly, androgen-treated chicks showed greater lymphocyte proliferation than controls in the first brood and an opposite trend in the second brood. Our results indicate that yolk androgen effects on nestling development and immunity depend on the environmental conditions of each breeding attempt. Variation in maternal androgen allocation to eggs could be explained as the result of context-dependent optimal strategies to maximize offspring fitness

Physiological and Biochemical Zoology, 2017

Avian embryos are exposed to yolk androgens that are incorporated into the egg by the ovulating f... more Avian embryos are exposed to yolk androgens that are incorporated into the egg by the ovulating female. These steroids can affect several aspects of embryo development, often resulting in increases in overall size or the speed of growth of different traits. However, several studies suggest that they also entail immune costs to the offspring. In this study, we explored whether variation in yolk androgen concentration affected several measures of the constitutive and cell-mediated immune axes in the spotless starling (Sturnus unicolor). Using a within-brood design, we injected different doses of androgens (testosterone and androstenedione) into the eggs. Our study showed that experimentally increased yolk androgens led to sex-specific immunosuppression in both the innate and adaptive axes of the immune system. Both cell-mediated immune response (CMI) and lysozyme activity decreased with increasing androgen levels injected into the egg in the case of male nestlings, whereas there were no effects on females. The effects that we found were always linear: no quadratic or threshold patterns were detected. We found no effects of the experimental treatment in hemolysis or agglutination capacity, but these measures were negatively correlated with CMI, suggesting negative correlation among different branches of the immune system. Blood (trypanosomes and hemosporidians) and intestinal (coccidia) parasites were not affected by the experimental increase of yolk androgen levels. Our results show that in our study species yolk androgens induce immunosuppression in some axes of the male nestling immune system. Further studies should analyze the proximate causes for these contrasting effects in different axes of the immune system and the reason for the differential impact on males and females.

Acta Oecologica, 2013

According to the Cort-Fitness Hypothesis, higher stress levels (glucocorticoids) in vertebrates a... more According to the Cort-Fitness Hypothesis, higher stress levels (glucocorticoids) in vertebrates are correlated to lower fitness. However, recent studies have failed to validate this hypothesis. A proposed wider framework suggests that reproduction can be perceived as an overload adds up to other environmental challenges that individuals must adjust to. In this case, elevated glucocorticoids could help individuals to allocate resources to reproduction without comprising other functions, leading to the expectation of a positive cort-fitness relationship. This has been proposed as the Cort-Adaptation Hypothesis. Stress levels result from a complex interaction between the environment and the neuroendocrine system of animals. Accounting for physiological functions involved in how animals cope with their environment would help to clarify the relationship between glucocorticoids and animal performance. We used roe deer (Capreolus capreolus) inhabiting diverse habitats in the Iberian Peninsula to: i) test the Cort-Fitness and Cort-Adaptation hypotheses by indexing fitness using a comprehensive physiological approach which takes into account fundamental physiological functions and their trade-offs; and ii) evaluate the link between primary productivity and individuals' condition in a seasonal environment. We evaluated spatial and temporal variation in stress levels, reproductive hormone levels, nutritional status and immune function from fecal samples collected in 2010. Lower stress levels were related to better condition in non-reproductive seasons but not to higher primary productivity. In contrast, stress levels were always positively related to reproductive condition, which was better in most productive habitats. Summer and winter were the less productive seasons and the more challenging for the species in the habitat gradient studied. In winter, reproductive condition traded off against immune function being biased toward immune function in less productive habitats. In summer reduced primary productivity limited roe deer nutritional and immunological condition but not reproductive condition. Overall our results match both the Cort-Fitness and Cort-Adaptation Hypotheses.

Comparative Biochemistry and Physiology Part A: Physiology, 1993

We studied the blood composition of common cranes (Grus grus) along the wintering period (October... more We studied the blood composition of common cranes (Grus grus) along the wintering period (October-March). 2. Plasma proteins decreased along the winter period whereas plasma urea increased. Both parameters were highly correlated. 3. Plasma levels of uric acid, triglycerides and cholesterol did not change during the winter. Young birds showed higher levels of plasma triglycerides. 4. Red blood cell number, hematocrit and blood hemoglobin content were similar in young and adult birds. Lower values of hematocrit and red cell number were recorded in early autumn. 5. Total white blood cell number did not change during the winter, young birds showing higher numbers than adults. Lymphocyte number decreased from November to March while heterophil counts increased.

Investigacion Y Ciencia, 1996

Pflugers Arch Eur J Physiol, 1994

Oestradiol and progesterone change b3-adrenergic receptor affinity and density in brown adipocytes

Canadian Journal of Physiology and Pharmacology, 1994

It has been previously shown that responsiveness to noradrenaline is reduced in brown adipocytes ... more It has been previously shown that responsiveness to noradrenaline is reduced in brown adipocytes isolated from estradiol-treated rats. The possibility that high plasma levels of progesterone could also alter adrenergic response was checked. The oxygen consumption of brown adipocytes isolated from control and progesterone-treated rats was monitored in basal conditions and in the presence of increasing concentrations of noradrenaline. In both situations, cells isolated from treated animals showed a lower respiratory rate than those from control animals. These results suggest that not only estradiol but also progesterone could modulate the adrenergic response of brown adipocytes. The study of α1- and β-adrenergic responses indicates that the β-response parallels the general reduction in oxygen consumption, although the α 1-response seems to be more deeply depressed. Estimation of cell number in brown fat depots indicates some hyperplasia induced by progesterone; this increase in cell n...

The Biochemical journal, 1997

Young female rats of 160-180 g were implanted with osmotic minipumps releasing 3.0 micromol/day p... more Young female rats of 160-180 g were implanted with osmotic minipumps releasing 3.0 micromol/day per kg of oleoyl-oestrone in liposomes (Merlin-2) into the bloodstream for up to 14 days. Merlin-2 induced a loss of appetite in the first days, later recovered, and a decrease in body weight of 7%, which contrasts with the 15% increase in controls during the 2-week period. Neither plasma glucose nor urea was affected by treatment, but liver glycogen increased by 50% in 14 days. Insulin decreased slightly with Merlin-2 treatment. Plasma corticotropin (ACTH) and corticosterone showed a transient increase by day 6 of treatment. The expression of the ob gene in adipose tissue fell during the period studied to practically nil on day 14; circulating leptin levels decreased more than 70% from day 1 to day 14. Oestrone levels increased from 0.3 nM (controls) to a maintained 40-60 nM level for the rest of the experiment. Oleoyl-oestrone levels first increased 4-fold, to decrease again to the init...

J Nutr Biochem, 2004

Estradiol is a potent hypophagic agent that reduces food intake and body weight without a concomi... more Estradiol is a potent hypophagic agent that reduces food intake and body weight without a concomitant fall in plasma leptin levels. We investigated whether the hypophagic effect of estradiol is mediated by stimulating POMC and/or inhibiting NPY neuronal pathways in the hypothalamus, which respectively inhibit and stimulate feeding. We examined hypothalamic gene expression of Ob-Rb, NPY, POMC, MC4-R, and AgRP in intact Wistar rats treated with estradiol for 48 hours. Food intake and body weight were reduced in estradiol-treated rats but fat mass was unchanged; plasma leptin and insulin levels were not significantly different from untreated, freely fed controls. In untreated rats that were pair-fed to match the estradiol-treated group, body weight was also reduced without changes in fat mass, although leptin and insulin levels decreased significantly. Ob-Rb expression was increased in both hypophagic groups despite serum leptin were only decreased in pair-fed animals, suggesting an estradiol-stimulating effect on Ob-Rb expression. No significant differences were found in POMC, AgRP, or MC4-R expression among any of the experimental groups. A significant but small decrease in NPY expression was also found in both hypophagic groups; this was explained by the combined effect of both surgery and reduced food intake. These results indicate that estradiol mediated hypophagia in intact rats could be brought about by an enhanced hypothalamic leptin sensitivity but is unlikely to be driven by changes in NPY or melanocortin system.

Archivos de farmacología y toxicología

Revista española de fisiología

Heat-acclimated rats show lighter IBAT deposit with different gross composition and lower GDP-bin... more Heat-acclimated rats show lighter IBAT deposit with different gross composition and lower GDP-binding than controls at thermoneutrality. A thermal disactivation of the tissue is then inferred. Cafeteria regime increased IBAT mass and GDP-binding when offered to rats at a thermoneutral ambient temperature. These results indicate that BAT thermogenesis at thermoneutrality is not the lowest one of the tissue and that diet-induced thermogenesis can take place even at thermoneutrality.

Journal of Endocrinology

Oestradiol is a potent anorectic agent that reduces both food intake and body weight. Since lepti... more Oestradiol is a potent anorectic agent that reduces both food intake and body weight. Since leptin is known to reduce food intake, we first analysed if the anorectic effect of oestradiol is driven by an increased leptin concentration in either cerebrospinal fluid or plasma. Oestradiol also reduces body weight and fat mass. Accordingly, a decrease in plasma leptin concentration can also be expected after an oestradiol-driven reduction in fat mass. To test this hypothesis was the second aim of this study. Female Wistar rats received oestradiol chronically during 14 days. During the first week of treatment there was a reduction in food intake, body weight and fat mass that returned to initial values during the second week, but no changes in ob mRNA levels were found in white adipose tissue depots. There was no effect of treatment or time on plasma and cerebrospinal fluid leptin concentrations. Therefore, the anorectic effect of oestradiol is not driven by an increase in leptin concentration either in plasma or in cerebrospinal fluid, and the reduction in fat mass that oestradiol produces is not followed by a reduction leptin concentration.

Pflügers Archiv : European journal of physiology, 1987

Both virgin and pregnant rats were maintained at two different ambient temperatures (28 degrees C... more Both virgin and pregnant rats were maintained at two different ambient temperatures (28 degrees C and 10 degrees C) for 19 days. Virgin rats maintained their daily food intake and body weight at both temperatures. At 28 degrees C pregnant rats showed a greater daily food intake and body weight than virgin ones and their brown adipose tissue suffered regressive changes in composition when compared with brown fat of virgin rats. At 10 degrees C the increases in daily food intake and body weight of pregnant rats took place from day 15-16 of pregnancy onward and foetuses taken from these pregnant rats were smaller than those taken from pregnant rats at 28 degrees C. It is concluded that pregnant rats at thermoneutrality, although hyperphagic, do not show diet-induced thermogenesis. However, it is proposed that pregnant rats in the cold may show BAT cold-induced thermogenesis.

Temperature Regulation, 1994

Comparative biochemistry and physiology. C, Comparative pharmacology and toxicology, 1983

1. Bile of guinea-pigs who have received [14C]-histamine contains 14C. 2. Both sexes eliminate in... more 1. Bile of guinea-pigs who have received [14C]-histamine contains 14C. 2. Both sexes eliminate in bile about 3.5% of the 14C administered. 3. Histamine metabolites in bile are mainly methylimidazolacetic acid and imidazolacetic acid and its riboside. 4. Acetylhistamine is present in bile. 5. Male bile contains more free histamine and methylhistamine than that of females.

The Biochemical journal, 1991

Cold acclimation increased the activities of superoxide dismutase, catalase, total and selenium (... more Cold acclimation increased the activities of superoxide dismutase, catalase, total and selenium (Se)-dependent glutathione peroxidases (GPx) and glutathione reductase by 2-4-fold in the brown adipose tissue (BAT) of cold-acclimated rats. Nevertheless, when expressed per unit protein, the antioxidant enzyme activities were unaltered. Sensitivity to lipid peroxidation and GSH levels both increased by one order of magnitude in the cold on a per weight basis and were still 3-5 times greater in the cold when expressed per mg of protein. We suggest that activation of BAT leads to a large increase in the potential for lipid peroxidation and that the tissue responds to this challenge by increasing practically all of its antioxidant defences. Nevertheless, GSH, and possibly GPx activity, seem to be the principal defences involved in adaptation of the tissue to a higher sensitivity to peroxidative damage after activation.