María G. Campos

Inhibitory Effect of Sex Steroids on Guinea-Pig Airway Smooth Muscle Contractions

We assessed the possible inhibition of airway smooth muscle contraction by progesterone and pregnanolones (5 alpha and 5 beta-reduced). Progesterone and 5 beta-pregnanolone prevented histamine- or carbachol-induced contraction in isolated guinea-pig trachea and potency was related to their respective chemical structure; progesterone was the most potent inhibitor in a concentration-dependent manner. The steroids also exhibited calcium antagonist activities in this tissue as assessed by their action on calcium entry in depolarized preparations; this event involved the immediate blockade of the extracellular calcium influx in the muscle cell membrane, indicating a nongenomic action. Classical GABAA antagonists did not block the progesterone response, implying no involvement of the GABAA-receptor complex. Our results suggest a bronchodilating effect induced by sex steroids, and probably by other related compounds, before the genomic mechanisms take place. This nongenomic action of steroids could have potential therapeutic usefulness in the treatment of asthma.

Histological and sex steroid hormone receptor changes in testes of immature, mature, and aged chickens

Sex steroid hormone receptors play a central role in the regulation of reproduction in male chickens. In this work, we evaluated by histomorphometric methods and Western blot analysis changes in the number of the different cell populations and in the content of sex steroid hormone receptors in testes from immature (1.5-month-old), mature (12-month-old), and aged (48-month-old) chickens. The number of Sertoli cells, germ cells, and Leydig cells per area of testicular tissue markedly changed according to chicken age. The highest number of Sertoli and Leydig cells was found in testes of immature chickens, with a dramatic decrease in those of mature chickens; however, the number of germ cells was the highest in mature chickens in comparison with other ages. The content of androgen receptor diminished in testes of mature and aged animals in comparison with that of immature chickens. In contrast, the content of estrogen receptor alpha and progesterone receptor was higher in testes of mature animals than in other ages. Both progesterone receptor isoforms were expressed in a similar proportion in testes of immature and mature animals. Interestingly, progesterone receptor isoform A was the predominant isoform in aged animals. These results suggest that there are marked age-dependent changes in chicken testes histology and in sex steroid hormone receptors content that should contribute to sex steroid hormone actions, in this tissue throughout the lifespan of chickens.

Regulation of the Phosphoinositide-3 Kinase and Mitogen-Activated Protein Kinase Signaling Pathways by Progesterone and Its Reduced Metabolites in the Rat Brain

Several growth factors, such as vascular endothelial growth factor, brain‐derived neurotrophic factor, and insulin‐like growth factor‐I are involved in the actions of progesterone in the central nervous system. Previous studies in neuronal and glial cultures have shown that progesterone may regulate growth factor signaling, increasing the phosphorylation of extracellular‐signal regulated kinase (ERK) and the phosphorylation of Akt, components of the mitogen‐activated protein kinase (MAPK) and the phosphoinositide‐3 kinase (PI3K) signaling pathways, respectively. In this study, we have evaluated whether progesterone and its reduced metabolites, dihydroprogesterone and tetrahydroprogesterone, regulate PI3K and MAPK signaling in the brain of ovariectomized rats in vivo. Significant increases in the phosphorylation of ERK, in the expression of the catalytic (p110) and the regulatory (p85) subunits of PI3K and in the phosphorylation of Akt were observed in the hypothalamus, the hippocampus, and the cerebellum 24 hr after progesterone administration. Progesterone metabolites partially mimicked the effect of progesterone and had a stronger effect on MAPK and PI3K signaling in the hypothalamus than in the other brain regions. These findings suggest that progesterone regulates MAPK and PI3K signaling pathways in the central nervous system in vivo by direct hormonal actions and by mechanisms involving progesterone metabolites.

Immunization with neural-derived antigens inhibits lipid peroxidation after spinal cord injury

Lipid peroxidation (LP) is one of the most harmful mechanisms developed after spinal cord (SC) injury. Several strategies have been explored in order to control this phenomenon. Protective autoimmunity is a physiological process based on the modulation of inflammatory cells that can be boosted by immunizing with neural-derived peptides, such as A91. Since inflammatory cells are among the main contributors to lipid peroxidation, we hypothesized that protective autoimmunity could reduce LP after SC injury. In order to test this hypothesis, we designed two experiments in SC contused rats. First, animals were immunized with a neural-derived peptide seven days before injury. With the aim of inducing the functional elimination of CNS-specific T cells, for the second experiment, animals were tolerized against SC-protein extract and thereafter subjected to a SC injury. The lipid-soluble fluorescent products were used as an index of lipid peroxidation and were assessed after injury. Immunization with neural-derived peptides reduced lipid peroxidation after SC injury. Functional elimination of CNS-specific T cells avoided the beneficial effect induced by protective autoimmunity. The present study demonstrates the beneficial effect of immunizing with neural-derived peptides on lipid peroxidation inhibition; besides this, it also provides evidence on the neuroprotective mechanisms exerted by protective autoimmunity.

Effect of kauranes from Montanoa spp. on rat uterus

The effect of kaurenoic acid (from Montanoa frutescens), grandifloric and kauradienoic acid (from M. tomentosa) and 16α‐hydroxy‐ent‐kauran‐19‐oic acid and its methyl ester (from M. hibiscifolia) were assayed on the contractions of rat uterus induced by acetylcholine, oxytocin and serotonin. The four kauranes assayed inhibited the contractile activity induced by the three agonists through a mechanism independent of either β2‐adrenergic or H2‐histaminergic receptors present in uterine smooth muscle. Oestrogenized uteri treated with kauradienoic acid underwent histological changes including epithelial flattening and desquamation.© 1997 John Wiley & Sons, Ltd.

Anatomical differences in uterine sensitivity to prostaglandin F2α and serotonin in non-pregnant rats

The ovarian steroids regulate the sensitivity of a population of uterine receptors to prostaglandin F(2alpha), serotonin and oxytocin. However, the uterine sensitivity to prostaglandin F(2alpha) and oxytocin does not coincide with the estrogen-induced increase in the number of receptors. Anatomical differences affect the uterine sensitivity to agonists. We investigated whether anatomical differences between ovarian and cervical uterine regions modulate the hormone-regulated sensitivity to prostaglandin F(2alpha), serotonin and oxytocin. Non-cumulative concentration-response curves for these agonists were recorded for ovarian and cervical uterine segments from adult ovariectomized rats treated with 17beta-estradiol, 17beta-estradiol+progesterone, or vehicle. The ovarian segments displayed a higher maximal response (E(max)) to prostaglandin F(2alpha) and a lower E(max) to serotonin than the cervical segments. Both uterine segments displayed a similar sensitivity to oxytocin. The ovariectomized controls displayed the highest E(max) and the lowest effective concentration 50 (EC(50)) for oxytocin and prostaglandin F(2alpha). Anatomical differences between ovarian and cervical uterine regions modulate the hormonal regulation of uterine sensitivity to serotonin and prostaglandin F(2alpha) in the non-pregnant rat uterus.

Xanthorrhizol induces endothelium-independent relaxation of rat thoracic aorta.

Xanthorrhizol, a bisabolene isolated from the medicinal plant Iostephane heterophylla, was assayed on rat thoracic aorta rings to elucidate its effect and likely mechanism of action, by measuring changes of isometric tension. Xanthorrhizol (1, 3, 10, 30 and 100 microg/mL) significantly inhibited precontractions induced by KCI-; (60mM), noradrenaline (10(-6) M) or CaCl2 (1.0 mM). Increasing concentrations of external calcium antagonized the inhibitory effect on KCl-induced contractions. The vasorelaxing effect of xanthorrhizol was not affected by indomethacin (10 microM) or L-NAME (100 microM) in intact rat thoracic aorta rings precontracted by noradrenaline, which suggested that the effect was not mediated through either endothelium-derived prostacyclin (PGI2) or nitric oxide release from endothelial cells. Endothelium removal did not affect the relaxation induced by xanthorrhizol on rat thoracic aorta rings, discarding the participation of any substance released by the endothelium. Xanthorrhizol inhibitory effect was greater on KCI- and CaCl2-induced contractions than on those induced by noradrenaline. Xanthorrhizol inhibitory effect in rat thoracic aorta is likely explained for interference with calcium availability by inhibiting calcium influx through both voltage- and receptor-operated channels.

Chemical composition and antispasmodic effect of Casimiroa pringlei essential oil on rat uterus.

The Casimiroa pringlei essential oil was analyzed to determine its chemical composition. Its effect on rat uterine smooth muscle was studied and compared with verapamil. Pure commercial piperitone, eucalyptol, and alpha-terpineol, the major constituents of C. pringlei essential oil, were tested on the uterine tonic contraction induced by high-potassium depolarizing solution (KCl 60 mM).

Antitubercular Activity and the Subacute Toxicity of (−)-Licarin A in BALB/c Mice: A Neolignan Isolated from Aristolochia taliscana

BACKGROUND AND AIMS Tuberculosis remains a worldwide health problem and requires long-term treatment with several antibiotics; therefore, compliance problems and the emergence of multidrug resistance (MDR) are involved. (-)-Licarin A (LA) was isolated from diverse plants such as Aristolochia taliscana and possesses antimycobacterial, antiinflammatory, trypanocidal, and neuroprotective activities. The aim of the study was to determine the antitubercular and subacute toxicity of LA isolated from A. taliscana in BALB/c mice. METHODS The antitubercular activity of LA was tested in a TB murine model inducing disease with M. tuberculosis H37Rv or MDR. Mice were treated with LA (5 mg/kg) for 30 and 60 days; post/treatment, lung bacilli loads and pneumonia percentage were determined. The subacute toxicity of LA (21 days) was evaluated in healthy mice. After treatment, biochemical and hematological parameters were determined and main organs were analyzed histologically. RESULTS In animals infected with drug-sensitive or MDR strains, LA produced a significant decrease of pulmonary bacillary burdens at day 30 of treatment, and a significant pneumonia reduction at days 30 and 60 of treatment. Regarding subacute toxicity, LA administration during 21 days showed no abnormalities in main-organ macro- and microarchitecture. Biochemical and hematological parameters analyzed showed no statistical differences between control and treated groups. CONCLUSIONS (-)-Licarin A reduces pneumonia of mice infected with both mycobacterium strains. Also, subacute toxicity of LA exhibits no major signs of damage. Biochemical and hematological parameters and histological analyses indicate that LA caused no significant changes at the doses assayed.

Chronic administration of tibolone modulates anxiety-like behavior and enhances cognitive performance in ovariectomized rats

Hormone replacement therapy (HRT) may be prescribed to prevent the symptoms of menopause. This therapy may include estrogenic and/or progestin components and may increase the incidence of endometrial and breast cancers. Tibolone (TIB), which is also made up of estrogen and progestin components, is often used to reduce the impact of HRT. However, the effect of TIB on the processes of learning, memory and anxiety has yet to be fully elucidated. The aim of this study was to evaluate the long-term effect on learning, memory processes and anxiety in ovariectomized rats caused by different doses of TIB (0 mg/kg, 0.01 mg/kg, 0.1 mg/kg 1.0 mg/kg and 10 mg/kg, administered daily via the oral route for 18 weeks). Two behavioral animal models, the autoshaping and T maze models were employed. The concentrations of acetyl choline transferase (ChAT) and tryptophan hydroxylase (TPH) in the hippocampus were directly measured by Western blot. No significant changes were observed in the autoshaping model and spontaneous activity test. In the T maze, increased latency was observed with TIB doses of 1 and 10 mg/kg compared to the vehicle. We observed that the ChAT content decreased with increasing doses of TIB, whereas TPH content increased with doses of 1 and 10 mg/kg of TIB. These data indicate that high doses of TIB improved emotional learning, which may be related to the modulation of the cholinergic and serotonergic systems by TIB.