Expresión de VEGF-A y VEGFR2 en Miocardio de Pollos Tratados con Ácido Acetilsalicílico (AAS) / VEGF-A and VEGFR2 Expression in Chicken Myocardium Treated with Acetylsalicylic Acid (AAS)

RESUMEN: Los niveles de VEGF y su unión a sus receptores son etapas claves en la regulación de la angiogénesis. El ácido acetilsalicílico (AAS), ampliamente utilizado en tratamiento post infarto al miocardio ha mostrado poseer un efecto antiangiogénico en modelos tumorales. Este efecto potencialmente contraproducente requiere ser estudiado en miocardio. El objetivo del presente trabajo es cuantificar el efecto de AAS y de ácido salicílico (AS) sobre la vascularización en membrana alantocoriónica (MAC) y sobre los niveles de VEGF-A y VEGFR2 en miocardio de embriones de pollo. Para ello, treinta fetos de pollo White Leghorn fueron instilados a los 10 días de gestación con 60 µL de DMSO 0,1 % (control) o conteniendo además 0,3 µmol de AAS o AS. A las 48 horas se realizó procesamiento histológico de MAC para recuento de vasos sanguíneos y de tejido cardíaco para cuantificar VEGF-A y VEGFR2 por inmunohistoquímica. La inmunorreactividad fue cuantificada mediante Image J. Tanto AAS como AS disminuyeron la densidad microvascular de MAC. En miocardio, AAS aunque no AS, disminuyó la concentración de VEGFR2. No hubo efecto sobre VEGF-A. En nuestro modelo experimental, fetos de pollo a los 10 días de gestación también se observó el efecto inhibidor de AAS sobre la angiogénesis en MAC. La disminución de VEGFR2 en cardiomiocitos sugiere que AAS también afecta la angiogénesis en miocardio sano, modificando la disponibilidad del receptor a VEGF. Estos hallazgos nos permiten postular que AAS podría interferir con la regeneración de tejido, en situaciones como post infarto al miocardio.

SUMMARY: The VEGF levels and its binding to its receptors are key stages in the regulation of angiogenesis. Acetylsalicylic acid (ASA), widely used in post-myocardial infarction treatment, has been shown to have an anti-angiogenic effect in tumor models. This potentially counterproductive effect requires to be studied in myocardium. The aim of this study is to quantify the effect of ASA and salicylic acid (SA) on the vascularization in chick allantochorionic membrane (CAM) and on the levels of VEGF-A and VEGFR2 in myocardium of chicken embryos. Thirty White Leghorn chicken fetuses were instilled at 10 days of gestation with 60 mL of 0.1 % DMSO (control) or also containing 0.3 mmol of ASA or SA. After 48 hours, CAM histological processing was performed to count blood vessels and heart tissue to quantify VEGFA and VEGFR2 by immunohistochemistry. Immunoreactivity was quantified by Image J. Both ASA and SA decreased CAM microvascular density. In myocardium, AAS, although not SA, decreased the concentration of VEGFR2. There was no effect on VEGF-A. In our experimental model, chicken fetuses at 10 days of gestation, the inhibitory effect of ASA on angiogenesis in CAM were also observed. The decrease in VEGFR2 in cardiomyocytes suggests that ASA also affects angiogenesis in healthy myocardium, modifying the availability of the receptor to VEGF. These findings allow us to postulate that ASA could interfere with tissue regeneration, when it is required, as post myocardial infarction.

Angiogenesis and tumor progression inhibition of cyclooxygenase-2 selective inhibitor celecoxib associated with poly (lactic-co-glycolic acid) in tumor cell line resistant to chemotherapy / Inhibición de angiogénesis y progresión tumoral por inhibidor selectivo de ciclooxigenasa-2 celecoxib asociado con ácido (poli láctico co-glicólico) en línea de células tumorales resistentes a quimioterapia

Although, antineoplastic therapies have now been developed reduction of tumor progression,itis necessarytofind new therapeutic alternatives to suppress angiogenesis.Thus celecoxib (Cx) has been used for its antiangiogenic action in combination with certain polymeric compounds such as poly (lactic co-glycolic acid) (PLGA) acid, which help to improve the bioavailability and avoid effects of long drug administrations. For this purpose we used a murine tumor modelinduced by mammary adenocarcinoma cells resistant to chemotherapy (TA3-MTXR). CX/PLGA inhibits the microvascular density, VEGF expression and cell proliferationinaddition to increased apoptosis (P <0.0001). Cx reduces tumor progression in a concentration of 1000 ppm associated with PLGA, reducing cell proliferation, the presence of VEGF and promoting apoptosis of multiresistant TA3 tumor cells.

Si bien actualmente se han desarrollado terapias antineoplásicas que permiten reducir de cierta manera el avance tumoral, es necesario buscar nuevas alternativas terapéuticas que permitan suprimir la angiogénesis. Es así como el Celecoxib (Cx) ha sido utilizado por su acción antiangiogénica en combinación con algunos compuestos poliméricos, tal como el ácido poli (láctico co-glicólico) (PLGA), el cual ayudaría a mejorar la biodisponibilidad y evitaría efectos derivados de largas administraciones del fármaco. Para tal efecto se ha utilizado un modelo tumoral murino, inducido por células tumorales de adenocarcinoma mamario resistente a la quimioterapia (TA3-MTXR). Los resultados indican que CX/PLGA inhibe la microvascularización, expresión de VEGF y la proliferación celular además del aumento de la apoptosis (P<0,0001). El efecto antitumoral del Cx está bien reportado en la literatura; este sumado a la microencapsulación con PLGA, aportarían un sistema de administración útil, ya que nos otorga una administración sostenida en el tiempo, los cual podría ayudar a mantener los niveles de droga durante un período más prolongado, lo cual sería beneficioso en la terapia tumoral.

Celecoxib/PLGA suprime angiogénesis y metástasis pulmonar de un cáncer mamario murino experimental / Celecoxib/PLGA suppresses angiogenesis and lung metastasis of murine experimental breast cancer

La angiogénesis y metástasis son eventos esenciales en el proceso de invasión tumoral. Su relación íntima los hace buenos blancos en la terapia antitumoral. El objetivo fue analizar el patrón de metástasis pulmonar y angiogénesis, luego de la aplicación del antiangiogénico Celecoxib microencapsulado en ácido poli(láctico-co-glicólico) en ratones. Se utilizó un modelo de tumor experimental, inducido por células TA3-MTX-R, en 18 ratones, separados en 3 grupos de 6 animales, los cuales fueron tratados con dos presentaciones de Celecoxib en administración intramuscular (Grupo Control; Grupo Cx 1000 ppm y Grupo Cx 1000 ppm+PLGA). Los ratones fueron sacrificados y procesados histológicamente para ser teñidos con H&E y Tricrómico de Arteta. El estudio reveló que el pulmón muestra una marcada heterogeneidad, y un patrón de metástasis perivascular; además, Celecoxib asociado a ácido poli(láctico-co-glicólico) redujo la invasión tumoral y angiogénesis en el pulmón. Los resultados son similares a descripciones parciales realizadas previamente y son comparables a otras líneas tumorales, siendo celecoxib/ácido poli(láctico-co-glicólico) un candidato potencial en la terapia antitumoral.

Angiogenesis and metastasis are critical events on the tumor invasion process. Their close association is related as a good target in antitumor therapy. The aim was to analyze lung metastasis pattern and angiogenesis following application of microencapsulated Celecoxib with poli(lactic-co-glycolic) acid in mice. An experimental tumor model was assessed, induced by TA3-MTX-R cells, in 18 mice, separated in 3 groups of 6 animals and treated with 2 intramuscular Celecoxib presentations (Group Control; Group Cx 1000 ppm and Group Cx 1000 ppm+PLGA). Mice were sacrificed and histologically processed to stain slides with H&E and Arteta Trichromic. The study revealed that the lung showed a significant heterogeneity, and a perivascular metastasis pattern; moreover, Celecoxib associated to poli(lactic-co-glycolic) acid reduces tumor invasion and pulmonary angiogenesis. The results are similar to partial previous descriptions and are comparable to other tumor lines, concluding that Celecoxib/poli(lactic-co-glycolic) acid is a potential candidate in antitumor therapy.

Ácido acetilsalicílico (AAS) inhibe angiogénesis en membrana alantocorionica de pollo (MAC) / Acetyl-salicylic acid inhibits angiogenesis in alanto chorionic chicken membrane

Introducción: El ácido acetilsalicílico (AAS) es ampliamente utilizado en el manejo de patología cardiovascular. En modelos "in vitro" el AAS restringe la angiogénesis, atribuyéndose este efecto al bloqueo de ciclooxigenasa-1, manteniendo íntegra la zona adhe-rente endotelial, citotoxicidad directa y otras vías de señalización. Hipótesis: El AAS en concentración terapéutica antiplaquetaria utilizada en humanos ejerce un efecto antiangiogénico en modelo de membrana alantocorió-nica de pollo (MAC). Objetivo: Comparar la capacidad antiangiogénica del AAS en distintas concentraciones en MAC utilizando como punto de comparación la angiogénesis fisiológica de la MAC. Método: Se incubaron 46 huevos fecundados de gallinas White Leghorn, en cámara temperada a 37°C, provenientes del Instituto de Salud Pública de Chile. Mediante procedimiento descrito por Ribatti (2006), se instiló sobre filtro de metilcelulosa 10uL de Dimetilsulfóxido al 0.1% + m199, sin fármaco al control, asociado a AAS y ácido salicílico (AS) a los grupos de estudio en concentraciones 2mM y 5 mM. Posteriormente se fijó y analizó la muestra en forma ciega. Resultados: El promedio de vasos del control fue 21.8. Para el grupo AAS 2mM y 5mM fue 11.3 y 10, siendo para el grupo AS 2mM y 5mM 15.6 y 12.4. El análisis estadístico mediante ANOVA y t-Student muestra que todos los grupos que recibieron fármacos tuvieron una disminución significativa en el numero de vasos sanguíneos en relación al grupo control. No hubo diferencias significativas entre ambo grupos de AAS. El AS demostró tener mayor potencia antiangiogénica dosis dependiente. Discusión: En este estudio se demuestra que el AAS ejerce un efecto antiangiogénico en concentración terapéutica en condiciones fisiológicas de un modelo "in vivo".

Background: Acetylsalicylic acid (ASA) is widely used in the treatment of various cardiovascular disorders. In vitro, AAS decreases angiogenesis, through cyclo-oxigenase-1 blockade while keeping active the adherent endothelial zone, direct toxicity and other signaling pathways. Hypothesis: AAS at therapeutic anti plaquetary doses exerts an anti-angiogenic effect in the alanto choronic chicken membrane (ACM) Method: 46 fertilized eggs form White Leghorn hens were incubated at 37oC. 10 uL of 0.1% Dimethyl sulfoxide +Ml 19 with no drug were used as control, while experimental groups received ASA and Salicylic acid (SA), 2mM. After fixation, samples were analyzed in a blind fashion Results: The mean number of vessels was 21.8 for controls, 11.3 and 10 for ASA 2mM and ASA 5mM, respectively. Corresponding values for SA 2 and SA 5mM were 15.6 and 12.4, respectively. Thus, a statistically significant (ANOVA and Student's t) decrease in the number of vessels was observed in both ASA groups. SA showed had a greater potential for anti-angiogenesis in a dose dependent way. Conclusion: This study shows that ASA in therapeutic concentrations has an anti-angiogenic effect in a physiologic model in vivo.

Efecto antimetastásico de celecoxib/PLGA en un modelo murino de adenocarcinoma mamario TA3-MTX-R / Antimetastatic effect of celecoxib/PLGA in a TA3-MTX-R murine breast adenocarcinoma model

La metástasis es el proceso de propagación de un foco cancerígeno a un órgano distinto de aquel en que se inició; ocurriendo generalmente por vía sanguínea o linfática. La localización más frecuentes de las metástasis son los órganos más irrigados como el cerebro, pulmones, hígado, huesos y glándulas suprarrenales. El objetivo fue analizar el patrón de metástasis hepática de tumor TA3-MTX-R, luego de la aplicación del antiangiogénico Celecoxib microencapsulado en PLGA en ratones, así como la disminución de áreas metastásicas a nivel lobulillar. Se utilizó un modelo de tumor experimental, inducido por células TA3-MTX-R, en 18 ratones, separados en 3 grupos de 6 animales, los cuales fueron tratados con dos presentaciones de Celecoxib en administración intramuscular (Grupo 1, Control: TA3-MTX-R; Grupo 2: TA3-MTX-R+Cx y Grupo 3: TA3-MTX-R+Cx/PLGA). Los ratones fueron sacrificados y procesados histológicamente para ser teñidos con H&E y Tricrómico de Arteta. El estudio reveló que el higado muestra una marcada heterogeneidad, y un patrón de metástasis perivascular y neovascularización central y periférica. Además, Celecoxib redujo significativamente la invasión tumoral en el hígado (p<0,0001). Los resultados son similares a descripciones parciales realizadas previamente y son comparables a otras líneas tumorales. Creemos que la vía de administración del fármaco es crítica para la interpretación de los resultados. Los hallazgos son importantes para la discusión de otras investigaciones en donde Celecoxib es usado como un fármaco antiangiogénico.

Metastasis is the propagation process of a cancerous focus to an organ other than that in which it started; usually occurring through blood or lymphatic route. The most common sites of metastases are the organs most irrigated such as the brain, lungs, liver, bones and adrenal glands. The objective was to analyze the pattern of liver tumor metastasis TA3-MTX-R, after application of antiangiogenic Celecoxib microencapsulated in PLGA in mice and decreased metastatic to lobular level areas. An experimental model of tumor induced TA3-MTX-R cells was used, 18 mice divided into 3 groups of 6 animals, which were treated with two presentations Celecoxib intramuscular (Group 1, control was used -R; Group 1: TA3-MTX-R+Cx and Group 3: TA3-MTX-R+Cx/PLGA). The mice were sacrificed and processed histologically to be stained with H&E and Arteta trichrome. The study revealed that the liver shows a marked heterogeneity, and a pattern of perivascular metastasis and central and peripheral neovascularization. Furthermore, Celecoxib significantly reduced tumor invasion in the liver (p <0.0001). The results are similar to partial descriptions made previously and are comparable to other tumor lines. It is believed that the route of administration of the drug is critical for the interpretation of the results. These are important for the discussion of other investigations in which Celecoxib is used as an antiangiogenic drug.

Celecoxib decreases growth and angiogenesis and promotes apoptosis in a tumor cell line resistant to chemotherapy

BACKGROUND: During the last few years it has been shown in several laboratories that Celecoxib (Cx), a non-steroidal anti-inflammatory agent (NSAID) normally used for pain and arthritis, mediates antitumor and antiangiogenic effects. However, the effects of this drug on a tumor cell line resistant to chemotherapeutical drugs used in cancer have not been described. Herein we evaluate the angiogenic and antitumor effects of Cx in the development of a drug-resistant mammary adenocarcinoma tumor (TA3-MTXR). RESULTS: Cx reduces angiogenesis in the chick embryonic chorioallantoic membrane assay (CAM), inhibits the growth and microvascular density of the murine TA3-MTXR tumor, reduces microvascular density of tumor metastases, promotes apoptosis and reduces vascular endothelial growth factor (VEGF) production and cell proliferation in the tumor. CONCLUSION: The antiangiogenic and antitumor Cx effects correlate with its activity on other tumor cell lines, suggesting that Prostaglandins (PGs) and VEGF production are involved. These results open the possibility of using Celecoxib combined with other experimental therapies, ideally aiming to get synergic effects.

Angiogenic potential of the cerebrospinal fluid (CSF) of patients with high-grade gliomas measured with the chick embryo chorioallantoic membrane assay (CAM)

High-grade gliomas are highly vascularized tumors. Neo-angiogenesis plays a key role in tumor growth and resistance to therapy. A cerebrospinal fluid (CSF) sample could be a useful way to obtain pro-angiogenic predictive or prognostic markers at different stages of the disease. As a first step we looked for pro-angiogenic activity in the CSF of patients with high-grade gliomas. We performed the chicken embryo chorio-allantoic membrane (CAM) assay to study the angiogenic potential of the cerebrospinal fluid (CSF), obtained either by lumbar puncture (LP) or craniotomy from six patients with high-grade brain tumors (three glioblastoma (WHO grade IV), one anaplastic oligodendroglioma (WHO grade III), two anaplastic ganglioglioma (WHO grade III)), and four healthy controls. Significantly increased neo-angiogenesis was observed on the surface of the growing CAM in the 6 patients with high-grade gliomas compared to controls (3.69 ± 1.23 versus 2.16 ± 0.97 capillaries per area (mean ± SD), p<0.005). There was no statistical difference related to the hystological grade of the tumor (WHO grade III or IV), previous treatment (radio-chemotherapy plus temozolomide, temozolomide alone or no treatment), or the site of CSF sample (surgery or lumbar puncture). Our results suggest a pro-angiogenic potential in the CSF of patients with high-grade gliomas.

Comparative in vivo antiangiogenic effects of calreticulin from Trypanosoma cruzi and Homo sapiens sapiens

Angiogenesis is a complex multi-step process of neovascularization arising from preexisting blood vessels whose generation is regulated by pro- and anti-angiogenic factors. Both Trypanosoma cruzi calreticulin (TcCRT) and its human counterpart (HuCRT) are antiangiogenic. This is the first report where the TcCRT and HuCRT anti-angiogenic properties are compared in vivo. In the chick embryonic chorioallantoid membrane assay (CAM) and at equimolar concentrations, TcCRT displayed significantly higher antiangiogenic activities than its human counterpart. LPS had marginal effects at the concentrations present in the recombinant protein preparations and the TcCRT antiangiogenic effects were largely inhibited by specific polyclonal antibodies, thus, reinforcing the fact that the observed TcCRT effects can be attributed to the parasite-derived molecule and not to the endotoxin. The antiangiogenic TcCRT effects correlate with its anti-tumor in vivo effects, as recently shown in our laboratory.

Betamethasone inhibits tumor development, microvessel density and prolongs survival in mice with a multiresistant adenocarcinoma TA3

Tumor resistance to traditional cancer treatments poses an important challenge to modern science. Thus, angiogenesis inhibition is an important emerging cancer treatment. Many drugs are tested and corticosteroids have shown interesting results. Herein we investigate the effect on microvessel density, survival time and tumoral volume of mice with TA3-MTX-R tumors. Twenty six mice were inoculated with lxlO6 tumor cells, 4-5 days after injection, six mice were injected with PBS (group A) and twenty mice were treated with p-met (group B). All animals from Group A died on day 22. Group B was divided into Bl (treated discontinued) and B2 (treated daily) and observed until day 88. All mice were processed for histo-immunohistochemical analysis and the blood vessels were counted. A decrease in microvessel density and tumoral volume and longer survival times were observed in the treated group. We propose that the antiangiogenic p-met effect explains, at least partially, its tumor inhibitory properties. As an important perspective, we will experimentally combine these strategies with those recently described by us with regard to the important antiangiogenic-antitumor effects of Trypanosoma cruzi calreticulin. Since the molecular targets of these strategies are most likely different, additive or synergic effects are envisaged.

Effects of steroidal and non steroidal drugs on the neovascularization response induced by tumoral TA3 supernatant on CAM from chick embryo

Angiogenesis, the development of new blood vessels from the existing vascular network, may result as a consequence of the increase or decrease of proangiogenic or antiangiogenic factors, respectively. The tumor itself could up-regulate the production of angiogenic factors. Recently, we established that the steroidal drug betamethasone in low concentration inhibit the neovascularization promoted by TA3 Ts on CAM of chick embryos. We describe here the effects of the non-steroidal drug ketoprofen, alone or in association with betamethasone, on the angiogenesis promoted by TA3 Ts on CAM. The main finding reported here is that the formation of new blood vessels is strongly inhibited by low concentrations of ketoprofen. The association of both drugs produced a synergistic effect, significantly decreasing tumoral supernatant angiogenesis. It is known that steroidal anti-inflammatory drugs inhibit the enzymes required for the production of prostaglandins through a nuclear GR mediated mechanism. This may operate as a general mechanism in endothelial cells as well. Considering that the induction of COX 1 and COX2 are inhibited by ketoprofen, and that these enzymes are located in the stromal compartment of the CAM, we propose that its antiangiogenic effect may occur via inhibition of the two COX isoforms. In fact, we found that ketoprofen induced apoptosis in both the stromal fibroblast and endothelial cells. The potentiated effect of the combination of betamethasone and ketoprofen may have some therapeutic projections in the control of pathological angiogenesis

Effects of betamethasone, sulindac and quinacrine drugs on the inflammatory neoangiogenesis response induced by polyurethane sponge implanted in mouse

In this study, we showed the effect of the betamethasone, sulindac and quinacrine alone or combined, on the inflammatory angiogenesis promoted by polyurethane sponge on mice. The main finding reported here is that the formation of new blood vessels was strongly inhibited by low concentration of betamethasone, sulindac or quinacrine, whether alone or in combination. It is known that steroidal anti-inflammatory drugs inhibit the enzymes required for the production of prostaglandins through a nuclear glucocorticoid receptor (GR) mediated mechanism. This mechanism may occur in endothelial cells as well. Considering that activity of cyclo-oxigenases 1 and 2 is inhibited by sulindac, and that these enzymes are located in the stromal tissue, we propose that the anti-angiogenic effect of these agents may occur via inhibition of both COX isoforms. On the other hand, quinacrine inhibited PLA2 activity, and we propose here that the anti-angiogenic effect occurs via inhibition of the enzyme PLA2. The potentiated effect of the association of betamethasone, sulindac and quinacrine may have some therapeutic benefit in the control of pathological angiogenesis. Further studies are required to validate these propositions

Antiangiogenic effect of betamethasone on the chick cam stimulated by TA3 tumor supernatant

Tumor growth is the result of combined cell proliferation overwhelming cell death and neoangiogenesis. This report shows CAM angiogenesis promoted by TA3 tumor supernatant with or without low dosis of betamethasone (Minimal antiangiogenic concentration: beta-MAAC). Methylcellulose discs instilled with 10 microliters of beta-MAAC (0.08 microgram/ml), 10 microliters of tumor supernatant (TA3ts), 5 microliters beta-MAAC + 5 microliters TA3ts, and 10 microliters of PBS as control were implanted in host chick eggs. On day 12, the grafts were removed, photographed and fixed. Sections were stained in parallel, one and three with hematoxylin-eosin, and section two by the Tunel method. The number of vessels was evaluated in a microscopic field of the CAM (2250 micron 2). The results show that beta-MAAC produced a significant inhibition of neovascularization in comparison to that observed in controls (P < 0.0025; Student t-Test). Discs instilled with TA3ts produced an intense stimulation of angiogenesis in contrast, when discs were instilled with 5 microliters of beta-MAAC + 5 microliters of TA3ts the angiogenesis was significantly inhibited (P < 0.001). The results show that effective antiangiogenic doses of betamethasone are in the range of 10(-7) M, (probably a genomic mediated action) and that this effect of low concentration may have clinical applications.

Effect of cholinergic agonists on muscular tonus of the lizard small intestine and esophagus

The underlying mechanisms of acetycholine-induced intestinal relaxation in the lizard Liolaemus tenuis tenuis are still unknows. By using a classical model of intestinal recording of isometric contraction and relaxation in conjunction with specific pharmacological tools, this article studies the possible influence of EDRF/NO and nicotinic ganglionar receptors on the Ach-induced relaxation in an effort to elucidate the probable mechanisms involved in ACh effect. It was observed that the relaxation of the lizard intestine elicited by ACh (10(-7) - 4 x 10(-4) M) was not affected by hexametonium (5 x 10(4) M) or tetrodotoxin (10(-6) M). Nicotine (10(-7) to 10(-4) M) induced relaxation was significantly antagonized by hexametonium; however, it was not influenced by tetrodotoxin. These results allow us to discard a neuronal pathway in cholinergic-induced relaxation, suggesting a more direct cholinergic effect on the smooth muscle, perhaps mediated by an unknown substance released by some specialized tissue. N-nitro-L-arginine, used to block NO-synthase and NO production, induced no changes in ACh-induced relaxation. Methylene blue, a soluble guanylate cyclase inhibitor, induced no changes in ACh-induced relaxation. These results allow us to dicard a probable role of EDRF/nitric oxide in the ACh-induced relaxation of lizard small intestine, providing evidence that this mechanism could be different from reported on other species.

Ethanol effect on the chick embryo ossification: a macroscopic and microscopic study

This study attempts to analyze anomalies in avian embryos induced macroscopically and microscopically when exposed to ethanol (EtOH) during the first stages of development. Fertilized chicken eggs were employed in this study. The eggs were incubated at 37.8§C. Some of the eggs were treated on day O with EtOH (20 per cent, 40 per cent and 60 per cent) by instillation in the air sac. The control group was instilled with 0.1 ml of NaCl at 0.9 per cent. Other eggs were treated on the 4th post-incubation day, employing the same methodology. The embryos in both groups were removed from eggs on the 11th incubation day and examined using a dissecting binocular micrsocope. After macroscopic analysis, the samples obtained were fixed in 10per cent formol, photographed and processed according to common histological techniques and the Picrosirius method. Embryos treated with EtOH demonstrated a significant weight decrease. Microscopic analysis by means of the Picrosirius method revealed that the intra-membranous ossification process presents less development, and therefore there wass less type I collagen in trabecular bone in the embryos post-exposure to EtOH with respect to the control.

Relación entre desplazamiento de melanosomas y cambios de color en lagartijas machos: liolaemus tenuis tenuis: un estudio ultraestructural / Relationship between melanosomes displacement and color change in male lizards: liolaemus tenuis tenuis: an ultrastructural study

La mayor parte de los organismos multicelulares se caracterizan por un patrón de color distintivo y, a menudo, particular. Uno de los efectores relacionados con el proceso corresponde a células especiales, los cromatóforos. En este trabajo se demuestra mediante técnicas de microscopía electrónica, que en el dermis de reptiles sometidos a 35§C por 12 min, se produce una fuerte concentración de melanosomas en torno al núcleo de los melanóforos. Por el contrario, a 0§ los melanóforos presentan expansiones citoplasmáticas que contienen numerosos melanosomas. Asociados a los melanosomas en dispersión, se observan microtúbulos. Esta característica permite plantear la posible existencia de algún tipo de relación entre microtúbulos y movimiento de melanosomas en este reptil, cuando es sometido a bajas temperaturas, momento en que se oscurecen. Se destacan también, gruesos manojos tridimensionales de fibras colágenas asociadas a fibroblastos, estructuras, que para algunos autores, representarían un primordio de esclerificación dérmica, fenómeno que predecería a la fase fibrilar de la osificación dérmica o directa. Otro tipo de célula, los iridóforos, contienen placas reflectantes que reflejan la luz en direcciones determinadas