Plains viscacha were established in the laboratory to Spanish by Llanos & Crespo (), and some details of reproduction were given. Llanos, A. and J. Crespo. Ecología de la vizcacha (Lagostomus maximus maximus Blainv.) en el nordeste de la provincia de Entre Ríos. Rev. Llanos, A. C. and J. A. Crespo. Ecología de la vizcacha (Lagostomus maximus maximus Blainv.) en el nordeste de la Provincia de Entre Ríos. Revista de.

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Vizcacha diets obtained in dif- ferent habitats Fig. PRL immunodetection was evidenced in the cytoplasm of lactotropic cells localized in the pars distalis as previously described by Cresop and Mohamed ceespo 55 ]. Higher availability of the preferred grass Poa in Escoriales may also facilitate a higher selectivity within cha- crezpo, dominated by the avoided Hyalis. Transects were traversed in the sampling areas to determine plant cover as an estimator of food availability by the point-quadrat method Daget and Poissonet We studied ovarian LHR expression as a key marker of luteinization Figure 1.

Genus level, and species level when possible, were reached during plant cuticle identification. Spatial and seasonal differences in quality and quantity of food availability in La Payunia were useful to test this hypothe- sis. PRL drives the process of lactation, and thus it would be expected to find at this stage the highest level of this hormone in the pituitary gland.

A seasonal and age-related study of interstitial cells in the pineal gland of male viscacha Lagostomus maximus maximus The Anatomical Record. The age and reproductive condition of viscachas were carefully assessed on the bases of a body weight [ 31 ] and b sexual maturity estimated by the ovaries histological analysis. Morphometric Analysis The pigmented cells were counted in pregnant and nonpregnant viscachas. Vizcacha’s diet in La Payunia, within the most arid and elevated region of its distribution, showed a similar variety since half of the plant species present in the field were included.

Variations in the number of pigmented cells and serum hormone levels between nonpregnant and pregnant viscachas. In order to establish the different groups, the time of capture was carefully planned according to the natural reproductive cycle of the vizcachas previously described by Llanos and Crespo vvizcacha 33 ] and also based on our own field expertise [ 28 — 3234 — 36 ].

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Postnatal evolution of the crsepo pineal gland. This method allows to correct the proportional loss of visibility with the distance from the transect, using a correlation between distances and frequencies of vizcacheras observed.

International Journal of Endocrinology

Such a positive mark had a grainy appearance and was evidenced in both small and large luteal cells Figure 1. Immunoexpression was mainly observed in the cytoplasm of isolated lactotrophs or lactotropic cells forming follicular structures. Maximum expression of PRLR recorded at midpregnancy coincides with the peak of serum P4, while the decrease of this steroid recorded right before parturition is accompanied by a drastic decrease in both PRLR immunoreactivity and transcript levels.

Di Giorgio et al. Scarcity of forbs could explain this low nutritional resources quality.

IUCN Red List of Threatened Species

A high selectivity ocurred in habitats and sea- sons with low plant diversity. Correspondence should be addressed to J. Epididymis of viscacha Lagostomus maximus maximus: Diet included 29 genera of plants, mostly grasses and forbs, Poa and Panicum being main dietary ele- ments.

Moreover, PRLR colocalized with LHR as well, throughout the 3 analyzed pregnancy stages, being midpregnancy the stage depicting maximum expression of both receptors Figure 5. It is likely that high levels of P4 in the first stage are linked to the activity of the primary corpora lutea, whereas the increase during the second stage is largely a result of what is secreted by the newly formed corpora lutea in the pseudoovulatory event at the end of the third month of pregnancy [ 3137 ].

In relation with this hypothesis, we suggest that vizcachas tend to display a higher selectivity in circumstances in which preferred species are more available; this could be interpreted as food quality becoming a less limiting resource. Introduction Melanin, a brownish-black pigment, is produced by the skin melanocytes which are derived from the neural crest and constitute the second most abundant cell in the epidermis [ 12 ]. The sections were examined using an Olympus BX light microscope.

Nonpregnant females were captured in mid-September after the end of the reproductive season. The inset shows the argentaffin reaction with greater detail.

Briefly, animals were anesthetized with ketamine chlorhydrate Neither tracks or faeces of vizcachas were found in the rocky elevations, even in those with vizcacheras at their foot.

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Semithin section stained with toluidine blue exhibited numerous pigmented cells in close relation to blood vessels Figure 4.

Profile and type of soils do not seem to be limitant factors for the construction of vizcacheras, since Llanos and Crespo found them in plain sites and also inside crevices between plates of compact sandstone, in a marginal humid grassland of Espinal Entre Rfos, Argentina.

Although the oocytes are ovulated literally in hundreds, just 10 to 12 of them will be eventually fertilized and implanted, but only those two implanted nearest the cervix will complete their embryonic development [ 2627 ]. Thus, the changes in the amount of pineal melanin seems to indicate a direct relationship between pigment content and gonadal hormone levels during pregnancy, when estradiol and progesterone levels remain elevated for a long time.

Differences were considered statistically significant when. Chemical analyses of shrubs would determine their nutritional quality for vizcachas in La Payunia.

Primer sequences are shown in Supplementary Table 2. The broadening vizcaacha vizcacha’s food niche when plant diversity increases could be explained as an adaptation to arid conditions Miller and Gaud The two main species for the vizcacha differed among the grasses. The hydrogen peroxide treatment was also carried out. The lack of PRL signaling rcespo to the impossibility of maintaining the implantation of the embryo mainly due to an insufficient production of luteal P4.

P4 is essential for the development of normal pregnancy, and inadequate production of this steroid from the corpus luteum is associated with pregnancy loss [ 43 ] for a review. Support Center Support Center.

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Assay sensitivity gizcacha 0. Endocrinology and Metabolismvol. This classification was established according to previous reports in our laboratory [ 32 — 34 ].

Ultrathin sections were stained with uranyl acetate and lead citrate [ 36 ] and were observed under a Siemens Elmiskop I electron microscope.