March 19, 2020 0 Comments

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.

Author: Vull Kazrara
Country: Azerbaijan
Language: English (Spanish)
Genre: Photos
Published (Last): 19 December 2017
Pages: 325
PDF File Size: 9.40 Mb
ePub File Size: 13.6 Mb
ISBN: 609-7-65369-272-2
Downloads: 76753
Price: Free* [*Free Regsitration Required]
Uploader: Gogal

Author information Article notes Copyright and License information Disclaimer. The occurrence of vizcaxha has been described in the pineal gland of some mammal species, but the reports are scarce [ 111416 — 20 ].

Immunohistochemical scoring was determined using a 4-point scale: Mammals of the Neotropics. Briefly, animals were anesthetized with ketamine chlorhydrate Transects were traversed in the sampling areas to determine plant cover as an estimator of food availability by the crewpo method Daget and Poissonet Since the ovaries of the nonpregnant groups of this study LCT and NP exhibited almost the total absence of corpora lutea, the luteal immunoreactivity was vizfacha only at the stages of pregnancy.

The irregular distribu- tion of volcanic stone outcrops has been pointed out vizcaxha a determinant factor of spatial differences in vegetation and soil characteristics Mendez ; Gonzalez Diaz After bleeding, animals were sacrificed by an intracardiac injection of Euthanyle 0. Ultrathin sections were stained with uranyl acetate and lead citrate [ 36 vizcahca and were observed under a Siemens Elmiskop I electron microscope. Selectivity of plant categories by the vizcacha Grasses 0.

However, the role of pigment in these nervous structures has not been clearly demonstrated. Revista de Investigaciones Agr co- las, VI: Effect of the photoperiod and administration of melatonin on folliculostellate cells of the pituitary pars distalis of adult male viscacha Lagostomus maximus maximus Acta Histochemica.

IUCN Red List of Threatened Species

The ovaries of adult specimens exhibit natural massive polyovulation that can go up to oocytes per cycle, the highest ovulatory rate so far recorded for a mammal. However, the biological significance of these pigments in the pineal gland has not yet been established.

The microhabitat and the distance to the nearest rocky elevation were identi- crespp for each observed vizcachera. View at Google Scholar J. Scarcity of forbs could explain this low nutritional resources quality.


Unlike these rodents and the vast majority of mammals, female vizcachas Lagostomus maximus have a peculiar reproductive biology characterized by an ovulatory event during pregnancy that generates secondary corpora lutea with a consequent increment of the circulating P4.

The electron micrograph shows a large amount of premelanosomes arrow and melanosomes m within a pinealocyte p and a pigmented cell pg. The melanocyte and the epidermal melanin unit: Introduction Melanin, a brownish-black pigment, is produced by the skin melanocytes which are derived from the neural crest vizcscha constitute the second most abundant cell in the epidermis [ 12 ].

This process of melanin transference has already been suggested in cat [ 18 ] and bat [ 16 cizcacha. This rise in LH leads to an ovulatory event that produces a great number of secondary corpora lutea with oocyte retention i.

In fact, pituitary PRL expression determined in this study is in agreement with the documented increased expression of PRLR in mammary glands of vizcachas throughout gestation and this is tightly related to the mammary gland preparation for the eventual nurturing of the forthcoming offspring [ 293856 ].

Spatial and seasonal differences in quality and quantity of food availability in La Payunia were useful to test this hypothe- sis.

International Journal of Endocrinology

This area is located within the northernmost unit of the Patagonian Biogeographical Province Cabrera and Willink A strong argentaffin reaction is exhibited in pigmented cells arrowheads and in extracellular space. The Australasian Journal of Dermatology.

In Huayquerfas Coloradas plains, forbs were the only category showing a significant difference between availability and diet. The American Journal of Anatomy. However, unlike what we had measured for the pituitary protein expression cresp immunohistochemistry, PRL mRNA levels remained significantly high during lactationper group Figure 6. A forced dietary selectivity was also detected in guanacos of La Payunia Puig et at.

Focusing on the implications of PRL actions over the reproductive process, it has been shown in transgenic mice models that ablation of either PRL or PRLR gene greatly impairs female fertility [ vizcacna20 ]. The extremely arid conditions vizcachas find in La Payunia allow to test this hypothesis.

Cortasa1,2 M. The amount of melanin in relation to sex varies according to the species.

Maximum expression of PRLR recorded at midpregnancy coincides with the peak of crdspo P4, while the decrease of this steroid recorded right before parturition is accompanied by a drastic decrease in both PRLR immunoreactivity and transcript levels.


Additionally, the uterine horns were examined to evaluate the presence of embryos, foetuses, and placental scars. 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.

The Masson-Fontana silver and the Schmorl histochemical techniques for melanin pigments determination were also performed. Midpregnant vizcachas exhibited high levels of transcription for PRLR as well, which could be indicative of a cross talk mechanism between these two hormones for a coordinated dialogue towards an accurate luteinization process in L.

In conclusion, the changes in the amount of pigment content and hormone levels may indicate that the pineal gland of female viscacha is susceptible vizaccha endocrine variations during pregnancy. The scarse plant cover and the high phane- rophytes availability distinguished rocky elevations of Escoriales from the other microhabitats.

In properly functioning nervous structures, the pigment is called neuromelanin [ 9 ]. Rocky elevations of La Payunia are the shelter of Lagidium viscacia.

LHR exhibited its most intense immunoreactivity during midpregnancy and then fell to almost imperceptible levels in the term pregnant group. Analysis of qPCR data showed a 4-fold rise when transitioning from early pregnancy to midpregnancy and a marked decline at the end of gestationper group Figure 2 a.

Higher availability of the preferred grass Poa in Escoriales may also facilitate a higher selectivity within cha- maephytes, dominated by the avoided Hyalis. The relative frequency of occurence of a species in the diet was detelmined for each sample by dividing the number of microscopic fields in which a given species occurred by the sum total of frequencies for all species identified Hole- chek and Gross However, it is now known that besides the mammary glands, PRL targets several other tissues expressing its membrane-bound receptor PRLR and modulates a great variety of biological functions [ 18 ] for a review.

Samplings corresponded to winter Julyspring Octobersummer December and Februaryand autumn May. The brains were exposed, and the pineal gland was immediately removed and used for light and electron microscopy.