Some Comparative Aspects of Implantation

Summary. The total number of corpora lutea developed in the left and right ovaries of 170 white-toothed shrews (Crocidura russula monacha) differed significantly, showing a functional dominance of the left ovary. Blastocysts were equally distributed in both uterine horns.In most birds, only the left ovary is functional, although rare instances of individuals with both or only right ovaries have been reported (see Sadleir, 1973). In other vertebrate groups ovarian asym¬ metry is an unusual phenomenon and is rare among mammals, although it has been found in the platypus, in some marsupials and in eutherians (see Mossman & Duke, 1973;Wimsatt, 1975). The asymmetry varies from minor differences in the average weight of the two ovaries, to the occurrence of a nonfunctional ovary which can be appreciably smaller than the functional ovary.The data in the present paper were obtained during a wider study of reproduction in the whitetoothed shrew, Crocidura russula monacha, which is common in the Eastern Mediterranean region. Ovulation in this shrew occurs after mating or can be induced by exogenous hormones (see Hellwing, 1971 ;Funkenstein, 1974). In the course of a broader experiment on ovulation, sufficient data have emerged showing differences in the number of ova shed and of corpora lutea (CL) produced in the two ovaries. The animals used were 26 pregnant shrews trapped in the wild and 144 mature nulliparous females, born and raised in the breeding colony maintained at the Research Zoo of the Tel-Aviv University. Ovulation in captive shrews was artificially induced using PMSG (Gestyl: Organon) and FSH (NIH-FSH-S9) and the details will be reported elsewhere. Shrews were injected s.c. with doses of 0-5,1-0,2-5, 5-0,10, 25, 50 or 100 i.u. PMSG. The percentage of animals ovulating and the number of ovulated ova were dose dependent up to 5 i.u. PMSG. The FSH doses were 0-5,1-0,2-5,5-0,10,50,100 and 200 µg: doses of 0-5 and 1-0 µg FSH yielded a nearly maximal ovula¬ tory response. Only shrews that ovulated were scored. The mean number of ova shed after injection of PMSG or FSH, 3-14 and 3-17, respectively, was about the same as the natural litter size (3-0).Tissues for histological examination (ovaries, oviducts and uteri) were fixed in Bouin's fluid, embedded in paraffin wax, serially sectioned and stained with haematoxylin and eosin. In Crocidura russula monacha the number of CL corresponds to the number of ova shed (Funkenstein, 1974). Consequently, ovarian activity in this paper is expressed as the total number of corpora lutea counted in each ovary.The results presented in Table 1 show that in wild Crocidura russula monacha there was a numerical dominance of CL in the left ovary (67 %) but not in the right (52 %). The difference in number of corpora lutea in left and right ovaries in the same individual was significant : < 005 (t test for paired comparison, Sokal & Rohlf, 1969). Notwithstanding this degree of functional ovarian asymmetry in wild shrews the number of blastocysts was found to be distributed equally betwe...

contrasting

confidence: 61%

mentioning

confidence: 99%

Ovarian asymmetry in the shrew, Crocidura russula monacha

Hellwing¹,

Funkenstein²

1977

“…Based on the different types of blastocyst -uterine cell interactions, implantation has been classified into three broad categories: centric, eccentric and interstitial (Wimsatt 1975). Centric implantation occurs when the blastocyst is able to grow large and form ample surface contact to fuse with the luminal epithelium without penetrating through it.…”

Section: Mechanisms Of Implantation In Animal Modelsmentioning

confidence: 99%

Animal models of implantation

Lee

DeMayo²

2004

234

155

Implantation is an intricately timed event necessary in the process of viviparous birth that allows mammals to nourish and protect their young during early development. Human implantation begins when the blastocyst both assumes a fixed position in the uterus and establishes a more intimate relationship with the endometrium. Due to the impracticalities of studying implantation in humans, animal models are necessary to decipher the molecular and mechanical events of this process. This review will discuss the differences in implantation between different animal models and describe how these differences can be utilized to investigate discrete implantation stages. In addition, factors that have been shown to be involved in implantation in the human and other various animal models including growth factors, cytokines, modulators of cell adhesion, and developmental factors will be discussed, and examples from each will be given.

“…In all species examined, asynchrony between uterus and embryo leads to reduced rates of embryonic survival (Adams, 1973), and in many species an obligatory or facultative delay in implantation is evident (Wimsatt, 1975;Aitken, 1977). It is accepted that the steroid hor¬ mones acting via uterine receptors mediate this control process (O'Grady & Bell, 1977 ;Surani, 1977).…”

Section: Introductionmentioning

confidence: 99%

The progesterone content of rabbit uterine flushings

Fowler¹,

Johnson²,

Walters³

et al. 1977

Summary. A detailed study has been made of the progesterone content of uterine flushings taken from rabbits of different endocrine states. A high content of progesterone was recovered from the uterine lumen of pregnant and pseudopregnant rabbits. The amount of progesterone recovered in the flushings was not simply dependent on the concentration in the plasma, because plasma progesterone concentrations rose before detection of progesterone in the flushings and remained high after uterine progesterone content had fallen. Progesterone did not appear in the uterine fluid unless uterine protein was present. This was particularly evident in rabbits treated with progesterone in which, despite abnormally high plasma concentrations, little progesterone was found in uterine fluid until the protein content increased. After treatment of rabbits with oestrogen at the time of ovulation, uterine progesterone was present in higher amounts concomitant with an elevation of protein content although the peak values of progesterone and protein were delayed by 2\p=n-\3days. Plasma progesterone concentrations of about 5 ng/ml were necessary before progesterone appeared in the uterine lumen.