Pre-implantation loss

Increased incidence of pre-implantation loss (number of corpora lutea - number of implants in utero)... 

The maternal ovaries are removed and examined at the time of necropsy and corpora lutea are counted. The corpus luteum (CL) is a transitory endocrine organ formed from the thecal and granulosa cells of the postovulatory follicle... Information on the number of copora lutea is useful in the interpretation of data on the viability of conceptuses (see below, pre-implantation loss). Corpora lutea counts can be conducted with fresh or fixed tissue, and are generally performed with the aid of a dissecting microscope. Minimal dissection of the ovarian tissue is required (13). 

Based on this, pre-implantation loss is the difference between the number of released oocytes and the number of conceptuses reaching the state of implantations and is calculated as ... 

Since treatment would normally start around implantation, one would not expect pre-implantation loss to be affected by treatment. However, if conceptuses are affected by the first treatment, they could be killed before leaving a scar on the uterus. To make very early resorptions visible, staining of the uteri in 20% ammonium sulphide is useful. After rinsing uteri in tap water, these resorptions can be seen as small black dots. This procedure... 

Determination of pre-implantation loss can be complicated if the number of implantation sites is higher than that of corpora lutea. Careful recounting of corpora lutea should be performed, but not always will this change the situation. This issue is handled differently in different laboratories some would automatically set the number equal to the number of implantation sites, alternatively (as handled in our laboratory) the actual value is documented, but pre-implantation loss is set to 0 since a negative number is unsound. 

Clearly, an expert interpretation of teratology data cannot be reduced to a mathematical algorithm or flowchart. The teratologist uses his knowledge of the test system to make sense of the fluctuations observed and also to rule out any implausible effects. For instance, a difference in pre-implantation loss in a routine teratology study with the start of dosing on gestation day (CD) 6 is unlikely to be due to the test item. Likewise, a treatment-related reduction in resorption incidence is implausible since zero loss is within the limits of normality. 

Pre-implantation loss, or number of corpora lutea in the ovaries relative to the number of implantation sites. 

No maternal or fetal deaths oeeurred, and pregnancy parameters (numbers of corpora lutca, implantation sites, pre-implantation losses) were not affected by formaldehyde exposure (Martin 1990). 

Oral exposure to high levels of zinc increased the incidence of pre- implantation loss in rats when exposure began on gestational day 0 and continued throughout the gestational period (Pal and Pal 1987). Failure to reproduce was observed in multiparous rats fed 250 mg zinc/kg/day as zinc carbonate for 150 days. In rats fed zinc for 21 days prior to mating, no reproductive effects were... 

Treatment starts when the embryo is attached to the uterine wall and has completed the first stages of implantation. Therefore, pre-implantation development should be unaffected by the test substance. However, even in controls, not all fertilized oocytes develop to the hatched blastocyst stage. A loss of up to two preimplantation embryos per female can be considered a normal finding in rats and rabbits. In studies where exposure begins at or before fertilization a dose-dependent increase in the number of females that show larger differences between corpora lutea and implantation sites may indicate toxicity to pre-implantation embryos or the process of implantation itself. 

In a dominant lethal assay, male CD rats were exposed to 55 ppm [220 ing/ni ] vinylidene chloride for 6 h per day on five days per week (Short et al., 1977). On week 11 of exposure, males were mated with untreated females. There was no evidence of pre-or post-implantation loss in the pregnant females. Male CD-I mice exposed to 10, 30 or 50 ppm [40, 120 or 200 mg/m ] vinylidene chloride for 6 h per day for five days and subsequently mated with untreated females exhibited no pre- or post-implantation loss (Anderson et al., 1977), indicating an absence of adverse effects on male reproduction. 

Species Death (LD50) Immunological effects (thymic atrophy) Reproductive effects (abortions, resorptions, or pre- and post-implantation losses) Developmental effects... 

Si02 layers pre-implanted with 140keV Si ions, and those with embedded Si nanociystals (Si-ncs) have been irradiated with 130 MeV Xe ions, HREM and photoluminescence spectroscopy wo e used for the characterizations. In the Si-implanted layers HREM revealed the 3-4 nm-size dark spots, whose number and size grew with increase in Xe ion dose. Photoluminescenoe showed the presence of two bands - at 780 nm and at 670 nm. The intensity and position of the bands depended on the dose. Changes of the spectra and the results of passivation were interpreted as transformation of Si-ncs (-780 nm) into damaged Si-ncs (-670 nm) and vice versa. It is concluded, that electronic losses are responsible for the formation of new Si-ncs, whereas elastic losses introduce the defects. 

The reproductive effects of MeHg exposure in animals are summarized in Table 5-4. Abortion and decreased litter size are the most commonly reported reproductive effects of MeHg in animal studies. Pre- and post-implantation losses have been experimentally induced in rats, mice, guinea pigs, and monkeys exposed to MeHg. 

The C-section ( litter ) values, i.e., gravid uterus weight, corpora lutea, total number of implants, and numbers of live and dead implants (including separate categories of dead implants) are presented as means, together with an indicator of variation, typically standard deviation. Additionally, pre- and postimplantation losses are calculated for each female ... 

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