Implantation, interference with

Bicomponent technology has been used to introduce functional and novelty effects other than stretch to nylon fibers. For instance, antistatic yams are made by spinning a conductive carbon-black polymer dispersion as a core with a sheath of nylon (188) and as a side-by-side configuration (189). At 0.1—1.0% implants, these conductive filaments give durable static resistance to nylon carpets without interfering with dye coloration. Conductive materials such as carbon black or metals as a sheath around a core of nylon interfere with color, especially light shades. 

After insertion of an lUD, polymorphonuclear leukocytes and macrophages accumulate in the uterine cavity. These cells appear to phagocytize sperm and Hberate a blastotoxic toxin (92,93). Intrauterine devices also may create a hostile environment, perhaps because antibodies are produced that interfere with implantation of the fertilized ovum (93). 

IUDs cause low-grade, intrauterine inflammation and increased prostaglandin formation. In addition, endometrial suppression is caused by the progestin-releasing IUD. They are spermicidal and also interfere with implantation of the fertilized ovum. Efficacy rates are greater than 99% with both perfect use and typical use. 

The uterus and its contents should also be examined prior to parturition to determine the number of live young and dead embryos and fetuses. The sum of these values equals the number of implantation sites. If the corpora lutea are counted (this may be very difficult in mice), then the difference between the number of implants and the number of corpora lutea indicates the extent of preimplantation loss. However, this is not necessarily accurate if the dam is dosed at the time of implantation, because it is possible to interfere with implantation to the extent that no visible sign remains. The difference between the total number of implants and the number of live implants gives the postimplantation loss, subject to the same caution as above. If there are no signs of implantation, the uterus can be stained with ammonium sulfide (Saleweski, 1964), which reveals completely resorbed implantation sites. The difficulty of distinguishing between preimplantation loss and very early postnatal implantation loss emphasizes the necessity of evaluating both parameters. 

Two other synthetic hormones with alkynyl appendages are RU 486 and levonorgestrel. RU 486 blocks the effects of progesterone, and because of this, prevents implantation of a fertilized egg. RU 486 is used to induce abortions within the first few weeks of pregnancy. Levonorgestrel interferes with ovulation, and so it prevents pregnancy if taken within a few days of unprotected sex. 

Another important class of ceramic biomateiials is based on AI2O3 (aluminum oxide or corundum). These materials are bioinert and are widely used for the knob of replacement hip joints and other joint endoprostheses. Other uses include tooth-root implants, parts for osteosynthesis, maxillofacial implants, and skull surgeryAluminum oxide ceramics prepared for use as biomateiials must have a low concentration of impurities such as silicon oxide and alkaline earth oxides, which can interfere with the bioinertness of the implant. ... 

The above discrepancies seem to be due mainly to the stringencies of the end-points in each test. However, one can also doubt the applicability of these tests for cannabinoids. These tests were developed for opiates and may not necessarily parallel and be fully relevant to THC activity in man. Indeed, recent work on electrodes implanted into several distinct brain areas of the rat led to the conclusion that the apparent analgesia produced by the cannabinoids is more related to their disruption of discharge in response to some synthetic impact rather than to a depression of pain pathways [130]. The question whether cannabinoids cause analgesia by interference with pain reception or with pain perception is still unresolved. 

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