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Post-operative infections in orthopaedic implants are severe complications that require urgent solutions. Owing to the presence of implants and the formation of bacterial biofilms, the efficacy of antibiotics is limited. Furthermore, osteoclasts can become extremely active, accompanied by bone loss in the infected microenvironment. Therefore, implants often need to be removed. To improve the concentrations of antibiotics in bony tissues and enhance their effectiveness in preventing bacterial biofilm formation, the infection rate must be controlled to preserve the implants. Enoxacin exerts combined antibacterial and osteoclast inhibitory effects. It also plays a role in limiting infections and preventing bone loss. Aspartic acid octapeptide (ASP8) can also recognize and combine with hydroxyapatite crystals in bones and can be targeted to increase antibiotic concentrations in bones. Our previous research showed that preparing mesoporous nanomaterials resulted in optimal drug loading, releasing, and bone-targeting properties. Based on earlier research, a new bone-targeted antibiotic release system was developed. Enoxacin and ASP8 were loaded on mesoporous silica nanoparticles (MSNs) to increase antibiotic concentrations, prevent bacterial biofilm formation, inhibit aberrant osteoclast activities, and reduce bone loss. Enoxacin-loaded MSNs (Gen@MSN-D) were assessed using a variety of experimental methods, including rat models. We studied the in vitro antibacterial properties of the new drug delivery system. We found that these materials had antibacterial properties in vivo, inhibitory effects on osteoclasts, and can be used to prevent and treat post-implantation infections and bone loss. Therefore, we believe these materials will provide a new method for preventing and treating post-operative, orthopaedic implant-associated infections.

Induction of chloramphenicol (Cm) acetyltransferase-encoding genes (cat) by Cm has been proposed to result from the destabilization of a stem-loop that sequesters the ribosome-binding site for the cat coding sequence. Destabilization is caused by the stalling of a ribosome at a specific site in the leader of cat transcripts that immediately precedes the stem-loop. By use of in vivo dimethylsulfate probing of cat-86 leader mRNA, we demonstrate the existence of the stemloop structure in cat transcripts isolated from uninduced cells and its release during induction. Leader mutations chosen to provide the mRNA with an alternative folding pattern that destabilizes the stem-loop cause constitutive cat expression. Our results establish the occurrence in vivo of the stem-loop in cat-86 transcripts and its role as a negative regulator of cat expression.

Oral administration of Gossypol acetic acid induced sterility in male hamsters and rats when given at a dose level of 5 or 10 mg/kg daily for 12 weeks. This was shown by the appearance of dead and abnormal sperm in the male tract and the failure of pregnancy or decrease in implantation sites in the females mated to the Gossypol-treated males. Similar treatment of male rabbits at dose levels varying from 1.25 to 10 mg/kg and given for 5 to 14 weeks did not affect the average number of sperm per ejaculate, although the motility of sperm was poor during treatment in some bucks. The pregnancy rates and the proportion of implantation sites were also not affected by insemination of female rabbits with sperm from males during treatment with Gossypol.

Two A-nor steroids, Anordrin and H241, showed a marked antifertility effect when given orally to hamsters at 10 mg/kg/day for three or four days after mating. Further study indicated that the antifertility effect was due to a disturbance of egg transport, retarded development and degeneration of fertilized eggs.