Effects of locally applied Insulin-like Growth Factor-I on osseointegration.

BACKGROUND: The aim of this study was to assess the effect of local application of IGF-I on osseointegration of dental implants placed in osteoporotic bones. MATERIAL AND METHODS: 16 rabbits were randomly distributed into two groups: eight animals were ovariectomized and fed a low-calcium diet for six weeks, in order to induce experimental osteoporosis, and the others were sham-operated and fed a standard diet. A titanium implant was inserted into the tibiae in both groups. In half of the rabbits, 4 µg of IGF-I was applied into the ostectomy, prior to the implant insertion. A total of 32 implants were placed. Animals were sacrificed two weeks after surgery and decalcified samples were processed for Bone-To-Implant Contact (BIC) and Bone Area Density (BAD) measurements. Analysis of variance (ANOVA) was used for statistical evaluation. P<0.05 was considered to be significant. RESULTS: Ovariectomy induced statistically significant lower BAD values (p=0.008) and a tendency towards lower BIC values when compared osteoporotic and healthy groups. The administration of 4 µg of IGF-I did not produce statistically significant differences neither on BIC nor on BAD values, neither in the osteoporotic animals nor in healthy. CONCLUSIONS: Within the limitations of this experimental study, local administration of 4 µg of IGF-I was not able to induce any changes in the osseointegration process two weeks after surgery, neither in healthy rabbits nor in the osteoporotic group.

Aging-induced alterations in female rat colon smooth muscle: the protective effects of hormonal therapy.

Aging is associated to oxidative damage and alterations in inflammatory and apoptotic pathways. Aging impairs secretion of several hormones, including melatonin and estrogens. However, the mechanisms involved in aging of smooth muscle are poorly known. We have studied the changes induced by aging in the colonic smooth muscle layer of female rats and the protective effect of hormonal therapy. We used young, aged, and ovariectomized aged female rats. Two groups of ovariectomized rats (22 months old) were treated either with melatonin or with estrogen for 10 weeks before sacrifice. Aging induced oxidative imbalance, evidenced by H(2)O(2) accumulation, lipid peroxidation, and decreased catalase activity. The oxidative damage was enhanced by ovariectomy. In addition, aged colonic muscle showed enhanced expression of the pro-inflammatory enzyme cyclooxygenase 2. Expression of the activated forms of caspases 3 and 9 was also enhanced in aged colon. Melatonin and estrogen treatment prevented the oxidative damage and the activation of caspases. In conclusion, aging of colonic smooth muscle induces oxidative imbalance and activation of apoptotic and pro-inflammatory pathways. Hormonal therapy has beneficial effects on the oxidative and apoptotic changes associated to aging in this model.

Mikro-knemometry: an accurate technique of growth measurement in rats.

A novel, noninvasive technique for accurate measurements is presented which determines the distance between knee and heel of the rear lower leg in the conscious rat (mikro-knemometry). Each measurement consists of initially six, later four subsequent and independent estimations of this distance. During a 14-day training study, the mean standard deviation (technical error) of five (six minus the first estimation) decreased from 196 microns to 101 microns. Measurements at exact 24-h intervals revealed nonlinear increments of rat lower leg growth, with marked infradian variation once every four to six days, similar to "mini growth spurts", described in rabbit and human growth. There was also a significant circadian periodicity of leg length increment (p < 0.01), with a minimum leg increment (after midnight dip) between 2400 h and 0300 h (mean: 4.8% (SEM 2.3%) of the total 24-h increment, p < 0.01), and a maximum increment (early morning spurt) between 0600 h and 0900 h (mean: 34.9% (SEM 2.5%) of the total 24-h increment, p < 0.001). Thus, the technique of mikro-knemometry seems to be a useful tool for the investigation of longitudinal growth in laboratory rats, and may replace conventional techniques of growth measurements such as measuring body weight, nose-tail, or tail length.