Scanning electron microscopic description of cellular activity and mineral changes in feline odontoclastic resorptive lesions.

The cellular activity and changes in mineral composition of dental tissues involved in feline odontoclastic resorptive lesions were investigated. Teeth with at least 1 lesion (n = 10) were extracted from 10 different cats that were presented primarily for chronic gingivostomatitis and/or severe periodontal disease. Scanning electron microscopic methods were used to determine the presence of resorptive cells in 8 teeth while 2 teeth were evaluated for pathologic changes in dental mineral composition. Observations were complicated by the presence of organic wear on the dental surfaces, however resorptive cells could be clearly identified in feline odontoclastic resorptive lesions. Resorptive cells had morphologic features indicative of "osteoclast-like" cells or odontoclasts. Resorptive cell activity created a resorption area of darker dentin continuous with physiologic dentin. The darker dentin area seemed poorly mineralized and showed a significantly lower calcium/phosphorous ratio compared with adjacent physiologic denting in 1 tooth. A significantly higher level of magnesium combined with available carbonate ions may have increased the solubility in areas of darker dentin.

Ultrastructural properties of bone mineral of control and tiludronate-treated osteoporotic rat.

Bisphosphonates have been widely used in the treatment of human bone pathologies including osteoporosis. In this case, bisphosphonates have been shown to reduce bone resorption, thereby increasing the mass and mechanical resistance of bone. Determining the effects of these molecules on the properties of the bone apatite crystals could provide a better insight into the mechanism of bisphosphonate/bone interaction. The aim of this study was to determine the ultrastructural effects of a third generation bisphosphonate (tiludronate) on the morphology, size, distribution, chemical composition, and structure of apatite crystals in bone (trabecular) in a rat osteoporotic model. Four groups of rats were studied: (1) sham operated, (2) untreated ovariectomized (OVX), (3) OVX rats which received 35 mg/kg of tiludronate, (4) OVX rats which received 160 mg/kg of tiludronate. The rats of groups 3 and 4 received tiludronate orally in 2 consecutive days every week for 1 year. Scanning electron microscopy (SEM), high and low resolution transmission electron microscopy (TEM), and electron microprobe analysis (EDX) were used for the ultrastructural characterization of the bone mineral. This study demonstrated that tiludronate slightly increased the width of bone apatite crystals without changing any other crystal characteristics.

Local treatment with indole-3-acetic acid induces differential growth responses in Zea mays L. roots.

Differential growth responses of primary Zea mays L. roots were induced after asymmetrical applications of IAA-loaded beads along their elongating zone (1.0-4.0 mm from tip) and were modulated according to the initial growth rates of the roots. The amplitude and location (midpoint) of curvature, the elongation of the roots and the uptake of IAA were measured after 4 h. The amount of curvature depended on the location of the bead and upon the amount of IAA taken up. Curvature occurred towards the site of IAA application and the zone (midpoint) of curvature was always found to be basipetal to the IAA-loaded bead, indicating the transport of a growth signal in a basipetal direction from the zone of IAA application towards the zone of curvature. Two regions within the elongation zone were thus characterized: an acropetal region (between 1.0-3.5 mm from the tip) in which IAA induced a growth signal and a basipetal region (3.5-6.5 mm from the tip) which displayed the growth response; neither of these regions were able to carry out both physiological functions. The acropetal region was extended in fast-growing roots or when the amount of applied IAA was increased. No significant growth stimulation of fast-growing roots was induced regardless of the amount of IAA supplied, but the growth of slow-growing roots was stimulated with very low amounts of IAA ([Symbol: see text]100 pg/root after 4 h). Inhibition of growth of both classes of roots increased with amounts of IAA between 100-600 pg/root after 4 h, but no further inhibition of growth appeared after treatment with greater amounts of IAA. A model based on these data shows a possible relationship between the uptake of IAA and root growth and indicates a clear relationship between an optimal level of IAA and root growth. The responses of the elongating cells of primary maize roots to applied IAA depend on their developmental stage and on the initial growth rates of the root.

Maize root growth and localized indol-3yl-acetic Acid treatment: a new methodological approach.

Resin beads loaded with indol-3yl-acetic acid (IAA) were used as asymmetrical donors along the elongation zone of intact primary Zea mays L. roots. A strong curvature, towards and above the bead, occurred when IAA was applied at a mean distance of 2.20 mm from the tip. No curvature was detected after applications at 3.89 and 5.71 mm from the tip. Correspondence analysis, a new methodological approach in plant hormone studies, permitted the evaluation of the relative influence of several factors on the curvature observed for each root. The parameters considered were the initial growth rate, the exact location of the bead (1.64-2.73 millimeters from tip) and the quantity of IAA absorbed. Roots which grew rapidly bent earlier than slowly growing ones and the more basal the treatment was, the less curvature occurred. Surprisingly, the amount of IAA taken up (between 1.2 and 2.2 times the endogenous IAA content) was found to have no influence on either the time-course or the magnitude of this growth inhibition (curvature). The usefulness of this multivariate analysis is also discussed.