Metatropic dysplasia accounts for approximately 5% of cases recorded by the International Skeletal Dysplasia Registry, with a single recorded lethal case. Four forms of the disease are currently recognized: type I, lethal autosomal recessive form; type II, nonlethal autosomal recessive form with survival to childhood; type III, autosomal dominant form with typical features, and type IV, a mild form with uncertain inheritance. The literature contains few well-documented reports of the histopathologic findings in metatropic dysplasia. In this report, we present the radiologic and histopathologic features in a cas e of type I metatropic dysplasia, with the unusual features of a persist ent tail, unique lung dysmorphology, and thyroidal agenesis.

Abnormalities, Multiple↗

PubMedDate not supplied

Regulation of myc gene expression in HL-60 leukaemia cells by a vitamin D metabolite.

HL-60, a cell line established from a patient with promyelocytic leukaemia, responds to a variety of inducing agents by ceasing division and acquiring some of the characteristics of either granulocytes or monocytes. Among the agents so far tested, only a comparative few occur naturally in vertebrates and would appear to have significant clinical potential in the treatment of leukaemic patients. One of the most promising of these is the dihydroxymetabolite of vitamin D3, 1,25(OH)2D3. This compound circulates in normal man and has a major role in calcium homeostasis. Moreover, it has recently been reported that 1,25(OH)2D3 increases the survival time of mice injected with myeloid leukaemia cells. We and McCarthy et al. have previously shown that HL-60 cells respond to near physiological levels of 1,25(OH)2D3 by rapidly acquiring a number of monocyte-like features. Here we document that these phenotypic changes are preceded by a marked decrement in the expression of the c-myc oncogene. In fact, the diminution in the level of c-myc mRNA parallels the dose dependency and metabolite specificity shown by the various other indicators of phenotypic change. In addition, we demonstrate that removal of vitamin D3, after the onset of maturational change, results in the reappearance of elevated myc mRNA levels. We believe this to be the first demonstration of a sequential relationship between the application of an exogenous inducing agent, a reduction in myc mRNA levels and the development of characteristics associated with normal cell maturation.

Animals↗

PubMedDate not supplied

[Continuous and intermittent mechanical forces in orthodontics].

Orthodontics is based upon the cellular response to biomechanical forces. To better investigate about the manner in which cells respond to such forces, we have devised an experimental model to permit morphologic and metabolic characterization of human cells subject to a range of cyclic or static mechanical stimuli similar to those which may prevail in orthodontic-orthopedic therapy. The most recent data in the literature indicated that cyclic forces could have bigger effect on cells than continuous ones. To better understand the rationale of the cyclic force effect, a morphological study on human fibroblast was performed. We found that stretching or compression delivered an immediate and proportional deformation on cells. After 10-15 minutes the morphology of cells readapt to the new mechanical environment, this causing the lost of the biological activation. A new mechanical stimuli should be necessary to determine a new biological reaction.

Cells, Cultured↗

PubMedDate not supplied

Relationships of static and kinetic histomorphometric features of bone.

Morphologic features of non-decalcified histologic sections of bone assessed by conventional staining techniques were quantitatively compared with kinetic parameters of the same sections as evaluated by time-spaced, fluorescent tetracycline markers. Double tetracycline labels appeared in apposition to more than 90% of osteoid seams lined by histologically characteristic osteoblasts in a biopsy exhibiting accelerated skeletal metabolism. In contrast, less than half of such surfaces exhibited a double tetracycline label in slowly remodeling bone. Furthermore, in actively metabolizing bone, double labels were found juxtaposed to approximately one-third of osteoid surfaces not lined by typical osteoblasts, and to more than 9% of surfaces exhibiting no osteoid seam at all. Single tetracycline labels were also present in association with non-osteoid lined surfaces in both biopsies. These data underscore the necessity of time-spaced tetracycline markers in ascribing kinetic features to histologic parameters of bone.

Adolescent↗