Rabbit marrow cells inoculated into diffusion chambers (10(7) cells/chamber) were implanted intraperitoneally into athymic mouse hosts and cultured in vivo for 20 days. A connective tissue consisting of bone, cartilage and fibrous tissues is formed by the stromal fibroblastic cells of marrow within the chambers. Cell kinetics and tissue differentiation have been studied using histomorphometric and biochemical analyses. Haemopoietic cell numbers decrease to less than 0.05% of the initial inoculum during the 20-day period. At 3 days an average of 15 stromal fibroblastic cells only are identifiable within the chambers. After 3 days there is a high rate of stromal cell proliferation with a doubling time of 14.5 h during the period from 3 to 8 days and an increase in the total stromal cell population by more than six orders of magnitude from 3 to 20 days. Thirteen to fourteen population doublings occur before expression of the first observable differentiation parameter, alkaline phosphatase activity. The data demonstrate that the mixture of connective tissues formed within the chamber is generated by a small number of cells with high capacity for proliferation and differentiation. This is consistent with the current hypothesis that stromal stem cells are present in bone marrow.
The authors report the case of a 15-year-old female who presented with a history of vague but constant pain about the medial aspect of her right knee. X-ray established the presence of an expanding lesion in the medial tibial plateau. Computerized axial tomography (CT) and magnetic resonance imaging (MRI) were used in the evaluation of the lesion. The authors compare the preoperative CT and MRI findings with the microscopic histopathology of the amputation specimen and note that the CT scan underestimated the extent of the microscopic tumor boundaries, whereas MRI showed altered activity beyond these boundaries.
Tissue samples obtained from human gingiva with soft tissue calcification were processed for light and transmission electron microscopy. The stroma in these specimens revealed numerous foci of calcification in a matrix that consisted of closely packed branching microfibrils, 12 nm in diameter and a maximum of 2.5 micron in length. Calcospherites, 0.25-1.11 micron in diameter, were present within the matrix. They were constructed of needle-like units shown by high resolution electron microscopy and energy dispersive X-ray microanalysis to be apatite. Larger calcified masses were composed of calcospherites which were fused together. Matrix vesicles or other forms of membraneous material could not be found. The relationship between the mineral and non-collagenous microfibrils may suggest a role for the latter in the onset of calcification in this ectopic site.
The present paper reports alterations in osteogenesis recorded in mandibular condyles 3-18 days after the removal of marrow tissue from tibial bones. Computerized histomorphometric evaluation of undecalcified condyles revealed a considerable increase in the thickness of condylar cartilage, in particular, the zone of provisional calcification. Measurements of the subcartilaginous trabecular bone suggested an increase in the number of osteoblasts and in their activity. The systemic enhancement of osteogenesis may be initiated by circulating factors released at the affected limb during regeneration of the marrow.
A review of data on oral cancer in Israel revealed a lower incidence and a later onset age than in other countries. These data are reviewed and consideration is given to the high prevalence of smoking and the low incidence of alcoholism in Israel.
In 1972, the World Health Organization's "Meeting of Investigators on the Histological Definitions in Precancerous Lesions" defined a precancerous lesion as a "morphologically altered tissue in which cancer is more likely to occur than in its apparently normal counter part" (Pindborg 1980). There are two generally accepted precancerous lesions in the oral cavity, leukoplakia and erythroplakia (Pindborg 1980). Leukoplakia is currently defined as "a white patch or plaque that cannot be characterized clinically or pathologically as any other disease" (WHO 1978). This definition has no histological connotation and is used in a strictly clinical sense (Pindborg 1980, Banoczy 1977). Erythroplakia is defined as a "bright red velvety plaque which cannot be characterized clinically or pathologically as being due to any other condition" (Pindborg 1980).