[The importance of cytogenetic examination in childhood malignancies].
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Acute Disease↗
Biomedical subjects
M Weinreb
Publications and source records attributed to M Weinreb.
Osteopenia in the immobilized rat hind limb is associated with increased bone resorption and decreased bone formation.
The lack of mechanical function (disuse) caused by paralysis, immobilization or weightlessness, leads to osteopenia. This study examines the contribution of bone resorption and bone formation to osteopenia of disuse, during six weeks of limb-immobilization in the growing rat. Male Sprague-Dawley rats of approximately 200 g underwent unilateral hind-limb immobilization by either tenotomy at the knee joint or sciatic neurectomy, while control rats were sham-operated. Animals were sacrificed at 30 and 72 hours, 10, 26 and 42 d postsurgery. Femora were ashed to determine the total mineral content and histomorphometric parameters, static and dynamic, were measured in the secondary spongiosa of the proximal tibial metaphysis. No difference was found in the femoral length of the immobilized legs. Bone loss in the immobilized leg versus the nonimmobilized one, at 10, 26 and 42 d post-surgery was 18.0, 14.0 and 11.2% of femoral mineral content in the tenotomy group, respectively, and 12.4, 16.1 and 15.7% in the neurectomy group. Loss of metaphyseal trabecular bone volume at 10, 26 and 42 days amounted to 67.8, 49.3 and 52.9% in the tenotomy group, respectively, and 70.5, 59.0 and 72.9% in the neurectomy group. The bone loss was caused by: (a) A rapid surge in bone resorption, reflected in a significant increase in the number of osteoclasts per mm bone surface at 30 and 72 h and in the osteoclast surface at 72 h but not at later times, and (b) a sustained decrease in bone mineral apposition rate and bone formation rate (osteoblast-referent) throughout the 42-day immobilization period suggesting osteoblastic hypofunction (reduced activity).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
A three-dimensional evaluation of the effects of functional occlusal forces on the morphology of dental and periodontal tissues of the rat incisor.
We examined the effect of function on tooth and periodontal ligament (PDL) morphology in 40 lower incisors of adult female rats. Ten teeth were exposed to occlusal hyperfunction for three months, ten to hypofunction for three weeks, ten to hypofunction for three months, while ten teeth in normal occlusion served as control. Transverse ground sections were cut at various levels perpendicular to the tooth long axis, and their distances from the apex were calculated. The outlines of the tissues were traced and fed into a computer. We plotted the measurements according to their location and fitted them by second-order polynomials. We calculated tissue volume for the proximal 18 mm of bone-embedded tooth. Hyperfunction affected tooth shape, in that it became more rounded. The volumes of the dental tissues remained unchanged, while width and volume of the cementum-bordering PDL increased. Hypofunction did not alter tooth shape, but influenced its size: After three weeks, tooth circumference decreased, and after three months, it expanded. Dentin width was reduced, with concomitant increase of pulp size. The amount of enamel diminished initially, but after three months returned to normal values. The PDL bordering enamel expanded proportionally to the duration of hypofunction. The changes in socket size reflected the total dimensional variations in the tooth and its PDL. The results demonstrate that the shape and size of growing teeth and their periodontium are influenced by functional occlusal forces.
Alveolar Process↗
Three-dimensional presentation of cell migration in the periodontal ligament of the rat incisor.
The progenitor compartments and cell migration were examined in the tooth-related periodontal ligament (t-PDL) of rat incisors. A pulse injection of 3H-Tdr was administered to 15 rats (200 gm each) and the animals were killed in groups of five, at 1 hr and at 1 and 2 weeks after injection. Three-dimensional analysis of cell counts and labeling index demonstrated the existence of two progenitor compartments (PC). The apical PC (responsible for 70% of synthesizing cells) was concentrated in the apical 5 mm of the t-PDL. The paracemental PC (30% of synthesizing cells) was located along and around the cementum, occupying 24 micron of the t-PDL. The cells from the apical PC migrated incisally at a rate of 6 mm/week, which is a rate similar to that of tooth eruption. The cells from the paracemental PC moved in a transverse direction toward either bone or cementum at the much slower rate of 16 micron/week.
Animals↗
Epstein-Barr virus (EBV) antibodies in children with non-Hodgkin's lymphomas.
Antibody titres against Epstein-Barr virus (EBV) antigens in children suffering from non-Hodgkin's lymphoma (NHL) were determined. IgG antibody titres against the viral capsid antigen (VCA) and early antigen (EA) exceeded those found in healthy control subjects. On the other hand, antibody titres against EBV-determined nuclear antigen (EBNA complex) were generally lower than in the control group. The most striking phenomenon observed in the patient group was the frequent activation of latent virus infection as revealed by the periodical appearance of anti-EA and IgM class anti-VCA antibodies. Antibody titres against EBV antigens were generally lower among patients with progressing disease than in those with a more favourable course of the illness. The closest relation to EBV based on serological findings, was detected in lymphoblastic lymphomas of Burkitt-type histology, poorly differentiated lymphocytic lymphomas, and in lymphomas localized in the abdomen. The question whether EBV might be involved in a certain proportion of the cases examined is discussed and further approaches to elucidate this problem are suggested.
Adolescent↗
Three-dimensional presentation of the fibroblast progenitor compartment in the periodontal ligament of the rat incisor.
The purpose of this study was to determine the shape, size, and spatial configuration of the fibroblast progenitor compartment (PC) of the tooth-related periodontal ligament (PDL). Five albino rats (weight 200 gm) were killed 1 hr following intraperitoneal injection of 3H-thymidine. The incisors were decalcified, embedded in glycol-methacrylate, and sectioned serially, perpendicularly to the long axis of the tooth. Ten 2-microns-thick sections along each tooth were selected, processed autoradiographically, and the distance from the apex measured. Labeled and unlabeled fibroblasts were counted in 8 x 80-microns consecutive layers. Cell density (CD) and labeling index (LI) were plotted on a three-dimensional system of coordinates depicting the directions: apex to incisal edge, cementum to bone, and cemento-enamel junction (CEJ) to lingual tooth surface. The CD along the tooth was constant, except at 2-6 mm distant from the apex, where it was significantly higher. The highest concentration of cells around the tooth was in the 20-microns region adjacent to the cementum. The PC on the mesial and lateral tooth sides extended 1-4 mm from the apex, with the LI peak (6.5%) occurring at 2 mm. The PC on the lingual tooth side was located at 2-6 mm from apex, peaking (14%) at 4 mm. On the cementum-bone coordinate, the PC extended to about 50 microns from the cementum on all sides, the LI peak appearing at a distance of 20-40 microns from the tooth. The LI was consistently higher on the lingual side than on the mesial and lateral aspects.
Animals↗
Long-term effect of loading on the fibroblast population of the periodontal ligament in the rat lower incisor.
The number and density of the cells in the tooth-related periodontal ligament (t-PDL) were related to the recovery of eruptive potential 2.5 months after load removal. Four left incisors in which eruption returned to normal (group A) and six in which eruption remained grossly impaired after a two-week application of latero-intrusive loads of 18.5 +/- 0.69 (group B) were compared to four control rats with unimpeded eruption. The incisors were demineralized, embedded in paraplast and cut into 6 micron transverse serial sections from which a three-dimensional reconstruction of the PDL was made by computerized histomorphometry, and the fibroblast population counted. The t-PDL volumes in controls and in groups A and B reached 1.15, 1.05 and 1.53 mm3, respectively; the estimated number of cells in the same PDL volumes were 2244 X 10(3), 1.659 X 10(3) and 2094 X 10(3) cells, respectively. The mean cell count/segment of PDL and the calculated number of cells/unit of periodontal tissue were significantly lower (p less than 0.001) in the formerly stressed, lateral periodontium of both experimental groups. In group B, these values were also decreased in the mesial periodontium.
Animals↗
Structural changes in the dental and periodontal tissues of the rat incisor following application of orthodontic loads.
The present study deals with the morphometric changes in the loaded rat incisor and its supporting structures 3 months after load removal. The material examined was limited to that part of the tooth that is located between 8 and 20 mm from the tooth apex. Of the ten albino rats in whom laterointrusive loads (19 +/- 0.6 g) were applied to the lower left incisor for a period of 2 weeks, the rate of tooth eruption returned to normal in four animals (group A); in six rats, eruption remained grossly impaired (group B). These two groups were compared with a control group of four rats in whom the incisors were allowed to erupt normally during the 3 months of the experiment. The left mandibles were dissected and fixed; the incisors were demineralized, embedded in paraplast, and cut into transverse serial sections of 6 micron, which were used to produce a three-dimensional reconstruction of all tissue components by means of computerized histomorphometry. The parameters of pulp and dentin, and the total tooth size and shape in group A were similar to those of the control group. In group B, pulp and dentin were changed significantly, tooth size increased, and the oval shape was altered into a more rounded contour, together with a significant enlargement of the socket. Although the total PDL volumes remained similar in all three groups, the tooth/socket relation, as expressed by PDL width and PDL area at the different tooth sides and at varying distances from tooth apex, diverged from normal significantly in all teeth that had been subjected to loading.
Alveolar Process↗
A computerized histomorphometric study of the effects of intoxication with vitamin D3 or 1,25 (OH)2D3 on growth and dentin production of impeded and unimpeded rat incisors.
The effects of Vitamin D3 and 1,25(OH)2D3 intoxication on growth and dentinogenesis were studied in impeded and unimpeded rat incisors. Animals were intoxicated either with Vitamin D3 (2 mg/kg/day) or 1,25(OH)2D3 (400 ng/kg/day) for 19 days. Undecalcified transverse sections were obtained from all lower incisors. The outlines of all dental tissues were traced and fed into a computer which depicted the changes in all variables measured (circumference and cross-sectional area of tooth, pulp and dentin, width of dentin, CEJ [cemento-enamel junction] diameter and maximal labio-lingual diameter). Eruption rates, which had been recorded previously every 48 h, were used to compute the physiological age of each tooth site, so that only areas of similar age be compared. Growth. External dimensions of all intoxicated teeth decreased as the experiment progressed in contrast with control incisors which continued to increase in size. This effect was more pronounced in unimpeded incisors and may be due to the inhibitory influence of 1,25(OH)2D3 on cellular proliferation at the apical progenitor end. Dentinogenesis. 1,25(OH)2D3 intoxication had no significant effect on the rate of eruption and dentin formation in both impeded and unimpeded incisors. The same was true for impeded incisors intoxicated with Vitamin D3 but, both eruption and dentin production rates were impaired in Vitamin D3 unimpeded incisors.
Animals↗
The effect of aging on tooth morphology: a study on impacted teeth.
The effect of age on dental tissues was studied on histologic sections of totally impacted teeth obtained from patients between 11 and 76 years of age. Impacted teeth were used in order to obviate the influence of the environmental effects prevalent in the oral cavity. The presence of concentric denticles and diffuse calcifications was determined, and the width of secondary dentin, predentin, and cementum was measured. The width of predentin and cementum increased linearly with age, whereas the aging process of secondary dentin formation and diffuse calcifications followed a different pattern. The incidence of concentric denticles was identical for all age groups.
Adolescent↗
The response of the fibroblast population in the periodontal ligament of rat incisors to altered eruption rates.
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Animals↗
Mandibular growth and histologic changes in condylar cartilage of rats intoxicated with vitamin D3 or 1,25(OH)2D3 and pair-fed (undernourished) rats.
The mandibular condyles of 1,25(OH)2D3 or Vitamin D3 intoxicated rats were studied and compared with those of normal as well as pair-fed controls. Experimental animals were injected with either Vitamin D3 (2 mg/kg/day) or 1,25(OH)2D3 (400 ng/kg/day) for 19 days. Controls were given the solvent only, while pair-fed animals were restricted in their food intake for the same period of time, so that they exhibited a weight-curve similar to that of the experimental rats. The length of the mandibular ramus was measured in lateral radiographs of all mandibles. Demineralized coronal sections were obtained from all mandibular condyles and were stained with Mallory's connective tissue stain. The width of each zone within the condylar cartilage was measured. Experimental animals showed significant reduction in width of all layers within the condylar cartilage, with total lack of distinction between the maturation and hypertrophic zones. They also exhibited a significant retardation in growth of the mandible. Pair-fed animals had a normal width of the chondroprogenitor layer but significantly smaller maturation + hypertrophic zones (vs. controls). They also exhibited a significant retardation in mandibular growth but not to the same degree as did the intoxicated animals. Reduction in growth attributed to 1,25(OH)2D3 or Vitamin D3 intoxication is partly caused by undernutrition, which is a by-product of this condition. A further kinetic study is indicated to elucidate the mechanism of growth retardation and the differential effect on the various cartilage layers.
Animals↗
Odontoblast turnover in the impeded and unimpeded rat incisor derived from computerized histomorphometry.
A computerized histomorphometric method was devised to estimate the kinetics of odontoblast turnover and dentinogenesis in rat incisors. The method was applied to two groups of rats: one group with lower incisors in impeded eruption and another group with the left lower incisor in the unimpeded state. The teeth were divided into six equal segments, from which consecutive ground sections were obtained. The distance of each ground section from the posterior border of the alveolar bone was calculated. Each section was magnified, traced, and the tracings fed into a computer by a sonic digitizer. The perimeters and areas of dentine and pulp in each ground section were calculated by the computer. The mean odontoblast density along the predentine was evaluated from histological sections taken both from the same tooth segments and from teeth sectioned midsagittally. These served for the estimation of the predentine area occupied by the average odontoblast. In the impeded group, this area was 11% larger than in the unimpeded one. Outer dimensions of teeth, namely the circumference of the dentine, the labiolingual width, and the mesiolateral width remained constant and equal for both groups. Daily rates of dentine apposition were computed and were found to vary according to the age of the odontoblasts. Odontoblasts of impeded teeth started to secrete matrix at a rate of 17 microns/day, which increased slightly to 19 microns/day and later declined to 7 microns/day on the 38th day. Dentine production of unimpeded odontoblasts, on the other hand, started at a rate of 16 microns/day and gradually increased to 34 microns/day on the 17th day.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The streaming liver.
Twenty male adult rats weighing 200 g were injected with tritiated thymidine (3HTdR). The animals were then killed in groups of five, at the following times: 1 h, 1, 3 and 5 weeks. Autoradiograms of sections through the liver were prepared. The distances between labelled cells and the portal space rim were measured. One hour after labelling most labelled cells were confined to a region extending from the portal space rim up to a distance of 700 micron, which roughly corresponds to Rappaport's hepatic acinus zones-1 and -2. Throughout the experiment lasting 5 weeks labelled cells entered zone-3 and advanced toward the terminal hepatic vein. Hepatocytes travelled at a daily velocity of 1.44 micron, covering daily 0.324% of the acinus diameter. During the experiment acinus size did not change appreciably. The estimated mean hepatocyte cell cycle time was 37 days and its life expectation, 201 days. These experiments show that the liver is essentially a slowly renewing cell population. Hepatocytes nascent at the portal space gradually stream toward the terminal hepatic vein where they are probably eliminated by apoptosis. Their journey lasts 201 days. Since hepatocytes are glued together with tight junctions, all have to advance toward their terminal hepatic veins en masse. During their voyage, they traverse the three acinus zones, and since in each they produce different enzymes, each zone represents a differentiation state of the advancing cell. It is suggested further that the streaming hepatocyte carries with it its nerve supply and is accompanied by sinusoidal endothelium and Kupffer cells.
Animals↗
Histomorphometric evaluation of the dimensional changes in rat-incisor tissues following histological processing and embedding in paraffin wax and glycol methacrylate.
A three-dimensional reconstruction of undemineralized and paraffin wax- or or glycol methacrylate-embedded demineralized rat incisors was made using a computerized histomorphometry. Compared to the undemineralized ground sections, the two demineralizing and embedding procedures grossly distorted the tooth sections. In general, embedding in wax caused shrinkage and in methacrylate caused swelling. Direction and magnitude of the deformation varied in the different tissues of the tooth and its surrounding structures. The distortion was influenced by the ratio between the soft and hard tissues at different cross-sectional levels of the tooth.
Animals↗
Possible mechanisms of induction of dentinogenesis.
The following hypothesis is proposed: The inner enamel epithelium influences all cells of the dental papilla very early during embryologic development--long before any morphologic changes due to histo-differentiation are noticeable. During normal odontogenesis, the epithelium acts as a second order inducer for the differentiation of odontoblasts and their subsequent production of dentin. Other mechanisms exist which can induce responding fibroblasts of the dental pulp to produce dentin or dentin-like tissue. Collagen matrix can act as such an inducer.
Animals↗
Discrimination between normal and malignant gastric epithelial cells by computer image analysis.
The nuclei of 21 normal and 23 malignant epithelial cells from gastric smears obtained by brushing were analyzed by a black-and-white video camera under computer control. Each nucleus was digitized and its relief smoothed and displayed. A Sobel operator determined the nuclear boundaries and nuclear core area. Eighteen nuclear parameters (form descriptors and gray-value descriptors) were extracted for each nucleus and used as variables for discriminant analysis. Nine of these parameters proved useful for discrimination between normal and malignant gastric epithelial cells, with a correct classification rate of 100%. Of these, the best discriminating variables were the maximal gray value in the core, the maximal horizontal and vertical diameters, the core area and the mean derivative value in the core.
Cell Nucleus↗
Three-dimensional reconstruction of the rat incisor by means of computerized histomorphometry.
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Animals↗