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Biomedical subjects

E A Tonna

Publications and source records attributed to E A Tonna.

At least 19 recordsLinked to original sources
PubMed1987

Autoradiographic evaluation of circadian periodicity in cell proliferation in the periodontal ligament of the young mouse.

Five-week-old BNL male mice were maintained on a 12-h light/dark cycle, subcutaneously injected with [3H]-thymidine 1 h before death and killed every 3 h for 24 h. Autoradiographs were made from demineralized, paraffin-wax embedded sagittal sections of maxillae. The labelling index was calculated for fibroblast-like cells of the periodontal ligament mesial to the first molar. A bimodal distribution of labelled cells was seen. Labelling index was highest at 0900 h (light period); a second, lower, peak was seen at 2400 h (dark period). Cell proliferation was significantly increased during the light period. The increased activity during the dark period may represent a superimposed secondary, ultradian, rhythm, differences in periodontal cell subtypes or may be related to the feeding and activity cycle of the mouse. Thus there is a 24-h cyclic rhythmicity in the proliferation of periodontal-ligament cells in the mouse.

Animals↗
PubMed1987

Circadian rhythms of gingival epithelium in young mice.

Five-week-old Brookhaven National Laboratory (BNL), Swiss-albino male mice were maintained on a 12-hour light/dark cycle and were subcutaneously injected with 3H-thymidine (1 micro Ci/gm body weight) one hour prior to sacrifice. Twenty-four mice (three each time-period) were killed at 3 hour intervals for 24 hours. Autoradiographs were prepared from 5-micron thick paraffin embedded decalcified sections of maxillary first molars and surrounding tissues. Labeling index was determined over the cells of the basal layer of the gingival epithelium. Crevicular and crestal gingival epithelium revealed a circadian rhythmic pattern in DNA synthesis in which two peaks were evident. Peak labeling of 5-week-old mouse gingiva exhibited a higher value than previously reported for nontraumatized gingiva. Rodents are nocturnal, as was peak activity, but a second peak is also evident in the light period. Consequently, not all peaks are synonymous with the period of animal activity and feeding. The observed continuous high labeling indices represent a significant potential of gingival epithelium to replenish its cells in response to physiological wear and tear.

Animals↗
PubMed1987

Autoradiographic investigation of circadian rhythms in alveolar bone periosteum and cementum in young mice.

This report presents circadian rhythms in cell proliferation of alveolar bone periosteum and cementum of the maxillary first molars of male 5-week-old BNL, Swiss albino mice which were maintained on a 12 hr light/dark cycle. Mice were injected with 3H-TDR (luCi/gm. body wt.) 1 hr prior to sacrifice and killed every 3 hrs for 24 hrs starting at 9 a.m. Maxillae were decalcified, routinely processed histologically and autoradiographs prepared. Cell labeling indices of alveolar bone and cementum mesial to the first molar were determined. Alveolar bone periosteal and cemental cells show circadian rhythm in their DNA synthetic processes. Peaks in percent labeling exhibit higher values than previously reported for nontraumatized, normal dental periosteum and cementum. While the outer periosteum reveals a single 24 hr peak (6 p.m.), inner periosteum and cementum reveal two ultradian peaks 9 to 12 hrs apart involving both light and dark periods. Rodents are nocturnal, but high peaks are also evident in the light periods, consequently, not all peaks are synonymous with the period of animal activity and feeding. Although the single daylight peak of the outer periosteum may indicate growth of that surface at night to about noon, the double peaks exhibited by inner periosteum and cementum indicate light/dark, continuously active surfaces in terms of DNA synthesis and growth.

Animals↗
PubMed1986

Incorporation and stabilization of 3H-tetracycline in embryonic chick bone: an autoradiographic study.

Tibiae from 11-day-old chick embryos, injected with 3H-tetracycline, were autoradiographically analyzed at different stages to localize and study the dynamics of the initial phases of bone mineralization. 3H-tetracycline was localized within newly formed trabeculae, but only at the surfaces of older trabeculae, indicating that the incorporation of tetracycline into bone occurs at active sites of calcification. It takes between 24 and 36 h for injected tetracycline to become stabilized and incorporated into the mineralized matrix. Absence of 3H-tetracycline grains over the osteoblasts suggests a paracellular pathway for incorporation of tetracycline into the mineralizing bone matrix.

Animals↗
PubMed1982

The autoradiographic utilization and distribution of [1-3H]-galactose by the dental tissues of ageing mice.

The uptake, turnover and distribution of [1-3H]-galactose by periodontal tissues associated with maxillary first molars of mice 5, 26 and 78 weeks of age showed that galactose was utilized by all oral tissues studied throughout the life-span. Uptake and turnover of the tracer revealed pulsed events. Synchrony of the pulsed events was noted. With increasing age, diminished utilization of galactose was evident, as well as a change in peak-time of the curves characteristic of ageing. The complex plots represent several metabolic events occurring simultaneously. The uptake of galactose by fibrogenic, osteogenic and cementogenic cells was low. Matrical output, on the other hand, remained high. Cementogenic cell output was the highest of all the tissues over the 30-day period. Despite decreased physiological activity with age and superimposed age changes, galactose utilization remained high throughout the study.

Aging↗
PubMed1978

Electron microscopic study of bone surface changes during aging. The loss of cellular control and biofeedback.

An electron microscopic study was made to determine (1) the effects of aging on periosteal and endosteal bone surfaces and (2) whether the membrane-like arrangement of osteoblasts at bone surfaces was retained during aging. Short-lived BNL inbred Swiss albino mice 5 to 130 weeks of age were perfused with glutaraldehyde. Femoral samples were taken and fixed in cold glutaraldehyde, decalcified in EDTA, and postfixed in OsO4. Epon sections were cut and stained with uranyl acetate and lead citrate. In young mice, during bone formation a zone of osteoid was observed while the preosseous zone above consisted of young collagen fibers in formation. The osteoblasts formed a tight membrane-like structure at all bone surfaces. Where bone formation did not occur, single and multiple osmiophilic laminae were observed. With increasing age collagen formation became diminished as did the width of the preosseous and osteoid zones. Subsequently, the zones disappeared. Increased surface structural complexity was seen in some areas, while other areas revealed simplification with advancing age. This depended upon the net accretionary or resorptive activity at a given surface. The membrane-like arrangement of osteogenic cells was lost in 104-week-old animals, exposing bone surfaces to physio-chemical changes not under cellular control and biofeedback.

Aging↗
PubMed1976

An autoradiographic assessment of the incorporation of H3-uridine into DNA and RNA of osteoblasts of aging mice.

Intracellular labeling of DNA and RNA after H3-uridine administration was investigated autoradiographically during aging. Five to 78 weeks old mice were injected with 5 muCi of H3-uridine/gm of body weight and were killed from 15 minutes to 30 days later. Five mum decalcified sagittal sections of femora were treated with RNAase, DNAase or appropriate buffers. Autoradiographs were prepared and grain counts were made over diaphyseal periosteal osteoblasts. Both DNA and RNA incorporated H3-uridine. RNA label was 88 to 95% of the total cell label. DNA labeling ranged from 2 to 5%. DNA labeling appeared slightly increased after longer exposure to H3-uridine, whereas, RNA labeling remained relatively unaltered. With increasing age, incorporation into DNA decreased, whereas, RNA label showed a slight increase. A variable amount of non-specific label was undigested by either enzyme and may reflect insoluble conversion and/or degradation products. Apparently, some conversion of uridine into a DNA precursor occurs without loss of tritium label, thus rendering uridine less than totally specific for RNA. Nevertheless, the uptake of H3-uridine is largely indicative of RNA biosynthesis especially in skeletal cells that are not normally highly proliferative.

Aging↗