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Biomedical subjects

J M Navia

Publications and source records attributed to J M Navia.

At least 55 records · Page 3Linked to original sources
PubMed1981

Biological rat assay for total fluoride availability in foods.

A fluoride (F) bioassay procedure based on the method of standard additions and using weanling rats was designed and tested. Rats were distributed between a control (C) group fed MIT 200 diet (F conc. less than 0.5 ppm) and an experimental (E) group fed this diet plus 1% dehydrated instant tea used as a model test food. Both groups were further divided into subgroups fed the C or E diets, but supplemented with 0.5, 10, 20 or 40 ppm F as NaF, and offered deionized water for a period of 10 days. Rats were then killed and femur (fm) and tibia (tb) dissected. Bone samples were treated in a closed system with HCl (6 N) and later with sodium citrate (30%) to determine F concentration using a specific ion electrode. F values (y) for fm and tb were plotted against F amounts added to the diets (xt). Weighted regression equations describing the linear relationship between the two variables were used to calculate the available F content of dehydrated tea which was 830 +/- 43 ppm F (using fm data) and 836 +/- 67 ppm (using tb data). Chemical assay of the dehydrated tea used as a test food gave a F concentration of 887 +/- 16 or 93.5 +/- 5.1% availability. This rat bioassay to determine total available fluoride in a dried food can be combined with a chemical assay to obtain a measure of percent availability of F.

Animals↗
PubMed1981

Effect of topically-applied solutions of iodine, sodium fluoride, or chlorhexidine on oral bacteria and caries in rats.

Antibacterial levels of iodine, chlorhexidine or sodium fluoride were topically applied to the molar teeth of rats. The effect of these agents on buccal and sulcal caries, as well as on certain oral bacterial populations was assayed. All three agents exerted a significant cariostatic effect which was site specific. Buccal caries incidence and reductions appeared correlated to S. mutans counts, while sulcal caries was better correlated to total cultivable counts. These studies suggested that the simultaneous application of iodine and NaF might exert an additive cariostatic effect.

Administration, Topical↗
PubMed1980

Zinc deficiency and bone formation in guinea pig alveolar implants.

Bone formation under zinc deficiency conditions was investigated using alveolar implants in guinea pigs, from which bone formed solely during the period of zinc deficiency could be obtaned. Thirty-six guinea pigs (GP) weighing 175-195 g were randomly divided into three groups: group 1 received a -Zn diet, (1.0 +/- 0.2 ppm Zn); group 2 pair fed control, and group 3 ad libitum control. After 3 weeks of dietary treatment, the right incisor was extracted and a nylon mesh tube (1.0 cm long) was implanted into the incisor alveolar cavity. Two weeks after implantation, all GP were killed and bone-containing nylon implants (BCNIs) and femurs were removed for Zn, Ca and P analyses. Compared to the two control groups, -Zn group showed two to fourfold less zinc in femurs and in BCNIs, respectively. Femur, but not BCNI, from pair-fed GP had significantly higher zinc concentration than that of GP in group 3, Ca and P concentrations in -Zn BCNI were not significantly reduced, but P in -Zn femur was. When BCNIs were cultured for 48 hours in BGJ media containing 35SO4 or 14C-glucosamine, -Zn BCNIs incorporated significantly more 14C and slightly higher 35S into their glycosaminoglycan (GAG) fraction. It is concluded that under our standardized conditions zinc deficiency does not show an effect on Ca and P depositions into bone, but it seems to interfere with glycosaminoglycan metabolism of membranous bone.

Animals↗
PubMed1980

Vitamin A influence on calcium metabolism and calcification.

Vitamin A deficiency has been shown to affect vision, reproduction, cellular differentiation, and maintenance of epithelial and skeletal tissues. Different vitamin A compounds, i.e., retinol and retinoic acid, vary in their ability to fulfill these biologic functions. Aside from vision, the exact molecular mechanisms of action for retinoids are largely unexplained. High doses of vitamin A are known to increase bone resorption through stimulation of lysosomal proteolytic activity, which also leads to increased secretion of PTH. Deficiency of retinol affects bone morphology by increasing bone thickness. Using a standardized guinea pig model, bone formed entirely during a retinol-deficient (A --) period contained less calcium and took up more 35S into glycosaminoglycan (GAG) fractions in vitro than did control (A+) samples. Using rat calvaria, a pulse-chase experiment indicated that the rate of 35S loss from calvaria cultured with A -- serum was lower than in controls. Thus, retinol deficiency seems to increase the amount of sulfated GAG in bone through a defect in the degradation of GAG.

Animals↗
PubMed1978

Sulfate metabolism in rat calvaria cultured under vitamin A deficient conditions.

The metabolism of sulfated glycosaminoglycans (GAG) in bone has been found to be altered in vitamin A deficiency. A neonatal rat calvarium model system was used to determine if these changes are related to catabolic defects. Two day old rat pup calvaria were cultured in media containing serum from A- or A+ rats and radiolabeled sulfate or glucosamine. The incorporation of 35S-sulfate into the GAG fraction of calvaria cultured with A- serum for 48 hours was significantly increased compared to the values found in calvaria cultured with A+ serum (A-, 1,970 +/- 300; A+, 940 +/- 177; X +/- SD). The uptake of 35S-sulfate into the GAG fraction of calvaria cultured with A- serum showed continuous increase over 96 hours,whereas, 35S-sulfate uptake leveled off after 24 hours in the A+ group. There was also a significant increase in [14C]glucosamine uptake into the GAG fractions of calvaria cultured with A-serum (A-, 1,966 +/- 537; A+, 1,662 +/- 244; X +/- SD). To determine if the alteration in metabolism of sulfated GAG was in the biosynthetic or degradative pathways, a chase study was performed in which the calvaria were prelabeled with 35SO4. The rate of tissue loss of 35S-sulfate was lower in the total digests and the GAG fractions from calvaria cultured with A- serum than those cultured with A+ serum. Thus, the alteration in the metabolism of the sulfated GAG resulting from A- culture conditions seems to be defect in the degradative process.

Animals↗
PubMed1978

Vitamin A deficiency and new bone growth: histologic changes.

Using a standardized guinea pig model system, the histologic appearance of newly formed bone from vitamin A deficient, vitamin A adequate and retinoic acid treated animals was compared. Microscopic examination of the histologic sections of bone collected from vitamin A deficient guinea pigs indicated the presence of highly cellular and loosely woven bone spicules. This model system is an osteoblastic model, since osteoclasts are essentially absent in tissue formed in 14-day implants. Thus, new bone formation in the vitamin A deficient guinea pig reveals morphologic changes which are principally mediated through the osteoblastic process.

Animals↗
PubMed1978

Sources of variability in rat caries studies: microbial infection and caging procedure.

Two sources of variability in rat caries experiments have been investigated: infection with two S mutans strains and two types of caging. Results indicated that strain 6715 was more virulent than was strain 10449 when 24-day-old rats were orally infected with the organism under standardized conditions. Caging of rats (2 per cage) in stainless steel, raised bottom cages resulted in higher level of caries than in plastic tubs (3 per cage) with hardwood bedding. Infection and caging conditions are two of the factors which may contribute to variability in caries pattern and severity in experimental rats.

Age Factors↗
PubMed1977

Sources of variability in rat caries studies: weaning age and diet fed during tooth eruption.

A factorial design (2x2) was used to study the caries effect of two diets (starch based versus stock) fed to rat dams and their litters, and also of variations in the weaning age (19 versus 25 days). Higher and reproducible caries scores were obtained in rats which were fed a purified starch-based diet, weaned at 19 days of age, and subsequently given a cariogenic challenge.

Age Factors↗
PubMed1977

Collaborative evaluation of a rat caries model in six laboratories.

When highly controlled parallel rat caries studies were run simultaneously in six laboratories, a similar pattern of caries developed in every laboratory with a range in mean values such that the results of no investigator were significantly different from those of at least two others. These results indicate that the major factors influencing development of rat caries have been recognized and can be controlled within reasonable limits.

Animals↗