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Biomedical subjects

J M Navia

Publications and source records attributed to J M Navia.

At least 37 records · Page 2Linked to original sources
PubMed1988

A case-control study of plasma ascorbate and acute necrotizing ulcerative gingivitis.

Data from animal studies and from studies of patients with acute necrotizing ulcerative gingivitis (ANUG) have provided suggestive evidence for an association between ascorbate deficiency and disease risk. Further, there is biological plausibility for such an association, due to the role of ascorbate in collagen synthesis and leukocyte function. A case-control study of plasma ascorbate and ANUG was performed on 60 patients with a history of ANUG infection and 60 age-race-sex-matched controls. No cases had had active lesions for at least two months prior to their vitamin assay to avoid any potential reduction of dietary intake of ascorbic acid due to the presence of painful mouth lesions. According to results obtained by use of a modification of the 2,4-dinitrophenylhydrazine method for determination of total plasma ascorbate, the mean and standard error of the mean of plasma ascorbate for all ANUG cases was 0.07 +/- 0.006 mmol/L; the mean for all controls was 0.10 +/- 0.006 mmol/L. Paired differences in plasma ascorbic acid concentrations between cases and controls were significantly different from zero (p less than 0.001). The unadjusted relative risk (RR) of ANUG as obtained by conditional logistic regression for subjects whose plasma ascorbic acid concentration was at or below the median value for controls, relative to subjects with higher values, was 7.3 (90% confidence interval, 3.0 - 17.4; one-sided p value less than 0.001). Patients with a history of ANUG ingested a daily average of 1.2 +/- 0.2 servings of dietary ascorbic acid, as compared with a daily average of 1.9 +/- 0.2 servings for healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1987

Effect of aluminium on mineralization of rat third molar in vitro.

Crl: COBS rat third-molar explants were cultured for 12 days in either 0.6 X 10(-2), 4 X 10(-2) or 6 X 10(-2) mM aluminium, or for 12 days with exposure to 13 X 10(-2) mM Al at different 6-day intervals. Total protein, alkaline phosphatase, calcium and phosphorous were measured to evaluate cell viability and the degree of mineralization. Al in concentrations above 4 X 10(-2) mM significantly reduced the Ca and P content of explants cultured for 12 days. Explants exposed to 13 X 10(-2) mM Al for the first 6 days had less Ca and P than those exposed for the last 6 days of culture. Haematoxylin and eosin-stained sections of explants showed no gross abnormalities.

Alkaline Phosphatase↗
PubMed1986

A technique for assessment of the cariogenic potential of foods by plaque pH changes on enamel surfaces of rat molars.

Plaque pH changes on rat molars subjected to cariogenic challenge were measured with an antimony microelectrode. Measurements were made after feeding one of seven different reference or snack foods. Resting plaque pH was measured after fasting and minimum plaque pH after feeding the various foods. This reproducible technique may be of use in determining the cariogenic potential of foods.

Animals↗
PubMed1986

The effects of dietary acid stress on bone metabolism in young ovariectomized and intact rats.

1. Two studies were performed to determine the effects of acid stress and ovariectomy on bone metabolism in young rats. In Expt 1, eighteen female weanling Sprague-Dawley-descended rats were ovariectomized, placed in one of three dietary groups and given a diet containing (g/kg): 6 calcium and 3, 6 or 12 phosphorus for 10 weeks. In Expt 2, thirty-two female weanling Sprague-Dawley-descended rats were ovariectomized, and thirty-two were left intact. Eight rats from each group were given a diet containing (g/kg): 6 Ca and 3 P, 12 P, 3 P + 1 S or 3 P + 20 ammonium chloride for 10 weeks. 2. Feeding diets containing 12 g P/kg resulted in decreased serum Ca and increased urinary P with no changes in femur composition. Feeding high-sulphate and ammonium chloride diets resulted in increased urinary Ca and, when combined with ovariectomy, lower femur Ca and P with no changes in femur hydroxyproline or hexosamines. 3. The findings reflect the more rapid turnover of the amorphous calcium phosphate salts found in greater amounts in bones of younger animals than for more stable apatitic crystals that predominate in bones of older animals.

Acids↗
PubMed1986

In vivo measurements of sulcal plaque pH in rats after topical applications of xylitol, sorbitol, glucose, sucrose, and sucrose plus 53 mM sodium fluoride.

In two series of experiments, Sprague-Dawley-derived rats were infected orally with cariogenic micro-organisms and fed caries-promoting diets. By means of an antimony electrode, resting pH values were measured in the mesial sulcus of the maxillary left first molar. 100 or 200 microL of the test solutions were applied, and the change in pH (delta pH) was recorded for three min. Test solutions were: (a) 10% sucrose, 10% glucose, 10% sorbitol, or 10% xylitol; (b) 0%, 10%, 20%, or 40% sucrose; (c) 0%, 3%, 7%, or 10% sucrose; and (d) 10% sucrose, 10% sucrose + 53 mmol/L NaF (1000 ppmF-), or 10% sucrose + 53 mmol/L NaCl. Experimental design was a 4 X 4 Latin square (a, b, c) or a cross-over design (d). Solutions of sucrose and glucose gave significantly greater decreases in pH than did sorbitol or xylitol. pH fall was maximal for 10% sucrose and significantly less for 40% sucrose during the three-minute experimental period. For sucrose solutions ranging in concentration from 3 to 10%, pH fall was highest after application of 10% sucrose when plaque was previously rinsed with water, but this pH fall did not differ significantly from that obtained using a 7% sucrose solution. Adding 1000 ppmF- to a 10% sucrose solution caused an increase in pH. Rinsing the teeth to remove saliva resulted in significantly lower resting pH values. The results of these experiments are in agreement with the results of human plaque pH measurements.

Administration, Topical↗
PubMed1986

In vivo measurements of sulcal plaque pH after topical applications of sorbitol and sucrose in rats fed sorbitol or sucrose.

To test whether adaptation to sorbitol could be observed in rat plaque, we made pH measurements of rat sulcal plaque in vivo, following topical application of 10% sorbitol solution. Rat pups were inoculated orally with S. mutans 6715 and fed diet MIT 305 (5% sucrose) for 16 days. Baseline sulcal plaque pH response of these rats to topical application of 10% sorbitol solution was measured. One group of 16 rats was then fed 20% sucrose in the diet, and a second group 20% sorbitol. After 13 days' feeding of the experimental diets (four days were used for accommodation to dose, and nine days at the 20% level for sorbitol), there was a significantly greater (p less than 0.01) drop in pH following topical application of 10% sorbitol in this group than in the sucrose-fed group. There was no difference in the pH response of the two groups to topical application of a 10% sucrose solution when tested six days later. The sulcal enamel caries score was significantly higher (p less than 0.001) in the sucrose group, but buccal enamel scores were similar in both groups. Adaptation in rat plaque took place, and could be measured in vivo as an increased drop in sulcal plaque pH following topical application of sorbitol. It is not clear whether this adaptation was primarily due to selection of sorbitol-fermenting micro-organisms, or, more likely, by induction of sorbitol-specific enzymes. Relative to the sucrose-containing diet, the sorbitol diet was hypocariogenic, even under experimental conditions.

Administration, Topical↗
PubMed1986

In vivo and in vitro study of the effects of vitamin A deficiency on rat third molar development.

We have examined the effect of in vivo vitamin A status on subsequent rat third molar formation and mineralization in an in vitro organ culture system. Vitamin A deficiency imposed during an eight-day in vitro period caused effects very similar to those of vitamin A deficiency imposed on rats in vivo. Analysis of the data also demonstrates that retinoic acid is capable of reversing the interference in mineralization of third molars induced by vitamin A deficiency in the organ culture system.

Animals↗
PubMed1984

Organ culture study of effect of vitamin-A-deficiency on rat third molar development.

A culture procedure for rat third molars suitable for nutritional-developmental studies is described. Unerupted third molars from 12-day-old rats were cultured in BGJb media containing 20 per cent rat serum and supplemented with 25 mM HEPES buffer, 25 mg ascorbic acid, 20 mg L-glutamine, 12 mg penicillin G and 10 mg streptomycin sulphate per 100 ml of media. Molars were cultured at the liquid-gas interphase using a 50 per cent O2, 45 per cent N2, 5 per cent CO2 gas mixture at 10 lb-psig (pounds per square inch guage). Molar cultures were maintained successfully for 9-14 days without evidence of necrosis, although they developed at a slower rate than in vivo. Molars cultured in 50 per cent O2 compared to those cultured in 21 per cent O2 for periods of 2, 4, 6 and 8 days had higher values for protein, alkaline phosphatase (AP), Ca, P and Ca/P. Vitamin-A-deficiency gave lower values for AP, Ca, P, Ca/P, 45Ca, 35S and [14C]-proline uptake. Histologically, A - molars had atrophic ameloblasts, some foci of squamous metaplasia and abnormal keratin formation. Thus, deficiency of vitamin A imposed during in-vitro development of rat third molars retarded dentinogenesis and interfered with early mineralization of enamel and dentine.

Aging↗
PubMed1984

Effects of vitamin A deficiency on rat incisor formation.

Vitamin A deficiency (A-) is known to cause morphologic changes in tooth structures. However, its effects on glycosaminoglycan (GAG) distribution in dental pulp, and the role of retinoic acid (RA) in altering these effects are not clearly defined. Tissue changes induced by vitamin A deficiency and RA administration were evaluated histologically in incisors of rats fed on one of 3 different diets: a) vitamin A sufficient (A+); b) vitamin A deficient (A-); and c) vitamin A deficient supplemented with retinoic acid (A-/RA). Four weeks after the onset of vitamin A deficiency, all rats were killed and their 4 continuously erupting incisors evaluated histologically. A- rats had altered dentine and pulp with disrupted histodifferentiation of pulpal mesenchymal cells to normal odontoblasts. The frequency of these abnormalities in dentine and pulp was lower in A-/RA rats. The enamel organ was unremarkable in the 4-week deficient period. Using special stains, we noted that pulpal GAG accumulation in A- and A-/RA rats was limited to the lingual area, while in A+ rats, GAG were distributed throughout. These data suggest that vitamin A deficiency affects histodifferentiation of pulpal mesenchymal cells to odontoblasts, as well as GAG distribution in pulp. RA administration reduces the A- changes and therefore, appears to have some activity in dentinogenesis.

Animals↗
PubMed1984

Interaction of vitamin A deficiency and excess fluoride in calcification of rat bones and teeth.

Using a 2 X 2 factorial design, we evaluated the possible interaction of vitamin A deficiency and excess fluoride in rat dentin and bone. Simultaneous presence of excess fluoride plus vitamin A deficiency resulted in a significant decrease in bone fluoride concentration compared to the presence of excess fluoride alone. Vitamin A deficiency alone significantly reduced calcium concentration in dentin formed during the deficient period.

Administration, Oral↗
PubMed1983

Biological assay for zinc availability in wheat germ.

Our objective was to develop a method to determine the bioavailability of zinc in wheat germ. Weanling rats were fed for 10 days a Zn-free diet supplemented with different levels of Zn, with or without 2% wheat germ. Zinc concentrations of either tibia or femurs were plotted directly against Zn added to the diet, giving two lines that were essentially parallel. A multiple regression model was used to obtain a common slope but different intercepts for the lines. The amount of available Zn was calculated by taking the ratio of the difference in intercepts to the common slope. The result showed that wheat germ contained 163.7 micrograms Zn/g, of which 86.7% was bioavailable to the rat.

Animal Feed↗
PubMed1983

Glycosaminoglycan alterations in rat bone due to growth and fluorosis.

Evidence in the literature has suggested that alterations in bone glycosaminoglycans (GAGs) are at least partially responsible for the defective calcification in skeletal fluorosis. The major objectives of this study were to quantitate the GAGs of bone from normal and fluorotic rats and to characterize the change in bone GAGs that occurred during maturation. Weanling male rats were fed a semipurified diet and deionized water with or without fluoride (125 ppm) for 1 or 2 months. Also, a control group of rats was pair-fed to the rats receiving fluoride. GAGs were isolated from dry, fat-free tibias and then quantitated by digestion with chondroitinases and chondrosulfatases. Chondroitin-4-sulfate (C4S) comprised 90% of the bone GAGs, while chondroitin-6-sulfate (C6S), dermatan sulfate (DS) and hyaluronic acid (HA) together comprised about 10% of the total bone GAGs. With increasing age, total GAGs, C4S and HA decreased in amount, but DS remained constant. Fluorotic bone (containing in excess of 5000 ppm of fluoride) had three times as much C6S and twice as much DS as bone from weight- and age-matched control rats. Thus, using a controlled experimental animal model, we have demonstrated that specific alterations of bone GAGs result from fluorosis independently of changes in body weight and age.

Animals↗
PubMed1983

Rat caries assay of reference foods and sugar-containing snacks.

Using standard reference snack foods, we tested a method, using rats fed in a programmed feeding machine, to evaluate the caries-promoting properties of foods. Results, which were expressed in relation to a control food, indicate that the method distinguished differences in caries potential among a number of different snack foods. Buccal and sulcal caries scores of rats fed snacks foods varied in their responses. A gel diet used to provide essential nutrients for the rat growth in this approach contributed minimally to the caries response which was related principally to the food being tested.

Animals↗