The effect of extracts from human dental plaque,oral streptococci and actinomyces bacteria on HeLa cell growth, [3H]-thymidine uptake and 51Cr release

Dialysed extracts from dental plaque and a number of species of oral streptococci and actinomycetes have been investigated for their effects on cell growth, [³H]-thymidine uptake and ⁵¹Cr release from HeLa cell cultures. Eight of the 15 extracts inhibited cell growth and all but one inhibited [³H]-thymidine incorporation. None of the extracts stimulated ⁵¹Cr release from prelabelled cells. These results suggest that many of the species of streptococci and actinomyces found in the mouth and in dental plaque are capable of producing high mol. wt substances that interfere with HeLa cell cultures by inhibiting [³H]-thymidine uptake and DNA synthesis but do not affect the degree of intactness of the external cell membrane.     

Influence of isoproterenol on the incorporation in vitro of [3H]-leucine and N-acetyl-[14C]-mannosamine into proteins and glycoproteins of the parotid glands of the mouse

The in-vitro incorporation of [³H]-Leu in murine parotid glands started rapidly and continued during the whole incubation period of 10 h and was not stimulated significantly by isoproterenol, except during the first half hour. Secretion of [³H]-Leu incorporated was already observed after 30 min and continued up to 10 h. Isoproterenol stimulated the secretion of ³H-labelled protein during the whole period, but maximally after 4 h. Incorporation of [¹⁴C]-ManNAc proceeded at a much slower rate than that of [³H]-Leu. It was at least 1 h before incorporated [¹⁴C]-ManNAc appeared in the incubation medium. The secretion of [¹⁴C]-ManNAc incorporated was increased by isoproterenol between 2 and 6 h. A major part of [³H]-Leu was incorporated in amylase. The electrophoretically slowest moving isoenzyme of amylase incorporated substantial amounts of [¹⁴C]-ManNAc, in agreement with the presence of sialic acid in the isoenzyme. The onset of the [¹⁴C]-ManNAc uptake in amylase was slow compared to [³H]-Leu uptake. The [¹⁴C]-label could be detected in the secreted amylase after at least 4 h of incubation. It is suggested that isoproterenol decreased the incorporation of [¹⁴C]-ManNAc relative to that of [³H]-Leu into the secreted amylase.     

Comparison in vitro of the incorporation of [3H]-leucine and N-acetyl-[14C]-mannosamine into proteins and glycoproteins of the parotid,submandibular and sublingual glands of the mouse

During incubation for 10 h, the glands remained active in both protein and glycoprotein secretion and incorporation of the radioactive precursors. The incorporation of [³H]-Leu was completely due to de-novo biosynthesis of protein. At least 80 per cent of the incorporated [¹⁴C]-ManNAc could be recovered as sialic acid. The incorporation of [³H]-Leu could be detected as early as 10 min after the onset of incubation and reached the maximum level in all glands after 4 h of incubation. The sublingual glands were more active in incorporating [³H]-Leu than the other two types of salivary glands per mg of glandular wet wt. The pattern of incorporation of [¹⁴C]-ManNAc differed from that of [³H]-Leu, in having a time lag in the parotid and submandibular glands of at least 1 h, and an acceleration of the incorporation after 6 h. In spite of their high content of sialomucin, [¹⁴C]-ManNAc was hardly incorporated by the sublingual glands. This was apparently not due to a slow cellular uptake of ManNAc, but possibly because the conversion to sialic acid was slow in the sublingual glands of the mouse.     

Inhibition of [3H]-thymidine uptake in human gingival fibroblasts by extracts from human dental plaque, oral bacteria of the Streptococcus and Actinomyces species

Extracts from human dental plaque, Streptococcus mutans, Streptococcus salivarius, Streptococcus faecalis, Streptococcus sanguis, Actinomyces israelli and Actinomyces odontolyticus inhibited [3H]-thymidine uptake by primary human gingival fibroblast cell lines as previous work has shown in respect of HeLa cells. The results show that a variety of oral bacteria, not usually considered to be periodontal pathogens, elaborate factors that adversely affect fibroblasts.     

Fluoride uptake by powdered human enamel treated with prolonged acting fluoride pellets in vitro

A preparation for the prolonged release of fluoride for topical use was developed. The delayed release of the fluoride was achieved by dispersing NaF or CaF₂ in ethyl cellulose with or without a stearic acid matrix. Orthodontic plates were used as delivery systems. The kinetics of fluoride release was controlled by diffusion mechanisms. The major compound resulting from enamel treatment with prolonged acting fluoride is fluoridated apatite.     

An autoradiographic study of the in-vivo incorporation of [3H]-palmitic acid into the dentine and enamel lipids of rat incisors,with a comparison of rapid-freezing freeze-substitution fixation and aldehyde fixation

Four and twenty-four hours after injection of the labelled precursor, there were twice as many silver grains scored with the cryotechniques as with conventional fixation. Absence of labelled-band formation in dentine, the diffusion of silver throughout the entire thickness of dentine as well as the layer of forming enamel. This suggests that lipids are membrane-associated components rather than true matrix-associated components.     

Effect of extracellular polysaccharides on diffusion of NaF and [14C]-sucrose in human dental plaque and in sediments of the bacterium Streptococcus sanguis 804 (NCTC 10904)

It has been postulated that extracellular polysaccharides form a barrier to diffusion in dental plaque. Diffusion coefficients, D, were measured for NaF and [¹⁴C]-sucrose in glucanfree and glucan-containing sediments of Strep. sanguis 804 at 37 °C. There was a tendency for NaF and [¹⁴C]-sucrose to diffuse faster as the carbohydrate concentration in the sediments increased. NaF diffused only 38 per cent more slowly in cell-free glucan sediment than in water, suggesting that glucan per se does not form a barrier to diffusion. The diffusion coefficient for NaF was positively correlated with carbohydrate concentration in individual plaque samples from 15 subjects and incubation of 3 plaque samples with sucrose resulted in both an increase in carbohydrate concentration in the plaque and an increase in D for NaF. Thus the presence of extracellular polysaccharides in plaque leads to slightly faster rates of diffusion. Nevertheless, the total time for diffusion through plaque may be increased if the presence of extracellular polysaccharides results in thicker layers of plaque.