摘要:

The activity of a commercial preparation of muscle enolase was determined photometrically. The sensitivity of the enzyme to fluoride and the kinetics of the inhibition was studied in the absence and in the presence of 5 mM phosphate. The effects of fluoride, magnesium, phosphate and fluorophosphate were investigated by introducing these ions alone or in combination in the assay medium during automatic recording. The inhibition of enolase in vitro started at 0.5 ppm fluoride in the presence of phosphate, and at 10 ppm in the absence of phosphate ions. The Lineweaver-Burk (1/V-1/[S]) and the Dixon (1/V-[F-])plots show that, in the presence of phosphate, the inhibition of enolase by fluoride is of the competitive type. In the absence of phosphate, the kinetics indicate a mechanism of inhibition identical to that found for enzymes without metal ion cofactors. When introduced in the assay medium during recording, fluoride produced a change of slope which was progressive and required 10-15 sec to be complete. The inhibition of enolase in the absence of phosphate, the results of the kinetic studies and those on the rapidity of the inhibitory action confirm that the inhibition of the enolase reaction is probably not caused by a purely inorganic complex.

ISSN:0008-6568    

DOI:10.1159/000259782

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Dental plaque was collected from approximately 3,500 schoolchildren, and immediately pooled and frozen. The lyophilized plaque was processed in several batches as follows:After an aqueous extraction the water-insoluble portion was further extracted with 1 N KOH. Both aqueous and alkaline extracts were further subfractionated by precipitation at different ethanol concentrations. Nature and composition of carbohydrates in sub-fractions were investigated using acid hydrolysis and end products were identified by gas liquid partition chromatography.29.6% of plaque dry weight, containing 6.9% carbohydrates, 1.2% nitrogen and more than 4% proteins, were water-soluble. The water-insoluble portion (67.1%), contained 11.3% carbohydrates and 7.4% nitrogen; in addition, 30.7% constituents insoluble in 1 N KOH were found. In all subfractions prepared by ethanol precipitations, substantial amounts of material other than carbohydrates were found. The sugar composition of hydrolysates showed glucose to be the main sugar constituent; however, small amounts of pentoses, other hexoses and disaccharides were also present. The water-insoluble matrix polysaccharides containing predominantly α-1,3 linkages were calculated to account for 1.35% of the plaque dry weight/ 5.6% of the plaque dry weight consisted of low molecular water-soluble carbohydrates. Glucose and oligosaccharides forming the bulk of this fraction were assumed to represent intermediates resulting from enzymatic breakdown of α-1,6-linked dextran. The high content of fermentable carbohydrates in dental plaque suggests that microbial activity is not limited by the supply of fermentable substrate

ISSN:0008-6568    

DOI:10.1159/000259783

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Enzyme preparations obtained from sonically-treated washed cells of Streptococcus mutans strain GS5 were found to contain ‘sucrase’ activity which was distinct from that of the glucosyl and fructosyl transferases known to be elaborated by this organism. This ‘sucrase’ activity was formed constitutively and could be separated from transferase activity by agarose chromatography. The enzyme appears similar, if not identical, to invertase on the basis of its catalytic action, its molecular size, and its heat sensitivity. Its presence in cells of Strep, mutans strain GS5 indicates that this organism is not solely dependent upon the glucosyl and fructosyl transferases for the utilization of sucrose for growth. The total observable ‘sucrase’ activity of glucose grown cells of Strep, mutans strains GS5 and 6715 was found to increase markedly when the organisms were treated with toluene, indicating they were relatively impermeable to sucrose. Untreated sucrose grown cells exhibited 10-fold higher total ‘sucrase’ activity than did untreated glucose grown cells, suggesting that growth in sucrose broth resulted in the induction of a sucrose t

ISSN:0008-6568    

DOI:10.1159/000259784

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

The aim of this study was to compare the chemical composition and susceptibility to enzymatic hydrolytic cleavage of several polysaccharides synthesized by glucosyltransferases obtained from oral streptococci. Glucosyltransferase enzymes were obtained from cultures of Streptococcus mutatis, strains HS-6 and AHT (antigen a), FA-1 (antigen b), Ingbritt and GS-5 (antigen c) and OMZ-176 (antigen d), and from Streptococcus sanguis, strain 804. These enzymes were partially purified by absorbing the culture supernatant fluid of the respective strains onto hydroxylapatite gel and eluting batchwise from the gel. Polysaccharides were prepared by incubating the eluted enzymes in the presence of sucrose, followed by precipitation with alcohol (1:1 v/v), washing, dialysis and finally lyophilization. Analyses indicated the polysaccharides were essentially homopolymers of glucose with 2–7% moisture, 85–98% total carbohydrate, 78–98% glucose, 0.9–2.6% fructose and about 0.5% nitrogen. Suspensions of each of the glucans were treated with 3 commercial preparations of dextranase or 3 commercially available amyloglucosidases. Amyloglucosidases were largely ineffective in hydrolyzing these bacterial glucans. The dextranase preparations hydrolized the various glucans at significantly different rates. The rate and degree of cleavage appears to be related to the antigenic grouping of the strain. The relative resistance of some glucans to degredation under these conditions may explain the ineffectiveness of the dextranase mouthwash in human clinical

ISSN:0008-6568    

DOI:10.1159/000259785

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Some factors were investigated which influence the calcium concentration of the saliva during the day. Variations in the relative contribution from the major saliva glands seem to be of great importance. Relative proportions as well as concentrations change with increasing intensity of stimulation. A nutritional influence via the serum concentration was not found.

ISSN:0008-6568    

DOI:10.1159/000259786

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

The chemical changes taking place in enamel during carious attack have been studied by analysing the histologically defined zones of the small approximal lesion. Sam- pies of altered enamel were dissected from each zone and compared with sound enamel from adjacent control areas. Enamel from the primary translucent zone, the area of the lesion presumed to be least affected by caries, contained about 1.2% by volume less mineral and about 12% by weight less magnesium than the adjacent, apparently sound enamel. The translucent zone, therefore, appeared to result from demineralisation, associated with a preferential loss of magnesium-rich mineral.

ISSN:0008-6568    

DOI:10.1159/000259787

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

The ratio between the mineral content in the radiolucent bands and in the underlying radiopaque bands parallei to the striae of Retzius, seen in microradiographs of two ground sections of a carious lesion, has been assessed by means of densitometric recordings. Ratios were calculated for 993 pairs of readings and were found to lie within a limited range. The findings uggest that the carious process is demineralizing adjacent incremental bands in relatively fixed proportions, predetermined by their structural and chemical constitution.

ISSN:0008-6568    

DOI:10.1159/000259788

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

A total of 49 rats was littermate-distributed into three dietary groups when 21 days old. The control group (C) was fed a cariogenic nutritionally adequate high- sucrose diet for 40 days. The second group (BP) received the same diet as group C except that 4% of the sucrose component of the diet was replaced by a combination Phosphate, dietary NaHCO3 + KH2PO4 (mole ratio 9.82/1). The third group (BPF) was fed the same diet as group BP except that NaF was also added to the sucrose to give 10 ppm F addition to the whole of diet. The mean gain of body weight in the BPF group was 55% higher than in group C (p < 0.001). In the BPF group, also the weight and length of the femurs were greater than in group C. The mean number of fissure cavities in lower molars was 76% less in group BP (p < 0.01) and 80% less in group BPF (p < 0.01) than in group C. The mean number of approximal lesions involving the dentino-enamel junction was in group BPF 65% less than in group C (p < 0.01) and 32% less in group BP than in group C (p < 0.1). A nearly tenfold increase in bone fluoride was found in the animals of the BPF group.

ISSN:0008-6568    

DOI:10.1159/000259789

出版商:S. Karger AG    

年代:1972

数据来源: Karger