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Biomedical subjects

D R McCall

Publications and source records attributed to D R McCall.

7 recordsLinked to original sources

Incisor enamel mottling prevalence in child cohorts which had or had not taken fluoride supplements from 0-12 years of age.

Blind photographic assessments were made of the permanent incisors of 322 children who had participated in two successful fluoride drop/tablet hygienist-based preventive dentistry programmes. Two groups of four dental and two lay assessors unanimously scored 57% of dentitions as mottling-free. The dental observers unanimously scored 37 children (12%) with some symmetrical homologous tooth-type mottling, although only 13 decisions (4%) were scored "unacceptable easthetically". The lay assessors rated 77 children (24%) with mottling, 15% being easthetically displeasing. However, no significant mottling differences were noted between cohorts which had commenced oral fluoride supplementation at birth and those which either commenced as late as 7 years of age, or which had never taken any such supplementation. Thus other fluoride sources must have been responsible for the non-drop/tablet diffuse symmetrical mottling noted, the most likely being highly fluoridated dentifrices ingested by youngsters unable to control the volume dispensed and swallowed. Hence the evidence does not suggest that this proven caries-inhibiting F- drop/tablet regime dosage should be reduced. There is, however, a clear and continuing need for both the dental profession and the public to be made more aware of the problem of uncontrolled fluoride ingestion from other sources.

Age Factors

Tetrapyrrole utilization by Bacteroids ruminocola.

Reduced versus oxidized difference spectra of whole cells and pyridine hemochromogens of heme-requiring isolates of Bacteroides ruminicola are altered when deuteroporphyrin or mesoporphyrin replaces protoheme as a growth factor. During growth in the presence of either deuteroporphyrin or mesoporphyrin, whole cells exhibit peaks at 545 t547, 515 to 518, and 412 to 413 nm. Pyridine hemochromogen spectra confirm the presence of meso -or deuteroheme in cells grown in the presence of meso- or deuteroporphyrin. No evidence was found for the conversion of either meso- or deuteroporphyrin to protoheme. Cells grown in the presence of the manganese of magnesium chelates of protoheme form iron-containing hemes. Neither spontaneous decomposition of noniron metalloporphyrin chelates nor spontaneous formation of hemes from Fe2+ and metal-free porphyrins was detected. Protoheme-synthesizing isolates of B. ruminicola fail to use preformed metal-free porphyrins, but form both protoheme- and deuteroheme-containing cytochromes when grown in the presence of manganese deuteroheme. Versatility in tetrapyrrole utilization by B. ruminicola appears to reflect the ability of the organism to mediate the removal of nonferrous ions and to insert Fe2+ into the tetrapyrrole nucleus. The orgamism also forms functional b-type cytochromes with prosthetic groups other than protoheme.

Bacteroides