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Biomedical subjects

J Kirkham

Publications and source records attributed to J Kirkham.

At least 73 records · Page 4Linked to original sources
PubMed1992

The role of albumin in developing rodent dental enamel: a possible explanation for white spot hypoplasia.

The uptake of serum albumin by maturation-stage rodent enamel and the resulting effects on the growth of enamel crystallites were investigated in vitro. Albumin uptake was demonstrated by means of gel electrophoresis and confirmed by Western blotting with use of monoclonal antibodies. Measurement of crystal size was carried out by direct TEM measurement of enamel crystallite outlines after incubations in metastable solutions of calcium phosphate. The ability of endogenous enamel enzymes to degrade albumin was investigated by substrate-specific zymography. The results showed that albumin could be taken up by maturation-stage enamel and produce inhibition of crystallite growth. There was no detectable proteolytic activity in the enamel against albumin substrate, which suggests that albumin entering enamel by extravasation in vivo may produce incomplete tissue maturation, resulting in a white, opaque appearance on eruption.

Animals↗
PubMed1991

Effect of periodontal disease ("broken mouth") on the distribution of matrix macromolecules in the sheep periodontium.

A topographical, biochemical analysis of the soft connective tissues of sheep periodontia diagnosed clinically as showing periodontitis was carried out and compared with healthy periodontal tissue. Protein content was mapped on a site-to-site basis and compared with the distribution of collagen for both healthy and diseased tissue using amino acid analysis. Diseased tissue was more biochemically homogeneous than corresponding healthy tissue. Protein content per cent was in general greater but collagen content was greatly reduced. Tissue adjacent to radicular cementum appeared to be most markedly affected by the disease process. The apparent selective loss of non-proteinaceous components along with loss of collagen attachment may explain the direction in which periodontal disease is propagated through the tissue.

Amino Acids↗
PubMed1991

Rates of protein turnover at specific sites of the rat incisor periodontal ligament.

Extraction of rat incisor periodontal ligament using neutral salt solutions was carried out on a site-specific basis following administration of 3H-labelled proline, the incorporation of 3H-proline into soluble proteins of different molecular weights was determined by SDS electrophoresis and scintillation counting. Tracer was incorporated primarily into 3 fractions with Mr = greater than 120K, 100K and 45-65K. Appearance of 3H-proline in low molecular weight components which cross-reacted with antibodies to Type 1 collagen (presumably collagen breakdown products) within 30 minutes of administration suggests a pool of collagen which is rapidly turning over. The rate of maturation of collagen from this soluble to insoluble forms may represent a level of post-translational control within the tissue which may be directly related to tissue morphostasis.

Animals↗
PubMed1991

An assessment of the control of matrix turnover by a quantitative ultrastructural analysis of fibroblasts of the periodontal ligament in rats.

A quantitative structural analysis of the synthetic and degradative organelles of fibroblasts of rat incisor and molar periodontal ligaments was conducted. The results showed that in these tissues which are reported to have significantly different rates of turnover of their functional matrix collagen the rate of synthetic activity was the same. However, there were differences in the pattern of degradation with the molar ligament having between 5 and 6 times more phagocytosed collagen than the incisor. It is suggested that post-synthesis processing may control collagen turnover rather than modulation of rates of synthesis.

Animals↗
PubMed1990

Effect of surface zone deproteinisation on the access of mineral ions into subsurface carious lesions of human enamel.

It has been proposed that the so-called intact surface zone of carious lesions of enamel could restrict the ingress of mineral ions and hinder remineralisation. The present study was intended to determine the role of organic (proteinaceous) material in restricting the movement of mineral ions into carious lesions in vitro. Natural carious lesion surfaces were divided into two halves. The experimental half was de-proteinised using hypochlorite, the control half remained untreated. The whole tooth was exposed to 45Ca in solution, and 45Ca uptake into experimental and control tissue was measured by image analysis of autoradiographs prepared from lesion sections. The results indicated that uptake was improved by removal of organic material.

Acid Etching, Dental↗
PubMed1990

The effect of fluoride on the developing mineralized tissues.

The work described considers the effects on calcified tissues of those concentrations of fluoride which are not overtly cyto-toxic, i.e., in the general region of up to 1-2 mumol/L. Plasma fluoride concentrations or those of the cellular environment are considered rather than dietary levels. The effect of fluoride ion on specific stages of tooth and bone development is discussed. Little effect has been observed on the modulation of gene expression as far as odontogenesis is concerned, although there is evidence that fluoride could be osteogenic in both embryonic and adult tissues. Expression of extracellular matrix protein genes seems not to be impaired, but subtle changes detected in the enamel matrix could be due to selective alterations in amino-acid uptake or interference with subsequent protein processing. This could also be due to an extension of the secretory period without concomitant changes in post-secretory matrix processing. Removal of matrix is apparently impaired, with concomitant incomplete maturation. While existing mineral phases can be affected, it is more likely that matrix and or mineral-matrix interaction is the site of action. Explant studies suggest that the effect may be reversible. Inhibition of proteolysis during enamel maturation may account for the reported inhibition of enamel crystal growth. This is supported by the finding that the normally incomplete maturation of porcine enamel is associated with a somewhat greater residual protein content. The use of animal models in the investigation of enamel dysplasia (fluoride-induced or otherwise) should therefore be viewed with caution.

Animals↗
PubMed1990

Extracellular processing of enamel matrix proteins and the control of crystal growth.

The origin, expression and role of matrix modifying enzymes in dental enamel was investigated by zymography and growth of enamel crystals in vitro. Gelatinase activity of the neutral metalloprotease type was detected at similar molecular weights in enamel organ, enamel and dentine. The activity was present throughout all developmental stages in enamel organ but was dramatically reduced in the maturation stage of the enamel. Activity of the serine protease type directed against enamel matrix was also detected in enamel, particularly in the maturation stage. No such activity was detected in the enamel organ. Phosphatase activity at alkaline pH was demonstrated at similar molecular weights in both enamel and enamel organ. This activity was maximal in the maturation stage. Further experiments showed that both serine proteases and alkaline phosphatase were able to facilitate enamel crystal growth in vitro. Matrix modification via temporally and spatially restricted enzymes may be directly involved in the control of enamel crystal growth and hence in the determination of final tissue architecture.

Animals↗
PubMed1989

Tuft protein: its relationship with the keratins and the developing enamel matrix.

The relationship among tuft protein derived from mature human molars, human skin keratins, and the developing enamel matrix of the rat incisor was investigated using polyclonal antibodies in immunocytochemical and Western blotting techniques. Antibodies to tuft protein and keratin cross-reacted with proteins in the Mr range 50-70 K from demineralized developing enamel, enamel organ, human skin, and tuft extract. An immunocytochemical technique was used to locate the site of cross-reactivity in situ within secretory ameloblasts, enamel, and keratinized epithelium at the ultrastructural level. Antibodies to keratin cross-reacted with cytoplasmic tonofilaments and those inserted into desmosomes. Antibodies to tuft protein, however, did not cross-react with cytoskeletal components but produced labeling of the golgi and secretory vesicles. Labeling with this antibody was also observed within the stratum granulosum of the rat foot pad. It is concluded that tuft protein contains secretory products of the ameloblast that may represent a less specialized product of other epithelial tissues, perhaps related to the keratins.

Ameloblasts↗
PubMed1989

Site-specific variations in the biochemical composition of healthy sheep periodontium.

A topographical biochemical analysis of the periodontal soft tissues was carried out. The protein distribution in the tooth-supporting structures was determined from site by amino acid analysis and was compared with the collagen distribution in tissue protein, based upon hydroxyproline content. The biochemical composition of the periodontal ligament was heterogeneous but some specific patterns of protein and collagen distribution emerged. Protein concentration was highest at the gingival epithelium and adjacent to the cementum. Collagen concentrations were highest at the alveolar bone and below the junctional epithelium adjacent to the tooth. Such patterns may influence the way in which periodontal disease is propagated through the tissue.

Amino Acids↗
PubMed1989

Control of crystal growth during enamel maturation.

Attempts to promote crystal growth in maturation stage enamel from rat incisors were carried out by incubation in saturated solutions of calcium phosphate. Resulting crystallites were visualised in the TEM and the dimensions of their profiles measured. No crystal growth was observed unless the maturation stage enamel was first pretreated with either 8M urea or sodium hypochlorite to remove residual protein matrix. The results suggest that the protein matrix plays an important role in the control of crystal growth in vivo.

Animals↗
PubMed1989

The enamelin/non-amelogenin problem. A brief review.

Non-amelogenin components can be isolated from enamel, these may be 1. True enamel components (more than one)? (a) Discrete protein(s). (b) Composite polypeptide, amelogenin/non-amelogenin, alternative splicing. (c) Stable physical complex, amelogenin/non-amelogenin aggregate. 2. Albumin/serum protein from circulation? 3. Keratin - (a) New secretory type? (b) Ameloblast cytoskeletal proteins embedded in matrix. 4. Actin - Ameloblast cytoskeleton embedded in matrix. 5. Enzymes (proteolytic, dephosphorylating).

Amelogenin↗
PubMed1988

Relationship between enamel formation and eruption rate in rat mandibular incisors.

The relationship between the formation of dental enamel and tooth eruption was investigated. Rat mandibular incisor eruption rate was accelerated by maintaining incisors out of occlusion. Rate of eruption, enamel thickness, secretory zone length and matrix breakdown were measured. Eruption rate increased by 120% in experimental teeth but enamel secretion increased by only 90%. There were no obvious differences between control and experimental teeth in final enamel thickness or in the molecular weight distribution of the enamel matrix proteins.

Animals↗
PubMed1988

Volume distribution and concentration of protein, mineral and water in developing bovine enamel.

The percentage volume of enamel occupied by mineral, matrix protein and water was determined at each of four stages. Protein decreased throughout development from 20 to 30 per cent to a minimum of 2-3 per cent in mature tissue. Mineral content remained fairly consistent during secretion (15-20%) rising to 70-80 per cent in mature enamel. Water content rose from varying levels to 60-70 per cent at the secretion/maturation boundary decreasing to about 20 per cent in mature enamel. The loss of protein and subsequent delay in the onset of mineral increment resulted in tissue porosity. The duration of this hydrated, porous stage may determine susceptibility of the tissue to, for example, fluoride ion.

Animals↗
PubMed1988

Increased risk of biliary tract cancer following gastric surgery.

Analysis of 4,466 peptic ulcer patients, who had undergone gastric surgery at least 25 years previously, showed no change in risk from biliary tract cancer within the first 20 years, but a 9.4 fold (P less than 0.001) excess risk thereafter. The increased risk was 15.8 fold (P less than 0.001) 20 years after operation for gastric ulcer patients and 5.1 fold (NS) in duodenal ulcer patients. When the risk was analysed by subsite it was found that there was no increased risk at any time after operation for cancer of the bile duct, and that all of the excess risk 20 or more years after operation (14.7 fold; P less than 0.001) was for cancer of the gallbladder.

Adult↗
PubMed1988

Mineral and protein concentrations in enamel of the developing permanent porcine dentition.

Calcium, phosphorus and protein analyses have been performed on developing permanent enamel from the mandibular dentition of the domestic pig. The pattern of mineralization and protein loss was similar from tooth to tooth and similar to teeth from other species. Comparison of different teeth at the same developmental stages (secretion--stage 1, transition--stage 2 and maturation - stage 3) revealed remarkably similar concentrations of calcium, phosphorus, and protein regardless of tooth type. These data were similar to those from other deciduous dentitions, except that maturing/mature tissue in the pig seemed less well mineralized.

Age Factors↗
PubMed1988

Maturation in developing permanent porcine enamel.

Mineral content per tissue volume was investigated in developing permanent porcine enamel and contrasted with weight-related data. Levels of mineralization were correlated directly with the histological appearance of the overlying enamel organ. Magnesium concentrations were measured at different stages of enamel development. Mineral levels rose from approximately 30% per volume of tissue during the secretory stage to approximately 60% in mature tissue. This is much lower than final mineral levels in enamel of other species. Enamel containing low mineral levels was adjacent to tall secretory ameloblasts which had reduced in height by approximately 50% at a point corresponding to the beginning of the maturation stage. Magnesium concentrations remained relatively constant throughout the secretory stage, at 0.2% Mg by weight. These rose by 3-4 times in the enamel of the maturation stage. The low levels of mineralization in the mature porcine enamel did not appear to be due to enamel pathology, and the possibility of porcine teeth erupting in an immature, partially porous condition is discussed.

Ameloblasts↗
PubMed1987

Developmental stages in permanent porcine enamel.

Developing permanent teeth of different ages were obtained from Danish Landrace pigs. Visibly distinct zones on their enamel surfaces were shown to correspond to changes in chemical composition previously reported for other species. The time of appearance, rate of progress and duration of each stage was determined for each tooth type.

Animals↗