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Biomedical subjects

R C Shore

Publications and source records attributed to R C Shore.

At least 55 records · Page 3Linked to original sources
PubMed1994

Uptake and metabolism of albumin by rodent incisor enamel in vivo and postmortem: implications for control of mineralization by albumin.

The distribution of albumin throughout enamel development in the rat mandibular incisor was investigated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) and Western blotting employing an anti-rat albumin antibody. Intact albumin was detectable at all stages of enamel development but was most evident during late secretion/transition. Its concentration was subsequently reduced during the maturation stage. Albumin degradation products appeared during the transition/early maturation stage indicating that albumin breakdown preceded its removal. As albumin inhibits apatite crystal growth, its degradation and removal may be a necessary prerequisite for normal enamel crystal growth, perhaps reflecting a general mechanism for removal of residual endogenous matrix or adventitious crystal growth inhibitors. Additional studies revealed that the maturation stage was particularly susceptible to albumin influx postmortem. Albumin could therefore form part of the natural crystal growth control process, which, if not removed, could hamper maturation and lead to white spot hypoplasias.

Albumins↗
PubMed1994

Effects of frequency and duration of acid exposure on demineralization/remineralization behaviour of human enamel in vitro.

An in vitro oscillating system, employing human enamel and realistic time intervals and temperature (approximately 35 degrees C) and measuring mineral loss/gain on a volume basis, was used to investigate the effects of both frequency and duration of exposure to low pH (< 5) on the demineralization and remineralization behaviour of human enamel. Sections of human teeth were cycled through one of three different regimens: (1) 3 x 20-min acid challenges; (2) 6 x 10-min acid challenges and (3) 6 x 20 min acid challenges, over single 24-hour periods. The acid challenge periods of 3 x 20, 6 x 10 and 6 x 20 min produced no significant differences in net mineral lost, i.e., the volume of mineral lost per volume of enamel exposed was similar irrespective of frequency or duration of acid exposure (approximately 0.5% vol/vol). Increased frequency of acid exposure did, however, tend to alter the total demineralization/total remineralization amounts, resulting in significantly greater amounts of mineral loss and gain. The data suggest that the remineralization capacity of enamel is considerable and that factors such as inhibition of remineralization may be important in determination of net mineral loss from the tooth.

Acetates↗
PubMed1993

The effect of rate of eruption on periodontal ligament glycosylaminoglycan content and enamel formation in the rat incisor.

The rate of eruption of rat mandibular incisors was either increased by cutting one tooth out of occlusion or eliminated by means of pinning. The effects of such changes in eruption rate on the sulphated glycosylaminoglycan content of the periodontal ligaments was analysed. The length of the enamel secretory zone and the composition of the developing enamel matrix protein was also compared. Sulphated glycosylaminoglycan content of the periodontal ligament increased fourfold (P < 0.001) during accelerated eruption but decreased to a corresponding extent (P < 0.001) in the absence of eruption, when compared with controls. The length of the enamel secretory zone was also significantly reduced in the immobilised teeth, although the protein content was similar compared with controls. The results demonstrate the differential response to varied eruption rates of the periodontal ligament and enamel, particularly in respect of the extracellular matrix. The data are consistent with the view that the ground substance of the periodontal ligament plays a role in the generation of the eruptive force.

Amelogenin↗
PubMed1993

An immunohistochemical study of the effects of fluoride on enamel development in the rat incisor.

A monoclonal antiamelogenin antibody was used to investigate the effects of fluoride on enamel development in the rat incisor. The results suggested that during secretion the enamel matrix molecules are arranged in such a way as to mask the epitope recognized by the monoclonal antibody. However, during the transition stage of development as the matrix begins to be degraded the epitope becomes exposed and labelling intensity increases to reach a maximum at the end of transition/start of maturation. The effect of fluoride is to delay the appearance of labelling within the enamel matrix until the end of transition. This suggests that the fluoride may inhibit enzymatic degradation or disaggregation of the matrix, the resulting residual matrix then inhibiting crystal growth.

Ameloblasts↗
PubMed1992

Immunohistochemical investigation of epidermal growth factor receptor expression during periods of accelerated rat incisor eruption.

The effect of accelerated odontogenesis of the rat mandibular incisor on the expression of receptors for epidermal growth factor (EGF) was examined using specific monoclonal antibodies to the receptor molecule. Acceleration of odontogenesis was achieved by regular trimming of the tooth crown. At normal eruption rates the major area of cross-reactivity was over the secretory ameloblasts. Some labelling of the papilla and preameloblasts was evident. When proliferation was increased the major area of effect was at the preodontoblast/odontoblast boundary where there was a marked increase in labelling, initially at the proximal end of the cell adjacent to the basal lamina. The ameloblasts did not show such a dramatic increase in receptor numbers. Increase in labelling was also evident in the remainder of the papilla. The results suggest that an increase in proliferation with normal morphogenesis is associated with an overall increase in the numbers of EGF receptors, particularly in a population of cells immediately before and after elongation and differentiation of odontoblasts.

Ameloblasts↗
PubMed1992

A flexible and rapid pH cycling procedure for investigations into the remineralisation and demineralisation behaviour of human enamel.

A rapid and flexible model system has been developed to study human enamel behaviour under conditions of oscillating pH similar to those experienced in the mouth. The model uses realistic time intervals and operates at in vivo temperatures (35-37 degrees C). Mineral loss or gain is measured quantitatively on a volume basis. Results indicate that for single 1-day periods with three 20-min exposures to acid, 1% v/v of enamel mineral was lost. These results, together with the histological appearance of the tissue, are in close agreement with previous studies of enamel caries.

Calcium↗
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

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↗
PubMed1991

A quantitative study of the ultrastructure of fibroblasts within the enamel-related connective tissue of the rat incisor.

A quantitative ultrastructural study was made of the fibroblasts of the enamel-related connective tissue and periodontal ligament of the rat incisor. The two populations of fibroblasts were very similar in morphology, the only difference found in the parameters measured being the increased number of microtubules in the enamel-related connective tissue. The data do not lend support to the idea that the fibroblasts of the periodontal ligament generate the eruptive force by their motility or contractility.

Actin Cytoskeleton↗
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

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↗
PubMed1990

Effects of inflammatory periodontal disease ('broken mouth') on the mobility of the sheep incisor.

Loads directed linguolabially and between 0.01 N and 0.2 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with evidence of inflammatory periodontal disease ('broken mouth'). For every incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. Each load chosen was suddenly applied and then maintained for five minutes, producing a biphasic, viscoelastic-like response (a phase of rapid displacement being followed by a more gradual phase of creep). A similar biphasic recovery response was seen on suddenly removing the load. Comparing the findings with those obtained in a previous study for incisors in healthy dentitions, there was a considerable increase in mobility with inflammatory periodontal disease. Surprisingly, however, the patterns of the responses did not differ. The reason for the change in the amount of mobility may be related simply to the quantity of the tooth supporting tissues which is lost, although there is some evidence that qualitative changes occurring in these tissues may also be important.

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

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

Effects of inflammatory periodontal disease ('broken mouth') on the ultrastructure of collagen fibrils in the sheep incisor periodontium.

The ultrastructure of the matrix of the sheep central incisor periodontium showing clinical signs of severe periodontitis was analysed quantitatively. The distribution of collagen fibril diameters in the lower dental pad changed from a bimodal distribution seen in healthy periodontia to a unimodal distribution. Collagen fibrils with an abnormal morphology were seen in the connective tissue adjacent to the crest of the alveolar bone. These results suggest that the deepening periodontal pocket resulting from inflammation removes the major area of support for the tooth and abnormal loads are applied to fibres deeper within the tissue.

Animals↗
PubMed1988

A quantitative ultrastructural study of the extracellular matrix of the sheep incisor periodontium.

The ultrastructure of the matrix of the sheep central incisor periodontium was quantitatively analysed. Ewes with healthy mouths were selected. The distribution of collagen fibril diameters was bimodal in the lower dental pad with a population standard deviation significantly larger than the unimodal distribution of fibril diameters found in the periodontal ligament. The lower dental pad connective tissue also contained significantly more oxytalan fibres, some of which resembled mature elastin. These results are consistent with the view that the sheep central incisor is supported primarily by tension within the fibres of the lower dental pad.

Animals↗