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Biomedical subjects

M R Sims

Publications and source records attributed to M R Sims.

At least 19 recordsLinked to original sources
PubMed2003

Upregulation of immunoreactivity of endothelin-1 and alpha-SMA in PDL microvasculature following acute tooth loading: an immunohistochemical study in the marmoset.

OBJECTIVES: To test the hypothesis that a continuous mechanical tooth load would elevate immunoreactivity of endothelin-1 (ET-1) and alpha-smooth muscle actin (alpha-SMA) in the periodontal ligament (PDL) microvasculature. DESIGN: A randomized control study employing 1.5 h of loading to first molars. SETTING AND SAMPLE POPULATION: Orthodontic Research Laboratory, Dental School, Adelaide University. Four young adult, male marmoset monkeys were consecutively anaesthetized and treated. EXPERIMENTAL VARIABLE: An external telescoping frame applied a jaw closing load (120-200 g) transmitted occlusally, via a rubber pad, to randomly assigned mandibular left or right first molars. Contralateral molars were used as controls. OUTCOME MEASURE: Undemineralized, midsagittal, mandibular molar slices, approximately 150 microm thick were immunolabelled with ET-1 and alpha-SMA antibodies and examined in a confocal laser scanning microscope (CLSM) for vascular endothelium and smooth muscle immunolabelling. RESULTS: Three categories of post-capillary-sized venule endothelial cell immunolabelling occurred: endothelium labelled solely with ET-1; endothelium labelled solely with alpha-SMA; endothelium labelled with both ET-1 and alpha-SMA. In endothelial cells, the alpha-SMA showed a moderate cytoplasmic distribution with dense peripheral concentration. Loading increased arteriole alpha-SMA actin labelling. CONCLUSION: Scattered expression of ET-1 is the default state in primate PDL endothelial cells. Increased antigenicity of endothelial cells to both ET-1 and alpha-SMA, and of arteriolar smooth muscle to alpha-SMA, is a response to shear and compression loads.

Actins↗
PubMed2001

Endothelin-1 expression in the microvasculature of normal and 3-hour continuously loaded rat molar periodontal ligament.

Endothelin-1 (ET-1) distribution is described in the microvascular bed (MVB) of normal rat molar periodontal ligament (PDL). Five male Sprague-Dawley rats, aged 90 days, were anaesthetized and an external pressure of 100 +/- 20 g, maintained for 3 hours, was transmitted occlusally to randomly allocated left or right molars. The controls were the contralateral molars. Rats were perfused for 5 minutes with 5 per cent paraformaldehyde, and the mandibles post-fixed and stored in 30 per cent sucrose. Sagittal, undemineralized, mandibular jaw sections, approximately 150 microns thick, were immunolabelled with ET-1 and alpha-smooth muscle actin (alpha-SMA) primary antibodies, and IgG/CY5 and IgG/CY3 secondary antibodies, respectively. Serial images were captured with a Bio-Rad MRC-1000 UV confocal laser scanning microscope (CLSM). In the control PDL, the ET-1 immunolabelling occurred sporadically in all categories of PDL blood vessels. ET-1 showed a punctate distribution within endothelial cells, producing longitudinal and circumferential pan-endothelial labelling. Immunoreactivity to the ET-1 antibody occurred at or adjacent to vessel branching sites, and affected blood vessels with and lacking alpha-SMA immunolabelling. Treatment effects on ET-1 immunofluorescence were analysed for vascular endothelium, socket bone surface cells, cementum surface cells and PDL background in the cervical, inter-radicular and apical regions. Significant (P < 0.05) region by treatment interactions occurred for the endothelium and bone. Cementum showed a significant (P < 0.05) region effect and a significant (P < 0.05) treatment effect. However, the region by treatment interaction was not significant. Background immunofluorescence showed significant (P < 0.05) region by treatment effects for the endothelium and bone. ET-1 activity is the default state for normal PDL vascular endothelium.

Alveolar Process↗
PubMed2001

Maxillary morphology in obstructive sleep apnoea syndrome.

The aim of this case-control study was to test the hypothesis that maxillary morphology differs between obstructive sleep apnoea (OSA) patients and non-snoring, non-apnoeic subjects. Forty randomly selected patients [36 M, 4 F; mean age 49 +/- 2 (SEM) years] with varying degrees of OSA (mean Apnoea/Hypopnoea Index 32 +/- 4/hour) were compared with 21 non-snoring, non-apnoeic control subjects (18 M, 3 F; mean age 40 +/- 2 years). An intra-oral assessment of the occlusion was carried out, particularly for the presence or absence of posterior transverse discrepancies. Maxillary dental arch width was assessed by standardized lateral inter-tooth measurements (inter-canine, inter-premolar, and inter-molar) from dental models. Palatal height and maxillary depth were also measured. The maxillary dental arch was described by a 4th order polynomial equation. The ratios of maxillary to mandibular width (max/mand) and maxillary to facial width (max/facial) were determined from standardized postero-anterior cephalometric radiographs in a subgroup of patients (n = 29) and all controls. Twenty patients (50 per cent) had evidence of posterior transverse discrepancies compared with one control subject (5 per cent; P < 0.01). All patients had significantly reduced inter-canine, inter-premolar, and inter-molar distances (P < 0.05). The maxillary depth was also shorter (P < 0.05), but palatal height was not different. The quadratic coefficient of the polynomial equation was greater in the patients than in the controls (P < 0.05), indicative of greater arch tapering. Patients had smaller maxillary to mandibular and maxillary to facial width ratios (P < 0.01). These results suggest that OSA patients have narrower, more tapered, and shorter maxillary arches than non-snoring, non-apnoeic controls. Further work is required to determine the relevance of these findings in the pathophysiology of OSA.

Adult↗
PubMed2001

Ultrastructural changes in postcapillary-sized venule morphology in aged mouse periodontal ligament.

The aim of this study was to compare the postcapillary-sized venule (PCV) morphology of four young ALCA mice (35 days) and four colony-related aged mice (365 days) using the transmission electron microscope (TEM). Right and left mandibular first molar mesial roots with associated periodontal ligament (PDL) and bony socket, were used for TEM assessment. Five PCV profiles were selected at each 160 microm interval, from the alveolar crest to the tooth apex. PCV profile dimensions were measured on standardised micrographs magnified x2900. Age affects were tested using multiple regression analysis. The number of PCV profiles in the tooth third of the PDL was higher in aged mice (p < 0.01) and comprised predominantly apericytic vessels (p < 0.001). The number of PCV profiles increased significantly (p < 0.001) in aged mice in the PDL middle circumferential third halfway down the molar root. Age had no significant affect on PCV diameter. Aged PDL permeability studies are needed to investigate whether the changes in aged PCV profile number are associated with functional modification of the PDL microvasculature.

Aging↗
PubMed2000

Early changes in the endothelium of alveolar bone microvasculature with continuous tooth loading: ET-1 and alpha-SMA immunolabelling.

A continuous load of 100 g (approximately 1 N) was applied externally to the mandible of rats for three hours and transferred to the alveolar bone via a molar interocclusal rubber pad. The animals were perfusion fixed and undecalcified sagittal molar slices approximately 150 microns thick were immunolabelled with endothelin-1 (ET-1) and alpha-smooth muscle actin (alpha-SMA) antibodies conjugated with CY5 and CY3 fluorophores, respectively. A confocal laser scanning microscope was used to capture the images as digital files in stacked layers for 3-D reconstructions. Blood vessel endothelium ET-1 immunolabelling occurred at disparate sites in the microvascular bed of normal and loaded alveolar bone. Three principal patterns of immunolabelling occurred: vessels labelled with either ET-1 or alpha-SMA, and vessels labelled with both antibodies. Short-term continuous loading produced upregulation of ET-1 immunofluorescence in the blood vessel endothelium, the surface cells of Haversian canals and bone marrow spaces. Pericytes were numerous along arterioles and postcapillary-sized venules.

Actins↗
PubMed1999

Blood volume in human bicuspid periodontal ligament determined by electron microscopy.

The microvascular volume of periodontal ligament is reported to range from 1.63 to 3.5% in man, whereas that of animals varies from 7.5 to 11.5%. This transmission electron-microscopic investigation was undertaken to determine stereologically the volume in human periodontal ligament. The hypothesis tested was that the ligament blood volume in man is similar to that in animals. Left and right segments of mandible containing first and second premolars came from an adult burns' victim who underwent jaw reconstruction. The segments were immersion-fixed in 2.5% glutaraldehyde, demineralized at 4 degrees C in 0.1 M EDTA and processed for microscopy. Segments of distal periodontal ligament were sectioned at 150-micron intervals from the alveolar crest to the root apex and random tissue quadrats recorded for point counting and data analysis using a generalized linear-regression statistical model. Mean adjusted microvascular luminal volume was 9.52 +/- 2.28% (SEM) and the abluminal volume 12.91 +/- 2.76%; the wall volume was 3.39%. Significant differences existed between the luminal and abluminal volumes of the different vessel type (p < 0.05) and their distribution across the circumferential thirds of the ligament (p < 0.05). Total length density of the blood vessels was 149.84 x 10(3) cm/cm3 and the surface density 330.19 cm2/cm3. Postcapillary-sized venules held 69.1% of the total blood volume and provided 49.3% of the luminal surface area. Venous capillaries were the most common vessel, comprising 48.5%, and they contributed 71.5% of the overall length density. This study confirmed the hypothesis for the blood volume in the periodontal ligament in man. Blood volumes do not reflect the configurations of microvascular beds.

Adult↗
PubMed1999

Beagle 2: a proposed exobiology lander for ESA's 2003 Mars Express mission.

The aim of the proposed Beagle 2 small lander for ESA's 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on the surface using a robotic arm. It will use a mechanical mole and grinder to obtain samples from below the surface, under rocks, and inside rocks. Sample analysis by a mass spectrometer will include isotopic analysis. An optical microscope, an X-ray spectrometer and a Mossbauer spectrometer will conduct in-situ rock studies.

Equipment Design↗
PubMed1999

Blood vessel response to pan-endothelium (RECA-1) antibody in normal and tooth loaded rat periodontal ligament.

Immunolabelling of the normal rat molar periodontal ligament (PDL) with RECA-1 antibody, an endothelial cell surface marker, demonstrated the endothelium in the different categories of blood vessels. The intensity of immunolabelling was similar for venous capillaries (VC), post-capillary-sized venules (PCV), and collecting venules (CV). Arterial capillaries (AC) and terminal arterioles (TA) showed a different response, both having a high intensity of endothelium and smooth muscle cell labelling, whether they were located in the PDL or alveolar bone. An experimental, continuous loading of approximately 100 g was applied unilaterally to the mandibular molars for 10 minutes. In the PDL apical compression zone this load resulted in a loss of RECA-1 immunolabelling of the VC, PCV, and CV. Adjacent to the alveolar crest, where shear and tension loads were judged to have occurred, there was enhanced immunoreactivity of VC, PCV, and CV. In the loaded PDL, the AC and TA, irrespective of their location in the ligament or bone, showed strong immunofluorescence of their endothelium and the enveloping smooth muscle layer. Vessel and PDL immunofluorescence were analysed with standardized grey scale densitometry, and the data subjected to ANOVA. Comparison between individual vessel means showed significant differences (P < 0.05). Control teeth showed no immunostaining difference between the coronal and apical region vessels, whereas in the loaded teeth the overall cervical vessel endothelium had a significantly higher value than the apical vessel endothelium (P < 0.001). These findings demonstrate that the endothelium of this microvascular bed can undergo significant immunoreactivity changes when exposed to short-term, continuous, tooth loading.

Alveolar Process↗
PubMed1999

Brackets, epitopes and flash memory cards: a futuristic view of clinical orthodontics.

Orthodontics continues to be a profession anchored in traditional technology using appliances that cause inflammatory periodontal ligament (PDL) responses. Existing concepts of biological tooth movement based largely on histological tissue observations and the application of physical principles require major reassessment. In the next millennium, the genome revolution and knowledge of protein production and control could lead to the genetic correction of dentofacial anomalies and pain-free, biomolecular methods of malocclusion correction and long-term stability. A fundamental change is likely to be the abolition of bracket systems and their replacement with preprogrammed microchips driven by computers, and the control of PDL blood vessels and cells by pharmacological targeting. Future survival of the profession will depend on a radically different specialist who will be educated with a postgraduate curriculum based on molecular biology and computer engineering.

Dental Research↗
PubMed1996

Microvascular luminal volume changes in aged mouse periodontal ligament.

Data for the microvascular bed in the aged periodontal ligament have not been established. This investigation tested the hypothesis that the luminal microvascular volume decreased in the aged ligament. Mice 35 days old and one year old were vascular-perfused and the mandibular first molar periodontal ligament processed for electron microscopy. Tissue quadrats from each circumferential third ligament region were recorded at 150-microns intervals from the alveolar crest to the apex for randomized sampling of blood vessel lumina. The data were analyzed with a generalized linear model at the p < 0.01 level for the interaction of the aging effect with differences across regions. Stereological parameters were established for vessel lumen volume, and for surface and length densities. Mean ligament width decreased from 119.9 +/- 16.94 (micron +/- SE) in young mice to 60.0 +/- 10.58 (micron +/- SE) in aged mice. The luminal volume of 8.63 +/- 1.37 (% +/- SE) in young ligament increased to 9.83 +/- 2.14 (% +/- SE) in aged ligament. Collecting venules and the combined group of arterio-venous anastomoses with terminal arterioles showed a two-fold increase in luminal volume density (p < 0.01). In aged ligament, regional shifts affected the microvascular bed distribution, but these changes were not consistent across regions, or with depth. The average cross-sectional tissue area served per capillary decreased from 2117 microns 2 to 1451 microns 2 for young and old. Average ligament thickness served per capillary dropped from 52.5 microns to 27.5 microns. These reductions in average diffusion distances indicated a change in the quality of the diffusion barrier with age.

Age Factors↗
PubMed1994

Ultrastructural morphology of vascular endothelial junctions in periodontal ligament.

The TEM was used to categorize vessels and their junctions in normal and tensioned rat maxillary molar periodontal ligament. In tensioned periodontal ligament mean luminal diameters of capillaries were significantly smaller (p < 0.001). Goniometer tilting of sections with apparent tight regions revealed that only 16 per cent were actual tight junctions. The other regions proved to be close junctions (85 per cent) and open junctions (4 per cent). No gap junctions were found. These findings establish that morphologically the periodontal ligament contains a microvascular bed of 'leaky' endothelium with a potentially high permeability factor.

Alveolar Process↗
PubMed1993

Evidence for endothelial junctions acting as a fluid flux pathway in tensioned periodontal ligament.

A continuous tension load of 1.0 N applied to the rat maxillary first molar for 30 min led to a significant increase (p < 0.05) in the mean number of junctions/microns of endothelial perimeter. The mean number of junctions/microns was compared with the mean number of tissue channels/microns 2 as previously reported by fitting linear and quadratic equations. An increase in the mean number of junctions/microns was associated with an increase in mean number of tissue channels/microns 2 (p < 0.01) in control and experimental periodontal ligament. Significant increases in the mean number of junctions/microns occurred in the middle-third zone for venous capillaries (p < 0.01) and in the tooth-third zone for postcapillary-sized venules (p < 0.001). It is concluded that the endothelial junctions of venous capillaries and postcapillary-sized venules provide significant pathways for fluid transport across the tensioned walls of the microvascular bed of the periodontal ligament.

Animals↗
PubMed1993

A T.E.M. stereological analysis of blood vessels and nerves in marmoset periodontal ligament following endodontics and magnetic incisor extrusion.

Maxillary incisor fracture is a common dental injury. It is frequently treated by endodontic therapy, orthodontic extrusion, and a retention period. The aim of the study was to mimic this regime and stereologically quantify the vascular and neural reconstitution of the periodontal ligament (PDL). Ten marmosets (Callithrix jacchus) had the right maxillary incisor crown removed, root canal treatment, and magnetic incisor root extrusion of 1.2 mm. After incisor retention for 9 weeks, the animals were perfusion fixed for electron microscopy. The incisor PDL was sectioned at 250 micron intervals from the cervical to apical region and recorded for stereological evaluation. Further evaluations were conducted with a two-way analysis of covariance using program 3V of the BMDP-81 statistical software package. The total luminal PDL vascular volume was statistically unchanged. An increased occurred in the mean number of venous capillaries from 0.07 +/- 0.3 to 0.17 +/- 0.3 per 560 microns 2 of PDL (P < 0.05). Vessel wall and luminal volume of post-capillary-sized venules decreased from 1.64 to 1.03 per cent, and 5.32 to 3.04 per cent (P < 0.05), respectively. Mean luminal and abluminal diameters for post-capillary-sized venules were reduced (P < 0.05). Myelinated and unmyelinated axons showed no significant change in volume (Vv), length (Lv), or surface (Sv) densities. Axon number/unit, PDL area, and mean diameters demonstrated no statistical differences. Since the PDL demonstrated almost complete morphological re-establishment of the microvascular and axon systems, it is considered that this clinical treatment is a justifiable rationale.

Analysis of Variance↗
PubMed1992

A TEM analysis of tissue channels in normal and orthodontically tensioned rat molar periodontal ligament.

This investigation tested the hypotheses that (1) tissue channels (TC) exist in normal periodontal ligament (PDL) between the cervical and apical zones, and (2) orthodontic tooth tension alters their number and distribution within this region. A continuous 1.0 N tension was applied to the maxillary first molar for 30 minutes and ionic tracer precipitate used to analyse TC in unstained TEM sections. In normal PDL, the mean number of tissue channels (MNTC) was 0.10 +/- 0.01/micron 2 in the 0-2-microns PDL zone extending from the vessel wall, 0.09 +/- 0.02/micron 2 in the 2-4-microns zone, and 0.06 +/- 0.02/micron 2 in the 4-6 microns zone. Differences were not statistically significant. Extrusion increased the MNTC to 0.28 +/- 0.01/micron 2, 0.20 +/- 0.02/micron 2, and 0.16 +/- 0.02/micron 2, in the 0-2-, 2-4- and 4-6-microns zones, respectively (P < 0.001). For normal PDL in the tooth, middle and bone circumferential thirds the TC distribution were even. In the tensioned PDL, TC in the circumferential tooth third (0.20 +/- 0.02/micron 2), middle third (0.19 +/- 0.01/micron 2), and bone third (0.23 +/- 0.02/micron 2) increased significantly (P < 0.001) from normal ligament. The total increase in experimental MNTC was associated mainly with the post-capillary-sized venules, venous capillaries, and arterial capillaries. With progression from the cervical to apical regions the MNTC in control PDL failed to significantly fit a quadratic regression pattern. By contrast, tensioned PDL showed a marked regression pattern (P < 0.001) indicating a reduction in MNTC with vertical depth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A scanning electron microscope study of microcorrosion casts of the microvasculature of the marmoset palate, gingiva and periodontal ligament.

In the hard palate, sagittally oriented capillary loops, 8-10 microns in diameter and 70-250 microns high, extended perpendicularly from a subcapillary plexus to the connective tissue papillae. These loops formed a well-delineated vascular spine beneath the rugal crests. Capillary loop density was estimated to be 200-270/mm2 on the rugal crest, 75-160/mm2 on the rugal slopes and 70-140/mm2 in the trough. In the gingiva, the crevicular loop system was separated by a gap from the vestibular, palatal and col loop systems. Anastomoses occurred between these systems at a deeper level. The crevicular circular plexus varied from 1 to 4 vessels. Apical to the gingival margin the buccal vasculature was composed of occluso-apically orientated loops draining towards the vestibular sulcus. The capillary loops were 60-120 microns high near the gingival margin, compared with 40-60 microns near the mucogingival junction. The mucogingival margin was demarcated by a change in capillary orientation. The periodontal ligament contained mainly postcapillary-sized venules, 10-25 microns in diameter, orientated occluso-apically. Capillary loops, 50-100 microns long and directed at right angles to the root surface, occurred in the cervical third. These microvascular patterns of the marmoset are different from those of the mouse and rat.

Animals↗
PubMed1991

An analysis of the effect of tooth intrusion on the microvascular bed and fenestrae in the apical periodontal ligament of the rat molar.

An analysis of the rat apical periodontal ligament (PDL) microvascular bed and fenestrae was conducted to evaluate the effect of a continuous 1.0 N intrusive tooth load for 30 minutes. The microvascular bed consisted of postcapillary-sized venules, venous and arterial capillaries, and terminal arterioles. Intrusion produced significant increases (p less than 0.01) in vascular volume for postcapillary-sized venules and venous capillaries in three of the four animals. Arterial capillaries, overall, showed a statistically significant increase (p less than 0.01). The endothelial surface area (micron2 x 10(6)) per cubic millimeter of PDL responded variably in postcapillary-sized venules and venous capillaries but showed a strong trend to increase in arterial capillaries. After tooth intrusion a significant reduction (p less than 0.01) occurred in the number of fenestrae per square micrometer of endothelium in postcapillary-sized venules and venous capillaries. Fenestrae in the control PDL had a mean diameter of 51.5 nm +/- 0.6 (SE), whereas those on the intrusion side were smaller (p less than 0.05), measuring 49.9 nm +/- 0.4 (SE).

Animals↗