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Biomedical subjects

W J Sampson

Publications and source records attributed to W J Sampson.

32 records · Page 2Linked to original sources
PubMed1988

The effect of inhibition of cholesterol esterification on the fate of cholesterol derived from HDL in rat hepatocyte monolayers.

Rat HDL2 is known to stimulate bile acid synthesis in rat hepatocyte monolayers. The intracellular fate of the cholesterol derived from the HDL2 was studied using the inhibitor of cholesterol esterification, Sandoz compound 58-035. Rat HDL2 added to rat hepatocyte monolayers caused a stimulation of cholesterol esterification of 32%. This stimulation could be inhibited by 58-035. A small significant increase in bile acid synthesis was also observed in cells in the presence of HDL2, confirming our earlier observations. 58-035 prevented this increase. These observations imply that cholesterol entering the cell from HDL2 is first esterified and can only enter the substrate pool for bile acid synthesis after subsequent intracellular hydrolysis.

Amides↗
PubMed1988

Effect of iodine deficiency on craniofacial growth in young common marmosets (Callithrix jacchus).

The effects of iodine deficiency on general and craniofacial growth were determined in young common marmosets. Examinations, including direct measurement, cephalometric radiology, and dental examination, were performed at three-month intervals from birth to 1 year on a cross-sectional sample of three groups of marmosets. The groups were those on a normal diet, n = 50; an iodine-deficient diet during gestation and for 1 year postnatally, n = 26; and an iodine-deficient diet only during gestation (returned to a normal diet at 1 month after birth), n = 18. The iodine-deficient animals were smaller in all dimensions, compared with controls, but they did not have typical cretin facies. Animals that were iodine deficient during gestation but subsequently fed a normal diet were small initially but displayed compensatory growth, so that by 1 year they were nearly normal in size.

Age Factors↗
PubMed1987

The role of acyl-CoA: cholesterol acyltransferase in the metabolism of free cholesterol to cholesteryl esters or bile acids in primary cultures of rat hepatocytes.

Sandoz compound 58-035 has been shown to inhibit acyl-CoA: cholesterol acyltransferase activity in a variety of cell types. We have shown that it does not inhibit rat liver microsomal cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme of bile-acid synthesis, but it does inhibit acyl-CoA: cholesterol acyltransferase in both the microsomal fraction and in rat hepatocyte monolayers. To test the role of acyl-CoA: cholesterol acyltransferase in these cells, monolayers were incubated over 5 h in the presence and absence of 58-035 and in the presence of increasing amounts of mevalonic acid to provide a source of cholesterol. The addition of mevalonic acid increased the secretion of bile acids by the cells, and this was further increased by the addition of 58-035. The secretion of cholesteryl esters was conversely inhibited by the addition of 58-035. The results help define the role of acyl-CoA: cholesterol acyltransferase in determining the fate of intracellular cholesterol.

Amides↗
PubMed1987

A cephalometric study of young marmosets (Callithrix jacchus).

Linear and angular measurements of young marmosets taken at three-month intervals from a series of cephalograms are presented. They show that linear craniofacial development was largely complete by six months of age, subsequent angular changes being mainly related to dental development. No sexual dimorphism was apparent, and there was substantial homogeneity in results for animals of the same age. Thus, marmosets, with their low cost, ease of handling, and rapid maturation, may provide a useful animal model for craniofacial research.

Age Factors↗
PubMed1985

Fluorine concentration changes in human periodontally diseased tooth roots following several treatment times with citric acid.

Citric acid conditioning of exposed cementum has become an important adjunct to the clinical management of periodontal disease, and aggressive root planing is recommended to remove hypermineralized and endotoxin-laden diseased cementum. A nuclear resonance reaction technique was used to examine fluorine concentration changes subsequent to application of citric acid (pH 1.0) to the periodontal disease-exposed cementum surfaces of human tooth roots. The technique does not require the test teeth to be sectioned, thereby permitting longitudinal assessments of changes in fluorine concentration and minimizing measurement errors due to the considerable biological variation found between individuals. Initial fluorine concentrations ranged from 0.9%-2.4%, and maxima occurred within 4-6 microns of the surface, suggesting the presence of a hypermineralized layer. Within 60 sec, the citric acid had effectively removed the hypermineralized layer and the previously observed fluctuations in fluorine concentration leveled out at 0.3%-0.5%. Although the results indicated rapid removal of the hypermineralized layer and establishment of fluorine levels normally found in healthy cementum, the experimental design did not permit appraisal of potential effects upon the organic components of periodontally-exposed cementum.

Citrates↗
PubMed1985

Prediction of mandibular incisor and canine crowding changes in the mixed dentition.

To test the hypothesis that preeruptive tooth positions and dental arch parameters might forecast crowding changes, a sample of 47 aboriginal children (26 males, 21 females) was selected stringently on the basis of Class 1 characteristics and an untreated dentition unaffected by caries or attrition. Crowding scores, radiographic relationships of 765E, and dental arch dimensions were evaluated for the mixed dentition (Stage 1, 8.91 +/- 1.05 years) and earliest emergence of the permanent dentition (Stage 2, 12.48 +/- 0.97 years). Changes between the stages were calculated and the sample was divided into two groups, according to an increase (Group 1) or decrease (Group 2) in incisor and canine crowding. Multivariate and multiple regression analyses were used to identify predictors (Stage 1 radiographic and dental arch parameters) of incisor and canine crowding behavior. Dental arch form and tooth size were important factors in measuring the amount of incisor or canine crowding at Stage 1 and Stage 2. Neither the radiographic nor the dental arch predictors proved useful in forecasting crowding changes. Group 2 dental arches tended to be initially narrower, shallower, and more crowded; however, they showed greater molar and canine width expansion and lessened arch depth reduction than Group 1 cases. Many cases showed a reduction in canine crowding from mixed to permanent dentition. This appeared to be largely independent of the observed incisor crowding. Sexual, racial, and individual variations in dentofacial pattern reinforce the need to carefully consider interceptive extraction or space-regaining therapy for each patient because of the unpredictability of crowding behavior during the transition from mixed to permanent dentition.

Australia↗
PubMed1985

Epithelial root-sheath changes during molar formation in the mouse.

The ultrastructure of the epithelial root-sheath was examined in the first mandibular molar teeth of 11, 16 and 21-day-old mice. The changing morphology of the sheath was related to root maturity. An initial, predominantly bicellular layer progressively shortened in an apical direction, the outer layer more so than the inner. The changing morphology appeared to involve maintenance of the inner layer largely at the expense of the outer. Some inner-layer cells persisted at spaced intervals adjacent to forming acellular cementum. Some epithelial rests, distant from the root surface, appeared to be formed early in root development at the time of initial root-sheath severance from the cervical loop of the enamel organ. Epithelial rests located along the acellular cementum appeared to arise from inner, rather than outer, epithelial root-sheath cells and at later stages in root development.

Animals↗
PubMed1983

Shallow fluorine depth profiles of cementum in periodontal disease--a pilot study.

A nuclear resonant reaction depth profiling technique was used to analyze elemental fluorine distribution in the first 20 microns of human dental cementum. A pilot sample of six periodontally-involved teeth indicated greater levels of fluorine in exposed cementum (0.9 leads to 2.4%) compared to cementum apical to the zone of epithelial attachment (0.4 leads to 1.1%). Furthermore, the exposed cementum appeared to have fluorine levels within the surface 5 microns comparable to the hypermineralized layer previously reported by x-ray diffraction and microprobe techniques. The nuclear resonant reaction is a non-destructive technique which yields useful information of surface elemental distribution as a function of depth, and may be regarded as a potential means of analyzing changes in the inorganic constitution of cementum during various physico-chemical pre-treatments.

Adolescent↗
PubMed1979

A comparative light microscopic evaluation of oxytalan fiber staining with a variety of dye substances.

Staining of oxytalan fibers in marsupial, eutherian and human periodontal ligaments was surveyed with 65 different dyes. Using the criteria of response to preoxidation, distribution, and morphologic appearance, 27 dye preparations in addition to the Gomori aldehyde-fuchsin, Taenzer-Unna orcein, and Weigert resorcin-fuchsin techniques displayed oxytalan fibers. With two exceptions all dyes were cationic and reacted with varying degrees of excellence with different animals. Most dyes produced their best staining results as concentrated solutions in 3% acetic acid, suggesting involvement of oxidatively engendered polyanions predominantly associated with an acid mucopolysaccharide component of the oxytalan fiber. The significance of carboxyl and sulfur-containing groups should not be overlooked in further studies aiming to elucidate oxytalan fiber chemistry and microstructure. This study supported the view that oxytalan fibers belong to the family of elastic tissues and represent a biologically important system within the periodontal ligament.

Animals↗
PubMed1977

Oxytalan fibre organization in marsupial mandibular periodontal tissues.

The arrangement and distribution of oxytalan fibres in Australian marsupials has not previously been reported. Periodontal tissues of wombat, wallaby, possum, and marsupial mouse were examined to ascertain oxytalan fibre organization. Despite adaptation of the marsupial masticatory apparatus to different diets the oxytalan fibre organization in the periodontal ligament shows a basic pattern which corresponds with that reported in other animals. The oxytalan system forms a continuous meshwork of fine, branching fibres which completely invests each tooth root and connects adjacent teeth. Thick ribbon-like apico-occlusally orientated oxytalan fibres, thought to form by the coalescence of thinner fibres, are restricted to the periodontal ligament. The oxytalan fibres are embedded in cementum and attached to blood vessels in the pariodontal ligament. Oxytalan fibres do not insert into alveolar bone. Histological evidence indicates functional remodelling of the oxytalan fibre system in continuously erupting teeth.

Animals↗