PubMed Health⌕ Search

Biomedical subjects

M Slater

Publications and source records attributed to M Slater.

At least 55 records · Page 3Linked to original sources
PubMed1998

The influence of body movement on subjective presence in virtual environments.

We describe an experiment to assess the influence of body movements on presence in a virtual environment. In the experiment 20 participants were to walk through a virtual field of trees and count the trees with diseased leaves. A 2 x 2 between subjects design was used to assess the influence of two factors on presence: tree height variation and task complexity. The field with greater variation in tree height required participants to bend down and look up more than in the lower variation tree height field. In the higher complexity task participants were told to remember the distribution of diseased trees in the field as well as to count them. The results showed a significant positive association between reported presence and the amount of body movement in particular, head yaw--and the extent to which participants bent down and stood up. There was also a strong interaction effect between task complexity and gender: Women in the more-complex task reported a much lower sense of presence than in the simpler task. For applications in which presence is an important requirement, the research in this paper suggests that presence will be increased when interaction techniques are employed that permit the user to engage in whole-body movement.

Female↗
PubMed1997

Mutations at codon 184 in simian immunodeficiency virus reverse transcriptase confer resistance to the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine.

Variants of simian immunodeficiency virus (SIV) that display greater than 2,000-fold resistance to the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine (3TC) were generated through in vitro passage and drug selection. The polymerase regions of several of these resistant viruses were sequenced and were found to share either of two codon alterations at site 184 in reverse transcriptase (ATG to ATA [methionine to isoleucine] and ATG to GTA [methionine to valine]). The biological relevance of these substitutions for 3TC was confirmed by site-directed mutagenesis with the SIVmac239 infectious recombinant clone of SIV.

Anti-HIV Agents↗
PubMed1997

Saving for retirement.

In September, New Zealanders will take part in a referendum on a new, compulsory retirement savings scheme. This looks to be far less equitable than the present universal superannuation scheme.

Humans↗
PubMed1996

Dynamic interactions of the extracellular matrix.

The extracellular matrix (ECM) is a dynamic assemblage of interacting molecules that reorganise and regulate cell functions in response to endogenous and exogenous stimulii. Matrix components may affect cell behaviour directly or indirectly through growth factor sequestration and transmembrane signalling, by controlling the speed of various molecules through the ECM, and the access of growth factors, hormones and neurotransmitters to the cell surface.

Animals↗
PubMed1995

Thrombospondin co-localises with TGF beta and IGF-I in the extracellular matrix of human osteoblast-like cells and is modulated by 17 beta estradiol.

Thrombospondin (TSP) is a multifunctional glycoprotein which is synthesised by several cell types including osteoblasts, and incorporated into the extracellular matrix (ECM) of these cells. The function and regulation of TSP in bone is not clear. In this study, using a long term culture model of human osteoblast-like cells, we examined the distribution of TSP in the ECM and its modulation by added estradiol. In this model the osteoblast-like cells form a regular multilayer which continues to increase in depth up to 50 days post confluence. In the ECM of these cultures and in 19-week fetal bone, the bone markers osteocalcin and alkaline phosphatase were diffusely distributed in the matrix. In contrast, labelling for TSP was concentrated, confined to the banded collagen and its immediately adjacent ECM. This pattern of labelling resembled that of the growth factors transforming growth factor beta-I (TGF beta), and insulin-like growth factor-I (IGF-I), with which TSP label co-localised. Labelling intensities were comparable between fetal bone and the in vitro material for TSP, TGF beta and IGF-I. TSP label was present by 10 days post confluence, reached a maximum by 20 days, and declined slowly thereafter, a time course which was similar to that of IGF-I. Incubation of osteoblast-like cell cultures with 17 beta estradiol resulted in an increase in multilayer depth and a maximal 3-fold increase in TSP labeling at 30 days as well as approximately 2-fold increases for TGF beta and IGF-I. The dose-response relationship for these responses to estradiol treatment was biphasic with maximal increases at 10(-10) M-10(-11) M of added estradiol. Treatment with 17 alpha estradiol produced labelling intensities that were not significantly different from controls. Studies with other cell types have suggested that TSP may be involved in modulation of growth factor activity. The similarities between TSP, TGF beta and IGF-I, in terms of their distribution and regulation by 17 beta estradiol treatment, may indicate a role for TSP in modulating bone cell proliferation and function through interaction with local growth factors.

Alkaline Phosphatase↗
PubMed1995

Involvement of platelets in stimulating osteogenic activity.

Osteoblast-like cells have been shown to be sensitive to the proliferative action of a wide variety of growth factors. Many of these growth factors have been isolated from platelets and are thought to be released at local sites in response to injury. In this study, we tested whether human platelet concentrate, as a supplement to basic medium, would support the proliferative and functional activity of human fetal osteoblast-like cells in both short-term and long-term culture. In short-term studies, uptake of [3H]thymidine was increased in platelet-treated cultures by more than 4-fold compared with 10% serum-supplemented controls. When cultured for prolonged periods on coverslips, the cells formed multilayers, with a collagen-based matrix separating the layers. Long-term cultures that were treated with 1.5% (vol/vol) platelets in serum-supplemented medium showed increases in the depth of the multilayers of as much as 36-fold at 30 days after confluence, compared with the 10% serum-supplemented controls; this difference persisted until day 50. Incorporation of growth factor in the matrix was examined with the use of colloidal gold immunoelectron microscopy. Immunogold labeling intensities for transforming growth factor-beta 1 were significantly lower in the platelet-treated cultures at 20 days and then increased to a maximum level of 2.1-fold more than in the controls at 40 days. Labeling intensities for insulin-like growth factor-I and basic fibroblast growth factor were significantly lower in the platelet-treated cultures than in the controls at all stages of culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1994

Role of chondroitin sulfate glycosaminoglycans in mineralizing osteoblast-like cells: effects of hormonal manipulation.

A monoclonal anti-chondroitin sulfate antibody (CS-56) that recognizes native chondroitin sulfate glycosaminoglycans (CSGAG) was used to quantify changes in CSGAG labeling levels in mineralizing human fetal osteoblast-like cell multilayers up to 40 days postconfluence. In control cultures, mean labeling of CSGAG increased in nonmineralized areas from around eight gold probes per micron 2 (gpm) at 20 days to 26 gpm at 40 days. Labeling was markedly increased in the mineralized tissue, to 560 gpm at 30 days and 580 gpm at 40 days. In beta-glycerophosphate-treated cultures, the mineralized areas were increased and appeared earlier (20 days) than in the control cultures. In these cultures, mean CSGASG labeling increased in nonmineralized areas from around 5 gpm at 20 days to 26 gpm at 30 days and was further increased in mineralized areas to 270 gpm at 20 days and 298 gpm at 30 days. Mineralization was not noted in cultures treated with 10(-8) M 1,25-dihydroxyvitamin D, and CSGAG labeling remained low (< 5 gpm) during the study period. These results indicate that an increase in immunoreactive CSGAG is associated with mineralization in this culture system. One possible interpretation of these findings is that proteoglycan molecules or at least their CSGAG side chains may be involved in the mineralization process.

Antibodies, Monoclonal↗
PubMed1994

Immunogold localization of TGF beta 1 protein and mRNA in human skin using a colloidal gold/digoxygenin system.

Tissue preservation, and immunogold cytochemical and in-situ hybridization labelling intensities vary according to the preparatory protocols used. We wished to determine which preparative protocols produce optimal preservation, protein and mRNA labelling. Nine combinations of fixative and embedding resin were therefore studied using postembedding immunoelectron microscopy and a novel immunogold digoxygenin in situ hybridization (ISH) system, to quantitate the presence of transforming growth factor beta 1 (TGF beta 1) protein and message in human skin. The best preservation was observed in tissue fixed in 1% glutaraldehyde and embedded in LR White resin or low acid glycolmethacrylate resin (LA-GMA). Preservation was poor in tissue fixed with 1% glutaraldehyde and fair in 4% paraformaldeyde, when embedded in Unicryl. Ethanediol dehydration coupled with LA-GMA embedding resulted in reasonable preservation. Based on quantitative measures of the labelling density for TGF beta 1 protein and mRNA, immunogold labelling was adequate with 1% glutaraldehyde fixation coupled with LR White or LA-GMA resins, and also with 4% paraformaldehyde and LR White resin, but was best with ethanediol dehydration and LA-GMA embedding. ISH labelling under basal conditions was best in LA-GMA with 1% glutaraldehyde or 4% paraformaldehyde. The ISH label in tissue fixed with 1% glutaraldehyde and embedded in LA-GMA was significantly increased by treatment with proteinase K. Overall, ethanediol dehydration was associated with a good immunoelectron microscopic (IEM) label while LA-GMA with 1% glutaraldehyde or 4% paraformaldehyde resulted in a consistently detectable ISH label. LA-GMA embedding with 1% glutaraldehyde fixation gave a good result with both IEM and ISH labelling.

Digoxigenin↗
PubMed1994

Modulation of growth factor incorporation into ECM of human osteoblast-like cells in vitro by 17 beta-estradiol.

Human fetal osteoblast-like cells formed a regular multilayered structure in vitro with an extensive collagen-based extracellular matrix. With colloidal gold immunocytochemistry, labels for alkaline phosphatase and osteocalcin were distributed in a relatively diffuse pattern, in contrast to the bone growth factors, insulin-like growth factors I and II (IGF-I and IGF-II), transforming growth factor-beta 1 (TGF-beta 1), and basic fibroblast growth factor, which were colocalized in the collagenous matrix of the multilayer. The inclusion of 17 beta-estradiol (10(-11) to 10(-9) M) in the culture medium increased multilayer depths, increased labeling for IGF-I, IGF-II, and TGF-beta 1, and resulted in earlier detection of TGF-beta 1 label. In contrast, the increase in multilayer depth resulting from treatment with human platelets, an exogenous source of growth factors, was not accompanied by an increase in matrix IGF-I, IGF-II, or TGF-beta 1 label, suggesting a particular effect of estradiol to facilitate this process. Because growth factors in bone matrix may act as coupling agents when released during resorption, reduced growth factor incorporation in the presence of reduced sex steroid concentrations may lead to uncoupling of resorption and subsequent formation.

Alkaline Phosphatase↗
PubMed1994

The determination of comparable labeling densities in quantitative immunoelectron microscopic double labeling studies.

In quantitative ultrastructural studies using colloidal gold immunocytochemical techniques, labeling intensities vary according to the size of the probe used. Using postembedded indirect two-sided double labeling and single labeling protocols, the labeling characteristics of four antigens were studied using two probe sizes commonly used in double labeling studies. It was determined that the labeling intensity variation resulting from the use of different probe sizes was unpredictable after correcting for the increased probe size alone. It was possible, however, to obtain comparable labeling densities by first determining the labeling intensities for each probe size with its antigen in single label studies on serial sections and using the same procedure as the double labeling studies. A probe size correction factor for each antigen was calculated from these data. This factor was used to obtain comparable measurements of the relative abundance of each label.

Antibodies↗
PubMed1994

Dental health of 14-year-old children in St. Ouen, France and Salford, England.

Fourteen-year-old children in two schools, 82 in St Ouen, France and 133 in Salford, England were examined to compare their dental health. The mean DMFT in St Ouen was 4.83 and in Salford 5.49. This difference was not significant. However, St Ouen children had significantly fewer fillings with a mean of 1.16 compared with 1.95 in Salford (P < 0.05). Eighty-two per cent of the Salford children said that they had visited the dentist in the past year compared with 54 per cent of the St Ouen children (P < 0.001). Significantly more Salford children considered that regular visits to the dentist were very/fairly important for preventing dental caries and periodontal disease.

Adolescent↗