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Biomedical subjects

M de Jager

Publications and source records attributed to M de Jager.

At least 19 recordsLinked to original sources
PubMed2003

Effect of brushing force and time on plaque removal using a powered toothbrush.

OBJECTIVES: Primary objective - To determine the effect of varying brushing forces and brushing times upon the plaque-removing efficacy of a powered toothbrush. Secondary objective - to determine the optimum combination of brushing force and time for plaque removal. MATERIAL AND METHODS: This randomised, single-blind, 16-cell, cross-over trial compared the efficacy of plaque removal of a powered toothbrush (PTB) used with four brushing forces (75, 150, 225 and 300 g) and over four brushing times (30, 60, 120 and 180 s). Twelve volunteers (18-30 years) were recruited and trained to use the Philips/Jordan Sensiflex 2000 PTB, which was modified so that specified forces and times could be recorded. Each subject was asked to abstain from all oral hygiene procedures for 24 hs prior to each brushing event, to allow plaque accumulation. Plaque was recorded using a modified Quigley & Hein index (PI) at six points per tooth before and after each episode of brushing, and the differences in the means (pre- to postbrushing) were compared. Three-way anova was undertaken to compare differences between plaque-removing efficacy for the 16 combinations of force and time. Subjects, brushing time and brushing force were used as fixed effects within the analysis. RESULTS: All 12 subjects participating completed the 16 combinations of force and time over which plaque removal was assessed. Statistically significant differences in PI reductions were found between different brushing times and forces over all tooth surfaces (p<0.001). The interaction of varying brushing force and brushing time was significant for full mouth (FM) and interproximal (IP) sites (p<0.03). No statistical significance was demonstrated for smooth surface (SS) sites, nor was it detected for the interaction of subjects with brushing force or subjects with brushing time (p>0.05). CONCLUSION: We conclude that brushing time and brushing force have significant effects upon the level of plaque removal by a PTB, and at 120 s brushing time the improvement in plaque removal with forces in excess of 150 g was negligible.

Adult↗
PubMed2003

Non-contact removal of coadhering and non-coadhering bacterial pairs from pellicle surfaces by sonic brushing and de novo adhesion.

Coadhesion between oral microbial pairs is an established factor in the spatiotemporal development and prevalence of mixed-species communities in early dental plaque in vivo. This study compares removal and de novo adhesion of pairs of coadhering and non-coadhering oral actinomyces and streptococci by sonic brushing on salivary pellicles in a non-contact mode as a function of the distance between the brush and the pellicle surface in vitro. First, actinomycetes were adhered to a pellicle surface, after which streptococci suspended in saliva were allowed to adhere. Removal was examined by non-contact, sonic brushing with a wetted brush on a either a wetted or a substratum immersed to a depth of 7 mm. After brushing, de novo adhesion of streptococci to brushed pellicles was studied. For coadhering and non-coadhering pairs, 34% and 9%, respectively, of the adhering bacteria were involved in aggregates comprising more than 10 organisms. Non-contact, sonic brushing removed up to 99% of the adhering bacteria, regardless of the state of immersion of the substratum. Bacterial removal decreased with increasing distance of up to 6 mm between brush and pellicle surface. For the non-coadhering pair, subsequent exposure of pellicles to a streptococcal suspension yielded about 6% of bacteria involved in large aggregates. Alternatively, de novo adhesion of the coadhering streptococcal strain to pellicles brushed on the wetted substratum yielded 31% of bacteria involved in large aggregates, but after brushing the immersed substratum only 12% of the adhering bacteria were found in large aggregates. It is concluded that non-contact sonic brushing, under immersion, removes high percentage of adhering bacterial pairs up to a distance of 6 mm between the brush and the pellicle surface. However, non-contact, sonic brushing with only a thin wet film on the substratum may leave footprints to which streptococci preferentially adhere.

Actinomyces↗
PubMed2002

Testing the efficacy of 2 prototype brush heads for a powered toothbrush: refining the model.

OBJECTIVES: To compare 2 prototype powered toothbrush (PTB) heads (A, B) to a marketed head (Sensiflex 2000) for plaque removing efficacy on the Philips/Jordan HX2550 PTB. MATERIALS AND METHODS: A 2-week, 3-group, single-blind trial recruited 78 volunteers (18-25). Plaque indices (PIs) were recorded at screening and 14 days later at baseline. Subjects were stratified (gender and PI) and then asked to abstain from oral hygiene measures for 48 h. A supervised episode of brushing with the allocated PTB head followed. Subjects then used the PTBs at home for the next 12 days before being asked to abstain from all oral hygiene measures for another 48 h prior to a second supervised brushing episode. Plaque was scored using a new modification of the Quigley & Hein Index (PI) at full mouth (FM), interproximal (IP) and smooth surfaces (SS). PIs were recorded before and after the supervised brushing episodes to enable the means of the within subject differences (pre- to post-brushing) to be compared between groups (ANOVA/t-tests). RESULTS: There were no significant differences in PI between groups at baseline or prior to the supervised brushings (p>0.05). Highly significant, mean reductions in PIs (approximately 1/2 of one PI unit) were observed for design B compared with the Sensiflex 2000 at FM and IP sites (p<0.0001) for both supervised brushing episodes. A significant reduction in PI at SS was seen only after the first brushing episode (p=0.0004). For design A, PI reductions were consistently greater than those for the Sensiflex 2000 but differences were only significant at the p<0.05 level. CONCLUSION: It is concluded that this model of clinical trial has sufficient power to demonstrate clinical superiority with respect to plaque removal for PTBs and can be used for testing one or more prototype designs of brush heads.

Adolescent↗
PubMed2001

DNA-binding and strand-annealing activities of human Mre11: implications for its roles in DNA double-strand break repair pathways.

DNA double-strand breaks (DSBs) in eukaryotic cells can be repaired by non-homologous end-joining or homologous recombination. The complex containing the Mre11, Rad50 and Nbs1 proteins has been implicated in both DSB repair pathways, even though they are mechanistically different. To get a better understanding of the properties of the human Mre11 (hMre11) protein, we investigated some of its biochemical activities. We found that hMre11 binds both double- and single-stranded (ss)DNA, with a preference for ssDNA. hMre11 does not require DNA ends for efficient binding. Interestingly, hMre11 mediates the annealing of complementary ssDNA molecules. In contrast to the annealing activity of the homologous recombination protein hRad52, the activity of hMre11 is abrogated by the ssDNA binding protein hRPA. We discuss the possible implications of the results for the role(s) of hMre11 in both DSB repair pathways.

Animals↗
PubMed2001

Human Rad50/Mre11 is a flexible complex that can tether DNA ends.

The human Rad50 protein, classified as a structural maintenance of chromosomes (SMC) family member, is complexed with Mre11 (R/M) and has important functions in at least two distinct double-strand break repair pathways. To find out what the common function of R/M in these pathways might be, we investigated its architecture. Scanning force microscopy showed that the complex architecture is distinct from the described SMC family members. R/M consisted of two highly flexible intramolecular coiled coils emanating from a central globular DNA binding domain. DNA end-bound R/M oligomers could tether linear DNA molecules. These observations suggest that a unified role for R/M in multiple aspects of DNA repair and chromosome metabolism is to provide a flexible, possibly dynamic, link between DNA ends.

DNA↗
PubMed2001

Side-effects of oral misoprostol in the third stage of labour--a randomised placebo-controlled trial.

BACKGROUND: Misoprostol, an inexpensive, stable, orally active prostaglandin analogue, has been suggested for use in the prevention of postpartum haemorrhage. Potential side-effects, however, need to be quantified. OBJECTIVE: To compare the rate of postpartum shivering and pyrexia following oral misoprostol 600 micrograms and placebo. DESIGN: A double-blind placebo-controlled trial. Women in labour were randomly allocated to receive either misoprostol 600 micrograms orally or placebo after delivery. Conventional oxytocics were given immediately if blood loss was thought to be more than usual. Side-effects were recorded. Postpartum blood loss in the first hour was measured by collection in a special flat plastic bedpan. SETTING: The labour ward of an academic hospital in Johannesburg, with 7,000 deliveries per annum. MAIN OUTCOME MEASURES: Shivering and pyrexia. RESULTS: The groups were well matched. Misoprostol use was associated with more shivering (44% versus 11%, relative risk (RR) 4.03, 95% confidence interval (CI) 2.85-5.70), pyrexia > or = 37.8 degrees C (38% v. 6%, RR 6.23, CI 3.89-9.97), 1-hour systolic blood pressure > or = 140 mmHg (33% v. 25%, RR 1.32, CI 1.03-1.70), and diastolic blood pressure > or = 90 mmHg (10.5% v. 3.0%, RR 3.44, CI 1.67-7.11). There were no other significant differences. The study was not designed to be large enough to assess a difference in blood loss > or = 1,000 ml (9% v. 9.7%, RR 0.93, CI 0.56-1.53). Possible effects on blood loss may have been obscured by the lesser use of additional oxytocics in the misoprostol group (14% v. 18%, RR 0.78, CI 0.54-1.13). CONCLUSIONS: This study has shown the association of postpartum oral misoprostol 600 micrograms with shivering, pyrexia and hypertension. The increased blood pressure, as for the trend towards increased abdominal pain, may be secondary to the uterotonic effect of misoprostol. Large randomised trials are needed to assess the effectiveness of misoprostol in the prevention of postpartum haemorrhage, against which the disadvantages demonstrated here can be weighed.

Adult↗
PubMed2001

Plaque removal efficacy of two rotating/oscillating electric toothbrushes.

This study compared the plaque removal efficacy of the Philips Jordan HP510 and Braun Oral-B D9 electric toothbrushes in two clinical trials. In Trial I, a single-blind randomized split-mouth study, 24 subjects received an oral prophylaxis and abstained from all oral hygiene procedures for 24 hours before each quadrant was professionally brushed for 30 seconds. Plaque was scored before and after brushing using the Turesky-modified Quigley and Hein index (Q&H) and the approximal plaque index (API). Trial II was a two-week, single-blind balanced cross-over study comprising 54 subjects. At baseline, the subjects received an oral prophylaxis and instruction in the use of the assigned brush. Two weeks later, they returned to the clinic with 24-hour plaque accumulation. Plaque (Q&H, API) was scored before and after supervised brushing (30 sec/quadrant). After a prophylaxis, the subjects received the other brush with instructions on use, and the procedure was repeated. In Trial I, plaque was removed almost equally well by both brushes, with the HP510 and the D9 reducing Q&H from 1.46 and 1.47 (baseline) to 0.53 and 0.58, respectively, on average over all teeth. For the premolars and molars in particular, use of the HP510 resulted in statistically significantly lower Q&H scores than the D9 (0.70 vs. 0.81). In Trial II, the HP510 resulted in significantly better plaque scores than the D9 on Q&H (0.55 vs. 0.67) and API (23% vs. 28%) for all teeth. The buccal surfaces contributed the largest difference in Q&H. Statistically significant differences were also found in scores of the posterior teeth for Q&H (0.75 vs. 0.86) and API (31% vs. 38%). In conclusion, both rotating/oscillating electric toothbrushes were highly effective in plaque removal. The HP510 removed more plaque than the D9, particularly from the posterior teeth. It appeared that the smaller height and the Active Tip of HP510's brush head could have resulted in better posterior and approximal access.

Adult↗
PubMed2001

Influence of a controlled pressure system on toothbrushing behavior.

The use of excessive brushing force has been shown to be a major cause of gingival abrasion. To aid in preventing over-vigorous brushing, the Philips/Jordan electric toothbrush incorporates a Controlled Pressure system (CPS) that causes the brush head to flex back when a toothbrushing force (TBF) in excess of a pre-determined threshold is exerted against the teeth or soft tissues. Two studies (I/II) were conducted to determine whether this mechanical feedback system is sufficiently sensitive to enable users to control their brushing behavior. In Study I, the learning pattern of brushing behavior as a response to the feedback system was evaluated. Seventeen subjects were asked to brush their teeth under observation at least twice a day for a two-week period. During these observations, the number of clicks, as well as the time the brush was pushed "through the click" were recorded. Ten of seventeen volunteers demonstrated a clear learning behavior; the mean number of clicks/minute (for all subjects) was reduced from 10 to 4 after 10 sessions of brushing, and then to 2 or 3 clicks at the end of two weeks. In Study II, 46 subjects used the electric toothbrush with the CPS click force set at various levels between 150-420 g (at 30 g intervals). After a 4-week learning period, the mean TBF was determined in each subject. TBF was most strongly influenced at pre-set click forces between 180 and 270 g. The mean TBF was lowest (about 80 g) when the threshold was set at 210 or 240 g; it then increased (to about 130-140 g TBF) both for smaller and larger values of the threshold setting. Hence, both studies indicate that the Controlled Pressure system is a functional feature that can be used to control the habitual brushing force in a learning period of less than 2 weeks.

Adult↗
PubMed2001

Plaque removal efficacy of an electric and a manual toothbrush with additional interdental tufts.

This clinical study compares the plaque removal efficacy of the Philips/Jordan 2-Action Plaque Remover electric toothbrush with that of the Oral-B 35 Advantage manual toothbrush. In this single-blind randomized split-mouth study, subjects brushed under supervision after having abstained from all oral hygiene for 24 hours. Plaque scored after brushing was used to compare the efficacy of the toothbrushes. Both toothbrushes have special tufts to promote interdental cleaning. It was found that these tufts improve interdental cleaning. Overall, the Philips/Jordan brush removed significantly more plaque than the Oral-B manual brush.

Adult↗
PubMed2001

Titrated oral misoprostol solution--a new method of labour induction.

BACKGROUND: Misoprostol, a cheap, stable, orally active prostaglandin analogue, is effective for labour induction when administered either vaginally or orally, but uterine hyperstimulation and rupture have been reported. Previous studies of oral misoprostol for labour induction have used fixed dosages 3-6-hourly. OBJECTIVES: To develop a new method of misoprostol use for labour induction using very small, frequent, titrated oral dosages, and to pilot effectiveness. STUDY DESIGN: Open clinical pilot study. SETTING: Coronation Hospital, an academic hospital in Johannesburg, South Africa. METHODS: We developed a method using 2-hourly titrated misoprostol doses commencing with 20 micrograms, increased after three doses to 40 micrograms. To administer such small doses we dissolved one misoprostol tablet in 200 ml water. A pilot study of this method was undertaken in 25 women with various indications for induction of labour. RESULTS: Eighteen women (72%) delivered vaginally within 32 hours of induction and two women developed uterine hyperstimulation. The caesarean section rate was 20%. CONCLUSIONS: Women may respond to much smaller dosages of misoprostol than are currently in use. A multicentre randomised trial of this method is underway. We emphasise the dangers inherent in the current unregistered use of misoprostol in clinical practice.

Administration, Oral↗
PubMed1998

A rapid and simple method for cryopreservation of human liver slices.

1. Precision-cut liver slices represent a suitable and convenient in vitro preparation for studying metabolism and toxicity mechanisms of drugs and toxic chemicals. Particularly in the case of human liver slices, cryopreservation would enable more efficient utilization of this scarce and irregularly available tissue. 2. Liver slices from consecutive human livers were cryopreserved using a method previously developed for rat and monkey liver slices. This procedure involves incubation in 12% dimethyl sulphoxide for 30 min on ice and direct immersion into liquid nitrogen. 3. Functional integrity of cryopreserved human liver slices, as compared with that of fresh liver slices, was maintained at 66 +/- 8% (alanine aminotransferase activity retained in the slices), 78 +/- 7% (urea synthesis), 88 +/- 14% (testosterone hydroxylation), 84 +/- 7% (N-deethylation of lidocaine) and 88 +/- 10% (total O-deethylation of 7-ethoxycoumarin). The ratios of testosterone metabolites did not change on cryopreservation. 4. These results show that the cryopreserved human liver slices retained the measured drug metabolism activities. Therefore, this cryopreservation method is suitable for storing liver slices to be used for comparing drug metabolism patterns, at least qualitatively, between species.

Animals↗
PubMed1998

The Collaborative Randomised Amnioinfusion for Meconium Project (CRAMP): 1. South Africa.

OBJECTIVE: To evaluate transcervical amnioinfusion for meconium stained amniotic fluid during labout. DESIGN: Multicentre randomised controlled trial. SETTING: Four urban academic hospitals in South Africa. Obstetric surveillance included the use of electronic fetal heart rate monitoring in most cases. PARTICIPANTS: Women in labour at term with moderate or thick meconium staining of the amniotic fluid. INTERVENTIONS: Transcervical amnioinfusion of 800 mL saline at 15 mL per minute, followed by a maintenance infusion at 3 mL per minute. The control group received routine care. Blinding of the intervention was not possible. MAIN OUTCOME MEASURES: Caesarean section, meconium aspiration syndrome and perinatal mortality. RESULTS: Caesarean section rates were similar (amnioinfusion group 70/167 vs control group 68/159; RR 0.98, 95% CI 0.76-1.26). The incidence of meconium aspiration syndrome was lower than expected on the basis of previous studies (4/162 vs 6/163; RR 0.67, 95% CI 0.19-2.33). There were no perinatal deaths. There were no significant differences between any of the subsidiary outcomes. CONCLUSIONS: This study concurred with three previous trials which found no effect of amnioinfusion for meconium-stained amniotic fluid on caesarean section rate, though the pooled data from all identified trials to date show a significant reduction. The findings with respect to meconium aspiration syndrome were inconclusive in this study alone because of the small number of babies affected, but the point estimate of the relative risk was consistent with the finding of a significant reduction in previous studies and with the Zimbabwe arm (CRAMP 2) of this study. Pooled data clearly support the use of amnioinfusion for meconium stained amniotic fluid to reduce the incidence of meconium aspiration syndrome.

Amnion↗
PubMed1998

A randomised placebo controlled trial of oral misoprostol in the third stage of labour.

OBJECTIVE: To compare oral misoprostol 400 microg with placebo in the routine management of the third stage of labour. DESIGN: A double-blind placebo controlled trial. Setting The labour ward of an academic hospital in Johannesburg, South Africa with 7000 deliveries per annum. PARTICIPANTS: Low-risk women expected to deliver vaginally. METHODS: Women in labour were randomly allocated to receive either misoprostol 400 microg orally or placebo after the birth. Conventional oxytocics were given immediately if blood loss was thought to be more than usual. Postpartum blood loss in the first hour was measured by collection in a special flat plastic bedpan. Side effects were recorded. MAIN OUTCOME MEASURES: Measured blood loss > or = 1000 ml within the first hour after birth. Use of additional oxytocics. RESULTS: The groups were well matched. Measured blood loss > or = 1000 ml occurred in 15/250 (6%) after misoprostol and 23/250 (9%) after placebo (relative risk 0.65; 95% confidence interval 0.35-1.22). The difference may have been reduced by the greater use of conventional oxytocics in the placebo group, which was statistically significant for intravenous oxytocin infusion (2.8% vs 8.4%, relative risk 0.33, 95% confidence interval 0.14-0.77). Shivering was more common in the misoprostol group (19% vs 5%, relative risk 3.69; 95% confidence interval 2.05-6.64). CONCLUSIONS: Shivering has been shown in this study to be a specific side effect of misoprostol administered orally in the puerperium. No serious side effects were noted. Misoprostol shows promise as a method of preventing postpartum haemorrhage. Because of the potential benefits for childbearing women, particularly those in developing countries, further research to determine its effects with greater certainty should be expedited.

Administration, Oral↗
PubMed1998

Fetal vibro-acoustic stimulation with a can--a clinical study.

OBJECTIVE: To assess the usefulness of the can as a fetal vibro-acoustic stimulator in the clinical environment. PATIENTS AND SETTING: 112 high-risk obstetric patients at Coronation Hospital, Johannesburg. METHOD: 161 vibro-acoustic stimulation tests with a can and 159 non-stress tests (NSTs) were performed. The results of the can test were compared with those of the NSTs and with fetal outcome at delivery. RESULTS: The can test showed poor sensitivity (5/9). Three of the 4 false-negative results were due to placental abruption that occurred subsequent to the can test. The ability of the can test to predict a reactive NST and good fetal outcome was 94% (negative predictive value). CONCLUSIONS: In view of the reasonable negative predictive value, the test should be evaluated further as a screening test at primary care level, where there are few or no cardiotocographic facilities.

Acoustic Stimulation↗
PubMed1998

Validation of the Edinburgh Postnatal Depression Scale on a cohort of South African women.

UNLABELLED: Postnatal depression occurs in 10-15% of women. The Edinburgh Postnatal Depression Scale (EPDS) is a 10-item self-report scale designed specifically as a screening instrument for the postnatal period. It was initially validated for use in the UK, but has subsequently been validated for other communities. It has not been validated for an African community. OBJECTIVE: To determine whether the EPDS is a valid screening scale for depression in a Johannesburg community cohort. PARTICIPANTS AND SETTING: 103 women attending the postnatal clinic at Coronation Hospital, Johannesburg, South Africa. METHOD: The EPDS was validated against the Diagnostic and Statistical Manual (DSM-IV) criteria for depression. It was administered verbally to participants and translated into one of six South African languages where necessary. RESULTS: A threshold of 11/12 on the EPDS identified 100% of women with major depression and 70.6% of women with minor depression. For major and minor depression combined, sensitivity was 80%, specificity 76.6%, positive predictive value 52.6% and negative predictive value 92.2%. CONCLUSION: The EPDS, administered verbally, is a valid screening instrument in this urban South African community.

Cohort Studies↗
PubMed1997

Different intrahepatic distribution of phosphatidylglycerol and phosphatidylserine liposomes in the rat.

Liposomes with diameters of 200 to 400 nm containing phosphatidylserine (PS) or phosphatidylglycerol (PG) were injected intravenously into rats. Two hours after injection, 75% of the injected dose of PS liposomes was found in the liver and only 10% found in the spleen, while 35% of the PG liposomes was found in the liver and as much as 40% was found in the spleen. Cell-isolation experiments revealed the following remarkable difference in the intrahepatic distribution between the two liposome formulations: the PS liposomes distributed in about equal amounts to Kupffer cells and hepatocytes, despite their size (200-400 nm) exceeding that of the endothelial fenestrae (average 150 nm), whereas the PG liposomes were only taken up by the Kupffer cells and not at all by the hepatocytes. Double-label studies, using liposomes in which the lipid-moiety was radio labeled with [3H]cholesteryloleylether ([3H]CE) and the water phase with [14C]sucrose, showed that the liposomes were taken up as intact particles. These observations were confirmed through electron microscopy by determining the in situ localization of liposome-encapsulated colloidal gold particles in thin sections of liver and spleen. The differences in organ distribution are ascribed to differences in opsonization patterns of the two liposomal surfaces. For the difference in intrahepatic distribution, we offer the following two explanations: the exploitation of the blood cell-mediated forced sieving concept and the indication of a PS-specific pharmacological effect on the dimensions of the fenestrations.

Animals↗