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Biomedical subjects

P van der Bijl

Publications and source records attributed to P van der Bijl.

At least 19 recordsLinked to original sources
PubMed2003

Enhancing effect of temperature on the transmucosal penetration kinetics of 17 beta-estradiol.

Human vaginal mucosa may be used as a model of buccal mucosa for in vitro permeability studies using various chemical compounds. Rectilinear temperature dependence of water flux across vaginal mucosa between 25 degrees C and 41 degrees C has been shown. The objective of this study was to examine the behaviour of the above barrier on fluxes of 17 beta-estradiol at various temperatures. Frozen vaginal mucosa specimens from a single patient were used (snap-frozen in liquid nitrogen and stored at -85 degrees C). The permeability to tritiated 17 beta-estradiol was determined using a continous flow-through perfusion system at temperatures of 20 degrees C, 25 degrees C, 30 degrees C, 37 degrees C and 41 degrees C. Histological examinations were performed before and after permeability experiments. Estimated steady state flux values were used at 20 degrees C, 25 degrees C and 30 degrees C. Estimated and true mean 17 beta-estradiol steady state flux rates (20-24 h) were found to be 415 +/- 27 standard error of the Mean (SEM), 848 +/- 60 SEM, 1355 +/- 77 SEM, 1436 +/- 37 SEM and 1482 +/- 35 SEM cpm.cm-2.min-1, at temperatures of 20 degrees C, 25 degrees C, 30 degrees C, 37 degrees C and 41 degrees C, respectively. A non-linear regression analysis and plot (R2 = 0.9941) displayed a curvilinear flux-temperature relationship. The results from this study showed that, notwithstanding cellular damage, the principal physical permeability barrier governing permeation kinetics was non-linearly temperature-dependent between the temperatures studied, providing further support for the concept that this barrier is lipoidal in nature.

Adult↗
PubMed2002

The effect of betel nut extract on cell growth and prostaglandin endoperoxide synthase in human epidermoid carcinoma cells.

The objective of this study was to find out whether prostaglandin endoperoxide synthase (PHS) involves the action of betel nut extract (BNE) on the growth of oral cancers. Therefore, growth and PHS activity were examined in two human oral carcinoma cell lines (OEC-M1 and KB) and one normal fibroblast cell line (NF) in the presence of increasing BNE concentration. BNE at concentrations above 50 microg/ml significantly inhibited the cell growth of OEC-M1 after 72 h in culture, of KB and NF after 48 h in culture. The IC50 of BNE in OEC-M1, KB and NF at 24 h in culture was about 406, 37.5 and 140 microg/ml respectively. PHS activity in OEC-M1 was significantly increased by low BNE concentrations (50 microg/ml, 114%; 100 microg/ml, 33%; 150 microg/ml, 30%) but significantly reduced at higher BNE concentrations (300 microg/ml, 33%; 500 microg/ml, 61%). The PHS activity in KB was significantly inhibited by BNE and this effect was intensified as concentrations increased (50 microg/ml, 31%; 100 microg/ml, 24%; 150 microg/ml, 43%; 300 microg/ml, 60%; 500 microg/ml, 92%). Similar to that in OEC-M1, the PHS activity in NF was significantly increased at low BNE concentrations (50 microg/ml, 139%; 100 microg/ml, 87%;150 microg/ml, 77%) but reduced at higher concentrations (300 microg/ml, 55%; 500 microg/ml, 72%). The PHS activity in all cell lines was almost completely blocked by indomethacin (5 x 10(-6) M). We conclude that these findings suggest that PHS may be an important biochemical mediator of the effect of BNE on the growth of two human oral carcinoma cell lines.

Arachidonic Acid↗
PubMed2002

Enhancement of transmucosal permeation of cyclosporine by benzalkonium chloride.

OBJECTIVES: Permeation of cyclosporin A (CsA) through intact and de-epithelialized human vaginal mucosa in the presence and absence of benzalkonium chloride (BZCl) was tested. MATERIALS AND METHODS: Human vaginal mucosa (snap-frozen in liquid nitrogen, stored at -85 degrees C) had been used for permeability experiments. CsA permeation through thawed frozen intact and de-epithelialized vaginal mucosa was determined using a flow-through diffusion apparatus (20 degrees C, 24 h). Flux rates for CsA across these two mucosae were determined in the presence and absence of 0.01% BZCl. ANOVA and Duncan's multiple range test were used to test for steady-state and an unpaired t-test with Welch's correction was used to test for differences between the mean flux values at each time point (significance level of 5%). A piece of thawed tissue from each patient, before and after de-epithelialization, was placed in formalin and histologically examined. RESULTS: Flux rates of CsA across intact vaginal mucosa tended to increase by 28-46% in the presence of 0.01% BZCl, and CsA across de-epithelialized mucosa by approximately 28%. The latter differences were statistically significantly higher after 10 h. Flux rates across de-epithelialized mucosa were 52-140% higher in the presence of 0.01% BZCl (statistically significantly higher after 12 h). CONCLUSIONS: The permeation of CsA through intact and de-epithelialized human vaginal mucosa can be enhanced by 0.01% BZCl.

Adult↗
PubMed2002

Effects of two barrier creams on the diffusion of benzo[a]pyrene across human skin.

Barrier hand creams, often containing antiseptic agents, may provide a form of protection not only for health care professionals, but also for workers in the chemical and pharmaceutical industries. To evaluate the efficacy of two such barrier creams available on the South African market, the in vitro diffusion of a model compound, benzo[a]pyrene, through human skin at 20 degrees and 37 degrees C was studied. Treated (10 min) and untreated human skin disks (4 mm in diameter) were mounted in flow cells of a continuous flow-through diffusion apparatus. Buffer/tritiated benzo[a]pyrene was collected from the acceptor chambers at 2-hour intervals for a total of 24 hours and counted in a liquid scintillation counter. At 20 degrees C no significant differences could be detected between the flux rates of benzo[a]pyrene across barrier cream treated and untreated skin. However, at 37 degrees C Skinguard significantly increased flux rates of this carcinogen. Skin barrier creams therefore need to be carefully scrutinised with respect to their protective effects because the latter may vary for molecules with different chemical properties.

Analysis of Variance↗
PubMed2002

The effect of radiation on the permeability of human saphenous vein to 17 beta-oestradiol.

Radiation therapy is an effective way of treating many forms of cancer, however, there are some indications that it may facilitate the development of metastasis. The question arises whether radiation therapy during cancer treatment might result in an alteration of the permeability of the tissues being treated. This alteration in the permeability might lead to metastatic cells escaping from the irradiated tissue, leading to the spread of cancer to other sites in the body. Because of the above implication, we determined the diffusion kinetics of a radioactive marker, 17 beta-oestradiol, through human saphenous vein before and after a single half hour exposure to 60 Gy of 60Co gamma-irradiation. Six clinically healthy saphenous vein specimens (mean patient age +/- standard deviation 57 +/- 13 years; age range 41-77 years) were obtained during cardiac surgery. In vitro flux rates of 17 beta-oestradiol were determined through use of a flow-through diffusion apparatus immediately after irradiation for a period of 24 hours. No statistically significant differences could be demonstrated for the flux rates of 17 beta-oestradiol through the non-irradiated and 60 Gy irradiated saphenous vein tissue. These findings strongly suggest that irradiation at 2 Gy/min and a total dose of 60 Gy would not alter the permeability of the venous wall. We have demonstrated that the in vitro flow-through diffusion method is capable of measuring permeability aspects of endothelial cell layers in saphenous vein biopsies under conditions resembling clinical reality.

Adult↗
PubMed2001

A comparative light-microscopic, electron-microscopic and chemical study of human vaginal and buccal epithelium.

The scarcity of sizeable specimens of normal oral mucosa for experimental purposes has hampered research on oral epithelium. Because large specimens of viable human vaginal mucosa are readily available and because vaginal and buccal epithelia are microscopically similar, vaginal mucosa has been used successfully to establish a human cyst model in experimental animals. The ultrastructure and distribution of keratin filaments in these epithelia are also similar, as is their permeability to water and a number of chemical substances. Therefore, if vaginal mucosa could be substituted for buccal mucosa it would expedite research on the epithelium of buccal mucosa. To strengthen further the concept that vaginal epithelium could replace buccal epithelium in certain experimental studies, the thickness of these epithelia, their patterns of surface keratinization, the presence or absence of intercellular lipid lamellae and their lipid contents were now compared. Thirty-three specimens of vaginal mucosa from postmenopausal women and 36 of buccal mucosa were investigated. To compare the thickness of the epithelial layers the number of cell layers in sections of 20 vaginal and 20 buccal mucosal specimens were counted in the three thickest and three thinnest regions of each specimen. Surface keratinization was evaluated on sections stained with the Picro-Mallory method. To demonstrate lipid lamellae two vaginal and two buccal mucosa specimens were examined electron microscopically after normal fixation and postfixation in ruthenium tetroxide. Following solvent extraction of 11 vaginal and 14 buccal epithelia, quantitative lipid analyses were performed using thin-layer chromatography. No statistically significant differences were found between the maximum and minimum number of epithelial cell layers. The patterns of surface keratinization and the distribution and appearance of the lipid lamellae in the intercellular spaces were similar. The lipid composition of the two epithelia corresponded, except for the cholesterol esters and glycosylceramides, which were higher in buccal epithelium. Ceramides for vaginal epithelium and triglycerides for buccal epithelium were not determined. Based on structural similarities, a similar lipid composition and earlier findings, it is concluded that vaginal epithelium can be used as a substitute for buccal epithelium in certain in vitro, and possibly for in vivo, studies.

Adult↗
PubMed2001

Areca nut extract lowers the permeability of vaginal mucosa to reduced arecoline and arecaidine.

Areca nut chewing has been implicated in the development of oral cancer and oral submucous fibrosis. Arecoline and arecaidine, which are alkaloids present in the areca nut, are thought to play a major role in the development of adverse effects resulting from this chewing habit. Because these alkaloids appear to be associated with the development of the above diseases, we determined their diffusion kinetics through human vaginal mucosa in the presence and absence of a 1% areca nut extract. Seven clinically healthy vaginal mucosa specimens (mean patient age+/-standard deviation, 52+/-13 years; age range, 38-74 years) were obtained during surgery. In vitro flux values of reduced arecoline and arecaidine (r-arecoline and r-arecaidine) were determined through use of a flow-through diffusion apparatus. Analysis of variance, a Duncan multiple range test, and an unpaired t-test were used to determine steady state kinetics and flux differences over time intervals. The flux values across vaginal mucosa of r-arecoline and r-arecaidine were decreased in the presence of 1% areca nut extract. For r-arecoline, these flux values were significantly lower statistically when compared to those obtained in the absence of areca nut extract. These findings concur with results previously obtained for water, where the astringent action of the tannins present in the areca nut extract was thought to alter the barrier properties of the epithelium, resulting in decreased permeability.

Adult↗
PubMed2001

Effects of three penetration enhancers on transcorneal permeation of cyclosporine.

PURPOSE: To investigate the permeation of cyclosporin A (CsA) through fresh and frozen human corneas in the presence and absence of three penetration enhancers: benzalkonium chloride (BZCl), dimethylsulfoxide (DMSO), and Cremophor-EL. METHODS: Human corneas, unsuitable for transplantation, were either freshly used for permeability experiments or snap-frozen in liquid nitrogen and stored at -85 degrees C. CsA permeation through either fresh or thawed frozen corneal tissue was determined using a flow-through diffusion apparatus (20 degrees C for 24 hours). Flux rates for CsA were determined in the presence and absence of the penetration enhancers 0.01% BZCl, 20% DMSO, and Cremophor-EL (10% and 20%). Analysis of variance and Duncan's multiple-range test were used to test for steady state, and an unpaired Student t test with Welch's correction was used to test for differences between the mean flux values at each time point. A significance level of 5% was used for all of the statistical tests. RESULTS: No statistically significant differences in flux values of CsA could be detected between fresh and frozen corneas. In the presence of Cremophor-EL (10% and 20%) and 0.01% BZCl, statistically significant increases in flux values of CsA before 16 hours and after 16 hours, respectively, could be observed. In the presence of 20% DMSO, no statistically significant increases in flux values could be detected. CONCLUSIONS: The permeation of CsA through human corneas appeared to be enhanced by the presence of BZCl and Cremophor-EL. Additionally, it was shown that the flux rate of CsA across fresh and frozen corneas was not significantly different.

Adolescent↗
PubMed2001

A literature review and pilot study to characterise the treatment of burning mouth syndrome.

Although the definition of burning mouth syndrome (BMS) can vary, the most commonly accepted is that of a burning sensation of normal appearing oral mucosa with no apparent underlying local or systemic contributing factors. The condition can be classified according to the patterns of burning experienced, the severity of the burning, as well as the pattern of onset. The management of these patients is difficult, since they are often seen by numerous clinicians and many unnecessary tests are performed in the hope of finding an underlying physical cause for the burning. No precise information pertaining to the natural history of BMS could be found. This paper consists of a selective review of the literature on BMS as well as a pilot study involving the standardised collection of data on 10 patients (9 women and 1 man) with BMS. These patients will be followed up in the long term in order to gather information pertaining to the natural history of this condition. No detectable local or systemic cause for the burning sensation could be found for any of the 10 subjects. The role of somatisation as a mechanism for burning sensation was investigated and certain proposals have been put forward regarding the management of such patients.

Aged↗
PubMed2000

Namibian chewing stick, Diospyros lycioides, contains antibacterial compounds against oral pathogens.

The twigs of Diospyros lycioides, a plant commonly known as "muthala", are frequently used as chewing sticks for the cleaning of teeth by rural and urban people in Namibia. Preliminary studies showed that a methanol extract of D. lycioides inhibited growth of selected oral pathogens. Subsequent bioassay-guided fractionation led to the isolation of four novel bioactive naphthalene glycosides, diospyrosides A, B, C, and D (1-4), and two known bioactive naphthoquinones, juglone (5) and 7-methyljuglone (6). The structures of the new compounds were elucidated using spectroscopic techniques including 1D and 2D NMR. These compounds inhibited the growth of oral cariogenic bacteria (Streptococcus mutans and Streptococcus sanguis) and periodontal pathogens (Porphyromonas gingivalis and Prevotella intermedia) at minimum inhibitory concentrations ranging from 0.019 to 1.25 mg/mL. Juglone exhibited the strongest inhibitory activity among these compounds.

Anti-Bacterial Agents↗
PubMed2000

Permeation of sumatriptan through human vaginal and buccal mucosa.

Continued interest in the various routes by which sumatriptan may be administered prompted us to investigate its passage through buccal mucosa. Because human buccal mucosa is scarce, we proposed using the relatively abundant vaginal mucosa, which has been shown to have comparable diffusion rates for a number of widely varying molecules, as a model of buccal mucosa. In addition, by comparing these two tissues with respect to their permeability to sumatriptan, the human vaginal/buccal mucosa model could be further evaluated. Clinically healthy human vaginal and buccal mucosa specimens were used in the permeability studies. Permeability to sumatriptan was determined using a continuous flow-through diffusion system in the presence and absence of permeation enhancers. No statistically significant differences in permeability could be demonstrated for both mucosae toward sumatriptan. Flux values obtained in the absence and presence of glycodeoxycholate and lauric acid (1:1 molar ratio) to sumatriptan of buccal and vaginal mucosa, respectively, were not significantly different. The results obtained further support the hypothesis of the vaginal/buccal mucosal in vitro permeability model and suggest that this model may be used in conjunction with various absorption enhancers. Further studies on the buccal route of absorption of sumatriptan are thus warranted.

Administration, Buccal↗
PubMed2000

Permeability of vaginal mucosa to water at normal and elevated temperatures.

A number of studies have clearly demonstrated that human vaginal mucosa may be used as a model of buccal mucosa for a variety of in vitro permeability studies on drugs and other chemical compounds. Furthermore, at between 25 degrees and 37 degrees C, a linear temperature-dependence of water flux across this mucosa, which was attributed to an increased fluidity of the principal lipoidal permeability barrier, was found to exist. The objective of the present study was to examine the behaviour of the above barrier on water fluxes at normal and elevated temperatures. Clinically healthy human vaginal mucosa specimens were obtained from excess tissue removed during a vaginal hysterectomy from a single patient, snap-frozen in liquid nitrogen and stored for 6 months at -85 degrees C. Seven sections from the mucosa were thawed in phosphate-buffered saline (PBS) and mounted in flow-through diffusion cells (exposed area 0.039 cm2). Their permeability to tritiated water was determined using a continuous flow-through perfusion system at temperatures of 37 degrees, 39 degrees and 41 degrees C. Three permeability experiments were performed at each temperature setting. Specimens were subjected to histological examination before and after permeability experiments. Mean water flux rates at steady state (10-24 h) were found to be 2,356 +/- 71 SEM, 3,020 +/- 38 SEM and 3,659 +/- 116 SEM cpm. cm-2.min-1, at temperatures of 37 degrees, 39 degrees and 41 degrees C, respectively. A linear regression analysis and plot (r2 = 0.99) displayed a slope of 325 +/- 4 SEM cpm.cm-2.min-1/degree C. The results of this study showed that, notwithstanding cellular damage, the principal physical permeability barrier was linearly temperature-dependent between the temperatures studied, providing further support for the concept that this barrier is lipoidal in nature.

Diffusion Chambers, Culture↗
PubMed1999

Penetration of benzo[a]pyrene through human buccal and vaginal mucosa.

OBJECTIVE: The aim of this study was to compare buccal and vaginal mucosa with respect to their permeability to a potent carcinogen, benzo[a]pyrene. STUDY DESIGN: Six clinically healthy vaginal mucosa specimens (mean patient age +/- standard deviation, 52+/-13.4 years; age range, 37-69 years) and 6 buccal mucosa specimens (from 5 male patients and 1 female patient: mean patient age +/- standard deviation, 32+/-5.2 years; age range, 24-39 years) were obtained during surgery. In vitro flux rates of benzo[a]pyrene across specimens were determined through use of a flow-through diffusion apparatus. Analysis of variance, a Duncan multiple range test, and an unpaired t test were used to determine steady state kinetics and flux differences over time intervals. RESULTS: No statistically significant differences were observed between the overall mean flux values of benzo[a]pyrene across the 2 kinds of mucosa. CONCLUSIONS: The findings further support the hypothesis that human vaginal mucosa can be used as a model for buccal mucosa in studies of permeability to various chemical compounds.

Adult↗
PubMed1998

Binaphthalenone glycosides from African chewing sticks, Diospyros lycioides.

Our laboratory has engaged in the exploration of active antimicrobial principles present in chewing sticks commonly used by the African and Middle Eastern countries as a mechanical oral hygiene aid in place of tooth brushing. During this investigation, a methanol extract from the twigs of Diospyros lycioides, a Namibia tooth cleaning stick, demonstrated antimicrobial activity against common oral pathogens including Streptococcus mutans and Porphyromonas gingivalis (MICs 2.5 and 0.156 mg/mL). Subsequent fractionation and purification of this extract led to the identification of two novel binaphathalenone glycosides: 1', 2-binaphthalen-4-one-2',3-dimethyl-1,8'-epoxy-1,4',5,5',8, 8'-hexahydroxy-8-O-beta-glucopyranosyl-5'-O-beta-xylopyranosyl(1-- >6) -beta-glucopyranoside (1) and 1',2-binaphthalen-4-one-2', 3-dimethyl-1,8'-epoxy-1,4',5,5',8,8'-hexahydroxy-5', 8-di-O-beta-xylopyranosyl(1-->6)-beta-glucopyranoside (2). Their structures were established using spectroscopic techniques. Examination of the antimicrobial activity of these two compounds revealed positive but only marginal growth inhibition against the test cariogenic pathogens, S. sanguis and Streptococcus mutans.

Anti-Bacterial Agents↗