Biomedical subjects

J van Marle

Publications and source records attributed to J van Marle.

At least 19 recordsLinked to original sources

PubMed2006

Lichen planus is associated with human herpesvirus type 7 replication and infiltration of plasmacytoid dendritic cells.

BACKGROUND: Lichen planus (LP) is a common inflammatory skin disease of unknown aetiology. Viral causes have been suggested. OBJECTIVES: To find candidate viruses associated with LP. METHODS: Lesional and nonlesional skin samples, peripheral blood mononuclear cells and serum were obtained from patients with LP. Ultrastructural, viral DNA, immunohistochemical and serological analyses were performed, and comparisons were made with psoriatic and normal skin. RESULTS: Electron microscopy revealed typical 120-200-nm enveloped particles with a 100-nm nucleus resembling human herpesvirus (HHV) virions both in dermis and in epidermis of lesional LP tissue. HHV-7 DNA was found in 11 of 18 lesional LP samples, as opposed to only one of 11 nonlesional LP samples (P =0.06), two of 11 lesional psoriasis samples (P = 0.05) and none of four normal skin samples. No relation was found between LP skin and DNA of other known HHVs (HHV-1-6 and 8). With immunohistochemistry, significantly more HHV-7+ cells were found in lesional LP epidermis than in normal epidermis. Lesional LP dermis contained significantly more HHV-7+ cells than nonlesional LP, psoriatic or normal dermis. Moreover, LP skin contained overwhelmingly and consistently more plasmacytoid dendritic cells (upregulated in virally induced conditions) than nonlesional LP samples. CONCLUSIONS: We conclude that HHV-7 replicates in LP lesions, but not in psoriasis, another inflammatory skin condition. HHV-7 is possibly involved in the pathogenesis of LP. These preliminary data make further research on this topic of interest.

Adult↗

PubMed2005

The effect of the antimicrobial peptide, Dhvar-5, on gentamicin release from a polymethyl methacrylate bone cement.

The objective of this study was to investigate the release mechanism and kinetics of the antimicrobial peptide, Dhvar-5, both alone and in combination with gentamicin, from a standard commercial polymethyl methacrylate (PMMA) bone cement. Different amounts of Dhvar-5 were mixed with the bone cement powders of Osteopal and the gentamicin-containing Osteopal G bone cement and their release kinetics from the polymerized cement were investigated. Additionally, the internal structure of the bone cements were analysed by scanning electron microscopy (SEM) of the fracture surfaces. Secondly, porosity was investigated with the mercury intrusion method and related to the observed release profiles. In order to obtain an insight into the mechanical characteristics of the bone cement mixtures, the compressive strength of Osteopal and Osteopal G with Dhvar-5 was also investigated. The total Dhvar-5 release reached 96% in the 100 mg Dhvar-5/g Osteopal cement, whereas total gentamicin release from Osteopal G reached only 18%. Total gentamicin release increased significantly to 67% with the addition of 50mg Dhvar-5/g, but the Dhvar-5 release was not influenced. SEM showed an increase of dissolved gentamicin crystals with the addition of Dhvar-5. The mercury intrusion results suggested an increase of small pores (< 0.1 microm) with the addition of Dhvar-5. Compressive strength of Osteopal was reduced by the addition of Dhvar-5 and gentamicin, but still remained above the limit prescribed by the ISO standard for clinical bone cements. We therefore conclude that the antimicrobial peptide, Dhvar-5, was released in high amounts from PMMA bone cement. When used together with gentamicin sulphate, Dhvar-5 made the gentamicin crystals accessible for the release medium presumably through increased micro-porosity (< 0.1 microm) resulting in a fourfold increase of gentamicin release.

Antimicrobial Cationic Peptides↗

PubMed2005

Mechanisms of biliary stent clogging: confocal laser scanning and scanning electron microscopy.

BACKGROUND AND STUDY AIMS: Endoscopic insertion of plastic biliary endoprostheses is a well-established treatment for obstructive jaundice. The major limitation of this technique is late stent occlusion. In order to compare events involved in biliary stent clogging and identify the distribution of bacteria in unblocked stents, confocal laser scanning (CLS) and scanning electron microscopy (SEM) were carried out on two different stent materials - polyethylene (PE) and hydrophilic polymer-coated polyurethane (HCPC). PATIENTS AND METHODS: Ten consecutive patients with postoperative benign biliary strictures were included in the study. Two 10-Fr stents 9 cm in length, one made of PE and the other of HCPC, were inserted. The stents were electively exchanged after 3 months and examined using CLS and SEM. RESULTS: No differences were seen between the two types of stent. The inner stent surface was covered with a uniform amorphous layer. On top of this layer, a biofilm of living and dead bacteria was found, which in most cases was unstructured. The lumen was filled with free-floating colonies of bacteria and crystals, surrounded by mobile laminar structures of mucus. An open network of large dietary fibers was seen in all of the stents. CONCLUSIONS: The same clogging events occurred in both PE and HCPC stents. The most remarkable observation was the identification of networks of large dietary fibers, resulting from duodenal reflux, acting as a filter. The build-up of this intraluminal framework of dietary fibers appears to be a major factor contributing to the multifactorial process of stent clogging.

Adult↗

PubMed2004

Morphological and functional alterations in glycerol preserved rat aortic allografts.

Glycerol preservation is an effective method for long-term preservation of skin allografts and has a potential use in preserving arterial allografts. We evaluated the effect of glycerol concentration and incubation period on vessel-wall integrity of rat aortic allografts. No significant differences were measured in breaking strength (2.3 +/- 0.3 N) and bursting pressure (223 +/- 32 kPa) between standard glycerolized and control segments (1.7 +/- 0.3 N, 226 +/- 17 kPa). Isometric tension measurements showed complete lack of functional contraction and relaxation capacity in allograft segments prepared according to all preservation protocols. Morphologically, thickness of the vessel-wall media diminished after preservation using low (30/50/75%) or high (70/85/98%) concentrations of glycerol, as compared to control segments (i.e. 81 +/- 2.4 microm, 95 +/- 5.6 microm and 125 +/- 3.5 microm, respectively). Confocal microscopy and Fourier analysis demonstrated that vascular collagen and elastin bundle orientation had remained unaltered. Electron microscopy showed defragmentation of luminal endothelial cells. In conclusion, glycerol preservation of rat aorta resulted in an acellular tissue matrix, which maintained biomechanical integrity and extracellular matrix characteristics. The next step in the investigation will be to test the concept of glycerol preservation of arterial allografts in a vascular transplantation model.

Animals↗

PubMed2003

Light scattering of human lens vesicles in vitro.

In passing through the lens, light crosses thousands of cell membranes. To explore the possible contribution of lipids to the scattering properties of the lens, we have carried out in vitro studies with lipids extracted from human lenses 1-90 years of age. Sphingomyelin and human lens lipids were extruded into large unilamellar vesicles (LUVs). The intensity of light scattered by human lens LUVs increased with age and lipid hydrocarbon chain order. Hydrocarbon chain order also correlated with light scattering intensity by sphingomyelin LUVs. Light scattered by LUVs composed of sphingomyelin (1-30 mg ml(-1)) was 20 to 100 times more intense than that scattered by the same concentration of alpha-crystallin in aqueous media. Increased lipid hydrocarbon chain order as well as variations in the headgroup and interfacial region of bilayers resulting from lipid compositional changes can influence membrane light scattering properties. In vitro measurements suggest that the contribution to light scattering by lipids may be significant and should not be disregarded in the investigation of factors and components that lead to the increase in light scattering by human lenses with age and cataract.

Adolescent↗

PubMed2002

Effects of hypergravity on the morphological properties of the vestibular sensory epithelium. II. Life-long exposure of rats including embryogenesis.

Rats were exposed to a hypergravity (HG) level of 2.5 x g from conception until the age of 14 weeks. The vestibular epithelia of four of these animals and four control animals were immunohistochemically labeled for actin and tubulin. The apical cross-sectional area of epithelial cells of HG exposed rats appeared to be larger in all end organs. Area increase was 7.0% in the utricle (p<0.005) and 8.2% in the crista (p<<0.001). Hair cells and supporting cells appeared to be intact. The cellular arrangement and the proportion of different cell types within the epithelia was normal.

Actins↗

PubMed2002

Effects of hypergravity on the morphological properties of the vestibular sensory epithelium. I. Long-term exposure of rats after full maturation of the labyrinths.

The effect of prolonged exposure to hypergravity on the morphology of vestibular epithelia of rats was investigated. At the age of 1 month, i.e., when vestibular end organs are fully maturated, three rats were transferred to a hypergravity environment of 2.5 g inside a large radius centrifuge. After 9 months, vestibular epithelia of these animals and of three control animals were immunohistochemically labeled for actin and tubulin. The apical cross-sectional area of epithelial cells of hypergravity exposed rats appeared to be smaller in all end organs. Area reduction was 1.9% in the saccule (not significant), 5.0% in the utricle (p < 0.005), and 11.6% in the crista (p<<0.001). No indications for a deterioration of vestibular functioning were observed.

Actins↗

PubMed2002

Histatin 5 and derivatives. Their localization and effects on the ultra-structural level.

Histatins, a family of cationic peptides present in saliva, are active against the opportunistic yeast Candida albicans. The mechanism of action is still unclear. Histatin 5 and more potent synthetic variants, dhvar4 and dhvar5, were used to study localization and effects on morphology on the ultra-structural level. Although all peptides induced leakage, no association with the plasma membrane, indicative for permanent pores, was observed with immuno-gold-labeling. Freeze-fracturing showed severe changes of the plasma membrane. Together with, for the dhvars, the loss of intracellular integrity, this suggests that leakage may be a secondary effect rather than an effect of formation of permanent pores.

Antifungal Agents↗

PubMed2002

Vascular disease in HIV/AIDS patients.

OBJECTIVES: An ongoing prospective clinical survey to determine the spectrum of vascular disease in HIV/AIDS patients and the risk factors affecting clinical outcome in order to formulate a management protocol for future use. METHODS: Comprehensive screening for risk factors for vascular disease as well as HIV/AIDS-related conditions. Disease pattern and presentation are noted and patients treated accordingly. Vascular emergencies are managed regardless of HIV status because this information is usually not available at the time of presentation. Elective management is based on immune status and risk stratification. RESULTS: 42 patients tested positive for HIV. The majority of patients presented with occlusive disease (57%), followed by aneurysms (21%) and vascular trauma (19%). A variety of vascular surgical procedures were performed on 36 patients. There was no surgical mortality and 10 patients developed complications, including 2 amputations and 7 cases of minor wound sepsis. The 3 patients who received preoperative antiretroviral therapy showed a marked reduction in viral count and a significant improvement in CD4 T-cell count. CONCLUSION: Surgery can be safe and effective in HIV-positive patients provided the necessary precautions are taken to reduce surgical morbidity.

Adult↗

PubMed2001

Normal IncA expression and fusogenicity of inclusions in Chlamydia trachomatis isolates with the incA I47T mutation.

To investigate the correlation between the incA I47T mutation in Chlamydia trachomatis and the nonfusogenic phenotype, the incA genes of 25 isolates were sequenced. Four major sequence types were identified. Seven isolates (28%) had the I47T mutation. Isolates representing the four sequence types expressed IncA in the membrane of one large single inclusion. In conclusion, the incA I47T mutation is not associated with the nonfusogenic phenotype.

Amino Acid Sequence↗

PubMed2001

The human kinesin-like protein RB6K is under tight cell cycle control and is essential for cytokinesis.

Several members of the kinesin superfamily are known to play a prominent role in the motor-driven transport processes that occur in mitotic cells. Here we describe a new mitotic human kinesin-like protein, RB6K (Rabkinesin 6), distantly related to MKLP-1. Expression of RB6K is regulated during the cell cycle at both the mRNA and protein level and, similar to cyclin B, shows a maximum during M phase. Isolation of the RB6K promoter allowed identification of a CDE-CHR element and promoter activity was shown to be maximal during M phase. Immunofluorescence microscopy using antibodies raised against RB6K showed a weak signal in interphase Golgi but a 10-fold higher signal in prophase nuclei. During M phase, the newly synthesized RB6K does not colocalise with Rab6. In later stages of mitosis RB6K localized to the spindle midzone and appeared on the midbodies during cytokinesis. The functional significance of this localization during M phase was revealed by antibody microinjection studies which resulted exclusively in binucleate cells, showing a complete failure of cytokinesis. These results substantiate a crucial role for RB6K in late anaphase B and/or cytokinesis, clearly distinct from the role of MKLP-1.

5' Untranslated Regions↗

PubMed2001

Conofocal microscopy study of undisturbed and chlorhexidine-treated dental biofilm.

Culturing of dispersed plaque samples and vitality staining of plaque smears are the most commonly used methods for evaluating the effects of antimicrobials on dental plaque. The visualization of the antimicrobial action on oral biofilm present on the substrate surface (in situ) would add valuable information to the existing knowledge about the treatment effects. This study aimed at combining the advantage of confocal laser scanning microscopy (CLSM) to visualize plaque non-destructively with a vitality staining technique to assess the immediate bactericidal effect of chlorhexidine (CHX) on biofilm. Three 200-microm-wide grooves were cut into bovine dentin discs for plaque accumulation. The discs were worn by six subjects for 6, 24, and 48 hrs, then broken into halves, one of which received a one-minute extraoral 0.2% CHX treatment, while the other served as control. Both halves were stained for vital fluorescence measurements and visualized by CLSM. Plaque vitality (in %) was quantified by image analysis in three plaque layers-outer, middle, and inner. The CHX effect was significant in six-hour samples (p < 0.001) and only in the outer layer of the 48-hour plaque (p < 0.001), demonstrating a resistant nature of dental biofilm to a single CHX treatment. With the present approach, we have shown that it is possible to visualize and quantitate the antimicrobial treatment effect on biofilm still present on the substrate on which it was grown.

Adult↗

PubMed2000

Zonal down-regulation and redistribution of the multidrug resistance protein 2 during bile duct ligation in rat liver.

We have studied regulation of the multidrug resistance protein 2 (mrp2) during bile duct ligation (BDL) in the rat. In hepatocytes isolated after 16, 48, and 72 hours of BDL, mrp2-mediated dinitrophenyl-glutathione (DNP-GS) transport was decreased to 65%, 33%, and 33% of control values, respectively. The impaired mrp2-mediated transport coincided with strongly decreased mrp2 protein levels, without any significant changes in mrp2 RNA levels. Restoration of bile flow after a 48-hour BDL period resulted in a slow recovery of mrp2-mediated transport and protein levels. Immunohistochemical detection of the protein in livers of rats undergoing BDL showed strongly reduced mrp2 staining after 48 hours, which was initiated in the periportal areas of the liver lobule and progressed toward the pericentral areas after 96 hours. Immunofluorescent detection of mrp2 in livers of rats undergoing 48 hours of BDL revealed decreased staining accompanied by intracellular localization of the protein in pericanalicular vesicular structures. Within this intracellular compartment, mrp2 colocalized with the bile salt transporter (bsep) and was still active as shown by vesicular accumulation of the fluorescent organic anion glutathione-bimane (GS-B). We conclude that down-regulation of mrp2 during BDL-induced obstructive cholestasis is mainly posttranscriptionally regulated. We propose that this down-regulation is caused by endocytosis of apical transporters followed up by increased breakdown of mrp2, probably in lysosomes. This breakdown of mrp2 is more severe in the periportal areas of the liver lobule.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2000

A scanning electron microscopic study of biliary stent materials.

BACKGROUND: Clogging of biliary stents remains an important problem. In vitro studies have shown less sludge formation in Teflon stents. Recently, clinical studies with Teflon stents have produced contradictory results. The aim of this study was to investigate whether the surface properties of the endoprostheses could explain the variation observed in clinical studies. METHODS: A total of 9 different types of unused 10F endoprostheses were examined by scanning electron microscopy (SEM): polyethylene Amsterdam-type, polyurethane Amsterdam-type, Teflon Amsterdam-type, Teflon Tannenbaum-type and a Tannenbaum-type stent with a thin stainless steel mesh between inner and outer layers. RESULTS: All polyethylene stents had a relief with tiny lumps. All Teflon stents had multiple shallow pits and ridges along the entire longitudinal axis. Both Tannenbaum-type stents also had multiple particles protruding into the stent lumen with adjacent holes in the wall of the stent. The polyurethane stent had an extremely smooth surface. CONCLUSION: SEM of Teflon made stents showed a markedly irregular inner surface, which may explain the controversial results of clinical studies. Our results indicate that the inner surface of a new stent should first be evaluated by SEM before clinical trials are initiated.

Cholestasis↗

PubMed2000

Dermal organization in scleroderma: the fast Fourier transform and the laser scatter method objectify fibrosis in nonlesional as well as lesional skin.

Scleroderma, a chronic, progressive disorder, is characterized by dermal fibrosis with collagen bundles orientated parallel to the epidermis. Simple objective parameters to evaluate disease progression and therapies are needed. We describe two methods, the laser scatter method and the fast Fourier transform (FFT), to measure collagen bundle orientation and spacing. Lesional sclerodermic skin (LS), nonlesional sclerodermic skin (nonLS), and control skin (CS) sections were evaluated for orientation ratio using the laser scatter method. The FFT was used to calculate orientation ratio, variation, and spacing of collagen bundles. Parameters were correlated with local and mean skin score measurements, on a scale of 0 (normal) to 3 (severely sclerotic). With both the laser scatter method and the FFT, orientation ratios of LS (respectively, 2.16 +/- 0.33 and 1.83 +/- 0.62) were significantly higher than CS (respectively, 1.70 +/- 0.35 and 1.38 +/- 0.15). NonLS orientation ratios (respectively, 1.92 +/- 0.15 and 1.48 +/- 0.44) were between LS and CS ratios. Orientation variation and bundle spacing of LS (respectively, 57.3 +/- 19.4 and 15.7 +/- 5.6 microm) were significantly reduced compared to CS (respectively, 73.8 +/- 15.0 and 18.9 +/- 1.9 microm). NonLS orientation ratios (respectively, 57.2 +/- 29.0 and 15.6 +/- 6.1 microm) were similar to LS. Bundles in LS are more parallel, show less variation in orientation, and are more densely packed than in CS. There was a linear correlation between mean skin score and orientation ratio. Local skin score was not linearly correlated to orientation ratio. Our findings suggest that nonLS dermis without clinical sclerosis already shows fibrotic characteristics. Both techniques were easy to use and suitable for objectifying dermal fibrosis in scleroderma lesions. FFT is more accurate and reproducible than the laser scatter method and allows simultaneous pathological evaluation of the location of the analyzed tissue sections. Future studies will need to focus on the correlation between clinical disease severity and collagen bundle characteristics.

Adolescent↗

PubMed2000

Repair in the rat lens after threshold ultraviolet radiation injury.

PURPOSE: To investigate the development and recovery of lens damage after in vivo close-to-threshold exposure to ultraviolet B radiation. METHODS: One eye of young, female Sprague-Dawley rats was exposed to 5 kJ/m2 narrowband ultraviolet radiation (UVR) (lambda(max) = 302 nm) for 15 minutes. Groups of rats were killed 1, 7, and 56 days after exposure. The structure of the exposed and nonexposed lenses was examined with light microscopy, scanning electron microscopy, transmission electron microscopy, freeze-fracture, fluorescent membrane staining, and Fourier transform analysis. RESULTS: One day after UVR exposure the lens surface had flakelike opacities. Seven days after exposure, the lens surface appeared opaque and corrugated, and the equatorial cortex had small opacities. At 56 days postexposure, the surface and equator appeared clear, but the cortex had a subtle shell-shaped opacity. At 1 day postexposure, apoptotic cell death occurred in the lens epithelium, but the cortical fibers were normal. At 7 days postexposure, the epithelium and the fibers between the 10th and 40th growth shell below the capsule contained extracellular spaces of different sizes. After 56 days, the epithelial layer appeared normal, and the extracellular spaces had disappeared; but abnormal fibers were found between the 60th and 100th growth shell below the capsule. Fibers above and below the damaged growth shells appeared fully normal. CONCLUSIONS: A close-to-threshold dose of UVR causes cataract, which is largely reversible. The UVR exposure leads to apoptosis in the lens epithelium, and after a latency period of several days, lens fibers are abnormal. Extracellular spaces develop in the epithelium and fibers. Within several weeks after exposure, the epithelium fully recovers and new fibers develop normally. The originally affected fibers are repaired. However, this repair is incomplete, leaving a small zone of enhanced light scattering in the equatorial cortex.

Animals↗

PubMed1999

Gap junctions containing alpha8-connexin (MP70) in the adult mammalian lens epithelium suggests a re-evaluation of its role in the lens.

A missense mutation in one of the three lens connexins, alpha8-connexin, has been recently shown to be the genetic basis of the zonular pulverant lens cataract. This connexin had been considered to be expressed only in lens fibre cells. The present studies show that alpha8-connexin is also expressed in the lens epithelial cell layer. For this study, the distribution of gap junctions in the adult bovine lens has been investigated by confocal immunofluorescence microscopy using antibodies against alpha8-connexin (MP70) and alpha1-connexin (Cx43). In addition to the anticipated localisation of alpha8-connexin to the broad faces of lens fibre cells as reported in other species, alpha8-connexin was also found colocalized with alpha1-connexin at plaques in the lateral epithelial-epithelial plasma membranes of the bovine lens. These data suggest that mixed alpha8-connexin/alpha1-connexin plaques are between epithelial cells at their apico-lateral plasma membranes, rather than between epithelial and fibre cells. Indeed, freeze fracture analyses of the epithelial-fibre cell interface failed to reveal gap junctions connecting the epithelium and the underlying fibre cells. Importantly, microdissection and subsequent immunoblotting of lens epithelium samples confirmed the immunolocalisation results. The data suggest mature mammalian lens epithelial cells could form either heteromeric, heterotypic and/or mixed homomeric-homotypic gap junctional complexes with unique physiological properties, an important point when considering the role of epithelial cell connexins in cataractogenesis.

Animals↗

PubMed1999

CART: a controlled algebraic reconstruction technique for electron microscope tomography of embedded, sectioned specimen.

Reconstruction of thick, embedded, sectioned material has to cope with the restricted tilt view of the electron microscope, with information not stemming from the object of interest in the projections, with aberrations of the objective lens and with a distorted relationship between the projected densities in the micrographs and the specimen mass densities due to incoherent electron interactions within the specimen. Micrograph densities over a full tilt-range show in general an averaged mass increase which is more than should be expected from the cosine dependency of the tilt-angles of the projections. The hereby presented reconstruction technique finds a solution for the under-determined system by a controlled algebraic iteration procedure. For this solution the procedure stabilises the region of interest by dynamically scaling the input data during the procedure. A model for the electron transport through thick specimens is proposed and microscope projection simulations are carried out to test the algorithms.

Algorithms↗