Wouter Kalle

Fluorescence in situ hybridization on human metaphase chromosomes detected by near-field scanning optical microscopy

Fluorescence in situ hybridization on human metaphase chromosomes is detected by near‐field scanning optical microscopy. This combination of cytochemical and scanning probe techniques enables the localization and identification of several fluorescently labelled genomic DNA fragments on a single chromosome with an unprecedented resolution. Three nucleic acid probes are used: pUC1. 77. p1–79 and the plasmid probe α‐spectrin. The hybridization signals are very well resolved in the near‐field fluorescence images, while the exact location of the probes can be correlated accurately with the chromosome topography as afforded by the shear force image.

A Microsphere-Lipoplex (Microplex) Vector for Targeted Gene Therapy of Cancer. I. Construction and In Vitro Evaluation

Plasmid DNA binding to cationic liposomes and the ability to bind these liposomes, both with and without complexed plasmid DNA, to cation-exchange microspheres were examined. The two plasmids tested were pCMV-CAT and pRcCMV-p53. Commercial Lipofectin, Lipofectace, Lipofectamine, and three formulation ratios of dimethyldioctadecyl ammonium bromide (DDAB):phosphatidylcholine and DDAB:dioleoylphosphatidyl ethanolamine liposomes were evaluated. The binding of empty liposomes onto microspheres increased and the release from microspheres decreased with increasing ratio of cationic:neutral lipid. Of all liposomes, Lipofectamine bound the most copy numbers of both plasmids. The amount of plasmid bound on the laboratory-formulated liposomes increased as the ratio of cationic:neutral lipid was increased. The amount of plasmid bound to the formulated liposomes was not affected by the type of neutral lipid used. On average, in terms of copy numbers, binding with pCMV-CAT was 1.38-fold higher than pRcCMV-p53. However,...

Microsphere‐liposome complexes protect adenoviral vectors from neutralising antibody without losses in transfection efficiency, in‐vitro

Adenoviral vectors have been commonly used in gene therapy protocols but the success of their use is often limited by the induction of host immunity to the vector. Following exposure to the adenoviral vector, adenoviral‐specific neutralising antibodies are produced, which limits further administration. This study examines the effectiveness of a novel combination of microspheres and liposomes for the shielding of adenovirus from neutralising antibodies in an in‐vitro setting. We show that liposomes are effective in the protection of adenovirus from neutralising antibody and that the conjugation of these complexes to microspheres augments the level of protection. This study further reveals that previously neutralised adenovirus may still be transported into the cell via liposome‐cell interactions and is still capable of expressing its genes, making this vector an effective tool for circumvention of the humoral immune response. We also looked at possible side effects of using the complexes, namely increases in cytotoxicity and reductions in transfection efficiency. Our results showed that varying the liposome:adenovirus ratio can reduce the cytotoxicity of the vector as well as increase the transfection efficiency. In addition, in cell lines that are adenoviral competent, transfection efficiencies on par with uncomplexed adenoviral vectors were achievable with the combination vector.

UV-induced photolesions, their repair and mutations

UV-induced cyclobutane pyrimidine dimers (CPD) are selectively removed from the transcribed strand of transcriptionally active genes in V79 Chinese hamster cells. This strand specificity of repair corresponds well with the observation that UV-induced mutations in the HPRT gene are primarily generated by DNA photolesions in the non-transcribed strand. This strand bias for mutations is, however, much more pronounced at 2 J/m2 than at the higher dose of 12 J/m2. An alternative explanation for strand specificity of mutations would be that most of the mutations are caused by pyrimidone 6-4 pyrimidine photoproducts (6-4 PP). Indeed experiments with a V79-derived cell line capable of repairing 6-4 PP but not CPD have revealed direct evidence for 6-4 PP as the mutagenic lesions in UV-irradiated hamster cells. This implies that 6-4 PP are also preferentially repaired in the transcribed strand. We have investigated the repair of DNA photolesions in the HPRT gene by measuring the distribution of bromodeoxyuridine-labeled repair patches in the transcribed and non-transcribed strands of genes employing a newly developed immunoextraction procedure. Three cell lines with different capacities to remove CPD and 6-4 PP from the HPRT gene and from the genome overall were used. We found no evidence for preferential repair of 6-4 PP in the transcribed strand of the HPRT gene in cells exposed to 10 J/m2. These data are in favor of a lack of strand-specific repair of 6-4 PP underlying the much less pronounced strand bias for induced mutations at high UV dose. However, the conclusive test would be the demonstration of preferential repair of 6-4 PP in the transcribed strand of transcriptionally active genes in cells exposed to 2 J/m2.

In vitro antioxidation activity and genoprotective effect of selected Chinese medicinal herbs.

Some traditional Chinese medicinal seeds and fruits are well known for their antioxidant properties. This research aims to investigate whether Fructus Lycii, Fructus Schisandrae Chinensis, Fructus Ligustri Lucidi and Semen Cuscutae protect DNA from oxidant challenge by hydrogen peroxide (H(2)O(2)). The standard comet assay was used to assess the genoprotective effect of these medicinal herbs. Blood was taken from three healthy adults, aged from 36 to 42. Lymphocytes were isolated and treated with different concentrations of aqueous herbal extracts, while controls were treated with phosphate buffered saline. The lymphocytes were stressed with 50 μM H(2)O(2). Treated cells were embedded in agarose and layered on slides. These sandwiched lymphocytes were lysed and afterwards subjected to an electric field in an alkaline environment. Damaged DNA was pulled out from the nucleus towards the positive electrode as a comet tail; its density was related to the degree of DNA damage. Finally, the slides were stained with fluorescence dye and tails were visually scored for 100 cells. The experiment was repeated three times and DNA damage in treated cells was compared to the controls. There was no statistical difference in DNA damage among the herb treated cells and untreated cells in the comet assay. Our data demonstrated that the selected medicinal herbs did not show in vitro DNA protection in the comet assay against oxidant challenge.

Developments in Using Scanning Probe Microscopy To Study Molecules on Surfaces — From Thin Films and Single-Molecule Conductivity to Drug–Living Cell Interactions

Scanning probe microscopy (SPM) techniques, including atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), have revolutionized our understanding of molecule–surface interactions. The high resolution and versatility of SPM techniques have helped elucidate the morphology of adsorbed surfactant layers, facilitated the study of electronically conductive single molecules and biomolecules connected to metal substrates, and allowed direct observation of real-time processes such as in situ DNA hybridization and drug–cell interactions. These examples illustrate the power that SPM possesses to study (bio)molecules on surfaces and will be discussed in depth in this review.

American ginseng tea protects cellular DNA within 2 h from consumption: results of a pilot study in healthy human volunteers

Abstract The acute genoprotective effect of Panax quinquefolius (American ginseng) has been investigated. The experiment was carried out to explore the DNA protective effect after a single dose of American ginseng tea bag infusion. Fourteen subjects (6 males and 8 females) were recruited in this study. Seven of them (3 males and 4 females) were asked to drink a cup of freshly prepared American ginseng infusions. Water was taken by the remaining subjects as the control group. Blood samples of both groups were taken before and 2 h post-ingestion. The blood samples were challenged with ultraviolet B irradiation followed by using comet assay. Completed slides were stained with Giemsa stain and DNA damage was assessed. Results showed a significant decrease in comet score after American ginseng supplementation and no change in the control group. The current study demonstrated a cup of American ginseng infusion could protect cellular DNA from oxidative stress at least within 2 h.

Efficient transduction of equine adipose-derived mesenchymal stem cells by VSV-G pseudotyped lentiviral vectors

Equine adipose-derived mesenchymal stem cells (EADMSC) provide a unique cell-based approach for treatment of a variety of equine musculoskeletal injuries, via regeneration of diseased or damaged tissue, or the secretion of immunomodulatory molecules. These capabilities can be further enhanced by genetic modification using lentiviral vectors, which provide a safe and efficient method of gene delivery. We investigated the suitability of lentiviral vector technology for gene delivery into EADMSC, using GFP expressing lentiviral vectors pseudotyped with the G glycoprotein from the vesicular stomatitis virus (V-GFP) or, for the first time, the baculovirus gp64 envelope protein (G-GFP). In this study, we produced similarly high titre V-GFP and G-GFP lentiviral vectors. Flow cytometric analysis showed efficient transduction using V-GFP; however G-GFP exhibited a poor ability to transduce EADMSC. Transduction resulted in sustained GFP expression over four passages, with minimal effects on cell viability and doubling time, and an unaltered chondrogenic differentiation potential.

The detection of Chlamydia pneumoniae in atherosclerotic plaques of Australian subjects.

Aim: To determine whether the common respiratory pathogen, Chlamydia pneumoniae, was associated with atherosclerotic plaques in Australian subjects. Methods: A total of 29 coronary atherosclerotic lesions and 18 normal coronary arterial samples were tested for the presence of C. pneumoniae by PCR and immunofluorescence methods. Results: Chlamydia pneumoniae was detected in 15 of the atheromatous lesions as well as in three of the normal tissues; the immunofluorescence assay was more sensitive ( P = 0.028) than PCR ( P = 0.26). Conclusions: These findings contradict previous Australian studies which did not detect C. pneumoniae in atherosclerotic plaques, thereby discounting the speculation that its absence was likely due to geographical variation. The detection of the bacterium in some of the normal tissues suggests that C. pneumoniae infection might be an initial trigger of atherosclerotic development.

Direct Conversion of Equine Adipose-Derived Stem Cells into Induced Neuronal Cells Is Enhanced in Three-Dimensional Culture

The ability to culture neurons from horses may allow further investigation into equine neurological disorders. In this study, we demonstrate the generation of induced neuronal cells from equine adipose-derived stem cells (EADSCs) using a combination of lentiviral vector expression of the neuronal transcription factors Brn2, Ascl1, Myt1l (BAM) and NeuroD1 and a defined chemical induction medium, with βIII-tubulin-positive induced neuronal cells displaying a distinct neuronal morphology of rounded and compact cell bodies, extensive neurite outgrowth, and branching of processes. Furthermore, we investigated the effects of dimensionality on neuronal transdifferentiation, comparing conventional two-dimensional (2D) monolayer culture against three-dimensional (3D) culture on a porous polystyrene scaffold. Neuronal transdifferentiation was enhanced in 3D culture, with evenly distributed cells located on the surface and throughout the scaffold. Transdifferentiation efficiency was increased in 3D culture, with an increase in mean percent conversion of more than 100% compared to 2D culture. Additionally, induced neuronal cells were shown to transit through a Nestin-positive precursor state, with MAP2 and Synapsin 2 expression significantly increased in 3D culture. These findings will help to increase our understanding of equine neuropathogenesis, with prospective roles in disease modeling, drug screening, and cellular replacement for treatment of equine neurological disorders.