Search PubMed⌕ Search

Biomedical subjects

A Baird

Publications and source records attributed to A Baird.

At least 19 recordsLinked to original sources
PubMed2005

Memory function after resolution of post-traumatic amnesia.

PRIMARY OBJECTIVES: The aims of this pilot study were (1) to examine neuropsychological, particularly memory functions immediately after post-traumatic amnesia (PTA) resolution according to the Galveston Orientation and Amnesia Test (GOAT), and (2) to provide a preliminary exploration of pattern of performance on GOAT items across PTA duration. METHODS AND PROCEDURES: Thirty-seven head injured patients were administered the Recognition Memory Tests on the day that PTA resolved. Formal neuropsychological assessment was conducted on average 10 days after PTA resolution. MAIN OUTCOMES AND RESULTS: All the patients in the series showed memory impairment which varied in severity but was typically characterized as global and severe. Deficits in executive and speed and attention functions were common. GOAT items relating to orientation were typically passed, while items concerning anterograde and retrograde recall were most commonly failed across all stages of PTA duration. CONCLUSIONS: These findings suggest that reliance on memory performance as a measure of PTA is not ideal and highlight the need for further research of this issue.

Adult↗
PubMed2004

CTb targeted non-viral cDNA delivery enhances transgene expression in neurons.

BACKGROUND: Efficient neuronal gene therapy is a goal for the long-term repair and regeneration of the injured central nervous system (CNS). We investigated whether targeting cDNA to neurons with cholera toxin b chain conjugated non-viral polyplexes led to increased efficiency of non-viral gene transfer in the CNS. Here, we illustrate the potential for this strategy by demonstrating enhanced transfection of a differentiated neuronal cell type, PC12. METHODS: In vitro transfection efficiency of a cholera toxin b chain-poly(D-lysine) molecular conjugate (CTb-K(100)) was compared by fluorescence-activated cell sorting (FACS) analysis of green fluorescent protein (GFP) expression and luminometric measurement of beta-galactosidase (beta-gal) expression, to untargeted poly(D-lysine) (K(100)) in undifferentiated and NGF-differentiated PC12 cells. RESULTS: Transfection of undifferentiated PC12 cells with CTb-K(100) polyplexes resulted in a 36-fold increase in levels of pCMV-DNA(LacZ) expression and a 20-fold increase in the frequency of transduction with pCMV-DNA(GFP), compared with untargeted K(100) polyplexes. Treatment of PC12 cells with 50 ng/ml/day of NGF for 14 days led to differentiation to a neuronal phenotype. Transfection of NGF-differentiated cells with CTb-K(100) polyplexes resulted in a 133-fold increase in levels of pCMV-DNA(LacZ) expression and a 11-fold increase in the percentage of cells transduced with pCMV-DNA(GFP), compared with untargeted K(100) polyplexes. Transfection was dependent on CTb, with CTb-K(100)-mediated transfections competitively inhibited with free CTb in both PC12 phenotypes. CONCLUSIONS: Non-viral systems for gene transfer in damaged CNS show superior toxicological profiles to most viruses but are limited by inefficient and non-selective gene expression in target tissue. Cholera toxin is known to interact preferentially with neuronal cells of the central and peripheral nervous systems, mediating binding through the b subunit, CTb, and the pentasaccharide moiety of the gangliosaccharide, GM1, which is present at high levels on the neuronal cell surface. Here, we show that a molecular conjugate of the CTb subunit, covalently linked to poly(D-lysine), is able to successfully target and significantly enhance transfection of a neuronal cell type, NGF-differentiated rat PC12 pheochromocytoma cells. This observation encourages the further development of non-viral strategies for the delivery of therapeutic genes to neurons.

Animals↗
PubMed2003

Breeding season and embryonic diapause in crabeater seals (Lobodon carcinophagus).

Direct observation of 387 embryos in the early stages of development was combined with observations on breeding behaviour and reproductive biology obtained from the published literature, to estimate the timing of births, oestrus, ovulation and implantation, and to derive estimates of the duration of pregnancy, embryonic diapause and active gestation for crabeater seals (Lobodon carcinophagus). The total duration of pregnancy (conception to birth) is estimated to be 11.3 months (344 days). It is estimated that the pupping season extends from late September to early November, with peak births in mid-October. The estimated mean duration of lactation is approximately 17 days; the mean date of weaning is 31 October (14 October to 17 November); and the mean date of conception is 4 November (18 October to 21 November). Oestrus, ovulation and conception occur approximately 4 days after weaning. Estimates of times of weaning and conception were made assuming that the preimplantation period is the same in all individuals. The mean date of implantation of the embryo is 24 January+/-17 days; the duration of embryonic diapause is 2.7 months (81 days); and the duration of active gestation (implantation to parturition) is 8.8 months (264 days).

Animals↗
PubMed2001

The conjoint importance of the hippocampus and anterior thalamic nuclei for allocentric spatial learning: evidence from a disconnection study in the rat.

A disconnection procedure was used to test whether the hippocampus and anterior thalamic nuclei form functional components of the same spatial memory system. Unilateral excitotoxic lesions were placed in the anterior thalamic (AT) nuclei and hippocampus (HPC) in either the same (AT-HPC Ipsi group) or contralateral (AT-HPC Contra group) hemispheres of rats. The behavioral effects of these combined lesions were compared in several spatial memory tasks sensitive to bilateral hippocampal lesions. In all of the tasks tested, T-maze alternation, radial arm maze, and Morris water maze, those animals with lesions placed in the contralateral hemispheres were more impaired than those animals with lesions in the same hemisphere. These results provide direct support for the notion that the performance of tasks that require spatial memory rely on the operation of the anterior thalamus and hippocampus within an integrated neural network.

Animals↗
PubMed2001

Receptor-mediated gene transfer by phage-display vectors: applications in functional genomics and gene therapy.

Recent studies have demonstrated targeted gene-delivery to mammalian cells using modified phage-display vectors. Specificity is determined by the choice of the genetically displayed targeting ligand. Without targeting, phage particles have virtually no tropism for mammalian cells. Thus, novel ligands can be selected from phage libraries by their ability to deliver a reporter gene to targeted cells. Together with advances in cDNA display technologies, these findings offer new opportunities for the use of phage-display technology in functional genomics. In addition, targeted phage particles have potential as alternative gene therapy vectors that can be further improved using directed evolution.

Journal Article↗
PubMed2001

A monoclonal antibody that enables specific immunohistological detection of prion protein in bovine spongiform encephalopathy cases.

The specificity of a monoclonal antibody (mAB) raised against recombinant bovine prion protein (PrP) for the immunohistological detection of PrP accumulation in the medulla oblongata of bovine spongiform encephalopathy (BSE) and ovine scrapie cases was investigated. mAB KG9 showed a diffuse low intensity reaction with the cytoplasm of neurones in normal cattle and sheep sections. In BSE sections the mAB detected widespread granular deposits of PrP associated with neurones and the neuropil. Although scrapie sections showed similar levels of granular deposits with another antibody to PrP these were not detected by KG9 which did however detect diffuse staining in neuronal cytoplasm. Possible explanations for the specificity of binding of KG9 are discussed.

Animals↗
PubMed2001

Human choroid plexus growth factors: What are the implications for CSF dynamics in Alzheimer's disease?

The choroid plexus plays a key role in supporting neuronal function by secreting cerebrospinal fluid (CSF) and may be involved in the regulation of various soluble factors. Because the choroid plexus is involved in growth factor secretion as well as CSF dynamics, it is important to understand how growth factors in CSF interact with the brain parenchyma as well as with cells in direct contact with the flowing CSF, i.e., choroid plexus and arachnoid villi. While the existence of growth factors in the choroid plexus has been documented in several animal models, the presence and distribution of growth factors in the human choroid plexus has not been extensively examined. This study describes the general distribution and possible functions of a number of key proteins in the human choroid plexus and arachnoid villi, including basic fibroblast growth factor, FGF receptor, and vascular endothelial growth factor. FGF and VEGF could both be readily demonstrated in choroid plexus epithelial cells. The presence of FGF and VEGF within the choroid plexus was also confirmed by ELISA analysis. Since Alzheimer's disease (AD) is known to be associated with a number of growth factor abnormalities, we examined the choroid plexus and arachnoid villi from AD patients. Immunohistochemical studies revealed the presence of FGF and VEGF within the AD choroid plexus and an increased density of FGFr in both the choroid plexus and the arachnoid villi of AD patients. No qualitative changes in the distribution of FGF and VEGF were observed in the AD choroid plexus. The appearance of FGFr in AD arachnoid was associated with robust amyloid and vimentin immunoreactivity. These findings confirm the presence of FGF and VEGF within the normal and AD choroid plexus and suggest that the alteration of growth factors and their receptors may contribute to the pathogenesis of the hydrocephalus ex vacuo that is characteristically seen in AD.

Alzheimer Disease↗
PubMed2001

Sustained effects of gene-activated matrices after CNS injury.

We show that when gene-activated matrices (GAM) are placed between the proximal and distal stumps of severed rat optic nerves, DNA is retained within the GAM, promoting sustained transgene expression in the optic nerve, in the GAM itself, and, more importantly, in axotomized retinal ganglion cells (RGC). Plasmids that encode basic fibroblast growth factor (FGF2), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3) promote sustained survival of RGC for over 3 months after the initial injury. These findings suggest that immobilized DNA implanted into a CNS lesion will be delivered by axon terminal uptake and retrograde transport to axotomized neurons. GAM may therefore be a useful agent for promoting sustained neuron survival and axon regeneration. Whether further optimization of the matrices, plasmids, promoters, and genes present in the GAM will promote even more survival or, alternatively, axon regeneration remains to be determined.

Animals↗
PubMed2001

Receptor-targeted gene delivery using multivalent phagemid particles.

Although growth factor- and antibody-targeted filamentous phage have recently been demonstrated to transduce mammalian cells, there is a significant need to increase transduction efficiency so as to improve the usefulness of targeted phage vectors for gene therapy and ligand discovery. Here, we describe the use of multivalent phagemid vectors that are specifically designed for ligand-targeted mammalian cell transduction. This phagemid system has certain advantages over phage vectors, such as larger insert size and vector stability, and it retains the multivalent display necessary for efficient cell binding and internalization. Immunoblotting revealed that the most efficient multivalent display (exceeding that of a phage vector) was achieved in the phagemid system when epidermal growth factor (EGF) was fused to the C-terminal domain of the pIII coat protein. We compared phagemid particles displaying EGF at high or low valence by rescuing the vector with R408d3 (pIII deleted) or wild-type R408 helper phage, respectively. More efficient display of EGF correlated with increased internalization, vector potency, and transduction efficiency ( approximately 9%). The findings described here support our original hypothesis that phage-based vectors can be modified for more efficient gene transfer and suggest that directed evolution may be applied to increase their potential even further.

Bacteriophages↗
PubMed2001

In-vitro cyclosporin sensitivity of proliferating lymphocytes is predictive of in-vivo therapeutic response in ulcerative colitis.

BACKGROUND: The efficacy of cyclosporin in the management of ulcerative colitis is recognized. Not all patients respond to this treatment. Existing clinical and laboratory parameters are of little use in identifying those most likely to respond. AIMS: To determine whether in-vitro sensitivity to cyclosporin as measured by a lymphocyte proliferation assay is predictive of in-vivo response to therapy. METHODS: The study comprised seven responders with ulcerative colitis, seven non-responders, and 14 healthy matched controls. A lymphocyte proliferation assay was carried out in the presence of a range of concentrations of cyclosporin and a dose-response curve constructed for each subject. The IC(50) value, the concentration of cyclosporin that resulted in 50% inhibition of proliferation, was calculated for each subject. IC(50) values for responders, non-responders and controls were compared using a Mann-Whitney test. RESULTS: There was a wide range of values obtained for the study group as a whole. IC(50) values for non-responders were significantly higher than those of responders (P < 0.05). CONCLUSIONS: There is a population-wide variation of in-vitro sensitivity to cyclosporin. This is reflected in in-vivo sensitivity as measured by clinical response to cyclosporin treatment. Future therapeutic strategies need to address this inherent variability of individual response to therapy.

Adult↗
PubMed2001

Complex real-world functioning and neuropsychological test performance in older adults.

In stepwise regression analyses with Independent Living Scales (ILS) summary and subscale scores as the dependent variables, 8 of 10 psychometric measures from our battery for older adults emerged as important predictors for 69 patients referred for clinical assessment. The Dementia Rating Scale (DRS) score entered first for 6/8 analyses. However, measures of confrontation naming, oral reading, verbal fluency, paragraph recall, visual perception, complex attention, and depression also added explanatory power. Multiple Rs ranged from .66 to .88 except for the Social Adjustment subscale, which correlated only with the depression scale.

Aged↗
PubMed2001

Flow cytometric analysis of Clostridium difficile adherence to human intestinal epithelial cells.

Clostridium difficile is the most common cause of diarrhoea in hospitalised patients. Bacterial adherence to gut epithelial cells is a likely prerequisite to infection and toxin production. A novel flow cytometric method was developed for detecting adherence of C. difficile to human colonic and small intestinal epithelial cells (EC) and human intestinal cell lines. Small intestinal and colonic EC were isolated from biopsy specimens with mucolytic and chelating agents. Adherence of fluorochrome-labelled C. difficile to EC was measured by flow cytometry and was calculated as increase in median fluorescent intensity (deltaMFI). Cells with bacteria attached could be distinguished easily from cells alone or cells with unlabelled bacteria attached. Toxin-positive C. difficile adhered to colonic and small intestinal EC (deltaMFI mean 21.2 SD 16.7, n = 33 and 16.5 SD 20.7, n = 19 respectively). The toxin-negative strain also adhered to both epithelial cell types (deltaMFI 26.1 SD 32.5, n = 17 and 18.3 SD 31.3, n = 16). Adherence of toxin-positive C. difficile to the intestinal cell lines Caco-2 (deltaMFI 9.4 SD 4.4, n = 14) and HT29 (deltaMFI 8.1 SD 3.1, n = 12) was quantifiable, although at a significantly lower level than with primary colonic epithelial cells. Adherence of the toxin-negative strain was slightly lower, deltaMFI 6.5 SD 1.8, n = 9 with Caco-2 cells and deltaMFI 6.0 SD 2.0, n = 10 with HT29 cells. Adherence of C. difficile to epithelial cell lines was blocked with C. difficile antiserum, confirming specificity of adherence. In conclusion, flow cytometry is a useful approach to quantifying adherence of C. difficile to human colonic and small intestinal epithelial cells. Binding of toxin-negative as well as toxin-positive bacteria was detectable by this approach. Analysis of C. difficile adherence to target cells may have important implications for the understanding of the pathogenesis of C. difficile-related disease.

Bacterial Adhesion↗
PubMed2001

Heart of the matter.

Explore the source record for details and available documents.

Cardiovascular Diseases↗
PubMed2001

Gene therapy for central nervous system repair.

The amelioration of the sequelae of CNS injury by gene therapy requires three post-injury events to be addressed: scarring, neuron death and axon regeneration. Administering anti-apoptotic, and axon growth promoting genes to neurons is inefficient, using nonviral vectors, because access to the transcriptional machinery is restricted by an intact nuclear membrane in G0 cells. Viral vectors have better transfection rates but a higher incidence of deleterious effects than non-viral vectors. Discrete targeted transfection of astrocytes, for example, about the wound with antifibrotic genes is essential to control scarring and for the inhibition of axon growth locally by gene products without transfecting neighboring and distant cells. Either rational or forced evolutionary design of vectors will ultimately achieve efficient safe gene transduction. Recombinant protein treatments for CNS repair have proved disappointing, probably because axotomized neurons are difficult to access in multiple disparate sites in the CNS after penetrant injury. Gene therapy has the potential to overcome these difficulties since sustained antiscarring/neurotrophic regimes are achievable after a single delivery to the site of injury by uptake by local injury responsive cells in the wound, and by axon terminals. Subsequent retrograde axonal transport delivers the therapeutic genes to all axotomized neurons throughout the CNS.

Active Transport, Cell Nucleus↗