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Biomedical subjects

A Baird

Publications and source records attributed to A Baird.

At least 37 records · Page 2Linked to original sources
PubMed2000

Translocation of FGF2 to the cell surface without release into conditioned media.

Like most cells in culture, stably transfected COS-1 cells (CF18) that constitutively overexpress basic fibroblast growth factor (FGF2) do not release the growth factor into conditioned media. Yet, when cells were biotinylated, 30% of the total cell-associated immunoreactive FGF2 was detected on the cell surface. Under similar conditions, up to 70% of the total immunoreactive FGF2 in transfected endothelial cells (MAE ZIP) or untransfected rat (C6) and human (U87MG) glioblastoma cell lines was detected on their cell surface. When peripheral plasma membrane proteins were removed from the cell surface with 0.1 M sodium carbonate, the amount of exported FGF2 was significantly reduced, whereas cell viability was unaffected. FGF2 then reappeared on the cell surface in a time-dependent manner. Ouabain, a cardenolide previously shown to inhibit the export of FGF2 from transiently transfected COS-1 cells, blocked the appearance of FGF2 onto the surface of transfected CF18 cells and MAE ZIP cells but had no detectable effect on C6 and U87MG cells. The observation that the translocation of FGF2 onto the cell surface is dissociated from its release into conditioned medium is consistent with FGF2's being rarely found in biological fluids but always cell associated and in the extracellular matrix. The findings point to a role played by the protein export pathway in controlling FGF2 activity and the normal physiological function that this growth factor plays in cell growth and differentiation. The widely accepted presumption that the absence of FGF2 in conditioned media reflects its inability to exit the cell needs to be reevaluated.

Animals↗
PubMed2000

Establishment and characterization of equine autonomic ganglion cell lines to enable direct testing of candidate toxins involved in equine dysautonomia (grass sickness).

To enable direct testing of a range of potential toxins or pathogens that might be involved in grass sickness, equine thoracic sympathetic chain ganglion cell lines were established from primary cell cultures by retroviral-mediated transduction of the temperature-sensitive mutant of the establishment oncogene encoding SV40 large T antigen. Morphological and behavioral features, temperature dependence, and immunocytochemical characteristics of the cell lines were investigated. The majority of cells were noradrenergic neurons in which dopamine-beta-hydroxylase, the enzyme that catalyzes norepinephrine synthesis, and neuropeptide Y coexisted. Cells treated with plasma from grass sickness cases that had previously been shown to induce autonomic nervous system damage when injected into normal horses showed significantly decreased mitochondrial function after 1 day. After 3 days exposure most cells showed severe degeneration in contrast to those treated with normal plasma. Liver and lung cell lines were also susceptible to plasma, suggesting that the toxin is not specifically neurotoxic.

Animals↗
PubMed2000

Differences in stroke subtypes among natives and caucasians in Boston and Buenos Aires.

BACKGROUND AND PURPOSE: Several issues regarding ethnic-cultural factors, sex-related variation, and risk factors for stroke have been described in the literature. However, there have been no prospective studies comparing ethnic differences and stroke subtypes between populations from South America and North America. It has been suggested that natives from Buenos Aires, Argentina, may have higher frequency of hemorrhagic strokes and penetrating artery disease than North American subjects. The aim of this study was to validate this hypothesis. METHODS: We studied the database of all consecutive acute stroke patients admitted to the Ramos Mejia Hospital (RMH) in Buenos Aires and to the Beth Israel Deaconess Medical Center (BIMC) in Boston, Massachusetts, from July 1997 to March 1999. Stroke subtypes were classified according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. All information on patients (demographic, clinical, and radiographic) was recorded prospective to the assessment of the stroke subtype. RESULTS: Three hundred sixty-one and 479 stroke patients were included at RMH and BIMC stroke data banks, respectively. Coronary artery disease was significantly more frequent in BIMC (P:<0.001), whereas tobacco and alcohol intake were significantly more frequent in RMH (P:<0.001). Intracerebral hemorrhage (P:<0.001) and penetrating artery disease (P:<0.001) were significantly more frequent in the RMH registry, whereas large-artery disease (P:<0.02) and cardioembolism (P:<0.001) were more common in the BIMC data bank. CONCLUSIONS: Penetrating artery disease and intracerebral hemorrhage were the most frequent stroke subtypes in natives from Buenos Aires. Lacunar strokes and intracerebral hemorrhage were more frequent among Caucasians from Buenos Aires than Caucasians from Boston. Poor risk factor control and dietary habits could explain these differences.

Adult↗
PubMed2000

Crown II: the implications of nurse prescribing for practice nursing.

Certain limited prescribing rights have now been granted to district nurses and health visitors. Proposals to extend prescribing rights to other health professionals have recently been put forward in the Review of Prescribing. Supply and Administration of Medicines (DoH, 1999). Practice nurses are one group who are likely to apply for such rights. This article reports on selected findings from a small-scale qualitative study designed to investigate the current and potential future of practice nurse in prescribing. It was found that practice nurses exercise considerable influence over prescribing in diverse therapeutic areas within general practice. However, it may be difficult to accommodate the prescribing requirements inherent in such a broad scope of practice within the framework of the present proposals. Important issues of accountability and patient safety are raised, and recommendations made for policy, research and education.

Attitude of Health Personnel↗
PubMed2000

Biological aspects of the link between smoking and depression.

A link between smoking and depressive symptoms has been described in the literature for over a decade. The neurotransmitter systems affected by cigarette smoke mirror the neurotransmitter pathways thought to be involved in the biological mechanisms of depression. Cigarette smoke contains several psychoactive chemicals; nicotine is the best studied among these and is widely accepted to be the addictive substance in tobacco. Nicotine binds to nicotinic receptors in the brain, augmenting the release of numerous neurotransmitters, including dopamine, serotonin, norepinephrine, acetylcholine, gamma-aminobutyric acid, and glutamate. Cigarette smoke has other psychoactive properties apart from nicotinic receptor stimulation. For example, it inhibits monoamine oxidase (the enzyme responsible for breaking down the biogenic amine neurotransmitters norepinephrine, serotonin, and dopamine) in the brain. Various antidepressants act through modulation of the biogenic amine neurotransmitter pathways. That the neural substrates modified by both smoking and antidepressant drugs overlap has relevance to smoking cessation. The use of antidepressants as adjuvants to smoking-cessation treatment can enhance cessation success rates. Understanding the neurobiological mechanisms underlying the association between smoking and depression may improve physicians' ability to assist smokers in their efforts to quit and will contribute to a more thorough comprehension of both the biology of addiction and the etiology of depression.

Affect↗
PubMed2000

Angiogenesis and angiogenic growth factors in middle ear cholesteatoma.

HYPOTHESIS: This study aimed to analyze the localization and distribution of vessels and of these angiogenic growth factors: basic fibroblast growth factor (FGF-2), transforming growth factor-alpha (TGF-alpha), transforming growth factor-beta1 (TGF-beta1), and vascular endothelial growth factor (VEGF) in middle ear cholesteatoma in comparison with normal middle ear mucosa and auditory meatal skin. BACKGROUND: Angiogenesis is particularly important in many normal and pathologic processes, including wound healing and inflammation. Because proliferating tissues require an enhanced blood supply, angiogenesis appears to be a prerequisite for the expansion of cholesteatoma. METHODS: The expression of FGF-2, TGF-alpha, TGF-beta1, and VEGF was studied by immunohistochemistry. The amount of vessels (collagen type IV staining) was determined by an automatic imaging analyzing system. RESULTS: The results showed an altered expression and distribution of VEGF, FGF-2, TGF-alpha, and TGF-beta1 in cholesteatoma in relation to middle ear mucosa and auditory meatal skin. The results were consistent with rapidly growing, activated keratinocytes and stromal cells. Vascularization within the perimatrix of cholesteatoma showed a 4.3-fold increase compared with middle ear mucosa and a twofold increase compared with ear canal skin. An increase of 3.2- to 4-fold in the number of vessels was observed. A close relationship was seen between the density of capillaries, degree of inflammation, and expression of the angiogenic factors investigated, and an increased number of microvessels in cholesteatoma tissue. CONCLUSIONS: Angiogenesis enables and supports the sustained migration of keratinocytes into the middle ear cavity. Therefore, it is a pivotal factor in the destructive behavior of middle ear cholesteatoma.

Angiogenesis Inducing Agents↗
PubMed1999

Genetic selection of phage engineered for receptor-mediated gene transfer to mammalian cells.

Although phage display is a powerful way of selecting ligands against purified target proteins, it is less effective for selecting functional ligands for complex targets like living cells. Accordingly, phage display has had limited utility in the development of targeting agents for gene therapy vectors. By adapting a filamentous bacteriophage for gene delivery to mammalian cells, however, we show here that it is possible to screen phage libraries for functional ligands capable of delivering DNA to cells. For example, when targeted with epidermal growth factor (EGF), M13 bacteriophage were capable of delivering a green fluorescent protein (GFP) gene to EGF receptor bearing cells in a ligand-, time-, and phage concentration-dependent manner. The EGF-targeted phage transduced COS-1 cells in a highly specific manner as demonstrated by competition with excess free EGF or alternatively with anti-EGF receptor antibodies. We further demonstrate that EGF-phage can be selected, by their ability to transduce EGF receptor bearing cells from libraries of peptide display phage. When phage were incubated with COS-1 cells, EGF ligand-encoding sequences were recovered by PCR from FACsorted, GFP-positive cells and the EGF-displaying phage were enriched 1 million-fold by four rounds of selection. These data suggest the feasibility of applying molecular evolution to phage gene delivery to select novel cell-specific DNA-targeting ligands. The same approach could be used to select genetically altered phage that are specifically designed and evolved as gene therapy vectors.

Animals↗
PubMed1999

Fibroblast growth factor 2 retargeted adenovirus has redirected cellular tropism: evidence for reduced toxicity and enhanced antitumor activity in mice.

Adenovirus (Ad) have been used as vectors to deliver genes to a wide variety of tissues. Despite achieving high expression levels in vivo, Ad vectors display normal tissue toxicity, transient expression, and antivector immune responses that limit therapeutic potential. To circumvent these problems, several retargeting strategies to abrogate native tropism and redirect Ad uptake through defined receptors have been attempted. Despite success in cell culture, in vivo results have generally not shown sufficient selectivity for target tissues. We have previously identified (C. K. Goldman et al., Cancer Res., 57: 1447-1451, 1997) the fibroblast growth factor (FGF) ligand and receptor families as conferring sufficient specificity and binding affinity to be useful for targeting DNA in vivo. In the present studies, we retargeted Ad using basic FGF (FGF2) as a targeting ligand. Cellular uptake is redirected through high-affinity FGF receptors (FGFRs) and not the more ubiquitous lower-affinity Ad receptors. Initial in vitro experiments demonstrated a 10- to 100-fold increase in gene expression in numerous FGFR positive (FGFR+) cell lines using FGF2-Ad when compared with Ad. To determine whether increased selectivity could be detected in vivo, FGF2-Ad was administered i.v. to normal mice. FGF2-Ad demonstrates markedly decreased hepatic toxicity and liver transgene expression compared with Ad treatment. Importantly, FGF2-Ad encoding the herpes simplex virus thymidine kinase (TK) gene transduces Ad-resistant FGFR+ tumor cells both ex vivo and in vivo, which results in substantially enhanced survival (180-260%) when the prodrug ganciclovir is administered. Because FGFRs are up-regulated on many types of malignant or injured cells, this broadly useful method to redirect native Ad tropism and to increase the potency of gene expression may offer significant therapeutic advantages.

Adenoviridae↗
PubMed1999

Prevalent expression of fibroblast growth factor (FGF) receptors and FGF2 in human tumor cell lines.

Basic fibroblast growth factor (FGF2) has potent mitogenic and angiogenic activities that have been implicated in tumor development and malignant progression. The biological effects of FGF2 and other members of the FGF ligand family are mediated by 4 transmembrane tyrosine kinase receptors (FGFRs). To better understand the roles of FGFRs in cancer, the expression of FGF2 and each of the 4 FGFRs was assessed by RNase protection analysis of 60 human tumor cell lines, representing 9 tumor types. Expression of at least one FGFR isoform was detected in 90% and FGF2 mRNA in 35% of the cell lines. Our comprehensive analysis of FGF2 and FGFR expression in human tumor cell lines provides evidence that FGF signaling pathways are active in a majority of human tumor cell lines, and lends support to the development of anti-tumor strategies that target FGFRs.

Fibroblast Growth Factor 2↗
PubMed1999

Decorin attenuates gliotic scar formation in the rat cerebral hemisphere.

The transforming growth factor-betas (TGF-betas) are potent fibrogenic factors implicated in numerous CNS pathologies in which fibrosis and neural dysfunction are causally associated. In this study, we aimed to demonstrate significant inhibition of fibrogenesis, glial scarring, and inflammation in penetrating incisional wounds of the rat brain using the proteoglycan decorin, which effectively inhibits TGF-beta activity. Adult rats were assigned to two treatment groups each receiving 14 daily intraventricular injections of 10 microliter total volume of: (i) saline plus 0.3% autologous rat serum = 30 microgram protein); or (ii) saline plus 30 microgram recombinant human decorin. On day 0 of the experiment, a stereotactically defined unilateral incisional lesion was placed through the cerebral cortex into the lateral ventricle and, after 14 days, brains were processed for immunohistochemical analysis of the lesion site. Specific antibodies were used to visualize the deposition within the wound of matrix molecules and the extent and nature of reactive astrocytosis and inflammation. Quantitative and qualitative image analysis of the fibrous scar was performed in sections from a defined anatomical plane through the wound to detect the antifibrotic effects of decorin treatment. Treatment of wounds with decorin led to a marked attenuation of all aspects of CNS scarring including matrix deposition, formation of an accessory glial limiting membrane, and inflammation. Our findings suggest that decorin is potentially applicable to a number of human CNS fibrotic diseases to arrest the deposition of excessive extracellular matrix components and maintain and/or restore functional integrity.

Animals↗
PubMed1999

Retargeted delivery of adenoviral vectors through fibroblast growth factor receptors involves unique cellular pathways.

A major goal of gene therapy is to improve target specificity by delivering vectors through alternative cellular receptors. We previously reported that adenoviral vector delivery through basic fibroblast growth factor (FGF2) receptors enhances both cellular transduction and in vivo efficacy. We now present studies addressing the cellular pathways and mechanisms underlying these events. Cellular receptors for adenoviruses are not required for transduction by FGF2-retargeted vectors. Moreover, alpha(V) integrins can antagonize FGF2 retargeting, in contrast to their obligatory role in non-retargeted vector delivery. By contrast, high-affinity FGF receptors, which are overexpressed on potential tumor targets, are required for FGF2-retargeted transduction. Low-affinity heparan sulfate proteoglycan interactions, however, are not a prerequisite, in marked contrast to their obligatory role in FGF2 mitogenic signaling. By comparing receptor expression and ligand binding with transgene expression, we also demonstrate that FGF2 retargeting enhances transduction by mechanisms other than increasing the number of targeted cells. Rather, the use of alternative targeting ligands supports the conclusion that specific receptor interactions and intracellular events serve to enhance transgene expression. Together, these studies highlight the unique delivery and transduction pathways used by FGF2-retargeted adenoviruses, and help define the basis for their enhanced in vivo efficacy.

Adenoviridae↗
PubMed1999

Gene transfer to mammalian cells using genetically targeted filamentous bacteriophage.

We have genetically modified filamentous bacteriophage to deliver genes to mammalian cells. In previous studies we showed that noncovalently attached fibroblast growth factor (FGF2) can target bacteriophage to COS-1 cells, resulting in receptor-mediated transduction with a reporter gene. Thus, bacteriophage, which normally lack tropism for mammalian cells, can be adapted for mammalian cell gene transfer. To determine the potential of using phage-mediated gene transfer as a novel display phage screening strategy, we transfected COS-1 cells with phage that were engineered to display FGF2 on their surface coat as a fusion to the minor coat protein, pIII. Immunoblot and ELISA analysis confirmed the presence of FGF2 on the phage coat. Significant transduction was obtained in COS-1 cells with the targeted FGF2-phage compared with the nontargeted parent phage. Specificity was demonstrated by successful inhibition of transduction in the presence of excess free FGF2. Having demonstrated mammalian cell transduction by phage displaying a known gene targeting ligand, it is now feasible to apply phage-mediated transduction as a screen for discovering novel ligands.

Animals↗
PubMed1999

Altered formation and bulk absorption of cerebrospinal fluid in FGF-2-induced hydrocephalus.

Upregulation of certain growth factors in the central nervous system can alter brain fluid dynamics. Hydrocephalus was produced in adult Sprague-Dawley rats by infusing recombinant basic fibroblast growth factor (FGF-2) at 1 microg/day into a lateral ventricle for 2, 3, 5, or 10-12 days. Lateral and third ventricular enlargement progressively increased from 2 to 10 days. Ventriculomegaly was also induced by a 75% reduced dose of FGF-2. At 10-12 days, there was a 29% attenuation in cerebrospinal fluid (CSF) formation rate, from 2. 5 to 1.8 microliter/min (P < 0.01). Choroid plexus, the main site of CSF secretion, had an augmented number of dark epithelial cells, which have previously been associated with decreased choroidal fluid formation. The twofold elevated resistance to CSF absorption, i.e., 0.8 to 1.7 mmHg. min(-1). microliter(-1), was attributable, at least in part, to enhanced fibrosis and collagen deposits in the arachnoid villi, a major site for CSF absorption. Normal CSF pressure (2-3 mmHg) was consistent with a patent cerebral aqueduct and reduced CSF formation rate. The FGF-2-induced ventriculomegaly is interpreted as an ex vacuuo hydrocephalus brought about by an altered neuropil and interstitium of the brain.

Absorption↗
PubMed1999

A mass in the buttock of a schizophrenic.

A 70-year-old man with a 10-year history of depot injections with anti-psychotic drugs for schizophrenia developed a diffuse large B-cell lymphoma at the injection site in the buttock. This would appear to be a unique case and lends weight to the suggestion that prolonged local antigenic stimulation may be responsible for the development of extranodal lymphomas.

Aged↗
PubMed1999

The significance of an 'insufficient' Pipelle sample in the investigation of post-menopausal bleeding.

BACKGROUND: Out-patient endometrial sampling is a commonly performed procedure in the investigation of post-menopausal bleeding. We hypothesized that an 'insufficient' Pipelle sample reliably reflected the absence of serious endometrial pathology. METHODS AND RESULTS: A review of 141 consecutive cases reported as 'insufficient' for diagnostic purposes revealed 29 (20%) cases to have uterine pathology after secondary investigation. These included two cases of endometrial carcinoma and two other cases of uterine malignancy. CONCLUSION: These results do not support the initial hypothesis and suggest that in women presenting with post-menopausal bleeding, an 'insufficient' sample is an indication for further investigation.

Biopsy↗
PubMed1998

Targeted delivery of DNA encoding cytotoxic proteins through high-affinity fibroblast growth factor receptors.

Nonviral DNA delivery strategies for gene therapy have generally been limited by a lack of specificity and efficacy. However, ligand-mediated endocytosis can specifically deliver DNA in vitro to cells bearing the appropriate cognate receptors. Similarly, in order to circumvent problems related to efficacy, DNA must encode proteins with high intrinsic activities. We show here that the ligand basic fibroblast growth factor (FGF2) can target FGF receptor-bearing cells with DNA encoding therapeutic proteins. Delivery of genes encoding saporin, a highly potent ribosomal inactivating protein, or the conditionally cytotoxic herpes simplex virus thymidine kinase, a protein that can kill cells by activating the prodrug ganciclovir, is demonstrated. The saporin gene was codon optimized for mammalian expression and demonstrated to express functional protein in a cell-free assay. FGF2-mediated delivery of saporin DNA or thymidine kinase DNA followed by ganciclovir treatment resulted in a 60 and 75% decrease in cell number, respectively. Specificity of gene delivery was demonstrated in competition assays with free FGF2 or with recombinant soluble FGF receptor. Alternatively, when histone H1, a ligand that binds to cell surface heparan sulfate proteoglycans ("low-affinity" FGF receptors), was used to deliver DNA encoding thymidine kinase, no ganciclovir sensitivity was observed. These findings establish the feasibility of using ligands such as FGF2 to specifically deliver genes encoding molecular chemotherapeutic agents to cells.

Amino Acid Sequence↗
PubMed1998

Targeting bacteriophage to mammalian cell surface receptors for gene delivery.

Filamentous bacteriophages represent one of nature's most elegant ways of packaging and delivering DNA. In an effort to develop novel methods for ligand discovery via phage gene delivery, we conferred mammalian cell tropism to filamentous bacteriophages by attaching basic fibroblast growth factor (FGF2), transferrin, or epidermal growth factor (EGF) to their coat proteins and measuring CMV promoter-driven reporter gene expression in target cells. In this system, FGF2 was a more effective targeting agent than transferrin or EGF. The detection of green fluorescent protein (GFP) or beta-galactosidase (beta-Gal) activity in cells required FGF2 targeting and was phage concentration dependent. Specificity of the targeting for high-affinity FGF receptors was demonstrated by competing the targeted phage with FGF2, by the failure of FGF2-targeted bacteriophage to transduce high-affinity FGF receptor-negative cells, and by their ability to transduce these same cells when stably transfected with FGFR1, a high-affinity FGF receptor. Long-term transgene expression was established by selecting colonies for G418 resistance, suggesting that with the appropriate targeted tropism, filamentous bacteriophage can serve as a vehicle for targeted gene delivery to mammalian cells.

Animals↗