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L J Feldman

Publications and source records attributed to L J Feldman.

At least 55 records · Page 3Linked to original sources
PubMed1997

Improved efficiency of arterial gene transfer by use of poloxamer 407 as a vehicle for adenoviral vectors.

Improvement in the efficiency of adenovirus-mediated arterial gene transfer may augment the utility of cardiovascular gene therapy. In vitro studies suggest that poloxamer 407 enhances transfection efficiency of adenoviral vectors in vascular smooth muscle cells. The aim of the present study was to investigate whether poloxamer 407 facilitates adenovirus-mediated arterial transfection in vivo as well. Gene transfer was performed in balloon-injured rat carotid arteries using E1- adenoviral vectors diluted in either poloxamer 407 or phosphate buffered saline (PBS). Transfection efficiency was significantly higher in rats transfected using a nuclear beta-galactosidase expressing adenovector diluted in poloxamer 407 versus PBS (morphometry, 13.2 +/- 1.3% versus 4.1 +/- 0.4% transfected medial cells, P = 0.0001; chemiluminescence; 1.4 +/- 0.2 versus 0.4 +/- 0.2 mU beta-galactosidase/mg protein, P = 0.004). Moreover, in the presence of poloxamer 407, it was possible to reduce the incubation time of adenoviral vectors from 20 to 10 min without compromising transfection efficiency. Poloxamer 407 did not evoke specific tissue toxicity. Site-specificity of arterial gene transfer, assessed by PCR, was not altered by administration of poloxamer 407. These findings suggest that poloxamer 407 may be useful to improve the efficiency of adenovirus-mediated arterial gene transfer.

Adenoviridae↗
PubMed1997

Floral determination and expression of floral regulatory genes in Arabidopsis.

The expression of the floral regulators LEAFY, APETALA1 and AGAMOUS-LIKE8 was examined during light treatments that induced flowering in Arabidopsis, and was compared to time points at which floral determination occurred. Extension of an 8-hour day by either continuous red- or far-red-enriched light induced LEAFY and AGAMOUS-LIKE8 expression within 4 hours. The 4 hours of additional light was sufficient for floral determination only in the far-red-enriched conditions, while 12-16 hours of additional light was required for floral determination in the red-enriched conditions. These results indicate that the induction of floral regulatory genes and induction of flower formation can be uncoupled under certain circumstances. Expression of LEAFY and AGAMOUS-LIKE8 in the shoot apex at the time of floral determination is also consistent with genetic data indicating that these genes are involved in the first steps of the transition from vegetative to reproductive development. In contrast to LEAFY and AGAMOUS-LIKE8, APETALA1 expression was first observed 16 hours after the start of photoinduction. Since this time point was always after floral determination, APETALA1 is an indicator of floral determination.

Arabidopsis↗
PubMed1997

[Orientated management towards reperfusion in the acute phase of myocardial infarction. Results in a cohort of 700 consecutive patients].

The principal objective of treatment of the acute phase of myocardial infarction is the obtention of TIMI 3 complete patency. Usually, only a minority of patients receives thrombolytic therapy and complete reperfusion in unusual. Between June 1988 and April 1996, 700 consecutive patients were admitted to Bichat hospital within 6 hours of the onset of transmural myocardial infarction (81% men; age 59 +/- 13 years). The objective of treatment was to obtain maximal coronary patency in the acute phase, either by thrombolysis (with systematic angiography at 90 minutes and salvage angioplasty in case of failure), or primary angioplasty or conventional treatment (usually in cases of spontaneous reperfusion). The emergency angiography and angioplasty procedures were performed by a medical team on 24 hour duty. During the acute phase, 316 patients received intravenous thrombolysis (angiography at 90' in 302 patients with salvage angioplasty in 79 patients), 304 underwent primary angioplasty (TIMI 3 artery in 85% of cases) and 80 underwent conventional treatment (including 52 cases of angiographically documented spontaneous reperfusion). Therefore, a 81% (566/700) rate of patent TIMI 3 arteries was obtained. The hospital mortality was 8.9%, lower in TIMI 3 arterial patency (6%) than TIMI 2 (20%) or TIMI 0-1 (23%), p < 0.001. The mortality was 4% in patients treated by thrombolysis. Therefore, a reperfusion strategy associating thrombolysis and/or angioplasty provides a high TIMI 3 patency rate in the acute phase of myocardial infarction with a low mortality (6%) in consecutive, unselected patients.

Aged↗
PubMed1996

Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism.

Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [35S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 microM KN-93, but binding is not affected by 5 microM KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 microM KN-93, but not by 5 microM KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.

Amino Acid Sequence↗
PubMed1996

Perspectives of arterial gene therapy for the prevention of restenosis.

Restenosis remains the main limitation of interventional cardiology. Restenosis is an important target for gene therapy since it is frequent (30% of patients), costly (estimated $2 billion annually), refractory to all pharmacological therapies, and related, at least in part, to smooth muscle cell proliferation which is an inviting target for antiproliferative molecular strategies. Because cell division is ultimately controlled by intranuclear events, the protein product of genes selected for their antiproliferative effects usually remains inside the cells. Consequently, the transfer of growth-inhibitory genes needs to be efficient-i.e., involve a large proportion of smooth muscle cells populating the angioplasty site. To date, adenoviral vectors are, by far, the most efficient vectors to perform in vivo arterial gene delivery. These vectors, as well as others, have been recently used to demonstrate that therapeutic genes encoding cytolytic (thymidine kinase) or cytostatic (hypophosphorylatable retinoblastoma protein, endothelial nitric oxide synthase, gax, etc.) products successfully inhibit smooth muscle cell proliferation and related intimal hyperplasia. Despite substantial progress, major technical issues remain to be addressed before gene therapy is applied to clinical restenosis. First-generation recombinant adenoviruses evoke both cellular and humoral immune responses leading to local toxicity and transient gene expression. Moreover, the low efficiency of gene transfer to atherosclerotic arteries may further impair the biological effect of antiproliferative genes. Finally, restenosis is a multifactorial phenomenon in which intimal hyperplasia plays an important but not exclusive role. Prevention of constrictive remodeling should also be taken into account in an integrated genetic strategy to prevent restenosis.

Angioplasty, Balloon, Coronary↗
PubMed1996

Adenovirus-mediated arterial gene therapy for restenosis: problems and perspectives.

Restenosis remains the main limitation of interventional cardiology. Restenosis occurs when angioplasty-induced intimal hyperplasia as well as arterial remodelling result in flow-limiting renarrowing of the arterial lumen at the angioplasty site. Intimal hyperplasia is an important candidate for gene therapy since it is related to smooth muscle cell proliferation, which is an inviting target for molecular antiproliferative strategies. To date, adenoviral vectors are, by far, the most efficient vectors to perform in vivo arterial gene transfer. These vectors, as well as others, have been recently used to demonstrate that therapeutic genes encoding cytotoxic (herpes virus thymidine kinase) or cytostatic (hypophosphorylatable Rb, Gax, endothelial nitric oxide synthase) products successfully inhibit smooth muscle cell proliferation and related intimal hyperplasia. Despite substantial progress, major technical issues, including the toxicity of first-generation adenoviral vectors, inefficient transduction of atherosclerotic arteries, and the risk of extra-arterial transfection remain to be addressed before gene therapy is applied to clinical restenosis.

Adenoviridae↗
PubMed1995

Gene therapy for the vulnerable plaque.

Acute coronary events result from the rupture of an atherosclerotic plaque, leading to formation of an occlusive coronary thrombus. Recent developments in the field of gene transfer provide the opportunity to genetically modify cells involved in plaque rupture as well as thrombus formation and thus prevent acute coronary syndromes. A first approach consists of transferring genes, the product of which may stabilize the vulnerable plaque by reducing the plaque content in lipids and macrophages. Alternatively, the introduction into the atherosclerotic plaque of genes encoding for thrombolytic proteins or growth factors able to restore physiologic antithrombotic functions of endothelial cells may inhibit thrombus formation should the plaque rupture. The success of such strategies depends on the efficiency with which the transgene is introduced and expressed into the target cell, the duration of transgene expression and the ability of the transgene product to ultimately prevent plaque rupture or thrombus formation, or both.

Animals↗
PubMed1995

Specification of chimeric flowering shoots in wild-type Arabidopsis.

Within wild-type Arabidopsis populations, a subset of the plants were found to have a single chimeric shoot on their primary shoot axes. The chimeric shoots were located below the lowest primary-axis flower; and they exhibited features of both flowers and paraclades (lateral flowering shoots). Morphological analyses of chimeric shoots indicated that they developed from single primordia. In each chimeric shoot, the side furthest from the apical meristem was specified as 'flower'--while the side closest to the meristem was specified as 'paraclade'--suggesting that a stimulus from outside the apical meristem can directly induce primordia to develop as flowers. It is concluded that the development of the teratological chimeric shoots resulted from the overlap of the vegetative and floral specification processes within single primordia.

Arabidopsis↗
PubMed1995

Prevention of restenosis after coronary angioplasty: towards a molecular approach?

Restenosis after coronary angioplasty, the main limitation of interventional cardiology, remains an unsolved issue. The failure to-date of all pharmacological attempts at prevention has prompted the development of alternative strategies. A mechanistic approach to the problem of restenosis is based on the assumption that creating a more satisfactory acute angioplasty result would reduce the development of restenosis. With the exception of coronary stenting, however, none of the new angioplasty devices have convincingly reached this goal. Furthermore, recent advances in the field of vascular biology have opened new avenues for a molecular approach of restenosis. Better understanding of the pathophysiology of restenosis, in conjunction with high-pace development of catheter, polymer, and virus technologies, provide opportunities to deliver agents--drugs, genes, or antisense oligonucleotides--locally, at the site of angioplasty to interfere specifically with the restenosis process. Some of these molecular strategies are currently being investigated in animal models. Clinical application of a molecular approach to prevent restenosis, however, will require close collaboration between physicians, molecular biologists, and bio-engineers.

Angioplasty, Balloon, Coronary↗
PubMed1995

Low-efficiency of percutaneous adenovirus-mediated arterial gene transfer in the atherosclerotic rabbit.

Recombinant adenoviruses are the most efficient vectors with which to perform arterial gene transfer. Previous in vivo studies of adenovirus-mediated arterial transfection, however, have been performed using normal or endothelium-denuded arteries. It is unclear whether these results can be extended to atherosclerotic arteries. Accordingly, this study was designed to (a) assess the feasibility of adenovirus-mediated gene transfer to atherosclerotic lesions, and (b) compare the transfection efficiency, anatomic distribution of transfected cells, and duration of transgene expression achieved in normal versus atherosclerotic arteries. A recombinant adenovirus including a nuclear-targeted beta-galactosidase gene was percutaneously delivered to the iliac artery of normal (n = 25) and atherosclerotic (n = 25) rabbits. Transgene expression, assessed by morphometric as well as chemiluminescent analyses, was documented in all normal and atherosclerotic arteries between 3 and 14 d after gene transfer, but was undetectable at later time points. Transfected cells were identified as smooth muscle cells located in the media of normal arteries, and in the neointima and the vasa-vasora of atherosclerotic arteries. Two percent of medial cells, but only 0.2% of medial and neointimal cells expressed the transgene in normal and atherosclerotic arteries, respectively (P = 0.0001). Similarly, nuclear beta-galactosidase activity was higher in normal than in atherosclerotic arteries (3.2 vs. 0.8 mU/mg protein, P = 0.02). These findings indicate that atherosclerosis reduces the transfection efficiency which can be achieved with adenoviral vectors, and thus constitutes a potential limitation to adenovirus-based, arterial gene therapy.

Adenoviruses, Human↗
PubMed1994

Physiological, biochemical and molecular processes associated with gravitropism in roots of maize.

This research aims to characterize regulation of the principal cytosolic protein kinases in maize, cultivar 'Merit' root tips, since much evidence indicates that stimuli which modulate the gravitropic response in this system act through regulation of activity of these enzymes. To this end, we have cloned a maize protein kinase belonging to a group of plant protein kinases with a catalytic domain similar in primary structure to the second messenger-regulated protein kinases known in animal and fungal systems. However, both the unique structural features conserved among plant protein kinases in this group, and lack of evidence for cyclic nucleotide signalling in plants point to operation of a novel protein kinase regulatory mechanism in plants. In order to test effects of possible regulators on protein kinase activity, we developed a sensitive method for detecting regulation of autophosphoryl labelling of protein kinases in unfractionated maize protein extracts. Regulation of protein kinase autophosphorylation in these extracts was different from that known in animals and fungi, further suggesting operation of unique protein kinase regulatory mechanisms in plants. Previous research has shown that light, or factors modulated by light, regulate plant protein kinase activity. We found that protein kinase activity was co-immunoprecipitated with the plant photoreceptor phytochrome, and was associated with phytochrome by high-affinity chemical interactions. Far-red reversibility of red-light regulation of phytochrome phosphorylation by the associated protein kinase indicates that it may modulate or transduce the light signals which lead to gravitropic sensitivity in 'Merit' maize.

Calcium↗
PubMed1994

Modulation of the expression of the granulocyte adhesion molecule, CR3, by percutaneous transluminal coronary angioplasty and contrast media.

RATIONALE AND OBJECTIVES: The effects of percutaneous transluminal coronary angioplasty (PTCA) and iodinated contrast media on the functional state of polymorphonuclear leukocytes (PMN) were determined; the expression of the PMN adhesion molecule, CR3, was assessed. METHODS: CR3 expression was measured by flow cytometry in whole blood samples in vivo, before and after PTCA (n = 17) or coronary angiography (n = 16); and in vitro, before and after incubation of PMNs with iodinated contrast media (n = 5). RESULTS: CR3 expression (mean +/- standard error of the mean, arbitrary units) decreased significantly after PTCA (221 +/- 25 to 168 +/- 21, P < .005) and coronary angiography (297 +/- 43 to 218 +/- 25, P < .05). In vitro, there was a dose-dependent decrease of CR3 expression and a significant and strong inverse correlation between CR3 expression and the contrast agent concentrations regardless of the type of contrast agent used. CONCLUSIONS: These data suggest that PTCA does not activate circulating PMNs, and that contrast media decrease CR3 expression. Whether this is related to the systemic adverse effects of contrast media remains to be clarified.

Angioplasty, Balloon, Coronary↗
PubMed1994

Pr-specific phytochrome phosphorylation in vitro by a protein kinase present in anti-phytochrome maize immunoprecipitates.

Protein kinase activity has repeatedly been found to co-purify with the plant photoreceptor phytochrome, suggesting that light signals received by phytochrome may be transduced or modulated through protein phosphorylation. In this study immunoprecipitation techniques were used to characterize protein kinase activity associated with phytochrome from maize (Zea mays L.). A protein kinase that specifically phosphorylated phytochrome was present in washed anti-phytochrome immunoprecipitates of etiolated coleoptile proteins. No other substrate tested was phosphorylated by this kinase. Adding salts or detergents to disrupt low-affinity protein interactions reduced background phosphorylation in immunoprecipitates without affecting phytochrome phosphorylation, indicating that the protein kinase catalytic activity is either intrinsic to the phytochrome molecule or associated with it by high-affinity interactions. Red irradiation (of coleoptiles or extracts) sufficient to approach photoconversion saturation reduced phosphorylation of immunoprecipitated phytochrome. Subsequent far-red irradiation reversed the red-light effect. Phytochrome phosphorylation was stimulated about 10-fold by a co-immunoprecipitated factor. The stimulatory factor was highest in immunoprecipitates when Mg2+ was present in immunoprecipitation reactions but remained in the supernatant in the absence of Mg2+. These observations provide strong support for the hypothesis that phytochrome-associated protein kinase modulates light responses in vivo. Since only phytochrome was found to be phosphorylated, the co-immunoprecipitated protein kinase may function to regulate receptor activity.

Antibodies↗
PubMed1994

Arterial gene transfer to rabbit endothelial and smooth muscle cells using percutaneous delivery of an adenoviral vector.

BACKGROUND: Previous investigations in live animals convincingly established that arterial gene transfer, while feasible, was compromised by a low transfection efficiency. More recent studies have shown that transfection efficiency may be substantially augmented by the use of recombinant adenoviral vectors. Most in vivo transfections reported to date, however, have used direct (operative) administration of the adenoviral vector. Clinical applications of arterial gene transfer (such as prevention of restenosis), however, would require local percutaneous delivery of the transgene. The present study was designed to extend in vivo intraoperative findings to percutaneous delivery system and to assess whether gene transfer remains site specific. METHODS AND RESULTS: A recombinant, replication-defective adenovirus modified to include an expression cassette for nucleus-targeted beta-galactosidase was introduced into rabbit iliac arteries in vivo using either a double-balloon catheter (DBC, n = 27) or a hydrogel-coated balloon catheter (HBC, n = 27). Contralateral arteries-normal, endothelium-denuded, or sham-transfected with a control adenoviral vector-served as controls. beta-Galactosidase expression was assessed by X-Gal staining. Cell-transduction efficiency was measured by morphometric analysis. Polymerase chain reaction (PCR) and histochemistry were used to detect the presence and/or expression of viral DNA in remote organs. Transgene expression was detected in all cases (46 of 46) between 3 and 14 days after transfection but was in no case detectable 28 days after transfection. In the DBC group, transgene expression was limited to endothelial cells when the endothelium was left intact and to rare medial cells (< 2.2%) when it had been removed. In contrast, HBC delivery resulted in transduction of up to 9.6% of medial smooth muscle cells (P = .0001). Optimized PCR and histochemistry failed to detect evidence of extra-arterial transfection except in a small number of cells (between 1 in 3 x 10(2) and 1 in 3 x 10(5) cells) in the livers of 2 animals in the DBC group. CONCLUSIONS: (1) Efficient, adenovirus-mediated, arterial gene transfer to endothelial and/or smooth muscle cells is feasible by percutaneous, clinically applicable techniques. (2) Consistent transfection of medial smooth muscle cells may be achieved when the endothelial layer is abraded. (3) Medial transfection is more efficient when an HBC, rather than a DBC, is used. (4) Percutaneous delivery of the adenoviral vector via HBC results in site-specific arterial gene transfer. Very-low-level extra-arterial transfection may occur, however, when the DBC is used.

Adenoviridae↗
PubMed1993

Inhibitory effects of KN-93, an inhibitor of Ca2+ calmodulin-dependent protein kinase II, on light-regulated root gravitropism in maize.

Light is essential for root gravitropism in Zea mays L., cultivar Merit. It is hypothesized that calcium mediates this light-regulated response. KN-93, an inhibitor of calcium/calmodulin kinase II (CaMK II), inhibits light-regulated root gravitropism but does not affect light perception. We hypothesize that CaMK II, or a homologue, operates late in the light/gravity signal transduction chain. Here we provide evidence suggesting a possible physiological involvement of CaMK II in root gravitropism in plants.

Benzylamines↗
PubMed1991

Regulation of phytochrome message abundance in root caps of maize.

In many cultivars of maize (Zea mays L.) red light affects root development via the photomorphogenetic pigment phytochrome. The site of perception for the light is the root cap. In the maize cultivar Merit, we investigated phytochrome-mediated events in the cap. We established that the message encoded by the phyA1 gene was most abundant in dark-grown tissue and was asymmetrically distributed in the root cap, with greatest expression in the cells which make up the central columella core of the cap. Phytochrome message was negatively autoregulated in a specific region within the root cap. This autoregulation was sensitive to very-low-fluence red light, and thus was characterized as a phytochrome-mediated, very-low-fluence event. The kinetics of message reaccumulation in the dark were also examined and compared to the kinetics of the light requirement for root gravitropism in this cultivar. Similarly, the degree of autoregulation present in two other maize cultivars with different light requirements for gravitropic sensitivity was investigated. It appears that the Merit cultivar expresses a condition of hypersensitivity to phytochrome-mediated light regulation in root tissues. We conclude that phytochrome regulates many activities within the cap, but the degree to which these activities share common phytochrome-mediated steps is not known.

Darkness↗