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W T Hermens

Publications and source records attributed to W T Hermens.

At least 37 records · Page 2Linked to original sources
PubMed1998

Binding of prothrombin and its fragment 1 to phospholipid membranes studied by the solvent relaxation technique.

The phospholipid headgroup mobility of small unilamellar vesicles composed of different mixtures of phosphatidyl-L-serine (PS) and phosphatidylcholine is characterized by the solvent relaxation behavior of the polarity sensitive dyes 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and 6-palmitoyl-2-[trimethylammoniumethyl]-methylamino]naphthalene chloride (Patman). If the PS content exceeds 10%, the addition of calcium leads to a substantial deceleration of the solvent relaxation of both dyes, indicating the formation of Ca(PS)2 complexes. Addition of prothrombin and its fragment 1 leads to a further decrease of the headgroup mobility, as explained by the binding of more than two PS-molecules by a single protein molecule. Prodan monitors the outermost region of the bilayer and it clearly distinguishes between the binding of prothrombin and its fragment 1. The deeper incalated Patman does not distinguish between both proteins. The validity of the solvent relaxation technique for the investigation of the membrane binding of peripheral proteins is demonstrated by the studies of prothrombin induced changes in the steady-state fluorescence anisotropies of 1,6-diphenyl-1,3, 5-hexatriene.

2-Naphthylamine↗
PubMed1998

Suppression of inflammation by dexamethasone prolongs adenoviral vector-mediated transgene expression in the facial nucleus of the rat.

Adenoviral vector directed gene transfer to rat facial motoneurons occurs efficiently following intra-parenchymal injection of relatively high dosages (> or =10(7) pfu per injection) of a prototype first generation adenoviral vector. However, high level of transgene expression, as observed during the first week following administration of the adenoviral vector, declines during the second and third weeks and is associated with a local inflammatory response. In the present study rats were treated with dexamethasone to suppress the inflammatory response that occurs following administration of a first generation adenoviral vector and the effect of dexamethasone treatment on the duration of transgene expression was studied. Dexamethasone-treated rats displayed a reduced infiltration of macrophages and intra-parenchymal T-cells were not detectable at 14 days post-infusion of the viral vector. Transduced astrocytes persisted following treatment with dexamethasone, whereas only a few transduced motoneurons survived. In conclusion, suppression of inflammation by dexamethasone has a beneficial effect on the survival of transduced astroglial cells but exerts only moderate protection on transduced facial motoneurons.

Adenoviridae↗
PubMed1998

Thrombolytic therapy does not change the release ratios of enzymatic and non-enzymatic myocardial marker proteins.

Measurements of cardiac marker proteins in plasma from patients with acute myocardial infarction (AMI) have become important in the evaluation of recanalization therapy. The validity of this approach has however been questioned, because it was claimed that coronary reperfusion may increase the recovery in plasma of cardiac enzymes, such as creatine kinase (CK). In the present study, possible effects of thrombolytic therapy on the release of enzymatic and nonenzymatic marker proteins were investigated. Activities of CK and lactate dehydrogenase (LDH), and concentrations of myoglobin (Mb) and fatty acid-binding protein (FABP) were determined in serial plasma samples obtained from 50 patients with confirmed AMI, of whom 36 received thrombolytic therapy, and 14 did not. Treatment delay was 2.8+/-1.6 (mean+/-SD) h, and hospital delay in untreated patients was 2.7+/-1.8 h. Average infarct size, expressed in gram-equivalents of heart muscle per litre of plasma (g-eq/l), varied between 5.5 and 7.2 g-eq/l for the four marker proteins in patients treated with thrombolytic therapy, and between 4.6 and 6.4 g-eq/l in untreated patients, with a tendency to larger infarct sizes for Mb and FABP than for CK and LDH. Thrombolytic therapy, although significantly accelerating protein release rates, did not influence the release ratios. These results indicate that thrombolytic therapy has no significant effects on the recovery of cardiac marker proteins in plasma.

Aged↗
PubMed1998

Fatty acid-binding protein and the early detection of acute myocardial infarction.

Fatty acid-binding protein (FABP) is a newly introduced plasma marker of acute myocardial infarction (AMI). The plasma kinetics of FABP (15 kD) closely resemble those of myoglobin (18 kD) in that elevated plasma concentrations are found within 3 h after AMI and return to normal generally within 12 to 24 h. This makes both myoglobin and FABP useful biochemical markers for the early assessment or exclusion of AMI. The myocardial tissue content of FABP (0.5 mg/g) is about five-fold lower than that of myoglobin (2.5 mg/g), but the reference plasma concentration of FABP (ca. 2 microg/l) is about 15-fold lower than that of myoglobin (ca. 32 microg/l), together suggesting a superior performance of FABP for the early detection of AMI. Indeed, in a study including blood samples from 83 patients with confirmed AMI, taken immediately upon admission to the hospital (< 6 h after AMI), the diagnostic sensitivity was significantly greater for FABP (78%, confidence interval 67-87%) than for myoglobin (53%, CI 40-64%) (P < 0.05). In addition, the differences in contents of myoglobin and FABP in heart and skeletal muscles and their simultaneous release upon muscle injury allow the plasma ratio of myoglobin/FABP to be applied for discrimination of myocardial (ratio 4-5) from skeletal muscle injury (ratio 20-70). Rapid and sensitive immunochemical assay systems for FABP in plasma are now being developed and soon will enable the introduction of this marker in clinical practice.

Adult↗
PubMed1998

Transgene expression in rat fetal brain grafts is maintained for 7 months after ex vivo adenoviral vector-mediated gene transfer.

Fetal brain tissue fragments containing the suprachiasmatic nucleus were infected with an adenoviral vector containing the marker gene LacZ encoding for beta-galactosidase, and subsequently cultured or transplanted in the third ventricle of SCN-lesioned adult Wistar rats. In previous studies we optimized the infection procedure and characterized the immunological response directed against the viral vector in this model. The present study reports on beta-gal expression for at least 7 months in neuronal and glial cells. Maturation of the transplanted fetal SCN with respect to immunoreactivity for vasoactive intestinal polypeptide and C-terminal propressophysin was not hampered by the viral infection.

Adenoviridae↗
PubMed1998

Demonstration of ischemia-reperfusion injury separate from postoperative infarction in coronary artery bypass graft patients.

BACKGROUND: In patients undergoing coronary artery bypass grafting there are two possible causes of myocardial injury: (1) global ischemic myocardial injury during aortic cross-clamping and subsequent reperfusion, and (2) postoperative myocardial infarction. We studied the use of cardiac marker proteins to specifically and separately detect such injury. METHODS: Serum levels of enzymes (creatine kinase and creatine kinase-MB) and nonenzymatic proteins (fatty acid-binding protein and myoglobin) were measured in 8 low-risk patients undergoing coronary artery bypass grafting with cardiopulmonary bypass, 8 low-risk patients undergoing coronary artery bypass grafting without cardiopulmonary bypass, and 39 high-risk patients undergoing coronary artery bypass grafting with cardiopulmonary bypass, of whom 7 experienced a postoperative myocardial infarction. RESULTS: At 0.5 hours after reperfusion significantly increased plasma levels of all markers were noted in patients having the operation with cardiopulmonary bypass, but not in patients having the operation without cardiopulmonary bypass. In patients who had a postoperative myocardial infarction, a second significant increase of each marker was found, but that of fatty acid-binding protein was recorded 4 hours earlier than that of creatine kinase, creatine kinase-MB, or myoglobin. CONCLUSIONS: Perioperative myocardial injury can be diagnosed from the release of cardiac marker proteins into plasma already at 0.5 hours after the start of reperfusion. For early assessment of postoperative myocardial infarction, fatty acid-binding protein is a more suitable plasma marker than are creatine kinase, creatine kinase-MB, or myoglobin.

Adult↗
PubMed1998

Viral vectors, tools for gene transfer in the nervous system.

Viral vectors are becoming increasingly important tools to investigate the function of neural proteins and to explore the feasibility of gene therapy to treat diseases of the nervous system. This gene transfer technology is based on the use of a virus as a gene delivery vehicle. In contrast to functional analysis of gene products in transgenic mouse, viral vectors can be applied to transfer genes to somatic, post-mitotic cells of fully developed animals. To date, five viral vector systems are available for gene transfer in the nervous system. These include recombinant and defective herpes viral vectors, adenoviral vectors, adeno-associated viral vectors and lentiviral vectors. Of these vectors herpes and adenoviral vectors are the most common in use. To date, one of the main hurdles in applying these two vector systems is the focal immune response that occurs following intraparenchymal infusion. Despite this limitation, herpes and adenoviral vectors have been used successfully to modify the physiological response to injury in several rodent models of neurodegeneration. The first purpose of this review is to describe the principles of the generation of viral vectors and to discuss the advantages and disadvantages of the viral vector systems currently in use for gene transfer in the nervous system. Secondly, we give an overview of the performance of these vectors following direct infusion in the nervous system and review the results obtained with these vectors in animal models of neurodegeneration and regeneration. The results of these initial studies have provided a framework for future experiments based on gene transfer strategies with viral vectors to study normal physiology and pathology of the nervous system.

Adenoviridae↗
PubMed1998

Adenoviral vector-mediated gene delivery to injured rat peripheral nerve.

Although much progress has been made, current treatments of peripheral nerve damage mostly result in only partial recovery. Local production of neurite outgrowth-promoting molecules, such as neurotrophins and/or cell adhesion molecules, at the site of damage may be used as a new means to promote the regeneration process. We have now explored the ability of an adenoviral vector encoding the reporter gene LacZ (Ad-LacZ) to direct the expression of a foreign gene to Schwann cells of intact and crushed rat sciatic nerves. Infusion of 8 x 10(7) PFU Ad-LacZ in the intact sciatic nerve resulted in the transduction of many Schwann cells with high levels of transgene expression lasting at least up to 12 days following viral vector administration. The efficacy of adenoviral vector delivery to a crushed nerve was investigated using three strategies. Injection of the adenoviral vector at the time of, or immediately after, a crush resulted in the transduction of only a few Schwann cells. Administration of the adenoviral vector the day after the crush resulted in the transduction of a similar number of Schwann cells 5 days after administration, as observed in uncrushed nerves. Regenerating nerve fibers were closely associated with beta-galactosidase-positive Schwann cells, indicating that the capacity of transduced Schwann cells to guide regenerating fibers was not altered. These results imply that the expression of growth-promoting proteins through adenoviral vector-mediated gene transfer may be a realistic option to promote peripheral nerve regeneration.

Adenoviridae↗
PubMed1997

Comparison of peak serum C-reactive protein and hydroxybutyrate dehydrogenase levels in patients with acute myocardial infarction treated with alteplase and streptokinase.

Peak serum C-reactive protein concentrations were measured in 146 patients randomized to receive streptokinase, alteplase, or a combination of streptokinase and alteplase in the GUSTO-I trial. Those receiving alteplase treatment had lower values than those receiving streptokinase or the combination treatment. Irrespective of treatment, complete reperfusion of the infarct-related artery (TIMI grade 3 flow) was associated with low peak serum C-reactive protein values.

Aged↗
PubMed1997

Adenoviral vector-mediated expression of B-50/GAP-43 induces alterations in the membrane organization of olfactory axon terminals in vivo.

B-50/GAP-43 is an intraneuronal membrane-associated growth cone protein with an important role in axonal growth and regeneration. By using adenoviral vector-directed expression of B-50/GAP-43 we studied the morphogenic action of B-50/GAP-43 in mature primary olfactory neurons that have established functional synaptic connections. B-50/GAP-43 induced gradual alterations in the morphology of olfactory synapses. In the first days after overexpression, small protrusions originating from the preterminal axon shaft and from the actual synaptic bouton were formed. With time the progressive formation of multiple ultraterminal branches resulted in axonal labyrinths composed of tightly packed sheaths of neuronal membrane. Thus, B-50/GAP-43 is a protein that can promote neuronal membrane expansion at synaptic boutons. This function of B-50/GAP-43 suggests that this protein may subserve an important role in ongoing structural synaptic plasticity in adult neurons and in neuronal membrane repair after injury to synaptic fields.

Adenoviridae↗
PubMed1997

Adenoviral vector-mediated gene expression in the nervous system of immunocompetent Wistar and T cell-deficient nude rats: preferential survival of transduced astroglial cells in nude rats.

In the present paper, we examined the effect of the adenoviral vector dosage, the role of T cells, and the influence of the presence of replication-competent adenovirus (RCA) in adenoviral vector stocks, on the efficacy of adenoviral vector-directed transgene expression in the facial nucleus of immunocompetent Wistar and athymic nude rats. A small number of motor neurons and glial cells was transduced at low dosages of viral vector (1 x 10(6) pfu) and in the absence of RCA, and transgene-expressing cells persisted throughout the 3-week period of observation. Intraparenchymal infusion of 2 x 10(7) pfu of a recombinant adenoviral vector free of RCA was required for optimal transduction of facial motor neurons. In Wistar rats, a biphasic immune response occurred at higher dosages of the vector (5 x 10(6) and 2 x 10(7) pfu) that was characterized by early infiltration of macrophages and the occurrence of T cells during the second week after injection of the vector. The immune response was associated with the loss of transduced neural cells. In nude rats, administration of an adenoviral vector free of RCA resulted in a macrophage response comparable to that in the Wistar rat and long-term survival of transduced astroglial cells. However, transduced motor neurons degenerated according to a similar time course as observed in Wistar rats. Small amounts of RCA (2 x 10(5) pfu) injected with 2 x 10(7) pfu recombinant viral vector particles resulted in an accelerated T cell response and a rapid elimination of transduced cells within 1 week in Wistar rats, whereas in nude rats transgene expression continued during this period. Taken together, these observations suggest that at the high viral vector loads necessary to achieve optimal transduction of the facial nucleus, T cells play a role in the degeneration of adenoviral vector-transduced astroglial cells. The adverse effects on neurons appear to be due to the observed inflammatory response or to direct adenoviral vector toxicity.

Adenoviridae↗
PubMed1997

Partial coverage of phospholipid model membranes with annexin V may completely inhibit their degradation by phospholipase A2.

Phospholipase A2 (PLA2)-mediated hydrolysis of membrane phospholipids was measured by ellipsometry, and the inhibition of this process by annexin V was studied. Planar membranes, consisting of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine (PC/PE/PS; 54:33:13, on molar basis), were degraded by pancreatic PLA2, and the rate of hydrolysis was limited to about 0.7%/min. The influence of graded coverage of the membrane with annexin V was studied. The degree of PLA2 inhibition was nonlinearly related to the amount of membrane-bound annexin V, and binding of only 12% and 54% of full membrane coverage resulted in, respectively, 50% and 93% inhibition. These findings indicate that the inhibition of PLA2-mediated hydrolysis by annexin V cannot be simply explained by shielding of phospholipid substrates from the enzyme. Moreover, the present results leave room for a role of endogenous annexin V in regulating phospholipid turnover in the plasma membrane of parenchymal cells such as cardiomyocytes.

Animals↗
PubMed1997

Adenoviral vector-directed expression of neurotrophin-3 in rat dorsal root ganglion explants results in a robust neurite outgrowth response.

The neurotrophins are a family of proteins that promote neuronal survival and neurite outgrowth during development and can also enhance the regeneration of injured adult neurons. The local and continuous delivery of these proteins at the site of injury is problematic, since this requires repeated intraparenchymal injections or the use of invasive canula-micropump devices. In the present study we report the generation and characterization of an adenoviral vector for a member of the neurotrophins, neurotrophin-3 (Ad-NT-3). Using Ad-NT-3, we examined the expression and biological activity of NT-3 in dorsal root ganglia (DRG) explant cultures. Gene transfer with Ad-NT-3 results in the synthesis of genuine NT-3 and in a dosage-dependent neurite outgrowth response in DRG explants. Transduction of DRG explants with a viral vector dosage of 5 x 10(5) to 5 x 10(6) plaque-forming units induced the formation of a dense halo of neurites comparable to outgrowth observed following the addition of 100 ng/mL exogenous NT-3. In addition, a single infection with Ad-NT-3 produced biologically active NT-3 for at least 20 days in culture, as evidenced by continued neurite extension. This indicates that adenoviral vector-mediated expression of NT-3 results in high-level production of biologically active NT-3 and could therefore be used as a strategy to promote the regeneration of injured peripheral and central nerve projections.

Adenoviridae↗
PubMed1997

Long-term transgene expression in fetal rat suprachiasmatic nucleus neurografts following ex vivo adenoviral vector-mediated gene transfer.

Ex vivo gene transfer to fetal suprachiasmatic nucleus (SCN)-containing solid piece neurografts was explored using a first-generation prototype adenoviral vector containing the reporter gene LacZ (Ad-LacZ). Transgene expression was examined at different intervals following grafting in the IIIrd ventricle of rat brain and was compared to that of explant cultures. Large numbers of beta-galactosidase-positive cells were observed 8 days postgrafting. The number of stained cells had decreased considerably at 21 days but transduced cells were still present at 70 days. In vitro culturing of infected SCN tissue revealed high expression up to 21 days, indicating that the in vivo and in vitro fates of Ad-LacZ-infected cells were different. The main reason for this difference appeared to be cell loss by necrosis in the initial phase after transplantation, a phenomenon not related to the infection with Ad-LacZ since it similarly occurred in control grafts. In vivo inflammatory responses, observed after immunostaining for macrophages and T-lymphocytes, were also comparable in control and Ad-LacZ-treated transplants, except that cytotoxic T-cells were observed in the Ad-LacZ-treated transplants and not in controls. The recruitment of these cells was, however, minor and primarily observed at 8 days postgrafting, indicating that a major immunological rejection of the transduced graft did not occur. In both control and Ad-LacZ-infected transplants similar survival and intraimplant neuritic growth of SCN cells were visible. Ex vivo gene transfer of solid piece fetal SCN grafts with adenoviral vectors therefore appeared to be a nontoxic long-term gene-introducing procedure. This would in principle enable the local production of neurotrophic factors within the transplant and has the potential to improve functional SCN neurografting.

Adenoviridae↗
PubMed1997

Thrombolysis-induced coronary reperfusion causes acute and massive interstitial release of cardiac muscle cell proteins.

OBJECTIVE: Reperfusion of the infarct-related artery in patients with acute myocardial infarction limits infarct size, but also causes accelerated release into plasma of cardiac tissue proteins. The latter effect could reflect either enhanced protein washout from the heart or abrupt disruption of myocyte membranes. The present study indicates that the latter mechanism prevails. METHODS: In 26 patients, patency of the infarct-related artery was determined by coronary angiography 90 min and 5-7 days after thrombolytic treatment. Continuous electrocardiography was performed during the first 24 h after admission. Cumulative release of myoglobin (Mb) and creatine kinase (CK) into plasma was calculated from frequently sampled plasma concentrations. RESULTS: In patients with a patent infarct-related artery after 90 min, onset of a rapid (> 50%) decrease in ST-vector magnitude coincided with an equally rapid increase in QRS-vector magnitude, and with a sudden onset of release into plasma of Mb as well as CK. In these patients, a maximal initial release rate was observed and cumulative release conformed closely to a simple model for sudden interstitial liberation of proteins. In contrast, protein release started more gradually and could not be fitted to this model, in patients with persistent occlusion of the infarct-related artery at 90 min and absence of ST-vector normalisation. CONCLUSIONS: Previous studies have demonstrated significant myocardial salvage by timely reperfusion therapy. Nevertheless, this study indicates that the moment of recanalisation of the infarct-related artery coincides with sudden and massive disruption of myocyte membranes. Attenuation of this effect, if possible, could further improve the benefits of reperfusion therapy.

Adult↗
PubMed1997

Transient gene transfer to neurons and glia: analysis of adenoviral vector performance in the CNS and PNS.

In this paper a detailed protocol is presented for neuroscientists planning to start work on first generation recombinant adenoviral vectors as gene transfer agents for the nervous system. The performance of a prototype adenoviral vector encoding the bacterial lacZ gene as a reporter was studied, following direct injection in several regions of the central and peripheral nervous system. The distribution of the cells expressing the transgene appears to be determined by natural anatomical boundaries and possibly by the degree of myelinization of a particular brain region. In highly myelinated areas with a compact cellular structure (e.g. the cortex and olfactory bulb) the spread of the viral vector is limited to the region close to the injection needle, while in areas with a laminar structure (e.g. the hippocampus and the eye) more widespread transgene expression is observed. Retrograde transport of the viral vector may serve as an attractive alternative route of transgene delivery. A time course of expression of beta-galactosidase in neural cells in the facial nucleus revealed high expression during the first week after AdLacZ injection. However, a significant decline in transgene expression during the second and third week was observed. This may be caused by an immune response against the transduced cells or by silencing of the cytomegalovirus promoter used to drive transgene expression. Taken together, the data underscore that for each application of adenoviral vectors as gene transfer agents in the nervous system it is important to examine vector spread in and infectability of the neural structure that is subject to genetic modification.

Adenoviruses, Human↗
PubMed1997

Adenovirus-mediated gene transfer in neurons: construction and characterization of a vector for heterologous expression of the axonal cell adhesion molecule axonin-1.

By homologous recombination, a first-generation adenovirus-based gene transfer vector, AdCMVax-1, was constructed as a means of manipulating the expression level of the axonal cell adhesion molecule axonin-1 in neurons and glial cells. AdCMVax-1 harbours the entire coding region of the chicken axonin-1 cDNA under the transcriptional control of the Cytomegalovirus enhancer/promoter in the early-region 1 of the viral genome. Characterization of AdCMVax-1 in vitro revealed highly efficient gene transfer and expression of recombinant axonin-1 in neurons and glial cells of dissociated rat dorsal root ganglia. Similar to its native counterpart, virus-derived axonin-1 was detected on the cell body, neurites, and growth cones of transduced neurons, occurred in a secreted and membrane-associated form, and could be cleaved from the membrane with phosphatidylinositol-specific phospholipase C. Functional characterization of recombinant axonin-1 revealed the same binding properties as previously reported for native axonin-1 isolated from the vitreous fluid of chicken embryos. In vivo gene transfer was studied by stereotactic injection of AdCMVax-1 in the dentate gyrus of the hippocampus and the facial nucleus in the brainstem of adult Wistar rats and revealed high level expression of recombinant axonin-1 in a subset of hippocampal neurons and motor neurons in the facial nucleus.

Adenoviruses, Human↗