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Biomedical subjects

J Van Pelt

Publications and source records attributed to J Van Pelt.

At least 19 recordsLinked to original sources
PubMed2005

Free fatty acid metabolism in the air-breathing African catfish (Clarias gariepinus) during asphyxia.

In several waterbreathing fish species, hypoxia induces a decrease in plasma free fatty acid (FFA) levels as opposed to an increase in air-breathing mammals. We hypothesised that this change is coupled to the mode of breathing. Therefore, we followed the metabolic response of cannulated air-breathing African catfish to an 8-h asphyxia period. The hematocrit and hemoglobin increased significantly upon asphyxia. However, no change was observed in the mean cellular hemoglobin concentration, indicating that more erythrocytes were brought into circulation. A continuous increase in plasma lactate concentration during asphyxia showed permanent activation of anaerobic glycolysis, pointing to a persistent oxygen shortage. Plasma glucose levels did not change, but FFA levels decreased significantly upon asphyxia with a concomitant increase in plasma noradrenaline levels. Thus, these results suggest that in the air-breathing African catfish noradrenaline mediated a decrease in plasma FFA levels similar to that in waterbreathing fish species.

Africa↗
PubMed2005

Cancer cell dissemination during curative surgery for colorectal liver metastases.

AIM: The amount of cancer cells disseminated during curative surgery for colorectal liver metastases (CRLM) may be responsible for recurrence. Haematogenous and intrahepatic cancer cell dissemination was evaluated, and its impact on cancer recurrence was assessed. METHOD: Twenty patients with resectable CRLM were included in a prospective study. Twelve patients underwent curative resection for 21 metastases. Ten selected metastases in eight patients were treated with radiofrequency ablation (RFA) followed by resection at the same operative session. Cancer cell dissemination was determined before, during and after surgery using 'real time' quantitative RT-PCR assay, based on detection and quantification of CEA and CK20 mRNA transcripts. RESULTS: Circulating cancer cells were detected in 80% and intrahepatic cancer cells in 37% of the patients, though without impact on cancer recurrence. The amounts of disseminated cancer cells were significantly increased after surgery. This increase was similar in patients treated with and without RFA. RFA caused complete tumour destruction. CONCLUSION: Curative surgery for CRLM significantly increases the amount of disseminated cancer cells. Radiofrequency ablation can completely destroy selected resectable CRLM without excessive cancer cell dissemination. Neither haematogenous nor intrahepatic cancer cell dissemination were related to cancer recurrence in this small patient series.

Aged↗
PubMed2004

Longterm stability and developmental changes in spontaneous network burst firing patterns in dissociated rat cerebral cortex cell cultures on multielectrode arrays.

Spontaneous action potentials were recorded longitudinally for 4-7 weeks from dissociated rat occipital cortex cells cultured on planar multi-electrode plates, during their development from isolated neurons into synaptically connected neuronal networks. Activity typically consisted of generalized bursts lasting up to several seconds, separated by variable epochs of sporadic firing at some of the active sites. These network bursts displayed discharge patterns with age-dependent firing rate profiles, and durations significantly increasing in the 3rd week in vitro and decreasing after about 1 month in vitro, when they evolved into short events with prompt onsets. These findings indicate that after about a month in vitro these cultured neuronal networks have developed a degree of excitability that allows almost instantaneous triggering of generalized discharges. Individual neurons tend to fire in specific and persistent temporal relationships to one another within these network bursts, suggesting that network connectivity maintains a core topology during its development.

Action Potentials↗
PubMed2004

Evaluation of the blood analyzer ABL 735 radiometer for determination of the percentage of fetal hemoglobin in fetal and neonatal blood.

OBJECTIVE: To evaluate the quality of measurements of percentage fetal hemoglobin (HbF) using the blood analyzer ABL 735 and to compare the results with the HbF measurements using the Biorad-Variant (the gold standard). METHODS: The percentage of HbF in fetal blood, obtained during intrauterine transfusions or from the umbilical cord blood of preterm and term babies, and from the red blood cells of adults who had given blood for transfusion, was determined spectrophotometrically (ABL-735) and by high pressure liquid chromatography (Biorad-Variant). Blood pH values were also measured with the ABL 735. Reproducibility (mean difference between duplo measurements) and the relationships between the HbF percentages measured by both methods were calculated. RESULTS: Reproducibility was independent of the HbF percentage and was more reliable with the Biorad-Variant method (0.3%) than with the ABL-735 method (2.1%). Regression analysis showed that the ABL-HbF percentages were often underestimated. Serious aberrations were observed at low pH values (<7.00) on the recalculated ABL-HbF percentages. For samples with pHs >7.00 a relatively good relationship was found between the pH-corrected ABL-HbF percentages and those of the Biorad-Variant values. CONCLUSION: The HbF percentage measured with the ABL blood analyzer is only moderately accurate if the HbF percentage is corrected for the pH.

Blood Chemical Analysis↗
PubMed1999

Use of digoxigenin-labelled probes for the quantitation of HBV-DNA in antiviral drug evaluation.

The use of digoxigenin-labelled probes was studied for quantitation of HBV-DNA during antiviral drug evaluation. Digoxigenin (dig)-labelled probes were generated either via incorporation of dig-dUTP in a polymerase chain reaction (PCR) or a random priming reaction. Using the PCR-labelled probe (delineating a 523 bp fragment in the core gene of the HBV) as little as 1 pg of immobilized HBV-DNA could be detected following an 8 h exposure of the hybridized membrane. A close correlation (r = 0.95) was found between the amount of HBV-DNA (range 2.5-200 pg) and the signal generated by the probe hybridized to its target DNA. By using a probe that was labelled with digoxigenin via random priming, the minimal quantity of immobilized HBV plasmid DNA that could be detected following an 8 h exposure was 4 pg, whereas a 32P-labelled probe, generated in parallel by random priming, allowed the detection of 16 pg of HBV plasmid DNA following a 4-day exposure. The PCR-generated digoxigenin-labelled probe proved to be useful for antiviral drug evaluation, i.e. to detect HBV-DNA in total cellular DNA from HBV-positive hepatoma cells (HepG2.2.15) that had either been treated with reference antiviral agents or left untreated. The 50% effective concentrations (EC50) that were calculated for inhibition of HBV-DNA production by lamivudine (3TC), penciclovir (PCV), lobucavir (LBV), adefovir (PMEA) and tenofovir (PMPA) were comparable to those reported in the literature. The use of digoxigenin-labelled probes thus appears to be a simple, convenient, rapid, reliable and non-radioactive method for use for anti-HBV screening. In addition, and in contrast to 32P-labelled probes, digoxigenin-labelled probes can be stored for >1 year without loss of specific activity, which makes these probes particularly attractive for large-scale antiviral drug evaluation purposes.

Antiviral Agents↗
PubMed1998

Growth of pyramidal, but not non-pyramidal, dendrites in long-term organotypic explants of neonatal rat neocortex chronically exposed to neurotrophin-3.

The present study was undertaken to determine the effects of neurotrophin-3 (NT3) and spontaneous bioelectric activity (SBA) on dendritic elongation and branching in long-term isolated organotypic explants of rat neocortex. Viral vector-directed expression of NT3 was used as an effective means to ensure a continuous, local production of the neurotrophic factor. Quantitative light microscopic measurement of dendritic branching patterns was carried out on Golgi-stained materials. Explants were exposed to an adenoviral vector encoding the genetic sequence for neurotrophin-3 (Ad-NT3), or to exogenous additions of the neuropeptide NT3. In order to test for activity-dependent growth effects under control and experimental conditions, explants were exposed to glutamatergic blockade using a cocktail of APV and DNQX. Both Ad-NT3 and NT3 peptide potently promoted apical and basal dendritic growth (elongation and branching) in pyramidal neurons. This growth was observed to be significant in layers II-IV and V. These growth effects were also not activity dependent, inasmuch as they were elicited from explants in which spontaneous bioelectric activity had been suppressed. Non-pyramidal neurons, throughout the neocortical slice, showed no significant dendritic responses to the prolonged presence of NT3. These findings show that pyramidal dendritic growth in long-term neocortical explants responds to at least one neurotrophic growth factor, NT3, and is independent of intrinsic bioelectric activity. The use of viral vectors in delivering a continuous high level of neurotrophic factor within developing neural tissues demonstrates its potential application to in vivo tissues during development, or in the stimulation of neuritogenesis and neuroregeneration following injuries.

Adenoviridae↗
PubMed1997

Cocultured, but not isolated, cortical explants display normal dendritic development: a long-term quantitative study.

Dendritic growth has been studied in long-term organotypic neonatal rat occipital neocortex grown either apart as isolated explants or in tandem as cocultures. Quantitative light microscopic measurement of dendritic and axonal branching patterns within the cortical slice was accomplished using rapid Golgi stained materials. In both isolates and cocultures the overall cellular organization of the slice was maintained over 4 weeks in vitro with morphologically distinguishable pyramidal and nonpyramidal neurons located within the same layers and with the same orientations as observed in situ. Long-term increases in the total length of basal dendrites, apical dendrite and axons were observed only in cocultures and were similar to growth patterns reported for in situ materials. Dendritic growth was mainly due to elongation of terminal dendritic segments. Surprisingly, isolated explants showed no long-term increases in total (basal) dendrites, apical dendrites or axons with time in vitro. A transient decrease in the number of basal dendritic segments and increase in terminal segment lengths at the end of the first week in vitro, however, was observed in nonpyramidal neurons. It is hypothesized that (i) afferent inputs and/or efferent targets develop only in cocultures and provide a crucial conditions for the continued growth of dendritic/axonal arborization for neocortical neurons in vitro, (ii) intrinsic interconnectivity within isolated explants is not sufficient to maintain long-term growth of neuritic arbors, and (iii) remodelling of dendritic arbors within isolated explants occurs at the same time as these explants are showing noticeable increases in the level of spontaneous bioelectric activity, which suggests that dendritic growth and network formation may be function dependent.

Animals↗
PubMed1995

Implications of activity dependent neurite outgrowth for neuronal morphology and network development.

Empirical studies have demonstrated that electrical activity of the neuron can directly affect neurite outgrowth. In this paper, we study the possible implications of activity-dependent neurite outgrowth for neuronal morphology and network development, using a model in which initially disconnected cells organize themselves into a network under the influence of their intrinsic activity. A neuron is modelled as a neuritic field, the growth of which depends on its own level of activity, and neurons become connected when their fields overlap. In a purely excitatory network, we have previously demonstrated that activity-dependent outgrowth in combination with a neuronal response function with some form of firing threshold is sufficient to cause a transient overproduction (overshoot) in the number of connections or synapses. Here we show that overshoot still takes place in a network of excitatory and inhibitory cells, and can even be enhanced. With delayed development of inhibition the growth curve of the number of inhibitory connections no longer exhibits overshoot. An interesting emergent property of the model is that, solely as the result of simple outgrowth rules and cell interactions, the (dendritic) fields of the inhibitory cells tend to become smaller than those of the excitatory cells, even if both type of cells have the same outgrowth properties. Other consequences of the interactions among outgrowth, excitation and inhibition are that (i) the spatial distribution of inhibitory cells becomes important in determining the level of inhibition; (ii) pruning of connections can no longer take place if the network has grown without proper electrical activity for longer than a certain critical period; (iii) inhibitory cells, by inducing outgrowth, can help to connect different parts of a structure. Further, the model predicts that excitatory cell death will be accompanied by an increased neuritic field of surviving neurons ("compensatory sprouting"). The similarities of the model with findings in developing tissue cultures of dissociated cells are extensively discussed.

Animals↗
PubMed1994

Neuritic growth rate described by modeling microtubule dynamics.

A model is developed to describe neuronal elongation as a result of the polymerization of microtubules and elastic stretching of the neurites by force produced by the growth cone. The model for a single segment with a single growth cone revealed a constant elongation rate, while the concentration of tubulin in the soma rises, and the concentration of tubulin becomes constant in the growth cone. Extending the model to a neurite with a single branch point and two growth cones revealed the same results. When the assembly or the disassembly rate of microtubules is unequal in both growth cones, transient retraction of one of the terminal segments occurs, which results in complete retraction of the segment when the difference in (dis)assembly rate between the two growth cones is large enough. When the model is applied to large trees, a maximal sustainable number of terminal segments as a function of the production rate of tubulin appears. Mechanisms to stop outgrowth are discussed in relation to the establishment of synaptical contacts between cells.

Animals↗
PubMed1992

Tree asymmetry--a sensitive and practical measure for binary topological trees.

The topological structure of a binary tree is characterized by a measure called tree asymmetry, defined as the mean value of the asymmetry of its partitions. The statistical properties of this tree-asymmetry measure have been studied using a growth model for binary trees. The tree-asymmetry measure appears to be sensitive for topological differences and the tree-asymmetry expectation for the growth model that we used appears to be almost independent of the size of the trees. These properties and the simple definition make the measure suitable for practical use, for instance for characterizing, comparing and interpreting sets of branching patterns. Examples are given of the analysis of three sets of neuronal branching patterns. It is shown that the variance in tree-asymmetry values for these observed branching patterns corresponds perfectly with the variance predicted by the used growth model.

Animals↗
PubMed1991

A comparative study of sialyloligosaccharides isolated from sialidosis and galactosialidosis urine.

Sialic acid-containing carbohydrates were isolated from sialidosis urine by a combination of gel-filtration on Bio-Gel P-6 and medium-pressure anion-exchange chromatography on Mono Q. The Mono Q fractions were subjected to 500-MHz 1H-NMR spectroscopy, sugar analysis and analytical HPLC on Lichrosorb-NH2. These methods indicated the presence of various N-acetyllactosamine type sialyloligosaccharides differing from each other in branching pattern and sialic acid linkage types. Among the structures were fully and partially sialylated mono-, di-, tri- and tetra-antennary compounds. A comparison with the results from galactosialidosis urine indicated that essentially the same carbohydrates were present in both urines, but that the relative amounts of the various sialyloligosaccharides differ to some extent. Sialidosis urinary oligosaccharides contained relatively more alpha 2-6 linked sialic acid than oligosaccharides from galactosialidosis urine. It could be concluded that the additional beta-galactosidase deficiency in galactosialidosis did not influence the nature of the excreted material and that the sialidase deficiency determined completely the defective catabolism of glycoproteins in both sialidosis and galactosialidosis.

Carbohydrate Conformation↗
PubMed1990

Analysis of binary trees when occasional multifurcations can be considered as aggregates of bifurcations.

The geometrical properties of neurons are important for the way they function within neural circuits. The arborescent processes of neurons that are necessary for the transmission of the information are formed by branching and elongation of segments. In studies that model the outgrowth the tree structures have generally been considered as binary. However, multifurcations do occur. It will be shown that if the multifurcations can be considered as aggregates of bifurcations they may be included in the topological analysis of neuronal branching patterns.

Animals↗
PubMed1988

Storage of sialic acid-containing carbohydrates in the placenta of a human galactosialidosis fetus. Isolation and structural characterization of 16 sialyloligosaccharides.

From the placenta of a human fetus with galactosialidosis, detected by prenatal diagnosis, sialyloligosaccharides were isolated by successively gel-permeation chromatography on Bio-Gel P-6, anion-exchange chromatography on Mono Q and high-performance liquid chromatography on Lichrosorb-NH2. 16 sialic acid-containing N-glycosidic N-acetyllactosamine type of structures were identified by sugar analysis and 500-MHz 1H-NMR spectroscopy. The fully sialylated oligosaccharides differ from each other in the type of branching (mono-, di-, tri-, tri'- and tetra-antennary) or sialic acid linkage types (alpha 2-3/alpha 2-6). The isolated carbohydrates, including six novel structures, can be presented as follows (the numerals in a column represents one compound). (formula; see text).

Carbohydrate Conformation↗
PubMed1988

Structural analysis of O-glycosidic type of sialyloligosaccharide-alditols derived from urinary glycopeptides of a sialidosis patient.

Sialidosis urine was fractionated by gel filtration on Bio-Gel P-6. All pooled fractions containing carbohydrates showed the presence of small amounts of GalNAc in non-reducing position, besides free N-acetyllactosamine type of oligosaccharides as major constituents. The fractions were subjected to reductive alkaline borohydride degradation, after which the major part of GalNAc was recovered as N-acetyl-D-galactosaminitol (GalNAc-ol). The GalNAc-ol-containing material was separated from the N-glycosidic oligosaccharides by a second gel-filtration step on AcA 202. Subsequently, the O-glycosidic sialyloligosaccharide-alditols were subfractionated by anion-exchange chromatography on Mono Q. Structural analysis by 500-MHz 1H-NMR spectroscopy revealed two major components in all fractions, namely: NeuAc alpha 2-3Gal beta 1-3GalNAc-ol and NeuAc alpha 2-3Gal beta 1-3[NeuAc alpha 2-6]GalNAc-ol. Furthermore, NeuAc alpha 2-3Gal beta 1-3[NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-6]GalNAc-ol was found as a minor component in some of the fractions. The presence of these carbohydrate chains in Bio-Gel fractions differing in molecular mass suggested that they are derived from glycopeptides which are heterogeneous in their peptide part.

Carbohydrate Conformation↗
PubMed1984

Sex-difference and left-right asymmetries in the prefrontal cortex during postnatal development in the rat.

Left over right asymmetries in volume have been found in two subareas of the medial prefrontal cortex (PFC), and a right over left in the orbital PFC. The asymmetries change during development, indicating differential growth rates for left and right PFC parts. The asymmetry of the medial PFC reached significance from day 10 until day 18 and at day 90. The asymmetry of the orbital PFC reached significance from day 30 until day 60. At day 90 no significant asymmetry is demonstrated in this part of the PFC. A significant sexual dimorphism was demonstrated for the dorsal agranular insular subarea (AId) in the orbital PFC.

Animals↗