Biomedical subjects

Dirk Petersen

Publications and source records attributed to Dirk Petersen.

16 recordsLinked to original sources

PubMed2006

Identification of fatty acid esters of pectenotoxin-2 seco acid in blue mussels (Mytilus edulis) from Ireland.

Pectenotoxins from marine dinoflagellates of the genus Dinophysis are rapidly hydrolyzed by many shellfish to give pectenotoxin-2 seco acid, which isomerizes to 7-epi-pectenotoxin-2 seco acid. Three series of fatty acid esters of pectenotoxin-2 seco acid (PTX-2 seco acid) and 7-epi-PTX-2 seco acid were detected by LC-MS analysis of extracts from blue mussels (Mytilus edulis) from Ireland. The locations of the fatty acid ester linkages were identified by a combination of LC-MSn in positive- and negative-ion modes, LC-MS analysis of the products from reaction of the esters with sodium periodate, and NMR analysis of purified samples of the two most abundant ester derivatives. The 37-O-acyl esters of PTX-2 seco acid were the most abundant, followed by the corresponding 11-O-acyl esters, accompanied by low levels of the 33-O-acyl esters. The most abundant fatty acid esters in the fractionated sample were, in order, the 16:0, 22:6, 14:0, 16:1, 18:4, and 20:5 fatty acids, although a wide array of other PTX-2 seco acid fatty acid esters were also present at low levels.

Animals↗

PubMed2006

Isolation and identification of a cis-C8-diol-ester of okadaic acid from Dinophysis acuta in New Zealand.

A cis-isomer of a C(8)-diol ester of okadaic acid (1) was isolated during large-scale purification of pectenotoxins (PTXs) from extracts of Dinophysis acuta collected from the west coast of South Island, New Zealand. The compound was identified by NMR spectroscopic and liquid chromatography-mass spectrometry (LC-MS) studies, and is the first reported cis-isomer of an okadaic acid C(8)-diol-ester identified in Dinophysis. The more abundant trans-C(8)-diol ester of okadaic acid (2) isolated from the same Dinophysis extract was rapidly hydrolyzed to okadaic acid in vitro by the supernatant from green-lipped mussel hepatopancreas.

Animals↗

PubMed2006

Thymidine secretion by hybridoma and myeloma cells.

Secretion of thymidine appeared to be a common property of hybridoma and myeloma cells, but not of other cell types, which were tested. Of three hybridoma cell lines tested, all secreted thymidine in amounts resulting in the accumulation of thymidine to concentrations of 10-20microM in the culture medium. Also three of five myeloma cell lines that were analyzed secrete thymidine, but none of the other cell types that were studied. Thymidine was purified to homogeneity (4mg purified from 3l of culture medium) and identified as such by nuclear magnetic resonance spectroscopy. The cells that secreted thymidine showed high resistance to the growth inhibitory effect of thymidine.

Animals↗

PubMed2006

Short communication controlling LC-SPE-NMR systems.

There are several stages of the LC-SPE-NMR process that should be monitored closely to ensure an efficient isolation and concentration of the target analyte, for instance analyte break-through and compound transfer from the LC-SPE to the NMR probe. In this study, analyte break-through monitoring was performed with a UV detector and a mass spectrometer placed after the SPE unit. Easy break-through was a problem when attempting multiple trapping of various compounds using C18 SPE cartridges with the original commercial system. However, on lowering the flow rate over the SPE system and using SPE cartridges packed with porous carbon, the number of trappings possible increased five-fold. To increase control over the on-line SPE-NMR transfer, a gradient pump-UV system was used to elute compounds trapped on an SPE to an NMR probe. The analyte band was placed in the active volume of the probe by a stop-flow mechanism. The modified LC-SPE system was also coupled with off-line NMR analysis for determination of a degradation product of the insecticide monuron, present in the low ppm range.

Journal Article↗

PubMed2006

Structures and structure-activity relationships of three mitogenic and complement fixing pectic arabinogalactans from the malian antiulcer plants Cochlospermum tinctorium A. Rich and Vernonia kotschyana Sch. Bip. ex Walp.

Structures of three pectic arabinogalactans, one from Vernonia kotschyana (Vk2a) and two from Cochlospermum tinctorium (Ct50A1 and Ct50A2), and their complement fixation and induction of B cell proliferation in vitro were compared. The polysaccharide Vk2a expressed potent biological activity in both assays compared with Ct50A1 and Ct50A2. Vk2a possessed a very high molecular weight (1150 +/- 20 kDa) compared with Ct50A1 and Ct50A2 which both showed a polydisperse nature with the highest molecular weight polymers in each fraction estimated at approximately 105 kDa (Ct1a) and 640 +/- 100 kDa (Ct2a), respectively. The HMW polymers showed complement fixation in the same range as the native fractions. The arabinogalactan II content was low in Vk2a (2%) compared with that in Ct50A1 (23%) and Ct50A2 (12%). The high molecular weight polymers were subjected to digestion with a beta-d-(1, 3)-galactanase-rich fraction from Driselase, oligomers were isolated by HPAEC, and their finer structures were determined by MALDI- and ES-qoToF-MS, linkage, and monosaccharide composition analyses. Vk2a consists of both a galacturonan core and a rhamnogalacturonan core rich in neutral side chains. The backbones of both Ct-polysaccharides consist mainly of RG-I regions with numerous neutral side chains dominated by galactosyl residues, whereas the homogalacturonan regions seem to be small. Differences in the chain lengths of the 6-linked galacto-oligosaccharides attached to the 3-linked galactan core could not be related to the differences in the potencies of the biological activities observed.

Amino Acids↗

PubMed2005

Synthesis and antimycobacterial activity of agelasine E and analogs.

Agelasine E, previously isolated from the marine sponge Agelas nakamurai, has been synthesized for the first time, together with analogs with various terpenoid side chains. Treatment of N6-methoxy-9-methyl-9H-purin-6-amine with allylic bromides gave the desired 7,9-dialkylpurinium salts together with minor amounts of the N6-alkylated isomer. The N6-methoxy group was finally removed reductively. 1H-15N HMBC and 1H-15N HSQC NMR spectroscopy gave additional information on tautomerism and charge delocalization in the purine derivatives studied. The heterocyclic products were screened for activity against Mycobacterium tuberculosis and agelasine analogs carrying a relatively long terpenoid substituent in the purine 7-position and a methoxy group at N-6 were potent inhibitors of bacterial growth. Since agelasine analogs with the geranylgeranyl chain at N-7 exhibited antimicrobial activity, several strategies for synthesis of geometrically pure (2E,6E,10E)-geranylgeranyl bromide from geranyllinalool were evaluated.

Anti-Bacterial Agents↗

PubMed2005

2-Amino-14,16-dimethyloctadecan-3-ol, a new sphingosine analogue toxin in the fungal genus Fusarium.

2-Amino-14,16-dimethyloctadecan-3-ol (2-AOD-3-ol) was isolated from the cytotoxic rice culture extract of a strain of Fusarium avenaceum, which had previously been isolated from Norwegian grain. The structural information was obtained from LC-MS/MS, GC-MS, NMR spectroscopy and high-resolution MS data. The metabolite has a striking similarity to sphinganine, an intermediate in the biosynthesis of the sphingolipids. This similarity is a major feature of the so-called sphingosine analogue toxins; the most studied being the AAL toxins and the fumonisins. 2-AOD-3-ol was found to be cytotoxic to the rat hepatoma cell line H4IIE-W and to the porcine epithelial kidney cell line PK(15) at concentrations (EC(50)) of 16 and 24 microM, respectively. The metabolite has been found in F. avenaceum inoculated wheat that was treated to support ideal conditions for Fusarium growth, demonstrating that the fungus has the potential to produce the metabolite under field conditions, which may occur in Northern Europe.

Animals↗

PubMed2005

Zebra sign: cerebellar bleeding pattern characteristic of cerebrospinal fluid loss. Case report.

Supratentorial subdural hematoma is a well-known complication following spinal interventions. Less often, spinal or supratentorial interventions cause remote cerebellar hemorrhage (RCH). The exact pathomechanism accounting for RCH remains unclear, but an interventional or postinterventional loss of cerebrospinal fluid (CSF) seems to be involved in almost all cases. Hemorrhage is often characterized by a typical, streaky bleeding pattern due to blood spreading in the cerebellar sulci. Three different cases featuring this bleeding pattern following spinal, supratentorial, and thoracic surgery are presented. Possible pathomechanisms leading to RCH are discussed. Based on data from the underlying cases and the reviewed literature, the authors concluded that this zebra-pattern hemorrhage seems to be typical in a postoperative loss of CSF, which should always be considered on presentation of this bleeding pattern.

Acute Disease↗

PubMed2004

Technical note: A toy as tool: a low-cost image analysis system for the evaluation of tumor size in experimental small animal models.

Image analysis systems are an essential tool in measurements of size of intraparenchymal tumors or lesions in experimental small animal models. Conventional image analysis systems are relatively expensive. We therefore compared the performance of a professional image analysis system with an inexpensive setup by evaluating tumor size in an orthotopic glioma mouse model. The maximum cross-sectional tumor area of H&E stained brain-slides of two groups of mice (treatment and control group) was measured by two independent investigators using a professional image analysis system (Leica DM IRB microscope) with the Leica Quantimet 500c software, and a low-cost-system (Intel QX3 microscope) with a non-commercial image analysis software. Mean tumor volumes were calculated and the results from each of the image analysis systems, investigators, and treatment effects were compared. The tumor volumes as measured with the low-cost and the professional system differed between -3.7 and +7.5% (P = 0.69-0.99). Measurements made by investigator A and B differed between -7.0 and +3.9% (P = 0.69-0.88). Treatment in all cases significantly reduced the tumor volume between 58.4 and 62.7% (P = 0.0002 or 0.0003), regardless of the investigator or the used image analysis system. We therefore conclude that the QX3 low-cost microscope in combination with a non-commercial image-analysis software represents an inexpensive solution to reliably analyze the size of regions of interest, if they provide a sufficient contrast. However, the low-cost setup due to its low resolution definitely limits a detailed analysis of histologic features.

Animals↗

PubMed2004

Prenylated flavonoids, monoterpenoid furanocoumarins and other constituents from the twigs of Dorstenia elliptica (Moraceae).

A monoprenylated flavan and two monoterpenoid substituted furanocoumarins were isolated from the twigs of Dorstenia elliptica along with 3-(3,3-dimethylallyl)-4,2',4'-trihydroxylchalcone, psoralen, bergapten, O-[3-(2,2-dimethyl-3-oxo-2H-furan-5-yl)butyl]bergaptol, beta-sitosterol and its beta-D-glucopyranoside. The structure of the flavan was determined as 6(1,1-dimethylallyl)-7,4'-dihydroxylflavan and the monoterpenoid substituted furanocoumarins were assigned as O-[3-(2,2-dimethyl-3-oxo-2H-furan-5-yl)-3-hydroxybutyl]-bergaptol and O-[2-(5-hydroxy-2,6,6-trimethyl-3-oxo-2H-pyran-2-yl)ethyl]bergaptol, respectively, using spectroscopic analysis, especially, 2D NMR spectra.

Flavonoids↗

PubMed2004

A novel pectenotoxin, PTX-12, in Dinophysis spp. and shellfish from Norway.

Two novel pectenotoxins (PTXs) were detected by LC-MS in solid phase extracts of net hauls taken at Flødevigen, Norway, in June 2002 that were dominated by Dinophysis acuminata and Dinophysis norvegica. The new compounds were isolated as minor components from a large collection of a Dinophysis acuta-dominated bloom obtained from Skjer, Sognefjorden, Norway, in October 2002. LC-MS and NMR analyses revealed that the new components, 36S-PTX-12 and 36R-PTX-12, occurred as a pair of equilibrating diastereoisomers differing from PTX-2 in that they contained an exocylic olefinic methylene rather than a methyl group at C-38. Analyses of shellfish extracts revealed that PTX-12 accumulated in Norwegian blue mussels (Mytilus edulis) and cockles (Cerastoderma edule), along with PTX-12 seco acids occurring as a complex mixture of diastereoisomers. LC-MS analysis of algal cells picked from the net haul from Flødevigen revealed that PTX-12 predominated in D. acuta and D. norvegica, whereas PTX-2 was the predominant pectenotoxin in D. acuminata. Preliminary observations indicate that the relative contents of PTX-2 and PTX-12 vary between sites and years in Norway, even within a single species of Dinophysis. Our data also suggest that heterotrophic dinoflagellates may accumulate toxins from their prey.

Animals↗

PubMed2004

Frontoethmoidal encephalocele with ocular leakage of cerebrospinal fluid. Case report.

The authors present the case of a 2-year-old boy who was born with a small bulging mass in the middle frontonasal area and hypertelorism. In the neonatal period he suffered from a continuous lacrimal secretion mistaken for recurrent conjunctivitis. Cranial computerized tomography scanning and magnetic resonance imaging revealed a frontoethmoidal encephalocele associated with an ocular leakage of cerebrospinal fluid. One-stage repair of the encephalocele, along with correction of hypertelorism and bone grafting of the forehead, was performed with good result. During a 2-year follow-up period no neurological deficits appeared.

Cerebrospinal Fluid↗

PubMed2003

Modulation of cerebellar activation by predictive and non-predictive sequential finger movements.

We investigated the modulation of cerebellar activation by predictive and non-predictive sequential finger movements. It is hypothesized that the prediction of desired movement sequences and adaptation to new movement parameters is mediated by the cerebellum. Using functional MRI at 1.5 T, seven normal subjects performed sequential finger to thumb opposition movements, either in predictive (repeatedly 2,3,4,5) or non-predictive (randomized) fashion at a constant frequency of 1 Hz. Performance and error rates were monitored by simultaneous recording of the finger movements. Predictive sequential finger opposition movements activated a cerebellar network including the lobuli IV-VI ipsilateral to the movements, the contralateral lobuli IV-VI, the vermis, and lobuli VIIB-VIII ipsilaterally. Non-predictive compared to predictive finger opposition movements activated a broader area within the ipsi- and contralateral anterior cerebellum, lobuli IV-VI, the vermis, and the ipsilateral lobuli VIIB-VIII. Additional activation foci were found in the contralateral lobuli VIIA and VIIB-VIII. Our study demonstrates a modulated information processing within the cerebellar network dependent on the predictability of movement sequences.

Brain Mapping↗

PubMed2002

Cerebral dicarboxylate transport and metabolism studied with isotopically labelled fumarate, malate and malonate.

Transport and metabolism of dicarboxylates may be important in the glial-neuronal metabolic interplay. Further, exogenous dicarboxylates have been suggested as cerebral energy substrates. After intrastriatal injection of [(14) C]fumarate or [(14) C]malate, glutamine attained a specific activity 4.1 and 2.6 times higher than that of glutamate, respectively, indicating predominantly glial uptake of these four-carbon dicarboxylates. In contrast, the three-carbon dicarboxylate [(14) C]malonate gave a specific activity in glutamate which was approximately five times higher than that of glutamine, indicating neuronal uptake of malonate. Therefore, neurones and glia take up different types of dicarboxylates, probably by different transport mechanisms. Labelling of alanine from [(14) C]fumarate and [(14) C]malate demonstrated extensive malate decarboxylation, presumably in glia. Intravenous injection of 75 micromol [U-(13) C]fumarate rapidly led to high concentrations of [U-(13) C]fumarate and [U-(13) C]malate in serum, but neither substrate labelled cerebral metabolites as determined by (13) C NMR spectroscopy. Only after conversion of [U-(13) C]fumarate into serum glucose was there (13) C-labelling of cerebral metabolites, and only at <10% of that obtained with 75 micromol [3-(13) C]lactate or [2-(13) C]acetate. These findings suggest a very low transport capacity for four-carbon dicarboxylates across the blood-brain barrier and rule out a role for exogenous fumarate as a cerebral energy substrate.

Acetates↗

PubMed2002

Complete asymptomatic thrombosis and resorption of a congenital giant intracranial aneurysm.

Intracranial aneurysms in infants are rare, but are associated with a high risk of rupture and subarachnoid hemorrhage. The authors report a case of an incidentally diagnosed, probably congenital, asymptomatic giant aneurysm of the posterior communicating artery in a 9-month-old girl, which completely thrombosed following a diagnostic superselective angiography without any neuropathological incident. Follow-up magnetic resonance imaging revealed that the aneurysm decreased further in size and was largely resorbed within 3 years after the initial finding. In single cases the natural history of congenital giant aneurysms may be better than previously assumed.

Cerebral Angiography↗

PubMed2001

Comparison in myelography between iodixanol 270 and 320 mgI/ml and iotrolan 300 mgI/ml: a multicentre, randomised, parallel-group, double-blind, phase III trial.

The objective of the trial was to compare the safety and efficacy of the non-ionic, dimeric, isotonic contrast medium iodixanol (Visipaque 270 and 320 mgI/ml) with those of iotrolan (Isovist 300 mgI/ml) in myelography. After lumbar or cervical puncture, 315 patients were examined in a multicentre, double-blind, randomised, comparative myelography study. Image quality, changes in vital signs, immediate and delayed adverse events were registered. There was a tendency for better images with iodixanol 320 than with iodixanol 270 and iotrolan 300, but the overall quality was good or excellent with all products. The frequency of patients reporting adverse events and headache varied much across centres, but there was no statistically significant difference between the contrast media. The incidence of events was higher after lumbar puncture than after cervical puncture, in women rather than in men, and after puncture with a 22-gauge (G) bevel-tipped needle compared with a 24 G Sprotte needle. The frequency of headache did not correlate with the absence of pathology. The higher iodine concentration in iodixanol 320 could be an advantage for film quality. When compared with iotrolan 300, iodixanol 320 and 270 give similar incidences of adverse events, including headache.

Contrast Media↗