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L Thomsen

Publications and source records attributed to L Thomsen.

At least 19 recordsLinked to original sources
PubMed2001

Indazolylamino quinazolines and pyridopyrimidines as inhibitors of the EGFr and C-erbB-2.

Described herein is the design and synthesis of indazolylaminopyridopyrimidines and quinazolines as inhibitors of the class 1 tyrosine kinase receptor family. Data is presented for N(4)-(1-benzyl-1H-indazol-5-yl)-N(6),N(6)-dimethylpyrido[3,4-d]pyrimidine-4,6-diamine 3B. This compound inhibited EGFr and c-erbB-2 enzymes selectively over other kinases. It inhibited the proliferation of a range of tumour cell lines in vitro and the growth of BT474 xenografts in SCID mice.

Animals↗
PubMed2001

Intra-epithelial vaccination with COPV L1 DNA by particle-mediated DNA delivery protects against mucosal challenge with infectious COPV in beagle dogs.

Protection against viral challenge with canine oral papillomavirus (COPV) was achieved by immunisation via particle-mediated DNA delivery (PMDD) of a plasmid encoding the COPV L1 gene to cutaneous and oral mucosal sites in beagle dogs. The initial dose of approximately 9 microg of DNA was followed by two booster doses at 6 week intervals. A similar approach was used to vaccinate a control group of animals with plasmid DNA encoding the Hepatitis B virus S gene. Following challenge at the oral mucosa with COPV all animals vaccinated with the COPV L1 gene were protected against disease. However five of six animals in the control group developed COPV induced papillomas at the oral mucosa. Both cell-mediated lymphoproliferative and humoral antibody responses to the DNA vaccine were observed. Our data indicate that PMDD of plasmid DNA can protect against mucosal challenge with papillomavirus.

Animals↗
PubMed2001

Intraspecific variation and host specificity of Entomophthora muscae sensu stricto isolates revealed by random amplified polymorphic DNA, universal primed PCR, PCR-restriction fragment length polymorphism, and conidial morphology.

The intraspecific variations of Entomophthora muscae s. str. associated with particular host species, Musca domestica and Delia radicum, sampled from different localities and different years in Denmark and the variation of E. muscae s. str. originating from different host taxa were investigated. The isolates were compared both by primary spore morphology and by three molecular methods: random amplified polymorphic DNA, universal primed PCR, and PCR-restriction fragment length polymorphism. Analyses of the different molecular data showed the same overall picture and separated E. muscae s. str. into two main groups with all the M. domestica isolates in one group and isolates from D. radicum, Coenosia tigrina, and Pegoplata infirma in the second group. E. muscae s. str. isolates from M. domestica also differ significantly from the rest of the E. muscae s. str. isolates with regard to the morphology of the primary conidia, which were bigger and contained significantly more nuclei per conidium. Several different E. muscae s. str. genotypes were documented and each type was restricted to a single host species, indicating a very high degree of host specificity at or below the level of the subfamily.

Animals↗
PubMed2000

Entomophthora muscae resting spore formation in vivo in the host Delia radicum.

The formation in vivo of Entomophthora muscae resting spores was investigated in the host, Delia radicum (cabbage root fly), by analysis of field data on the seasonal occurrence of E. muscae resting spores over 4 years. E. muscae resting spores in D. radicum were spherical with an average diameter of 39.4 microm, and the average numbers produced were estimated at 5.7 x 10(4) resting spores/female cadaver. Resting spores were found only after midsummer in D. radicum and almost exclusively in females. The proportion of infected females with resting spores was negatively correlated with average weekly day length after midsummer. We did not detect any significant year effect; thus, the results support the hypothesis that the photoperiod is the most important abiotic factor controlling E. muscae resting spore formation in D. radicum.

Animals↗
PubMed2000

The search for the origin of rhythmicity in intestinal contraction; from tissue to single cells.

More than a century ago, rhythmic propulsive contractile activity was observed in the intestine after blockade of nerve conduction, thus demonstrating a form of peristalsis that appeared to be under myogenic control. During this century, light and electron microscopic investigations provided the hypothesis that interstitial cells of Cajal (ICC) could be the cells of origin for this rhythmicity. In recent years, physiological studies demonstrated a link between the presence of electrical slow wave activity and the presence of ICC. The recognition that the ICC cell membrane harbours the Kit protein sparked rapid advancement in ICC research, and has been essential in the identification of ICC in tissue and in culture through Kit immunohistochemistry and kit mRNA reverse transcriptase polymerase chain reaction (RT-PCR). With these techniques, electrophysiology was carried out on positively identified single ICC in culture. These methods revealed that single ICC generate spontaneous rhythmic inward currents and slow waves in membrane potential, thus providing strong evidence that ICC generate the electrical pacemaker activity for the gut musculature.

Animals↗
PubMed2000

LabPatch, an acquisition and analysis program for patch-clamp electrophysiology.

An acquisition and analysis program, "LabPatch," has been developed for use in patch-clamp research. LabPatch controls any patch-clamp amplifier, acquires and records data, runs voltage protocols, plots and analyzes data, and connects to spreadsheet and database programs. Controls within LabPatch are grouped by function on one screen, much like an oscilloscope front panel. The software is mouse driven, so that the user need only point and click. Finally, the ability to copy data to other programs running in Windows 95/98, and the ability to keep track of experiments using a database, make LabPatch extremely versatile. The system requirements include Windows 95/98, at least a 100-MHz processor and 16 MB RAM, a data acquisition card, digital-to-analog converter, and a patch-clamp amplifier. LabPatch is available free of charge at http://www.fhs.mcmaster.ca/huizinga/.

Computer Graphics↗
PubMed1998

Morphological adaptations to induced changes in transepithelial sodium transport in chicken lower intestine (coprodeum): a study of resalination, aldosterone stimulation, and epithelial turnover.

Transepithelial sodium transport and epithelial morphology during short-term adaptation to resalination or aldosterone stimulation were studied in the chicken coprodeum. Coprodeum was sampled for light and electron microscopy after 0-3 days of resalination in hens on a low-NaCl diet and after 0-6 days of aldosterone stimulation in hens on a high-NaCl diet. Sodium transport was measured in vitro with Ussing chambers. Plasma osmolality and electrolyte concentrations were measured in aldosterone-stimulated hens. Epithelial proliferation and migration between 1 h and 16 days were investigated in chickens on high-NaCl and low-NaCl diets using a bromodeoxyuridine technique. Resalination abolished the otherwise high sodium transport within 1 day, while the height and number of microvilli, as well as the number of brush cells, decreased over 3 days. Aldosterone stimulation increased sodium transport, the height and number of microvilli, and the brush-cell number. Bromodeoxyuridine studies indicated an epithelial cell turnover of more than 16 days. The results thus demonstrate that epithelial cells have an unusual capacity to adjust rap- idly to variations in sodium intake. A strong correlation between structure and function was apparent.

Aldosterone↗
PubMed1998

Interstitial cells of Cajal generate a rhythmic pacemaker current.

Networks of interstitial cells of Cajal embedded in the musculature of the gastrointestinal tract are involved in the generation of electrical pacemaker activity for gastrointestinal motility. This pacemaker activity manifests itself as rhythmic slow waves in membrane potential, and controls the frequency and propagation characteristics of gut contractile activity. Mice that lack a functional Kit receptor fail to develop the network of interstitial cells of Cajal associated with Auerbach's plexus in the mouse small intestine and do not generate slow wave activity. These cells could provide an essential component of slow wave activity (for example, a biochemical trigger that would be transferred to smooth muscle cells), or provide an actual pacemaker current that could initiate slow waves. Here we provide direct evidence that a single cell, identified as an interstitial cell of Cajal by light microscopy, electron microscopy and expression of Kit mRNA, generates spontaneous contractions and a rhythmic inward current that is insensitive to L-type calcium channel blockers. Identification of the pacemaker of gut motility will aid in the elucidation of the pathophysiology of intestinal motor disorders, and provide a target cell for pharmacological treatment.

Animals↗
PubMed1997

Electrophysiological properties of neurones in the internal and external submucous plexuses of newborn pig small intestine.

1. Intracellular microelectrodes were used to identify three major electrophysiological categories of neurone in both the internal and external submucous plexuses of the porcine small intestine. 2. Two classes of neurone with a long-lasting after-hyperpolarization following their action potential were differentiated by the presence or absence of fast excitatory synaptic inputs (EPSPs) and were termed AH neurones. S neurones received fast EPSPs but did not display after-hyperpolarizations. 3. The mean resting membrane potentials of the three groups of neurones showed a similar trend in both plexuses, with significantly higher values for the two populations of AH neurone than for S neurones. No significant variation of input resistance with cell type was detected. Neuronal input resistance was significantly greater in the internal submucous plexus than in the external submucous plexus. 4. Over 80% of AH neurones in the internal submucous plexus displayed fast EPSPs but a similar percentage of AH neurones in the external submucous plexus did not show fast EPSPs. S neurones constituted 60% of cells studied in the internal submucous plexus but less than 30% of the cell population in the external submucous plexus. 5. This study of porcine submucous neurones has revealed both similarities and differences to previous work in the guinea-pig small intestine. The most contrasting features are the relative abundance and subclassification of AH neurones in the pig in addition to the apparent paucity of slow synaptic potentials. The differences in the neuronal profiles of the internal and external submucous plexuses may reflect a differentiation of function between the two enteric nerve networks.

Animals↗
PubMed1997

Synaptic communication between external and internal submucosal plexus neurones in the jejunum of the newborn pig?

Intracellular recordings were made from neurones in the internal submucosal plexus (ISP) of porcine small intestine and synaptic inputs were investigated by focal stimulation of nerve fiber tracts. Nicotinic fast excitatory potentials (e.p.s.p.s) were recorded in all neurones, but slow e.p.s.p.s and slow inhibitory potentials (i.p.s.p.s) were rarely seen. Membrane potential changes similar to those occurring during the slow e.p.s.p. and slow i.p.s.p. could be evoked by exogenous application of neurotransmitters, even in neurones failing to display a nerve-mediated response. We suggest that the predominant source of the slow synaptic inputs to the ISP may be the neurones of the external submucosal plexus (ESP). The failure to record slow e.p.s.p.s and i.p.s.p.s could be a consequence of the anatomical arrangement of the submucosal plexuses whereby interconnecting strands between the ISP and ESP are inaccessible to the focal stimulation.

Animals↗
PubMed1997

Electrophysiological classification of submucosal plexus neurones in the jejunum of the newborn pig.

Intracellular recordings were made from the internal and external submucosal ganglia of the porcine small intestine and neuronal properties were classified using two existing schemes for guinea-pig enteric neurones. In the first analysis, 77% of cells were designated as Type 4 since they were a heterogeneous population of neurones with the overlapping properties of S/Type 1 and AH/Type 2. The simplicity and usefulness of the second classification scheme was due to its emphasis on a single electrophysiological event, namely, the long-lasting after-hyperpolarization (AH) following the action potential. Eighty-eight percent of the cells studied were thus categorized as either AH (with an AH) or S (without an AH). All S neurones displayed fast synaptic potentials in response to stimulation of interganglionic fibre strands. AH neurones were subdivided into two groups dependent on whether they received fast synaptic inputs. Only by employing the second scheme of classification were differences in the neuronal characteristics and synaptic profiles between the two submucosal plexuses detected. It is concluded that the S and AH system of classification is the most appropriate method for the analysis of intracellular recordings from submucosal neurones in the porcine small intestine.

Animals↗
PubMed1997

Dissection of the external and internal submucous plexuses of the pig small intestine.

The submucous plexus of large mammals like dog, horse, cow, sheep, pig and man consists of more than one easily identified plexus. The divisions of the submucous plexus are known as the external submucous plexus and the internal submucous plexus. Recently findings have shown that there exists functional differences between the neuronal populations in the subdivisions of the submucous plexus in the small intestine of pigs. We report here how to obtain whole mounts of the submucous plexus containing both the internal and the external submucous plexus. The whole mounts from the submucous plexus of the pig contains almost no muscle and can be used in intracellular neuronal studies without adding nifedipine or equivalent L-type Ca2+ channel blockers to inhibit the contractions of the smooth muscle.

Animals↗
PubMed1996

Advanced computer control of electrophysiological experimentation.

A special configuration of the data acquisition software package Spike2 (CED) has been developed to allow interactive computer control of a current-clamp intracellular recording system. Using the 1401plus dedicated computer (CED) as an interface between the electrophysiological apparatus and a personal computer it was possible to have keyboard-control of intracellular current injection, single and repetitive pulse nerve stimulation, pressure ejection as well as on-going data acquisition. An analysis program was designed using the Spike2 programming language for the investigation of resting membrane properties, spike characteristics and synaptic input profiles of enteric neurones. The hardware configurations and associated software of our set-up may be of interest to electrophysiologists wishing to implement or extend a computer-based experimental system.

Data Display↗
PubMed1995

Cloning of two chitin synthase gene fragments from a protoplastic entomophthorale.

Chitin synthase expression was studied in spontaneously produced protoplasts and in hyphal bodies of the Entomophthorale species Entomophaga aulicae. The absence of wall in protoplasts was correlated to an absence of chitin synthase. Two chitin synthase activities with different biochemical characteristics have been detected in the hyphal bodies. Two chitin synthase gene fragments EaCHS1 and EaCHS2 of 600 bp were obtained using PCR amplification of genomic DNA. Their amino acid sequences showed 75% identity. Compared with other fungal chitin synthases, they belong to class II. EaCHS1 and EaCHS2 were used to probe total RNA from E. aulicae hyphal bodies and protoplasts. A single transcript of 2.4 kb hybridized only with EaCHS1 in protoplasts and hyphal bodies.

Amino Acid Sequence↗
PubMed1995

Unsaturated fatty acids are the active molecules of a glucan-synthase-inhibitory fraction isolated from entomophthoralean protoplasts.

A few entomophthoralean species are able to multiply in a protoplast form. The polysaccharide synthases which synthesize the cell wall are inactivated in this form. An inhibitor of one of the key enzymes of wall synthesis, glucan synthase, was isolated from entomophthoralean protoplasts, using silica column chromatography and HPLC. Thin-layer and gas chromatography revealed free fatty acids in the inhibitory fractions. These fatty acids, including long-chain unsaturated fatty acids, were shown to be responsible for the inhibition of glucan synthase. The fatty acids were generated during incubation of a protoplast homogenate for 36 h at 37 degrees C and were shown to be non-competitive and non-specific inhibitors of glucan synthase.

Aspergillus fumigatus↗
PubMed1994

Association between biosynthesis of nitric oxide and changes in immunological and vascular parameters in patients treated with interleukin-2.

Hypotension is a dose-limiting side effect of interleukin-2 (IL-2) therapy. This may be due to increased biosynthesis of the potent vasodilator nitric oxide (NO) induced by cytokines such as tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), which are known to be generated during IL-2 therapy. We describe the relationship between NO biosynthesis and changes in immunological and vascular parameters during IL-2 therapy in 13 patients with metastatic cancer. Plasma concentrations of neopterin and nitrite plus nitrate (NOx) were higher in cancer patients prior to treatment compared with normal subjects (neopterin; 10.8 +/- 1.4 vs. 2.0 +/- 0.4 ng ml-1, P < 0.001: NOx; 45 +/- 6 vs. 28 +/- 2 microM, P < 0.005). Pretreatment TNF-alpha and IFN-gamma plasma concentrations were not significantly different in cancer patients from those in controls. During infusion of IL-2 (18 x 10(6) international units m-2 per day for 5 days) these parameters increased, reaching maximal concentrations at day 3 for IFN-gamma and day 5 for TNF-alpha, neopterin and NOx. The maximal induced NOx correlated with maximal TNF-alpha (r = 0.60, P < 0.04), IFN-gamma (r = 0.63, P < 0.02) and neopterin (r = 0.66, P < 0.01). As plasma NOx concentrations increased, systolic blood pressure fell, reaching a minimum at day 3 despite a continued rise in NOx concentrations. These changes were accompanied by a continuous increase in pulse rate throughout the infusion period. These findings indicate that induction of NO biosynthesis contributes to hypotension induced during IL-2 therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopterins↗