PubMed Health⌕ Search

Biomedical subjects

R Amann

Publications and source records attributed to R Amann.

At least 37 records · Page 2Linked to original sources
PubMed2001

The species concept for prokaryotes.

The species concept is a recurrent controversial issue that preoccupies philosophers as well as biologists of all disciplines. Prokaryotic species concept has its own history and results from a series of empirical improvements parallel to the development of the techniques of analysis. Among the microbial taxonomists, there is general agreement that the species concept currently in use is useful, pragmatic and universally applicable within the prokaryotic world. However, this empirically designed concept is not encompassed by any of the, at least, 22 concepts described for eukaryotes. The species could be described as 'a monophyletic and genomically coherent cluster of individual organisms that show a high degree of overall similarity in many independent characteristics, and is diagnosable by a discriminative phenotypic property'. We suggest to refer it as a phylo-phenetic species concept. Here, we discuss the validity of the concept in use which we believe is more pragmatic in comparison with those concepts described for eukaryotes.

Bacteria↗
PubMed2001

Quantitative molecular analysis of the microbial community in marine arctic sediments (Svalbard).

Fluorescence in situ hybridization (FISH) and rRNA slot blot hybridization with 16S rRNA-targeted oligonucleotide probes were used to investigate the phylogenetic composition of a marine Arctic sediment (Svalbard). FISH resulted in the detection of a large fraction of microbes living in the top 5 cm of the sediment. Up to 65.4% +/- 7.5% of total DAPI (4',6'-diamidino-2-phenylindole) cell counts hybridized to the bacterial probe EUB338, and up to 4.9% +/- 1.5% hybridized to the archaeal probe ARCH915. Besides delta-proteobacterial sulfate-reducing bacteria (up to 16% 52) members of the Cytophaga-Flavobacterium cluster were the most abundant group detected in this sediment, accounting for up to 12.8% of total DAPI cell counts and up to 6.1% of prokaryotic rRNA. Furthermore, members of the order Planctomycetales accounted for up to 3.9% of total cell counts. In accordance with previous studies, these findings support the hypothesis that these bacterial groups are not simply settling with organic matter from the pelagic zone but are indigenous to the anoxic zones of marine sediments. Members of the gamma-proteobacteria also constituted a significant fraction in this sediment (6.1% +/- 2.5% of total cell counts, 14.4% +/- 3.6% of prokaryotic rRNA). A new probe (GAM660) specific for sequences affiliated with free-living or endosymbiotic sulfur-oxidizing bacteria was developed. A significant number of cells was detected by this probe (2.1% +/- 0.7% of total DAPI cell counts, 13.2% +/- 4. 6% of prokaryotic rRNA), showing no clear zonation along the vertical profile. Gram-positive bacteria and the beta-proteobacteria were near the detection limit in all sediments.

Archaea↗
PubMed2001

Isolation of novel pelagic bacteria from the German bight and their seasonal contributions to surface picoplankton.

We tested new strategies for the isolation of abundant bacteria from coastal North Sea surface waters, which included reducing by several orders of magnitude the concentrations of inorganic N and P compounds in a synthetic seawater medium. Agar plates were resampled over 37 days, and slowly growing colonies were allowed to develop by repeatedly removing all newly formed colonies. A fivefold increase of colonies was observed on plates with reduced nutrient levels, and the phylogenetic composition of the culture collection changed over time, towards members of the Roseobacter lineage and other alpha-proteobacteria. Novel gamma-proteobacteria from a previously uncultured but cosmopolitan lineage (NOR5) formed colonies only after 12 days of plate incubation. A time series of German Bight surface waters (January to December 1998) was screened by fluorescence in situ hybridization (FISH) with isolate-specific and general probes. During spring and early summer, a prominent fraction of FISH-detectable bacteria (mean, 51%) were affiliated with the Cytophaga-Flavobacterium group (CF) of the Bacteroidetes. One Cytophaga sp. lineage with cultured representatives formed almost 20% of the CF group. Members of the Roseobacter cluster constituted approximately 50% of alpha-proteobacteria, but none of the Roseobacter-related isolates formed populations of >1% in the environment. Thus, the readily culturable members of this clade are probably not representative of Roseobacter species that are common in the water column. In contrast, members of NOR5 were found at high abundances (>10(5) cells ml(-1)) in the summer plankton. Some abundant pelagic bacteria are apparently able to form colonies on solid media, but appropriate isolation techniques for different species need to be developed.

Animals↗
PubMed2001

Comparison of cellular and biomass specific activities of dominant bacterioplankton groups in stratified waters of the Celtic Sea.

A flow-sorting technique was developed to determine unperturbed metabolic activities of phylogenetically characterized bacterioplankton groups with incorporation rates of [(35)S]methionine tracer. According to fluorescence in situ hybridization with rRNA targeted oligonucleotide probes, a clade of alpha-proteobacteria, related to Roseobacter spp., and a Cytophaga-Flavobacterium cluster dominated the different groups. Cytometric characterization revealed both these groups to have high DNA (HNA) content, while the alpha-proteobacteria exhibited high light scatter (hs) and the Cytophaga-Flavobacterium cluster exhibited low light scatter (ls). A third abundant group with low DNA (LNA) content contained cells from a SAR86 cluster of gamma-proteobacteria. Cellular specific activities of the HNA-hs group were 4- and 1.7-fold higher than the activities in the HNA-ls and LNA groups, respectively. However, the higher cellular protein synthesis by the HNA-hs could simply be explained by their maintenance of a larger cellular protein biomass. Similar biomass specific activities of the different groups strongly support the main assumption that underlies the determination of bacterial production: different bacteria in a complex community incorporate amino acids at a rate proportional to their protein synthesis. The fact that the highest growth-specific rates were determined for the smallest cells of the LNA group can explain the dominance of this group in nutrient-limited waters. The metabolic activities of the three groups accounted for almost the total bacterioplankton activity, indicating their key biogeochemical role in the planktonic ecosystem of the Celtic Sea.

Animals↗
PubMed2001

Alpha- and beta-Proteobacteria control the consumption and release of amino acids on lake snow aggregates.

We analyzed the composition of aggregate (lake snow)-associated bacterial communities in Lake Constance from 1994 until 1996 between a depth of 25 m and the sediment surface at 110 m by fluorescent in situ hybridization with rRNA-targeted oligonucleotide probes of various specificity. In addition, we experimentally examined the turnover of dissolved amino acids and carbohydrates together with the microbial colonization of aggregates formed in rolling tanks in the lab. Generally, between 40 and more than 80% of the microbes enumerated by DAPI staining (4',6'-diamidino-2-phenylindole) were detected as Bacteria by the probe EUB338. At a depth of 25 m, 10.5% +/- 7.9% and 14.2% +/- 10.2% of the DAPI cell counts were detected by probes specific for alpha- and beta-Proteobacteria. These proportions increased to 12.0% +/- 3.3% and 54.0% +/- 5.9% at a depth of 50 m but decreased again at the sediment surface at 110 m to 2.7% +/- 1.4% and 41.1% +/- 8.4%, indicating a clear dominance of beta-Proteobacteria at depths of 50 and 110 m, where aggregates have an age of 3 to 5 and 8 to 11 days, respectively. From 50 m to the sediment surface, cells detected by a Cytophaga/Flavobacteria-specific probe (CF319a) comprised increasing proportions up to 18% of the DAPI cell counts. gamma-Proteobacteria always comprised minor proportions of the aggregate-associated bacterial community. Using only two probes highly specific for clusters of bacteria closely related to Sphingomonas species and Brevundimonas diminuta, we identified between 16 and 60% of the alpha-Proteobacteria. In addition, with three probes highly specific for close relatives of the beta-Proteobacteria Duganella zoogloeoides (formerly Zoogloea ramigera), Acidovorax facilis, and Hydrogenophaga palleroni, bacteria common in activated sludge, 42 to 70% of the beta-Proteobacteria were identified. In the early phase (<20 h) of 11 of the 15 experimental incubations of aggregates, dissolved amino acids were consumed by the aggregate-associated bacteria from the surrounding water. This stage was followed by a period of 1 to 3 days during which dissolved amino acids were released into the surrounding water, paralleled by an increasing dominance of beta-Proteobacteria. Hence, our results show that lake snow aggregates are inhabited by a community dominated by a limited number of alpha- and beta-Proteobacteria, which undergo a distinct succession. They successively decompose the amino acids bound in the aggregates and release substantial amounts into the surrounding water during aging and sinking.

Alphaproteobacteria↗
PubMed2001

In situ accessibility of Escherichia coli 23S rRNA to fluorescently labeled oligonucleotide probes.

One of the main causes of failure of fluorescence in situ hybridization with rRNA-targeted oligonucleotides, besides low cellular ribosome content and impermeability of cell walls, is the inaccessibility of probe target sites due to higher-order structure of the ribosome. Analogous to a study on the 16S rRNA (B. M. Fuchs, G. Wallner, W. Beisker, I. Schwippl, W. Ludwig, and R. Amann, Appl. Environ. Microbiol. 64:4973-4982, 1998), the accessibility of the 23S rRNA of Escherichia coli DSM 30083(T) was studied in detail with a set of 184 CY3-labeled oligonucleotide probes. The probe-conferred fluorescence was quantified flow cytometrically. The brightest signal resulted from probe 23S-2018, complementary to positions 2018 to 2035. The distribution of probe-conferred cell fluorescence in six arbitrarily set brightness classes (classes I to VI, 100 to 81%, 80 to 61%, 60 to 41%, 40 to 21%, 20 to 6%, and 5 to 0% of the brightness of 23S-2018, respectively) was as follows: class I, 3%; class II, 21%; class III, 35%; class IV, 18%; class V, 16%; and class VI, 7%. A fine-resolution analysis of selected areas confirmed steep changes in accessibility on the 23S RNA to oligonucleotide probes. This is similar to the situation for the 16S rRNA. Indeed, no significant differences were found between the hybridization of oligonucleotide probes to 16S and 23S rRNA. Interestingly, indications were obtained of an effect of the type of fluorescent dye coupled to a probe on in situ accessibility. The results were translated into an accessibility map for the 23S rRNA of E. coli, which may be extrapolated to other bacteria. Thereby, it may contribute to a better exploitation of the high potential of the 23S rRNA for identification of bacteria in the future.

Escherichia coli↗
PubMed2001

Community structure and activity dynamics of nitrifying bacteria in a phosphate-removing biofilm.

The microbial community structure and activity dynamics of a phosphate-removing biofilm from a sequencing batch biofilm reactor were investigated with special focus on the nitrifying community. O(2), NO(2)(-), and NO(3)(-) profiles in the biofilm were measured with microsensors at various times during the nonaerated-aerated reactor cycle. In the aeration period, nitrification was oxygen limited and restricted to the first 200 microm at the biofilm surface. Additionally, a delayed onset of nitrification after the start of the aeration was observed. Nitrate accumulating in the biofilm in this period was denitrified during the nonaeration period of the next reactor cycle. Fluorescence in situ hybridization (FISH) revealed three distinct ammonia-oxidizing populations, related to the Nitrosomonas europaea, Nitrosomonas oligotropha, and Nitrosomonas communis lineages. This was confirmed by analysis of the genes coding for 16S rRNA and for ammonia monooxygenase (amoA). Based upon these results, a new 16S rRNA-targeted oligonucleotide probe specific for the Nitrosomonas oligotropha lineage was designed. FISH analysis revealed that the first 100 microm at the biofilm surface was dominated by members of the N. europaea and the N. oligotropha lineages, with a minor fraction related to N. communis. In deeper biofilm layers, exclusively members of the N. oligotropha lineage were found. This separation in space and a potential separation of activities in time are suggested as mechanisms that allow coexistence of the different ammonia-oxidizing populations. Nitrite-oxidizing bacteria belonged exclusively to the genus Nitrospira and could be assigned to a 16S rRNA sequence cluster also found in other sequencing batch systems.

Ammonia↗
PubMed2001

Combined use of 16S ribosomal DNA and 16S rRNA to study the bacterial community of polychlorinated biphenyl-polluted soil.

The bacterial diversity assessed from clone libraries prepared from rRNA (two libraries) and ribosomal DNA (rDNA) (one library) from polychlorinated biphenyl (PCB)-polluted soil has been analyzed. A good correspondence of the community composition found in the two types of library was observed. Nearly 29% of the cloned sequences in the rDNA library were identical to sequences in the rRNA libraries. More than 60% of the total cloned sequence types analyzed were grouped in phylogenetic groups (a clone group with sequence similarity higher than 97% [98% for Burkholderia and Pseudomonas-type clones]) represented in both types of libraries. Some of those phylogenetic groups, mostly represented by a single (or pair) of cloned sequence type(s), were observed in only one of the types of library. An important difference between the libraries was the lack of clones representative of the Actinobacteria in the rDNA library. The PCB-polluted soil exhibited a high bacterial diversity which included representatives of two novel lineages. The apparent abundance of bacteria affiliated to the beta-subclass of the Proteobacteria, and to the genus Burkholderia in particular, was confirmed by fluorescence in situ hybridization analysis. The possible influence on apparent diversity of low template concentrations was assessed by dilution of the RNA template prior to amplification by reverse transcription-PCR. Although differences in the composition of the two rRNA libraries obtained from high and low RNA concentrations were observed, the main components of the bacterial community were represented in both libraries, and therefore their detection was not compromised by the lower concentrations of template used in this study.

Bacteria↗
PubMed2001

Predator-specific enrichment of actinobacteria from a cosmopolitan freshwater clade in mixed continuous culture.

We investigated whether individual populations of freshwater bacteria in mixed experimental communities may exhibit specific responses to the presence of different bacterivorous protists. In two successive experiments, a two-stage continuous cultivation system was inoculated with nonaxenic batch cultures of the cryptophyte Cryptomonas sp. Algal exudates provided the sole source of organic carbon for growth of the accompanying microflora. The dynamics of several 16S rRNA-defined bacterial populations were followed in the experimental communities. Although the composition and stability of the two microbial communities differed, numerous members of the first assemblage could again be detected during the second experiment. The introduction of a size-selectively feeding mixotrophic nanoflagellate (Ochromonas sp.) always resulted in an immediate bloom of a single phylotype population of members of the class Actinobacteria (Ac1). These bacteria were phylogenetically affiliated with an uncultured lineage of gram-positive bacteria that have been found in freshwater habitats only. The Ac1 cells were close to the average size of freshwater bacterioplankton and significantly smaller than any of the other experimental community members. In contrast, no increase of the Ac1 population was observed in vessels exposed to the bacterivorous ciliate Cyclidium glaucoma. However, when the Ochromonas sp. was added after the establishment of C. glaucoma, the proportion of population Ac1 within the microbial community rapidly increased. Populations of a beta proteobacterial phylotype related to an Aquabacterium sp. decreased relative to the total bacterial communities following the addition of either predator, albeit to different extents. The community structure of pelagic microbial assemblages can therefore be influenced by the taxonomic composition of the predator community.

Actinobacteria↗
PubMed2001

Changes in bacterial community composition and dynamics and viral mortality rates associated with enhanced flagellate grazing in a mesoeutrophic reservoir.

Bacterioplankton from a meso-eutrophic dam reservoir was size fractionated to reduce (<0.8-microm treatment) or enhance (<5-microm treatment) protistan grazing and then incubated in situ for 96 h in dialysis bags. Time course samples were taken from the bags and the reservoir to estimate bacterial abundance, mean cell volume, production, protistan grazing, viral abundance, and frequency of visibly infected cells. Shifts in bacterial community composition (BCC) were examined by denaturing gradient gel electrophoresis (DGGE), cloning and sequencing of 16S rDNA genes from the different treatments, and fluorescence in situ hybridization (FISH) with previously employed and newly designed oligonucleotide probes. Changes in bacterioplankton characteristics were clearly linked to changes in mortality rates. In the reservoir, where bacterial production about equaled protist grazing and viral mortality, community characteristics were nearly invariant. In the "grazer-free" (0.8-microm-filtered) treatment, subject only to a relatively low mortality rate (approximately 17% day(-1)) from viral lysis, bacteria increased markedly in concentration. While the mean bacterial cell volume was invariant, DGGE indicated a shift in BCC and FISH revealed an increase in the proportion of one lineage within the beta proteobacteria. In the grazing-enhanced treatment (5-microm filtrate), grazing mortality was approximately 200% and viral lysis resulted in mortality of 30% of daily production. Cell concentrations declined, and grazing-resistant flocs and filaments eventually dominated the biomass, together accounting for >80% of the total bacteria by the end of the experiment. Once again, BCC changed strongly and a significant fraction of the large filaments was detected using a FISH probe targeted to members of the Flectobacillus lineage. Shifts of BCC were also reflected in DGGE patterns and in the increases in the relative importance of both beta proteobacteria and members of the Cytophaga-Flavobacterium cluster, which consistently formed different parts of the bacterial flocs. Viral concentrations and frequencies of infected cells were highly significantly correlated with grazing rates, suggesting that protistan grazing may stimulate viral activity.

Animals↗
PubMed2001

Growth patterns of two marine isolates: adaptations to substrate patchiness?

During bottle incubations of heterotrophic marine picoplankton, some bacterial groups are conspicuously favored. In an earlier investigation bacteria of the genus Pseudoalteromonas rapidly multiplied in substrate-amended North Sea water, whereas the densities of Oceanospirillum changed little (H. Eilers, J. Pernthaler, and R. Amann, Appl. Environ. Microbiol. 66:4634-4640, 2000). We therefore studied the growth patterns of two isolates affiliating with Pseudoalteromonas and Oceanospirillum in batch culture. Upon substrate resupply, Oceanospirillum lagged threefold longer than Pseudoalteromonas but reached more than fivefold-higher final cell density and biomass. A second, mobile morphotype was present in the starved Oceanospirillum populations with distinctly greater cell size, DNA and protein content, and 16S rRNA concentration. Contrasting cellular ribosome concentrations during stationary phase suggested basic differences in the growth responses of the two strains to a patchy environment. Therefore, we exposed the strains to different modes of substrate addition. During cocultivation on a single batch of substrates, the final cell densities of Oceanospirillum were reduced three times as much as those Pseudoalteromonas, compared to growth yields in pure cultures. In contrast, the gradual addition of substrates to stationary-phase cocultures was clearly disadvantageous for the Pseudoalteromonas population. Different growth responses to substrate gradients could thus be another facet affecting the competition between marine bacteria and may help to explain community shifts observed during enrichments.

Bacterial Proteins↗
PubMed2001

Ketoprofen-induced cyclooxygenase inhibition in renal medulla and platelets of rats treated with caffeine.

It has been suggested that caffeine can augment analgesic activity and aggravate side effects of nonsteroidal anti-inflammatory drugs (NSAIDs). The aim of the present study was to investigate a possible interaction between ketoprofen and caffeine on prostaglandin (PG) biosynthesis and cyclooxygenase (COX) mRNA expression in the rat renal medulla ex vivo. Treatment of rats with ketoprofen (60 min before) resulted in a dose-dependent (estimated ID(50) 0.3 mg/kg p.o.) reduction of PGE(2) biosynthesis in renal medulla ex vivo. Ketoprofen (0.3 mg/kg)-induced inhibition of PGE(2) biosynthesis was stable between 30 and 180 min and still detectable 300 min after drug administration. Caffeine (10 mg/kg) did not cause a detectable effect on its own, nor did it significantly affect ketoprofen-induced inhibition of renal medullary PGE(2) biosynthesis. Similar results were obtained with repeated daily drug administration for 1 week: there was no significant effect of caffeine on ketoprofen-induced inhibition of renal medullary PGE(2) biosynthesis. The absence of significant caffeine effects on ketoprofen-induced inhibition of renal medullary PGE(2) biosynthesis was paralleled by experiments showing no significant effect of caffeine on ketoprofen-induced inhibition of platelet thromboxane (TX)B(2) biosynthesis. Additional experiments showed increased COX-2 mRNA expression in the renal medulla 60 min after ketoprofen administration, that was not significantly influenced by concomitant caffeine treatment. Treatment of rats with ketoprofen for 1 week had no significant effects on COX-2 mRNA expression. The present results show that ketoprofen caused inhibition of PGE(2) biosynthesis in the rat renal medulla ex vivo with a potency similar to that reported for in vivo models suggesting that the ex vivo approach is a valid model to test a possible interference of caffeine with ketoprofen-induced COX inhibition. The absence of detectable effects of caffeine on time course or magnitude of ketoprofen-induced suppression of PGE(2) biosynthesis in this model indicates, therefore, that possible adverse actions of co-administered caffeine on renal function are not related to interference with renal COX inhibition.

Animals↗
PubMed2000

A marine microbial consortium apparently mediating anaerobic oxidation of methane.

A large fraction of globally produced methane is converted to CO2 by anaerobic oxidation in marine sediments. Strong geochemical evidence for net methane consumption in anoxic sediments is based on methane profiles, radiotracer experiments and stable carbon isotope data. But the elusive microorganisms mediating this reaction have not yet been isolated, and the pathway of anaerobic oxidation of methane is insufficiently understood. Recent data suggest that certain archaea reverse the process of methanogenesis by interaction with sulphate-reducing bacteria. Here we provide microscopic evidence for a structured consortium of archaea and sulphate-reducing bacteria, which we identified by fluorescence in situ hybridization using specific 16S rRNA-targeted oligonucleotide probes. In this example of a structured archaeal-bacterial symbiosis, the archaea grow in dense aggregates of about 100 cells and are surrounded by sulphate-reducing bacteria. These aggregates were abundant in gas-hydrate-rich sediments with extremely high rates of methane-based sulphate reduction, and apparently mediate anaerobic oxidation of methane.

Anaerobiosis↗
PubMed2000

Identification of novel Archaea in bacterioplankton of a boreal forest lake by phylogenetic analysis and fluorescent in situ hybridization(1).

We report here on novel groups of Archaea in the bacterioplankton of a small boreal forest lake studied by the culture-independent analysis of the 16S rRNA genes amplified directly from lake water in combination with fluorescent in situ hybridization (FISH). Polymerase chain reaction products were cloned and 28 of the 160 Archaea clones with around 900-bp-long 16S rRNA gene inserts, were sequenced. Phylogenetic analysis, including 642 Archaea sequences, confirmed that none of the freshwater clones were closely affiliated with known cultured Archaea. Twelve Archaea sequences from lake Valkea Kotinen (VAL) belonged to Group I of uncultivated Crenarchaeota and affiliated with environmental sequences from freshwater sediments, rice roots and soil as well as with sequences from an anaerobic digestor. Eight of the Crenarchaeota VAL clones formed a tight cluster. Sixteen sequences belonged to Euryarchaeota. Four of these formed a cluster together with environmental sequences from freshwater sediments and peat bogs within the order Methanomicrobiales. Five were affiliated with sequences from marine sediments situated close to marine Group II and three formed a novel cluster VAL III distantly related to the order Thermoplasmales. The remaining four clones formed a distinct clade within a phylogenetic radiation characterized by members of the orders Methanosarcinales and Methanomicrobiales on the same branch as rice cluster I, detected recently on rice roots and in anoxic bulk soil of flooded rice microcosms. FISH with specifically designed rRNA-targeted oligonucleotide probes revealed the presence of Methanomicrobiales in the studied lake. These observations indicate a new ecological niche for many novel 'non-extreme' environmental Archaea in the pelagic water of a boreal forest lake.

Journal Article↗
PubMed2000

Inhibition of carrageenan-induced edema by indomethacin or sodium salicylate does not prevent the increase of nerve growth factor in the rat hind paw.

It is known that the concentration of nerve growth factor (NGF) is increased in inflamed tissue, a phenomenon thought to induce long-lasting sensitization of afferent neurons. Although the effects of NGF may be of pathophysiological relevance, there is little known about the effects of non-steroidal anti-inflammatory drugs on the inflammation-induced increase in NGF. In the present study, therefore, we used the non-steroidal anti-inflammatory drugs indomethacin and sodium salicylate in carrageenan-induced rat paw inflammation, in order to compare their anti-inflammatory action (determined as inhibition of edema) with their effects on the concentration of NGF in inflamed tissue. Carrageenan-induced inflammation increased the concentration of NGF in the paw 2-fold compared to non-inflamed controls. Indomethacin (0.66-2 mg/kg) and sodium salicylate (100-300 mg/kg) inhibited carrageenan-induced paw edema and indomethacin also inhibited the ex-vivo release of immunoreactive prostaglandin E2 from inflamed paw skin. However, at these doses, neither anti-inflammatory agent reduced the elevated levels of NGF. In contrast, a supramaximal dose of indomethacin (6 mg/kg) partially inhibited, and dexamethasone completely prevented the carrageenan-induced increase in NGF. These results suggest that the anti-inflammatory potency of drugs as determined in the carrageenan edema model is not necessarily predictive for their ability to inhibit the NGF response. It seems possible, therefore, that even if anti-inflammatory treatment prevents the appearance of visible signs of inflammation, there may be still long-lasting effects of NGF on the phenotype of primary afferent neurons.

Animals↗
PubMed2000

The tachykinin NK(1) receptor antagonist SR140333 prevents the increase of nerve growth factor in rat paw skin induced by substance P or neurogenic inflammation.

Target-derived nerve growth factor provides trophic support for adult primary afferent neurons containing calcitonin gene-related peptide and tachykinins. Noxious chemical or thermal stimuli cause the release of these mediators from peripheral afferent nerve endings. However, little is known of the extent to which these mediators, in turn, influence nerve growth factor expression in the innervated tissue. The aim of this study was therefore to investigate the possible effect of exogenous substance P, or neurogenic inflammation on the nerve growth factor concentration in the skin of the rat hindpaw. Our results show that substance P as well as topical application of mustard oil cause a significant increase in detectable nerve growth factor, an effect that was prevented by treatment of rats with the tachykinin NK(1) receptor antagonist SR140333. We did not observe a significant inhibitory effect of SR140333 on the nerve growth factor content in non-treated skin, or the nerve growth factor increase caused by carrageenan or allergic inflammation. The results provide evidence that substance P as well as neurogenic inflammation cause a rapid increase in detectable nerve growth factor in the paw skin and suggest the involvement of NK(1) receptors in this effect. We obtained no evidence for the participation of a NK(1) receptor-mediated nerve growth factor increase in models of inflammation induced by non-neurogenic stimuli.

Animals↗