Post-interface signal suppression, a phenomenon observed in a single-stage Orbitrap mass spectrometer coupled to an electrospray interfaced liquid chromatograph

Signal suppression is a common issue when analyzing compounds by liquid chromatography coupled to mass spectrometry (LC/MS/MS). Suppression of signals is caused by co-eluting matrix compounds and is thought to take place in the interface. This paper reports strong signal suppression effects which were observed when using a single-stage Orbitrap instrument which was coupled by an electrospray interface to a liquid chromatograph. This type of signal suppression (often the complete loss of certain analyte signal) is observed in addition to signal suppression originating in the electrospray interface. The location of where this phenomenon occurs was shown to be clearly beyond the interface region. It was suspected that not the Orbitrap cell itself, but the C-trap, which is an integral part within the Orbitrap instrument, was the probable location. Such post-interface signal suppression was observed--and could be experimentally induced--when multiply charged ions (e.g. electrospray protonated proteins) were co-eluting with the analytes. High concentrations of proteins, yet not exceeding the maximum ion capacity of the trap, can cause a complete loss of all low m/z masses. This paper describes the practical implication when analyzing heavy matrix samples and discusses strategies to reduce such detrimental effects.

A plasmid collection for PCR-based gene targeting in the filamentous ascomycete Ashbya gossypii

PCR-based gene targeting with heterologous markers is an efficient method to delete genes, generate gene fusions, and modulate gene expression. For the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, several plasmid collections are available covering a wide range of tags and markers. For several reasons, many of these cassettes cannot be used in the filamentous ascomycete Ashbya gossypii. This article describes the construction of 93 heterologous modules for C- and N-terminal tagging and promoter replacements in A. gossypii. The performance of 12 different fluorescent tags was evaluated by monitoring their brightness, detectability, and photostability when fused to the myosin light-chain protein Mlc2. Furthermore, the thiamine-repressible S. cerevisiae THI13 promoter was established to regulate gene expression in A. gossypii. This collection will help accelerate analysis of gene function in A. gossypii and in other ascomycetes where S. cerevisiae promoter elements are functional.

Neuropeptide Y is expressed by rat mononuclear blood leukocytes and strongly down-regulated during inflammation

Neuropeptide Y (NPY), a classical sympathetic comediator, regulates immunological functions including T cell activation and migration of blood leukocytes. A NPY-mediated neuroimmune cross-talk is well conceivable in sympathetically innervated tissues. In denervated, e.g., transplanted organs, however, leukocyte function is not fundamentally disturbed. Thus, we hypothesized that NPY is expressed by blood leukocytes themselves and regulated during inflammation. NPY mRNA and peptide expression were analyzed in mononuclear leukocytes isolated from the blood vessels of healthy rat kidneys, as well as from the blood vessels of isogeneic and allogeneic renal grafts transplanted in the Dark Agouti to Lewis or in the Fischer 344 to Lewis rat strain combination. Depending on the donor strain, acute allograft rejection is either fatal or reversible but both experimental models are characterized by massive accumulation of intravascular leukocytes. Leukocytes, predominantly monocytes, isolated from the blood vessels of untreated kidneys and isografts expressed high amounts of NPY mRNA and peptide, similar to expression levels in sympathetic ganglia. During acute allograft rejection, leukocytic NPY expression drastically dropped to approximately 1% of control levels in both rat strain combinations. In conclusion, NPY is an abundantly produced and tightly regulated cytokine of mononuclear blood leukocytes.

The Paxillin-like protein AgPxl1 is required for apical branching and maximal hyphal growth in A.gossypii

The development from young, slowly growing hyphae to fast growing hyphae in filamentous fungi is referred to as hyphal maturation. We have identified the Paxillin-like protein AgPxl1 in Ashbyagossypii as a developmental protein that is specifically required for hyphal maturation. The early development of A.gossypii strains lacking AgPxl1 is indistinguishable from wild-type. However, at later developmental stages the maximal hyphal extension rate is less than half compared to wild-type and apical branching is affected. Apical branching is characterised as the symmetric division of fast growing hyphal tips resulting in two sister hyphae. In Agpxl1Delta strains two thirds of the apical branching events lead to asymmetric sister hyphae where growth of one branch is either completely aborted or slowed down while extension of the other branch is not affected. This suggests that AgPxl1 plays a role in the organisation of growth and efficient division of growth upon apical branching in mature mycelia. The conserved C-terminal LIM domains are necessary for AgPxl1 function and also contribute to tip localisation. AgCLA4, a PAK-like kinase, is epistatic to AgPXL1 and robust localisation of AgPxl1 depends on AgCla4. This suggests that AgCla4 acts upstream of AgPxl1.

Recognition of nucleic acid and nucleic acid analogs by Toll-like receptors 7, 8 and 9

The mammalian immune system senses pathogens through pattern recognition receptors (PRR) and responds with activation. Toll-like receptors (TLRs) that are expressed on immune and non-immune cells play a critical role in this process. As part of the innate immune response, TLRs lead to cellular activation and cytokine production with subsequent initiation of an adaptive immune response. TLR7-9 recognize single-stranded RNA, nucleoside analogs and single-stranded CpG-DNA, respectively, and their activation initiates the immune response against viruses and bacteria. Furthermore, the stimulation of these TLRs may be exploited for adjuvant therapy, vaccination and anti-tumor responses. However, a role in the generation or perpetuation of autoimmune diseases such as systemic lupus erythematosus (SLE) has also been suggested.

High proportion of large genomic deletions and a genotype phenotype update in 80 unrelated families with juvenile polyposis syndrome

BACKGROUND

In patients with juvenile polyposis syndrome (JPS) the frequency of large genomic deletions in the SMAD4 and BMPR1A genes was unknown.

METHODS

Mutation and phenotype analysis was used in 80 unrelated patients of whom 65 met the clinical criteria for JPS (typical JPS) and 15 were suspected to have JPS.

RESULTS

By direct sequencing of the two genes, point mutations were identified in 30 patients (46% of typical JPS). Using MLPA, large genomic deletions were found in 14% of all patients with typical JPS (six deletions in SMAD4 and three deletions in BMPR1A). Mutation analysis of the PTEN gene in the remaining 41 mutation negative cases uncovered a point mutation in two patients (5%). SMAD4 mutation carriers had a significantly higher frequency of gastric polyposis (73%) than did patients with BMPR1A mutations (8%) (p<0.001); all seven cases of gastric cancer occurred in families with SMAD4 mutations. SMAD4 mutation carriers with gastric polyps were significantly older at gastroscopy than those without (p<0.001). In 22% of the 23 unrelated SMAD4 mutation carriers, hereditary hemorrhagic telangiectasia (HHT) was also diagnosed clinically. The documented histologic findings encompassed a wide distribution of different polyp types, comparable with that described in hereditary mixed polyposis syndromes (HMPS).

CONCLUSIONS

Screening for large deletions raised the mutation detection rate to 60% in the 65 patients with typical JPS. A strong genotype-phenotype correlation for gastric polyposis, gastric cancer, and HHT was identified, which should have implications for counselling and surveillance. Histopathological results in hamartomatous polyposis syndromes must be critically interpreted.

Acute rejection of experimental lung allografts: Characterization of intravascular mononuclear leukocytes

Leukocytes interacting with endothelia of lung allografts probably play a seminal role in acute rejection, but have not been characterized before. Transplantation was performed in the Lewis to Lewis and in the Dark Agouti to Lewis rat strain combinations. DNA replication was detected in T-cells on day 2 after pulse-labelling in vivo with 5-bromo-2'-deoxyuridine (BrdU). On day 5, leukocytes were isolated by intensive perfusion the graft, subject to flow cytometry and to quantitative RT-PCR. About 34 million leukocytes accumulated in allograft vessels, but only 10 and 6 million cells in isografts and control lungs, respectively. During rejection, IFN-gamma, IL-1beta and IL-10 mRNA expression increased, IL-12 mRNA decreased, whereas IL-2, IL-6, TNF-alpha, and TGF-beta mRNA did not change. The phenotype of graft monocytes was partially activated and intravascular T-cells proliferated. In conclusion, during rejection, monocytes with unusual properties accumulate and T-lymphocytes are activated in lung allograft blood vessels.

Laparoscopic endopelvic sacral implantation of a Brindley controller for recovery of bladder function in a paralyzed patient

BACKGROUND

A number of techniques are being investigated to accomplish bladder control recovery in paralyzed patients using the neurostimulation, but currently, all techniques are based on the dorsal implantation of the electrodes using a laminectomy.

METHODS

On 27 April 2006 we performed a laparoscopic implantation of a Finetech-Brindley bladder controller on the endopelvic sacral roots in a Th8 completely paralyzed woman who had previously undergone the removal of a Brindley controller due to an arachnoiditis after extrathecal implantation with intradural sacral deafferentation.

RESULTS

We required about 3.5 h for the entire surgical procedure; no complications occurred and the patients went home on 5th postoperative day. The patient is now able to void empty her bladder and her rectum using the controller without further need for self-catheterisation.

CONCLUSIONS

The presented new technique of laparoscopic implantation of electrodes on the endopelvic portion of the sacral nerve roots is an option to be considered in all paralyzed patients with further wish for electrical induced miction/defecation after previous deafferentation.

Macrophages in experimental rat lung isografts and allografts: infiltration and proliferation in situ

Alveolar macrophages (AMs) and peribronchial/perivascular macrophages are probably involved in lung allograft damage. We investigate leukocyte infiltration into graft tissue and address the question whether proliferation in situ contributes to macrophage homeostasis and accumulation. Lung transplantation was performed in the Lewis (LEW)-to-LEW and in the Dark Agouti-to-LEW rat strain combination. Graft infiltration by ED1+ and ED2+ (CD163) macrophages was analyzed by immunohistochemistry (IHC) and compared with infiltration by lymphocytes. Cells in the S-phase of the cell cycle were pulse-labeled with BrdU and detected immunohistochemically. Finally, the donor or recipient origin of AMs was determined by IHC and in situ hybridization. ED1+ AMs in allogeneic transplants increased by more than 25-fold from Days 1 to 5. In addition, large, peribronchial/perivascular infiltrates developed containing numerous ED1+ cells. Although AMs in normal rat lungs are CD163-, AMs up-regulated CD163 between Days 4 and 5, reaching maximum values on Day 6. Lymphocytes were less numerous than macrophages. About 16% of the AMs and 10% of the peribronchial/perivascular macrophages were in the S-phase of the cell cycle on Day 2 post-transplantation. No differences in the frequency of BrdU+ macrophages were obvious between isografts and allografts. AMs of donor origin increased in number considerably during allograft rejection. In conclusion, the cellular infiltrate in lung allografts is dominated by macrophages, which exhibit an unusual phenotype and a strong capacity for mitotic self-renewal.

Analysis of polyphosphates in fish and shrimps tissues by two different ion chromatography methods: implications on false-negative and -positive findings

Inorganic polyphosphates (di-, tri- and higher polyphosphates) can be used to treat fish, fish fillets and shrimps in order to improve their water-binding capacity. The practical relevance of this treatment is a significant gain of weight caused by the retention/uptake of water and natural juice into the fish tissues. This practice is legal; however, the use of phosphates has to be declared. The routine control testing of fish for the presence of polyphosphates, produced some results that were difficult to explain. One of the two analytical methods used determined low diphosphate concentrations in a number of untreated samples, while the other ion chromatography (IC) method did not detect them. This initiated a number of investigations: results showed that polyphosphates in fish and shrimps tissue undergo a rapid enzymatic degradation, producing the ubiquitous orthophosphate. This led to the conclusion that sensitive analytical methods are required in order to detect previous polyphosphate treatment of a sample. The polyphosphate concentrations detected by one of the analytical methods could not be explained by the degradation of endogenous high-energy nucleotides like ATP into diphosphate, but by a coeluting compound. Further investigations by LC-MS-MS proved that the substance responsible for the observed peak was inosine monophsosphate (IMP) and not as thought the inorganic diphosphate. The method producing the false-positive result was modified and both methods were ultimately able to detect polyphosphates well separated from natural nucleotides. Polyphosphates could no longer be detected (<0.5 mg kg-1) after modification of the analytical methodology. The relevance of these findings lies in the fact that similar analytical methods are employed in various control laboratories, which might lead to false interpretation of measurements.

From function to shape: a novel role of a formin in morphogenesis of the fungus Ashbya gossypii

Morphogenesis of filamentous ascomycetes includes continuously elongating hyphae, frequently emerging lateral branches, and, under certain circumstances, symmetrically dividing hyphal tips. We identified the formin AgBni1p of the model fungus Ashbya gossypii as an essential factor in these processes. AgBni1p is an essential protein apparently lacking functional overlaps with the two additional A. gossypii formins that are nonessential. Agbni1 null mutants fail to develop hyphae and instead expand to potato-shaped giant cells, which lack actin cables and thus tip-directed transport of secretory vesicles. Consistent with the essential role in hyphal development, AgBni1p locates to tips, but not to septa. The presence of a diaphanous autoregulatory domain (DAD) indicates that the activation of AgBni1p depends on Rho-type GTPases. Deletion of this domain, which should render AgBni1p constitutively active, completely changes the branching pattern of young hyphae. New axes of polarity are no longer established subapically (lateral branching) but by symmetric divisions of hyphal tips (tip splitting). In wild-type hyphae, tip splitting is induced much later and only at much higher elongation speed. When GTP-locked Rho-type GTPases were tested, only the young hyphae with mutated AgCdc42p split at their tips, similar to the DAD deletion mutant. Two-hybrid experiments confirmed that AgBni1p interacts with GTP-bound AgCdc42p. These data suggest a pathway for transforming one axis into two new axes of polar growth, in which an increased activation of AgBni1p by a pulse of activated AgCdc42p stimulates additional actin cable formation and tip-directed vesicle transport, thus enlarging and ultimately splitting the polarity site.

Homologues of yeast polarity genes control the development of multinucleated hyphae in Ashbya gossypii

A few years ago, A. gossypii became recognized as an attractive model to study the growth of long and multinucleated fungal cells (hyphae) because of its small genome, haploid nuclei, and efficient gene targeting methods. It is generally assumed that a better understanding of filamentous fungal growth will greatly stimulate the development of novel fungicides. The use of Ashbya gossypii as a model is particularly promising because of the high level of gene order conservation (synteny) between the genomes of A. gossypii and the yeast Saccharomyces cerevisiae. Thus, a similar set of genes seems to control the surprisingly different growth modes of these two organisms, which predicts that orthologous growth control genes might not play identical cellular roles in both systems. Analyzing the phenotypes of A. gossypii mutants lacking factors with known functions in yeast morphogenesis and nuclear dynamics confirm this hypothesis. Comparative genomics of both organisms also reveals rare examples of differences in the gene sets for some cellular processes, which as shown for phosphate homeostasis can be associated with differences in control levels.

Influence of catecholamines on cytokine production and expression of adhesion molecules of human neutrophils in vitro

The impact of catecholamines on cytokine production and expression of adhesion molecules by human neutrophils was evaluated in vitro. Neutrophils were separated from venous blood of healthy subjects. The generation of intracellular cyclic adenosine monophosphate (cAMP) and Ca2+ was determined after incubation with catecholamines. Resting and lipopolysaccharide (LPS)-activated neutrophils were tested for synthesis of interleukins (IL-6, IL-8) and tumor necrosis factor alpha (TNF-alpha). In addition, the expression of the adhesion molecules CD15, CD44, and CD54 was evaluated in resting and activated neutrophils. Increasing concentrations (1 nM-1 mM) of epinephrine (EPI) were used to study the influence of activation of beta2-adrenergic receptors (beta2R) on cytokine production and adhesion molecule expression. Incubation with catecholamines induced an increase in cAMP but not Ca2+ in neutrophils. Only IL-8 was detected following stimulation with LPS and was unchanged upon co-incubation with EPI. The expression of CD15 and CD44 decreased spontaneously in vitro. The density of CD44 increased in the presence of very high doses of EPI (1 mM). Expression of CD54 on resting neutrophils increased upon activation. The density of CD54 on activated neutrophils was reduced upon co-incubation with 1 mM EPI for 6 h. However, 1 mM EPI for 12 and 18 h decreased the spontaneous loss of CD54 on resting neutrophils. Beta2R are functionally coupled to signalling cascades in human neutrophils. Nevertheless, the impact of catecholamines on IL-8 synthesis and expression of CD15, CD44, and CD54 is limited.

"Host tissue damage" signal ATP promotes non-directional migration and negatively regulates toll-like receptor signaling in human monocytes

The activation of Toll-like receptors (TLRs) by lipopolysaccharide or other ligands evokes a proinflammatory immune response, which is not only capable of clearing invading pathogens but can also inflict damage to host tissues. It is therefore important to prevent an overshoot of the TLR-induced response where necessary, and here we show that extracellular ATP is capable of doing this in human monocytes. Using reverse transcription-PCR, we showed that monocytes express P2Y(1), P2Y(2), P2Y(4), P2Y(11), and P2Y(13) receptors, as well as several P2X receptors. To elucidate the function of these receptors, we first studied Ca(2+) signaling in single cells. ATP or UTP induced a biphasic increase in cytosolic Ca(2+), which corresponded to internal Ca(2+) release followed by activation of store-operated Ca(2+) entry. The evoked Ca(2+) signals stimulated Ca(2+)-activated K(+) channels, producing transient membrane hyperpolarization. In addition, ATP promoted cytoskeleton reorganization and cell migration; however, unlike chemoattractants, the migration was non-directional and further analysis showed that ATP did not activate Akt, essential for sensing gradients. When TLR2, TLR4, or TLR2/6 were stimulated with their respective ligands, ATPgammaS profoundly inhibited secretion of proinflammatory cytokines (tumor necrosis factor-alpha and monocyte chemoattractant protein-1) but increased the production of interleukin-10, an anti-inflammatory cytokine. In radioimmune assays, we found that ATP (or ATPgammaS) strongly increased cAMP levels, and, moreover, the TLR-response was inhibited by forskolin, whereas UTP neither increased cAMP nor inhibited the TLR-response. Thus, our data suggest that ATP promotes non-directional migration and, importantly, acts as a "host tissue damage" signal via the G(s) protein-coupled P2Y(11) receptor and increased cAMP to negatively regulate TLR signaling.

CD14 is required for influenza A virus-induced cytokine and chemokine production

Infection of monocytes and macrophages by influenza A virus leads to proinflammatory and chemotactic cytokine production. The signalling pathways linking innate immune virus recognition to cytokine expression are little understood. Here, we report that blocking of CD14 on human monocytes by specific antibody or use of CD14-deficient murine macrophages abolished influenza A virus-induced cytokine production. Toll-like receptor (TLR) 2 and 4-deficient murine macrophages remained fully responsive. These results suggest that CD14, together with a TLR other than TLR2 or 4, is an essential coreceptor of the influenza A virus sensing recognition system.