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.

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.

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.

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.

Contamination of honey by the herbicide asulam and its antibacterial active metabolite sulfanilamide

A number of antibacterial drugs (antibiotics) like sulfonamides, tetracyclines and streptomycin are used for the treatment of bacterial diseases in beehives. Yet, the finding of sulfanilamide residues in some 15 Swiss honeys out of some 350 samples could not be explained by such apicultural practice. Bees occasionally collect nectar from meadows treated with the herbicide asulam. Such honey is not only contaminated by asulam, but also by its degradation product sulfanilamide. This is the first report that the use of a herbicide causes the appearance of residues of an antibacterial active metabolite belonging to the category of sulfonamide drugs in food. The relevance of this finding lies in the fact that the use of the herbicide asulam might cause unacceptable residue levels of sulfanilamide in a product fbr human consumption.

Anthrax in Europe: its epidemiology, clinical characteristics, and role in bioterrorism

In the 2001 bioterrorist attack in the United States, in which at least 22 cases of anthrax occurred, there was initial uncertainty as to whether the index case was acquired from natural sources, and many of the additional cases posed diagnostic challenges to clinicians unfamiliar with the disease. The existence in Europe of terrorist groups with demonstrated violent tendencies suggests Europe is not immune to bioterrorist attack, and the same epidemiological and clinical confusion could happen here. Bacillus anthracis is distributed widely in the soils of Europe and foci of animal disease occur, notably in southern and eastern Europe. Sporadic human cases occur in these areas, and occasional additional cases have been acquired from contaminated, imported materials or acquired in countries outside of Europe, where anthrax may be common. Depending upon the intent of a bioterrorist, illness-caused B. anthracis could take one of several clinical forms-inhalational, cutaneous or gastrointestinal-and each would pose diagnostic difficulties. Understanding the epidemiologic, pathophysiologic and bioterrorism principles of anthrax are the clinician's best means of early detection of cases.

Defense against influenza A virus infection: essential role of the chemokine system

Monocytes/macrophages are highly susceptible to an infection with influenza A virus. After infection, de novo virus protein synthesis is detectable but rapidly interrupted before completion of the first viral replication cycle. Within 24-48 hours the infected monocytes die by apoptosis. Before cell death, infected monocytes initiate a cell-specific immune response. This includes the transcription and subsequent release of TNF-alpha (tumor necrosis factor alpha), IL-1beta (Interleukin 1beta), IL-6, type I inferferons and CC chemokines. Enhanced cytokine mRNA expression is due to a prolonged mRNA stability and an augmented gene transcription. Activation of transcription factors such as NF-kappaB (nuclear factor kappaB) and AP-1 are involved in activation of cytokine mRNA transcription. Infection of monocytes with influenza A virus induces the selective expression of mononuclear leukocyte attracting chemokines, such as MCP-1 (monocyte chemotactic protein 1), MIP-1alpha (macrophage inflammatory protein 1alpha) and RANTES (regulated upon activation, normal T cell expressed and secreted). In striking contrast, the release of the neutrophil-specific chemokines IL-8 (interleukin 8) and GRO-alpha (growth stimulatory activity alpha) is entirely suppressed. This differentially regulated chemokine expression may explain the mononuclear cell infiltrate characteristic for virus-infected tissue. Thus, infection of monocytes/macrophages with influenza A virus primes for a rapid proinflammatory reaction and induces an enhanced immigration of mononuclear cells into infected tissue. Taken together, these mechanisms may prepare the infected host for a fast and virus-specific immune response.

Molecular investigation of the Aum Shinrikyo anthrax release in Kameido, Japan

In 1993, the Aum Shinrikyo cult aerosolized Bacillus anthracis spores over Kameido, Japan. Spore samples were obtained from the release site, cultured, and characterized by molecular genetic typing. The isolates were consistent with strain Sterne 34F2, which is used in Japan for animal prophylaxis against anthrax.

Comparison of visually evoked peak systolic and end diastolic blood flow velocity using a control system approach

Transcranial Doppler sonography measures blood flow velocity in basal cerebral vessels with high accuracy. For quantification, time averaged mean blood flow velocities are used most because the peak systolic and end diastolic blood flow velocities mark the velocity extremes of one heart cycle. It is known, from hemodynamic measurements of the neurovascular coupling mechanism, that the end diastolic velocity is more sensitive for change in hemodynamics than the peak systolic velocity. Thus, we used a recently introduced control system approach to compare both indices for their use in functional transcranial Doppler tests focusing on hemodynamics of blood flow velocity change. We enrolled 65 healthy young volunteers without a medical history of cardiovascular risk factors, and performed a visual stimulation test. Peak systolic and end diastolic maximal blood flow velocities were used after transformation to relative data for control-system analysis. Due to Doppler artefacts, 95% of peak systolic and 86% of end diastolic data sets were analyzed. Results showed statistically significant differences for resting blood flow velocity and the control system parameter gain, attenuation and rate time, whereas the parameters' natural frequency and time delay were equal. Increase in relative blood flow velocity in the posterior cerebral artery due to visual-cortical stimulation was higher in end diastolic values than peak systolic data. Using a complex visual stimulation paradigm, the higher sensitivity of the end diastolic index is of no practical use. Being less influenced by Doppler artefacts, the peak systolic velocity index is more feasible for control-system analysis of dynamic blood flow regulation.

Cytarabine treatment of human T-lymphoid cells induces decreased HIV-1 receptor expression and reduced HIV-1 susceptibility

Continuous cultivation of T-lymphoid C8166 cells in the presence of pharmacological relevant concentration of cytarabine (Ara-C) results in significantly decreased expression of CD4 and CXCR4 molecules, the major cellular receptor and co-receptor of T-lymphotropic HIV-1 isolates. This change in receptor expression leads to decreased susceptibility of Ara-C resistant cells to HIV-1 infection demonstrated by reduced binding and penetration of HI-virus.

Increase of CCR1 and CCR5 expression and enhanced functional response to MIP-1 alpha during differentiation of human monocytes to macrophages

Chemokines and their receptors regulate migration of leukocytes under normal and inflammatory conditions. In this study, we analyzed the CC chemokine receptor (CCR) expression of monocytes differentiating in vitro to macrophages. We observed a time-dependent change of expression and functional responsiveness of CCR1, CCR2, and CCR5 within 48 h. Whereas freshly harvested monocytes were strongly attracted by monocyte chemotactic protein 1 (MCP-1), a specific ligand for CCR2, only a weak response was observed to macrophage inflammatory protein 1alpha (MIP-1alpha), which binds to CCR1 and CCR5. In striking contrast, differentiated macrophages displayed a strong chemotactic response to MIP-1alpha and only a weak response to MCP-1. These findings were paralleled by intracellular calcium shifts. During the time course of monocyte to macrophage differentiation, mRNA levels and surface expression of CCR2 decreased, whereas that of CCR1 and CCR5 increased. The time-dependent switch from CCR2 on monocytes to CCR1 and CCR5 on mature macrophages reflects a functional change belonging to the differentiation process of monocytes to macrophages and may form the basis for a differential responsiveness of monocytes and macrophages to distinct sets of chemokines.

Multiresidue analysis of tranquilizers and the beta-blocker Carazolol in meat by liquid chromatography/tandem mass spectrometry

A fast and simple method for the quantification of a number of tranquilizers and the beta-blocker Carazolol in pork and bovine kidney is described. Extracts are purified/concentrated by a solid phase extraction step and separated on a reversed phase column with an alkaline (ammonia) acetonitrile gradient. The electrospray tandem mass spectrometer is operated in positive ion multireaction monitoring mode. Resulting chromatograms are free of interfering peaks. The recovery is >75% for all analytes and the limit of detection <1 ppb, which is well below the current maximum residue limit for the various compounds.

Differential desensitization of lipopolysaccharide-inducible chemokine gene expression in human monocytes and macrophages

Bacterial lipopolysaccharide (LPS) has been shown to induce a wide variety of pro-inflammatory cytokines and chemokines. An initial challenge with minute amounts of LPS causes tolerance to later LPS effects which is characterized by a much lower or abrogated release of pro-inflammatory cytokines. To explore the relationship between the production of chemokines and the induction of LPS tolerance, we pretreated human monocytes with increasing LPS doses and thereafter restimulated with LPS. The re-expression of the CC chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and RANTES was substantially suppressed after pre-incubation with low LPS doses. In striking contrast, the re-expression of neutrophil-attracting IL-8 and melanoma growth stimulatory activity-alpha and of the monocyte-attracting monocyte chemotactic protein-1 remained high and was, in part, initially increased after restimulation with LPS. The corresponding gene expression pattern as determined by Northern blot analyses correlated closely with the release of chemokines and cytokines. Thus, a basic set of chemotactic mediators that are still produced by otherwise LPS-desensitized monocytes/macrophages may ensure the continuing recruitment of monocytes and neutrophils into an inflammatory process caused by gram-negative bacteria.

The quadriceps tendon cyst: an uncommon cause of chronic anterior knee pain

The causes of knee pain are manifold. One of the uncommon causes of chronic anterior knee pain are cysts and ganglia. Magnetic resonance imaging not only reveals the intra-articular pathology but also accurately depicts such cystic structures about the knee. As part of this case report, a cyst of the lateral border of the quadriceps tendon is presented as a cause of such discomfort. Although cystic lesions around the knee are a common clinical problem, the described location is rare. After surgical revision of the lateral border of the quadriceps tendon and excision of the cyst, the patient was found to be asymptomatic.