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Biomedical subjects

A Sander

Publications and source records attributed to A Sander.

At least 19 recordsLinked to original sources
PubMed2002

Clinical experience with quinupristin-dalfopristin as rescue treatment of critically ill patients infected with methicillin-resistant staphylococci.

OBJECTIVES: To describe the efficacy and safety of quinupristin-dalfopristin (Q-D) as rescue therapy in critically ill patients with severe infections caused by methicillin-resistant staphylococci unresponsive to vancomycin treatment. DESIGN: Observational study in the context of the compassionate use programme for Q-D. METHODS: Twelve mechanically ventilated patients suffering from severe staphylococcal infections, pretreated unsuccessfully with vancomycin despite in vitro sensitivity, were included. Patients received, intravenously, Q-D 7.5 mg/kg body weight 3 times daily. The duration of Q-D therapy averaged 11.8 days (range: 1-26 days). The outcome variables were clinical efficacy and bacteriological eradication. RESULTS: Methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE) were isolated in three patients each, and both bacteria were isolated from six patients. Eradication of pathogen(s) was achieved in 7 of 12 patients (66%). Five patients (42%) died due to severe co-morbidity. Adverse events related to Q-D were not observed and neither renal nor liver function was adversely affected. CONCLUSIONS: Quinupristin-dalfopristin appears to be an efficient and safe antimicrobial drug for the rescue treatment of staphylococcal infections in critically ill patients. It may be considered as a treatment option in cases of vancomycin treatment failure.

Adult↗
PubMed2001

MuSK induces in vivo acetylcholine receptor clusters in a ligand-independent manner.

Muscle-specific receptor tyrosine kinase (MuSK) is required for the formation of the neuromuscular junction. Using direct gene transfer into single fibers, MuSK was expressed extrasynaptically in innervated rat muscle in vivo to identify its contribution to synapse formation. Spontaneous MuSK kinase activity leads, in the absence of its putative ligand neural agrin, to the appearance of epsilon-subunit-specific transcripts, the formation of acetylcholine receptor clusters, and acetylcholinesterase aggregates. Expression of kinase-inactive MuSK did not result in the formation of acetylcholine receptor (AChR) clusters, whereas a mutant MuSK lacking the ectodomain did induce AChR clusters. The contribution of endogenous MuSK was excluded by using genetically altered mice, where the kinase domain of the MuSK gene was flanked by loxP sequences and could be deleted upon expression of Cre recombinase. This allowed the conditional inactivation of endogenous MuSK in single muscle fibers and prevented the induction of ectopic AChR clusters. Thus, the kinase activity of MuSK initiates signals that are sufficient to induce the formation of AChR clusters. This process does not require additional determinants located in the ectodomain.

Animals↗
PubMed2001

Acetylcholine receptors are required for agrin-induced clustering of postsynaptic proteins.

We have investigated the role of acetylcholine receptors (AChRs) in an early step of postsynaptic assembly at the neuromuscular synapse, the clustering of postsynaptic proteins induced by nerve-released agrin. To achieve this, we used two variants of C2 myotubes virtually lacking AChRs and C2 cells in which surface AChRs were down-regulated by AChR antibodies. In all cases, agrin caused normal clustering of the agrin receptor component MuSK, alpha-dystrobrevin and utrophin, but failed to aggregate AChRs, alpha- and beta-dystroglycan, syntrophin isoforms and rapsyn, an AChR-anchoring protein necessary for postsynaptic assembly and AChR clustering. In C2 variants, the stability of rapsyn was decreased, whereas in antibody-treated cells, rapsyn efficiently co-localized with remaining AChRs in microaggregates. Upon ectopic injection into myofibers in vivo, rapsyn did not form clusters in the absence of AChRs. These results show that AChRs and rapsyn are interdependent components of a pre-assembled protein complex that is required for agrin-induced clustering of a full set of postsynaptic proteins, thus providing evidence for an active role of AChRs in postsynaptic assembly.

Agrin↗
PubMed2001

Serodiagnosis of cat scratch disease: response to Bartonella henselae in children and a review of diagnostic methods.

In this study, sera from 116 children without clinical evidence of cat scratch disease (CSD) and sera from 19 children with CSD were investigated by two different immunofluorescent assays (test A and test B) to evaluate the seroprevalence of Bartonella henselae antibodies in this population. Antibodies against Bartonella henselae were found in noninfected children only in low titers: 13% and 3.5% of serum samples were positive by test A and test B, respectively. IgG titers as determined by test A ranged from 1:64 to 1:256, whereas test B did not yield titers >1:64. Of the 19 children with CSD, 7 (37%) and 5 (26%) had low antibody titers (1:64-1:256) on admission by test A and test B, respectively. In such cases, IgM antibodies against Bartonella henselae and/or a titer increase in the following weeks are required to prove suspected CSD. The results indicate that the seroprevalence of Bartonella henselae antibodies in children without evidence of CSD is low, and that the results may differ depending on the tests being used. Low antibody titers, however, were found not only in healthy children but also among patients with CSD, which could be indicative of the beginning or of the end of an illness. Currently, only few data are available concerning the seroprevalence of antibodies to Bartonella spp. among children. Although children are often affected by CSD, the specificity of most tests has been evaluated by investigating blood donors, who are usually adults. Several different serological tests are used for the diagnosis of CSD, including the immunofluorescence assay, the enzyme-linked immunosorbent assay, and Western blot (WB) analysis. The sensitivities of different IFAs range from 14 to 100%, depending on the antigen used, the cut-off chosen, and the test procedures. The current diagnostic value of different serological tests for diagnosis of CSD is reviewed.

Adolescent↗
PubMed2001

Assembly and clustering of acetylcholine receptors containing GFP-tagged epsilon or gamma subunits: selective targeting to the neuromuscular junction in vivo.

Acetylcholine receptor (AChR) gamma and epsilon subunits were tagged by green fluorescent protein (GFP) to analyse assembly and targeting in live muscle fibers at the neuromuscular junction. N- or C-terminal fusion polypeptides showed no fluorescence upon transfection of HEK cells. When GFP was inserted into the cytoplasmic loop connecting putative transmembrane regions M3 and M4, the gamma/GFP and epsilon/GFP subunits were fluorescent and formed together with the alpha, beta, and delta subunits GFP-tagged AChR complexes that were integrated into the plasma membrane. As the AChR were also clustered by rapsyn, the results indicate that the cytoplasmatic domains of the gamma and epsilon subunits may not be required for assembly and rapsyn-dependent clustering. The gamma/GFP and epsilon/GFP subunit-containing receptors were expressed in X. laevis oocytes and have affinities for acetylcholine similar to that of the wild-type receptors. Direct gene transfer into single muscle fibers reveals that gamma/GFP or epsilon/GFP polypeptides are expressed at the site of injection and are transported within the endoplasmatic reticulum. When reaching subsynaptic regions, both gamma/GFP or epsilon/GFP subunits compete with endogenous epsilon subunits to assemble GFP-tagged receptors, which are selectively targeted to the postsynaptic membrane.

Animals↗
PubMed2001

Bartonella schoenbuchii sp. nov., isolated from the blood of wild roe deer.

The genus Bartonella comprises two human-specific pathogens and a growing number of zoonotic or animal-specific species. Domesticated as well as wild mammals can serve as reservoir hosts for the zoonotic agents and transmission to humans may occur by blood sucking arthropods or by direct blood to blood contact. Humans may come into intimate contact with free-ranging mammals during hunting, especially during evisceration with bare hands, when accidental blood to blood contact frequently occurs. The objective of this work was to determine the presence and the polymorphism of Bartonella strains in wild roe deer (Capreolus capreolus) as the most widely spread game in Western Europe. We report the isolation of four Bartonella strains from the blood of five roe deer. These strains carry polar flagella similar to Bartonella bacilliformis and Bartonella clarridgeiae. Based on their phenotypic and genotypic characteristics, three of the four roe deer isolates were different and they were all distinct from previously described Bartonella species. They can be distinguished from each other and from other Bartonella species by their protein profile, ERIC-PCR pattern, 16S rRNA and citrate synthase (gitA) gene sequences, as well as by whole DNA-DNA hybridization. In spite of their considerable heterogeneity, all four strains fulfil the criteria for belonging to a single new species. The name Bartonella schoenbuchii is proposed for this new species. The type strain R1T of Bartonella schoenbuchii has been deposited in the National Collection of Type Cultures as NCTC 13165T and the Deutsche Sammlung von Mikroorganismen und Zellkulturen as DSM 13525T.

Animals↗
PubMed2000

Hemin-dependent growth and hemin binding of Bartonella henselae.

Bartonella henselae causes cat-scratch disease and bacillary angiomatosis peliosis. The bacteria reside in erythrocytes of asymptomatic cats, which represent the natural reservoir for this pathogen. B. henselae is usually grown on blood-enriched media. Growth experiments on Brucella medium without blood demonstrated that heme compounds are essential for the growth of B. henselae and can completely substitute the addition of blood components. The heme precursor protoporphyrin IX alone, or in combination with FeCl(2) or FeCl(3), as well as transferrin or lactoferrin did not support growth, indicating that B. henselae cannot synthesize heme itself. Hemin supported growth even when free iron was chelated, indicating that hemin is also used as an iron source. Binding assays showed that hemin starvation increased the binding capacity of B. henselae for hemin, providing evidence that the bacteria carry a specific hemin uptake system, which might be regulated by hemin.

Bartonella henselae↗
PubMed2000

Electrical activity and postsynapse formation in adult muscle: gamma-AChRs are not required.

Skeletal muscle fibers will not accept hyperinnervation by foreign motor axons unless they are paralyzed, suggesting that paralysis makes them receptive to innervation, e.g., by upregulating extrasynaptic expression of gamma-AChRs and/or of the agrin receptor MuSK. To examine the involvement of these parameters in paralysis-mediated synapse induction, ectopic expression of agrin, a factor from motor neurons controlling neuromuscular synapse formation, was made dependent on the administration of doxycycline in innervated adult muscle fibers. In response to doxycycline-induced agrin secretion, adult fibers did form ectopic postsynaptic specializations, even when they were electrically active, lacked fetal AChRs, and expressed normal low levels of MuSK. These data demonstrate that paralysis and changes associated with it are not required for agrin-induced postsynapse formation. They suggest that paralyzed muscle induces synapse formation via the release of factors that make motor neurites contact muscle fibers and secrete agrin.

Agrin↗
PubMed2000

Gene transfer into individual muscle fibers and conditional gene expression in living animals.

Pressure injection of DNA directly into individual fibers of surgically exposed soleus muscle leads to efficient and reliable expression of the transgene. Conditionally regulated gene expression in a single muscle fiber was analyzed in vivo by co-injecting a tetracycline-regulated lacZ reporter construct and a transactivator (rtTA) expression vector. The tetracycline-responsive element revealed significant basal transcriptional activity that was further increased by rtTA even in the absence of the effector doxycycline (dox). The high basal activity of the simple two-component system precludes tight gene regulation in muscle. Concomitant expression of the silencer tTS(Kid), however, reduced the basal activity to low or undetectable levels. This allowed the specific activation of the tetracycline-responsive element by the application of dox. Direct gene transfer can thus be employed to express transgenic proteins in distinct muscle fibers at spatially defined regions and to regulate gene expression conditionally.

Animals↗
PubMed2000

[Parotid involvement in cat scratch disease: a differential diagnosis with increased significance].

BACKGROUND: Bartonella henselae is the causative agent of cat-scratch disease (CSD), an inflammatory infection of the lymph nodes. So far, only few cases of atypical manifestations in the head and neck, especially manifestations in the parotid gland have been reported. PATIENTS AND METHODS: Between January 1997 and June 1999 seven patients with manifestations of CSD in the parotid gland were observed at the ENT-department Freiburg. The positive diagnosis was confirmed serologically by an indirect immunofluorescence assay and by detection of Bartonella henselae-DNA with PCR-amplification and subsequent hybridization or sequencing. RESULTS: An intraglandular abscessed lymphadenitis was found in five patients, two of these cases were based on a Parinaud's oculoglandular syndrome. A diffuse affection of the parotid gland, initially misinterpreted as a parotid tumor, was seen in two patients. CONCLUSIONS: Antibiotic treatment is recommended in order to reduce the duration of the disease, in cases of pain and lymph node abscesses. In uncommon manifestations of CSD, the nosological assignment can be difficult on the basis of the heterogeneous symptomatic in the individual patient and the CSD diagnosis can only be confirmed by serology or PCR-based techniques. CSD should be considered in the differential diagnosis of all equivocal masses in the head and neck, even in unusual localisations like the parotid gland.

Abscess↗
PubMed2000

[Neck abscess as primary manifestation of head and neck carcinoma: implications for diagnostic management].

BACKGROUND: Neck abscesses and deep neck infections are common diseases in the field of otorhinolaryngology. However, malignant lymph node metastases presenting as abscesses are uncommon and have rarely been described up to now. PATIENTS: A retrospective review between March 1997 and August 1999 was conducted of 40 patients with deep neck abscesses. RESULTS: In five patients (12.5%) the histological diagnostics revealed a malignancy. From these, in 3 cases the cervical abscess was the primary clinical symptom of an oropharyngeal as well as a hypopharyngeal carcinoma. With further 2 patients, the neck-abscess was located as first clinical sign of a metachronous lymph node metastases after oropharyngeal carcinoma. Aerobic bacteria were recovered in 18 patients, anaerobes alone in 3 and mixed aerobic and anaerobic bacteria in 6 patients. Bartonella henselae was recovered in 7, Mycobacterium tuberculosis in 3 and Actinomyces israelii in 1 patient. CONCLUSIONS: A biopsy of the abscess wall is recommended in establishing the diagnosis. The indication for a simultaneous panendoscopy--especially in patients with typical risk for malignancies--to exclude a primary tumor in the aerodigestive tract should be regarded generously. Neck abscesses should be considered in the differential diagnosis of head and neck carcinoma.

Abscess↗
PubMed2000

Antimicrobial susceptibility patterns of Streptococcus agalactiae in a German university hospital.

Group B streptococci (GBS) are the major cause of neonatal sepsis and meningitis. GBS infection in neonates is usually treated with a combination of penicillin and gentamicin. According to consensus guidelines, pregnant women at risk receive intrapartum prophylaxis with either ampicillin or penicillin or, in case of allergy, with erythromycin or clindamycin. We investigated the susceptibility patterns of 190 GBS strains from neonates isolated from 1993-1999 and 150 GBS strains collected from adult women in 1997 and 1999. All isolates were susceptible to penicillin, ampicillin and cefotaxime. Erythromycin resistance among all isolates from neonates and from adult women in 1997 was 4.7% and 6%, respectively. In contrast, 12% of the isolates from adult women in 1999 were resistant to erythromycin and 7% were resistant to clindamycin. These findings show an increasing macrolide resistance in recent GBS strains and indicate the need for further surveillance.

Adult↗
PubMed2000

Portal vein and bone involvement in disseminated cat-scratch disease: report of 2 cases.

Cat-scratch disease (CSD) is a common cause of regional lymphadenopathy. We describe 2 children with an unusual presentation of disseminated CSD, the first one presenting with persistent fever, multilocular abscesses in liver and spleen as well as osteolytic lesions in the lumbar spine and the second one with portal vein thrombosis and severe ascites.

Bone and Bones↗
PubMed2000

Characterization of Bartonella clarridgeiae flagellin (FlaA) and detection of antiflagellin antibodies in patients with lymphadenopathy.

Cat scratch disease (CSD) is a frequent clinical outcome of Bartonella henselae infection in humans. Recently, two case reports indicated Bartonella clarridgeiae as an additional causative agent of CSD. Both pathogens have been isolated from domestic cats, which are considered to be their natural reservoir. B. clarridgeiae and B. henselae can be distinguished phenotypically by the presence or absence of flagella, respectively. Separation of the protein content of purified flagella of B. clarridgeiae by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis indicated that the flagellar filament is mainly composed of a polypeptide with a mass of 41 kDa. N-terminal sequencing of 20 amino acids of this protein revealed a perfect match to the N-terminal sequence of flagellin (FlaA) as deduced from the sequence of the flaA gene cloned from B. clarridgeiae. The flagellin of B. clarridgeiae is closely related to flagellins of Bartonella bacilliformis and several Bartonella-related bacteria. Since flagellar proteins are often immunodominant antigens, we investigated whether antibodies specific for the FlaA protein of B. clarridgeiae are found in patients with CSD or lymphadenopathy. Immunoblotting with 724 sera of patients suffering from lymphadenopathy and 100 healthy controls indicated specific FlaA antibodies in 3.9% of the patients' sera but in none of the controls. B. clarridgeiae FlaA is thus antigenic and expressed in vivo, providing a valuable tool for serological testing. Our results further indicate that B. clarridgeiae might be a possible etiologic agent of CSD or lymphadenopathy. However, it remains to be clarified whether antibodies to the FlaA protein of B. clarridgeiae are a useful indicator of acute infection.

Amino Acid Sequence↗
PubMed2000

Altered heart rate and blood pressure variability in mice lacking the Mas protooncogene.

Heart rate variability is a relevant predictor of cardiovascular risk in humans. A significant genetic influence on heart rate variability is suggested, although the genes involved are ill-defined. The Mas-protooncogene encodes a G-protein-coupled receptor with seven transmembrane domains highly expressed in testis and brain. Since this receptor is supposed to interact with the signaling of angiotensin II, which is an important regulator of cardiovascular homeostasis, heart rate and blood pressure were analyzed in Mas-deficient mice. Using a femoral catheter the blood pressure of mice was measured for a period of 30 min and 250 data values per second were recorded. The mean values and range of heart rate and blood pressure were then calculated. Neither heart rate nor blood pressure were significantly different between knockout mice and controls. However, high resolution recording of these parameters and analysis of the data by non-linear dynamics revealed significant alterations in cardiovascular variability in Mas-deficient animals. In particular, females showed a strong reduction of heart rate variability. Furthermore, the data showed an increased sympathetic tone in knockout animals of both genders. The marked alterations detected in Mas-deficient mice of both genders suggest that the Mas-protooncogene is an important determinant of heart rate and blood pressure variability.

Angiotensin II↗
PubMed1999

Identification and characterization of a novel splice variant of MuSK.

MuSK is a receptor tyrosine kinase that initiates the formation of neuromuscular junctions in response to agrin. Little is known about the ligand-induced activation and kinase-dependent signalling that leads to the clustering of acetylcholine receptors. The ectodomain of these molecule is composed of four Ig-like domains. We describe here the isolation of a novel MuSK splice variant that lacks the third Ig-like domain in its ectodomain. The corresponding RNA is the result of alternative splicing which eliminates two exons. There is 10 times less mRNA for this shorter form than for the long form of MuSK and both forms are regulated coordinately. They decrease strongly after birth and are elevated in denervated muscle. Gene transfer by muscle injection of MuSK DNA into individual muscle fibers demonstrates that kinase-induced acetylcholine receptor clustering caused by overexpression of the two kinases does not depend on the presence of the third Ig-like domain.

Alternative Splicing↗