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Biomedical subjects

M Jäger

Publications and source records attributed to M Jäger.

At least 73 records · Page 4Linked to original sources
PubMed1999

Epstein-Barr virus infection of human astrocyte cell lines.

Epstein-Barr virus (EBV) is implicated in different central nervous system syndromes. The major cellular receptor for EBV, complement receptor type 2 (CR2) (CD21), is expressed by different astrocyte cell lines and human fetal astrocytes, suggesting their susceptibility to EBV infection. We demonstrated the infection of two astrocyte cell lines, T98 and CB193, at low levels. As infection was mediated by CR2, we used two stable CR2 transfectant astrocyte cell lines (T98CR2 and CB193CR2) to achieve a more efficient infection. We have monitored EBV gene expression for 2 months and observed the transient infection of T98 and T98CR2 cells and persistent infection of CB193 and CB193CR2 cells. The detection of BZLF1, BALF2, and BcLF1 mRNA expression suggests that the lytic cycle is initiated at early time points postinfection. At later time points the pattern of mRNA expressed (EBER1, EBNA1, EBNA2, and LMP1) differs from latency type III in the absence of LMP2A transcription and in the expression of BALF2 and BcLF1 but not BZLF1. A reactivation of the lytic cycle was achieved in CB193CR2 cells by the addition of phorbol esters. These studies identify astrocyte cell lines as targets for EBV infection and suggest that this infection might play a role in the pathology of EBV in the brain.

Astrocytes↗
PubMed1998

Epstein-Barr virus-infected B cells of males with the X-linked lymphoproliferative syndrome stimulate and are susceptible to T-cell-mediated lysis.

Primary infection with the Epstein-Barr virus (EBV) results in fatal infectious mononucleosis in up to 70% of males affected by the X-linked lymphoproliferative syndrome (XLP). This rare disease is often associated with diverse natural killer (NK)-, B- and T-cell deficiencies. We describe experiments testing whether the B lymphocytes of affected males play a role in the pathogenesis of XLP due to a low susceptibility to T-cell-mediated immunity. Using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry we detected in these B cells the expression of viral proteins EBNA-1, EBNA-2, EBNA-3A, EBNA-3C, LMP-1 and LMP-2A, which provide targets for cytotoxic T cells. Major histocompatibility complex (MHC) class I, MHC class II and the B7 costimulatory molecule were present on the cell surface. Accordingly, the EBV-infected B cells were lysed in 51Cr-release assays by T lymphocytes sharing MHC determinants with the targets. This MHC-restricted and specific lysis was confirmed in competition experiments using MHC-specific monoclonal antibodies (MAbs) and synthetic peptides. XLP-derived LCLs could also induce MHC class I-restricted memory and cytotoxic T lymphocytes. Thus, these XLP-derived B cells resembled normal LCIs in vitro with respect to induction of EBV-specific cytotoxic T cells (CTL), the ability to present EB viral antigens and the susceptibility to EBV-specific and MHC-restricted CTL-mediated killing. The failure of the immune system to eliminate these virus-infected B cells in XLP is clearly not caused by a B-cell-specific defect.

Antigens, Viral↗
PubMed1998

[Stretching--do current explanatory models suffice?].

The opinion that mobility in the usual performance if the "straight leg raise" test for the evaluation of stretching techniques is subject to solety muscular limitations is critically appraised. With integration of recent results from molecular biological research and our own measurements, we can show that not only mechanical but also neurophysiological factors must be considered in the limitation of mobility. In the majority of the examined patients stretching of the ischiadic nerve seems to be responsible for restrictions in movement. The presented results cast doubt on the currently held assumptions and basic principles of stretching in therapy and sport.

Adult↗
PubMed1998

Epstein-Barr virus small RNA (EBER) genes: differential regulation during lytic viral replication.

In every latently Epstein-Barr virus-infected cell the viral genes EBER-1 and EBER-2 are transcribed by polymerase III. In lytically infected cells in vivo the EBER genes could not be detected. However, in cell culture downregulation could not be confirmed, and hence the relevance of this shutdown to the replication of the virus was not clear. We assayed the transcriptional activity of the EBER genes by nuclear run-on assays with enriched lytically infected cells and demonstrated that EBER-1 and EBER-2 are differentially downregulated on the transcriptional level during the switch to lytic viral replication. This downregulation was an early event during the lytic replication of the virus.

Base Sequence↗
PubMed1998

Epstein-Barr viral gene expression in B-lymphocytes.

The strategy of the Epstein-Barr virus to persist lifelong in the host depends on establishing a reservoir, which cannot be detected by the immune system but allows reactivation of the virus for shedding and transmission to a new host. Epithelial cells and B-cells play a major role in this viral strategy of EBV, since differentiating epithelial tissues were shown to be permissive for lytic replication in vivo, whereas the B-lymphocytes become predominantly latently infected. However, which cells are the reservoir and which the sites of lytic replication are not quite clear. With the technique of reverse transcription, PCR and immunohistochemistry, we demonstrated that the B-cells of the peripheral blood are a major site of virus production during the primary infection during infectious mononucleosis. These permissive B-cells were also detected after convalescence, however, the absence of any lytic transcripts suggested an efficient immunological control very early in the viral lytic cycle. Serological data on reactivation of EBV correlated with the detection of lytic cycle transcripts in the blood and thus demonstrated that the site of virus production during infectious mononucleosis must be different from that of the persistent state. In those cases, where the infection takes a chronic active course, control of lytic replication is insufficient, either on the level of immune surveillance or of viral gene regulation. We have demonstrated a virus strain with a lytic phenotype in an individual suffering chronic active infection. The impaired capability of this virus to immortalise B-cells correlated with an enhanced expression of the lytic switch gene BZLF-1 and down-regulation of latent regulatory genes in the early phase of infection.

B-Lymphocytes↗
PubMed1998

The control of lytic replication of Epstein-Barr virus in B lymphocytes (Review).

Uncontrolled replication of a virus, which is harmful to the host is also disadvantageous to the virus. Most viruses cannot compete with the various immune mechanisms and become eliminated in the course of infection. Therefore, only the time between infection and eradication remains for these viruses to proliferate. A few viruses, like the Herpesviruses or the papillomaviruses, however, have developed a sophisticated strategy for persisting lifelong, usually asymptomatically in the host, hiding from the immune system and producing infectious progeny at the same time. This strategy depends on a separation of latency and the lytic replication, either by time due to differentiation-dependent mechanisms or by spatial separation as the result of different host cell types. Both are true for the Epstein-Barr virus (EBV). B cells and epithelial cells have a pivotal role in the life cycle of the virus. The former can become latently infected and are thought to be the virus reservoir in vivo, whereas the latter were shown to be permissive for lytic replication. However, replication of EBV in vivo is controlled primarily by host immune mechanisms selecting for cells that are not permissive for viral replication as the result of a particular set of transcription factors. These factors control the activity of the regulatory immediate-early genes and, in addition, lytic and latent cycle regulatory genes negatively interfere with each other and thus link cellular and viral gene regulatory mechanisms. Disturbance of both the immune surveillance as well as viral gene regulation may result in EBV-associated disease.

Animals↗
PubMed1997

The rate-limiting steps for the folding of an antibody scFv fragment.

The refolding kinetics of a single-chain Fv (scFv) fragment, derived from the phosphorylcholine binding antibody McPC603, was investigated. Both prolyl-peptide bonds which are cis in the native state affect the refolding kinetics of long-term denatured protein. The rate-limiting step is the trans --> cis isomerization at the ProL95-peptide bond, which is catalyzed by peptidyl-prolyl-cis/trans-isomerase (PPIase), and is the prerequisite for correct V(H)/V(L) domain association. Refolding of short-term denatured protein resulted in complex refolding kinetics, too. This kinetic heterogeneity could be ascribed to cis --> trans re-isomerization at the ProL95-peptide bond to the wrong conformation in a folding intermediate. PPIase was shown to increase the fraction of slowly folding species, thereby competing with the fast folding of short-term denatured scFv, having native proline conformations. A trapped intermediate is rapidly populated, and the return from this state becomes rate-limiting.

Amino Acid Sequence↗
PubMed1997

Lytic replication of Epstein-Barr virus in the peripheral blood: analysis of viral gene expression in B lymphocytes during infectious mononucleosis and in the normal carrier state.

Epstein-Barr virus (EBV) has been shown to establish latency in resting B lymphocytes of the peripheral blood. This creates a virus reservoir in contrast to lytic virus replication, which is thought to be restricted to differentiated epithelial cells in vivo. So far, the route of transmission between B cells and the production of progeny virus in the epithelial tissue has remained unclear. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry analysis of 16 patients with acute infectious mononucleosis (IM) and 25 healthy seropositive donors was performed to detect lytic replication gene products in B lymphocytes of the peripheral blood. Transcriptional activity was found in peripheral blood B lymphocytes (PBLs) for BZLF1 in 88%, BALF2 in 50%, and BcLF1 in 25% of the tested IM patients. All positive results were further confirmed in enriched B-cell populations by antigen determination using immunostaining with the APAAP technique. Furthermore, we detected transcripts for BZLF1 in 72% and for BALF2 in 16% of peripheral B lymphocytes of healthy seropositive donors. In contrast to patients with IM, no signals for BcLF1 were ever found in healthy seropositive donors. In these individuals, lytic replication of EBV is probably restricted by immunologic and gene regulatory mechanisms, whereas in the absence of immunologic control, reflected here by IM patients, the production of infectious virus becomes visible in PBLs.

B-Lymphocytes↗
PubMed1996

Purification and characterization of cysteine-S-conjugate N-acetyltransferase from pig kidney.

Microsomal cysteine-S-conjugate N-acetyltransferase catalyses the N-acetylation of various S-substituted cysteines in liver and kidney. We describe here the purification and more detailed characterization of this enzyme catalysing the final reaction of mercapturic acid biosynthesis, and thus playing a crucial role in the detoxicating metabolism of many xenobiotics. The solubilization of cysteine-S-conjugate N-acetyltransferase by deoxy-BIGCHAP [N,N'-bis-(3-D-gluconamidopropyl)deoxycholamide] was the prerequisite for partial purification by means of anion-exchange chromatography. The molecular mass of the enzyme was determined by gel filtration. A polyclonal antiserum was raised against the excised protein band from SDS/PAGE and purified antibodies were used for the complete purification of native cysteine-S-conjugate N-acetyltransferase by immuno-affinity chromatography. A dimeric form of the enzyme was sometimes detected on SDS/PAGE, depending on the degree of purification. For further characterization of cysteine-S-conjugate N-acetyltransferase, the stability of catalytic activity, the pH optimum and K(m) values were determined. The inhibitory effects of various agents were tested, revealing a substantial, yet not complete, loss of cysteine-S-conjugate N-acetyltransferase activity after treatment with cysteine proteinase inhibitors or probenecid under various conditions.

Acetyltransferases↗
PubMed1996

Pathogenesis of chronic Epstein-Barr virus infection: detection of a virus strain with a high rate of lytic replication.

In rare cases Epstein-Barr virus (EBV) leads to chronic active infection (CAEBV) which is characterized by persistant symptoms of infectious mononucleosis. Previously we described a case of persisting polyclonal B-cell lymphocytosis (PPBL) that was associated with CAEBV. Using reverse transcription and polymerase chain reaction we showed that in late passages of a spontaneous cell line, SM, latent EB viral genes such as EBNA1, EBNA2, EBNA3A/3B/ 3C, LMP1 and LMP2A were active. The master gene of the lytic cycle, BZLF1, was silent. This indicated that there was no general defect in immortalization and establishing latency by this CAEBV isolate SM. We obtained virus from the standard immortalizing strain B95-8 and the CAEBV strain SM from latently infected LCL quantified the number of virus particles by competitive PCR and demonstrated that the impaired capacity to immortalize umbilical cord blood lymphocytes was a virus strain-specific property, and was not due to an incapability to infect purified CD19+ B lymphocytes. Transcription of latency- and immortalization-associated genes such as EBNA1, EBNA2 and LMP2A was reduced, in contrast to a strongly enhanced activity of the master gene of the lytic cycle, BZLF1. A scenario for an antagonistic regulation of lytic and latent cycle genes is presented and a role for the pathogenesis of CAEBV is discussed.

B-Lymphocytes↗
PubMed1996

Electromyographical study on surgeons in urology. II. Determination of muscular fatigue.

An electromyographical fatigue analysis was performed in the operating theatre on four surgeons during 14 urological operations in which 'direct endoscopy' (cf. Luttmann et al. 1996, Part I) was applied. Surface electromyograms (EMG) were derived from the m. trapezius on both sides of the body, the right m. deltoideus, and the left m. erector spinae. The surgeons' activities were documented by simultaneously recording an electrical activity code signal parallel to the EMGs. The electrical activity (EA) was formed from the raw EMG by rectification and continuous averaging. For purposes of spectral analysis, the EMGs were digitized and converted to the frequency domain by Fast Fourier Transformation. During the performance of endoscopic surgery, an increase in EA, as well as a spectral shift towards lower frequencies, are observed for at least one of the muscles under test in all of the operations. This indicates the development of muscular fatigue in the course of the operations. The finding is confirmed by applying a newly developed method for the joint analysis of the spectrum and the amplitude of EMGs (JASA) which permits discrimination between fatigue-induced and force-related changes in the EMG. Utilizing this method, the development of fatigue was confirmed for 11 of the 14 operations in the case of the right m. trapezius. The right trapezius muscle therefore constitutes a bottleneck for the performance of the operations. The endurance time was estimated from the increase in EA and compared with the actual duration of the operations. Since both are of the same order of magnitude, it is concluded that the final part of an operation has to be performed when the muscles are already fatigued. Application of the newly available method known as 'monitor endoscopy' (cf. Part I) can lead to a reduction in muscular strain and fatigue. This, in turn, will enable operations to be performed at less risk to the patient.

Cystoscopes↗
PubMed1994

A nonradioactive assay for microsomal cysteine-S-conjugate N-acetyltransferase activity by high-pressure liquid chromatography.

Microsomal cysteine-S-conjugate N-acetyltransferase, an enzyme specific for S-substituted cysteines, plays an important role in the detoxicative metabolism of xenobiotics by catalyzing the N-acetylation of cysteine-S-conjugates. Cysteine-S-conjugate N-acetyl-transferase activity is generally assayed by measuring the amount of N-[14C]acetyl-S-benzyl-L-cysteine generated from the model compound S-benzyl-L-cysteine and [14C]acetyl-CoA and subsequent extraction of the product. Although sensitive, this method is costly and time consuming. For safety and environmental reasons we developed a nonradioactive assay for cysteine-S-conjugate N-acetyltransferase activity. Our method depends upon the acetylation of the uv-sensitive model compound 4-nitro-S-benzyl-L-cysteine. The test mixture is separated by HPLC, guaranteeing that no by-products interfere with the determination of product formation. Radioactive and nonradioactive methods were compared using different porcine kidney samples. With the nonradioactive test we determined values of Km and Vmax of both 4-nitro-S-benzyl-L-cysteine and acetyl-CoA. In summary, this new nonradioactive assay is sensitive, less costly, safer, less time-consuming, and less laborious than radioactive assays for cysteine-S-conjugate N-acetyltransferase.

Acetyl Coenzyme A↗
PubMed1994

Gastrin-releasing peptide and CCK after intraduodenal inhibition of proteases in dogs.

The intraduodenal application of a potent protease inhibitor (camostate, 600 mg) causes a significant increase in basal pancreatic secretion in the manner of a negative-feedback mechanism. The integrated protein secretion during the entire study period was 9.9 +/- 1.8 g in 120 min. The iv application of anti-GRP immunoglobulin caused a significant reduction to 5.0 +/- g in 120 min. No significant changes in the plasma concentrations of GRP and CCK were detectable. The increased secretion occurring after the administration of the protease inhibitor could be mediated by neural GRP-dependent mechanisms. These may also be relevant for CCK-dependent factors, which are only briefly mentioned.

Animals↗
PubMed1994

[Control of the placement of central venous catheters using x-ray and sonographic methods. A comparative controlled study].

At present there is no method available meeting all demands for accurate, simple and non-invasive verification of the position of central venous catheters. Using sonographic methods, it should be possible to verify central venous catheters intracardially or in the superior vena cava. We investigated whether the sonographic imaging of central venous catheters using a mobile echo camera presented an alternative to the usual control method using fluoroscopy. Since the investigated method has a rate of 20 to 30% false positive results and 8 to 26% false-negative results, it cannot be used as a routine alternative to fluoroscopy.

Adult↗
PubMed1992

Logistical and ergonomic transportation capacity for refuse collection workers: a work physiology field study.

In a work physiology field study, the work flow and the electrocardiogram were recorded throughout whole shifts for six male refuse (garbage) collection workers who transported and emptied 1.1 m3 refuse containers. The work rate (WR), indicated by the number of 1.1 m3 containers emptied per unit of time, and the work pulse rate (WPR) were determined in the data evaluation. The work pulse rate increases with the work rate. The functional relationship can be approximated by a linear regression function (WPR = 20.9 + 35.8.WR). The work pulse rate reaches such high values that it must be assumed that the work cannot be performed continuously throughout the whole working day. Consequently, regular breaks should be provided. When determining the necessary duration of the breaks, it was assumed that an equilibrium between fatigue and recovery should be maintained during the working day. The recovery breaks should be at least long enough for the heart rate to return to the resting level. The necessary duration of the breaks was determined on the basis of the present field study and the laboratory investigations described in the literature. A minimum duration of 10 min per working hour results from the calculations. The breaks should be taken regularly at about hourly intervals. A transportation-capacity model is provided for the planning of the deployment of refuse workers. It permits calculation of the number of 1.1 m3 containers a three-man crew, comprising the refuse collection truck driver and two loaders, can empty during one shift. Both the logistical and ergonomic transportation capacities can be determined using the model. The logistical transportation capacity (TCL) indicates the number of containers which can be emptied per shift by a crew when only criteria such as the optimal utilization of the working time are considered. The ergonomic transportation capacity (TCE) is understood as the number of containers which can be emptied per shift taking into consideration the workers' strain and the recovery breaks they require. TCE amounts to between about 140 and 160 containers per shift depending on the type of city district. TCL is higher by between 20 and 30 containers per shift. In order to meet the demand of protecting workers' health, the number of containers to be emptied per shift by a three-man crew should not exceed the ergonomic transportation capacity.

Adult↗
PubMed1991

The helminth fauna of the common seal (Phoca vitulina vitulina, Linné, 1758) from the Wadden Sea in Lower Saxony. Part 1: Trematodes, cestodes and acanthocephala.

Between August 1988 and January 1989 110 common seals found dead along the coast of Lower Saxony were investigated for the occurrence of trematodes, cestodes and acanthocephala. Two fluke species, Cryptocotyle lingua Creplin, 1825 and Phagicola septentrionalis Van Den Broek, 1967, two tapeworm species Diphyllobothrium cordatum Leuckart, 1863 and Diphyllobothrium elegans Krabbe, 1865, and the acanthocephala species Corynosoma strumosum Rudolphi, 1802 were found. Phagicola septentrionalis and the cestodes were always found together with Cryptocotyle lingua. The prevalence of Phagicola septentrionalis, the diphyllobothriids and the acanthocephala increased with increasing age of the pinniped host. The worm counts of all species appeared to increase with increasing age of the host. The adult male seals were more often infested with Phagicola septentrionalis and cestodes than the female adults and the younger pinnipeds. There was no correlation between blubber thickness of the seals and parasitic infection. The prevalence of the diphyllobothriids and the intensity of the infection with acanthocephala were higher in seals found in the eastern part of the Wadden Sea.

Acanthocephala↗
PubMed1991

The helminth fauna from the common seal (Phoca vitulina vitulina, Linné, 1758) of the Wadden Sea in Lower Saxony. Part 2: Nematodes.

During the seal epidemic in 1988 and the beginning of 1989, 115 common seals found dead on the shores of the Wadden Sea of Lower Saxony were investigated for the presence of nematodes. The lungworm Otostrongylus circumlitus Railliet 1899 was found in 26.1% of the seals, the lungworm Parafilaroides gymnurus Railliet 1899 in 26.9% and the heartworm Dipetalonema spirocauda Leidy 1858 in 32.2% of the seals. In the digestive tract, two anisakid species were found, Pseudoterranova decipiens Mozgovoi 1951 in 87.8% and Contracaecum osculatum Rudolphi 1802 in 10.4% of the seals. Statistical analysis revealed a negative correlation between age of the seals and prevalence and intensity of infestation with the two lungworm species and the heartworms. Adult seals were found not to be infected with Dipetalonema spirocauda and Parafilaroides gymnurus, whereas the prevalence of the two anisakid species increased with increasing age of the seals. Pseudoterranova decipiens was found more often in autumn and winter than in summer. This parasite was more prevalent and had higher worm counts in the eastern part of the Wadden Sea than in the western part. Parafilaroides gymnurus and Dipetalonema spirocauda were found more often in seals with smaller blubber thickness than in well fed seals.

Age Factors↗