LmxMPK4, a mitogen-activated protein (MAP) kinase homologue essential for promastigotes and amastigotes of Leishmania mexicana

BACKGROUND

Leishmania parasites undergo profound morphological and biochemical changes while passing through their life cycle. Protein kinases have been shown to be involved in the differentiation from the extracellular flagellated promastigotes to the intracellular "non-flagellated" amastigotes and vice versa. Moreover, these enzymes are likely involved in the regulation of the proliferation of the different life stages.

RESULTS

Here, we characterize LmxMPK4, a mitogen-activated protein (MAP) kinase homologue from Leishmania mexicana. The kinase reveals all sequence motifs for classification as a MAP kinase. LmxMPK4 proved to be active as a recombinant protein. The kinase is expressed in promastigotes and amastigotes. It was impossible to generate homozygous gene deletion mutants for LmxMPK4 in promastigotes. Moreover, amastigotes bearing only an episomal copy of the gene stably retained LmxMPK4 over a prolonged period without antibiotic pressure in infected mice.

CONCLUSION

LmxMPK4 is essential for promastigotes and amastigotes of Leishmania. It shows significant amino acid sequence divergence to mammalian MAP kinases. Thus, LmxMPK4 is a promising new drug target.

LmxPK4, a mitogen-activated protein kinase kinase homologue of Leishmania mexicana with a potential role in parasite differentiation

Members of the mitogen-activated protein (MAP) kinase cascade are important for the establishment of a Leishmania mexicana infection and are involved in flagellar length control, although the underlying molecular mechanisms remain to be elucidated. This study reports the cloning and characterization of LmxPK4, a MAP kinase kinase homologue of L. mexicana displaying putative plant-like regulatory phosphorylation sites. The recombinant protein has autophosphorylating activity and phosphorylates myelin basic protein. An LmxPK4 gene deletion mutant showed a proliferation defect after infection of macrophages and no or delayed lesion development in mice. Irrespective of the onset of lesion development parasites showed an early and homogeneous lesion development in re-infection experiments. This is indicative for a compensation of the null mutant phenotype. Additionally, this phenotype could be reverted by reintroduction of the wild-type gene into the deletion background. Mutants expressing loss-of-function or N-terminally truncated versions of LmxPK4 retained the null mutant phenotype. LmxPK4 is stage-specifically expressed in promastigotes and during differentiation to amastigotes, but is not detectable in amastigotes isolated from the mammalian host. Moreover, its in vitro kinase activity increases with temperature rise up to 40 degrees C. Our results suggest that LmxPK4 is involved in the differentiation process and affects virulence of Leishmania mexicana.

Binding affinity and capacity of putative adaptor-mediated sorting of a Type I membrane protein in Leishmania mexicana

The membrane-bound acid phosphatase (MBAP), a Type I membrane protein predominantly associated with endosomal/lysosomal structures of Leishmania mexicana promastigotes, contains motifs in its cytosolic COOH-terminal tail (-MEVWRRYMKFKNKQSEAIIV-COOH) akin to tyrosine- and di-leucine-based sorting signals in multicellular organisms. Here, we first show that the COOH-terminal residues IIV of MBAP, but not the Y-residue, are required for endosomal targeting, suggesting specific binding to an adaptor complex at the cell surface. We then determine whether specific binding can be saturated by analysing the efficiency of endosomal targeting for increasing numbers of MBAP molecules per cell. The ratio of the steady-state abundance of wild-type MBAP on the cell surface to MBAP on endosomes increases until the distribution is no longer different from that observed for a mutant MBAP which lacks the IIV-motif or for a glycosylphosphatidylinositol-anchored form, both of which are distributed according to bulk membrane flow. A quantitative analysis of these in vivo results indicates specific binding to a putative adaptor complex with an affinity of about 10-4M to 50,000 sorting sites on the cell surface.

[Surgical anatomy of the lumbar spine]

The success and risks of spinal surgery depend on a correct diagnosis and detailed knowledge of anatomy. This report provides information on relevant structures of the lumbar spine and possible surgical complications. Anatomical topography and different surgical approaches are described step by step.

Medizinische und ökonomische Effizienz des Eigenblutverfahrens bei Endoprothesenimplantation des Hüft- oder Kniegelenkes

AIM

Preoperative autologous blood donation before joint replacement has become standard practice. However, this procedure is discussed controversially regarding medical benefit and cost-effectiveness.

METHOD

In a retrospective study the data of 994 patients scheduled for hip (THR) or knee arthroplasty (TKR) between 1/2000 and 9/2002 were analysed.

RESULTS

Altogether 612 patients donated autologous blood (61.6 %). 50.2 % of the patients got blood transfusions during surgery or in the course of their hospitalisation. Donors received blood units more often than non-donors (55.2 vs. 41.9 %). On average 1.4 +/- 1.7 blood units were given during or after THR and 0.8 +/- 1.1 units during or after TKR. Clear predispositions for an increased use of blood transfusions were cemented endoprosthesis, old age (> 70 years) as well as exclusive general anaesthesia. Since 57.8 % of the blood units were wasted, the additional expenses (only laboratory and material costs were calculated) for each retransfused autologous blood unit were calculated to be 28.76.

CONCLUSION

Besides saving homologous blood, autologous blood donation causes mainly an increased probability of giving transfusions and higher costs. Therefore autologous blood donation should be indicated more critically, especially in younger patients and knee replacements.

LmxMPK9, a mitogen-activated protein kinase homologue affects flagellar length in Leishmania mexicana

Components of mitogen-activated signal transduction pathways have been shown to be involved in flagellum biogenesis and maintenance. A mitogen-activated protein kinase homologue, designated LmxMPK9 from Leishmania mexicana, has been recently identified in a homology screen and its mRNA found to be present in all life stages. Three different splice-addition sites were used for mRNA maturation in trans-splicing in the different life stages. However, here we show that LmxMPK9 protein is exclusively found in the promastigote stage. Recombinant expression of LmxMPK9 in Escherichia coli and kinase assays revealed a temperature optimum at 27 degrees C, the optimal growth temperature for L. mexicana promastigotes, and a preference for manganese to promote substrate phosphorylation of myelin basic protein. A deletion mutant for the single-copy gene revealed significantly elongated flagella, whereas overexpression led to a subpopulation with rather short to no flagella suggesting a role for LmxMPK9 in flagellar morphogenesis.

[In vitro effects of diclofenac and selective cyclooxygenase-2 inhibitors on prostaglandin release from inflamed bursa subacromialis tissue in patients with subacromial syndrome]

BACKGROUND

To compare the in vitro effects of selective COX-2 inhibitors (L-745,337, NS-398 and DFU) and of COX-unspecific diclofenac on release of PGE(2 )and 6-keto-PGF(1alpha) from inflamed bursa subacromialis tissue (IBST) obtained from a total of 35 patients with shoulder impingement syndrome (SIS).

PATIENTS AND METHODS

Bursal specimens were incubated in the presence of drugs (0.01-1000 microM) for 20 min and 16 h.

RESULTS

After 20 min 10 microM diclofenac significantly inhibited formation of PGE(2) and 6-keto-PGF(1alpha), whereas L-745,337 and NS-398 (10-1000 microM) induced significant inhibition only at concentrations > or =100 microM. In contrast to equimolar diclofenac, DFU (0.01-10 microM) induced no inhibition of bursal PGE(2) release but a dose-dependent, although statistically not significant inhibition after 16 h. The inhibitory potency of diclofenac (0.01-10 microM) was even more increased during long-term incubation showing greater inhibition than DFU at all concentrations studied.

CONCLUSION

The data suggest that in IBST in SIS in vitro the majority of PG is generated via the COX-1 pathway.

[Cup placement in hip replacement surgery -- A comparison of free-hand and computer assisted cup placement in total hip arthroplasty -- a multi-center study]

AIM

The purpose of the current study was to determine the accuracy of free hand and computer-assisted (CAS) cup placement.

MATERIAL AND METHODS

Between June 1985 and August 2001, 105 free-hand and from March to November 1999 80 total hip arthroplasties under computer assistance were implanted in the above mentioned centers. To determine the accuracy of the cups, the inclination and anteversion angles were measured. In all cases the cup position was measured with a CT-investigation of the pelvis. Statistical analysis was performed with the F-test.

RESULTS

With regard to the inclination and anteversion angles the variability of the cup position was significantly higher in the group of free hand implanted cups. In the CAS group we could not find any "extreme" positions.

CONCLUSION

Using computer-assisted surgery a significantly higher reproducible cup position can be obtained. Long time survey may present a lowering of the rate of early and late complications caused by better prostheses alignment in the follow up.

The accuracy of free-hand cup positioning--a CT based measurement of cup placement in 105 total hip arthroplasties

We studied 105 patients who received a total hip arthroplasty between June 1985 and August 2001 using freehand positioning of the acetabular cup. Using pelvic CT scan and the hip-plan module of SurgiGATE-System (Medivision, Oberdorf, Switzerland), we measured the angles of inclination and anteversion of the cup. Mean inclination angle was 45.8 degrees +/-10.1 degrees (range: 23.0-71.5 degrees ) and mean anteversion angle was 27.3 degrees +/-15.0 degrees (range: -23.5 degrees to 59.0 degrees ). We compared the results to the "safe" position as defined by Lewinnek et al. and found that only 27/105 cups were implanted within the limits of the safe position. We conclude that a safe position as defined by Lewinnek et al. [13] was only achieved in a minority of the cups that were implanted freehand.

[Mid-term clinical results of in-patient conservative treatment of cervicobrachialgia syndromes]

AIM

The aim of this study was to evaluate the mid-term results of an in-patient conservative therapy regimen for discogenic cervicobrachialgia.

METHODS

A retrospective follow-up of 100 patients after an average of 4.01 years with clinical examination and a questionnaire was performed.

RESULTS

The subjective outcome rating for pain on a scale from 0 (pain-free) to 10 (maximum imaginable pain) was reduced from 7.91 at beginning of the therapy to 3.19 at the end of the therapy and to 1.5 at follow-up (p < 0.005). Duration of pain, reductions of motion and palsy improved significantly. The patients' appraisal of required surgical therapy could be reduced from 26 % at beginning to 2 % at the end of the therapy.

CONCLUSION

The intensive conservative in-patient treatment for discogenic cervicobrachialgia shows a high satisfaction of the treated patients even after a follow-up of four years. The natural course of the disease shows a rapid and stable remission after wearing off the acute or subacute complaints.

Identification of mitogen-activated protein kinase homologues from Leishmania mexicana

Mitogen-activated protein kinases are key-regulatory elements in the differentiation, proliferation, apoptosis and stress response of eukaryotic cells. Our recent identification of a mitogen-activated protein kinase homologue in Leishmania mexicana which is essential for the proliferation of the amastigote stage of the parasite living in the parasitophorous vacuole of the infected macrophage prompted us to screen the genome of L. mexicana for additional mitogen-activated protein kinase homologues using degenerate oligonucleotide primers in a polymerase chain reaction amplification approach. We cloned and sequenced the genes for eight new mitogen-activated protein kinase homologues which were subsequently shown to be present in one copy per haploid genome. The mRNA levels of the kinases varied significantly in pro- and amastigote life stages of the parasite. We used the structural information of the p38 stress-activated protein kinase, which belongs to the family of mitogen-activated protein kinases, for the alignment of the deduced proteins and the verification of the predicted secondary structure elements. All new mitogen-activated protein kinases reveal the typical 12 subdomain primary structure, the conserved residues characterising serine/threonine protein kinases and the characteristic TXY motif in the phosphorylation lip. Typical features of some of the molecules are amino acid insertions between the subdomains and long carboxy-terminal amino acid extensions carrying putative src-homology 3-binding motifs.

Ikterus und schwere Leberfunktionsst�rung bei der hormonablativen Behandlung des Prostatakarzinoms

Flutamide is an antiandrogen and frequently used for the treatment of prostatic cancer. Severe hepatotoxicity occurs in few patients but may be fatal. We report on two patients with prostatic cancer who received a therapy with flutamide. They showed different degrees of liver damage. One patient recovered completely after withdrawal of Flutamide under medication with steroids. Clinical symptoms and laboratory findings returned to normal within four weeks. Despite immediate withdrawal of Flutamide, the other patient showed a severe course with progressive liver dysfunction and hepatorenal syndrome. He finally died under the clinical picture of fulminant hepatic coma. This case represents the first death associated with flutamide in Germany. The literature concerning the metabolism of flutamide and the published cases of hepatotoxicity of this drug are reviewed.

[Participatory mapping as a tool for public health decision-making in nomadic settings. A case study among Dazagada pastoralists of the Bahr-el-Ghazal region in Chad]

Integrating the strategies of the point of view of nomadic breeders of cattle into a geographic information system (GIS) highlights the complexity of the temporospatial context associated with point of view of nding health care seeking by nomadic pastoralists. The method used in this study was based on a combination of participatory mapping with group discussions and semi-structured interviews. The resulting data allowed georeferencing of the pastoral environment in the inner Lake Chad Basin according to the representation of Dazagada pastoralists of the Bahr-el-Ghazal region (Kanem, Tchad). By providing better insight into the day-to-day life of nomadic people determining their capacities to make use of primary health care, this holistic approach provides a tool to assist public health decision-makers in optimizing the use of health care facilities by nomadic communities.

[Health care centre attendance by Arab nomadic pastoralists. A case study in Kanem, Chad]

Attendence at a rural health centre in a nomadic setting was monitored over several months to gain insight into factors determining accessibility to permanent primary health facilities by nomadic people. Multiple interactions between favorable and unfavorable factors for health care seeking in a nomadic setting were identified for a health care center particularly appreciated by pastoral nomads.

Protein kinase involved in flagellar-length control

During its life cycle, the parasitic protozoon Leishmania mexicana differentiates from a flagellated form, the promastigote, to an amastigote form carrying a rudimentary flagellum. Besides biochemical changes, this process involves a change in overall cell morphology including flagellar shortening. A mitogen-activated protein kinase kinase homologue designated LmxMKK was identified in a homology screening and found to be critically involved in the regulation of flagellar assembly and cell size. LmxMKK is exclusively expressed in the promastigote stage and is likely to be regulated by posttranslational mechanisms such as phosphorylation. A deletion mutant for the single-copy gene revealed motile flagella dramatically reduced in length and lacking the paraflagellar rod, a structure adjacent to the axoneme in kinetoplastid flagella. Moreover, a fraction of the cells showed perturbance of the axonemal structure. Complementation of the deletion mutant with the wild-type gene restored typical promastigote morphology. We propose that LmxMKK influences anterograde intraflagellar transport to maintain flagellar length in Leishmania promastigotes; as such, it is the first protein kinase known to be involved in organellar assembly.

[Occupational diseases of the spine]

Since 1993 occupational influences of the spine are included into the German workman's compensation law (Berufskrankheitenverordnung). Because it is difficult to differentiate degenerative from occupational disc diseases only 3 % of the proposals have been accepted in the last years. Unfortunately most of the epidemiologic studies only consider morphologic changes of the spine but not discogenic diseases. More efforts have to be made to prevent spine diseases in the working place by exercises and back training. Our results of medical opinions in 256 cases of occupational spine diseases are presented and analysed.

Early response gene expression during differentiation of cultured Leishmania donovani

The promastigote form of the unicellular parasite, Leishmania donovani, must differentiate into the amastigote form to establish an infection in a mammalian host. Identification of genes whose expression changes during differentiation could help reveal mechanisms of Leishmania gene regulation and identify targets for controlling the diseases caused by this human pathogen. Two genomic clones were isolated, P9 that is more highly expressed in promastigotes than in axenic amastigotes and A14 that is preferentially expressed in axenic amastigotes. Analysis of the DNA sequences revealed open reading frames that would encode 55.5 kDa and 100 kDa proteins, respectively, with no homology to known proteins. The mRNA level for these genes during 24 h time courses of parasite differentiation in culture was compared to two genes known to be differentially expressed, c-lpk2 and mkk. Changes in RNA level occurred within 2 h for each gene and continued in advance of morphological changes. The expression levels of these four genes in axenic amastigotes correlated with results from animal-derived parasites.