New antibacterial microporous CaP materials loaded with phages for prophylactic treatment in bone surgery

Hydroxyapatite and beta-tricalcium phosphate (β-TCP) are materials commonly used in bone repair. The most important problem occurring in bone repair surgery is bacterial infection which is usually overcome by treatment with antibiotics. Currently, emergence of multidrug resistant strains has led to development of alternative treatments such as phage therapy. Phages are bacterial viruses with several advantages over chemotherapy such as specificity of bacterial strain, no side effects and fast response. This study evaluates the possibility of loading hydroxyapatite and β-tricalcium phosphate ceramics used as bone substitutes with phages and their antibacterial activity against Escherichia coli K12. The majority of phages were retained in dense and microporous HA and β-TCP samples during at least 6 days suggesting the occurrence of strong interaction between phages and ceramics, which did not prevent bacterial attachment and lysis. This study has shown for the first time that phage loaded ceramics could be used in prophylactic treatments.

Molecular cloning, characterization, genomic organization and promoter analysis of the α1,6-fucosyltransferase gene (fut8) expressed in the rat hybridoma cell line YB2/0

Background

The rat hybridoma cell line YB2/0 appears a good candidate for the large-scale production of low fucose recombinant mAbs due to its lower expression of fut8 gene than other commonly used rodent cell lines. However, important variations of the fucose content of recombinant mAbs are observed in production culture conditions. To improve our knowledge on the YB2/0 fucosylation capacity, we have cloned and characterized the rat fut8 gene.

Results

The cDNAs encoding the rat α1,6-fucosyltransferase (FucT VIII) were cloned from YB2/0 cells by polymerase chain reaction-based and 5' RNA-Ligase-Mediated RACE methods. The cDNAs contain an open reading frame of 1728 bp encoding a 575 amino acid sequence showing 94% and 88% identity to human and pig orthologs, respectively. The recombinant protein expressed in COS-7 cells exhibits a α1,6-fucosyltransferase activity toward human asialo-agalacto-apotransferrin. The rat fut8 gene is located on chromosome 6 q and spans over 140 kbp. It contains 9 coding exons and four 5'-untranslated exons. FISH analysis shows a heterogeneous copy number of fut8 in YB2/0 nuclei with 2.8 ± 1.4 mean copy number. The YB2/0 fut8 gene is expressed as two main transcripts that differ in the first untranslated exon by the usage of distinct promoters and alternative splicing. Luciferase assays allow defining the minimal promoting regions governing the initiation of the two transcripts, which are differentially expressed in YB2/0 as shown by duplex Taqman QPCR analysis. Bioinformatics analysis of the minimal promoter regions upstream exons E-2 and E-3, governing the transcription of T1 and T2 transcripts, respectively, evidenced several consensus sequences for potential transcriptional repressors. Transient transfections of Rat2 cells with transcription factor expression vectors allowed identifying KLF15 as a putative repressor of T1 transcript in Rat2 cells.

Conclusion

Altogether, these data contribute to a better knowledge of fut8 expression in YB2/0 that will be useful to better control the fucosylation of recombinant mAbs produced in these cells.

Direct evidence of O-GlcNAcylation in the apicomplexan Toxoplasma gondii: a biochemical and bioinformatic study

Toxoplasma gondii and Plasmodium falciparum are apicomplexan parasites responsible for serious diseases in humans. Many studies have focused on the post-translational modifications (PTMs) found in the two protists including phosphorylation, acetylation or SUMOylation but only a few of these are concerned with the nuclear and cytosolic-specific glycosylation O-GlcNAcylation. O-GlcNAcylation is a highly dynamic PTM-regulated by the ON and OFF enzymes: O-GlcNAc transferase and O-GlcNAcase-that can compete with phosphorylation but its function remains unclear. In this work, we directly prove the O-GlcNAcylation in T. gondii using antibodies specifically directed against the modification and we strongly suggest its occurrence in P. falciparum. We found that the inducible 70 kDa-Heat Shock Protein is O-GlcNAcylated, or associated with an O-GlcNAc-partner, in T. gondii. Using anti-OGT antibodies we were able to detect the expression of the glycosyltransferase in T. gondii cultured both in human foreskin fibroblast and in Vero cells and report its putative sequence. For the first time the presence of O-GlcNAcylation is unequivocally shown in T. gondii and suspected in P. falciparum. Since the O-GlcNAcylation is implicated in many biological fundamental processes this study opens a new research track in the knowledge of apicomplexans' life cycle and pathogenic potential.

Regulation of protein phosphatase type 1 and cell cycle progression by PfLRR1, a novel leucine-rich repeat protein of the human malaria parasite Plasmodium falciparum

The protein called 'suppressor of the dis2 mutant (sds22+)' is an essential regulator of cell division in fission and budding yeasts, where its deletion causes mitotic arrest. Its role in cell cycle control appears to be mediated through the activation of protein phosphatase type 1 (PP1) in Schizosaccharomyces pombe. We have identified the Plasmodium falciparum Sds22 orthologue, which we designated PfLRR1 as it belongs to the leucine-rich repeat protein family. We showed by glutathione-S-transferase pull-down assay that the PfLRR1 gene product interacts with PfPP1, that the PfLRR1-PfPP1 complex is present in parasite extracts and that PfLRR1 inhibits PfPP1 activity. Functional studies in Xenopus oocytes revealed that PfLRR1 interacted with endogenous PP1 and overcame the G2/M cell cycle checkpoint by promoting progression to germinal vesicle breakdown (GVBD). Confirmatory results showing the appearance of GVBD were observed when oocytes were treated with anti-PP1 antibodies or okadaic acid. Taken together, these observations suggest that PfLRR1 can regulate the cell cycle by binding to PP1 and regulating its activity.

Prediction of the general transcription factors associated with RNA polymerase II in Plasmodium falciparum: conserved features and differences relative to other eukaryotes

BACKGROUND

To date, only a few transcription factors have been identified in the genome of the parasite Plasmodium falciparum, the causative agent of malaria. Moreover, no detailed molecular analysis of its basal transcription machinery, which is otherwise well-conserved in the crown group of eukaryotes, has yet been reported. In this study, we have used a combination of sensitive sequence analysis methods to predict the existence of several parasite encoded general transcription factors associated with RNA polymerase II.

RESULTS

Several orthologs of general transcription factors associated with RNA polymerase II can be predicted among the hypothetical proteins of the P. falciparum genome using the two-dimensional Hydrophobic Cluster Analysis (HCA) together with profile-based search methods (PSI-BLAST). These predicted orthologous genes encoding putative transcription factors include the large subunit of TFIIA and two candidates for its small subunit, the TFIIE beta-subunit, which would associate with the previously known TFIIE alpha-subunit, the TFIIF beta-subunit, as well as the p62/TFB1 subunit of the TFIIH core. Within TFIID, the putative orthologs of TAF1, TAF2, TAF7 and TAF10 were also predicted. However, no candidates for TAFs with classical histone fold domain (HFD) were found, suggesting an unusual architecture of TFIID complex of RNA polymerase II in the parasite.

CONCLUSION

Taken together, these results suggest that more general transcription factors may be present in the P. falciparum proteome than initially thought. The prediction of these orthologous general transcription factors opens the way for further studies dealing with transcriptional regulation in P. falciparum. These alternative and sensitive sequence analysis methods can help to identify candidates for other transcriptional regulatory factors in P. falciparum. They will also facilitate the prediction of biological functions for several orphan proteins from other apicomplexan parasites such as Toxoplasma gondii, Cryptosporidium parvum and Eimeria.

Transcriptional regulation of two stage-specifically expressed genes in the protozoan parasite Toxoplasma gondii

The protozoan parasite Toxoplasma gondii differentially expresses two distinct enolase isoenzymes known as ENO1 and ENO2, respectively. To understand differential gene expression during tachyzoite to bradyzoite conversion, we have characterized the two T.gondii enolase promoters. No homology could be found between these sequences and no TATA or CCAAT boxes were evident. The differential activation of the ENO1 and ENO2 promoters during tachyzoite to bradyzoite differentiation was investigated by deletion analysis of 5′-flanking regions fused to the chloramphenicol acetyltransferase reporter followed by transient transfection. Our data indicate that in proliferating tachyzoites, the repression of ENO1 involves a negative distal regulatory region (nucleotides −1245 to −625) in the promoter whereas a proximal regulatory region in the ENO2 promoter directs expression at a low level. In contrast, the promoter activity of ENO1 is highly induced following the conversion of tachyzoites into resting bradyzoites. The ENO2 promoter analysis in bradyzoites showed that there are two upstream repression sites (nucleotides −1929 to −1067 and −456 to −222). Furthermore, electrophoresis mobility shift assays demonstrated the presence of DNA-binding proteins in tachyzoite and bradyzoite nuclear lysates that bound to stress response elements (STRE), heat shock-like elements (HSE) and other cis-regulatory elements in the upstream regulatory regions of ENO1 and ENO2. Mutation of the consensus AGGGG sequence, completely abolished protein binding to an oligonucleotide containing this element. This study defines the first characterization of cis-regulatory elements and putative transcription factors involved in gene regulation of the important pathogen T.gondii.

[The effect of neuroleptics in a attempt at understanding the vulnerability to schizophrenia]

Animal and human data suggest that neuroleptic drugs act by decreasing the special significance of some stimulations, especially those of importance for the subject. The two following hypotheses are therefore considered as a basis for the work presented in this paper: 1) the target of neuroleptic drugs is a neuro-psychological mechanism whose function is to focalize the subject on important stimulations and to involve the subject in responding; 2) schizophrenia vulnerability could imply an excessive and abnormal propensity to be over-involved, especially in existentially loaded problems. A careful clinical study of the mode of decrease, and sometimes of disappearance, of schizophrenic delusions under the influence of neuroleptic treatment confirms the hypotheses. Results are of interest for clinical treatment and for research.

[Overall results of attempts to treat schizophrenia by hemodialysis. Reflections on the placebo effect in a psychosis]

A review is made of 325 published cases of schizophrenic patients who underwent series of hemodialysis. In 211 cases the series of dialysis were open studies; 49 of these patients (23%) were markedly improved. In 114 other patients the effects of actual and sham dialysis were compared in a double blind experiment. A marked improvement was found in 24 cases (21%). But results of sham and actual hemodialysis did not differ significantly. Hemopurification is therefore not the cause of improvement. The rate of marked improvement is however clearly higher than what one could expect in chronic schizophrenics from a simple placebo effect. The various possible causes for this special effect are discussed. It is proposed that about 20% of schizophrenic patients could favorably react to the strong healing involvement of the psychiatrist, especially when a magic aspect is implied. This should encourage to approach patients not responding to conventional therapy with more optimism and possibly with new methods.

[Therapeutic trials in schizophrenia with dialysis. State of the art and one case study (author's transl)]

The literature reveals 184 cases of chronic schizophrenia treated with dialysis, of which 51 with a good result. Success seems more frequent in women. Methodologies are often not well controlled, with poor clinical description. No confirmation of endorphin secretion can be found. However, positive results in some centers should stimulate more researches. Retrospective studies of available cases should be done to determine characteristics of responders. We have elaborated a questionnaire to select such responder patients and design controlled or cross-over studies. A placebo effect is possible in light of the magic and suggestive impact of such procedure. A mean aged 27 years, delusional for 9 years despite high doses of neuroleptics, was not helped by dialysis.

Operant behavior and the galvanic skin potential under DRL schedule

Motor and galvanic skin potential (GSP) activity were investigated during the conditioning, extinction, and reconditioning of motor responses under a differential reinforcement of low rate (DRL) schedule of reinforcement. Interresponse time (IRT) distributions for motor responses during conditioning and reconditioning gradually stabilized at a peak just beyond the minimal IRT required for reinforcement. Few unreinforced motor responses and "bursts" of motor responses were observed during conditioning and reconditioning. Relative to conditioning and reconditioning, extinction effected larger IRTs and smaller GSP amplitudes. GSP amplitudes were greater for unreinforced than for reinforced motor responses during conditioning and reconditioning. However, GSP amplitudes associated with the unreinforced extinction responses were smaller than either the reinforced or unreinforced responses during conditioning and reconditioning.