Intracavity Raman scattering couples soliton molecules with terahertz phonons

Ultrafast atomic vibrations mediate heat transport, serve as fingerprints for chemical bonds and drive phase transitions in condensed matter systems. Light pulses shorter than the atomic oscillation period can not only probe, but even stimulate and control collective excitations. In general, such interactions are performed with free-propagating pulses. Here, we demonstrate intra-cavity excitation and time-domain sampling of coherent optical phonons inside an active laser oscillator. Employing real-time spectral interferometry, we reveal that Terahertz beats of Raman-active optical phonons are the origin of soliton bound-states – also termed “Soliton molecules” – and we resolve a coherent coupling mechanism of phonon and intra-cavity soliton motion. Concurring electronic and nuclear refractive nonlinearities generate distinct soliton trajectories and, effectively, enhance the time-domain Raman signal. We utilize the intrinsic soliton motion to automatically perform highspeed Raman spectroscopy of the intra-cavity crystal. Our results pinpoint the impact of Raman-induced soliton interactions in crystalline laser media and microresonators, and offer unique perspectives toward ultrafast nonlinear phononics by exploiting the coupling of atomic motion and solitons inside a cavity

Oscillations and temporal signalling in cells

ArXiv pre-print: http://arxiv.org/abs/q-bio/0703047.-- Final full-text version of the paper available at: http://dx.doi.org/10.1088/1478-3975/4/2/R01.PMID: 17664651The development of new techniques to quantitatively measure gene expression in cells has shed light on a number of systems that display oscillations in protein concentration. Here we review the different mechanisms which can produce oscillations in gene expression or protein concentration using a framework of simple mathematical models. We focus on three eukaryotic genetic regulatory networks which show ultradian oscillations, with a time period of the order of hours, and involve, respectively, proteins important for development (Hes1), apoptosis (p53) and immune response (NF-κB). We argue that underlying all three is a common design consisting of a negative feedback loop with time delay which is responsible for the oscillatory behaviour.SK, MHJ and KS acknowledge support from the Danish National Research Foundation and Villum Kann Rasmussen Foundation. GT acknowledges support from the FIRB 2003 program of the Italian Ministry for University and Scientific Research

Antigen-Specific vs. Neutralizing Antibodies Against Conditioned Media of Patients With Clostridioides difficile Infection: A Prospective Exploratory Study

The immunological response against Clostridioides difficile (C. difficile) is crucial for an improved understanding of disease mechanisms and the development of novel therapeutic strategies. From April 2014 to February 2015, adult patients with C. difficile infection (CDI) were recruited, and the clinical course and treatment response were carefully monitored. On day 1, 3, and 6 after diagnosis, patient plasma samples were screened for anti-GDH (glutamate dehydrogenase), anti-TcdA, anti-TcdB, and anti-CWP84 (cell-wall protein 84) antibodies by ELISA. Additionally, neutralization assays of toxins from conditioned media of clinical isolates (RT010, RT014, and RT027) were performed. Most patients with CDI (n=46) had antibodies against GDH (85%) and CWP84 (61%), but only few had antibodies against TcdA (11%) and TcdB (28%). We found patients with neutralizing antibodies against C. difficile toxins (conditioned media) produced by RT027 (26%). A subgroup of these samples could neutralize both toxins from RT027 and RT014 [11%, (5/46)]; however, no single sample neutralized only RT014. Overall, neutralizing antibody titers were low (≤1:16). In a one week follow-up of acute infection, we never observed an early booster effect with seroconversion or antibody increases, irrespective of disease severity. No correlation was found between the presence of antigen-specific (ELISA) or neutralizing antibodies and the clinical course of disease. Anti-TcdB but not anti-TcdA antibodies correlated with the occurrence of neutralizing antibodies. In conclusion, natural antibody titers against C. difficile toxins were absent or low and were not associated with disease severity. The correlation between the anti-TcdB with toxin neutralization confirms the importance of TcdB for virulence of CDI. Alternative sensitization strategies, e.g., through vaccine development, are required to overcome the regular low-titer antibody production following natural intestinal C. difficile exposure

Application and clinical impact of the RESIST-4 O.K.N.V. rapid diagnostic test for carbapenemase detection in blood cultures and clinical samples

Invasive infections caused by carbapenemase-producing bacteria are associated with excess mortality. We applied a rapid diagnostic test (RDT) on clinical samples with an elevated likelihood of carbapenemase-producing bacteria and documented its impact on antibiotic treatment decisions. Among 38 patients, twelve tested positive for infections caused by carbapenemase-producing bacteria (31.6%), mainly in blood cultures. KPC (n = 10) was more frequent than OXA-48 (n = 2). RDT-based carbapenemase detection led to a treatment modification to ceftazidime/avibactam-containing regimens in all patients before detailed antibiotic testing results became available. Eleven patients (92%) survived the acute infection, whereas one patient with a ceftazidime/avibactam- and colistin-resistant OXA-48-positive isolate died

Molecular epidemiology and antimicrobial resistance of Clostridioides difficile in Germany, 2014-2019

Clostridioides difficile is a Gram positive spore-forming rod and mainly responsible for nosocomial diarrhea in developed nations. Molecular and antimicrobial surveillance is important for monitoring the strain composition including genotypes of high epidemiological importance such as ribotype 027 (RT027) and corresponding resistance patterns. 1535 isolates obtained from samples sent between 2014 and 2019 to the German National Reference Center (NRC) for diagnostic reasons (NRC strain set), and 1143 isolates from a Tertiary Care University Center in Saarland, Germany (non-NRC strain set), were evaluated using antibiotic susceptibility testing and ribotyping. In the NRC strain set, RT027 overtook RT001, the main RT found in the preceding studies, and dominated with 36.2%, followed by RT001 (13.3%), and RT014 (8.5%). Of note, since 2016 a constant decrease of RT027 could be noticed. In the non-NRC strain set a large strain diversity was present with RT014 (18%) and RT001 (8.9%) being most prevalent. In NRC samples, resistance towards metronidazole, vancomycin, moxifloxacin, clarithromycin and rifampicin was 2.7%, 0%, 57.1%, 53.2% and 19.2%, respectively. Metronidazole resistance was almost exclusively found in RT027 isolates. Rifampicin resistance was also observed predominantly in isolates of RT027, constituting an almost four-fold increase, when compared to preceeding studies in this region. In conclusion these data demonstrate that RT027 is a driver for rifampicin and metronidazole resistance, underlining the importance of continuous surveillance efforts

Prevalence of Giardia intestinalis Infection in Schistosomiasis-Endemic Areas in South-Central Mali

Intestinal parasite infections are frequent causes of diarrhea and malnutrition among children in the tropics. Transmission of helminths and intestinal protozoa is intimately connected with conditions of poverty, including inadequate sanitation and hygiene. Concurrent infections with several intestinal pathogens may lead to excess morbidity. Yet, there is a paucity of epidemiological data from Mali. In this study, stool samples from 56 individuals, aged 2–63 years, from Bamako and Niono, south-central Mali were examined for intestinal parasites using stool microscopy. Additionally, stool samples were subjected to a rapid diagnostic test (RDT) and polymerase chain reaction (PCR) for the detection of Cryptosporidium spp. and Giardia intestinalis. The predominant pathogens were Schistosoma mansoni and G. intestinalis with prevalences of 41% and 38%, respectively. Hymenolepis nana was detected in 4% of the participants, while no eggs of soil-transmitted helminths were found. Concurrent infections with G. intestinalis and S. mansoni were diagnosed in 16% of the participants. For the detection of G. intestinalis, PCR was more sensitive (100%) than RDT (62%) and microscopy (48%). As helminth-protozoa coinfections might have important implications for morbidity control programs, future studies should employ diagnostic tools beyond stool microscopy to accurately assess the co-endemicity of giardiasis and schistosomiasis

Lymphocyte predominant cells detect Moraxella catarrhalis-derived antigens in nodular lymphocyte-predominant Hodgkin lymphoma.

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is a rare lymphoma of B-cell origin with frequent expression of functional B-cell receptors (BCRs). Here we report that expression cloning followed by antigen screening identifies DNA-directed RNA polymerase beta' (RpoC) from Moraxella catarrhalis as frequent antigen of BCRs of IgD <sup>+</sup> LP cells. Patients show predominance of HLA-DRB1*04/07 and the IgVH genes encode extraordinarily long CDR3s. High-titer, light-chain-restricted anti-RpoC IgG1/κ-type serum-antibodies are additionally found in these patients. RpoC and MID/hag, a superantigen co-expressed by Moraxella catarrhalis that is known to activate IgD <sup>+</sup> B cells by binding to the Fc domain of IgD, have additive activation effects on the BCR, the NF-κB pathway and the proliferation of IgD <sup>+</sup> DEV cells expressing RpoC-specific BCRs. This suggests an additive antigenic and superantigenic stimulation of B cells with RpoC-specific IgD <sup>+</sup> BCRs under conditions of a permissive MHC-II haplotype as a model of NLPHL lymphomagenesis, implying future treatment strategies

Adaptive evolution of drug targets in producer and non-producer organisms

Mycophenolic acid (MPA) is an immunosuppressive drug produced by several fungi in Penicillium subgenus Penicillium. This toxic metabolite is an inhibitor of IMP dehydrogenase (IMPDH). The MPA biosynthetic cluster of P. brevicompactum contains a gene encoding a B-type IMPDH, IMPDH-B, which confers MPA-resistance. Surprisingly, all members of subgenus Penicillium contain genes encoding IMPDHs of both the A and B type, regardless of their ability to produce MPA. Duplication of the IMPDH gene occurred prior to and independent of the acquisition of the MPA biosynthetic cluster. Both P. brevicompactum IMPDHs are MPA-resistant while the IMPDHs from a nonproducer are MPA-sensitive. Resistance comes with a catalytic cost: while P. brevicompactum IMPDH-B is >1000-fold more resistant to MPA than a typical eukaryotic IMPDH, its value of k(cat)/K(m) is 0.5% of “normal”. Curiously, IMPDH-B of Penicillium chrysogenum, which does not produce MPA, is also a very poor enzyme. The MPA binding site is completely conserved among sensitive and resistant IMPDHs. Mutational analysis shows that the C-terminal segment is a major structural determinant of resistance. These observations suggest that the duplication of the IMPDH gene in Pencillium subgenus Penicillium was permissive for MPA production and that MPA production created a selective pressure on IMPDH evolution. Perhaps MPA production rescued IMPDH-B from deleterious genetic drift

Regulation of the Interaction of Inosine Monophosphate Dehydrogenase with Mycophenolic Acid by GTP

Inosine monophosphate dehydrogenase (IMPDH), a rate-limiting enzyme in the de novo synthesis of guanine nucleotides, is a major therapeutic target. A prototypic uncompetitive inhibitor of IMPDH, mycophenolic acid (MPA), is the active form of mycophenolate mofeteil (CellCept), a widely used immunosuppressive drug. We have found that MPA interacts with intracellular IMPDH in vivo to alter its mobility on SDS-polyacrylamide gels. MPA also induces a striking conformational change in IMPDH protein in intact cells, resulting in the formation of annular aggregates of protein with concomitant inhibition of IMPDH activity. These aggregates are not associated with any known intracellular organelles and are reversible by incubating cells with guanosine, which repletes intracellular GTP, or with GTPgammaS. GTP also restores IMPDH activity. Treatment of highly purified IMPDH with MPA also results in the formation of large aggregates of protein, a process that is both prevented and reversed by the addition of GTP. Finally, GTP binds to IMPDH at physiologic concentrations, induces the formation of linear arrays of tetrameric protein, and prevents the aggregation of protein induced by MPA. We conclude that intracellular GTP acts as an antagonist to MPA by directly binding to IMPDH and reversing the conformational changes in the protein