T follicular helper (Tfh) cells are the prototypic T helper cell subset specialized to enable B cells to form germinal centers (GCs) and produce high affinity antibodies. Tfh cell differentiation ...begins very early in the immune response, coinciding with rapid proliferation that expands the pool of responding cells. Here we show that T cells lacking all microRNAs completely failed to differentiate into Tfh cells in vivo. MicroRNA-deficient T cells exhibited impaired proliferation as expected, but they also displayed an independent defect in the induction of the functionally critical Tfh cell proteins BCL6 and CXCR5. We found that the miR-17∼92 cluster was required for robust Tfh cell differentiation and function in a cell intrinsic manner that also occurred regardless of changes in proliferation. Conversely, miR-17∼92 overexpression in T cells promoted Tfh cell differentiation and GC B cell induction. Early in the response to protein antigen, these effects were partially dependent on altered expression of the miR-17∼92 target gene Pten, a known inhibitor of Tfh cell differentiation. In a viral infection model, Tfh cells depended on the miR-17∼92 cluster to restrain the expression of Tfh subset-inappropriate genes, including Ccr6, Il1r2, Il1r1, and the cytokine Il22. Conserved regions in the RAR-related orphan receptor alpha (Rora) 3’ UTR were directly targeted by all 4 miRNA families in the cluster. Genetically removing one Rora allele significantly rescued the inappropriate gene expression signature in miR-17∼92-deficient Tfh cells. Our results identify the miR-17∼92 cluster as a critical regulator of T cell-dependent antibody responses, Tfh cell differentiation, and the fidelity of the Tfh cell gene expression program.
Paromomycin is an aminocyclitol aminoglycoside antibiotic used for the treatment of leishmaniasis. In view of the central role of mitochondria in cellular energetics and metabolism, its effect on in ...vivo mitochondrial activities of Leishmania donovani promastigotes-the parasite flagellate form-was investigated. The approach used flow cytometry, amperometric measure of O2 consumption, and, as a global estimate of mitochondrial dehydrogenases, thiazolyl blue reduction (MTT test); some in vitro controls were also made. When added to promastigote cultures for 24-72 h at 150-200 microM (= LC50), paromomycin doubled the generation time, inhibited respiration, and lowered its associated electric potential difference across mitochondrial membranes, as measured by rhodamine 123 fluorescence. The chemical analogue neomycin was ineffective. Furthermore, the in vivo mitochondrial dehydrogenase activities were lower, seemingly because of the shortage of respiratory substrates. Indeed, succinate addition to paromomycin-treated cultures partly restored mitochondrial membrane potential. However, no immediate effect of paromomycin on respiration was observed, neither inhibition of redox chain nor increase of membrane permeability (uncoupling). It is proposed that paromomycin acts at a metabolic level upstream of the respiratory chain itself. This would have the observed delayed consequence because the cell energy supply would progressively decline since it depends upon the proton gradient-viz., membrane potential-generated by respiration. In conclusion, paromomycin is an antibiotic affecting the cell's energetic metabolism; the respiratory dysfunction it induces may be a crucial aspect of its action against Leishmania and possibly other cells.
The symbiosis between Rhizobium meliloti and Medicago sativa (Leguminosae) involves the interaction of lipochito-oligosaccharides (Nod factors) excreted by bacteria with specific proteins of the host ...plant. The cleavage of Nod factors can be used as an enzymic assay to identify novel hydrolytic enzymes. Here a soluble extract of 3-day-old roots was fractionated by anion exchange, affinity chromatography, gel filtration and native electrophoresis. Two acidic chitinases (pI 4.6-5.4), CHIT24 and CHIT36, designated in accordance with their molecular mass in kDa, were separated. CHIT24 cleaves all tested Nod factors to produce lipotrisaccharides with the preference NodRm-V(S)>NodRm-IV >NodRm-IV(S)>=NodRm-IV(Ac,S); it also hydrolyses colloidal 3H-chitin and has lysozyme activity. The kinetics of Nod factor degradation by CHIT24 depends on substrate structural parameters, namely the length of the oligosaccharide chain and sulphation (S) at the reducing end, but not much on acetylation (Ac) at the non-reducing end. The 25-residue N-terminal sequence of CHIT24 has no similarity with known chitinases or lysozymes, indicating that it is a novel type of hydrolase. CHIT36 also hydrolyses NodRm-V(S) into NodRm-III, but it is inactive towards NodRm-IV(S) and NodRm-IV(Ac,S) formed by R. meliloti. Finally, a 17 kDa protein, P17, was co-purified with CHIT24. It neither degrades Nod factors nor exhibits lysozyme activity and shows complete identity, at the 15-residue N-terminal sequence, with a class 10 pathogenesis-related protein, PR-10.
In this work, BV RI light curves of 55 Type II supernovae (SNe II) from the Lick Observatory Supernova Search program obtained with the Katzman Automatic Imaging Telescope and the 1 m Nickel ...telescope from 2006 to 2018 are presented. Additionally, more than 150 spectra gathered with the 3 m Shane telescope are published. We conduct an analyse of the peak absolute magnitudes, decline rates, and time durations of different phases of the light and colour curves. Typically, our light curves are sampled with a median cadence of 5.5 days for a total of 5093 photometric points. In average V-band plateau declines with a rate of 1.29 mag (100 days)-1, which is consistent with previously published samples. For each band, the plateau slope correlates with the plateau length and the absolute peak magnitude: SNe II with steeper decline have shorter plateau duration and are brighter. A time-evolution analysis of spectral lines in term of velocities and pseudoequivalent widths is also presented in this paper. Our spectroscopic sample ranges between 1 and 200 days post-explosion and has a median ejecta expansion velocity at 50 days post-explosion of 6500 km/s (Halpha line) and a standard dispersion of 2000 km/s. Nebular spectra are in good agreement with theoretical models using a progenitor star having a mass <16 Msol. All the data are available to the community and will help to understand SN II diversity better, and therefore to improve their utility as cosmological distance indicators.
We have previously shown that in Nicotiana sylvestris cytoplasmic male-sterile (CMS) mutants where the mtDNA lacks the nad7 gene coding for a subunit of respiratory Complex I (NADH:ubiquinone ...oxidoreductase, EC 1.6.5.3), glycine (Gly) oxidation was lower than in the wild type and insensitive to rotenone, suggesting Complex I dysfunction. In contrast, the oxidation rate of exogenous NADH and the capacity of the cyanide-resistant respiration (AOX) were enhanced. Here we report that, in contrast to Gly, the rate of malate oxidation was not affected, but proceeded totally in a rotenone-insensitive pathway, strongly suggesting that survival of CMS plants depends on the activation of internal and external alternative NAD(P) H dehydrogenases and that Gly decarboxylase activity depends on Complex I functioning. A similar defect in Complex I activity and Gly oxidation was found in the NMS1 nuclear mutant, defective in the processing of the nad4 transcript, but alternative NAD(P) H dehydrogenases were less activated. In CMS and NMS1, the fraction of the AOX pathway was increased, as compared to wild type, associated with higher amounts of aox transcripts, AOX protein, and plant resistance to cyanide. Non-phosphorylating respiratory enzymes maintained normal in vivo respiration levels in both mutants, but photosynthesis was decreased, in correlation with lower leaf conductance, emphasizing mitochondrial control on photosynthesis.
The question of the possible identity of catalytic and regulatory proton pathways in the chloroplast FoF1 ATPase has been studied using different energy-transfer inhibitors. Venturicidin, a ...reversible inhibitor of Fo, affects neither the delta mu H(+)-dependent thiol reduction of the membrane-bound chloroplast ATPase nor its ability to be activated by the proton gradient. It seems therefore to block only the proton flow required by the catalytic function of the enzymes. Venturicidin, however, also slows down the deactivation of the thiol-reduced ATPases during uncoupled ATP hydrolysis, following a delta mu H+ activation, but phloridzin, a reversible F1 inhibitor, has the same effect. Tentoxin, an irreversible F1 inhibitor, decreases the rate of ATP hydrolysis but does not affect the rate of deactivation. These findings suggest that catalytic and regulatory H(+)-binding sites are different. No distinction can be made, if any, between protons involved in unmasking the thiol-sensitive groups of F1 and in activating the enzyme. The effect of venturicidin and phloridzin on the deactivation is consistent with an inhibitory effect of newly formed--by ATP hydrolysis--ADP molecules, which might affect the enzyme without passing through the medium. Phosphate at millimolar concentration has an effect similar to low concentrations of phloridzin and venturicidin, probably by a simple back-reaction effect.
We present BVRI and unfiltered Clear light curves of 70 stripped-envelope supernovae (SESNe), observed between 2003 and 2020, from the Lick Observatory Supernova Search (LOSS) follow-up program. Our ...SESN sample consists of 19 spectroscopically normal SNe~Ib, two peculiar SNe Ib, six SN Ibn, 14 normal SNe Ic, one peculiar SN Ic, ten SNe Ic-BL, 15 SNe IIb, one ambiguous SN IIb/Ib/c, and two superluminous SNe. Our follow-up photometry has (on a per-SN basis) a mean coverage of 81 photometric points (median of 58 points) and a mean cadence of 3.6d (median of 1.2d). From our full sample, a subset of 38 SNe have pre-maximum coverage in at least one passband, allowing for the peak brightness of each SN in this subset to be quantitatively determined. We describe our data collection and processing techniques, with emphasis toward our automated photometry pipeline, from which we derive publicly available data products to enable and encourage further study by the community. Using these data products, we derive host-galaxy extinction values through the empirical colour evolution relationship and, for the first time, produce accurate rise-time measurements for a large sample of SESNe in both optical and infrared passbands. By modeling multiband light curves, we find that SNe Ic tend to have lower ejecta masses and lower ejecta velocities than SNe~Ib and IIb, but higher \(^{56}\)Ni masses.
We carried out spectroscopic monitoring of 21 low-redshift Seyfert 1 galaxies using the Kast double spectrograph on the 3-m Shane telescope at Lick Observatory from April 2016 to May 2017. Targeting ...active galactic nuclei (AGN) with luminosities of {\lambda}L{\lambda} (5100 Å) = 10^44 erg/s and predicted H{\beta} lags of 20-30 days or black hole masses of 10^7-10^8.5 Msun, our campaign probes luminosity-dependent trends in broad-line region (BLR) structure and dynamics as well as to improve calibrations for single-epoch estimates of quasar black hole masses. Here we present the first results from the campaign, including H{\beta} emission-line light curves, integrated H{\beta} lag times (8-30 days) measured against V-band continuum light curves, velocity-resolved reverberation lags, line widths of the broad H{\beta} components, and virial black hole mass estimates (10^7.1-10^8.1 Msun). Our results add significantly to the number of existing velocity-resolved lag measurements and reveal a diversity of BLR gas kinematics at moderately high AGN luminosities. AGN continuum luminosity appears not to be correlated with the type of kinematics that its BLR gas may exhibit. Follow-up direct modeling of this dataset will elucidate the detailed kinematics and provide robust dynamical black hole masses for several objects in this sample.
We have modeled the velocity-resolved reverberation response of the H\b{eta} broad emission line in nine Seyfert 1 galaxies from the Lick Active Galactic Nucleus (AGN) Monitioring Project 2016 ...sample, drawing inferences on the geometry and structure of the low-ionization broad-line region (BLR) and the mass of the central supermassive black hole. Overall, we find that the H\b{eta} BLR is generally a thick disk viewed at low to moderate inclination angles. We combine our sample with prior studies and investigate line-profile shape dependence, such as log10(FWHM/{\sigma}), on BLR structure and kinematics and search for any BLR luminosity-dependent trends. We find marginal evidence for an anticorrelation between the profile shape of the broad H\b{eta} emission line and the Eddington ratio, when using the root-mean-square spectrum. However, we do not find any luminosity-dependent trends, and conclude that AGNs have diverse BLR structure and kinematics, consistent with the hypothesis of transient AGN/BLR conditions rather than systematic trends.
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