Infection of myeloid dendritic cells with Listeria monocytogenes leads to the suppression of T cell function by multiple inhibitory mechanisms

Myeloid dendritic cells (DC) and macrophages play an important role in pathogen sensing and antimicrobial defense. In this study we provide evidence that myeloid DC respond to infection with Listeria monocytogenes with simultaneous induction of multiple stimulatory and inhibitory molecules. However, the overall impact of infected DC during T cell encounter results in suppression of T cell activation, indicating that inhibitory pathways functionally predominate. Inhibitory activity of infected DC is effected mainly by IL-10 and cyclooxygenase 2-mediated mechanisms, with soluble CD25 acting as an IL-2 scavenger as well as by the products of tryptophan catabolism. These inhibitory pathways are strictly TNF-dependent. In addition to direct infection, DC bearing this regulatory phenotype can be induced in vitro by a combination of signals including TNF, TLR2, and prostaglandin receptor ligation and by supernatants derived from the infected cells. Both infection-associated DC and other in vitro-induced regulatory DC are characterized by increased resistance to infection and enhanced bactericidal activity. Furthermore, myeloid DC expressing multiple regulatory molecules are identified in vivo in granuloma during listeriosis and tuberculosis. Based on the in vivo findings and the study of in vitro models, we propose that in granulomatous infections regulatory DC may possess dual function evolved to protect the host from disseminating infection via inhibition of granuloma destruction by T cells and control of pathogen spreading.     

A 14C age calibration curve for the last 60 ka: the Greenland-Hulu U/Th timescale and its impact on understanding the Middle to Upper Paleolithic transition in Western Eurasia

This paper combines the data sets available today for ¹⁴C-age calibration of the last 60 ka. By stepwise synchronization of paleoclimate signatures, each of these sets of ¹⁴C-ages is compared with the U/Th-dated Chinese Hulu Cave speleothem records, which shows global paleoclimate change in high temporal resolution. By this synchronization we have established an absolute-dated Greenland-Hulu chronological framework, against which global paleoclimate data can be referenced, extending the ¹⁴C-age calibration curve back to the limits of the radiocarbon method. Based on this new, U/Th-based Greenland_Hulu chronology, we confirm that the radiocarbon timescale underestimates calendar ages by several thousand years during most of Oxygen Isotope Stage 3. Major atmospheric ¹⁴C variations are observed for the period of the Middle to Upper Paleolithic transition, which has significant implications for dating the demise of the last Neandertals. The early part of “the transition” (with ¹⁴C ages > 35.0 ka ¹⁴C BP) coincides with the Laschamp geomagnetic excursion. This period is characterized by highly-elevated atmospheric ¹⁴C levels. The following period ca. 35.0-32.5 ka ¹⁴C BP shows a series of distinct large-scale ¹⁴C age inversions and extended plateaus. In consequence, individual archaeological ¹⁴C dates older than 35.0 ka ¹⁴C BP can be age-calibrated with relatively high precision, while individual dates in the interval 35.0-32.5 ka ¹⁴C BP are subject to large systematic age-‘distortions,’ and chronologies based on large data sets will show apparent age-overlaps of up to ca. 5,000 cal years. Nevertheless, the observed variations in past ¹⁴C levels are not as extreme as previously proposed (“Middle to Upper Paleolithic dating anomaly”), and the new chronological framework leaves ample room for application of radiocarbon dating in the age-range 45.0-25.0 ka ¹⁴C BP at high temporal resolution.     

Identification and analysis of the chivosazol biosynthetic gene cluster from the myxobacterial model strain Sorangium cellulosum So ce56

Myxobacteria belonging to the genus Sorangium are known to produce a variety of biologically active secondary metabolites. Chivosazol is a macrocyclic antibiotic active against yeast, filamentous fungi and especially against mammalian cells. The compound specifically destroys the actin skeleton of eucaryotic cells and does not show activity against bacteria. Chivosazol contains an oxazole ring and a glycosidically bound 6-deoxyglucose (except for chivosazol F). In this paper we describe the biosynthetic gene cluster that directs chivosazol biosynthesis in the model strain Sorangium cellulosum So ce56. This biosynthetic gene cluster spans 92 kbp on the chromosome and contains four polyketide synthase genes and one hybrid polyketide synthase/nonribosomal peptide synthetase gene. An additional gene encoding a protein with similarity to different methyltransferases and presumably involved in post-polyketide modification was identified downstream of the core biosynthetic gene cluster. The chivosazol biosynthetic gene locus belongs to the recently identified and rapidly growing class of trans-acyltransferase polyketide synthases, which do not contain acyltransferase domains integrated into the multimodular megasynthetases.     

Actions of gonadotropin-releasing hormone analogues in pituitary gonadotrophs and their modulation by ovarian steroids

Recently, GnRH antagonists (GnRHant) like cetrorelix and ganirelix have been introduced in protocols of controlled ovarian hyperstimulation for assisted reproductive techniques to prevent premature luteinizing hormone (LH) surges. Here we tested, whether the actions of cetrorelix and the GnRH agonist (GnRHag) triptorelin in gonadotrophs are dependent on the steroid milieu. Furthermore, we characterized the actions of cetrorelix and triptorelin on LH secretion and the total LH pool. Female rat pituitary cells were treated either with 0.1 nM triptorelin for 1, 2, 4 and 6 days or for 1, 3, 5 and 6 h or with 1, 10 or 100 nM cetrorelix for 1, 2, 3 and 5 h or for 10 min. Cells were stimulated for 3h with different concentrations of GnRH (10 pM-1 microM). For analysis of the total LH pool, which is composed of stored and released LH, cells were lysed with 0.1% Triton X-100 at -80 degrees C overnight. To test, whether the steroid milieu affects the actions of cetrorelix and triptorelin, cells were incubated for 52 h with 1 nM estradiol (E) alone or with combinations of 100 nM progesterone (P) for 4 or 52 h, respectively. Cells were then treated with 0.1 nM triptorelin for 9 h or 1 nM cetrorelix for 3 h and stimulated for 3 h with different concentrations of GnRH (10 pM-1 microM). The suppressive effect of triptorelin on LH secretion was fully accomplished after 3 h of treatment, for cetrorelix only 10 min were sufficient. The concentration of cetrorelix must be at least equimolar to GnRH to block LH secretion. Cetrorelix shifted the EC50s of the GnRH dose-response curve to the right. Triptorelin suppressed total LH significantly (from 137 to 36 ng/ml) after 1 h in a time-dependent manner. In contrast, only high concentrations of cetrorelix increased total LH. In steroid treated cells the suppressive effects of triptorelin were more distinct. One nanomolar cetrorelix suppressed GnRH-stimulated LH secretion of cells not treated with steroids from 10.1 to 3.5 ng/ml. In cells, additionally treated with estradiol alone or estradiol and short-term progesterone, LH levels were higher (from 3.5 to 5.4 or 4.5 ng/ml, respectively). In cells co-treated with estradiol and progesterone for 52 h LH secretion was only suppressed from 10.1 to 9.5 ng/ml. Steroid treatments diminished the suppressive effect of cetrorelix on LH secretion. In conclusion, the depletion of the total LH pool contributes to the desensitizing effect of triptorelin. The actions of cetrorelix and triptorelin are dependent on the steroid milieu.     

Adrenal expression of orexin receptor subtypes is differentially regulated in experimental streptozotocin induced type-1 diabetes

Orexins (hypocretins) are involved in the regulation of energy homeostasis and sleeping behavior. Orexins were also implicated in the regulation of neuroendocrine and autonomic functions. Recent data show the expression of orexin receptors within the hypothalamic-pituitary-adrenal (HPA) axis and suggest specific actions of orexins at the pituitary and adrenal glands. To further evaluate the role of orexin in the HPA axis, we investigated the mRNA expression of prepro-orexin (PPO) and orexin receptors within the HPA axis of streptozotocin-injected (STZ) rats showing type-1 like diabetes. PPO, as well as OX(1) and OX(2) receptor levels were analyzed by quantitative real-time PCR (qPCR). STZ rats were characterized by decreased body weight, plasma insulin, and leptin levels and by increased plasma glucose. Hypothalamic PPO mRNA levels were significantly reduced in STZ compared to non-diabetic control rats. No differences were found in the mRNA levels of hypothalamic or pituitary OX(1) and OX(2) receptors between control and STZ rats. In adrenals, OX(1) receptor mRNA levels were significantly elevated in STZ rats while OX(2) receptors were significantly reduced. Our results imply distinct functions of adrenal orexin receptor subtypes during type-1 like diabetes.     

Substrate recognition of type III secretion machines--testing the RNA signal hypothesis

Secretion by the type III pathway of Gram-negative microbes transports polypeptides into the extracellular medium or into the cytoplasm of host cells during infection. In pathogenic Yersinia spp., type III machines recognize 14 different Yop protein substrates via discrete signals genetically encoded in 7-15 codons at the 5' portion of yop genes. Although the signals necessary and sufficient for substrate recognition of Yop proteins have been mapped, a clear mechanism on how proteins are recognized by the machinery and then initiated into the transport pathway has not yet emerged. As synonymous substitutions, mutations that alter mRNA sequence but not codon specificity, affect the function of some secretion signals, recent work with several different microbes tested the hypothesis of an RNA-encoded secretion signal for polypeptides that travel the type III pathway. This review summarizes experimental observations and mechanistic models for substrate recognition in this field.     

No Effects of Successful Bidirectional SMR Feedback Training on Objective and Subjective Sleep in Healthy Subjects

There is a growing interest in the application of psychophysiological signals in more applied settings. Unidirectional sensory motor rhythm-training (SMR) has demonstrated consistent effects on sleep. In this study the main aim was to analyze to what extent participants could gain voluntary control over sleep-related parameters and secondarily to assess possible influences of this training on sleep metrics. Bidirectional training of SMR as well as heart rate variability (HRV) was used to assess the feasibility of training these parameters as possible brain computer interfaces (BCI) signals, and assess effects normally associated with unidirectional SMR training such as the influence on objective and subjective sleep parameters. Participants (n?=?26) received between 11 and 21 training sessions during 7 weeks in which they received feedback on their personalized threshold for either SMR or HRV activity, for both up- and down regulation. During a pre- and post-test a sleep log was kept and participants used a wrist actigraph. Participants were asked to take an afternoon nap on the first day at the testing facility. During napping, sleep spindles were assessed as well as self-reported sleep measures of the nap. Although the training demonstrated successful learning to increase and decrease SMR and HRV activity, no effects were found of bidirectional training on sleep spindles, actigraphy, sleep diaries, and self-reported sleep quality. As such it is concluded that bidirectional SMR and HRV training can be safely used as a BCI and participants were able to improve their control over physiological signals with bidirectional training, whereas the application of bidirectional SMR and HRV training did not lead to significant changes of sleep quality in this healthy population.     

Beta-amyloid peptide variants in brains and cerebrospinal fluid from amyloid precursor protein (APP) transgenic mice: comparison with human Alzheimer amyloid

In this study, we report a detailed analysis of the different variants of amyloid-β (Aβ) peptides in the brains and the cerebrospinal fluid from APP23 transgenic mice, expressing amyloid precursor protein with the Swedish familial Alzheimer disease mutation, at different ages. Using one- and two-dimensional gel electrophoresis, immunoblotting, and mass spectrometry, we identified the Aβ peptides Aβ(1-40), -(1-42), -(1-39), -(1-38), -(1-37), -(2-40), and -(3-40) as well as minor amounts of pyroglutamate-modified Aβ (Aβ(N3pE)) and endogenous murine Aβ in brains from 24-month-old mice. Chemical modifications of the N-terminal amino group of Aβ were identified that had clearly been introduced during standard experimental procedures. To address this issue, we additionally applied amyloid extraction in ultrapure water. Clear differences between APP23 mice and Alzheimer disease (AD) brain samples were observed in terms of the relative abundance of specific variants of Aβ peptides, such as Aβ(N3pE), Aβ(1-42), and N-terminally truncated Aβ(2/3-42). These differences to human AD amyloid were also noticed in a related mouse line transgenic for human wild type amyloid precursor protein. Taken together, our findings suggest different underlying molecular mechanisms driving the amyloid deposition in transgenic mice and AD patients.     

Functional diversity of marine macrobenthic communities from sublittoral soft-sediment habitats off northern Chile

Benthic communities show changes in composition and structure across different environmental characteristics and habitats. However, incorporating species biological traits into the analysis can provide a better understanding of system functioning within habitats. We compare the functional diversity of macrobenthic communities from a contrasting shallow (15 m) and deep (50 m) sublittoral soft-sediment habitats in northern Chile, using biological traits analysis. Our aim was to highlight the biological characteristics responsible for differences between habitats and the implications for ecosystem functioning. Trait analysis showed that the deep habitat was restricted in providing functionally important biogenic structure and bioturbation and supports less diverse feeding-related energy pathways. The shallow habitat is characterized by more diverse energy pathways and a higher potential for matter exchange through bioturbation. We provide support to the predictions of transfer of energy from the benthos to upper trophic levels in the shallow, which is characterized mainly by normoxia and little organic matter content in the sediment. In the deep habitat, characterized by hypoxia and more organic matter, energy appears to be transferred to microbial components. We suggest that trait analysis should be added to the traditional approaches based on species diversity, because it provides indicators of ecosystem stress.