Dimethylformamide dimethyl acetal reagent for in situ chiral analyses of organic molecules on Titan with the Dragonfly mass spectrometer space instrument (Dragonfly mission)

Thanks to the Cassini-Huygens space mission between 2004 and 2017, a lot was learned about Titan, the biggest satellite of Saturn, and its intriguing atmosphere, surface, and organic chemistry complexity. However, key questions about the potential for the atmosphere and surface chemistry to produce organic molecules of direct interest for prebiotic chemistry and life did not find an answer. Due to Titan potential as a habitable world, NASA selected the Dragonfly space mission to be launched in 2027 to Titan's surface and explore the Shangri-La surface region for minimum 3 years. One of the main goals of this mission will be to understand the past and actual abundant prebiotic chemistry on Titan, especially using the Dragonfly Mass Spectrometer (DraMS). Two recently used sample pre-treatments for Gas Chromatography - Mass Spectrometry (GC-MS mode of DraMS) analyses are planned prior analysis to extract refractory organic molecules of interest for prebiotic chemistry and astrobiology. The dimethylformamide dimethylacetal (DMF-DMA) derivatization reaction offers undoubtedly an opportunity to detect biosignatures by volatilizing refractory biological or prebiotic molecules and conserving the chiral carbons' conformation while an enantiomeric excess indicates a chemical feature induced primarily by life (and may be aided on the primitive systems by light polarization). The goal of this study is to investigate the ageing of DMF-DMA in DraMS (and likely MOMA) capsules prior to in situ analysis on Titan (or Mars). The main results highlighted by our work on DMF-DMA are first its satisfactory stability for space requirements through time (no significant degradation over a year of storage and less than 30 % of lost under thermal stress) to a wide range of temperature (0 °C to 250 °C), or the presence of water and oxidants during the derivatization reaction (between 0 and 10 % of DMF-DMA degradation). Moreover, this reagent derivatized very well amines and carboxylic acids in high or trace amounts (ppt to hundreds of ppm), conserving their molecular conformation during the heat at 145 °C for 3 min (0 to 4% in the enantiomeric form change).

Splicing factor Prp18p promotes genome-wide fidelity of consensus 3'-splice sites

The fidelity of splice site selection is critical for proper gene expression. In particular, proper recognition of 3'-splice site (3'SS) sequences by the spliceosome is challenging considering the low complexity of the 3'SS consensus sequence YAG. Here, we show that absence of the Prp18p splicing factor results in genome-wide activation of alternative 3'SS in S. cerevisiae, including highly unusual non-YAG sequences. Usage of these non-canonical 3'SS in the absence of Prp18p is enhanced by upstream poly(U) tracts and by their potential to interact with the first intronic nucleoside, allowing them to dock in the spliceosome active site instead of the normal 3'SS. The role of Prp18p in 3'SS fidelity is facilitated by interactions with Slu7p and Prp8p, but cannot be fulfilled by Slu7p, identifying a unique role for Prp18p in 3'SS fidelity. This fidelity function is synergized by the downstream proofreading activity of the Prp22p helicase, but is independent from another late splicing helicase, Prp43p. Our results show that spliceosomes exhibit remarkably relaxed 3'SS sequence usage in the absence of Prp18p and identify a network of spliceosomal interactions centered on Prp18p which are required to promote the fidelity of the recognition of consensus 3'SS sequences.

Influence of pH and salts on DMF-DMA derivatization for future Space Applications

For gas chromatography - mass spectrometry (GC-MS) analyses performed in situ, pH and salts (e.g., chlorides, sulfates) may enhance or inhibit the detection of targeted molecules of interest for astrobiology (e.g. amino acids, fatty acids, nucleobases). Obviously, salts influence the ionic strength of the solutions, the pH value, and the salting effect. But the presence of salts may also produce complexes or mask ions in the sample (masking effect on hydroxide ion, ammonia, etc.). For future space missions, wet chemistry will be conducted before GC-MS analyses to detect the full organic content of a sample. The defined organic targets for space GC-MS instrument requirements are generally strongly polar or refractory organic compounds, such as amino acids playing a role in the protein production and metabolism regulations for life on Earth, nucleobases essential for DNA and RNA formation and mutation, and fatty acids that composed most of the eukaryote and prokaryote membranes on Earth and resist to environmental stress long enough to still be observed on Mars or ocean worlds in geological well-preserved records. The wet-chemistry chemical treatment consists of reacting an organic reagent with the sample to extract and volatilize polar or refractory organic molecules (i.e. dimethylformamide dimethyl acetal (DMF-DMA) in this study). DMF-DMA derivatizes functional groups with labile H in organics, without modifying their chiral conformation. The influence of pH and salt concentration of extraterrestrial materials on the DMF-DMA derivatization remains understudied. In this research, we studied the influence of different salts and pHs on the derivatization of organic molecules of astrobiological interest with DMF-DMA, such as amino acids, carboxylic acids, and nucleobases. Results show that salts and pH influence the derivatization yield, and that their effect depend on the nature of the organics and the salts studied. Second, monovalent salts lead to a higher or similar organic recovery compared to divalent salts regardless of pH below 8. However, a pH above 8 inhibits the DMF-DMA derivatization influencing the carboxylic acid function to become an anionic group without labile H. Overall, considering the negative effect of the salts on the detection of organic molecules, future space missions may have to consider a desalting step prior to derivatization and GC-MS analyses.

Spliceosomal mutations decouple 3' splice site fidelity from cellular fitness

The fidelity of splice site selection is thought to be critical for proper gene expression and cellular fitness. In particular, proper recognition of 3'-splice site (3'SS) sequences by the spliceosome is a daunting task considering the low complexity of the 3'SS consensus sequence YAG. Here we show that inactivating the near-essential splicing factor Prp18p results in a global activation of alternative 3'SS, many of which harbor sequences that highly diverge from the YAG consensus, including some highly unusual non-AG 3'SS. We show that the role of Prp18p in 3'SS fidelity is promoted by physical interactions with the essential splicing factors Slu7p and Prp8p and synergized by the proofreading activity of the Prp22p helicase. Strikingly, structure-guided point mutations that disrupt Prp18p-Slu7p and Prp18p-Prp8p interactions mimic the loss of 3'SS fidelity without any impact on cellular growth, suggesting that accumulation of incorrectly spliced transcripts does not have a major deleterious effect on cellular viability. These results show that spliceosomes exhibit remarkably relaxed fidelity in the absence of Prp18p, and that new 3'SS sampling can be achieved genome-wide without a major negative impact on cellular fitness, a feature that could be used during evolution to explore new productive alternative splice sites.

Protocol for High-Resolution Mapping of Splicing Products and Isoforms by RT-PCR Using Fluorescently Labeled Primers

We describe an RT-PCR protocol that allows high-resolution mapping of splicing products and isoforms using fluorescently labeled primers. Each species contains one fluorescent group allowing a direct comparison of the different isoforms despite size differences. A custom-size ladder enables the precise determination of cDNA lengths and discrimination of isoforms differing by less than five nucleotides on polyacrylamide gels. This protocol also allows the detection of products from in vitro splicing reactions, circumventing the need to use radiolabeled transcripts. For complete details on the use and execution of this protocol, please refer to Gabunilas and Chanfreau (2016).

BC200 (BCYRN1) - The shortest, long, non-coding RNA associated with cancer

With the discovery that the level of RNA synthesis in human cells far exceeds what is required to express protein-coding genes, there has been a concerted scientific effort to identify, catalogue and uncover the biological functions of the non-coding transcriptome. Long, non-coding RNAs (lncRNAs) are a diverse group of RNAs with equally wide-ranging biological roles in the cell. An increasing number of studies have reported alterations in the expression of lncRNAs in various cancers, although unravelling how they contribute specifically to the disease is a bigger challenge. Originally described as a brain-specific, non-coding RNA, BC200 (BCYRN1) is a 200-nucleotide, predominantly cytoplasmic lncRNA that has been linked to neurodegenerative disease and several types of cancer. Here we summarise what is known about BC200, primarily from studies in neuronal systems, before turning to a review of recent work that aims to understand how this lncRNA contributes to cancer initiation, progression and metastasis, along with its possible clinical utility as a biomarker or therapeutic target.

Noise-induced time-dependent changes in oxidative stress in the mouse cochlea and attenuation by D-methionine

Oxidative stress in the cochlea is considered to play an important role in noise-induced hearing loss. This study determined changes in superoxide dismutase (SOD), catalase, lipid peroxidation (LPO) and the auditory brainstem response (ABR) in the cochlea of C57BL/6 mice prior to and immediately, 1, 3, 7, 10, 14 and 21 days after noise exposure (4 kHz octave band at the intensity of 110 dB SPL for 4 h). A significant increase in SOD activity immediately and on 1st day after noise exposure, without a concomitant increase in catalase activity suggested a difference in the time dependent changes in the scavenging enzymes, which facilitates the increase in LPO observed on day 7. The ABR indicated significant noise-induced functional deficits which stabilized in 2 weeks with a permanent threshold shift (PTS) of 15 dB at both 4 kHz and 8 kHz. The antioxidant D-methionine (D-Met) reversed the noise-induced changes in LPO levels and enzyme activities. It also significantly reduced the PTS observed on the 14th day from 15 dB to 5 dB for 4 kHz. In summary, the findings indicate that time-dependent alterations in scavenging enzymes facilitate the production of reactive oxygen species and that D-met effectively attenuates noise-induced oxidative stress and the associated functional loss in the mouse cochlea.

Serotonin turnover in different duration of sleep recovery in discrete regions of young rat brain after 24 h REM sleep deprivation

Sleep plays an important role in restorative function and serotonin (5-hydroxytryptamine: 5HT) equally plays important roles in sleep. Though various studies have revealed the roles of 5HT in sleep/wake cycle, the mechanism involved is yet unclear. In the present study we investigated alteration of the 5HT turnover in various regions of the young rat brains after 24 hours (h) REM sleep (sREM) deprivation to elucidate the roles of 5HT in sleep restoration function in the these regions. The 5HT turnover was evaluated by the ratio of 5-hydroxyindole acetic acid against 5HT. The sREM deprivation was performed by the inverted flowerpot technique. The 5HT turnover showed significant alteration in the all regions of the brain examined after 24h sREM deprivation, particular depending on the brain region. These results revealed that sREM modulates the 5HT turnover in the brain with region specificity and this may be one of the restorative functions of sleep indicating that sREM is regionally generated.

Serotonin turnover in discrete regions of young rat brain after 24 h REM sleep deprivation

The present study has attempted to elucidate the alteration of serotonin turnover after 24 h REM sleep deprivation in different regions in brain of young rat. Sleep deprivation was induced by the inverted flower pot technique. Results of this study show increased serotonin turnover after 24 h REM sleep deprivation in all the brain regions except in the hypothalamus. The decreased 5-HT ratio shows increased serotonin in the hypothalamus after 24 h sleep deprivation. This study indicates increased activity of serotonergic neurons in the hypothalamus after 24 h sleep deprivation. This also indicates that the hypothalamus plays a role in the immediate compensatory mechanism during 24 h REM sleep deprivation in young rats.

Periapical central giant cell granuloma misdiagnosed as odontogenic cyst

AIM

To present the clinicopathological features of a series of four periapically located central giant cell granulomas (CGCGs) that were misdiagnosed and treated as being of endodontic origin.

SUMMARY

Four cases of periapical CGCGs were submitted with a clinical diagnosis of either radicular or residual cyst. In two cases, root canal treatment had been performed previously. The patients were two women and two men whose age ranged from 31 to 85 years. Two cases were located in the mandibular premolar-molar region, and two in the anterolateral region of the maxilla. Two lesions were submitted for histological examination with a diagnosis of radicular cyst whereas the remaining two were submitted with a diagnosis of residual cyst.

KEY LEARNING POINTS

Periapical giant cell lesions may be unilocular and therefore misdiagnosed as an endodontic lesion because of their radiographic similarity to an inflammatory periradicular lesion, especially if the teeth have been root filled or if the vitality is negative or doubtful. It is important to follow up the healing process of a periapical radiolucency related to a root filled tooth and, in case of persistence, to perform surgery and to submit the specimen for histological examination.

Biogenic amine changes in brain regions and attenuating action of Ocimum sanctumin noise exposure

Broadband white noise exposure (100 dB) in wistar strain male albino rats significantly increased the levels of dopamine (DA), serotonin (5-HT) and 5-HT turnover in many of the discrete brain regions (cerebral cortex, cerebellum, hypothalamus, hippocampus, pons-medulla and corpus striatum) during sub-chronic noise exposure (4 h daily for 15 days). In acute (4 h for 1 day) and chronic noise exposures (4 h daily for 30 days) the levels were significantly altered only in certain regions. The turnover study of serotonin clearly indicates that neurotransmitter level alone cannot be an indicator, as in some brain regions the rate of synthesis matched with the degradation in order to maintain the normal levels. The intraperitoneal administration of 70% ethanolic extract of Ocimum sanctum(OS) at the dosage of 100 mg/kg body weight to animals subjected to noise exposure has prevented the noise induced increase in neurotransmitter levels without affecting the normal levels. This indicates that OS can be a probable herbal remedy for noise induced biogenic amine alterations.

Ostéonécrose des maxillaires chez des patients traités par bisphosphonates

INTRODUCTION

The latest generations of bisphosphonates constitute a major advance in the management of disorders including Paget's disease, osteoporosis, and osteolytic bone tumors. Recent reports describe numerous cases of osteonecrosis of the jaw in patients treated with bisphosphonates. Some of these reports mention predisposing factors, including surgical procedures, chemotherapy, and radiotherapy.

CASES

In the past 12 months, we have observed and treated 9 cases of maxillary osteonecrosis, which we present summarily.

DISCUSSION

Some of our cases (3 of 9), like many of those described in literature, do not present predisposing factors. The osteonecrosis may thus be due mainly to the effect of bisphosphonates that, by blocking bone remodeling, may cause excessive bone mineralization. If this hypothesis is confirmed, these cases of osteonecrosis may be due to excess doses. Better dose adjustment should thus help prevent this complication.

Effect of noise stress on free radical scavenging enzymes in brain

The levels of free radical scavenging enzymes in six discrete brain regions (cerebral cortex, cerebellum, midbrain, pons medulla, hippocampus and hypothalamus), after exposure to three different durations of noise stress (broadband white noise, 100dB, 4h/day, in acute: 1 day, sub acute: 15 days and chronic stress: 30 days) was studied in Wister strain male albino rats. Acute noise stress significantly increases the levels of superoxide dismutase (SOD: EC 1.15.1.1), catalase (EC 1.11.1.6), glutathione peroxidase (GPx: EC 1.11.1.9), oxidized glutathione (GSSG) and lipid peroxidation (LPO) and decreases the levels of reduced glutathione (GSH), GSH/GSSG ratio and protein thiols. The free radical scavenging enzymes levels, in sub acute and chronic noise stress also showed marked deviation in certain regions from the controls within the study duration. The results indicate that adaptation to noise stress does not occur immediately in all the brain regions. The noise induced alterations in free radicals may be assumed to serve as a linkage between the environmental noise and the manifestation of multifactorial diseases attributed to noise exposure. Moreover the quantification of the health effects of noise by the alterations in free radicals seems inappropriate in chronic noise stress.

Orofacial granulomas after injection of cosmetic fillers. Histopathologic and clinical study of 11 cases

BACKGROUND

Purposely, cosmetic injections in orofacial tissues of various resorbable, biodegradable, or permanent fillers may be followed by development of foreign-body granulomas. The aim of this article is to contribute to the histologic identification of the filler material.

METHODS

Histologic and clinical features of 11 cases of granulomas on orofacial fillers are described.

RESULTS

Only 3/11 patients knew the nature of the injected product. Four histologic patterns were found: (i) Artecoll, (ii) Dermalive, and (iii) New-Fill granuloma, all three of the classic giant cell granuloma type, differing in respect of foreign particles; and (iv) Liquid Silicone granuloma, which featured a cystic and macrophagic type. Information was often missing or misleading, patients or practitioners being reluctant to give the details.

CONCLUSION

Increasing demand for orofacial tissue augmentation makes pathologists face new, and sometimes, puzzling granuloma types. Identification of the foreign product might be required for therapeutic or medico-legal reasons.

Focal cemento-osseous dysplasia involving a mandibular lateral incisor

AIM

To report a case of focal cemento-osseous dysplasia (FCOD) affecting a single tooth misdiagnosed as an inflammatory periapical lesion.

SUMMARY

The patient, a black 47-year-old woman complained of pain affecting the right side of the mandible. Routine X-ray examination discovered a periapical radiolucency on the mandibular left lateral incisor (tooth 32), which was otherwise normal and not carious. As the response of this tooth to a vitality test was doubtful, the lesion was diagnosed as a periapical granuloma or cyst secondary to pulpal necrosis. Endodontic treatment and curettage of the periapical lesion were performed, and histological examination of the curettage material revealed a localized osseous dysplasia.

KEY LEARNING POINTS

FCOD may rarely affect only one tooth, resembling a periapical granuloma or cyst. Careful diagnosis is of paramount importance in cases of questionable periapical lesions affecting normal-looking teeth, before beginning treatment. FCOD generally requires no treatment. Biopsy is warranted in case of doubt.