A repeating fast radio burst associated with a persistent radio source.

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately [Formula: see text] parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications.

A bimodal burst energy distribution of a repeating fast radio burst source.

The event rate, energy distribution and time-domain behaviour of repeating fast radio bursts (FRBs) contain essential information regarding their physical nature and central engine, which are as yet unknown1,2. As the first precisely localized source, FRB 121102 (refs. 3-5) has been extensively observed and shows non-Poisson clustering of bursts over time and a power-law energy distribution6-8. However, the extent of the energy distribution towards the fainter end was not known. Here we report the detection of 1,652 independent bursts with a peak burst rate of 122 h-1, in 59.5 hours spanning 47 days. A peak in the isotropic equivalent energy distribution is found to be approximately 4.8 × 1037 erg at 1.25 GHz, below which the detection of bursts is suppressed. The burst energy distribution is bimodal, and well characterized by a combination of a log-normal function and a generalized Cauchy function. The large number of bursts in hour-long spans allows sensitive periodicity searches between 1 ms and 1,000 s. The non-detection of any periodicity or quasi-periodicity poses challenges for models involving a single rotating compact object. The high burst rate also implies that FRBs must be generated with a high radiative efficiency, disfavouring emission mechanisms with large energy requirements or contrived triggering conditions.

Cytotoxic and genotoxic actions of Casiopeina III-Ea (Cas III-Ea) in somatic and germ cells of Drosophila melanogaster.

Casiopeinas® are a group of newly synthesized drugs designed to treat cancer. These copper (Cu) complexes exhibit cytostatic, cytotoxic, genotoxic, and antineoplastic activities through different mechanisms of action. To evaluate the influence of these compounds, some in vivo studies were performed using predominantly somatic cells. The aim of the present study was to examine the cytotoxic and genotoxic actions of Casiopeina III-Ea (Cas III-Ea) in somatic as well as germ cells of Drosophila melanogaster. For cytotoxicity, the productivity and some morphometric parameters were measured and genotoxicity was assessed by means of the somatic mutation and recombination test assay in the wing. For this purpose, second-instar larvae of the Canton-S strain were treated with different concentrations of Cas III-Ea. The emerged adults were weighed, the area of the wings determined, and the number of trichomes of the region C' counted. The productivity of treated males was measured by a brood method to monitor the influence of Cas III-Ea on spermatozoa, meiotic stage cells, and spermatogonia. For genotoxicity, mwh + /+ flr3 larvae 48 hr age were chronically treated within the same concentration range. Results indicated that Cas III-Ea at all concentrations tested significantly increased the productivity per couple in Brood III (spermatids) while at 1 mM a marked elevation was noted in the three broods tested. In contrast, the weight and size of individuals as well as the size and number of cells in the wing were decreased significantly. Data suggest that Cas III-Ea is a weak genotoxic but selective mutagen. Failure to obtain a dose-related genotoxic response suggests that one of the preferred mechanisms of action of Cas III-Ea is to induce apoptosis.

A study of the inhibition/promotion effects of sodium-copper chlorophyllin (SCC)-mediated mutagenesis in somatic cells of Drosophila.

Sodium-copper chlorophyllin (SCC), a copper-porphyrin complex, has been shown to act as an inhibitor as well as a promoter of DNA-damage induction by a variety of mutagens in several test systems. In order to investigate the basis of this dual effect, experiments were carried out to compare the influence of pretreatment with intact SCC and that of its constituents, the metal-free protoporphyrin (PP-IX) and copper as CuCl(2). The wing-spot test was employed to monitor mutational events in somatic cells of Drosophila melanogaster. Heterozygous mwh+/+flr(3) larvae were treated for 24h with SCC, PP-IX, CuCl(2) or sucrose. Following this treatment, one group of larvae were immediately allowed to feed on instant medium containing 0.5mM N-nitroso-N-ethylurea (ENU) dissolved in phosphate buffer to reach pH 6. The remaining larvae received treatment with ENU with a delay of 1, 2 or 3days (DTD). Results revealed an (a) overall inhibitory effect for 0-DTD and 1-DTD after pretreatment with SCC, (b) only in 0-DTD after PP-IX, and (c) in all DTDs after treatment with CuCl(2). These results provide evidence that the copper ion plays a central role in the antimutagenic effect of SCC, and for a sustained period of time. Pretreatment with SCC and PP-IX produced a promoter effect at 2-DTD and 3-DTD. The results could be explained as an effect of the accumulation of metal-free porphyrin following the dissociation of the copper-porphyrin complex (SCC), the copper-ion reaching proteins to form complexes and participated in anabolic pathways.

[Quinacrine in the treatment of cutaneous lupus erythematosus: practical aspects and a case series]. / Aspectos prácticos de la quinacrina como tratamiento del lupus eritematoso cutáneo: serie de casos.

Hydroxychloroquine and chloroquine are antimalarials used as first-line treatment of cutaneous lupus. Quinacrine is not often employed by Spanish physicians due to a lack of information about its use and the fact that it is not marketed in Spain. It is effective in monotherapy or in combination therapy with other antimalarials. One of the advantages of quinacrine over chloroquine and hydroxychloroquine is that it does not appear to cause retinal toxicity. Quinacrine is used as second-line therapy in patients with pre-existing eye problems that contraindicate treatment with chloroquine or hydroxychloroquine (after evaluation of which drug has the better risk-benefit relationship), and in combination therapy with other antimalarials inpatients with resistance or only a partial response to chloroquine or hydroxychloroquine. We report 8 cases of patients with cutaneous lupus who received treatment with quinacrine in monotherapy or in combination with others antimalarials. Lesions resolved in 5 patients and improved in 3. Therapy had to be withdrawn in 1 patient due to an exacerbation of his psoriasis.

Radioprotective effect of chloropyllin, protoporphyrin-IX and bilirubin compared with amifostine® in Drosophila melanogaster.

The identification of substances that prevent or minimize the detrimental effects of ionizing radiation is an essential undertaking. The aim of this paper was to evaluate and compare the radioprotective potential of chlorophyllin, protoporphyrin and bilirubin, with amifostine®, an US Food & Drug Administration approved radioprotector Using the somatic mutation and recombination assay in the Drosophila melanogaster wing, it was found that pretreatment (1-9 h) with any of the porphyrins or amifostine® alone, did not affect the larva-adult viability or the basal frequency of mutation. However, they were associated with significant reductions in frequency of somatic mutation and recombination compared with the gamma-irradiated (20 Gy) control as follows: bilirubin (69.3 %)> chlorophyllin (40.0 %)> protoporphyrin (39.0 %)> amifostine® (19.7 %). Bilirubin also caused a 16 % increase in larva-adult viability with 3 h of pretreatment respect to percentage induced in 20 Gy control group. Whilst amifostine® was associated with lower genetic damage after pre-treatment of 1 and 3 h, this did not attain significance. These findings suggest that the tested porphyrins may have some potential as radioprotectant agents.

Evidence that low concentrations of chlorophyllin (CHLN) increase the genetic damage induced by gamma rays in somatic cells of Drosophila.

It was first demonstrated in Salmonella that higher and lower concentrations of chlorophyllin (CHLN) may have effects in opposite directions, higher doses inhibiting and lower doses promoting the mutagenic activity of certain tobacco-related nitrosamines. Previous work of our group demonstrated that CHLN may have both a promoter and an inhibitory effect on mutagenesis in Drosophila. The present paper reviews the evidence obtained in our laboratory using gamma rays as the mutagenic agent, that higher and lower pretreatment concentrations of CHLN are associated with inhibitory and promoting effects, respectively, as in Salmonella. Employing the wing spot test, 48h larvae were pretreated with various concentrations of CHLN from 0 to 69 mM and then treated with 10 Gy gamma rays. With the highest concentration of CHLN, an approximate 54% reduction in mutagenesis was observed. At 35 mM a remnant of this inhibitory effect was found in that a significant decrease was limited to the twin spot category. Evidence of promotion was first seen at 4.3mM CHLN, an effect which persisted for the remaining five lower concentrations, the most pronounced evidence of promotion being found at the four lowest concentrations, 0.03-1.1 mM CHLN. It should be noted that no evidence of genotoxicity was found for CHLN alone, an observation consistent with the several reports in the literature. The results are taken as strong evidence that pretreatment with low concentrations of CHLN promotes DNA damage induced by gamma rays in somatic cells of Drosophila.

Different radiation dose rate as radioprotection and the cross effect with chromium using in vivo somatic cells of Drosophila.

Ionizing radiation plays a key role in the adaptation of an individual organism to environmental pollution, at the same time, it has biological effects that depend on radiation intensity or dose rate (DR). Although the effect of DR has been studied in vitro, the phenomenon known as the inverse effect of DR, which indicates as it decreases that the induction of damage is greater, has not been widely studied in vivo. The present study is aimed to test 0.5 and 1 Gy in somatic cells of the wing of D. melanogaster, administered at 5.4 or 34.3 Gy/h and from 0.037 to 0.3 mM of CrO3 as conditioning treatment. No changes were found in larva-to-adult viability. A protective as well as a cross effect of pre-exposure to different DR and CrO3 concentrations against genetic damage induced by 20 Gy or 1 mM CrO3 was evident.

Study on the relationship of genotoxic and oxidative potential of a new mixed chelate copper antitumoral drug, Casiopeina II-gly (Cas II-gly) in Drosophila melanogaster.

The present study evaluates the superoxide dismutase (SOD) and catalase (CAT) activities in a wild strain of Drosophila melanogaster and the genotoxic potential induced by Cas II-gly (a new antineoplastic drug) using the somatic mutation and recombination test. Larvae 48h old were treated with Cas II-gly in a range of 0-1.5mM and aliquot were taken every 24h to have individuals treated for 24, 48, 72h and adulthood as well. A dose-dependent toxicity and a significant increase in SOD and CAT activities were found after a 24 and 48h treatment with 0.5-1.5mM concentrations. The comparison of the effect in enzymes with mutation indicated a positive correlation with increased genetic damage, after 24 and 48h of exposure for all concentrations tested. The addition of the genetic damage induced in each exposure time showed a significant effect, but only the small single spots had a concentration-related increase.

The kinetics of monoamine oxidase inhibition by three 2-indolylmethylamine derivatives.

The inhibition of bovine brain mitochondrial MAO-A and MAO-B by three acetylenic and non-acetylenic derivatives of 2-indolylmethylamine, chosen among more than 100 new compounds, were studied. The non-acetylenic derivative N-methyl-2(5-hydroxy-1-methylindolyl)methylamine (1) was a weak non-selective inhibitor which was shown to act in a reversible and competitive manner towards the deamination of tyramine. The two acetylenic derivatives N-methyl-N-(2-propynyl)-2-(5-benzyloxy-1-methylindolyl)methylamine (2) and N-methyl-N-(2-propynyl)-2-(5-hydroxy-1-methylindolyl)methylamine (3) were potent MAO inhibitors, one of them non-selective (compound 2) and the other MAO-A selective inhibitor (compound 3). Both of them were irreversible and competitive inhibitors, compound 2 towards the deamination of tyramine and compound 3 towards the deamination of serotonin and beta-phenylethylamine. A mechanism for the inhibition of the enzyme by both irreversible inhibitors is proposed and the inhibition parameters are determined.

Infantile pyramidal protrusion as a manifestation of lichen sclerosus et atrophicus.

BACKGROUND: A perineal infantile lesion previously described as "skin tag/fold" had recently been named infantile perianal pyramidal protrusion. It appears on the perineal median raphe of girls as a pyramidal soft tissue swelling, covered by smooth, red or rose-colored skin. Its pathogenesis is unknown. As in the case of other perianal lesions, knowledge about it is important, as concern about signs of child abuse grows. OBSERVATIONS: Four girls, 2 of them sisters, with infantile perianal pyramidal protrusion were studied. Three of these girls showed subtle clinical evidence of classic lichen sclerosus et atrophicus on first examination. The other girl developed vulvar lesions of lichen sclerosus et atrophicus months after the diagnosis of infantile perianal pyramidal protrusion. All 4 protrusions disclosed histopathological findings diagnostic of lichen sclerosus et atrophicus. CONCLUSIONS: Infantile perianal pyramidal protrusion is, at least in some patients, a peculiar form of lichen sclerosus et atrophicus that can precede other, more characteristic manifestations. We suggest changing the name to the more precise infantile perineal protrusion. Knowledge of this hitherto unrecognized clinical form of lichen sclerosus et atrophicus can help to explain anogenital symptoms and avoid its misinterpretation as a sign of sexual abuse.

Enzymatic acylation of di- and trisaccharides with fatty acids: choosing the appropriate enzyme, support and solvent.

Enzymatic synthesis of fatty acid esters of di- and trisaccharides is limited by the fact that most biological catalysts are inactivated by the polar solvents (e.g. dimethylsulfoxide, dimethylformamide) where these carbohydrates are soluble. This article reviews the methodologies developed to overcome this limitation, namely those involving control over the reaction medium, the enzyme and the support. We have proposed the use of mixtures of miscible solvents (e.g. dimethylsulfoxide and 2-methyl-2-butanol) as a general strategy to acylate enzymatically hydrophilic substrates. We observed that decreasing the hydrophobicity of the medium (i.e. lowering the percentage of DMSO) the molar ratio sucrose diesters versus sucrose monoesters can be substantially enhanced. The different regioselectivity exhibited by several lipases and proteases makes feasible to synthesise different positional isomers, whose properties may vary considerably. In particular, the lipase from Thermomyces lanuginosus displays a notable selectivity for only one hydroxyl group in the acylation of sucrose, maltose, leucrose and maltotriose, compared with lipase from Candida antarctica. We have examined three immobilisation methods (adsorption on polypropylene, covalent coupling to Eupergit C, and silica-granulation) for sucrose acylation catalysed by T. lanuginosus lipase. The morphology of the support affected significantly the reaction rate and/or the selectivity of the process.

Radioresistance of sibling Drosophila species from Laguna Verde, Veracruz, México.

PURPOSE: To identify and quantify if the generation of electricity by nuclear power plants produces an increase in background radiation that might affect the radioresistance of organisms that live in that area. MATERIALS AND METHODS: Natural populations of two sibling species of Drosophila, D. melanogaster and D. simulans, living in the immediate vicinity of the Mexican Nuclear Power Plant in Laguna Verde were studied for 10 years. Collections of flies were made at two sites, one close to and one further from two reactors, during both the pre-operational and operational stages of the reactors. The effect of exposure to various doses of gamma-rays on egg-to-adult survival of the flies was analysed. RESULTS: The data obtained indicate that in both sites, egg-to-adult survival was higher in D. melanogaster than in D. simulans. There was an increase in the egg-to-adult survival during the pre-operational period of one of the reactors and the possible causes are discussed. No differences were found between the two sites. CONCLUSIONS: The analysis indicates that the reactors do not have a negative impact on the Drosophila populations studied.

Evidence that chlorophyllin (CHLN) may behave as an inhibitor or a promoter of radiation-induced genetic damage in somatic cells of drosophila.

Irradiation of 96h old Drosophila following a 24h pretreatment with 5% chlorophyllin (CHLN) was delayed 0-4 days. The antimutagenic effect of CHLN in somatic cells monitored by the wing spot test persisted for 3 days after completion of the pretreatment and appeared to terminate at a time corresponding to the cessation of mitotic divisions of wing anlagen cells. Within the same population of cells, CHLN demonstrated both an inhibitory effect as measured in mwh single spot classes, and contrarily, a promoting effect in the class of mwh/flr twin spots and to an extent in the class of large flr spots. The reason for the contrasting effects of CHLN remains to be determined.

On the persistence of the radioprotective effect of chlorophyllin (CHLN) in somatic cells of Drosophila.

By delaying the time of gamma irradiation of 72 h larvae, pretreated at 48 h with 5% chlorophyllin (CHLN), it was established that the overall inhibiting effect of CHLN in somatic cells of Drosophila, as measured in the wing spot test, persists for about 4 days or until the time of cessation of the proliferation of wing anlagen. In the same population of cells, some spot classes gave evidence of an inhibitory effect whereas others did not arguing against the suggestion that the radioprotective effect of CHLN is a consequence of an induced delay in development, shrinking of the potential radiation target and lowering the probability of induced events. Other observations of interest are described.

Evidence suggesting that chlorophyllin (CHLN) may act as an inhibitor or a promoter of genetic damage induced by chromium(VI) oxide (CrO3) in somatic cells of Drosophila.

In Drosophila, 48h-old larvae were pretreated for 24h with chlorophyllin (CHLN) or sucrose and then treated with chromium(VI) oxide (CrO(3)) immediately following completion of the pretreatment period (0-day delay) or delayed 1, 2 or 3 days. The effects were scored in the wing spot test. After delays of 0 and 1 day, clear evidence of a protective effect of CHLN was found. Contrarily, after delays of 2 and 3 days, the results showed a reversal, i.e. CHLN-related events appeared more frequently than those in the sucrose control suggesting a promoting effect. It would appear prudent that CHLN be tested in a variety of situations in any given organism before decisions are reached regarding its inhibitor/promoter effects.

On the recovery of single spots with the flr phenotype in the wing spot test in Drosophila.

Graf et al. (U. Graf, F.E. Würgler, A.J. Katz, H. Frei, H. Juon, C.B. Hall, P.G. Kale, Somatic mutation and recombination test in Drosophila, Environment Mutagen. 6 (1984) 153-188.) described the overall results of assays of a series of compounds in the Drosophila wing spot test as indicating that single mwh spots appeared most frequently, followed by less frequent twin spots with both mwh and flr cells and lastly the 'quite rare' single flr spots. Data are presented below demonstrating that some compounds behave in a manner consistent with the above description, whereas others do not in that the frequency of single flr spots is equal to or exceeds that of twin spots and cannot be described as occurring 'rarely'. It is suggested that (large) flr singles be used as a measure of mutations/deletions directly from treated transheterozygotes. An argument is presented questioning the use of treated mwh +/+ TM3 individuals as an assay of mutations/deletions at the mwh+ locus.