Inactive Nuclei Research Articles

Photometric Analysis of the Nucleus of the Main-belt Comet 2010 LH15

We analyzed the inactive nucleus of the main-belt comet 2010 LH15 at a true anomaly of 262°. Observations using the Gemini North Telescope in 2023 July yielded an absolute R-band magnitude of (18.4 ± 0.2) mag. Assuming a C-type geometric albedo and phase function, we estimated the nucleus radius to be (0.5 ± 0.1) km. The examination of the lightcurve profile did not yield clear evidence for a rotational period shorter than 2 hr.

Förster resonance energy transfer from Hoechst 33258 to SYBR Green I in cholesteric liquid-crystalline DNA

In the present work Förster resonance energy transfer (FRET) between DNA-specific fluorescent dyes Hoechst 33258 (Ht58; donor) and SYBR Green I (SG; acceptor) is compared in isotropic DNA solution and in its cholesteric liquid-crystalline dispersion (DNA CLCD). At a fixed donor concentration of 3.57 × 10−6 М in the spatially ordered system, FRET starts at lower acceptor concentration than in the isotropic system and at the SG concentration below 1.05 × 10−7 M, its efficiency in DNA CLCD is up to ≈4-fold higher than in DNA solution (3D-FRET vs. 1D-FRET). However, the maximum FRET efficiency is higher in isotropic solution (≈70% vs. ≈50%, respectively) apparently due to the absence of steric restrictions on intermolecular interactions imposed by the dense packaging of the DNA molecules. In isotropic DNA solution FRET from Ht58 to SG is accompanied by the displacement of Ht58 from the minor-groove complex as the SG concentration increased, while the displacement of Ht58 in DNA CLCD seems to be limited. Using FRET between Ht58 and SG, the formation of DNA CLCD particles via stopped-flow method was investigated and for the first time the subsecond stage of the DNA CLCD particle formation, generation of “precholesteric” optically inactive nuclei, was demonstrated.

Tidal disruption events as a site of an evolving relativistic spectral line

AbstractIn nuclei of galaxies, strong tidal forces can destroy stars passing within a critical distance from the central supermassive black hole (SMBH). Observational signatures of tidal disruption events (TDEs) depend on the environment around the SBMH horizon and the level of its accretion activity. Evidence for optical and ultraviolet spectral features has been reported in TDE flares; nevertheless, to test the effects of general relativity in the immediate vicinity of SMBH, the relativistically broadened and skewed X‐ray line would tell us significantly more useful information. This will require to proceed beyond inactive nuclei. To this end, we consider a system where the material from a disrupted star forms a gaseous ring that circularizes near the tidal radius around SMBH, it gradually spreads in radius by viscous processes and resides embedded within a hot corona. In our test calculation, the remnant trail is assumed to be fully circularized and embedded in a hot environment and illuminated by X‐rays from a surrounding corona or a jet base of (mild) active galactic nucleus activity. We show the expected effects on the observed profile and the centroid energy. In the future, the evolving spectral features can enhance the diagnostic capability and provide a novel way to reveal the parameters of TDEs in such sources; the distance of the remnant gas from the SMBH, the radial extent of the gaseous trail, and the spin of the SMBH could be measured.

Research of activity of Main Belt Comets 176P/LINEAR, 238P/Read and 288P/(300163) 2006 VW139

As a new class of comet, main belt comets (MBCs) have attracted more and more attention in recent years. To study activity and physical properties of three MBCs 176P/LINEAR, 238P/Read and 288P/(300163) 2006 VW139, we carried out broadband CCD photometry of three MBCs on UT 2016 November 18–19 with the 1-m optical telescope at Lulin Observatory in Taiwan. By comparing cometary surface brightness profiles to stellar surface brightness profiles, and by comparing cometary absolute magnitude to the expected magnitude of inactive nucleus, we found that 176P/LINEAR was inactive, while 238P/Read and 288P/(300163) 2006 VW139 were active. By photometric studies, we obtained the Afρ values and the dust production rates. Finally, the activity of three MBCs were discussed. Our photometric results show that the total dust mass of 238P/Read and 288P/(300163) 2006 VW139 obtained in this work are of the same magnitude as the majority of known MBCs.

Protective effects of curcumin on ischemic reperfusion of rat retina

Ischemic reperfusion is an optic neuropathy in which photoreceptor cells may die through an apoptotic process. Free radicals are involved in the apoptotic process of ischemic reperfusion disorders. Previous research indicates that curcumin is an antioxidant found in plants which reduces neurodegenerative changes in aged animals. The purpose of this research was to survey whether curcumin has preventive effects on ischemic reperfusion of the retina. Twenty male Wistar rats were grouped into four (n = 5): 1, control group; 2, ischemic reperfusion group; 3, experimental group II: received 0.01% curcumin in diet (low dose) for 2 days before ischemic reperfusion; 4, experimental group III: received 0.25% curcumin in diet (high dose) for 2 days before ischemic reperfusion. The eye was enucleated and the retina separated. Routine tissue processing in transmission electron microscopy was done. Results showed that ischemic reperfusion created major signs of injury in the photoreceptor layer such as disappearance of the outer segment, cell swelling, and karyolitic and pyknotic nuclei, but cell swelling and karyolitic nuclei were not seen after receiving a low dose of curcumin. Also, the photoreceptor layer appeared normal after receiving a high dose of curcumin, but decreased vacuolization and dark and inactive nuclei were obvious. This study concluded that a high dose of curcumin confers a more preventive effect on retinal injury by ischemic reperfusion than a low dose.

Black Scorpionfish (Scorpaena porcus) Hemopoiesis: Analysis by Flow Cytometry and Light Microscopy.

Cell suspensions of head kidney and spleen of black scorpionfish (Scorpaena porcus L.) have been studied using flow cytometry and light microscopy. On the basis of forward scatter (FS) and side scatter (SS) distribution and light microscopy, two main types of cells in the hemopoietic organs were identified: "small cells" (5.1-8.9 µm) and "large cells" (10.8-15.3 µm). Subpopulation of small cells was formed by thrombocytes, lymphocytes, and elements with functionally inactive nuclei. Euchromatin level in their nuclei was low and acidophilic cytoplasm corresponded to negligible nucleic acids content. No proliferative activity was observed using SYBR Green I fluorescence analysis. Morphological characteristics of these cells coincided with colony forming units of mammals. Large cells in head kidney consisted of two subpopulations of cells differing in granularity and DNA content. Proliferating blast cells and differentiating cells of all hemopoietic lines were identified among them. Macrophages and apoptotic cells were also detected in head kidney. In spleen large cells cluster mainly included aged red blood cells with extended lengthwise axis. Blast cells and differentiating elements in spleen were not observed. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:1993-1999, 2017. © 2017 Wiley Periodicals, Inc.

OGLE16aaa - a Signature of a Hungry Super Massive Black Hole

Abstract We present the discovery and first three months of follow-up observations of a currently on-going unusual transient detected by the OGLE-IV survey, located in the centre of a galaxy at redshift z=0.1655. The long rise to absolute magnitude of -20.5 mag, slow decline, very broad He and H spectral features make OGLE16aaa similar to other optical/UV Tidal Disruption Events (TDEs). Weak narrow emission lines in the spectrum and archival photometric observations suggest the host galaxy is a weak-line Active Galactic Nucleus (AGN), which has been accreting at higher rate in the past. OGLE16aaa, along with SDSS J0748, seems to form a sub-class of TDEs by weakly or recently active super-massive black holes (SMBHs). This class might bridge the TDEs by quiescent SMBHs and flares observed as “changing-look QSOs”, if we interpret the latter as TDEs. If this picture is true, the previously applied requirement for identifying a flare as a TDE that it had to come from an inactive nucleus, could be leading to observational bias in TDE selection, thus affecting TDE-rate estimations.

COLOR SYSTEMATICS OF COMETS AND RELATED BODIES

Most comets are volatile-rich bodies that have recently entered the inner solar system following long-term storage in the Kuiper belt and the Oort cloud reservoirs. These reservoirs feed several distinct, short-lived "small body" populations. Here, we present new measurements of the optical colors of cometary and comet-related bodies including long-period (Oort cloud) comets, Damocloids (probable inactive nuclei of long-period comets) and Centaurs (recent escapees from the Kuiper belt and precursors to the Jupiter family comets). We combine the new measurements with published data on short-period comets, Jovian Trojans and Kuiper belt objects to examine the color systematics of the comet-related populations. We find that the mean optical colors of the dust in short-period and long-period comets are identical within the uncertainties of measurement, as are the colors of the dust and of the underlying nuclei. These populations show no evidence for scattering by optically-small particles or for compositional gradients, even at the largest distances from the Sun, and no evidence for ultrared matter. Consistent with earlier work, ultrared surfaces are common in the Kuiper belt and on the Centaurs, but not in other small body populations, suggesting that this material is hidden or destroyed upon entry to the inner solar system. The onset of activity in the Centaurs and the disappearance of the ultrared matter in this population begin at about the same perihelion distance ($\sim$10 AU), suggesting that the two are related. Blanketing of primordial surface materials by the fallback of sub-orbital ejecta, for which we calculate a very short timescale, is the likely mechanism. The same process should operate on any mass-losing body, explaining the absence of ultrared surface material in the entire comet population.

A LUMINOUS X-RAY FLARE FROM THE NUCLEUS OF THE DORMANT BULGELESS SPIRAL GALAXY NGC 247

NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity up to 2*10^39 erg/s in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by factor of almost 20. The spectral and temporal behaviors of the nuclear source are well consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to accretion onto a possible low-mass nuclear black hole, fed by a tidally disrupted star or a gas cloud; the MAXI observations limit the peak luminosity of the flare to less than ~10^43 erg/s, suggesting that it is either a low mass black hole or an inefficient tidal disruption event (TDE).

Possible origin of the Damocloids: the scattered disk or a new region?

The Damocloids are a group of unusual asteroids that recently added a new member: 2010 EJ104. The dynamical evolution of the Damocloids may reveal a connection from the Main Belt to the Kuiper Belt and beyond the scattered disk. According to our simulations, two regions may be considered as possible origins of the Damocloids: the scattered disk, or a part of the Oort cloud, which will be perturbed to a transient region located between 700 AU and 1000 AU. Based on their potential origin, the Damocloids can be classified into two types, depending on their semi-major axes, and about 65.5% of the Damocloids are classified into type I which mainly originate from the Oort cloud. Whether the Damocloids are inactive nuclei of the Halley Family of Comets may depend on their origin.

THE NUCLEUS OF MAIN-BELT COMET 259P/GARRADD

We present observations of the main-belt comet 259P/Garradd, previously known as P/2008 R1 (Garradd), obtained in 2011 and 2012 using the Gemini North Telescope on Mauna Kea in Hawaii, and the SOAR Telescope at Cerro Pachon in Chile, with the goal of computing the object's phase function and nucleus size. We find an absolute magnitude of $H_R=19.71\pm0.05$ mag and slope parameter of $G_R=-0.08\pm0.05$ for the inactive nucleus, corresponding to an effective nucleus radius of $r_e=0.30\pm0.02$ km, assuming an $R$-band albedo of $p_R=0.05$. We also revisit observations reported for 259P while it was active in 2008 to quantify the dust mass loss and compare the object with other known main-belt comets.

A quantitative analysis of transcriptionally active syncytiotrophoblast nuclei across human gestation

The syncytiotrophoblast (STB) epithelial covering of the human placenta is a unique terminally differentiated, multi-nucleated syncytium. No mitotic bodies are observed in the STB, which is sustained by continuous fusion of underlying cytotrophoblast cells (CTB). As a result, STB nuclei are of different ages. Morphologically, they display varying degrees of chromatin compaction, suggesting progressive maturational changes. Until recently, it was thought that STB nuclei were transcriptionally inactive, with all the mRNAs required by the syncytium being incorporated upon fusion of CTB. However, recent research has shown the presence of the active form of RNA polymerase II (RNA Pol II) in some STB nuclei. In this study, we confirm the presence of transcriptional activity in STB nuclei by demonstrating immunoreactivity for a transcription factor and an RNA polymerase I (RNA Pol I) co-factor, phospho-cAMP response element-binding protein and phospho-upstream binding factor, respectively. We also show, through immunoco-localisation studies, that a proportion of STB nuclei are both RNA Pol I and II transcriptionally active. Finally, we quantify the numerical densities of nuclei immunopositive and immunonegative for RNA Pol II in the STB of normal placentas of 11-39 weeks gestational age using an unbiased stereological counting tool, the physical disector. These data were combined with estimates of the volume of trophoblast to calculate total numbers of both types of nuclei at each gestational age. We found no correlation between gestational age and the numerical density of RNA Pol II-positive nuclei in the villous trophoblast (r = 0.39, P > 0.05). As the number of STB nuclei increases exponentially during gestation, we conclude that the number of transcriptionally active nuclei increases in proportion to trophoblast volume. The ratio of active to inactive nuclei remains constant at 3.9:1. These findings confirm that the majority of STB nuclei have intrinsic transcriptional activity, and that the STB is not dependent on CTB fusion for the provision of transcripts.

EPOXI at Comet Hartley 2

Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus.

Reorganisation of human sperm nuclear architecture during formation of pronuclei in a model system

By fertilisation, two terminally differentiated cells, namely the egg and spermatozoon, are combined to create a totipotent zygote. During this process, the inactive sperm nucleus is transformed into a functional male pronucleus. Recent studies demonstrate that human sperm chromatin has an elaborate multilevel organisation, but almost nothing is known about how sperm chromosomes are transformed during fertilisation. Because of ethical reasons and technical complications, experimentation with human embryos is generally unworkable and adequate model systems are necessary to study the formation of male pronuclei. Here, we analyse remodelling of human sperm chromatin and chromosome architecture in Xenopus egg extracts using immunofluorescent localisation of protamines and centromere protein A, as well as fluorescence in situ hybridisation localisation of major alpha-satellite DNA and whole chromosome territory (CT). We demonstrate noticeable relocalisation of centromeres and remodelling of CT during the decondensation-recondensation cycle, mimicking cellular events that occur in the paternal genome in vivo during fertilisation.

Hypercondylia

Condylar hyperplasia is a rare disease that alters the anatomy of one of the two condylus of the mandible as a consequence of the abnormal growth of the interested condylus and results in facial asymmetry and functional problems at puberty. Both sexes are affected. Two cases were analyzed, including an active and an inactive nucleus. Histopathologically, two types are distinguished: active and inactive hypercondylia. Diagnosis is usually achieved through clinical and radiographic approach and is utterly important to distinguish the consequent therapeutic approach. Thanks to the development of new diagnostic techniques, it is possible to quantify in advance the risk of skeletal relapse in case of hyperactive nucleus. This study points out the need to identify the type of hyperplasty to treat as active or inactive. Surgery should be based on scintigraphy results to evaluate active center of ossification. Clinical manifestations depend on the date of onset of this pathology and the speed of growth of the anomaly. We underline the importance of a precise diagnosis, clinical and instrumental, to plan the correct treatment achieved through a correct anamnesis, a standardized diagnostic protocol, supported by the indispensable scintigraphy.

Functions of transcription factor TRF2 Drosophila melanogaster

A study was made of the function of the Drosophila melanogaster TRF2 protein. Expression analysis of the trf2(P1) mutation implicated TRF2 in the D. melanogaster embryo development. High-level expression of the trf2 gene was observed in female germline cells. A high level of TRF2 was detected in primary spermatocytes and trophocytes, characterized by intense transcription. In the female gonads, TRF2 was detected in both nurse cells with intense transcription and transcriptionally inactive oocyte nuclei. In addition, TRF2 proved to be necessary for premeiotic chromatin condensation and further differentiation of germline cells.

Ultrastructure of the digestive tract of Diacyclops thomasi (Cyclopoida, Copepoda) during different stages of encystment during a summer diapause

AbstractBaud, A., Cuoc, C. and Alekseev, V. 222_. Ultrastructure of the digestive tract of Diacyclops thomasi (Cyclopoida, Copepoda) during different stages of encystment during a summer diapause. — Acta Zoologica (Stockholm) 85: 181–189 Diacyclops thomasi (Forbes, 1882) has a life cycle comprising a summer diapause with whole‐body encystment at the copepodid IV stage. Formed progressively, the cyst can indicate the extent of entry into diapause. In this study the ultrastructure of the midgut epithelium during encystment of CIV was compared with that of active CIV and females.In active individuals two well‐differentiated epithelial cell types were observed: vacuolar cells (B‐cells), and cells without vacuoles but with more densely packed microvilli and abundant rough endoplasmic reticulum and mitochondria (F/R cells). In encysted specimens a striking transformation of the midgut epithelial layer was noted. Only inactive nuclei with highly concentrated euchromatin and encircled by a thin rim of hyaloplasm were observed. Compartments of both urosome and especially cephalothorax displayed large lipid‐rich lacunae. At the beginning of encystment, the midgut epithelium showed an intermediate state.Changes in ultrastructure observed in the midgut epithelium of D. thomasi clearly reflect different stages of diapause, and represent clear evidence of profound reorganization, which is progressively induced by diapause in the organism.

Association of the nuclear matrix component NuMA with the Cajal body and nuclear speckle compartments during transitions in transcriptional activity in lens cell differentiation

The transcriptional status of cells can be deduced from the staining pattern of various nuclear markers such as the Cajal body, nucleolus and nuclear speckles. In this study we have used these markers to correlate transcriptional status with cell differentiation in the lens. As a closed system with no cell loss and with each stage being spatially preserved, it is particularly well suited to such studies. To confirm that the nuclear markers in lens cells follow the same trends as in other cells, primary bovine lens epithelial cells were cultured and then treated with actinomycin D to inhibit transcription. This reduced the Cajal body markers to one or two foci per nucleus and the nucleoli became compacted as revealed by fibrillarin staining. The nuclear speckles, containing snRNPs (e.g. Sm) and the splicing factor, SC35, also became larger and more numerous while the signal for trimethylguanine (TMG) decreased suggesting a role hierarchy for the various speckle factors during transcriptional shutdown. The signal for survival of motor neurones gene product (SMN) also decreased at this point. In the lens epithelium, postmitotic cells near the equatorial region had one or two Cajal bodies per nucleus, indicating these cells had only basal levels of transcription. Sm was also present as large foci in these cells. Interestingly, both the speckles and Cajal bodies were NuMA-positive in these post-mitotic cells. At the epithelial-fibre cell transition, Cajal body number increased, while their size decreased indicative of increased transcriptional activity. Fibrillarin adopted the open floret pattern indicating increased transcriptional activity. The nuclear speckles adopted a more diffuse nucleoplasmic pattern, although some spots were still observed. All NuMA colocalisation with the Cajal bodies and nuclear speckles was lost at this stage of lens cell differentiation. Transcriptional shutdown occurs at a later stage in fibre cell differentiation, prior to programmed nuclear destruction. In the lens, both the Cajal bodies and nuclear speckles again became NuMA-positive, although separate NuMA spots were also formed during transcriptional shutdown. These data suggest the nuclear matrix is important in the concentration of Cajal body and speckle components into large, distinct spots in transcriptionally inactive nuclei and also suggest a new role for NuMA in post-mitotic cells to assist in these sub-nuclear reorganisations.

On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei

We use a comprehensive database of black hole masses and nuclear luminosities to investigate the relationship between radio emission and black hole mass. Our sample covers a wide range of nuclear activity, from nearby inactive nuclei to classical Seyfert 1 nuclei and luminous quasars. Contrary to some previous studies, we find that the radio continuum power, either integrated for the entire galaxy or isolated for the core, correlates poorly with black hole mass. The degree of nuclear radio loudness, parameterized by the radio-to-optical luminosity ratio R, also shows no clear dependence on black hole mass. Radio-loud nuclei exist in galaxies with a wide range of black hole mass, from \~ 10^6 to a few X 10^9 solar masses, and in a variety of hosts, from disk-dominated spirals to giant ellipticals. We demonstrate that R is strongly inversely correlated with L/L_E, the ratio of nuclear luminosity to the Eddington luminosity, and hence with mass accretion rate. Most or all of the weakly active nuclei in nearby galaxies are radio-loud, highly sub-Eddington systems that are plausibly experiencing advection-dominated accretion.

The Drosophila maternal gene sésame is required for sperm chromatin remodeling at fertilization.

The spermatozoon features an extremely condensed and inactive nucleus. The unique sperm chromatin organization is acquired during the late stages of spermatid differentiation by the replacement of somatic histones with sperm-specific chromosomal proteins. At fertilization, the inactive sperm nucleus must be rapidly transformed into a DNA replication competent male pronucleus before the formation of the zygote. The sequential events of this crucial process are well conserved among animals and are controlled by molecules present in the egg. We have previously identified a Drosophila maternal effect mutation called sésame, which specifically arrests male pronucleus formation at a late stage of chromatin decondensation. In this study, we show that sésame affects maternal histone incorporation in the male pronucleus, a situation that is expected to prevent nucleosomal organization of the paternal chromatin. As an apparent consequence, the male pronucleus is arrested before the first S-phase and does not condense mitotic chromosomes. However, centromeric heterochromatin is present on paternal centromeres, which occasionally interact with microtubules. The abnormal chromatin organization of the male pronucleus does not prevent the formation of a male pronuclear envelope, which breaks down and reassembles in synchrony with maternally derived nuclei present in the same cytoplasm.