Extranuclear Regions Research Articles

High-resolution radio observations of Seyfert galaxies in the extended 12- m sample - II. The properties of compact radio components

We discuss the properties of compact nuclear radio components in Seyfert galaxies from the extended 12-μm AGN sample of Rush et al. Our main results can be summarized as follows. Type 1 and type 2 Seyferts produce compact radio components which are indistinguishable in strength and aspect, indicating that their central engines are alike, as proposed by the unification model. Infrared IRAS fluxes are more closely correlated with low-resolution radio fluxes than high-resolution radio fluxes, suggesting that they are dominated by kiloparsec-scale, extranuclear emission regions; extranuclear emission may be stronger in type 2 Seyferts. Early-type Seyfert galaxies tend to have stronger nuclear radio emission than late-type Seyfert galaxies. V-shaped extended emission-line regions, indicative of ‘ionization cones’, are usually found in sources with large, collimated radio outflows. Hidden broad lines are most likely to be found in sources with powerful nuclear radio sources. Type 1 and type 2 Seyferts selected by their IRAS 12-μm flux densities have well-matched properties.

Direct visualization of sarcoplasmic reticulum regions discharging Ca2+sparks in vascular myocytes

Localized Ca2+-release events, Ca2+sparks, have been suggested to be the 'elementary building blocks' of the calcium signalling system in all types of muscles. In striated muscles these occur at regular intervals along the fibre corresponding to the sarcomeric structures which do not exist in smooth muscle. We showed previously that in visceral and vascular myocytes Ca2+sparks occurred much more frequently at certain sites (frequent discharge sites [FDSs]). In this paper, we have related the position of FDSs to the distribution of the sarcoplasmic reticulum in the same living myocyte. The three-dimensional distribution of the SR in freshly isolated rabbit portal vein myocytes was visualized by means of high-resolution confocal imaging after staining with DiOC6and/or BODIPY TR-X ryanodine. Both fluorochromes revealed a similar staining pattern indicating a helical arrangement of well-developed superficial SR which occupied about 6% of the cell volume. Computing the frequency of spontaneous Ca2+sparks detected by means of fluo-4 fluorescence revealed that in about 70% of myocytes there was only one major FDS located on a prominent portion of superficial SR network usually within 1–2μm of the nuclear envelope, although a few sparks occurred at other sites scattered generally in superficial locations throughout the cell. Polarized mitochondria were readily identified by accumulation of tetramethylrhodamine ethyl ester (TMRE). These were closely associated with the SR network in extra-nuclear regions. TMRE staining, however, failed to reveal any mitochondria near the FDS-related SR element. When observed, propagating [Ca2+]iwaves and associated myocyte contractions were initiated at FDSs. This study provide first insight into the three-dimensional arrangement of the SR in living smooth muscle cells and relates the peculiarity of the structural organization of the myocyte to the features of Ca2+signalling at subcellular level.

High‐Resolution Imaging of Molecular Gas and Dust in the Antennae (NGC 4038/39): Super Giant Molecular Complexes

We present new aperture synthesis CO maps of the Antennae (NGC 4038/39) obtained with the Caltech Millimeter Array. These sensitive images show molecular emission associated with the two nuclei and a partial ring of star formation to the west of NGC 4038, as well as revealing the large extent of the extranuclear region of star formation (the region), which dominates the CO emission from this system. The largest molecular complexes have masses of × 108 M☉, typically an order of magnitude larger than the largest structures seen to date in more quiescent galaxy disks. The extremely red luminous star clusters identified previously with the Hubble Space Telescope are well correlated with the CO emission, which supports the conclusion that they are highly embedded young objects rather than old globular clusters. There is an excellent correlation between the CO emission and the 15 μm emission seen with the Infrared Space Observatory, particularly for the brightest regions. The most massive complexes in the overlap region have similar [Ne III]/[Ne II] ratios, which implies that all these regions are forming many massive stars. However, only the brightest mid-infrared peak shows strong, rising continuum emission longward of 10 μm, indicative of very small dust grains heated to high temperatures by their proximity to nearby luminous stars. Since these grains are expected to be removed rapidly from the immediate environment of the massive stars, it is possible that this region contains very young (<1 Myr) sites of star formation. Alternatively, fresh dust grains could be driven into the sphere of influence of the massive stars, perhaps by the bulk motions of two giant molecular complexes. The kinematics and morphology of the CO emission in this region provide some support for this second scenario.

Keck Observations of the Hidden Quasar IRAS P09104+4109

We present imaging and spectropolarimetric observations of the ultraluminous infrared galaxy IRAS P09104+4109 using the Keck 10 m Telescope. We detect the clear presence of broad Hβ, Hγ, and Mg II λ2800 emission lines in the polarized flux spectra of the nucleus and of an extranuclear emission region ~4'' away, confirming the presence of a hidden central quasar. The polarization of the broad Mg II emission line is high (~29%), consistent with the remarkably high polarization (~30%–40%) observed in the extended continuum emission. This indicates that the off-nuclear continuum is dominated by light scattered from the hidden quasar, most probably by dust mixed with the line-emitting gas. The high polarizations, combined with the foreshortened morphology of the polarized brightness distribution, allow us to constrain the scattering biconical structure to be at inclination i ≈ 50° with a half-opening cone angle θc ≈ 40°. The narrow emission lines are polarized in a stratified fashion, with the high-ionization lines ([O III], [Ne V], [Fe VII]) being polarized 0.7%–1.7% and [O II] essentially unpolarized. The line polarizations are positively correlated with critical density, ionization potential, and velocity width of the emission lines. This indicates that, as is the case with the narrow-line radio galaxies, which also often contain powerful quasars, the narrow emission line region may be partially shadowed by the putative torus, with the higher ionization lines originating closer to the nucleus. One notable characteristic of the extranuclear knot is that all species of Fe are markedly absent in its spectrum, while they appear prominently in the nucleus. In addition, narrow Mg II is observed to be much weaker than predicted by ionization models. Our favored interpretation is that there is a large amount of dust in the extranuclear regions, allowing gaseous refractory metals to deposit. Near the nucleus, dust is destroyed in the strong radiation field of the quasar, inhibiting metal depletion onto grains. The extended emission regions are most likely material shredded from nearby cluster members and not gas condensed from the cooling flow or expelled from the obscured quasar. The higher temperature inferred from [O III] lines compared to that from [N II] and the general better agreement with models of line ratios, especially [O III] λ5007/λ4363 and He II/Hβ, provide strong evidence for matter-bounded clouds in addition to ionization-bounded clouds in the narrow-line region. Ionization by pure velocity shocks can be ruled out. Shocks with photoionizing precursors may be present but are probably not a dominant contributor to the energy input.

Hubble Space Telescope/Faint Object Spectrograph Spectroscopy of Spatially Resolved Narrow‐Line Regions in the Seyfert 2 Galaxies NGC 2110 and NGC 5929

We present the results of UV and optical Hubble Space Telescope/Faint Object Spectrograph spectros- copy of bright, extranuclear regions of line emission in the Seyfert galaxies NGC 2110 and NGC 5929. We have obtained spectra of the brightest region of the ii nuclear jet ˇˇ of NGC 2110 (75 pc from the nucleus) and of the southwest emission-line cloud of NGC 5929 (90 pc from the nucleus), in the G130H (1090¨1605 G190H (1570¨2310 G400H and G570H (4570¨6820 con—gurations. Ae ), Ae ), (3235¨4780 Ae ), Ae ) The observed line ratios are compared with the predictions of the two component (matter- and ionization-bounded, MB-IB), central source photoionization models of Binette, Wilson, & Storchi- Bergmann and of the fast, photoionizing (ii autoionizing ˇˇ) shock models of Dopita & Sutherland. In both objects, the signi—cant reddening inferred from the Balmer line ratios and/or its uncertainty limit the utility of the ultraviolet carbon lines C IV j1549 and C III) j1909 for discrimination between the central source and shock-induced photoionization mechanisms. In NGC 2110, shock)precursor models with a shock velocity of ^400 km s~1 provide a better match to the data than the MB-IB models. However, given the simplifying assumptions made in the latter models, photoionization by a central source cannot be ruled out. We investigate whether photoionizing shocks in the emission-line region of NGC 2110 can power the extended, soft X-ray emission north of the nucleus and —nd that shock veloci- ties higher than 500 km s~1 are required. In NGC 5929, the MB-IB models have problems reproducing the strengths of the neon lines, while shock)precursor models with a velocity ^300 km s~1 provide a good match to the data. For both galaxies, the emission-line powers and volumes of the ionized gas inferred from observations imply that both the preshock density and magnetic parameter

Functional expression of exogenous proteins in mammalian sensory hair cells infected with adenoviral vectors.

To understand the function of specific proteins in sensory hair cells, it is necessary to add or inactivate those proteins in a system where their physiological effects can be studied. Unfortunately, the usefulness of heterologous expression systems for the study of many hair cell proteins is limited by the inherent difficulty of reconstituting the hair cell's exquisite cytoarchitecture. Expression of exogenous proteins within hair cells themselves may provide an alternative approach. Because recombinant viruses were efficient vectors for gene delivery in other systems, we screened three viral vectors for their ability to express exogenous genes in hair cells of organotypic cultures from mouse auditory and vestibular organs. We observed no expression of the genes for beta-galactosidase or green fluorescent protein (GFP) with either herpes simplex virus or adeno-associated virus. On the other hand, we found robust expression of GFP in hair cells exposed to a recombinant, replication-deficient adenovirus that carried the gene for GFP driven by a cytomegalovirus promoter. Titers of 4 x 10(7) pfu/ml were sufficient for expression in 50% of the approximately 1,000 hair cells in the utricular epithelium; < 1% of the nonhair cells in the epithelium were GFP positive. Expression of GFP was evident as early as 12 h postinfection, was maximal at 4 days, and continued for at least 10 days. Over the first 36 h there was no evidence of toxicity. We recorded normal voltage-dependent and transduction currents from infected cells identified by GFP fluorescence. At longer times hair bundle integrity was compromised despite a cell body that appeared healthy. To assess the ability of adenovirus-mediated gene transfer to alter hair cell function we introduced the gene for the ion channel Kir2.1. We used an adenovirus vector encoding Kir2.1 fused to GFP under the control of an ecdysone promoter. Unlike the diffuse distribution within the cell body we observed with GFP, the ion channel-GFP fusion showed a pattern of fluorescence that was restricted to the cell membrane and a few extranuclear punctate regions. Patch-clamp recordings confirmed the expression of an inward rectifier with a conductance of 43 nS, over an order of magnitude larger than the endogenous inward rectifier. The zero-current potential in infected cells was shifted by -17 mV. These results demonstrate an efficient method for gene transfer into both vestibular and auditory hair cells in culture, which can be used to study the effects of gene products on hair cell function.

Nuclear and cytosolic calcium changes in osteoclasts stimulated with ATP and integrin-binding peptide

Cytosolic calcium modulates the activity of osteoclasts, large multinucleate cells that resorb bone. Nuclear events, such as gene transcription, are also calcium-regulated in these cells, and fluorescence imaging has suggested that calcium signals produced by some stimuli are specifically targeted to, or amplified within, osteoclast nuclei. We used two alternative techniques of dye loading to examine the changes of intracellular calcium induced in rat osteoclasts by three stimuli. Osteoclasts loaded with the calcium indicator Fura-2 by the acetoxymethyl (AM) ester technique appeared to display marked nuclear calcium amplification. During stimulation with integrin-binding peptides, ATP, or high extracellular calcium, fluorescence ratios recorded from the nuclei rose higher than did ratios recorded from extranuclear regions. In contrast, nuclear calcium amplification was not observed after AM loading in the presence of the anion transport inhibitor sulfinpyrazone, nor in osteoclasts injected with Fura-2 conjugated to a high MW dextran. In these cells, nuclear fluorescence ratios were equal to the extranuclear values at all times: upon stimulation by an agonist, the nuclear and cytosolic calcium concentrations increased by the same amount. The calcium changes seen in stimulated osteoclasts can no longer be taken as evidence for the general validity of the phenomenon of nuclear calcium amplification.

The Supernova Rate in Starburst Galaxies

ABSTRACTWe conducted an optical CCD search for supernovae in a sample of 142 bright [m(B)≤16 mag], nearby (z≤0.03) starburst galaxies over the period 1988 December to 1991 June, to a limiting R‐band magnitude of 18. Five supernovae were found, in all cases outside the host galaxy's nucleus. We determine supernova rates (in supernova units or SNU) in the extranuclear regions to be 0.7 h2 SNU for Type Ia, 0.7 h2 SNU for Type Ib/c, and ∼0.6 h2 SNU for Type II, with large uncertainties but upper limits of 2.2 h2, 2.5 h2, and 1.7 h2 SNU, respectively. These rates are similar to those measured in “normal” galaxies. We found no evidence for a supernova‐induced brightening in any galactic nucleus and, with a few reasonable assumptions, can place upper limits of 9 h2, 12 h2, and 7 h2 SNU on the rates of unobscured supernovae Types Ia, Ib/c, and II, respectively, inside the nuclei.

Inverse correlation between expression of phosphatidylethanolamine N-methyltransferase-2 and growth rate of perinatal rat livers

Our previous studies have implicated the liver-specific phosphatidylethanolamine N-methyltransferase-2 (PEMT2) in suppression of hepatocarcinoma proliferation (Cui et al. (1994) J. Biol. Chem. 269, 24531–24533). It was not known if this phenomenon in cell culture had relevance to liver growth and PEMT2 expression in an intact animal. Hence, we investigated the relationship between normal proliferation of liver and the expression of PEMT2 during the perinatal period of developing rats. PEMT2 protein was completely absent, and PEMT activity was very low, in prenatal livers in which liver growth is rapid. At birth, a decrease of liver growth coincided with the rapid appearance in liver of a high level of PEMT2 protein that was sustained throughout adult life. Northern blots revealed that the postnatal expression of PEMT2 correlated with the level of its mRNA. Immunohistochemical staining of liver sections showed a distinctive pattern of PEMT2 expression at birth. A high level of PEMT2 was expressed in defined extranuclear regions of hepatocytes from newborn rats whereas the protein was dispersed in the extranuclear areas in adult hepatocytes. The inverse correlation between the rate of liver growth and PEMT2 expression together with other results suggest that this enzyme, or its product, is involved in control of normal liver proliferation. © 1997 Elsevier Science B.V. All rights reserved.

Variation of Molecular Line Ratios and Cloud Properties in the Arp 299 Galaxy Merger

High resolution observations of 12CO (2.''3), 13CO (3.''9), and HCN (5.''4) J=1--0 in the galaxy merger Arp 299 (IC 694 and NGC 3690) show the line ratios vary dramatically across the system. The 12CO/13CO ratio is unusually large, 60 +- 15, at the IC 694 nucleus, where 12CO emission is very strong, and much smaller, 10 +- 3, in the southern extended disk of that galaxy. Elsewhere, the 12CO/13CO line ratio is 5-20, typical of spiral galaxies. The line ratio variation in the overlap between the two galaxies is smaller, ranging from 10 +- 3 in the east to 20 +- 4 in the west. The 12CO/HCN line ratio also varies across Arp 299, although to a lesser degree. HCN emission is bright towards each galaxy nucleus and in the extranuclear region of active star formation; it was not detected in the IC 694 disk, or the eastern part of the overlap region, leading to lower limits of 25 and 20 respectively. By contrast, at the nuclei of IC 694 and NGC 3690 the ratios are 9 +- 1 and 14 +- 3 respectively. In the western part of the overlap region it is 11 +- 3.

The knotty structure of the HII dwarf galaxy F348

Abstract[OIII] images and blue spectra of the emission‐line dwarf galaxy F348 are presented. In [OIII] light, the object contains two knots about 9” NE of the nucleus and one large extended knot 11” to the SW. The nuclear region is hundred times less luminous in emission‐line light than the knots. Despite the presence of line intensity ratios [OIII]λ5007/Hβ &gt; 3 the prior classification as a Seyfert‐2 object cannot be upheld. This clinches an earlier suggestion by Veron‐Cetty &amp; Veron (1986). In particular, we show that the line spectra can be modeled with photoionization models employing stellar input continua. Also, the line luminosities of the extranuclear knots are typical for giant HII regions. There is neither evidence for tidal tails nor for high velocity differences between the knots. In addition, the linear arrangement of the knots does not support interaction. It rather suggests self‐propagating star formation In this picture, the faintness of the nuclear region can be understood by an edge‐on view. In addition, the nuclear starburst appears to be fading in contrast to the young extranuclear star formation regions. Within the scheme of Melnick (1987), F348 has to be classified as a multiple‐system HII galaxy.

Toward an Understanding of the Seyfert Galaxy NGC 5252: A Spectroscopic Study

view Abstract Citations (20) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Toward an Understanding of the Seyfert Galaxy NGC 5252: A Spectroscopic Study Acosta-Pulido, Jose A. ; Vila-Vilaro, Baltasar ; Perez-Fournon, Ismael ; Wilson, Andrew S. ; Tsvetanov, Zlatan I. Abstract We present long-slit spectra of the Seyfert 2 galaxy NGC 5252, covering the nucleus and part of the extranuclear emission-line region. All the regions sampled by our spectra have emission-line ratios characteristic of photoionization by an active galactic nucleus-like (AGN-like) continuum source. The spectrum of the nucleus differs from those measured in extranuclear regions, showing higher values of the line ratios [O I] λ6300/Hα, [S II] λλ6716, 6731/Hα, and [N II] λ6584/Hα, and a lower value of He II λ4686/Hα. These differences can be understood in terms of either a larger fraction of matter-bounded (optically thin) clouds in the extended gas than at the nucleus, or an additional excitation mechanism in the nucleus, such as interaction with the radio-emitting plasma. The excitation of the gas in the extended emission-line region, as measured by the line ratios [O III] λ5007,/Hα, [O III] λ5007/[O II] λ3727, and [O III] λ5007/[N II] λ6584, is correlated with the emission-line brightness. This result is another piece of evidence favoring an important contribution from matter-bound clouds in the extranuclear gas. The electron temperatures in the extended emission-line regions are in the range 20,000-24,000 K, higher than predicted by the simplest photoionization models but similar to the temperatures found in other extended emission- line regions associated with active galactic nuclei. The higher spectral resolution observations are used to study the kinematics of the line-emitting gas. Very close to the nucleus, two different kinematical components are found: one extending toward the northwest of the nucleus and blueshifted with respect to the adopted systemic velocity and the other extending toward the southeast and redshifted. Such kinematical components may be associated with the nuclear jet-like radio structure or with bright, compact knots recently detected in Hubble Space Telescope images. Outside the nucleus, the velocity field of the gas is complex, suggesting that radial motions, perhaps driven by the active nucleus, in addition to rotation, are present. A broad Hα component (FWHM ~ 2500 km s^-1^) is detected in the nucleus, but no similar one is found for Hβ. The luminosity derived for the nucleus using recombination lines is relatively high for a Seyfert 2 nucleus. Both results are consistent with the hypothesis that NGC 5252 contains a partially hidden broad-line region and a more luminous nucleus than is directly observed. Publication: The Astrophysical Journal Pub Date: June 1996 DOI: 10.1086/177310 Bibcode: 1996ApJ...464..177A Keywords: GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5252; GALAXIES: NUCLEI; GALAXIES: SEYFERT full text sources ADS | data products SIMBAD (8) NED (1)

Intracellular recordings from neurons of the arcuate nucleus in superfused explants of rat hypothalamus.

The membrane properties of arcuate nucleus (ARN) neurons and their connections with extranuclear regions were examined in vitro, using intracellular recordings obtained in superfused explants of rat hypothalamus. Current-clamp analysis revealed that the electroresponsive properties of a large proportion of ARN neurons are influenced by the expression of various forms of low threshold rectification. When the initial membrane potential of a neuron was maintained negative to -70 mV, depolarizing current injection could precipitate an immediate bursting response, due to the activation of a low-threshold spike, or delay firing as a result of transient outward rectification. These properties represent a means by which changes in membrane potential may modulate the responsiveness of ARN neurons to synaptic input. Indeed, electrical stimulation revealed that in addition to efferent projections to the supraoptic nucleus, medial preoptic area, or neurointermediate pituitary, subgroups of ARN neurons may receive a reciprocal, or collateral innervation from each of these areas. This functional diversity of intrinsic and synaptic mechanisms provides ARN neurons with a high capacity for the complex local processing of afferent information.

The ionizing radiation field of NGC 4388 and its relation to the extranuclear emission-line regions

view Abstract Citations (22) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Ionizing Radiation Field of NGC 4388 and Its Relation to the Extranuclear Emission-Line Regions Colina, Luis Abstract New long-slit spectroscopic observations of NGC 4388 and the extranuclear emission line regions around it are used to investigate the characteristics of the ionizing source and the structure of the extended emission-line regions. The measured luminosity of the [Fe VII) λ6087 emission line detected in the nucleus of NGC 4388 is interpreted as evidence for the existence of a powerful ionizing source with N_ph_(>= 100 eV) >~ 2 x 10^50^ photons s^-1^ and for the presence of clouds of gas with electron densities N_e_~10^7^ cm^-3^. A comparison between the far-infrared luminosity and the UV- extrapolated ionizing luminosity as measured along our line of sight suggests that NGC 4388 has a hidden UV luminous source in its nucleus which is around 6 times brighter than observed; it should therefore be obscured by A_v_ = 0.31 mag. This places NGC 4388 among the intermediate luminosity Seyfert 1 galaxies with log L_UV_ 43.23 ergs s^-1^ and confirm the suggestion by Shields and Filippenko that NGC 4388 has a hidden luminous Seyfert 1 nucleus. The excitation conditions in the extranuclear emission-line regions are best accounted for by the ionization from a nonthermal central source in the nucleus of NGC 4388. Other alternative ionization sources, like star clusters or relativistic particles and shocks associated with the radio emission, are seen to play a minor role, if any. Publication: The Astrophysical Journal Pub Date: February 1992 DOI: 10.1086/170992 Bibcode: 1992ApJ...386...59C Keywords: Active Galactic Nuclei; Emission Spectra; Ionizing Radiation; Seyfert Galaxies; Ultraviolet Astronomy; Astronomical Spectroscopy; Cosmic Dust; Iue; Star Clusters; Ultraviolet Emission; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4388; GALAXIES: NUCLEI; GALAXIES: SEYFERT full text sources ADS | data products SIMBAD (8) NED (1) MAST (1) INES (1)

Recent star formation in the interacting galaxy system NGC 520

New optical spectroscopy, near-infrared spectroscopy, and mid-infrared imaging of the interacting system NGC 520 are presented. The data show that the heavily obscured primary nucleus has a current star-forming rate about 35 times the typical rate for a late-type galaxy nucleus, which may account for most of the large far-infrared luminosity of NGC 520. The secondary nucleus has little current star formation but has recently undergone a mild starburst. Optical colors and absorption line equivalent widths suggest that the extranuclear regions in both galaxies have experienced enhanced star formation roughly at the same time as the secondary nucleus, though at a lesser intensity. The extent of the extranuclear burst is large; at least half of the projected surface area of the two disks took part to varying degrees in the episode. Determining the exact age and strength of the recent star-formation episode in NGC 520 is uncertain. The best estimate for the initiation time of about few x 10 exp 8 yrs ago is consistent with the system-wide starburst being caused by the galaxy collision.

The influence of high-density environment on the radio-far-infrared correlation of spiral galaxies

It is found that the far-infrared and radio luminosities of a sample of spirals in high-density environments from the Hickson Compact Group Catalogue 1982 (Hickson1982) are highly correlated even though the radio radiation originates almost entirely in extranuclear regions for most of the spirals. A comparison of the above correlation with that for a sample of isolated spirals shows that, statistically, the total radio emission from the group spirals is lower by about a factor of 2 than the isolated spirals. These results can be interpreted on the basis of a model in which interactions among group galaxies produce inflow of gas toward the centers, resulting in enhanced star formation, which in turn produces enhancement of far-infrared and radio radiation from those regions. At the same time, removal of gas and magnetic fields from the disk of the galaxies results in a decrease of total radio emission from those galaxies. It is interesting that, except for one Seyfert galaxy, the radio luminosities of all the group galaxies are less than about 10 22 W/Hz -1 at 20 cm, which suggests that the high-density environment is not conducive for the development of powerful radio sources at the present epoch.

Physiological and morphological analysis of cat digastric motoneurons after intracellular staining with horseradish peroxidase.

Horseradish peroxidase was injected into the somata of cat digastric motoneurons. Twelve motoneurons for which the spatial distribution of dendritic arborization and axon trajectory were iden-tified physiologically were studied with reference to the location of cell bodies in the trigeminal motor nucleus. It was revealed that, irrespective of the rostrocaudal level of the soma, dendrities of digastric motoneurons were present mainly in the medial half of the nucleus as well as in extranuclear regions. Interestingly very few dendritic branches were observed in the lateral half of the motor nucleus, this “unoccupied” region corresponding to the masseter subdivision of the nucleus. The axons ran a dorsomedial course and descended to the motor root without giving rise to collaterals. The average size of the soma was 44.2μm with a range of 36.9-50.1μm. A linear correlation was observed between the total stem dendrite diameter and the mean soma diameter, giving a coefficient of 0.534. No excitatory postsynaptic potential was recorded from the soma upon stimulation of the digastric nerve with a current below the threshold, indicating a lack of muscle spindles.

Dose-modification factor for accumulated dose to cell nucleus due to protein-bound 3H.

The purpose of this work was to estimate the dose-modification factor for accumulated dose in the cell nucleus due to protein-bound 3H in animal organs. The animal tissues were modeled to make a simplified theoretical estimation of the extent of dose modification due to the differential distribution of proteins between the cell nucleus and the extranuclear region. The results of theoretical calculation were applied to the case of mouse organs for which various cytological factors were determined experimentally. It was found that the dose-modifying factor (f) for mouse organs was between about 0.8 and 1.5, indicating that dose modification due to protein localization is of minor importance for the dosimetry of internally retained 3H.

Luminous extranuclear star formation in the interacting galaxy ARP 118 - NGC 1143/44

The interacting system Arp 118 (NGC 1143/44) has been observed at infrared and radio wavelengths. The interaction has produced a pair of distorted loops and several luminous radio and infrared sources in NGC 1144 which emit a total power of 2.5 x 10 to the 11th lunar masses, 80 percent of which is reradiated in the thermal infrared. Remarkably, the present observations reveal that much of the midinfrared emission originates in an extra-nuclear star-forming region. Arp 118 has many of the same characteristics as the well-studied interacting system Arp 299 (NGC 3690), including luminous extranuclear activity; the main difference between the two systems is that the nuclei of NGC 1143/44 are much less luminous at 10 microns than their counterparts in NGC 3690.

A blue, polarized continuum source near radio galaxy PKS2152–69

The frequent occurrence of extranuclear emission line regions in radio galaxies and quasars is well known1,2, but the origin and excitation of gas at temperatures of (l–2) × 104 K, extending to distances beyond 100 kpc from the nucleus, are not understood in detail. In some cases there is evidence that highly excited gas is associated with the transport of energy from the active nucleus of the galaxy out to the extended radio structures, and in one such case, the radio galaxy PKS2152–69, Tadhunter et al.3 reported a blue continuum source coincident with the highest ionization region of a gas cloud, at a projected distance of 8 kpc from the nucleus and lying approximately along the radio axis. Here we report optical observations of the continuum showing that its spectrum rises into the near ultraviolet with fv∝v3±1 and that its degree of polarization is about 10% with the electric vector perpendicular to the radius vector from the nucleus. In the absence of a workable intrinsic emission mechanism, we propose that a beamed nuclear source could excite the highly ionized extranuclear cloud and scatter off associated dust to produce the observed continuum.