Possible effects of clustering structure in the competition between fast emission processes and compound nucleus decay / Posibles efectos de estructura de agrupamiento en la competencia entre los procesos de emisión rápida y desintegración del núcleo compuesto

Abstract The attention to nuclear clustering has been renewed due to the study of weakly bound nuclei at the drip lines. In particular, clustering structural properties in medium-mass systems have been studied by looking at the competition between the evaporation and pre-equilibrium particle emission in central collisions. Although for light nuclei at an excitation energy close to the particle separation value there are experimental evidence of such structure effects, this is still not the case for heavier systems since the determination of pre-formed clusters within nuclear matter is less obvious. Two systems, leading to the same 81Rb* compound nucleus, have been studied at the same beam velocity 16 AMeV: 16O + 65Cu and 19F + 62Ni. The experiment has been performed using the GARFIELD + RCo detection system installed at the Legnaro National Laboratories.Light charged particles energy distributions and multiplicities have been compared with different statistical and dynamical model calculations. From the first comparison between the two systems a difference in the fast α-decay channel has been evidenced, which can be related to the difference in the projectile structure. Recent data analysis results and comparisons with model calculations are presented in this contribution.

Resumen La atención a la agrupación nuclear se ha renovado debido al estudio de núcleos débilmente unidos en las líneas de goteo. En particular, se han estudiado las propiedades estructurales del agrupamiento en sistemas de masa media al observar la competencia entre la evaporación y la emisión de partículas de preequilibrio en colisiones centrales. Aunque para núcleos ligeros a una energía de excitación cercana al valor de separación de la partícula hay evidencia experimental de tales efectos de estructura, este no es el caso para sistemas más pesados ya que la determinación de agrupamientos preformados dentro de la materia nuclear es menos obvia. Se han estudiado dos sistemas, que conducen al mismo núcleo compuesto 81Rb *, a la misma velocidad de haz 16 AMeV: 16O + 65Cu y 19F + 62Ni. El experimento se ha realizado utilizando el sistema de detección GARFIELD + RCo instalado en los Laboratorios Nacionales Legnaro. Las distribuciones de energía y las multiplicidades de partículas de carga ligera se han comparado con diferentes cálculos de modelos estadísticos y dinámicos. Desde la primera comparación entre los dos sistemas, se ha evidenciado una diferencia en el canal de desintegración α rápida, que se puede relacionar con la diferencia en la estructura del proyectil. En esta contribución se presentan los resultados del análisis de datos recientes y las comparaciones con los cálculos del modelo.

Action of three bioavailable antioxidants in orbital fibroblasts from patients with Graves' orbitopathy (GO): a new frontier for GO treatment?

OBJECTIVE: Oxidative stress is involved in the pathogenesis of Graves' orbitopathy (GO) and an antioxidant approach has been advocated for GO treatment. Here, we investigated the action of three antioxidants in orbital fibroblasts, namely, vitamin C, N-acetyl-L-cysteine, and melatonin. METHODS: Primary cultures of orbital fibroblasts from six GO patients and six control subjects were established. Cells were treated with H2O2 to induce oxidative stress. Cell vitality assays were performed to determine the non-cytotoxic dose of each antioxidant. The following assays were performed: glutathione disulfide (GSSG), as a measure of oxidative stress, cell proliferation, hyaluronic acid (HA), TNFα, IFNγ, and IL1ß. RESULTS: H2O2 induced oxidative stress (augmented GSSG), increased cell proliferation as well as cytokine release, but did not affect HA release. All of the three antioxidant substances reduced H2O2-dependent oxidative stress. Vitamin C reduced proliferation in GO, but not in control fibroblasts. N-acetyl-L-cysteine reduced proliferation and IFNγ in GO, and HA and IL1ß in both GO and control fibroblasts. Melatonin reduced IL1ß and HA in GO and control fibroblasts, and IFNγ only in GO fibroblasts. CONCLUSIONS: Our study provides evidence in support of an antioxidant role of vitamin C, N-acetyl-L-cysteine and melatonin in orbital fibroblasts. Some of the effects of these compounds are exclusive to GO fibroblasts, whereas some other are observed also in control fibroblasts. Our observations provide a basis for a possible clinical use of these substances in patients with GO.

Antioxidant effects of ß-carotene, but not of retinol and vitamin E, in orbital fibroblasts from patients with Graves' orbitopathy (GO).

BACKGROUND: Oxidative stress is involved in the pathogenesis of Graves' orbitopathy (GO) and several antioxidant agents, namely, selenium, quercetin, enalapril, vitamin C, N-acetyl-L-cysteine, and melatonin, have been shown to reduce oxidative stress and its consequences in primary culture of orbital fibroblasts. In addition, selenium is effective for the treatment of mild GO. Here, we investigated the action of three additional antioxidants in orbital fibroblasts, namely, retinol, ß-carotene, and vitamin E. METHODS: Primary cultures of orbital fibroblasts were established from GO patients and control subjects. To induce oxidative stress, cells were treated with H2O2, after which glutathione disulfide (GSSG) (a parameter of oxidative stress), cell proliferation, hyaluronic acid, TNFα, IFNγ, and IL1ß were measured. RESULTS: H2O2-dependent oxidative stress (augmented GSSG) was associated with increased cell proliferation and cytokine release. All the three antioxidant substances reduced GSSG in both GO and control fibroblasts. ß-carotene reduced proliferation in GO, but not in control fibroblasts. IL1ß was reduced by all three substances. Retinol reduced IFNγ in GO and control fibroblasts. CONCLUSIONS: Our study supports an antioxidant role of retinol, ß-carotene, and vitamin E in orbital fibroblasts from patients with GO and provides a basis for a possible clinical use these substances.

Graves' orbitopathy, idiopathic orbital inflammatory pseudotumor and Epstein-Barr virus infection: a serological and molecular study.

OBJECTIVE: One of the hypotheses on the pathogenesis of autoimmune diseases, including Graves' disease (GD) and Graves' orbitopathy (GO), involves bacterial or viral infections. Recently, Epstein-Barr virus (EBV) has been proposed to play a role in the pathogenesis of idiopathic orbital inflammatory pseudotumor (IOIP) in Asians. The aim of the present study was to investigate the possible association of GO with EBV infection/exposure, as compared with IOIP, using serum and tissue samples, as well as primary cultures of orbital fibroblasts. METHODS: Thirty-one patients were studied, including four with IOIP, ten with GO, nine with GD without GO and eight control patients without IOIP, GD and GO. All patients with IOIP and GO underwent orbital decompression. Control patients underwent palpebral surgery. Fibroadipose orbital tissue samples were collected. Serum anti-EBV antibodies were measured in all patients. EBV-DNA was measured in blood samples, orbital tissue samples and primary cultures of orbital fibroblasts. RESULTS: Serum assays showed that the vast majority of patients have had a previous exposure to EBV, but no one had an acute infection. EBV-DNA was detected in ~40% of blood samples from GO, GD and control patients, but in none of the IOIP samples. EBV-DNA was not detected in any of the orbital tissue samples tested or in primary cultures of orbital fibroblasts. CONCLUSIONS: EBV infection does not seem to be associated with GD, GO and IOIP in Caucasians. Whether EBV is involved in IOIP in Asians or other populations remains to be confirmed.

The Neuropeptide Systems and their Potential Role in the Treatment of Mammalian Retinal Ischemia: A Developing Story.

The multiplicity of peptidergic receptors and of the transduction pathways they activate offers the possibility of important advances in the development of specific drugs for clinical treatment of central nervous system disorders. Among them, retinal ischemia is a common clinical entity and, due to relatively ineffective treatment, remains a common cause of visual impairment and blindness. Ischemia is a primary cause of neuronal death, and it can be considered as a sort of final common pathway in retinal diseases leading to irreversible morphological damage and vision loss. Neuropeptides and their receptors are widely expressed in mammalian retinas, where they exert multifaceted functions both during development and in the mature animal. In particular, in recent years somatostatin and pituitary adenylate cyclase activating peptide have been reported to be highly protective against retinal cell death caused by ischemia, while data on opioid peptides, angiotensin II, and other peptides have also been published. This review provides a rationale for harnessing the peptidergic receptors as a potential target against retinal neuronal damages which occur during ischemic retinopathies.

Quercetin decreases proliferation of orbital fibroblasts and their release of hyaluronic acid.

BACKGROUND: Inhibition of fibroblast (FB) proliferation and hyaluronic acid (HA) production may be a therapeutic approach to Graves' ophthalmopathy (GO). The flavonoid quercetin has a wide range of activities, including reduction of FB growth. AIM: To investigate the effects of quercetin in orbital FB from GO patients and control subjects. METHODS: Primary cultures of orbital FB were treated with quercetin or with its glycosides rutin and quercitrin. Cell proliferation, necrosis, apoptosis, HA production, and cell cycle were measured. RESULTS: Beginning at a 30 µM concentration, quercetin, but not rutin and quercitrin, reduced cell proliferation, with no difference between GO and control FB. The effect of quercetin on proliferation was due to necrosis and cell cycle blockade, whereas apoptosis was unaffected. Quercetin reduced HA in the cell media, with no difference between GO and control FB. CONCLUSIONS: Quercetin reduces cell proliferation and HA release in orbital FB. Whether these initial findings have any potential for the use of quercetin in the clinical practice remains to be established.

Long-term effects of nicotine on rat fungiform taste buds.

Nicotine, an alkaloid found in tobacco smoke, has been recognized as capable of inducing changes in taste functionality in conditions of chronic exposure. The mechanisms underlying these sensory alterations, however, are currently unknown. We addressed this issue by studying the long-term effects of nicotine on the anatomical features of taste buds, the peripheral end-organs of taste, in rat fungiform papillae. Nicotine was administered to rats via drinking water over a period of 3 weeks, which represents a standard method to achieve chronic drug exposure in laboratory animals. We found that prolonged administration of nicotine induced a significant reduction in the size of fungiform taste buds, without affecting their total number on the rat tongue. Morphometric measurements as well as evaluations of taste cell membrane capacitance suggested that the reduced size of taste organs was determined by a decrease in the number of cells per taste bud. In addition, chronic treatment with nicotine caused an increase in the relative density of cells expressing gustducin, a specific G protein alpha-subunit found in some taste cells and involved in bitter/sweet transduction. Interestingly, changes in the expression pattern of gustducin turned out to be more pronounced in periadolescent/adolescent than in adult rats. As a whole, our data indicate that long-term nicotine administration induces significant changes in the anatomical properties of taste buds in rat fungiform papillae. These changes could have a profound impact on the sensory information relayed to the brain; therefore, they may be responsible, at least in part, for the alterations in taste functionality observed during chronic nicotine exposure, a condition found in regular smokers.

Giant dipole resonance in the hot and thermalized 132Ce nucleus: damping of collective modes at finite temperature.

The gamma decay of the giant dipole resonance (GDR) in the 132Ce compound nucleus with temperature up to approximately 4 MeV has been measured, using the reaction 64Ni + 68Zn at E(beam) = 300, 400, and 500 MeV. The gamma and charged particles measured in coincidence with recoils are consistent with a fully equilibrated compound nucleus emission. The GDR width, obtained with the statistical model analysis, is found to increase almost linearly with temperature. This increase is rather well reproduced within a model including thermal shape fluctuations and the lifetime of the compound nucleus.

Expression of substance P, neurokinin 1 receptors (NK1) and neurokinin 3 receptors in the developing mouse retina and in the retina of NK1 knockout mice.

To complete a series of studies on the expression of substance P and neurokinin receptors in mammalian retinas, we investigated the occurrence of these molecules in developing mouse retinas and in retinas of mice with genetic deletion of the neurokinin 1 receptor, the preferred substance P receptor. Using semi-quantitative reverse transcription-polymerase chain reaction, we measured detectable levels of the gamma isoform of preprotachykinin A (a substance P precursor) mRNA at postnatal day 4. Neurokinin 1 receptor and neurokinin 3 receptor mRNAs were also detected at postnatal day 4. While gamma preprotachykinin A and neurokinin 1 receptor mRNA levels significantly increased up to eye opening (postnatal day 11), neurokinin 3 receptor mRNA levels remained constant throughout development. Substance P, neurokinin 1 receptor and neurokinin 3 receptor immunoreactivities were present at postnatal day 5. Substance P was in amacrine cells, neurokinin 1 receptor in developing amacrine and bipolar cells and neurokinin 3 receptor in OFF-type cone bipolar cells. Interestingly, a transient increase in the density of neurokinin 1 receptor immunoreactive processes was observed at eye opening in lamina 3 of the inner plexiform layer, suggesting a role of substance P and neurokinin 1 receptor in this developmental phase. However, in neurokinin 1 receptor knockout retinas, besides a significant increase of the gamma preprotachykinin A mRNA levels, no major changes were detected: neurokinin 3 receptor mRNA levels as well as substance P and neurokinin 3 receptor immunostainings were similar to wild types. Together with previous studies, these observations indicate that there are major differences in neurokinin 1 receptor expression patterns among developing mammalian retinas. The observations in neurokinin 1 receptor knockout mice may not be applicable to rats or rabbits, and substance P and neurokinin 1 receptor may play different developmental roles in different species.

Neuropeptides and retinal development.

Different peptidergic systems have been investigated with some detail during retinal development, including substance P (SP), vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase activating polypeptide (PACAP) and somatostatin (SRIF). Concerning possible developmental actions of neuropeptides, VIP and PACAP exert protective and growth-promoting actions that may sustain retinal neurons during their development. In addition, the presence of transient SRIF expressing cells and recent observations in SRIF receptor knock out mice indicate variegated roles of this peptide in the development of the retina and of retinofugal projections. Finally, recent studies have shown that, in the developing rabbit retina, changes in the expression pattern of SP receptors are accompanied by modifications of SP physiological effects, indicating that retinal circuits where SP is involved are likely to function in a substantially different manner before the retina becomes involved in the processing of visual stimuli. SP neurotransmission in the immature retina may subserve developmental events, and SP is likely to represent an important developmental factor for the maturation of retinal neurons and circuitries.

Functional aspects of the somatostatinergic system in the retina and the potential therapeutic role of somatostatin in retinal disease.

The somatostatinergic system of the retina has been investigated in a variety of studies. A considerable amount of experimental evidence is available concerning the patterns of expression of somatostatin (SRIF) and its receptors in vertebrate retinas. However the functional roles of this peptidergic system in retinal physiology are far from being elucidated. Nonetheless, data have been provided concerning the regulatory action of SRIF on the excitability of different retinal cell types and on the modulation of ion channels in different vertebrate retinas. The present review is focused on recent and unpublished investigations of the mouse retina relative to the involvement of specific SRIF receptors in the regulation of ion channels and transmitter release, the transduction pathways coupled to SRIF receptors, and the mechanisms regulating the expression of SRIF and its receptors as derived from studies in transgenic animal models. In these models, altered expression levels of SRIF or of specific SRIF receptors have also been found to affect the morphology of retinal cell types (namely the rod bipolar cells) and to result in functional alterations at the level of both ion channel regulation and transmitter release. These new pieces of evidence constitute an important step forward in the understanding of the functional actions of the retinal somatostatinergic system, although our current knowledge is far from being exhaustive. The ultimate goal of understanding SRIF functional actions in the retina is concerned with the possibility of using SRIF or its analogs as therapeutic agents to cure retinal diseases. Indeed, encouraging results are being obtained in clinical investigations focused on the use of SRIF analogs to treat diabetic retinopathy, a retinal disease with high social impact and originating as a complication of diabetes. The closing part of the present paper examines the evidence supporting SRIF as a promising therapeutic agent in this disease.

Energetics of midvelocity emissions in peripheral heavy ion collisions at Fermi energies.

Peripheral and semiperipheral collisions have been studied in the system 93Nb+93Nb at 38A MeV. The evaporative and midvelocity components of the light charged particle and intermediate mass fragment emissions have been carefully disentangled. In this way it was possible to obtain the average amount not only of charge and mass, but also of energy, pertaining to the midvelocity emission, as a function of an impact parameter estimator. This emission has a very important role in the overall balance of the reaction, as it accounts for a large fraction of the emitted mass and for more than half of the dissipated energy. As such, it may give precious clues on the microscopic mechanism of energy transport from the interaction zone toward the target and projectile remnants.

Expression of the neurokinin 1 receptor in the mouse retina.

Previous studies have revealed that the expression pattern of the neurokinin 1 receptor (the preferred receptor for substance P, SP) varies in different mammalian retinas. We investigated NK1 receptor expression in the mouse retina to provide background information for future studies in transgenic mice on SP functional roles in the retina. Mouse retinal sections were treated for single and double-label immunofluorescence. NK1 receptor immunoreactivity was in bipolar cells and in numerous amacrine cells. Double-label studies showed that NK1 receptor-expressing bipolar cells constituted a population of ON-type cone bipolar cells, since they were distinct from rod bipolar cells and contained glycine. They were nonrandomly distributed with highest density in central retina. These cells were similar and may correspond to the population of NK1 receptor-expressing bipolar cells of the rabbit retina. Different subsets of NK1 receptor-expressing amacrine cells were identified on the basis of the expression of selected neurotransmitter substances: i) about 23% of NK1 receptor-expressing amacrine cells also contained glycine; ii) the remaining 77% were likely to be GABAergic, although some inconsistency was observed in the GABA immunostaining obtained with two different GABA antibodies; iii) all dopaminergic amacrine cells also expressed NK1 receptors; iv) about one third of SP-containing amacrine cells also expressed NK1 receptors. These findings confirm and expand previous observations in rat and rabbit retinas. In particular, common to all three species is the expression of NK1 receptors in dopaminergic amacrine cells, indicating that SP neurotransmission may be a universal feature of the circuitry of the dopaminergic amacrine cell. Peculiar to the mouse retina is the presence of putative NK1 autoreceptors expressed by SP-containing amacrine cells.

Neurokinin 1 receptor expression and substance P physiological actions are developmentally regulated in the rabbit retina.

We investigated the expression of the substance P (SP) receptor (the neurokinin 1 receptor, NK1 receptor) and SP functional effects in developing rabbit retinas. NK1 receptors in adult retinas were in a population of cone bipolar cells and in dopaminergic amacrine cells, as previously described. In contrast, at birth and at postnatal day (PND) 6, NK1 receptors were exclusively expressed by cholinergic amacrine and displaced amacrine cells. NK1 receptor expression in cholinergic cells was still observed at PND10 (eye opening), while at PND21 it was confined to cholinergic cells of the inner nuclear layer. Starting at PND10, NK1 receptors were also in bipolar cells and in dopaminergic amacrine cells. A fully mature NK1 receptor expression pattern was observed at PND35. Dopamine release was assessed in isolated retinas in the presence of SP, the NK1 receptor agonist GR73632 or the NK1 receptor antagonist GR82334. At PND35, extracellular dopamine was significantly increased by 10 microM SP or 0.01-100 microM GR73632, and it was decreased by 0.01-10 microM GR82334. No effects were detected in developing retinas up to PND21. Ca2+ imaging experiments were performed in single cholinergic cells identified by their "starburst" morphology in perinatal retinas. Intracellular Ca2+ levels were significantly increased by 1 microM SP or GR73632. This effect was reversibly inhibited by 1 microM GR82334. These data demonstrate that both NK1 receptor expression and SP physiological actions are developmentally regulated in the retina. SP neurotransmission in the immature retina may subserve developmental events, and SP is likely to represent an important developmental factor for the maturation of retinal neurons and circuitries.

Expression of neuropeptides and their receptors in the developing retina of mammals.

The present review examines various aspects of the developmental expression of neuropeptides and of their receptors in mammalian retinas, emphasizing their possible roles in retinal maturation. Different peptidergic systems have been investigated with some detail during retinal development, including substance P (SP), somatostatin (SRIF), vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), neuropeptide Y (NPY), opioid peptides and corticotrophin-releasing factor (CRF). Overall, the developmental expression of most peptides is characterized by early appearance, transient features and achievement of the mature pattern at the time of eye opening. Concerning possible developmental actions of neuropeptides, recent studies imply a role of SP in the modulation of cholinergic neurotransmission in early postnatal rabbit retinas, when cholinergic cells participate in the retinal spontaneous waves of activity. In addition, the presence of transient SRIF expressing ganglion cells and recent observations in SRIF receptor knock-out mice indicate variegated roles of this peptide in the development of the retina and of retinofugal projections. Furthermore, VIP and PACAP exert protective and growth-promoting actions that may sustain retinal neurons during their development, and opioid peptides may control cell proliferation in the developing retina. Finally, a peak in the expression of certain peptides, including VIP, NPY and CRF, is present around the time of eye opening, when the retina begins the analysis of structured visual information, suggesting important roles of these peptides during this delicate phase of retinal development. In summary, although the physiological actions of peptides during retinal development are far from being clarified, the data reviewed herein indicate promising perspectives in this field of study.

Expression of the neurokinin 1 receptor in the rabbit retina.

Substance P is the preferred ligand for the neurokinin 1 (NK1) receptor. In vertebrate retinas, substance P is expressed by amacrine, interplexiform and ganglion cells. Substance P influences the activity of amacrine and ganglion cells and it is reported to evoke dopamine release. We investigated NK1 receptor expression in the rabbit retina using affinity-purified NK1 receptor antibodies. NK1 receptors were expressed by two distinct populations of retinal neurons. One is a population of ON-type bipolar cells characterized by axonal arborizations that ramified in the inner plexiform layer near the ganglion cell layer. Double-label studies showed that NK1 receptor-expressing bipolar cells were distinct from rod bipolar cells and from other immunocytochemically identified types of cone bipolar cells. Their density was about 2250 cells/mm2 in the visual streak and 1115 cells/mm2 in ventral mid-periphery. They were distributed in a non-random pattern. In the outer plexiform layer, the dendrites of these bipolar cells converged into heavily immunostained clusters having a punctate appearance. The density of these clusters in mid-peripheral ventral regions (about 13000 clusters/mm2) was similar to the reported cone density [Famiglietti and Sharpe (1995) Vis. Neurosci. 12, 1151-1175], suggesting these dendrites contact all cone photoreceptors. The second NK1 receptor expressing cell population corresponds to the tyrosine hydroxylase-containing amacrine cell population. NK1 receptor immunostaining was localized to the cell body and processes, but not to the processes that form the 'rings' that are known to encircle somata of AII amacrine cells. These findings show that NK1 receptor immunoreactivity is localized to a population of ON-type cone bipolar cells and to dopaminergic amacrine cells, suggesting that substance P acting on NK1 receptors influences multiple retinal circuits in the rabbit retina.

Intermediate mass fragment emission pattern in peripheral heavy-ion collisions at Fermi energies.

The emission pattern in the v(perp)-v(par) plane of intermediate mass fragments with Z = 3--7 (IMF) has been studied in the collision 116Sn+ 93Nb at 29.5A MeV as a function of the total kinetic energy loss of the reaction. This pattern shows that for peripheral reactions most IMF's are emitted at velocities intermediate between those of the projectile- and target-like products. Coulomb trajectory calculations show that these IMF's are produced in the interaction zone in a short time interval at the end of the target-projectile interaction.

Papillomavirus capsid protein expression in Escherichia coli: purification and assembly of HPV11 and HPV16 L1.

The L1 major capsid proteins of human papillomavirus (HPV) types 11 and 16 were purified and analyzed for structural integrity and in vitro self-assembly. Proteins were expressed in Escherichia coli as glutathione-S-transferase-L1 (GST-L1) fusions and purified to near homogeneity as pentamers (equivalent to viral capsomeres), after thrombin cleavage from the GST moiety and removal of tightly associated GroEL protein. Sequences at the amino and carboxy termini contributing to formation of L1 pentamers and to in vitro capsid assembly were identified by deletion analysis. For both HPV11 and HPV16 L1, up to at least ten residues could be deleted from the amino terminus (Delta N10) and 30 residues from the carboxy terminus (Delta C30) without affecting pentamer formation. The HPV16 pentamers assembled into relatively regular, 72-pentamer shells ("virus-like particles" or VLPs) at low pH, with the exception of HPV16 L1 Delta N10, which assembled into a 12-pentamer, T=1 capsid (small VLP) under all conditions tested. The production of large quantities of assembly-competent L1, using the expression and purification protocol described here, has been useful for crystallographic analysis, and will be valuable for studies of virus-receptor interactions and potentially for vaccine design.