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L Simoncini

Publications and source records attributed to L Simoncini.

33 records · Page 2Linked to original sources
PubMed1998

The Cys607-->Tyr change in the UL97 phosphotransferase confers ganciclovir resistance to two human cytomegalovirus strains recovered from two immunocompromised patients.

Two ganciclovir (GCV)-resistant human cytomegalovirus (HCMV) strains recovered from an AIDS patient (strain VR4990) and a heart transplant recipient (strain VR5474) showed a Cys607-->Tyr change in the UL97-encoded phosphotransferase. No amino acid substitutions were observed in the viral DNA polymerase. Marker transfer experiments showed marked reduction in GCV phosphorylation and drug susceptibility of the recombinant HCMV strain VR4990rec2-1-1. These results further extend the region of the carboxy-terminal domain of the UL97 phosphotransferase involved in GCV substrate recognition.

AIDS-Related Opportunistic Infections↗
PubMed1997

Dissociation between word reading and word copying in a patient with left visual neglect.

A patient with left visual neglect following a right hemisphere infarction is described. When presented with isolated words and nonwords, she made left neglect errors in reading aloud, but not in direct copying. This finding suggests a distinction between two ways of processing orthographic stimuli: depending on the task, the unit of processing can be the letter string or the single letter. In reading, the letter string is treated as a whole while in copying it is processed element-by-element. Left neglect differentially affects the processing of single words: in reading errors involve the left, initial letters, while in copying they involve the single letters, or the left part of the letters, independently of their position within the stimulus.

Aged↗
PubMed1996

Human cytomegalovirus pp65 lower matrix phosphoprotein harbours two transplantable nuclear localization signals.

Human cytomegalovirus phosphoprotein pp65 is targeted to the cell nucleus immediately after infection. Deletion and point mutation analysis of the pp65 gene expressed in insect cells showed that two hydrophilic regions (HP1 and HP2) within the pp65 C-terminal 40% each harboured an independent nuclear localization signal (NLS); strong association to the nuclear stroma also requires the N-terminal domain. Either region, when fused to chloramphenicol acetyltransferase, localized the reporter protein to the nucleus in insect cells as well as in NIH 3T3 cells and human lung fibroblasts. In addition, HP1 was found to be the target of pp65 Ser/Thr phosphorylation in insect cells and a prokaryotically expressed HP1 was actively phosphorylated in vitro by casein kinase II, for which two site clusters map in HP1. These findings indicate that pp65 includes two NLSs, one of which has the potential to be modulated by phosphorylation.

3T3 Cells↗
PubMed1991

Dependence of Ca2+ and K+ current development on RNA and protein synthesis in muscle-lineage cells of the ascidian Boltenia villosa.

The early development of excitability of muscle-lineage cells of the ascidian Boltenia villosa is characterized by the appearance, just after gastrulation, of a Ca2+ current and a delayed outward K+ current, while an inwardly rectifying K+ current, present since fertilization, disappears. The muscle-lineage cells are the first cells in which we detect tissue-specific electrical properties after gastrulation. Here, we show that the development of electrical properties in these cells involves RNA and protein synthesis. If transcription or translation is blocked, the Ca2+ and outward K+ currents fail to appear, whereas the inward K+ current disappears normally. For the Ca2+ current, the sensitive period for transcription extends until just before gastrulation, while the sensitive period for translation extends until after gastrulation. The oocyte has a Ca2+ current present at about 5-10% the density of that in the muscle-lineage cells; this current disappears by gastrulation. A comparison of the oocyte and muscle Ca2+ currents indicates that they are similar in voltage dependence and inactivation mechanism. A small difference in permeability sequence can be attributed to different surface charge properties at the two stages of development.

Animals↗
PubMed1990

Changes in voltage-dependent currents and membrane area during maturation of starfish oocytes: species differences and similarities.

Full grown starfish oocytes are arrested at meiotic prophase I in the ovary. The natural hormone 1-methyladenine triggers oocyte maturation which involves meiosis reinitiation along with a variety of morphological, biochemical, and electrical changes. In studying oocytes of two species, Henricia leviuscula and Asterina miniata, using the voltage-clamp technique, we found interesting differences and similarities in the electrophysiological changes which occurred during maturation. Oocytes of both species have three major voltage-dependent currents: an inward Ca2+ current, an inwardly rectifying K+ current, and a transient outward K+ current (A-current). The Ca2+ current and the A-current were similar in the two species but the inward rectifier in Henricia had activation kinetics that were more than 10-fold slower than in Asterina. Nonetheless, all three currents were affected similarly during maturation: the inward Ca2+ currents remained constant in both species, while the two K+ currents decreased in amplitude. In Henricia the membrane surface area decreased substantially during maturation, while in Asterina it remained constant. This may be explained by the more highly infolded state of the membrane in the immature Henricia oocyte. The selective loss of K+ current followed the time course of the area decrease in Henricia, but the same percentage decrease in current occurred in Asterina without a net membrane loss.

Adenine↗
PubMed1988

Lineage-specific development of calcium currents during embryogenesis.

The development of electrophysiological properties of isolated, identified ascidian blastomeres was followed from the fertilized egg to the neurula, and the stage at which cells of different lineages first express different functional ion channel populations was determined. Little has been known about such events because of the difficulties of making voltage-clamp recordings from small embryonic cells and of identifying their developmental fates in dissociated preparations. The problem of small cell size was circumvented by using the whole-cell patch clamp, and identification was facilitated by the use of a species of ascidian, Boltenia villosa, in which endogenous pigment marks cells of specific developmental fates. Within approximately 3 hours after gastrulation, muscle-lineage blastomeres in these embryos developed a voltage-dependent calcium current while surrounding blastomeres of other lineages did not. At about the same time, all cells developed delayed outward potassium currents and lost the inwardly rectifying potassium currents present at earlier stages.

Animals↗
PubMed1988

Fertilization events induced by neurotransmitters after injection of mRNA in Xenopus eggs.

Fertilization initiates in the egg a dramatic increase in intracellular calcium that opens ion channels and causes exocytosis. To explore the possibility that these events might involve a receptor-mediated pathway, receptors for serotonin or acetylcholine (M1 muscarinic) were expressed in the Xenopus egg; serotonin or acetylcholine then could initiate a series of responses similar to those normally initiated by sperm. Thus, there may be an endogenous receptor in the egg membrane that is activated by sperm, and the serotonin or M1 muscarinic receptor may replace the sperm receptor in this pathway.

Animals↗
PubMed1988

Slow sodium channel inactivation in mammalian muscle: a possible role in regulating excitability.

Sodium currents were recorded in rat fast and slow twitch muscle fibers. Changes in the membrane potential around the resting potential produced slow changes in the sodium current amplitude due to alterations of the slow inactivation process that was increased by steady depolarization and removed by prolonged hyperpolarization. In contrast, classical fast inactivation was not operative around the resting potential, and depolarizations of greater than 20 mV were required to close half of the channels by fast inactivation. Because slow inactivation is operative around the resting potential of mammalian muscle fibers, it may partially explain why small depolarizations, such as those that occur in some patients with periodic paralysis, can reduce excitability.

Animals↗
PubMed1987

Slow sodium channel inactivation in rat fast-twitch muscle.

1. Voltage-clamp Na+ currents (INa) were measured in rat fast-twitch fibres using the loose-patch-clamp technique. Changes in the conditioning membrane potential produced slow changes in the peak INa elicited by short test depolarizations, due to a slow inactivation process. 2. Inactivation was increased by application of steady depolarizing potentials and was reversed by steady hyperpolarizations. These changes in peak INa could be well fitted by single-exponential functions with time constants in the range of 1-4 min. 3. The steady-state values of the maximum peak INa at any potential could be well fitted by a function identical to the one describing the fast inactivation process. This gave a potential of -108 mV at which 50% of the channels were closed due to slow inactivation. 4. The maximum peak current densities obtained with the slow inactivation fully removed were as large as 20 mA cm-2.

Animals↗
PubMed1987

Comparison between slow sodium channel inactivation in rat slow- and fast-twitch muscle.

1. Voltage-clamp Na+ currents (INa) were studied in rat soleus slow-twitch muscle fibres at about 18 degrees C using the loose-patch-clamp technique. The maximum inward current density was produced by depolarizations to about -19 mV. 2. Fast inactivation was studied utilizing 20 ms conditioning potentials. INa was reduced by 50% with conditioning potentials to about -70 mV. 3. Changes in the conditioning membrane potential produced slow changes in the peak INa due to a slow inactivation process. INa was reduced by 50% at about -86 mV due to slow inactivation. 4. The mean maximum inward INa when slow inactivation was fully removed was 6.83 mA cm-2. 5. Due to the slow inactivation process, slow-twitch fibres were less susceptible to reduction in INa than fast-twitch fibres.

Animals↗
PubMed1985

Acetylcholine-induced currents at plasma membrane of the frog oocyte.

Although with remarkable variability, membrane permeability in Rana oocytes can be modified by application of acetylcholine. The experiments were carried out in voltage-clamp conditions. Like in Xenopus, the responses proved to be related to activation of muscarinic receptors operating membrane channels probably selective for Cl-. At differences with Xenopus, the net acetylcholine-induced current showed remarkable deviation from linearity, displaying outward-going rectification. Application of acetylcholine typically produced opening of membrane channels, while in late spring, we observed the opposite effect in several batches of oocytes.

Acetylcholine↗
PubMed1984

Maturation involves suppression of voltage-gated currents in the frog oocyte.

Voltage- and time-dependent currents having slow kinetics have been studied in plasma membranes of immature oocytes of the european frog, Rana esculenta. IK, corresponding to an outward flow of K+, is activated at potentials more positive than about -40 mV, and subserves outward rectification; Iir, corresponding to an outward flow of Cl-, is activated at potentials more negative than about -80 mV and subserves inward rectification. Such currents can act as negative feedback mechanisms in the control of membrane potential in the immature oocyte and limit to a somewhat restricted range its possible deviations from resting values. Besides IK, membrane depolarizations to potentials more positive than about +30 mV are capable of activating INa, corresponding to outflow of Na+. By contrast, the frog mature egg-cell has a single voltage- and time-dependent current, IM, activated at potentials more positive than +30 mV, with properties similar to INa. The disappearance of IK and Iir along with remarkable reduction in leakage lowers impedance in the egg membrane. It seems reasonable to suggest that the observed changes in membrane permeability reflect changes which have taken place along the maturation process and are of importance for successful fertilization.

Animals↗
PubMedDate not supplied

Clinical evaluation of the effective use of magnetic fields in podology.

The use of magnetic fields in medicine has obtained encouraging results and it has stimulated the research conducted so that the use of this method of treatment may be better and more widespread. A double blind study was conducted to evaluate the effectiveness of the generation of magnetic fields on edema and on pain in patients submitted to surgery for bilateral hallux valgus.

Activities of Daily Living↗