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M Pellegrini

Publications and source records attributed to M Pellegrini.

At least 19 recordsLinked to original sources
PubMed1991

Use of conditioned distributions in the analysis of ion channel recordings.

A method to test the Markov nature of ion channel gating is proposed. It makes use of singly and doubly conditional distributions. The application of this method to recordings from single BK channels provides evidence that at least two states of the underlying kinetic scheme are left at a constant rate. Moreover, the probabilities, when leaving a state, of reaching another given state are shown to be constant for all the states of the system.

Animals↗
PubMed1991

The nucleotide sequence of a CpG island demonstrates the presence of the first exon of the gene encoding the human lysosomal membrane protein lamp2 and assigns the gene to Xq24.

An EagI-EcoRI clone of human genomic DNA, p2-7, mapped to Xq24 has been sequenced. This analysis has confirmed the presence of a CpG island and has identified the first exon of the human LAMP2 gene, encoding a glycoprotein of the lysosomal membrane. Since the p2-7 clone corresponds to single-copy DNA, we can assign the human LAMP2 gene to Xq24.

Amino Acid Sequence↗
PubMed1990

Ribosome subunit to polysome ratios affect the synthesis of rRNA in Drosophila cells.

Many investigations have revealed that ribosome numbers increase in parallel with the growth rate of cells. Here we show that the absolute level of protein synthesis may not be the only factor influencing rRNA synthesis in a nondividing eukaryotic cell. Under conditions of complete (greater than 99%) inhibition of protein synthesis by four different antibiotics, there is a corresponding inhibition of rRNA synthesis. At lower levels of inhibition of protein synthesis (70%), a different effect of individual antibiotics on rRNA synthesis is observed. Cycloheximide and anisomycin, which cause a decrease in the free subunit pool due to a buildup of polysomes, stimulate rRNA synthesis, whereas puromycin and pactamycin, which cause an increase in the free subunit pool, cause a decrease in rRNA synthesis. These effects on rRNA synthesis are not solely due to a low level of completed proteins. Pactamycin treatment allows completed proteins to be made yet lowers rRNA labeling, while anisomycin treatment does not show synthesis of complete proteins yet increases rRNA labeling. The result suggest that eukaryotic cells may regulate ribosome synthesis in response to the number of free versus translating (polysomal) ribosomes as do Escherichia coli cells.

Animals↗
PubMed1990

Stretch-activated cation channels with large unitary conductance in leech central neurons.

Stretch-activated cation channels were identified in the soma membrane of leech central neurons. These channels were almost silent under normal experimental conditions and were distinctly activated by application of negative pressure to the patch pipette. The channels exhibited a preferential selectivity for K+ and a slope conductance of about 200 pS, in symmetrical K+ solution. In cell-attached patches these cation channels were activated by cell swelling.

Animals↗
PubMed1990

Axotomy affects density but not properties of potassium leak channels, in the leech AP neurons.

Leech AP neurons react to axotomy by increasing excitability and resting potential of the cell body membrane. In a previous report we described single potassium channels contributing to the leak conductance in the soma membrane of AP cells. Here we compare both properties and density of single potassium leak channels in cell-free patches from normal and axotomized AP neurons. We show that properties such as single channel conductance, outward rectification, time constants of open and shut interval distributions and absence of inactivation do not significantly differ between normal and axotomized cells. On the other hand, we find that the number of channels per patch progressively increases with time after axotomy. We conclude that changes in density rather than alterations in properties of single channels can account for the increase in the resting potential, observed after axotomy.

Animals↗
PubMed1989

Two types of K+ channels in excised patches of somatic membrane of the leech AP neuron.

The patch-clamp technique has been applied to the somatic membrane of the leech AP neurons. Ionic currents from single potassium channels were recorded in inside-out configuration. Two types of channels, sharing close values of conductance in symmetrical K+, were identified as distinct, according to their properties of rectification, Ca2+ sensitivity and voltage dependence. The channels designated as VCI exhibited an outward rectification and their gating was quite independent on changes of patch potential and of [Ca2+]i. The channels designated as VCD showed a linear I-V relationship and their activity was dependent on both the membrane potential and the intracellular [Ca2+].

Animals↗
PubMed1989

[Clinical implications of the infiltration level of early gastric cancer].

Sixty-nine cases of early gastric cancer (EGC) were taken into consideration, out of a series of 585 operations for gastric cancer, carried out between January 1976 and June 1988. Differences between two groups (I: EGC limited to the mucosa; II: EGC with invasion of both the mucosa and submucosa) have been assessed with reference to familiarity for gastric cancer, previous gastric and duodenal pathology, symptoms, site of the lesion, histological features, lymph node metastatic involvement and results. Despite some pathological and clinical differences, modification of current surgical treatment with endoscopic management is not justified by any features, even when dealing with intramucosal, intestinal type EGC, because of possible lymph node involvement or long-term recurrences.

Aged↗
PubMed1985

The induction of ribosome biosynthesis in a nonmitotic secretory tissue.

Many investigations of the biosynthesis of ribosomes have revealed that ribosome numbers increase with growth rate in a parallel fashion. However, we have now shown that there is also a need for active ribosome synthesis in a nonmitotic tissue which is induced to secrete. The paragonial glands of Drosophila melanogaster produce and secrete proteins that are found in the seminal fluid. Following even a single copulation event these glands are substantially reduced in size, but rapidly refill, synthesizing new secretion proteins (Chen, P.S. 1980) in Invertebrate Systems in Vitro (Kurstak, E., Maramorosch, K., and Dubendorfer, A., eds) pp. 303-313, Elsevier, Amsterdam) Anticipating that paragonial gland cells might require more ribosomes to accomplish this burst of protein synthesis, we injected 10-day-old adult male flies with either [32P] phosphate or [35S]methionine, allowed them to copulate (40 +/- 20 min after injection), and then measured the amounts of rRNA and ribosomal protein synthesis taking place with time. There is clearly a burst of ribosome synthesis starting as early as 30 min after copulation and declining after 6 h. This is evidenced by the coordinate accumulation of labeled rRNAs and ribosomal proteins. However, further experiments showed that there is no concomitant rise in the accumulation of ribosomal protein mRNAs. This suggests that these mRNAs are underutilized in the paragonial glands before copulation and more actively translated after copulation. A stimulation of translation of ribosomal proteins is then well-coordinated with increased rRNA transcription, but an increase of ribosomal protein mRNAs is not coordinated with these events. Both the up- and down-regulation of ribosome biosynthesis need not be coupled to cell growth or a specific developmental schedule, but rather may be due to the need for secretory protein synthesis.

Animals↗
PubMed1979

Affinity labeling of a reactive sulfhydryl residue at the peptidyl transferase P site in Drosophila ribosomes.

An affinity label has been prepared that is specific for the P site of a eucaryotic peptidyl transferase, that of Drosophila melanogaster. It has the sequence C-A-C-C-A-(Ac[3H]Leu) with a mercury atom added at the C-5 position of all three cytosine residues (referred to as the mercurated fragment). This label is an analogue of the 3' terminus of N-acetylleucyl-tRNA. The mercurated fragment binds specifically to the P site of peptidyl transferase. It participates fully in peptide bond formation as judged by its ability to transfer N-acetylleucine to puromycin with at least the same efficiency as a nonmercurated fragment. Once bound to the P site, the mercurated fragment reacts covalently with a ribosomal protein(s). This affinity-labeling process can be effectively competed by nonmercurated fragment, which indicates a site-specific reaction. The covalent attachment of the affinity label to a ribosomal protein(s) occurs through the formation of a mercury-sulfur bond, as judged by its lability in the presence of thiol reducing agents. The major ribosomal protein labeled at the P site of D. melanogaster was found to be a small, basic protein. The electrophoretic behavior of this protein parallels that of major P site proteins found in Escherichia coli ribosomes and in other eucaryotes. These results suggest conservation of some of the overall properties of the P site proteins from these organisms.

Acyltransferases↗
PubMed1979

Ultrastructure of supraspinal dorsal root projections in the toad. II. The cerebellar granular layer.

Following section of the left dorsal roots, degenerating fibres and boutons were observed in the granular layer of the ipsilateral cerebellum. The degenerating terminals were identified as large en passant varicosities of mossy fibres contacting the dendrites of presumptive granule cells. They contained round synaptic vesicles and neurofilaments and established Gray type I contacts. The terminals initially underwent filamentous degeneration with neurofilamentous hypertrophy, swollen mitochondria and loss of synaptic vesicles. At later survival times (6--30 days) they acquired an electron-dense appearance due to an increase and clumping of the filamentous component. After injection of horseradish peroxidase into the left cerebellum, all ipsilateral spinal ganglia showed a few (2--3%) labelled cells, indicating that a primary afferent contribution to this pathway originated from each segment of the spinal cord.

Afferent Pathways↗
PubMed1978

Ultrastructure of supraspinal dorsal root projections in the toads. I. The obex region.

The ultrastructure of the dorsal column nucleus (DCN) has been investigated at the level of the obex region in normal and experimental toads. Large 'isolated' neurons (greater than 20 micrometer) and clusters of small neurons (less than 20 micrometer) have been identified in this region. Synaptic profiles have been classified into three types: large 'en passant' LR boutons, containing round synaptic vesicles and neurofilaments, small R boutons with round vesicles and F boutons with pleomorphic vesicles. The axon terminals exhibited synaptic contacts with cell somata, with dendrites of varying calibers and with other axons. The terminals involved in the axo-axonic contact were the F boutons which were presynaptic to the LR boutons, thus representing the morphological basis for presynaptic inhibition. Transection of the second dorsal root was performed in order to identify the terminals of the primary afferents to the DCN, after different survival periods (16 h--50 days). Only the LR boutons underwent degeneration, thus representing the central endings of the primary dorsal root afferents. The functional significance of these findings was discussed.

Animals↗
PubMed1978

The kinetics of plasma noradrenaline in normal and hypertensive subjects.

1. The kinetics of plasma noradrenaline have been determined in normal and essential hypertensive patients by intravenous injection of tritiated noradrenaline and serial mixed venous sampling. 2. The metabolic clearance rate of plasma noradrenaline in normal subjects was approximately 1 1 min-1 m-2, whereas in essential hypertensive patients it was significantly reduced to approximately 0.6 1 min-1 m-2. 3. Metabolic clearance rate was negatively correlated to mean arterial blood pressure and total peripheral resistances. 4. Particularly low values of metabolic clearance rate were found in two patients with congestive heart failure and one with phaeochromocytoma. 5. We propose that the access of plasma noradrenaline to the main removal mechanisms takes place in competition with the flow of unlabelled endogenous noradrenaline directly released by nerve endings. The slower removal of plasma noradrenaline in essential hypertension could then express a larger release of endogenous noradrenaline in this condition.

Adrenal Gland Neoplasms↗
PubMed1977

A method for gene enrichment based on the avidin-biotin interaction. Application to the Drosophila ribosomal RNA genes.

A method of enriching, from the total DNA of an organism, for long DNA strands carrying a particular gene is described. The purified RNA corresponding to the gene is covalently attached to biotin via a cytochrome c bridge. This modified RNA is hybridized to the total DNA. Those DNA strands which hybridize are separated from all the other DNA, using the avidin-biotin interaction, by one of two methods. Avidin is covalently attached to submicroscopic polymer spheres; the complexes of avidin spheres with the DNA: RNA-biotin hybrids band in CsCl at a much lower buoyant density than does free DNA. Alternatively, the DNA:RNA-biotin hybrids are isolated by affinity chromatography on an avidin-solid support column. These methods have been used to prepare long single strands of Drosophila ribosomal DNA (rDNA) in high yield and 42 to 80% pure.

Animals↗
PubMed1977

Identification of different size motoneurons labeled by the retrograde axonal transport of horseradish peroxidase.

Three main groups of motoneurons of different size have been labeled in adult cats by using the method for retrograde axonal transport following injection of horseradish peroxidase in the medial gastrocnemius and soleus muscles. In particular small, medium-size and large neurons which probably correspond respectively to gamma, small alpha and large alpha motoneurons innervating the calf muscles, have been identified and the corresponding area measured.

Animals↗
PubMed1977

Sequence arrangement of the rDNA of Drosophila melanogaster.

The sequence arrangement of genes coding for stable rRNA species and of the interspersed spacers on long single strands of rDNA purified from total chromosomal DNA of Drosophila melanogaster has been determined by a study of the structure of rRNA:DNA hybrids which were mounted for electron microscope observation by the gene 32-ethidium bromide technique. One repeat unit contains the following sequences in the order given. First, an 18 S gene of length 2.13 +/- 0.17 kb. Second, an internal transcribed spacer (Spl) of length 1.58 +/- 0.15 kb. A short sequence coding for the 5.8S and perhaps the 2S rRNA species is located within this spacer. Third, the 28S gene with a length of 4.36 +/- 0.23 kb. About 55% of the 28S genes are unbroken or continuous (C genes). However, about 45% of the 28S genes contain an insertion of an additional segment of DNA that is not complementary to rRNA (l genes). The insertion occurs at a reproducible point 2.99 +/- 0.26 kb from the junction with Spl. The insertions are heterogeneous in length and occur in three broad size classes: 1.42 +/- 0.47, 3.97 +/- 0.55, and 6.59 +/- 0.62 kb. Fourth, an external spacer between the 28S gene and the next 18S gene which is presumably mainly nontranscribed and which has a heterogeneous length distribution with a mean length and standard deviation of 5.67 +/- 1.92 kb. Short inverted repeat stems (100-400 nucleotide pairs) occur at the base of the insertion. It is known from other studies that I genes occur only on the X chromosome. The present study shows that the I and C genes on the X chromosomes are approximately randomly assorted. The sequence arrangement on the plasmid pDm103 containing one repeat of rDNA (Glover et al., 1975) has been determined by similar methods. The I gene on this plasmid contains an inverted repeat stem. The occurrence of inverted repeat sequences flanking the insertion supports the speculation that these sequences are translocatable elements similar to procaryotic translocons.

DNA↗