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A Poletti

Publications and source records attributed to A Poletti.

At least 55 records · Page 3Linked to original sources
PubMed1993

Identification of a hormone-dependent phosphorylation site adjacent to the DNA-binding domain of the chicken progesterone receptor.

We have previously identified three phosphorylation sites in chicken progesterone receptor (PR) isolated from the cytosol of chicken oviducts. Several lines of evidence suggested that there might be additional phosphorylations that occur only in the nuclear compartment. We have reexamined the phosphorylation of the PR using whole cell extracts and have identified a second hormone-dependent phosphorylation site (Ser367) which is located on the amino-terminal side of the DNA-binding domain. This site also contains a Ser-Pro consensus sequence, as do the three previously reported sites. There are four Ser-Pro sequences in chicken PR, and all four are phosphorylated. Two of the sites showed substantial phosphorylation in the absence of hormone, with some enhancement in response to hormone, whereas two of the sites showed very little phosphorylation in the absence of hormone. This suggests either that despite the Ser-Pro consensus sequences, the sites are phosphorylated by different enzymes, or that binding hormone changes the conformation of the protein sufficiently to expose the two hormone-dependent phosphorylation sites.

Amino Acid Sequence↗
PubMed1993

Cardiac fibroma and heart transplantation.

Successful orthotopic heart transplantation was performed in a 38-day-old child with a fetal echocardiographic diagnosis of a left ventricular mass and in a 40-year-old woman with cardiac murmur since childhood and an echocardiographic diagnosis of asymmetric septal hypertrophy. Pathologic examination of the removed hearts, consisting of gross, histologic, immunohistochemical, and ultrastructural studies, led to the final diagnosis of cardiac fibroma. Both patients were alive and in good condition at 35 and 28 months, respectively, after operation.

Adult↗
PubMed1992

A novel, highly regulated, rapidly inducible system for the expression of chicken progesterone receptor, cPRA, in Saccharomyces cerevisiae.

A rapidly inducible and tightly regulated system for the expression of protein in yeast is based on a chimeric promoter constructed of two copies of a vitellogenin-estrogen-response element (ERE) which are inserted upstream from the promoter of the yeast gene encoding iso-1-cytochrome c. The chimeric promoter was inserted in a yeast expression plasmid upstream from the coding sequence of ubiquitin fused in frame to a cDNA encoding the full-length chicken progesterone receptor A (cPRA). The resultant plasmid (YEpA2) was co-transformed in Saccharomyces cerevisiae with a plasmid which encodes the human estrogen receptor. Estradiol (E2)-induced transactivation of the chimeric promoter results in transcription of the cPRA gene from YEpA2, and synthesis of cPRA. The fusion protein, ubiquitin-cPRA, is rapidly cleaved in vivo to produce cPRA. Analysis of samples by Western immunoblot shows that cPRA is almost undetectable in the absence of E2, and that treatment with 50 nM E2 results in a 500-1000-fold induction of cPRA (0.06-0.3% of the total protein) after 1 h. The plasmid-expressed soluble receptor is stable and demonstrates the correct affinity for its ligand. We have prepared yeast extracts using enzymatic digestion of the cell wall with oxalyticase followed by hypotonic shock. This has resulted in a dramatic increase in the % of receptor which binds hormone compared to previous studies which used mechanical disruption techniques. The cPRA is biologically active since it activates transcription of a co-transformed reporter gene containing its response element.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Fine-needle aspiration cytology of malignant nerve sheath tumors.

Precise preoperative diagnosis of three malignant nerve sheath tumors (MNST) was based on their remarkably uniform and highly characteristic cytologic appearance. The differential diagnosis with benign nerve sheath tumors and other spindle cell sarcomas is addressed, and the possibility of achieving confident diagnosis on cytologic material from at least some soft-tissue sarcomas is confirmed.

Aged↗
PubMed1992

Simultaneous visualization of immunodetected antigens and tissue components revealed by non-enzymatic histochemical stains.

We explored the possibility of simultaneous application of histochemical and immunohistochemical staining techniques on the same paraffin-embedded human tissue section. Conventional histological stains (PAS, Alcian, Alcian-PAS, Van Gieson, Gomori silver impregnation, and Giemsa) were used in association with a battery of markers (keratins, leucocyte common antigen, S-100 protein, Factor VIII-related antigen) that are widely employed in diagnostic and experimental studies. We found that the best procedure was to perform immunostaining before the histochemical reaction, as this enables all the other possible combinations to be carried out. In addition, several detection systems, such as peroxidase-anti-peroxidase (PAP), alkaline phosphatase-anti-alkaline phosphatase (APAAP), and avidin-biotin complex (ABC), were tested and all gave consistent results. Some minor modifications of the histological staining methods were necessary, but the current immunohistochemical techniques could be used as established. Preliminary findings indicate that immunohistochemistry can be combined with histochemistry techniques by means of a relatively simple procedure whose only disadvantage is the time required to carry out the double staining.

Alkaline Phosphatase↗
PubMed1992

[Perception threshold of angina and transient myocardial ischemia in ambulatory electrocardiography].

AIM OF THE STUDY: We studied the predictive value of prolonged angina perception threshold in identifying patients with stable coronary artery disease at risk of silent myocardial ischemia during daily life. METHODS AND RESULTS: 71 patients with documented coronary artery disease (previous myocardial infarction or stenotic lesion > 60% at angiography) underwent a symptom-limited exercise test and out-of-hospital Holter monitoring after drug withdrawal. A second exercise test was performed before disconnecting the dynamic EKG in order to validate the ST-depression recorded during ambulatory monitoring. 23 patients (32.4%) (Group A) had angina perception threshold > 60 sec after onset of ischemia (ST > 1 mm), while in 48 (67.7%) the delay in the perception of angina was shorter than 60 sec (Group B). The demographic, clinical and angiographic variables did not influence the angina perception threshold; however, this parameter was the most powerful predictor of ambulatory ischemia among the two groups (4.8 vs 2.8 p < 0.02), and in particular of the painless episodes (3.8 vs 1.8 p < 0.002). Moreover, the silent ischemic time was longer in patients of group A (4362 vs 1774 sec p < 0.017). Finally, the event-free survival was similar in the two groups of patients during the 2 years of follow-up (cardiac death 1 vs 3, nonfatal myocardial infarction 1 vs 1, aorto-coronary bypass 2 vs 7, PTCA 2 vs 2, unstable angina 0 vs 2), total events 6 vs 15 p = ns. CONCLUSIONS: These results demonstrate that the patients at risk for silent ischemia during ambulatory monitoring may be identified simply by evaluating their angina perception threshold during exercise test; however, silent ischemia does not have an adverse prognostic value.

Aged↗
PubMed1991

Testosterone metabolism in brain cells and membranes.

The central nervous system (CNS) is considered a target structure for the action of all the classes of hormonal steroids produced by the organism. Well-characterized genomic and less well-understood membrane mechanisms of action are probably involved in the steroid modulation of brain activities. Moreover, some classes of steroids need to be converted into "active" metabolites before interacting with their effector systems. In particular, testosterone (T) exerts many of its effects after conversion to 5 alpha-dihydrotestosterone (DHT) and estrogens. The CNS possesses both the 5 alpha-reductase, the enzyme which produces DHT and the aromatase which transforms T into estrogens; however, the relative role and distribution of these enzymes in the various structural components of the CNS has not been clarified so far. The 5 alpha-reductase has been found to be present in high concentrations in brain white matter structures because these are particularly rich in myelin membranes, to which the enzymatic activity appears to be associated. This membrane localization might suggest a possible involvement of steroidal 5 alpha-reduced metabolites in membrane-mediated events in the CNS. Moreover, the distribution of 5 alpha-reductase was studied in neurons, astrocytes and oligodendrocytes isolated from the brain of male rats by density gradient ultracentrifugation, as well as in neurons and glial cells grown in culture. The aromatase activity was also evaluated in neurons and glial cells grown in culture and in isolated oligodendrocytes. Among the three cell types isolated, neurons appear to be more active than oligodendrocytes and astrocytes, respectively, in converting T into DHT. Also, in cell culture experiments, neurons are more active in forming DHT than glial cells. Only neurons possess aromatase activity, while glial cells are apparently unable to aromatize T.

Animals↗
PubMed1991

Effects of hydrostatic pressure on sensory discharge in frog semicircular canals.

The effects of endolymphatic and perilymphatic pressure changes on resting and mechanically evoked responses were studied in isolated posterior semicircular canals of the frog. The results demonstrated that ampullar receptors are extremely sensitive to hydrostatic pressure changes (0.25 mm H2O were sufficient to produce distinct changes), being inhibited by endolymphatic pressure increases and facilitated by perilymphatic ones. Intracellular recordings from single afferent axons showed that the effects of hydrostatic pressure result from a modified transmitter release from the synaptic pole of the hair cells. Unlike resting activity, mechanically evoked activity was always depressed in the presence of a hydrostatic pressure. This indicates that the sensitivity of ampullar receptors to mechanical stimuli, i.e. the gain of the conversion process, is maximal when no pressure is present between the inner and the outer fluid. The possible action of hydrostatic pressure on vestibular receptors is discussed.

Afferent Pathways↗
PubMed1990

5 alpha-reductase activity in isolated and cultured neuronal and glial cells of the rat.

The distribution of the 5 alpha-reductase, the enzyme which converts testosterone into its 'active' metabolite dihydrotestosterone (DHT), has been studied in neurons, astrocytes and oligodendrocytes isolated from the brain of male rats by density gradient ultracentrifugation and in neurons and glial cells grown in cultures. Purity of cellular preparations was examined by electron and light microscopy. Purified neurons, astrocytes and oligodendrocytes, obtained from the brain of adult male rats, are all able to form DHT from testosterone and consequently possess a 5 alpha-reductase activity. Among the 3 cell types studied, neurons appear to be more active than oligodendrocytes and astrocytes. Moreover, between the two population of glial cells, the oligodendrocytes seem to possess a slightly higher enzymatic activity than that present in the astrocytes. Neurons appeared more active in metabolizing testosterone than glial cells also in cell culture experiments. It is presently believed that the 5 alpha-reduction of testosterone to DHT provides one of the mechanisms through which the hormone becomes effective in the CNS. This is supported by the present findings, which indicate that neurons are the cell population in which the 5 alpha-reductase is more concentrated. However, the presence of a considerable 5 alpha-reductase activity in glial cells indicates that also non-neuronal cells might participate in androgen-mediated events occurring in the brain.

Animals↗
PubMed1990

Kinetic properties of the 5 alpha-reductase of testosterone in the purified myelin, in the subcortical white matter and in the cerebral cortex of the male rat brain.

The 5 alpha-reductase, the enzyme which converts testosterone into dihydrotestosterone (DHT), is present in several CNS structures of the rat. Recent reports from this laboratory indicate that the subcortical white matter and the myelin possess a 5 alpha-reductase activity several times higher than that present in the cerebral cortex. Moreover, previous ontogenetic observations indicate that in all cerebral tissues examined (including the myelin) the 5 alpha-reductase has a higher activity in immature animals. This study was performed in order to verify whether the differences in the 5 alpha-reductase activity on the various brain components might be due to the presence of different concentrations of the same enzyme or to different isoenzymes. To this purpose, the kinetic properties Km and Vmax were measured in the purified myelin as well as in homogenates of the subcortical white matter and of the cerebral cortex, obtained from the brain of adult (60-90-day-old), immature (23-day-old), and aged (greater than 20-month-old) male rats. The results indicate that the enzymes present in the myelin, in the subcortical white matter and in the cerebral cortex of adult male rats possess a very similar apparent Km (1.93 +/- 0.2, 2.72 +/- 0.73 and 3.83 +/- 0.49 microM respectively). On the contrary, the Vmax values obtained in the myelin (34.40 +/- 5.54), in the white matter (19.57 +/- 2.36) and in the cerebral cortex (6.47 +/- 1.03 ng/h/mg protein) of adult animals have been found to be consistently different. Very similar Km values were found in the myelin obtained from the brain of immature and very old rats (2.14 +/- 0.11 and 3.39 +/- 0.75 microM respectively). The Vmax measured in the myelin purified from the immature rat brain (62.25 +/- 4.52) showed a value which was much higher than that found in the myelin of adult animals (34.40 +/- 5.54); a Vmax (34.31 +/- 9.41) almost identical to that of adult animals was found in the myelin prepared from the brain of aged rats.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1990

Testosterone metabolism in peripheral nerves: presence of the 5 alpha-reductase-3 alpha-hydroxysteroid-dehydrogenase enzymatic system in the sciatic nerve of adult and aged rats.

Previous reports from this laboratory indicate that the 5 alpha-reductase, the enzyme which converts testosterone into its "active" metabolite 5 alpha-androstan-17 beta-ol-3-one (dihydrotestosterone, DHT) is highly concentrated in the white matter structures of the CNS, which are mainly composed of myelinated fibers. No studies have been performed up to now, in order to evaluate the possible presence of the 5 alpha-reductase activity in peripheral myelinated nerves. To this purpose the 5 alpha-reductase activity has been evaluated in the sciatic nerve of the rat and compared to that present in the cerebral cortex and in the subcortical white matter, a central structure mainly composed of myelinated fibers. The study has been performed in normal adult male rats (60-90-day-old) and in aged (20-month-old) animals. The data obtained in 60-90-day-old animals indicate the presence of an active metabolism of testosterone at the level of the sciatic nerve. In this structure, testosterone is actively transformed into DHT and 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol); in the sciatic nerve, the formation of DHT is equal to that found in the subcortical white matter and higher than that found in the cerebral cortex. Moreover, at variance with what happens in CNS structures, where 3 alpha-diol is produced only in small amounts, in the sciatic nerve this metabolite is produced in amounts similar to those of DHT. The study in aged rats has shown that in the sciatic nerve, the formation of DHT and particularly that of 3 alpha-diol are much lower than in younger animals. No age-related variations in the 5 alpha-reductase activity in the cerebral cortex and in the subcortical white matter have been observed.

3-Hydroxysteroid Dehydrogenases↗
PubMed1989

Intermediate lymphocytic lymphoma encompassing diffuse and mantle zone pattern variants. A distinct entity among low-grade lymphomas?

Intermediate lymphocytic lymphoma has been operationally included among low-grade lymphomas, but few clinical data appeared to support definitely such an inclusion. The clinicopathologic features of 13 out of 14 cases of intermediate lymphocytic lymphoma either encompassing diffuse or mantle-zone pattern variants (ILL or MZL, respectively), diagnosed by conventional histology according to established criteria, are reported. Frozen section immunophenotypic analysis was also performed in 10 cases and enzyme studies were done in five. The 14 cases formed 6.9% of 203 non-Hodgkin's lymphomas (NHL) histologically diagnosed over a 2-year period. Among the 13 cases studied, there were nine males (five with ILL and four with MZL) and four females (one with ILL and three with MZL). Median age was 59 years. Splenomegaly (46%), high stage diseases (100%), involvement of bone marrow (92%) and peripheral blood (38%), and diffusion to and/or involvement of extranodal sites (38%), all were common findings at presentation. The 34 low-grade NHL of the total series classified according to the Working Formulation did not significantly differ from the ILL/MZL group in terms of frequency of involvement of bone marrow (69%) and peripheral blood (56%) as well as diffusion to and/or involvement of extranodal sites (26%). In ILL/MZL, therapy modalities were not uniform and the short follow-up time precluded firm conclusions on prognosis. Immunohistology demonstrated that ILL/MZL diagnosed by adequate morphologic criteria is a fairly homogeneous entity, also sharing most of its consistent immunological features with low-grade NHL. Thus, ILL/MZL is a relatively frequent and consistently recognizable clinical and pathological entity that may deserve a distinct place among NHL according to the Working Formulation. Proper clinical studies are needed to establish on a firmer basis the prognosis and optimal treatment of ILL/MZL.

Adenosine Triphosphatases↗
PubMed1989

Effect of postnatal starvation on the 5 alpha-reductase activity of the brain and of the isolated myelin membranes.

The 5 alpha-reductase, the enzyme which converts testosterone into its major "active" metabolite (dihydrotestosterone, DHT), has been found to be present in high concentration in brain structures particularly rich of myelin (white matter structures), as well as in myelin membranes. Previous ontogenetic observations seem to indicate that, during the process of myelinogenesis, the enzyme might be synthesized in the oligodendrocytes, and subsequently incorporated into the myelin membranes. It is well established that postnatal malnutrition produces a decreased formation of myelin, when starvation is performed from birth until to the 2nd or 3rd week of life; on the contrary food deprivation does not produce any significant effect on myelin accumulation when performed after the 14th day of life. The present experiments have been performed in the rat in order to study the effects of postnatal undernutrition (from birth to the 19th day of life: long malnutrition; and from the 14th to the 19th day of life: short malnutrition) on the 5 alpha-reductase activity present in the following brain structures: cerebral cortex, hypothalamus, corpus callosum, pyramidal tract, as well as in isolated myelin membranes. Undernourished animals have been killed at 20 days of age. Normally nourished animals served as controls. Long undernutrition induced a statistically significant decrease of the formation of DHT in the corpus callosum and in the pyramidal tract vs controls. On the contrary, the nutritional deficiency did not decrease the 5 alpha-reductase activity in the cerebral cortex and in the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1989

Extracellular matrix of lymphoid tissues in the chick.

We describe the immunohistochemical distribution of components of the extracellular matrix of the chick lymphoid system. In the thymus, basement membranes of epithelial cells bordering the lobules were intensely stained by laminin antibodies; fibronectin antibodies labeled the capsule and the septal matrix, and similar reactivity was seen with tropoelastin and gp 115 antibodies. No positivity was detected with any of the antibodies within the cortical parenchymal cells. Laminin was not detected in the medullary parenchyma, whereas fibronectin was present as coarse fibers. Tropoelastin and gp 115 appeared as a finer and more diffuse meshwork. In the bursa, laminin antibodies outlined the epithelial cells separating the cortex from the medulla. Fibronectin, tropoelastin, and gp 115 antibody stained the interfollicular septa and the cortical matrix, although to a different extent. Laminin was also detected in association with the interfollicular epithelium (IFE) basement membrane, whereas no staining was found underneath the follicle-associated epithelium (FAE). FAE cells not only lack a proper basement membrane but are also not separated from medullary lymphocytes by any of the other extracellular matrix components were investigated. Consequently, medullary lymphocytes are not sequestered, and can come easily into contact with antigens present in the intestinal lumen. All four antibodies stained the spleen capsule and spleen blood vessels, tropoelastin and gp 115 antibodies giving the strongest reactivity. A fine trabecular staining pattern was detected with gp 115 antibodies in the white pulp.

Animals↗