PubMed Health⌕ Search

Biomedical subjects

M Di Stefano

Publications and source records attributed to M Di Stefano.

At least 91 records · Page 5Linked to original sources
PubMed1995

Receptive field properties of areas 17-18 neurons in strabismic cats with the early section of the optic chiasm.

In cats raised with surgically induced esotropia and early section of the optic chiasm visually responsive neurons were recorded from areas 17-18 ipsilaterally and contralaterally to the deviated eye. In these animals both cortices were monocularly activated only through the ipsilateral eye. In addition, unlike to that occurring in otherwise intact strabismic animals, the esotropic eye drove a number of neurons equivalent to that driven by the non-deviated eye. We suggest that an inhibitory influence exterted over the ipsilateral afferents of the deviated eye is removed by the early section of the crossed retinal projections.

Animals↗
PubMed1994

The biological phenotype of HIV-1 is usually retained during and after sexual transmission.

The biological phenotype of HIV-1 isolates from 21 subjects with primary HIV-1 infection was determined in primary lymphocytes and monocyte-derived macrophages as well as in three T-cell lines (MT-2, HUT78, and C8166). Seven isolates (33%) replicated on at least one cell line and were classified as rapid/high (n = 6) or intermediate (n = 1), while 14 isolates (67%) did not replicate in cell lines and were classified as slow/low. All isolates replicated in primary monocyte-derived macrophage cultures. Studies on 10 pairs consisting of index case and seroconverting sexual partner showed that the biological phenotype of HIV-1 was unchanged in nine transmissions, including 5 pairs where a rapid/high virus was transmitted. Most individuals (5 of 6) infected by a rapid/high virus retained this phenotype after seroconversion. These individuals also had significantly lower CD4 lymphocyte counts 1-3 years after infection. Thus, in contrast to what has been suggested by others, we found that HIV-1 variants with rapid/high phenotype were usually not suppressed, neither during sexual transmission nor after seroconversion in the new host. These findings have important implications for the understanding of HIV-1 transmission and pathogenesis as well as for vaccine design.

Cell Line↗
PubMed1994

Metabolic markers for the early diagnosis of postmenopausal osteoporosis.

We performed a cross-sectional study in 147 women, 41 in premenopausal age and 106 in menopause for 1-5 years: bone mineral density (BMD) at the distal radius and annual bone loss (as shown by plasma alkaline phosphatase and osteocalcin levels, and by calcium/creatinine and hydroxyproline/creatinine in the second urine of the morning) were evaluated. A significant reduction of BMD with a significant increase of bone loss was observed with increasing duration of menopause. Furthermore, when the women were subdivided into two groups according to annual bone loss (over or under 1.7%), significant differences were found between bone mineral density in the second and third years of menopause. As this is a cross-sectional and not a longitudinal study, it confirms that, in the presence of a higher bone loss, the BMD levels are lower and consequently the theoretical definition of this parameter can allow useful information on the presumable behavior of BMD.

Adult↗
PubMed1994

Influence of cholesterol on phospholipid bilayers phase domains as detected by Laurdan fluorescence.

Coexisting gel and liquid-crystalline phospholipid phase domains can be observed in synthetic phospholipid vesicles during the transition from one phase to the other and, in vesicles of mixed phospholipids, at intermediate temperatures between the transitions of the different phospholipids. The presence of cholesterol perturbs the dynamic properties of both phases to such an extent as to prevent the detection of coexisting phases. 6-Lauroyl-2-dimethylaminopahthalene (Laurdan) fluorescence offers the unique advantage of well resolvable spectral parameters in the two phospholipid phases that can be used for the detection and quantitation of coexisting gel and liquid-crystalline domains. From Laurdan fluorescence excitation and emission spectra, the generalized polarization spectra and values were calculated. By the generalized polarization phospholipid phase domain coexistence can be detected, and each phase can be quantitated. In the same phospholipid vesicles where without cholesterol domain coexistence can be detected, above 15 mol% and, remarkably, at physiological cholesterol concentrations, > or = 30 mol%, no separate Laurdan fluorescence signals characteristic of distinct domains can be observed. Consequences of our results on the possible size and dynamics of phospholipid phase domains and their biological relevance are discussed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Cholesterol modifies water concentration and dynamics in phospholipid bilayers: a fluorescence study using Laurdan probe.

The effect of cholesterol on the gel, the liquid-crystalline, and mixed phospholipid phases has been studied using the fluorescence properties of 2-dimethylamino-6-lauroylnaphthalene (Laurdan). Laurdan sensitivity to the polarity and to the dynamics of its environment reveals that cholesterol affects phospholipid bilayers in the gel phase by expelling water and by increasing the amount of dipolar relaxation. In the liquid-crystalline phase, the effect of cholesterol is a reduction of both water concentration and amount of dipolar relaxation. Detailed studies of Laurdan excitation and emission spectral contours as a function of cholesterol concentration show that there are some cholesterol concentrations at which Laurdan spectral properties changes discontinuously. These peculiar cholesterol concentrations are in agreement with recent observations of other workers showing the formation of local order in the liquid-crystalline phase of phospholipids upon addition of phospholipid derivatives of pyrene. A local organization of phospholipids around cholesterol molecule seems to be produced by the presence of peculiar concentrations of cholesterol itself. This local organization is stable enough to be observed during the excited state lifetime of Laurdan of approximately 5-6 ns.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

HPV and HIV: HPV-DNA identification of colpocytologic smears in HIV positive females through "in situ" hybridization technique.

Test statistics show a progressive increase of AIDS cases which can be attributed to heterosexual intercourse. Cervicovaginal withdrawals were carried out on 18 HIV positive women for identification of HPV-DNA through "In Situ" hybridization with three probes 6-11 (A); 16-18 (B); 31-33-51 (C). 61% of patients tested positive at DNA Probe as follows: A = 27.27%; B = 18.18%; C = 72.72%. HIV could act as cofactor in increasing HPV manifestations. In future, the number of AIDS cases in Italy will depend on its prevalence among the sexually active population. Therefore, the most useful intervention, will be the prevention of transmission through heterosexual intercourse.

Adolescent↗
PubMed1994

Therapeutic prospects of natural alpha interferon from normal human leucocytes in the treatment of genital condylomata in HIV positive women.

Various Authors underline that HIV positive women have a higher CIN incidence and a higher prevalence of HPV. HIV could act as cofactor in the proliferation of HPV manifestation, because of a hypothetical deficit of local immunity. 5 HIV positive patients have been examined: 3 of them presenting vulvocondylomas and/or VIN were treated with 1.000.000 IU alpha IFNn three times a week for three weeks. 2 of them presenting CIN and/or HPV were treated with a two-phase therapy: A) Induction therapy: 3.000.000 IU 3 times a week for three cycles. B) Maintenance therapy: 1.000.000 IU 3 times a week for three months. IFN was the primary treatment for viral lesions, even though an improvement of prognostic indices (CD4, CD4/CDB, 2M), has shown its usefulness in association or in alternative to AZT.

Adolescent↗
PubMed1993

Amyloid beta protein does not interact with tachykinin receptors coupled to inositol phospholipid hydrolysis in human astrocytoma cells.

We have tested the interaction between amyloid beta protein (A beta P) and tachykinin receptors in cultured UC-11MG astrocytoma cells, which express high affinity substance P receptors and respond to substance P with an unusually large stimulation of polyphosphoinositide hydrolysis. Both the full-length A beta P (A beta P1-40) and the fragment 25-35 (A beta P25-35) did not affect the stimulation of [3H]inositolmonophosphate (InsP) formation by substance P. A beta P25-35 was also inactive when applied to the cultures 18 or 72 h prior to the assay. In addition, A beta P25-35 did not displace specifically bound [3H]SarMet substance P from its recognition sites in intact UC-11MG cells. These results suggest that, at least in this specific cell type, amyloid peptides do not interact with substance P receptors.

Amyloid beta-Peptides↗
PubMed1993

Treatment of pancreatic ascites with somatostatin.

Pancreatic ascites is a rare complication of chronic pancreatitis, whose treatment continues to represent a difficult clinical problem. In this report we describe a case of a patient with chronic pancreatitis and pancreatic ascites who was successfully treated with somatostatin given by continuous intravenous infusion of 1.5 micrograms/kg/h for 2 weeks.

Amylases↗
PubMed1993

Preliminary data on the establishment of permanent cell lines continuously producing HIV-1: factors affecting the transmissibility and adaptability of "wild" HIV-1 isolates.

This study examines some technical aspects of the transmission to and permanent adaptability in continuous cell lines of wild HIV-1 isolates. Three cell systems (the lymphocytic cell lines Molt-3 and H-9 and the monocytoid cell line U-937) and two transmission protocols (cell to cell and cell-free) were used. Two different replicative behaviours were observed among isolates efficiently transmitted: a) transmissibility but not adaptability (consisting in a limited length of viral replication); aa) transmissibility and adaptability (consisting in a stable and long term virus production). The second type of replication was confined to viruses from patients with severe immunodeficiency. Technical and viral factors can affect the rate of transmissibility and adaptability: the modality of infection (cell to cell transmission appeared to be the most efficient) and the tropism of the virus (some viruses could infect only one T cell line).

Adaptation, Physiological↗
PubMed1992

Membrane aging during cell growth ascertained by Laurdan generalized polarization.

The sensitivity of the fluorescent probe Laurdan to the phase state of lipids has been utilized to detect modifications in the composition and physical state of cell membranes during cell growth. In phospholipid vesicles, the Laurdan emission spectrum shows a 50-nm red shift by passing from the gel to the liquid-crystalline phase. The Generalized Polarization (GP) value has been used for the data treatment instead of the ratiometric method common in investigations utilizing other fluorescent probes that display spectral sensitivity to medium properties. The GP value can be measured easily and quickly and possesses all the properties of "classical" polarization, including the additivity rule. Once Laurdan limiting GP values have been established for the gel and the liquid-crystalline phase of lipids, the quantitative determination of coexisting phases in natural samples is possible. In the present work the observation of a relevant decrease in the fractional intensity of the liquid-crystalline phase in K562 cell membranes during 5 days of asynchronous growth is reported. A decrease in the "fluidity" of cell membranes in K562 cells kept in culture for several months is also reported. The procedure developed for labeling cell membranes with Laurdan is reported and the influence of cell metabolism on fluorescence parameters is discussed. Also discussed is the influence of cholesterol on Laurdan GP.

2-Naphthylamine↗
PubMed1992

Influence of anatomical factors and spatial compatibility on the stimulus-response relationship in the absence of the corpus callosum.

Simple and choice reaction times (RTs) to lateralized flashes of light were measured in two acallosal subjects, a callosotomized patient with sparing of the splenium, six IQ-matched controls and six controls with above average IQ. The aim of the study was to investigate the influence of stimulus-response factors on visuomotor integration in the absence of the corpus callosum. The results showed that simple-RTs are faster for all groups when sensory input and motor output are coordinated in the same hemisphere, regardless of the spatial relationship between stimulus (S) and response (R). The difference between ipsilateral and contralateral RTs, taken as a measure of interhemispheric transmission time (ITT), was more than three times longer in the patients lacking the corpus callosum than in the controls. In the choice-RT paradigm, the main determinant of the response speed was S-R spatial compatibility rather than the anatomical relationship between the neural structures receiving the visual input and those controlling the motor output. Spatially compatible S-R pairings were always faster than incompatible pairings. The compatibility effect was present in all subjects but it was significantly larger in the callosum-deprived patients and their IQ-matched controls with respect to the high-IQ controls. The latter finding suggests that cognitive factors may be involved in the production of the spatial compatibility effect.

Adult↗
PubMed1992

Developmental changes in the modulation of cyclic AMP formation by the metabotropic glutamate receptor agonist 1S,3R-aminocyclopentane-1,3-dicarboxylic acid in brain slices.

Metabotropic glutamate receptors (mGluRs) have been recently described as a family of guanine nucleotide-binding regulatory protein-coupled receptors with multiple signal transduction pathways. At least one of these receptors appears to be negatively coupled to adenylyl cyclase when stably expressed in transfected cells. We have studied how activation of native mGluRs modulates cyclic AMP (cAMP) formation in brain slices prepared from rats at different ages. 1S,3R-1-Aminocyclopentane-1,3-dicarboxylic acid (1S,1R-ACPD), a selective agonist of mGluRs, slightly increased basal cAMP formation but reduced forskolin-stimulated cAMP formation in adult hippocampal slices, in agreement with previous results. The action of 1S,3R-ACPD on basal cAMP formation was not reproduced by the ionotropic receptor agonists N-methyl-D-aspartate, kainate, and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate and was antagonised by L-2-amino-3-phosphonopropionate (L-AP-3). L-AP-3, however, did not prevent but rather mimicked the inhibitory action of 1S,3R-ACPD on forskolin-stimulated cAMP formation. In hippocampal slices from 1-, 8-, or 15-day-old rats, 1S,3R-ACPD increased basal cAMP formation but failed to reduce the action of forskolin. A similar development pattern of modulation was observed in hypothalamic slices with the difference that 1S,3R-ACPD did not stimulate basal cAMP formation in the hypothalamus of adult animals. These results suggest that inhibition of forskolin-stimulated cAMP formation by 1S,3R-ACPD is mediated by a specific mGluR subtype that is preferentially expressed in the adult.

Aging↗
PubMed1992

HIV-1 isolation from small amounts of whole blood: a technical evaluation.

We have evaluated a simple and sensitive culture technique for isolation of Human Immunodeficiency Virus Type-1 (HIV-1) from small amounts of whole blood. Data shown in the paper demonstrate that: 1) cell cultures from small amounts of heparinized whole blood (HWB) allow a high isolation rate in infected subjects at all stages of diseases; 2) among asymptomatic subjects the HIV-1 isolation rate is increased in cell cultures from HWB, with respect to cell cultures from peripheral blood mononuclear cells; 3) cultural results from HWB are not influenced by the presence of detectable serum p24 antigen, but a good correlation was found with the titre of anti p24 antibodies in serum; 4) continuous cell lines (such as Molt-3 cells) instead of peripheral blood mononuclear cells can be used, obtaining good results, for HIV-1 isolation from HWB; 5) frozen samples of HWB can be used in cell cultures for HIV-1 isolation; 6) the type of anticoagulant (Heparin or EDTA) used for the collection of blood does not influence viral replication in cell cultures from whole blood; 7) viral isolation from HWB is highly sensitive; amounts so small as five microliters of whole blood are sufficient, in some cases, to obtain viral replication in cell cultures; 8) the minimal dose of HWB sufficient to infect cell cultures (HWB M.D.I.) varied among different patients. Although this work failed to establish a correlation between this parameter and the clinical and immunological status of patients, it is conceivable that HWB M.D.I. could give information about viral load in blood and have a prognostic significance; 9) the HWB M.D.I. rise in patients treated with Zidovudine, suggesting that this method could be employed in the virological evaluation of trials with antiretroviral drugs.

Acquired Immunodeficiency Syndrome↗
PubMed1991

[Analysis of the replication kinetics in primary culture of isolates of HIV-1 from infected patients in various stages of the disease].

The authors have studied the replicative kinetics and the induction of cytopathic effects of HIV-1 in primary co-cultures from infected subjects at various stages of the disease. Cultures from subjects with ARC or AIDS yielded HIV-1 replication more precociously and at higher levels compared to those from asymptomatic subjects; cytopathic effect "in vitro" were observed more frequently and earlier in cell cultures from ARC/AIDS subjects. Presented data indicate that the clinical and immunological deterioration during HIV-1 infection is related to viral replicative activity and suggest that the study of HIV-1 replicative kinetics in primary co-cultures may be helpful in predicting who will progress to AIDS.

AIDS-Related Complex↗
PubMed1991

[Isolation of human immunodeficiency virus (HIV) from whole blood].

The authors describe a simple and sensitive technique for HIV isolation from small amounts of heparinized whole blood. This method demonstrated a high efficiency in detecting HIV at all stages of disease and appeared more sensitive with respect to viral isolation from peripheral blood mononuclear cells. Although further studies are needed to better understand the biological significance of a positive cultural result obtained by this method, HIV isolation from whole blood can be routinely employed, especially when small amounts of blood are available.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Different biological properties of paired HIV-1 isolates from peripheral blood mononuclear cells and cerebrospinal fluid.

Seven paired HIV-1 isolates from peripheral blood mononuclear cells (PMCs) and cerebrospinal fluid (CSF) of infected subjects at various stages of the disease were studied for their capacity to replicate in continuous cell lines (Molt-3 and U-937 cells) and to induce cytopathic effects "in vitro". Obtained results indicate that paired HIV-1 isolates from PMCs and CSF of the same patient can differ in their replicative activity "in vitro", suggesting that, at least in some cases, CSF isolates may represent a distinct subtype of HIV-1.

AIDS-Related Complex↗