Search PubMed⌕ Search

Biomedical subjects

C Marchetti

Publications and source records attributed to C Marchetti.

At least 163 records · Page 9Linked to original sources
PubMed1984

GM1 micelles modify the transport properties of the ionophore gramicidin D in artificial planar bilayers.

We have analyzed the effects induced in different phospholipid planar bilayers by monosialoganglioside micelles containing the ionophore gramicidin D. The membrane conductance increases after the addition of GM1 micelles at various ionophore/ganglioside ratios. We believe this fact may be ascribed to gramicidin molecules that incorporate into the bilayer together with gangliosides. In the presence of micelles the mean lifetime and the amplitude of the gramicidin single channel did not present relevant modifications when dioleoylphosphatidylcholine or phosphatidylserine were used to form the bilayer. Calcium proved to trigger the interaction between phosphatidylethanolamine membranes and GM1 micelles containing gramicidin. In this case the ionic pore presents a longer lifetime and a lower amplitude with respect to pure gramicidin. We suggest that different properties developed by gramicidin may depend on structural organization of gangliosides when incorporated into the phospholipid bilayer.

Biophysical Phenomena↗
PubMed1984

Hemiplegic atrophy. Morphological findings in the anterior tibial muscle of patients with cerebral vascular accidents.

Anterior tibial muscle biopsies of the hemiplegic side of 16 patients with a cerebrovascular accident in the middle cerebral artery region were analyzed qualitatively and quantitatively by enzyme histochemistry and electron microscopy. Patients grouped according to the time lapsed as from the occurrence of the accident (1-17 months) demonstrated a progressive decrease in the fiber diameter and changes in fiber type distribution with predominant type II atrophy and type I predominance. Nuclear internalization, myopathic alterations, and perifascicular fatty infiltrations were observed constantly. In the affected fibers the ultrastructural findings were myofibrillar alterations with the formation of rods and cytoplasmic bodies. There was accumulation of lipofuscin, glycogen, and lipid droplets. Microvascular changes were observed frequently. Biopsies from the asymptomatic legs were either normal or showed age-related muscle alterations. Correlation was noted between the clinical and functional status of the patients and the morphological aspects seen in muscle biopsies.

Adult↗
PubMed1984

Effect of gangliosides on phospholipid bilayers: a study with the lipophilic ions relaxation method.

The presence of monosialoganglioside GM1 in dioleoylphosphatidylcholine black lipid membranes modifies the transport properties of the hydrophobic ion tetraphenylborate and the kinetics of relaxation of this ion after the application of a voltage step. At zero applied voltage, the difference in the relaxation time constants between pure phospholipid and ganglioside-phospholipid mixed membranes is large. This difference may possibly rise from changes in the membranes fluidity since it has been found that the two types of membranes do not show appreciable difference in thickness. A uniform distribution of GM1 in the membrane seems to be more probable than the presence of lateral phase separation phenomena. The partition coefficient of tetraphenylborate between the bathing NaCl solution and the membrane appears to depend on the ionic strength, which controls the screening effect of the Na+ ions on the COO- charged groups of the sialic acid of the ganglioside polar heads. Effects of dipolar potentials on the partition coefficient can be excluded, being the absorption plane of tetraphenylborate probably located outside the dipolar layer of the membrane.

Biological Transport↗
PubMed1984

[Stereotaxic irradiation with a linear accelerator].

At least two fundamental requirements must subsist for every stereotaxic radiotherapy treatment: 1) a capacity to administer extremely high doses of radiation to small areas which have been precisely defined in three dimensions; 2) the presence of a steep gradient between adjacent isodose curves so that damage to the tissues close to the target may be reduced to the minimum. The authors have built a special stereotaxic device for the fixing of the head of the patient (together with the chosen intracranial target), once the indispensable neuroradiological evaluations and bioptic controls have been effected, at the isocenter of a linear accelerator (Varian Clinac 4). Once the dimensions of the collimator have been chosen in accordance with the volume and the three dimensional conformation of the target and the dose to be administered has been decided upon in accordance with the histological nature of the lesion, both the linear accelerator and the patient are rotated about the isocenter of the therapy unit. It this way it is possible to reach extremely high dosages with very steep isodose gradients, centered exclusively upon the target ("gamma knife"). The procedure employed is described in full. The dosimetric evaluations which preceded the use of the set-up in clinical practice are illustrated as well. The advantages that this technique offers when compared with interstitial brachytherapy and/or Leksell's radiosurgical procedures are stressed. The described procedure, which is entirely bloodless and thus applicable also to high vascularized lesions, has so far been used in a limited series of cases.

Brain Diseases↗
PubMed1984

Adrenal cortex hormones and small intestine of adult rat: morphology, purity and enzymatic activities of isolated microvillous vesicles.

An electron microscopic and enzymatic investigation was carried out to assess the purity as well as the morphologic integrity of small intestine microvillous membrane vesicles prepared from the following groups of adult rats: untreated (normals); adrenalectomized and pair-fed controls; treated for 8 days with corticosterone (1 and 10 mg X 100 g-1 body weight X day-1), and relative controls. Electron microscopy observation of ultrathin sections of ruthenium red stained vesicles from all groups showed that the microvillous membranes were structurally intact and virtually uncontaminated by material from other subcellular structures. The vesicles presented a fuzzy, intensely ruthenium red positive layer in their outer membranes. Apparently no alteration was induced in microvillous membrane by adrenalectomy, semistarvation or corticosterone treatment. The values of the enrichment factors for alkaline phosphatase and sucrase were similar for all the groups, indicating a high grade of purity of the preparations. Adrenalectomy and high dose of corticosterone decreased the vesicles content of alkaline phosphatase; sucrase was increased by semistarvation and adrenalectomy.

Adrenalectomy↗
PubMed1984

Ophthalmoplegia plus: CSF and CT features of seven cases.

The authors describe the clinical and laboratory results relative to 7 cases of Ophthalmoplegia Plus, with special reference to the histochemical, ultra-structural and CFS findings and to the data obtained by Computerized Tomography (CT) of the brain. The CSF was altered in all the examined patients: 3 out of 7 presented an abnormal albumin quotient, 1 patient had an increased IgG Index; the isoelectrofocusing of the CSF proteins, carried out in 6 out of 7 cases, showed an abnormal protein content referred to gamma trace in 3 cases, oligoclonal bands in the CSF in one case, a double Tau fraction in one case, a damaged blood-brain barrier in 5 cases. The CT-performed in 6 out of 7 cases-revealed in one patient a diffuse hypodensity of the periventricular white matter, without signs of atrophy; 2 cases showed a mild atrophy of the posterior fossa involving the cerebellar hemispheres and vermis in one case, the vermis and the brain stem in the other one; no patient revealed signs of cortical or ventricular atrophy. The boundaries of the Ophthalmoplegia Plus are here discussed on the ground of the results obtained by the employment of the various research methods.

Adult↗
PubMed1983

Interactions between tumor cells and vascular endothelium.-I) Adhesion properties of cell lines with different metastasizing capacity.

The authors describe the adhesive properties of four murine tumor lines, chemically and virus induced, with different metastasizing potential. Cancer cells show similar behaviour in attachment kinetics when tested with endothelium monolayer or plastic surfaces, without differences between the lines with high or low malignancy. The time required for a complete adhesion to endothelial cells is three hours while to plastic surfaces is 90 min. The role of divalent cations is not required in the first phases of cellular attachment of tumor lines to plastic dishes.

Animals↗
PubMed1983

Interactions between tumor cells and vascular endothelium.-II) Light and electron microscopic studies.

Electron microscope technique was used to investigate the passage across the endothelial monolayer by murine tumor lines. After the initial adhesion, cancer cells induce a retraction of endothelium and migrate under vascular intima. Subsequently they spread on basement membrane showing a flattened shape, meanwhile endothelial cells reconstitute the monolayer. The four tumor lines show a similar behaviour being able to induce endothelial retraction and exposure of extracellular matrix and cross through the monolayer. The technique appears useful to study in details this multi-step process.

Animals↗
PubMed1983

Capacitance--voltage relationship in phospholipid bilayers containing gangliosides.

Changes in the position of the minimum of the parabolic capacitance-voltage curve allow the measurement of the amount of ganglioside present in artificial bilayers made with phosphatidylcholine-ganglioside mixtures and asymmetrically shielded with Ca2+. The screening effect of the ionic solution must be considered. With ganglioside/phospholipid molar ratios of up to 15%, all glycolipids can be found at the membrane surfaces.

Gangliosides↗
PubMed1982

Properties of ionic transport through phospholipid-glycolipid artificial bilayers.

The ionic transport properties of dioleoylphosphatidylcholine (DOPC) membranes containing various sphingolipids were studied. Particular attention was paid to membranes formed from beta-D-glucosylceramide (GlcCer) and DOPC. They showed a marked increase in ionic permeability (up to a factor 30 with respect to pure DOPC membranes), slight cation selectivity and almost linear behaviour of the current-voltage characteristic. Bilayers containing GlcCer showed a typical conductance decrease upon increasing the temperature. We suggest the formation of clusters containing GlcCer molecules in a solid-crystalline phase. The conductance increase might be due to ionic pathways through disordered boundary regions. An increase in the mechanical breakdown potential was observed in all membranes which contain sphingolipids.

Electric Conductivity↗
PubMed1982

Muscle fiber type morphology and distribution in paraplegic patients with traumatic cord lesion. Histochemical and ultrastructural aspects of rectus femoris muscle.

Biopsies of the rectus femoris muscle of 22 paraplegic patients with complete acute spinal cord transection due to trauma were taken for enzyme-histochemical and electron-microscopic studies in successive stages starting from occurrence of the accident (1-17 months). Ingravescent muscular atrophy was demonstrated with a progressive decrease in the fiber diameter and changes in the fiber type distribution with predominant type II atrophy in the first stage and type I atrophy in the later stage of the cord transection. Muscular "neurogenic" changes, such as angular dark atropic fibers, targetoid fibers, and type predominance are frequently observed. Myopathic alterations are observed in a low percentage in the later stages of the lesion. The ultrastructural findings are characterized by myofibrillar alterations and by dilatation and proliferative phenomena of the sarcoplasmic reticulum and T-system. There are ingravescent accumulation of lipid, interstitial fibrosis and microcirculatory alterations. The possible mechanism of "central" muscle atrophy is reviewed and discussed with reference to the morphological findings.

Adolescent↗
PubMed1982

Chronic progressive external ophthalmoplegia. Clinical, electrophysiological, histochemical and ultrastructural studies of 14 cases.

Clinical, histochemical and ultrastructural findings concerning 14 cases with diagnosis of Chronic Progressive External Ophthalmoplegia are described. According to the clinical features the patients have been rated in two groups: the first including subjects with isolated ptosis or ptosis with external ophthalmoplegia and the second including subjects with a spreading of the muscular deficit and involvement of the neck and limbs. The most frequent histological and histochemical features are type I fibre atrophy, ragged-red fibres, DPNH-diaphorase reaction disorders and abnormal accumulation of lipids into the fibres. Electron microscopy reveal myofibrillar disorganization and clusters of polymorphous, abnormal mitochondria. In five cases mitochondria contain a variety of crystalline inclusions. Correlations between clinical data and histochemical and ultrastructural findings are discussed. Mitochondrial abnormalities are postulated to be a characteristic physiopathological pattern in CPEO.

Adult↗
PubMed1981

An ocular myopathy with glycogen storage and abnormal mitochondria in muscle fibres. Histochemical and ultrastructural findings.

The case of a 66-year-old woman with progressive external ophthalmoplegia and involvement of the proximal muscles of the upper and lower limbs is described. EMG examinations show signs of myopathic involvement. Histochemical and biochemical studies exclude a primary defect in glycogenolysis. The authors stress the peculiarity of the histochemical findings, characterized by the rare associated appearance of both mitochondrial changes and glycogen accumulation in muscle fibres. The most prominent ultrastructural findings are evidence of increased glycogen, usually present in vesicles or in mitochondria, and changes in number, size and structure of mitochondria. Quantitative biochemical examination of muscle homogenates confirmed the increased content of glycogen in muscle fibres.

Aged↗
PubMed1980

Histochemical and ultrastructural aspects of m. vastus lateralis in sedentary old people (age 65--89 years).

Biopsies for histochemical and ultrastructural studies were taken from the M. vastus lateralis of 45 healthy sedentary men and women aged 65--89 years. With increasing age the histochemical reactions reveal changes inthe fibre type distribution characterized by a decrease in the percentage and predominant atrophy of type II fibres. The most frequent changes in the oldest subjects are: targetoid fibres, type I fibre predominance, and type grouping phenomena; expressions of denervation. Myopathic alterations are observed unusually. Electron microscopic findings are characterized by myofibrillar disorder, streaming of Z line and rod formation, and dilatation and increase of sarcoplasmic reticulum. As the age increases, the fibres become richer in intracellular lipid droplets and lysosomes. Intramuscular microcirculatory alterations, consisting of arteriolosclerotic changes and increase in width of the capillary basement membrane, are also observed and discussed.

Aged↗
PubMed1977

A case of progressive external ophthalmoplegia (Kiloh-Nevin type) with abnormal mitochondria. Clinical, histochemical and ultrastructural findings.

A case of progressive external ophthalmoplegia is described, in which the onset of the illness was at 28--30 years, with fatigability and muscular pains in the lower limbs as presenting symptoms. At 36--37 years weakness of the mimic muscles also appeared and fatigability and muscular pains spread to the upper limbs: EMG examination showed signs of light myopathic involvement of the shoulder-girdle muscles, so that a muscular biopsy was performed (right deltoid). Histoenzymologic studies showed the presence of generally atrophic dark fibres, which can be brought about to red-ragged fibres. Ultrastructural study showed bizarrely shaped mitochondria, with dense matrix and circular and confluent cristae, which were found in fibres with plenty of indifferent sarcoplasm and with anomalies in myofibrils. No mitochondrial inclusions were seen.

Adult↗
PubMed1977

Mitochondrial abnormalities in some human muscular diseases and in experimental ischemic myopathy.

Morphologic abnormalities have been observed in two cases of human polymyositis and in three cases of ocular myopathies. Similar findings can be observed in experimental ischemic myopathy. "Ragged red" fibres, with anomalous distribution of oxidative enzymes, mitochondrial alterations, with presence of intracristal paracrystalline inclusions and degenerative myofibrillar changes are the similar features. The similarity between some of these alterations, expecially mitochondrial changes, is remarkable, but it is difficult to correlate them to the primary etiology of described human myopathies.

Adult↗