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Biomedical subjects

C Marchetti

Publications and source records attributed to C Marchetti.

At least 163 records · Page 9Linked to original sources
PubMed1987

Ultrastructural study of the adjoining areas between the endothelial cells of the rabbit heart lymph vessels.

The transendothelial transport across the lymph vessel wall is connected to the morphological and ultrastructural features of the lymph vessel endothelium. In the present study the lymph vessel wall and the adhesion areas between contiguous endothelial cells of the rabbit heart were examined also by means of serial sections. This examination allowed us to reconstruct the whole intercellular connecting areas and to clarify some discussed adhesion structures. The adjoining cells are connected by three types of contact: end to end, overlapping and interdigitation. In addition the cellular processes form intraendothelial, tortuous channels with focal specialized junctional areas. Only occasional open junctions are present. Our features are discussed and compared with the sometimes conflicting literature data on the morphological properties of these adjoining areas for their significance in the mechanisms of lymph formation.

Animals↗
PubMed1986

[Systemic and nonsystemic causes of pathological mandibular fractures].

The problem of pathological fractures of the lower jaw with particular reference to their aetiology is examined in the light of personal experience. Odontogenic and hematogenic osteomyelitis, primary and metastatic tumours, degenerative lesions, traumas, inclusions of the teeth and the whole apparatus are discussed individually.

Fractures, Spontaneous↗
PubMed1986

[Hand-Schüller-Christian syndrome arising in the mandible. A case report].

The history of Letterer-Siwe, Hand-Schüller-Christian disease, and eosinophilic granuloma of the bone, and the evolution of the concept of grouping them together under the common term of histiocytosis X are presented. The characteristics of the disease, with particular emphasis on oral manifestations, are reviewed. The therapy for the disease is briefly outlined. One case of Hand-Schüller-Christian syndrome is presented. The discussion is focused on the problem of chemotherapy in disseminated forms.

Adult↗
PubMed1986

Effects of dopamine and noradrenaline on Ca channels of cultured sensory and sympathetic neurons of chick.

The effects of noradrenaline and dopamine on voltage-dependent Ca currents were investigated in cultured dorsal root and sympathetic ganglion neurons from chick embryos. At concentrations of 1 to 10 microM, bath application of the neurotransmitters caused a general depression of inward Ca currents. Above -20 mV the decrease of the current amplitude was reversible and accompanied by a 2-10-fold prolongation of the activation time course. Below -20 mV, where a low voltage-activated Ca component is turned on, the size of the currents was reduced by 40% with little effect on the time course. Despite extensive wash-out, little sign of reversibility was observed in this case. Single-channel current recording in outside-out membrane patches revealed that at low membrane potentials dopamine and noradrenaline reversibly reduced single Ca-channel activity. This finding supports the view that in sensory and sympathetic neurons, both neurotransmitters affect the membrane conductance by modulating Ca permeability and not by activating catecholamine-specific channels able to carry transient outward currents. The probability of Ca channel opening is strongly reduced by addition of 10 microM of either catecholamine to the bath. The possible involvement of a voltage-dependent block of Ca channels by the neurotransmitters is discussed.

Animals↗
PubMed1986

Radiosurgery using a 4MV linear accelerator. Technique and radiobiologic implications.

In the authors' technique, the stereotactically localized target is fixed to the isocenter of a 4 MV linear accelerator. The irradiation is carried out along 9-17 non-coplanar arcs distributed on a 160 degrees cylindrical sector. High doses (10-50 Gy) are delivered in one or two sessions. From 1982, 65 patients have been treated (shortest follow-up 6 months). The dose was chosen according to the pathology and to the volume of the lesion. Good clinical results have been obtained in low-grade gliomas, acoustic neuromas, arteriovenous malformations, and other selected types of intracranial lesions. Therapeutic effects in terms of clinical condition and size of the lesions have been plotted in relation to time elapsed and dose employed.

Adolescent↗
PubMed1986

Lymph vessels of the rabbit heart: distribution and fine structure in atria.

The distribution and fine structure of lymph capillaries in the atria of the rabbit heart were examined. A lymph capillary network extends into both the right and left atria but its distribution is not uniform. It is developed in the subepicardium but not in the myocardium and subendocardium of the atrial wall; overall it is less extensive than the corresponding network in the ventricles. In the atrial conduction system and in particular the sino-atrial node and the crista terminalis, the lymph network is more widely distributed; small lymph capillaries are also detected between the myocardial cells of the conduction system. A large lymph channel consistently runs along the medial side of the crista terminalis. The morphologic characteristics of atrial lymph capillaries include irregular shape, thinness of the endothelial wall, superimpositions and interlockings of the cells in the contact areas with complex junctional processes, thin and discontinuous basal membrane.

Animals↗
PubMed1986

Cytoplasmic bodies in lymphatic endothelial cell.

Although micropinocytotic vesicles and other large vesicular structures have been observed in lymphatic endothelial cells on electron microscopy, in this study ultrastructure attention was focused on a variety of other membrane-bounded structures in the cytoplasm of these cells in the rabbit heart. The first type was oval or round in transverse section and elongated in longitudinal section, was 100-200 nm in diameter and contained regularly spaced tubules. These features resembled rod-shaped bodies detected thus far only in blood vascular endothelial cells. A second type of cytoplasmic body was also frequently seen in lymphatic endothelium. It contained irregularly spaced small vesicles, 5-7 in number and 45 nm in diameter. A third type of vesiculated body was only occasionally found. This latter structure was greater than the previously described bodies and ranged from 3-5 micron in diameter, and filled with granular, inhomogeneous material and filamentous-like components. The functional significance of these intraendothelial bodies is as yet unexplained.

Animals↗
PubMed1986

Lymph vessels of the heart. A comparative study of various techniques for light and electron microscopy.

This investigation was carried out in order to find out which was the best technique, among those reported in the literature, to recognize the small lymph vessels by light microscopy, while at the same time allowing a good ultrastructural preservation of tissues. The study was performed with rabbit hearts according to the following methods: (1) injection of India ink into the wall of the heart followed by perfusion with aldehyde fixative; (2) injection of India ink into the wall of the heart followed by immersion in aldehyde fixative; (3) treatment of the animals with histamine dihydrochloride by e.v. route and aldehyde (4) fixation by immersion; (5) fixation by immersion in osmium tetroxide fixative; fixation by immersion in aldehyde fixative; (6) fixation by perfusion with the same mixture as in (5). In cases (1), (2), (3), (5), and (6), the tissue specimens were postfixed in osmium tetroxide according to conventional methods. The validity of the different methods was checked by examining semithin sections of varying thickness at the light microscope and ultrathin sections at the transmission electron microscope. A comparative examination of the preparation showed that the method allowing the promptest recognition of the small lymph vessels, together with the best ultrastructural preservation and a good reproducibility of results was perfusion of the coronary circle.

Animals↗
PubMed1985

Stereotactic radiosurgery utilizing a linear accelerator.

The authors have developed a radiosurgical technique based on multiple arc irradiations. The target is fixed to the rotational isocenter of a Varian 4 MV linear accelerator. The first irradiation is carried out while the radiating source is rotating on a 100-140 degrees arc. The patient is then rotated around a vertical axis passing through the target, and arc irradiations are repeated in different angular positions. By this technique it is possible to obtain very steep dose gradients at the borders of the target volume. High doses are usually delivered in two shots. 47 patients have been treated so far in a clinical trial that started in November 1982. The paper deals with the preliminary results (more than 6 months' follow-up) obtained in patients affected by nonresectable brain tumors and AVMs.

Adolescent↗
PubMed1985

External stereotactic irradiation by linear accelerator.

Stereotactic radiotherapy has two advantages: (a) the possibility of giving high radiation doses to small but spatially well-defined target volumes and (b) the presence of a stepped dose gradient between the target volume and the surrounding healthy tissues. To utilize these advantages, the authors built a new stereotactic head frame by which the intracranial target is fixed to the rotational isocenter of a 4-MV linear accelerator. The collimator openings are selected according to the volume and the three-dimensional configuration of the target, and the radiation dose is based on the radiosensitivity of the lesion. After the patient is fixed to the frame, the radiation source and the patient are rotated so that the target is irradiated through infinite portals distributed over the convexity of the skull. It is thereby possible to obtain very high radiation doses centered into the target with a stepped dose gradient. The preliminary radiodosimetric tests and the operative technique are described. The advantages of this technique compared to interstitial radiotherapy and Leksell's radiosurgery are emphasized. This noninvasive procedure has been used to treat a series of intracranial tumors.

Adolescent↗
PubMed1985

Lymph vessels of the rabbit heart: distribution and fine structure in ventricles.

We examined the distribution and fine morphology of small lymph channels in the rabbit heart, and particularly in the ventricular myocardium. Light microscopy showed many small subendocardial lymphatics in both ventricles and especially in the subendocardium of papillary muscles and right side of the septum. Electron microscopy revealed that the endothelial ultrastructure of these lymphatics was similar at different sites. The cytoplasm exhibited frequent adluminal expansions and contained numerous micropinocytotic vesicles opening both into the lumen and surrounding interstitium. Bundles of microfilaments, commonly arranged in a parallel fashion, were also visible. Between laminations of the endothelial wall were relatively dense, finely granular material. Intercellular contacts were characterized by cell superimpositions and interlockings, specialized junctions and occasionally maculae adherentes. The basal membrane was discontinuous and often of variable thickness. In the surrounding connective tissue, thin filaments appeared adjacent to the abluminal surface of the endothelial wall. Although the fine structure of the walls of small lymphatics in the rabbit ventricular myocardium was similar to that of small lymphatics at other sites, their distribution varied from other mammalian species.

Animals↗
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↗