PubMed Health⌕ Search

Biomedical subjects

C Marchetti

Publications and source records attributed to C Marchetti.

At least 55 records · Page 3Linked to original sources
PubMed1988

Dosimetric considerations on multiple arc stereotaxic radiotherapy.

The aim of this paper is to present the physical and dosimetrical features of the stereotaxic radiosurgical method already published by the authors. This method concentrates the dose into the stereotaxic target volume, placed at the isocenter of a 4 MV X-ray beam. Computer calculations showed that: 9-17 arcs provide almost spherical dose distributions; the optimal photon beam quality is about 4-6 MV. The angle between adjacent rotation planes is 20-40 degrees and the arcs are 100-160 degrees wide. In this way the dose to healthy tissue is minimized. The dose distribution was experimentally verified both by ionometric and photodensitometric methods. The procedure for dose calculation at isocenter of fields as small as required by the radiotherapist, has been investigated.

Calibration↗
PubMed1988

A whole-cell and single-channel study of the voltage-dependent outward potassium current in avian hepatocytes.

Voltage-dependent membrane currents were studied in dissociated hepatocytes from chick, using the patch-clamp technique. All cells had voltage-dependent outward K+ currents; in 10% of the cells, a fast, transient, tetrodotoxin-sensitive Na+ current was identified. None of the cells had voltage-dependent inward Ca2+ currents. The K+ current activated at a membrane potential of about -10 mV, had a sigmoidal time course, and did not inactivate in 500 ms. The maximum outward conductance was 6.6 +/- 2.4 nS in 18 cells. The reversal potential, estimated from tail current measurements, shifted by 50 mV per 10-fold increase in the external K+ concentration. The current traces were fitted by n2 kinetics with voltage-dependent time constants. Omitting Ca2+ from the external bath or buffering the internal Ca2+ with EGTA did not alter the outward current, which shows that Ca2+-activated K+ currents were not present. 1-5 mM 4-aminopyridine, 0.5-2 mM BaCl2, and 0.1-1 mM CdCl2 reversibly inhibited the current. The block caused by Ba was voltage dependent. Single-channel currents were recorded in cell-attached and outside-out patches. The mean unitary conductance was 7 pS, and the channels displayed bursting kinetics. Thus, avian hepatocytes have a single type of K+ channel belonging to the delayed rectifier class of K+ channels.

4-Aminopyridine↗
PubMed1988

Protein kinase activator 1-oleoyl-2-acetyl-sn-glycerol inhibits two types of calcium currents in GH3 cells.

Two types of Ca2+ currents, high-threshold, long-lasting, or L currents and low-threshold, transient, or T currents, are present in many excitable cells. L-type Ca2+ current is modulated by, among others, beta- and alpha-adrenoreceptors and intracellular Ca2+, but modulation of T-type Ca2+ current is less well established. 1-Oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic activator of protein kinase C (PKC), modulates whole cell Ca2+ currents in a variety of excitable cells. Whether activators of PKC affect preferentially L and T types of Ca2+ currents is unknown. We tested OAGs effects on whole cell Ca2+ currents in the clonal GH3 line of anterior pituitary cells. The currents were measured using the whole cell patch-clamp method. Four to 60 microM OAG reversibly reduced Ca2+ currents produced by test potentials to 10 mV, and the inhibition was half maximal at approximately 25 microM. Such concentrations depress Ca2+ currents in chick embryo dorsal root ganglion (DRG) cells and clonal AtT-20 pituitary cells. To test whether OAG acted preferentially on L or T current, we separated the two using depolarizing prepulses to inactivate T current. OAG (40 microM) attenuated T currents by 60% and L currents by 50%. The current waveforms were not changed and were simply scaled, and the effects on both occurred approximately 15 s after OAG was applied. In chick embryo DRGs OAG inhibited the T current by 30% and the L current by 50%. We conclude that PKC modulates Ca2+ currents by acting on both L and T Ca2+ channels.

Animals↗
PubMed1988

Lymphatic system in human dilated cardiomyopathy.

Lymph capillary features have been investigated in human hearts from subjects affected by dilated cardiomyopathy. The edematous myocardial regions present dilated lymph capillaries with a slightly indented endothelial wall. The intercellular adhesions are not especially intricate; the open junctions between contiguous endothelial cells are more numerous than in normal conditions. In the myocardial areas affected by interstitial fibrosis the lymph capillaries are scanty and subtle. The morphological features, evident in the edematous and the fibrotic regions of the hearts affected by dilated cardiomyopathy, are compared with those induced in the myocardium by damaging the lymph flow experimentally. Our observations suggest a differential response of the lymph system to modified conditions of the tissue and the interstitium.

Cardiomyopathy, Dilated↗
PubMed1988

An immunocytochemical method for studying embryo cytokinetics.

The immunocytochemical detection by a monoclonal antibody of bromodeoxyuridine incorporated into S-phase cells allows the identification of proliferating cells. In this study we demonstrate that the labelling of embryo tissues is achieved by a single administration of BrdUrd to the mother after a 1 hour-labelling period. This simple and rapid technique facilitates the detection of proliferating cells within the embryo for the study of developing tissues and embryo cytokinetics.

Animals↗
PubMed1987

Automatic morphometric analysis of skeletal muscle fibers in the aging man.

A qualitative and quantitative analysis of M. vastus lateralis fibers from 40 male sedentary subjects, ranging in age from 30 to 89 years, was carried out by light and electron microscopy and by an automatic Interactive Image Analysis System. Biopsies for enzyme histochemical and ultrastructural studies were taken from subjects subdivided into four age groups: 30-50, 60-70, 71-80, and 81-89 years. Attention was focused on the fiber type size and distribution, the size and the amount of mitochondria, and the amount of lipid droplets. Main changes observed in the four age groups are indicative of a sequence of events within senescent skeletal muscle fibers. With increasing age the enzyme histochemical reactions reveal changes in fiber type distribution characterized by decrease in muscle fiber diameter and by type I fiber predominance. Type II fiber atrophy is consistent. Type I fiber predominance seen in older subjects could be related to a selective decrease of type II fibers with age. It also suggests a possible conversion of type II fibers to type I fibers. Lipid droplet percentage per fiber area increases, while mitochondrial size and mitochondrial percentage per fiber area decrease with age. It is possible that energy requirements decline with age and that the decrease in mitochondrial size and percentage represents a response to a reduced metabolic demand.

Adult↗
PubMed1987

New technique for three-dimensional linear accelerator radiosurgery.

A new method for external stereotactic focal irradiation of three-dimensional irregular target volumes is proposed. In this method the target is irradiated by a linear accelerator set in various angular positions around the isocenter. During the irradiation the target is translated in a direction perpendicular to the beam. By controlling the velocity of the translation it is possible to modify the configuration of therapeutic isodoses so as to make them follow the borders of the target.

Brain Diseases↗
PubMed1987

Membrane currents of identified isolated rat corticotropes and gonadotropes.

Membrane currents of identified, isolated corticotropes and gonadotropes from mammalian anterior pituitary gland have been evaluated. Pituitary gonadotropes and corticotropes were isolated enzymatically and stained in the living state using biotinylated gonadotropin-releasing hormone (Bio-GnRH) or biotinylated corticotropin-releasing hormone (Bio-CRF) followed by avidin fluorescein. Electrophysiological recordings were made with patch-clamp electrodes in the whole-cell clamp configuration. Tetrodotoxin (TTX)-sensitive sodium currents were larger in corticotropes than in gonadotropes. Corticotropes showed two components of calcium currents, a transient low-threshold component and a longer lasting high-threshold component. Small TTX-resistant inward currents were present also in gonadotropes, and both cell types had transient and steady potassium currents.

Animals↗
PubMed1987

Secretion from corticotropes after avidin-fluorescein stains for biotinylated ligands (CRF or AVP).

Viable pituitary target cells were identified with biotin-labeled corticotropin-releasing factor (1-Bio-CRF) or arginine vasopressin (Bio-AVP) and avidin-fluorescein (cell sorter grade). Stain was reduced from 8-10% of pituitary cells to less than 3% if nonbiotinylated ligands were added to compete with their respective biotinylated ligand for specific binding sites. However, AVP did not decrease the stain for 1-Bio-CRF nor did CRF decrease the Bio-AVP stain. Media adrenocorticotropin (ACTH) levels increased 4-18 times when 1-Bio-CRF or Bio-AVP were added during the staining process. One hour after staining, the cells secreted ACTH at levels identical to prestain basal levels. When challenged with CRF or AVP after this hour, the cells responded again with increases not different from those seen during staining. Tests of stained cell populations also showed that the cells were fully responsive 24 h after staining. The reverse hemolytic plaque assay for ACTH, which was used to study secretion from individual stained cells, showed that approximately 80% of plaques contained a stained cell and that plaque numbers and areas were like those of unstained populations. These data show that corticotropes are not chronically desensitized during exposure to low doses of biotinylated ligands (50-500 pM).

Adrenocorticotropic Hormone↗
PubMed1987

Involvement of sodium channels and two types of calcium channels in the regulation of adrenocorticotropin release.

Recent electrophysiological studies from this laboratory demonstrated that anterior lobe corticotropes exhibited a tetrodotoxin-sensitive sodium current and two types of voltage-dependent calcium currents, consisting of low threshold (transient) and high threshold (long lasting) components. The present report describes cytophysiological and cytochemical studies that used specific blockers of each of these currents to assess their role in the regulation of CRF binding and ACTH secretion and storage. Two dihydropyridines, nimodipine and the pure antagonist enantiomer (-)R202-791, which block high threshold Ca2+ channels, decreased 1 h basal release by 54-74% and CRF-mediated (5 min or 3 h) release completely. Percentages of CRF-bound cells were reduced as much as 74%; however, the inhibitory effect on percentages of CRF-bound cells could be reversed by adding 10 nM Bay K 8644, (a pure dihydropyridine agonist) with the antagonists. CdCl2, which blocks both high and low threshold calcium currents, inhibited basal and CRF-stimulated ACTH release, but only the highest concentration (0.1 mM) reduced percentages of CRF-bound cells. Involvement of the low threshold Ca2+ channels could not be proved by adding dihydropyridine antagonists with 0.1 mM CdCl2. Basal and CRF-mediated ACTH release were blocked by the potent sodium channel blocker tetrodotoxin, and the highest concentration (3 microM) reduced percentages of CRF-bound cells. Basal (1 h) and CRF-stimulated (5 min) ACTH release were also inhibited in medium containing 1 mM EGTA and no Ca2+; however, percentages of CRF-bound cells were within the normal range. Densitometric analysis of stains for ACTH showed an increase in the concentration of stain per cell after a 1-h exposure to the highest concentrations of the inhibitors or to no Ca2+ and 1 mM EGTA coupled with a significant (10%) decrease in corticotrope cell area. Finally, in the last series of tests, the Bay K 8644 agonist or arginine vasopressin were used to study mechanisms of augmentation of basal or CRF-mediated ACTH release. Bay K 8644 augmented basal release in a concentration of 1 microM and CRF-mediated release in a concentration of 100 nM or 1 microM. After pretreatment with either Bay K 8644 or arginine vasopressin (10 nM) there was a significant (30%) increase in the percentage of CRF-bound cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗
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↗