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Biomedical subjects

C Marchetti

Publications and source records attributed to C Marchetti.

At least 37 records · Page 2Linked to original sources
PubMed1990

Voltage-dependent calcium currents in rat gonadotropes separated by centrifugal elutriation.

Centrifugal elutriation of rat pituitary cells yielded two functionally active fractions (6 and 7) that contained 30-40 and 50-60% gonadotropes, respectively. We studied the membrane ionic currents of these cells with the whole cell patch-clamp method. In physiological solution, cells from the enriched fractions displayed a tetrodotoxin-sensitive sodium current. In 20 mM external calcium and zero sodium, the inward current contained two components that were different in threshold, steady-state inactivation, and deactivation. One component was half activated at approximately -25 mV, half inactivated from a holding potential of -61 mV, and deactivated with a time constant of 3 ms. The second component was half activated at 6 mV and deactivated with a time constant of 0.35 ms. These two currents resembled the high-voltage-activated and low-voltage-activated calcium current described in many preparations, including clonal and primary pituitary cells. Bath application of 20 nM gonadotropin-releasing hormone caused a transient and reversible decrease of the calcium current at depolarized voltages and a negative shift of 10 mV in the activation curve. Both effects were observed in a percentage of cells that closely matches the percentage of gonadotropes in the fraction. The shift appeared to affect both components of the current and can partially account for the increased activity of Ca2+ channels at potentials close to the resting value.

Animals↗
PubMed1990

Linear accelerator radiosurgery of three-dimensional irregular targets.

Current radiosurgical techniques allow concentration of radiation from external sources into spherical targets. Nonspherical target volumes require a modification of the irradiation technique. Moreover, isodose shaping is sometimes necessary to spare nearby important radiosensitive structures. To meet these prerequisites we have introduced some technical refinements: (1) computer-controlled rectilinear translations of the target in combination with different angular positions of the source and (2) computer-controlled rotations of the target around a vertical axis in combination with different angular positions of the source. The first solution has proven efficient for treating irregular targets, while the second one was employed for focusing the radiation dose inside volumes obtained by rotation of ellipses.

Brain Neoplasms↗
PubMed1990

An enzyme-histochemical, ultrastructural and morphometric study on fetal and neonatal rat diaphragms.

The organogenesis of the rat diaphragm was studied with enzyme-histochemical, ultrastructural and morphometrical methods. 18 to 20 and 22 day in utero diaphragms were examined as well as 2-8-14 and 25 day old ones, in order to determine the age related changes in the diameter and the percentage of muscle fibers and mitochondria. In all examined ages, morphometric data showed type II fiber predominance. Type I and II fibers were equivalent in diameter. During fetal life, mitochondrial size increases appreciably with age while the mitochondrial percentage does not. Instead in postnatal life, the mitochondrial diameter is almost constant both for the small type I fibers and for the large ones (type II fibers). The mitochondrial percentage gradually increases particularly in the small fibers.

Adenosine Triphosphatases↗
PubMed1990

Immunocytochemical labelling of Merkel cells of human oral mucosa by means of antibodies to protein gene product 9.5.

Merkel cell (MC) are one of the non-keratinocyte cell populations that reside in oral epithelium. Protein gene product 9.5 (PGP 9.5) is a protein specifically present in the cytoplasm of neurons and neuroendocrine cells. It is demonstrated by immunofluorescence and immunoperoxidase that MC of oral human mucosa express PGP 9.5-like immunoreactivity. This finding is in agreement with the hypothesis that oral MC are paraneurons or neuroendocrine cells. The use of anti-PGP 9.5 serum may be of value for future studies of MC in normal and pathological oral tissues.

Antibodies↗
PubMed1990

[Photon or electron irradiation of the internal breast lymph node chain. Experimental dosimetry and clinical implications].

The radiation therapy of internal mammary chain, according to many other authors, is indicated in patients with N + breast cancer or with inner quadrant disease. Since the direct field with gamma radiation seems to induce important adverse effects on myocardium, the authors were induced to check experimentally dose distributions of 12-15 MeV electron beams and compare the results to gamma photon dose distribution. Materials and dosimetric methods as well as experimental results are described. Moreover theoretic and practical point of view are discussed coming to the conclusion that electron beams are more suitable for myocardial saving. Nevertheless some technical variations are required, to maintain the typical homogeneity of photon beams.

Breast Neoplasms↗
PubMed1990

[Light microscopy and electron microscopy study of the lymphatic capillaries of human dental pulp].

The existence and the morphological characteristics of the lymphatic capillaries of the dental pulp have been and are yet discussed. In this study the morphological properties of the lymphatic capillaries of the healthy human dental pulp have been described at light and electron microscopy. For the investigation human enclosed incisive and canine teeth surgically extracted and permanent premolars extracted for orthodontic reasons were used. On semithin sections the lymph capillaries are detectable as vessels of 15-50 microns in diameter with a very irregular shape and a subtle wall. No pericytes or muscular cells surround the endothelial lining. At ultrastructural level the lymph capillaries show a very thin and indented wall with protrusions towards the vessels lumen or the interstitium. The connections between adjacent endothelial cells are different and variously shaped: end to end contacts, overlapping between cellular protrusions and complex interdigitations among multiple protrusions of the endothelial cells. Sometimes the overlappings between endothelial cells determine intraparietal channels in communications with the interstitium and the vessel lumen. A discontinuous basal lamina and a network of filaments and fibrils surround the endothelial wall. Between the cytoplasmic organelles micropinocytotic vesicles, multivesicular bodies and the Weibel-Palade bodies are present.

Basement Membrane↗
PubMed1990

[Gardner syndrome. A report of 3 cases in members of the same family].

The aim of the present report is to describe the overall mandibular and extramandibular lesions correlated to Gardner's syndrome which were found in the same family (mother and two daughters). In two cases (mother and one daughter) mandibular lesions consisted of osteoma. In the latter, these were associated with composite odontoma. In the other daughter the lesions consisted of desmoid fibroma. The two daughters revealed single colonic polyposis whereas the mother was affected by multiple colonic polyposis and subcutaneous lipoma. Such a constellation of lesions may be attributed to Gardner's syndrome, a Mendelian hereditary syndrome which is often incomplete. In fact, intestinal polyposis can only be associated with one of the various extraintestinal manifestations of the syndrome. The recognition of the syndrome is important given the high percentage of intestinal polyp-adenocarcinoma associations.

Adolescent↗
PubMed1989

[Use of nimesulide in orthognathic surgery of the jaws].

The aim of this clinical study was to value the antiphlogistic and analgesic efficiency of Nimesulide on 40 patients suffering from facial anomalies and subjected to corrective surgery with many facial osteotomies (Le Fort 1, sagittal osteotomy of mandibular ramus sec. Obwegeser-Dal Pont). Nimesulide was effective in reducing post-surgery oedema and spontaneous and caused pain. Besides it was of easy assumption and well suffered from the major part of the patients subjected to this kind of surgery.

Adolescent↗
PubMed1989

A transient voltage-dependent outward current in cultured cerebellar granules.

Granule cells were dissociated from rat cerebella with a procedure that yields a 98% pure cell population. Potassium currents in these cells were studied using the patch-clamp technique. Depolarizing pulses of 10 mV step and 100 ms duration from a holding potential of -80 mV elicited two different potassium outward currents: a transient, low-voltage activated component and a long lasting, high-voltage activated component. At +30 mV, the total current reached an amplitude of 2 nA (mean value of 15 experiments). The reversal potential of the transient current, estimated by measuring tail currents, was -77 mV, close to that predicted by the Nernst equation. The transient current was half inactivated with a holding potential of -78 mV and completely inactivated with -50 mV or more positive holding potentials. Finally, the current decay could be fitted by the sum of two exponentials with time constants of about 20 and 250 ms.

Animals↗
PubMed1989

Growth hormone response to thyrotropin releasing hormone and placebo in a group of insulin dependent diabetic patients.

In order to evaluate if the assessment of the paradoxical GH responses to TRH in diabetic subjects could be altered by the presence of spontaneous fluctuations in plasma GH levels, we compared GH responses to TRH and to saline injection in 19 insulin-dependent diabetic patients. We observed significant increments (greater than 5 ng/ml) in plasma GH levels after TRH iv administration in 5 of 19 patients (26%); on the other hand, a significant increase was also observed in 6 patients (31%) after saline. We conclude that, at least in some diabetics, spontaneous GH pulses might be misinterpreted as paradoxical GH responses after a nonspecific stimulus administration. Moreover, the real existence of the paradoxical GH response to TRH has to be assessed using the following strict criteria: a sufficient magnitude in GH increment (greater than 5 ng/ml), the comparison of the kinetics of GH secretion after TRH and saline in the same patient, the presence of a significant GH rise above basal levels within the first 30 min after TRH injection.

Adolescent↗
PubMed1989

Immunocytochemical detection of proliferating cells in the rat tooth germ by monoclonal antibodies against 5-bromo-2'-deoxyuridine.

5-Bromo-2'-deoxyuridine incorporated into DNA synthesizing cells in vivo is detected by a monoclonal antibody. The results are similar to those obtained with cytoautoradiography, but show variance with data from some past autoradiographic studies. This immunocytochemical technique may be a useful tool for study of cell kinetics in the oral tissues.

Animals↗
PubMed1989

Guanosine-5'-O-(3-thiotriphosphate) modifies kinetics of voltage-dependent calcium current in chick sensory neurons.

Internal perfusion with the G-protein activator guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma S) mimics the effect of noradrenaline and dopamine on the voltage-dependent calcium current in chick dorsal root ganglion (DRG) cells. With 100 microM GTP-gamma S in the pipette, the current at +10 mV was depressed by approximately 50%, with a 10-fold increase of its time to peak. The activation time course of the control calcium current could be approximated with a single exponential curve, whereas with GTP-gamma S the activation time course was double exponential, with time constants tau 1 and tau 2. 2 mM Mg-ATP in the pipette prevented the GTP-gamma S-induced current decrease in 70% of the cells, but the time course of the current was always double exponential. From -50 mV, the current at +10 mV was best fitted with tau 1 = 1.7 +/- 0.5 and tau 2 = 25.6 +/- 5.5 in seven cells. Both time constants decreased with increasing depolarizations. In the first 2 min of recording, the current changed with time. However, both tau 1 and tau 2 were constant, whereas the relative contribution of the slow component increased from 10 to 70%. In addition, the effect was independent of the holding potential in the range from -100 to -30 mV. These results suggest that the activation of a G-protein causes a fraction of the high-threshold calcium channels to switch to a new closed state, with slower opening kinetics.

Action Potentials↗
PubMed1989

Low-grade astrocytomas: treatment with unconventionally fractionated external beam stereotactic radiation therapy.

Fourteen patients with nonoperable low-grade astrocytomas were treated with unconventionally fractionated stereotactic radiation therapy. The target volume was defined with computed tomography (CT) performed under stereotactic conditions. The treatment was carried out with a technique producing multiple noncoplanar arc irradiation, with the center of the target volume placed at the isocenter of the linear accelerator. A total dose of 16-50 Gy was administered in either one fraction or two fractions 8 days apart. The concentration of dose within the target volume allowed reduction of dose absorbed by adjacent critical structures of the intact brain. Patients were followed up for 11-48 months. Twelve of 14 patients had a partial or complete response to treatment, as demonstrated by CT. Stereotactic radiation therapy appears to be effective in the control of small radioresistant cerebral neoplasms, without damaging surrounding healthy tissues.

Adolescent↗
PubMed1989

Microscopic and ultrastructural study of the lymphatic system in the human parotid gland.

The localization and fine structure of the lymphatic system vessels are examined in the human parotid gland. A network of lymphatic capillaries extends in the intralobular connective septa around the striated ducts. These lymphatics converge in collectors frequently bordering the excretory ducts. On the contrary, no lymphatics are present next to the intercalated ducts and adhenomers. Ultrastructurally, the lymphatic capillaries are characterized by a very thin endothelial wall and by slightly complicated intercellular adhesions. Open junctions are also present. The presence of numerous lymphatic capillaries bordering the striated ducts and their blood microvasculature is discussed in relation to the functional activities of the striated ducts in the modification of the saliva.

Humans↗
PubMed1989

Morphometric data on the lymph capillaries of the ventricles of the rabbit heart.

A morphometric analysis was done on the lymph capillaries of both left and right ventricles from the rabbit heart. The measurements were made on the lymphatics identified in the subepicardium, myocardium and subendocardium of the ventricular walls. Quantitative evaluations were carried out on light and electron microscopic sections by a computerized image analysis system. The following parameters were selected and measured: (1) the diameter (of area-equivalent circle) of lymph capillaries, (2) the diameter of the uncoated micropinocytotic vesicles (located on the abluminal and adluminal side and in the cytoplasm of the endothelial cell) and the area occupied by the vesicles per unit area of cytoplasm. Differences in the size of the lymph capillaries were found in the three layers (subepicardium, myocardium and subendocardium) of the ventricular walls. The largest vessels were present in the subepicardium both in the left ventricle and in the right one. No significant variations were found in the lymphatics of corresponding regions on both ventricles. Little variations on the mean diameter of the uncoated micropinocytotic vesicles are present in the three regions of the endothelial wall. In the left ventricle only, the subendocardial vesicles are significantly larger than the subepicardial and the myocardial ones (p less than 0.05). The areal density occupied by vesicular system in the three layers of the ventricular wall showed significant differences in both ventricles (p less than 0.05). The vesicles present in the subepicardial vessels occupied the smallest areal density. No significant variations existed in the vesicular areal density between the two ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Linear accelerator radiosurgery of cerebral arteriovenous malformations.

A technique for linear accelerator radiosurgery has been used in clinical practice since 1982. The technique is based on multiple intersecting arc irradiations focused on a stereotactic target. From November 1984 to October 1988, 97 patients with cerebral arteriovenous malformations have been treated. Seventy-nine patients suffered one or more than one hemorrhage. Four patients had progressive neurological symptoms. In 14 patients, epilepsy was the principal complaint. Stereotactic localization was performed by stereotactic angiography. Lesion dimensions varied from 4 to 40 mm in diameter. Doses from 18.7 to 40 Gy were delivered in one or two sessions. Mean follow-up is 17.1 months (from 1 to 49). Four instances of minor rebleeding were observed after treatment; 3 patients complained of transient neurological deterioration. Of 56 patients who were followed longer than 1 year, 50 underwent 12-month follow-up angiography. In 26 patients complete obliteration of the malformation was demonstrated (52%), in 12 patients subtotal obliteration was obtained (24%), in 11 patients the obliteration was evident but not significant (22%), and in 1 patient the AVM was unchanged. Other angiographic features in incompletely obliterated cases were a significant reduction of flow velocity through the malformation together with a reduction in diameter of both feeding arteries and draining veins.

Adolescent↗
PubMed1989

[Immunocytochemical study of the development of the oral cavity in the rat].

Flow cytometry and autoradiography are extensively used for the evaluation of the number of cells in S-phase in order to study the proliferative activity within tissues and organs. The recent development of a monoclonal antibody against 5-bromo-2'deoxyuridine (BrdUrd), a nonradioactive thymidine analogue that is incorporated within DNA-synthetizing cells, allows the immunochemical detection of proliferating cells. The use of this antibody allows an immunocytochemical detection of proliferating cells "in situ" on tissue sections. We have applied this new technique for the identification of proliferating cells within the tooth and other organs of rat mouth during development. We believe that this technique, for its precision and simplicity, may be a powerful tool for studying the cytokinetic and the differentiation of normal and neoplastic cells within the mouth as well as in other districts of the body.

Animals↗