Biomedical subjects

C Marchetti

Publications and source records attributed to C Marchetti.

At least 145 records · Page 8Linked to original sources

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↗

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↗