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Biomedical subjects

F Colombo

Publications and source records attributed to F Colombo.

At least 145 records · Page 8Linked to original sources
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

Adenosine modulates the dopaminergic function in the nigro-striatal system by interacting with striatal dopamine dependent adenylate cyclase.

Behavioral and pharmacological evidences suggest that dopaminergic mechanisms in striatum might be counteracted by adenosine or potentiated by its pharmacological antagonists methylxanthines. To test whether adenosine modulation of the dopaminergic function could be, at least in part, due to an interaction at the level of the adenylate cyclase complex, we studied the effects of the adenosine analog R-Phenyl-isopropil-adenosine (R-PIA) on basal and dopamine-sensitive adenylate cyclase in rat striatum. R-PIA, which interacts with both adenosine A1-inhibitory and A2-stimulatory receptors, dose-dependently inhibited the stimulation induced by dopamine, and seemed to utilize the same pool of enzyme linked to dopaminergic D1 receptors. Two experimental approaches leading to supersensitivity of striatal dopaminergic receptors, (i.e., 6-hydroxy-dopamine injection in substantia nigra and reserpine administration) also induced upregulation of adenosine-dependent adenylate cyclase in striatum, and altered R-PIA modulation of dopamine-sensitive adenylate cyclase. Conversely, after subchronic treatment with neuroleptics such as haloperidol or sulpiride, upregulation of 3H-Spiroperidol binding in striatum was not associated with changes of R-PIA dependent adenylate cyclase in this area. It is concluded that adenosine might modulate post-synaptic responses to dopamine via adenosine receptors which functionally interact with dopaminergic D1 receptors in striatum.

Adenosine↗
PubMed1987

Linear accelerator radiosurgery of arteriovenous malformations.

Forty-five patients affected by cerebral arteriovenous malformations not suitable to open surgery have been treated by a radiosurgical technique employing a linear accelerator. One-year follow-up angiography is available for 10 cases. Therapeutic effect of focalized irradiation is presented.

Adolescent↗
PubMed1987

[Angiodysplasia of the right colon. Angiographic findings in 5 cases].

The authors present five cases of angiodysplasia of the right colon diagnosed by selective arteriography of the superior mesenteric artery. The patients, affected by repeated digestive haemorrhages, underwent angiography after many endoscopic and radiological examinations, all without significative findings. Clinical patterns, methods and angiographic findings are described, together with surgical specimen.

Angiography↗
PubMed1987

Development of nonreducible technetium-99m(III) cations as myocardial perfusion imaging agents: initial experience in humans.

A series of 15 nonreducible technetium-99m(III) complexes of formula tr-[99mTcL(Y)2]+ has been prepared by a general synthetic route based on reductive addition of Y to the technetium-99m (99mTc) intermediate [99mTcL(O)]+. In these complexes, selected for potential use as myocardial imaging agents, L represents one of the two tetradentate Schiff base ligands N,N'-ethylenebis(acetylacetone iminato), (en), or N,N'-propylene-1,2-bis(acetylacetone iminato), (pn), while Y represents a monodentate phosphine, phosphite or isonitrile ligand as exemplified by P(CH3)3, P(OCH3)3 and CN-C(CH3)3. Of these 15 complexes, several with octanol/saline partition coefficients in the range 0.04-20 exhibit significant myocardial uptake in rats and dogs. Of these, none exhibit detectable myocardial washout, providing strong support for the hypothesis that myocardial washout occurs only for those 99mTc(III) cations that undergo in vivo reduction to the neutral 99mTc(II) form. Evaluation of the prototypical complex tr-[99mTc(en)(P(CH3)3)2]+ in seven normal volunteers and patients establishes that it is only a mediocre myocardial imaging agent in man.

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↗
PubMed1985

Osteogenic osteosarcoma of the calvaria following radiotherapy for cerebellar astrocytoma: report of a case in childhood.

Sarcoma as a second malignant neoplasm following radiotherapy is a rare occurrence in childhood. A case of osteogenic osteosarcoma of temporoparietal bone that developed 56 months after irradiation for a cerebellar astrocytoma in a 10-year-old child is reported and the pertinent literature is briefly reviewed. The possibility of an association (in the same patient) between these two rather uncommon lesions is extremely unlikely. Therefore, it is possible that radiotherapy played a role in the induction of the sarcoma. The indolent course of the latter is stressed.

Astrocytoma↗
PubMed1985

Reproductive and hormonal factors and breast cancer in a Northern Italian population.

Between January 1980 and March 1983, data were collected to evaluate risk factors for breast cancer in a case-control study based on 368 women with breast cancer admitted to the General Hospital of Pordenone (a district in North Eastern Italy with a particularly high breast cancer mortality rate), and 373 age-matched controls. Nulliparity or low parity, late age at first birth and later menopause were associated with an increased risk of breast cancer. The elevated risk associated with nulliparity could be almost completely explained by marital status, thus pointing to a specific protection given by parity, rather than some putative influence of infertility or subfertility in breast cancer cases. Likewise, risk did not vary materially according to history of abortions when marital status was controlled for. Increased risk associated with later age at first birth, on the other hand, was not accounted for by marital status or parity. The population studied, though frequently multiparous, showed late average at first birth: this might, at least partly, explain its high mortality rate from breast cancer. The risk estimate was higher if menarche occurred below age 15; however, there was no evidence of a trend for the relative risk to rise with lower age at menarche. The use of oral contraceptives or other female hormones (such as oestrogen replacement therapy) did not appear to be related to the risk of breast cancer. The role of the major menstrual and reproductive variables considered (age at menarche, parity, age at first birth) was apparently stronger in pre-menopausal women, thus suggesting an influence of these factors (and possibly, their hormonal correlates) on one of the latter stages of the process of carcinogenesis.

Abortion, Spontaneous↗
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

Ventilatory response to carbon dioxide and to isometric muscle contraction after administration of placebo, propranolol, mepindolol and salbutamol.

Healthy males (23-29 years) volunteered as subjects. We studied the ventilatory response to carbon dioxide and to isometric exercise (50% of maximum voluntary contraction) after administration of propranolol (20 mg), mepindolol (5 mg), salbutamol (20 mg) and placebo (single dose orally). The increase of pulmonary ventilation (VE) activated by central (CO2) and reflex stimulus (hand-grip) did not differ statistically between the four drugs. Analysis of VE in terms of inspiratory drive (Vt/Ti) and timing ratio (Ti/Ttot) showed that during CO2 stimulation mepindolol and salbutamol increased VE predominantly by the increase of Vt/Ti, presumably through the direct stimulation on the respiratory center. During rebreathing, Ti/Ttot increased significantly after administration of placebo and propranolol, so VE increased by a rise of Vt/Ti and by an increase of an effective 'timing component' (Ti/Ttot). Propranolol does not modify the ventilatory response to CO2 and hand-grip when VE is analyzed in terms of Vt/Ti and Ti/Ttot.

Adult↗
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↗
PubMed1984

[Biopsy and stereotaxic radiotherapy of cerebral gliomas].

The Authors report their experience on a series of 125 patients that underwent stereotactic biopsy. The procedure has proved reliable and almost risk -free. The diagnosis obtained from the bioptic specimen by smear technique-cytological examination and by paraffin embedding-histological examination are compared. Neuropathologic data were also checked by the examination of the tumor bulk in cases that underwent surgical removal or autoptic verification. The preliminary results obtained in 8 patients with the new technique of external stereotactic irradiation by means of a linear accelerator are also shown.

Biopsy↗
PubMed1984

Preparation and evaluation of [99mTc]DEPE as a cardiac perfusion agent.

Technetium-99m labeled bis(1,2-diethylphosphino)ethane was evaluated as a cardiac perfusion agent in mice, dogs and normal human volunteers. The agent produced as a single cationic compound was prepared by a simple kit type method and had a rapid myocardial uptake in animals. The cardiac uptake of the agent in dogs averaged 4.6% of administered dose and delineated left and right ventricles by in vivo imaging. In dogs with experimental myocardial infarction, the agent was distributed according to the regional myocardial blood flow, had excellent correlation with myocardial distribution of 85Sr microspheres (r = 0.96, 0.93)] and 201Tl (r = 0.91 and 0.83), and enabled us to detect perfusion defects by in vivo scintigraphy. The agent, however, failed to have a useful degree of cardiac uptake in humans.

Animals↗