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Biomedical subjects

L Leonardi

Publications and source records attributed to L Leonardi.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Relationship between the shape and size of radiofrequency induced thermal lesions and hepatic vascularization.

AIMS AND BACKGROUND: The aim of this study was to evaluate the relationship between hepatic vascularisation and the final size and shape of radiofrequency (RF) induced thermal lesions. METHODS: Series of four RF thermal lesions were created in explanted calf livers and in pig livers maintaining the following experimental conditions throughout the procedure: normal hepatic perfusion, occlusion of the hepatic artery, occlusion of the portal vein, occlusion of both hepatic artery and portal vein (Pringle maneuver) and subtotal occlusion of the hepatic veins. A 14G expandable needle electrode was used to make the thermal lesions. Each lesion was created applying predetermined temperatures ranging between 95 and 115 degrees C and an exposure time of 20 minutes. RESULTS: Occlusion of the hepatic artery during the RF procedure resulted in moderate and not significant increases in thermal lesion diameter compared with those obtained in normally perfused liver (3.0 +/- 0.4 cm vs 3.0 +/- 0.2 cm), while occlusion of the portal vein resulted in larger lesion diameters (3.5 +/- 0.3 cm). In both these cases the diameters of the thermal lesions were smaller than those obtained in explanted calf liver (4.0 +/- 0.3 cm) and their shape showed peripheral irregularities. Thermal lesions larger than those seen in normally perfused liver and equaling those observed in explanted calf liver were created both during the Pringle maneuver (4.0 +/- 0.2 cm) and after subtotal occlusion of the hepatic veins (4.0 +/- 0.3 cm). In both these cases the thermal lesions were regular in shape. CONCLUSIONS: Occlusion of the blood flow during the RF procedure avoids heat loss by convection, resulting in the creation of larger thermal lesions than those obtained in normally vascularized liver using the same electrode, temperatures and exposure time. This technique could therefore be employed in humans to destroy large hepatic tumor nodules.

Animals↗
PubMedDate not supplied

Influence of dehydroepiandrosterone and 5-en-androstene-3 beta, 17 beta-diol on the growth of MCF-7 human breast cancer cells induced by 17 beta-estradiol.

The effects of dehydroepiandrosterone (DHEA) and 5-en-androstene-3 beta, 17 beta-diol (ADIOL) on the proliferation of MCF-7 cells were studied both in steroid - free and estradiol (E2) supplemented media. Growth was evaluated by counting the cells after six days of culture. The results show that DHEA 500 nM and ADIOL 2 nM stimulate MCF-7 cell growth in steroid-free medium, while in medium supplemented with E2 1 nM they partly antagonize the stimulatory effect of the estrogen. The latter action is also shown by lower DHEA concentrations (20 nM, 100 nM), which have no effect when added to the steroid-free medium. Incubations carried out in the presence of labeled DHEA show its conversion to ADIOL. Moreover, tamoxifen counteracts in a dose-depended manner the stimulatory effect of DHEA and ADIOL, suggesting that it is mediated by an interaction with estrogen receptors.

Androstenediol↗
PubMedDate not supplied

[Health education and people's participation in health in Nicaragua: research on the profile, role and function of the "brigadistas populares" in health].

The Nicaraguan democratic government has been building, since the defeat of somozism in 1979, a very extensive and uniform health system in the whole country, giving special attention to the problems of prevention and health education, promoting and utilizing a wide participation of the population. The most emblematic representative of the Nicaraguan model of participation is the Brigadista Popular en Salud, a voluntary figure in urban and rural areas, working along side the Sole National Health System. The work and role of the Brigadista is integrated in a health education action defined "Educaciòn Popular en Salud", intended as a dialogue through which the educator and educated, beginning with the specific political and economical social reality, accomplish work of observation, analysis and syntesis of the different phenomena that deal with health-sickness. The Brigadista is a member of the community that works voluntarily for the community to carry out health actions, in coordination with the "Puesto de Salud" of the community. The authors refer to a research study done in the field in 1987, geared to study the profile, role and activities of the Brigadista. The research was done in the "Las Segovias" Region, in the Northern part of the country, in two Health Areas, involving three urban centers and six rural communities: 73 Brigadistas were interviewed, of which 50 (predetermined) of urban centers and 23 (total population) in rural communities. The article represents in a comparative manner the operative Brigadista respectively, in urban areas on the one hand and in rural areas on the other. The article examines: sex; age; schooling; work activity; social-cultural background; collective systems background; participation in Literacy Campaigns; motivation; length and continuity of activities; relationship with the territory; activities done. The Brigadista that works in rural areas seems actually to be more attached, even to the formal image of his role, that the urban Brigadista. This is shown by the reduced turn-over, the wider span of functions, the closer relationship with collective systems that represent categories, a more intense relationship with colleagues of the health system as well as with other Brigadistas, the operative reference to specificity defined territories, more continuity in the functions of the Brigadista Popular en Salud.

Adult↗
PubMedDate not supplied

Dehydroepiandrosterone antiestrogenic action through androgen receptor in MCF-7 human breast cancer cell line.

The possible mechanisms of the inhibitory effect of Dehydroepiandrosterone (DHEA) on the estrogen-induced growth of MCF-7 human breast cancer cells were explored. The impairment of metabolic pathways, via the inhibition of glucose-6-phosphate dehydrogenase (G6PD) activity, was excluded: G6PD activity in MCF-7 homogenate was reduced by DHEA only at a very high concentration (50 microM), while no inhibitory action on the enzyme activity was detected when DHEA was added at the antimitotic concentrations (0.02-0.5 microM). A steroid receptor mediated effect was explored: DHEA might either activate androgen receptors (AR) or partially displace E2 from estrogen receptor (ER). The pure antiandrogens Flutamide and Hydroxyflutamide reversed the inhibitory effect of DHEA on MCF-7 cell growth, whereas both the nonsteroidal estrogen Diethylstilbestrol and the antiestrogen Tamoxifen were ineffective. Results demonstrate that the AR activation plays a pivotal role in the inhibitory action of DHEA on the E2-induced MCF-7 growth.

Breast Neoplasms↗
PubMedDate not supplied

Dihydrotestosterone affects the growth of hormone-unresponsive breast cancer cells: an indirect action.

Cell to cell interaction, which plays a crucial role in breast cancer growth, may be regulated by steroid hormones. This study examined dihydrotestosterone (DHT) effects on the interaction between the steroid receptor positive MCF-7 and the steroid receptor negative MDA-MB-231 breast cancer cell lines. The growth of MDA-MB-231 cells was inhibited by medium conditioned by MCF-7 cells grown in presence of DHT but not by medium conditioned by MCF-7 cells grown in presence of both DHT and the antiandrogen hydroxyflutamide. Trypsin pretreatment of conditioned medium abolished its growth-inhibitory effect on hormone-unresponsive cells. DHT itself did not affect the growth of MDA-MB-231 cells when directly added to their culture medium. Data suggest that DHT stimulates, via the androgen receptor, the androgen-responsive breast cancer cells to produce a peptide factor(s) capable of inhibiting the growth of hormone-unresponsive cells.

Adenocarcinoma↗