PubMed Health⌕ Search

Biomedical subjects

L Roa

Publications and source records attributed to L Roa.

At least 19 recordsLinked to original sources
PubMed2000

NEWBET: telemedicine platform for burn patients.

Problems detected in the current healthcare services for burn patients and emergency situations are taken into consideration in the development of a telemedicine platform, which is proposed in this paper. Taking as a reference the user requirements and the client-server architecture, a model of communications that allows a bidirectional exchange of information is reported. Special attention is focused towards the methodology applied and the design of a friendly user interface compatible with the current prevailing clinical protocols. The platform is based on a Microsoft Windows environment, and communications are implemented by using sockets.

Burns↗
PubMed1999

Digital imaging in remote diagnosis of burns.

Images are capable of giving an accurate representation of skin color and have been used extensively in teaching about and researching burn therapy. The advance from analogue to digital imaging allows the remote transmission of the clinical information contained in the digital image of a burn, using a suitable system. The large size of these image files reduces transmission speed and makes data compression desirable. Compression, by means of the JPEG algorithm, of up to 50 times the original size of 38 digital images of burns suffered by 22 consecutive patients did not lessen its great usefulness in determining the depth of burn injuries, according to a group of experts in burn care. The success rate was close to 90%, both for non-compressed images in original BMP format (mean size:1500 Kb) and for compressed images with a Q index of 50 (30 Kb files), when compared with the clinical diagnoses confirmed one week after the accident.

Adult↗
PubMed1998

Demonstration of aromatase activity and its regulation in breast tumor and benign breast fibroblasts.

Breast tumors from post-menopausal women contain higher amounts of estradiol than would be predicted from levels circulating in plasma. This observation raised the hypothesis that tumors may synthesize estradiol in situ and increase their tissue estradiol levels via this mechanism. The key enzyme involved in tissue estrogen synthesis, aromatase, is present in breast tumors but, according to some investigators, not in sufficient concentration to be biologically meaningful. We postulated that foci of cells in breast tumors might contain high amounts of aromatase and this locally produced estrogen might act in a paracrine or autocrine fashion. To test this hypothesis, we utilized immunohistochemistry to localize the aromatase enzyme, an histological scoring system to quantitate it, and culture of isolated breast cells to demonstrate its potential regulation. In 26 archival breast tumors, 16 (62%) contained aromatase by radiometric assay. With the immunohistochemical method, we detected areas with staining in the stroma as well as tumor epithelial cells. Staining ranged from the intensity approaching that seen in placenta to levels just distinguishable from background. We adopted an histological scoring system (H-score) from that used to quantitate progesterone receptor levels in tissue and used it to quantitate aromatase activity. A higher histologic score was found in stromal spindle cells (13) than in tumor epithelial cells (4.8). The biochemical aromatase results correlated with the H-score of stromal but not epithelial cells. To further study stromal cells from tumors, we isolated stromal cells from breast tumors and the benign areas of breast distal to the tumor and grew them in culture. Addition of dexamethasone, phorbol esters, and cyclic AMP analogues stimulated aromatase enzyme and messenger RNA levels substantially. Use of aromatase enzyme inhibitors such as letrozole blocked estrogen production but did not alter aromatase message levels. Epithelial cells, whether nonmalignant or cancer derived, exhibited no regulation by dexamethasone, phorbol esters, or cAMP analogues. These data, taken together, suggest that stromal cells may be more important than epithelial cancer cells for estrogen production in breast tumors. The ability to stimulate aromatase activity substantially with various enhancers of aromatase provides further credence for an important biologic role of estrogen production in tumor tissue.

Aromatase↗
PubMed1994

Stromal spindle cells contain aromatase in human breast tumors.

In situ synthesis of estrogens by breast cancer tissue provides a potential explanation for the high concentrations of estradiol in mammary neoplasms in postmenopausal women. A major metabolic pathway for estrogen biosynthesis is the conversion of androstenedione to estrone via the enzyme aromatase. Biochemical studies have demonstrated aromatase in tumor tissue, but at relatively low and not clearly biologically significant levels. The present study tested the hypothesis that tumor levels of aromatase, albeit low, could be biologically important if present in high concentrations in focal clusters of specific cell types. A pilot study used an immunohistochemical method in frozen sections of fresh breast tumors as an optimal means to detect aromatase. Twelve of 18 tumors contained aromatase-positive cells, some with highly intense staining. A follow-up study then attempted to precisely define the types of cells containing aromatase and correlate the immunohistochemical findings with biochemical aromatase activity. A modified H-score (histological scoring system) was used to semiquantitate the amount of aromatase staining in tumor epithelial, stromal spindle, stromal inflammatory, and normal breast epithelial cells. We found that immunohistochemical staining for aromatase predominated in stromal spindle cells with a median H-score of 13, whereas tumor epithelial, stromal inflammatory, and normal breast elements contained lesser amounts (median H-scores of 4.8, 0.03, and 0.5, respectively). The H-score for stromal spindle cells, but not those for other cell types, correlated highly with the biochemical aromatase assay (P < 0.01). Using a cut-off parameter estimated by a sensitivity/specificity (receiver operating curve) analysis, 62% of tumors were classified as aromatase positive based on stromal spindle cell staining. A similar number were also positive by biochemical assay, with concordance between the two methods of 77%. These observations provide substantial evidence for the presence of aromatase in human breast tumors, particularly in stromal spindle cells, and support the biological importance of aromatase for in situ production of estradiol.

Aromatase↗
PubMed1993

A burn patient resuscitation therapy designed by computer simulation (BET). Part 1: Simulation studies.

This study presents an analysis of the fluid, electrolyte and colloid needs of burn patients during the shock phase. A digital simulation technique was used which had previously been validated and published in burned patients (Roa et al., 1988). After analysing the repercussions of both burns and various resuscitation procedures, a fluid therapy method (BET) has been designed using a burn patient simulator, which has been characterized by its effectiveness and minimal side-effects. The characteristics of the BET method are a low volume of infusion resuscitation solution (220 ml/h/m2 burned body surface area (BBSA)) and a rapid and large volume of colloidal substances (with colloid concentrations of 10, 7.5 and 5 g/100 ml during the first three 8 h periods of the first postburn day and 2.5 g/100 ml until the 40th h postburn).

Burns↗
PubMed1993

A burn patient resuscitation therapy designed by computer simulation (BET). Part 2: Initial clinical validation.

The clinical results obtained from the first 40 burned patients resuscitated with 220 ml/h x BBSA (m2) of human serum albumin with concentrations of 10, 7.5, 5 and 2.5 per cent in lactated Ringer's (0-8, 8-16, 16-24 and 24-40 h post injury respectively), which we have called BET fluid therapy, were compared with those obtained in 58 patients resuscitated with lactated Ringer's 4 ml/kg of body weight/%BBSA during the first 24 h after burning. The results confirm the effectiveness of the BET form of fluid therapy during the shock phase after burning. The BET fluid therapy method differs from other procedures because of its lower volume of infused resuscitation solution with the rapid infusion of large amounts of colloid. These preliminary results have encouraged us to continue analysing this new method of fluid therapy.

Adolescent↗
PubMed1993

Immunohistochemical localization of renin and angiotensin in the ovary: comparison between normal women and patients with histologically proven polycystic ovarian disease.

OBJECTIVE: This study was designed to test the hypothesis that the ovarian renin-angiotensin system may play a role in polycystic ovarian disease (PCOD). DESIGN: The immunohistochemical distribution of renin and angiotensin in ovaries from seven women with histologic diagnosis of PCOD was compared with that of normal ovaries. RESULTS: The large cystic follicles of polycystic ovaries (PCO) presented intense immunostaining for renin and angiotensin in both theca and granulosa cells (GCs). In developing follicles of normal ovaries, the immunostaining was restricted to the theca cell layer, with the exception of the immediately preovulatory follicles which displayed intense positivity of granulosa as well as theca cells. Atretic follicles of normal ovaries showed staining of both theca and GCs. In both normal and PCO, patches of hilus cells were intensely stained. Luteal cells also consistently stained both in normal ovaries and in the occasional corpus luteum present in polycystic ovaries. CONCLUSIONS: This study highlights the link between the ovarian renin-angiotensin system and those ovarian compartments known to be actively engaged in androgen secretion and/or luteinization and suggests that there may be an association between the ovarian renin-angiotensin system and PCOD.

Adult↗
PubMed1993

Digital simulation as a teaching tool: the distribution and transport of fluids in humans.

We present a mathematical model to analyze the distribution and transport of fluids in humans. The interest of this model is that is based on a strong physiological structure. Some classical experiments of the physiological sciences are show. We have simulated the intravenous infusion of isotonic, hypertonic and colloid solutions in a patient of average physical characteristics. In our opinion, the digital simulation, in the context of the classic techniques of distribution and transport of fluids analysis, is a supplementary teaching tool.

Biological Transport↗
PubMed1992

Analysis by digital simulation of the peripheral and renal resistance in hypovolemic hypotension.

A haemorrhage was simulated and analysis of dynamic behaviour of renal resistance, renal nervous activity and peripheral resistances were processed, with the aim of studying the paradoxical behaviour of renal resistance as opposed to peripheral resistances and the increase of sympathetic activity in hypovolemic shock situations using both non-linear models of the renal blood flow and arterial pressure and body fluids. The following conclusions can be made after comparing the results obtained by simulation with data related to animal experimentation models: the model is useful for its use in the analysis of nervous activity, resistance and renal flow in hypovolemic shock situations in humans and the control structure it puts forward can explain the paradoxical behaviour of renal vascular resistance as opposed to the peripheral resistances and the increase in the renal nervous activity in the aforementioned circumstances.

Blood Pressure↗
PubMed1990

Pulmonary capillary dynamics and fluid distribution after burn and inhalation injury.

A non-linear macroscopic mathematical model is described for the simulation of the different mechanisms that regulate the pulmonary capillary dynamics in patients with thermal injury. The techniques used in the construction of the model are those of 'system's dynamics'. This model has been incorporated into a patient simulator, which makes it possible to analyse the fluid and protein exchanges in a burn patient. The regulating mechanisms involved are: the pulmonary circulation, the fluid and protein transfer between the plasma and the interstitial space at the pulmonary capillary level, and the pulmonary lymphatic system. As a result of the sensitivity analyses of the model we propose that, for the simulation of the effects of an inhalation injury at the pulmonary capillary level, the parameters to be altered will be the pulmonary capillary permeability coefficient for proteins and the pulmonary capillary surface damaged by the injury. To verify the validity and utility of the model, the clinical progress of a series of burn patients with lung injuries has been compared with the results obtained using simulation.

Burns↗