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Biomedical subjects

L Guerra

Publications and source records attributed to L Guerra.

At least 127 records · Page 7Linked to original sources
PubMed1991

Characterization of in vitro chemosensitivity of perioperative human ovarian malignancies by adenosine triphosphate chemosensitivity assay.

We report the in vitro chemosensitivity of primary and recurrent human ovarian tumor samples analyzed by adenosine triphosphate chemosensitivity assay. We defined sensitivity as a greater than or equal to 70% decrease in intracellular adenosine triphosphate versus control at 20% of the reported peak plasma concentration per agent tested. Twenty of 21 assays (95.24%) were completed successfully. Single-agent and combined dose-response patterns consisting of decreasing viability with increasing drug concentration were observed consistently. Thirteen primary tumors were assayed, with 15.4% sensitive to cisplatin, 7.7% sensitive to 4-hydroxycyclophosphamide and 53.8% sensitive to their combination. Seven recurrent tumors were assayed, with 14.3% sensitive to cisplatin, 28.6% sensitive to 5-fluorouracil, and 42.9% sensitive to their combination. Dose-response characteristics and in vitro sensitivity rates reported in this article are consistent with reports of patient response in the literature. We conclude that adenosine triphosphate chemosensitivity assay is an efficient and reliable instrument for the in vitro chemosensitivity assessment of human tumors and warrants further clinical investigation.

Adenosine Triphosphate↗
PubMed1991

Melanin content and hydroperoxide metabolism in human melanoma cells.

Human melanoma cells were grown to exponential and stationary phases showing melanin contents of 4.2 +/- 0.3 and 11.3 +/- 0.6 micrograms/10(6) cells, respectively. The cells were separated in four subpopulations by a Percoll gradient; the subpopulation of density 1.07 (g/ml) was the most enriched in pigmented cells and produced 28 and 58% of the cells in exponential and stationary phases, respectively. Melanoma cells had similar superoxide dismutase and glutathione peroxidase activities in exponential and stationary phases. Moreover melanoma cells exhibited a higher catalase activity in the stationary phase: whole homogenate and cytosol activities were 7.0 +/- 0.3 and 10.8 +/- 0.6 U/mg protein, whereas in exponential phase the activities were 4.9 +/- 0.1 and 7.6 +/- 0.3 U/mg protein for whole homogenate and cytosol, respectively. The intracellular H2O2 steady-state concentration was 3.3 +/- 0.2 and 2.1 +/- 0.2 microM H2O2 for exponential and stationary phases, respectively. The spontaneous chemiluminescence of the two culture phases was 169 +/- 27 cps/10(6) cells (exponential) and 78 +/- 24 cps/10(6) cells (stationary). The cytotoxicity of H2O2 generated extracellularly by glucose oxidase was determined after 60 min of exposure. IC50 values for exponential and stationary cell cultures were 0.9 and 2.4 mU/ml of glucose oxidase, respectively. The increased catalase activities in the stationary phase as compared with the exponential phase are consistent with the decreased intracellular H2O2, with the decreased spontaneous chemiluminescence, and with the increased resistance to exogenous H2O2.

Catalase↗
PubMed1991

Alopecia totalis: is treating nonresponder patients useful?

The purpose of this study was to assess the effectiveness of different treatments in patients with alopecia totalis or universalis who did not respond to sensitizing therapies. Twenty-six patients, who had been receiving sensitizing therapy for at least 1 year without any response, were randomly assigned to receive the following treatments: topical 10% cyclosporine in oily solution (eight patients), PUVA (eight patients), and intravenous thymopentin (ten patients). None of them had any acceptable regrowth after at least 6 months of treatment. Our results suggest that other treatments are not useful in patients with 100% hair loss who fail to respond to sensitizing therapies.

Administration, Topical↗
PubMed1991

Euxyl K 400: a new sensitizer in cosmetics.

Euxyl K 400 is a preservative for cosmetics and toiletries containing 2 active ingredients, 1,2-dibromo-2,4-dicyanobutan and 2-phenoxyethanol. 2057 consecutive patients with contact dermatitis were patch tested with Euxyl K 400 2.5% pet. and ethanol. A positive patch test occurred in 24 patients (1.2%). The source of sensitization was traced in 8 patients to their cosmetics. Both leave-on and rinse-off products were responsible. Further patch tests with Euxyl K 400 0.5% pet. and phenoxyethanol 5% pet. were performed in 11 patients. A positive patch test to phenoxyethanol was detected in 1 of them. Only 3 patients showed a mild reaction to Euxyl K 400 0.5%. A provocative use test with a lotion preserved with Euxyl K 400 0.1% was positive in 5 of these 11 patients. Patients with Euxyl K 400 sensitivity showed a high prevalence of positive patch tests to other common ingredients of cosmetics. Since the use of Euxyl K 400 in cosmetic products is rapidly increasing, it should be included in the patch test series for patients with suspected cosmetic allergy.

Adolescent↗
PubMed1991

Comparative efficacy of short-term versus long-term cefoxitin prophylaxis against postoperative infection after radical hysterectomy: a prospective study.

We report the results of a randomized, double-blind comparison of short-term versus long-term cefoxitin prophylaxis against infections after radical abdominal hysterectomy with pelvic and para-aortic lymphadenectomy. Of 113 evaluable patients, 54 (47.8%) received short-term (three doses) and 59 (52.2%) long-term (12 doses) prophylaxis with intravenous cefoxitin (2 g per dose). No significant differences in demographics, preoperative risk factors, or clinical course were detected between the two groups; nor did we detect significant differences in the incidence of surgical-site-related infections (7.4 versus 5.1%, respectively, P = .61), postoperative urinary tract infection, or other febrile morbidity. We conclude that short-term and long-term cefoxitin prophylaxis are equally effective for the prevention of post-operative surgical-site-related infections after radical hysterectomy.

Adult↗
PubMed1990

Cooperative mechanosensitive ion channels in Escherichia coli.

A patch-clamp investigation was carried out on giant Escherichia coli spheroplasts. The membrane exhibited stretch-induced as well as "spontaneous" activity, with similar characteristics, i.e., a large number of conductance values arising from the cooperative behavior of channels in functional clusters. It appears likely that the same molecular species are responsible for both stretch-induced and "spontaneous" current conduction; the channel multiplexes can either respond to membrane stretch or function in an activate state, presumably brought about by the previous application of the mechanical stimulus.

Cell Membrane↗
PubMed1990

Differentiating effect of L-tyrosine on the human melanoma cell line IIB-MEL-J.

IIB-MEL-J is a highly heterogeneous newly established human melanoma cell line. The addition of 3 mM L-tyrosine to the culture medium produced (1) a great decrease in the cell growth rate, (2) a loss of the anchor-age-independent growth capacity, and (3) a change in the morphology of the cells to a fibroblastoid aspect. Coincident with these changes, an increase in subpopulations I and II and a decrease in subpopulations III and IV took place. In view of this evidence we consider that the cells have differentiated. The melanin production was not increased by the L-tyrosine treatment, suggesting that differentiation and melanin expression are not strictly correlated.

Cell Adhesion↗
PubMed1990

Morphological and immunohistochemical study of immediate contact dermatitis of the hands due to foods.

This histological and immunohistochemical study of 6 food handlers affected by immediate contact dermatitis due to foods shows that apparently normal skin of patients with this condition presents several histological and immunohistochemical abnormalities. Skin biopsies of normal hand skin showed focal parakeratosis and moderately dense dermal infiltrates. Immunohistochemistry showed an increased number of Langerhans cells in the epidermis and in the superficial dermis and a mononuclear dermal infiltrate consisting of peripheral T lymphocytes with a CD4/CD8 ratio of 5-6/1. Biopsies of the immediate vesicular reactions induced by foods showed spongiotic vesicles within the epidermis and a moderate to dense mononuclear dermal perivascular infiltrate. The immunohistochemical features were similar to those described in apparently normal skin. The mechanism of this immediate vesicular reaction requires further research. The rapid appearance of the lesions (after 20-30 min) probably excludes an immunological cell-mediated pathogenesis. A non-immunological mechanism due to direct liberation of mediators by foods is more readily conceivable than an immediate immunological type of contact reaction.

Adolescent↗
PubMed1990

Prevalence and sources of sensitization to emulsifiers: a clinical study.

737 patients with suspected cosmetic- or medicament-related contact dermatitis were patch tested with 6 emulsifier agents: triethanolamine, cetyl stearyl alcohol, sorbitan sesquioleate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate, and Amerchol L 101. 39 patients (5.3%) gave 1 or more positive patch tests to emulsifiers. A total of 54 positive reactions were found, 23 of which were clinically relevant, triethanolamine being the most frequent sensitizer. Patients with emulsifier sensitivity generally give a high prevalence of positive patch tests to other common ingredients of topical preparations, such as preservatives or active ingredients. Cosmetics and topical medicaments were detected as the source of sensitization in an equal number of patients. Patch tests with patients' own causative preparations were frequently negative. To avoid overlooking emulsifier sensitivity, it is advisable to test these compounds in patients with contact dermatitis that is possibly due to topical preparations, regardless of whether they have other clinically relevant positive reactions or whether patch tests with their own products are negative.

Administration, Cutaneous↗
PubMed1990

Lung function, hypoxic and hypercapnic ventilatory responses, and respiratory muscle strength in normal subjects taking oral theophylline.

Methylxanthines are known to be respiratory stimulants and are thought by some to augment hypercapnic and hypoxic ventilatory drive and improve respiratory muscle strength. Hypoxic and hypercapnic ventilatory responses were measured in 10 normal subjects before, during, and after administration of theophylline for three and a half days. Pulmonary function, carbon dioxide production, and mouth pressures during maximal static inspiratory and expiratory efforts were also measured. The mean (SD) serum theophylline concentration was 13.8 (3.2) mg/l. Lung volumes and flow rates did not change significantly with theophylline. The mean (SD) values for maximum static inspiratory pressure were 152 (27), 161 (25), and 160 (24) cm H2O, respectively before, during, and after theophylline. Neither these values nor peak expiratory pressure measurements were significantly changed. The slopes of the hypercapnic ventilatory responses were 2.9 (0.9), 3.3 (1.2), and 3.3 (1.4) l/min/mm Hg carbon dioxide tension (PCO2) respectively before, during, and after theophylline administration. The respective values for the slopes of the hypoxic response were -1.4 (0.9), -1.3 (0.8), and -1.1 (0.9) l/min/1% oxyhaemoglobin saturation. None of these values changed significantly with theophylline. Theophylline, however, increased carbon dioxide production (200 to 236 ml/min) and alveolar ventilation (4.7 to 5.7 l/min) significantly, with a concomitant fall of end tidal PCO2 (35.5 to 32.9 mm Hg). It is concluded that in man oral theophylline at therapeutic blood concentrations increases carbon dioxide production and ventilation without changing pulmonary function, respiratory muscle strength, or the hypoxic or hypercapnic ventilatory response significantly.

Adult↗
PubMed1990

The influence of the geometry of the dialyzer and the composition of the dialysate in activating the complement system.

During hemodialysis there is a complex interaction between the patient and the extracorporeal circuit that activates the complement system, among others. To better understand the influence of the dialyzer geometry and the dialysate composition, we compared hollow fiber versus parallel plate dialyzers and acetate versus bicarbonate dialysates and their role in the production of C3a, C4a and C5a. There was no significant difference in the plasmatic levels of these anaphylotoxins and their des-Arg derivates, as measured by RIA, in either dialyzer. The same was true when the dialysate in question had a different composition. We thus concluded that neither the geometric configuration of the dialyzer nor the composition of the dialysate influence their biocompatibility as regards the activation of the complement system, and that the differences that have been described shall have to be explained in another manner or assessed by methods other than those used in this study.

Adult↗
PubMed1990

Long-term incidence of peritonitis in CAPD patients treated by the Y set technique: experience in a single center.

Our experience of peritonitis in 156 patients over an 8-year period represents 186 episodes of peritonitis and 4,964 patient-months of CAPD. The incidence of peritonitis was significantly greater (1 episode every 8.6 patient-months) when the Oreopoulos technique was used and dropped to 1 episode every 43.3 patient-months when the Y set system was used. Of the 109 patients using the Y set system, 88 (80.7%) never had episodes of peritonitis, whereas only 7 (16.7%) of the 42 patients using the Oreopoulos technique were free of peritonitis. For 23 patients shifted from the Oreopoulos to the Y set technique, the incidence of peritonitis dropped from 1/9.8 to 1/35.2 episodes/patient-months.

Bacterial Infections↗