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Biomedical subjects

J L Parra

Publications and source records attributed to J L Parra.

47 records · Page 3Linked to original sources
PubMedDate not supplied

Liposomes as alternative vehicles for sun filter formulations.

The aim of our study was to determine the influence of several types of liposomes with a different lipid composition on the percutaneous absorption of one conventional sun filter with a lipophilic character (ethyl hexyl methoxycinnamate) using both in vitro and in vivo methodologies. Three different liposomes were prepared with unsaturated and saturated phosphatidylcholine (PC, HPC), and with a wool lipid mixture (IWL) with a composition similar to that of the stratum corneum lipids. Results showed that the liquid crystalline state associated with PC liposomes plays a key role in enhancing skin penetration. when liposomes with a composition and structural organization similar to that of the stratum corneum lipids (HPC and IWL) are used, the skin penetration is retarded, suggesting a certain reinforcement of the stratum corneum barrier. These two types of liposomes could be regarded as alternatives to conventional oil/water emulsions in the formulations of lipidic sun filters. Finally, an acceptable correlation was obtained using both in vitro and in vivo methodologies to evaluate the corresponding skin absorption profile.

Animals↗
PubMedDate not supplied

Effect of internal wool lipid liposomes on skin repair.

Intercellular lipids of the stratum corneum (SC) play a crucial role in keeping an optimal skin barrier function and in regulating the water-holding capacity. Recently, the internal lipids have been extracted from wool fibre. This lipid extract has a composition similar to that of the SC lipids. Two parameters were used to test the effect of topically applied internal wool lipids (IWL), structured as liposomes, on the water barrier functions of disturbed and intact skin: transepidermal water loss and skin capacitance. Liposomes made up of lipids that simulate the composition of the SC were also applied for comparison. The single application of the IWL liposomes on disturbed skin resulted in an accelerated recovery of water barrier functions. Daily application of these liposomes on intact skin for 5 days reinforced the skin barrier and increased the water-holding capacity. The repairing effect of the IWL enhances their suitability in the treatment, prevention and care of skin.

Adult↗
PubMedDate not supplied

Structural modifications in the stratum corneum by effect of different solubilizing agents: a study based on high-resolution low-temperature scanning electron microscopy.

The action of different solubilizing agents (chloroform-methanol mixtures and the nonionic surfactant octyl glucoside, OG) on the structural organization of the stratum corneum (SC) was investigated by means of the double-layer high-resolution low-temperature scanning electron microscopy technique. Chloroform-methanol mixtures were able to remove mainly the lipid without a significant loss of cohesion in the SC tissue. However, OG treatment caused a partial disaggregation of the corneocytes and their envelopes and, at a macroscopic level, a loss of cohesion in the whole SC tissue. As for lipid domains, after OG treatment the formation of rough structures was detected, probably associated with the disorder in the lipid lamellae. The formation of these new structures could be attributable to the interaction of the lipids with the proteins liberated from the corneocytes. Hence, a direct correlation may be established between the preservation of the structure of the corneocytes and the corneocyte envelope and the cohesion of the whole SC tissue.

Animals↗
PubMedDate not supplied

The effect of liposomes on skin barrier structure.

The present work deals with the 'in vivo' stripping technique to evaluate the percutaneous absorption of sodium fluorescein (NaFl) vehiculized in two different liposome preparations formed by phosphatidylcholine (PC) and lipids mimicking the stratum corneum (SC; ceramides, cholesterol, palmitic acid and cholesteryl sulphate), respectively. Furthermore, the possible effect of these vesicles on the SC lipid alkyl chain conformational order were evaluated at different depths of SC by non-invasive biophysical techniques: Corneometer, Tewameter and especially ATR-FTIR. The results of NaFl percutaneous absorption indicate the highest penetration in the case of incorporation in PC liposomes, which could be related to the increase in SC lipid disorder detected by ATR-FTIR, i.e. a decrease in skin barrier function. On the other hand, SC lipid liposomes have been shown to have a higher affinity for SC owing to the high amount of NaFl found in this layer, suggesting a greater reservoir capacity of SC when similar lipid composition formulation is applied. A lipid order increase is observed by infrared spectroscopy, when these types of liposomes are topically applied, resulting in a strong barrier effect. These results could be useful in designing specific liposomal topical applications.

Adult↗
PubMedDate not supplied

EEMCO guidance for the in vivo assessment of skin surface pH.

The pH of the skin follows a sharp gradient across the stratum corneum (SC), which is suspected to play an important role in controlling the enzymatic activities involved in cellular metabolism and renewal. This gradient is maintained by several systems, such as sweat and sebum secretion and degradation as well as cellular metabolism. At the surface of the skin, what is measured is in fact an apparent skin pH due to extracted material from the SC diffusing into water applied at the surface. pH values recorded at the surface of a semi hydrophobic milieu such as the SC should be interpreted with great caution because it is obvious that hydrogen ions are not in a pure solution at the surface of the skin. For a correct measurement of skin surface pH, it is recommended to follow all practical operating conditions. Care must be taken in identifying the skin site, healthy controls (age, gender, skin type), the time of day of the measurement and the environmental conditions. Also, subjects should receive precise instructions before the test, mainly in terms of hygiene procedure or use of topical products. The interpretation of data should not overlook the fact that even small differences in pH may reflect significant modifications at the molecular level. Although it is usually agreed that the pH of the skin surface may influence the cutaneous microflora, much remains to be learnt about the role of the acid mantle of the skin with regard to defensins and other protective mechanisms.

Epidermis↗
PubMedDate not supplied

[Neoplasm invasion of the renal vein by transitional cell carcinoma of the kidney pelvis].

We present two cases of renal pelvis transitional cell carcinoma with invasion of the renal vein. We emphasize the importance of preoperative diagnosis and review the diagnostic methods available for revealing this uncommon eventuality. Owing to the prognostic importance and subsequent surgical treatment, this possibility should be evaluated in those cases of renal pelvis transitional cell carcinoma with extensive parenchymatous invasion or in those cases in which kidney function cancellation occurs in the excretory urograph.

Aged↗
PubMedDate not supplied

[Giant urethral lithiasis].

We present a case of giant urethral lithiasis, housed in the penile urethra. Owing to the scant incidence of this pathology and its rarity, as well as the small number of bibliographic references found, we believe it of interest to offer this fresh case.

Aged↗