Functionalization of hydrocolloids: principal component analysis applied to the study of correlations between parameters describing the consistency of hydrogels.

This work was part of a pure research project on the functionalization of three families of hydrocolloids: cellulose derivatives, carrageenates, and alginates. Principal component analysis (PCA), a powerful statistical method, was used to demonstrate the relations existing among these different parameters that describe the consistency of hydrogels and their spreadability. This approach therefore provides a basis for modeling hydrogel consistency. PCA also afforded a classification of hydrogels that demonstrated the remarkable adhesiveness of very stiff gels based on cellulose derivatives and sodium or potassium alginates. The corresponding semi-fluid gels and all the gels based on carrageenates and mixed sodium-calcium alginates, whatever their spreadability, were found to be very poorly adhesive. Generalized to all the many colloids currently marketed, this approach can be used to set up a databank for the formulation of mucoadhesive excipients.

Comparative texturometric analysis of hydrogels based on cellulose derivatives, carraghenates, and alginates: evaluation of adhesiveness.

This paper reports a texturometric study of hydrogels based on cellulose derivatives, carraghenates (with or without Na+ or K+), and alginates (associated or not with Ca++). The stiffness, elasticity, and cohesiveness are evaluated and the influence of the nature and the concentration of gelling agent on the adhesiveness, an indicator of bioadhesion, is discussed. The highest adhesiveness values are found among the semi-stiff gels, particularly with those based on either sodium or potassium alginate, or cellulose derivatives. The least satisfactory results are obtained with the formulations associating carraghenates and Na+ or K+.

[Post-radiotherapy cutaneous neuro-endocrine carcinoma]. / Carcinome neuro-endocrine cutané en zone irradiée.

INTRODUCTION: Merkel cell carcinoma or cutaneous neuroendocrine carcinoma is an uncommon severe disease. The carcinogenic effect of ionizing radiations has been suspected in exceptional observations. We report the sixth case of Merkel cell neuroendocrine carcinoma in a patient with prior radiotherapy. CASE REPORT: An 86-year-old man underwent radiotherapy for a basal cell carcinoma of the tip of the nose and developed a highly aggressive Merkel cell carcinoma at the same location 6 years later. DISCUSSION: The development of Merkel cell carcinoma on irradiated tissue accounts for 2.6 p. 100 of the 227 publications where dermatological history was reported. This percentage may be underestimated. The similar localizations of the irradiated zone and the site of cancer development 5 years later suggest that the Merkell cell carcinoma may be a radio-induced tumor. The delay may vary from 5 to 47 years. The similarity of the carcinogenic factors involved in Merkel cell carcinoma and squamous cell or basal cell carcinomas (ultraviolet, ionizing irradiation) and the frequent association of different types favor an epidermal origin for Merkel cell carcinoma. In clinical practice, past history of radiotherapy in an area where Merkell cell carcinoma develops indicates that therapeutic management must exclude post-operative radiotherapy.