Development of an in vitro model for premature neonatal skin: biophysical characterization using transepidermal water loss.

The objective was to develop an in vitro model for the developing skin of the premature neonate. Barriers of different levels of efficiency were produced by differentially tape-stripping the stratum corneum (SC) from the skin of excised porcine ears, and were characterized by measurements of transepidermal water loss (TEWL). In this way, it was possible to express the recorded TEWL as a function of percentage SC thickness (F) generating the following relationship: TEWL = 2.7 + 41.exp [- 0.028.F]. These data were then compared to previously published in vivo measurements of TEWL obtained from a population of premature neonates at various post-conceptional ages (PCA). The latter conformed to a remarkably parallel relationship to that found in vitro with the porcine skin model, namely TEWL = 3.3 + 41.exp [-0.026.(PCA-160)]. It can be suggested, therefore, that the empirically adjusted PCA (i.e., PCA-160) correlates closely with the developing thickness of the neonate's SC. The corollary is that porcine skin, in vitro, tape-stripped to a particular level, can provide a barrier corresponding to a specific degree of neonate maturation and can serve, hence, as a useful tool with which to explore whether transdermal drug delivery in this unique patient population may be beneficial.

Biophysical study of porcine ear skin in vitro and its comparison to human skin in vivo.

The goal of this work was to establish, using biophysical characterization, that porcine ear skin in vitro is a valid model for its human counterpart. Specifically, stratum corneum (SC) barrier function was evaluated during its progressive removal by adhesive tape-stripping using the techniques of transepidermal water loss (TEWL) and impedance spectroscopy. TEWL increased slowly at first and then more rapidly with the degree of SC impairment. In contrast, low-frequency skin impedance declined exponentially as a function of progressive SC removal. The methods provide complementary and correlated information about SC barrier function. Biophysical parameters, including the diffusivity and permeability coefficient of water across the SC, and the thickness of the barrier were determined from the TEWL data using Fick's first law of diffusion. Furthermore, an ionic partition coefficient-mobility product was estimated from the skin impedance measurements. Comparison of the results with those previously reported for human skin in vivo strongly supports the validity of the porcine membrane as an in vitro model.

Reverse iontophoretic monitoring in premature neonates: feasibility and potential.

Premature neonates represent a fragile patient population, often subjected to intensive clinical care and multiple drug therapy, which must be monitored carefully and continuously. The difficult and painful nature of repetitive blood sampling, particularly in this population, has provided considerable impetus for the development of noninvasive methods for monitoring blood analytes. Reverse iontophoresis, a relatively new technology already used for the transdermal monitoring of blood glucose levels in adults, may be particularly well-suited to exploit the unique properties of preterm neonatal skin. The underdevelopment of the premature infant's epidermis, and more specifically the stratum corneum (SC), results in an increased permeability to molecular transport. In this study, we have investigated the feasibility of reverse iontophoretic monitoring of two model drugs, caffeine and theophylline, which are often administered to premature neonates. To this purpose, tape-stripped porcine skin in vitro, which has been previously demonstrated to be an excellent model for premature neonatal skin, was employed. Reverse iontophoresis across intact membranes enabled a quantifiable extraction of both drugs predominantly at the cathode compartment. The mechanism of extraction of these essentially neutral drugs (caffeine and theophylline being uncharged at pH 7.4) was electroosmosis. However, when the SC was removed by progressive tape-stripping, the amounts of drugs extracted by reverse iontophoresis were equivalent to those obtained by passive diffusion. In these circumstances, therefore, the benefit and usefulness of the applied electric field had been lost. In summary, the absence of an at least partially functional skin barrier obviates, in the case of neutral molecules, the control (and directional transport) offered by iontophoresis; in contrast, for ionized species, where the principal iontophoretic transport mechanism is electromigration, the approach should be valid.

Study of the interactions between copper, cadmium, and ferbam using the protozoan Colpidium campylum bioassay.

The toxicity of a copper-cadmium-ferbam mixture has been studied using the protozoan Colpidium campylum bioassay. The assays were designed according to the factorial experiments method, associated with multiple regression analysis. The results show that, at the concentrations tested, a synergy occurs between cadmium and ferbam, whereas the copper is only oligodynamic.

[Peritoneal tuberculosis in adults. Study of 207 cases]. / La tuberculose péritonéale chez l'adulte. Etude de 207 cas.

The authors report their experience about 207 cases of peritoneal tuberculosis in the adult, diagnosed and treated at the University Hospital Ibn Rochd in Casablanca, between january 1976 and october 1986. It concerned 139 women and 68 men--mean age 29.5 years. The most frequent clinical form was painful and febrile ascites (70% of the cases). The diagnosis was established most of the time by laparoscopy (180 examinations) which disclosed peritoneal granulations in 87% of the cases. Laparoscopy was impossible in 27 cases. Evolution was favorable in all patients except 5: 3 deaths, one relapse and one evolution to a fibro-adhesive form. During the long-term evolution in 50 patients (follow-up exceeding two years): one patient developed an occlusion and 7 had gynecological complications.