Biomedical subjects
Publications and source records attributed to A Verain.
To optimize a pharmaceutical formulation, one has to take into account physicochemical, biopharmaceutical, therapeutical and technological properties of the active principle. These properties are investigated in the PREFORMULATION phase. The authors envisage dosage form (capsule) of magnesium and describe two aspects of the active principle: therapeutic and biopharmaceutic.
The in vitro properties of twelve brands of paracetamol (nine tablets and three capsules), commercialized in France, are studied. Among the brands tested (tablets), Latepyrine and Gynospasmine are characterized by faster and Panasorb by slower dissolution rate. Total time of dissolution varies between 7 and 60 min. In some brands, paracetamol is liberated from the surface of the disintegrated particles and in others the active principle is released by progressive erosion. The presence of a surface active agent enhances liquid penetration in the case of capsules.
The authors attempt to explain differences observed in dissolution rate of twelve different brands of paracetamol (nine tablets and three capsules) in terms of pore structure and tensile strength; the pore structure of both tablets and capsules is investigated by mercury porosimetry. Brands (tablets) which liberate paracetamol rapidly are characterized by a higher porosity value. Higher mean pore diameter signifies less t50 and higher porosity. An increase in tensile strength results in an increase in t50 and a decrease in porosity. Porosity alone cannot dictate the dissolution behaviour of capsules.
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In vivo kinetics of radioiodine incorporation have been established for 70 newts, collected from Triturus helveticus Raz. populations where spontaneous neoteny occurs. Fifty of these newts which appeared to present four degrees of neoteny (more or less metamorphosed), have been studied. Main results obtained were: 1) The intensity of the iodine incorporation varies according to the degree of neoteny. The higher is this one, the lower is the intensity. 2) In general, iodine uptake rates are more or less similar to these of adults, but more often the evolution of the 125I uptake approaches a plateau-curve. From thyroid radioautographies on some animals (17 neotenic and 2 adult newts) for which in vivo iodine kinetics have been examined and on 9 normal larvae in premetamorphosis or in metamorphosis, we have noticed in those neotenic thyroids, a very small number of silver grains on apical vesicles and colloidal lumina when the degree of neoteny is the highest. This number of marked apical vesicles and colloid is more important in the neotenics which have lost some larval characters. Silver grains on colloid droplets indicating thyroid hormone excretion are inexistent in the most larval neotenics, more numerous in most metamorphosed neotenics. But they always are less numerous than in metamorphosing larvae. For a few animals, the fixation curve is very high, probably because of a stimulation of thyroid function, induced by the test and not because of a goitrous tendancy, as radioautographic observation of their thyroid shows. Thyroid function and its relation with the origin of this total and accidental neoteny are discussed.
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The industrial pharmacist, a "pharmaceutical engineer"? The prospect is tempting if only beneficial to drug quality. The Pharmaceutical Engineering comes from Chemical Engineering and Engineer sciences and allows the pharmacist to achieve his aim. We define here the basis of this recent concept, its intervention and interest in the pharmaceutical sciences, more particularly in formulation.
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Explore the source record for details and available documents.
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Certain facts must be clearly understood before any attempt is made to analyse the sensations produced by electrical stimulation of the structures of the middle ear. Firstly, when the current passes from an electrode to the skin or to any polarised structure whatsoever, the point at which the electrode is applied and the skin behave like the two plates of a condenser microphone. Electrical vibrations are transformed into ordinary acoustic resonances which can travel through air or bone. These acoustic resonances are fairly pure in comparison with electrical vibrations, judged by the standards under investigation. If a continuous polarisation potential, which gives better distribution of the electrical charges, is added, the capacity of the microphone is increased and greater purity obtained. Consequently, the quality of sound heard in this way depends not only on the quality of this electro-physiological microphone but also on the quality of the internal ear. The acoustic effect produced in this way is called an electrophonic effect. Stevens, Jones and Flottorp described this. Therefore an internal ear which has lost the ability to hear high-pitched sound cannot hear them by means of this electrophonic effect any more than it can by ordinary auditory stimulation. Stimulation of the skin of the mastoid and of the external auditory meatus can be sensed by means of this electrophonic effect. Next, sensations recorded by means of direct stimulation of the acoustic nerve (DJOURNO and EYRIES) or by implantation of intra-cochlear electrodes (SIMMONS, DOYLE, MICHELSON) were studied. Sounds heard through stimulation of the structures of the middle ear should be analysed in the light of these findings and bearing in mind that very strong stimulation of the promontory or of the auditory meatus always causes an auditory sensation without frequency awareness due to global stimulation of the acoustic nerve (faciaestations appeared when experiments, the results of which are described, were carried out, although there is a possibility of episode vestibular irritation. These stimulations were in fact always very weak. Our results were analysed in relation to the quality of the internal ear: completely deaf, serious condition, internal ear normal. The impulses were provided by a direct current battery: these were square with a frequency of between 50 and 900 Hertz, a tension of 0 to 8 volts per 1/10 volt. The electrode was bipolar. The experiments were monitored from time to time by oscilloscope. Mention should be made of the technical and psychological precautions to be observed when stimulation of this kind is carried out if results of any value are to be obtained: a relaxed, sensible patient with whom one can communicate easily. Not much can be gathered from a person deaf in both ears. With the ear opened, the posterior part of the tympanum pulled forward, stimulation of the round window always results in production of a sound at a threshold of 0.5 to 2.5 volts.