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Notes: The topical application to human skin of a 1:1 aqueous solution of ammonium hydroxide in a well drilled into a plastic block will provoke an infra-epidermal blister in an average time of about 13 min.The blister roof can be used for physico-chemical analyses of the horny layer while the base is suitable for studies of wound healing, bacterial infections, etc.The minimal blistering time (MBT) increases directly as the number of cell layers of the stratum corneum and ranges from 3 to 57 min in different regions and persons. The intensity of the dermatitis provoked by a 24 h exposure to sodium lauryl sulphate is strongly correlated with the MBT. The latter is therefore a reliable measure of cutaneous irritability.The blisters are virtually painless. The inflammatory reaction clinically and histologically is slight. Healing is rapid without scarring.

Notes: For accurate and reliable EEG recording. electrode resistances must be kept relatively low and constant. To ensure that these conditions are met, a fixing agent, collodian, is usually used to fix the electrodes firmly to the scalp. Collodian, however, produces many unwanted side effects. A “double-cllar” method of electrode placement is described whereby electrodes may be firmly fixed to the scalp without the use of collodian. This technique is both faster and less troublesome than the use of collodian. Using this technique, electrode resistances at vertex and occiput were well below generally acceptable criteria (averaging under 5000 ohms) and there was no significant increase in resistance at either placement following nearly 2 hrs of continuous EEG recordings. It is concluded that, under certain laboratory conditions, the “double-collar” method of electrode preparation and placement is superior to the use of collodian.

Notes: A procedure has been designed (the chamber-scarification test), which possesses greatly increased sensitivity for assessing the irritancy of topically applied materials. A forearm test site is criss-cross scarified by drawing a 30-gauge needle over the skin with just enough pressure to cleave the epidermis without drawing blood. The test agent is applied in an aluminum chamber once daily for 3 days.The advantages of the method over conventional patch testing are: enhanced capacity to measure mild irritants, reduced time (3 days versus 10 to 21 days), less effort, less cost, less discombort for the volunteers and greater reproducibility.

Notes: For assessing skin reactions in irritants and allergens, chambers which confine the test substance to the site of application are much superior to conventional patch tests. Because the concentration and volume do not change appreciably, the method allows for quantification and yields more reproducible results.A new aluminum chamber has been designed which is more useful than its predecessor, the Finn chamber, mainly because of its increased capacity. Data are given to show that the intensity of irritant and allergic reactions is dependent on the quantities applied.

Notes: Summary By means of a lengthy method of continuous cytologic and histologic study, an experimentally produced reactive process in lymphnodes was analyzed. This analysis was made both qualitatively and quantitatively, in an attempt to clarify the mechanisms of reaction and the underlying cellular alterations producing this change. The reaction begins in the medullary cords and gradually spreads to the cortex. New cells are formed. This cytopoesis, considered “accidental”, quantitatively exceeds the physiologic process, and depends upon stimulation of the reticulo-cellular system. The cells of this “accidental” cytopoesis are characteristically very variable in form. A constant transition of forms occurs. This dynamic cell, as it is seen in the reactive formation of new cells, can be observed only by continuous study. The small reticulum cell proves to be a particularly adaptable and plastic element, and is the real basis of the reaction. Large and small lymphocytes, as well as transitional forms and plasma cells are derived from it. For these cell types, no other “parent” cells can be postulated. The reactive formation of new cells reaches its maximum between the 20th and 26th day, and then shows a steady decrease in spite of further “stimulation” of the lymphnode. During the course of the reaction numerous quantitative interrelationsships among the individual groups of cells can be found. The conclusions gained from the cellular preparations are substantiated by means of histological controls and supplemented by a few important other points. The observation of the cytologic and histologic cellular movements, of the quantitative interrelationships among the individual groups of cells, and of the continuous change in form of the cells during the reaction are made the basis for the survey of the cytopoesis in lymphatic tissue. The large reticulum cell is considered to be the “parent” cell for the accidental formation of cells in reactive processes. The cellular supply is maintained probably by means of hemihomo-hemiheteroplastic reproduction. The small reticulum cell with the highest mitotic rate apparently reproduces itself in the homoplastic way. Those cells derived from it are responsible for the polymorphous picture of cells in the reactive processes of the lymphatic tissue. The theories of determinate developmental processes and the retrograde transformation of cells in lymphatic tissues are rejected. Both the bud-like formations on the nuclei of the small reticulum cells, and the appearance of dwarfed nuclei, in conjunction with the quantitative relation to the number of binucleated reticulum cells, suggest a mechanism of growth which shows similarity to the karyonomia or meroamitosis.

Notes: LIBROS NUEVOS: RESEÑAS

Notes: LIBROS NUEVOS: RESEÑAS