The preference for one limb in rats--the result of learning in an experiment or an individual characteristic?

The problem was studied whether an initial preference of one limb exists in rats connected with interhemispheric asymmetry or it appears during the procedure of testing (the first successful movement of one limb becomes consolidated). The work consisted in obtaining experimental retrograde amnesia after preliminary determination of the preferred limb and in the following testing of the preference after a definite time interval. In this case the trace of preceding learning must not influence the following choice of the limb. It is shown that the preference in rats is not a result of accidental learning in the experiment but initially exists before testing procedure. Retaining of memory trace for a long time (2-4 weeks) is also shown even after a very short learning (one-three successful movements).     

Chronic extracellular recording of fetal medullary neuronal activity

A technique for chronic extracellular recording of neuronal activity in the medullary region of fetal sheep during different sleep states is described. Of 51 recorded neurones, 54% were associated with respiration, blood pressure changes, or muscle electromyograms, and 46% were nonspecific. During apnea (nonrapid-eye-movement sleep) both inspiratory and expiratory neurons had random intermittent activity. Thus apnea is not associated with tonic expiratory neuronal activity.     

Fluorescent probe--a cholesterol analog: localization in plasma lipoproteins and in model lipid particles

The absorption spectrum of fluorescent probe--a cholesterol analog cholesta-5,7, 9(11)-trien-3 beta-ol has a vibrational structure with the maximum 326 nm. Its fluorescence spectra maximum is 370 nm. The localization of the probe in lipoproteins of high, low and very low density and in lipid spheres is studied. There are measured the areas, which occupied one molecule of cholesterol and phosphatidyl choline on the surface of lipid spheres and the radius of the lipid spheres. The localization of the probe in lipoproteins and lipid spheres is determined. The areas which occupied one molecule of phosphatidyl choline on the surface of lipid sphere is equal to the same area in mono- and bilayers. Cholesterol has the same condensing action on phosphatidyl choline in lipid spheres as in mono- and bilayers. All the probe molecules are localized on the surface of lipid spheres and lipoproteins and the B-ring of the molecule is immersed on 1.3 +/- 0.2 nm relative to polar groups. The hydroxyl group of cholesterol is arranged near the carbonyl group of phospholipid and the formation of the H-bond between these groups is possible.