Use of bioelectrical impedance analysis to estimate body fluid compartments after acute variations of the body hydration level.

Physiological measurements including body mass, plasma osmolality, natremia, plasma volume measured by Evans Blue dilution, and total body water (TBW) and extracellular water (ECW) volumes estimated by bioelectrical impedance analysis (BIA) were recorded in eight healthy young Caucasian subjects before and after acute variations of their body hydration state on four separate occasions: 1) euhydration or control trial (C); 2) heat-induced dehydration of 2.8% body mass (D); 3) exercise-induced dehydration of 2.8% body mass (E); and 4) glycerol-hyperhydration (H). Heart rate, rectal and mean skin temperatures were also recorded throughout the experiment. The main result of the study is that BIA only half predicted the body water loss after exercise, although conditions were standardized (electrode placement, side of the body, limb position, posture, and ambient temperature). Differences in body temperatures cannot explain such an unexpected result, nor did the study of plasma osmolality and sodium concentration. If BIA appears to adequately predict changes in TBW after heat-induced dehydration and glycerol hyperhydration, further studies including measures of TBW and ECW by dilution tracer methods would be necessary to establish the validity of using the BIA method to measure such changes and to interpret ECW variations.

[The effect of hypervitaminosis D3 on the bones of the chicken. 2. Electron microscopic studies]. / Untersuchungen über die Auswirkungen einer hypervitaminose D3 im Knochen des Huhnes.

In an experiment of 36 days duration 46 one-day-old chicks were divided into 5 groups and fed with different concentrations of vitamin D3. The animals of the group which lacked vitamin D3, showed the typical rachitic lesions. After a 15 days lack of vitamin D3 the chicks of another group were treated with standard food (2000 I.U. vitamin D3/kg food) with the consequence of an approximation of the analyzed parameters to those of the control group within 3 weeks. When fed with 60,000 I.U. of vitamin D3 after a 15 days lack of this vitamin, the animals showed an over-hasty healing process, ending up with signs of intoxication which were even more conspicuous when fed with 120,000 I.U. of vitamin D3. Besides an increasing calcification of osteoblasts and endothelial cell membranes as well as a degeneration of osteoblasts, a clear increase of eosinophilic granulocytes could be noticed. In all groups free erythrocytes within the ground substance were found. There was no evidence of necroses of osteocytes or of bone.

The time-course of rod-cone interaction.

The time-course of rod-cone interaction (change of scotopic sensitivity caused by photopic background stimulation) was measured in the presence of briskly exchanged, scotopically matched, 490- and 630-nm background disks. In all conditions, interaction rose and fell quickly with changes of photopic stimulation. When the background was a small 0.6 degree-diameter disk, photopic stimulation produced relatively constant maintained interaction of about 0.6 log units. When the background was a large 7.8 degree-dia disk, photopic stimulation produced larger initial (0.6-1.0 log unit) than maintained (0.2 log unit) interaction. When a 0.6 degree by 7.8 degree annulus was used instead of a background, photopic stimulation produced substantial interaction only at offset, a transitory interaction. Thus, the spatial dependence of transitory interactions differs from that of maintained interaction: transitory interactions can be large even when maintained interaction is small or absent. The results are discussed in terms of a simple center-surround model of rod-cone interaction that unifies both maintained and transient interaction.

The coordination of eye and head movements during early infancy: a selective review.

A review of work dealing with the human infant's ability to use coordinated eye and head movements is presented. Primary emphasis is given to performance under two conditions: (1) the shifting of fixation to a visual stimulus in the periphery; and (2) the use of eye movements to maintain fixation by compensating for the effects of externally imposed head movements.

[Effect of vitamin D3 on the formation of proteoglycans and tissue calcification]. / Wirkung von Vitamin D3 auf die Bildung von Proteoglykanen und die Gewebeverkalkung.

Nonspecific calcinosis engendered by vitamin D3 is associated with extraosseous calcium deposits, in connection with which proteoglycans (PG) can be observed. After administration of vitamin D3 tissue samples from cardiac muscle and aorta of rats were taken and traced ultrahistochemically by means of the acriflavin-phosphotungstic acid contrast-method. The calcification began first with an increase in PG in the cell membranes of the sarcolemma, in the ground substance, and in the capillaries of the interstice. Subsequently circularly formed concentric layers of calcium encrustations appear in the above-mentioned locations. Large amounts of PG were also observed prior to the formation of crystalline fascicular calcium deposits in the ground substance and in the elastic fibers of the media of the aorta. This process began at the outer edges of the media and continued towards their interior, resulting in a loosening of the bond between the elastic fibers and the sarcoplasmic continuations of the smooth muscle cells. The extraosseous calcification resulting after the administration of vitamin D3 can therefore be considered not only as a result of hypercalcemia, but also as a result of stimulation of the production of ground substance through vitamin D3. This form of calcification represents a characteristic pathophysiological process which is differentiated from the dystrophic form in that it begins without previous cell damage.

Evoked potentials during recovery from blindness recorded serially from an infant and his normally sighted twin.

Visual evoked potentials (VEPs) elicited by diffuse field flashes wee recorded from a behaviourally blind infant with his twin as control. The patient was tested at ages 4, 5, 6, 8, 10 and 15 months. In spite of his behavioural blindness, clear VEPs were recorded from the patient at age 4 months, although the wave form was monophasic as contrasted with the multiphasic wave form recorded from his twin at the same age. Latency to first deflection and to first peak were considerably longer for the patient. The patient's VEP wave forM grew progressively more complex with age, paralleling recovery of useful vision. However, the VEP development anticipated behavioural recovery.

Astigmatism and acuity in two primate infants.

The development of grating acuity was followed in two astigmatic primate infants, one a human being and one a pigtail macaque monkey. Both infants showed variations of acuity with grating orientation, predictable from the orientation and type of astigmatism present. Optical correction of the human infant during testing virtually eliminated the variation of acuity with orientation, suggesting that a neurally based meridional amblyopia had not yet been established.