Compositional differences between soil humic acids extracted by various methods as evidenced by photosensitizing and electrophoretic properties.

Humic acids (HAs) were isolated from Elliott soil provided by the International Humic Substances Society (1BS102M) by three commonly used methods: (i) 0.1M NaOH (EI-HA), (ii) neutral 0.1M Na(4)P(2)O(7) (L-HA) and subsequent 0.1M NaOH (S-HA), and (iii) 0.1M NaOH+0.1M Na(4)P(2)O(7) (NP-HA). The objective was to evaluate the impact of these extractants on the photosensitizing properties of the isolated HAs. HAs were analyzed for their elemental composition, functional acid groups content, absorption and emission properties, electrophoretic characteristics and ability to produce singlet oxygen using furfuryl alcohol (FFA) as a scavenger. L-HA was slightly more aromatic and oxygenated than the other HAs and contained a higher portion of long-wavelength fluorophores and macromolecules showing low molecular size (MS) and high electrophoretic mobility. L-HA also gave a rate of FFA photooxygenation between 1.25- and 1.6-fold higher than the other HAs. This suggests that the free humic macromolecules ionized at pH 7 and/or weakly bounded on mineral surfaces via cation bridges are of relatively low MS and contribute significantly to the photosensitizing and long-wavelength emitting properties. Differences among the other HAs were more subtle, but the parallel evolution of the reactivity and electrophoretic characteristics was observed. Photochemical and electrophoretic measurements seem to be sensitive indicators to evaluate differences among the extraction procedures of HAs.

Key role of the low molecular size fraction of soil humic acids for fluorescence and photoinductive activity.

The IHSS soil humic acid (HA) standard and two HAs from soils of very different origin (Chernozem and Ranker) were fractionated by tandem size-exclusion chromatography-polyacrylamide gel electrophoresis. From each HA, three fractions with different molecular sizes (MSs) and electrophoretic mobilities were obtained and investigated for their fluorescence properties and abilityto photoinduce the transformation of 2,4,6-trimethylphenol and herbicide fenuron. Regardless of the source of the HA, the two high MS fractions were found to be very weakly fluorescent. They photoinduced the degradations of fenuron and 2,4,6-trimethylphenol less efficiently than the bulk HA (10-50-fold and 1.4-5.3-fold, respectively). In contrast, the low MS fraction was proved to be fluorescent and to photoinduce the transformation of probes as least as efficiently than the bulk HA. These results show that (i) most of fluorophores and a great part of photoinductive chromophores are located in the low MS fractions of soil HAs and (ii) this distribution of photochemically active constituents may be characteristic across broad soil types.

Performance of field-dependent and field-independent subjects on a rod and frame discrimination task.

This study assessed the relative ability of 7 field-independent and 8 field-dependent persons to detect changes in rod and frame positions. Each subject received 90 discrimination trials. Each trial consisted of the standard stimulus (both rod and frame tilted 15 degrees to the subject's left) followed by a comparison stimulus (rod or frame differing from the standard by 3 degrees, 6 degrees, 9 degrees, or 12 degrees). Results supported the hypothesized superiority of field-independent persons in detecting frame changes; however, detections of rod changes did not differentiate field-dependent from field-independent persons.

Field dependence in the institutionalized elderly.

The institutional-inducement hypothesis of field dependence regression in the elderly was assessed by administering the Children's Embedded Figures Test (CEFT) to a group of elderly upon admission to a nursing home and to a group of community-living elderly. Both groups were retested four months later. The institutionalized group exhibited significantly lower CEFT scores on initial testing than the community-living group. In addition, the CEFT scores for the institutionalized group declined significantly from pretest to posttest. The results suggested that greater field dependence in the institutionalized elderly may be due to pre-institutional dependence regression that continues after institutionalization. Additional measures of mental status and activity levels were also lower in the institutionalized group upon admission supporting a pre-institutional generalized regression effect.

[Adapto-electroretinographic study of regeneration of the visual pigments in the fauve de Bourgogne and albino rabbit after photobleaching with monochromatic light]. / Etude adapto-électrorétinographique de la régénération des pigments visuels chez les lapins fauve de Bourgogne et albinos après éblouissement en lumière monochromatique.

Kinetics of rod pigment regeneration were studied in vivo in Fauve de Bourgogne and Albino rabbits by adapto-electroretinography (AERG). Electroretinography in the rabbit using polychromatic flashes affords the means to dissociate the response of the cones (a-wave, b1-wave: photopic function), from that of the rods (b2-wave scotopic function). After photobeachting, electroretinograms were recorded at two minutes' intervals during dark adaptation of one hour duration. Variations of b2/b1 with time of dark adaptation provide an adapto-electroretinogram giving relative measurements of rod pigment concentration at various stages of regeneration. In the present study, photobleaching was provoked by monochromatic light (at 405, 436 and 546 nm) actinometrically controlled. Studies were conducted in two Fauve de Bourgogne and two Albino rabbits. The effect of four doses, varying from 4.10(17) photon.cm-2 to 1.10(19) photon.cm-2, was measured at each wavelength on the AERG in the four rabbits. First order kinetics for rod pigment regeneration were observed, mainly at 546 nm and at high dose levels: overall regeneration rate is apparently controlled by the isomerization step. For Fauve de Bourgogne and Albino rabbits, the regeneration rate depends on the bleaching wavelength and on the dose. At high dose levels and for long wavelengths, delayed recoveries are observed in the Fauve de Bourgogne animals. However, durations of delays are shorter with monochromatic light experiments than with polychromatic light bleaching, at the same dose. Differences of ocular media transmission may be responsible for a faster regeneration process at shorter than at longer wavelengths.

Two-point tactual discrimination on the back: a signal-detection approach.

This investigation determined if subthreshold two-point aesthesiometer separations could be discriminated from one-point on the back, using a fixed-based matching signal detection technique. Subjects reliably discriminated two-point separations as small as 2 mm from one point on the back. In addition, the back appears to be more sensitive to discriminating two points from one point than the dorsal forearm.

Two-point tactual discrimination: a signal detection approach.

This investigation determined if subthreshold two-point aesthesiometer separations could be discriminated from one-point on the dorsal forearm. A fixed-based matching signal-detection technique was employed. The results indicated that subjects can reliably discriminate two-point separations as small as 2 mm when compared to one point.

Early social isolation of the domestic cat: responses to separation from social and nonsocial rearing stimuli.

The relative contributions of social-rearing stimuli (a mother and/or a littermate) and nonsocial-rearing stimuli (a brooder) to the formation and decline of infant kitten attachments were assessed by counting the frequency of distress cries produced by separation from the following rearing conditions: (1) mother-littermate; (2) mother-only; (3) brooder-littermate; and (4) brooder-only. Four male and 4 female kittens were reared in each condition. Each kitten was separated from its rearing condition once a week, from 2 until 5 weeks of age, and placed in open field for 15 min. The frequency of distress cries in both littermate-reared groups did not significantly differ throughout the experiment. The frequency was consistently high until 5 weeks of age when distress cries were significantly reduced. The frequency of distress cries consistently increased in the mother-only-reared kittens with repeated separations, but consistently decreased in the brooder-only-reared kittens. The results were interpreted as being commensurate with the social conditions at the time of separation.

The effects of social isolation on the behavior of juvenile domestic cats.

The effects of social isolation on the behavior of juvenile domestic cats were assessed by rearing 4 male and 4 female infant kittens in each of the following rearing conditions: (1) mother-littermate; (2) mother-only; (3) brooder-littermate; and (4) brooder-only. They were then tested twice a week individually and twice a week socially from 2 to 6 1/2 months of age in a playroom, utilizing multiple categories of behavior. The mother-only-reared juveniles were hyperactive in both object play (when tested individually) and social play. The brooder-only-reared kittens displayed enhanced socially directed behavior and were generally hypergregarious, whereas the brooder-littermate-reared kittens displayed retarded social behavior. Observations indicated that littermate-deprived kittens did not learn social communication skills and that some prolonged separation effects existed for littermate-reared kittens. The results suggest that the determinants of social play are more complex than the determinants of object play.

Physical fitness and Embedded Figures Test performance of elementary school children.

The relationship between physical fitness and field independence was assessed by measuring embedded-figures test performance in the following four groups of children in Grades 4 through 6: (1) 93 boys high in physical fitness, (2) 92 girls high in physical fitness, (3) 67 boys low in physical fitness, and (4) 77 girls low in physical fitness. The group of girls low in physical fitness was significantly more field dependent than the other three groups. No significant differences were found among the other three groups. It appears that skill in physical activities may be related to the embedded-figures test performance of girls, but not boys. In fact, girls skilled in physical activities may be as field independent as boys.

[Chlorophyllin in choroïdal angiography on rabbit (author's transl)]. / La chlorophylline en angiographie choroïdienne chez le lapin.

The intravenous injection of sodium chlorophyllin carried out on Rabbit leads to the observation of the choroidal vessels and to a complete series of the angiographic times. This technique allows also the use of classical colour slides films.