Age related size invariance in perception of illusory and fragmented contours

We investigated invariant perception to sizes of images. Observers were schoolmates of 7-17 years and adults. Two types of stimuli were used: fragmented line drawing of common objects and discs with deleted sectors, which represented illusory Kanizsa contours when discs were in particular positions. In experiments with fragmented images, we found an improvement in image recognition with observers' age, increasing up to 13-14 years. The probability of recognition of fragmented line drawings increased significantly with decreasing stimulus size for children of 7-12 years, indicating that size invariance at recognition for fragmented line drawings was absent in these children. However, size invariance was found for observers of 13-17 years and for adults in this task. At Kanizsa illusion appearance, the ratio of the separation between discs and disc diameter was smaller when we used larger disc diameters. This ratio increased with increasing age of observers. Obtained results provide evidence for the absence of size invariance when perceiving the Kanizsa illusion in our experimental conditions.     

Perception of visual image size by school students of different ages

In psychophysical experiments, 209 high school students with normal vision, 8 to 16 years old, were examined to study the perception of visual image sizes. Observers assessed the length of linear arrow-like figures (the Müller-Lyer illusion) or the length of single lines without arrow-like ends. Distortion of line size perception by 17–21% was obtained in the Müller-Lyer illusion independent of the age of observers. Distortion of size perception was absent in the case of estimation of the length of single line segments. The size differentiation thresholds gradually decreased in both cases with increasing age of observers and were correlated with the acuity of vision. For single lines, they were, on average, 1.3 times lower than the thresholds in the Müller-Lyer illusion. The probable mechanisms of the Müller-Lyer illusion are discussed. The experimental results demonstrate stability of illusion for observers aged 8–16 years, which may be connected with preferential contribution of the lower levels of the visual system to the appearance of the illusion.     

Immunolocalization of type X collagen in human lumbar intervertebral discs during ageing and degeneration

 Type X collagen has so far not been reported to occur in human intervertebral discs. The objective of this study was therefore to investigate the occurrence of type X collagen in human lumbar intervertebral discs during ageing and degeneration. Ninety intervertebral discs with adjacent endplates were excised in toto from individuals (0–86 years) without known spinal disease and were processed for routine decalcified histology. Appropriate slices of each disc were processed for immunohistochemistry using a type-spec ific, monoclonal antibody raised against human type X collagen. Each intervertebral disc was examined for macroscopic and histomorphological features of disc degeneration. Immunohistochemically, a positive specific type X staining was observed in the hypertrophic zone of the growth plate and only in the interstitial matrix of juvenile (<2 years) nucleus pulposus. In adult discs, type X collagen could be localized in conjunction with advanced disc degeneration and first occurred in the disc matrix (i.e., pericellular region) of a 47-year-old specimen. Positive type X staining of the disc matrix was more frequently found in senile (>70 years) discs with end stages of disc degeneration. This study provides the first evidence for the occurrence of type X collagen in human lumbar intervertebral discs and it appears that type X collagen is re-expressed in late stages of disc degeneration. Accepted: 24 April 1997     

Neurophysiological mechanisms of recognition fragmented images in 5 to 6-year-old children

Behavioral indices and ERP parameters were analyzed in 5-6 years old children who were shown a previously unseen set of fragmented drawings of familiar objects. Within this set, each object was represented by a series of drawings of different degree of fragmentation. It is found that children of 5-6, when compared to 7-8 years old children, are capable to recognize less fragmented drawings. In these children, no increase was found in N350-400 prefrontal negativity and late positive complex, otherwise a typical feature of mature recognition involving executive control. A comparison of ERP for recognized vs. unrecognized stimuli showed a significant increase in P300 and N400 amplitude over the right occipital area. A key feature of children of this age is a lack of significant difference between ERP to recognized vs. unrecognized stimuli over extrastriatal cortex (T5/T6) which is the crucial structure for recognition of fragmented objects via integration of their sensory features. The data we obtained suggest that both executive control immaturity and insufficient involvement of the ventral visual system constitute a specifics of recognition in children of 5-6.     

Tenascin in the human intervertebral disc: alterations with aging and disc degeneration

Our objective for this study was to determine the presence and distribution of tenascin in the human intervertebral disc. The tenascins are a family of extracellular matrix proteins with repeated structural domains homologous to epidermal growth factor, fibronectin type III and the fibrinogens. Little is known about the presence of this protein in the disc. Ten normal human discs donated from subjects newborn to 15 years old, 10 control discs from adult donors aged 24-41 years, and 11 surgical disc specimens from patients aged 26-76 years were examined for immunolocalization of tenascin. In young discs, tenascin was localized throughout the annulus; in the nucleus, localization was confined to pericellular matrix. In adult control and degenerating disc specimens, tenascin in the annulus was localized primarily in pericellular matrix regions encircling either single cells or clusters of disc cells; in rare instances localization was more diffuse in the intraterritorial matrix. In young, healthy disc, tenascin was abundant throughout the annulus. In contrast, degenerating discs in adults showed a localization restricted to the pericellular, and rarely, more restricted intraterritorial matrix. These observations indicate that changes in the amount and distribution of tenascin may have a role in disc aging and degeneration, possibly by modulating fibronectin-disc-cell interactions, and causing alterations in the shape of disc cells.     

Female-specific wing degeneration is triggered by ecdysteroid in cultures of wing discs from the bagworm moth, Eumeta variegata (Insecta: Lepidoptera, Psychidae)

Female adults of the bagworm moth, Eumeta variegata, are completely wingless; by contrast, the male adults have functional wings. Sex-specific differences in the development of wing discs appear to arise during the 8th (penultimate) larval instar. We have previously found that the wing discs of female E. variegata terminate development and disappear during the prepupal period, whereas the wing discs of males continue to develop fully into adult wings. We have investigated the effects of ecdysteroid (20-hydroxyecdysone, 20E) when cultured with larval wing discs, which are normally attached to the larval integument of both male and female larvae. Male wing discs cultured with 20E undergo a remarkable transformation: the discs undergo apolysis and then differentiation. Female wing discs cultured with 20E also undergo apolysis; however, the disc cells enter apoptosis. We have observed condensed chromatin, fragmented nuclei, and secondary lysosomes in the epithelial cells of these female discs. This report establishes that the reduction of female wing discs arises through apoptotic events triggered by ecdysteroid in vitro.     

Analysis of fragmented images perception: local features and global description

Analysis of experimental investigations of the perception of incomplete images is presented. It illustrates two different approaches to work of the brain mechanisms involved: one approach is based on the perception of whole images and another on local informative features. These approaches describe two different mechanisms, which are possibly used by brain systems for incomplete image recognition. Performance on the Gollin test (measuring recognition thresholds for fragmented line drawings of everyday objects and animals) depends upon recognition based on image informational-statistical characteristics. We suggest that recognition thresholds for Gollin stimuli in part reflect the extraction of signal from noise. The brain uses local informative features as an additional source of information about them. We have suggested that fragmented images in the Gollin-test are perceived as whole structures. This structure is compared with a template in memory which is extracted with the help of selective attention mechanism in accordance with a matched filtration model. The Gollin-test is a tool for differential diagnosis of a various forms of cognitive disorders.     

Chondroadherin Fragmentation Mediated by the Protease HTRA1 Distinguishes Human Intervertebral Disc Degeneration from Normal Aging

Chondroadherin, a member of the leucine-rich repeat family, has previously been demonstrated to be fragmented in some juveniles with idiopathic scoliosis. This observation led us to investigate adults with disc degeneration. Immunoblotting analysis demonstrated that non-degenerate discs from three different age groups show no chondroadherin fragmentation. Furthermore, the chondroadherin fragments in adult degenerate disc and the juvenile scoliotic disc were compared via immunoblot analysis and appeared to have a similar size. We then investigated whether or not chondroadherin fragmentation increases with the severity of disc degeneration. Three different samples with different severities were chosen from the same disc, and chondroadherin fragmentation was found to be more abundant with increasing severity of degeneration. This observation led us to the creation of a neoepitope antibody to the cleavage site observed. We then observed that the cleavage site in adult degenerate discs and juvenile scoliotic discs was identical as confirmed by the neoepitope antibody. Consequently, investigation of the protease capable of cleaving chondroadherin at this site was necessary. In vitro digests of disc tissue demonstrated that ADAMTS-4 and -5; cathepsins K, B, and L; and MMP-3, -7, -12, and -13 were incapable of cleavage of chondroadherin at this site and that HTRA1 was indeed the only protease capable. Furthermore, increased protein levels of the processed form of HTRA1 were demonstrated in degenerate disc tissues via immunoblotting. The results suggest that chondroadherin fragmentation can be used as a biomarker to distinguish the processes of disc degeneration from normal aging.     

Neurophysiological mechanisms of recognition fragmented images by five- to six-year-old children

Behavioral indices and event-related potentials (ERP) were analyzed in five- to six-year-old children who were shown a set of previously unseen fragmented drawings of familiar images. These children recognized less fragmented images than seven- to eight-year-old children. At the age of five to six years, there was no increase in N350–400 prefrontal negativity and slow positive complex, which is characteristic of mature recognition that involves executive control. Comparison of ERP for recognized vs. unrecognized stimuli revealed a significant increase in the P300 and N400 amplitudes in the right occipital area. Note that, in children of this age, there were no significant differences between reactions to recognized and unrecognized images in the lateral extrastriate cortex (T₅/T₆), which is the key structure for recognition of familiar images via integration of their sensory features. Our data suggest that in five- to six-year-old children recognition of fragmented images has specific features determined by immaturity of the executive control and insufficient involvement of the ventral visual system.     

Homocysteine concentrations in a German cohort of 500 individuals: Reference ranges and determinants of plasma levels in healthy children and their parents

Summary. Elevated plasma homocysteine is a risk factor for cardiovascular disease and a sensitive marker of inadequate vitamin B12 and folate status. We studied 257 pupils (120 boys, 137 girls, aged 6–17 years) and their parents (88 males, 172 females, aged 26–50 years). Our measurements were part of a national Bavarian health and nutrition examination survey evaluating cardiovascular risk factors. A mild hyperhomocysteinemia (Hcys >15 μmol/l) occurred in 7% of the adults, but in none of the children. Men had significantly higher Hcys levels than women (p < 0.0001), boys and girls had comparable concentrations. For adults and children, Hcys correlated inversely with vitamin B12 and folate and positively with the lean body mass and creatinine in serum, but not with cystatin C. Genetic and nutritional factors are determinants of Hcys metabolism. The correlation of Hcys and serum creatinine is dependent on the metabolic link between Hcys production and creatine synthesis. Received July 4, 1999 Accepted May 22, 2000     

Relative contribution of surface and edge to ion absorption by leaf discs

Summary Phosphorus (H₃P³²O₄) absorption was studied in detached bean leaves and leaf discs and later computed per unit surface area and per unit edge length vis-a-vis discs of 4–18 mm diameters. Not only absorption through edge predominantly contributed to total disc absorption it was also directly proportional to disc diameter. Part of the work carried out during senior author's (BKG) tenure as IAEA expert at Bogota.     

Measurement Invariance of the WHODAS 2.0 in a Population-Based Sample of Youth

The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) is a brief measure of global disability originally developed for adults, which has since been implemented among samples of children and youth. However, evidence of its validity for use among youth, particularly measurement invariance, is lacking. Investigations of measurement invariance assess the extent to which the psychometric properties of observed items in a measure are generalizable across samples. Satisfying the assumption of measurement invariance is critical for any inferences about between-group differences. The objective of this paper was to empirically assess the measurement invariance of the 12-item interview version of the WHODAS 2.0 measure in an epidemiological sample of youth (15 to 17 years) and adults (≥ 18 years) in Canada. Multiple-group confirmatory factor analysis using a categorical variable framework allowed for the sequential testing of increasingly restrictive models to evaluate measurement invariance of the WHODAS 2.0 between adults and youth. Findings provided evidence for full measurement invariance of the WHODAS 2.0 in youth aged 15 to 17 years. The final model fit the data well: χ²(159) = 769.04, p < .001; CFI = 0.950, TLI = 0.958, RMSEA (90% CI) = 0.055 [0.051, 0.059]. Results from this study build on previous work supporting the validity of the WHODAS 2.0. Findings indicate that the WHODAS 2.0 is valid for making substantive comparisons of disability among youth as young as 15 years of age.     

HLA-A2-restricted peripheral blood cytolytic T lymphocyte response to HPV type 16 proteins E6 and E7 from patients with neoplastic cervical lesions

 The DNA from human papillomavirus (HPV) can be detected in 90% of cervical carcinomas. To address whether patients infected with HPV can mount efficient T cell responses to this pathogen we examined the cytotoxic T lymphocyte (CTL) response of peripheral blood mononuclear cells (PBMC) from patients with abnormal genital epithelial cells. PBMC from 11 HLA-A2⁺ patients were stimulated with CaSki, a cervical carcinoma cell line that is HPV 16⁺ and HLA-A2⁺. The CTL were screened for reactivity to the cervical carcinoma cell line C33A (HPV^–, HLA-A2⁺) transfected with the HPV 16 E6 or E7 genes or the plasmid without insert. The CTL of 1 patient showed particularly strong CaSki and HPV E6 or E7 protein-specific cytotoxicity in a HLA-A2-restricted fashion. In contrast, these CTL lysed neither a vector-only transfectant, the natural killer cell (NK) target, K562 nor the lymphokine-activated killer cell (LAK) target, Daudi. HLA-A2 restriction was demonstrated by the lack of recognition of a HLA-A2^– CaSki cell line developed in our laboratory. The CTL line was cloned and 99 clones were harvested and screened; 51 clones lysed CaSki, of which 17 did not lyse the A2^– CaSki. Of these HLA-A2^– restricted clones, 8 did not lyse C33A transfectants, 6 lysed all C33A transfectants, 3 lysed C33A-E7 only and none lysed C33A-E6 only. These data imply that, within the bulk CTL line, HLA-A2-restricted recognition of antigens was restricted to CaSki antigens, antigens common to cervical carcinoma (CaSki plus C33A), or HPV-16-E7-derived antigen on the clonal level. The E7-restricted clones were negative for recognition of known HLA-A2-binding peptides from E7. Received: 16 November 1995 / Accepted: 15 January 1996     

Growth, metastasis, and invasiveness of Drosophila tumors caused by mutations in specific tumor suppressor genes

 More than 50 genes have been identified in Drosophila by loss-of-function mutations that lead to overgrowth of specific tissues. Loss-of-function mutations in the lethal giant larvae, discs large, or brain tumor genes cause neoplastic overgrowth of larval brains and imaginal discs. In the present study, the growth and metastatic potential of tumors resulting from mutations in these genes were quantified. Overgrown brains and imaginal discs were transplanted into adults and β-galactosidase accumulation was used as a marker to identify donor cells. Mutations in these three genes generated tumors with similar metastatic patterns. For brain tumors, the metastatic index (a measure we defined as the fraction of hosts that acquired secondary tumors normalized for the amount of primary tumor growth) of each of the three mutants was similar. Analysis of cell proliferation in mutant brains suggests that the tumors arise from a population of several hundred cells which represent only 1–2% of the cells in third instar larval brains. For imaginal disc tumors from lethal giant larvae and brain tumor mutants, it is shown for the first time that they can be metastatic and invasive. Primary imaginal disc tumors from lethal giant larvae and brain tumor mutants formed secondary tumors in 43 and 53% of the hosts, respectively, although the secondary tumors were, in general, smaller than the secondary tumors derived from primary brain tumors. Received: 18 August 1997 / Accepted: 16 October 1997     

Effects of light and temperature on the attachment and development of <Emphasis Type="BoldItalic">Gloiopeltis tenax</Emphasis> and <Emphasis Type="BoldItalic">Gloiopeltis furcata</Emphasis> tetraspores

Two 60-day experiments were conducted to study the influence of photon flux density (PFD) and temperature on the attachment and development of Gloiopeltis tenax and Gloiopeltis furcata tetraspores. In the first experiment, tetraspores of the two Gloiopeltis species were incubated at five temperature ranges (8°C, 12°C, 16°C, 20°C, 24°C) under a constant PFD of 80 μmol photons m⁻² s⁻¹ with a photoperiod of 12:12. In a second experiment, tetraspores were incubated under five PFD gradients (30, 55, 80, 105, 130 μmol photons m⁻² s⁻¹) at a constant temperature of 16°C with a photoperiod of 12:12. Maximum density of attached tetraspores was observed at 16°C for both species. Maximum per cent of spore germinating into disc was recorded at 12–16°C for G. tenax and 8–12°C for G. furcata. Maximum per cent of discs producing erect axes for G. tenax and G. furcata were recorded at 24°C and 20°C, respectively. Light had no significant effect on tetraspore attachment and developing into disc, but it affected the growth, sprouting and survival of its discs. Under 30–55 μmol photons m⁻² s⁻¹, the discs of the two species of Gloiopeltis did not form thallus until the end of the experiment. Optimum PFD range for G. tenax discs was 80–105 μmol photons m⁻² s⁻¹, whilst it was 80–130 μmol photons m⁻² s⁻¹ for G. furcata. Results presented in this study are expected to assist the progress of artificial seeding of Gloiopeltis.     

Isolated, distal blade discs of the brown alga Laminaria digitata form sorus, but not discs, near to the meristematic transition zone

Blade discs of vegetative thalli of Laminaria digitata (Huds.) Lamour. from Helgoland (North Sea) cut at 5–15 cm distance from the blade/stipe transition, formed sorus in the laboratory after 7–12weeks, 5 months earlier than whole fronds in the field. Sorus formation occurred in a broad range of daylength regimes or temperatures, at 8–16 h light pe rday and 6–12 ^°C. No sorus was developed during three months by meristematic blade discs cut from the lowermost 3 cm portion of the blade, nor from whole thalli cultured in parallel to isolated blade discs. These findings point to the possible existence of sporulation inhibitors produced by the laminarian meristem. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparison of prehension force control in young and elderly individuals

Age-related changes were investigated in the control of precision grip force during the lifting and holding of objects with slippery (silk) and nonslippery (sandpaper) surface textures. Two groups of active elderly adults comprising individuals aged 69–79 years (n = 10), and 80–93 years (n = 10) together with a group of young adults aged 18–32 years (n = 10) participated in the study. Each subject lifted a free weight (3N) during which time gripping and lifting forces were monitored. The elderly subjects, especially the individuals in the 81–93 year group, had a larger number of fluctuations in the grip force rate curve and longer force application time than the younger subjects during lifting. The effect of prior experience with one surface on the following different surface was more pronounced in the younger subjects than the elderly subjects. These results suggest a decline in programmed force production capacity with increased age. The fingers of the elderly subjects were more slippery and they exhibited a greater safety margin of the grip force while holding the object than the younger adults. The overall results demonstrated that precision grip force control capacity declines with advancing age. It is suggested that this decline is due mainly to age-related changes in skin properties, and cutaneous sensibility functions, and in part to central nervous system function.     

Smaller nests of the hornet Vespa analis (Hymenoptera, Vespidae) are more severely affected by the strepsipteran parasite Xenos moutoni (Strepsiptera, Stylopidae) than are larger nests

The parasite Xenos moutoni inactivates workers and castrates reproductives of the Japanese hornet Vespa analis. Using over 500 nests, we investigated the relationship between hornet nest size (number of cells) and the proportion of parasitized adults (i.e., prevalence) in central Japan. Over 3 years, 36–48% of nests had more than one parasitized adult, and approximately 3–5% of female adults (mostly workers) and 1–3% of male adults were parasitized within the population. The number of cells did not differ between nests with and without parasitized workers; therefore, the effects of parasite-caused losses within the worker force on nest size appear to be negligible. However, the prevalence of parasitized workers tended to decrease with an increase in the number of cells. Our analysis indicated that the number of parasitized workers was consistently low and did not increase with nest size, resulting in a relatively high prevalence in small nests.     

Effects of the ecdysteroid agonists RH 5849 an RH 5992, alone and in combination with a juvenile hormone analogue, pyriproxyfen, on larvae ofSpodoptera exigua

Biological activity assays with RH 5849 and RH 5992 indicated that both compounds affected growth and development of last-instar larvae ofSpodoptera exigua (Hübner) (Lepidoptera: Noctuidae) in a dose-dependent manner. Within the first 24 h after treatment by continuously offering leaves dipped in a water solution of ≥50 mg/l RH 5849 and ≥0.5 mg/l RH 5992, symptoms of a prematurely induced larval moult and head capsule apolysis were visible. Intoxicated larvae died shortly afterwards, showing signs of unsuccessful ecdysis. LC₅₀-values of RH 5849 and RH 5992 for fifth-instarS. exigua larvae were 110 and 2.5 mg/l, respectively. Pyriproxyfen alone affected the larval stage and disturbed normal metamorphosis. One supernumerary larval instar occurred occasionally. LC₅₀-value for pyriproxyfen was 1.7 mg/l. Larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, continued to grow until they attained a size and weight about 2–3 times that of the controls. This growth was accompanied by at least one and sometimes two supernumerary moults. Concerning thein vivo imaginal wing disc growth and development, only in larvae treated with 10 and 50 mg/l RH 5849 or 0.5 mg/l RH 5992, tracheole migration was observed earlier than in the controls. When applying 300 mg/l RH 5849 or 3–7 mg/l RH 5992, the discs remained small and no signs of tracheole migration were observed. In larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, tracheole migration was not prematurely induced and a pupal cuticle was produced in the discs of larvae, undergoing a supernumerary moult. No clear signs of evagination were observed.     

Tactile size discrimination by a California sea lion (Zalophus californianus) using its mystacial vibrissae

The capability of a blindfolded California sea lion (Zalophus californianus) to discriminate diameter differences of circular discs by means of active touch with its mystacial vibrissae was studied. Using a forced choice paradigm the sea lion was required to choose the larger of two simultaneously presented perspex discs. Absolute difference thresholds (D) were determined for 3 standard discs (1.12 cm Ø, 2.52 cm Ø, 8.74 cm Ø) by the psychophysical method of constants. Increasing disc size resulted in an increase in the absolute difference threshold from 0.33 cm for the smallest disc size to 1.55 cm for the largest disc size. The relative difference threshold (Weber fraction) remained approximately constant at a mean value of 0.26. According to a video analysis the sea lion did not move its vibrissae when touching the discs. Instead, it performed precisely controlled lateral head movements, with the touched disc located centrally between the vibrissae of both sides of the muzzle. Since the extent of these head movements was identical at discs to be compared, discs of different size must have led to different degrees of deflection of vibrissae involved in the tactile process, resulting in quantitatively different mechanical stimulations of mechanoreceptors in the follicles. This suggests that the accuracy of the sea lion's size discrimination was determined by the efficiency of two sensory systems: the mechanosensitivity of follicle receptors as well as kinaesthesis.Abbreviations D starting stimulus size - D _i size of the interpolated comparison disc at 75% correct choices - D absolute difference threshold