The epithelial origin of lymphocytes in the palatine tonsil of rabbits

Lymphopoiesis was studied by electron microscopy in the palatine tonsil of the rabbit from 18 days gestation to 5 days after birth. At 18 days tonsils formed as mounds of mesenchyma covered with epithelium. At 19 days the basal epithelial cells started to increase in number, eventually forming 'buds' which projected into the mesenchyme. Simultaneously, lymphocytes appeared nearthe epithelium or buds. There was marked resemblance between the basal epithelial cells and the lymphocytes. Budding slowed down after the 25th day, but individual basal cells continued to migrate into the mesenchyme and lymphocytes increased in number. Ultrastructure wassimilar in both types of cells, and differentfrom mesenchymal cells. At 29 days lymphocytes were found in the basal epithelial layer behind an intact basement membrane. The evidence indicated that lymphocytes were derived from epithelium.     

The Influence of Learning on Host Plant Preference in a Significant Phytopathogen Vector,Diaphorina citri

Although specialist herbivorous insects are guided by innate responses to host plant cues, host plant preference may be influenced by experience and is not dictated by instinct alone. The effect of learning on host plant preference was examined in the Asian citrus psyllid, Diaphorina citri; vector of the causal agent of citrus greening disease or huanglongbing. We investigated: a) whether development on specific host plant species influenced host plant preference in mature D. citri; and b) the extent of associative learning in D. citri in the form of simple and compound conditioning. Learning was measured by cue selection in a 2-choice behavioral assay and compared to naïve controls. Our results showed that learned responses in D. citri are complex and diverse. The developmental host plant species influenced adult host plant preference, with female psyllids preferring the species on which they were reared. However, such preferences were subject to change with the introduction of an alternative host plant within 24–48 hrs, indicating a large degree of experience-dependent response plasticity. Additionally, learning occurred for multiple sensory modalities where novel olfactory and visual environmental cues were associated with the host plant. However, males and females displayed differing discriminatory abilities. In compound conditioning tasks, males exhibited recognition of a compound stimulus alone while females were capable of learning the individual components. These findings suggest D. citri are dynamic animals that demonstrate host plant preference based on developmental and adult experience and can learn to recognize olfactory and visual host plant stimuli in ways that may be sex specific. These experience-based associations are likely used by adults to locate and select suitable host plants for feeding and reproduction and may suggest the need for more tailored lures and traps, which reflect region-specific cultivars or predominate Rutaceae in the area being monitored.     

Lysozyme catalysis: kinetics of the hydrolysis of cell wall oligosaccharides.

The cleavage of cell wall tetrasaccharide, the beta(1 leads to 4)-linked dimer of the basic repeating disaccharide N-acetyl-D-glucosamine-beta(1 leads to 4)-N-acetyl-D-muramic acid, by lysozyme has been studied at various concentrations of lysozyme and over long time ranges. A theoretical analysis of the kinetic results indicates that direct hydrolysis of the tetrasaccharide by binding in subsities CDEF of the active site of lysozyme is significant at long times relative to the transglycosylation pathway. The binding constant for tetrasaccharide in CDEF is shown to be 10(3) times larger than that determined on the basis of an analysis of kinetic data over a more restricted range of times and concentrations.     

Nuclear peptides from calf liver: large scale isolation and fractionation; control of gene expression in cell-free systems, and inhibition of growth of cells in culture

DNA and nuclear RNA fractions contain small peptides (mol. wt. 600 - 1500) attached noncovalently. A large scale isolation procedure was developed for the extraction of such peptides directly from the lysed nuclei. Further purification and fractionation was performed with the chromatography on Sephadex, silica gel and h.p.l.c. C18 reverse phase columns. H.p.l.c. fractionation yielded eleven peaks. The peptides are rich in serine, glycine, alanine and acidic amino acids. They do not contain sulphur-containing amino acids. Only occasionally tyrosine, phenylalanine, histidine, arginine, and very moderate amount of lysine are found. These peptides are active in inhibiting gene expression in cell-free systems and incorporation of labeled thymidine in L 1210 murine leukemic cell culture. Thorough and exhaustive analysis demonstrated that the isolated peptides are not degradative products of histone or nonhistone chromosomal proteins.     

Short-Term Evaluation of the Impact of a Food Program on the Micronutrient Nutritional Status of Argentinean Children Under the Age of Six

This study was undertaken to evaluate the impact of Plan Más Vida (PMV) on the micronutrient nutritional condition of children aged 1 to 6?years 1?year after PMV implementation. The food program was intended for low-income families from the province of Buenos Aires, Argentina and provided supplementary diets. A prospective, nonexperimental study was carried out. Children (472 at baseline and 474 after 1?year) were divided into two groups (1-2 and 2-6?years of age). Biochemical tests (hemogram, ferritin, zinc, vitamin A, and folic acid), anthropometric assessments (weight and height), and dietary surveys (24-h recall) were performed. Chronic growth retardation (-2 height/age Z-score) was present in 2.8% and 8.7% of 1-2- and 2-6-year-old children, respectively; 14.4% in the former and 8.8% in the latter group had overweight/obesity. No significant changes were recorded 1?year after PMV implementation. Whereas anemia values decreased (55.3% to 39.1%, p?=?0.003) and serum zinc values increased in 1-2-year-old children, the risk for vitamin A deficiency decreased significantly in both age groups. The evaluation of the early impact of PMV actions provided important nutritional data that should be used by provincial health authorities to conduct future evaluations.     

Visual Hierarchical Processing and Lateralization of Cognitive Functions through Domestic Chicks' Eyes

Hierarchical stimuli have proven effective for investigating principles of visual organization in humans. A large body of evidence suggests that the analysis of the global forms precedes the analysis of the local forms in our species. Studies on lateralization also indicate that analytic and holistic encoding strategies are separated between the two hemispheres of the brain. This raises the question of whether precedence effects may reflect the activation of lateralized functions within the brain. Non-human animals have perceptual organization and functional lateralization that are comparable to that of humans. Here we trained the domestic chick in a concurrent discrimination task involving hierarchical stimuli. Then, we evaluated the animals for analytic and holistic encoding strategies in a series of transformational tests by relying on a monocular occlusion technique. A local precedence emerged in both the left and the right hemisphere, adding further evidence in favour of analytic processing in non-human animals.     

Odor-based recognition of nectar in cursorial spiders

Carnivorous arthropods are known to rely on non‐prey foods, such as honeydew, pollen, and nectar. Consumption of plant‐based nutrients by spiders also appears to be widespread, especially in cursorial species. This is not surprising, as studies have shown that these spiders’ activity levels, survivorship, and reproduction are increased when their diet includes plant‐based nutrients, especially under conditions of prey scarcity. However, the sensory and behavioral means by which they recognize and locate non‐prey food is unknown. Here we show that immatures of a nectarivorous spider [Hibana futilis Banks (Araneae: Anyphaenidae)] can recognize and remember particular chemical stimuli associated with nectar. Following ingestion of minute amounts of sugar, these spiders exhibited counterturning and other local searching behaviors that increased their chances of finding more nectar. When placed on test arenas, spiders that were naïve with respect to nectar aroma located artificial nectaries composed of diluted honey significantly faster than unscented nectaries composed of 1 m sucrose solution. These results indicate that H. futilis is neurophysiologically and behaviorally adapted for recognizing olfactory stimuli. Interestingly, only spiders that ingested sugar and were engaged in local search responded to nectar aroma, suggesting that stimulation into local search is necessary to prime olfactory responses. We found that H. futilis could be conditioned to associate the presence of nectar with a novel aroma, in this case vanilla, and remember this aroma over the course of several hours. In arenas with vanilla‐scented nectaries, spiders that had previous experience feeding on vanilla‐scented sucrose droplets located the nectaries significantly faster than did vanilla‐naïve spiders. The capacity to remember specific aromas could enhance the spiders’ ability to find nectar, either when moving between different parts of the same plant or among different plant species. The results here indicate that nectarivorous spiders possess the sensory capabilities and programed behaviors necessary for efficient detection, recognition, and location of nectar sources.