Dermal fibroblasts respond to mechanical conditioning in a strain profile dependent manner

Fibroblasts within tissues are exposed to a dynamic mechanical environment, which influences the structural integrity of both healthy and healing soft tissues. Various systems have been proposed to subject such cells to mechanical stimulation in culture. However the diverse nature of the studies, in terms of the strain profiles and the cell types, makes direct comparisons almost impossible. The present study addresses this issue by examining the metabolic response of two cell types subjected to three well defined strain profiles.A young fibroblast cell population, represented by HuFFs, showed both greater cell proliferation and collagen production than adult dermal fibroblasts under unstrained conditions. The three strain profiles produced differing effects on both cell types. Uniaxial strains enhanced [(3)H]-thymidine incorporation for both cell types, whilst biaxial strains either inhibited or had no effect on its incorporation. In contrast, [(3)H]-proline incorporation was inhibited under biaxial and uniaxial strains for the adult fibroblasts, whilst the HuFF cells showed a small increase in proline incorporation under non-uniform and uniaxial strains.     

Carbon dioxide release in Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar): effects of caste, mass, and movement

Movement and carbon dioxide (CO(2)) release of individual Formosan, Coptotermes formosanus Shiraki and Eastern, Reticulitermes flavipes (Kollar) subterranean termites were recorded simultaneously in real time. Worker, soldier, and pre-alate (nymph) caste termites were recorded over 1-h periods at ambient temperature and normoxia in dry, CO(2)-free air. No evidence of discontinuous gas exchange cycles (DGCs) was observed in 344 recordings. Intensity of movement was constant in video tape recordings of termites under respirometry conditions. Duration of movement did not have a significant effect on residuals of &Vdot;(CO(2)) regressed on mass. Thus, movement did not effect &Vdot;(CO(2)) for these two species. Overall CO(2) release values were calculated for all recordings resulting in mean &Vdot;(CO(2)) (ml CO(2) g(-1) h(-1)), and compared among caste, colony, and species with a nested ANOVA. There was significant interaction (P=0.0161) only for species. Mean CO(2) release was significantly greater for R. flavipes (0.507 ml CO(2) g(-1) h(-1)) than C. formosanus (0.310 ml CO(2) g(-1) h(-1)). Mass scaling of termite &Vdot;(CO(2)) was investigated by regressing log(10)&Vdot;(CO(2)) on log(10)mass. The overall model combining species gave a mass scaling coefficient of 0.861(+/-0.0791), which approximates a previously published value for the arthropods as a whole (0.825).     

Nonwoven fiber barriers for control of cabbage maggot and onion maggot (Diptera: Anthomyiidae).

We investigated the use of nonwoven fiber barriers for control of cabbage maggot, Delia radicum (L.), and onion maggot, D. antiqua (Meigen). The barriers consist of arrangements of minute fibers loosely intertwined in "web" form. Results from a greenhouse experiment showed that manually applied graphite fibers placed at the base of broccoli plants reduced the number of D. radicum eggs by 64-98%, and that efficacy increased with greater fiber density. Using a melt extrusion process, we devised a method for on-site creation of nonwoven fibers of ethylene vinyl acetate (EVA). In field trials with broccoli and onion plants, EVA fibers significantly reduced the number of cabbage and onion maggots infesting plants. Fiber barriers provided comparable control to standard insecticide applications. The addition of blue, yellow, red, or black pigments, as well as optical brighteners that absorb UV light did not enhance fiber efficacy. Incorporation of capsaicin olfactory repellent to EVA also did not enhance fiber efficacy. Nonwoven fiber barriers may offer an alternative to insecticides for control of cabbage maggot and onion maggot and possibly other insect pests. Additional research is needed to improve the application process and to identify economically feasible and biodegradable compounds for fibers.     

Regulatory responses to an oral D-glutamate load: formation of D-pyrrolidone carboxylic acid in humans

Previously published studies have shown D-glutamate to be the most potent natural inhibitor of glutathione synthesis known, yet how D-glutamate is handled in humans is unknown. Therefore, we administered an oral D-glutamate load to four healthy volunteers and monitored the plasma D-glutamate concentration and excretion over a 3-h postload period. Compared with time controls, the plasma D-glutamate concentration increased 10-fold in the 1st h and then reached a plateau over the remaining time course. In contrast, plasma D-pyrrolidone carboxylic acid increased progressively throughout the 3-h time course to a level 10-fold higher than the D-glutamate plasma concentration. Excretion of D-glutamate progressively increased despite a constant filtered D-glutamate load rising from only 5 to 95% of the filtered amount. Excretion of D-pyrrolidone carboxylic acid increased with the rise in filtered load without significant reabsorption. The amount of D-pyrrolidone carboxylic acid excreted over the 3-h time course was 10 times the amount excreted as D-glutamate and accounted for almost 20% of the administered D-glutamate. These findings indicate that plasma D-glutamate concentration is tightly regulated through two mechanisms: 1) the transport into cells and metabolic conversion to D-pyrrolidone carboxylic acid and excretion, and 2) the enhancement of D-glutamate clearance by the kidneys.     

Learning in brains and machines

The problem of learning is arguably at the very core of the problem of intelligence, both biological and artificial. In this paper we sketch some of our work over the last ten years in the area of supervised learning, focusing on three interlinked directions of research: theory, engineering applications (that is, making intelligent software) and neuroscience (that is, understanding the brain's mechanisms of learning).     

Mutagenicity in lung of big Blue((R)) mice and induction of tandem-base substitutions in Salmonella by the air pollutant peroxyacetyl nitrate (PAN): predicted formation of intrastrand cross-links

Peroxyacetyl nitrate (PAN) is a ubiquitous air pollutant formed from NO(2) reacting with acetoxy radicals generated from ambient aldehydes in the presence of sunlight and ozone. It contributes to eye irritation associated with photochemical smog and is present in most urban air. PAN was generated in a chamber containing open petri dishes of Salmonella TA100 (gas-phase exposure). After subtraction of the background mutation spectrum, the spectrum of PAN-induced mutants selected at 3.1-fold above the background mutant yield was 59% GC-->TA, 29% GC-->AT, 2% GC-->CG, and 10% multiple mutations - primarily GG-->TT tandem-base substitutions. Using computational molecular modeling methods, a mechanism was developed for producing this unusual tandem-base substitution. The mechanism depends on the protonation of PAN near the polyanionic DNA to release NO(2)(+) resulting in intrastrand dimer formation. Insertion of AA opposite the dimerized GG would account for the tandem GG-->TT transversions. Nose-only exposure of Big Blue((R)) mice to PAN at 78ppm (near the MTD) was mutagenic at the lacI gene in the lung (mutant frequency +/-S.E. of 6.16+/-0.58/10(5) for controls versus 8.24+/-0.30/10(5) for PAN, P=0.016). No tandem-base mutations were detected among the 40 lacI mutants sequenced. Dosimetry with 3H-PAN showed that 24h after exposure, 3.9% of the radiolabel was in the nasal tissue, and only 0.3% was in the lung. However, based on the molecular modeling considerations, the labeled portion of the molecule would not have been expected to have been bound covalently to DNA. Our results indicate that PAN is weakly mutagenic in the lungs of mice and in Salmonella and that PAN produces a unique signature mutation (a tandem GG-->TT transversion) in Salmonella that is likely due to a GG intrastrand cross-link. Thus, PAN may pose a mutagenic and possible carcinogenic risk to humans, especially at the high concentrations at which it is present in some urban environments.     

FIZZ1, a novel cysteine-rich secreted protein associated with pulmonary inflammation, defines a new gene family

Bronchoalveolar lavage fluid from mice with experimentally induced allergic pulmonary inflammation contains a novel 9.4 kDa cysteine-rich secreted protein, FIZZ1 (found in inflammatory zone). Murine (m) FIZZ1 is the founding member of a new gene family including two other murine genes expressed, respectively, in intestinal crypt epithelium and white adipose tissue, and two related human genes. In control mice, FIZZ1 mRNA and protein expression occur at low levels in a subset of bronchial epithelial cells and in non-neuronal cells adjacent to neurovascular bundles in the peribronchial stroma, and in the wall of the large and small bowel. During allergic pulmonary inflammation, mFIZZ1 expression markedly increases in hypertrophic, hyperplastic bronchial epithelium and appears in type II alveolar pneumocytes. In vitro, recombinant mFIZZ1 inhibits the nerve growth factor (NGF)-mediated survival of rat embryonic day 14 dorsal root ganglion (DRG) neurons and NGF-induced CGRP gene expression in adult rat DRG neurons. In vivo, FIZZ1 may modulate the function of neurons innervating the bronchial tree, thereby altering the local tissue response to allergic pulmonary inflammation.     

The role of CAF derived exosomal microRNAs in the tumour microenvironment of melanoma

Exosomes play a crucial role in the crosstalk between cancer associated fibroblasts (CAFs) and cancer cells, contributing to carcinogenesis and the tumour microenvironment. Recent studies have revealed that CAFs, normal fibroblasts and cancer cells all secrete exosomes that contain miRNA, establishing a cell-cell communication network within the tumour microenvironment. For example, miRNA dysregulation in melanoma has been shown to promote CAF activation via induction of epithelial-mesenchymal transition (EMT), which in turn alters the secretory phenotype of CAFs in the stroma. This review assesses the roles of melanoma exosomal miRNAs in CAF formation and how CAF exosome-mediated feedback signalling to melanoma lead to tumour progression and metastasis. Moreover, efforts to exploit exosomal miRNA-mediated network communication between tumour cells and their microenvironment, and their potential as prognostic biomarkers or novel therapeutic targets in melanoma will also be considered.     

Gibberellin levels and cold-induced floral stalk elongation in tulip

To investigate the role of gibberellins (GAs) in the cold requirement of tulip ( Tulipa gesneriana L. cv. Apeldoorn), bulbs were dry-stored at 5°C or at 17°C for 12 weeks prior to planting at 20°C. Only precooled bulbs showed rapid sprout growth and developed a full-grown flower. Endogenous GA levels were measured in sprouts and basal plates at the time of planting and in the second week after planting, by combined gas chromatography-mass spectrometry using deuterated internal standards. GA₄ was the major gibberellin. while GA₁, GA₉ and GA₃₄ were present in lower amounts. At the time of planting, sprouts from non-cooled bulbs contained significantly more GA₄ and GA₁, per sprout than those from precooled bulbs. Hence, there is no direct correlation between rapid sprout growth after planting and high GA levels at planting. In the second week after planting, floral stalks of precooled bulbs contained 2 to 3 times more GA₄ and its metabolite GA₃₄ per floral stalk and per g fresh weight than those of non-cooled bulbs. The results are discussed with regard to the role of gibberellins in the cold-induced floral stalk elongation of tulip.