Multiple interactions networks: towards more realistic descriptions of the web of life

Ecological communities are defined by species interacting dynamically in a given location at a given time, and can be conveniently represented as networks of interactions. Pairwise interactions can be ascribed to one of five main types, depending on their outcome for the species involved: amensalism, antagonism (including predation, parasitism and disease), commensalism, competition or mutualism. While most studies have dealt so far with networks involving one single type of interaction at a time, often focusing on a specific clade and/or guild, recent studies are being developed that consider networks with more than one interaction type and across several levels of biological organisation. We review these developments and suggest that three main frameworks are in use to investigate the properties of multiple interactions networks: ‘expanded food‐webs’, ‘multilayer networks’ and ‘equal footing networks’. They differ on how interactions are classified and implemented in mathematical models, and on whether the effect of different interaction types is expressed in the same units. We analyse the mathematical and ecological assumptions of these three approaches, and identify some of the questions that can be addressed with each one of them. Since the overwhelming majority of studies on multiple interactions are theoretical and use artificially generated data, we also provide recommendations for the incorporation of field data in such studies.     

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.     

X-linked adrenoleukodystrophy (X-ALD): clinical presentation and guidelines for diagnosis, follow-up and management

Background

Pompe disease (Glycogen storage disease type II, GSD II, acid alpha-glucosidase deficiency, acid maltase deficiency, OMIM # 232300) is an autosomal-recessive lysosomal storage disorder due to a deficiency of acid alpha-glucosidase (GAA, acid maltase, EC 3.2.1.20, Swiss-Prot P10253). Clinical manifestations are dominated by progressive weakness of skeletal muscle throughout the clinical spectrum. In addition, the classic infantile form is characterised by hypertrophic cardiomyopathy.

Methods

In a cross-sectional single-centre study we clinically assessed 3 patients with classic infantile Pompe disease and 39 patients with non-classic presentations, measured their acid alpha-glucosidase activities and analysed their GAA genes.

Results

Classic infantile patients had nearly absent residual enzyme activities and a typical clinical course with hypertrophic cardiomyopathy until the beginning of therapy. The disease manifestations in non-classic patients were heterogeneous. There was a broad variability in the decline of locomotive and respiratory function. The age of onset ranged from birth to late adulthood and correlated with enzyme activities. Molecular analysis revealed as many as 33 different mutations, 14 of which are novel. All classic infantile patients had two severe mutations. The most common mutation in the non-classic group was c.-32-13?T?>?G. It was associated with a milder course in this subgroup.

Conclusions

Disease manifestation strongly correlates with the nature of the GAA mutations, while the variable progression in non-classic Pompe disease is likely to be explained by yet unknown modifying factors. This study provides the first comprehensive dataset on the clinical course and the mutational spectrum of Pompe disease in Germany.     

Vitamin K in combination with other biochemical markers to diagnose osteoporosis.

The significance of a multiparametric classification approach of vitamin K is analysed to differentiate premenopausal (CTRL), postmenopausal non-osteoporotic (nOSP) and osteoporotic (OSP) women. Data records of women between 28 and 74 years of age were used for evaluation. Bone mineral density was determined by quantitative computed tomography of the lumbar spine using the T-score to diagnose osteoporosis. Vitamin K and biochemical markers of bone formation and resorption--alkaline phosphatase (AP), bone alkaline phosphatase (bAP), osteocalcin (OC), undercarboxylated osteocalcin (ucOC), procollagen type I carboxyterminal propeptide (PICP), pyridinoline (PYD), deoxypyridinoline (DPD), N-terminal cross-linked telopeptide of type I collagen (NTx) and bone sialo protein (BSP)--were analysed in all women on days 1 and 42. Vitamin K was significantly lower in the OSP group versus nOSP and CTRL. The odds ratio results revealed the following: vitamin K, 16.7; PYD, 7.5; NTx, 6.0; DPD, 2.7; and ucOC, 2.7. Vitamin K represented a sensitivity rate of 64% and a specificity rate of 82%. In the receiver operating curve analysis, vitamin K reached the highest area under curve (AUC) score. The combination of vitamin K and AP, bAP and PYD resulted in increased AUC scores (>0.9). The parameter combination of vitamin K/PYD and vitamin K/bAP demonstrated a sensitivity rate of 75-88%, with a specificity rate of more than 82%. The data suggests that a combination of vitamin K with other biochemical bone indices might be a useful tool for assessing bone metabolism, especially in metabolic bone diseases such as osteoporosis.     

The covalent binding of 3-methylindole metabolites to bovine tissue

Tritiated 3-methylindole (3MI) was administered intravenously to calves. Total and covalent bound radioactivity were measured in different tissues. Pulmonary tissue showed the highest concentration of covalent bound radioactivity. (G-³H) or (methyl-¹⁴C) 3MI became covalently bound to microsomal protein when incubated with bovine lung microsomes. This covalent binding was dependent on time, temperature, oxygen and NADPH and was inhibited by SKF-525A, cytochrome c, a carbon monoxide enriched atmosphere and cysteine. The microsomal enzyme system catalysing covalent binding of 3MI has the classical characteristics of a cytochrome P-450 dependent mixed function oxidase. Metabolic activation of 3MI to a highly electrophilic intermediate, may be fundamental in the pathogenesis of 3MI induced pulmonary damage.     

Infants' exploration of scented toys: effects of prior experiences

To evaluate breastfed infants' responses to scented objects, we videotaped the facial and bodily reactions of sixty-three infants as they explored, in succession, three toys that were identical in appearance but different in their characteristic odor. Two of the toys were scented with odorants previously shown to be transmitted to human milk, one with ethanol and the other with vanilla, whereas the third toy was unscented. Each videotape was subjected to frame-by-frame analysis to measure a variety of behaviors that are considered either to be exploratory in nature in that they lead to perceptual information about the object or to reflect the infants' hedonic reaction. Analyses of these behaviors revealed that the infants looked more and vocalized less in the presence of the vanilla-scented toy and spent less time manipulating the ethanol-scented toy when compared with the unscented toy. Moreover, differential exposure to the odors of ethanol and vanilla, as indicated by differential consumption of alcohol by a parent or use of vanilla-scented product by the mother, was related to differential responses to these odors. These findings suggest that human infants are able to detect and retain information about the chemical features of their environment.