A shift in protein S-palmitoylation, with persistence of growth-associated substrates, marks a critical period for synaptic plasticity in developing brain.

In the mammalian cortex, the initial formation of synaptic connections is followed by a prolonged period during which synaptic circuits are functional, but retain an elevated capacity for activity-dependent remodeling and functional plasticity. During this period, synaptic terminals appear fully mature, morphologically and physiologically. We show here, however, that synaptic terminals during this period are distinguished by their simultaneous accumulation of multiple growth-associated proteins at levels characteristic of axonal growth cones, and proteins involved in synaptic transmitter release at levels characteristic of adult synapses. We show further that newly formed synapses undergo a switch in the dynamic S-palmitoylation of proteins early in the critical period, which includes a large and specific decrease in the palmitoylation of GAP-43 and other major substrates characteristic of growth cones. Previous studies have shown that a similar reduction in ongoing palmitoylation of growth cone proteins is sufficient to stop advancing axons in vitro, suggesting that a developmental switch in protein S-palmitoylation serves to disengage the molecular machinery for axon extension in the absence of local triggers for remodeling during the critical period. Only much later does a decline in the availability of major growth cone components mark the molecular maturation of cortical synapses at the close of the critical period.     

Gibberellin-like substances in root exudate of Vitis vinifera

Summary The levels of gibberellin (GA)-like activity in the root exudate of two seedless varieties of Vitis vinifera were examined by the barley endosperm assay, and compared with levels determined for other parts of the plant. That activity was due to GA-like substances was confirmed with dwarf-5 corn.When acidic, ethyl acetate soluble GA-like substances from sap and leaf extracts were chromatogrammed on thin layers of silica gel in chloroform/ethyl acetate/formic acid (50:50:1), activity moved to the same Rf as GA₃ and GA₁ (Rf 0.05–0.25). However, substances inhibitory to the barley endosperm assay were detected in both sap and leaf extracts. In the above solvent system the inhibitor(s) co-chromatogrammed with a GA₁/GA₇ mixture, and with abscisin II. The GA-like activity co-chromatogrammed with GA₃ on paper developed in isopropanol/ammonia/water (10:1:1).Calculations on the rate of gibberellin movement from the roots seemed to be compatible with levels of activity in the leaves, although these levels could also be a reflection of the general gibberellin level in the plant.The relevance of the findings is discussed.     

Changes in nutrient heterogeneity along sand dune and slack chronosequences at Tentsmuir Point,Eastern Scotland

Summary

Recent models have attempted to explain species coexistence and community structure by resource heterogeneity at a spatial scale below that of the individual plant. In this paper, we examine how heterogeneity changes through time. A comparative study of the heterogeneity of pH, phosphate, nitrate and nitrite levels was made within and along a transect inland from the shore at Tentsmuir Point, Fife, Scotland, an example of primary sand dune succession. This locality provided marked topographic relief created by dunes and slacks, and a well-characterised chronosequence. Soil samples were taken at the intersections of grids in quadrats. To examine macroscale heterogeneity in soil constituents, these intersections were 1 m apart in each direction in a large quadrat (5 m × 2m); for microscale heterogeneity they were 0.1m apart in a smaller quadrat (50 cm × 20 cm).

Mean concentration levels, and spatial heterogeneity of the values of nutrients and pH changed with time through the stages of the succession. pH and nitrate showed a simple decrease with time, whereas the other nutrients showed a more complex pattern of change.

Microscale heterogeneity was found to be greater than macroscale heterogeneity. Furthermore, principal components analysis of the two data sets showed differences in the main axes of variation, such that in the macroscale data set the main axis showed a trend from dune sites, through fresh water slacks to those influenced by salt water, while in the microscale data set the main axis related to levels of nitrogen.

‘The natural world is a patchy place … from the arrangement of continents and oceans to the alternation of the solid grains of beach sand and the spaces between them.’ (Dale, 1999)     

Protecting Future Children from In‐Utero Harm

The actions of pregnant women can cause harm to their future children. However, even if the possible harm is serious and likely to occur, the law will generally not intervene. A pregnant woman is an autonomous person who is entitled to make her own decisions. A fetus in‐utero has no legal right to protection. In striking contrast, the child, if born alive, may sue for injury in‐utero; and the child is entitled to be protected by being removed from her parents if necessary for her protection. Indeed, there is a legal obligation for health professionals to report suspected harm, and for authorities to protect the child's wellbeing. We ask whether such contradictory responses are justified. Should the law intervene where a pregnant woman's actions risk serious and preventable fetal injury? The argument for legal intervention to protect a fetus is sometimes linked to the concept of ‘fetal personhood’ and the moral status of the fetus. In this article we will suggest that even if the fetus is not regarded as a separate person, and does not have the legal or moral status of a child, indeed, even if the fetus is regarded as having no legal or moral status, there is an ethical and legal case for intervening to prevent serious harm to a future child. We examine the arguments for and against intervention on behalf of the future child, drawing on the example of excessive maternal alcohol intake.     

The evolution of physiology and development in the cluster root: teaching an old dog new tricks?

In this paper we examine the key elements of cluster or proteoid roots, and trace their origins back to regular root properties. By viewing the root system as being composed of two categories of surface, the high transport capacity (HTC) area, just behind the meristem, and the low transport capacity (LTC) area (the rest of the root system), based on export and import capacities, we examine root system architecture in terms of structure–function relationships, and conclude that measuring total root exudation per unit area, volume or mass will not give useful comparative data for root transport properties. Furthermore, the cluster root represents a manipulation of the HTC to LTC root surface area ratio. Increased exudation and P uptake may be no higher in individual rootlets than in other HTC regions of the root system. We also examine the transformation theory (the theory of form resulting from a series of forces, which, when altered, lead to a change, or transformation in form) as an explanation of cluster root evolution, and conclude that the cluster root requires only a change in pericycle response to depleted internal nutrient levels, with the other characteristics representing consequences stemming from the form and constraints of the root system.     

Metal content in insects associated with ultramafic and non-ultramafic sites in the Scottish Highlands

1. Concentrations of magnesium, manganese, chromium, and cadmium were measured in Coleoptera, Diptera, Hemiptera, and Hymenoptera captured at ultramafic and non-ultramafic sites in the Highlands of Scotland. 2. The Hemiptera showed the greatest concentration differences between the ultramafic and non-ultramafic sites in manganese, magnesium, and chromium, with greatly increased levels in ultramafic sites. 3. The Coleoptera and Hymenoptera had lower levels of manganese, magnesium, and chromium at the ultramafic site than at the non-ultramafic sites. The Diptera had increased levels of manganese and magnesium at the ultramafic site, but showed no difference in chromium levels from any site. 4. Cadmium occurred at lower levels in all insect orders at the ultramafic site.