The relationship between cell injury and osmotic volume reduction: III. Freezing injury and frost resistance in winter wheat

In order to distinguish between several possible mechanisms of frost hardening in winter wheat (Triticum aestivum L.) cells from two hardy and two tender cultivars were plasmolyzed in CaCl₂ solution at room temperature and cell volumes estimated by microscopic examination. Analyses of Boyle-van't Hoff plots of these data reveal that all cells from cultivars progressively increase their intracellular solute concentration up to 20 days hardening. This increase, which we had predicted from published calorimetric data to be the sole mechanism of hardening explained less than half of the increase in hardening seen in the most hardy cultivar, Kharkov. Hardening also increased the osmotically inactive volume.At CaCl₂ concentrations greater than 5%, plasmolyzed protoplasts departed further from the Boyle-van't Hoff prediction, remaining larger than expected until some higher concentration of CaCl₂, where protoplast volume again sharply decreased. In all cultivars except hardened Kharkov, the concentration of CaCl₂ producing this abrupt volume decrease had a freezing point corresponding to the killing temperature. If this concentration was exceeded during plasmolysis, then the protoplasts burst during deplasmolysis at some volume less than their original volume.We interpret these data to mean that, in addition to the often described hardening mechanism of increased cell solute and water binding, winter wheat shows a third mechanism, a mechanical resistance to protoplast shrinkage which produces volumes larger than those predicted during osmotic stress. The resisting element appears to be the plasma membrane itself. Shrinkage brings the membrane under compressive stress, developing tangential pressure within it. Cell injury occurs when the cell membrane area has been reduced to the point at which irreversible loss of membrane material is inevitable. Cell death occurs during deplasmolysis when the protoplast bursts because its membrane contains insufficient material to subtend the area of the cell wall.Of the cultivars tested, hardened Kharkov was unique in avoiding injury. Hardened Kharkov was injured only after the volume inflection had been greatly exceeded. Refractile droplets of lipid appeared in the cytoplasm of hardened Kharkov protoplasts during plasmolysis but disappeared during deplasmolysis suggesting that hardy Kharkov was able reversibly to store membrane lipids in cytoplasmic vesicles and return them to the membrane on deplasmolysis.     

More evidence for a slender growth habit in Mesozoic cycadophytes

From the Pekin Formation (Upper Triassic) of the Deep River basin in central North Carolina, U.S.A., originate remains of a slender cycadeoidalean (bennettitalean) stem with leaves of a type combining features of the form genera Otozamites and Zamites. The plant, placed in the new genus and species Ischnophyton iconicum, is additional evidence that the common growth habit of Triassic and Jurassic cycadophytes was one involving a slender stem, without closely spaced, persistent leaf bases.     

Bovine Spongiform Encephalopathy Statement of Possible Relation With New Variant Creutzfeldt--Jakob Disease: Effects on the Welfare of United Kingdom Cattle

Although measures to control bovine spongiform encephalopathy (BSE) had been in force in the United Kingdom for many years and had resulted in a marked decline in clinical cases, the announcement by the Secretary of State for Health on March 20, 1996, that a new variant form of Creutzfeldt-Jakob Disease may be linked with exposure to BSE, resulted in the introduction of several new control measures. These measures included a scheme banning human consumption of meat from cattle who were more than 30 months old (the so-called "over 30-month scheme;" OTMS), a subsidy for slaughter of calves, and additional inspections of abattoirs. The altered slaughter procedures and lack of rendering facilities meant an initial backlog of OTMS animals having to remain on farms. This placed pressures on accommodation and feed stocks, the latter being in short supply because of a poor grass growth the previous summer. Initially, the long delay before the removal of casualty animals from the farm resulted in increased summer mastitis problems for nonlactating cows. The export of calves to the European Union for veal production was banned, thereby allowing the cessation of a previously legal trade that was considered distasteful by many members of the general public. Financial concerns disturbed and continue to disturb affected farmers.     

Unique gene alterations are induced in FACS‐purified Fos‐positive neurons activated during cue‐induced relapse to heroin seeking

Cue‐induced heroin seeking after prolonged withdrawal is associated with neuronal activation and altered gene expression in prefrontal cortex (PFC). However, these previous studies assessed gene expression in all neurons regardless of their activity state during heroin seeking. Using Fos as a marker of neural activity, we describe distinct molecular alterations induced in activated versus non‐activated neurons during cue‐induced heroin seeking after prolonged withdrawal. We trained rats to self‐administer heroin for 10 days (6 h/day) and assessed cue‐induced heroin seeking in extinction tests after 14 or 30 days. We used fluorescent‐activated cell sorting (FACS) to purify Fos‐positive and Fos‐negative neurons from PFC 90 min after extinction testing. Flow cytometry showed that Fos‐immunoreactivity was increased in less than 10% of sparsely distributed PFC neurons. mRNA levels of the immediate early genes fosB, arc, egr1, and egr2, as well as npy and map2k6, were increased in Fos‐positive, but not Fos‐negative, neurons. In support of these findings, double‐label immunohistochemistry indicated substantial coexpression of neuropeptide Y (NPY)‐ and Arc‐immunoreactivity in Fos‐positive neurons. Our data indicate that cue‐induced relapse to heroin seeking after prolonged withdrawal induces unique molecular alterations within activated PFC neurons that are distinct from those observed in the surrounding majority of non‐activated neurons.     

Do foods imported into the UK have a greater environmental impact than the same foods produced within the UK?

Purpose

This study of seven foods assessed whether there are modes or locations of production that require significantly fewer inputs, and hence cause less pollution, than others. For example, would increasing imports of field-grown tomatoes from the Mediterranean reduce greenhouse gas (GHG) emissions by reducing the need for production in heated greenhouses in the UK, taking account of the additional transport emissions? Is meat production in the UK less polluting than the import of red meat from the southern hemisphere?

Methods

We carried out a life-cycle inventory for each commodity, which quantified flows relating to life-cycle assessment (LCA) impact categories: primary energy use, acidification, eutrophication, abiotic resource use, pesticide use, land occupation and ozone depletion. The system boundary included all production inputs up to arrival at the retail distribution centre (RDC). The allocation of production burdens for meat products was on the basis of economic value. We evaluated indicator foods from which it is possible to draw parallels for foods whose production follows a similar chain: tomatoes (greenhouse crops), strawberries (field-grown soft fruit), apples (stored for year-round supply or imported during spring and summer), potatoes (early season imports or long-stored UK produce), poultry and beef (imported from countries such as Brazil) and lamb (imported to balance domestic spring–autumn supply).

Results and discussion

Total pre-farm gate global warming potential (GWP) of potatoes and beef were less for UK production than for production in the alternative country. Up to delivery to the RDC, total GWP were less for UK potatoes, beef and apples than for production elsewhere. Production of tomatoes and strawberries in Spain, poultry in Brazil and lamb in New Zealand produced less GWP than in the UK despite emissions that took place during transport. For foods produced with only small burdens of GWP, such as apples and strawberries, the burden from transport may be a large proportion of the total. For foods with inherently large GWP per tonne, such as meat products, burdens arising from transport may only be a small proportion of the total.

Conclusions

When considering the GWP of food production, imports from countries where productivity is greater and/or where refrigerated storage requirement is less will lead to less total GWP than axiomatic preference for local produce. However, prioritising GWP may lead to increases in other environmental burdens, in particular leading to both greater demands on and decreasing quality of water resources.     

The Drosophila melanogaster homolog of UBE3A is not imprinted in neurons

In mammals, expression of UBE3A is epigenetically regulated in neurons and expression is restricted to the maternal copy of UBE3A. A recent report claimed that Drosophila melanogaster UBE3A homolog (Dube3a) is preferentially expressed from the maternal allele in fly brain, inferring an imprinting mechanism. However, complex epigenetic regulatory features of the mammalian imprinting center are not present in Drosophila, and allele specific expression of Dube3a has not been documented. We used behavioral and electrophysiological analysis of the Dube3a loss-of-function allele (Dube3a^15b) to investigate Dube3a imprinting in fly neurons. We found that motor impairment (climbing ability) and a newly-characterized defect in synaptic transmission are independent of parental inheritance of the Dube3a^15b allele. Furthermore, expression analysis of coding single nucleotide polymorphisms (SNPs) in Dube3a did not reveal allele specific expression differences among reciprocal crosses. These data indicate that Dube3a is neither imprinted nor preferentially expressed from the maternal allele in fly neurons.     

Urban living alters moult dynamics in a passerine

Urbanization and habitat fragmentation can alter the timing of life history events, potentially leading to phenological mismatches, carryover effects, and fitness costs. Whereas urbanization and fragmentation are known to alter important aspects of breeding in many bird species, little is known about the effects of urbanization and habitat fragmentation on moult. To investigate the effects of urbanization and fragmentation on the annual moult, we compared the moult dynamics (onset, duration, and intensity) of urban, fragmented forest, and contiguous forest populations of the Carolina chickadee, a North American resident passerine that moults once per year immediately following the breeding season. Over three years, moult dynamics were similar in contiguous and fragmented forest populations, but wing moult started significantly earlier, and onset of moult varied less among years, in urban chickadees than in forest chickadees (fragmented and contiguous habitats pooled). Duration of wing moult did not differ between urban and forest populations, but urban birds moulted significantly fewer feathers simultaneously during peak moult, suggesting that individual feathers grew more rapidly. Our results show that urban living alters critical aspects of moult dynamics in a widespread songbird. Given the importance of moult dynamics for fitness during subsequent life history stages, and the large number of songbird species inhabiting urban areas, these results reveal previously unrecognized and potentially costly carryover effects of urban living on songbirds.