Aquaporins in complex tissues: distribution of aquaporins 1-5 in human and rat eye

Multiple physiological fluid movements areinvolved in vision. Here we define the cellular and subcellular sitesof aquaporin (AQP) water transport proteins in human and rat eyes byimmunoblotting, high-resolution immunocytochemistry, and immunoelectronmicroscopy. AQP3 is abundant in bulbar conjunctival epithelium andglands but is only weakly present in corneal epithelium. In contrast, AQP5 is prominent in corneal epithelium and apical membranes of lacrimal acini. AQP1 is heavily expressed in scleral fibroblasts, corneal endothelium and keratocytes, and endothelium covering thetrabecular meshwork and Schlemm's canal. Although AQP1 is plentiful inciliary nonpigmented epithelium, it is not present in ciliary pigmentedepithelium. Posterior and anterior epithelium of the iris and anteriorlens epithelium also contain significant amounts of AQP1, but AQP0(major intrinsic protein of the lens) is expressed in lens fiber cells.Retinal Müller cells and astrocytes exhibit notableconcentrations of AQP4, whereas neurons and retinal pigment epitheliumdo not display aquaporin immunolabeling. These studies demonstrateselective expression of AQP1, AQP3, AQP4, and AQP5 in distinct ocularepithelia, predicting specific roles for each in the complex networkthrough which water movements occur in the eye.

     

Boosted regression trees with errors in variables

In this article, we consider nonparametric regression when covariates are measured with error. Estimation is performed using boosted regression trees, with the sum of the trees forming the estimate of the conditional expectation of the response. Both binary and continuous response regression are investigated. An approach to fitting regression trees when covariates are measured with error is described, and the boosting algorithms consist of its repeated application. The main feature of the approach is that it handles situations where multiple covariates are measured with error. Some simulation results are given as well as its application to data from the Framingham Heart Study.     

Reproductive biology of the arctic collembolan Hypogastrura tullbergi

Terrestrial organisms of the Arctic are faced with strong climatic fluctuations. Predictable seasonality with cold/long winters and short/cool summers are combined with unpredictable between and within year variation. This indicates that various selection pressures act on the reproductive strategies of the populations. The arctic collembolan Hypogastrura tullbergi reproduces in a short period following snow melt. Hatching occurs in late summer, the animals grow to adult size within their second summer and reproduce for the first time in the beginning of their third summer. We performed several experiments to determine the reproductive investment and proximate mechanism that regulate timing and duration of reproduction. We found that H. tullbergi entered a reproductive diapause when reared at constant temperature, a diapause that was terminated by a cold exposure (winter). Surprisingly, cold exposure of small juveniles may also prevent development of a reproductive diapause in adults. Thus, the life-cycle normally spanning 2 yr can potentially be reduced to one year if the overwintering juveniles reach maturity before the end of the reproductive period in the field. After termination of the diapause, the animals reproduced up to 3 times during a period of 6 weeks at 15°C. This reproductive period was considerably longer (measured in degree days) than the one observed in the field. Our results suggested that temperature quiescence, i.e. the inability to reproduce under a certain temperature threshold, may adjust the termination of the reproductive period with current temperature before a new diapause occurs in late summer. The cost of reproduction was low and suggests that it can be adaptive to spread reproduction over more than one year. The results are discussed in relation to the arctic climate and strategies favoured by unpredictable and predictable (seasonal) variations in the environment. The present study forms part of a larger investigation on population dynamics and life history strategies of H. tullbergi from the Arctic.     

Nitrogen redistribution from the roots in post-anthesis plants of spring wheat

The aim of this study was to investigate post-anthesis N redistribution from the roots to other organs in the wheat plant. Two cultivars of spring wheat (Triticum aestivum L.) Sport and WL were grown to maturity in culture solution with stepwise-decreasing N supply and ¹⁵N before sampling. The N concentration of dry weight in the roots decreased from anthesis to full maturity. At maturity the root N concentration was 5.5 mg g⁻¹ dry weight for Sport and 4.9 mg g⁻¹ dry weight for WL, while the main shoot N concentration was 2.1 mg g⁻¹ dry weight for Sport and 2.2 mg g⁻¹ dry weight for WL. The roots were a major sink for N taken up post-anthesis and contained the main proportion of the ¹⁵N during the whole post-anthesis period. The N redistributed from the roots contributed 24.3% of the total N amount in the grains at maturity in cv Sport and 8.7% in cv WL. For cv Sport, 46.3% of the root N amount was redistributed to other parts of the plant and for WL 25.4%. The tiller grains were supplied with N from the ¹⁵N applied post-anthesis to a higher degree than the main shoot grains. The transport capability was maintained until 12 days after complete yellowness. We concluded that wheat has a great ability to redistribute nitrogen from the root system to the grains.     

Access to mates in a territorial ungulate is determined by the size of a male's territory, but not by its habitat quality

1. Territoriality is commonly associated with resource defence polygyny, where males are expected to gain access to females by anticipating how resources will influence female distribution and competing for resource-rich sites to establish their zone of dominance. 2. We tested this hypothesis in European roe deer (Capreolus capreolus) by simultaneously assessing the influence of resources on female distribution and the influence of female distribution on male distribution and breeding success using paternity analyses. 3. Females did not fully distribute themselves among male territories in relation to resources. As a result, relative female abundance in a male's territory depended on territory size, but not on its habitat quality. In turn, relative female abundance in a male's territory determined, at least partially, his breeding success. 4. Interestingly, male territory size, and hence access to females, was partly determined by male body mass (all males) and by residual antler size (subadults only). The latter result suggests that large antlers may be important to young males for establishing their first territory, which is then usually retained for all subsequent reproductive seasons. 5. To conclude, although territoriality of male roe deer has certainly evolved as a tactic for ensuring access to mates, our results suggest that it does not really conform to a conventional resource defence polygyny strategy, as males seem to gain no obvious benefit from defending a territory in an area of high habitat quality in terms of enhanced access to mates. 6. This may explain the stability of male territories between years, suggesting that male territoriality conforms to an 'always stay' and 'low risk-low gain' mating strategy in roe deer.     

A trypsin-like protease with apparent dual function in early Lepeophtheirus salmonis (Kr?yer) development

Background  

Trypsin-like serine proteases are involved in a large number of processes including digestive degradation, regulation of developmental processes, yolk degradation and yolk degradome activation. Trypsin like peptidases considered to be involved in digestion have been characterized in Lepeophtheirus salmonis. During these studies a trypsin-like peptidase which differed in a number of traits were identified.     

Anti-dsDNA Antibodies Promote Initiation,and Acquired Loss of Renal Dnase1 Promotes Progression of Lupus Nephritis in Autoimmune (NZBxNZW)F1 Mice

Background

Lupus nephritis is characterized by deposition of chromatin fragment-IgG complexes in the mesangial matrix and glomerular basement membranes (GBM). The latter defines end-stage disease.

Methodology/Principals

In the present study we determined the impact of antibodies to dsDNA, renal Dnase1 and matrix metalloprotease (MMP) mRNA levels and enzyme activities on early and late events in murine lupus nephritis. The major focus was to analyse if these factors were interrelated, and if changes in their expression explain basic processes accounting for lupus nephritis.

Findings

Early phases of nephritis were associated with chromatin-IgG complex deposition in the mesangial matrix. A striking observation was that this event correlated with appearance of anti-dsDNA antibodies and mild or clinically silent nephritis. These events preceded down-regulation of renal Dnase1. Later, renal Dnase1 mRNA level and enzyme activity were reduced, while MMP2 mRNA level and enzyme activity increased. Reduced levels of renal Dnase1 were associated in time with deficient fragmentation of chromatin from dead cells. Large fragments were retained and accumulated in GBM. Also, since chromatin fragments are prone to stimulate Toll-like receptors in e.g. dendritic cells, this may in fact explain increased expression of MMPs.

Significance

These scenarios may explain the basis for deposition of chromatin-IgG complexes in glomeruli in early and late stages of nephritis, loss of glomerular integrity and finally renal failure.     

Cross-continental differences in patterns of predation: will naive moose in Scandinavia ever learn?

Predation has been recognized as a major selective force in the evolution of behavioural characteristics of mammals. As a consequence of local predator extinction, prey may lose knowledge about natural predators but usually express behavioural adjustments after return of predators. Human harvest may replace natural predation but prey selection may differ from that of natural predators leading to a change in the behavioural response of prey. We show that hunting success (HS) of re-colonizing wolves (Canis lupus) on moose (Alces alces) in Scandinavia was higher than reported in North America, where moose have been continuously exposed to wolves and grizzly bears. We found no evidence that moose expressed behavioural adjustments that lowered the HS of wolves in territories that had been occupied by wolves for up to 21 years. Moose behaviour towards wolves and humans typically differs in Scandinavia compared to North America. We explain the differences found to be caused by variation in predation pressure by large carnivores and the rate, and mode, of human harvest during the twentieth century.     

Renal Dnase1 Enzyme Activity and Protein Expression Is Selectively Shut Down in Murine and Human Membranoproliferative Lupus Nephritis

Background

Deposition of chromatin-IgG complexes within glomerular membranes is a key event in the pathogenesis of lupus nephritis. We recently reported an acquired loss of renal Dnase1 expression linked to transformation from mild to severe membranoproliferative lupus nephritis in (NZBxNZW)F1 mice. As this may represent a basic mechanism in the progression of lupus nephritis, several aspects of Dnase1 expression in lupus nephritis were analyzed.

Methodology/Principal Findings

Total nuclease activity and Dnase1 expression and activity was evaluated using in situ and in vitro analyses of kidneys and sera from (NZBxNZW)F1 mice of different ages, and from age-matched healthy controls. Immunofluorescence staining for Dnase1 was performed on kidney biopsies from (NZBxNZW)F1 mice as well as from human SLE patients and controls. Reduced serum Dnase1 activity was observed in both mesangial and end-stage lupus nephritis. A selective reduction in renal Dnase1 activity was seen in mice with massive deposition of chromatin-containing immune complexes in glomerular capillary walls. Mice with mild mesangial nephritis showed normal renal Dnase1 activity. Similar differences were seen when comparing human kidneys with severe and mild lupus nephritis. Dnase1 was diffusely expressed within the kidney in normal and mildly affected kidneys, whereas upon progression towards end-stage renal disease, Dnase1 was down-regulated in all renal compartments. This demonstrates that the changes associated with development of severe nephritis in the murine model are also relevant to human lupus nephritis.

Conclusions/Significance

Reduction in renal Dnase1 expression and activity is limited to mice and SLE patients with signs of membranoproliferative nephritis, and may be a critical event in the development of severe forms of lupus nephritis. Reduced Dnase1 activity reflects loss in the expression of the protein and not inhibition of enzyme activity.