Numerical study of the effect of head and eye movement on progression of retinal detachment

Rhegmatogenous retinal detachment (RD) is a sight threatening condition. In this type of RD a break in the retina allows retrohyaloid fluid to enter the subretinal space. The prognosis concerning the patients’ visual acuity is better if the RD has not progressed to the macula. The patient is given a posturing advice of bed rest and semi-supine positioning (with the RD as low as possible) to allow the utilisation of gravity and immobilisation in preventing progression of the RD. It is, however, unknown what external loads on the eye contribute the most to the progression of a RD. The goal of this exploratory study is to elucidate the role of eye movements caused by head movements and saccades on the progression of an RD. A finite element model is produced and evaluated in this study. The model is based on geometric and material properties reported in the literature. The model shows that a mild head movement and a severe eye movement produce similar traction loads on the retina. This implies that head movements—and not eye movements—are able to cause loads that can trigger and progress an RD. These preliminary results suggest that head movements have a larger effect on the progression of an RD than saccadic eye movements. This study is the first to use numerical analysis to investigate the development and progression of RD and shows promise for future work.     

Micro-computed tomography of pupal metamorphosis in the solitary bee Megachile rotundata

Insect metamorphosis involves a complex change in form and function. In this study, we examined the development of the solitary bee, Megachile rotundata, using micro-computed tomography (μCT) and volume analysis. We describe volumetric changes of brain, tracheae, flight muscles, gut, and fat bodies in prepupal, pupal, and adult M. rotundata. We observed that individual organ systems have distinct patterns of developmental progression, which vary in their timing and duration. This has important implications for commercial management of this agriculturally relevant pollinator.     

Diversity of Phage Types among Archived Cultures of the Demerec Collection of Salmonella enterica serovar Typhimurium Strains

The existence of several thousand Salmonella enterica serovar Typhimurium LT2 and LT7 cultures originally collected by M. Demerec and sealed in agar stab vials for 33 to 46 years is a resource for evolutionary and mutational studies. Cultures from 74 of these vials, descendants of cells sealed and stored in nutrient agar stabs several decades ago, were phage typed by the Callow and Felix, Lilleengen, and Anderson systems. Among 53 LT2 archived strains, 16 had the same phage type as the nonarchival sequenced LT2 strain. The other 37 archived cultures differed in phage typing pattern from the sequenced strain. These 37 strains were divided into 10 different phage types. Among the 19 LT7 strains, only one was similar to the parent by phage typing, while 18 were different. These 18 strains fell into eight different phage types. The typing systems were developed to track epidemics from source to consumer, as well as geographic spread. The value of phage typing is dependent upon the stability of the phage type of any given strain throughout the course of the investigation. Thus, the variation over time observed in these archived cultures is particularly surprising. Possible mechanisms for such striking diversity may include loss of prophages, prophage mosaics as a result of recombination events, changes in phage receptor sites on the bacterial cell surface, or mutations in restriction-modification systems.     

Anterior sensory organs in Sabellariidae (Annelida)

Sensory organs in Annelida are very diverse and may be useful for assessments of morphological adaptation and character evolution. We used several methods to provide new insights into processes underlying the evolutionary radiation of anterior sensory organs in Sabellariidae. The presence and morphological diversity of the median organ (MO) found in the group was reviewed in order to test its phylogenetic significance and possible relationships to the distribution and ecological traits of the lineages. To test the intraspecific phenotypic plasticity of the MO, molecular analyses were conducted that focused on mitochondrial and nuclear genes from populations of Idanthyrsus australiensis exhibiting variation in the morphology of the MO. We used an integrative microscopical study of the ontogeny of Sabellaria alveolata to describe the anterior sensory structures present in the larvae and the morphological changes occurring before, during, and after settlement. In larval stages, the palps and the dorsal hump (DH) exhibit distinct innervation. The larval DH organ, which is likely to play a major role in chemoreception for settlement, is interpreted as being the incipient form of the adult MO. These results suggest that annelid sensory organs including the MO may be useful for phylogenetic and developmental investigations.     

Plant growth and ectomycorrhiza formation by transplants on deglaciated land near Exit Glacier, Alaska

 Ectomycorrhiza (EM) formation on plant roots in successional communities may vary with plant species, plant age, and age of vegetation after disturbance. To evaluate differences in mycorrhizal fungus communities on roots of same-aged seedlings across a deglaciated chronosequence, indoor-grown bioassay plants of four dominant species Epilobium latifolium L. (dwarf fireweed), Populus balsamifera ssp. trichocarpa (Torr.&Gray) Hult. (black cottonwood), Alnus sinuata (Regel) Rydb. (Sitka alder), and Picea sitchensis (Bong.) Carr. (Sitka spruce) were transplanted into five successional stages (Barren, Isolated Plant, Patchy, Alder, and Cottonwood) following deglaciation near Exit Glacier, Alaska. The species were selected for their successional status and mycorrhiza formation potential [EM or arbuscular mycorrhiza (AM) or both]. Seedlings were transplanted in June 1992, and half were harvested at the ends of the two subsequent growing seasons. The EM communities on P. balsamifera differed across the chronosequence while those of the other species did not. Morphotype B dominated the EM on P. balsamifera after the Barren stage, and the greatest EM colonization was in the Isolated Plant and Patchy stages. No AM were found. The EM observed on even-aged seedlings in this study were a subset of the EM found on naturally occurring plants (seedlings to mature trees) in a prior study, and some were common to multiple plant species. Most plant growth responses were not significant across stages or were inconsistent among plant species. Accepted: 25 December 1998     

A Novel Ribosomal S6-Kinase (RSK4; RPS6KA6) Is Commonly Deleted in Patients with Complex X-Linked Mental Retardation

Large deletions in Xq21 often are associated with contiguous gene syndromes consisting of X-linked deafness type 3 (DFN3), mental retardation (MRX), and choroideremia (CHM). The identification of deletions associated with classic CHM or DFN3 facilitated the positional cloning of the underlying genes, REP-1 and POU3F4, respectively, and enabled the positioning of the MRX gene in between these genes. Here, we report the cloning and characterization of a novel gene, ribosomal S6-kinase 4 (RSK4; HGMW-approved symbol RPS6KA6), which maps in the MRX critical region. RSK4 is completely deleted in eight patients with the contiguous gene syndrome including MRX, partially deleted in a patient with DFN3 and present in patients with an Xq21 deletion and normal intellectual abilities. RSK4 is most abundantly expressed in brain and kidney. The predicted protein of 746 amino acids shows a high level of homology to three previously isolated members of the human RSK family. RSK2 is involved in Coffin–Lowry syndrome and nonspecific MRX. The localization of RSK4 in the interval that is commonly deleted in mentally retarded males together with the high degree of amino acid identity with RSK2 suggests that RSK4 plays a role in normal neuronal development. Further mutation analyses in males with X-linked mental retardation must prove that RSK4 is indeed a novel MRX gene.     

Programmed and flexible: long‐term Zugunruhe data highlight the many axes of variation in avian migratory behaviour

Studies of Zugunruhe – the ‘migratory restlessness’ behaviour of captive birds – have been integral to our understanding of animal migration, revealing an inherited propensity to migrate and an endogenous timing and navigation system. However, differences between Zugunruhe in captivity and migration in the wild call for more data, in particular on variation within and among taxa with diverse migration strategies. Here, we characterise Zugunruhe in a long‐term dataset of activity profiles from stonechats (genus Saxicola) with diverse migratory phenotypes (976 migration periods from 414 birds), using a flexible and consistent quantitative approach based on changepoint analysis. For east African, Austrian, Irish, and Siberian stonechats and hybrids, we report key inter‐population differences in the occurrence, timing, and intensity of Zugunruhe. In line with expectations, we found the highest Zugunruhe intensity in the longest‐distance migrants, more variable patterns in short‐distance migrants, and intermediate characteristics of hybrids relative to their parental groups. Inter‐population differences imply high evolutionary lability of Zugunruhe timing within a robustly structured annual cycle. However, counter to theory, Irish partial migrants showed no segregation between migrant and resident individuals, and previously reported nocturnal restlessness was confirmed for resident African stonechats. Further features of nocturnal restlessness that did not align with migratory behaviour of stonechats were juvenile nocturnal restlessness even prior to postjuvenile moult, and protandry in spring, although stonechats winter in heterosexual pairs. Importantly, Zugunruhe of all populations declined with age, and the intensity of an individual bird's Zugunruhe was correlated with activity levels during other parts of the annual cycle. Our results confirm endogenous, population‐specific migration programmes but also reveal apparent discrepancies between Zugunruhe and migration in the wild. We thus highlight both the continued potential of Zugunruhe study and the need for circumspect interpretation when using migratory restlessness to make inferences about migration in the wild.     

Multiple environmental changes drive forest floor vegetation in a temperate mountain forest

Human‐induced changes of the environment and their possible impacts on temperate forest understory plant communities have been examined in many studies. However, the relative contribution of individual environmental factors to these changes in the herb layer is still unclear. In this study, we used vegetation survey data covering a time period of 21 years and collected from 143 permanent plots in the Northern Limestone Alps, Austria. Data on soil chemistry (49 plots), light condition (51 plots), soil temperature and moisture (four and six plots), disturbance (all plots), climate (one station in a clearing area), and airborne sulfur (S) and nitrogen (N) deposition (two forest stands) were available for analyses. We used these data together with plot mean Ellenberg indicator values in a path analysis to attribute their relative contributions to observed vegetation changes. Our analysis reveals a strong directional shift of the forest understory plant community. We found strong evidence for a recovery of the ground‐layer vegetation from acidification as response to decreased S deposition. We did not observe a community response to atmospheric N deposition, but we found a response to altered climatic conditions (thermophilization and drying). The path analysis revealed that changes in the light regime, which were related to small‐scale disturbances, had most influence on herb layer community shifts. Thermophilization and drying were identified as drivers of understory community changes independent of disturbance events.