Atmospheric detection of water dimers via near-infrared absorption

Weakly bonded pairs of water molecules (H2O)2, or water dimers (WDs), may play an important role in photochemistry and climate, but the overlap of most of its spectral features with the water monomer (WM) has made detection difficult. We report on WD absorption measurements by means of atmospheric long-path (18.34 kilometers) differential optical absorption spectroscopy of the near-infrared OH stretching mode 0>f 4>b overtone transition predicted to be located near 746 nanometers. Our observation is in reasonable agreement with the known thermochemistry, calculated and measured structure, and spectroscopy (band strength, shape, and width) of the WD. The observation implies that the WD 0>f 4>b band is located at 749.5 nanometers, with a full width at half maximum of approximately 19.4 wave numbers, and that its band strength ranges between 1.23 x 10(-22) and 5.25 x 10(-22) centimeters per molecule.     

Damage of potato tubers,a review

Summary Damage to potato tubers due to mechanical forces is among the most important causes of loss of quality reported throughout the world. The causes of such damage are mechanical injuries that occur primarily in association with harvesting and grading. The extent of damage is dependent on the condition of the tubers and also reflects the history of the potatoes. Although important advances have been made, there is still a considerable need for research on this subject since knowledge of the combined effects of essential physiological proceses within the cells is still lacking. The avoidance of exposure to mechanical forces constitutes the most effective protection against tuber damage.     

Impacts of elevated atmospheric CO2 and temperature on plant community structure of a temperate grassland are modulated by cutting frequency

To determine the impacts of climate change and defoliation on the community structure and plant diversity of a semi‐natural temperate grassland, monoliths of a permanent grassland were exposed to ambient or elevated atmospheric CO₂ concentrations (ambient + 235 ppmv) and temperature (ambient + 3°C) from October 1998 to December 2000. The monoliths were subjected to two different cutting frequencies, either two or six cuts per year. The grassland community structure changed during the course of the experiment and was more responsive to changes in management than to changes in climate. Increased cutting frequency stimulated plant diversity by enhancing the number of forb species, but plant diversity was not significantly affected by climate change. The contribution of individual plant species to the vegetation cover revealed species‐specific responses to climate change and cutting frequency, but for most species significant interactions between climate change and cutting frequency were present. There were no clear‐cut effects of treatments on the total annual yield and the proportion of forbs present, as significant interactions between climate change and cutting frequency occurred. It is concluded that differential grassland management will modify plant species‐specific responses to climate change and resulting changes in the botanical composition of mixed‐species, temperate grasslands.     

The susceptibility of chicken kidney and oviduct organ cultures to a vaccine strain of avian infectious bronchitis virus.

The minimal infectious dose of the H52 strain of infectious bronchitis virus for organ cultures of oviduct and kidney was compared in chickens of different ages. Organ cultures of oviduct were found to be highly susceptible to infection regardless of the age of chicken and no difference in susceptibility could be demonstrated between cultures of the magnum and uterus regions of the mature oviduct. Kidney organ cultures were less susceptible and resistance to infection increased significantly (P less than 0.001) with the age of the chicken from which cultures were prepared.     

A well-preserved Archaeopteryx specimen with theropod features

A nearly complete skeleton of Archaeopteryx with excellent bone preservation shows that the osteology of the urvogel is similar to that of nonavian theropod dinosaurs. The new specimen confirms the presence of a hyperextendible second toe as in dromaeosaurs and troodontids. Archaeopteryx had a plesiomorphic tetraradiate palatine bone and no fully reversed first toe. These observations provide further evidence for the theropod ancestry of birds. In addition, the presence of a hyperextendible second toe blurs the distinction of archaeopterygids from basal deinonychosaurs (troodontids and dromaeosaurs) and challenges the monophyly of Aves.     

Two mosaic terminal inverted duplications arising post-zygotically: Evidence for possible formation of neo-telomeres

Objective

To elucidate the structure of terminal inverted duplications and to investigate potential mechanisms of formation in two cases where there was mosaicism with cells of apparently normal karyotype.

Results

A karyotype [46,XY,inv dup(4)(p16.3p15.1)/46,XY] performed on blood lymphocytes from a patient referred for developmental delay (case 1) demonstrated a normal karyotype in 60% of cells with a terminal inverted duplication 4p in the remainder. In case 2, referred for multiple fetal anomalies on an ultrasound scan, 33% of amniocyte colonies were karyotypically normal, with a terminal inv dup 10p in the remainder [46,XX,inv dup(10)(p15.3p11)/46,XX]. Duplicated FISH signals for GATA3 and NEBL loci (in case 2), and for the Wolf-Hirschhorn locus (case 1) confirmed the inverted structure of both duplications. In the GTL banded normal cells from both cases, there was a cryptic deletion detected by FISH of one copy of the subtelomere 4p (case 1, probe GS-36P21), and subtelomere 10p (case 2, probe GS-306F7). At pter on both inv dup chromosomes there was no FISH signal present for the specific subtelomere probe. However, a positive pantelomeric probe signal was detected at 4 pter and 10 pter in both the cryptically-deleted chromosomes and the inv dup chromosomes in the respective cell lines of both cases.

Conclusion

An inv dup structure was evident for both cases on GTL bands, and confirmed by the various FISH studies. The presence of telomere (TTAGGG repeat) sequences at pter on the inv dup chromosomes (where more proximal chromosome specific subtelomeric probes were negative) was indicated by the pantelomeric probe signals in both cases. We conclude the most likely mechanism of origin in both cases was by sub-telomeric breakage in the zygote at pter, and delayed repair/rearrangement until after one or more subsequent mitotic divisions. In these divisions, at least one breakage-fusion-bridge cycle occurred, to produce inverted duplications. It is proposed then that two differently "repaired" daughter cells proliferated in parallel. In one daughter cell line (with an overtly normal karyotype) there was deletion of the subtelomere and presumed repair through capping by a neo-telomere (i.e. "healing", as initially proposed by McClintock). This occurred in both cases presented. In the other daughter cell of each case, it is proposed that chromosome stabilization was achieved (after replication) by sister chromatid reunion to form a dicentric, which broke at a subsequent anaphase, to form an inverted duplication (with loss of the reciprocal product, and the other daughter cell line). One inv dup was repaired without an interstitial specific subtelomere (case 1) and one was repaired with a duplicated specific interstitial subtelomere (case 2). After repair TTAGGG repeats were detected by FISH at each respective new pter.

     

American foulbrood of the honey bee: Occurrence and distribution of different genotypes of Paenibacillus larvae in the administrative district of Arnsberg (North Rhine‐Westphalia)

Between March 2003 and October 2004, Paenibacillus larvae, the aetiological agent of American foulbrood disease of the honey bee, was isolated from broodcombs and honey samples of 54 apiaries in the administrative district of Arnsberg (North Rhine‐Westphalia, Germany). Genotyping of 176 P. larvae isolates with repetitive element polymerase chain reaction fingerprinting (rep‐PCR) using BOX A1R and MBO REP1 primers revealed five different genotypes (AB, Ab, ab, aß, AБ). In samples of three apiaries, more than one genotype was detected. A combination of two genotypes was isolated from honey samples of the same hive two times (ab/aß and Ab/ab). The five genotypes were not randomly distributed in the district, but revealed a certain geographical clustering. Possible factors with impact on the genotype diversity and the distribution pattern are discussed.