An Abortion of Monozygotic Twins in a Warmblood Mare

Naturally occurring monozygotic twins are extremely rare in the horse. This paper describes an abortion in a mare after 260 days of pregnancy with monozygotic twins, one a fresh foal and the other a mummified foal.     

Gene expression responses to a Salmonella infection in the chicken intestine differ between lines

Poultry products are an important source of Salmonella enterica. An effective way to reduce food poisoning due to Salmonella would be to breed chickens more resistant to Salmonella. Unfortunately host responses to Salmonella are complex with many factors involved. To learn more about responses to Salmonella in young chickens, a cDNA microarray analysis was performed to compare gene expression profiles between two chicken lines under control and Salmonella infected conditions. Newly hatched chickens were orally infected with S. enterica serovar Enteritidis. Since the intestine is the first barrier the bacteria encounter after oral inoculation, intestinal gene expression was investigated at different timepoints. Differences in gene expression between the two chicken lines were found in control as well as Salmonella infected conditions. In response to the Salmonella infection a fast growing chicken broiler line induced genes that affect T-cell activation, whereas in a slow growing broiler line genes involved in macrophage activation seemed to be more affected at day 1 post-infection. At days 7 and 9 most gene expression differences between the two chicken lines were identified under control conditions, indicating a difference in the intestinal development between the two chicken lines which might be linked to the difference in Salmonella susceptibility. The findings in this study have lead to the identification of novel genes and possible cellular pathways, which are host dependent.     

Double-bridge hybrids of Solanum bulbocastanum and cultivars of Solanum tuberosum

Summary Solanum bulbocastanum (2n=2x=24) has valuable characters for potato breeding, but cannot be hybridized directly with S. tuberosum cultivars. Both S. acaule (2n=4x) and S. phureja (2n=2x) were used as bridging species. Triploid S. acaule × S. bulbocastanum were doubled with colchicine and the resulting fertile hexaploid F₁'s crossed with S. phureja. The triple hybrids obtained were tetraploid or nearly so. The two genomes of S. acaule in these triple hybrids probably pair preferentially, which may provoke pairing and possibly crossing over between the chromosomes of S. bulbocastanum and S. phureja.More than 20000 pollinations of the triple hybrids with four potato cultivars had to be made to produce 40 quadruple hybrids. These highly vigorous hybrids varied greatly in many morphological characters, resistance to Phytophthora infestans, fertility and crossability. The chromosome numbers are 48 (24 hybrids), 49 and 46, but some higher ploidy levels (65, 66, 72 chromosomes) were found as well. Their origin is to be sought in the fusion of an unreduced egg cell from triple hybrids (either euploid or hypoploid) and a reduced male gamete from the cultivars. This view is corroborated by their extreme resistance to Phytophthora. Also some 48-chromosome hybrids are highly resistant, which may indicate introgression from S. bulbocastanum.Most quadruple hybrids are readily inter-crossable and crossable as females with cultivars; several also as males. Two could be hybridized with S. bulbocastanum, but the few seeds dit not germinate.Studies of pachytene stage of meiosis revealed the presence of a S. bulbocastanum chromosome in at least one tetraploid hybrid, which is highly resistant to Phytophthora. At metaphase I of meiosis chromosome associations higher than quadrivalents were not found. Except in one hybrid, the frequency of quadrivalents did not exceed one per cell and the average proportion of chromosomes associated as bivalents amounted to 90%.The quadruple hybrids (double-bridge hybrids) appear good starting material for breeding programmes aimed at introducing genes from S. bulbocastanum into S. tuberosum cultivars.     

Sulfur cycling in a dutch moorland pool under elevated atmospheric S-deposition

Atmospheric S deposition, sulfate reduction and the accumulation of reduced S components were investigated in sediments of a Dutch moorland pool. Laboratory ³⁵SO42? tracer experiments indicated that the variation in reduction rate with depth in the sediment could be described by an exponential fit, suggesting first order kinetics. Sulfate reduction rates calculated from a kinetic transport model were highest in June and July (>0.6 mmol m^?2 day^?1), and decreased towards the end of the summer (<0.2 mmol m^?2 day^?1). Winter reduction rates were low, but increased towards the beginning of the spring. Concentrations of total, organic and inorganic S decreased with depth, consistent with an increasing depositional flux of S over the last century. Increased atmospheric sulfate deposition rates and consumption in the upper sedimentary layers caused a continuous increase in subsurface S concentrations. Present day S-immobilization rates were estimated between 25 to 30 mmol S in^?2 yr^?1, in the order of the annual input of S from wet atmospheric deposition. Sulfate metabolism in anaerobic moorland pool sediments may be the most important mechanism of long-term S-accumulation.     

Aluminosilicate phases during initial clay formation: H+-Al3+–oxalic acid–silicic acid–Na+ system

The solid phases and the precipitation boundary characterizing the system H⁺-Al³⁺-oxalic acid-silicic acid-Na⁺ are discussed. Model experiments have been used to throw more light on two environmental problems: the formation of sparingly soluble aluminium silicates in oceans and alkaline lakes, which could be determining aluminium and silicate concentrations in pore waters of sediments, and the validity of inorganic and organic mechanisms of podzolization and their significance for soil science. pH and Tyndallometric measurements were performed at constant ionic strength of 0.6 M NaCl at 25°C. Three phases Al(OH)₄, H₄SiO₄ (phase Vi^a), Al₂, (OH)₆.H₄SiO₄ (phase VI^b) and NaAl(OH)₄.(H₄SiO₄), (phase VIII) determine the precipitation boundary. Phase NaAl(OH)₄.H₄SiO₄ (phase VII precipitates at 0.4pH units above NaAl(OH)₄.(H₄SiO₄)₂. Using a set of previously determined binary and ternary complexes, and phases of the subsystems, the following formation constants were deduced: Phases VI^a and VI^b are described as end-members of the allophane series with Si: Al ratios of 1:1 and 1.2. Phase VI^b was identified with protoimogolite allophane. These two phases are good model clays for podzolic soils and are extremely soluble at pH < 4. Sodium phases could be hydrous feldspathoids. These phases are possible in sediments of seawater or saline lakes. It is suggested that organic and inorganic mechanisms of podzolization operate sequentially and that neither of them alone can completely describe the process.