Sperm sexing in sheep and cattle: the exception and the rule

Flow cytometric sorting for the preselection of sex has progressed considerably in the 20 years since its inception. This technique has allowed the production of pre-sexed offspring in a multitude of species and become a commercial success in cattle around the world. However, due to the stress inherent to the sex-sorting process, sex-sorted spermatozoa are widely recognized as functionally compromised in terms of their fertilizing lifespan within the female reproductive tract as a result of reduced motility and viability and changed functional state. These characteristics, when compared to non-sorted controls, are manifest in vivo as lower fertility. However, improvements to the technology and a greater understanding of its biological impact have facilitated recent developments in sheep, showing sex-sorting is capable of selecting a functionally superior population in terms of both in vitro and in vivo function. These results are reviewed in the context of recent developments in other species and the reasons for success after artificial insemination with sex-sorted ram spermatozoa are discussed.     

Small cysteine-rich peptides resembling antimicrobial peptides have been under-predicted in plants

Multicellular organisms produce small cysteine-rich antimicrobial peptides as an innate defense against pathogens. While defensins, a well-known class of such peptides, are common among eukaryotes, there are other classes restricted to the plant kingdom. These include thionins, lipid transfer proteins and snakins. In earlier work, we identified several divergent classes of small putatively secreted cysteine-rich peptides (CRPs) in legumes [Graham et al. (2004)Plant Physiol. 135, 1179-97]. Here, we built sequence motif models for each of these classes of peptides, and iteratively searched for related sequences within the comprehensive UniProt protein dataset, the Institute for Genomic Research's 33 plant gene indices, and the entire genomes of the model dicot, Arabidopsis thaliana, and the model monocot and crop species, Oryza sativa (rice). Using this search strategy, we identified approximately 13,000 plant genes encoding peptides with common features: (i) an N-terminal signal peptide, (ii) a small divergent charged or polar mature peptide with conserved cysteines, (iii) a similar intron/exon structure, (iv) spatial clustering in the genomes studied, and (v) overrepresentation in expressed sequences from reproductive structures of specific taxa. The identified genes include classes of defensins, thionins, lipid transfer proteins, and snakins, plus other protease inhibitors, pollen allergens, and uncharacterized gene families. We estimate that these classes of genes account for approximately 2-3% of the gene repertoire of each model species. Although 24% of the genes identified were not annotated in the latest Arabidopsis genome releases (TIGR5, TAIR6), we confirmed expression via RT-PCR for 59% of the sequences attempted. These findings highlight limitations in current annotation procedures for small divergent peptide classes.     

Comparative metabolism of the cis and trans isomers of N-nitroso-2-6-dimethylmorpholine in rats,hamsters and guinea pigs

The in vivo metabolism of the cis and trans isomers of N-[3,5-³H] nitroso-2,6-dimethylmorpholine (NDMM) was studied in female Fischer rats, Syrian golden hamsters and guinea pigs by analysis of urinary metabolites using high pressure liquid chromatography (HPLC). Animals were treated by gavage with 12 mg/kg body wt. of NDMM, composed of both isomers and 12 μCi/kg body wt. of either of the separated radioactive isomers (cis or trans). Control animals received 12 mg, 12 μCi/kg body wt. NDMM with both isomers labeled in their natural proportion.There was a substantial increase in the excretion of a particular metabolite, 2-(2-hydroxyl-methyl)ethoxy propanoic acid, in the urine of rats, hamsters and guinea pigs 24 h after received the trans isomer (24, 22 and 13% of the total dose excreted, respectively). A minor metabolite was determined to be 2,6-dimethylmorpholine-3-one, another product of α-oxidation. The metabolite 1-amino-2-hydroxypropanol was identified, indicating that NDMM was metabolized by both α-and β-oxidation.In all three species, animals administered the cis isomer excreted larger amounts of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) and N-nitroso-bis(2-hydroxypropyl)amine (BHP) products of beta oxidation, than those treated with the trans isomer. Hamsters and guinea pigs treated with the more carcinogenic cis isomer in these species, also excreted twice as much of two other metabolites than was found in the urine of animals given the trans isomer.The trans isomer of NDMM appeared to be preferentially metabolized by α-oxidation and from earlier studies this metabolic pathway seemed to be important in carcinogenesis by NDMM in the rat. The cis isomer might be in a conformation more favorable for β-oxidation and this pathway may be of primary importance in carcinogenesis by NDMM in hamsters and guinea pigs.     

Flower-specific expression of the Agrobacterium tumefaciens isopentenyltransferase gene results in radial expansion of floral organs in Petunia hybrida

Biotechnology has the potential to modify commercially important traits of crops, such as fruit size and stress tolerance. To date, the floricultural industry has not profited significantly from these possibilities to manipulate, for example, flower size. Cytokinins are known to be involved in many aspects of plant development, including cell division. Increasing the amount of cytokinins has the potential to increase the size of an organ, such as the flower or the fruit. The Agrobacterium tumefaciens cytokinin biosynthesis gene isopentenyltransferase ( ipt ) has been shown to increase cytokinin levels when introduced into plants. Moreover, it has a dramatic effect on the vegetative development of plants. The expression of the ipt gene under the control of the flower-specific Arabidopsis APETALA3 promoter in petunia ( Petunia hybrida ) increases the flower size dramatically, but with no effect on vegetative development. The resulting transgenic plants produced flowers with larger corolla diameter and greater total floral fresh weight. This strategy has the potential for use in the production of ornamental crops with large flowers and crop species with larger fruit.     

Identifying and understanding ecological preferences for habitat or prey

Patchy, non-random associations of species with habitats and of consumers with particular types of food are commonly found in the ecological literature. In many cases, these patterns are reported to show some preference by an animal making choices about its environment. Generally, however, what is reported is simply the pattern of association and the process that gives rise to this pattern is not further examined. Nevertheless, there are numerous concepts that need to be considered simply to demonstrate the pattern, including the spatial and temporal scales at which the observations are made. When animals make choices between two objects, it is difficult to separate out potential negative, neutral or positive responses to either or both of the objects, without well thought-out manipulative experiments. Apparent preference for food may be influenced by “catchability” or “acceptability” of the prey and/or the past history of the consumer and the experiments to separate these effects are naturally complex. Many experiments examining preferences are beset by problems of non-independence and lack of appropriate controls, which makes them difficult to interpret. This review introduces some of the logical, conceptual, experimental and statistical problems that beset many studies of preference and proposes important steps that must be considered in further studies to unravel this fascinating topic.     

CALCIUM RELEASE FROM INTRACELLULAR STORES IS NECESSARY FOR THE PHOTOPHOBIC RESPONSE IN THE BENTHIC DIATOM NAVICULA PERMINUTA (BACILLARIOPHYCEAE)1

Complex photoreceptor pathways exist in algae to exploit light as a sensory stimulus. Previous studies have implicated calcium in blue‐light signaling in plants and algae. A photophobic response to high‐intensity blue light was characterized in the marine benthic diatom Navicula perminuta (Grunow) in van Heurck. Calcium modulators were used to determine the involvement of calcium in the signaling of this response, and the fluorescent calcium indicator Calcium Crimson was used to image changes in intracellular [Ca²⁺] during a response. A localized, transient elevation of Calcium Crimson fluorescence was seen at the cell tip at the time of cell reversal. Intracellular calcium release inhibitors produced a significant decrease in the population photophobic response. Treatments known to decrease influx of extracellular calcium had no effect on the population photophobic response but did cause a significant decrease in average cell speed. As the increase in intracellular [Ca²⁺] at the cell tip corresponded to the time of direction change rather than the onset of the light stimulus, it would appear that Ca²⁺ constitutes a component of the switching mechanism that leads to reversal of the locomotion machinery. Our current evidence suggests that the source of this Ca²⁺ is intracellular.     

Expression of the Ror1 and Ror2 receptor tyrosine kinase genes during mouse development

Ror1 and Ror2 are orphan receptor tyrosine kinases that are most closely related to MuSK and the Trk family of neurotrophin receptors. We report the results of an extensive in situ hybridisation survey of the expression of these genes during mouse development. Expression of Ror1 and Ror2 differs markedly at early stages (E8.5--E9.5). At these times, Ror2 is expressed much more widely than Ror1, expression of which is largely restricted to head mesenchyme. At later stages of development (E12.5--E14.5), Ror1 expression expands and Ror2 expression becomes more restricted than at earlier times, although expression of Ror1 continues to be more restricted than that of Ror2. These changes result in overlapping expression domains but with major differences remaining. In many cases Ror1 is expressed in a sub-set of Ror2-expressing tissues; in others, there is complementary expression of Ror1 and Ror2. Ror1 and Ror2 are both expressed in derivatives of all three germ layers and in most organ systems, including the nervous, circulatory, respiratory, digestive, urogenital and skeletal systems. Conspicuous themes are the expression in major sense organs, and in neural crest and its derivatives.