Multi-colour brightfield in situ hybridisation on tissue sections

 We describe the brightfield microscopical detection of multiple DNA target sequences in cell and tissue preparations. For this purpose, chromosome-specific DNA probes labelled with biotin, digoxigenin or fluorescein were simultaneously hybridised and detected by enzyme cytochemistry using two horseradish peroxidase (PO) reactions and one alkaline phosphatase (APase) reaction. For triple-colour detection on single cell preparations, the combination of the enzyme precipitates PO/diaminobenzidine (DAB, brown colour), APase/fast red (FR, red colour) and PO/tetramethylbenzidine (TMB, green colour) resulted in an accurate detection of DNA targets. Embedding of the preparations in a thin cross-linked protein layer further stabilised the enzyme reaction products. For in situ hybridisation on tissue sections, however, this detection procedure showed some limitations with respect to both the stability of the APase/FR and PO/TMB precipitates, and the sequence of immunochemical layers in multiple-target procedures. For this reason, the APase/FR reaction was replaced by the APase/new fuchsin (NF, red colour) reaction and the washing steps after the PO/TMB reaction were restricted to the use of phosphate buffer pH 6.0. Furthermore, to improve the efficiency of the ISH reaction, APase/NF was applied in an avidin-biotin complex detection system and, to avoid target shielding in the triple-target ISH, the third primary antibody was applied prior to the second enzyme cytochemical reaction. These adaptations resulted in stable, well contrasting brown, red and green coloured precipitates. After quick haematoxylin counterstaining, the tissue preparations were directly mounted in phosphate buffer and, optionally, embedded in the cross-linked protein layer. Accepted: 27 June 1997     

Molecular evolution of a portion of the mitochondrial 16S ribosomal gene region in scleractinian corals

Relationships among families and suborders of scleractinian corals are poorly understood because of difficulties 1) in making inferences about the evolution of the morphological characters used in coral taxonomy and 2) in interpreting their 240-million-year fossil record. Here we describe patterns of molecular evolution in a segment of the mitochondrial (mt) 16S ribosomal gene from taxa of 14 families of corals and the use of this gene segment in a phylogenetic analysis of relationships within the order. We show that sequences obtained from scleractinians are homologous to other metazoan 16S ribosomal sequences and fall into two distinct clades defined by size of the amplified gene product. Comparisons of sequences from the two clades demonstrate that both sets of sequences are evolving under similar evolutionary constraints: they do not differ in nucleotide composition, numbers of transition and transversion substitutions, spatial patterns of substitutions, or in rates of divergence. The characteristics and patterns observed in these sequences as well as the secondary structures, are similar to those observed in mt 16S ribosomal DNA sequences from other taxa. Phylogenetic analysis of these sequences shows that they are useful for evaluating relationships within the order. The hypothesis generated from this analysis differs from traditional hypotheses for evolutionary relationships among the Scleractinia and suggests that a reevaluation of evolutionary affinities in the order is needed. Received: 4 September 1996 / Accepted: 7 April 1997     

Mate choice in lekking sage grouse revisited: the roles of vocal display, female site fidelity, and copying

In lekking sage grouse (Centrocercus urophasianus), femalesexhibit relatively unanimous mate choice for particular males,but a satisfactory explanation for this unanimity has been elusive.We present analyses of mating distributions from two leks over4 years that provide evidence for female choice based on differencesin vocal display performance of males, the locations at whichhens mated in the previous year, and the choices of other females(copying). The unanimity of female choice varied markedly amongleks and years in correlation with changes in the mean numbersof hens that mated at the same time and hence the opportunityto copy. The results confirm that hens assess phenotypic traitsof males directly but also indicate that the secondary tacticsof site fidelity and copying are often important componentsof female choice. The occurrence of these secondary tacticshas three implications: the variance in mating success amonglek males will be a poor predictor of the intensity of sexualselection on specific traits; female preferences may generatemore clustered dispersions of displaying males than predictedby hotspot settlement models; and direct assessment of malesby females may be difficult or costly, a conclusion that supportsadaptive models of sexual selection over a nonadaptive Fisherianprocess. [Behav Ecol 1991;2:165–180]     

Fibronectin gene expression in proliferating, quiescent, and SV40-infected mouse kidney cells

To study alterations in cellular gene expression in mouse kidney cell cultures infected with simian virus 40 (SV40) or polyomavirus, we performed a differential screening of a mouse kidney cDNA library with probes prepared from mRNAs of virus-infected and mock-infected cells. We isolated and characterized cDNA recombinant pKT13 which detected increased mRNA levels in infected cells. Sequence analysis of pKT13 revealed close to 100% homology with the 3'-end of mouse fibronectin (FN) mRNA. Since primary cultures of baby mouse kidney cells have been extensively characterized in our laboratories, we studied FN gene expression at different stages of uninfected and virus-infected cultures. High levels of FN and of its mRNA were found in the kidneys of suckling mice, while in primary cultures of proliferating epithelial kidney cells the expression of FN was very low until the cultures became confluent. Thereafter FN increased and reached high levels in cells which were irreversibly arrested in phase Go and which had apparently exhausted their finite division potential. Infection of confluent cultures with polyomavirus or SV40 resulted in a further stimulation of FN gene expression. However, during abortive infection with SV40, FN mRNA and FN levels decreased with emergence of transformed cells and were low in an established SV40-transformed mouse kidney cell line. These changes in FN gene expression suggest that high levels of FN might be indicative in vivo for terminal differentiation and in vitro for cellular senescence.     

Conditions for selective degradation of lignin by the fungus Ganoderma australis

Summary The white-rot fungus Ganoderma australis selectively degrades lignin in the ecosystem palo podrido. Using conditions that simulate those of palo podrido in the laboratory, it was found that low nitrogen content and low O₂ tension stimulate the productio of manganese peroxidase and lignin degradation, and depress cellulose degradation and cellulase production. The inverse is found at high nitrogen concentration and high O₂ tension. This agrees with previous results indicating that low O₂ tension and low nitrogen stimulate selective lignin degradation by this fungus. Correspondence to: J. Eyzaguirre     

Ultrastructural localization of arachidonic acid in stimulated macrophages

The distribution of 3[H] arachidonic acid incorporated into cultured mouse peritoneal macrophages was assessed upon stimulation of the cells with either the calcium ionophore A23187 or zymosan. After a labeling time of 24 h, cells were stimulated and processed for light and electron microscopic autoradiography. Grains were primarily localized over the plasma membrane and lipid-containing vesicles of both control and stimulated cells. In macrophages stimulated with ionophore, a decreased labeling density was evident in both of these cell compartments. Similar alterations in labeling pattern were observed in zymosan treated cells, although a larger decline in grain density occurred from the plasma membrane compartment. Immunocytochemical localization of PGE2, a major eicosanoid product released upon ionophore stimulation, revealed the presence of the prostaglandin in clear vesicular structures, many of which appear to be continuous with the plasma membrane. These results provide morphological evidence that different cellular pools of arachidonic acid may be differentially mobilized for eicosanoid production as a function of the mode of stimulation.     

THE MATING SYSTEM GENETICALLY AFFECTS OFFSPRING PERFORMANCE IN WOODHOUSE'S TOAD (BUFO WOODHOUSEI)

To determine if the nonrandom, non-resource-based mating system of Bufo woodhousei affects tadpole performance, I performed a series of controlled matings and reared the tadpoles to metamorphosis in the laboratory and field. I asked whether differences in paternal identity, mating status, or body size were related to differences in tadpole mass, larval period duration, metamorphic mass, or survival of offspring. Although both laboratory and field rearings indicated that male and female parentage affected most offspring traits, no correspondence existed between either laboratory and field metamorphic mass or laboratory and field survival of offspring sired by the same male. The lack of correspondence between sire breeding values in the laboratory and field for two of three traits raises doubts as to the validity of drawing conclusions concerning how evolution might be expected to work from laboratory studies. Paternal effects were more pronounced in the field than in the laboratory, despite what is usually presumed to be a greater amount of environmental variation in the field. In the laboratory neither sire body size nor mating status affected any trait, but in the field larger males produced offspring that were 10% heavier at transformation than offspring sired by small males. This predictable relationship between sire phenotype (body size) and offspring performance means that nonrandom mating based on male body size could have a directional effect on offspring performance. Because larger males mate disproportionately often in this population (Woodward, 1982a; Mitchell, unpubl.), the mating system may exert a directional effect on metamorphic body size.     

Evidence for increased intracellular transport of m-sarcolysine (alkylating moiety) when combined with two amino acid analogs (PTT-119)

PTT-119 is an antineoplastic agent in which an alkylating moiety, m-sarcolysine, is linked to two amino acid analogs. Previous studies showed a higher "in vitro" cytotoxicity of PTT-119 when compared to free m-sarcolysine; the mechanisms of this enhanced activity are not completely understood. In this study we incubated peripheral blood cells from 8 chronic lymphocytic leukemia patients with both m-sarcolysine and equimolar concentrations of PTT-119, measuring the intracellular concentration of the alkylating moiety. We observed a significantly higher intracellular concentration of m-sarcolysine in cells incubated with the peptide-bound drug than with the free drug (58.3 +/- 39.6 versus 4.4 +/- 1.9 ng/10(6) cells; P = 0.013). This observation could explain the higher cytotoxic activity of PTT-119 and the lack of cross-resistance with melphalan.     

MICROSPOROGENESIS IN PEANUT (ARACHIS HYPOGAEA)

The stage of pollen development at the time of anther culture is an important factor in the production of haploids. The objectives of the current study were to develop a staining procedure for peanut (Arachis hypogaea L., ssp. hypogaea) microspores, to describe and document the stages of microsporogenesis in peanut, and to confirm a previous report concerning correlations of peanut floral bud shape with stage of microspore development. A staining procedure using propionic carmine provided adequate staining of pollen mother cells, microspores, and pollen. Pollen mother cells and microspores could easily be differentiated by their size and cell wall structure. Plants grown in a controlled environment were found to have highly synchronized microspore development, both within an anther and among anthers contained in the same bud. In addition, floral bud shape was confirmed as a reliable indicator of anther stage in peanuts.     

Biological Control of Damping-Off of Alfalfa Seedlings with Bacillus cereus UW85

We explored the potential of biological control of alfalfa (Medicago sativa L.) seedling damping-off caused by Phytophthora megasperma f. sp. medicaginis by screening root-associated bacteria for disease suppression activity in a laboratory bioassay. A total of 700 bacterial strains were isolated from the roots of field-grown alfalfa plants by using Trypticase soy agar. A simple, rapid assay was developed to screen the bacteria for the ability to reduce the mortality of Iroquois alfalfa seedlings that were inoculated with P. megasperma f. sp. medicaginis zoospores. Two-day-old seedlings were planted in culture tubes containing moist vermiculite, and each tube was inoculated with a different bacterial culture. Sufficient P. megasperma f. sp. medicaginis zoospores were added to each tube to result in 100% mortality of control seedlings. Of the 700 bacterial isolates tested, only 1, which was identified as Bacillus cereus and designated UW85, reduced seedling mortality to 0% in the initial screen and in two secondary screens. Both fully sporulated cultures containing predominantly released spores and sterile filtrates of these cultures of UW85 were effective in protecting seedlings from damping-off; filtrates of cultures containing predominantly vegetative cells or endospores inside the parent cell had low biocontrol activity. Cultures grown in two semidefined media had significantly greater biocontrol activities than cultures grown in the complex tryptic soy medium. In a small-scale trial in a field infested with P. megasperma f. sp. medicaginis, coating seeds with UW85 significantly increased the emergence of alfalfa. The results suggest that UW85 may have potential as a biocontrol agent for alfalfa damping-off, thus providing an alternative to current disease control strategies.