Age at maturity in landlocked and anadromous Atlantic salmon parr from two Québec rivers

Synopsis Age at maturity in male Atlantic salmon parr from landlocked populations in the Watshishou and Musquaro Rivers is significantly greater than in anadromous populations from the same rivers. We conclude that high post-smolt mortality in anadromous stocks is conducive to male parr maturity at an early age. We also suggest that the lower proportion of maturing male parr in landlocked stocks may be related to competition among males for mates and the smaller ultimate size of spawning adult landlocked salmon.     

A miniaturised parallel-plate shearing apparatus for the measurement of cell adhesion

The design and construction of a miniaturised shearing apparatus is described. Cultures (24 h) of an established epithelial cell line (BEB) were exposed to flow conditions in the shearing chamber at 37 degrees C, and subsequently glass coverslip cultures were prepared for photography. The critical shear radius (CSR) was determined by densitometry from a negative film and the minimum distraction force (MDF) at the CSR calculated using predetermined viscosity values of the flow medium. The mean calculated MDF of BEB cells ranged from 1.04-1.36 Nm-2, and was independent of the culture inoculation density (9 to 37 X 10(4) cells cm-2) and the time (5-20 min) of exposure to shearing conditions. The MDF was increased to 3.3 Nm-2 by a 30 min exposure of cultures to concanavalin A (50 micrograms ml-1), and this effect was abolished by treating with mannose (0.05 M). The results demonstrated that the radial flow chamber principle is applicable to the measurement of cell to substratum adhesion of cultured mammalian cells.     

Ecological aspects of swidden cultivation among the Andoke and Witoto Indians of the Colombian Amazon

The investigation of crop and soil-crop conditions among Andoke and Witoto cultivators in southeast Colombia is used as a basis for assessing Geertz' (1963) model of swidden cultivation. In this respect, the extent to which maniocdominated swiddens in the study area simulate the structure and composition of the forest climax community is questioned. As Geertz (1963) indicates, an initial nutrient boost for crop cultivation results from the preliminary burning of forest debris, but weed competition, rather than progressive loss of soil fertility, is reported to be the primary cause of abandoning manioc cultivation after 2–3 years. While the Andoke and Witoto crop system remains adaptive at the individual field level, particularly in its constituent species, its fundamental adaptation is considered to be its integration into the broader field and fallow system that juxtaposes crop production with extended periods of forest regeneration.     

Flow cytometric analysis of protein thiol groups in relation to the cell cycle and the intracellular content of glutathione in rat hepatocytes

The relationship between protein thiols (PSH) and cell proliferation was examined in ethanol-fixed rat hepatocytes. A new protocol was developed for simultaneous measurement of protein thiol vs. DNA content by flow cytometry. The fluorescent dye o-phthalaldehyde (OPT) was used for flow cytometric measurements of protein thiol groups. The influence of nonprotein thiols was examined by monitoring the cell cycle of cells in which the glutathione content (GSH) was modified by treatment with buthionine sulphoximine (BSO). Three rat liver cell lines (IAR 20, IAR 6.1, IAR 6.1RT7) were used: these cell lines possess different growth characteristics and degrees of tumorigenicity, which made it possible to analyse changes in PSH during normal and deranged cell proliferation. The effects on the cell cycle of the changes in PSH due to the depletion of GSH were measured by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation and flow cytometry. The data obtained can be summarised as follows: a) OPT fluorescence increases with increasing DNA content in all rat liver cell lines examined; b) the greatest variation in PSH content occurs in G1. There is a smaller variation in G2 + M, and PSH levels are relatively invariant throughout S-phase; c) a higher content of PSH is found in the tumorigenic cell lines; d) the amount and distribution of PSH is not affected by BSO treatment; e) kinetic studies indicate that BSO treatment has no effect on the ability of the IAR rat liver cell lines to progress through the cycle.     

Hydrogen peroxide cytotoxicity. Low-temperature enhancement by ascorbate or reduced lipoate.

The principal mechanism of H2O2 toxicity is thought to involve the generation of hydroxyl (HO.) radicals through its interactions with Fe2+ ions by the Fenton reaction. Of particular interest has been the demonstration by Ward, Blakely & Joner [(1985) Radiat. Res. 103, 383-392] that the cytotoxicity of H2O2 is diminished at low temperature. We have now examined this phenomenon further with a mammalian epithelial cell line (CNCMI-221). Resistance of these cells to 100 microM-H2O2 added extracellularly exhibits a transition in the temperature range between 27 degrees C and 22 degrees C. We have found that the low-temperature resistance to cytotoxic concentrations of H2O2 is abolished by preincubation of cells with reductants such as ascorbate or reduced lipoic acid. This implies that the low-temperature resistance to H2O2 cytotoxicity may be due to inhibition of cellular reductive processes. The restoration of the cytotoxic action of H2O2 at 4 degrees C by ascorbate is prevented by pre-exposure of cells to desferrioxamine. This is evidence that transition-metal ions (such as iron ions) are involved in the cytotoxicity and is consistent with a mechanism of cell damage that depends on the Fenton reaction and a metal ion in the reduced state. Restoration of H2O2 cytotoxicity at low temperature by ascorbate is consistent with the artificial production of an intracellular reducing environment that at normal temperatures is sustained by cellular metabolism.     

Synthesis and evaluation of some novel phosphate and phosphinate derivatives of araA. Studies on the mechanism of action of phosphate triesters.

A number of novel phosphinate and phosphate triester derivatives of the anti-viral nucleoside analogue araA have been prepared. Spectroscopic and analytical data have been collected on both the reagents and the nucleotides. An in vitro assay indicated inhibition of DNA synthesis by mammalian cells, by each of the nucleotide derivatives, in the range 3-30 microM. Inhibition was reduced, but not abolished, for the phosphinates relative to the phosphates. These results are consistent with a mode of action involving release of the free nucleoside araA and the nucleotide araAMP.     

A novel, rapid method for the isolation of terminal sequences from yeast artificial chromosome (YAC) clones.

The recent development of yeast artificial chromosome (YAC) vectors has provided a system for cloning fragments that are over ten times larger than those that can be cloned in more established systems. We have developed a method for the rapid isolation of terminal sequences from YAC clones. The YAC clone is digested with a range of restriction enzymes, a common linker is ligated to the DNA fragments and terminal sequences are amplified using a vector specific primer and a linker specific primer. Sequence data derived from these terminal specific products can be used to design primers for a further round of screening to isolate overlapping clones. The method also provides a convenient method of generating Sequence Tagged Sites for the mapping of complex genomes.     

A 3.5 genome equivalent multi access YAC library: construction, characterisation, screening and storage.

The construction of a yeast artificial chromosome (YAC) primary gridded library of 35,000 clones from human lymphoblastoid (48,XXXX) cell line DNA is described. The average YAC size is approximately 350kb representing a greater than 3.5 times coverage of the genome. The library is stored at -70 degrees C as gridded clones on nylon filters impregnated with 20% glycerol and as glycerol suspensions of individual clones in microtitre plates providing a prolonged multi-user potential. To date we have used 14 single copy probes to screen this library by colony hybridisation as well as PCR and have isolated between 1 and 5 YAC clones for every probe.     

Diagnosis of alpha 1-antitrypsin deficiency by enzymatic amplification of human genomic DNA and direct sequencing of polymerase chain reaction products.

We have compared sequencing of cloned "polymerase chain reaction" (PCR) products and the direct sequencing of PCR products in the examination of individuals from six families affected with alpha 1-antitrypsin (AAT) deficiency. In families where paternity was in question we confirmed consanguinity by DNA fingerprinting using a panel of locus-specific minisatellite probes. We demonstrate that direct sequencing of PCR amplification products is the method of choice for the absolutely specific diagnosis of AAT deficiency and can distinguish normals, heterozygotes and homozygotes in a single, rapid and facile assay. Furthermore, we demonstrate the reproducibility of the PCR and a rapid DNA isolation procedure. We have also shown that two loci can be simultaneously amplified and that the PCR product from each locus can be independently examined by direct DNA sequencing.     

Recovery of murine lens epithelial cells from single and fractionated doses of X rays and neutrons

Subpopulations of mouse lens epithelial cells, differing in proliferative status, were irradiated with either X rays or fission spectrum neutrons given singly or in four weekly fractions. After various times, epithelia were mitogenically stimulated by wounding and DNA synthesis responses were determined by incorporation of [3H]thymidine. At 1 h following both X and neutron irradiations, significant suppression of the wound response after single doses and a sparing effect of fractionation were evident in both the mitotically quiescent and the slowly proliferating subpopulations. At 1 week following single or fractionated doses of both radiations, recovery was evident in both subpopulations. By 4 weeks, the quiescent subpopulation showed significant recovery after both single and fractionated doses of X rays or neutrons. In contrast, a marked decreased ability to respond after neutron irradiation and, in addition, a significant enhancement effect of neutron fractionation were observed for the slowly proliferating subpopulation. Per gray, neutrons were about 7.5 times more effective than X rays as a single dose and 25 times more effective in four equal fractions. The shift from an initial sparing to a final enhancing effect of neutron fractionation for the slowly proliferating subpopulation has importance for understanding divergent early and late radiation responses following dose fractionation.