Discontinuities in technological and natural systems caused by exotic species

This discussion focuses on discontinuities in both natural and technological systems caused by the introduction of exotic species into areas which they would not have been able to reach without human assistance or other alterations to native communities. The case histories of both the Asian clam and the zebra mussel are particularly instructive because of their recent introductions and the dramatic impact they have had on both natural and technological systems. Control of these mollusc species in technological systems (e.g. water intake systems) is effective to a degree but requires constant attention and utilization of resources. If control is neglected there could be extremely serious consequences. At present, no inexpensive means exist for controlling their effects, and further geographical distribution in North America is highly probable. The mollusc case histories do not appear to be linear and, in some instances, may not be continuous. Some importations of exotic species were deliberate (such as the gypsy moth, Porthetria dispar), but their escape into natural systems has often been accidental or, a less charitable person might say, careless. A viable strategy for coping with discontinuities is elusive. Discontinuities will, undoubtedly, have a major effect on the possibility of sustainable use of the planet or, to use the currently popular term, sustainable development.     

Microsomal and cytosolic cytochrome P450 mediated benzo(a)pyrene hydroxylation in Pleurotus pulmonarius

Summary Microsomal and soluble fractions of Pleurotus pulmonarius exhibited a reduced carbon monoxide difference spectrum with P450 maxima at 448nm and 450–452nm respectively. Substrate induced Type I spectra were observed on addition of benzo(a)pyrene to both fractions. Benzo(a)pyrene hydroxylation was measured using the aryl hydrocarbon hydroxylase assay and was observed to be P450 dependent as indicated by carbon monoxide inhibition together with the substrate binding characteristics. The activity of the fractions were observed to give K_m of 200mM and 660mM and V_max of 1.25 nmol/min/nmol P450 and 0.57 nmol/min/nmol P450 for the microsomal and cytosolic fractions respectively.     

An evaluation of the micronuclei test using triethylenemelamine,trimethylphosphate, hycanthone and niridazole

To determine the feasibility of the micronuclie procedure for cytogenetic studies, a comparatively weak chromosome breaking agent, trimethylphosphate (TMP) and the potent alkylating agent, triethylenemelamine (TEM) were evaluated. The procedure followed was that of Matter and Schmid with the following modifications: (a) direct flushing of bone marrow with 0.2 ml calf fetal serum, (b) air drying slides for a period of only 1 h, and (c) the use of pH 6.0 phosphate buffer to dilute both the Wright and Giemsa stains.With this technique a dose-response curve was generated for both TMP and TEM, using mice as the experimental animal. With TMP, a doubling over background was found when a concentration of 0.5 g/kg per day for five days was administered. To establish a statistically significant doubling dose over the control, a minimum of five animals must be used woth 2000 polychromatic cells being analyzed per animal.Of the two antischistosomal agents tested, hycanthone yielded an increase of 20-fold in the number of mircronuclei over control at 40 mg/kg administered i.p. for five days, while with niridazole no increase in micronuclei at several concentrations tested both by single and multiple injection was found.The results obtained with these compounds compare favorably woth what has been reported for the standard in vivo metaphase analysis.     

A new method for restoring ditches in peatlands: ditch filling with fiber bales

Ditching is a common practice to dewater wetlands, including peatlands, and ditch blocking is a common method for restoring wetlands because substrate is often unavailable for filling the ditches. However, filling has many advantages compared to blocking ditches. Our goal was to test whether ditches could be filled in a Colorado sloping fen (Chattanooga Fen) using bales created from shredded aspen (Populus tremuloides) tree‐fiber. We monitored water table levels before and after we filled two ditches (combined length of approximately 165 m × 3 m wide) as well as an undisturbed reference portion of Chattanooga fen. The reference site had stable water tables that rarely dropped more than 20 cm below the soil surface. The ditches had been dewatering large areas of the fen for at least 100 years. Filling the ditches with fiber bales resulted in a water table increase between 2 and 22 cm in an area up to 150 m below the ditch. Native sedges now cover the area where we filled the ditches, with no erosion or compression/settling of the ground observed and no water backing up behind the filled ditches. Filling the ditches with shredded fiber bales is a good option for restoration in wilderness areas, or areas lacking peat or mineral soil fill because it is a natural material that is easily transported and placed in the ditches.     

Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.