Electron microscope study of the structures of the Bacillus subtilis prophages, SPO2 and phi105

Circular duplex structures of the correct length are observed in the electron microscope in hybridization mixtures of lysogen DNA and mature phage DNA for the case of the temperate Bacillus subtilis bacteriophage SPO2. This result shows that the sequence order of the prophage is a circular permutation of that of the mature phage. By making heteroduplexes of prophage DNA with that of the SPO2 deletion mutants, R90 and S25, the att site of the phage has been mapped at 61.2 ± 0.6% from one end of the mature phage DNA, which has a length of 38,600 base pairs. In the same co-ordinate system, the R90 deletion extends from 58.9 ± 0.7 to 66.8 ± 0.8% on the SPO2 chromosome, whereas the S25 deletion extends from 63.2 ± 0.6 to 66.9 ± 0.7%. In similar experiments with lysogen and mature phage DNA's of the temperate B. subtilis phage, φ105, no circular structures were seen. This result shows that the sequence order in the prophage and the phage are colinear, without circular permutation.     

Tissue glycogen concentrations in hypophysectomized pig fetuses following infusion with cortisol

The role of cortisol as a factor controlling the deposition of glycogen in the pig fetus was examined by infusing either a low dose (1 mg/day) or a high dose (3 mg/day) of cortisol into chronically-catheterized hypophysectomized fetal pigs for five days beginning on day 100-104 of gestation. After infusion, liver glycogen was significantly higher (P less than 0.05) and lung glycogen significantly lower (P less than 0.05) than in uninfused hypophysectomized litter mates although concentrations were significantly different from intact litter mates (P less than 0.05). Although skeletal and cardiac muscle content increased after infusion this difference was not significant. Changes in tissue glycogen content were similar for both the low and high rates of infusion. These observations indicate that exogenous cortisol alone is able to stimulate liver glycogen deposition and reverse the effect of hypophysectomy. Although other factors may be necessary for maximal response this suggests that cortisol is an important stimulant for liver glycogen deposition in the fetal pig. The effect of cortisol on muscle glycogen was equivocal suggesting that other hormones may play a more important role in this tissue.     

Late Glacial and Holocene environmental and climatic changes from a limnological transect through Colombia, northern South America

We present a synthesis of the palaeolimnological and palaeoclimatic reconstructions of four sites in Colombia. The record from Lake El Caimito, the westernmost site on the Pacific Coast, dates from the Late Holocene and shows lacustrine sedimentation frequently interrupted by fluvial pulses. These pulses probably reflect periods of increased precipitation related to La Niña phases. East of El Caimito site is the Patía swamp, situated between the Western and Central Andean Cordilleras. The Patía records the dynamics of forest expansion/reduction and changes in water levels. Although the climatic signal of the Patia core is difficult to reconstruct, there is a clear increase in humidity in the Mid-Holocene. The Fúquene Lake record, on the Eastern Andean Cordillera, records dry and cold conditions during the Late Pleistocene, very humid conditions for the early Mid-Holocene, and dry conditions during the mid-Late Holocene. Las Margaritas site, on the eastern savannas, records dry conditions during the Early Holocene and overall humid conditions for the Mid- and Late Holocene. Climate conditions from the Fuquene and Las Margaritas sites seem to reflect the Holocene movements of the Intertropical Convergence Zone (ITCZ); the latter site being more affected by humidity coming from the Amazon region.     

Phylogeography of the cactophilic species Drosophila gouveai: demographic events and divergence timing in dry vegetation enclaves in eastern Brazil

Aim  The aim of this study was to assess the causal mechanisms underlying populational subdivision in Drosophila gouveai , a cactophilic species associated with xeric vegetation enclaves in eastern Brazil. A secondary aim was to investigate the genetic effects of Pleistocene climatic fluctuations on these environments.
Location  Dry vegetation enclaves within the limits of the Cerrado domain in eastern Brazil.
Methods  We determined the mitochondrial DNA haplotypes of 55 individuals (representing 12 populations) based on sequence data of a 483-bp fragment from the cytochrome c oxidase subunit II (COII) gene. Phylogenetic and coalescent analyses were used to test for the occurrence of demographic events and to infer the time of divergence amongst genetically independent groups.
Results  Our analyses revealed the existence of two divergent subclades (G1 and G2) plus an introgressed clade restricted to the southernmost range of D. gouveai . Subclades G1 and G2 displayed genetic footprints of range expansion and segregated geographical distributions in south-eastern and some central highland regions, east and west of the Paraná River valley. Molecular dating indicated that the main demographic and diversification events occurred in the late to middle Pleistocene.
Main conclusions  The phylogeographical and genetic patterns observed for D. gouveai in this study are consistent with changes in the distribution of dry vegetation in eastern Brazil. All of the estimates obtained by molecular dating indicate that range expansion and isolation pre-dated the Last Glacial Maximum, occurring during the late to middle Pleistocene, and were probably triggered by climatic changes during the Pleistocene. The current patchy geographical distribution and population subdivision in D. gouveai is apparently closely linked to these past events.     

Littoral diatoms as indicators for the eutrophication of shallow lakes

The littoral zone of shallow water bodies in the Czech Republic has been studied quite consistently at several fishponds. The use of algae, especially diatoms, for the monitoring of the state of lotic freshwater also has a long tradition. The main objective of the presented paper is to validate the feasibility of the use of littoral periphyton comunities for the biomonitoring of standing waters. At the investigated sites, littoral periphytic diatoms were studied together with selected enviromental variables (pH, conductivity, nutrients – especially total phosphorus) on three types of natural substrates (epilithon, epiphyton, epipelon). The evaluation of the diatom community was performed on the basis of the checklists of algal indicator species published by authors from the Czech Republic, Austria and the Netherlands. The data were subjected to statistical software NCCS 2000 (GLM Anova and ``Ward's minimum'' variance cluster analysis). Littoral periphytic diatoms appear to be good indicators of the fishpond water quality. The selected substrates show non-significant differences therefore the average values from all substrates were used. The best indicatory system for evaluation of Czech fishponds was van Dam's index.