Allozyme differentiation of various chromosomal forms of the spotted suslik (Spermophilus suslicus Guld, 1770, Rodentia)]

Eleven enzyme and four nonenzyme protein systems controlled by 25 loci were electrophoretically analyzed in the allopatric karyotypic forms (2n = 34 and 2n = 36) of the spotted souslik Spermophilus suslicus. Genetic variability and differentiation for the forms with different chromosome sets were estimated. Two discriminative loci (Alb and Tf) for the studied chromosome forms were found. The UPGMA dendrogram was constructed, which summarizes genetic (allozyme) relationships found for the forms of the spotted souslik with different chromosome sets. Subdividing the species into two karyotypic forms was shown to be followed by differentiating these forms at the allozyme level.     

Productivity of forests in the Eurosiberian boreal region and their potential to act as a carbon sink –- a synthesis

Based on review and original data, this synthesis investigates carbon pools and fluxes of Siberian and European forests (600 and 300 million ha, respectively). We examine the productivity of ecosystems, expressed as positive rate when the amount of carbon in the ecosystem increases, while (following micrometeorological convention) downward fluxes from the atmosphere to the vegetation (NEE = Net Ecosystem Exchange) are expressed as negative numbers. Productivity parameters are Net Primary Productivity (NPP=whole plant growth), Net Ecosystem Productivity (NEP = CO₂ assimilation minus ecosystem respiration), and Net Biome Productivity (NBP = NEP minus carbon losses through disturbances bypassing respiration, e.g. by fire and logging). Based on chronosequence studies and national forestry statistics we estimate a low average NPP for boreal forests in Siberia: 123 gC m^–2 y^–1. This contrasts with a similar calculation for Europe which suggests a much higher average NPP of 460 gC m^–2 y^–1 for the forests there. Despite a smaller area, European forests have a higher total NPP than Siberia (1.2–1.6 vs. 0.6–0.9 × 10¹⁵ gC region^–1 y^–1). This arises as a consequence of differences in growing season length, climate and nutrition. For a chronosequence of Pinus sylvestris stands studied in central Siberia during summer, NEE was most negative in a 67-y old stand regenerating after fire (– 192 mmol m^–2 d^–1) which is close to NEE in a cultivated forest of Germany (– 210 mmol m^–2 d^–1). Considerable net ecosystem CO₂-uptake was also measured in Siberia in 200- and 215-y old stands (NEE:174 and – 63 mmol m^–2 d^–1) while NEP of 7- and 13-y old logging areas were close to the ecosystem compensation point. Two Siberian bogs and a bog in European Russia were also significant carbon sinks (– 102 to – 104 mmol m^–2 d^–1). Integrated over a growing season (June to September) we measured a total growing season NEE of – 14 mol m^–2 summer^–1 (– 168 gC m^–2 summer^–1) in a 200-y Siberian pine stand and – 5 mol m^–2 summer^–1 (– 60 gC m^–2 summer^–1) in Siberian and European Russian bogs. By contrast, over the same period, a spruce forest in European Russia was a carbon source to the atmosphere of (NEE: + 7 mol m^–2 summer^–1 = + 84 gC m^–2 summer^–1). Two years after a windthrow in European Russia, with all trees being uplifted and few successional species, lost 16 mol C m^–2 to the atmosphere over a 3-month in summer, compared to the cumulative NEE over a growing season in a German forest of – 15.5 mol m^–2 summer^–1 (– 186 gC m^–2 summer^–1; European flux network annual averaged – 205 gC m^–2 y^–1). Differences in CO₂-exchange rates coincided with differences in the Bowen ratio, with logging areas partitioning most incoming radiation into sensible heat whereas bogs partitioned most into evaporation (latent heat). Effects of these different surface energy exchanges on local climate (convective storms and fires) and comparisons with the Canadian BOREAS experiment are discussed. Following a classification of disturbances and their effects on ecosystem carbon balances, fire and logging are discussed as the main processes causing carbon losses that bypass heterotrophic respiration in Siberia. Following two approaches, NBP was estimated to be only about 13–16 mmol m^–2 y^–1 for Siberia. It may reach 67 mmol m^–2 y^–1 in North America, and about 140–400 mmol m^–2 y^–1 in Scandinavia. We conclude that fire speeds up the carbon cycle, but that it results also in long-term carbon sequestration by charcoal formation. For at least 14 years after logging, regrowth forests remain net sources of CO₂ to the atmosphere. This has important implications regarding the effects of Siberian forest management on atmospheric concentrations. For many years after logging has taken place, regrowth forests remain weaker sinks for atmospheric CO₂ than are nearby old-growth forests.     

Using wintergreen oil for mounting mosquito larvae: a safer alternative to xylene

Permanent mounting of fourth instar mosquito larvae is essential for identifying Aedes spp. This procedure requires extensive exposure to xylene, a clearing agent in the mounting process. We investigated wintergreen oil as a substitute for xylene. Five hundred larvae were mounted on slides to evaluate shrinkage or expansion of specimens after clearing using xylene or wintergreen oil. We examined the ventral brush and siphonal hair tufts for species identification and for preservation of morphological characteristics after clearing specimens in xylene or wintergreen oil. Shrinkage of the length of whole larvae and width of the head, thorax and abdomen after mounting was significantly greater after clearing with xylene than with wintergreen oil. The length of the comb scale nearest the ventral brush was similar for both clearing agents. The clarity of the specimens after mounting was improved by clearing with wintergreen oil, but the integrity of the ventral brush and siphonal hair tufts were similar for both clearing agents.     

Synthesis and antiproliferative activity of a novel N-acyl derivative of doxorubicin]

Doxorubicin was acylated with estrone 3-hemisuccinate. The modified derivative exhibited high antiproliferative activity in vitro toward cell cultures of the MCF-7 human mammary adenocarcinoma and HepG2 human hepatoma.     

Template synthesis and structure of mono- and trisubstituted ribbed-functionalized iron(II) clathrochelates

The template condensation of three methylchloroglyoximate molecules with phenylboronic acid and with BF₃ · O(C₂H₅)₂ on an iron(II) ion afforded reactive trichloride phenylboron- and fluoroboron-capped precursors, respectively. The monochloride FeBd₂(CH₃ClGm)(BF)₂ precursor (where Bd²⁻ and CH₃ClGm²⁻ are α-benzyldioxime and methylchloroglyoxime dianions) was synthesized by condensation of macrocyclic iron(II) α-benzyldioximate FeBd₂(BF₂)₂(CH₃CN)₂ with CH₃ClGmH₂. Mono- and trifunctionalized amine, alkylsulfide, and arylsulfide clathrochelate iron(II) tris-dioximates were prepared starting from these precursors by nucleophilic substitution reactions. The complexes obtained were characterized using elemental analysis, PD mass, IR, UV-Vis, ¹H, ¹³C NMR, and ⁵⁷Fe Mössbauer spectra, and X-ray crystallography. An encapsulated low-spin iron(II) ion was found to have distorted trigonal-prismatic coordination N₆-environment in all clathrochelates synthesized.