Utilization of milk energy by suckling mink kits

A total of 36 mink dams and their litters of 3, 6 or 9 kits were used for determination of milk intake of the suckling young by means of deuterium dilution technique, and chemical composition of milk and of kit bodies. Measurements were performed during lactation weeks 1?–?4, each week with 3 dams with each litter size. Milk intake was determined over a 48?h measurement period, and by the end of this milk samples were collected and 2 kits (litters of 6 and 9) or 1 kit per litter (litters of 3) were killed for body chemical composition. Based on the results, different models were applied for calculation of the energetic efficiency of milk. Dam milk yield increased steadily from week 1 until week 3 but only slightly from week 3 to 4. The increase declined with increasing litter size, and for dams suckling 9 kits the increment from week 3 to week 4 was only 2?g. The dry matter content of milk increased significantly as lactation progressed, being reflected in crude protein increasing from 6.9% in lactation week 1 to 8.1% in week 4. Milk fat increased concomitantly from 5.6% to 8.0%. In kit bodies, crude protein content increased from 9.4% in week 1 to about 12% in weeks 3 and 4. Body fat content increased from week 1 (4.1%) to week 3 (8.4%) and then declined in week 4 (7.1%). Animals suckled in litters of 3 kits had the highest milk intake and live weight and kits suckled in litters of 9 had the lowest milk intake, live weight and daily gain. In terms of milk intake per g gain kits in litters of 6 were the most efficient, with 4.1?g milk per g body gain. The metabolizable energy requirement for maintenance (MEm) was estimated to 448 kJ/kg^0.75 and the efficiency of utilization of ME for body gain (k_g) to 0.67, the estimates being higher (MEm) or in good agreement with previous findings (k_g) in suckling mink kits.     

The production of auxins by the endophytic bacteria of winter rye

The ability of the actinomycetes and coryneform bacteria isolated from the root tissues of winter rye to produce auxin in a liquid culture was studied. The isolates of coryneform bacteria produced indolyl-3-acetic acid (IAA) into the medium in the amount of 9.0–95.0 μg/ml and the isolates of actinomycetes in the amount of 39.5–83.0 μg/ml. The maximal IAA accumulation in culture liquid of actinomycetes coincided, in general, with the beginning of the stationary growth phase. The dependences of IAA synthesis by actino-mycetes on the composition and pH of nutrient medium, tryptophan concentration, and aeration conditions were determined. Biological activity of the bacterial IAA was assessed. Treatment of winter rye seeds with coryneform auxin-producing bacteria increased the germination capacity and enhanced an intensive seedling growth in vitro.     

A study of the competitive properties of the aluminum-tolerant strain Rhizobium leguminosarum bv. trifolii 9-4A by the antibiotic resistance method

The virulence, competitive ability, and symbiotic efficiency of 2 Rhizobium leguminosarum bv. trifolii strains--the wild aluminum tolerant strain 9-4A and the commercial strain 348a-were compared when introducing their variants marked with antibiotic resistance into the rhizosphere of red clover (Trifolium pratense L.) plants. High virulence and competitive ability of the strain tolerant to aluminum was demonstrated by a concurrent inoculation of the seeds with these two strains. The resistance acquisition by the commercial strain was accompanied by a decrease in its symbiotic efficiency. Presumably, the resistant variant of aluminum-tolerant isolate retains its symbiotic properties due to its adaptation to acidity factors at the level of membrane function.     

The fidelity of translation initiation: reciprocal activities of eIF1, IF3 and YciH

Eukaryotic initiation factor eIF1 and the functional C-terminal domain of prokaryotic initiation factor IF3 maintain the fidelity of initiation codon selection in eukaryotes and prokaryotes, respectively, and bind to the same regions of small ribosomal subunits, between the platform and initiator tRNA. Here we report that these nonhomologous factors can bind to the same regions of heterologous subunits and perform their functions in heterologous systems in a reciprocal manner, discriminating against the formation of initiation complexes containing codon-anticodon mismatches. We also show that like IF3, eIF1 can influence initiator tRNA selection, which occurs at the stage of ribosomal subunit joining after eIF5-induced hydrolysis of eIF2-bound GTP. The mechanisms of initiation codon and initiator tRNA selection in prokaryotes and eukaryotes are therefore unexpectedly conserved and likely involve related conformational changes induced in the small ribosomal subunit by factor binding. YciH, a prokaryotic eIF1 homologue, could perform some of IF3's functions, which justifies the possibility that YciH and eIF1 might have a common evolutionary origin as initiation factors, and that IF3 functionally replaced YciH in prokaryotes.     

Fluctuating asymmetry in bank vole populations (Rodentia, Arvicolinae) reflects stress caused by landscape fragmentation in the Mont-Saint-Michel Bay

In intensively farmed, reclaimed areas (polders) of Mont-St-Michel Bay, France, bank voles ( Clethrionomys glareolus ) live in fragmented hedgerows, where populations are small and dispersal rates and genetic diversity are low. These small populations are likely to have been exposed to potential environmental and/or genetic stress. The sensitivity of development to stress can be measured by fluctuating asymmetry (FA). FA was calculated for three samples from a disturbed area and one sample from an adjacent, more connected and undisturbed landscape. Size FA was estimated from 16 measurements of the skull and teeth whilst shape asymmetry was estimated from the skull alone. Bank voles in fragmented hedgerows of the disturbed area had a higher degree of FA than bank voles from the more extensive and more connected hedges of the undisturbed area. These results were confirmed by the study of shape asymmetry, body mass and centroid size of the skull. There were no differences in FA between the three disturbed area samples. We conclude that FA does not reveal differences in the development of bank voles living in isolation under different local conditions in the various parts of the disturbed area. However, FA may allow differentiation between populations from greatly contrasting landscapes.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 37–44.     

Abundance and structure of actinomycete complexes in the rhizosphere of winter rye, oats, and red clover

Actinomycete complexes were studied in the rhizosphere of three crop species using luminescence microscopy and plating. The concentration of the total prokaryotic biomass and the length of actinomycete mycelium proved higher in the rhizosphere than in root-free soil. Actinomycetes in the rhizosphere of oats (Avena sativa L.), winter rye (Secale cereale L.), and red clover (Trifolium pratense L.) were represented by the genera Streptomyces and Micromonospora and oligosporous species. The length and biomass of actinomycete mycelium proved to decrease while the generic diversity increased in the following sequence: winter rye—oats—red clover. Increasing soil suppression and plant resistance to phytopathogens using mycelial prokaryotes is discussed in the context of environmental safety.     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.