Changes in protein phosphorylation during the cell cycle of Chinese hamster ovary cells

The phosphorylation patterns of proteins were examined during the cell cycle of Chinese hamster ovary cells. This was accomplished by labeling synchronized cells at various times with [32P]orthophosphate and separating the proteins by both isoelectric focusing and nonequilibrium pH gradient two-dimensional gel electrophoresis. The most dramatic changes occurred during late G2/M when approximately eight proteins (including vimentin, lamin B, and histones 1 and 3) showed increased phosphorylation. Ten other proteins appeared to be uniquely phosphorylated during late G2/M. Of these 10 proteins, seven were no longer phosphorylated shortly after mitosis. There is also at least one protein which showed a relative decrease in phosphorylation during late G2/M.     

Rearrangements in the long terminal repeat of extra mouse mammary tumor proviruses in T-cell leukemias of mouse strain GR result in a novel enhancer-like structure.

Male GR mice develop T-cell leukemia at low frequency late in life. These leukemia cells invariably contain large amounts of mouse mammary tumor virus (MMTV) RNA and MMTV proteins and have extra MMTV proviruses integrated in their DNA. We show here that the extra MMTV proviruses are all derived from the endogenous MMTV provirus associated with the Mtv-2 locus and that the T-cell leukemias are clonal with respect to the acquired MMTV proviruses. The extra MMTV proviruses in six transplantable T-cell leukemia lines studied had rearranged, shortened long terminal repeats (LTRs); each T-cell leukemia, however, had a different LTR rearrangement within its extra MMTV provirus. The alteration within the extra LTRs of T-cell leukemia line 42 involved deletion of 453 nucleotides and generation of a tandem repeat region consisting of regions flanking the deletion. This alteration generated a sequence similar to the adenovirus enhancer core sequence. The viral RNAs in the T-cell leukemias contained corresponding alterations in their U3 regions. These results demonstrate that expression of MMTV in T-cell leukemias of GR mice may be the consequence of the generation of a novel enhancer, which could also stimulate expression of any adjacent cellular oncogene.     

Soil nitrogen transformations and nitrate utilization by Deschampsia flexuosa (L.) Trin. at two contrasting heathland sites

Two Dutch heathland sites Hoorneboeg (HB) and Ede, dominated by Deschampsia flexuosa and differing in nitrate production, were sampled for an entire growing season. A large number of soil and plant parameters were monitored in an attempt to assess the contribution of nitrate in the N supply and its assimilation by Deschampsia.Average NO₃ ^– and NH₄ ⁺ concentrations (mg kg^–1) in the top 10-cm depth were 0.03 and 2.2, respectively, for HB, and 2.1 and 6.7, respectively, for Ede. Laboratory incubations of intact cores and experiments with FH-layer suspensions showed significantly higher mineralization and nitrification rates for the Ede site during most of the season. Nitrification was largely controlled by the rate of net N-mineralization, which in turn was highly affected by soil moisture. Nitrate production was virtually zero at HB and accounted for 25% of the net N-mineralization at Ede.Shoot chemical composition showed no essential differences for the two sites, but mean in vivo (current) foliar NRA was almost 2-fold higher at Ede than at HB, indicating some utilization of nitrate at the former location. At the HB site with essentially no nitrate production, however, enzyme activities were clearly higher than basal constitutive levels in NH₄ ⁺-fed plants. Apparently, shoot NRA at the HB site became positively affected by factors other than nitrate availability and/or showed disproportional increases in response to atmospheric nitrate inputs. Root NRA displayed the same low basal level at the two sites. Nitrate fertilization (100 kg N ha^–1) yielded maximally induced foliar NRAs similar to levels found in hydroponic nitrate plants. Although no accumulation of free NO₃ ^– was observed in shoots from fertilized plots, increases in foliar concentrations of both organic N and carboxylates clearly indicated nitrate assimilation. Root NRA showed no response to nitrate addition.It is concluded that current NRA measurements in Deschampsia at heathland sites are of limited value only, especially when interpreted in isolation. A combined approach, using concurrently conducted soil and plant analyses, will allow the extent of nitrate utilization in the field to be best characterized.Publication 2013 of the Netherlands Institute of Ecology.FAX no corresponding author: +31 8306 23227     

Hydrolysis of bile acid conjugates by selected fungi

Summary Fungi which have been previously shown to hydrolyse glycocholic acid, with liberation of the free bile acid, have now been shown to be similarly capable of hydrolysing glycodeoxycholic acid. Sodium taurocholate, however, is much less susceptible and its hydrolysis has been demonstrated with only one of the selected fungi, Penicillium chrysogenum, growing in a medium containing the conjugate as the sole sulphur source. It is concluded that the nature of the amino acid moiety is important in determining the ease of hydrolysis of bile acid conjugates by whole cells of the fungi under test.     

A QTL with major effect on milk yield and composition maps to bovine Chromosome 14

A whole genome scan was undertaken in a granddaughter design comprising 1158 progeny-tested bulls in order to map QTL influencing milk yield and composition. In this paper we report the identification of a locus on the centromeric end of bovine Chromosome (Chr) 14, with major effect on fat and protein percentage as well as milk yield. The genuine nature of this QTL was verified using the grand²-daughter design, that is, by tracing the segregating QTL alleles from heterozygous grandsires to their maternal grandsons and confirming the predicted QTL allele substitution effect. Received: 30 December 1997 / Accepted: 21 February 1998     

Single introductions of soil biota and plants generate long‐term legacies in soil and plant community assembly

Recent demonstrations of the role of plant–soil biota interactions have challenged the conventional view that vegetation changes are mainly driven by changing abiotic conditions. However, while this concept has been validated under natural conditions, our understanding of the long‐term consequences of plant–soil interactions for above‐belowground community assembly is restricted to mathematical and conceptual model projections. Here, we demonstrate experimentally that one‐time additions of soil biota and plant seeds alter soil‐borne nematode and plant community composition in semi‐natural grassland for 20 years. Over time, aboveground and belowground community composition became increasingly correlated, suggesting an increasing connectedness of soil biota and plants. We conclude that the initial composition of not only plant communities, but also soil communities has a long‐lasting impact on the trajectory of community assembly.