Neurological presentation of a congenital disorder of glycosylation CDG-Ia: implications for diagnosis and genetic counseling.

The congenital disorders of glycosylation (CDG) constitute a new group of recessively inherited metabolic disorders that are characterized biochemically by defective glycosylation of proteins. Several types have been identified. CDG-Ia, the most frequent type, is a multisystemic disorder affecting the nervous system and numerous organs including liver, kidney, heart, adipose tissue, bone, and genitalia. A phosphomannomutase (PMM) deficiency has been identified in CDG-Ia patients and numerous mutations in the PMM2 gene have been identified in patients with a PMM deficiency. We report on a French family with 3 affected sibs, with an unusual presentation of CDG-Ia, remarkable for 1) the neurological presentation of the disease, and 2) the dissociation between intermediate PMM activity in fibroblasts and a decreased PMM activity in leukocytes. This report shows that the diagnosis of CDG-Ia must be considered in patients with non-regressive early-onset encephalopathy with cerebellar atrophy, and that intermediate values of PMM activity in fibroblasts do not exclude the diagnosis of CDG-Ia.

Fate of nitrogen released from 15N-labeled litter in European beech forests.

The decomposition and fate of 15N-labeled beech litter was monitored in three European beech (Fagus sylvatica L.) forests (Aubure, France; Ebrach, Germany; and Collelongo, Italy) for 3 years. Circular plots around single beech trees were isolated from roots of neighboring trees by soil trenching, and annual litterfall was replaced by 15N-labeled litter. Nitrogen was continuously released from the decomposing litter. However, over a 2-year period, this release was balanced by the incorporation of exogenous N. Released N accumulated mainly at the soil surface and in the topsoil. Microbial biomass remained almost constant during the experiment at all sites except for considerably lower values at Ebrach. The 15N enrichment of the microbial biomass increased strongly during the first year and then remained stable. The 15N released from the decomposing litter was rapidly detected in roots and leaves of the beech trees, increasing regularly and linearly over the course of the experiment. The uptake of litter-released 15N by the trees was reduced under conditions that reduced tree growth. Under these conditions, leaves and fine roots were the dominant N sinks, and little N was allocated to other plant parts. By contrast, N uptake and N allocation from leaves to stem and bark tissues increased when tree growth was enhanced. Budgets for 15N showed that 2 to 4% of litter-released N was incorporated into the trees, about 35% remained in the litter and about 50% reached the topsoil.

Decomposition of 15N-labelled beech litter and fate of nitrogen derived from litter in a beech forest.

The decomposition and the fate of 15N- labelled beech litter was monitored in a beech forest (Vosges mountains, France) over 3 years. Circular plots around beech trees were isolated from neighbouring tree roots by soil trenching. After removal of the litter layer, 15N-labelled litter was distributed on the soil. Samples [labelled litter, soil (0-15 cm depths], fine roots, mycorrhizal root tips, leaves) were collected during the subsequent vegetation periods and analysed for total N and 15N concentration. Mass loss of the 15N-labelled litter was estimated using mass loss data from a litterbag experiment set up at the field site. An initial and rapid release of soluble N from the decomposing litter was balanced by the incorporation of exogenous N into the litter. Fungal N accounted for approximately 35% of the N incorporation. Over 2 years, litter N was continuously released and rates of N and mass loss were equivalent, while litter N was preferentially lost during the 3rd year. Released 15N accumulated essentially at the soil surface. 15N from the decomposing litter was rapidly (i.e. in 6 months) detected in roots and beech leaves and its level increased regularly and linearly over the course of the labelling experiment. After 3 years, about 2% of the original litter N had accumulated in the trees. 15N budgets indicated that soluble N was the main source for soil microbial biomass. Nitrogen accumulated in storage compounds was the main source of leaf N, while soil organic N was the main source of mycorrhizal N. Use of 15N-labelled beech litter as decomposing substrate allowed assessment of the fate of litter N in the soil and tree N pools in a beech forest on different time scales.

A semi-automated data processing system for root growth analysis: application to a growing oak seedling.

A data acquisition and processing system for analyzing root structure and growth is presented. Two-dimensional drawings are made of root systems growing against the inclined, transparent wall of a rhizotron. For analysis, a root is treated as a number of straight segments between points determined by the position of root apices at successive times of observation and the insertion points of lateral roots. The coordinates of the points are digitized by means of a graphics tablet and the description of the root system completed with information about root branching pattern and root order. From the recorded data, various root characteristics and growth parameters can be computed with a program available from the authors. Use of the data processing system in studies of root architecture is discussed and its application in the analysis of root growth of a pedunculate oak seedling (Quercus robur L.) reported.