Lymphocyte 5'-nucleotidase deficiency in hypogammaglobulinemia: Clinical characteristics

Twelve patients with congenital agammaglobulinemia, 2 of 10 patients with selective IgA deficiency, and 4 of 15 patients with common variable immunodeficiency have reduced 5'-nucleotidase activity on lymphocyte plasma membranes. In congenital agammaglobulinemia and common variable immunodeficiency, enzyme-deficient patients have an early onset of immune dysfunction, low levels or an absence of circulating B-lymphocytes, and a positive family history of similar immunodeficiency. The enzyme deficiency involves peripheral E-rosette-forming lymphocytes, suggesting an abnormality of T-lymphocytes in these diseases. No systemic disorder of purine nucleotide degradation to uric acid is detectable in the enzyme-deficient patients. No direct relationship between 5'-nucleotidase activity and in vitro production of IgG is evident, since inhibition of the enzyme did not decrease IgG synthesis. At present the data do not allow a distinction between two hypotheses to explain the role of 5'-nucleotidase in hypogamma-globulinemia, that is, whether 5'-nucleotidase deficiency causes the immune dysfunction or is simply a marker for an intrinsic lymphocyte abnormality. However, this enzyme deficiency may provide a useful means of classifying disorders of immunoglobulin synthesis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23149/1/0000074.pd

Nitrogen mineralization, nitrification and denitrification in upland and wetland ecosystems

Nitrogen mineralization, nitrification, denitrification, and microbial biomass were evaluated in four representative ecosystems in east-central Minnesota. The study ecosystems included: old field, swamp forest, savanna, and upland pin oak forest. Due to a high regional water table and permeable soils, the upland and wetland ecosystems were separated by relatively short distances (2 to 5 m). Two randomly selected sites within each ecosystem were sampled for an entire growing season. Soil samples were collected at 5-week intervals to determine rates of N cycling processes and changes in microbial biomass. Mean daily N mineralization rates during five-week in situ soil incubations were significantly different among sampling dates and ecosystems. The highest annual rates were measured in the upland pin oak ecosystem (8.6 g N m −2 yr −1 ), and the lowest rates in the swamp forest (1.5 g N m −2 yr −1 ); nitrification followed an identical pattern. Denitrification was relatively high in the swamp forest during early spring (8040 μg N 2 O−N m −2 d −1 ) and late autumn (2525 μg N 2 O−N m −2 d −1 ); nitrification occurred at rates sufficient to sustain these losses. In the well-drained uplands, rates of denitrification were generally lower and equivalent to rates of atmospheric N inputs. Microbial C and N were consistently higher in the swamp forest than in the other ecosystems; both were positively correlated with average daily rates of N mineralization. In the subtle landscape of east-central Minnesota, rates of N cycling can differ by an order of magnitude across relatively short distances.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47791/1/442_2004_Article_BF00320810.pd