Serum levels of IgG subclasses in relation to IgE and atopic disease in early infancy

The levels of IgG1, IgG2, IgG3, and IgG4 were analysed by ELISA in cord serum and in serum samples collected at 6 and 18 months of age from infants whose mothers were atopic. None of the four IgG subclasses was significantly influenced on any sampling occasion by infant atopy, gender, month of birth, maternal IgE or maternal diet during pregnancy and early lactation. However, at 18 months of age, significantly higher levels of IgG1 (P less than 0.05) and of IgG4 (P less than 0.01) were found in infants with an elevated IgE (greater than or equal to 8.0 kU/l) than in those with a lower level. A weak positive correlation (rs = 0.26; P = 0.05) between IgE and IgG4 was also observed. Despite the fact that the serum levels of IgG4 at 18 months were significantly higher (P less than 0.01) among infants with positive IgE-RAST (greater than or equal to 0.15 PRU/ml) to ovomucoid or beta-lactoglobulin, our data suggest that the the concentration of IgG4 relates more to the level of IgE than to the clinical symptoms of atopy. Determination of IgG subclasses seems to be of limited value for prediciting atopy during early infancy.     

Existence and Uniqueness of Solutions to the Multispecies Virtual Population Analysis Equations

This paper deals with the question of existence and uniquenessof solutions of multispecies virtual population analysis equationsfor predator–systems. By formulating the question as afized-point problem for a certain function F, it is shown thatat least one solution always exits. By using Brouwer degree,sufficient conditions for uniqueness are derived which are morelikely to be satisfied than those based on the requirement thatF be a contraction. Some of these are formulated as inequlitieswhich could be verified in the course of solving the equationsnumerically.     

Abnormality of adenylate cyclase regulation in human platelet membranes in renal insufficiency

Adenylate cyclase in human platelets is under dual control of prostaglandins (PGI2 and PGE1) and catecholamines. The adenylate cyclase complex in membranes of platelets from ten patients with uraemia was investigated. The activation of the platelet cyclase by PGE1 is increased in the uraemic state, Vmax 4436 +/- 607 pmol cAMP mg-1 15 min-1. In the normal state Vmax is 2098 +/- 309 pmol cAMP mg-1 15 min-1. The alpha 2-adrenergic receptor was assayed with 3H-yohimbine binding. The density of receptors was equal in the uraemic (175 fmol mg-1 membrane protein) and the normal (170 fmol mg-1 membrane protein) states. Norepinephrine/3H-yohimbine competition binding revealed that catecholamines were bound with normal affinity in platelets in uraemia. Yet the inhibition of adenylate cyclase through the alpha 2-adrenergic receptor was diminished since Vmax values of adenylate cyclase with PGE1 and PGE2 + norepinephrine did not significantly differ. In the normal state, norepinephrine significantly (P less than 0.05) inhibited the PGE1 stimulated cyclase. It is concluded that platelet adenylate cyclase in the uraemia has an increased capacity for activation which is the result of both a sensitized stimulatory mechanism (prostaglandin mediated) and a deficient inhibitory mechanism (catecholamine mediated). It is suggested that a defect exists in the inhibitory nucleotide binding protein (NI) which is the coupling unit between the adenylate cyclase catalytic subunit (C).