Plasmodium berghei: Specific stimulation of rat lymphocytes by soluble antigens released in vitro from infected erythrocytes

Soluble components released in vitro from rat erythrocytes parasitized with Plasmodium berghei have been shown to stimulate nonadherent spleen lymphocytes from rats convalescent from homologous infection. The active product is released from the infected erythrocytes either spontaneously during incubation, or as the result of artificial rupture of infected erythrocytes by freezing and thawing or sonication. This antigen produced precipitation lines with antiplasmodial antibodies from sera of convalescent and hyperimmune rats and from immunized rabbits.     

Induction of Growth Cone Formation by Transient and Localized Increases of Intracellular Proteolytic Activity

The formation of a growth cone at the tip of a transected axon is a crucial step in the subsequent regeneration of the amputated axon. During this process, the transected axon is transformed from a static segment into a motile growth cone. Despite the importance of this process for regeneration of the severed axon, little is known about the mechanisms underlying this transformation.     

Calcium concentration threshold and translocation kinetics of EGFP-DOC2B expressed in cultured Aplysia neurons

The double C2 domain protein family (DOC2) is characterized by two calcium-binding domains (C2). Upon binding to calcium, the affinity of the protein to phospholipids is significantly increased, leading to translocation of the protein from the cytosol to the plasma membrane. These properties, and the binding domain of DOC2B to Munc13, suggested that DOC2B could play a role in augmentation and potentiation of synaptic release. Nevertheless, the level of the free intracellular calcium concentration ([Ca(2+)](i)) which triggers its translocation under in vivo conditions, is not known. Using cultured Aplysia neurons that express rat EGFP-DOC2B, we found that the [Ca(2+)](i) increment necessary to induce EGFP-DOC2B translocation is approximately 200 nM in the bulk of the cytoplasm. The rate of EGFP-DOC2B recruitment to the plasma membrane is slower than the [Ca(2+)](i) elevation rate, while the detachment of EGFP-DOC2B from it is faster than the calcium removal. The extent of EGFP-DOC2B translocation to the plasma membrane reflects local submembrane [Ca(2+)](i). Our observations are consistent with the view that DOC2B can participate in the regulation of neurotransmitter release. It should be noted that EGFP-DOC2B could be used as a tool to map sub-membrane calcium dynamics under physiological conditions.     

Alterations in gene expression in T1α null lung: a model of deficient alveolar sac development

Background  

Development of lung alveolar sacs of normal structure and size at late gestation is necessary for the gas exchange process that sustains respiration at birth. Mice lacking the lung differentiation gene T1α [T1α(-/-)] fail to form expanded alveolar sacs, resulting in respiratory failure at birth. Since little is known about the molecular pathways driving alveolar sacculation, we used expression microarrays to identify genes altered in the abnormal lungs and, by inference, may play roles in normal lung morphogenesis.     

Acetylcholinesterase-ISFET based system for the detection of acetylcholine and acetylcholinesterase inhibitors

A bioelectronic hybrid system for the detection of acetylcholine esterase (AChE) catalytic activity was assembled by way of immobilizing the enzyme to the gate surface of an ion-sensitive field-effect transistor (ISFET). Photometric methods used to characterize bonded enzyme and linker layers on silicon substrates confirm the existence of a stable amino-cyanurate containing AChE monolayer. The transduction of the enzyme-functionalized ISFET, in ionic solutions, is detected in response to application of acetylcholine (ACh). Recorded sensitivity of the modified ISFET to ACh has reached levels of up to 10(-5)M. The Michaelis-Menten constant of the immobilized AChE is only moderately altered. Nevertheless, the maximum reaction velocity is reduced by over an order of magnitude. The ISFET response time to bath or ionophoretic application of ACh from a micropipette was in the range of a second. The catalytic activity of the immobilized AChE is inhibited in a reversible manner by eserine, a competitive inhibitor of AChE. We conclude that the immobilized enzyme maintains its pharmacological properties, and thus the described bioelectronic hybrid can serve as a detector for reagents that inhibit AChE activity.