Lipolysis drives expression of the constitutively active receptor GPR3 to induce adipose thermogenesis

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The shape of compass termite mounds and its biological significance

Summary In northern Australia, compass termites build tall wedge-shaped mounds with an elongated axis that has a striking north-south orientation. Various hypotheses have been advanced to account for this remarkable mound architecture. However, behavioural aspects of mound orientation have rarely been investigated. The currently accepted hypothesis considers mound orientation as an adaptation to local long-term environmental conditions to maintain a temperature plateau at the eastern face of the mound. According to this hypothesis termites should concentrate at the eastern face when ambient temperature conditions are not ideal. This was tested in the current study by applying a new, non-destructive technique that allows monitoring of termites through solid material. Termatrac®, a tool developed for termite pest detection, uses microwaves to detect the movement of termites. As predicted by the eastern- face-plateau hypothesis, termites concentrated in the morning at the eastern face of the mound. However, this pattern was not found at sunrise or noon despite a similar temperature gradient between eastern and western face. This might indicate that only the morning heating of the eastern face is important for the termites, while it plays no prominent role during the rest of the day. The eastern-face-plateau hypothesis is then compared with other hypotheses to develop a general framework that addresses the different characteristics of compass mound architecture: shape, orientation and geographic variation in orientation.Received 1 November 2002; revised 28 January 2003; accepted 12 February 2003.     

Use of a radioimmunoassay technique to measure the titer of anti-cow-zona antibodies in marmoset monkeys

A double antibody radioimmunoassay technique is described for the measurement of anti-zona antibodies in the peripheral plasma of marmosets actively immunized against intact cow zonae pellucidae. The method has been shown to be a reliable, repeatable indicator of antibody titer, enabling direct comparison of the response obtained between marmosets. This is the first report of a procedure describing the active immunization of a primate against zona antigens, and the first time a radioimmunoassay technique has been used to monitor profiles of anti-cow zona antibody production following active immunization. The method should prove to be a useful tool in the evaluation of zona antigens as agents for immunocontraception.     

Dimer–monomer equilibrium of human thymidylate synthase monitored by fluorescence resonance energy transfer

An ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43′ with an excitation energy donor/acceptor pair. The dimer–monomer equilibrium of the enzyme is then characterized through steady‐state fluorescence determination of the intersubunit resonance energy transfer efficiency.     

Modeling of substrate and inhibitor binding to phospholipase A2.

Molecular graphics and molecular mechanics techniques have been used to study the mode of ligand binding and mechanism of action of the enzyme phospholipase A2. A substrate-enzyme complex was constructed based on the crystal structure of the apoenzyme. The complex was minimized to relieve initial strain, and the structural and energetic features of the resultant complex analyzed in detail, at the molecular and residue level. The minimized complex was then used as a basis for examining the action of the enzyme on modified substrates, binding of inhibitors to the enzyme, and possible reaction intermediate complexes. The model is compatible with the suggested mechanism of hydrolysis and with experimental data about stereoselectivity, efficiency of hydrolysis of modified substrates, and inhibitor potency. In conclusion, the model can be used as a tool in evaluating new ligands as possible substrates and in the rational design of inhibitors, for the therapeutic treatment of diseases such as rheumatoid arthritis, atherosclerosis, and asthma.     

Why there are photodamages to photosystem II at low light intensities

An explanation of photodamages to PS II at low light intensities is proposed. The explanation is based on the two following postulates: 1. Intermediate states of the water-oxidizing complex can undergo parasitic reduction to lower degrees of oxidation. 2. Photosynthetic apparatus can minimize the unfavorable effect of such reduction by changes in the number of active reaction centers of PS II. Some steady-state characteristics were calculated under these assumptions. The results obtained show that the frequency of P680 excitations at low light intensities becomes as high as that at saturating light provided that the rate of parasitic reduction is comparable with the rate of the slowest reaction in the cycle of the water- oxidizing complex conversions.