Molecular genetics of cell death in the nematode Caenorhabditis elegans

In C. elegans, cell death can be readily studied at the cellular, genetic, and molecular levels. Two types of death have been characterized in this nematode: (1) programmed cell death, which occurs as a normal component in development; and (2) pathological cell death which occurs aberrantly as a consequence of mutation. Analysis of mutations that disrupt programmed cell death in various ways has defined a genetic pathway for programmed cell death which includes genes that perform such functions as the determination of which cells die, the execution of cell death, the engulfment of cell corpses, and the digestion of DNA from dead cells. Molecular analysis is providing insightinto the nature of the molecules that function in these aspects of programmed cell death. Characterization of some genes that mutate to induce abnormal cell death has defined a novel gene family called degenerins that encode putative membrane proteins. Dominant alleles of at least two degenerin genes, mec-4 and deg-1, can cause cellular swelling and late onset neurodegeneration of specific groups of cells. © 1992 John Wiley & Sons, Inc.     

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.     

Collagen targeting using multivalent protein-functionalized dendrimers

Collagen is an attractive marker for tissue remodeling in a variety of common disease processes. Here we report the preparation of protein dendrimers as multivalent collagen targeting ligands by native chemical ligation of the collagen binding protein CNA35 to cysteine-functionalized dendritic divalent (AB₂) and tetravalent (AB₄) wedges. The binding of these multivalent protein constructs was studied on collagen-immobilized chip surfaces as well as to native collagen in rat intestinal tissues. To understand the importance of target density we also created collagen-mimicking surfaces by immobilizing synthetic collagen triple helical peptides at various densities on a chip surface. Multivalent display of a weak-binding variant (CNA35-Y175K) resulted in a large increase in collagen affinity, effectively restoring the collagen imaging capacities for the AB₄ system. In addition, dissociation of these multivalent CNA35 dendrimers from collagen surfaces was found to be strongly attenuated.     

Measurement of extracellular space in the rabbit AV node

We used quantitative histochemistry to measure the size of the extracellular space (ESC) in various regions of the rabbit heart. When inulin, sucrose, and sorbitol were used as ECS markers, the ECS of the AV-nodal tissue was found to be, respectively, 2.4, 2.2, and 2.5 times larger than that of left ventricular muscle. Glucose was also measured over a 50-fold serum concentration range as an extracellular marker for AV-nodal tissue, left ventricular muscle, and Purkinje fibers. Measurements with glucose also revealed that the ECS of the AV node was 2.5-2.8 times larger than that of ventricular muscle. In contrast, the ECS of the AV node was the same as that of Purkinje fibers when glucose was used as an extracellular marker. ATP content, measured as an intracellular marker, was similar in both AV-nodal and contractile tissue. Collectively, the data obtained with all extracellular markers indicate that the ECS of the AV-nodal region is approximately 2.5 times larger than that of adjacent contractile tissue. Differences in the size of the ECS in various regions of the heart probably have functional significance and should be considered appropriately during the interpretation of data obtained by biochemical and densitometric approaches.     

Cluster analysis of behavioural and event-related potentials during a contingent negative variation paradigm in remitting-relapsing and benign forms of multiple sclerosis

Background  

Event-related potentials (ERPs) may be used as a highly sensitive way of detecting subtle degrees of cognitive dysfunction. On the other hand, impairment of cognitive skills is increasingly recognised as a hallmark of patients suffering from multiple sclerosis (MS). We sought to determine the psychophysiological pattern of information processing among MS patients with the relapsing-remitting form of the disease and low physical disability considered as two subtypes: 'typical relapsing-remitting' (RRMS) and 'benign MS' (BMS). Furthermore, we subjected our data to a cluster analysis to determine whether MS patients and healthy controls could be differentiated in terms of their psychophysiological profile.     

The use of GMOs (genetically modified organisms): agricultural biotechnology or agricultural biopolitics?

Agricultural biotechnologies embrace a large array of conventional and modern technologies, spanning from composting organic by-products of agriculture to innovative improvement of quality traits of about twenty out of the mostly cultivated plants. In EU a rather restrictive legislative framework has been installed for GMOs, requiring a risk assessment disproportionate with respect to conventional agriculture and organic farming products. The latter are far from being proved safe for human and animal health, and for the environment.Biotechnology of GMOs has been overtaken by biopolitics. On one side there are biotechnological challenges to be tackled, on another side there is plenty of ground for biopolitical decisions about GMOs. Perhaps the era of harsh confrontation could be fruitfully replaced by sensible cooperation, in order to get a sustainable agricultural development.     

Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes

A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent. ¹Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA ²Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA