Drosophila DBT Autophosphorylation of Its C-Terminal Domain Antagonized by SPAG and Involved in UV-Induced Apoptosis

Drosophila DBT and vertebrate CKIε/δ phosphorylate the period protein (PER) to produce circadian rhythms. While the C termini of these orthologs are not conserved in amino acid sequence, they inhibit activity and become autophosphorylated in the fly and vertebrate kinases. Here, sites of C-terminal autophosphorylation were identified by mass spectrometry and analysis of DBT truncations. Mutation of 6 serines and threonines in the C terminus (DBT^C/ala) prevented autophosphorylation-dependent DBT turnover and electrophoretic mobility shifts in S2 cells. Unlike the effect of autophosphorylation on CKIδ, DBT autophosphorylation in S2 cells did not reduce its in vitro activity. Moreover, overexpression of DBT^C/ala did not affect circadian behavior differently from wild-type DBT (DBT^WT), and neither exhibited daily electrophoretic mobility shifts, suggesting that DBT autophosphorylation is not required for clock function. While DBT^WT protected S2 cells and larvae from UV-induced apoptosis and was phosphorylated and degraded by the proteasome, DBT^C/ala did not protect and was not degraded. Finally, we show that the HSP-90 cochaperone spaghetti protein (SPAG) antagonizes DBT autophosphorylation in S2 cells. These results suggest that DBT autophosphorylation regulates cell death and suggest a potential mechanism by which the circadian clock might affect apoptosis.     

Suction lipoplasty: biohazardous aerosols and exhaust mist--the clouded issue

With the increased popularity of suction lipoplasty procedures, attention has been focused on their safety. One significant concern involves the rotary vane aspirators used to provide the suction required for the procedure. A series of experiments was carried out to determine whether aerosols are produced during the use of a rotary vane aspirator, since aerosols are known to be hazardous under appropriate conditions. Using a viable strain of Pseudomonas aeruginosa, we challenged the system through the suction port, and the exhaust from the aspirator was then cultured in a particle sampler. Results indicate that viable pathogens are released from the exhaust in physiologically significant particles capable of penetrating to the level of the alveolus in the normal human lung. These infectious particles were produced for 3 hours after the initial challenge. When an appropriate filtration device was attached to the aspirator outflow, the aspirator pump and environment were protected. In the absence of an appropriate filtration device, the aerosolized particles may constitute a hazard to patients or medical workers in the vicinity of the aspirator.     

Ochratoxin A,an in vivo inhibitor of renal phosphoenolpyruvate carboxykinase

Ochratoxin A, a nephrotoxin produced as a secondary metabolite by A. ochraceus, is a potent inhibitor of renal PEPCK activity, in vivo. When fed orally to rats for 2 days, renal PEPCK activity is reduced 50% by a total dose of 0.3-0.5 mg toxin. Renal gluconeogenic capacity is reduced only after PEPCK activity is inhibited by 50%. Hepatic PEPCK activity is unaffected up to 1.5-2.0 mg ochratoxin A, which were the highest doses tested. Other enzymes located in proximal convoluted tubules, including phosphatedependent glutaminase, γ-glutamyl transpeptidase, pyruvate carboxylase, and Na,K-ATPase, are not affected. Renal protein synthesis from [³H]phenylalanine or [³H]leucine is inhibited 30–40% by ochratoxin A in vivo. By covalently coupling the toxin to albumin with carbodiimide or mixed anhydride, the inhibitory effect on renal PEPCK activity is retained, but protein synthesis is not affected and cytological evidence of nephrotoxicity is lost. Injection of the ochratoxin A-albumin carbodiimide complex results in a decrease of hepatic PEPCK activity as well. Removal of the phenylalanine group from the toxin prevents the in vivo inhibition of PEPCK activity, as well as protein synthesis. We conclude that the decrease in renal PEPCK activity, in vivo, requires the phenylalanine group of ochratoxin A, and occurs by a mechanism independent of the known nephrotoxicity effects.     

Ascorbate-independent carotenoid de-epoxidation in intact spinach chloroplasts

Slow (> 1 s) light-induced absorbance changes in the 475–530 nm spectral region were examined in Type A chloroplasts from spinach. The most prominent absorption change occurred at 505 nm. The difference spectrum for this light-induced increase, its absence in osmotically shocked chloroplasts and restoration by ascorbate, and its sensitivity to dithiothreitol indicate that the absorption change is due to carotenoid de-epoxidation. The reaction in intact chloroplasts is characterized by its independence of exogenous ascorbate and a rate constant 3- to 8-fold higher than that reported previously for chloroplasts supplemented with ascorbate.The relevance of carotenoid de-epoxidation to other photosynthetic processes was examined by comparing their sensitivities to dithiothreitol. Levels of dithiothreitol that eliminate the 505 nm shift are without effect on saturated rates of CO₂ fixation and do not appreciably inhibit fluorescence quenching. We conclude that carotenoid de-epoxidation is not directly involved in the reactions of photosynthesis or in the regulation of excitation allocation between the photosystems.     

The impact of ticks on pheasant territoriality

Pheasants are competent reservoir hosts for the Lyme disease spirochaete, Borrelia burgdorferi s.l., and carry large, but highly over-dispersed, infestations of the vector ticks, Ixodes ricinus . The effects of experimental reduction of tick infestation levels on the survival and territorial behaviour of male pheasants were studied. Over three years in two woodlands in southern England, birds were marked individually and half were fitted with a slow-release acaricide, which substantially reduced their tick burdens from March to August. Acaricide treatment affected reproductive success but had no discernible impact on the survival rates of male pheasants. The degree of wattle inflation by males, an indicator of territorial status and a correlate of harem acquisition, was significantly greater among treated males. In each year, a significantly higher proportion of treated (overall 44%) than control (22%) males acquired harems. Males that acquired females ranged over small areas on field edges. By contrast, those with no females ranged more widely in woods and the adjoining fields, increasing their exposure to questing ticks. The relative contribution of such roving males to tick-borne pathogen transmission may thus increase.     

FLAVONOID EVOLUTION IN DENDROSERIS (COMPOSITAE,LACTUCEAE) FROM THE JUAN FERNANDEZ ISLANDS,CHILE

Leaf flavonoid chemistry was examined from the three subgenera and 11 species of the endemic genus Dendroseris (Compositae, Lactuceae) of the Juan Fernandez Islands, Chile. Eight of the species are restricted to the older island (Masatierra, ca. 4 million years old), which is also closer to the mainland. Three species, one from each subgenus, are restricted to Masafuera, which is younger geologically (1–2 million years old) and 145 km further west of Masatierra. A total of 16 compounds was identified, with the 7-0-glucosides of the flavones apigenin and luteolin accounting for 12 of the constituents. Two glucosides of the flavonol quercetin were detected. Despite considerable interpopulation variation within species, six of the taxa have distinctive flavonoid profiles. Although there are few absolute differences among the subgenera, they can be distinguished chemically. Subgenus Rea contains the greatest number of compounds, and a previous cladistic analysis based on morphological features suggested this subgenus as most primitive. Subgenus Phoenicoseris is considered highly derived morphologically, and it has a reduced flavonoid chemistry. Very little reduction in flavonoid diversity was seen in the morphologically specialized subg. Dendroseris as compared to subg. Rea. A trend in reduction of numbers of compounds was seen for two of the three species on the younger island of Masafuera when compared to their presumed ancestors on Masatierra. Flavonoids of selected species of Hieracium and Hypochaeris, presumptive mainland progenitors of Dendroseris, reveal a close chemical affinity with the former genus.     

Prehistoric Warfare in the American Southwest

Prehistoric Warfare in the American Southwest. Steven A. LeBlanc. Salt Lake City: University of Utah Press, 1999 400 pp.     

Coexistence of natural enemies in a multitrophic host–parasitoid system

Abstract.  1. This study explored the temporal and spatial aspects of coexistence over many generations in a multispecies host–parasitoid assemblage.
2. The long-term interaction between the cabbage root fly, Delia radicum (Diptera: Anthomyiidae), and two of its natural enemies, Trybliographa rapae (Hymenoptera: Fitigidae) and Aleochara bilineata (Coleoptera: Staphylinidae), in a cultivated field at Silwood Park over 19 years was explored.
3. Although time series showed that the populations were regulated, the impact of the natural enemies was highly variable. Within-year determinants showed that the spatial response of the specialist parasitoid, T. rapae , was predominantly independent of host density while A. bilineata acted simply as a randomly foraging generalist parasitoid.
4. These findings are compared and contrasted with an earlier investigation of the same system when only the first 9 years of the time series were available. This study demonstrated the potential of long-term field studies for exploring hypotheses on population regulation, persistence, and coexistence.