Hormonal control of the yolk precursor vitellogenin regulates immune function and longevity in honeybees.

A striking example of plasticity in life span is seen in social insects such as ants and bees, where different castes may display distinct ageing patterns. In particular, the honeybee offers an intriguing illustration of environmental control on ageing rate. Honeybee workers display a temporal division of labour where young bees (or 'hive bees') perform tasks within the brood nest, and older bees forage for nectar, pollen propolis and water. When bees switch from the hive bee to the forager stage, their cellular defence machinery is down-regulated by a dramatic reduction in the number of functioning haemocytes (immunocytes). This study documents that the yolk precursor vitellogenin is likely to be involved in a regulatory pathway that controls the observed decline in somatic maintenance function of honeybee foragers. An association between the glyco-lipoprotein vitellogenin and immune function has not previously been reported for any organism. Honeybee workers are functionally sterile, and via the expression of juvenile hormone, a key gonotrophic hormone in adult insects, their vitellogenin levels are influenced by social interactions with other bees. Our results therefore suggest that in terms of maintenance of the cellular immune system, senescence of the honeybee worker is under social control.

Evaluations of solid electrodes for use in voltammetric monitoring of heavy metals in samples from metallurgical nickel industry.

Evaluation of different solid electrode systems for detection of zinc, lead, cobalt, and nickel in process water from metallurgical nickel industry with use of differential pulse stripping voltammetry has been performed. Zinc was detected by differential pulse anodic stripping voltammetry (DPASV) on a dental amalgam electrode as intermetallic Ni-Zn compound after dilution in ammonium buffer solution. The intermetallic compound was observed at -375 mV, and a linear response was found in the range 0.2-1.2 mg L(-1) (r(2)=0.98) for 60 s deposition time. Simultaneous detection of nickel and cobalt in the low microg L(-1) range was successfully performed by use of adsorptive cathodic stripping voltammetry (AdCSV) of dimethylglyoxime complexes on a silver-bismuth alloy electrode, and a good correlation was found with corresponding AAS results (r(2)=0.999 for nickel and 0.965 for cobalt). Analyses of lead in the microg L(-1) range in nickel-plating solution were performed with good sensitivity and stability by DPASV, using a working electrode of silver together with a glassy carbon counter electrode in samples diluted 1:3 with distilled water and acidified with H(2)SO(4) to pH 2. A new commercial automatic at-line system was tested, and the results were found to be in agreement with an older mercury drop system. The stability of the solid electrode systems was found to be from one to several days without any maintenance needed.