Ann Pulsford

Evidence for environmentally derived immunomodulation in mussels from the Venice Lagoon

Abstract Mussels, Mytilus galloprovincialis , were sampled at three times of year, from various sites within the Venice Lagoon and a reference Platform site in the north Adriatic. The immune response of the mussels was assessed using a range of assays which included total and differential cell counts, phagocytosis, degradative enzyme levels and release of reactive oxygen metabolites. Chlorinated hydrocarbons, including lindane, DDT and PCBs, together with trace metal levels were measured in digestive gland tissues from the mussels. The measurements of immune response and the contaminant levels showed seasonal fluctuations. However, the results did demonstrate significant differences in a number of immunocompetence assays which in some instances showed some correlation with the levels of contaminants measured in the tissues. In particular, total and differential cell counts, phagocytosis and release of reactive oxygen metabolites showed a degree of correlation with contaminant burdens although other factors were clearly involved. The results confirm the requirement for using a range of assays for monitoring pollution effects.

Effects of cadmium and benzo(a)pyrene on the immune system, gill ATPase and EROD activity of European sea bass Dicentrarchus labrax

Juvenile European sea bass (Dicentrarchus labrax) were exposed to cadmium (40 μg l−1) for 15 days and then injected with benzo(a)pyrene (BaP) (20 mg kg−1) for 14 h. In the immune system, phagocytosis was reduced both in spleen and kidney macrophages after cadmiumexposure and/or BaP injection, with a synergistic effect of the combined pollutants. Spleen and kidney respiratory burst (measured by hydrogen peroxide production) showed different patterns of response to cadmium and BaP. Cadmium exposure had no effect on spleen macrophages, although BaP totally inhibited the respiratory burst. In kidney macrophages, cadmiumexposure and BaP injection resulted in enhanced hydrogen peroxide production. After BaP injection, hepatic micrososomal 7-ethoxyresorufin-O-deethylase (EROD) activity was increased 21-fold compared with the control, but the induction was even greater (34.5 times compared with the control) in cadmium-exposed fish. However, although an induction (11 times compared to the control) occurred after cadmium exposure the effects of both pollutants were not synergistic (not additional). No perturbation of the gill Na+/K+-ATPase activity was observed in cadmium-exposed fish, but the activity was increased in BaP-injected fish. The role of BaP metabolites and cadmium as both direct effectors and indirect stressors, responsible for the changes in the immune system and gill and liver biochemistry of the fish are discussed.

The Communication between Individuals in Salp Chains I. Morphology of the System

The plaque consists on one side of a small button of modified epithelial cells (plate 1, 5 and 6) and on the other of a small group of sensory cells, which are less conspicuous than the button cells. At the light microscope level, the button cells can be seen to form a sort of small button or mushroom protuding from the epithelium of the plaque (plate 1, 11 and 12; figure 2) into the test material separating the two epithelial layers. Opposite this button are a group of sensory cells, the axons of which pass to the brain shrouded in the bases of the epithelial cells (plate 1, 8 and 9). The arrangement of the button cells and opposing sensory cells is a constant one, so that, on a single zooid, one of the pair of plaques joining it to an adjacent zooid has a group of sensory cells, the other (the non-innervated plaque), a group of button cells. The plaques at the outer ends of the horns are innervated, as are those near the horn bases, while those on the ventral surface and at the inner end of the horns are not innervated, and have the button cells. In consequence of this, it is a simple matter to separate one or other of the plaques joining two zooids to investigate their physiological properties (Anderson & Bone 1980). Fedele (1920) first described the sensory cells of the attachment plaques, but he supposed that they occurred at both sides in each plaque. In fact, they lie only on one side of the plaque, as described above, and this asymmetry has important consequences for the way in which the system operates. Apart from the specialized region of the plaque, where these cells are found, the plaque is symmetrical, and the two epithelial layers are some 5 μm apart, separated by test material (plate 1, 7). The epithelial cells are flattened (like those of the outer epithelium outside the plaques), and are some 2–5 pm thick (plate 2, 1). They contain an extensive smooth endoplasmic reticulum, mitochondria with tubular cristae, flattened nuclei, and occasional vesicles of various sizes

Possible transmitter functions of acetylcholine and an RFamide-like substance in Sagitta (Chaetognatha)

The locomotor muscle fibres of the chaetognath Sagitta are probably multiply innervated and, although linked by numerous gap junctions, do not appear to be coupled electrically. Acetylcholine evokes contraction of the locomotor muscle; iontophoretic application of acetylcholine evokes membrane depolarizations and a series of spikes resembling those seen during spontaneous activity. Both effects are reversibly abolished by (+)-tubocurarine. Acetylcholinesterase is found associated with the sarcolemmata, and it is suggested that acetylcholine is a possible candidate for the neuromuscular transmitter. Immunocytochemical studies with antisera raised against the sequence Arg-Phe-amide (RFamide) show that many neurons in the brain and ventral ganglia contain an RFamide-like material. Some of these neurons are associated with the innervation of sensory organs; others may belong to coordinating systems. At present, these observations do not indicate the affinity of the Chaetognatha to any other invertebrate phylum.