Mid-mantle deformation inferred from seismic anisotropy

With time, convective processes in the Earth's mantle will tend to align crystals, grains and inclusions. This mantle fabric is detectable seismologically, as it produces an anisotropy in material properties—in particular, a directional dependence in seismic-wave velocity. This alignment is enhanced at the boundaries of the mantle where there are rapid changes in the direction and magnitude of mantle flow, and therefore most observations of anisotropy are confined to the uppermost mantle or lithosphere and the lowermost-mantle analogue of the lithosphere, the D" region. Here we present evidence from shear-wave splitting measurements for mid-mantle anisotropy in the vicinity of the 660-km discontinuity, the boundary between the upper and lower mantle. Deep-focus earthquakes in the Tonga–Kermadec and New Hebrides subduction zones recorded at Australian seismograph stations record some of the largest values of shear-wave splitting hitherto reported. The results suggest that, at least locally, there may exist a mid-mantle boundary layer, which could indicate the impediment of flow between the upper and lower mantle in this region

Viroplasm and large virus-like particles in the dinoflagellate Gymnodinium uberrimum

Virus-like particles (VLPs) measuring 385±5 nm in diameter are described in the freshwater dinoflagellate Gymnodinium uberrimum . The VLPs are found in association with, and “budding” from a vesicular viroplasmic area. A similar viroplasm was also found in a chrysophycean alga, Mallomonas sp. collected from the same general area in Saginaw Bay of Lake Huron. The nature of these VLPs and their virogenic stroma, in these algae from the Laurentian Great Lakes are discussed in the present report.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41733/1/709_2005_Article_BF01275735.pd

Influence of the 5-HT(2C) receptor antagonist SB242,084 on behaviour produced by the 5-HT(2) agonist Ro60-0175 and the indirect 5-HT agonist dexfenfluramine

1. Ro60-0175 has been described as a selective agonist at the 5-HT(2C) receptor, yet it has only 10- fold higher affinity at the 5-HT(2C) compared to the 5-HT(2A) subtype, and equivalent affinity for the 5-HT(2B) receptor. 2. The selective 5-HT(2C) receptor antagonist SB242,084 (0.5 mg kg(−1) i.p.), blocked the hypoactivity and penile grooming induced by Ro60-0175 (1 mg kg(−1) s.c.). The combination of SB242,084 (0.5 mg kg(−1) i.p.) and Ro60-0175 (3 – 10 mg kg(−1)) produced a completely different pattern of behaviours including wet-dog shakes, hyperactivity and back muscle contractions. These latter effects were blocked by the selective 5-HT(2A) receptor antagonist MDL100,907 (0.5 mg kg(−1) i.p.), but not the 5-HT(2B) receptor antagonist SB215,505 (3 mg kg(−1) p.o.). 3. The indirect 5-HT releaser/reuptake inhibitor dexfenfluramine (1 – 10 mg kg(−1) i.p.) produced a mild increase in locomotor activity, penile grooming, and occasional back muscle contractions and wet-dog shakes. Pre-treatment with SB242,084 (0.5 mg kg(−1)), blocked the incidence of penile grooming, and markedly potentiated both the dexfenfluramine-induced hyperactivity, the incidence of back muscle contractions, and to a lesser extent wet-dog shakes. Some toxicity was also evident in animals treated with dexfenfluramine (10 mg kg(−1))/SB242,084 (0.5 mg kg(−1)), but not in any other treatment groups. 4. The hyperactivity and toxicity produced by the dexfenfluramine (10 mg kg(−1))/SB242,084 (0.5 mg kg(−1)) combination was replicated in a further study, and hyperthermia was also recorded. Both hyperthermia and toxicity were blocked by MDL100,907 (0.5 mg kg(−1)) but not SB215,505 (3 mg kg(−1)). An attenuation of the hyperlocomotor response was also observed following MDL100,907. 5. These findings suggest that 5-HT(2C) receptor activation can inhibit the expression of behaviours mediated through other 5-HT receptor subtypes