The laminated sediments of Loch Ness, Scotland: Preliminary report on the construction of a chronology of sedimentation and its potential use in assessing Holocene climatic variability

Two sediment cores, ca. 6 m long, have been recovered from the north basin of Loch Ness, Scotland. Each consists of ca. 4.5 m of laminated gyttja, terminating in a basal grey, unlaminated clay. A suite of three ¹⁴C AMS dates have been obtained, and place the base of the gyttja at ca. 9500 yr B.P. Investigations into the structure, composition and formation of the laminae are in progress. Analysis by Backscatter Scanning Electron Microscopy (BSEM) has demonstrated that they consist of couplets comprising dark, clay-rich sediments thought to be deposited from spring to autumn, and pale, silt-rich layers believed to represent sedimentation through winter. The laminae are thus thought to record incidence and intensity of streamflow into the Loch over the past nine millennia, and thus illustrate environmental change over the region for most of the Holocene. X-ray densitometry has been utilised in order to count the laminations and test the hypothesis that they are varves. It has, however, proved difficult to obtain a continuous sequence of countable laminations, although it has been possible to construct a fragmented, floating chronology which indicates that the hypothesis may be correct. Examination of lamination thickness reveals that although the average rate of sedimentation throughout the time periods studied seems to have remained fairly constant, significant variations have occurred. As Loch Ness is located on the northwest oceanic fringe of Europe, any climatic signal which the laminations contain will be closely related to even larger scale events over and within the North Atlantic Ocean, which is a major controller of global climate. Preliminary statistical investigation of sequences of laminae is being carried out in order to search for periodicity of sedimentation which may then be related to appropriate climatic indices.     

Identification and characterization of the cAMP binding proteins of yeast by photoaffinity labeling.

Modulation of a membrane glycoprotein, approximate molecular weight 200,000, in concert with active ionic flux has been shown in a human neuroblastoma cell line. The modulating agent was 2% dimethyl sulfoxide. Other neuronal properties, acetylcholinesterase and choline acetyltransferase, were also modulated but to a lesser extent. The appearance of this glycoprotein on the surface of both human and mouse neuroblastoma cells only under conditions of differentiation leads to the suggestion that it is directly involved with the active Na⁺ channels.     

Interaction of soluble pig heart glutamate-aspartate transaminase with various beta,gamma-unsaturated amino acids

beta-Ethylidene-DL-aspartate (beta EA) and beta-methylene-DL-glutamate (beta MG) were synthesized and tested as potential suicide inhibitors of soluble pig heart glutamate-aspartate transaminase (sGAT). beta MG was found to be a) a substrate with a very low turnover number relative to glutamate and b) a competitive inhibitor with respect to aspartate (albeit with a large binding constant). At high concentrations beta MG inactivated the enzyme but only very slowly. beta EA was also found to be a substrate with a very low turnover number; it did not inactivate the enzyme (1 hr, 25 degrees C) even at a high concentration. However, beta EA was found to bind to the enzyme with an affinity comparable to that of aspartate and glutamate. beta-Methylene-DL-aspartate (beta MA) has been shown to rapidly inactivate glutamate-aspartate transaminase. Therefore, it appears that glutamate-aspartate transaminase can bind analogues of aspartate with alkene groups in the beta position. The conjugated carbonyl groups of beta MA and beta EA will enhance Michael addition in comparison with that expected for vinylglycine. On the other hand, the presence of the methyl groups should reduce the electrophilicity of the double bond of beta EA compared to beta MA. This deactivation and/or steric hindrance to Michael attack may account for the inability of beta EA to inactivate sGAT. Therefore, it may be possible to design selective suicide inhibitors of glutamate-aspartate++ transaminase with the following structure: HO2CC(= CHX)CH(CO2H)NH2, where X is an electron-withdrawing group. Ideally, X would increase the reactivity of the double bond while affording a minimum of steric hindrance to susceptible enzyme-bound bases.     

Parasitoids of obscure mealybug,Pseudococcus viburni (Hem.: Pseudococcidae) in California: establishment of Pseudaphycus flavidulus (Hym.: Encyrtidae) and discussion of related parasitoid species

To improve natural suppression of the obscure mealybug, Pseudococcus viburni (Signoret), the parasitoids Pseudaphycus flavidulus (Brèthes) and Leptomastix epona (Walker) (Hymenoptera: Encyrtidae) of Chilean origin were released in California's Central Coast vineyards from 1997 to 1999. A survey for parasitoids of P. viburni was conducted in the Edna Valley appellation wine grape region from 2005 to 2007, 6–8 years after classical biological control releases were discontinued. Two survey methods were used. First, field collections of obscure mealybugs from commercial vineyard blocks (2005–2007) and, second, placement of “sentinel mealybugs” on potted (1 L) grape vines (2006 only). From both survey methods, P. flavidulus was recovered, albeit levels of parasitism were low (less than 0.6%). We also placed longtailed mealybug, Pseudococcus longispinus (Targioni Tozzetti), on potted plants concurrent with placement of sentinel obscure mealybugs in the vineyard in order to measure parasitoid activity on this closely-related mealybug species. No P. flavidulus were recovered from P. longispinus. Other encyrtid parasitoids reared from either P. viburni or P. longispinus were Anagyrus pseudococci (Girault), Leptomastix dactylopii Howard, Leptomastidea abnormis (Girault), Coccidoxenoides perminutus Girault, and Tetracnemoidea peregrina (Compere). A hyperparasitoid, Chaetocerus sp., was also reared. The data are discussed with respect to biological control of vineyard mealybugs and newly developed controls for the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae). Because Pseudaphycus species reared from mealybugs are superficially very similar a taxonomic key and discussion of host relationships for selected Pseudaphycus species are provided.     

Infertile spermatozoa of c-ros tyrosine kinase receptor knockout mice show flagellar angulation and maturational defects in cell volume regulatory mechanisms.

Homozygous c-ros knockout male mice that lack prepubertal differentiation of the epididymal initial segment are healthy but sterile, despite normal sperm production and mating. Detailed computerized analysis of the motility of spermatozoa maturing in the epididymis revealed only minor defects. However, the majority of motile mature sperm released from the cauda epididymidis showed various extents of flagellar angulation that could not be corrected by raising extracellular osmolality. Measurement of the osmolality of cauda epididymal fluid showed no difference from the wild type. Studies in wild-type mice indicated a maturational change in the ability of motile sperm to maintain straight flagella during incubation, but angulation was induced in cauda sperm by the volume-sensitive ion channel blockers quinine, 5-nitro-2-(3-phenylpropylamino)-benzoic acid and BaCl(2), or by exposure to hypotonic media. Flagellar angulation, induced in the wild type or intrinsic to the knockout, was relieved upon demembranation by Triton X-100, confirming that it was a cell swelling phenomenon. A lack of response of immature wild-type sperm and mature knockout sperm to the channel blockers suggests that there is normally a development of the volume regulatory mechanisms upon maturation that is defective in sperm from the knockout animal. The resultant flagellar angulation may account for the reduction in sperm numbers in the oviduct of mated females and the failure to fertilize in vivo.