Mutant p21ras in vinyl chloride exposed workers

The production of mutations in cellular oncogenes such as ras is involved in the development of many human cancers. These mutations result in the expression of mutant forms of the encoded p21 protein which can potentially serve as a biomarker for this carcinogenic process. Workers exposed to vinyl chloride (VC) who are at risk for the development of the sentinel neoplasm angiosarcoma of the liver (ASL) represent a model population for the study of such a mutant p21ras biomarker, since VC is known to cause a specific ras mutation in ASL. In order to determine the relationship between VC exposure and this biomarker, serum samples from a cohort of 225 French VC workers and 111 age-sex-race-smoking-drinking matched unexposed controls were examined for the presence of mutant p21ras by immunoblotting with a mouse monoclonal antibody specific for the mutant protein. Stratifying the exposed workers by degree of VC exposure in estimated ppm-years by quartiles yielded a statistically significant trend for increasing odds ratio for sero-positivity of the p21ras biomarker with increasing exposure. These results suggest that this serum biomarker is related to VC exposure and may be an early indicator of carcinogenic risk in exposed individuals.     

Sperm transfer by spermatophore in Diptera: new results from the Diopsidae

Sperm transfer by spermatophore is reported as a common and possibly primitive feature of the Diopsidae (Diptera, Schizophora). Spermatophores occur in four out of five investigated genera, in Cyrtodiopsis, Diasemopsis, Teleopsis , and in Sphyracephala , which is positioned close to the base of the family. Within the genus Diopsis the spermatophore is subject to reduction. Spermatophore size and copulation duration are positively correlated across the species. This is only partially explained by the time requirement of sperm transfer. Parsimony in time and material seems to be favoured in species with high mating frequency at special aggregation sites, whereas high investment in time and material occurs in species that do not mate preferentially at certain times or locations. The utilization of spermatophores has strong implications on the possibilities of sperm competition and cryptic female choice and may account for the occurrence of a postcopulatory passive phase or prolonged mating in some species. The increasing number of records of spermatophores in Diptera is reviewed.     

INTRA-POPULATION VARIATION OF THE SHELL OF LITTORINA RUDIS (MATON) (MOLLUSCA: PROSOBRANCHIA)

Shell variation within a single population of Litlorina rudis(Maton), collected near the Biological Station at Trondheim,Norway, was studied. The variation of the shell features studied, which includedthe shape of the basal part of the outer lip, and the relativeheight of the spire, width of the shell and of the aperture,were found to be at least partially related to shell height.Furthermore, the shell shape in the population investigated,besides varying with age, also varies due to shell damage. Nosignificant differences were found between the shapes of theshells of males and females. The shell characteristics of different populations of L. rudisalso vary greatly, one of the causes being differences in theenvironmental conditions. When studying this variation betweendifferent populations, however, it must be emphasized that onlyundamaged shells of individuals of about the same age shouldbe compared, in order to obviate the effects of the variabilitydue to age differences and shell damage within each individualpopulation. ^*Contribution from Trondhjem Biological Station no. 199 (Received 18 February 1980;     

Detection of phytoecdysteroids by gustatory sensilla on chelicerae of the brown dog tick Rhipicephalus sanguineus

Ecdysteroids are polyhydroxylated steroids that act as moulting hormones in arthropods and regulate several important life‐cycle processes. Phytoecdysteroids are ecdysteroid analogues produced by some plants that disrupt the growth and development of insects feeding on them, and can be perceived by the taste receptors of insects. The present study tested the hypothesis that the blood‐feeding tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) is capable of detecting phytoecdysteroids. By recording from the chelicerae, six phytoecdysteroids are tested: α‐ecdysone, 20‐hydroxyecdysone, ponasterone A, makisterone A, inokosterone and pterosterone. In unfed ticks, makisterone A and pterosterone elicit frequencies of neural impulses higher than in a negative control (a KCl solution at 10^?3m ), with detection thresholds of 10^?6m and 10^?12m , respectively. The spike amplitudes of the responses to these compounds, and also for 20‐hydroxyecdysone and ponasterone A, are higher than in the control, indicating that a different neurone may be involved: perhaps a deterrent cell, as observed in insects. In fed ticks, only pterosterone at 10^?4m remains active. In behavioural attachment assays, no difference is observed between electrophysiologically active compounds and the negative control. These results show the capability of R. sanguineus ticks to detect phytoecdysteroids, although they do not clarify the role of ecdysteroids in tick biology, for which further studies are required.     

THE MANNER OF TRANSMISSION OF SOME BARLEY YELLOW-DWARF VIRUSES BY DIFFERENT APHID SPECIES

Some barley yellow-dwarf (BYD) viruses isolated from cereal crops in Great Britain were transmitted by Rhopalosiphum padi , L. and others were not. Sitobion fragariae (Walker), S. avenae (Fabricius), and Metopolophium dirhodum (Walker) all transmitted viruses of both types, but they usually transmitted those of which Rhopalosiphum was a vector less readily than did R. padi. The transmissibility of a virus by a given aphid species was not affected by transmission with another, less efficient, vector species. Neomyzus circumflexus (Buckt.) and Rhopalosiphum maidis (Fitch) transmitted the few viruses with which they were tested.
A few R. padi acquired virus from infected leaves during 30 min. feeding and inoculated healthy seedlings during 15 min. feeding, but the minimum total time taken to acquire and transmit was 10 hr. and 32 hr. were needed for about half the aphids that were able to acquire and transmit virus to do so. This may indicate the existence of a short latent period of the virus in the vector, although the evidence is not conclusive. The times spent on infected plants influenced the results more than those spent on healthy ones; many transmissions occurred with short feeding times on healthy plants so long as the time spent on infected leaves was long, but the reverse was not true. Nymphs of R. padi that moulted after they left infected plants on which they fed long enough to become infective, infected slightly fewer plants than adults fed for the same times.     

Solute Leakage from the Isolated Parenchyma of Allium cepa and Kalanchoe daigremontiana

Efflux of different solutes from leaf slices of Kalanchoëdaigremontiana and from slices of the onion bulb scale was reinvestigatedwith respect to (1) dependence on turgor, (2) selectivity, (3)integrity of protoplasts and cellular changes. In both materials efflux of solutes (electrolytes or sugars)is non-selective and strongly dependent on turgor. Treatmentof tissue slices with hypotonic solutions (below a criticalosmotic pressure) resulted in high leakage rates, an increasein free space and an increased number of damaged cells. Lowconcentrations of calcium did not prevent this loss of retentionand cell stability. Part of the surviving cells were found to have a strongly decreasedosmotic pressure of cell sap. Leakage did not occur simultaneouslyat all cells of the tissue slice. It can be concluded that effluxfrom parenchyma cells in hypotonic solutions results from irreversibleosmotic breakdown and reversible membrane defects both favouredby high turgor. Key words: Parenchyma cells, Allium cepa, Kalanchoé daigremontiana, Solute efflux, Viability, Permeability, Plasmoptysis     

Inhibition of the development of the reproductive tract in parasitized snails

Summary

Myoblasts, muscle cells with the capacity to divide, have been detected in “Anlagen” of the male copulation organ of Lymnaea stagnalis. They only occur in the apical part of the penis. Here they could be found throughout life. Mitotic activity of these cells can be demonstrated by using an antiserum to a S-phase specific cell cycle marker, PCNA [see, e.g., Baserga (1991)]. The number/percentage of PCNA positive myoblasts is a good parameter for growth of this male copulation organ and hence also for inhibition of its growth and development as occurs in parasitized snails. In transplantation experiments, “Anlagen” of the copulation organ were used from snails 7–9 weeks after being parasitized as they can be excised in this stage and transplanted into either parasitized or nonparasitized snails. These experiments have indicated that humoral, parasitic excretory/secretory factors can be responsible for the inhibition of growth and differentiation of the copulation organ in parasitized snails as reflected by a relatively low number of PCNA positive myoblasts compared to the controls. Data obtained in in vitro experiments showed a significant decrease of the number of myoblasts in “Anlagen” cultured in the presence of parasitic E/S products. The fact that no significant effect was found on the relative low number of PCNA positive myoblasts is discussed. The effect of parasitic E/S products on these myoblasts appeared to be exerted in a direct way, not mediated by CNS-derived factors or by factors from cells in the connective tissue sheath around the CNS. Although it appears possible to use transplantation and/or in vitro culturing of these “Anlagen” as a bioassay for identification of the parasitic factor(s) responsible for the inhibitory effects on myoblasts, the methods are very laborious and do not seem very appropriate for testing many fractions of E/S products.