Purification and serology of the W strain of cucumber mosaic virus

During studies on the purification of cucumber mosaic virus (strain W) it was found that preparations were most infective and stable when made from tobacco leaves (10–12 days after inoculation) homogenized in phosphate buffer containing EDTA and thioglycollic acid and clarified with diethyl ether. The preparations were further purified by centrifugation in sucrose density gradients containing EDTA at pH 9.0 and were then stable at 2 °C for > 100 days. When mounted in neutralized ammonium molybdate they were shown to consist of predominantly intact particles. In tube and ring precipitin tests and in agar gel-diffusion tests, specific precipitation with homologous antiserum occurred only in media containing alkaline adjusted solutions (ammonium molybdate and dipotassium hydrogen phosphate).     

Degradation of native and exotic riparian plant leaf litter in a floodplain pond

1. A litter‐bag experiment was undertaken in a pond on the margins of a large temperate floodplain in south‐western France to assess the potential influence of the replacement of native by exotic riparian species on organic matter degradation. We determined initial litter chemical composition, breakdown rates and the invertebrate assemblages associated with the litter for five pairs of native dominant and exotic invasive species co‐occurring at different stages along a successional gradient. 2. Litter chemical composition, breakdown rates and abundance and diversity of detritivorous invertebrates were similar for the exotic and native species overall. No overall changes in organic matter degradation can thus be predicted from the replacement of dominant natives by exotic invasives. Breakdown rates were primarily driven by the C/N ratio. 3. One invasive species (Buddleja davidii) showed significantly higher breakdown rates than its native counterpart (Populus nigra), resulting in the disappearance of leaf litter 6 months prior to the next litterfall. In some cases, therefore, invasion by exotic species may result in discontinuity of resource supply for decomposers.     

Studies in the Nutrition of Apple Rootstocks: 1. Effects of Deficiencies of Iron and Magnesium on Growth

Plants of the apple rootstock M.VII were grown for a singleseason by spraying their roots continuously with nutrient solutions:(a) complete, (b) low iron, (c) low magnesium, and (d) low ironand low magnesium. Detailed records were taken throughout theseason of fresh weight, shoot length, diameter, and leaf area,while the fresh and dry weights of component parts were determinedon harvested samples. The leaves of the iron-deficient plants were chlorotic and hada lower dry weight and higher water content per unit area thanthose of the control plants. Growth and net assimilation ratewere both reduced but the distribution of assimilates was similarto that in the controls. Total growth was also markedly reduced by the low-magnesiumtreatment, but the leaf symptoms were different and the plantswere morphologically distinct from the control plants. Verylittle chlorosis occurred, but necrosis and severe defoliation,progressing up the shoot, reduced the leaf area ratio and probablylargely accounted for the low net assimilation rate and relativegrowth rate. The diameter of the shoot was affected much morethan its length and the shoot/root ratio was greatly increased. Plants deficient in both iron and magnesium showed less defoliationthan when magnesium alone was low. More dry matter accumulatedin the old stem and less in the new shoot than would have occurredwith a simple combination of the single deficiencies.     

Measurement of 7 methyl and 7 2 hydroxyethyl guanine DNA adducts in white blood cells of smokers and non smokers

The goal of the present study was to measure the levels of 7-methylguanine and 7-(2- hydroxyethyl)guanine DNA adducts in human white blood cells in relation to smoking. DNA was isolated from samples of 11 smokers and eight non-smokers. The 32P-postlabelled 7-methylguanine and 7-(2-hydroxyethyl)guanine adducts were analysed by thin-layer chromatography (TLC) combined with a high pressure liquid chromatography (HPLC) assay. In smokers the mean 7-methylguanine and 7-(2-hydroxyethyl)guanine levels were 32.3 +/- 7.1 and 6.6 +/- 2.3 adducts per 108 nucleotides respectively. The corresponding values in non-smokers were 25.0 +/- 7.0 and 3.7 +/- 2.4 adducts per 108 nucleotides. There were significantly higher levels of 7-methylguanine and 7-(2-hydroxyethyl)guanine adducts in WBC in smokers than in non-smokers (p = 0.041; p = 0.018), respectively. A positive correlation between 7-methylguanine and 7-(2-hydroxyethyl)guanine levels was observed.     

Nothobranchius cooperi (Teleostei: Cyprinodontiformes): a new species of annual killifish from the Luapula River drainage,northern Zambia

Nothobranchius cooperi, Nagy, Watters and Bellstedt, new species, is described from seasonal streams and ephemeral pools associated with the upper Mansa River system in the middle Luapula drainage and systems draining into the low-lying area marginal to the southwestern part of Lake Bangweulu, in the Luapula province of northern Zambia. It belongs to the N. brieni species group. Males of Nothobranchius cooperi are distinguished from congeners by the following unique combination of characters: body scales with broad orange posterior margin, forming a highly irregular cross-barred pattern; anal fin fairly uniform orange-red with irregular to regular, light blue-green zone close to the base; caudal peduncle length 1.2–1.3 times its depth; prepelvic length 48.8–51.9% SL; and head depth 75–77% of head length. Genetic divergence of the mitochondrial COI and ND2 genes and nuclear S7 gene support the distinction of the new species from its closest known relative, N. rosenstocki and confirms its position in the N. brieni species group.     

Components of male fitness in relation to body size in Epirrita autumnata (Lepidoptera, Geometridae)

Abstract. 1. The effect of body size on different components of male fitness was studied for Epirrita autumnata , a geometrid known for its eruptive population dynamics. Body size is the main determinant of female fecundity in this species.
2. Longevity of males was found to have a weak negative correlation with body size at low temperatures. No significant correlation was found at higher temperatures.
3. We found no correlation between male size and female fecundity or egg size which is consistent with the small size of spermatophores in this species.
4. Small and large males were equally successful when allowed to compete for females in laboratory conditions.
5. In one or two field collections, males found mating were larger than males found singly. Large males also had an advantage in finding of virgin females, offered experimentally. No size-assortative mating was recorded.
6. We conclude that size-dependent mate location ability is the factor accounting for most of the variance in male fitness in E.autumnata. The dependence of fitness on body size may well be equally strong in males and females.     

<Emphasis Type="Italic">De novo</Emphasis> Synthesis of Transfer and 55 RNA<Superscript>1f</Superscript> in Cleaving Sea Urchin Embryos

SIGNIFICANT changes in RNA metabolism have been described during early sea urchin development. Until recently the only detectable class of RNA synthesized during cleavage stages was that with a low G + C base composition and heterogeneous sedimentation properties (DNA-Jike RNA)¹. The genes for nucleolar ribosomal RNA (26S and 18S) were believed to become active only following gastrulation^2–4 and the products of nuclear transfer RNA (4S) genes were first detected at the mesenchyme blastula stage⁵. Any label in the 4S region of sucrose gradients of RNA from the cleavage stages of embryogenesis was interpreted as reflecting the turnover of the pCpCpA region of pre-existing transfer RNA (tRNA) molecules.     

Variation in temperature and dietary nitrogen affect performance of the gypsy moth (Lymantria dispar L.)

Abstract. . The independent and interactive effects of temperature and dietary nitrogen content on performance of the gypsy moth (Lymantria dispar L.) were examined. In long-term feeding trials, larvae were reared from egg hatch to pupation on low (1.5%) and high (3.7% dry weight) nitrogen diets, under three temperature regimes. Short-term feeding trials with fourth instars and the same treatments were conducted in order to calculate nutritional indices.
Higher temperatures did not influence larval survival and marginally increased final pupal weights, but strongly decreased long-term development rates. They also accelerated short-term growth and consumption rates, and tended to improve food processing efficiencies. High concentrations of dietary nitrogen increased survival rates and final pupal weights markedly, but decreased long-term development rates only marginally. A high content of dietary nitrogen also accelerated short-term development and growth rates, reduced consumption rates, and improved food digestibility. Insects responded to low nitrogen-content diets primarily by eating faster, rather than by altering efficiency of nitrogen use. In the short-term feeding trials, thermal regime and dietary nitrogen interacted to influence growth rates, overall food processing efficiencies and nitrogen consumption rates. No interactive effects were observed in long-term studies.
This research demonstrates that small changes in thermal regime and ecologically relevant variation in dietary nitrogen content can strongly affect gypsy moth performance. Moreover, various performance parameters are differentially sensitive to the direct and interactive effects of temperature and diet.