Two new genera, Crassoseta and Brachysternopsis, of the family Diplogyniidae (Acari, Mesostigmata, Trigynaspida)

The genus Crassoseta is erected for three new species of diplogyniid mites taken from passalid beetles collected in Mexico, Brazil and Costa Rica; Brachysternum cornutum Hyatt, 1964 is transferred to this genus and a key to species is given. Brachysternopsk gen.n. is established for B. flechtmanni gen. et sp.n. taken from an ant, Atrica capiguara. in Brazil.     

A COMPARISON OF TWO MULTIVARIATE METHODS FOR THE ANALYSIS OF SENSORY PROFILE DATA

Tables of means, over assessors, are often used to summarize the results of sensory profile experiments. These tables are sometimes further summarized by Principal Components Analysis (PCA) to give plots of the samples in the principal sensory dimensions. An alternative procedure is to use Generalized Procrutes Analysis (GPA) on the assessor data to allow for differences in usage of the vocabulary and in the proportion of the scale used. It is shown that these methods give different configurations in the principal sensory dimensions when applied to the data from a study of cheeses (Muir et al. 1995). Using a Jackknife method to calculate the variability of the samples in the principal sensory dimensions, the results from the GPA method are shown to have a higher dimensionality than from the PCA method. Jackknife estimates of variability are used to calculate confidence ellipses to attach to the sensory space maps.     

Proton density and apoplastic domains within soybean nodules in relation to the oxygen diffusion barrier

A spin-echo pulse sequence was used to obtain ¹H nuclear magnetic resonance microimages of soybean nodules, with resolution to 40 mm and 3D presentation. At an acquisition time (TR) of c. 270 ms and a short echo time (TE) of 8.3 ms, a high proton intensity was detected in infected tissue and vascular strands, relative to the cortex. A longer TE of 15.5 ms was associated with a relatively low proton intensity in infected tissue. Thus protons in infected tissue were characterized by a short T₂. Following detopping of the plant, or treatment of the root system with Ar:O₂, proton intensity (TE 5.9, TR 120 ms) decreased exponentially in a zone corresponding to the inner cortex-outer infected region. This result is interpreted as being caused by a loss of water mobility (i.e. increase in viscosity) or a filling of intercellular air spaces with fluid (i.e. loss of air-water interfaces). The membrane impermeant tracer lucifer yellow was observed to infiltrate from the rhizosphere through the nodule cortex into the infected region in intact nodules of detopped and Ar:O₂-treated, but not control, plants. This result is consistent with the filling of air spaces with fluid following the imposed treatments, allowing infiltration of aqueous tracers. Variation in intercellular air space volume within the inner cortex has been suggested as a mechanism to allow a variable rate of diffusion of O₂ into soybean nodules.     

Myosin light-chain expression during avian muscle development

Monoclonal antibodies to adult chicken myosin light chains were generated and used to quantitate the types of myosin light-chain (MLC) isoforms expressed during development of the pectoralis major (PM), anterior latissimus dorsi (ALD), and medial adductor (MA) muscles of the chicken. These are muscles which, in the adult, are composed predominantly of fast, slow, and a mixture of fiber types, respectively. Three distinct phases of MLC expression characterized the development of the PM and MA muscles. The first identifiable pase occurred during the period of 5-7 d of incubation in ovo. Extracts of muscles from the pectoral region (which included the presumptive PM muscle) contained only fast MLC isoforms. This period of exclusive fast light-chain synthesis was followed by a phase (8- 12 d of incubation in ovo) in which coexpression of both fast and slow MLC isoforms was apparent in both PM and MA muscles. During the period, the composition of both fast and slow MLC isoforms in the PM and MA muscles was identical. Beginning at day 12 in ovo, the ALD was also subjected to immunochemical analyses. The proportion of fast and slow MLCs in this muscle at day 12 was similar to that present in the other muscles studied. The third development phase of MLC expression began at approximately 12 d of incubation in ovo and encompassed the transition in MLC composition to the isoform patterns incubation in ovo and encompassed the transition in MLC composition to the isoform patterns typical of adult muscle. During this period, the relative proportion of slow MLC rose in both the MA and ALD and fell in the PM. By day 16, the third fast light chain, LC(3f), was apparent in extracts of both the PM and MA. These results show that there is a developmental progression in the expression of MLC in the two avian muscles studied from day 5 in ovo; first, only fast MLCs are accumulated, then both fast and slow MLC isoforms are expressed. Only during the latter third of development in ovo is the final MLC isoform pattern characteristic of a particular muscle type expressed.     

The distribution of bait pellets for slug control

Observations were made on the movement and mortality of Agriolimax reticulatus (Müller) on plots with various densities of metaldehyde and methiocarb pellets. The optimum density of pellets was found to lie between 25 and 100/m² (pellets 20 and 10 cm apart). This confirmed an estimate derived from a theoretical model.     

Antigenic Heterogeneity in Cell Populations of Cloned Polyoma,Virus-induced Tumour Lines

WALLS and Negroni¹ isolated in tissue culture two cell clones from a polyoma virus-induced fibrosarcoma of H₃B/Bi mice. One (malignant cell line 7₁) produced transplantable tumours in adult syngeneic mice; the other (transformed non-malignant line 7₂) was not tumorigenic but induced resistance to the growth of the malignant cells. We have now confirmed these results and extended them to show that other malignant cells (tissue culture clones C₄ and C₅) from a polyoma virus-induced parotid tumour of syngeneic mice are also inhibited by pre-immunization with a non-malignant line (7₂). The number of cells required to induce tumours in 50% of the animals is ten times higher in the preimmunized mice than in the controls, for both fibrosarcoma and parotid malignant lines (Table 1).     

THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY

The influence of varying levels of iron and substrate pH on the uptake of nickel and the intensity of toxicity symptoms in oat plants have been investigated using sand-and water-culture techniques.
Nickel-toxicity symptoms (both necrosis and chlorosis) are less severe when the concentration of iron in the nutrient solution is high. The reduction in degree of necrosis is related to a reduced content of nickel in the leaf blades, whilst that of chlorosis is related to the Ni/Fe ratio in the leaf blades—an internal antagonism being indicated in the latter case.
A reciprocal relationship exists between the nickel and iron contents of the leaf blades; the nickel content is materially reduced by high concentrations of iron in the nutrient solution, and the iron content by nickel, the former being the more pronounced effect.
Uptake of nickel increases with increasing pH for a constant iron level in the substrate, although the degree of necrotic symptoms is similar over pH range 4–7. Iron uptake is reduced by both nickel and increasing pH and results in chlorosis at pH values of 5·5 and above.
For a constant level of iron supply the phosphate content of the stem extracts is higher the greater the degree of nickel toxicity; the phosphorus status of the plant may be a factor in producing nickel toxicity but if so, it has to be considered in relation to other factors.     

TRACE-ELEMENT TOXICITIES IN OAT PLANTS

Excessive amounts of nickel, cobalt, chromium, copper, zinc, manganese, molybdenum and aluminium in nutrient solutions supplied to oat plants in sand culture produce ( a ) chlorosis and ( b ) other symptoms specific to the element involved. The specific symptoms are distinct for each metal, although those of cobalt and nickel might be confused.
The toxic effects of nickel, cobalt, copper, zinc, manganese and molybdenum are associated with high concentrations of the element in the leaf tissue, but this is not always so with chromium and aluminium.
The toxic effects of nickel, chromium, copper and molybdenum are associated with a reduced nitrogen content of the plant. Nickel, cobalt, chromium, zinc and manganese increase the concentration of phosphorus in the tissue whilst aluminium decreases it, probably to a deficiency level.
Aluminium reduces the intensity of toxic symptoms produced by nickel—probably by reducing the uptake of nickel and phosphorus. Copper effectively reduces the leaf necrosis produced by nickel, but not the nickel content of the leaf tissue; it is suggested that one factor in nickel toxicity may be inhibition of one or more functions of copper. The other elements slightly increase chlorosis and some increase necrosis.
The order of activitjl of the elements in producing chlorosis is found to be Ni>Cu>Co>Cr>Zn>Mo>Mn. This order, which is related to that giving yield reduction and is similar to the order of stability of metal complexes, is discussed in relation to induced iron deficiency.     

Opposing effects of spring defoliation on late season oak caterpillars

ABSTRACT. 1. The pedunculate oak, Quercus rohur L., suffers high annual levels of spring defoliation in Wytham Woods. near Oxford.
2. This spring defoliation affects late season caterpillars through a variety of damage-induced changes in the leaves.
3. Diurnea fagella (D. & S.), one of the commonest late season caterpillars, shows reduced larval survival and pupal weight on regrowth foliage when compared to undamaged primary foliage.
4. D. fagella also suffer higher larval mortality on naturally damaged primary foliage than they do on undamaged foliage.
5. Despite this, the three commonest late season caterpillar species are more abundant on damaged trees than undamaged ones. and their distributions are biased towards damaged leaves within the canopy.
6. Other factors that may be more important than leaf damage in determining the distribution and abundance of late season caterpillars are discussed. D.fagella larvae spin their larval refuges more rapidly on damaged than undamaged foliage, and this may reduce mortality by natural enemies, or ameliorate adverse effects of weather.