Allergen-specific IgG antibodies in cats with allergic skin disease

An enzyme-linked immunosorbent assay was developed for quantifying feline serum allergen-specific IgG directed against selected house dust, pollen and flea allergens. The assay was used to compare allergen-specific IgG concentrations in sera from healthy cats, cats with non-dermatologic illness, confirmed allergic cats and undiagnosed pruritic cats. Our results demonstrate that cats with confirmed allergic skin disease have significantly more IgG directed against house dust, flea and ryegrass allergens than other cat groups examined. These results support the theory that cats with allergic skin disease have an underlying T_H2 lymphocyte response that directs production of both allergen-specific IgG and IgE.     

Variation in the expression of self-fertility inLolium perenne L.

Summary A series of experiments was conducted to determine the variations arising between replicate selfing units, to compare self-fertility and cross-fertility in the same environment and to measure the variation in expression of self-fertility by different techniques and in different environments.Variation in self-fertility between selfing units within genotypes was relatively high, representing approximately one-third of the total observed variation in a series of duplicate selfings of over 60 genotypes tested in one environment. In order to differentiate clearly between the self-fertility of a limited number of genotypes as many as four replicates were needed, although this number varied with the environment in which the tests were conducted. Levels of self-fertility were similar in bag selfing units placed inside or outside a glasshouse in an average year, but were greater outside than inside in a year which was drier and warmer than average. In a highly humid environment the mean level of self-fertility attained was reduced by a factor of three. Removal of flag leaf laminae had an adverse effect on self-fertility, reducing it by half. Shaking the pollination bags, as is the usual practice to promote pollen dispersal, increased self-fertility very considerably over that of unshaken controls. Assisting pollen dispersal by blowing filtered air into the bags was time-consuming and did not prove to be superior to the shaking technique. It is clear that self-fertility can neither be considered in isolation from the environment in which it is determined, nor can it justifiably be related to cross-fertility unless both are determined in the same environment. A sample of over 60 genotypes tested in one environment was on average 2.2% as self-fertile as they were cross-fertile, with a range for individual genotypes from 0–31%. Optimum conditions for maximum expression of self-fertility, essential in the exploitation of this character in ryegrass breeding, have yet to be fully established.     

Dynamic Modelling of Spatially Variable Catchment Hydrochemistry for Critical Loads Assessment

Concern about acidification in upland areas has brought about the need to model the stream hydrochemical response to deposition and land-use changes and calculate critical loads. Application of dynamic models such as MAGIC are preferable to steady-state methods, since they are able to produce an estimate of the time scale required to meet some water chemistry target given a reduction in acid deposition. These models typically consider annual changes in stream chemistry at one point. However, in order to protect biota from 'acid episodes', quantification of temporal variability needs to encompass event responses; in addition spatial variability across the catchment also needs to be considered. In this paper, modelling of both spatial and temporal variability is combined in a new framework which enables quantification of catchment hydrochemical variability in time and space. Both low and high flow hydro-chemical variability are quantified in terms of statistical distributions of ANC (Acid Neutralisation Capacity). These are then input as stochastic variables to an EMMA (End-Member Mixing Analysis) model which accounts for temporal variability and ANC is hence predicted as a function of time and space across the whole catchment using Monte-Carlo simulation. The method is linked to MAGIC to predict future scenarios and may be used by iteration to calculate critical loads. The model is applied to the headwaters of the River Severn at Plynlimon, Wales, to demonstrate its capabilities.     

Acidic deposition: What is fact,what is speculation,what is needed?

In this presentation research findings from the symposium and from the literature are utilized to examine some of the major hypotheses that link acidic deposition with impairment of forest health and productivity in central Europe and eastern North America. Although unequivocal evidence of acid rain damage may be lacking, there is a considerable body of knowledge that implicates air pollutants in recent interference with forest nutrition and health. The nature of the evidence and the inferences that can be drawn from it are still being vigorously debated. The problem of verifying the mechanisms by which air pollutants affect forests still remains. Reports that climatic irregularities have acted as inciting or triggering factors in forest declines are relevant to understanding regional damage. More emphasis on experimental studies that assess interactions of air pollutants and natural stresses with forests is needed.     

Long-range electronic perturbations caused by defects using scanning tunneling microscopy

Real-space observations of long-range electronic perturbations caused by defects have been made with scanning tunneling microscopy. The defects are isolated adsorbed molecules on the surface of graphite. These defects perturb the charge density, giving periodic oscillations similar to Friedel oscillations. The oscillations have a wavelength radical3 times that of the graphite lattice, and the symmetry of the oscillations reflects the nature of the defect.     

Hemolysin production in the development of staphylococcal lesions

The presence of hemolysin in staphylococcal lesions of the rabbit kidney was detected by overlaying sections of kidney with blood agar. Hemolytic activity against rabbit, human, sheep, calf, and guinea pig erythrocytes was present and was not abolished by heating the sections to 60 degrees C for 30 minutes. In developing lesions, hemolytic activity appeared before necrosis or exudation.     

Paleomagnetic study of antarctic deep-sea cores

The magnetic inclinations and inten sities of about 650 samples from seven deepsea cores taken in the Antarctic were measured on a spinner magnetometer. This series of measurements provided a magnetic stratigraphy, based on zones of normally or reversally polar ized specimens for each core, which was then correlated with the magnetic stra tigraphy of Cox et al. (1). One core (V16-134) gave a continuous record of the paleomagnetic field back to about 3.5 million years. When selected samples were subject ed to alternatingfield demagnetization, most were found to have an unstable component that was removed by fields of 150 oersteds; all samples from two cores were partially demagnetized in a field of 150 oersteds. The average inclination in these two cores was then in good agreement with the average inclination of the ambient field for the latitude of the core site. It was also found that the intensities of the samples decreased at the points of reversal; this finding is to be expected if, as has been postulated by the dynamo theory, the intensity of the dipole field decreases to zero and builds again with opposite polarity. We believe that the magnetiza tion of the cores results from the pres ence of detrital magnetite, although other magnetic minerals also may be present. Four faunal zones (, X, , and ) have been recognized in these Antarctic cores on the basis of upward sequential disappearance of Radiolaria. The faunal boundaries and reversals consistently have the same relations to one another, indicating that they are both timedependent phenomena. Using previously determined times of reversal, one may date the following events in the cores: 1) Radiolarian faunal boundaries:-X, 2 million years; X-, 0.7 million years; -, 0.4 to 0.5 million years. These dates are in good agreement with ages previously extrapolated from radio metric dates. 2) Initiation of Antarctic diatom ooze deposition, approximately 2.0 mil-lion years ago. 3) First occurrence of ice- rafted detritus, approximately 2.5 million years ago. One can also calculate rates of sedi mentation, which vary in the cores studied from 1.1 to about 8.0 millimeters per 1000 years. Sedimentation rates for the Indian Ocean cores are higher than for the Bellingshausen Sea cores. The near coincidence of faunal changes and reversals in the cores suggests but does not prove a causal relation. We conclude from this study that paleomagnetic stratigraphy is a unique method for correlating and dating deep sea cores, and that future work with such cores may provide a complete or nearly complete record of the history of the earth's magnetic field beyond 4 million years.