A new species-time method for visual assessment of fishes and its comparison with established methods

Synopsis Relative abundances for 80 species in a fish assemblage were estimated using three visual assessment methods. Results of two species-time methods, the Rapid Visual Census (RVC) of Jones & Thompson (1978) and a new method, the Visual Fast Count (VFC), are compared to the traditional transect method. The VFC is similar to the RVC but it is an attempt to improve: on the quantitative nature of the results. Results from each method were significantly correlated, but important differences between methods were found. With an equal number of replicates both RVC and VFC methods yielded significantly more species than the transect method. Relative abundances estimated by the RVC were significantly different from those determined by either VFC or transect methods, but VFC and transect results were not different. A qualitative similarity index using presence-absence data was calculated and compared among methods. Values ranged from 84.3 to 85.9%, illustrating a consistent level of similarity for the faunas censused regardless of census method. Quantitative similarities (percent similarity), however, ranged from 45.8 to 85.7% and suggest a closer agreement between the transect and the VFC methods than between these methods and the RVC. If transect results are assumed to be the most accurate, the comparison suggests that the VFC method yields more accurate relative abundances than does the RVC. Ranges in percent similarity values calculated within each method (8 replicate samples) were used to compare precision among methods. While transect and RVC scores are slightly more precise (ranges of 3.10% and 2.20% respectively) than the VFC method (range = 4.89%), no method was statistically more precise than another (P<0.001).     

Noninvasive techniques for measuring body elemental composition

In the past 20 yr, in vivo analysis of body elements by neutron activation has become an important tool in medical research. In particular, it provides a much needed means to make quantitative assessments of body composition of human beings in vivo. The data are useful both for basic physiological understanding and for diagnosis and management of a variety of diseases and disorders. This paper traces the development of the in vivo neutron activation technique from basic systems to the present state of the art facilities. A scan of some of the numerous clinical applications that have been made with this technique reveals the broad potentialities of in vivo neutron activation. The paper also considers alternative routes of future development and raises some of the questions now faced in making the technique more widely available to both medical practitioners and medical investigtors. In vivo neutron activation has opened a new era of both clinical diagnosis and therapy evaluation, and investigation into the modeling of body composition. The techniques are new, but it is already clear that considerable strides can be made in increasing accuracy and precision, increasing the number of elements susceptible to measurement, and reducing the dose required for the measurement.     

Effects of retinoic acid (RA) on the growth and phenotypic expression of several human neuroblastoma cell lines

It has been shown that retinoic acid (RA) can promote morphologic differentiation and inhibit the growth of a human neuroblastoma cell line, LA-N-1. The present study tests the histological generality of these phenomena by determining the effects of RA on seven other human neuroblastoma cell lines. Results show that RA strongly inhibited anchorage-dependent growth and induced morphologic alterations in six of seven of the cell lines. These alterations included morphologic differentiation as evidenced by formation of neurite extensions in four of the lines, cellular enlargement and vacuolization in one culture, and formation of large, flattened epithelial or fibroblastic-like cells in another culture. Although one cell line was relatively insensitive to the effects of RA in monolayer culture, all seven were strongly inhibited by RA in soft agar assays. Cellular RA-binding proteins were detected in 2/2 lines tested. These findings suggest that, as a histological group, human neuroblastoma cells are extremely sensitive to RA-induced growth inhibition and morphological alterations generally associated with reduced expression of the malignant phenotype of this type of cancer.     

National and international services for primate animal research

Extensive use of nonhuman primates for biomedical research has contributed to periodic acute shortages of these animals. As a result, various resources have been developed to assist investigators in maintaining healthy colonies and conserving stocks. A wide range of expertise is available at the national and international levels to investigators working with nonhuman primates.     

Scanning electron microscopical comparisons of insect virus occlusion bodies prepared by several techniques

Samples of baculoviruses, a cytoplasmic polyhedrosis virus, and an entomopoxvirus were prepared by several techniques for study in the scanning electron microscope. The techniques which gave satisfactory definition of surface ultrastructure were: (1) double fixation in glutaraldehyde and osmium tetroxide with critical point drying; and (2) double fixation as in (1) with a further postfixation by ligand-mediated osmium binding using thiocarbohydrazide as the ligand (OTO method) followed by critical point drying. The latter technique was superior to the former technique. Air drying of samples gave acceptable but inferior definition when compared with critical point-dried samples prepared by these techniques.     

Fasciola hepatica: The effect of challenge by the subcutaneous or intraperitoneal route with living adult flukes in sensitized rats

When rats, sensitized either by subcutaneous implantation of adult F. hepatica or by a normal oral infection with F. hepatica metacercariae, were challenged by implanting adult flukes in the peritoneal cavity, 23% of these flukes were killed in rats sensitized by subcutaneous implantation and 71% in the rats sensitized by the oral route. In contrast neither of these sensitization routes were effective against subcutaneous challenge with adult fluke. Histological evidence suggested that about half of the dead flukes found were killed shortly after transfer and these flukes were surrounded with mononuclear cells. The remaining dead flukes appear to have died after becoming surrounded with a cyst. These latter flukes were surrounded by neutrophils and this cell type was very prominent in the cysts of sensitized rats.     

Radioimmunoassay for the determination of digoxin and related compounds in Digitalis lanata

A radioimmunoassay technique has been developed for the measurement of digoxigenin glycosides in crude extracts from both fresh and dried leaf material of Digitalis lanata, The antibody, obtained by immunizing rabbits against a conjugate of digoxin with human serum albumin, had a high affinity (K_a = 0.8 × 10¹⁰ l/mol) for digoxin and permitted detection of as little as 60 fmol digoxin (45 pg) per 0.1 ml of sample. The antiserum was highly specific for digoxigenin and its glycosides, with only diginatin showing a substantial cross reactivity (3?0%). The use of [³H]-labelled and [¹²⁵I]-labelled digoxin as tracer and of dextran-coated charcoal or ammonium sulfate for separation did not change the specificity of the assay nor the properties of the standard curve. This method has been found to correlate with the usual fluorimetric determination of digoxin, but is more sensitive by a factor of 10⁴. A correlation analysis of 8 and 30 different D. lanata plants (leaf discs and drugs analysed with both methods) gave correlation coefficients of r = 0.989 and r = 0.907 respectively. The analysis of a single leaf disc, 3 mm in diameter (obtained from a fresh leaf), gave an exact measure of the digoxin content found in the dried leaf drug (r = 0.973). With a semi-automated technique, about 2000 quantitative analyses per week can be performed by one person, thus providing the potential to screen plants for use in breeding or tissue culture work. The distribution of digoxigenin equivalents in single seeds, seedlings and plants of different ages has also been investigated.     

Removal of the Schwann sheath from the giant nerve fiber of the squid: An electron-microscopic study of the axolemma and associated axoplasmic structures

Summary Surgical thyroidectomies were used as means of altering the thyroid state of adult recipients to study the possible influence of thyroid hormones on fibre formation in irides by immature noradrenaline neurons of the locus coeruleus grafted to the eye. Whole-mount preparations of irides were analysed using fluorescence histochemistry according to Falck-Hillarp, subjectively estimating on a blind basis the number of fibres, their pattern of distribution and individual morphology in the iris dilator plate. Neurones of the locus coeruleus formed nerve fibres in irides of thyroidectomized recipients to the same extent as in controls. Distribution and fine structure of these fibres, however, differed markedly. The numerous thick axon bundles from the attachment of the brain graft, normally seen to radiate out from locus coeruleus-neurones in oculo, were almost totally lacking in the thyroidectomized group. Also, the individual nerve fibres showed abundant peripheral accumulations of fluorescent material. This appearance of the outgrowth of fluorescent fibres in the experimental group, indicative of a disturbed formation of nerve fibres during development in oculo, was abolished by reversal of the thyroid hormone deficiency using daily injections of 1-thyroxin to the recipients throughout the experiment. This strongly indicates a role for thyroxin in the process of formation of nerve fibres originating from the neurones of the locus coeruleus during perinatal development. The present paper is supportive of recent reports claiming that during the development of the CNS thyroxin plays a crucial role in tubulin assembly, and thus presumably for the ability of neurones to form processes.     

Populations of strongyloid nematode infective stages in sheep pastures: Comparison between direct pasture sampling and tracer lambs as estimators of larval abundance

Waller P.J., Dobson R.J., Donald A.D. and Thomas R.J. 1981. Populations of strongyloid nematode infective stages in sheep pastures : comparison between direct pasture sampling and tracer lambs as estimators of larval abundance. International Journal for Parasitology11: 359–367. Over a 2-year period, numbers of infective larvae in samples of pasture herbage, and numbers of worms in previously worm-free “tracer” lambs allowed 4 weeks grazing, were compared as estimators of the abundance of infective larvae on pastures.Transformation of sample estimates of infective larval numbers per 100 g herbage dry matter (DM) and of worm numbers in tracer sheep, according to the expression y = log₁₀ (x+25), was effective in stabilizing variances. Estimates of error variance for each technique did not differ significantly among the genera Haemonchus, Ostertagia or Trichostrongylus and the pooled estimate for the tracer sheep method was 4 times greater than that for pasture sampling. From these results, more tracer sheep than pasture samples would be required to achieve the same level of precision with the two techniques. Using conventional statistical methods, the effects of numbers of pasture samples or tracer sheep on the size of the difference between two means which can be detected as significant and on the width of the confidence interval about a single mean, are illustrated. These can be used as a guide in the choice of sample sizes. Error variances for Nematodirus spp. were significantly less than for the other genera by pasture sampling, and greater by the tracer sheep technique. Possible reasons for this are discussed, but it is concluded that pasture sampling is likely to be much the more precise method for estimating Nematodirus spp. infective larval availability.Changes with time in infective larval abundance, for Haemonchus, Trichostrongylus and Nematodirus spp. which were present in moderate to low numbers, followed similar trends by both techniques. However, for Ostertagia spp. larvae, which were much more abundant, peak levels were defined more sharply and occurred earlier by pasture sampling than by the tracer method. It is suggested that worm counts from tracer sheep, especially those grazing for 4 weeks rather than shorter periods, may systematically underestimate the infective larval population on pasture at high levels of abundance owing to density-dependent worm loss.