Some problems in assessing the fluorescein diacetate-active fungal biomass in the soil

A technique for assessing the metabolically-active fungal biomass by means of fluorescein diacetate (FDA) staining was recently described (Söderström, 1977). In this note some practical details in the application of this technique to studies of FDA-active fungal biomass in the soil are discussed.     

Cellular immune response in rainbow trout Salmo gairdneri Richardson to Yersinia ruckeri O-antigen monitored by the passive haemolytic plaque assay test

Abstract. The specificity and kinetics of the immune response of rainbow trout ( Salmo gairdneri ) to single injections of an O-antigen extracted from the bacterial pathogen Yersinia ruckeri , which causes enteric redmouth in fish, were investigated by the passive haemolytic plaque assay and serum antibody quantitation. Doses ranging from 5 ng to 500 mg in 10-fold increments were injected intraperitoneally into groups of trout held at 17 × 1°5°C. The occurrence of plaque forming cells (PFC) and humoral antibody was followed for 35 days after injection. Trout gave an immune response to doses of 500 ng and above. Seven days after injection no humoral antibody was detected, but PFC were found in the spleen. The maximum PFC numbers occurred 11 days after injection. On day 21, few PFC were found, whereas serum antibody titres were highest. The antibody from immunized trout showed little or no cross-reactions with sheep red blood cells passively labelled With antigens from other fish pathogens.     

Photoperiod induced off-season spawning of pink salmon (Oncorhynchus gorbuscha)

Four groups of pink salmon, which had been reared under artificial light, became sexually mature and produced viable gametes: 59 days prior to, and 19 – 32 days, 115 days and 220 days after their expected date of reaching sexual maturity. Altered times of sexual maturation were obtained by accelerating, leaving unchanged, or decelerating the rate of change of photoperiod which each group of fish would normally receive during its first year of life. All groups of fish were exposed to a normal rate of change in photoperiod during their final year of life. Mean fecundity was reduced from the 800–2000 ova observed in wild stocks, and ranged from 629 for the 59 day advanced fish, to 862 for the 115 day delayed fish. Egg mortality during the period from fertilization to eyeing was much greater in the three groups of fish subjected to accelerated or decelerated rates of change in photoperiod than in the fish subjected to the normal rate of change in photoperiod. Some of the progeny of the 220 day delayed fish, which were reared under artificial light with the normal rate of change in photoperiod set 220 days out-of-phase, became sexually mature 2 years after they had begun life as fertilized eggs.     

Effects of grazing by lambs in autumn on a red clover-perennial ryegrass sward

In 1976, 1977 and 1978 a red clover-perennial ryegrass sward was cut twice for silage, and in the autumn of 1976 and 1977 it was either grazed at low and high stocking rates, i.e. seventeen and thirty-four lambs per ha respectively, or was cut with a forage harvester. The effects of grazing on yield in the following year were examined. Herbage growth in the grazing period was slow and did not differ significantly between the treatments. The yield of silage dry matter taken in May and July was highest in ungrazed plots (9·8 and 8·1 t ha^-1 in 1977 and 1978 respectively) and lowest in plots stocked at the high rate (5·9 and 5·7 t ha^-1 in 1977 and 1978 respectively). The aftermath yield for grazing in 1977 was slightly but significantly greater on treatments grazed in the previous year compared with ungrazed treatments. Red clover content decreased markedly during grazing, the high stocking rate treatment containing 2·4% clover and the ungrazed treatment 57·3% clover. The high stocking rate treatment also had the lowest red clover content in the first silage cut. Red clover content in grazed plots increased to a level similar to that in ungrazed plots by the start of the grazing period in the subsequent harvest year. Animal performance was higher at the low than at the high stocking rate but herbage consumption per head did not differ significantly between the two grazing treatments. Possible reasons for the adverse effect of grazing on the red clover are defoliation and treading. It is concluded that such experiments can form the basis of an economic assessment of red clover and help the farmer decide whether or not he should integrate the crop into his system.     

Influence of dietary protein and energy on growth,food consumption and food conversion efficiency in Penaeus merguiensis de Man

The requirement of juvenile Penaeus merguiensis for dietary protein and energy was assessed in growth trials performed in indoor recirculation systems using rations based on freeze-dried Mytilus edulis meal. From the results of these experiments evidence was obtained to indicate that the rate of food consumption in this prawn is related to the energy content of the diet. The implications of this are that the protein level required to support maximum growth and optimum protein conversion efficiency are also energy dependent. Optimum protein levels were estimated in the range 34.0–42.0% for diets of energy content 2.9–4.4 kcal/g. A possible scheme relating food consumption, energy production and growth in P. merguiensis is presented.     

Relations between stratigraphy,geomorphology and soils in Coastal Plain areas of Southeastern U.S.A.

Small infiltrometers were used to measure infiltration rates into strongly and maderately developed compound prisms, sampled individually from surface layers of two dry clay soils. Initially, both rates were equally high but after three hours a higher rate was measured for the moderately developed compound prisms. These data were used to interpret adsorption and outflow phenomena of water in undisturbed, large and initially dry soil cores (diameter 20 cm) sampled from the upper 20 cm of the two soils, following application rates of about 8 mm/h and 28 mm/h. The two soils adsorbed an average of 6.4 mm water before the start of discharge, independent of the applied intensity. They discharged water at a constant and high rate for several hours, allowing adsorption of about 10% of the applied water. This represents a high degree of “short-circuiting” for all treatments, except one: adsorption was 40% at the 28 mm/h rate for the soil with the moderately developed prisms. The moisture content in the transmission zone was not constant as it would have been in homogeneous soil but increased regularly as a function of time. Slow wetting of both soils through a crust, followed by rain with an intensity of 30 mm/h, resulted in the adsorption of only about 3% of the applied rain in both soils.In general, more effective wetting of a dry clay surface soil at a given rainfall intensity is initially associated with less “short-circuiting” to deeper horizons. However, the resulting higher moisture content allows less adsorption in the surface layer and is therefore associated with increased “short-circuiting” thereafter, as long as large vertical pores have not been closed by swelling.     

Proton magnetic resonance spectroscopic determination of disulfiram: collaborative study

A proton magnetic resonance spectroscopic method for determining disulfiram in the bulk drug product and in the formulated material was collaboratively studied. The method depends on the use of chloroform-d as a solvent and hexamethylcyclotrisiloxane as the internal standard. No interference from tablet excipients was observed. The method is rapid and specific. Eighteen laboratories analyzed duplicate samples of a bulk drug product, a 250 mg tablet composite, and a 500 mg tablet composite. The average per cent results and standard deviations were 99.7 +/- 1.4, 100.9 +/- 2.0, and 99.9 +/- 2.2, respectively.     

Gas-liquid chromatographic determination of kepone residues in finfish, shellfish, and crustaceans.

Finfish, shellfish, and crustacean samples are extracted with isopropanol and benzene; the extract is filtered and then concentrated. The extract, dissolved in hexane, is treated with oleum and extracted with aqueous alkali. The aqueous phase is acidified and extracted with petroleum ether-ethyl ether (1 + 1). The Kepone residue is determined by electron capture gas-liquid chromatography (GLC). Recoveries obtained by 8 laboratories from 15 species of finfish fortified at 0.02-0.23 ppm ranged from 37 to 107% with a mean +/- relative standard deviation of 79.4 +/- 14.5%. For oysters fortified at 0.01-0.10 ppm, recoveries range from 63 to 129% with a mean of 78.8 +/- 20.8%. For crustaceans fortified at 0.05-0.26 ppm, recoveries ranged from 52 to 110% with a mean of 78 +/- 16.4%. The approximate limits of quantitation for finfish and for shellfish and crustaceans are 0.02 and 0.05 ppm, respectively, under the GLC conditions used in this study.     

Microbiological method for assaying lincomycin in animal feed: collaborative study.

A microbiological assay for determining lincomycin in swine feed, supplement, and a vitamin-mineral premix was studied collaboratively in 16 laboratories. The design of the study involved a complete feed, feed supplement, and a vitamin-mineral premix covering a range of fortification from 20 to 80 g/ton and 80 to 2600 g/ton. Two methods of sample preparation were used depending on the concentration of lincomycin in the sample. Statistical evaluation of the results from the 2 methods indicated that 10 and 11 collaborators, respectively, had mean recoveries which were not significantly different from one another. Ten laboratories obtained a mean recovery of 112.2% (range 102.3--123.5%) for the lower level, and 11 laboratories obtained a mean recovery of 104.4% (range 100.0--107.7%) for the higher level. The method has been adopted as official first action.