POLYRIBOSOMES: SIZE IN NORMAL AND POLIO- INFECTED HELA CELLS

HeLa cells normally contain a distribution of polysome sizes, and the largest polysomes contain over 40 ribosomes. After infection with polio virus and actinomycin-D treatment, a new class of polio-induced polysomes are found, some of which contain up to 60 ribosomes. Examinaton of these polysomes suggests a mechanism for protein synthesis with this polycistronic RNA.     

X-ray fluorescence analysis in biology

Our efforts to understand the important biological roles of many "minor" elements are limited by the capabilities of the existing instruments. X-ray fluorescence analysis is not the most sensitive method for the assay of minor elements, but it is the instrumental technique of choice both for certain clinical studies and for certain research problems. The technique will be more widely used as it becomes more widely known (25).     

An amended functional leaching model applicable to structured soils. I. Model description

A functional model designed to simulate the transport of non-interactive solutes through macroporous soil is described. The concept of mobile and immobile water is used but the pore volume available for mobile water is partitioned to allow for flow through smaller water-filled pores and rapid preferential flow through larger macropores and fissures. The general performance of the model under steady infiltration following an injection of solute is presented. The sensitivity of the output to variations in the model parameters is also discussed. A second paper compares the model with bromide and chloride leaching data on two texturally contrasting soils.     

Chlortetracycline in swine-bioavailability and pharmacokinetics in fasted and fed pigs

Chlortetracycline hydrochloride was administered intra-arterially (11 mg/kg) and as an oral drench (33 mg/kg) to ten 21.0-31.5-kg pigs. Five of the pigs were fasted 18 h prior to dosing and five of the pigs were fed ad libitum prior to dosing. The mean volume of distribution determined by area-under-the-curve calculations for the fasted pigs (0.967 +/- 0.210 l/kg) was significantly less (P less than 0.05) than the mean volume of distribution for the fed pigs (1.39 +/- 0.31 l/kg). Mean total body clearance of the drug was also significantly less (P less than 0.05) in the fasted pigs (0.165 +/- 0.055 l/kg/h) as compared to the fed pigs (0.307 +/- 0.053 l/kg/h). The elimination constants (beta) were not found to be statistically different (P less than 0.05): 0.1811 +/- 0.0057 for the fasted pigs; 0.2260 +/- 0.0461 for the fed pigs. The bioavailability for both groups was similar; 19.12 +/- 8.3% for the fasted pigs and 17.88 +/- 5.3% for the fed pigs. In a second experiment three groups of six pigs which weighed 34.5-44.1 kg were fed a corn-soy diet ad libitum. The rations were fortified with chlortetracycline at 100, 400 or 1000 mg chlortetracycline hydrochloride/kg feed. Chlortetracycline concentrations were determined in plasma samples collected over a 6-day period. Plasma chlortetracycline concentrations reach a plateau within 24 h after initial access to the trial diets and were highly correlated with the dose of the drug consumed (r2 = 0.97).     

Isolation and pathogenicity of Australian strains of Eimeria praecox and Eimeria mitis

Objective To determine the presence of E praecox and E mitis in Australia, to isolate representative strains of these species from chickens and determine their pathogenicity.
Design Morphological, physiological and cross protection studies were undertaken to confirm the identity of Australian isolates of E praecox and E mitis.
Procedure Oocysts were isolated from a backyard flock at Jimboomba, southeastern Queensland and numbers of E praecox and E mitis enriched by passage in chickens immune to five other species of poultry Eimeria . Oocysts of mean conformation and size of the two species were purified by single oocyst passage. Two isolates that closely matched recorded parameters for E praecox and E mitis were selected and designated JP and JM respectively. The cross protection between the isolates and E acervulina was determined by infection and challenge experiments. The virulence of the two isolates was determined by comparing weight gains of groups of birds inoculated with JP isolate or JM isolate with untreated groups.
Results Isolates JP and JM most closely matched recorded parameters of E praecox and E mitis respectively. Groups of chickens, previously infected with JP and JM isolates, showed no significant protection against infection with E acervulina . In a separate trial, groups of susceptible chickens inoculated with 10⁵ oocysts of JP and JM isolates showed significantly reduced weight gains compared with untreated controls.
Conclusion Isolates JP and JM are E praecox and E mitis respectively, confirming the presence of these species in Australia. These isolates were found capable of causing significant reductions in weight gains in susceptible chickens.     

The control of bubble diseases and cobweb disease of mushrooms with prochloraz

Fungicides were compared for the control of the mushroom pathogens Verticillium fungicola (dry bubble disease), Mycogone perniciosa (wet bubble disease) and Hypomyces rosellus (cobweb disease). Prochloraz, applied as a manganese complex, consistently gave significantly greater control of a benomyl-resistant strain of V. fungicola. Captafol gave some reduction in disease. Benomyl, thiabendazole and prochloraz all gave significant control of M. perniciosa and H. rosellus. Prochloraz residues in mushrooms were measured by gas chromatography after extraction in acetone and purification by means of solvent partition, When pure prochloraz was added to homogenized mushroom tissue, 77–98% was recovered by this procedure. The residue levels in sporophores from crops treated with prochloraz were low, Prochloraz appears to be an effective fungicide for the control of the major fungal pathogens of the mushroom crop, particularly where benzimidazole-resistant strains of V. fungicola occur.