Density Centrifugation Method for Recovering Rhizobium spp. from Soil for Fluorescent-Antibody Studies

A density centrifugation procedure has been developed as a replacement for soil flocculation and clarification steps employed in quantitative fluorescent-antibody studies on Rhizobium in soils. Near-quantitative recovery of added cells of two strains of Rhizobium japonicum and two strains of R. phaseoli was achieved from six soils with various properties. It is proposed that this technique may prove useful in separating other soil microorganisms from soil particles in ecological studies employing fluorescent-antibody techniques.     

A Rapid Method of Isolation and Fractionation of Proteoglycans Using a Vertical Tube Rotor for Isopycnic Centrifugation

A comparison was made between a vertical tube rotor and a fixed angle rotor for isopycnic centrifugation of proteoglycans. In the vertical tube rotor, isopycnic gradient was achieved much faster than in the conventional fixed angle rotor. The use of a vertical tube rotor for isopycnic centrifugation shortens the time considerably for the isolation of proteoglycans fron various tissues.     

Agar Diffusion Method for Negative Staining of Microbial Suspensions in Salt Solutions

Microbial suspensions in a saline medium can be prepared for negative staining by a simple agar diffusion method that achieves a high degree of particle concentration.     

Simple Method for Preparation of Homogeneous Spore Suspensions Useful in Industrial Strain Selection

Homogeneous suspensions of streptomycete spores were desirable for plating after mutagenesis. Filtration through 8-mum membrane filters (Millipore Corp.) more effectively separated hyphae and spore clumps from single spores than did filtration through cotton wefts or paper.     

New Method for Purifying Coxiella burnetii by Dextran Sulfate Precipitation Followed by Centrifugation

This paper describes a simple method for purifying Coxiella burnetii cultivated in the chick embryo. The procedure is based upon the preliminary clarification of infected whole-egg suspensions by precipitating the low-density lipoproteins and other extraneous solids with dextran sulfate, calcium chloride, and sodium chloride solutions, and then concentrating the rickettsiae by centrifugation.     

A Centrifugation Technique for Preparing Medium-Free Resinous Mounts of Feulgen-Stained Pollen Tubes

Air-dried pollen of Tradescantia paludosa and a colchicine doubled Allium ascalonium-fistulosum interspecific hybrid was sown in culture tubes on an inorganic salt-lactose liquid medium containing 0.02% colchicine. After a 16-20 hr incubation at 22 C, pollen tubes were harvested by centrifugation for 3-5 min at 1100-1400 rev/min and fixed with acetic-alcohol (1:3). Feulgen staining was carried out in the culture tubes with fluid changes made after the centrifugation following each step. Single drops of the final pollen-45% acetic acid suspension were flattened under silicone-treated coverglasses which were removed by the quick freeze technique prior to counterstaining with fast green, dehydration, and mounting in Diaphane or Canada balsam. Medium-free, Feulgen-stained, resin-mounted preparations of well-dispersed pollen tubes with arrested metaphases were obtained.     

Centrifugation protocol for the NASA Artificial Gravity-Bed Rest Pilot Study

We have implemented a 41-day ground-based study to investigate the effects of daily artificial gravity loading on bed rest deconditioned human subjects. Each subject underwent 21 days of 6 degree head-down bed rest. Treatment subjects received 60 min daily doses of inertial mechanical loading (2.5 G at the feet decreasing to 1 G at the heart) produced by a short radius centrifuge. During rotation, the subject's cardiovascular responses were monitored via ECG, blood pressure and pulse oximetry, and subjective assessment of motion sickness and overall health were periodically requested. The subject's weight distribution at the feet was measured using a force plate, and lower leg muscle activity was monitored via surface electromyography. Control subjects were instrumented but did not receive any centrifugation. This paper provides details on the centrifuge protocol development and efficacy.     

5A. Concentration of Solutes by Freezing and Centrifugation

The virus extraction rotor may be usefully applied for concentrating solutes such as low molecular weight substances, proteins, virus soluble antigens and picorna viruses by centrifuging frozen dilute solutions at moderately high rotor velocities in the virus extraction rotor which had been fitted with the filters and precooled to 0?C. To accomplish this a circular stainless steel container with inner diameter equal to the inner diameter of the insert minus 5 mm was made. The reason for the smaller diameter was to allow for the thickness of the set of filters which lined the inner surface of the rotor insert. A rod attached to a flat circular metal slab closed a hole in the base of the cylinder by means of an 0 ring in the metal slab.

To conduct a concentration experiment the surface of the 0 ring was covered lightly with silicon grease and inserted in the groove on the bottom of the metal slab.     

Automated Needle‐free Injection Method for Delivery of Bacterial Suspensions into Citrus Leaf Tissues

A prototype needle‐free device was evaluated for delivery of Xanthomonas citri subsp. citri bacteria into the leaves of cultivars susceptible and resistant to citrus canker. The device delivered a precisely controlled volume of bacterial suspension through infiltration of stomata by injection with pressurized gas. The device produced a uniform inoculation of bacteria into the leaves as measured by the volume of infiltration and diameter of the infiltrated area. No damage to the leaves was observed after inoculation with the automated device, even though a higher number of canker lesions developed compared to a hand‐held needleless syringe injection method. The level of practice needed for operation of the automated device was minimal compared to considerable skill required to perform the hand‐held injection. Results from inoculations with the automated device are in accord with the results with the hand‐held syringe method that demonstrated kumquats are highly resistant to citrus canker while rough lemon and ‘Hamlin’ sweet orange are susceptible.     

Pretreatment of Cell Suspensions as a Method to Increase the Protoplast Yield of Haplopappus gracilis

A low yield of free protoplasts was obtained when fast-growing cell suspensions of Haplopappus gracilis were treated with Driselase, an active mixture of cellulase and pectinase. If the cells in the suspension culture were pretreated by increased levels of auxin, reduced sugar concentration, addition of sulphur-containing amino acids, or by the reducing agent mercaptoethanol, protoplasts were released from a higher proportion of the cells. These pretreatments did not adversely effect division of the protoplasts.     

A New Technique for Demonstration of Trichinella Spiralis Larvae in Suspensions of Digested Muscle Tissue

Up to now, a sedimentation technique has been used for demonstration of Trichinella spiralis larvae released by artificial digestion (Henriksen 1973, Skovgaard 1975, Thomsen 1976, 1977, and others).     

A Comparison of Membrane Filters for Counting Thermoactinomyces Endospores in Spore Suspensions and River Water

Streptococci were isolated from dental plaque samples collected from 25 animals representing 18 species. Strains were characterized by biochemical, physiological and serological tests. Extracellular polysaccharide-producing strains of Streptococcus mutans, Str. sanguis and Str. salivarius were found to be confined mainly to primate species. Streptococcus mutans was not widely distributed, being isolated from 2 of 18 animal species. Enterococci were isolated from the mouths of about one-third of the animals, whilst Str. bovis was found mainly in the herbivores. Strains resembling Str. mitior were isolated from most animals. Of 271 strains. 34 could not be allocated to any known species. Streptococci known to be associated with diseases of animals, especially those belonging to Lancefield group C, were not isolated. A few strains representing Lancefield groups D, L, G and M were found, but with low frequency.     

A Rabbit Model for Peripheral Nerve Reconstruction Studies Avoiding Automutilation Behavior

Background  The rabbit sciatic nerve injury model may represent a valuable alternative for critical gap distance seen in humans but often leads to automutilation. In this study, we modified the complete sciatic nerve injury model for avoiding autophagy. Materials and Methods  In 20 adult female New Zealand White rabbits, instead of transecting the complete sciatic nerve, we unilaterally transected the tibial portion and preserved the peroneal portion. Thereby loss of sensation in the dorsal aspect of the paw was avoided. The tibial portion was repaired in a reversed autograft approach in a length of 2.6 cm. In an alternative repair approach, a gap of 2.6 cm in length was repaired with a chitosan-based nerve guide. Results  During the 6-month follow-up period, there were no incidents of autotomy. Nerve regeneration of the tibial portion of the sciatic nerve was evaluated histologically and morphometrically. A clear difference between the distal segments of the healthy contralateral and the repaired tibial portion of the sciatic nerve was detectable, validating the model. Conclusion  By transecting the isolated tibial portion of the rabbit sciatic nerve and leaving the peroneal portion intact, it was possible to eliminate automutilation behavior.