Biomedical subjects

S S Thompson

Publications and source records attributed to S S Thompson.

6 recordsLinked to original sources

PubMed1999

Bacteriophage inactivation at the air-water-solid interface in dynamic batch systems.

Bacteriophages have been widely used as surrogates for human enteric viruses in many studies on virus transport and fate. In this investigation, the fates of three bacteriophages, MS2, R17, and phiX174, were studied in a series of dynamic batch experiments. Both MS2 and R17 readily underwent inactivation in batch experiments where solutions of each phage were percolated through tubes packed with varying ratios of glass and Teflon beads. MS2 and R17 inactivation was the result of exposure to destructive forces at the dynamic air-water-solid interface. phiX174, however, did not undergo inactivation in similar studies, suggesting that this phage does not accumulate at air-water interfaces or is not affected by interfacial forces in the same manner. Other batch experiments showed that MS2 and R17 were increasingly inactivated during mixing in polypropylene tubes as the ionic strength of the solution was raised (phiX174 was not affected). By the addition of Tween 80 to suspensions of MS2 and R17, phage inactivation was prevented. Our data suggest that viral inactivation in simple dynamic batch experiments is dependent upon (i) the presence of a dynamic air-water-solid interface (where the solid is a hydrophobic surface), (ii) the ionic strength of the solution, (iii) the concentration of surface active compounds in the solution, and (iv) the type of virus used.

Adsorption↗

PubMed1998

Acquisition of oral phencyclidine (PCP) self-administration in rhesus monkeys: effects of dose and an alternative non-drug reinforcer.

The effects of drug dose and a non-drug alternative reinforcer on acquisition of oral PCP self-administration in rhesus monkeys were examined. Acquisition was studied using three groups of monkeys (seven subjects per group). One group received a low PCP dose (0.0375 mg/delivery) and the other two received a high PCP dose (0.15 mg/delivery). One of the high dose groups had concurrent access to a saccharin solution (0.03% w/v) and water during the intersession (17.5-h) period. Food non-restricted monkeys were initially given access to water under a fixed-ratio (FR) 1 schedule during daily 3-h sessions. Water was then replaced with PCP during the session. The monkeys were then reduced to 85% of their free-feeding body weights and fed before the session, and the FR value was increased from 1 to 2, 4 and 8. Subsequently, food was given post-session and water and PCP were available under concurrent FR 8 schedules. At this final step of the procedure, acquisition of PCP self-administration was considered to occur if PCP intake consistently exceeded water intake. When all three groups were given concurrent access to PCP and water, PCP intake was greater than water intake only in the group of monkeys receiving the high PCP dose. PCP intake increased when water replaced saccharin during intersession in the high PCP dose group. Within-group data revealed that 85.7% of monkeys acquired PCP reinforcement in the group given access to the high PCP dose while only 42.8% acquired in the other two groups. These data suggest that drug dose and presence of alternative non-drug reinforcers affect acquisition of drug self administration in non-human primates.

Administration, Oral↗

PubMed1998

Role of the air-water-solid interface in bacteriophage sorption experiments.

Batch sorption experiments were carried out with the bacteriophages MS2 and phi X174. Two types of reactor vessels, polypropylene and glass, were used. Consistently lower concentrations of MS2 were found in the liquid phase in the absence of soil (control blanks) than in the presence of soil after mixing. High levels of MS2 inactivation (approximately 99.9%) were observed in control tubes made of polypropylene (PP), with comparatively little loss of virus seen in PP tubes when soil was present. Minimal inactivation of MS2 was observed when the air-water interface was completely eliminated from PP control blanks during mixing. All batch experiments performed with reactor tubes made of glass demonstrated no substantial inactivation of MS2. In similar experiments, bacteriophage phi X174 did not undergo inactivation in either PP or glass control blanks, implying that this virus is not affected by the same factors which led to inactivation of MS2 in the PP control tubes. When possible, phage adsorption to soil was calculated by the Freundlich isotherm. Our data suggest that forces associated with the air-water-solid interface (where the solid is a hydrophobic surface) are responsible for inactivation of MS2 in the PP control tubes. The influence of air-water interfacial forces should be carefully considered when batch sorption experiments are conducted with certain viruses.

Adsorption↗

PubMed1997

Effects of buprenorphine and an alternative nondrug reinforcer, alone and in combination on smoked cocaine self-administration in monkeys.

The abuse of smoked cocaine base, also known as 'crack', continues to be a major public health problem and to date the success of pharmacological or behavioral interventions has been limited. The purpose of this study was to evaluate the efficacy of a behavioral (alternative reinforcer-saccharin) and pharmacological (0.01 mg/kg buprenorphine) treatment alone and in combination. Five adult male rhesus monkeys self-administered cocaine base (1.0 mg/kg/delivery) via the smoking/inhalation route. Each day ten smoke deliveries were available contingent upon completion of a chained FR (lever press), FR (inhalation response) response schedule during 4 hr sessions. The data were analyzed using a behavioral economic framework in which the lever press response requirements were varied from 64 to 1024 to generate a demand function (consumption x FR) for cocaine under the following conditions: (1) buprenorphine pretreatment alone (0.01 mg/kg, i.m., 30 min presession); (2) concurrent access to saccharin alone (0.03% wt/vol); and (3) buprenorphine pretreatment in the presence of concurrent access to saccharin. Under all conditions, increases in the lever FR resulted in significant decreases in smoked cocaine base deliveries. Neither buprenorphine pretreatment alone nor concurrent saccharin alone produced significant decreases in smoked cocaine deliveries; however, the combination of buprenorphine pretreatment and concurrent saccharin significantly decreased the mean number of smoked cocaine deliveries from the no treatment baseline and from the buprenorphine alone condition. These data suggest that the combination of pharmacotherapy and alternative reinforcers may be an effective treatment strategy to alter smoked cocaine self-administration.

Animals↗

PubMed1997

Smoked heroin and cocaine base (speedball) combinations in rhesus monkeys.

The purpose of this investigation was to compare the self-administration of heroin and cocaine base, alone and in combination, in rhesus monkeys (Macaca mulatta) self-administering a combination of heroin (0.1 mg/kg/delivery) and cocaine base (1.0 mg/kg/delivery) via the smoking route. Smoke deliveries were contingent on completion of a chained fixed ratio (FR; lever press), FR 5 (inhalation) schedule. The lever press FR values (64, 128, 256, 512, and 1024) represented increasing drug price. Demand functions (Consumption X price) were obtained for the heroin and cocaine combination and compared with previously determined demand functions for smoked heroin and cocaine alone. As the FR increased and the number of responses emitted increased, the number of drug deliveries decreased. The demand functions were not different for heroin versus cocaine alone or for the cocaine alone versus the cocaine-heroin combination. However, the demand for heroin alone was significantly less than the demand for the cocaine-heroin combination, suggesting that smoked cocaine base enhances the behavioral effects of smoked heroin.

Administration, Inhalation↗

PubMed1985

Ultrastructural localization of an extracellular protease in Pseudomonas fragi by using the peroxidase-antiperoxidase reaction.

An extracellular protease, which previously has been found to correlate with the appearance of bleblike evaginations on the cell wall of Pseudomonas fragi ATCC 4973, was purified 38-fold by ammonium sulfate precipitation and Sephadex chromatography to yield a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polyclonal rabbit antiserum raised against the purified enzyme had an enzyme-linked immunosorbent assay titer of 4 X 10(7). The peroxidase antiperoxidase method was used to localize the neutral protease in P. fragi at the ultrastructural level. Electron microscopy of cell sections of this organism revealed that high concentrations of positive immunoperoxidase reaction product were located near the cell wall, whereas control sections stained with preimmune or heterologous serum did not show similar deposits to be present. These results are consistent with the hypothesis that blebs appearing on P. fragi contain high concentrations of neutral protease.

Cell Fractionation↗