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Biomedical subjects

C Wallis

Publications and source records attributed to C Wallis.

At least 91 records · Page 5Linked to original sources
PubMed1983

In vivo regional levels of PGE and thromboxane in mouse brain: effect of decapitation, focused microwave fixation, and indomethacin.

A focused microwave fixation technique was tested for use in determining basal PGE and thromboxane B2 levels of mouse brain. Focused microwave irradiation (3.5 Kw/0.4 sec) to the head of C3H mice produced basal values of PGE and TXB2 which were five-fold less than those in animals killed by decapitation. Indomethacin (10 mg/kg) pretreatment blocked the decapitation rise in PGE and TXB2 levels and gave values similar to focused microwave irradiation. Indomethacin pretreatment combined with microwave fixation did not reduce PG levels more than microwave treatment alone. When microwave fixation was used, there was no difference in regional (cerebral cortex, whole cerebellum, midbrain, hypothalamus) levels of either PGE or TXB2. However, PGE levels were significantly higher than TXB2 in all regions. After decapitation there was a greater increase in TXB2 than PGE. The cerebellum produced less PGE and TXB2 after decapitation compared to the other regions. Our results confirm the usefulness of the focused microwave irradiation technique for examining in vivo basal prostaglandin levels in mouse brain.

Animals↗
PubMed1983

A system for dual-energy radiography.

A system has been developed and theoretically analysed for the generation of chemical information from conventional radiography. A specially modified cassette has enabled dual-energy radiographs to be taken during a single exposure. A simple theoretical model has demonstrated that the concept of an optical density "standardised" to the local surroundings allows adequate quantification of the dual-energy radiographs. Using this method, data can be obtained relating to the effective atomic number of a radiographed material provided some estimate of its physical density is known. Simulated in vivo analysis of gall-stone composition has been demonstrated using these techniques.

Calibration↗
PubMed1981

Colorimetric method for rapid determination of bacteriuria.

An inexpensive, rapid, and simple colorimetric test for detection of bacteriuria is described. This test does not require bacterial growth and has the marked advantage of being able to quantify bacteria, even when the organisms are present in the urine of bacteriuric patients who are being treated with antibiotics. The test is carried out with 1 ml of urine, which is processed through a 10-mm-diameter filter than entraps the bacteria on its surface. Safranine dye is passed through the filter to stain the bacteria and the filter fibers. A decolorizer, which removes the dye from the filter fibers but not from the bacteria, is then passed through the filter. If there are greater than or equal to 10(5) colony-forming units of bacteria per ml in the sample, the 10-mm filter disk manifests a pink to red color. If there are less than 10(5)colony-forming units of bacteria per ml, the filter disk remains white or becomes slightly yellow. The entire procedure has been adapted to a semiautomated instrument and the time required per test is less than 1 min. The results obtained on the test card are a permanent record to be filled with the patient's chart. The bacteria can be quickly classified as gram positive or gram negative by selective staining of a second milliliter of urine on the filter. Of 441 urine specimens tested, 430 (98%) were correctly classified as containing more or less than 10(5) colony-forming units per ml. A total of 62 urine specimens were positive by bacterial plating (greater than or equal to 10(5) colony-forming units per ml), and 59 were positive by the colorimetric test. Eight false-positives (colorimetric test positive, plate counts less than 10(5)) were encountered in patients (bacteriuric) being prescribed antibiotics. Removal of the antibiotics from these urine specimens, with subsequent replating of the samples, indicated the presence of greater than or equal to 10(5) colony-forming units of bacteria per ml in three representative cases tested, indicating that the results of the colorimetric tests were not false-positives but that the plate counts were low because of the inhibition of bacterial growth by the residual antibiotics present in the urine.

Bacteria↗
PubMed1980

Rapid isolation of bacteria from septicemic patients by use of an antimicrobial agent removal device.

The new Antimicrobial Removal Device increased the efficacy of conventional methods for isolating bacteria from the blood of septicemic patients. The device removes as much as 100 microgram of antibiotics per ml from whole blood without a significant decrease in bacteria. Of 51 patients studied, 31 yielded positive cultures, and the Antimicrobial Removal Device permitted earlier isolation of the causative agent from blood. Subcultured within the first 12 h yielded 12 positive isolates, as the 31 agents were isolated more rapidly after Antimicrobial Removal Device permitted earlier isolation of the causative agent from blood. Subcultures within the first 12 h yielded 12 positive isolates, as compared to 2 when subcultured without processing in the device. Overall, 21 of the 31 agents were isolated more rapidly after Antimicrobial Removal Device treatment, and four samples were positive only after such treatment. One agent was not isolated in the treated culture.

Anti-Bacterial Agents↗
PubMed1979

Mitochondrial activity of 2,6-diaminopurine in Saccharomyces cerevisiae.

2,6-diaminpurine (DAP) selectively inhibited mitochondrial protein synthesis in yeast cells with concomitant failure of cells to grow in non-fermentable (yeast extract, glycerol) medium. The selectivity was pronounced in all strains tested (15) nearly all of which were able to grow in yeast extract, glucose medium containing 5 mg/ml DAP (maximum solubility) whereas growth was arrested in all strains at 250-500 microgram/ml DAP in the glycerol medium. The inhibition was reversed by further addition of adenine to the culture medium. RNA synthesis in rat liver mitochondria was depressed by DAP suggesting that the analogue affected RNA polymerase activity. There was no evidence of nuclear mutagenicity by DAP but resistance to the antibiotics chloramphenicol and oligomycin was induced by the drug. Genetic evidence, although limited, indicated that the resistance mutations were cytoplasmic. The mitochondrial petite mutation was also induced by DAP but only at comparatively high concentrations. The mutagenic effects were seen only in the glycerol medium.

2-Aminopurine↗
PubMed1978

Concentration of enteroviruses from large volumes of tap water, treated sewage, and seawater.

Methods are described for the efficient concentration of an enterovirus from large volumes of tap water, sewage, and seawater. Virus in acidified water (pH 3.5) in the presence of aluminum chloride was adsorbed to a 10-inch (ca. 25.4 cm) fiberglass depth cartridge and a 10-inch pleated epoxy-fiberglass filter in a series at flow rates of up to 37.8 liters (10 gallons) per min. Adsorbed viruses were eluted from the filters with glycine buffer (pH 10.5 to 11.5), and the eluate was reconcentrated by using a combination of aluminum flocculation followed by hydroextraction. With this procedure, poliovirus in large volumes of tap water, seawater, and sewage could be concentrated with an average efficiency of 52, 53, and 50%, respectively. It was demonstrated that this method is capable of detecting surface solid-associated viruses originating from sewage treatment plants. No difference in virus recovery between laboratory batch studies and a set-up with acid-salt injection was found. This unified scheme for the concentration of viruses has many advantages over previously described systems. These include: high operating flow rates, low weight and small size, effectiveness with a variety of waters with widely varying qualities, and filters with a high resistance to clogging.

Enterovirus↗
PubMed1978

Concentration of poliovirus from tap water onto membrane filters with aluminum chloride at ambient pH levels.

A method is described for the concentration of an enterovirus from large volumes of tap water by addition of small amounts of aluminum chloride to enhance virus removal by membrane filters. Tap water treated with 2 X 10(-5) M aluminum chloride showed a slight decrease in pH (less than 0.5), a slight increase in turbidity, and enhanced removal of poliovirus by membrane filters. Virus was quantitatively recovered by treating the filters with a basic buffer, and this eluate was reconcentrated to a small volume by adsorption to aluminum hydroxide flocs. Using these procedures, virus from 1,000 liters of water was reduced to a final eluate of 20 to 80 ml with a mean recovery of 70%.

Adsorption↗