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Biomedical subjects

W G Murrell

Publications and source records attributed to W G Murrell.

36 records · Page 2Linked to original sources
PubMed1983

Type C botulism in young dogs.

A diffuse lower motor neurone paralysis developed in a 6-month-old male Australian cattle dog pup 4 days after it had eaten the carcase of a rotting duck in Centennial Park, Sydney. Two other dogs which ate smaller portions of the same carcase were less severely affected. Clostridium botulinum type C was isolated from and C. botulinum type C toxin was detected in faeces from the severely affected dog. The serum contained 25 LD50 of toxin/ml. The high C. botulinum count and toxin level in the faeces declined progressively during the ensuing weeks, but 114 days after ingesting the carcase C. botulinum type C was still present in faeces and a low toxin titre persisted. Soil, mud and water samples in the area of the duck ponds in the park contained C. botulinum type C spores. Spores and high toxin titres were also found in the intestine of the carcases of 2 birds in the area.

Animals↗
PubMed1981

Scanning electron probe x-ray microanalysis of elemental distributions in freeze-dried cryosections of Bacillus coagulans spores.

High-resolution scanning electron probe X-ray microanalysis had been employed to examine elemental distributions in freeze-dried cryosections of Bacillus coagulans spores. Calcium, manganese, and phosphorus were concentrated in the protoplast and the coat. Iron was found in the coat but not in the protoplast, whereas the silicon seen on the coat of other spore species was absent. Sulfur was present in the coat, but was distributed over a broader area than the other elements, which suggested that phosphorus and the metal ions were located in the outer coat layer.

Bacillus↗
PubMed1980

Infant botulism.

Explore the source record for details and available documents.

Botulism↗
PubMed1980

Rapid radiometric method for detection of Salmonella in foods.

A radiometric method for the detection of Salmonella in foods has been developed which is based on Salmonella poly H agglutinating serum preventing Salmonella from producing 14CO2 from [14C]dulcitol. The method will detect the presence or absence of Salmonella in a product within 30 h compared to 4 to 5 days by routine culture methods. The method has been evaluated against a routine culture method using 58 samples of food. The overall agreement was 91%. Five samples negative for Salmonella by the routine method were positive by the radiometric method. These may have been false positives. However, the routine method may have failed to detect Salmonella due to the presence of large numbers of lactose-fermenting bacteria which hindered isolation of Salmonella colonies on the selective agar plates.

Animals↗
PubMed1980

Distribution of calcium and other elements in cryosectioned Bacillus cereus T spores, determined by high-resolution scanning electron probe x-ray microanalysis.

The distribution of a number of key elements in Bacillus cereus T spores was determined by high-resolution scanning electron probe X-ray microanalysis. To circumvent the redistribution of soluble or weakly bound elements, freeze-dried cryosections of spores, which had been rapidly frozen in 50% aqueous polyvinyl pyrrolidone, were employed. The sections were examined by using a modified Philips EM400 electron microscope fitted with a field emission gun, scanning transmission electron microscopy attachment, and a computer-linked energy-dispersive X-ray microanalysis system. X-ray maps for selected elements and the corresponding electron image were produced simultaneously by scanning the cryosections with a fine electron beam in a raster pattern, using the scanning transmission electron microscopy attachment. The results indicated that almost all of the calcium, magnesium, and manganese, together with most of the phosphorus, was located in the core region. An unexpectedly high concentration of silicon was found in the cortex/coat layer. Granules containing high concentrations of calcium, manganese, and phosphorus were demonstrated in spores containing reduced levels of dipicolinic acid. Spot mode analyses, in which a stationary beam was located over the region of interest in the spore cryosection, confirmed the results obtained with the scanning mode and also provided a more accurate quantitation of the elemental concentrations on a dry weight bases.

Bacillus cereus↗
PubMed1977

Initiation of Bacillus spore germination by hydrostatic pressure: effect of temperature.

Suspensions of Bacillus cereus T, B. subtilis, and B. pumilus spores in water or potassium phosphate buffer were germinated by hydrostatic pressures of between 325 and 975 atm. Kinetics of germination at temperatures within the range of 25 to 44 degrees C were determined, and thermodynamic parameters were calculated. The optimum temperature for germination was dependent on pressure, species, suspending medium, and storage time after heat activation. Germination rates increased significantly with small increments of pressure, as indicated by high negative deltaV values of -230 +/- 5 cm3/mol for buffered B. subtilis (500 to 700 atm) and B. pumilus (500 atm) spores and -254 +/- 18 cm3/mol for aqueous B. subtilis (400 to 550 atm) spores at 40 degrees C and -612 +/- 41 cm3/mol for B. cereus (500 to 700 atm) spores at 25 degrees C. The ranges of thermodynamic constants calculated at 40 degrees C for buffered B. pumilus and B. subtilis spores at 500 and 600 atm and for aqueous B. subtilis spores at 500 atm were: Ea = 181,000 to 267,000 J/mol; deltaH = 178,000 to 264,000 J/mol; deltaG = 94,000 to 98,300 J/mol; deltaS = 264 to 544 J/mol per degree K. These values are consistent with the concept that the transformation of a dormant to a germinating spore induced by hydrostatic pressure involves either hydration or a reduction in the visocosity of the spore core and a conformational change of an enzyme.

Bacillus↗
PubMed1976

Heat-induced requirements for sucrose or magnesium for expression of heat resistance in Bacillus cereus forespores.

The addition of 0.6 M sucrose of 0.016 M Mg2+ to the enumeration medium was required for early expression of heat resistance (10 min at 70 degrees C) in stage V Bacillus cereus forspores. The addition of Mg2+ to the sporulation medium did not remove this requirment for sucrose of Mg2+. The heat damage did not affect forespore germination or outgrowth, but injured cells in the absence of sucrose or Mg2+ were not capable of cell division. The heat-induced sublethal damage apparently affected the forspore component(s) that could be repaired or was capable of normal function in the presence of added Mg2+ or sucrose.

Bacillus cereus↗
PubMed1974

Use of ultraviolet radiation to locate dipicolinic acid in Bacillus cereus spores.

A novel method is described that allows a direct determination of the location of a portion of the dipicolinic acid (DPA) in spores. Ultraviolet (UV) irradiation is shown to cause cross-linkage of DPA to spore proteins which have the characteristics of membrane proteins. We suggest that DPA resides in the inner forespore membrane (IFSM) and spore cytoplasm (i.e., the spore protoplast). Only that portion of the DPA in the vicinity of the IFSM appeared to form UV-induced DPA-protein adducts.

Bacillus cereus↗
PubMed1974

Photoreactivation, photoproduct formation, and deoxyribonucleic acid state in ultraviolet-irradiated sporulating cultures of Bacillus cereus.

Photoreactivation of ultraviolet-irradiated Bacillus cereus T declined markedly during the development of stage IV forespores. During ultraviolet irradiation of a culture containing early and late stage IV forespores, both vegetative- and spore-type photoproducts were formed. The formation of vegetative-type photoproducts (mainly thymine dimers) decreased to nearly half during late stage IV, remaining constant until lysis of the mother cells began, when it fell to zero. Spore-type photoproducts were first observed during late stage IV and increased with the increase in numbers of late stage IV forespores. The occurrence of spore-type photoproducts preceded the development of refractile forespores by about 1 h. At stage III the nuclear material occupied a central position, and the ribosomes were at the periphery of the forespore protoplast. During stage IV the deoxyribonucleic acid (DNA) occurred in a peripheral position, and bundles of fibers ("transition" DNA) could be seen. By stage V, all of the DNA appeared to be of the spore type and was peripheral, and the forespore protoplast center was packed with ribosomes. Forespore stages II, III, and IV were classified by light and electron microscopy. The curve for electron microscope classifications preceded that for light microscope classifications by approximately one stage. The formation of spore-type photoproducts preceded differentiation of DNA by about 1 h, the latter coinciding with the development of refractility. Spore-type photoproducts have been associated with DNA in the A state, and the progressive change of the forespore DNA into this state is discussed in relation to the spore differentiation process.

Bacillus cereus↗
PubMed1973

Exosporium and spore coat formation in Bacillus cereus T.

The exosporium of Bacillus cereus T was first observed as a small lamella in the cytoplasm in proximity to the outer forespore membrane (OFSM) near the middle of the sporangium. Serial sections, various staining methods, and enzyme treatments failed to show any connections between the small lamella and the OFSM. The advancing edge of the exosporium moved toward the polar end of the cell until the spore was completely enveloped. The middle coat was formed between the exosporium and the OFSM from a three-layered single plate or "belt," consisting of two electron-dense layers separated by an electron-transparent layer. This "belt," usually first observed toward the center of the sporangium, developed without changing thickness or appearance over the surface of the forespore. Between the middle coat and the OFSM, a layer of cytoplasm about 50-nm thick was enclosed by the developing coat; this became the inner coat. Electron-dense material was deposited on the outer surface of the middle coat to form the outer coat.

Bacillus cereus↗
PubMed1973

Development of ultraviolet resistance in sporulating Bacillus cereus T.

Ultraviolet (UV) resistance patterns of sporulating Bacillus cereus were determined. Six different categories of UV resistance were discernible as the organism progressed from exponential growth to the free, mature spore. Light microscope observations allowed the assignment of certain sporulation stages to specific UV resistance categories. Marked changes in UV resistance were associated with stages III, mid-IV, and post-IV of sporulation. Dipicolinic acid was shown to sensitize forespores to UV radiation. Mechanisms invoked to explain the different UV categories are discussed.

Bacillus cereus↗