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W G Murrell

Publications and source records attributed to W G Murrell.

At least 19 recordsLinked to original sources
PubMed1995

Chromatin structure and the expression of cardiac genes.

Actively transcribed genes are more susceptible to nuclease digestion, an observation suggested to reflect an altered state of chromatin organization. It has been hypothesized that exposure or sequestration of chromatin domains is a higher order gene regulatory mechanism. In order to test whether tissue lineage is organized by mechanisms at the level or chromatin structure, three cardiac phenotype-conferring genes (atrial natriuretic factor, myosin light chain-1-ventricular and alpha-tropomyosin) have been assessed for DNase 1 sensitivity in nuclei prepared from tissues of the developing guinea pig. These data have been related to the level of tissue mRNA expression of these genes to ascertain whether the exposed state of genes can occur when transcription is low or undetectable. Although this phenomenon was evident in some cases, the data were not consistent with mechanisms at the level of chromatin structure directing tissue type.

Aging↗
PubMed1995

Is cardiorespiratory failure induced by bacterial toxins the cause of sudden infant death syndrome? Studies with an animal model (the rabbit).

Recent studies have implicated various toxigenic bacteria and their toxins in the aetiology of sudden infant death syndrome (SIDS). Therefore the effect of six bacterial toxins on the cardiorespiratory system of the rabbit was studied as a model for SIDS. The toxins' effect on the heart rate, arterial blood pressure, and breathing of anaesthetized rabbits was determined and their action compared to that of endotoxin. Intravenous injection of Clostridium perfringens enterotoxin and alpha-toxin, Staphylococcus enterotoxin B, Escherichia coli heat-stable toxin (STa), Clostridium difficile toxin A and B reduced heart rate, blood pressure, respiration and increased, slowed and prolonged thorax expansion, and at higher concentrations caused sudden death without visible stress or trauma. A combination of a low concentration of enterotoxins caused a greater reduction of these activities and sudden death. These effects were generally similar to those produced by endotoxin. In non-anaesthetized rabbits, the toxins slowed metabolism until death occurred without agitation, spasms, visible distress or prolonged illness. Intestinal production of these toxins by toxigenic strains, when conditions are suitable, and their systemic absorption, could therefore cause SIDS by an endotoxin-like shock mechanism.

Animals↗
PubMed1994

On the ontogeny of cardiac gene transcripts.

As a prerequisite to investigating the specification and differentiation of cardiac tissue in vitro, the ontogeny of a number of putative cardiac-specific, and striated muscle-specific gene transcripts has been studied. The probes used include cDNAs of alpha-actins, myosin heavy chains, myosin light chains, alpha-tropomyosin, troponin-T and atrial natriuretic factor. The expression of these genes was monitored by Northern analysis of heart and various other tissues at three developmental ages, viz, adult, neonatal and mid-foetal. The aim of this exercise was to confirm the efficacy of a number of markers to represent a cardiac-specific subset of gene expression in our mammalian model, the guinea pig. Our results indicate predominantly cardiac expression for the mRNA transcripts of cardiac alpha-actin (c alpha-actin), cardiac myosin heavy chain-alpha (MHC alpha), cardiac myosin heavy chain-beta (MHC beta), myosin light chain-1A (MLC1A), myosin light chain-1V (MLC1V), alpha-tropomyosin (alpha TM), cardiac troponin-T (cTnT) and atrial natriuretic factor (ANF). Furthermore, cardiac-specific expression at the midfoetal time point was observed for five gene transcripts, MLC1V, MHC alpha, MHC beta, striated alpha TM and ANF. No genes were expressed exclusively in cardiac tissue; for example, expression of the genes for c alpha-actin, both cardiac MHCs, both MLCs, alpha TM and cTnT was evident in skeletal and vascular smooth muscles at some stages of development. An interesting difference between this species and those of previous studies was the minor contribution of skeletal alpha-actin to cardiac phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1994

Sudden infant death syndrome (SIDS): are common bacterial toxins responsible, and do they have a vaccine potential?

Despite extensive research, no unifying concept has satisfactorily explained the cause of the sudden infant death syndrome (SIDS). The details are briefly outlined of some of the evidence supporting the hypothesis that common bacterial toxins are important in the aetiology of SIDS. These bacterial toxins act as triggers to initiate a biochemical cascade resulting in death. Data from four research groups, each working independently, indicated that the bacteria Clostridium perfringens, Escherichia coli, Staphylococcus aureus, Streptococcus spp. and Enterococcus spp. were present in higher numbers in infants who had suffered SIDS than in control infants. Certainly more detailed studies need to be performed on the role of bacterial infections in infants. There are many implications arising from this work, particularly the use of vaccination as a means of reducing infections, and consequently the number of SIDS deaths.

Bacterial Toxins↗
PubMed1993

An epidemiological survey of SIDS in the Sydney metropolitan area.

Records of 1049 cases of Sudden Infant Death Syndrome (SIDS) (100%) in the Sydney metropolitan area (SMA) from 1980 to 1989 were analysed in relation to ambient temperature, geographical distribution and socio-economic scale. The SIDS rate varied between eastern and western Sydney and between statistical subdivisions; it peaked sharply in July, coinciding with the monthly mean minimum daily temperature (MMMDT; 6.5 and 5.4 degrees C, respectively). The inverse linear relationship between the SIDS rate and the MMMDT for the regions and the subdivisions was highly significant (P < 0.001). The SIDS rate showed a significant inverse linear relationship to two socio-economic scales (allotment and house value) for 82 of the 87 suburbs (94%) of the SMA. Temperature, indicative of cold weather, was the major factor determining SIDS rates, and this, together with socio-economic factors, largely explains the observed geographical distribution of SIDS rates in the SMA.

Cold Temperature↗
PubMed1983

A comparison of UV induced DNA photoproducts from isolated and non-isolated developing bacterial forespores.

UV-induced photoproduct formation has been compared in non-isolated and isolated developing forespores. We have found that levels of spore type photoproducts are greatly affected by mother cell DNA. We have also observed the presence of the photoproduct 6-4'-(pyrimidin-2'-one)-thymine in developing forespores. We conclude from these and other data in the literature that the degree of hydration around the forespore DNA is reduced by the presence of dipicolinic acid which influences photoproduct formation without causing a change in conformational state.

Bacillus megaterium↗
PubMed1983

A method for the isolation of intact, viable forespores from Bacillus species using high pressure.

Large-scale preparation of Bacillus forespores was performed using nitrogen gas under high pressure to force an osmotically stable spheroplast suspension through a micrometer needle valve. Ninety-nine percent recovery of intact viable forespores at various stages of sporulation was achieved with a variety of Bacillus species. The isolated forespores are stable for up to 7 days when kept under nongerminating conditions.

Bacillus↗
PubMed1983

Botulism in New South Wales, 1980-1981.

The isolation of Clostridium botulinum from the home environment of New South Wales patients with infant botulism is reported. Of the three cases of infant botulism type B, the bacteria were isolated from soil around the dwelling in one, and from tank rainwater in another. In one case with type A, the bacteria were present in the soil, vacuum-cleaner dust, and tank rainwater. The bacteria were not detected in the environment of two adult patients and a child with C. botulinum in their stools. The home location of the patients with infant botulism, and the frequency of isolation of the bacteria from rainwater, soil and vacuum-cleaner dust in Cobar, Nyngan, some Sydney suburbs, and at five pastoral homesteads suggest that infants in rural areas are more at risk than those in large metropolitan areas. The age of the infants with diagnosed botulism in New South Wales, compared with those reported in the United States data, strongly suggests that the disease is not being fully recognised in younger infants.

Aged↗
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↗