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D T Jones

Publications and source records attributed to D T Jones.

At least 127 records · Page 7Linked to original sources
PubMed1990

Radiobiological intercomparison of two clinical neutron beams using the regeneration of mouse intestinal crypts.

Determination of dose modification factor greatly facilitates the introduction of clinically proven neutron therapy schedules at new installations. We have compared the biological performance of the p(66)+Be neutron facility at Faure, South Africa, with the established p(65)+Be installation at Louvain-la-Neuve, Belgium. Filtration, D gamma/DT, dose rate and HVT 5/15 for the Louvain and Faure beam are: 2 cm, 2.5 cm polyethylene; 3%, 5%; 0.2 Gy/min, 0.4 Gy/min; and 20 cm and 19 cm respectively. Dosimetry was done in A-150 plastic. Irradiation of BALB/C mice was carried on according to the dose accumulation method in a perspex phantom at 5 cm depth and at an SSD of 150 cm at a field size of 28 X 28 cm2. Sections of the jejunum were prepared at each centre and analyzed by both. The RBE of the Faure beam determined at a survival level of 50 crypts ranged from 1.64 to 1.69. The dose modification factor RBE of the Louvain beam given by Beauduin et al. was 1.61 +/- 0.14. The dose modification factor of the Faure beam relative to the Louvain beam is thus 1.03 +/- 0.13 which could be expected from the similarity of the physical characteristics. Independent RBE measurements in a variety of systems also suggest similar biological properties. The depth variation of the RBE was found to be 4% (mouse gut) using 3 cm polyethylene filter over the depth range of 2.5 to 13.5 cm. This is in agreement with microdosimetry measurements using polyethylene filters of various thicknesses and with V79 measurements reported by Slabbert et al.

Animals↗
PubMed1990

Evaluation of a nonequilibrium isoelectric focusing (IEF) method for the simultaneous typing of esterase D (EsD), red cell acid phosphatase (AcP1), phosphoglucomutase (PGM1), adenylate kinase (AK), and adenosine deaminase (ADA).

A nonequilibrium isoelectric focusing method incorporating the chemical spacers MOPS and HEPES was developed and subsequently evaluated for its ability to reliably discriminate common and rare phenotypes in the esterase D (EsD), red cell acid phosphatase (AcP1), phosphoglucomutase (PGM1), adenylate kinase (AK), and adenosine deaminase (ADA) isoenzyme systems. The validation procedures used were blind testing, comparison of results to conventional methods, and evaluation of known rare variant phenotypes. This method proved to be a quick and reliable method for typing all five isoenzyme systems, while providing an excellent probability of discrimination (PD = 0.96).

Acid Phosphatase↗
PubMed1990

A comparison of the gamma component of two high energy neutron therapy beams.

Reciprocal neutron dosimetry intercomparisons have been undertaken between the National Accelerator Centre (NAC), South Africa, and the Université Catholique de Louvain (UCL), Belgium. A comparison of the gamma components measured in the respective therapy beams using the classic twin-detector method formed part of the study. This is important in clinical applications since the biological effects of neutrons and gamma rays are different. The gamma component under various irradiation conditions was derived from pairs of measurements with tissue equivalent ionization chambers and Geiger-Müller counters. The gamma component expressed as a fraction of the gamma dose relative to the total dose agreed within less than 0.01, with the measurements with the NAC Geiger-Müller counters being consistently higher than those with the UCL counter. A re-evaluation of the kU value of the UCL Geiger-Müller counter reduces the differences to less than 0.005 at NAC and less than 0.002 for the measurements at UCL. The results obtained are highly satisfactory in view of the complexity and difficulty of the measurements.

Fast Neutrons↗
PubMed1990

Neutron dosimetry intercomparisons between National Accelerator Centre, Université Catholique de Louvain and Clatterbridge Hospital.

Neutron dosimetry intercomparison studies have been undertaken at three neutron therapy facilities which have similar beam characteristics; viz. National Accelerator Centre, South Africa [p(66 MeV)+Be], Université Catholique de Louvain, Belgium, [p(65 MeV)+Be] and MRC Cyclotron Unit, Clatterbridge Hospital, U. K. [p(62 MeV)+Be]. The procedures followed at all centres were the same: tissue equivalent (TE) ionization chambers were first calibrated in 60Co beams and then exposed under various conditions in the respective neutron therapy beams. Measurements were made with the chambers flushed with TE gas or filled with static air. The neutron beam measurements differed by a maximum of 2.4%, whereas if only one particular type of ionization chamber is considered the spread in values is reduced to +/- 0.5%. The TE gas/air response ratios are consistent with calculated values. The results obtained are highly satisfactory and confirm that the dosimetry procedures adopted by the participating institutes conform to international standards.

Belgium↗
PubMed1989

Molecular analysis and nucleotide sequence of the adh1 gene encoding an NADPH-dependent butanol dehydrogenase in the Gram-positive anaerobe Clostridium acetobutylicum.

The nucleotide sequence of a 2081-bp fragment of Clostridium acetobutylicum DNA containing the adh1 gene was determined. The butanol dehydrogenase gene is referred to as the adh1 gene since it was shown to have activity using butanol and ethanol as substrates. The adh1 gene consisted of 1164 bp and encoded an alcohol dehydrogenase (ADH) enzyme of 388 aa residues with an Mr of 43,274. The adh1 gene was separated from an upstream open reading frame by an intergenic region of 354 bp. No promoter consensus sequences were identified in the intergenic upstream region and the adh1 gene did not appear to be expressed off its own promoter in Escherichia coli. Three separate types of ADH have been recognized. The ADH1 from C. acetobutylicum exhibited 39% homology with the Fe-containing ADH2 from Zymomonas mobilis and 37% homology with the ADH4 from Saccharomyces cerevisiae, but showed little or no homology with the other characterised types of ADH.

Alcohol Oxidoreductases↗
PubMed1989

Golf: an olfactory neuron specific-G protein involved in odorant signal transduction.

Biochemical and electrophysiological studies suggest that odorants induce responses in olfactory sensory neurons via an adenylate cyclase cascade mediated by a G protein. An olfactory-specific guanosine triphosphate (GTP)-binding protein alpha subunit has now been characterized and evidence is presented suggesting that this G protein, termed Golf, mediates olfaction. Messenger RNA that encodes Golf alpha is expressed in olfactory neuroephithelium but not in six other tissues tested. Moreover, within the olfactory epithelium, Golf alpha appears to be expressed only by the sensory neurons. Specific antisera were used to localize Golf alpha protein to the sensory apparatus of the receptor neurons. Golf alpha shares extensive amino acid identity (88 percent) with the stimulatory G protein, Gs alpha. The expression of Golf alpha in S49 cyc- kin- cells, a line deficient in endogenous stimulatory G proteins, demonstrates its capacity to stimulate adenylate cyclase in a heterologous system.

Adenylyl Cyclases↗
PubMed1989

Cloning and sequencing of an endoglucanase (end1) gene from Butyrivibrio fibrisolvens H17c.

The nucleotide sequence of a 2.8 kb DNA segment containing an endoglucanase gene (end1) from Butyrivibrio fibrisolvens H17c was determined. The B. fibrisolvens H17c gene was expressed from its own regulatory region in Escherichia coli and three putative consensus promoter sequences were identified upstream of a ribosome binding site and an ATG start codon. The complete amino acid sequence (547 residues) was deduced and homology with the Clostridium thermocellum celE gene product (EGE) was demonstrated. The endoglucanase contained a typical amino-terminal signal sequence and five repeated sequences (PDPTPVD) between amino acids 412-447. The endoglucanase showed relatively high endoglucanase activity against endoglucanase-specific substrates with beta 1-4 linkages but low activity against xylan and an exoglucanase-specific substrate, p-nitrophenyl-beta-D-cellobioside.

Amino Acid Sequence↗
PubMed1989

Molecular analysis of a novel glutamine synthetase of the anaerobe Bacteroides fragilis.

The nucleotide sequence of a 2777 bp DNA segment containing the Bacteroides fragilis glnA gene was determined. The B. fragilis glnA open reading frame of 2187 bp encoded a glutamine synthetase (GS) subunit of 729 amino acid residues with a calculated Mr of 82,827. The apparent Mr of the GS subunit determined by SDS-PAGE was approximately 75,000. A single mRNA transcription start point was identified upstream of the B. fragilis glnA open reading frame. The B. fragilis GS subunit is approximately 270 and 400 amino acids longer than the GSI and GSII subunits, respectively, of other prokaryotes and eukaryotes. The GSI and GSII holoenzymes are dodecamers and octamers respectively, whereas the GS of B. fragilis is a hexamer. Although GSI and GSII subunits show amino acid similarity in five conserved regions, this similarity is not strongly conserved in the B. fragilis GS. The GS of B. fragilis is not regulated by adenylylation and lacks the adenylylation site. It also lacks the Trp residue associated with the active site in GSI and GSII enzymes from other prokaryotes and eukaryotes.

Amino Acid Sequence↗
PubMed1989

Homology between hydroxybutyryl and hydroxyacyl coenzyme A dehydrogenase enzymes from Clostridium acetobutylicum fermentation and vertebrate fatty acid beta-oxidation pathways.

The enzymes NAD-dependent beta-hydroxybutyryl coenzyme A dehydrogenase (BHBD) and 3-hydroxyacetyl coenzyme A (3-hydroxyacyl-CoA) dehydrogenase are part of the central fermentation pathways for butyrate and butanol production in the gram-positive anaerobic bacterium Clostridium acetobutylicum and for the beta oxidation of fatty acids in eucaryotes, respectively. The C. acetobutylicum hbd gene encoding a bacterial BHBD was cloned, expressed, and sequenced in Escherichia coli. The deduced primary amino acid sequence of the C. acetobutylicum BHBD showed 45.9% similarity with the equivalent mitochondrial fatty acid beta-oxidation enzyme and 38.4% similarity with the 3-hydroxyacyl-CoA dehydrogenase part of the bifunctional enoyl-CoA hydratase:3-hydroxyacyl-CoA dehydrogenase from rat peroxisomes. The pig mitochondrial 3-hydroxyacyl-CoA dehydrogenase showed 31.7% similarity with the 3-hydroxyacyl-CoA dehydrogenase part of the bifunctional enzyme from rat peroxisomes. The phylogenetic relationship between these enzymes supports a common evolutionary origin for the fatty acid beta-oxidation pathways of vertebrate mitochondria and peroxisomes and the bacterial fermentation pathway.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1989

Estimation of left ventricular function on ECG-gated thallium-201 myocardial perfusion images.

ECG-gated thallium-201 perfusion images (GT) may provide information concerning left ventricular contraction. To assess the objectivity of this information, qualitative and quantitative evaluations of left anterior oblique GT images were performed in 600 patients and compared with contrast ventriculography (n = 180) and gated blood pool scintigraphy (n = 60). Cinematic playback of GT allowed qualitative rating of ventricular performance in 98% of studies. Abnormal GT (focal or global hypokinesis) was found in 41% of cases and could be related to myocardial infarction, nonischemic cardiomyopathy or left bundle branch block. Blinded readings showed reasonable interobserver agreement and correlation with blood pool scintigraphy regarding segmental and overall left ventricular function; decreased tracer uptake in an abnormally perfused segment presented only occasional difficulty. A quantitative index was derived by relating the increment in left ventricular cavity activity during contraction to myocardial count density; results were expressed as a planar ejection fraction (PEF). PEF correlated well with ejection fraction on blood pool scintigraphy (r = 0.83, P less than 0.001) and with contractility scores derived from ventriculography (P less than 0.001) and seemed suited for identification of hypokinetic ventricles. Thus, GT allows objective estimation of left ventricular function as an addendum to myocardial perfusion imaging.

Cardiac Output↗
PubMed1988

Chromosomal localization of genes encoding guanine nucleotide-binding protein subunits in mouse and human.

A variety of genes have been identified that specify the synthesis of the components of guanine nucleotide-binding proteins (G proteins). Eight different guanine nucleotide-binding alpha-subunit proteins, two different beta subunits, and one gamma subunit have been described. Hybridization of cDNA clones with DNA from human-mouse somatic cell hybrids was used to assign many of these genes to human chromosomes. The retinal-specific transducin subunit genes GNAT1 and GNAT2 were on chromosomes 3 and 1; GNAI1, GNAI2, and GNAI3 were assigned to chromosomes 7, 3, and 1, respectively; GNAZ and GNAS were found on chromosomes 22 and 20. The beta subunits were also assigned--GNB1 to chromosome 1 and GNB2 to chromosome 7. Restriction fragment length polymorphisms were used to map the homologues of some of these genes in the mouse. GNAT1 and GNAI2 were found to map adjacent to each other on mouse chromosome 9 and GNAT2 was mapped on chromosome 17. The mouse GNB1 gene was assigned to chromosome 19. These mapping assignments will be useful in defining the extent of the G alpha gene family and may help in attempts to correlate specific genetic diseases with genes corresponding to G proteins.

Animals↗
PubMed1988

G protein mRNA mapped in rat brain by in situ hybridization.

Guanine nucleotide-binding regulatory proteins (G proteins) mediate many receptor-coupled signal transduction events. We have localized in rat brain by in situ hybridization the mRNA for the G protein subunits--G alpha s, G alpha o, and G beta. Oligonucleotide probes were radiolabeled by a technique that resulted in a probe of defined specific activity and uniform length. mRNA species encoding G alpha s and G beta occur in high densities heterogeneously throughout the brain, especially in large neuronal cell bodies--e.g., hippocampal pyramidal cells, granule cells of the dentate gyrus, hypothalamic nuclei, and neurons of brainstem nuclei and the reticular formation. G alpha o mRNA has a more limited distribution and abundance, being detectable in the claustrum, endopiriform nucleus, habenula, hippocampal pyramidal cells, granule cells of the dentate gyrus, and cerebellar Purkinje cells.

Animals↗
PubMed1988

Structure of an endo-beta-1,4-glucanase gene from Clostridium acetobutylicum P262 showing homology with endoglucanase genes from Bacillus spp.

The nucleotide sequence of an endo-beta-1,4-glucanase gene of Clostridium acetobutylicum contained two putative extended promoter consensus sequences, a Shine-Dalgarno sequence and a TTG initiation codon. The nucleotide sequence of the gene coding for the C-terminal region of this enzyme was not required for activity. Extensive homology in the nucleotide and amino acid sequences of the endoglucanase genes from C. acetobutylicum and Bacillus spp. was demonstrated.

Amino Acid Sequence↗
PubMed1988

Molecular analysis and regulation of the glnA gene of the gram-positive anaerobe Clostridium acetobutylicum.

The nucleotide sequence of a 2.0-kilobase DNA segment containing the Clostridium acetobutylicum glnA gene was determined. The upstream region of the glnA gene contained two putative extended promoter consensus sequences (p1 and p2), characteristic of gram-positive bacteria. A third putative extended gram-positive promoter consensus sequence (p3), oriented towards the glnA gene, was detected downstream of the structural gene. The sequences containing the proposed promoter regions p1 and p2 or p3 were shown to have promoter activity by subcloning into promoter probe vectors. The complete amino acid sequence (444 residues) of the C. acetobutylicum glutamine synthetase (GS) was deduced, and comparisons were made with the reported amino acid sequences of GS from other organisms. To determine whether the putative promoter p3 and a downstream region with an extensive stretch of inverted repeat sequences were involved in regulation of C. acetobutylicum glnA gene expression by nitrogen in Escherichia coli, deletion plasmids were constructed lacking p3 and various downstream sequences. Deletion of the putative promoter p3 and downstream inverted repeat sequences affected the regulation of GS and reduced the levels of GS approximately fivefold under nitrogen-limiting conditions but did not affect the repression of GS levels in cells grown under nitrogen-excess conditions.

Amino Acid Sequence↗
PubMed1987

Molecular cloning of five GTP-binding protein cDNA species from rat olfactory neuroepithelium.

Biochemical studies in vertebrate olfactory tissue indicate that certain odorants stimulate adenylyl cyclase in a GTP-dependent manner. Additionally, immunochemical and toxin-labeling studies demonstrate the presence of several GTP-binding protein (G-protein) species in vertebrate olfactory epithelium. To identify the G-protein(s) responsible for olfactory signal transduction, we screened a rat olfactory cDNA library with an oligonucleotide probe and isolated 32 recombinant clones encoding five distinct types of G-protein alpha subunits. The majority of the clones encoded G alpha s, while the remaining clones encoded G alpha o, G alpha i1, G alpha i2, and a novel species, G alpha i3. Messenger RNA corresponding to each G alpha was detectable in all tissues examined; however, the levels for a given G alpha varied in a tissue-specific manner. In olfactory tissue, G alpha s was the most abundant of these messages and in combination with the biochemical studies suggests that G alpha s is the G-protein component of the olfactory signal transduction cascade.

Amino Acid Sequence↗
PubMed1987

Some family social background, developmental, and behavioural characteristics of nine year old children with asthma.

Children with moderate and severe, mild, and trivial asthma were compared with a group of children who did not have asthma on a range of measures including family social background (socioeconomic status, family adversity, family environment), intelligence, reading, spelling, and behaviour. None of the background measures significantly differentiated among the groups. The group of children with moderate and severe asthma was found to have a significantly lower mean score for verbal intelligence, full scale intelligence, and spelling than those with mild asthma, but did not differ significantly from the remainder of the sample. Children with mild asthma were found to have slightly higher reading scores.

Asthma↗
PubMed1987

Open access to orthopaedic appliances for general practitioners.

A clinic to which general practitioners can refer patients for some types of orthopaedic appliances was opened in North Clwyd in 1983. During 1985, 956 patients were referred by 82 general practitioners; 860 patients received an appliance, and the average waiting time was less than five weeks. Most referrals were for soft collars (44%), lumbar sacral supports (30%), and dorsilumbar supports (7%). Thirty eight patients failed to attend, 54 declined an appliance, and four referrals were considered to be inappropriate. A few patients were subsequently referred to consultant outpatient clinics, 22 for physiotherapy and 34 were referred simultaneously to the open access clinic. The referral rates for general practitioners with access to community hospitals were low. Such an arrangement merits wider consideration.

Aged↗