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Biomedical subjects

D J Wright

Publications and source records attributed to D J Wright.

At least 163 records · Page 9Linked to original sources
PubMed1989

The negative charge of Glu-111 is required to activate the cleavage center of EcoRI endonuclease.

King et al. (King, K., Benkovic, S. J., and Modrich, P. (1989) 264, 11807-11815) have shown that Glu-111 is required for DNA cleavage by EcoRI endonuclease and have suggested that this residue is required for activation of the cleavage center upon specific recognition. We have substituted Gln or Asp for Glu-111 by oligonucleotide-directed mutagenesis. First and second strand cleavage rate constants are reduced by a factor of more than 10(4) by the Gln-111 substitution. However, these rate constants are enhanced 9-fold when pH is increased from 7.6 to 8.5, which enhances strand cleavage at EcoRI sites by wild type endonuclease to a similar degree. The specific affinity of Gln-111 endonuclease for EcoRI sites is 1000 times greater than that of wild type enzyme reflecting a decrease in the rate constant governing specific complex dissociation. In contrast to Gln-111 endonuclease, the equilibrium specific affinity of Asp-111 endonuclease for the EcoRI sequence is similar to that of wild type enzyme, and first and second strand cleavage rate constants are reduced only 100-fold relative to wild type enzyme. These results suggest that a negative charge on residue 111 is required for strand cleavage and are consistent with participation of Glu-111 in activation of the DNA cleavage center, with energy associated with specific sequence recognition driving this process.

DNA, Bacterial↗
PubMed1989

Collateralization of the amygdaloid projections of the rat prelimbic and infralimbic cortices.

Previous studies indicate that the distribution of corticoamygdaloid neurons in the rat prelimbic (PL) and infralimbic (IL) cortices overlaps with the distribution of neurons projecting to the contralateral medial prefrontal cortex (MPC), insular cortex, mediodorsal thalamus, and dorsal medulla. In view of the poorly differentiated cytoarchitecture of PL and IL, and their designation as cortical regions transitional between the allocortex and isocortex, the present study sought to determine whether several cortical and subcortical projections from these areas arise as collaterals of corticoamygdaloid neurons. Injections of the fluorescent dyes Fast Blue (FB) or bisbenzimide (BB) were made into the amygdaloid complex and the following areas: agranular and granular insular cortices; mediodorsal thalamic nucleus (MD); nucleus tractus solitarii/dorsal medulla (NTS); contralateral amygdaloid complex; and ipsilateral and contralateral MPC. Neurons projecting to the ipsilateral amygdaloid complex were located mainly in layers II and V with fewer cells in layer III. Concomitant injections into the insular cortex, MD, and NTS labeled populations of neurons arranged in laminae that partially overlapped with, but were essentially separate from, corticoamygdaloid neurons. Projections to the insular cortex arose from layers II and V; those to MD arose from layers V and VI. Corticobulbar projections from IL originated from neurons arranged in a thin lamina in the deep part of layer V. Very few neurons projecting to both the amygdaloid complex and any of these areas were observed. Bilateral injections of FB and BB into the amygdaloid complex producted very few double-labeled cells in PL and IL. Further, in layer V, ipsilaterally projecting corticoamygdaloid neurons tended to be located more deeply than contralaterally projecting neurons. Combined injections of BB and FB into the amygdaloid complex and the contralateral (but not ipsilateral) MPC resulted in significant numbers of double-labeled neurons in layers II, III, and V of PL and IL. Control injections of fluorescent dyes into the cerebrospinal fluid labeled few neurons in the superficial layers of PL and IL and a combined injection into the amygdaloid complex (FB) and subarachnoid space (BB) resulted in a very small number of double-labeled cells in layer II only. The results suggest that a significant proportion of neurons in PL and IL projecting to the amygdaloid complex issue collaterals innervating the contralateral MPC. Evidence is discussed that suggests that the interhemispheric collaterals of MPC corticoamygdaloid neurons may serve to correlate the amygdaloid outputs of the MPC bilaterally.

Amygdala↗
PubMed1989

Verotoxin-producing Escherichia coli infections in Sheffield: cattle as a possible source.

During 1986 and 1987, faecal samples from patients with haemorrhagic colitis (HC) or haemolytic-uraemic syndrome (HUS) were examined for evidence of infection by verotoxin-producing Escherichia coli (VTEC). During the 2-year period VTEC infections were found in 31 (78%) of 40 patients initially presenting with HC, and in 5 (63%) of 8 patients initially presenting with HUS. VTEC were found in only 2 (0.9%) of 229 age and sex matched control patients with acute non-bloody diarrhoea. All but one VTEC belonged to E. coli serogroup O 157. During 1987 this serogroup was isolated from 2 (1%) of 207 samples of faeces taken from cattle arriving at a Sheffield abattoir, indicating a possible source of these infections for man. We are unaware of previous reports of isolation of this organism from cattle in England.

Adolescent↗
PubMed1989

Comparison of immunofluorescence and enzyme linked immunosorbent assays for diagnosing Lyme disease.

A new enzyme linked immunosorbent assay (ELISA) method was assessed in parallel with an indirect immunofluorescence assay (IFA) for the serological testing of specimens submitted for detection of Lyme disease. Wells of an ELISA microtitre plate were coated with sonicated whole cells of Borrelia burgdorferi in carbonate buffer. After overnight incubation at 4 degrees C the plates were washed three times, then incubated at 37 degrees C for an hour sequentially with a blocking solution, diluted test serum, anti-human IgG horseradish peroxidase conjugate, and finally for half an hour at room temperature with o-phenylenediamine substrate before being read at 492 nm. Absorbance results were converted into arbitrary ELISA units. Of a total of 1760 sera, 146 (8.3%) were positive: of these 92 (63%) were positive by both methods, five (3.4%) by IFA alone, and 49 (33.6%) by ELISA alone. The ELISA was better suited for testing large numbers of specimens and easier to interpret than IFA.

Antibodies, Bacterial↗
PubMed1989

Serum albumin and the specificity of free tri-iodothyronine as a test for hypothyroidism.

Serum free tri-iodothyronine (FT3), using two different radioimmunoassays, and serum albumin, using bromocresol green dye-binding method, were measured prospectively in 1374 adults investigated for thyroid disease. The results of similar pairs of measurements in 6608 serum specimens obtained from adults, but using one of the radioimmunoassays for FT3, were examined retrospectively. A close correlation was observed between the FT3 values and serum albumin concentration. Normalisation of the FT3 level using a standard albumin value of 43 g/L in the absence of chemical evidence of hypothyroidism (serum thyrotrophin less than 6.5 mIU/L) gave a distribution of FT3 values which closely resembled that from a normal population. The effects of acute illness and old age, which may lower the FT3 value, can be corrected by this transformation.

Adult↗
PubMed1989

Interpretation of chorionic villus sampling laboratory results is just as reliable as amniocentesis.

Karyotypes of chorionic villi have been said to be less accurate than karyotypes of amniocytes. Karyotypic differences between placental and fetal tissue and maternal-cell contamination could potentially complicate clinical management. We compared cytogenetic results obtained by chorionic villus sampling and amniotic fluid cells in our center during a 2-year period (1986-1987). Chorionic villus sampling material was processed for direct analysis and backed up when indicated (now routinely) with tissue cultures. The incidence of inconclusive results requiring additional studies was 1.2% for chorionic villus sampling and 0.75% for amniotic fluid cells. Mosaicism was the most common problem for both chorionic villus sampling and amniotic fluid cells. Failure of growth was more frequent in amniocentesis material (0.35 versus 0.09%), but polyploidy and atypical aneuploidies were greater with chorionic villus sampling. The accuracy of cytogenetic evaluation by chorionic villus sampling and amniotic fluid cells and the need for additional invasive procedures appear to be equal in our laboratory.

Amniocentesis↗
PubMed1988

Isolation and expression of a pea vicilin cDNA in the yeast Saccharomyces cerevisiae.

A cDNA clone containing the complete coding sequence for vicilin from pea (Pisum sativum L.) was isolated. It specifies a 50,000-Mr protein that in pea is neither post-translationally processed nor glycosylated. The cDNA clone was expressed in yeast from a 2 micron plasmid by using the yeast phosphoglycerate kinase promoter and initiator codon. The resultant fusion protein, which contains the first 16 amino acid residues of phosphoglycerate kinase in addition to the vicilin sequence, was purified and subsequently characterized. It has slightly slower mobility on SDS/polyacrylamide-gel electrophoresis than standard pea vicilin and forms a mixture of multimers, some of which resemble the native protein.

Amino Acid Sequence↗
PubMed1988

Segmental splenectomy using the ultrasonic surgical aspirator.

The technique described seems to significantly decrease blood loss in segmental splenectomy. Resection of the damaged splenic segments offers the potential advantage of reducing rebleeding and secondary hemorrhage from sites of repaired lacerations. Also, the viable splenic fragment that is left behind may afford protection from postsplenectomy sepsis. The ultrasonic surgical aspirator seems well suited for the purpose of segmental splenectomy in both the trauma and staging laparotomy setting.

Humans↗
PubMed1988

Interleukin-1 and tumour necrosis factor cause hypotension in the conscious rabbit.

1. The cardiovascular effects of intravenous injections of interleukin-1 (IL-1) and tumour necrosis factor (TNF) have been investigated in the conscious rabbit. They have been compared with the effects of bacterial lipopolysaccharide (LPS) because both IL-1 and TNF are released from macrophages by LPS. 2. IL-1, TNF and Escherichia coli J5-LPS all caused hypotension when given intravenously in a dose with low mortality. The time course of the hypotension caused by IL-1 and LPS was similar, although the maximal fall in mean blood pressure occurred earlier after IL-1. TNF produced a more sustained fall in blood pressure. Hypotension was not accompanied by a compensatory tachycardia after any of the test substances. Hypotension was associated with a fever after TNF, hypothermia after LPS and no significant change in temperature after IL-1. 3. The packed cell volume did not change during hypotension in any of the study groups, implying that the hypotension was not due to fluid loss resulting from increased capillary permeability. 4. IL-1 and TNF are candidates for the role of effectors of LPS-induced hypotension.

Animals↗
PubMed1988

Segmented arrangement of Borrelia duttonii DNA and location of variant surface antigen genes.

The DNA of an isolate of Borrelia duttonii, an agent of relapsing fever is present as seven major species ranging in size from 10 kb to greater than 150 kb. Additionally, this isolate contains low copy number species, both smaller and larger than these seven major elements. No one of these individual DNA species obviously corresponds to the bacterial chromosome, unlike the situation in Borrelia hermsii, another relapsing fever Borrelia. Thus it appears that B. duttonii has a unique segmented arrangement of its genetic material. Cloned DNA fragments containing coding sequences specific for variant surface antigens of B. duttonii hybridize to a closely migrating, high copy number subset of these genetic elements.

Animals↗
PubMed1988

The neurological complications of Borrelia burgdorferi in the New Forest area of Hampshire.

The neurological complications of Borrelia burgdorferi infection have only recently been recognised in the United Kingdom. Eight cases are reported which were all contracted in the New Forest area of Hampshire. The majority of patients had Bannwarth's syndrome though meningism and parenchymal lesions also occurred. All patients made a virtually complete neurological recovery in contrast to some patients with Lyme disease.

Adult↗
PubMed1988

Why the assay of serum cystine by protein precipitation and chromatography should be abandoned.

The higher bias of serum cystine estimations by a HPLC method compared with those by ion exchange techniques is shown to be largely due to differences in the sample preparation procedures of the two techniques. The ion exchange methods utilised sulphosalicylic acid serum protein precipitation and post-column ninhydrin derivatisation of cystine, whilst the high pressure liquid chromatography technique employed automated dialysis for removal of proteins and pre-column ortho-phthalaldehyde derivatisation of cystine after its conversion to cysteine and then to S-carboxymethylcysteine. Examination of these procedures showed that whilst the high pressure liquid chromatographic method accurately estimates total serum cystine and cysteine, many factors affect the precision and accuracy of serum cystine estimations using the ion exchange techniques. In particular, serum protein precipitation techniques that are currently employed for the preparation of samples for cystine analysis by ion exchange chromatography should be abandoned.

Blood Proteins↗
PubMed1988

Changing concepts of deep venous thrombosis of the upper extremity--report of a series and review of the literature.

Deep venous thrombosis (DVT) of the upper extremity has recently been recognized as being more common than previously reported (probably because of the increasingly frequent use of subclavian venous access). A retrospective review of patients in whom subclavian or axillary DVT had developed in the past 6 years (1980 to 1986) was conducted at the Akron General Medical Center. The major cause identified was related to subclavian venous catheterization, which accounted for 39% of all instances of subclavian and axillary DVT. Our results are correlated with a review of the literature. In our review of studies in which subclavian venous catheterizations were prospectively examined with use of objective means of diagnosis, we found that 28% of all subclavian catheterizations had venous thrombosis develop, often subclinically. This is not an innocuous disease, as suggested in the past; in our series 12% of upper-extremity DVT had pulmonary embolization (PE). In reviewing the recent literature, we found an average 12.4% incidence of PE, which often occurs during anticoagulation treatment. Diagnostic modalities are discussed and treatment regimens are reviewed along with an extensive literature review.

Arm↗
PubMed1988

Lyme disease.

Lyme disease is being increasingly diagnosed in the UK. The clinical picture, laboratory diagnosis and treatment of the disease are described and aspects of the pathology and epidemiology are highlighted.

Humans↗
PubMed1987

Application of high-performance liquid chromatography to the assessment of subunit heterogeneity in plant 11S storage globulins.

Plant 11S storage proteins from a wide range of species have been resolved into their component subunits by ion-exchange fast protein liquid chromatography under denaturing conditions. The complex profiles obtained were reproducible and characteristic for each plant species analysed. The technique is shown to have distinct advantages over the more conventional electrophoretic approaches used to assess 11S subunit heterogeneity. The potential for the fast protein liquid chromatographic method as a simple screening system is discussed.

Chromatography, High Pressure Liquid↗