Biomedical subjects
Publications and source records attributed to D Walker.
A method is described for facilitating staffing decisions by determining productivity standards for each defined nursing unit. Results include improved patient care, reduced staffing costs and team building among hospital departments.
A collaborative study has been organised by NIBSC to examine the performance of FIXa assays between laboratories, and to investigate the need for a standard. Ampoules of 3 materials, one monocomponent concentrate (coded C) and 2 different preparations of purified human FIXa (one proposed reference preparation, coded A and a test material coded B), have been assayed in 11 laboratories for FIXa using either the NIBSC method or a local method, with local standards (if available, coded D) to determine their potencies. The data showed high between assay variability; with the exception of one laboratory, most of the between assay variation expressed as %geometric coefficients of variation (gcv) were over 15%. The interlaboratory gcv when preparation B was assayed against the local standard was over 1700%, suggesting that most of the local standards are poorly calibrated. The %gcv was improved to 80% when reference A was used as the standard. These data clearly show that an international reference standard for FIXa would help to standardise FIXa preparations and would also improve in house assays for FIXa. However, an accelerated degradation study has shown that reference A is not suitable as a long term standard and another material with suitable stabilizers has to be established as an international standard for FIXa.
We have identified a second hepatic control region (HCR-2) in the human apolipoprotein (apo) E gene locus that confers liver expression of the human apoE gene in transgenic mice. This HCR-2 sequence is located 27 kilobases downstream of the apoE gene and 10 kilobases downstream of the previously described liver-specific enhancer (HCR-1). Nucleotide sequence analysis of the HCR-2 region revealed a sequence that shares 85% identity to the functional 319-base pair domain of HCR-1. To test its activity, transgenic mice were prepared with a fusion construct containing a human apoE gene fragment, which is not normally expressed in the liver, ligated to a 632-base pair region containing the HCR-2 sequence. This construct resulted in high levels of liver-specific apoE transgene expression, indicating that HCR-2 can function as a hepatic enhancer and has an activity similar to that of HCR-1. Hence, these findings suggest that there are at least two hepatic control regions, HCR-1 and HCR-2, capable of controlling the liver expression of this human apolipoprotein gene locus.
The specificity of expression in the liver of the human apolipoprotein (apo) E/C-I gene locus is determined by a hepatic control region (HCR) that is located 15 kilobases downstream of the apoE gene. DNase I footprint studies of this sequence using nuclear extracts identified a region of the HCR that is enriched in nuclear protein-binding sites. Nuclease analysis of chromatin revealed liver-specific DNase I-hypersensitive sites that were associated with this region, and additional liver-specific nuclease-sensitive sites associated with the apoE gene were identified. The HCR domain has a limited binding affinity for the nuclear scaffold. The specific domain required for liver expression was tested by ligating subfragments of the HCR to the apoE gene and examining their activity in transgenic mice. A segment of 319 nucleotides that contained several potential regulatory sequences was required for full activity of liver-specific transcription with shorter segments yielding much lower levels of expression in the liver. All constructs that contained a fully active HCR were expressed in approximately a copy-dependent manner, suggesting that transgene expression was independent of integration position. Taken together, the properties of the HCR are consistent with its function as a locus control region for the liver-specific expression of the apoE gene.
Proteins are translocated across the thylakoid membrane by two distinct pathways in higher plant chloroplasts, one of which is related to prokaryotic Sec-dependent translocation mechanisms. SecY is an essential, hydrophobic component of the membrane-bound translocase complex in bacteria, and we report here the nucleotide sequence of a full-length cDNA encoding a homolog of SecY from Arabidopsis thaliana. The predicted protein of 551 residues includes an amino-terminal extension of approximately 120 residues when compared with other SecY proteins. The deduced sequence of the mature protein, cpSecY, is 41% identical with SecY from Synechococcus and 33% identical with the Escherichia coli protein. The extension serves to target the protein into chloroplasts; transcription-translation of the cDNA yields a 58-kDa precursor protein which is imported into pea chloroplasts, processed to a product of 46 kDa, and targeted into the thylakoid membrane.
We have identified and characterized a previously unreported human gene that is found within the apolipoprotein (apo) E/C-I/C-II gene locus. On the basis of its location and its properties, this new gene has been designated APOC4. Nucleotide sequence analysis of genomic DNA and liver cDNA clones revealed a 3.3-kb gene consisting of three exons and two introns. Its 3' terminus lies 555 bp upstream of APOC2, giving both genes the same transcriptional orientation. The promoter of the APOC4 gene lacks a typical TATA box, consistent with an apparent heterogeneity in transcription start sites. RNase protection analysis indicated relatively low apoC-IV mRNA levels in human liver, compared to apoC-II mRNA levels. The predicted apoC-IV protein sequence, comprising 127 amino acid residues, contains a putative 25-residue signal peptide and two potential amphipathic alpha-helical domains. Amino acid sequence comparisons indicate a limited homology between apoC-IV and either apoC-I or apoC-II. Since its hepatic expression and predicted protein structure are characteristic of the other genes in this cluster, we propose that the APOC4 gene is a member of the apolipoprotein gene family.
The single-cell gel electrophoretic (SCGE) technique for detecting the presence of DNA strand breaks and alkali-labile damage in individual cells was used to examine the effect on newborn infants of maternal exposure to cigarette smoke. The levels of DNA damage in the lymphocytes of 21 newborns of mothers with different smoking habits were compared to those in 10 newborn infants whose mothers had never smoked and 8 newborns whose mothers were passively exposed for at least 40 h per week in the workplace and home. DNA damage was undetected in lymphocytes of newborns of passively exposed mothers or newborns with mothers of low smoking habit by conditions allowing 40 min DNA unwinding and 40 min electrophoresis. Presumably longer times were needed for lower levels of damage to be detected by SCGE. The mean length of DNA migration in lymphocytes between the newborns of smoking mothers did not show any significance but the percentage of damaged cells increased with the frequency of smoking when assessed by non-parametric Mann-Whitney U test. The results of SCGE were compared with our results published in the same individuals of sister-chromatid exchange (SCE) frequency. The results show similar trends with mean measures of DNA damage increasing with frequency and long history of maternal smoking. These observations encourage the application of SCGE as a sensitive and useful technique for quantitating DNA damage in individual cells.
BACKGROUND: The incidence of nosocomial bloodstream infections has increased twofold to threefold in the past decade, and central venous catheter infections account for about 90% of catheter-related nosocomial bloodstream infections. Many studies of risk factors for central venous catheter complications have been conducted, resulting in recommendations for preventive strategies, but few data are available regarding the frequency with which such strategies are employed in clinical practice. METHODS: A survey was conducted of persons attending a meeting of the National Association of Vascular Access Networks in New Orleans on September 25, 1992. The survey contained 15 questions related to central venous catheters regarding infection control measures, measures to maintain patency, and use of the catheter for obtaining blood specimens for diagnostic tests. RESULTS: Ninety-two persons from 24 states completed the questionnaire as representatives of 23 teaching hospitals, 21 nonteaching hospitals, and 48 home health agencies. Transparent dressings were used more frequently (88%) than cotton gauze (27%). Alcohol and povidone-iodine solutions were the most frequently used antiseptics. Antimicrobial ointment was used by fewer than half; of these 86% used povidone-iodine and 26% used polymyxin-neomycin-bacitracin. Heparin flushes were still being used by 97% to maintain patency. Most (82%) used central venous catheters to draw blood cultures; of these, 68% drew only qualitative cultures and 32% drew quantitative cultures in addition to or instead of qualitative cultures. CONCLUSIONS: Significant diversity of practice was documented among the health care organizations represented in this survey. Some of the practices documented in this survey have been associated with higher rates of bloodstream infection; this may partially explain the observed increase during the past decade in the incidence of nosocomial bloodstream infections.
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Assessment of perioperative bleeding disorders, especially those related to platelet dysfunction, remains a clinical challenge. The management of the bleeding patient in the operating theatre or on the postoperative ward is often empirical with little scientific basis. Much of the reason for this is that conventional clotting studies are not immediately available and there is a perceived urgency, particularly among trainee doctors, to treat bleeding disorders without first establishing the exact nature of the coagulopathy. SCT provides useful information on platelet function, particularly in patients after cardiopulmonary bypass, and has enabled practitioners to rationalize the management of bleeding disorders and not expose their patients to the risks of unnecessary transfusion of blood products. Undoubtedly further studies are required before this instrument can be used reliably in the clinical setting but it may prove to be a useful addition to the available techniques for monitoring perioperative bleeding disorders.
A total of nearly 800 base pairs of mitochondrial DNA sequence was assayed in each of 52 musk turtles (Sternotherus minor) collected across the species' range in the south-eastern USA. About one-half of the sequence information in effect was accessed by conventional recognition-site assays of the entire mtDNA molecule; the remainder came from direct sequence assays of a normally hypervariable 5' section of the noncoding control region. The two assay methods produced essentially nonoverlapping sets of variable character states that were compared with respect to magnitudes and phylogeographic patterns of mtDNA variation. The two assay procedures yielded nearly identical outcomes with regard to: (a) total levels of species-wide mtDNA genetic variation; (b) mean levels of within-locale variation; (c) extremely high population genetic structure; (d) a phylogenetically significant separation of samples from the north-western half of the species' range vs. those in the south-eastern segment; and (e) considerably lower genetic variability within the north-western clade. The micro- and macro-phylogeographic mtDNA patterns in the musk turtle are consistent with a low-dispersal natural history, and with a suspected longer-term biogeographic history of the species, respectively.
A stop codon in the precore genome of the hepatitis B virus (HBV) in anti-HBe positive HBV carriers may be associated with a more progressive form of HBV infection. Earlier studies, however, were mainly performed in patients from the Mediterranean area who had severe infection. The aim of this study was to evaluate the prevalence of precore mutants in an unselected population living in northern Europe. Twenty of 42 of these patients are infected predominantly with a virus strain, which has the typical stop codon in the precore genome, characterised by a mutation at base 83. In six patients there was an additional G to A mutation at base 86 of the precore genome. Statistical analysis showed no difference between the patients with or without a stop codon in the precore genome. When patients with a double mutation at base 83 and 86 of the precore genome were compared with the other anti-HBe positive HBV carriers, however, the corresponding clinical data were worse. Therefore we suggest, that it is not the stop codon in the precore gene itself, but the occurrence of a double mutation at bases 83 and 86, which is associated with a more severe course of disease in anti-HBe positive HBV carriers.
We describe the use of a fat-based low density oral contrast agent in computed tomography (CT) of the upper abdomen. It has a CT number of -71 Hounsfield units (HU) and allows excellent visualization of the bowel wall and adjacent structures as well as reducing the artefacts seen with iodinated high density contrast.
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Tourette's syndrome (TS) is a complex inherited neuropsychiatric disorder that is characterized by multiple motor and phonic tics. Stress-related fluctuations in symptom severity and medication responsiveness are common, and patients often report that tics are worsened by fatigue, emotional trauma, and anxiety. We examined the effects of lumbar puncture (LP) stress on plasma adrenocorticotropin (ACTH) and cortisol, urinary catecholamines, and self- and clinician ratings of anxiety in 13 medication-free TS patients and 10 normal controls, ages 17 to 41 years. The TS patients secreted significantly more ACTH than the normal controls in response to the stress of the lumbar puncture. Compared to the controls the TS patients had significantly greater postLP mean and postLP peak ACTH levels. The TS patients also excreted significantly more norepinephrine in the 20 hr preceding the lumbar puncture and reported higher levels of anxiety before and during the procedure than the controls. In addition, urinary norepinephrine excretion of the TS patients was significantly correlated with clinician ratings of tic severity. The results were not related to current levels of depression and anxiety. Taken together, these findings suggest that a subset of TS patients may be characterized by heightened reactivity of the hypothalamic-pituitary-adrenal axis and related noradrenergic sympathetic systems.
Two NADPH-dependent metabolic routes for the anticancer drug ifosfamide, 4-hydroxylation (activation) and N-dechloroethylation (a detoxication pathway), were studied in human liver microsomes to identify the cytochrome P450 enzymes involved. Naringenin, a grapefruit aglycone and an inhibitor of cytochrome P450 3A4 (CYP3A4)-catalysed reactions, was found to inhibit ifosfamide activation and N-dechloroethylation by human liver microsomes. IC50 for both reactions was of the order of 70 microM. The CYP3A4-specific inhibitor triacetyloleandomycin inhibited ifosfamide N-dechloroethylation by human liver microsomes with an IC50 of approximately 10 microM. Furthermore, anti-human CYP3A4 antiserum inhibited by about 80% N-dechloroethylation of ifosfamide by human liver microsomes. The relative levels of cytochromes P450 1A, 2C, 2E and 3A4 in 12 human livers were determined by western blotting analysis. A strong correlation (P < 0.001) was observed between CYP3A4 expression and both activation and N-dechloroethylation of ifosfamide. A role for human CYP3A4 in both pathways of ifosfamide metabolism was thus demonstrated. This was substantiated by the observation that the nifedipine oxidase activities of the 12 samples of human liver microsomes correlated with ifosfamide activation (P < 0.009) and N-dechloroethylation (P < 0.001). These findings have important clinical implications. The involvement of the same key cytochrome P450 enzyme in both reactions prohibits selective inhibition of the N-dechloroethylation pathway, as might be desirable to reduce toxic side effects. They also demonstrate the need to consider interaction with co-administered drugs that are CYP3A4 substrates.