Biomedical subjects
Publications and source records attributed to D Chapman.
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In order to examine the status of G-proteins in congestive heart failure due to myocardial infarction, the left coronary artery in rats was ligated and animals assessed after 4, 8 and 16 weeks. Sham-operated control and experimental animals were used for the preparation of membranes from the viable (uninfarcted) left and right ventricles. Adenylyl cyclase activities in the presence of pertussis toxin and cholera toxin were increased and decreased in left ventricles from all groups, respectively. On the other hand, adenylyl cyclase activities in 8 and 16-week experimental right ventricles were unaltered in the presence of pertussis toxin and increased in the presence of cholera toxin. Depression of adenylyl cyclase activities in left ventricles from all groups as well as in the right ventricle at 4 weeks were not evident when enzyme activity was determined in the pertussis toxin-treated membranes in the absence or presence of Gpp(NH)p. Cholera toxin-catalyzed ADP ribosylation was decreased in left ventricles from all infarcted groups and increased in the right ventricles at 8 and 16 weeks whereas the pertussis toxin-catalyzed ADP ribosylation was increased in all experimental tissues except in the right ventricles at 8 and 16 weeks. G(s alpha)-protein content was decreased in the left ventricle at 16 weeks and increased in the right ventricles at 8 and 16 weeks of myocardial infarction. On the other hand, G(i alpha)-protein content was increased in left ventricles from all infarcted groups and the 4-week right ventricle but was unaltered in 8 and 16-week right ventricles. An increase in mRNA abundance for G(i alpha)-protein was seen in both left and right ventricles following myocardial infarction. A significant increase in mRNA level for G(s alpha)-protein was observed in all left ventricles and 8-week right ventricle following the coronary occlusion. These results suggest that changes in Gs- and Gi-proteins in the failing heart due to myocardial infarction are chamber-specific and are dependent upon the stage of congestive heart failure.
In April 1997 the ILCOR Basic Life Support advisory statements were announced in conjunction with changes to the recovery position for use in the UK. This study compared the new and old positions by using a questionnaire to assess how well each position satisfied the ILCOR statements. The study was carried out over six different hospital trusts by eight resuscitation training officers. Each tutor alternately taught the 1992 or 1997 recommended positions. After the practical session each student completed a questionnaire on ease of learning and use of the position, as well as other factors such as spinal stability. They were also asked to score the position when they were placed in recovery by other students. Their competency was assessed using the ALS criteria. Over the duration of the study 687 forms were suitable for analysis. For every question there was a significant trend in favour of the 92 position, with students finding the technique easier to learn and use, simpler for positioning for CPR and with less spinal movement during rolling. Possible sources of bias such as previous training, tutor or staff grade made no statistical difference to the results. When performed competently the 1997 position appears to cause less brachial compression, but other problems with learning or use of the 97 position outweigh this advantage. The 1992 position currently provides the best compromise between ease of use, spinal stability and other factors, and better satisfies the ILCOR advisory statements.
Synovial sarcoma is a relatively common sarcoma in adults, which in its classic bimorphic form infrequently poses a diagnostic problem. Monomorphic spindled variants, as well as the less common poorly differentiated variants, may be confused with other soft-tissue sarcomas; the poorly differentiated variant (PDSS), in particular, may be histologically indistinguishable from other small, blue, round cell tumors, including primitive neuroectodermal tumors (PNETs). Detection of the synovial sarcoma-associated t(X;18) by either cytogenetic or molecular genetic approaches may be necessary to confirm the diagnosis of synovial sarcoma in difficult cases. We evaluated 10 cases of PDSS from eight patients using a panel of antibodies (including those to intermediate filament proteins, nerve-sheath associated markers, and neuronal and neuroectodermal associated markers) in order to better establish the immunophenotype of this tumor and to help distinguish it from the tumors with which it may be confused, particularly PNETs and high-grade malignant peripheral nerve sheath tumors (MPNSTs). Our results showed PDSS to have significant immunophenotypic overlap with both PNETs and MPNSTs. In most instances these three entities may be differentiated by a panel of antibodies that should include those to both low and high molecular weight cytokeratins, epithelial membrane antigen, type IV collagen, CD99, CD56, and S-100 protein. Our results also suggest that synovial sarcoma may be a tumor showing combined neuroectodermal and nerve sheath differentiation--perhaps because of translocation-associated expression of specific proteins--rather than a carcinosarcoma of soft tissues or a tumor of specialized arthrogenous mesenchyme.
Lung hernia is an uncommon entity usually resulting from trauma or inadequate healing from recent or remote thoracic surgery. A small percentage may be congenital. Four cases are reported, each demonstrating lung herniation resulting from either accidental or postsurgical trauma. Most of the previous cases have been reviewed in various surgical and radiological journals with only rare mention in the emergency medicine literature. Because emergency physicians may be the most immediate contact for patients who develop a lung herniation, they should be cognizant of this entity as a possible delayed complication to chest wall injury. Awareness of the clinical and radiological appearance of lung hernia will help to avoid its confusion with other conditions such as subcutaneous emphysema, chest tumor, pneumothorax, or a focus of infection.
Diffraction enhanced imaging is a new x-ray radiographic imaging modality using monochromatic x-rays from a synchrotron which produces images of thick absorbing objects that are almost completely free of scatter. They show dramatically improved contrast over standard imaging applied to the same phantom. The contrast is based not only on attenuation but also the refraction and diffraction properties of the sample. This imaging method may improve image quality for medical applications, industrial radiography for non-destructive testing and x-ray computed tomography.
A system for area-beam energy-subtraction monochromatic radiography was developed and tested. It utilizes a bent Laue crystal monochromator developed at the National Synchrotron Light Source (NSLS), and a compact rotating anode X-ray source developed at the Science Research Laboratory (SRL). The K(alpha) characteristic lines (both K(alpha 1) and K(alpha 2) of the cerium and barium targets were diffracted by the monochromator and used for the above- and below-K-edge imaging, respectively, of phantoms with iodine contrast agents. Digital subtraction of the images produced an iodine image.
BACKGROUND: The management of pediatric oncology patients with fever and neutropenia assumes that all patients are at risk for bacteremia, and therefore generally involves hospitalization and broad-spectrum parenteral antibiotics for all patients. The determination of which patients are at low risk for having positive blood cultures and for developing complications related to bacteremia is of potential benefit. METHODS: The records of 161 pediatric patients with neoplastic disease hospitalized for 509 episodes of fever and neutropenia between January 1990 and June 1992 were retrospectively reviewed. Clinical features at initial presentation, clinical and microbiologic documentation of infection, and outcome were analyzed. RESULTS: The only presenting clinical features that correlated with an increased likelihood of having positive blood cultures were chills, hypotension, the requirement for fluid resuscitation (P < 0.001), or a diagnosis of leukemia or lymphoma (P < 0.041). Leukemia patients with relapse admitted for fever and neutropenia were no more likely to have positive blood cultures than those patients in remission. There were ten episodes of fever and neutropenia in which patients were transferred to the intensive care unit (ICU), and two sepsis related deaths. Nine episodes involving ICU management and both deaths were in patients who had persistent fever and an absolute neutrophil count (ANC) of less than 100 after 48 hours of hospitalization (n = 177). Patients with an ANC of less than 100 after 48 hours were twice as likely to have antibiotic changes, 15 times more likely to receive amphotericin B, and were hospitalized twice as long as patients with an ANC of 100 or higher after 48 hours. CONCLUSIONS: Children hospitalized for fever and neutropenia who have persistent fever and an ANC of less than 100 after 48 hours are at high risk for morbidity and are more likely to require antibiotic changes and antifungal therapy. Children who initially lack signs of sepsis, are afebrile, and have an ANC of 100 or higher after 48 hours are at low risk for complications and could be selectively discharged on antimicrobials after a 48-hour period of inpatient hospitalization.
This paper describes a method for selecting a small, highly diverse subset from a large pool of molecules. The method has been employed in the design of combinatorial synthetic libraries for use in high-throughput screening for pharmaceutical lead generation. It computes diversity in terms of the main factors relevant to ligand-protein binding, namely the three-dimensional arrangement of steric bulk and of polar functionalities and molecular entropy. The method was used to select a set of 20 carboxylates suitable for use as side-chain precursors in a polyamine-based library. The method depends on estimates of various physical-chemical parameters involved in ligand-protein binding; experiments examined the sensitivity of the method to these parameters. This paper compares the diversity of randomly and rationally selected side-chain sets; the results suggest that careful design of synthetic combinatorial libraries may increase their effectiveness several-fold.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Fourier-transform infrared spectroscopy (FTIR) has been employed to investigate the structural properties of the 28-kDa channel-forming integral membrane protein (CHIP28) present in phospholipid vesicles suspended in aqueous media. This study reports the FTIR spectra of this membrane protein present in H2O and 2H2O. The secondary structure of the protein was determined and found to consist of 36% alpha-helical and 42% beta-sheet structures. These results are in close agreement with the results of a previous CD study [Van Hoek, A. N., Wiener, M., Bicknese, S., Miercke, L., Biwersi, J. & Verkman, A. S. (1993) Biochemistry 32, 11,847-11,856]. However, the results differ from those given in an FTIR analysis by the same workers who recorded FTIR spectra of the CHIP28 protein in a dehydrated state. An unusually high extent of hydrogen-deuterium exchange of the peptide groups of this protein occurs. The magnitude of the spectral changes observed upon exposure of the protein to 2H2O is greater than has been observed with any other membrane protein previously studied. Thus, over 80% of the peptide groups exchange within 5 min and the amide I band maximum shifts to low frequency by approximately 20 cm-1. This high hydrogen-deuterium exchange observed with the CHIP28 protein is consistent with the presence of an aqueous pore within the protein structure.
Combinatorial mismatch-primer mutagenesis was used to make simultaneous changes of codons for residues Trp19 and Trp99 of the Escherichia coli trp aporepressor (TrpR protein) to codons for other residues. Among 21 different single- and double-mutant repressors obtained from this round of mutagenesis, proteins with Trp-->Leu and Trp-->Met changes at one or both positions were found to be nearly as active as the wild type (wt). Genes encoding repressors with each of the eight possible combinations of single- and double-mutant changes of Trp19 and Trp99 to Leu and Met were constructed by recombination in vitro. Whereas three of these eight mutant repressors are unstable in E. coli, all are made at similar steady-state levels in Salmonella typhimurium. Three of the eight mutant holorepressors are lethal when overproduced in S. typhimurium, because they confer an induced auxotrophy. Two different activity assays in vivo show that one of the four double-mutant repressors (Trp19-->Leu; Trp99-->Met) is similar to wt TrpR in its interactions with both Trp and DNA. These results show that more general approaches to engineering active proteins with fewer Trp residues may give rise to functional mutants without aromatic substitutions, and that aliphatic changes should be considered in cases where engineered changes of Trp to Phe or Tyr do not work.
Fourier transform infrared (FTIR) spectroscopy has been used to study temperature-induced structural changes which occur in albumin, immunoglobulin G, fibrinogen, lysozyme, alpha-lactalbumin, and ribonuclease S when dissolved in 2H2O. In order to analyze the data, a new method was developed in which the data were analyzed globally with the aid of a spectral model. Seven or eight bands were sufficient to fit the full data set of spectra ranging from 1420 to 1760 cm-1 with a root mean square error of 1-2% of the maximum. Subsequently, the estimated band amplitude curves which showed a sigmoidal progression with increasing temperature were (globally) fitted with a two-state thermodynamic model. In this way, information on structural changes as well as on the thermal stability of the proteins was obtained. In all proteins investigated, enhanced 1H-2H exchange occurred at temperatures well below the unfolding of the secondary structure. This was interpreted as a change in tertiary structure leading to enhanced solvent accessibility. In all the proteins investigated, except for ribonuclease S, an intermolecular beta-sheet band indicative of aggregation appeared concomitant with the denaturation of the secondary structure. The results are compared with data from other techniques and discussed in terms of local unfolding and folding intermediates.
We describe 2 cases of balanced reciprocal translocation (BRT) mosaicism. The frequency of this aberration in the population referred to our laboratory was determined and compared to those frequencies reported in the literature by other clinical cytogenetics laboratories. The extent of BRT mosaicism was also examined in surveys of parental populations, which are less likely to have a bias due to ascertainment on the basis of abnormal phenotype. the frequencies in the postnatal and prenatal populations examined in this study were calculated to be 5.7 x 10(-5) (95% confidence interval is 3.2-8.2 x 10(-5)) and 4.1 x 10(-5) (95% confidence interval is 2.0-6.2 x 10(-5)). However, in view of the extent of variation reported in the various studies, these estimates should be considered first approximations of the true frequency.
FT-IR spectroscopy has been applied to study the secondary structure of the major coat protein of Pf1 and M13 as present in the phage and reconstituted in DOPG and mixed DOPC/DOPG (4/1) bilayers. Infrared absorbance spectra of the samples were examined in dehydrated films and in suspensions of D2O and H2O. The secondary structure of the coat protein is investigated by second-derivative analysis, Fourier self-deconvolution, and curve fitting of the infrared bands in the amide I region (1600-1700 cm-1). It is found that, in dehydrated films of Pf1 and M13 phage, the amide I region contains three bands located at about 1633, 1657, and 1683 cm-1, that are assigned to hydrogen-bonded turn, alpha-helix/random coil, and non-hydrogen-bonded turn, respectively. From a comparison of the infrared spectra in dehydrated film with those in aqueous suspension, the percentages of secondary structure were found with an accuracy of about +/- 5%. For the coat protein of Pf1 phage, the FT-IR quantification gives 69% alpha-helix conformation, 19% turn structure, and 12% random coil structure. For Pf1 coat protein in the membrane-embedded state, the amount of alpha-helix is 57%, whereas 42% is in a turn structure and 1% in a random coil structure. The same assignment strategy was used for the analysis of the data obtained for M13 coat protein reconstitution into phospholipid systems. For M13 coat protein in the phage, this gives 75% alpha-helix conformation, 21% turn structure, and 4% random coil structure.(ABSTRACT TRUNCATED AT 250 WORDS)