End-of-life care in HIV disease: let's talk.
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Acquired Immunodeficiency Syndrome↗
Biomedical subjects
I B Wilson
Publications and source records attributed to I B Wilson.
Virtual resource development in the glycosciences.
The development of Internet-based virtual resources is a relatively new area of scientific and technical activity that is currently undergoing rapid expansion. Major factors fuelling recent growth include the emergence of multimedia capabilities through the rapid evolution of the World Wide Web, the reduction in cost of high quality personal computers and graphics workstations and the provision of mass-marketed provider services. Prior to 1995 the presence of Internet resources in the glycosciences was virtually non-existent. Existing scientific knowledge was primarily made available on the Net through the provision of databases from gopher and ftp sites. A particular example in the glycosciences is the Carbbank database of biological carbohydrate sequences. We will describe here our efforts in 1994-95 in establishing The Glycoscience Network (TGN, http:@ bellatrix.pcl.ox.ac.uk/TGN/). These activities included the establishment of a newsgroup, mailing lists, Web resources and the running of the First Electronic Glycoscience Conference (EGC-1, http:@bellatrix.pcl.ox.ac.uk/egc/). EGC-1 included many novel initiatives in the glycosciences including electronic posters and papers, a Virtual Conference Centre, a Web-based hyperglossary, Virtual Trade and Employment Centres, refereed electronic publishing, and the creation of a Virtual Reality Gallery. We would like to look towards the near future and discuss several initiatives in virtual resource creation that we believe will have significant scientific impact on the glycosciences including the development of bioinformatics-based servers, sophisticated interactive databases, and videoconferencing. Furthermore, we cherish the belief that these resources will foster international scientific collaboration and progress of an extent never previously possible. Finally, we indulge in speculation and make some suggestions on the form and long-term impact of Glycoscience Virtual Resources. We predict that their development may completely reconstruct the scientific environment that we work in as scientists and we reflect on the probable benefits and pitfalls to be encountered.
Carbohydrates↗
A new direction in conferencing: the First Electronic Glycoscience Conference.
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Carbohydrates↗
Clinical predictors of functioning in persons with acquired immunodeficiency syndrome.
To help clinicians better assess and treat functional disabilities in persons with acquired immunodeficiency syndrome (AIDS), the authors estimate empirical relations among biologic and physiologic variables, symptoms, and physical functioning in persons with AIDS. The sample of 305 persons with AIDS for this cross-sectional analysis came from three sites in Boston, Massachusetts: a hospital-based group practice, a human immunodeficiency virus clinic at a city hospital, and a staff-model health maintenance organization. Physical functioning, 10 AIDS-specific symptoms, and mental health were assessed by interview. Clinical diagnoses, comorbidities, health habits such as smoking, laboratory results, and selected medication use were assessed by chart review. Significant predictors of physical functioning P < 0.01, R2 = .58) in a multivariable regression model included energy/fatigue, neurologic symptoms, fever symptoms, a lower hemoglobin level, and current non-pneumonia bacterial infection. Ninety-six percent of the explained variance in physical functioning was accounted for by three symptom complexes: energy/fatigue, neurologic symptoms, and fever symptoms. Significant predictors of energy/fatigue in multivariable models included poorer mental health, lower white blood cell count, longer time since diagnosis, and weight loss (P < 0.01, R2 =.36). Significant predictors of neurologic symptoms included poorer mental health, weight loss, and no zidovudine use (P < 0.001, R2 = .30). Predictors of fever symptoms included poorer mental health, no zidovudine use, weight loss, and history of asthma or chronic obstructive pulmonary disease (P < 0.05, R2 = .25). In conclusion, symptom reports were strong predictors of physical functioning. Poorer mental health and weight loss were correlated consistently with worse symptoms, and not using zidovudine was correlated with worse neurologic and fever symptoms. These variables, and the others the authors identified, may represent mutable determinants of physical functioning in persons with AIDS, and potential targets for specific clinical interventions.
Acquired Immunodeficiency Syndrome↗
Dolichol is not a necessary moiety for lipid-linked oligosaccharide substrates of the mannosyltransferases involved in in vitro N-linked-oligosaccharide assembly.
Dolichol is utilized in vivo as an unusually large anchor on which the precursor for N-linked oligosaccharides is assembled by a series of glycosyltransferases. The role of dolichol in enzyme substrate recognition is investigated. Thus the biosynthetic intermediate NN'-diacetylchitobiose was chemically linked to either dolichol or the much shorter fully saturated tetraisoprenoid phytanol. Both lipids were used as substrates by a recombinant, soluble beta-1,4-mannosyltransferase. beta-[3H]Mannosylated lipids from this reaction were then used as substrates for the subsequent mannosyltransferases from yeast or rat liver microsomes. It was found that both the dolichyl- and phytanyl-linked substrates were easily mannosylated to form Man5GlcNAc2, with some further mannosylation to Man7GlcNAc2 and Man9GlcNAc2 at low concentrations of lipid-linked substrate. It is concluded that dolichol is not necessary in vitro as part of the substrate for the mannosyltransferases in the biosynthetic pathway for N-glycosylation.
Animals↗
Linking clinical variables with health-related quality of life. A conceptual model of patient outcomes.
Our model proposes a taxonomy or classification scheme for different measures of health outcome. We divide these outcomes into five levels: biological and physiological factors, symptoms, functioning, general health perceptions, and overall quality of life. In addition to classifying these outcome measures, we propose specific causal relationships between them that link traditional clinical variables to measures of HRQL. As one moves from left to right in the model, one moves outward from the cell to the individual to the interaction of the individual as a member of society. The concepts at each level are increasingly integrated and increasingly difficult to define and measure. AT each level, there are an increasing number of inputs that cannot be controlled by clinicians or the health care system as it is traditionally defined.
Activities of Daily Living↗
Clinical practice and patients' health status: how are the two related?
Now that we have the ability to measure patients' health outcomes, physicians and health care systems need to know how to manage these outcomes. What are the causal pathways that link clinical and health status concepts? What are the key points at which physicians and health care systems can intervene in effective and cost-effective ways? We have argued that the elegant biomedical model that physicians use to understand disease is a blunt tool in the dissection of illness and that valid, reliable, and richly descriptive measures of HRQL fail at clinical tasks because causal linkages between clinical processes and health status outcomes have not yet been made convincingly, at either the conceptual or the empiric level. One approach to this problem is to develop and test causal models that explore the relationships among different measures of health status in an attempt to elucidate the "genesis" and "pathogenesis" of disorders of HRQL. Once physicians and health care systems know more about the determinants of poor health status and the mechanisms by which it occurs, creative attempts to intervene at multiple points in a causal pathway may be possible, making outcomes management a more realistic goal.
Health Status↗
Quality of care and HIV infection: theory and practice.
The first section of this article provides a brief, conceptually oriented overview of the "state of the art" in quality assessment. The second section examines what we know about quality assessment in HIV disease. The third section attempts to synthesize this information and make some practical recommendations. These recommendations are starting points on a road to understanding quality assessment in HIV disease, not a destination. Scant empiric data underpin these recommendations, and it is my expectation and hope that they will evoke discussion and debate. Although this article touches only briefly on quality improvement, decisions about what to do with the information gathered may be just as important as decisions about what to measure. The concepts described in the continuous quality improvement literature, even though they are only beginning to be applied to health care, may be an important guidepost on the road to improved quality.
Ambulatory Care↗
The potential dolichol recognition sequence of beta-1,4-mannosyltransferase is not required for enzymic activity using phytanyl-pyrophosphoryl-alpha-N,N'- diacetylchitobioside as acceptor.
The ALG1 gene of Saccharomyces cerevisiae encodes beta-1,4-mannosyltransferase, an essential membrane-associated enzyme involved in the assembly of dolichyl-linked oligosaccharide precursors for N-glycosylation [Albright and Robbins (1990) J. Biol. Chem. 265, 7042-7049], which catalyses the transfer of a mannose residue from GDP-mannose to dolichyl-pyrophosphoryl-alpha-N,N'- diacetylchitobioside; it also possesses a putative transmembrane domain, bearing an 11-amino-acid consensus sequence, which has been proposed to mediate dolichol recognition. Here we report the construction and bacterial expression of a mutant beta-1,4-mannosyltransferase derived from ALG1, which carries a 34-amino-acid deletion resulting in the absence of the entire N-terminal transmembrane domain. This truncated enzyme has an apparent Km value of 17 microM for phytanyl-pyrophosphoryl-alpha-N,N'-diacetylchitobioside, a known acceptor for beta-1,4-mannosyltransferase [Flitsch, Pinches, Taylor and Turner (1992) J. Chem. Soc., Perkin Trans. 1, 2087-2093]. The intact enzyme, expressed in the same system, has an apparent Km value of 25 microM. These figures are in good agreement with previously reported values for wild-type beta-1,4-mannosyl-transferase incubated with the natural dolichyl-linked substrate. Gel-filtration chromatography (before and after beta-mannosidase digestion) of the products of both forms of the enzyme verifies the formation of Man beta 1-->4GlcNAc beta 1-->4GlcNAc. We therefore conclude that the putative dolichol recognition sequence is not necessary for recognition of the phytanyl analogue of its natural dolichol substrate and suggest it probably also is not needed for its natural substrate.
Base Sequence↗
The alkylating properties of chlorambucil.
Previous work has indicated an aziridinium ion mechanism in the hydrolysis of chlorambucil, and the present work on the alkylation of nucleophiles fully supports this mechanism. This mechanism forms the basis for understanding the kinetics of alkylation reactions because their rates are limited by the rate of formation of the aziridinium ion and the alkylation reaction competes with the hydrolytic reaction. We have measured alpha N, where alpha N(N) is the rate of reaction of the aziridinium ion with a nucleophile N relative to its reaction with water for several nucleophiles that are related to those found in proteins. The alpha values for hydroxide ion and some other bases are greater than 10(3), but the effective values at pH 7.5 are much smaller because there is little base present. The kinetic equations show that it is very difficult to alkylate a nucleophile extensively at pH 7.5 before chlorambucil has hydrolyzed. Therefore, it is not clear why angiotensin-converting enzyme is completely inhibited by low concentrations of chlorambucil. On the other hand, damage to DNA is easily understood.
Alkylating Agents↗
The chemoenzymatic synthesis of neoglycolipids and lipid-linked oligosaccharides using glycosyltransferases.
The application of glycosyltransferases to the chemoenzymatic synthesis of neoglycosphingolipids and lipid-linked oligosaccharides allows the regio- and stereoselective formation of glycosidic bonds. In our laboratory galactosyl-, sialyl-, and fucosyltransferases have been used to assemble oligosaccharide headgroups directly on a sphingosine derivative without the need for any protection group strategies, including the Lewisx antigen. In complementary studies on N-linked oligosaccharide biosynthesis, chemically phosphorylated dolichol analogues have been tested as substrates for Dol-P-Man synthetase. Also, the substrate recognition of the core beta-1,4-mannosyltransferase from yeast has been investigated using a range of chitobiose derivatives as potential substrates.
Carbohydrate Sequence↗
Galactosylation of human IgG monoclonal anti-D produced by EBV-transformed B-lymphoblastoid cell lines is dependent on culture method and affects Fc receptor-mediated functional activity.
Human monoclonal antibodies to the Rh D blood group antigen were produced by EBV-transformed B cell lines grown in serum-free medium in low density (LD) static cultures or high density (HD) hollow fiber bioreactors. Glycosylation analysis of the purified IgG was determined by the binding of anti-GlcNAc monoclonal antibody (GN7) and by analysis of oligosaccharides released by hydrazinolysis. The LD MAbs had only trace levels of agalactosyl oligosaccharides (G0), the major species (> 70%) being digalactosyl structures (G2). The HD MAbs, by contrast, contained about 10% G0 and relatively high levels (over 50%) of monogalactosyl (G1) oligosaccharides. beta 1-4 galactosyltransferase activity in the LD cell lines was similar to that found previously for other EBV-transformed B cell lines. The predominant oligosaccharides of an IgG3 anti-D, BRAD-3, contained bisecting N-acetylglucosamine. In functional assays with Fc receptor (Fc gamma R) positive effector cells, the highly galactosylated LD form of BRAD-3 was more active than the HD form in monocyte (Fc gamma RI) and K cell (Fc gamma RIII) mediated lysis of erythrocytes in ADCC assays, although these preparations showed no difference in Fc gamma RI-mediated rosette formation with U937 cells. One MAb, JAC10, was over 10-fold less active than two other IgG1 MAbs, 2B6 and BRAD-5, at mediating lysis of erythrocytes by Fc gamma RIII+ K cells; differences in sialylation may have contributed to this heterogeneity.(ABSTRACT TRUNCATED AT 250 WORDS)
Antibodies, Monoclonal↗
A novel mono-branched lipid phosphate acts as a substrate for dolichyl phosphate mannose synthetase.
Dolichyl phosphate mannose synthetase (GDP-mannose: dolichyl-phosphate O-beta-D-mannosyltransferase; EC 2.4.1.83) is an enzyme that is involved in glycoconjugate biosynthesis and possesses a putatively conserved dolichol binding site. In order to probe the interaction between the enzyme and the dolichol chain, lipid phosphates varying in length and extent of branching have been tested as substrates in crude microsomal preparations from Saccharomyces cerevisiae. It was found that phytanyl (3,7,11,15-tetramethylhexadecanyl) phosphate was utilized at 60-70% of the efficiency of the natural dolichyl lipid in transfer of [3,4,-3H]mannose from GDP-Man to organic soluble material, whereas addition of S-3-methyloctadecanyl phosphate, which is of similar length to the phytanyl analogue but with only one branch, resulted in approximately 25% of the incorporation of the natural substrate. Incubations with the unbranched tetradecanyl phosphate and with the short, doubly branched R- and S-dihydrocitronellyl (3,7-dimethyloctanyl) phosphates exhibited levels of activity similar to incubations with no exogenous acceptor. These results were qualitatively confirmed with experiments on Escherichia coli harbouring the S. cerevisiae DPM1 gene. The [3H]mannosylated lipid-linked material from microsomal incubations was purified by anion-exchange chromatography. The major saccharide component recovered after hydrolysis was determined to be mannose, but a mannose-containing disaccharide was also present. It is concluded that branching of lipid phosphates is essential for substrates of dolichyl phosphate mannose synthetase and that significant transfer of mannose occurs even if only branching at C-3 is present.
Amino Acid Sequence↗
Re: Conservation and evolution of glycosylation sites on immunoglobulin-type domains.
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Amino Acid Sequence↗
Endothelin-converting enzyme: the binding of metal ions.
The metal ion of endothelin-converting enzyme (ECE) was investigated by inhibiting the enzyme with ethylenediaminetetraacetic acid (EDTA) and restoring activity by adding divalent metal salts in quantities less than the concentration of EDTA. Under these conditions, only metal ions that bind to ECE with high affinity can affect the enzyme. The ferrous enzyme had an activity of 76% relative to the native enzyme, the manganous enzyme 76%, the nickelous enzyme 77%, the cupric enzyme 17%, the zinc enzyme 98% and the cobaltous enzyme 122%. Of these first transition series elements only zinc can be the metal of the native enzyme. The zinc enzyme has the same Km and turnover number as the native enzyme.
Amino Acid Sequence↗
Aberrant control of galactosyltransferase in peripheral B lymphocytes and Epstein-Barr virus transformed B lymphoblasts from patients with rheumatoid arthritis.
It is now well established that hypogalactosylation of IgG is a molecular marker for rheumatoid arthritis (RA). However, the mechanism for the alteration of the galactosylation status has not been resolved. We compared the galactosyltransferase activities of anti-CD19 selected peripheral B lymphocytes of healthy subjects and patients with RA using ovalbumin as the acceptor substrate. In addition, certain samples of lymphocytes were assayed after Epstein-Barr virus (EBV) transformation and, also, the ability of bovine milk galactosyltransferase to galactosylate IgG in vitro was examined. Our results indicate that there is a significant difference between the galactosyltransferase activities of rheumatoid and control peripheral B lymphocytes and that EBV transformation causes a variable increase (15-1225%) in galactosyltransferase activity, over that present in the peripheral B lymphocytes from which the transformed cells were derived. Also the ubiquitous "lactose synthetase" type galactosyltransferase (EC 2.4.1.38) will galactosylate normal native IgG at concentrations of 500 mU/ml in vitro. We conclude that there is no evidence from our study for an IgG specific galactosyltransferase and that galactosyltransferase is an enzyme that is aberrantly modulated in peripheral B lymphocytes and EBV transformed B lymphoblasts derived from patients with RA.
Adult↗
Identification of endothelin converting enzyme in bovine lung membranes using a new fluorogenic substrate.
An enzyme partially purified from bovine lung membranes appears to be endothelin converting enzyme (ECE). This enzyme specifically cleaves big endothelin-1 (big ET-1) at the proper site, between Trp21 and Val22, with maximum activity at pH 7.5 and with a Km of roughly 3 microM, to produce endothelin-1 (ET-1) and C-terminal peptide (CTP). This same enzyme hydrolyzes the fluorogenic substrate succinyl-Ile-Ile-Trp-methylcoumarinamide to release the highly fluorescent 7-amino-4-methylcoumarin. The peptide derivative has the same amino acid sequence as big ET-1 and is a good substrate with a Km of about 27 microM. This enzyme is a metalloproteinase. It is not inhibited by five common proteinase inhibitors (pepstatin A, PMSF, NEM, E-64 and thiorphan) but it is inhibited by phosphoramidon and chelating compounds. The apoenzyme is restored to nearly full activity by a zinc-EDTA buffer with pZn = 13.
Animals↗
Amino acid distributions around O-linked glycosylation sites.
To study the sequence requirements for addition of O-linked N-acetylgalactosamine to proteins, amino acid distributions around 174 O-glycosylation sites were compared with distributions around non-glycosylated sites. In comparison with non-glycosylated serine and threonine residues, the most prominent feature in the vicinity of O-glycosylated sites is a significantly increased frequency of proline residues, especially at positions -1 and +3 relative to the glycosylated residues. Alanine, serine and threonine are also significantly increased. The high serine and threonine content of O-glycosylated regions is due to the presence of clusters of several closely spaced glycosylated hydroxy amino acids in many O-glycosylated proteins. Such clusters can be predicted from the primary sequence in some cases, but there is no apparent possibility of predicting isolated O-glycosylation sites from primary sequence data.
Acetylgalactosamine↗