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Biomedical subjects

R W Carlson

Publications and source records attributed to R W Carlson.

At least 109 records · Page 6Linked to original sources
PubMed1993

Cecal ligation and puncture is associated with pulmonary injury in the rat: role of cyclooxygenase pathway products.

The present studies evaluated the role cyclooxygenase products play in bacterial sepsis induced pulmonary injury in the rat. Lung injury was assessed by determining the pulmonary capillary filtration coefficient (Kf) and the lung lavage protein concentration four and 18 hours after cecal ligation and puncture. Four hours after cecal ligation, the Kf was unchanged from control, however, by 18 hours, the Kf was increased 171% (p < .05). Similarly, lung lavage protein levels were unchanged four hours after cecal ligation but were significantly (p < .05) elevated at 18 hours. On the other hand, pulmonary lavage immunoreactive thromboxane B2 (iTXB2) levels were increased both four and 18 hours after the initiation of sepsis. In order to determine if cyclooxygenase products played a role in the sepsis associated lung injury, ibuprofen was administered prior to cecal ligation. Ibuprofen pretreatment prevented the sepsis associated increase in both Kf and lung lavage protein concentration. These studies suggest that bacterial sepsis in the rat is associated with pulmonary injury and that early administration of ibuprofen ameliorates this damage.

Animals↗
PubMed1993

Association of hypomagnesemia and mortality in acutely ill medical patients.

OBJECTIVE: To test the hypothesis that the mortality rate of acutely ill patients admitted to a medical ward or medical ICU is higher for those patients who present with hypomagnesemia than for those patients who do not present with hypomagnesemia. DESIGN: Prospective, observational study. SETTING: Emergency Department admissions to the medical ward and medical ICU of a tertiary care teaching hospital serving an inner city patient population. SUBJECTS: A total of 381 consecutive acutely ill patients. MEASUREMENTS: Serum magnesium concentrations and other metabolic variables were measured on admission from the Emergency Department. Acute Physiology and Chronic Health Evaluation (APACHE II) scores were computed for all patients, and mortality rates were determined for hypomagnesemic and normomagnesemic groups. MAIN RESULTS: Hypomagnesemic and normomagnesemic groups had comparable APACHE II scores and other variables. However, the mortality rates of the hypomagnesemic ward and medical ICU groups were approximately twice (p < .01) the rate of the normomagnesemic groups. Additionally, the duration of hospital survival in those patients who died was approximately 8 days less for hypomagnesemia than normomagnesemia, but not for ward admissions. Other associated metabolic abnormalities were frequently observed in both hypomagnesemic and normomagnesemic groups, including hypokalemia and hypocalcemia. CONCLUSIONS: Hypomagnesemia detected at the time of admission of acutely ill medical patients is associated with an increased mortality rate for both ward and medical ICU patients.

Adolescent↗
PubMed1993

The presence of a novel type of surface polysaccharide in Rhizobium meliloti requires a new fatty acid synthase-like gene cluster involved in symbiotic nodule development.

Bacterial exopolysaccharide (EPS) and lipopolysaccharide (LPS) molecules have been shown to play important roles in plant-bacterium interactions. Here we have demonstrated that the fix-23 loci, which compensate for exo mutations during symbiotic nodule development, are involved in the production of a novel polysaccharide that is rich in 3-deoxy-D-manno-2-octulosonic acid (Kdo) but is not the classical LPS. This molecule is likely to be a surface antigen since antiserum to whole Rhizobium meliloti cells reacts strongly with it, and since mutations in fix-23 result in an inability to produce this polysaccharide and to bind bacteriophage 16-3. It is likely that this Kdo-rich polysaccharide is analogous to certain Escherichia coli K-antigens which are anchored to the membrane via a phospholipid moiety. DNA sequence analysis of one gene cluster of this region revealed that the predicted protein products of six genes exhibit a high degree of homology and similar organization to those of the rat fatty acid synthase multifunctional enzyme domains.

Amino Acid Sequence↗
PubMed1993

Resistance to nodulation of cv. Afghanistan peas is overcome by nodX, which mediates an O-acetylation of the Rhizobium leguminosarum lipo-oligosaccharide nodulation factor.

Only some strains of Rhizobium leguminosarum biovar viciae can efficiently nodulate varieties of peas such as cv. Afghanistan, which carry a recessive allele that blocks efficient nodulation by most western isolates of R.I. viciae. One strain (TOM) which can nodulate cv. Afghanistan peas has a gene (nodX) that is required to overcome the nodulation resistance. Strain TOM makes significantly lower amounts of lipo-oligosaccharide nodulation factors than other strains of R.I. viciae and this effect appears to be due to lower levels of nod gene induction. These nodulation factors are similar to those from other R.I. viciae strains in that they consist of an oligomer of four or five beta 1-4-linked N-acetylglucosamine residues in which the terminal non-reducing glucosamine carries an O-acetyl group and a C18:4 or C18:1 N-acyl group. However, one of the nodulation factors made by strain TOM differs from the factors made by other strains of R.I. viciae in that it carries an O-acetyl group on the C-6 of the reducing N-acetylglucosamine residue. This acetylation is NodX-dependent and the pentameric nodulation factor is acetylated on the reducing N-acetylglucosamine residue whereas the tetrameric nodulation factor is not. Although the nodL gene product is also an O-acetyl transferase (it O-acetylates the C-6 of the terminal non-reducing glucosamine), there is very little similarity between the amino acid sequences of these two acetyl transferases.

Acetylation↗
PubMed1993

Rhizobium fredii and Rhizobium meliloti produce 3-deoxy-D-manno-2-octulosonic acid-containing polysaccharides that are structurally analogous to group II K antigens (capsular polysaccharides) found in Escherichia coli.

The polysaccharide components from cultured cells of Rhizobium fredii USDA205 and Rhizobium meliloti AK631 were extracted with hot phenol-water and separated by repetitive gel filtration chromatography. Polyacrylamide gel electrophoresis, nuclear magnetic resonance spectrometry, and gas chromatography analyses showed that both of these bacterial species produce unique polysaccharides that contain a high proportion of 3-deoxy-D-manno-2-octulosonic acid (Kdo). These polysaccharides, which constituted a major portion of the extracted carbohydrate, are not excreted into the growth media (i.e., they are not extracellular polysaccharides) and are structurally distinct from the lipopolysaccharides. The primary structure of the preponderant polysaccharide from R. fredii USDA205 was determined by high-performance anion-exchange liquid chromatography, nuclear magnetic resonance spectrometry, fast atom bombardment-mass spectrometry, and gas chromatography-mass spectrometry; it consists of repeating units of [-->3)-alpha-D-Galp-(1-->5)-beta-D-Kdop-(2-->]n. This molecule is structurally analogous to the constituents of one subgroup of K antigens (capsular polysaccharides) produced by Escherichia coli. Polysaccharides of this type have not previously been identified as components of rhizobial cells. The Kdo-containing polysaccharide from R. meliloti, which has not been completely characterized, appears to be structurally related to that of R. fredii.

Antigens, Bacterial↗
PubMed1993

Toward an interim standard for patient-centered knowledge-access.

Most care-giver "knowledge" needs arise at the point of care and are "patient-centered." Many of these knowledge needs can be met using existing on-line knowledge sources, but the process is too time-consuming, currently, for even the computer-proficient. We are developing a set of public domain standards aimed at bringing potentially relevant knowledge to the point of care in a straight-forward and timely fashion. The standards will a) make use of selected items from a Computer-based Patient Record (CPR), e.g., a diagnosis and measure of severity, b) anticipate certain care-giver knowledge needs, e.g., "therapy," "protocols," "complications," and c) try to satisfy those needs from available knowledge sources, e.g., knowledge-bases, citation databases, practice guidelines, and on-line textbooks. The standards will use templates, i.e., fill-in-the-blank structures, to anticipate knowledge needs and UMLS Metathesaurus enhancements to represent the content of knowledge sources. Together, the standards will form the specification for a "Knowledge-Server" (KS) designed to be accessed from any CPR system. Plans are in place to test an interim version of this specification in the context of medical oncology. We are accumulating anecdotal evidence that a KS operating in conjunction with a CPR is much more compelling to users than either a CPR or a KS operating alone.

Artificial Intelligence↗
PubMed1993

A methodology for determining patients' eligibility for clinical trials.

The task of determining patients' eligibility for clinical trials is knowledge and data intensive. In this paper, we present a model for the task of eligibility determination, and describe how a computer system can assist clinical researchers in performing that task. Qualitative and probabilistic approaches to computing and summarizing the eligibility status of potentially eligible patients are described. The two approaches are compared, and a synthesis that draws on the strengths of each approach is proposed. The result of applying these techniques to a database of HIV-positive patient cases suggests that computer programs such as the one described can increase the accrual rate of eligible patients into clinical trials. These methods may also be applied to the task of determining from electronic patient records whether practice guidelines apply in particular clinical situations.

Clinical Trials as Topic↗
PubMed1993

Fluid resuscitation in circulatory shock.

Over the past century, the treatment of various forms of circulatory shock has included fluid resuscitation with either crystalloidal or colloidal solutions. Despite decades of investigation, there still is considerable controversy over the beneficial and adverse effects of each fluid type. Most authors agree that the initial resuscitation of any form of shock should be performed with crystalloid solutions. Trauma resuscitation uses crystalloid therapy almost exclusively. Much controversy exists when the shock state involves increased microvascular permeability, such as seen in sepsis, anaphylaxis, and burns. Concerns involve increased permeability pulmonary edema and whether colloid or crystalloid therapy may contribute to its formation. Regardless of fluid type used for resuscitative efforts, it is essential to ensure adequate invasive and noninvasive monitoring to guide therapy. Endpoints to resuscitation should include stabilization of vital signs, adequate urine output, adequate cardiac output, and evidence of supply-independent oxygen consumption. Side effects of aggressive fluid loading are frequent and include intravascular volume overload, pulmonary edema, increased myocardial water content, brain swelling, gastrointestinal ischemia, and massive systemic edema. These complications can best be minimized by careful fluid titration, using physiologic and hemodynamic endpoints.

Clinical Protocols↗
PubMed1992

Complete structure of the adhesin receptor polysaccharide of Streptococcus oralis ATCC 55229 (Streptococcus sanguis H1).

This report describes the determination of the complete primary structure of the adhesin receptor polysaccharide of Streptococcus oralis ATCC 55229 (previously characterized as Streptococcus sanguis H1), a Gram-positive bacteria implicated in dental plaque formation. The polysaccharide was isolated from S. oralis ATCC 55229 cells after deproteination, enzymatic hydrolysis, and ion exchange chromatography. It was shown to consist of rhamnose, galactose, glucose, glycerol, and phosphate, in molar ratios of 2:3:1:1:1. Sequence and linkage assignments of the glycosyl residues were obtained by methylation analysis followed by gas-liquid chromatography and electron-impact mass spectrometry. 31P NMR spectroscopy revealed that phosphate was present in a diester, connecting glycerol to one of the galactosyl residues. High-performance liquid chromatography of a partial acid hydrolysate of the polysaccharide confirmed this finding by showing galactose 6-phosphate and glycerol 1-phosphate. The structural determination was completed by the combination of two-dimensional homonuclear Hartmann-Hahn and NOE experiments and heteronuclear [1H,13C] and [1H,31P] multiple-quantum coherence experiments. Thus, the adhesin receptor polysaccharide of S. oralis ATCC 55229 was found to be a polymer composed of hexasaccharide repeating units that contain glycerol linked through a phosphodiester to C6 of the alpha-galactopyranosyl residue and are joined end-to-end through galactofuranosyl-beta(1-->3)-rhamnopyranosyl linkages: [formula: see text] This structure is novel among bacterial cell surface polysaccharides in general and specifically among those implicated in dental plaque formation.

Bacterial Proteins↗
PubMed1992

A 2-O-methylfucose moiety is present in the lipo-oligosaccharide nodulation signal of Bradyrhizobium japonicum.

Bradyrhizobium japonicum is a soil bacterium that forms nitrogen-fixing nodules on the roots of the agronomically important legume soybean. Microscopic observation of plant roots showed that butanol extract of B. japonicum strain USDA110 cultures induced for nod gene expression elicited root hair deformation, an early event in the nodulation process. The metabolite produced by B. japonicum responsible for root hair deformation activity was purified. Chemical analysis of the compound revealed it to be a pentasaccharide of N-acetylglucosamine modified by a C18:1 fatty acyl chain at the nonreducing end. In these respects, the B. japonicum metabolite is similar to the lipo-oligosaccharide signals described from Rhizobium species. However, the B. japonicum compound is unique in that an additional sugar, 2-O-methylfucose, is linked to the reducing end. Comparative analysis of the B. japonicum Nod metabolite and those characterized from Rhizobium species suggests that the presence of the fucosyl residue plays an important role in the specificity of the B. japonicum-soybean symbiosis. The availability of the purified B. japonicum nodulation signal should greatly facilitate further studies of soybean nodulation.

Carbohydrate Sequence↗
PubMed1992

Structures of the oligosaccharides obtained from the core regions of the lipopolysaccharides of Bradyrhizobium japonicum 61A101c and its symbiotically defective lipopolysaccharide mutant, JS314.

The only core oligosaccharide released from the lipopolysaccharide (LPS) of Bradyrhizobium japonicum 61A101c by prolonged (5 h) mild hydrolysis with acid, and the major core oligosaccharide obtained from its symbiotic and LPS-defective mutant, JS314, was the trisaccharide alpha-D-Man p-(1----4)-alpha-D-Glc p-(1----4)-2,7-anhydro-alpha-Kdof. The 2,7-anhydro-3-deoxy-alpha-D-manno-2- octulofuranosonic acid moiety was probably formed during the prolonged mild hydrolysis with acid. A disaccharide core component, also released by mild acid hydrolysis of the mutant LPS, had the structure 4-O-Me-alpha-D-Man p-(1----5)-Kdo. The Kdo residue in this disaccharide is present as the normal pyranose form and as an anhydro derivative, possibly 4,8-anhydro-3-deoxy-D-manno-2-octulosonic acid, which may have formed also during prolonged mild hydrolysis with acid. Mild acid hydrolysis of the LPS of the parent strain does not produce this disaccharide, but 4-O-Me-Man is found exclusively in the O-chain fraction released from the parent LPS. Additionally, a small amount of O-chain is found in the mutant LPS. The results imply that the O-chain is attached to the remainder of the LPS through the 4-O-Me-Man-Kdo disaccharide component of the core region.

Carbohydrate Conformation↗
PubMed1992

Bradyrhizobium japonicum nodD1 can be specifically induced by soybean flavonoids that do not induce the nodYABCSUIJ operon.

Besides genistein and daidzein, which are active inducers of the nodYABCSUIJ operon in Bradyrhizobium japonicum, soybean seeds also excrete compounds that are not inducers of the nodYABCSUIJ genes but enhance induction of this operon in the presence of a suboptimal genistein concentration. This synergism was studied in detail, and specific compounds were identified in seed exudate which specifically induce the nodD1 gene but not the nodYABCSUIJ operon. Therefore, our current hypothesis is that the observed synergism is caused by a specific induction of nodD1. The specific nodD1 inducers from soybean seed extract have been purified and characterized chemically. They appear to be derivatives of genistein, glycitein, and daidzein with glucose, malonyl, and acetyl groups attached. Both root and seed exudate appear to contain these compounds, with the seed being the major source. No hydrolysis of these compounds to their aglycone forms was detected in the presence of B. japonicum. A model for nod gene induction in B. japonicum is discussed.

Bacterial Proteins↗
PubMed1992

Fatal rodenticide poisoning with brodifacoum.

The increased prevalence of rodents resistant to warfarin led to the development of the hydroxycoumarin anticoagulant brodifacoum. A 25-year-old man attempted suicide by consuming four boxes of d-CON Mouse-Prufe II; each box contains 42 g of bait that is 0.005% brodifacoum. He presented to a hospital nine days later with syncope, hematochezia, gross hematuria, epistaxis, anemia, and a severe coagulopathy. Radiographic studies were consistent with pleural, pericardial, and mediastinal hemorrhages. Vitamin K and fresh frozen plasma were given, and he was later discharged on oral phytonadione (vitamin K1). The patient's coagulopathy recurred, necessitating multiple plasma transfusions and prolonged treatment with oral phytonadione. Fifteen weeks after hospital discharge, he presented again with a history of additional brodifacoum ingestion. Neurologic status was initially normal, but in the emergency department he suddenly became comatose soon after emesis was induced with syrup of ipecac. Computed tomography of the brain revealed a subarachnoid hemorrhage that led to brain death less than 24 hours later. This case demonstrates the severe and prolonged coagulopathy that can result from ingestion of brodifacoum, a compound that has a toxic potency about 200-fold that of warfarin and a half-life as much as 60 times longer.

4-Hydroxycoumarins↗
PubMed1992

A new method for the analysis of amide-linked hydroxy fatty acids in lipid-As from gram-negative bacteria.

Lipid-A represents the ubiquitous, covalently bound hydrophobic component of bacterial lipopolysaccharides (endotoxins). Lipid-As isolated and characterized from rhizobial species have large variations in their backbone sugars, as well as in their hydroxy fatty acid substituents. The sugar backbones consist of either glucosamine and galacturonic acid or glucosamine and 2,3-diaminoglucose. The published procedures for characterizing amide-linked fatty acids do not release all these fatty acids, hence a new method was developed to characterize the amide-linked hydroxy fatty acids. This method involves a mild methanolysis procedure to release glucosamine methyl glycosides which still contain the amide-bound hydroxy fatty acids. The products were analysed by fast atom bombardment mass spectrometry (FAB-MS) and, after trimethylsilylation, by electron impact (E.I.) and chemical ionization (C.I.) gas chromatography-mass spectrometry (GC-MS). The procedure was applied to lipid-A preparations from several gram-negative bacteria. This method allows the unequivocal identification of amide-linked hydroxy fatty acids and also allows determination of the microheterogeneity of the N-acyl substituents in lipid-As from gram-negative bacteria.

Amides↗
PubMed1992

Formation of Novel Polysaccharides by Bradyrhizobium japonicum Bacteroids in Soybean Nodules.

Certain strains of Bradyrhizobium japonicum form a previously unknown polysaccharide in the root nodules of soybean plants (Glycine max (L.) Merr.). The polysaccharide accumulates inside of the symbiosome membrane-the plant-derived membrane enclosing the bacteroids. In older nodules (60 days after planting), the polysaccharide occupies most of the symbiosome volume and symbiosomes become enlarged so that there is little host cytoplasm in infected cells. The two different groups of B. japonicum which produce different types of polysaccharide in culture produce polysaccharides of similar composition in nodules. Polysaccharide formed by group I strains (e.g., USDA 5 and USDA 123) is composed of rhamnose, galactose, and 2-O-methylglucuronic acid, while polysaccharide formed by group II strains (e.g., USDA 31 and USDA 39) is composed of rhamnose and 4-O-methylglucuronic acid. That the polysaccharide is a bacterial product is indicated by its composition plus the fact that polysaccharide formation is independent of host genotype but is dependent on the bacterial genotype. Polysaccharide formation in nodules is common among strains in serogroups 123, 127, 129, and 31, with 27 of 39 strains (69%) testing positive. Polysaccharide formation in nodules is uncommon among other B. japonicum serogroups, with only 1 strain in 18 (6%) testing positive.

Journal Article↗
PubMed1992

Chemical characterization of pH-dependent structural epitopes of lipopolysaccharides from Rhizobium leguminosarum biovar phaseoli.

Lipopolysaccharide (LPS) was isolated from free-living Rhizobium leguminosarum bv. phaseoli CE3 cells grown at pH 4.8 (antigenically similar to bacteroid LPS) and compared with that from cells grown at pH 7.2 (free-living bacteria). Composition analysis revealed that pH 7.2 LPS differs from pH 4.8 LPS in that 2,3,4-tri-O-methylfucose is replaced by 2,3-di-O-methylfucose. The amount of 2-O-methylrhamnose is greater in the pH 4.8 LPS than in the pH 7.2 LPS. Analysis of the structural components of LPS (O-chain polysaccharide, core oligosaccharides, and the lipid A) revealed that all the composition differences in the various LPSs occur in the O-chain polysaccharide. These structural variations between pH 4.8 and pH 7.2 LPSs provide a chemical basis for the observed lack of cross-reactivity with pH 4.8 LPS of two monoclonal antibodies, JIM28 and JIM29, raised against free-living bacteria grown at pH 7.2. An LPS preparation isolated from bacteroids contained both 2,3,4-tri-O- and 2,3-di-O-methylfucose residues. This result is consistent with the finding that the two monoclonal antibodies react weakly with bacteroid LPS. It is concluded that methylation changes occur on the LPS O-chain of R. leguminosarum bv. phaseoli when the bacteria are grown at low pH and during nodule development.

Antibodies, Bacterial↗