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Biomedical subjects

R W Carlson

Publications and source records attributed to R W Carlson.

At least 19 recordsLinked to original sources
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

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↗
PubMed1992

Acute aortic insufficiency in a patient with presumed Reiter's syndrome.

Cardiac disease is rare in patients with Reiter's syndrome. There have been 15 reported cases of aortic insufficiency in patients with Reiter's syndrome, with the aortic insufficiency developing over several years. This paper reports the case of a black HLA-B27 negative woman who presented with Reiter's syndrome and acute aortic insufficiency. An antecedent streptococcal infection is suggested as the inciting factor. To our knowledge, this is the first report of Reiter's syndrome in a black woman with acute aortic insufficiency.

Adult↗
PubMed1992

Terminal weaning from mechanical ventilation: ethical and practical considerations for patient management.

Decisions to withdraw life-sustaining therapy are being made more often as patients and healthcare providers increase their awareness of patient rights. The process of withdrawal of mechanical ventilation must be conducted in a humane fashion. An understanding of the ethical, legal and practical considerations for patient management during this type of intervention will enhance the ability of the healthcare provider to participate.

Advance Directives↗
PubMed1992

T-HELPER: automated support for community-based clinical research.

There are increasing expectations that community-based physicians who care for people with HIV infection will offer their patients opportunities to enroll in clinical trials. The information-management requirements of clinical investigation, however, make it unrealistic for most providers who do not practice in academic centers to participate in clinical research. Our T-HELPER computer system offers community-based physicians the possibility of enrolling patients in clinical trials as a component of primary care. T-HELPER facilitates data management for patients with HIV disease, and can offer patient-specific and situation-specific advice concerning new protocols for which patients may be eligible and the treatment required by those protocols in which patients currently are enrolled. We are installing T-HELPER at three county-operated AIDS clinics in the San Francisco Bay Area, and plan a comprehensive evaluation of the system and its influence on clinical research.

Clinical Trials as Topic↗
PubMed1992

Reducing the cardiotoxicity of the anthracyclines.

Most patients are not at risk for anthracycline-associated cardiotoxicity, since the cancer usually develops resistance before a dangerously high cumulative dose can be given. However, select patients may benefit from continued therapy. The physician's goal is to continue to treat these patients without risking drug-related cardiomyopathy. A simple maneuver is to switch from bolus administration to a weekly low-dose or continuous-infusion schedule. Pretreatment with ICRF-187, a new cardioprotective agent currently under investigation, may prove highly useful in the near future. Perhaps most important, the physician must be able to spot the early signs of drug-related cardiac injury. This can be accomplished with radionuclide ventriculography to determine both resting and exercise ejection fractions. Patients shown to be at high risk can then be withdrawn from the drug or further monitored with endomyocardial biopsy and right heart catheterization.

Antibiotics, Antineoplastic↗
PubMed1992

Fluid resuscitation in patients with increased vascular permeability.

Fluid therapy is a uniformly accepted, logical, and highly effective therapeutic intervention for the treatment of patients with reductions in circulating intravascular volume. This article discusses fluid resuscitation of shock associated with increased vascular permeability and addresses the use of colloids and crystalloids in these disorders.

Anaphylaxis↗
PubMed1991

Late consolidative radiation therapy in the treatment of limited-stage small cell lung cancer.

Two hundred twenty-three patients were enrolled on this randomized Phase III trial testing the value of late consolidative involved-field radiation therapy in the treatment of limited-stage small cell lung cancer (SCLC). Patients were treated with induction chemotherapy consisting of alternating cycles of procarbazine, vincristine, lomustine, and cyclophosphamide (POCC) and etoposide, doxorubicin, and methotrexate (VAM) for 6 to 9 months. Responding patients were then randomized at 6 or 9 months to chemotherapy alone or to involved-field radiation therapy. All partial and complete responders received prophylactic cranial irradiation. Of the 180 eligible and evaluable patients, 80 (44%) achieved a complete response and 39 (22%) achieved a partial response (overall rate of response, 66%). Actuarial median survival time was 11.6 months, with 16% of patients surviving 2 years and 11% surviving 5 years. Forty-eight patients were randomized to chemotherapy alone (24 patients) versus chemotherapy plus involved-field radiation therapy (24 patients). There were no significant differences in time to progression or survival between those patients receiving or not receiving involved-field radiation therapy. The thorax was the site of first relapse in 58% of patients randomized to chemotherapy alone versus 29% in patients randomized to chemotherapy plus involved-field radiation therapy (P equals 0.042). The major acute toxicity was reversible myelosuppression, and the major late toxicity was chronic central nervous system dysfunction. The authors conclude that the addition of late consolidative radiation therapy to induction chemotherapy in the treatment of limited-stage SCLC is well tolerated and improves local control, but does not improve time to progression or rates of survival.

Adult↗
PubMed1991

Compensatory growth in fibrotic lung injury.

We induced severe left-sided lung fibrosis by the unilateral endobronchial instillation of paraquat (1.0 mg/kg) into the left lungs of adult Fischer 344 male rats. Growth of the contralateral lung as well as its proliferative activity were measured 6 or 14 days later. Whereas the left lung underwent severe fibrosis and shrinkage with more than 85% reduction in lung volume, the right lung more than doubled in size. In addition, there was a significant increase in total protein content, DNA content, and DNA synthesis. We conclude that unilateral lung injury resulting in ipsilateral fibrosis and loss of parenchyma is associated with compensatory growth of the contralateral lung.

Animals↗