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R W Carlson

Publications and source records attributed to R W Carlson.

At least 73 records · Page 4Linked to original sources
PubMed1997

Scientific review of tamoxifen. Overview from a medical oncologist.

Tamoxifen is a widely used, effective, and well-tolerated agent in the treatment of primary and recurrent breast cancer. In the adjuvant setting, tamoxifen decreases the annual odds of recurrence and death by 25% and 16%, respectively. The toxicities of tamoxifen are of minor concern in the poor-prognosis group of women with metastatic breast cancer. In the more favorable group of women with early breast cancer, the benefits of tamoxifen appear to substantially outweigh the known toxicities. In retrospective analysis, tamoxifen has been consistently demonstrated to decrease the occurrence of contralateral second breast cancer and to be associated with an increased frequency of diagnosis of endometrial carcinoma. It is not known whether tamoxifen is promoting the growth of pre-existing, clinically occult endometrial carcinomas or is truly etiologic for the development of new cancers. The endometrial carcinomas that are associated with tamoxifen appear to have a biology and natural history similar to non-tamoxifen-associated endometrial carcinomas. There is no evidence supporting an association between hepatocellular carcinomas and tamoxifen in humans. Retrospective analysis of the association of colorectal carcinoma and gastric carcinoma provides little convincing evidence of a causal relationship, although further study is warranted.

Antineoplastic Agents, Hormonal↗
PubMed1996

A special acyl carrier protein for transferring long hydroxylated fatty acids to lipid A in Rhizobium.

Lipid A, the hydrophobic anchor of lipopolysaccharides in the outer membranes of Gram-negative bacteria, varies in structure among different Rhizobiaceae. The Rhizobium meliloti lipid A backbone, like that of Escherichia coli, is a beta1'-6-linked glucosamine disaccharide that is phosphorylated at positions 1 and 4'. Rhizobium leguminosarum lipid A lacks both phosphates, but contains aminogluconate in place of the proximal glucosamine 1-phosphate, and galacturonic acid instead of the 4'-phosphate. A peculiar feature of the lipid As of all Rhizobiaceae is acylation with 27-hydroxyoctacosanoic acid, a long hydroxylated fatty acid not found in E. coli. We now describe an in vitro system, consisting of a membrane enzyme and a cytosolic acyl donor from R. leguminosarum, that transfers 27-hydroxyoctacosanoic acid to (Kdo)2-lipid IVA, a key lipid A precursor common to both E. coli and R. leguminosarum. The 27-hydroxyoctacosanoic acid moiety was detected in the lipid product by mass spectrometry. The membrane enzyme required the presence of Kdo residues in the acceptor substrate for activity. The cytosolic acyl donor was purified from wild-type R. leguminosarum using the acylation of (Kdo)2-[4'-32P]-lipid IVA as the assay. Amino-terminal sequencing of the purified acyl donor revealed an exact 19-amino acid match with a partially sequenced gene (orf*) of R. leguminosarum. Orf* contains the consensus sequence, DSLD, for attachment of 4'-phosphopantetheine. When the entire orf* gene was sequenced, it was found to encode a protein of 92 amino acids. Orf* is a new kind of acyl carrier protein because it is only approximately 25% identical both to the constitutive acyl carrier protein (AcpP) and to the inducible acyl carrier protein (NodF) of R. leguminosarum. Mass spectrometry of purified active Orf* confirmed the presence of 4'-phosphopantetheine and 27-hydroxyoctacosanoic acid in the major species. Smaller mass peaks indicative of Orf* acylation with hydroxylated 20, 22, 24, and 26 carbon fatty acids were also observed. Given the specialized function of Orf* in lipid A acylation, we suggest the new designation AcpXL.

Acyl Carrier Protein↗
PubMed1996

Does a full-time, 24-hour intensivist improve care and efficiency?

This article reviews the hypothesis that staffing with full-time intensive care physicians leads to improvements in the management of ICUs and in the outcome for ICU patients. Variations in the professional organization of critical care units in the United States are discussed. The advantages and disadvantages of open, closed, and transitional (comanagement) ICU organizational structures are presented.

Decision Making, Organizational↗
PubMed1996

A novel relationship between O-antigen variation, matrix formation, and invasiveness of Salmonella enteritidis.

Salmonella enterica Enteritidis in chickens serves as a reservoir for salmonellosis in humans and the structure of its lipopolysaccharide (LPS) has been used to assess invasiveness. Culture from chick spleens generated colonies with an unusual wrinkled morphology, and it is designated the lacy phenotype. The characterize the nature of the morphological change, three isogenic variants were compared. Only the lacy phenotype produced a temperature-dependent cell surface matrix composed of several proteins in association with LPS high molecular weight O-antigen. Flagellin and a 35 kDa protein were identified as specific proteinaceous components of matrix. Both proteins cross-reacted with a monoclonal antibody previously determined to specifically detect the g-epitope of the Enteritidis monophasic flagella (H-antigen). These results suggest that O-antigen in association with protein contributes to cross-reactivity between molecules. The lacy phenotype was more organ invasive in 5-day-old chicks than isogenic variants producing low molecular weight O-antigen. However, it was no more efficient at contaminating eggs after oral inoculation of hens than a variant that completely lacked O-antigen, thus the lacy phenotype is classified as an intermediately invasive organism. The distinctive colonial phenotype of SE6-E21lacy was used to investigate environmental factors that decreased O/C ratios and contributed to attenuation. In so doing, it was found that growth in complement at 46 degrees C caused matrix producing cells to hyperflagellate and migrate across agar surfaces. These results suggest that the structure of O-antigen might influence the secretion and/or the function of Enteritidis cell-surface proteins. The data also reveal a greater heterogeneity than has been assumed in the phenotype, and possibly the infectious behaviour, of Enteritidis.

Animals↗
PubMed1996

Separation of bacterial capsular and lipopolysaccharides by preparative electrophoresis.

Preparative gel electrophoresis was used to separate and purify extracellular, capsular and lipopolysaccharides (EPSs, CPSs, and LPSs, respectively) from crude bacterial extracts. The procedure effectively separates CPS from LPSs. In addition discreet size ranges of these various polysaccharides can be isolated. The 'rough' (R-type), 'smooth' (S-type), and 'semi-smooth' LPSs were separated from one another. In addition different size classes of 'semi-smooth', or S-type LPS, can be separated. This procedure was demonstrated for diverse bacterial species, including the soil bacteria Rhizobium fredii, and the enteric bacterial species, Salmonella enteritidis and Proteus mirabilis. In the latter case, it was also possible to separate capsular polysaccharide from its lipid-bound form.

Electrophoresis, Polyacrylamide Gel↗
PubMed1996

Cooperative action of lipo-chitin nodulation signals on the induction of the early nodulin, ENOD2, in soybean roots.

Various lipo-chitin molecules were tested for their ability to induce the expression of the early nodulin, ENOD2, in Glycine soja roots. When inoculated separately onto G. soja roots, LCO-V (C18:1 delta 11,Mefuc), LCO-V (C18:1 delta 9,Mefuc), LCO-V (C16:0,Mefuc), and LCO-IV (C16:0) were unable to induce ENOD2 expression, even though these compounds had previously been shown to induce root hair curling, the formation of nodule-like primordia, and induction of the early nodulin, ENOD40. ENOD2 expression, however, was induced when any two of these molecules were inoculated in combination. Thus, the lipo-chitin nodulation signals appear to act cooperatively to induce ENOD2 expression. B. japonicum strains USDA110 and USDA135 and B. elkanii strain USDA61, all symbionts of soybean, were found to produce at least two distinct nod signals ([i.e., NodBj-V[C18:1,Mefuc] and NodBj-V[C16:0,Mefuc]). These two compounds were mixed in various ratios and tested for their ability to induce ENOD2 expression. The results indicate that the former compound must be present in equivalent or excess amount in order to obtain maximum ENOD2 expression. Additional nonspecific LCOs (e.g., LCO-IV[C16:2 delta 2,9; SO3]), incapable of inducing root hair curling or cortical cell division, were tested in combination with the four active LCOs listed above. It was found that any combination of one active LCO with a nonspecific LCO was sufficient to induce ENOD2 mRNA expression. The ENOD2 mRNA expression pattern detected by in situ hybridization closely resembled that found in bacterial-induced nodules with expression detected in cortical cells between primary and secondary meristems and around the vascular strands. These data demonstrate that the cooperative action of at least two LCO nodulation signals leads to a greater progression of nodule ontogeny as demonstrated by the expression of ENOD2, a marker gene for the differentiation of nodule parenchyma.

Carbohydrate Sequence↗
PubMed1996

Genetic and chemical characterization of a mutant that disrupts synthesis of the lipopolysaccharide core tetrasaccharide in Rhizobium leguminosarum.

A 2-kb region that complements the Tn5-derived lipopolysaccharide (LPS) rough mutant Rhizobium leguminosarum RU301 was sequenced. Two open reading frames (ORFs) were identified. The first ORF (lpcA) is homologous to a family of bacterial sugar transferases involved in LPS core tetrasaccharide biosynthesis. ORF2 (lpcB), in which Tn5 transposed, has no significant homology to any DNA in the GenBank-EMBL databases. Chemical characterization of LPS produced by strain RU301 demonstrated that the 3-deoxy-D-manno-2-octulosonic acid (Kdo) residue which normally attaches the core tetrasaccharide to the O chain was missing, suggesting that IpcB may encode a CMP-Kdo:LPS Kdo transferase.

Amino Acid Sequence↗
PubMed1996

Two glycosyltransferase genes, lgtF and rfaK, constitute the lipooligosaccharide ice (inner core extension) biosynthesis operon of Neisseria meningitidis.

We have characterized an operon required for inner-core biosynthesis of the lipooligosaccharide (LOS) of Neisseria meningitidis. Using Tn916 mutagenesis, we recently identified the alpha-1,2-N-acetylglucosamine (GlcNAc) transferase gene (rfaK), which when inactivated prevents the addition of GlcNAc and alpha chain to the meningococcal LOS inner core (C. M. Kahler, R. W. Carlson, M. M. Rahman, L. E. Martin, and D. S. Stephens, J. Bacteriol. 178:1265-1273, 1996). During the study of rfaK, a second open reading frame (lgtF) of 720 bp was found upstream of rfaK. An amino acid sequence homology search of the GenBank and EMBL databases revealed that the amino terminus of LgtF has significant homology with a family of beta-glycosyltransferases involved in the biosynthesis of polysaccharides and O antigen of lipopolysaccharides. The chromosomal copy of lgtF was mutagenized with a nonpolar antibiotic resistance cassette to minimize potential polar effects on rfaK. Tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis and composition analysis of the LOS from the nonpolar lgtF mutant showed that this strain produced a truncated LOS structure which contained a LOS inner core of GlcNAc1Hep2KDO2lipid A but without the addition of lacto-N-neotetraose to HepI or glucose to HepII. These results and the amino acid homology with beta-glycosyltransferases suggest that lgtF encodes the UDP-glucose:LOS-beta-1,4-glucosyltransferase which attaches the first glucose residue to HepI of LOS. Reverse transcriptase PCR and primer extension analysis indicate that both lgtF and rfaK are cotranscribed as a polycistronic message from a promoter upstream of lgtF. This arrangement suggests that completion of the LOS inner core and the initiation of the alpha chain addition are tightly coregulated in N. meningitidis.

Amino Acid Sequence↗
PubMed1996

Inner core biosynthesis of lipooligosaccharide (LOS) in Neisseria meningitidis serogroup B: identification and role in LOS assembly of the alpha1,2 N-acetylglucosamine transferase (RfaK).

A lipooligosaccharide (LOS) mutant of Neisseria meningitidis serogroup B strain NMB (immunotype L3,7,9) was identified in a Tn916 (tetM) mutant bank by loss of reactivity with monoclonal antibody 3F11, which recognizes the terminal Galbeta1-->4GlcNAc epitope in the lacto-N-neotetraose moiety of the wild-type LOS structure. The mutant, designated 559, was found to express a truncated LOS of 3.0 kDa. Southern and PCR analyses demonstrated that there was a single intact Tn916 insertion (class I) in the mutant 559 chromosome. Linkage of the LOS phenotype and the Tn916 insertion was confirmed by transformation of the wild-type parent. Nucleotide sequence analysis of the region surrounding the transposition site revealed a 1,065-bp open reading frame (ORF). A homology search of the GenBank/EMBL database revealed that the amino acid sequence of this ORF had 46.8% similarity and 21.2% identity with the alpha1,2 N-acetylglucosamine transferase (RfaK) from Salmonella typhimurium. Glycosyl composition and linkage analysis of the LOS produced by mutant 559 revealed that the lacto-N-neotetraose group which is attached to heptose I (HepI) and the N-acetylglucosamine and glucose residues that are attached to HepII in the inner core of the parental LOS were absent. These analyses also showed that the HepII residue in both the parent and the mutant LOS molecules was phosphorylated, presumably by a phosphoethanolamine substituent. The insertion of nonpolar and polar antibiotic resistance cartridges into the parental rfaK gene resulted in the expression of LOS with the same mobility as that produced by mutant 559. This result indicated that the inability to add the lacto-N-neotetraose group to the 559 LOS is not due to a polar effect on a gene(s) downstream of rfaK. Our data indicate that we have identified the meningococcal alpha1,2 N-acetylglucosamine transferase responsible for the addition of N-acetylglucosamine to HepII. We propose that the lack of alpha-chain extension from HepI in the LOS of mutant 559 may be due to structural constraints imposed by the incomplete biosynthesis of the LOS inner core.

Amino Acid Sequence↗
PubMed1996

Trade-offs between survival and breast preservation for three initial treatments of ductal carcinoma-in-situ of the breast.

PURPOSE: To assess the trade-offs between survival and breast preservation of currently accepted approaches for ductal carcinoma-in-situ (DCIS) of the breast. PATIENTS AND METHODS: Decision analysis was performed using the Markov model of hypothetical cohorts of 55-year-old white women with nonpalpable mammographic abnormalities found to be DCIS. Strategies were breast-conserving surgery (BCS), BCS with 50-Gy radiation (RT) or initial mastectomy. Recurrence rates were derived from the published literature. Main outcomes were overall, breast cancer-free, and event-free survival plus years of both breasts preserved. RESULTS: Using the conditions defined in this model, the actuarial survival rates at 10 and 20 years were 91.7% and 74.1% for the initial mastectomy strategy, 91.0% and 72.1% for BCS plus RT, and 89.6% and 68.2% for BCS alone. At 20 years, the initial mastectomy strategy also had a greater breast cancer-free survival rate of 74.5%, compared with 63.3% for BCS plus RT, or 46.8% for BCS alone. However, BCS alone had the highest survival rate with both breasts preserved (64.2%) compared with BCS plus RT (56.0%) or initial mastectomy (0%). Of the breast-conserving strategies at 20 years, the breast event-free survival rate (no invasive cancer or DCIS) was greater for BCS plus RT (47.2%) compared with BCS alone (28.4%). Using just survival as the primary end point, mastectomy is the optimal strategy by a small margin. However, if quality-adjusted survival is at issue, mastectomy is the choice only if the yearly reduction in quality of life due to mastectomy is less than 1%. CONCLUSION: BCS with or without radiation compared with mastectomy as initial management of DCIS of the breast trades a slight decrease in survival rates for the value of breast preservation. This model should aid clinicians in matching treatments to their patients' preferences.

Aged↗
PubMed1996

Toward reusable software components at the point of care.

An architecture built from five software components -a Router, Parser, Matcher, Mapper, and Server -fulfills key requirements common to several point-of-care information and knowledge processing tasks. The requirements include problem-list creation, exploiting the contents of the Electronic Medical Record for the patient at hand, knowledge access, and support for semantic visualization and software agents. The components use the National Library of Medicine Unified Medical Language System to create and exploit lexical closure-a state in which terms, text and reference models are represented explicitly and consistently. Preliminary versions of the components are in use in an oncology knowledge server.

Computer Systems↗
PubMed1995

Lipid A biosynthesis in Rhizobium leguminosarum: role of a 2-keto-3-deoxyoctulosonate-activated 4' phosphatase.

Lipid A from several strains of the N2-fixing bacterium Rhizobium leguminosarum displays significant structural differences from Escherichia coli lipid A, one of which is the complete absence of phosphate groups. However, the first seven enzymes of E. coli lipid A biosynthesis, leading from UDP-GlcNAc to the phosphorylated intermediate, 2-keto-3-deoxyoctulosonate (Kdo2)-lipid IVA, are present in R. leguminosarum. We now describe a membrane-bound phosphatase in R. leguminosarum extracts that removes the 4' phosphate of Kdo2-lipid IVA. The 4' phosphatase is selective for substrates containing the Kdo domain. It is present in extracts of R. leguminosarum biovars phaseoli, viciae, and trifolii but is not detectable in E. coli and Rhizobium meliloti. A nodulation-defective strain (24AR) of R. leguminosarum biovar trifolii, known to contain a 4' phosphatase residue on its lipid A, also lacks measurable 4' phosphatase activity. The Kdo-dependent 4' phosphatase appears to be a key reaction in a pathway for generating phosphate-deficient lipid A.

Carbohydrate Sequence↗
PubMed1995

The importance of the lumpectomy surgical margin status in long-term results of breast conservation.

BACKGROUND: The impact of the surgical margin status on long-term local control rates for breast cancer in women treated with lumpectomy and radiation therapy is unclear. METHODS: The records of 289 women with 303 invasive breast cancers who were treated with lumpectomy and radiation therapy from 1972 to 1992 were reviewed. The surgical margin was classified as positive (transecting the inked margin), close (less than or equal to 2 mm from the margin), negative, or indeterminate, based on the initial biopsy findings and reexcision specimens, as appropriate. Various clinical and pathologic factors were analyzed as potential prognostic factors for local recurrence in addition to the margin status, including T classification, N classification, age, histologic features, and use of adjuvant therapy. The mean follow-up was 6.25 years. RESULTS: The actuarial probability of freedom from local recurrence for the entire group of patients at 5 and 10 years was 94% and 87%, respectively. The actuarial probability of local control at 10 years was 98% for those patients with negative surgical margins versus 82% for all others (P = 0.007). The local control rate at 10 years was 97% for patients who underwent reexcision and 84% for those who did not. Reexcision appears to convey a local control benefit for those patients with close, indeterminate, or positive initial margins, when negative final margins are attained (P = 0.0001). Final margin status was the most significant determinant of local recurrence rates in univariate analysis. By multivariate analysis, the final margin status and use of adjuvant chemotherapy were significant prognostic factors. CONCLUSIONS: The attainment of negative surgical margins, initially or at the time of reexcision, is the most significant predictor of local control after breast-conserving treatment with lumpectomy and radiation therapy.

Adult↗
PubMed1995

Lipopolysaccharide core structures in Rhizobium etli and mutants deficient in O-antigen.

Lipopolysaccharide (LPS) is a major component of the bacterial outer membrane, and for Rhizobium spp. has been shown to play a critical role in the establishment of an effective nitrogen-fixing symbiosis with a legume host. Many genes required for O-chain polysaccharide synthesis are in the lps alpha region of the CE3 genome; this region may also carry lps genes required for core oligosaccharide synthesis. The LPSs from several strains mutated in the alpha region were isolated, and their mild acid released oligosaccharides, purified by high performance anion-exchange chromatography, were characterized by electrospray- and fast atom bombardment-mass spectrometry, NMR, and methylation analysis. The LPSs from several mutants contained truncated O-chains, and the core region consisted of a (3-deoxy-D-manno-2-octulosomic acid) (Kdo)-(2-->6)-alpha-Galp-(1-->6)-[alpha-GalpA-(1-->4)]-alpha-Ma np-(1-->5)- Kdop (3-deoxy-D-manno-2-octulosomic acid) (Kdo)pentasaccharide and a alpha-GalpA-(1-->4)-[alpha-GalpA-(1-->5)]-Kdop trisaccharide. The pentasaccharide was altered in two mutants in that it was missing either the terminal Kdo or the GalA residue. These results indicate that the lps alpha region, in addition to having the genes for O-chain synthesis, contains genes required for the transfer of these 2 residues to the core region. Also, the results show that an LPS with a complete core but lacking an O-chain polysaccharide is not sufficient for an effective symbiosis.

Carbohydrate Sequence↗
PubMed1995

The structure of a novel polysaccharide produced by Bradyrhizobium species within soybean nodules.

Certain strains of Bradyrhizobium japonicum and B. elkanii produce a polysaccharide within the root nodules of their legume host, soybean. These nodule polysaccharides (NPSs) were isolated and characterized. The NPS produced by B. elkanii strains proved to be identical in glycosyl composition and linkages to the extracellular polysaccharide (EPS) of this species indicating that the NPS and EPS for B. elkanii have identical structures (W.F. Dudman, Carbohydr. Res., 66 (1978) 9-23), [formula: see text] However, the structure of the NPS from B. japonicum proved to be quite different from that of its EPS. Methylation analysis of this NPS showed that it consists of 3-linked Gal, 3-linked Rha, 2,4-linked Rha, 4-linked Rha, and terminal 2-O-methyl GlcA in a 1:1:1:1:1 ratio. Stereochemical configurations of the glycosyl residues were determined by the preparation and analysis of trimethylsilyl (Me3Si) (-)-2-butyl glycosides. NMR spectroscopy (both 1H and 13C) showed that the Gal residue is alpha-linked, while all the other glycosyl residues are beta-linked. Oligosaccharides produced by periodate oxidation-Smith degradation were purified, as were oligosaccharides produced by partial acid hydrolysis. Characterization of the Smith degradation products by methylation analysis. NMR spectroscopy, electrospray-mass spectrometry, and characterization of the partial acid hydrolysate oligosaccharides showed that the repeating oligosaccharide unit of the NPS has the structure, [formula: see text]

Carbohydrate Sequence↗