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Biomedical subjects

R B Day

Publications and source records attributed to R B Day.

14 recordsLinked to original sources
PubMed2001

Binding site for chitin oligosaccharides in the soybean plasma membrane.

Affinity cross-linking of the plasma membrane fraction to an (125)I-labeled chitin oligosaccharide led to the identification and characterization of an 85-kD, chitin binding protein in plasma membrane-enriched fractions from both suspension-cultured soybean cells and root tissue. Inhibition analysis indicated a binding preference for larger (i.e. degrees of polymerization = 8) N-acetylated chitin molecules with a 50% inhibition of initial activity value of approximately 50 nM. N-Acetyl-glucosamine and chitobiose showed no inhibitory effects at concentrations as high as 250 microM. It is noteworthy that the major lipo-chitin oligosaccharide Nod signal produced by Bradyrhizobium japonicum was also shown to be a competitive inhibitor of ligand binding. However, the binding site appeared to recognize the chitin portion of the Nod signal, and it is unlikely that this binding activity represents a specific Nod signal receptor. Chitooligosaccharide specificity for induction of medium alkalinization and the generation of reactive oxygen in suspension-cultured cells paralleled the binding activity. Taken together, the presence of the chitin binding protein in the plasma membrane fraction and the specificity and induction of a biological response upon ligand binding suggest a role for the protein as an initial response mechanism for chitin perception in soybean (Glycine max).

Binding Sites↗
PubMed2000

Differential expression of two soybean apyrases, one of which is an early nodulin.

Two cDNA clones were isolated from soybean (Glycine soja) by polymerase chain reaction with primers designed to conserved motifs found in apyrases (nucleotide phosphohydrolase). The two cDNAs are predicted to encode for two, distinct, apyrase proteins of approximately 50 kDa (i.e., GS50) and 52 kDa (i.e., GS52). Phylogenetic analysis indicated that GS52 is orthologous to a family of apyrases recently suggested to play a role in legume nodulation. GS50 is paralogous to this family and, therefore, likely plays a different physiological role. Consistent with this analysis, GS50 mRNA was detected in root, hypocotyls, flowers, and stems, while GS52 mRNA was found in root and flowers. Neither gene was expressed in leaves or cotyledons. Inoculation of roots with Bradyrhizobium japonicum, nitrogen-fixing symbiont of soybean, resulted in the rapid (<6 h) induction of GS52 mRNA expression. The level of GS50 mRNA expression was not affected by bacterial inoculation. Western blot (immunoblot) analysis of GS50 expression mirrored the results obtained by mRNA analysis. However, in contrast to the mRNA results, GS52 protein was found in stems. Interestingly, anti-GS52 antibody recognized a 50-kDa protein found only in nodule extracts. Treatment of roots with anti-GS52 antibody, but not anti-GS50 antibody or preimmune serum, blocked nodulation by B. japonicum. Fractionation of cellular membranes in sucrose density gradients and subsequent Western analysis of the fractions revealed that GS50 colocalized with marker enzymes for the Golgi, while GS52 colocalized with marker enzymes for the plasma membrane. Restriction fragment length polymorphism (RFLP)-based mapping placed the gs52 gene on major linkage group J of the integrated genetic map of soybean. These data suggest that GS50 is likely an endo-apyrase involved in Golgi function, while GS52 is localized on the root surface and appears to play an important role in nodulation.

Amino Acid Sequence↗
PubMed2000

Anti-human immunodeficiency virus type 1 (HIV-1) CD8(+) T-lymphocyte reactivity during combination antiretroviral therapy in HIV-1-infected patients with advanced immunodeficiency.

The long-term efficacy of combination antiretroviral therapy may relate to augmentation of anti-human immunodeficiency virus type 1 (HIV-1) CD8(+) T-cell responses. We found that prolonged treatment of late-stage HIV-1-infected patients with a protease inhibitor and two nucleoside reverse transcriptase inhibitors failed to restore sustained, high levels of HIV-1-specific, HLA class I-restricted, cytotoxic-T-lymphocyte precursors and gamma interferon (IFN-gamma) production by CD8(+) T cells. In some patients, particularly those initiating three-drug combination therapy simultaneously rather than sequentially, there were early, transient increases in the frequency of anti-HIV-1 CD8(+) T cells that correlated with decreases in HIV-1 RNA and increases in T-cell counts. In the other patients, HIV-1-specific T-cell functions either failed to increase or declined from baseline during triple-drug therapy, even though some of these patients showed suppression of plasma HIV-1 RNA. These effects of combination therapy were not unique to HIV-1 specific T-cell responses, since similar effects were noted for CD8(+) T cells specific for the cytomegalovirus pp65 matrix protein. The level and breadth of CD8(+) cell reactivity to HLA A*02 HIV-1 epitopes, as determined by IFN-gamma production and HLA tetramer staining after combination therapy, were related to the corresponding responses prior to treatment. There was, however, a stable, residual population of potentially immunocompetent HIV-1-specific T cells remaining after therapy, as shown by tetramer staining of CD8(+) CD45RO(+) cells. These results indicate that new strategies will be needed to target residual, immunocompetent HIV-1-specific CD8(+) T cells to enhance the effectiveness of antiretroviral therapy in patients with advanced immunodeficiency.

Adult↗
PubMed1999

A nod factor binding lectin with apyrase activity from legume roots.

A lectin isolated from the roots of the legume, Dolichos biflorus, binds to Nod factors produced by rhizobial strains that nodulate this plant and has a deduced amino acid sequence with no significant homology to any lectin reported to date. This lectin also is an enzyme that catalyzes the hydrolysis of phosphoanhydride bonds of nucleoside di- and triphosphates; the enzyme activity is increased in the presence of carbohydrate ligands. This lectin-nucleotide phosphohydrolase (LNP) has a substrate specificity characteristic of the apyrase category of phosphohydrolases, and its sequence contains four motifs characteristic of this category of enzymes. LNP is present on the surface of the root hairs, and treatment of roots with antiserum to LNP inhibits their ability to undergo root hair deformation and to form nodules on exposure to rhizobia. These properties suggest that this protein may play a role in the rhizobium-legume symbiosis and/or in a related carbohydrate recognition event endogenous to the plant.

Amino Acid Sequence↗
PubMed1999

Aberrant nodulation response of Vigna umbellata to a Bradyrhizobium japonicum NodZ mutant and nodulation signals.

The (Brady)rhizobium nodulation gene products synthesize lipo-chitin oligosaccharide (LCO) signal molecules that induce nodule primordia on legume roots. In spot inoculation assays with roots of Vigna umbellata, Bradyrhizobium elkanii LCO and chemically synthesized LCO induced aberrant nodule structures, similar to the activity of these LCOs on Glycine soja (soybean). LCOs containing a pentameric chitin backbone and a reducing-end 2-O-methyl fucosyl moiety were active on V. umbellata. In contrast, the synthetic LCO-IV(C16:0), which has previously been shown to be active on G. soja, was inactive on V. umbellata. A B. japonicum NodZ mutant, which produces LCO without 2-O-methyl fucose at the reducing end, was able to induce nodule structures on both plants. Surprisingly, the individual, purified, LCO molecules produced by this mutant were incapable of inducing nodule formation on V. umbellata roots. However, when applied in combination, the LCOs produced by the NodZ mutant acted cooperatively to produce nodulelike structures on V. umbellata roots.

Bacterial Proteins↗
PubMed1999

Lymphocytic alveolitis, bronchoalveolar lavage viral load, and outcome in human immunodeficiency virus infection.

Lymphocytic alveolitis portends a poor prognosis in human immunodeficiency virus (HIV)-infected subjects. Because alveolar lymphocytes consist predominantly of HIV-specific CD8(+) cytotoxic T lymphocytes (CTL), they could represent an appropriate immune response to infected cells in the lung, and be a surrogate marker for a high pulmonary viral burden. We assessed long-term outcome in a cohort of asymptomatic HIV-infected subjects who underwent bronchoscopy between 1990 and 1993 and had bronchoalveolar lavage fluid (BALF) available for determination of viral load by reverse transcription-polymerase chain reaction. The ability to detect HIV in BALF increased with disease progression. Lymphocytic alveolitis, although present at all stages of HIV infection, was most pronounced in patients with middle stage disease. The HIV viral load as measured by bronchoalveolar lavage correlated with the percentage of alveolar lymphocytes in patients with peripheral blood CD4(+) cell counts above 200/microliter. Including patients with CD4(+) cell counts < 200/microliter weakened this correlation, possibly because of replacement of CD8(+) CTL by CD8(+) suppressor cells in advanced disease. Free virus in BALF was a stronger predictor of HIV disease progression than was lymphocytic alveolitis. These data suggest that lymphocytic alveolitis in HIV-infected subjects occurs in response to viral antigens in the lung and that the poor prognosis associated with lymphocytic alveolitis reflects a high pulmonary viral burden.

Adult↗
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↗
PubMed1989

Aminoglycoside dosing in pediatric patients.

We assessed the performance of a predictive algorithm for dosing aminoglycoside antibiotics in 75 pediatric patients and Bayesian feedback in 36. The absolute errors for peak and trough concentrations were 1.83 and 0.80 micrograms/ml, respectively, which seem clinically acceptable for most patients. However, the algorithm had significant negative bias for both peaks and troughs. Implementation of Bayesian feedback eliminated bias in a second set of concentrations and significantly decreased its magnitude for both peaks (p = 0.028) and troughs (p = 0.005). This method may allow more accurate dosing of aminoglycoside antibiotics in pediatric patients, though it would most likely be improved by better definition of population parameters and their variability.

Algorithms↗
PubMed1987

Bayesian and least-squares methods for vancomycin dosing.

The authors assessed the performance of a Bayesian and a least squares method for predicting individual pharmacokinetic parameters for vancomycin. For clearance, the best performance of both methods was an absolute error of approximately 5%. This level of accuracy required 4 serum vancomycin concentrations with the least squares method but could be achieved with a peak and trough concentration with the Bayesian method. For volume of distribution, the best performance occurred with 3 or 4 levels with both methods and amounted to an error of about 15%. In conclusion, both methods of estimating vancomycin pharmacokinetics perform comparably, but the Bayesian method appears to require fewer data.

Bayes Theorem↗
PubMed1986

Accuracy of Bayesian and Sawchuk-Zaske dosing methods for gentamicin.

The derived pharmacokinetic variable estimates from a Bayesian aminoglycoside dosing program were compared with those from the Sawchuk-Zaske method to determine which variable estimates were the most accurate in fitting the test dose and in predicting subsequent peak and trough serum concentrations. Data on 17 patients with moderately impaired but stable renal function were analyzed. All patients received gentamicin sulfate for treatment of their infections. To determine the individualized variables using the Bayesian program, demographic data, dosing history, and one (midpoint), two (peak and trough), or four serum drug concentrations were entered into the program. The Sawchuk-Zaske method used three serum concentrations determined following a first dose or four concentrations before and after a subsequent dose to derive individualized pharmacokinetic variables. The estimates of pharmacokinetic variables determined using the Bayesian method with one, two, or four serum concentrations did not differ significantly from those obtained using all the available serum concentrations with the Sawchuk-Zaske method. Although the actual numeric differences of prediction, absolute, and squared errors for fitting the test dose were minimal, significant differences were seen. All methods were similar in predicting serum concentrations from continued dosing. For the prediction error from continued dosing, a slight but significant difference was observed with the Bayesian method using one serum concentration when compared with the other methods. The Bayesian method using one, two, or four serum gentamicin concentrations individualized pharmacokinetic variables as well as the Sawchuk-Zaske method.

Aged↗
PubMed1985

A Bayesian feedback method of aminoglycoside dosing.

We assessed the accuracy of a Bayesian method in providing dosing regimens to achieve desired serum aminoglycoside concentrations. This method calculates individual kinetics based on serum drug concentration data. Performance was analyzed by determining accuracy, bias, correlations of observed to desired serum drug concentrations, and the ability to achieve a target serum drug concentration. We also compared results from the Bayesian method with those resulting from the use of the predictive algorithm portion of the computer program and with routine physician dosing. The Bayesian method resulted in a high correlation coefficient (r = 0.913) between observed and predicted serum concentrations. Analysis of peak aminoglycoside concentrations indicated that the Bayesian method was more accurate and less biased than the predictive algorithm portion of the program or routine physician dosing. A similar trend occurred for trough concentrations. Finally, there were no statistically significant differences between the predicted and observed peak (6.4 +/- 1.5 and 5.9 +/- micrograms/ml) and trough (1.2 +/- 0.9 and 1.4 +/- 0.8 micrograms/ml) serum aminoglycoside concentrations with the Bayesian dosing method. There were significant differences for peak concentrations with the predictive algorithm portion of the program and for peak and trough concentrations with physician dosing. These data demonstrate the accuracy of the Bayesian dosing method in attaining desired peak and trough serum aminoglycoside concentrations.

Bayes Theorem↗