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Biomedical subjects

B Prescott

Publications and source records attributed to B Prescott.

At least 19 recordsLinked to original sources
PubMed1994

Predicting falls: the role of mobility and nonphysical factors.

OBJECTIVE: Our purpose was to test a four-domain predictive model of recurrent falls developed for this study. In this model, limited mobility is considered a necessary but not sufficient element in risk of recurrent falls. Three other domains, attitudinal, social, and environmental, are proposed to influence fall risk only in persons with impaired mobility. DESIGN: Prospective cohort study. SETTING: Veterans Affairs Ambulatory Care Service serving rural and urban central North Carolina. SUBJECTS: Male Veterans aged 70 or older (n = 306) were monitored prospectively for falls. At baseline, 159 screened as high-risk mobility status and 147 as low-risk mobility status. MEASUREMENTS: The primary outcome was recurrent falls. The mobility screen used for risk assignment defined immobile as unable to sit without support for 60 seconds, mobile and stable as meeting criteria for normal ambulation and stair climbing, and mobile but unstable as those who met neither of the above criteria. The high-risk subjects were further assessed in their homes for mobility in more detail, attitude toward risk, social supports, and environmental status. Other data included demographics, functional status, diagnoses, and medications. RESULTS: Recurrent falls occurred in 37 (23.3%) high-risk subjects and seven (4.8%) low-risk subjects (relative risk = 4.8, confidence interval 2.5 to 9.6, P < 0.001). Within the high-risk group, the probability of recurrent falls was significantly affected by degree of impaired mobility (P < 0.001), attitude toward risk (P = 0.005), and environment score (P = 0.03). CONCLUSIONS: A simple mobility screen can identify elders at increased risk for recurrent falls. Risk within this group is further modified by risk-taking behavior and environment.

Accidental Falls↗
PubMed1993

How do physiological components of balance affect mobility in elderly men?

The purpose of this study was to assess the relationship between physiological components of balance and mobility in elderly men without significant disease. Our a priori hypothesis was that physical function is influenced more by accumulated modest impairments than by a single deficit. We examined 39 ambulatory men (> 69 years). Subjects were classified functionally as high, intermediate, or low. Assessment included mobility functions (6-minute walk, mobility skills, reach, 10ft walk time) and physiological components of balance: sensory (vibration, proprioception, vision, vestibular), effector (ankle, knee, hip strength, range of motion), and central processing (response time to perturbations). All mobility functions were significantly (p < .05) different between groups. Impairments in components of postural control were rarely different between groups: the major differences were in ankle strength and visual fields. The number of impaired domains differed across the three groups. Nineteen percent of the low group had at least three domains impaired; none of the intermediate or high groups were impaired in three domains. Fifty-six percent of the low, 20% of the intermediate, and 7% of the high were impaired in two or more domains. Variability in specific mobility measures was also predicted by the number of impaired domains. The decline in physical function may be better explained by the accumulation of deficits across multiple domains than by any single specific impairment.

Accidental Falls↗
PubMed1992

Functional reach: predictive validity in a sample of elderly male veterans.

A new measure of balance, functional reach, has been recently developed. Functional reach is the maximal distance one can reach forward beyond arm's length while maintaining a fixed base of support in the standing position. Reliability, criterion, and concurrent construct validity of functional reach have been established. The purpose of this study was to assess the predictive validity of functional reach in identifying elderly subjects at risk for recurrent falls. Two hundred and seventeen elderly, community-dwelling male veterans (aged 70-104) underwent baseline screening and were followed for 6 months to monitor falls. Subjects with two or more falls during the 6-month follow-up were classified as recurrent fallers. Logistic regression reveals that if individuals were unable to reach, the adjusted odds ratio (OR) of having two falls was 8.07 (2.8-23.71); if their reach was less than or equal to 6 inches the OR was 4.02 (1.84-8.77); and if reach was greater than 6 inches but less than 10 inches the OR was 2.00 (1.35-2.98). The association between functional reach and recurrent falls was not confounded by age, depression, or cognition. We conclude that functional reach is a simple and easy-to-use clinical measure that has predictive validity in identifying recurrent falls.

Accidental Falls↗
PubMed1988

Sugar pucker and phosphodiester conformations in viral genomes of filamentous bacteriophages: fd, If1, IKe, Pf1, Xf, and Pf3.

The laser Raman spectra of filamentous viruses contain discrete bands which are assignable to molecular vibrations of the encapsidated, single-stranded DNA genomes and which are informative of their molecular conformations. Discrimination between Raman bands of the DNA and those of the coat proteins is facilitated by analysis of viruses containing deuterium-labeled amino acids. Specific DNA vibrational assignments are based upon previous studies of A-, B-, and Z-DNA oligonucleotide crystals of known structure [Thomas, G.J., Jr., & Wang, A.H.-J. (1988) in Nucleic Acids and Molecular Biology (Eckstein, F., & Lilley, D.M.J., Eds.) Vol. 2, Springer-Verlag, Berlin]. The present results show that canonical DNA structures are absent from six filamentous viruses: fd, If1, IKe, Pfl, Xf, and Pf3. The DNAs in three viruses of symmetry class I (fd, If1, IKe) contain very similar nucleoside sugar puckers and glycosyl torsions, deduced to be C3'-endo/anti. However, nucleoside conformations are not the same among the three class II viruses examined: Pf1 and Xf DNAs contain similar conformers, deduced to be C2'-endo/anti, whereas Pf3 DNA exhibits bands usually associated with C3'-endo/anti conformers. Conformation-sensitive Raman bands of the DNA 3'-C-O-P-O-C-5' groups show that in all class I viruses and in Pf1 the ssDNA backbones do not contain regularly ordered phosphodiester group geometries, like those found in ordered single- and double-stranded nucleic acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophages↗
PubMed1988

Raman spectroscopy of mercury (II) binding to two filamentous viruses: Ff (fd, M13, f1) and Pf1.

Ff and Pf1 are filamentous bacteriophages. Each contains, in a central core region surrounded by protein, a circular single-stranded DNA molecule, and it is known that the DNA bases are sites of Hg(II) binding. In the present study, Raman spectra were obtained for the two viruses in the presence of increasing amounts of Hg(II), with ratios (m) of Hg(II) added per nucleotide residue in the range 0 less than m less than 2.0. Hg(II) binding to the viruses induces Raman intensity changes in previously assigned Raman lines of viral DNA, demonstrating metal binding to the DNA bases, but also in many lines assigned to protein. The overall structures of the viruses do not change with Hg(II) binding, and the Raman spectra indicate little, if any, change in protein secondary structure. Changes in certain protein Raman lines induced by Hg(II) binding to the DNA for low values of m are attributed to altered interactions between solvent and protein side chains, aliphatic groups being the most affected. The nature of such changes for both viruses suggests DNA-protein linkage. In Pf1, lines assigned to ring vibrations of all four bases are perturbed upon initial addition of Hg(II) to m = 0.25. In Ff, however, lines assigned to base ring vibrations are not perturbed until m greater than or equal to 0.5. The results provide additional evidence for fundamentally different DNA structures in Ff and Pf1.

Coliphages↗
PubMed1988

Examination of the differential characteristics of amplifier and contrasuppressor T cells.

Vicia villosa lectin-adherent Lyt-1+ spleen cells, obtained 4 days after immunization with an optimally immunogenic dose (0.5 micrograms) of Type III pneumococcal polysaccharide (SSS-III), increased the magnitude of the antibody response of mice to SSS-III upon transfer to recipients also immunized with the same antigen; however, the ability to demonstrate such enhancement depended greatly upon when such cells were transferred relative to immunization of recipients. Lectin-adherent cells augmented the antibody response of athymic nude (nu/nu) mice to SSS-III, and abrogated the expression - but not the induction - of low-dose immunological paralysis, a form of unresponsiveness mediated by suppressor T cells. These findings are consistent with effects usually attributed to the action of amplifier, rather than contrasuppressor, T cells.

Animals↗
PubMed1988

Ability of monophosphoryl lipid A to augment the antibody response of young mice.

Treatment with nontoxic monophosphoryl lipid A increased the magnitude of the immunoglobulin M (IgM) antibody response to type III pneumococcal polysaccharide in young (2- to 4-week-old) mice. This was accompanied by the appearance of significant numbers of IgG1- and IgG3- secreting antibody-forming cells in 4-week-old mice. These findings indicate that monophosphoryl lipid A can be used as an adjuvant to improve the immunogenicity of poorly immunogenic antigens in young, immunologically immature animals.

Adjuvants, Immunologic↗
PubMed1988

Inactivation of suppressor T-cell activity by nontoxic monophosphoryl lipid A.

Treatment with nontoxic monophosphoryl lipid A (MPL), which was derived from a polysaccharide-deficient, heptoseless Re mutant of Salmonella typhimurium, was found to inactivate suppressor T-cell activity, as evidenced by a decrease in the degree of low-dose immunological paralysis expressed and an increase in the magnitude of the antibody response to type III pneumococcal polysaccharide. The effects produced, which could not be attributed to the polyclonal activation of immune B cells by MPL, were dependent upon the dose of MPL used, as well as the time when MPL was given relative to low-dose priming or immunization with type III pneumococcal polysaccharide. Neither amplifier nor helper T-cell activity was decreased by treatment with the same, or larger, doses of MPL. The significance of these findings to the use of MPL as an immunological adjuvant or an immunomodulating agent is discussed.

Adjuvants, Immunologic↗
PubMed1987

Phage phi X174 probed by laser Raman spectroscopy: evidence for capsid-imposed constraint on DNA secondary structure.

The Raman spectrum of the isometric bacteriophage phi X174 contains a number of well-resolved bands which have been assigned unambiguously to proteins of the capsid or to the single-stranded DNA (ssDNA) genome. Additional Raman bands of protein and DNA, which are partially overlapped in the spectrum of virus, have been resolution enhanced by Fourier deconvolution to permit improved semiquantitative measurement of spectral intensities and frequencies for structural conclusions. Raman conformation markers indicate that the ssDNA molecule within the capsid contains nucleosides of C2'-endo sugar pucker and anti-glycoside bond orientation, but the nucleic acid backbone lacks the geometry characteristic of B-form DNA. The Raman profile of encapsidated phi X DNA indicates a backbone more similar to heat-denatured DNA than to DNA containing hairpinlike secondary structure. This finding suggests limited interbase interactions in the packaged genome, which is presumably the result of constraints imposed by the viral capsid. Thus, the extensive pairing and stacking of bases indicated by Raman profiles from ssRNA viruses are not evident for the phi X174 chromosome. Overall, the proteins of the virion contain extensive beta-sheet and irregular secondary structures. Fourier deconvolution of the Raman amide I band provides an estimate of the percentage of total beta-sheet structure (approximately 60%) in all proteins of the virion. The amide III region of the spectrum confirms that beta-sheet and irregular domains are the predominant protein secondary structures. Samples of phi X174 concentrated for Raman spectroscopy by either ultracentrifugation or ultrafiltration exhibit nearly identical Raman spectra, indicating that either method can be employed to prepare intact virus without significant loss of DNA or protein components.

Bacteriophage phi X 174↗
PubMed1987

Increased activation of antigen-primed or memory B cells by bacterial lipopolysaccharide.

Treatment with bacterial lipopolysaccharide elicits the appearance of greater numbers of background antigen-specific plaque-forming cells (PFC) in the spleens of mice previously exposed or primed to subimmunogenic amounts of various non-cross-reacting antigens so as to generate detectable immunological memory. These findings suggest that treatment with lipopolysaccharide results in the activation of increased numbers of antigen-primed or memory B cells in mice previously exposed to antigen.

Animals↗
PubMed1986

N-terminal domain of the bacteriophage lambda repressor: investigation of secondary structure and tyrosine hydrogen bonding in wild-type and mutant sequences by Raman spectroscopy.

Laser Raman spectroscopy has been employed to investigate structures of the lambda repressor N-terminal fragment, which recognizes operator DNA. Examination of repressor fragments containing deuterated amide groups and specifically labeled deuteriotyrosines has enabled the assignment of many of the conformation-sensitive Raman bands. By use of Fourier deconvolution and signal averaging techniques, the spectra of both wild-type and mutant sequences have been obtained as a function of the total protein concentration in aqueous solution over the range 5-100 mg/mL. This analysis has permitted monitoring of the monomer-dimer association of the repressor fragment and determination of the effects of dimerization upon individual side-chain interactions and main-chain secondary structure. The spectra are interpreted to reveal the hydrogen-bonding environments of four tyrosines of the N-terminal fragment (Y22, Y60, Y85, and Y88). The fifth tyrosine (Y101) is known from NMR experiments to be exposed to solvent molecules. The results show that in the dimer Y22 and Y85 are each acceptors of a strong hydrogen bond from a positive donor group, while Y88 is the donor of a strong hydrogen bond to a negative acceptor and Y60, like Y101, is involved in both a donor role and an acceptor role. Y60, Y85, and Y88, which are all near the dimer interface, undergo a collective change in hydrogen-bonding environment with dissociation of the dimer. The net effect of this change is the conversion of one acceptor tyrosine, deduced to be Y88, to a combined donor and acceptor role. The Raman results also indicate a predominantly alpha-helical structure for the N-terminal fragment in aqueous solution, with 70 +/- 4% of the residues incorporated into helical domains. The amount of alpha-helix determined from the Raman spectrum is consistent with X-ray and prediction results and is altered neither by the mutations C85----Y85 and C88----Y88 nor by dissociation of the dimer.

Amino Acid Sequence↗
PubMed1986

A Raman spectroscopic study of hen egg yolk phosvitin: structures in solution and in the solid state.

Laser Raman spectroscopy has been employed to study the structure of the hen egg yolk protein phosvitin in H2O and D2O solutions at neutral and acidic pH (pD) and in the solid state. The Raman data indicate an unusual conformation for phosvitin in neutral aqueous solution, which is deficient in both alpha-helix and conventional beta-sheet conformations. This unusual pH 7 structure is, however, largely converted to a beta-sheet conformation in strongly acidic media (pH less than 2). beta-Sheet is also the predominant secondary structure for phosvitin in the solid state, obtained by lyophilization of the protein from aqueous solution at neutral pH. The imidazolium rings of histidyl residues remain significantly protonated near neutrality, which suggests substantial elevation of the pK for imidazolium ring ionizations of phosvitin in aqueous solution. This may result from extensive ion-pair interactions involving positively charged histidines and negatively charged phosphoserines, which are prevalent in the phosvitin sequence. The present results suggest that antiparallel beta-sheets may not be the secondary structure most characteristic of native phosvitin (physiological pH), even though beta-sheet is the predominant conformation for phosvitin in acidic solutions (pH 1.5) and in the lyophilized solid. Phosvitin appears to be the first protein for which the major component to the Raman amide I band is centered near 1685 cm-1, which is 10-40 cm-1 higher than proteins heretofore examined in aqueous solution by Raman spectroscopy.

Animals↗
PubMed1986

Separation of immunomodulatory effects of mannan from Candida albicans into stimulatory and suppressive components.

Mannan extracted from Candida albicans was studied for its immunomodulatory activity on in vivo antibody responses to type III pneumococcal polysaccharide (SSS-III), a helper-T-cell-independent antigen, and to sheep erythrocytes (SRBC), a helper-T-cell-dependent antigen. In some studies, the antibody response to SSS-III was converted to a helper-T-cell-dependent response by attaching it to a carrier (horse erythrocytes, HRBC); this complex then was used to immunize mice primed with a subimmunogenic dose of HRBC. Mannan enhanced the antibody response to both SSS-III and SRBC when administered at the same time or 1 or 2 days after immunogen. However, when both mannan and SSS-III were coated onto HRBC for immunization, either enhancement or suppression was noted; the effect depended upon the amount of mannan used. Larger amounts stimulated, whereas smaller amounts suppressed, the antibody response to SSS-III. The enhancing and suppressive components of mannan could be separated by molecular size or charge by chromatography on Sepharose 4B or on DEAE-Sephadex A-50 columns, indicating that mannan extracts contain individual components having opposing immunomodulatory properties. These components can be separated on the basis of molecular size and charge.

Animals↗
PubMed1985

Protein-RNA interactions in belladonna mottle virus investigated by laser Raman spectroscopy.

Raman difference spectroscopy of the belladonna mottle virus (BDMV) and its separated RNA and protein components indicates that molecular interaction occurs between the single-stranded RNA genome and capsid subunits. The molecular interactions that stabilize the virion at pH 5.0 are altered or eliminated at pH 8.0, even though release of the RNA from the capsid is prevented by the addition of divalent metal cations (Ca2+). From the perturbations that occur to Raman lines of cytosine and adenine rings of the encapsidated RNA molecule between pH values of 5.0 and 8.0, it is concluded that cytosines are protonated in significant numbers at the conditions which maintain the native virus structure and that the stacking of adenines is altered by changes in pH. The degree of protonation of RNA bases can be reduced by elevation of the pH to 8.0 for encapsidated RNA or by release of the RNA from the capsid at pH 5.0. Although the protein groups that interact with the viral RNA cannot be identified unambiguously from the Raman spectra, it is apparent that the molecular environments of aromatic amino acid side chains are altered with the same changes in pH (from 5.0 to 8.0) that perturb the cytosine and adenine ring structures. No significant change in secondary structures of the capsid subunit can be detected with changes in pH or with RNA release. On the other hand, the characteristic Raman lines of the phosphate groups of packaged RNA differ from those of naked RNA at all pH values examined, most likely as a result of specific electrostatic binding of divalent cations to RNA phosphates within the virus shell.

Capsid↗
PubMed1985

Genes on different chromosomes influence the antibody response to bacterial antigens.

B6.C congenic strains of mice, possessing histocompatibility (H) alleles from high responding BALB/cBy (C) mice on the genetic background of low responding C57BL/6By (B6) mice, were assayed for their ability to make an antibody response to Type III pneumococcal polysaccharide (SSS-III) and the alpha(1----3) epitope of bacterial (Leuconostoc) dextran B-1355. The results affirmed that the antibody response to SSS-III is multigenic and that genes making a positive contribution to responsiveness are located on different chromosomes, i.e., chromosomes 1, 3, 4, 5, and 9. At least one other gene also influences responsiveness to SSS-III; it is linked to the H-17 locus, which has not yet been assigned to a specific chromosome. Genes on chromosomes 1, 4, and 5 influence the magnitude of the antibody response to dextran B-1355. Some of these genes may be antigen-specific in their mode of action; however, others may not since they appear to exert a positive influence on the antibody response to both SSS-III and dextran B-1355.

Animals↗