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Biomedical subjects

R D Brown

Publications and source records attributed to R D Brown.

At least 271 records · Page 15Linked to original sources
PubMed1986

Relaxometry of ferritin solutions and the influence of the Fe3+ core ions.

The magnetic field dependence of 1/T1 over the range 0.01 to 50 MHz proton Larmor frequency (NMRD profile) is reported for water protons in solutions of horse spleen apoferritin, and of ferritin reconstituted at both low and high iron levels. The apoferritin results are in every way typical of diamagnetic spherical proteins of their size (K. Hallenga and S. H. Koenig, Biochemistry 15, 4255 (1976)). Titration of up to 24 ferrous ions per protein molecule, with subsequent oxidation to ferric, shows a nonlinear saturating contribution to the NMRD profile which is interpreted as arising from a small number of ferric ions (six to eight) bound close to the outside of each ferritin molecule, and a comparable number of interior sites. The latter become multiply occupied as the core grows and do not contribute measurably to 1/T1 in this state. The former sites are never more than singly occupied, and their contribution to the solvent proton relaxation rates is independent of the loading of the core. Measurements of 1/T2 at 20 MHz are quite in accord with theoretical expectations for apoferritin and ferritin with up to 24 ferric ions per molecule. However, a marked increase in 1/T2 is observed at higher iron loadings that we are unable to account for within the framework of the theory of outer sphere relaxation, even when the effects arising from inhomogeneities in the local magnetic field are included. A sample of human spleen hemosiderin was found to have the same 1/T1 NMRD profile as a comparable sample of ferritin.

Animals↗
PubMed1986

Relaxation of water protons in the intra- and extracellular regions of blood containing Gd(DTPA).

The magnetic field dependence of the longitudinal relaxation rates 1/T1 (NMRD profiles) of blood and plasma from rabbits before and after injection of Gd(DTPA) are reported as a function of magnetic field strength from 0.01 to 50 MHz. Over 100 values along the time-dependent magnetization were recorded for each 1/T1 and analyzed for multiple exponentials. From these data, which indicate a single exponential, from the measured Gd content of each sample, and the NMRD profiles, we show that Gd is in the extracellular space only and is present as rotationally mobile Gd(DTPA), uncomplexed with protein or blood cells; and that the water protons exchange rapidly between the intra- and extracellular regions.

Animals↗
PubMed1986

Plasma lactoferrin in patients with neutropenia.

This study examines the role of plasma lactoferrin in the assessment of neutropenia. In particular, we have studied lactoferrin as an inhibitor of granulopoiesis and as an indicator of the size of the total blood granulocyte pool (TBGP). Plasma lactoferrin concentration was determined in a heterogeneous group of 30 patients with neutropenia. Serial plasma lactoferrin levels in a patient with cyclic neutropenia correlated with the cycles of the neutrophil count. Patients with splenomegaly had a grossly elevated lactoferrin:neutrophil ratio. Most chronic idiopathic neutropenia patients had no real clinical problems and a normal plasma lactoferrin level. The results provide further evidence to support the concept that plasma lactoferrin indicates the size of the TBGP and the lactoferrin: neutrophil ratio indicates the degree of granulocyte margination. There was no evidence to suggest that lactoferrin acting as a feedback inhibitor of granulopoiesis caused neutropenia in these patients.

Agranulocytosis↗
PubMed1986

Magnetic field dependence (NMRD profile) of 1/T1 of rabbit kidney medulla and urine after intravenous injection of Gd(DTPA).

The measurement of NMRD profiles of water protons of excised tissues containing paramagnetic metal ions is one of the few ways of determining the biochemical and biophysical state of these ions in vivo. It is of critical importance, for example, to verify that Gd, injected as Gd(DTPA) to enhance contrast in MRI, remains chelated, since free Gd ions are highly toxic. We have investigated this in the renal medulla of rabbits. Fitting the magnetization data at each field of the dispersion to a single exponential shows that Gd accumulates predominantly in the renal medulla, from which it is cleared within 18 hours, and that Gd(DTPA) introduced intravenously into rabbits is excreted as Gd(DTPA) in the urine as rotationally mobile as in neat water. Taking a larger data set at each field and fitting it to the sum of two exponentials, since the errors of the single exponential analysis were larger than for other tissues, shows that the relaxation behavior of the renal medulla, free of contrast agent, can be well-described by a single relaxation rate at 37 degrees C. For increasing concentrations of Gd in the medulla, as determined by ICP analysis, two relaxation rates are required to account for the data, due to compartmentalization of tissue water and inhomogeneous distribution of Gd. These results, and similar data after mild mechanical disruption of renal structures, show unequivocally that the Gd in the renal medulla remains the chelate complex Gd(DTPA) and rotationally mobile, for dosages up to 300 mumoles/kg injected.

Animals↗
PubMed1986

Effect of caffeine sodium benzoate, ketamine hydrochloride, and yohimbine hydrochloride on xylazine hydrochloride-induced anorexia in white-tailed deer.

Fifteen male white-tailed deer (Odocoileus virginianus) were administered xylazine hydrochloride (1 mg/kg BW i.m.), xylazine hydrochloride (1 mg/kg i.m.) followed by caffeine sodium benzoate (10 mg/kg i.m.), xylazine hydrochloride (0.5 mg/kg i.m.) and ketamine hydrochloride (4.5 mg/kg i.m.), and xylazine hydrochloride (1 mg/kg i.m.) followed by yohimbine hydrochloride (0.125 mg/kg i.m.), in a Latin Square design. Mean dry matter intake (DMI) for 4 days pre-treatment was compared to each of 4 days post-treatment. A significant (P less than 0.01) decrease in DMI was found only on the first day following treatment for each of the four drug combinations. The percent decreases in DMI on the first 24-hr period after immobilization were: xylazine hydrochloride 47%, xylazine hydrochloride/caffeine sodium benzoate 36%, xylazine hydrochloride/yohimbine hydrochloride 36%, and xylazine hydrochloride/ketamine hydrochloride 31%. The xylazine hydrochloride/ketamine hydrochloride combination was found to be insufficient to adequately sedate the deer. The use of caffeine or yohimbine hydrochloride is recommended to reduce recumbency time, but offers no improvement in xylazine hydrochloride-induced anorexia.

Animals↗
PubMed1986

Alpha 1-adrenergic and H1-histamine receptor control of intracellular Ca2+ in a muscle cell line: the influence of prior agonist exposure on receptor responsiveness.

Activation of alpha 1-adrenergic receptors in BC3H-1 muscle cells has been shown previously to mobilize intracellular Ca2+, which can be monitored as enhanced 45Ca2+ unidirectional efflux. We report here that histamine also stimulates 45Ca2+ efflux in these cells (Kact = 5.50 microM, nH = 0.94 +/- 0.04), reflecting mobilization of intracellular Ca2+ from a source similar to that accessed by alpha 1-adrenergic receptor activation. In addition, histamine stimulates substantial transmembrane 45Ca2+ influx into BC3H-1 cells. The actions of histamine are inhibited by the H1-selective antagonist, diphenhydramine (IC50 = 1.01 microM), but are unaffected by the H2-selective antagonist, cimetidine (1 nM-10 microM) indicating that histamine regulates cellular Ca2+ via a functional H1 receptor. The presence of independent receptor types which mobilize Ca2+ originating from common intracellular stores has been exploited in order to evaluate the determinants of receptor responsiveness following prior agonist exposure. After exposure with 45Ca2+ to achieve radioisotopic equilibrium, 30 min incubation with increasing concentrations of norepinephrine reduces to similar extents (30-40%) the unidirectional 45Ca2+ efflux responses to subsequent challenges by maximally effective concentrations of norepinephrine or histamine. The decrement in response following norepinephrine exposure appears to reflect an altered disposition of agonist-sensitive intracellular Ca2+, whereas the concentration dependence for alpha 1-adrenergic receptor activation remains unchanged. Prior exposure of cells to increasing concentrations of histamine also reduces the efflux response to norepinephrine challenge (approximately 30% decrease), whereas the response to subsequent histamine challenge is specifically and completely abolished. The loss of histamine responsiveness is accompanied by a marked shift in the concentration dependence for histamine receptor activation toward higher histamine concentrations. These results indicate that substantial alpha 1-receptor responsiveness is maintained following agonist exposure and that the observed reduction in response occurs distally to the receptor itself at some point common to alpha 1- and H1-receptor-effector coupling. By contrast, the H1-histamine receptor exhibits refractoriness, indicative of agonist-induced receptor desensitization.

Animals↗
PubMed1986

Stimulation of persisting colonies in agar cultures by sera from patients with CML and AML.

Cord plasma contains colony-stimulating activity (CSA) which stimulates the in vitro clonal growth of neutrophils, eosinophils, macrophages, erythrocytes, and persisting mast cells in semisolid cultures. Analysis of day 35 colonies in agar cultures was found to be a suitable means of demonstrating this activity and discriminating between it and granulocyte-macrophage colony-stimulating factor (GM-CSF). Serum (10%) from patients with acute and chronic myeloid leukemia (AML and CML) was added to normal human bone marrow cultures to search for similar activity in these patient's serum. Although the number of colonies on day 12 (predominantly neutrophils and macrophages) was not significantly different from the number of colonies in cultures containing normal serum, the number of colonies increased 500% in cultures containing CML serum on day 35. Serum from patients with AML during regeneration also stimulated an increased number of colonies on day 35. Although both eosinophil and mast cell colonies were still present on day 35, only mast cell colonies persisted for 150 days. On day 35, cultures containing 10% CML serum contained predominantly eosinophil colonies (84%), whereas cultures containing AML serum contained predominantly mast cell colonies (76%). Although serum contains various CSFs, the specific factor which stimulates persisting mast cell colonies may be the human equivalent of murine persisting (P) cell-stimulating factor (Multi-CSF).

Agar↗
PubMed1986

Human bone marrow progenitor cells stimulated by cord blood.

Agar cultures of human bone marrow cells stimulated by cord plasma or irradiated cord blood feeder layers demonstrated the presence of a multilineage hemopoietic growth factor in cord blood. When bone marrow cultures stimulated with giant cell tumor-conditioned medium (GCT-CM) were supplemented with this cord blood-derived growth factor, total colony numbers increased by more than 50% after day 23 and persisted in culture for approximately 40 days. Marrow cultures stimulated by the cord blood-derived growth factor formed colonies of neutrophils, monocyte-macrophages, eosinophils, mast cells, and a few colonies containing a mixed cell population. The results suggest that, while GCT-CM contains granulocyte-monocyte colony-stimulating factor (GM-CSF), cord blood contains a high concentration of a multilineage hemopoietic growth factor, which may be multi-CSF.

Bone Marrow Cells↗
PubMed1986

Measurement of skin mobility in the upper back.

On manual testing for skinfold tenderness greater resistance has been reported in patients with marked skinfold tenderness. On objective measurement of skin mobility, by raising a skinfold with a vacuum pump and by establishing a stress/strain curve, no difference in skin mobility was found between subjects with and without skinfold tenderness. Furthermore, contrary to manual testing, the suction testing causes no pain in subjects with clinical skinfold tenderness. In a second series of suction tests, comparing skin mobility in a subject with relaxed and contracted underlying muscles, it was found that muscular contraction reduces skin mobility by 50%. The conclusion is that resistance felt by manual skinfold testing is not inherent in the structures, but is caused by contraction of underlying muscles because of pain caused by the manual skinfold test.

Back↗
PubMed1985

Separation of [1-3H]cellooligosaccharides by thin-layer chromatography: assay for cellulolytic enzymes.

A thin-layer chromatographic method for the separation with high resolution of [1-3H]cellooligosaccharides on silica gel plates has been developed. Reducing end-labeled glucose through cellohexaose were separated on silica gel plates with three ascents of ethyl acetate:water: methanol (40:15:20; v:v) and each was extracted with an efficiency of 88 +/- 3%. Separations of cellooligosaccharides using other adsorbents, solvents, and impregnants are also described. This thin-layer chromatographic method facilitated analysis of the activity of cellulolytic enzymes.

Cellulose↗
PubMed1985

Tricarbon monoxide in TMC-1.

We report the measurement of three new lines of C3O in TMC-1. The observed peak antenna temperatures, appropriately corrected for atmospheric and telescope losses, are found to be consistent with a large velocity gradient radiative transfer model whose parameters span the range of standard values for this cloud. The derived fractional abundance for C3O is 1.4 x 10(-10), comparable with the results predicted from a model calculation based on a gas-phase ion-molecule reaction scheme. The results of negative searches for C3O in six other sources are not inconsistent with expected conditions in these clouds.

Astronomical Phenomena↗
PubMed1985

Preparation and properties of metal ion derivatives of the lentil and pea lectins.

Lentil lectin (LcH) and pea lectin (PSA) belong to the class of D-glucose/D-mannose binding lectins and resemble concanavalin A (Con A) closely in physicochemical, structural, and biological properties. LcH and PSA, like Con A, are Ca2+-Mn2+ metalloproteins that require the metal ions for their saccharide binding and biological activities. Studies of the relationship between the metal ions binding and saccharide binding activity in LcH and PSA have been difficult due to the problem of metal ion replacement in these proteins. We now report a method of metal ion replacement in both lectins that allows substitution of the Mn2+ in the native proteins with a variety of transition metal ions, as well as substitution of the Ca2+ with Cd2+ in a particular complex. The following metal ion derivatives of both LcH and PSA have been prepared: Ca2+-Zn2+, Ca2+-Co2+, Ca2+-Ni2+, and Cd2+-Cd2+. All of these derivatives are as active as the native lectins, as demonstrated by precipitation with specific polysaccharides, saccharide inhibition of precipitation, and hemagglutination assays. The yields of these derivatives are good (generally greater than 70%), and the degree of metal ion incorporation is high (generally greater than 90%). The method of preparation is quite different from that for metal ion substitution in Con A, which proceeds via the apoprotein. In contrast, the apoproteins of LcH and PSA are unstable, aggregate above pH 4.0, and cannot be remetallized once formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1985

Proton and deuteron nuclear magnetic relaxation dispersion studies of Ca2+-Mn2+-concanavalin A: evidence for two classes of exchanging water molecules.

We have measured the magnetic field dependence of the nuclear magnetic relaxation rates (NMRD profiles) of solvent protons and deuterons in solutions of Ca2+-Mn2+-concanavalin A (Con A) with and without saccharide present. Data were obtained over the range -8 to 35 degrees C; the extension to the lowest temperature was made possible by the presence of 5 M salt. Since previous theoretical analyses, using accepted relaxation theories of 1H NMRD profiles alone, led to unsatisfactory conclusions, we have attempted to take advantage of the fact that the residence lifetime of a water ligand of the metal ions can influence the relaxation behavior of protons and deuterons differently. From a comparison of the present proton and deuteron results, we find that Ca2+-Mn2+-Con A has two classes of binding sites: one, associated with the inner coordiation sphere of the Mn2+ ions, having a resident lifetime for solvent water of approximately 10(-5) s that is reduced by the presence of saccharide and another having a lifetime of approximately 5 X 10(-9) s, located with the protons of the bound waters approximately 4.4 A from the Mn2+ ions (assuming two equivalent water molecules in this class), which is well beyond the coordination environment of the Mn2+ ions. The relaxation contribution of these more distant sites is unaffected by saccharide. The conclusions are corroborated by measurements of the temperature dependences of the proton NMRD profiles, which show quite clearly that the profiles are composite, containing two contributions with opposite dependences on temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1985

Proton and deuteron nuclear magnetic relaxation dispersion studies of Ca2+-Mn2+-lentil lectin and Ca2+-Mn2+-pea lectin: evidence for a site of solvent exchange in common with concanavalin A.

Measurements of the magnetic field dependence of the longitudinal magnetic relaxation rates (NMRD profiles) of solvent protons and deuterons led to the discovery of two classes of solvent binding sites in Ca2+-Mn2+-concanavalin A (CMPL) [Koenig, S. H., Brown, R. D., III, & Brewer, C. F. (1985) Biochemistry (second of three papers in this issue)]. In this paper, we compare proton and deuteron NMRD profiles of Ca2+-Mn2+-lentil lectin (CMLcH) and Ca2+-Mn2+-pea lectin (CMPSA) with those of CMPL. All three metalloproteins are D-mannose/D-glucose-specific lectins that have a high degree of structural similarity and require the metal ions for their biological activities. We have developed a method for the preparation of fully active metal ion derivatives of lentil lectin (LcH) and pea lectin (PSA), including the diamagnetic derivatives Ca2+-Zn2+-LcH and Ca2+-Zn2+-PSA [Bhattacharyya, L., Brewer, C. F., Brown, R. D., III, & Koenig, S. H.(1984) Biochem. Biophys. Res. Commun. 124, 857-862]. The behavior of these two lectins with regard to their NMRD profiles is essentially identical, for both the paramagnetic and diamagnetic forms. Together with CMPL, all three lectins have a common paramagnetic contribution with a negative temperature dependence of the rates, while CMPL contributes an additional component with a positive temperature dependence. The common contribution derives from the class of fast exchanging water molecules observed in the proton NMRD profile of CMPL (Koenig et al., 1985); their protons are calculated to be relatively remote from the Mn2+ ions (4.4 A for CMPL and 5.5 A for LcH and PSA).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1985

Comparison of the spectroscopic and saccharide binding properties of lentil and pea isolectins.

The lentil isolectins, CMLcH A and CMLcH B, and pea isolectins, CMPSA A and CMPSA B, are compared in terms of their spectroscopic and saccharide binding properties. The paramagnetic contribution to the solvent proton magnetic relaxation dispersion profiles of solutions of the isolectins of each protein are found to be essentially identical. Electron paramagnetic resonance spectra suggest a high degree of octahedral symmetry at the Mn2+ site for both pairs of isolectins. The near-ultraviolet absorption spectra of CMLcH A and CMLcH B are identical, as are the spectra of CMPSA A and CMPSA B. Carbohydrate binding activities of the isolectins of each protein are compared using hemagglutination, precipitation, and precipitation-inhibition assays, and are found to be identical, although the activities of CMLcH and CMPSA differ somewhat. These results demonstrate that the spectroscopic and saccharide binding properties of the isolectins of CMLcH are essentially identical, as are those of the isolectins of CMPSA, and suggest that native mixtures of the isolectins may be treated as single proteins in further studies.

Disaccharides↗