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L Brand

Publications and source records attributed to L Brand.

At least 73 records · Page 4Linked to original sources
PubMed1987

Nanosecond time-resolved fluorescence kinetic studies of the 5,5'-dithiobis(2-nitrobenzoic acid) reaction with enzyme I of the phosphoenolpyruvate:glycose phosphotransferase system.

Enzyme I of the bacterial phosphotransferase system is a protein component which undergoes a temperature-dependent monomer/dimer equilibrium. Reaction of sulfhydryl residues with SH-specific reagents inhibits both activity and dimerization. There are four cysteine residues available in each subunit, one of which (Cys 502) is proximate to one of the two tryptophan residues (Trp 498). Previous studies revealed two major lifetimes and spectra, suggesting distinct environments for tryptophan. In this paper, we examine the dynamic quenching of tryptophanyl fluorescence that occurs when an energy transfer acceptor, thio-2-nitrobenzoic acid (TNB), is covalently attached to the sulfhydryl groups. More precisely, we have traced the recovery of nativelike fluorescence lifetime components (and the concomitant loss of "reduced lifetime" amplitudes) that accompanies TNB release. The course of lifetime changes seen when a reducing reagent removes the quencher may be sensitive to a variety of effects, including different SH affinities, different proximities to Trp, changing availability for dimerization, or conformational changes. The prospective value of separating each lifetime component from the mixture is illustrated.

Dithionitrobenzoic Acid↗
PubMed1987

NE-19550: a novel, orally active anti-inflammatory analgesic.

NE-19550, N-(3-methoxy-4-hydroxybenzyl)oleamide, is a capsaicin analogue that has been shown to possess oral activity in the 55 degrees C rat hot-plate and mouse phenylquinone abdominal constriction analgesia tests. The compound also displayed anti-inflammatory activity orally in the carrageenan-inflamed rat-paw test and topically in the croton oil-inflamed mouse-ear test. NE-19550 activity in the thermal analgesia assay was not blocked by the opioid antagonist naloxone, and no inhibition of prostanoid synthesis in rat platelets or tissues was seen following a high analgesic and anti-inflammatory oral dose (300 mg/kg). A wide variety of known neuronal antagonists (adrenergic, serotonergic, dopaminergic, cholinergic, GABA-ergic, histaminergic) were found not to inhibit NE-19550 analgesia, further indicating a lack of involvement of known drug receptors mediating analgesic responses. Analgesic doses of NE-19550 were also found to lack the acute toxicity and thermoregulatory desensitization characteristics of the parent natural product capsaicin. It appears to represent a new class of potent-acting, non-narcotic, anti-inflammatory analgesic agents.

Administration, Oral↗
PubMed1986

Tomato golden mosaic virus A component DNA replicates autonomously in transgenic plants.

Phenotypically normal petunia plants carrying chromosomal inserts of either the tomato golden mosaic virus (TGMV) A or the B component DNA, as single or tandem inserts, were obtained using an Agrobacterium tumefaciens Ti plasmid-based transformation system. Southern hybridization analysis revealed that the tandem, direct-repeat A plants contained free single and double stranded A component DNAs. No free B component DNA was detected in plants carrying tandem repeats of the B component. Progeny of self-fertilized plants appeared normal. In contrast, one-quarter of the progeny from tandem A by tandem B plant crosses showed chlorotic lesions on their leaves similar to virus symptoms. The significance of these results and the use of this method for the study of virus functions involved in TGMV replication and symptom production are discussed.

DNA Replication↗
PubMed1986

Anisotropy decay associated fluorescence spectra and analysis of rotational heterogeneity. 1. Theory and applications.

Individual fluorescence spectra for species in a heterogeneous system can be determined by using differences between the rotational correlation times of those components. Each spectrum derived is associated with a particular fluorescence anisotropy decay function; hence, they are anisotropy decay associated spectra (ADAS). We have previously shown [Knutson, J. R., Walbridge, D. G., & Brand, L. (1982) Biochemistry 21, 4671-4679] that a system containing different decay functions for total intensity can be resolved into constituent decay-associated spectra. ADAS extends the technique into the realm of fluorescence polarization, making use of the often disparate Brownian rotations found in heterogeneous biochemical systems. In this paper, we present the basic theory for ADAS in various heterogeneous systems and then present an example of ADAS resolving a binary mixture of macromolecules into "fast-rotor" (smaller or more mobile) and "slow-rotor" (larger or less mobile) components. They correctly superimpose spectra taken for the unmixed components. In the companion paper [Davenport, L., Knutson, J. R., & Brand, L. (1986) Biochemistry (following paper in this issue)], a specific application to a problem of importance of lipid biochemistry--e.g., the origin of the membrane probe order parameter in lipid bilayers--is presented, demonstrating the role rotational heterogeneity may play in biochemical fluorescence.

Fluorescence Polarization↗
PubMed1986

Anisotropy decay associated fluorescence spectra and analysis of rotational heterogeneity. 2. 1,6-Diphenyl-1,3,5-hexatriene in lipid bilayers.

The application of a new spectroscopic tool [Knutson, J. R., Davenport, L., & Brand, L. (1986) Biochemistry (preceding paper in this issue)] for studying rotational microheterogeneity of probe location in lipid bilayer systems is described. Anisotropy decay associated spectra are derived from experimentally obtained polarized emission components. "Early" difference spectra (IV - IH) contain contributions from both fast and slow rotors, while "late" difference spectra predominantly reflect the emission from slowly rotating fluorophores. Anisotropy decay associated spectra have been used to resolve the emission spectra of 1,6-diphenyl-1,3,5-hexatriene (DPH) imbedded within a known rotationally heterogeneous mixture of two vesicle types (L-alpha-dimyristoyllecithin and L-alpha-dipalmitoyllecithin). At 29 degrees C, diphenylhexatriene within pure dimyristoyllecithin vesicles rotates rapidly, with a small r infinity, while diphenylhexatriene in dipalmitoyllecithin vesicles exhibits a large r infinity. Spectra for diphenylhexatriene imbedded in the two vesicle types show small but significant spectral differences. A spectrum of a mixture of the two vesicle types with DPH lies between these characteristic component spectra. The spectrum extracted for "immobilized" probes in the mixture correctly overlays the dipalmitoyllecithin spectrum. Further studies have shown that diphenylhexatriene exhibits more than one emission anisotropy decay associated spectrum in vesicles of a single lipid type, when that lipid is near its phase transition temperature. Diphenylhexatriene apparently inhabits more than one rotational environment even in these "homogeneous" vesicle preparations.

Dimyristoylphosphatidylcholine↗
PubMed1986

Excited-state proton transfer of equilenin and dihydroequilenin: interaction with bilayer vesicles.

The two-state excited-state proton-transfer process for d-equilenin [d-3-hydroxyestra-1,3,-5(10),6,8-pentaen-17-one] and dihydroequilenin is found to depend both on pH and on proton acceptor concentration. Both the protonated and deprotonated forms of the excited molecule are fluorescent. As is the case for 2-naphthol, the excited-state pKa (pKa*) is substantially lower than the ground-state pKa. Fluorescence decay studies have been performed as a function of emission wavelength in aqueous solutions at pH 6.9 in the presence of acetate anion (0.1 M). At this pH, both back-reaction from the excited-state and ground-state heterogeneity are minimal. A monoexponential decay is found in the blue region of the spectrum and a biexponential decay on the red edge. The lifetimes measured across both regions are constant, with a negative preexponential term, characteristic of an excited-state reaction, evident at longer wavelengths. Decay-associated spectra (DAS), the preexponential terms associated with the measured lifetimes, have been acquired for these aqueous solutions. Equilenin and dihydroequilenin are found to adsorb to dimyristoyllecithin (DML) vesicles. Rates for excited-state proton transfer are greatly reduced when dihydroequilenin adsorbs to vesicles. The accessibility of the bound probe to acetate as a proton acceptor depends on the cholesterol content of the vesicles.

17-Ketosteroids↗
PubMed1986

Time-resolved fluorescence and 1H NMR studies of tyrosine and tyrosine analogues: correlation of NMR-determined rotamer populations and fluorescence kinetics.

The time-resolved fluorescence properties of phenol and straight-chained phenol derivatives and tyrosine and simple tyrosine derivatives are reported for the pH range below neutrality. Phenol and straight-chained phenol derivatives exhibit single exponential fluorescence decay kinetics in this pH range unless they have a titratable carboxyl group. If a carboxyl group is present, the data follow a two-state, ground-state, Henderson-Hasselbalch relationship. Tyrosine and its derivatives with a free carboxyl group display complex fluorescence decay behavior as a function of pH. The complex kinetics cannot be fully explained by titration of a carboxyl group; other ground-state processes are evident, especially since tyrosine analogues with a blocked carboxyl group are also multiexponential. The fluorescence kinetics can be explained by a ground-state rotamer model. Comparison of the preexponential weighting factors (amplitudes) of the fluorescence decay constants with the 1H NMR determined phenol side-chain rotamer populations shows that tyrosine derivatives with a blocked or protonated carboxyl group have at least one rotamer exchanging more slowly than the radiative and nonradiative rates, and the fluorescence data are consistent with a slow-exchange model for all three rotamers, the shortest fluorescence decay constant is associated with a rotamer where the carbonyl group can contact the phenol ring, and in the tyrosine zwitterion, either rotamer interconversion is fast and an average lifetime is seen or rotamer interconversion is slow and the individual fluorescence decay constants are similar.

Hydrogen-Ion Concentration↗
PubMed1986

Simultaneous analysis of multiple fluorescence decay curves by Laplace transforms. Deconvolution with reference or excitation profiles.

The properties and potentials of the noniterative Laplace deconvolution (LAP2) (M. Ameloot and H. Hendrickx, Biophys. J. 44 (1983) 27) are further investigated. It is shown that LAP2 is exact and that no extrapolations have to be calculated or assumed for the data measured in the actual time window if the impulse response function of the investigated system can be described by a sum of exponentials. The formulas for the LAP2 deconvolution against the measured decay of a reference compound instead of the recorded excitation profile are derived. The procedure for the simultaneous analysis of multiple fluorescence decay curves by LAP2 is described in detail. This global analysis allows one to link any decay parameter, is fast and compares favorably with the nonlinear least-squares iterative reconvolution methods. Because of its short computation time the global analysis by LAP2 provides an efficient way to analyze the fluorescence decay surface in terms of decay associated spectra.

Anthracenes↗
PubMed1985

Somatosensory evoked potentials as an aid in the diagnosis and intraoperative management of spinal stenosis.

The use of somatosensory evoked potentials (SEPs) in localizing the level, extent, and laterality of nerve root entrapment is clinically important. In patients with lumbar spinal stenosis, this is especially true. This study defines a prospective investigation of 20 patients with preoperative SEPs of which 11 patients had intraoperative SEPs correlated with their computed tomographic (CT) scan and/or myelographic findings. The results confirm a high incidence of 4th and 5th lumbar and 1st sacral nerve root involvement. The posterior tibial nerve was abnormal in 95%, the peroneal in 90%, and the sural in 60% in the symptomatical lower extremity. Upper lumbar segments were barely affected as evident by the low incidence of saphenous nerve abnormality in only 12% of the patients. The posterior tibial nerve had the highest yield and was useful for screening. Bilateral lower extremity abnormalities were found in seven of 20 cases studied with two patients having bilateral symptoms and findings. Therefore, bilateral lower extremity SEP evaluation can reveal previously unsuspected pathology and is strongly recommended in preoperative evaluations. SEPs can serve as a useful intraoperative tool to guide the surgeon during a decompressive surgical procedure. SEPs are specifically helpful in spinal stenosis with a paucity of clinical findings and equivocal CT scan or myelographic studies. SEPs seem much more sensitive and effective than conventional electrodiagnostic tests in detecting spinal nerve root compression secondary to spinal stenosis.

Adult↗
PubMed1985

Lumbar spinal stenosis: analysis of pre- and postoperative somatosensory evoked potentials.

Cortical somatosensory evoked potential (CSEP) examinations were performed of 20 patients with lumbar spinal stenosis a day prior to surgery and 10 to 12 days after spinal decompression and bilateral lateral fusion. CSEPs were recorded to Cz-Fz (10-20 international EEG system) following stimulation of 32 tibial, peroneal and sural nerves and 16 saphenous nerves. A total of 110 nerves were examined. Using CSEP P1 latency as criteria for inclusion in the study, 21 tibial, 20 peroneal and 17 sural nerves were subjected to paired two-tailed t tests to determine whether the CSEP changes that occurred postoperatively were statistically significant (p less than 0.05). Postoperative P1 latencies of tibial, peroneal, and sural nerves changed significantly as well as N1 latencies and P1-N1 amplitudes of tibial and peroneal nerves. Nineteen patients improved clinically. It is postulated that pathologic narrowing of the spinal canal in spinal stenosis leads to nerve root compression and ischemia with resultant dysfunction primarily affecting large diameter myelinated fibers and that decompression procedure may adequately relieve the underlying pathologic processes. Improvement in CSEPs may be from increase in available numbers of functioning large diameter myelinated fibers, conversion to normal from a conduction block, and, perhaps, improved axoplasmic flow.

Adult↗
PubMed1984

Nanosecond time-resolved emission anisotropy of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene in human amniotic fluid.

The fluorescence emission anisotropy of 1,6-diphenyl-1,3,5-hexatriene in human amniotic fluid has been studied using nanosecond time-resolved emission techniques. These studies demonstrate that the previously reported decrease in the steady state emission anisotropy, [r], with gestational age is due to a change in the rate of rotational motion of the probe. The emission anisotropy decays to a limiting value (r infinity) greater than zero, suggesting a hindered rotation of the probe, and this is independent of gestational age. The decay function for the emission anisotropy of amniotic fluids from 17, 29, 40 and 41 weeks in gestational age can be best expressed as a single exponential plus a constant term, with rotational correlation times varying from 17 ns to 2.2 ns, respectively. The zero time emission anisotropy remains approx. 0.30 for both early and late gestational times.

Amniotic Fluid↗
PubMed1984

Fibroblast feeder layers inhibit differentiation of retinoic acid-treated embryonal carcinoma cells by increasing the probability of stem cell renewal.

The appearance of differentiated cells in embryonal carcinoma (EC) cultures can be inhibited by culturing the cells on fibroblast feeder layers. To determine whether or not feeder layers act by increasing the probability of stem cell renewal, growth and differentiation were monitored in cultures of F9 (subclone OTF9 -63) EC cells exposed to retinoic acid (RA) in either the presence or absence of feeder layers. By measuring the fraction of laminin-positive TROMA 1-positive or alkaline phosphatase-negative cells, it was determined that the frequency of differentiated cells in RA-treated F9 cultures was reduced by 70-80% when cells were cultured on fibroblast feeder layers instead of gelatin-coated dishes. Experiments in which EC cells were cultured in close proximity to a feeder layer demonstrated that cell-cell contact was required for maximal inhibition of differentiation. The probability of stem cell renewal was determined by measuring the number of colony-forming cells in RA-treated cultures as a function of time. Analysis of the data demonstrated that the probabilities of stem cell renewal were 0.5 and 0.25 during the first and second 48 h periods, respectively, following addition of RA for cells cultured without feeder layers. Cultures maintained on feeder layers exhibited a stem cell renewal probability of 0.72. Thus, feeder layers reduce the frequency of differentiated cells in RA-treated cultures by increasing the probability of stem cell renewal. Determining the mechanism by which feeder layers counteract the effect of a chemically defined differentiation inducer should help to uncover the processes that regulate the probability of stem cell renewal.

Animals↗
PubMed1984

Identification of a cloned cytokinin biosynthetic gene.

A small region of the Ti plasmid (the tmr locus), thought to be involved in phytohormone metabolism in Agrobacterium tumefaciens-transformed plant tissue, was cloned and expressed in Escherichia coli. By enzyme assay, the tmr locus was shown to encode isopentenyltransferase, an enzyme that catalyzes the first step in cytokinin biosynthesis.

Journal Article↗
PubMed1984

Quantification of intraoperative somatosensory evoked potential.

Cortical (C) and spinal (S) somatosensory evoked potentials (SEP) were measured and quantified in 30 patients undergoing scoliosis surgery during the following periods: I, preincision; II, hypotension; III, instrumentation; IV, postinstrumentation; and V, skin closure. Paired two-tailed t tests were performed on all commonly measured SEP parameters comparing values obtained at periods I and II with each subsequent period. CSEP were obtained with Cz-Fz recording sites of the international 10-20 system while SSEP were obtained with recording electrodes at C7-Fz, following bilateral posterior tibial nerve stimulation at the ankles. From period I, CSEP P1 prolonged significantly across all periods but not from period II to subsequent periods. N1 remained stable from either period I or II until period V when latencies increased. P1-N1 amplitude decreased significantly between period I and other periods until period V when near base value was regained. Compared to period II however, P1-N1 amplitude did not differ significantly until period V when it increased beyond base. CSEP P2 and N2 latencies and amplitudes were less distinct and had high variability under our anesthetic technique which consisted of N2O-O2 and isoflurane 0.25%-0.50%, narcotics, nondepolarizing blocking agents, and induced hypotension. When attainable, they behaved in a similar pattern to the early CSEP. SSEP were obtained in 23 cases. The stability of latencies and amplitudes compared favorably with CSEP P1 and N1. Graphs of relative percent changes were developed for clinical use. It is concluded that the noninvasive monitoring technique described is practical, and that P1 and N1 CSEP and SSEP values are reliable monitoring parameters.

Adolescent↗