Isolation of proteoglycans from tendon.
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Animals↗
Biomedical subjects
J A Peters
Publications and source records attributed to J A Peters.
Ion-pair interactions of lanthanide(III) complexes in aqueous solutions.
The formation of ion-pair adducts between the cationic complex La(THP)3+ (THP = 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane) and the anionic complexes Tm(DOTA)- (DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetate), Tm(DTPA)2- (DTPA = diethylenetriamine-N,N,N',N",N"-pentaacetate), Tm(TTHA)3- (TTHA = triethylenetetraamine-N,N,N',N",N"',N"'-hexaacetate), and Tm(DOTP)5- (DOTP = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetrakis(methylenephosphonate)) is examined by 13C NMR spectroscopy. The induced 13C shifts of the La(THP)3+ complex are followed by titration of the Tm(III) complexes of DOTA, DTPA, and TTHA at pH 7. From these data, the stability constants are calculated to be beta 1 = 64 M-1 (1:1), beta 1 = 296 M-1 (1:1), and beta 2 = 26,000 M-2 (2:1) for the ion pairs of La(THP)3+, with Tm(DOTA)-, Tm(DTPA)2-, and Tm(TTHA)3-, respectively. The La(THP)3+,Tm(DOTP)5- system elicits chiral resolution of the rapidly interconverting Tm(DOTP)5- isomers.
Journal Article↗
Hydrogenation of fructose on Ru/C catalysts.
The hydrogenation of D-fructose on Ru/C catalysts was studied. Under the conditions applied (1 bar H2, 72 degrees C), the furanose forms of D-fructose react, while the pyranose forms do not. However, all anomers adsorb with comparable strength on the surface. The reaction rate is controlled by product inhibition. The selectivity to D-mannitol can be increased from 47 to 63% by promotion of Pd/C and Pt/C catalysts with Sn.
Carbohydrate Conformation↗
The 4'lysine in the putative channel lining domain affects desensitization but not the single-channel conductance of recombinant homomeric 5-HT3A receptors.
The 5-HT3 receptor is a transmitter-gated ion channel of the Cys-loop superfamily. Uniquely, 5-HT3 receptor subunits (5-HT3A and 5-HT3B) possess a positively charged lysine residue within the putative channel lining M2 domain (4' position). Using whole cell recording techniques, we examined the role of this residue in receptor function using wild-type (WT) and mutant 5-HT3A receptor subunits of murine origin transiently expressed in human embryonic kidney (HEK 293) cells. WT 5-HT3A receptors mediated rapidly activating currents in response to 5-HT (10-90 % rise time, 103 ms; EC50, 2.34 microM; Hill coefficient, nH, 2.87). The currents rectified inwardly, reversed in sign at a potential of -9 mV and desensitized in the continuous presence of agonist (half-time of desensitization, t(1/2), 2.13 s). 5-HT3A receptor subunits in which the 4'lysine was mutated to arginine, glutamine, serine or glycine formed functional receptors. 5-HT EC50 values were approximately 2-fold lower than for WT 5-HT3A receptors, but Hill coefficients, kinetics of current activation, rectification, and reversal potentials were unaltered. Each of the mutants desensitized more slowly than the WT 5-HT3A receptor, with the arginine and glycine mutations exhibiting the greatest effect (5-fold reduction). The rank order of effect was arginine > glycine > serine > glutamine. The single-channel conductance of the WT 5-HT3A receptor, as assessed by fluctuation analysis of macroscopic currents, was 390 fS. A similar value was obtained for the 4'lysine mutant receptors. Thus it appears unlikely that 4'lysine is exposed to the channel lumen. Mutation of residues immediately adjacent to 4'lysine to glutamate or lysine resulted in lack of receptor expression or function. We conclude that 4'lysine does not form part of the channel lining, but may play an important role in 5-HT3 receptor desensitization.
Algorithms↗
Genetics and the multidisciplinary breast center.
The cancer genetics consultation and comprehensive breast centers logically go hand in hand. Breast surgeons may be interacting for the first time with a relatively new class of colleagues-genetics professionals, such as medical geneticists and genetic counselors. This article introduces surgical oncologists to the current applications of genetic counseling in oncology practice through the involvement of genetics professionals on interdisciplinary teams, in case conference, at grand rounds and oncology meetings, and through genetic risk assessment, counseling, and possible susceptibility testing. Surgeons interacting with the cancer genetics specialists have critical roles to play in the organization of cancer genetics programs, recognition of patients and families at increased genetic risk, appropriate referrals for genetic counseling and testing, and management of high-risk families.
Breast Neoplasms↗
Equity MSO (management services organization) benefits hospital and physicians.
Equity MSOs offer an alternative to hospital's employment of physicians and acquisition of their practices. In one example, several primary care physicians, organized into a single professional corporation, entered an agreement with a hospital to establish an equity MSO that was jointly owned by both parties. The partnership enabled the physicians to negotiate managed care contracts more skillfully and improve their bottom line. Under the agreement, the physicians' income is determined by their productivity. The hospital is confident that this new entity will help it sustain relationships with the physicians.
Efficiency↗
Complementary regulation of anaesthetic activation of human (alpha6beta3gamma2L) and Drosophila (RDL) GABA receptors by a single amino acid residue.
1. The influence of a transmembrane (TM2) amino acid located at a homologous position in human beta1 (S290) and beta3 (N289) GABAA receptor subunits and the RDL GABA receptor of Drosophila (M314) upon allosteric regulation by general anaesthetics has been investigated. 2. GABA-evoked currents mediated by human wild-type (WT) alpha6beta3gamma2L or WT RDL GABA receptors expressed in Xenopus laevis oocytes were augmented by propofol or pentobarbitone. High concentrations of either anaesthetic directly activated alpha6beta3gamma2L, but not RDL, receptors. 3. GABA-evoked currents mediated by human mutant GABAA receptors expressing the RDL methionine residue (i.e. alpha6beta3N289Mgamma2L) were potentiated by propofol or pentobarbitone with approximately 2-fold reduced potency and, in the case of propofol, reduced maximal effect. Conspicuously, the mutant receptor was refractory to activation by either propofol or pentobarbitone. 4. Incorporation of the homologous GABAA beta1-subunit residue in the RDL receptor (i.e. RDLM314S) increased the potency, but not the maximal effect, of GABA potentiation by either propofol or pentobarbitone. Strikingly, either anaesthetic now activated the receptor, an effect confirmed for propofol utilizing expression of WT or mutant RDL subunits in Schnieder S2 cells. At RDL receptors expressing the homologous beta3-subunit residue (i.e. RDLM314N) the actions of propofol were similarly affected, whereas those of pentobarbitone were unaltered. 5. The results indicate that the identity of a homologous amino acid affects, in a complementary manner, the direct activation of human (alpha6beta3gamma2L) and RDL GABA receptors by structurally distinct general anaesthetics. Whether the crucial residue acts as a regulator of signal transduction or as a component of an anaesthetic binding site per se is discussed.
Amino Acids↗
The 5-HT3B subunit is a major determinant of serotonin-receptor function.
The neurotransmitter serotonin (5-hydroxytryptamine or 5-HT) mediates rapid excitatory responses through ligand-gated channels (5-HT3 receptors). Recombinant expression of the only identified receptor subunit (5-HT3A) yields functional 5-HT3 receptors. However, the conductance of these homomeric receptors (sub-picosiemens) is too small to be resolved directly, and contrasts with a robust channel conductance displayed by neuronal 5-HT3 receptors (9-17 pS). Neuronal 5-HT3 receptors also display a permeability to calcium ions and a current-voltage relationship that differ from those of homomeric receptors. Here we describe a new class of 5-HT3-receptor subunit (5-HT3B). Transcripts of this subunit are co-expressed with the 5-HT3A subunit in the amygdala, caudate and hippocampus. Heteromeric assemblies of 5-HT3A and 5-HT3B subunits display a large single-channel conductance (16 pS), low permeability to calcium ions, and a current-voltage relationship which resembles that of characterized neuronal 5-HT3 channels. The heteromeric receptors also display distinctive pharmacological properties. Surprisingly, the M2 region of the 5-HT3B subunit lacks any of the structural features that are known to promote the conductance of related receptors. In addition to providing a new target for therapeutic agents, the 5-HT3B subunit will be a valuable resource for defining the molecular mechanisms of ion-channel function.
Amino Acid Sequence↗
General anaesthetic action at transmitter-gated inhibitory amino acid receptors.
Research within the past decade has provided compelling evidence that anaesthetics can act directly as allosteric modulators of transmitter-gated ion channels. Recent comparative studies of the effects of general anaesthetics across a structurally homologous family of inhibitory amino acid receptors that includes mammalian GABAA, glycine and Drosophila RDL GABA receptors have provided new insights into the structural basis of anaesthetic action at transmitter-gated channels. In this article, the differential effects of general anaesthetics across inhibitory amino acid receptors and the potential relevance of such actions to general anaesthesia will be discussed.
Allosteric Regulation↗
The interaction of general anaesthetics and neurosteroids with GABA(A) and glycine receptors.
The positive allosteric effects of four structurally distinct general anaesthetics (propofol, pentobarbitone, etomidate and 5alpha-pregnan-3alpha-ol-20-one [5alpha3alpha]) upon recombinant GABA(A) (alpha6beta3gamma2L), invertebrate GABA (RDL) and glycine (alpha1) receptors expressed in Xenopus laevis oocytes have been determined. Propofol and pentobarbitone enhanced agonist (GABA or glycine as appropriate) evoked currents at GABA(A), glycine, and RDL receptors, whereas etomidate and 5alpha3alpha were highly selective for the GABA(A) receptor. Utilizing site-directed mutagenesis, we demonstrate that the nature of the interaction of propofol, pentobarbitone and etomidate (but not 5alpha3alpha) with mammalian and invertebrate ionotropic GABA receptors depends critically upon the nature of a single amino acid located in the second transmembrane region (TM2) of these receptors. These data are discussed in relation to the specificity of action of general anaesthetics.
Anesthetics↗
A single amino acid confers barbiturate sensitivity upon the GABA rho 1 receptor.
Many structurally diverse general anaesthetics enhance inhibitory neurotransmission in the central nervous system by interacting with the GABAA receptor. By contrast, GABA receptors composed of the rho 1 subunit are anaesthetic-insensitive. Here, we demonstrate that both delta-hexachlorocyclohexane (delta-HCH; 1-100 microM), a positive allosteric modulator of the GABAA receptor, and the anaesthetic pentobarbitone (10-600 microM) have no effect on GABA-evoked currents mediated by wild-type rho 1 recombinant receptors (expressed in Xenopus laevis oocytes). By contrast, these agents produce up to a 10 fold enhancement of GABA responses transduced by a rho 1 receptor in which a transmembrane located isoleucine residue is replaced by serine. However, not all general anaesthetics were similarly influenced by this mutation, because propofol and 5 beta-pregnan-3 alpha-ol-20-one (5 beta 3 alpha) remained ineffective. These data are discussed in relation to the specificity of general anaesthetic action.
Anesthetics, General↗
Molecular determinants of (+)-tubocurarine binding at recombinant 5-hydroxytryptamine3A receptor subunits.
The 5-hydroxytryptamine type 3 (5-HT3) receptor is a transmitter-gated ion channel mediating neuronal excitation. The receptor native to neurons, or as a homopentameric assembly of 5-HT3A receptor subunits, displays a species-dependent pharmacology exemplified by a 1800-fold difference in the potency of (+)-tubocurarine [(+)-Tc] as an antagonist of the current response mediated by mouse and human receptor orthologs. Here, we attempt to identify amino acid residues involved in binding (+)-Tc by use of chimeric and mutant 5-HT3A subunits of mouse and human expressed in Xenopus laevis oocytes. Replacement of the entire extracellular N-terminal domain of the mouse 5-HT3A (m5-HT3A) subunit by that of the human ortholog and vice versa exchanged the differential potency of (+)-Tc, demonstrating the ligand binding site to be contained wholly within this region. Mutagenesis of multiple amino acid residues within a putative binding domain that exchanged nonconserved residues between mouse and human receptors shifted the apparent affinity of (+)-Tc in a reciprocal manner. The magnitude of the shift increased with the number of residues (3, 5, or 7) exchanged, with septuple mutations of m5-HT3A and human 5-HT3A subunits producing a 161-fold decrease and 53-fold increase in the apparent affinity of (+)-Tc, respectively. The effect of point mutations was generally modest, the exception being m5-HT3A D206E, which produced a 9-fold decrease in apparent affinity. We conclude that multiple amino acids within a binding loop of human and mouse 5-HT3A subunits influence the potency of (+)-Tc.
Amino Acid Sequence↗
Ion permeation and conduction in a human recombinant 5-HT3 receptor subunit (h5-HT3A).
1. A human recombinant homo-oligomeric 5-HT3 receptor (h5-HT3A) expressed in a human embryonic kidney cell line (HEK 293) was characterized using the whole-cell recording configuration of the patch clamp technique. 2. 5-HT evoked transient inward currents (EC50 = 3.4 microM; Hill coefficient = 1.8) that were blocked by the 5-HT3 receptor antagonist ondansetron (IC50 = 103 pM) and by the non-selective agents metoclopramide (IC50 = 69 nM), cocaine (IC50 = 459 nM) and (+)-tubocurarine (IC50 = 2.8 microM). 3. 5-HT-induced currents rectified inwardly and reversed in sign (E5-HT) at a potential of -2.2 mV. N-Methyl-D-glucamine was finitely permeant. Permeability ratios PNa/PCs and PNMDG/PCs were 0.90 and 0.083, respectively. 4. Permeability towards divalent cations was assessed from measurements of E5-HT in media where Ca2+ and Mg2+ replaced Na+. PCa/PCs and PMg/PCs were calculated to be 1.00 and 0.61, respectively. 5. Single channel chord conductance (gamma) estimated from fluctuation analysis of macroscopic currents increased with membrane hyperpolarization from 243 fS at -40 mV to 742 fS at -100 mV. 6. Reducing [Ca2+]o from 2 to 0.1 mM caused an increase in the whole-cell current evoked by 5-HT. A concomitant reduction in [Mg2+]o produced further potentiation. Fluctuation analysis indicates that a voltage-independent augmentation of gamma contributes to this phenomenon. 7. The data indicate that homo-oligomeric receptors composed of h5-HT3A subunits form inwardly rectifying cation-selective ion channels of low conductance that are permeable to Ca2+ and Mg2+.
Calcium↗
The platinum-catalyzed oxidation of inulin.
The oxidation of inulin with Pt/C as catalyst was studied. Methyl alpha-D-fructofuranoside was used as a model compound for the monomeric unit of inulin. Oxidation occurred selectively at the C-6 position in a high yield (79%). The rate of oxidation and the degree of oxidation obtained for inulin oligosaccharides decreased upon increase of the chain length of the substrate. Inulin could only be oxidized partially: the oxidation degree obtained was 20% of the primary hydroxy groups for inulin with an average dp 30. Possible explanations for these relatively low conversions are discussed. Adsorption and desorption phenomena appear to play and important role during the oxidation process.
Adsorption↗
Preparation of O-(Aminopropyl)inulin.
Inulin ethers carrying primary amino groups have many potential applications. O-(Aminopropyl)inulin is obtained from O-(cyanoethyl)inulin by reduction of the nitrile groups. Heterogeneously catalyzed hydrogenation using Raney-cobalt as the catalyst resulted in only partial conversion of the O-cyanoethyl into O-aminopropyl groups. Complete conversion of the nitriles to primary amines was achieved by a homogeneous reduction with an excess of sodium borohydride and cobaltous chloride or with metals in liquid ammonia-methanol. Optimal results were obtained with the latter method; 83% of the substituents were converted into primary amines and 17% were lost by dealkylation.
Carbohydrate Conformation↗
Spirometric reference equations for older adults.
The objective of this study was to develop spirometric reference equations for healthy, never-smoking, older adults. It was designed as a cross-sectional observational study consisting of 1510 Seventh Day Adventists, ages 43-79 years enrolled in a study of health effects of air pollutants. Individuals were excluded from the reference group (n = 565) for a history of current respiratory illness, smoking, or chronic respiratory disease, and for a number of 'non-respiratory' conditions which were observed in these data to be related to lower values of FEV1. Gender-specific reference equations were developed for the entire reference group and for a subset above 65 years of age (n = 312). Controlling for height and age, lung function was found to be positively related to the difference between armspan and height, and in males was found to be quadratically related to age. The predicted values for this population generally fell within the range of those of other population groups containing large numbers of adults over the age of 65 years. Individuals with lung function below the 5th percentile in this sample, however, could not be reliably identified by using the lower limits of normal predictions commonly used in North America and Europe.
Adult↗
Pharmacological characterization of a rat 5-hydroxytryptamine type3 receptor subunit (r5-HT3A(b)) expressed in Xenopus laevis oocytes.
The present study has utilized the two electrode voltage-clamp technique to examine the pharmacological profile of a splice variant of the rat orthologue of the 5-hydroxytryptamine type 3A subunit (5-HT3A(b)) heterologously expressed in Xenopus laevis oocytes. At negative holding potentials, bath applied 5-HT (300 nM - 10 microM) evoked a transient, concentration-dependent (EC50 = 1.1+/-0.1 microM), inward current. The response reversed in sign at a holding potential of -2.1+/-1.6 mV. The response to 5-HT was mimicked by the 5-HT3 receptor selective agonists 2-methyl-5-HT (EC50= 4.1+/-0.2 microM), 1-phenylbiguanide (EC50=3.0+/-0.1 microM), 3-chlorophenylbiguanide (EC50 = 140+/-10 nM), 3,5-dichlorophenylbiguanide (EC50 = 14.5+/-0.4 nM) and 2,5-dichlorophenylbiguanide (EC50 = 10.2+/-0.6 nM). With the exception of 2-methyl-5-HT, all of the agonists tested elicited maximal current responses comparable to those produced by a saturating concentration (10 microM) of 5-HT. Responses evoked by 5-HT at EC50 were blocked by the 5-HT3 receptor selective antagonist ondansetron (IC50=231+/-22 pM) and by the less selective agents (+)-tubocurarine (IC50=31.9+/-0.01 nM) and cocaine (IC50 = 2.1+/-0.2 microM). The data are discussed in the context of results previously obtained with the human and mouse orthologues of the 5-HT3A subunit. Overall, the study reinforces the conclusion that species differences detected for native 5-HT3 receptors extend to, and appear largely explained by, differences in the properties of homo-oligomeric receptors formed from 5-HT3A subunit orthologues.
Algorithms↗
How to optimize an MSO's financial performance.
Many hospitals and health systems create financial and strategic alignments with physicians to increase market share. One way to implement such an alignment is to form a management services organization (MSO). Forming an MSO, however, does not automatically guarantee success. To avoid financial losses, executives of hospitals and health systems need to diagnose potential problem areas in their MSOs and take control of problems before the organization and the physicians suffer financial losses. Among the areas that should be evaluated are the business scope of the MSO, the nature of practice acquisitions, physician compensation, governance, management skills, management information systems capabilities, organizational structure, and fee structure. Fee structures, in particular, can be used to align physician and MSO incentives.
Efficiency, Organizational↗