Eminent pathologist,educator—surgeon and ethicist receive CMA honours

During the CMA''s 128th annual meeting in Winnipeg in August, 33 physicians were awarded senior membership in the association and 2 physicians and an ethicist were honoured for their outstanding contributions to medicine. Pathologist Donald Penner of Winnipeg was awarded the CMA''s highest honour, the F.N.G. Starr Award. Toronto surgeon and educator Donald Wilson received the Medal of Service, and Montreal ethicist David Roy was awarded the Medal of Honour.     

Role of the PAR1 receptor 8th helix in signaling: the 7-8-1 receptor activation mechanism

The protease-activated receptors are tethered ligand G protein-coupled receptors that are activated by proteolytic cleavage of the extracellular domain of the receptor. The archetypic protease-activated receptor PAR1 strongly activates G(q) signaling pathways, but very little is known regarding the mechanism of signal transference between receptor and internally located G protein. The recent x-ray structure of rhodopsin revealed the presence of a highly conserved amphipathic 8th helix that is likely to be physically interposed between receptor and G protein. We found that the analogous 8th helix region of PAR1 was critical for activation of G(q)-dependent signaling. Engineering an 8th helix alpha-aneurysm with a downwards-directed alanine residue markedly interfered with signal transference to G(q). The 8th helix-anchoring cysteine palmitoylation sites were important for the affinity of ligand-dependent G protein coupling but did not affect the maximal signal. A network of H-bond and ionic interactions was found to connect the N-terminal portion of the 8th helix to the nearby NPXXY motif on transmembrane helix 7 and also to the adjacent intracellular loop-1. Disruption of these pairwise interactions caused additive defects in coupling to G protein, indicating that the transmembrane 7-8th helix-i1 loop may move in a coordinated manner to transfer the signal from PAR1 to G protein. This "7-8-1" interaction network was found to be prevalent in G protein-coupled receptors involved in endothelial signaling and angiogenesis.     

The NVVC: here, there and everywhere

When I started my cardiology training, back in 1976, cardiology in the Netherlands was highly dependent on internal medicine. Coronary care and intensive care units were led by internal medicine physicians in most hospitals in the Netherlands whereas in the US (where I had worked for a while) cardiology was a discipline in its own right, at least in university centres. In our country, this changed rapidly in the ensuing years and the Netherlands Society of Cardiology (NVVC) played a key role in this process.     

Conscientious objection in healthcare: How much discretionary space best supports good medicine?

Daniel Sulmasy has recently argued that good medicine depends on physicians having a wide discretionary space in which they can act on their consciences. The only constraints Sulmasy believes we should place on physicians’ discretionary space are those defined by a form of tolerance he derives from Locke, whereby people can publicly act in accordance with their personal religious and moral beliefs as long as their actions are not destructive to society. Sulmasy also claims that those who would reject physicians’ right to conscientious objection eliminate discretionary space, thus undermining good medicine and unnecessarily limiting religious freedom. I argue that, although Sulmasy is correct that some discretionary space is necessary for good medicine, he is wrong in thinking that proscribing conscientious objection entails eliminating discretionary space. I illustrate this using Julian Savulescu and Udo Schuklenk’s system for restricting conscientious objections as a counter‐example. I then argue that a narrow discretionary space constrained by professional ideals will promote good medicine better than Sulmasy’s wider discretionary space constrained by his conception of tolerance. Sulmasy’s version of discretionary space would have us tolerate actions that are at odds with aspects of good medicine, including aspects that Sulmasy himself explicitly values, such as fiduciary duty. Therefore, if we want the degree of religious freedom in the public sphere that Sulmasy favours then we must decide whether it is worth the cost to the healthcare system.     

An H-bond between two residues from different loops of the acetylcholine binding site contributes to the activation mechanism of nicotinic receptors

The molecular mechanisms of nicotinic receptor activation are still largely unknown. The crystallographic structure of the acetylcholine binding protein (AChBP) reveals a single H-bond between two different acetylcholine binding loops. Within these homologous loops we systematically introduced alpha4 residues into the alpha7/5HT(3) chimeric receptor and found that the single point mutations G152K (loop B) and P193I (loop C) displayed a non-additive increase of equilibrium binding affinity for several agonists compared with the double mutant G152K/P193I. In whole-cell patch-clamp recordings, G152K, P193I and G152K/P193I mutants displayed an increase up to 5-fold in acetylcholine potency with a large decrease of the apparent Hill coefficients (significantly smaller than one). Concomitantly, the G152K/P193I mutant showed a dramatic loss of high-affinity alpha-bungarotoxin binding (100-fold decrease), thus pinpointing a new contact area for the toxin. Fitting the data with an allosteric-kinetic model, together with molecular dynamic simulations, suggests that the presence of the inter-backbone H-bond between positions 152 and 193, revealed in alpha4 and in alpha7 double mutant but not in alpha7, coincides with a large stabilization of both open and desensitized states of nicotinic receptors.     

New Constitution for the International Palaeontological Association

At the General Assembly of the International Paleontological Union (I.P.U.), 20th August, 1968 a Policy Committee was formed and charged to formulate an entirely new Constitution; this was adopted 25th August, 1972 by the General Assembly. To conform with regulations of the International Union of Geological Sciences (I.U.G.S.), the new name is International Palaeontological Association (I.P.A.).     

Malic enzyme,phosphoglucomutase and phosphoglucose isomerase isozymes inTrichogramma [Hym.: Trichogrammatidae]

ME, PGM and PGI electrophoretic banding patterns in 20 laboratory cultures representing 14 species ofTrichogramma were studied. Variations in PGM were found inT. exiguum, T. marylandense, andT. pretiosum. PGI also showed variation inT. exiguum, T. marylandense, T. minutum, andT. parkeri. However, ME variations were found only inT. pretiosum. Based on progeny analyses, we concluded that ME is a tetramer inTrichogramma with fast and slow alleles at a single locus, and that both PGM and PGI have a single locus and each has four alleles. PGM is a monomer, but PGI is a dimer.

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Résumé Les bandes électrophorétiques de l'enzyme malique, de la P.G.M. et de la P.G.I. ont été étudiées chez 20 souches de laboratoire représentant 14 espèces deTrichogramma. Des variations de la P.G.M. ont été trouvées chezT. exiguum, T. marylandense etT. pretiosum. La. P.G.I. montre aussi des variations chezT. exiguum, T. marylandense, T. minutum etT. parkeri. Par contre, des variations de l'enzyme malique ne sont trouvées que chezT. pretiosum. En nous basant, sur l'analyse de progénitures, nous avons conclu que l'enzyme malique est un tétramère chezTrichogramma comprenant un allèle “lent” et un alléle “rapide”, à un seul locus, et que la P.G.M. et la P.G.I. ont chacune un seul locus à quatre allèles. La P.G.M. est un monomère mais la P.G.I. est un dimère.

     

The emergence of integrative medicine in Australia: the growing interest of biomedicine and nursing in complementary medicine in a southern developed society

In this article, I examine the process by which some biomedical physicians and nurses in Australia have come to adopt various alternative therapies in their regimens of practice, largely in response to (1) the growing interest on the part of many Australians in what is generally called "complementary medicine", and (2) a recognition that biomedicine is not particularly effective in treating an array of chronic ailments. Some Australian biomedical physicians and nurses have come to embrace "integrative medicine," which purports to blend the best of biomedicine and complementary medicine, and have even created an Australasian Integrative Medical Association and established integrative medical training programs and centers. I argue that the adoption of alternative therapies and the development of integrative medicine on the part of Australian biomedical physicians and nurses constitute another national manifestation of the co-option of complementary and alternative medicine.     

Functional characterization of mutants in the predicted pore region of the rabbit cardiac muscle Ca(2+) release channel (ryanodine receptor isoform 2).

A highly conserved amino acid sequence, GVRAGGGIGD(4831), which may form part of the Ca(2+) release channel pore in RyR2, was subjected to Ala scanning or Ala to Val mutagenesis; function was then measured by expression in HEK-293 cells, followed by Ca(2+) photometry, high affinity [(3)H]ryanodine binding, and single-channel recording. All mutants except I4829A and I4829T (corresponding to the I4897T central core disease mutant in RyR1) displayed caffeine-induced Ca(2+) release in HEK-293 cells; only mutants G4826A, I4829V, and G4830A retained high affinity [(3)H]ryanodine binding; and single-channel function was found for all mutants tested, except for G4822A and A4825V. EC(50) values for caffeine-induced Ca(2+) release were increased for G4822A, R4824A, G4826A, G4828A, and D4831A; decreased for V4823A; and unchanged for A4825V, G4827A, I4829V, and G4830A. Ryanodine (10 microm), which did not stimulate Ca(2+) release in wild type (wt), did so in Ala mutants in amino acids 4823-4827. It inhibited the caffeine response in wt and most mutants, but enhanced the amplitude of caffeine-induced Ca(2+) release in mutant G4828A. It also restored caffeine-induced Ca(2+) release in mutants I4829A and I4829T. In single-channel recordings, mutants I4829V and G4830A retained normal conductance, whereas all others had decreased unitary channel conductances ranging from 27 to 540 picosiemens. Single-channel modulation was retained in G4826A, I4829V, and G4830A, but was lost in other mutants. In contrast to wt and G4826A, I4829V, and G4830A, in which divalent metals were preferentially conducted, mutants with loss of modulation had no selectivity of divalent cations over a monovalent cation. Analysis of Gly(4822) to Asp(4831) mutants in RyR2 supports the view that this highly conserved sequence constitutes part of the ion-conducting pore of the Ca(2+) release channel and plays a key role in ryanodine and caffeine binding and activation.     

Humanities and medicine (a slightly dissident view).

Programs for humanities and medicine are growing in a number of medical schools in the U.S.A. Proponents of the programs, which are intended to bring together humanists, scientists, physicians, and others, believe that broadening the background of physicians will put a more human face on the practice of medicine, despite its increasingly technological nature. There is little to support this premise, and its successes and failures are not measurable. There are reasons to support the programs, however, but they have more to do with what physicians like and want to do than with what is therapeutic for them.     

Cross-cultural communication in the physician's office.

Physicians are increasingly called on to provide care for patients whose cultures differ from their own. I describe strategies, attitudes, and investigative methods that will enhance the experience of cross-cultural medicine for both patients and physicians.     

The other side of trust in health care: prescribing drugs with the potential for abuse

Defining a nonpaternalistic yet achievable form of trust in medicine in an era of simultaneous patient empowerment and institutional control has been and remains an important task of bioethics. The 'crisis of trust' in medicine has been viewed mainly as the problem of getting patients to trust their health care providers, especially physicians. However, since paradigmatic cases of trust are mutual, bioethicists must pay more attention to physician trust in patients. A physician's view of the reasonableness of trust in a particular patient is affected not just by his or her relationship with that patient, but also by what is going on institutionally, professionally, legally and politically with regard to a given treatment or intervention. Since general moral principles are insufficient in determining the moral value and reasonableness of trust in particular instances, I discuss in detail the role of trust and distrust in the specific case of treating patients with medications implicated in drug abuse. I conclude that it is important to become aware, first, of the clinical significance of physician trust and distrust in patients, and second, of the many factors which inform both of these moral attitudes. These two claims together suggest that a central, but overlooked, virtue of medical practice is reflective, context-responsive trust in patients.     

Recognition elements for 5' exon substrate binding to the Candida albicans group I intron

A group I intron precursor and ribozyme were cloned from the large subunit rRNA of the human pathogen Candida albicans. Both the precursor and ribozyme are functional as determined from in vitro assays. Comparisons of dissociation constants for oligonucleotide binding to the ribozyme and to a hexanucleotide mimic of its internal guide sequence lead to a model for recognition of the 5' exon substrate by this intron. In particular, tertiary contacts with the P1 helix that help align the splice site include three 2'-hydroxyl groups, a G.U pair that occurs at the intron's splice junction, and a G.A pair. The free energy contribution that each interaction contributes to tertiary binding is determined. When the G.A pair is replaced with a G-C pair, tertiary interactions to 5' exon mimic 2'-hydroxyl groups are significantly weakened. When the G.A pair is replaced with a G.U pair, tertiary interactions are retained and binding is 10-fold tighter. These results expand our knowledge of substrate recognition by group I introns, and also provide a basis for rational design of oligonucleotide-based therapeutics for targeting group I introns by binding enhancement by tertiary interactions and suicide inhibition strategies.     

REVIEWS

Book Reviewed in this article:
The Structure of New Zealand Woods . By B. A. M eylan and B. G. B utterfield .
Rice in Africa . Ed. by I. W. B uddenhagen and G. J. P ersley .
Plant Life in Anaerobic Environments . Ed. by D. D. H ook and R. M. M. C rawford .
Jes mécanismes de l'évolution . By J. G énermont .
Crassulacean Acid Metabolism. Analysis of an Ecological Adaptation . By M. K luge and I. P. T ing
Plant Disease: an Advanced Treatise. Volume 3. How Plants Suffer from Disease . Ed. J.G. H orsfall and E.B. C owling     

Optimizing the Solution Conditions to Solve the Structure of the Connexin43 Carboxyl Terminus Attached to the 4th Transmembrane Domain in Detergent Micelles

Abstract

pH-mediated gating of Cx43 channels following an ischemic event is believed to contribute to the development of lethal cardiac arrhythmias. Studies using a soluble version of the Cx43 carboxyl-terminal domain (Cx43CT; S255–I382) have established the central role it plays in channel regulation; however, research in the authors' laboratory suggests that this construct may not be the ideal model system. Therefore, we have developed a more ‘native-like’ construct (Cx43CT attached to the 4th transmembrane domain [TM4-Cx43CT; G178–I382]) than the soluble Cx43CT to further investigate the mechanism(s) governing this regulation. Here, we utilize circular dichroism and nuclear magnetic resonance (NMR) were used to validate the TM4-Cx43CT for studying channel gating and optimize solution conditions for structural studies. The data indicate that, unlike the soluble Cx43CT, the TM4-Cx43CT is structurally responsive to changes in pH, suggesting the presence of the TM4 facilitates pH-induced structural alterations. Additionally, the optimal solution conditions for solving the NMR solution structure include 10% 2,2,2 trifluoroethanol and removal of the 2nd extracellular loop (G178-V196).     

Structural investigations of DNA-histone complexes. A spin label study.

We have prepared two acridine spin labels, 6-chloro-9-[4-(2,2,6,6-tetramethyl-1-piperidinyloxy)amino]-2-methoxyacridine (I) and 9-[4-(2,2,6,6-tetramethyl-1-piperidinyloxy)amino]-acridine (II) and have used them to study the binding of lysine-rich histone (H1) to DNA using electron spin resonance (ESR). ESR spectra of I in the presence of DNA, polydA-polydT and polydG-polydC were characteristic of highly immobilized radicals with maximum hyperfine splitting (2T11) of 59G, 62.5G and 59G respectively. However, the 2T11 values for II in the same systems were 55.5G, 55.5G and 62.5G respectively. Addition of H1 at a low P/D released ionically bound I and II from DNA. In the presence of 0.1 M NaCl, which prevents ionic binding, H1 still caused a significant release of bound II but not I from DNA. At a high P/D (with or without NaCl) H1 caused no displacement of either I or II. Our findings suggest that H1 does not affect the intercalating sites and probably binds to one of the grooves of DNA, most probably the major groove, and specifically in the A-T-rich regions.     

REVIEWS

Book reviewed in this article:
Methods for Estimating Primary Production of Forests . I.B.P. Handbook No. 2. By P. J. N ewbould .
The Teaching of Ecology . British Ecological Society Symposium No. 7. Ed. by J. M. L ambert
Chemistry and Enzymology of Marine Algal Polysaccharides . By E lizabeth P ercival and R ichard H. M c D owell .
Dicionário Micológico . By O swaldo F idalgo and M aria E neyda P. K. F idalgo .
Taxonomic Studies of Subgenus Podosemum and Section Epicampes of Muhlenbergia ( Gramineae ). By T homas R. S oderstrom .
Studies of Fern Types, I . By C. V. M orton .
The Genus Melochia L. (Sterculiaceae ). By A aron G oldberg .
Guide pour l'Étude de quelques Plantes Tropicales . By L. P aulian de F élice .
Symposia of the Society for Experimental Biology. No . 21. Aspects of the Biology of Ageing . Ed. by H. W. W oolhouse .
Euglenoid Flagellates . By G. F. L eedale .
Encyclopaedia of Plant Physiology . Ed. by W. R uhland .
Annual Review of Plant Physiology , Vol. 18. Ed. by L. M achlis .     

Acylation of glycerol 3-phosphate is the sole pathway of de novo phospholipid synthesis in Escherichia coli.

The inhibition of phospholipid synthesis engendered by starving glycerol 3-phosphate (G3P) auxotrophs of Escherichia coli (plsB or gpsA) for G3P is incomplete; 5 to 10% of the normal rate of phospholipid synthesis remains, even after prolonged starvation. We report that G3P starvation of a strain having lesions in both the gpsA and plsB genes resulted in essentially complete (greater than 98.5%) inhibition of phospholipid synthesis, indicating that all de novo glycerolipid synthesis in E. coli proceeds by acylation of G3P.     

The Père David's deer MHC class I genes show unexpected diversity patterns, with monomorphic classical genes but polymorphic nonclassical genes and pseudogenes

Père David's deer (Elaphurus davidianus) is a highly inbred species that arose from 11 founders but now comprises a population of about 3,000 individuals, making it interesting to investigate the adaptive variation of this species from the major histocompatibility complex (MHC) perspective. In this study, we isolated Elda-MHC class I loci using magnetic bead-based cDNA hybridization, and examined the molecular variations of these loci using single-strand conformation polymorphism (SSCP) and sequence analysis. We obtained seven MHC class I genes, which we designated F1, F12, G2, I7, AF, I8, and C1. Our analyses of stop codons, phylogenetic trees, amino acid conservation, and G+C content revealed that F1, F12, G2, and I7 were classical genes, AF was a nonclassical gene, and I8 and C1 were pseudogenes. Our subsequent molecular examinations showed that the diversity pattern in the Père David's deer was unusual. Most mammals have more polymorphic classical class I loci vs. the nonclassical and neutral genes. In contrast, the Père David's deer was found to be monomorphic at classical genes F1, F12, G2, and I7, dimorphic at the nonclassical AF gene, dimorphic at pseudogene I8, and tetramorphic at pseudogene C1. The adverse polymorphism patterns of Elda-I genes might provide evidence for selection too faster deplete MHC variation than drift in the bottlenecked populations, while the postbottleneck tetramorphism of the C1 pseudogene appears to be evidence of strong historical balancing selection.