Decision-Making in the Era of New Medical Technologies in Pediatric Hematology-Oncology: The Death of Palliative Care?

BACKGROUND

Recent advances in immunology, genomics, and cellular therapy have opened numerous therapeutic possibilities in pediatric hematology-oncology, generating new hope in poor prognosis situations. How decisions are made when it comes to treatments and aims needs to be explored in this new technologic context. In particular, their impact on the gold standard of early referral to palliative care must be assessed.

MATERIALS AND METHODS

Stemming from an ethnographic study combining semistructured interviews and observations carried out in a hematopoietic stem cell transplant unit in a Montréal Pediatric Hospital, we discuss the decision-making process when a patient faces poor prognosis.

RESULTS AND DISCUSSION

Although health care providers individually envisioned that palliative care may be the best course of action for patients receiving emergent therapy, they remained collectively in the curative mode. The intricate relationship between science, hope, caregiver, and care receiver sustains this perspective even when (near) death is the probable outcome. When proven treatment fails, emerging therapeutic possibilities offer new hope that can delay the referral to the palliative care team.

Decision-making and Poor Prognosis: When Death is Silenced by Action

In the hospital milieu, daily questions relate to highly invested areas such as quality of life and death issues, choices to continue or stop active treatment, and the legitimacy of those who take part in such decisions. Stemming from an ethnographic study carried out in a hematology-oncology transplant unit in a Montreal pediatric hospital, we discuss the decision-making process (or lack thereof) when a patient faces poor prognosis and the change of trajectory from a curative/disease directed to a palliative perspective. The intricate relationship between science, caregiver, and care receiver sustains action even when (near) death is the probable outcome.

Nouvelles perspectives sur la mixité conjugale : le sujet et l’acteur au coeur de l’analyse

En prenant la teinte des préoccupations sociopolitiques et intellectuelles d’une période donnée, les travaux en sciences sociales reflètent « l’air du temps » (Varro, ce numéro). La façon dont les chercheurs appréhendent leurs objets d’étude est donc liée au temps, mais également à l’espace, c’est-à-dire au contexte dans lequel ils sont ancrés. Il nous a donc semblé intéressant de faire un survol des différentes perspectives théoriques ayant structuré le champ des études sur la mixité conjugale en débutant par une synthèse des cadres théoriques qui ont longtemps dominé les recherches sur les couples mixtes pour ensuite mettre au jour l’émergence de perspectives récentes qui accordent une place privilégiée aux acteurs et placent l’identité personnelle au coeur de leur analyse. Ces perspectives, qui ouvrent sur des thèmes et des points de vue nouveaux tout en contribuant à la transformation du langage même qui structure ce domaine de recherche, reflètent incontestablement les préoccupations de notre époque.

L’adaptation des soins sociosanitaires de première ligne à la diversité religieuse

La diversité religieuse croissante de la population québécoise soulève certaines questions essentielles pour les institutions médicales, dont celle de leur adaptation aux différences religieuses. À partir de cas cliniques recueillis lors d’une recherche récente sur les défis et enjeux posés par la diversité religieuse dans l’intervention de première ligne, nous examinons dans cet article la manière dont la diversité religieuse est prise en compte par les intervenants dans leur travail. Nous cherchons également à voir comment se manifeste la religion dans la rencontre clinique et quelles sont les réactions des intervenants face aux requêtes des usagers.

Néonatalité et constitution des savoirs en contexte migratoire : familles et services de santé. Enjeux théoriques, perspectives anthropologiques

Ce texte, inspiré d’une recherche naissante et des expériences de terrain des auteures, aborde la période périnatale comme un moment charnière pour la transmission de savoirs familiaux. En contexte migratoire, cette période prend un sens particulier, à la fois en raison de l’éloignement des proches et de l’investissement du projet parental (l’avenir des enfants étant souvent au coeur du projet migratoire). La naissance d'un enfant permet également à plusieurs de prendre connaissance des services médicaux québécois. Le questionnement est alors double : comment les savoirs et les pratiques familiales périnatales sont-ils transmis (et réinterprétés) dans la société locale, et comment ceux-ci trouvent-ils écho auprès des experts dans les services de santé locaux? Les musulmans étant d’une immigration récente et croissante au Québec, nous nous attardons davantage à ce groupe en ce qu’il témoigne à la fois d’une diversité culturelle, ethnique et religieuse.

The primary and three-dimensional structures of a nine-haem cytochrome c from Desulfovibrio desulfuricans ATCC 27774 reveal a new member of the Hmc family

BACKGROUND

Haem-containing proteins are directly involved in electron transfer as well as in enzymatic functions. The nine-haem cytochrome c (9Hcc), previously described as having 12 haem groups, was isolated from cells of Desulfovibrio desulfuricans ATCC 27774, grown under both nitrate- and sulphate-respiring conditions.

RESULTS

Models for the primary and three-dimensional structures of this cytochrome, containing 292 amino acid residues and nine haem groups, were derived using the multiple wavelength anomalous dispersion phasing method and refined using 1.8 A diffraction data to an R value of 17.0%. The nine haem groups are arranged into two tetrahaem clusters, with Fe-Fe distances and local protein fold similar to tetrahaem cytochromes c3, while the extra haem is located asymmetrically between the two clusters.

CONCLUSIONS

This is the first known three-dimensional structure in which multiple copies of a tetrahaem cytochrome c3-like fold are present in the same polypeptide chain. Sequence homology was found between this cytochrome and the C-terminal region (residues 229-514) of the high molecular weight cytochrome c from Desulfovibrio vulgaris Hildenborough (DvH Hmc). A new haem arrangement in domains III and IV of DvH Hmc is proposed. Kinetic experiments showed that 9Hcc can be reduced by the [NiFe] hydrogenase from D. desulfuricans ATCC 27774, but that this reduction is faster in the presence of tetrahaem cytochrome c3. As Hmc has never been found in D. desulfuricans ATCC 27774, we propose that 9Hcc replaces it in this organism and is therefore probably involved in electron transfer across the membrane.

Cloning and sequencing of the genes encoding the large and small subunits of the periplasmic (NiFeSe) hydrogenase of Desulfovibrio baculatus

The genes coding for the large and small subunits of the periplasmic hydrogenase from Desulfovibrio baculatus have been cloned and sequenced. The genes are arranged in an operon with the small subunit gene preceding the large subunit gene. The small subunit gene codes for a 32 amino acid leader sequence supporting the periplasmic localization of the protein, however no ferredoxin-like or other characteristic iron-sulfur coordination sites were observed. The periplasmic hydrogenases from D. baculatus (an NiFeSe protein) and D. vulgaris (an Fe protein) exhibit no homology suggesting that they are structurally different, unrelated entities.

EPR determination of the oxidation-reduction potentials of the hemes in cytochrome c3 from Desulfovibrio vulgaris

EPR spectroscopy in conjunction with oxidation-reduction potentiometry has been used to determine the half-reduction potentials of the four hemes of cytochrome c3. As predicted, the four hemes of cytochrome c3 have different mid-point potentials. The Em values are: Heme I,--284 mV; Heme II,--310 mV; Heme III,--324 mV and Heme IV,--319 mV. The n-values in each case was near one.

Reactivity of Desulfovibrio gigas hydrogenase toward artificial and natural electron donors or acceptors

A purified preparation of hydrogenase from D. gigas was inactive toward ferredoxin, flavodoxin or rubredoxin in the absence of cytochrome c3 (M.W. 13,000), in an atmosphere of hydrogen, although direct reduction of benzyl viologen or FMN was possible. The hydrogen evolution reaction from dithionite was possible with methyl viologen. The same reaction also occured with cytochrome c3 (M.W. 13,000) or cytochrome c3 (M.W. 26,000). Addition of either ferredoxin or flavodoxin did not accelerate the reaction.

NMR characterization of three forms of ferredoxin from Desulphovibrio gigas, a sulphate reducer

A NMR and magnetic susceptibility study of the oxidized and reduced states of three different oligomers (forms) of a [4Fe-4S] ferrodoxin protein from Desulphovibrio gigas, FdI, FdI', and FdII was carried out. FdI and FdI' are different trimers and FdII a tetramer of the same basic subunit. A probable assignment of the contact shifted resonances is indicated. Since the temperature dependences of the contact shifted responances associated with each [4Fe-4S] are not all similar a delocalized model for the spin densities on the 4Fe does not apply. The exchange rate between oxidized and reduced states is slow on the NMR time scale. The three oligomers are not magnetically equivalent. Using the "three state hypothesis" terminology it is shown that FdIox is predominantly in the C2- state and changes upon reduction into the C3- state, while FdIIox is in the C- state and changes into the C2- state. FdI' does not easily fit into this classification. This study shows a similarity of magnetic behaviour between FdI and bacterial ferredoxins (e.g. Bacillus polymyxa) and between FdII and HiPIP from Chromatium sp. The influence of the quaternary structure on the stabilization of the different oxidation states of ferredoxins as well as on their redox potentials is discussed.

Purification and characterization of cytochrome c3, ferredoxin, and rubredoxin isolated from Desulfovibrio desulfuricans Norway

Different electron carriers of the non-desulfoviridin-containing, sulfate-reducing bacterium Desulfovibrio desulfuricans (Norway strain) have been studied. Two nonheme iron proteins, ferredoxin and rubredoxin, have been purified. This ferredoxin contains four atoms of non-heme iron and acid-labile sulfur and six residues of cysteine per molecule. Its amino acid composition suggests that it is homologous with the other Desulfovibrio ferredoxins. The rubredoxin is also an acidic protein of 6,000 molecular weight and contains one atom of iron and four cysteine residues per molecule. The amino acid composition and molecular weight of the cytochrome c3 from D. desulfuricans (strain Norway 4) are reported. Its spectral properties are very similar to those of the other cytochromes c3 (molecular weight, 13,000) of Desulfovibrio and show that it contains four hemes per molecule. This cytochrome has a very low redox potential and acts as a carrier in the coupling of hydrogenase and thiosulfate reductase in extracts of Desulfovibrio gigas and Desulfovibrio desulfuricans (Norway strain) in contrast to D. gigas cytochrome c3 (molecular weight, 13,000). A comparison of the activities of the cytochrome c3 (molecular weight, 13,000) of D. gigas and that of D. desulfuricans in this reaction suggests that these homologous proteins can have different specificity in the electron transfer chain of these bacteria.