Chemical modification of chalcone isomerase by mercurials and tetrathionate. Evidence for a single cysteine residue in the active site

Chalcone isomerase from soybean is inactivated by stoichiometric amounts of p-mercuribenzoate or HgCl2. Spectral titration of the enzyme with p-mercuribenzoate indicates that a single thiol group is modified. Treatment of modified enzyme with KCN or thiols results in a complete restoration of enzyme activity demonstrating that the inactivation is not due to irreversible protein denaturation. A product of the enzymatic reaction, naringenin, provides complete kinetic protection against inactivation by both mercurials. The binding constant (33 microM) for naringenin determined from the concentration dependence of the protection agrees with the inhibition constant (34 microM) for naringenin as a competitive inhibitor of the catalytic reaction. This agreement demonstrates that the observed kinetic protection results from the specific binding of naringenin to the active site. Incubation of native chalcone isomerase with sodium tetrathionate (0.1 M) results in a slow time-dependent loss of enzymatic activity. The inactivation of chalcone isomerase by tetrathionate and N-ethylmaleimide becomes very rapid in the presence of 6 M urea, indicating that the native tertiary structure is responsible for the low reactivity of the enzymatic thiol. The stoichiometric modification of reduced and denatured chalcone isomerase by [3H] N-ethylmaleimide indicates that the enzyme contains only a single cysteine residue and does not contain any disulfides. The evidence presented suggests that the only half-cystine residue in chalcone isomerase is located in the active site and thereby provides the first clue to the location of the active site in chalcone isomerase.     

On being ethnic: The politics of identity breaking and making in Canada,or, Nevra on Sunday

The creation of ethnically sensitive health care is a major federal and provincial government concern in Canada at present. The concept of multiculturalism is used to reinforce the notion of rights for minority groups and the Canadian mozaic is explicitly contrasted with the American melting pot. In this paper, the lives of Greek immigrant women in Montreal are used to illustrate how class and gender are as relevant to the immigrant experience as is ethnicity. It is shown how values which were central to female identity in Greece can become a liability after immigration and how the notion of Greek identity in Canada is a fluid category which is subject to repeated transformations. It is suggested that medical anthropologists who ignore the complexity of social categories and whose focus is limited to the cultural construction of illness and the expression of distress are in danger of reinforcing a notion of the quaint ethnic, a stereotype to which the concept of multiculturalism is often reduced.

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Résumé La création de services de santé sensibles aux besoins des différents groupes ethniques est présentement un socci majeur des gouvernements fédéral et provincial au Canada. Le concept de multiculturalisme est utilisé pour renforcer I'idée des droits des groupes minoritaires et la mosaïque canadienne est explicitement contrastée avec the American melting pot. Dans cet exposé, j'utilise la vie des femmes immigrantes grecques à Montréal pour démontrer que la classe et le sexe sont aussi pertinent par rapport à l'expérience des immigrants que l'ethnicité. On montre de quelle façon les valeurs qui sont centrales à l'identité féminine en Grèce peuvent en venir à constituer un problème après l'immigration et comment la notion d'identité grecque au Canada est une catégorie fluide qui est sujette à de multiples transformations. On suggère que les anthropologues médicaux qui ne tiennent pas compte de la complexité des catégories sociales et dont le centre d'intérêt est limité à la cultural construction of illness et à l'expression of distress courent le danger de renforcer la notion de quaint ethnic, un stéréotype auquel le concept de multiculturalisme se trouve souvent réduit. Notes 1 See, for example, Low 1985; Davis 1989; Dunk 1989; Guarnaccia et al. 1989; Van Schaik 1989. 2 Data for this study were obtained initially from eighty-three fast generation Greek immigrant women living in Montreal who were given semi-structured interviews in Greek in their homes. It became apparent in the course of carrying out these interviews that the concept of nevra was central in the narratives given by virtually all of the respondents. This term was inevitably used to link environmental and psychosocial variables to distress and painful physical states. In the second phase of the research, 19 of the original women were selected for in-depth open-ended interviews during which the concept of nevra was discussed in detail. A further data set was obtained from twenty five women who were interviewed in the office of a Greek Canadian general practitioner and 15 more attending a poly-clinic in a Montreal teaching hospital. These interviews were carried out in order to establish if nevra is used as a presenting complaint in clinical settings, and if so, how it is managed by health care professionals. Several internists, psychiatrists, family and general practitioners, and social workers who have daily contact with Greek patients were also interviewed.

     

Structural regularities in tetraether lipids of Caldariella and their biosynthetic and phyletic implications

Individual di(biphytanyl) diglycerol tetraether lipids from thermoacidophile archaebacteria of the Caldariella series, with differently cyclized biphytanyl components, are separated and shown to have structures 8–12, with the glycerol and biphytanyl components demonstrably both antiparallel and with partial assignments of stereochemistry. Tetraethers with alternative arrangements of the components are absent. The structures allow previous observations on these and related lipids to be rationalized both biosynthetically and phyletically.     

The disappearance of four leaf leachates in a hard and soft water stream in South Western Ontario,Canada

The disappearance of ‘dissolved’ organic carbon (D. O. C.) leached from maple, aspen, cedar and pine leaves was followed in hard and soft stream water and hard and soft stream water plus sediment. Differences were found in the rates and extent of the disappearance of D. O. C. between the leaves and the water types. These are discussed in relation to the productivity of two extreme stream types.     

Effects of aerobic exercise therapy and cognitive behavioural therapy on functioning and quality of life in amyotrophic lateral sclerosis: protocol of the FACTS-2-ALS trial

Background

Neuropathic pain must be correctly diagnosed for optimal treatment. The questionnaire named Neuropathic Pain Symptom Inventory (NPSI) was developed in its original French version to evaluate the different symptoms of neuropathic pain. We hypothesized that the NPSI might also be used to differentiate neuropathic from non-neuropathic pain.

Methods

We translated the NPSI into German using a standard forward-backward translation and administered it in a case-control design to patients with neuropathic (n = 68) and non-neuropathic pain (headache and osteoarthritis, n = 169) to validate it and to analyze its discriminant properties, its sensitivity to change, and to detect neuropathic pain subgroups with distinct profiles.

Results

Using a sum score (the NPSI-G score), we found sensitivity to change (r between 0.37 and 0.5 for pain items of the graded chronic pain scale) and could distinguish between neuropathic and other pain on a group basis, but not for individual patients. Post hoc development of a discriminant score with optimized diagnostic properties to distinguish neuropathic pain from non-neuropathic pain resulted in an instrument with high sensitivity (91%) and acceptable specificity (70%). We detected six different pain profiles in the patient group with neuropathic pain; three profiles were found to be distinct.

Conclusions

The NPSI-G potentially combines the properties of a diagnostic tool and an instrument to identify subtypes of neuropathic pain.