Intragenic suppression of an active site mutation in the human apurinic/apyrimidinic endonuclease

The apurinic/apyrimidinic endonucleases (APE) contain several highly conserved sequence motifs. The glutamic acid residue in a consensus motif, LQE96TK98 in human APE (hAPE-1), is crucial because of its role in coordinating Mg2+, an essential cofactor. Random mutagenesis of the inactive E96A mutant cDNA, followed by phenotypic screening in Escherichia coli, led to isolation of an intragenic suppressor with a second site mutation, K98R. Although the Km of the suppressor mutant was about sixfold higher than that of the wild-type enzyme, their kcat values were similar for AP endonuclease activity. These results suggest that the E96A mutation affects only the DNA-binding step, but not the catalytic step of the enzyme. The 3' DNA phosphoesterase activities of the wild-type and the suppressor mutant were also comparable. No global change of the protein conformation is induced by the single or double mutations, but a local perturbation in the structural environment of tryptophan residues may be induced by the K98R mutation. The wild-type and suppressor mutant proteins have similar Mg2+ requirement for activity. These results suggest a minor perturbation in conformation of the suppressor mutant enabling an unidentified Asp or Glu residue to substitute for Glu96 in positioning Mg2+ during catalysis. The possibility that Asp70 is such a residue, based on its observed proximity to the metal-binding site in the wild-type protein, was excluded by site-specific mutation studies. It thus appears that another acidic residue coordinates with Mg2+ in the mutant protein. These results suggest a rather flexible conformation of the region surrounding the metal binding site in hAPE-1 which is not obvious from the X-ray crystallographic structure.

Cyclosporiasis associated with imported raspberries, Florida, 1996

OBJECTIVES

Until 1995, infection with Cyclospora cayetanenis, a parasite that causes gastroenteritis, was diagnosed in the US primarily in overseas travelers; its modes of transmission were largely unknown. In 1995, 45 cases of cyclosporiasis were diagnosed in Florida residents who had no history of recent foreign travel, but an investigation could not pinpoint a source for the parasite. In 1996, a North American outbreak of cyclosporiasis resulted in more than 1400 cases, 180 of them in Florida. The authors investigated the 1996 Florida outbreak to identify the vehicle of transmission.

METHODS

The authors conducted a matched case-control study in which each of 86 laboratory-confirmed sporadic cases was matched with up to four controls. They also investigated nine clusters of cases associated with common meals and attempted to trace implicated foods to their countries of origin.

RESULTS

In the case control study, eating raspberries was strongly associated with cyclosporiasis (matched odds ratio = 31.9; 95% confidence interval [CI] 7.4, 138.2). In the cluster investigation, raspberries were the only food common to all nine clusters of cases; a summary analysis showed a strong association between consumption of raspberries and confirmed or probable cyclosporiasis (risk ratio = 17.6; 95% CI 1.9, 188.8). Guatemala was the sole country of origin for raspberries served at six of nine events.

CONCLUSIONS

Guatemalan raspberries were the vehicle for the 1996 Florida cyclosporiasis outbreak. Cyclospora is a foodborne pathogen that may play a growing role in the etiology of enteric disease in this country as food markets become increasingly international.

Childhood trauma and anorexia nervosa: from body image to embodiment

Contemporary understandings of anorexia nervosa are framed by the body-image paradigm. The body-image framework considers that women's bodily experiences are reflected through distorted mental images of their bodies or disordered thinking and behavior around food and eating. Body image has come to symbolize all that can go wrong with women's relationships with their bodies, food, and eating. The problem with this approach is its failure to consider the experience of women who have survived childhood abuse. Women's bodily disturbances are not easily discernible through objective measures because they lie within the inner subjective realm of the embodied 'self' and embodied emotional experience. Consideration of the different ways that women inhabit their bodies informs this paper's examination of the conceptual framework of embodiment as an alternative to the body-image paradigm.

Creutzfeldt-Jakob disease in a recipient of a dura mater graft processed in the US: cause or coincidence?

Iatrogenic Creutzfeldt-Jakob disease (CJD) has never been reported among recipients of dura mater grafts processed in the US. We recently investigated a report of such a case in a 72-year-old man with a typical clinical presentation of CJD. We found no evidence of CJD in either the 34-year-old donor or in other, proximal patients undergoing craniotomies. Although the graft may have caused the illness, sporadic CJD is a more likely explanation, with the graft being coincidental.

Passive immunization of pregnant goats against ovine LH

Groups of three goats at 50, 90 and 130 days of gestation were passively immunized against ovine LH (oLH) by i.v. infusion of 8 ml serum equivalent of the immunoglobulin fraction of rabbit anti-oLH serum (LHAS). Goats at the same stages of gestation as above served as controls and received 8 ml serum equivalent of the immunoglobulin fraction of normal rabbit serum (NRS). Plasma concentrations of progesterone were determined by specific radioimmunoassay of blood collected at 20-min intervals from 6 h before infusion of LHAS or NRS to 12 h after infusion. Less frequent sampling was performed from 2 days before to 6 days after infusion. Plasma from all LHAS-immunized goats exhibited binding of oLH. Twelve hours after immunization, titres ranged from 1:135 to 1:215. All LHAS-treated goats had titres of less than 1:10 by 5 days after immunization, but a low level of oLH binding was still detectable. Treatment with LHAS or NRS did not shorten the length of gestation, with all goats delivering live offspring between 142 and 147 days after conception. Plasma concentrations of LH ranged from less than 0.15 micrograms/l to 4.8 micrograms/l and were greater than 0.15 micrograms/l in 181 of 255 samples (71%) for both the NRS-treated group, throughout the experiment, and the LHAS-treated groups before infusion of antiserum. Luteinizing hormone was not detectable in plasma samples obtained after LHAS infusion in goats at 50 or 130 days of pregnancy. Plasma concentrations of LH exceeded 0.15 micrograms/l in only five of 51 (10%) samples in 90-day-pregnant goats treated with LHAS, the maximum value reached being 0.80 micrograms/l.(ABSTRACT TRUNCATED AT 250 WORDS)

The sequential mechanism of guanidine hydrochloride-induced denaturation of cAMP receptor protein from Escherichia coli. A fluorescent study using 8-anilino-1-naphthalenesulfonic acid

cAMP receptor protein (CRP) regulates expression of a number of genes in Escherichia coli. The protein is a homodimer and each monomer is folded into two structural domains. The biological activation of CRP upon cAMP binding may involve the subunit realignment as well as reorientation between the domains within each subunit. In order to study the interactions between the subunits or domains, we performed stopped-flow measurements of the guanidine hydrochloride (GuHCI)-induced denaturation of CRP. The changes in CRP structure induced by GuHCl were monitored using both intrinsic Trp fluorescence as well as the fluorescence of an extrinsic probe, 8-anilino-1-Naphthalenesulfonic acid (ANS). Results of CRP denaturation using Trp fluorescence detection are consistent with a two-step model [Malecki, and Wasylewski, (1997), Eur. J. Biochem. 243, 660], where the dissociation of dimer into subunits is followed by the monomer unfolding. The denaturation of CRP monitored by ANS fluorescence reveals the existence of two additional processes. One occurs before the dissociation of CRP into subunits, whereas the second takes place after the dissociation, but prior to proper subunit unfolding. These additional processes suggest that CRP denaturation is described by a more complicated mechanism than a simple three-state equilibrium and may involve additional changes in both inter- and intrasubunit interactions. We also report the effect of cAMP on the kinetics of CRP subunit unfolding and refolding.

The embodiment of childhood abuse and anorexia nervosa: A body mapping study

Childhood trauma has long been implicated in the development of anorexia nervosa and is known to impact more women than men. Still, less is known about the meaning women attribute to food and bodily practices and how they contribute to feminine subjectivity. In this article, we examine the subjective experiences of women with histories of childhood abuse and anorexia and women who did not develop an eating disorder. Through a visual narrative analysis of eight body maps and narratives, we identified five themes: "time and the body have a way of showing what matters," "femininity and family," "sexual subjectivities and food meanings," "voices, dissociation, and sexual subjectivities," and "religion and healthism." In women with anorexia, specific eating and bodily practices reconstructed the traumatic events to align with the available cultural discourses related to health, religion, and family and had implications for their feminine and sexual subjectivities and self-worth. This research showcased how arts-based methodologies add value and advance knowledge about the role of culturally available representations in the development of anorexia and has implications for therapy and prevention of anorexia.

A feminist phenomenological approach to the analysis of body maps: Childhood trauma and anorexia nervosa

Body mapping is an arts-based research technique that uses a life-sized outline of the participant's body and symbols that visually represent their lived experiences. In this article, we describe the methods of body mapping and analytic techniques used in a research inquiry exploring how child abuse influenced the embodied processes in anorexia. We aim to contribute to methodological research practice in anorexia using a method that can potentially add value in other areas of ED research or be adapted for treatment settings. Our research findings suggest that body mapping can add value to the interview method and extend the range of methods for researchers interested in interrogating the hard-to-reach subjective embodied processes.