Pigment gallstone pathogenesis: slime production by biliary bacteria is more important than beta-glucuronidase production

Pigment stones are thought to form as a result of deconjugation of bilirubin by bacterial beta-glucuronidase, which results in precipitation of calcium bilirubinate. Calcium bilirubinate is then aggregated into stones by an anionic glycoprotein. Slime (glycocalyx), an anionic glycoprotein produced by bacteria causing foreign body infections, has been implicated in the formation of the precipitate that blocks biliary stents. We previously showed that bacteria are present within the pigment portions of gallstones and postulated a bacterial role in pigment stone formation through beta-glucuronidase or slime production. Ninety-one biliary bacterial isolates from 61 patients and 12 control stool organisms were tested for their production of beta-glucuronidase and slime. The average slime production was 42 for biliary bacteria and 2.5 for stool bacteria (P <0.001). Overall, 73% of biliary bacteria and 8% of stool bacteria produced slime (optical density >3). In contrast, only 38% of biliary bacteria produced beta-glucuronidase. Eighty-two percent of all patients, 90% of patients with common bile duct (CBD) stones, 100% of patients with primary CBD stones, and 93% of patients with biliary tubes had one or more bacterial species in their stones that produced slime. By comparison, only 47% of all patients, 60% of patients with CBD stones, 62% of patients with primary CBD stones, and 50% of patients with biliary tubes had one or more bacteria that produced beta-glucuronidase. Most biliary bacteria produced slime, and slime production correlated better than beta-glucuronidase production did with stone formation and the presence of biliary tubes or stents. Patients with primary CBD stones and biliary tubes had the highest incidence of slime production. These findings suggest that bacterial slime is important in gallstone formation and the blockage of biliary tubes.

Expression of human topoisomerase I with a partial deletion of the linker region yields monomeric and dimeric enzymes that respond differently to camptothecin

Human topoisomerase I is a 765-residue protein composed of four major domains as follows: the unconserved and highly charged NH(2)-terminal domain, a conserved core domain, the positively charged linker region, and the highly conserved COOH-terminal domain containing the active site tyrosine. Previous studies of the domain structure revealed that near full topoisomerase I activity can be reconstituted in vitro by fragment complementation between recombinant polypeptides approximating the core and COOH-terminal domains. Here we demonstrate that deletion of linker residues Asp(660) to Lys(688) yields an active enzyme (topo70DeltaL) that purifies as both a monomer and a dimer. The dimer is shown to result from domain swapping involving the COOH-terminal and core domains of the two subunits. The monomeric form is insensitive to the anti-tumor agent camptothecin and distributive during in vitro plasmid relaxation assays, whereas the dimeric form is camptothecin-sensitive and processive. However, the addition of camptothecin to enzyme/DNA mixtures causes enhancement of SDS-induced breakage by both monomeric and dimeric forms of the mutant enzyme. The similarity of the dimeric form to the wild type enzyme suggests that some structural feature of the dimer is providing a surrogate linker. Yeast cells expressing topo70DeltaL were found to be insensitive to camptothecin.

Amelioration of established collagen induced arthritis by systemic IL-10 gene delivery

A novel formulation of cationic liposomes containing the novel cytofectin ACHx was used for delivery of an anti-inflammatory cytokine gene, IL-10, to mice with established collagen induced arthritis. A single intraperitoneal injection of human IL-10 expression plasmid complexed with liposomes 2 to 4 days after the onset of arthritis was sufficient to give significant and prolonged amelioration of arthritis for 30 days. Preliminary experiments suggested that the therapeutic effect was IL-10 dose-dependent. The distribution of the human IL-10 DNA after injection was widespread, including the inflamed paws. Human IL-10 mRNA was also detected in the paws 24 h after injection. IL-10 protein was below the level of detection in paws and serum but was detected in some tissues up to 10 days after injection. The target cell of transfection was demonstrated to be the macrophage. These results suggest that systemic therapy with plasmid DNA complexed with cationic liposomes merits further development as an alternative method for anti-inflammatory treatment of arthritis.

Postcholecystectomy abdominal bile collections

HYPOTHESIS

The clinical syndromes caused by bile collections in the abdomen span a wide spectrum and their natural history and risks are not fully appreciated.

DESIGN

Analysis of 179 patients with bile fistulas after cholecystectomy, of which 154 patients had undrained bile collections.

OBJECTIVE

To characterize the manifestations and natural history of abdominal bile collections.

SETTING

A tertiary care teaching hospital.

PATIENTS AND METHODS

The clinical findings in 179 patients with bile fistulas resulting from iatrogenic laparoscopic bile duct injuries and other miscellaneous operations between 1990 and 1999 were analyzed. The group of main interest consisted of 154 patients with undrained bile collections. Of these 154 patients, 21% had serious complications, including sepsis and multiorgan failure. The data were analyzed to identify the variables associated with this undesirable outcome.

MAIN OUTCOME MEASURES

Symptoms, physical findings, course of illness, and laboratory and imaging findings.

RESULTS

The clinical manifestations of intra-abdominal bile collections were initially discounted in 77% of patients, so the problem went unsuspected for a variable and often lengthy period. Abdominal pain and tenderness (bile peritonitis) gradually developed in 18% of patients with bile ascites. There were no differences in the initial clinical findings in this group compared with those who did not develop peritonitis. Nineteen percent of patients with undrained bile collections experienced serious morbidity. The initial clinical findings did not differ in these patients compared with those with a less complicated illness. Serious illness, however, was associated with the following: (1) a longer period of undrained bile (15.4 vs 9.2 days, P=.04) and (2) a higher incidence of infected bile (45% vs 7%, P=.001).

CONCLUSIONS

(1) Prominent abdominal pain and tenderness developed in only 21% of patients with abdominal bile collections; (2) the symptoms caused by bile collections were often subtle and their significance was overlooked, which resulted in a delay in diagnosis; (3) the early clinical findings could not distinguish patients who did become critically ill from those who did not; and (4) seriously ill patients more often had delayed drainage and infected bile. Still, failure to drain a bile collection within just 5 days resulted in serious illness in a few patients. Surgeons must watch for the clinical manifestations of bile ascites after laparoscopic cholecystectomy. This diagnosis should be suspected whenever persistent bloating and anorexia last for more than a few days; failure to recover as smoothly as expected is the most common early symptom of bile ascites. If bile collections were promptly diagnosed and drained, the rate of serious illness resulting from this complication would decline.

Treatment outcome among child psychiatric outpatients in a community mental health center

The study evaluated the effectiveness of mental health center treatments for children aged 5-12 years. The Child Behavior Checklist (CBCL) was administered before and after treatment to the parents of the treatment group (N = 71). The results were analyzed and compared to the results of the pretest and posttest CBCL administered to the parents of a matched group of comparison subjects (N = 33). The results showed that the treatment subjects significantly improved on both the externalizing and internalizing scales of the CBCL. The controls showed no significant change between pretest and posttest scores. As a result, it appears that clinic treatments can help clients with measurable problems decrease problematic behaviors. More data is needed to determine whether clinic treatments such as the ones described in this study can substantially help the most seriously disturbed school-age children.

Fat absorption in cystic fibrosis after correction of hypokalaemia

Extracellular potassium up-regulates exocrine pancreatic function in tissue preparations of mammalian pancreatic lobules. We report on a child with cystic fibrosis in whom clinical evidence suggested that this laboratory observation may be of relevance to clinical practice.

Developing a model of collaborative research: the complexities and challenges of implementation

While the benefits of collaborative research have been well documented, fewer publications exist regarding the complex, problematic issues involved in these undertakings. This paper offers an integrated collaborative research model to depict the complexities and challenges of initiation and implementation of a 2 1/2 year joint research project between a community hospital and a university school of nursing in Southern Ontario, Canada. A sampling of the experiences of the researchers are analyzed to clarify the dynamic and often competing issues and interactions involved in encouraging hospital-wide research involvement during periods of organizational growth and change. The model reflects the simultaneous interaction of organizational, change and collaborative processes while maintaining the rigor of the research (RCT), and ensuring minimal disruption to the service agency. Quantitative outcomes of this collaboration are presented through an analysis of participant involvement on multiple organizational levels. Recommendations for future collaborative research, including design and methodological issues and collaborative and change strategies are offered. The complexity of balancing the necessary trade-offs required of successful collaborative research are highlighted and will be useful to those considering and planning future collaborations.

The manifestation and nursing management of agitation in institutionalised residents with dementia

This participatory action research study is the first formal research study undertaken by nurses in a nursing development unit. The study emerged as the result of nurses brainstorming issues that they perceived to be problematic in their nursing practice and their unit environment. The nurses of the psycho-geriatric nursing development unit, Wallsend Aged Care Facility, New South Wales, Australia identified that the management of agitated behaviour manifested by their severely demented clients was a major challenge in their practice. As a result, a pilot participatory action research study was designed to measure how agitation manifested, to measure the severity of agitation and to identify current nursing practices used to manage it and their outcome. Results of the study demonstrated that nurse actions triggered the majority of most highly rated episodes of agitated behaviour in this group of elderly residents, and that the majority of these nurse actions related to those involved in carrying out activities of daily living for the residents.

Chemotherapy for advanced ovarian cancer. Advanced Ovarian Cancer Trialists Group

BACKGROUND

Ovarian carcinoma is the seventh most common cancer of women in the world and is responsible for the greatest number of deaths from gynaecological malignancy in Europe and North America. Although many studies have explored the use of chemotherapy in this disease, most individual trials have been too small to show clear benefit of one type of chemotherapy over another.

OBJECTIVES

The type and intensity of chemotherapy used routinely for women with advanced ovarian cancer has varied because of uncertainty about the effectiveness of the different regimens. The objective of this review was to compare single drugs versus combinations of drugs, platinum versus non-platinum, and carboplatin versus cisplatin-based chemotherapy in women with advanced ovarian cancer.

SEARCH STRATEGY

Search strategy: We searched MEDLINE, and CancerLit bibliographic databases and the National Cancer Institute and the UK Co-ordinating Committee on Cancer Research registers of trials. We also handsearched the proceedings of meetings and contacted experts in the field and drug companies.

SELECTION CRITERIA

Randomised trials of: (1) single non-platinum versus non-platinum combination chemotherapy (2) single non-platinum versus platinum combination chemotherapy (3) non-platinum regimen versus the same regimen plus cisplatin (4) single platinum versus platinum combination chemotherapy (5) cisplatin versus carboplatin-based chemotherapy in women with advanced ovarian cancer.

DATA COLLECTION AND ANALYSIS

Individual patient data were obtained from the trial investigators, checked by the reviewers and finally verified by the trial investigator.

MAIN RESULTS

Main results: 49 trials involving 8763 women were included. The data were combined to calculate hazard ratios (HR) for survival on an intention-to-treat basis. For single non-platinum versus platinum combination chemotherapy the overall HR for survival was 0.93, 95% confidence interval (CI) 0.83-1.05 in favour of platinum-based combination chemotherapy. For non-platinum regimens compared with the same regimen plus cisplatin the survival HR was 0.88, 95% CI 0.79- 0.98 in favour of the addition of platinum to drug regimens. Single platinum compared with platinum combination therapy gave a HR of 0.91, 95% CI 0.79-1.05 in favour of combination chemotherapy. Cisplatin versus carboplatin gave a HR of 1.02, 95% CI 0.93-1.12. Sub-group analyses for age, stage, grade, histology, resection, bulk of residual tumour and performance status were undertaken for cisplatin versus carboplatin only. No difference in effect was found.

REVIEWER'S CONCLUSIONS

The available evidence, although not conclusive, suggests that platinum-based chemotherapy is better than non-platinum therapy. There is some evidence that combination therapy improves survival compared with platinum alone. No difference in effect has been shown between cisplatin and carboplatin.

Community action to reduce rural drink and drive crashes in New Zealand: adapting approaches in dynamic environments

This paper discusses the evolution of a two-and-a-half year pilot community action project aimed at developing strategies to reduce alcohol-use-related crashes in a rural police district in New Zealand. Formative evaluation aimed to assist an intersectoral coordinating group identify and implement strategies. Initially the idea was to establish community-based committees to mobilize on drinking and driving around the district. However, it became clear that the original concept impeded action. The focus was changed to provide more support to strengthen existing initiatives, particularly those relating to police traffic enforcement and drinking environments. This helped give the project renewed life and direction. The paper focuses on process, organizational, and external community issues affecting the project and the use of formative evaluation to assist the project to respond and adapt to dynamic circumstances.

Air flight disaster, posttraumatic stress, and postventive rescue and response: the aftermath of the San Diego PSA 182 plane crash recovery operation, 20 years on

San Diego in 1978 was the scene of one of the USA's most tragic and traumatic air flight disasters, when an inbound Boeing 727 collided with a small private Cessna 172. The collision occurred in the vicinity of North Park, a suburb of San Diego. All aircraft occupants were killed or injured and many residents were injured. The wreckage was mainly concentrated in an area about the size of a city block, in a temperature of 100 degrees F or more. The whole experience was unlike anything any of the professionals involved had been prepared for, and beyond anything the civilians involved could have imagined. Many sought out intervention and help and counselling, and this paper examines the implications of the event 20 years on.

A functional linker in human topoisomerase I is required for maximum sensitivity to camptothecin in a DNA relaxation assay

Human topoisomerase I is composed of four major domains: the highly charged NH(2)-terminal region, the conserved core domain, the positively charged linker domain, and the highly conserved COOH-terminal domain. Near complete enzyme activity can be reconstituted by combining recombinant polypeptides that approximate the core and COOH-terminal domains, although DNA binding is reduced somewhat for the reconstituted enzyme (Stewart, L., Ireton, G. C., and Champoux, J. J. (1997) J. Mol. Biol. 269, 355-372). A reconstituted enzyme comprising the core domain plus a COOH-terminal fragment containing the complete linker region exhibits the same biochemical properties as a reconstituted enzyme lacking the linker altogether, and thus detachment of the linker from the core domain renders the linker non-functional. The rate of religation by the reconstituted enzyme is increased relative to the forms of the enzyme containing the linker indicating that in the intact enzyme the linker slows religation. Relaxation of plasmid DNA by full-length human topoisomerase I or a 70-kDa form of the enzyme that is missing only the non-essential NH(2)-terminal domain (topo70) is inhibited approximately 16-fold by the anticancer compound, camptothecin, whereas the reconstituted enzyme is nearly resistant to the inhibitory effects of the drug despite similar affinities for the drug by the two forms of the enzyme. Based on these results and in light of the crystal structure of human topoisomerase I, we propose that the linker plays a role in hindering supercoil relaxation during the normal relaxation reaction and that camptothecin inhibition of DNA relaxation depends on a direct effect of the drug on DNA rotation that is also dependent on the linker.

Loss of responsiveness to transforming growth factor beta induces malignant transformation of nontumorigenic rat prostate epithelial cells

Transforming growth factor (TGF)-betas are multifunctional growth factors, the properties of which include the potent inhibition of epithelial cell growth. Expression patterns of TGF-betas and TGF-beta receptors in the normal prostate indicate that these growth regulators play key roles in prostatic development and proliferative homeostasis. Importantly, TGF-beta receptor levels are frequently diminished in malignant human prostate tissue. To test the hypothesis that loss of TGF-beta responsiveness is causally involved in the tumorigenic process, we have used retroviral transduction to introduce a dominant-negative mutant type II TGF-beta receptor (DNR) into the premalignant rat prostatic epithelial cell line, NRP-152. High-level expression of the DNR abolished the ability of TGF-beta to inhibit cell growth, to promote cell differentiation, and to induce apoptosis, and it partially blocked the induction of extracellular matrix gene expression. When injected into nude mice, NRP-152-DNR cells formed carcinomas at 13 of 34 sites, compared with 0 of 30 sites for parental and control cells (P = 0.0001). We conclude that the type II TGF-beta receptor is an important tumor suppressor in the prostate, and furthermore, that loss of TGF-beta responsiveness can contribute early in the tumorigenic process by causing the malignant transformation of preneoplastic cells.

Structural flexibility in human topoisomerase I revealed in multiple non-isomorphous crystal structures

Human topoisomerase I plays a critical role in chromosomal stability by relaxing the DNA superhelical tension that arises from a variety of nuclear processes, including replication, transcription, and chromatin remodeling. Human topoisomerase I is a approximately 91 kDa enzyme composed of four major domains: a 24 kDa N-terminal domain, a56 kDa core domain, a7 kDa linker domain, and a6 kDa C-terminal domain containing the active-site Tyr723 residue. A monoclinic crystal structure of a 70 kDa N-terminally truncated form of human topoisomerase I in non-covalent complex with a 22 bp DNA duplex exhibited remarkable crystal-to-crystal non-isomorphism; shifts in cell constants of up to 9 A in the b -axis length and up to 8.5 degrees in the beta-angle were observed. Eight crystal structures of human topoisomerase I - DNA complexes from this crystal form were determined to between 2.8 and 3.25 A resolution. These structures revealed both dramatic shifts in crystal packing and functionally suggestive regions of conformational flexibility in the structure of the enzyme. Crystal packing shifts of up to 20.5 A combined with rotations of up to 11.5 degrees were observed, helping to explain the variability in cell constants. When the core subdomain III regions of the eight structures are superimposed, the "cap" (core subdomains I and II) of the molecule is observed to rotate by up to 4.6 degrees and to shift by up to 3.6 A. The linker domain shows the greatest degree of conformational flexibility, rotating and shifting by up to 2.5 degrees and 4.6 A, respectively, in five of eight structures, and becoming disordered altogether in the remaining three. These observed regions of conformational flexibility in the cap and the linker domain are consistent with the structural flexibility invoked in the "controled rotation" mechanism proposed for the relaxation of DNA superhelical tension by human topoisomerase I.

First observations of the safety and tolerability of a competitive antagonist to the glutamate NMDA receptor (CGS 19755) in patients with severe head injury

A dose escalation, safety, and tolerability study of a competitive antagonist to the N-methyl-D-aspartate (NMDA) glutamate receptor (CGS 19755, Selfotel) in patients with severe head injury is reported. The drug was administered i.v. on two separate occasions, 24 h apart, to 31 patients. The dosage was escalated during the study from 1 mg/kg to 6 mg/kg. Continuous monitoring of mean arterial pressure (MABP), intracranial pressure (ICP), cerebral pressure (CPP), arterial oxygen saturation (SaO2), jugular bulb oxygen saturation (SjO2), and temperature was performed. Intermittent measurements of middle cerebral artery (MCA) velocity via transcranial Doppler ultrasound were also made 2 h before drug administration and continued for 24 h after dosing. The patients were ventilated and sedated with morphine and either midazolam or propofol. There were no behavioral changes during or after administration of the drug, and disorders of perception were reported by only three subjects, several days after relatively low doses; these were transient and were not recalled at later follow-up. We did not detect consistent changes in any of the hemodynamic parameters monitored, up to dosages of 3 mg/kg. After higher doses, some patients showed changes in MABP, ICP, and temperature during the 4 to 8-h period following the first bolus of the drug, with a return toward baseline afterwards. No consistent, serious, adverse events were considered to be due to drug effects, and death, in the one patient who died, was due to the effects of the injury. Our results indicate that CGS 19755 may be given at dosages < or = 3-5 mg/kg with acceptable safety and tolerability in stable, ventilated, and carefully monitored severe head-injured patients.

Providers' perceptions of an immunization registry

OBJECTIVE

To determine providers' perceptions of a statewide immunization registry.

DESIGN

Mail survey.

SETTING

King County, Washington.

METHODS

A random sample of 700 pediatricians, family physicians, and RN/NPs were surveyed. In addition to their perceptions of registries, respondents reported their immunization procedures in the absence of immunization histories.

RESULTS

Of 544 eligible participants, 344 returned surveys (63% response rate). Seventy-seven percent of RN/NPs, 60% of pediatricians and 47% of family physicians (p < 0.001) responded that they thought that electronic immunization registries represented the "best chance to solve the lack of documentation problem." Fifty-seven percent of RN/NPs, 61% of pediatricians, and 43% of family physicians reported that the incompleteness of registry data presented a barrier to their using one (p < 0.01). Fewer than 14% of all specialties had concerns about potential compromises of patient confidentiality as a result of registries, although RN/NPs were more concerned about this possibility than both pediatricians and family physicians (p = 0.02). In a multivariate analysis, pediatricians were 43% less likely (p = 0.15) and family physicians were 73% less likely (p < 0.01) than RN/NPs to think registries are the solution to the lack of documentation problem. Familiarity with the existing registry was associated with a significant decrease in the likelihood of thinking that registries are the solution (OR .49 [.26-.90]) and an increase in the likelihood of thinking that registries will take a long time to become of practical value (OR 2.21 [1.09-4.29]).

CONCLUSIONS

Specialties differ with respect to their opinions regarding the promise immunization registries hold. Immunization registries appear to be well regarded in theory but may disappoint in practice. Incompleteness of immunization data may be the largest obstacle for registries to overcome.

Gadolinium-containing copolymeric chelates--a new potential MR contrast agent

RATIONALE AND OBJECTIVES

To develop and partially characterize a new class of potential blood pool magnetic resonance (MR) contrast agents.

METHODS

Various copolymeric chelates of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) were prepared with differing molecular weights of polyethylene glycol (PEG) or polypropylene glycol (PPG) as linkers between the monomeric chelate units. Gadolinium content of the polymeric chelates was determined by atomic absorption spectra. Relaxivity of the polymeric chelates was measured at 1.5 Tesla and compared with Gadolinium DTPA. MR angiography (MRA) was performed in rabbits comparing Gd-DTPA with Gd copolymers.

RESULTS

The gadolinium content of the copolymeric chelates ranged from 2.95 to 22.2% on weight basis. The molecular weight of the PEG linkers in the copolymers ranged from about 150 to about 3400. The r1 (1/T1, mM(-1) s(-1)) for Gd DTPA = 4.1. The r1 values for the different Gd-containing polymers ranged from 3.8 to 5.8, with the lowest r1 for the polymer prepared with the lowest-molecular-weight complex. The higher-molecular-weight complexes resulted in moderately higher relaxivity. MRA with Gd-copolymers, in rabbits, showed markedly greater vascular enhancement relative to an equivalent dose of Gd-DTPA. Vascular enhancement was much more sustained with the copolymeric agent and confined to vascular space; i.e. no appreciable background tissue enhancement--a reflection of distribution into extravascular fluid space--was observed.

CONCLUSIONS

Relative to Gd-DTPA monomers, PEG-containing Gd DTPA polymeric complexes provided moderate increases in relaxivity but markedly greater efficacy during in vivo MRA. In vitro relaxivity studies of Gd-copolymers showed only an approximately 50% increase in r1 relaxivity compared with Gd-DTPA. The PEG-containing complex's lack of rigidity may have diminished the effect of spin diffusion on relaxation, thereby accounting for this modest increase. The greater efficacy of Gd-copolymers during in vivo MRA may reflect compartmentalization within the vascular space and possibly enhanced relaxation of the macromolecular copolymers in the blood. Gd-copolymers are promising agents that merit additional study.

Kinetic parameters for dimeric and tetrameric forms of bovine dopamine beta-monooxygenase and their relationship to non-Michaelis-Menten behavior

Bovine dopamine beta-monooxygenase has been assayed over a 10,000-fold range in protein concentration, to approximate conditions where the enzyme was shown to be a dimer or tetramer. Michaelis-Menten kinetics are observed with k(cat) and k(cat)/Km for dissociated enzyme reduced 30% and 200-300% relative to tetramer. Addition of chloride ions to very dilute enzyme or the use of intermediate enzyme concentrations causes non-Michaelis-Menten behavior, attributed to an equilibration between dimer and tetramer. This is not expected to contribute to activity within the chromaffin vesicle, where enzyme and chloride ions are at high levels.

Extracting summary statistics to perform meta-analyses of the published literature for survival endpoints

Meta-analyses aim to provide a full and comprehensive summary of related studies which have addressed a similar question. When the studies involve time to event (survival-type) data the most appropriate statistics to use are the log hazard ratio and its variance. However, these are not always explicitly presented for each study. In this paper a number of methods of extracting estimates of these statistics in a variety of situations are presented. Use of these methods should improve the efficiency and reliability of meta-analyses of the published literature with survival-type endpoints.

Extracting summary statistics to perform meta-analyses of the published literature for survival endpoints

Meta-analyses aim to provide a full and comprehensive summary of related studies which have addressed a similar question. When the studies involve time to event (survival-type) data the most appropriate statistics to use are the log hazard ratio and its variance. However, these are not always explicitly presented for each study. In this paper a number of methods of extracting estimates of these statistics in a variety of situations are presented. Use of these methods should improve the efficiency and reliability of meta-analyses of the published literature with survival-type endpoints.

Extracting summary statistics to perform meta-analyses of the published literature for survival endpoints

Meta-analyses aim to provide a full and comprehensive summary of related studies which have addressed a similar question. When the studies involve time to event (survival-type) data the most appropriate statistics to use are the log hazard ratio and its variance. However, these are not always explicitly presented for each study. In this paper a number of methods of extracting estimates of these statistics in a variety of situations are presented. Use of these methods should improve the efficiency and reliability of meta-analyses of the published literature with survival-type endpoints.

Familial prion disease mutation alters the secondary structure of recombinant mouse prion protein: implications for the mechanism of prion formation

A considerable body of data supports the model that the infectious agent (called a prion) which causes the transmissible spongiform encephalopathies is a replicating polypeptide devoid of nucleic acid. Prions are believed to propagate by changing the conformation of the normal cellular prion protein (PrPc) into an infectious isoform without altering the primary sequence. Proteins equivalent to the mature form of the wild-type mouse prion protein (residues 23-231) or with a mutation equivalent to that associated with Gerstmann-Straüssler-Scheinker disease (proline to leucine at codon 102 in human; 101 in mouse) were expressed in E. coli. The mutation did not alter the relative proteinase K susceptibility properties of the mouse prion proteins. The wild-type and mutant proteins were analyzed by circular dichroism under different pH and temperature conditions. The mutation was associated with a decrease in alpha-helical content, while the beta-sheet content of the two proteins was unchanged. This suggests the mutation, while altering the secondary structure of PrP, is not sufficient to induce proteinase K resistance and could therefore represent an intermediate isoform along the pathway toward prion formation.