Stability of a Novel PEGylation Site on a Putative Haemoglobin-Based Oxygen Carrier.

PEGylation of protein sulfhydryl residues is a common method used to create a stable drug conjugate to enhance vascular retention times. We recently created a putative haemoglobin-based oxygen carrier using maleimide-PEG to selectively modify a single engineered cysteine residue in the α subunit (αAla19Cys). However, maleimide-PEG adducts are subject to deconjugation via retro-Michael reactions, with consequent cross-conjugation to endogenous plasma thiols such as those found on human serum albumin or glutathione. In previous studies mono-sulfone-PEG adducts have been shown to be less susceptible to deconjugation. We therefore compared the stability of our maleimide-PEG Hb adduct with one created using a mono-sulfone PEG. The corresponding mono-sulfone-PEG adduct was significantly more stable when incubated at 37 °C for 7 days in the presence of 1 mM reduced glutathione, 20 mg/mL human serum albumin, or human serum. In all cases haemoglobin treated with mono-sulfone-PEG retained >90% of its conjugation whereas maleimide-PEG showed significant deconjugation, especially in the presence of 1 mM reduced glutathione where <70% of the maleimide-PEG conjugate remained intact. Although maleimide-PEGylation of Hb seems adequate for an oxygen therapeutic intended for acute use, if longer vascular retention is required reagents such as mono-sulfone-PEG may be more appropriate.

Novel Redox Active Tyrosine Mutations Enhance the Regeneration of Functional Oxyhemoglobin from Methemoglobin: Implications for Design of Blood Substitutes.

Heme mediated oxidative toxicity has been linked to adverse side effects in Hemoglobin Based Oxygen Carriers (HBOC), initiated by reactive ferryl (FeIV) iron and globin based free radical species. We recently showed that the addition of a redox active tyrosine residue in the beta subunit (ßF41Y) of recombinant hemoglobin had the capability to decrease lipid peroxidation by facilitating the reduction of FeIV iron by plasma antioxidants such as ascorbate. In order to explore this functionality further we created a suite of tyrosine mutants designed to be accessible for both reductant access at the protein surface, yet close enough to the heme cofactor to enable efficient electron transfer to the FeIV. The residues chosen were: ßF41Y; ßK66Y; ßF71Y; ßT84Y; ßF85Y; and ßL96Y. As with ßF41Y, all mutants significantly enhanced the rate of ferryl (FeIV) to ferric (FeIII) reduction by ascorbate. However, surprisingly a subset of these mutations (ßT84Y, and ßF85Y) also enhanced the further reduction of ferric (FeIII) to ferrous (FeII) heme, regenerating functional oxyhemoglobin. The largest increase was seen in ßT84Y with the percentage of oxyhemoglobin formed from ferric hemoglobin in the presence of 100 µM ascorbate over a time period of 60 min increasing from 10% in ßF41Y to over 50% in ßT84Y. This increase was accompanied by an increased rate of ascorbate consumption. We conclude that the insertion of novel redox active tyrosine residues may be a useful component of any recombinant HBOC designed for longer functional activity without oxidative side effects.

The ßLys66Tyr Variant of Human Hemoglobin as a Component of a Blood Substitute.

It has been proposed that introducing tyrosine residues into human hemoglobin (e.g. ßPhe41Tyr) may be able to reduce the toxicity of the ferryl heme species in extracellular hemoglobin-based oxygen carriers (HBOC) by facilitating long-range electron transfer from endogenous and exogenous antioxidants. Surface-exposed residues lying close to the solvent exposed heme edge may be good candidates for mutations. We therefore studied the properties of the ßLys66Tyr mutation. Hydrogen peroxide (H2O2) was added to generate the ferryl protein. The ferryl state in ßLys66Tyr was more rapidly reduced to ferric (met) by ascorbate than recombinant wild type (rwt) or ßPhe41Tyr. However, ßLys66Tyr suffered more heme and globin damage following H2O2 addition as measured by UV/visible spectroscopy and HPLC analysis. ßLys66Tyr differed notably from the rwt protein in other ways. In the ferrous state the ßLys66Tyr forms oxy, CO, and NO bound heme complexes similar to rwt. However, the kinetics of CO binding to the mutant was faster than rwt, suggesting a more open heme crevice. In the ferric (met) form the typical met Hb acid-alkaline transition (H2O to -OH) appeared absent in the mutant protein. A biphasicity of cyanide binding was also evident. Expression in E. coli of the ßLys66Tyr mutant was lower than the rwt protein, and purification included significant protein heterogeneity. Whilst, ßLys66Tyr and rwt autoxidised (oxy to met) at similar rates, the oxygen p50 for ßLys66Tyr was very low. Therefore, despite the apparent introduction of a new electron transfer pathway in the ßLys66Tyr mutant, the heterogeneity, and susceptibility to oxidative damage argue against this mutant as a suitable starting material for a HBOC.

Assessing older adults' perceptions of sensor data and designing visual displays for ambient environments. An exploratory study.

INTRODUCTION: This article is part of the Focus Theme of Methods of Information in Medicine on "Using Data from Ambient Assisted Living and Smart Homes in Electronic Health Records". OBJECTIVES: Our objectives were to: 1) characterize older adult participants' perceived usefulness of in-home sensor data and 2) develop novel visual displays for sensor data from Ambient Assisted Living environments that can become part of electronic health records. METHODS: Semi-structured interviews were conducted with community-dwelling older adult participants during three and six-month visits. We engaged participants in two design iterations by soliciting feedback about display types and visual displays of simulated data related to a fall scenario. Interview transcripts were analyzed to identify themes related to perceived usefulness of sensor data. RESULTS: Thematic analysis identified three themes: perceived usefulness of sensor data for managing health; factors that affect perceived usefulness of sensor data and; perceived usefulness of visual displays. Visual displays were cited as potentially useful for family members and health care providers. Three novel visual displays were created based on interview results, design guidelines derived from prior AAL research, and principles of graphic design theory. CONCLUSIONS: Participants identified potential uses of personal activity data for monitoring health status and capturing early signs of illness. One area for future research is to determine how visual displays of AAL data might be utilized to connect family members and health care providers through shared understanding of activity levels versus a more simplified view of self-management. Connecting informal and formal caregiving networks may facilitate better communication between older adults, family members and health care providers for shared decision-making.

Should noncurative resection of the primary tumour be performed in patients with stage iv colorectal cancer? A systematic review and meta-analysis.

PURPOSE: Surgical resection of the primary tumour in patients with advanced colorectal cancer (crc) remains controversial. This review compares survival in patients with advanced crc who underwent surgical resection of the primary tumour with that in patients not undergoing resection, and determines rates of post-operative mortality and nonfatal complications, the primary tumour complication rate, the non-resection surgical procedures rate, and quality of life (qol). METHODS: Reports in the central, medline, and embase databases were searched for relevant studies, which were selected using pre-specified eligibility criteria. The search was also restricted to publication dates from 1980 onward, the English language, and studies involving human subjects. Screening, evaluation of relevant articles, and data abstraction were performed in duplicate, and agreement between the abstractors was assessed. Articles that met the inclusion criteria were assessed for quality using the Newcastle-Ottawa Scale. Data were collected and synthesized per protocol. RESULTS: From among the 3379 reports located, fifteen retrospective observational studies were selected. Of the 12,416 patients in the selected studies, 8620 (69%) underwent surgery. Median survival was 15.2 months (range: 10-30.7 months) in the resection group and 11.4 months (range: 3-22 months) in the non-resection group. Hazard ratio for survival was 0.69 [95% confidence interval (ci): 0.61 to 0.79] favouring surgical resection. Mean rates of postoperative mortality and nonfatal complications were 4.9% (95% ci: 0% to 9.7%) and 25.9% (95%ci: 20.1% to 31.6%) respectively. The mean primary tumour complication rate was 29.7% (95% ci: 18.5% to 41.0%), and the non-resection surgical procedures rate in the non-resection group was 27.6% (95 ci: 15.4% to 39.9%). No study provided qol data. CONCLUSIONS: Although this review supports primary tumour resection in advanced crc, the results have significant biases. Randomized trials are warranted to confirm the findings.

Topology of feather melanocyte progenitor niche allows complex pigment patterns to emerge.

Color patterns of bird plumage affect animal behavior and speciation. Diverse patterns are present in different species and within the individual. Here, we study the cellular and molecular basis of feather pigment pattern formation. Melanocyte progenitors are distributed as a horizontal ring in the proximal follicle, sending melanocytes vertically up into the epithelial cylinder, which gradually emerges as feathers grow. Different pigment patterns form by modulating the presence, arrangement, or differentiation of melanocytes. A layer of peripheral pulp further regulates pigmentation via patterned agouti expression. Lifetime feather cyclic regeneration resets pigment patterns for physiological needs. Thus, the evolution of stem cell niche topology allows complex pigment patterning through combinatorial co-option of simple regulatory mechanisms.

Health providers' perceptions of novel approaches to visualizing integrated health information.

OBJECTIVES: We evaluated the design of three novel visualization techniques for integrated health information with health care providers in older adult care. Through focus groups, we identified generalizable themes related to the visualization and interpretation of health information. Using these themes we address challenges with visualizing integrated health information and provide recommendations for designers. METHODS: We recruited ten health care providers to participate in three focus groups. We applied a qualitative descriptive approach to code and extract themes related to the visualization of graphical displays. RESULTS: We identified a set of four common themes across focus groups related to: 1) Trust in data for decision-making; 2) Perceived level of detail for visualization (subthemes: holistic, individual components); 3) Cognitive issues (subthemes: training and experience; cognitive overload; contrast); and 4) Application of visual displays. Furthermore, recommendations are provided as part of the iterative design process for the visualizations. CONCLUSIONS: Data visualization of health information is an important component of care, impacting both the accuracy and speed of decision making. There are both functional and cognitive elements to consider during the development of appropriate visualizations that integrate different components of health.

Body mass index versus waist circumference as predictors of mortality in Canadian adults.

BACKGROUND: Elevated body mass index (BMI) and waist circumference (WC) are associated with increased mortality risk, but it is unclear which anthropometric measurement most highly relates to mortality. We examined single and combined associations between BMI, WC, waist-hip ratio (WHR) and all-cause, cardiovascular disease (CVD) and cancer mortality. METHODS: We used Cox proportional hazard regression models to estimate relative risks of all-cause, CVD and cancer mortality in 8061 adults (aged 18-74 years) in the Canadian Heart Health Follow-Up Study (1986-2004). Models controlled for age, sex, exam year, smoking, alcohol use and education. RESULTS: There were 887 deaths over a mean 13 (SD 3.1) years follow-up. Increased risk of death from all-causes, CVD and cancer were associated with elevated BMI, WC and WHR (P<0.05). Risk of death was consistently higher from elevated WC versus BMI or WHR. Ascending tertiles of each anthropometric measure predicted increased CVD mortality risk. In contrast, all-cause mortality risk was only predicted by ascending WC and WHR tertiles and cancer mortality risk by ascending WC tertiles. Higher risk of all-cause death was associated with WC in overweight and obese adults and with WHR in obese adults. Compared with non-obese adults with a low WC, adults with high WC had higher all-cause mortality risk regardless of BMI status. CONCLUSION: [corrected] BMI and WC predicted higher all-cause and cause-specific mortality, and WC predicted the highest risk for death overall and among overweight and obese adults. Elevated WC has clinical significance in predicting mortality risk beyond BMI.

Home versus center based physical activity programs in older adults.

BACKGROUND: Physical inactivity is a leading cause of preventable death and morbidity in developed countries. In addition physical activity can potentially be an effective treatment for various medical conditions (e.g. cardiovascular disease, osteoarthritis). Many types of physical activity programs exist ranging from simple home exercise programs to intense highly supervised hospital (center) based programs. OBJECTIVES: To assess the effectiveness of 'home based' versus 'center based' physical activity programs on the health of older adults. SEARCH STRATEGY: The reviewers searched the Cochrane Central Register of Controlled Trials (CENTRAL) (1991-present), MEDLINE (1966-Sept 2002), EMBASE (1988 to Sept 2002), CINAHL (1982-Sept 2002), Health Star (1975-Sept 2002), Dissertation Abstracts (1980 to Sept 2002), Sport Discus (1975-Sept 2002) and Science Citation Index (1975-Sept 2002), reference lists of relevant articles and contacted principal authors where possible. SELECTION CRITERIA: Randomised or quasi-randomised controlled trials of different physical activity interventions in older adults (50 years or older) comparing a 'home based' to a 'center based' exercise program. Study participants had to have either a recognised cardiovascular risk factor, or existing cardiovascular disease, or chronic obstructive airways disease (COPD) or osteoarthritis. Cardiac and post-operative programs within one year of the event were excluded. DATA COLLECTION AND ANALYSIS: Three reviewers selected and appraised the identified studies independently. Data from studies that then met the inclusion/exclusion criteria were extracted by two additional reviewers. MAIN RESULTS: Six trials including 224 participants who received a 'home based' exercise program and 148 who received a 'center based' exercise program were included in this review. Five studies were of medium quality and one poor. A meta-analysis was not undertaken given the heterogeneity of these studies. CARDIOVASCULAR. The largest trial (accounting for approximately 60% of the participants) looked at sedentary older adults. Three trials looked at patients with peripheral vascular disease (intermittent claudication). In patients with peripheral vascular disease center based programs were superior to home at improving distance walked and time to claudication pain at up to 6 months. However the risk of a training effect may be high. There are no longer term studies in this population. Notably home based programs appeared to have a significantly higher adherence rate than center based programs. However this was based primarily on the one study (with the highest quality rating of the studies found) of sedentary older adults. This showed an adherence rate of 68% in the home based program at two year follow-up compared with a 36% adherence in the center based group. There was essentially no difference in terms of treadmill performance or cardiovascular risk factors between groups. CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD). Two trials looked at older adults with COPD. In patients with COPD the evidence is conflicting. One study showed similar changes in various physiological measures at 3 months that persisted in the home based group up to 18 months but not in the center based group. The other study showed significantly better improvements in physiological measures in the center based group after 8 weeks but again the possibility of a training effect is high. OSTEOARTHRITIS. No studies were found. None of the studies dealt with measures of cost, or health service utilization. AUTHORS' CONCLUSIONS: In the short-term, center based programs are superior to home based programs in patients with PVD. There is a high possibility of a training effect however as the center based groups were trained primarily on treadmills (and the home based were not) and the outcome measures were treadmill based. There is conflicting evidence which is better in patients with COPD. Home based programs appear to be superior to center based programs in terms of the adherence to exercise (especially in the long-term).

Quality of life evaluations of caregivers of ovarian cancer patients during chemotherapy treatment.

OBJECTIVES: (1) To examine the quality of life (QOL) of caregivers of women undergoing chemotherapy for advanced ovarian cancers, and (2) to correlate the QOL measures of caregivers to those of the women undergoing chemotherapy. METHODS: Over a 9-month period, all women undergoing chemotherapy for ovarian cancer at the Saskatoon Cancer Centre, and their caregivers, were offered participation. Two well-validated instruments were used to measure the "quality of life" concept. Women with ovarian cancer completed the Functional Assessment of Cancer Therapy--Ovarian (FACT-O) questionnaire in the clinic prior to each course of chemotherapy. Each caregiver completed a Caregiver Quality of Life Index--Cancer (CQOL-C) questionnaire at home at the start and conclusion of each chemotherapy regimen (cycle 1 and after the last chemotherapy treatment). The demographics of the caregivers were described. A paired t test was used to detect changes to caregivers' QOL scores before and after chemotherapy treatment. Correlation analysis was carried out to examine the relationship between the caregivers' total QOL scores and the various subscale and total scores of the FACT-O questionnaires completed by the women with ovarian cancer. Multivariate regression models were constructed to examine the relative importance of each of the QOL domain measures of the woman with cancer in predicting the effect on her caregiver's QOL. RESULTS: Thirty different patient-caregiver pairs participated in the study, providing 50 separate assessments since not all pairs had completed the post-chemotherapy assessments. There was improvement (P <.05) in the caregiver's QOL scores at the conclusion of the chemotherapy treatment compared to the baseline assessments. The improvement was unrelated to the performance status or response to chemotherapy of the woman undergoing treatment. There was also a correlation (P <.05) between an increase in a caregiver's distress and worsening scores in the "emotional," "functional," and "concerns" QOL domain assessments of the woman undergoing treatment. Stepwise regression analysis showed the "concerns" score, measuring specific ovarian cancer-related symptoms, to be the only predictor of a caregiver's distress (P <.05). CONCLUSIONS: Standard chemotherapy for ovarian cancer does not worsen a caregiver's QOL. There is a direct relationship between the QOL of women with cancer and that of their caregivers. Future research is required to identify how best to integrate the results of QOL assessments in cancer treatment protocols and to examine the long-term effects of ovarian cancer and its treatment on both caregivers and the women for whom they care.

Quality of life evaluations in patients with ovarian cancer during chemotherapy treatment.

OBJECTIVES: To examine the impact of treatment- and disease-related factors on the quality of life of patients with ovarian cancers undergoing chemotherapy. PATIENTS AND METHODS: Over 18 months period, all patients with ovarian cancer receiving chemotherapy at the Saskatoon Cancer Center were recruited. The Functional Assessment of Cancer Therapy-Ovarian (FACT-O) questionnaire was used to assess patients' quality of life before each chemotherapy cycle. Platinum-based chemotherapy was used initially or in patients with a platinum-free interval of more than 6 months in a recurrence setting. After progression on the platinum-based regimens, liposomal doxorubicin, topotecan, and cisplatinum/etoposide were used as salvage chemotherapy pending on drug availability and convenience of administration to patients. Regression analysis was used to identify significant disease and treatment-related factors that can significantly affect patients' quality of life measures. RESULTS: Seventy-two patients participated in the study providing 270 separate observations. The mean age was 57.81 years with a standard deviation of 13.40. The median duration of chemotherapy-free interval for patients with recurrent disease was 7 months. All patients had stage 3 or 4 disease. About half (52.2%) of the patients had optimal surgical resection with small (<1 cm) residual cancer masses before primary adjuvant chemotherapy. Seventy percent of the patients had either a first diagnosis or a first recurrence of cancer with the other 30% previously treated with two or more chemotherapy regimens. Sixty-two percent had an initial complete response to platinum-based chemotherapy. Multivariate regression analysis showed the use of topotecan or cisplatinum/etoposide, patients' poor responses to chemotherapy, experience with two or more previous line of chemotherapy treatment, and younger ages were significant predictors of poor quality of life during chemotherapy. CONCLUSION: There were significant differences in side effects of commonly used chemotherapy regimens on patients' quality of life. Quality of life assessments should be routinely incorporated in selecting specific chemotherapy to be used. Future research should be carried out to identify the best strategies to further integrate the results of quality of life assessments in cancer treatment protocols and to examine the long-term effects of cancer and its treatment on patients and their families.

Quality-of-life issues in patients with ovarian cancer and their caregivers: a review.

UNLABELLED: Significant progress has been made towards the treatment of ovarian cancer resulting in longer median survival despite a persistent low cure rate. Relatively few studies have examined the impact of the cancer and its treatment on the patients and their caregivers due to the difficulty in the definition and measurement of the Quality of Life (QOL) concept. A review of the literature revealed significant alterations in the quality of life of ovarian cancer patients during treatment and long term follow ups. For the caregivers, it is important for health care providers to realize that: 1) caregivers are being asked to assume an increasing number of complex care giving tasks at home, 2) there exists a high proportion of unmet caregiver needs, 3) the care giving experience includes both positive and negative elements and, 4) perception of caregivers' burden is positively linked to negative reactions to care giving. Supportive programs for patients and caregivers should be designed with these needs in mind. Future research should study the best way to incorporate results of quality of life assessments into routine treatment decision-making. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians. LEARNING OBJECTIVES: After completion of this article, the reader should be able to outline the current data on QOL issues in patients with ovarian cancer, and to describe potential working definitions of QOL.

Protective effect of melatonin on experimental spinal cord ischemia.

STUDY DESIGN: Experimental animal model to assess ischemic spinal cord injury following occlusion of the thoraco-abdominal aorta. OBJECTIVES: To measure whether melatonin administered to rabbits before and after occlusion exerts an effect on the repair of ischemia-reperfusion (IR) injury. SETTING: Medical Biology Laboratory, Inonu University, Malatya, Turkey. METHODS: Rabbits were divided into three IR treatment groups and one sham-operated (ShOp) control group. The three treatment groups had their infrarenal aorta temporarily occluded for 25 min, while the ShOp group had laparotomy without aortic occlusion. Melatonin was administered either 10 min before aortic occlusion or 10 min after the clamp was removed. Physiologic saline was administered to the control animals. After treatment, the animals were euthanized and lumbosacral spinal cord tissue was removed for the determination of relevant enzyme activities. RESULTS: Malondialdehyde levels, indicating the extent of lipid peroxidation, were found to be significantly increased in the nonmelatonin treated (IR) group when compared to the ShOp group. Melatonin, whether given to pre- or post occlusion groups, suppressed malondialdehyde levels below that of the ShOp group. Catalase (CAT) and glutathione peroxidase (GSH-Px) enzyme activities were increased in the IR group compared to the ShOp group. Melatonin given preocclusion resulted in a significant decrease in both CAT and GSH-Px enzyme levels. The superoxide dismutase (SOD) enzyme activity was decreased in the ischemia-reperfusion treatment group. However, the melatonin treatment increased SOD enzyme activity to levels approximating that of the ShOp group. CONCLUSION: To our knowledge, this is the first study that shows the effects of melatonin administered both pre- and postischemia on induced oxidative damage to injured spinal cords. Our data also expands on reports that melatonin administration may significantly reduce the incidence of spinal cord injury following temporary aortic occlusion.

Toxicity of myoglobin and haemoglobin: oxidative stress in patients with rhabdomyolysis and subarachnoid haemorrhage.

Haemolytic events, such as those following rhabdomyolysis and subarachnoid haemorrhage, often result in pathological complications such as vasoconstriction. Haem-protein cross-linked myoglobin and haemoglobin are generated by ferric-ferryl redox cycling, and thus can be used as markers of oxidative stress. We have found haem-protein cross-linked myoglobin in the urine of patients suffering from rhabdomyolysis and haem-protein cross-linked haemoglobin in the cerebrospinal fluid of patients following subarachnoid haemorrhage. These findings provide strong evidence that these respiratory haem proteins can be involved in powerful oxidation processes in vivo. We have previously proposed that these oxidation processes in rhabdomyolysis include the formation of potent vasoconstrictor molecules, generated by the myoglobin-catalysed oxidation of membranes, inducing nephrotoxicity and renal failure. Haem-protein cross-linked haemoglobin in cerebrospinal fluid suggests that a similar mechanism of lipid oxidation is present and that this may provide a mechanistic basis for the delayed vasospasm that follows subarachnoid haemorrhage.

Trends in overweight and obesity among adults in Canada (1970-1992): evidence from national surveys using measured height and weight.

PURPOSE: To examine secular trends in obesity and overweight among Canadian adults between 1970 and 1992. The impact of education level and smoking on weight trends is explored. DATA: Adults aged 20-69 participating in three national health surveys which obtained measured height and weight: the Nutrition Canada Survey conducted between 1970 and 1972 (analysis sample n=5963); the Canada Health Survey of 1978-1979 (analysis sample n=3622); and the Canadian Heart Health Surveys conducted between 1986 and 1992 (analysis sample n=17 699). METHODS: Comparison of percentage overweight (age-standardized body mass index (BMI) 25.0-29.9) and obese (age-standardized BMI > or = 30.0) by sex, education level and smoking status across the three surveys. RESULTS: Among men, the proportion overweight and obese increased steadily from 1970-1972 to 1986-1992. Among women, there was a substantial increase in the proportion overweight and obese between 1970-1972 and 1978-1979, then an increase in proportion obese, but not overweight, between 1978-1979 and 1986-1992. Although the prevalence of obesity increased in all education levels, the sub-groups with the greatest relative increase are men in the primary education category, and women in the secondary and post-secondary between 1970-1972 and 1986-1992. An increase in the prevalence of obesity was greatest among current smokers and, to a lesser extent, among former smokers. CONCLUSION: While excess weight has become an increasing public health problem among Canadian adults, the rate of increase in prevalence of obesity since 1970 varied with sex, education level and smoking status. There is a need for new data on measured heights and weights of Canadian adults and children and youth to update trends.

The Saskatchewan dissemination story.

The Saskatchewan Heart Health Program (SHHP) Dissemination Phase "Building Health Promotion Capacity" is a five-year program funded by Health Canada, Saskatchewan Health and the Heart and Stroke Foundation of Saskatchewan. This phase began in July 1998 and builds on two previous SHHP phases: the provincial heart health survey (Saskatchewan Health, 1990), and the community demonstration projects (SHHP, 1998a, b, c, d). The evolution of the SHHP has occurred in a dynamic provincial context. Saskatchewan is a Canadian prairie province of one million people with most living in the southern and central parts of the province. The population is ageing and urbanizing, and the economy is shifting away from agricultural production toward a diversified service sector. In 1993, health reform created 30 Districts in southern and central Saskatchewan; the formation of three northern Districts followed five years later. All but two Districts are rural-based. Population served ranges from 2,261 to 237,274; total area ranges from 4,019 to 133,900 square kilometers.

Extracellular heme peroxidases in actinomycetes: a case of mistaken identity.

Actinomycetes secrete into their surroundings a suite of enzymes involved in the biodegradation of plant lignocellulose; these have been reported to include both hydrolytic and oxidative enzymes, including peroxidases. Reports of secreted peroxidases have been based upon observations of peroxidase-like activity associated with fractions that exhibit optical spectra reminiscent of heme peroxidases, such as the lignin peroxidases of wood-rotting fungi. Here we show that the appearance of the secreted pseudoperoxidase of the thermophilic actinomycete Thermomonospora fusca BD25 is also associated with the appearance of a heme-like spectrum. The species responsible for this spectrum is a metalloporphyrin; however, we show that this metalloporphyrin is not heme but zinc coproporphyrin. The same porphyrin was found in the growth medium of the actinomycete Streptomyces viridosporus T7A. We therefore propose that earlier reports of heme peroxidases secreted by actinomycetes were due to the incorrect assignment of optical spectra to heme groups rather than to non-iron-containing porphyrins and that lignin-degrading heme peroxidases are not secreted by actinomycetes. The porphyrin, an excretory product, is degraded during peroxidase assays. The low levels of secreted peroxidase activity are associated with a nonheme protein fraction previously shown to contain copper. We suggest that the role of the secreted copper-containing protein may be to bind and detoxify metals that can cause inhibition of heme biosynthesis and thus stimulate porphyrin excretion.

The effects of pH on the mechanism of hydrogen peroxide and lipid hydroperoxide consumption by myoglobin: a role for the protonated ferryl species.

Myoglobin catalyses the breakdown of lipid hydroperoxides (e.g., HPODE) during which the absorption band of the lipid conjugated diene (234 nm) is partially bleached. The constant for this process is strongly pH-dependent (k = 9.5 x 10(-3)s(-1), pH 7: k = 2.3 x 10(-1)s(-1), pH 5). This rate enhancement is not due to acid-induced changes in protein conformation or the involvement of protein-based radical species, as demonstrated by an almost identical pH dependence of the same reaction catalyzed by ferric haemin. The rate constants for ferryl formation and auto-reduction show different pH dependencies, with a pK of 8.3 for ferryl formation and a projected pK of 3.5 for ferryl auto-reduction. The pH dependence for the auto-reduction of the ferryl species is the same as that of the myoblobin catalyzed breakdown of HPODE. We propose that the protonated form of ferryl myoglobin (Fe(4+) - OH(-)) is the reactive species regulating the peroxidatic activity of myoglobin. The protonated ferryl species abstracts an electron from either the protein or porphyrin, allowing fast regeneration of the ferric species. Alkaline conditions stabilize the ferryl species, making myoglobin considerably less reactive towards lipids and lipid hydroperoxides. These findings are significant for understanding myoglobin-induced oxidative stress in vivo and the development of therapies.