Cellular toxicity of fecal water depends on diet.

To determine whether concentrations of potentially toxic lipids in the aqueous phase of human stool are responsive to changes in dietary fat, calcium, and fiber, 20 male volunteers were placed on a high-fat, low-calcium, low-fiber or a low-fat, high-calcium, high-fiber diet for 4 days. To assess toxicity of the fecal fractions, we examined the ability of fecal supernatants to lyse human erythrocytes. Bile acid concentrations in fecal water from the low-fat group were reduced significantly from 180 +/- 60 microM to 100 +/- 70 microM; in the high-fat group, increased from 190 +/- 60 microM to 250 +/- 100 microM. Erythrocyte lysis was 76% for the high-fat group, 37% for the low-fat group. There was a significant weak correlation between aqueous bile acid concentration and cell lysis. Results suggest that diet can influence concentrations of detergents in the aqueous phase of human stool and the potential toxicity of this fraction to cell membranes.

Perioperative preservation of myocardial ultrastructure and high-energy phosphates in man.

To establish whether hypothermic crystalloid potassium cardioplegia given in multidose fashion provides adequate preservation of myocardial ultrastructure and high-energy phosphates, we studied 25 patients with an ejection fraction of 50% or higher who were undergoing cardiac procedures. Eight patients had three biopsy specimens taken from the left ventricular apex for determination of adenosine triphosphate (ATP) and creatine phosphate (CP). Specimens were taken immediately prior to aortic cross-clamping, immediately after the release of the aortic cross-clamp, and 30 minutes after the release of the cross-clamp. Seventeen patients had six specimens taken form the left ventricular apex at the above-stated times, three for ATP and CP determination and three additional specimens for electron microscopy. One patient had a small perioperative infarction and another patient died on the fifth postoperative day of an aortic dissection. The mitochondria on the electron microscopic specimens were graded on a scale from 0 to 4 (4 = severe changes). There was no significant difference in the mitochondrial scores. The preservation oh high-energy phosphates was less complete. ATP was reduced to 78% (3.4.2) of control and CP was reduced in the immediate postclamp period to 32% (081/2.5)of control. The difference are particularly significant if one looks at patients whose aortic cross-clamp time was 90 minutes or more (12 patients). In this group, ATP an CP preservation were 71% of control (3.33/4.60 mmoles/kg. wet weight) and 53% of control (l.48/2.81), 30 minutes after clamp removal (p equal to or less than 0.01). We conclude that hypothermic potassium cardioplegia gives excellent preservation of the myocardial ultrastructure in man. However, the preservation of high-energy phosphates with this technique is imperfect.

Hospital- and community-based surveillance of methicillin-resistant Staphylococcus aureus: previous hospitalization is the major risk factor.

OBJECTIVE: The purpose of the study was to determine the incidence and risk factors for the acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in our community. DESIGN: This study used a cross-sectional design to assess patients colonized or infected with MRSA. PATIENTS: The study population consisted of residents of London, Ontario, Canada, who were identified as MRSA-positive for the first time in 1997. SETTING: All acute- and chronic-care hospitals, long-term healthcare facilities, and community physicians' offices in the city of London participated in the study. MAIN OUTCOME MEASURE: Incidence of MRSA in the community, risk factors for acquisition, especially previous hospitalization over a defined period, and strain type were evaluated. RESULTS: In 1997, 331 residents of London were newly identified as MRSA-positive, representing an annual incidence of 100/100,000 persons (95% confidence interval, 88.8-110.7). Thirty-one (9.4%) individuals were not healthcare-facility patients in the previous month, and 11 (3.3%), 10 (3.0%), and 6 (1.8%) individuals had no such contact in the previous 3, 6, and 12 months, respectively. One hundred seventy-seven strains, including five of the isolates from patients with no healthcare-facility contact in the previous year, were typed. One hundred sixty (90.3%) of these isolates, including all typed strains from patients with no healthcare facility contact, belonged to a single clone. CONCLUSION: These findings demonstrate that the incidence of MRSA is higher than previously reported and that hospital contact is the single most important risk factor for the acquisition of MRSA in our community. Screening for MRSA in previously hospitalized patients at the time of hospitalization may reduce nosocomial spread and indirectly reduce the incidence of MRSA in the community.

T(h)-symmetrical N8(C=C)6 and P8(C=C)6; an extraordinary contrast in heterofullerene stability.

[structure: see text]. T(h)-symmetrical P8(C=C)6, 1, is predicted to be a remarkably stable small heterofullerene with carbon atoms less pyramidal than in C60. T(h)-N8(C=C)6, 2, in sharp contrast, is strongly destabilized relative to T(h)-(HC)8(C=C)6. The causes of this extraordinarily large difference (nearly 1000 kJ x mol(-1) between 1 and 2 are explained.

Complementary distribution of the phosphoproteins DARPP-32 and I-1 in the cerebellar system.

DARPP-32 (a dopamine and adenosine 3':5'-monophosphate (cAMP) regulated phosphoprotein of M(r) 32 kDa) and I-1 (phosphatase inhibitor-1) are related phosphoproteins that have distinct regional distributions in some specific neuronal structures. To determine whether they are also expressed in different types of neurons we investigated their distribution in the cerebellum, whose cellular structure is well characterized. In the cerebellar cortex, antibodies to DARPP-32 labeled Purkinje cells and antibodies to I-1 labeled granule cells. The two phosphoproteins were also in synaptic apposition in the deep cerebellar nuclei as well as in nuclei that project to the cerebellum via the climbing fiber and mossy fiber systems. This pattern was consistent in different mammalian species, including the mouse, marmoset, rhesus monkey and the mutant mouse reeler. We suggest that DARPP-32 and I-1 have distinct roles in regulating neuronal excitability in the cerebellum and may play different parts in the phenomenon of long-term depression (LTD).

An analysis of blood lead data in clinical records by external data on lead pipes and age of household.

This study examined the possibility that lead pipes in the drinking water distribution system were elevating the blood lead levels of children in London, Ontario, Canada. Based on their postal codes, 164 children admitted between 1984 and 1989 to an institution for the behaviorally disordered or developmentally challenged were categorized according to whether they lived in the area of the city known by the local Public Utilities Commission to be serviced by lead pipes. Analysis of covariance was used to obtain confounder-adjusted geometric means in each area. After adjusting for gender, year of lead test (a surrogate for gasoline source), and census tract prevalence of low family income, children in the lead service area (LSA) were found not to have higher blood lead levels (geometric means: LSA = 4.7 micrograms/dl, Non-LSA = 4.8 micrograms/dL; p = 0.839). The average blood lead level declined 60.9% between 1984 and 1989. Using municipal tax assessment data on the age of each child's home, those children living in homes built during or before 1945 (when interior paints were as much as 50% lead by dry weight) had an average blood lead level that was 62.3% higher (p = 0.011) than that of those in homes built since 1975 (when interior paints were limited to no higher than 0.5% lead by dry weight). A clear gradient was observed. This association with age of home remained significant after adjusting for gender, diagnosis, and year of lead test. Variables indicating the amount of industry near the child's residence and the presence of lead service pipes did not enter the model after house-age. In conclusion, no evidence indicated that the lead service pipes were elevating blood lead levels in these London children. The data suggest that with the removal of lead from gasoline, lead-based paint is a significant remaining source of lead exposure. Little data are available on childhood lead exposure from paint in Canada. The present descriptive data suggest that more research into this potential problem in Canada is warranted.

Learning needs as perceived by women less than or equal to 16 weeks pregnant.

In April 1997, 120 women < or = 16 weeks gestation responded to a survey conducted by the Middlesex-London Health Unit, which identified learning needs of women in their first trimester of pregnancy. This survey was part of a larger community initiative to plan, develop and implement first trimester "Prenatal Health Fairs" in London, Ontario. A listing of topics identified by women as most salient to their learning needs is included. There was a strong emergence of the need to include environmental health issues in the first trimester curriculum. The ranking of topics was unrelated to age, education and employment status with the exception that employed women were more likely to rank coping with discomforts of pregnancy, reasons for regular prenatal care and physical changes of pregnancy as important. Specific information related to reasons for attending a health fair, best times, locations and methods of advertising is addressed.

Small area variation in low birthweight: looking beyond socioeconomic predictors.

The main objectives of this study were to determine the geographic distribution of low birthweight rates in London. Ontario and to identify small areas within the city that have low birthweight rates not adequately explained by the areas' socioeconomic characteristics. The following socioeconomic variables were used in a weighted, ecological, multiple regression analysis; % unwed mothers, % teen mothers, % low income, % low education, % unemployment and % immigrants. The overall variation in low birthweight rates was statistically significant and largely, but not entirely, explained by the socioeconomic characteristics of the areas. Two out of 31 census tract clusters were identified as having low birthweight rates which were higher than would be expected based on their socioeconomic profile. This methodologic approach may interest health planners as it draws attention to local factors other than socioeconomic ones which may be important when developing local strategies for low birthweight prevention.

Quality improvement of spray-dried, protein-loaded D,L-PLA microspheres by appropriate polymer solvent selection.

The aim was to study the effect of the type of polymer solvent on characteristics of microspheres produced by spray drying. The water-soluble model protein, bovine serum albumin (BSA) was microencapsulated into biodegradable poly(D,L-lactic acid) using the following 10 different polymer solvents: acetaldehyde dimethyl acetal, acetone, dichloromethane, dioxane, ethyl acetate, ethyl vinyl ether, nitromethane, tetrahydrofuran, 1,1,1-trichloroethane, and 1,1,2-trichloroethylene. These solvents having similar toxicity levels differ greatly in their physico-chemical characteristics such as boiling point, vapour pressure, miscibility and interfacial tension with an aqueous phase, and solubility parameter. The effect of these solvents on microsphere morphology was studied by SEM-micrographs. Regular particle morphology was obtained when dichloromethane, ethyl acetate, or nitromethane was used as the polymer solvent, whereas the trichlorinated solvents, tetrahydrofuran, and dioxane produced a substantial number of coalesced particles. The results are interpreted in terms of boiling point, vapour pressure, and polymer-solvent affinity. Further, BSA-loading and -integrity in the microspheres, and burst release were analysed. The theoretical loading of 2.9% was attained with dichloromethane, ethyl acetate and nitromethane, in agreement with observations of particle morphology. HPLC- and SDS-PAGE analysis of the microencapsulated BSA did not show any protein degradation or dimerization, whereas solid-phase ELISA clearly revealed that the in vitro protein antigenicity was substantially reduced (50%), particularly by water miscible solvents. Dichloromethane and ethyl acetate did not show any detrimental effect on protein antigenicity. Finally, burst release could be related again to particle morphology, with dichloromethane and nitromethane giving a burst release of only 5%. In conclusion, dichloromethane, ethyl acetate and nitromethane proved to be the most suitable solvents for the polymer-protein system studied.

Randomized trial of the effect of calcium supplementation on fecal risk factors for colorectal cancer.

Newmark et al. (J Natl Cancer Inst 1984; 72:1323-8) hypothesized that supplementation with calcium would decrease the concentration of bile acids in aqueous phase feces and that such a reduction would reduce the risk of malignant disease in the bowel. A randomized trial was therefore undertaken to examine the effects of calcium supplementation on fecal biochemistry. A total of 68 men between 40 and 60 years of age volunteered to participate after having been selected randomly from population lists in Scarborough, a city in the Toronto area, Ontario, Canada. Participants were randomly assigned to receive a daily supplement of 3 g of calcium carbonate or a sucrose placebo for a period of 1 week. Fecal samples were collected for 2 days prior to supplementation and for the last 2 days of supplementation. Records of all foods consumed were kept throughout the study period. The average concentration of total soluble bile acids fell in the placebo group (-11.2 g/ml) but increased slightly in the calcium group (1.4 g/ml). Similar patterns of change were observed for deoxycholic acid (placebo, -3.0 g/ml; calcium, 4.5 g/ml). The distribution of changes in total bile acids and deoxycholic acid differed between randomization groups at the 10 percent level of significance in univariate analysis. After adjustment for initial stool chemistry and initial levels and changes in nutrient intake, no reduction in fecal bile acid levels was observed in association with calcium supplementation. In fact, a statistically significant (p = 0.05) increase in deoxycholic acid concentration remained in the calcium supplemental group. Thus, this study was unable to support the hypothesis that calcium supplementation alters aqueous phase bile acids in the manner hypothesized to be consistent with protection from colorectal cancer.

Inhibition of succinimide formation in aqueous Zn-rHirudin suspensions.

PURPOSE: The formation of succinimide intermediates at Asp-Gly sites and their hydrolysis products, e.g., isoAsp isomers, represents a common source of microheterogeneity in therapeutic proteins. Here we report on the stabilization effect of a zinc chloride induced precipitation of recombinant hirudin HV1 (rHir), an anticoagulant protein. METHODS: rHir was precipitated by zinc chloride at neutral pH to form a Zn-rHir suspension. An Arrhenius-type study (at 50, 40, 30, and 25 degrees C) and a 4 degrees C stability study were performed. Monitoring of rHir, rHir succinimides at Asp33-Gly34 (Q5) and Asp53-Gly54 (Q4), and further side products was by capillary electrophoresis (CE). RESULTS: The activation energies of rHir degradation in both aqueous rHir solution and Zn-rHir suspension were similar, i.e. 104.5 and 110.3 kJ/mol, respectively. Zn-rHir suspension demonstrated improved shelf-life stability (t90%, 95% confidence limit) versus rHir solution, i.e., 23 versus 3 days at 25 degrees C and 292 versus 147 days at 4 degrees C, respectively. In rHir solution, Q4 (Asp53-Gly54 succinimide) levels were slightly above Q5 (Asp33-Gly34 succinimide) levels. In Zn-rHir suspension, however, Q4 succinimide levels dropped markedly whereas Q5 levels were not affected. Correspondingly, in Zn-rHir isoAsp53-rHir levels were reduced but not isoAsp33-rHir levels. CONCLUSIONS: In Zn-rHir suspensions, interactions of zinc and rHir show site-specific inhibition of succinimide formation only at Asp53-Gly54 (Q4), located in the highly flexible C-terminal tail of rHir. In contrast, succinimide formation at Asp33-Gly34 (Q5), located in a less flexible loop domain is not affected, reflecting steric hindrance.

Chemical degradation kinetics of recombinant hirudin (HV1) in aqueous solution: effect of pH.

PURPOSE: To gain information on the chemical stability pattern and the kinetics of the degradation of recombinant hirudin variant HV1 (rHir), a thrombin-specific inhibitor protein of 65 amino acids, in aqueous solution as a function of pH. METHODS: Stability of rHir was monitored at 50 degrees C in the framework of a classical pH-stability study in aqueous buffers pH 1-9.5. Two capillary electrophoresis (CE) protocols were used: one for the kinetics of succinimide formation at Asp53-Gly54 (C-terminal tail) and Asp33-Gly34 (loop section), the other for the kinetics of rHir degradation. To check for potential effects of conformational changes by thermal denaturation, circular dichroism (CD) measurements were performed between 25 and 80 degrees C. RESULTS: Throughout the pH range studied no effect of thermal denaturation on rHir confirmation at 50 degrees C was observed. rHir was most stable at a neutral pH whereas, at slightly acidic pH, an intermediate stability plateau was found. Both, strongly acidic and alkaline conditions led to fast rHir degradation. Depending on the pH of degradation, rHir was found to degrade in various combinations of multiple parallel and sequential degradation patterns. Special focus was on succinimide formation at Asp53-Gly54 (C-terminal tail) and Asp33-Gly34 (loop) and on the potential of isoAsp formation in position 53 and 33. CONCLUSIONS: Chemical rHir stability in the intermediate pH range depends strongly on succinimide formation. At slightly acidic conditions succinimides represent the major degradation product (up to 40%). Around neutral pH succinimides react further, presumably by isoAsp formation, and concentrations remain low. Relative preference of succinimide formation in the C-terminal tail domain versus the loop domain is explained by higher backbone flexibility in the tail.