New concepts and advances of immobilization of long bones

OBJECTIVE

To present some new concepts in the treatment of fractures and bone defects of long bones with internal fixation.

METHODS

Animal experiments, mechanical tests and clinical analyses were done.

RESULTS AND CONCLUSIONS

Reduction of fracture should be perfect, bone defect can be reconstructed by intramedullary and extramedullary bone graft. Relatively rigid fixation at the early stage and elastic fixation at the later stage are beneficial not only for fracture healing, but also for bone remodeling. In order to avoid complications including non-union, immobilization syndrome of the bone and joint, and implant failure, radiographs should be taken periodically; if there is any bone resorption, weight-bearing should be restricted.

The relationship of lead in soil to lead in blood and implications for standard setting

As part of a soil lead regulation process, this review was conducted to determine the association between lead in soil and established human health effects of lead or validated biomarkers of lead exposure. We reviewed only studies where soil exposure could be distinguished from other sources of lead and whose design could reasonably be used to infer a causal relationship between soil lead and either biomarkers or health effects. No such studies of health effects were found. Studies describing a quantitative relationship between soil lead and blood lead did meet our criteria: 22 cross-sectional studies in areas with polluted soil; and three prospective studies of soil lead pollution abatement trials. The cross-sectional studies indicated that, compared to children exposed to soil lead levels of 100 ppm, those exposed to levels of 1000 ppm had mean blood lead concentrations 1.10-1.86 times higher and those exposed to soil lead levels of 2000 ppm had blood lead concentrations 1.13-2.25 times higher. The prospective studies showed effects within the ranges predicted by the cross-sectional studies. Differences in results between studies were surprisingly modest and likely explainable by random sampling error, different explanatory variables included in data analyses and differences in methods of measuring lead in environmental specimens.

High dose baclofen is neuroprotective but also causes intracerebral hemorrhage: a quantal bioassay study using the intraluminal suture occlusion method

Agonists of the GABA-A receptor are neuroprotective after experimental stroke, but studies of GABA-B agonists have contradicted each other. To further investigate whether GABA-B agonists may be neuroprotective, we devised a quantal bioassay using the intraluminal occlusion method of inducing reversible cerebral ischemia. Subjects underwent middle cerebral artery occlusion for varying amounts of time, ranging from 5 to 90 min. Behavioral outcome was measured 48 h later with a quantal observational scale: score of abnormal given for any one of asymmetric forepaw flexion on tail lift, asymmetric grip, circling, reduced exploration, seizures, or death. To the grouped response data the logistic equation was used to find the ED50, the duration of occlusion that caused one-half of the subjects to be abnormal. To find the potency ratio for each drug, we divided the ED50 for treatment by that for vehicle. We administered baclofen, a GABA-B agonist, intraperitoneally 5 min after the onset ofischemia. Baclofen (20 mg/kg) was neuroprotective (potency ratio of 3.0, P < 0.05), but a lower dose (10 mg/kg) was not. However, both doses of baclofen caused significantly more intracerebral hemorrhages than control. In awake animals, both baclofen doses caused significant increases in mean arterial pressure, but no changes in other cardiorespiratory variables. The glutamate antagonist MK-801, the GABA-A agonist muscimol, and hypothermia were all protective using the bioassay (potency ratios ranging from 1.5 to 3.0). We conclude that although baclofen (20 mg/kg) may be neuroprotective, its utility is complicated by postischemic hypertension and cerebral hemorrhages.

Blood lead levels in children aged 24 to 36 months in Vancouver

OBJECTIVES

To determine the blood lead levels in children and to identify risk factors for elevated levels.

DESIGN

Cross-sectional study.

SETTING

Vancouver.

PARTICIPANTS

Random sample of children aged 24 to 36 months, born and still resident in Vancouver. The sample was stratified proportionally by the median annual family income in the census tract where each family resided.

OUTCOME MEASURES

Blood lead levels and risk factors for elevated blood lead levels, determined from a questionnaire administered to parents.

RESULTS

Of the children in the sample, 42% (178/422) were ineligible or could not be located. Of the remaining children, 73% (177/244) participated and adequate blood specimens were obtained from 172. The mean blood lead level was 0.29 mumol/L (standard deviation 0.13 mumol/L). (A blood lead level of 1 mumol/L is equivalent to 20.7 micrograms/dL.) The lowest level was 0.06 mumol/L, and the highest was 0.85 mumol/L. Of children with adequate samples, 8.1% (14/172) had blood lead levels of 0.48 mumol/L or higher, and 0.6% (1/172) had a level higher than 0.72 mumol/L. The logarithms of the levels were normally distributed, with a geometric mean (GM) of 0.26 mumol/L (geometric standard deviation 1.56). Of approximately 70 possible predictors of blood lead levels analysed, those that showed a statistically significant association (p < 0.05) with increased blood lead levels were soldering performed in the home as part of an electronics hobby (GM blood lead level 0.34 mumol/L, 95% confidence interval [CI] 0.27 to 0.39 mumol/L), aboriginal heritage (GM blood lead level 0.33 mumol/L, 95% CI 0.28 to 0.39 mumol/L), dwelling built before 1921 (GM blood lead level 0.32 mumol/L, 95% CI 0.28 to 0.37 mumol/L), age of water service connection to dwelling (predicted blood lead level 0.00087 mumol/L [95% CI 0.00005 to 0.00169 mumol/L] higher per year since service connection) and decreased stature (predicted blood lead level 0.018 mumol/L [95% CI 0.0353 to 0.0015 mumol/L] higher for every standard deviation below the age-specific mean height).

CONCLUSIONS

This study found much lower blood lead levels in children than those found in previous Canadian studies. The authors believe that this result is not an artefact due to differences in population sampling or methods of collection of blood specimens. The study showed no clear risk factors for elevated blood lead levels: although a few factors had a statistically significant association with increased blood lead levels, the differences in levels were small and unimportant.

New restriction endonuclease CviRI cleaves DNA at TG/CA sequences

A new type II restriction endonuclease, CviRI, was isolated from virus XZ-6E infected chlorella cells. CviRI is the first restriction endonuclease to recognize the sequence 5'-TGCA-3' and cleaves DNA between the G and C residues to produce blunt-end termini. Methylation of the adenine or cytosine in 5'-TGCA-3' sequences prevents CviRI cleavage. Due to its sequence specificity, CviRI may be especially useful for detecting mutant alleles of many heritable human genetic diseases.

Strategies for determining occupational exposures in risk assessments: a review and a proposal for assessing fungicide exposures in the lumber industry

To select an exposure monitoring protocol for assessing the occupational risk of fungicides in the lumber industry, the main strategies for determining exposures for risk assessment were reviewed. A survey of lumber industry work sites using fungicides observed the methods of application and opportunities for exposure. In addition, a review of existing measurement data was done. These investigations indicated that fungicide application techniques and process locations were varied from site to site, such that it would be extremely difficult to select a few representative locations for quasi-experimental studies, as is usually done in agricultural pesticide exposure assessment. Existing measurement data mainly describe exposures to fungicides no longer in use, and do not cover the range of application techniques or process technology observed in the survey. A probability sample of the exposed population was therefore proposed.

Liquid hybridization analysis of TSH receptor mRNA in normal and abnormal human thyroid tissues

Radiolabeled human TSH receptor (hTSHR) cRNA probes encoding nucleotides 37-2298 and 37-209, with unlabeled sense RNA control segments, were used in a liquid hybridization assay and found to be highly specific and sensitive enabling detection of 0.5 fmol of hTSHR mRNA. Using normal human thyroid monolayer cell cultures we calculated that the average number of TSHR mRNA transcripts was 95 +/- 5 per cell under in vitro basal conditions. We found no significant difference between the hTSHR mRNA concentrations of intact normal human thyroid tissue (n = 4) and specimens from patients with multinodular goiter (n = 5) and Graves' disease thyroid tissues (n = 5) (23.0, 25.2, and 27.6 fmol of hTSHR and mRNA/mg total cellular RNA, respectively). However, there was a relative deficiency of hTSHR mRNA in some samples of thyroid papillary carcinoma tissue (n = 5) (12 fmol of hTSHR mRNA/mg total RNA, p < 0.05). The hTSHR 37-2298 probe was fully protected in normal and abnormal thyroid tissues, consistent with the absence of large deletions or insertions in the hTSHR mRNA transcripts but additional bands were present, consistent with the production of splicing variants.

Immunomodulatory activity of a novel nucleoside, 7-thia-8-oxoguanosine. II. Characterization of induced effector cells and the mechanism of induction

In a preceding paper we characterized the in vivo and in vitro induction of cytotoxic effector cells elicited by a novel synthetic immuno-stimulator 7-thia-8-oxoguanosine (7T8OG)2. In the present study we further characterized the cells responsible for the induced cytotoxicity and the mechanisms together with the lymphokines mediating the immunological response to 7T8OG. Removal of macrophages from 7T8OG activated spleen cell suspensions by various methods resulted in a significant increase in cytotoxicity to YAC-1 targets. 7T8OG induced effectors did not exert cytotoxic effect on macrophage sensitive P815 target cells. In vivo activated effectors when incubated with anti-asialo-GM1 antibody plus complement lost completely their ability to lyse YAC-1 targets. Together, these findings indicate that the 7T8OG induced effector cells are not macrophage like. Spleen cells from nude mice were readily activated by 7T8OG. The induced effectors were resistant to complement mediated lysis using anti-L3T4, anti-Lyt1 or anti-Lyt2 antibodies. Pretreatment of spleen cells with macrophage depleting agents both, in vitro and in vivo and subsequent activation of cells by 7T8OG resulted in effectors with reduced cytotoxicity. When injected in vivo, 7T8OG induced strong IFN production which paralelled the kinetics of NK cell activation. Furthermore, antibodies to alpha & beta-IFN but not to gamma-IFN diminished the induction of the cytotoxic activity. Although these findings suggest that activation of NK cells by 7T8OG is most likely to be mediated by alpha & beta-IFN involvement of other cytokines can not be ruled out.

Successful immunotherapy of murine melanoma metastases with 7-thia-8-oxoguanosine

We have recently reported that a synthetic nucleoside, 7-thia-8-oxoguanosine (7T8OG) is a potent activator of a number of effectors which are involved in anti-tumor immune responses. 7T8OG was found to induce interferon (IFN) production, to activate asialo-GM1 positive (AGM+1) killer cells, and to enhance specific antibody responses. In the present study, we investigated the effect of 7T8OG on growth of the murine pulmonary B16 melanoma and on formation of metastases. C57BL/6 mice were injected i.p. with 50-150 mg/kg 7T8OG before or after i.v. inoculation of B16 melanoma tumor cells, and 17-19 days after tumor inoculation, the number of metastases in the lungs were counted. 7T8OG given systemically in a single or a divided dose 24 h prior to the challenge of tumor cells reduced the number of lung tumor metastases by 89-99% which is highly significant as compared to untreated control (P less than 0.001). Occasional extra pulmonary tumor growth in the thoracic cavity and neck lymph node was also completely inhibited. The reduction in the number of tumor nodules was dose dependent. A single dose of 150 mg/kg of 7T8OG was also effective in inhibiting the growth of 3-5 day old metastatic tumors. The cytotoxic activity of killer cells induced in vivo by 7T8OG was completely abolished by in vitro treatment of cells with anti-AGM1 antibody plus complement. Administration of anti-AGM1 antibody following the 7T8OG treatment completely abrogated the anti-tumor effect of 7T8OG, resulting in a massive increase in the number of tumor foci in the lungs. Administration of carageenan or silica followed by injection of 7T8OG caused a significant increase (P less than 0.01) in the number of pulmonary tumor nodules compared to treatment with 7T8OG only. These findings indicate that activated macrophages or perhaps their cytokine (tumor necrosis factor) also contribute to the host tumor defense by 7T8OG.

Potentiation of the efficacy of murine L1210 leukemia vaccine by a novel immunostimulator 7-thia-8-oxoguanosine: increased survival after immunization with vaccine plus 7-thia-8-oxoguanosine

We have investigated the ability of a novel immunopotentiator, 7-thia-8-oxoguanosine (7T8OG) to increase the efficacy of a weakly immunogenic murine L1210 leukemia vaccine. The vaccine was prepared by irradiating L1210 leukemia cells in a cesium source with a total of 6000-R dose. DBA/2 mice were treated with 150 mg/kg 7T8OG and/or with vaccine consisting of 10(7) irradiated cells. In combination therapy, mice first received the vaccine and then were injected with 75 mg/kg 7T8OG 2 h and 4 h after vaccination. One week after the last treatment all mice were inoculated with 10(4) live leukemia cells intraperitoneally. Control, untreated mice (n = 66) injected with 10(4) live leukemia cells had a mean survival time +/- standard error of 10.5 +/- 0.2 days. Treating mice (n = 66) with one, two or three doses of 7T8OG administered i.p. 1 week apart did not increase survival (mean survival time = 10.7 days). Mice immunized with one, two or three doses of vaccine had 14.5 +/- 1.1, 45.4 +/- 6.2 and 68.3 +/- 10.6 days mean survival, respectively. 7T8OG-stimulated vaccination increased the survival dramatically. The best survival was noted when the mice were treated with 2x (vaccine + 7T8OG). Immunization of mice (n = 30) with this treatment regimen increased the mean survival to 156 +/- 10.0 days. Over 90% of mice that were treated this way had a cumulative survival time greater than 160 days. In contrast, only 12% of the mice immunized twice with the leukemia vaccine alone survived over 160 days. These results suggest a rationale for the use of this immuno-potentiator with various vaccines for a more effective immunization.

Immunoenhancing properties and antiviral activity of 7-deazaguanosine in mice

The nucleotide analog 7-deazaguanosine has not previously been reported to possess biological (antiviral or antitumor) properties in cell culture or in vivo. Up to 10(5) U of interferon per ml was detected in mouse sera 1 to 4 h following oral (200-mg/kg of body weight) and intraperitoneal (50-mg/kg) doses of the compound. 7-Deazaguanosine also caused significant activation of natural killer and phagocytic cells but did not augment T- and B-cell blastogenesis. Intraperitoneal treatments of 50, 100, and 200 mg/kg/day administered 24 and 18 h before virus inoculation were highly protective in mice inoculated with lethal doses of Semliki Forest or San Angelo viruses. Less but still significant survivor increases were evident in treated mice infected with banzi or encephalomyocarditis viruses. In most cases, the degree of antiviral activity was similar to that exhibited by the biological response modifier 7-thia-8-oxoguanosine. 7-Thia-8-oxoguanosine was more potent than 7-deazaguanosine against encephalomyocarditis virus in mice, however. Oral efficacy was achieved with 7-deazaguanosine treatments of greater than or equal to 100 mg/kg against all virus infections, whereas 7-thia-8-oxoguanosine is reported to be devoid of oral activity in rodents. Thus, 7-deazaguanosine represents the first reported orally active nucleoside biological response modifier exhibiting broad-spectrum antiviral activity against particular types of RNA viruses.

Guanosine analogues. Synthesis of nucleosides of certain 3-substituted 6-aminopyrazolo[3,4-d]pyrimidin-4(5H)-ones as potential immunotherapeutic agents

Several guanosine analogues were synthesized in the pyrazolo[3,4-d]pyrimidine ring system with various substituents at the 3-position. The new analogues prepared here include the CH3 (2-amino-3-methyl-1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4 (5H)-one, 13a), the phenyl (2-amino-3-phenyl-1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4 (5H)-one, 13b), and the NH2 (3,6-diamino-1-beta-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4(5H)- one, 17) substituted derivatives. These new agents, as well as several other 3-substituted derivatives including H, Br, OCH3, COOH, and oxo, were evaluated for their ability to potentiate certain murine immune functions relative to the known active agent 5-amino-3-beta-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,7(3H,6H) -dione (4, 7-thia-8-oxoguanosine). The biological evaluation included the (1) ex vivo determination of increased natural killer cell function and (2) in vivo antiviral protection against a lethal challenge of Semliki Forest virus. The 3-unsubstituted (5a) and the 3-bromo (5c) derivatives were found to be the most active immunopotentiators in this series.

A novel guanosine analog, 7-thia-8-oxoguanosine, enhances macrophage and lymphocyte antibody-dependent cell-mediated cytotoxicity

Intraperitoneal treatment of mice with a novel guanosine analog, 7-thia-8-oxoguanosine (7-thia-8-oxoGuo), gives rise to activated splenic lymphocytes and peritoneal macrophages with enhanced capacity to mediate antibody-dependent cellular cytotoxicity (ADCC). ADCC activities against both chicken red blood cells and P815 murine plasmacytoma cells were enhanced, indicating that macrophages as well as lymphocytes functioning as K-cells in the two distinct cytolytic systems, were activated by 7-thia-8-oxoGuo. Furthermore, 7-thia-8-oxoGuo enhanced lymphocyte-mediated ADCC activity in beige (bgJ/bgJ) mice against P815, thus indicating the ability of 7-thia-8-oxoGuo to function as a potent immunomodulator even in an animal that is known to possess selective impairment of naturally occurring killer lymphocytes. These results suggest that 7-thia-8-oxoGuo could serve as an agent for immunomodulation and immunorestoration.

Roles of interferon and natural killer cells in the antiviral activity of 7-thia-8-oxoguanosine against Semliki Forest virus infections in mice

7-Thia-8-oxoguanosine is a novel biological response modifier with broad-spectrum antiviral activity against many DNA and RNA viruses in vivo. Since two of its properties are to induce interferon and to activate natural killer (NK) cells, we investigated the roles of the lymphokine and NK cells in the antiviral activity of the compound against Semliki Forest virus. Antibody to interferon alpha/beta could completely abolish the protective activity of the nucleoside against virus infection in mice, whereas antibodies to interferons beta and gamma could not, indicating that interferon alpha was of major importance to confer protection to the animals. Reduced activation of NK cells was also observed in mice treated with 7-thia-8-oxoguanosine and antibody to interferon alpha/beta. The role of NK cells in the protective activity of the compound was directly assessed in beige mice or in Swiss Webster mice treated with asialo GM1 antibody. In both experiments, the animals were protected from lethal virus infection by treatment with nucleoside. Spleen cells primed by 7-thia-8-oxoguanosine and adoptively transferred to untreated mice could not save them from virus-induced mortality. These three results provide evidence that natural killer cells activated by 7-thia-8-oxoguanosine play a minimal role in protection from acute Semliki Forest virus infections in mice.

Thiazolo[4,5-d]pyrimidine nucleosides. The synthesis of certain 3-beta-D-ribofuranosylthiazolo[4,5-d]pyrimidines as potential immunotherapeutic agents

Novel analogues of the naturally occurring purine nucleosides were synthesized in the thiazolo[4,5-d]pyrimidine ring system to determine the immunomodulatory effects of insertion of a sulfur atom in place of nitrogen at position 7 of the purine ring. In particular, 5-amino-3-beta-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,7(3H,6H) -dione (7, guanosine analogue), 3-beta-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,5,7(3H,4H,6H) trione (8, xanthosine analogue), 3-beta-D-ribofuranosylthiazolo[4,5-d]pyrimidine-2,7(3H,6H)-dione (10, inosine analogue), and 7-amino-3-beta-D-ribofuranosylthiazolo[4,5-d]pyrimidin-2(3H)-one (32, adenosine analogue) were prepared, as well as the 8-mercaptoguanosine (14) and 6-mercaptoguanosine (17) analogues. Single-crystal X-ray studies confirmed the structural assignment of 17 and 32 as having the beta-configuration with the site of glycosylation at N3. The nucleosides were evaluated for their ability to potentiate various murine immune functions in direct comparison to the known active agents 8-bromoguanosine (1), 8-mercaptoguanosine (2), and 7-methyl-8-oxoguanosine (3). Two of the guanosine analogues, 7 and 14, were found to exhibit significant immunoactivity relative to the positive control compounds (1-3), while the adenosine, inosine, xanthosine, and 6-mercaptoguanosine analogues were devoid of activity. Compound 7 exhibited greater immunoactivity than any of the other guanosine analogues and derivatives in all test systems. Specifically, 7 was shown to be about twice as potent as 3 in the murine spleen cell mitogenicity assay. In addition, treatment with 7 produced about a 4-fold increase in natural killer cell cytotoxicity, while treatment with 3 afforded a 3-fold increase over controls. Finally, 7 provided excellent protection (92% survivors compared to 0% for placebo controls) against Semliki Forest virus in mice. Induction of interferon may account for the major mode of action of these guanosine analogues.

Collagen-platelet interaction: inhibition by a monoclonal antibody which binds a 90,000 dalton platelet glycoprotein

Polyclonal antiserum prepared to purified type I collagen receptor, a 65,000 molecular weight protein, isolated from human platelets reacted with two other proteins with molecular weights of 90,000 and 58,000 in immunoblots of solubilized platelet membranes. The immunoreactive proteins were purified to homogeneity with molecular sieve chromatography and preparative gel electrophoreses. Periodic acid Schiff stain showed that both the 90,000 and 65,000 proteins were glycoproteins. These purified proteins reacted with immunoglobulin G (IgG) fractions isolated from antiserum raised against the 65,000 protein and poly- and monoclonal antibody specific for the glycoprotein IIb-IIIa suggesting that these three proteins are immunocross reactive with GPIIb-IIIa. To further examine the immunocross-reactivity of these proteins, a monoclonal antibody was raised against the 90,000 glycoprotein. This monoclonal antibody also reacted with all three proteins in enzyme-linked immunosorbent assays and transblot experiments suggesting that these three possess a common antigenic determinant. The monoclonal antibody prepared to the 90,000 glycoprotein also inhibited platelet aggregation induced by the addition of collagen and ADP but not alpha-thrombin and epinephrine-induced aggregation. This suggests that the monoclonal antibody binds a protein on the platelet surface which plays a role in platelet aggregation induced by the addition of these agonists.

Platelet-collagen interaction. Inhibition by a monoclonal antibody raised against collagen receptor

Monoclonal antibodies to the purified platelet type I collagen receptor were produced to study platelet receptor function. The antibody specifically reacted with the platelet receptor in immunoblot experiments. The IgG purified from the monoclonal antibodies and isolated Fab' fragments inhibited the binding of radiolabeled alpha 1(I) chain to washed platelets competitively. Soluble and fibrillar type I collagen-induced platelet aggregations were inhibited by purified IgG suggesting that soluble and fibrillar collagens shared a common receptor. The adhesion of platelets to an artificial collagen matrix was also inhibited by the monoclonal antibody. However, adenosine diphosphate-induced platelet aggregation was not inhibited by the same amount of IgG that inhibited collagen-induced platelet aggregation. The results suggest that collagen-induced platelet aggregation is mediated through the interaction of collagen with the platelet receptor.

Platelet-collagen interaction. Inhibition by a monoclonal antibody raised against collagen receptor

Monoclonal antibodies to the purified platelet type I collagen receptor were produced to study platelet receptor function. The antibody specifically reacted with the platelet receptor in immunoblot experiments. The IgG purified from the monoclonal antibodies and isolated Fab' fragments inhibited the binding of radiolabeled alpha 1(I) chain to washed platelets competitively. Soluble and fibrillar type I collagen-induced platelet aggregations were inhibited by purified IgG suggesting that soluble and fibrillar collagens shared a common receptor. The adhesion of platelets to an artificial collagen matrix was also inhibited by the monoclonal antibody. However, adenosine diphosphate-induced platelet aggregation was not inhibited by the same amount of IgG that inhibited collagen-induced platelet aggregation. The results suggest that collagen-induced platelet aggregation is mediated through the interaction of collagen with the platelet receptor.

The frequency of malignant neoplasms in patients with polymyositis-dermatomyositis. A controlled study

Seventy-one patients with polymyositis-dermatomyositis (PM/DM) admitted to the Wellesley Hospital Rheumatic Disease Unit (RDU) in Toronto between 1965 and 1980 were followed up to 1981. The frequencies of malignant neoplasms occurring prior to or concurrent with initial RDU admission were compared, using case-control methods, with age- and sex-matched control groups with a diagnosis of any non-PM/DM rheumatic disease (rheumatic disease controls) or osteoarthritis, fibrositis, or fracture (noninflammatory musculoskeletal controls). In a cohort analysis, the incidence of malignant neoplasm subsequent to initial RDU admission in patients with PM/DM was compared with the expected incidence in the Canadian population. Fifteen of 71 patients with PM/DM had an antecedent or concurrent cancer compared with four of 71 rheumatic disease controls and one of 71 noninflammatory musculoskeletal controls. Cohort analysis showed no increase in the number of subsequent malignant neoplasms in patients with PM/DM compared with the age- and sex-matched Canadian population.