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PubMed2005

The 'experimental stable' of the BCG vaccine: safety, efficacy, proof, and standards, 1921-1933.

The anti-tuberculosis BCG (Bacille Calmette-Guérin) vaccine was conceived and developed between 1905 and 1921 at Pasteur Institutes in France. Between 1921 and A. Calmette's death in 1933, the vaccine went through a first period of national and international production and distribution for its use in humans. In France these activities were exclusively carried out by Calmette and his collaborators at the Pasteur Institute in Paris. Initially improvised production in a small room in the cellar gave way in 1931 to the construction of the spacious and magnificent 'New laboratories for research on tuberculosis and the preparation of the BCG' within the premises of the Pasteur Institute. Presentation and image-building of the vaccine in France insisted on the fact that the BCG was not a commercial specialty but distributed free of charge. The technical monopoly of its production nevertheless lay with the Paris Pasteur Institute and standardization of scientific proof of safety, efficacy and stability was dominated by that Institute in France. In contrast, the international production and distribution of the vaccine was entrusted and transferred, free of charge, to trustworthy laboratories outside France. Multiplication of producers and users led to an increased need for standardization. For this process the analysis distinguishes between the standardization of scientific proof concerning safety, efficacy and stability of the vaccine and standardization of its medical uses. Whereas standardization was rather successful in the inter-war period in France, the international efforts remained rather unsuccessful. Only after world war II under Scandinavian leadership and in the context of mass vaccination programs supported by the WHO and UNICEF was the international standardization effectively implemented and succeeded at least to some extend.

Academies and Institutes↗
PubMed2006

Utilization of standardized patients to evaluate clinical and interpersonal skills of surgical residents.

BACKGROUND: This project was designed to determine the growth of interpersonal skills during the first year of a surgical residency. METHODS: All categorical surgical residents were given a clinical skills examination of abdominal pain using standardized patients during their orientation (T1). The categorical residents were retested after 11 months (T2). The assessment tool was based on a 12-item modified version of the 5-point Likert Interpersonal Scale (IP) used on the National Board of Medical Examiners prototype Clinical Skills Examination and a 24-item, done-or-not-done, history-taking checklist. Residents' self-evaluation scores were compared to standardized patients' assessment scores. Data were analyzed using the Pearson correlation coefficient, Wilcoxon signed rank test, Student t test, and Cronbach alpha. RESULTS: Thirty-eight categorical residents were evaluated at T1 and T2. At T1, in the history-taking exercise, the scores of the standardized patients and residents correlated (Pearson = .541, P = .000). In the interpersonal skills exercise, the scores of the standardized patients and residents did not correlate (Pearson = -0.238, P = .150). At T2, there was a significant improvement in the residents' self-evaluation scores in both the history-taking exercise (t = -3.280, P = .002) and the interpersonal skills exercise (t = 2.506, P = 0.017). In the history-taking exercise, the standardized patients' assessment scores correlated with the residents' self-evaluation scores (Pearson = 0.561, P = .000). In the interpersonal skills exercise, the standardized patients' assessment scores did not correlate with the residents' self-evaluation scores (Pearson = 0.078, P = .646). CONCLUSIONS: Surgical residents demonstrate a consistently low level of self-awareness regarding their interpersonal skills. Observed improvement in resident self-evaluation may be a function of growth in self-confidence.

Abdominal Pain↗
PubMed2006

Counting coccidial oocysts in chicken faeces: a comparative study of a standard McMaster technique and a new rapid method.

For the assessment of coccidial oocyst production by chickens, some modified form of the McMaster counting method is commonly used. The objective of this study was to evaluate a standard method and to compare it to a new, faster method, in which all the preparative stages before counting are carried out in the same container into which the original faecal sample was collected. A stock suspension containing purified oocysts of all seven valid Eimeria species that parasitize chickens was prepared, from which seven concentrations of oocyst suspensions were made. Since the faecal material in a sample influences the ability of oocysts to float up in a McMaster chamber, the new method was tested to establish the optimal amount of faeces in the original sample. Control oocyst suspensions containing no faeces were also tested, and three series of counts using the new method were compared with the standard McMaster method. The results were statistically analysed by agreement analysis. Repeatability and between-operator variation of both methods were also tested by agreement analysis. Counting by the standard McMaster method underestimated the true number of oocysts. The new method gave counts in agreement with the true number of oocysts if using 1 g of faeces per sample. With 2 g of faeces, counts were obtained that agreed with counts by the standard McMaster method. Both methods showed agreement between repeated measurements. The new method used on a sample containing 2 g of faeces provides a convenient alternative to the standard modified McMaster method. A 1-g faecal sample increases agreement with the true numbers of oocysts. Processing of a sample with the new method is about nine times faster than with the standard method.

Animals↗
PubMed2001

Standards of professional practice: measuring the beliefs and realities of Consultant Dietitians in Health Care Facilities.

A dietetic practice group of the American Dietetic Association (ADA), Consultant Dietitians in Health Care Facilities (CD-HCF), surveyed members (n = 5930) on agreement with the six standards of professional practice and frequency of completing indicators within each standard. Sampling approaches included placing a survey in the publication, The Consultant Dietitian, and disseminating at the following CD-HCF activities: the 1998 business meeting at ADA's Annual Meeting & Exhibition, a multi-state teleconference in December 1998, and conferences held between November 1998 to April 1999. Duplication was monitored using the RD or RD-eligible registration number. The final sample included 553 surveys and represented 10% of the membership. Of the survey responders, 50% were individual consultants and 43% were employees; 88% consulted to facilities providing skilled care (geriatrics/adults) and 48% consulted to intermediate care facilities. With the exception of one, all standards and indicators met acceptance criterion. The standard statement "participation in research to enhance practice" did not attain the validation criterion. Study findings indicated that consulting to a facility conducting nutrition research increased chances of agreement with the research participation standard. The Executive Committee approved all standards, indicators and outcomes as a document defining quality consultation and business services conduct for consultant dietitians in health care facilities.

Attitude of Health Personnel↗
PubMed1995

Standards of practice for gerontological nutritionists: a mandate for action. The American Dietetic Association.

Dietitians who had been members of the Gerontological Nutritionists dietetic practice group for more than 2 years were sent a questionnaire to determine demographics of members and to ascertain their level of agreement and compliance with 26 suggested criteria and supporting documentation for standards of practice. Standards of practice for gerontological nutritionists were based on the six Standards of Practice of The American Dietetic Association. Of the 1,571 questionnaires mailed, 415 were returned. Data were analyzed using the StatPac Gold statistical analysis package. All correlation analyses were positive with correlation coefficients in the range of 0.0 to 1.0. Correlation coefficients and mean scores were highest for the standards related to maintaining credentials and adhering to a code of ethics. Compliance was weakest for standards related to conducting research to justify reimbursement for nutrition services (correlation of 0.22) and advocating public policies to ensure quality nutrition care and dissemination of information (correlation of 0.25). Results indicate that to comply with the standards of practice, members need to be proactive in showing efficacy and cost-effectiveness of medical nutrition therapy; conduct, document, and apply outcome research to practice; and advocate public policies affecting older people.

Aged↗
PubMed1995

Comparison of high-pass resolution perimetry and standard automated perimetry in glaucoma.

PURPOSE: We sought to ascertain whether high-pass resolution perimetry would provide results comparable to those of standard perimetry. METHODS: Thirty-four eyes with primary open-angle glaucoma, 37 eyes suspected of having glaucoma, and 36 normal control eyes were matched for age and lens density. We controlled for refraction, pupil size, and learning effects. Standard and ring visual fields were obtained with the Humphrey perimeter and the Frisén ring perimeter, respectively. Each test was judged according to the Glaucoma Hemifield Test (a statistical visual field analysis method) to be outside normal limits (abnormal) or not outside normal limits (normal or borderline). RESULTS: Under these conditions, both tests identified 19 of 34 (56%) glaucoma eyes as outside normal limits. High-pass resolution perimetry determined that 34 of 36 (94%) normal eyes were not outside normal limits; standard perimetry determined that all 36 normal eyes were not outside normal limits. High-pass resolution perimetry determined 12 of 37 (32%) eyes that were glaucoma suspects were outside normal limits; standard perimetry determined three of the 37 (8%) glaucoma suspect eyes were outside normal limits. Overall agreement between the two tests was 65%. CONCLUSION: With the Glaucoma Hemifield Test, high-pass resolution perimetry was comparable to standard perimetry in sensitivity and specificity, and identified a slightly higher percentage of patients at risk for glaucoma as abnormal. These results suggest that high-pass resolution perimetry should continue to be explored as an alternative to standard perimetry for the diagnosis and treatment of glaucoma.

Female↗
PubMed2001

Standards for the medical laboratory--harmonization and subsidiarity.

An International Standard, ISO 15189, specifically for 'Quality management in the medical laboratory' for use by accrediting 'bodies that recognize the competence of medical laboratories,' is expected to be published shortly. The origins, content and limitations of the new standard are discussed and the diversity of current arrangements for accreditation is reviewed. A new International Standard is an important step towards harmonization of laboratory practice but an accreditation system is more than its standards and a harmonized approach to the treatment of noncompliances found at inspection is important. Experience gained in writing national standards can improve the approach to the drafting and improvement of International Standards. Recognition of the principle of subsidiarity aids rather than hinders progress to harmonization and empowers the 'fourth element' (the laboratories to be accredited) to be a part of the accreditation process.

Chemistry, Clinical↗
PubMed1995

Map representation and diagnostic performance of the standard 12-lead ECG.

The diagnostic information contained in the standard 12-lead electrocardiogram was assessed by comparing the classification results produced by the standard leads for various clinical settings, such as normal versus myocardial infarction or versus left ventricular hypertrophy to those achieved by 120-lead data or body surface potential maps (BSPMs). Separately, optimal signal leads were extracted from the BSPM by ranking all leads in function of their capability of reconstructing the BSPM. Ranking was achieved by deriving eigenvalues from the covariance matrix calculated from all leads and corresponding measurements. Thus, while comparing the results from the standard leads (diagnostic leads) to those from the original raw map data, a comparison was also performed with respect to the best signal leads, namely the four best and the eight best. From the results observed for all bi- and multigroup classifications, it appeared that the diagnostic yield of the 12 standard leads matched those obtained with a number of signal leads lying between 4 and 8. This indicated that a large overlap still existed between the leads composing the 12-lead ECG (in fact, only 8 independent leads). Another interesting observation resulted from this investigation: although classifiers (discriminating variables) used for classification were identical, whether they originated from the raw standard leads (derived from the raw maps) or from standard leads reconstructed with four or eight signal leads, reconstructed measurements performed better than original measurements. This paradox can be explained by looking at the respective F values. Indeed, since increased F values result from higher ratios between the difference of group means and the composite variance from the pooled groups, higher differences and/or smaller variances produce larger ratios and hence, better group separations.

Body Surface Potential Mapping↗
PubMed1997

Standardizing the immunological measurement of advanced glycation endproducts using normal human serum.

Advanced glycation endproducts (AGEs) have been linked to many sequelae of diabetes, renal disease and aging. To detect AGE levels in human tissues and blood samples, a competitive enzyme-linked immunosorbent assay (ELISA) has been widely used. As no consensus or standard research method for the quantitation of AGEs currently exists, nor a universally defined AGE unit available, the comparative quantitation of AGEs between research laboratories is problematic and restricts the usefulness of interlaboratory clinical data. By comparing the cross-reactivities of five different anti-AGE antisera with five different in vitro AGE-modified proteins, we found that the immunological recognition of AGEs by competitive ELISA is both AGE-carrier protein- and anti-AGE antibody-dependent. This suggests that in vitro AGE-modified proteins might not be appropriate standards for AGEs that occur naturally in vivo. Based on our observation that serum AGE levels in the normal human population are consistently within a narrow range and several folds lower than in diabetics, we propose a method to standardize AGE units against normal human serum (NHS). In this new method, one AGE unit is defined as the inhibition that results from 1:5 diluted NHS in the competitive AGE-ELISA; thus the AGE value in NHS is 5 units/ml. This NHS method requires a competitive AGE-ELISA with reasonable sensitivity such that 1:5 NHS produces a 25 to 40% inhibition of anti-AGE antibody binding to immobilized AGE-proteins. By using this standardized method we found that the AGE levels in normal human serum (5.0 +/- 2.2 units/ml; mean +/- SD, n = 34) fit a normal distribution (chi 2-test, p < 0.01), and the serum AGE levels in diabetic patients (20.3 +/- 3.8 units/ml, n = 7) are significantly higher than that of the normal population (p < 0.0001). Since AGE units can now be defined against a universally available standard, NHS, the results of quantitative AGE measurements using this method should be comparable between assays and between different laboratories. Taken together, standardizing the AGE-ELISA protocol as described here provides a simple and quantitative method that should facilitate the expanded application of clinical AGE data.

Adult↗
PubMed1999

Bicaval and standard techniques in orthotopic heart transplantation: medium-term experience in cardiac performance and survival.

OBJECTIVE: The aim of this study was to compare the medium-term results of right heart pressures, tricuspid valve dysfunction, overall cardiac performance, and survival between the bicaval and standard techniques. METHOD: Between 1991 and 1997, 201 heart transplantations were performed in our center. Right heart catheterization was performed up to 12 months after transplantation. Echocardiography was used to assess left ventricular and tricuspid valve function. RESULT: The standard technique was used in 105 cases, and the bicaval technique was used in 96 cases. There was no difference in the age, preoperative parameters, pulmonary hemodynamics, or ischemic time between the 2 groups. Right atrial pressure (4.3 +/- 4.0 mm Hg for the bicaval vs 10.9 +/- 4.8 mm Hg for standard technique) and mean pulmonary artery pressure (17.5 +/- 5.3 mm Hg and 22.5 +/- 5.2 mm Hg, respectively) were lower for the bicaval recipients up to 12 months after the operation (P =.001 and. 01, respectively). Left ventricular ejection fraction was higher for the recipients of the bicaval technique up to the most recent measurement (P =.005). The prevalence of moderate or severe tricuspid regurgitation was higher in the recipients of the standard technique up to the most recent measurement (28% vs 7%; P =.02). The actuarial survival at 1, 3, and 5 years was 74%, 70%, and 62% for the recipients of the standard technique versus 87%, 82%, and 81% for the recipients of the bicaval technique (P <.03, <.04, and <.02, respectively). CONCLUSION: The bicaval technique maintains good left ventricular function, lower incidence and severity of tricuspid valve dysfunction, and improved survival compared with the standard technique.

Actuarial Analysis↗
PubMed1999

Diagnosis of chronic pancreatitis. Is a gold standard necessary?

The question that serves as this article's title is rhetorical. Clinicians have diagnosed and managed chronic pancreatitis without a gold standard for decades and must continue to do so in the foreseeable future. Although clinicians have a much wider array of diagnostic tools available for the diagnosis of chronic pancreatitis, a single readily applied gold standard remains elusive. Diagnostic studies are rarely compared with a true gold standard--histopathology. Furthermore, even if a safe biopsy technique were available, it might fall short of a gold standard, given the patchy nature of early-stage chronic pancreatitis. Indeed, different stages of chronic pancreatitis require not only recognition of the different clinical presentations but also different levels of intensity of diagnostic testing to establish the diagnosis confidently. The diagnosis in most patients with chronic pancreatitis can be made confidently with a good clinical history and a limited number of currently available structural and functional tests. No single diagnostic study, functional or structural, suffices for all patients. It is also axiomatic that patients with intractable abdominal pain in whom early-stage chronic pancreatitis is suspected represent a challenge for clinicians partly because of this lack of a single, dependable gold standard. Perhaps we have reached the point at which further refinements of current tests of structure or function are not beneficial because increased sensitivity is countered by loss of specificity. We suggest that a new approach to developing a gold standard for the diagnosis of chronic pancreatitis is necessary. With advances in the understanding of the mediators of the inflammatory process, it may be possible to devise a test to assess the earliest events in this disease.

Chronic Disease↗
PubMed2002

The extended version of the computer package CST for conversions, standardization and transformations of the spin Hamiltonian and the crystal-field Hamiltonian.

The computer package CST (Conversions, Standardization and Transformations) is useful for general manipulations of the zero-field splitting (ZFS) and crystal field (CF) parameters for various systems, especially for transition ions at orthorhombic and lower symmetry sites in crystals. The ZFS parameters are extensively used in the EMR and related spectroscopic and magnetic studies (e.g. magnetic susceptibility, magnetic anisotropy, Mössbauer spectroscopy), whereas the CF parameters in optical absorption spectroscopy, inelastic neutron scattering, and infrared spectroscopy. An extended version of the CST package developed recently is presented in this paper. The standardization, including the standardization errors, for the five possible non-standard ranges of the 'rhombicity' parameter for monoclinic and triclinic symmetry in the local axis system has been worked out. The handling of the border points in the standardization module has been improved. The rotational invariants used before only for the transformations of the CF parameters have been incorporated into the standardization module for the CF and ZFS parameters expressed in any of the major tensor operator notations. The input option in the Euler angles has been added into the transformation module, and the newest physical constants in the unit conversions module have been adopted. Specific applications of the CST package for the CF and ZFS parameters will be presented elsewhere.

Journal Article↗
PubMed1980

Ecological considerations in the creation and the use of child growth standards.

There is no proper substitute for a country, especially a developing country, having its own child growth standards or norms for clinical use, based on a representative sample of the population. Separate standards may be derived for subgroups of the population, but the application to the whole population of standards based on an economically privileged group is inappropriate, as is the use of an international standard. The screening or clinical use of growth standards should be sharply distinguished from the use of growth measurements to compare disadvantaged with privileged groups or populations. In particular, the use of growth standards to screen individual children should not divert attention from the need to change existing differences between disadvantaged and privileged groups.

Child↗
PubMed2002

A postmarketing, open-label study to evaluate the tolerability and effectiveness of replacing standard-formulation doxazosin with doxazosin in the gastrointestinal therapeutic system formulation in adult patients with hypertension.

BACKGROUND: The antihypertensive doxazosin works to decrease perivascular muscular tone, causing vasodilatation and hence a decrease in peripheral vascular resistance. To prevent the sharp decrease in blood pressure (BP), syncope, and other postural effects that may occur at the beginning of therapy with this drug, the dose must be adjusted. A new formulation, doxazosin gastrointestinal therapeutic system (GITS), allows slow release of the active agent so therapeutic serum levels are reached within 24 hours, rendering dose adjustment unnecessary and eliminating any first-dose effects. OBJECTIVES: The goals of this study were to evaluate the tolerability and effectiveness of (1) using doxazosin in the standard and new GITS formulations in adult patients with hypertension who either had uncontrolled or newly diagnosed disease, and (2) replacing standard-formulation doxazosin with doxazosin in the GITS formulation. METHODS: This was a postmarketing, open-label, noncomparative, multicenter clinical study covering primary care patients diagnosed with essential uncontrolled arterial hypertension (AHT). Subjects could be patients who were undergoing drug therapy before enrollment or those diagnosed with AHT and/or treated for the disease for the first time on entering the study. The study covered a period of 6 to 9 months, divided into 2 phases. Phase 1 involved a minimum of 3 and maximum of 6 months of treatment with standard-formulation doxazosin. Phase 2 commenced with the changeover from standard-formulation doxazosin to the GITS formulation and lasted 12 weeks. The principal study variables included BP and the development of adverse events (AEs). At every visit, the patients were asked by an investigator whether they had suffered any AEs since the previous contact. RESULTS: Of the total of 4,512 patients initially enrolled, 3537 (78.4%) completed the study. A total of 285 patients were excluded for failing to comply with the inclusion criteria, leaving 4,227 patients for analysis. In most instances, premature withdrawal from the study (16.3% [690/4,227]) was due to loss to follow-up (37.2% [257/690]), followed by the development of AEs (27.8% [192/690]). Fifty-nine percent (2,493/4,226) of patients analyzed were men and 41.0% (1,733/4,226) were women (sex data not recorded for 1 patient), with a mean age of 62.4 years (SD, 10.6). Among the patients participating, 54.8% (2,316/4,227) presented with some type of associated disease. The percentage of patients undergoing monotherapy was 70.7% (2,987/4,227); the remainder (29.3% [1,240/4,227]) underwent a combined-therapy regimen using another antihypertensive drug in conjunction with doxazosin. The mean initial systolic and diastolic BPs were 160 +/- 10.63 mm Hg and 95.26 +/- 7.21 mm Hg, respectively. Reduction in systolic BP was 20.9 mm Hg in phase 1 and 3.8 mm Hg in phase 2. In the case of diastolic BP, the reduction was 13.3 mm Hg in phase 1 and 2.6 mm Hg in phase 2. The percentage of patients with controlled disease was 47.9% (1,891/3,949) by the end of phase 1 and 63.4% (2,242/3,537) by the end of phase 2. A total of 322 (7.6%) patients presented with 343 AEs. 37 (0.9%) of which were deemed severe (0.6% in phase 1 and 0.3% in phase 2). Limitations included the following: (1) the design of this study did not allow comparison of the 2 formulations regarding effectiveness or tolerability: (2) the patients who remained in the study after phase 1 were those less susceptible to toxicity from doxazosin; and (3) it is probable that the nonresponders were more likely to drop out of the study. CONCLUSIONS: Doxazosin in the standard formulation was effective and well tolerated for the purpose of lowering BP. Patients who tolerated the standard formulation also tolerated the switch to the GITS formulation. Finally, this substitution did not negatively impact the effectiveness of treatment of AHT.

Adult↗
PubMedDate not supplied

Performance standards improve American Board of Surgery In-Training Examination scores.

PURPOSE: Although several studies have evaluated factors affecting American Board of Surgery In-Training Examination (ABSITE) performance, none has examined the impact of setting a minimally acceptable standard. It was hypothesized that establishing such a criterion would improve ABSITE scores. METHODS: An expectation for residents to score at the 35th percentile or higher was established in 1996. The proportion of test scores above or below the 35th and 50th percentiles for the time periods before and after institution of the standard were compared using Fisher's exact test. The subsequent performance of residents scoring below the 35th percentile was analyzed for the 2 time periods. RESULTS: After the institution of the standard, the proportion of scores below the 35th percentile decreased from 46.7% to 21.9% (p = 0.0005). Similarly, the proportion of scores at or above the national average increased from 42.1% to 65.6% (p = 0.0005). After establishing the standard, fewer residents continued to have scores below the criterion in subsequent years. CONCLUSIONS: Establishing a performance criterion improved ABSITE scores. The decision to institute a standard must be individualized for each program. The rationale for the standard and a plan to assist residents failing to achieve the benchmark must be communicated.

Journal Article↗
PubMedDate not supplied

[Double-blind randomized comparative study of enoxaparin and standard heparin in the prevention of thromboembolic disease during insertion of total hip replacement].

237 patients with a non-traumatic disease of the hip requiring total hip replacement entered a multicentre trial. Treatments were allocated at random in a double-blind manner: 113 patients received 5000 IU of standard heparin t.d.s.; 124 patients received enoxaparin 40 mg once a day. Treatment lasted from 10 to 15 days until bilateral ascending phlebography of the lower limbs (BAPLL) was performed. Its effectiveness was assessed by the results of BAPLL, by evaluation of the risk of bleeding on examination of the surgical wound, by the units of blood required for perfusion and by daily blood count and differential. BAPLL was performed in 228 patients: 15 phlebographies (12.5 p. 100) were positive in the 120 assessed patients of the enoxaparin group, while 27 (25 p. 100) were positive in the 108 assessed patients of the standard heparin group (p = 0.014). Proximal deep vein thrombosis was significantly (p = 0.03) less frequent in the enoxaparin group (7.5 p. 100) than in the standard heparin group (18.5 p. 100). Pulmonary embolism was observed in a patient on standard heparin. The units of blood required for perfusion were significantly (p = 0.03) smaller in the enoxaparin group (3.37 +/- 1.81 U) than in the standard heparin group (3.84 +/- 1.70 U). Thus, one single subcutaneous injection of enoxaparin 40 mg daily was significantly more effective and safer than standard heparin 5000 IU t.d.s. in the prevention of deep vein thrombosis after total hip replacement.

Aged↗
PubMed2002

Setting ambient air quality standards for particulate matter.

Ambient air particulate matter (PM), unspecified as to chemical composition, is of concern because of its health effects. Air quality standards for PM have been established in many countries. The earliest standards were based on threshold models and use of a margin of safety. Initially, standards were based on the mass of total suspended material. In the 1980s a shift to a size-specific standard, PM(10), began. PM(10) is the fraction of PM captured with 50% efficiency at 10 microm and greater efficiency at smaller sizes. In the late 1990s, standards were proposed for PM(2.5), which is captured with 50% efficiency at 2.5 microm. The standards for PM are based almost exclusively on human epidemiological data, with laboratory animal and in vitro data used in a supporting role. During the 1990s, new statistical tools began to be used and demonstrated an association between increased PM and an increase in cardiorespiratory morbidity and mortality. The analyses are complicated by the effects of other pollutants such as ozone. Effects have been observed down to 10-20 microg of PM(10) per cubic meter, levels equal to or below background in many parts of the world. In many studies there has been no evidence of a threshold. In the absence of a threshold, a critical issue becomes how to determine how low is low enough? This paper reviews the current literature on PM health effects and suggests research avenues that may yield data which, combined with public policy considerations, may be able to address the issue of 'how low is low enough?'

Air↗
PubMed1998

Further evaluation of the incorporation of an immunotoxicological functional assay for assessing humoral immunity for hazard identification purposes in rats in a standard toxicology study.

A previous study (Ladics et al., 1995) conducted in our laboratory using the known immunosuppressant agent, cyclophosphamide, indicated that a functional assay for assessment of humoral immunity may be conducted in rats in a standard toxicology study. The objective of this study was to further examine the feasibility of conducting an immunotoxicological assay for assessing humoral immunity in rats in a standard toxicology study using a chemical, carbon tetrachloride (CCl4), whose principal target organ of toxicity is not the immune system. Specifically, the previous study and this study were done to determine whether the conduct of an assay for assessing humoral immune function would affect standard toxicological endpoints. Male CD rats were untreated or dosed orally for 30 or 90 days, excluding weekends, with vehicle or 12.5 or 25 mg/kg CCl4. Six days prior to sacrifice, selected rats were injected intravenously with sheep red blood cells (SRBC) for assessment of humoral immune function. One day prior to necropsy, blood for hematological and clinical chemical measurements was collected from each rat. On the day of necropsy standard protocol tissues were collected, weighed, processed to slides, and later examined microscopically. One-half of each spleen was used to assess spleen cell numbers and quantitate lymphocyte subsets (Thelper; Tcyt/sup; total T- and B-cells) by flow cytometry. Serum was analyzed for anti-SRBC IgM antibody by using an enzyme-linked immunosorbent assay. Administration of 12.5 and 25 mg/kg CCl4 for 30 days decreased SRBC-specific serum IgM levels 42 and 45%, respectively, while 25 mg/kg CCl4 for 90 days increased SRBC-specific IgM levels by 50%. CCl4 did not alter splenic lymphocyte subset numbers nor the weight nor morphology of lymphoid organs. Exposure to 25 mg/kg CCl4 did increase liver weight and serum sorbitol dehydrogenase levels, as well as produce centrilobular fatty change. SRBC administration did not alter any hematological or clinical chemistry parameters, nor lymphocyte subset numbers. With the expected exception of the spleen (slight increase in number and size of germinal centers), administration of SRBC did not significantly alter the weights or morphology of routine protocol tissues. Furthermore, administration of SRBC did not mask the rather mild hepatotoxic effects of CCL4 exposure observed in this study. Based on these and previous findings, it appears that a functional assay for assessing humoral immunity may be conducted in animals on standard toxicology study without altering standard toxicological endpoints.

Animals↗