A novel approach to simultaneously scan genes at fragile sites

BACKGROUND

Fragile sites are regions of the genome sensitive to replication stress and to exposure to environmental carcinogens. The two most commonly expressed fragile sites FRA3B and FRA16D host the histidine triad (FHIT) and WW domain containing oxidoreductase (WWOX) genes respectively. There is growing evidence that both genes contribute to cancer development and they are frequently altered by allelic and homozygous deletions in a variety of tumors. Their status is linked to prognosis in several malignancies and they are thought to be involved in early tumorigenesis. The loci for FHIT and WWOX both span over a megabase but the genes encode for small transcripts. Thus the screening of intragenic deletion can be difficult and has relied on loss of heterozygosity LOH assays, or genomic arrays.

METHODS

Multiplex ligation dependent probe amplification MLPA, allows for the detection of deletions/duplications and relative quantification of up to 40 specific probes in a single assay. A FHIT/WWOX MLPA assay was designed, applied and validated in five esophageal squamous cell carcinoma ESCC, cell lines established in South Africa where this cancer is of high prevalence. Sixteen probes covered all FHIT exons and 7 probes covered WWOX.

RESULTS

Both homozygous and hemizygous deletions were detected in FHIT, in four of the cell lines with a preferential deletion of exons 5 and 4. Chromosome 3 short arm was present in normal copy number indicating that deletions were site specific. In contrast WWOX was not altered in any cell lines. RT-PCR expression pattern paralleled the pattern of deletions. Ten primary ESCC tumor specimens were subsequently screened with this assay. FHIT exon deletions were found in four of them.

CONCLUSION

This method offers an alternative to loss of heterozygosity studies. Simultaneous scanning of FHIT and WWOX exons in the context of early tumorigenesis and tumor progression, may help clarify the mechanistic events related to cancer development which are not revealed by immuno histochemistry assays. The presence of site specific deletions of FHIT in these cell lines and primary tumors support its possible role in South African ESCC and justifies a wider screening.

Detection of cryptic subtelomeric chromosome abnormalities and identification of anonymous chromatin using a quantitative multiplex ligation-dependent probe amplification (MLPA) assay

The need to detect clinically significant segmental aneuploidies beyond the range of light microscopy demands the development of new cost-efficient, sensitive, and robust analytical techniques. Multiplex ligation-dependent probe amplification (MLPA) has already been shown to be particularly effective and flexible for measuring copy numbers in a multiplex format. Previous attempts to develop a reliable MLPA to assay all chromosome subtelomeric regions have been confounded by unforeseen copy number variation in some genes that are very close to the telomeres in healthy individuals. We addressed this shortcoming by substituting all known polymorphic probes and using two complementary multiplex assays to minimize the likelihood of false results. We developed this new quantitative MLPA strategy for two important diagnostic applications. First, in a group of cases with high clinical suspicion of a chromosome abnormality but normal, high-resolution karyotypes, MLPA detected subtelomeric abnormalities in three patients. Two were de novo terminal deletions (del(4p) and del(1p)), and one was a derivative chromosome 1 from a maternal t(1p;17p). The range of these segmental aneuploidies was 1.8-6.6 Mb, and none were visible on retrospective microscopy. Second, in a group of six patients with apparently de novo single-chromosome abnormalities containing anonymous chromatin, MLPA identified two cases with simple intrachromosomal duplications: dup(6p) and dup(8q). Three cases showed derivative chromosomes from translocations involving the distal regions of 9q and 4q, 5p and 11q, and 6q and 3p. One case showed a nonreciprocal, interchromosomal translocation of the distal region of 10p-7p. All abnormalities in both groups were confirmed by fluorescence in situ hybridization (FISH) using bacterial artificial chromosomes (BACs). This quantitative MLPA technique for subtelomeric assays is compared with previously described alternative techniques.

High-throughput analysis of chromosome abnormality in spontaneous miscarriage using an MLPA subtelomere assay with an ancillary FISH test for polyploidy

Chromosome analysis of spontaneous miscarriages is clinically important but is hampered by frequent tissue culture failure and relatively low-resolution analysis. We have investigated replacement of conventional karyotype analysis with a quantitative subtelomere assay performed on uncultured tissue samples, which is based on Multiplex Ligation-Dependent Probe Amplification. This assay is suitable for this purpose as approximately 98% of all observed karyotype abnormalities in spontaneous miscarriages involve copy-number change to one or more subtelomere regions. A pilot study has compared karyotyping and subtelomere analysis on 78 samples. Extensive tissue necrosis accounted for failure of both karyotyping and subtelomere testing in four (5.1%) samples. Excluding these, there were no (0/74) subtelomere test failures compared to 9.5% (7/74) karyotype failures. Twenty-two (30%) whole chromosome aneuploidies and five (6.8%) structural abnormalities were detected using the subtelomere assay. With the exception of three cases of triploidy, all karyotype abnormalities were detected by the subtelomere assay. Following on from this study, a further 100 samples were tested using the subtelomere assay in conjunction with a simple ancillary FISH test using uncultured cells to exclude polyploidy in the event of a normal subtelomere assay result. Except for three necrotic samples, tests results were obtained for all cases revealing 18 abnormalities including one case of triploidy. Taking into consideration the high success rate for the combined MLPA and FISH test results, and the very significant additional advantages of cost-effective, high-throughput batching, and automated, objective analysis, this approach greatly facilitates routine investigation of chromosome abnormalities in spontaneous miscarriage.

Smoking cessation, lung function, and weight gain: a follow-up study

BACKGROUND

Only one population-based study in one country has reported effects of smoking cessation and weight change on lung function, and none has reported the net effect. We estimated the net benefit of smoking cessation, and the independent effects of smoking and weight change on change in ventilatory lung function in the international European Community Respiratory Health Survey.

METHODS

6654 participants in 27 centres had lung function measured in 1991-93, when aged 20-44 years, and in 1998-2002. Smoking information was obtained from detailed questionnaires. Changes in lung function were analysed by change in smoking and weight, adjusted for age and height, in men and women separately and together with interaction terms.

FINDINGS

Compared with those who had never smoked, decline in FEV1 was lower in male sustained quitters (mean difference 5.4 mL per year, 95% CI 1.7 to 9.1) and those who quit between surveys (2.5 mL, -1.9 to 7.0), and greater in smokers (-4.8 mL, -7.9 to -1.6). In women, estimates were 1.3 mL per year (-1.5 to 4.1), 2.8 mL (-0.8 to 6.3) and -5.1 mL (-7.5 to -2.8), respectively. These sex differences were not significant. FEV1 changed by -11.5 mL (-13.3 to -9.6) per kg weight gained in men, and by -3.7 mL per kg (-5.0 to -2.5) in women, which diminished the benefit of quitting by 38% in men, and by 17% in women.

INTERPRETATION

Smoking cessation is beneficial for lung function, but maximum benefit needs control of weight gain, especially in men.

ICF Core Sets for stroke

OBJECTIVE

To report on the results of the consensus process integrating evidence from preliminary studies to develop the first version of the Comprehensive ICF Core Set and the Brief ICF Core Set for stroke.

METHODS

A formal decision-making and consensus process integrating evidence gathered from preliminary studies was followed. Preliminary studies included a Delphi exercise, a systematic review, and an empirical data collection. After training in the ICF and based on these preliminary studies relevant ICF categories were identified in a formal consensus process by international experts from different backgrounds.

RESULTS

The preliminary studies identified a set of 448 ICF categories at the second, third and fourth ICF levels with 193 categories on body functions, 26 on body structures, 165 on activities and participation, and 64 on environmental factors. Thirty-nine experts from 12 different countries attended the consensus conference on stroke. Altogether 130 second-level categories were included in the Comprehensive ICF Core Set with 41 categories from the component body functions, 5 from body structures, 51 from activities and participation, and 33 from environmental factors. The Brief ICF Core Set included a total of 18 second-level categories (6 on body functions, 2 on body structures, 7 on activities and participation, and 3 on environmental factors).

CONCLUSION

A formal consensus process integrating evidence and expert opinion based on the ICF framework and classification led to the definition of ICF Core Sets for stroke. Both the Comprehensive ICF Core Set and the Brief ICF Core Set were defined.

ICF Core Sets for rheumatoid arthritis

OBJECTIVE

To report on the results of the consensus process integrating evidence from preliminary studies to develop the first version of a Comprehensive ICF Core Set and a Brief ICF Core Set for rheumatoid arthritis.

METHODS

A formal decision-making and consensus process integrating evidence gathered from preliminary studies was followed. Preliminary studies included a Delphi exercise, a systematic review, and an empirical data collection. After training in the ICF, and based on these preliminary studies, relevant ICF categories were identified in a formal consensus process by international experts from different backgrounds.

RESULTS

The preliminary studies identified a set of 530 ICF categories at the second, third and fourth ICF levels with 203 categories on body functions, 76 on body structures, 188 on activities and participation, and 63 on environmental factors. Seventeen experts from 12 different countries attended the consensus conference on rheumatoid arthritis (7 physicians with at least a specialization in physical and rehabilitation medicine, 7 rheumatologists, one nurse, one occupational therapist, and one physical therapist). Altogether 96 categories (76 second-level and 20 third-, and fourth-level categories) were included in the Comprehensive ICF Core Set with 25 categories from the component body functions, 18 from body structures, 32 from activities and participation, and 21 from environmental factors. The Brief ICF Core Set included a total of 39 second-level categories, with 8 on body functions, 7 on body structures, 14 on activities and participation, and 10 on environmental factors.

CONCLUSION

A formal consensus process integrating evidence and expert opinion based on the ICF framework and classification led to the definition of ICF Core Sets for rheumatoid arthritis. Both the Comprehensive ICF Core Set and the Brief ICF Core Set were defined.

Two-color multiplex ligation-dependent probe amplification: detecting genomic rearrangements in hereditary multiple exostoses

Genomic deletions and duplications play an important role in the etiology of human disease. Versatile tests are required to detect these rearrangements, both in research and diagnostic settings. Multiplex ligation-dependent probe amplification (MLPA) is such a technique, allowing the rapid and precise quantification of up to 40 sequences within a nucleic acid sample using a one-tube assay. Current MLPA probe design, however, involves time-consuming and costly steps for probe generation. To bypass these limitations we set out to use chemically synthesized oligonucleotide probes only. The inherent limitations of this approach are related to oligonucleotide length, and thus the number of probes that can be combined in one assay is also limited. This problem was tackled by designing a two-color assay, combining two sets of probes, each amplified by primers labeled with a different fluorophore. In this way we successfully combined 28 probes in a single reaction. The assay designed was used to screen for the presence of deletions and duplications in patients with hereditary multiple exostoses (HME). Screening 18 patients without detectable point mutations in the EXT1 and EXT2 genes revealed five cases with deletions of one or more exons: four in EXT1 and one in EXT2. Our results show that a two-color MLPA assay using only synthetic oligonucleotides provides an attractive alternative for probe design. The approach is especially suited for cases in which the number of patients to be tested is limited, making it financially unattractive to invest in cloning.

Improved testing for CMT1A and HNPP using multiplex ligation-dependent probe amplification (MLPA) with rapid DNA preparations: comparison with the interphase FISH method

Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are the two most common peripheral neuropathies, with incidences of about 1 in 2,500. Several techniques can be used to detect the typical 1.5-Mb duplication or deletion associated with these respective conditions, but none combines simplicity with high sensitivity. MLPA is a new technique for measuring sequence dosage. We have assessed its performance for the detection of the specific 1.5-Mb duplication/deletion by prospectively testing 50 patients referred with differential diagnoses of CMT or HNPP. Probes were designed to evaluate the TEKT3, PMP22, and COX10 genes within the CMT1A/HNPP region. We have compared the results with our existing fluorescence in situ hybridization (FISH) assay, which was performed in parallel. There was concordance of results for 49 patients. Of note, one patient showed an intermediate multiplex ligation-dependent probe amplification (MLPA) result with an abnormal FISH result, which is consistent with mosaicism. The assay works equally well with either purified DNA or rapid DNA preparations made by direct cell lysis. The use of the latter significantly reduces the cost of the assay. MLPA is a sensitive, specific, robust, and cost-effective technique suitable for fast, high-throughput testing and offers distinct advantages over other testing methods.

Increase in diagnosed asthma but not in symptoms in the European Community Respiratory Health Survey

BACKGROUND

Information on the epidemiology of asthma in relation to age is limited and hampered by reporting error. To determine the change in the prevalence of asthma with age in young adults we analysed longitudinal data from the European Community Respiratory Health Survey.

METHODS

A self-administered questionnaire was completed by 11 168 randomly selected subjects in 14 countries in 1991-3 when they were aged 20-44 years and 5-11 years later from 1998 to 2003. Generalised estimating equations were used to estimate net change in wheeze, nocturnal tightness in chest, shortness of breath, coughing, asthma attacks in the last 12 months, current medication, "diagnosed" asthma, and nasal allergies.

RESULTS

Expressed as change in status per 10 years of follow up, subjects reporting asthma attacks in the previous 12 months increased by 0.8% of the population (95% CI 0.2 to 1.4) and asthma medication by 2.1% (95% CI 1.6 to 2.6), while no statistically significant net change was found in reported symptoms. Reported nasal allergies increased, especially in the youngest age group.

CONCLUSIONS

As this cohort of young adults has aged, there has been an increase in the proportion treated for asthma but not in the proportion of those reporting symptoms suggestive of asthma. Either increased use of effective treatments has led to decreased morbidity among asthmatic subjects or those with mild disease have become more likely to label themselves as asthmatic.

Treatment with an anti-CD14 monoclonal antibody delays and inhibits lipopolysaccharide-induced gene expression in humans in vivo

CD14 is a receptor important for activation of cells by lipopolysaccharide (LPS). Treatment with the CD14 antibody IC14 was previously found to attenuate the release of proinflammatory cytokines and some chemokines into the circulation of healthy humans intravenously injected with LPS. To determine the role of circulating leukocytes in CD14-dependent gene expression, 16 healthy volunteers received LPS preceded by either IC14 or placebo. At different time points, mRNA was isolated from whole blood and gene expression was determined by multiplex ligation-dependent probe amplification (MLPA). LPS induced MIP-1alpha, MIP-1beta, IL-8, IL-1beta, and IL-1Ra mRNA production, which was delayed by 1 hr and reduced twofold by IC14 treatment. TNFR1 was unresponsive, whereas other investigated cytokines remained undetectable. Further, LPS showed differential effects on NFkappaB gene expression. LPS induced IkappaBalpha production, whereas p50 was unresponsive and p65 and p49/p100 remained undetectable. LPS induced IkappaBalpha expression was delayed (1 hr) and reduced by IC14. Gene expression profiles in blood cells corresponded poorly with observed changes in plasma levels. These data suggest that peripheral blood cells are of negligible importance in LPS-induced production of inflammatory mediators in vivo and that LPS may activate genes via a CD14-independent pathway that is slower and less efficient.

High-level expression of recombinant IgG in the human cell line per.c6

The number of therapeutic monoclonal antibodies in production is expected to rise rapidly in the next few years. As a result, there is much focus on the optimization of antibody expression platforms. Several issues are important including the speed of transition from bench to manufacturing, yield of IgG, and quality (particularly of the glycan structures present on immunoglobulins). We have characterized the human cell line PER.C6 for its ability to produce recombinant IgG. Production yields are still being optimized, but in nonfed batch culture, PER.C6 is able to grow to a cell density of 5 x 10(6) cells/mL and produce 300-500 mg/L IgG; this is likely to increase significantly in fed batch cultures. The generation of antibody-producing cell lines is fast, as rounds of amplification of inserted genes are not required for high production yields. The gene copy number of inserted genes is in the region of 1-10 copies per genome. In addition, PER.C6 is a human cell line, and so does not add glycans, which are immunogenic in humans. A core fucose molecule is essentially always present, and galactose residues are present at a physiological level (0, 1, and 2 galactose residues per glycan are present at a ratio of 1:2:1). No hybrid or high-mannose structures are seen.

Growth factors can activate ATF2 via a two-step mechanism: phosphorylation of Thr71 through the Ras-MEK-ERK pathway and of Thr69 through RalGDS-Src-p38

Transcription factor ATF2 regulates gene expression in response to environmental changes. Upon exposure to cellular stresses, the mitogen-activated proteinkinase (MAPK) cascades including SAPK/JNK and p38 can enhance ATF2's transactivating function through phosphorylation of Thr69 and Thr71. How ever, the mechanism of ATF2 activation by growth factors that are poor activators of JNK and p38 is still elusive. Here, we show that in fibroblasts, insulin, epidermal growth factor (EGF) and serum activate ATF2 via a so far unknown two-step mechanism involving two distinct Ras effector pathways: the Raf-MEK-ERK pathway induces phosphorylation of ATF2 Thr71, whereas subsequent ATF2 Thr69 phosphorylation requires the Ral-RalGDS-Src-p38 pathway. Cooperation between ERK and p38 was found to be essential for ATF2 activation by these mitogens; the activity of p38 and JNK/SAPK in growth factor-stimulated fibroblasts is insufficient to phosphorylate ATF2 Thr71 or Thr69 + 71 significantly by themselves, while ERK cannot dual phosphorylate ATF2 Thr69 + 71 efficiently. These results reveal a so far unknown mechanism by which distinct MAPK pathways and Ras effector pathways cooperate to activate a transcription factor.

Cloning by pathway activation in yeast: identification of an Arabidopsis thaliana F-box protein that can turn on glucose repression

We describe a method for identifying signal transducing proteins from other organisms by their ability to turn on a signalling pathway when they are expressed at high level in yeast. The method was tested on a cDNA library from Arabidopsis thaliana, which was screened for clones that can activate glucose repression in the absence of glucose. Six clones were characterized. One of them codes for AtGRH1, a new F-box protein that shows similarity to GRR1, a yeast protein involved in glucose repression. The ability of AtGRHI to activate glucose repression is dependent on the MIG1 repressor. Two-hybrid experiments revealed that AtGRH1 can interact with AtSKP1a and AtSKP1b, two recently identified SKP1 homologues in Arabidopsis. Other clones identified in the screen encode the transcription factor AtEBP, the 14-3-3 protein AtGF14 and two new proteins: AtMYR1 and AtPOZ1. None of these proteins turn on glucose repression. Instead, they illustrate various other ways by which foreign proteins can interfere with expression of a yeast gene. We conclude that our method worked as expected in at least one case, and that it could be applied to other signalling pathways that are conserved between yeast and higher eukaryotes.

TE-AFLP: combining rapidity and robustness in DNA fingerprinting

A new type of fingerprinting technique is presented, based on amplified fragment length polymorphism (AFLP). Rather than two endonucleases as in AFLP, we propose the use of three enzymes, hence the method is called three endonuclease (TE)-AFLP. Genomic DNA is digested and two sets of adapters are selectively ligated onto the restriction fragments in a single reaction volume. No adapters complementary to the ends generated by a frequent cutter are added. Due to the addition of a third endonuclease, the TE-AFLP method provides a high discriminatory power and a reduction in the number of bands. The latter makes it especially suitable for the analysis of complex genomes. TE-AFLP fingerprints are suitable for detection by automatic fluorescent sequencers and are obtained in less than half the time and at reduced costs compared to a typical AFLP. The reliability of this method was investigated by determining the influence of varying digestion, ligation and PCR components on the fingerprint. Moreover, cross-experiments to study inheritance of loci were performed with a primitive insect and with tomato strains. The features of TE-AFLP are discussed in comparison with conventional AFLP.

Preliminary guidelines for the evaluation and management of dyslipidemia in adults infected with human immunodeficiency virus and receiving antiretroviral therapy: Recommendations of the Adult AIDS Clinical Trial Group Cardiovascular Disease Focus Group

Dyslipidemia is a prevalent condition that affects patients infected with human immunodeficiency virus (HIV) who are receiving antiretroviral therapy. These preliminary recommendations summarize the current understanding in this area and propose guidelines for management. Existing guidelines for the management of dyslipidemia in the general population formed the general basis for our recommendations. Data on the prevalence and treatment of dyslipidemia of HIV-infected patients, implications of treatment-related dyslipidemia in other chronically ill populations, and pharmacokinetic profiles for the available hypolipidemic agents in non-HIV populations were considered. Although the implications of dyslipidemia in this population are not fully known, the frequency, type, and magnitude of lipid alterations in HIV-infected people are expected to result in increased cardiovascular morbidity. We propose that these patients undergo evaluation and treatment on the basis of existing guidelines for dyslipidemia, with the caveat that avoidance of interactions with antiretroviral agents is paramount.

The Dutch 'Folic Acid Campaign'--have the goals been achieved?

Periconceptional folic acid use considerably reduces the risk of neural tube defects. The aim of this study was to measure the effect of the national and the local 'Folic Acid Campaign' on periconceptional folic acid use. Before (1995 survey) and 1 year after the campaign (1996 survey), the awareness and use of folic acid was measured among pregnant women in four regions of the Netherlands. To this end, pregnant women who visited the midwife, general practitioner or obstetrician for the first or second prenatal visit were asked to complete a questionnaire. The results showed that use of folic acid for any period around conception increased from 25.1% in 1995 to 53.5% in 1996. Appropriate use (4 weeks before until 8 weeks after conception) increased from 4.8% in 1995 to 21.0% in 1996. No additional effect of the local Folic Acid Campaign was found (adjusted odds ratio= 1.0; 95% confidence interval = 0.7, 1.4). It was possible to conclude that folic acid use at the recommended time increased considerably as a result of the national and the local Folic Acid Campaign, but the target (use in 46% of women wishing to conceive) was not achieved. New health education programmes are needed to increase further its use at the appropriate times.

Overexpression of Arabidopsis thaliana SKP1 homologues in yeast inactivates the Mig1 repressor by destabilising the F-box protein Grr1

The timed destruction of cell cycle regulatory proteins is of key importance in controlling cell cycle progression in eukaryotes. Recently, Skp1 from yeast (Saccharomyces cerevisiae) was shown to play an important role in the ubiquitin-mediated proteolysis of these proteins via the Skp1-Cdc53-F-box (SCF) pathway. Here we describe the fortuitous cloning of cDNAs for two Skp1 homologues from the plant Arabidopsis thaliana on account of their ability to activate reporter gene expression in yeast directed by the cyt-1 element from the promoter of the Agrobacterium tumefaciens T-cyt gene, which is essential for expression of the gene in plants. This element is strikingly similar in sequence to the binding site for the yeast Migl protein, a transcriptional repressor of genes involved in the utilisation of carbohydrates other than glucose. We report that Mig1 protein binds to the cyt-1 element with similar specificity as a previously described plant nuclear protein factor, and that the cyt-1 element is a target for an unknown yeast transcriptional activator when Mig1 itself is inactivated. Interestingly, our data further indicate that A. thaliana Skp1 inactivates Mig1 by destabilising the yeast F-box protein Grr1, which is required for cyclin degradation and is thus involved in control of the cell cycle, and for glucose-regulated gene repression. Our results suggest that the plant counterpart of yeast Skp1 is probably also instrumental in ubiquitin-mediated proteolysis of specific proteins via an SCF-like pathway.

Suitability of the Charm HVS and a microbiological multiplate system for detection of residues in raw milk at EU maximum residue levels

In this paper we assessed the suitability of the Charm HVS and a newly developed microbiological multiplate system as post-screening tests to confirm the presence of residues in raw milk at or near the maximum permissible residue level (MRL). The multiplate system is composed of Bacillus stearothermophilus var. calidolactis plate at pH 8.0 for detection of beta-lactam antibiotics and tylosin, Bacillus cereus plate at pH 6.0 for detection of tetracyclines, Micrococcus luteus plate at pH 8.0 for detection of macrolides, Bacillus subtilis BGA plate at pH 8.0 for detection of aminoglycosides, trimethoprim-containing plate seeded with B. subtilis BGA at pH 7.0 for detection of sulphonamides, Escherichia coli plate at pH 6.0 for detection of quinolone and polymyxin, and Staphylococcus epidermidis plate at pH 6.0 for detection of novobiocin. For each test plate an action level is proposed in such a way that residues can be detected in raw bulk tank milk at levels near or below the established EU MRLs of beta-lactam antibiotics, tetracyclines, aminoglycosides, macrolides, sulphonamides, colistin, and quinolones. The Charm HVS test used to confirm the presence of tetracycline and macrolide residues gave false-positive results near the EU MRLs. The multiplate system gave valid results. Based on data for raw bulk tank milk samples and the proposed action level for each test plate for suspected samples, we demonstrated that the multiplate system is a reliable post-screening method that can be performed easily and cheaply in microbiological laboratories.

Peak expiratory flow variability, bronchial responsiveness, and susceptibility to ambient air pollution in adults

Bronchial hyperresponsiveness (BHR) and peak expiratory flow (PEF) variability are associated expressions of airway lability, yet probably reflect different underlying pathophysiologic mechanisms. We investigated whether both measures can be used interchangeably to identify subjects who are susceptible to ambient air pollution. Data on BHR (>= 20% fall in FEV1), PEF variability (ampl%mean PEF > 5% on any day during an 8-d period with low air pollution levels) and diary data on upper and lower respiratory symptoms, cough, and phlegm were collected in 189 subjects (48-73 yr). The acute effects (lag0) of particulate matter with a diameter less than 10 micrometers (PM10), black smoke, SO2 and NO2 on the prevalence of symptoms were estimated with logistic regression. In subjects with airway lability, both when expressed as PEF variability (69%) and BHR (28%), the prevalence of symptoms increased significantly with increasing levels of air pollution, especially in those with the greater PEF variability (n = 55, 29%). We found no such consistent positive associations in adults without airway lability. PEF variability, and to a smaller extent BHR, can be used to identify adults who are susceptible to air pollution. Though odds ratios were rather low (ranging from 1.13 to 1.41), the impact on public health can be substantial because it applies to large populations.

Testing of raw milk for tetracycline residues

A newly improved Bacillus calidolactis tube diffusion test and two postscreening test systems--a receptor assay (Charm HVS; Charm Sciences, Inc., Malden, MA) and a newly developed Bacillus cereus ATCC 11778 mycoides test system--were evaluated for the detection and identification of tetracycline residues using 973 samples of bulk milk taken at random in The Netherlands. All milk samples were assayed with the B. calidolactis tube and the receptor test. The milk samples testing as suspect or positive with one or both of the test systems were analyzed with HPLC (limit of detection, 10 ng/ml) and the recently developed B. cereus test system. The B. calidolactis tube diffusion test detected tetracycline residues > 45 ng/ml in milk. With the B. cereus test plate, residues of oxytetracycline and tetracycline of > 30 ng/ml milk were detected; for chlortetracycline and doxycycline, the detection limit was 10 ng/ml. Raw milk exhibiting inhibition diameters of < 20 mm on the B. cereus test plate fulfilled the European Union criterion for maximum residue level for tetracyclines of < 100 ng/ml (including their 4-epimer derivatives). The detection limits of the receptor assay depended on the type of milk used. The scintillation counts that were obtained for control samples of bulk milk were considerably lower than for the milks obtained from Charm Sciences, Inc. or processed using UHT pasteurization. One of 973 milk samples was suspect for tetracycline residues by means of the B. calidolactis tube test as well as by the receptor assay; 8 other samples were also considered to be positive using the receptor assay alone. The presence of tetracycline residues could not be proved for these 9 samples (residue concentration, < 10 ng/ml) with HPLC. We concluded that the receptor assay was not reliable to detect tetracycline residues in raw milk at < 150 ng/ml. The B. cereus test plate was determined to be an inexpensive, reliable alternative for the receptor assay for detection of tetracycline residues.