Doubling Doses Research Articles

Desensitization to co-trimoxazole (trimethoprim-sulphamethoxazole) in HIV-infected patients: is patch testing a useful predictor of reaction?

To establish the safety and efficacy of desensitization to co-trimoxazole in hypersensitive HIV-infected subjects. To assess if delayed hypersensitivity (type IV) to co-trimoxazole predicts those unable to be desensitized. desensitization to co-trimoxazole, comprising trimethoprim (T) 0.4 mg and sulphamethoxazole (S) 2 mg initially with doubling dose daily, full strength co-trimoxazole (T/S 160 mg/800 mg) at 10 days. Patch testing with 4.5% and 9% co-trimoxazole in yellow soft paraffin, CMI Multitest. nineteen patients, 18 male and one female, were recruited and completed the desensitization regime. Of these 80%(15) achieved successful desensitization. Three of those who reacted did so within 18 days. All patients were successfully managed in an outpatient setting. There were no major adverse reactions. Of those reacting none gave a positive patch test to co-trimoxazole and all showed absent delayed type hypersensitivity reactions to recall antigens. co-trimoxazole desensitization is a safe and efficacious procedure, with a success rate of 80% using the above regime. Patch testing with co-trimoxazole gives no useful information about those that reacted.

Effects of Genetic Polymorphism on Ex Vivo and In Vivo Function of β2-Adrenoceptors in Asthmatic Patients

Genetic polymorphism determines agonist-induced down-regulation and desensitization of beta2-adrenoceptors. The aim of the present study was to investigate the effects of genetic polymorphism on ex vivo (lymphocytes) and in vivo (bronchoprotection) function of beta2-adrenoceptors in asthmatic patients, having been washed out of previous beta2-agonist exposure. Sixty patients with stable mild-to-moderate asthma were evaluated, with a post hoc analysis of genotype performed at end of study. Having withheld treatment with long-acting beta2-agonists for > or = 48 h and short-acting beta2-agonists for > or = 12 h, measurements of lymphocyte beta2-adrenoceptors were made for binding density, binding affinity, basal cyclic adenosine monophosphate (cAMP), and maximal cAMP response to isoproterenol (Emax). In addition, in 48 of these patients who were methacholine responsive (PD20 < 1,000 microg), the acute protective effect of formoterol as a 24-microg single dose (at 1 h) was also evaluated. Comparisons were made according to homozygous and heterozygous (Het) polymorphisms at codon 16 and codon 27. There were no significant differences in age, FEV1 percent predicted, or inhaled corticosteroid dose, when comparing mean values for polymorphisms at either codon-16 or codon 27. There were also no significant differences between polymorphisms for any of the measured lymphocyte beta2-adrenoceptor parameters apart from basal cAMP between Glu-27 and Het-27. Mean values for Emax (after-before isoproterenol as pmol/10(6) cells) were as follows: Gly-16 (3.4), Arg-16 (3.5), Het-16 (4.0), Glu-27 (3.9), Gln-27 (3.5), and Het-27 (3.7). Polylorphism had no significant effect on formoterol protection as doubling dose shift in methacholine PD20 (geometric mean): Gly-16 (5.3), Arg-16 (5.4), Het-16 (4.6), Glu-27 (5.3), Gln-27 (5.3), Het-27 (4.5). Our results show that genetic polymorphism at codon 16 or 27 does not influence stimulated coupling of lymphocyte beta2-adrenoceptors and similarly did not influence the degree of functional antagonism exhibited by formoterol. Thus, a single dose of beta2-agonist when used on demand affords equal protection against bronchoprotection regardless of genetic polymorphism.

HCF-dependent nuclear import of VP16.

Transactivation by VP16 requires the formation of a multicomponent complex, the TAATGAAAT recognition factor complex (TRF.C), that contains in addition to VP16, two cellular proteins, Oct-1 and HCF. HCF binds directly to VP16 and this promotes subsequent interaction of the VP16-HCF complex with the POU DNA-binding domain of Oct-1 and selective assembly onto target sites. Here we demonstrate a novel role of HCF in the intracellular compartmentalization of VP16. We show that while VP16 does not contain a consensus nuclear localization signal (NLS) and is largely cytoplasmic, co-expression with HCF resulted in VP16 nuclear accumulation. A candidate NLS within the C-terminus of HCF was identified and insertion of this motif into green fluorescent protein (GFP) promoted nuclear accumulation. Conversely, removal of this signal from HCF (HCFDeltaNLS) resulted in its cytoplasmic accumulation. Co-expression of HCFDeltaNLS with wild-type (wt) VP16, or of wt HCF with VP16 mutants lacking HCF-binding activity failed to promote the nuclear enrichment of VP16. These results indicate that in addition to its role in stabilizing TRF.C, HCF acts as a nuclear import factor for VP16.

A unified approach to the study of mutation, from bacteria to humans: some potentialities of the new DNA technologies.

Let me at the outset express my deep appreciation at the receipt of the Annual Award of the Environmental Mutagen Society. In the 27 years since this Award was established, it has recognized many persons for seminal contributions to the field of mutagenesis, and I am honored to join those previous recipients. I was impressed by how many different facets of the subject of mutagenesis they represented. Today, in the course of my brief remarks, I hope to direct attention to still another aspect of our complex field. As many of you know, for more than 50 years I have been involved in studies of spontaneous and radiation-induced mutation rates in humans. This work has been in collaboration with quite a number of American and Japanese colleagues, to whom I am very grateful and whose contributions will be recognized in the citations that follow. Now, my genetic roots were formed in the course of studies with two eminent Drosophilists, Warren P. Spencer and Curt Stern, and you can be certain that after my transition into human genetics and my involvement with the genetic effects of the atomic bombs, I have kept a close eye on developments in experimental radiation genetics, especially those involving the fruit fly and the mouse. Some 17 years ago, in the Wilhemina E. Key Lecture of the American Genetic Association [Neel, 1983], I attempted to compare spontaneous mutation rates in the fruit fly, the house mouse, and humans. It was a pretty unsatisfactory business, but what emerged was, to me, an apparent surprising similarity in the spontaneous mutation rates per gene per generation of these three species, considering the great differences in their life cycles. Then, some 9 years ago, Susan Lewis and I [Neel and Lewis, 1990] attempted to compare radiationinduced rates in humans and mice, and again it was a frustrating undertaking. Now the issue was to what extent did the genetic findings on radiation effects in humans agree with those on mice. This is a whole other story I do not propose to get into today, other than to comment that recent developments regarding mosaic mutation in mice [Russell and Russell, 1996] and the prevalence of cluster mutations in mice [Selby, 1998] seem to be bringing the estimates of the genetic doubling dose based on mice closer to the higher estimate based on the findings in Japan [Neel, 1999]. But today, rather than dwelling on the past, I propose to engage in a fantasy for the future. The fantasy emerges out of the truly amazing developments in molecular genetics and genomics over the past several decades. The fantasy involves the concept that we may soon be able to study comparative mutagenesis, both spontaneous and induced, at the DNA level, thus providing the ultimate basis for acrossspecies comparisons. As I say this, I realize that many EMS members have already been engaged in analyzing at the molecular level a variety of mutations detected through some phenotypic effect. I want to talk about a method of screening for mutations that begins at the molecular level.

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This paper is focused on baseline frequencies of mendelian diseases and the conceptual basis for calculating doubling doses both of which are relevant for the doubling dose method of estimating genetic risks of exposure of human populations to ionizing radiation. With this method, the risk per unit dose is obtained as a product of three quantities, namely, the baseline frequency of the disease class under consideration, the relative mutation risk (which is the reciprocal of the doubling dose, which in turn, is calculated as a ratio of spontaneous and induction rates of mutations) and mutation component, i.e., the responsiveness of the disease class to an increase in mutation rate. The estimates of baseline frequencies of mendelian diseases that are currently used in risk estimation date back to the late 1970s. Advances in human genetics during the past two decades now permit an upward revision of these estimates. The revised estimates are 150 per 104 livebirths for autosomal dominants (from the earlier estimate of 95 per 104), 75 per 104 livebirths for autosomal recessives (from 25 per 104) and to 15 per 104 livebirths for X-linked diseases (from 5 per 104). The revised total frequency of mendelian diseases is thus 240 per 104 livebirths and is about twice the earlier figure of 125 per 104 livebirths. All these estimates, however, pertain primarily to Western European and Western European-derived populations. The fact that in several population isolates or ethnic groups, some of these diseases (especially the autosomal recessives) are more common as a result of founder effects and/or genetic drift is well known and many more recent examples have come to light. These data are reviewed and illustrated with data from studies of the Ashkenazi Jewish, Finnish, French Canadian, Afrikaner and some other populations to highlight the need for caution in extrapolating radiation risks between populations. The doubling dose of 1 Gy that has been used for the past 20 years for risk estimation is based on mouse data for both spontaneous and induction rates of mutations. In extrapolating the mouse-data-based doubling dose to humans, it is assumed that the spontaneous rates in mice and humans are similar. This assumption is incorrect because of the fact that in humans, for several well-studied mendelian diseases, the mutation rate differs between the two sexes and it increases with paternal age. In estimates of spontaneous mutation rates in humans (which represent averages over both sexes), however, paternal age effects are automatically incorporated. In the mouse, these effects are expected to be much less (if they exist at all), but the problem has not been specifically addressed. The complexities and uncertainties associated with assessing the potential impact of spontaneous mutations which arise as germinal mosaics (and which can result in clusters of mutations in the following generation) on mutation rate estimates (in the mouse) and on mutation rate estimates and disease frequencies (in humans) are discussed. In view of (i) the lack of comparability of spontaneous mutation rates in mice and humans and (ii) the fact that these estimates for human genes already include both paternal age effects and correction for clusters (if they had occurred), it is suggested that a prudent procedure now is to base doubling dose calculations on spontaneous mutation rates of human genes (and induction rates of mouse genes, in the absence of a better alternative). This concept, however, is not new and was used by the US National Academy's Committee on the Biological Effects of Ionizing Radiation in its 1972 report.

Repeatability of lung function tests during methacholine challenge in wheezy infants

BACKGROUNDThe repeatability of lung function tests and methacholine inhalation tests was evaluated in recurrently wheezy infants over a one month period using the rapid thoracic compression technique.METHODSEighty one wheezy, symptom...

The occurrence of late asthmatic response to exercise after allergen challenge.

The determinants of late asthmatic responses to exercise remain unknown. It has been reported that they may develop in some adult subjects with asthma following a late asthmatic response to allergen. We intended to corroborate this finding in children with asthma and to investigate which aspect of airway responses to allergen is associated with late asthmatic responses to exercise. We studied 17 children with allergic asthma, who showed late asthmatic responses to inhaled allergen (Dermatophagoides pteronyssinus). Each underwent an exercise challenge test two days before (pre-allergen) and two days after (postallergen) an allergen inhalation challenge. FEV1 was measured at regular intervals up to ten hours after each challenge. Methacholine PC20 was measured before the allergen challenge and before the postallergen exercise challenge. After the pre-allergen exercise test, all the subjects showed isolated early asthmatic responses. After the postallergen exercise test, seven showed dual responses (early and late asthmatic responses) (group I) and the remaining ten showed isolated early asthmatic responses (group II). Bronchial responses to pre-allergen exercise or inhaled allergen and the severity of early asthmatic responses to postallergen exercise were similar in groups I and II. Neither before allergen inhalation nor before the postallergen exercise was methacholine PC20 different between the two groups. Methacholine dose shift caused by allergen challenge, however, was significantly greater in group I than in group II (-2.00+/-0.39 versus -1.36+/-0.53 doubling doses; P < .05). There was significant correlation between the dose shift and the magnitude of late response to the postallergen exercise in the whole group (r = 0.51, P < .05). Late asthmatic responses to exercise may develop in some children with asthma following a late asthmatic response to allergen. This phenomenon was related neither to the baseline nor to postallergen methacholine PC20 but to the extent of increased sensitivity to methacholine caused by allergen challenge.

Ionizing radiation and genetic risks IX. Estimates of the frequencies of mendelian diseases and spontaneous mutation rates in human populations: a 1998 perspective.

This paper is focused on baseline frequencies of mendelian diseases and the conceptual basis for calculating doubling doses both of which are relevant for the doubling dose method of estimating genetic risks of exposure of human populations to ionizing radiation. With this method, the risk per unit dose is obtained as a product of three quantities, namely, the baseline frequency of the disease class under consideration, the relative mutation risk (which is the reciprocal of the doubling dose, which in turn, is calculated as a ratio of spontaneous and induction rates of mutations) and mutation component, i.e., the responsiveness of the disease class to an increase in mutation rate. The estimates of baseline frequencies of mendelian diseases that are currently used in risk estimation date back to the late 1970s. Advances in human genetics during the past two decades now permit an upward revision of these estimates. The revised estimates are 150 per 10(4) livebirths for autosomal dominants (from the earlier estimate of 95 per 10(4)), 75 per 10(4) livebirths for autosomal recessives (from 25 per 10(4)) and to 15 per 10(4) livebirths for X-linked diseases (from 5 per 10(4)). The revised total frequency of mendelian diseases is thus 240 per 10(4) livebirths and is about twice the earlier figure of 125 per 10(4) livebirths. All these estimates, however, pertain primarily to Western European and Western European-derived populations. The fact that in several population isolates or ethnic groups, some of these diseases (especially the autosomal recessives) are more common as a result of founder effects and/or genetic drift is well known and many more recent examples have come to light. These data are reviewed and illustrated with data from studies of the Ashkenazi Jewish, Finnish, French Canadian, Afrikaner and some other populations to highlight the need for caution in extrapolating radiation risks between populations. The doubling dose of 1 Gy that has been used for the past 20 years for risk estimation is based on mouse data for both spontaneous and induction rates of mutations. In extrapolating the mouse-data-based doubling dose to humans, it is assumed that the spontaneous rates in mice and humans are similar. This assumption is incorrect because of the fact that in humans, for several well-studied mendelian diseases, the mutation rate differs between the two sexes and it increases with paternal age. In estimates of spontaneous mutation rates in humans (which represent averages over both sexes), however, paternal age effects are automatically incorporated. In the mouse, these effects are expected to be much less (if they exist at all), but the problem has not been specifically addressed. The complexities and uncertainties associated with assessing the potential impact of spontaneous mutations which arise as germinal mosaics (and which can result in clusters of mutations in the following generation) on mutation rate estimates (in the mouse) and on mutation rate estimates and disease frequencies (in humans) are discussed. In view of (i) the lack of comparability of spontaneous mutation rates in mice and humans and (ii) the fact that these estimates for human genes already include both paternal age effects and correction for clusters (if they had occurred), it is suggested that a prudent procedure now is to base doubling dose calculations on spontaneous mutation rates of human genes (and induction rates of mouse genes, in the absence of a better alternative). This concept, however, is not new and was used by the US National Academy's Committee on the Biological Effects of Ionizing Radiation in its 1972 report.

Effect of Exposure to Low Levels of Ozone on the Response to Inhaled Allergen in Allergic Asthmatic Patients

In a previous study published by our group, six out of nine subjects with mild allergic asthma were shown to have an enhanced response to allergen challenge following a 1-h exposure in an 0.8-m3 exposure chamber (modified from a body plethysmograph) to an average of 120 parts per billion (ppb) ozone at rest. Other studies failed to confirm this effect. In the present study, using a similar design, we reexamined this effect using a larger group of asthmatics and a larger chamber allowing minimal fluctuations in ozone levels during exposures. Prospective, randomized single-blinded crossover study. Pulmonary function laboratory equipped with an exposure chamber. Fifteen subjects had mild allergic asthma; 9 men and 6 women; the mean (SD) age was 32.5 (10) years; FEV1 was 3.4 (0.8) L; baseline methacholine provocation concentration causing a 20% fall in FEV1 was (PC20) 3.28 (4.1) mg/mL. Each participant was exposed, at rest, on 1 day to filtered air and on another day to ozone (mean level=120 ppb) in a larger exposure chamber than the one used in our first study with less variability in ozone level (110 to 130 vs 85 to 175 ppb) using a random, single-blinded design. After each exposure, the subject was challenged with allergen (nine with grass pollen extract and six with ragweed extract) and allergen PC15 was measured. Ozone preexposure did not affect allergen PC15 when compared with clean air preexposure (allergen PC15 dilution 1/114 vs 1/119, respectively). Ozone vs air preexposure resulted in an allergen PC15 that was lower in five subjects, higher in six, and unchanged (within one doubling dose) in four. At this low level with less variability and lower peaks than our previous study, ozone had no significant effect on airway allergen responsiveness.

The human corpus luteum: reduction in macrophages during simulated maternal recognition of pregnancy.

It has been shown that immune cells, particularly macrophages, accumulate in the corpus luteum during luteolysis. This study aimed to investigate the effect of maternal recognition of pregnancy on the localization and numbers of macrophages in the human corpus luteum. Corpora lutea (n = 12) were obtained from normally cycling women at the time of hysterectomy and were dated on the basis of serial urinary luteinizing hormone (LH) estimation. In addition, corpora lutea (n = 4) were collected from women who had received daily doubling doses of human chorionic gonadotrophin (HCG) to mimic the hormonal changes of early pregnancy. Macrophages were localized by immunohistochemistry using an anti-CD68 antibody. Steroidogenic cells, steroidogenic cells of thecal origin and endothelial cells were identified on serial sections by immunohistochemistry for 3beta-hydroxysteroid dehydrogenase, 17alpha-hydroxylase and von Willebrand factor, respectively. The luteal cells capable of responding directly to HCG were identified by isotopic in-situ hybridization for messenger RNA encoding LH/HCG receptors. Macrophages were localized primarily to the vascular connective tissue and theca-lutein areas of the corpus luteum, although some were found in the granulosa-lutein cell layer. Macrophage numbers increased throughout the luteal phase to a maximum in the late-luteal phase (P < 0.05). Luteal 'rescue' with HCG was associated with a marked reduction in the numbers of tissue macrophages when compared with those of the late-luteal phase (P < 0.001). One of the effects of HCG during maternal recognition of pregnancy is to prevent the normal influx of macrophages into the corpus luteum. As LH/HCG receptors localized to the steroidogenic cells, this implies a fundamental role for steroidogenic cell products in the control of macrophage influx into the human corpus luteum.

Increase in non-specific bronchial hyperresponsiveness without specific response to isocyanate in isocyanate-induced asthma: a pilot study

Increased non-specific bronchial hyperresponsiveness (BHR) has been reported after positive reaction to isocyanates in patients with isocyanate-sensitive asthma. The increased responsiveness may, however, also precede the asthma attack. We therefore compared non-specific BHR to a cholinergic agent before and after exposure to toluenediisocyanate (TDI) that induced no asthma symptoms in 11 workers with isocyanate-related asthma. Patients were exposed for 3 consecutive days to progressively increasing doses of TDI (5, 10, and 20 ppb min −1 for 20 min) in an exposure chamber with continuous TDI monitoring. No immediate nor late asthmatic bronchial reaction was observed in any patient after any dose of TDI during or after challenge. A significant increase in non-specific BHR was noted 24 h after the last dose of TDI challenge, however. This increase was at least one doubling dose for seven of 11 patients. In conclusion, our study shows that, in patients with isocyanate-induced asthma, exposure to TDI induces a slight but significant increase in non-specific BHR in the absence of any immediate or late bronchial response to isocyanate. This result, which requires further confirmation, may justify a proposal to measure non-specific BHR, even after a negative specific inhalation test to TDI, as an additional diagnostic element for TDI-induced occupational asthma, to help lower the percentage of the undetected occupational asthma cases.

Pranlukast, a cysteinyl leukotriene receptor antagonist, attenuates allergen-induced early- and late-phase bronchoconstriction and airway hyperresponsiveness in asthmatic subjects

Background: The cysteinyl leukotrienes (cysLTs) have been implicated in the pathogenesis of allergen-induced airway responses. The purpose of this study was to evaluate the effects of pretreatment with the cysLT receptor antagonist pranlukast on allergen-induced early asthmatic responses (EARs) and late asthmatic responses (LARs) and on allergen-induced airway hyperresponsiveness (AHR). Methods: Ten atopic, nonsmoking patients with mild asthma and previously demonstrated early- and late-phase allergen-induced asthmatic responses participated in a double-blind, placebo-controlled, cross-over study, comparing treatment with either 450 mg pranlukast given twice daily or placebo for 5.5 days. A methacholine challenge was performed before administration of medication, and the result was expressed as the PC 20. An allergen inhalation challenge was performed on the morning of the fifth day of treatment 2 hours after administration of medication. Methacholine challenges were also performed 2 hours after medication on days 4 and 6 (24 hours before and 24 hours after allergen administration) to examine allergen-induced AHR. Results: Pranlukast attenuated allergen-induced early responses, late responses, and AHR. The mean (SEM) maximal percent fall in FEV 1 from baseline during the early response was 30.0% (5.1%) during placebo treatment and 15.5% (3.5%) during pranlukast treatment (mean difference, 14.5%; 95% confidence interval [CI], 5.3 to 23.7; P = .007), with a mean protection afforded by pranlukast of 48.3%. The mean maximal percent fall in FEV 1 during the late response was 34.7% (5.3%) during placebo treatment and 24.0% (4.4%) during pranlukast treatment (mean difference, 10.7%; 95% CI, 4.1 to 17.3; P = .006), with a mean protection afforded by pranlukast of 30.8%. The mean allergen-induced shift in PC 20 was –1.76 (0.32) doubling doses during placebo treatment and –0.38 (0.31) doubling doses during pranlukast treatment (mean difference, –1.38 doubling doses; 95% CI, 0.44 to 2.32; P = .012), with a mean protection afforded by pranlukast of 78.4%. Conclusion: These results demonstrate that pranlukast can attenuate allergen-induced early and late airways responses and AHR and adds further support for an important role for the cysLTs in mediating allergen-induced asthmatic responses. (J Allergy Clin Immunol 1998;102:177-83.)

Possible interaction between exposure to environmental tobacco smoke and therapy in children with asthma

1. The aim of the study was to determine the carbachol and albuterol responsiveness in treated and untreated asthmatic and allergic children exposed to environmental tobacco smoke assessed by urinary cotinine measurements. 2. Forty-six asthmatic and allergic children with normal spirometric values were recruited. The doubling dose, concentration of carbachol producing a 2-fold increase in specific airway resistance (SRaw) was determined and 200 micrograms of albuterol were administered via a Volumatic(R) spacer. The percentage of bronchodilatation was defined as the difference between the largest obtained SRaw and the post-beta2 SRaw divided by the largest SRaw. Data were compared by a Mann-Whitney U-test. 3. The 23 children with a high urinary cotinine, compared with the 23 children without urinary cotinine, had a decreased doubling dose (108.2+/-14.7 micrograms versus 160.9+/-19.5 micrograms; P=0.04) and an increased percentage of bronchodilatation (74.8+/-1.4% versus 68.8+/-1.8%; P=0.03). A prophylactic anti-inflammatory treatment induced a weaker bronchial reactivity to carbachol and a slightly greater bronchodilatation in children exposed to environmental tobacco smoke. 4. Environmental tobacco smoke increases bronchial reactivity in asthmatic and allergic children. This effect might be reduced by anti-inflammatory therapy. The bronchodilator response may be enhanced in exposed children and may be caused by one or several direct interactions between tobacco smoke compounds and albuterol.

The Effect of Luteal “Rescue” on the Expression and Localization of Matrix Metalloproteinases and Their Tissue Inhibitors in the Human Corpus Luteum

Luteolysis is associated with tissue remodeling probably involving the matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs). This study investigated the expression and localization of the major MMPs and TIMPs in the human corpus luteum throughout the luteal phase and after luteal rescue with hCG. Corpora lutea (n = 9) were collected at hysterectomy and were dated by serial urinary LH estimation. In addition, corpora lutea (n = 3) were collected from women who had received daily doubling doses of hCG to mimic the hormonal changes of early pregnancy. MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2, and TIMP-3 were investigated by zymography, reverse zymography, Northern blotting, and in situ hybridization. There was no change in the expression of MMP-1, TIMP-1, and TIMP-2 throughout the luteal phase or after luteal rescue. Little TIMP-3 could be detected in the corpus luteum. MMP-9 activity peaked in the early and late luteal phase. The expression and activity of MMP-2 were maximal in the late luteal phase. Exposure to hCG during luteal rescue in vivo was associated with a reduction (P < 0.05) in the expression and activity of MMP-2. Messenger ribonucleic acids (mRNAs) for MMP-1, MMP-2, and TIMP-2 were localized to the connective tissue stroma and the thecal-lutein cells of the corpus luteum. In contrast, TIMP-1 mRNA was localized to the granulosa-lutein cells, and MMP-9 mRNA was expressed in scattered cells within the steroidogenic and nonsteroidogenic cell layers. In conclusion, during maternal recognition of pregnancy, hCG prevents the normal increase in MMP-2 in the late luteal phase. MMPs can function in an environment containing large amounts of TIMP-1, as they have a different cellular localization.

Effect of endogenous nitric oxide inhibition on airway responsiveness to histamine and adenosine-5′-monophosphate in asthma

BACKGROUNDNitric oxide (NO) may be bronchoprotective in asthma, possibly due to a direct action on airway smooth muscle or through mast cell stabilisation. To investigate this the effects of two...

Stage specificity, dose response, and doubling dose for mouse minisatellite germ-line mutation induced by acute radiation.

Germ-line mutation induction at mouse minisatellite loci by acute irradiation with x-rays was studied at premeiotic and postmeiotic stages of spermatogenesis. An elevated paternal mutation rate was found after irradiation of premeiotic spermatogonia and stem cells, whereas the frequency of minisatellite mutation after postmeiotic irradiation of spermatids was similar to that in control litters. In contrast, paternal irradiation did not affect the maternal mutation rate. A linear dose-response curve for paternal mutation induced at premeiotic stages was found, with a doubling dose of 0.33 Gy, a value close to those obtained in mice after acute spermatogonia irradiation using other systems for mutation detection. High frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be evaluated at low doses of exposure in very small population samples, which currently makes minisatellite DNA the most powerful tool for monitoring radiation-induced germ-line mutation.

An overview of nine clinical trials of salmeterol in an asthmatic population

In an attempt to establish the protection afforded by regular salmeterol use against induced bronchoconstriction in asthmatic patients, a meta-analysis was conducted on nine double-blind clinical trials that fulfilled the inclusion criteria. In each trial, subjects were randomly assigned to receive either salmeterol 50 μg twice daily or a comparator (placebo or salbutamol). Two hundred and twenty-five asthmatic subjects had at least one PC 20 or PD 20 (histamine or methacholine concentration or dose producing 20% fall in forced expiratory volume in 1 s) measurement recorded within 1 h to 16 weeks after the first dose, and up to 31 days after the last dose, of medication. One hour after the first dose of salmeterol, there was a 3·5-fold increase in doubling dose compared to baseline. Within 12 h of the first dose, the level of protection was 1·5 doubling doses, and protection was maintained at 0·5–1·5 doubling doses over 16 weeks' treatment. This level of protection was maintained for up to 60 h after the last dose. At no time during the washout period did the level of protection fall below zero. Salmeterol afforded significantly greater protection at all time points during the treatment period than comparator agents, but there was no significant difference during the washout period. In conclusion, salmeterol affords protection against bronchoconstrictor stimuli, and any reduction in this bronchoprotective effect occurred during the first few days of treatment. During long-term salmeterol treatment, there was maintained significant protection that showed no evidence of attenuation after 16 weeks' treatment. Furthermore, there was no evidence of rebound deterioration in bronchial responsiveness after cessation of salmeterol treatment.

A comparison of regular salmeterol vs ‘as required’ salbutamol therapy in asthmatic children

In a multicentre, double-blind, randomized, parallel study, 426 asthmatic children aged 5–15 years old received salmeterol 50 μg b.i.d. or placebo b.i.d. via the Diskhaler™. All patients had access to inhaled salbutamol to be used on an ‘as required’ (p.r.n.) basis for symptomatic relief. The study design comprised a 2-week baseline, a 12-month treatment period incorporating a 2-week ‘off treatment’ after 6 months, and a 2-week follow-up period at the end of the trial. At the end of 12 months of treatment with salmeterol, the adjusted change from baseline for morning and evening peak expiratory flow rate (PEF) was 56 and 471 min −1, respectively, and this was significantly greater than placebo ( P<0·01; P<0·05). Exacerbation rates did not differ between groups and results were not dependent upon concurrent inhaled steroid use. Neither treatment caused a change of ≥ 1 doubling dose in PC 20 PD 20 either during or on stopping treatment. Treatment with regular salmeterol 50 μg b.i.d. over a 12-month treatment period provides a significant, rapid and well-maintained improvement in lung function without increasing bronchial reactivity or asthma exacerbation rates compared to p.r.n. salbutamol.

Discovery of numerous clusters of spontaneous mutations in the specific-locus test in mice necessitates major increases in estimates of doubling doses.

Both the precision with which mutations can be quickly identified and the extensive application of the method make results from specific-locus experiments in mice especially important for estimating the doubling dose, which is the radiation exposure that induces a mutation frequency equal to the total spontaneous mutation frequency per generation. Because of gonadal mosaicism and the mechanism by which it occurs, the frequency with which new spontaneous mutations occur per generation is much higher than has been thought. While it will be some time before many of the newly-apparent uncertainties related to understanding this phenomenon can be resolved, consideration of what is known suggests that it would already be reasonable to raise the doubling dose from 1 to 5 Gy for low-dose-rate exposures to X and gamma radiation. Doing so would reduce risk estimates made by the doubling-dose method fivefold. Because the doubling dose for chemical mutagens is also calculated by division of the total spontaneous mutation frequency per generation by the induced mutation frequency per unit of chemical exposure, hereditary risks for chemicals have also been considerably overestimated if they are based on specific-locus data.

Major impacts of gonadal mosaicism on hereditary risk estimation, origin of hereditary diseases, and evolution.

The specific-locus test in mice is by far the most extensively applied method for precisely defining gene mutation frequencies in mammals. Computer simulations of control experiments involving 57.4 million offspring, based on vast amounts of historical data, show that because of gonadal mosaicism, the total frequency of spontaneous mutations per generation is much higher than has been thought. The estimated combined spontaneous mutation frequency for both sexes for the seven genes tested in specific-locus experiments is 39.6 x 10(-5) mutation/gamete. Division of this frequency by the combined induced mutation frequencies in parents of both results in an estimate of the doubling-dose (DD) of from 5.4 to 7.7 Gy. For decades, the DD has been thought to be about 1 Gy. As the DD increases, estimates of hereditary risk that are based upon it decrease. Thus, one important ramification of this new understanding is that estimates of the hereditary risk to humans from radiation, commonly made by the doubling-dose (DD) approach, are probably at least five times too high. It also appears that gonadal mosaicism is likely to play a much more important role both in evolution and the origin of hereditary diseases than has been appreciated in the past.