P129 Quantification of longitudinal joint and cartilaginous changes within ankles with haemophilia joint degeneration using MRI imaging

Background/Aims

Haemophilia is an X-linked recessive genetic disorder characterised by episodes of spontaneous and traumatic intra-articular bleeding. 90% of bleeds are of musculoskeletal origin, with the ankle being most affected joint. Recurrent bleeding results in haemosiderin accumulation, linked to progressive, end-stage ankle haemarthropathy in adolescent and adult patients. Magnetic Resonance Imaging (MRI) is gold-standard for the evaluation of early soft tissue and cartilage changes in ankles with haemarthropathy. This study utilised MRI sequences to quantify longitudinal changes within the ankle joint, via changes in cartilage thickness (CT), subchondral thickness (ST) and joint space width (JS) over time.

Methods

Clinical T1 Sagittal MRI scans of HJD ankles were selected (N = 5). Each patient had a minimum of two MRI scans available, at least one year apart, to allow for comparison of longitudinal changes. All images were identity coded but fully anonymised. The earliest available and most recent MRI scan were measured in three slices (medial, lateral and middle slice) and at different points along the joint space (anterior, middle and posterior). Measurements taken were cartilage thickness on the talar dome (CT) and the distance between the subchondral bone of the tibial plafond and talar dome (ST). The joint space width (JS) was then determined by subtracting CT from ST.

Results

Chondral thickness measurements showed most reduction, particularly at the antero-lateral aspect (-0.4mm) compared to the antero-medial and middle sections, with -0.24mm and -0.34mm (Table 1). ST and JS reduction was predominantly seen in the anterior joint, with most reduction in antero-lateral joint (-1.13mm). The posterior joint showed minimal reduction in the postero-medial and middle sections, with the posterior-lateral joint space width increasing (0.2mm). Subchondral thickness and joint space measurements were variable and did not demonstrate linear change over time.

Conclusion

A systematic longitudinal decrease in cartilage thickness was seen in the antero-lateral and antero-medial aspect of the ankle joint. The antero-lateral aspect of the ankle showed the greatest reduction in joint space and cartilage thickness. This suggests that this area of the joint is likely to provide the best early indications of haemarthropathy when using MRI as a diagnostic tool.

Disclosure

M. Schaper: None. M. Sharrock: None. R.A. Wilkins: None. A.C. Redmond: None.

Preliminary image findings of lower limb stress fractures to aid ultrasonographic diagnoses: A systematic review and narrative synthesis

INTRODUCTION

This systematic review investigates which image appearances are most common when diagnosing lower limb stress fractures using ultrasound imaging, with the aim of outlining an image critique guideline for operators to support confident diagnoses.

METHOD

A comprehensive literature search of medical databases and handsearching was undertaken to identify relevant studies. All studies were critically examined for quality using the CASP critical appraisal tool. Results from eight studies were combined and interpreted using a narrative synthesis.

FINDINGS

A clear outline of common stress fracture appearances using ultrasound were identified in a combined total of 119 participants. Each finding was ranked according to its popularity. Periosteal thickening (78/119) and cortical disruption/irregularity (83/119) were noted in all eight studies. Hypervascularity of the periosteum visualised by colour Doppler imaging (66/119) was reported in six of the eight studies. Soft tissue hypervascularity (13/119), bony callus formation (5/119) and cortical break (22/119) were seen in three studies.

CONCLUSIONS

Based on the findings, we offer a guideline of the most significant preliminary image findings to be utilised by operators when examining athletes suspected of having lower limb stress fractures. The results show a gap in research for evaluating changes in appearance depending on the injury severity. Further research into distinguishing stress fractures from pathological involvement may in future reduce reliance on plain film radiography.

[Fax Survey to Elucidate the Information Needs of General Practitioners in Lower Saxony Regarding the Topic of Medical Implants]

Background: Medial implants help a multitude of patients to gain more health, mobility and thus, quality of life. In collaboration with a still growing expectation of life especially, i.e., within Western industrial countries, this has led to an increasing use of implants over the last years. However, although biomechanical characteristics of modern implant materials have improved considerably, one big challenge still exists - the implant-associated infection. Early diagnostic and therapeutic interventions could clearly mitigate this issue, but are general practitioners sufficiently informed regarding this topic? Material and Methods: In March 2013 and in close cooperation with the Lower Saxony association of general practitioners, we initiated a survey to elucidate the information demands of general practitioners regarding the topic of medical implants. A total of 939 members of the association were contacted via fax and 101 (10.8 %) responded. Based on the obtained data, we then evaluated which topics are most interesting for this group of medical professionals. Results: The survey clearly indicates that general practitioners request more general implant-related data, e.g., type and specification of an implant as well as its location within the individual patient and contact addresses of the implanting hospital, but also want more specific information regarding diagnostic and therapeutic strategies in the case of implant-associated complications. Conclusion: The present article reports in detail on the conducted fax survey and shows some initial strategies as to how the identified challenges might be faced.

Clinical outcome of acute and chronic hepatitis delta over time: a long-term follow-up study

Long-term changes in the frequency and outcome of hepatitis delta virus (HDV) infection have seldom been analysed. This retrospective, longitudinal study includes 398 consecutive hepatitis B surface antigen (HBsAg)-positive patients with anti-HDV antibodies who attended our institution between 1983 and 2008. At enrolment, 182 patients had acute and 216 chronic hepatitis. Patients were grouped into two periods. Those who attended between 1983 and 1995 and those between 1996 and 2008. The former group was significantly younger, mainly intravenous drugs users, and had a greater incidence of acute HDV and HIV and HCV coinfection. Patients with acute HBV/HDV coinfection cleared both infections in 90% of cases, while all patients with HDV superinfection evolved to chronic disease. One hundred and fifty-eight patients with chronic HDV were followed for a median period of 158months. Seventy-two per cent of the patients remained stable, 18% had hepatic decompensation, 3% developed hepatocellular carcinoma, and 8% cleared HBsAg. Liver-related death was observed in 13% of patients and mainly occurred in patients from the first period (P=0.012). These results indicate an outbreak of HDV at the end of the 1980s and the beginning of the 1990s, with a large number of acute HDV cases affecting predominately young, male intravenous drug users. Currently, patients with chronic HDV disease are older, and factors associated with worse prognosis include the presence of cirrhosis and age at the time of diagnosis.

Main mutations in the hepatitis B virus basic core promoter (A1762T/G1764A) before HBeAg loss are markers that identify patients who will require long-term treatment

BACKGROUND

Some patients continue to have detectable HBV-DNA levels with liver disease progression after hepatitis B e antigen (HBeAg) loss. It is important to identify these patients, candidates for long-term treatment.

AIMS

To evaluate hepatitis B virus (HBV) genotype and the main mutations in the basic core promoter (BCP, A1762T/G1764A) and precore (G1896A) sequences as markers of persistent HBV-DNA after HBeAg loss.

METHODS

We analysed 60 serum samples from 20 Caucasian, HBeAg-positive, chronic hepatitis B patients, who lost HBeAg and were followed-up longitudinally. HBV genotype and precore and BCP mutations were determined before, at the time of, and after HBeAg loss.

RESULTS

After HBeAg loss, eight (40%) patients continued to have undetectable HBV-DNA and 12 (60%) had persistent HBV-DNA (median level 4.7 log(10) copies/mL). The presence of BCP mutations prior to therapy was the only variable associated with persistently detectable viraemia (P = 0.017). Four patients with genotype A and no mutations in the BCP region experienced hepatitis B surface antigen (HBsAg) loss after a mean period of 35 months from baseline.

CONCLUSIONS

Main BCP mutations in HBeAg-positive patients are useful markers to identify patients who will not have sustained virological suppression after HBeAg loss and therapy discontinuation and could benefit from long-term treatment.

Cytopathological screening in indigenous women from Parque Indigena do Xingu

Over the years, there have been many deaths due to cervical cancer among indigenous women of the Parque Indigena do Xingu as a consequence of low screening coverage. Since 2005, however, the coverage index of cervical lesion screening has been high: 97.6% among at-risk women in 2005 and 92.6% in 2007. Cytological alterations occurred in 12.6% and 6% of the cases in the respective years. After complete diagnosis and treatment of uterine lesions, by staff trained in lower tract pathology, negative results were seen in all cases of high-grade lesions and invasive neoplasia and no case of invasive carcinoma was detected in 2007. We conclude, therefore, that health actions have been effective in decreasing the incidence of cytological alterations and invasive carcinoma.

Uterine cervical neoplasia prevention in Parque Indigena do Xingu

Results of preventive health measures, diagnosis and treatment applied to Parque Indigena do Xingu native women were studied. Thirty-seven cases of uterine cervical intraepithelial lesions and invasive neoplasias were treated in the local villages without referral to an advanced medical center. LEEPs were carried out in 32 women, three cold knife conizations, one vaginal hysterectomy and one Wertheim Meigs procedure. Results of 53.1% of LEEP surgical procedures did not have margin involvement by the lesions. Bleeding complications were seen in 15.6%. Regular follow-up with two or three cytologic and colposcopic tests in 32 women was carried out. All cases were negative for lesions. Five women were not followed-up due mainly to logistical reasons. Health endeavors adopted in the period 2005-2007 brought about a significant reduction of precursor lesions in this native aboriginal population without screening resources.

Hepatitis B virus polymerase variants associated with entecavir drug resistance in treatment-naive patients

It has been suggested that lamivudine therapy can preselect for hepatitis B virus (HBV) variants associated with resistance to entecavir (ETV) treatment. The aim of this study was to determine the prevalence of HBV variants associated with ETV resistance (rtI169T, rtT184G, rtS202I, rtM250V) in naive patients before and during lamivudine therapy. This retrospective study includes 111 untreated patients with chronic HBV infection, who were later treated with lamivudine therapy for at least 18 months. Serum samples were obtained before and during treatment. Variants related with ETV drug resistance were analysed by sequencing the HBV reverse transcriptase. Prior to lamivudine treatment, three cases (2.7%) had substitutions in the HBV polymerase gene corresponding to variants associated with ETV resistance (rtS202S/I). None of these patients had lamivudine-resistant variants. During lamivudine treatment, substitutions associated with ETV resistance were detected in 10 (9%) nonresponding patients who had not presented these changes before treatment. In 2/10 cases, these changes were observed before detection of lamivudine-resistant substitutions. In 10 of 12 nonresponders, one of them with ETV-related variants prior to treatment, these variants persisted to the end of therapy. Detection of variants related to ETV drug resistance in untreated patients with chronic HBV infection indicates that these variants are present in a significant proportion of the HBV quasispecies. This fact, as well as the emergence of ETV-resistant variants during lamivudine treatment, should be kept in mind when selecting candidates for ETV therapy.

Hepatitis B virus polymerase variants associated with entecavir drug resistance in treatment-naive patients

It has been suggested that lamivudine therapy can preselect for hepatitis B virus (HBV) variants associated with resistance to entecavir (ETV) treatment. The aim of this study was to determine the prevalence of HBV variants associated with ETV resistance (rtI169T, rtT184G, rtS202I, rtM250V) in naive patients before and during lamivudine therapy. This retrospective study includes 111 untreated patients with chronic HBV infection, who were later treated with lamivudine therapy for at least 18 months. Serum samples were obtained before and during treatment. Variants related with ETV drug resistance were analysed by sequencing the HBV reverse transcriptase. Prior to lamivudine treatment, three cases (2.7%) had substitutions in the HBV polymerase gene corresponding to variants associated with ETV resistance (rtS202S/I). None of these patients had lamivudine-resistant variants. During lamivudine treatment, substitutions associated with ETV resistance were detected in 10 (9%) nonresponding patients who had not presented these changes before treatment. In 2/10 cases, these changes were observed before detection of lamivudine-resistant substitutions. In 10 of 12 nonresponders, one of them with ETV-related variants prior to treatment, these variants persisted to the end of therapy. Detection of variants related to ETV drug resistance in untreated patients with chronic HBV infection indicates that these variants are present in a significant proportion of the HBV quasispecies. This fact, as well as the emergence of ETV-resistant variants during lamivudine treatment, should be kept in mind when selecting candidates for ETV therapy.

Hepatitis B virus genotypes and G1896A precore mutation in 486 Spanish patients with acute and chronic HBV infection

This study aims to determine the prevalence of hepatitis B virus (HBV) genotypes (A-F) and their association with the G1896A precore mutation in 486 patients positive for HBV surface antigen. Genotypes were determined by RFLP and precore mutation by real-time PCR. Genotypes D (48.1%) and A (39.5%) were the most common, followed by F (4.1%) and B, C and E (<1%). The A to D ratio (A:D) was 1.4 in HBeAg+ chronic hepatitis B (CHB), 0.6 in HBeAg- CHB and 1.4 in HBeAg- inactive carriers. Distribution of these genotypes was different between HBeAg+ CHB and HBeAg- CHB (P = 0.02), and between HBeAg- CHB and HBeAg- inactive carriers (P = 0.009). Genotype A was the most prevalent in HBeAg+ CHB with elevated alanine aminotransferase (ALT) (68.6%) and genotype D in HBeAg+ CHB with fluctuating ALT (60.7%). There was a difference in genotype prevalence between chronic and acute infection (P = 0.03). The precore mutant correlated with high levels of HBV-DNA in genotype d HBeAg- CHB. Genotype D is not as highly prevalent in Spanish patients as would be expected in a Mediterranean area. The unequal prevalence of genotypes between acute and chronic infection suggests that genotype A is associated with a higher tendency to cause chronic infection.

Changes in different regions of hepatitis B virus gene in hepatitis B 'e' antigen-negative patients with chronic hepatitis B: the effect of long-term lamivudine therapy

BACKGROUND

Lamivudine therapy for chronic hepatitis B has been associated with changes in different regions of the hepatitis B virus nucleotide sequence.

AIM

To study changes in the sequences of polymerase and precore/core promoter regions of hepatitis B virus, before and during 5 years of therapy with lamivudine.

METHODS

Eighty consecutive samples were taken from 10 chronic hepatitis B 'e' antigen-negative patients.

RESULTS

Nine patients carried hepatitis B virus precore mutations during the study. Before therapy, wild type was replaced by A1896 in two (20%) cases. During treatment, A1896 reverted transitory to wild type in five cases (50%) and in one case wild type was replaced by A1896. The continuous detection of precore mutations during therapy was associated with a lower response rate. YMDD mutations were observed in nine cases and both, L180M and M204V/I mutations were simultaneously detected in six cases. About 75% of the patients with M204V mutations were responders and none with M204I or mixed pattern sustained response.

CONCLUSION

Hepatitis B 'e' antigen-negative patients exhibit changes in the precore regions both spontaneously and under lamivudine therapy, the transitory reversion to wild type being most frequently witnessed. Patients carrying M204V mutations are more likely to respond to therapy. If, in further studies, these results are confirmed some patients with YMDD mutations could benefit from prolonging the duration of lamivudine therapy.

Comparative resistance of phage isolates of four genotypes of f-specific RNA bacteriophages to various inactivation processes

The effect of natural inactivation in freshwater, chlorination, ammonia, extreme pHs, temperature, and salt content on phage inactivation was evaluated on mixtures of F-specific RNA bacteriophage isolates belonging to genotypes I, II, III, and IV. The bacteriophages studied were previously but recently isolated from natural samples, characterized as F-specific RNA bacteriophages and genotyped by plaque hybridization with genotype-specific probes. Natural inactivation in river water was modeled by in situ incubation of bacteriophages inside submerged dialysis tubes. After several days bacteriophages of genotype I showed the highest persistence, which was significantly different from that of bacteriophages of genotype II, IV, or III. The pattern of resistance of phages belonging to the various genotypes to extreme pHs, ammonia, temperature, salt concentration, and chlorination was similar. In all cases, phages of genotype I showed the highest persistence, followed by the phages of genotypes II, III, and IV. The phages of genotypes III and IV were the least resistant to all treatments, and resistance of genotypes III and IV to the treatments was similar. Bacteriophages of genotype II showed intermediate resistance to some of the treatments. The resistance of four phages of genotype I to natural inactivation and chlorination did not differ significantly. These results indicate that genotypes III and IV are much more sensitive to environmental stresses and to treatments than the other genotypes, especially than genotype I. This should be taken into consideration in future studies aimed at using genotypes of F-specific RNA bacteriophages to fingerprint the origin of fecal pollution.

Distribution of genotypes of F-specific RNA bacteriophages in human and non-human sources of faecal pollution in South Africa and Spain

AIMS

To assess whether the distribution of genotypes of F-specific RNA bacteriophages reflects faecal pollution of human and animal origin in water environments.

METHODS AND RESULTS

Stool samples, animal feedlot waste slurries and a wide variety of faecally polluted waters were studied in South Africa and Spain. Genotyping was performed by plaque and spot hybridization with genotype-specific probes. Only genotypes II and III were detected in human stool. Animal faeces contained predominantly, but not exclusively, genotypes I and IV. Raw hospital and municipal sewage contained mostly genotypes II and III, whereas genotypes I and II prevailed in settled sewage, secondary treated sewage and non-point diffuse effluents from developing communities. Abattoir wastewaters contained mostly genotypes I and IV. No differences were observed between the distribution of genotypes in Spain and South Africa.

CONCLUSIONS

Although the association of genotypes II and III with human excreta and I and IV with animal excreta was statistically significant, the results suggest that the association cannot be used for absolute distinction between faecal pollution of human and animal origin.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study contributes greatly to understanding the usefulness of genotypes of F-specific RNA bacteriophages in source tracking of faecal wastes.

Immunodetection of 3-nitrotyrosine in the liver of zymosan-treated rats with a new monoclonal antibody: comparison to analysis by HPLC

Zymosan-induced peritonitis is associated with an increased production of reactive nitrogen oxides that may contribute to the often-observed failure of multiple organ systems in this model of acute inflammation. Quantitative biochemical evidence is provided for a marked 13-fold increase in protein-bound 3-nitrotyrosine (NTyr), a biomarker of reactive nitrogen oxides, in liver tissue of zymosan-treated rats. In order to investigate the localization of NTyr in this affected tissue, a monoclonal antibody, designated 39B6, was raised against 3-(4-hydroxy-3-nitrophenylacetamido) propionic acid-bovine serum albumin conjugate and its performance characterized. 39B6 was judged by competition ELISA to be approximately 2 orders of magnitude more sensitive than a commercial anti-NTyr monoclonal antibody. Binding characteristics of 39B6 were similar, but not identical, to that of a commercial affinity-purified polyclonal antibody in ELISA and immunohistochemical analyses. Western blot experiments revealed high specificity of 39B6 against NTyr and increased immunoreactivity of specific proteins from liver tissue homogenates of zymosan-treated rats. Immunohistochemical analysis of liver sections indicated a marked zymosan-induced increase in immunofluorescent staining, which was particularly intense in or adjacent to nonparenchymal cells, but not in the parenchymal cells of this tissue. Quantitative analysis of fractions enriched in these cell populations corroborated the immunofluorescent data, although the relative amounts detected in response to zymosan treatment was greatly reduced compared to whole liver tissue. These results demonstrate the high specificity of the newly developed antibody and its usefulness in Western blot and immunohistochemical analysis for NTyr, confirm the presence of NTyr by complementary methods, and suggest the possible involvement of reactive nitrogen oxides in hepatic vascular dysfunction.

Oxidative stress in brain during experimental bacterial meningitis: differential effects of alpha-phenyl-tert-butyl nitrone and N-acetylcysteine treatment

Antioxidant treatment has previously been shown to be neuroprotective in experimental bacterial meningitis. To obtain quantitative evidence for oxidative stress in this disease, we measured the major brain antioxidants ascorbate and reduced glutathione, and the lipid peroxidation endproduct malondialdehyde in the cortex of infant rats infected with Streptococcus pneumoniae. Cortical levels of the two antioxidants were markedly decreased 22 h after infection, when animals were severely ill. Total pyridine nucleotide levels in the cortex were unaltered, suggesting that the loss of the two antioxidants was not due to cell necrosis. Bacterial meningitis was accompanied by a moderate, significant increase in cortical malondialdehyde. While treatment with either of the antioxidants alpha-phenyl-tert-butyl nitrone or N-acetylcysteine significantly inhibited this increase, only the former attenuated the loss of endogenous antioxidants. Cerebrospinal fluid bacterial titer, nitrite and nitrate levels, and myeloperoxidase activity at 18 h after infection were unaffected by antioxidant treatment, suggesting that they acted by mechanisms other than modulation of inflammation. The results demonstrate that bacterial meningitis is accompanied by oxidative stress in the brain parenchyma. Furthermore, increased cortical lipid peroxidation does not appear to be the result of parenchymal oxidative stress, because it was prevented by NAC, which had no effect on the loss of brain antioxidants.

Comparison of methods for detecting genotypes of F-specific RNA bacteriophages and fingerprinting the origin of faecal pollution in water samples

The performance of Salmonella typhimurium WG49 and Escherichia coli HS(pFamp)R was compared on detecting the different genotypes of F-specific RNA bacteriophages by plaque hybridisation. The sensitivity of this assay was also compared with the sensitivity of RT-PCR followed by Southern blotting for detecting F-specific RNA bacteriophages belonging to genotype III in water. S. typhimurium WG49 detected slightly higher numbers of F-specific RNA bacteriophages than E. coli HS(pFamp)R both in mixtures of pure culture bacteriophage suspensions and in water samples. There were no differences between the two host strains with regard to detection of the four genotypes of F-specific RNA phages both in mixtures of pure culture bacteriophage suspensions and in environmental samples. In urban sewage samples, the host strains detected genotypes II and III as the predominant F-RNA bacteriophages. Plaque transfer to a N(+) hybond membrane and posterior hybridisation was easier using S. thyphimurium WG49 as the host strain. The efficiency of detection in sewage of genotype III F-specific RNA bacteriophages by RT-PCR was inferior to that of plaque hybridisation with the assay conditions described below. Hybridisation of plaques obtained on WG49 seems to be the most sensitive method to study the distribution of genotypes of F-specific RNA bacteriophages in water samples.

Transport of the new chemotherapeutic agent beta-D-glucosylisophosphoramide mustard (D-19575) into tumor cells is mediated by the Na+-D-glucose cotransporter SAAT1

For beta-D-glucosylisophosphoramide mustard (beta-D-Glc-IPM), a new alkylating drug in which isophosphoramide mustard is stabilized, a higher selectivity and lower myelotoxicity was observed than for the currently used cytostatic ifosfamide. Because beta-D-Glc-IPM is hydrophilic and does not diffuse passively through the lipid bilayer, we investigated whether a transporter may be involved in the cellular uptake. A variety of cloned Na+-sugar cotransporters were expressed in Xenopus oocytes, and uptake measurements were performed. By tracer uptake and electrical measurements it was found that beta-D-Glc-IPM was transported by the low-affinity Na+-D-glucose cotransporter SAAT1, which had been cloned from pig and is also expressed in humans. At membrane potentials between -50 and -150 mV, a 10-fold higher substrate affinity (Km approximately 0.25 mM) and a 10-fold lower Vmax value were estimated for beta-D-Glc-IPM transport than for the transport of D-glucose or methyl-alpha-D-glucopyranoside (AMG). Transport of beta-D-Glc-IPM and glucose by SAAT1 is apparently performed by the same mechanism because similar sodium dependence, dependence on membrane potential, electrogenicity, and phlorizin inhibition were determined for beta-D-Glc-IPM, D-glucose, and AMG. Transcription of human SAAT1 was demonstrated in various human carcinomas and tumor cell lines. In one of these, the human carcinoma cell line T84, phlorizin inhibitable uptake of beta-D-Glc-IPM was demonstrated with substrate saturation and an apparent Km of 0.4 mM. The data suggest that the Na+-D-glucose cotransporter SAAT1 transports beta-D-Glc-IPM into human tumor cells and may accumulate the drug in the cells. They provide an example for drug targeting by employing a plasma membrane transporter.

Structure-activity relationships of volatile organic chemicals as sensory irritants

We used a database of 145 volatile organic chemicals for which the sensory irritation potency (RD50) has been reported in mice. Chemicals were first separated into two groups: nonreactive and reactive, using Ferguson's rule. This rule suggests that nonreactive chemicals induce their effect via a physical (p) mechanism (i.e., weak forces or interactions between a chemical and a biological receptor). Therefore, appropriate physicochemical descriptors can be used to estimate their potency. For reactives, a chemical (c) mechanism (i.e., covalent bonding with the receptor) would explain their potency. All chemicals were also separated on the basis of functional groups and subgroups into 24 classifications. Our results indicated that the potency of nonreactive chemicals, regardless of their chemical structure, can be estimated using a variety of physicochemical descriptors. For reactive chemicals, we identified five basic reactivity mechanisms which explained why their potency was higher than that estimated from physicochemical descriptors. We concluded that Ferguson's proposed rule is adequate initially to classify two separate mechanisms of receptor interactions, p vs c. Several physicochemical descriptors can be used to estimate the potency of p chemicals, but chemical reactivity descriptors are needed to estimate the potency for c chemicals. At present, this is the largest database for nonreactive-reactive chemicals in toxicology. Because of the wide variety of c chemicals presented, a semi-quantitative estimate of the potency of new, or not previously evaluated, c chemicals can be arrived at via comparison with those presented and the basic chemical reactivity mechanisms presented.

Pharmacokinetics and whole-body distribution of the new chemotherapeutic agent beta-D-glucosylisophosphoramide mustard and its effects on the incorporation of [methyl-3H]-thymidine in various tissues of the rat

beta-D-Glucosylisophosphoramide mustard (beta-D-Glc-IPM) is a new, potential chemotherapeutic agent currently under investigation. Its pharmacokinetics in plasma and elimination of the parent drug and its metabolites via urine, bile, and exhaled air were studied in female Sprague-Dawley rats after bolus injection of 315 mg/kg. Typically, the drug's disposition from plasma follows a linear two-compartment model with half-lives (t1/2) of 1.8 (t1/2 alpha) and 32 min (t1/2 beta). The rate of clearance is 0.0046 (range 0.0030-0.0071) 1 min-1 kg-1, and the steady-state volume of distribution (Vss) is 0.18 (0.08-0.042) 1/kg (mean +/- inter-individual standard deviation). In human plasma, 28.1 +/- 2.6% (mean +/- SD) of the drug (concentration range 0.5-5 mg/ml) is bound to plasma proteins (predominantly to albumin). Biliary excretion of the parent drug accounts for 2.9 +/- 1.7% of the dose; its elimination in the form of 14CO2 via exhaled air is less than 1%. Within 24 h, 63.5 +/- 4.9% of the 14C-labeled drug is excreted unchanged in the urine, whereas 17.5 +/- 5.1% is excreted in the urine as metabolites. In addition, beta-D-Glc-[14C]-IPM was given as a bolus injection to female Sprague-Dawley rats at dose levels of 315 and 56.2 mg/kg. The distribution of radioactivity into tissue was examined qualitatively by whole-body autoradiography (WBA). Parallel experiments were carried out using the high dose of the L-derivative. After dosing with the D-compound, the highest levels of radioactivity were found in the liver, kidneys, thymus, thyroid gland, and central nervous system, including the brain. A similar distribution pattern was observed for the L-compound, except in the brain, which contained negligible levels of radioactivity. The distribution of the D-compound (high dose) was also investigated in male Copenhagen rats bearing a Dunning prostate tumor. The results were similar to those obtained in healthy Sprague-Dawley rats. Additionally, radioactivity was found in the tumor at 1 h after dosing with the drug and remained there even after 24 h. The effects of beta-D-Glc-IPM on the incorporation of [methyl-3H]-thymidine into the DNA of the liver, kidneys, thymus, spleen, esophagus, and bone marrow of the rat were examined following tissue excision and liquid scintillation counting at 2, 8, and 24 h after administration of the drug. beta-D-Glc-IPM showed no effect on the incorporation of [methyl-3H]-thymidine in the liver and an insignificant reduction in kidney DNA (maximal reduction: -27.3%). However, after 8 h there was a marked reduction in the incorporation rate in the thymus (-83.7%), spleen (-74.6%), and esophagus (-87.2%), with a tendency toward recovery within 24 h. In bone marrow cells a reduction of -75.5% (8 h) and -73.3% (24 h) was observed.

Estimating the sensory irritating potency of airborne nonreactive volatile organic chemicals and their mixtures

This article describes the possibility of estimating whether or not a mixture of nonreactive volatile organic chemicals (NRVOC) is likely to elicit complaints of sensory irritation in humans. For this estimation we rely on: a) the sensory irritating potency of individual NRVOC can be estimated from a variety of physicochemical properties of these chemicals, b) at low exposure concentrations, the additivity rule can be applied using the potency of each chemical in a mixture and c) a threshold concentration exists below which no sensory irritation will occur. We used this estimating approach and we compared the results obtained with those obtained experimentally in humans exposed to a well defined mixture. The approach presented can be used to arrive at a decision as to whether or not exposure to a mixture of NRVOC is likely to result in sensory irritation complaints by humans, either in the general indoor air situation or for industrial workers.

Evaluation of respiratory effects of thermal decomposition products following single and repeated exposures of guinea pigs

Groups of guinea pigs were exposed to the thermal decomposition products (TDP) released from acrylonitrile butadiene styrene (ABS), polypropylene-polyethylene copolymer (CP), polypropylene homopolymer (HP), or plasticized polyvinyl chloride (PVC). In single 50-min exposures to the TDP, guinea pigs exhibited sensory irritation, coughing, and airways constriction. Significant decreases in respiratory frequency (f) occurred during TDP exposure which were magnified during CO2 challenge conducted immediately post-exposure. For each resin, it was possible to demonstrate a linear relationship between the logarithm of heated mass and the percent decrease in f during CO2 challenge. From these relationships, the mass of each resin producing a 50% decrease in f during CO2 challenge (RD50 mass) was obtained. RD50 masses of 2744, 25.2, 16.0, and 6.7 g were obtained for ABS, CP, HP, and PVC, respectively. Thus, the relative potency of their TDP was PVC > CP approximately HP >> ABS. Using the RD50 mass of each resin, guinea pigs were exposed to TDP for 50 min/day on 5 consecutive days. These repeated exposures also resulted in sensory irritation, coughing, and airways constriction. However, deaths occurred during exposures, and there was evidence of cumulative respiratory effects, and slower recoveries among survivors. Data obtained in guinea pigs were compared to a previous study with mice exposed to the TDP of the same four resins (Schaper et al. 1994). On the basis of heated mass, mice were 20-500 times more sensitive to the acute respiratory effects of TDP than guinea pigs. Thus, the exposure limits of 0.63, 0.11, 0.08, and 0.35 mg/m3 proposed by Schaper et al. (1994) on the basis of particulates released from ABS, CP, HP and PVC should prevent not only irritation, but also possible coughing, and airways constriction in workers.

Computer assisted recognition and quantitation of the effects of airborne chemicals acting at different areas of the respiratory tract in mice

The pattern and timing of a normal breath in unanesthetized mice was analyzed from measurement of inspiratory and expiratory airflows (VI and VE). Airflow was measured via a differential pressure transducer, attached to a pneumotachograph, which itself was attached to a body plethysmograph into which a mouse was placed. The analog voltage from the differential pressure transducer was digitized and stored for analysis on a microcomputer. Criteria were developed to classify each breath as normal (N) or belonging into one of seven abnormal categories. The abnormal categories were arrived at by computer analysis, recognizing specific modifications of the normal pattern into patterns of: sensory irritation of the upper respiratory tract (S), airflow limitation within the conducting airways of the lungs (A) or pulmonary irritation at the alveolar level (P). Combinations of these effects, i.e., S+A, P+A, P+S and P+S+A were also recognized. Computer analysis of each breath also permitted quantitative evaluation of the degree of S, A or P abnormalities. To induce each type of effect we used inhalation exposures to 2-chlorobenzylchloride, carbamylcholine or propranolol. We propose that this approach will permit rapid evaluation of the possible effects of airborne chemicals at three levels of the respiratory tract, with the classification of the type of effect easily obtained in an objective way using well defined criteria, followed by quantitation of the degree of each effect.

Development of a database for sensory irritants and its use in establishing occupational exposure limits

A database was developed for chemicals whose sensory-irritating properties had been investigated using a previously described animal bioassay. In this bioassay, mice were exposed to an airborne chemical, and changes in their respiratory pattern were determined. For each chemical tested, the concentration capable of producing a 50% decrease in respiratory rate (RD50) was obtained and its relative potency estimated. For the current study, 295 such airborne materials, including single chemicals and mixtures, were found in the literature. A total of 154 RD50 values were obtained in male mice of various strains for the 89 chemicals in the database for which there were also TLVs. An examination of the TLVs and RD50 values demonstrated, as previously with the smaller dataset (n = 40), a high correlation (R2 = 0.78) of the TLVs with 0.03 x RD50. This supports the continued use of the animal bioassay for establishing exposure limits to prevent sensory irritation in the workplace. No other bioassay provides this type of information or has been used so extensively to suggest guidelines for occupational exposures.

Characteristic modifications of the breathing pattern of mice to evaluate the effects of airborne chemicals on the respiratory tract

A system was developed for exposure of unanesthetized mice to airborne chemicals and for continuous measurement of their breathing pattern prior to, during and following exposure. By measuring inspiratory and expiratory airflows (VI and VE), and integration with time to yield tidal volume (VT), we obtained characteristic modifications to the normal breathing pattern. These permitted recognition that a specific portion of the respiratory tract was affected by the selected airborne chemicals. Following recognition, we also quantitated the degree of effect using one specific measurement in each case. An effect on the upper respiratory tract, induced by the sensory irritant, 2-chlorobenzylchloride, was quantitated by measuring a decrease in respiratory frequency. An effect on the conducting airways, induced by the airway constrictor, carbamylcholine, was quantitated by a decrease in VE at the mid-point of VT. An effect at the alveolar level, induced either by the vagal nerve ending stimulant, propranolol, or by the pulmonary irritant, machining fluid G, was quantitated by an increase in the length of a pause induced at the end of expiration. The system is easy to construct and operate and can be used to rapidly evaluate the effects of airborne chemicals on the respiratory tract.

Improved immunosuppression with aerosolized cyclosporine in experimental pulmonary transplantation

Rejection remains a major obstacle to long-term success of pulmonary transplantation. Direct delivery of cyclosporine to lung allografts may produce better control of rejection by generating high intragraft concentrations of drug with decreased systemic delivery and toxicity. The efficacy of inhaled cyclosporine in preventing allograft rejection was compared with systemic delivery by intramuscular injections in a rat model of lung transplantation (Brown-Norway to Lewis). Group 1 animals were given no immunosuppression. Group 2 received a single i.m. injection of 25 mg/kg CsA on the day of operation while group 3 received daily doses on postoperative days 0-3. Groups 4-7 received aerosolized CsA daily for seven days. The aerosol generator produced an airborne concentration of CsA of 180 mg/m3 with a mean particle size of 0.7 mu and estimated pulmonary depositions of CsA of 0.98-3.6 mg/kg/day. Animals were killed on POD 7, and the transplanted lungs graded histologically in a blinded fashion. All control animals showed destructive grade 4 changes by POD 7. Animals receiving high-dose aerosolized CsA (groups 6 and 7) showed minimal changes with a mean rejection grade of 1.3. A single i.m. dose of CsA (group 2) failed to prevent rejection; the mean grade was 2.2. Animals given four i.m. doses of CsA had a mean grade of 1.8. Aerosolized CsA provided significantly better control of rejection than did systemic CsA (groups 6 and 7 vs. groups 2 and 3; P less than 0.0002 and less than 0.0054, respectively). Local delivery of CsA by aerosol inhalation is effective in limiting acute rejection of the rat lung allograft.

Respiratory effects of trimellitic anhydride aerosols in mice

Groups of mice were exposed to trimellitic anhydride (TMA) aerosols for 30 min at concentrations ranging from approximately 2 to 150 mg/m3. The sensory and pulmonary irritating properties of TMA were assessed during these exposures. Sensory irritation, as evidenced by a lenghthening of the time of expiration (TE), was not evoked in any exposure. However, TMA aerosols evoked other rapid, reversible alterations of respiratory cycle timing, suggestive of pulmonary irritation. The time of inspiration (TI) and expiration (TE) decreased as TMA exposure concentration was increased. Also, characteristic pauses (i.e., apneic periods) occurred between breaths. The length of these pauses (TP) increased as TMA exposure concentration was raised. Respiratory frequency (f) was dependent upon the magnitude of increase in TP. At lower TMA concentrations, TP was short and f was elevated, whereas at higher concentrations, TP was long and f was reduced. Interestingly, there was no other evidence of pulmonary irritation besides the alterations in respiratory cycle timing. Histopathological evaluation of the respiratory tracts of TMA-exposed animals revealed no changes from those of controls. Finally, there was no evidence of cumulative or delayed pulmonary effects in mice repeatedly exposed to TMA aerosols. These acute changes in respiratory cycle timing may have occurred as a result of stimulation of vagal nerve endings along the conducting airways and in the deep lung, directly produced by TMA aerosols.

Evaluation of the acute respiratory effects of aerosolized machining fluids in mice

Using a previously developed bioassay, the sensory and pulmonary irritating properties of a group of 10 aerosolized machining fluids were evaluated in mice. Single, 3-hr inhalation exposures were conducted with the fluids at exposure concentrations ranging from 20 to 2000 mg/m3. The results have shown that all 10 were capable of inducing sensory and pulmonary irritation, with little or no change in pulmonary histopathology. A concentration-response relationship was developed for each fluid which revealed that, for the 10 fluids studied here, the synthetic/semisynthetic and soluble fluids were more potent irritants than the straight oils. Also, 3 of the 10 fluids which had been collected from workplace operations (i.e., "in use" fluids) were found to be similar in potency to the same fluids prior to their introduction into the workplace (i.e., "neat" fluids). From concentration-response relationships, the RD50 value (i.e., concentration inducing a 50% response) was obtained for each of the 10 fluids. The RD50 values ranged from 100 to 1000 mg/m3 for all fluids except the straight oils whose RD50 values were over 100,000 mg/m3. Using these values, exposure limits were then suggested for workers in industry to prevent irritation. This bioassay may be a good first step in evaluating new machining fluids whose formulations may change depending upon the current industrial needs.

Immunosuppression with aerosolized cyclosporine for prevention of lung rejection in a rat model

The efficacy of local delivery of aerosol cyclosporine (CsA) for prevention of lung rejection was compared with the intramuscular route (IM) in a fully allogeneic rat model (BN/LEW) of lung transplantation (LTx). Control rats (group 1, n = 6) received no CsA after LTx. Rats in group 2 (n = 10) received 4 doses of CsA in olive oil (25 mg/kg) intramuscularly starting on postoperative day (POD) 0. Group 3 (n = 9) was treated with aerosolized CsA for 3 h/day for 7 days starting on POD 0. All animals were sacrificed on POD 6. Transplanted lungs were graded histologically in a blind manner on a 0-4 scale. Control animals all showed grade 4 rejection. i.m. CsA therapy reduced lung rejection with a rejection grade of 1.8 +/- 0.35 (mean +/- SD) but was associated with a 50% incidence of pneumonia. Aerosol CsA provided better control of rejection with a rejection grade of 1.2 +/- 0.4 (group 3 vs. group 2: P less than 0.05 Wilcoxon) and none of these animals had penumonia. Trough blood levels of CsA were significantly lower in the group treated with aerosolized CsA when compared with the IM group (P less than 0.05). Therefore we conclude that: (1) aerosol CsA is effective in preventing lung allograft rejection following lung transplantation in rats, and (2) local delivery of aerosol CsA is superior to the i.m. route because better control of rejection is achieved with a lower systemic delivery of CsA.

Aerosolized cyclosporine as single-agent immunotherapy in canine lung allografts

Current systemic immunosuppressive regimens are unable to prevent lung allograft rejection consistently and are associated with significant morbidity and death. Acute rejection has occurred in 40% and chronic rejection in 50% of our lung recipients. We hypothesized that regional immunotherapy with aerosolized cyclosporine would prevent or reduce lung allograft rejection while allowing for low systemic drug delivery. In a canine model of unilateral lung allotransplantation, aerosolized cyclosporine was delivered directly to the allograft. Acute rejection was prevented or reduced in all treated recipients. All control animals had severe acute rejection. Intragraft cyclosporine concentration was high and systemic drug delivery was low, as evidenced by low whole-blood cyclosporine levels and low tissue cyclosporine levels in skeletal muscle. Ninety-five percent of whole-blood trough cyclosporine levels were less than 150 ng/ml. Aerosolized cyclosporine was able to prevent or reduce acute pulmonary rejection and resulted in minimal systemic drug delivery.

Alteration of respiratory cycle timing by propranolol

The present study was undertaken to explore the effect of propranolol on respiratory cycle timing and breathing pattern using mice and guinea pigs. Propranolol was administered via aerosol or via injection. Mice exposed to propranolol aerosols exhibited a breathing pattern that was characterized by a pause between breaths. The length of such pauses (TP) increased as the propranolol exposure concentration was raised. We also observed at increasing propranolol concentrations that the time of inspiration (TI) and time of expiration (TE) decreased. Thus, the respiratory rate of these animals was seen to increase, remain unchanged, or decrease depending on the balance between TP versus TI and TE. Guinea pigs also exhibited pauses between breaths during exposure to propranolol aerosols, but such pauses were not observed as consistently as in mice. TP again rose while TI and TE fell in guinea pigs exposed to increasing propranolol concentrations. This species was, however, less sensitive than mice. Intraperitoneal injections of propranolol failed to elicit such alterations in respiratory pattern or timing in either species. These changes in respiratory timing obtained with an aerosol of propranolol were most probably due to a local effect on vagal nerve endings or to its bronchoconstricting effect.

Induction of abnormal ventilatory responses to CO2 and evaluation of agents given to prevent or reverse these responses

This study demonstrates how a previously described animal model can be utilized to evaluate the effects of multiple aerosols. For the exposures presented in this report, unanesthetized but mildly restrained guinea pigs were used. Airflow (V), tidal volume (VT), and respiratory frequency (f) were continuously measured in all animals and their flow-volume (V-VT) loops were also obtained. The animals were first exposed to room air and then challenged with a 10% CO2 (in 19% O2, 71% N2) mixture. The normal ventilatory response to 10% CO2 consists of increases in V, VT, and f. This response is very stable for long periods of time and is highly reproducible. It is possible, however, to alter the normal CO2 response by adding an aerosol to the CO2 mixture. Two types of acute responses can be induced, Type I and Type II. In this study, histamine and carbamylcholine aerosols were used to induce the Type I response while propranolol aerosols were used to induce the Type II response. Serotonin aerosols were used to induce both types of effects. We report that the bronchodilator, isoproterenol, reversed the Type I pulmonary effects where the level of reversal was dependent upon isoproterenol concentration. The rapid, shallow breathing, characteristic of the Type II response, was not reversed by isoproterenol but could be prevented by blocking the vagus nerve with cocaine. Since no invasive techniques are required and the same animals can be used repeatedly, combinations of aerosols can be tested in order to delineate how Type I or Type II abnormal ventilatory responses to CO2 are induced by a wide variety of airborne chemicals.

Pulmonary effects of a polyisocyanate aerosol: hexamethylene diisocyanate trimer (HDIt) or Desmodur-N (DES-N)

Desmodur-N (DES-N) or hexamethylene diisocyanate trimer (HDIt), a biuret structure of hexamethylene diisocyanate, is a viscous liquid used for durable coatings and is applied by brushing or spraying. DES-N aerosol has been shown to be primarily a pulmonary irritant following a single exposure in mice. To explore the pulmonary effects of this agent further, groups of guinea pigs were exposed to concentrations ranging from 8 to 121 mg/m3 of DES-N for 3 hr. Prior to and following exposure, each animal was challenged with 10% CO2 in 20% O2 and 70% N2 to evaluate their pulmonary performance. Following a single exposure, these animals displayed a concentration-dependent increase in respiratory rate and decrease in tidal volume, as well as coughing and apnea. Their ventilatory response to 10% CO2 was abnormal and characteristic of a lung restriction response. Some airflow limitation was seen during expiration but this occurred more often during air breathing than during CO2 challenge. With daily exposures repeated for 11 consecutive days, guinea pigs began to adapt to the exposures as indicated by a return to a normal ventilatory response to CO2. This adaptation occurred within the first 5 days of exposures. From Days 6 to 11, there was a demonstrable effect, but the level of response was much less than that following the first exposure. No cumulative effect could be demonstrated with this polyisocyanate and the effect was found to be different than that for mono- or diisocyanates. Acceptable levels of exposure to this polyisocyanate for industrial workers are suggested.

Sensory and pulmonary irritation of methyl isocyanate in mice and pulmonary irritation and possible cyanidelike effects of methyl isocyanate in guinea pigs

Methyl isocyanate (MIC) was evaluated for sensory and pulmonary irritation in mice. MIC was found to be both a potent sensory and pulmonary irritant in this species. From these results, a safe level of exposure for a period of 8 hr was estimated to be about 0.02 ppm for humans. Guinea pigs were also exposed to MIC for a single 3-hr exposure at a concentration of 37 ppm. During exposure to MIC, coughing was observed in all animals. Pulmonary function was evaluated immediately following exposure and intermittently on the next 35 days using CO2 challenges and flow-volume loops. Highly abnormal responses to CO2 were observed immediately after exposure in all animals. Six of the eight animals exposed to MIC died. In the two survivors, an apparent recovery was seen during the 5 days following exposure, but a worsening effect was observed at days 21 and 28, with a partial recovery at day 35. The data clearly demonstrated that the primary pulmonary effect of MIC was one of airways obstruction. Oxygen uptake and carbon dioxide output were also measured in the guinea pigs following exposure to MIC. No evidence of a cyanidelike effect was observed, in contrast to a severe depression of oxygen uptake following exposure to hydrogen cyanide.

Sensory and pulmonary irritation with exposure to methyl isocyanate

Methyl isocyanate (MIC) was tested for its potency as a sensory irritant and as a pulmonary irritant in mice. To evaluate sensory irritation, animals were exposed to MIC at concentrations between 0.5 and 7.6 ppm for a period of 90 min. A characteristic reflex decrease in respiratory rate indicating sensory irritation was observed. The concentration evoking a 50% decrease in respiratory rate (RD50) was found to be 1.3 ppm. To evaluate pulmonary irritation, animals were first anesthetized and fitted with a tracheal cannula. Following recovery from anesthesia, they were exposed to MIC at concentrations between 0.4 and 7.3 ppm for a period of 90 min. A characteristic decrease in respiratory rate indicating pulmonary irritation in tracheally cannulated (TC) mice was observed. The concentration evoking a 50% decrease in respiratory rate (RD50TC) was found to be 1.9 ppm. Thus, MIC was found to be a potent sensory and pulmonary irritant.

A method to classify airborne chemicals which alter the normal ventilatory response induced by CO2

Guinea pigs inhaling 10% CO2, 19% O2, and 71 N2 increase their tidal volume (VT) by a factor of 2 to 3 and their respiratory frequency (f) by a factor of 1.2 to 1.5 above their normal values while breathing room air. While exposing guinea pigs to 10% CO2, a variety of aerosols can be added to determine how they modify the normal ventilatory response to this agent. Aerosols of carbamylcholine, serotonin, or propranolol all decreased VT of guinea pigs when added to 10% CO2. We propose here that chemicals evoking reductions in tidal volume can be classified into two groups based on the set of concurrent respiratory responses. Those chemicals evoking "obstruction," not only reduced VT but also decreased (f), increased resistance to airflow in conducting airways, and interrupted airflow. The prototype of this family would be carbamylcholine. The second group of chemicals evoked what is described as "reflex restriction." These agents reduced VT but increased f and lowered resistance to airflow. Propranolol would be the prototype for this family. Serotonin, however, evoked both types of response patterns which were time dependent. At the beginning of exposure, obstruction was prevalent while at the end of a 30-min exposure, reflex restriction was prevalent.

The effects of aerosols of carbamylcholine, serotonin and propranolol on the ventilatory response to CO2 in guinea pigs and comparison with the effects of histamine and sulfuric acid

A new method is introduced to recognize the acute pulmonary effect of airborne contaminants in guinea pigs. The method avoids anaesthesia and invasive techniques and requires minimal restraint of the animal. To recognize the acute pulmonary effect, the inspiratory volume of the animal was increased by continuous inhalation of a mixture containing 10% CO2 in 18% O2 and 72% N2. Once a plateau increase in inspiratory volume was reached, the aerosol to be studied was added to this mixture and its effect in reducing inspiratory volume measured. By exposing the animals to different exposure concentrations of carbamylcholine, serotonin and propranolol aerosols, concentration-response relationships were obtained which permitted comparison of their potency. Comparisons were also made with histamine and sulfuric acid aerosols previously studied.

Evaluation of concentration-response relationships for histamine and sulfuric acid aerosols in unanesthetized guinea pigs for their effects on ventilatory response to CO2

Through the addition of aerosols to 10% CO2 mixtures, acute respiratory responses can be detected in unanesthetized guinea pigs. This conclusion was supported by results from a previous study conducted in our laboratory in which animals were exposed to nebulized histamine or sulfuric acid while placed in a whole-body plethysmograph. In that study, only one concentration of each agent was examined. The present data were collected over a wider range of histamine and sulfuric acid exposure concentrations and the results served to reinforce the previous conclusion regarding the ease in detecting acute responses with this approach. Again, inspiratory volume (VI) and pressure changes (delta P), proportional to inspired volume, were measured continously and significant decreases in these parameters occurred during aerosol challenges. In addition, respiratory frequency (f) was evaluated during all exposures but few changes in frequency were observed other than the increases induced by 10% CO2 alone. Measurements of VI and delta P indicated similar levels of response to the tested aerosols, except during intense bronchoconstriction evoked by higher concentrations of histamine. In such constricted states, VI was a more sensitive indicator. Concentration-response relationships for histamine and sulfuric acid using VI measurements were comparable to those of other investigators who measured airflow resistance. Therefore, the new method offers many advantages over previous methods through its noninvasive and simple features yet there is comparable sensitivity to detect acute responses, as demonstrated by this study.