Considerations for study design in the DAHANCA 35 trial of protons versus photons for head and neck cancer

Proton radiotherapy offers a dosimetric advantage compared to photon therapy in sparing normal tissue, but the clinical evidence for toxicity reductions in the treatment of head and neck cancer is limited. The Danish Head and Neck Cancer Group (DAHANCA) has initiated the DAHANCA 35 randomised trial to clarify the value of proton therapy (NCT04607694). The DAHANCA 35 trial is performed in an enriched population of patients selected by an anticipated benefit of proton therapy to reduce the risk of late dysphagia or xerostomia based on normal tissue complication probability (NTCP) modelling. We present our considerations on the trial design and a test of the selection procedure conducted before initiating the randomised study.

Abnormal glucose tolerance and lung function in children with cystic fibrosis. Comparing oral glucose tolerance test and continuous glucose monitoring

BACKGROUND

Cystic fibrosis (CF) related diabetes (CFRD) is a common complication of CF. CFRD is associated with declining lung function even before its onset. Regular screening for CFRD using oral glucose tolerance test (OGTT) is recommended. Additionally, continuous glucose monitoring (CGM) has surfaced as a possible surveillance method, but evidence for its use and concordance with OGTT has not been established.

METHODS

Children were prospectively recruited at CF center Lund to undergo both intermittent scan CGM (isCGM) and OGTT. Lung function was evaluated by spirometry and multiple breath washout. Demographic and clinical data were collected from the Swedish national CF registry.

RESULTS

32 patients participated in the study, yielding 28 pairs of isCGMs and OGTTs. The OGTTs showed that two patients met the criteria of CFRD, seven had impaired glucose tolerance (IGT) and indeterminate glycemia (INDET) was found in eleven cases. The isCGM percent of measurements >8mmol/L and the number of peaks per day >11 mmol/L have correlations with intermediate OGTT glucose time points, but not the 2hour glucose value. Patients with abnormal glucose tolerance (AGT) had lower lung function than those with normal glucose tolerance demonstrated by both FEV1% predicted and lung clearance index (LCI).

CONCLUSION

Correlations can be found between isCGM and OGTT in regards to the latter's intermediate time points. LCI demonstrates as well as FEV1% of predicted, worse lung function in children and adolescents with abnormal glucose tolerance in CF.

Prediction of radiation-induced mucositis of H&N cancer patients based on a large patient cohort

PURPOSE/OBJECTIVE

Radiation-induced mucositis is a severe acute side effect, which can jeopardize treatment compliance and cause weight loss during treatment. The study aimed to develop robust models to predict the risk of severe mucositis.

MATERIALS/METHODS

Mucosal toxicity scores were prospectively recorded for 802 consecutive Head and Neck (H&N) cancer patients and dichotomised into non-severe event (grade 0-2) and severe event (grade 3+) groups. Two different model approaches were utilised to evaluate the robustness of the models. These used LASSO and Best Subset selection combined with 10-fold cross-validation performed on two-thirds of the patient cohort using principal component analysis of DVHs. The remaining one-third of the patients were used for validation. Model performance was tested through calibration plot and model performance metrics.

RESULTS

The main predicted risk factors were treatment acceleration and the first two principal dose components, which reflect the mean dose and the balance between high and low doses to the oral cavity. For the LASSO model, gender and current smoker status were also included in the model. The AUC values of the two models on the validation cohort were 0.797 (95%CI: 0.741-0.857) and 0.808 (95%CI: 0.749-0.859), respectively. The two models predicted very similar risk values with an internal Pearson coefficient of 0.954, indicating their robustness.

CONCLUSIONS

Robust prediction models of the risk of severe mucositis have been developed based on information from the entire dose distribution for a large cohort of patients consisting of all patients treated H&N for within our institution over a five year period.

NTCP model validation method for DAHANCA patient selection of protons versus photons in head and neck cancer radiotherapy

Introduction: Prediction models using logistic regression may perform poorly in external patient cohorts. However, there is a need to standardize and validate models for clinical use. The purpose of this project was to describe a method for validation of external NTCP models used for patient selection in the randomized trial of protons versus photons in head and neck cancer radiotherapy, DAHANCA 35. Material and methods: Organs at risk of 588 patients treated primarily with IMRT in the randomized controlled DAHANCA19 trial were retrospectively contoured according to recent international recommendations. Dose metrics were extracted using MatLab and all clinical parameters were retrieved from the DAHANCA database. The model proposed by Christianen et al. to predict physician-rated dysphagia was validated through the closed testing, where change of the model intercept, slope and individual beta's were tested for significant prediction improvements. Results: Six months prevalence of dysphagia in the validation cohort was 33%. The closed testing procedure for physician-rated dysphagia showed that the Christianen et al. model needed an intercept refitting for the best match for the Danish patients. The intercept update increased the risk of dysphagia for the validation cohort by 7.9 ± 2.5% point. For the raw model performance, the Brier score (mean squared residual) was 0.467, which improved significantly with a new intercept to 0.415. Conclusions: The previously published Dutch dysphagia model needed an intercept update to match the Danish patient cohort. The implementation of a closed testing procedure on the current validation cohort allows quick and efficient validation of external NTCP models for patient selection in the future.

Relationship between patient and physician-rated xerostomia and dose distribution to the oral cavity and salivary glands for head and neck cancer patients after radiotherapy

Introduction: Xerostomia is a frequent complication after curative intended radiotherapy (RT) for head and neck squamous cell carcinoma (HNSCC). Assessment of xerostomia is commonly done by the physician. The aim of this study is to investigate the relation between patient and physician-rated xerostomia and to predict the degree of xerostomia from patients with self-reported xerostomia based on delivered doses to the oral cavity, parotid, and submandibular glands. Material and methods: During a 2-year period, consecutive HNSCC patients attending the follow-up clinic were included. All included patients had self-reported xerostomia, and completed the disease-specific EORTC QLQ-H&N35 questionnaire. The physician assessed the degree of xerostomia with the DAHANCA toxicity scale and was blinded for the EORTC score. Oral cavity, parotid, and submandibular glands (OAR) were delineated on the planning CT according to international guidelines. DVH were extracted from treatment plans. Logistic regression tested the relation between mean doses, patient characteristics, and xerostomia scores. Differences between DVH values and scoring of xerostomia were analyzed with a Kruskal-Wallis test. The relation between xerostomia and dose distributions was further investigated using principal component analysis (PCA). Results: In total, 109 patients were included in the study. A weak correlation was seen between patient and physician-rated toxicity (p = .001), however, in general patients reported more toxicity than physicians. For EORTC score ≥2, the multi-variable analysis was significant for doses to the oral cavity, tobacco status and use of xerogenic medication. Neither the DVH analysis nor the PCA found any clear distinction between xerostomia scores for EORTC or DAHANCA and investigated OARs. Conclusion: Patients tended to report higher scores of xerostomia than the physician. PCA indicated a complex relation between doses to the OAR and xerostomia scores, showing e.g., that reducing doses in one organ was on the expense of increased dose to another organ.

Osteoradionecrosis of the mandible after radiotherapy for head and neck cancer: risk factors and dose-volume correlations

Background: The project aimed at determining the incidence of mandibular osteoradionecrosis (ORN) after radiotherapy, possible risk factors, and mandibular dose-volume effects in a large cohort of head and neck cancer patients (HNC). Methods: The cohort consisted of 1224 HNC patients treated with 66-68 Gy in 2007-2015 predominantly with IMRT. ORN cases were defined from clinical observations at follow-up and through hospital code diagnostics after oral-maxillofacial surgery and cross-checked with the national Danish Head and Neck Cancer database. In a nested case-control study, patients with ORN cases were matched with two controls (1:2) and pre-RT dental procedures including surgery to the mandible were documented. Multivariable Cox regression analysis was applied using demographic and treatment variables including dental procedures, smoking and tumor characteristics, and combined with dosimetric data. Mean mandibular dose (D_mean) was pre-selected for the multivariable model. Results: ORN was recorded in 56 cases (4.6%) with a median time to event of 10.9 months (range 1.8-89.7) after RT, 90% occurred within 37.4 months. Median follow-up time was 22 months (0.3-95). Average D_mean was significantly higher in the ORN event cohort and significant dose-volume differences were observed for population mean DVH doses between 30 Gy and 60 Gy. In univariable analysis, smoking (HR = 1.69; CI 1.14-2.5), pre-RT surgery/tooth extraction (HR = 2.76; 1.48-5.14), and several dosimetric parameters including D_mean (HR = 1.05, 1.02-1.08) were all significantly associated with ORN. D_mean and surgery/tooth extraction remained significant predictors of ORN in multivariable analysis, HR = 1.04 (CI 1.01-1.07) and HR = 2.09 (CI 1.1-3.98), respectively, while smoking only retained its significance in an interaction analysis with pre-RT dental procedures. Conclusion: The onset of ORN of the mandible was early (median 10.8 months) and the incidence low (4.6%) after IMRT in HNC cancer patients. Surgery to the mandible and pre-RT tooth extraction, tobacco smoking, and treatment dose were associated with the development of ORN.

8 ANTI-MÜLLERIAN HORMONE AT WEANING AND BREEDING AS A PREDICTOR OF BEEF HEIFER FERTILITY

This study examined the relationship between serum anti-Müllerian hormone (AMH) concentration at weaning and breeding to determine if either or both measures could predict subsequent fertility of beef heifers. Blood was collected from 71 Angus based heifers at ~7 and 14 months of age and serum stored frozen (−20°C) until analysis for AMH, using bovine AMH ELISA kits (AL115; Ansh Laboratories, Webster, TX, USA). Before breeding, transrectal ultrasonography was used to determine cyclic status of heifers. Heifers received 25 mg of prostaglandin F2α (PGF) and those detected in oestrus were AI ~12 h after detected oestrus. Heifers not detected in oestrus after 7 days received a second PGF injection and oestrus detection and AI continued for 4 days. Ten days later, the heifers were exposed to fertile bulls for a 45-days breeding season. At 50 to 60 days after insemination, transrectal ultrasonography was used to identify pregnant heifers and to confirm conception date based on fetal size. At 60 days after bull removal, ultrasonography was performed to determine pregnancy in heifers conceiving during the breeding season and confirm continuing pregnancy in heifers previously identified as pregnant. Based on fetal size at ultrasonography, the oestrous cycle after initiation of breeding when conception occurred was estimated. For comparison, AI pregnancies were considered cycle 1, and pregnancies initiated during subsequent 21-day intervals of the breeding season were classified as cycles 2, 3, and 4, respectively. For analysis, frequency distribution was used to assign serum AMH concentration measured at weaning, breeding, and the change from weaning to breeding, into quartiles. Comparisons were then made via Chi-squared analysis for heifers in each quartile that were cyclic at synchronization, detected in oestrus, conceived after AI, pregnant at the end of the breeding season, and the estimated cycle that conception occurred. Comparison of heifers based on serum AMH quartiles at weaning failed (P ≥ 0.35) to detect any effect of AMH on subsequent heifer cyclicity at breeding, oestrous response after synchronization, AI conceptions, overall pregnancy rate, or estimated oestrous cycle of the breeding season when conception occurred. Based on AMH concentration at breeding, heifers in the lowest quartile (Q1) had a lower (10%; P = 0.02) AI conception rate than heifers in other quartiles (43 to 73%), and conceived at a later oestrous cycle (P = 0.03) in the breeding season. Comparison of heifers based on the change in AMH concentrations from weaning to breeding revealed that none of the heifers in the lowest quartile (Q1) conceived after AI, compared with 80% in the highest quartile (Q4; P < 0.001). Heifers in the lowest quartile also conceived at a later oestrous cycle in the breeding season than heifers in the other quartiles (P = 0.01). Results indicate that either AMH concentration at breeding or the change in AMH from weaning to breeding can identify beef heifers more likely to conceive to AI and to conceive early in the breeding season.

Nitric oxide production by polymorphonuclear leucocytes in infected cystic fibrosis sputum consumes oxygen

Chronic Pseudomonas aeruginosa lung infection in cystic fibrosis (CF) patients is characterized by persisting mucoid biofilms in hypoxic endobronchial mucus. These biofilms are surrounded by numerous polymorphonuclear leucocytes (PMNs), which consume a major part of present molecular oxygen (O(2)) due to production of superoxide (O(2)(-)). In this study, we show that the PMNs also consume O(2) for production of nitric oxide (NO) by the nitric oxide synthases (NOS) in the infected endobronchial mucus. Fresh expectorated sputum samples (n = 28) from chronically infected CF patients (n = 22) were analysed by quantifying and visualizing the NO production. NO production was detected by optode measurements combined with fluorescence microscopy, flow cytometry and spectrophotometry. Inhibition of nitric oxide synthases (NOS) with N(G) -monomethyl-L-arginine (L-NMMA) resulted in reduced O(2) consumption (P < 0·0008, n = 8) and a lower fraction of cells with fluorescence from the NO-indicator 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM) (P < 0·002, n = 8). PMNs stained with DAF-FM and the superoxide indicator hydroethidine (HE) and host cells with inducible NOS (iNOS) were identified in the sputum. In addition, the production of the stable end-products of NO in CF sputum was correlated with the concentration of PMNs; NO(3)(-) (P < 0·04, r = 0·66, n = 10) and NO(2)(-) (P< 0·006, r = 0·78, n = 11). The present study suggests that besides consumption of O(2) for production of reactive oxygen species, the PMNs in CF sputum also consume O(2) for production of NO.

Achromobacter species in cystic fibrosis: cross-infection caused by indirect patient-to-patient contact

BACKGROUND AND METHODS

Achromobacter species leads to chronic infection in an increasing number of CF patients. We report 2 cases of Achromobacter ruhlandii cross-infection between patients after well-described indirect contact.

RESULTS

Both cases were young, stable, CF patients without chronic infections and with normal FEV1, but experienced clinical deterioration after visits to the home of a CF patient with A. ruhlandii infection and after sharing facilities with an A. ruhlandii infected CF patient on a skiing vacation, respectively. Both cases became positive for A. ruhlandii in airway secretions and were colonized with A. ruhlandii in their sinuses. Aggressive, long-term antibiotic treatment led to clinical stability. One of the cases developed chronic A. ruhlandii infection.

CONCLUSION

A. species can cause cross-infection even after a short period of indirect contact between infected and non-infected CF patients. Patients should be followed closely for several months before the possibility of cross-infection is ruled out.

Long-term, low-dose azithromycin treatment reduces the incidence but increases macrolide resistance in Staphylococcus aureus in Danish CF patients

BACKGROUND

Since 2001, long-term, low-dose azithromycin treatment has been used for CF patients chronically infected with Pseudomonas aeruginosa in the Copenhagen CF centre. Our study investigates changes in incidence of colonization with Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis and changes in macrolide sensitivity in these microorganisms during azithromycin treatment.

METHODS

CF patients treated continuously with azithromycin for at least 3 months were included. Results of microbiological examination, including phage typing results of S. aureus, obtained during treatment were compared to results obtained 2 years before treatment.

RESULTS

70 patients (median age 29.1 years) treated for a median of 4 years (range 0.7-5.1) were included. Before treatment, 44 patients had at least one culture positive for S. aureus compared to 25 patients during treatment (p<0.01). Mean percentage of sputum samples with growth of S. aureus decreased from 12.1% (range 0-82.6%) before treatment to 6.1% (range 0-93.2) during treatment (p<0.0006). Prevalence's of H. influenzae and S. pneumoniae also decreased significantly. Fifteen of 214 isolates (7%) of S. aureus were macrolide resistant before treatment, increasing to 95 of 181 isolates (52.5%) during treatment (p<0.001). Macrolide resistant strains were found in 3 of 44 S. aureus colonized patients before treatment and in 11 of 25 patients at some time during treatment (p<0.03), all belonging to different phage types. First resistant S. aureus isolate was isolated after a median treatment duration of 1.5 years (range 0.3-2.9). No MRSA were isolated. Only 1 macrolide resistant isolate of M. catarrhalis was found during treatment. No macrolide resistance was found in H. influenzae or S. pneumoniae.

CONCLUSION

Long-term, low-dose treatment with azithromycin in CF patients leads to reduced prevalence of S. aureus, S. pneumoniae, and H. influenzae, but increased macrolide resistance in S. aureus. Reduction in the prevalence of S. aureus will make increasing macrolide resistance clinically insignificant in these patients.

Rapid construction of Campylobacter jejuni deletion mutants

AIMS

To develop a novel method for rapid construction of Campylobacter jejuni deletion mutants.

METHODS AND RESULTS

We used overlapping extension PCR protocol to amplify a target sequence region of Camp. jejuni genomic DNA in which an internal fragment, Cj0618 coding sequence, was replaced by a chloramphenicol resistance cassette. After the resulting PCR product was introduced into electrocompetent Camp. jejuni 81-176, chloramphenicol-resistant mutants in which the wild type allele has been replaced by the deletion cassette were selected. DNA sequencing confirmed precise deletion in the Cj0618 gene. As expected from the previously reported role of Cj0618 in chick colonization, the resulting deletion mutant showed a caecal colonization defect in chick infection.

CONCLUSIONS

This method can be used for rapid construction of Camp. jejuni deletion mutants.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of this method should facilitate functional characterization of various Camp. jejuni genes.

Long-term results of repair of the internal ring for primary inguinal hernia

OBJECTIVE

To evaluate the long-term results of repair of the internal ring for primary inguinal hernia.

DESIGN

Retrospective study.

SETTING

University hospital, Denmark.

SUBJECTS

1159 patients with primary unilateral inguinal hernia.

INTERVENTIONS

Repair of the internal ring--annulorrhaphy.

MAIN OUTCOME MEASURES

Recurrence during the median observation period of 10 years (range 1-17).

RESULTS

Eighty-four (7%) were women, and the overall median age was 49 years (range 18-90). The overall recurrence rate calculated by life table analysis was 18%. Twenty-one of the recurrences were indirect hernias (49%), 11 were direct (26%), 8 were combined direct and indirect (19%) and 3 (7%) were femoral hernias.

CONCLUSION

Repair of the internal ring alone carries an unacceptably high recurrence rate.

Extended outpatient rehabilitation: its influence on symptom frequency, fatigue, and functional status for persons with progressive multiple sclerosis

OBJECTIVE

To determine the influence of an extended outpatient rehabilitation program on symptom frequency, fatigue, and functional status for persons with multiple sclerosis (MS).

DESIGN

Nonequivalent pretest/posttest control-group design, with posttest 1 year after initial assessment. Multiple regression analysis and analysis of covariance were used to control for symptom severity at the initial assessment and comorbid factors including depression, cognitive function, and social interaction. Effect sizes (ES) provided a descriptive measure of the change in outcomes.

SETTING

Outpatient multidisciplinary rehabilitation clinic.

PATIENTS

Forty-six patients with definite chronic progressive MS; 20 received treatment and 26 were in a nontreatment comparison group ("waiting list").

INTERVENTION

Rehabilitation services for 5 hours, 1 day per week, over 1 year.

MAIN OUTCOME MEASURES

The MS-Related Symptom Checklist composite score, fatigue frequency, and selected items from the Rehabilitation Institute of Chicago Functional Assessment Scale.

RESULTS

Receiving treatment was a significant predictor of reduced symptom frequency (partial r2 = .26) at the 1-year follow-up. The ES adjusted for baseline values indicated substantial reductions in symptom frequency for the treatment group (EStreatment = .27 vs ESwaitlist = -.32). Fatigue was significantly reduced at the time of follow-up for the treatment group compared with the waiting list group (EStreatment = .46 vs ESwaitlist = -.20). There were no statistically significant differences among groups regarding functional status, but there appeared to be less loss of functional status in the treatment group compared with the waiting list group (EStreatment = -.07 vs ESwaitlist = -.70).

CONCLUSIONS

An extended outpatient rehabilitation program for persons with definite progressive MS appears to effectively reduce fatigue and the severity of other symptoms associated with MS.

Health-related quality of life for patients with progressive multiple sclerosis: influence of rehabilitation

BACKGROUND AND PURPOSE

The health-related quality of life of patients with multiple sclerosis (MS) is an important aspect of care outcome. The purpose of this study was to compare health-related quality of life between patients who received weekly comprehensive outpatient rehabilitation for 1 year and a group that did not receive rehabilitation.

SUBJECTS

Twelve patients receiving outpatient care for chronic progressive MS (mean age = 44.5 years, SD = 11.6) were compared with 19 similar patients (mean age = 49.2 years, SD = 9.2) on a waiting list who were not receiving outpatient care.

METHODS

A pretest-posttest longitudinal design was used to descriptively compare outcome measures. Multivariate regression analyses were used to determine which variables, controlled for baseline health status and other relevant patient characteristics, were related to the best outcomes at the time of the 1-year follow-up.

RESULTS

The treatment group showed improvements in six health status measures on the Rand 36-Item Health Survey 1.0 (SF-36) that were not improved in the wait-listed group. Outpatient treatment was the sole predictor of positive outcome for energy/fatigue (partial R2 = .43) and change in general health (partial R2 = .19). In addition, the treatment group was associated with a positive outcome (together with other independent variables) in the domains of social function and social support.

CONCLUSION AND DISCUSSION

Patients with chronic progressive forms of MS appear to derive benefits from an ongoing comprehensive outpatient rehabilitation program. [Di Fabio RP, Choi T, Soderberg J, Hansen CR. Health-related quality of life for patients with progressive multiple sclerosis: influence of rehabilitation.

Effect of octreotide on anal pressure and rectal compliance

PURPOSE

The somatostatin analog, octreotide, has previously been found to influence rectal sensation and may also influence anal resting pressure.

METHODS

We studied the effect of octreotide on anal resting pressure and rectal compliance in eight healthy patients. Octreotide was administered intravenously as a bolus injection in doses of 100 and 10 micrograms or as infusion of 250 micrograms/hour on separate days and compared with placebo.

RESULTS

Within one minute after a bolus injection of 100 micrograms of octreotide, anal resting pressure increased from 56 +/- 12 to 96 +/- 16 cm H2O (P < 0.005). Octrotide had no effect on rectal sensitivity or compliance measurements. Octreotide counteracted rectoanal reflex by increasing anal pressure almost to the level found with an empty rectum.

CONCLUSION

Somatostatin thus seems to contribute to the regulation of rectoanal reflex.

Bilateral gluteus maximus transposition for anal incontinence

Seven patients (five women and two men) with anal incontinence in whom previous surgery had failed, were treated by bilateral gluteus maximus transposition. All patients were incontinent to solid stool. Previous surgery was postanal repair in four women and secondary overlapping suture for obstetric tear in one. The two men were treated in childhood for anal atresia. No covering stoma was used. Wound infection occurred in three patients, requiring surgical drainage in two. After follow-up of more than 1 year three patients experienced improved continence but in four continence was unchanged. Anorectal physiology studies showed moderately increased resting and squeeze pressures in patients who were improved by the operation, but none could retain more than 200 ml of viscous fluid instilled into the rectum. No change in rectal sensitivity or volume tolerance was found. This preliminary series does not indicate that better results are obtained by gluteus maximus transposition than by unstimulated graciloplasty.

[Fatal transmural colitis caused by Entamoeba histolytica. Differential diagnosis of chronic inflammatory bowel disease and colon cancer]

Perforation of the colon is a rare but frequently fatal complication of amoebiasis. We report a case of a 53 year-old male, with no history of travel abroad, who was admitted to hospital with haematochezia. A tumor of the rectum was diagnosed clinically. Due to acute intestinal obstruction, laparotomy was performed, revealing multiple perforations of the large bowel and severe peritonitis leading to subtotal colectomy. The histological examinations revealed transmural amoebic colitis. The patient died due to multi-organ failure.

Whole blood serotonin in autistic and normal subjects

Whole blood serotonin and tryptophan were measured in 87 normal subjects and in 40 autistic subjects. Whole blood serotonin concentrations (mean +/- SE) were significantly higher in drug-free (N = 21) autistics (205 +/- 16 ng/ml) than in normals (136 +/- 5.4 ng/ml). The Gaussian distribution of serotonin levels in the unmedicated autistic group suggests the elevation was not due to a subgroup of autistic subjects. Autistics medicated with anticonvulsants or neuroleptics had significantly lower serotonin levels than did drug-free autistic subjects. Whole blood tryptophan levels and platelet counts were similar in the autistic and normal groups. The possible causes of the hyperserotonemia of autism are discussed.

Multimodality approaches in the treatment of attention deficit disorders

This article describes the diagnostic process and various etiologic considerations that underpin the formulation of a comprehensive treatment program for a child with attention deficit disorder and then goes on to describe treatment modalities and strategies. The authors then suggest that the coordinated use of problem-specific treatment modalities is likely to prove more therapeutic and cost-effective than a global treatment.

Whole-body distribution an Malpighian tubule transport of 2',5-dichloro-4'-nitrosalicylanilide (Bayer 73) and 3-trifluoromethyl-4-nitrophenol in larvae of the aquatic midge Chironomus tentans

1. Residues of the lampricides 14C-Bayer 73 (2',5-dichloro-4'-nitrosalicylanilide) and 14C-TFM (3-trifluoromethyl-4-nitrophenol) were absorbed from aqueous sublethal concn. by aquatic larvae of the midge Chironomus tentans. 2. Toxicant residues were widely distributed during early hours of exposure, but later and during a 24-h post-exposure period, they became concentrated in the trunk and intestinal tract; the posterior movement of Bayer 73 was more rapid than that of TFM. 3. During 4-h tests, Malpighian tubules of the chironomid actively transported Bayer 73 and TFM in vitro, and on a per tubule basis, more TFM was transported than Bayer 73. 4. Potassium cyanide inhibited tubule transport; serotonin had no effect.