Specificities of Meningitis and Meningo-Encephalitis After Kidney Transplantation: A French Retrospective Cohort Study.

Kidney transplant recipients develop atypical infections in their epidemiology, presentation and outcome. Among these, meningitis and meningoencephalitis require urgent and adapted anti-infectious therapy, but published data is scarce in KTRs. The aim of this study was to describe their epidemiology, presentation and outcome, in order to improve their diagnostic and management. We performed a retrospective, multicentric cohort study in 15 French hospitals that included all 199 cases of M/ME in KTRs between 2007 and 2018 (0.9 case per 1,000 KTRs annually). Epidemiology was different from that in the general population: 20% were due to Cryptococcus neoformans, 13.5% to varicella-zoster virus, 5.5% to Mycobacterium tuberculosis, and 4.5% to Enterobacteria (half of which produced extended spectrum beta-lactamases), and 5% were Post Transplant Lymphoproliferative Disorders. Microorganisms causing M/ME in the general population were infrequent (2%, for Streptococcus pneumoniae) or absent (Neisseria meningitidis). M/ME caused by Enterobacteria, Staphylococci or filamentous fungi were associated with high and early mortality (50%-70% at 1 year). Graft survival was not associated with the etiology of M/ME, nor was impacted by immunosuppression reduction. Based on these results, we suggest international studies to adapt guidelines in order to improve the diagnosis and the probabilistic treatment of M/ME in SOTRs.

Impact of age on survival in radioiodine refractory differentiated thyroid cancer patients.

OBJECTIVE: The objectives of our study were to analyze the influence of age on the survival of patients with RAIR-DTC and to determine their prognostic factors according to age. METHODS: This single-center, retrospective study enrolled 155 patients diagnosed with RAIR-DTC. The primary end point was overall survival (OS) according to different cutoff (45, 55, 65, 75 years). Secondary endpoints were progression free survival (PFS) and prognostic factors in patients under and over 65 years. RESULTS: Median OS after RAIR diagnosis was 8.2 years (95% IC: 5.3-9.6). There was no difference according to age with a 65 (P = 0.47) and 55 years old cutoff (P = 0.28). Median OS improved significantly before 45 years old (P = 0.0043). After 75 years old, median OS significantly decreased (P = 0.0008). Median PFS was 2.1 years (95% CI: 0.8-3) in patients < 65 years old, and 1 year in patients ≥ 65 years old (95% CI: 0.8-1.55) with no statistical difference (P = 0.22). There was no impact of age on PFS with any cutoff. In both groups, progressive disease despite 131I treatment reduced OS. In patients < 65 years old, an interval of less than 3 years between the initial diagnosis and the diagnosis of RAIR metastatic disease was predictive of poor survival. In patients > 65 years old, the presence of a mediastinum metastasis was a significant factor for mortality (HR: 4.55, 95% CI: 2.27-9.09). CONCLUSION: In RAIR-DTC patients, a cut-off age of 65 years old was not a significant predictive factor of survival. Forty-five and 75-years-old cutoff were predictive for OS but not PFS.

Characterization of Skull Base Lesions Using Pseudo-Continuous Arterial Spin Labeling.

PURPOSE: Pseudo-continuous arterial spin labeling (pCASL) is a non-invasive magnetic resonance (MR) perfusion technique. Our study aimed at estimating the diagnostic performance of the pCASL sequence in assessing the perfusion of skull base lesions both qualitatively and quantitatively and at providing cut-off values for differentiation of specific skull base lesions. METHODS: In this study 99 patients with histopathologically confirmed skull base lesions were retrospectively enrolled. Based on a pathological analysis, the lesions were classified as hypervascular and non-hypervascular. Patients were divided into two subgroups according to the anatomical origin of each lesion. The MRI study included pCASL and 3D T1-weighted fat-saturated post-contrast sequences. Of the patients seven were excluded due to technical difficulties or patient movement. The lesions were classified by two raters, blinded to the diagnosis as either hyperperfused or non-hyperperfused, based on the pCASL sequence. The normalized tumor blood flow (nTBF) of each lesion was determined. Qualitative and quantitative characteristics of hypervascular and non-hypervascular lesions were compared. RESULTS: Visual assessment enabled correct classification of 98% of the lesions to be performed. Quantitatively, we found significant differences between the nTBF values for hypervascular and non-hypervascular lesions (p < 0.001) and provided cut-off values, allowing meningioma and schwannoma to be distinguished from meningioma and adenoma. Significant differences were also found within the hypervascular group, namely, paraganglioma was more hyperperfused than meningioma (p = 0.003) or metastases (p = 0.009). CONCLUSION: The present study demonstrates the high diagnostic performance of pCASL in characterizing skull base lesions by either visual assessment or nTBF quantification. Adding the pCASL sequence to the conventional protocol of skull base assessment can be recommended.

INFLIXIMAB and ADALIMUMAB in Uveitic Macular Edema.

PURPOSE: To compare the efficacy of infliximab and adalimumab in patients with refractory uveitis-related macular edema (ME). METHODS: A retrospective study was conducted in all patients with refractory uveitis-related ME treated with infliximab or adalimumab in Pitié-Salpêtrière hospital between January 1, 2006 and January 1, 2016. All patients underwent a complete ophthalmologic examination, OCT and retinal angiography at baseline, and 6 (M6) and 24 months (M24) after treatment initiation. Main outcome was a decrease in central foveal thickness (CFT) on OCT. RESULTS: Twenty-five patients were included: 12 treated with adalimumab and 13 treated with infliximab. The median baseline CFT was 381 µm (Q1 = 254; Q3 = 470) in the adalimumab group and 469 µm (307; 539) in the infliximab group. At M6, 6/12 adalimumab-treated patients (50%) and 8/13 infliximab-treated patients (61%) were responders. The median CFT decrease from baseline was 61 µm (17-136) and 66 µm (-59-119) respectively at M6 and M24 in the adalimumab group versus 92 µm (9-165) and 52 µm (33-130) respectively at M6 and M24 in the infliximab group (all p > 0.05). CONCLUSION: No significant difference in efficacy was observed between infliximab and adalimumab at M6 and M24.

Current practice and access to prostate MR imaging in France.

PURPOSE: To obtain an overview of the degree of discrepancy between current clinical practice of prostate magnetic resonance imaging (MRI) in France and recommendations. MATERIALS AND METHODS: A brief survey was sent to 1229 members of the French society of urology in order to identify their indications of prostate MRI and its impact on patient management. The urologists were asked to answer several questions regarding age, practice modality, prostate MRI examinations (technique, indication before first biopsy, second biopsy, cancer staging, active surveillance, recurrence, focal therapy) and quality of reports. RESULTS: A total of 445 responses were received (participation rate of 36%). The mean delay for obtaining an appointment for prostate MRI ranged between 15-30 days in 54%. Fifty-four percent of MRI reports contained a PIRADS score and 23% a Likert score. The indications of multiparametric-MRI were tumor detection/location prior to repeat biopsy (90%), cancer staging (85%), management of patients under active surveillance (85%), selection of candidates to focal therapy (63%), tumor detection/location in biopsy naïve patients (53%), detection of local recurrence after radical (51%). Only 119 urologists (28.6%) had access to image fusion (MRI and transrectal ultrasound) and 351 (85.4%) used cognitive fusion. Mostly, targeted biopsies are done by urologists alone (nearly 80%), a very few are done by radiologists (8%) or by the two of them in collaboration (12%). CONCLUSION: The majority of urologists consider that prostate MRI is essential for the management of patients with prostate cancer. Practices are ahead of recommendations particularly before the first biopsy and in active surveillance.

Care-related pain in hospitalized patients: severity and patient perception of management.

BACKGROUND: Hospitalized patients commonly undergo painful procedures, but little is known about care-related pain (CRP) in the overall population of inpatients. We conducted a cross-sectional 1-day survey to assess the prevalence and characteristics of CRP and its management in all units of a university hospital in Paris and determined the factors linked to severe CRP. METHODS: All patients who were able to communicate and were hospitalized for at least 24 h but not in a day-care or neonatal unit were included. RESULTS: From 938 patients who completed the questionnaire, 554 patients reported pain within the previous 24 h, for a 59% prevalence of pain, and 540 (58%) had experienced CRP in the previous 15 days (51% males; mean [SD] age 54 [18] years). Of 907 procedures, 330 (37%) resulted in severe pain. The most-often reported painful procedures were vascular punctures and patient mobilization. Severe CRP was associated with long hospitalization; non-vascular invasive punctures, catheterization, mobilization or radiological examination; or pain during the previous 24 h due to surgery or treatment. Only half of the patients declared that they had received information regarding the painful procedure. Treatment for pain was proposed and delivered in less than one quarter of cases. CONCLUSIONS: Our results of a survey of pain management in hospitalized patients relate to a wide variety of medical conditions and procedures. Health-care workers should be more systematic in managing CRP, and attention should be paid to patients at greatest risk of severe CRP.

Determinants of patient satisfaction regarding pain care.

BACKGROUND: The management of pain in hospitalized patients remains a major public hospital priority. It has been the object of three French national programs since 1999. The purpose of this study was to reassess pain prevalence, pain intensity and patient perception of its management ten years after the first national program and to determine the factors related to the patient satisfaction with efforts to decrease pain intensity. METHODS: A 1-day cross-sectional survey in a university hospital. RESULTS: Pain prevalence was 59%. Pain intensity varied according to the medical department with lower intensity in surgery and obstetrics than medicine departments. Eighty-one percent of patients were satisfied with their pain management. Patient satisfaction was higher when doctors and nurses were heavily involved in the process of pain relief (OR=6.6; 95% CI 3.8, 11.4), and when their pain had decreased (OR=2.9; 1.7, 5.0). The magnitude of decrease in pain were higher when the medical team was involved (OR=1.9; 95% IC 1.1, 3.3) and pain intensity was measured (OR=1.6; 1.0, 2.4). Perceptions of doctor and nurse involvement in the patient's care was higher when pain intensity was measured (OR=6.0; 3.4, 10.5), an immediate treatment offered (OR=3.5; 2.0, 6.2), encouragement to ask for an analgesic was provided (OR=2.0; 1.1, 3.5) and for patients with acute pain (OR=2.2; 1.0, 4.7). CONCLUSIONS: This study identifies the factors related to patient satisfaction with pain management and the magnitude of the decrease in pain which should allow further efforts to improve the management of pain and reduce its intensity in hospital inpatients.

The natural history of spinocerebellar ataxia type 1, 2, 3, and 6: a 2-year follow-up study.

OBJECTIVE: To obtain quantitative data on the progression of the most common spinocerebellar ataxias (SCAs) and identify factors that influence their progression, we initiated the EUROSCA natural history study, a multicentric longitudinal cohort study of 526 patients with SCA1, SCA2, SCA3, or SCA6. We report the results of the 1- and 2-year follow-up visits. METHODS: As the primary outcome measure we used the Scale for the Assessment and Rating of Ataxia (SARA, 0-40), and as a secondary measure the Inventory of Non-Ataxia Symptoms (INAS, 0-16) count. RESULTS: The annual increase of the SARA score was greatest in SCA1 (2.18 ± 0.17, mean ± SE) followed by SCA3 (1.61 ± 0.12) and SCA2 (1.40 ± 0.11). SARA progression in SCA6 was slowest and nonlinear (first year: 0.35 ± 0.34, second year: 1.44 ± 0.34). Analysis of the INAS count yielded similar results. Larger expanded repeats and earlier age at onset were associated with faster SARA progression in SCA1 and SCA2. In SCA1, repeat length of the expanded allele had a similar effect on INAS progression. In SCA3, SARA progression was influenced by the disease duration at inclusion, and INAS progression was faster in females. CONCLUSIONS: Our study gives a comprehensive quantitative account of disease progression in SCA1, SCA2, SCA3, and SCA6 and identifies factors that specifically affect disease progression.

Basal ganglia dysfunction in OCD: subthalamic neuronal activity correlates with symptoms severity and predicts high-frequency stimulation efficacy.

Functional and connectivity changes in corticostriatal systems have been reported in the brains of patients with obsessive-compulsive disorder (OCD); however, the relationship between basal ganglia activity and OCD severity has never been adequately established. We recently showed that deep brain stimulation of the subthalamic nucleus (STN), a central basal ganglia nucleus, improves OCD. Here, single-unit subthalamic neuronal activity was analysed in 12 OCD patients, in relation to the severity of obsessions and compulsions and response to STN stimulation, and compared with that obtained in 12 patients with Parkinson's disease (PD). STN neurons in OCD patients had lower discharge frequency than those in PD patients, with a similar proportion of burst-type activity (69 vs 67%). Oscillatory activity was present in 46 and 68% of neurons in OCD and PD patients, respectively, predominantly in the low-frequency band (1-8 Hz). In OCD patients, the bursty and oscillatory subthalamic neuronal activity was mainly located in the associative-limbic part. Both OCD severity and clinical improvement following STN stimulation were related to the STN neuronal activity. In patients with the most severe OCD, STN neurons exhibited bursts with shorter duration and interburst interval, but higher intraburst frequency, and more oscillations in the low-frequency bands. In patients with best clinical outcome with STN stimulation, STN neurons displayed higher mean discharge, burst and intraburst frequencies, and lower interburst interval. These findings are consistent with the hypothesis of a dysfunction in the associative-limbic subdivision of the basal ganglia circuitry in OCD's pathophysiology.

Modifier locus of the skeletal muscle involvement in Emery-Dreifuss muscular dystrophy.

Autosomal dominant Emery-Dreifuss muscular dystrophy is caused by mutations in LMNA gene encoding lamins A and C. The disease is characterized by early onset joint contractures during childhood associated with humero-peroneal muscular wasting and weakness, and by the development of a cardiac disease in adulthood. Important intra-familial variability characterized by a wide range of age at onset of myopathic symptoms (AOMS) has been recurrently reported, suggesting the contribution of a modifier gene. Our objective was to identify a modifier locus of AOMS in relation with the LMNA mutation. To map the modifier locus, we genotyped 291 microsatellite markers in 59 individuals of a large French family, where 19 patients carrying the same LMNA mutation, exhibited wide range of AOMS. We performed Bayesian Markov Chain Monte Carlo-based joint segregation and linkage methods implemented in the Loki software, and detected a strong linkage signal on chromosome 2 between markers D2S143 and D2S2244 (211 cM) with a Bayes factor of 28.7 (empirical p value = 0.0032). The linked region harbours two main candidate genes, DES and MYL1 encoding desmin and light chain of myosin. Importantly, the impact of the genotype on the phenotype for this locus showed an overdominant effect with AOMS 2 years earlier for the homozygotes of the rare allele and 37 years earlier for the heterozygotes than the homozygotes for the common allele. These results provide important highlights for the natural history and for the physiopathology of Emery-Dreifuss muscular dystrophy.

Does clinical rapid eye movement behavior disorder predict worse outcomes in Parkinson's disease?

Our purpose of this study was to investigate whether clinical rapid eye movement sleep behavior disorder (RBD) is indicative of more widespread degenerative changes in Parkinson's disease (PD), using a longitudinal cohort. In 2005 and 2007, we prospectively collected clinical and treatment characteristics of 61 consecutive patients with PD. The presence of RBD was assessed by spouse interview. Sixty-four percent of patients had clinical RBD in 2005, versus 52% of patients in 2007. The yearly incidence rate of clinical RBD onset was 9%, while clinical RBD disappeared in 14% of patients per year. The motor disability scores (when treated) were worse in patients with than without clinical RBD in 2005, but not in 2007. There was no difference between groups for frequency of freezing, falls, and hallucinations, or for scores on the depression scale, sleepiness scale, mini-mental state examination and frontal assessment battery at the beginning versus the end of the study. Patients with clinical RBD were disabled earlier than patients without RBD, but there was no specific worsening in the RBD group with time, either for motor or non-motor symptoms. The fluctuation and disappearance of clinical RBD in some patients may be due to functional abnormalities rather than lesions.

Anemia in the period immediately following renal transplantation.

INTRODUCTION: Anemia remains frequent in the first month following renal transplantation and is a risk factor for cardiovascular accidents. The purpose of this study was to analyze the prevalence of anemia during this period notably among different immunosuppressive treatment groups. METHODS: In this study, we entered the patients who had received a renal allograft in our transplant unit from 1993 to 2003, including patients who had received azathioprine (AZA) from 1993 to 1996 and mycophenolate mofetil (MMF) from 1996 to 2003. No patient received rHu-erythropoietin after transplantation during that period. A mathematical model normalized the hemoglobin (Hb) threshold level at which blood transfusion was decided and Hb on admission. RESULTS: One hundred and eighty-eight patients on AZA and 223 on MMF were included in the analysis. The mean age +/- SD was 41 +/- 12 years in the AZA group, and 45 +/- 12 years in the MMF group (P < .006). Before the transplantation, Hb was higher in the MMF group (11.4 +/- 1.9 vs 10.2 +/- 2 g/dL, P < .0001). After normalization at a threshold level of transfusion of 7 g/dL, transfusions were more frequent among the MMF group (72% vs 48%, P < .0001). Double therapy with MMF (1500 mg/d) + steroids or therapy with MMF (750 mg/d) + tacrolimus + steroids increased the risk of transfusion compared to the AZA group. MMF (750 mg/d) + cyclosporine conferred a similar risk of transfusion compared with the AZA group. CONCLUSION: MMF alone or in association with tacrolimus is associated with an increased risk of anemia and transfusion in the immediate posttransplantation period.

Parkinson's disease with camptocormia.

BACKGROUND: Camptocormia is defined as an abnormal flexion of the trunk that appears when standing or walking and disappears in the supine position. The origin of the disorder is unknown, but it is usually attributed either to a primary or a secondary paravertebral muscle myopathy or a motor neurone disorder. Camptocormia is also observed in a minority of patients with parkinsonism. OBJECTIVE: To characterise the clinical and electrophysiological features of camptocormia and parkinsonian symptoms in patients with Parkinson's disease and camptocormia compared with patients with Parkinson's disease without camptocormia. METHODS: Patients with parkinsonism and camptocormia (excluding patients with multiple system atrophy) prospectively underwent a multidisciplinary clinical (neurological, neuropsychological, psychological, rheumatological) and neurophysiological (electromyogram, ocular movement recording) examination and were compared with age-matched patients with Parkinson's disease without camptocormia. RESULTS: The camptocormia developed after 8.5 (SD 5.3) years of parkinsonism, responded poorly to levodopa treatment (20%) and displayed features consistent with axial dystonia. Patients with camptocormia were characterised by prominent levodopa-unresponsive axial symptoms (ie, axial rigidity, gait disorder and postural instability), along with a tendency for greater error in the antisaccade paradigm. CONCLUSION: We suggest that (1) the salient features of parkinsonism observed in patients with camptocormia are likely to represent a specific form of Parkinson's disease and camptocormia is an axial dystonia and (2) both camptocormia and parkinsonism in these patients might result from additional, non-dopaminergic neuronal dysfunction in the basal ganglia.

Epsilon sarcoglycan mutations and phenotype in French patients with myoclonic syndromes.

BACKGROUND: Myoclonus dystonia syndrome (MDS) is an autosomal dominant movement disorder caused by mutations in the epsilon-sarcoglycan gene (SGCE) on chromosome 7q21. METHODS: We have screened for SGCE mutations in index cases from 76 French patients with myoclonic syndromes, including myoclonus dystonia (M-D), essential myoclonus (E-M), primary myoclonic dystonia, generalised dystonia, dystonia with tremor, and benign hereditary chorea. All coding exons of the SGCE gene were analysed. The DYT1 mutation was also tested. RESULTS: Sixteen index cases had SGCE mutations while one case with primary myoclonic dystonia carried the DYT1 mutation. Thirteen different mutations were found: three nonsense mutations, three missense mutations, three splice site mutations, three deletions, and one insertion. Eleven of the SGCE index cases had M-D and five E-M. No SGCE mutations were detected in patients with other phenotypes. The total number of mutation carriers in the families was 38, six of whom were asymptomatic. Penetrance was complete in paternal transmissions and null in maternal transmissions. MDS patients with SGCE mutation had a significantly earlier onset than the non-carriers. None of the patients had severe psychiatric disorders. CONCLUSION: This large cohort of index patients shows that SGCE mutations are primarily found in patients with M-D and to a lesser extent E-M, but are present in only 30% of these patients combined (M-D and E-M).

Disorganized somatotopy in the putamen of patients with focal hand dystonia.

OBJECTIVE: To explore the selectivity of neuronal somatotopic representation in the striatum of patients with unilateral task-specific dystonia of the right arm. MATERIALS AND METHODS: The authors used fMRI in 14 right-handed dystonic subjects to examine putaminal organization. Subjects performed flexion/extension of the right and left fingers and toes, and contraction of the lips. RESULTS: Compared to healthy volunteer subjects, dystonic subjects had altered somatotopic organization in the left putamen, contralateral to the affected hand. Disease severity correlated with underactivation and decreased distance between right hand and lip representations. In the right putamen, ipsilateral to the affected hand, the somatotopic organization was not altered but disease severity also correlated with reduced distances between limbs. CONCLUSION: In dystonia there may be a dedifferentiation of the normally segregated cortico-subcortical sensorimotor maps in the putamen, which may contribute to the loss of functional selectivity of muscle activity observed in these dystonic subjects.

Candidate gene studies in focal dystonia.

BACKGROUND: Genetic susceptibility factors for focal idiopathic torsion dystonia (F-ITD) are not established. Mutations in the DYT1 gene can cause focal dystonia, and an association with a polymorphism in the D5 receptor gene (DRD5) has been reported but not confirmed. OBJECTIVE: To investigate a possible role of DYT1 polymorphisms, a CA repeat in the D5 receptor gene (DRD5), the human leukocyte antigen (HLA)-DRB locus, and four polymorphisms in the homocysteine metabolism in the pathogenesis of F-ITD. METHODS: Initially, 100 German patients and 100 matched control subjects were investigated. A second French population with 121 F-ITD patients and matched control subjects was also studied. RESULTS: Two polymorphisms of the beta-cystathionine synthase gene were associated with F-ITD in the German population, but this finding was not replicated in a second independent F-ITD patient and control group of French origin. None of the other investigated polymorphisms was associated with F-ITD. The authors failed to confirm a previously reported association with a polymorphism in DRD5. CONCLUSION: No evidence for an involvement of DYT1, DRD5, HLA-DRB, or polymorphisms in the homocysteine pathway in the pathogenesis of F-ITD was found.

Clinical predictive factors of subthalamic stimulation in Parkinson's disease.

High-frequency stimulation of the subthalamic nucleus (STN) constitutes one of the most effective treatments for advanced forms of Parkinson's disease. The cost and potential risks of this procedure encourage the determination of clinical characteristics of patients that will have the best postoperative outcome. Forty-one Parkinson's disease patients underwent surgery for bilateral STN stimulation. The selection criteria were severe parkinsonian motor disability, clear response of symptoms to levodopa, occurrence of disabling levodopa-related motor complications and the absence of dementia and significant abnormalities on brain MRI. Clinical evaluation was performed 1 month before and 6 months after surgery. The improvement in the activities of daily living subscale of the Unified Parkinson's Disease Rating Scale, Part II (UPDRS II) and parkinsonian motor disability (UPDRS III) was greater when the preoperative scores for activities of daily living and parkinsonian motor disability, in particular axial symptoms, such as gait disorders and postural instability assessed at the time of maximal clinical improvement (on drug), were lower. Age and disease duration were not predictive, but parkinsonian motor disability tended to be more improved in patients with younger age and shorter disease duration. The severity of levodopa-related motor complications was not a predictive factor. The outcome of STN stimulation was excellent in levodopa-responsive forms of Parkinson's disease, i.e. in patients with selective brain dopaminergic lesions, and moderate in patients with axial motor symptoms and cognitive impairment known to be less responsive or unresponsive to levodopa treatment, i.e. when brain non-dopaminergic lesions develop in addition to the degeneration of the nigrostriatal dopaminergic system. The results are consistent with the classical inclusion criteria for STN stimulation, but imply that the decision to operate on the oldest patients and/or patients with gait and postural disorders, who are poorly responsive to levodopa, should be weighed carefully.

Modeling the HLA component in rheumatoid arthritis: sensitivity to DRB1 allele frequencies.

Rheumatoid arthritis is an inflammatory disease for which positive associations have been described with some HLA-DRB1 alleles. The associated alleles share a similar amino acid sequence in the third hypervariable region, the shared epitope, but differ at position 71 and 86. It has been suggested that HLA susceptibility to rheumatoid arthritis could be due not only to the shared epitope but could also be influenced by specific amino acids at positions 71 and 86. In this study, we investigated the role of these amino acids in rheumatoid arthritis on 203 unrelated patients. An involvement of amino acid 71 was detected but no conclusion was possible regarding amino acid 86. A study of the sensitivity of the conclusions to marker allele frequencies was performed. We showed that the results obtained for amino acid 71 are not very sensitive to allele frequencies but those obtained at position 86 are highly sensitive. This emphasizes the importance of studying the robustness of results to variations in allele frequencies before conclusions are drawn.

Baclofen eliminates cluster lung breathing of the tadpole brainstem, in vitro.

Intermittent lung ventilation is a respiratory pattern wherein breaths occur in clusters. Intermittent lung ventilation is common in amphibians and can occur in mammals. Isolated brainstems from postmetamorphic tadpoles exhibiting episodic lung ventilatory bursts were superfused with baclofen, a potent gamma-aminobutyric acid (GABA)(B) receptor agonist. At moderate concentrations (0.125 to 0.5 microM), the number of lung bursts per episode decreased but their overall frequency was unchanged. At 0.5 microM, only 1.22+/-0.24 lung bursts occurred per episode, indicating virtually no clustering. Only at higher concentrations was overall breathing frequency decreased. Therefore, at moderate concentrations of baclofen continuous ventilation replaced episodic ventilation, suggesting that a GABA(B) receptor-dependent pathway may regulate the clustering of lung breaths.