Paediatric Laryngeal Synovial Sarcoma: Dilemmas and Decision-Making

Primary laryngeal synovial sarcoma is a rare head and neck cancer. We describe a case of synovial sarcoma of the larynx in a previously well 9-year-old boy with a one-month history of a progressively enlarging neck lump. He was referred to our institution after incomplete surgical excision of the then undifferentiated neck mass. A partial laryngectomy including wide local excision of the residual mass was performed. An ipsilateral level I-III neck dissection was also performed concurrently. Clear re-excision margins were achieved. The neck nodes were all negative for metastatic disease. Adjuvant local radiotherapy treatment was administered to reduce the probability of local recurrence. Four years following treatment completion, the patient remains in remission with no signs of treatment-related morbidity. A review of the published literature on laryngeal synovial sarcoma was undertaken. This case represents the youngest patient to be diagnosed with the condition. Surgical excision represents the mainstay of treatment of laryngeal synovial sarcoma. At more common sites of disease, adjuvant radiotherapy has been associated with lower rates of recurrence. However, there is the potential for significant morbidity from irradiating the neck of a paediatric patient. This case report explores the challenges in treating young patients with aggressive head and neck cancers when faced with little available evidence to guide decision-making.

Systematic review of head and neck lymphedema assessment

Head and neck lymphedema (HNL) is an increasingly recognized complication of head and neck cancer and its treatment. However, no consensus exists on the "gold-standard" assessment tool for the purposes of diagnosis, classification, or monitoring of HNL. We conducted a systematic review of the literature regarding HNL assessment to determine the optimal method/s of assessment for patients with HNL. A review of publications between January 2000 and September 2021 was undertaken on four electronic databases. Studies were excluded if no clear assessment method of HNL was documented. Sixty-seven articles were included in the study. A wide range of assessment methods for HNL have been reported in the literature. For the purposes of diagnosis and classification of physical findings, computed tomography (CT) appears the most promising tool available for both external and internal HNL. In terms of monitoring, ultrasound appears optimal for external HNL, while a clinician-reported rating scale on laryngoscopy is the gold standard for internal HNL. Patient-reported assessment must be considered alongside objective methods to classify symptom burden and monitor improvement with treatment.

Timing of Ansa Cervicalis-to-recurrent Laryngeal Nerve Reinnervation: A Systematic Review

BACKGROUND

Ansa cervicalis-to-recurrent laryngeal nerve anastomosis (ARA) is an established technique for the treatment of recurrent laryngeal nerve (RLN) injury after head and neck surgery. However, the optimal timing of ARA remains unclear, and the evidence bases for ARA performed at each timepoint after RLN injury have not previously been clearly distinguished. We conducted a systematic review of the literature to evaluate the efficacy of ARA performed at different timepoints on postoperative voice outcomes.

METHODS

A review of English-language journal articles published in the last 20 years was undertaken on three electronic databases: Ovid MEDLINE, PubMed and Embase. Studies with a focus on paediatric RLN injury, bilateral RLN injury, ansa cervicalis anatomy and non-ARA techniques alone were excluded.

RESULTS

Twenty eight articles were included in the review. ARA was performed as a delayed surgery in 16/28 studies (57%), while immediate ARA was utilized in 14/28 studies (50%). On qualitative synthesis, delayed ARA was shown to be effective in improving patient-reported, subjective observer-reported and objective observer-reported voice outcomes. Likewise, a substantial body of evidence was identified demonstrating postoperative voice improvement with immediate ARA. On direct comparison of timepoints, some benefit was shown for early delayed ARA relative to late delayed operations, while no comparative data for immediate versus delayed repair were available in the literature.

CONCLUSIONS

ARA at both delayed and immediate timepoints is effective in the treatment of patients with RLN injury after head and neck surgery. The timing of ARA may have some influence on its efficacy, with early delayed repair potentially associated with superior outcomes to late delayed operations, and immediate ARA offering several practical advantages relative to delayed repair. Further comparative studies are required to better characterize the optimal timing of ARA after RLN injury.

Tranexamic acid in otorhinolaryngology - A contemporary review

Tranexamic acid (TXA) is an anti-fibrinolytic agent which has been proven beneficial in multiple surgical specialties where significant bleeding can occur. Whilst it has been widely available for over 40 years its use within Otorhinolaryngology is still limited. Operations in Otorhinolaryngology are particularly varied with some such as tonsillectomy having the potential for significant life threatening bleeding. Other operations are performed within small confined surgical fields and even small amounts of bleeding can significantly detriment surgical field and increase technical difficulty and operative time. This review evaluated the current literature on the benefits of tranexamic acid within the field of Otorhinolaryngology and Head and Neck Surgery. Overall TXA was demonstrated to be a safe drug with no major adverse effects including thromboembolic events reported in any study. It has been shown to be of particular benefit in rhinology by improving surgical field, reducing operative time and reducing postoperative swelling and ecchymosis. The benefit in tonsillectomy is less clear and further studies are required to evaluate its potential use in the reduction of post tonsillectomy haemorrhage rates.

Meta-analysis on the rate of pharyngocutaneous fistula in early oral feeding in laryngectomy patients

BACKGROUND

Laryngectomy remains a common operation in head and neck units. The operation holds significant risk of post-operative morbidity including swallowing dysfunction. The most significant post-operative concern is the formation of a pharyngocutaneous fistula [PCF], the reported incidence of which is between 3% and 65%. The purpose of this systematic review and meta-analysis was to assess the safety of initiating early oral feeding following laryngectomy and the risk of PCF formation.

METHODS

A literature search was conducted through online databases: MEDLINE, EMBASE and PubMed. Eligible studies were included which contained cohorts of patients who had undergone laryngectomy, with early oral feeding commencing within seven days compared to late oral feeding. The primary outcome assessed was the incidence of PCF. Studies were excluded if cohorts had not included laryngectomy or if no comment was made on PCF formation. Meta-analysis was used to examine associations between oral feeding and PCF formation using Fixed Effect models.

RESULTS

Twelve studies and 1883 patients were included after systematic review. Six studies were non-interventional whereas the remaining were randomized clinical trials. Exposure included those with early oral feeding (before seven days) or late feeding oral feeding (after seven days) and the outcome assessed was the risk of PCF formation. Results from observational studies showed a higher risk of PCF formation for early feeders compared to late feeders [RR = 1.56, 95% CI: 1.15, 2.11]. Higher risk was also observed for RCT but was not significant [RR = 1.40, 95% CI: 0.85, 2.30]. Overall, there was a 50% greater risk of PCF formation for early oral feeding compared to late oral feeding [RR = 1.51, 95% CI: 1.17, 1.96].

CONCLUSION

While early oral feeding can reduce post-laryngectomy patients' hospital stay and improve psychological wellbeing, there is a significant relative risk of PCF development within this group. However, this must be taken in context of the significant heterogeneity that exists within the literature.

Acinic cell carcinoma of the salivary gland in the adult and paediatric population: a survival analysis

BACKGROUND

Acinic cell carcinoma (AcCC) is a rare malignant neoplasm of the salivary glands and generally considered to be a low-grade tumour. Surgical treatment is often curative, but a more aggressive high-grade variant has been associated with poorer survival and propensity for distant metastasis. No standard treatment guidelines exist and the approach to treatment is varied in the published series. The aim of this study is to present the experience of three major hospitals in Sydney, Australia, in treating AcCC of the salivary gland, with a focus on clinico-pathological features of disease and their associations with survival outcomes.

METHODS

Adult and paediatric cases of AcCC of the salivary gland during the time period 1979-2018 were retrospectively included. Demographic, clinico-pathological, treatment and survival outcome data were extracted. Survival analysis was undertaken to assess the effect of clinical and pathological variables on overall and disease-free survival.

RESULTS

Thirty-two cases were reviewed (29 adult and three paediatric). Thirty tumours (93.8%) were parotid gland primary tumours. Mean overall and disease-free survival was 17.0 ± 0.7 and 16.0 ± 0.9 years, respectively. Features associated with poorer survival were cT staging >1, presence of preoperative clinical facial nerve deficit and local recurrence. Positive margins were associated with recurrence.

CONCLUSION

These data suggest that disease-free and overall survival in AcCC of the salivary gland is excellent with surgery as the first-line treatment. Poor survival outcomes are uncommon and may be associated with locally advanced disease in the presence of other well-established high-risk features.

Systematic review of laryngocele and pyolaryngocele management in the age of robotic surgery

OBJECTIVE

A laryngocele is a space that develops as a result of pathological dilatation of the laryngeal saccule. However, the reported management of laryngoceles varies. We conducted a systematic review of the literature regarding the surgical management of laryngoceles and pyolaryngoceles, to understand the evolving nature of treatment for this rare condition.

METHODS

We searched for publications in the PubMed, Cochrane Library, JBI Library of Systematic Reviews, and Ovid databases using the terms "laryngocele", "pyolaryngocele", and "laryngopyocele", and reviewed the identified articles.

RESULTS

After removal of repeated studies and filtering for relevance and studies written in English, a total of 227 studies were included in this review. No meta-analyses or randomized controlled trials have been published. The identified studies have been summarized in 14 reviews conducted since 1946. The meta-analysis determined that endoscopy was the preferred approach for internal laryngoceles, while combined laryngoceles benefited from both internal and external surgical approaches.

CONCLUSIONS

Laryngocele management has progressed since its initial description, from open surgery to an endoscopic approach, and more recently to a robotic-assisted surgical approach. The uptake of robotic surgery as a possible treatment modality over the last decade shows much promise for the treatment of these conditions.

Operative team checklist for aerosol generating procedures to minimise exposure of healthcare workers to SARS-CoV-2

OBJECTIVES

In many countries around the world, the COVID-19 pandemic has resulted in health services being diverted to manage patients with the condition. There are situations however that still require the undertaking of aerosol generating procedures (AGP) with potentially high exposure of healthcare workers to SARS-CoV-2 transmission through droplet, contact and possibly airborne routes. The objective of this paper is to explore a structured way for the operative team to approach AGP to reduce aerosolisation of secretions, decrease open airway time and minimise staff exposure.

METHODS

The authors (otolaryngologists, anaesthetists and nursing staff) created a unified operative team checklist based on collation of national and international specialty society statements, local state government recommendations, hospital policies and literature review. Simulation was undertaken and the checklist was refined after performing AGP on patients with unknown (presumed positive) COVID-19 status.

RESULTS

An 8 step operative team checklist is provided describing details for the immediate pre-operative, intra-operative and post-operative journey of the patient to encourage healthcare workers to reflect upon and modify usual practice during AGP to mitigate exposure to SARS-CoV-2. The example of paediatric laryngo-bronchoscopy for diagnostic purposes or retrieval of an inhaled airway foreign body is used to illustrate the steps however the checklist structure is modifiable for other AGP and adaptable for local needs.

CONCLUSIONS

At a time of overwhelming and changing information and recommendations, an operative team checklist may provide some structure to healthcare workers undertaking AGP to reduce anxiety, maintain focus, prompt consideration of alternatives and potentially reduce risk.

Laryngeal Synovial Sarcoma: A Systematic Review of the Last 40 Years of Reported Cases

Primary laryngeal synovial sarcoma is an extremely rare tumor predominantly affecting young adults. There are currently no well-defined guidelines to direct investigation and management, and treatment is largely based on what is known for synovial sarcoma of the upper and lower limbs. This PROSPERO-registered study aims to review the diagnostic methods, treatment regimens, and survival outcomes for patients with synovial sarcoma of the larynx. A systematic search of databases Medline, Embase, SCOPUS, and Web of Science was undertaken in December 2017. The literature search identified 1031 potentially relevant studies, and after the deletion of duplicates and excluded papers, 98 full-text articles were screened. A total of 39 cases were reviewed from 32 studies in the data extraction. The average age at the time of laryngeal synovial sarcoma diagnosis was 32 years (range, 11-79 years). In all cases (n = 39), patients underwent wide surgical excision, with 20 patients requiring a partial or total laryngectomy. A total of 18 patients received adjuvant and 3 received neoadjuvant radiotherapy. Chemotherapy was used in 10 cases, with ifosfamide the most frequently used agent. There was considerable variability in the order and combinations of the abovementioned treatments. No clinicopathologic factors or treatment regimens were associated with improved overall survival or lower rate of recurrence. There is a paucity of literature and heterogeneity in clinical approaches to this highly aggressive sarcoma. Reporting of cases must be standardized and formal guidelines must be established to guide clinical management.

B cell activating factor (BAFF) in the natural history of chronic hepatitis C virus liver disease and mixed cryoglobulinaemia

B cell activating factor (BAFF) plays a crucial role in the process of development, maturation and activation of B lymphocytes. Chronic hepatitis C virus (HCV) infection is characterized by multiple B cell disorders. It is a major cause of type II mixed cryoglobulinaemia (MC). We measured serum BAFF levels in several clinical situations to elucidate the potential role of BAFF in chronic HCV infection. We used a commercially available solid phase enzyme-linked immunosorbent assay. We estimated serum BAFF in stored sera from uninfected controls (n = 8), patients with chronic hepatitis B virus infection HBV (n = 5) and chronic HCV infection with (n = 16) and without mixed cryoglobulinaemia (n = 14). In two patients with HCV and MC we correlated BAFF with HCV RNA after pegylated interferon (peg-I). We correlated serum BAFF levels at baseline and at 12 weeks with treatment response: sustained virological response SVR (n = 5), non-responders (n = 6) and relapsers (n = 2). Finally, we estimated BAFF levels after complete depletion of B cells with rituximab in patients with chronic HCV with MC (n = 3). Serum levels of BAFF were increased in chronic HCV with MC, but not in chronic HBV infection, suggesting an association between BAFF and cryoglobulinaemia. Peg-I increased BAFF levels in serum and this paralleled HCV RNA very closely. Serum BAFF levels at week 12 of therapy with peg-I and R were significantly higher in responders than non-responders. Finally, B cell depletion was associated with markedly increased levels of BAFF.

Absolute and relative contraindications to pegylated-interferon or ribavirin in the US general patient population with chronic hepatitis C: results from a US database of over 45 000 HCV-infected, evaluated patients

BACKGROUND

Chronic hepatitis C (HCV) treatment with pegylated-interferon (PEG-IFN)/ribavirin (RBV) is often limited by preexisting medical, psychiatric and psychosocial contraindications. However, limited data exist in general patient populations.

AIM

To evaluate the percentage of HCV-infected patients in the general US population who may have contraindications to PEG-IFN/RBV.

METHODS

The General Electric (GE) Centricity dataset was used to screen the US population between 2004 and 2009 for HCV infection and contraindications to PEG-IFN/RBV. HCV diagnosis and contraindications were identified using ICD-9-CM codes or laboratory values. Only patients with an encounter 180 days prior to HCV diagnosis were included. Demographic differences were calculated using Pearson's chi-squared test. Frequencies and percentages for absolute and relative contraindications to PEG-IFN and/or RBV were determined and proportions and rates/1000 person-months were calculated.

RESULTS

A total of 15 561 021 patients were screened, and 45 690 (0.3%) were HCV-positive and were evaluated. Those with contraindications were significantly younger, female, White, not currently married and receiving Medicare or Medicaid coverage (all P < 0.0001). 17.3% had at least one contraindication to PEG-IFN/RBV (5.5 events/1000 person-months); bipolar disorder (6.5%), anaemia (Hgb < 10 g/dL; 5.9%), pregnancy (1.9%) and neutropenia (neutrophils <750 cells/mm(3) ; 1.2%) were most frequently cited.

CONCLUSIONS

Approximately, 17% of HCV-infected patients in the general US population had at least one contraindication to PEG-IFN/RBV. Most contraindications were relative and potentially modifiable. Clinical assessment of contraindications as relative and/or modifiable should be considered and used to determine if patients could benefit from current PEG-IFN-containing triple therapy or future PEG-IFN- or RBV-free regimens.

Injuries among Swedish female elite football players: a prospective population study

Injury occurrence in all 12 female elite senior football teams in premiere league was registered during 1 year. Of 269 players, 129 (48%) sustained 237 injuries. The total injury incidence was 4.6/1000 h of football. The injury incidence during practice was 2.7 and during the game time was 13.9/1000 h. The highest injury incidence during practice was to the knee (0.8/1000 h) and thigh (0.5/1000 h), and during game time was to the knee (4.4/1000 h) and head (2.2/1000 h). In total, the location for the highest injury incidence was the knee with 1.5 injuries/1000 h of football. The majority of injuries (82%) were localized to the lower extremities. Sixty-six injuries (28%) were re-occurring injuries (re-injuries). The incidence of traumatic injuries was 3.3/1000 h of football and for overuse injuries 1.3/1000 h. Overuse injuries occurred mainly during the preseason and at the beginning of the spring season. Thirty-nine percent of the injuries were slight or minor causing absence from practice or game time of less than 1 week, 39% were moderate (absence 7-28 days) and 22% were major (absence more than 28 days). The major injuries occurred often owing to trauma and were mainly to the knee.

Optimisation and validation of a medium-throughput electrophysiology-based hERG assay using IonWorks™ HT

INTRODUCTION

Regulatory and competitive pressure to reduce the QT interval prolongation risk of potential new drugs has led to focus on methods to test for inhibition of the human ether-a-go-go-related gene (hERG)-encoded K+ channel, the primary molecular target underlying this safety issue. Here we describe the validation of a method that combines medium-throughput with direct assessment of channel function.

METHODS

The electrophysiological and pharmacological properties of hERG were compared using two methods: conventional, low-throughput electrophysiology and planar-array-based, medium-throughput electrophysiology (IonWorks HT). A pharmacological comparison was also made between IonWorks HT and an indirect assay (Rb+ efflux).

RESULTS

Basic electrophysiological properties of hERG were similar whether recorded conventionally (HEK cells) or using IonWorks HT (CHO cells): for example, tail current V1/2 -12.1+/-5.0 mV (32) for conventional and -9.5+/-6.0 mV (46) for IonWorks HT (mean+/-S.D. (n)). A key finding was that as the number of cells per well was increased in IonWorks HT, the potency reported for a given compound decreased. Using the lowest possible cell concentration (250,000 cells/ml) and 89 compounds spanning a broad potency range, the pIC50 values from IonWorks HT (CHO-hERG) were found to correlate well with those obtained using conventional methodology (HEK-hERG)(r=0.90; p<0.001). Further validation using CHO-hERG cells with both methods confirmed the correlation (r=0.94; p<0.001). In contrast, a comparison of IonWorks HT and Rb+ efflux data with 649 compounds using CHO-hERG cells showed that the indirect assay consistently reported compounds as being, on average, 6-fold less potent, though the differences varied depending on chemical series.

DISCUSSION

The main finding of this work is that providing a relatively low cell concentration is used in IonWorks HT, the potency information generated correlates well with that determined using conventional electrophysiology. The effect on potency of increasing cell concentration may relate to a reduced free concentration of test compound owing to partitioning into cell membranes. In summary, the IonWorks HT hERG assay can generate pIC50 values based on a direct assessment of channel function in a timeframe short enough to influence chemical design.

Analysis of the formed track in solid state materials using atomic force microscopy

The track formation in solid state materials, from the theoretical point of view, is still under study. One way to understand the track formation mechanisms and radiation damage of the charged particles in some materials such as polymers, glasses and minerals, is to analyse the surface topography effects. In this work, the track formation analysis in polycarbonate material is presented using an atomic force microscope (AFM) to characterise the evolution of the track on the material surface and beyond a thin layer of the surface material. The AFM is very useful to obtain valuable information at the level of the atomic structure of the materials and of the nuclear tracks, due to its high resolution and very easy operation involving also a simple sample preparation. The results show the development of the formed track by means of induced surface effects after being exposed to ionising radiation and chemical etching.

Chronic oesophagitis in the cat

BACKGROUND

Our understanding of the pathophysiology of gastro-oesophageal reflux disease (GERD) in man is limited. The aim of the present study was to establish a long-term (>1 year) animal model for reflux oesophagitis which would allow us to study various aspects of the development of chronic reflux oesophagitis.

METHODS

Myotomy was carried out in the gastro-oesophageal junction in eight cats; seven other cats were sham-operated. Before the operation, and every 2 months thereafter, oesophagoscopy was carried out, biopsies were taken for histology, and manometry was performed to determine the lower oesophageal sphincter pressure (LESP). The cats were killed 1 year after the operation.

RESULTS

The myotomy operation resulted in a significantly decreased LESP. In oesophageal biopsies from these cats, there was a varying degree of oesophagitis starting already 2 months after surgery. In six of the eight myotomized cats there was hyperplasia of the stratum basale, and cardiac type metaplasia was observed in two cats. The control cats showed no significant changes in LESP or in the histology of the oesophagus.

CONCLUSIONS

In cats followed for more than a year, myotomy in the gastro-oesophageal junction results in reflux oesophagitis similar to that seen in patients with chronic gastro-oesophageal reflux.

Screening of ion channel receptor agonists using capillary electrophoresis-patch clamp detection with resensitized detector cells

Efficient techniques for identifying endogenous and synthetic ligands of ion channels are important in understanding neuronal communication and for screening drug libraries. This paper describes a technique based on capillary electrophoresis (CE) separation coupled to patch-clamp (PC) detection where a pulsed-flow superfusion scheme was implemented for improved detection. The nicotinic acetylcholine receptor (nAChr) agonists acetylcholine, carbachol, and (-)-nicotine were fractionated and detected by patch-clamped pheochromcytoma detector cells. The high-conductance state of the nAChr during CE-PC detection was maintained and repetitively resensitized using pulsed-flow superfusion with agonist-free buffer. In this way, each agonist evoked an ensemble of peak currents that reflected the spatiotemporal distribution for the ligand at the cell surface. The technique takes advantage of the intrinsic high selectivity and sensitivity of membrane-expressed receptors and allowed for resolution and identification of closely migrating ligands. The method was employed for determination of acetylcholine content in cell lysates.

Management of interferon relapsers

Relapse in patients who have evidenced an initial response to a course of interferon monotherapy for chronic hepatitis C virus (HCV) infection has been a major frustration. At least 70% of responders will relapse after a 6-month course of treatment and more than 50% will relapse after a 12-month course of treatment, usually within the first 3 to 6 months after treatment discontinuation. At most, half of patients relapsing after an initial 6-month course will have a sustained response to a second, 12-month course of interferon monotherapy. A more promising second-line regimen is the combination of interferon plus ribavirin. A recent multicenter international trial has shown that this regimen results in a sustained virologic response rate of nearly 50%, fully 10-fold higher than the sustained response rate observed with a second 6-month course of interferon alone (49% vs 5%, respectively). In patients with non-1 genotype and viral levels no greater than 2 million copies/mL, the likelihood of sustained response to the second course of combination therapy was 100%. Biochemical and virologic responses (normalization of liver enzymes and disappearance of HCV RNA from the serum) were frequently accompanied by histologic improvement. HCV-RNA levels < or = 2 million copies/mL and non-1 viral genotype predicted treatment response, whereas age, gender, body weight, source of infection, type of interferon used for the first round of treatment, and elapsed time since first treatment had no effect. Based on these data, combination therapy with interferon and ribavirin is now considered the treatment of choice for relapsers. It is not clear whether 12 months of combination therapy might have produced even better rates of viral eradication in relapsed patients.

Lectin histochemistry of the esophagus in several mammalian species

The mucosa of the esophagus consists of stratified squamous epithelium that has a considerable resistance to injury. Intercellular glycoconjugates appear to constitute a major permeability barrier in the superficial portion of the esophageal mucosa. In the present study, we used a panel of lectins to investigate the differences in glycoconjugate production among different mammalian species. A battery of 12 lectins was used to study binding in sections from the esophagus of 6 mammalian species, including man. In general, the strongest staining was obtained in the stratum superficiale and the weakest staining in the stratum germinativum. In rabbit esophagus, exposure to pepsin/HCl produced a superficial damage to the epithelium, a considerable decrease in electrical resistance and a decreased staining of the esophageal epithelium with selected lectins. Pretreatment of the esophageal mucosa with sucrose octasulfate, a compound with protective properties, prevented, to some extent, the decrease in resistance and lectin staining.

Screening of receptor antagonists using agonist-activated patch clamp detection in chemical separations

We present a capillary electrophoresis-patch clamp detection system optimized for screening of antagonists and inhibitors of ligand-gated ion channels. In this system, highly selective receptor agonists are delivered through the electrophoresis capillary to the cell surface where they continuously activate a receptor, resulting in increased steady-state transmembrane currents. Thus, receptor selection and biosensor functionality is simply achieved by selection of an appropriate agonist. The antagonists are fractionated in the same electrophoresis capillary and inhibit the agonist-evoked response, resulting in transiently decreased steady-state transmembrane currents. Specifically, a mixture containing 6-cyano-7-nitroquinoxaline-2,3-dione, that reversibly blocks alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and kainate receptors, and 6,7-dichloro-3-hydroxy-2-quinoxaline-carboxylate, a broad-spectrum glutamate receptor antagonist, were separated and detected by kainate-activated patch-clamped interneurons freshly dissociated from rat brain olfactory bulb. In addition, Mg2+ that reversibly blocks the N-methyl-D-aspartate receptor in a voltage-dependent way was detected using the same cell detector system when activated by N-methyl-D-aspartate and the co-agonist glycine. The presented method offers new possibilities for drug screening and for identifying endogenous receptor antagonists and to determine their mode of action on any ionotropic receptor system of interest.

Patch clamp detection in capillary electrophoresis

We describe a capillary electrophoresis-patch clamp (CE-PC) analysis of biomolecules that activate ligand-gated ion channels. CE-PC offers a powerful means for identifying receptor ligands based on the combination of the characteristic receptor responses they evoke and their differential electrophoretic migration rates. Corner frequencies, membrane reversal potentials, and mean and unitary single-channel receptor responses were calculated from currents recorded with patch clamp detection. This information was then combined with the electrophoretic mobility of the receptor ligand, which is proportional to the charge-to-frictional-drag ratio of that species. We applied CE-PC to separate and detect the endogenous receptor agonists gamma-aminobutyrate and L-glutamate and the synthetic glutamate receptor agonists N-methyl-D-aspartate and kainic acid. We present dose-response data for electrophoretically separated kainic acid and discuss its implications for making the CE-PC detection system quantitative.

Idiopathic subglottic stenosis: diagnosis and endoscopic laser treatment

The records of 15 patients with idiopathic subglottic stenosis treated at Royal North Shore Hospital, Sydney, between 1980 and 1994 were reviewed. All were female and had similar characteristic clinical and histopathologic features. Endoscopic laser vaporization was the primary treatment in 12 patients and was successful in maintaining the airway of 8 of these 12; this outcome indicates that the disease can be managed, at least initially, by endoscopic laser treatment in most cases.

Ca2+ ion permeability properties of (R,S) alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors in isolated interneurons from the olfactory bulb of the rat

The aim of the study was to investigate the divalent cation permeability of native alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors expressed in interneurons of the olfactory bulb. Kainic acid (KA) was used as agonist to activate AMPA-receptor-mediated currents, which were recorded with the use of the patch-clamp technique. In interneurons acutely isolated from the olfactory bulb, the current responses to KA showed linear/outwardly rectifying current-voltage (I-V) relationships with a positive average reversal potential of +7 mV in normal external medium (1 mM Ca2+, 1 mM Mg2+). Raising the external Ca2+ concentration to 10 mM suppressed the amplitude, whereas omission of Ca2+ enhanced the amplitude of the current. Spectral analysis of the increase in current variance produced by KA indicated that the decreased amplitude observed in 10 mM Ca2+ was accompanied by a reduction in the apparent single-channel conductance. Raising the concentration of Mg2+ from 1 to 10 mM had a weak depressant effect on the KA-evoked current amplitude. No shift in the reversal potential was observed when the concentration of Ca2+ or Mg2+ was changed from 1 to 10 mM. Increasing the external medium concentration of Ca2+ to 60 mM not only further depressed the amplitudes of the KA-evoked currents but also gave a pronounced leftward shift in the average reversal potential to -32 +/- 9 (SE) mV (N = 7). For neurons in primary culture, current responses to KA also showed linear/outwardly rectifying I-V relationships with a positive average reversal potential in normal external medium. Substituting N-methylglucamine for Na+ and increasing the Ca2+ concentration to 10 mM gave a leftward shift in the average reversal potential from +9 +/- 3 mV to -47 +/- 4 mV (N = 11) and caused a marked reduction in the amplitude of the KA-evoked currents at negative potentials. The permeability properties of the studied AMPA receptors were well predicted by the Eyring rate model (symmetrical, 2 barriers, 1 site). The model gave a pCa2+/pK+ permeability ratio of 0.06 for acutely isolated interneurons and 0.14 for interneurons in primary culture. The constant field theory, which failed to successfully reproduce all the experimental data, gave corresponding low permeability ratios of 0.18 and 0.40 for acutely isolated cells and cells in primary culture, respectively. Thus it is concluded that interneurons in the olfactory bulb mainly express AMPA receptors with low permeability to Ca2+ ions.

Patch-clamp detection of neurotransmitters in capillary electrophoresis

Gamma-aminobutyrate acid, L-glutamate, and N-methyl-D-aspartate were separated by capillary electrophoresis and detected by the use of whole-cell and outside-out patch-clamp techniques on freshly dissociated rat olfactory interneurons. These neuroactive compounds could be identified from their electrophoretic migration times, unitary channel conductances, and power spectra that yielded corner frequencies and mean single-channel conductances characteristic for each of the different agonist-receptor interactions. This technique has the sensitivity to observe the opening of a single ion channel for agonists separated by capillary electrophoresis.

Studies on the identity of the rat optic nerve transmitter

The possible role of glutamate, aspartate, sulfur-containing excitatory amino acids and gamma-glutamyl peptides as major transmitters in the rat optic nerve was evaluated. Four days following optic nerve lesion the K(+)-evoked Ca(2+)-dependent glutamate release was reduced to 31 +/- 16% (+/- S.D., n = 9) comparing release from slices of the denervated (contralateral to the lesion) and non-denervated (ipsilateral) superior colliculus, indicative of a major transmitter function for glutamate. However, significant decreases in glutamate release could not be detected seven days following the lesion (n = 5). Other studies have shown that optic nerve denervation induce formation of synapses of non-retinal origin and cause other cellular changes which may reduce the effect of deafferentation on glutamate release after 7 days. No significant change was observed in aspartate release following the lesion. The concentrations of cysteine sulfinate, cysteate, homocysteine sulfinate, homocysteate and O-sulfo-serine in the optic layers of the superior colliculus were below 1 nmol/g tissue (n = 6). Theoretical considerations indicate that this level is too low for a function of any of these as a major optic nerve transmitter. All postsynaptic components in the rat superior colliculus response, evoked by electrical optic nerve stimulation, were reduced by kynurenate (1-10 mM), a broad spectrum glutamate-receptor antagonist. The study gives further support for the view that glutamate is a major transmitter in the rat optic nerve.

Pentobarbitone modulation of NMDA receptors in neurones isolated from the rat olfactory brain

1. The action of pentobarbitone on the N-methyl-D-aspartate (NMDA) receptors of neurones freshly dissociated from the olfactory bulb and olfactory tubercle has been studied using patch-clamp techniques. 2. Pentobarbitone produced a concentration-dependent depression of the currents evoked by NMDA with an IC50 value of c. 250 microM. 3. Analysis of the NMDA-evoked noise produced power spectra that could be fitted by the sum of two Lorentzians with corner frequencies of 17 and 82 Hz. Pentobarbitone increased the corner frequency of the high frequency component but did not alter the apparent single channel conductance estimated from the noise. 4. Single channel recordings in either the cell-attached or outside-out patch configurations revealed that NMDA (20 or 50 microM) opened channels with a main conductance level around 55 pS and a principal subconductance around 44 pS. The uncorrected mean open time of the channels was 3.4 ms and mean burst length was 6.0 ms. Mean cluster length was about 12 ms. 5. Pentobarbitone produced a concentration-dependent reduction in both mean open time and burst length. Mean cluster length was much less affected. Pentobarbitone did not decrease unitary current amplitude or bias the open-state current amplitude distribution in favour of a particular substate. 6. From these data it appears that pentobarbitone depresses the inward current evoked by NMDA by reducing the probability of channel opening and this results from a shortening of the lifetime of the channel open state and by decreasing burst length.

Expression of Ca(2+)-ion permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors in Xenopus oocytes injected with total RNA from human epileptic temporal lobe

By using the Xenopus oocyte as an expression system, we have performed a series of experiments in order to examine the divalent cation-permeability of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors from the human epileptic temporal lobe. Xenopus oocytes, injected with total RNA from the epileptic temporal lobe, were tested for expression of receptors by a conventional two electrode voltage-clamp technique. Administration of glutamate and AMPA gave small or no clear current responses, whereas kainate produced large inward non-desensitizing currents. The current responses evoked by kainate were concentration dependent. Experimental data gave a Hill coefficient of 1.06 and an EC50 value of 87 microM. The current to voltage relationship showed an inward rectification and when the concentration of divalent cations were enhanced, there was a shift in the reversal potential from -11 mV (2 mM Ca2+) to 12 mV (60 mM Ba2+). This yielded a pBa2+/pK+ permeability ratio of 1.6 when the constant field equation was used. The amplitude of the currents evoked by 600 microM kainate in solutions containing higher Ba(2+)-ion concentrations was markedly diminished (46% in 10 mM Ba(2+)- and 75% in 60 mM Ba(2+)-solution), when compared to those obtained in normal Ringer's solution, suggesting interactions between different cation species and/or screening of surface charges.

The effect of anosmia on MK-801-induced behaviour in mice

Systemic administration of N-methyl-D-aspartate (NMDA) receptor antagonists induces a well defined behaviour in rodents characterized by, for example increased locomotion and ataxia. It is not clear in what brain region(s) NMDA antagonists induce this behaviour. We have studied the possible involvement of olfactory pathways by making adult mice anosmic via intranasal injection of zinc sulphate, a procedure that is known to destroy the olfactory epithelium. The NMDA antagonist MK-801 was given intraperitoneally (0.1-1.0 mg/kg) and the animals were scored for locomotion and ataxia 60-90 min later. Before MK-801 administration, olfactory-lesioned mice did not differ from non-lesioned controls with regard to locomotion or ataxia. MK-801 caused locomotor activation (> or = 0.2 mg/kg) and ataxia (> or = 0.5 mg/kg) in both groups. In general, olfactory-lesioned animals showed more locomotion and less ataxia after MK-801 administration than non-lesioned animals. Lesioned animals displayed 2.0- (P < 0.05) and 3.7-fold (P < 0.05) more extensive locomotor activation than non-lesioned animals after 0.5 and 1.0 mg/kg of MK-801, respectively. No difference in the degree of ataxia was seen between the two groups at 0.5 mg/kg, whereas non-lesioned animals showed a 2.1-fold higher degree of ataxia after 1.0 mg/kg of MK-801, indicating that the enhanced MK-801-induced locomotor activation in olfactory-lesioned mice was not simply due to less ataxia. These results suggest that olfactory input is involved in NMDA antagonist-induced behaviour.

Bilateral aneurysms of the cavernous internal carotid arteries following yttrium-90 implantation

We present a case of bilateral aneurysms of the cavernous internal carotid arteries probably caused by radiation damage due to yttrium-90 implantation for a pituitary adenoma. Other possible aetiological factors are discussed.

Ciprofloxacin and sparfloxacin penetration into human brain tissue and their activity as antagonists of GABAA receptor of rat vagus nerve

Patients undergoing elective surgery for removal of brain tumors, aneurysms, or other vascular malformations were administered a single oral dose of sparfloxacin (400 mg; 16 patients) or ciprofloxacin (750 mg; 5 patients) either 3 to 5 h or 22 to 26 h before surgery. Serum samples were taken from all patients at 0, 1, 3 to 5, 7 to 9, and 22 to 26 h after dosing; an additional serum sample was obtained at 48 h from patients who received sparfloxacin. A single sample of brain tissue was taken from all patients; a sample of cerebrospinal fluid (CSF) uncontaminated with blood was obtained from five patients. Serum and brain tissue samples were assayed by high-pressure liquid chromatography. Drug concentrations in brain tissue exceeded those in CSF by 1.8- to 19.4-fold. Kinetic modeling suggested that peak sparfloxacin concentrations in brain tissue may have occurred later than 3 to 5 h and that actual peak concentrations may therefore have been higher (up to 10 micrograms/g of tissue). The activities of ciprofloxacin and sparfloxacin as antagonists of the gamma-aminobutyric acid antagonist (GABAA) receptor were measured with the rat vagus nerve preparation. The 50% inhibitory concentration (IC50) of ciprofloxacin was 250 microM (95.25 micrograms/ml), but in the presence of biphenyl acetic acid (BPAA), the IC50 of ciprofloxacin was only 0.6 microM (0.23 microgram/ml). In contrast, the IC50 of sparfloxacin alone or in the presence of BPAA was > 300 microM (> 100 micrograms/ml). We conclude that the concentrations of ciprofloxacin and sparfloxacin in brain tissue may exceed serum drug concentrations and cannot be predicted from the concentrations in CSF. Sparfloxacin does not have any activity as a GABA antagonist, either alone or in the presence of BPAA, at the concentrations which are likely to be reached in human brain tissue.

Gamma-L-glutamyl-L-glutamate is an endogenous dipeptide in the rat olfactory bulb which activates N-methyl-D-aspartate receptors

The concentration of gamma-L-glutamyl-L-glutamate (gamma-glu-glu), a potent displacer of excitatory amino acid receptor binding, and other structurally related dipeptides were determined in extracts of the rat olfactory bulb by a novel liquid chromatographic method. Whole-cell patch clamp recordings of currents from freshly isolated neurons showed that gamma-glu-glu produced inward currents at negative holding potentials, provided microM concentrations of glycine were added and no Mg(2+)-ions were present, indicating activation of N-methyl-D-aspartate receptors. Consistently, geometry optimization of gamma-glu-glu using molecular mechanics calculations, suggested a bent conformer with structural features supporting this view.

Enhanced calcium uptake by CA1 pyramidal cell dendrites in the postischemic phase despite subnormal evoked field potentials: excitatory amino acid receptor dependency and relationship to neuronal damage

After 6-12 h of recovery from transient cerebral ischemia, the pyramidal cells of the hippocampal CA1 region take up excessive amounts of calcium upon electrical stimulation, which has been suggested to be important for the development of delayed neuronal death. The aim of this study was to further characterize this enhanced calcium uptake with respect to time-course of development, relationship to neuronal damage, and amplitude of evoked field potentials as well as the dependency on N-methyl-D-aspartate (NMDA) and non-NMDA receptors. Adult Wistar rats were used and calcium-sensitive microelectrodes were placed in the stratum radiatum of the CA1 hippocampus for recording of the extracellular calcium concentration ([Ca2+]ec) during 20 min of ischemia and for 6 h of reflow. High-frequency stimulation of the perforant pathway elicited burst firing in CA1 and a transient decrease in [Ca2+]ec which reflects neuronal uptake. Shifts in [Ca2+]ec could not be evoked 0-1 h after ischemia. However, from 1-2 h burst firing could be evoked and the accompanying shift in [Ca2+]ec increased thereafter in amplitude with prolonged reflow, exceeded preischemic levels after 4 h, and reached 250 +/- 116% (mean +/- SD) of control after 6 h of reflow (p less than 0.05). The extracellular reference potential shift during electrical stimulation and the amplitude of evoked field potentials were still subnormal after 6 h [85 +/- 25% and 83 +/- 25%, respectively (mean +/- SD)]. There was a significant correlation between the degree of stimulated calcium uptake at 6 h postischemia and the extent of CA1 damage evaluated 7 days after the ischemic insult (r = 0.849; p less than 0.001). The shifts in [Ca2+]ec were reduced by the NMDA antagonist MK-801 (0.5-2 mg/kg, i.v.) to approximately 50% of the initial level during both control and postischemic conditions (p less than 0.01). The non-NMDA antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo[F]quinoxaline (NBQX) (42 +/- 13 mg/kg, i.p.; mean +/- SD) decreased the amplitude of the evoked field potentials (to 30 +/- 28% of control, p less than 0.05) and completely abolished the evoked shifts in [Ca2+]ec. In conclusion, the uptake of calcium into CA1 pyramidal cells during electrical stimulation was enhanced already 4 h after ischemia in spite of the fact that other measures of excitability were subnormal. This calcium uptake correlated to the extent of CA1 pyramidal cell damage and was dependent on both NMDA and non-NMDA receptor activation.

Idiopathic epidural lipomatosis as a cause of pain and neurological symptoms attributed initially to radiation damage

Epidural lipomatosis is a rare condition in which overgrowth of extradural fat can lead to back pain, spinal cord compression and radiculopathy. A 51-year-old man developed back pain and reduced mobility following a standard course of radiotherapy for a Stage I seminoma. His symptoms and radiological appearances were initially attributed to radiation fibrosis. Further investigations and operative intervention revealed epidural lipomatosis. The excess lipomatous tissue was removed with complete resolution of his symptoms.

The mechanism by which procaine inhibits catecholamine secretion from bovine chromaffin cells

1. We have investigated the action of procaine on stimulus-secretion coupling in bovine adrenal chromaffin cells. 2. Procaine inhibited the catecholamine secretion evoked by 500 microM carbachol (CCh) with an IC50 of 35 microM and the associated calcium influx (IC50 60 microM). It inhibited the catecholamine secretion evoked by depolarization with high potassium by less than 20% even at the highest concentrations tested (3.2 mM). 3. The secretion evoked by CCh was associated with an increase in sodium influx. This evoked influx was also inhibited by procaine (IC50 80 microM). 4. This selective action of procaine on the CCh-evoked catecholamine secretion was investigated further by patch-clamp techniques. 5. In agreement with the ion flux studies, procaine inhibited the inward current evoked by CCh. Procaine also altered the spectral characteristics of the noise associated with the agonist-induced current by adding an additional high frequency component. The amplitude of this component showed an e-fold increase for a 55 mV membrane hyperpolarization. 6. Data from cell-attached patches showed that increasing concentrations of procaine produced a progressive fall in the mean channel open time and an increase in mean blocked time. This combination led to a decrease in mean burst length. In addition, Popen was reduced by 50 microM procaine. These changes in channel conducting time were sufficient to account for the reduction in inward current. A limited study of the action of procaine on nicotinic channels in outside-out patches gave similar results. 7. The data were considered in relation to various schemes of anaesthetic-channel interactions. The data did not fit the sequential blocking model or the extended channel block model but could be fitted to a modified sequential blocking model in which the rate constant for channel reopening after block was itself subject to modulation by the anaesthetic and the blocked channel could close without passing through the open state.

Microdialysis sampling of the neuronal environment in basic and clinical research

Microdialysis is a technique for sampling extracellular fluid (ECF) which has been employed in brain research for about 10 years, and is now in experimental and clinical use in a number of biomedical disciplines. We report on microdialysis of neuroactive amino acids in the central nervous system (CNS) and discuss some technical problems of microdialysis, such as tissue reactions, calibration and the difficulties involved, as well as strategies for determination of the true extracellular concentration of various compounds. Possible mechanisms of nerve cell death in ischaemia and hypoglycaemia are among the factors that have been elucidated using data obtained by microdialysis. The neuronal environment overflows with excitatory amino acids both in brain ischaemia and in hypoglycaemia.

Effects of pentobarbitone on the properties of nicotinic channels of chromaffin cells

We have used the whole cell patch clamp technique to investigate the action of pentobarbitone on the nicotinic channels of bovine chromaffin cells. Application of agonists induced an inward current associated with a large increase in current noise. The noise could be fitted by Lorentzian functions with time constants of 17 +/- 2 ms for 10 microM acetylcholine and 10 +/- 1 ms for 10 microM carbachol. The single channel conductance estimated from the current variance was about 25 pS in each case. Pentobarbitone decreased the time constants in a concentration-dependent fashion, but the unit conductances were unaffected. Single channel events were recorded in chromaffin cells held under voltage clamp. Pentobarbitone did not reduce the amplitude of channel openings or the probability of channel opening but reduced the mean channel open time. This reduction was sufficient to account for the decrease in inward current produced by pentobarbitone.

Extracellular acidic sulfur-containing amino acids and gamma-glutamyl peptides in global ischemia: postischemic recovery of neuronal activity is paralleled by a tetrodotoxin-sensitive increase in cysteine sulfinate in the CA1 of the rat hippocampus

An excessive activation of the excitatory amino acid system has been proposed as one possible mediator of the ischemia-induced delayed death of CA1 pyramidal cells in the hippocampus. Using dialytrodes in the CA1 of the rat, we have investigated multiple-unit activity and extracellular changes in acidic sulfur-containing amino acids and gamma-glutamyl peptides during ischemia (20-min, four-vessel occlusion) and during 8 h of reflow. Multiple-unit activity was abolished during ischemia and for the following 1 h, but then recovered, gradually reaching preischemic levels after 8 h of reflow. Extracellular cysteate, cysteine sulfinate, and gamma-glutamyltaurine increased (1.5- to threefold) during ischemia, and extracellular glutathione and gamma-glutamylaspartate plus gamma-glutamylglutamine increased during early reflow (two- to threefold). The recovery of neuronal activity at 4-8 h was paralleled by an increase in extracellular cysteine sulfinate (2.5-fold at 8 h of reflow). Perfusion with 10 microM tetrodotoxin at 8 h of reflow abolished the multiple-unit activity and reduced extracellular cysteine sulfinate. Considering the glutamate-like properties of cysteine sulfinate, the observed postischemic increase may be involved in the development of the delayed neuronal death.