Adequate menstrual suppression in adolescents with inherited bleeding disorders often requires multiple treatment changes: Retrospective cohort study of a multidisciplinary clinic

Heavy menstrual bleeding (HMB) is often the presenting symptom for females with inherited bleeding disorders (IBD). Multidisciplinary clinics leverage the expertise of hematologists and women's health specialists. This study characterizes the complexity of HMB management for adolescents with IBDs from a large multidisciplinary clinic. Adolescents often required multiple different menstrual suppression treatments, with only about 20% achieving acceptable suppression with their first treatment. Adolescents switched therapy most often for uncontrolled bleeding, followed by adverse effects, and patient preference. Given the difficulty in achieving adequate menstrual suppression, multidisciplinary clinics offer necessary expertise in accomplishing bleeding control with minimal adverse effects.

Procedural outcomes in children with mild type 1 von Willebrand disease

Background

In patients with mild type 1 von Willebrand disease (VWD), treatment guidelines suggest individualization of surgical management. However, these conditional recommendations are based on very low-certainty evidence due to limited data on surgical outcomes in this population.

Objectives

To characterize procedural bleeding prophylaxis strategies and outcomes in children with mild type 1 VWD.

Methods

This is a retrospective cohort study that included patients aged between 0 and 21 years with mild type 1 VWD (defined as von Willebrand factor antigen and/or an activity of 30-50 IU/dL) who underwent a procedure from July 1, 2017, to July 1, 2022. Demographic, surgical, medication, and bleeding data were collected by manual chart review.

Results

A total of 161 procedures were performed in 108 patients. The population was primarily female (75%), White (77.8%), and non-Hispanic (79.6%). Median age was 15.8 years (IQR, 8.2-17.6). Fifty-nine surgeries were classified as major, 66 as minor, and 36 as dental. For most procedures, patients received only antifibrinolytics for bleeding prophylaxis (n = 128, 79.5%); desmopressin was used in 17 (10.6%) procedures, and von Willebrand factor concentrate was used in 12 (7.5%) procedures. Bleeding complications occurred in 8 (5.0%) procedures: these included 1 major, 4 clinically relevant nonmajor, and 3 minor bleeding events. No patient required blood transfusion or an additional procedure to achieve hemostasis. Most bleeding complications were seen following intrauterine device (IUD) placement (5/8). Nearly 30% of patients who underwent IUD placement reported bleeding.

Conclusion

Pediatric patients with mild type 1 VWD can safely undergo procedures using a tailored approach. Bleeding complications were uncommon, with the majority following IUD placement.

Dental habits and oral health in children and adolescents with bleeding disorders: A single-institution cross-sectional study

INTRODUCTION

Oral health is an important component of care at haemophilia treatment centres (HTCs). Correlations between oral health and inflammation suggest that proper oral health may improve joint health.

AIM

To evaluate the dental habits, needs, and oral health status of paediatric patients with bleeding disorders, and identify predicters of poor oral health.

METHODS

From May 2016 to October 2017, consecutive paediatric HTC patients completed a 14-question survey and were examined by dental professionals. Descriptive analyses, chi-square tests and logistic regression models identified characteristics associated with four main dental outcomes.

RESULTS

Evaluations from 226 consecutive patients (age 1-20 years) were included. Diagnoses included haemophilia A and B (64%), von Willebrand disease (25%) and other bleeding disorders (13%). Nearly half of patients reported not brushing their teeth twice a day (44%). One-quarter of patients did not currently have a dentist (27%), and 15% reported specific challenges with access to dental care. Oral screening demonstrated significant pathology: 89% of patients had plaque accumulation, 37% had gingivitis and 8% had lesions suggestive of dental caries. Multivariate analysis revealed that having a primary caregiver with active decay was associated with significantly higher rates of suspicious lesions (OR 4.34, CI 1.41-13.35) and gingival erythema (OR 3.44, CI 1.63-7.25) and lower rates of twice daily teeth brushing (OR .17, CI .08-.37).

CONCLUSION

Children with bleeding disorders commonly have significant dental pathology and report obstacles to dental care, posing the potential risk for morbidity. Primary caregiver dental health is strongly associated with dental pathology in children.

Elevated von Willebrand factor levels during heavy menstrual bleeding episodes limit the diagnostic utility for von Willebrand disease

BACKGROUND

Heavy menstrual bleeding (HMB) is often the first bleeding symptom for female individuals with inherited bleeding disorders. Guidelines recommend performing the hemostatic evaluation at HMB presentation. Von Willebrand factor (VWF) levels increase with stress, making it unclear if VWF studies during acute bleeding are beneficial in diagnosing von Willebrand disease (VWD).

OBJECTIVES

To determine the utility of testing for VWD during acute HMB.

PATIENTS/METHODS

This retrospective cohort study evaluated VWF levels of individuals presenting to the emergency department (ED) with HMB from January 1, 2017, to December 31, 2018, after prospective implementation of a clinical practice guideline recommending hemostatic evaluation in the ED. We compared VWF and factor VIII (FVIII) levels between acute presentation and follow-up visit after bleeding resolution. We compared the diagnostic accuracy of initial and follow-up labs.

RESULTS

During the study period, 221 individuals were seen in the ED for acute HMB, and 39 had VWD testing at both time points. Median FVIII and VWF levels were higher during acute bleeding than at follow-up. The difference in VWF levels between visits was negligible when initial FVIII value was normal. Overall incidence of VWD was 7.5%; 69% of those with VWD had low VWF levels during acute HMB.

CONCLUSION

VWD testing during acute HMB detects the majority of individuals with VWD but also leads to elevated levels of VWF, potentially limiting at the accuracy of diagnostic labs during acute bleeding episodes. Delayed testing until resolution of anemia and active bleeding may provide more accurate diagnostic evaluation for VWD.

Longitudinal health utilities, symptoms and toxicities in patients with ALK-rearranged lung cancer treated with tyrosine kinase inhibitors: a prospective real-world assessment

Background

Tyrosine kinase inhibitors (tkis) have dramatically improved the survival of patients with ALK-rearranged (ALK+) non-small-cell lung cancer (nsclc). Clinical trial data can generally compare drugs in a pair-wise fashion. Real-world collection of health utility data, symptoms, and toxicities allows for the direct comparison between multiple tki therapies in the population with ALK+ nsclc.

Methods

In a prospective cohort study, outpatients with ALK+ recruited between 2014 and 2018, treated with a variety of tkis, were assessed every 3 months for clinico-demographic, patient-reported symptom and toxicity data and EQ-5D-derived health utility scores (hus).

Results

In 499 longitudinal encounters of 76 patients with ALK+ nsclc, each tki had stable longitudinal hus when disease was controlled, even after months to years: the mean overall hus for each tki ranged from 0.805 to 0.858, and longitudinally from 0.774 to 0.912, with higher values associated with second- or third-generation tkis of alectinib, brigatinib, and lorlatinib. Disease progression was associated with a mean hus decrease of 0.065 (95% confidence interval: 0.02 to 0.11). Health utility scores were inversely correlated to multiple symptoms or toxicities: rho values ranged from -0.094 to -0.557. Fewer symptoms and toxicities were associated with the second- and third-generation tkis compared with crizotinib. In multivariable analysis, only stable disease state and baseline Eastern Cooperative Oncology Group performance status were associated with improved hus.

Conclusions

There was no significant decrease in hus when patients with ALK+ disease were treated longitudinally with each tki, as long as patients were clinically stable. Alectinib, brigatinib, and lorlatinib had the best toxicity profiles and exhibited high mean hus longitudinally in the real-world setting.

Combined cancer patient-reported symptom and health utility tool for routine clinical implementation: a real-world comparison of the ESAS and EQ-5D in multiple cancer sites

Background

We assessed whether the presence and severity of common cancer symptoms are associated with the health utility score (hus) generated from the EQ-5D (EuroQol Research Foundation, Rotterdam, Netherlands) in patients with cancer and evaluated whether it is possible pragmatically to integrate routine hus and symptom evaluation in our cancer population.

Methods

Adult outpatients at Princess Margaret Cancer Centre with any cancer were surveyed cross-sectionally using the Edmonton Symptom Assessment System (esas) and the EQ-5D-3L, and results were compared using Spearman correlation coefficients and regression analyses.

Results

Of 764 patients analyzed, 27% had incurable disease. We observed mild-to-moderate correlations between each esas symptom score and the hus (Spearman coefficients: -0.204 to -0.416; p < 0.0001 for each comparison), with the strongest associations being those for pain (R = -0.416), tiredness (R = -0.387), and depression (R =-0.354). Multivariable analyses identified pain and depression as highly associated (both p < 0.0001) and tiredness as associated (p = 0.03) with the hus. The ability of the esas to predict the hus was low, at 0.25. However, by mapping esas pain, anxiety, and depression scores to the corresponding EQ-5D questions, we could derive the hus using partial esas data, with Spearman correlations of 0.83-0.91 in comparisons with direct EQ-5D measurement of the hus.

Conclusions

The hus derived from the EQ-5D-3L is associated with all major cancer symptoms as captured by the esas. The esas scores alone could not predict EQ-5D scores with high accuracy. However, esas-derived questions assessing the same domains as the EQ-5D-3L questions could be mapped to their corresponding EQ-5D questions to generate the hus, with high correlation to the directly measured hus. That finding suggests a potential approach to integrating routine symptom and hus evaluations after confirmatory studies.

Health utility scores from EQ-5D and health-related quality of life in patients with esophageal cancer: a real-world cross-sectional study

Esophageal cancer and its treatment can cause serious morbidity/toxicity. These effects on health-related quality of life (HRQOL) can be measured using disease-specific scales such as FACT-E, generic scales such as EQ-5D-3L, or through symptoms. In a two-year cross-sectional study, we compared HRQOL across esophageal cancer patients treated in an ambulatory clinic and across multiple disease states, among patients with all stages of esophageal cancer. Consenting patients completed FACT-E, EQ-5D, a visual analog scale, and patient reported (PR)-ECOG. Symptom complexes were constructed from FACT-E domains. Responses were categorized by disease state: pre-, during, and post-treatment, surveillance, progression, and palliative chemotherapy. Spearman correlation and multivariable linear regression characterized these associations. In total, 199 patients completed 317 questionnaires. Mean FACT-E and subscale scores dropped from baseline through treatment and recovered during post-treatment surveillance (P < 0.001); EQ-5D health utility scores (HUS) displayed a similar pattern but with smaller differences (P = 0.07), and with evidence of ceiling effect. Among patients with stage II/III esophageal cancer, mean EQ-5D HUS varied across disease states (P < 0.001), along with FACT-E and subscales (P < 0.001). Among patients with advanced disease, there was no significant difference between baseline and on-treatment total scores, but improved esophageal cancer-specific scales were noted (P = 0.003). Strong correlation was observed between EQ-5D and FACT-E (R = 0.73), along with physical and functional subscales. In addition, the association between FACT-E and EQ-5D HUS was maintained in a multivariable model (P < 0.001). We interpret these results to suggest that in a real-world clinic setting, FACT-E, EQ-5D HUS, and symptoms were strongly correlated. Most HRQOL and symptom parameters suggested that patients had worse HRQOL and symptoms during curative therapy, but recovered well afterwards. In contrast, palliative chemotherapy had a neutral to positive impact on HRQOL/symptoms when compared to their baseline pre-treatment state.

Linkage of clinical trial and administrative data: a survey of cancer patient preferences

BACKGROUND

Personal health information, including diagnoses and hospital admissions, is routinely collected in administrative databases. Patients enrolling on clinical trials consent to separate collection and storage of their personal health information. We evaluated patient preferences for linking long-term data from administrative databases with clinical trials.

METHODS

Adults with cancer attending outpatient clinics at 3 Ontario hospitals were surveyed about their willingness, when faced with the hypothetical scenario of participating in a clinical trial, to provide potentially identifying information such as initials and date of birth to facilitate long-term research access to normally deidentified publicly collected databases.

RESULTS

Of 569 patients surveyed, 335 (59%) were women, 452 (79%) were white, 385 (68%) had a post-secondary education, and 386 (68%) had never participated in a clinical trial. Median age in the group was 59 years. Most participants (93%, cohort 1) would allow long-term access to their information and allow personal information to be used to match clinical trial with administrative data. At the time of clinical trial closure, two thirds of participants (68%, cohort 2) preferred to make additional clinical information available through linkage with administrative databases, and 8 (9%) preferred to have no further information made available to researchers. No significant differences were found in the subset of patients who were part of a clinical trial and those who had never participated (p = 0.65).

INTERPRETATION

Almost all patients would allow a clinical trial research team to access their confidential information, providing a more comprehensive assessment of an intervention's long-term risks and benefits.

Polymorphisms of the FOXF1 and MHC locus genes in individuals undergoing esophageal acid reflux assessments

Gastroesophageal reflux disease (GERD) may lead to Barrett's esophagus (BE). Previously, a large genome-wide association study found two germline markers to be associated with BE, FOXF1 rs9936833 (C allele) and MHC rs9257809 (A allele). This study evaluated whether these two polymorphisms are associated with gastroesphageal acid reflux as measured by 24-hour pH testing. Patients with acid reflux symptoms referred for esophageal manometry and 24-hour pH monitoring at University Health Network (Toronto, ON) were enrolled. DNA extracted from blood was genotyped using a Taqman Polymerase Chain Reaction (PCR) assay. DeMeester scores of ≥14.7 or prior evidence of reflux esophagitis on endoscopy defined individuals with esophageal acid reflux. Logistic regression analysis, adjusted for clinical risk factors, was used to calculate odds ratios with 95% confidence intervals for each polymorphism in relation to the presence of acid reflux. Of 182 patients, the median age was 50 years and 62% were female; 95 (52%) met the definition of GERD. In the multivariable analysis, both FOXF1 rs9936833 (OR = 1.82; 95%CI: 1.12-2.96; P = 0.02) and MHC rs9257809 (OR = 9.36; 95%CI: 2.92-29.99; P < 0.001) remained significantly associated with presence of acid reflux. When both polymorphisms were placed in the same model, the adjusted ORs were 2.10 (95%CI: 1.24-3.53; P = 0.005) and 10.95 (95%CI: 3.32-36.09; P < 0.001), respectively. The association for risk allele C in FOXF1 rs9936833 and risk allele A in MHC rs9257809 with the presence of acid reflux suggests a potential pathophysiologic mechanism for the role of genetic influences in BE development.

Socioeconomic status and lifestyle behaviours in cancer survivors: smoking and physical activity

PURPOSE

Smoking cessation and increased physical activity (pa) have been linked to better outcomes in cancer survivors. We assessed whether socioeconomic factors influence changes in those behaviours after a cancer diagnosis.

METHODS

As part of a cross-sectional study, a diverse group of cancer survivors at the Princess Margaret Cancer Centre (Toronto, ON), completed a questionnaire about past and current lifestyle behaviours and perceptions about the importance of those behaviours with respect to their health. The influence of socioeconomic indicators on smoking status and physical inactivity at 1 year before and after diagnosis were assessed using multivariable logistic regression with adjustment for clinico-demographic factors.

RESULTS

Of 1222 participants, 1192 completed the smoking component. Of those respondents, 15% smoked before diagnosis, and 43% of those smokers continued to smoke after. The proportion of survivors who continued to smoke increased with lower education level (p = 0.03). Of the 1106 participants answering pa questions, 39% reported being physically inactive before diagnosis, of whom 82% remained inactive afterward. Survivors with a lower education level were most likely to remain inactive after diagnosis (p = 0.003). Lower education level, household income, and occupation were associated with the perception that pa had no effect or could worsen fatigue and quality of life (p ≤ 0.0001).

CONCLUSIONS

In cancer survivors, education level was a major modifier of smoking and pa behaviours. Lower socioeconomic status was associated with incorrect perceptions about pa. Targeting at-risk survivors by education level should be evaluated as a strategy in cancer survivorship programs.

Patient preference: a comparison of electronic patient-completed questionnaires with paper among cancer patients

In this study, we compared cancer patients preference for computerised (tablet/web-based) surveys versus paper. We also assessed whether the understanding of a cancer-related topic, pharmacogenomics is affected by the survey format, and examined differences in demographic and medical characteristics which may affect patient preference and understanding. Three hundred and four cancer patients completed a tablet-administered survey and another 153 patients completed a paper-based survey. Patients who participated in the tablet survey were questioned regarding their preference for survey format administration (paper, tablet and web-based). Understanding was assessed with a 'direct' method, by asking patients to assess their understanding of genetic testing, and with a 'composite' score. Patients preferred administration with tablet (71%) compared with web-based (12%) and paper (17%). Patients <65 years old, non-Caucasians and white-collar professionals significantly preferred the computerised format following multivariate analysis. There was no significant difference in understanding between the paper and tablet survey with direct questioning or composite score. Age (<65 years) and white-collar professionals were associated with increased understanding (both P = 0.03). There was no significant difference in understanding between the tablet and print survey in a multivariate analysis. Patients overwhelmingly preferred computerised surveys and understanding of pharmacogenomics was not affected by survey format.

Impact of dialect use on a basic component of learning to read

Can some black-white differences in reading achievement be traced to differences in language background? Many African American children speak a dialect that differs from the mainstream dialect emphasized in school. We examined how use of alternative dialects affects decoding, an important component of early reading and marker of reading development. Behavioral data show that use of the alternative pronunciations of words in different dialects affects reading aloud in developing readers, with larger effects for children who use more African American English (AAE). Mechanisms underlying this effect were explored with a computational model, investigating factors affecting reading acquisition. The results indicate that the achievement gap may be due in part to differences in task complexity: children whose home and school dialects differ are at greater risk for reading difficulties because tasks such as learning to decode are more complex for them.

Women's perception of future risk following pregnancies complicated by preeclampsia

OBJECTIVE

To elicit women's personal understanding of future cardiovascular risk, following a pregnancy complicated by preeclampsia, and to identify the postnatal needs of these women.

METHODS

Semi-structured interviews with 12 women with a recent history of preeclampsia who had attended a postnatal follow-up clinic.

RESULTS

The interviews were held at a median of 47 weeks postpartum (range 24-62 weeks). Family history of cardiovascular disease was associated with a greater awareness of future cardiovascular risk. Women without traditional risk factors found it hard to envisage themselves as being at risk and may not see the relevance of such information. It may take several months after delivery for a woman to be able to fully consider her own health as well as the baby's; a reminder of risk and health information is needed.

CONCLUSIONS

Although receptive to follow-up, the situational factors of being a new mother need to be taken into account to engage successfully with this patient group. Further research is needed to help clarify the extent to which a history of preeclampsia is an independent factor for future cardiovascular disease to provide a solid foundation for effective risk communication.

Dendrites of medial olivocochlear neurons in mouse

Stains for acetylcholinesterase (AChE) and retrograde labeling with Fluorogold (FG) were used to study olivocochlear neurons and their dendritic patterns in mice. The two methods gave similar results for location and number of somata. The total number of medial olivocochlear (MOC) neurons in the ventral nucleus of the trapezoid body (VNTB) is about 170 per side. An additional dozen large olivocochlear neurons are located in the dorsal periolivary nucleus (DPO). Dendrites of all of these neurons are long and extend in all directions from the cell bodies, a pattern that contrasts with the sharp frequency tuning of their responses. For VNTB neurons, there were greater numbers of dendrites directed medially than laterally and those directed medially were longer (on average, 25-50% longer). Dendrite extensions were most pronounced for neurons located in the rostral portion of the VNTB. When each dendrite from a single neuron was represented as a vector, and all the vectors summed, the result was also skewed toward the medial direction. DPO neurons, however, had more symmetric dendrites that projected into more dorsal parts of the trapezoid body, suggesting that this small group of olivocochlear neurons has very different physiological properties. Dendrites of both types of neurons were somewhat elongated rostrally, about 20% longer than those directed caudally. These results can be interpreted as extensions of dendrites of olivocochlear neurons toward their synaptic inputs: medially to meet crossing fibers from the cochlear nucleus that are part of the MOC reflex pathway, and rostrally to meet descending inputs from higher centers.

Acute renal infarction due to renal fibromuscular dyplasia: a case of mistaken identity

A 53 year old male presented with right sided loin pain in the absence of other distinguishing symptoms, past medical history or examination findings. Investigation, a week later, revealed a right sided renal mass. He underwent laparascopic nephrectomy for presumed renal malignancy. Surprisingly, the mass was an area of infarction and the renal artery had intimal-type fibromuscular dysplasia (FMD). This case demonstrates three important points. Firstly, renal infarction is a cause of acute loin pain. Secondly, delayed investigation can alter the radiological appearance of renal infarction. Lastly, FMD is a rare condition, particularly in men, and can cause renal infarction.

Removal of eye movement artefacts from single channel recordings of retinal evoked potentials using synchronous dynamical embedding and independent component analysis

A system is described for the removal of eye movement and blink artefacts from single channel pattern reversal electroretinogram recordings of very poor signal-to-noise ratios. Artefacts are detected and removed by using a blind source separation technique based on the jadeR independent component analysis algorithm. The single channel data are arranged as a series of overlapping time-delayed vectors forming a dynamical embedding matrix. The structure of this matrix is constrained to the phase of the stimulation epoch: the term synchronous dynamical embedding is coined. A novel method using a marker channel with a non-independent synchronous feature is employed to identify the single most relevant source estimation for reconstruction and signal recovery. This method is non-lossy, all underlying signal being recovered. In synthetic datasets of defined noise content and in standardised real data recordings, the performance of this technique is compared to conventional fixed-threshold hard-limit rejection. The most significant relative improvements are achieved when movement and blink artefacts are greatest: no improvement is demonstrable for the random noise only situation.

Evidence-based analysis of field testing of medical electrical equipment

Field testing of medical electrical equipment remains a topic of debate amongst biomedical engineers. A questionnaire was circulated among members of the main professional body for Medical Engineering Departments in the UK and Ireland and in the Medical Physics and Engineering Mailbase Server. The aim of the questionnaire was to establish consensus on common practice on the frequency and type of safety tests carried out in the field and common sources of hazards and risk management. Twenty-six replies were received in total. A clear majority of 54% of the respondents reported that they carried out safety tests on hospital-based medical equipment on a yearly basis. For other equipment, regular tests were carried out by 58% on loan equipment and by 69% on medical electrical systems. Laboratory equipment on the other hand were not tested in 42% of the cases. Domiciliary and research equipment were only tested in 11% and 15% of the cases respectively. A clear majority of 93% said that they label equipment after tests, 34% said that they always record the actual values (as opposed to pass or fail) and 54% said they carry out functional test as part of the safety test. Although 61% of failures were attributed to the mains lead, only 50% of the respondents said that they had a management system in place for detachable mains leads.

Responses of medial olivocochlear neurons. Specifying the central pathways of the medial olivocochlear reflex

Medial olivocochlear (MOC) neurons project to outer hair cells (OHC), forming the efferent arm of a reflex that affects sound processing and offers protection from acoustic overstimulation. The central pathways that trigger the MOC reflex in response to sound are poorly understood. Insight into these pathways can be obtained by examining the responses of single MOC neurons recorded from anesthetized guinea pigs. Response latencies of MOC neurons are as short as 5 ms. This latency is consistent with the idea that type I, but not type II, auditory-nerve fibers provide the major inputs to the reflex interneurons in the cochlear nucleus. This short latency also implies that the cochlear-nucleus interneurons have rapidly conducting axons. In the cochlear nucleus, lesions of the posteroventral subdivision (PVCN), but not the anteroventral (AVCN) or dorsal (DCN) subdivisions, produce permanent disruption of the MOC reflex, based on a metric of adaptation of the distortion-product otoacoustic emission (DPOAE). This finding supports earlier anatomical results demonstrating that some PVCN neurons project to MOC neurons. Within the PVCN, there are two general types of units when classified according to poststimulus time histograms: onset units and chopper units. The MOC response is sustained and cannot be produced solely by inputs having an onset pattern. The MOC reflex interneurons are thus likely to be chopper units of PVCN. Also supporting this conclusion, chopper units and MOC neurons both have sharp frequency tuning. Thus, the most likely pathway for the sound-evoked MOC reflex begins with the responses of hair cells, proceeds with type I auditory-nerve fibers, PVCN chopper units, and MOC neurons, and ends with the MOC terminations on OHC.

Comparison of matrix metalloproteinase expression during Wallerian degeneration in the central and peripheral nervous systems

The matrix metalloproteinases (MMPs) are a large family of zinc-dependent enzymes which are able to degrade the protein components of the extracellular matrix. They can be placed into subgroups based on structural similarities and substrate specificity. Aberrant expression of these destructive enzymes has been implicated in the pathogenesis of immune-mediated neuroinflammatory disorders. In this study we investigate the involvement of MMPs, from each subgroup, in Wallerian degeneration in both the central and peripheral nervous systems. Wallerian degeneration describes the process initiated by transection of a nerve fibre and entails the degradation and removal of the axon and myelin from the distal stump. A similar degenerative process occurs as the final shared pathway contributing to most common neuropathies. MMP expression and localisation in the peripheral nervous system are compared with events in the CNS during Wallerian degeneration. Within 3 days after axotomy in the peripheral nervous system, MMP-9, MMP-7 and MMP-12 are elevated. These MMPs are produced by Schwann cells, endothelial cells and macrophages. The temporospatial expression of activated MMP-9 correlates with breakdown of the blood-nerve barrier. In the CNS, 1 week after optic nerve crush, four MMPs are induced and primarily localised to astrocytes, not microglia or oligodendrocytes. In the degenerating optic nerve, examined at later time points (4, 8, 12 and 18 weeks), MMP expression was down-regulated. The absence of MMPs in oligodendrocytes and mononuclear phagocytes during Wallerian degeneration may contribute to the slower removal of myelin debris observed in the CNS. The low level of the inactive pro-form of MMP-9 in the degenerating optic nerve may explain why the blood-brain barrier remains intact, while the blood-nerve barrier is rapidly broken down. We conclude that the difference in the level of expression, activation state and cellular distribution of MMPs may contribute to the different sequence of events observed during Wallerian degeneration in the peripheral compared to the CNS.

Effects of anesthesia on efferent-mediated adaptation of the DPOAE

Distortion product otoacoustic emissions (DPOAE) adapt after primary tone onset, with an approximately 100 ms time constant, due to feedback effects of medial olivocochlear (MOC) activity elicited by the primary tones. We tracked DPOAE postonset adaptation as a metric of MOC reflex strength, before during and after induction of anesthesia in guinea pigs. Reflex strength was significantly diminished by the barbiturate/neuroleptic anesthesia most commonly used in this species. The MOC reflex recovered more slowly than toe-pinch or startle reflexes, correlating better with recovery of general mobility. When individual anesthetic agents were assessed, the barbiturate (pentobarbital) significantly diminished MOC reflex strength, whereas fentanyl or droperidol did not. These results suggest that previous studies using anesthetized preparations may have underestimated the magnitude of sound-evoked responses in the OC pathway.

Evidence that Very Slow Wallerian Degeneration in C57BL/Ola Mice is an Intrinsic Property of the Peripheral Nerve

We have described a mutant mouse, C57BL/Ola, in which Wallerian degeneration following peripheral nerve transection is very slow. Our previous results suggested that recruited monocytes play a role in rapid Wallerian degeneration. The nature of the mutation in C57BL/Ola mice is not known and we have investigated whether the defect is intrinsic to the nerve or due to a defect in the circulating monocytes. We have made chimaeric mice in which bone marrow from histocompatible mice, with rapidly degenerating nerves and normal monocyte recruitment, was used to reconstitute irradiated C57BL/Ola mice and vice-versa. A substantial degree of donor repopulation of the hosts was confirmed by measures of the levels of glucose-phosphate isomerase alloenzymes in blood and tissue samples from the two different strains. The rate of degeneration of the transected sciatic nerve was found to be host-dependent, providing evidence that the mutation affects cell populations intrinsic to the nerve and not the circulating monocytes. We provide additional evidence that the peripheral nerves of C57BL/Ola mice are different from those of other mice as they degenerate at a slower rate in vitro.

Very Slow Retrograde and Wallerian Degeneration in the CNS of C57BL/Ola Mice

Wallerian degeneration following peripheral nerve transection in C57BL/Ola mice is very slow in comparison to other strains of mice. We show that following optic nerve transection, the axons of retinal ganglion cells in C57BL/Ola mice undergo very slow Wallerian degeneration and that retrograde degeneration of the ganglion cell bodies is much slower than in other strains of mice. The results suggest that the gene product affecting Wallerian degeneration in the peripheral nervous system (PNS) also confers a greater resistance to degeneration on central nervous system (CNS) neurons.

Evidence that the Rate of Wallerian Degeneration is Controlled by a Single Autosomal Dominant Gene

In a substrain of C57BL mice, C57BL/Ola, Wallerian degeneration in the distal segment of the severed sciatic nerve is extremely slow when compared to other mice. Despite this very slow degeneration in the distal segment regeneration of the motor nerves is not impaired. From suitable genetic outcrosses and backcrosses, the authors provide evidence that the rate of Wallerian degeneration in this strain is controlled by a single autosomal gene product. The authors have also shown that the rate of degeneration, in C57BL/Ola mice, is influenced by the environment in which the animals were bred and housed. Wallerian degeneration in the sciatic nerves of mice raised in isolators is slower than in those raised in a conventional animal house. This strain of mouse may prove to be of value in the understanding of nerve degeneration and regeneration.

Poor growth of Mammalian motor and sensory axons into intact proximal nerve stumps

Wallerian degeneration is very slow in the mouse strain now known as C57BL/Ola. Sensory axon regrowth following peripheral nerve lesions is very poor in these animals but motor axons succeed in reinnervating the distal nerve stump even while the majority of severed axons are still intact (Lunn et al., Eur. J. Neurosci., 1, 27 - 33, 1989). To see if motor axons could grow into a completely undegenerated portion of nerve, the proximal stumps of the peroneal and tibial nerves were sutured together in six BALB/c mice and the ability of large motor and sensory fibres from the tibial nerve to grow into the peroneal nerve was examined electrophysiologically in four of them. For the acute experiment the peroneal nerve was cut approximately 7 mm central to the point of suture to the tibial nerve. Both at 2 weeks and 7 weeks after surgery the size of the potential recorded in the ventral roots on stimulating the portion of peroneal nerve into which tibial axons were directed to grow was only approximately 8% of the potential recorded when the tibial nerve was itself stimulated. The potential recorded in the dorsal roots was only approximately 2%. Counts of axon numbers in electron micrographs showed a small but non-significant increase over normal in the number of unmyelinated axons in the peroneal nerves which had been connected to the tibial nerve in this way. It is concluded, in agreement with Langley and Anderson (J. Physiol., 31, 365 - 391, 1904), that axon growth into intact nerves is extremely limited in mammals and that the distal nerve stump of C57BL/Ola mice, although it degenerates very slowly, is not therefore equivalent to an intact peripheral nerve.

The Effectiveness of the Gene Which Slows the Rate of Wallerian Degeneration in C57BL/Ola Mice Declines With Age

The rate of Wallerian degeneration is unusually slow in severed axons of mice of the C57BL/Ola strain. Within mice of that strain we have now found that the rate of degeneration increases with the age of the animal. In 4-week-old mice nerve stimulation evokes muscle contractions even 5 days after sciatic nerve section and compound action potentials can be recorded in the distal nerve stump up to 3 weeks after section. In 1-year-old animals no action potentials can be excited 5 days after nerve section. Heterozygous mice carrying only one copy of the dominant gene show the same age-related decline in viability of the distal nerve stump after axotomy, and the rate of decline is no greater than for homozygous mice. The more rapid rate of degeneration of severed axons of mice of the C57BL/6J strain was affected in the opposite way by age, degeneration occurring more slowly in older animals.

Absence of Wallerian Degeneration does not Hinder Regeneration in Peripheral Nerve

Wallerian degeneration of the distal stump of a severed peripheral nerve involves invasion by myelomonocytic cells, whose presence is necessary for destruction of myelin and for initiating mitosis in Schwann cells (Beuche and Friede, 1984). Degeneration of the distal ends of the axons themselves is assumed to occur by autolytic mechanisms. We describe a strain of mice (C57BL/6/Ola) in which leucocyte invasion is slow and sparse. In these mice, confirming Beuche and Friede, myelin removal is extremely slow. A new finding is that axon degeneration is also very slow. This is a consequence of lack of recruitment of myelomonocytic cells for if such recruitment is prevented in other mouse strains by a monoclonal antibody against the complement type 3 receptor (Rosen and Gordon, 1987) axon degeneration is again slowed. We have also, surprisingly, found that nerve regeneration in the C57BL/6/Ola mice is not impeded by the presence of largely intact axons in the distal stump and absence of recruited cells, myelin debris and the absence of Schwann cell mitosis.

Response adaptation of medial olivocochlear neurons is minimal

Response adaptation is a general characteristic of neurons. A number of studies have investigated the adaptation characteristics of auditory-nerve fibers, which send information to the brain about sound stimuli. However, there have been no previous adaptation studies of olivocochlear neurons, which provide efferent fibers to hair cells and auditory nerve dendrites in the auditory periphery. To study adaptation in efferent fibers, responses of single olivocochlear neurons were recorded to characteristic-frequency tones and noise, using anesthetized guinea pigs. To measure short-term adaptation, stimuli of 500 ms duration were presented, and the responses were displayed as peristimulus time histograms. These histograms showed regular peaks, indicating a "chopping" pattern of response. The rate during each chopping period as well as the general trend of the histogram could be well fit by an equation that expresses the firing rate as a sum of 1) a short-term adaptive rate that decays exponentially with time and 2) a constant steady-state rate. For the adaptation in medial olivocochlear (MOC) neurons, the average exponential time constant was 47 ms, which is roughly similar to that for short-term adaptation in auditory-nerve fibers. The amount of adaptation (expressed as a percentage decrease of onset firing rate), however, was substantially less in MOC neurons (average 31%) than in auditory-nerve fibers (average 63%). To test for adaptation over longer periods, we used noise and tones of 10 s duration. After the short-term adaptation, the responses of MOC neurons were almost completely sustained (average long-term adaptation 3%). However, in the same preparations, significant long-term adaptation was present in auditory-nerve fibers. These results indicate that the MOC response adaptation is minimal compared with that of auditory-nerve fibers. Such sustained responses may enable the MOC system to produce sustained effects in the periphery, supporting a role for this efferent system during ongoing stimuli of long duration.

Cell motility: ARNOand ARF6 at the cutting edge

The transition of epithelial cells from a stationary to a motile state is important in embryogenesis, wound repair and metastasis. Recent studies have shown that ARNO and ARF6 play significant roles in coordinating this transition, providing new insight into the interplay between the Rho and ARF families of GTPases.

Mice overexpressing genes from the 22q11 region deleted in velo-cardio-facial syndrome/DiGeorge syndrome have middle and inner ear defects

Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS) is a congenital anomaly disorder associated with hemizygous 22q11 deletions. We previously showed that bacterial artificial chromosome (BAC) transgenic mice overexpressing four transgenes, PNUTL1, (CDCrel-1), GP1B beta, TBX1 and WDR14, had reduced viability, cardiovascular malformations and thymus gland hypoplasia. Since these are hallmark features of VCFS/DGS, we analyzed the mice for additional anomalies. We found that the mice have important defects in the middle and inner ear that are directly relevant to the disorder. The most striking defect was the presence of chronic otitis media, a common finding in VCFS/DGS patients. In addition, the mice had a hyperactive circling behavior and sensorineural hearing loss. This was associated with middle and inner ear malformations, analogous to Mondini dysplasia in humans reported to occur in VCFS/DGS patients. We propose that overexpression of one or more of the transgenes is responsible for the etiology of the ear defects in the mice. Based upon its pattern of expression in the ear and functional studies of the gene, TbX1 likely plays a central role. Haploinsufficiency of TBX1 may be responsible for ear disorders in VCFS/DGS patients.

Paxillin-ARF GAP signaling and the cytoskeleton

Several new families of ARF GTPase activating proteins (ARF GAPs) have been described recently that associate with paxillin and other cytoskeletal and signaling proteins. Important insights have been gained regarding their subcellular distribution, enzymatic specificity and protein scaffold function. Evidence suggests an important role for ARF GAPs in mediating changes in the cell's actin cytoskeleton in response to adhesion and growth factor stimulation.

Development and use of microsatellite DNA loci for genetic ecotoxicological studies of the fathead minnow (Pimephales promelas)

The development of new DNA technologies has increased the opportunities to study the effect of genetic variation as a factor in selection, resistance, and fitness of individuals and populations. Genetic composition affects the evolutionary potential of an organism; however, whether genetic variation has a role in adaptation and survival due to chemical stress is still under debate. The strategy of measuring such variation should be based on the desired number of loci needed and degree of polymorphism at each locus. Microsatellite DNA loci (also known as Simple Tandem Repeats, STRs) have among the highest levels of variation within most eukaryotic genomes. Methods to determine the high levels of variation in individuals and populations have become more refined, making DNA-based studies in ecotoxicology more feasible. Herein, we describe the general characteristics of microsatellite DNA loci, their isolation, and their applications to toxicological studies using the fathead minnow (Pimephales promelas) as a focal species.

The LD4 motif of paxillin regulates cell spreading and motility through an interaction with paxillin kinase linker (PKL)

The small GTPases of the Rho family are intimately involved in integrin-mediated changes in the actin cytoskeleton that accompany cell spreading and motility. The exact means by which the Rho family members elicit these changes is unclear. Here, we demonstrate that the interaction of paxillin via its LD4 motif with the putative ARF-GAP paxillin kinase linker (PKL) (Turner et al., 1999), is critically involved in the regulation of Rac-dependent changes in the actin cytoskeleton that accompany cell spreading and motility. Overexpression of a paxillin LD4 deletion mutant (paxillinDeltaLD4) in CHO.K1 fibroblasts caused the generation of multiple broad lamellipodia. These morphological changes were accompanied by an increase in cell protrusiveness and random motility, which correlated with prolonged activation of Rac. In contrast, directional motility was inhibited. These alterations in morphology and motility were dependent on a paxillin-PKL interaction. In cells overexpressing paxillinDeltaLD4 mutants, PKL localization to focal contacts was disrupted, whereas that of focal adhesion kinase (FAK) and vinculin was not. In addition, FAK activity during spreading was not compromised by deletion of the paxillin LD4 motif. Furthermore, overexpression of PKL mutants lacking the paxillin-binding site (PKLDeltaPBS2) induced phenotypic changes reminiscent of paxillinDeltaLD4 mutant cells. These data suggest that the paxillin association with PKL is essential for normal integrin-mediated cell spreading, and locomotion and that this interaction is necessary for the regulation of Rac activity during these events.

Modification of the tear function index and its use in the diagnosis of Sjögren's syndrome

BACKGROUND

The tear function index (TFI) has been shown to be of value in the diagnosis of patients suffering from Sjögren's syndrome. It is dependent, however, on introducing into the conjunctival fornix the correct concentration of fluorescein in at least one and a half times the normal tear volume. The stimulus and effect of this added volume on the tear dynamics is likely to vary between individuals. These factors, together with the method of performing the test, limit its general applicability.

AIM

To devise a method of performing the TFI with less variability and more general applicability. To present a theoretical and in vitro assessment of the dynamics of the TFI.

METHOD

The study was divided into three parts. The first part was to compare the results obtained using a prepared strip containing 1.3 microl of 0.5% fluorescein with the introduction of the same amount of fluorescein as a drop. The second part was to compare the results obtained with prepared strips with the standard method of performing the TFI, both with and without topical anaesthetic. The third part was an in vitro study of the rate of flow of graded volumes on a filter paper strip. 42 subjects with a diagnosis of Sjögren's syndrome according to the European criteria and 126 without Sjögren's syndrome were included.

RESULTS

There was no significant difference between the results obtained with a prepared strip and the introduction of 1.3 microl into the eye before performing the Schirmer's test and TFI (0.1<p<0.93). There was, likewise, no significant difference between using the prepared strips and the standard method of performing the TFI (0.36<p<0.93). There was, however, less interocular difference (p=0.01) and variability (p=0.001) using the prepared strips than using a drop of fluorescein. Patients with Sjögren's syndrome had mean TFIs of 11.7 and 8.61 with upper 95% confidence values of 15 and 12 without and with topical anaesthetic, respectively. The theoretical calculation of the TFI was similar to the observed values. The in vitro results allow the filter paper to be removed from the eye at any interval and to estimate the volume of tears that the filter paper was in contact with.

CONCLUSION

The proposed method of performing the TFI is easy to perform, reliable, and therefore has general applicability for primary care and general practitioners. It allows the rapid identification of subjects who may be suffering from Sjögren's syndrome.

Innervation of supporting cells in the apical turns of the guinea pig cochlea is from type II afferent fibers

The outer supporting cells in the apical turns of the guinea pig cochlea receive a dense innervation. Our previous study (Fechner et al. [1998] J. Comp. Neurol. 400:299-300) suggested that this innervation of the Deiters' and Hensen's supporting cells was not derived from efferent fibers of the olivocochlear bundle, but its origin has not been further specified. To test the hypothesis that the innervation was afferent in origin, we traced apical afferent fibers that were retrogradely labeled by extracellular injections of horseradish peroxidase. Labeled afferent fibers were of two types: type I fibers contacted inner hair cells, whereas type II fibers crossed the tunnel and contacted outer hair cells. Significantly, most of the type II fibers also formed branches to the outer supporting cells. Although a few olivocochlear efferent fibers formed such branches, counts indicated that the overwhelming majority of the branches were produced by type II afferent fibers. These branches were not produced by basal type II fibers. Apical type II fibers also differed from basal fibers by having shorter lengths, spiraling both apically and basally, and contacting all three rows of outer hair cells. These innervation differences suggest differences in the ways that information from outer hair cells is processed in the apex versus the base of the cochlea.

Fast, but not slow, effects of olivocochlear activation are resistant to apamin

Olivocochlear (OC) efferent suppression of auditory-nerve responses comprises a fast effect lasting tens of milliseconds and a slow effect building and decaying over tens of seconds. Both fast and slow effects are mediated by activation of the same alpha 9 nicotinic receptor. We have hypothesized that fast effects are generated at the OC synapse, but that slow effects reflect activation of calcium-activated potassium (K(Ca)) channels by calcium release from the subsurface cisternae on the basolateral wall of the hair cells. We measured in vivo effects of apamin, a blocker of small-conductance (SK) K(Ca) channels, and charybdotoxin, a blocker of large-conductance K(Ca) channels, perfused through scala tympani, on fast and slow effects evoked by electrical stimulation of the OC bundle in anesthetized guinea pigs. Apamin selectively and reversibly reduced slow-effect amplitude without altering fast effects or baseline amplitude of the auditory-nerve response, but only when perfused at concentrations of 100 microM. In contrast, the effects of charybdotoxin were noted at 30 nM, but were not specific, reducing both afferent and efferent responses. The very high concentrations of apamin needed to block efferent effects contrasts with the high sensitivity of isolated hair cells to apamin's block of acetylcholine's effects. The results suggest that in vivo fast OC effects are dominated by a conductance that is not apamin sensitive.

Magnetic detection to position human nasogastric tubes

Placement of nasogastric tubes is one of the most commonly performed diagnostic and therapeutic medical procedures. Proper placement of the tube in the digestive tract below the diaphragm is crucial for efficacy and safety. This study evaluates a magnet detection system that allows percutaneous non-radiographic localization of the nasogastric tube tip. Each volunteer subject had the magnet detector placed over the abdomen, and was then intubated with a magnet-tagged nasogastric tube. Eighty-eight nasogastric tube placements were performed in 22 volunteers. The detection system located the nasogastric tube tip below the diaphragm in all 88 placements. Location in all attempts was confirmed by fluoroscopy. This method of correctly locating the tip of nasogastric tubes may obviate the need for radiographic imaging in most cases.

Cancer metastasis at percutaneous endoscopic gastrostomy stomata is related to the hematogenous or lymphatic spread of circulating tumor cells

Percutaneous endoscopic gastrostomy (PEG) has become a mainstay in providing enteral access for patients with obstructive oropharyngeal and esophageal tumors. PEG tube placement is considered safe, and complications are infrequent. One complication, although rare, that is being increasingly reported is the metastasis of cancer at PEG stomata. Herein, a case of metastasis of an esophageal cancer at a PEG stoma is described. Although it has been previously suggested that cancer metastasis is due to direct seeding of the stoma, an analysis of the literature suggests that this phenomenon is related to the hematogenous or lymphatic spread of cancer cells to a susceptible site.

Ejection from an aircraft following photorefractive keratectomy: a case report

A 32-yr-old active duty United States Navy Lieutenant Naval Flight Officer (NFO), 6 mo status post photorefractive keratectomy (PRK) in both eyes performed as part of the first protocol to evaluate laser refractive surgery in aviators, ejected from a Navy S-3B Viking aircraft while performing field carrier landing practice. Neither the pilot nor the NFO suffered physical consequences as a result of the ejection. Coincidentally, the NFO had been examined just 1 wk before the mishap and was noted to have uncorrected visual acuity of 20/16 in each eye. Examination 1 wk following the mishap could not detect a change in vision. The NFO's vision status and his post-PRK status was not listed as a causal factor in the mishap. While this case report will not settle the debate regarding the appropriateness of refractive surgery in aviators, it does provide anecdotal evidence to support the safety of PRK in the aviation community.

Paxillin localizes to the lymphocyte microtubule organizing center and associates with the microtubule cytoskeleton

Paxillin is a focal adhesion-associated protein that functions as a multi-domain adapter protein, binding several structural and signaling molecules. alpha-Tubulin was identified as an interacting protein in a two-hybrid screen using the paxillin C-terminal LIM domain as a bait. In vitro binding assays with glutathione S-transferase-paxillin demonstrated an interaction of alpha-tubulin with the C terminus of paxillin. Another member of the tubulin family, gamma-tubulin, bound to both the N and the C terminus of paxillin. The interaction between paxillin and both alpha- and gamma-tubulin in vivo was confirmed by co-immunoprecipitation from human T lymphoblasts. Immunofluorescence studies revealed that, in adherent T cells, paxillin localized to sites of cell-matrix interaction as well as to a large perinuclear region. Confocal microscopy revealed that this region corresponds to the lymphocyte microtubule organizing center, where paxillin colocalizes with alpha- and gamma-tubulin. The localization of paxillin to this area was observed in cells in suspension as well as during adhesion to integrin ligands. These data constitute the first characterization of the interaction of paxillin with the microtubule cytoskeleton, and suggest that paxillin, in addition to its well established role at focal adhesions, could also be associated with the lymphocyte microtubule network.

Bradyzide, a potent non-peptide B(2) bradykinin receptor antagonist with long-lasting oral activity in animal models of inflammatory hyperalgesia

Bradyzide is from a novel class of rodent-selective non-peptide B(2) bradykinin antagonists (1-(2-Nitrophenyl)thiosemicarbazides). Bradyzide has high affinity for the rodent B(2) receptor, displacing [(3)H]-bradykinin binding in NG108-15 cells and in Cos-7 cells expressing the rat receptor with K(I) values of 0.51+/-0.18 nM (n=3) and 0.89+/-0.27 nM (n=3), respectively. Bradyzide is a competitive antagonist, inhibiting B(2) receptor-induced (45)Ca efflux from NG108-15 cells with a pK(B) of 8.0+/-0.16 (n=5) and a Schild slope of 1.05. In the rat spinal cord and tail preparation, bradyzide inhibits bradykinin-induced ventral root depolarizations (IC(50) value; 1.6+/-0.05 nM (n=3)). Bradyzide is much less potent at the human than at the rodent B(2) receptor, displacing [(3)H]-bradykinin binding in human fibroblasts and in Cos-7 cells expressing the human B(2) receptor with K(I) values of 393+/-90 nM (n=3) and 772+/-144 nM (n=3), respectively. Bradyzide inhibits bradykinin-induced [(3)H]-inositol trisphosphate (IP(3)) formation with IC(50) values of 11.6+/-1.4 nM (n=3) at the rat and 2.4+/-0.3 microM (n=3) at the human receptor. Bradyzide does not interact with a range of other receptors, including human and rat B(1) bradykinin receptors. Bradyzide is orally available and blocks bradykinin-induced hypotension and plasma extravasation. Bradyzide shows long-lasting oral activity in rodent models of inflammatory hyperalgesia, reversing Freund's complete adjuvant (FCA)-induced mechanical hyperalgesia in the rat knee joint (ED(50), 0.84 micromol kg(-1); duration of action >4 h). It is equipotent with morphine and diclofenac, and 1000 times more potent than paracetamol, its maximal effect exceeding that of the non-steroidal anti-inflammatory drugs (NSAIDs). Bradyzide does not exhibit tolerance when administered over 6 days. In summary, bradyzide is a potent, orally active, antagonist of the B(2) bradykinin receptor, with selectivity for the rodent over the human receptor. British Journal of Pharmacology (2000) 129, 77 - 86

Gentamicin blocks both fast and slow effects of olivocochlear activation in anesthetized guinea pigs

The medial olivocochlear (MOC) efferent system, which innervates cochlear outer hair cells, suppresses cochlear responses. MOC-mediated suppression includes both slow and fast components, with time courses differing by three orders of magnitude. Pharmacological studies in anesthetized guinea pigs suggest that both slow and fast effects on cochlear responses require an initial acetylcholine activation of alpha-9 nicotinic receptors on outer hair cells and that slow effects require additional intracellular events downstream from those mediating fast effects. Gentamicin, an aminoglycoside antibiotic, has been reported to block fast effects of sound-evoked OC activation following intramuscular injection in unanesthetized guinea pigs, without changing slow effects. In the present study, we show that electrically evoked fast and slow effects in the anesthetized guinea pig are both blocked by either intramuscular or intracochlear gentamicin, with similar time courses and/or dose-response curves. We suggest that sound-evoked slow effects in unanesthetized animals are fundamentally different from electrically evoked slow effects in anesthetized animals, and that the former may arise from effects of the lateral OC system.

Monocular and binocular depth discrimination thresholds

BACKGROUND

Measurement of stereoacuity at varying distances, by real or simulated depth stereoacuity tests, is helpful in the evaluation of patients with binocular imbalance or strabismus. Although the cue of binocular disparity underpins stereoacuity tests, there may be variable amounts of other binocular and monocular cues inherent in a stereoacuity test. In such circumstances, a combined monocular and binocular threshold of depth discrimination may be measured--stereoacuity conventionally referring to the situation where binocular disparity giving rise to retinal disparity is the only cue present. A child-friendly variable distance stereoacuity test (VDS) was developed, with a method for determining the binocular depth threshold from the combined monocular and binocular threshold of depth of discrimination (CT).

METHODS

Subjects with normal binocular function, reduced binocular function, and apparently absent binocularity were included. To measure the threshold of depth discrimination, subjects were required by means of a hand control to align two electronically controlled spheres at viewing distances of 1, 3, and 6m. Stereoacuity was also measured using the TNO, Frisby, and Titmus stereoacuity tests. BTs were calculated according to the function BT= arctan (1/tan alphaC - 1/tan alphaM)(-1), where alphaC and alphaM are the angles subtended at the nodal points by objects situated at the monocular threshold (alphaM) and the combined monocular-binocular threshold (alphaC) of discrimination.

RESULTS

In subjects with good binocularity, BTs were similar to their combined thresholds, whereas subjects with reduced and apparently absent binocularity had binocular thresholds 4 and 10 times higher than their combined thresholds (CT). The VDS binocular thresholds showed significantly higher correlation and agreement with the TNO test and the binocular thresholds of the Frisby and Titmus tests, than the corresponding combined thresholds (p = 0.0019).

CONCLUSION

The VDS was found to be an easy to use real depth (distance) stereoacuity test. The method described for calculating the BT provides one simple nonlinear solution for determining the respective contributions of binocular and monocular (MT) depth discrimination to the combined depth threshold.