Managing Selected Chronic Conditions in Hospitalized Patients.

The management of chronic illnesses should continue during hospitalization. Some chronic conditions require immediate intervention, whereas intensification of therapy for other conditions may be delayed until after discharge. Factors such as pain, anxiety, poor sleep hygiene, and concurrent illness can result in a transient elevation of blood pressure. Acute lowering of blood pressure in hospitalized patients who do not have target-organ damage is not recommended and may lead to harm. If treatment is needed, intravenous antihypertensive agents should be avoided. Patients with diabetes mellitus require continued management of their blood glucose while hospitalized. Noninsulin agents are typically discontinued. Blood glucose levels should be managed using basal, prandial, and/or correction insulin. During hospitalization, conservative blood glucose targets (140 to 180 mg per dL) are preferred vs. lower targets to reduce length of stay, mortality, and the risk of hypoglycemic events in critically ill patients. Alcohol use disorder is common and hospitalization for other conditions necessitates identification and management of alcohol withdrawal syndrome. The mainstay of therapy for alcohol withdrawal syndrome is benzodiazepines; however, phenobarbital is an alternative treatment option. The risk of venous thromboembolic disease is significantly increased for hospitalized patients. Venous thromboprophylaxis is recommended for all but low-risk patients. Pharmacologic prophylaxis with subcutaneous low-molecular-weight heparin is preferred; mechanical prophylaxis is an alternative for patients who are at high risk of bleeding or have contraindications to anticoagulation.

Asbestos and Iron.

Theories of disease pathogenesis following asbestos exposure have focused on the participation of iron. After exposure, an open network of negatively charged functional groups on the fiber surface complexes host metals with a preference for iron. Competition for iron between the host and the asbestos results in a functional metal deficiency. The homeostasis of iron in the host is modified by the cell response, including increased import to correct the loss of the metal to the fiber surface. The biological effects of asbestos develop in response to and are associated with the disruption of iron homeostasis. Cell iron deficiency in the host following fiber exposure activates kinases and transcription factors, which are associated with the release of mediators coordinating both inflammatory and fibrotic responses. Relative to serpentine chrysotile, the clearance of amphiboles is incomplete, resulting in translocation to the mesothelial surface of the pleura. Since the biological effect of asbestos is dependent on retention of the fiber, the sequestration of iron by the surface, and functional iron deficiency in the cell, the greater clearance (i.e., decreased persistence) of chrysotile results in its diminished impact. An inability to clear asbestos from the lower respiratory tract initiates a host process of iron biomineralization (i.e., asbestos body formation). Host cells attempt to mobilize the metal sequestered by the fiber surface by producing superoxide at the phagosome membrane. The subsequent ferrous cation is oxidized and undergoes hydrolysis, creating poorly crystalline iron oxyhydroxide (i.e., ferrihydrite) included in the coat of the asbestos body.

Bringing Radiology Education to a New Reality: A Pilot Study of Using Virtual Reality as a Remote Educational Tool.

Purpose: We investigated virtual reality (VR) during a 2-week, undergraduate, radiology elective to determine if it improved learning outcomes and user satisfaction. Methods: Eighteen students enrolled between August 2021 and February 2022. Each student had a collaborative Zoom teaching session with a preceptor using a Picture Archive and Communications System (PACS)-like viewing system Online DICOM Image Navigator (ODIN), followed by a teaching session using a VR, Digital Imaging and Communications in Medicine (DICOM) viewer (SieVRt). After each teaching session, the students independently reviewed 8 imaging cases and completed case related questions. The students completed a survey, rating their subjective experiences using ODIN and SieVRt. Results: There was no difference in total test scores between the two learning strategies. However, students did perform statistically better on two of five questions designed to test the detection/measurement capabilities of SieVRt vs ODIN. Students stated that they preferred using SieVRt over ODIN and agreed that they were able to view subtle imaging findings and abnormalities better using SieVRt. However, students found that some of the functions of SieVRt (measuring angles/lengths, and multitasking) were difficult. There were technical challenges with VR and minor undesirable physical effects (dizziness, nausea, etc.). Conclusions: Virtual reality has the potential to enhance radiology education by providing an immersive and engaging experience. Objectively, students were able to perform two tasks better with SieVRt. Subjectively, the VR platform received favourable reviews from students for a variety of features. There were reported technical and physical challenges related to using VR. Future developments in VR systems should focus on improving the user experience.

Preparedness of Residents and Medical Students for the Transition to Competence by Design in Diagnostic Radiology Post-Graduate Medical Education.

Introduction: This needs assessment evaluated residents' and medical students' knowledge of Competence by Design (CBD), perceived benefits of and challenges or barriers to the transition to CBD for residents, and perceived overall preparedness for the transition to CBD in diagnostic radiology. Materials and Methods: All diagnostic radiology residents and medical students in Canada were eligible to participate in this national cross-sectional, questionnaire-based needs assessment. Knowledge of CBD was evaluated through participants' self-reported rating of their knowledge of CBD on a 5-point Likert scale. Perceived benefits of and challenges or barriers to the transition to CBD for residents were rank ordered. Participants' overall self-reported preparedness for the transition to CBD was assessed on a 5-point Likert scale. Data were summarized by descriptive statistics and bivariate analyses were conducted as appropriate. Results: Ninety-four residents (n = 77) and medical students (n = 17) participated in this needs assessment. Participants' mean ± standard deviation self-reported rating of their overall knowledge of CBD was 2.86 ± .94. Provision of meaningful feedback to learners and learners' ability to identify their own educational needs were among the highest ranked perceived benefits of the transition to CBD, while demands on time and increased frequency of evaluation were among the highest ranked perceived challenges or barriers to the transition to CBD. Few participants reported being either "prepared" (4.7%) or "somewhat prepared" (14.0%) for the transition to CBD. Conclusion: Preparedness for the transition to CBD in diagnostic radiology may be improved. Targeted interventions to augment the preparedness of residents and medical students should be considered.

Partitioning of Organonitrates in the Production of Secondary Organic Aerosols from α-Pinene Photo-Oxidation.

The chemical pathways for the production of secondary organic aerosols (SOA) are influenced by the concentration of nitrogen oxides (NOx), including the production of organonitrates (ON). Herein, a series of experiments conducted in an environmental chamber investigated the production and partitioning of total organonitrates from α-pinene photo-oxidation from <1 to 24 ppb NOx. Gas-phase and particle-phase organonitrates (gON and pON, respectively) were measured by laser-induced fluorescence (LIF). The composition of the particle phase and the particle mass concentration were simultaneously characterized by online aerosol mass spectrometry. The LIF and MS measurements of pON concentrations had a Pearson correlation coefficient of 0.91 from 0.3 to 1.1 µg m-3. For 1-6 ppb NOx, the yield of SOA particle mass concentration increased from 0.02 to 0.044 with NOx concentration. For >6 ppb NOx, the yield steadily dropped, reaching 0.034 at 24 ppb NOx. By comparison, the yield of pON steadily increased from 0.002 to 0.022 across the range of investigated NOx concentrations. The yield of gON likewise increased from 0.005 to 0.148. The gas-to-particle partitioning ratio (pON/(pON + gON)) depended strongly on the NOx concentration, changing from 0.27 to 0.13 as the NOx increased from <1 to 24 ppb. In the atmosphere, there is typically a cross-over point between clean and polluted conditions that strongly affects SOA production, and the results herein quantitatively identify 6 ppb NOx as that point for α-pinene photo-oxidation under these study conditions, including the production and partitioning of organonitrates. The trends in SOA yield and partitioning ratio as a function of NOx occur because of the changes in pON volatility.

River Winds and Transport of Forest Volatiles in the Amazonian Riparian Ecoregion.

Volatile organic compounds (VOCs) emitted from forests are important chemical components that affect ecosystem functioning, atmospheric chemistry, and regional climate. Temperature differences between a forest and an adjacent river can induce winds that influence VOC fate and transport. Quantitative observations and scientific understanding, however, remain lacking. Herein, daytime VOC datasets were collected from the surface up to 500 m over the "Rio Negro" river in Amazonia. During time periods of river winds, isoprene, α-pinene, and ß-pinene concentrations increased by 50, 60, and 80% over the river, respectively. The concentrations at 500 m were up to 80% greater compared to those at 100 m because of the transport path of river winds. By comparison, the concentration of methacrolein, a VOC oxidation product, did not depend on river winds or height. The differing observations for primary emissions and oxidation products can be explained by the coupling of timescales among emission, reaction, and transport. This behavior was captured in large-eddy simulations with a coupled chemistry model. The observed and simulated roles of river winds in VOC fate and transport highlight the need for improved representation of these processes in regional models of air quality and chemistry-climate coupling.

Retroviral association with ovarian adenocarcinoma in laying hens.

The laying hen has been used as a model for ovarian adenocarcinoma (OAC) in women. Previous work has shown an association between expression of endogenous retroviral proteins and elevated envelope mRNA and occurrence of OAC in humans, but causality has not been demonstrated. The objective of this study was to determine whether there is a similar association between retrovirus presence and OAC in a commercial laying hen flock at the University of Illinois Poultry Research facility with a history of a high OAC prevalence in older hens. Laying hens of three age strata were randomly selected for a cross-sectional study. Blood samples were collected, and serum was tested for antigens of endogenous or exogenous avian leukosis virus (ALV) by ELISA. Birds were humanely euthanized, and spleens, ovaries, and any tissues with gross lesions were sampled. Ovaries and gross lesions were examined histologically and spleens were used for RT-PCR to detect endogenous ALV via ALV-E env mRNA expression. Overall, hens with OAC were 5.2 times more likely to be ALV positive than hens without OAC (95% C.I. 2.06-13.14). Controlled for age, OAC positive hens were 3.6 times more likely to be positive for ALV via antigen-capture ELISA (95% C.I. 1.08-11.96). Endogenous ALV-E in hens may be analogous to human endogenous retroviruses, which have also been associated with OAC in women. Further studies to establish causation are warranted to better understand the potential for laying hens to serve as a laboratory model for viral-induced ovarian tumours in humans. RESEARCH HIGHLIGHTSOAC in hens was associated with age, seropositivity for ALV, and endogenous ALV mRNA expression.Older hens with OAC were more likely to be ALV seropositive by ELISA and ALV-E mRNA-positive.Associations between OAC, age, and endogenous retrovirus expression have been reported in humans.These findings support the use of hens as models for OAC in humans.

Thermostability-based binding assays reveal complex interplay of cation, substrate and lipid binding in the bacterial DASS transporter, VcINDY.

The divalent anion sodium symporter (DASS) family of transporters (SLC13 family in humans) are key regulators of metabolic homeostasis, disruption of which results in protection from diabetes and obesity, and inhibition of liver cancer cell proliferation. Thus, DASS transporter inhibitors are attractive targets in the treatment of chronic, age-related metabolic diseases. The characterisation of several DASS transporters has revealed variation in the substrate selectivity and flexibility in the coupling ion used to power transport. Here, using the model DASS co-transporter, VcINDY from Vibrio cholerae, we have examined the interplay of the three major interactions that occur during transport: the coupling ion, the substrate, and the lipid environment. Using a series of high-throughput thermostability-based interaction assays, we have shown that substrate binding is Na+-dependent; a requirement that is orchestrated through a combination of electrostatic attraction and Na+-induced priming of the binding site architecture. We have identified novel DASS ligands and revealed that ligand binding is dominated by the requirement of two carboxylate groups in the ligand that are precisely distanced to satisfy carboxylate interaction regions of the substrate-binding site. We have also identified a complex relationship between substrate and lipid interactions, which suggests a dynamic, regulatory role for lipids in VcINDY's transport cycle.

Patient experiences of sialendoscopy with monitored anesthesia care versus general anesthesia.

OBJECTIVE: To compare the experiences of patients who received sialendoscopy under general anesthesia (GA) with those who received monitored anesthesia care (MAC). METHODS: Patients who underwent sialendoscopy for sialadenitis or sialolithiasis from July 1, 2020, to July 31, 2021, were offered inclusion to this prospective observational study. A survey was sent to consenting patients on post-operative day 1 to record aspects of their pre-, intra-, and post-operative experience. The primary outcome was overall satisfaction. Secondary outcomes included pain tolerability and preference for similar anesthetic modality in the future. RESULTS: Seventy-five patients completed the post-operative survey (86% response rate), of which 39 patients received GA and 36 received MAC. Patient overall satisfaction was similar between groups (GA: "Poor/Average/Good" = 23%, "Excellent" = 77%; MAC: "Poor/Average/Good" = 25%, "Excellent" = 75%, p = 1.00). Tolerability of immediate post-operative pain was likewise similar between the GA (82%) and MAC (97%) groups (p = 0.058). Patients who received MAC reported intra-operative pain as "none/tolerable" 72% of the time and "uncomfortable" 28% of the time. Patients who received GA would prefer the same anesthetic in the future more often than in the MAC group (85% versus 61%, respectively, OR 3.50, 95% CI 1.17-10.50, p = 0.035). CONCLUSION: In regard to patient satisfaction, both MAC and GA are acceptable anesthetic choices in sialendoscopy for appropriate cases. Patients report similar overall satisfaction and post-operative pain tolerance under either anesthetic modality. Patients who undergo GA report higher rates of preference for similar anesthetic modality in the future. Further study is needed to determine the most appropriate criteria for anesthesia modality selection.

Otologic opioid usage and pain control in the postoperative period: An observational prospective study.

PURPOSE: Evaluate opioid prescribing patterns, opioid consumption, and patient pain patterns following otologic surgery. MATERIALS AND METHODS: Patients were included if they were ≥18 years old and received otologic surgery between November 2019 and August 2020. Patients were provided a survey which included a visual analog scale for recording their pain postoperatively and the amount of opioid they had remaining. Patients who did not complete all portions of the survey were excluded. RESULTS: Ninety-one patients completed the post-operative questionnaire. Collectively, patients were prescribed 5797 morphine milligram equivalents and used 3092: approximately 47% went unused. Of patients receiving a transcanal incision (n = 28/91, 31%), 70% went unused, whereas patients receiving a postauricular incision (n = 57/91, 63%), 38% went unutilized. The utilization difference between transcanal and postauricular cohorts was significant (p = 0.002). On multivariate analysis, patients who received a postauricular incision had 60% more opioid usage (p < 0.001), whereas those with a transcanal incision had an average reduction of 40% in opioid usage (p < 0.001). CONCLUSIONS: A significant amount of opioid medication went unused in this study. Patients with postauricular incisions had significantly increased opioid utilization as compared to those with transcanal incisions. Otologists may be able to successfully manage pain in the postoperative period with a reduced opioid prescription multimodal analgesia and increased patient education. Further study is needed to support this suggestion.

Reduced gastroesophageal reflux disease symptom severity following upper airway surgery for comorbid obstructive sleep apnea.

PURPOSE: To evaluate patient-reported quality of life pertaining to gastroesophageal reflux disease symptoms in patients undergoing upper airway surgery for comorbid obstructive sleep apnea. MATERIALS AND METHODS: A prospective survey-based study was conducted on patients with gastroesophageal reflux disease and comorbid obstructive sleep apnea receiving surgery from July 2020-December 2020. Patients completed the Gastroesophageal Reflux Disease-Health Related Quality of Life Questionnaire at two time-points: one week before surgery and at 6 months following surgery. Disease-related symptoms were rated from 0 (no symptoms) to 5 (incapacitating symptoms). Patient survey scores, demographics, medications, and sleep study parameters were collected for analysis. A p-value <0.05 indicated statistical significance. RESULTS: Twenty-two patients completed the baseline preoperative and 6-month postoperative questionnaires. Median baseline vs. 6-month survey scores significantly decreased for symptoms including heartburn in general (3.0 vs. 2.0, p = 0.006), when lying down (2.5 vs. 1.5, p = 0.046), when standing (2.0 vs 1.0, p = 0.003), following meals (2.0 vs. 2.0, p = 0.042), and cumulative survey score (15.5 vs. 11.0, p = 0.029). Heartburn altering diet or sleep, odynophagia, dysphagia, and medication burden did not change following surgery (p > 0.05). More patients were satisfied with their postoperative condition compared to baseline, however this did not reach statistical significance (40.9% vs. 18.2%, p = 0.18). CONCLUSIONS: Our results suggest that upper airway surgery to treat obstructive sleep apnea may have a positive impact on patient-reported symptoms of gastroesophageal reflux disease, and further investigation into the role of surgery in this setting for improvement of both quality of life and true clinical disease severity is merited.

Performance of predictive models of survival in horses undergoing emergency exploratory laparotomy for colic.

OBJECTIVE: To evaluate previously published predictive survival models in a population of horses undergoing colic surgery in the midwestern United States. STUDY DESIGN: Retrospective cohort study; single referral hospital. ANIMALS: A total of 260 horses met the inclusion criteria. METHODS: Medical records of horses undergoing surgical treatment for colic were reviewed. Previously published models were applied to cohort data to predict outcome. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for prediction of short-term survival were calculated. RESULTS: Single-variable and multivariable models performed similarly for prediction of survival, with a mean 79% sensitivity (range: 44%-94%), 48% specificity (range: 22%-83%), 63% PPV (range: 56%-72%), 73% NPV (range: 60%-83%), and 64% accuracy (range: 59%-72%). Blood lactate ≤6 mmol/l and the colic severity score (CSS) were highly sensitive for prediction of survival; however, both had poor specificity. CONCLUSION: Single-variable and multivariable predictive models did not perform as well for prediction of survival in the study cohort compared to original reports, suggesting that population-specific factors contribute to patient survival. CLINICAL SIGNIFICANCE: Predictive models of survival developed in one population may be less reliable when used to predict outcome in horses undergoing colic surgery from an independent population. Additional model testing and refinement using data from multiple surgical centers could be considered to improve prediction of outcome for horses undergoing laparotomy for treatment of colic.

Solvent accessibility changes in a Na+-dependent C4-dicarboxylate transporter suggest differential substrate effects in a multistep mechanism.

The divalent anion sodium symporter (DASS) family (SLC13) plays critical roles in metabolic homeostasis, influencing many processes, including fatty acid synthesis, insulin resistance, and adiposity. DASS transporters catalyze the Na+-driven concentrative uptake of Krebs cycle intermediates and sulfate into cells; disrupting their function can protect against age-related metabolic diseases and can extend lifespan. An inward-facing crystal structure and an outward-facing model of a bacterial DASS family member, VcINDY from Vibrio cholerae, predict an elevator-like transport mechanism involving a large rigid body movement of the substrate-binding site. How substrate binding influences the conformational state of VcINDY is currently unknown. Here, we probe the interaction between substrate binding and protein conformation by monitoring substrate-induced solvent accessibility changes of broadly distributed positions in VcINDY using a site-specific alkylation strategy. Our findings reveal that accessibility to all positions tested is modulated by the presence of substrates, with the majority becoming less accessible in the presence of saturating concentrations of both Na+ and succinate. We also observe separable effects of Na+ and succinate binding at several positions suggesting distinct effects of the two substrates. Furthermore, accessibility changes to a solely succinate-sensitive position suggests that substrate binding is a low-affinity, ordered process. Mapping these accessibility changes onto the structures of VcINDY suggests that Na+ binding drives the transporter into an as-yet-unidentified conformational state, involving rearrangement of the substrate-binding site-associated re-entrant hairpin loops. These findings provide insight into the mechanism of VcINDY, which is currently the only structurally characterized representative of the entire DASS family.

Upper airway stimulation: Fewer complications, ED presentations, readmissions, and increased surgical success.

OBJECTIVES: Evaluate the rate of complications, readmissions, emergency department presentations, and surgical success rates amongst three standard surgical treatment options for obstructive sleep apnea: upper airway stimulation, transoral robotic surgery, and expansion sphincter pharyngoplasty. STUDY DESIGN: Retrospective cohort. SETTING: Tertiary care center. METHODS: Patients were included who were aged ≥18 years old and underwent upper airway stimulation, transoral robotic surgery, or expansion sphincter pharyngoplasty between January 2011 and May 2020. RESULTS: 345 patients were identified: 58% (n = 201) underwent upper airway stimulation, 10% (n = 35) underwent transoral robotic surgery, and 32% (n = 109) patients underwent expansion sphincter pharyngoplasty. There were 22 emergency department presentations and 19 readmissions, most of which were experienced by patients receiving transoral robotic surgery (six emergencies, seven readmissions) and expansion sphincter pharyngoplasty (12 emergencies, 11 readmissions). Patients with upper airway stimulation had four emergencies and one readmission. Only 2% of the upper airway stimulation cohort had a complication, whereas this was 20% and 12% for the transoral robotic surgery and expansion sphincter pharyngoplasty cohorts, respectively. Patients experienced the highest surgical success rate with upper airway stimulation (69%), whereas patients who received transoral robotic surgery and expansion sphincter pharyngoplasty had success rates of 50% and 51%, respectively. CONCLUSION: Treating obstructive sleep apnea with upper airway stimulation led to lower rates of complications, emergency department presentations, and readmissions in this series. In those for whom upper airway stimulation is appropriate, it may be more effective in successfully treating obstructive sleep apnea than transoral robotic surgery and expansion sphincter pharyngoplasty.

Improved efficiency of sialendoscopy procedures at an ambulatory surgery center.

OBJECTIVES: To compare time spent on day of surgery and post-surgical outcomes for sialendoscopy procedures at an ambulatory surgery center versus in a hospital operating room. METHODS: Retrospective chart review for patients who underwent sialendoscopy for sialadenitis or sialolithiasis from March 2017 to May 2020 were included. Surgery location (ambulatory surgery center or hospital operating room) was compared. Primary outcomes included total time in hospital, operative time, total time in operating room. and recovery time. Secondary outcomes included rate of symptoms resolutions, requiring further medical management, and requiring further surgical intervention. RESULTS: A total of 321 procedures were included. Sialendoscopy in an ambulatory surgery center compared to main operating room decreased median hospital time (166 min reduction, p < 0.001), operative time (18 min reduction, p < 0.001), total time in operating room (34 min reduction, p < 0.001), and recovery time (64 min reduction, p < 0.001). Sialendoscopy in an ambulatory surgery center had similar rates of post-operative resolution of symptoms and further medical or surgical intervention compared to procedures in a hospital operating room. CONCLUSION: Sialendoscopy can be safely performed in an ambulatory surgery center for sialadenitis or appropriate sialolithiasis cases while decreasing hospital time, operative time, total time in operating room time, and recovery time.

Comparison of general anesthesia and monitored anesthesia care for sialendoscopy procedures.

OBJECTIVES: The literature remains scarce in terms of comparing different anesthesia modalities in sialendoscopy. Due to the lack of a standard of care or guidelines to anesthetic care, it is generally accepted that surgeons perform these surgeries under the anesthetic modality in which they are most comfortable. In this study, we evaluate time spent on the day of surgery and post-surgical outcomes for patients receiving sialendoscopy under monitored anesthesia care versus general anesthesia. MATERIALS AND METHODS: We retrospectively assessed patients who underwent sialendoscopy using a solely endoscopic approach for sialadenitis or sialolithiasis from March 2017 to December 2019. Anesthesia modality (monitored anesthesia care versus general anesthesia) was compared. Main outcomes included total time in hospital, operative time, total time in operating room, anesthesia time, and recovery time. Secondary outcomes included rate of resolution of symptoms, requiring further medical management, requiring further surgical intervention, and complications. RESULTS: A total of 172 procedures were included. Sialendoscopy under monitored anesthesia care center compared to general anesthesia decreased median hospital time (141 min reduction), anesthesia time (46 min reduction), operative time (24 min reduction), time in operating room (43 min reduction), and recovery time (56 min reduction). Utilizing monitored anesthesia care demonstrated similar rates of post-operative resolution of symptoms, complications, and further medical or surgical intervention compared to the general anesthesia cohort. CONCLUSION: Sialendoscopy can be safely performed under monitored anesthesia care for appropriate sialadenitis or sialolithiasis cases while decreasing hospital time, operative time, time in operating room, anesthesia time, and recovery time while maintaining similar post-operative outcomes. Monitored anesthesia care should be considered for solely endoscopic cases as guided by surgeon and patient comfort.

Preferential use of total intravenous anesthesia in ambulatory otolaryngology surgery during the COVID-19 pandemic.

The novel coronavirus (SARS-CoV-2 or COVID-19) pandemic has impacted nearly every aspect of otolaryngologic practice. The transition from office-based evaluation to telemedicine and the number of postponed elective surgical cases is unprecedented. There is a significant need to resume elective surgical care for these patients at the appropriate time. As practices begin to move towards resuming elective and same day ambulatory surgery, safety of both the patient and healthcare team is of paramount importance. Usage of total intravenous anesthesia (propofol and remifentanil) over volatile gas anesthesia (e.g., sevoflurane) may increase the number of patients able to safely receive care by reducing potential spread of the virus through reduction in coughing and significantly decreasing the time spent in the recovery room.

Diagnostic implications of the double deficit model for young adolescents with dyslexia.

Considerable support exists for both the phonological core deficit and the naming speed deficit models of dyslexia. The double deficit model proposed that many students with dyslexia might also be impaired in both underlying processes. Employing either performance thresholds (i.e., scores below the 16th or 25th percentile) or k-means clustering as classification methods, the current study investigated whether 154 young adolescents with dyslexia could be categorized into subtypes according to the presence or absence of phonological deficits alone, naming speed deficits alone, or a combination of the two and whether group composition changed depending on classification method. Results support the existence of both single and double deficit groups and confirm that those with both deficits are the most severely impaired across multiple measures. Contrary to previous research, most adolescents were classified as either naming speed only (about a third of the group) or double deficit when defining impairment using performance thresholds to classify groups. This may suggest that although early phonological deficits are amenable to remediation, identification of language symbols fails to become automatized in most individuals with dyslexia and may require more targeted intervention. Classification differences reported in the literature may depend on age and methods employed for classification.

Potential Role of Synaptic Activity to Inhibit LTD Induction in Rat Visual Cortex.

Long-term depression (LTD), a widely studied form of activity-dependent synaptic plasticity, is typically induced by prolonged low-frequency stimulation (LFS). Interestingly, LFS is highly effective in eliciting LTD in vitro, but much less so under in vivo conditions; the reasons for the resistance of the intact brain to express LTD are not well understood. We examined if levels of background electrocorticographic (ECoG) activity influence LTD induction in the thalamocortical visual system of rats under very deep urethane anesthesia, inducing a brain state of reduced spontaneous cortical activity. Under these conditions, LFS applied to the lateral geniculate nucleus resulted in LTD of field postsynaptic potentials (fPSPs) recorded in the primary visual cortex (V1). Pairing LFS with stimulation of the brainstem (pedunculopontine) reticular formation resulted in the appearance of faster, more complex activity in V1 and prevented LTD induction, an effect that did not require muscarinic or nicotinic receptors. Reticular stimulation alone (without LFS) had no effect on cortical fPSPs. These results show that excitation of the brainstem activating system blocks the induction of LTD in V1. Thus, higher levels of neural activity may inhibit depression at cortical synapses, a hypothesis that could explain discrepancies regarding LTD induction in previous in vivo and in vitro work.