Resolution of chronic regurgitation in an 8 month old Babydoll sheep by thoracoscopic treatment of a vascular ring anomaly

OBJECTIVE

The objective was to describe the successful thoracoscopic treatment of esophageal entrapment resulting from a vascular ring anomaly (VRA) comprising a persistent right aortic arch (PRAA) and left ligamentum arteriosum (LA) in a Babydoll sheep wether.

STUDY DESIGN

Case report.

ANIMAL

Eight month old Babydoll sheep wether, 13 kg.

METHODS

The patient presented with a weight half that of its sibling, persistent regurgitation following eating, and delayed growth noted from the age of approximately 2 months, coinciding with the introduction of solid feed into the diet. Plain thoracic radiographs were within normal limits but computed tomography angiography (CTA) confirmed multiple congenital vascular anomalies. The primary finding was esophageal and tracheal entrapment by a PRAA and left LA. Thoracoscopic transection of the LA was performed with a bipolar vessel sealing device with the aid of transesophageal endoscopy.

RESULTS

Immediate improvement in attitude and absence of regurgitation were observed. The patient was discharged and subsequently reintroduced to grazing and long-stem hay, which were previously not tolerated. By 6 months post discharge, the patient's weight was 36 kg, comparable to an age-matched sibling and considered appropriate for the stage of growth.

CONCLUSION

Thoracoscopic transection of the LA in sheep is a feasible treatment for esophageal compression resulting from a VRA. Surgical intervention resolved the clinical signs and allowed normal digestive rumination, restoring bidirectional esophageal function in a ruminant.

Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion

BACKGROUND

The recurrence rate of atrial fibrillation (AF) in horses after cardioversion to sinus rhythm (SR) is relatively high. Atrial fibrillatory rate (AFR) derived from surface ECG is considered a biomarker for electrical remodelling and could potentially be used for the prediction of successful AF cardioversion and AF recurrence.

OBJECTIVES

Evaluate if AFR was associated with successful treatment and could predict AF recurrence in horses.

STUDY DESIGN

Retrospective multicentre study.

METHODS

Electrocardiograms (ECG) from horses with persistent AF admitted for cardioversion with either medical treatment (quinidine) or transvenous electrical cardioversion (TVEC) were included. Bipolar surface ECG recordings were analysed by spatiotemporal cancellation of QRST complexes and calculation of AFR from the remaining atrial signal. Kaplan-Meier survival curve and Cox regression analyses were performed to assess the relationship between AFR and the risk of AF recurrence.

RESULTS

Of the 195 horses included, 74 received quinidine treatment and 121 were treated with TVEC. Ten horses did not cardiovert to SR after quinidine treatment and AFR was higher in these, compared with the horses that successfully cardioverted to SR (median [interquartile range]), (383 [367-422] vs 351 [332-389] fibrillations per minute (fpm), P < .01). Within the first 180 days following AF cardioversion, 12% of the quinidine and 34% of TVEC horses had AF recurrence. For the horses successfully cardioverted with TVEC, AFR above 380 fpm was significantly associated with AF recurrence (hazard ratio = 2.4, 95% confidence interval 1.2-4.8, P = .01).

MAIN LIMITATIONS

The treatment groups were different and not randomly allocated, therefore the two treatments cannot be compared. Medical records and the follow-up strategy varied between the centres.

CONCLUSIONS

High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC. As a noninvasive marker that can be retrieved from surface ECG, AFR can be clinically useful in predicting the probability of responding to quinidine treatment as well as maintaining SR after electrical cardioversion.

Heart rate variability analysis in horses for the diagnosis of arrhythmias

Heart rate variability (HRV) analysis has been performed on ECG-derived data sets for more than 170 years but is currently undergoing a rapid evolution, thanks to the expansion of the human and veterinary medical technology sector. Traditional HRV analysis was initially performed to identify changes in vago-sympathetic balance, while the most recent focus has expanded to include the use of complex computer algorithms, neural networks and machine learning technology to identify cardiac arrhythmias, particularly atrial fibrillation (AF). Some of these techniques have recently been translated for use in the field of equine cardiology, with particular focus on improving the diagnosis of arrhythmias both at rest and during exercise. This review focuses on understanding the basic HRV variables and important factors to consider when collecting data for use in HRV analysis. In addition, the use of HRV analysis for the diagnosis of arrhythmias is discussed from human, small animal and equine perspectives. Finally, the future of HRV analysis is briefly introduced, including an overview of future developments in this rapidly expanding and exciting field.

Diagnostic value of noninvasive pulse pressure measurements in Warmblood horses with aortic regurgitation

Background

Noninvasive blood pressures (NIBP) and pulse pressures (PP) have not been published in horses with aortic and mitral regurgitation (AR or MR).

Objectives

To investigate NIBP and PP in healthy Warmblood horses and horses with AR and MR and propose PP cutoffs to identify and stage AR severity.

Animals

Seventy‐three Warmblood horses (healthy, 10; AR, 31; MR, 32).

Methods

Retrospective study. All horses had NIBP and an echocardiogram recorded. Cases were categorized based on severity of regurgitation. Pulse pressures were compared among healthy, MR, and AR groups and among AR severity groups. Cutoffs were determined by receiver operating characteristic curve analyses.

Results

Horses with AR had higher PP than horses with MR (mean difference [95% confidence interval (CI)], +17 [9‐26] mm Hg, P < .001) and controls (+17 [5‐30] mm Hg; P =.004). Horses with severe AR had higher PP compared those with mild (+38 [20‐54] mm Hg; P < 0.001) and moderate AR (+33 [18‐47] mm Hg; P < .001). The PP cutoffs to distinguish AR from MR and controls were 38 mm Hg (sensitivity [Sn], 100%; specificity [Sp], 19%) for maximal Sn and 61 mm Hg (Sn, 43%; Sp, 100%) for maximal Sp. The PP cutoffs to distinguish severe AR from mild and moderate AR were 57 mm Hg (Sn, 100%; Sp, 70%) for maximal Sn and 77 mm Hg (Sn, 75%; Sp, 100%) for maximal Sp.

Conclusions and Clinical Importance

Horses with AR have increased PP. Noninvasive PP measurements interpreted with provided cutoffs may aid clinicians in diagnosing and staging severity of AR in horses.

The use of heart rate variability analysis to detect arrhythmias in horses undergoing a standard treadmill exercise test

Background

Little is known about normal heart rate variability (HRV) in horses during exercise. It can be difficult to separate premature beats from normal beat‐to‐beat variation at higher heart rates.

Objectives

The aim was to quantify HRV in healthy horses during a high‐speed treadmill‐standardized exercise test (HSET) and to compare with the HRV in horses observed to have arrhythmias during exercise.

Animals

Thirteen healthy horses (Group H), 30 horses with arrhythmias (Group A), and 11 horses with poor performance but no observed arrhythmias (Group O).

Methods

Prospective, observational study. All horses performed a HSET with simultaneous electrocardiograph (ECG) recorded. The ECGs were corrected for artifacts, and arrhythmias noted. Percent instantaneous beat‐to‐beat cycle length variation (% R‐R variation) was calculated, and HRV analyses were performed on trot, canter, and recovery segments.

Results

Group H showed between −4.4 and +3.8% R‐R variation during trot and between −6.1 and +5.4% R‐R variation during the canter phase of the HSET. Group A had significantly larger maximum and 1st percentile R‐R shortening and lengthening compared with Group H and Group O during the recovery phase where most arrhythmias were observed. During recovery, a cutoff of 6% maximum % R‐R shortening predicted the presence of arrhythmia with 88% sensitivity and 97% specificity and likelihood ratio of 26.

Conclusions and Clinical Importance

Healthy horses have little instantaneous R‐R variation during exercise. If a cardiac cycle shortens more than 6% from the previous cycle during the recovery phase, this R‐R interval is likely to represent an arrhythmic event.

Echocardiographic Assessment of Left Ventricular Function in Healthy Horses and in Horses with Heart Disease Using Pulsed-Wave Tissue Doppler Imaging

Background

Assessment of left ventricular (LV) function by tissue Doppler imaging (TDI) is not well established in horses with heart disease.

Objectives

To describe the use of pulsed‐wave (PW) TDI for the assessment of LV function, establish reference intervals, investigate effects of mitral regurgitation (MR), aortic regurgitation (AR), and primary myocardial disease (MD), and provide proof of concept for the use of PW TDI in Warmblood horses with heart disease.

Animals

Thirty healthy horses, 38 horses with MR, 25 with AR, 8 with MD.

Methods

Echocardiograms were retrospectively analyzed. Reference intervals were calculated. PW TDI indices of healthy horses and horses with MR, AR, and MD were compared by one‐way ANOVA and Dunnett's test.

Results

A complete set of PW TDI variables could be obtained in 94 of 101 horses. Variables corresponding to isovolumic intervals were most difficult to measure. Valvular regurgitation influenced variables describing isovolumic contraction and ejection. Horses with MD had significantly shortened ET_m (−118.5 [−154.1 to −82.9] ms; mean difference [95% CI of difference of means]), increased PEP_m/ET_m (0.11 [0.05 to 0.17]), prolonged IMP_m (0.28 [0.18 to 0.37]), increased S₁ (8.9 [5.2 to 12.6] cm/s), and decreased E₁ (−2.6 [−4.7 to −0.5] cm/s), E_m (−14.2 [−19.9 to −8.5] cm/s), and E_m/A_m ratio (−1.6 [−2.6 to −0.6]).

Conclusions and Clinical Importance

Pulsed‐wave TDI might be useful for detection of LV dysfunction in horses with primary MD. The clinical value of TDI in horses with MR and AR remains uncertain.

Hemodynamic Assessment of a Murine Heterotopic Biventricularly Loaded Cardiac Transplant in vivo Model

BACKGROUND

Heterotopic heart transplantation (HHT) in rodent animal models represents an important technique enabling studies on organ transplantation immunology and pharmaceutical development. Recent investigations used nonworking HHT designs, with the left ventricle (LV) bypassed in the anastomosis system. In spite of their principal success, the lack of orthogonal ventricular filling leads to myocardial atrophy. However, when focusing on the cellular and molecular mechanisms involved in the in vivo remodeling of the myocardium or cell-based cardiovascular implants, a nonworking model is suboptimal as it lacks the native-analogous hemodynamic and metabolic situation. Here we present the hemodynamic and electrical assessment of a biventricularly loaded murine HHT method without the need for a combined heart-lung transplantation approach.

METHODS

Heterotopic transplantations (n = 13) were performed on C57BL/6J-(H-2b) inbred mice (n = 13 donors, n = 13 recipients) by creating end-to-side anastomoses between the donors' cranial vena cava (CrVC) and the recipients' abdominal caudal vena cava (CVC), between the donors' ascending aorta and the recipients' abdominal aorta (aAo), and between the grafts' pulmonary trunk and the left atrium. After transplantation, a hemodynamic assessment using echocardiography (including 2D speckle tracking analysis) and electrocardiography was performed.

RESULTS

The loaded HHT procedure in the mice was performed with an overall success rate of 61%. In 3 of the remaining 5 cases, only atrial function was restored. The median duration of the entire surgical procedure for the recipient animal was 190 (IQR 180-250) min. The mean heart rate in the loaded HHT group was 355 ± 6 bpm in comparison to the control group with an in situ heart rate of 418 ± 61 bpm. A native-like closing and opening pattern of the aortic and mitral valves (visible on both 2D and M-mode images) was observed, confirming a native-analogous loading of the LV. Pulsed-wave Doppler provided visualization of the flow across the region of anastomoses between the pulmonary trunk and the left atrium, reaching a mean maximum velocity of 382 ± 12 mm/s. Exemplary 2D speckle tracking analysis of the LV free wall and interventricular septum revealed some differences in vector directions in one animal when compared to the orthotopic native heart, indicating an asynchronous movement of the LV.

CONCLUSIONS

These results demonstrate the technical (micro)surgical feasibility of a fully loaded HHT procedure in the murine model without using a combined heart-lung transplantation approach. The acute hemodynamic performance of the HHT grafts approximated the native orthotopic situation. This model may open up new options for the investigation of cellular and molecular questions in the murine cardiovascular in vivo system in the near future.

Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables

Background

Echocardiographic assessment of left atrial (LA) size and function in horses is not standardized.

Objectives

The aim of this study was to establish reference intervals for echocardiographic indices of LA size and function in Warmblood horses and to provide proof of concept for allometric scaling of variables and for the clinical use of area‐based indices.

Animals

Thirty‐one healthy Warmblood horses and 91 Warmblood horses with a primary diagnosis of mitral regurgitation (MR) or aortic regurgitation (AR).

Methods

Retrospective study. Echocardiographic indices of LA size and function were measured and scaled to body weight (BWT). Reference intervals were calculated, the influence of BWT, age, and valvular regurgitation on LA size and function was investigated and agreement between different measurements of LA size was assessed.

Results

Allometric scaling of variables of LA size allowed for correction of differences in BWT. Indices of LA size documented LA enlargement with moderate and severe MR and AR, whereas most indices of LA mechanical function were not significantly altered by valvular regurgitation. Different indices of LA size were in fair to good agreement but still lead to discordant conclusions with regard to assessment of LA enlargement in individual horses.

Conclusions and Clinical Importance

Allometric scaling of echocardiographic variables of LA size is advised to correct for differences in BWT among Warmblood horses. Assessment of LA dimensions should be based on an integrative approach combining subjective evaluation and assessment of multiple measurements, including area‐based variables. The clinical relevance of indices of LA mechanical function remains unclear when used in horses with mitral or aortic regurgitation.

PGA (polyglycolic acid)-P4HB (poly-4-hydroxybutyrate)-Based Bioengineered Valves in the Rat Aortic Circulation

BACKGROUND AND AIM OF THE STUDY

Bioengineered living autologous valves with remodeling and growth capacity represent a promising concept for future cardiac and venous valve repair. A meticulous understanding of the mechanisms involved in recellularization and remodeling is essential for the safe and efficient clinical translation of this technology. In this context, the first investigations of bioengineered vascular grafts in immune-incompetent or transgenic rodents represented an important step. However, the in-vivo assessment of bioengineered synthetic scaffold-based (biodegradable) valve replacements in rodent models has not been achieved to date.

METHODS

Miniaturized monocuspid PGA (polyglycolic acid)-P4HB (poly-4-hydroxybutyrate)-based valves were created, incorporated into metallic stents (length 2.0 mm, diameter 1.1 mm) and introduced into catheter-based implantation devices. Wistar outbred rats (n = 8) underwent a laparotomy, abdominal aorta arteriotomy and valve delivery into the abdominal aorta. Valve placement and function were evaluated following deployment using ultrasound (Doppler- and M-mode). Explanted tissues were analyzed both macroscopically and histopathologically.

RESULTS

No significant physiological or hemodynamic changes were observed, including heart rate, pressure gradients, velocity values and cardiac output before and after valve implantation. The cross-sectional area at the level of the stented valve was reduced by 22%. Valvular leaflet oscillation was observed in two animals, and thrombus formation in the stent was observed in one animal. Histological evaluation revealed cellular infiltration within 3 h in vivo, and no signs of thrombus deposition on the valvular surface.

CONCLUSIONS

This study demonstrated the technical feasibility of the transcatheter implantation of bioengineered stented miniaturized valves into the infrarenal rat aorta, without affecting the animal's physiological and hemodynamic variables and with valvular oscillation in part of the implants. These results could serve as a basis for the implementation of a chronic rat in-vivo model for mechanistic studies in bioengineered valvular tissues under systemic hemodynamic conditions. Video 1: 2D ultrasonographic projection revealing graft's leaflet oscillation.

Salmonella enterica serovar Oranienburg outbreak in a veterinary medical teaching hospital with evidence of nosocomial and on-farm transmission

Nosocomial salmonellosis continues to pose an important threat to veterinary medical teaching hospitals. The objectives of this study were to describe an outbreak of salmonellosis caused by Salmonella enterica serovar Oranienburg within our hospital and to highlight its unique features, which can be used to help mitigate or prevent nosocomial outbreaks in the future. We retrospectively analyzed data from patients that were fecal culture-positive for Salmonella Oranienburg between January 1, 2006, and June 1, 2011, including historical, clinical, and pulsed-field gel electrophoresis (PFGE) data. Salmonella Oranienburg was identified in 20 horses, five alpacas, and three cows during this time frame, with dates of admission spanning the period from August, 2006, through January, 2008. We consider most of these patients to have become infected through either nosocomial or on-farm transmission, as evidenced by molecular subtyping results and supportive epidemiologic data. Interpretation of PFGE results in this outbreak was challenging because of the identification of several closely related Salmonella Oranienburg subtypes. Furthermore, a high percentage of cases were fecal culture-positive for Salmonella Oranienburg within 24 h of admission. These patients initially appeared to represent new introductions of Salmonella into the hospital, but closer inspection of their medical records revealed epidemiologic links to the hospital following the index case. Cessation of this outbreak was observed following efforts to further heighten biosecurity efforts, with no known cases or positive environmental samples after January, 2008. This study demonstrates that a Salmonella-positive culture result within 24 h of admission does not exclude the hospital as the source of infection, and it underscores the important role played by veterinary medical teaching hospitals as nodes of Salmonella infection that can promote transmission outside of the hospital setting.

Formative evaluation of ontology learning methods for entity discovery by using existing ontologies as reference standards

OBJECTIVE

Developing a two-step method for formative evaluation of statistical Ontology Learning (OL) algorithms that leverages existing biomedical ontologies as reference standards.

METHODS

In the first step optimum parameters are established. A 'gap list' of entities is generated by finding the set of entities present in a later version of the ontology that are not present in an earlier version of the ontology. A named entity recognition system is used to identify entities in a corpus of biomedical documents that are present in the 'gap list', generating a reference standard. The output of the algorithm (new entity candidates), produced by statistical methods, is subsequently compared against this reference standard. An OL method that performs perfectly will be able to learn all of the terms in this reference standard. Using evaluation metrics and precision-recall curves for different thresholds and parameters, we compute the optimum parameters for each method. In the second step, human judges with expertise in ontology development evaluate each candidate suggested by the algorithm configured with the optimum parameters previously established. These judgments are used to compute two performance metrics developed from our previous work: Entity Suggestion Rate (ESR) and Entity Acceptance Rate (EAR).

RESULTS

Using this method, we evaluated two statistical OL methods for OL in two medical domains. For the pathology domain, we obtained 49% ESR, 28% EAR with the Lin method and 52% ESR, 39% EAR with the Church method. For the radiology domain, we obtain 87% ESA, 9% EAR using Lin method and 96% ESR, 16% EAR using Church method.

CONCLUSION

This method is sufficiently general and flexible enough to permit comparison of any OL method for a specific corpus and ontology of interest.

Fecal shedding of Cryptosporidium oocysts in healthy alpaca crias and their dams

OBJECTIVE

To determine the apparent prevalence of shedding of Cryptosporidium spp in healthy alpaca crias and their dams on 14 farms in New York and 1 farm in Pennsylvania.

DESIGN

Cross-sectional study.

ANIMALS

110 alpaca crias and their 110 dams.

PROCEDURES

Fecal samples were obtained from 220 alpacas at 14 alpaca farms in New York and 1 farm in Pennsylvania. For each animal, age, sex, and health condition were recorded. A fecal score (1 = normally formed; 2 = soft or loose; 3 = diarrhetic) was recorded for each cria. Cryptosporidium oocysts were identified in fecal samples by a direct immunofluorescence assay.

RESULTS

Apparent prevalence of fecal shedding of Cryptosporidium oocysts was 8% (95% confidence interval, 4% to 15%) in dams and was 7% (95% confidence interval, 3% to 13%) in crias. There was no significant difference in age between dams with positive fecal test results for Cryptosporidium oocysts (median age, 4 years; range, 3 to 8 years) and dams with negative results (median age, 4 years; range, 2.5 to 19 years). No significant difference was found in age between crias with positive fecal test results (median age, 20 days; range, 7 to 53 days) and those with negative results (median, 36 days; range, 2 to 111 days). No significant difference in fecal scores was found between crias with positive versus negative fecal test results.

CONCLUSIONS AND CLINICAL RELEVANCE

A higher than previously reported apparent prevalence of fecal shedding of Cryptosporidium oocysts in healthy alpacas was found. A zoonotic risk should be considered, especially for Cryptosporidium parvum.

Rethinking the genetic architecture of schizophrenia

BACKGROUND

For many years, the prevailing paradigm has stated that in each individual with schizophrenia (SZ) the genetic risk is due to a combination of many genetic variants, individually of small effect. Recent empirical data are prompting a re-evaluation of this polygenic, common disease-common variant (CDCV) model. Evidence includes a lack of the expected strong positive findings from genome-wide association studies and the concurrent discovery of many different mutations that individually strongly predispose to SZ and other psychiatric disorders. This has led some to adopt a mixed model wherein some cases are caused by polygenic mechanisms and some by single mutations. This model runs counter to a substantial body of theoretical literature that had supposedly conclusively rejected Mendelian inheritance with genetic heterogeneity. Here we ask how this discrepancy between theory and data arose and propose a rationalization of the recent evidence base.

METHOD

In light of recent empirical findings, we reconsider the methods and conclusions of early theoretical analyses and the explicit assumptions underlying them.

RESULTS

We show that many of these assumptions can now be seen to be false and that the model of genetic heterogeneity is consistent with observed familial recurrence risks, endophenotype studies and other population-wide parameters.

CONCLUSIONS

We argue for a more biologically consilient mixed model that involves interactions between disease-causing and disease-modifying variants in each individual. We consider the implications of this model for moving SZ research beyond statistical associations to pathogenic mechanisms.

Rural–urban differences in the presentation, management and survival of breast cancer in Western Australia

From all women diagnosed with invasive breast cancer in 1999 in Western Australia, rural and urban women were compared with regard to mode of detection, tumour characteristics at presentation, diagnostic investigations, treatment and survival. Women from rural areas with breast cancer (n=206, 23%) were less likely to have open biopsy with frozen section (P<0.001), breast-conserving surgery (P<0.001), adjuvant radiotherapy (P=0.004) and hormonal therapy (P=0.03), and were less likely to be treated by a high caseload breast cancer surgeon (P<0.001). Adjusting for age and tumour characteristics, rural women had an increased likelihood of death within 5 years of breast cancer diagnosis (HR 1.62, 95% CI 1.10-2.38). This difference was not significant after adjustment for treatment factors (HR 1.36, 95% CI 0.90-2.04).

Intracellular ATP-sensitive K+ channels in mouse pancreatic beta cells: against a role in organelle cation homeostasis

AIMS/HYPOTHESIS

ATP-sensitive K(+) (K(ATP)) channels located on the beta cell plasma membrane play a critical role in regulating insulin secretion and are targets for the sulfonylurea class of antihyperglycaemic drugs. Recent reports suggest that these channels may also reside on insulin-containing dense-core vesicles and mitochondria. The aim of this study was to explore these possibilities and to test the hypothesis that vesicle-resident channels play a role in the control of organellar Ca(2+) concentration or pH.

METHODS

To quantify the subcellular distribution of the pore-forming subunit Kir6.2 and the sulfonylurea binding subunit SUR1 in isolated mouse islets and clonal pancreatic MIN6 beta cells, we used four complementary techniques: immunoelectron microscopy, density gradient fractionation, vesicle immunopurification and fluorescence-activated vesicle isolation. Intravesicular and mitochondrial concentrations of free Ca(2+) were measured in intact or digitonin-permeabilised MIN6 cells using recombinant, targeted aequorins, and intravesicular pH was measured with the recombinant fluorescent probe pHluorin.

RESULTS

SUR1 and Kir6.2 immunoreactivity were concentrated on dense-core vesicles and on vesicles plus the endoplasmic reticulum/Golgi network, respectively, in both islets and MIN6 cells. Reactivity to neither subunit was detected on mitochondria. Glibenclamide, tolbutamide and diazoxide all failed to affect Ca(2+) uptake into mitochondria, and K(ATP) channel regulators had no significant effect on intravesicular free Ca(2+) concentrations or vesicular pH.

CONCLUSIONS/INTERPRETATION

A significant proportion of Kir6.2 and SUR1 subunits reside on insulin-secretory vesicles and the distal secretory pathway in mouse beta cells but do not influence intravesicular ion homeostasis. We propose that dense-core vesicles may serve instead as sorting stations for the delivery of channels to the plasma membrane.

Unilateral nephrectomy as a treatment for renal trauma in a foal

A 2-day-old Warmblood colt foal was referred for evaluation of progressive abdominal distension and lethargy. Haemoperitoneum was diagnosed and a ventral midline laparotomy revealed capsular rupture, sub capsular haematoma and haemorrhage of the left kidney. Unilateral nephrectomy was performed and the foal recovered uneventfully, with no reported complications 1 year later.

Dense core secretory vesicles revealed as a dynamic Ca(2+) store in neuroendocrine cells with a vesicle-associated membrane protein aequorin chimaera

The role of dense core secretory vesicles in the control of cytosolic-free Ca(2+) concentrations ([Ca(2+)](c)) in neuronal and neuroendocrine cells is enigmatic. By constructing a vesicle-associated membrane protein 2-synaptobrevin.aequorin chimera, we show that in clonal pancreatic islet beta-cells: (a) increases in [Ca(2+)](c) cause a prompt increase in intravesicular-free Ca(2+) concentration ([Ca(2+)]SV), which is mediated by a P-type Ca(2+)-ATPase distinct from the sarco(endo) plasmic reticulum Ca(2+)-ATPase, but which may be related to the PMR1/ATP2C1 family of Ca(2+) pumps; (b) steady state Ca(2+) concentrations are 3-5-fold lower in secretory vesicles than in the endoplasmic reticulum (ER) or Golgi apparatus, suggesting the existence of tightly bound and more rapidly exchanging pools of Ca(2+); (c) inositol (1,4,5) trisphosphate has no impact on [Ca(2+)](SV) in intact or permeabilized cells; and (d) ryanodine receptor (RyR) activation with caffeine or 4-chloro-3-ethylphenol in intact cells, or cyclic ADPribose in permeabilized cells, causes a dramatic fall in [Ca(2+)](SV). Thus, secretory vesicles represent a dynamic Ca(2+) store in neuroendocrine cells, whose characteristics are in part distinct from the ER/Golgi apparatus. The presence of RyRs on secretory vesicles suggests that local Ca(2+)-induced Ca(2+) release from vesicles docked at the plasma membrane could participate in triggering exocytosis.

Functional analysis of secreted and transmembrane proteins critical to mouse development

We describe the successful application of a modified gene-trap approach, the secretory trap, to systematically analyze the functions in vivo of large numbers of genes encoding secreted and membrane proteins. Secretory-trap insertions in embryonic stem cells can be transmitted to the germ line of mice with high efficiency and effectively mutate the target gene. Of 60 insertions analyzed in mice, one-third cause recessive lethal phenotypes affecting various stages of embryonic and postnatal development. Thus, secretory-trap mutagenesis can be used for a genome-wide functional analysis of cell signaling pathways that are critical for normal mammalian development and physiology.

Source ROCs are (typically) curvilinear: comment on Yonelinas (1999)

On the basis of his assumption that recollection is a threshold process, A. P. Yonelinas (1999) predicted linear source-identification receiver operating characteristics (ROCs) and recently reported data that were consistent with this prediction. In this article, the authors present data showing curvilinear source-identification ROCs across various encoding and test conditions. On the basis of the source-monitoring framework (e.g., M. K. Johnson, S. Hashtroudi, & D. S. Lindsay, 1993), the authors argue that curvilinearity of source-identification ROCs is a result of differences in the qualitative characteristics of memories rather than simply the influence of undifferentiated familiarity as the dual-process model might suggest.

Risk factors for and impact of online sexual solicitation of youth

CONTEXT

Health care professionals, educators, and others are increasingly called upon to advise parents and policymakers about risks posed to children by Internet use. However, little scientific information exists on the experiences of children online.

OBJECTIVE

To assess the risk factors surrounding online sexual solicitations of youth and distress due to solicitation.

DESIGN, SETTING, AND PARTICIPANTS

Telephone survey (August 1999-February 2000) of a random sample of 1501 youth aged 10 through 17 years who were regular Internet users.

MAIN OUTCOME MEASURES

Demographic and behavioral characteristics associated with solicitation risk and distress due to solicitation.

RESULTS

Nineteen percent of youth who used the Internet regularly were the targets of unwanted sexual solicitation in the last year. Girls (P<.001), older teens (P =.005), troubled youth (P =.004), frequent Internet users (P =.01), chat room participants (P<.001), and those who communicated online with strangers (P<.001) were at greater risk. Twenty-five percent of the solicited youth reported high levels of distress after solicitation incidents. Risk of distress was more common among the younger youth (P =.005), those who received aggressive solicitations (the solicitor attempted or made offline contact) (P =.001), and those who were solicited on a computer away from their home (P =.001).

CONCLUSIONS

Many young people who use the Internet encounter unwanted sexual overtures. Health care professionals, educators, and parents should be prepared to educate youth about how to respond to online sexual solicitations, including encouraging youth to disclose and report such encounters and to talk about them.

Contextual overlap and eyewitness suggestibility

Studies of eyewitness suggestibility have traditionally used a paradigm that maximizes the extent to which the postevent interview overlaps with the witnessed event in terms of narrative content, narrative structure, and environmental context. The present study explored whether these dimensions of overlap contribute to people's tendency to confuse suggested details for those they have actually witnessed. We systematically manipulated the extent to which the postevent questionnaire overlapped with the witnessed event. Across two experiments, overlap in narrative content, narrative structure, or environmental context was not found to increase suggestibility effects, even though the manipulation did have other memory effects (e.g., it improved cued recall of the actual source of the suggestions, Experiment 2). These findings suggest that understanding the interaction between the structure and content of the objective context in which misinformation is encountered and various remembering contexts (e.g., recognition vs. recall) is important for advancing our understanding of source confusion in an eyewitness situation.

Defining brain wiring patterns and mechanisms through gene trapping in mice

The search to understand the mechanisms regulating brain wiring has relied on biochemical purification approaches in vertebrates and genetic approaches in invertebrates to identify molecular cues and receptors for axon guidance. Here we describe a phenotype-based gene-trap screen in mice designed for the large-scale identification of genes controlling the formation of the trillions of connections in the mammalian brain. The method incorporates an axonal marker, which helps to identify cell-autonomous mechanisms in axon guidance, and has generated a resource of mouse lines with striking patterns of axonal labelling, which facilitates analysis of the normal wiring diagram of the brain. Studies of two of these mouse lines have identified an in vivo guidance function for a vertebrate transmembrane semaphorin, Sema6A, and have helped re-evaluate that of the Eph receptor EphA4.

Aging and reflective processes of working memory: binding and test load deficits

It was hypothesized that age-related deficits in episodic memory for feature combinations (e.g., B. L. Chalfonte & M. K. Johnson, 1996) signal, in part, decrements in the efficacy of reflective component processes (e.g., M. K. Johnson, 1992) that support the short-term maintenance and manipulation of information during encoding (e.g., F. 1. M. Craik. R. G. Morris. & M. L. Gick, 1990; T. A. Salthouse, 1990). Consistent with this, age-related binding deficits in a working memory task were found in 2 experiments. Evidence for an age-related test load deficit was also found: Older adults had greater difficulty than young adults when tested on 2 features rather than 1, even when binding was not required. Thus, disruption of source memory in older adults may involve deficits in both encoding processes (binding deficits) and monitoring processes (difficulty accessing multiple features, evaluating them, or both).

fMRI evidence of age-related hippocampal dysfunction in feature binding in working memory

Richly detailed memories for particular events depend on processes that bind individual features of experience together. Previous cognitive behavioral research indicates that older adults have more difficulty than young adults in conditions requiring feature binding. We used functional magnetic resonance imaging (fMRI) during a working memory task to identify neural substrates of this age-related deficit in feature binding. For young, but not older, adults there was greater activation in left anterior hippocampus on combination trials (remember objects together with their locations) than on trials in which participants were told to remember only which objects or only which locations occurred. The results provide neuroimaging evidence for an age-related hippocampal dysfunction in feature binding in working memory.

Genetic analysis of the mechanisms controlling target selection: complementary and combinatorial functions of netrins, semaphorins, and IgCAMs

The molecular mechanisms controlling the ability of motor axons to recognize their appropriate muscle targets were dissected using Drosophila genetics to add or subtract Netrin A, Netrin B, Semaphorin II, and Fasciclin II alone or in combination. Fas II and Sema II are expressed by all muscles where they promote (Fas II) or inhibit (Sema II) promiscuous synaptogenesis. NetB is expressed by a subset of muscles where it attracts some axons and repels others. However, growth cones in this system apparently do not rely solely on single molecular labels on individual targets. Rather, these growth cones assess the relative balance of attractive and repulsive forces and select their targets based on the combinatorial and simultaneous input of multiple cues.

Roundabout controls axon crossing of the CNS midline and defines a novel subfamily of evolutionarily conserved guidance receptors

The robo gene in Drosophila was identified in a large-scale mutant screen for genes that control the decision by axons to cross the CNS midline. In robo mutants, too many axons cross and recross the midline. Here we show that robo encodes an axon guidance receptor that defines a novel subfamily of immunoglobulin superfamily proteins that is highly conserved from fruit flies to mammals. For those axons that never cross the midline, Robo is expressed on their growth cones from the outset; for the majority of axons that do cross the midline, Robo is expressed at high levels on their growth cones only after they cross the midline. Transgenic rescue experiments reveal that Robo can function in a cell-autonomous fashion. Robo appears to function as the gatekeeper controlling midline crossing.

Antibiotic prophylaxis and open groin hernia repair

Antibiotic prophylaxis is not routinely given for nonimplant, clean operations, although this view has recently been challenged. We have conducted a randomized multicenter, double-blind prospective trial to compare co-amoxiclav with placebo in 619 patients undergoing open groin hernia repair. Altogether 563 (91%) patients fulfilled the protocol; 283 received co-amoxiclav and 280 placebo. There was no difference between the groups in the number of patients receiving local or general anesthetic, the type of repair performed, the use of a subcutaneous fat suture, the type of skin closure used, the use of wound analgesia, or the use of a wound drain. Patients were given a card to return to the hospital in the event of their wound discharging or their needing to see their general practitioner. All patients were reviewed at approximately 6 weeks after operation. Fifty (8.9%) patients sustained a wound infection, 25 in the co-amoxiclav group and 25 in the placebo group. We conclude that antibiotic prophylaxis is of no benefit to patients undergoing open groin hernia repair.

frazzled encodes a Drosophila member of the DCC immunoglobulin subfamily and is required for CNS and motor axon guidance

We have identified a Drosophila member of the deleted in colorectal cancer (DCC) gene family. The frazzled gene encodes transmembrane proteins that contain four immunoglobulin C2 type domains, six fibronectin type III repeats, and a cytoplasmic domain of 278 amino acids. Like vertebrate members of the DCC family, Frazzled is expressed on axons in the embryonic central nervous system and on motor axons in the periphery. Frazzled is also expressed on epidermis and gut epithelium. Null mutants in frazzled are defective in axon guidance in the central nervous system and in motor axon guidance and targeting in the periphery. The phenotypes strongly resemble those of a deletion of the two Drosophila Netrin genes. We have rescued the frazzled CNS and motor axon defects by expressing Frazzled specifically in neurons; expression in target tissues does not rescue the phenotype. These data, together with vertebrate studies showing binding of DCC to netrin, suggest that Frazzled may function in vivo as a receptor or component of a receptor mediating Netrin-dependent axon guidance.

Genetic analysis of Netrin genes in Drosophila: Netrins guide CNS commissural axons and peripheral motor axons

Two tandem Netrin genes in Drosophila are expressed at the midline of the developing CNS and in different subsets of neurons, muscles, and epidermal patches. In embryos carrying a small deficiency that deletes both genes, CNS axon commissures are partially missing or thinner. This phenotype is rescued by expressing either Netrin gene at the midline. Pan-neural expression of either gene causes disruption of commissural and longitudinal tracts, indicating that the pattern of Netrin expression is crucial and that Netrins function as instructive cues. The double mutant also shows defects in motor axon projections. Expression of either Netrin gene in all muscles also results in aberrant motor projections. Thus, Drosophila Netrins are required for the guidance of commissural axons at the midline, and of motor axons to their target muscles.

Primary malignant small bowel tumors: an atypical abdominal emergency

Primary malignant tumors of the small bowel are uncommon in the United States. They comprise less than 1% of all gastrointestinal malignancies, with an incidence of 2200 cases per year. The clinical presentation of small bowel tumors is frequently insidious and often overlooked by physicians. The low incidence and lack of pathognomonic symptoms are the reasons that the early diagnosis of malignant small bowel tumor is uncommon. To better understand the clinical presentation, diagnostic evaluation, management, and outcome, a review of Howard University patients with primary malignant small bowel tumors between 1970 and 1990 was conducted. Our experience concurs with the reported literature and supports the conclusion that a high index of suspicion is necessary. The diagnosis of a malignant small bowel tumor should be considered in patients with vague chronic abdominal complaints.

Evaluation of massive volume replacement in the penetrating trauma patient

The records of 163 penetrating trauma patients who required surgery in a 36-month period between 1988 and 1990 were reviewed. Those patients with head trauma were excluded. Thirty patients were identified as having: similar Injury Severity Scores (ISS), received at least 8 L of crystalloid, and received at least 4 units of packed red blood cells during the first 24 hours after admission. There were 22 (73%) survivors and 8 (27%) nonsurvivors. Charts were reviewed for a variety of variables to determine which characteristics distinguished nonsurvivors from survivors. The mean ISS was 30.5 +/- 5.5. As a group, nonsurvivors received more blood transfusions (14.9 +/- 4.9 versus 5.0 +/- 1.14), had longer durations of shock (55.6 +/- 18 minutes versus 19.3 +/- 11.7 minutes), and had lower core body temperatures (92.6 degrees F +/- 2.2 versus 95.1 degrees F +/- 2.4) than survivors. Nonsurvivors also had lower hemoglobin levels (7.84 +/- 1 versus 9.1 +/- 2.3) and platelet counts (134.2 +/- 14.1 versus 188.6 +/- 6.3) than survivors. In addition, nonsurvivors demonstrated greater incidence of three major risk factors than did the survivors: hypothermia (75% versus 41%), acidosis (100% versus 27%), and coagulopathy (62% versus 4.5%). Therapeutic measures to limit these risk factors for increased mortality may maximize the chance of survival in these patients.

Dietary abomasal impaction in a herd of dairy replacement heifers

An episode of dietary abomasal impaction in a herd of dairy replacement heifers was found to be caused by excess almond shells in the ration. Clinical signs and necropsy findings led to the diagnosis. Removal of the almond shells and increasing the energy and digestibility of the ration corrected the problem. Factors contributing to the dietary impactions included advanced stages of pregnancy, high energy demands of growing heifers, and cold weather. Dietary abomasal impactions are not common in dairy cattle because of the high-quality ration a dairy cow generally receives. Replacement heifers in advanced stages of pregnancy have nutritional requirements similar to those of dairy cows, yet are often nutritionally neglected. The clinical findings in this report may help make veterinarians aware of the possibility of dietary abomasal impactions in dairy replacement heifers fed low-quality feeds.

Traditional predictors of performance in medical school

This paper addresses the predictive value for performance in medical school of undergraduate grades, the Medical College Admission Test (MCAT), information on the selectivity of the undergraduate institution, and selected transcript data. The performance data examined were basic science grades; clinical science grades; scores on National Board of Medical Examiners examinations, Parts I, II, and III; and information on academic difficulty. Methodological sources of differences in validity data, including restriction in range, criterion attenuation, and method specificity, are discussed. Reported validity data affirm the substantial value of traditional academic predictors of performance in medical school. Selection committees should, nevertheless, supplement academic data with nonacademic and interview information. Their inclusion is particularly important for minority and disadvantaged applicants. Medical schools should assess the validity of their selection systems. Additional research on the relations between academic predictors and performance-based indexes of clinical competence and on the role of traditional predictors with regard to the recently declining medical school applicant pool is suggested.

Survey of calcineurin activity towards nonprotein compounds and identification of phosphoenol pyruvate as a substrate

Calcineurin, originally identified as a calmodulin-dependent phosphoprotein phosphatase (Stewart, A.A. et al. (1982) FEBS Lett. 137, 80-84) also uses p-nitrophenyl phosphate and phosphotyrosine as substrates (Pallen, C.J. and Wang, J.H. (1983) J. Biol. Chem. 258, 8550-8553). We have surveyed a wide range of nonprotein phosphocompounds and found that several synthetic aryl phosphocompounds serve as calcineurin substrates. Among more than 20 naturally occurring phosphocompounds tested, only phosphoenol pyruvate possesses significant calcineurin substrate activity. The phosphoenol pyruvate phosphatase activity is dependent on Ni2+ and Mn2+, is stimulated by calmodulin, and is inhibited by a monoclonal antibody to calcineurin, thus indicating that it is an intrinsic property of calcineurin. The results suggest that functional roles of calcineurin may include actions of the enzyme toward nonprotein phosphocompounds.

A prospective reappraisal of emergency endoscopy in patients with portal hypertension

In a prospective study of emergency endoscopy in patients with portal hypertension and oesophageal varices referred to King's College Hospital with acute upper gastrointestinal bleeding, initial endoscopic examination on 90 separate consecutive hospital admissions carried out within 24 h of clinical haemorrhage showed active variceal bleeding in only 21 (23.3%) cases. Coexisting upper gastrointestinal lesions were present in 38.8% of examinations, but active bleeding from these sites was seen in only five cases (5.6%). Of the 64 cases in which no active bleeding was seen at initial endoscopy, 39 (60.9%) rebled during that admission, and repeat endoscopy in 27 of these, carried out within 1 h of this episode, revealed active variceal haemorrhage in 20 (74.1%) cases. These results indicate that variceal haemorrhage is intermittent, and, although bleeding may often stop spontaneously, a high proportion of patients subsequently rebleed, and this is invariably from varices rather than from coexisting upper gastrointestinal lesions. In addition, these findings confirm the importance of emergency endoscopy in making the correct decision about acute management.

Prospective controlled trial of injection sclerotherapy in patient with cirrhosis and recent variceal haemorrhage

64 patients with cirrhosis and recent variceal haemorrhage were studied in a prospective randomised trial of injection sclerotherapy by means of a flexible oesophageal sheath. 12 (33%) of the 36 patients in the sclerotherapy group, suffered further bleeds from varices compared with 19 (68%) of the 28 patients receiving standard medical treatment. The risk of bleeding per patient-month of follow up decreased more than threefold with sclerotherapy and the number of patients rebleeding after 2, 6, and 12 months was significantly reduced (p < 0.05). 1-year survival without further bleeding improved significantly with sclerotherapy (46% compared with 6%, p < 0.02), although the difference in overall survival assessed by cumulative life-table analysis was not statistically significant. The main complication of the technique was the development of oesophageal ulcers in some patients.

Intolerance of eight ounces of milk in healthy lactose-intolerant teen-agers

The ability of lactose-intolerant individuals to tolerate 8 ounces of milk was determined in healthy teen-agers. Thirty-two blacks were studied with 50-gm lactose tolerance tests. Nineteen (59%) had a flat blood sugar curve and 13 (39%) also developed bloating, cramps, loose stools, or diarrhea with the test. These latter 13 were defined as lactose-intolerant. Seven of the 13 lactose-intolerant teen-agers (54%) developed abdominal bloating and/or cramps after drinking 8 ounces of milk (half-pint). None had diarrhea. Eight were symptomatic with the equivalent amount of lactose (12 gm) while only one had symptoms with the monosaccharide components of lactose, glucose and galactose. The symptoms with milk and 12 gm of lactose were less severe than with the 50-gm tolerance test. A history of a prior awareness of milk intolerance was obtained from 11 of the 13 lactose-intolerant subjects. At least one half of lactose intolerant teen-agers might be expected to be symptomatic after drinking 8 ounces of milk without other food. Milk intolerance should be considered in the nutritional planning for teen-agers with special attention to members of population groups with a high prevalence of lactose intolerance.