Vitality in relation to litter size of crossbred pigs and the effect of the terminal sire line

Context Most research on sire lines is linked to growth and carcass traits. Only a limited number of field trials explore the effect of sire line on piglet vitality, litter size and the interactions between these traits. Aim The aim of this study was to examine the effect of sire line on the growth performance and vitality of progeny from birth to weaning and to evaluate the lines with respect to their impact on litter size. Methods Data included 150 litters of a Synthetic sire line (A) and 154 of a Piétrain sire line (B), with 4209 piglets born alive, which resulted from matings to 337 dams (Camborough PIC). The numbers of total born and born alive piglets per litter were recorded. Within 24 h after birth, piglet individual birthweight (BWbirth), sex (male/female) and body temperature (BT) were also recorded. At weaning, mortality rates and weaned pigs per sow were registered. At the day of weaning, 665 randomly chosen pigs were individually weighed. Weaning weights (WW) were used to calculate the weaning average daily gain (WADG). Key results Sire line significantly affected number of total born (P < 0.0001), number born alive (P < 0.01) and number of weaned pigs per sow (P < 0.01). Across lines, each additional piglet per litter resulted in a 31.2 g decline in BWbirth (P < 0.001). Larger litter sizes, higher BWbirth (P < 0.01) and piglets with a lower BT (P < 0.0001) were detected in litters of Sire line B compared with litters of Sire line A. No differences between lines were detected for WADG, WW and pre-weaning mortality (P > 0.05). A positive correlation between birthweight and WW resulted in a correspondingly higher WADG (P < 0.0001). Overall, heavier BWbirth piglets had a higher BT (P < 0.0001). Conclusions The present study indicates that Sire line B would offer a possibility to maintain litter size at a high level and, simultaneously, achieve higher BWbirth, with consequently more vital piglets. Implication It is important to emphasise that further selection for litter size in dam lines is not indicated in terms of animal welfare but also production efficiency. Instead, it seems feasible to follow the above strategy and stabilise litter size at a high level, while at the same time breeding for vitality and survivability in sire lines.

Anesthesia, Sedation, and Pain Management of Donkeys and Mules

The number of donkeys in the world may not be increasing but awareness of their use and concern for welfare and pain recognition and treatment are receiving increasing veterinary interest. Therefore, accurate information about anesthesia and analgesia in donkeys and mules is important to more equine practitioners. This review highlights the current knowledge on various anesthetic and analgesic approaches in donkey and mules. The authors emphasize that there is still much information that is not available about donkeys and mules; in many circumstances, the clinician must use available equine information to treat the patient, while monitoring for differences in response.

Auditory prediction errors as individual biomarkers of schizophrenia

Schizophrenia is a complex psychiatric disorder, typically diagnosed through symptomatic evidence collected through patient interview. We aim to develop an objective biologically-based computational tool which aids diagnosis and relies on accessible imaging technologies such as electroencephalography (EEG). To achieve this, we used machine learning techniques and a combination of paradigms designed to elicit prediction errors or Mismatch Negativity (MMN) responses. MMN, an EEG component elicited by unpredictable changes in sequences of auditory stimuli, has previously been shown to be reduced in people with schizophrenia and this is arguably one of the most reproducible neurophysiological markers of schizophrenia.

EEG data were acquired from 21 patients with schizophrenia and 22 healthy controls whilst they listened to three auditory oddball paradigms comprising sequences of tones which deviated in 10% of trials from regularly occurring standard tones. Deviant tones shared the same properties as standard tones, except for one physical aspect: 1) duration - the deviant stimulus was twice the duration of the standard; 2) monaural gap - deviants had a silent interval omitted from the standard, or 3) inter-aural timing difference, which caused the deviant location to be perceived as 90° away from the standards.

We used multivariate pattern analysis, a machine learning technique implemented in the Pattern Recognition for Neuroimaging Toolbox (PRoNTo) to classify images generated through statistical parametric mapping (SPM) of spatiotemporal EEG data, i.e. event-related potentials measured on the two-dimensional surface of the scalp over time. Using support vector machine (SVM) and Gaussian processes classifiers (GPC), we were able classify individual patients and controls with balanced accuracies of up to 80.48% (p-values = 0.0326, FDR corrected) and an ROC analysis yielding an AUC of 0.87. Crucially, a GP regression revealed that MMN predicted global assessment of functioning (GAF) scores (correlation = 0.73, R² = 0.53, p = 0.0006).

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The diagnostic utility of multiple auditory oddball stimulus paradigms is assessed.

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Greatest classification accuracy was achieved using a monaural gap stimulus paradigm.

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The full post-stimulus epoch contains relevant discriminatory components.

Rare DNA variants in the brain-derived neurotrophic factor gene increase risk for attention-deficit hyperactivity disorder: a next-generation sequencing study

Attention-deficit hyperactivity disorder (ADHD) is a prevalent and highly heritable disorder of childhood with negative lifetime outcomes. Although candidate gene and genome-wide association studies have identified promising common variant signals, these explain only a fraction of the heritability of ADHD. The observation that rare structural variants confer substantial risk to psychiatric disorders suggests that rare variants might explain a portion of the missing heritability for ADHD. Here we believe we performed the first large-scale next-generation targeted sequencing study of ADHD in 152 child and adolescent cases and 188 controls across an a priori set of 117 genes. A multi-marker gene-level analysis of rare (<1% frequency) single-nucleotide variants (SNVs) revealed that the gene encoding brain-derived neurotrophic factor (BDNF) was associated with ADHD at Bonferroni corrected levels. Sanger sequencing confirmed the existence of all novel rare BDNF variants. Our results implicate BDNF as a genetic risk factor for ADHD, potentially by virtue of its critical role in neurodevelopment and synaptic plasticity.

Tumour-suppression function of KLF12 through regulation of anoikis

Suppression of detachment-induced cell death, known as anoikis, is an essential step for cancer metastasis to occur. We report here that expression of KLF12, a member of the Kruppel-like family of transcription factors, is downregulated in lung cancer cell lines that have been selected to grow in the absence of cell adhesion. Knockdown of KLF12 in parental cells results in decreased apoptosis following cell detachment from matrix. KLF12 regulates anoikis by promoting the cell cycle transition through S phase and therefore cell proliferation. Reduced expression levels of KLF12 results in increased ability of lung cancer cells to form tumours in vivo and is associated with poorer survival in lung cancer patients. We therefore identify KLF12 as a novel metastasis-suppressor gene whose loss of function is associated with anoikis resistance through control of the cell cycle.

SETD2 loss-of-function promotes renal cancer branched evolution through replication stress and impaired DNA repair

Defining mechanisms that generate intratumour heterogeneity and branched evolution may inspire novel therapeutic approaches to limit tumour diversity and adaptation. SETD2 (Su(var), Enhancer of zeste, Trithorax-domain containing 2) trimethylates histone-3 lysine-36 (H3K36me3) at sites of active transcription and is mutated in diverse tumour types, including clear cell renal carcinomas (ccRCCs). Distinct SETD2 mutations have been identified in spatially separated regions in ccRCC, indicative of intratumour heterogeneity. In this study, we have addressed the consequences of SETD2 loss-of-function through an integrated bioinformatics and functional genomics approach. We find that bi-allelic SETD2 aberrations are not associated with microsatellite instability in ccRCC. SETD2 depletion in ccRCC cells revealed aberrant and reduced nucleosome compaction and chromatin association of the key replication proteins minichromosome maintenance complex component (MCM7) and DNA polymerase δ hindering replication fork progression, and failure to load lens epithelium-derived growth factor and the Rad51 homologous recombination repair factor at DNA breaks. Consistent with these data, we observe chromosomal breakpoint locations are biased away from H3K36me3 sites in SETD2 wild-type ccRCCs relative to tumours with bi-allelic SETD2 aberrations and that H3K36me3-negative ccRCCs display elevated DNA damage in vivo. These data suggest a role for SETD2 in maintaining genome integrity through nucleosome stabilization, suppression of replication stress and the coordination of DNA repair.

Recurrent cerebral metastasis from a cardiac myxoma: case report and review of literature

We report the case of a 65-year-old patient who had complete excision of an atrial myxoma and subsequently presented to our unit with recurrent cerebral metastasis. The case demonstrates that cardiac myxoma despite benign histological appearance is capable of metastatic spread.

Phase II trial of FOLFOX6, bevacizumab and cetuximab in patients with Colorectal Cancer

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Background: Bevacizumab (B) + FOLFOX is widely accepted as a standard first-line therapy for metastatic colorectal cancer (mCRC). Recent treatment strategies have included the use of targeted therapies combined with chemotherapy to improve efficacy and to reduce chemotherapy-related toxicities. This Phase II study assesses first-line mFOLFOX6 + B + cetuximab (C), a monoclonal antibody approved for use in irinotecan-refractory mCRC. Methods: All pts had ECOG PS = 1, normal bone marrow, hepatic and renal function. Pts received mFOLFOX6 + B (5mg/kg) biweekly and C weekly (initially at 400 mg/m2, then subsequent doses at 250 mg/m2). Tumor assessment by imaging was done every 8 weeks. Primary endpoints are response rate, progression free-survival (PFS), overall survival (OS), and safety. The regimen would be considered promising if there were = 32 responses, or if = 60% of pts were progression-free for at least 8 months. Results: 67 pts (37 males, 30 females) were enrolled from 12/04–11/06. Median age was 57. Toxicities included Grade 4: neutropenia (6%), thrombosis/embolism (5%). Grade 3: neutropenia (13%), rash (13%), fatigue (11%), diarrhea (11%), abdominal pain (6%), neuropathy (5%), infection with ≤ Grade 2 ANC (4.5%). There were 2 deaths, 1 due to neutropenia and diarrhea and 1 to pulmonary fibrosis. As of 12/06, 9 pts were too early to evaluate. Of the remaining 58 pts, there were 32 responses (55%; 95% CI: 42%, 68%), including 3 CRs and 29 PRs; Median PFS was 9.6 months (95% CI: 8.8, 13.9 months), 71% were progression-free for at least 8 months, and median OS was not reached after a median follow-up of 11.4 months (range 1.5–25.2 months). Conclusions: Treatment with mFOLFOX6+ B + C met the pre-specified criteria for objective response and PFS to be considered promising. This regimen is associated with an acceptable toxicity profile and merits further evaluation. Supported by N01-CA-62204.

No significant financial relationships to disclose.

Phase II study of PS-341 (bortezomib) with or without irinotecan in patients (pts) with advanced gastric adenocarcinomas (AGA)

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Background: We are conducting a phase II trial of the proteasome inhibitor, PS-341, with or without irinotecan in pts with AGA. The combination of PS-341 and irinotecan has been studied in preclinical tumor models including a murine xenograft model of colon cancer, where the combination achieved significantly more tumor shrinkage than either agent alone. The primary objective of this study is to determine response rates, toxicities, progression-free survival, and overall survival in pts with AGA receiving PS-341 alone or in combination with irinotecan. Methods: All pts had gastric adenocarcinoma beyond the scope of surgical resection, measurable disease, and normal bone marrow, hepatic and renal function. All gave informed consent. In previously untreated patients, PS-341 was administered at 1.3 mg/m2 on days 1, 4, 8, and 11 as IV bolus every 21 days. Irinotecan was administered IV at 125 mg/m2 over 90 mins on days 1 and 8 every 21 days (Arm A). For previously treated patients, PS-341 was administered as a single agent at 1.3mg/m2 on days 1, 4, 8, 11 as an IV bolus every 21 days (Arm B). Radiologic evaluation and tumor measurements were performed every 8 weeks. Results: Thirty-seven pts have been enrolled; 29 are evaluable (4 never treated, 4 TETE). Twenty-two pts were treated in Arm A, and 11 in Arm B. All pts were eligible and the 29 treated pts were fully evaluable. Median age 58 (33–87); 26 males/7 females; median number of cycles received was 2.0. Most common toxicities: Grade 4 cardiac arrest (1), stomach perforation (1), leukopenia (2), diarrhea (1), edema (1); Grade 3 nausea (6), vomiting (7), diarrhea (4), febrile neutropenia (3), thrombocytopenia (6), anemia (6); Grade 5 death (3). Severe toxicities likely attributed to disease progression. Response rate was 33% for Arm A, 9% for Arm B. Progression-free survival was 1.8 mo. in Arm A, 1.4 mo. in Arm B. Median overall survival was 4.8 mo. in Arm A, 5.4 mo. in Arm B. Conclusions: The combination of PS-341 and irinotecan, a non-cisplatin containing therapy, is active in AGA and should be considered a key regimen. Monotherapy with PS-341 has a 9% response rate in this population of pre-treated patients with advanced disease. Accrual to this study is continuing.

[Table: see text]

Bioequivalence of an ezetimibe/simvastatin combination tablet and coadministration of ezetimibe and simvastatin as separate tablets in healthy subjects

OBJECTIVE

To assess the bioequivalence of an ezetimibe/simvastatin (EZE/SIMVA) combination tablet compared to the coadministration of ezetimibe and simvastatin as separate tablets (EZE + SIMVA).

METHODS

In this open-label, randomized, 2-part, 2-period crossover study, 96 healthy subjects were randomly assigned to participate in each part of the study (Part I or II), with each part consisting of 2 single-dose treatment periods separated by a 14-day washout. Part I consisted of Treatments A (EZE 10 mg + SIMVA 10 mg) and B (EZE/SIMVA 10/10 mg/mg) and Part II consisted of Treatments C (EZE 10 mg + SIMVA 80 mg) and D (EZE/SIMVA 10/80 mg/mg). Blood samples were collected up to 96 hours post-dose for determination of ezetimibe, total ezetimibe (ezetimibe + ezetimibe glucuronide), simvastatin and simvastatin acid (the most prevalent active metabolite of simvastatin) concentrations. Ezetimibe and simvastatin acid AUC(0-last) were predefined as primary endpoints and ezetimibe and simvastatin acid Cmax were secondary endpoints. Bioequivalence was achieved if 90% confidence intervals (CI) for the geometric mean ratios (GMR) (single tablet/coadministration) of AUC(0-last) and Cmax fell within prespecified bounds of (0.80, 1.25).

RESULTS

The GMRs of the AUC(0-last) and Cmax for ezetimibe and simvastatin acid fell within the bioequivalence limits (0.80, 1.25). EZE/ SIMVA and EZE + SIMVA were generally well tolerated.

CONCLUSIONS

The lowest and highest dosage strengths of EZE/SIMVA tablet were bioequivalent to the individual drug components administered together. Given the exact weight multiples of the EZE/SIMVA tablet and linear pharmacokinetics of simvastatin across the marketed dose range, bioequivalence of the intermediate tablet strengths (EZE/SIMVA 10/20 mg/mg and EZE/SIMVA 10/40 mg/mg) was inferred, although these dosages were not tested directly. These results indicate that the safety and efficacy profile of EZE + SIMVA coadministration therapy can be applied to treatment with the EZE/SIMVA tablet across the clinical dose range.

Motion rivalry impairs motion repulsion

In their classic study on motion repulsion, Marshak and Sekuler (Science 205 (1979) 1399) reported a repulsion of up to 10 degrees when two different directions of motion were presented dichoptically. However, subjects in that study did not experience binocular rivalry, presumably because of the brief presentation time. In the present study, we measured repulsion during binocular rivalry by requiring subjects to dichoptically view the stimuli until one direction of motion appeared to exclusively dominate the other (Blake, Yu, Lokey, & Norman (1998). J. Cogn. Neurosci., 10, 46-60). We found that motion repulsion was significantly reduced during exclusive dominance. Indeed, after controlling for reference repulsion--the misjudgment of a single direction of motion (Rauber & Treue (1998). Perception, 27, 393-402)--we found no significant motion repulsion during exclusive dominance. These data suggest that motion repulsion may require the perception, rather than merely the physical presence, of multiple directions.

Transcranial magnetic stimulation differentially affects speed and direction judgments

This study was conducted to determine whether humans' judgments about the speed and direction of moving stimuli was differentially affected by transcranial magnetic stimulation (TMS). Subjects viewed two successively presented moving stimuli that differed from each other both in speed and direction of motion. Single-pulse TMS was applied either medially (approximately 2 cm above the inion) or laterally (approximately 5 cm lateral to and 4 cm above the inion), while subjects judged the speed and direction differences. The physical stimulation (visual and TMS) was identical on the two tasks, as was discriminability (d') when TMS was not applied. We found significant criterion (beta) shifts on the speed discrimination task at both stimulation sites. Specifically, on TMS trials the proportion of "slower" judgments increased significantly, consistent with subjective reports that stimuli often appeared to slow when TMS was applied. The subjective reports indicated no corresponding change in perceived direction. We also found that speed discriminability was impaired significantly more than direction discriminability, but only when TMS was applied medially. Indeed, after controlling for TMS-related changes in reaction time, speed discriminability was impaired significantly, while direction discriminability remained largely intact. This dissociation suggests that the sensory response constraining speed discrimination is at least partially independent from the sensory response constraining direction discrimination. Combined with previous psychophysical data, the present data suggest a double dissociation between speed and direction discrimination in humans.

The effect of orientation learning on contrast sensitivity

Regan and Beverley [Regan, D., & Beverley, K. I. (1985). Postadaptation orientation discrimination. Journal of the Optical Society of America A, 2(2), 147-155] previously demonstrated that adapting to an oriented visual stimulus improves sensitivity to subtle orientation differences while impairing contrast sensitivity. Here, we investigated whether practice-based improvements in orientation sensitivity would, like adaptation, impair contrast sensitivity. To the contrary, we found that contrast sensitivity actually improved significantly after observers demonstrated practice-based increases in orientation sensitivity. Therefore, while orientation sensitivity can be enhanced either by orientation-discrimination training or by adapting to visual stimuli, these two procedures have opposite effects on contrast sensitivity. This difference suggests that adaptation and perceptual learning on orientation discrimination cannot be explained sufficiently by a shared underlying cause, such as a reduction in neural activity.

The dependence of motion repulsion and rivalry on the distance between moving elements

We investigated the extent to which motion repulsion and binocular motion rivalry depend on the distance between moving elements. The stimuli consisted of two sets of spatially intermingled, finite-life random dots that moved across each other. The distance between the dots moving in different directions was manipulated by spatially pairing the dot trajectories with various precisions. Data from experiment 1 indicated that motion repulsion occurred reliably only when the average distance between orthogonally moving elements was at least 21.0 arc min. When the dots were precisely paired, a single global direction intermediate to the two actual directions was perceived. This result suggests that, at a relatively small spatial scale, interaction between different directions favors motion attraction or coherence, while interaction at a somewhat larger scale generates motion repulsion. Similarly, data from experiment 2 indicated that binocular motion rivalry was significantly diminished by spatially pairing the dots, which moved in opposite directions in the two eyes. This supports the recent proposal that rivalry occurs at or after the stage of binocular convergence, since monocular cells could not have directly responded to our interocular pairing manipulation. Together, these findings suggest that the neural mechanisms underlying motion perception are highly sensitive to the fine spatial relationship between moving elements.

Perceptual learning on orientation and direction discrimination

Two experiments were conducted to determine the extent to which perceptual learning transfers between orientation and direction discrimination. Naive observers were trained to discriminate orientation differences between two single-line stimuli, and direction differences between two single-moving-dot stimuli. In the first experiment, observers practiced the orientation and direction tasks along orthogonal axes in the fronto-parallel plane. In the second experiment, a different group of observers practiced both tasks along a single axis. Perceptual learning was observed on both tasks in both experiments. Under the same-axis condition, the observers' orientation sensitivity was found to be significantly elevated after the direction training, indicating a transfer of learning from direction to orientation. There was no evidence of transfer in any other cases tested. In addition, the rate of learning on the orientation task was much higher than the rate on the direction task. The implications of these findings on the neural mechanisms subserving orientation and direction discrimination are discussed.

Serotonin transporter (5-HTT) and gamma-aminobutyric acid receptor subunit beta3 (GABRB3) gene polymorphisms are not associated with autism in the IMGSA families. The International Molecular Genetic Study of Autism Consortium

Previous studies have suggested that the serotonin transporter (5-HTT) gene and the gamma-aminobutyric acid receptor subunit beta3 (GABRB3) gene, or other genes in the 15q11-q13 region, are possibly involved in susceptibility to autism. To test this hypothesis we performed an association study on the collection of families from the International Molecular Genetic Study of Autism (IMGSA) Consortium, using the transmission disequilibrium test. Two polymorphisms in the 5-HTT gene (a functional insertion-deletion polymorphism in the promoter and a variable number tandem repeat in the second intron) were examined in 90 families comprising 174 affected individuals. Furthermore, seven microsatellite markers spanning the 15q11-q13 region were studied in 94 families with 182 affected individuals. No significant evidence of association or linkage was found at any of the markers tested, indicating that the 5-HTT and the GABRB3 genes are unlikely to play a major role in the aetiology of autism in our family data set.

pABC11 (also known as MOAT-C and MRP5), a member of the ABC family of proteins, has anion transporter activity but does not confer multidrug resistance when overexpressed in human embryonic kidney 293 cells

Several members of the ABC family of proteins have been implicated in multidrug resistance associated with cancer therapies. A novel member of this gene family, designated pABC11, has been identified using degenerate polymerase chain reaction. The full-length cDNA spans 5881 base pairs and encodes an open reading frame of 1437 amino acids predicted to contain two sets of transmembrane domains and two nucleotide binding domains characteristic of ABC proteins. The nucleotide sequence described herein extends that of three recently reported sequences, MRP5 (Kool, M., de Haas, M., Scheffer, G., Scheper, R., van Eijk, M., Juijn, J., Baas, F., and Borst, P. (1997) Cancer Res. 57, 3537-3547), SMRP (Suzuki, T., Nishio, K., Sasaki, H., Kurokawa, H., Saito-Ohara, F., Ikeuchi, T., Tanabe, S., Terada, M., and Saijo, N. (1997) Biochem. Biophys. Res. Commun. 238, 790-794), and MOAT-C (Belinsky, M., Bain, L., Balsara, B., Testa, J., and Kruh, G. (1998) J. Natl. Cancer Inst. 90, 1735-1741), in the 5' direction. Northern blot analysis detected five transcripts that were differentially expressed in several tissue types, and the gene encoding pABC11 was mapped to chromosome 3. Confocal imaging of HEK293 cells expressing a green fluorescent protein-pABC11 construct confirmed plasma membrane localization of the fusion protein. Overexpression of pABC11 resulted in reduced labeling with the fluorochromes 5-chloromethylfluorescein diacetate, fluorescein diacetate, and 2',7'-bis-(2-carboxyethyl)-5 (and-6)-carboxyfluorescein acetoxymethyl ester but not with calcein or rhodamine derivatives, consistent with pABC11 being an anion transporter. Fluorochrome export was ATP-dependent but glutathione-independent. We also show that this export pump does not confer resistance to various classes of cytotoxic drugs but does provide small but significant resistance to CdCl(2) and potassium antimonyl tartrate.

Axis-of-motion affects direction discrimination, not speed discrimination

The motion of an object can be described by a single velocity vector, or equivalently, by direction and speed separately. Similarly, our ability to see subtle differences in the motion of two objects could be constrained by either a velocity-based sensory response, or separate sensory responses to direction and speed. To distinguish between these possibilities we investigated whether direction discrimination and speed discrimination were differentially affected by changes in the axis-of-motion. Psychophysical data from 12 naive observers indicated that direction discrimination depended on axis-of-motion, but speed discrimination did not. The difference suggests that a velocity-based sensory response is not the limiting factor on the two tasks. Instead, the results imply that the sensory response which constrains speed discrimination is at least partially independent from the sensory response which constrains direction discrimination.

A simple, sensitive and reproducible assay for pyridoxal 5'-phosphate and 4-pyridoxic acid in human plasma

We describe a procedure for the measurement of pyridoxal 5'-phosphate and of 4-pyridoxic acid in human plasma samples. It is based on the conversion of pyridoxal 5'-phosphate to 4-pyridoxic acid 5'-phosphate by cyanide in alkaline medium, followed by a high pressure liquid chromatographic separation, with fluorescence detection at acid pH. The assay is robust, sensitive, linear over a wide range, reproducible, and simple to perform. Samples stored at -80 degrees C are stable. Satisfactory agreement was obtained with results from the tyrosine decarboxylase-based assay for pyridoxal 5'-phosphate, in two other laboratories. Plasma samples from a National Survey of older British people were analyzed, and reference intervals for plasma pyridoxal 5'-phosphate intervals were derived. From the lower 2.5 percentile of the reference group, taken as the lower cut-off of the normal range, ca. 20% of elderly men and 11% of elderly women in the UK showed evidence of biochemical deficiency.

Neutral amino acid uptake by the microvillous plasma membrane of the human placenta is inversely related to fetal size at birth in normal pregnancy

Understanding the physiological regulation of fetal growth is important, as normal variations in size at birth relate to differences in neonatal and adult health. Although fetal growth directly reflects net placental transfer, little is known about how normal fetal growth relates to the transfer capabilities of the placental epithelium, the syncytiotrophoblast. The Na(+)-dependent and Na(+)-independent uptakes of methylaminoisobutyric acid (MeAIB) by vesicles prepared from the syncytiotrophoblast microvillous plasma membrane give measurements of system A neutral amino acid transporter activity and diffusive permeability, respectively. In 62 normal pregnancies, we related vesicle MeAIB uptakes to neonatal anthropometry. Smaller babies with a lower abdominal circumference had higher placental system A activity per mg membrane protein (P = 0.004); activity rose from 0.020 to 0.043 nmol/30 sec/mg protein as abdominal circumference fell from 34.6 cm or more to 32.0 cm or less. Within the normal range of fetal and placental size, this may reflect a tendency toward compensatory up-regulation of the placental system A transporter in smaller babies. Babies with a lower abdominal circumference also had higher Na(+)-independent MeAIB uptakes (P = 0.0005); this could reflect important compositional changes in the microvillous plasma membrane, leading in vivo to increased back-diffusion of amino acids out of the syncytiotrophoblast.

The effect of inducer polarity and contrast on the perception of illusory figures

A study designed to determine how inducer-surround contrast and inducer polarity affect the contour clarity and the lightness of illusory figures is reported. Using magnitude estimation procedures, ten naive subjects rated both the contour clarity and the lightness of Kanizsa squares. The magnitude of the inducer-surround contrast and the inducer polarity (all-black, all-white, or black-and-white) were varied randomly on each trial. The data indicate that contour clarity increases with contrast at the same rate across polarity conditions but that contour clarity at any given contrast level depends significantly on polarity. Contour clarity judgments were significantly lower when the inducers were all-white than when the inducers were all-black or black-and-white, and significantly greater in the 'mixed' polarity case (black-and-white inducers) than in the 'same' polarity case (the average of the all-black and all-white inducer conditions). Inducer contrast and polarity significantly affected the lightness of the illusory figure in a manner consistent with simultaneous spatial contrast. Also, for a given increment in contrast, contour clarity altered significantly more than surface lightness, regardless of inducer polarity. The findings suggest that the mechanism which mediates boundary formation is sensitive to the direction of contrast, and that the boundary formation mechanism is more sensitive than the surface lightness mechanism to changes in contrast magnitude. The results are considered within the context of neural network models of form perception.

Continuous veno-venous hemodiafiltration using bicarbonate dialysate

We report our experience with 11 children treated by continuous veno-venous hemodiafiltration. The median age was 5.0 years (range 3 days to 14 years). Access was via dual-lumen subclavian or femoral vein catheters. Hemofilters were chosen on the basis of patient size and dialysis requirements. Bicarbonate-buffered dialysis solution was prepared shortly before use by supplementation of a specially prepared base solution with commercially available electrolyte solutions. The mean ultrafiltration rate was 37.4 +/- 27 ml/kg body weight per hour. Urea and creatinine clearances were 15.1 +/- 6.4 ml/kg body weight per min and 16.4 +/- 8.4 ml/kg body weight per min, respectively. Metabolic acidosis was readily controlled in all patients. Of the 11 patients, 7 ultimately recovered normal renal function.

Velocity-dependent improvements in single-dot direction discrimination

Thirty-six Brown University students participated in three experiments designed to address perceptual learning. In each experiment, visual discrimination thresholds were tracked over 4,200 trials. Results from Experiment 1 suggest that the pattern of threshold reduction on a single-dot motion-direction discrimination task was stimulus direction specific and matched (in a velocity-dependent manner) the threshold reduction pattern previously reported for a line-orientation discrimination task. In Experiment 2, it was determined that the stationary-line-orientation-specific practice effects originally reported by Vogels and Orban (1985) could be replicated but were contingent on line length. Similarly, the results from Experiment 3 suggest that practice effects originally reported by Ball and Sekuler (1987) could be replicated but were contingent on stimulus velocity. Implications for the mechanisms underlying direction and orientation discrimination are considered.