[Mucopolysaccharidoses]

Mucopolysaccharidoses are a family of metabolic disorders characterized by a deficiency in the catabolic lysosomal pathways. They are rare, inherited diseases which lead to progressive cellular, tissue and organ damage across a broad spectrum of phenotypes. To prevent irreversible damage early diagnosis is essential. Typical signs and symptoms are the thoracolumbar gibbus, shortened and plumped metacarpal bones, hip dysplasia, deformed ribs and ovoid vertebral bodies. Due to the typical deformation of the pelvis hip dislocation occurs often in childhood. Bilateral carpal tunnel syndrome is frequent. Bone marrow transplantation and enzyme replacement therapy are available. Orthopaedic interventions are based on individual therapeutic decisions and indications.

Oral administration of the growth hormone secretagogue NN703 in adult patients with growth hormone deficiency

OBJECTIVE

Little is known of the usefulness of GH secretagogues (GHSs) in GH-deficient (GHD) adults. The objective of this study was to determine the number of responders to treatment with NN703 in GHD adults.

DESIGN

A multicentre, randomized, double-blind, and placebo-controlled study.

PATIENTS

Ninety-seven GHD adults were included.

MEASUREMENTS

The GH response before and after 1 week of oral treatment with NN703 (n = 83) or placebo (n = 14) was determined. The first and last dose of NN703 was 3 mg/kg, whereas the dose of NN703 was 1.5 mg/kg/day during the 6 days between the first and last doses. Furthermore, all 97 patients received 1 micro g/kg GH-releasing hormone (GHRH) 3 weeks after the last dose of NN703.

RESULTS

Serum GH peak and area under curve (AUC) values after the first NN703 administration were greater than those after placebo administration (P < 0.05). However, after correction for the lower body mass index (BMI) in the NN703 group, this difference lost statistical significance. After 1 week of therapy, GH peak and AUC values were similar following the final doses of NN703 and placebo. Serum peak and AUC values of other anterior pituitary hormones were similar between the NN703 and placebo groups both after the first and last administration of study drug. Nine of the 83 patients (11%) responded with a serum peak GH concentration >or= 5 micro g/l after the first and/or last NN703 administration, whereas no patient responded after placebo administration. Serum IGF-I was unaffected by 1-week NN703 treatment, whereas serum IGFBP-3 was increased (P < 0.05 vs. placebo) also after correction for BMI. Mean serum peak GH concentration after GHRH administration was 2.1 micro g/l (+/-0.3, SEM), which was higher than that after the first NN703 administration (1.32 +/- 0.3, P < 0.05).

CONCLUSION

NN703 administration was generally well tolerated. Eleven per cent of the GHD adult patients responded with a peak GH response >or= 5 micro g/l after the first and/or last administration of oral NN703. Although a majority of GHD adults will not respond to NN703, the present results suggest that oral NN703 treatment could be useful in some adult patients with moderately severe GHD. These patients may be identified by a test dose of GHS.

Breathing pattern and perception at different levels of volume assist and pressure support in volunteers

OBJECTIVE

Volume assist (VA) amplifies the breathing effort whereas pressure support ventilation (PSV) provides a fixed, effort-independent ventilatory support. According to the concept of VA, its level should compensate for the pathologically increased (additional) elastance (Eadd). However, it is unclear whether breathing subjects prefer an exact compensation of Eadd and whether they are able to adjust the support level by themselves.

DESIGN

Prospective, interventional study.

SETTING

Laboratory.

SUBJECTS

Twelve healthy volunteers, nine females, three males, aged 21-33 yrs.

INTERVENTIONS

Increased Eadd was generated by banding of the thorax and abdomen. Volunteers breathed via a mouthpiece with VA or PSV using a positive end-expiratory pressure of 5 cm H2O (0.5 kPa). The study was subdivided into two parts. In part I, volunteers were instructed to adjust the level of VA and PSV themselves starting from three different, randomly applied levels in each mode (2, 8, 14 cm H2O or cm H2O/L; 0.2, 0.8, 1.4 kPa[/L]). In part II, 20 levels of VA and PSV (1-20 cm H2O or cm H2O/L, 0.1-2 kPa[/L]) were randomly selected by an investigator and estimated by the volunteers using a visual analog scale. Additionally, the breathing pattern was characterized.

MEASUREMENTS AND MAIN RESULTS

Eadd (7.1 +/- 1.5 cm H2O/L [0.7 +/- 0.2 kPa/L], mean +/- sd) corresponded almost exactly to the "self-adjusted" VA level of part I (7.0 +/- 3.3 cm H2O/L [0.7 +/- 0.3 kPa/L]) and to the adequate level of part II (8-9 cm H2O/L [0.8-0.9 kPa/L]). The accordant PSV levels were 5.7 +/- 2.6 cm H2O (0.6 +/- 0.3 kPa) and 6-7 cm H2O (0.6-0.7 kPa). The breathing pattern was less influenced by changes of the support level with VA compared with PSV, which may explain in part the greater comfort of VA.

CONCLUSIONS

We confirmed the theoretical assumption that VA should be adapted to Eadd. Furthermore, we demonstrated that conscious subjects are able to adjust the level of VA and PSV themselves.

On the other side of the mean: the perception of dissimilarity in human faces

We created a 'face space' using a laser-scan representation of faces. In this space, a caricature can be made by moving a face away from the average face, along the line connecting the particular face to the average face. Here, we move the face along this line in the other direction, proceeding through the mean and 'out the other side'. This results in a face that is 'opposite', in a computational sense, to the original face. We morphed several faces into their anti-faces and sampled the morph trajectory in five discrete steps. We then collected similarity ratings from human participants for all possible pairs of morphed faces to determine how the distances in the 'physical face space' related to the distances in the 'psychological face space'. The data indicate that there is a perceptual discontinuity of face identity as the face crosses over to the 'other side of the mean'. We consider these results in the context of face-space models of human face processing.

Prototype-referenced shape encoding revealed by high-level aftereffects

We used high-level configural aftereffects induced by adaptation to realistic faces to investigate visual representations underlying complex pattern perception. We found that exposure to an individual face for a few seconds generated a significant and precise bias in the subsequent perception of face identity. In the context of a computationally derived 'face space,' adaptation specifically shifted perception along a trajectory passing through the adapting and average faces, selectively facilitating recognition of a test face lying on this trajectory and impairing recognition of other faces. The results suggest that the encoding of faces and other complex patterns draws upon contrastive neural mechanisms that reference the central tendency of the stimulus category.

The face typicality-recognizability relationship: encoding or retrieval locus?

Using a crossover recognition memory testing paradigm, we tested whether the effects on face recognition of the memorability component of face typicality (Vokey & Read, 1992, 1995) are due primarily to the encoding process occurring during study or to the retrieval process occurring at test. At study, faces were either veridical in form or at moderate (Experiment 1) or extreme (Experiment 2) levels of caricature. The variable of degree of facial caricature at study was crossed with the degree of caricature at test. The primary contribution of increased memorability to increased hit rate was through increased distinctiveness at study. Increased distinctiveness at test contributed to substantial reductions in the false alarm rate, too. Signal detection analyses confirmed that the mirror effects obtained were primarily stimulus/memory-based, rather than decision-based. Contrary to the conclusion of Vokey and Read (1992), we found that increments in face memorability produced increments in face recognition that were due at least as much to enhanced encoding of studied faces as they were to increased rejection of distractor faces.

An integrated head-holder/coil for intraoperative MRI in open neurosurgery

With the invention of "open" magnetic resonance imaging (MRI) systems, access to the patient is possible during the imaging procedure. An important application of these systems is intraoperative MRI to control the extent of resection during tumor surgery. Up to now flexible surface coils wrapped around, or placed at each side of the head, were used for imaging. These flexible coils have several disadvantages such as unreliability, interindividual problems, difficult handling, poor hygienic properties, and often unsatisfactory or inhomogeneous image quality. To solve most of these problems, an MR-compatible head-holder in combination with an integrated surface coil for use in a 0.2 T C-shaped magnet was developed. Forty-eight patients with known cranial tumors underwent MRI intraoperatively. In 32 patients (67%), residual tumor was found, and additional surgical resection was performed. The integrated head-holder/coil is a safe and practical tool for intraoperative MRI, providing efficient and reliable resection control during neurosurgical procedures.

Facial aging, attractiveness, and distinctiveness

A standard facial caricature algorithm has been applied to a three-dimensional (3-D) representation of human heads, those of Caucasian male and female young adults. Observers viewed unfamiliar faces at four levels of caricature--anticaricature, veridical, moderate caricature, and extreme caricature--and made ratings of attractiveness and distinctiveness (experiment 1) or learned to identify them (experiment 2). There were linear increases in perceived distinctiveness and linear decreases in perceived attractiveness as the degree of facial caricature (Euclidean distance from the average face in 3-D-grounded face space) increased. Observers learned to identify faces presented at either level of positive caricature more efficiently than they did with either uncaricatured or anticaricatured faces. Using the same faces, 3-D representation, and caricature levels, O'Toole, Vetter, Volz, and Salter (1997, Perception 26 719-732) had shown a linear increase in judgments of face age as a function of degree of caricature. Here it is concluded that older-appearing faces are less attractive, but more distinctive and memorable than younger-appearing faces, those closer to the average face.

Three-dimensional shape and two-dimensional surface reflectance contributions to face recognition: an application of three-dimensional morphing

We measured the three-dimensional shape and two-dimensional surface reflectance contributions to human recognition of faces across viewpoint. We first divided laser scans of human heads into their two- and three-dimensional components. Next, we created shape-normalized faces by morphing the two-dimensional surface reflectance maps of each face onto the average three-dimensional head shape and reflectance-normalized faces by morphing the average two-dimensional surface reflectance map onto each three-dimensional head shape. Observers learned frontal images of the original, shape-normalized, or reflectance-normalized faces, and were asked to recognize the faces from viewpoint changes of 0, 30 and 60 degrees. Both the three-dimensional shape and two-dimensional surface reflectance information contributed substantially to human recognition performance, thus constraining theories of face representation to include both types of information.

Use of continuous retropleural bupivacaine in postoperative pain management for pediatric thoracotomy

BACKGROUND/PURPOSE

The aim of this study was to evaluate the use of a continuous bupivacaine infusion into the retropleural space as an adjunct for postoperative pain management in pediatric thoracotomy.

METHODS

A retrospective chart review was performed on 13 pediatric patients undergoing thoracotomy over a 3-year period (April 1995 through July 1997). In seven patients, insertion of a retropleural catheter was accomplished before closure of the thoracotomy by placing an epidural catheter posterior to the parietal pleura. This potential space was entered two intercostal levels below the incision and advanced superiorly four intercostal spaces. Bupivacaine (0.125% or 0.25%) was infused at 0.5 mL/kg/h. Postoperative intravenous narcotic requirement was compared between the study population (n = 7) and the control population (n = 6). Statistical analysis was conducted using the "separate" Student's t test.

RESULTS

Thirteen pediatric patients (age range, 7 to 18 years) were evaluated for total morphine use after thoracotomy. Seven patients had anterior spinal release and fusion, whereas five had mediastinal operations, and one patient had a lobectomy. The two groups were comparable in age, weight, and type of operation. Infusion through the retropleural catheter continued for an average of 3.8 days (range, 3 to 6 days). The total mean postoperative morphine requirement was 2.32 mg/kg (0.544 mg/kg/day) in the control population and 0.88 mg/kg (0.204 mg/kg/day) for the patients with a retropleural catheter (P<.001).

CONCLUSION

A continuous infusion of bupivacaine through a unique retropleural technique decreases the postoperative need for morphine in postoperative pediatric thoracotomy patients.

Three-dimensional caricatures of human heads: distinctiveness and the perception of facial age

A standard facial-caricaturing algorithm was applied to a three-dimensional representation of human heads. This algorithm sometimes produced heads that appeared 'caricatured'. More commonly, however, exaggerating the distinctive three-dimensional information in a face seemed to produce an increase in the apparent age of the face--both at a local level, by exaggerating small facial creases into wrinkles, and at a more global level via changes that seemed to make the underlying structure of the skull more evident. Concomitantly, de-emphasis of the distinctive three-dimensional information in a face made it appear relatively younger than the veridical and caricatured faces. More formally, face-age judgments made by human observers were ordered according to the level of caricature, with anticaricatures judged younger than veridical faces, and veridical faces judged younger than caricatured faces. These results are discussed in terms of the importance of the nature of the features made more distinct by a caricaturing algorithm and the nature of human representation(s) of faces.

Top-down learning of low-level vision tasks

Perceptual tasks such as edge detection, image segmentation, lightness computation and estimation of three-dimensional structure are considered to be low-level or mid-level vision problems and are traditionally approached in a bottom-up, generic and hard-wired way. An alternative to this would be to take a top-down, object-class-specific and example-based approach. In this paper, we present a simple computational model implementing the latter approach. The results generated by our model when tested on edge-detection and view-prediction tasks for three-dimensional objects are consistent with human perceptual expectations. The model's performance is highly tolerant to the problems of sensor noise and incomplete input image information. Results obtained with conventional bottom-up strategies show much less immunity to these problems. We interpret the encouraging performance of our computational model as evidence in support of the hypothesis that the human visual system may learn to perform supposedly low-level perceptual tasks in a top-down fashion.

Hamartoma of the triceps surae muscle

A 9-year-old, otherwise healthy girl presented with a 5-year history of pain in her right calf with retarded growth and development of an equinus contracture of her right leg. Magnetic resonance imaging showed an irregular mass with heterogeneous enhancement after contrast in her right triceps surae muscles, especially the soleus. Histological studies of this triceps surae muscle tissue revealed a haphazard distribution of adipose and connective tissue, striated and smooth muscle cells, vessels and lymphoid follicles, as well as nerve bundles which, together, were considered components of a hamartoma.

Sex classification is better with three-dimensional head structure than with image intensity information

The sex of a face is perhaps its most salient features. A principal components analysis (PCA) was applied separately to the three-dimensional (3-D) structure and graylevel image (GLI) data from laser-scanned human heads. Individual components from both analyses captured information related to the sex of the face. Notably, single projection coefficients characterized complex differences between the 3-D structure of male and female heads and between male and female GLI maps. In a series of simulations, the quality of the information available in the 3-D head versus GLI data for predicting the sex of the face has been compared. The results indicated that the 3-D head data supported more accurate sex classification than the GLI data, across a range of PCA-compressed (dimensionality-reduced) representations of the heads. This kind of dual face representation can give insight into the nature of the information available to humans for categorizing and remembering faces.

Pixel-Based versus Correspondence-Based Representations of Human Faces: Implications for Sex Discrimination

In human perception, as well as in machine vision, a crucial step in solving any object recognition task is an appropriate description of the object class under consideration. We emphasise this issue when considering the object class ‘human faces’. We discuss different representations that can be characterised by the degree of alignment between the images they provide for. The representations used span the whole range between a purely pixel-based image representation and a sophisticated model-based representation derived from the pixel-to-pixel correspondence between the faces [Vetter and Troje, 1995, in Mustererkennung Eds G Sagerer, S Posch, F Kummert (Berlin: Springer)]. The usefulness of these representations for sex classification was compared. This was done by first applying a Karhunen — Loewe transformation on the representation to orthogonalise the data. A linear classifier was trained by means of a gradient-descent procedure. The classification error in a completely cross-validated simulation ranged from 15% in the simplest version of the pixel-based representation to 2.5% for the correspondence-based representation. However, even with intermediate representations very good performance was achieved.

Transport of small organic cations in the rat liver. The role of the organic cation transporter OCT1

The kidneys and the liver are the principal organs for the inactivation of circulating organic cations. Recently, an organic cation transporter (OCT1) has been cloned from rat kidney. In order to answer the question whether OCT1 is involved also in hepatic uptake of organic cations, the pharmacological characteristics of organic cation transport in hepatocytes were compared to the characteristics of transiently expressed OCT1. Primary cultures of rat hepatocytes avidly accumulated the small organic cation 3H-1-methyl-4-phenylpyridinium (3H-MPP+). At equilibrium, the hepatocytes accumulated 3H-MPP+ 56-fold. Initial rates of specific 3H-MPP+ transport in hepatocytes were saturable. The half-saturating concentration was 13 mumol/l. 3H-MPP+ transport was sensitive to quinine (Ki = 0.79 mumol/l) and cyanine863 (Ki = 0.097 mumol/l). Quinine and cyanine863 are known inhibitors of type I hepatic transport of cationic drugs and of renal excretion of organic cations, respectively. To compare the functional characteristics of 3H-MPP+ transport in hepatocytes with those of OCT1, OCT1 has been heterologously expressed and characterized in a mammalian cell line (293 cells). Initial rates of 3H-MPP+ transport were saturable, the Km being 13 mumol/l. The rank order of inhibitory potencies of various inhibitors was almost identical in hepatocytes and 293 cells transiently transfected with OCT1. There was a positive correlation between the Ki's for the inhibition of 3H-MPP+ transport in isolated hepatocytes and transfected 293 cells (r = 0.85; P < 0.01; n = 8). The results indicate that OCT1 is functionally expressed not only in the kidney but also in hepatocytes where it is responsible for the transport of small organic cations which, in the past, have been classified as type I substrates.

View-based models of 3D object recognition: invariance to imaging transformations

This report describes the main features of a view-based model of object recognition. The model does not attempt to account for specific cortical structures; it tries to capture general properties to be expected in a biological architecture for object recognition. The basic module is a regularization network (RBF-like; see Poggio and Girosi, 1989; Poggio, 1990) in which each of the hidden units is broadly tuned to a specific view of the object to be recognized. The network output, which may be largely view independent, is first described in terms of some simple simulations. The following refinements and details of the basic module are then discussed: (1) some of the units may represent only components of views of the object--the optimal stimulus for the unit, its "center," is effectively a complex feature; (2) the units' properties are consistent with the usual description of cortical neurons as tuned to multidimensional optimal stimuli and may be realized in terms of plausible biophysical mechanisms; (3) in learning to recognize new objects, preexisting centers may be used and modified, but also new centers may be created incrementally so as to provide maximal view invariance; (4) modules are part of a hierarchical structure--the output of a network may be used as one of the inputs to another, in this way synthesizing increasingly complex features and templates; (5) in several recognition tasks, in particular at the basic level, a single center using view-invariant features may be sufficient.

The importance of symmetry and virtual views in three-dimensional object recognition

BACKGROUND

Human observers can recognize three-dimensional objects seen in novel orientations, even when they have previously seen only a relatively small number of different views of the object. How our visual system does this is a key problem in vision research. Recent theories and experiments suggest that the human visual system might store a relatively small number of sample two-dimensional views of a three-dimensional object, and recognize novel views by a process of interpolation between the stored sample views. These sample views may be collected during a training phase as the visual system familiarizes itself with the object.

RESULTS

Here, we investigate whether constraints on the shapes of objects commonly encountered in the real world can reduce the number of training views required for recognition of three-dimensional objects. We are particularly concerned with the constraint of object symmetry. We show that if an object is bilaterally symmetrical, then additional 'virtual views' can automatically be generated from one sample view by symmetry transformations. These virtual views should make it more easy to recognize novel views of a symmetric than an asymmetric object, when a single sample view has been seen. Recognition should be particularly facilitated when the novel views are close to the virtual view. We present psychophysical results that bear out these predictions.

CONCLUSIONS

Our results show that the human visual system can indeed exploit symmetry to facilitate object recognition, and support the model for object recognition in which a small number of two-dimensional views are remembered and combined to recognize novel views of the same object. These results raise questions about how symmetry is recognized, and symmetry transformations implemented, in real, biological neural networks.

Symmetric 3D objects are an easy case for 2D object recognition

According to the 1.5-views theorem (Poggio, Technical Report #9005-03, IRST, Povo, 1990; Ullman and Basri, IEEE Trans. PAMI 13, 992-1006, 1991) recognition of a specific 3D object (defined in terms of pointwise features) from a novel 2D view can be achieved from at least two 2D model views (for each object, for orthographic projection). This note considers how recognition can be achieved from a single 2D model view by exploiting prior knowledge of an object's symmetry. It is proved that, for any bilaterally symmetric 3D object, one non-accidental 2D model view is sufficient for recognition since it can be used to generate additional 'virtual' views. It is also proved that, for bilaterally symmetric objects, the correspondence of four points between two views determines the correspondence of all other points. Symmetries of higher order allow the recovery of Euclidean structure from a single 2D view.

Cable properties of arborized Retzius cells of the leech in culture as probed by a voltage-sensitive dye

Retzius cells of Hirudo medicinalis were cultivated on extracellular matrix protein so that extended arborizations were formed. The propagation of voltage transients along 1-microns-thick neurites was observed at a resolution of 8 microns at 10 kHz by use of a voltage-sensitive dye. Delay and width of the fluorescence transients caused by hyperpolarization of the soma are described by passive spread of voltage in a homogeneous cable (time constant, 10 ms; space constant, 320 microns). The local sensitivity of the dye was determined from a comparison of the amplitudes of fluorescence and of fitted voltage. The fluorescence transients caused by depolarization were scaled using the sensitivity profile. Action potentials were found to pervade the neurites without significant change of amplitude but with enhanced pulse width.

[Discovery of pancreatic diabetes in Strasbourg]

Although many clinical aspects of diabetes were already known in the second half of the XIXth century, its pathogenesis remained mysterious. The German Medical School of Strasbourg, rich of numerous eminent teachers and researchers such as A. Kussmaul and B. Naunyn in the 1880ies, represented by this time one of the leading centers in diabetes research. The studies of Joseph Freiherr Von Mering on phloridzin-induced glycosuria are an example between others, but the discovery by Oskar Minkowski of the pancreatic origin of the disease undoubtedly stands as the most famous. This discovery was partly indebted to luck since Von Mering and Minkowski were studying a problem of digestive absorption of lipids, but it was greatly due to the excellent clinical and experimental training of Minkowski, as well as his operatory skill. These works, initially criticized by some authors, turned out to stimulate in several countries researchs on the isolation from pancreas of an hypoglycemic substance. Several investigators gave up or failed near the end, which was reached in 1921 by F. Banting and C. Best, subsequently opening the therapeutic era of diabetology.

Guided outgrowth of leech neurons in culture

Sensory neurons of Hirudo medicinalis were cultivated on patterns of extracellular matrix (ECM) protein which were prepared by UV irradiation using copper grid masks. The relation of the patterns and of the outgrowth of neurites was observed by scanning electronmicroscopy after gold decoration. The neurites were guided by narrow (10 microM) lanes of ECM protein. Branching of neurites was induced by branched lanes. Bent neurites were pulled off bent lanes at some distance behind the growth cone such that their length was reduced. Regularly spaced sites of adhesion became visible which remained connected to the neurites by extended filaments.

Propagation of voltage transients in arborized neurites of Retzius cells of the leech in culture

Propagation of electrical signals is studied in Retzius cells of the leech in culture using voltage-sensitive fluorescent dyes at a spatial resolution of 8 x 8 microns 2 and 14 x 14 microns 2 and at a sampling interval of 0.12 ms. The neurons are stimulated by a microelectrode impaled in the soma. Action potentials of a half width of 2-3 ms are triggered close to the end of the primary neurite dissociated from the leech. They propagate back to the soma at invariant half width at a velocity of 50-230 microns/ms. They pervade extended aborized secondary neurites which are grown on extracellular matrix protein. Their width is enhanced up to a factor two. The velocity is around 100-150 microns/ms such that delays up to 3.5 ms are observed. Accordingly the neuritic trees are not isopotential. The features of propagation are found to be incompatible with passive spread.

A neuron-silicon junction: a Retzius cell of the leech on an insulated-gate field-effect transistor

An identified neuron of the leech, a Retzius cell, has been attached to the open gate of a p-channel field-effect transistor. Action potentials, spontaneous or stimulated, modulate directly the source-drain current in silicon. The electronic signals match the shape of the action potential. The average voltage on the gate was up to 25 percent of the intracellular voltage change. Occasionally weak signals that resemble the first derivative of the action potential were observed. The junctions can be described by a model that includes capacitive coupling of the plasma membrane and the gate oxide and that accounts for variable resistance of the seal.