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PubMed1998

Going, going, gone...? Implicit and explicit test of conceptual knowledge in a longitudinal study of semantic dementia.

Patients suffering from semantic dementia provide important constraints on theories of the structure and organisation of semantic memory. In this article we report one such patient, AM, whose progressive deterioration of semantics enables us to address the much-debated issue of whether conceptual structure is hierarchically organised. The hierarchical account predicts that brain damage should impair lower levels of the hierarchy (property information) before affecting higher level (category) information (Warrington and Shallice, Q. J. Exp. Psychol. 1975, 27, 635-657). We evaluate this prediction by repeated testing of AM in two studies--a semantic priming task and a verification task--over an 18 month period, contrasting the progressive deterioration of properties (functional and perceptual) and category relations (category co-ordinates and category labels). Properties were preserved longer than category information, arguing against a hierarchical account of semantic memory. In addition, functional properties were most robust to brain damage, supporting our claim that functional information plays a special role in semantic representations (Durrant-Peatfield et al., Proc. 19th Ann. Conf. of the Cognitive Science Society. Erlbaum, Mahwah, NJ, 1997. pp. 193-198. Tyler et al., Cognitive Neuropsychol. 1997, 14, 511-545).

Anomia↗

PubMed2003

Bioinformatics-based identification of chemosensory proteins in African Malaria Mosquito, Anopheles gambiae.

Chemosensory proteins (CSPs) are identifiable by four spatially conserved Cysteine residues in their primary structure or by two disulfide bridges in their tertiary structure according to the previously identified olfactory specific-D related proteins. A genomics- and bioinformatics-based approach is taken in the present study to identify the putative CSPs in the malaria-carrying mosquito, Anopheles gambiae. The results show that five out of the nine annotated candidates are the most possible Anopheles CSPs of A. gambiae. This study lays the foundation for further functional identification of Anopheles CSPs, though all of these candidates need additional experimental verification.

Amino Acid Sequence↗

PubMed2003

A narwhal is an animal: partial word knowledge biases adults' decisions.

Adults' accuracy on a sentence verification task was measured to assess reliable biases in their responses as a function of their level of knowledge about the target words, as well as adults' ability to reject incorrect ontological category membership for their partially known words. Three levels of word knowledge (known, frontier, and unknown) were assessed in two experiments. Results indicated that participants were conservative decision-makers about sentences using the vocabulary words and that the conservative bias increased in strength as their level of knowledge about the target word increased. When biased guessing was discouraged, results indicated that participants were able to accurately identify both correct and incorrect sentences using targets at all three levels of knowledge, including their partially known words, but were least reliable at rejecting false sentences using unknown targets. Implications for the role of "knowing not" in adults' vocabulary acquisition are discussed.

Adult↗

PubMed2004

Serial mechanisms in lexical access: the rank hypothesis.

There is general agreement that the effect of frequency on lexical access time is roughly logarithmic, although little attention has been given to the reason for this. The authors argue that models of lexical access that incorporate a frequency-ordered serial comparison or verification procedure provide an account of this effect and predict that the underlying function directly relates access time to the rank order of words in a frequency-ordered set. For both group data and individual data, it is shown that rank provides a better fit to the data than does a function based on log frequency. Extensions to a search model are proposed that account for error rates and latencies and the effect of age of acquisition, which is interpreted as an effect of cumulative frequency.

Analysis of Variance↗

PubMed1999

Posttraumatic hypertension secondary to adrenal hemorrhage mimicking pheochromocytoma: case report.

We report the case of a 68-year-old man who presented with a mass 3 x 4 cm in size located in the right adrenal gland together with extreme hypertension, tripled urine levels for normetanephrine, and normal plasmatic levels of metanephrines. The patient had suffered a fall from a height of 2.5 meters before hospitalization. [123I]MIBG-scan was repeatedly positive in the area of the right adrenal gland. At laparotomy under alpha-adrenergic blocking agents, the suspected pheochromocytoma was histologically confirmed as hematoma. After resection of the adrenal gland, blood pressure returned to normal without drug therapy as did metanephrine levels in urine. Although adrenal insufficiency after distension of the gland caused by hemorrhage has been reported, there are no data available regarding the mimicking of a hormonally active pheochromocytoma. We conclude that intra-adrenal pressure rise caused by hematoma may cause partial ischemic necrosis to the gland but may also induce reactive hyperplasia with periodic excessive secretion of catecholamines. This interpretation is consistent with the finding that plasma levels of catecholamines were normal in contrast to the urinary normetanephrines in the presented case. It might be worthwhile to investigate patients with intra-adrenal hemorrhage immediately after sustaining multiple injuries and in the posttraumatic course of several months up to 1 or more years together with verification of abnormal urinary excretion of metanephrines as a sign of impaired adrenal function.

Adrenal Gland Diseases↗

PubMedDate not supplied

[Posterior cortical atrophy].

INTRODUCTION: Posterior cortical atrophy (PCA) is a dementing syndrome characterized by an early alteration of higher visual functions. Patients usually develop a perceptive visual agnosia related to Balint syndrome. DEVELOPMENT: Verification showed Alzheimer s disease (AD) in most PCA observations (13/14 cases), and it can be concluded that there is a posterior variant of AD with prominent visual symptomatology. However, most PCA cases have not been verified and the nature of the disorder remains unknown in these observations. An early and severe unilateral occipital horn dilatation was found in one out of every six cases with non verified PCA. To the best of our knowledge, this image has not been described in AD and these observations could be of different nature. On the other hand, some non verified PCA cases have occasionally manifested as an associative visual agnosia. The nature of this type of associative disorder is unknown, but it could be similar to the nature of semantic dementia, a non Alzheimer s syndrome related to unspecific lesions of temporal lobes.

Agnosia↗

PubMed2000

Simulated hypogravity stimulates cell spreading and wound healing in cultured human vascular endothelial cells.

It is well known that endothelial cells (EC) are highly sensitive to mechanical influences such as hemodynamic conditions or pulsatile stretch. However, it is still unknown, how endothelium responds to the changed gravity. The results of some studies suggest that cellular elements of vascular wall and, particularly, endothelium, may directly participate in development of physiological responces to microgravity. On our suggestion, this is extremely attractive since vascular endothelium is one of the main regulators of vascular tone (via its interaction with vascular smooth muscle cells) and, consequently, can play not last role in maintaining of normal cardiovascular system operation in microgravity. On the other hand, the endothelium itself may be regarded as a widely dispersed organ of approximately 1.5 kg in weight (in the adult human organism). Finally, endothelium is not just a passive barrier between vascular wall and circulating blood but synthesizes, metabolizes, and releases a substances which act on adjacent cell systems or distant cell structures. The main aims of this study were: 1) the development of experimental model, allowing to study functional parameters of human endothelial cells in hypogravity conditions in vitro; 2) the verification of endothelial sensitivity to gravitational micro-environment.

Cell Division↗

PubMed2003

[Environmental control and life support system of spacecraft].

Environment control and life support system is a very complicated and important subsystem of manned spacecraft. It is a key technology must be broken through for the realization of manned space flight. Its functions, technical requirements and main technology were reviewed in this paper. Its test verification was also discussed.

Ecological Systems, Closed↗

PubMedDate not supplied

[Current methods for studying the functional morphology of apud cells].

The paper reviews methods for studying functional morphology of endocrine cells histochemistry and immunohistochemistry, radioautography and methods of ultrastructural verification of secretory granules. Methodological approach is illustrated by the authors' results on the influence of ionizing radiation and tumor growth on the cells of the diffuse endocrine system.

APUD Cells↗

PubMed2003

Evaluation of cost functions for gray value matching of two-dimensional images in radiotherapy.

In external beam radiotherapy, portal imaging is applied for verification of the patient setup. Current automatic methods for portal image registration, which are often based on segmentation of anatomical structures, are especially successful for images of the pelvic region. For portal images of more complicated anatomical structures, e.g., lung, these techniques are less successful. It is desirable to have a method for image registration that is applicable for a wide range of treatment sites. In this study, a registration method for two-dimensional (2D) registration of portal and reference images based on intensity values was tested on portal images of various anatomical sites. Tests were performed with and without preprocessing (unsharp mask filtering followed by histogram equalization) for 96 image pairs and six cost functions. The images were obtained from treatments of the rectum, salivary gland, brain, prostate, and lung. To get insight into the behavior of the various cost functions, cost function values were computed for each portal image for 20,000 transformations of the corresponding reference image, translating the reference image in a range of +/- 1 cm and rotating +/- 10 degrees with respect to the clinical match. The automatic match was defined as the transformation associated with the global minimum (found by an exhaustive search). Without preprocessing, the registration reliability was low (less than 27%). With preprocessing, about 90% of the matches were successful, with a difference with our gold standard (manual registration) of about 1 mm and 1 degree SD. All tested cost functions performed similarly. However, the number of local minima using mutual information was larger than for the other tested cost functions. A cost function based on the mean product of the corresponding pixel values had the least number of local minima. In conclusion, gray value based registration of portal images is applicable for a wide range of treatment sites. However, pre-processing of the images is essential.

Algorithms↗

PubMed1994

Amnesia for arithmetic facts: a single case study.

We report the case of an anarithmetic patient with a selective deficit of memory for elementary arithmetic facts, who produced, for instance, "25" in answer to "4 x 5." The patient showed good language comprehension and production abilities, had minimal number transcoding difficulties, and mastered normally multidigit arithmetic procedures. She was submitted to a series of calculation, verification, and number classification tasks. The arithmetic deficit was evident in both recognition and recall tasks, was consistent across testing sessions, and did not vary as a function of the format used for presentation of the problems. The patient failed even when only implicit access to arithmetic facts was expected: In a timed addition verification task, she did not show a normal inhibition effect when rejecting addition problems in which the proposed result was the product of the two operands (e.g., "3 + 4 = 12"). We suggest that the deficit resulted from a specific and permanent degradation of some connections and nodes in arithmetic long-term memory.

Adult↗

PubMed1997

Gastrocnemius muscle length in relation to knee and ankle joint angles: verification of a geometric model and some applications.

BACKGROUND: For understanding the relationship between skeletal muscle architecture and muscle function in vivo, the development of accurate geometric models relating muscle length to joint angles is crucial. Therefore, a geometric model of the calf of mammals was developed to predict the length of the gastrocnemius muscle-tendon complex from knee and ankle angles. METHODS: The model requires three skeletal length measurements (radius of femoral condyle, ankle lever, and tibia length) to predict muscle-tendon length. The model was tested on the hopping mouse (Notomys alexis) by comparing polynomial fittings with geometrical fits of muscle length-joint angle measurements (i.e., the equation of the geometric model was used for least square fitting of the data). The model was applied to the hopping mouse and the rat to study (in vivo) joint-angle-muscle length-force relationships. RESULTS: It appeared that small and, on average, statistically nonsignificant length adjustments of the skeletal lengths were needed for the geometrical fit. Combinations of joint angles that normally occur during locomotion yielded muscle lengths close to optimum (i.e., with the highest isometric force potential). CONCLUSIONS: By relying on the geometry of the animal's leg, the calculated moment arms of the model appeared more reliable than those calculated from the polynomial fit. It was concluded that the architecture regarding length-force properties of the gastrocnemius muscle in both hopping mouse and rat is well adapted for the locomotion patterns.

Animals↗

PubMed1992

Magnetic resonance imaging and electromyography as indexes of muscle function.

Electromyography (EMG) is commonly used to determine the electrical activity of skeletal muscle during contraction. To date, independent verification of the relationship between muscle use and EMG has not been provided. It has recently been shown that relaxation- (e.g., T2) weighted magnetic resonance images (MRI) of skeletal muscle demonstrate exercise-induced contrast enhancement that is graded with exercise intensity. This study was conducted to test the hypothesis that exercise-induced magnetic resonance (MR) contrast shifts would relate to EMG amplitude if both measures reflect muscle use during exercise. Both MRI and EMG data were collected for separate eccentric (ECC) and concentric (CON) exercise of increasing intensity to take advantage of the fact that the rate of increase and amplitude of EMG activity are markedly greater for CON muscle actions. Seven subjects 30 +/- 2 (SE) yr old performed five sets of 10 CON or ECC arm curls with each of four resistances representing 40, 60, 80, and 100% of their 10 repetition maximum for CON curls. There was 1.5 min between sets and 30 min between bouts (5 sets of 10 actions at each relative resistance). Multiple echo, transaxial T2-weighted MR images (1.5 T, TR/TE 2,000/30) were collected from a 7-cm region in the middle of the arm before exercise and immediately after each bout. Surface EMG signals were collected from both heads of the biceps brachii and the long head of the triceps brachii muscles. CON and ECC actions resulted in increased integrated EMG (IEMG) and T2 values that were strongly related (r = 0.99, P < 0.05) with relative resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1999

Accuracy verification of the photostereometric system KKN/1B developed for intraoperative measurement of knee movement immediately after total knee arthroplasty.

The function and integrity of the knee joint following total knee arthroplasty (TKA) is determined at first by the design and implantation of the prosthesis, and later by the tension of soft tissues surrounding it. Accurate post-TKA motion data obtained intraoperatively could be used not only to optimize implantation techniques from a kinematic standpoint, but also to improve prosthetic design. We therefore developed a system specifically geared to photostereometric measurement of 6 d.o.f. knee motion. A total of eight LEDs are mounted on the prosthetic components in two sets of four by means of connecting measuring-bows. The positions of the LEDs are detected in three-dimensions by two sets of three linear CCD cameras, located bilaterally relative to the knee. The position and orientation of the femoral component relative to the tibial one are estimated from the positions of all LEDs in the sense of least-squares. Based upon results of various accuracy validation experiments performed after precise camera calibration, static overall accuracy and spatial resolution were considered to lie within 0.52 and 0.11 mm, respectively, at any point on the femoral articular surface.

Arthroplasty, Replacement, Knee↗

PubMed2005

Donor-site morbidity of the pedicled rectus femoris muscle flap.

The rectus femoris muscle flap is well known for its reliable anatomy, the ease with which it can be harvested, and its great versatility. As a pedicled or free flap, it is used to cover soft-tissue defects and to recreate motor function. Although the muscle is very reliable, it is not well respected because of its assumed donor-site morbidity, such as weakened knee extension force and decreased range of motion of the knee. To date, these clinical assumptions have only rarely been quantified in terms of objective scores, concerning force deficit and functional or aesthetic outcome. From 1995 to 2002, the authors treated 24 patients with pedicled rectus femoris muscle flaps. Fourteen patients were followed up. Follow-up time ranged from 3 to 56 months postoperatively. The results were evaluated by a standard questionnaire in which pain in relation to walking distance, subjective feeling of weakness, sensibility disorders, everyday function, and aesthetic aspects were assessed. Range of motion in the hip and the knee was measured. For objective verification of a decrease of maximal voluntary contraction force of the remaining quadriceps muscle and for detecting differences in true muscular capacity and voluntary activation, 10 patients with unilateral rectus femoris flaps were tested using the twitch interpolation technique. The authors' patients assessed the remaining function and the aesthetic result of the thigh as at least satisfactory. Two patients complained about pain and weakness in the thigh. Eight patients reported hypesthesia in the lateral suprapatellar region. The maximal voluntary contraction and true muscular capacity values were reduced by 21.8 percent and 18 percent, respectively, when compared with the healthy leg. The range of motion in the knee and hip was not influenced by muscle harvesting. The twitch interpolation technique revealed a mild voluntary activation deficit, probably caused by inhibitory regulation in the spinal cord. In conclusion, donor-site morbidity of the rectus femoris muscle flap is evident but well compensated. There is no decrease in active range of motion in the knee and hip. Patient satisfaction with the functional and aesthetic outcome was high.

Adult↗

PubMed1995

The national settlement system of Italy at the beginning of the 1990s.

"The paper presents recent changes in the Italian settlement system and variations in urban hierarchical relations. Functional classification of towns and their new position compared with the situation at the beginning of [the] 1980s is...proposed in terms of three categories of cities, medium-sized towns and small towns. The analysis and verification attempted in this study have revealed a marked reduction in the number of small towns as well as shifts in functional characteristics within urban areas in Italy."

Classification↗

PubMed2004

Clustered components analysis for functional MRI.

A common method of increasing hemodynamic response (SNR) in functional magnetic resonance imaging (fMRI) is to average signal timecourses across voxels. This technique is potentially problematic because the hemodynamic response may vary across the brain. Such averaging may destroy significant features in the temporal evolution of the fMRI response that stem from either differences in vascular coupling to neural tissue or actual differences in the neural response between two averaged voxels. Two novel techniques are presented in this paper in order to aid in an improved SNR estimate of the hemodynamic response while preserving statistically significant voxel-wise differences. The first technique is signal subspace estimation for periodic stimulus paradigms that involves a simple thresholding method. This increases SNR via dimensionality reduction. The second technique that we call clustered components analysis is a novel amplitude-independent clustering method based upon an explicit statistical data model. It includes an unsupervised method for estimating the number of clusters. Our methods are applied to simulated data for verification and comparison to other techniques. A human experiment was also designed to stimulate different functional cortices. Our methods separated hemodynamic response signals into clusters that tended to be classified according to tissue characteristics.

Algorithms↗

PubMed1982

Some functional and morphological characteristics of an acutely dispersed purified cell suspension of rat lactotrophs prepared with Percoll.

A cell suspension containing more than 90% lactotrophs can be prepared from enzymically dispersed adenohypophyses obtained from male rats pretreated with estradiol. The lactotrophs are separated from the mixed cell population by centrifugation on a discontinuous density gradient prepared from a commercial preparation of colloidal silica (Percoll, Pharmacia). The method allows isopycnic separation of these delicate cells under very mild conditions; normal ionic strength and normal pH were maintained throughout the gradient, centrifugal acceleration did not exceed 1600 X g, and all procedures were done at room temperature. Histological verification that at least 90% of the cells were lactotrophs was done using specific immunoperoxidase staining. The functional capability of the lactotrophs was established by measuring the dose--response to the dopamine agonist bromocriptine and to thyrotropin-releasing hormone (TRH). Bromocriptine decreased spontaneous release in a dose-related way over the concentration range of 10(-10) to 10(-8) M. TRH, which causes an in vivo release of prolactin (PRL) in estrogen-primed rats, produced a dose-related increase in the release of PRL over the concentration range of 3 X 10(-10) to 3 X 10(-8) M after the high spontaneous release had been previously reduced by bromocriptine (3 X 10(-8) M).

Adrenocorticotropic Hormone↗