Spatial heterogeneity of inhibitory surrounds in the middle temporal visual area.

A recurrent theme in the organization of vertebrate visual cortex is that of receptive fields with an associated "silent" opponency component. In the middle temporal area (area MT), a cortical visual area involved in the analysis of retinal motion in primates, this opponency appears in the form of a region outside the classical receptive field (CRF) that in itself gives no response but suppresses responses to motion evoked within the CRF. This antagonistic motion surround has been described as very large and symmetrically arrayed around the CRF. On the basis of this view, the primary function of the surround has long been thought to consist of simple figure-ground segregation based on movement. We have made use of small stimulus patches to map the form and extent of the surround and find evidence that the surround inhibition of many MT cells is in fact confined to restricted regions on one side or on opposite sides of the CRF. Such regions endow MT cells with the ability to make local-to-local motion comparisons, capable of extracting more complex features from the visual environment, and as such, may be better viewed as intrinsic parts of the receptive field, rather than as separate entities responsible for local-to-global comparisons.     

Regional brain activity during shape recognition impaired by a scopolamine challenge to encoding

In the present positron emission tomography (PET) study, we examine the effect of a scopolamine-induced challenge to encoding upon the pattern of regional cerebral blood flow during recognition of a list of abstract visual shapes 3 days after encoding of these shapes. This study was conducted to test hypotheses concerning the fusiform and thalamic contributions to object recognition arising from a previous imaging study of impaired recognition. In that study, we demonstrated that activity in the fusiform cortex and the thalamus during shape recognition was modulated by memory challenges. These memory challenges included, on one hand, impaired storage as a consequence of diazepam administration during encoding, and, on the other hand, impaired retrieval caused by a perceptual challenge. Activation in the fusiform cortex decreased during impaired recognition, irrespective of the type of challenge. In contrast, thalamic activation increased only when the recognition deficit resulted from impaired memory storage. Based on these results, we hypothesized that fusiform activation during recognition reflects the matching of an incoming stimulus with a stored one, whereas thalamic activation reflects retrieval attempts. These hypotheses would receive considerable support if scopolamine, which also impairs memory storage, induced similar modulations of fusiform and thalamic activation. In the present study, we observed that a scopolamine challenge to encoding does indeed modulate the activity in the very same regions that were previously modulated by a diazepam challenge. Hence, a similar memory deficit, although primarily effected through different neurochemical pathways, was paralleled by a similar modulation of activity in the same set of nodes in the shape recognition network. In the fusiform cortex, scopolamine decreased recognition-related activity, as did the sensory challenge of retrieval. Furthermore, covariate analysis demonstrated that the level of fusiform activity linearly correlates with behavioural performance. In the thalamus, activation increased following impaired encoding. This is in accordance with the idea that enhanced thalamic activity reflects increased effort expended in retrieval. In addition, in the intraparietal sulcus, differential activation also increased following impaired memory storage, possibly reflecting enhanced visuospatial attention in an effort to compensate for impaired performance.     

H1-receptor blocker antihistamine, terfenadine durably influences the glucocorticoid receptor, and lymphocyte histamine content of weanling rats.

Hormonal imprinting takes place perinatally when a hormone and its maturing target receptor meet. As a consequence of imprinting the receptor accomplishes its maturation reaching the binding capacity characteristic to the adult age. In this critical period the presence of foreign molecules which are able to bind to the receptor can cause faulty imprinting with life-long consequences. In the recent years it was cleared that not only receptors are influenced by faulty imprinting, however, also the hormone production of the given cell. In addition imprinting was provoked at non-perinatal periods (adolescence and adult age) in cytogenic organs. In the present experiment the prolonged effect of a non-perinatal imprinting by an antihistamine to the histamine content of white blood cells and glucocorticoid receptors of liver and thymus was studied. Two weeks after 3-day terfenadine treatment at weaning, flow cytometry of peritoneal cells and blood lymphocytes for histamine, and receptor kinetic analysis of dexamethasone binding were done. Histamine content of blood lymphocytes and glucocorticoid receptor density of liver cells were significantly decreased. This means that a short treatment with a H(1)-receptor blocker antihistamine durably influences physiological indexes which were not known till now. This means that not only the acute effects, but the prolonged side-effects must be considered.     

PRENATAL DETECTION OF THE DELTA F 508 MUTATION USING FLUORESCENT PCR AND COMPARISON OF THE RESULTS WITH CONVENTIONAL PCR

Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasians. The most frequent mutation associated with cystic fibrosis has been identified as the 3 bp deletion Delta F 508. While existing polymerase chain reactions (PCR) (allele specific amplification) used to screen for CF are both sensitive and specific, we tested the prenatal application of fluorescent polymerase chain reaction and subsequent DNA fragment analysis that appears to be fast and sensitive. DNA samples (n=146) isolated from amniotic fluid (n=108), chorion villus biopsies (n=6), and human peripheral blood (n=32) were analyzed for the presence of Delta F 508 using the fluorescent method. Of these, 10 carriers of Delta F 508 mutation were detected. We achieved the same results with conventional PCR and fluorescent PCR.     

Expression of invasion markers CD44v6/v3, NM23 and MMP2 in laryngeal and hypopharyngeal carcinoma

Twelve laryngeal squamous cell carcinoma cases (7 laryngeal and 5 hypopharyngeal cancer; 15 samples) were analysed by immunohistochemistry for the expression of invasion markers CD44v6/v3, NM23 and matrix metalloproteinase, MMP2. The laryngeal epithelium showed CD44v6⁺v3⁺NM23^- /MMP2^- phenotype. When tumors were grouped into TNM categories the phenotype of the T2 and T3 tumors was similar, characterised by decreased CD44v3⁺ and lack of MMP2 expressions. Meanwhile the NM23 expression was more frequent in T3 tumors. In T4 stage the frequency of NM23 and MMP2 positive cases increased (5/6 and 4/6, respectively) but there was no correlation with the appearence of lymph node metastasis. Comparison of the phenotype of laryngeal and hypopharyngeal tumors, irrespective of the TNM stages, revealed characteristic differences: T2 stage laryngeal tumors showed decreased CD44v3 and occasional NM23 and MMP2 positivity, while in T3 stage these tumors were characterised by increased frequency of NM23 positivity. The phenotype of the hypopharyngeal tumors was significantly different with a high frequency of MMP2 positive cases (5/6) and NM23⁺1ow CD44v3⁺ phenotype. The sharp differences in the phenotypes of laryngeal and hypopharyngeal carcinomas were connected to the differences in their invasive capacity unlike to the size of the tumors, since the T4 stage hypopharyngeal tumors had a significantly smaller size than laryngeal ones, even at lower stages. This work was supported by the Hungarian Ministry of Welfare: ETT No: T-11-100/93     

Velocity discrimination in the cat

After considerable training (over 2 years) we measured the just noticeable differences (JNDs) in velocity as a function of reference velocity in three cats. The velocity discrimination curve plotting JNDs in velocity, expressed as Weber fractions as a function of reference velocity is U-shaped with optimal performance at reference speeds between 25 and 60 degrees/sec. The discrimination curve changed little with a tenfold change in slit width. Compared to the human velocity discrimination curve determined with the same test apparatus, the feline curve is narrower and shifted towards faster velocities and larger Weber fractions. These results support our specific linking hypothesis between velocity tuned cells as observed in cortical areas 17 and 18 of the cat, and velocity discrimination.