329 research outputs found
Fractional cable models for spiny neuronal dendrites
Cable equations with fractional order temporal operators are introduced to model electrotonic properties of spiny neuronal dendrites. These equations are derived from Nernst-Planck equations with fractional order operators to model the anomalous subdiffusion that arises from trapping properties of dendritic spines. The fractional cable models predict that postsynaptic potentials propagating along dendrites with larger spine densities can arrive at the soma faster and be sustained at higher levels over longer times. Calibration and validation of the models should provide new insight into the functional implications of altered neuronal spine densities, a hallmark of normal aging and many neurodegenerative disorders
Toekomstschets Ambrosia
De hooikoortsplant ambrosia breidt zich in Nederland uit. De pollenconcentratie is tot nu toe echter nog laag. Uit onderzoek van PPO blijkt dat 70% van het Nederlandse landoppervlak geschikt is voor vestiging van ambrosia en dat Nederland over 10 jaar bij vrijwel alle klimaatscenario’s in de risicozone terecht komt. Naar verwachting kan 10 tot 20% van de Nederlandse bevolking gezondheidsklachten ontwikkelen na blootstelling aan ambrosiapolle
Multiple Disguises for the Same Party: The Concepts of Morphogenesis and Phenotypic Variations in Cryptococcus neoformans†
Although morphological transitions (such as hyphae and pseudohyphae formation) are a common feature among fungi, the encapsulated pathogenic yeast Cryptococcus neoformans is found during infection as blastoconidia. However, this fungus exhibits striking variations in cellular structure and size, which have important consequences during infection. This review will summarize the main aspects related with phenotypic and morphological variations in C. neoformans, which can be divided in three classes. Two of them are related to changes in the capsule, while the third one involves changes in the whole cell. The three morphological and phenotypic variations in C. neoformans can be classified as: (1) changes in capsule structure, (2) changes in capsule size, and (3) changes in the total size of the cell, which can be achieved by the formation of cryptococcal giant/titan cells or microforms. These changes have profound consequences on the interaction with the host, involving survival, phagocytosis escape and immune evasion and dissemination. This article will summarize the main features of these changes, and highlight their importance during the interaction with the host and how they contribute to the development of the disease
Upper eyelid motility in blepharoptosis and in the aging eyelid
PURPOSE. To study the metrics of lid saccades in blepharoptosis and to
distinguish any differences in the dynamics of eyelid movements that are
related to the cause of blepharoptosis and to aging. METHODS. The lid and
vertical eye saccades of 7 patients with congenital blepharoptosis and
those of 18 patients with aponeurogenic blepharoptosis, either
involutional or rigid-contact-lens-induced, were recorded with
electromagnetic search coils. For each saccade, two parameters were
assessed: amplitude and peak velocity. Two age-matched control groups were
assessed in the same manner. Repeated measures analysis of variance was
used to investigate any observed differences between the included groups.
RESULTS. Congenital and rigid-contact-lens-induced blepharoptosis were
readily distinguishable from one another, as well as from the age-matched
control group, in both lid saccadic amplitude and peak velocity. For
example, 40 degrees downward lid saccades in the congenital blepharoptosis
group averaged 22.9 degrees +/- 4.0 degrees (SD), whereas 30.0 degrees +/-
4.7 degrees lid saccades were made by the age-matched control group. The
subjects in the two groups with aponeurogenic blepharoptosis also made lid
saccades that were distinctive for their group (P: < 0.02), in both
amplitude and peak velocity. For 40 degrees downward saccades in
involutional and rigid-contact-lens-induced blepharoptosis, lid saccadic
amplitude averaged 32.7 degrees +/- 4.3 degrees and 40.3 degrees +/- 3.5
degrees, respectively. Lid saccadic peak velocity declined significantly
with age. Lid saccadic peak velocity for 40 degrees upward saccades in the
younger control group averaged 401.7 +/- 11.4 deg/sec, whereas the older
control group achieved an average peak velocity of 360.7 +/- 60.4 deg/sec.
The lid saccadic dynamics in the involutional blepharoptosis group proved
to be similar (P: > 0.05) in saccadic amplitude and peak velocity to those
of age-matched controls. CONCLUSIONS. In diffe
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