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PubMed2005

Local versus systemic effect of ovulation-inducing factor in the seminal plasma of alpacas.

BACKGROUND: Camelids are induced (reflex) ovulators. We have recently documented the presence of an ovulation-inducing factor (OIF) in the seminal plasma of alpacas and llamas. The objective was to test the hypothesis that OIF exerts its effect via a systemic rather than a local route and that endometrial curettage will enhance the ovulatory response to intrauterine deposition of seminal plasma in alpacas. METHODS: Female alpacas were assigned randomly to 6 groups (n = 15 to 17 per group) in a 2 x 3 factorial design to test the effect of seminal plasma versus phosphate-buffered saline (PBS) given by intramuscular injection, by intrauterine infusion, or by intrauterine infusion after endometrial curettage. Specifically, alpacas in the respective groups were given 1) 2 ml of alpaca seminal plasma intramuscularly, 2) 2 ml of PBS intramuscularly (negative control group), 3) 2 ml of alpaca seminal plasma by intrauterine infusion, 4) 2 ml of PBS by intrauterine infusion (negative control group), 5) 2 ml of alpaca seminal plasma by intrauterine infusion after endometrial curettage, or 6) 2 ml of PBS by intrauterine infusion after endometrial curettage (negative control group). The alpacas were examined by transrectal ultrasonography to detect ovulation and measure follicular and luteal diameters. RESULTS: Intramuscular administration of seminal plasma resulted in a higher ovulation rate than intrauterine administration of seminal plasma (93% versus 41%; P < 0.01), while intrauterine seminal plasma after endometrial curettage was intermediate (67%). None of the saline-treated controls ovulated. The diameter of the CL after treatment-induced ovulation was not affected by the route of administration of seminal plasma. CONCLUSION: We conclude that 1) OIF in seminal plasma effects ovulation via a systemic rather than a local route, 2) disruption of the endometrial mucosa by curettage facilitated the absorption of OIF and increased the ovulatory effect of seminal plasma, and 3) ovulation in alpacas is not associated with a physical stimulation of the genital tract, and 4) the alpaca represents an excellent biological model to evaluate the bioactivity of OIF.

Absorption↗
PubMed2005

Expectation of sensory stimulation modulates brain activation during visual motion stimulation.

The differential effects of visual hemifield motion stimulation during fixation of a stationary target were compared under two conditions: fixation straight ahead without any further instructions and fixation straight ahead with attention shifted to the "dark hemifield." Data from nine right-handed volunteers revealed that striate and extrastriate right hemispheric visual areas exhibited larger activations during left hemifield motion stimulation when attention was shifted to the right dark hemifield. Montreal Neurological Institute (MNI) coordinates (26, -98, -4) of the additional clusters activated in the latter condition corresponded best to the kinetic occipital region, which is known to process both shape and motion information, and to parts of area V3 posterior to V3A, which has been shown repeatedly to mediate motion perception. A simple computational model of transhemispheric visuovisual interaction is proposed. The basic mechanism of this model is a central predictor formed by a feedback loop that detects a mismatch between input to the two hemispheres. Predicted stimulation is then compared with the actual input. If the sensed motion of a visual hemifield is larger than the predicted net motion in the model, activation of the respective neural population is increased; conversely, a smaller actual motion causes less activation.

Adult↗
PubMed1995

Circulating chromogranin A and catecholamines in human fetuses at uneventful birth.

Chromogranin A (CGA), a large acidic 48-kD protein, costored and coreleased by exocytosis with catecholamines, has been shown to be a precursor of peptides that exert feedback regulatory control on catecholamine secretion. In plasma, CGA levels increase in response to a large-amplitude physical stimulation in adult subjects and may be related to catecholamine levels. Any skin information is not yet available when the sympathoadrenal system is highly active during birth. This activation is strongly related to parturition circumstances such as the mode of delivery. The aim of our study was to determine CGA plasma levels in infants delivered vaginally or by elective cesarean section and to investigate the possible correlation between CGA and catecholamine concentrations. Plasma levels of catecholamines (norepinephrine and epinephrine) and CGA were assessed by HPLC with electrochemical detection and immunoenzymology, respectively. CGA and norepinephrine concentrations were significantly higher (p < 0.0002 and p < 0.02) in infants vaginally born than in the group delivered by elective cesarean section. A significant relationship (p < 0.04) was found between CGA and norepinephrine levels. However, for epinephrine, no significant difference was found between both groups. These results demonstrate the fetus' ability to corelease CGA and norepinephrine massively in response to stress of birth.

Adult↗
PubMed2004

Cortical reorganization in malformations of cortical development: a magnetoencephalographic study.

BACKGROUND: The evaluation for epilepsy surgery of patients with malformations of cortical development (MCDs) in areas of clinically important cerebral function is a challenge because of the unpredictable localization of critical sensory, motor, and cognitive function. Magnetoencephalography (MEG) source localization of evoked fields can address whether functional reorganization of primary sensory modalities exists in MCDs. METHODS: Consecutive patients with MRI-demonstrated rolandic and calcarine cortex MCDs were identified who had a 148-channel whole-head MEG study to identify the localization of primary somatosensory and visual cortices. Reorganization was considered when localization contrasted that expected upon general anatomic or homuncular rules and was defined against controls. RESULTS: Twelve patients (n = 12) were studied. Six had focal cortical dysplasia, two had polymicrogyria and schizencephaly, and four had isolated polymicrogyria. In the patients with cortical dysplasias, the somatosensory cortices were identified outside the rolandic area. In the two patients with polymicrogyria and schizencephaly, the somatosensory cortices remained in the rolandic areas as long as the anatomy was not distorted by the presence of the schizencephalic cleft. In the patients with isolated polymicrogyria, the somatosensory cortex was mapped without evidence of reorganization. CONCLUSION: In patients with epileptic MCDs involving rolandic and calcarine regions, cortical function may be reorganized if the MCDs are due to an abnormal neuronal or glial proliferation (i.e., cortical dysplasia) but may not be in MCDs caused by abnormal cortical organization (i.e., polymicrogyria).

Adult↗
PubMed2004

The effect of tactile feedback on pantomime of tool use in apraxia.

OBJECTIVE: To investigate whether apraxic patients' better performance with real tools compared to miming is due to the tactile feedback provided by holding the tool. METHODS: Ten patients with aphasia and apraxia from left hemisphere damage were asked to demonstrate the use of 12 tools and objects under three conditions: miming with empty hands, miming with an implement shaped like the handle of the tool, and using the real tool with its corresponding object. RESULTS: Whereas real tool use was much better than pantomime in all patients, tactile feedback from the isolated handle facilitated miming only in some and deteriorated it in others so that across the group there was no significant improvement. CONCLUSIONS: The better performance of real than of pretended tool use does not depend on tactile feedback per se, but on the mechanical affordances and constraints of tools and objects transmitted by this feedback in real use. Tactile feedback deprived of these contents and restricted to the shape of the handle does not substantially help produce the appropriate action.

Adult↗
PubMed1994

Visual extinction.

Explore the source record for details and available documents.

Acoustic Stimulation↗
PubMed2003

A comparison of visual and haltere-mediated equilibrium reflexes in the fruit fly Drosophila melanogaster.

Flies exhibit extraordinary maneuverability, relying on feedback from multiple sensory organs to control flight. Both the compound eyes and the mechanosensory halteres encode angular motion as the fly rotates about the three body axes during flight. Since these two sensory modalities differ in their mechanisms of transduction, they are likely to differ in their temporal responses. We recorded changes in stroke kinematics in response to mechanical and visual rotations delivered within a flight simulator. Our results show that the visual system is tuned to relatively slow rotation whereas the haltere-mediated response to mechanical rotation increases with rising angular velocity. The integration of feedback from these two modalities may enhance aerodynamic performance by enabling the fly to sense a wide range of angular velocities during flight.

Animals↗
PubMed1976

Activities of antennal and ocellar interneurones in the protocerebrum of the honey-bee.

1. Unit responses to olfactory and mechanical stimuli of the antennae, and illumination of the ocelli, were recorded extracellularly in the protocerebrum of the honey-bee. 2. Bimodal units responded both to antennal and to ocellar stimuli; antennal units responded to the former and the ocellar units to the latter. Some antennal units responded to olfactory stimuli (olfactory units), and others responded to mechanical stimuli (mechanical units). 3. Ocellar units in the brain showed phasic responses at the start and/or cessation of illumination. Six types of responses were found. 4. About two-thirds of the bimodal units showed the same type of response to stimulation of the antennae as to stimulation of the ocelli. Most of them showed excitation by each stimulus. 5. Bimodal units were distributed around the alpha-lobe in the protocerebral lobe, whereas the antennal and the ocellar units were widely distributed. 6. By turning off the ocellar illumination, background discharge frequency, and the pattern and magnitude of responses to antennal stimuli, were changed. The activities of the ocellar units were altered by inputs from the antenna. 7. It was postulated that antennal and ocellar inputs converge and interact with each other in the protocerebral lobe of the honey-bee.

Action Potentials↗
PubMed1977

The mechanism for co-ordinating metachronal limb movements between joined male and female Artemia salina during precopulatory behaviour.

Male and female Artemia salina swim in tandem pairs before copulation and during this period the metachronal rhythms of the individuals are entrained. Artemia entrain to pulsatile water stimulation of the head at frequencies between 4 and 6 Hz. The antennules are mechano-sensitive. Antennular responsiveness to phasic input is very probably the actual mechanism by which interorganism co-ordination is achieved, as mechano-stimulation of other Artemia structures, electro-stimulation and photo-stimulation are ineffective modes of entraining metachronal movements.

Animals↗
PubMed1978

Patterns of activity and the effects of activation of the fast conducting system on the behaviour of unrestrained leeches.

1. The neural activity of the nerve cord of Hirudo medicinalis has been recorded in unrestrained animals by means of chronically implanted electrodes. 2. The Fast Conducting System (FCS) is inactive both in motionless animals and during various kinds of active behaviour (creeping, swimming, ventilation). 3. Photic and tactile stimuli applied to a motionless animal elicit a FCS discharge, which may be followed by generalized shortening. 4. Photic and tactile stimuli applied during ventilation are followed by a reversible blockade of the ongoing activity only if they are able to elicit a FCS discharge. No such effect is observed on swimming. 5. An explanation of these findings in terms of the known connexions of leech neurones is offered and a role in the control of reafferent inputs is attributed to the rectifying synapses made by FCS and T cells on the L motor neurones.

Animals↗
PubMed2006

The cutaneous rabbit illusion affects human primary sensory cortex somatotopically.

We used functional magnetic resonance imaging (fMRI) to study neural correlates of a robust somatosensory illusion that can dissociate tactile perception from physical stimulation. Repeated rapid stimulation at the wrist, then near the elbow, can create the illusion of touches at intervening locations along the arm, as if a rabbit hopped along it. We examined brain activity in humans using fMRI, with improved spatial resolution, during this version of the classic cutaneous rabbit illusion. As compared with control stimulation at the same skin sites (but in a different order that did not induce the illusion), illusory sequences activated contralateral primary somatosensory cortex, at a somatotopic location corresponding to the filled-in illusory perception on the forearm. Moreover, the amplitude of this somatosensory activation was comparable to that for veridical stimulation including the intervening position on the arm. The illusion additionally activated areas of premotor and prefrontal cortex. These results provide direct evidence that illusory somatosensory percepts can affect primary somatosensory cortex in a manner that corresponds somatotopically to the illusory percept.

Adult↗
PubMed1990

Unilateral bronchospasm during pleurodesis in an asthmatic patient.

A case of unilateral bronchospasm during pleurodesis in a patient with a history of recurrent pneumothorax and asthma is presented. The etiology of this event is not clear; however, it likely includes reflex parasympathetic bronchoconstriction due to physical stimulation of the pleural surface during pleurodesis. Treatment involved independent lung ventilation, corticosteroids, and aminophylline.

Adult↗