(1/2605) Complete compensation in skilled reaching success with associated impairments in limb synergies, after dorsal column lesion in the rat.
Each of the dorsal columns of the rat spinal cord conveys primary sensory information, by way of the medullary dorsal column nucleus, to the ventrobasal thalamus on the contralateral side; thus the dorsal columns are an important source of neural input to the sensorimotor cortex. Damage to the dorsal columns causes impairments in synergistic proximal or whole-body movements in cats and distal limb impairments in primates, particularly in multiarticulated finger movements and tactile foviation while handling objects, but the behavioral effects of afferent fiber lesions in the dorsal columns of rodents have not been described. Female Long-Evans rats were trained to reach with a forelimb for food pellets and subsequently received lesions of the dorsomedial spinal cord at the C2 level, ipsilateral to their preferred limb. Reaching success completely recovered within a few days of dorsal column lesion. Nevertheless, a detailed analysis of high-speed video recordings revealed that rotatory limb movements (aiming, pronation, supination, etc.) were irreversibly impaired. Compensation was achieved with whole-body and alternate limb movements. These results indicate the following: (1) in the absence of the dorsal columns, other sensorimotor pathways support endpoint success in reaching; (2) sensory input conveyed by the dorsal columns is important for both proximal and distal limb movements used for skilled reaching; and (3) detailed behavioral analyses in addition to endpoint measures are necessary to completely describe the effects of dorsal column lesions. (+info)
(2/2605) Blood flow influences vascular growth during tumour angiogenesis.
Many factors play a role in tumour angiogenesis. We observed growing tumour vessels in vivo to study the relationship between blood flow and vascular enlargement. Mammary adenocarcinoma was implanted into Fisher-344 rat with dorsal skin-fold transparent chambers. Vascular growth was observed and recorded on videotape through a microscope for 6 h. Vascular networks were photographed and traced every 30 min to identify changes over time. Tumour sections were stained with Masson's trichrome and anti-Factor VIII-related antigen. Tumour growth was rapid enough for differences to be seen each hour. Vessels with a high blood flow showed an increase in diameter within a few hours and new branches formed from these vessels. In contrast, vessels without an increase in blood flow showed no change in diameter. Vessels within the interstitium surrounding the tumour were lined by endothelium that was positive for anti-Factor VIII-related antigen staining. Vessels in the tumour had extremely rare endothelial cells detectable by Masson's trichrome or anti-Factor VIII-related antigen staining. In conclusion, increased blood flow may cause vascular enlargement and some primitive vessels seem to lack endothelium. (+info)
(3/2605) Biventricular repair approach in ducto-dependent neonates with hypoplastic but morphologically normal left ventricle.
OBJECTIVES: Increased afterload and multilevel LV obstruction is constant. We assumed that restoration of normal loading conditions by relief of LV obstructions promotes its growth, provided that part of the cardiac output was preoperatively supported by the LV, whatever the echocardiographic indexes. BACKGROUND: Whether to perform uni- or biventricular repair in ducto dependent neonates with hypoplastic but morphologically normal LV (hypoplastic left heart syndrome classes II & III) remains unanswered. Echocardiographic criteria have been proposed for surgical decision. METHODS: Twenty ducto dependent neonates presented with this anomaly. All had aortic coarctation associated to multilevel LV obstruction. Preoperative echocardiographic assessment showed: mean EDLW of 12.4 +/- 3.03 ml/m2 and mean Rhodes score of -1.73 +/-0.8. Surgery consisted in relief of LV outflow tract obstruction by coarctation repair in all associated to aortic commissurotomy in one and ASD closure in 2. RESULTS: There were 3 early and 2 late deaths. Failure of biventricular repair and LV growth was obvious in patients with severe anatomic mitral stenosis. The other demonstrated growth of the left heart. At hospital discharge the EDLVV was 19.4+/-3.12 ml/m2 (p = 0.0001) and the Rhodes score was -0.38+/-1.01 (p = 0.0003). Actuarial survival and freedom from reoperation rates at 5 years were 72.5% and 46%, respectively. CONCLUSIONS: Biventricular repair can be proposed to ducto dependent neonates with hypoplastic but morphologically normal LV provided that all anatomical causes of LV obstruction can be relieved. Secondary growth of the left heart then occurs; however, the reoperation rate is high. (+info)
(4/2605) In vivo targeting of acoustically reflective liposomes for intravascular and transvascular ultrasonic enhancement.
OBJECTIVES: The purpose of this study was to target acoustically reflective liposomes to atherosclerotic plaques in vivo for ultrasound image enhancement. BACKGROUND: We have previously demonstrated the development of acoustically reflective liposomes that can be conjugated for site-specific acoustic enhancement. This study evaluates the ability of liposomes coupled to antibodies specific for different components of atherosclerotic plaques and thrombi to target and enhance ultrasonic images in vivo. METHODS: Liposomes were prepared with phospholipids and cholesterol using a dehydration/ rehydration method. Antibodies were thiolated for liposome conjugation with N-succinimidyl 3-(2-pyridyldithio) propionate resulting in a thioether linkage between the protein and the phospholipid. Liposomes were conjugated to antifibrinogen or anti-intercellular adhesion molecule-1 (anti-ICAM-1). In a Yucatan miniswine model, atherosclerosis was developed by crush injury of one carotid and one femoral artery and ingestion of a hypercholesterolemic diet. After full plaque development the arteries were imaged (20-MHz intravascular ultrasound catheter and 7.5-MHz transvascular linear probe) after injection of saline, unconjugated liposomes and antibody conjugated liposomes. RESULTS: Conjugated liposomes retained their acoustically reflective properties and provided ultrasonic image enhancement of their targeted structures. Liposomes conjugated to antifibrinogen attached to thrombi and fibrous portions of the atheroma, whereas liposomes conjugated to anti-ICAM-1 attached to early atheroma. CONCLUSIONS: Our data demonstrate that this novel acoustic agent can provide varying targeting with different antibodies with retention of intravascular and transvascular acoustic properties. (+info)
(5/2605) Recovery of the vestibulocolic reflex after aminoglycoside ototoxicity in domestic chickens.
Avian auditory and vestibular hair cells regenerate after damage by ototoxic drugs, but until recently there was little evidence that regenerated vestibular hair cells function normally. In an earlier study we showed that the vestibuloocular reflex (VOR) is eliminated with aminoglycoside antibiotic treatment and recovers as hair cells regenerate. The VOR, which stabilizes the eye in the head, is an open-loop system that is thought to depend largely on regularly firing afferents. Recovery of the VOR is highly correlated with the regeneration of type I hair cells. In contrast, the vestibulocolic reflex (VCR), which stabilizes the head in space, is a closed-loop, negative-feedback system that seems to depend more on irregularly firing afferent input and is thought to be subserved by different circuitry than the VOR. We examined whether this different reflex also of vestibular origin would show similar recovery after hair cell regeneration. Lesions of the vestibular hair cells of 10-day-old chicks were created by a 5-day course of streptomycin sulfate. One day after completion of streptomycin treatment there was no measurable VCR gain, and total hair cell density was approximately 35% of that in untreated, age-matched controls. At 2 wk postlesion there was significant recovery of the VCR; at this time two subjects showed VCR gains within the range of control chicks. At 3 wk postlesion all subjects showed VCR gains and phase shifts within the normal range. These data show that the VCR recovers before the VOR. Unlike VOR gain, recovering VCR gain correlates equally well with the density of regenerating type I and type II vestibular hair cells, except at high frequencies. Several factors other than hair cell regeneration, such as length of stereocilia, reafferentation of hair cells, and compensation involving central neural pathways, may be involved in behavioral recovery. Our data suggest that one or more of these factors differentially affect the recovery of these two vestibular reflexes. (+info)
(6/2605) Electrophysiological and behavioral analysis of lip touch as a component of the food stimulus in the snail Lymnaea.
Electrophysiological and video recording methods were used to investigate the function of lip touch in feeding ingestion behavior of the pond snail Lymnaea stagnalis. Although this stimulus was used successfully as a conditioning stimulus (CS) in appetitive learning experiments, the detailed role of lip touch as a component of the sensory stimulus provided by food in unconditioned feeding behavior was never ascertained. Synaptic responses to lip touch in identified feeding motoneurons, central pattern generator interneurons, and modulatory interneurons were recorded by intracellular electrodes in a semi-intact preparation. We showed that touch evoked a complex but characteristic sequence of synaptic inputs on each neuron type. Touch never simply activated feeding cycles but provided different types of synaptic input, determined by the feeding phase in which the neuron was normally active in the rhythmic feeding cycle. The tactile stimulus evoked mainly inhibitory synaptic inputs in protraction-phase neurons and excitation in rasp-phase neurons. Swallow-phase neurons were also excited after some delay, suggesting that touch first reinforces the rasp then swallow phase. Video analysis of freely feeding animals demonstrated that during normal ingestion of a solid food flake the food is drawn across the lips throughout the rasp phase and swallow phase and therefore provides a tactile stimulus during both these retraction phases of the feeding cycle. The tactile component of the food stimulus is strongest during the rasp phase when the lips are actively pressed onto the substrate that is being moved across them by the radula. By using a semi-intact preparation we demonstrated that application of touch to the lips during the rasp phase of a sucrose-driven fictive feeding rhythm increases both the regularity and frequency of rasp-phase motoneuron firing compared with sucrose applied alone. (+info)
(7/2605) Chlorpromazine inhibits miniature GABAergic currents by reducing the binding and by increasing the unbinding rate of GABAA receptors.
Recent studies have emphasized that nonequilibrium conditions of postsynaptic GABAA receptor (GABAAR) activation is a key factor in shaping the time course of IPSCs (Puia et al., 1994; Jones and Westbrook, 1995). Such nonequilibrium, resulting from extremely fast agonist time course, may affect the interaction between pharmacological agents and postsynaptic GABAARs. In the present study we found that chlorpromazine (CPZ), a widely used antipsychotic drug known to interfere with several ligand and voltage-gated channels, reduces the amplitude and accelerates the decay of miniature IPSCs (mIPSCs). A good qualitative reproduction of the effects of CPZ on mIPSCs was obtained when mIPSCs were mimicked by responses to ultrafast GABA applications to excised patches. Our experimental data and model simulations indicate that CPZ affects mIPSCs by decreasing the binding (kon) and by increasing the unbinding (koff) rates of GABAARs. Because of reduction of kon by CPZ, the binding reaction becomes rate-limiting, and agonist exposure of GABAARs during mIPSC is too short to activate the receptors to the same extent as in control conditions. The increase in unbinding rate is implicated as the mechanism underlying the acceleration of mIPSC decaying phase. The effect of CPZ on GABAAR binding rate, resulting in slower onset of GABA-evoked currents, provides a tool to estimate the speed of synaptic clearance of GABA. Moreover, the onset kinetics of recorded responses allowed the estimate the peak synaptic GABA concentration. (+info)
(8/2605) Parallel information processing in the dorsal striatum: relation to hippocampal function.
We investigated the effects of localized medial and lateral CPu lesions and fornix/fimbria lesions on responses to a local cue and to behavior based on cognitive-spatial information in the water maze. Rats were trained concurrently on the cue (visible platform) and spatial (submerged platform) components of the task, followed by a test in which responses to the two types of information were dissociated by a measure of competing response tendencies. Bilateral lesions of lateral CPu did not affect acquisition of either cue or spatial responding but produced a preference for the spatial response on the competition test. Bilateral lesions of the medial CPu retarded but did not prevent learning both components and produced a preference for the cue response on the competition test. The latter effect was accompanied by increased thigmotaxis (swimming in the periphery of the pool), primarily during the early acquisition trials, which was attributed to an impaired ability to respond to learned spatial information. Fornix/fimbria lesions prevented spatial but not cue learning and produced a preference for the cue response on the competition test. Asymmetric lesions (unilateral hippocampus and contralateral medial CPu) produced mild retardation of acquisition of both the cue and spatial tasks and a preference for the cue response on the competition test. These findings dissociate the functions of the lateral and medial CPu and suggest that the hippocampus and medial CPu may be parts of a system that promotes responding based on learned cognitive-spatial information, particularly in competitive cue-place response situations. (+info)