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PubMed1992

Visual demonstration of the limb-forming zone in the chick embryo lateral plate.

The present study was undertaken to determine whether a visible Wolffian ridge, distinct from the lateral fold, can be identified in chick embryos. Ectoderm thickness was measured in stage 11-17 chick embryos. There was a general trend, from thin ectoderm in the midline, to an ectodermal thickening over the somites, intermediate mesoderm, and lateral plate. Other embryos were cut from the yolk, pinned out, and photographed. The lateral fold was then eliminated, and the embryo was rephotographed. The photographs reveal a definite opaic zone, distinct from the lateral fold, in stage 11-18 chick embryos. Furthermore, there is a direct correlation between the opacity of this cellular band and the limb-forming potential of grafted wing, flank, and leg regions (see Stephens et al., '89). At stages 11-14, the wing, flank, and leg exhibit a uniform opacity, and a uniform capacity for limb formation when grafted to a host celom. From stage 15 to stage 18, the opacity in the flank diminishes, and its limb-forming capability disappears. This study demonstrates the presence of an opaic zone, which we have called the limb-forming zone (LFZ) along the lateral side of early chick embryos, which is independent of the lateral fold, is not as extensive as the lateral plate, and is not simply associated with ectodermal thickening, but which is directly correlated with limb-forming potential in the lateral plate.

Animals↗

PubMed1993

Dynamic elongation behavior in the medial collateral and anterior cruciate ligaments during lateral impact loading.

The objectives of this experimental study were to determine (a) how quickly the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) elongate when a lateral impact force is imparted to the knee and if a person can react rapidly enough to provide protective muscle forces in the case of such an impact, (b) if the MCL and the ACL elongate simultaneously during a lateral impact, and (c) if resection of the ACL affects elongation of the MCL during a lateral impact. Eight whole-leg cadaver specimens were used. Each leg was mounted vertically in a testing-frame with the knee in 0 and 30 degrees of flexion. A submaximal impact was delivered from the lateral side by a pendulum instrumented with a force transducer. Elongation of the midsubstance of the MCL and the ACL was measured with Hall-effect displacement transducers. The ACL was resected and the entire test sequence was repeated. Following a lateral impact, elongation of the MCL and ACL reached peak values by 70 ms. This study indicated that contraction of the leg musculature would not protect the MCL and ACL from injury when a lateral impact load is applied to the knee. The MCL and the ACL never elongated simultaneously during a lateral impact. After lateral impact loading, the time required to reach maximum elongation (peak delay) averaged 52 ms in the anterior MCL fibers and 61 ms in the ACL when the knee was in 0 degrees of flexion. At 30 degrees of flexion, the peak delay averaged 38 ms in the anterior MCL fibers and 22 ms in the ACL.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1997

Lateralized changes in regional cerebral blood flow during performance of verbal and facial recognition tasks: correlations with performance and "effort".

Functional neuroimaging has been used to investigate neural substrates of mnemonic processes, and cerebral blood flow (CBF) measures have been sensitive to activation with memory tasks. Studies of memory with two-dimensional 133Xenon clearance techniques found that word and face recognition tasks produced contralateral CBF changes in mid-temporal cortical regions. This study replicated the activation paradigm, expanding to the three-dimensional resolution of positron emission tomography (PET). Word and face recognition, and a control baseline task were administered to 19 healthy right-handed volunteers (11 men, 8 women) during successive 10 min PET 15O-water measures of CBF. Quantitative CBF rates were calculated with the arterial input function and the equilibrium model. Redistributions of blood flow were compared across tasks-using both absolute and relative (region/ whole brain) CBF. Replicating the 133Xenon clearance findings, CBF was "appropriately" lateralized during task performance (left-right for words > left-right for faces) in the mid-temporal region. Contrary to predictions, the recognition tasks did not activate expected mesolimbic or prefrontal areas. The task-induced CBF changes also correlated with performance. Bilateral CBF in mid-temporal and parahippocampal gyrus regions of interest correlated with the ability to correctly identify word targets (sensitivity). Left-lateralized CBF in the amygdala and hippocampus correlated with better word sensitivity as well as specificity (ability to correctly reject foils). Complementally, right-lateralized CBF in the parahippocampal gyrus correlated with better face specificity performance. In addition, left-lateralized CBF in the amygdala and right-lateralized CBF in the parahippocampal gyrus and hippocampus correlated with "mental effort" indices (task performance relative to basal ability) for word and face memory tasks, respectively. Thus, whereas this recognition task showed the expected lateralized increase in the mid-temporal region and not in frontal and limbic areas, lateralized activation in some of these areas was associated with better performance. Exploratory analyses on other regions showed lateralized changes in one additional temporal region, the occipital-temporal, and several limbic regions.

Adult↗

PubMed1996

When neural crest and placodes collide: interactions between melanophores and the lateral lines that generate stripes in the salamander Ambystoma tigrinum tigrinum (Ambystomatidae).

A prominent element of the early larval pigment pattern in the salamander Ambystoma tigrinum tigrinum (family Ambystomatidae) is a horizontal stripe over the lateral surface of the myotomes where otherwise abundant, neural crest-derived melanophores are not found. This study examines the formation of this "melanophore-free region". When the trunk lateral lines were ablated (by removing cranial lateral line placodes), the melanophore-free region did not form; instead, melanophores populated the middle of the flank and the distribution of yellow, neural chest-derived zanthophores was perturbed. Time-lapse videomicrography demonstrated that during normal development, the melanophore-free region is established because melanophores retreat from the midbody lateral line primordium as it migrates caudally along the inner side of the epidermis. Melanophores do not repopulate the middle of the flank after primordium migration and heterochronic grafting experiments suggest that extracellular factors contribute to maintaining the melanophore-free region during these later stages. Finally, photographic series, microsurgical manipulations, electron microscopy, and staining for molecules of the extracellular matrix (peanut agglutinin-binding components, tenascin, chondroitin sulfate proteoglycans, fibronectin, laminin) suggest that several factors contribute to establishing and maintaining the melanophore-free region, including steric effects of the lateral lines, interactions between melanophores and xanthophores, lateral line-dependent alterations of the subepidermal basement membrane, and a general elaboration of the extracellular matrix. Lateral line effects on melanophores are inferred to be a shared, ancestral feature of pigment pattern development for the families Ambystomatidae and Salamandridae (D.M. Parichy, Dev. Biol. 174, 265-282. 1996). The results of this study thus provide insights into a phylogenetically primitive mechanism for stripe formation, and a context for interpreting evolutionary innovations in pattern-forming mechanisms.

Ambystoma↗

PubMed2002

A direct test for lateralization of language activation using fMRI: comparison with invasive assessments in children with epilepsy.

This study introduces a direct method of assessing cerebral lateralization for language based on fMRI activation. The method, derived from a voxel-based morphometry study by C. H. Salmond et al. (2000, Hum. Brain Mapping 11, 223-232), bases lateralization on the direct statistical comparison of the magnitude of task-induced activation in homotopic regions of the two hemispheres. Lateralization results obtained with this direct method were compared to those obtained with a widely used method which involves the calculation of a laterality index (LI) based on the number of significantly activated voxels in the inferior frontal gyrus of each hemisphere. In order to compare the validity of the two methods, a covert verb-generation task was performed by eight children with epilepsy whose language lateralization was examined using invasive techniques. Lateralization results derived from fMRI activation showed that the calculation of a LI presented some limitations. Importantly, the LI value was dependent on the activation threshold chosen to calculate that LI. As a consequence, the correlation between the LI and the invasive methods could vary with the chosen threshold. By contrast, the proposed direct method gave some indication of the reliability of the lateralization and provided results that, in all eight children, were consistent with those obtained using invasive techniques. It is suggested that the direct method could be used in future fMRI studies to establish hemispheric lateralization for cognitive functions.

Adolescent↗

PubMed1975

Dorsal column nuclei afferents in the lateral funiculus of the cat: distribution pattern and absence of sprouting after chronic deafferentation.

In adult cats the successive degeneration technique has been used to demonstrate the existence and distribution pattern of lateral funicular fibers to the dorsal column nuclei (DCN) originating from the brachial and thoracic cord. In a first operation, interruption of the dorsal columns at appropriate cervical levels and of the lateral funiculus at low thoractic levels was performed. Thirteen months later, a lesion was made in the lateral funiculus at upper brachial or uppermost thoracic levels. Fiber degeneration in the DCN consequent to this second operation is not contaminated by damage to dorsal roots or by interruption of lateral funicular afferents from lumbo-sacro-coccygeal segments. All animals were sacrificed 7 days after the second operation. Serial sections through the medulla oblongata, impregnated with the Fink-Heimer technique, show that fibers ascending from brachial levels in the dorsal part of the lateral funiculus reach the cuneate nucleus either by a dorsomedial route through the tegmentum or by cuneate nucleus either by a dorsomedial route through the tegmentum or by ascending in the restiform body. Degenerated fibers distribute selectively to the rostral part, and to a lesser extent to the base of the cuneate nucleus. Only very few fibers ascending from thoracic levels in the lateral funiculus distribute to the DCN. In another group of animals, not previously deafferented, a lesion of the lateral funiculus was made at upper brachial levels. This group served as a control to assess whether sprouting had occurred in the chronic preparations as a consequence of the long-term deafferentation. Comparison of the results in the cuneate nucleus of the two groups of animals shows no difference in the pattern of distribution or in the amount of degenerated fibers in this nucleus. These observations are discussed in relation to the question of collateral sprouting in the adult mammalian central nervous system.

Animals↗

PubMed1995

Ultrastructure of cerebrospinal fluid-contacting neurons immunoreactive to vasoactive intestinal peptide and properties of the blood-brain barrier in the lateral septal organ of the duck.

Immuno-electron-microscopic investigations of cerebrospinal fluid (CSF)-contacting neurons immunoreactive to vasoactive intestinal peptide in the duck lateral septum have revealed that this cell type gives rise to an adventricular dendrite terminating with a bulbous swelling in the lateral ventricle. The swelling bears a cilium and contains mitochondria and immunolabeled dense-core vesicles. Two types of processes emerge from the basal part of the perikaryon. The first has a large diameter, contains diffusely distributed immunoreaction, and receives synaptic input, indicating that this process is a basal dendrite. The other type is of a beaded appearance, displays immunolabeled dense-core vesicles, and represents the axon of the CSF-contacting neuron. VIP-immunoreactive terminal formations are located within the neuropil of the lateral septum and the nucleus accumbens. Some of them form synaptic contacts with immunonegative profiles. No VIP-immunoreactive terminal formations are seen in the perivascular spaces of the lateral septum. Tracer experiments with horseradish peroxidase have revealed that the blood-brain barrier is lacking in the lateral septal organ and nucleus accumbens of the duck. Capillaries, arterioles, and venoles of this region are coated by nonfenestrated endothelial cells connected by "leaky" junctions, allowing the tracer to penetrate from the lumen into the perivascular space and further into the intercellular clefts of the neuropil. Our immuno-electron-microscopic investigations show that VIP-immunoreactive CSF-contacting neurons of the lateral septum closely resemble CSF-contacting neurons occurring in other brain regions, e.g., the hypothalamus. The arrangement of VIP-immunoreactive terminal formations suggests that, in the lateral septum, the VIP-like neuropeptide serves as a neurotransmitter (-modulator). The lack of a blood-brain barrier in the lateral septal organ and the nucleus accumbens raises the possibility that this region is a window in the avian brain allowing exchange of information between the central nervous system and the bloodstream; it thus resembles a circumventricular organ.

Animals↗

PubMed1994

Electron-microscopic investigations of vasoactive intestinal peptide (VIP)-like immunoreactive terminal formations in the lateral septum of the pigeon.

Vasoactive intestinal peptide (VIP)-like immunoreactive terminal fields were examined in the lateral septum of the pigeon by means of immunocytochemistry. According to light-microscopic observations, these projections originated from VIP-like immunoreactive cerebrospinal fluid (CSF)-contacting neurons, which are located in the ependymal layer of the lateral septum and form a part of the lateral septal organ. The processes of these cells gave rise to dense terminal-like structures in the lateral septum. Pre-embedding immuno-electron microscopy revealed that VIP-like immunoreactive axon terminals had synaptoid contacts with perikarya of small VIP-immunonegative neurons of the lateral septum, which were characterized by an invaginated nucleus, numerous mitochondria, a well-developed Golgi apparatus, endoplasmic reticulum and a small number of dense-core vesicles (about 100 nm in diameter). VIP-like immunoreactive axons were also seen in contact with immunonegative dendrites in the lateral septum. In both axosomatic and axodendritic connections, VIP-like immunoreactive presynaptic terminals contained large dense-core vesicles, clusters of small vesicles and mitochondria. These findings suggest that VIP-immunoreactive neurons of the lateral septal organ project to small, presumably peptidergic nerve cells of the lateral septum and that the VIP-like neuropeptide serves as a neuromodulator (-transmitter) in this area.

Animals↗

PubMed1997

Lateralized processing of speech prosodies in the temporal cortex: a 3-T functional magnetic resonance imaging study.

Prosodic modulation of speech provides information about emotional states of speakers (affective prosodies) or serves as syntactic markers to change linguistic aspects of speech (linguistic prosodies). Previous electrophysiological investigations and studies on patients with right or left hemisphere damage showed nonuniform results with respect to lateralization of prosodic processing. In this study 20 healthy right-handed volunteers were investigated with functional magnetic resonance imaging of the acoustically responsive areas on the supratemporal plane while detecting phonemes as control targets or prosodies in strings of nonsense syllables and adjectives, the latter randomly intonated in a declarative, interrogative, commanding, happy, or sad fashion. In control task A the phoneme /a/ was detected in the syllables. In control task B the phoneme /a/ was detected in the adjectives, and in the experimental task C the sad intonations (affective) and in the experimental task D the interrogative intonations (linguistic) had to be detected in the same material. In task A intensity-weighted volumes of activated voxels were not different in the two hemispheres (laterality index 0). In task B with an irrelevant phoneme detection with respect to prosodic material, the population split into two subgroups with similar right or left hemispheric lateralization of activity leading to an absolute laterality index of 26.8 across all subjects. During detection of affective prosodies (task C), lateralization was maintained yet the absolute laterality index reduced to 14.5, while there was no lateralization during detection of linguistic prosodies. The sum of activations in the two hemispheres was the same across all tasks and subgroups, which suggests that the lateralizations occurring with presentation and detection of prosodic material depend on a redistribution of activity between hemispheres.

Adolescent↗

PubMed2007

Dynamic measurement of patellofemoral kinematics and contact pressure after lateral retinacular release: an in vitro study.

The purpose of this study was to investigate the influence of lateral retinacular release and medial and lateral retinacular deficiency on patellofemoral position and retropatellar contact pressure. Human knee specimens (n = 8, mean age = 65 SD 7 years, all male) were tested in a kinematic knee-simulating machine. During simulation of an isokinetic knee extension cycle from 120 degrees to full extension, a hydraulic cylinder applied sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm. The position of the patella was measured using an ultrasound based motion analysis system (CMS 100, Zebris). The amount of patellofemoral contact pressure and its pressure distribution was measured using a pressure sensitive film (Tekscan, Boston). Patellar position and contact pressure were first investigated in intact knee conditions, after a lateral retinacular release and a release of the medial and lateral retinaculum. After lateral retinacular release the patella continuously moved from a significant medialised position at flexion (P = 0.01) to a lateralised position (P = 0.02) at full knee extension compared to intact conditions, the centre of patellofemoral contact pressure was significantly medialised (0.04) between 120 degrees and 60 degrees knee flexion. Patellofemoral contact pressure did not change significantly. In the deficient knee conditions the patella moved on a significant lateralised track (P = 0.04) through the entire extension cycle with a lateralised centre of patellofemoral pressure (P = 0.04) with a trend (P = 0.08) towards increased patellofemoral pressure. The results suggest that lateral retinacular release did not inevitably stabilise or medialise patellar tracking through the entire knee extension cycle, but could decrease pressure on the lateral patellar facet in knee flexion. Therefore lateral retinacular release should be considered carefully in cases of patellar instability.

Aged↗

PubMed2006

The medial branch of the lateral branch of the posterior ramus of the spinal nerve.

UNLABELLED: In the needle insertion of epidural anesthesia with the paramedian approach, the needle can pass through the longissimus muscle in the dorsum of the patients. When the needle touches a nerve in the muscles, the patients may experience pain in the back. Obviously, the needle should avoid the nerve tract. To provide better anesthetic service, analysis of the structure and where the concerned nerves lie in that region is inevitable. MATERIAL AND METHOD: We studied five cadavers in this study. Two cadavers were fixed with Thiel's method. With these cadavers, we studied the nerve running of the posterior rami of the spinal nerve from the nerve root to the distal portion. Three of them were used for the study of transparent specimen, with which we studied the course and size of the nerve inside the longissimus muscle. RESULTS: We observed there were three branches at the stem of the posterior rami of the spinal nerves between the body segment T3 and L5, i.e. medial branch, medial branch of the lateral branch and lateral branch of the lateral branch. The medial branch of the lateral branch supplied to the longissimus muscle. With the transparent specimen, we found that there were different nerve layouts between the upper thoracic, lower thoracic, upper lumbar, and lower lumbar segments in the medial branch of the lateral branch in the longissimus muscle. In the lower thoracic and upper lumbar segments, the medial branch of the lateral branch of the upper lumbar segments produced layers nerve network in the longissimus muscle. L1 and L2 nerves were large in size in the muscle. CONCLUSION: In the upper lumbar segments the medial branch of the lateral branch of the posterior rami of the spinal nerve produced dense network in the longissimus muscle, where the epidural needle has high possibility to touch the nerve. Anesthetists have to consider the existence of the medial branch of the lateral branch of the posterior rami of the spinal nerve when they insert the needle in the paramedical approach to the spinal column.

Cadaver↗

PubMed1999

Projections of the mediolateral part of the lateral septum to the hypothalamus, revealed by Fos expression and axonal tracing in rats.

The lateral septum participates in a variety of functions involving the hypothalamus. The present study investigated the effect of an electrical stimulation of the mediolateral part of the lateral septum on the expression of Fos in the hypothalamic nuclei by using immunohistochemical methods in anaesthetised and free-moving rats. We analysed in another series of rats the direct projections of the lateral septum by axonal anterograde tracing with biotinylated dextran-amine. Tracing was used in combination with Fos labelling in a third series of animals. Stimulation induced an expression of Fos in neurones located in anteroventral and anterodorsal preoptic nuclei, medial preoptic area, anterior hypothalamic nucleus, subparaventricular zone, dorsomedial nucleus, lateral hypothalamic area and mammillary nucleus. The distribution of Fos-immunoreactive neurones conforms to the topographic organisation of direct projections from the lateral septum, as revealed by axonal tracing. These results suggest that the lateral septum activates definite hypothalamic structures by a direct link. Some structures displayed substantial Fos labelling whereas they received a slight, or no projection, from the lateral septum. This was particularly evident in the core of the ventromedial nucleus and in areas known to contain tubero-infundibular neurones. This observation suggests that the lateral septum may also exert an indirect control, via polysynaptic links, on hypothalamic structures including nuclei involved in neuroendocrine mechanisms.

Animals↗

PubMed1983

The origin of the vasopressinergic and oxytocinergic innervation of the rat brain with special reference to the lateral septum.

The origin of the vasopressin-containing fibers in the rat lateral septum was studied by means of lesioning specific areas, in which vasopressin-containing cells are found, or by surgically separating the septum from the underlying structures. Following these procedures sections of the brain were stained immunocytochemically for the presence of vasopressin. In addition, retrograde labeling tracers were injected in the lateral septum. Lesioning of the paraventricular nucleus did not result in the disappearance of vasopressin fibers from the lateral septum, nor from the various other areas studied. It did, however, cause the disappearance of fibers from the nucleus of the solitary tract and the nucleus ambiguus. By contrast, after the same lesion practically the whole oxytocinergic innervation of the brain disappeared. Injection of tracers into the lateral septum revealed retrograde labeled cells, e.g. in the bed nucleus of the stria terminalis, but not in the paraventricular and supraoptic nucleus. Horizontal cuts under the lateral septum, intersecting the diagonal band of Broca, resulted in a dramatic decrease of the vasopressin fibers in the lateral septum, suggesting that the fibers enter the septum via this structure. Moreover, since the vasopressin fiber density was found to decrease drastically in the lateral septum after lesioning the bed nucleus of the stria terminalis, the vasopressin cells found in this area are probably the source of these fibers. Other areas where fibers were seen to decrease after lesions of the bed nucleus are the diagonal band of Broca, the area of the anterior amygdala, the lateral habenular nucleus, the periventricular gray, and the locus coeruleus.

Animals↗

PubMed1989

Differential regulation of androgen receptors in the separate rat prostate lobes: androgen independent expression in the lateral lobe.

In order to understand the hormonal regulation of androgen receptors (AR) in the separate lobes of the rat prostate gland, the present study examined AR levels in the ventral, dorsal and lateral prostate lobes as a function of androgen withdrawal to complete prostatic regression and subsequent testosterone replacement. In the intact rat, the 3 prostate lobes contained significantly different amounts of androgen binding sites. Mean number of total cellular AR in the ventral, dorsal and lateral lobes was 7370, 1690, and 1015 fm/mg DNA, respectively. These receptors were primarily localized within the nuclear fraction of homogenized tissue: ventral, 86%; dorsal, 83%; and lateral, 100% nuclear localization. Androgen withdrawal was initiated via castration and rats were sacrificed 1, 2, 3, 5, 7, 10 and 14 days thereafter. Nuclear AR levels fell rapidly to 5, 24 and 30% of intact values by 48 h in the ventral, dorsal and lateral lobes, respectively. Levels of nuclear AR continued to decline in the ventral and dorsal lobes to undetectable levels by Day 10. In marked contrast, lateral lobe nuclear AR began to increase on Day 3 postcastration, reaching intact values by Day 7 and 133% intact levels by Day 14. Cytosolic AR in the ventral and dorsal lobes initially increased following castration, but subsequently declined to low levels by Day 14. Cytosolic AR were not detectable in the lateral prostate at any time point following castration. To determine the nuclear AR response to testosterone at this time, 14 day castrate rats were given 2 cm testosterone implants and sacrificed 1, 3, 5, 7, 10 and 14 days thereafter. As expected, nuclear AR rapidly returned in the ventral and dorsal lobes by Day 1 and reached a plateau by Day 5. A short term response to androgen exposure occurred in the lateral lobe where an immediate 9-fold increase in nuclear AR quantity was observed; however, these levels rapidly declined to pre-implant values by Day 5 and remained at that level despite continued exposure to testosterone. These f findings indicate that while nuclear AR levels in the ventral and dorsal prostate are primarily regulated by androgens, a testosterone-independent component exists within the lateral lobe.

Androgens↗

PubMed1987

Electrical self-stimulation in the parabrachial area is depressed after ibotenic acid lesion of the lateral hypothalamus.

The involvement of lateral hypothalamic intrinsic neurons on electrical self-stimulation of the parabrachial area was analyzed. Rats were bilaterally implanted in the parabrachial area and with a guide cannula located above each lateral hypothalamus. They were subsequently tested for intracranial self-stimulation. Then, the lateral hypothalamus on one side of the brain was injected with ibotenic acid. The effect of the induced lesion was tested 8 days later on self-stimulation of the ipsilateral and contralateral parabrachial areas. The intrinsic neurons of the non-lesioned lateral hypothalamus were then destroyed with ibotenic acid. Self-stimulation was then tested 8, 12 and 30 days later. The unilateral lesion produced a significant decrease of self-stimulation using the electrode ipsilateral to the lesion, without any modification of the stimulation using the contralateral electrode. After bilateral lesion, self-stimulation was greatly reduced bilaterally. The results suggest that the main effect of the lesion was to increase the self-stimulation threshold. Given that the parabrachial area is a relay station for the gustatory inputs and that the intrinsic neurons of the lateral hypothalamus project back to the parabrachial area, the present results are tentatively interpreted as an indication that self-stimulation in this pontine area results from the activation of feedback loops between the lateral hypothalamus and the parabrachial area.

Animals↗

PubMed1986

The structural and functional characteristics of striate cortical neurons that innervate the superior colliculus and lateral posterior nucleus in hamster.

Intracellular recording and horseradish peroxidase injection techniques were used to structurally and functionally characterize the striate cortical neurons in hamster that projected to the superior colliculus and/or lateral posterior nucleus of the thalamus. With two exceptions, the receptive field properties and morphological characteristics of the neurons antidromically activated from the colliculus and lateral posterior nucleus were quite similar. Striate corticotectal and striate cortico-lateral posterior neurons generally had non-oriented receptive fields which gave either "on-off' or no responses to flashed stimuli. Only a small number (less than 5%) were orientation selective, but about one-third were directionally selective. Most of the cells preferred movement with an upward component. Most striate corticotectal and cortico-lateral posterior cells responded to a wide range of stimulus velocities and exhibited little spatial summation. With the possible exception of two cells, all the projection neurons we recovered were large lamina V pyramidal cells whose apical dendrites extended to and branched extensively in layer I. All had extensive (in some cases over 1 mm) tangential axon collaterals, primarily in layers V and/or VI. The electrophysiological experiments also demonstrated that some (50% of a sample of 20 cells) corticotectal neurons also sent an axon collateral to the lateral posterior nucleus. Finally, our recordings showed that many (56% of a sample of 27 neurons) cells which could be antidromically activated from the lateral posterior nucleus, but not the superior colliculus had response latencies which exceeded those of almost all the cells which could be antidromically activated from the tectum. Retrograde transport of diamidino yellow and true blue confirmed the electrophysiological result that individual cortical neurons projected to both the superior colliculus and lateral posterior nucleus. These experiments showed that 20% of the striate cortical cells that projected into colliculus also sent an axon collateral to the lateral posterior nucleus.

Animals↗

PubMed1996

Striatal and cortical projections of single neurons from the central lateral thalamic nucleus in the rat.

Striatal and cortical projections arising from the central lateral thalamic nucleus were studied in rats by tracing the axons of small pools of neurons labeled anterogradely with biocytin. Cells of the central lateral nucleus have a morphology that conforms to the classic descriptions of the bushy cells which represent the main neuronal type of most thalamic nuclei. They display many short radiating dendrites studded with sessile spines, protrusions and grapelike appendages. The total extent of their dendritic fields is about 250 mu m. After leaving the nucleus, all central lateral axons course through the rostrolateral pole of the thalamic reticular nucleus, where they branch profusely, enter the striatum, where they distribute collaterals, and arborize in the motor cortex. At striatal level, central lateral fibers form a loosely organized network composed of varicose axonal branches that appear to contact en passant several striatal neurons. In the cortex. central lateral axons from multiple (four to five patches of terminations in layers Va and III aligned along the rostrocaudal extent of the motor area. The projection to layers I and II is very sparse, consisting of occasional branches which show few ramifications. Our results indicate that most, and perhaps all, central lateral relay neurons project to both the striatum and cerebral cortex. The patchy innervation of mid cortical layers of the frontal motor areas by central lateral afferents strongly argues against the nonspecific character of this projection. It is proposed that the central lateral nucleus, which receives a strong innervation from brainstem cholinergic afferents, takes part in a mechanism of attention related to the central initiation of directed patterns of movements.

Animals↗

PubMed1996

Phenotypic development of the human embryonic striatal primordium: a study of cultured and grafted neurons from the lateral and medial ganglionic eminences.

Basic parameters which are crucial for the survival of human embryonic striatal grafts need to be investigated before initiating clinical trials in Huntington's disease. In order to define the dissection of human striatal-donor tissue which gives rise to the largest amount of striatal neurons after intrastriatal transplantation, we studied the lateral and medial ganglionic eminences of embryonic striatal primordia obtained from human embryos sized 17-30 mm in crown-to-rump length (corresponding to Carnegie stages 18-23). Anatomical landmarks that demarcated the lateral and medial ganglionic eminences from each other were present only in embryos with 20 mm crown-to-rump length or larger. In monolayer cultures, the lateral ganglionic eminence gave rise to a six-fold higher yield of dopamine- and cyclic AMP-regulated phosphoprotein 32-immunoreactive striatal neurons as compared to the medial ganglionic eminence. We also xenografted the lateral and medial ganglionic eminences from five embryos sized 21-30 mm in crown-to-rump length to the ibotenate lesioned striatum of immunosuppressed rats. The grafts were evaluated with respect to general morphology, survival and integration using (immuno-) histochemical stains for acetylcholinesterase/Cresyl Violet, nicotinamide adenine dinucleotide phosphate-diaphorase, dopamine- and cyclic AMP-regulated phosphoprotein-32, tyrosine hydroxylase and calbindin-D28KD. As assessed 9-25 weeks after implantation, 13 out of 16 and 8 out of 13 grafts, in the groups grafted with the medial and lateral ganglionic eminences, respectively, had survived. Previous studies with rat donor tissue have indicated that the functional efficacy of striatal grafts is related to the development of striatal-specific P-zone regions and that these are enriched in transplants derived from the lateral as opposed to the medial ganglionic eminence. Also in the human striatal xenografts of the present study, P-zones appeared more abundant when the donor tissue was derived from the lateral ganglionic eminence. However, the proportion of graft tissue that expressed P-zone properties was always very low (at most 30%) and never approached the 80-90% previously observed in transplants of rat lateral ganglionic eminence. We conclude that the relative yield of striatal neurons in grafts of the human embryonic striatal primordium has to be improved before neural transplantation should be applied in patients with Huntington's disease.

Acetylcholinesterase↗