SEARCH · Search PubMed

Results for “Fasciculation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources

PubMed1992

A specific brain tract guides follower growth cones in two regions of the zebrafish brain.

Neurons of the nucleus of the posterior commissure (nuc PC), an identifiable cluster of neurons in the embryonic zebrafish brain, project growth cones ventrally along the posterior commissure to the anterior tegmentum where the PC intersects two longitudinal tracts, the tract of the postoptic commissure (TPOC) and the medial longitudinal fasciculus (MLF). Once at the intersection, nuc PC growth cones turn posteriorly onto the TPOC in the dorsal tegmentum and follow it to the hindbrain. Previously we showed that in the absence of the TPOC, nuc PC growth cones often extended along aberrant pathways suggesting that fasciculation, that is, contact with TPOC axons is an important factor in guiding growth cones along their normal pathway. However, a significant number of nuc PC growth cones also followed their normal pathway suggesting that cues associated with the dorsolateral tegmentum, independent of the TPOC, can also guide nuc PC growth cones. We have now confirmed using electron microscopy that nuc PC growth cones fasciculate with axons in the TPOC. In the absence of the TPOC, the nuc PC growth cones that extend along their normal pathway do so in contact with dorsolateral neuroepithelial cells. This suggests that cues associated with these cells can also guide the nuc PC growth cones. Furthermore, in the absence of the TPOC axons, these growth cones now inappropriately turn onto axons that normally intersect the TPOC near the border of the midbrain and hindbrain, that is, at a second intersection of tracts. This suggests that fasciculation with TPOC axons may also guide nuc PC growth cones in this second region of the brain.

Animals↗

PubMed1996

Changes in the segmental pattern of sensory neuron projections in the chick hindlimb under conditions of altered cell adhesion molecule function.

In the developing chick hindlimb, pathfinding by sensory axons is affected by their interactions with other axons entering the limb. Cell adhesion molecules (CAMs) expressed on the growing axons are likely to influence these interactions. Accordingly, to elucidate how CAMs affect sensory axon pathfinding, we injected antibodies that block the functions of NCAM, G4/L1, or N-cadherin into the hindlimb, starting at St. 25, when all motoneuron axons but only a few sensory axons had entered the plexus. In each case, the segmental pattern of projections was assessed 2-3 days later by retrogradely labeling individual peripheral nerves. With all perturbations, the gross anatomical nerve pattern developed normally; that is, some sensory axons formed cutaneous nerves while other sensory axons projected to muscles. However, the segmental pattern of sensory projections was changed when either G4/L1 or N-cadherin function was blocked in that fewer sensory axons crossed the anterior-posterior axis of the plexus. A likely reason for this effect is that anti-G4/L1 and anti-N-cadherin each decreased the amount of fasciculation and that sensory axons are less able to travel across the plexus when they are defasciculated. Anti-G4/L1 affected both cutaneous and muscle sensory projections while anti-N-cadherin affected cutaneous but not muscle sensory projections, in accord with known differences in the expression of these two CAMs on sensory and motoneuron axons. Although anti-NCAM did not appear to alter sensory projections, when polysialic acid (PSA) was enzymatically removed from NCAM, there was a marked increase in cutaneous projections from the most proximate DRG, although muscle sensory projections were unchanged. PSA removal may cause an increase in fasciculation that forces sensory axons to track along neighboring axons. Thus, without PSA, cutaneous axons project more in accord with the relative anterior-posterior positions they had as they entered the plexus. Taken together, these studies suggest that axonal fasciculation mediated by CAMs and regulated by PSA influences the ability of sensory growth cones to navigate through the plexus and project along the correct peripheral nerves.

Afferent Pathways↗

PubMed1996

Developmental pattern of axonal pathways in the house shrew maxillary nerve.

The topographic patterns of peripheral receptors and effectors seem to contribute to the construction of the neuronal circuit in the central nervous system (CNS) in mammals. Many patterns replicating those of the periphery have been found in the CNS, and fasciculation has been regarded as having a central role in the pattern replication. The house shrew, Suncus murinus, is an excellent species in which to study this topic because it has a vibrissae system arranged in a single ordered fashion and extraordinarily well-developed trigeminal spinal tracts. Using immunostaining and retrograde-tracing techniques, we examined the developmental pattern of the maxillary nervous system in the house shrew. The results indicate that the basic pattern of axonal extension reiterates with a parallel arrangement throughout the course of development except at a site in the brainstem where the central processes bifurcate into ascending and descending branches. Dorsoventral inversion of the peripheral pattern in the spinal tract occurs with this dual-leveled bifurcation in association with the mediolaterally ordered entry of the central processes into the brainstem. The basic pattern of the central processes is established prior to the appearance of the vibrissae, indicating that the basic topographic pattern of the maxillary nerve is not related to the vibrissae system. The fasciculation pattern does not correspond to the overall layout of the arrays of vibrissae, and there are frequent exchanges of axons between fascicles both in the periphery and centrally. The parallel organization of the majority of the processes, together with the free exchange of processes between fascicles, suggests that these processes have an important role in the formation of the fasciculation and somatotopic patterns.

Age Factors↗

PubMed1979

Three dimensional organization of mammalian adrenal cortex. A scanning electron microscopic study.

The adrenal cortex of different mammals was studied by SEM in order to demonstrate its actual three-dimensional organization. In the rat, as well as in the cat and pig, the adrenal cortex appeared as a "tunnelled continuum" of polyhedral cells arranged in plate-like structures (laminae). This laminar arrangement was more evident in the inner fasciculate and reticular zones where the cortex revealed a striking similarity to liver tissue. The polyhedral cells of all cortical zones possessed regular facets populated by small pits, larger invaginations and numerous microvilli with the exception of very short and smooth areas probably corresponding to attachment zones and/or gap junctions. This cellular architecture produced a labyrinthic system of intercellular channels or lacunae in which the capillaries were suspended. The pericapillary areas of this labyrinth contained microvilli, amorphous material, a delicate net of fibrils and occasional cells. The intercellular compartment of this lacunar system was mainly bordered by numerous microvilli arising from endocrine cells. The luminal surface of the capillary wall showed not only irregularly protruding margins (interpretable as endothelial junctions) but also clearly overlapping and flattened endothelial extensions. In all the animals and areas of the adrenal cortex examined, the endothelial wall was provided with abundant clusters of small fenestrations (about 50 nm in diameter) generally arranged in sieve plates. Larger fenestrations were noted mainly in the fasciculate and reticular zones of the cat and pig and occasionally in the rat. A final point related to the nature and significance of sinusoidal fenestrations was the occurrence of irregularly shaped and intracapillary located cells mainly noted in the deeper zones of the fasciculate and reticular zones of the gland. These elements--possessing the surface characteristics of macrophages--were observed, with their irregular and slender evaginations, in close proximity to the large fenestrations in a manner reminiscent of Kupffer cells within the lumen of liver sinusoids.

Adrenal Cortex↗

PubMed1998

Lower oesophageal sphincter tone increases after induction of anaesthesia in pigs with full stomach.

PURPOSE: The lower oesophageal sphincter (LOS) is the man mechanism that prevents gastro-oesophageal regurgitation during anaesthesia. The aim of this study was to assess the effect on lower oesophageal sphincter pressure (LOSP) of rapid sequence induction in pigs with full stomachs. METHODS: Lower oesophageal sphincter pressure and oesophageal barrier pressure (BrP = LOSP minus gastric pressure) were measured using a water-perfused manometric catheter method in 12 pigs after gastric filling with 500 ml of liquid nutrient mixture. Six pigs were randomly allocated to receive 5 mg.kg-1 propofol and 3 mg.kg-1 succinylcholine i.v. and six pigs received 8 mg.kg-1 thiopentone and 3 mg.kg-1 succinylcholine i.v. RESULTS: After induction, mean LOSP increased during the period with fasciculations from 19 +/- 4 mmHg to 28 +/- 5 mmHg in the propofol-succinylcholine group and from 23 +/- 6 mmHg to 36 +/- 7 mmHg in the thiopentone-succinylcholine group. The LOSP remained elevated after the fasciculations. LOSP and BrP were not different between the groups. CONCLUSIONS: Induction of anaesthesia with propofol-succinylcholine or thiopentone-succinylcholine increases LOSP and, consequently, BrP in pigs with a full stomach. This increase begins before fasciculations and remains elevated for the period when intubation would occur.

Anesthesia↗

PubMed1987

Decreasing post-succinylcholine myalgia in outpatients.

The effectiveness of four pretreatment regimens in decreasing succinylcholine-induced myalgias was studied in healthy outpatients undergoing general anaesthesia for ambulatory surgery. Four hundred and forty adult females were randomly assigned to one of four pretreatment groups. Three hundred and ninety-five patients completed the study. One of the following pretreatments was given prior to injection of 1.5 mg X kg-1 of succinylcholine: normal saline IV three minutes and again immediately prior to succinylcholine; 0.06 mg X kg-1 d-tubo-curarine (dTc) IV three minutes prior and normal saline IV immediately prior; normal saline IV three minutes prior and 1.5 mg X kg-1 lidocaine IV immediately prior; 0.06 mg X kg-1 dTc IV three minutes prior and 1.5 mg X kg-1 lidocaine IV immediately prior. Fasciculations after injection of succinylcholine were observed and recorded. Patients were contacted by telephone 40-48 hours postoperatively and questioned about the presence of muscle pains. These pains, if present, were graded either mild or moderate to severe. The patients in the two dTc-containing groups exhibited less fasciculations than patients in the other two experimental groups. The dTc-lidocaine group had a lower incidence of moderate to severe fasciculations than in any of the other three groups. Patients in the dTc, lidocaine, and dTc-lidocaine experimental groups reported a higher incidence of absence of muscle pain and a lower incidence of moderate-severe pain than did patients in the saline group. The dTc-lidocaine group had more patients without myalgia and less patients with moderate to severe myalgias than any of the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1983

Influence of ganglion age, nonneuronal cells and substratum on neurite outgrowth in culture.

This study characterizes the outgrowth patterns of superior cervical ganglia (SCG) obtained from embryonic (E15), perinatal (E20-21), and adult (P35) rats when placed in culture on various substrata. Outgrowth morphology, degree of fasciculation, and outgrowth length were examined on collagen (COL), polyornithine (PO), polylysine (PL), fibronectin (FN), and nonneuronal cells (NNCs) from the ganglion. COL and FN supported extensive neuritic outgrowth; PO and PL provided poor support. Outgrowth pattern, degree of fasciculation, neurite growth rate, and the number of NNCs in the outgrowth varied considerably depending upon the COL configuration. When undiluted COL (approximately 5 mg/ml) was air dried, a three-dimensional loose fibrillar network was formed. Upon COL dilution or gelling undiluted COL by ammoniation, an essentially two-dimensional layer was formed. On two-dimensional COL, NNCs were able to proliferate and migrate extensively from ganglia of all ages; their presence influenced the form and extent of neurite growth. E15, E20, and P35 neurites responded differently to their endogenous NNCs. E15 neurites extended in relation to NNC surfaces and were predominantly nonfasciculated. E20 neurites became more fasciculated in the presence of NNCs that exhibited morphological and behavioral differences from those migrating from E15 ganglia. E20 neurite bundles became defasciculated when they extended into E15 outgrowth. Far fewer neurites grew from P35 explants in the presence of their NNCs. Three-dimensional COL greatly slowed NNC migration and thus allowed investigation of neurite outgrowth from ganglia of differing age in the absence of NNCs. We conclude that neuritic outgrowth patterns on varying substrata reflect not only neurite differences depending upon ganglion age but also variation in the behavior of accompanying NNCs.

Age Factors↗

PubMed1993

An immunohistochemical study of neurofilament and microtubule-associated Tau protein in the enteric innervation in Hirschsprung's disease.

The distribution and localization of neurofilament (NF) and microtubule-associated tau protein (Tau) in the colon from Hirschsprung's disease were examined by immunohistochemistry. Specimens of the normoganglionic, oligoganglionic, and aganglionic segments of colons from nine patients with Hirschsprung's disease were used in this study. Normal colon specimens obtained at the time of colostomy closure from two patients with anorectal malformations were also examined as controls. In normoganglionic segments, anti-NF-H and anti-NF-M immunoreactivity appeared within the nerve fibers of both the myenteric and submucosal plexuses. These findings were also observed in the oligoganglionic segments. In the aganglionic segment, hypertrophic nerve fascicules and the nerve fibers in circular muscle were positively stained with anti-NF-H and anti-NF-M antibodies. Anti-Tau staining appeared in the ganglion cell bodies of both myenteric and submucosal plexuses and in nerve fibers distributed among the circular muscles of the normal control colons, and the normoganglionic and oligoganglionic Hirschsprung's specimens. Nerve fibers in the circular muscle layer of aganglionic segments were also stained with anti-Tau serum, although the hypertrophic nerve fascicules in the intermuscular and submucosal layers did not stain. The so-called nerve fascicules distributed in the subserosal layer also did not stain with anti-Tau. These results suggest that Tau may be used as a specific marker to identify ganglion cells and intrinsic nerve fibers in colons affected by Hirschsprung's disease.

Animals↗

PubMed1986

Mechanisms of toxicity and tolerance to diisopropylphosphorofluoridate at the neuromuscular junction of the rat.

Diisopropylphosphorofluoridate (DFP), an irreversible inhibitor of acetylcholinesterase (AChE) activity, when given as an acute dose (1.5 mg/kg, sc) caused fasciculations and induced necrosis in rat skeletal muscle fibers. No adaptation was seen to daily dosing of DFP (1.5 mg/kg, sc) since all rats died after the second or third injection. Daily dosing of DFP in a concentration (0.5 mg/kg, sc) that as a single dose did not cause symptoms, produced onset of fasciculations on the third day associated with a reduced number of muscle fiber lesions. Further administration of DFP (14 days) caused disappearance of fasciculations and loss of sensitivity to the necrotizing actions in all muscles tested (diaphragm, soleus, and extensor digitorum longus). Activity of all molecular forms of AChE was reduced to 20-24% of control when symptoms of cholinergic hyperactivity appeared. Continuous injections of DFP (0.5 mg/kg/day, sc) up to 14 days did not cause greater inhibition of AChE activity. Instead, recovery of enzyme activity, especially of the 4S and 10S forms, was seen. During this period choline acetyltransferase activity (ChAT) was increased in muscle (intramuscular nerves) while the postsynaptic nicotinic acetylcholine receptor (nAChR) density (Bmax) was decreased to 44% without a change in the affinity constant (KD). It is concluded that neuromuscular adaptation to DFP is caused by recovery of AChE activity due to de novo synthesis and reduction in the number of nAChR.

Acetylcholinesterase↗

PubMed1995

Comparative localisation of CRYP alpha, a CAM-like tyrosine phosphatase, and NgCAM in the developing chick visual system.

The avian CRYP alpha gene is expressed in the embryonic nervous system and encodes a receptor-like protein tyrosine phosphatase with structural similarity to neural cell adhesion molecules. To gain further insight into the role of the CRYP alpha phosphatase in neural development, this study addresses the protein's cellular distribution in the well characterised embryonic visual system. High levels of CRYP alpha protein localise in retinal axons extending from the eye to the tectum throughout the major growth periods of these nerve processes. In addition, primitive inner plexiform layer processes in the retina, tectobulbar axons, and non-retinal fibres of the tectal stratum opticum, contain large amounts of CRYP alpha. Its presence in non-fasciculated processes suggests that CRYP alpha has a role other than in fasciculation in short range fibres. In contrast to CRYP alpha, NgCAM is confined largely to axon fascicles in the retina and tectum, consistent with its demonstrated role in fasciculation of cultured neurites. In cultured retinal neurons CRYP alpha proteins reside both in neurite processes and in growth cone membranes, implicating both of these as potential functional locations for the protein. Although CRYP alpha continues to be expressed in the later embryo, the strong, early expression suggests a significant developmental role in the initial growth or guidance of nerve processes. This applies both over the longer range in the retinotectal and tectobulbar projections and over the shorter range within plexiform layers.

Animals↗

PubMed1990

Immunoelectron microscopic localization of cell adhesion molecule L1 in developing rat pyramidal tract.

The glycoprotein L1 is a cell adhesion molecule that has been proposed to function in the peripheral nervous system in axon fasciculation and onset of myelination. In this report we localize L1 during the development of a major central pathway: the pyramidal tract. The (sub)cellular localization of L1 was determined both by pre-embedding staining on Vibratome sections and by immunogold labelling on ultracryosections in developing rat pyramidal tract at the fifth cervical segment. On arrival at the fifth cervical segment, i.e. at postnatal day 1, growth cones of pioneer fibres did not exhibit L1-immunoreactivity. In the contact zone between pyramidal tract growth cones and glial processes no L1-immunoreactivity was observed. A clear L1-immunoreactivity was noted on small unmyelinated other axons situated in the entrance area of the pyramidal tract growth cones. Also on later arriving, i.e. between postnatal days 2 and 10, small unmyelinated fasciculating pyramidal tract axons L1 were present. It is our impression that L1 is localized in an irregular patchy way on the outer side of the axonal membrane. During the onset of myelination, i.e. between postnatal days 10 and 14, L1 could not be detected on axons ensheathed by oligodendrocytic processes. When myelination is largely completed, i.e. at postnatal day 21, the L1 antigen could be localized within the axoplasma of both unmyelinated and myelinated pyramidal tract axons. Furthermore, L1 could be observed occasionally on small unmyelinated pyramidal tract axons. Whereas compact myelin was always L1-negative, L1 was noted periaxonally between the axolemma and compact myelin and at (para)nodal regions at the contact zone between axolemma and oligodendrocytic processes. From these results it may be deduced that: (1) L1 is involved in fasciculation of outgrowing later arriving pyramidal tract fibres: (2) L1 is not involved in the onset of myelination in this central tract; (3) L1 might play an additional adhesive role in myelinated rat pyramidal tract.

Aging↗

PubMed1989

Surface ultra-architecture of supraependymal elements in the vicinity of the area postrema of rhesus monkeys.

The caudal part of the fourth ventricle in adult rhesus monkeys, of both sexes, revealed the area postrema (AP) to be composed of bilateral spindle-shaped elevations located ventromedial to the gracile tubercles. Supraependymal (SE) elements, comprised of SE cells and/or fibre processes could be seen near the medial margin of a narrow oligociliated strip separating the nonciliated AP from the profusely ciliated vagal triangle (VT). In general, these consisted of multilobed ganglion-like cell clusters interconnected by fasciculated fibre processes with varicosities along their lengths. Thinner processes radiating from the cell clusters and varicosities traversed towards the VT for short distances and often appeared to penetrate the underlying ependyma. The thicker fibre processes which exhibited a fasciculated configuration extended between raised nodule-like areas in the ventricular floor. The majority of such areas exhibited an uneven surface due to the presence of numerous membranous folds over them. Near the periphery of nodular areas as well as along the fasciculated fibre processes interconnecting them, a few bouton-like protrusions were discernible. The SE elements observed in the caudal portion of the fourth ventricular floor are suggestive of comprising some integrative pathways between the ventricular cerebrospinal fluid and subependymal functional centres in the vicinity of the AP, a circumventricular organ having diverse functions.

Animals↗

PubMed2005

The midbrain of sauropsides shares a common subdivision pattern defined by embryonic radial glia.

In a previous study of the embryonic midbrain radial glia in a lizard, we observed that these cells define boundaries and regional subdivisions in a pattern that largely supports the adult model [C. Diaz, C. Yanes, C.M feminine. Trujillo, L. Puelles, Cytoarchitectonic subdivisions in the subtectal midbrain of the lizard Gallotia galloti, J. Neurocytol. 29 (2000) 569-593]. With the goal to check whether the midbrain of chick embryos has a similar pattern, we examined the radial glia distribution in this model using a lipophilic dye (DiI) injected intraventriculary. As in the lizard, chick radial glia distribution and fasciculation defines at least six regional subdivisions in the midbrain, five of which are alar and one basal. Each territory corresponds to a particular cytoarchitectonic area, recognized previously. The rostral mesencephalic limit (m/d) is underlined in the alar zone by a thick band of fasciculated radial glia intercalated between the griseum tectale and the posterior commissure. A fasciculated radial glia band also defines the caudal mesencephalic limit (m/r) across the alar and basal zones. These glial specializations, not described previously in the chick, give physical entity to the limits deduced from gene expression studies and suggested by descriptive cytoarchitectonic analysis. We conclude that the midbrain of sauropsides shares a common subdivision pattern co-defined by radial glia arrangements.

Amino Acids↗

PubMed2005

Differences in sensory projections between macro- and microchaetes in Drosophilid flies.

From examination of the central axonal projections of sensory bristles on the notum of several species of Drosophilidae, we demonstrate different features that may indicate different functions for macro- and microchaetes. The large macrochaetes have conserved arborizations that correlate with their conserved position. Nevertheless, we find evidence for only two discrete projection patterns for bristles in the dorsocentral (DC) row, even when there may be four or five bristles present. We show that the small microchaetes of Drosophila melanogaster display regional specificity and subsets of contiguous bristles project to a common region in the thoracic ganglion. Interestingly, the axons of each of these subsets also form a specific fasciculation group on the scutum before joining the axon of a particular macrochaete. The positions of microchaetes on the scutum and the shape of the fasciculation groups vary between closely related species. There is no correlation between body size, bristle patterns, and fasciculation patterns. Furthermore, none of these traits correlate with the phylogenetic relationships between the species studied. We discuss the possibility that macro- and microchaetes may have different functions and that these have implications for evolutionary constraints on bristle patterns.

Animals↗

PubMed1997

Successful treatment of crotalid-induced neurotoxicity with a new polyspecific crotalid Fab antivenom.

STUDY OBJECTIVE: To report the effectiveness of a new polyvalent crotalid antivenom on neurotoxicity associated with North American rattlesnake envenomation. Two syndromes of crotalid-induced neurotoxicity have been reported. In severe envenomation by Crotalus scutulatus scutulatus (Mojave rattlesnake), weakness and fasciculations of various muscle groups, including those innervated by cranial nerves, may develop. Occasionally respiratory insufficiency develops. The second neurotoxic effects is myokymia, a type of fasciculation most frequently reported after bites by Crotalus horridus horridus (timber rattlesnake) and Crotalus atrox (Western diamondback rattlesnake). Conventional polyvalent antivenom is often ineffective in the treatment of venom-induced neurotoxicity. METHODS: We report a case series of three patients envenomated by North American rattlesnakes, one of which was identified as C scutulatus scutulatus. All three patients experienced neurotoxicity with weakness, paresthesias, and dramatic fasciculations, along with other signs and symptoms of crotalid venom poisoning. RESULTS: The administration of new polyspecific crotalid antivenom made of ovine Fab was successful in immediately and completely reversing neurotoxicity in each of these patients. CONCLUSION: We report the use of a new antivenom for North American crotalid envenomation that seems to have efficacy in reversing neurotoxicity associated with these bites.

Adult↗

PubMed1997

Prediction of teratogenic potency of valproate analogues using cerebellar aggregation cultures.

The aim of this study was to develop a novel in vitro system suitable for preclinical testing for developmental toxicity of drugs. An assay system consisting of primary cultures of dissociated cerebella from 6-day-old mice was chosen, since it allowed quantification of neuronal aggregation and fasciculated neurites. A human teratogen, the antiepileptic drug valproic acid (VPA), as well as its structural analogues, ( +/- )-4-en-VPA and E-2-en-VPA, with varying teratogenic activities, were tested and found to affect aggregation and fiber formation of cerebellar neurons. Based on a dose-response study, the concentrations of compounds causing 50%, inhibition (IC50) of formation of thick and thin fibers were determined. The lowest IC50 values were found for VPA (52 +/- 7 and 86 +/- 11 microM for thick and thin fibers, respectively), which in vivo caused the highest rate of exencephaly among the three compounds tested, ( +/- )-4-en-VPA exhibited intermediate values (150 +/- 30 and 300 +/- 40 microM), whereas the highest IC50 values were found for E-2-en-VPA (260 +/- 42 and 430 +/- 40 microM). The latter compound does not induce neural tube defects, but has been shown to have neurobehavioral effects in prenatally exposed animals. Subsequently, the purified S- and R-enantiomers of 4-yn-VPA (teratogenic and non-teratogenic, respectively) were tested for their effects on aggregation and fiber formation of the cerebellar neurons. Treatment with S-4-yn-VPA resulted in pronounced changes in numbers of aggregates and fasciculated processes compared to the cultures treated with R-4-yn-VPA, indicating that the intrinsic stereoselective potency of the enantiomers may be correlated to the difference in their effects on cerebellar neurons in vitro. Thus, the teratogenic potency of VPA and its analogues correlated with their effects on aggregation of neural cells and formation of fasciculated neurites in primary cultures of dissociated cerebella, indicating that the in vitro assay system employed may be used as a pre-screening test for prediction of teratogenic potency of drugs.

Animals↗

PubMedDate not supplied

Transient expression of a surface antigen on a small subset of neurones during embryonic development.

During development, neurones find and interconnect with their targets in a remarkably precise way. The unfolding of neuronal specificity involves a series of highly specific recognition events which are likely to be coordinated by the spatial and temporal expression of many different surface molecules. At early stages of development, neuronal recognition occurs most dramatically at the tips of growing axons, at growth cones and their filopodia. Previous studies on the grasshopper embryo suggest that specific filopodial contacts lead to the stereotyped patterns of selective axonal fasciculation; these results support the 'labelled pathways' hypothesis which predicts that the different neighbouring axon fascicles in the embryonic neuropil within filopodial grasp are differentially labelled. To uncover the molecular labels on fasciculating embryonic axons, we screened 2,000 monoclonal antibodies generated against the embryonic neuroepithelium. Here we describe three antibodies which reveal surface antigens whose temporal and spatial expression during embryogenesis correlate with the predictions of the model. In particular, the Mes-2 antibody recognizes an antigen which is transiently expressed on the surface of only 4 out of approximately 1,000 neurones in each metathoracic hemisegment during a short period of embryogenesis. The growth cones of two of these neurones fasciculate in the periphery and innervate the same target. Moreover, they transiently express the Mes-2 surface antigen while doing so.

Animals↗

PubMed1987

Prevention of phospholine-induced myopathy with d-tubocurarine, atropine sulfate, diazepam, and creatine phosphate.

Acute administration of phospholine [diethyl-S-(2-dimethyl aminoethyl)phosphorothioate] at 0.2 mg/kg sc produces a myopathy characterized by initial focal changes in the subsynaptic area of the skeletal muscle. The onset of the myopathy is associated with fasciculations of high frequency. Agents that either prevent or reduce the fasciculations, such as d-tubocurarine, atropine sulfate, and diazepam, were effective in reducing the number of muscle lesions. These agents may reduce spontaneous muscle activity by blocking the postsynaptic receptor, by modifying the ionic-channel characteristics, by reducing presynaptic acetylcholine (ACh) release, or by a combination of any of these mechanisms. Creatine phosphate (CP) does not reduce fasciculations, but it is effective in reducing the number of necrotic fibers, probably by stimulating and sustaining the mechanism of Ca2+ uptake into the sarcoplasmic reticulum. It is postulated that an increase in the sarcoplasmic Ca2+ concentration triggers the events that lead to muscle necrosis.

Animals↗