Afferent and sympathetic neurons projecting into lumbar visceral nerves of the male rat.

The cell bodies of thoracolumbar sensory and sympathetic pre- and postganglionic neurons that project to the colon and pelvic organs of the male rat were labeled retrogradely with horseradish peroxidase (HRP) in order to study numbers, segmental distribution, and location of the somata of these neurons quantitatively. HRP was applied to one hypogastric nerve (HGN), to the lumbar colonic nerves (LCN) and to the intermesenteric nerve (IMN). In order to estimate the significance of the branching of one axon into both hypogastric nerves a double-labeling technique with fluorogold and HRP was used. About 2640 neurons project into the two HGN added together (800 afferent, 1320 pre-, and 520 postganglionic), 4650 neurons into the LCN (360 afferent, 0 pre- and 4290 postganglionic), and 5990 into the IMN (1500 afferent, 1250 pre-, and 3240 postganglionic). About 4190 sympathetic postganglionic prevertebral neurons innervate the colon and pelvic organs, 1900 are located in the inferior mesenteric ganglion and 2290 in ganglia of the IMN. Considering the efferent component, the HGN mainly are preganglionic and the LCN exclusively postganglionic nerves. Branching of one axon into both HGN is a rare event and quantitatively negligible (less than 3%). Afferent neurons of all three nerves were found in the dorsal root ganglia (DRG) T12-L2 with the maximum in L1 and L2. The distribution of afferent neurons projecting into the LCN is shifted slightly more rostrally compared to neurons projecting into the HGN. The IMN distribution is located in a position in between. Preganglionic neurons projecting into the IMN are located in the spinal cord segments T12-L3 with the maximum in L1 and L2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sympathetic and afferent somata projecting in hindlimb nerves and the anatomical organization of the lumbar sympathetic nervous system of the rat

The anatomy of the sympathetic pathways from the spinal cord to the lumbar sympathetic trunk and the inferior mesenteric ganglion was studied systematically in the rat. Details of the arrangements of white and gray rami communicantes, sympathetic trunk ganglia, the intermesenteric nerve, and the lumbar splanchnic nerves are summarized. A modified nomenclature for the segmental ganglia of the paravertebral sympathetic chain is proposed. Cell bodies of sensory and sympathetic axons projecting to the skin and skeletal muscle of the rat hindlimb were labeled retrogradely with horseradish peroxidase (HRP) in order to study numbers, segmental distribution, and location of the somata of these neurons quantitatively. HRP was applied to the nerves supplying skeletal muscle (gastrocnemius-soleus, GS), hairy skin (sural, SU; saphenous, SA) and to a mixed nerve (tibial, TI). All sensory somata and 96.4% of the sympathetic cell bodies were located ipsilaterally. Sensory somata were commonly restricted to two adjacent dorsal root ganglia (usually L3-4 for SA; L4-5 for GS, TI; L5-6 for SU). Although the sympathetic somata were more widely distributed rostrocaudally (four to six segments), their maximum was always located one or two segments more cranially than the sensory outflow, i.e., corresponding to the rami communicantes grisei. From the data, it is estimated that 420 sympathetic and 530 afferent neurons project into GS, 590 and 3,610 into SU, 920 and 3,750 into SA, and 1,070 and 5,760 into TI. These absolute neuron numbers are compared with electron microscopic fiber counts from the literature.     

Neural mechanisms involved in the inhibition of intestinal motility induced by intestinal electrical stimulation in conscious dogs

The effects and mechanisms of intestinal electrical stimulation (IES) with long pulses on intestinal motility were investigated in conscious dogs. Eighteen dogs were equipped with serosal electrodes and an intestinal cannula in the small bowel. The first experiment was designed to study the effect of one-channel IES on intestinal motility and the extent of this effect. The second experiment was conducted to study the effect of IES on intestinal motility and the involvement of neural pathway. The IES with long pulses significantly inhibited intestinal motility. Intestinal motility of the entire measured segment (40-220 cm distal to the stimulation electrodes) was inhibited by 60-74% with the single-channel IES with long pulses. Hexamethonium, guanethidine, phentolamine, propranolol partially, but not N(omega)-nitro-L-arginine (L-NNA), ondansetron and naloxone prevented the inhibitory effect of IES on intestinal motility. We conclude that single-channel IES inhibits intestinal motility within a distance of at least 2 m. This inhibitory effect induced by IES with long pulses is mediated via sympathetic but not nitrergic, serotoninergic 5-HT(3) and opiate pathway.     

Using tissue clearing and light sheet fluorescence microscopy for the three-dimensional analysis of sensory and sympathetic nerve endings that innervate bone and dental tissue of mice

Bone and dental tissues are richly innervated by sensory and sympathetic neurons. However, the characterization of the morphology, molecular phenotype, and distribution of nerves that innervate hard tissue has so far mostly been limited to thin histological sections. This approach does not adequately capture dispersed neuronal projections due to the loss of important structural information during three-dimensional (3D) reconstruction. In this study, we modified the immunolabeling-enabled imaging of solvent-cleared organs (iDISCO/iDISCO+) clearing protocol to image high-resolution neuronal structures in whole femurs and mandibles collected from perfused C57Bl/6 mice. Axons and their nerve terminal endings were immunolabeled with antibodies directed against protein gene product 9.5 (pan-neuronal marker), calcitonin gene–related peptide (peptidergic nociceptor marker), or tyrosine hydroxylase (sympathetic neuron marker). Volume imaging was performed using light sheet fluorescence microscopy. We report high-quality immunolabeling of the axons and nerve terminal endings for both sensory and sympathetic neurons that innervate the mouse femur and mandible. Importantly, we are able to follow their projections through full 3D volumes, highlight how extensive their distribution is, and show regional differences in innervation patterns for different parts of each bone (and surrounding tissues). Mapping the distribution of sensory and sympathetic axons, and their nerve terminal endings, in different bony compartments may be important in further elucidating their roles in health and disease.     

Central neuronal projections and neuromuscular organization of the basal region of the shore crab leg

The musculature and associated skeleton, peripheral nervous system, and central projections of motor and sensory neurones of the two basal (thoracic and coxal) segments of the shore crab leg (fifth pereiopod, P5) were examined in vivo and with methylene blue or cobalt staining. Each of the four main basal muscles, promotor/remotor, levator/depressor, controlling the thoracico-coxal (T-C) and coxo-basal (C-B) limb joints, respectively, comprises several more or less discrete fibre bundles (total 14), with little morphological segregation of different functional groups. The innervation to the basal leg region is carried in two nerve roots arising from the thoracic ganglion. The anterior Th-Cx root carries both sensory and motor axons, while the posterior Th-Cx root is purely motor. Three previously undescribed sensory branches (two "epidermal" nerves and an "accessory" branch), in addition to that innervating the coxobasal chordotonal receptor, have been found in the distal part of the anterior Th-Cx root. Two clusters of 10 to 15 multipolar somata (diam. 30-125 micron) are located proximally at the bifurcation of the accessory nerve and distally where the latter enters the basipodite. The cell bodies (diameter 20-80 micron) of basal leg motoneurones (total ca. 30) lie in the dorsal cortex of the ganglion, with somata of functionally related motoneurones tending to form discrete structural groups. The morphology of individual motoneurones conforms to the general arthropod pattern. All are confined to the ipsilateral hemiganglion and their main neuropilar processes run parallel and in close apposition to each other with overlapping dendritic structures. Sensory projections arising from the CB chordotonal organ also ramify in the region of the neuropile invaded by motoneurones. The possible physiological significance of such structural associations within the CNS is discussed, as are the functional implications of basal limb anatomy in general.     

Electrical stimulation of the anterior ethmoidal nerve produces the diving response

Stimulation of the upper respiratory tract usually produces apnea, but it can also produce a vagally mediated bradycardia and a sympathetically mediated increase in peripheral vascular resistance. This cardiorespiratory response, often called the diving response, is usually initiated by nasal stimulation. The purpose of this research was to investigate the anterior ethmoidal nerve (AEN) that innervates the nasal mucosa of muskrats (Ondatra zibethicus). Electrical stimulation of the AEN (typically 50 Hz, 100 micros and 500 microA) produced immediate and sustained bradycardia and cessation of respiration similar to that of the diving response. Heart rate (HR) significantly decreased from 264+/-18 to 121+/-8 bpm, with a concurrent 4.2+/-0.9 s apnea, during the 5 s stimulation period. BP decreased from 97.9+/-4.8 to 91.2+/-6.4 mmHg. Using estimations from (1) cross-sectional areas of AEN trigeminal ganglion cells labeled with WGA-HRP, and (2) electron microscopic analysis of the AEN, we found that approximately 65% of the AEN is composed of unmyelinated C-fibers. In addition, 72.4% of myelinated fibers from the nerves that innervate the nasal passages were of small diameter (<6 microm, presumably Adelta fibers). Thus, the AEN of the muskrat contains a high concentration of small diameter fibers (89.8%). We conclude that electrical stimulation of small diameter fibers within the AEN of muskrats can produce the cardiovascular and respiratory responses similar to that of the diving response.     

Neural control of leg movements in a metamorphic insect: sensory and motor elements of the larval thoracic legs in Manduca sexta

During the metamorphosis of the hawkmoth Manduca sexta the larval thoracic legs degenerate to be replaced in the adult by legs of very different form and function. This change must be accompanied by a reorganization of the neural circuits controlling leg movements. As an initial step in the study of this reorganization we describe here the sensory and motor elements of this circuitry in the larval stage of life. Sensory neurons innervating mechanoreceptive hairs on the thoracic surface were stained individually with cobalt. Those innervating hairs on the general thoracic surface project topographically into two ventral regions of the segmental ganglia. Sensory neurons innervating leg sensilla also map topographically to the more ventral of these regions but in addition have arborizations in a midlateral region. The density of branching within this lateral "leg neuropil" is greatest for sensory neurons form sensilla on the more distal leg segments. Leg motor neurons were identified with intracellular recording and cobalt injection techniques. Those innervating muscles controlling distal leg segments have dense dendritic arbors in the lateral "leg neuropil," while motor neurons controlling more proximal segments and muscles of the ventral body wall have extensive arborizations in a dorsomedial region of the ganglion. In general, flexor motor neurons are excited by medial and inhibited by lateral leg sensilla, while the opposite is true of extensors. Distal segment motor neurons respond most strongly to sensory neurons from distal segments, thus suggesting some interaction within the lateral "leg neuropil." Thus, in the larval nervous system a highly ordered array of of sensory and motor elements underlies the specific behavioral responses of the legs to tactile stimulation.     

Use and misuse of conventional electrodiagnosis,quantitative sensory testing,thermography, and nerve blocks in the evaluation of painful neuropathic syndromes

A number of laboratory tests are critically important in the quest to diagnose presence or absence of organic neuropathic dysfunction and to establish the relevance of such to the subjective pain complaints. However, none of these tests has absolute diagnostic value and their results must be interpreted in the light of the clinical picture. Conventional electrophysiology evaluates function of large caliber afferent and motor fibers leaving the function of small caliber afferent fibers unexplored, and cannot explore the basis for positive sensory phenomena. The quantitative somatosensory thermotest is the best test available to explore function of small caliber afferents. It allows documentation of positive sensory phenomena in the form of thermal hyperalgesia. Because it is a psychophysical test, it lacks localizing value. Thermography sensitively detects and precisely delineates areas of cutaneous thermal change of neural origin. Three types of diagnostic neurologic blocks are used in the clinic: compression-ischemia, local anesthetic and sympathetic blocks. Although they may provide important information about the pathophysiology of pain and hyperalgesias, adequate placebo control is of the essence because chronic neuropathic pain patients may express a high incidence of placebo response. © 1993 John Wiley & Sons, Inc.     

Modulation of the myotatic reflex gain in man during intentional movements

Human subjects were asked to perform sinusoidal tracking movements (0.5–3.0 Hz) with their forearms while external torque disturbances were applied at the elbow. The changes in angular position, velocity, and acceleration produced by these disturbances were found to be represented in the reflex changes in EMG activity of both biceps and triceps muscles. The gain of each of these reflex components varied during the tracking task, their maxima being about the same as those measured when the torque disturbances were applied in the absence of movements and the subjects attempted to maintain a constant forearm position. Such changes in gain were found to be centrally regulated since they were shown not to depend on the movement itself, being also present during force tracking, i.e. under nearly isometric conditions. Also, their minima and maxima did not coincide with those of the EMG activity.These results suggest that an internal plan (or model) of the learned task is present, whereby reflex gains can be regulated independently from the motion and α-motoneuron activity. Such regulation effectively uncouples the reflex motor output from the intentionally controlled motion and maintains spindle sensitivity to external disturbances independent of large changes in muscle length. These conclusions are discussed in the context of the functional role of γ-motoneurons in the control of movements.     

Immunohistochemical characterization of the innervation of human colonic mesenteric and submucosal blood vessels

Abstract The aim was to characterize quantitatively the classes of nerves innervating human mesenteric and submucosal vessels. Specimens of uninvolved normal human mesentery and colon were obtained with prior informed consent from patients undergoing elective surgery for bowel carcinoma. Mesenteric and submucosal vessels were processed for double‐labelling immunohistochemical localization of tyrosine hydroxylase (TH), neuropeptide Y (NPY), calcitonin gene‐related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), nitric oxide synthase (NOS), somatostatin (SOM), vesicular acetylcholine transporter (VAChT) and enkephelin (ENK), each compared to the pan‐neuronal marker protein gene product 9.5. Branching patterns of individual nerve fibres were investigated using in vitro anterograde tracing. Sympathetic neurons containing TH and NPY were the largest population, accounting for more than 85% on all vessels. Extrinsic sensory axons, containing SP but not CGRP comprised a second major population on mesenteric vessels: these axons generally lacked TH, NPY and VAChT. On submucosal, but not mesenteric vessels, an additional population of SOM‐immunoreactive fibres was present: these axons did not co‐localize with TH. Major similarities and differences with enteric vessel innervation in laboratory animals were identified. Sympathetic neurons comprise the largest input. Extrinsic sensory neurons in humans largely lack CGRP but contain SP. Submucosal vessels receive an additional source of innervation not present in mesenteric vessels, which contain SOM, but are rarely cholinergic. These results have significant implications for understanding the control of blood flow to the human gut.     

Differential localization of Ca2+ channel α1 subunits in the enteric nervous system: Presence of α1B channel-like immunoreactivity in intrinsic primary afferent neurons

Immunocytochemistry was employed to locate calcium (Ca²⁺) channel proteins in the enteric nervous system (ENS) of the rat and guinea pig. Anti-peptide antibodies that specifically recognize the α₁ subunits of class A (P/Q-type), B (N-type), C and D (L-type) Ca²⁺ channels were utilized. α_1B channel-like immunoreactivity was abundant in both enteric plexuses, the mucosa, and circular and longitudinal muscle layers. Immunoreactivity was predominantly found in cholinergic varicosities, supporting a role for Ca²⁺ channels, which contain the α_1B subunit, in acetylcholine release. Immunoreactivity was also associated with the cell soma of calbindin-immunoreactive submucosal and myenteric neurons, cells that have been proposed to be intrinsic primary afferent neurons. α_1C channel-like immunoreactivity was distributed diffusely in the cell membrane of a large subset of neuronal cell bodies and processes, whereas α_1D was found mainly in the cell soma and proximal dendrites of vasoactive intestinal polypeptide-immunoreactive neurons in the guinea pig gut. α_1A channel-like immunoreactivity was found in a small subset of cell bodies and processes in the rat ENS. The differential localization of the α₁ subunits of Ca²⁺ channels in the ENS implies that they serve distinct roles in neuronal excitation and signaling within the bowel. The presence of α_1B channel-like immunoreactivity in putative intrinsic primary afferent neurons suggested that class B Ca²⁺ channels play a role in enteric sensory neurotransmission; therefore, we determined the effects of the N-type Ca²⁺ channel blocker, ω-conotoxin GVIA (ω-CTx GVIA), on the reflex-evoked activity of enteric neurons. Demonstrating the phosphorylation of cyclic AMP (cAMP)-responsive element-binding protein (pCREB) identified neurons that became active in response to distension. Distension elicited hexamethonium-resistant pCREB immunoreactivity in calbindin-immunoreactive neurons in each plexus; however, in preparations stimulated in the presence of ω-CTx GVIA, pCREB immunoreactivity was found only in calbindin-immunoreactive neurons in the submucosal plexus and not in myenteric ganglia. These data confirm that intrinsic primary afferent neurons are located in the submucosal plexus and that N-type Ca²⁺ channels play a role in sensory neurotransmission. J. Comp. Neurol. 409:85–104, 1999. © 1999 Wiley-Liss, Inc.     

Electrophysiology and morphometry of the Aalpha- and Abeta-fiber populations in the normal and regenerating rat sciatic nerve

We studied electrophysiological and morphological properties of the Aalpha- and Abeta-fibers in the regenerating sciatic nerve to establish whether these fiber types regenerate in numerical proportion and whether and how the electrophysiological properties of these fiber types are adjusted during regeneration. Compound action potentials were evoked from isolated sciatic nerves 12 weeks after autografting. Nerve fibers were gradually recruited either by increasing the stimulus voltage from subthreshold to supramaximal levels or by increasing the interval between two supramaximal stimuli to obtain the cumulative distribution of the extracellular firing thresholds and refractory periods, respectively. Thus, the mean conduction velocity (MCV), the maximal charge displaced during the compound action potential (Q(max)), the mean firing threshold (V(50)), and the mean refractory period (t(50)) were determined. The number of myelinated nerve fibers and their fiber diameter frequency distributions were determined in the peroneal nerve. Mathematical modeling applied to fiber recruitment and diameter distributions allowed discrimination of the Aalpha- and Abeta-fiber populations. In regenerating nerves, the number of Aalpha-fibers increased fourfold while the number of Abeta-fibers did not change. In regenerating Aalpha- and Abeta-fibers, the fiber diameter decreased and V(50) and t(50) increased. The regenerating Aalpha-fibers' contribution to Q(max) decreased considerably while that of the Abeta-fibers remained the same. Correlation of the electrophysiological data to the morphological data provided indications that the ion channel composition of both the Aalpha- and Abeta-fibers are altered during regeneration. This demonstrates that combining morphometric and electrophysiological analysis provides better insight in the changes that occur during regeneration.     

The organization of visceral sensory neurons in thoracic dorsal root gangla (DRG) of the cat studied by horseradish peroxidase (HRP) reaction using the cryostat

The organization of visceral sensory neurons in thoracic dorsal root ganglia (DRG) was studied by retrograde transport of horseradish peroxidase (HRP) from the central cut end of the left major splanchnic nerve of the cat. The majority of HRP-labeled cells were concentrated between T5 and T11. Within a DRG, labeled splanchnic neurons were found in all sectors. There was no consistent pattern of localization within the ganglion although clustering of visceral cell bodies was apparent. It may be that each clustered group of cells innervates individual viscera or reflects a degree of functional segregation.     

Effect of GABA‐ergic mechanisms on synaptosomal NO synthesis and the nitrergic component of NANC relaxation in rat ileum

Background  γ‐Aminobutyric acid (GABA) acts on specific neural receptors [A, B and C(Aρ)] to modulate gastrointestinal function. The precise role of GABA receptor activation in the regulation of presynaptic nitric oxide (NO) synthesis in nerve terminals is unknown. Methods  Rat ileal nerve terminals were isolated by differential centrifugation. Nitric oxide synthesis was analysed using a L‐[³H]arginine assay. In vitro studies were performed under non‐adrenergic non‐cholinergic (NANC) conditions on isolated ileal segments. Key Results  γ‐Aminobutyric acid inhibited NO synthesis significantly (n = 6, P < 0.05) [(fmol mg⁻¹ min⁻¹) control: 27.7 ± 1.5, 10⁻⁶ mol L⁻¹: 19.7 ± 1.3; 10⁻⁵ mol L⁻¹: 17.5 ± 3.0]. This effect was antagonized by the GABA A receptor antagonist bicuculline and the GABA C receptor antagonist (1,2,5,6‐tetrahydropyridin‐4‐yl)methylphosphinic acid (TPMPA), but not by the GABA B receptor antagonist SCH 50911. The GABA A receptor agonist muscimol [(fmol mg⁻¹ min⁻¹) control: 27.6 ± 1.0, 10⁻⁶ mol L⁻¹: 19.1 ± 1.7, n = 5, P < 0.05] and the GABA C receptor agonist cis‐4‐aminocrotonic acid (CACA) [(fmol mg⁻¹ min⁻¹) control: 29.5 ± 3.2, 10⁻³ mol L⁻¹: 20.3 ± 2.5, n = 6, P < 0.05], mimicked the GABA‐effect, whereas the GABA B agonist baclofen was ineffective. Bicuculline reversed the inhibitory effect of muscimol, TPMPA antagonized the effect of CACA. In functional experiments the GABA A and C receptor agonists reduced the NANC relaxation induced by electrical field stimulation in rat ileum by about 40%. After NOS‐inhibition by Nε‐nitro‐l ‐arginine methyl ester (l ‐NAME) the GABA A receptor agonist had no effect, whereas the GABA C receptor agonist still showed a residual response. Conclusions & Inferences  γ‐Aminobutyric acid inhibits neural NO synthesis in rat ileum by GABA A and GABA C(Aρ) receptor‐mediated mechanisms.     

A GABAergic mechanism in the inhibition of cardiac vagal reflexes

A depressor response and bradycardia were produced by aortic nerve stimulation in urethane-chloralose-anaesthetized, paralyzed and artificially ventilated rabbits. Stimulation of the superficial peroneal nerve (SP) or rostral ventrolateral medulla (rVLM) inhibited the aortic nerve stimulation-evoked bradycardia, which was also inhibited by direct microinjection of GABA into the dorsal vagus nucleus (DVN). Application of bicuculline methiodide into the same medullary area antagonized the effect of GABA and partially or completely abolished the SP or rVLM stimulation-produced inhibition. However, strychnine hydrochloride had no effect on the SP or rVLM stimulation-produced inhibition. These observations indicate that GABAergic system present at the DVN is possibly involved in the inhibition of evoked bradycardia during somatic afferent and rVLM stimulation.     

Naloxone effects on the blood pressure response induced by thin-fiber muscular afferents

Naloxone effects on the blood pressure level and on the blood pressure responses induced by thin-fiber muscular afferent stimulation were studied in anesthetized, bilaterally vagotomized and carotid sinus nerve-denervated dogs under artificial ventilation. Repetitive pulses of 8 Hz with various intensities were applied to the gastrocnemius nerve for 1 min while monitoring the compound action potentials. The mean arterial pressure significantly(P < 0.001) rose by10.95 ± 1.78mmHg (mean ± S.E.) about 5 min after a naloxone injection. Compared with the reflexive response in the control period, the depressor effect significantly decreased by3.80 ± 1.06mHg and the pressor effect significantly increased by3.63 ± 0.73mHg for 30 min after the injection of naloxone. No correlation was found between naloxone effects on the blood pressure level and on the reflex response, indicating an involvement of different mechanisms with these naloxone effects. We suggest that endogenous opiates might participate in the regulation of the blood pressure level, as well as of the blood pressure responses caused by thin-fiber muscular afferents.     

Cardiovascular afferent inputs to neurons in the ventrolateral medulla projecting directly to the central autonomic area of the thoracic cord in the cat

Experiments were done in chloralosed, paralyzed and artificially ventilated cats to identify single units in the ventrolateral medulla (VLM) projecting directly to the central autonomic area of the thoracic cord (CA) and responding to peripheral and central inputs carrying cardiovascular information. Forty-three single units were antidromically activated in the VLM to stimulation of either ipsilateral or contralateral CA with latencies corresponding to conduction velocities of 27.5 ± 2.0m/s. Of these 43 units, only 14 (33%) responded orthodromically to stimulation of either the carotid sinus nerve (CSN) or of pressor sites in the paraventricular nucleus of the hypothalamus (PVM) or both. These experiments have demonstrated a bilateral projection of VLM neurons to the CA and have provided evidence for their role in integrating and mediating cardiovascular information from the CNS and PVH directly to spinal sympathetic centers.     

Cytoskeletal organization of the developing mouse olfactory nerve layer

Olfactory sensory neuron (OSN) axonal extension and targeting occur within the olfactory nerve layer (ONL) of the olfactory bulb (OB). The ONL can be differentiated into sublaminae: the outer (ONLo), where axons broadly target regions of the OB in tight fascicles, and inner (ONLi), where axons perform final targeting in loosely organized fascicles. During perinatal development, cadherin-2 and its binding partner, gamma-catenin, are preferentially expressed by OSN axons in the ONLo vs. the ONLi. Given the expression of these cytoskeleton-associated molecules, we hypothesized that cytoskeletal elements of OSN axons may be differentially expressed across the ONL. We therefore examined cytoskeletal organization of OSN axons in the ONL, focusing on the day of birth (P0). We show that microfilaments, microtubules, and the intermediate filament (IF) vimentin are homogeneously expressed across the ONL at P0. In contrast, the IFs peripherin and alpha-internexin are preferentially localized to the ONLo at P0, with alpha-internexin expressed by a restricted subset of OSNs. We also show that OSN axons in the ONLo are significantly smaller than those in the ONLi. The data demonstrate that, as OSN axons begin to exit the ONLo and target a specific region of the OB, there is a down-regulation of cytoskeletal elements and bound extracellular adhesion molecules. The increase in axon diameter may reflect additional mechanisms involved in glomerular targeting or the formation of the large terminal boutons of OSN axons within glomeruli.     

Somatosensory evoked potentials during the ideation and execution of individual finger movements

Scalp somatosensory evoked potentials (SEPs) were recorded in 10 volunteers after median nerve stimulation, in four experimental conditions of hand movements performance/ideation, and compared with the baseline condition of full relaxation. The experimental conditions were (a) self-improvised hand-finger sequential movements; (b) the same movements according to a read sequence of numbers; (c) mental ideation of finger movements; and (d) passive displacement of fingers in complete relaxation. Latencies and amplitudes of the parietal (N20, P25, N33, and P45) and frontal peaks (P20–22, N30, and P40) were analyzed. Latencies did not vary in any of the paradigms. Among the parietal complexes, only the P25-N33 amplitude was significantly reduced in (a), (b), (c), and (d) and the N20-P25 was reduced in (a) and (d); among frontal waves, N30 and P40 were significantly reduced (20–75%) in (a) and (b). Coronal electrodes showed amplitude decrements maximal at the frontal-rolandic positions contralateral to the stimulated side. © 1996 John Wiley & Sons, Inc.     

A deficiency in Aα chain's N-terminal alanine residue as a major cause of the slow coagulation of fetal fibrinogen

To clarify the mechanism which causes the coagulation time of fetal fibrinogen to be longer than that of adult fibrinogen, the N-terminal amino acid residues of fetal fibrinogen were analyzed. The results showed that the amount of Aa chain's N-terminal alanine residues in fetal fibrinogen was only 54% of that in adult fibrinogen. When the amount of Aα chain's N-terminal residual alanine in adult fibrinogen was decreased to 57% of the normal level by digestion with aminopeptidase M, the adult fibrinogen yielded a prolonged thrombin time and a retarded release rate for fibrino-peptides A and B, both values approximating to those of fetal fibrinogen. The results suggest that the deficiency in alanine residue at the N-terminus of the Aa chain is a major cause of the slow coagulation of fetal fibrinogen.