External Cortex Research Articles

A classification of NOergic neurons in the inferior colliculus of rat according to co-existence with classical amino acid transmitters

Since the localization of nitric oxide synthase (NOS) can be identified by enzyme histochemistry for NADPH-diaphorse (NADPH-d), this method has been used widely for mapping NOS-containing (presumably NOergic) neurons in the central nervous system. So far several studies suggest that NADPH-d is present in distinct neuronal populations in the inferior colliculus (IC), a major processing center for both the ascending and descending auditory pathway, and NO may play an important role in audition. On one hand, there is evidence from several lines of research that the IC makes extensive use of the neuroactive amino acids, in particular the inhibitory transmitter g-aminobutyric acid (GABA) and the excitatory amino acid glutamate (GLU). However, lacking is a description of the distribution of NOergic neurons to which traditional neurotransmitters may be linked. The present research utilized NADPH-d enzyme histochemistry in combination with immunocytochemistry to determine if NO may colocalize with either or both GABA and glutamate in distinct subpopulations of IC neurons. The NADPH-d positive neurons were predominantly found in two main subdivisions of the IC: the external cortex (ECIC) and the dorsal cortex (DCIC). The large numbers of these NADPH-d positive neurons appeared immunostained for GLU while only a small number, seemed to belong to the small cells (somatic area < 100 microm2) similarity to stellate cells group was positive for GABA throughout the cortex of the IC. Owing to no coexistence between GABA and GLU in the same NADPH-d positive neuron in the pairs of adjacent sections of the IC by the mirror-image technique, the present results consequently support that NOergic neurons could be subdivided into at least three distinct populations with a large proportion of about 77% being GLUergic, much lower frequency of about 11% being GABAergic and the remaining 12% expressing non-GABA and non-GLU. In summary, the existence of two functionally distinct populations of NO/GABAergic and NO/GLUergic neurons in the NOergic neurons of IC suggest that at least two differential pattern of GLU-mediated excitatory NO transmission and GABA-mediated inhibitory NO transmission are involved in the networking of auditory communication in the cortex of IC.

Atrial natriuretic factor decreases renal dopamine turnover and catabolism without modifying its release

Atrial natriuretic factor (ANF) and dopamine (DA) are both important regulators of sodium and water transport across renal proximal tubules. Many evidences suggest that some of ANF inhibitory effects on sodium and water reabsorption are mediated by dopaminergic mechanisms. We have previously reported that ANF stimulates extraneuronal DA uptake in external renal cortex by activation of NPR-A receptors coupled to cGMP signal and PKG. Moreover, ANF enhanced DA-induced inhibition of Na +–K + ATPase activity. The aim of the present study was to evaluate if ANF could alter also renal DA release, catabolism and turn over. The results indicate that ANF did not affect basal secretion of the amine in external renal cortex or its KCl-induced release, but diminished DA turn over. Moreover, ANF diminished COMT and did not alter MAO activity. In conclusion, present results as well as previous findings show that ANF modifies DA metabolism in rat external renal cortex by enhancing DA uptake and decreasing COMT activity. All those effects, taken together, may favor DA accumulation into renal cells and increase its endogenous content and availability. This would permit D1 receptor recruitment and stimulation and in turn, Na +, K +-ATPase activity over inhibition that results in decreased sodium reabsorption. Therefore, ANF and DA could act via a common pathway to enhance natriuresis and diuresis.

Poster 207: Mandibular Angle Contour Surgery

Angular prominence of the mandible is an esthetic problem for some Asian women. Reduction of a prominent angle of the mandible is often requested to improve body image. We approach the reduction of the angle of the mandible differently depending on the lower facial contours. A prominent mandibular genial angle is reduced by angle resection. Oscillating saws are used to reshape the prominent mandibular angle into a smooth and round curve at the angle. A curved rasp, in a reciprocating saw hand piece, is helpful for smoothing the irregular bony cut surface. A square face with wide mandibular angles is reduced by a capital ostectomy of the outer cortex of the mandibular angle and posterior body. A horizontal bony incision is made from the external oblique ridge to the posterior border of the mandible. Then a reciprocating saw is used to osteotomize the external cortex of the lower third of the ramus and the lower two thirds of the posterior body of the mandible. An additional reduction procedure is added in patients with masseteric hyperplasia. Condylar fracture, bleeding from the facial artery, asymmetry, hypoesthesia of the lower lip, and unnatural appearance are the possible complications associated with mandible reduction surgery. Experienced oral and maxillofacial surgeons with advanced knowledge of the anatomy, physiology and pathology with the appropriate surgical skills should be able to avoid these complications.

Deafness associated changes in two-pore domain potassium channels in the rat inferior colliculus

Two-pore potassium channels can influence neuronal excitability by regulating background leakage of potassium ions and resting membrane potential. The present study used quantitative real time PCR and in situ hybridization to determine if the decreased activity from deafness would induce changes in two-pore potassium channel subunit expression in the rat inferior colliculus (IC). Ten subunits were assessed with quantitative real-time PCR at 3 days, 3 weeks and 3 months following bilateral cochlear ablation. TASK-1, TASK-5 and THIK-2 showed significant decreases in expression at all three times assessed. TASK-5, relatively specific to auditory neurons, had the greatest decrease. TWIK-1 was significantly decreased at 3 weeks and 3 months following deafness and TREK-2 was only significantly decreased at 3 days. TASK-3, TWIK-2, THIK-1, TRAAK and TREK-1 did not show any significant changes in gene expression. In situ hybridization was used to examine TASK-1, TASK-5, TWIK-1 and THIK-2 in the central nucleus, dorsal cortex and lateral (external) cortex of the IC in normal hearing animals and at 3 weeks following deafening. All four subunits showed expression in neurons throughout IC subdivisions in normal hearing rats, with TASK-5 having the greatest overall number of labeled neurons. There was no co-localization of subunit expression with glial fibrillary acidic protein immunostaining, indicating no expression in glia. Three weeks following deafening there was a significant decrease in the number of neurons expressing TASK-1 and THIK-2 in the IC, while TASK-5 had significant decreases in the central nucleus and dorsal cortex and TWIK-1 in the lateral and dorsal cortices.

A plywood structure in the shell of fossil and living soft-shelled turtles (Trionychidae) and its evolutionary implications

The shell of soft-shelled turtles (Cryptodira: Trionychidae) can be characterised by a flexible bridge region, the loss of peripherals and a flattened carapace that is covered not with keratinous shields but with a leathery dermis. Here, we give a detailed description of the bone histology of this natural body armour that is unique not only among turtles but also among all known vertebrates. The flat bone elements have a sandwich-like morphology, with an internal and external compact bone layer framing inner cancellous bone. The external cortex is subdivided into two separate zones. The outer zone of the external cortex, which encompasses the ornamentation pattern typical for trionychid turtle shell bones, is comprised of lamellar bone. Similarly, the whole of the internal cortex is comprised of lamellar bone. The inner zone of the external cortex, however, consists of a highly ordered, plywood-like arrangement of structural collagen fibre bundles within the bone and skin of the shell. The orientation of the collagenous fibres also prescribes the orientation of the mineral phase of the bone, the hydroxyl-apatite crystallites. Strikingly, this peculiar fibre bundle arrangement strongly resembles artificial reinforced fibre-strengthened polymeric materials that combine superior mechanical strength with low weight. We hypothesise that the evolutionary success of soft-shelled turtles is tied to this plywood-like structure of the skin and bone. It may have been the key adaptation that allowed trionychids to greatly reduce and flatten their protective shell, resulting in decreased mineral needs for hard tissues, improved camouflage and hunting performance, biomechanical stability of the shell, as well as overall increased agility and short-term swimming boosts. Significantly, it also may have enabled more efficient cutaneous breathing while still retaining effective armour in both the fossil and Recent trionychid turtles.

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

The superior olivary complex (SOC) and inferior colliculus (IC) are targets of cortical projections as well as sources of major ascending auditory pathways. This study examines whether the cortical projections contact cells in the SOC or IC that project to higher levels. First, we placed an anterograde tracer into the auditory cortex to label cortico-olivary axons and a retrograde tracer into the IC to label olivocollicular cells in guinea pigs. Cortical axons contacted many labeled cells in the ipsilateral SOC and fewer labeled cells in the contralateral SOC. Contacted cells projected to the ipsilateral or contralateral IC. In a second experiment, we labeled corticocollicular axons with an anterograde tracer and injected retrograde tracers into the medial geniculate (MG) to label colliculogeniculate cells. In the IC ipsilateral to the cortical injection, many cortical axons contacted colliculogeniculate cells in the dorsal cortex and external cortex of the IC. The contacted cells projected to the ipsilateral MG or, less often, to the contralateral MG. The results indicate that cortical projections are likely to contact cells in the SOC and IC that project to higher centers. This suggests that auditory cortex can modulate the ascending auditory pathways at multiple levels of the brainstem.

S13.C RLS-like activity and PLM in rat after bicuculline microinfusion into the ventral external cortex of the inferior colliculus

S13.C RLS-like activity and PLM in rat after bicuculline microinfusion into the ventral external cortex of the inferior colliculus

Intrinsic membrane properties and synaptic response characteristics of neurons in the rat’s external cortex of the inferior colliculus

The inferior colliculus (IC) can be divided into three anatomical subdivisions: the central nucleus (ICc), the dorsal cortex (ICd) and the external cortex (ICx). ICx receives its primary auditory inputs from ICc and auditory cerebral cortical areas, and non-auditory inputs from regions of motor and other sensory systems. This wide array of projections makes the ICx a distinct structure within the auditory brainstem. The purpose of the current study was to comprehensively characterize the neuronal population of ICx, by intrinsic and synaptic response properties. Visual whole-cell patch clamp recordings were taken from ICx neurons ( N=129) from rats between postnatal days 8 to 12. Neurons displayed various types of firing patterns in response to current injection, including regular, adapting, pauser and bursting. The regular cells constitute the majority (66%), followed by adapting (18%), pauser (13%) and bursting cells (2%). In response to hyperpolarizing current injection, many neurons illustrated a pronounced sag in the membrane potential, representing a hyperpolarization-activated current (I h ). Some neurons (25%) displayed a Ca 2+-dependent rebound depolarization following negative current injection. In response to depolarizing current injection, 70% of ICx neurons displayed a Ca 2+-mediated potential expressed as Ca 2+ spikes/humps, uncovered when Na + and K + currents were removed. Also, spikes displayed an undershoot which was in part mediated by Ca 2+. Stimulation of the ICc elicited graded synaptic responses, which displayed a combination of excitatory and/or inhibitory potentials, with excitation being predominant across firing patterns. Neurons displayed temporal summation in response to repetitive stimulation at 20 Hz and higher. The results indicate a relatively modest diversity in firing pattern and in intrinsic membrane properties, making this subnucleus distinct from its counterparts within the IC. The data show that ICx receives major excitatory input from ICc, supporting its role in integrating signals from brainstem and directing information to higher brain centers.

Angiotensin II Regulates Extraneuronal Dopamine Uptake in the Kidney

Background/Aims: Angiotensin II (ANG II) and dopamine (DA) are both important regulators of sodium and water transport across renal proximal tubules. Previous studies demonstrate that atrial natriuretic factor (ANF) can regulate renal DA uptake and thereby Na⁺,K⁺-ATPase activity in the external renal cortex. As ANG II counteracts most of the ANF biological effects, the aim of the present study was to evaluate ANG II effects on renal DA metabolism and identify the receptor involved. Methods: To determine ANG II effects on renal DA metabolism, we evaluated ³H-DA uptake in vitro in kidney tissue samples from Sprague-Dawley rats. Results: The results indicate that ANG II decreased DA uptake at 30 min, in a concentration-response fashion, in the external and juxtamedullar cortex. DA uptake was characterized as an extraneuronal uptake and decreased at 0°C and in sodium-free medium. The biological receptor type involved was AT₁, since losartan reversed ANG II effects on DA uptake while AT₂ receptors were not involved since PD 123319 did not affect ANG II effects. The absence of sodium did not alter the ANG II response. Conclusion: ANG II inhibits DA uptake by kidney tubular cells. These effects implicate AT₁ receptors without participation of AT₂ receptors. This mechanism could be related to the DA effects on sodium reabsorption and linked to ANG II antinatriuretic effects in the kidney.

Intracortical remodeling during human bone development—A histomorphometric study

Although intracortical bone remodeling is a key aspect of bone physiology, very little is known about this process during human bone development. In this study, we examined transiliac bone samples from 56 individuals between 1.5 and 22.9 years of age (31 female; tetracycline labeling present in 42 subjects) who did not have evidence of metabolic bone disease. Parameters of osteonal structure (osteon diameter, wall thickness, diameter of osteonal canals) and dynamic measures of intracortical remodeling were determined separately for the external and internal cortex. We found that measures of osteonal structure were independent of age. However, the percentage of osteons showing metabolic activity was lower in the older study subjects, corresponding to a slowdown in the turnover of cortical bone. Most dynamic parameters of bone metabolism were higher in the internal cortex than in the external cortex. Cortical porosity was negatively associated with age on the external, but not on the internal cortex. The bone forming activity that refills the remodeling cavities seemed to favor the side of the osteonal canal that faced towards the periosteum. In summary, intracortical remodeling activity varies markedly during bone development, and is slightly asymmetric between the two cortices of an iliac bone specimen. Remodeling during development is thus an age-dependent process that varies with location even within the same bone.

Relationship of opioid receptors with GABAergic neurons in the rat inferior colliculus

The inferior colliculus is a critical structure for processing auditory information and receives ascending and descending synaptic auditory projections. In addition to GABAergic and glutamatergic innervations, other neurotransmitter systems are also reported in the inferior colliculus, including opioid peptides. In the present study, the relative distribution of each type of opioid receptor, mu (MOR), delta (DOR) and kappa (KOR) within GABAergic neurons in the inferior colliculus was examined. GABA immunoreactivity was expressed by small, medium and large neurons and distributed in the central nucleus and the pericentral nucleus of the inferior colliculus. Immunostaining for MOR, DOR and KOR receptors was found in both disc-shaped cells and stellate cells. Punctiform beta-endorphin immunolabelling was observed in the proximity of GABA-positive neurons. Co-localization of GABA and MOR receptors was observed in neurons and nerve terminals in the central nucleus, dorsal cortex and external cortex of the inferior colliculus. Quantification of the co-localization patterns determined that a higher proportion of GABA neurons was associated with MOR receptors compared with KOR or DOR receptors.

Signaling pathways involved in atrial natriuretic factor and dopamine regulation of renal Na +, K +-ATPase activity

Dopamine (DA) and atrial natriuretic factor (ANF) share a number of physiological effects. We hypothesized that ANF and the renal dopaminergic system could interact and enhance the natriuretic and diuretic effects of the peptide. We have previously reported that the ANF-stimulated DA uptake in renal tubular cells is mediated by the natriuretic peptide type-A receptor (NPR-A). Our aim was to investigate the signaling pathways that mediate ANF effects on renal 3H-DA uptake. Methylene blue (10 μM), an unspecific inhibitor of guanylate cyclase (GC), blunted ANF elicited increase of DA uptake. ODQ (10 μM) a specific inhibitor of soluble GC, did not modify DA uptake and did not reverse ANF-induced increase of DA uptake; then the participation of nitric oxide-dependent pathways must be discarded. The second messenger was the cGMP since the analogous 125 μM 8-Br-cGMP mimicked ANF effects. The specific inhibitor of the protein kinase G (PKG), KT 5823 (1 μM) blocked ANF effects indicating that PKG is involved. We examined if ANF effects on DA uptake were able to modify Na +, K +-adenosine triphosphatase (Na +, K +-ATPase) activity. The experiments were designed by means of inhibition of renal DA synthesis by carbidopa and neuronal DA uptake blocked by nomifensine. In these conditions renal Na +, K +-ATPase activity was increased, in agreement with the decrease of DA availability. When in similar conditions, exogenous DA was added to the incubation medium, the activity of the enzyme tended to decrease, following to the restored availability of DA. The addition of ANF alone had similar effects to the addition of DA on the sodium pump, but when both were added together, the activity of Na +, K +-ATPase was decreased. Moreover, the extraneuronal uptake blocker, hydrocortisone, inhibited the latter effect. In conclusion, ANF stimulates extraneuronal DA uptake in external cortex tissues by activation of NPR-A receptors coupled to GC and it signals through cGMP as second messenger and PKG. Dopamine and ANF may achieve their effects through a common pathway that involves reversible deactivation of renal tubular Na +, K +-ATPase activity. This mechanism demonstrates a DA–ANF relationship involved in the modulation of both decreased sodium reabsorption and increased natriuresis.

A comparison of cortical elastic properties in the craniofacial skeletons of three primate species and its relevance to the study of human evolution

When a force is applied to an object, the resulting pattern of strain is a function of both the object's geometry and its elastic properties. Thus, knowledge of elastic properties in craniofacial cortical bone is indispensable for exploring the biomechanics and adaptation of primate skulls. However, elastic properties, such as density and stiffness, cannot be measured in all species, particularly extinct species known only from fossils. In order for advanced engineering techniques such as finite element analysis (FEA) to be applied to questions of primate and hominid craniofacial functional morphology, it is important to understand interspecific patterns of variation in elastic properties. We hypothesized that closely related species would have similar patterns of bone elastic properties, and that similarities with extant species should allow reasonable predictions of elastic properties in the skeletons of extinct primate species. In this study, we tested this hypothesis by measuring elastic properties in five areas of the external cortex of the baboon craniofacial skeleton using an ultrasonic technique, and by comparing the results to existing data from macaque and human crania. Results showed that cortical density, thickness, elastic and shear moduli, and anisotropy varied among areas in the baboon cranium. Similar variation had previously been found in rhesus and human crania, suggesting area-specific elastic patterns in the skulls of each species. Comparison among species showed differences, suggesting species-specific patterns. These patterns were more similar between macaques and baboons for density, maximum elastic and shear stiffness, and anisotropy than between either of these and humans. This finding demonstrates that patterns of cortical elastic properties are generally similar in closely related primate species with similar craniofacial morphology. Thus, reasonable estimates of cortical bone elastic properties should be possible for extinct species through the study of phylogenetically related and functionally similar modern forms. For example, reasonable elastic property estimates of cortical bone from fossil hominid skulls should be possible once adequate information about such properties in extant great apes is added to our current data from humans, macaques, and baboons. Such data should eventually allow FEA of craniofacial function in fossil hominids.

Elastic properties of external cortical bone in the craniofacial skeleton of the rhesus monkey

Knowledge of elastic properties and of their variation in the cortical bone of the craniofacial skeleton is indispensable for creating accurate finite-element models to explore the biomechanics and adaptation of the skull in primates. In this study, we measured elastic properties of the external cortex of the rhesus monkey craniofacial skeleton, using an ultrasonic technique. Twenty-eight cylindrical cortical specimens were removed from each of six craniofacial skeletons of adult Macaca mulatta. Thickness, density, and a set of longitudinal and transverse ultrasonic velocities were measured on each specimen to allow calculation of the elastic properties in three dimensions, according to equations derived from Newton's second law and Hooke's law. The axes of maximum stiffness were determined by fitting longitudinal velocities measured along the perimeter of each cortical specimen to a sinusoidal function. Results showed significant differences in elastic properties between different functional areas of the rhesus cranium, and that many sites have a consistent orientation of maximum stiffness among specimens. Overall, the cortical bones of the rhesus monkey skull can be modeled as orthotropic in many regions, and as transversely isotropic in some regions, e.g., the supraorbital region. There are differences from human crania, suggesting that structural differences in skeletal form relate to differences in cortical material properties across species. These differences also suggest that we require more comparative data on elastic properties in primate craniofacial skeletons to explore effectively the functional significance of these differences, especially when these differences are elucidated through modeling approaches, such as finite-element modeling.

Cellular Activity on the Seven Surfaces of Iliac Bone: A Histomorphometric Study in Children and Adolescents

Transiliac cortical bone histomorphometry was performed in 56 metabolic bone disease-free individuals 1.5-22.9 years of age. During the growing years, the two cortices of an iliac bone specimen differ with regard to bone cell activity on their surfaces, probably reflecting a modeling drift. Standard bone histomorphometry in the clinical setting is typically limited to the analysis of cancellous bone. However, during the growth period, important changes occur also in the cortical compartment. Transiliac bone samples from 56 individuals between 1.5 and 22.9 years of age (25 male; tetracycline labeling present in 42 subjects) and without evidence of metabolic bone disease were analyzed. Each of the three bone surface types (periosteal, intracortical, endocortical) of each cortex was evaluated separately. Results were expressed relative to those obtained in trabecular bone. A significant increase in cortical width with age was detected only for the internal cortex. Porosity of the external cortex was highest in the 7- to 10.9-year age group and decreased thereafter, whereas there was no clear trend with age for the porosity of the internal cortex. Intracortical remodeling activity decreased after 14 years of age. Periosteal bone formation was very active until 13 years of age, but was close to zero in subjects above that age. As to endocortical surfaces, all bone surface-based parameters of bone formation were higher on the internal cortex than on the external cortex, whereas bone resorption parameters were higher on the external cortex. In growing subjects, the two cortices of an iliac bone specimen differ with regard to bone cell activity on their surfaces. These data raise fundamental questions about the regulation of bone cell activity in children and adolescents.

Convergence of spinal trigeminal and cochlear nucleus projections in the inferior colliculus of the guinea pig

In addition to ascending auditory inputs, the external cortex of the inferior colliculus (ICX) receives prominent somatosensory inputs. To elucidate the extent of interaction between auditory and somatosensory representations at the level of IC, we explored the dual projections from the cochlear nucleus (CN) and the spinal trigeminal nucleus (Sp5) to the inferior colliculus (IC) in the guinea pig, using both retrograde and anterograde tracing techniques. Injections of retrograde tracers into ICX resulted in cell-labeling primarily in the contralateral DCN and pars interpolaris and caudalis of Sp5. Labeled cells in DCN were either fusiform or multipolar cells, whereas those in Sp5 varied in size and shape. Injections of anterograde tracers into either CN or Sp5 resulted in terminal labeling in ICX primarily on the contralateral side. Most projection fibers from Sp5 terminated in a laminar pattern from ventromedial to dorsolateral within the ventrolateral ICX, the ventral border of IC, and the ventromedial edge of IC (collectively termed "the ventrolateral border region of IC," ICXV). Less dense anterograde labeling was observed in lateral and rostral ICX. Injecting different tracers into both Sp5 and CN confirmed the overlapping areas of convergent projections from Sp5 and CN in IC: The most intense dual labeling was seen in the ICXV, and less intense dual labeling was also observed in the rostral part of ICX. This convergence of projection fibers from CN and Sp5 provides an anatomical substrate for multimodal integration in the IC.

Novelty detector neurons in the mammalian auditory midbrain

Novel stimuli in all sensory modalities are highly effective in attracting and focusing attention. Stimulus-specific adaptation (SSA) and brain activity evoked by novel stimuli have been studied using population measures such as imaging and event-related potentials, but there have been few studies at the single-neuron level. In this study we compare SSA across different populations of neurons in the inferior colliculus (IC) of the rat and show that a subclass of neurons with rapid and pronounced SSA respond selectively to novel sounds. These neurons, located in the dorsal and external cortex of the IC, fail to respond to multiple repetitions of a sound but briefly recover their excitability when some stimulus parameter is changed. The finding of neurons that respond selectively to novel stimuli in the mammalian auditory midbrain suggests that they may contribute to a rapid subcortical pathway for directing attention and/or orienting responses to novel sounds.

DEFINITION OF INTERNAL MORPHOLOGY AND STRUCTURAL CHANGES DUE TO DEHYDRATION OF RADISH (RAPHANUS SATIVUS L. CV. SUPRELLA) USING MAGNETIC RESONANCE IMAGING SPECTROSCOPY

ABSTRACT Magnetic resonance imaging (MRI) spectroscopy is a promising nondestructive analytical technique in food science. It offers the unique opportunity of studying vegetables, fruits and other foods in general, in their wholeness without any preparative manipulation of the sample. The aim of this study was to investigate the internal structure of radish and to monitor the variations induced by postharvest storage at low relative humidity. The MRI allowed for a clear definition of the internal structure of radishes with distinct visibility of xylematic and phloematic vessels distributed in a radial way. A decrease in water content, which results in the breakdown of tissues and the formation of large cavities with the detachment of the external cortex, is the main consequence of a few days' storage in low relative humidity. Both of these are factors that drastically decrease the quality of the radish's fleshy root. The MRI images give a novel insight into the internal organization of the hypocotyl, and this offers opportunities for further studies with regard to the structural differences related to the cultivars as well as the cultivation system.

Tyrosine hydroxylase in rat auditory midbrain: Distribution and changes following deafness

Tyrosine hydroxylase (TH), a key enzyme in the catecholaminergic pathway, allows for the differentiation of dopaminergic neurons. We previously showed decreases in TH gene expression in the rat inferior colliculus (IC) 3 and 21 days following deafness. In the present study, we characterized the normal distribution of TH as well as changes following deafness (bilateral cochlear ablation) in the IC and nuclei of the lateral lemniscus. Immunostaining was compared in three groups of rats: normal hearing ( n = 8), 21 day deaf ( n = 5) and 90 days following deafening ( n = 5). Many TH immunoreactive fibers and puncta were identified in the IC and nuclei of the lateral lemniscus of normal hearing animals and labeling was most dense in the external cortex of the IC. We also identified immunolabeling for fibers and puncta for another catecholaminergic enzyme, dopamine β hydroxylase (DBH), but not phenylethanolamine- N-methyltranferase (PNMT). Neurons immunopositive for TH but not DBH or PNMT were observed in the dorsal cortex and dorsal horn of the central nucleus of the IC and ventral and intermediate lemniscus. In the central nucleus of the IC and dorsal lateral lemniscus many lightly labeled TH neurons were also DBH positive. Although the number of immunopositive cells in the IC and lemniscus declined 3 weeks and 3 months after deafening, the decline was not significant at three weeks in the VNLL nor after three months in the dorsal cortex. Immunolabeling for TH decreased significantly in IC and lemniscus 3 weeks and 3 months following deafening. These results suggest a role for dopaminergic neurons and fibers in deafness-related plasticity.

The effect of low-intensity pulsed ultrasound on callus maturation in tibial distraction osteogenesis

Callus distraction is currently the most popular method of bone lengthening. Prolonged treatment time is one of its major problems. In this study, we investigated the effect of low-intensity pulsed ultrasound on tibial distraction osteogenesis. We managed 20 patients with tibial defects ranging from 5 cm to 8 cm with distraction osteogenesis using the Ilizarov external fixator. After the completion of distraction, ten patients received daily 20 min of low-intensity pulsed ultrasound stimulation (30 mW/cm2) onto the bone lengthening site (group A) while rigid fixation was maintained in the remaining patients (group B). All patients were followed with weekly radiographs to determine the formation of an external cortex and an intramedullary canal, at which time the fixator was removed. The mean healing index in group A was 30 (27-36) days/cm while it was 48 (42-75) days/cm in group B. In group B, one patient failed to consolidate the regenerated bone. Low-intensity pulsed ultrasound stimulation is highly effective in achieving maturation of bone and reducing time of distraction osteogenesis.