Caudal Cortex Research Articles

Differential Gene Expression between Sensory Neocortical Areas: Potential Roles for Ten_m3 and Bcl6 in Patterning Visual and Somatosensory Pathways

Adult neocortical areas are characterized by marked differences in cytoarchitecture and connectivity that underlie their functional roles. The molecular determinants of these differences are largely unknown. We performed a microarray analysis to identify molecules that define the somatosensory and visual areas during the time when afferent and efferent projections are forming. We identified 122 molecules that are differentially expressed between the regions and confirmed by quantitative polymerase chain reaction 95% of the 20 genes tested. Two genes were chosen for further investigation: Bcl6 and Ten_m3. Bcl6 was highly expressed in the superficial cortical plate corresponding to developing layer IV of somatosensory cortex at postnatal day (P) 0. This had diminished by P3, but strong expression was found in layer V pyramidal cells by P7 and was maintained until adulthood. Retrograde tracing showed that Bcl6 is expressed in corticospinal neurons. Ten_m3 was expressed in a graded pattern within layer V of caudal cortex that corresponds well with visual cortex. Retrograde tracing and immunostaining showed that Ten_m3 is highly expressed along axonal tracts of projection neurons of the developing visual pathway. Overexpression demonstrated that Ten_m3 promotes homophilic adhesion and neurite outgrowth in vivo. This suggests an important role for Ten_m3 in the development of the visual pathway.

Fibroblast growth factor receptor 3 kinase domain mutation increases cortical progenitor proliferation via mitogen‐activated protein kinase activation

We have previously shown that mice carrying the K644E kinase domain mutation in fibroblast growth factor receptor 3 (Fgfr3) (EIIa;Fgfr3(+/K644E)) have enlarged brains with increased proliferation and decreased apoptosis of the cortical progenitors. Despite its unique rostral-low caudal-high gradient expression in the cortex, how Fgfr3 temporally and spatially influences progenitor proliferation is unknown. In vivo BrdU labelling now showed that progenitor proliferation was 10-46% higher in the EIIa;Fgfr3(+/K644E) cortex compared with wild type during embryonic day 11.5 (E11.5)-E13.5. The difference in proliferation between the EIIa;Fgfr3(+/K644E) and wild-type cortices was the greatest in the caudal cortex at E12.5 and E13.5. Inhibition of mitogen-activated or extracellular signal-regulated protein kinase (MEK) in vitro at E11.5 reduced the proliferation rate of the EIIa;Fgfr3(+/K644E) cortical progenitors to similar levels observed in the wild type, indicating that the majority of the increase in cell proliferation caused by the Fgfr3 mutation is mitogen-activated protein kinase (MAPK) pathway-dependent at this stage. In addition, elevated levels of Sprouty were observed in the EIIa;Fgfr3(+/K644E) telencephalon at E14.5, indicating the presence of negative feedback that may have suppressed further MAPK activation. We suggest that temporal activation of MAPK is largely responsible for cell proliferation caused by the Fgfr3 mutation during early stages of cortical development.

Retinoic acid delineates the topography of neuronal plasticity in postnatal cerebral cortex

Retinoic acid is well recognized to promote neuronal differentiation in the embryonic nervous system, but how it influences the postnatal cerebral cortex remains largely unknown. The domain of highest retinoic acid actions in the cortex of the mouse constricts postnatally to a narrow band that includes the dorsal visual stream and the attentional and executive networks. This band of cortex, which is distinguished by the retinoic acid-synthesizing enzyme RALDH3, exhibits signs of delayed maturation and enhanced plasticity compared to the surrounding cortex, as indicated by suppression of parvalbumin, neurofilament, cytochrome oxidase and perineuronal net maturation, and persistence of the embryonic, polysialated form of the neural cell-adhesion molecule PSA-NCAM. During the first postnatal week, the RALDH3-expressing territory translocates in the caudal cortex from the medial limbic lobe to the adjacent neocortex. This topographical shift requires the neurotrophin NT-3 because in mice lacking neuronal NT-3 the RALDH3 enzyme maintains its early postnatal pattern up to adulthood. In the NT-3-null mutants, expression of the markers, whose topography colocalizes with RALDH3 in the normal cortex, matches the abnormal RALDH3 pattern. This indicates that the uneven retinoic acid distribution serves a role in patterning the maturation and to some extent function of the normal postnatal cerebral cortex.

Robo1 regulates the development of major axon tracts and interneuron migration in the forebrain

The Slit genes encode secreted ligands that regulate axon branching, commissural axon pathfinding and neuronal migration. The principal identified receptor for Slit is Robo (Roundabout in Drosophila). To investigate Slit signalling in forebrain development, we generated Robo1 knockout mice by targeted deletion of exon 5 of the Robo1 gene. Homozygote knockout mice died at birth, but prenatally displayed major defects in axon pathfinding and cortical interneuron migration. Axon pathfinding defects included dysgenesis of the corpus callosum and hippocampal commissure, and abnormalities in corticothalamic and thalamocortical targeting. Slit2 and Slit1/2 double mutants display malformations in callosal development, and in corticothalamic and thalamocortical targeting, as well as optic tract defects. In these animals, corticothalamic axons form large fasciculated bundles that aberrantly cross the midline at the level of the hippocampal and anterior commissures, and more caudally at the medial preoptic area. Such phenotypes of corticothalamic targeting were not observed in Robo1 knockout mice but, instead, both corticothalamic and thalamocortical axons aberrantly arrived at their respective targets at least 1 day earlier than controls. By contrast, in Slit mutants, fewer thalamic axons actually arrive in the cortex during development. Finally, significantly more interneurons (up to twice as many at E12.5 and E15.5) migrated into the cortex of Robo1 knockout mice, particularly in both rostral and parietal regions, but not caudal cortex. These results indicate that Robo1 mutants have distinct phenotypes, some of which are different from those described in Slit mutants, suggesting that additional ligands, receptors or receptor partners are likely to be involved in Slit/Robo signalling.

Heteromodal connections supporting multisensory integration at low levels of cortical processing in the monkey

While multisensory integration is thought to occur in higher hierarchical cortical areas, recent studies in man and monkey have revealed plurisensory modulations of activity in areas previously thought to be unimodal. To determine the cortical network involved in multisensory interactions, we performed multiple injections of different retrograde tracers in unimodal auditory (core), somatosensory (1/3b) and visual (V2 and MT) cortical areas of the marmoset. We found three types of heteromodal connections linking unimodal sensory areas. Visuo-somatosensory projections were observed originating from visual areas [probably the ventral and dorsal fundus of the superior temporal area (FSTv and FSTd), and middle temporal crescent (MTc)] toward areas 1/3b. Somatosensory projections to the auditory cortex were present from S2 and the anterior bank of the lateral sulcus. Finally, a visuo-auditory projection arises from an area anterior to the superior temporal sulcus (STS) toward the auditory core. Injections in different sensory regions allow us to define the frontal convexity and the temporal opercular caudal cortex as putative polysensory areas. A quantitative analysis of the laminar distribution of projecting neurons showed that heteromodal connections could be either feedback or feedforward. Taken together, our results provide the anatomical pathway for multisensory integration at low levels of information processing in the primate and argue against a strict hierarchical model.

STRESS REMODELING AND STRESS FRACTURE OF THE HUMERUS IN FOUR STANDARDBRED RACEHORSES

Two 2-year-old pacers, a 3-year-old pacer and a 2-year-old-trotter with acute forelimb lameness were admitted for nuclear scintigraphic examination. Horses were grade 3-4/5 lame. There was increased radiopharmaceutical uptake (IRU) in the distal cranial medial aspect of the humerus in one horse and along the caudal humeral cortex in the other three horses. Two of the four horses were affected bilaterally. Radiographic abnormalities consisted of thickening of the caudal cortex of the mid-diaphysis of the humerus but radiographic changes were not present in all horses. All horses were managed with stall rest initially then stall rest with hand-walking followed by limited turn out for a total of four months. None of the horses had raced before injury. One horse has returned to race training and the other three horses have returned to racing. Average time to return to racing was 329 days. Humeral stress fractures in Standardbred horses are rare. Diffuse patterns of IRU have not been reported in the humerus and are likely indicative of severe stress remodeling. Standardbred racehorses with stress fractures or stress remodeling of the humerus appear to have a good prognosis for return to racing.

Lesions in the brains of three cattle resembling the lesions of enterotoxaemia in lambs

CASE HISTORY: A 3-month-old female Angus calf was found dead, and two adult Friesian dairy cows died soon after developing nervous signs. PATHOLOGICAL FINDINGS: Grossly, bilateral and mostly symmetrical areas of haemorrhage were evident that mainly involved areas of grey matter in the brainstem from the level of the caudal colliculi to the thalamus and, in one, the internal capsule and caudate nucleus. In the occipital and caudal parietal cortex, there was extensive oedema of white matter. Histologically, in addition to haemorrhage, there was protein-rich oedema around arterioles and venules in the cerebrum, hippocampus, internal capsule, thalamus, midbrain, dorsal medulla, and central cerebellar and cerebellar folial white matter. The calf's brain had bilateral and symmetrical oedema and necrosis affecting several brainstem nuclei and the occipital grey matter overlying areas of oedema of the corona radiata. DIAGNOSIS: Although the cause was not established, the perivascular lesions resembled those produced in calves by the intravenous administration of epsilon toxin. CLINICAL RELEVANCE: It is possible that epsilon toxin-induced enterotoxaemia occurs naturally in cattle, and where bilateral haemorrhage is recognised in the brains of cattle, small intestinal contents should be collected for analysis of epsilon toxin.

Early adaptations in somatosensory cortex after focal ischemic injury to motor cortex

In response to a lesion, intact regions of cortex in both hemispheres undergo adaptive changes in network function. For example, changes in excitability and intracortical inhibition in primary motor cortex (M1) were reported after lesioning contralateral or ipsilateral brain regions. Close interactions exist between M1 and primary somatosensory cortex (S1) within one hemisphere. Therefore, we hypothesized that lasting modifications would occur in S1 excitability after lesioning ipsilateral M1. Imaging of intrinsic optical signals (IOS, at 570 nm) was used to investigate the evolution of the somatosensory cortical response evoked by contralateral median nerve stimulation during the first hour after a photothrombotic lesion to M1 (caudal motor cortex) of the rat (n=10). Control rats (n=6) received no lesion. Perfusion was monitored by Laser speckle imaging and the extent of the resulting lesion was determined histologically. Control animals did not show evidence for reduced perfusion, infarction, or changes in IOS. M1 infarction led to a significant increase in evoked response amplitude, duration, and area of activation, and a shortening of latencies. These parameters reached a plateau around 50 min after ischemia. These results indicate S1 hyperexcitability after M1 injury. Whether these adaptations contribute to functional deficits or play a role in recovery, remains to be determined.

Erratum to “Relationships of loading history and structural and material characteristics of bone: Development of the mule deer calcaneus,” DOI: 10.1002/jmor.10167

The authors of the above article would like to apologize for an error and an omission contained within the text of the original article. This omission/error relates to the definition and quantification of osteocyte lacuna population density, and is twofold in nature: 1. The Materials and Methods section of the original article did not elaborate on methods employed for the quantification of osteocyte lacuna population density. These methods should have appeared under the subheading “Microstructure” on page 285. The methods, as applicable to our study, are as follows: The population density of osteocyte lacunae (N.Lac/B.Ar) was manually quantified in each 100× backscattered electron image. The N.Lac/B.Ar was defined as the total number of osteocyte lacunae (N.Lac) divided by the total area of bone (B.Ar; area of bone per image area minus nonlacunar porosity). The N.Lac/B.Ar is meant to represent the concentration of osteocytes, although no differentiation could be made between empty lacunae and those containing viable osteocytes at the time of animal death/tissue harvesting. 2. There is some confusion in our study as to the rigorous definition of osteocyte lacuna population density, and what the numbers we provided actually represent. The methods reported above in #1 are accurate, and reflect the original intent of our study—to report the number of lacunae per bone area. A subset of data provided in the original, however, did not reflect this intent. Data for the young fawns, as reported in the original study, showed a relatively lower N.Lac/Ar compared to older animals. In this case, the N.Lac/Ar was erroneously calculated as total number of osteocyte lacunae (N.Lac) divided by the total image area (Ar), without the subtraction of nonlacunar porosity. In all other age classifications, the above methods (i.e., calculation of N.Lac/B.Ar) were employed. Thus, in young fawns the data represent “N.Lac/Ar,” and reflect the number of osteocyte lacunae per total area, rather than per bone area. Therefore, for definitive clarification of the original submission, all instances of the abbreviation “N.Lac/Ar” should be revised to the more accurate abbreviation “N.Lac/B.Ar”. Furthermore, this clarification requires some adjustments to figures and tables containing N.Lac/B.Ar data, including some descriptive statistics and correlations. Revised tables and figures are provided herewith (revised Tables 4, 5a,b, revised Figs. 3f, 9b). In young fawns there are no significant N.Lac/B.Ar differences. In older fawns there are significantly more osteocyte lacunae in the caudal cortex compared to the cranial cortex. In subadults and adults, the cranial cortex has significantly more lacunae than the other cortices (*P < 0.01). There were no significant differences in N.Lac/B.Ar between medial and lateral cortices in any age group. The adult bones contained significantly fewer osteocyte lacunae when compared with all other groups (P < 0.001). The section on page 288, entitled Osteocyte lacuna population density (N.Lac/Ar) should read as follows: Osteocyte lacuna population density (N.Lac/B.Ar) (Table 4; Fig. 3f). There are significantly more osteocyte lacunae per bone area in younger and older fawns when compared to adults and subadults (P < 0.001). In adult bones, the cranial cortex has the greatest N.Lac/B.Ar. The cranial cortex contains significantly more osteocyte lacunae than the caudal cortex in subadults and adults (P < 0.05), but is similar to the caudal cortex in the young fawn group and lower than the caudal cortex in older fawns (P < 0.05). This difference is further illustrated in revised Figure 9b. There were no significant differences in N.Lac/B.Ar between medial and lateral cortices in any age group. The adult bones contained significantly fewer osteocyte lacunae when compared with all other groups (P < 0.001). The revised figure legend for Figure 3f should also read as follows: In young fawns there are no significant N.Lac/B.Ar differences. In older fawns there are significantly more osteocyte lacunae in the caudal cortex compared to the cranial cortex. In subadults and adults, the cranial cortex has significantly more lacunae than the other cortices (P < 0.01). Despite the confusion in the original study, there is some utility in the calculation of N.Lac/Ar, as was originally erroneously reported for the young fawns. Vashishth et al. (2002) used calculations of osteocyte lacunar number per tissue area (similar to N.Lac/Ar) to show correlations between osteocyte number and bone volume fraction in compact and cancellous bone. The corrected values for N.Lac/B.Ar show lacunar density to differ by ∼32% when comparing values for the young fawns vs. adults (679.9/mm2 for young fawns vs. 465.6/mm2 for adults). These values reflect trends recently reported in the literature, which describe osteocyte lacuna density to be ∼40–100% greater in woven bone than in lamellar bone (Hernandez et al.,2004). This is important, since the histology of the young fawns in the present study resembled woven bone morphology.

Descending projections from the auditory cortex to the inferior colliculus in the gerbil, Meriones unguiculatus

Corticofugal projections to the auditory midbrain, the inferior colliculus (IC), influence the way in which specific sets of IC neurons process acoustic signals. We used retrograde tracer (Fluorogold, Fluororuby, microbeads) injections in the IC to study the morphology and location of cortico-collicular projecting neurons and anterograde tracer (dextran biotin) injections in auditory cortical fields to describe the distribution of terminals in the IC. Nissl staining, cytochrome oxidase activity, and neurofilament SMI32 immunostaining were used to delimit the different auditory areas. We defined a primary or "core" auditory cortex and a secondary "caudal" auditory area containing layer V pyramidal neurons that project to the IC. These projections target the central nucleus of the IC (CNIC) ipsilaterally and the IC cortices bilaterally, with the ipsilateral component predominant. Other secondary auditory areas, dorsal and ventral to the core, do not directly participate in this projection. The ventral secondary cortex targets midbrain periaqueductal gray. The projection from the core cortex originates from two classes of layer V pyramidal cells. Cells presenting a tufted apical dendrite in layer I have dense terminal fields in the IC cortices. Pyramids lacking layer I dendritic tufts target the CNIC in a less dense but tonotopic manner. The caudal cortex projection originates from smaller layer V pyramids and targets the IC cortices with dense terminal fields. Descending auditory inputs from the core and caudal areas converge in the dorsal and external cortices of the IC. Descending connections to the gerbil IC form a segregated system in which multiple descending channels originating from different neuronal subpopulations may modulate specific aspects of ascending auditory information.

Exostoses of the caudal perimeter of the radial physis as a cause of carpal synovial sheath tenosynovitis and lameness in horses: 10 cases (1999-2003).

To determine the clinical, radiographic, ultrasonographic, and arthroscopic findings associated with tenosynovitis of the carpal synovial sheath induced by exostoses that originate from the caudal surface of the physeal scar of the distal radius and determine the results of surgical removal of those exostoses in horses. Retrospective study. 10 horses. Medical records of horses with effusion in the carpal synovial sheath and lameness evaluated from 1999 to 2003 were examined. All horses had a history of intermittent mild to moderate effusion of the carpal synovial sheath and lameness of 1 forelimb. Results of regional perineural and intrathecal anesthesia of the carpal synovial sheath confirmed that the lameness originated in the carpal synovial sheath. Radiography revealed exostoses originating from the caudal cortex of the distal radius at the level of the closed physis. Arthroscopy was performed for confirmation and removal of exostoses that penetrated the carpal synovial sheath and impinged on the deep digital flexor tendon. All horses returned to previous athletic activity. One horse had a recurrence of clinical signs 12 months after surgery, which resolved with medical treatment. Tenosynovitis of the carpal synovial sheath and lameness were caused by impingement of exostoses of the caudal radius on the lining and contents of the carpal synovial sheath. Although the clinical signs and surgical treatment were similar to that caused by osteochondromas, these exostoses developed at the level of the closed physis of the distal radius and were not radiographically or histologically similar to osteochondromas.

Ontogenetic and regional morphologic variations in the turkey ulna diaphysis: Implications for functional adaptation of cortical bone

This study examines relationships between bone morphology and mechanically mediated strain/fluid-flow patterns in an avian species. Using mid-diaphyseal transverse sections of domestic turkey ulnae (from 11 subadults and 11 adults), we quantified developmental changes in predominant collagen fiber orientation (CFO), mineral content (%ash), and microstructure in cortical octants or quadrants (i.e., %ash). Geometric parameters were examined using whole mid-diaphyseal cross-sections. The ulna undergoes habitual bending and torsion, and demonstrates nonuniform matrix fluid-flow patterns, and high circumferential strain gradients along the neutral axis (cranial-caudal) region at mid-diaphysis. The current results showed significant porosity differences: 1) greater osteocyte lacuna densities (N.Lac/Ar) (i.e., "non-vascular porosity") in the caudal and cranial cortices in both groups, 2) greater N.Lac/Ar in the pericortex vs. endocortex in mature bones, and 3) greater nonlacunar porosity (i.e., "vascular porosity") in the endocortex vs. pericortex in mature bones. Vascular and nonvascular porosities were not correlated. There were no secondary osteons in subadults. In adults, the highest secondary osteon population densities and lowest %ash occurred in the ventral-caudal, caudal, and cranial cortices, where shear strains, circumferential strain gradients, and fluid displacements are highest. Changes in thickness of the caudal cortex explained the largest proportion of the age-related increase in cranial-caudal breadth; the thickness of other cortices (dorsal, ventral, and cranial) exhibited smaller changes. Only subadult bones exhibited CFO patterns corresponding to habitual tension (ventral) and compression (dorsal). These CFO variations may be adaptations for differential mechanical requirements in "strain-mode-specific" loading. The more uniform oblique-to-transverse CFO patterns in adult bones may represent adaptations for shear strains produced by torsional loading, which is presumably more prevalent in adults. The micro- and ultrastructural heterogeneities may influence strain and fluid-flow dynamics, which are considered proximate signals in bone adaptation.

Transcranial magnetic stimulation induces increases in extracellular levels of dopamine and glutamate in the nucleus accumbens.

Transcranial magnetic stimulation (TMS) is a non-invasive approach used for stimulating the human brain. Repetitive stimulation over the prefrontal cortex has proven effective in the treatment of major depression, however the mechanism of the antidepressant action is unknown. Since the nucleus accumbens is a major region implicated in reward circuitry and depressive disorders, we used the microdialysis technique to study some of the neurochemical changes induced in that region during and after acute TMS. Magnetic stimulation was applied over the frontal or the caudal cortex of the rat brain using a special coil design and microdialysis samples were collected before, during and after the stimulation session. The extracellular levels of both dopamine and glutamate in the nucleus accumbens were increased during the stimulation while the extracellular levels of acetylcholine were not affected. Stimulation over the caudal cortex caused a greater increase in dopamine levels than the stimulation over the frontal cortex, while such difference was not observed for glutamate levels. The changes in dopamine and glutamate extracellular levels in the nucleus accumbens may play a role in the antidepressant effect of TMS and it is therefore suggested that the effect of stimulation over caudal cortical sites on depressive patients will be examined.

Neonatal development of projections to the basolateral amygdala from prefrontal and thalamic structures in rat.

Recently an animal model for neurodevelopmental disorders has been developed. In this model the effects of an early neonatal [postnatal day 7 (Pd7)] basolateral amygdala lesion are compared with the effects of a lesion later in life (Pd21). Early amygdala damage results in enduring behavioral disturbances that become more manifest after puberty. These disturbances were not present in animals lesioned at Pd21. Accordingly it was postulated that the early damage may affect the neuroanatomical and neurochemical organization and functioning of other brain structures. To obtain information on the innervation of the amygdala during normal development, we used the retrograde tracer fluoro-gold. From neonatal day 7 onward (studied until Pd19), retrogradely labeled cells were present in the caudal and rostral thalamus, the substantia innominata, and the prefrontal but not the caudal cortex. Development of the topography of the projecting cells differed substantially for the thalamic regions and substantia innominata vs. the cortical regions. In thalamic regions and substantia innominata, no changes were observed during the studied period (Pd7-Pd9). In the prefrontal cortex, the number of labeled cells increased (from Pd7 to Pd13), the topography of the location of the cells changed from unilateral to bilaminar (from Pd9 to Pd13), and the number of subareas in which the cells were present increased (from Pd7 to Pd13). In the caudal cortex, relatively few cells were present up to Pd15. From Pd17 onward, a bilaminar topography of the location of the cells was observed. These data provide information on the circuitry that may be involved in the aberrant neurodevelopment of neonatally amygdala-lesioned rats, which has been proposed as an animal model for neurodevelopmental psychopathological disorders.

The properties of convergence eye movements evoked from the rostral and caudal lateral suprasylvian cortex in the cat.

Convergence eye movements were evoked in the lateral suprasylvian cortex (LS cortex) in the cat. Three effective regions were found: the rostral and caudal parts of the postero-medial LS cortex (the PMLS) and the rostral part of the postero-lateral LS cortex (the PLLS). These three areas represent the central and paracentral visual fields in the published retinotopic map (Palmer et al., 1978). Convergence eye movements evoked from the caudal PMLS were divided into two groups based on their latencies; the short-latency components (SLC) and long-latency components (LLC). The SLC and the LLC had differences in their symmetry of right and left eye movements during vergence eye movement. The SLC had symmetric right and left eye components and the LLC had dominant contralateral eye components. In the rostral PMLS, latencies of evoked convergence eye movement were comparable to those of the caudal PMLS, but they did not divided into two groups. Convergence eye movements evoked from the PLLS had longer latencies than those from the PMLS and asymmetric right and left eye components. It is suggested that different subregions in the LS cortex contribute to the control of convergence eye movement, playing different roles.

Expression of redox factor-1, p53-activated gene 608 and caspase-3 messenger RNAs following repeated unilateral common carotid artery occlusion in gerbils—Relationship to delayed cell injury and secondary failure of energy state

The temporospatial expression pattern of the nuclear DNA repair enzyme redox factor-1 ( ref-1), the p53- activated gene ( pag) 608 and the effector caspase-3 was examined by in situ hybridization histochemistry in gerbils subjected to two 10-min episodes of unilateral common carotid artery occlusion, separated by 5 h. Gene responses were correlated with the metabolic state, as revealed by regional adenosine 5′-triphosphate bioluminescent imaging, and with the degree of histological damage, as assessed by haematoxylin-eosin staining and terminal deoxynucleotidyl transferase-mediated-dUTP nick end labeling (TUNEL), in order to evaluate the role of these genes in the maturation of injury. Focal infarcts developed in the dorsolateral cerebral cortex at the bregma level and the nucleus caudate–putamen within four days after repeated unilateral ischemia, as indicated by a secondary adenosine 5′-triphosphate loss after initial adenosine 5′-triphosphate recovery and by histomorphological signs of pannecrosis. The more caudal cortex at hippocampal levels and the hippocampus (CA1>CA3 area), however, exhibited selective neuronal injury without adenosine 5′-triphosphate depletion. TUNEL(+) cells appeared starting 5 h after repeated unilateral ischemia. TUNEL(+) cells reached maximum levels in the caudate–putamen at 12–24 h, but much later in the cortex and hippocampus at two days after ischemia. Remarkably few TUNEL(+) cells were noticed in the thalamus, where adenosine 5′-triphosphate state did not recover after reperfusion. Following repeated unilateral ischemia, a transient elevation of ref-1 mRNA was detected after 5 h in the cerebral cortex and hippocampal CA1 area. Ref-1 mRNA levels decreased within 12–24 h, before the onset of tissue damage. Subsequently, pag608 and caspase-3 mRNA levels increased, closely in parallel with the appearance of DNA fragmented cells, but slightly prior to the deterioration of adenosine 5′-triphosphate state. In the caudate–putamen, pag608 and caspase-3 mRNAs reached maximum levels already 12–24 h after repeated common carotid artery occlusion, when DNA fragmentation was most prominent, and declined thereafter. In the cortex and hippocampal CA1-3 areas, where DNA damage appeared more slowly, pag608 and caspase-3 mRNAs were induced starting 24 h after ischemia, and remained elevated even after two to four days. The levels of pag608 and caspase-3 mRNAs were similar at rostral and caudal levels of the cortex, as well as in the hippocampal CA1 and CA3 area, although the degree of injury differed considerably between these structures. Notably, pag608 and caspase-3 mRNAs were not elevated in the thalamus after repeated unilateral ischemia. The present report shows a close temporal association between the induction of ref-1, pag608 and caspase-3 mRNAs, the manifestation of cell injury and the secondary adenosine 5′-triphosphate depletion in infarcting brain areas, suggesting (i) that de novo responses of these genes may be involved in the maturation of cell injury and (ii) that apoptotic programs and the secondary deterioration of cerebral energy state may interfere with each other after ischemia.

Alterations of amino acids and monoamine metabolism in male Fmr1 knockout mice: a putative animal model of the human fragile X mental retardation syndrome.

The Fragile X syndrome, a common form of mental retardation in humans, is caused by silencing the fragile X mental retardation (FMR1) geneleading to the absence of the encoded fragile X mental retardation protein 1 (FMRP). We describe morphological and behavioral abnormalities for both affected humans and Fmr1 knockout mice, a putative animal model for the human Fragile X syndrome. The aim of the present study was to identify possible neurochemical abnormalities in Fmr1 knockout mice, with particular focus on neurotransmission. Significant region-specific differences: of basal neurotransmitter and metabolite levels were found between wildtype and Fmr1 knockout animals, predominantly in juveniles (post-natal days 28 to 31). Adults (postnatal days 209 to 221) showed only few abnormalities as compared with the wildtype. In juvenile knockout mice, aspartate and taurine were especially increased in cortical regions, striatum, hippocampus, cerebellum, and brainstem. In addition, juveniles showed an altered balance between excitatory and inhibitory amino acids in the caudal cortex, hippocampus, and brainstem. We detected very few differences in monoamine turnover in both age stages. The results presented here provide the first evidence that lack of FMRP expression in FMRP knockout mice is accompanied by age-dependent, region-specific alterations in neurotransmission.

Postexercise and positional variation in mechanical properties of the radius in young horses.

The metacarpal of the horse is severely loaded during vigorous exercise. Metacarpal specimens have a greater impact strength in young horses that have been exercised than in those that have only been walked. We did not find a corresponding difference in the radius of the same horses. We show that cranial (anterior) cortical bone from the radius, which is loaded in tension during locomotion, has a greater Young's modulus, and tensile and bending strength, than bone from the caudal (posterior) cortex, which is loaded in compression. Caudal bone is, however, stronger in compression. The differences can be explained by differences in the histological structure developed by the 2 cortices and are presumably adaptive. This work confirms the work of others. Furthermore, we demonstrate that the impact energy absorption of cranial bone is nearly twice as great as that of caudal bone. The caudal cortex has apparently paid a heavy price in its reduction in resistance to accidental impact loading for being stronger than the cranial cortex in compressive loading.

Loading conditions and cortical bone construction of an artiodactyl calcaneus.

Customary nonuniform distributions of physiological bone strains are thought to evoke heterogeneous material adaptation in diaphyseal cortices of some limb bones. Recent studies of artiodactyl calcanei have suggested that the regional prevalence of specific mechanical strain features such as mode and magnitude correlate with specific variations in cortical bone ultrastructure, microstructure and mineralization. These data are also consistent with predictions of current algorithms of mechanically induced bone adaptation. However, detailed characterization of the customary functional strain environment of these bones is needed to understand better the mechanisms of these adaptations. An in vitro loading method and rosette strain gauges were used to record principal strains, maximum shear strains and principal strain angles at multiple locations on ten calcanei of adult male mule deer (Odocoileus hemionus hemionus). Each hind limb was fixed in an apparatus to mimic the mid-support phase of the gait and loaded via the Achilles tendon over a broad range of functional loads (0 to 2943 N). Strains were recorded on the craniolateral, craniomedial, caudal, medial and lateral cortices at mid-diaphysis. Loading variations included the progressive elimination of the ligament and tendon along the caudal calcaneus. The results showed that the cranial cortex experiences longitudinal compressive strains that are nearly equal to the principal minimum strains and that the caudal cortex receives longitudinal tensile strains that are nearly equal to the principal maximum strains. With a 981 N load, the mean principal compressive strain on the cranial cortex was -636+/-344 micro(&egr;) (mean +/- s.d., N=9) and the mean principal tensile strain on the caudal cortex was 1112+/-68 micro;(&egr;)x (N=9). In contrast to the cranial and caudal cortices, principal strains in the medial and lateral cortices displayed relatively large deviations from the longitudinal axis (medial, 24 degrees cranial; lateral, 27 degrees caudal). Although shear strains predominated at all gauge sites, variations in maximum shear strains showed no apparent regional pattern or consistent regional predominance. The plantar ligament and tendon of the superficial digital flexor muscle were shown to have important load-sharing functions. These results demonstrate that the functionally loaded artiodactyl calcaneus generally behaves like a cantilevered beam with longitudinal compression and tension strains predominating in opposing cranial and caudal cortices, respectively. Differences in osteon remodeling rates, osteon morphology and mineral content reported previously between the cranial and caudal cortices correlate, in part, with the magnitudes of the principal compressive and tensile strains, respectively. However, material differences that distinguish the medial and lateral cortices from the cranial and caudal cortices could not be primarily attributed to locally increased shear strains as previously suggested. Variations in osteon and/or collagen fiber orientation may correlate more strongly with principal strain direction.

Serotonin-immunoreactive structures in the central nervous system of the garfish Lepisosteus productus (Semionotiformes, Osteichthyes)

Serotonin-immunoreactive (5HT-IR) neurons were investigated in the brain and rostral (cervical) spinal cord of the garfish, a non-teleost actinopterygian. The diencephalon contained a prominent 5HT-IR cell group consisting mainly of liquor-contacting neurons in the hypothalamic periventricular wall. Their ependymofugal processes formed thick bundles or patches within the hypothalamus and then arborized profusely. Other groups of 5HT-IR cells were found in the dorsal thalamus and in the caudal cortex of the hypothalamic inferior lobe. In the caudal brainstem, 5HT-IR cells were predominant in the raphe region. The spinal 5HT-IR cells were scattered rostrocaudally in the ventromedial zone. The structure corresponding to the submeningeal serotonergic system in the ventral spinal cord of the lamprey and stingray was demonstrated also in the garfish.