Clinical characteristics of children with mental retardation of unknown etiology in Korea.

The purpose of this study was to investigate the clinical characteristics of children with mental retardation (MR) of unknown etiology for early recognition and intervention. In this study, we defined children with MR of unknown etiology as those without clear etiologies for MR despite extensive evaluation and were not associated with pathological behavioral problems such as pervasive developmental disorders and attention-deficit/hyperactivity disorder. The clinical characteristics of children with MR of unknown etiology were as follows. 1) MR of unknown etiology was 48.8% of all MR. 2) MR of unknown etiology was more common in males. 3) Delayed language development was a leading factor that made the parents of children with MR of unknown etiology seek help from physicians. However, most of the children with MR of unknown etiology showed a relatively uniform delay in several areas of development. 4) Most children with MR of unknown etiology were delayed walkers. 5) Most children with MR of unknown etiology were mild cases.     

Possible association of rare autosomal folate sensitive fragile sites and idiopathic mental retardation: a blind controlled population study

The expression of folate sensitive fragile sites (FS) was assessed in cord blood lymphocyte cultures obtained from 790 newborns (NB) and in peripheral blood lymphocyte cultures from 326 institutionalized mentally retarded residents (MR). The mean rate of expression of common FS and the occurrence of rare FS was significantly higher in the MR population. Age, sex and history of chronic medication use did not appear to influence common FS expression in the MR population, 3/790 (0.38%) NB and 5/326 (1.53%) MR exhibited rare autosomal folate sensitive FS, a 4-fold difference in incidence (P = 0.009, Poisson test). Four of the five MR who expressed rare FS were considered to have idiopathic MR (4/179 or 2.2%). The occurrence of rare FS in 1/147 (0.68%) MR with known etiology is not significantly different from the frequency of occurrence in the NB population (P = 0.428, Poisson test). In this population, rare FS appear to be overrepresented in the idiopathic etiology MR group.     

Mannose-resistant Proteus-like fimbriae are produced by most Proteus mirabilis strains infecting the urinary tract, dictate the in vivo localization of bacteria, and contribute to biofilm formation

Proteus mirabilis, an etiologic agent of complicated urinary tract infections, expresses mannose-resistant Proteus-like (MR/P) fimbriae whose expression is phase variable. Here we examine the role of these fimbriae in biofilm formation and colonization of the urinary tract. The majority of wild-type P. mirabilis cells in transurethrally infected mice produced MR/P fimbriae. Mutants that were phase-locked for either constitutive expression (MR/P ON) or the inability to express MR/P fimbriae (MR/P OFF) were phenotypically distinct and swarmed at different rates. The number of P. mirabilis cells adhering to bladder tissue did not appear to be affected by MR/P fimbriation. However, the pattern of adherence to the bladder surface was strikingly different. MR/P OFF colonized the lamina propria underlying exfoliated uroepithelium, while MR/P ON colonized the luminal surfaces of bladder umbrella cells and not the exfoliated regions. Wild-type P. mirabilis was usually found colonizing intact uroepithelium, but it occasionally adhered to exfoliated areas. MR/P ON formed significantly more biofilm than either P. mirabilis HI4320 (P = 0.03) or MR/P OFF (P = 0.05). MR/P OFF was able to form a biofilm similar to that of the wild type. MR/P ON formed a three-dimensional biofilm structure as early as 18 h after the initiation of the biofilm, while MR/P OFF and the wild type did not. After 7 days, however, P. mirabilis HI4320 formed a 65-mum-thick biofilm, while the thickest MR/P ON and MR/P OFF biofilms were only 12 mum thick. We concluded that MR/P fimbriae are expressed by most P. mirabilis cells infecting the urinary tract, dictate the localization of bacteria in the bladder, and contribute to biofilm formation.     

The dendritic cell mannose receptor mediates allergen internalization and maturation involving notch 1 signalling

Dendritic cells (DCs) have been shown recently to play a key role in inducing and mediating T helper type 2 (Th2) responses associated with atopic disease. These responses are mediated in part by ligation to different Toll‐like receptors (TLRs) and C‐type lectins, e.g. the mannose receptor (MR), depending upon the DC subset involved and the respective microenvironments. Because ovalbumin (OVA) (which is structurally related to various allergens) can engage the MR, we can use OVA stimulation as a model for understanding the roles of both TLRs and the MR in allergic inflammatory responses. We examined TLR‐ and MR‐mediated responses from mouse bone marrow‐derived DCs in the context of antigen recognition and presentation in addition to examining the relationship between notch 1, TLRs and MR signalling pathways. This work demonstrated that OVA‐mediated signalling up‐regulated both TLR‐2 and MR and that MR RNA interference (RNAi) but not TLR2 RNAi inhibited DC internalization of fluorescein isothiocyanate–OVA. Furthermore, MR RNAi inhibited OVA‐ and house dust mite allergen extract‐induced DC maturation and MR RNAi and TLR2 RNAi influenced DC interleukin‐12 production independently. Finally, we demonstrated that blocking notch 1 signalling inhibited both notch 1 and TLR‐2 expression but not MR expression levels. However, MR RNAi inhibited the expression of MR, TLR‐2 and notch 1. These results indicate that MR is the primary receptor mediating the internalization of environmental allergen glycoproteins. In addition, TLR‐2 and notch 1 play important roles in DC maturation and antigen presentation and signals originating from the MR and TLR‐2 receptors converge with the notch 1 signalling pathway.     

MR microscopy and high resolution small animal MRI: applications in neuroscience research

The application of magnetic resonance (MR) imaging in the study of human disease using small animals has steadily evolved over the past two decades and strongly established the fields of "small animal MR imaging" and "MR microscopy." An increasing number of neuroscience related investigations now implement MR microscopy in their experiments. Research areas of growth pertaining to MR microscopy studies are focused on (1). phenotyping of genetically engineered mice models of human neurological diseases and (2). rodent brain atlases. MR microscopy can be performed in vitro on tissue specimens, ex vivo on brain slice preparations and in vivo (typically on rodents). Like most new imaging technologies, MR microscopy is technologically demanding and requires broad expertise. Uniform guidelines or "standards" of a given MR microscopy experiment are non-existent. The main focus therefore of this review will be on biological applications of MR microscopy and the experimental requirements. We also take a critical look at the biological information that small animal (rodent) MR imaging has provided in neuroscience research.     

Mapping of three novel loci for non‐syndromic autosomal recessive mental retardation (NS‐ARMR) in consanguineous families from Pakistan

Rafiq MA, Ansar M, Marshall CR, Noor A, Shaheen N, Mowjoodi A, Khan MA, Ali G, Amin‐ud‐Din M, Feuk L, Vincent JB, Scherer SW. Mapping of three novel loci for non‐syndromic autosomal recessive mental retardation (NS‐ARMR) in consanguineous families from Pakistan. To date, of 13 loci with linkage to non‐syndromic autosomal recessive mental retardation (NS‐ARMR), only six genes have been established with associated mutations. Here we present our study on NS‐ARMR among the Pakistani population, where people are traditionally bound to marry within the family or the wider clan. In an exceptional, far‐reaching genetic survey we have collected more than 50 consanguineous families exhibiting clinical symptoms/phenotypes of NS‐ARMR. In the first step, nine families (MR2‐9 and MR11) with multiple affected individuals were selected for molecular genetic studies. Two families (MR3, MR4) showed linkage to already know NS‐ARMR loci. Fifteen affected and 10 unaffected individuals from six (MR2, MR6, MR7, MR8, MR9 and MR11) families were genotyped by using Affymetrix 5.0 or 6.0 single‐nucleotide polymorphism (SNP) microarrays. SNP microarray data was visually inspected by dChip and genome‐wide homozygosity analysis was performed by HomozygosityMapper. Additional mapping was performed (to exclude false‐positive regions of homozygosity called by HomozygosityMapper and dChip) on all available affected and unaffected members in seven NS‐ARMR families, using microsatellite markers. In this manner we were able to map three novel loci in seven different families originating from different areas of Pakistan. Two families (MR2, MR5) showed linkage on chromosome 2p25.3‐p25.2. Three families (MR7, MR8, and MR9) that have been collected from the same village and belong to the same clan were mapped on chromosome 9q34.3. MR11 maps to a locus on 9p23‐p13.3. Analysis of MR6 showed two positive loci, on chromosome 1q23.2‐q23.3 and 8q24.21‐q24.23. Genotyping in additional family members has so far narrowed, but not excluded the 1q locus. In summary, through this study we have identified three new loci for NS‐ARMR, namely MRT14, 15 and 16.     

Long-term echocardiographic follow-up after posterior mitral annuloplasty using a vascular strip for ischemic mitral regurgitation: ten-years of experience at a single center

Management of ischemic mitral regurgitation (MR) is challenging. The aim of this study was to investigate long-term clinical and echocardiographic results of restrictive mitral annuloplasty for ischemic MR. From 2001 through 2010, 96 patients who underwent myocardial revascularization with restrictive mitral annuloplasty using a vascular strip for ischemic MR were analyzed. Patients were stratified into two groups based on left ventricular ejection fraction (LVEF): group I, n = 50, with LVEF > 35% and group II, n = 46, with LVEF ≤ 35%. The early mortality rate was 2.1% (2/96) and the late cardiac mortality rate was 11.5% (11/96). MR grade was reduced at discharge (0.8 ± 0.7) but increased during follow-up (1.1 ± 0.8, P = 0.001). There was no intergroup difference in terms of freedom from recurrent MR ≥ moderate eight years after surgery (94.1% ± 5.7%, group I vs 87.8% ± 7.2%, group II; P = 0.575). NYHA functional class (odds ratio [OR], 2.2; P = 0.044) and early postoperative residual MR ≥ mild (OR, 25.4; P < 0.001) were independent predictors of recurrent MR. Restrictive mitral annuloplasty using a vascular strip is effective in ischemic MR. It is important to avoid early postoperative residual MR.     

Seizure-induced changes of mineralocorticoid and glucocorticoid receptors in the hippocampus in seizure sensitive gerbils

Abnormal corticosteroid hormone levels during stress and resultant mineralocorticoid receptor (MR)/glucocorticoid receptor (GR) imbalance enhance the vulnerability of specific hippocampal neurons. In the present study, we investigated the distribution of MR and GR in seizure resistant (SR) and seizure sensitive (SS) gerbils, and observed the seizure-induced changes of MR and GR in the hippocampus of SS gerbils using immunohistochemistry and western blot analysis. MR and GR immunoreactivities were higher in the SS pre-seizure gerbils than that in SR gerbils. In the SR gerbils, the immunodensity of GR was high compared to that of MR. The changes of MR and GR immunoreactivities were significant in the stratum pyramidale of the hippocampal CA1 region and the infrablade of the dentate gyrus after seizure on-set. MR immunoreactivity in the CA1 region was significantly increased at 12h after seizure on-set, thereafter MR immunoreactivity was decreased. MR immunoreactivity in the dentate gyrus was decreased time-dependently after seizure on-set. GR immunoreactivity was decreased in the CA1 region and dentate gyrus time-dependently after seizure on-set. At 12h after seizure on-set, differences in MR and GR immunodensity diminished in the CA1 region and dentate gyrus. This imbalance of MR and GR immunoreactivity in these regions may be associated with seizure generation in the Mongolian gerbil, which is a hereditary seizure model.     

Paramagnetic dysprosium oxide nanoparticles and dysprosium hydroxide nanorods as T₂ MRI contrast agents

We report here paramagnetic dysprosium nanomaterial-based T(2) MRI contrast agents. A large r(2) and a negligible r(1) is an ideal condition for T(2) MR imaging. At this condition, protons are strongly and nearly exclusively induced for T(2) MR imaging. The dysprosium nanomaterials fairly satisfy this because they are found to possess a decent r(2) but a negligible r(1) arising from L + S state 4f-electrons in Dy(III) ion ((6)H(15/2)). Their r(2) will also further increase with increasing applied field because of unsaturated magnetization at room temperature. Therefore, MR imaging and various physical properties of the synthesized d-glucuronic acid coated ultrasmall dysprosium oxide nanoparticles (d(avg) = 3.2 nm) and dysprosium hydroxide nanorods (20 × 300 nm) are investigated. These include hydrodynamic diameters, magnetic properties, MR relaxivities, cytotoxicities, and 3 tesla in vivo T(2) MR images. Here, MR imaging properties of dysprosium hydroxide nanorods have not been reported so far. These two samples show r(2)s of 65.04 and 181.57 s(-1)mM(-1), respectively, with negligible r(1)s at 1.5 tesla and at room temperature, no in vitro cytotoxicity up to 100 μM Dy, and clear negative contrast enhancements in 3 tesla in vivo T(2) MR images of a mouse liver, which will be even more improved at higher MR fields. Therefore, d-glucuronic acid coated ultrasmall dysprosium oxide nanoparticles with renal excretion can be a potential candidate as a sensitive T(2) MRI contrast agent at MR field greater than 3 tesla.     

Case fatality ratio and mortality rate trends of community-onset Staphylococcus aureus bacteraemia

Lethal outcomes can be expressed as a case fatality ratio (CFR) or as a mortality rate per 100 000 population per year (MR). Population surveillance for community-onset methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus bacteraemia was conducted in Canada, Australia, Sweden and Denmark to evaluate 30-day CFR and MR trends between 2000 and 2008. The CFR was 20.3% (MSSA 20.2%, MRSA 22.3%) and MR was 3.4 (MSSA 3.1, MRSA 0.3) per 100 000 per year. Although MSSA CFR was stable the MSSA MR increased; MRSA CFR decreased while its MR remained low during the study. Community-onset S. aureus bacteraemia, particularly MSSA, is associated with major disease burden. This study highlights complementary information provided by evaluating both CFR and MR.     

High occurrence of mitral valve prolapse in cardiac catheterization patients with pure isolated mitral regurgitation

The aetiological spectrum of angiographically verified pure isolated mitral regurgitation (MR) was studied in 48 consecutive adult patients (35 males). Severe MR was found in 35 patients (73%) and moderate MR in 13 patients (27%). Mitral valve prolapse (MVP) syndrome was found in 21 patients (44%). These were younger than the rest of the study population (55 +/- 13 vs. 62 +/- 6 years, p less than 0.05) and 15 (71%) of them were men. Endocarditis and chordal rupture occurred in 19% and 43% of the MVP patients. Sixteen patients (33%) had MR secondary to myocardial infarction while only three patients (6%) had MR of rheumatic aetiology. Bacterial endocarditis, hypertensive heart disease, hypertrophic obstructive cardiomyopathy and mitral annulus calcification were less frequently found. Mitral valve replacement was done in 20 (57%) of the patients with severe MR and MVP was the underlying disease in 15 (75%) of these patients. In conclusion, MVP is a frequent cause of pure isolated MR and of mitral valve replacement. In contrast to the preponderance of young females amongst MVP patients in population surveys, most of the MVP patients with MR in this study are middle-aged and elderly men.     

Functional role of mucoid exopolysaccharide (alginate) in antibiotic-induced and polymorphonuclear leukocyte-mediated killing of Pseudomonas aeruginosa.

We evaluated in vitro the functional role of mucoid exopolysaccharide (MEP) of Pseudomonas aeruginosa in blocking antibiotic-induced and polymorphonuclear leukocyte (PMN)-mediated pseudomonal killing. The serum-resistant P. aeruginosa isolates used were mucoid strain 144MR and its nonmucoid revertant, strain 144NM. By timed kill curves, early bacterial effects of amikacin against mucoid strain 144MR were substantially less than those observed with nonmucoid strain 144NM; this effect was reversible with enzymatic hydrolysis of MEP of strain 144MR by alginase. Also, early tobramycin uptake (15 to 30 min) by mucoid 144MR cells was less than that seen with nonmucoid strain 144NM; pretreatment of 144MR cells with alginase substantially enhanced early tobramycin uptake compared with untreated 144MR cells (P = 0.08). In strain 144NM (but not in strain 114MR) there was a notable postantibiotic leukocidal enhancement effect manifested by increased nonopsonic killing following brief exposure of these cells to supra-MIC amikacin; pretreatment of strain 144MR with alginase rendered these cells more susceptible to amikacin-induced postantibiotic leukocidal enhancement. Similarly, direct PMN-mediated nonopsonic killing of mucoid strain 144MR was significantly less than that observed with strain 144NM (P less than 0.05); pretreatment of 144MR cells with alginase rendered this strain equal to strain 144NM in susceptibility to nonopsonic killing. In addition, exogenous sodium alginate or extracted MEP of strain 144MR interfered with effective nonopsonic killing of strain 144NM by PMNs. Studies also indicated that mucoid strain 144MR was phagocytosed significantly less well than its nonmucoid mate (P less than 0.00001), an effect reversed by pretreatment of the mucoid cells with alginase. These data confirm that P. aeruginosa MEPs functionally decrease the uptake and early bactericidal effect of aminoglycosides in vitro and interfere with effective PMN-mediated nonopsonic phagocytosis and killing of mucoid strains.     

Carbohydrate-independent recognition of collagens by the macrophage mannose receptor

Mannose receptor (MR) is the best characterised member of a family of four endocytic molecules that share a common domain structure; a cysteine-rich (CR) domain, a fibronectin-type II (FNII) domain and tandemly arranged C-type lectin-like domains (CTLD, eight in the case of MR). Two distinct lectin activities have been described for MR. The CR domain recognises sulphated carbohydrates while the CTLD mediate binding to mannose, fucose or N-acetylglucosamine. FNII domains are known to be important for collagen binding and this has been studied in the context of two members of the MR family, Endo180 and the phospholipase A2 receptor. Here, we have investigated whether the broad and effective lectin activity mediated by the CR domain and CTLD of MR is favoured to the detriment of FNII-mediated interaction(s). We show that MR is able to bind and internalise collagen in a carbohydrate-independent manner and that MR deficient macrophages have a marked defect in collagen IV and gelatin internalisation. These data have major implications at the molecular level as there are now three distinct ligand-binding sites described for MR. Furthermore our findings extend the range of endogenous ligands recognised by MR, a molecule firmly placed at the interface between homeostasis and immunity.     

Focal lesions in cirrhotic liver: comparing MR imaging during arterial portography with Gd-enhanced dynamic MR imaging

The purpose of this study was to document the additional value of MR imaging during arterial portography (MRAP) in patients examined with intravenous contrast-enhanced dynamic MR imaging for the assessment of focal lesions in patients with cirrhosis or chronic viral hepatitis. The MR images of 24 patients with 39 hepatocellular carcinomas and 18 benign hepatocellular nodules examined with dynamic MR imaging and MRAP within a 14-day interval were retrospectively reviewed. For 39 hepatocellular carcinomas, MRAP revealed 37 perfusion defects (95%), while dynamic MR imaging demonstrated 35 occurrences of nodular contrast-enhancement (90%) on arterial dominant phases. Among the 11 benign nodules misinterpreted as hepatocellular carcinoma due to their high signal intensities on arterial-dominant phases of dynamic MR imaging, eight (73%) showed intratumoral portal venous perfusion on MRAP and were regarded as benign nodules. As a result of its high sensitivity and its potential ability to enable differentiation of benign and malignant hepatocellular nodules, MRAP can be added to dynamic MR imaging for planning future management in patients with equivocal hepatocellular nodules in the cirrhotic liver.     

A study of artefacts in simultaneous PET and MR imaging using a prototype MR compatible PET scanner.

We have assessed the possibility of artefacts that can arise in attempting to perform simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) using a small prototype MR compatible PET scanner (McPET). In these experiments, we examine MR images for any major artefacts or loss in image quality due to inhomogeneities in the magnetic field, radiofrequency interference or susceptibility effects caused by operation of the PET system inside the MR scanner. In addition, possible artefacts in the PET images caused by the static and time-varying magnetic fields or radiofrequency interference from the MR system were investigated. Biological tissue and a T2-weighted spin echo sequence were used to examine susceptibility artefacts due to components of the McPET scanner (scintillator, optical fibres) situated in the MR field of view. A range of commonly used MR pulse sequences was studied while acquiring PET data to look for possible artefacts in either the PET or MR images. Other than a small loss in signal-to-noise using gradient echo sequences, there was no significant interaction between the two imaging systems. Simultaneous PET and MR imaging of simple phantoms was also carried out in different MR systems with field strengths ranging from 0.2 to 4.7 T. The results of these studies demonstrate that it is possible to acquire PET and MR images simultaneously, without any significant artefacts or loss in image quality, using our prototype MR compatible PET scanner.     

New fimbrial hemagglutinin in Serratia species.

Strains of Serratia marcescens, Serratia liquefaciens, Serratia marinorubra, and Serratia plymuthica produced one or more of the following hemagglutinins (HAs): mannose-sensitive HA and mannose-resistant K-HA (MR/K-HA) and P-HA (MR/P-HA) (J. P. Duguid and D. C. Old, in E. H. Beachey (ed.), Bacterial adherence, vol. 6., p. 185-217, 1980). Most strains (82%) were multiply hemagglutinating. The properties of the three HAs are described. Each HA was associated with a distinct type of fimbria: mannose-sensitive HA with type 1 fimbriae. MR/K-HA with type 3 fimbriae, and MR/P-HA with a new type of thin fimbriae provisionally called MR/P fimbriae. This is the first report of the production of MR/P-HA and MR/P fimbriae by Serratia species. The range of Serratia HAs, which may reflect in vivo colonization potential, is more complex than previously reported.     

Binding properties of the mannose receptor

A comprehensive approach to the study of mannose receptor (MR) biology has unveiled an unexpected level of complexity and stresses the importance of post-translational modifications and gene regulation in the analysis of protein function. The existence of endogenous tissue ligands for the MR highlights the need to reduce MR expression in antigen presenting cells and/or to regulate T cell stimulation after presentation of MR ligands, in order to avoid autoimmunity. This regulation might be achieved by down modulation of the antigen presenting cell stimulatory capacity upon MR ligation. In macrophages there are conflicting evidence regarding the outcome of MR recognition. These results are not unexpected if endogenous mannosylated and sulphated self-antigens, that need to be shielded from the immune system, are being eliminated through this receptor. The presence of counter receptors for the cysteine rich (CR) domain of the MR in specialized myeloid cells in lymphoid organs adds a new dimension to this system. It opens the possibility for a delivery pathway for MR carbohydrate recognition domains (CRDs) ligands that needs to be investigated further.     

Analysis of mannose receptor regulation by IL-4, IL-10, and proteolytic processing using novel monoclonal antibodies

The study of the murine macrophage mannose receptor (MR) has been hampered by the lack of specific reagents. We have generated and characterized novel anti-MR monoclonal antibodies and used them to analyze MR expression in primary mouse macrophages (M(phi)). In BioGel- and thioglycollate-elicited M(phi), interleukin (IL)-4 up-regulated total cell-associated MR (cMR), correlating with enhanced surface expression. We investigated the influence of IL-10, a well-characterized deactivator of M(phi) function, on MR levels and observed that it had a similar effect to IL-4. In both cases, enhanced cMR levels translated into increased production of the soluble form of the receptor (sMR). We have demonstrated the presence of sMR in cultures of stable non-M(phi) transductants expressing full-length MR, indicating that the proteolytic activity responsible for cMR cleavage is not M(phi)-restricted. These data support a role for the MR in T helper cell type 2 cytokine-driven, immune responses and suggest a non-M(phi) contribution to sMR production in vivo.     

Correlation of MR imaging findings and open exploration of medial patellofemoral ligament injuries in acute patellar dislocations

The purpose of this investigation was to correlate magnetic resonance (MR) images of medial patellofemoral ligament (MPFL) injuries with gross macroscopic findings. Twenty-seven knees with MPFL injury following an initial patellar dislocation were examined using axial proton-density and T2-weighted fast spin-echo MR imaging. MR findings were subsequently correlated with open exploration. MPFL injury was observed in 26 (96%) of the 27 knees. From the MR images, discontinuity, irregularity and/or high-signal intensity changes anterior to the femoral attachment were seen in 13 (82%) of the 16 knees with substantial-tear type injuries of the MPFL. In 8 (80%) of the 10 knees with avulsion-tear type injuries, detachment of the MPFL from the femoral attachment, accompanied with or without high-signal intensity changes, was confirmed. MPFL injury types could be accurately diagnosed on 21 (81%) out of 26 knees using MR imaging. MR imaging was an acceptable method in diagnosing MPFL injury types.     

Arborization of axons in oculomotor nucleus identified by vestibular stimulation and intra-axonal injection of horseradish peroxidase

Summary Axons in the medial rectus (MR) subdivisions of the oculomotor nucleus were identified by horizontal rotation and by electrical stimulation of the vestibular nerves and abducens nuclei. Three types of axons (vestibular type I and II and abducens interneurons) were then injected intra-axonally with horseradish peroxidase (HRP). Each injected axon was reconstructed under the microscope in the frontal and horizontal planes and terminal arborization and boutons contacting with MR motoneurons were studied. The MR motoneurons were identified by retrograde uptake of HRP, HRP being injected in the MR muscle prior to the intra-axonal experiment.The main types of horizontal canal-related axons were as follows: (1) ATD-unilateral termination axons: Most type I axons were of this type. Axons ascended in ascending tract of Deiters (ATD) to the oculomotor nucleus and terminated in ipsilateral MR area. (2) ATD-bilateral termination axons: Very few secondary canal responsive axons were in this group. Axons ascended in ATD to the oculomotor nucleus and terminated in MR motoneuron areas bilaterally and in the Edinger-Westphal nucleus. (3) MLF-bilateral termination axons: Most type II neurons were in this group. Axons went up in the contralateral MLF and into both oculomotor nuclei. Their branches distributed to several motoneuron areas but only infrequently to the MR area; and to the Edinger-Westphal nucleus. (4) AB interneuron axons: Axons ascended in the MLF contralateral to cells of origin and terminated in the contralateral MR motoneuron area.Supported by USPHS Grant No. 06658